Plutonium Elastic Moduli, Electron Localization, and Temperature
International Nuclear Information System (INIS)
Migliori, Albert; Mihut-Stroe, Izabella; Betts, Jon B.
2008-01-01
In almost all materials, compression is accompanied naturally by stiffening. Even in materials with zero or negative thermal expansion, where warming is accompanied by volume contraction it is the volume change that primarily controls elastic stiffness. Not so in the metal plutonium. In plutonium, alloying with gallium can change the sign of thermal expansion, but for the positive thermal- expansion monoclinic phase as well as the face-centered-cubic phase with either sign of thermal expansion, and the orthorhombic phase, recent measurements of elastic moduli show soften on warming by an order of magnitude more than expected, the shear and compressional moduli track, and volume seems irrelevant. These effects point toward a novel mechanism for electron localization, and have important implication for the pressure dependence of the bulk compressibility. (authors)
Li, Huaiyong; Zhang, Siyuan; Zhou, Shihong; Cao, Xueqiang
2009-09-01
Theoretical researches are performed on the alpha-R2MoO6 (R = Y, Gd, Tb Dy, Ho, Er, Tm and Yb) and pyrochlore-type R2Mo2O7 (R = Y, Nd, Sm, Gd, Tb and Dy) rare earth molybdates by using chemical bond theory of dielectric description. The chemical bonding characteristics and their relationship with thermal expansion property and compressibility are explored. The calculated values of linear thermal expansion coefficient (LTEC) and bulk modulus agree well with the available experimental values. The calculations reveal that the LTECs and the bulk moduli do have linear relationship with the ionic radii of the lanthanides: the LTEC decreases from 6.80 to 6.62 10(-6)/K and the bulk modulus increases from 141 to 154 GPa when R goes in the order Gd, Tb Dy, Ho, Er, Tm, and Yb in the alpha-R2MoO6 series; while in the R2Mo2O7 series, the LTEC ranges from 6.80 to 6.61 10(-6)/K and the bulk modulus ranges from 147 to 163 GPa when R varies in the order Nd, Sm, Gd, Tb and Dy. Copyright 2008 Wiley Periodicals, Inc.
Correlations between elastic moduli and properties in bulk metallic glasses
International Nuclear Information System (INIS)
Wang Weihua
2006-01-01
A survey of the elastic, mechanical, fragility, and thermodynamic properties of bulk metallic glasses (BMGs) and glass-forming liquids is presented. It is found that the elastic moduli of BMGs have correlations with the glass transition temperature, melting temperature, mechanical properties, and even liquid fragility. On the other hand, the elastic constants of available BMGs show a rough correlation with a weighted average of the elastic constants for the constituent elements. Although the theoretical and physical reasons for the correlations are to be clarified, these correlations could assist in understanding the long-standing issues of glass formation and the nature of glass and simulate the work of theorists. Based on the correlation, we show that the elastic moduli can assist in selecting alloying components for controlling the elastic properties and glass-forming ability of the BMGs and thus can guide BMG design. As case study, we report the formation of the families of rare-earth-based BMGs with controllable properties
Simultaneous measurements of bulk moduli and particle dynamics in a sheared colloidal glass
Massa, Michael V.; Eisenmann, Christoph; Kim, Chanjoong; Weitz, David A.
2007-03-01
We present a novel study of glassy colloidal systems, using a stress-controlled rheometer in conjunction with a confocal microscope. This experimental setup combines the measurement of bulk moduli, using conventional rheology, with the ability to track the motion of individual particles, through confocal microscopy techniques. We explore the response of the system to applied shear, by simultaneously monitoring the macroscopic relaxation and microscopic particle dynamics, under conditions from the quiescent glass to a shear-melted liquid.
Zhang, Siyuan; Zhou, Shihong; Li, Huaiyong; Li, Ling
2008-09-01
The chemical bond properties, lattice energies, linear expansion coefficients, and mechanical properties of ReVO 4 (Re = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Sc, Y) are investigated systematically by the dielectric chemical bond theory. The calculated results show that the covalencies of Re-O bonds are increasing slightly from La to Lu and that the covalencies of V-O bonds in crystals are decreasing slightly from La to Lu. The linear expansion coefficients decrease progressively from LaVO 4 to LuVO 4; on the contrary, the bulk moduli increase progressively. Our calculated results are in good agreement with some experimental values for linear expansion coefficients and bulk moduli.
