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Sample records for 12-232 solid mechanics

  1. Solution-solid-solid mechanism: superionic conductors catalyze nanowire growth.

    PubMed

    Wang, Junli; Chen, Kangmin; Gong, Ming; Xu, Bin; Yang, Qing

    2013-09-11

    The catalytic mechanism offers an efficient tool to produce crystalline semiconductor nanowires, in which the choice, state, and structure of catalysts are active research issues of much interest. Here we report a novel solution-solid-solid (SSS) mechanism for nanowire growth catalyzed by solid-phase superionic conductor nanocrystals in low-temperature solution. The preparation of Ag2Se-catalyzed ZnSe nanowires at 100-210 °C is exampled to elucidate the SSS model, which can be extendable to grow other II-VI semiconductor (e.g., CdSe, ZnS, and CdS) nanowires by the catalysis of nanoscale superionic-phase silver or copper(I) chalcogenides (Ag2Se, Ag2S, and Cu2S). The exceptional catalytic ability of these superionic conductors originates from their structure characteristics, known for high-density vacancies and fast mobility of silver or copper(I) cations in the rigid sublattice of Se(2-) or S(2-) ions. Insights into the SSS mechanism are provided based on the formation of solid solution and the solid-state ion diffusion/transport at solid-solid interface between catalyst and nanowire. PMID:23919513

  2. Resonance Scattering Mechanisms in Solids and at Solid Surfaces.

    NASA Astrophysics Data System (ADS)

    Gerber, Andrew D.

    1987-09-01

    The concept of resonance electron scattering is applied to two very different solid state systems, one at the surface of a solid and one in the bulk. In part I, the problem of resonance scattering of electrons from molecules adsorbed on a metallic surface is examined. An analysis is made of the factors leading to the broadening and energy shift of the e -N _{2} vibrational excitation cross sections as compared to their gas phase analogues. Two effects are found to be important: the breaking of the molecular symmetry by the surface, and the influence of the metallic image potential. Multiple scattering calculations verify that these mechanisms produce a broadening and energy shift in the range of those seen experimentally. In part II, a new mechanism is formulated for the attenuation of ultrasound in mixed valence metals. The mechanism is based on the coupling of phonons to electrons in localized, atomic-like f-levels. The local nature of the interaction gives rise to a large enhancement over the standard (Pippard) result, especially in the limit of short electron mean free path. The mechanism also produces a 'bump' in the attenuation coefficient as a function of temperature, offering an explanation for the experimentally observed 12 K feature of UPt_{3} . A calculation of the attenuation coefficient for a mixed valence lattice reveals further enhancement and structure caused by coherent absorption at f-levels in many unit cells. The effects of degeneracy and correlation are examined in a calculation of the ultrasound attenuation for a system containing dilute Kondo impurities. The unifying theme of this work is the strong interaction between electrons and vibrational modes resulting from the trapping of electrons in localized resonance states. This mechanism has previously been seen to be of great importance for electron-molecule collisions in the gas phase. In the present work, its importance is demonstrated for scattering processes in solids and at solid surfaces

  3. The Mechanism of Atomization Accompanying Solid Injection

    NASA Technical Reports Server (NTRS)

    Castleman, R A , Jr

    1933-01-01

    A brief historical and descriptive account of solid injection is followed by a detailed review of the available theoretical and experimental data that seem to throw light on the mechanism of this form of atomization. It is concluded that this evidence indicates that (1) the atomization accompanying solid injection occurs at the surface of the liquid after it issues as a solid stream from the orifice; and (2) that such atomization has a mechanism physically identical with the atomization which takes place in an air stream, both being due merely to the formation, at the gas-liquid interface, of fine ligaments under the influence of the relative motion of gas and liquid, and to their collapse, under the influence of surface tension, to form the drops in the spray.

  4. Research in nonlinear structural and solid mechanics

    NASA Technical Reports Server (NTRS)

    Mccomb, H. G., Jr. (Compiler); Noor, A. K. (Compiler)

    1981-01-01

    Recent and projected advances in applied mechanics, numerical analysis, computer hardware and engineering software, and their impact on modeling and solution techniques in nonlinear structural and solid mechanics are discussed. The fields covered are rapidly changing and are strongly impacted by current and projected advances in computer hardware. To foster effective development of the technology perceptions on computing systems and nonlinear analysis software systems are presented.

  5. For nanowire growth, vapor-solid-solid (vapor-solid) mechanism is actually vapor-quasisolid-solid (vapor-quasiliquid-solid) mechanism

    NASA Astrophysics Data System (ADS)

    Noor Mohammad, S.

    2009-12-01

    Vapor-phase mechanisms [e.g., vapor-liquid-solid (VLS), vapor-solid-solid, oxide-assisted growth, and the self-catalytic growth mechanisms] for the unidirectional nanowire (NW) growth are not yet well understood. For this understanding, growths of GaN and InN NWs in our laboratory, without and with the assistance of foreign element catalytic agents (FECAs), such as Au and In, were performed. GaN NW growth, in the presence of FECA≡Ni, was possible at temperatures below the Ni/Ga eutectic temperature. InN NWs were grown, in the presence of Au, and at temperatures in the vicinity of Au/In eutectic temperature. They were found to have Au at the NW tip, NW base, and NW sidewalls. Extensive investigation of the fundamentals underlying these anomalies has been carried out. The temperature dependence of the VLS mechanism has also been elucidated. A large number of available elemental and compound semiconductor NWs exhibiting similar characteristics have been considered for the investigation. Based on this investigation, a chemicophysical mechanism called the vapor-quasisolid-solid (VQS) (or vapor-semisolid-solid, or vapor-quasiliquid-solid, or vapor-semiliquid-solid) mechanism has been proposed. The cause of temperature dependence of the VLS growth under different growth conditions and growth environments, and the possible relationship between the VLS and the VQS mechanisms has been presented. To better describe the vapor-phase mechanisms, including the VQS mechanism, a unified definition of droplets has been proposed. A series of experimental evidences has been set forth to substantiate the validity of the proposed mechanism, and to justify the definition of the unified droplet model. They together appear to explain the fundamental basis of the NW growth by various mechanisms, including the VQS mechanisms. They also provide solutions of many known problems, conflicts, confusions, and controversies involving NW growth.

  6. Variational time integrators in computational solid mechanics

    NASA Astrophysics Data System (ADS)

    Lew, Adrian Jose

    This thesis develops the theory and implementation of variational integrators for computational solid mechanics problems, and to some extent, for fluid mechanics problems as well. Variational integrators for finite dimensional mechanical systems are succinctly reviewed, and used as the foundations for the extension to continuum systems. The latter is accomplished by way of a space-tune formulation for Lagrangian continuum mechanics that unifies the derivation of tyre balance of linear momentum, energy and configurational forces, all of there as Euler-Lagrange equations of an extended Hamilton's principle. In this formulation, energy conservation and the path independence of the J- and L-integrals are conserved quantities emanating from Noether's theorem. Variational integrators for continuum mechanics are constructed by mimicking this variational structure, and a discrete Noether's theorem for rather general space-tune discretizations is presented. Additionally, the algorithms are automatically (multi)symplectic, and the (multi)symplectic form is uniquely defined by the theory. For instance, in nonlinear elastodynamics the algorithms exactly preserve linear and angular momenta, whenever the continuous system does. A class of variational algorithms is constructed, termed asynchronous variational integrators (AVI), which permit: the selection of independent time steps in each element of a finite element mesh, and the local time steps need riot bear an integral relation to each other. The conservation properties of both synchronous and asynchronous variational integrators are discussed in detail. In particular, AVI are found to nearly conserve energy both locally and globally, a distinguishing feature of variational integrators. The possibility of adapting the elemental time step to exactly satisfy the local energy balance equation, obtained from the extended variational principle, is analyzed. The AVI are also extended to include dissipative systems. The excellent

  7. Statistical Mechanics Model of Solids with Defects

    NASA Astrophysics Data System (ADS)

    Kaufman, M.; Walters, P. A.; Ferrante, J.

    1997-03-01

    Previously(M.Kaufman, J.Ferrante,NASA Tech. Memor.,1996), we examined the phase diagram for the failure of a solid under isotropic expansion and compression as a function of stress and temperature with the "springs" modelled by the universal binding energy relation (UBER)(J.H.Rose, J.R.Smith, F.Guinea, J.Ferrante, Phys.Rev.B29, 2963 (1984)). In the previous calculation we assumed that the "springs" failed independently and that the strain is uniform. In the present work, we have extended this statistical model of mechanical failure by allowing for correlations between "springs" and for thermal fluctuations in strains. The springs are now modelled in the harmonic approximation with a failure threshold energy E0, as an intermediate step in future studies to reinclude the full non-linear dependence of the UBER for modelling the interactions. We use the Migdal-Kadanoff renormalization-group method to determine the phase diagram of the model and to compute the free energy.

  8. Mechanisms of bacterial metals removal from solids

    SciTech Connect

    Torma, A.E.; Pryfogle, P.A.

    1990-01-01

    The Great Lakes area sediments are contaminated with varying amounts of heavy metals and polychlorinated organic matter. With respect to the bioremediation of metallic contents of these sediments, it was shown that a number of microorganisms exist which can effectively solubilize heavy metals. The basic reaction mechanisms of bioleaching processes were discussed and the effects of semiconductor character of the sulfide substrate explained. A special emphasis was made to comment on INEL's bioremediation capability. 37 refs.

  9. Movement mechanisms of gross solids in intermittent flow.

    PubMed

    Littlewood, K; Butler, D

    2003-01-01

    Gross solids, such as used tampons, sanitary towels and faecal stools, are introduced into the sewer network via the WC. Although small diameter pipes (< or = 150mm diameter) make up a large proportion of most sewer networks, the transport behaviour of gross solids in these smaller pipes is not fully established. In particular, there are concerns about the effect of water conservation measures on the transport of gross solids in the intermittent flow regime prevalent in small pipes. This paper introduces a study carried out on the movement of solids in this flow regime. An extensive series of experiments has been carried out to investigate the movement mechanisms and behaviour in detail. It was found that there are three different mechanisms of movement, and photographic evidence is provided in the paper. The concept and implications of the "limiting solid transport distance" is also introduced. It is argued that solid movement is dependent on factors other than just WC flush volume and that increased blockage potential is not inevitable. PMID:12666800

  10. Modeling Aging and Mechanical Rejuvenation of Amorphous Solids

    NASA Astrophysics Data System (ADS)

    Semkiv, Mykhailo; Hütter, Markus

    2016-04-01

    The elasto-viscoplasticity of amorphous solids is modeled, with a focus on the effects of physical aging and mechanical rejuvenation. Using nonequilibrium thermodynamics, the concept of kinetic and configurational subsystems has been employed. The Hamiltonian structure of reversible dynamics is exploited to derive a constitutive relation for the stress tensor. Furthermore, it is demonstrated that accounting for mechanical rejuvenation results in a modification of the driving force for viscoplastic flow.

  11. Solids between the mechanical extremes of order and disorder

    NASA Astrophysics Data System (ADS)

    Goodrich, Carl P.; Liu, Andrea J.; Nagel, Sidney R.

    2014-08-01

    For more than a century, physicists have described real solids in terms of perturbations about perfect crystalline order. Such an approach takes us only so far: a glass, another ubiquitous form of rigid matter, cannot be described in any meaningful sense as a defected crystal. Is there an opposite extreme to a crystal--a solid with complete disorder--that forms an alternative starting point for understanding real materials? Here, we argue that the solid comprising particles with finite-ranged interactions at the jamming transition constitutes such a limit. It has been shown that the physics associated with this transition can be extended to interactions that are long ranged. We demonstrate that jamming physics is not restricted to amorphous systems, but dominates the behaviour of solids with surprisingly high order. Just as the free-electron and tight-binding models represent two idealized cases from which to understand electronic structure, we identify two extreme limits of mechanical behaviour. Thus, the physics of jamming can be set side by side with the physics of crystals to provide an organizing structure for understanding the mechanical properties of solids over the entire spectrum of disorder.

  12. Mechanical anisotropy at the nanoscale in amorphous solids

    SciTech Connect

    Luo, Yun; Li, Qi-Kai; Li, M.

    2015-01-28

    Amorphous solids are randomly disordered without any long-range periodic atomic arrangement and thus appear isotropic. Here, we show in metallic glasses that this view does not hold at small scales: Strong mechanical anisotropy emerges when the sample size decreases below about 15 nm as shown by the marked deviation in stress-strain relations as well as elastic modulus along different loading directions. The size induced mechanical anisotropy is naturally related to structural anisotropy that is absent before loading. The anisotropic stress and modulus versus the size yield different scaling exponents in different stages of deformation, hinting at different deformation mechanisms. The size effect discovered here points to the existence of intrinsic heterogeneity defined by the anisotropy, which may play an important role in structure-property relations in amorphous solids.

  13. Real time observation of ZnO nanostructure formation via the solid-vapor and solid-solid-vapor mechanisms

    NASA Astrophysics Data System (ADS)

    Kim, B. J.; Kim, M. W.; Jang, J. S.; Stach, E. A.

    2014-05-01

    We report in situ transmission electron microscopy studies of the formation of ZnO nanostructures - nanoscale depressions, nanoholes, nanoribbons, and nanosheets - and the phase stability and kinetics of Au catalysts on ZnO. During annealing, the ZnO layer produces hexagonally shaped, vertical nanoscale depressions, which increase in size along the <0001> growth direction through preferential dissociation from the {101&cmb.macr;0} facet and which subsequently form hexagonal islands at their six-fold junctions. Real time observations of the annealing of Au deposited on ZnO show that the catalysts remain solid up to 900 °C, an observation that has implications regarding ZnO nanowire growth via the vapor-solid-solid mechanism (VSS). The Au also creates hexagonal nanoscale holes only at the location of solid Au catalysts, via the solid-solid-vapor (SSV) mechanism. Importantly, coarsening of the Au particles is negligible due to limited Au diffusion on the side facets of the nanoscale depressions, suggesting an approach to the growth of uniform hybrid nanowires with control over both diameter and location. Furthermore, we directly monitor the evolution of the transformation of a nanoribbon into a nanosheet with {101&cmb.macr;0} facets. This process takes place through a periodic, kinetic roughening transition of the surface, which is controlled by the kinetic competition between surface growth and the transfer of evaporated gases. In total, these observations give new insights into multiple growth processes occurring in this important materials system.We report in situ transmission electron microscopy studies of the formation of ZnO nanostructures - nanoscale depressions, nanoholes, nanoribbons, and nanosheets - and the phase stability and kinetics of Au catalysts on ZnO. During annealing, the ZnO layer produces hexagonally shaped, vertical nanoscale depressions, which increase in size along the <0001> growth direction through preferential dissociation from the {101

  14. Sierra/solid mechanics 4.22 user's guide.

    SciTech Connect

    Thomas, Jesse David

    2011-10-01

    Sierra/SolidMechanics (Sierra/SM) is a Lagrangian, three-dimensional code for the analysis of solids and structures. It provides capabilities for explicit dynamic and implicit quasistatic and dynamic analyses. The explicit dynamics capabilities allow for the efficient and robust solution of models subjected to large, suddenly applied loads. For implicit problems, Sierra/SM uses a multi-level iterative solver, which enables it to effectively solve problems with large deformations, nonlinear material behavior, and contact. Sierra/SM has a versatile library of continuum and structural elements, and an extensive library of material models. The code is written for parallel computing environments, and it allows for scalable solutions of very large problems for both implicit and explicit analyses. It is built on the SIERRA Framework, which allows for coupling with other SIERRA mechanics codes. This document describes the functionality and input structure for Sierra/SM.

  15. Experimental measurement of chaotic attractors in solid mechanics(a)).

    PubMed

    Moon, Francis C.

    1991-07-01

    In this paper a review is given of experimental techniques in chaotic dynamics of solid mechanical systems based on modern ideas of nonlinear dynamics. These methods include Poincare maps, double Poincare sections, symbol dynamics, and fractal dimension. The physical problems discussed include nonlinear elastic beams, forced motion of a string, flow-induced vibration of a rod, forced motions of a magnetic pendulum, and rigid body dynamics of a magnet and high-temperature superconductor. PMID:12779894

  16. Solid breeder/structure mechanical interaction and thermal stability

    SciTech Connect

    Liu, Y.Y.; Billone, M.C.; Taghavi, K.

    1985-04-01

    Solid breeder/structure mechanical interaction (BSMI) during fusion reactor blanket operation is a potential failure mode which could limit the lifetime of the blanket. The severity of BSMI will generally depend on the materials, specific blanket designs, and blanket operating conditions. Thermomechanical analyses performed for a helium-cooled blanket employing Li/sub 2/O/HT-9 plates indicate that BSMI could be a serious concern for this blanket.

  17. An integrated introduction to the mechanics of solids and fluids: Continuum mechanics as the first mechanics course

    NASA Astrophysics Data System (ADS)

    Rossmann, Jenn Stroud; Dym, Clive; Bassman, Lori

    2014-11-01

    We have developed an introduction to continuum mechanics for sophomore students without any prior knowledge of mechanics. The essence of continuum mechanics, the internal response of materials to external loading, is often obscured by the complex mathematics of its formulation. By building gradually from one- to two- and three-dimensional formulations, we are able to make the essence of the subject more accessible to undergraduates. From this gradual development of ideas, with many illustrative real-world case studies, students develop both physical intuition for how solids and fluids behave, and the mathematical techniques needed to begin to describe this behavior. At the same time they gain a unique appreciation for the connections between solid and fluid mechanics. It is particularly valuable for students interested in biological applications to appreciate the behavior of engineering materials as a spectrum with Hookean solids at one extreme, and Newtonian fluids at another, with many complex behaviors in between..This approach demonstrates the connections between solid and fluid mechanics, as well as the larger mathematical issues shared by both fields, to students who have not yet taken courses in fluid mechanics and/or strength of materials. The context and foundation provided by this educational strategy are available to students as they continue to study either solid or fluid mechanics, or specialize in the connections themselves by returning to a deeper study of the overarching field of continuum mechanics.

  18. Microscopic mechanisms of equilibrium melting of a solid

    NASA Astrophysics Data System (ADS)

    Samanta, Amit; Tuckerman, Mark E.; Yu, Tang-Qing; E, Weinan

    2014-11-01

    The melting of a solid, like other first-order phase transitions, exhibits an intrinsic time-scale disparity: The time spent by the system in metastable states is orders of magnitude longer than the transition times between the states. Using rare-event sampling techniques, we find that melting of representative solids—here, copper and aluminum—occurs via multiple, competing pathways involving the formation and migration of point defects or dislocations. Each path is characterized by multiple barrier-crossing events arising from multiple metastable states within the solid basin. At temperatures approaching superheating, melting becomes a single barrier-crossing process, and at the limit of superheating, the melting mechanism is driven by a vibrational instability. Our findings reveal the importance of nonlocal behavior, suggesting a revision of the perspective of classical nucleation theory.

  19. Mechanisms of dynamic nuclear polarization in insulating solids

    NASA Astrophysics Data System (ADS)

    Can, T. V.; Ni, Q. Z.; Griffin, R. G.

    2015-04-01

    Dynamic nuclear polarization (DNP) is a technique used to enhance signal intensities in NMR experiments by transferring the high polarization of electrons to their surrounding nuclei. The past decade has witnessed a renaissance in the development of DNP, especially at high magnetic fields, and its application in several areas including biophysics, chemistry, structural biology and materials science. Recent technical and theoretical advances have expanded our understanding of established experiments: for example, the cross effect DNP in samples spinning at the magic angle. Furthermore, new experiments suggest that our understanding of the Overhauser effect and its applicability to insulating solids needs to be re-examined. In this article, we summarize important results of the past few years and provide quantum mechanical explanations underlying these results. We also discuss future directions of DNP and current limitations, including the problem of resolution in protein spectra recorded at 80-100 K.

  20. Space Shuttle solid rocket motor slag expulsion mechanisms

    NASA Technical Reports Server (NTRS)

    Hopson, Charles B.

    1995-01-01

    A 13 psi pressure perturbation occurred at approximately 68 seconds on the right Redesigned Solid Rocket Motor (RSRM) during the STS-54 space shuttle mission. While pressure perturbations are a normal characteristic of RSRM operation, the magnitude of the STS-54 perturbation and the resulting thrust imbalance between the left and right motors was outside of flight experience. A joint Marshall Space Flight Center (MSFC) and Thiokol Corporation (RSRM manufacturer) team soon narrowed the probable cause to a temporary nozzle restriction due to slag expulsion. In support of the team, Rockwell Aerospace performed fluid finite element simulations and vehicle flight dynamic correlations to investigate possible slag expulsion mechanisms responsible for pressure perturbations. Results of the simulations and analyses provided evidence that the combination of flight induced accelerations acting on accumulated slag and nozzle vectoring were the most probable cause of RSRM slag expulsion.

  1. Mechanisms of Dynamic Nuclear Polarization in Insulating Solids

    PubMed Central

    Can, T.V.; Ni, Q.Z.; Griffin, R.G.

    2015-01-01

    Dynamic nuclear polarization (DNP) is a technique used to enhance signal intensities in NMR experiments by transferring the high polarization of electrons to their surrounding nuclei. The past decade has witnessed a renaissance in the development of DNP, especially at high magnetic fields, and its application in several areas including biophysics, chemistry, structural biology and materials science. Recent technical and theoretical advances have expanded our understanding of established experiments: for example, the cross effect DNP in samples spinning at the magic angle. Furthermore, new experiments suggest that our understanding of the Overhauser effect and its applicability to insulating solids needs to be re-examined. In this article, we summarize important results of the past few years and provide quantum mechanical explanations underlying these results. We also discuss future directions of DNP and current limitations, including the problem of resolution in protein spectra recorded at 80–100 K. PMID:25797002

  2. Quantum mechanical theory of dynamic nuclear polarization in solid dielectrics

    PubMed Central

    Hu, Kan-Nian; Debelouchina, Galia T.; Smith, Albert A.; Griffin, Robert G.

    2011-01-01

    Microwave driven dynamic nuclear polarization (DNP) is a process in which the large polarization present in an electron spin reservoir is transferred to nuclei, thereby enhancing NMR signal intensities. In solid dielectrics there are three mechanisms that mediate this transfer—the solid effect (SE), the cross effect (CE), and thermal mixing (TM). Historically these mechanisms have been discussed theoretically using thermodynamic parameters and average spin interactions. However, the SE and the CE can also be modeled quantum mechanically with a system consisting of a small number of spins and the results provide a foundation for the calculations involving TM. In the case of the SE, a single electron–nuclear spin pair is sufficient to explain the polarization mechanism, while the CE requires participation of two electrons and a nuclear spin, and can be used to understand the improved DNP enhancements observed using biradical polarizing agents. Calculations establish the relations among the electron paramagnetic resonance (EPR) and nuclear magnetic resonance (NMR) frequencies and the microwave irradiation frequency that must be satisfied for polarization transfer via the SE or the CE. In particular, if δ, Δ < ω0I, where δ and Δ are the homogeneous linewidth and inhomogeneous breadth of the EPR spectrum, respectively, we verify that the SE occurs when ωM = ω0S ± ω0I, where ωM, ω0S and ω0I are, respectively, the microwave, and the EPR and NMR frequencies. Alternatively, when Δ > ω0I > δ, the CE dominates the polarization transfer. This two-electron process is optimized when ω0S1−ω0S2=ω0I and ωM∼ω0S1 orω0S2, where ω0S1 and ω0S2 are the EPR Larmor frequencies of the two electrons. Using these matching conditions, we calculate the evolution of the density operator from electron Zeeman order to nuclear Zeeman order for both the SE and the CE. The results provide insights into the influence of the microwave irradiation field, the

  3. Computational thermal, chemical, fluid, and solid mechanics for geosystems management.

    SciTech Connect

    Davison, Scott; Alger, Nicholas; Turner, Daniel Zack; Subia, Samuel Ramirez; Carnes, Brian; Martinez, Mario J.; Notz, Patrick K.; Klise, Katherine A.; Stone, Charles Michael; Field, Richard V., Jr.; Newell, Pania; Jove-Colon, Carlos F.; Red-Horse, John Robert; Bishop, Joseph E.; Dewers, Thomas A.; Hopkins, Polly L.; Mesh, Mikhail; Bean, James E.; Moffat, Harry K.; Yoon, Hongkyu

    2011-09-01

    This document summarizes research performed under the SNL LDRD entitled - Computational Mechanics for Geosystems Management to Support the Energy and Natural Resources Mission. The main accomplishment was development of a foundational SNL capability for computational thermal, chemical, fluid, and solid mechanics analysis of geosystems. The code was developed within the SNL Sierra software system. This report summarizes the capabilities of the simulation code and the supporting research and development conducted under this LDRD. The main goal of this project was the development of a foundational capability for coupled thermal, hydrological, mechanical, chemical (THMC) simulation of heterogeneous geosystems utilizing massively parallel processing. To solve these complex issues, this project integrated research in numerical mathematics and algorithms for chemically reactive multiphase systems with computer science research in adaptive coupled solution control and framework architecture. This report summarizes and demonstrates the capabilities that were developed together with the supporting research underlying the models. Key accomplishments are: (1) General capability for modeling nonisothermal, multiphase, multicomponent flow in heterogeneous porous geologic materials; (2) General capability to model multiphase reactive transport of species in heterogeneous porous media; (3) Constitutive models for describing real, general geomaterials under multiphase conditions utilizing laboratory data; (4) General capability to couple nonisothermal reactive flow with geomechanics (THMC); (5) Phase behavior thermodynamics for the CO2-H2O-NaCl system. General implementation enables modeling of other fluid mixtures. Adaptive look-up tables enable thermodynamic capability to other simulators; (6) Capability for statistical modeling of heterogeneity in geologic materials; and (7) Simulator utilizes unstructured grids on parallel processing computers.

  4. Solving Nonlinear Solid Mechanics Problems with the Jacobian-Free Newton Krylov Method

    SciTech Connect

    J. D. Hales; S. R. Novascone; R. L. Williamson; D. R. Gaston; M. R. Tonks

    2012-06-01

    The solution of the equations governing solid mechanics is often obtained via Newton's method. This approach can be problematic if the determination, storage, or solution cost associated with the Jacobian is high. These challenges are magnified for multiphysics applications with many coupled variables. Jacobian-free Newton-Krylov (JFNK) methods avoid many of the difficulties associated with the Jacobian by using a finite difference approximation. BISON is a parallel, object-oriented, nonlinear solid mechanics and multiphysics application that leverages JFNK methods. We overview JFNK, outline the capabilities of BISON, and demonstrate the effectiveness of JFNK for solid mechanics and solid mechanics coupled to other PDEs using a series of demonstration problems.

  5. Local-equilibrium formalism applied to mechanics of solids

    SciTech Connect

    Kestin, J.

    1992-08-01

    The lecture starts with an expression of good wishes to George Herrmann on the occasion of his seventieth birthday and continues with a lament that the majority of research workers in the field of solid mechanics have failed to appreciate the power and relevance of ``conventional`` thermodynamics which is based on the acceptance of the hypothesis of local equilibrium (principle of local state). The lecture then proceeds to motivate the essential concepts of conventional thermodynamics and emphasizes the differences between the description of nonequilibrium states in physical space and equilibrium states in the Gibbsian phase space. It is asserted that the subject acquires its simplest form by the recognition of the relevance of Bridgman`s internal variables. With their aid it is possible to define the accompanying equilibrium state and the accompanying reversible process. An elimination of internal energy between the field equation of energy (First Law) and the Gibbs equation in rate form results in an explicit expression for the local rate of entropy production, {theta}. It is asserted that the preceding elements supplemented with appropriate rate equations result in a closed system of partial differential equations whose solution, subject to appropriate initial and boundary conditions, constitutes the process (``history``) under consideration. 11 refs.

  6. Local-equilibrium formalism applied to mechanics of solids

    SciTech Connect

    Kestin, J.

    1992-01-01

    The lecture starts with an expression of good wishes to George Herrmann on the occasion of his seventieth birthday and continues with a lament that the majority of research workers in the field of solid mechanics have failed to appreciate the power and relevance of conventional'' thermodynamics which is based on the acceptance of the hypothesis of local equilibrium (principle of local state). The lecture then proceeds to motivate the essential concepts of conventional thermodynamics and emphasizes the differences between the description of nonequilibrium states in physical space and equilibrium states in the Gibbsian phase space. It is asserted that the subject acquires its simplest form by the recognition of the relevance of Bridgman's internal variables. With their aid it is possible to define the accompanying equilibrium state and the accompanying reversible process. An elimination of internal energy between the field equation of energy (First Law) and the Gibbs equation in rate form results in an explicit expression for the local rate of entropy production, {theta}. It is asserted that the preceding elements supplemented with appropriate rate equations result in a closed system of partial differential equations whose solution, subject to appropriate initial and boundary conditions, constitutes the process ( history'') under consideration. 11 refs.

  7. Microalloying and the mechanical properties of amorphous solids

    NASA Astrophysics Data System (ADS)

    Hentschel, H. George E.; Moshe, Michael; Procaccia, Itamar; Samwer, Konrad

    2016-05-01

    The mechanical properties of amorphous solids like metallic glasses can be dramatically changed by adding small concentrations (as low as 0.1%) of foreign elements. The glass-forming-ability, the ductility, the yield stress and the elastic moduli can all be greatly effected. This paper presents theoretical considerations with the aim of explaining the magnitude of these changes in light of the small concentrations involved. The theory is built around the experimental evidence that the microalloying elements organise around them a neighbourhood that differs from both the crystalline and the glassy phases of the material in the absence of the additional elements. These regions act as isotropic defects that in unstressed systems modify the shear moduli. When strained, these defects interact with the incipient plastic responses which are quadrupolar in nature. It will be shown that this interaction interferes with the creation of system-spanning shear bands and increases the yield strain. We offer experimentally testable estimates of the lengths of nano-shear bands in the presence of the additional elements.

  8. Mechanical properties of Municipal Solid Waste by SDMT

    SciTech Connect

    Castelli, Francesco; Maugeri, Michele

    2014-02-15

    Highlights: • The adoption of the SDMT for the measurements of MSW properties is proposed. • A comparison between SDMT results and laboratory tests was carried out. • A good reliability has been found in deriving waste properties by SDMT. • Results seems to be promising for the friction angle and Young’s modulus evaluation. - Abstract: In the paper the results of a geotechnical investigation carried on Municipal Solid Waste (MSW) materials retrieved from the “Cozzo Vuturo” landfill in the Enna area (Sicily, Italy) are reported and analyzed. Mechanical properties were determined both by in situ and laboratory large-scale one dimensional compression tests. While among in situ tests, Dilatomer Marchetti Tests (DMT) is used widely in measuring soil properties, the adoption of the DMT for the measurements of MSW properties has not often been documented in literature. To validate its applicability for the estimation of MSW properties, a comparison between the seismic dilatometer (SDMT) results and the waste properties evaluated by laboratory tests was carried out. Parameters for “fresh” and “degraded waste” have been evaluated. These preliminary results seems to be promising as concerns the assessment of the friction angle of waste and the evaluation of the S-wave in terms of shear wave velocity. Further studies are certainly required to obtain more representative values of the elastic parameters according to the SDMT measurements.

  9. Significance of Strain in Formulation in Theory of Solid Mechanics

    NASA Technical Reports Server (NTRS)

    Patnaik, Surya N.; Coroneos, Rula M.; Hopkins, Dale A.

    2003-01-01

    The basic theory of solid mechanics was deemed complete circa 1860 when St. Venant provided the strain formulation or the field compatibility condition. The strain formulation was incomplete. The missing portion has been formulated and identified as the boundary compatibility condition (BCC). The BCC, derived through a variational formulation, has been verified through integral theorem and solution of problems. The BCC, unlike the field counterpart, do not trivialize when expressed in displacements. Navier s method and the stiffness formulation have to account for the extra conditions especially at the inter-element boundaries in a finite element model. Completion of the strain formulation has led to the revival of the direct force calculation methods: the Integrated Force Method (IFM) and its dual (IFMD) for finite element analysis, and the completed Beltrami-Michell formulation (CBMF) in elasticity. The benefits from the new methods in elasticity, in finite element analysis, and in design optimization are discussed. Existing solutions and computer codes may have to be adjusted for the compliance of the new conditions. Complacency because the discipline is over a century old and computer codes have been developed for half a century can lead to stagnation of the discipline.

  10. Two-step nucleation mechanism in solid-solid phase transitions

    NASA Astrophysics Data System (ADS)

    Peng, Yi; Wang, Feng; Wang, Ziren; Alsayed, Ahmed M.; Zhang, Zexin; Yodh, Arjun G.; Han, Yilong

    2015-01-01

    The microscopic kinetics of ubiquitous solid-solid phase transitions remain poorly understood. Here, by using single-particle-resolution video microscopy of colloidal films of diameter-tunable microspheres, we show that transitions between square and triangular lattices occur via a two-step diffusive nucleation pathway involving liquid nuclei. The nucleation pathway is favoured over the direct one-step nucleation because the energy of the solid/liquid interface is lower than that between solid phases. We also observed that nucleation precursors are particle-swapping loops rather than newly generated structural defects, and that coherent and incoherent facets of the evolving nuclei exhibit different energies and growth rates that can markedly alter the nucleation kinetics. Our findings suggest that an intermediate liquid should exist in the nucleation processes of solid-solid transitions of most metals and alloys, and provide guidance for better control of the kinetics of the transition and for future refinements of solid-solid transition theory.

  11. Micro-mechanical lengthscales in soft elastic solids

    NASA Astrophysics Data System (ADS)

    Lerner, Edan; Degiuli, Eric; Düring, Gustavo; Wyart, Matthieu

    2014-03-01

    We provide numerical evidence and supporting scaling arguments that the response of soft elastic solids to a local force dipole is characterized by a lengthscale lc that diverges as unjamming is approached as lc ~(z - 2 d) - 1 / 2 , where z >= 2 d is the mean coordination, and d is the spatial dimension, at odds with previous claims based on numerics. We also show how the magnitude of the lengthscale lc is amplified by the presence of internal stresses in the disordered solid. Our data raise the possibility of a divergence of lc with proximity to a critical internal stress at which a buckling instability takes place.

  12. Solid state amorphization kinetic of alpha lactose upon mechanical milling.

    PubMed

    Caron, Vincent; Willart, Jean-François; Lefort, Ronan; Derollez, Patrick; Danède, Florence; Descamps, Marc

    2011-11-29

    It has been previously reported that α-lactose could be totally amorphized by ball milling. In this paper we report a detailed investigation of the structural and microstructural changes by which this solid state amorphization takes place. The investigations have been performed by Powder X-ray Diffraction, Solid State Nuclear Magnetic Resonance ((13)C CP-MAS) and Differential Scanning Calorimetry. The results reveal the structural complexity of the material in the course of its amorphization so that it cannot be considered as a simple mixture made of a decreasing crystalline fraction and an increasing amorphous fraction. Heating this complexity can give rise to a fully nano-crystalline material. The results also show that chemical degradations upon heating are strongly connected to the melting process. PMID:21983262

  13. Curved mesh generation and mesh refinement using Lagrangian solid mechanics

    SciTech Connect

    Persson, P.-O.; Peraire, J.

    2008-12-31

    We propose a method for generating well-shaped curved unstructured meshes using a nonlinear elasticity analogy. The geometry of the domain to be meshed is represented as an elastic solid. The undeformed geometry is the initial mesh of linear triangular or tetrahedral elements. The external loading results from prescribing a boundary displacement to be that of the curved geometry, and the final configuration is determined by solving for the equilibrium configuration. The deformations are represented using piecewise polynomials within each element of the original mesh. When the mesh is sufficiently fine to resolve the solid deformation, this method guarantees non-intersecting elements even for highly distorted or anisotropic initial meshes. We describe the method and the solution procedures, and we show a number of examples of two and three dimensional simplex meshes with curved boundaries. We also demonstrate how to use the technique for local refinement of non-curved meshes in the presence of curved boundaries.

  14. Mechanism to synthesize a `moving optical mark' at solid-ambient interface for the estimation of thermal diffusivity of solid

    NASA Astrophysics Data System (ADS)

    Balachandar, Settu; Shivaprakash, N. C.; Kameswara Rao, L.

    2016-01-01

    A novel mechanism is proposed, involving a novel interaction between solid-sample supporting unsteady heat flow with its ambient-humidity; invokes phase transformation of water-vapour molecule and synthesize a `moving optical-mark' at sample-ambient-interface. Under tailored condition, optical-mark exhibits a characteristic macro-scale translatory motion governed by thermal diffusivity of solid. For various step-temperature inputs via cooling, position-dependent velocities of moving optical-mark are measured at a fixed distance. A new approach is proposed. `Product of velocity of optical-mark and distance' versus `non-dimensional velocity' is plotted. The slope reveals thermal diffusivity of solid at ambient-temperature; preliminary results obtained for Quartz-glass is closely matching with literature.

  15. ELECTRON TRANSFER MECHANISM AT THE SOLID-LIQUID INTERFACE OF PHYLLOSILICATES

    EPA Science Inventory

    Interfacial electron transfer processes on clay minerals have significant impact in natural environments and geochemical systems. Nitrobenzene was used as molecular probes to study the electron transfer mechanism at the solid-water interfaces of Fe-containing phyllosicates. For...

  16. Nanoscopic mechanisms of singlet fission in amorphous molecular solid

    NASA Astrophysics Data System (ADS)

    Mou, Weiwei; Hattori, Shinnosuke; Rajak, Pankaj; Shimojo, Fuyuki; Nakano, Aiichiro

    2013-04-01

    Fission of a spin-singlet exciton into two triplet excitons, if realized in disordered organic solid, could revolutionize low-cost fabrication of efficient solar cells. Here, a divide-conquer-recombine approach involving nonadiabatic quantum molecular dynamics and kinetic Monte Carlo simulations identifies the key molecular geometry and exciton-flow-network topology for singlet-fission "hot spots" in amorphous diphenyl tetracene, where fission occurs preferentially. The simulation reveals the molecular origin of experimentally observed two time scales in exciton population dynamics and may pave a way to nanostructural design of efficient solar cells from first principles.

  17. A review of interaction mechanisms in fluid-solid flows

    SciTech Connect

    Johnson, G.; Rajagopal, K.R. . Dept. of Mechanical Engineering); Massoudi, M. )

    1990-09-01

    Multiphase flows have become the subject of considerable attention because of their importance in many industrial applications, such as fluidized beds, pneumatic transport of solids, coal combustion, etc. Fundamental research into the nature of pneumatic transport has made significant progress in identifying key parameters controlling the characteristics of these processes. The emphasis of this study is on a mixture composed of spherical particles of uniform size and a linearly viscous fluid. Section 1 introduces our approach and the importance of this study. In Section 2, the dynamics of a single particle as studied in classical hydrodynamics and fluid dynamics is presented. This has been a subject of study for more than 200 years. In Section 3, we review the literature for the constitutive relations as given in multiphase studies, i.e., generalization of single particle and as given in literature concerning the continuum theories of mixtures or multicomponent systems. In Section 4, a comparison between these representations and the earlier approach, i.e., forces acting on a single particle will be made. The importance of flow regimes, particle concentration, particle size and shape, rotation of the particle, effect of solid walls, etc. are discussed. 141 refs.

  18. Spectral mapping of heat transfer mechanisms at liquid-solid interfaces.

    PubMed

    Sääskilahti, K; Oksanen, J; Tulkki, J; Volz, S

    2016-05-01

    Thermal transport through liquid-solid interfaces plays an important role in many chemical and biological processes, and better understanding of liquid-solid energy transfer is expected to enable improving the efficiency of thermally driven applications. We determine the spectral distribution of thermal current at liquid-solid interfaces from nonequilibrium molecular dynamics, delivering a detailed picture of the contributions of different vibrational modes to liquid-solid energy transfer. Our results show that surface modes located at the Brillouin zone edge and polarized along the liquid-solid surface normal play a crucial role in liquid-solid energy transfer. Strong liquid-solid adhesion allows also for the coupling of in-plane polarized modes in the solid with the liquid, enhancing the heat-transfer rate and enabling efficient energy transfer up to the cutoff frequency of the solid. Our results provide fundamental understanding of the energy-transfer mechanisms in liquid-solid systems and enable detailed investigations of energy transfer between, e.g., water and organic molecules. PMID:27300863

  19. Spectral mapping of heat transfer mechanisms at liquid-solid interfaces

    NASA Astrophysics Data System (ADS)

    Sääskilahti, K.; Oksanen, J.; Tulkki, J.; Volz, S.

    2016-05-01

    Thermal transport through liquid-solid interfaces plays an important role in many chemical and biological processes, and better understanding of liquid-solid energy transfer is expected to enable improving the efficiency of thermally driven applications. We determine the spectral distribution of thermal current at liquid-solid interfaces from nonequilibrium molecular dynamics, delivering a detailed picture of the contributions of different vibrational modes to liquid-solid energy transfer. Our results show that surface modes located at the Brillouin zone edge and polarized along the liquid-solid surface normal play a crucial role in liquid-solid energy transfer. Strong liquid-solid adhesion allows also for the coupling of in-plane polarized modes in the solid with the liquid, enhancing the heat-transfer rate and enabling efficient energy transfer up to the cutoff frequency of the solid. Our results provide fundamental understanding of the energy-transfer mechanisms in liquid-solid systems and enable detailed investigations of energy transfer between, e.g., water and organic molecules.

  20. Quantum-Mechanical Combinatorial Design of Solids with Target Properties

    NASA Astrophysics Data System (ADS)

    Zunger, Alex

    2009-10-01

    One of the most striking aspects of solid-state physics is the diversity of structural forms in which crystals appear in Nature. The already rich repertoire of such (equilibrium) forms has recently been significantly enriched by the advent of artificial growth techniques (MBE, STM- atom positioning, etc) that can create desired structural forms, such as superlattices and geometric atomic clusters even in defiance of the rules of equilibrium thermodynamics. As is well known, different atomic configurations generally lead to different physical properties even at fixed chemical composition. While the most widely-known illustration of such ``form controls function'' rule is the dramatically different color, conductivity and hardness of the allotropical forms of pure carbon, the physics of semiconductor superstructures and nanostructures is full of striking examples of how optical, magnetic and transport properties depend sensitively on atomic configuration (e.g, compare the properties of random to ordered alloys). Yet, the history of material research generally proceeded via accidental discoveries of materials configuration with interesting physical property (semiconductivity, ferromagnetism; superconductivity etc). Given the ability of growing many different atomic configurations, and given the often sensitive dependence of physical properties on atomic configuration, makes one wonder: can one first articulate the desired target physical property, then search (within a class) for the configuration that has this property? This talk describes the recent steps made by solid-state theory and computational physics to address this ``Inverse Design'' problem. I will show how Genetic Algorithms, in combination with efficient (``Order N'') solutions to the Pseudopotential Schr"odinger equation allow us to investigate astronomical spaces of atomic configurations in search of the structure with a target physical problem. Only a small fraction of all ( ˜10^14 in our case

  1. Determining mechanical behavior of solid materials using miniature specimens

    DOEpatents

    Manahan, M.P.; Argon, A.S.; Harling, O.K.

    1986-02-04

    A Miniaturized Bend Test (MBT) capable of extracting and determining mechanical behavior information from specimens only so large as to have at least a volume or smallest dimension sufficient to satisfy continuum behavior in all directions is disclosed. The mechanical behavior of the material is determined from the measurements taken during the bending of the specimen and is processed according to the principles of linear or nonlinear material mechanics or both. In a preferred embodiment the determination is carried out by a code which is constructed according to the finite element method, and the specimen used for the determinations is a miniature disk simply supported for central loading at the axis on the center of the disk. 51 figs.

  2. Determining mechanical behavior of solid materials using miniature specimens

    DOEpatents

    Manahan, Michael P.; Argon, Ali S.; Harling, Otto K.

    1986-01-01

    A Miniaturized Bend Test (MBT) capable of extracting and determining mechanical behavior information from specimens only so large as to have at least a volume or smallest dimension sufficient to satisfy continuum behavior in all directions. The mechanical behavior of the material is determined from the measurements taken during the bending of the specimen and is processed according to the principles of linear or nonlinear material mechanics or both. In a preferred embodiment the determination is carried out by a code which is constructed according to the finite element method, and the specimen used for the determinations is a miniature disk simply supported for central loading at the axis on the center of the disk.

  3. Finite element procedures for coupled linear analysis of heat transfer, fluid and solid mechanics

    NASA Technical Reports Server (NTRS)

    Sutjahjo, Edhi; Chamis, Christos C.

    1993-01-01

    Coupled finite element formulations for fluid mechanics, heat transfer, and solid mechanics are derived from the conservation laws for energy, mass, and momentum. To model the physics of interactions among the participating disciplines, the linearized equations are coupled by combining domain and boundary coupling procedures. Iterative numerical solution strategy is presented to solve the equations, with the partitioning of temporal discretization implemented.

  4. Thermal fluctuations, mechanical response, and hyperuniformity in jammed solids

    NASA Astrophysics Data System (ADS)

    Ikeda, Atsushi; Berthier, Ludovic

    2015-07-01

    Jamming is a geometric phase transition occurring in dense particle systems in the absence of temperature. We use computer simulations to analyze the effect of thermal fluctuations on several signatures of the transition. We show that scaling laws for bulk and shear moduli only become relevant when thermal fluctuations are extremely small, and propose their relative ratio as a quantitative signature of jamming criticality. Despite the nonequilibrium nature of the transition, we find that thermally induced fluctuations and mechanical responses obey equilibrium fluctuation-dissipation relations near jamming, provided the appropriate fluctuating component of the particle displacements is analyzed. This shows that mechanical moduli can be directly measured from particle positions in mechanically unperturbed packings, and suggests that the definition of a "nonequilibrium index" is unnecessary for amorphous materials. We find that fluctuations of particle displacements are spatially correlated, and define a transverse and a longitudinal correlation length scale which both diverge as the jamming transition is approached. We analyze the frozen component of density fluctuations and find that it displays signatures of nearly hyperuniform behavior at large length scales. This demonstrates that hyperuniformity in jammed packings is unrelated to a vanishing compressibility and explains why it appears remarkably robust against temperature and density variations. Differently from jamming criticality, obstacles preventing the observation of hyperuniformity in colloidal systems do not originate from thermal fluctuations.

  5. Growing TiO2 nanowires by solid-liquid-solid mechanism including two factors (Ti and O)

    NASA Astrophysics Data System (ADS)

    Pishekloo, S. Piri; Dariani, R. S.

    2016-04-01

    Identifying the growth factors of nanowires helps in controlling their structure and morphology and determining their optimal growth conditions. This study investigates the effect of titanium substrate in growing TiO2 nanowires (NWs) with evaporation method. It reveals that the titanium in substrate is indeed the main source of growth. Using the substrate as the only source of growth with regulated amount of accessible oxygen in the furnace, NWs with lengths ranging from 1 to 70 µm were obtained. The results of the experiments show that the nanowires' growth is mainly controlled by diffusion of titanium atoms from the substrate through TiO2 grain boundaries and surface diffusion toward NWs' tips rather than adsorption from vapor phase. The solid-liquid-solid mechanism including two factors (Ti and O) is proposed and discussed for growth of TiO2 NWs.

  6. Molecular mechanisms for surfactant-aided oil removal from a solid surface

    NASA Astrophysics Data System (ADS)

    Wang, Shumeng; Li, Zhi; Liu, Bei; Zhang, Xianren; Yang, Qingyuan

    2015-12-01

    In this work, the detachment mechanism of oil molecules from the hydrophobic solid surface in the aqueous surfactant solution is studied with lattice Monte Carlo simulations. Three different mechanisms for oil removal, including oil carrying microemulsion model, oil film stripping model, and surfactant-aided diffusion model are identified. The molecular mechanisms that agree with experimental observations are found to be dependent sensitively on surfactant structure.

  7. The ideal strength and mechanical hardness of solids

    NASA Astrophysics Data System (ADS)

    Krenn, Christopher Robert

    2000-10-01

    Relationships between intrinsic mechanical hardness and atomic-scale properties are reviewed. Hardness scales closely and linearly with shear modulus for a given class of material (covalent, ionic or metallic). A two-parameter fit and a Peierls-stress model produce a more universal scaling relationship, but no model can explain differences in hardness between the transition metal carbides and nitrides. Calculations of "ideal strength" (defined by the limit of elastic stability of a perfect crystal) are proposed. The ideal shear strengths of fcc aluminum and copper are calculated using ab initio techniques and allowing for structural relaxation of all five strain components other than the imposed strain. The strengths of Al and Cu are similar (8-9% of the shear modulus), but the geometry of the relaxations in Al and Cu is very different. The relaxations are consistent with experimentally measured third-order elastic constants. The general thermodynamic conditions of elastic stability that set the upper limits of mechanical strength are derived. The conditions of stability are shown for cubic (hydrostatic), tetragonal (tensile) and monoclinic (shear) distortions of a cubic crystal. The implications of this stability analysis to first-principles calculations of ideal strength are discussed, and a method to detect instabilities orthogonal to the direction of the applied stress is identified. The relaxed ideal shear and tensile strengths of bcc tungsten are also calculated using ab initio techniques and are favorably compared to recent nano-indentation measurements. The {100} tensile strength (29.5 GPa) is governed by the Bain instability. The shear strengths in the weak directions on {110}, {112}, and {123} planes are very nearly equal (≈18 GPa) and occur at approximately the same strain (17-18%). This isotropy is a function of the linear elastic isotropy for shear in directions containing <111> in bcc and of the atomic configurations of energetic saddle points

  8. The ideal strength and mechanical hardness of solids

    SciTech Connect

    Krenn, Christopher

    2000-04-01

    Relationships between intrinsic mechanical hardness and atomic-scale properties are reviewed, Hardness scales closely and linearly with shear modulus for a given class of material (covalent, ionic or metallic). A two-parameter fit and a Peierls-stress model produce a more universal scaling relationship, but no model can explain differences in hardness between the transition metal carbides and nitrides. Calculations of ''ideal strength'' (defined by the limit of elastic stability of a perfect crystal) are proposed. The ideal shear strengths of fcc aluminum and copper are calculated using ab initio techniques and allowing for structural relaxation of all five strain components other than the imposed strain. The strengths of Al and Cu are similar (8-9% of the shear modulus), but the geometry of the relaxations in Al and Cu is very different. The relaxations are consistent with experimentally measured third-order elastic constants. The general thermodynamic conditions of elastic stability that set the upper limits of mechanical strength are derived. The conditions of stability are shown for cubic (hydrostatic), tetragonal (tensile) and monoclinic (shear) distortions of a cubic crystal. The implications of this stability analysis to first-principles calculations of ideal strength are discussed, and a method to detect instabilities orthogonal to the direction of the applied stress is identified. The relaxed ideal shear and tensile strengths of bcc tungsten are also calculated using ab initio techniques and are favorably compared to recent nano-indentation measurements. The {l_brace}100{r_brace} tensile strength (29.5 GPa) is governed by the Bain instability. The shear strengths in the weak directions on {l_brace}110{r_brace}, {l_brace}112{r_brace}, and {l_brace}123{r_brace} planes are very nearly equal ({approx} 18 GPa) and occur at approximately the same strain (17-18%). This isotropy is a function of the linear elastic isotropy for shear in directions containing {l

  9. Parallel solid mechanics codes at Sandia National Laboratories

    SciTech Connect

    McGlaun, M.

    1994-08-01

    Computational physicists at Sandia National Laboratories have moved their production codes to distributed memory parallel computers. The codes include the multi-material CTH Eulerian code, structural mechanics code. This presentation discusses our experiences moving the codes to parallel computers and experiences running the codes. Moving large production codes onto parallel computers require developing parallel algorithms, parallel data bases and parallel support tools. We rewrote the Eulerian CTH code for parallel computers. We were able to move both ALEGRA and PRONTO to parallel computers with only a modest number of modifications. We restructured the restart and graphics data bases to make them parallel and minimize the I/O to the parallel computer. We developed mesh decomposition tools to divide a rectangular or arbitrary connectivity mesh into sub-meshes. The sub-meshes map to processors and minimize the communication between processors. We developed new visualization tools to process the very large, parallel data bases. This presentation also discusses our experiences running these codes on Sandia`s 1840 compute node Intel Paragon, 1024 processor nCUBE and networked workstations. The parallel version of CTH uses the Paragon and nCUBE for production calculations. The ALEGRA and PRONTO codes are moving off networked workstations onto the Paragon and nCUBE massively parallel computers.

  10. Solid-on-solid single-block dynamics under mechanical vibration.

    PubMed

    Giacco, F; Lippiello, E; Pica Ciamarra, M

    2012-07-01

    The suppression of friction between sliding objects, modulated or enhanced by mechanical vibrations, is well established. However, the precise conditions of occurrence of these phenomena are not well understood. Here we address these questions focusing on a simple spring-block model, which is relevant to investigate friction both at the atomistic as well as the macroscopic scale. This allows us to investigate the influence on friction of the properties of the external drive, of the geometry of the surfaces over which the block moves, and of the confining force. Via numerical simulations and a theoretical study of the equations of motion, we identify the conditions under which friction is suppressed and/or recovered, and we evidence the critical role played by surface modulations and by the properties of the confining force. PMID:23005494

  11. Interfacial interactions between hydrocarbon liquids and solid surfaces used in mechanical oil spill recovery.

    PubMed

    Broje, Victoria; Keller, Arturo A

    2007-01-15

    The goal of this research was to study wetting and adhesion processes between various petroleum products and solid surfaces. When a liquid interacts with a solid surface, wetting, spreading and adhesion processes determine its behavior. These processes are of great importance for understanding oil spill response as well as oil spill behavior on land and in near shore environments, and oil extraction from the reservoir rock. The current study aimed at analyzing oil affinity and adhesion to surfaces used in the mechanical recovery of oil spills. A number of crude oils and petroleum products were tested with the surface materials that are used or may potentially be used to recover oil spills. Through the study of contact angles and recovered mass, it was found that the behavior of the oils at the solid surface is largely determined by the roughness of the solid. For smooth solids, contact angle hysteresis is a good indicator of the ability of the solid to retain oil. For rougher elastomers, the advancing contact angle can be used to predict wetting and adhesion processes between oil and solid. This study showed that oleophilic elastomers (e.g., Neoprene and Hypalon) have higher oil recovery potential than smooth polymers. PMID:17064718

  12. Positron annihilation studies in binary solid solutions and mechanical mixtures of lanthanide dipivaloylmethanate complexes

    NASA Astrophysics Data System (ADS)

    Fulgêncio, F.; Oliveira, F. C.; Windmöller, D.; Araujo, M. H.; Marques-Netto, A.; Machado, J. C.; Magalhães, W. F.

    2015-11-01

    Measurements using positron annihilation lifetime (PALS) and Doppler broadening annihilation radiation lineshape (DBARLS) spectroscopies were performed in several lanthanide dipivaloylmethanate complexes, Ln(dpm)3 where Ln = Sm3+, Gd3+, Tb3+, Ho3+, Er3+, Yb3+ and dpm = 2,2,6,6-tetramethyl-3,5-pentanedionate, and also on their binary solid solutions and mechanical mixtures, biphasic systems, of the general formula Ln1-xEux(dpm)3. Expressive positronium formation was observed in all Ln(dpm)3 complexes, except in Eu(dpm)3 complex. The results indicate formation of solid solutions in the Sm3+, Gd3+and Tb3+ systems, where total inhibition of positronium formation was observed. A Stern-Volmer type equation, I30/I3 = 1 + kx, was used to fit the data, enabling the calculation of the inhibition constants, k. A mechanical mixture behavior, with linear variation of I3 between the I3 values of the pure complexes, was observed in systems containing Ho3+, Er3+ and Yb3+ complexes, where no effective solid solution formation occurred due to differences between the crystalline structures of these complexes and Eu(dpm)3. No positronium quenching reactions were observed in the solid solutions. DBARLS results confirmed those of PALS, evidencing that the positron annihilation spectroscopies are useful techniques to characterize the formation of solid solutions. PALS measurements at 80 K were performed in the Sm1-xEux(dpm)3 and Gd1-xEux(dpm)3 solid solutions. The results indicate that, despite a contraction in the crystalline structures, the solid solution structure remains intact at low temperatures. The temperature dependence of the inhibition constant do not seem to be understood from the positronium formation spur model and might be related to intra and intermolecular energy and charge transfer processes in the solid solutions, which is currently being studied.

  13. Determination of the mechanical properties of solid and cellular polymeric dosage forms by diametral compression.

    PubMed

    Blaesi, Aron H; Saka, Nannaji

    2016-07-25

    At present, the immediate-release solid dosage forms, such as the oral tablets and capsules, are granular solids. They release drug rapidly and have adequate mechanical properties, but their manufacture is fraught with difficulties inherent in processing particulate matter. Such difficulties, however, could be overcome by liquid-based processing. Therefore, we have recently introduced polymeric cellular (i.e., highly porous) dosage forms prepared from a melt process. Experiments have shown that upon immersion in a dissolution medium, the cellular dosage forms with polyethylene glycol (PEG) as excipient and with predominantly open-cell topology disintegrate by exfoliation, thus enabling rapid drug release. If the volume fraction of voids of the open-cell structures is too large, however, their mechanical strength is adversely affected. At present, the common method for determining the tensile strength of brittle, solid dosage forms (such as select granular forms) is the diametral compression test. In this study, the theory of diametral compression is first refined to demonstrate that the relevant mechanical properties of ductile and cellular solids (i.e., the elastic modulus and the yield strength) can also be extracted from this test. Diametral compression experiments are then conducted on PEG-based solid and cellular dosage forms. It is found that the elastic modulus and yield strength of the open-cell structures are about an order of magnitude smaller than those of the non-porous solids, but still are substantially greater than the stiffness and strength requirements for handling the dosage forms manually. This work thus demonstrates that melt-processed polymeric cellular dosage forms that release drug rapidly can be designed and manufactured to have adequate mechanical properties. PMID:27178343

  14. Investigating the Retention Mechanisms of Liquid Chromatography Using Solid-Phase Extraction Cartridges

    ERIC Educational Resources Information Center

    O'Donnell, Mary E.; Musial, Beata A.; Bretz, Stacey Lowery; Danielson, Neil D.; Ca, Diep

    2009-01-01

    Liquid chromatography (LC) experiments for the undergraduate analytical laboratory course often illustrate the application of reversed-phase LC to solve a separation problem, but rarely compare LC retention mechanisms. In addition, a high-performance liquid chromatography instrument may be beyond what some small colleges can purchase. Solid-phase…

  15. Two-beam high-order harmonics from solids: Coupling mechanisms

    SciTech Connect

    Tarasevitch, A.; Wieczorek, J.; Kohn, R.; Bovensiepen, U.; Linde, D. von der

    2010-11-15

    The polarization of the two beam (driver-probe) high-order harmonic generation from solids is measured. The experiments, together with computer simulations, allow us to distinguish two different coupling mechanisms of the driver and the probe, resulting in different harmonic efficiencies and spectral slopes. We find that in the nonrelativistic regime the coupling is mostly due to the nonlinear plasma density modulation.

  16. A Process and Environment Aware Sierra/SolidMechanics Cohesive Zone Modeling Capability for Polymer/Solid Interfaces

    SciTech Connect

    Reedy, E. D.; Chambers, Robert S.; Hughes, Lindsey Gloe; Kropka, Jamie Michael; Stavig, Mark E.; Stevens, Mark J.

    2015-09-01

    The performance and reliability of many mechanical and electrical components depend on the integrity of po lymer - to - solid interfaces . Such interfaces are found in adhesively bonded joints, encapsulated or underfilled electronic modules, protective coatings, and laminates. The work described herein was aimed at improving Sandia's finite element - based capability to predict interfacial crack growth by 1) using a high fidelity nonlinear viscoelastic material model for the adhesive in fracture simulations, and 2) developing and implementing a novel cohesive zone fracture model that generates a mode - mixity dependent toughness as a natural consequence of its formulation (i.e., generates the observed increase in interfacial toughness wi th increasing crack - tip interfacial shear). Furthermore, molecular dynamics simulations were used to study fundamental material/interfa cial physics so as to develop a fuller understanding of the connection between molecular structure and failure . Also reported are test results that quantify how joint strength and interfacial toughness vary with temperature.

  17. SEACAS Theory Manuals: Part III. Finite Element Analysis in Nonlinear Solid Mechanics

    SciTech Connect

    Laursen, T.A.; Attaway, S.W.; Zadoks, R.I.

    1999-03-01

    This report outlines the application of finite element methodology to large deformation solid mechanics problems, detailing also some of the key technological issues that effective finite element formulations must address. The presentation is organized into three major portions: first, a discussion of finite element discretization from the global point of view, emphasizing the relationship between a virtual work principle and the associated fully discrete system, second, a discussion of finite element technology, emphasizing the important theoretical and practical features associated with an individual finite element; and third, detailed description of specific elements that enjoy widespread use, providing some examples of the theoretical ideas already described. Descriptions of problem formulation in nonlinear solid mechanics, nonlinear continuum mechanics, and constitutive modeling are given in three companion reports.

  18. A comparison of element-by-element preconditioned iterative methods for solid and structural mechanics

    SciTech Connect

    Ferencz, R.M.

    1988-10-01

    Past work with element-by-element (EBE) preconditioned conjugate gradient iterative solution strategies has shown these techniques can be effective for large-scale, three-dimensional calculations in solid and structural mechanics. Significant gains over the profile storage direct solution method traditionally used in implicit finite element codes have been observed for a variety of real engineering analyses, especially in solid mechanics. Structural mechanics applications have proved less successful due to the ill-conditioned linear systems engendered by standard structural discretizations. This lack of robustness has recently motivated reconsideration of Lanczos-based algorithms as alternative iterative drivers. In this paper we compare the relative strengths of the conjugate gradient and Lanczos drivers when coupled with EBE preconditioning. The performance of the two methods is characterized, and compared with direct solution, using a model problem and a number of real engineering meshes. 26 refs., 14 figs., 2 tabs.

  19. Isostructural solid-solid phase transition in monolayers of soft core-shell particles at fluid interfaces: structure and mechanics.

    PubMed

    Rey, Marcel; Fernández-Rodríguez, Miguel Ángel; Steinacher, Mathias; Scheidegger, Laura; Geisel, Karen; Richtering, Walter; Squires, Todd M; Isa, Lucio

    2016-04-13

    We have studied the complete two-dimensional phase diagram of a core-shell microgel-laden fluid interface by synchronizing its compression with the deposition of the interfacial monolayer. Applying a new protocol, different positions on the substrate correspond to different values of the monolayer surface pressure and specific area. Analyzing the microstructure of the deposited monolayers, we discovered an isostructural solid-solid phase transition between two crystalline phases with the same hexagonal symmetry, but with two different lattice constants. The two phases corresponded to shell-shell and core-core inter-particle contacts, respectively; with increasing surface pressure the former mechanically failed enabling the particle cores to come into contact. In the phase-transition region, clusters of particles in core-core contacts nucleate, melting the surrounding shell-shell crystal, until the whole monolayer moves into the second phase. We furthermore measured the interfacial rheology of the monolayers as a function of the surface pressure using an interfacial microdisk rheometer. The interfaces always showed a strong elastic response, with a dip in the shear elastic modulus in correspondence with the melting of the shell-shell phase, followed by a steep increase upon the formation of a percolating network of the core-core contacts. These results demonstrate that the core-shell nature of the particles leads to a rich mechanical and structural behavior that can be externally tuned by compressing the interface, indicating new routes for applications, e.g. in surface patterning or emulsion stabilization. PMID:26948023

  20. Thermal fluid-solid interaction model and experimental validation for hydrostatic mechanical face seals

    NASA Astrophysics Data System (ADS)

    Huang, Weifeng; Liao, Chuanjun; Liu, Xiangfeng; Suo, Shuangfu; Liu, Ying; Wang, Yuming

    2014-09-01

    Hydrostatic mechanical face seals for reactor coolant pumps are very important for the safety and reliability of pressurized-water reactor power plants. More accurate models on the operating mechanism of the seals are needed to help improve their performance. The thermal fluid-solid interaction (TFSI) mechanism of the hydrostatic seal is investigated in this study. Numerical models of the flow field and seal assembly are developed. Based on the mechanism for the continuity condition of the physical quantities at the fluid-solid interface, an on-line numerical TFSI model for the hydrostatic mechanical seal is proposed using an iterative coupling method. Dynamic mesh technology is adopted to adapt to the changing boundary shape. Experiments were performed on a test rig using a full-size test seal to obtain the leakage rate as a function of the differential pressure. The effectiveness and accuracy of the TFSI model were verified by comparing the simulation results and experimental data. Using the TFSI model, the behavior of the seal is presented, including mechanical and thermal deformation, and the temperature field. The influences of the rotating speed and differential pressure of the sealing device on the temperature field, which occur widely in the actual use of the seal, are studied. This research proposes an on-line and assembly-based TFSI model for hydrostatic mechanical face seals, and the model is validated by full-sized experiments.

  1. Solid State Reactions in the Mo/O--Fe System under Mechanical Alloying

    SciTech Connect

    Elsukov, E. P.; Protasov, A. V.; Povstugar, I. V.

    2010-07-13

    Two types of solid state reactions that occur during mechanical alloying of Mo/O --20 at. % Fe system with various oxygen concentrations were studied by Moessbauer spectroscopy and X-ray diffraction. The first type of solid state reaction, Mo/O+Fe{yields}bcc Mo(O)-Fe, was observed for Mo samples with 8 at. % of oxygen. The second type of solid state reaction proceeds as Mo/O+Fe{yields}bcc Mo(O)-Fe+hcp Mo(O)-Fe{yields}bcc Mo(O)-Fe+Am Mo(O)-Fe for Mo samples with 14 at. % of oxygen and 1.6 at. % of MoO{sub 3} phase. The assumption about correlation between the second component dissolution rate and mixture components yield point ratio is confirmed.

  2. Mechanism of dilute-spin-exchange in solid-state NMR

    SciTech Connect

    Lu, George J.; Opella, Stanley J.

    2014-03-28

    In the stationary, aligned samples used in oriented sample (OS) solid-state NMR, {sup 1}H-{sup 1}H homonuclear dipolar couplings are not attenuated as they are in magic angle spinning solid-state NMR; consequently, they are available for participation in dipolar coupling-based spin-exchange processes. Here we describe analytically the pathways of {sup 15}N-{sup 15}N spin-exchange mediated by {sup 1}H-{sup 1}H homonuclear dipolar couplings. The mixed-order proton-relay mechanism can be differentiated from the third spin assisted recoupling mechanism by setting the {sup 1}H to an off-resonance frequency so that it is at the “magic angle” during the spin-exchange interval in the experiment, since the “magic angle” irradiation nearly quenches the former but only slightly attenuates the latter. Experimental spectra from a single crystal of N-acetyl leucine confirm that this proton-relay mechanism plays the dominant role in {sup 15}N-{sup 15}N dilute-spin-exchange in OS solid-state NMR in crystalline samples. Remarkably, the “forbidden” spin-exchange condition under “magic angle” irradiation results in {sup 15}N-{sup 15}N cross-peaks intensities that are comparable to those observed with on-resonance irradiation in applications to proteins. The mechanism of the proton relay in dilute-spin-exchange is crucial for the design of polarization transfer experiments.

  3. Surface tension and the mechanics of liquid inclusions in compliant solids.

    PubMed

    Style, Robert W; Wettlaufer, John S; Dufresne, Eric R

    2015-01-28

    Eshelby's theory of inclusions has wide-reaching implications across the mechanics of materials and structures including the theories of composites, fracture, and plasticity. However, it does not include the effects of surface stress, which has recently been shown to control many processes in soft materials such as gels, elastomers and biological tissue. To extend Eshelby's theory of inclusions to soft materials, we consider liquid inclusions within an isotropic, compressible, linear-elastic solid. We solve for the displacement and stress fields around individual stretched inclusions, accounting for the bulk elasticity of the solid and the surface tension (i.e. isotropic strain-independent surface stress) of the solid-liquid interface. Surface tension significantly alters the inclusion's shape and stiffness as well as its near- and far-field stress fields. These phenomena depend strongly on the ratio of the inclusion radius, R, to an elastocapillary length, L. Surface tension is significant whenever inclusions are smaller than 100L. While Eshelby theory predicts that liquid inclusions generically reduce the stiffness of an elastic solid, our results show that liquid inclusions can actually stiffen a solid when R<3L/2. Intriguingly, surface tension cloaks the far-field signature of liquid inclusions when R=3L/2. These results are have far-reaching applications from measuring local stresses in biological tissue, to determining the failure strength of soft composites. PMID:25503573

  4. Non-destructive determination of anisotropic mechanical properties of pharmaceutical solid dosage forms.

    PubMed

    Akseli, I; Hancock, B C; Cetinkaya, C

    2009-07-30

    The mechanical property anisotropy of compacts made from four commercially available pharmaceutical excipient powders (microcrystalline cellulose, lactose monohydrate, ascorbic acid, and aspartame) was evaluated. The speed of pressure (longitudinal) waves in the uni-axially compressed cubic compacts of each excipient in the three principle directions was determined using a contact ultrasonic method. Average Young's moduli of each compact in the axial (x) and radial (y and z) directions were characterized. The contact ultrasonic measurements revealed that average Young's modulus values vary with different testing orientations which indicate Young's modulus anisotropy in the compacts. The extent of Young's modulus anisotropy was quantified by using a dimensionless ratio and was found to be significantly different for each material (microcrystalline cellulose>lactose>aspartame>ascorbic acid). It is also observed that using the presented contact method, compacts at high solid fraction (0.857-0.859) could be differentiated than those at the solid fraction of 0.85 in their groups. The presented contact ultrasonic method is an attractive tool since it has the advantages of being sensitive to solid fraction ratio, non-destructive, requiring small amount of material and rapid. It is noteworthy that, since the approach provides insight into the performance of common pharmaceutical materials and fosters increased process knowledge, it can be applied to broaden the understanding of the effect of the mechanical properties on the performance (e.g., disintegration profiles) of solid oral dosage forms. PMID:19426791

  5. Heat generation and thermo-mechanical effect modeling in longitudinally diode-pumped solid state lasers

    NASA Astrophysics Data System (ADS)

    Lakhdari, Fouad; Osmani, Ismahen; Tabet, Saida

    2015-09-01

    Thermal management in solid state laser is a challenge to the high power laser industry's ability to provide continued improvements in device and system performance. In this work an investigation of heat generation and thermo-mechanical effect in a high-power Nd:YAG and Yb:YAG cylindrical-type solid state laser pumped longitudinally with different power by fibre coupled laser diode is carried out by numerical simulation based on the finite element method (FEM). Impact of the dopant concentration on the power conversion efficiency is included in the simulation. The distribution of the temperature inside the lasing material is resolute according to the thermal conductivity. The thermo-mechanical effect is explored as a function of pump power in order to determine the maximum pumping power allowed to prevent the crystal's fracture. The presented simulations are in broad agreement with analytical solutions; provided that the boundary condition of the pump induced heat generation is accurately modelled.