International Nuclear Information System (INIS)
Jo, Hyu Sang; Kang, Hee Yong; Lee, Gyo Woo
2015-01-01
In this experimental study, the thermal stability values of micrometer-sized silica particle-reinforced epoxy composite specimens were evaluated by measuring their thermal expansion coefficients and Young's moduli. For all specimens used in this study (from the baseline specimen to that containing 70 wt% silica filler), the thermal expansion coefficients and Young's moduli were gradually reduced down to 25% and increased up to 51%, respectively. The results of the experiment were compared with those of certain empirical models. The experimental results of the measurement of thermal expansion coefficients corresponded well with those of Kerner's model, which considers the bulk and shear moduli of the matrix and silica filler. However, the results of the measurement of Young's moduli using the empirical Mori-Tanaka model were observed to match better with those of the experiment. The comparison of the results of the experiment with those of the empirical models demonstrated that a reliable model for measuring the thermal expansion coefficients and Young's moduli of composite specimens needs to consider certain property variations in the composites in addition to volume fraction changes in the filler and matrix
Thermal expansion and elastic moduli of the silicide based intermetallic alloys Ti5Si3(X) and Nb5Si3
International Nuclear Information System (INIS)
Zhang, L.; Wu, J.
1997-01-01
Silicides are among those potential candidates for high temperature application because of their high melting temperature, low density and good oxidation resistance. Recent interest is focused on molybdenum silicides and titanium silicides. Extensive investigation has been carried out on MoSi 2 , yet comparatively less work was performed on titanium silicides such as Ti 5 Si 3 and Ti 3 and TiSi 2 which are of lower density than MoSi 2 . Fundamental understanding of the titanium silicides' properties for further evaluation their potential for practical application are thus needed. The thermal expansion coefficients and elastic moduli of intermetallic compounds are two properties important for evaluation as a first step. The thermal expansion determines the possible stress that might arise during cooling for these high melting point compounds, which is crucial to the preparation of defect free specimens; and the elastic moduli are usually reflections of the cohesion in crystal. In Frommeyer's work and some works afterwards, the coefficients of thermal expansion were measured on both polycrystalline and single crystal Ti 5 Si 3 . The elastic modulus of polycrystalline Ti 5 Si 3 was measured by Frommeyer and Rosenkranz. However, in the above works, the referred Ti 5 Si 3 was the binary one, no alloying effect has been reported on this matter. Moreover, the above parameters (coefficient of thermal expansion and elastic modulus) of Nb 5 Si 3 remain unreported so far. In this paper, the authors try to extend the knowledge of alloyed Ti 5 Si 3 compounds with Nb and Cr additions. Results on the coefficients of thermal expansion and elastic moduli of Ti 5 Si 3 compounds and Nb 5 Si 3 are presented and the discussion is focused on the alloying effect
Energy Technology Data Exchange (ETDEWEB)
Jo, Hyu Sang; Kang, Hee Yong; Lee, Gyo Woo [Chonbuk National University, Jeonju (Korea, Republic of)
2015-02-15
In this experimental study, the thermal stability values of micrometer-sized silica particle-reinforced epoxy composite specimens were evaluated by measuring their thermal expansion coefficients and Young's moduli. For all specimens used in this study (from the baseline specimen to that containing 70 wt% silica filler), the thermal expansion coefficients and Young's moduli were gradually reduced down to 25% and increased up to 51%, respectively. The results of the experiment were compared with those of certain empirical models. The experimental results of the measurement of thermal expansion coefficients corresponded well with those of Kerner's model, which considers the bulk and shear moduli of the matrix and silica filler. However, the results of the measurement of Young's moduli using the empirical Mori-Tanaka model were observed to match better with those of the experiment. The comparison of the results of the experiment with those of the empirical models demonstrated that a reliable model for measuring the thermal expansion coefficients and Young's moduli of composite specimens needs to consider certain property variations in the composites in addition to volume fraction changes in the filler and matrix.