  6. Regression relations for estimating the mechanical properties of steels subjected to solid-solution hardening

    NASA Astrophysics Data System (ADS)

    Protopopov, E. A.; Val'ter, A. I.; Protopopov, A. A.; Malenko, P. I.

    2015-07-01

    An approach is proposed to obtain regression relations to estimate the mechanical properties of steels subjected to solid-solution hardening. The applicability of the developed approach is shown for hot-rolled sheet austenitic iron-nickel and nickel alloys after quenching, toughened low-alloy structural steels with a sorbite structure in the case of full hardenabilty, sheet corrosion-resistant ferritic steels after softening heat treatment, and corrosion-resistant austenitic steels after austenitization. The derived regression relations serve as the basis for correcting the chemical composition of a metal melt to ensure the required level of the mechanical properties of ready products by controlling the degree of solid-solution hardening.

  7. Reaction and degradation mechanism in all-solid-state lithium-air batteries.

    PubMed

    Kitaura, Hirokazu; Zhou, Haoshen

    2015-12-25

    The reaction and degradation mechanism in all-solid-state Li-air batteries was investigated to improve the cycling performance. It is suggested that Li2O2 is first produced by the H2O-mediated electrochemical reactions during discharging and Li2CO3 is produced by the following chemical reactions. Disruption of the CNTs and residual discharge products, which cause the capacity degradation during cycling, were observed. PMID:26478218

  8. Solid State Bonding Mechanics In Extrusion And FSW: Experimental Tests And Numerical Analyses

    SciTech Connect

    Buffa, G.; Fratini, L.; Donati, L.; Tomesani, L.

    2007-04-07

    In the paper the authors compare the different solid state bonding mechanics for both the processes of hollow profiles extrusion and Friction Stir Welding (FSW), through the results obtained from a wide experimental campaign on AA6082-T6 aluminum alloys. Microstructure evaluation, tensile tests and micro-hardness measurements realized on specimens extracted by samples of the two processes are discussed also by means of the results obtained from coupled FEM simulation of the processes.

  9. Sierra/SolidMechanics 4.22 user's guide : addendum for shock capabilities.

    SciTech Connect

    Not Available

    2011-10-01

    This is an addendum to the Sierra/SolidMechanics 4.22 User's Guide to document additional capabilities that are available for use in the Presto{_}ITAR code that are not available for use in the standard version of Sierra/SolidMechanics (Sierra/SM). Presto{_}ITAR is an enhanced version of Sierra/SM that provides capabilities that make it regulated under the U.S. Department of State's International Traffic in Arms Regulations (ITAR) export-control rules. This code is part of the Vivace product, and is only distributed to entities that comply with ITAR regulations. The enhancements primarily focus on material models that include an energy-dependent pressure response, appropriate for very large deformations and strain rates. Since this is an addendum to the standard Sierra/SolidMechanics User's Guide, please refer to that document first for general descriptions of code capability and use. This addendum documents material models and element features that support energy-dependent material models.

  10. Mechanical force-induced polymerization and depolymerization of F-actin at water/solid interfaces

    NASA Astrophysics Data System (ADS)

    Zhang, Xueqiang; Hu, Xiuyuan; Lei, Haozhi; Hu, Jun; Zhang, Yi

    2016-03-01

    Actin molecules are among the three main cytoskeleton proteins of cells and undergo rapid cycling to regulate critical processes such as endocytosis, cytokinesis, cell polarity, and cell morphogenesis. Although extensive studies have been carried out on the dynamics as well as biological functions of actin polymerization and depolymerization both in vivo and in vitro, the molecular mechanisms by which cells sense and respond to mechanical signals are not fully understood. In particular, little attention has been paid to the effect of a physical force that is exerted directly on the actin cytoskeleton. In this paper, we have explored how the mechanical force affects the actin polymerization and depolymerization behaviors at water/solid interfaces using an atomic force microscope (AFM) operated in liquid. By raster scanning an AFM probe on a substrate surface with a certain load, it was found that actin monomers could polymerize into filaments without the help of actin related proteins (ARPs). Further study indicated that actin monomers were inclined to form filaments only under a small scanning load. The polymerized actin filaments would be depolymerized when the mechanical force was stronger. A possible mechanism has been suggested to explain the mechanical force induced actin polymerization.Actin molecules are among the three main cytoskeleton proteins of cells and undergo rapid cycling to regulate critical processes such as endocytosis, cytokinesis, cell polarity, and cell morphogenesis. Although extensive studies have been carried out on the dynamics as well as biological functions of actin polymerization and depolymerization both in vivo and in vitro, the molecular mechanisms by which cells sense and respond to mechanical signals are not fully understood. In particular, little attention has been paid to the effect of a physical force that is exerted directly on the actin cytoskeleton. In this paper, we have explored how the mechanical force affects the actin

  11. Inorganic Solid-State Electrolytes for Lithium Batteries: Mechanisms and Properties Governing Ion Conduction.

    PubMed

    Bachman, John Christopher; Muy, Sokseiha; Grimaud, Alexis; Chang, Hao-Hsun; Pour, Nir; Lux, Simon F; Paschos, Odysseas; Maglia, Filippo; Lupart, Saskia; Lamp, Peter; Giordano, Livia; Shao-Horn, Yang

    2016-01-13

    This Review is focused on ion-transport mechanisms and fundamental properties of solid-state electrolytes to be used in electrochemical energy-storage systems. Properties of the migrating species significantly affecting diffusion, including the valency and ionic radius, are discussed. The natures of the ligand and metal composing the skeleton of the host framework are analyzed and shown to have large impacts on the performance of solid-state electrolytes. A comprehensive identification of the candidate migrating species and structures is carried out. Not only the bulk properties of the conductors are explored, but the concept of tuning the conductivity through interfacial effects-specifically controlling grain boundaries and strain at the interfaces-is introduced. High-frequency dielectric constants and frequencies of low-energy optical phonons are shown as examples of properties that correlate with activation energy across many classes of ionic conductors. Experimental studies and theoretical results are discussed in parallel to give a pathway for further improvement of solid-state electrolytes. Through this discussion, the present Review aims to provide insight into the physical parameters affecting the diffusion process, to allow for more efficient and target-oriented research on improving solid-state ion conductors. PMID:26713396

  12. A unified approach for a posteriori high-order curved mesh generation using solid mechanics

    NASA Astrophysics Data System (ADS)

    Poya, Roman; Sevilla, Ruben; Gil, Antonio J.

    2016-06-01

    The paper presents a unified approach for the a posteriori generation of arbitrary high-order curvilinear meshes via a solid mechanics analogy. The approach encompasses a variety of methodologies, ranging from the popular incremental linear elastic approach to very sophisticated non-linear elasticity. In addition, an intermediate consistent incrementally linearised approach is also presented and applied for the first time in this context. Utilising a consistent derivation from energy principles, a theoretical comparison of the various approaches is presented which enables a detailed discussion regarding the material characterisation (calibration) employed for the different solid mechanics formulations. Five independent quality measures are proposed and their relations with existing quality indicators, used in the context of a posteriori mesh generation, are discussed. Finally, a comprehensive range of numerical examples, both in two and three dimensions, including challenging geometries of interest to the solids, fluids and electromagnetics communities, are shown in order to illustrate and thoroughly compare the performance of the different methodologies. This comparison considers the influence of material parameters and number of load increments on the quality of the generated high-order mesh, overall computational cost and, crucially, the approximation properties of the resulting mesh when considering an isoparametric finite element formulation.

  13. A unified approach for a posteriori high-order curved mesh generation using solid mechanics

    NASA Astrophysics Data System (ADS)

    Poya, Roman; Sevilla, Ruben; Gil, Antonio J.

    2016-09-01

    The paper presents a unified approach for the a posteriori generation of arbitrary high-order curvilinear meshes via a solid mechanics analogy. The approach encompasses a variety of methodologies, ranging from the popular incremental linear elastic approach to very sophisticated non-linear elasticity. In addition, an intermediate consistent incrementally linearised approach is also presented and applied for the first time in this context. Utilising a consistent derivation from energy principles, a theoretical comparison of the various approaches is presented which enables a detailed discussion regarding the material characterisation (calibration) employed for the different solid mechanics formulations. Five independent quality measures are proposed and their relations with existing quality indicators, used in the context of a posteriori mesh generation, are discussed. Finally, a comprehensive range of numerical examples, both in two and three dimensions, including challenging geometries of interest to the solids, fluids and electromagnetics communities, are shown in order to illustrate and thoroughly compare the performance of the different methodologies. This comparison considers the influence of material parameters and number of load increments on the quality of the generated high-order mesh, overall computational cost and, crucially, the approximation properties of the resulting mesh when considering an isoparametric finite element formulation.

  14. Structural-mechanical model of wax crystal networks—a mesoscale cellular solid approach

    NASA Astrophysics Data System (ADS)

    Miyazaki, Yukihiro; Marangoni, Alejandro G.

    2014-04-01

    Mineral waxes are widely used materials in industrial applications; however, the relationship between structure and mechanical properties is poorly understood. In this work, mineral wax-oil networks were characterized as closed-cell cellular solids, and differences in their mechanical response predicted from structural data. The systems studied included straight-chain paraffin wax (SW)-oil mixtures and polyethylene wax (PW)-oil mixtures. Analysis of cryogenic-SEM images of wax-oil networks allowed for the determination of the length (l) and thickness (t) of the wax cell walls as a function of wax mass fraction (Φ). A linear relationship between t/l and Φ (t/l ˜ Φ 0.89) suggested that wax-oil networks were cellular solids of the closed-cell type. However, the scaling behavior of the elastic modulus with the volume fraction of solids did not agree with theoretical predictions, yielding the same scaling exponent, μ = 0.84, for both waxes. This scaling exponent obtained from mechanical measurements could be predicted from the scaling behavior of the effective wax cell size as a function of wax mass fraction in oil obtained by cryogenic scanning electron microscopy. Microscopy studies allowed us to propose that wax-oil networks are structured as an ensemble of close-packed spherical cells filled with oil, and that it is the links between cells that yield under simple uniaxial compression. Thus, the Young’s moduli for the links between cells in SW and PW wax systems could be estimated as E L (SW) = 2.76 × 109 Pa and E L (PW) = 1.64 × 109 Pa, respectively. The structural parameter responsible for the observed differences in the mechanical strength between the two wax-oil systems is the size of the cells. Polyethylene wax has much smaller cell sizes than the straight chain wax and thus displays a higher Young’s modulus and yield stress.

  15. Flexible microfluidic device for mechanical property characterization of soft viscoelastic solids such as bacterial biofilms

    PubMed Central

    Hohne, Danial N.; Younger, John G.; Solomon, Michael J.

    2009-01-01

    We introduce a flexible microfluidic device to characterize the mechanical properties of soft viscoelastic solids such as bacterial biofilms. In the device, stress is imposed on a test specimen by application of a fixed pressure to a thin, flexible poly(dimethyl siloxane) (PDMS) membrane that is in contact with the specimen. The stress is applied by pressurizing a microfabricated air channel located above the test area. The strain resulting from the applied stress is quantified by measuring the membrane deflection with a confocal laser-scanning microscope. The deflection is governed by the viscoelastic properties of the PDMS membrane and of the test specimen. The relative contributions of the membrane and test material to the measured deformation are quantified by comparing a finite element analysis and an independent (control) measurement of the PDMS membrane mechanical properties. The flexible microfluidic rheometer was used to characterize both the steady-state elastic modulus and transient strain recoil of two soft materials: gellan gums and bacterial biofilms. The measured linear elastic moduli and viscoelastic relaxation times of gellan gum solutions were in good agreement with the results of conventional mechanical rheometry. The linear Young’s moduli of biofilms of Staphylococcus epidermidis and Klebsiella pneumoniae, which could not be measured using conventional methods, were found to be 3.2 kPa and 1.1 kPa, respectively, and the relaxation time of the S. epidermidis biofilm was 13.8 s. Additionally, strain hardening was observed in all the biofilms studied. Finally, design parameters and detection limits of the method show that the device is capable of characterizing soft viscoelastic solids with elastic moduli in the range of 102 – 105 Pa. The flexible microfluidic rheometer addresses a need for mechanical property characterization of soft viscoelastic solids common in fields such as biomaterials, food and consumer products. It requires only ~ 200 p

  16. Flexible microfluidic device for mechanical property characterization of soft viscoelastic solids such as bacterial biofilms.

    PubMed

    Hohne, Danial N; Younger, John G; Solomon, Michael J

    2009-07-01

    We introduce a flexible microfluidic device to characterize the mechanical properties of soft viscoelastic solids such as bacterial biofilms. In the device, stress is imposed on a test specimen by the application of a fixed pressure to a thin, flexible poly(dimethyl siloxane) (PDMS) membrane that is in contact with the specimen. The stress is applied by pressurizing a microfabricated air channel located above the test area. The strain resulting from the applied stress is quantified by measuring the membrane deflection with a confocal laser scanning microscope. The deflection is governed by the viscoelastic properties of the PDMS membrane and of the test specimen. The relative contributions of the membrane and test material to the measured deformation are quantified by comparing a finite element analysis with an independent (control) measurement of the PDMS membrane mechanical properties. The flexible microfluidic rheometer was used to characterize both the steady-state elastic modulus and the transient strain recoil of two soft materials: gellan gums and bacterial biofilms. The measured linear elastic moduli and viscoelastic relaxation times of gellan gum solutions were in good agreement with the results of conventional mechanical rheometry. The linear Young's moduli of biofilms of Staphylococcus epidermidis and Klebsiella pneumoniae, which could not be measured using conventional methods, were found to be 3.2 and 1.1 kPa, respectively, and the relaxation time of the S. epidermidis biofilm was 13.8 s. Additionally, strain hardening was observed in all the biofilms studied. Finally, design parameters and detection limits of the method show that the device is capable of characterizing soft viscoelastic solids with elastic moduli in the range of 102-105 Pa. The flexible microfluidic rheometer addresses the need for mechanical property characterization of soft viscoelastic solids common in fields such as biomaterials, food, and consumer products. It requires only 200 p

  17. First-principles quantum-mechanical investigations of biomass conversion at the liquid-solid interfaces

    NASA Astrophysics Data System (ADS)

    Dang, Hongli; Xue, Wenhua; Liu, Yingdi; Jentoft, Friederike; Resasco, Daniel; Wang, Sanwu

    2014-03-01

    We report first-principles density-functional calculations and ab initio molecular dynamics (MD) simulations for the reactions involving furfural, which is an important intermediate in biomass conversion, at the catalytic liquid-solid interfaces. The different dynamic processes of furfural at the water-Cu(111) and water-Pd(111) interfaces suggest different catalytic reaction mechanisms for the conversion of furfural. Simulations for the dynamic processes with and without hydrogen demonstrate the importance of the liquid-solid interface as well as the presence of hydrogen in possible catalytic reactions including hydrogenation and decarbonylation of furfural. Supported by DOE (DE-SC0004600). This research used the supercomputer resources of the XSEDE, the NERSC Center, and the Tandy Supercomputing Center.

  18. Probabilistic Fracture Mechanics and Optimum Fracture Control Analytical Procedures for a Reusable Solid Rocket Motor Case

    NASA Technical Reports Server (NTRS)

    Hanagud, S.; Uppaluri, B.

    1977-01-01

    A methodology for the reliability analysis of a reusable solid rocket motor case is discussed. The analysis is based on probabilistic fracture mechanics and probability distribution for initial flaw sizes. The developed reliability analysis is used to select the structural design variables of the solid rocket motor case on the basis of minimum expected cost and specified reliability bounds during the projected design life of the case. Effects of failure prevention plans such as nondestructive inspection and the material erosion between missions are also considered in the developed procedure for selection of design variables. The reliability-based procedure can be modified to consider other similar structures of reusable space vehicle systems with different failure prevention plans.

  19. Characterization of HTPB-based solid fuel formulations: Performance, mechanical properties, and pollution

    NASA Astrophysics Data System (ADS)

    DeLuca, L. T.; Galfetti, L.; Maggi, F.; Colombo, G.; Merotto, L.; Boiocchi, M.; Paravan, C.; Reina, A.; Tadini, P.; Fanton, L.

    2013-12-01

    Features such as safety, low-cost, and throttleability make hybrid rocket engines an attractive option for suborbital flights and space exploration missions in general. While the domain of possible liquid oxidizers is well characterized, the choice of a suitable solid fuel is still a matter of investigation. Space Propulsion Laboratory (SPLab) at Politecnico di Milano has developed a series of proprietary techniques to evaluate, on a relative grading, the quality of innovative solid fuels while visualizing at the same time their flame structure. But a serious alert was recently notified that soot emission from hydrocarbon fuels has the potential to contribute to global climate change. In this paper, HTPB polymer has been taken as baseline and characterized at laboratory level in terms of ballistic properties, mechanical testing, and thermochemical calculations.

  20. Combined solid-state and mechanically-switched transformer tap-changer

    SciTech Connect

    Eitzmann, M.A.; Hill, A.T.

    1995-04-18

    Disclosed is an End-Turn Solid-State Switching (ETSS) transformer tap which makes use of a high-speed solid-state switching network to select either the end-turn lead or one of a number of non-isolated taps on a transformer regulating winding, and connects the selected tap to, while disconnecting the previously selected tap from, a single output conductor carrying the transformer load current. ETSS effectively changes the reference to one of the possible taps interfaced to a solid-state switching network. The same transformer regulating winding connected to ETSS can also be connected in series with a slow-speed mechanically-switched tap-changer (LTC). ETSS selects one connection point on the regulating winding while LTC operation selects the second point. A difference voltage is produced, depending on the number of turns between the ETSS selected tap and the LTC selected tap. The sign of the difference in voltage depends on whether the ETSS selected tap is higher or lower than the LTC selected tap. The difference or tap selected voltage is in series with the transformer load current. In one embodiment, the high-speed solid-state switching network uses a ``Staggered Progression of Solid-State Switches`` (SPSS) to select one of a number of non-isolated taps on a transformer regulating winding and connect the selected tap in series with the load circuit. A switching network arranged according to the method SPSS reduces the necessary total switch power rating, and steady-state losses. ETSS can accomplish modulation of the tap-selected voltage about the nominal value established by the LTC. 9 figs.

  1. Mechanism and microstructures in Ga2O3 pseudomartensitic solid phase transition.

    PubMed

    Zhu, Sheng-Cai; Guan, Shu-Hui; Liu, Zhi-Pan

    2016-07-21

    Solid-to-solid phase transition, although widely exploited in making new materials, challenges persistently our current theory for predicting its complex kinetics and rich microstructures in transition. The Ga2O3α-β phase transformation represents such a common but complex reaction with marked change in cation coordination and crystal density, which was known to yield either amorphous or crystalline products under different synthetic conditions. Here we, via recently developed stochastic surface walking (SSW) method, resolve for the first time the atomistic mechanism of Ga2O3α-β phase transformation, the pathway of which turns out to be the first reaction pathway ever determined for a new type of diffusionless solid phase transition, namely, pseudomartensitic phase transition. We demonstrate that the sensitivity of product crystallinity is caused by its multi-step, multi-type reaction pathway, which bypasses seven intermediate phases and involves all types of elementary solid phase transition steps, i.e. the shearing of O layers (martensitic type), the local diffusion of Ga atoms (reconstructive type) and the significant lattice dilation (dilation type). While the migration of Ga atoms across the close-packed O layers is the rate-determining step and yields "amorphous-like" high energy intermediates, the shearing of O layers contributes to the formation of coherent biphase junctions and the presence of a crystallographic orientation relation, (001)α//(201[combining macron])β + [120]α//[13[combining macron]2]β. Our experiment using high-resolution transmission electron microscopy further confirms the theoretical predictions on the atomic structure of biphase junction and the formation of (201[combining macron])β twin, and also discovers the late occurrence of lattice expansion in the nascent β phase that grows out from the parent α phase. By distinguishing pseudomartensitic transition from other types of mechanisms, we propose general rules to predict the

  2. Solid Insulated Switchgear and Investigation of its Mechanical and Electrical Reliability

    NASA Astrophysics Data System (ADS)

    Sato, Junichi; Kinoshita, Susumu; Sakaguchi, Osamu; Miyagawa, Masaru; Shimizu, Toshio; Homma, Mitsutaka

    SF6 gas is applied widely to medium voltage switchgear because of its high insulation reliability and down-sizing ability. However, SF6 gas was placed on the list of greenhouse gases under the Kyoto Protocol in 1997. Since then, the investigation and development concerning SF6-free or less has carried out activity. Therefore, we paid attention to the solid material which has higher dielectric strength than SF6, and we have newly developed solid insulated switchgear (SIS) achieved by molding all main circuit. A new epoxy casting material is applied, which contains a great deal of spherical silica and a small amount of rubber particles. This new material has the high mechanical strength, high thermal resistance, high toughness, and also high dielectric strength because of directly molding the vacuum bottle, down-sizing and reliability. This paper describes about the technology of a new epoxy casting material which achieves the SIS. In addition, the mechanical and electrical reliability test of SIS applied a new epoxy resin are carried out, and effectiveness of the development material and the mechanical and electrical reliability of SIS are verified.

  3. Mechanical force-induced polymerization and depolymerization of F-actin at water/solid interfaces.

    PubMed

    Zhang, Xueqiang; Hu, Xiuyuan; Lei, Haozhi; Hu, Jun; Zhang, Yi

    2016-03-21

    Actin molecules are among the three main cytoskeleton proteins of cells and undergo rapid cycling to regulate critical processes such as endocytosis, cytokinesis, cell polarity, and cell morphogenesis. Although extensive studies have been carried out on the dynamics as well as biological functions of actin polymerization and depolymerization both in vivo and in vitro, the molecular mechanisms by which cells sense and respond to mechanical signals are not fully understood. In particular, little attention has been paid to the effect of a physical force that is exerted directly on the actin cytoskeleton. In this paper, we have explored how the mechanical force affects the actin polymerization and depolymerization behaviors at water/solid interfaces using an atomic force microscope (AFM) operated in liquid. By raster scanning an AFM probe on a substrate surface with a certain load, it was found that actin monomers could polymerize into filaments without the help of actin related proteins (ARPs). Further study indicated that actin monomers were inclined to form filaments only under a small scanning load. The polymerized actin filaments would be depolymerized when the mechanical force was stronger. A possible mechanism has been suggested to explain the mechanical force induced actin polymerization. PMID:26928199

  4. A meshfree method based on the peridynamic model of solid mechanics.

    SciTech Connect

    Silling, Stewart Andrew; Askari, Ebrahim

    2005-01-01

    An alternative theory of solid mechanics, known as the peridynamic theory, formulates problems in terms of integral equations rather than partial differential equations. This theory assumes that particles in a continuum interact with each other across a finite distance, as in molecular dynamics. Damage is incorporated in the theory at the level of these two-particle interactions, so localization and fracture occur as a natural outgrowth of the equation of motion and constitutive models. A numerical method for solving dynamic problems within the peridynamic theory is described. Accuracy and numerical stability are discussed. Examples illustrate the properties of the method for modeling brittle dynamic crack growth.

  5. Fabrication of the supersaturated solid solution of carbon in copper by mechanical alloying

    SciTech Connect

    Liu Xueran; Liu Yongbing; Ran Xu; An Jian; Cao Zhanyi . E-mail: caozy@jlu.edu.cn

    2007-06-15

    Mechanical alloying of powder mixtures of copper and graphite was performed in a high energy ball mill. The as-milled powder was characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy, respectively. These investigations indicated that high energy ball milling could largely extend the solid solubility of carbon in copper and the 4 wt.% C was dissolved in Cu. It was ascribed to the decrease of the grain size and the increase of the lattice strain. Nanostructures, amorphous carbon and lamellar graphite were observed in the as-milled powder after milling for 24 h.

  6. Electrostrictive Mechanism of Nanostructure Formation at Solid Surfaces Irradiated by Femtosecond Laser Pulses.

    PubMed

    Pavlyniuk, Oleg R; Datsyuk, Vitaly V

    2016-12-01

    The significance of the mechanical pressure of light in creation of laser-induced periodic surface structures (LIPSSs) is investigated. Distributions of the electrically induced normal pressure and tangential stress at the illuminated solid surface, as well as the field of volume electrostrictive forces, are calculated taking into account surface plasmon polariton (SPP) excitation. Based on these calculations, we predict surface destruction and structure formation due to inelastic deformations during single femtosecond pulses. The calculated fields of the electromagnetic forces are found to agree well with the experimental ripple structures. We thus conclude that the electrostrictive forces can explain the origin of the periodic ripple structures. PMID:26754942

  7. Observation of a Dislocation-Related Interfacial Friction Mechanism in Mobile Solid 4He

    NASA Astrophysics Data System (ADS)

    Eyal, Anna; Livne, Ethan; Polturak, Emil

    2016-04-01

    We report a study of the temperature and stress dependence of the friction associated with a relative motion of crystallites of solid 4He in contact with each other. A situation where such motion exists emerges spontaneously during a disordering of a single crystal contained inside an annular sample space of a torsional oscillator (TO). Under the torque applied by the oscillating walls of the TO these crystallites move relative to each other, generating measurable dissipation at their interface. We studied this friction between 0.5 and 1.8 K in solid samples grown from commercially pure 4He and from a 100 ppm 3He-4He mixture. The data were analyzed by modeling the TO as a driven harmonic oscillator. In this model, an analysis of the resonant frequency and amplitude of the TO yields the temperature dependence of the friction coefficient. By fitting the data to specific forms, we found that over our temperature range, the dominant friction mechanism associated with the interfacial motion of the crystallites results from climb of individual dislocations. The characteristic energy scale associated with this friction can be 3 or 6 K, depending on the sample. The motion of the solid in the presence of such friction can perhaps be described as the low limit of "slip-stick" motion.

  8. Controlling mechanisms of ignition of solid fuel in a sudden-expansion combustor

    SciTech Connect

    Yang, J.; Wu, C.Y.Y.

    1995-05-01

    Ignition of solid fuel by a hot oxidizing flow in a sudden-expansion combustor was investigated experimentally. The controlled variables of the experiments were concentration of oxygen (12-25%), gas temperature (750-850 C), and flow velocity (19-46 m/s). The step height was 29 mm. The corresponding Reynolds numbers based on the flow velocity and the step heights were 12 x 10(sup 4)-31 x 10(sup 4). The controlling mechanisms of ignition in the flow with abundant oxygen were distinct from those with little oxygen. The initial flame kernels formed near the reattachment point and adjacent to the surface of solid fuel when the oxygen concentration was large. The process was controlled by diffusion and the ignition delay decreased with increased flow velocity. For the flow containing oxygen at a small concentration, the initial flame kernels formed within the recirculation zone and away from the surface of the solid fuel. The process was then controlled by the chemical kinetics and the ignition delay increased with increased flow velocity. 15 refs.

  9. 3D printed cellular solid outperforms traditional stochastic foam in long-term mechanical response

    NASA Astrophysics Data System (ADS)

    Maiti, A.; Small, W.; Lewicki, J. P.; Weisgraber, T. H.; Duoss, E. B.; Chinn, S. C.; Pearson, M. A.; Spadaccini, C. M.; Maxwell, R. S.; Wilson, T. S.

    2016-04-01

    3D printing of polymeric foams by direct-ink-write is a recent technological breakthrough that enables the creation of versatile compressible solids with programmable microstructure, customizable shapes, and tunable mechanical response including negative elastic modulus. However, in many applications the success of these 3D printed materials as a viable replacement for traditional stochastic foams critically depends on their mechanical performance and micro-architectural stability while deployed under long-term mechanical strain. To predict the long-term performance of the two types of foams we employed multi-year-long accelerated aging studies under compressive strain followed by a time-temperature-superposition analysis using a minimum-arc-length-based algorithm. The resulting master curves predict superior long-term performance of the 3D printed foam in terms of two different metrics, i.e., compression set and load retention. To gain deeper understanding, we imaged the microstructure of both foams using X-ray computed tomography, and performed finite-element analysis of the mechanical response within these microstructures. This indicates a wider stress variation in the stochastic foam with points of more extreme local stress as compared to the 3D printed material, which might explain the latter’s improved long-term stability and mechanical performance.

  10. 3D printed cellular solid outperforms traditional stochastic foam in long-term mechanical response.

    PubMed

    Maiti, A; Small, W; Lewicki, J P; Weisgraber, T H; Duoss, E B; Chinn, S C; Pearson, M A; Spadaccini, C M; Maxwell, R S; Wilson, T S

    2016-01-01

    3D printing of polymeric foams by direct-ink-write is a recent technological breakthrough that enables the creation of versatile compressible solids with programmable microstructure, customizable shapes, and tunable mechanical response including negative elastic modulus. However, in many applications the success of these 3D printed materials as a viable replacement for traditional stochastic foams critically depends on their mechanical performance and micro-architectural stability while deployed under long-term mechanical strain. To predict the long-term performance of the two types of foams we employed multi-year-long accelerated aging studies under compressive strain followed by a time-temperature-superposition analysis using a minimum-arc-length-based algorithm. The resulting master curves predict superior long-term performance of the 3D printed foam in terms of two different metrics, i.e., compression set and load retention. To gain deeper understanding, we imaged the microstructure of both foams using X-ray computed tomography, and performed finite-element analysis of the mechanical response within these microstructures. This indicates a wider stress variation in the stochastic foam with points of more extreme local stress as compared to the 3D printed material, which might explain the latter's improved long-term stability and mechanical performance. PMID:27117858

  11. 3D printed cellular solid outperforms traditional stochastic foam in long-term mechanical response

    DOE PAGESBeta

    Maiti, A.; Small, W.; Lewicki, J.; Weisgraber, T. H.; Duoss, E. B.; Chinn, S. C.; Pearson, M. A.; Spadaccini, C. M.; Maxwell, R. S.; Wilson, T. S.

    2016-04-27

    3D printing of polymeric foams by direct-ink-write is a recent technological breakthrough that enables the creation of versatile compressible solids with programmable microstructure, customizable shapes, and tunable mechanical response including negative elastic modulus. However, in many applications the success of these 3D printed materials as a viable replacement for traditional stochastic foams critically depends on their mechanical performance and micro-architectural stability while deployed under long-term mechanical strain. To predict the long-term performance of the two types of foams we employed multi-year-long accelerated aging studies under compressive strain followed by a time-temperature-superposition analysis using a minimum-arc-length-based algorithm. The resulting master curvesmore » predict superior long-term performance of the 3D printed foam in terms of two different metrics, i.e., compression set and load retention. To gain deeper understanding, we imaged the microstructure of both foams using X-ray computed tomography, and performed finite-element analysis of the mechanical response within these microstructures. As a result, this indicates a wider stress variation in the stochastic foam with points of more extreme local stress as compared to the 3D printed material, which might explain the latter’s improved long-term stability and mechanical performance.« less

  12. 3D printed cellular solid outperforms traditional stochastic foam in long-term mechanical response

    PubMed Central

    Maiti, A.; Small, W.; Lewicki, J. P.; Weisgraber, T. H.; Duoss, E. B.; Chinn, S. C.; Pearson, M. A.; Spadaccini, C. M.; Maxwell, R. S.; Wilson, T. S.

    2016-01-01

    3D printing of polymeric foams by direct-ink-write is a recent technological breakthrough that enables the creation of versatile compressible solids with programmable microstructure, customizable shapes, and tunable mechanical response including negative elastic modulus. However, in many applications the success of these 3D printed materials as a viable replacement for traditional stochastic foams critically depends on their mechanical performance and micro-architectural stability while deployed under long-term mechanical strain. To predict the long-term performance of the two types of foams we employed multi-year-long accelerated aging studies under compressive strain followed by a time-temperature-superposition analysis using a minimum-arc-length-based algorithm. The resulting master curves predict superior long-term performance of the 3D printed foam in terms of two different metrics, i.e., compression set and load retention. To gain deeper understanding, we imaged the microstructure of both foams using X-ray computed tomography, and performed finite-element analysis of the mechanical response within these microstructures. This indicates a wider stress variation in the stochastic foam with points of more extreme local stress as compared to the 3D printed material, which might explain the latter’s improved long-term stability and mechanical performance. PMID:27117858

  13. Mechanisms of reduced solute diffusivity at nanoconfined solid-liquid interface

    NASA Astrophysics Data System (ADS)

    Mahadevan, T.; Kojic, M.; Ferrari, M.; Ziemys, A.

    2013-06-01

    We report results from molecular simulations that reveal the causes of reduced diffusivity at solid-liquid interfaces in the presence of nanoscale confinement. The diffusion of a 2 M glucose solution was simulated inside a 10 nm silica channel together with the calculated thermodynamic properties of diffusion. A strong energy-entropy compensation mechanism was found at the interface with a free energy minimum of -0.6 kcal/mol. Using the Eyring equation the average jump length was reduced by 15% at interface. The complete loss of solute diffusivity at silica surface was explained by the substantial loss of the probability of productive displacements. The results suggested that glucose molecule diffusivity close to the surface might be related to a stiffer cage of the hydration shell, which affects the probability of cage breaking. These results help in understanding of diffusion mechanisms at interface and predicting mass transport in nanoconfinement for engineering and biomedical applications.

  14. Mechanisms of lubrication and wear of a bonded solid lubricant film

    NASA Technical Reports Server (NTRS)

    Fusaro, R. L.

    1980-01-01

    To obtain a better understanding of how bonded solid lubricant films lubricate and wear (in general), the tribological properties of polyimide-bonded graphite fluoride films were studied (in specific). A pin-on-disk type of testing apparatus was used; but in addition to sliding a hemispherically tipped rider, a rider with a 0.95 mm diameter flat area was slid against the film. This was done so that a lower, less variable contact stress could be achieved. Two stages of lubrication occurred. In the first, the film supported the load. The lubricating mechanism consisted of the shear of a thin surface layer (of the film) between the rider and the bulk of the film. The second occurred after the bonded film had worn to the substrate, and consisted of the shear of very thin lubricant films between the rider and flat plateaus generated on the metallic substrate asperities. The film wear mechanism was strongly dependent on contact stress.

  15. Polarizing agents and mechanisms for high-field dynamic nuclear polarization of frozen dielectric solids.

    PubMed

    Hu, Kan-Nian

    2011-09-01

    This article provides an overview of polarizing mechanisms involved in high-frequency dynamic nuclear polarization (DNP) of frozen biological samples at temperatures maintained using liquid nitrogen, compatible with contemporary magic-angle spinning (MAS) nuclear magnetic resonance (NMR). Typical DNP experiments require unpaired electrons that are usually exogenous in samples via paramagnetic doping with polarizing agents. Thus, the resulting nuclear polarization mechanism depends on the electron and nuclear spin interactions induced by the paramagnetic species. The Overhauser Effect (OE) DNP, which relies on time-dependent spin-spin interactions, is excluded from our discussion due the lack of conducting electrons in frozen aqueous solutions containing biological entities. DNP of particular interest to us relies primarily on time-independent, spin-spin interactions for significant electron-nucleus polarization transfer through mechanisms such as the Solid Effect (SE), the Cross Effect (CE) or Thermal Mixing (TM), involving one, two or multiple electron spins, respectively. Derived from monomeric radicals initially used in high-field DNP experiments, bi- or multiple-radical polarizing agents facilitate CE/TM to generate significant NMR signal enhancements in dielectric solids at low temperatures (<100 K). For example, large DNP enhancements (∼300 times at 5 T) from a biologically compatible biradical, 1-(TEMPO-4-oxy)-3-(TEMPO-4-amino)propan-2-ol (TOTAPOL), have enabled high-resolution MAS NMR in sample systems existing in submicron domains or embedded in larger biomolecular complexes. The scope of this review is focused on recently developed DNP polarizing agents for high-field applications and leads up to future developments per the CE DNP mechanism. Because DNP experiments are feasible with a solid-state microwave source when performed at <20K, nuclear polarization using lower microwave power (<100 mW) is possible by forcing a high proportion of biradicals to

  16. Polarizing Agents and Mechanisms for High-Field Dynamic Nuclear Polarization of Frozen Dielectric Solids

    PubMed Central

    Hu, Kan-Nian

    2011-01-01

    This article provides an overview of polarizing mechanisms involved in high-frequency dynamic nuclear polarization (DNP) of frozen biological samples at temperatures maintained using liquid nitrogen, compatible with contemporary magic-angle spinning (MAS) nuclear magnetic resonance (NMR). Typical DNP experiments require unpaired electrons that are usually exogenous in samples via paramagnetic doping with polarizing agents. Thus, the resulting nuclear polarization mechanism depends on the electron and nuclear spin interactions induced by the paramagnetic species. The Overhauser Effect (OE) DNP, which relies on time-dependent spin-spin interactions, is excluded from our discussion due the lack of conducting electrons in frozen aqueous solutions containing biological entities. DNP of particular interest to us relies primarily on time-independent, spin interactions for significant electron-nucleus polarization transfer through mechanisms such as the Solid Effect (SE), the Cross Effect (CE) or Thermal Mixing (TM), involving one, two or multiple electron spins, respectively. Derived from monomeric radicals initially used in DNP experiments, bi- or multiple-radical polarizing agents facilitate CE/TM to generate significant NMR signal enhancements in dielectric solids at low temperatures (< 100 K). For example, large DNP enhancements (~300 times at 5 T) from a biologically compatible biradical, 1-(TEMPO-4-oxy)-3-(TEMPO-4-amino)propan-2-ol (TOTAPOL), have enabled high-resolution MAS NMR in sample systems existing in submicron domains or embedded in larger biomolecular complexes. The scope of this review is focused on recently developed DNP polarizing agents for high-field applications and leads up to future developments per the CE DNP mechanism. Because DNP experiments are feasible with a solid-state microwave source when performed at <20 K, nuclear polarization using lower microwave power (< 100 mW) is possible by forcing a high proportion of biradicals to fulfill the

  17. Shear strength characteristics of mechanically biologically treated municipal solid waste (MBT-MSW) from Bangalore

    SciTech Connect

    Sivakumar Babu, G.L.; Lakshmikanthan, P.; Santhosh, L.G.

    2015-05-15

    Highlights: • Shear strength properties of mechanically biologically treated municipal solid waste. • Effect of unit weight and particle size on the shear strength of waste. • Effect of particle size on the strength properties. • Stiffness ratio and the strength ratio of MSW. - Abstract: Strength and stiffness properties of municipal solid waste (MSW) are important in landfill design. This paper presents the results of comprehensive testing of shear strength properties of mechanically biologically treated municipal solid waste (MBT-MSW) in laboratory. Changes in shear strength of MSW as a function of unit weight and particle size were investigated by performing laboratory studies on the MSW collected from Mavallipura landfill site in Bangalore. Direct shear tests, small scale and large scale consolidated undrained and drained triaxial tests were conducted on reconstituted compost reject MSW samples. The triaxial test results showed that the MSW samples exhibited a strain-hardening behaviour and the strength of MSW increased with increase in unit weight. Consolidated drained tests showed that the mobilized shear strength of the MSW increased by 40% for a unit weight increase from 7.3 kN/m{sup 3} to 10.3 kN/m{sup 3} at 20% strain levels. The mobilized cohesion and friction angle ranged from 5 to 9 kPa and 8° to 33° corresponding to a strain level of 20%. The consolidated undrained tests exhibited reduced friction angle values compared to the consolidated drained tests. The friction angle increased with increase in the unit weight from 8° to 55° in the consolidated undrained tests. Minor variations were found in the cohesion values. Relationships for strength and stiffness of MSW in terms of strength and stiffness ratios are developed and discussed. The stiffness ratio and the strength ratio of MSW were found to be 10 and 0.43.

  18. Life Cycle Assessment of mechanical biological pre-treatment of Municipal Solid Waste: a case study.

    PubMed

    Beylot, Antoine; Vaxelaire, Stéphane; Zdanevitch, Isabelle; Auvinet, Nicolas; Villeneuve, Jacques

    2015-05-01

    The environmental performance of mechanical biological pre-treatment (MBT) of Municipal Solid Waste is quantified using Life Cycle Assessment (LCA), considering one of the 57 French plants currently in operation as a case study. The inventory is mostly based on plant-specific data, extrapolated from on-site measurements regarding mechanical and biological operations (including anaerobic digestion and composting of digestate). The combined treatment of 46,929 tonnes of residual Municipal Solid Waste and 12,158 tonnes of source-sorted biowaste (as treated in 2010 at the plant) generates 24,550 tonnes CO2-eq as an impact on climate change, 69,943kg SO2-eq on terrestrial acidification and 19,929kg NMVOC-eq on photochemical oxidant formation, in a life-cycle perspective. On the contrary MBT induces environmental benefits in terms of fossil resource depletion, human toxicity (carcinogenic) and ecotoxicity. The results firstly highlight the relatively large contribution of some pollutants, such as CH4, emitted at the plant and yet sometimes neglected in the LCA of waste MBT. Moreover this study identifies 4 plant-specific operation conditions which drive the environmental impact potentials induced by MBT: the conditions of degradation of the fermentable fraction, the collection of gaseous flows emitted from biological operations, the abatement of collected pollutants and NOx emissions from biogas combustion. Finally the results underline the relatively large influence of the operations downstream the plant (in particular residuals incineration) on the environmental performance of waste MBT. PMID:25708404

  19. Tribological and Mechanical Behaviors of Polyamide 6/Glass Fiber Composite Filled with Various Solid Lubricants

    PubMed Central

    Li, Duxin; Xie, Ying; Li, Wenjuan; You, Yilan; Deng, Xin

    2013-01-01

    The effects of polytetrafluoroethylene (PTFE), graphite, ultrahigh molecular weight polyethylene (UHMWPE), and their compounds on mechanical and tribological properties of glass-fiber-reinforced polyamide 6 (PA6/GF) were studied. The polymeric materials were blended using twin-screw extruder and subsequently injection molded for test samples. Mechanical properties were investigated in terms of hardness, tensile strength, and impact strength. Friction and wear experiments were run under ambient conditions at a rotating speed of 200 rpm and load of 100 N. The morphologies of the worn surfaces were also observed with scanning electron microscope. The results showed that graphite could increase the tensile strength of PA6/GF-15 composite, but the material became soft. Graphite/UHMWPE complex solid lubricants were effective in increasing the already high impact strength of PA6/GF-15 composite. 5% PTFE gave the maximum reduction in the coefficient of friction. However, PTFE/UHMWPE complex solid lubricants were the best choice for improving both friction and wear behaviors due to the lower friction coefficient and mass wear rate. Moreover, the worn surface of PA6 composites revealed that adhesive wear, abrasive wear, and fatigue wear occurred in this study. PMID:23766687

  20. An Overview of Combustion Mechanisms and Flame Structures for Advanced Solid Propellants

    NASA Technical Reports Server (NTRS)

    Beckstead, M. W.

    2000-01-01

    Ammonium perchlorate (AP) and cyclotretamethylenetetranitramine (HMX) are two solid ingredients often used in modern solid propellants. Although these two ingredients have very similar burning rates as monopropellants, they lead to significantly different characteristics when combined with binders to form propellants. Part of the purpose of this paper is to relate the observed combustion characteristics to the postulated flame structures and mechanisms for AP and HMX propellants that apparently lead to these similarities and differences. For AP composite, the primary diffusion flame is more energetic than the monopropellant flame, leading to an increase in burning rate over the monopropellant rate. In contrast the HMX primary diffusion flame is less energetic than the HMX monopropellant flame and ultimately leads to a propellant rate significantly less than the monopropellant rate in composite propellants. During the past decade the search for more energetic propellants and more environmentally acceptable propellants is leading to the development of propellants based on ingredients other than AP and HMX. The objective of this paper is to utilize the more familiar combustion characteristics of AP and HMX containing propellants to project the combustion characteristics of propellants made up of more advanced ingredients. The principal conclusion reached is that most advanced ingredients appear to burn by combustion mechanisms similar to HMX containing propellants rather than AP propellants.

  1. Tribological and mechanical behaviors of polyamide 6/glass fiber composite filled with various solid lubricants.

    PubMed

    Li, Duxin; Xie, Ying; Li, Wenjuan; You, Yilan; Deng, Xin

    2013-01-01

    The effects of polytetrafluoroethylene (PTFE), graphite, ultrahigh molecular weight polyethylene (UHMWPE), and their compounds on mechanical and tribological properties of glass-fiber-reinforced polyamide 6 (PA6/GF) were studied. The polymeric materials were blended using twin-screw extruder and subsequently injection molded for test samples. Mechanical properties were investigated in terms of hardness, tensile strength, and impact strength. Friction and wear experiments were run under ambient conditions at a rotating speed of 200 rpm and load of 100 N. The morphologies of the worn surfaces were also observed with scanning electron microscope. The results showed that graphite could increase the tensile strength of PA6/GF-15 composite, but the material became soft. Graphite/UHMWPE complex solid lubricants were effective in increasing the already high impact strength of PA6/GF-15 composite. 5% PTFE gave the maximum reduction in the coefficient of friction. However, PTFE/UHMWPE complex solid lubricants were the best choice for improving both friction and wear behaviors due to the lower friction coefficient and mass wear rate. Moreover, the worn surface of PA6 composites revealed that adhesive wear, abrasive wear, and fatigue wear occurred in this study. PMID:23766687

  2. Kinetics and mechanism of reaction between silver molybdate and mercuric iodide in solid state

    SciTech Connect

    Beg, M.A.; Rafiuddin

    1987-05-01

    The kinetics and the mechanism of the reaction between silver molybdate and mercuric iodide were studied in the solid state by X-ray, chemical analysis, and electrical conductivity measurements. This is a multistep reaction where Ag/sub 2/HgI/sub 4/ is formed as an intermediate. In an equimolar mixture of Ag/sub 2/MoO/sub 4/ and HgI/sub 2/, AgI an HgMoO/sub 4/ are formed, whereas in a 1:2 molar mixture Ag/sub 2/HgI/sub 4/ and HgMoO/sub 4/ are formed. The data for lateral diffusion best fit the equation X/sup n/ = kt, where X is the product thickness, t is time, and k and n are constants. This is a multistep solid state ionic reaction initiated by the diffusion of HgI/sub 2/ molecules as such and not through counterdiffusion of cations.

  3. Mechanically switchable solid inhomogeneous phantom for performance tests in diffuse imaging and spectroscopy.

    PubMed

    Pifferi, Antonio; Torricelli, Alessandro; Cubeddu, Rinaldo; Quarto, Giovanna; Re, Rebecca; Sekar, Sanathana K V; Spinelli, Lorenzo; Farina, Andrea; Martelli, Fabrizio; Wabnitz, Heidrun

    2015-12-01

    A mechanically switchable solid inhomogeneous phantom simulating localized absorption changes was developed and characterized. The homogeneous host phantom was made of epoxy resin with black toner and titanium dioxide particles added as absorbing and scattering components, respectively. A cylindrical rod, movable along a hole in the block and made of the same material, has a black polyvinyl chloride cylinder embedded in its center. By varying the volume and position of the black inclusion, absorption perturbations can be generated over a large range of magnitudes. The phantom has been characterized by various time-domain diffuse optics instruments in terms of absorption and scattering spectra, transmittance images, and reflectance contrast. Addressing a major application of the phantom for performance characterization for functional near-infrared spectroscopy of the brain, the contrast was measured in reflectance mode while black cylinders of volumes from ≈20  mm3 to ≈270  mm3 were moved in lateral and depth directions, respectively. The new type of solid inhomogeneous phantom is expected to become a useful tool for routine quality check of clinical instruments or implementation of industrial standards provided an experimental characterization of the phantom is performed in advance. PMID:26220211

  4. Mechanical Properties of Mg-Gd and Mg-Y Solid Solutions

    NASA Astrophysics Data System (ADS)

    Kula, Anna; Jia, Xiaohui; Mishra, Raj K.; Niewczas, Marek

    2015-12-01

    The mechanical properties of Mg-Gd and Mg-Y solid solutions have been studied under uniaxial tension and compression between 4 K and 298 K (-269 °C and 25 °C). The results reveal that Mg-Gd alloys exhibit higher strength and ductility under tension and compression attributed to the more effective solid solution strengthening and grain-boundary strengthening effects. Profuse twinning has been observed under compression, resulting in a material texture with strong dominance of basal component parallel to compression axis. Under tension, twining is less active and the texture evolution is controlled mostly by slip. The alloys exhibit pronounced yield stress asymmetry and significantly different work-hardening behavior under tension and compression. Increasing of Gd and/or Y concentration leads to the reduction of the tension-compression asymmetry due to the weakening of the recrystallization texture and more balanced twinning and slip activity during plastic deformation. The results suggest that under compression of Mg-Y alloys slip is more active than twinning in comparison to Mg-Gd alloys.

  5. Mechanically switchable solid inhomogeneous phantom for performance tests in diffuse imaging and spectroscopy

    NASA Astrophysics Data System (ADS)

    Pifferi, Antonio; Torricelli, Alessandro; Cubeddu, Rinaldo; Quarto, Giovanna; Re, Rebecca; Sekar, Sanathana K. V.; Spinelli, Lorenzo; Farina, Andrea; Martelli, Fabrizio; Wabnitz, Heidrun

    2015-12-01

    A mechanically switchable solid inhomogeneous phantom simulating localized absorption changes was developed and characterized. The homogeneous host phantom was made of epoxy resin with black toner and titanium dioxide particles added as absorbing and scattering components, respectively. A cylindrical rod, movable along a hole in the block and made of the same material, has a black polyvinyl chloride cylinder embedded in its center. By varying the volume and position of the black inclusion, absorption perturbations can be generated over a large range of magnitudes. The phantom has been characterized by various time-domain diffuse optics instruments in terms of absorption and scattering spectra, transmittance images, and reflectance contrast. Addressing a major application of the phantom for performance characterization for functional near-infrared spectroscopy of the brain, the contrast was measured in reflectance mode while black cylinders of volumes from ≈20 mm3 to ≈270 mm3 were moved in lateral and depth directions, respectively. The new type of solid inhomogeneous phantom is expected to become a useful tool for routine quality check of clinical instruments or implementation of industrial standards provided an experimental characterization of the phantom is performed in advance.

  6. Microstructural coarsening effects on redox instability and mechanical damage in solid oxide fuel cell anodes

    NASA Astrophysics Data System (ADS)

    Abdeljawad, F.; Haataja, M.

    2013-11-01

    In state-of-the-art high temperature solid oxide fuel cells (SOFCs), a porous composite of nickel and yttria stabilized zirconia (Ni/YSZ) is employed as the anode. The rapid oxidation of Ni into NiO is regarded as the main cause of the so-called reduction-oxidation (redox) instability in Ni/YSZ anodes, due to the presence of extensive bulk volume changes associated with this reaction. As a consequence, the development of internal stresses can lead to performance degradation and/or structural failure. In this study, we employ a recently developed continuum formalism to quantify the mechanical deformation behavior and evolution of internal stresses in Ni/YSZ porous anodes due to re-oxidation. In our approach, a local failure criterion is coupled to the continuum framework in order to account for the heterogeneous damage accumulation in the YSZ phase. The hallmark of our approach is the ability to track the spatial evolution of mechanical damage and capture the interaction of YSZ damaged regions with the local microstructure. Simulation results highlight the importance of the microstructure characterized by Ni to YSZ particle size ratio on the redox behavior and damage accumulation in as-synthesized SOFC anode systems. Moreover, a redox-strain-to-failure criterion is developed to quantify the degree by which coarsened anode microstructures become more susceptible to mechanical damage during re-oxidation.

  7. Solid lipid nanoparticles as nucleic acid delivery system: properties and molecular mechanisms.

    PubMed

    de Jesus, Marcelo B; Zuhorn, Inge S

    2015-03-10

    Solid lipid nanoparticles (SLNs) have been proposed in the 1990s as appropriate drug delivery systems, and ever since they have been applied in a wide variety of cosmetic and pharmaceutical applications. In addition, SLNs are considered suitable alternatives as carriers in gene delivery. Although important advances have been made in this particular field, fundamental knowledge of the underlying mechanisms of SLN-mediated gene delivery is conspicuously lacking, an imperative requirement in efforts aimed at further improving their efficiency. Here, we address recent advances in the use of SLNs as platform for delivery of nucleic acids as therapeutic agents. In addition, we will discuss available technology for conveniently producing SLNs. In particular, we will focus on underlying molecular mechanisms by which SLNs and nucleic acids assemble into complexes and how the nucleic acid cargo may be released intracellularly. In discussing underlying mechanisms, we will, when appropriate, refer to analogous studies carried out with systems based on cationic lipids and polymers, that have proven useful in the assessment of structure-function relationships. Finally, we will give suggestions for improving SLN-based gene delivery systems, by pointing to alternative methods for SLNplex assembly, focusing on the realization of a sustained nucleic acid release. PMID:25578828

  8. Mechanical properties of solid oxide fuel cell glass-ceramic seal at high temperatures

    SciTech Connect

    Milhans, Jacqueline; Li, Dongsheng; Khaleel, Mohammad A.; Sun, Xin; Al-Haik, Marwan; Harris, Adrian; Garmestani, Hamid

    2011-04-20

    Mechanical properties of solid oxide fuel cell glass-ceramic seal material, G18, are studied at high temperatures. Samples of G18 are aged for either 4h or 100h, resulting in samples with different crystallinity. Reduced modulus, hardness, and time-dependent behavior are measured by nanoindentation. The nanoindentation is performed at room temperature, 550, 650, and 750°C, using loading rates of 5 mN/s and 25 mN/s. Results show a decrease in reduced modulus with increasing temperature, with significant decrease above the glass transition temperature (Tg). Hardness generally decreases with increasing temperature, with a slight increase before Tg for the 4h aged sample. Dwell tests show that creep increases with increasing temperature, but decrease with further aging.

  9. Atomistic-continuum coupling for solid mechanics enforcing momentum balance and continuity

    NASA Astrophysics Data System (ADS)

    Kraczek, B.; Johnson, D. D.; Xia, C.; Haber, R. B.

    2004-03-01

    We investigate an atomistic-continuum coupling strategy for solid mechanics based on the theoretical framework of Spacetime Discontinuous Galerkin (SDG) finite element methods. SDG methods weakly enforce momentum balance and continuity over computational cells that directly discretize a spacetime analysis domain. The explicit incorporation of spacetime momentum flux within this formulation supports a straightforward exchange of stress and force between the continuum and atomistic regions with no ad hoc coupling assumptions. We employ a simple MD model for the atomistics and only consider problems in 1d øtimes time. However, this coupling strategy should be applicable to other O(N) atomistic methods and extensible to higher spatial dimensions. We focus on the effects of continuum basis truncation and unresolved length-scales in the present investigation.

  10. Broad compositional tunability of indium tin oxide nanowires grown by the vapor-liquid-solid mechanism

    SciTech Connect

    Zervos, M. Giapintzakis, J.; Mihailescu, C. N.; Luculescu, C. R.; Florini, N.; Komninou, Ph.; Kioseoglou, J.; Othonos, A.

    2014-05-01

    Indium tin oxide nanowires were grown by the reaction of In and Sn with O{sub 2} at 800 °C via the vapor-liquid-solid mechanism on 1 nm Au/Si(001). We obtain Sn doped In{sub 2}O{sub 3} nanowires having a cubic bixbyite crystal structure by using In:Sn source weight ratios > 1:9 while below this we observe the emergence of tetragonal rutile SnO{sub 2} and suppression of In{sub 2}O{sub 3} permitting compositional and structural tuning from SnO{sub 2} to In{sub 2}O{sub 3} which is accompanied by a blue shift of the photoluminescence spectrum and increase in carrier lifetime attributed to a higher crystal quality and Fermi level position.

  11. Excited-state absorption of pump radiation as a loss mechanism in solid-state lasers

    SciTech Connect

    Kliewer, M.L.; Powell, R.C.

    1989-08-01

    The characteristics of optical pumping dynamics occuring in laser-pumped rare earth-doped, solid-state laser materials were investigated by using a tunable alexandrite laser to pump Y3Al5O12:Nd(3+) in an optical cavity. It was found that the slope efficiency of the Nd laser operation depends strongly on the wavelength of the pump laser. For pump wavelength resulting in low slope efficiencies, intense fluorescence emission is observed form the sample in the blue-green spectral region. This is attributed to the excited state absorption of pump photons which occurs during radiationless relaxation from the pump band to the metastable state. This type of process will be an important loss mechanism for monochromatic pumping of laser systems at specific pump wavelengths.

  12. Excited state absorption of pump radiation as a loss mechanism in solid-state lasers

    NASA Technical Reports Server (NTRS)

    Kliewer, Michael L.; Powell, Richard C.

    1989-01-01

    The characteristics of optical pumping dynamics in laser-pumped, rare-earth-doped, solid-state laser materials are investigated by using a tunable alexandrite laser to pump Y3Al5O12:Nd(3+) in an optical cavity. It is found that the slope efficiency of the Nd laser operation depends strongly on the wavelength of the pump laser. For pump wavelengths resulting in low slope efficiencies, intense fluorescence emission is observed from the sample in the blue-green spectral region. This is attributed to the excited-state absorption of pump photons which occurs during radiationless relaxation from the pump band to the metastable state. This type of process is an important loss mechanism for monochromatic pumping of laser systems at specific pump wavelengths.

  13. Excited state absorption of pump radiation as a loss mechanism in solid-state lasers

    SciTech Connect

    Kliewer, M.L.; Powell, R.C.

    1989-08-01

    The characteristics of optical pumping dynamics occurring in laser-pumped rare earth-doped, solid-state laser materials were investigated by using a tunable alexandrite laser to pump Y/sub 3/Al/sub 5/O/sub 12/:Nd/sup 3+/ in an optical cavity. It was found that the slope efficiency of the Nd laser operation depends strongly on the wavelength of the pump laser. For pump wavelengths resulting in low slope efficiencies, intense fluorescence emission is observed from the sample in the blue-green spectral region. This is attributed to the excited state absorption of pump photons which occurs during radiationless relaxation from the pump band to the metastable state. This type of process will be an important loss mechanism for monochromatic pumping of laser systems at specific pump wavelengths.

  14. Probabilistic fracture mechanics and optimum fracture control of the solid rocket motor case of the shuttle

    NASA Technical Reports Server (NTRS)

    Hanagud, S.; Uppaluri, B.

    1977-01-01

    Development of a procedure for the reliability analysis of the solid rocket motor case of the space shuttle is described. The analysis is based on probabilistic fracture mechanics and consideration of a probability distribution for the initial flaw sizes. The reliability analysis can be used to select design variables, such as the thickness of the SRM case, projected design life and proof factor, on the basis of minimum expected cost and specified reliability bounds. Effects of fracture control plans such as the non-destructive inspections and the material erosion between missions can also be considered in the developed methodology for selection of design variables. The reliability-based procedure can be easily modified to consider other similar structures and different fracture control plans.

  15. Solid electrically tunable dual-focus lens using freeform surfaces and microelectro-mechanical-systems actuator.

    PubMed

    Zou, Yongchao; Zhang, Wei; Chau, Fook Siong; Zhou, Guangya

    2016-01-01

    In this Letter, a miniature solid tunable dual-focus (DF) lens, which is designed using freeform optical surfaces and driven by one microelectro-mechanical-systems rotary actuator, is reported. Such a lens consists of two optical elements, each having a flat surface and one freeform surface optimized by ray-tracing technology. By changing the relative rotation angle of the two lens elements, the lens configuration can form double foci with corresponding focal lengths varied simultaneously, resulting in a tunable DF effect. Results show that one of the focal lengths is tuned from about 30 to 20 mm, while the other one is varied from about 30 to 60 mm, with a maximum rotation angle of about 8.2 deg. PMID:26696143

  16. Thermal chemical-mechanical reactive flow model of shock initiation in solid explosives

    SciTech Connect

    Nicholls, A L., III; Tarver, C M

    1998-08-26

    The three dimensional Arbitrary Lagrange Eulerian hydrodynamic computer code ALE3D with fully coupled thermal-chemical-mechanical material models provides the framework for the development of a physically realistic model of shock initiation and detonation of solid explosives. The processes of hot spot formation during shock compression, subsequent ignition of reaction or failure to react, growth of reaction in individual hot spots, and coalescence of reacting hot spots during the transition to detonation can now be modeled using Arrhenius chemical kinetic rate laws and heat transfer to propagate the reactive flow. This paper discusses the growth rates of reacting hot spots in HMX and TATB and their coalescence during shock to detonation transition. Hot spot deflagration rates are found to be fast enough to consume explosive particles less than 10 mm in diameter during typical shock duration times, but larger particles must fragment and create more reactive surface area in order to be rapidly consumed.

  17. SOLID OXIDE FUEL CELL CATHODES: Polarization Mechanisms and Modeling of the Electrochemical Performance

    NASA Astrophysics Data System (ADS)

    Fleig, Jurgen

    2003-08-01

    Several recent experimental and numerical investigations have contributed to the improved understanding of the electrochemical mechanisms taking place at solid oxide fuel cell (SOFC) cathodes and yielded valuable information on the relationships between alterable parameters (geometry/material) and the cathodic polarization resistance. Efforts to reduce the polarization resistance in SOFCs can benefit from these results, and some important aspects of the corresponding studies are reviewed. Experimental results, particularly measurements using geometrically well-defined Sr-doped LaMnO3 (LSM) cathodes, are discussed. In regard to simulations, the different levels of sophistication used in SOFC electrode modeling studies are summarized and compared. Exemplary simulations of mixed conducting cathodes that show the capabilities and limits of different modeling levels are described.

  18. Third-order thermo-mechanical properties for packs of Platonic solids using statistical micromechanics

    PubMed Central

    Gillman, A.; Amadio, G.; Matouš, K.; Jackson, T. L.

    2015-01-01

    Obtaining an accurate higher order statistical description of heterogeneous materials and using this information to predict effective material behaviour with high fidelity has remained an outstanding problem for many years. In a recent letter, Gillman & Matouš (2014 Phys. Lett. A 378, 3070–3073. ()) accurately evaluated the three-point microstructural parameter that arises in third-order theories and predicted with high accuracy the effective thermal conductivity of highly packed material systems. Expanding this work here, we predict for the first time effective thermo-mechanical properties of granular Platonic solid packs using third-order statistical micromechanics. Systems of impenetrable and penetrable spheres are considered to verify adaptive methods for computing n-point probability functions directly from three-dimensional microstructures, and excellent agreement is shown with simulation. Moreover, a significant shape effect is discovered for the effective thermal conductivity of highly packed composites, whereas a moderate shape effect is exhibited for the elastic constants. PMID:27547103

  19. Intermetallic Compound Formation Mechanisms for Cu-Sn Solid-Liquid Interdiffusion Bonding

    NASA Astrophysics Data System (ADS)

    Liu, H.; Wang, K.; Aasmundtveit, K. E.; Hoivik, N.

    2012-09-01

    Cu-Sn solid-liquid interdiffusion (SLID) bonding is an evolving technique for wafer-level packaging which features robust, fine pitch and high temperature tolerance. The mechanisms of Cu-Sn SLID bonding for wafer-level bonding and three-dimensional (3-D) packaging applications have been studied by analyzing the microstructure evolution of Cu-Sn intermetallic compounds (IMCs) at elevated temperature up to 400°C. The bonding time required to achieve a single IMC phase (Cu3Sn) in the final interconnects was estimated according to the parabolic growth law with consideration of defect-induced deviation. The effect of predominantly Cu metal grain size on the Cu-Sn interdiffusion rate is discussed. The temperature versus time profile (ramp rate) is critical to control the morphology of scallops in the IMC. A low temperature ramp rate before reaching the bonding temperature is believed to be favorable in a SLID wafer-level bonding process.

  20. Reciprocated suppression of polymer crystallization toward improved solid polymer electrolytes: Higher ion conductivity and tunable mechanical properties

    SciTech Connect

    Bi, Sheng; Sun, Che-Nan; Zawodzinski, Thomas A.; Ren, Fei; Keum, Jong Kahk; Ahn, Suk-Kyun; Li, Dawen; Chen, Jihua

    2015-08-06

    Solid polymer electrolytes based on lithium bis(trifluoromethanesulfonyl) imide and polymer matrix were extensively studied in the past due to their excellent potential in a broad range of energy related applications. Poly(vinylidene fluoride) (PVDF) and polyethylene oxide (PEO) are among the most examined polymer candidates as solid polymer electrolyte matrix. In this paper, we study the effect of reciprocated suppression of polymer crystallization in PVDF/PEO binary matrix on ion transport and mechanical properties of the resultant solid polymer electrolytes. With electron and X-ray diffractions as well as energy filtered transmission electron microscopy, we identify and examine the appropriate blending composition that is responsible for the diminishment of both PVDF and PEO crystallites. Laslty, a three-fold conductivity enhancement is achieved along with a highly tunable elastic modulus ranging from 20 to 200 MPa, which is expected to contribute toward future designs of solid polymer electrolytes with high room-temperature ion conductivities and mechanical flexibility.

  1. Temperature Dependence of the Mechanical Properties of Equiatomic Solid Solution Alloys with FCC Crystal Structures

    SciTech Connect

    Wu, Zhenggang; Bei, Hongbin; Pharr, George M.; George, Easo P.

    2014-10-03

    We found that compared to decades-old theories of strengthening in dilute solid solutions, the mechanical behavior of concentrated solid solutions is relatively poorly understood. A special subset of these materials includes alloys in which the constituent elements are present in equal atomic proportions, including the high-entropy alloys of recent interest. A unique characteristic of equiatomic alloys is the absence of “solvent” and “solute” atoms, resulting in a breakdown of the textbook picture of dislocations moving through a solvent lattice and encountering discrete solute obstacles. Likewise, to clarify the mechanical behavior of this interesting new class of materials, we investigate here a family of equiatomic binary, ternary and quaternary alloys based on the elements Fe, Ni, Co, Cr and Mn that were previously shown to be single-phase face-centered cubic (fcc) solid solutions. The alloys were arc-melted, drop-cast, homogenized, cold-rolled and recrystallized to produce equiaxed microstructures with comparable grain sizes. Tensile tests were performed at an engineering strain rate of 10-3 s-1 at temperatures in the range 77–673 K. Unalloyed fcc Ni was processed similarly and tested for comparison. The flow stresses depend to varying degrees on temperature, with some (e.g. NiCoCr, NiCoCrMn and FeNiCoCr) exhibiting yield and ultimate strengths that increase strongly with decreasing temperature, while others (e.g. NiCo and Ni) exhibit very weak temperature dependencies. Moreover, to better understand this behavior, the temperature dependencies of the yield strength and strain hardening were analyzed separately. Lattice friction appears to be the predominant component of the temperature-dependent yield stress, possibly because the Peierls barrier height decreases with increasing temperature due to a thermally induced increase of dislocation width. In the early stages of plastic flow (5–13% strain, depending on material), the

  2. Temperature Dependence of the Mechanical Properties of Equiatomic Solid Solution Alloys with FCC Crystal Structures

    DOE PAGESBeta

    Wu, Zhenggang; Bei, Hongbin; Pharr, George M.; George, Easo P.

    2014-10-03

    We found that compared to decades-old theories of strengthening in dilute solid solutions, the mechanical behavior of concentrated solid solutions is relatively poorly understood. A special subset of these materials includes alloys in which the constituent elements are present in equal atomic proportions, including the high-entropy alloys of recent interest. A unique characteristic of equiatomic alloys is the absence of “solvent” and “solute” atoms, resulting in a breakdown of the textbook picture of dislocations moving through a solvent lattice and encountering discrete solute obstacles. Likewise, to clarify the mechanical behavior of this interesting new class of materials, we investigate heremore » a family of equiatomic binary, ternary and quaternary alloys based on the elements Fe, Ni, Co, Cr and Mn that were previously shown to be single-phase face-centered cubic (fcc) solid solutions. The alloys were arc-melted, drop-cast, homogenized, cold-rolled and recrystallized to produce equiaxed microstructures with comparable grain sizes. Tensile tests were performed at an engineering strain rate of 10-3 s-1 at temperatures in the range 77–673 K. Unalloyed fcc Ni was processed similarly and tested for comparison. The flow stresses depend to varying degrees on temperature, with some (e.g. NiCoCr, NiCoCrMn and FeNiCoCr) exhibiting yield and ultimate strengths that increase strongly with decreasing temperature, while others (e.g. NiCo and Ni) exhibit very weak temperature dependencies. Moreover, to better understand this behavior, the temperature dependencies of the yield strength and strain hardening were analyzed separately. Lattice friction appears to be the predominant component of the temperature-dependent yield stress, possibly because the Peierls barrier height decreases with increasing temperature due to a thermally induced increase of dislocation width. In the early stages of plastic flow (5–13% strain, depending on material), the temperature

  3. In-drop capillary spooling of spider capture thread inspires hybrid fibers with mixed solid-liquid mechanical properties.

    PubMed

    Elettro, Hervé; Neukirch, Sébastien; Vollrath, Fritz; Antkowiak, Arnaud

    2016-05-31

    An essential element in the web-trap architecture, the capture silk spun by ecribellate orb spiders consists of glue droplets sitting astride a silk filament. Mechanically this thread presents a mixed solid-liquid behavior unknown to date. Under extension, capture silk behaves as a particularly stretchy solid, owing to its molecular nanosprings, but it totally switches behavior in compression to now become liquid-like: It shrinks with no apparent limit while exerting a constant tension. Here, we unravel the physics underpinning the unique behavior of this "liquid wire" and demonstrate that its mechanical response originates in the shape-switching of the silk filament induced by buckling within the droplets. Learning from this natural example of geometry and mechanics, we manufactured programmable liquid wires that present previously unidentified pathways for the design of new hybrid solid-liquid materials. PMID:27185930

  4. Aggrecan nanoscale solid-fluid interactions are a primary determinant of cartilage dynamic mechanical properties.

    PubMed

    Nia, Hadi Tavakoli; Han, Lin; Bozchalooi, Iman Soltani; Roughley, Peter; Youcef-Toumi, Kamal; Grodzinsky, Alan J; Ortiz, Christine

    2015-03-24

    Poroelastic interactions between interstitial fluid and the extracellular matrix of connective tissues are critical to biological and pathophysiological functions involving solute transport, energy dissipation, self-stiffening and lubrication. However, the molecular origins of poroelasticity at the nanoscale are largely unknown. Here, the broad-spectrum dynamic nanomechanical behavior of cartilage aggrecan monolayer is revealed for the first time, including the equilibrium and instantaneous moduli and the peak in the phase angle of the complex modulus. By performing a length scale study and comparing the experimental results to theoretical predictions, we confirm that the mechanism underlying the observed dynamic nanomechanics is due to solid-fluid interactions (poroelasticity) at the molecular scale. Utilizing finite element modeling, the molecular-scale hydraulic permeability of the aggrecan assembly was quantified (kaggrecan = (4.8 ± 2.8) × 10(-15) m(4)/N·s) and found to be similar to the nanoscale hydraulic permeability of intact normal cartilage tissue but much lower than that of early diseased tissue. The mechanisms underlying aggrecan poroelasticity were further investigated by altering electrostatic interactions between the molecule's constituent glycosaminoglycan chains: electrostatic interactions dominated steric interactions in governing molecular behavior. While the hydraulic permeability of aggrecan layers does not change across species and age, aggrecan from adult human cartilage is stiffer than the aggrecan from newborn human tissue. PMID:25758717

  5. Overlapping solid solubility in mechanically alloyed Fe-Ni and Fe-Cu

    NASA Astrophysics Data System (ADS)

    Schilling, P. J.; Palshin, V.; Tittsworth, R. C.; He, J. H.; Ma, E.

    2003-12-01

    Solid solutions formed by mechanical alloying in the negative heat of mixing Fe-Ni system and the positive heat of mixing Fe-Cu system were studied. X-ray absorption near edge structure (XANES) spectroscopy data were analyzed to obtain the phase fractions and phase compositions for various overall compositions across the bcc/fcc two-phase region. For both systems, at each nominal composition of the powder mixture, the two solutions formed both have the same composition as the overall alloy. It is concluded that the two-phase coexistence represents an extended region of overlapping solubility for the two phases, rather than the usual two-phase region or a clear switchover at the concentration where the two phases have the same free energy. In terms of these features, the two binary systems, one with negative heat of mixing and one with positive heat of mixing, behave the same way. The external forcing action of mechanical alloying at low temperatures drives the system toward composition homogenization. There is no stable or metastable equilibrium, and the common tangent construction and lever rule are not applicable. What results is a novel two-phase coexistence which is defined by a region of overlapping solubility, rather than the normal solubility gap. That there can be two polymorphs at each composition even after the long ball-milling treatment represents a new type of steady-state two-phase coexistence that is completely different from the normal two-phase region dictated by thermodynamics.

  6. Characterization of compost-like outputs from mechanical biological treatment of municipal solid waste.

    PubMed

    Donovan, Sally M; Bateson, Thomas; Gronow, Jan R; Voulvoulis, Nikolaos

    2010-06-01

    Throughout the world, most municipal solid waste consists of biodegradable components. The most abundant biological component is cellulose, followed by hemicellulose and lignin. Recycling of these components is important for the carbon cycle. In an attempt to reduce the environmental impacts of biodegradable wastes, mechanical biological treatments (MBTs) are being used as a waste management process in many countries. MBT plants attempt to mechanically separate the biodegradable and nonbiodegradable components. The nonbiodegradable components are then sent for reprocessing or landfilled, whereas the biodegradable components are reduced in biological content through composting or anaerobic digestion, leaving a compost-like output (CLO). The further use of these partially degraded residues is uncertain, and in many cases it is likely that they will be landfilled. The implications of this for the future of landfill management are causing some concern because there is little evidence that the long-term emissions tail will be reduced. In this study, the CLOs from four different biological treatment processes were characterized for physical contamination through visual inspection and for biological content using a sequential digestion analysis. The results indicate that the composition of the incoming waste, dependent on the way the waste was collected/segregated, was the factor that influenced biological content most, with length of treatment process the second most important. PMID:20564995

  7. Joining technologies for the 1990s: Welding, brazing, soldering, mechanical, explosive, solid-state, adhesive

    NASA Technical Reports Server (NTRS)

    Buckley, John D. (Editor); Stein, Bland A. (Editor)

    1986-01-01

    A compilation of papers presented in a joint NASA, American Society for Metals, The George Washington University, American Welding Society, and Society of Manufacturing Engineers Conference on Welding, Bonding, and Fastening at Langley Research Center, Hampton, VA, on October 23 to 25, 1984 is given. Papers were presented on technology developed in current research programs relevant to welding, bonding, and fastening of structural materials required in fabricating structures and mechanical systems used in the aerospace, hydrospace, and automotive industries. Topics covered in the conference included equipment, hardware and materials used when welding, brazing, and soldering, mechanical fastening, explosive welding, use of unique selected joining techniques, adhesives bonding, and nondestructive evaluation. A concept of the factory of the future was presented, followed by advanced welding techniques, automated equipment for welding, welding in a cryogenic atmosphere, blind fastening, stress corrosion resistant fasteners, fastening equipment, explosive welding of different configurations and materials, solid-state bonding, electron beam welding, new adhesives, effects of cryogenics on adhesives, and new techniques and equipment for adhesive bonding.

  8. Solid-state and mechanical properties of aqueous chitosan-amylose starch films plasticized with polyols.

    PubMed

    Cervera, Mirna Fernández; Heinämäki, Jyrki; Krogars, Karin; Jörgensen, Anna C; Karjalainen, Milja; Colarte, Antonio Iraizoz; Yliruusi, Jouko

    2004-03-01

    The film-forming ability of chitosan and binary mixtures of chitosan and native amylose corn starch (Hylon VII) was evaluated with free films prepared by a casting/solvent evaporation method. Unplasticized and plasticized free chitosan films in aqueous acetic acid and respective films containing a mixture of chitosan and native amylose starch in acetic acid were prepared. Glycerol, sorbitol, and i-erythritol were used as plasticizers. Solid-state and mechanical properties of the films were studied by powder x-ray diffractometry (XPRD), differential scanning calorimetry (DSC), and a materials testing machine. The films composed of a mixture of chitosan and native amylose starch in acetic acid were clear and colorless. A plasticizer concentration of 20% wt/wt (of the polymer weight) was sufficient to obtain flexible films with all samples tested. X-ray diffraction patterns and DSC thermograms indicated an amorphous state of the films independent of the type of plasticizer used. In conclusion, incorporation of native amylose corn starch into chitosan films improves the consistency and the mechanical properties of the films. PMID:15198536

  9. Solid-state synthesis and mechanical unfolding of polymers of T4 lysozyme.

    PubMed

    Yang, G; Cecconi, C; Baase, W A; Vetter, I R; Breyer, W A; Haack, J A; Matthews, B W; Dahlquist, F W; Bustamante, C

    2000-01-01

    Recent advances in single molecule manipulation methods offer a novel approach to investigating the protein folding problem. These studies usually are done on molecules that are naturally organized as linear arrays of globular domains. To extend these techniques to study proteins that normally exist as monomers, we have developed a method of synthesizing polymers of protein molecules in the solid state. By introducing cysteines at locations where bacteriophage T4 lysozyme molecules contact each other in a crystal and taking advantage of the alignment provided by the lattice, we have obtained polymers of defined polarity up to 25 molecules long that retain enzymatic activity. These polymers then were manipulated mechanically by using a modified scanning force microscope to characterize the force-induced reversible unfolding of the individual lysozyme molecules. This approach should be general and adaptable to many other proteins with known crystal structures. For T4 lysozyme, the force required to unfold the monomers was 64 +/- 16 pN at the pulling speed used. Refolding occurred within 1 sec of relaxation with an efficiency close to 100%. Analysis of the force versus extension curves suggests that the mechanical unfolding transition follows a two-state model. The unfolding forces determined in 1 M guanidine hydrochloride indicate that in these conditions the activation barrier for unfolding is reduced by 2 kcal/mol. PMID:10618384

  10. Organic fraction of municipal solid waste from mechanical selection: biological stabilization and recovery options.

    PubMed

    Cesaro, Alessandra; Russo, Lara; Farina, Anna; Belgiorno, Vincenzo

    2016-01-01

    Although current trends address towards prevention strategies, the organic fraction of municipal solid waste is greatly produced, especially in high-income contexts. Its recovery-oriented collection is a common practice, but a relevant portion of the biodegradable waste is not source selected. Mechanical and biological treatments (MBT) are the most common option to sort and stabilize the biodegradable matter ending in residual waste stream. Following the changes of the framework around waste management, this paper aimed at analyzing the quality of the mechanically selected organic waste produced in MBT plants, in order to discuss its recovery options. The material performance was obtained by its composition as well as by its main chemical and physical parameters; biological stability was also assessed by both aerobic and anaerobic methods. On this basis, the effectiveness of an aerobic biostabilization process was assessed at pilot scale. After 21 days of treatment, results proved that the biomass had reached an acceptable biostabilization level, with a potential Dynamic Respirometric Index (DRIP) value lower than the limit required for its use as daily or final landfill cover material. However, the final stabilization level was seen to be influenced by scaling factors and the 21 days of treatment turned to be not so adequate when applied in the existing full-scale facility. PMID:26377969

  11. Chromium vaporization from mechanically deformed pre-coated interconnects in Solid Oxide Fuel Cells

    NASA Astrophysics Data System (ADS)

    Falk-Windisch, Hannes; Sattari, Mohammad; Svensson, Jan-Erik; Froitzheim, Jan

    2015-11-01

    Cathode poisoning, associated with Cr evaporation from interconnect material, is one of the most important degradation mechanisms in Solid Oxide Fuel Cells when Cr2O3-forming steels are used as the interconnect material. Coating these steels with a thin Co layer has proven to decrease Cr vaporization. To reduce production costs, it is suggested that thin metallic PVD coatings be applied to each steel strip before pressing the material into interconnect shape. This process would enable high volume production without the need for an extra post-coating step. However, when the pre-coated material is mechanically deformed, cracks may form and lower the quality of the coating. In the present study, Chromium volatilization is measured in an air-3% H2O environment at 850 °C for 336 h. Three materials coated with 600 nm Co are investigated and compared to an uncoated material. The effect of deformation is investigated on real interconnects. Microscopy observations reveal the presence of cracks in the order of several μm on the deformed pre-coated steel. However, upon exposure, the cracks can heal and form a continuous surface oxide rich in Co and Mn. As an effect of the rapid healing, no increase in Cr vaporization is measured for the pre-coated material.

  12. Extracting material response from simple mechanical tests on hardening-softening-hardening viscoplastic solids

    NASA Astrophysics Data System (ADS)

    Mohan, Nisha

    Compliant foams are usually characterized by a wide range of desirable mechanical properties. These properties include viscoelasticity at different temperatures, energy absorption, recoverability under cyclic loading, impact resistance, and thermal, electrical, acoustic and radiation-resistance. Some foams contain nano-sized features and are used in small-scale devices. This implies that the characteristic dimensions of foams span multiple length scales, rendering modeling their mechanical properties difficult. Continuum mechanics-based models capture some salient experimental features like the linear elastic regime, followed by non-linear plateau stress regime. However, they lack mesostructural physical details. This makes them incapable of accurately predicting local peaks in stress and strain distributions, which significantly affect the deformation paths. Atomistic methods are capable of capturing the physical origins of deformation at smaller scales, but suffer from impractical computational intensity. Capturing deformation at the so-called meso-scale, which is capable of describing the phenomenon at a continuum level, but with some physical insights, requires developing new theoretical approaches. A fundamental question that motivates the modeling of foams is `how to extract the intrinsic material response from simple mechanical test data, such as stress vs. strain response?' A 3D model was developed to simulate the mechanical response of foam-type materials. The novelty of this model includes unique features such as the hardening-softening-hardening material response, strain rate-dependence, and plastically compressible solids with plastic non-normality. Suggestive links from atomistic simulations of foams were borrowed to formulate a physically informed hardening material input function. Motivated by a model that qualitatively captured the response of foam-type vertically aligned carbon nanotube (VACNT) pillars under uniaxial compression [2011,"Analysis of

  13. Shear strength characteristics of mechanically biologically treated municipal solid waste (MBT-MSW) from Bangalore.

    PubMed

    Sivakumar Babu, G L; Lakshmikanthan, P; Santhosh, L G

    2015-05-01

    Strength and stiffness properties of municipal solid waste (MSW) are important in landfill design. This paper presents the results of comprehensive testing of shear strength properties of mechanically biologically treated municipal solid waste (MBT-MSW) in laboratory. Changes in shear strength of MSW as a function of unit weight and particle size were investigated by performing laboratory studies on the MSW collected from Mavallipura landfill site in Bangalore. Direct shear tests, small scale and large scale consolidated undrained and drained triaxial tests were conducted on reconstituted compost reject MSW samples. The triaxial test results showed that the MSW samples exhibited a strain-hardening behaviour and the strength of MSW increased with increase in unit weight. Consolidated drained tests showed that the mobilized shear strength of the MSW increased by 40% for a unit weight increase from 7.3kN/m(3) to 10.3kN/m(3) at 20% strain levels. The mobilized cohesion and friction angle ranged from 5 to 9kPa and 8° to 33° corresponding to a strain level of 20%. The consolidated undrained tests exhibited reduced friction angle values compared to the consolidated drained tests. The friction angle increased with increase in the unit weight from 8° to 55° in the consolidated undrained tests. Minor variations were found in the cohesion values. Relationships for strength and stiffness of MSW in terms of strength and stiffness ratios are developed and discussed. The stiffness ratio and the strength ratio of MSW were found to be 10 and 0.43. PMID:25746176

  14. Theoretical study of β-HMX decomposition mechanism of the solid phase under shock loadings

    NASA Astrophysics Data System (ADS)

    Ji, Guangfu; Ge, Nina; Chen, Xiangrong

    2015-06-01

    Study material properties under extreme conditions is a fundamental problem in the field of condensed matter physics. The decomposition mechanisms of energetic materials under the shock wave become a hot topic in recent years. In this paper, molecular dynamics simulations combined with multi-scale shock technology (MSST) are used to study the decomposition mechanism, shock sensitivity and electronic structure of β-HMX. First, the decomposition mechanism of β-HMX perfect crystal were studied at different shock speeds. We found that when the shock wave at a speed 8 km / s is loaded, the decomposition reaction start at N-NO2 bond breakage; when the shock wave at a speed of 10 km / s and 11 km / s is loaded, the the first decomposition reaction is CH bond breaking, and accompanied by the formation of five-membered ring and transfer of hydrogen ions. The simulation results also show that when the shock wave velocity is increased, the higher the pressure generated in the high-pressure N-NO2 bond cleavage was inhibited significantly. Secondly, the impact of its initial chemical reaction process along different crystal axis directions were studied, the results showed that along the a-axis and c-axis shock sensitivity is higher, and along the b-axis sensitivity is lower. We believe that the system of all sensitivity of direction is due to the rotation of the friction between the slip plane of crystals and molecules. Finally, we discussed the solid phase β-HMX electronic properties change under the shock wave loadings. We found that in the 11 km/s under the impact load, when the pressure reaches 130 GPa, zero bandgap is reached.

  15. Oxygen transport in perovskite-type solid oxide fuel cell materials: insights from quantum mechanics.

    PubMed

    Muñoz-García, Ana B; Ritzmann, Andrew M; Pavone, Michele; Keith, John A; Carter, Emily A

    2014-11-18

    CONSPECTUS: Global advances in industrialization are precipitating increasingly rapid consumption of fossil fuel resources and heightened levels of atmospheric CO2. World sustainability requires viable sources of renewable energy and its efficient use. First-principles quantum mechanics (QM) studies can help guide developments in energy technologies by characterizing complex material properties and predicting reaction mechanisms at the atomic scale. QM can provide unbiased, qualitative guidelines for experimentally tailoring materials for energy applications. This Account primarily reviews our recent QM studies of electrode materials for solid oxide fuel cells (SOFCs), a promising technology for clean, efficient power generation. SOFCs presently must operate at very high temperatures to allow transport of oxygen ions and electrons through solid-state electrolytes and electrodes. High temperatures, however, engender slow startup times and accelerate material degradation. SOFC technologies need cathode and anode materials that function well at lower temperatures, which have been realized with mixed ion-electron conductor (MIEC) materials. Unfortunately, the complexity of MIECs has inhibited the rational tailoring of improved SOFC materials. Here, we gather theoretically obtained insights into oxygen ion conductivity in two classes of perovskite-type materials for SOFC applications: the conventional La1-xSrxMO3 family (M = Cr, Mn, Fe, Co) and the new, promising class of Sr2Fe2-xMoxO6 materials. Using density functional theory + U (DFT+U) with U-J values obtained from ab initio theory, we have characterized the accompanying electronic structures for the two processes that govern ionic diffusion in these materials: (i) oxygen vacancy formation and (ii) vacancy-mediated oxygen migration. We show how the corresponding macroscopic oxygen diffusion coefficient can be accurately obtained in terms of microscopic quantities calculated with first-principles QM. We find that the

  16. Diabatic Mechanisms of Higher-Order Harmonic Generation in Solid-State Materials under High-Intensity Electric Fields

    NASA Astrophysics Data System (ADS)

    Tamaya, T.; Ishikawa, A.; Ogawa, T.; Tanaka, K.

    2016-01-01

    We theoretically investigate mechanisms of higher-order harmonic generation in solid-state materials under a high-intensity ac electric field. A new theoretical framework presented in this Letter holds the legitimacy of Bloch's theorem even under the influence of the high-intensity electric field and provides an exact treatment of the diabatic processes of Bloch electrons. Utilizing this framework, we first discovered that the diabatic processes, namely, ac Zener tunneling and semimetallization of semiconductors, are key factors for nonperturbative mechanisms of HHG. These mechanisms are classified by the field intensity and could be understood by an extended simple man model based on an analogy between tunnel ionization in gaseous media and Zener tunneling in semiconductors. These conclusions would stimulate the universal understanding of HHG mechanisms in both atomic and solid cases.

  17. Investigation of mechanisms contributing to slow desorption of hydrophobic organic compounds from mineral solids

    SciTech Connect

    Farrell, J.; Grassian, D.; Jones, M.

    1999-04-15

    Predicting the transport and fate of hydrophobic organic contaminants in underground aquifers requires a mechanistic understanding of sediment-contaminant interactions. This research investigates the mechanisms contributing to the slow desorption of hydrophobic organic compounds from water-saturated mineral solids. The mechanisms investigated were adsorption-retarded aqueous diffusion, micropore diffusion, high-energy micropore adsorption, and micropore blockage by precipitated minerals. To reduce the potential confounding effects of adsorbent heterogeneity, a set of homogeneous silica gel and glass bead adsorbents were used in the investigation. Desorption rates for the slow-desorbing fractions of chloroform (CF), trichloroethylene (TCE), and perchloroethylene (PCE) from silica gel did not conform to the pore-diffusion model for adsorption-retarded aqueous diffusion. This indicated that diffusion through adsorbent mesopores was not responsible for slow desorption from silica gel. Micropore-diffusion modeling of TCE desorption from three silica gels and microporous glass beads indicated that pores less than 2 nm in diameter were responsible for slow desorption. Desorption rates of CF, TCE, and PCE from silica gel were also measured in methanol solutions. Under methanol extraction conditions, desorption rates for all three compounds were 1--2 orders of magnitude less than under water-saturated conditions. The activation energy for TCE desorption from water-saturated silica gel was measured using temperature-programmed desorption. The TCE desorption activation energy of 15 kJ/mol was close to the dissolution enthalpy for silica gel of 13 kJ/mol. This supported the hypothesis that micropore blockage by precipitated minerals may be limiting contaminant desorption rates under water-saturated conditions.

  18. Mechanical stress in a dielectric solid from a uniform electric field

    SciTech Connect

    Anderson, R.A.

    1986-01-15

    Mechanical stress in a dielectric solid from application of a uniform electric field is usually assumed to be described by ''Maxwell stress,'' proportional to the first power of the relative dielectric constant, kappa. Significant corrections are found from energy minimization when the dependence of permittivity on strain is included. Electrostriction coefficients are evaluated by the use of a model dielectric consisting of a simple-cubic lattice of linearly polarizable point dipoles. Compressive stress in the applied-field direction is larger than expected by more than a factor of kappa. The force density exerted on internal space charge needs to be corrected by the same factor. Stress components also have been calculated, with identical results, through direct summation of microscopic forces. This method permits identification of the origins of electrically induced stress. The dominant contribution is a compressive stress in the field direction, proportional to kappaS, from attraction between free charge at the electrodes. This component can attain tens of MPa at fields approaching the intrinsic dielectric strength. A lateral tensile stress independent of kappa also is present, which may assist electrical breakdown in some crystalline dielectrics. These stress components are augmented by short-range, dipolar forces throughout the bulk of the dielectric. Deformations accompanying poling of poly(vinylidene fluoride) are considered and found to be influenced by electrically induced stress.

  19. Thermochemical pretreatments of organic fraction of municipal solid waste from a mechanical-biological treatment plant.

    PubMed

    Álvarez-Gallego, Carlos José; Fdez-Güelfo, Luis Alberto; de los Ángeles Romero Aguilar, María; Romero García, Luis Isidoro

    2015-01-01

    The organic fraction of municipal solid waste (OFMSW) usually contains high lignocellulosic and fatty fractions. These fractions are well-known to be a hard biodegradable substrate for biological treatments and its presence involves limitations on the performance of anaerobic processes. To avoid this, thermochemical pretreatments have been applied on the OFMSW coming from a full-scale mechanical-biological treatment (MBT) plant, in order to pre-hydrolyze the waste and improve the organic matter solubilisation. To study the solubilisation yield, the increments of soluble organic matter have been measured in terms of dissolved organic carbon (DOC), soluble chemical oxygen demand (sCOD), total volatile fatty acids (TVFA) and acidogenic substrate as carbon (ASC). The process variables analyzed were temperature, pressure and NaOH dosage. The levels of work for each variable were three: 160-180-200 °C, 3.5-5.0-6.5 bar and 2-3-4 g NaOH/L. In addition, the pretreatment time was also modified among 15 and 120 min. The best conditions for organic matter solubilisation were 160 °C, 3 g NaOH/L, 6.5 bar and 30 min, with yields in terms of DOC, sCOD, TVFA and ASC of 176%, 123%, 119% and 178% respectively. Thus, predictably the application of this pretreatment in these optimum conditions could improve the H2 production during the subsequent Dark Fermentation process. PMID:25671816

  20. The effect of mechanical twisting on oxygen ionic transport in solid-state energy conversion membranes

    NASA Astrophysics Data System (ADS)

    Shi, Yanuo; Bork, Alexander Hansen; Schweiger, Sebastian; Rupp, Jennifer Lilia Marguerite

    2015-07-01

    Understanding `electro-chemo-mechanics’ in oxygen ion conducting membranes represents a foundational step towards new energy devices such as micro fuel cells and oxygen or fuel separation membranes. For ionic transport in macro crystalline electrolytes, doping is conventionally used to affect oxygen ionic association/migration energies. Recently, tuning ionic transport in films through lattice strain conveyed by substrates or heterostructures has generated much interest. However, reliable manipulation of strain states to twist the ionic conduction in real micro energy devices remains intractable. Here, we demonstrate that the oxygen ionic conductivity clearly correlates with the compressive strain energy acting on the near order of the electrolyte lattices by comparing thin-film ceria-based membrane devices against substrate-supported flat structures. It is possible to capitalize on this phenomenon with a smart choice of strain patterns achieved through microelectrode design. We highlight the importance of electro-chemo-mechanics in the electrolyte material for the next generation of solid-state energy conversion microdevices.

  1. High temperature mechanical properties of zirconia tapes used for electrolyte supported solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Fleischhauer, Felix; Bermejo, Raul; Danzer, Robert; Mai, Andreas; Graule, Thomas; Kuebler, Jakob

    2015-01-01

    Solid-Oxide-Fuel-Cell systems are efficient devices to convert the chemical energy stored in fuels into electricity. The functionality of the cell is related to the structural integrity of the ceramic electrolyte, since its failure can lead to drastic performance losses. The mechanical property which is of most interest is the strength distribution at all relevant temperatures and how it is affected with time due to the environment. This study investigates the impact of the temperature on the strength and the fracture toughness of different zirconia electrolytes as well as the change of the elastic constants. 3YSZ and 6ScSZ materials are characterised regarding the influence of sub critical crack growth (SCCG) as one of the main lifetime limiting effects for ceramics at elevated temperatures. In addition, the reliability of different zirconia tapes is assessed with respect to temperature and SCCG. It was found that the strength is only influenced by temperature through the change in fracture toughness. SCCG has a large influence on the strength and the lifetime for intermediate temperature, while its impact becomes limited at temperatures higher than 650 °C. In this context the tetragonal 3YSZ and 6ScSZ behave quite different than the cubic 10Sc1CeSZ, so that at 850 °C it can be regarded as competitive compared to the tetragonal compounds.

  2. Mechanism of generation of drug nanocrystals in celecoxib: mannitol nanocrystalline solid dispersion.

    PubMed

    Bhatt, Varun; Shete, Ganesh; Bansal, Arvind Kumar

    2015-11-10

    Objective of this work was to understand the mechanism of formation of celecoxib nanocrystals in celecoxib: mannitol nanocrystalline solid dispersion (NSD). Solution of celecoxib and mannitol was spray dried in 1:1 (g:g) proportion to obtain NSD, with average crystallite size of 214.07 ± 45.27 nm. Solubility parameters of celecoxib and mannitol were 23.1 MPa(1/2) and 38.5 MPa(1/2), respectively, hinting their immiscibility. Formation of nanocrystals during NanoCrySP proceeds via intermediate amorphous form of the drug. Earlier work from our lab on hesperetin-mannitol system, had underlined the role of plasticization of amorphous drug by excipient in the formation of nanocrystals. However, in present case, mannitol failed to plasticize amorphous celecoxib and Tg of amorphous celecoxib (56.8°C) showed a negligible change (54.8°C) in presence of mannitol. However, DSC data also suggested crystallization inducing potential of mannitol on amorphous celecoxib. Polarized light microscopy provided evidence that, mannitol facilitated heterogeneous nucleation of amorphous celecoxib at their interface. Transmission electron microscopy analysis suggested that, mannitol acted as a physical barrier to crystal growth of celecoxib crystallites. Thus, though mannitol did not plasticize amorphous celecoxib, it aided in nanocrystal generation by heterogeneous nucleation and providing physical barrier to crystal growth. PMID:26327627

  3. Mechanism of Dissolution-Induced Nanoparticle Formation from a Copovidone-Based Amorphous Solid Dispersion.

    PubMed

    Harmon, Paul; Galipeau, Kendra; Xu, Wei; Brown, Chad; Wuelfing, W Peter

    2016-05-01

    Amorphous solid dispersions (ASDs) have been increasingly used to maximize human exposures from poorly soluble drug candidates. One well-studied advantage of ASDs is the increased amorphous drug solubility compared to crystalline forms. This provides more rapid dissolution rates. An additional advantage of ASDs is that the dissolution process of the ASD particle may also rapidly transform much of the drug present in the ASD particle to small (<1 μm) amorphous drug nanoparticles which will have fast dissolution rates. This work examines the mechanism by which this nanoparticle formation occurs by studying an ASD consisting of 70-80% copovidone, 20% anacetrapib (a low solubility lipophilic drug), and 0-10% TPGS (d-α-tocopheryl polyethylene glycol 1000 succinate, a surfactant). Nanoparticle formation is found to derive from a rapid amorphous drug domain formation within the ASD particle, driven by copovidone dissolution from the particle. The role of surfactant in the ASD particle is to prevent an otherwise rapid, local drug domain aggregation event, which we term "hydrophobic capture". Surfactant thus allows the amorphous drug domains to escape hydrophobic capture and diffuse to bulk solution, where they are reported as nanoparticles. This view of surfactant and nanoparticle formation is compared to the prevailing view in the literature. The work here clarifies the different roles that surfactant might play in increasing nanoparticle yields and extending the useful drug loading ranges in copovidone-based ASDs. PMID:27019407

  4. Thermochemical Pretreatments of Organic Fraction of Municipal Solid Waste from a Mechanical-Biological Treatment Plant

    PubMed Central

    Álvarez-Gallego, Carlos José; Fdez-Güelfo, Luis Alberto; Romero Aguilar, María de los Ángeles; Romero García, Luis Isidoro

    2015-01-01

    The organic fraction of municipal solid waste (OFMSW) usually contains high lignocellulosic and fatty fractions. These fractions are well-known to be a hard biodegradable substrate for biological treatments and its presence involves limitations on the performance of anaerobic processes. To avoid this, thermochemical pretreatments have been applied on the OFMSW coming from a full-scale mechanical-biological treatment (MBT) plant, in order to pre-hydrolyze the waste and improve the organic matter solubilisation. To study the solubilisation yield, the increments of soluble organic matter have been measured in terms of dissolved organic carbon (DOC), soluble chemical oxygen demand (sCOD), total volatile fatty acids (TVFA) and acidogenic substrate as carbon (ASC). The process variables analyzed were temperature, pressure and NaOH dosage. The levels of work for each variable were three: 160–180–200 °C, 3.5–5.0–6.5 bar and 2–3–4 g NaOH/L. In addition, the pretreatment time was also modified among 15 and 120 min. The best conditions for organic matter solubilisation were 160 °C, 3 g NaOH/L, 6.5 bar and 30 min, with yields in terms of DOC, sCOD, TVFA and ASC of 176%, 123%, 119% and 178% respectively. Thus, predictably the application of this pretreatment in these optimum conditions could improve the H2 production during the subsequent Dark Fermentation process. PMID:25671816

  5. Kinematics analysis and optimization of the fast shearing-extrusion joining mechanism for solid-state metal

    NASA Astrophysics Data System (ADS)

    Zhang, Shuangjie; Yao, Yunfeng; Li, Lingchong; Wang, Lijuan; Li, Junxia; Li, Qiang

    2015-11-01

    Dynamical Joining of the solid-state metal is the key technology to realize endless hot rolling. The heating and laser welding method both require long joining time. Based on super deformation method, a 7-bar and 2-slider mechanism was developed in Japan, and the joining time is less than 0.5 s, however the length of each bar are not reported and this mechanism is complex. A relatively simple 6-bar and 1-slider mechanism is put forward, which can realize the shearing and extrusion motion of the top and bottom blades with a speed approximately equal to the speed of the metal plates. In order to study the kinematics property of the double blades, based on complex vector method, the multi-rigid-body model is built, and the displacement and speed functions of the double blades, the joining time and joining thickness are deduced, the kinematics analysis shows that the initial parameters can't satisfy the joining process. Hence, optimization of this mechanism is employed using genetic algorithm(GA) and the optimization parameters of this mechanism are obtained, the kinematics analysis show that the joining time is less than 0.1 s, the joining thickness is more than 80% of the thickness of the solid-state metal, and the horizontal speeds of the blades are improved. A new mechanism is provided for the joining of the solid-state metal and a foundation is laid for the design of the device.

  6. Different control mechanisms regulate glucoamylase and protease gene transcription in Aspergillus oryzae in solid-state and submerged fermentation.

    PubMed

    te Biesebeke, R; van Biezen, N; de Vos, W M; van den Hondel, C A M J J; Punt, P J

    2005-04-01

    Solid-state fermentation (SSF) with Aspergillus oryzae results in high levels of secreted protein. However, control mechanisms of gene expression in SSF have been only poorly studied. In this study we show that both glucoamylase (glaB) and protease (alpA, nptB) genes are highly expressed during surface cultivation on wheat-based solid medium, and even higher during cultivation on wheat kernels. In wheat-based liquid medium, low levels of gene expression are observed. Typical SSF cultivation conditions, such as low water activity and the formation of aerial hyphae, did not contribute to the high-level gene expression on wheat-based solid medium. Analysis of wheat-based solid and liquid cultivations showed differences in carbon and nitrogen utilisation and external pH. The results presented show that the difference in regulation of transcription of the alpA and nptB genes in wheat-based liquid and solid medium could be pH dependent, involving a pH-dependent transcription regulator. The results obtained suggest that the difference in regulation of transcription of the glaB gene in wheat-based liquid and solid medium is caused by a difference in carbohydrate degradation and consumption under the different culture conditions. PMID:15800731

  7. Carbon dioxide sensing mechanisms of an electrocatalytic sensor/cell based on a tungsten stabilized bismuth oxide solid electrolyte

    NASA Astrophysics Data System (ADS)

    Shoemaker, Erika Leigh

    This work describes the specific O2/CO2 sensing mechanisms of a solid-state, thick-film, electrocatalytic cermet (ceramic/metallic) gas sensor based on a tungsten stabilized bismuth oxide (WBO) solid electrolyte. The sensors embody the same configuration of classical planar oxygen sensors with two catalytic electrodes sandwiching an oxygen ion conducting solid electrolyte and a buried metal oxide reference. The technique of cyclic voltammetry is used where a cyclic voltage is ramped across the electrodes to promote electrochemical reactions on the surface of the sensor. These reactions alter the ionic current flow through the solid electrolyte, generating voltage-current related responses (voltammograms) which are gas specific. The WBO sensors have the identical configuration of previously investigated sensors of this type based on a yttria stabilized zirconia (YSZ) solid electrolyte which show good response to O 2 but do not respond to CO2 to any degree. This dissertation examines the specific function of each solid electrolyte layer and relates them to both the WBO sensors ability to respond uniquely to CO2 and the YSZ sensors incapability to respond to CO2. The research suggests that the tungsten component of the WBO electrolyte along with the porosity of the WBO layer together are responsible for the unique CO 2 response of this sensor.

  8. Growth of epitaxial silicon and germanium nanowires using the gold catalyzed vapor-liquid-solid mechanism

    NASA Astrophysics Data System (ADS)

    Dailey, Eric J.

    The growth of silicon and germanium nanowires and their nanowire heterostructures has been investigated using the gold catalyzed vapor-liquid-solid (VLS) mechanism. The Au catalyst particles were deposited under ultra high vacuum (UHV) conditions onto vicinal Si(111) surfaces using physical vapor deposition. Nanowires were grown in a home built UHV-chemical vapor deposition (CVD) chamber using silane, disilane, germane, and digermane as gas precursors. Silicon nanowire morphology was determined to be dependent on the stability of the gold catalyst particle at the tip of the nanowire. Specifically, silicon nanowires grow along <111> orientations when gold wets the nanowire sidewalls and along <112> orientations when gold does not wet the nanowire sidewalls except under a very narrow pressure range. The dependence of gold coverage on CVD parameters on the sidewalls of <111> and <112> silicon nanowires was also determined revealing a liquid metal wetting of cylinders phenomenon. A new "seedless" VLS mechanism for nanowire growth was also determined in which the Stranski-Krastanov planar gold layer on Si(111) dewets under certain CVD conditions resulting in 15 nm diameter gold seeds that then form nanowires via the VLS mechanism. Both core/shell and axial nanowire heterostructures were also investigated with a focus on the effect of nanowire orientation on heterostructure formation. For core/shell heterostructures, only the <110> germanium core/silicon shell heterostructures were determined to form with smooth shell deposition while all other orientations underwent shell roughening. Various germanium core diameters and silicon shell thicknesses for <110> germanium core/silicon shell heterostructures were analyzed to determine the effect of nanowire diameter on shell coherency limits and to determine the strain within the nanowire heterostructures. Lastly, axial nanowire heterostructures were investigated to determine the ability to form axial heterostructures using

  9. Combination of fluid and solid mechanical stresses contribute to cell death and detachment in a microfluidic alveolar model.

    PubMed

    Douville, Nicholas J; Zamankhan, Parsa; Tung, Yi-Chung; Li, Ran; Vaughan, Benjamin L; Tai, Cheng-Feng; White, Joshua; Christensen, Paul J; Grotberg, James B; Takayama, Shuichi

    2011-02-21

    Studies using this micro-system demonstrated significant morphological differences between alveolar epithelial cells (transformed human alveolar epithelial cell line, A549 and primary murine alveolar epithelial cells, AECs) exposed to combination of solid mechanical and surface-tension stresses (cyclic propagation of air-liquid interface and wall stretch) compared to cell populations exposed solely to cyclic stretch. We have also measured significant differences in both cell death and cell detachment rates in cell monolayers experiencing combination of stresses. This research describes new tools for studying the combined effects of fluid mechanical and solid mechanical stress on alveolar cells. It also highlights the role that surface tension forces may play in the development of clinical pathology, especially under conditions of surfactant dysfunction. The results support the need for further research and improved understanding on techniques to reduce and eliminate fluid stresses in clinical settings. PMID:21152526

  10. Thermal and mechanical stabilization process of the organic fraction of the municipal solid waste.

    PubMed

    Giudicianni, Paola; Bozza, Pio; Sorrentino, Giancarlo; Ragucci, Raffaele

    2015-10-01

    In the present study a thermo-mechanical treatment for the disposal of the Organic Fraction of Municipal Solid Waste (OFMSW) at apartment or condominium scale is proposed. The process presents several advantages allowing to perform a significant volume and moisture reduction of the produced waste at domestic scale thus producing a material with an increased storability and improved characteristics (e.g. calorific value) that make it available for further alternative uses. The assessment of the applicability of the proposed waste pretreatment in a new scheme of waste management system requires several research steps involving different competences and application scales. In this context, a preliminary study is needed targeting to the evaluation and minimization of the energy consumption associated to the process. To this aim, in the present paper, two configurations of a domestic appliance prototype have been presented and the effect of some operating variables has been investigated in order to select the proper configuration and the best set of operating conditions capable to minimize the duration and the energy consumption of the process. The performances of the prototype have been also tested on three model mixtures representing a possible daily domestic waste and compared with an existing commercially available appliance. The results obtained show that a daily application of the process is feasible given the short treatment time required and the energy consumption comparable to the one of the common domestic appliances. Finally, the evaluation of the energy recovered in the final product per unit weight of raw material shows that in most cases it is comparable to the energy required from the treatment. PMID:26209343

  11. A NOVEL INTEGRATED STACK APPROACH FOR REALIZING MECHANICALLY ROBUST SOLID OXIDE FUEL CELLS

    SciTech Connect

    Scott A. Barnett; Tammy Lai; Jiang Liu

    2001-11-01

    SOFCs are a very promising energy conversion technology for utilization of fossil fuels. The proposed project is to improve the viability of SOFCs by introducing a novel stacking geometry. The geometry involved has all active SOFC components and the interconnect deposited as thin layers on an electrically insulating support. This allows the choice of a support material that provides optimal mechanical toughness and thermal shock resistance. The supports are in the form of flattened tubes, providing relatively high strength, high packing densities, and minimizing the number of seals required. The integration of SOFCs and interconnects on the same support has several other advantages including the reduction of electrical resistances associated with pressure contacts between the cells and interconnects, relaxation of fabrication tolerances required for pressure contacts, reduction of ohmic losses, and reduction of interconnect conductivity requirements. In this report, we describe the processing methodologies that have been developed for fabricating the integrated solid oxide fuel cell (ISOFC), along with results on characterization of the component materials: support, electrolyte, anode, cathode, and interconnect. Screen printing was the primary processing method developed. A centrifugal casting technique was also developed for depositing thin 8 mol % yttrium stabilized zirconia (YSZ) electrolyte layers on porous NiO-YSZ anode substrates. Dense pinhole-free YSZ coatings were obtained by co-sintering the bi-layers at 1400 C. After depositing La{sub 0.8}Sr{sub 0.2}MnO{sub 3} (LSM)-YSZ cathodes, single SOFCs produced near-theoretical open-circuit voltages and power densities of 0.55 W/cm{sup 2} at 800 C. Initial stack operation results are also described.

  12. Mechanical properties of (Bi,Sb)2Te3 solid solutions obtained by directional crystallization and spark plasma sintering

    NASA Astrophysics Data System (ADS)

    Lavrent'ev, M. G.; Osvenskii, V. B.; Pivovarov, G. I.; Sorokin, A. I.; Bulat, L. P.; Bublik, V. T.; Tabachkova, N. Yu.

    2016-01-01

    We have studied the temperature dependence of the mechanical strength at uniaxial compression for solid solutions based on bismuth and antimony chalcogenides, which were prepared by three methods: (i) vertical zone melting (VZM), (ii) hot extrusion, and (iii) spark plasma sintering (SPS). In the samples of solid solutions obtained by VZM and extrusion, a brittle-ductile transition was observed in a wised temperature interval of 200-350°C. In nanostructured SPS samples, transition from brittle to plastic fracture was observed within 170-200°C. The room-temperature strength of nanostructured samples was eight to nine times as large as that of VZM samples, and the stress-strain curves of these materials were significantly different. At a temperature of about 300°C, the strength of nanostructured solid solutions decreases to nearly zero.

  13. Reciprocated suppression of polymer crystallization toward improved solid polymer electrolytes: Higher ion conductivity and tunable mechanical properties

    DOE PAGESBeta

    Bi, Sheng; Sun, Che-Nan; Zawodzinski, Thomas A.; Ren, Fei; Keum, Jong Kahk; Ahn, Suk-Kyun; Li, Dawen; Chen, Jihua

    2015-08-06

    Solid polymer electrolytes based on lithium bis(trifluoromethanesulfonyl) imide and polymer matrix were extensively studied in the past due to their excellent potential in a broad range of energy related applications. Poly(vinylidene fluoride) (PVDF) and polyethylene oxide (PEO) are among the most examined polymer candidates as solid polymer electrolyte matrix. In this paper, we study the effect of reciprocated suppression of polymer crystallization in PVDF/PEO binary matrix on ion transport and mechanical properties of the resultant solid polymer electrolytes. With electron and X-ray diffractions as well as energy filtered transmission electron microscopy, we identify and examine the appropriate blending composition thatmore » is responsible for the diminishment of both PVDF and PEO crystallites. Laslty, a three-fold conductivity enhancement is achieved along with a highly tunable elastic modulus ranging from 20 to 200 MPa, which is expected to contribute toward future designs of solid polymer electrolytes with high room-temperature ion conductivities and mechanical flexibility.« less

  14. Supersaturated Al(Ti) solid solutions with partial L1{sub 2} ordering prepared by mechanical alloying

    SciTech Connect

    Fan, G.J.; Quan, M.X.; Hu, Z.Q.

    1995-08-01

    The authors report phase formation during mechanical alloying of Al rich Ti-Al powder blends. Their experimental results further support the idea that the synthesis of Al rich supersaturated solid solutions in the Al-Ti system occurs in the following two steps. First, the ordered L1{sub 2}-Al{sub 3}Ti intermetallic compound is formed at Al/Ti interfaces. Second, the ordered L1{sup 2}-Al{sub 3}Ti compound was partially disordered by mechanical deformation. Meanwhile, Ti or Al atoms dissolve into the partially disordered phase and a supersaturated solid solution is finally obtained. However, the disordering is not complete and the resulting alloys may exhibit partial L1{sub 2} ordering.

  15. A wavelet Galerkin method employing B-spline bases for solid mechanics problems without the use of a fictitious domain

    NASA Astrophysics Data System (ADS)

    Tanaka, Satoyuki; Okada, Hiroshi; Okazawa, Shigenobu

    2012-07-01

    This study develops a wavelet Galerkin method (WGM) that uses B-spline wavelet bases for application to solid mechanics problems. A fictitious domain is often adopted to treat general boundaries in WGMs. In the analysis, the body is extended to its exterior but very low stiffness is applied to the exterior region. The stiffness matrix in the WGM becomes singular without the use of a fictitious domain. The problem arises from the lack of linear independence of the basis functions. A technique to remove basis functions that can be represented by the superposition of the other basis functions is proposed. The basis functions are automatically eliminated in the pre conditioning step. An adaptive strategy is developed using the proposed technique. The solution is refined by superposing finer wavelet functions. Numerical examples of solid mechanics problems are presented to demonstrate the multiresolution properties of the WGM.

  16. The interplay between the solid effect and the cross effect mechanisms in solid state 13C DNP at 95 GHz using trityl radicals

    NASA Astrophysics Data System (ADS)

    Banerjee, Debamalya; Shimon, Daphna; Feintuch, Akiva; Vega, Shimon; Goldfarb, Daniella

    2013-05-01

    The 13C solid state Dynamic Nuclear Polarization (DNP) mechanism using trityl radicals (OX63) as polarizers was investigated in the temperature range of 10-60 K. The solutions used were 6 M 13C urea in DMSO/H2O (50% v/v) with 15 mM and 30 mM OX63. The measurements were carried out at ˜3.5 T, which corresponds to Larmor frequencies of 95 GHz and 36 MHz for the OX63 and the 13C nuclei, respectively. Measurements of the 13C signal intensity as a function of the microwave (MW) irradiation frequency yielded 13C DNP spectra with temperature dependent lineshapes for both samples. The maximum enhancement for the 30 mM sample was reached at 40 K, while that of the 15 mM sample at 20-30 K. Furthermore, the lineshapes observed showed that both the cross effect (CE) and the solid effect (SE) DNP mechanisms are active in this temperature range and that their relative contribution is temperature dependent. Simulations of the spectra with the relative contributions of the CE and SE mechanisms as a fit parameter revealed that for both samples the CE contribution decreases with decreasing temperature while the SE contribution increases. In addition, for the 15 mM sample the contributions of the two mechanisms are comparable from 20 K to 60 K while for the 30 mM the CE dominates in this range, as expected from the higher concentration. The steep decrease of the CE contribution towards low temperatures is however unexpected. The temperature dependence of the OX63 longitudinal relaxation, DNP buildup times and 13C spin lattice relaxation times did not reveal any obvious correlation with the DNP temperature dependence. A similar behavior of the CE and SE mechanism was observed for 1H DNP with the nitroxide radical TEMPOL as a polarizer. This suggests that this effect is a general phenomenon involving a temperature dependent competition between the CE and SE mechanisms, the source of which is, however, still unknown.

  17. A Meshfree Cell-based Smoothed Point Interpolation Method for Solid Mechanics Problems

    NASA Astrophysics Data System (ADS)

    Zhang, Guiyong; Liu, Gui-Rong

    2010-05-01

    In the framework of a weakened weak (W2) formulation using a generalized gradient smoothing operation, this paper introduces a novel meshfree cell-based smoothed point interpolation method (CS-PIM) for solid mechanics problems. The W2 formulation seeks solutions from a normed G space which includes both continuous and discontinuous functions and allows the use of much more types of methods to create shape functions for numerical methods [1]. When PIM shape functions are used, the functions constructed are in general not continuous over the entire problem domain and hence are not compatible. Such an interpolation is not in a traditional H1 space, but in a G1 space. By introducing the generalized gradient smoothing operation properly, the requirement on function is now further weakened upon the already weakened requirement for functions in a H1 space and G1 space can be viewed as a space of functions with weakened weak (W2) requirement on continuity [1-3]. The cell-based smoothed point interpolation method (CS-PIM) is formulated based on the W2 formulation, in which displacement field is approximated using the PIM shape functions, which possess the Kronecker delta property facilitating the enforcement of essential boundary conditions [3]. The gradient (strain) field is constructed by the generalized gradient smoothing operation within the cell-based smoothing domains, which are exactly the triangular background cells. A W2 formulation of generalized smoothed Galerkin (GS-Galerkin) weak form is used to derive the discretized system equations [2]. It was found that the CS-PIM possesses the following attractive properties: (1) It is very easy to implement and works well with the simplest linear triangular mesh without introducing additional degrees of freedom; (2) it is at least linearly conforming; (3) this method is temporally stable and works well for dynamic analysis; (4) it possesses a close-to-exact stiffness, which is much softer than the overly-stiff FEM model

  18. A Meshfree Cell-based Smoothed Point Interpolation Method for Solid Mechanics Problems

    SciTech Connect

    Zhang Guiyong; Liu Guirong

    2010-05-21

    In the framework of a weakened weak (W{sup 2}) formulation using a generalized gradient smoothing operation, this paper introduces a novel meshfree cell-based smoothed point interpolation method (CS-PIM) for solid mechanics problems. The W{sup 2} formulation seeks solutions from a normed G space which includes both continuous and discontinuous functions and allows the use of much more types of methods to create shape functions for numerical methods. When PIM shape functions are used, the functions constructed are in general not continuous over the entire problem domain and hence are not compatible. Such an interpolation is not in a traditional H{sup 1} space, but in a G{sup 1} space. By introducing the generalized gradient smoothing operation properly, the requirement on function is now further weakened upon the already weakened requirement for functions in a H{sup 1} space and G{sup 1} space can be viewed as a space of functions with weakened weak (W{sup 2}) requirement on continuity. The cell-based smoothed point interpolation method (CS-PIM) is formulated based on the W{sup 2} formulation, in which displacement field is approximated using the PIM shape functions, which possess the Kronecker delta property facilitating the enforcement of essential boundary conditions [3]. The gradient (strain) field is constructed by the generalized gradient smoothing operation within the cell-based smoothing domains, which are exactly the triangular background cells. A W{sup 2} formulation of generalized smoothed Galerkin (GS-Galerkin) weak form is used to derive the discretized system equations. It was found that the CS-PIM possesses the following attractive properties: (1) It is very easy to implement and works well with the simplest linear triangular mesh without introducing additional degrees of freedom; (2) it is at least linearly conforming; (3) this method is temporally stable and works well for dynamic analysis; (4) it possesses a close-to-exact stiffness, which is much

  19. Thermal and mechanical stabilization process of the organic fraction of the municipal solid waste

    SciTech Connect

    Giudicianni, Paola; Bozza, Pio; Sorrentino, Giancarlo; Ragucci, Raffaele

    2015-10-15

    Graphical abstract: Display Omitted - Highlights: • A domestic scale prototype for the pre-treatment of OFMSW has been tested. • Two grinding techniques are compared and thermopress is used for the drying stage. • Increasing temperature up to 170 °C reduces energy consumption of the drying stage. • In the range 5–10 bar a reduction of 97% of the initial volume is obtained. • In most cases energy recovery from the dried waste matches energy consumption. - Abstract: In the present study a thermo-mechanical treatment for the disposal of the Organic Fraction of Municipal Solid Waste (OFMSW) at apartment or condominium scale is proposed. The process presents several advantages allowing to perform a significant volume and moisture reduction of the produced waste at domestic scale thus producing a material with an increased storability and improved characteristics (e.g. calorific value) that make it available for further alternative uses. The assessment of the applicability of the proposed waste pretreatment in a new scheme of waste management system requires several research steps involving different competences and application scales. In this context, a preliminary study is needed targeting to the evaluation and minimization of the energy consumption associated to the process. To this aim, in the present paper, two configurations of a domestic appliance prototype have been presented and the effect of some operating variables has been investigated in order to select the proper configuration and the best set of operating conditions capable to minimize the duration and the energy consumption of the process. The performances of the prototype have been also tested on three model mixtures representing a possible daily domestic waste and compared with an existing commercially available appliance. The results obtained show that a daily application of the process is feasible given the short treatment time required and the energy consumption comparable to the one of

  20. Studies of epitaxial silicon nanowire growth by the vapor-liquid-solid mechanism

    NASA Astrophysics Data System (ADS)

    Aella, Pavan Reddy K.

    2007-12-01

    Silicon nanowires were grown epitaxially on Si (100) and (111) surfaces using the Vapor-Liquid-Solid (VLS) mechanism under both thermal and plasma enhanced growth conditions. Silane and disilane were used as source gases. Plasma excitation at low growth temperatures is found to strongly enhance nanowire growth rates and promote the nucleation of smaller diameter <110> oriented silicon nanowires relative to the larger diameter <111> nanowires. The higher nucleation rate for <110> nanowires during plasma excitation is attributed to a plasma-induced increase in silicon chemical potential. From this study, plasma excitation can be concluded to enable an additional degree of control over nanowire orientation. In low power radio frequency silane plasma, SiH3 are the dominant radical species in the gas phase. These reactive radicals formed in the plasma "bypass" the SiH 4 → SiH3 decomposition step on the liquid AuSi interface required for growth under thermal growth conditions, thereby leading to faster incorporation rates into the melt and hence promoting higher growth rates. Also consistent with this interpretation is the strong reduction in nucleation times in the presence of plasma. The nanowire growth rate shows a linear dependence with plasma power. The activation energy decreases from 0.78 eV under thermal growth conditions to 0.23 eV for a 2.5 W radio frequency plasma stimulated conditions. This decreased activation energy for growth under plasma excitation indicates that the rate limiting step for VLS growth of Si nanowires using Au as a catalyst is at the vapor-liquid interface. The growth under plasma conditions is dominated by the plasma influenced decomposition step and this strong reduction in the activation energy under silane plasma is consistent with a change in the rate limiting step. Growth kinetics between silane and disilane reveals an incorporation coefficient of Si, 60 to 80 times higher with disilane. This results in higher growth rates with

  1. CO Self-Shielding as a Mechanism to Make 16O-Enriched Solids in the Solar Nebula

    NASA Astrophysics Data System (ADS)

    Nuth, Joseph A., III; Johnson, Natasha M.; Hill, Hugh G. M.

    2014-05-01

    Photochemical self-shielding of CO has been proposed as a mechanism to produce solids observed in the modern, 16O-depleted solar system. This is distinct from the relatively 16O-enriched composition of the solar nebula, as demonstrated by the oxygen isotopic composition of the contemporary sun. While supporting the idea that self-shielding can produce local enhancements in 16O-depleted solids, we argue that complementary enhancements of 16O-enriched solids can also be produced via C16O-based, Fischer-Tropsch type (FTT) catalytic processes that could produce much of the carbonaceous feedstock incorporated into accreting planetesimals. Local enhancements could explain observed 16O enrichment in calcium-aluminum-rich inclusions (CAIs), such as those from the meteorite, Isheyevo (CH/CHb), as well as in chondrules from the meteorite, Acfer 214 (CH3). CO self-shielding results in an overall increase in the 17O and 18O content of nebular solids only to the extent that there is a net loss of C16O from the solar nebula. In contrast, if C16O reacts in the nebula to produce organics and water then the net effect of the self-shielding process will be negligible for the average oxygen isotopic content of nebular solids and other mechanisms must be sought to produce the observed dichotomy between oxygen in the Sun and that in meteorites and the terrestrial planets. This illustrates that the formation and metamorphism of rocks and organics need to be considered in tandem rather than as isolated reaction networks.

  2. CO Self-Shielding as a Mechanism to Make O-16 Enriched Solids in the Solar Nebula

    NASA Technical Reports Server (NTRS)

    Nuth, Joseph A. III; Johnson, Natasha M.; Hill, Hugh G. M.

    2014-01-01

    Photochemical self-shielding of CO has been proposed as a mechanism to produce solids observed in the modern, O-16 depleted solar system. This is distinct from the relatively O-16 enriched composition of the solar nebula, as demonstrated by the oxygen isotopic composition of the contemporary sun. While supporting the idea that self-shielding can produce local enhancements in O-16 depleted solids, we argue that complementary enhancements of O-16 enriched solids can also be produced via CO-16 based, Fischer-Tropsch type (FTT) catalytic processes that could produce much of the carbonaceous feedstock incorporated into accreting planetesimals. Local enhancements could explain observed O-16 enrichment in calcium-aluminum-rich inclusions (CAIs), such as those from the meteorite, Isheyevo (CH/CHb), as well as in chondrules from the meteorite, Acfer 214 (CH3). CO selfshielding results in an overall increase in the O-17 and O-18 content of nebular solids only to the extent that there is a net loss of CO-16 from the solar nebula. In contrast, if CO-16 reacts in the nebula to produce organics and water then the net effect of the self-shielding process will be negligible for the average oxygen isotopic content of nebular solids and other mechanisms must be sought to produce the observed dichotomy between oxygen in the Sun and that in meteorites and the terrestrial planets. This illustrates that the formation and metamorphism of rocks and organics need to be considered in tandem rather than as isolated reaction networks.

  3. [Theophylline semi-solid matrices containing polyethyleneglycols. 3--Mechanism of release].

    PubMed

    Ortigosa, A Cl; Lasserre, Y J

    2005-09-01

    Some rheologic mesures made on a PEG range ranking from PEG 300 to PEG 6000 and containing, as a theophylline plot indicate an expected result: the viscosity increases with the molecular mass of the polymer. These same measures made on a binary mixture of PEG composed of 95% PEG 300, liquid, and 5% of solid, thickening, make appear the peculiarity of the binary mixtures of PEG: the viscosity of the binary mixture of PEG is higher than the one of the solid PEG. This "paradoxical" viscosity results, apparently, on one side from the concomitant translation and opposed of the respective points of vitrous transition of the vehicle (liquid PEG) and of the thickening (solid PEG); and on the other side, of the different solidifications of the chains of different polymers forming the binary mixture. PMID:16385786

  4. Simulating left ventricular fluid-solid mechanics through the cardiac cycle under LVAD support

    NASA Astrophysics Data System (ADS)

    McCormick, M.; Nordsletten, D. A.; Kay, D.; Smith, N. P.

    2013-07-01

    In this study we have integrated novel modifications of the standard Newton-Raphson/line search algorithm and optimisation of the interpolation scheme at the fluid-solid boundary to enable the simulation of fluid-solid interaction within the cardiac left ventricle under the support of a left ventricular assist device (LVAD). The line search modification combined with Jacobian reuse produced close to an order of magnitude improvement in computational time across both test and whole heart simulations. Optimisation of element interpolation schemes on the fluid-solid boundary highlights the impact this choice can have on problem stability and demonstrates that, in contrast to linear fluid elements, higher order interpolation produces improved error reduction per degree of freedom. Incorporating these modifications enabled a full heart cycle under LVAD support to be modelled. Results from these simulations show that there is slower clearance of blood entering the chamber during early compared to late diastole under conditions of constant LVAD flow.

  5. Augmented finite-element method for arbitrary cracking and crack interaction in solids under thermo-mechanical loadings.

    PubMed

    Jung, J; Do, B C; Yang, Q D

    2016-07-13

    In this paper, a thermal-mechanical augmented finite-element method (TM-AFEM) has been proposed, implemented and validated for steady-state and transient, coupled thermal-mechanical analyses of complex materials with explicit consideration of arbitrary evolving cracks. The method permits the derivation of explicit, fully condensed thermal-mechanical equilibrium equations which are of mathematical exactness in the piece-wise linear sense. The method has been implemented with a 4-node quadrilateral two-dimensional (2D) element and a 4-node tetrahedron three-dimensional (3D) element. It has been demonstrated, through several numerical examples that the new TM-AFEM can provide significantly improved numerical accuracy and efficiency when dealing with crack propagation problems in 2D and 3D solids under coupled thermal-mechanical loading conditions. This article is part of the themed issue 'Multiscale modelling of the structural integrity of composite materials'. PMID:27242303

  6. Rheology in papermaking — from fibre suspension flows to mechanics of solid paper

    NASA Astrophysics Data System (ADS)

    Hämäläinen, Jari; Eskola, Roope; Erkkilä, Anna-Leena; Leppänen, Teemu

    2011-12-01

    Mathematical modelling of both papermaking fibre suspension flows and solid paper are considered in this paper. The authors own research work has mainly been carried out in the University of Eastern Finland by Paper Physics Group since 2004. The paper also consists of review of other related publications on rheology of paper and fibre suspension flows.

  7. Demonstration Experiments for Solid-State Physics Using a Table-Top Mechanical Stirling Refrigerator

    ERIC Educational Resources Information Center

    Osorio, M. R.; Morales, A. Palacio; Rodrigo, J. G.; Suderow, H.; Vieira, S.

    2012-01-01

    Liquid-free cryogenic devices are acquiring importance in basic science and engineering. But they can also lead to improvements in teaching low temperature and solid-state physics to graduate students and specialists. Most of the devices are relatively expensive, but small-sized equipment is slowly becoming available. Here, we have designed…

  8. Effects of Interfacial Layers Fracture on the Dissolution Mechanism of Solid Fe in Liquid Al

    NASA Astrophysics Data System (ADS)

    Rezaei, H.; Akbarpour, M. R.; Shahverdi, H. R.

    2015-07-01

    Solid Fe and liquid Al interaction was studied in the temperature range of 750-900°C by immersion tests in the absence of convection to better understand interfacial reactions during the first instances of immersion (10-80 s). Solidified interface profiles were characterized using a scanning electron microscope and an electron probe micro-analyzer. The results showed the formation of a transition layer with a composition close to pure Fe on the Fe side as a result of Al diffusion from the melt into the solid at initial times of the immersion test, before the formation of an intermetallic compound. At longer immersion times, two intermetallic layers were observed, Fe2Al5 and FeAl3. With increasing immersion time, the intermetallic compounds were thickened, and cracks formed at the interface layers. The formation of cracks accelerated the fracture of the interfacial layers and enhanced the Al diffusion toward solid Fe. As a result of the detachment and dissolution of the intermetallic phases in liquid Al, precipitates of FeAl3 with needle-like morphology were found in the Al phase. A model is proposed for the interface reaction of solid Fe with liquid Al at the first instance of immersion.

  9. Detailed monitoring of two biogas plants and mechanical solid-liquid separation of fermentation residues.

    PubMed

    Bauer, Alexander; Mayr, Herwig; Hopfner-Sixt, Katharina; Amon, Thomas

    2009-06-01

    The Austrian "green electricity act" (Okostromgesetz) has led to an increase in biogas power plant size and consequently to an increased use of biomass. A biogas power plant with a generating capacity of 500 kW(el) consumes up to 38,000 kg of biomass per day. 260 ha of cropland is required to produce this mass. The high water content of biomass necessitates a high transport volume for energy crops and fermentation residues. The transport and application of fermentation residues to farmland is the last step in this logistic chain. The use of fermentation residues as fertilizer closes the nutrient cycle and is a central element in the efficient use of biomass for power production. Treatment of fermentation residues by separation into liquid and solid phases may be a solution to the transport problem. This paper presents detailed results from the monitoring of two biogas plants and from the analysis of the separation of fermentation residues. Furthermore, two different separator technologies for the separation of fermentation residues of biogas plants were analyzed. The examined biogas plants correspond to the current technological state of the art and have designs developed specifically for the utilization of energy crops. The hydraulic retention time ranged between 45.0 and 83.7 days. The specific methane yields were 0.40-0.43 m(3)N CH(4) per kg VS. The volume loads ranged between 3.69 and 4.00 kg VS/m(3). The degree of degradation was between 77.3% and 82.14%. The screw extractor separator was better suited for biogas slurry separation than the rotary screen separator. The screw extractor separator exhibited a high throughput and good separation efficiency. The efficiency of slurry separation depended on the dry matter content of the fermentation residue. The higher the dry matter content, the higher the proportion of solid phase after separation. In this project, we found that the fermentation residues could be divided into 79.2% fluid phase with a dry matter

  10. [Preparation of two poor water soluble drugs - nanoporous ZnO solid dispersions and the mechanism of drug dissolution improvement].

    PubMed

    Gao, Bei; Sun, Chang-shan; Zhi, Zhuang-zhi; Wang, Yan; Chang, Di; Wang, Si-ling; Jiang, Tong-ying

    2011-11-01

    Nanoporous ZnO was used as a carrier to prepare drug solid dispersion, the mechanism of which to improve the drug dissolution was also studied. Nanoporous ZnO, obtained through chemical deposition method, was used as a carrier to prepare indomethacin and cilostazol solid dispersions by melt-quenching method, separately. The results of scanning electron microscope, surface area analyzer, fourier transform infra-red spectroscopy, differential scanning calorimeter and X-ray diffraction showed that drugs were implanted into nanopores of ZnO by physical adsorption effect and highly dispersed into nanopores of ZnO in amorphous form, moreover, these nanopores strongly inhibited amorphous recrystallization in the condition of 45 degrees C and 75% RH. In addition, the results of the dissolution tested in vitro exhibited that the accumulated dissolutions of indomethacin and cilostazol solid dispersions achieved about 90% within 5 min and approximately 80% within 30 min. It was indicated in this study that the mechanism of drug dissolution improvement was associated with the effects of nanoporous ZnO carrier on increasing drug dispersion, controlling drug in nanopores as amorphous form and inhibiting amorphous recrystallization. PMID:22260037

  11. Mechanical alloying synthesis of K{sub 2}Bi{sub 8}Se{sub 13}-type solid solutions.

    SciTech Connect

    Toumpas, N.; Kyratsi, T.; Hatzikraniotis, E.; Tsiappos, A.; Pavlidou, E.; Paraskevopoulos, K. M.; Chung, D. Y.; Kanatzidis, M. G.; Materials Science Division; Univ. of Cyprus; Aristotle Univ. Thessaloniki; Northwestern Univ.

    2008-01-01

    Solid solutions of K{sub 2}Bi{sub 8-x}Sb{sub x}Se{sub 13} are an interesting series of materials for thermoelectric investigations due to their very low thermal conductivity and highly anisotropic electrical properties. In this work, we aimed to synthesize solid solutions of O-K{sub 2}Bi{sub 8-x}Sb{sub x}Se{sub 13} type materials using powder techniques. The synthesis was based on mechanical alloying as well as sintering procedures. The products were studied in terms of structural features, composition and purity with powder x-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy. Preliminary results on thermoelectric properties as well as IR reflectivity measurements are presented.

  12. Solid-state photochemistry as a formation mechanism for Titan's stratospheric C4N2 ice clouds

    NASA Astrophysics Data System (ADS)

    Anderson, C. M.; Samuelson, R. E.; Yung, Y. L.; McLain, J. L.

    2016-04-01

    We propose that C4N2 ice clouds observed in Titan's springtime polar stratosphere arise due to solid-state photochemistry occurring within extant ice cloud particles of HCN-HC3N mixtures. This formation process resembles the halogen-induced ice particle surface chemistry that leads to condensed nitric acid trihydrate (NAT) particles and ozone depletion in Earth's polar stratosphere. As our analysis of the Cassini Composite Infrared Spectrometer 478 cm-1 ice emission feature demonstrates, this solid-state photochemistry mechanism eliminates the need for the relatively high C4N2 saturation vapor pressures required (even though they are not observed) when the ice is produced through the usual procedure of direct condensation from the vapor.

  13. Stability of amorphous pharmaceutical solids: crystal growth mechanisms and effect of polymer additives.

    PubMed

    Sun, Ye; Zhu, Lei; Wu, Tian; Cai, Ting; Gunn, Erica M; Yu, Lian

    2012-09-01

    We review recent progress toward understanding and enhancing the stability of amorphous pharmaceutical solids against crystallization. As organic liquids are cooled to become glasses, fast modes of crystal growth can emerge. One such growth mode, the glass-to-crystal or GC mode, occurs in the bulk, and another exists at the free surface, both leading to crystal growth much faster than predicted by theories that assume diffusion defines the kinetic barrier of crystallization. These phenomena have received different explanations, and we propose that GC growth is a solid-state transformation enabled by local mobility in glasses and that fast surface crystal growth is facilitated by surface molecular mobility. In the second part, we review recent findings concerning the effect of polymer additives on crystallization in organic glasses. Low-concentration polymer additives can strongly inhibit crystal growth in the bulk of organic glasses, while having weaker effect on surface crystal growth. Ultra-thin polymer coatings can inhibit surface crystallization. Recent work has shown the importance of molecular weight for crystallization inhibitors of organic glasses, besides "direct intermolecular interactions" such as hydrogen bonding. Relative to polyvinylpyrrolidone, the VP dimer is far less effective in inhibiting crystal growth in amorphous nifedipine. Further work is suggested for better understanding of crystallization of amorphous organic solids and the prediction of their stability. PMID:22434258

  14. Stress-mediated progression of solid tumors: effect of mechanical stress on tissue oxygenation, cancer cell proliferation, and drug delivery.

    PubMed

    Mpekris, Fotios; Angeli, Stelios; Pirentis, Athanassios P; Stylianopoulos, Triantafyllos

    2015-11-01

    Oxygen supply plays a central role in cancer cell proliferation. While vascular density increases at the early stages of carcinogenesis, mechanical solid stresses developed during growth compress tumor blood vessels and, thus, drastically reduce not only the supply of oxygen, but also the delivery of drugs at inner tumor regions. Among other effects, hypoxia and reduced drug delivery compromise the efficacy of radiation and chemo/nanotherapy, respectively. In the present study, we developed a mathematical model of tumor growth to investigate the interconnections among tumor oxygenation that supports cancer cell proliferation, the heterogeneous accumulation of mechanical stresses owing to tumor growth, the non-uniform compression of intratumoral blood vessels due to the mechanical stresses, and the insufficient delivery of oxygen and therapeutic agents because of vessel compression. We found that the high vascular density and increased cancer cell proliferation often observed in the periphery compared to the interior of a tumor can be attributed to heterogeneous solid stress accumulation. Highly vascularized peripheral regions are also associated with greater oxygenation compared with the compressed, less vascularized inner regions. We also modeled the delivery of drugs of two distinct sizes, namely chemotherapy and nanomedicine. Model predictions suggest that drug delivery is affected negatively by vessel compression independently of the size of the therapeutic agent. Finally, we demonstrated the applicability of our model to actual geometries, employing a breast tumor model derived from MR images. PMID:25968141

  15. Stress-mediated progression of solid tumors: effect of mechanical stress on tissue oxygenation, cancer cell proliferation and drug delivery

    PubMed Central

    Mpekris, Fotios; Angeli, Stelios; Pirentis, Athanassios P.; Stylianopoulos, Triantafyllos

    2015-01-01

    Oxygen supply plays a central role in cancer cell proliferation. While vascular density increases at the early stages of carcinogenesis, mechanical solid stresses developed during growth compress tumor blood vessels and, thus, drastically reduce the supply of oxygen, but also the delivery of drugs at inner tumor regions. Among other effects, hypoxia and reduced drug delivery compromise the efficacy of radiation and chemo/nano therapy, respectively. In the present study, we developed a mathematical model of tumor growth to investigate the interconnections among tumor oxygenation that supports cancer cell proliferation, the heterogeneous accumulation of mechanical stresses owing to tumor growth, the non-uniform compression of intratumoral blood vessels due to the mechanical stresses, and the insufficient delivery of oxygen and therapeutic agents because of vessel compression. We found that the high vascular density and increased cancer cell proliferation often observed in the periphery compared to the interior of a tumor can be attributed to heterogeneous solid stress accumulation. Highly vascularized peripheral regions are also associated with greater oxygenation compared with the compressed, less vascularized inner regions. We also modeled the delivery of drugs of two distinct sizes, namely chemotherapy and nanomedicine. Model predictions suggest that drug delivery is affected negatively by vessel compression independently of the size of the therapeutic agent. Finally, we demonstrated the applicability of our model to actual geometries, employing a breast tumor model derived from MR images. PMID:25968141

  16. Work-in-progress presented at the Army symposium on solid mechanics, 1980, designing for extremes: Environment, loading, and structural behavior

    NASA Astrophysics Data System (ADS)

    1980-09-01

    Work-in-Progress was presented at the Army Symposium on solid Mechanics, 1980. Designing for Extremes: Environment, Loading, and Structural Behavior, held at Bass River (Cape Cod), Massachusetts, 29 September through 2 October 1980 were presented.

  17. Numerical Simulations and Experiments about Contamination Mechanism of Solid Immersion Lens System Concerning Hole and Geometries of Lens Holder

    NASA Astrophysics Data System (ADS)

    Choi, Moon-Ho; Yang, Tae-Man; Rhim, Yoon-Chul; Seo, Jeong-Kyo; Choi, In-Ho; Min, Byung-Hoon

    2008-07-01

    The air flow field around a conical type solid immersion lens (SIL) system is simulated numerically and confirmed with experiment using a micro-particle image velocimetry (PIV) system. It is found that the back-flow from the downstream of the SIL is a major candidate for the contamination of the SIL. Five modifications are proposed to suppress the particle conveying mechanism, the back-flow. Among these modifications a method using two flow-bypasses reduces the back-flow most effectively, which connects the top surface of the SIL system and two side-holes of the lens holder where the static pressure is the minimum.