Braneworld gravity: Influence of the moduli fields
International Nuclear Information System (INIS)
Barcelo, Carlos; Visser, Matt
2000-01-01
We consider the case of a generic braneworld geometry in the presence of one or more moduli fields (e.g., the dilaton) that vary throughout the bulk spacetime. Working in an arbitrary conformal frame, using the generalized junction conditions of gr-qc/0008008 and the Gauss-Codazzi equations, we derive the effective ''induced'' on-brane gravitational equations. As usual in braneworld scenarios, these equations do not form a closed system in that the bulk can exchange both information and stress-energy with the braneworld. We work with an arbitrary number of moduli fields described by an arbitrary sigma model, with arbitrary curvature couplings, arbitrary self interactions, and arbitrary dimension for the bulk. (The braneworld is always codimension one.) Among the novelties we encounter are modifications of the on-brane stress-energy conservation law, anomalous couplings between on-brane gravity and the trace of the on-brane stress-energy tensor, and additional possibilities for modifying the on-brane effective cosmological constant. After obtaining the general stress-energy ''conservation'' law and the ''induced Einstein equations'' we particularize the discussion to two particularly attractive cases: for a (n-2)-brane in ([n-1]+1) dimensions we discuss both the effect of (1) generic variable moduli fields in the Einstein frame, and (2) the effect of a varying dilaton in the string frame. (author)
On moduli stabilisation and de Sitter vacua in MSSM heterotic orbifolds
Energy Technology Data Exchange (ETDEWEB)
Parameswaran, Susha L. [Uppsala Univ. (Sweden). Dept. of Physics and Astronomy; Ramos-Sanchez, Saul [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Zavala, Ivonne [Bonn Univ. (Germany). Bethe Center for Theoretical Physics and Physikalisches Inst.
2010-09-15
We study the problem of moduli stabilisation in explicit heterotic orbifold compactifications, whose spectra contain the MSSM plus some vector-like exotics that can be decoupled. Considering all the bulk moduli, we obtain the 4D low energy effective action for the compactification, which has contributions from various, computable, perturbative and non-perturbative effects. Hidden sector gaugino condensation and string worldsheet instantons result in a combination of racetrack, KKLT and cusp-form contributions to the superpotential, which lift all the bulk moduli directions. We point out the properties observed in our concrete models, which tend to be missed when only ''generic'' features of a model are assumed. We search for interesting vacua and find several de Sitter solutions, but so far, they all turn out to be unstable. (orig.)
Moduli effective action in warped brane-world compactifications
Energy Technology Data Exchange (ETDEWEB)
Garriga, Jaume E-mail: garriga@ifae.es; Pujolas, Oriol; Tanaka, Takahiro
2003-04-07
We consider a class of 5D brane-world solutions with a power-law warp factor a(y){proportional_to}y{sup q}, and bulk dilaton with profile phi{proportional_to}lny, where y is the proper distance in the extra dimension. This class includes the heterotic M-theory brane-world of [Phys. Rev. D 59 (1999) 086001, and] and the Randall-Sundrum (RS) model as a limiting case. In general, there are two moduli fields y{sub {+-}}, corresponding to the 'positions' of two branes (which live at the fixed points of an orbifold compactification). Classically, the moduli are massless, due to a scaling symmetry of the action. However, in the absence of supersymmetry, they develop an effective potential at one loop. Local terms proportional to K{sub {+-}}{sup 4}, where K{sub {+-}}=q/y{sub {+-}} is the local curvature scale at the location of the corresponding brane, are needed in order to remove the divergences in the effective potential. Such terms break the scaling symmetry and hence they may act as stabilizers for the moduli. When the branes are very close to each other, the effective potential induced by massless bulk fields behaves like V{approx}d{sup -4}, where d is the separation between branes. When the branes are widely separated, the potentials for each one of the moduli generically develop a 'Coleman-Weinberg'-type behaviour of the form a{sup 4}(y{sub {+-}})K{sub {+-}}{sup 4}ln(K{sub {+-}}/{mu}{sub {+-}}), where {mu}{sub {+-}} are renormalization scales. In the RS case, the bulk geometry is AdS and K{sub {+-}} are equal to a constant, independent of the position of the branes, so these terms do not contribute to the mass of the moduli. However, for generic warp factor, they provide a simple stabilization mechanism. For q > or approx. 10, the observed hierarchy can be naturally generated by this potential, giving the lightest modulus a mass of order m{sub -} < or approx. TeV.