  18. Role of Constitutive Behavior and Tumor-Host Mechanical Interactions in the State of Stress and Growth of Solid Tumors

    PubMed Central

    Papageorgis, Panagiotis; Odysseos, Andreani D.; Stylianopoulos, Triantafyllos

    2014-01-01

    Mechanical forces play a crucial role in tumor patho-physiology. Compression of cancer cells inhibits their proliferation rate, induces apoptosis and enhances their invasive and metastatic potential. Additionally, compression of intratumor blood vessels reduces the supply of oxygen, nutrients and drugs, affecting tumor progression and treatment. Despite the great importance of the mechanical microenvironment to the pathology of cancer, there are limited studies for the constitutive modeling and the mechanical properties of tumors and on how these parameters affect tumor growth. Also, the contribution of the host tissue to the growth and state of stress of the tumor remains unclear. To this end, we performed unconfined compression experiments in two tumor types and found that the experimental stress-strain response is better fitted to an exponential constitutive equation compared to the widely used neo-Hookean and Blatz-Ko models. Subsequently, we incorporated the constitutive equations along with the corresponding values of the mechanical properties - calculated by the fit - to a biomechanical model of tumor growth. Interestingly, we found that the evolution of stress and the growth rate of the tumor are independent from the selection of the constitutive equation, but depend strongly on the mechanical interactions with the surrounding host tissue. Particularly, model predictions - in agreement with experimental studies - suggest that the stiffness of solid tumors should exceed a critical value compared with that of the surrounding tissue in order to be able to displace the tissue and grow in size. With the use of the model, we estimated this critical value to be on the order of 1.5. Our results suggest that the direct effect of solid stress on tumor growth involves not only the inhibitory effect of stress on cancer cell proliferation and the induction of apoptosis, but also the resistance of the surrounding tissue to tumor expansion. PMID:25111061

  19. Experimental study of thermo-mechanical behavior of SiC composite tubing under high temperature gradient using solid surrogate

    NASA Astrophysics Data System (ADS)

    Alva, Luis; Shapovalov, Kirill; Jacobsen, George M.; Back, Christina A.; Huang, Xinyu

    2015-11-01

    Nuclear grade silicon carbide fiber (SiCf) reinforced silicon carbide matrix (SiCm) composite is a promising candidate material for accident tolerance fuel (ATF) cladding. A major challenge is ensuring the mechanical robustness of the ceramic cladding under accident conditions. In this work the high temperature mechanical response of a SiCf-SiCm composite tubing is studied using a novel thermo-mechanical test method. A solid surrogate tube is placed within and bonded to the SiCf-SiCm sample tube using a ceramic adhesive. The bonded tube pair is heated from the center using a ceramic glower. During testing, the outer surface temperature of the SiC sample tube rises up to 1274 K, and a steep temperature gradient develops through the thickness of the tube pair. Due to CTE mismatch and the temperature gradient, the solid surrogate tube induces high tensile stress in the SiC sample. During testing, 3D digital image correlation (DIC) method is used to map the strains on the outer surface of the SiC-composite, and acoustic emissions (AE) are monitored to detect the onset and progress of material damage. The thermo-mechanical behavior of SiC-composite sample is compared with that of monolithic SiC samples. Finite element models are developed to estimate stress-strain distribution within the tube assembly. Model predicted surface strain matches the measured surface strain using the DIC method. AE activities indicated a progressive damage process for SiCf-SiCm composite samples. For the composites tested in this study, the threshold mechanical hoop strain for matrix micro-cracking to initiate in SiCf-SiCm sample is found to be ∼300 microstrain.

  20. Experimental study of thermo-mechanical behavior of SiC composite tubing under high temperature gradient using solid surrogate

    NASA Astrophysics Data System (ADS)

    Alva, Luis; Shapovalov, Kirill; Jacobsen, George M.; Back, Christina A.; Huang, Xinyu

    2015-11-01

    Nuclear grade silicon carbide fiber (SiCf) reinforced silicon carbide matrix (SiCm) composite is a promising candidate material for accident tolerance fuel (ATF) cladding. A major challenge is ensuring the mechanical robustness of the ceramic cladding under accident conditions. In this work the high temperature mechanical response of a SiCf-SiCm composite tubing is studied using a novel thermo-mechanical test method. A solid surrogate tube is placed within and bonded to the SiCf-SiCm sample tube using a ceramic adhesive. The bonded tube pair is heated from the center using a ceramic glower. During testing, the outer surface temperature of the SiC sample tube rises up to 1274 K, and a steep temperature gradient develops through the thickness of the tube pair. Due to CTE mismatch and the temperature gradient, the solid surrogate tube induces high tensile stress in the SiC sample. During testing, 3D digital image correlation (DIC) method is used to map the strains on the outer surface of the SiC-composite, and acoustic emissions (AE) are monitored to detect the onset and progress of material damage. The thermo-mechanical behavior of SiC-composite sample is compared with that of monolithic SiC samples. Finite element models are developed to estimate stress-strain distribution within the tube assembly. Model predicted surface strain matches the measured surface strain using the DIC method. AE activities indicated a progressive damage process for SiCf-SiCm composite samples. For the composites tested in this study, the threshold mechanical hoop strain for matrix micro-cracking to initiate in SiCf-SiCm sample is found to be ˜300 microstrain.

  1. Discussion on a mechanical equilibrium condition of a sessile drop on a smooth solid surface

    NASA Astrophysics Data System (ADS)

    Yonemoto, Yukihiro; Kunugi, Tomoaki

    2009-04-01

    Young's equation describes an interfacial equilibrium condition of a liquid droplet on a smooth solid surface. This relation is derived by Thomas Young in 1805. It has been discussed until today after his work. In general, Young's equation is discussed from the viewpoint of thermodynamics and derived by minimizing the total free energy of the system with intensive parameters in the total free energy kept constant, i.e., the variation in the total free energy is zero. In the derivation, the virtual work variations in the horizontal and vertical directions of the droplet on the smooth solid are considered independently. However, the virtual work variation at the droplet surface depends on the variation of the horizontal and vertical directions, which are related to an incline of the droplet surface. This point has been overlooked in past studies. In this study, by considering this directional dependency, we derive the modified Young's equation based on the thermodynamics. Finally, we evaluate the modified Young's equation by comparing the analytical solution of the relationship between a contact angle and the contact line radii of the droplet with some experimental data. Moreover, we investigated the line tension itself.

  2. Solid State Nuclear Track Detectors--I: Track Characteristics and Formation Mechanisms.

    ERIC Educational Resources Information Center

    Lal, Nand

    1991-01-01

    Heavily ionizing charged particles produce radiation damage tracks in a wide variety of insulating materials. The experimental properties of these tracks and track recorders are described. The mechanisms by which the tracks are produced are discussed. (Author/KR)

  3. Anaerobic digestion of residual municipal solid waste using biological-mechanical pre-treatment: the plant of Varennes Jarcy.

    PubMed

    Fruteau de Laclos, H; Thiebaut, E; Saint-Joly, C

    2008-01-01

    Residual municipal solid waste can be treated by anaerobic digestion after a sorting process in order to remove the unwanted materials. After a mechanical sorting the quality of the final compost can hardly cope with requirements for agriculture use. In this way, a more efficient sorting process using a specific equipment that provides a combined biological and mechanical effect, has been implemented on the plant of Varennes Jarcy prior to anaerobic digestion. This paper presents the main results obtained on this plant. The reduction of biodegradable organics in particle lower than 10 mm allows a very efficient separation by screening. An additional ballistic sorting removes the remaining glass. The composition of the resulting sorted waste was close to a source-sorted organic fraction. The sorted waste exhibit methane yields comparable with raw biodegradable organics, showing that the pre-treatment had little impact on anaerobic digestion performance. PMID:18957758

  4. Fracture Toughness, Mechanical Property, And Chemical Characterization Of A Critical Modification To The NASA SLS Solid Booster Internal Material System

    NASA Technical Reports Server (NTRS)

    Pancoast, Justin; Garrett, William; Moe, Gulia

    2015-01-01

    A modified propellant-liner-insulation (PLI) bondline in the Space Launch System (SLS) solid rocket booster required characterization for flight certification. The chemical changes to the PLI bondline and the required additional processing have been correlated to mechanical responses of the materials across the bondline. Mechanical properties testing and analyses included fracture toughness, tensile, and shear tests. Chemical properties testing and analyses included Fourier transform infrared (FTIR) spectroscopy, cross-link density, high-performance liquid chromatography (HPLC), gas chromatography (GC), gel permeation chromatography (GPC), and wave dispersion X-ray fluorescence (WDXRF). The testing identified the presence of the expected new materials and found the functional bondline performance of the new PLI system was not significantly changed from the old system.

  5. Effect of Particle Size on the Mechanical Properties of Semi-Solid, Powder-Rolled AA7050 Strips

    NASA Astrophysics Data System (ADS)

    Luo, Xia; Liu, Yunzhong

    2016-07-01

    The AA7050 alloy strips can be successfully prepared by semi-solid powder rolling. The effect and factors of particle size on the microstructure, relative density, and mechanical properties were discussed. The results show that coarse starting powders require less liquid to achieve high relative density, and the formed strips have lower elongation compared with that prepared with the fine starting powders. The strength is more related to defects, whereas elongation partially depends on the grain size. Additionally, the fracture mechanism of strips prepared with fine powders is the ductile fracture because many dimples are observed. For relative density, when the initial liquid fraction is lower than 10%, the difference of deformation degree is the main factor. When the liquid fraction is higher than 10-20%, premature solidification and more particle interfaces are the two main factors.

  6. Thermo-mechanical and optical analysis and modeling for a diamond-cooled solid-state Nd:YAG laser

    NASA Astrophysics Data System (ADS)

    Chou, Hsian P.; Sadovnik, Isaac; Tammaro, Eric J.; Wang, Yu-Lin; Bass, Michael; Chen, Ying

    2006-05-01

    In 2000, Textron Systems Corporation (TSC) initiated the development of an advanced diamond cooled solid-state laser concept suitable for ultra compact medium and high-power lasers. The resulting laser configuration is applicable to laser diode pumping and a wide variety of lasing materials. In order to further improve the performance and determine the limitation of this laser concept, the detailed physical understanding of the interface between diamond and YAG disks was identified as a critical issue. Numerical analyses had been conducted for investigating the thermal-mechanical interaction in the interface between the gain medium and the diamond disks when the lasing process is in progress. Following this analyses, a computer model has been developed to simulate the phenomena of light interaction with the active medium. Subsequently, this computer model has been applied to optimize the laser design, in which the performance in terms of efficiency and compactness for a diamond-cooled laser has shown significant improvements. The understanding of the thermo-mechanical/optical issues at the interface, in general, will be beneficial to a variety of solid-state laser design activities.

  7. Growth of giant membrane lobes mechanically driven by wetting fronts of phospholipid membranes at water-solid interfaces.

    PubMed

    Suzuki, Kenji; Masuhara, Hiroshi

    2005-01-18

    We report on the growth of giant membrane lobes that is mechanically driven by wetting fronts of phospholipid membranes at water-solid interfaces and a strategy to control the two-dimensional structure of the membrane lobes on a solid surface. The growth of giant membrane lobes was observed on a single-lipid bilayer which spread from a lump of phospholipid deposited on a silica-glass substrate or an oxidized silicon wafer in aqueous solutions of NaCl, KCl, MgCl2, or CaCl2 at relatively high salt concentrations. Most of the membrane lobes were very flat unilamellar tubes elongating from the lump of phospholipid, and their length reached 1 mm in 5 h. Experimental findings clearly indicate that the membrane lobes are adherent to the surface of the single-lipid bilayer and are mechanically elongated from the lump of phospholipid by the sliding motion of the single-lipid bilayer. We could control the two-dimensional structure of the membrane lobes on the substrate by controlling the spreading direction of the single-lipid bilayer using Pt micropatterns that were deposited on the smooth surface of the oxidized silicon wafer. PMID:15641821

  8. Structural and mechanical design challenges of space shuttle solid rocket boosters separation and recovery subsystems

    NASA Technical Reports Server (NTRS)

    Woodis, W. R.; Runkle, R. E.

    1985-01-01

    The design of the space shuttle solid rocket booster (SRB) subsystems for reuse posed some unique and challenging design considerations. The separation of the SRBs from the cluster (orbiter and external tank) at 150,000 ft when the orbiter engines are running at full thrust meant the two SRBs had to have positive separation forces pushing them away. At the same instant, the large attachments that had reacted launch loads of 7.5 million pounds thrust had to be servered. These design considerations dictated the design requirements for the pyrotechnics and separation rocket motors. The recovery and reuse of the two SRBs meant they had to be safely lowered to the ocean, remain afloat, and be owed back to shore. In general, both the pyrotechnic and recovery subsystems have met or exceeded design requirements. In twelve vehicles, there has only been one instance where the pyrotechnic system has failed to function properly.

  9. Mechanical Yield in Amorphous Solids: A First-Order Phase Transition

    NASA Astrophysics Data System (ADS)

    Jaiswal, Prabhat K.; Procaccia, Itamar; Rainone, Corrado; Singh, Murari

    2016-02-01

    Amorphous solids yield at a critical value of the strain (in strain-controlled experiments); for larger strains, the average stress can no longer increase—the system displays an elastoplastic steady state. A long-standing riddle in the materials community is what the difference is between the microscopic states of the material before and after yield. Explanations in the literature are material specific, but the universality of the phenomenon begs a universal answer. We argue here that there is no fundamental difference in the states of matter before and after yield, but the yield is a bona fide first-order phase transition between a highly restricted set of possible configurations residing in a small region of phase space to a vastly rich set of configurations which include many marginally stable ones. To show this, we employ an order parameter of universal applicability, independent of the microscopic interactions, that is successful in quantifying the transition in an unambiguous manner.

  10. Solidification and solid-state transformation mechanisms in Si alloyed high-chromium white cast irons

    SciTech Connect

    Laird, G. II ); Powell, G.L.F. )

    1993-04-01

    Chromium white cast irons are widely used in environments where severe abrasion resistance is a dominant requirement. To improve the wear resistance of these commercially important irons, the US Bureau of Mines and CSIRO Australia are studying their solidification and solid-state transformation kinetics. A ternary Fe-Cr-C iron with 17.8 wt pct (pct) Cr and 3.0 pct C was compared with commercially available irons of similar Cr and C contents with Si contents between 1.6 and 2.2 pct. The irons were solidified and cooled at rates of 0.03 and 0.17 K/s to 873 K. Differential thermal analysis (DTA) showed that Si depresses the eutectic reaction temperature and suggests that it has no effect upon the volume of eutectic carbides formed during solidification. Microprobe analysis revealed that austenite dendrites within the Si alloyed irons cooled at 0.03 and 0.17 K/s had C and Cr contents that were lower than those of dendrites within the ternary alloy cooled at the same cooling rate and a Si alloyed iron that was water quenched from the eutectic temperature. These lower values were shown by image analysis to be the result of both solid-state growth (coarsening) of the eutectic carbides and some secondary carbide formation. Hardness measurements in the as-cast condition and after soaking in liquid nitrogen suggest an increase in the martensite start temperature as the Si content was increased. It is concluded that Si's effect on increasing the size and volume fraction of eutectic carbides and increasing the matrix hardness should lead to improved wear resistance over regular high-chromium white cast irons.

  11. An Evaluation of Liquid, Solid, and Grease Lubricants for Space Mechanisms Using a Spiral Orbit Tribometer

    NASA Technical Reports Server (NTRS)

    Buttery, Michael

    2010-01-01

    We present the findings of the test program performed by The European Space Tribology Laboratory (ESTL) to evaluate the performance (friction and lifetime) of a number of space lubricants under vacuum using a Spiral Orbit Tribometer (SOT). Focus was given to a comparison of various popular space oils, a comparison study between the old and new MAPLUB grease formulations, and the performance of commonly used solid lubricants under various conditions. Tests demonstrated that the lifetimes of hydrocarbon NYE oils 2001 & 2001A outperformed those of the perfluroropolyalkylether (PFPE) oils Fomblin Z25 & Z60, though these pairs displayed similar behavior. This relationship was also generally seen for greases; with the lifetimes of the multiple alkylated cyclopentane (MAC)-based greases being extended in comparison to the PFPE-based greases. Testing on greases also demonstrated similar performance between the old (-a) and new (-b) formulations when considering PFPE-based MAPLUB greases, and indeed for all tested PFPE-based non-MAPLUB greases, but significantly shorter lifetimes for the new formulations when considering MAC-based MAPLUB greases. MAPLUB MAC greases containing molybdenum disulphide (MoS2) thickener were also found to display reduced lifetimes. For solid lubricants, lead displayed significantly extended lifetimes over MoS2, speculated to be caused by redistribution of lead from the ball onto all contact surfaces during the test. Friction coefficients were seen to be some 2.5x higher for lead than for MoS2 under similar conditions, a result that corresponds well with conventional bearing tests. The work described was performed under contract for the European Space Agency as part of the Tribology Applications Program, with all funding for testing and apparatus provided by European Space Agency (ESA).

  12. Halogen bonding: a new retention mechanism for the solid phase extraction of perfluorinated iodoalkanes.

    PubMed

    Yan, Xiao Qing; Shen, Qian Jin; Zhao, Xiao Ran; Gao, Hai Yue; Pang, Xue; Jin, Wei Jun

    2012-11-13

    For the first time, halogen-bonding interaction is utilised in the solid phase extraction of perfluorinated iodoalkane (PFI). Nine PFIs, as model analytes, were tested, and analyses by UV, (19)F NMR and Raman spectroscopies demonstrate that the PFIs are extracted by a strong anion exchange (SAX) sorbent from n-hexane due to the C-I···Cl(-) halogen-bonding interactions. The results also show that the adsorptivities of SAX for the diiodoperfluoro-alkanes (diiodo-PFIs) were much stronger than those for the perfluoroalkyl iodides (monoiodo-PFIs). Specifically, the recoveries for 1,6-diiodoperfluorohexane and 1,8-diiodoperfluorooctane were higher than 80% when 100mL of sample spiked with a 5 ng mL(-1) analyte mixture was extracted. Interestingly, SAX had no adsorption for hexafluorobenzene at all, which is known to be unable to form a halogen bond with Cl(-). The analytical performance of the halogen bond-based SPE-GC-MS method for the diiodo-PFIs was also examined in soil samples. The sorbent SAX enabled the selective extraction of four diiodo-PFIs successfully from soil samples. The recoveries of the diiodo-PFIs extracted from 5 g soil sample at the 100 ng g(-1) spike level were in the range of 73.2-93.8% except 26.8% for 1,2-diiodoperfluoroethane. The limit of detection varied from 0.02 to 0.04 ng g(-1) in soil samples. Overall, this work reveals the great application potential of halogen bonding in the field of solid phase extraction to selectively extract compounds with strong halogen-bonding abilities. PMID:23107136

  13. Nano/micro/meso scale interactions in mechanics of pharmaceutical solid dosage forms

    NASA Astrophysics Data System (ADS)

    Akseli, Ilgaz

    Oral administration in form tablets has been the most common method for delivering drug to the human systemic blood circulation accurately and reproducibly due to its established manufacturing methods and reliability as well as cost. The mechanical criteria for a successful powder-to-tablet processing are good flowability, compressibility and compactibility that are closely related to the mechanical and adhesion properties of the particles and particle strength. In this thesis, air-coupled acoustic and ultrasonic techniques are presented and demonstrated as noncontact and nondestructive methods for physical (mechanical) integrity monitoring and mechanical characterization of tablets. A testing and characterization experimental platform for defect detection, coating thickness and mechanical property determination of tablets was also developed. The presented air-coupled technique was based on the analysis of the transient vibrational responses of a tablet in both temporal and spectral domains. The contact ultrasonic technique was based on the analysis of the propagation speed of an acoustic pulse launched into a tablet and its reflection from the coat-core interface of the tablet. In defect monitoring, the ultimate objective is to separate defective tablets from nominal ones. In the case of characterization, to extract the coating layer thicknesses and mechanical properties of the tablets from a subset of the measured resonance frequencies, an iterative computational procedure was demonstrated. In the compaction monitoring experiments, an instrumented punch and a cylindrical die were employed to extract the elasticity properties of tablets during compaction. To study the effect of compaction kinetics on tablet properties and defect, finite element analyses of single layer and bilayer tablets were performed. A noncontact work-of-adhesion technique was also demonstrated to determine the work-of-adhesion of pharmaceutical powder particles.

  14. On the mechanism of catalysis induced by mechano-activation of solid body

    NASA Astrophysics Data System (ADS)

    Kulczycki, Andrzej; Kajdas, Czesław K.; Liang, Hong

    2014-12-01

    The paper presents a new model of the mechanism of mechanocatalysis and tribocatalysis. The reason for the increase in heterogeneous catalysis effect after mechanical activation of a catalyst has not been fully understood yet. There is no known theory, which would explain the mechanism of the influence of mechanical energy introduced to catalyst particles on the rate of chemical reaction. All existing theories are based on Arrhenius equation and assume that catalysts increase reaction rate due to decreasing of activation energy E a . We hypothesize that both for standard and catalyzed heterogeneous reactions the same E a (real activation energy) is needed to trigger the reaction processes and the catalytic effect is the result of energy introduced to the reaction system, its accumulation by a catalyst and then emission of high flux of energy to the space near the catalyst particles. This energy emitted by molecules of reagents can reach a value equal to the value of E a at lower ambient temperature than it would result from Arrhenius equation. This hypothesis is based on α i model described in previous papers by Kajdas and Kulczycki as well as the results of tribochemical research described by Hong Liang et al., which demonstrate that the reaction rate is higher than that resulting from temperature.

  15. Are scaling laws on strength of solids related to mechanics or to geometry?

    PubMed

    Carpinteri, Alberto; Pugno, Nicola

    2005-06-01

    One of the largest controversial issues of the materials science community is the interpretation of scaling laws on material strength. In spite of the prevailing view, which considers mechanics as the real cause of such effects, here, we propose a different argument, purely based on geometry. Thus, as happened for relativity, geometry could again hold an unexpected and fundamental role. PMID:15928689

  16. Altering the interfacial activation mechanism of a lipase by solid-phase selective chemical modification.

    PubMed

    López-Gallego, Fernando; Abian, Olga; Guisán, Jose Manuel

    2012-09-01

    This study presents a combined protein immobilization, directed mutagenesis, and site-selective chemical modification approach, which was used to create a hyperactivated semisynthetic variant of BTL2. Various alkane chains were tethered at three different positions in order to mimic the lipase interfacial activation exogenously triggered by detergents. Optimum results were obtained when a dodecane chain was introduced at position 320 by solid-phase site-selective chemical modification. The resulting semisynthetic variant showed a 2.5-fold higher activity than the wild-type nonmodified variant in aqueous conditions. Remarkably, this is the maximum hyperactivation ever observed for BTL2 in the presence of detergents such as Triton X-100. We present evidence to suggest that the endogenous dodecane chain hyperactivates the enzyme in a similar fashion as an exogenous detergent molecule. In this way, we also observe a faster irreversible enzyme inhibition and an altered detergent sensitivity profile promoted by the site-selective chemical modification. These findings are also supported by fluorescence studies, which reveal that the structural conformation changes of the semisynthetic variant are different to those of the wild type, an effect that is more pronounced in the presence of detergent. Finally, the optimal immobilized semisynthetic variant was successfully applied to the selective synthesis of oxiran-2-yl butyrate. Significantly, this biocatalyst is 12-fold more efficient than the immobilized wild-type enzyme, producing the S-enantiomer with higher enantiospecificity (ee = 92%). PMID:22876885

  17. Atomic-Scale Mechanisms of Oxygen Electrode Delamination in Solid Oxide Electrolyzer Cells

    SciTech Connect

    Sergey N. Rashkeev; Michael V. Glazoff

    2012-01-01

    Materials used for different components (electrodes, electrolyte, steel interconnects, etc.) of solid oxide electrolyzer cell (SOEC) devices for hydrogen production have to function in aggressive, corrosive environments and in the presence of electric fields. This results in a number of degradation processes at interfaces between components. In this study, we used a combination of first-principles, density-functional-theory (DFT) calculations and thermodynamic modeling to elucidate the main processes that contribute into the oxygen delamination in typical SOEC device consisting of yttria-stabilized zirconia (YSZ) electrolyte and Sr-doped LaMnO3 (LSM) oxygen electrode. We found that high temperature inter-diffusion of different atoms across the LSM/YSZ interface significantly affects structural stability of the materials and their interface. In particular, we found that La and Sr substitutional defects positioned in ZrO2 oxide and near LSM/YSZ interface significantly change oxygen transport which may develop pressure buildup in the interfacial region and eventually develop delamination process. Simple models for estimating these effects are proposed, and different possibilities for inhibiting and/or mitigating undesirable delamination processes are discussed.

  18. Mechanical and thermal characterization of a ceramic/glass composite seal for solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Dev, Bodhayan; Walter, Mark E.; Arkenberg, Gene B.; Swartz, Scott L.

    2014-01-01

    Solid oxide fuel cells (SOFCs) require seals that can function in harsh, elevated temperature environments. Comprehensive characterization and understanding of seals is needed for commercially viable SOFCs. The present research focuses on a novel ceramic/glass composite seal that is produced by roller compaction or tape casting of glass and ceramic powders and an organic binder. Upon heat treatment, micro-voids and surface anomalies are formed. Increased heating and cooling rates during the heat treatment resulted in more and larger voids. The first goal of the current research is to suggest an appropriate heating and cooling rate to minimize the formation of microstructural defects. After identifying an appropriate cure cycle, seals were thermally cycled and then characterized with laser dilatometry, X-ray diffraction, and sonic resonance. From these experiments the crystalline phases, thermal expansion, and elastic properties were determined. Subsequently compression testing with an acoustic emission (AE) sensor and post-test microstructural analysis were used to identify the formation of damage. By fully understanding the characteristics of this ceramic/glass composite seal, next generation seals can be fabricated for improved performance.

  19. New mechanism of ultra-deep drilling of solids by high-power lasers

    NASA Astrophysics Data System (ADS)

    Kudryashov, Sergey I.; Pakhomov, Andrew V.; Allen, Susan D.

    2005-04-01

    A new mechanism of ultra-deep drilling and related molten material expulsion during high-power short-pulse laser ablation of metals, semiconductors and dielectrics is proposed. In this mechanism ultra-deep (multi-micron) heat penetration and melting depths in these materials are assumed to result from their bulk absorption of thermal short-wavelength con-tinuous and characteristic radiation emitted by hot near-surface ablative laser plasmas. Multi-microsecond delays for expulsion of subsonic jets of micron-size droplets and for re-radiation of UV bursts from the irradiated targets are ex-plained by subsurface explosive boiling in bulk of the resulting ultra-deep melt pool.

  20. Mechanisms of lubrication and wear of a bonded solid-lubricant film

    NASA Technical Reports Server (NTRS)

    Fusaro, R. L.

    1980-01-01

    The tribological properties of polyimide-bonded graphite fluoride films were investigated. A pin-on-disk type of testing apparatus was used; in addition to sliding a hemispherically tipped rider, a rider with a 0.95-mm-diameter flat area was slid against the film so that a lower, less variable contact stress could be achieved. Two stages of lubrication occurred: in the first, the film supported the load and the lubricating mechanism consisted of the shear of a thin surface layer between the rider and the bulk of the film. The second occurred after the bonded film had worn to the substrate, and consisted of the shear of very thin lubricant films between the rider and flat plateaus generated on the metallic substrate asperities. The film wear mechanism was strongly dependent on contact stress.

  1. Spontaneous fragmentation of an alpha-active ceramic: a mechanism for dispersion of solid waste

    SciTech Connect

    Clinard, F.W. Jr.; Rohr, D.L.

    1980-01-01

    Studies underway to characterize spontaneous fragmentation in /sup 238/PuO/sub 2/ and to determine the mechanism(s) responsible are reported. Results reported here show that: spontaneous fragmentation of /sup 238/PuO/sub 2/ generates a wide range of particle sizes, from a few mm to 1000 A or less; the phenomenon may continue with time or may saturate, depending on starting material; the magnitude of the effect is dependent on storage environment. Neither thermal stresses nor lattice damage appear to be solely responsible for fragmentation, but radiolysis of the environment could play an important role. Work is continuing in an effort to identify the controlling factors in this phenomenon.

  2. Mechanical Properties of Solid-State Recycled 4xxx Aluminum Alloy Chips

    NASA Astrophysics Data System (ADS)

    Tokarski, Tomasz

    2016-06-01

    The direct production of aluminum from bauxite ores is known to be a very energetic-intensive operation compared to other metallurgical processes. Due to energy issues and the rapid increase in aluminum demand, new kinds of aluminum production processes are required. Aluminum waste recycling, which has an advantage of lowering the cost of electric power consumption, is considered to be an alternative route for material manufacturing. In this work, the way of reusing aluminum EN-AC 44000 alloy scraps by hot extrusion was presented. Metal chips of different sizes and morphology were cold compacted into billet form and then hot extruded. Mechanical properties investigations combined with microstructure observations were performed. Mechanical anisotropy behavior of material was evaluated on the base of tensile test experiments performed on samples machined at 0°, 45°, and 90°, respectively, to the extrusion direction. It was found that the initial size of the chips has an influence on the mechanical properties of the received profiles. Samples produced from fine chips revealed higher tensile strength in comparison to larger chips, which can be attributed to a refined microstructure containing fine, hard Si particles and Fe-rich intermetallic phases. Finally, it was found that anisotropic behavior of chip-based profiles is similar to conventionally cast and extruded materials which prove good bonding quality between chips.

  3. Mechanical joining with self piercing solid-rivets at elevated tool velocities

    SciTech Connect

    Neugebauer, R.; Jesche, F.; Kraus, C.; Hensel, S.

    2011-05-04

    In the present paper the influence of a higher setting velocity in the joining process of self piercing solid-rivets is shown. In the conventional process tool velocities well below 1 m/s are common. The present research results show the potential of increasing them in the range of about 5 m/s. The results are especially relevant for joining high-strength steels. These steel sheets often cause problems in the process of riveting mixed materials, e. g. aluminium-steel compound. The high strength of the steel sometimes leads to undesirable material flow in the joining process or unwanted burr development. These effects, which are described in detail in the article, can be reduced significantly for the investigated cases by the use of higher tool velocities. Using a high speed camera and a load cell, a test setup based on a drop tower was realized. It was used to time the force signals and the motion profile of the high speed riveting process. The results of the force analysis show an oscillating force progression. Within a numerical research the principal effects influencing the results of the riveting process can be shown. It was found that the pulse-like force transmission between riveting machine and punch, results in various vibrations especially of long and thin tool parts. Hence the rivet penetrates the sheet metal with non-uniform velocities. As a result the early indentation of die into the lower sheet metal at the beginning of the process is reduced, so that the final process step provides a sufficient material flow into the circular rivet groove. A strain-rate dependent process model with elastic tool properties and consideration of inertia effects is presented.

  4. Rapid Ice-Sheet Changes and Mechanical Coupling to Solid-Earth/Sea-Level and Space Geodetic Observation

    NASA Astrophysics Data System (ADS)

    Adhikari, S.; Ivins, E. R.; Larour, E. Y.

    2015-12-01

    Perturbations in gravitational and rotational potentials caused by climate driven mass redistribution on the earth's surface, such as ice sheet melting and terrestrial water storage, affect the spatiotemporal variability in global and regional sea level. Here we present a numerically accurate, computationally efficient, high-resolution model for sea level. Unlike contemporary models that are based on spherical-harmonic formulation, the model can operate efficiently in a flexible embedded finite-element mesh system, thus capturing the physics operating at km-scale yet capable of simulating geophysical quantities that are inherently of global scale with minimal computational cost. One obvious application is to compute evolution of sea level fingerprints and associated geodetic and astronomical observables (e.g., geoid height, gravity anomaly, solid-earth deformation, polar motion, and geocentric motion) as a companion to a numerical 3-D thermo-mechanical ice sheet simulation, thus capturing global signatures of climate driven mass redistribution. We evaluate some important time-varying signatures of GRACE inferred ice sheet mass balance and continental hydrological budget; for example, we identify dominant sources of ongoing sea-level change at the selected tide gauge stations, and explain the relative contribution of different sources to the observed polar drift. We also report our progress on ice-sheet/solid-earth/sea-level model coupling efforts toward realistic simulation of Pine Island Glacier over the past several hundred years.

  5. Investigation of Polar Stratospheric Cloud Solid Particle Formation Mechanisms Using ILAS and AVHRR Observations in the Arctic

    NASA Technical Reports Server (NTRS)

    Irie, H.; Pagan, K. L.; Tabazadeh, A.; Legg, M. J.; Sugita, T.

    2004-01-01

    Satellite observations of denitrification and ice clouds in the Arctic lower stratosphere in February 1997 are used with Lagrangian microphysical box model calculations to evaluate nucleation mechanisms of solid polar stratospheric cloud (PSC) particles. The occurrences of ice clouds are not correlated in time and space with the locations of back trajectories of denitrified air masses, indicating that ice particle surfaces are not always a prerequisite for the formation of solid PSCs that lead to denitrification. In contrast, the model calculations incorporating a pseudoheterogeneous freezing process occurring at the vapor-liquid interface can quantitatively explain most of the observed denitrification when the nucleation activation free energy for nitric acid dihydrate formation is raised by only approx.10% relative to the current published values. Once nucleated, the conversion of nitric acid dihydrate to the stable trihydrate phase brings the computed levels of denitrification closer to the measurements. INDEX TERMS: 0305 Atmospheric Composition and Structure: Aerosols and particles (0345, 4801); 0320 Atmospheric Composition and SblctureC: loud physics and chemistry; 0340 Atmospheric Composition and Structure: Middle atmosphere-composition and chemistry

  6. Assessment of the effectiveness of an industrial unit of mechanical-biological treatment of municipal solid waste.

    PubMed

    Bayard, R; Morais, J de Araújo; Ducom, G; Achour, F; Rouez, M; Gourdon, R

    2010-03-15

    An assessment of the French municipal solid waste (MSW) mechanical-biological treatment (MBT) unit of Mende was performed in terms of mass reduction, biogas emissions reduction and biostability of the biologically treated waste. The MBT unit consists of mechanical sorting operations, an aerobic rotating bioreactor, forced-aeration process in open-air tunnels (stabilization), ripening platforms and a sanitary landfill site for waste disposal in separated cells. On the overall plant, results showed a dry matter reduction of 18.9% and an oxidative organic matter reduction of 39.0%. A 46.2% biogas production decrease could also be observed. Concerning the biotreatment steps, high reductions were observed: 88.1% decrease of biogas potential and 57.7% decrease of oxidative organic matter content. Nevertheless, the usually considered stabilization indices (biogas potential, respirometric index) remained higher than recommended by the German or Austrian regulation for landfilling. Mass balance performed on each step of the treatment line showed that several stages needed improvement (especially mechanical sorting operations) as several waste fractions containing potentially biodegradable matter were landfilled with very few or no biological treatment. PMID:19913357

  7. In-Situ AFM Investigation of Solid Electrolyte Interphase Formation and Failure Mechanisms in Lithium -Ion Batteries

    NASA Astrophysics Data System (ADS)

    Mueller, Thomas; Kumar, Ravi; Tokranov, Anton; Huang, Teddy; Li, Chunzeng; Xiao, Xingcheng; Sheldon, Brian

    The formation and evolution of the solid electrolyte interphase (SEI) is critical for lifetime and performance of lithium-ion batteries (LIBs), particularly for LIBs with high energy density materials such as silicon. Si has almost ten time theoretical specific capacity vs graphite, but its volume changes during cycling (up to 400%) put enormous strains on the SEI layer, resulting in continuous capacity loss. In this study we report in situ atomic force microscopy (AFM) investigation on the formation and failure mechanisms of SEI layer using patterned Si island structures. Due to the shear lag effect, patterned Si islands go through lateral expansion and Contraction, putting the SEI layer in tension and compression during lithiation and delithiation, respectively. Experimentally, we performed the studies in a glovebox with <1 ppm O2 and H2O, using PeakForce Tapping to image the extremely fragile SEI layer. We show for the first time the in operando cracking of SEI layer. To understand the mechanics of the SEI layer, the critical strain for cracking was derived from a progression of the AFM images. Our studies provide new insight into SEI formation, evolution and its mechanical response, and offer guidance to tailor passivation layers for optimal performance.

  8. Direct Numerical Simulations in Solid Mechanics for Quantifying the Macroscale Effects of Microstructure and Material Model-Form Error

    NASA Astrophysics Data System (ADS)

    Bishop, Joseph E.; Emery, John M.; Battaile, Corbett C.; Littlewood, David J.; Baines, Andrew J.

    2016-05-01

    Two fundamental approximations in macroscale solid-mechanics modeling are (1) the assumption of scale separation in homogenization theory and (2) the use of a macroscopic plasticity material model that represents, in a mean sense, the multitude of inelastic processes occurring at the microscale. With the goal of quantifying the errors induced by these approximations on engineering quantities of interest, we perform a set of direct numerical simulations (DNS) in which polycrystalline microstructures are embedded throughout a macroscale structure. The largest simulations model over 50,000 grains. The microstructure is idealized using a randomly close-packed Voronoi tessellation in which each polyhedral Voronoi cell represents a grain. An face centered cubic crystal-plasticity model is used to model the mechanical response of each grain. The overall grain structure is equiaxed, and each grain is randomly oriented with no overall texture. The detailed results from the DNS simulations are compared to results obtained from conventional macroscale simulations that use homogeneous isotropic plasticity models. The macroscale plasticity models are calibrated using a representative volume element of the idealized microstructure. Ultimately, we envision that DNS modeling will be used to gain new insights into the mechanics of material deformation and failure.

  9. Direct numerical simulations in solid mechanics for quantifying the macroscale effects of microstructure and material model-form error

    DOE PAGESBeta

    Bishop, Joseph E.; Emery, John M.; Battaile, Corbett C.; Littlewood, David J.; Baines, Andrew J.

    2016-03-16

    Two fundamental approximations in macroscale solid-mechanics modeling are (1) the assumption of scale separation in homogenization theory and (2) the use of a macroscopic plasticity material model that represents, in a mean sense, the multitude of inelastic processes occurring at the microscale. With the goal of quantifying the errors induced by these approximations on engineering quantities of interest, we perform a set of direct numerical simulations (DNS) in which polycrystalline microstructures are embedded throughout a macroscale structure. The largest simulations model over 50,000 grains. The microstructure is idealized using a randomly close-packed Voronoi tessellation in which each polyhedral Voronoi cellmore » represents a grain. An face centered cubic crystal-plasticity model is used to model the mechanical response of each grain. The overall grain structure is equiaxed, and each grain is randomly oriented with no overall texture. The detailed results from the DNS simulations are compared to results obtained from conventional macroscale simulations that use homogeneous isotropic plasticity models. The macroscale plasticity models are calibrated using a representative volume element of the idealized microstructure. Furthermore, we envision that DNS modeling will be used to gain new insights into the mechanics of material deformation and failure.« less

  10. Mechanical properties of crystalline solids. Progress report, December 1, 1979-November 30, 1980

    SciTech Connect

    Li, C Y; Mukherjee, S; Hart, E W

    1980-09-01

    The work performed during the past fiscal year included in the materials area: the development of microstructural basis for a second generation state variable deformation model; the continuation of the work on a unified model for grain boundary anelasticity and grain boundary sliding; the continued investigation of the grain boundary cavitation process in the Zircaloys; and the application of a state variable approach in materials characterization. In the mechanics area: a finite element analysis of thermal stress transients in structures; and the application of the boundary element method to plate bending and fracture. Type 316 stainless steel, Nickel 270, and Zircaloy-2 and -4 were the materials used. 35 figures.

  11. Recycling and processing of several typical crosslinked polymer scraps with enhanced mechanical properties based on solid-state mechanochemical milling

    NASA Astrophysics Data System (ADS)

    Lu, Canhui; Zhang, Xinxing; Zhang, Wei

    2015-05-01

    The partially devulcanization or de-crosslinking of ground tire rubber (GTR), post-vulcanized fluororubber scraps and crosslinked polyethylene from cable scraps through high-shear mechanochemical milling (HSMM) was conducted by a modified solid-state mechanochemical reactor. The results indicated that the HSMM treated crosslinked polymer scraps can be reprocessed as virgin rubbers or thermoplastics to produce materials with high performance. The foamed composites of low density polyethylene/GTR and the blend of post-vulcanized flurorubber (FKM) with polyacrylate rubber (ACM) with better processability and mechanical properties were obtained. The morphology observation showed that the dispersion and compatibility between de-crosslinked polymer scraps and matrix were enhanced. The results demonstrated that HSMM is a feasible alternative technology for recycling post-vulcanized or crosslinked polymer scraps.

  12. Recycling and processing of several typical crosslinked polymer scraps with enhanced mechanical properties based on solid-state mechanochemical milling

    SciTech Connect

    Lu, Canhui; Zhang, Xinxing; Zhang, Wei

    2015-05-22

    The partially devulcanization or de-crosslinking of ground tire rubber (GTR), post-vulcanized fluororubber scraps and crosslinked polyethylene from cable scraps through high-shear mechanochemical milling (HSMM) was conducted by a modified solid-state mechanochemical reactor. The results indicated that the HSMM treated crosslinked polymer scraps can be reprocessed as virgin rubbers or thermoplastics to produce materials with high performance. The foamed composites of low density polyethylene/GTR and the blend of post-vulcanized flurorubber (FKM) with polyacrylate rubber (ACM) with better processability and mechanical properties were obtained. The morphology observation showed that the dispersion and compatibility between de-crosslinked polymer scraps and matrix were enhanced. The results demonstrated that HSMM is a feasible alternative technology for recycling post-vulcanized or crosslinked polymer scraps.

  13. An iterative Riemann solver for systems of hyperbolic conservation law s, with application to hyperelastic solid mechanics

    SciTech Connect

    Miller, Gregory H.

    2003-08-06

    In this paper we present a general iterative method for the solution of the Riemann problem for hyperbolic systems of PDEs. The method is based on the multiple shooting method for free boundary value problems. We demonstrate the method by solving one-dimensional Riemann problems for hyperelastic solid mechanics. Even for conditions representative of routine laboratory conditions and military ballistics, dramatic differences are seen between the exact and approximate Riemann solution. The greatest discrepancy arises from misallocation of energy between compressional and thermal modes by the approximate solver, resulting in nonphysical entropy and temperature estimates. Several pathological conditions arise in common practice, and modifications to the method to handle these are discussed. These include points where genuine nonlinearity is lost, degeneracies, and eigenvector deficiencies that occur upon melting.

  14. Influence of pH on mechanical relaxations in high solids LM-pectin preparations.

    PubMed

    Alba, K; Kasapis, S; Kontogiorgos, V

    2015-01-01

    The influence of pH on the mechanical relaxation of LM-pectin in the presence of co-solute has been investigated by means of differential scanning calorimetry, ζ-potential measurements and small deformation dynamic oscillation in shear. pH was found to affect the conformational properties of the polyelectrolyte altering its structural behavior. Cooling scans in the vicinity of the glass transition region revealed a remarkable change in the viscoelastic functions as the polyelectrolyte rearranges from extended (neutral pH) to compact conformations (acidic pH). This conformational rearrangement was experimentally observed to result in early vitrification at neutral pH values where dissociation of galacturonic acid residues takes place. Time-temperature superposition of the mechanical shift factors and theoretical modeling utilizing WLF kinetics confirmed the accelerated kinetics of glass transition in the extended pectin conformation at neutral pH. Determination of the relaxation spectra of the samples using spectral analysis of the master curves revealed that the relaxation of macromolecules occurs within ∼ 0.1s regardless of the solvent pH. PMID:25965472

  15. Damage mechanism involved in the solid particle erosion of CVD diamond

    NASA Astrophysics Data System (ADS)

    Davies, Alun R.; Field, John E.

    2001-09-01

    Sophisticated electro-optic sensors are employed on aircraft and missiles, and it is essential to protect them from relatively high-speed impacts with airborne dust particles. A loss in transmission caused by such an event can impair guidance, and catastrophic failure may occur. Protection is afforded by the installation of a hard cover that is transparent in the relevant regime. Diamond is potentially by far the most attractive window material due to excellent optical and mechanical properties, but it is difficult to shape. Chemical vapor deposited (CVD) diamond is a polycrystalline synthetic with properties that approach those of single crystal diamond, and it can be more easily shaped. The aims of the present research were to quantify the erosion and transmission losses, and to understand the material removal mechanisms involved. Steady-state erosion rates were obtained for CVD diamond of different grain sizes, using 300-600 micrometers quartz erodent at velocities between 60 and 140 m/s. Images of CVD diamond at various stages of erosion, obtained using an optical microscope and an environmental scanning electron microscope (ESEM), reveal that erosion initially occurs at grain boundaries and that so-called micro-features also have some influence on erosion.

  16. Anti-glioma activity and the mechanism of cellular uptake of asiatic acid-loaded solid lipid nanoparticles.

    PubMed

    Garanti, Tanem; Stasik, Aneta; Burrow, Andrea Julie; Alhnan, Mohamed A; Wan, Ka-Wai

    2016-03-16

    Asiatic acid (AA), a pentacyclic triterpene found in Centella Asiatica, has shown neuroprotective and anti-cancer activity against glioma. However, owing to its poor aqueous solubility, effective delivery and absorption across biological barriers, in particular the blood brain barrier (BBB), are challenging. Solid lipid nanoparticles (SLNs) have shown a promising potential as a drug delivery system to carry lipophilic drugs across the BBB, a major obstacle in brain cancer therapy. Nevertheless, limited information is available about the cytotoxic mechanisms of nano-lipidic carriers with AA on normal and glioma cells. This study assessed the anti-cancer efficacy of AA-loaded SLNs against glioblastoma and their cellular uptake mechanism in comparison with SVG P12 (human foetal glial) cells. SLNs were systematically investigated for three different solid lipids; glyceryl monostearate (MS), glyceryl distearate (DS) and glyceryl tristearate (TS). The non-drug containing MS-SLNs (E-MS-SLNs) did not show any apparent toxicity towards normal SVG P12 cells, whilst the AA-loaded MS-SLNs (AA-MS-SLNs) displayed a more favourable drug release profile and higher cytotoxicity towards U87 MG cells. Therefore, MS-SLNs were chosen for further in vitro studies. Cytotoxicity studies of SLNs (± AA) were performed using MTT assay where AA-SLNs showed significantly higher cytotoxicity towards U87 MG cells than SVG P12 normal cells, as confirmed by flow cell cytometry. Cellular uptake of SLNs also appeared to be preferentially facilitated by energy-dependent endocytosis as evidenced by fluorescence imaging and flow cell cytometry. Using the Annexin V-PI double staining technique, it was found that these AA-MS-SLNs displayed concentration-dependent apoptotic activity on glioma cells, which further confirms the potential of exploiting these AA-loaded MS-SLNs for brain cancer therapy. PMID:26775062

  17. The Consistent Kinetics Porosity (CKP) Model: A Theory for the Mechanical Behavior of Moderately Porous Solids

    SciTech Connect

    BRANNON,REBECCA M.

    2000-11-01

    A theory is developed for the response of moderately porous solids (no more than {approximately}20% void space) to high-strain-rate deformations. The model is consistent because each feature is incorporated in a manner that is mathematically compatible with the other features. Unlike simple p-{alpha} models, the onset of pore collapse depends on the amount of shear present. The user-specifiable yield function depends on pressure, effective shear stress, and porosity. The elastic part of the strain rate is linearly related to the stress rate, with nonlinear corrections from changes in the elastic moduli due to pore collapse. Plastically incompressible flow of the matrix material allows pore collapse and an associated macroscopic plastic volume change. The plastic strain rate due to pore collapse/growth is taken normal to the yield surface. If phase transformation and/or pore nucleation are simultaneously occurring, the inelastic strain rate will be non-normal to the yield surface. To permit hardening, the yield stress of matrix material is treated as an internal state variable. Changes in porosity and matrix yield stress naturally cause the yield surface to evolve. The stress, porosity, and all other state variables vary in a consistent manner so that the stress remains on the yield surface throughout any quasistatic interval of plastic deformation. Dynamic loading allows the stress to exceed the yield surface via an overstress ordinary differential equation that is solved in closed form for better numerical accuracy. The part of the stress rate that causes no plastic work (i.e-, the part that has a zero inner product with the stress deviator and the identity tensor) is given by the projection of the elastic stressrate orthogonal to the span of the stress deviator and the identity tensor.The model, which has been numerically implemented in MIG format, has been exercised under a wide array of extremal loading and unloading paths. As will be discussed in a companion

  18. Mechanical Property Allowables Generated for the Solid Rocket Booster Composite Note Cap

    NASA Technical Reports Server (NTRS)

    Hodge, A. J.

    2000-01-01

    Mechanical property characterization was performed on AS4/3501-6 graphite/epoxy and SC350G syntactic foam for the SRB Composite Nose Cap Shuttle Upgrades Project. Lamina level properties for the graphite/epoxy were determined at room temperature, 240 F, 350 F, 480 F, 600 F, and 350 F after a cycle to 600 F. Graphite/epoxy samples were moisture conditioned prior to testing. The syntactic foam material was tested at room temperature, 350 F, and 480 F. A high-temperature test facility was developed at MSFC. Testing was performed with quartz lamp heaters and high resistance heater strips. The thermal history profile of the nose cap was simulated in order to test materials at various times during launch. A correlation study was performed with Southern Research Institute to confirm the test methodology and validity of test results. A-basis allowables were generated from the results of testing on three lots of material.

  19. Metastable alloy materials produced by solid state reaction of compacted, mechanically deformed mixtures

    DOEpatents

    Atzmon, M.; Johnson, W.L.; Verhoeven, J.D.

    1987-02-03

    Bulk metastable, amorphous or fine crystalline alloy materials are produced by reacting cold-worked, mechanically deformed filamentary precursors such as metal powder mixtures or intercalated metal foils. Cold-working consolidates the metals, increases the interfacial area, lowers the free energy for reaction, and reduces at least one characteristic dimension of the metals. For example, the grains of powder or the sheets of foil are clad in a container to form a disc. The disc is cold-rolled between the nip of rollers to form a flattened disc. The grains are further elongated by further rolling to form a very thin sheet of a lamellar filamentary structure containing filaments having a thickness of less than 0.01 microns. Thus, diffusion distance and time for reaction are substantially reduced when the flattened foil is thermally treated in oven to form a composite sheet containing metastable material dispersed in unreacted polycrystalline material. 4 figs.

  20. Mechanisms during suspended solids and phosphate concentration variations in wastewater coagulation process.

    PubMed

    Manamperuma, Lelum Duminda; Ratnaweera, Harsha Chandima; Martsul, A

    2016-10-01

    Coagulation-flocculation process is one of the most commonly used treatment process in water and wastewater treatment. Particles (PA) and phosphates (P) removal are the main objectives in wastewater coagulation. There is a general agreement on the dominant mechanism of PA and P removal during coagulation. While it is agreed that the PA and P removal reactions are competitive and takes place simultaneously, there is no clear understanding on the ratio of distribution of coagulants among the PA and P removal. The ratio can be significantly influenced by the content of PA and P, in addition to other water and coagulant quality factors. This paper attempts to provide a qualitative ratio of coagulant distribution based on PA:P proportion in raw water and OH:Al ratio in coagulants. PMID:26857441

  1. Molecular mechanisms of lymphatic metastasis in solid tumors of the gastrointestinal tract

    PubMed Central

    Langheinrich, Melanie C; Schellerer, Vera; Perrakis, Aristotelis; Lohmüller, Clemens; Schildberg, Claus; Naschberger, Elisabeth; Stürzl, Michael; Hohenberger, Werner; Croner, Roland S

    2012-01-01

    Tumor cell dissemination from the primary tumor site to distant organs is one of the characteristic properties of malignant tumors and represents a crucial step in the progression of disease. Although the pattern of spread may vary in different types of carcinomas, dissemination via the lymphatic system represents a common event in metastasis. The extent of lymph node metastasis is one of the major determinants for the prognosis of patients with gastrointestinal carcinomas and guides the therapeutically management. During the last decades, significant attention has been given to the molecular mechanisms that control lymphatic metastasis. The process of lymphangiogenesis has come into the focus. Lymphangiogenesis, the formation of newly lymphatics, comprises a series of complex cellular events and is controlled by a balance between pro- and anti-lymphangiogenic signals. This article will briefly describe the lymphatic system and then provide an overview of the molecular players involved in tumor lymphangiogenesis. PMID:22977656

  2. Mini-review of the geotechnical parameters of municipal solid waste: Mechanical and biological pre-treated versus raw untreated waste.

    PubMed

    Petrovic, Igor

    2016-09-01

    The most viable option for biostabilisation of old sanitary landfills, filled with raw municipal solid waste, is the so-called bioreactor landfill. Even today, bioreactor landfills are viable options in many economically developing countries. However, in order to reduce the biodegradable component of landfilled waste, mechanical and biological treatment has become a widely accepted waste treatment technology, especially in more prosperous countries. Given that mechanical and biological treatment alters the geotechnical properties of raw waste material, the design of sanitary landfills which accepts mechanically and biologically treated waste, should be carried out with a distinct set of geotechnical parameters. However, under the assumption that 'waste is waste', some design engineers might be tempted to use geotechnical parameters of untreated raw municipal solid waste and mechanical and biological pre-treated municipal solid waste interchangeably. Therefore, to provide guidelines for use and to provide an aggregated source of this information, this mini-review provides comparisons of geotechnical parameters of mechanical and biological pre-treated waste and raw untreated waste at various decomposition stages. This comparison reveals reasonable correlations between the hydraulic conductivity values of untreated and mechanical and biological pre-treated municipal solid waste. It is recognised that particle size might have a significant influence on the hydraulic conductivity of both municipal solid waste types. However, the compression ratios and shear strengths of untreated and pre-treated municipal solid waste do not show such strong correlations. Furthermore, another emerging topic that requires appropriate attention is the recovery of resources that are embedded in old landfills. Therefore, the presented results provide a valuable tool for engineers designing landfills for mechanical and biological pre-treated waste or bioreactor landfills for untreated raw

  3. Modelling of biogas extraction at an Italian landfill accepting mechanically and biologically treated municipal solid waste.

    PubMed

    Calabrò, Paolo S; Orsi, Sirio; Gentili, Emiliano; Carlo, Meoni

    2011-12-01

    This paper presents the results of the modelling of the biogas extraction in a full-scale Italian landfill by the USEPA LandGEM model and the Andreottola-Cossu approach. The landfill chosen for this research ('Il Fossetto' plant, Monsummano Terme, Italy) had accepted mixed municipal raw waste for about 15 years. In the year 2003 a mechanical biological treatment (MBT) was implemented and starting from the end of the year 2006, the recirculation in the landfill of the concentrated leachate coming from the internal membrane leachate treatment plant was put into practice. The USEPA LandGEM model and the Andreottola-Cossu approach were chosen since they require only input data routinely acquired during landfill management (waste amount and composition) and allow a simplified calibration, therefore they are potentially useful for practical purposes such as landfill gas management. The results given by the models are compared with measured data and analysed in order to verify the impact of MBT on biogas production; moreover, the possible effects of the recirculation of the concentrated leachate are discussed. The results clearly show how both models can adequately fit measured data even after MBT implementation. Model performance was significantly reduced for the period after the beginning of recirculation of concentrated leachate when the probable inhibition of methane production, due to the competition between methanogens and sulfate-reducing bacteria, significantly influenced the biogas production and composition. PMID:21930528

  4. Metastable alloy materials produced by solid state reaction of compacted, mechanically deformed mixtures

    DOEpatents

    Atzmon, Michael; Johnson, William L.; Verhoeven, John D.

    1987-01-01

    Bulk metastable, amorphous or fine crystalline alloy materials are produced by reacting cold-worked, mechanically deformed filamentary precursors such as metal powder mixtures or intercalated metal foils. Cold-working consolidates the metals, increases the interfacial area, lowers the free energy for reaction, and reduces at least one characteristic dimension of the metals. For example, the grains (13) of powder or the sheets of foil are clad in a container (14) to form a disc (10). The disc (10) is cold-rolled between the nip (16) of rollers (18,20) to form a flattened disc (22). The grains (13) are further elongated by further rolling to form a very thin sheet (26) of a lamellar filamentary structure (FIG. 4) containing filaments having a thickness of less than 0.01 microns. Thus, diffusion distance and time for reaction are substantially reduced when the flattened foil (28) is thermally treated in oven (32) to form a composite sheet (33) containing metastable material (34) dispersed in unreacted polycrystalline material (36).

  5. Compatibility Condition in Theory of Solid Mechanics (Elasticity, Structures, and Design Optimization)

    NASA Technical Reports Server (NTRS)

    Patnaik, Surya N.; Pai, Shantaram S.; Hopkins, Dale A.

    2007-01-01

    The strain formulation in elasticity and the compatibility condition in structural mechanics have neither been understood nor have they been utilized. This shortcoming prevented the formulation of a direct method to calculate stress. We have researched and understood the compatibility condition for linear problems in elasticity and in finite element analysis. This has lead to the completion of the method of force with stress (or stress resultant) as the primary unknown. The method in elasticity is referred to as the completed Beltrami-Michell formulation (CBMF), and it is the integrated force method (IFM) in structures. The dual integrated force method (IFMD) with displacement as the primary unknown has been formulated. IFM and IFMD produce identical responses. The variational derivation of the CBMF yielded the new boundary compatibility conditions. The CBMF can be used to solve stress, displacement, and mixed boundary value problems. The IFM in structures produced high-fidelity response even with a modest finite element model. The IFM has influenced structural design considerably. A fully utilized design method for strength and stiffness limitation has been developed. The singularity condition in optimization has been identified. The CBMF and IFM tensorial approaches are robust formulations because of simultaneous emphasis on the equilibrium equation and the compatibility condition.

  6. A mechanism for orbital angular momentum and giant spin-splitting in solids and nanostructures

    NASA Astrophysics Data System (ADS)

    Oh, Sehoon; Choi, Hyoung Joon

    Giant spin-splitting (GSS) of electronic bands, which is several orders of magnitude greater than Rashba model, has been observed in various systems including noble-metal surfaces, thin film of transition-metal dichalcogenides, often accompanied by the orbital angular momentum (OAM). Here, we study structural and orbital conditions for emergence of a GSS by using tight-binding and first-principles calculations. We find that broken mirror symmetry of local atomic structure around an atom can produce non-zero OAM at the atom. This OAM results in a GSS if the atom is a high-atomic number element. We demonstrate these structural and orbital conditions in the cases of simple atomic chains, WSe2 monolayer, Au(111) surface, and bulk HgTe. Based on this mechanism of the spin-splitting, we suggest methods to control the GSS, which can be used in applications such as spintronic devices. This work was supported by NRF of KOREA (Grant No. 2011-0018306) and KISTI supercomputing center (Project No. KSC-2015-C3-039).

  7. Lamb Wave Dispersion Ultrasound Vibrometry (LDUV) Method for Quantifying Mechanical Properties of Viscoelastic Solids

    PubMed Central

    Nenadic, Ivan Z.; Urban, Matthew W.; Mitchell, Scott A.; Greenleaf, James F.

    2011-01-01

    Diastolic dysfunction is the inability of the left ventricle to supply sufficient stroke volumes under normal physiological conditions and is often accompanied by stiffening of the left-ventricular myocardium. A noninvasive technique capable of quantifying viscoelasticity of the myocardium would be beneficial in clinical settings. Our group has been investigating the use of Shearwave Dispersion Ultrasound Vibrometry (SDUV), a noninvasive ultrasound based method for quantifying viscoelasticity of soft tissues. The primary motive of this study is the design and testing of viscoelastic materials suitable for validation of the Lamb wave Dispersion Ultrasound Vibrometry (LDUV), an SDUV-based technique for measuring viscoelasticity of tissues with plate-like geometry. We report the results of quantifying viscoelasticity of urethane rubber and gelatin samples using LDUV and an embedded sphere method. The LDUV method was used to excite antisymmetric Lamb waves and measure the dispersion in urethane rubber and gelatin plates. An antisymmetric Lamb wave model was fitted to the wave speed dispersion data to estimate elasticity and viscosity of the materials. A finite element model of a viscoelastic plate submerged in water was used to study the appropriateness of the Lamb wave dispersion equations. An embedded sphere method was used as an independent measurement of the viscoelasticity of the urethane rubber and gelatin. The FEM dispersion data were in excellent agreement with the theoretical predictions. Viscoelasticity of the urethane rubber and gelatin obtained using the LDUV and embedded sphere methods agreed within one standard deviation. LDUV studies on excised porcine myocardium sample were performed to investigate the feasibility of the approach in preparation for open-chest in vivo studies. The results suggest that the LDUV technique can be used to quantify mechanical properties of soft tissues with a plate-like geometry. PMID:21403186

  8. Landfill gas generation after mechanical biological treatment of municipal solid waste. Estimation of gas generation rate constants.

    PubMed

    Gioannis, G De; Muntoni, A; Cappai, G; Milia, S

    2009-03-01

    Mechanical biological treatment (MBT) of residual municipal solid waste (RMSW) was investigated with respect to landfill gas generation. Mechanically treated RMSW was sampled at a full-scale plant and aerobically stabilized for 8 and 15 weeks. Anaerobic tests were performed on the aerobically treated waste (MBTW) in order to estimate the gas generation rate constants (k,y(-1)), the potential gas generation capacity (L(o), Nl/kg) and the amount of gasifiable organic carbon. Experimental results show how MBT allowed for a reduction of the non-methanogenic phase and of the landfill gas generation potential by, respectively, 67% and 83% (8 weeks treatment), 82% and 91% (15 weeks treatment), compared to the raw waste. The amount of gasified organic carbon after 8 weeks and 15 weeks of treatment was equal to 11.01+/-1.25kgC/t(MBTW) and 4.54+/-0.87kgC/t(MBTW), respectively, that is 81% and 93% less than the amount gasified from the raw waste. The values of gas generation rate constants obtained for MBTW anaerobic degradation (0.0347-0.0803y(-1)) resemble those usually reported for the slowly and moderately degradable fractions of raw MSW. Simulations performed using a prediction model support the hypothesis that due to the low production rate, gas production from MBTW landfills is well-suited to a passive management strategy. PMID:18954969

  9. Solid recovered fuel: materials flow analysis and fuel property development during the mechanical processing of biodried waste.

    PubMed

    Velis, Costas A; Wagland, Stuart; Longhurst, Phil; Robson, Bryce; Sinfield, Keith; Wise, Stephen; Pollard, Simon

    2013-03-19

    Material flows and their contributions to fuel properties are balanced for the mechanical section of a mechanical-biological treatment (MBT) plant producing solid recovered fuel (SRF) for the UK market. Insights for this and similar plants were secured through a program of sampling, manual sorting, statistics, analytical property determination, and material flow analysis (MFA) with error propagation and data reconciliation. Approximately three-quarters of the net calorific value (Q(net,p,ar)) present in the combustible fraction of the biodried flow is incorporated into the SRF (73.2 ± 8.6%), with the important contributors being plastic film (30.7 MJ kg(ar)(-1)), other packaging plastic (26.1 MJ kg(ar)(-1)), and paper/card (13.0 MJ kg(ar)(-1)). Nearly 80% w/w of the chlorine load in the biodried flow is incorporated into SRF (78.9 ± 26.2%), determined by the operation of the trommel and air classifier. Through the use of a novel mass balancing procedure, SRF quality is understood, thus improving on the understanding of quality assurance in SRF. Quantification of flows, transfer coefficients, and fuel properties allows recommendations to be made for process optimization and the production of a reliable and therefore marketable SRF product. PMID:23398118

  10. High basicity adsorbents from solid residue of cellulose and synthetic polymer co-pyrolysis for phenol removal: Kinetics and mechanism

    NASA Astrophysics Data System (ADS)

    Lorenc-Grabowska, Ewa; Rutkowski, Piotr

    2014-10-01

    The activated carbons (ACs) produced from solid residue of cellulose and synthetic polymer co-pyrolysis (CACs) and commercial activated carbon from coconut shell (GC) were used for phenol removal. The adsorption kinetics and mechanism were investigated. All studied activated carbons are predominantly microporous and are characterized by basic surface characteristics. Surface area SBET varies between 1235 and 1499 m2/g, whereas the pHPZC changes from 7.70 to 10.63. The bath adsorption of phenol (P) was carried out at ambient temperature. The equilibrium time and equilibrium sorption capacity were determined. It was found that the boundary layer effect is bigger in AC with high basic characteristics of the surface. The rate controlling step is the intraparticle diffusion in CACs only, whereas in ACs with higher amount of acidic functionalities the adsorbate-surface interaction influences the rate of kinetic as well. The equilibrium isotherms are L2 type for commercial AC and L4 for CACs. The CACs are characterized by very high adsorption capacity that vary between 312 and 417 mg/g. The main mechanism of phenol adsorption is micropore filling within pores smaller than 1.4 nm. In the absence of solvent effect further adsorption of phenol on CACs takes place. The enhanced adsorption is due to dispersive/repulsive interaction induced by oxygen functionalities.

  11. Nanoscale Infrared, Thermal, and Mechanical Characterization of Telaprevir-Polymer Miscibility in Amorphous Solid Dispersions Prepared by Solvent Evaporation.

    PubMed

    Li, Na; Taylor, Lynne S

    2016-03-01

    Miscibility is of great interest for pharmaceutical systems, in particular, for amorphous solid dispersions, as phase separation can lead to a higher tendency to crystallize, resulting in a loss in solubility, decreased dissolution rate, and compromised bioavailability. The purpose of this study was to investigate the miscibility behavior of a model poorly water-soluble drug, telaprevir (TPV), with three different polymers using atomic force microscopy-based infrared, thermal, and mechanical analysis. Standard atomic force microscopy (AFM) imaging together with nanoscale infrared spectroscopy (AFM-IR), nanoscale thermal analysis (nanoTA), and Lorentz contact resonance (LCR) measurements were used to evaluate the miscibility behavior of TPV with three polymers, hydroxypropyl methylcellulose (HPMC), HPMC acetate succinate (HPMCAS), and poly(vinylpyrrolidone-co-vinyl acetate) (PVPVA), at different drug to polymer ratios. Phase separation was observed with HPMC and PVPVA at drug loadings above 10%. For HPMCAS, a smaller miscibility gap was observed, with phase separation being observed at drug loadings higher than ∼30-40%. The domain size of phase-separated regions varied from below 50 nm to a few hundred nanometers. Localized infrared spectra, nano-TA measurements, images from AFM-based IR, and LCR measurements showed clear contrast between the continuous and discrete domains for these phase-separated systems, whereby the discrete domains were drug-rich. Fluorescence microscopy provided additional evidence for phase separation. These methods appear to be promising to evaluate miscibility in drug-polymer systems with similar Tgs and submicron domain sizes. Furthermore, such findings are of obvious importance in the context of contributing to a mechanistic understanding of amorphous solid dispersion phase behavior. PMID:26859046

  12. On some problems in a theory of thermally and mechanically interacting continuous media. Ph.D. Thesis; [linearized theory of interacting mixture of elastic solid and viscous fluid

    NASA Technical Reports Server (NTRS)

    Lee, Y. M.

    1971-01-01

    Using a linearized theory of thermally and mechanically interacting mixture of linear elastic solid and viscous fluid, we derive a fundamental relation in an integral form called a reciprocity relation. This reciprocity relation relates the solution of one initial-boundary value problem with a given set of initial and boundary data to the solution of a second initial-boundary value problem corresponding to a different initial and boundary data for a given interacting mixture. From this general integral relation, reciprocity relations are derived for a heat-conducting linear elastic solid, and for a heat-conducting viscous fluid. An initial-boundary value problem is posed and solved for the mixture of linear elastic solid and viscous fluid. With the aid of the Laplace transform and the contour integration, a real integral representation for the displacement of the solid constituent is obtained as one of the principal results of the analysis.

  13. Non-invasive insight into the release mechanisms of a poorly soluble drug from amorphous solid dispersions by confocal Raman microscopy.

    PubMed

    Punčochová, Kateřina; Vukosavljevic, Branko; Hanuš, Jaroslav; Beránek, Josef; Windbergs, Maike; Štěpánek, František

    2016-04-01

    In this study, we investigated the release mechanism of the poorly water soluble drug aprepitant from different amorphous solid dispersions using confocal Raman microscopy (CRM). Solid dispersions were fabricated based on either Soluplus®, as an amphiphilic copolymer and solubilizer, or on polyvinylpyrrolidone, as a hydrophilic polymer, in order to elucidate the influence of the polymer characteristics on the drug form and dissolution mechanisms. Aprepitant exhibited its amorphous form in both solid dispersions. However, the release differed depending on the polymer. The high complexation effect of Soluplus was shown to be a crucial factor for stabilization of the amorphous drug, resulting in continuous release without any recrystallization of aprepitant. In contrast, solid dispersions based on polyvinylpyrrolidone showed a different mechanism of dissolution; due to the good affinity of PVP and water, the polymer is dissolving fast, leading to phase separation and local recrystallization of the drug. The study highlights the complexity of release processes from solid dispersions and elucidates the influence of the polymer on drug release kinetics. PMID:26861928

  14. Gaseous pollutants emitted from a mechanical biological treatment plant for municipal solid waste: odor assessment and photochemical reactivity.

    PubMed

    Fang, Jingjing; Zhang, Hua; Yang, Na; Shao, Liming; He, Pinjing

    2013-11-01

    The concentrations and chromatographic profiles of gaseous pollutants emitted from a municipal solid waste (MSW) biological treatment plant were investigated to identify the major odor substances and atmospheric photochemical reactive species (PRS). Four methods were used to measure different gaseous pollutants in this study, including colorimetric tubes, gas chromatography with mass spectrometry/flame ionization detection/pulsed flame photometric detection (GC-MS/FID/PFPD) preceded by cold trap concentration, GC-FID preceded by solid-phase microextraction (SPME), and high-performance liquid chromatography (HPLC) after derivation by 2,4-dinitrophenylhydrazine (DNPH). Seventy-five gaseous compounds belonging to nine groups (nitrogen compounds, sulfur compounds, alkanes, alkenes, aromatics, terpenes, alcohols, carbonyls, and volatile fatty acids [VFAs]) were identified. In the pre-biotreatment facility, the total concentration of the gaseous pollutants reached the maximum value on day 7 (317 ppm). During the post-biotreatment process, the total concentration of gaseous pollutants decreased from 331 ppm at the beginning to 162 ppm in the end. The group with the greatest decrease was carbonyls, from 64 to 7.4 ppm, followed by alcohols, from 40 to 4.5 ppm, which were both oxygenated compounds. The proportion of aromatics was notably high in the pre-mechanical treatment facility, accounting for 50.6% of the total, revealing the xenobiotic compounds disseminated by stirring and agitating the waste in the initial stage. The proportions of nitrogen compounds were lower in the pre- and post-mechanical treatment facilities (1.5% and 6.9%) than in the pre- and post-biotreatment facilities (11.9% and 13:8%), suggesting that their generation was closely associated with waste degradation. The major odor compounds in the facilities were acetic acid, butyric acid, valeric acid, isovaleric acid, and dimethyl sulfide. The major PRS in the facilities were aromatics, acetaldehyde

  15. Measurement of moisture, soluble solids, and sucrose content and mechanical properties in sugar beet using portable visible and near-infrared spectroscopy

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Visible and near-infrared spectroscopy, coupled with partial least squares regression, was used to predict the moisture, soluble solids and sucrose content and mechanical properties of sugar beet. Interactance spectra were acquired from both intact and sliced beets, using two portable spectrometers ...

  16. Comparison of Microstructures and Mechanical Properties for Solid and Mesh Cobalt-Base Alloy Prototypes Fabricated by Electron Beam Melting

    NASA Astrophysics Data System (ADS)

    Gaytan, S. M.; Murr, L. E.; Martinez, E.; Martinez, J. L.; Machado, B. I.; Ramirez, D. A.; Medina, F.; Collins, S.; Wicker, R. B.

    2010-12-01

    The microstructures and mechanical behavior of simple, as-fabricated, solid geometries (with a density of 8.4 g/cm3), as-fabricated and fabricated and annealed femoral (knee) prototypes, and reticulated mesh components (with a density of 1.5 g/cm3) all produced by additive manufacturing (AM) using electron beam melting (EBM) of Co-26Cr-6Mo-0.2C powder are examined and compared in this study. Microstructures and microstructural issues are examined by optical metallography (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectrometry (EDS), and X-ray diffraction (XRD), while mechanical properties included selective specimen tensile testing and Vickers microindentation hardness (HV) and Rockwell C-scale hardness (HRC) measurements. Orthogonal (X-Y) melt scanning of the electron beam during AM produced unique, orthogonal and related Cr23C6 carbide (precipitate) arrays (a controlled microstructural architecture) with dimensions of 2 μm in the build plane perpendicular to the build direction, while connected carbide columns were formed in the vertical plane, parallel to the build direction, with microindentation hardnesses ranging from 4.4 to 5.9 GPa, corresponding to a yield stress and ultimate tensile strength (UTS) of 0.51 and 1.45 GPa with elongations ranging from 1.9 to 5.3 pct. Annealing produced an equiaxed fcc grain structure with some grain boundary carbides, frequent annealing twins, and often a high density of intrinsic {111} stacking faults within the grains. The reticulated mesh strut microstructure consisted of dense carbide arrays producing an average microindentation hardness of 6.2 GPa or roughly 25 pct higher than the fully dense components.

  17. THE MECHANISM OF SURFACE DIFFUSION OF H AND D ATOMS ON AMORPHOUS SOLID WATER: EXISTENCE OF VARIOUS POTENTIAL SITES

    SciTech Connect

    Hama, Tetsuya; Kuwahata, Kazuaki; Watanabe, Naoki; Kouchi, Akira; Chigai, Takeshi; Kimura, Yuki; Pirronello, Valerio

    2012-10-01

    To understand elementary processes leading to H{sub 2} formation, and the hydrogenation and deuteration reactions of adsorbed species on dust grains in dense clouds, we experimentally investigated the diffusion of atomic hydrogen and deuterium on amorphous solid water (ASW) at temperatures of 8-15 K. The present study extended our previous study for selective detections of H and D atoms, and of H{sub 2} (J = 0 and 1) and D{sub 2} (J = 0 and 1) molecules adsorbed on ASW using both photo-stimulated desorption and resonance-enhanced multiphoton ionization, to investigate potential sites on ASW for diffusion, recombination dynamics, and the diffusion mechanism of H and D atoms. Our results demonstrate that the ASW surface contains various potential sites that can be categorized into at least three groups: very shallow, middle-, and deep-potential sites, with diffusion activation energies of {<=}18, 22 (23 meV for D atoms), and {>=}30 meV, respectively. The present study pictured the outline of H{sub 2} formation on cosmic ice dust at low temperatures: H atoms landing on the dust will diffuse rapidly at the abundant shallow and middle sites on ASW, and finally become trapped at deep sites. The H atoms that arrive next recombine with such trapped H atoms to yield H{sub 2} molecules. The small isotopic difference between the diffusion of H and D atoms on ASW indicates that the diffusion mechanism can be explained by thermal hopping, at least at middle-potential sites.

  18. Interaction mechanism of in-situ nano-TiN-AlN particles and solid/liquid interface during solidification.

    PubMed

    Cui, Chunxiang; Li, Yanchun; Shen, Yutian; Sun, Jibing; Wang, Ru

    2003-10-01

    This paper deals with the interaction mechanism between in situ nanometer-grade TiN-AlN particles and the solid/liquid (S/L) interface during the solidification of an in situ TiN-AlN/Al composite. According to the setting of a force balance for the particles in front of the S/L interface during solidification, F = F(buoyant) + F(repulsive) + F(viscous). We obtained the relationship between the critical cooling velocity of the liquid composite, Vr, and the size of the ceramic particle, rp. By this relationship formula, we can know that the S/L interface engulfs particles or pushes them to the crystal grain boundary during the solidification of a TiN-AlN/Al composite. It is found that Vr is proportional to the radius of ceramic particles by transmission electron microscope (TEM) observation. The TEM test indicates that the smaller the particle is, the more easily the S/L interface engulfs particles. PMID:14733152

  19. Mechanically delaminated few layered MoS2 nanosheets based high performance wire type solid-state symmetric supercapacitors

    NASA Astrophysics Data System (ADS)

    Krishnamoorthy, Karthikeyan; Pazhamalai, Parthiban; Veerasubramani, Ganesh Kumar; Kim, Sang Jae

    2016-07-01

    Two dimensional nanostructures are increasingly used as electrode materials in flexible supercapacitors for portable electronic applications. Herein, we demonstrated a ball milling approach for achieving few layered molybdenum disulfide (MoS2) via exfoliation from their bulk. Physico-chemical characterizations such as X-ray diffraction, field emission scanning electron microscope, and laser Raman analyses confirmed the occurrence of exfoliated MoS2 sheets with few layers from their bulk via ball milling process. MoS2 based wire type solid state supercapacitors (WSCs) are fabricated and examined using cyclic voltammetry (CV), electrochemical impedance spectroscopy, and galvanostatic charge discharge (CD) measurements. The presence of rectangular shaped CV curves and symmetric triangular shaped CD profiles suggested the mechanism of charge storage in MoS2 WSC is due to the formation of electrochemical double layer capacitance. The MoS2 WSC device delivered a specific capacitance of 119 μF cm-1, and energy density of 8.1 nW h cm-1 with better capacitance retention of about 89.36% over 2500 cycles, which ensures the use of the ball milled MoS2 for electrochemical energy storage devices.

  20. A Silicon-Based Nanothin Film Solid Oxide Fuel Cell Array with Edge Reinforced Support for Enhanced Thermal Mechanical Stability.

    PubMed

    Baek, Jong Dae; Yu, Chen-Chiang; Su, Pei-Chen

    2016-04-13

    A silicon-based micro-solid oxide fuel cell (μ-SOFC) with electrolyte membrane array embedded in a thin silicon supporting membrane, featuring a unique edge reinforcement structure, was demonstrated by utilizing simple silicon micromachining processes. The square silicon supporting membrane, fabricated by combining deep reactive ion etching and through-wafer wet etching processes, has thicker edges and corners than the center portion of the membrane, which effectively improved the mechanical stability of the entire fuel cell array during cell fabrication and cell operation. The 20 μm thick single crystalline silicon membrane supports a large number of 80 nm thick free-standing yttria-stabilized zirconia (YSZ) electrolytes. The fuel cell array was stably maintained at the open circuit voltage (OCV) of 1.04 V for more than 30 h of operation at 350 °C. A high peak power density of 317 mW/cm(2) was obtained at 400 °C. During a rigorous in situ thermal cycling between 150 and 400 °C at a fast cooling and heating rate of 25 °C/min, the OCV of the μ-SOFC recovered to its high value of 1.07 V without any drop caused by membrane failure, which justifies the superior thermal stability of this novel cell architecture. PMID:26990604

  1. Upgrading of a mechanical biological treatment plant with a solid anaerobic digestion batch: a real case study.

    PubMed

    Di Maria, Francesco

    2012-10-01

    The energetic and treatment efficiency analysis of an existing mechanical biological treatment (MBT) plant shows that more than 60% of the 25 kWh consumed per each tonne of non-differentiated waste (NDW) treated is due to the electric fans. About 7.5 kWh per tonne of NDW is used for supplying the process air for stabilizing the waste organic fraction (WOF). Exploitation of the solid anaerobic digestion batch (SADB) for processing the WOF before it enters the aerobic section of the MBT leads to the production of biogas and, when subsequently fed to a gas engine, electric power at a magnitude of about 150 kWh per tonne of WOF, resulting in an energy surplus of about 48 kWh per tonne of NDW treated by the MBT facility. The SADB can also reduce the organic load rate at which the aerobic section operates up to 40%, leading to further positive effects on the whole MBT process. PMID:22751849

  2. Spectral, mechanical, thermal, optical and solid state parameters, of metal-organic bis(hydrogenmaleate)-CO(II) tetrahydrate crystal

    NASA Astrophysics Data System (ADS)

    Chandran, Senthilkumar; Jagan, R.; Paulraj, Rajesh; Ramasamy, P.

    2015-10-01

    Metal-organic bis(hydrogenmaleate)-Co(II) tetrahydrate single crystals have been grown by slow evaporation solution growth technique at room temperature. The crystal structure and the unit cell parameters were analyzed from the X-ray diffraction studies. Single-crystal X-ray diffraction analyses reveal that the grown crystal belongs to triclinic system with the space group P-1. Functional groups in bis(hydrogenmaleate)-Co(II) tetrahydrate were identified by Fourier transform infrared spectral analysis. The peak observed at 663 cm-1 is assigned to the (Co-O) stretching vibrations. The optical transmission of the crystal was studied by UV-vis-NIR spectral analysis. The photoluminescence emission studies were carried out for the title compound in a wide wavelength range between 350 nm and 550 nm at 303 K. Mechanical strength was tested by Vickers microhardness test. The laser damage threshold value has been determined using Nd:YAG laser operating at 1064 nm. At various frequencies and temperatures the dielectric behavior of the material was investigated. Solid state parameters such as plasma energy, Penn gap, Fermi energy and electronic polarizability were evaluated. Photoconductivity measurements were carried out for the grown crystal in the presence of DC electric field at room temperature. Thermal stability and decomposition of the crystal were studied by TG-DTA. The weight loss of the title compound occurs in different steps.

  3. Kinetic Growth of Ultralong Metastable Zincblende MnSe Nanowires Catalyzed by a Fast Ionic Conductor via a Solution-Solid-Solid Mechanism.

    PubMed

    Zhang, Li; Yang, Qing

    2016-07-13

    The metastable semiconductor phase allows for the exploration of unusual properties and functionalities of abnormal structures, although it is often difficult to prevent thermodynamic transformations to lower energy structures from higher, unfavored energy states. Here, we show for the first time the preparation of high-quality ultralong metastable zincblende (ZB)-MnSe nanowires with a four-coordinate structure via solution-solid-solid (SSS) growth in a mild solution-phase synthetic environment (120-220 °C) in the presence of a trace amount of Ag(I). The metastable ZB-MnSe nanowires are stabilized kinetically due to the catalysis of early formed body-centered cubic (bcc) fast-ionic (superionic) Ag2Se nanocrystals from the Ag(I) source, and the ZB-MnSe nanowires grow epitaxially along the ⟨110⟩ axis rather than the ⟨111⟩ axis, as commonly observed for typical four-coordinate Grimm-Sommerfeld bonding solids. Our method provides a new route for the growth of metastable nanostructures. PMID:27254244

  4. A coupled transport and solid mechanics formulation with improved reaction kinetics parameters for modeling oxidation and decomposition in a uranium hydride bed.

    SciTech Connect

    Salloum, Maher N.; Shugard, Andrew D.; Kanouff, Michael P.; Gharagozloo, Patricia E.

    2013-03-01

    Modeling of reacting flows in porous media has become particularly important with the increased interest in hydrogen solid-storage beds. An advanced type of storage bed has been proposed that utilizes oxidation of uranium hydride to heat and decompose the hydride, releasing the hydrogen. To reduce the cost and time required to develop these systems experimentally, a valid computational model is required that simulates the reaction of uranium hydride and oxygen gas in a hydrogen storage bed using multiphysics finite element modeling. This SAND report discusses the advancements made in FY12 (since our last SAND report SAND2011-6939) to the model developed as a part of an ASC-P&EM project to address the shortcomings of the previous model. The model considers chemical reactions, heat transport, and mass transport within a hydride bed. Previously, the time-varying permeability and porosity were considered uniform. This led to discrepancies between the simulated results and experimental measurements. In this work, the effects of non-uniform changes in permeability and porosity due to phase and thermal expansion are accounted for. These expansions result in mechanical stresses that lead to bed deformation. To describe this, a simplified solid mechanics model for the local variation of permeability and porosity as a function of the local bed deformation is developed. By using this solid mechanics model, the agreement between our reacting bed model and the experimental data is improved. Additionally, more accurate uranium hydride oxidation kinetics parameters are obtained by fitting the experimental results from a pure uranium hydride oxidation measurement to the ones obtained from the coupled transport-solid mechanics model. Finally, the coupled transport-solid mechanics model governing equations and boundary conditions are summarized and recommendations are made for further development of ARIA and other Sandia codes in order for them to sufficiently implement the model.

  5. Mechanically-biologically treated municipal solid waste as a support medium for microbial methane oxidation to mitigate landfill greenhouse emissions.

    PubMed

    Einola, Juha-Kalle M; Karhu, A Elina; Rintala, Jukka A

    2008-01-01

    The residual fraction of mechanically-biologically treated municipal solid waste (MBT residual) was studied in the laboratory to evaluate its suitability and environmental compatibility as a support medium in methane (CH(4)) oxidative biocovers for the mitigation of greenhouse gas emissions from landfills. Two MBT residuals with 5 and 12 months total (aerobic) biological stabilisation times were used in the study. MBT residual appeared to be a favourable medium for CH(4) oxidation as indicated by its area-based CH(4) oxidation rates (12.2-82.3 g CH(4) m(-2) d(-1) at 2-25 degrees C; determined in CH(4)-sparged columns). The CH(4) oxidation potential (determined in batch assays) of the MBT residuals increased during the 124 d column experiment, from <1.6 to a maximum of 104 microg CH(4) g(dw)(-1) h(-1) (dw=dry weight) at 5 degrees C and 578 microg CH(4) g(dw)(-1) h(-1) at 23 degrees C. Nitrous oxide (N(2)O) production in MBT residual (<15 microg N(2)O kg(dw)(-1) d(-1) in the CH(4) oxidative columns) was at the lower end of the range of N(2)O emissions reported for landfills and non-landfill soils, and insignificant as a greenhouse gas source. Also, anaerobic gas production (25.6 l kg(dw)(-1) during 217 d) in batch assays was low, indicating biological stability of the MBT residual. The electrical conductivities (140-250 mS m(-1)), as well as the concentrations of zinc (3.0 mg l(-1)), copper (0.5 mg l(-1)), arsenic (0.3 mg l(-1)), nickel (0.1 mg l(-1)) and lead (0.1 mg l(-1)) in MBT residual eluates from a leaching test (EN-12457-4) with a liquid/solid (L/S) ratio of 10:1, suggest a potential for leachate pollutant emissions which should be considered in plans to utilise MBT residual. In conclusion, the laboratory experiments suggest that MBT residual can be utilised as a support medium for CH(4) oxidation, even at low temperatures, to mitigate greenhouse gas emissions from landfills. PMID:17360174

  6. Efficient Reformulation of Solid Phase Diffusion in Electrochemical-Mechanical Coupled Models for Lithium-Ion Batteries: Effect of Intercalation Induced Stresses

    SciTech Connect

    De, S; Suthar, B; Rife, D; Sikha, G; Subramanian, VR

    2013-07-23

    Lithium-ion batteries are typically modeled using porous electrode theory coupled with various transport and reaction mechanisms with an appropriate discretization or approximation for the solid phase diffusion within the electrode particle. One of the major difficulties in simulating Li-ion battery models is the need for simulating solid-phase diffusion in the second radial dimension r within the particle. It increases the complexity of the model as well as the computation time/cost to a great extent. This is Particularly true for the inclusion of pressure induced diffusion inside particles experiencing volume change. A computationally efficient representation for solid-phase diffusion is discussed in this paper. The operating condition has a significant effect on the validity, accuracy, and efficiency of various approximations for the solid-phase transport governed by pressure induced diffusion. This paper introduces efficient methods for solid phase reformulation - (1) parabolic profile approach and (2) a mixed order finite difference method for approximating/representing solid-phase concentration variations within the active materials of porous electrodes for macroscopic models for lithium-ion batteries. (C) 2013 The Electrochemical Society. All rights reserved.

  7. Mechanism of formation of humus coatings on mineral surfaces 3. Composition of adsorbed organic acids from compost leachate on alumina by solid-state 13C NMR

    USGS Publications Warehouse

    Wershaw, R. L.; Llaguno, E.C.; Leenheer, J.A.

    1996-01-01

    The adsorption of compost leachate DOC on alumina is used as a model for elucidation of the mechanism of formation of natural organic coatings on hydrous metal oxide surfaces in soils and sediments. Compost leachate DOC is composed mainly of organic acid molecules. The solid-state 13C NMR spectra of these organic acids indicate that they are very similar in composition to aquatic humic substances. Changes in the solid-state 13C NMR spectra of compost leachate DOC fractions adsorbed on alumina indicate that the DOC molecules are most likely adsorbed on metal oxide surfaces through a combination of polar and hydrophobic interaction mechanisms. This combination of polar and hydrophobic mechanism leads to the formation of bilayer coatings of the leachate molecules on the oxide surfaces.

  8. Solid lipid particles for oral delivery of peptide and protein drugs I--elucidating the release mechanism of lysozyme during lipolysis.

    PubMed

    Christophersen, P C; Zhang, L; Yang, M; Nielsen, H Mørck; Müllertz, A; Mu, H

    2013-11-01

    The mechanism of protein release from solid lipid particles was investigated by a new lipolysis model in a biorelevant medium containing both bile salts and phospholipids. Lysozyme, a model protein, was formulated into solid lipid particles using four different types of lipids, two triglycerides with different chain-length of fatty acyl groups i.e. trimyristin (TG14) and tristearin (TG18), and two lipid blends dominated by diglycerides and monoglycerides, respectively. The release of lysozyme from the solid lipid particles and the lipid hydrolysis process were assessed in the lipolysis model, while the change in particle surface during the lipolysis process was evaluated using scanning electron microscopy. The lysozyme release profiles from TG14 and TG18 as well as diglyceride particles correlated well with the release of free fatty acids from the lipid particles during the lipolysis and therefore exhibited a lipase-mediated degradation-based release mechanism. The release of lysozyme from monoglyceride particles was independent on lipase degradation due to the instability of the lipid matrix in the lipolysis medium. In conclusion, the established lipolysis model is successfully used to elucidate the drug release mechanism from solid lipid particles and can potentially be used in rational selection of lipid excipients for oral delivery of peptide/protein drugs. PMID:23911434

  9. Measurement of Mechanical Coherency Temperature and Solid Volume Fraction in Al-Zn Alloys Using In Situ X-ray Diffraction During Casting

    NASA Astrophysics Data System (ADS)

    Drezet, Jean-Marie; Mireux, Bastien; Kurtuldu, Güven; Magdysyuk, Oxana; Drakopoulos, Michael

    2015-09-01

    During solidification of metallic alloys, coalescence leads to the formation of solid bridges between grains or grain clusters when both solid and liquid phases are percolated. As such, it represents a key transition with respect to the mechanical behavior of solidifying alloys and to the prediction of solidification cracking. Coalescence starts at the coherency point when the grains begin to touch each other, but are unable to sustain any tensile loads. It ends up at mechanical coherency when the solid phase is sufficiently coalesced to transmit macroscopic tensile strains and stresses. Temperature at mechanical coherency is a major input parameter in numerical modeling of solidification processes as it defines the point at which thermally induced deformations start to generate internal stresses in a casting. This temperature has been determined for Al-Zn alloys using in situ X-ray diffraction during casting in a dog-bone-shaped mold. This setup allows the sample to build up internal stress naturally as its contraction is prevented. The cooling on both extremities of the mold induces a hot spot at the middle of the sample which is irradiated by X-ray. Diffraction patterns were recorded every 0.5 seconds using a detector covering a 426 × 426 mm2 area. The change of diffraction angles allowed measuring the general decrease of the lattice parameter of the fcc aluminum phase. At high solid volume fraction, a succession of strain/stress build up and release is explained by the formation of hot tears. Mechanical coherency temperatures, 829 K to 866 K (556 °C to 593 °C), and solid volume fractions, ca. 98 pct, are shown to depend on solidification time for grain refined Al-6.2 wt pct Zn alloys.

  10. Electron Scattering and Doping Mechanisms in Solid-Phase-Crystallized In2O3:H Prepared by Atomic Layer Deposition.

    PubMed

    Macco, Bart; Knoops, Harm C M; Kessels, Wilhelmus M M

    2015-08-01

    Hydrogen-doped indium oxide (In2O3:H) has recently emerged as an enabling transparent conductive oxide for solar cells, in particular for silicon heterojunction solar cells because its high electron mobility (>100 cm(2)/(V s)) allows for a simultaneously high electrical conductivity and optical transparency. Here, we report on high-quality In2O3:H prepared by a low-temperature atomic layer deposition (ALD) process and present insights into the doping mechanism and the electron scattering processes that limit the carrier mobility in such films. The process consists of ALD of amorphous In2O3:H at 100 °C and subsequent solid-phase crystallization at 150-200 °C to obtain large-grained polycrystalline In2O3:H films. The changes in optoelectronic properties upon crystallization have been monitored both electrically by Hall measurements and optically by analysis of the Drude response. After crystallization, an excellent carrier mobility of 128 ± 4 cm(2)/(V s) can be obtained at a carrier density of 1.8 × 10(20) cm(-3), irrespective of the annealing temperature. Temperature-dependent Hall measurements have revealed that electron scattering is dominated by unavoidable phonon and ionized impurity scattering from singly charged H-donors. Extrinsic defect scattering related to material quality such as grain boundary and neutral impurity scattering was found to be negligible in crystallized films indicating that the carrier mobility is maximized. Furthermore, by comparison of the absolute H-concentration and the carrier density in crystallized films, it is deduced that <4% of the incorporated H is an active dopant in crystallized films. Therefore, it can be concluded that inactive H atoms do not (significantly) contribute to defect scattering, which potentially explains why In2O3:H films are capable of achieving a much higher carrier mobility than conventional In2O3:Sn (ITO). PMID:26168056

  11. Spectral, mechanical, thermal, optical and solid state parameters, of metal-organic bis(hydrogenmaleate)-CO(II) tetrahydrate crystal

    SciTech Connect

    Chandran, Senthilkumar; Jagan, R.; Paulraj, Rajesh; Ramasamy, P.

    2015-10-15

    Metal-organic bis(hydrogenmaleate)-Co(II) tetrahydrate single crystals have been grown by slow evaporation solution growth technique at room temperature. The crystal structure and the unit cell parameters were analyzed from the X-ray diffraction studies. Single-crystal X-ray diffraction analyses reveal that the grown crystal belongs to triclinic system with the space group P-1. Functional groups in bis(hydrogenmaleate)-Co(II) tetrahydrate were identified by Fourier transform infrared spectral analysis. The peak observed at 663 cm{sup −1} is assigned to the (Co–O) stretching vibrations. The optical transmission of the crystal was studied by UV–vis–NIR spectral analysis. The photoluminescence emission studies were carried out for the title compound in a wide wavelength range between 350 nm and 550 nm at 303 K. Mechanical strength was tested by Vickers microhardness test. The laser damage threshold value has been determined using Nd:YAG laser operating at 1064 nm. At various frequencies and temperatures the dielectric behavior of the material was investigated. Solid state parameters such as plasma energy, Penn gap, Fermi energy and electronic polarizability were evaluated. Photoconductivity measurements were carried out for the grown crystal in the presence of DC electric field at room temperature. Thermal stability and decomposition of the crystal were studied by TG–DTA. The weight loss of the title compound occurs in different steps. - Graphical abstract: Molecular structure of the bis(hydrogenmaleate)-Co(II) tetrahydrate drawn at 40% ellipsoid probability level. - Highlights: • Bis(hydrogenmaleate)-Co(II) tetrahydrate single crystal is grown by slow evaporation method. • Structural and optical properties were discussed. • The title complex crystal is thermally stable up to 91 °C. • Plasma energy, Fermi energy and electronic polarizability are evaluated. • It exhibits positive photoconductivity.

  12. Mechanism for enhanced absorption of a solid dispersion formulation of LY2300559 using the artificial stomach duodenum model.

    PubMed

    Polster, Christopher S; Wu, Sy-Juen; Gueorguieva, Ivelina; Sperry, David C

    2015-04-01

    An artificial stomach duodenum (ASD) model has been used to demonstrate the performance difference between two formulations of LY2300559, a low-solubility acidic developmental drug. The two formulations investigated were a conventional high-shear wet granulation (HSWG) formulation and a solid dispersion formulation. A pharmacokinetic study in humans demonstrated the enhanced performance of the solid dispersion formulation relative to the HSWG formulation. The Cmax and AUC of the solid dispersion was 2.6 and 1.9 times greater, respectively, compared to the HSWG formulation. In the ASD, the solid dispersion formulation performance was characterized by three main phases: (1) rapid release in the stomach, creating a supersaturated concentration of drug, (2) precipitation in the stomach, and (3) rapid redissolution of the precipitate in the duodenum to concentration levels that are supersaturated relative to crystalline drug. A series of complementary experiments were employed to describe this performance behavior mechanistically. Imaging experiments with a pH indicating dye showed that local pH gradients from meglumine in the solid dispersion formulation were responsible for creating a high initial supersaturation concentration in the stomach. Upon dissipation of meglumine, the drug precipitated in the stomach as an amorphous solid. Because the precipitated drug is in an amorphous form, it can then rapidly redissolve as it transits to the more neutral environment of the duodenum. This unexpected sequence of physical state changes gives a mechanistic explanation for the enhanced in vivo performance of the solid dispersion formulation relative to the HSWG formulation. PMID:25723790

  13. Conformational transitions and fibrillation mechanism of human calcitonin as studied by high-resolution solid-state 13C NMR.

    PubMed Central

    Kamihira, M.; Naito, A.; Tuzi, S.; Nosaka, A. Y.; Saitô, H.

    2000-01-01

    Conformational transitions of human calcitonin (hCT) during fibril formation in the acidic and neutral conditions were investigated by high-resolution solid-state 13C NMR spectroscopy. In aqueous acetic acid solution (pH 3.3), a local alpha-helical form is present around Gly10 whereas a random coil form is dominant as viewed from Phe22, Ala26, and Ala31 in the monomer form on the basis of the 13C chemical shifts. On the other hand, a local beta-sheet form as viewed from Gly10 and Phe22, and both beta-sheet and random coil as viewed from Ala26 and Ala31 were detected in the fibril at pH 3.3. The results indicate that conformational transitions from alpha-helix to beta-sheet, and from random coil to beta-sheet forms occurred in the central and C-terminus regions, respectively, during the fibril formation. The increased 13C resonance intensities of fibrils after a certain delay time suggests that the fibrillation can be explained by a two-step reaction mechanism in which the first step is a homogeneous association to form a nucleus, and the second step is an autocatalytic heterogeneous fibrillation. In contrast to the fibril at pH 3.3, the fibril at pH 7.5 formed a local beta-sheet conformation at the central region and exhibited a random coil at the C-terminus region. Not only a hydrophobic interaction among the amphiphilic alpha-helices, but also an electrostatic interaction between charged side chains can play an important role for the fibril formation at pH 7.5 and 3.3 acting as electrostatically favorable and unfavorable interactions, respectively. These results suggest that hCT fibrils are formed by stacking antiparallel beta-sheets at pH 7.5 and a mixture of antiparallel and parallel beta-sheets at pH 3.3. PMID:10850796

  14. Adsorption of radionuclides on minerals studies illustrating the effect of solid phase selectivity and of mechanisms controlling sorption processes

    SciTech Connect

    Netus, B.

    1996-02-01

    Currently, extensive research is being done on the geochemistry of Yucca Mountain, Nevada. The purpose of this research is to determine whether this location would be suitable as a permanent high-level radioactive waste repository. Site characterization tests must prove that Yucca Mountains` geology will safely isolate radioactive waste from the environment for at least 10,000 years before approval is granted. In order for this to occur, it is necessary to study the sorptive properties of the host rock, and its selectivity in sorption of solutions containing multiple radionuclides. Validation of this must occur, because in the case of a catastrophic leak, the host rock must have properties that will retard the migration of radionuclides. Columnar experimental techniques were employed using goethite, (a hydrous iron oxide), beidellite (clay mineral), & {open_quotes}nonscents{close_quotes} (a zeolitized volcanic tuff) as sorbents. These sorbents were used to measure the isotherms of an identical binary solution (Ni-Sr) to illustrate the selectivity that occurs in different minerals. In beidellite, the sorption process was ideal, while for {open_quotes}nonscents{close_quotes} there was a strong preference for Sr{sup 2+}. The sorption process was modeled (Ni-Sr {open_quotes}Nonscents{close_quotes}) using ion exchange theory as the mechanism. In goethite, the sorption of Ni-Sr showed a complete preference for Ni{sup 2+} at a pH of 7. In various other systems for goethite. Co-Ni (pH=7) was ideal (no selectivity) where the ratios in the solid and solution phases were relatively equal. Conversely in the case of the Pb-Ni system, the Pb{sup 2+} ion predominated completely in the solidphase over Ni{sup 2+} at a pH of 5.5. Noting the strong effect of pH on the sorption process in goethite, the selectivity could not necessarily be credited to ion-exchange because of possible exclusion from charged sites at low pH values.

  15. Microstructural and nuclear magnetic resonance studies of solid-state amorphization in Al-Ti-Si composites prepared by mechanical alloying

    SciTech Connect

    Manna, I.; Nandi, P.; Bandyopadhyay, B.; Ghoshray, K.; Ghoshray, A

    2004-08-16

    Three Al{sub 30}Ti{sub 70-x} Si{sub x} (x=10, 20, 30), along with an Al-rich (Al{sub 50}Ti{sub 40}Si{sub 10}) and an Al-lean (Al{sub 10}Ti{sub 60}Si{sub 30}) elemental powder blends were subjected to mechanical alloying by high-energy planetary ball milling to yield a composite microstructure with varying proportions of amorphous and nanocrystalline intermetallic phases. Microstructural characterization at different stages of milling was carried out by X-ray diffraction, high-resolution transmission electron microscopy and energy dispersive X-ray spectroscopy. Furthermore, {sup 27}Al nuclear magnetic resonance (NMR) studies were undertaken to probe the mechanism of solid-state amorphization. Ball milling leads to alloying, nanocrystallization and partial solid-state amorphization followed/accompanied by strain-induced nucleation of nanocrystalline intermetallic phases from an amorphous solid solution. Both these amorphous and nano-intermetallic phases are associated with characteristic NMR peaks at lower frequencies (than that of pure Al). Thus, mechanical alloying of Al-Ti-Si appears a suitable technique for developing nanocrystalline intermetallic phase/compound dispersed amorphous matrix composites.

  16. Kinetics and Mechanisms of Cr(VI) Formation via the Oxidation of Cr(III) Solid Phases by Chlorine in Drinking Water.

    PubMed

    Chebeir, Michelle; Liu, Haizhou

    2016-01-19

    Hexavalent chromium Cr(VI), typically existing as the oxyanion form of CrO4(2-), is being considered for more stringent drinking water standards by regulatory agencies. Cr(VI) can be inadvertently produced via the oxidation of trivalent chromium Cr(III) solids. This study investigated the kinetics and mechanisms of Cr(III) solids oxidation by chlorine in drinking water and associated Cr(VI) formation. Batch experiments were carried out with three Cr(III) solids of environmental relevance, i.e., chromium hydroxide Cr(OH)3(s), chromium oxide Cr2O3(s), and copper chromite Cu2Cr2O5(s). Impacts of water chemical parameters including pH (6.0-8.5) and bromide concentration (0-5 mg/L) were examined. Results showed that the rapid oxidation of Cr(III) solid phases by chlorine was accompanied by Cr(VI) formation and an unexpected production of dissolved oxygen. Analysis of reaction stoichiometry indicated the existence of Cr intermediate species that promoted the autocatalytic decay of chlorine. An increase in pH modestly enhanced Cr(VI) formation due to changes of reactive Cr(III) surface hydroxo species. Bromide, a trace chemical constituent in source waters, exhibited a catalytic effect on Cr(VI) formation due to an electron shuttle mechanism between Cr(III) and chlorine and the bypass of Cr intermediate formation. The kinetics data obtained from this study suggest that the oxidation of Cr(III) solids by chlorine in water distribution systems can contribute to Cr(VI) occurrence in tap water, especially in the presence of a trace level of bromide. PMID:26647114

  17. Microstructure, excess solid solubility, and elevated-temperature mechanical behavior of spray-atomized and codeposited Al-Ti-SiCP

    NASA Astrophysics Data System (ADS)

    Gupta, M.; Juarez-Islas, J.; Frazier, W. E.; Mohamed, F. A.; Lavernia, E. J.

    1992-12-01

    In the present study, the microstructure, thermal stability, and elevated temperature mechanical behavior of Al-Ti-SiCP metal matrix composites (MMCs) processed by spray atomization and codeposition were investigated. The evolution of the microstructure of the spray-deposited material before and after thermal annealing was studied using X-ray diffractometry, transmission electron microscopy (TEM), scanning electron microscopy (SEM), and optical microscopy. The thermal stability of the spray-deposited materials was determined by monitoring the changes in hardness after isochronal thermal anneals at various temperatures. The results of X-ray and microanalysis studies revealed the presence of a supersaturated solid solution of Ti in α Al in the spray-atomized and codeposited material, with Ti concentrations in the 0.8 to 1.1 wt pet range. The formation of an extended solid solution was discussed in light of the cooling rates present during atomization and, subsequently, during deposition. Regarding mechanical behavior, the present results suggest that the as-spray deposited and hot extruded Al-Ti matrix is thermally stable up to a temperature of 400 °C and that the excess solid solubility of Ti in a Al, resulting from the rapid quench during processing, is maintained up to a temperature of 300 °C. The elevated-temperature mechanical properties of the hot extruded spray-deposited materials were studied following a 100-hour exposure at 250 °C, 350 °C, and 450 °C; the roomtemperature mechanical properties were also determined. Results show that the elevated-temperature yield strength of the spray-deposited and extruded materials compared favorably to those of an equivalent alloy made by powder metallurgical materials, were superior to those of the ingot material, but were inferior to those of mechanically alloyed Al-Ti materials. In addition, TEM studies showed no evidence of interfacial reactions at the Al-Ti/SiCP interface.

  18. Mechanical and Combustion Performance of Multi-Walled Carbon Nanotubes as an Additive to Paraffin-Based Solid Fuels for Hybrid Rockets

    NASA Technical Reports Server (NTRS)

    Larson, Daniel B.; Boyer, Eric; Wachs, Trevor; Kuo, Kenneth, K.; Koo, Joseph H.; Story, George

    2012-01-01

    Paraffin-based solid fuels for hybrid rocket motor applications are recognized as a fastburning alternative to other fuel binders such as HTPB, but efforts to further improve the burning rate and mechanical properties of paraffin are still necessary. One approach that is considered in this study is to use multi-walled carbon nanotubes (MWNT) as an additive to paraffin wax. Carbon nanotubes provide increased electrical and thermal conductivity to the solid-fuel grains to which they are added, which can improve the mass burning rate. Furthermore, the addition of ultra-fine aluminum particles to the paraffin/MWNT fuel grains can enhance regression rate of the solid fuel and the density impulse of the hybrid rocket. The multi-walled carbon nanotubes also present the possibility of greatly improving the mechanical properties (e.g., tensile strength) of the paraffin-based solid-fuel grains. For casting these solid-fuel grains, various percentages of MWNT and aluminum particles will be added to the paraffin wax. Previous work has been published about the dispersion and mixing of carbon nanotubes.1 Another manufacturing method has been used for mixing the MWNT with a phenolic resin for ablative applications, and the manufacturing and mixing processes are well-documented in the literature.2 The cost of MWNT is a small fraction of single-walled nanotubes. This is a scale-up advantage as future applications and projects will require low cost additives to maintain cost effectiveness. Testing of the solid-fuel grains will be conducted in several steps. Dog bone samples will be cast and prepared for tensile testing. The fuel samples will also be analyzed using thermogravimetric analysis and a high-resolution scanning electron microscope (SEM). The SEM will allow for examination of the solid fuel grain for uniformity and consistency. The paraffin-based fuel grains will also be tested using two hybrid rocket test motors located at the Pennsylvania State University s High Pressure

  19. Storage of solid propellants in a dry environment. [mechanical properties resulting from long term exposure to aerospace environments

    NASA Technical Reports Server (NTRS)

    Udlock, D. E.

    1978-01-01

    Storage of solid propellants in either a dry or a vacuum environment causes a significantly greater increase in the propellants' modulus and maximum tensile strength than does ambient storage. It is postulated that these physical property changes can be attributed to the effect trace amount of moisture has on the bond between the propellants' binder and oxidizer.

  20. Mechanism of Solid-State Thermolysis of Ammonia Boraine: 15N NMR Study Using Fast Magic-Angle Spinning and Dynamic Nuclear Polarization

    SciTech Connect

    Kobayashi, Takeshi; Gupta, Shalabh; Caporini, Marc A; Pecharsky, Vitalij K; Pruski, Marek

    2014-08-28

    The solid-state thermolysis of ammonia borane (NH3BH3, AB) was explored using state-of-the-art 15N solid-state NMR spectroscopy, including 2D indirectly detected 1H{15N} heteronuclear correlation and dynamic nuclear polarization (DNP)-enhanced 15N{1H} cross-polarization experiments as well as 11B NMR. The complementary use of 15N and 11B NMR experiments, supported by density functional theory calculations of the chemical shift tensors, provided insights into the dehydrogenation mechanism of AB—insights that have not been available by 11B NMR alone. Specifically, highly branched polyaminoborane derivatives were shown to form from AB via oligomerization in the “head-to-tail” manner, which then transform directly into hexagonal boron nitride analog through the dehydrocyclization reaction, bypassing the formation of polyiminoborane.

  1. Mathematical modeling of desorption with intraparticle and external film diffusion as rate controlling mechanism: application to coal conversion solid waste

    SciTech Connect

    Erdogan, H.

    1981-01-01

    The performance of a fixed bed desorption column was investigated and a mathematical model describing the process was developed. Four grades of slagging coal conversion solid waste particles with mesh sizes of 20 to 40, 40 to 60, 60 to 100, and 100 to 200 were used in this study. Experimental desorption curves were generated to quantify intraparticle and external film diffusional resistances, an equilibrium isotherms. Leachable initial solid phase pollutant concentration, external mass transfer coefficients for the liquid, and equilibrium constants were determined experimentally. Intraparticle diffusivity was calculated via a curve matching technique. The curve matching was done on computer minimizing the sum of squares of experimental and theoretical concentration data. Liquid dispersion coefficient was determined from plot of dispersion constant versus Reynolds number on a log-log scale. Mathematical model was solved by a finite-difference technique to generate concentration profiles. The model was verified by the comparison of the calculated and experimental concentration profiles.

  2. A nonlinear, implicit, three-dimensional finite element code for solid and structural mechanics - User`s Manual

    SciTech Connect

    Maker, B.N.

    1995-04-14

    This report provides a user`s manual for NIKE3D, a fully implicit three-dimensional finite element code for analyzing the finite strain static and dynamic response of inelastic solids, shells, and beams. Spatial discretization is achieved by the use of 8-node solid elements, 2-node truss and beam elements, and 4-node membrane and shell elements. Over twenty constitutive models are available for representing a wide range of elastic, plastic, viscous, and thermally dependent material behavior. Contact-impact algorithms permit gaps, frictional sliding, and mesh discontinuities along material interfaces. Several nonlinear solution strategies are available, including Full-, Modified-, and Quasi-Newton methods. The resulting system of simultaneous linear equations is either solved iteratively by an element-by-element method, or directly by a factorization method, for which case bandwidth minimization is optional. Data may be stored either in or out of core memory to allow for large analyses.

  3. Natural binders and solid bridge type binding mechanisms in briquettes and pellets made from corn stover and switchgrass.

    PubMed

    Kaliyan, Nalladurai; Morey, R Vance

    2010-02-01

    Corn stover and switchgrass are two important feedstocks considered for producing renewable fuels and energy in the US. Densification of these biomass feedstocks into briquettes/pellets would help reduce the problems and costs of bulk transportation, handling, and storage of biomass feedstocks. In this study, the role of the natural binders in corn stover and switchgrass to make durable particle-particle bonding in briquettes/pellets was investigated by micro-structural analyses. Scanning Electron Microscopy (SEM) images of briquettes made by using a uniaxial piston-cylinder densification apparatus in the laboratory, briquettes made by using a pilot-scale roll-press briquetting machine, and pellets made by using a pilot-scale conventional ring-die pelleting machine were analysed. The SEM images showed that the bonding between particles was created mainly through solid bridges. The solid bridges between particles were made by natural binders in the biomass expressed during the densification process. UV auto-fluorescence images of briquettes and pellets further confirmed that the solid bridges were made mainly by natural binders such as lignin and protein. It was found that activating (softening) the natural binders using moisture and temperature in the range of glass transition is important to make durable particle-particle bonding. PMID:19796933

  4. High order ADER schemes for a unified first order hyperbolic formulation of continuum mechanics: Viscous heat-conducting fluids and elastic solids

    NASA Astrophysics Data System (ADS)

    Dumbser, Michael; Peshkov, Ilya; Romenski, Evgeniy; Zanotti, Olindo

    2016-06-01

    This paper is concerned with the numerical solution of the unified first order hyperbolic formulation of continuum mechanics recently proposed by Peshkov and Romenski [110], further denoted as HPR model. In that framework, the viscous stresses are computed from the so-called distortion tensor A, which is one of the primary state variables in the proposed first order system. A very important key feature of the HPR model is its ability to describe at the same time the behavior of inviscid and viscous compressible Newtonian and non-Newtonian fluids with heat conduction, as well as the behavior of elastic and visco-plastic solids. Actually, the model treats viscous and inviscid fluids as generalized visco-plastic solids. This is achieved via a stiff source term that accounts for strain relaxation in the evolution equations of A. Also heat conduction is included via a first order hyperbolic system for the thermal impulse, from which the heat flux is computed. The governing PDE system is hyperbolic and fully consistent with the first and the second principle of thermodynamics. It is also fundamentally different from first order Maxwell-Cattaneo-type relaxation models based on extended irreversible thermodynamics. The HPR model represents therefore a novel and unified description of continuum mechanics, which applies at the same time to fluid mechanics and solid mechanics. In this paper, the direct connection between the HPR model and the classical hyperbolic-parabolic Navier-Stokes-Fourier theory is established for the first time via a formal asymptotic analysis in the stiff relaxation limit. From a numerical point of view, the governing partial differential equations are very challenging, since they form a large nonlinear hyperbolic PDE system that includes stiff source terms and non-conservative products. We apply the successful family of one-step ADER-WENO finite volume (FV) and ADER discontinuous Galerkin (DG) finite element schemes to the HPR model in the stiff

  5. Holographic velocimetry using object-conjugate reconstruction (OCR): a new approach for simultaneous, 3D displacement measurement in fluid and solid mechanics

    NASA Astrophysics Data System (ADS)

    Barnhart, D. H.; Chan, V. S. S.; Halliwell, N. A.; Coupland, J. M.

    2002-08-01

    This paper reports on a new form of holographic metrology that enables displacement measurement in both fluid and solid mechanics simultaneously. In such instances, existing holographic methods for displacement measurement would require the application of multiple techniques in a hybrid fashion. Known as object-conjugate reconstruction (OCR), our new approach unifies the disciplines of holographic velocimetry and holographic interferometry. Using complex correlation processing, it provides a sub-wavelength resolution for all three components of displacement and enables automated data extraction at selected points throughout a volume in space.

  6. Statistical Continuum Mechanics Analysis of Effective Elastic Properties in Solid Oxide Fuel Cell Glass–Ceramic Seal Material

    SciTech Connect

    Milhans, Jacqueline; Li, Dongsheng; Khaleel, Mohammad A.; Sun, Xin; Garmestani, Hamid

    2010-09-01

    A full statistical analysis of the microstructure of glass–ceramic solid oxide fuel cell (SOFC) seal material, G18, is performed to calculate elastic properties. Predictions are made for samples aged for 4 h and 1000 h, giving different crystallinity levels. Microstructure of the glass–ceramic G18 is characterized by correlation function for each individual phase. Predicted results are compared with the Voigt and Reuss bounds in this study. The weak contrast analysis results in elastic modulus predictions between the upper and lower bounds but closer to the upper bound.

  7. Unified system for holographic measurement in fluid and solid mechanics: use of the system for 3D velocity measurement in fluids through a thick curved window

    NASA Astrophysics Data System (ADS)

    Chan, Victor S. S.; Barnhart, Donald H.; Halliwell, Neil A.; Coupland, Jeremy M.

    1999-10-01

    A new holographic technique has been developed to measure displacement in solid and fluid mechanics. The method uses double exposure holograms of large numerical aperture to record the light scattered from a solid surface or seeding particles that are assumed to follow the fluid motion. Analysis of the resulting hologram is performed in a piece- wise fashion through spatial correlation of the field that passes through a sampling aperture placed in the real image. In this way it is possible to map 3D displacement of an irregular surface or map the movement of seeding throughout an extended volume of fluid. This paper discusses the cancellation of gross aberrations using a phase conjugate holographic optical element to generate a converging reference wave. Seeded flow or solid surfaces recorded with this reference wave geometry can be reconstructed efficiently using a fiber-optic probe. In addition to aberration cancelling the technique allows a method of image shifting to be introduced thus resolving the direction of the flow or surface displacement.

  8. Effect of Molecular Weight on Mechanical and Electrochemical Performance of All Solid-State Polymer Electrolyte Membranes

    NASA Astrophysics Data System (ADS)

    He, Ruixuan; Ward, Daniel; Echeverri, Mauricio; Kyu, Thein

    2015-03-01

    Guided by ternary phase diagrams of polyethylene glycol diacrylate (PEGDA), succinonitrile plasticizer, and LiTFSI salt, completely amorphous solid-state transparent polymer electrolyte membranes (ss-PEM) were fabricated by UV irradiation in the isotropic melt state. Effects of PEGDA molecular weight (700 vs 6000 g/mol) on ss-PEM performance were investigated. These amorphous PEMs have superionic room temperature ionic conductivity of ~10-3 S/cm, whereby PEGDA6000-PEM outperforms its PEGDA700 counterpart, which may be ascribed to lower crosslinking density and greater segmental mobility. The longer chain between crosslinked points of PEGDA6000-PEM is responsible for greater extensibility of ~80% versus ~7% of PEGDA700-PEM. Besides, both PEMs exhibited thermal stability up to 120 °C and electrochemical stability versus Li+/Li up to 4.7V. LiFePO4/PEM/Li and Li4Ti5O12 /PEM/Li half-cells exhibited stable cyclic behavior up to 50 cycles tested with a capacity of ~140mAh/g, suggesting that LiFePO4/PEM/Li4Ti5O12 may be a promising full-cell for all solid-state lithium battery. We thank NSF-DMR 1161070 for providing funding of this project.

  9. Structure and Mechanism of Beta-Hairpin Antimicrobial Peptides in Lipid Bilayers from Solid-State NMR Spectroscopy

    PubMed Central

    Tang, Ming; Hong, Mei

    2010-01-01

    The membrane-bound structure, lipid interaction, and dynamics of the arginine-rich β-hairpin antimicrobial peptide PG-1 as studied by solid-state NMR is highlighted here. A variety of solid-state NMR techniques, including paramagnetic relaxation enhancement, 1H and 19F spin diffusion, dipolar recoupling distance experiments, and 2D anisotropic-isotropic correlation experiments, are used to elucidate the structural basis for the membrane disruptive activity of this representative β-hairpin antimicrobial peptide. We found that PG-1 structure is membrane dependent: in bacteria-mimetic anionic lipid membranes the peptide forms oligomeric transmembrane β-barrels, whereas in cholesterol-rich membranes mimicking eukaryotic cells the peptide forms β-sheet aggregates on the surface of the bilayer. PG-1 causes toroidal pore defects in the anionic membrane, suggesting that the cationic arginine residues drag the lipid phosphate groups along as the peptide inserts. Mutation of PG-1 to reduce the number of cationic residues or to change the arginine guanidinium structure significantly changes the degree of insertion and orientation of the peptide in the lipid membrane, resulting in much weaker antimicrobial activities. PMID:19396367

  10. Exploratory Investigation of Failure Mechanisms in Transition Regions between Solid Laminates and X-cor(registered tm) Truss Sandwich

    NASA Technical Reports Server (NTRS)

    OBrien, T. Kevin; Paris, Isabelle L.

    2004-01-01

    Small sub-component specimens consisting of solid laminates at the ends that transition to X-cor(R) truss sandwich in the center, were tested in a combination of three point bending, uni-axial tension, and combined tension and bending. The failure process in the transition region was documented for each loading using digital video and high-resolution cameras. For the 3-point bending tests, most of the deformation occurred in the solid laminate regions on either end of the specimen. Some pin debonding from the skin of the X-cor(R) truss sandwich was observed in the transition region and was accompanied by audible "pings" throughout the loading. Tension loaded specimens failed in the sandwich skin in the middle of the gage length, accompanied by separation of the sandwich core from the back skin and by delamination between the top skin and bottom skin at the transition region. The pinging associated with pin debonding occurred as the load was increased. However, the frequency of the pinging exceeded any visual observations of pin debonding in the video of the transition region. For specimens tested in combined tension and bending, the greatest amount of pinging occurred during initial application of the axial load. High-resolution images in the transition region indicated that the pinging corresponded to pins debonding and buckling due to the through-thickness Poisson contraction of the specimen. This buckling continued to a much smaller extent as the transverse load was applied.

  11. Predicting temperature-dependent solid vapor pressures of explosives and related compounds using a quantum mechanical continuum solvation model.

    PubMed

    Alnemrat, Sufian; Hooper, Joseph P

    2013-03-01

    Temperature-dependent vapor pressures of solid explosives and their byproducts are calculated to an accuracy of 0.32 log units using a modified form of the conductor-like screening model for real solvents (COSMO-RS). Accurate predictions for solids within COSMO-RS require correction for the free energy of fusion as well as other effects such as van der Waals interactions. Limited experimental data on explosives is available to determine these corrections, and thus we have extended the COSMO-RS model by introducing a quantitative structure-property relationship to estimate a lumped correction factor using only information from standard quantum chemistry calculations. This modification improves the COSMO-RS estimate of ambient vapor pressure by more than 1 order of magnitude for a range of nitrogen-rich explosives and their derivatives, bringing the theoretical predictions to within typical experimental error bars for vapor pressure measurements. The estimated temperature dependence of these vapor pressures also agrees well with available experimental data, which is particularly important for estimating environmental transport and gas evolution for buried explosives or environmentally contaminated locations. This technique is then used to predict vapor pressures for a number of explosives and degradation products for which experimental data is not readily available. PMID:23398143

  12. Numerical analysis of the thermal and mechanical effects of laser windows of a high-power all-solid-state 2-μm laser system

    NASA Astrophysics Data System (ADS)

    Liu, Wenwen; Niu, Yanxiong; Liu, Haixia; Wang, Caili; Hu, Shuling; Zhang, Chao; Niu, Haisha; Li, Jiyang

    2014-02-01

    The output window of a high-power laser system is vulnerable to damage, and this is the main limiting factor on the power scaling and structure integrity of the laser system. In endeavoring to obtain higher output powers from the laser system, the impact of the thermal and mechanical effects and the damage mechanism of the output window must be considered. In order to study these issues, a thermal model of the laser window is established based on the heat transfer and thermoelastic theories, and the expressions for the transient thermal and mechanical stress distributions of the output window are deduced in terms of the integral-transform method. Taking the infrared quartz window material as an example, the temperature and mechanical field distributions of a high-power all-solid-state 2-μm laser system window are simulated, and the laser-induced damage mechanism is deeply analyzed. The calculation results show that the laser window-induced damage is mainly caused by melting damage when the temperature exceeds the melting point of the material. The presented theoretical analysis and numerical simulation results are significant for the design and optimization of high-power laser windows.

  13. Solid State Kinetic Parameters and Chemical Mechanism of the Dehydration of CoCl2.6H2O.

    ERIC Educational Resources Information Center

    Ribas, Joan; And Others

    1988-01-01

    Presents an experimental example illustrating the most common methods for the determination of kinetic parameters. Discusses the different theories and equations to be applied and the mechanism derived from the kinetic results. (CW)

  14. Mechanical performance of reactive-air-brazed (RAB) ceramic/metal joints for solid oxide fuel cells at ambient temperature

    NASA Astrophysics Data System (ADS)

    Kuhn, B.; Wetzel, F. J.; Malzbender, J.; Steinbrech, R. W.; Singheiser, L.

    Mechanical integrity of the sealants in planar SOFC stacks is a key prerequisite for reliable operation. In this respect joining with metals rather than brittle glass-ceramics is considered to have advantages. Hence, as one of the joining solutions for SOFCs of planar design, reactive air brazing of ceramic cells into metallic frames gains increasing interest. Fracture experiments are carried out to characterize fracture energy and failure mechanisms of silver-based reactive-air-brazes, used for joining the zirconia electrolytes of anode supported planar cells with metallic Crofer22APU frames. The specimens are mechanically tested in notched beam bending geometry. In-situ observation in optical and SEM resolution reveals specific failure mechanisms. The influence of braze formulation and associated interfacial reactions on the crack path location is addressed. Discussion of the results focuses in particular on the role of oxide scale formation.

  15. Impact of solid second phases on deformation mechanisms of naturally deformed salt rocks (Kuh-e-Namak, Dashti, Iran) and rheological stratification of the Hormuz Salt Formation

    NASA Astrophysics Data System (ADS)

    Závada, P.; Desbois, G.; Urai, J. L.; Schulmann, K.; Rahmati, M.; Lexa, O.; Wollenberg, U.

    2015-05-01

    Viscosity contrasts displayed in flow structures of a mountain namakier (Kuh-e-Namak - Dashti), between 'weak' second phase bearing rock salt and 'strong' pure rock salt types are studied for deformation mechanisms using detailed quantitative microstructural study. While the solid inclusions rich ("dirty") rock salts contain disaggregated siltstone and dolomite interlayers, "clean" salts reveal microscopic hematite and remnants of abundant fluid inclusions in non-recrystallized cores of porphyroclasts. Although the flow in both, the recrystallized "dirty" and "clean" salt types is accommodated by combined mechanisms of pressure-solution creep (PS), grain boundary sliding (GBS), transgranular microcracking and dislocation creep accommodated grain boundary migration (GBM), their viscosity contrasts observed in the field outcrops are explained by: 1) enhanced ductility of "dirty" salts due to increased diffusion rates along the solid inclusion-halite contacts than along halite-halite contacts, and 2) slow rates of intergranular diffusion due to dissolved iron and inhibited dislocation creep due to hematite inclusions for "clean" salt types Rheological contrasts inferred by microstructural analysis between both salt rock classes apply in general for the "dirty" salt forming Lower Hormuz and the "clean" salt forming the Upper Hormuz of the Hormuz Formation and imply strain rate gradients or decoupling along horizons of mobilized salt types of different composition and microstructure.

  16. Mechanical property of different corn stover morphological fractions and its correlations with high solids enzymatic hydrolysis by periodic peristalsis.

    PubMed

    Liu, Zhi-Hua; Chen, Hong-Zhang

    2016-08-01

    Selective structure fractionation combined with periodic peristalsis was exploited to improve the conversion performance of corn stover. The increase of glucan and lignin content and the decrease of xylan content in stem pith were highest after SE, whereas they were lowest in stem node. Glucan conversion increased in this order: steam nodesolids enzymatic hydrolysis efficiency of different corn stover morphological fractions. PMID:27140819

  17. Volumetric influence on the mechanical behavior of organic solids: The case of aspirin and paracetamol addressed via dispersion corrected DFT

    NASA Astrophysics Data System (ADS)

    Adhikari, Kapil; Flurchick, Kenneth M.; Valenzano, Loredana

    2015-06-01

    The elastic and mechanical properties of the most stable polymorphs of aspirin and paracetamol are obtained at B3LYP-D2* level of theory to show how effects arising from volumetric expansions related to thermal variations influence the behavior of these materials. Results are in fair agreement with experimental values reported at temperatures far from 0 K, showing that the proposed approach can describe the elastic response of molecular crystals as rationalized in terms of inter-molecular forces. The computational approach, despite its semi-empirical nature, allows achieving a qualitative chemical understanding of the macroscopic mechanical properties of molecular crystals with respect to changes in temperature.

  18. Conduction mechanisms in concentrated LiI-polyethylene oxide-Al{sub 2}O{sub 3}-based solid electrolytes

    SciTech Connect

    Golodnitsky, D.; Ardel, G.; Strauss, E.; Peled, E.; Lareah, Y.; Rosenberg, Y.

    1997-10-01

    The ionic conductivity of concentrated LiI-polyethylene oxide P(EO){sub n} high surface area oxide composite polymer electrolytes has been investigated. Two different Arrhenius dependences for concentrated composite polymer electrolytes (CPEs) have been identified. The first one is characterized by an inflection point at about 80 C, and the second, by a conductivity jump. The authors have suggested that in CPEs, where 3solid phase is major contributor to the overall ionic conductivity at temperatures above, but close to the melting point of the eutectic (T{sub m}solid electrolytes (CSEs, n{le}3), is about 40% of that for CPEs. The authors believe that the preferred conduction path in even more concentrated CPEs, which are defined as CSEs, is interfacial conduction. Differential scanning calorimetry, scanning electron microscopy, and X-ray data, presented here, are evidence supporting the view. The effects of several parameters including type and content of oxide matrix, Li salt to ethylene oxide ratio, copolymers, and solvents on polymer electrolyte conductivity (especially at T >T{sub k}orT{sub jump}) and on Ea have been studied (T{sub jump}=temperature of the conductivity jump). The addition of small quantities of ethylene carbonate, poly(methyl methacrylate), and polyacrylonitrile were found to be beneficial while poly(methyl acrylate), poly(butyl acrylate), and poly(vinylidene fluoride) additions made the polymer electrolyte stiffer and less conductive. MgO, Al{sub 2}O{sub 3}, and potassium aluminosilicate muscovite mica based CSEs have similar conductivity. Results clearly demonstrated the depression of CPE crystallinity by addition of fine Al{sub 2}O{sub 3} powder, ethylene carbonate, and poly(ethylene glycol) dimethyl ether, in agreement with the conductivity enhancement of the CPE.

  19. The role of mechanical and biological treatment in reducing methane emissions from landfill disposal of municipal solid waste in the United Kingdom.

    PubMed

    Pan, Jilang; Voulvoulis, Nickolaos

    2007-02-01

    In Europe, the European Union Landfill Directive aims to reduce the negative environmental impacts of landfilling. This is mainly to be achieved by reducing the quantity of organic matter deposited, through measures such as the separate collection and recycling of the organic waste stream or pretreatment of residual wastes before landfilling. Other than incineration or other thermal processes, mechanical biological treatment is playing an increasingly important role. This study was conducted to seek the benefits of municipal solid waste (MSW) pretreatment, as well as the differences in methane production from the landfilling of untreated and mechanically/biologically treated (MBT) MSW using GasSim simulation. Results demonstrated that methane production rates vary significantly among waste fractions. Those that contribute most to methane generation (organic material and potentially reusable or recyclable material) could be targeted and treated before landfilling. The statistic relationship from the first phase of the study indicated that to match the increasingly stringent landfill waste organic content allowance, local councils should prioritize the reduction/sorting of certain targeted fractions, such as paper, card, green waste, and other putrescibles from MSW. Moreover, mechanical treatment alone produces organic-rich waste called mechanically sorted organic residues (MSORs), which can be viewed as an organic content concentration process. Mechanically and biologically pretreated waste, on the other hand, differs significantly from untreated MSW and MSORs. This work demonstrated that if efficient mechanical-biological treatment is used, considerable reductions in biological activity, landfill gas production, and energy content/total organic carbon could be achieved. Using GasSim, reductions in methane production of >74% have been simulated if a 90% organic content reduction can be achieved during biological treatment on MSORs. A 50-60% organic content reduction

  20. Paradyn a parallel nonlinear, explicit, three-dimensional finite-element code for solid and structural mechanics user manual

    SciTech Connect

    Hoover, C G; DeGroot, A J; Sherwood, R J

    2000-06-01

    ParaDyn is a parallel version of the DYNA3D computer program, a three-dimensional explicit finite-element program for analyzing the dynamic response of solids and structures. The ParaDyn program has been used as a production tool for over three years for analyzing problems which range in size from a few tens of thousands of elements to between one-million and ten-million elements. ParaDyn runs on parallel computers provided by the Department of Energy Accelerated Strategic Computing Initiative (ASCI) and the Department of Defense High Performance Computing and Modernization Program. Preprocessing and post-processing software utilities and tools are designed to facilitate the generation of partitioned domains for processors on a massively parallel computer and the visualization of both resultant data and boundary data generated in a parallel simulation. This manual provides a brief overview of the parallel implementation; describes techniques for running the ParaDyn program, tools and utilities; and provides examples of parallel simulations.

  1. Model anodes and anode models for understanding the mechanism of hydrogen oxidation in solid oxide fuel cells.

    PubMed

    Bessler, Wolfgang G; Vogler, Marcel; Störmer, Heike; Gerthsen, Dagmar; Utz, Annika; Weber, André; Ivers-Tiffée, Ellen

    2010-11-14

    This article presents a literature review and new results on experimental and theoretical investigations of the electrochemistry of solid oxide fuel cell (SOFC) model anodes, focusing on the nickel/yttria-stabilized zirconia (Ni/YSZ) materials system with operation under H(2)/H(2)O atmospheres. Micropatterned model anodes were used for electrochemical characterization under well-defined operating conditions. Structural and chemical integrity was confirmed by ex situ pre-test and post-test microstructural and chemical analysis. Elementary kinetic models of reaction and transport processes were used to assess reaction pathways and rate-determining steps. The comparison of experimental and simulated electrochemical behaviors of pattern anodes shows quantitative agreement over a wide range of operating conditions (p(H(2)) = 8×10(2) - 9×10(4) Pa, p(H(2)O) = 2×10(1) - 6×10(4) Pa, T = 400-800 °C). Previously published experimental data on model anodes show a strong scatter in electrochemical performance. Furthermore, model anodes exhibit a pronounced dynamics on multiple time scales which is not reproduced in state-of-the-art models and which is also not observed in technical cermet anodes. Potential origin of these effects as well as consequences for further steps in model anode and anode model studies are discussed. PMID:20820576

  2. Seed-Mediated Hot-Injection Synthesis of Tiny Ag Nanocrystals on Nanoscale Solid Supports and Reaction Mechanism.

    PubMed

    Barhoum, Ahmed; Rehan, Mohamed; Rahier, Hubert; Bechelany, Mikhael; Van Assche, Guy

    2016-04-27

    Controlling the size and shape of noble Ag nanocrystals (NCs) is of great interest because of their unique size- and shape-dependent properties, especially below 20 nm, and because of interesting applications in drug delivery, sensing, and catalysis. However, the high surface energy and tendency of these tiny NCs to aggregate deteriorates their unique properties and limits their applications. To avoid the aggregation of Ag NCs and improve their performance, we report a seed-mediated hot injection approach to synthesize highly dispersed tiny Ag NCs on a nanosized solid CaCO3 support. This simple, low-cost, and effective chemical approach allows for synthesizing highly uniform Ag NCs (∼10 nm) on the surface of presynthesized CaCO3 single NCs (∼52 nm) without any aggregation of the Ag NCs. Viscose fibers were coated with the Ag@CaCO3 composite nanoparticles (NPs) produced, as well as with ∼126 nm Ag NPs for reference. The Ag@CaCO3 composite NPs show excellent UV protection and antibacterial activity against Escherichia coli. In addition, they give a satin sheen gold to a dark gold color to the viscose fibers, while the Ag NPs (∼126 nm) result in a silver color. The proposed synthesis approach is highly versatile and applicable for many other noble metals, like Au or Pt. PMID:27025589

  3. Conducting oxide formation and mechanical endurance of potential solid-oxide fuel cell interconnects in coal syngas environment

    SciTech Connect

    Liu, Kejia; Luo, Junhang; Johnson, Christopher; Liu, Xingbo; Lang, J.; Mao, S.X.

    2008-08-15

    The oxidation properties of potential SOFCs materials Crofer 22 APU, Ebrite and Haynes 230 exposed in coal syngas at 800 °C for 100 h were studied. The phases and surface morphology of the oxide scales were characterized by X-ray diffraction, scanning electron microscopy and energy-dispersive X-ray analysis (EDX). The mechanical endurance and electrical resistance of the conducting oxides were characterized by indentation and electrical impedance, respectively. It was found that the syngas exposure caused the alloys to form porous oxide scales, which increased the electrical resistant and decreased the mechanical stability. As for short-term exposure in syngas, neither carbide nor metal dusting was found in the scales of all samples.

  4. WAFER-SCALE, SOLID FREEFORM FABRICATION OF FULLY-ASSEMBLED METAL MICRO-MECHANISMS FOR MINIMALLY-INVASIVE MEDICAL DEVICES

    PubMed Central

    Cohen, A.; Chen, R.; Frodis, U.; Wu, M.; Folk, C.

    2013-01-01

    The EFAB process was first presented at the SFF Symposium in 1998, at a very early stage of its development. Currently, the technology is able to produce complex 3-D devices—including mechanisms built pre-assembled—in production volumes, using a three-step process of selective electrodeposition of one metal, blanket electrodeposition of another metal, and planarization. Layer thickness is as small as 4 μm, minimum feature size is down to 10 μm, and linear tolerances are ~2 μm. Metals are biocompatible materials with mechanical properties similar to stainless steel. The technology enables new instruments for minimally-invasive surgical and interventional procedures. PMID:25284969

  5. Conducting oxide formation and mechanical endurance of potential solid-oxide fuel cell interconnects in coal syngas environment

    NASA Astrophysics Data System (ADS)

    Liu, Kejia; Luo, Junhang; Johnson, Chris; Liu, Xingbo; Yang, J.; Mao, Scott X.

    The oxidation properties of potential SOFCs materials Crofer 22 APU, Ebrite and Haynes 230 exposed in coal syngas at 800 °C for 100 h were studied. The phases and surface morphology of the oxide scales were characterized by X-ray diffraction, scanning electron microscopy and energy-dispersive X-ray analysis (EDX). The mechanical endurance and electrical resistance of the conducting oxides were characterized by indentation and electrical impedance, respectively. It was found that the syngas exposure caused the alloys to form porous oxide scales, which increased the electrical resistant and decreased the mechanical stability. As for short-term exposure in syngas, neither carbide nor metal dusting was found in the scales of all samples.

  6. Microstructures and mechanical properties of compositionally complex Co-free FeNiMnCr18 FCC solid solution alloy

    DOE PAGESBeta

    Wu, Z.; Bei, H.

    2015-07-01

    Recently, a structurally-simple but compositionally-complex FeNiCoMnCr high entropy alloy was found to have excellent mechanical properties (e.g., high strength and ductility). To understand the potential of using high entropy alloys as structural materials for advanced nuclear reactor and power plants, it is necessary to have a thorough understanding of their structural stability and mechanical properties degradation under neutron irradiation. Furthermore, this requires us to develop a similar model alloy without Co because material with Co will make post-neutron-irradiation testing difficult due to the production of the 60Co radioisotope. In order to achieve this goal, a FCC-structured single-phase alloy with amore » composition of FeNiMnCr18 was successfully developed. This near-equiatomic FeNiMnCr18 alloy has good malleability and its microstructure can be controlled by thermomechanical processing. By rolling and annealing, the as-cast elongated-grained-microstructure is replaced by homogeneous equiaxed grains. The mechanical properties (e.g., strength and ductility) of the FeNiMnCr18 alloy are comparable to those of the equiatomic FeNiCoMnCr high entropy alloy. Both strength and ductility increase with decreasing deformation temperature, with the largest difference occurring between 293 and 77 K. Extensive twin-bands which are bundles of numerous individual twins are observed when it is tensile-fractured at 77 K. No twin bands are detected by EBSD for materials deformed at 293 K and higher. Ultimately the unusual temperature-dependencies of UTS and uniform elongation could be caused by the development of the dense twin substructure, twin-dislocation interactions and the interactions between primary and secondary twinning systems which result in a microstructure refinement and hence cause enhanced strain hardening and postponed necking.« less

  7. Elucidation of intestinal absorption mechanism of carvedilol-loaded solid lipid nanoparticles using Caco-2 cell line as an in-vitro model.