Moduli effective action in warped brane-world compactifications
International Nuclear Information System (INIS)
Garriga, Jaume; Pujolas, Oriol; Tanaka, Takahiro
2003-01-01
We consider a class of 5D brane-world solutions with a power-law warp factor a(y)∝y q , and bulk dilaton with profile phi∝lny, where y is the proper distance in the extra dimension. This class includes the heterotic M-theory brane-world of [Phys. Rev. D 59 (1999) 086001, and] and the Randall-Sundrum (RS) model as a limiting case. In general, there are two moduli fields y ± , corresponding to the 'positions' of two branes (which live at the fixed points of an orbifold compactification). Classically, the moduli are massless, due to a scaling symmetry of the action. However, in the absence of supersymmetry, they develop an effective potential at one loop. Local terms proportional to K ± 4 , where K ± =q/y ± is the local curvature scale at the location of the corresponding brane, are needed in order to remove the divergences in the effective potential. Such terms break the scaling symmetry and hence they may act as stabilizers for the moduli. When the branes are very close to each other, the effective potential induced by massless bulk fields behaves like V∼d -4 , where d is the separation between branes. When the branes are widely separated, the potentials for each one of the moduli generically develop a 'Coleman-Weinberg'-type behaviour of the form a 4 (y ± )K ± 4 ln(K ± /μ ± ), where μ ± are renormalization scales. In the RS case, the bulk geometry is AdS and K ± are equal to a constant, independent of the position of the branes, so these terms do not contribute to the mass of the moduli. However, for generic warp factor, they provide a simple stabilization mechanism. For q > or approx. 10, the observed hierarchy can be naturally generated by this potential, giving the lightest modulus a mass of order m - < or approx. TeV
Theory of thermal expansivity and bulk modulus
International Nuclear Information System (INIS)
Kumar, Munish
2005-01-01
The expression for thermal expansivity and bulk modulus, claimed by Shanker et al. to be new [Physica B 233 (1977) 78; 245 (1998) 190; J. Phys. Chem. Solids 59 (1998) 197] are compared with the theory of high pressure-high temperature reported by Kumar and coworkers. It is concluded that the Shanker formulation and the relations based on this are equal to the approach of Kumar et al. up to second order
Ullemeyer, Klaus; Lokajíček, Tomás; Vasin, Roman N.; Keppler, Ruth; Behrmann, Jan H.
2018-02-01
In this study elastic moduli of three different rock types of simple (calcite marble) and more complex (amphibolite, micaschist) mineralogical compositions were determined by modeling of elastic moduli using texture (crystallographic preferred orientation; CPO) data, experimental investigation and extrapolation. 3D models were calculated using single crystal elastic moduli, and CPO measured using time-of-flight neutron diffraction at the SKAT diffractometer in Dubna (Russia) and subsequently analyzed using Rietveld Texture Analysis. To define extrinsic factors influencing elastic behaviour, P-wave and S-wave velocity anisotropies were experimentally determined at 200, 400 and 600 MPa confining pressure. Functions describing variations of the elastic moduli with confining pressure were then used to predict elastic properties at 1000 MPa, revealing anisotropies in a supposedly crack-free medium. In the calcite marble elastic anisotropy is dominated by the CPO. Velocities continuously increase, while anisotropies decrease from measured, over extrapolated to CPO derived data. Differences in velocity patterns with sample orientation suggest that the foliation forms an important mechanical anisotropy. The amphibolite sample shows similar magnitudes of extrapolated and CPO derived velocities, however the pattern of CPO derived velocity is closer to that measured at 200 MPa. Anisotropy decreases from the extrapolated to the CPO derived data. In the micaschist, velocities are higher and anisotropies are lower in the extrapolated data, in comparison to the data from measurements at lower pressures. Generally our results show that predictions for the elastic behavior of rocks at great depths are possible based on experimental data and those computed from CPO. The elastic properties of the lower crust can, thus, be characterized with an improved degree of confidence using extrapolations. Anisotropically distributed spherical micro-pores are likely to be preserved, affecting
Dynamic elastic moduli of rocks under pressure
Energy Technology Data Exchange (ETDEWEB)
Schock, R N [Lawrence Radiation Laboratory, University of California, Livermore, CA (United States)
1970-05-01