    PubMed

    Shah, Mansi K; Madan, Parshotam; Lin, Senshang

    2014-07-29

    Abstract Enhanced oral bioavailability of poorly aqueous soluble drugs encapsulated in solid lipid nanoparticles (SLNs) via lymphatic delivery has been documented. Since no in-vitro lymphoid tissue is currently available, human excised Caco-2 cell monolayer could be alternative tissue for development of an in-vitro model to be used as a screening tool before animal studies are undertaken. Therefore, optimized carvedilol-loaded SLNs (FOPT-SLNs) were prepared, characterized, and evaluated using Caco-2 cell line as an in-vitro model. Physical mixture of components of FOPT-SLNs (FOPT-PM) and carvedilol solution were used as control groups. From the studies of effect of SLNs concentration and cells incubation time, suitable carvedilol concentration and incubation time were selected for the model in which cells were subjected to five pretreatments for 24 h or 1 h of cell incubation and then followed with treatment of FOPT-SLNs, FOPT-PM or 100 µg/mL solution of carvedilol, for additional 24 h of cell incubation. The results obtained in this model suggest that main absorption mechanism of FOPT-SLNs could be endocytosis and, more specifically, clathrin-mediated endocytosis. When Transwell® permeable supports were used for the cells, carrier-mediated mechanism for FOPT-SLNs and passive absorption mechanism (transcellular and paracellular) for FOPT-PM and drug solution were concluded. PMID:25069593

  8. Thermal activation mechanisms and Labusch-type strengthening analysis for a family of high-entropy and equiatomic solid-solution alloys

    DOE PAGESBeta

    Wu, Zhenggang; Gao, Yanfei; Bei, Hongbin

    2016-11-01

    To understand the underlying strengthening mechanisms, thermal activation processes are investigated from stress-strain measurements with varying temperatures and strain rates for a family of equiatomic quinary, quaternary, ternary, and binary, face-center-cubic-structured, single phase solid-solution alloys, which are all subsystems of the FeNiCoCrMn high-entropy alloy. Our analysis suggests that the Labusch-type solution strengthening mechanism, rather than the lattice friction (or lattice resistance), governs the deformation behavior in equiatomic alloys. First, upon excluding the Hall-Petch effects, the activation volumes for these alloys are found to range from 10 to 1000 times the cubic power of Burgers vector, which are much larger thanmore » that required for kink pairs (i.e., the thermal activation process for the lattice resistance mechanism in body-center-cubic-structured metals). Second, the Labusch-type analysis for an N-element alloy is conducted by treating M-elements (M < N) as an effective medium and summing the strengthening contributions from the rest of N-M elements as individual solute species. For all equiatomic alloys investigated, a qualitative agreement exists between the measured strengthening effect and the Labusch strengthening factor from arbitrary M to N elements based on the lattice and modulus mismatches. Furthermore, the Labusch strengthening factor provides a practical critique to understand and design such compositionally complex but structurally simple alloys.« less

  9. Mechanisms of high-temperature, solid-state flow in minerals and ceramics and their bearing on the creep behavior of the mantle

    USGS Publications Warehouse

    Kirby, S.H.; Raleigh, C.B.

    1973-01-01

    The problem of applying laboratory silicate-flow data to the mantle, where conditions can be vastly different, is approached through a critical review of high-temperature flow mechanisms in ceramics and their relation to empirical flow laws. The intimate association of solid-state diffusion and high-temperature creep in pure metals is found to apply to ceramics as well. It is shown that in ceramics of moderate grain size, compared on the basis of self-diffusivity and elastic modulus, normalized creep rates compare remarkably well. This comparison is paralleled by the near universal occurrence of similar creep-induced structures, and it is thought that the derived empirical flow laws can be associated with dislocation creep. Creep data in fine-grained ceramics, on the other hand, are found to compare poorly with theories involving the stress-directed diffusion of point defects and have not been successfully correlated by self-diffusion rates. We conclude that these fine-grained materials creep primarily by a quasi-viscous grain-boundary sliding mechanism which is unlikely to predominate in the earth's deep interior. Creep predictions for the mantle reveal that under most conditions the empirical dislocation creep behavior predominates over the mechanisms involving the stress-directed diffusion of point defects. The probable role of polymorphic transformations in the transition zone is also discussed. ?? 1973.

  10. Influence of magnesia-to-phosphate molar ratio on microstructures, mechanical properties and thermal conductivity of magnesium potassium phosphate cement paste with large water-to-solid ratio

    SciTech Connect

    Xu, Biwan; Ma, Hongyan; Li, Zongjin

    2015-02-15

    This paper describes the influence of the magnesia-to-phosphate (M/P) molar ratios ranging from 4 to 12, on the properties and microstructures of magnesium potassium phosphate cement (MKPC) pastes with a large water-to-solid ratio (w/s) of 0.50. The setting behavior, compressive strength, tensile bonding strength and thermal conductivity of the MKPC pastes, were investigated. The results show that an increase in the M/P ratio can slow down the setting reaction, and clearly degrade the mechanical strengths, but clearly improve the thermal conductivity of MKPC pastes. Furthermore, micro-characterizations including X-ray diffraction, scanning electron microscopy and thermogravimetric analysis, on the MKPC pastes reveal that a lower M/P ratio can facilitate better crystallization of the resultant magnesium potassium phosphate hexahydrate (MKP) and a denser microstructure. Moreover, strong linear correlations are found between the mechanical strengths and the MKP-to-space ratio, and between thermal conductivity and the volume ratio of the unreacted magnesia to the MKP. - Highlights: • Increase of M/P molar ratio causes clear mechanical degradations on MKPC pastes. • Thermal conductivity of MKPC pastes is improved with increase of M/P molar ratio. • Lower M/P ratio leads to better MKP crystallization and denser microstructure. • Strengths of MKPC pastes are linearly correlated to the MKP-to-space ratios. • Thermal conductivity is affected by the volume ratio of unreacted magnesia to MKP.

  11. The Solid Solution Sr(1-x)Ba(x)Ga2: Substitutional Disorder and Chemical Bonding Visited by NMR Spectroscopy and Quantum Mechanical Calculations.

    PubMed

    Pecher, Oliver; Mausolf, Bernhard; Lamberts, Kevin; Oligschläger, Dirk; Niewieszol, Carina; Englert, Ulli; Haarmann, Frank

    2015-09-28

    Complete miscibility of the intermetallic phases (IPs) SrGa2 and BaGa2 forming the solid solution Sr(1-x)Ba(x)Ga2 is shown by means of X-ray diffraction, thermoanalytical and metallographic studies. Regarding the distances of Sr/Ba sites versus substitution degree, a model of isolated substitution centres (ISC) for up to 10% cation substitution is explored to study the influence on the Ga bonding situation. A combined application of NMR spectroscopy and quantum mechanical (QM) calculations proves the electric field gradient (EFG) to be a sensitive measure of different bonding situations. The experimental resolution is boosted by orientation-dependent NMR on magnetically aligned powder samples, revealing in first approximation two different Ga species in the ISC regimes. EFG calculations using superlattice structures within periodic boundary conditions are in fair agreement with the NMR spectroscopy data and are discussed in detail regarding their application on disordered IPs. PMID:26272697

  12. Unified system for holographic measurement in fluid and solid mechanics: use of the system for 3D displacement measurement on surfaces

    NASA Astrophysics Data System (ADS)

    Barnhart, Donald H.; Chan, Victor S. S.; Halliwell, Neil A.; Coupland, Jeremy M.

    1999-10-01

    This paper reports the use of a new holographic measurement system in the study of 3D surface displacements. Although equally applicable to fluid and solid mechanics, the aim of this report is to demonstrate the system's use in quantitative surface displacement measurements with a classical cantilever experiment, using a continuous-wave diode-pumped YAG laser system. The reported results exhibit an accuracy corresponding to other interferometric systems, but with a much larger displacement range. The measurement system employs a novel optical image shifting method to eliminate the problem of directional ambiguity. In addition, the reported system uses 3D complex correlation rather than 2D real correlation, thereby offering a direct method for measuring 3D displacement in 3D space. FInally, with the novel use of an optical fiber to probe the recorded holographic image space, it is found to be a simple matter to directly obtain 3D displacement measurements at precisely known surface locations.

  13. The biogenic content of process streams from mechanical-biological treatment plants producing solid recovered fuel. Do the manual sorting and selective dissolution determination methods correlate?

    PubMed

    Séverin, Mélanie; Velis, Costas A; Longhurst, Phil J; Pollard, Simon J T

    2010-07-01

    The carbon emissions trading market has created a need for standard methods for the determination of biogenic content (chi(B)) in solid recovered fuels (SRF). We compare the manual sorting (MSM) and selective dissolution methods (SDM), as amended by recent research, for a range of process streams from a mechanical-biological treatment (MBT) plant. The two methods provide statistically different biogenic content values, as expressed on a dry mass basis, uncorrected for ash content. However, they correlate well (r(2)>0.9) and the relative difference between them was <5% for chi(B) between 21% (w)/w(d) and 72% (w)/w(d) (uncorrected for ash content). This range includes the average SRF biogenic content of ca. 68% (w)/w(d). Methodological improvements are discussed in light of recent studies. The repeatability of the SDM is characterised by relative standard deviations on triplicates of <2.5% for the studied population. PMID:20116991

  14. Relationship between the results of laser-induced breakdown spectroscopy and dynamical mechanical analysis in composite solid propellants during their aging.

    PubMed

    Farhadian, Amir Hossein; Tehrani, Masoud Kavosh; Keshavarz, Mohammad Hossein; Karimi, Mehran; Reza Darbani, Seyyed Mohammad

    2016-06-01

    Laser-induced breakdown spectroscopy (LIBS) has been used to analyze thermal aging in AP/HTPB composite solid propellants, where AP and HTPB are ammonium perchlorate and hydroxyl-terminated polybutadiene, respectively. The method of accelerated aging was used to obtain samples of different ages. Dynamical mechanical analysis results have been provided in order to validate the LIBS results. Many methods have been used for the accurate investigation of spectra. First, molecular bands, such as CN, C2, and AlO, were compared in different samples so that their intensity ratios could be considered. In order to discriminate more accurately between different sample spectra, principle component analysis (PCA) was used as a suitable chemometric method. All these results represent changes in the chemical structure due to increasing time and temperature. PMID:27411188

  15. Superconducting and mechanical properties of the bulk Bi(pb)SCCO system prepared via solid state and ammonium nitrate precipitation methods

    NASA Astrophysics Data System (ADS)

    Safran, S.; Kılıçarslan, E.; Ozturk, H.; Alp, M.; Akdogan, M.; Asikuzun, E.; Ozturk, O.; Kılıç, A.

    2015-09-01

    We have investigated the effect of preparation method on superconducting and mechanical properties of Bi(Pb)-2223 bulk samples using Bi1.85Pb0.35Sr2Ca2Cu3O10±y stoichiometry. Solid-state reaction and ammonium nitrate precipitation methods have been used for fabrication of the bulk samples. In addition, the effect of annealing time on BSCCO samples have been studied. Structural, electrical, magnetic and microhardness analyses of samples are performed by the X-ray powder diffraction (XRD), the Scanning Electron Microscopy (SEM), DC resistivity, AC susceptibility and Vickers microhardness test. The critical transition temperature, phase purity, surface morphology and crystallinity of the prepared bulk samples are compared with each other. Elasticity (E), brittleness (Bi), fracture toughness (KIC) and yield strength (Y) values are also determined according to annealing time, applied load and production parameters of materials.

  16. LETTER TO THE EDITOR: Tumour anti-vascular alpha therapy: a mechanism for the regression of solid tumours in metastatic cancer

    NASA Astrophysics Data System (ADS)

    Allen, Barry J.; Raja, Chand; Rizvi, Syed; Song, Emma Y.; Graham, Peter

    2007-07-01

    Targeted alpha therapy (TAT) is an emerging therapeutic modality, thought to be best suited to cancer micrometastases, leukaemia and lymphoma. TAT has not been indicated for solid tumours. However, several melanoma patients in a phase 1 clinical trial of systemic targeted alpha therapy for melanoma experienced marked regression of subcutaneous and internal tumours. This response cannot be ascribed to killing of all cancer cells in the tumours by targeted alpha therapy. These new observations support the original hypothesis that tumours can be regressed by a mechanism called tumour anti-vascular alpha therapy. This effect depends on the expression of targeted receptors by capillary pericytes and contiguous cancer cells, and on the short-range and high-energy transfer of alpha radiation.

  17. Effect of load, area of contact, and contact stress on the wear mechanisms of a bonded solid lubricant film

    NASA Technical Reports Server (NTRS)

    Fusaro, R. L.

    1980-01-01

    A pin on disk type of friction and wear apparatus was used to study the effect of load, contact stress and rider area of contact on the friction and wear properties of polyimide bonded graphite fluoride films. Different rider area contacts were obtained by initially generating flats (with areas of 0.0035, 0.0071, 0.0145, and 0.0240 cm) on 0.476-cm radius hemispherically tipped riders. Different projected contact stresses were obtained by applying loads of 2.5- to 58.8-N to the flats. Two film wear mechanisms were observed. The first was found to be a linear function of contact stress and was independent of rider area of contact. The second was found to increase exponentially as the stress increased. The second also appeared to be a function of rider contact area. Wear equations for each mechanism were empirically derived from the experimental data. In general, friction coefficients increased with increasing rider contact area and with sliding duration. This was related to the build up of thick rider transfer films.

  18. The solid state blending of polymers via cryogenic mechanical alloying: Effects on blend morphology and thermal transitions

    NASA Astrophysics Data System (ADS)

    Schexnaydre, Ryan J.

    Preliminary investigations of mechanical attrition (MA) resulted in particle size reduction, amorphization of semicrystalline polymers, and relatively insignificant effects on PEO or PVP molecular weight distributions. Cryogenic mechanical alloying (CMA) was extensively used to blend immiscible polymers. Globar FT-IR confirmed that no chemical compatibilizaton occurred during CMA, while a novel chemical mapping protocol developed with synchrotron FT-IR microspectroscopy allowed for qualitative and quantitative estimation of blend heterogeneities. The uniqueness of the PS/PET system led to extensive study of domain characteristics, the extent of compatibilization, and changes in PET crystallizability with CMA. Various PS/PET blend compositions (nominal 30, 50, and 70 weight percent PET) were processed by CMA and extrusion and studied comparatively. CMA compatibilized PS and PET more efficiently and controllably than extrusion. These results agreed with trends observed for domain size distribution, and CMA also created nonspheroidal domains, i.e., an efficient way to increase interphase contact. CMA, in effect, created a rigid amorphous PET phase that served the dual purpose of enhancing compatibility and stabilizing the morphology during post-CMA heating.

  19. Direct observation of solid-phase adsorbate concentration profile in powdered activated carbon particle to elucidate mechanism of high adsorption capacity on super-powdered activated carbon.

    PubMed

    Ando, Naoya; Matsui, Yoshihiko; Matsushita, Taku; Ohno, Koichi

    2011-01-01

    Decreasing the particle size of powdered activated carbon (PAC) by pulverization increases its adsorption capacities for natural organic matter (NOM) and polystyrene sulfonate (PSS, which is used as a model adsorbate). A shell adsorption mechanism in which NOM and PSS molecules do not completely penetrate the adsorbent particle and instead preferentially adsorb near the outer surface of the particle has been proposed as an explanation for this adsorption capacity increase. In this report, we present direct evidence to support the shell adsorption mechanism. PAC particles containing adsorbed PSS were sectioned with a focused ion beam, and the solid-phase PSS concentration profiles of the particle cross-sections were directly observed by means of field emission-scanning electron microscopy/energy-dispersive X-ray spectrometry (FE-SEM/EDXS). X-ray emission from sulfur, an index of PSS concentration, was higher in the shell region than in the inner region of the particles. The X-ray emission profile observed by EDXS did not agree completely with the solid-phase PSS concentration profile predicted by shell adsorption model analysis of the PSS isotherm data, but the observed and predicted profiles were not inconsistent when the analytical errors were considered. These EDXS results provide the first direct evidence that PSS is adsorbed mainly in the vicinity of the external surface of the PAC particles, and thus the results support the proposition that the increase in NOM and PSS adsorption capacity with decreasing particle size is due to the increase in external surface area on which the molecules can be adsorbed. PMID:20851447

  20. Ligand-exchange mechanism: new insight into solid-phase extraction of uranium based on a combined experimental and theoretical study.

    PubMed

    Tian, Yin; Fu, Jia; Zhang, Yi; Cao, Kecheng; Bai, Chiyao; Wang, Dongqi; Li, Shoujian; Xue, Ying; Ma, Lijian; Zheng, Chong

    2015-03-21

    In numerous reports on selective solid-phase extraction (SPE) of uranium, the extraction of uranium is generally accepted as a direct coordination of the ligands on the solid matrix with the uranyl, in which the critical effect of the hydration shell on the uranyl is neglected. The related mechanism in the extraction process remains unclear. Herein, the detailed calculation of activation energy and the geometry of the identified transition states reveal that the uranium extraction by a newly-synthesized urea-functionalized graphite oxide (Urea-GO) is in essence an exchange process between the ligands on Urea-GO and the coordinated water molecules in the first hydration shell of the uranyl. Moreover, we demonstrate that it is the ketone oxygen in the urea ligand to displace the coordinated water molecule of uranyl due to its stronger bonding ability and lower steric-hindrance, whereas the nitrogen atom in the same ligand is proved to be an electron donor that enables the oxygen atom to have stronger affinity for uranium through electron delocalization effects evaluated on the basis of calculations of the second-order interaction energy between donor and acceptor orbitals. We therefore propose a new ligand-exchange mechanism for the SPE process. This study advances the fundamental understanding of uranium extraction, and provides theoretical and practical guidance on ligand design for selective complexation of uranium(VI) and other metal ions in aqueous solution. Finally, the effect of nitrate ions on the extraction of uranyl was successfully explained based on the experimental and theoretical study. PMID:25690182

  1. Advances and trends in structural and solid mechanics; Proceedings of the Symposium, Washington, DC, October 4-7, 1982

    NASA Technical Reports Server (NTRS)

    Noor, A. K. (Editor); Housner, J. M.

    1983-01-01

    The mechanics of materials and material characterization are considered, taking into account micromechanics, the behavior of steel structures at elevated temperatures, and an anisotropic plasticity model for inelastic multiaxial cyclic deformation. Other topics explored are related to advances and trends in finite element technology, classical analytical techniques and their computer implementation, interactive computing and computational strategies for nonlinear problems, advances and trends in numerical analysis, database management systems and CAD/CAM, space structures and vehicle crashworthiness, beams, plates and fibrous composite structures, design-oriented analysis, artificial intelligence and optimization, contact problems, random waves, and lifetime prediction. Earthquake-resistant structures and other advanced structural applications are also discussed, giving attention to cumulative damage in steel structures subjected to earthquake ground motions, and a mixed domain analysis of nuclear containment structures using impulse functions.

  2. Solid-state flow, mechanical alloying, and melt-related phenomena for [001] single-crystal tungsten ballistic rod penetrators interacting with steel targets

    NASA Astrophysics Data System (ADS)

    Pizana, Carlos

    This research program consists of a detailed microstructural investigation of in-target, single-crystal [001], clad (with Inconel 718) and unclad, W long-rod, ballistic penetrators. The rods were shot into rolled homogeneous armor (RHA) steel targets approximately 76 mm in thickness at impact velocities ranging from 1100 m/s to 1350 m/s. A comprehensive microstructural overview of the penetration process was obtained from this investigation. Solid-state flow/erosion, solid-state target/rod mixing as well as influencing factors such as strain rate, penetration performance, cladding interference and the interaction between target and projectile were emphasized. Some of the microstructural features observed, including deformation twins, cleaving, adiabatic shear bands and DRX support an overall solid-state penetration process. Furthermore they provide for a unifying perspective for the applicability of the hydrodynamic paradigm (DOP ≈ l∘rp/rt ) and earlier mechanistic erosion approaches. DRX and grain growth within adiabatic shear bands observed at specific high strain/strain-rate zones within the rods suggest that the projectile erodes by means of these microstructures in a solid-state form. This erosion process contributes to the performance of the rod by either allowing optimum flow of rod material which would increase penetration depth, or by maximizing rod material consumption which would reduce it. Since flow and/or erosion are also necessary in the target for perforation to occur, it is not surprising that the erosion process in the target was observed to mirror the one in the projectile. That is both target and projectile developed erosion zones with DRX facilitating the extreme deformation via dense overlapping shear band formation. Mechanical alloying and/or mixing of the target (steel) and rod (W, or W-Inconel 718) was also observed and investigated. Selective etching techniques as well as energy-dispersive x-ray mapping revealed unambiguous evidence of

  3. Computer studies of the surface mechanism of preferential sputtering of two-component solids. Ion beam analysis of surface composition in low dose regime

    NASA Astrophysics Data System (ADS)

    Samoilov, Vladimir N.; Tatur, Andrei E.; Yastrzhembsky, Vladimir I.

    1996-09-01

    We investigated the process of collision cascade propagation through the solid-vacuum boundary for two-component targets: WSi, MoSi and VSi. The surface mechanism of preferential sputtering of atoms of light component based on stronger deflection of light atoms towards surface normal when scattering by heavy neighbouring surface atoms during ejection was studied. Simulations for ejection of 450 000 Si or W atoms from the surface of WSi for cos {ϑ 0}/{E 02} and {1}/{E 02} initial distributions gave {Si}/{W} sputtering ratio equal to 1.29-1.55 (for 1:1 {Si}/{W} concentration ratio at the surface) giving necessary addition to the Andersen-Sigmund formula which underestimated that ratio in comparison with available experimental data. Analysis of integral energy distributions of atoms of the components gave {Si}/{W} ratio maximum equal to 3.18-5.00 for energy interval 0.0-0.4 eV. Maxima of integral energy distributions of sputtered atoms were observed at 1.8 eV for Si and 3.4 eV for W in calculations with equal binding energies for atoms of light and heavy components in good agreement with experiment. The surface mechanism was shown to be the alternative mechanism in formation of observed maxima difference with respect to nonidentity of binding energy values for atoms of components proposed by Szymonski [Phys. Lett. A 82 (1981) 203]. The two-cone structure of ejection vs. initial polar angle for Si atoms sputtered was revealed and explained. Results obtained gave the new approach to solve the inverse problem of reconstruction of surface composition in low dose SNMS and showed that the surface mechanism of preferential sputtering is to be accounted for in analytical calculations of surface composition. Ejection was simulated in the plane containing the neighbouring surface atom.

  4. Effects of the first heat up procedure on mechanical properties of solid oxide fuel cell sealing materials

    NASA Astrophysics Data System (ADS)

    Rautanen, Markus; Pulkkinen, Valtteri; Tallgren, Johan; Himanen, Olli; Kiviaho, Jari

    2015-06-01

    SOFC stack seals need to be correctly dimensioned to achieve a gas tight stack with low electrical contact resistances. Mechanical properties of SOFC stack sealing materials are presented for three assembly and first heat up procedures: applying full compressive stress at room temperature before first heat up (1), applying no compressive stress before first heat up and applying the full compressive stress at operating temperature (2), applying partial compressive stress at room temperature and full compressive stress at operating temperature after first heat up (3). The behaviour of the glass seal (Schott GM31107) is not affected significantly by compressive force during heat up. Compressibility of both compressible sealing material (Thermiculite CL87) and hybrid sealing material (Thermiculite CL87LS) was found to be about 40% (between 0.1 and 0.9 MPa) at room temperature but only about 4% (between 0.1 and 0.9 MPa) at 700 °C. Therefore it is beneficial to carry out as much of the compression as possible at room temperature before first heat up. This allows for maximum amount of deformability in the sealing materials resulting in the highest ability to compensate for stack manufacturing and assembly tolerances, which is needed to realize a gas tight stack with low electrical contact resistances.

  5. Polymer films removed from solid surfaces by nanostructured fluids: microscopic mechanism and implications for the conservation of cultural heritage.

    PubMed

    Raudino, Martina; Selvolini, Giulia; Montis, Costanza; Baglioni, Michele; Bonini, Massimo; Berti, Debora; Baglioni, Piero

    2015-03-25

    Complex fluids based on amphiphilic formulations are emerging, particularly in the field of conservation of works of art, as effective and safe liquid media for the removal of hydrophobic polymeric coatings. The comprehension of the cleaning mechanism is key to designing tailored fluids for this purpose. However, the interaction between nanostructured fluids and hydrophobic polymer films is still poorly understood. In this study, we show how the combination of confocal laser scanning microscopy (CLSM) and atomic force microscopy (AFM) provides interesting and complementary insight into this process. We focused on the interaction between an ethyl methacrylate/methyl acrylate 70:30 copolymer film deposited onto a glass surface and a water/nonionic surfactant/2-butanone (MEK) ternary system, with MEK being a good solvent and water being a nonsolvent for the polymer. Our results indicate a synergy between the organic solvent and the surfactant assemblies: MEK rapidly swells the outer layers of the polymer film allowing for the subsequent diffusion of solvent molecules, while the amphiphile decreases the interfacial energy between the polymeric coating and the liquid phase, favoring dewetting and dispersion of swollen polymer droplets in the aqueous phase. The chemical nature of the surfactant and the microstructure of the assemblies determine both the kinetics and the overall efficiency of polymer removal, as assessed by comparing the behavior of similar formulations containing an anionic surfactant (sodium dodecyl sulfate, SDS). PMID:25723546

  6. Structural characterization and observation of variable range hopping conduction mechanism at high temperature in CdSe quantum dot solids

    NASA Astrophysics Data System (ADS)

    Sinha, Subhojyoti; Kumar Chatterjee, Sanat; Ghosh, Jiten; Kumar Meikap, Ajit

    2013-03-01

    We have used Rietveld refinement technique to extract the microstructural parameters of thioglycolic acid capped CdSe quantum dots. The quantum dot formation and its efficient capping are further confirmed by HR-TEM, UV-visible and FT-IR spectroscopy. Comparative study of the variation of dc conductivity with temperature (298 K ≤ T ≤ 460 K) is given considering Arrhenius formalism, small polaron hopping and Schnakenberg model. We observe that only Schnakenberg model provides good fit to the non-linear region of the variation of dc conductivity with temperature. Experimental variation of ac conductivity and dielectric parameters with temperature (298 K ≤ T ≤ 460 K) and frequency (80 Hz ≤ f ≤ 2 MHz) are discussed in the light of hopping theory and quantum confinement effect. We have elucidated the observed non-linearity in the I-V curves (measured within ±50 V), at dark and at ambient light, in view of tunneling mechanism. Tunnel exponents and non-linearity weight factors have also been evaluated in this regard.

  7. Making Solid Geometry Solid.

    ERIC Educational Resources Information Center

    Hartz, Viggo

    1981-01-01

    Allowing students to use a polystyrene cutter to fashion their own three-dimensional models is suggested as a means of allowing individuals to experience problems and develop ideas related to solid geometry. A list of ideas that can lead to mathematical discovery is provided. (MP)

  8. Mass-independent isotope effect in the earliest processed solids in the solar system: a possible chemical mechanism.

    PubMed

    Marcus, R A

    2004-11-01

    (ads) and other adsorbed metal atoms or metallic monoxides to form CAIs. The latter are thereby mass-independently poor in (17)O and (18)O. Some O (ads) used to form the minerals are necessarily in excess of the XO (ads), because of the stoichiometry of the mineral, and modify the fractionation pattern. This effect is incorporated into the mechanistic and mathematical scheme. A merit of this chemical mechanism for the oxygen isotope anomaly is that only one oxygen reservoir is required in the solar nebula. It also does not require a sequestering of intermediate products which could undergo isotopic exchange, hence undoing the original isotopic fractionations. The gas phase source of adsorbed O atoms in this environment is either O or H(2)O. As inferred from data on the evaporation of Mg(2)SiO(4) taken as an example, the source of O (ads) is primarily H(2)O rather than O and is accompanied by the evolution of H(2). Nonisotopic kinetic experiments can determine more sharply the mechanism of condensed phase growth of these minerals. Laboratory tests are proposed to test the existence of a surface eta effect on the growing CAI surfaces at these high temperatures. PMID:15511139

  9. Investigation of various growth mechanisms of solid tumour growth within the linear-quadratic model for radiotherapy

    NASA Astrophysics Data System (ADS)

    McAneney, H.; O'Rourke, S. F. C.

    2007-02-01

    The standard linear-quadratic survival model for radiotherapy is used to investigate different schedules of radiation treatment planning to study how these may be affected by different tumour repopulation kinetics between treatments. The laws for tumour cell repopulation include the logistic and Gompertz models and this extends the work of Wheldon et al (1977 Br. J. Radiol. 50 681), which was concerned with the case of exponential re-growth between treatments. Here we also consider the restricted exponential model. This has been successfully used by Panetta and Adam (1995 Math. Comput. Modelling 22 67) in the case of chemotherapy treatment planning.Treatment schedules investigated include standard fractionation of daily treatments, weekday treatments, accelerated fractionation, optimized uniform schedules and variation of the dosage and α/β ratio, where α and β are radiobiological parameters for the tumour tissue concerned. Parameters for these treatment strategies are extracted from the literature on advanced head and neck cancer, prostate cancer, as well as radiosensitive parameters. Standardized treatment protocols are also considered. Calculations based on the present analysis indicate that even with growth laws scaled to mimic initial growth, such that growth mechanisms are comparable, variation in survival fraction to orders of magnitude emerged. Calculations show that the logistic and exponential models yield similar results in tumour eradication. By comparison the Gompertz model calculations indicate that tumours described by this law result in a significantly poorer prognosis for tumour eradication than either the exponential or logistic models. The present study also shows that the faster the tumour growth rate and the higher the repair capacity of the cell line, the greater the variation in outcome of the survival fraction. Gaps in treatment, planned or unplanned, also accentuate the differences of the survival fraction given alternative growth

  10. Effects and Mechanisms of Surface Topography on the Antiwear Properties of Molluscan Shells (Scapharca subcrenata) Using the Fluid-Solid Interaction Method

    PubMed Central

    Tian, Limei; Tian, Ximei; Hu, Guoliang; Wang, Yinci; Ren, Luquan

    2014-01-01

    The surface topography (surface morphology and structure) of the left Scapharca subcrenata shell differs from that of its right shell. This phenomenon is closely related to antiwear capabilities. The objective of this study is to investigate the effects and mechanisms of surface topography on the antiwear properties of Scapharca subcrenata shells. Two models are constructed—a rib morphology model (RMM) and a coupled structure model (CSM)—to mimic the topographies of the right and left shells. The antiwear performance and mechanisms of the two models are studied using the fluid-solid interaction (FSI) method. The simulation results show that the antiwear capabilities of the CSM are superior to those of the RMM. The CSM is also more conducive to decreasing the impact velocity and energy of abrasive particles, reducing the probability of microcrack generation, extension, and desquamation. It can be deduced that in the real-world environment, Scapharca subcrenata's left shell sustains more friction than its right shell. Thus, the coupled structure of the left shell is the result of extensive evolution. PMID:24982928

  11. A Study on Enhancing Data Storage Capacity and Mechanical Reliability of Solid Immersion Lens-Based Near-Field Recording System

    NASA Astrophysics Data System (ADS)

    Park, No-Cheol; Yang, Hyun-Seok; Rhim, Yoon-Cheol; Park, Young-Pil

    2008-08-01

    In this study, several technical issues on solid immersion lens (SIL)-based near-field recording (NFR) are explored, namely, to enhance storage capacity and to guarantee mechanical reliability of the device. For the purpose of enhancing the storage capacity of the NFR system, two optical configurations using radial polarization and dual recording layers are proposed. Through a feasibility analysis of the proposed optical configuration with radial polarization, it was determined that illumination of radial polarization is not a suitable solution to achieve higher areal density. To apply highly focusing characteristics of incidence of radial polarized light to cover-layer protected data storage, an annular pupil filtering method was introduced. Complete field analysis of the proposed dual layered NFR optics verified its feasibility, and the assembly of the SIL of the proposed model was successfully achieved. In addition, to improve mechanical reliability of the SIL-based NFR system, improved near-field (NF) air-gap servo methods and air flow analysis around the low part of the SIL have been evaluated. With improved NF gap servo methods using an error-based disturbance observer (EDOB) on a base air-gap controller, residual gap errors were markebly reduced by 26.26% while controlling the NF air-gap to 30 nm. Air flow near the head media interface was visualized and an undesirable effect of backward flow climbing from the bottom surface of the SIL was ovserved.

  12. Fluid Mechanical Matching of H+-ATP Synthase Subunit c-Ring with Lipid Membranes Revealed by 2H Solid-State NMR

    PubMed Central

    Kobayashi, Masatoshi; Struts, Andrey V.; Fujiwara, Toshimichi; Brown, Michael F.; Akutsu, Hideo

    2008-01-01

    The F1Fo-ATP synthase utilizes the transmembrane H+ gradient for the synthesis of ATP. Fo subunit c-ring plays a key role in transporting H+ through Fo in the membrane. We investigated the interactions of Escherichia coli subunit c with dimyristoylphosphatidylcholine (DMPC-d54) at lipid/protein ratios of 50:1 and 20:1 by means of 2H-solid-state NMR. In the liquid-crystalline state of DMPC, the 2H-NMR moment values and the order parameter (SCD) profile were little affected by the presence of subunit c, suggesting that the bilayer thickness in the liquid-crystalline state is matched to the transmembrane hydrophobic surface of subunit c. On the other hand, hydrophobic mismatch of subunit c with the lipid bilayer was observed in the gel state of DMPC. Moreover, the viscoelasticity represented by a square-law function of the 2H-NMR relaxation was also little influenced by subunit c in the fluid phase, in contrast with flexible nonionic detergents or rigid additives. Thus, the hydrophobic matching of the lipid bilayer to subunit c involves at least two factors, the hydrophobic length and the fluid mechanical property. These findings may be important for the torque generation in the rotary catalytic mechanism of the F1Fo-ATPse molecular motor. PMID:18310246

  13. Dioxins and their fingerprint in size-classified fly ash fractions from municipal solid waste incinerators in China--mechanical grate and fluidized bed units.

    PubMed

    Lu, Sheng-Yong; Du, Yingzhe; Yan, Jian-Hua; Li, Xiao-Dong; Ni, Ming-Jiang; Cen, Ke-Fa

    2012-06-01

    The distribution of polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs), in brief dioxins, has seldom been addressed systematically in fly ash from municipal solid waste incinerators (MSWIs). This study shows the amount and fingerprint of PCDD/Fs in fly ash from four different Chinese MSWIs, that is, three mechanical grate units and one circulating fluidized bed unit. In these fly ash samples, dioxins-related parameters (international toxic equivalent quantity, total amount of PCDD/Fs, individual isomer classes, and 17 toxic 2,3,7,8-substituted congeners) all tend to increase with decreasing particle size for mechanical grate incinerators, yet only for the finest fraction for fluidized bed units. Moreover, the fluidized bed incinerator seems superior to grate incineration in controlling dioxins, yet a comparison is hampered by internal differences in the sample, for example, the fluidized bed fly ash has much lower carbon and chlorine contents. In addition, the presence of sulfur from mixing coal as supplemental fuel to the MSW may poison the catalytic steps in dioxins formation and thus suppress the formation of dioxins. With more residual carbon and chlorine in the fly ash, it is easier to form dioxins during cooling. Nevertheless, there is no apparent relation between Fe, Cu, and Zn contents and that of dioxins in fly ash. PMID:22788110

  14. Effects and mechanisms of surface topography on the antiwear properties of molluscan shells (Scapharca subcrenata) using the fluid-solid interaction method.

    PubMed

    Tian, Limei; Tian, Ximei; Hu, Guoliang; Wang, Yinci; Ren, Luquan

    2014-01-01

    The surface topography (surface morphology and structure) of the left Scapharca subcrenata shell differs from that of its right shell. This phenomenon is closely related to antiwear capabilities. The objective of this study is to investigate the effects and mechanisms of surface topography on the antiwear properties of Scapharca subcrenata shells. Two models are constructed-a rib morphology model (RMM) and a coupled structure model (CSM)-to mimic the topographies of the right and left shells. The antiwear performance and mechanisms of the two models are studied using the fluid-solid interaction (FSI) method. The simulation results show that the antiwear capabilities of the CSM are superior to those of the RMM. The CSM is also more conducive to decreasing the impact velocity and energy of abrasive particles, reducing the probability of microcrack generation, extension, and desquamation. It can be deduced that in the real-world environment, Scapharca subcrenata's left shell sustains more friction than its right shell. Thus, the coupled structure of the left shell is the result of extensive evolution. PMID:24982928

  15. Fabrication of Nb3Al superconducting wires by utilizing the mechanically alloyed Nb(Al)ss supersaturated solid-solution with low-temperature annealing

    NASA Astrophysics Data System (ADS)

    Pan, X. F.; Yan, G.; Qi, M.; Cui, L. J.; Chen, Y. L.; Zhao, Y.; Li, C. S.; Liu, X. H.; Feng, Y.; Zhang, P. X.; Liu, H. J.; Li, L. F.

    2014-07-01

    High-performance Nb3Al superconducting wire is a promising candidate to the application of high-field magnets. However, due to the production problem of km-grade wires that are free from low magnetic field instability, the Nb3Al wires made by rapid heating, quenching and transformation (RHQT) are still not available to the large-scale engineering application. In this paper, we reported the properties of the in situ powder-in-tube (PIT) Nb3Al superconducting wires, which were made by using the mechanically alloyed Nb(Al)ss supersaturated solid solution, as well as the low temperature heat-treatment at 800 °C for 10 h. The results show that Nb3Al superconductors in this method possess very fine grains and well superconducting properties, though a little of Nb2Al and Nb impurities still keep being existence at present work. At the Nb3Al with a nominal 26 at.% Al content, the onset Tc reaches 15.8 K. Furthermore, a series of Nb3Al wires and tapes with various sizes have been fabricated; for the 1.0 mm-diameter wire, the Jc at 4.2 K, 10 T and 14 T have achieved 12,700 and 6900 A/cm2, respectively. This work suggests it is possible to develop high-performance Cu-matrix Nb3Al superconducting wires by directly using the Nb(Al)ss supersaturated solid-solution without the complex RHQT heat-treatment process.

  16. Effect of graphene layer thickness and mechanical compliance on interfacial heat flow and thermal conduction in solid-liquid phase change materials.

    PubMed

    Warzoha, Ronald J; Fleischer, Amy S

    2014-08-13

    Solid-liquid phase change materials (PCMs) are attractive candidates for thermal energy storage and electronics cooling applications but have limited applicability in state-of-the-art technologies due to their low intrinsic thermal conductivities. Recent efforts to incorporate graphene and multilayer graphene into PCMs have led to the development of thermal energy storage materials with remarkable values of bulk thermal conductivity. However, the full potential of graphene as a filler material for the thermal enhancement of PCMs remains unrealized, largely due to an incomplete understanding of the physical mechanisms that govern thermal transport within graphene-based nanocomposites. In this work, we show that the number of graphene layers (n) within an individual graphene nanoparticle has a significant effect on the bulk thermal conductivity of an organic PCM. Results indicate that the bulk thermal conductivity of PCMs can be tuned by over an order of magnitude simply by adjusting the number of graphene layers (n) from n = 3 to 44. Using scanning electron microscopy in tandem with nanoscale analytical techniques, the physical mechanisms that govern heat flow within a graphene nanocomposite PCM are found to be nearly independent of the intrinsic thermal conductivity of the graphene nanoparticle itself and are instead found to be dependent on the mechanical compliance of the graphene nanoparticles. These findings are critical for the design and development of PCMs that are capable of cooling next-generation electronics and storing heat effectively in medium-to-large-scale energy systems, including solar-thermal power plants and building heating and cooling systems. PMID:24983698

  17. Solid-state drawing of post-consumer isotactic poly(propylene): Effect of melt filtration and carbon black on structural and mechanical properties.

    PubMed

    Luijsterburg, B J; Jobse, P S; Spoelstra, A B; Goossens, J G P

    2016-08-01

    Post-consumer plastic waste obtained via mechanical recycling is usually applied in thick-walled products, because of the low mechanical strength due to the presence of contaminants. In fact, sorted post-consumer isotactic poly(propylene) (i-PP) can be considered as a blend of 95% i-PP and 5% poly(ethylene), with traces of poly(ethylene terephthalate) (PET). By applying a treatment such as solid-state drawing (SSD) after melt extrusion, the polymer chains can be oriented in one direction, thereby improving the stiffness and tensile strength. In this research, molecular processes such as crystal break-up and chain orientation of these complex blends were monitored as a function of draw ratio. The melt filter mesh size - used to exclude rigid PET particles - and the addition of carbon black (CB) - often added for coloration in the recycling industry - were varied to investigate their influence on the SSD process. This research shows that despite the blend complexity, the molecular processes during SSD compare to virgin i-PP and that similar draw ratios can be obtained (λmax=20), albeit at reduced stiffness and strength as a result of the foreign polymers present in post-consumer i-PP. It is observed that the process stability improves with decreasing mesh size and that higher draw ratios can be obtained. The addition of carbon black, which resides in the dispersed PE phase, also stabilizes the SSD process. Compared to isotropic post-consumer i-PP, the stiffness can be improved by a factor 10 to over 11GPa, while the tensile strength can be improved by a factor 15-385MPa, which is approx. 70% of the maximum tensile strength achieved for virgin i-PP. PMID:27216728

  18. Mechanisms of H{sub 2}O desorption from amorphous solid water by 157-nm irradiation: An experimental and theoretical study

    SciTech Connect

    DeSimone, Alice J.; Crowell, Vernon D.; Sherrill, C. David; Orlando, Thomas M.

    2013-10-28

    The photodesorption of water molecules from amorphous solid water (ASW) by 157-nm irradiation has been examined using resonance-enhanced multiphoton ionization. The rotational temperature has been determined, by comparison with simulations, to be 425 ± 75 K. The time-of-flight spectrum of H{sub 2}O (v= 0) has been fit with a Maxwell-Boltzmann distribution with a translational temperature of 700 ± 200 K (0.12 ± 0.03 eV). H{sup +} and OH{sup +} fragment ions have been detected with non-resonant multiphoton ionization, indicating vibrationally excited parent water molecules with translational energies of 0.24 ± 0.08 eV. The cross section for water removal from ASW by 7.9-eV photons near 100 K is (6.9 ± 1.8) × 10{sup −20} cm{sup 2} for >10 L H{sub 2}O exposure. Electronic structure computations have also probed the excited states of water and the mechanisms of desorption. Calculated electron attachment and detachment densities show that exciton delocalization leads to a dipole reversal state in the first singlet excited state of a model system of hexagonal water ice. Ab Initio Molecular Dynamics simulations show possible desorption of a photo-excited water molecule from this cluster, though the non-hydrogen bonded OH bond is stretched significantly before desorption. Potential energy curves of this OH stretch in the electronic excited state show a barrier to dissociation, lending credence to the dipole reversal mechanism.

  19. Unified system for 3D holographic displacement and velocity measurements in fluid and solid mechanics: design and construction of the recording camera and interrogation assembly

    NASA Astrophysics Data System (ADS)

    Barnhart, Donald H.; Chan, Victor S. S.; Halliwell, Neil A.; Coupland, Jeremy M.

    1999-10-01

    This paper introduces a new approach to 3D displacement and velocity measurements that unifies the disciplines of holographic interferometry and holographic particle image velocimetry (HPIV). Equally applicable to fluid and solid mechanics, the overall system enables quantitative displacement measurements between two holographically recorded events from either particle or surface scattering sites, working with both pulsed and continuous-wave laser systems. The resulting measurements exhibit an accuracy corresponding to interferometric system, but with a dynamic range found with PIV systems. Most importantly, this paper introduces the novel use of an optical fiber to specify the measurement points, remove optical aberrations of windows, and eliminate directional ambiguity. An optical fiber is used to probe the recorded holographic image space at each 3D measurement point in order to extract the 3D displacement vectors. This fiber system also employs a novel optical image shifting method to eliminate the problem of directional ambiguity. In addition, the reported system uses 3D complex optical correlation rather than 2D real digital correlation. It is therefore a simple matter to directly obtain 3D displacement and velocity measurements at precisely known 3D locations in the object space. By correlating both the amplitude and phase information in the holographic image, this system can measure spatial distributions of displacements even when the presence of severe aberrations preclude the detection of sharp images.

  20. Mechanical Characterization of ZnSe Windows for Use With the Flow Enclosure Accommodating Novel Investigations in Combustion of Solids (FEANICS) Module

    NASA Technical Reports Server (NTRS)

    Salem, Jonathan A.

    2006-01-01

    Mechanical and physical properties of ZnSe windows to be used with the FEANICS (Flow Enclosure Accommodating Novel Investigations in Combustion of Solids) experiments were measured in order to determine design allowables. The average Young s modulus, Poisson's ratio, equibiaxial fracture strength, flaw size, grain size, Knoop hardness, Vicker s hardness, and branching constant were 74.3 +/- 0.1 GPa, 0.31, 57.8 +/- 6.5 MPa, 21 +/- 4 mm, 43 +/- 9 microns, 0.97 +/- 0.02 GPa, 0.97 +/- 0.02 GPa, and 1.0 +/- 0.1 MPa(square root of)m, respectively. The properties of current ZnSe made by chemical vapor deposition are in good agreement with those measured in the 1970 s. The hardness of CVD ZnSe windows is about one-twentieth of the sapphire window being replaced, and about one-sixth of that of window glass. Thus the ZnSe window must be handled with great care. The large grain size relative to the inherent crack size implies the need to use single crystal crack growth properties in the design process. In order to determine the local failure stresses in one of the test specimens, a solution for the stresses between the support ring and the edge of a circular plate load between concentric rings was derived

  1. Solid State Reduction of MoO3 with Carbon via Mechanical Alloying to Synthesize Nano-Crystaline MoO2

    NASA Astrophysics Data System (ADS)

    Saghafi, M.; Ataie, A.; Heshmati-Manesh, S.

    In this research, effect of milling time on solid state reduction of MoO3 with carbon has been investigated. It was found that mechanical activation of a mixture of MoO3 and carbon at ambient temperature by high energy ball milling was not able to reduce MoO3 to metallic molybdenum. MoO3 was converted to MoO2 at the first stage of reduction and peaks of the latter phase in X-ray diffraction patterns were detected when the milling time exceeded from 50 hours. The main effect of increased milling time at this stage was decreasing of MoO3 peak intensities and significant peak broadening due to decrease in size of crystallites. After prolonged milling, MoO3 was fully reduced to nano-crystalline MoO2 and its mean crystallite size was calculated using Williamson-Hall technique and found to be 17.5 nm. Thermodynamic investigations also confirm the possibility of reduction of MoO3 to MoO2 during the milling operation at room temperature. But, further reduction to metallic molybdenum requires thermal activation at higher temperature near 1100 K. XRD and SEM techniques were employed to evaluate the powder particles characteristics.

  2. Fabrication and electrical characterization of homo- and hetero-structure Si/SiGe nanowire Tunnel Field Effect Transistor grown by vapor-liquid-solid mechanism

    NASA Astrophysics Data System (ADS)

    Brouzet, V.; Salem, B.; Periwal, P.; Alcotte, R.; Chouchane, F.; Bassani, F.; Baron, T.; Ghibaudo, G.

    2016-04-01

    We demonstrate the fabrication and electrical characterization of Ω -gate Tunnel Field Effect Transistors (TFET) based on p-Si/i-Si/n+Si0.7Ge0.3 heterostructure nanowires grown by Chemical Vapor Deposition (CVD) using the vapor-liquid-solid (VLS) mechanism. The electrical performances of the p-Si/i-Si/n+Si0.7Ge0.3 heterostructure TFET device are presented and compared to Si and Si0.7Ge0.3 homostructure nanowire TFETs. We observe an improvement of the electrical performances of TFET with p-Si/i-Si/n+Si0.7Ge0.3 heterostructure nanowire (HT NW). The optimized devices present an Ion current of about 245 nA at VDS = -0.5 V and VGS = -3 V with a subthreshold swing around 135 mV/dec. Finally, we show that the electrical results are in good agreement with numerical simulation using Kane's Band-to-Band Tunneling model.

  3. Novel integrated mechanical biological chemical treatment (MBCT) systems for the production of levulinic acid from fraction of municipal solid waste: A comprehensive techno-economic analysis.

    PubMed

    Sadhukhan, Jhuma; Ng, Kok Siew; Martinez-Hernandez, Elias

    2016-09-01

    This paper, for the first time, reports integrated conceptual MBCT/biorefinery systems for unlocking the value of organics in municipal solid waste (MSW) through the production of levulinic acid (LA by 5wt%) that increases the economic margin by 110-150%. After mechanical separation recovering recyclables, metals (iron, aluminium, copper) and refuse derived fuel (RDF), lignocelluloses from remaining MSW are extracted by supercritical-water for chemical valorisation, comprising hydrolysis in 2wt% dilute H2SO4 catalyst producing LA, furfural, formic acid (FA), via C5/C6 sugar extraction, in plug flow (210-230°C, 25bar, 12s) and continuous stirred tank (195-215°C, 14bar, 20min) reactors; char separation and LA extraction/purification by methyl isobutyl ketone solvent; acid/solvent and by-product recovery. The by-product and pulping effluents are anaerobically digested into biogas and fertiliser. Produced biogas (6.4MWh/t), RDF (5.4MWh/t), char (4.5MWh/t) are combusted, heat recovered into steam generation in boiler (efficiency: 80%); on-site heat/steam demand is met; balance of steam is expanded into electricity in steam turbines (efficiency: 35%). PMID:27085988

  4. Enhanced nanoscale resistive switching memory characteristics and switching mechanism using high-Ge-content Ge0.5Se0.5 solid electrolyte

    PubMed Central

    2012-01-01

    We demonstrate enhanced repeatable nanoscale bipolar resistive switching memory characteristics in Al/Cu/Ge0.5Se0.5/W, as compared with Al/Cu/Ge0.2Se0.8/W structures, including stable AC endurance (>105 cycles), larger average SET voltage (approximately 0.6 V), excellent data retention (>105 s) at 85°C, and a high resistance ratio (>104) with a current compliance of 8 μA and a small operation voltage of ±1.5 V. A small device size of 150 × 150 nm2 and a Cu nanofilament with a small diameter of 30 nm are both observed by high-resolution transmission electron microscope in the SET state. The GexSe1 − x solid electrolyte compositions are confirmed by both energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. The switching mechanism relies on the smaller barrier heights for holes rather than for electrons; the positively charged Cuz+ ions (i.e., holes) migrate through the defects in the GexSe1 − x solid electrolytes during SET/RESET operations. Hence, the Cu nanofilament starts to grow at the Ge0.5Se0.5/W interface, and starts to dissolve at the Cu/Ge0.5Se0.5 interface, as illustrated in the energy band diagrams. Owing to both the higher barrier for hole injection at the Cu/Ge0.5Se0.5 interface than at the Cu/Ge0.2Se0.8 interface and greater thermal stability, the resistive switching memory characteristics of the Al/Cu/Ge0.5Se0.5/W are improved relative to the Al/Cu/Ge0.2Se0.8/W devices. The Al/Cu/Ge0.5Se0.5/W memory device can also be operated with a low current compliance of 1 nA, and hence, a low SET/RESET power of 0.61 nW/6.4 pW is achieved. In addition, a large memory size of 1,300 Pbit/in2 is achieved with a small nanofilament diameter of 0.25 Å for a small current compliance of 1 nA. PMID:23130908

  5. Immobilized Multifunctional Polymersomes on Solid Surfaces: Infrared Light-Induced Selective Photochemical Reactions, pH Responsive Behavior, and Probing Mechanical Properties under Liquid Phase.

    PubMed

    Iyisan, Banu; Janke, Andreas; Reichenbach, Philipp; Eng, Lukas M; Appelhans, Dietmar; Voit, Brigitte

    2016-06-22

    Fixing polymersomes onto surfaces is in high demand not only for the characterization with advanced microscopy techniques but also for designing specific compartments in microsystem devices in the scope of nanobiotechnology. For this purpose, this study reports the immobilization of multifunctional, responsive, and photo-cross-linked polymersomes on solid substrates by utilizing strong adamantane-β-cyclodextrin host-guest interactions. To reduce nonspecific binding and retain better spherical shape, the level of attractive forces acting on the immobilized polymersomes was tuned through poly(ethylene glycol) passivation as well as decreased β-cyclodextrin content on the corresponding substrates. One significant feature of this system is the pH responsivity of the polymersomes which has been demonstrated by swelling of the immobilized vesicles at acidic condition through in situ AFM measurements. Also, light responsivity has been provided by introducing nitroveratryloxycarbonyl (NVOC) protected amine molecules as photocleavable groups to the polymersome surface before immobilization. The subsequent low-energy femtosecond pulsed laser irradiation resulted in the cleavage of NVOC groups on immobilized polymersomes which in turn led to free amino groups as an additional functionality. The freed amines were further conjugated with a fluorescent dye having an activated ester that illustrates the concept of bio/chemo recognition for a potential binding of biological compounds. In addition to the responsive nature, the mechanical stability of the analyzed polymersomes was supported by computing Young's modulus and bending modulus of the membrane through force curves obtained by atomic force microscopy measurements. Overall, polymersomes with a robust and pH-swellable membrane combined with effective light responsive behavior are promising tools to design smart and stable compartments on surfaces for the development of microsystem devices such as chemo/biosensors. PMID

  6. ELECTRON IRRADIATION OF SOLIDS

    DOEpatents

    Damask, A.C.

    1959-11-01

    A method is presented for altering physical properties of certain solids, such as enhancing the usefulness of solids, in which atomic interchange occurs through a vacancy mechanism, electron irradiation, and temperature control. In a centain class of metals, alloys, and semiconductors, diffusion or displacement of atoms occurs through a vacancy mechanism, i.e., an atom can only move when there exists a vacant atomic or lattice site in an adjacent position. In the process of the invention highenergy electron irradiation produces additional vacancies in a solid over those normally occurring at a given temperature and allows diffusion of the component atoms of the solid to proceed at temperatures at which it would not occur under thermal means alone in any reasonable length of time. The invention offers a precise way to increase the number of vacancies and thereby, to a controlled degree, change the physical properties of some materials, such as resistivity or hardness.

  7. Fabrication and mechanical properties of ZrO{sub 2} solid solution and composite ceramics in the system ZrO{sub 2}(Y{sub 2}O{sub 3})-Al{sub 2}O{sub 3}

    SciTech Connect

    Yamaguchi, O.; Hirota, K.; Inamura, S.

    1995-12-31

    In the system ZrO2-Al2O3, dense ZrO2 solid solution ceramics containing 25 mol% Al2O3 are fabricated by the HIP technique using metastable ZrO2 solid solution powders prepared from alkoxides. The ceramics with nanometer grain size show excellent high fracture toughness of {approx}23 MPa{center_dot}m1/2, although they exhibit weak bending strength of {approx}600 MPa. To improve the strength, metastable ZrO2 solid solutions containing 25 mol% Al2O3 and (0.75-3.75) mol% Y2O3 are hot isostatically pressed at 1130{degrees}C and 1230{degrees}C. Two kinds of materials are fabricated: (1) ZrO2 solid solution ceramics and (2) composite ceramics of ZrO2 solid solution and {alpha}-Al2O3. Their mechanical properties are examined in connection with the microstructures and t/m ZrO2 ratios.

  8. Solid lubricants

    NASA Technical Reports Server (NTRS)

    Sliney, Harold E.

    1993-01-01

    The state of knowledge of solid lubricants is reviewed. The results of research on solid lubricants from the 1940's to the present are presented from a historical perspective. Emphasis is placed largely, but not exclusively, on work performed at NASA Lewis Research Center with a natural focus on aerospace applications. However, because of the generic nature of the research, the information presented in this review is applicable to most areas where solid lubricant technology is useful.

  9. Solid lubricants

    NASA Technical Reports Server (NTRS)

    Sliney, Harold E.

    1991-01-01

    The state of knowledge of solid lubricants is reviewed. The results of research on solid lubricants from the 1940's to the present are presented from a historical perspective. Emphasis is placed largely, but not exclusively, on work performed at NASA Lewis Research Center with a natural focus on aerospace applications. However, because of the generic nature of the research, the information presented in this review is applicable to most areas where solid lubricant technology is useful.

  10. Thermochromic Solids

    NASA Astrophysics Data System (ADS)

    Hughes, Jeffrey G.

    1998-01-01

    Thermochromism is the reversible change of color of a solid when it is heated or cooled. Previous reported examples of thermochromic solids involve color changes due to changes of stereochemistry. Salts of mercuric iodide, M2HgI4 [M=Cu(I), Ag(I)] are easily prepared and exhibit sharp, reversible thermochromic transitions at moderately low temperatures. The Ag(I) solid changes color from yellow to orange at 50 °C and the Cu(I) solid at 67 °C. The color changes are due to subtle changes in crystal structure. Signs can be prepared for lecture demonstrations using pieces of filter paper saturated in the solids

  11. (Nbx, Zr1-x)4AlC3 MAX Phase Solid Solutions: Processing, Mechanical Properties, and Density Functional Theory Calculations.

    PubMed

    Lapauw, Thomas; Tytko, Darius; Vanmeensel, Kim; Huang, Shuigen; Choi, Pyuck-Pa; Raabe, Dierk; Caspi, El'ad N; Ozeri, Offir; To Baben, Moritz; Schneider, Jochen M; Lambrinou, Konstantina; Vleugels, Jozef

    2016-06-01

    The solubility of zirconium (Zr) in the Nb4AlC3 host lattice was investigated by combining the experimental synthesis of (Nbx, Zr1-x)4AlC3 solid solutions with density functional theory calculations. High-purity solid solutions were prepared by reactive hot pressing of NbH0.89, ZrH2, Al, and C starting powder mixtures. The crystal structure of the produced solid solutions was determined using X-ray and neutron diffraction. The limited Zr solubility (maximum of 18.5% of the Nb content in the host lattice) in Nb4AlC3 observed experimentally is consistent with the calculated minimum in the energy of mixing. The lattice parameters and microstructure were evaluated over the entire solubility range, while the chemical composition of (Nb0.85, Zr0.15)4AlC3 was mapped using atom probe tomography. The hardness, Young's modulus, and fracture toughness at room temperature as well as the high-temperature flexural strength and E-modulus of (Nb0.85, Zr0.15)4AlC3 were investigated and compared to those of pure Nb4AlC3. Quite remarkably, an appreciable increase in fracture toughness was observed from 6.6 ± 0.1 MPa/m(1/2) for pure Nb4AlC3 to 10.1 ± 0.3 MPa/m(1/2) for the (Nb0.85, Zr0.15)4AlC3 solid solution. PMID:27159119

  12. Solid polymer membrane program

    NASA Technical Reports Server (NTRS)

    1971-01-01

    The results are presented for a solid polymer electrolyte fuel cell development program. Failure mechanism was identified and resolution of the mechanism experienced in small stack testing was demonstrated. The effect included laboratory analysis and evaluation of a matrix of configurations and operational variables for effects on the degree of hydrogen fluoride released from the cell and on the degree of blistering/delamination occurring in the reactant inlet areas of the cell and to correlate these conditions with cell life capabilities. The laboratory evaluation tests were run at conditions intended to accelerate the degradation of the solid polymer electrolyte in order to obtain relative evaluations as quick as possible. Evaluation of the resolutions for the identified failure mechanism in space shuttle configuration cell assemblies was achieved with the fabrication and life testing of two small stack buildups of four cell assemblies and eight cells each.

  13. Solid Lubrication Fundamentals and Applications

    NASA Technical Reports Server (NTRS)

    Miyoshi, Kazuhisa

    2001-01-01

    Solid Lubrication Fundamentals and Applications description of the adhesion, friction, abrasion, and wear behavior of solid film lubricants and related tribological materials, including diamond and diamond-like solid films. The book details the properties of solid surfaces, clean surfaces, and contaminated surfaces as well as discussing the structures and mechanical properties of natural and synthetic diamonds; chemical-vapor-deposited diamond film; surface design and engineering toward wear-resistant, self-lubricating diamond films and coatings. The author provides selection and design criteria as well as applications for synthetic and natural coatings in the commercial, industrial and aerospace industries..

  14. Towards void formation and permeability predictions in LCM processes: A computational bifluid-solid mechanics framework dealing with capillarity and wetting issues

    NASA Astrophysics Data System (ADS)

    Liu, Yujie; Moulin, Nicolas; Bruchon, Julien; Liotier, Pierre-Jacques; Drapier, Sylvain

    2016-04-01

    A bifluid-solid contact model involving surface tension and wetting effects is developed within a finite element framework, in order to provide an accurate characterization of the fluids and fibrous behaviours during Liquid Composite Molding processes. This model is based on a Eulerian approach of two immiscible fluid (resin/air) domains with boundary conditions which prescribe wetting phenomena at fluid/fiber interfaces. The fluid interface is described by the Level Set method, on which capillary force is considered. Numerical simulations of a drop evolution with wetting effects are used to illustrate this challenging physical problem. xml:lang="fr"

  15. Solid electrolytes

    DOEpatents

    Abraham, Kuzhikalail M.; Alamgir, Mohamed

    1993-06-15

    This invention pertains to Li ion (Li.sup.+) conductive solid polymer electrolytes composed of solvates of Li salts immobilized (encapsulated) in a solid organic polymer matrix. In particular, this invention relates to solid polymer electrolytes derived by immobilizing complexes (solvates) formed between a Li salt such as LiAsF.sub.6, LiCF.sub.3 SO.sub.3 or LiClO.sub.4 and a mixture of aprotic organic solvents having high dielectric constants such as ethylene carbonate (EC) (dielectric constant=89.6) and propylene carbonate (PC) (dielectric constant=64.4) in a polymer matrix such as polyacrylonitrile, poly(tetraethylene glycol diacrylate), or poly(vinyl pyrrolidinone).

  16. Growth mechanism and magnetic properties of monodisperse L1(0)-Co(Fe)Pt@C core-shell nanoparticles by one-step solid-phase synthesis.

    PubMed

    Bian, Baoru; He, Jianghai; Du, Juan; Xia, Weixing; Zhang, Jian; Liu, J Ping; Li, Wei; Hu, Chunfeng; Yan, Aru

    2015-01-21

    In this report, we present a novel one-step solid-phase reaction method for the synthesis of L10-CoPt@C core-shell nanoparticles (NPs) using organic metal precursors without surfactants. The obtained CoPt@C NPs have a good face-centered tetragonal single crystal structure and regular shape. The mean size of CoPt is 14 nm with a uniform carbon shell. The evolution of the core-shell structure during the synthesizing process is investigated in detail. Firstly organic metal precursors are decomposed, followed by the formation of grains/clusters in a metal-carbon intermediate state. Then the metal-carbon small grains/clusters agglomerate and recrystallize into single crystal metal alloy NPs covered with a carbon layer. The carbon shell is effective in preventing the coalescence of L10-CoPt NPs during high temperature sintering. The prepared L10-FePt nanoparticles have a high coercivity of up to 12.2 kOe at room temperature. This one-step solid-state synthesizing method could also be employed for the preparation of other types of nanostructures with high crystallinity, monodispersity and chemically ordered phase. PMID:25462862

  17. NIKE3D a nonlinear, implicit, three-dimensional finite element code for solid and structural mechanics user's manual update summary

    SciTech Connect

    Puso, M; Maker, B N; Ferencz, R M; Hallquist, J O

    2000-03-24

    This report provides the NIKE3D user's manual update summary for changes made from version 3.0.0 April 24, 1995 to version 3.3.6 March 24,2000. The updates are excerpted directly from the code printed output file (hence the Courier font and formatting), are presented in chronological order and delineated by NIKE3D version number. NIKE3D is a fully implicit three-dimensional finite element code for analyzing the finite strain static and dynamic response of inelastic solids, shells, and beams. Spatial discretization is achieved by the use of 8-node solid elements, 2-node truss and beam elements, and 4-node membrane and shell elements. Thirty constitutive models are available for representing a wide range of elastic, plastic, viscous, and thermally dependent material behavior. Contact-impact algorithms permit gaps, frictional sliding, and mesh discontinuities along material interfaces. Several nonlinear solution strategies are available, including Full-, Modified-, and Quasi-Newton methods. The resulting system of simultaneous linear equations is either solved iteratively by an element-by-element method, or directly by a direct factorization method.

  18. DYNA3D: A nonlinear, explicit, three-dimensional finite element code for solid and structural mechanics, User manual. Revision 1

    SciTech Connect

    Whirley, R.G.; Engelmann, B.E.

    1993-11-01

    This report is the User Manual for the 1993 version of DYNA3D, and also serves as a User Guide. DYNA3D is a nonlinear, explicit, finite element code for analyzing the transient dynamic response of three-dimensional solids and structures. The code is fully vectorized and is available on several computer platforms. DYNA3D includes solid, shell, beam, and truss elements to allow maximum flexibility in modeling physical problems. Many material models are available to represent a wide range of material behavior, including elasticity, plasticity, composites, thermal effects, and rate dependence. In addition, DYNA3D has a sophisticated contact interface capability, including frictional sliding and single surface contact. Rigid materials provide added modeling flexibility. A material model driver with interactive graphics display is incorporated into DYNA3D to permit accurate modeling of complex material response based on experimental data. Along with the DYNA3D Example Problem Manual, this document provides the information necessary to apply DYNA3D to solve a wide range of engineering analysis problems.

  19. Solid-state dimer method for calculating solid-solid phase transitions

    SciTech Connect

    Xiao, Penghao; Henkelman, Graeme; Sheppard, Daniel; Rogal, Jutta

    2014-05-07

    The dimer method is a minimum mode following algorithm for finding saddle points on a potential energy surface of atomic systems. Here, the dimer method is extended to include the cell degrees of freedom for periodic solid-state systems. Using this method, reaction pathways of solid-solid phase transitions can be determined without having to specify the final state structure or reaction mechanism. Example calculations include concerted phase transitions between CdSe polymorphs and a nucleation and growth mechanism for the A15 to BCC transition in Mo.

  20. 2,3,5-Trimethoxy-4-cresol, an anti-metastatic constituent from the solid-state cultured mycelium of Antrodia cinnamomea and its mechanism.

    PubMed

    Lin, Chin-Chung; Chen, Ching-Chun; Kuo, Yueh-Hsiung; Kuo, Jong-Tar; Senthil Kumar, K J; Wang, Sheng-Yang

    2015-10-01

    Antrodia cinnamomea is a valuable and unique edible fungus originating from the forests of Taiwan. In this study, an anti-metastatic compound, 2,3,5-trimethoxy-4-cresol (TMC), was isolated from the solid-state cultured mycelium of A. cinnamomea. According to the results obtained from cell wound healing, cell migration and invasion assays, TMC effectively suppressed movement, migration and invasion of lung cancer cells at the dosage of 5-40 μM, which was non-toxic to A549 cells. In addition, TMC reduced protein expression of Akt, MMP-2 and MMP-9 and enhanced E-cadherin and TIMP-1 protein expression, which are known to regulate cell adhesion, migration and invasion. Taken together, TMC effectively suppresses movement, migration and invasion of lung cancer cells, and achieves an anti-cancer metastasis effect. PMID:25951809

  1. Reaction kinetics for the solid state synthesis of the AlH3/MgCl2 nano-composite by mechanical milling.

    PubMed

    Duan, C W; Hu, L X; Sun, Y; Zhou, H P; Yu, H

    2015-09-14

    The process of mechanical milling has been proved to be a cost-effective way to synthesize the AlH3/MgCl2 nano-composite by using MgH2 and AlCl3 as reagents. However, so far there is no comprehensive knowledge of the kinetics of this process. In an effort to predict the reaction progress and optimize the milling parameters, the kinetics of the synthesis of the AlH3/MgCl2 nano-composite by mechanical milling of MgH2 and AlCl3 is experimentally investigated in the present work. The reaction progress or the transformation fraction upon milling for different times is evaluated using the isothermal hydrogen desorption test of the as-milled samples at 220 °C, which is much lower than the threshold temperature for the de-hydriding of the reagent MgH2 but enough for the de-hydriding of the as-synthesized nano-sized AlH3. The effects of milling parameters on the reaction kinetics as well as the underlying mechanism are discussed by referring to the mechanical energy input intensity, the vial temperature and the Gibbs free energy change for the reaction. Furthermore, it is found that the Johnson-Mehl-Avrami (JMA) model can well describe the kinetics theoretically. By fitting the experimental data with the JMA expression, the theoretical kinetics expressions, the equation parameters, and the activation energy are obtained. PMID:26256935

  2. Solid-solid phase transitions via melting in metals.

    PubMed

    Pogatscher, S; Leutenegger, D; Schawe, J E K; Uggowitzer, P J; Löffler, J F

    2016-01-01

    Observing solid-solid phase transitions in-situ with sufficient temporal and spatial resolution is a great challenge, and is often only possible via computer simulations or in model systems. Recently, a study of polymeric colloidal particles, where the particles mimic atoms, revealed an intermediate liquid state in the transition from one solid to another. While not yet observed there, this finding suggests that such phenomena may also occur in metals and alloys. Here we present experimental evidence for a solid-solid transition via the formation of a metastable liquid in a 'real' atomic system. We observe this transition in a bulk glass-forming metallic system in-situ using fast differential scanning calorimetry. We investigate the corresponding transformation kinetics and discuss the underlying thermodynamics. The mechanism is likely to be a feature of many metallic glasses and metals in general, and may provide further insight into phase transition theory. PMID:27103085

  3. Rarefied solids

    NASA Technical Reports Server (NTRS)

    Noever, D. A.; Nikora, V. I.

    1994-01-01

    One important limit to creating low density materials is the objects' own weight. As a solid or colloidal matrix becomes more rarefied, gravity acts destructively to compress its suporting skeleton. We describe experimental results and propose a model which matches the low gravity behavior of rarefied or fractal solids. On parabolic airplane flights, we sought to demonstrate a key component of producing higher surface area fractals. Flight paths were selected to give a range of gravity levels: 0.01 g/g(sub 0) (low), 0.16 g(sub 0) (Lunar), 0.33 g/g(sub 0) (Martian), 1 g/g(sub 0) (Earth) and 1.8 g/g(sub 0) (high) (where g(sub 0) = 980 cm/sq s). Results using the model material of hydrophobic silica indicated that stable agglomeration of such tenuous objects can increase markedly in reduced gravity. Optical characterization revealed that fractal dimension changed directly with varying gravity. As measured by fractal dimension, effective surface area and roughness increased by 40% in low gravity. This finding supports the conclusion that relieving internal weight stresses on delicate aggregates can enhance their overall size (by two orders of magnitude) and internal surface area. We conclude that gravitational restructuring limits the overall size and void content of low-density solids. These sparse colloidal regimes may present new and technologically attractive physics, ranging from improved insulators, liquid-like tension in a 'solid' matrix, and characteristically low conductivities for sound and (8 to 14 micrometers wavelength) infrared radiation.

  4. Manganese Tetraboride, MnB4: High-Temperature Crystal Structure, p-n Transition, (55)Mn NMR Spectroscopy, Solid Solutions, and Mechanical Properties.

    PubMed

    Knappschneider, Arno; Litterscheid, Christian; Brgoch, Jakoah; George, Nathan C; Henke, Sebastian; Cheetham, Anthony K; Hu, Jerry G; Seshadri, Ram; Albert, Barbara

    2015-05-26

    The structural and electronic properties of MnB4 were studied by high-temperature powder X-ray diffraction and measurements of the conductivity and Seebeck coefficient on spark-plasma-sintered samples. A transition from the room-temperature monoclinic structure (space group P2(1)/c) to a high-temperature orthorhombic structure (space group Pnnm) was observed at about 650 K. The material remained semiconducting after the transition, but its behavior changed from p-type to n-type. (55)Mn NMR measurements revealed an isotropic chemical shift of -1315 ppm, confirming an oxidation state of Mn close to I. Solid solutions of Cr(1-x)Mn(x)B4 (two phases in space groups Pnnm and P2(1)/c) were synthesized for the first time. In addition, nanoindentation studies yielded values of (496±26) and (25.3±1.7) GPa for the Young's modulus and hardness, respectively, compared to values of 530 and 37 GPa obtained by DFT calculations. PMID:25891681

  5. Microstructure and polarization characteristics of anode supported tubular solid oxide fuel cell with co-precipitated and mechanically mixed Ni-YSZ anodes

    NASA Astrophysics Data System (ADS)

    Shikazono, Naoki; Sakamoto, Yusuke; Yamaguchi, Yu; Kasagi, Nobuhide

    An anode support tubular solid oxide fuel cell (SOFC) is fabricated and the dependence of its polarization resistance on anode microstructural parameters is investigated by means of stereology and concept of contiguity (c-c) theory. Nickel yttria-stabilized zirconia (Ni-YSZ) anode supported cell with YSZ electrolyte, lanthanum-strontium-manganite (LSM)-YSZ composite cathode, and LSM cathode layers is fabricated by dip coating. Submicrometer resolution images of anode microstructure are successfully obtained by low voltage SEM-EDX and quantified by stereological analysis. Cell voltage measurements and impedance spectroscopy are performed at temperatures of 650 and 750 °C with hydrogen and nitrogen mixture gas as a fuel. A quantitative relationship between polarization resistance and microstructural parameters such as circularity, three-phase boundary length, contiguity, etc. is investigated using the concept of contiguity (c-c) theory. The effectiveness of correlating polarization resistance of anode supported tubular SOFC using stereology and c-c theory is evaluated.

  6. Solid state theory of competitive diffusion of associated Na+ and K+ in cells by free cation and vacancy (hole) mechanisms, with application to nerve.

    PubMed

    Cope, F W

    1977-01-01

    If, as recent evidence indicates, most cell potassium is associated with macromolecular fixed charge, then diffusion of potassium ions in cells might occur by (1) diffusion of the small fraction of free potassium in cell water (analogous to electrons in the conduction band of a semiconductor) or by (2) diffusion of vacancies on association sites (analogous to holes in a semiconductor). Derivations of the Fick first law of diffusion predict that partial substitution of sodium for potassium in the cell produces opposite effects on the effective diffusion constant of potassium for those mechanisms. Application of that substitution to nerve data suggests that rubidium ions diffuse by a free cation result when the nerve is clamped at its resting potential, but by a vacancy mechanism when the nerve is clamped at zero voltage. PMID:613332

  7. Water and magmas: insights about the water solution mechanisms in alkali silicate melts from infrared, Raman, and 29Si solid-state NMR spectroscopies

    NASA Astrophysics Data System (ADS)

    Le Losq, Charles; Mysen, Bjorn O.; Cody, George D.

    2015-12-01

    Degassing of water during the ascent of hydrous magma in a volcanic edifice produces dramatic changes in the magma density and viscosity. This can profoundly affect the dynamics of volcanic eruptions. The water exsolution history, in turn, is driven by the water solubility and solution mechanisms in the silicate melt. Previous studies pointed to dissolved water in silicate glasses and melts existing as molecules (H2Omol species) and hydroxyl groups, OH. These latter OH groups commonly are considered bonded to Si4+ but may form other bonds, such as with alkali or alkaline-earth cations, for instance. Those forms of bonding influence the structure of hydrous melts in different ways and, therefore, their properties. As a result, exsolution of water from magmas may have different eruptive consequences depending on the initial bonding mechanisms of the dissolved water. However, despite their importance, the solution mechanisms of water in silicate melts are not clear. In particular, how chemical composition of melts affects water solubility and solution mechanism is not well understood. In the present experimental study, components of such information are reported via determination of how water interacts with the cationic network of alkali (Li, Na, and K) silicate quenched melts. Results from 29Si single-pulse magic-angle spinning nuclear magnetic resonance (29Si SP MAS NMR), infrared, and Raman spectroscopies show that decreasing the ionic radius of alkali metal cation in silicate melts results in decreasing fraction of water dissolved as OH groups. The nature of OH bonding also changes as the alkali ionic radius changes. Therefore, as the speciation and bonding of water controls the degree of polymerization of melts, water will have different effects on the transport properties of silicate melts depending on their chemical composition. This conclusion, in turn, may affect volcanic phenomena related to the viscous relaxation of hydrous magmas, such as for instance the

  8. Mechanism for the Direct Synthesis of H2O2 on Pd Clusters: Heterolytic Reaction Pathways at the Liquid-Solid Interface.

    PubMed

    Wilson, Neil M; Flaherty, David W

    2016-01-20

    Direct synthesis (H2 + O2 → H2O2) is a promising reaction for producing H2O2, which can replace chlorinated oxidants in industrial processes. The mechanism of this reaction and the reasons for the importance of seemingly unrelated factors (e.g., Pd cluster size and solvent pH) remain unclear despite significant research. We propose a mechanism for H2O2 formation on Pd clusters consistent with steady-state H2O2 and H2O formation rates measured as functions of reactant pressures and temperature and the interpretations of proton concentration effects. H2O2 forms by sequential proton-electron transfer to O2 and OOH surface intermediates, whereas H2O forms by O-O bond rupture within OOH surface species. Direct synthesis, therefore, does not proceed by the Langmuir-Hinshelwood mechanism often invoked. Rather, H2O2 forms by heterolytic reaction pathways resembling the two-electron oxygen reduction reaction (ORR); however, the chemical potential of H2 replaces an external electrical potential as the thermodynamic driving force. Activation enthalpies (ΔH(⧧)) for H2O formation increase by 14 kJ mol(-1) when Pd cluster diameters increase from 0.7 to 7 nm because changes in the electronic structure of Pd surface atoms decrease their propensity to cleave O-O bonds. ΔH(⧧) values for H2O2 remain nearly constant because barriers for proton-electron transfer depend weakly on the coordinative saturation of Pd surface atoms. Collectively, these results provide a self-consistent mechanism, which clarifies many studies in which H2O2 rates and selectivities were shown to depend on the concentration of acid/halide additives and Pd cluster size. These findings will guide the rational design of selective catalysts for direct synthesis. PMID:26597848

  9. Interplay between solid state transitions, conductivity mechanisms, and electrical relaxations in a [PVBTMA] [Br]-b-PMB diblock copolymer membrane for electrochemical applications.

    PubMed

    Di Noto, Vito; Giffin, Guinevere A; Vezzù, Keti; Nawn, Graeme; Bertasi, Federico; Tsai, Tsung-han; Maes, Ashley M; Seifert, Soenke; Coughlin, E Bryan; Herring, Andrew M

    2015-12-14

    Understanding the structure-property relationships and the phenomena responsible for ion conduction is one of the keys in the design of novel ionomers with improved properties. In this report, the morphology and the mechanism of ion exchange in a model anion exchange membrane (AEM), poly(vinyl benzyl trimethyl ammonium bromide)-block-poly(methylbutylene) ([PVBTMA][Br]-b-PMB), is investigated with small angle X-ray scattering, high-resolution thermogravimetry, modulated differential scanning calorimetry, dynamic mechanical analysis, and broadband electrical spectroscopy. The hyper-morphology of the material consists of hydrophilic domains characterized by stacked sides of [PVBTMA][Br] which are sandwiched between "spaghetti-like" hydrophobic cylindrical parallel domains of the PMB block. The most important interactions in the hydrophilic domains occur between the dipoles of ammonium bromide ion pairs in the side chains of adjacent chains. A reordering of the ion pair dipoles is responsible for a disorder-order transition (Tδ) at high temperature, observed here for the first time in AEMs, which results in a dramatic decrease of the ionic conductivity. The overall mechanism of long range charge transfer, deduced from a congruent picture of all of the results, involves two distinct ion conduction pathways. In these pathways, hydration and the motion of the ionic side groups are crucial to the conductivity of the AEM. Unlike the typical perfluorinated sulfonated proton-conducting polymer, the segmental motion of the backbone is negligible. PMID:26538312

  10. Fluid Mechanics Prize-Otto Laporte Lecture: The Art of Mixing with an Admixture of Art: Fluids, Solids, and Visual Imagination

    NASA Astrophysics Data System (ADS)

    Ottino, Julio Mario

    2008-11-01

    Arguably, fluid dynamics is intimately linked with visual imagination more than any other branch of physical sciences. A particular example is mixing. Fluid mixing, and under more limited circumstances, granular mixing, can be placed in the framework of dynamical systems and a geometric viewpoint. On the fluid mixing side, the physical connection can be traced back to the stretching and folding of fluid elements and possibility of representation motions in terms of transformations. This opens a wealth of possibilities --- the mathematical machinery of dynamical systems on the theory side, and the possibility of inventing devices on the practical side. There are notable differences as well: granular materials un-mix or segregate, often spectacularly so, and some aspects of segregation can also be incorporated in the mathematical framework. A technical review will highlight key points in both areas -- experiments, applications, and the many branches that have taken root since the mid-1980s. However, much of this could have taken place sooner. The basic mechanisms and key experimental results in both areas were identified early: the stretching and folding mechanism of mixing was pointed out by Osborne Reynolds in 1893-1895, and a key segregation mechanism of granular mixtures was noted by Yositisi Oyama in 1939. In what may appear surprising on a first viewing, these leads were not followed. Ideas, in order to be embraced, need to fit with the canonical knowledge of the times.

  11. The effects of the mechanical-chemical stabilization process for municipal solid waste incinerator fly ash on the chemical reactions in cement paste.

    PubMed

    Chen, Cheng-Gang; Sun, Chang-Jung; Gau, Sue-Huai; Wu, Ching-Wei; Chen, Yu-Lun

    2013-04-01

    A water extraction process can remove the soluble salts present in municipal solid waste incinerator (MSWI) fly ash, which will help to increase the stability of the synthetic materials produced from the MSWI fly ash. A milling process can be used to stabilize the heavy metals found in the extracted MSWI fly ash (EA) leading to the formation of a non-hazardous material. This milled extracted MSWI fly ash (MEA) was added to an ordinary Portland cement (OPC) paste to induce pozzolanic reactions. The experimental parameters included the milling time (96h), water to binder ratios (0.38, 0.45, and 0.55), and curing time (1, 3, 7 and 28 days). The analysis procedures included inductively coupled plasma atomic emission spectroscopy (ICP/AES), BET, mercury intrusion porosimetry (MIP), X-ray diffraction (XRD), and nuclear magnetic resonance (NMR) imaging. The results of the analyses indicate that the milling process helped to stabilize the heavy metals in the MEA, with an increase in the specific surface area of about 50times over that of OPC. The addition of the MEA to the OPC paste decreased the amount of Ca(OH)2 and led to the generation of calcium-silicate-hydrates (C-S-H) which in turned increased the amount of gel pores and middle sized pores in the cement. Furthermore, a comparison shows an increase in the early and later strength over that of OPC paste without the addition of the milled extracted ash. In other words, the milling process could stabilize the heavy metals in the MEA and had an activating effect on the MEA, allowing it to partly substitute OPC in OPC paste. PMID:23375995

  12. Investigation of reaction mechanisms of drug degradation in the solid state: a kinetic study implementing ultrahigh-performance liquid chromatography and high-resolution mass spectrometry for thermally stressed thyroxine.

    PubMed

    Neu, Volker; Bielow, Chris; Schneider, Peter; Reinert, Knut; Stuppner, Hermann; Huber, Christian G

    2013-02-19

    A reaction scheme was derived for the thermal degradation of thyroxine in the solid state, using data obtained from ultrahigh-performance liquid chromatography and high-resolution mass spectrometry (UHPLC-HRMS). To study the reaction mechanism and kinetics of the thermal degradation of the pharmaceutical in the solid state, a workflow was developed by generating compound-specific, time-dependent degradation or formation curves of at least 13 different degradation products. Such curves allowed one to distinguish between first- and second-generation degradation products, as well as impurities resulting from chemical synthesis. The structures of the degradation products were derived from accurate molecular masses and multistage mass spectrometry. Deiodination and oxidative side chain degradation were found to be the major degradation reactions, resulting in the formation of deiodinated thyroxines, as well as acetic acid, benzoic acid, formaldehyde, acetamide, hydroxyacetic acid, oxoacetic acid, hydroxyacetamide, or oxoacetamide derivatives of thyroxine or deiodinated thyroxine. Upon additional structural verification of mass spectrometric data using nuclear magnetic resonance spectroscopy, this comprehensive body of data sheds light on an elaborate, radical-driven reaction scheme, explaining the presence or formation of impurities in thermally stressed thyroxine. PMID:23311729

  13. Effect composition of SiCp and TiB to the mechanical properties of composite Al7Si-Mg-SiCp by the method of semi solid stir casting

    NASA Astrophysics Data System (ADS)

    Bhiftime, E. I.; Sulardjaka, Nugroho, Sri

    2016-04-01

    Recently, studies on Aluminum Matrix Composite (AMC) were growing rapidly. AMC reinforced with SiCp particles in the semi solid stir casting method was the most simple way. In particular, the purpose of the present study was to investigate the effect composition of SiCp and TiB to the mechanical properties of the composites Al7Si-Mg-SiCp and Al7Si-Mg-TiB-SiCp. The composites used were Al7Si as the matrix and SiCp as the reinforcement (10, 15, 20 wt%). The casting method used on the study was the semi solid stir casting. The matrix was melted at the temperature of 800 °C. Then, the stirring process started at 590 °C with the speed of 500 rpm for 180 seconds. The composites was heated again until the pouring temperature was at 750 °C. The results of the present study indicated to be successful in which SiCp particles dispersed uniformly in the matrix composites. Further, the hardness value and porosity of the composites Al7Si-Mg-SiCp and Al7Si-Mg-TiB-SiCp increased along with the addition of TiB. Besides, the hardness value increased in the average of 10.5% at the variation of 20% SiCp. Whereas, the porosity value increased in the average of 54.3% at the variation of 20% SiCp.

  14. Microstructures and mechanical properties of compositionally complex Co-free FeNiMnCr18 FCC solid solution alloy

    SciTech Connect

    Wu, Z.; Bei, H.

    2015-07-01

    Recently, a structurally-simple but compositionally-complex FeNiCoMnCr high entropy alloy was found to have excellent mechanical properties (e.g., high strength and ductility). To understand the potential of using high entropy alloys as structural materials for advanced nuclear reactor and power plants, it is necessary to have a thorough understanding of their structural stability and mechanical properties degradation under neutron irradiation. Furthermore, this requires us to develop a similar model alloy without Co because material with Co will make post-neutron-irradiation testing difficult due to the production of the 60Co radioisotope. In order to achieve this goal, a FCC-structured single-phase alloy with a composition of FeNiMnCr18 was successfully developed. This near-equiatomic FeNiMnCr18 alloy has good malleability and its microstructure can be controlled by thermomechanical processing. By rolling and annealing, the as-cast elongated-grained-microstructure is replaced by homogeneous equiaxed grains. The mechanical properties (e.g., strength and ductility) of the FeNiMnCr18 alloy are comparable to those of the equiatomic FeNiCoMnCr high entropy alloy. Both strength and ductility increase with decreasing deformation temperature, with the largest difference occurring between 293 and 77 K. Extensive twin-bands which are bundles of numerous individual twins are observed when it is tensile-fractured at 77 K. No twin bands are detected by EBSD for materials deformed at 293 K and higher. Ultimately the unusual temperature-dependencies of UTS and uniform elongation could be caused by the development of the dense twin substructure, twin-dislocation interactions and the interactions between primary and secondary twinning systems which result in a microstructure refinement and hence cause enhanced strain hardening and postponed necking.

  15. An efficient approach for numerical treatment of some inequalities in solid mechanics on examples of Kuhn-Tucker and Signorini-Fichera conditions

    NASA Astrophysics Data System (ADS)

    Kindrachuk, Vitaliy M.; Galanov, Boris A.

    2014-02-01

    A computationally efficient solution scheme is presented for the mechanical problems whose formulations include the Kuhn-Tucker or Signorini-Fichera conditions. It is proposed to reformulate these problems replacing inequalities in these conditions by equations with respect to new unknowns. The solutions of the modified problems have simple physical meanings and determine uniquely the unknowns of the original problems. The approach avoids application of multi-valued operators (inclusions or inequalities) in formulation of the problems. Hence, the modified formulations are suitable for numerical analysis using established powerful mathematical methods and corresponding solvers developed for solving systems of non-linear equations.

  16. Stiffening solids with liquid inclusions

    NASA Astrophysics Data System (ADS)

    Style, Robert W.; Boltyanskiy, Rostislav; Allen, Benjamin; Jensen, Katharine E.; Foote, Henry P.; Wettlaufer, John S.; Dufresne, Eric R.

    2015-01-01

    From bone and wood to concrete and carbon fibre, composites are ubiquitous natural and synthetic materials. Eshelby’s inclusion theory describes how macroscopic stress fields couple to isolated microscopic inclusions, allowing prediction of a composite’s bulk mechanical properties from a knowledge of its microstructure. It has been extended to describe a wide variety of phenomena from solid fracture to cell adhesion. Here, we show experimentally and theoretically that Eshelby’s theory breaks down for small liquid inclusions in a soft solid. In this limit, an isolated droplet’s deformation is strongly size-dependent, with the smallest droplets mimicking the behaviour of solid inclusions. Furthermore, in opposition to the predictions of conventional composite theory, we find that finite concentrations of small liquid inclusions enhance the stiffness of soft solids. A straightforward extension of Eshelby’s theory, accounting for the surface tension of the solid-liquid interface, explains our experimental observations. The counterintuitive stiffening of solids by fluid inclusions is expected whenever inclusion radii are smaller than an elastocapillary length, given by the ratio of the surface tension to Young’s modulus of the solid matrix. These results suggest that surface tension can be a simple and effective mechanism to cloak the far-field elastic signature of inclusions.

  17. Aerosol assisted chemical vapour deposition of gas sensitive SnO2 and Au-functionalised SnO2 nanorods via a non-catalysed vapour solid (VS) mechanism

    PubMed Central

    Vallejos, Stella; Selina, Soultana; Annanouch, Fatima Ezahra; Gràcia, Isabel; Llobet, Eduard; Blackman, Chris

    2016-01-01

    Tin oxide nanorods (NRs) are vapour synthesised at relatively lower temperatures than previously reported and without the need for substrate pre-treatment, via a vapour-solid mechanism enabled using an aerosol-assisted chemical vapour deposition method. Results demonstrate that the growth of SnO2 NRs is promoted by a compression of the nucleation rate parallel to the substrate and a decrease of the energy barrier for growth perpendicular to the substrate, which are controlled via the deposition conditions. This method provides both single-step formation of the SnO2 NRs and their integration with silicon micromachined platforms, but also allows for in-situ functionalization of the NRs with gold nanoparticles via co-deposition with a gold precursor. The functional properties are demonstrated for gas sensing, with microsensors using functionalised NRs demonstrating enhanced sensing properties towards H2 compared to those based on non-functionalised NRs. PMID:27334232

  18. Aerosol assisted chemical vapour deposition of gas sensitive SnO2 and Au-functionalised SnO2 nanorods via a non-catalysed vapour solid (VS) mechanism

    NASA Astrophysics Data System (ADS)

    Vallejos, Stella; Selina, Soultana; Annanouch, Fatima Ezahra; Gràcia, Isabel; Llobet, Eduard; Blackman, Chris

    2016-06-01

    Tin oxide nanorods (NRs) are vapour synthesised at relatively lower temperatures than previously reported and without the need for substrate pre-treatment, via a vapour-solid mechanism enabled using an aerosol-assisted chemical vapour deposition method. Results demonstrate that the growth of SnO2 NRs is promoted by a compression of the nucleation rate parallel to the substrate and a decrease of the energy barrier for growth perpendicular to the substrate, which are controlled via the deposition conditions. This method provides both single-step formation of the SnO2 NRs and their integration with silicon micromachined platforms, but also allows for in-situ functionalization of the NRs with gold nanoparticles via co-deposition with a gold precursor. The functional properties are demonstrated for gas sensing, with microsensors using functionalised NRs demonstrating enhanced sensing properties towards H2 compared to those based on non-functionalised NRs.

  19. Aerosol assisted chemical vapour deposition of gas sensitive SnO2 and Au-functionalised SnO2 nanorods via a non-catalysed vapour solid (VS) mechanism.

    PubMed

    Vallejos, Stella; Selina, Soultana; Annanouch, Fatima Ezahra; Gràcia, Isabel; Llobet, Eduard; Blackman, Chris

    2016-01-01

    Tin oxide nanorods (NRs) are vapour synthesised at relatively lower temperatures than previously reported and without the need for substrate pre-treatment, via a vapour-solid mechanism enabled using an aerosol-assisted chemical vapour deposition method. Results demonstrate that the growth of SnO2 NRs is promoted by a compression of the nucleation rate parallel to the substrate and a decrease of the energy barrier for growth perpendicular to the substrate, which are controlled via the deposition conditions. This method provides both single-step formation of the SnO2 NRs and their integration with silicon micromachined platforms, but also allows for in-situ functionalization of the NRs with gold nanoparticles via co-deposition with a gold precursor. The functional properties are demonstrated for gas sensing, with microsensors using functionalised NRs demonstrating enhanced sensing properties towards H2 compared to those based on non-functionalised NRs. PMID:27334232

  20. Laser cooling of solids

    NASA Astrophysics Data System (ADS)

    Nemova, Galina; Kashyap, Raman

    2010-08-01

    Laser cooling of solids, sometimes also known as optical refrigeration, is a fast developing area of optical science, investigating the interaction of light with condensed matter. Apart from being of fundamental scientific interest, this topic addresses a very important practical issue: design and construction of laser pumped solid-state cryocoolers, which are compact, free from mechanical vibrations, moving parts, fluids and can cause only low electromagnetic interference in the cooled area. The optical cryocooler has a broad area of applications such as in the development of magnetometers for geophysical sensors, in biomedical sensing and can be beneficial for satellite instrumentations and small sensors, where compactness and the lack of vibrations are very important. Simply, a laser cooler works on the conversion of low energy pump photons into high-energy anti-Stokes fluorescence photons by extracting some of the phonons (heat energy) in a material. That is, the process of laser cooling of solids is based on anti-Stokes fluorescence also known as luminescence upconversion, when light quanta in the red tail of the absorption spectrum are absorbed from a pump laser, and blue-shifted photons are spontaneously emitted. The extra energy extracted from the solid-state lattice in the form of the phonons is the quanta of vibrational energy which generates heat. The idea to cool solids with anti-Stokes fluorescence was proposed in 1929 by Peter Pringsheim and first demonstrated experimentally by Epstein's research team in 1995. In 1999, Steven Bowman proposed to use the optical refrigeration by anti-Stokes fluorescence within the laser medium to balance the heat generated by the Stokes shifted stimulated emission in a high-power solid-state bulk laser. Such a laser without internal heating named radiation-balanced or athermal laser was experimentally demonstrated for the first time in 2002. At the present time laser cooling of solids can be largely divided into three

  1. Study the Effects of Mechanical Activation on Li-N-H Systems With 1H and 6Li Solid-State NMR

    SciTech Connect

    Lu, Chun; Hu, Jian Zhi; Kwak, Ja Hun; Yang, Z Gary; Ren, Ruiming; Markmaitree, Tippawan; Shaw, Leonard D.

    2007-07-10

    To gain insight into the effects of mechanical activation (MA) on the hydrogen desorption of the lithium amide (LiNH2) and lithium hydride (LiH) mixture, LiNH2 and LiH+LiNH2 were mechanically activated by high-energy ball milling. The formed products were studied with in situ 1H and 6Li nuclear magic angle spinning (MAS) magnetic resonance (NMR) spectroscopy from ambient temperature to 180 degrees C. Up-field chemical shift was observed in 6Li MAS NMR spectra with increased milling time, indicating that average local electronic structure around Li nuclei was modified during MA. 1H MAS NMR was used to dynamically probe ammonia release from the activated LiNH2 at temperature as low as 50 degrees C. In the case of activated LiH+LiNH2 mixtures, the 1H MAS NMR results implied that MA enhanced the dehydrogenation reaction of LiNH2+LiH=Li2NH+H2 and suppressed ammonia generation as well.

  2. Study the effects of mechanical activation on Li-N-H systems with 1H and 6Li solid-state NMR

    NASA Astrophysics Data System (ADS)

    Lu, Chun; Hu, Jianzhi; Kwak, Ja Hun; Yang, Zhenguo; Ren, Ruiming; Markmaitree, Tippawan; Shaw, Leon L.

    To gain insight into the effects of mechanical activation (MA) on the hydrogen desorption of the lithium amide (LiNH 2) and lithium hydride (LiH) mixture, LiNH 2 and LiH + LiNH 2 were mechanically activated by high-energy ball milling. The formed products were studied with in situ 1H and 6Li nuclear magic angle spinning (MAS) magnetic resonance (NMR) spectroscopy from ambient temperature to 180 °C. Up-field chemical shift was observed in 6Li MAS NMR spectra with increased milling time, indicating that average local electronic structure around Li nuclei was modified during MA. 1H MAS NMR was used to dynamically probe ammonia release from the activated LiNH 2 at temperature as low as 50 °C. In the case of activated LiH + LiNH 2 mixtures, the 1H MAS NMR results implied that MA enhanced the dehydrogenation reaction of LiNH 2 + LiH = Li 2NH + H 2.

  3. A New Mechanism for Ozonolysis of Unsaturated Organics on Solids: Phosphocholines on NaCl as A Model for Sea Salt particles

    SciTech Connect

    Karagulian, Federico; Lea, Alan S; Dilbeck, Christopher W; Finlayson-Pitts, Barbara J

    2008-01-28

    The ozonolysis of an approximately one monolayer film of 1-oleoyl-2-palmitoyl-sn-glycero-3-phosphocholine (OPPC) on NaCl was followed in real time using diffuse reflectance infrared Fourier transform spectrometry (DRIFTS) at 23 °C. Matrix-assisted laser desorption/ionization (MALDI) mass spectrometry and AUGER electron spectroscopy were used as complementary analytical techniques. Ozone concentrations ranged from 1.7 x 1012 to 7.0 x 1013 molecules cm-3 (70 ppb to 2.5 ppm). Upon exposure to O3, there was a loss of C=C accompanied by the formation of a strong band at ~1110 cm-1 due to the formation of a stable secondary ozonide (1,3,4-trioxolane, SOZ). The yield of the SOZ was lower when the reaction was carried out in the presence of water vapor at concentrations corresponding to relative humidities between 2 and 25 %. The dependencies of the rate of SOZ formation on the concentrations of ozone and water vapor are consistent with the initial formation of a primary ozonide (1,2,3-trioxolane, POZ) that can react with O3 or H2O in competition with its thermal decomposition to a Criegee intermediate and aldehyde. This interpretation is also consistent with the measured dependence of the SOZ yield on the ozone concentration. Estimates were obtained for the rate constants for the POZ thermal decomposition and for its reactions with O3 and H2O, as well as for the initial reaction of O3 with OPPC. The SOZ decomposed upon photolysis at x > 300 nm, generating aldehydes, carboxylic acids and anhydrides. These studies show that the primary ozonide has a sufficiently long lifetime when formed on a solid substrate that direct reactions with O3 and H2O can compete with its thermal decomposition. In dry polluted atmospheres, ozone-alkene reactions may lead in part to the formation of stable secondary ozonides whose chemistry, photochemistry and toxicity should be taken into account in models of such regions.

  4. Solid state heat engine

    SciTech Connect

    Cory, J.S.

    1981-12-15

    A compact solid state turbine heat engine can be devised by pairing the nitinol elements. Each element is characterized by being in thermal contact with at least one hot water and one cold water bath and mechanically coupled to at least one driven pulley and driver pulley. A second nitinol element is similarly configured with a driver pulley, driven pulley, hot and cold water bath. The driver pulley associated with the first nitinol element is mechanically coupled to the driven pulley of the second nitinol element. Similarly, the driver pulley of the second nitinol element is mechanically coupled to the driven pulley of the first nitinol element. The paired nitinol elements form a compound solid state turbine engine wherein each nitinol element lies in a single plane and wherein the engine may be combined with a plurality of such pairs for increased power output. The nitinol elements may also incorporate a snubber to limit the strain on the element and the engine may further incorporate a variable radius pulley to increase the efficiency of mechanical conversion.

  5. Cytocompatibility, gene-expression profiling, apoptotic, mechanical and (29)Si, (31)P solid-state nuclear magnetic resonance studies following treatment with a bioglass-chitosan composite.

    PubMed

    Samira, Jebahi; Hassane, Oudadesse; Mongi, Saoudi; Fakhri, Kallabi; Pellen, Pascal; Treq, Rebai; Abdelfatteh, Elfeki; Hassib, Keskes

    2014-12-01

    The performance therapy of chitosan (CH)-doped bioactive glass (BG) has been evaluated in vitro and in vivo. In vitro, the effect of CH-BG was assessed on human Saos-2 osteoblast cells. In vivo, Wistar rats were ovariectomized (OVX) and CH, BG and CH-BG were implanted in bone tissue. After 3 days of CH-BG contact, cell viability of Saos-2 osteoblast increased by 16.4% as compared to the control group. The runt-related transcription factor 2 (RUNX2/Cbfa1) and osteocalcin (OC) gene expressions were significantly increased with 600 and 300%, respectively, in contact of CH-BG as compared with CH. In vivo, the apoptotic index in the OVX-CH-BG group was decreased by 80%. A mechanical hardness test showed a significant bone strength improvement after CH-BG implantation (40%). The CH-BG composite may therefore prove clinically useful as a bioactive bone substitute. PMID:25214211

  6. Solid-state Reaction of Azolium Hydrohalogen Salts with Silver Dicyanamide--Unexpected Formation of Cyanoguanidine-azoles, Reaction Mechanism and Their Hypergolic Properties.

    PubMed

    Liu, Wei; Lin, Qiu-han; Li, Yu-chuan; Chen, Peng-wan; Fang, Tao; Zhang, Ru-bo; Pang, Si-ping

    2015-01-01

    Cyanoguanidines as well as azoles are important bioactive groups, which play an important role in the medical application; meanwhile, the high nitrogen content makes them excellent backbones for energetic materials. A Novel and simple method that combined these two fragments into one molecular compound was developed through the transformation of dicyanamide ionic salts. In return, compounds 4-11 were synthesized, and fully characterized by IR, MS, NMR and elemental analysis. Meanwhile, the structures of compounds 4, 8 and 11 were confirmed by X-ray crystal diffraction. Detailed reaction mechanisms were studied through accurate calculations on the reaction energy profiles of the azolium cations and DCA anion, which revealed the essence of the transformation proceeding. Meanwhile, compound 8 exhibits excellent hypergolic property, which could be potentially novel molecular hypergolic fuel. PMID:26039324

  7. Solid-state Reaction of Azolium Hydrohalogen Salts with Silver Dicyanamide – Unexpected Formation of Cyanoguanidine-azoles, Reaction Mechanism and Their Hypergolic Properties

    PubMed Central

    Liu, Wei; Lin, Qiu-han; Li, Yu-chuan; Chen, Peng-wan; Fang, Tao; Zhang, Ru-bo; Pang, Si-ping

    2015-01-01

    Cyanoguanidines as well as azoles are important bioactive groups, which play an important role in the medical application; meanwhile, the high nitrogen content makes them excellent backbones for energetic materials. A Novel and simple method that combined these two fragments into one molecular compound was developed through the transformation of dicyanamide ionic salts. In return, compounds 4–11 were synthesized, and fully characterized by IR, MS, NMR and elemental analysis. Meanwhile, the structures of compounds 4, 8 and 11 were confirmed by X-ray crystal diffraction. Detailed reaction mechanisms were studied through accurate calculations on the reaction energy profiles of the azolium cations and DCA anion, which revealed the essence of the transformation proceeding. Meanwhile, compound 8 exhibits excellent hypergolic property, which could be potentially novel molecular hypergolic fuel. PMID:26039324

  8. Solid-state Reaction of Azolium Hydrohalogen Salts with Silver Dicyanamide - Unexpected Formation of Cyanoguanidine-azoles, Reaction Mechanism and Their Hypergolic Properties

    NASA Astrophysics Data System (ADS)

    Liu, Wei; Lin, Qiu-Han; Li, Yu-Chuan; Chen, Peng-Wan; Fang, Tao; Zhang, Ru-Bo; Pang, Si-Ping

    2015-06-01

    Cyanoguanidines as well as azoles are important bioactive groups, which play an important role in the medical application; meanwhile, the high nitrogen content makes them excellent backbones for energetic materials. A Novel and simple method that combined these two fragments into one molecular compound was developed through the transformation of dicyanamide ionic salts. In return, compounds 4-11 were synthesized, and fully characterized by IR, MS, NMR and elemental analysis. Meanwhile, the structures of compounds 4, 8 and 11 were confirmed by X-ray crystal diffraction. Detailed reaction mechanisms were studied through accurate calculations on the reaction energy profiles of the azolium cations and DCA anion, which revealed the essence of the transformation proceeding. Meanwhile, compound 8 exhibits excellent hypergolic property, which could be potentially novel molecular hypergolic fuel.

  9. The effect of water on the solid state characteristics of pharmaceutical excipients: Molecular mechanisms, measurement techniques, and quality aspects of final dosage form

    PubMed Central

    Szakonyi, Gergely; Zelkó, Romána

    2012-01-01

    In this paper we give an overview about the interaction of water molecules with pharmaceutical excipients. Most of these excipients are amorphous or partially amorphous polymers and their characteristics are very sensitive to the water content. In the course of the manufacturing processes water sorption is possible, therefore in some cases it is important to strictly control the residual moisture content of a dosage form. There are several mechanisms of water sorption, like water is able to bind to polar groups of hygroscopic excipients and could also exist in the capillary system of amorphous excipients. Several techniques are available to characterise the states of water inside the materials and the effects of residual water on polymers. For this purpose water sorption measurements, differential scanning calorimetry and the Fourier-transform infrared spectroscopy are reviewed. The importance of water content and storage conditions of pharmaceuticals on the properties of the final dosage forms are also demonstrated with practical examples. PMID:23071956

  10. Mechanism on heavy metals vaporization from municipal solid waste fly ash by MgCl2⋅6H2O.

    PubMed

    Yu, Jie; Sun, Lushi; Ma, Chuan; Qiao, Yu; Xiang, Jun; Hu, Song; Yao, Hong

    2016-03-01

    This work aims to study the mechanism of heavy metals vaporization by MgCl2⋅6H2O. Firstly, the decomposition mechanism of MgCl2⋅6H2O was investigated by thermodynamic equilibrium calculations, XRD and TG. Upon heating, MgCl2⋅6H2O went through the processes of dehydration and hydrolysis simultaneously accompanied by the release of HCl between 150 and 500°C. At temperature higher than 500°C, Mg(OH)Cl gradually release part of HCl. MgCl2⋅6H2O followed the similar processes of decomposition at both oxidative and reductive atmospheres. In oxidative atmosphere, vaporization of Zn and Cu was significantly accelerated by MgCl2⋅6H2O. However, in inert atmosphere, vaporization of Cu was not promoted since copper chloride was only stable in oxidative atmosphere. Under slow heating condition, vaporization of heavy metals were close to that under fast heating condition. This may be partially attributed to that most heavy metals already reacted with HCl forming metal chlorides below 500°C, which can be vaporized at higher temperature. Moreover, the Mg(OH)Cl contributed to release HCl up to 800°C. At such high temperature, the metal chlorides continue to be formed and then vaporized. After treatment, the leaching concentration of heavy metals from treated fly ashes were much lower than that from raw fly ash and met the regulatory limit of leachate. Since a large amount of MgSiO3 were formed during thermal treatment, the fly ash treated with MgCl2⋅6H2O can be used as raw materials for glass-ceramics production. PMID:26748437

  11. Solid lipid nanoparticles (SLN) of Efavirenz as lymph targeting drug delivery system: Elucidation of mechanism of uptake using chylomicron flow blocking approach.

    PubMed

    Makwana, Vivek; Jain, Rashmi; Patel, Komal; Nivsarkar, Manish; Joshi, Amita

    2015-11-10

    The aim of the present work was to develop a lymph targeted SLN formulation of antiretroviral (ARV) drug and to have an understanding of its underlying mechanism of uptake by the lymphatics. The lymphatics are the inaccessible reservoirs of HIV in human body. Efavirenz (EFV) is a BCS class II, ARV drug that undergoes extensive first pass metabolism. The EFV SLN formulation was prepared using Gelucire 44/14, Compritol 888 ATO, Lipoid S 75 and Poloxamer 188 by hot homogenization technique followed by ultrasonication method, with mean particle size of 168 nm, polydispersity index (PDI) <0.220, and mean zeta potential of -35.55 mV. DSC and XRPD studies revealed change in crystallinity index of drug when incorporated into SLN. In vitro drug release was found to be prolonged and biphasic in PBS pH 6.8. There was no significant change in the mean particle size, PDI, zeta potential and entrapment efficiency of EFV SLN after storage at 30 ± 2°C/60 ± 5%RH for two months. The results from lymphatic transport and tissue distribution study indicate that a significant part of the EFV had by-passed portal system and was recovered in the lymph via chylomicron uptake mechanism. Reduction in the amount (44.70%) of the EFV reaching to liver indicates that major amount of EFV bypasses the liver and thereby, enhances the oral bioavailability of the EFV. A significant amount of EFV was found in spleen, a major lymphatic organ. EFV SLN seems to have potential to target the ARV to lymphatics for the better management of HIV. PMID:26367780

  12. Direct observation of the nucleation in colloidal solid-solid transitions

    NASA Astrophysics Data System (ADS)

    Peng, Yi; Wang, Feng; Wang, Ziren; Han, Yilong

    2013-03-01

    Solid-solid phase transitions are ubiquitous in nature, but their microscopic mechanisms remain poorly understood. We employed thermally sensitive microgels to study the solid-solid transitions between square and triangular lattices in colloidal thin films. Two types of nucleation processes were directly observed by video microscopy and studied at the single-particle level. Under low flow rates, the nucleation is a two-step process: square lattice --> liquid nucleus --> triangle nucleus and its precursor is a local particle-exchange loop, whereas under high flow rates the nucleus of the triangle lattice forms directly from a dislocation pair by a martensitic mechanism. We measured the critical nucleus size, the energy barrier height and the hysteresis loop of the solid-solid transitions. Our results cast new light to solid-solid transitions in carbon systems, nano-crystals and geophysics. Hong Kong GRC grants 601208 and 601911

  13. Excited state kinetics in crystalline solids: self-quenching in nanocrystals of 4,4'-disubstituted benzophenone triplets occurs by a reductive quenching mechanism.

    PubMed

    Kuzmanich, Gregory; Simoncelli, Sabrina; Gard, Matthew N; Spänig, Fabian; Henderson, Bryana L; Guldi, Dirk M; Garcia-Garibay, Miguel A

    2011-11-01

    We report an efficient triplet state self-quenching mechanism in crystals of eight benzophenones, which included the parent structure (1), six 4,4'-disubstituted compounds with NH(2) (2), NMe(2) (3), OH (4), OMe (5), COOH (6), and COOMe (7), and benzophenone-3,3',4,4'-tetracarboxylic dianhydride (8). Self-quenching effects were determined by measuring their triplet-triplet lifetimes and spectra using femtosecond and nanosecond transient absorption measurements with nanocrystalline suspensions. When possible, triplet lifetimes were confirmed by measuring the phosphorescence lifetimes and with the help of diffusion-limited quenching with iodide ions. We were surprised to discover that the triplet lifetimes of substituted benzophenones in crystals vary over 9 orders of magnitude from ca. 62 ps to 1 ms. In contrast to nanocrystalline suspensions, the lifetimes in solution only vary over 3 orders of magnitude (1-1000 μs). Analysis of the rate constants of quenching show that the more electron-rich benzophenones are the most efficiently deactivated such that there is an excellent correlation, ρ = -2.85, between the triplet quenching rate constants and the Hammet σ(+) values for the 4,4' substituents. Several crystal structures indicate the existence of near-neighbor arrangements that deviate from the proposed ideal for "n-type" quenching, suggesting that charge transfer quenching is mediated by a relatively loose arrangement. PMID:21936539

  14. Solid inflation

    SciTech Connect

    Endlich, Solomon; Nicolis, Alberto; Wang, Junpu E-mail: nicolis@phys.columbia.edu

    2013-10-01

    We develop a cosmological model where primordial inflation is driven by a 'solid', defined as a system of three derivatively coupled scalar fields obeying certain symmetries and spontaneously breaking a certain subgroup of these. The symmetry breaking pattern differs drastically from that of standard inflationary models: time translations are unbroken. This prevents our model from fitting into the standard effective field theory description of adiabatic perturbations, with crucial consequences for the dynamics of cosmological perturbations. Most notably, non-gaussianities in the curvature perturbations are unusually large, with f{sub NL} ∼ 1/(εc{sub s}{sup 2}), and have a novel shape: peaked in the squeezed limit, with anisotropic dependence on how the limit is approached. Other unusual features include the absence of adiabatic fluctuation modes during inflation — which does not impair their presence and near scale-invariance after inflation — and a slightly blue tilt for the tensor modes.

  15. Computational mechanics

    SciTech Connect

    Goudreau, G.L.

    1993-03-01

    The Computational Mechanics thrust area sponsors research into the underlying solid, structural and fluid mechanics and heat transfer necessary for the development of state-of-the-art general purpose computational software. The scale of computational capability spans office workstations, departmental computer servers, and Cray-class supercomputers. The DYNA, NIKE, and TOPAZ codes have achieved world fame through our broad collaborators program, in addition to their strong support of on-going Lawrence Livermore National Laboratory (LLNL) programs. Several technology transfer initiatives have been based on these established codes, teaming LLNL analysts and researchers with counterparts in industry, extending code capability to specific industrial interests of casting, metalforming, and automobile crash dynamics. The next-generation solid/structural mechanics code, ParaDyn, is targeted toward massively parallel computers, which will extend performance from gigaflop to teraflop power. Our work for FY-92 is described in the following eight articles: (1) Solution Strategies: New Approaches for Strongly Nonlinear Quasistatic Problems Using DYNA3D; (2) Enhanced Enforcement of Mechanical Contact: The Method of Augmented Lagrangians; (3) ParaDyn: New Generation Solid/Structural Mechanics Codes for Massively Parallel Processors; (4) Composite Damage Modeling; (5) HYDRA: A Parallel/Vector Flow Solver for Three-Dimensional, Transient, Incompressible Viscous How; (6) Development and Testing of the TRIM3D Radiation Heat Transfer Code; (7) A Methodology for Calculating the Seismic Response of Critical Structures; and (8) Reinforced Concrete Damage Modeling.

  16. Polymer-assisted photogeneration of metal nanoparticles in fluids and within elastic solid matrices: Characterization, mechanism of formation and direct photopatterning

    NASA Astrophysics Data System (ADS)

    Korchev, Andriy S.

    Efficient light-induced formation of metal particles in polymers is a required first step in efforts to develop photoadaptive polymer films and fibers. This process is also relevant to the preparation of metallized plastics, which are of technological significance in a number of areas including the automotive, microcircuitry and space industries. A novel method for controlled photogeneration of metal nanocrystallites in solutions and within flexible polymer films has been developed and reported herein. It has been shown that excitation (lambda = 350 nm) of the matrices containing sulphonated poly(ether ether ketone) and poly(vinyl alcohol) has resulted in the formation of long-lived polymeric ketyl radicals able to reduce efficiently metal ions such as Ag(I), Au(III) and Cu(II). Concurrently, the generated metallic crystallites are stabilized from uncontrolled growth by the polymers, yielding nanosized metallic dispersions. Generation of polymeric radicals, formation of metal nanoparticles and photodegradation of polymer films were characterized with UV-Vis, FT-IR, EPR/ENDOR, XPS and TEM techniques. Systematic studies on the factors influencing the rates of photoreduction (concentrations of metal complexes and of polymer components, solution pH, light intensity and temperature) were employed to determine the kinetics of metal formation in aqueous solutions and in polymer films. A mechanism for the polymer-assisted metal nanoparticle photogeneration has been proposed that is consistent with the experimental data. From a practical point of view, the photochemical method developed in this investigation has permitted direct metal photopatterning of polymer film surfaces with mild UV photons using a conventional lithographic mask. In addition, a fluorescence scanning microscopic procedure has been found to be useful not only to obtain information about the spatial arrangement of the patterned regions of the films, but also to study the dynamics of metal generation.

  17. In situ Raman spectroscopic analysis of the coking resistance mechanism on SrZr0.95Y0.05O3-x surface for solid oxide fuel cell anodes

    NASA Astrophysics Data System (ADS)

    Nagasawa, Tsuyoshi; Chen, Dongchang; Lai, Samson Yuxiu; Liu, Meilin; Hanamura, Katsunori

    2016-08-01

    While the coking resistance of Ni/yttria-stabilized zirconia (YSZ) anodes in solid oxide fuel cells (SOFCs) toward hydrocarbon fuel can be improved by adding SrZr0.95Y0.05O3-x (SZY) as a proton conductor, the exact mechanism is still unclear. In this study, the surface chemistry of SZY is investigated using in situ Raman spectroscopy to clarify the coking resistance mechanism. Upon exposure to dry propane at 500 °C, the intensity of the Raman peaks corresponding to sbnd CO3 species decreases with time, suggesting that the surface-located sbnd CO3 groups are consumed through a reaction with deposited carbon or dry reforming of propane, which reduces the tendency of coking. These consumed sbnd CO3 groups can then be regenerated through a reaction between water vapor and deposited carbon. The presence of adsorbed water on SZY, which facilitates a carbon removal reaction and the steam reforming of propane, is confirmed by thermogravimetric analysis (TGA). The reactivity of the sbnd CO3 groups and the adsorbed water on SZY thus contribute to removing deposited carbon, resulting in the improved coking resistance of Ni/YSZ-SZY anode.

  18. In situ Raman spectroscopic analysis of the coking resistance mechanism on SrZr0.95Y0.05O3-x surface for solid oxide fuel cell anodes

    NASA Astrophysics Data System (ADS)

    Nagasawa, Tsuyoshi; Chen, Dongchang; Lai, Samson Yuxiu; Liu, Meilin; Hanamura, Katsunori

    2016-08-01

    While the coking resistance of Ni/yttria-stabilized zirconia (YSZ) anodes in solid oxide fuel cells (SOFCs) toward hydrocarbon fuel can be improved by adding SrZr0.95Y0.05O3-x (SZY) as a proton conductor, the exact mechanism is still unclear. In this study, the surface chemistry of SZY is investigated using in situ Raman spectroscopy to clarify the coking resistance mechanism. Upon exposure to dry propane at 500 °C, the intensity of the Raman peaks corresponding to sbnd CO3 species decreases with time, suggesting that the surface-located sbnd CO3 groups are consumed through a reaction with deposited carbon or dry reforming of propane, which reduces the tendency of coking. These consumed sbnd CO3 groups can then be regenerated through a reaction between water vapor and deposited carbon. The presence of adsorbed water on SZY, which facilitates a carbon removal reaction and the steam reforming of propane, is confirmed by thermogravimetric analysis (TGA). The reactivity of the sbnd CO3 groups and the adsorbed water on SZY thus contribute to removing deposited carbon, resulting in the improved coking resistance of Ni/YSZ-SZY anode.

  19. Growth of fullerene-like carbon nitride thin solid films by reactive magnetron sputtering; role of low-energy ion irradiation in determining microstructure and mechanical properties

    NASA Astrophysics Data System (ADS)

    Neidhardt, J.; Czigány, Zs.; Brunell, I. F.; Hultman, L.

    2003-03-01

    structures define the mechanical response of the films as revealed by nano-indentation. The material is highly elastic and fracture tough, and has reasonable hardness and elastic modulus values. On a nano-structured level, it is inferred the CNx stores deformation energy elastically by compression of the interplanar lattice spacing and buckling of the sheets, while crosslinks between sheets prevent gliding. Increasing the bias voltage from -25 to -40 V multiplies hardness and modulus values, while keeping their high ratio of up to 0.2, due to a higher degree of cross-linking.

  20. Radiation sensitive solid state switch

    NASA Technical Reports Server (NTRS)

    Hutto, R. J. (Inventor)

    1973-01-01

    A mechanically operable solid state switch suited for use in achieving a variable circuit-switching function is described. This switch is characterized by an annular array of photoresponsive switching devices, disposed in communication with an included source of radiation, and a plurality of interchangeable, mechanically operable interrupter disks. Each disk has a predetermined pattern of transparent and opaque portions. Operative displacement of each disk serves to make and break selected electrical circuits through the photo responsive devices of said array.

  1. Photoinduced and thermal denitrogenation of bulky triazoline crystals: insights into solid-to-solid transformation.

    PubMed

    de Loera, Denisse; Stopin, Antoine; Garcia-Garibay, Miguel A

    2013-05-01

    The photoinduced and thermal denitrogenation of crystalline triazolines with bulky substituents leads to the quantitative formation of aziridines in clean solid-to-solid reactions despite very large structural changes in the transition from reactant to product. Analysis of the reaction progress by powder X-ray diffraction, solid-state (13)C CPMAS NMR, solid-state FTIR spectroscopy, and thermal analysis has revealed that solid-to-solid reactions proceed either through metastable phases susceptible to amorphization or by mechanisms that involve a reconstructive phase transition that culminates in the formation of the stable phase of the product. While the key for a solid-to-solid transformation is that the reaction occurs below the eutectic temperature of the reactant and product two-component system, experimental evidence suggests that those reactions will undergo a reconstructive phase transition when they take place above the glass transition temperature. PMID:23547729

  2. Synthesis, characterization and mechanical properties of NiO - GDC20 (Ce0.8Gd0.2O1.9) nano composite anode for solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Reddy, M. Narsimha; Rao, P. Vijaya Bhaskar; Sharma, R. K.

    2016-05-01

    In the present research work, X (NiO) +1-X(Ce0.8Gd0.2O1.9) where X = 30,40 and 45 wt% Nano Composite Anodes are synthesized for low temperature operating solid oxide fuel cells (SOFC). NiO and Ce0.8Gd0.2O1.9 (GDC20) are synthesized by sol-gel citrate method and the nanopowders of NiO, GDC20 were calcined from 650 °c to 750 °c. For anode materials, pelletized the nanocomposites of X(NiO)+ (1-X) GDC20 (X = 30,40,45 wt.%) and sintered at 1200 °c. systematic study of atomic structure, purity, phase and structural parameters such as Lattice parameters, crystallite size of as-synthesized nanopowders and anode materials were carried out by XRD and SEM. For mechanical strength, Vickers micro-hardness of anode composites were estimated and observed that micro-hardness of composites were increasing with NiO wt.% and the density of sintered samples, which is varying from 4.35 to 5.54 Gpa at 500g load.

  3. Fluctuation of dissolved heavy metal concentrations in the leachate from anaerobic digestion of municipal solid waste in commercial scale landfill bioreactors: The effect of pH and associated mechanisms.

    PubMed

    Xie, S; Ma, Y; Strong, P J; Clarke, W P

    2015-12-15

    Heavy metals present in landfill leachate have infrequently been related to complete anaerobic degradation municipal solid waste (MSW) due to discrete ages of deposited MSW layers and leachate channelling in landfills. In this study, anaerobic digestion of MSW was performed in two enclosed 1000 tonne bioreactors using a unique flood and drain process. Leachates were characterised in terms of pH, soluble chemical oxygen demand, volatile fatty acids (VFAs), ammonium nitrogen and heavy metals over the entire course of digestion. All parameters, including pH, fluctuated during acidogenesis, acetogenesis and methanogenesis, which strongly impacted on the dynamics of dissolved heavy metal concentrations. The simulation of dissolution and precipitation processes indicated that metal sulphide precipitation was not a factor as metal concentrations exceeded solubility limits. The correlation of pH and dissolved heavy metal concentrations indicated that other, mechanisms were involved in the homogenised conditions within the bioreactors. Beside dissolution and precipitation, the main processes most likely involved in metal distributions were adsorption (Zn, Cu, Ni, Pb and Cd), complexation (Cr) or combinations of both process (As and Co). PMID:26259097

  4. Research in nonlinear structural and solid mechanics

    NASA Technical Reports Server (NTRS)

    Mccomb, H. G., Jr. (Compiler); Noor, A. K. (Compiler)

    1980-01-01

    Nonlinear analysis of building structures and numerical solution of nonlinear algebraic equations and Newton's method are discussed. Other topics include: nonlinear interaction problems; solution procedures for nonlinear problems; crash dynamics and advanced nonlinear applications; material characterization, contact problems, and inelastic response; and formulation aspects and special software for nonlinear analysis.

  5. Mechanism of combustion of solid carbon

    NASA Technical Reports Server (NTRS)

    Degraaf, J. G. A.

    1978-01-01

    Measurements of temperature distribution in the reaction zone above the surface of carbon were studied. Using a method of spectral line reversal it was found that the minimum temperature in that zone is several hundred degrees higher than that of the carbon surface.

  6. Solid Propellant Grain Structural Integrity Analysis

    NASA Technical Reports Server (NTRS)

    1973-01-01

    The structural properties of solid propellant rocket grains were studied to determine the propellant resistance to stresses. Grain geometry, thermal properties, mechanical properties, and failure modes are discussed along with design criteria and recommended practices.

  7. Solid state and dynamic solution structures of O-carbamidine amidoximes gives further insight into the mechanism of zinc(II)-mediated generation of 1,2,4-oxadiazoles

    NASA Astrophysics Data System (ADS)

    Kulish, Kirill I.; Novikov, Alexander S.; Tolstoy, Peter M.; Bolotin, Dmitrii S.; Bokach, Nadezhda A.; Zolotarev, Andrey A.; Kukushkin, Vadim Yu.

    2016-05-01

    Three new iminium salts [H2Ndbnd C(R)ONdbnd C(R‧)NH2](p-TolSO3)·½H2O ([1-3](p-TolSO3)·½H2O; R/R‧ = NMe2/PhCH21, NMe2/p-BrC6H42, N(CH2)5/p-BrC6H43) were synthesized via ZnII-mediated amidoxime-cyanamide coupling and their solid structures were studied by X-ray diffraction. Solution structure and conformational changes of [1-3](p-TolSO3)·½H2O were studied by dynamic NMR. The obtained quantitative data were supported by DFT calculations. All the obtained results help to understand the relative stability of the salts [H2Ndbnd C(R)ONdbnd C(R‧)NH2](X) (R = NAlk2, Alk, Ar) and give a further insight into the mechanism of ZnII-mediated generation of 1,2,4-oxadiazoles. The electron delocalization and sesquialteral bonds in the [H2Ndbnd C(NR2)ONdbnd C(R‧)NH2]+ system was recognized by estimation of values of activation energy barriers (14-18 kcal/mol by DNMR and 16-17 kcal/mol by DFT calculations) for the rotation around the CN bonds for the NR2 groups and inspection of the solid-state X-ray data along with the Wiberg bond indices (intermediate single/double bond order for the CN distances). This electron delocalization is responsible for the stabilization of the positively charged iminium cation. The moderate strength hydrogen bonding between the oxime N atom and the =NH2 group, which is verified from the X-ray, DNMR experiments, and by using quantum chemical calculations, stabilizes the iminium salt, but it is still weak to prevent the heterocyclization. Theoretical calculations of the heterocyclization of [H2Ndbnd C(R)ONdbnd C(R‧)NH2]+ to 1,2,4-oxadiazoles demonstrated that it is kinetically hindered to a greater extent for R = NAlk2 and this explains their lower reactivity as compared to the iminium salts with R = Alk, Ar.

  8. Solid evacuated microspheres of hydrogen

    DOEpatents

    Turnbull, Robert J.; Foster, Christopher A.; Hendricks, Charles D.

    1982-01-01

    A method is provided for producing solid, evacuated microspheres comprised of hydrogen. The spheres are produced by forming a jet of liquid hydrogen and exciting mechanical waves on the jet of appropriate frequency so that the jet breaks up into drops with a bubble formed in each drop by cavitation. The drops are exposed to a pressure less than the vapor pressure of the liquid hydrogen so that the bubble which is formed within each drop expands. The drops which contain bubbles are exposed to an environment having a pressure just below the triple point of liquid hydrogen and they thereby freeze giving solid, evacuated spheres of hydrogen.

  9. SolidShperal

    2013-12-22

    SolidSpheral is an extension of the Spheral open source meshless hydrodynamics method. SolidSpheral adds the capability to model solid materials using analytic equations of state, and a simple damage model to allow for the modeled materials to undergo dynamic damage evolution. SolidSpheral is a distributed parallel code employing MPI for the parallel framework.

  10. Solids fluidizer-injector

    DOEpatents

    Bulicz, Tytus R.

    1990-01-01

    An apparatus and process for fluidizing solid particles by causing rotary motion of the solid particles in a fluidizing chamber by a plurality of rotating projections extending from a rotatable cylinder end wall interacting with a plurality of fixed projections extending from an opposite fixed end wall and passing the solid particles through a radial feed orifice open to the solids fluidizing chamber on one side and a solid particle utilization device on the other side. The apparatus and process are particularly suited for obtaining intermittent feeding with continual solids supply to the fluidizing chamber. The apparatus and process are suitable for injecting solid particles, such as coal, to an internal combustion engine.

  11. Modern solid state laser materials

    SciTech Connect

    Krupke, W.F.

    1984-06-20

    This document contains visual aids used in an invited talk entitled Modern Solid State Laser Materials, presented at the Conference on Lasers and Electro-Optics (CLEO) held in Anaheim, California, on June 20, 1984. Interest at LLNL in solid state lasers focuses on evaluating the potential of solid state laser media for high average power applications, including inertial fusion power production. This talk identifies the relevant bulk material parameters characterizing average power capacity and uses chromium and neodymium co-doped gadolinium scandium gallium garnet (Nd:Cr:GSGG) as an example of a laser material with improved laser properties relative to Nd:YAG (plausible large-scale growth, more efficient spectral coupling to xenon flashlamp radiation, reduced stimulated emission cross section, adequate thermal shock and optical damage threshold parameters, etc.). Recently measured spectroscopic, kinetic, and thermo-mechanical properties of Nd:Cr:GSGG are given.

  12. Solids mass flow determination

    DOEpatents

    Macko, Joseph E.

    1981-01-01

    Method and apparatus for determining the mass flow rate of solids mixed with a transport fluid to form a flowing mixture. A temperature differential is established between the solids and fluid. The temperature of the transport fluid prior to mixing, the temperature of the solids prior to mixing, and the equilibrium temperature of the mixture are monitored and correlated in a heat balance with the heat capacities of the solids and fluid to determine the solids mass flow rate.

  13. A modified liquid-phase-assisted sintering mechanism for La0.8Sr0.2Cr1-xFexO3-δ-A high density, redox-stable perovskite interconnect for solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Wei, Tao; Liu, Xiaojuan; Yuan, Chun; Gao, Qingyu; Xin, Xianshuang; Wang, Shaorong

    2014-03-01

    Fe-doped lanthanum strontium chromites, i.e., La0.8Sr0.2Cr1-xFexO3-δ (x = 0.1, 0.2, 0.3, 0.4, and 0.5), are synthesised and evaluated as potential interconnect materials for SOFCs. A modified liquid-phase-assisted sintering mechanism is employed to improve the sintering abilities of La0.8Sr0.2Cr1-xFexO3-δ powders. A distinct transient liquid phase forms during the sintering process, which spreads into a uniform layer and covers the grain boundaries, thereby enhancing densification. Additionally, it is determined that the amount of liquid phase formed during liquid-phase-assisted sintering significantly affects the densification of doped lanthanum chromites. Relative densities of 94.6% and 96.6% are successfully obtained for La0.8Sr0.2Cr0.6Fe0.4O3-δ and La0.8Sr0.2Cr0.5Fe0.5O3-δ, respectively. Furthermore, these compounds are also redox-stable after being heated to 900 °C in flowing H2 for 6 h. The electrical conductivity increases with Fe-doping levels, and the conductivity of La0.8Sr0.2Cr0.5Fe0.5O3-δ is measured to be 21.88 S cm-1 in air and 6.45 S cm-1 in 5% H2/Ar at 800 °C. Therefore, dense La0.8Sr0.2Cr0.5Fe0.5O3-δ is a promising interconnect alternative for solid oxide fuel cells.

  14. Solid state power controllers

    NASA Technical Reports Server (NTRS)

    Gibbs, R. S.

    1973-01-01

    The rationale, analysis, design, breadboarding and testing of the incremental functional requirements are reported that led to the development of prototype 1 and 5 Amp dc and 1 Amp ac solid state power controllers (SSPC's). The SSPC's are to be considered for use as a replacement of electro-mechanical relays and circuit breakers in future spacecraft and aircraft. They satisfy the combined function of both the relay and circuit breaker and can be remotely controlled by small signals, typically 10 mA, 5 to 28 Vdc. They have the advantage over conventional relay/circuit breaker systems in that they can be located near utilization equipment and the primary ac or dc bus. The low level control, trip indication and status signals can be circuited by small guage wire for control, computer interface, logic, electrical multiplexing, unboard testing, and power management and distribution purposes. This results in increased system versatility at appreciable weight saving and increased reliability.

  15. Solid state television camera

    NASA Technical Reports Server (NTRS)

    1976-01-01

    The design, fabrication, and tests of a solid state television camera using a new charge-coupled imaging device are reported. An RCA charge-coupled device arranged in a 512 by 320 format and directly compatible with EIA format standards was the sensor selected. This is a three-phase, sealed surface-channel array that has 163,840 sensor elements, which employs a vertical frame transfer system for image readout. Included are test results of the complete camera system, circuit description and changes to such circuits as a result of integration and test, maintenance and operation section, recommendations to improve the camera system, and a complete set of electrical and mechanical drawing sketches.

  16. Effects of Solid-Liquid Mixing on Microstructure of Semi-Solid A356 Aluminum Alloy

    NASA Astrophysics Data System (ADS)

    Guo, H. M.; Wang, L. J.; Wang, Q.; Yang, X. J.

    2014-08-01

    The desired starting material for semi-solid processing is the semi-solid slurry in which the solid phase is present as fine and globular particles. A modified solid-liquid mixing (SLM) is reported wherein semi-solid slurry can be produced by mixing a solid alloy block into a liquid alloy, and mechanical vibration is utilized to enhance the mixing. Effects such as liquid alloy temperature, mass ratio, and mixing intensity on the microstructure and the cooling curves during SLM were evaluated. 2D and 3D microstructure analysis of treated A356 aluminum alloy shows that microstructure can be refined significantly with a considerable morphology change in primary Al phase. It is critical that the temperature of mixture after mixing is lower than its liquidus temperature to obtain a valid SLM process. Specially, mixing intensity is identified as a primary factor for a favorable microstructure of semi-solid slurry.

  17. Multicellular Streaming in Solid Tumours

    NASA Astrophysics Data System (ADS)

    Kas, Josef

    As early as 400 BCE, the Roman medical encyclopaedist Celsus recognized that solid tumours are stiffer than surrounding tissue. However, cancer cell lines are softer, and softer cells facilitate invasion. This paradox raises several questions: Does softness emerge from adaptation to mechanical and chemical cues in the external microenvironment, or are soft cells already present inside a primary solid tumour? If the latter, how can a more rigid tissue contain more soft cells? Here we show that in primary tumour samples from patients with mammary and cervix carcinomas, cells do exhibit a broad distribution of rigidities, with a higher fraction of softer and more contractile cells compared to normal tissue. Mechanical modelling based on patient data reveals that, surprisingly, tumours with a significant fraction of very soft cells can still remain rigid. Moreover, in tissues with the observed distributions of cell stiffnesses, softer cells spontaneously self-organize into lines or streams, possibly facilitating cancer metastasis.

  18. Path-integral simulation of solids.

    PubMed

    Herrero, C P; Ramírez, R

    2014-06-11

    The path-integral formulation of the statistical mechanics of quantum many-body systems is described, with the purpose of introducing practical techniques for the simulation of solids. Monte Carlo and molecular dynamics methods for distinguishable quantum particles are presented, with particular attention to the isothermal-isobaric ensemble. Applications of these computational techniques to different types of solids are reviewed, including noble-gas solids (helium and heavier elements), group-IV materials (diamond and elemental semiconductors), and molecular solids (with emphasis on hydrogen and ice). Structural, vibrational, and thermodynamic properties of these materials are discussed. Applications also include point defects in solids (structure and diffusion), as well as nuclear quantum effects in solid surfaces and adsorbates. Different phenomena are discussed, as solid-to-solid and orientational phase transitions, rates of quantum processes, classical-to-quantum crossover, and various finite-temperature anharmonic effects (thermal expansion, isotopic effects, electron-phonon interactions). Nuclear quantum effects are most remarkable in the presence of light atoms, so that especial emphasis is laid on solids containing hydrogen as a constituent element or as an impurity. PMID:24810944

  19. Model the Deformation and Failure of Solids

    2001-10-19

    EMU models the deformation and failure of solids based on a reformulated theory of continuum mechanics known as the Peridynamic model. This approach allows dynamic fracture and other failure mechanisms to be simulated with a minimum of mesh effeces and without a need for supplementary kinetic relations for crack growth. Penetration by a rigid projectile is also included in the code.

  20. Laser cooling of solids

    SciTech Connect

    Epstein, Richard I; Sheik-bahae, Mansoor

    2008-01-01

    We present an overview of solid-state optical refrigeration also known as laser cooling in solids by fluorescence upconversion. The idea of cooling a solid-state optical material by simply shining a laser beam onto it may sound counter intuitive but is rapidly becoming a promising technology for future cryocooler. We chart the evolution of this science in rare-earth doped solids and semiconductors.

  1. ROTARY BULK SOLIDS DIVIDER

    DOEpatents

    Maronde, Carl P.; Killmeyer JR., Richard P.

    1992-03-03

    An apparatus for the disbursement of a bulk solid sample comprising, a gravity hopper having a top open end and a bottom discharge end, a feeder positioned beneath the gravity hopper so as to receive a bulk solid sample flowing from the bottom discharge end, and a conveyor receiving the bulk solid sample from the feeder and rotating on an axis that allows the bulk solid sample to disperse the sample to a collection station.

  2. Rotary bulk solids divider

    DOEpatents

    Maronde, Carl P.; Killmeyer, Jr., Richard P.

    1992-01-01

    An apparatus for the disbursement of a bulk solid sample comprising, a gravity hopper having a top open end and a bottom discharge end, a feeder positioned beneath the gravity hopper so as to receive a bulk solid sample flowing from the bottom discharge end, and a conveyor receiving the bulk solid sample from the feeder and rotating on an axis that allows the bulk solid sample to disperse the sample to a collection station.

  3. Overhauser effects in insulating solids

    NASA Astrophysics Data System (ADS)

    Can, T. V.; Caporini, M. A.; Mentink-Vigier, F.; Corzilius, B.; Walish, J. J.; Rosay, M.; Maas, W. E.; Baldus, M.; Vega, S.; Swager, T. M.; Griffin, R. G.

    2014-08-01

    We report magic angle spinning, dynamic nuclear polarization (DNP) experiments at magnetic fields of 9.4 T, 14.1 T, and 18.8 T using the narrow line polarizing agents 1,3-bisdiphenylene-2-phenylallyl (BDPA) dispersed in polystyrene, and sulfonated-BDPA (SA-BDPA) and trityl OX063 in glassy glycerol/water matrices. The 1H DNP enhancement field profiles of the BDPA radicals exhibit a significant DNP Overhauser effect (OE) as well as a solid effect (SE) despite the fact that these samples are insulating solids. In contrast, trityl exhibits only a SE enhancement. Data suggest that the appearance of the OE is due to rather strong electron-nuclear hyperfine couplings present in BDPA and SA-BDPA, which are absent in trityl and perdeuterated BDPA (d21-BDPA). In addition, and in contrast to other DNP mechanisms such as the solid effect or cross effect, the experimental data suggest that the OE in non-conducting solids scales favorably with magnetic field, increasing in magnitude in going from 5 T, to 9.4 T, to 14.1 T, and to 18.8 T. Simulations using a model two spin system consisting of an electron hyperfine coupled to a 1H reproduce the essential features of the field profiles and indicate that the OE in these samples originates from the zero and double quantum cross relaxation induced by fluctuating hyperfine interactions between the intramolecular delocalized unpaired electrons and their neighboring nuclei, and that the size of these hyperfine couplings is crucial to the magnitude of the enhancements. Microwave power dependent studies show that the OE saturates at considerably lower power levels than the solid effect in the same samples. Our results provide new insights into the mechanism of the Overhauser effect, and also provide a new approach to perform DNP experiments in chemical, biophysical, and physical systems at high magnetic fields.

  4. Overhauser effects in insulating solids

    SciTech Connect

    Can, T. V.; Corzilius, B.; Walish, J. J.; Griffin, R. G.; Caporini, M. A.; Rosay, M.; Maas, W. E.; Mentink-Vigier, F.; Vega, S.; Baldus, M.; Swager, T. M.

    2014-08-14

    We report magic angle spinning, dynamic nuclear polarization (DNP) experiments at magnetic fields of 9.4 T, 14.1 T, and 18.8 T using the narrow line polarizing agents 1,3-bisdiphenylene-2-phenylallyl (BDPA) dispersed in polystyrene, and sulfonated-BDPA (SA-BDPA) and trityl OX063 in glassy glycerol/water matrices. The {sup 1}H DNP enhancement field profiles of the BDPA radicals exhibit a significant DNP Overhauser effect (OE) as well as a solid effect (SE) despite the fact that these samples are insulating solids. In contrast, trityl exhibits only a SE enhancement. Data suggest that the appearance of the OE is due to rather strong electron-nuclear hyperfine couplings present in BDPA and SA-BDPA, which are absent in trityl and perdeuterated BDPA (d{sub 21}-BDPA). In addition, and in contrast to other DNP mechanisms such as the solid effect or cross effect, the experimental data suggest that the OE in non-conducting solids scales favorably with magnetic field, increasing in magnitude in going from 5 T, to 9.4 T, to 14.1 T, and to 18.8 T. Simulations using a model two spin system consisting of an electron hyperfine coupled to a {sup 1}H reproduce the essential features of the field profiles and indicate that the OE in these samples originates from the zero and double quantum cross relaxation induced by fluctuating hyperfine interactions between the intramolecular delocalized unpaired electrons and their neighboring nuclei, and that the size of these hyperfine couplings is crucial to the magnitude of the enhancements. Microwave power dependent studies show that the OE saturates at considerably lower power levels than the solid effect in the same samples. Our results provide new insights into the mechanism of the Overhauser effect, and also provide a new approach to perform DNP experiments in chemical, biophysical, and physical systems at high magnetic fields.

  5. Overhauser effects in insulating solids

    PubMed Central

    Can, T. V.; Caporini, M. A.; Mentink-Vigier, F.; Corzilius, B.; Walish, J. J.; Rosay, M.; Maas, W. E.; Baldus, M.; Vega, S.; Swager, T. M.; Griffin, R. G.

    2014-01-01

    We report magic angle spinning, dynamic nuclear polarization (DNP) experiments at magnetic fields of 9.4 T, 14.1 T, and 18.8 T using the narrow line polarizing agents 1,3-bisdiphenylene-2-phenylallyl (BDPA) dispersed in polystyrene, and sulfonated-BDPA (SA-BDPA) and trityl OX063 in glassy glycerol/water matrices. The 1H DNP enhancement field profiles of the BDPA radicals exhibit a significant DNP Overhauser effect (OE) as well as a solid effect (SE) despite the fact that these samples are insulating solids. In contrast, trityl exhibits only a SE enhancement. Data suggest that the appearance of the OE is due to rather strong electron-nuclear hyperfine couplings present in BDPA and SA-BDPA, which are absent in trityl and perdeuterated BDPA (d21-BDPA). In addition, and in contrast to other DNP mechanisms such as the solid effect or cross effect, the experimental data suggest that the OE in non-conducting solids scales favorably with magnetic field, increasing in magnitude in going from 5 T, to 9.4 T, to 14.1 T, and to 18.8 T. Simulations using a model two spin system consisting of an electron hyperfine coupled to a 1H reproduce the essential features of the field profiles and indicate that the OE in these samples originates from the zero and double quantum cross relaxation induced by fluctuating hyperfine interactions between the intramolecular delocalized unpaired electrons and their neighboring nuclei, and that the size of these hyperfine couplings is crucial to the magnitude of the enhancements. Microwave power dependent studies show that the OE saturates at considerably lower power levels than the solid effect in the same samples. Our results provide new insights into the mechanism of the Overhauser effect, and also provide a new approach to perform DNP experiments in chemical, biophysical, and physical systems at high magnetic fields. PMID:25134564

  6. Tetraphenylborate Solids Stability Tests

    SciTech Connect

    Walker, D.D.; Edwards, T.B.

    1997-12-19

    Tetraphenylborate solids provide a potentially large source of benzene in the slurries produced in the In-Tank Precipitation process. The stability of the solids is an important consideration in the safety analysis of the process and we desire an understanding of the factors that influence the rate of conversion of the solids to benzene.

  7. Solid State Division

    SciTech Connect

    Green, P.H.; Watson, D.M.

    1989-08-01

    This report contains brief discussions on work done in the Solid State Division of Oak Ridge National Laboratory. The topics covered are: Theoretical Solid State Physics; Neutron scattering; Physical properties of materials; The synthesis and characterization of materials; Ion beam and laser processing; and Structure of solids and surfaces. (LSP)

  8. Thermal dryers for solids

    SciTech Connect

    Billings, C.H.

    1993-12-01

    This article describes an indirect thermal dryer added to dewater solids before incineration of sewage sludge at a Buffalo, New York waste water treatment plant. In the first three months of operation, the solids inventory was reduced from about 799 tons to 250 tons. The solids processed in the plant's multiple hearth incinerators varied from 12 to 14 tons per hour.

  9. Batteries: Getting solid

    NASA Astrophysics Data System (ADS)

    Hu, Yong-Sheng

    2016-04-01

    Materials with high ionic conductivity are urgently needed for the development of solid-state lithium batteries. Now, an inorganic solid electrolyte is shown to have an exceptionally high ionic conductivity of 25 mS cm‑1, which allows a solid-state battery to deliver 70% of its maximum capacity in just one minute at room temperature.

  10. Solid aerosol generator

    DOEpatents

    Prescott, D.S.; Schober, R.K.; Beller, J.

    1992-03-17

    An improved solid aerosol generator used to produce a gas borne stream of dry, solid particles of predetermined size and concentration is disclosed. The improved solid aerosol generator nebulizes a feed solution of known concentration with a flow of preheated gas and dries the resultant wet heated aerosol in a grounded, conical heating chamber, achieving high recovery and flow rates. 2 figs.

  11. Improved solid aerosol generator

    DOEpatents

    Prescott, D.S.; Schober, R.K.; Beller, J.

    1988-07-19

    An improved solid aerosol generator used to produce a gas borne stream of dry, solid particles of predetermined size and concentration. The improved solid aerosol generator nebulizes a feed solution of known concentration with a flow of preheated gas and dries the resultant wet heated aerosol in a grounded, conical heating chamber, achieving high recovery and flow rates. 2 figs.

  12. Solid aerosol generator

    DOEpatents

    Prescott, Donald S.; Schober, Robert K.; Beller, John

    1992-01-01

    An improved solid aerosol generator used to produce a gas borne stream of dry, solid particles of predetermined size and concentration. The improved solid aerosol generator nebulizes a feed solution of known concentration with a flow of preheated gas and dries the resultant wet heated aerosol in a grounded, conical heating chamber, achieving high recovery and flow rates.

  13. A study on solid modelling with surface trimming method

    NASA Astrophysics Data System (ADS)

    Hung, Ching-Yun; Chang, San-Cheng

    1993-07-01

    This paper proposes a Surface Trimming Method based on the intersection curves between free-form surfaces so that a complex solid model with several primitive surfaces can be constructed. These solid models will not only be used by the mechanical engineering industry to design and analyze conventional mechanical parts, but will also be used by the civil engineers to design and analyze structures of irregular shape. The scope of solid modelling application is thus enhanced.

  14. Molecular beam epitaxy of III-P{sub x}As{sub 1−x} solid solutions: Mechanism of composition formation in the sublattice of a group V element

    SciTech Connect

    Emelyanov, E. A. Putyato, M. A.; Semyagin, B. R.; Feklin, D. F.; Preobrazhensky, V. V.

    2015-02-15

    The effect of substrate temperature, As{sub 2} and P{sub 2} molecular flux densities, and growth rate on the composition of III-P{sub x}As{sub 1−x} solid solution layers prepared by molecular beam epitaxy is experimentally investigated. Experimental data in a wide range of growth conditions are analyzed. The results obtained are presented in the form of a kinetic model for describing the process of formation of the composition in the Group V sublattice of the III-P{sub x}As{sub 1−x} solid solution upon molecular beam epitaxy. The model can be used for choosing the growth conditions of the III-P{sub x}As{sub 1−x} (001) solid-solution layers of a specified composition.

  15. Combustibility of tetraphenylborate solids

    SciTech Connect

    Walker, D.D.

    1989-05-03

    Liquid slurries expected under normal in-tank processing (ITP) operations are not ignitible because of their high water content. However, deposits of dry solids from the slurries are combustible and produce dense, black smoke when burned. The dry solids burn similarly to Styrofoam and more easily than sawdust. It is the opinion of fire hazard experts that a benzene vapor deflagration could ignite the dry solids. A tetraphenylborate solids fire will rapidly plug the waste tank HEPA ventilation filters due to the nature of the smoke produced. To prevent ignition and combustion of these solids, the waste tanks have been equipped with a nitrogen inerting system.

  16. Solid expellant plasma generator

    NASA Technical Reports Server (NTRS)

    Stone, Nobie H. (Inventor); Poe, Garrett D. (Inventor); Rood, Robert (Inventor)

    2010-01-01

    An improved solid expellant plasma generator has been developed. The plasma generator includes a support housing, an electrode rod located in the central portion of the housing, and a mass of solid expellant material that surrounds the electrode rod within the support housing. The electrode rod and the solid expellant material are made of separate materials that are selected so that the electrode and the solid expellant material decompose at the same rate when the plasma generator is ignited. This maintains a point of discharge of the plasma at the interface between the electrode and the solid expellant material.

  17. A commentary on solid lubricants and wear resistant solids for use in extreme environments

    NASA Technical Reports Server (NTRS)

    Sliney, H. E.

    1982-01-01

    The need for high temperature tribological coatings and self-lubricating materials in advanced technology is discussed. A qualitative model for the mechanism of solid lubrication is proposed. The model is based upon microscopic observations of the dynamics of third-body solids in lubricated contacts. In this model, the rheology of plastic flow is suggested as a more general criterion for predicting the lubricating potential of a solid material than, for example, a specific crystal structure. Some examples of layer-lattice and nonlayer-lattice solids that lubricate by virtue of their extreme plasticity, film coherence, and adhesion to the lubricated metal are described. Circumstantial evidence for the model is presented for low shear-strength solids at room temperature and for solids such as calcium fluoride that become lubricative only when their brittle-to-ductile transition temperature is exceeded. Some materials considerations in the selection of hard-coat materials for wear control are also presented.

  18. Exploration of Vacancies in Solid 4^He

    NASA Astrophysics Data System (ADS)

    Clark, Bryan; Ceperley, David

    2006-03-01

    Experiments by Kim and Chan [1] have renewed interest in the understanding of supersolids and whether mechanisms exist in solid ^4He to allow for supersolid-like effects. Ground state vacancies would lead to bose condensation and superfluidity. Using Path Integral Monte Carlo we examine vacancy formation energies, vacancy-vacancy interactions and the effect of vacancies on supersolid behavior in solid ^4He. [1] E. Kim and M. H. Chan, Science 305, 1941 (2004).

  19. Solids fluidizer-injector

    DOEpatents

    Bulicz, T.R.

    1990-04-17

    An apparatus and process are described for fluidizing solid particles by causing rotary motion of the solid particles in a fluidizing chamber by a plurality of rotating projections extending from a rotatable cylinder end wall interacting with a plurality of fixed projections extending from an opposite fixed end wall and passing the solid particles through a radial feed orifice open to the solids fluidizing chamber on one side and a solid particle utilization device on the other side. The apparatus and process are particularly suited for obtaining intermittent feeding with continual solids supply to the fluidizing chamber. The apparatus and process are suitable for injecting solid particles, such as coal, to an internal combustion engine. 3 figs.

  20. Ultrasonic hammer produces hot spots in solids

    NASA Astrophysics Data System (ADS)

    You, Sizhu; Chen, Ming-Wei; Dlott, Dana D.; Suslick, Kenneth S.

    2015-04-01

    Mechanical action can produce dramatic physical and mechanochemical effects when the energy is spatially or temporally concentrated. An important example of such phenomena in solids is the mechanical initiation of explosions, which has long been speculated to result from ‘hot spot’ generation at localized microstructures in the energetic material. Direct experimental evidence of such hot spots, however, is exceptionally limited; mechanisms for their generation are poorly understood and methods to control their locations remain elusive. Here we report the generation of intense, localized microscale hot spots in solid composites during mild ultrasonic irradiation, directly visualized by a thermal imaging microscope. These ultrasonic hot spots, with heating rates reaching ~22,000 K s-1, nucleate exclusively at interfacial delamination sites in composite solids. Introducing specific delamination sites by surface modification of embedded components provides precise and reliable control of hot spot locations and permits microcontrol of the initiation of reactions in energetic materials including fuel/oxidizer explosives.

  1. SOLID-STATE SENSORS FOR CONTROL AND DATA ACQUISITION ON SMALL WIND TURBINES

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Two different solid-state sensor packages were evaluated for use on small wind turbines (<200 kW) for control and data acquisition. The two solid-state sensor packages were compared to three mechanical sensor packages that have been used to measure small turbine performance parameters. The solid-s...

  2. Electrons in Solids^*

    NASA Astrophysics Data System (ADS)

    Watson, R. E.

    1997-03-01

    The first one-electron theory of electrons in solids followed J.J. Thompson's discovery by a few years and had benefit of neither quantum mechanics nor Fermi-Dirac statistics. After consideration of the early models we will inspect, in hindsight, an observation made by Wigner and Seitz. In 1953, when we had our first digital computers, they suggested ``if one had a great calculating machine'' it could be used to solve the Schroedinger equation and thereby obtain all interesting physical quantities. They continue by saying ``Presumably the results would agree with the experimentally determined quantities and nothing vastly new would be learned....It would be preferable instead to have a vivid picture....a simple description of the essence of the factors which determine...'' the behavior of atoms. Despite many computational successes we do not yet have that great calculating machine but we have gained insights from our imperfect calculations and there has been room for simple models. ^* This work was supported by the U.S. Department of Energy under Contract No. DE-AC02-76CH00016.

  3. Thermal dryer dewaters solids

    SciTech Connect

    DiMascio, F.J.; Burrowes, P.A.

    1993-09-01

    Solids incineration is traditionally an energy-intensive solids handling process at wastewater treatment plants. To reduce energy costs, the Buffalo (N.Y.) Sewer Authority has added an indirect thermal dryer to its treatment plant to dewater solids before incineration. In the first 3 months of operation, the authority reduced its solids inventory from 634,400 to 227,300 kg. Solids processed in the plant`s multiple-hearth incinerators varied from 11 to 12.75 wet Mg/hr at feed concentrations averaging 21% total solids. And, the dryer was operated with less than 5% downtime. The cost of this indirect thermal dryer system, including construction and equipment, was $995,000. 1 fig., 2 tabs.

  4. Consistent formulation of solid dissipative effects in stability analysis of flow past a deformable solid

    NASA Astrophysics Data System (ADS)

    Giribabu, D.; Shankar, V.

    2016-07-01

    The linear stability of plane Couette flow past a deformable solid is analyzed in the creeping-flow limit with an objective towards elucidating the consequences of employing two widely different formulations for the dissipative stresses in the deformable solid. One of the formulations postulates that the dissipative stress is proportional to the strain-rate tensor based on the left Cauchy-Green tensor, while in the other the dissipative stress in the solid is proportional to the rate-of-deformation tensor. However, it is well known in continuum mechanics that the rate-of-deformation tensor obeys the fundamental principle of material-frame indifference while the strain-rate-tensor formulation does not and hence it is more appropriate to employ the rate-of-deformation tensor in the description of dissipative stresses in deformable solids. In this work we consider the specific context of stability of plane Couette flow past a deformable solid and demonstrate that the results concerning the stability of the system from both models differ drastically. In the rate-of-deformation formulation for the dissipative stress, there is a range of solid-fluid thickness ratios (between 1.21 and 1.46) wherein the system is always stable for nonzero values of solid viscosity, unlike the strain-rate-tensor formulation wherein the system is unstable at all values of solid thickness. Further, for a solid-fluid thickness ratio less than 1, incorporation of dissipative effects in the solid using the rate-of-deformation formulation shows that the flow is more unstable compared to a purely elastic neo-Hookean solid, while for strain-rate-tensor formulation the flow is stabilized with an increase in viscosity of the solid. Using the fundamentally correct dissipative stress formulation, we also address the stability of pressure-driven flow in a deformable channel, wherein previous work carried out for an elastic neo-Hookean solid has shown that only the short-wave instability (driven by the

  5. Solid propellant rocket motor

    NASA Technical Reports Server (NTRS)

    Dowler, W. L.; Shafer, J. I.; Behm, J. W.; Strand, L. D. (Inventor)

    1973-01-01

    The characteristics of a solid propellant rocket engine with a controlled rate of thrust buildup to a desired thrust level are discussed. The engine uses a regressive burning controlled flow solid propellant igniter and a progressive burning main solid propellant charge. The igniter is capable of operating in a vacuum and sustains the burning of the propellant below its normal combustion limit until the burning propellant surface and combustion chamber pressure have increased sufficiently to provide a stable chamber pressure.

  6. Mixed oxide solid solutions

    DOEpatents

    Magno, Scott; Wang, Ruiping; Derouane, Eric

    2003-01-01

    The present invention is a mixed oxide solid solution containing a tetravalent and a pentavalent cation that can be used as a support for a metal combustion catalyst. The invention is furthermore a combustion catalyst containing the mixed oxide solid solution and a method of making the mixed oxide solid solution. The tetravalent cation is zirconium(+4), hafnium(+4) or thorium(+4). In one embodiment, the pentavalent cation is tantalum(+5), niobium(+5) or bismuth(+5). Mixed oxide solid solutions of the present invention exhibit enhanced thermal stability, maintaining relatively high surface areas at high temperatures in the presence of water vapor.

  7. Computational mechanics

    SciTech Connect

    Raboin, P J

    1998-01-01

    The Computational Mechanics thrust area is a vital and growing facet of the Mechanical Engineering Department at Lawrence Livermore National Laboratory (LLNL). This work supports the development of computational analysis tools in the areas of structural mechanics and heat transfer. Over 75 analysts depend on thrust area-supported software running on a variety of computing platforms to meet the demands of LLNL programs. Interactions with the Department of Defense (DOD) High Performance Computing and Modernization Program and the Defense Special Weapons Agency are of special importance as they support our ParaDyn project in its development of new parallel capabilities for DYNA3D. Working with DOD customers has been invaluable to driving this technology in directions mutually beneficial to the Department of Energy. Other projects associated with the Computational Mechanics thrust area include work with the Partnership for a New Generation Vehicle (PNGV) for ''Springback Predictability'' and with the Federal Aviation Administration (FAA) for the ''Development of Methodologies for Evaluating Containment and Mitigation of Uncontained Engine Debris.'' In this report for FY-97, there are five articles detailing three code development activities and two projects that synthesized new code capabilities with new analytic research in damage/failure and biomechanics. The article this year are: (1) Energy- and Momentum-Conserving Rigid-Body Contact for NIKE3D and DYNA3D; (2) Computational Modeling of Prosthetics: A New Approach to Implant Design; (3) Characterization of Laser-Induced Mechanical Failure Damage of Optical Components; (4) Parallel Algorithm Research for Solid Mechanics Applications Using Finite Element Analysis; and (5) An Accurate One-Step Elasto-Plasticity Algorithm for Shell Elements in DYNA3D.

  8. Solid-state configurations

    NASA Technical Reports Server (NTRS)

    Schroeder, K. G.

    1980-01-01

    Two prototype solid-state phased array systems concepts developed for the solar power satellite (SPS) are described. In both concepts, the beam was centered on the rectenna by means of phase conjugation of a pilot signal emanating from the ground. Also discussed are results of solid state studies.

  9. High solids fermentation reactor

    DOEpatents

    Wyman, Charles E.; Grohmann, Karel; Himmel, Michael E.; Richard, Christopher J.

    1993-03-02

    A fermentation reactor and method for fermentation of materials having greater than about 10% solids. The reactor includes a rotatable shaft along the central axis, the shaft including rods extending outwardly to mix the materials. The reactor and method are useful for anaerobic digestion of municipal solid wastes to produce methane, for production of commodity chemicals from organic materials, and for microbial fermentation processes.

  10. High solids fermentation reactor

    DOEpatents

    Wyman, Charles E.; Grohmann, Karel; Himmel, Michael E.; Richard, Christopher J.

    1993-01-01

    A fermentation reactor and method for fermentation of materials having greater than about 10% solids. The reactor includes a rotatable shaft along the central axis, the shaft including rods extending outwardly to mix the materials. The reactor and method are useful for anaerobic digestion of municipal solid wastes to produce methane, for production of commodity chemicals from organic materials, and for microbial fermentation processes.

  11. Polyimide Precursor Solid Residuum

    NASA Technical Reports Server (NTRS)

    Weiser, Erik S. (Inventor); St.Clair, Terry L. (Inventor); Echigo, Yoshiaki (Inventor); Kaneshiro, Hisayasu (Inventor)

    2001-01-01

    A polyimide precursor solid residuum is an admixture of an aromatic dianhydride or derivative thereof and an aromatic diamine or derivative thereof plus a complexing agent, which is complexed with the admixture by hydrogen bonding. The polyimide precursor solid residuum is effectively employed in the preparation of polyimide foam and the fabrication of polyimide foam structures.

  12. Solid adenocarcinoma —

    Cancer.gov

    Uniformly solid character of the lesions is usually indicative of a well differentiated tumor. No solid adenocarcinomas have observed in our series. However, rare cases have been described by others. In human pathology this diagnosis is usually based on detection of mucin after periodic acid-Schiff reaction with diastase (α-amylase) digestion.

  13. Solid Waste: Health Concerns

    ERIC Educational Resources Information Center

    Duel, Ward

    1975-01-01

    In this article the means of disposing solid wastes are discussed with reference to their health hazards and environmental desirability. Included in the discussion are solid waste dumps, landfills, incinerators, and grinders. Some attention is given to the reclamation of mineral resources from trash. (MA)

  14. Lubrication with solids.

    NASA Technical Reports Server (NTRS)

    Buckley, D. H.; Johnson, R. L.

    1972-01-01

    Brief discussion of the historical background, variety range, chemistry, physics, and other properties of solid lubricants, and review of their current uses. The widespread use of solid lubricants did not occur until about 1947. At present, they are the object of such interest that a special international conference on their subject was held in 1971. They are used at temperatures beyond the useful range of conventional lubricating oils and greases. Their low volatility provides them with the capability of functioning effectively in vacuum and invites their use in space applications. Their high load carrying ability makes them useful with heavily loaded components. Solid lubricants, however, do lack some of the desirable properties of conventional lubricants. Unlike oils and greases, which have fluidity and can continuously be carried back into contact with lubricated surfaces, solid lubricants, because of their immobility, have finite lives. Also, oils and greases can carry away frictional heat from contacting surfaces, while solid lubricants cannot.

  15. Solid-state proton conductors

    SciTech Connect

    Jewulski, J.R.; Osif, T.L.; Remick, R.J.

    1990-12-01

    The purpose of this program was to survey the field of solid-state proton conductors (SSPC), identify conductors that could be used to develop solid-state fuel cells suitable for use with coal derived fuel gases, and begin the experimental research required for the development of these fuel cells. This document covers the following topics: the history of developments and current status of the SSPC, including a review of proton conducting electrolyte structures, the current status of the medium temperature SSPC development, electrodes for moderate temperature (SSPC) fuel cell, basic material and measurement techniques applicable for SSPC development, modeling and optimization studies. Correlation and optimization studies, to include correlation studies on proton conduction and oxide cathode optimization for the SSPC fuel cell. Experiments with the SSPC fuel cells including the fabrication of the electrolyte disks, apparatus for conducting measurements, the strontium-cerium based electrolyte, the barium-cerium based electrolyte with solid foil electrodes, the barium-cerium based electrolyte with porous electrodes, and conduction mechanisms. 164 refs., 27 figs., 13 tabs.

  16. Solid electrolyte oxygen regeneration system

    NASA Technical Reports Server (NTRS)

    Shumar, J. W.; See, G. G.; Schubert, F. H.; Powell, J. D.

    1976-01-01

    A program to design, develop, fabricate and assemble a one-man, self-contained, solid electrolyte oxygen regeneration system (SX-1) incorporating solid electrolyte electrolyzer drums was completed. The SX-1 is a preprototype engineering model designed to produce 0.952 kg (2.1 lb)/day of breathable oxygen (O2) from the electrolysis of metabolic carbon dioxide (CO2) and water vapor. The CO2 supply rate was established based on the metabolic CO2 generation rate for one man of 0.998 kg (2.2 lb)/day. The water supply rate (0.254 kg (0.56 lb)/day) was designed to be sufficient to make up the difference between the 0.952 kg (2.1 lb)/day O2 generation specification and the O2 available through CO2 electrolysis, 0.726 kg (1.6 lb)/day. The SX-1 was successfully designed, fabricated and assembled. Design verification tests (DVT) or the CO Disproportionators, H2 separators, control instrumentation, monitor instrumentation, water feed mechanism were successfully completed. The erratic occurrence of electrolyzer drum leakage prevented the completion of the CO2 electrolyzer module and water electrolyzer module DVT's and also prevented the performance of SX-1 integrated testing. Further development work is required to improve the solid electrolyte cell high temperature seals.

  17. Fluid-solid coupled simulation of the ignition transient of solid rocket motor

    NASA Astrophysics Data System (ADS)

    Li, Qiang; Liu, Peijin; He, Guoqiang

    2015-05-01

    The first period of the solid rocket motor operation is the ignition transient, which involves complex processes and, according to chronological sequence, can be divided into several stages, namely, igniter jet injection, propellant heating and ignition, flame spreading, chamber pressurization and solid propellant deformation. The ignition transient should be comprehensively analyzed because it significantly influences the overall performance of the solid rocket motor. A numerical approach is presented in this paper for simulating the fluid-solid interaction problems in the ignition transient of the solid rocket motor. In the proposed procedure, the time-dependent numerical solutions of the governing equations of internal compressible fluid flow are loosely coupled with those of the geometrical nonlinearity problems to determine the propellant mechanical response and deformation. The well-known Zeldovich-Novozhilov model was employed to model propellant ignition and combustion. The fluid-solid coupling interface data interpolation scheme and coupling instance for different computational agents were also reported. Finally, numerical validation was performed, and the proposed approach was applied to the ignition transient of one laboratory-scale solid rocket motor. For the application, the internal ballistics were obtained from the ground hot firing test, and comparisons were made. Results show that the integrated framework allows us to perform coupled simulations of the propellant ignition, strong unsteady internal fluid flow, and propellant mechanical response in SRMs with satisfactory stability and efficiency and presents a reliable and accurate solution to complex multi-physics problems.

  18. Solid propellant motor

    NASA Technical Reports Server (NTRS)

    Shafer, J. I.; Marsh, H. E., Jr. (Inventor)

    1978-01-01

    A case bonded end burning solid propellant rocket motor is described. A propellant with sufficiently low modulus to avoid chamber buckling on cooling from cure and sufficiently high elongation to sustain the stresses induced without cracking is used. The propellant is zone cured within the motor case at high pressures equal to or approaching the pressure at which the motor will operate during combustion. A solid propellant motor with a burning time long enough that its spacecraft would be limited to a maximum acceleration of less than 1 g is provided by one version of the case bonded end burning solid propellant motor of the invention.

  19. Low density solid ozone

    SciTech Connect

    Teolis, B. D.; Fama, M.; Baragiola, R. A.

    2007-08-21

    We report a very low density ({approx}0.5 g/cm{sup 3}) structure of solid ozone. It is produced by irradiation of solid oxygen with 100 keV protons at 20 K followed by heating to sublime unconverted oxygen. Upon heating to 47 K the porous ozone compacts to a density of {approx}1.6 g/cm{sup 3} and crystallizes. We use a detailed analysis of the main infrared absorption band of the porous ozone to interpret previous research, where solid oxygen was irradiated by UV light and keV electrons.

  20. Computational methods in nonlinear structural and solid mechanics; Proceedings of the Symposium, Washington, D.C., October 6-8, 1980. Symposium sponsored by the George Washington University and NASA

    NASA Technical Reports Server (NTRS)

    Noor, A. K. (Editor); Mccomb, H. G., Jr.

    1981-01-01

    Topics discussed include computational strategies for nonlinear problems in structural mechanics, time integration techniques and the numerical solution of nonlinear algebraic equations, material characterization and nonlinear fracture mechanics, nonlinear interaction problems, and seismic response and the nonlinear analysis of concrete structures. Also considered are nonlinear problems for nuclear reactors, crash dynamics and impact problems, nonlinear problems of fibrous composites and advanced nonlinear applications, and computerized symbolic manipulation and nonlinear analysis software systems.

  1. Diffusion of Dissipative Correlation in the Dynamic Failure of Solids

    NASA Astrophysics Data System (ADS)

    Grady, Dennis

    A property identified as the dissipative action has found application as a unifying attribute underlying the dynamic failure of solid materials. Failure modes include tensile spall, impact-induced dynamic shear, shock compaction and steady shock-wave compression. The present work explores the possible application of Langevin dynamics and related statistical mechanical implications as underlying the extreme dynamic failure of solids.

  2. Fracture of Materials Undergoing Solid-Solid Phase Transformation

    NASA Astrophysics Data System (ADS)

    Penmecha, Bharat

    A large number of technologically important materials undergo solid-solid phase transformations. Examples range from ferroelectrics (transducers and memory devices), zirconia (Thermal Barrier Coatings) to nickel superalloys and (lithium) iron phosphate (Li-ion batteries). These transformations involve a change in the crystal structure either through diffusion of species or local rearrangement of atoms. This change of crystal structure leads to a macroscopic change of shape or volume or both and results in internal stresses during the transformation. In certain situations this stress field gives rise to cracks (tin, iron phosphate etc.) which continue to propagate as the transformation front traverses the material. In other materials the transformation modifies the stress field around cracks and effects crack growth behavior (zirconia, ferroelectrics). These observations serve as our motivation to study cracks in solids undergoing phase transformations. Understanding these effects will help in improving the mechanical reliability of the devices employing these materials. In this thesis we present work on two problems concerning the interplay between cracks and phase transformations. First, we consider the directional growth of a set of parallel edge cracks due to a solid-solid transformation. We conclude from our analysis that phase transformations can lead to formation of parallel edge cracks when the transformation strain satisfies certain conditions and the resulting cracks grow all the way till their tips cross over the phase boundary. Moreover the cracks continue to grow as the phase boundary traverses into the interior of the body at a uniform spacing without any instabilities. There exists an optimal value for the spacing between the cracks. We ascertain these conclusion by performing numerical simulations using finite elements. Second, we model the effect of the semiconducting nature and dopants on cracks in ferroelectric perovskite materials, particularly

  3. Solids Accumulation Scouting Studies

    SciTech Connect

    Duignan, M. R.; Steeper, T. J.; Steimke, J. L.

    2012-09-26

    The objective of Solids Accumulation activities was to perform scaled testing to understand the behavior of remaining solids in a Double Shell Tank (DST), specifically AW-105, at Hanford during multiple fill, mix, and transfer operations. It is important to know if fissionable materials can concentrate when waste is transferred from staging tanks prior to feeding waste treatment plants. Specifically, there is a concern that large, dense particles containing plutonium could accumulate in poorly mixed regions of a blend tank heel for tanks that employ mixing jet pumps. At the request of the DOE Hanford Tank Operations Contractor, Washington River Protection Solutions, the Engineering Development Laboratory of the Savannah River National Laboratory performed a scouting study in a 1/22-scale model of a waste staging tank to investigate this concern and to develop measurement techniques that could be applied in a more extensive study at a larger scale. Simulated waste tank solids: Gibbsite, Zirconia, Sand, and Stainless Steel, with stainless steel particles representing the heavier particles, e.g., plutonium, and supernatant were charged to the test tank and rotating liquid jets were used to mix most of the solids while the simulant was pumped out. Subsequently, the volume and shape of the mounds of residual solids and the spatial concentration profiles for the surrogate for heavier particles were measured. Several techniques were developed and equipment designed to accomplish the measurements needed and they included: 1. Magnetic particle separator to remove simulant stainless steel solids. A device was designed and built to capture these solids, which represent the heavier solids during a waste transfer from a staging tank. 2. Photographic equipment to determine the volume of the solids mounds. The mounds were photographed as they were exposed at different tank waste levels to develop a composite of topographical areas. 3. Laser rangefinders to determine the volume of

  4. Solid and Gaseous Fuels.

    ERIC Educational Resources Information Center

    Schultz, Hyman; And Others

    1989-01-01

    This review covers methods of sampling, analyzing, and testing coal, coke, and coal-derived solids and methods for the chemical, physical, and instrumental analyses of gaseous fuels. The review covers from October 1986, to September 1988. (MVL)

  5. The solid waste dilemma

    USGS Publications Warehouse

    Amey, E.B.; Russell, J.A.; Hurdelbrink, R.J.

    1996-01-01

    In 1976, the U.S. Congress enacted the Resource Conservation and Recovery Act (RCRA) to further address the problem of increasing industrial and municipal waste. The main objectives of RCRA were to responsibly manage hazardous and solid waste and to procure materials made from recovered wastes. To fulfill these objectives, four main programs of waste management were developed. These programs were defined under Subtitle C, the Hazardous Waste Program; Subtitle D, the Solid Waste Program; Subtitle I, the Underground Storage Tank Program; and Subtitle J, the Medical Waste Program. Subtitle D illustrates the solid waste dilemma occurring in the United States. Under this program, states are encouraged to develop and implement their own waste management plans. These plans include the promotion of recycling solid wastes and the closing and upgrading of all environmentally unsound dumps. ?? 1996 International Association for Mathematical Geology.

  6. Solid adenoma —

    Cancer.gov

    Round to oval cells fill alveolar spaces. Fixation of the lung without inflation results in predominance of solid over alveolar pattern. Cells usually have abundant eosinophilic cytoplasm with fine granularity and/or vacuoles.

  7. Solid Waste Treatment Technology

    ERIC Educational Resources Information Center

    Hershaft, Alex

    1972-01-01

    Advances in research and commercial solid waste handling are offering many more processing choices. This survey discusses techniques of storage and removal, fragmentation and sorting, bulk reduction, conversion, reclamation, mining and mineral processing, and disposal. (BL)

  8. Why solid modeling?

    NASA Astrophysics Data System (ADS)

    Boulter, T. W.

    1985-01-01

    The potentials of solid modeling to permit truly automated CAD/CAM are explored in comparisons with the limitations of wire frame (WF) and surface (SM) models. WF cannot differentiate between inner and outer surfaces and SM does not permit computation of mass properties. Solid models eliminate ambiguity and require large computer storage capabilities and fast processing. Physical properties such as moments of inertia, mass, center of gravity, and kinematical behavior can be calculated. The models are built from primitive solids and connected by Boolean operators or from solid segments (SS). SS permits storage of physical data for each segment while the PS must be calculated from the entire shape. Research directions being followed to display dynamic situations, cross-sections, and composite structure components are discussed.

  9. The Organic Solid State.

    ERIC Educational Resources Information Center

    Cowan, Dwaine O.; Wlygul, Frank M.

    1986-01-01

    Reviews interesting and useful electrical, magnetic, and optical properties of the organic solid state. Offers speculation as to areas of fruitful research. Discusses organic superconductors, conducting organic polymers, organic metals, and traces recent history of creation of organic metals. (JM)

  10. What Are Solid Fats?

    MedlinePlus

    ... animal foods and can also be made from vegetable oils through a process called hydrogenation. Some common solid ... that are liquid at room temperature, like the vegetable oils used in cooking. Oils come from many different ...

  11. Solid state switch

    DOEpatents

    Merritt, Bernard T.; Dreifuerst, Gary R.

    1994-01-01

    A solid state switch, with reverse conducting thyristors, is designed to operate at 20 kV hold-off voltage, 1500 A peak, 1.0 .mu.s pulsewidth, and 4500 pps, to replace thyratrons. The solid state switch is more reliable, more economical, and more easily repaired. The switch includes a stack of circuit card assemblies, a magnetic assist and a trigger chassis. Each circuit card assembly contains a reverse conducting thyristor, a resistor capacitor network, and triggering circuitry.

  12. Solid electrolyte cell

    NASA Technical Reports Server (NTRS)

    Richter, R. (Inventor)

    1982-01-01

    A solid electrolyte cell including a body of solid ionized gas-conductive electrolyte having mutually spaced surfaces and on which is deposited a multiplicity of mutually spaced electrodes is described. Strips and of bare substances are interposed between electrodes, so that currents of ionic gas may be established between the electrodes via the bare strips, whereby electrical resistance for the cells is lowered and the gas conductivity is enhanced.

  13. Solid polymer electrolytes

    DOEpatents

    Abraham, Kuzhikalail M.; Alamgir, Mohamed; Choe, Hyoun S.

    1995-01-01

    This invention relates to Li ion (Li.sup.+) conductive solid polymer electrolytes composed of poly(vinyl sulfone) and lithium salts, and their use in all-solid-state rechargeable lithium ion batteries. The lithium salts comprise low lattice energy lithium salts such as LiN(CF.sub.3 SO.sub.2).sub.2, LiAsF.sub.6, and LiClO.sub.4.

  14. Solid model design simplification

    SciTech Connect

    Ames, A.L.; Rivera, J.J.; Webb, A.J.; Hensinger, D.M.

    1997-12-01

    This paper documents an investigation of approaches to improving the quality of Pro/Engineer-created solid model data for use by downstream applications. The investigation identified a number of sources of problems caused by deficiencies in Pro/Engineer`s geometric engine, and developed prototype software capable of detecting many of these problems and guiding users towards simplified, useable models. The prototype software was tested using Sandia production solid models, and provided significant leverage in attacking the simplification problem.

  15. Solid polymer electrolytes

    DOEpatents

    Abraham, K.M.; Alamgir, M.; Choe, H.S.

    1995-12-12

    This invention relates to Li ion (Li{sup +}) conductive solid polymer electrolytes composed of poly(vinyl sulfone) and lithium salts, and their use in all-solid-state rechargeable lithium ion batteries. The lithium salts comprise low lattice energy lithium salts such as LiN(CF{sub 3}SO{sub 2}){sub 2}, LiAsF{sub 6}, and LiClO{sub 4}. 2 figs.

  16. Phase Field Fracture Mechanics.

    SciTech Connect

    Robertson, Brett Anthony

    2015-11-01

    For this assignment, a newer technique of fracture mechanics using a phase field approach, will be examined and compared with experimental data for a bend test and a tension test. The software being used is Sierra Solid Mechanics, an implicit/explicit finite element code developed at Sandia National Labs in Albuquerque, New Mexico. The bend test experimental data was also obtained at Sandia Labs while the tension test data was found in a report online from Purdue University.

  17. Keep solids in suspension

    SciTech Connect

    Gladki, H.Z.

    1997-10-01

    Mixing is an important operation in the CPI. It is not synonymous with agitation. Mixing is a random distribution into and through one another of two or more initially separate phases. Within that broad definition is the important specialty area of liquid-solid dispersion. This paper addresses the dispersion of solids in lower concentrations that don`t affect the rheological properties of the fluid. The just suspended condition represents the lowest grade of complete suspension, but this level of agitation is the most efficient for solids-liquid agitation. Higher mixing speeds waste energy. Undersized mixers need replacing. The top-entering mixer has a long history in the CPI and the environmental area. Many suspension studies were run with this type. These papers result in empirical correlations for just suspension conditions to scale up from laboratory measurement. Variables considered are the agitation speed, liquid and solids physical properties, solids concentration, system geometry and impeller type. Lately, submersible mixers are becoming more popular, but there are no published sizing methods. This article will explain how to define the critical hydraulic conditions in the tank to reach just solids suspension for a submersible agitator of the type described here as FJFA (Free Jet Flow Agitator).

  18. Lyophilization -Solid Waste Treatment

    NASA Technical Reports Server (NTRS)

    Litwiller, Eric; Flynn, Michael; Fisher, John; Reinhard, Martin

    2004-01-01

    This paper discusses the development of a solid waste treatment system that has been designed for a Mars transit exploration mission. The technology described is an energy-efficient lyophilization technique that is designed to recover water from spacecraft solid wastes. Candidate wastes include feces, concentrated brines from water processors, and other solid wastes that contain free water. The system is designed to operate as a stand-alone process or to be integrated into the International Space Station Waste Collection System. In the lyophilization process, water in an aqueous waste is frozen and then sublimed, separating the waste into a dried solid material and liquid water. The sublimed water is then condensed in a solid ice phase and then melted to generate a liquid product. In the subject system the waste solids are contained within a 0.2 micron bio-guard bag and after drying are removed from the system and stored in a secondary container. This technology is ideally suited to applications such as the Mars Reference Mission, where water recovery rates approaching 100% are desirable but production of CO2 is not. The system is designed to minimize power consumption through the use of thermoelectric heat pumps. The results of preliminary testing of a prototype system and testing of the final configuration are provided. A mathematical model of the system is also described.

  19. Solid-State Synthesis of a Thermochromic Compound

    NASA Astrophysics Data System (ADS)

    Changyun, Chen; Zhihua, Zhou; Yiming, Zhou; Jiangyan, Du

    2000-09-01

    Bis(diethylammonium) tetrachloronickelate(II) was prepared by solid-state reaction at mild temperature. Classroom demonstration of the synthesis and discussions of thermochromic mechanism of the compound prepared were described.

  20. Sensitivity of solid explosives: Minimum energy of a dangerous impact

    NASA Technical Reports Server (NTRS)

    Afanasyev, G. T.

    1986-01-01

    A method which uses initiating explosives for determining the sensitivity of solid explosives is described. The energy index of sensitivity is determined by the mechanical properties of the explosives. The results of the calculations are discussed.

  1. Athermal nonlinear elastic constants of amorphous solids.

    PubMed

    Karmakar, Smarajit; Lerner, Edan; Procaccia, Itamar

    2010-08-01

    We derive expressions for the lowest nonlinear elastic constants of amorphous solids in athermal conditions (up to third order), in terms of the interaction potential between the constituent particles. The effect of these constants cannot be disregarded when amorphous solids undergo instabilities such as plastic flow or fracture in the athermal limit; in such situations the elastic response increases enormously, bringing the system much beyond the linear regime. We demonstrate that the existing theory of thermal nonlinear elastic constants converges to our expressions in the limit of zero temperature. We motivate the calculation by discussing two examples in which these nonlinear elastic constants play a crucial role in the context of elastoplasticity of amorphous solids. The first example is the plasticity-induced memory that is typical to amorphous solids (giving rise to the Bauschinger effect). The second example is how to predict the next plastic event from knowledge of the nonlinear elastic constants. Using the results of our calculations we derive a simple differential equation for the lowest eigenvalue of the Hessian matrix in the external strain near mechanical instabilities; this equation predicts how the eigenvalue vanishes at the mechanical instability and the value of the strain where the mechanical instability takes place. PMID:20866874

  2. Athermal nonlinear elastic constants of amorphous solids

    NASA Astrophysics Data System (ADS)

    Karmakar, Smarajit; Lerner, Edan; Procaccia, Itamar

    2010-08-01

    We derive expressions for the lowest nonlinear elastic constants of amorphous solids in athermal conditions (up to third order), in terms of the interaction potential between the constituent particles. The effect of these constants cannot be disregarded when amorphous solids undergo instabilities such as plastic flow or fracture in the athermal limit; in such situations the elastic response increases enormously, bringing the system much beyond the linear regime. We demonstrate that the existing theory of thermal nonlinear elastic constants converges to our expressions in the limit of zero temperature. We motivate the calculation by discussing two examples in which these nonlinear elastic constants play a crucial role in the context of elastoplasticity of amorphous solids. The first example is the plasticity-induced memory that is typical to amorphous solids (giving rise to the Bauschinger effect). The second example is how to predict the next plastic event from knowledge of the nonlinear elastic constants. Using the results of our calculations we derive a simple differential equation for the lowest eigenvalue of the Hessian matrix in the external strain near mechanical instabilities; this equation predicts how the eigenvalue vanishes at the mechanical instability and the value of the strain where the mechanical instability takes place.

  3. Micromechanically Based Constitutive Relations for Polycrystalline Solids

    NASA Technical Reports Server (NTRS)

    Nemat-Nasser, S.; Iwakuma, T.

    1983-01-01

    A basic method to estimate the overall mechanical response of solids which contain periodically distributed defects is presented. The method estimates the shape and growth pattern of voids periodically distributed over the grain boundaries in a viscous matrix. The relaxed moduli are obtained for a polycrytalline solid that undergoes relaxation by grain boundary sliding which accounts for the interaction effects. The overall inelastic nonlinear response at elevated temperatures in terms of a model which considers nonlinear power law creep within the grains, and linear viscous flow in the grain boundaries is discussed.

  4. Advanced Solid Rocket Motor case design status

    NASA Technical Reports Server (NTRS)

    Palmer, G. L.; Cash, S. F.; Beck, J. P.

    1993-01-01

    The Advanced Solid Rocket Motor (ASRM) case design aimed at achieving a safer and more reliable solid rocket motor for the Space Shuttle system is considered. The ASRM case has a 150.0 inch diameter, three equal length segment, and 9Ni-4CO-0.3C steel alloy. The major design features include bolted casebolted case joints which close during pressurization, plasma arc welded factory joints, integral stiffener for splash down and recovery, and integral External Tank attachment rings. Each mechanical joint has redundant and verifiable o-ring seals.

  5. Advanced Solid Rocket Motor case design status

    NASA Astrophysics Data System (ADS)

    Palmer, G. L.; Cash, S. F.; Beck, J. P.

    1993-06-01

    The Advanced Solid Rocket Motor (ASRM) case design aimed at achieving a safer and more reliable solid rocket motor for the Space Shuttle system is considered. The ASRM case has a 150.0 inch diameter, three equal length segment, and 9Ni-4CO-0.3C steel alloy. The major design features include bolted casebolted case joints which close during pressurization, plasma arc welded factory joints, integral stiffener for splash down and recovery, and integral External Tank attachment rings. Each mechanical joint has redundant and verifiable o-ring seals.

  6. Transverse photothermal beam deflection within a solid

    SciTech Connect

    Spear, J.D.; Russo, R.E. )

    1991-07-15

    The mirage effect within a transparent solid substrate was used for monitoring optical absorption of a thin film. Refractive index gradients, which accompany thermal gradients below the film-coated surface, cause a probe laser beam to be deflected. The spectrum of copper, deposited onto a piece of clear acrylic, was recorded by this method of photothermal deflection. The influence of thermally induced mechanical stresses can alter the effective value of the thermo-optic coefficient of the solid, {ital dn}/{ital dT}.

  7. Solid State Lasers from an Efficiency Perspective

    NASA Technical Reports Server (NTRS)

    Barnes, Norman P.

    2007-01-01

    Solid state lasers have remained a vibrant area of research because several major innovations expanded their capability. Major innovations are presented with emphasis focused on the laser efficiency. A product of efficiencies approach is developed and applied to describe laser performance. Efficiency factors are presented in closed form where practical and energy transfer effects are included where needed. In turn, efficiency factors are used to estimate threshold and slope efficiency, allowing a facile estimate of performance. Spectroscopic, thermal, and mechanical data are provided for common solid state laser materials.

  8. Nanocrystalline cerium oxide materials for solid fuel cell systems

    DOEpatents

    Brinkman, Kyle S

    2015-05-05

    Disclosed are solid fuel cells, including solid oxide fuel cells and PEM fuel cells that include nanocrystalline cerium oxide materials as a component of the fuel cells. A solid oxide fuel cell can include nanocrystalline cerium oxide as a cathode component and microcrystalline cerium oxide as an electrolyte component, which can prevent mechanical failure and interdiffusion common in other fuel cells. A solid oxide fuel cell can also include nanocrystalline cerium oxide in the anode. A PEM fuel cell can include cerium oxide as a catalyst support in the cathode and optionally also in the anode.

  9. Ultrasonic characterization of solid liquid suspensions

    DOEpatents

    Panetta, Paul D.

    2010-06-22

    Using an ultrasonic field, properties of a solid liquid suspension such as through-transmission attenuation, backscattering, and diffuse field are measured. These properties are converted to quantities indicating the strength of different loss mechanisms (such as absorption, single scattering and multiple scattering) among particles in the suspension. Such separation of the loss mechanisms can allow for direct comparison of the attenuating effects of the mechanisms. These comparisons can also indicate a model most likely to accurately characterize the suspension and can aid in determination of properties such as particle size, concentration, and density of the suspension.

  10. Nonclassical Nucleation in a Solid-Solid Transition of Confined Hard Spheres

    NASA Astrophysics Data System (ADS)

    Qi, Weikai; Peng, Yi; Han, Yilong; Bowles, Richard K.; Dijkstra, Marjolein

    2015-10-01

    A solid-solid phase transition of colloidal hard spheres confined between two planar hard walls is studied using a combination of molecular dynamics and Monte Carlo simulation. The transition from a solid consisting of five crystalline layers with square symmetry (5 □ ) to a solid consisting of four layers with triangular symmetry (4 △ ) is shown to occur through a nonclassical nucleation mechanism that involves the initial formation of a precritical liquid cluster, within which the cluster of the stable 4 △ phase grows. Free-energy calculations show that the transition occurs in one step, crossing a single free-energy barrier, and that the critical nucleus consists of a small 4 △ solid cluster wetted by a metastable liquid. In addition, the liquid cluster and the solid cluster are shown to grow at the planar hard walls. We also find that the critical nucleus size increases with supersaturation, which is at odds with classical nucleation theory. The △-solid-like cluster is shown to contain both face-centered-cubic and hexagonal-close-packed ordered particles.

  11. Anisotropy in solid inflation

    SciTech Connect

    Bartolo, Nicola; Matarrese, Sabino; Ricciardone, Angelo; Peloso, Marco E-mail: sabino.matarrese@pd.infn.it E-mail: angelo.ricciardone@pd.infn.it

    2013-08-01

    In the model of solid / elastic inflation, inflation is driven by a source that has the field theoretical description of a solid. To allow for prolonged slow roll inflation, the solid needs to be extremely insensitive to the spatial expansion. We point out that, because of this property, the solid is also rather inefficient in erasing anisotropic deformations of the geometry. This allows for a prolonged inflationary anisotropic solution, providing the first example with standard gravity and scalar fields only which evades the conditions of the so called cosmic no-hair conjecture. We compute the curvature perturbations on the anisotropic solution, and the corresponding phenomenological bound on the anisotropy. Finally, we discuss the analogy between this model and the f(φ)F{sup 2} model, which also allows for anisotropic inflation thanks to a suitable coupling between the inflaton φ and a vector field. We remark that the bispectrum of the curvature perturbations in solid inflation is enhanced in the squeezed limit and presents a nontrivial angular dependence, as had previously been found for the f(φ)F{sup 2} model.

  12. Defects in flexoelectric solids

    NASA Astrophysics Data System (ADS)

    Mao, Sheng; Purohit, Prashant K.

    2015-11-01

    A solid is said to be flexoelectric when it polarizes in proportion to strain gradients. Since strain gradients are large near defects, we expect the flexoelectric effect to be prominent there and decay away at distances much larger than a flexoelectric length scale. Here, we quantify this expectation by computing displacement, stress and polarization fields near defects in flexoelectric solids. For point defects we recover some well known results from strain gradient elasticity and non-local piezoelectric theories, but with different length scales in the final expressions. For edge dislocations we show that the electric potential is a maximum in the vicinity of the dislocation core. We also estimate the polarized line charge density of an edge dislocation in an isotropic flexoelectric solid which is in agreement with some measurements in ice. We perform an asymptotic analysis of the crack tip fields in flexoelectric solids and show that our results share some features from solutions in strain gradient elasticity and piezoelectricity. We also compute the energy release rate for cracks using simple crack face boundary conditions and use them in classical criteria for crack growth to make predictions. Our analysis can serve as a starting point for more sophisticated analytic and computational treatments of defects in flexoelectric solids which are gaining increasing prominence in the field of nanoscience and nanotechnology.

  13. First-Principles Study of LiPON Solid Electrolyte

    NASA Astrophysics Data System (ADS)

    Santosh, K. C.; Xiong, Ka; Cho, Kyeongjae

    2011-03-01

    There has been much interest in the thin-film solid electrolyte for solid state battery and ionics applications. LiPON is a representative material developed by Oak Ridge National Laboratory. In this work, we use first principles calculations based on the density functional theory to investigate the Li- ion migration mechanisms of LiPON family materials. We investigate atomic structures, electronic structures and defect formation energies of these materials. To determine the migration path of Li diffusion, the activation energies are calculated. This study helps us to understand fundamental mechanisms of Li-ion migration and to improve Li ion conductivity in the solid electrolytes.

  14. A Different Cone: Bursting Drops in Solids

    NASA Astrophysics Data System (ADS)

    Zhao, Xuanhe

    2013-03-01

    Drops in fluids tend to be spheres--a shape that minimizes surface energy. In thunderstorm clouds, drops can become unstable and emit thin jets when charged beyond certain limits. The instability of electrified drops in gases and liquids has been widely studied and used in applications including ink-jet printing, electrospinning nano-fibers, microfluidics and electrospray ionization. Here we report a different scenario: drops in solids become unstable and burst under sufficiently high electric fields. We find the instability of drops in solids morphologically resembles that in liquids, but the critical electric field for the instability follows a different scaling due to elasticity of solids. Our observations and theoretical models not only advance the fundamental understanding of electrified drops but also suggest a new failure mechanism of high-energy-density dielectric polymers, which have diverse applications ranging from capacitors for power grids and electric vehicles to muscle-like transducers for soft robots and energy harvesting.

  15. First Principles Simulations of Nanoparticle Solids

    NASA Astrophysics Data System (ADS)

    Greenwood, Arin; Vörös, Márton; Galli, Giulia

    Nanoparticle solids are gaining popularity as materials for optoelectronic devices such as solar cells. However, there is still much debate regarding the transport regime governing the charge carriers. To date, no comprehensive description of transport mechanisms in nanoparticle solids has been established, and there is a lack of computational studies predicting electron mobilities and transport rates at the ab initio level. In order to understand electron transport properties, it is an essential prerequisite to build realistic structural models of nanoparticle solids to use for prediction of electronic structure and eventually transport properties. Here we present Ab Initio Molecular Dynamics simulations of lead chalcogenide nanoparticles and surrounding ligands to extract relevant electronic structure properties for charge transport calculations. We tested the validity of recently observed ''band-like'' transport by assessing the formation of bands and their dependence on nanoparticle surface structure and ligands. Work supported by DOE-BES under DE-FG02-06ER46262.

  16. Hydrogenation of organic solid wastes

    SciTech Connect

    Wu, W.R.K.; Kawa, W.

    1980-02-01

    Eight organic solid wastes, six cellulosic and two noncellulosic, were hydrogenated batchwise with and without a catalyst. Conversions obtained range from 64 to 98 % of moisture- and ash-free (maf) raw material; oil yields, 10 to 59 %; and gaseous hydrocarbon yields, 7 to 16 %. Based on batch hydrogenation results, the oil production from large-scale hydrogenation of the wastes is projected to be 1.6 to 3.5 bbl/ton of maf raw material; the gaseous-hydrocarbon production, 2000 to 4100 standard cubic feet (scf). Activities of the two catalysts (SnCl/sub 2// and a combination of Fe/sub 2/O/sub 3/ and H/sub 2/S) used in the hydrogenation of the wastes are discussed. Also discussed are the chemical reactions and mechanisms involved in the hydrogenation, potential market for the product oil, and possible improvement of the oil yield. Elemental compositions of the hydrogenation oils and types of hydrocarbons including oxygenated hydrocarbons found in the oils are presented. The energy equivalent of the organic solid wastes generated in the United States in 1973 is shown to be 27 % of the nation's total 1972 energy production.

  17. Solid-state array cameras.

    PubMed

    Strull, G; List, W F; Irwin, E L; Farnsworth, D L

    1972-05-01

    Over the past few years there has been growing interest shown in the rapidly maturing technology of totally solid-state imaging. This paper presents a synopsis of developments made in this field at the Westinghouse ATL facilities with emphasis on row-column organized monolithic arrays of diffused junction phototransistors. The complete processing sequence applicable to the fabrication of modern highdensity arrays is described from wafer ingot preparation to final sensor testing. Special steps found necessary for high yield processing, such as surface etching prior to both sawing and lapping, are discussed along with the rationale behind their adoption. Camera systems built around matrix array photosensors are presented in a historical time-wise progression beginning with the first 50 x 50 element converter developed in 1965 and running through the most recent 400 x 500 element system delivered in 1972. The freedom of mechanical architecture made available to system designers by solid-state array cameras is noted from the description of a bare-chip packaged cubic inch camera. Hybrid scan systems employing one-dimensional line arrays are cited, and the basic tradeoffs to their use are listed. PMID:20119094

  18. Solid state switch

    DOEpatents

    Merritt, B.T.; Dreifuerst, G.R.

    1994-07-19

    A solid state switch, with reverse conducting thyristors, is designed to operate at 20 kV hold-off voltage, 1,500 A peak, 1.0 [mu]s pulsewidth, and 4,500 pps, to replace thyratrons. The solid state switch is more reliable, more economical, and more easily repaired. The switch includes a stack of circuit card assemblies, a magnetic assist and a trigger chassis. Each circuit card assembly contains a reverse conducting thyristor, a resistor capacitor network, and triggering circuitry. 6 figs.

  19. Solid handling valve

    DOEpatents

    Williams, William R.

    1979-01-01

    The present invention is directed to a solids handling valve for use in combination with lock hoppers utilized for conveying pulverized coal to a coal gasifier. The valve comprises a fluid-actuated flow control piston disposed within a housing and provided with a tapered primary seal having a recessed seat on the housing and a radially expandable fluid-actuated secondary seal. The valve seals are highly resistive to corrosion, erosion and abrasion by the solids, liquids, and gases associated with the gasification process so as to minimize valve failure.

  20. WET SOLIDS FLOW ENHANCEMENT

    SciTech Connect

    Hugo S. Caram; Natalie Foster

    1999-07-01

    The strain-stress behavior of a wet granular media was measured using a split Parfitt tensile tester. In all cases the stress increases linearly with distance until the maximum uniaxial tensile stress is reached. The stress then decreases exponentially with distance after this maximum is reached. The linear region indicates that wet solids behave elastically for stresses below the tensile stresses and can store significant elastic energy. The elastic deformation cannot be explained by analyzing the behavior of individual capillary bridges and requires accounting for the deformation of the solids particles. The elastic modulus of the wet granular material remains unexplained.

  1. WET SOLIDS FLOW ENHANCEMENT

    SciTech Connect

    Hugo S. Caram; Natalie Foster

    1998-03-30

    The strain-stress behavior of a wet granular media was measured using a split Parfitt tensile tester. In all cases the stress increases linearly with distance until the maximum uniaxial tensile stress is reached. The stress then decreases exponentially with distance after this maximum is reached. The linear region indicates that wet solids behave elastically for stresses below the tensile stresses and can store significant elastic energy. The elastic deformation cannot be explained by analyzing the behavior of individual capillary bridges and may require accounting for the deformation of the solids particles. The elastic modulus of the wet granular material remains unexplained.

  2. New mechanism of structuring associated with the quasi-merohedral twinning by an example of Ca{sub 1–x}La{sub x}F{sub 2+x} ordered solid solutions

    SciTech Connect

    Maksimov, S. K.; Maksimov, K. S.; Sukhov, N. D.; Lovygin, M. V.

    2015-10-15

    Merohedry is considered an inseparable property of atomic structures, and uses for the refinement of structural data in a process of correct determination of structure of compounds. Transformation of faulty structures stimulated by decreasing of systemic cumulative energy leads to generation of merohedral twinning type. Ordering is accompanied by origin of antiphase domains. If ordering belongs to the CuAu type, it is accompanied by tetragonal distortions along different (100) directions. If a crystal consists of mosaic of nanodimensional antiphase domains, the conjugation of antiphase domains with different tetragonality leads to monoclinic distortions, at that, conjugated domains are distorted mirrorly. Similar system undergoes further transformation by means of quasi-merohedral twinning. As a result of quasi-merohedry, straight-lines of lattices with different monoclinic distortions are transformed into coherent lattice broken-lines providing minimization of the cumulative energy. Structuring is controlled by regularities of the self-organization. However stochasticity of ordering predetermines the origin areas where few domains with different tetragonality contact which leads to the origin of faulty fields braking regular passage of structuring. Resulting crystal has been found structurally non-uniform, furthermore structural non-uniformity permits identifying elements and stages of a process. However there is no precondition preventing arising the origin of homogenous states. Effect has been revealed in Ca{sub 1–x}La{sub x}F{sub 2+x} solid solution, but it can be expected that distortions of regular alternation of ions similar to antiphase domains can be obtained in non-equilibrium conditions in compounds and similar effect of the quasi-merohedry can falsify results of structural analysis.

  3. Torrefaction Processing for Human Solid Waste Management

    NASA Technical Reports Server (NTRS)

    Serio, Michael A.; Cosgrove, Joseph E.; Wójtowicz, Marek A.; Stapleton, Thomas J.; Nalette, Tim A.; Ewert, Michael K.; Lee, Jeffrey; Fisher, John

    2016-01-01

    This study involved a torrefaction (mild pyrolysis) processing approach that could be used to sterilize feces and produce a stable, odor-free solid product that can be stored or recycled, and also to simultaneously recover moisture. It was demonstrated that mild heating (200-250 C) in nitrogen or air was adequate for torrefaction of a fecal simulant and an analog of human solid waste (canine feces). The net result was a nearly undetectable odor (for the canine feces), complete recovery of moisture, some additional water production, a modest reduction of the dry solid mass, and the production of small amounts of gas and liquid. The liquid product is mainly water, with a small Total Organic Carbon content. The amount of solid vs gas plus liquid products can be controlled by adjusting the torrefaction conditions (final temperature, holding time), and the current work has shown that the benefits of torrefaction could be achieved in a low temperature range (< 250 C). These temperatures are compatible with the PTFE bag materials historically used by NASA for fecal waste containment and will reduce the energy consumption of the process. The solid product was a dry material that did not support bacterial growth and was hydrophobic relative to the starting material. In the case of canine feces, the solid product was a mechanically friable material that could be easily compacted to a significantly smaller volume (approx. 50%). The proposed Torrefaction Processing Unit (TPU) would be designed to be compatible with the Universal Waste Management System (UWMS), now under development by NASA. A stand-alone TPU could be used to treat the canister from the UWMS, along with other types of wet solid wastes, with either conventional or microwave heating. Over time, a more complete integration of the TPU and the UWMS could be achieved, but will require design changes in both units.

  4. Preliminary Results of Solid Gas Generator Micropropulsion

    NASA Technical Reports Server (NTRS)

    deGroot, Wilhelmus A.; Reed, Brian D.; Brenizer, Marshall

    1999-01-01

    A decomposing solid thruster concept, which creates a more benign thermal and chemical environment than solid propellant combustion, while maintaining, performance similar to solid combustion, is described. A Micro-Electro-Mechanical (MEMS) thruster concept with diode laser and fiber-optic initiation is proposed, and thruster components fabricated with MEMS technology are presented. A high nitrogen content solid gas generator compound is evaluated and tested in a conventional axisymmetric thrust chamber with nozzle throat area ratio of 100. Results show incomplete decomposition of this compound in both low pressure (1 kPa) and high pressure (1 MPa) environments, with decomposition of up to 80% of the original mass. Chamber pressures of 1.1 MPa were obtained, with maximum calculated thrust of approximately 2.7 N. Resistively heated wires and resistively heated walls were used to initiate decomposition. Initiation tests using available lasers were unsuccessful, but infrared spectra of the compound show that the laser initiation tests used inappropriate wavelengths for optimal propellant absorption. Optimal wavelengths for laser ignition were identified. Data presented are from tests currently in progress. Alternative solid gas generator compounds are being evaluated for future tests.

  5. Solid polymer electrolyte compositions

    DOEpatents

    Garbe, James E.; Atanasoski, Radoslav; Hamrock, Steven J.; Le, Dinh Ba

    2001-01-01

    An electrolyte composition is featured that includes a solid, ionically conductive polymer, organically modified oxide particles that include organic groups covalently bonded to the oxide particles, and an alkali metal salt. The electrolyte composition is free of lithiated zeolite. The invention also features cells that incorporate the electrolyte composition.

  6. Silicone containing solid propellant

    NASA Technical Reports Server (NTRS)

    Ramohalli, K. N. R. (Inventor)

    1980-01-01

    The addition of a small amount, for example 1% by weight, of a liquid silicone oil to a metal containing solid rocket propellant provides a significant reduction in heat transfer to the inert nozzle walls. Metal oxide slag collection and blockage of the nozzle are eliminated and the burning rate is increased by about 5% to 10% thus improving ballistic performance.

  7. A new solid lubricant

    NASA Technical Reports Server (NTRS)

    Fusaro, R. L.; Sliney, H. E.

    1969-01-01

    Friction and wear life studies on burnished films of the compound graphite fluoride have demonstrated its potential as a solid lubricant material. It is effective in moist air, dry air, or in dry argon at temperatures up to approximately 400 degrees C.

  8. Thiokol Solid Rocket Motors

    NASA Technical Reports Server (NTRS)

    Graves, S. R.

    2000-01-01

    This paper presents viewgraphs on thiokol solid rocket motors. The topics include: 1) Communications; 2) Military and government intelligence; 3) Positioning satellites; 4) Remote sensing; 5) Space burial; 6) Science; 7) Space manufacturing; 8) Advertising; 9) Space rescue space debris management; 10) Space tourism; 11) Space settlements; 12) Hazardous waste disposal; 13) Extraterrestrial resources; 14) Fast package delivery; and 15) Space utilities.

  9. Solid-State Devices.

    ERIC Educational Resources Information Center

    Sutliff, Ronald D.; And Others

    This self-study course is designed to familiarize Marine Corps enlisted personnel with the principles of solid-state devices and their functions. The course contains four study units. Each study unit begins with a general objective, which is a statement of what the student should learn from the unit. The study units are divided into numbered work…

  10. Solid State Lighting

    SciTech Connect

    Hastbacka, Mildred; Dieckmann, John; Bouza, Antonio

    2013-03-30

    The article discusses solid state lighting technologies. This topic was covered in two previous ASHRAE Journal columns (2010). This article covers advancements in technologies and the associated efficacies. The life-cycle, energy savings and market potential of these technologies are addressed as well.

  11. Solid-Waste Management

    ERIC Educational Resources Information Center

    Science Teacher, 1973

    1973-01-01

    Consists of excerpts from a forthcoming publication of the United States Environmental Protection Agency, Student's Guide to Solid-Waste Management.'' Discusses the sources of wastes from farms, mines, factories, and communities, the job of governments, ways to collect trash, methods of disposal, processing, and suggests possible student action.…

  12. Solid electrolyte structure

    DOEpatents

    Fraioli, Anthony V.

    1984-01-01

    A solid electrolyte structure for fuel cells and other electrochemical devices providing oxygen ion transfer by a multiplicity of exposed internal surfaces made of a composition containing an oxide of a multivalent transition metal and forming small pore-like passages sized to permit oxygen ion transfer while limiting the transfer of oxygen gas.

  13. INCINERATION OF SOLID WASTE

    EPA Science Inventory

    The concern over solid waste disposal and dump-site clean-up has resulted in the passage of three major U.S. environmental laws. They are the Resource Conservation and Recovery Act (RCRA) of 1976, Public Law 94-580, the Toxic Substances Control Act (TSCA) of 1976, Public Law 94-4...

  14. Solid rocket motors

    NASA Technical Reports Server (NTRS)

    Carpenter, Ronn L.

    1993-01-01

    Structural requirements, materials and, especially, processing are critical issues that will pace the introduction of new types of solid rocket motors. Designers must recognize and understand the drivers associated with each of the following considerations: (1) cost; (2) energy density; (3) long term storage with use on demand; (4) reliability; (5) safety of processing and handling; (6) operability; and (7) environmental acceptance.

  15. Gelation Mechanisms

    NASA Astrophysics Data System (ADS)

    Pekcan, Önder; Kara, Selim

    2012-10-01

    In this paper, we survey the gelation mechanisms for various polymeric systems which are classified by the type and the strength of the cross-linkages. These are the "irreversible" gels that are cross-linked chemically by covalent bonds and the "reversible" gels that are cross-linked physically by hydrogen or ionic bonds and by the physical entanglement of polymer chains. Some of the natural polymer gels fall into the class of physical gels, among which the red algae that has attracted attention for various applications is discussed in detail. Various composite gels, formed from mixture of physical and chemical gels are also discussed in the last section of the article. Theoretical models describe the gelation as a process of random linking of subunits to larger and larger molecules by formation of an infinite network, where no matter what type of objects are linked, there is always a critical "gel point" at which the system behaves neither as a liquid nor as a solid on any length scale. The Flory-Stockmayer theory and percolation theory provide bases for modeling this sol-gel phase transition. The experimental techniques for measuring the critical exponents for sol-gel phase transitions in different polymeric systems are introduced and the validation of various theoretical predictions are surveyed.

  16. Mass, energy and material balances of SRF production process. Part 3: solid recovered fuel produced from municipal solid waste.

    PubMed

    Nasrullah, Muhammad; Vainikka, Pasi; Hannula, Janne; Hurme, Markku; Kärki, Janne

    2015-02-01

    This is the third and final part of the three-part article written to describe the mass, energy and material balances of the solid recovered fuel production process produced from various types of waste streams through mechanical treatment. This article focused the production of solid recovered fuel from municipal solid waste. The stream of municipal solid waste used here as an input waste material to produce solid recovered fuel is energy waste collected from households of municipality. This article presents the mass, energy and material balances of the solid recovered fuel production process. These balances are based on the proximate as well as the ultimate analysis and the composition determination of various streams of material produced in a solid recovered fuel production plant. All the process streams are sampled and treated according to CEN standard methods for solid recovered fuel. The results of the mass balance of the solid recovered fuel production process showed that 72% of the input waste material was recovered in the form of solid recovered fuel; 2.6% as ferrous metal, 0.4% as non-ferrous metal, 11% was sorted as rejects material, 12% as fine faction and 2% as heavy fraction. The energy balance of the solid recovered fuel production process showed that 86% of the total input energy content of input waste material was recovered in the form of solid recovered fuel. The remaining percentage (14%) of the input energy was split into the streams of reject material, fine fraction and heavy fraction. The material balances of this process showed that mass fraction of paper and cardboard, plastic (soft) and wood recovered in the solid recovered fuel stream was 88%, 85% and 90%, respectively, of their input mass. A high mass fraction of rubber material, plastic (PVC-plastic) and inert (stone/rock and glass particles) was found in the reject material stream. PMID:25568089

  17. Minicipal-solid-waste biconversion technologies

    NASA Astrophysics Data System (ADS)

    Leeper, S. A.; Wolfram, J. H.; Chow, M. L.; Dawley, L. J.

    1982-10-01

    The bioconversion approach in which municipal solid waste (MSW) is a resource from which methane, ethanol, and chemicals can be produced by anaerobic digestion and fermentation is discussed. The quantity and volume of MSW requiring disposal are reduced and stabilized. The relevant literature was surveyed and is reviewed. The availability, composition, and properties of MSW are reported. Pretreatment of lignocellulosic material, the predominant compound of MSW, is described and discussed, including mechanical chemical, and physical processes.

  18. Solid Lubrication Fundamentals and Applications. Properties of Clean Surfaces: Adhesion, Friction, and Wear

    NASA Technical Reports Server (NTRS)

    Miyoshi, Kazuhisa

    1998-01-01

    This chapter presents the adhesion, friction, and wear behaviors of smooth, atomically clean surfaces of solid-solid couples, such as metal-ceramic couples, in a clean environment. Surface and bulk properties, which determine the adhesion, friction, and wear behaviors of solid-solid couples, are described. The primary emphasis is on the nature and character of the metal, especially its surface energy and ductility. Also, the mechanisms of friction and wear for clean, smooth surfaces are stated.

  19. General view of the Solid Rocket Booster's (SRB) Solid Rocket ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    General view of the Solid Rocket Booster's (SRB) Solid Rocket Motor Segments in the Surge Building of the Rotation Processing and Surge Facility at Kennedy Space Center awaiting transfer to the Vehicle Assembly Building and subsequent mounting and assembly on the Mobile Launch Platform. - Space Transportation System, Solid Rocket Boosters, Lyndon B. Johnson Space Center, 2101 NASA Parkway, Houston, Harris County, TX

  20. Solid Phase Characterization of Solids Recovered from Failed Sluicer Arm

    SciTech Connect

    Cooke, Gary A.

    2015-03-09

    The Enclosure to this memo discusses the solid phase characterization of a solid sample that was retrieved from the single-shell Tank 241-C-111 extended reach sluicer #2. This sluicer, removed from riser #3 on September 25, 2014, was found to have approximately 0.4 gallons of solid tank waste adhering to the nozzle area.