Elastic moduli are determined as a function of confining pressure to 10 kb on rocks in which Plowshare shots are to be fired. Numerical simulation codes require accurate information on the mechanical response of the rock medium to various stress levels in order to predict cavity dimensions. The theoretical treatment of small strains in an elastic medium relates the propagation velocity of compressional and shear waves to the elastic moduli. Velocity measurements can provide, as unique code input data, the rigidity modulus, Poisson' ratio and the shear wave velocity, as well as providing checks on independent determinations of the other moduli. Velocities are determined using pulsed electro-mechanical transducers and measuring the time-of-flight in the rock specimen. A resonant frequency of 1 MHz is used to insure that the wavelength exceeds the average grain dimension and is subject to bulk rock properties. Data obtained on a variety of rock types are presented and analyzed. These data are discussed in terms of their relationship to moduli measured by static methods as well as the effect of anisotropy, porosity, and fractures. In general, fractured rocks with incipient cracks show large increases in velocity and moduli in the first 1 to 2 kb of compression as a result of the closing of these voids. After this, the velocities increase much more slowly. Dynamic moduli for these rocks are often 10% higher than corresponding static moduli at low pressure, but this difference decreases as the voids are closed until the moduli agree within experimental error. The discrepancy at low pressure is a result of the elastic energy in the wave pulse being propagated around cracks, with little effect on propagation velocity averaged over the entire specimen. (author)
Dynamic elastic moduli of rocks under pressure
International Nuclear Information System (INIS)
Schock, R.N.
1970-01-01
Elastic moduli are determined as a function of confining pressure to 10 kb on rocks in which Plowshare shots are to be fired. Numerical simulation codes require accurate information on the mechanical response of the rock medium to various stress levels in order to predict cavity dimensions. The theoretical treatment of small strains in an elastic medium relates the propagation velocity of compressional and shear waves to the elastic moduli. Velocity measurements can provide, as unique code input data, the rigidity modulus, Poisson' ratio and the shear wave velocity, as well as providing checks on independent determinations of the other moduli. Velocities are determined using pulsed electro-mechanical transducers and measuring the time-of-flight in the rock specimen. A resonant frequency of 1 MHz is used to insure that the wavelength exceeds the average grain dimension and is subject to bulk rock properties. Data obtained on a variety of rock types are presented and analyzed. These data are discussed in terms of their relationship to moduli measured by static methods as well as the effect of anisotropy, porosity, and fractures. In general, fractured rocks with incipient cracks show large increases in velocity and moduli in the first 1 to 2 kb of compression as a result of the closing of these voids. After this, the velocities increase much more slowly. Dynamic moduli for these rocks are often 10% higher than corresponding static moduli at low pressure, but this difference decreases as the voids are closed until the moduli agree within experimental error. The discrepancy at low pressure is a result of the elastic energy in the wave pulse being propagated around cracks, with little effect on propagation velocity averaged over the entire specimen. (author)
International Nuclear Information System (INIS)
Pokrivnyj, V.V.; Bekenev, V.L.
2006-01-01
Equation of states, energy band structure, electronic density of states, and bulk moduli of the boron nitride fulborenite crystals: B 12 N 12 with a diamond lattice and B 24 N 24 , B 12 N 12 with a simple cubic lattice have been calculated for the first time by FLAPW method. Calculated parameters of these compounds are as follows: equilibrium lattice parameter, the length of B-N bond, the number of atoms per conventional cell, density, bulk modulus, band gap. Hyperdiamond B 12 N 12 is shown to have the record bulk modulus B 0 = 658 GPa [ru
Hygroscopicity and bulk thermal expansion in Y2W3O12
International Nuclear Information System (INIS)
Sumithra, S.; Umarji, A.M.
2005-01-01
Negative thermal expansion material, Y 2 W 3 O 12 has been synthesized by the solid-state method and bulk thermal expansion of the material has been investigated from 300 to 1100 K. The material reversibly forms a trihydrate composition whose X-ray diffraction pattern can be indexed to an orthorhombic unit cell with a = 10.098(1) A, b = 13.315(3) A, c = 9.691(4) A. The cell volume of the hydrated pattern is 7% smaller than the unhydrated cell volume. According to the dilatometric studies, the material shows a 3-6% increase in the linear strain at about 400 K, which can be attributed to the removal of water. Sintering the material at 1473 K leads to large grain size of >100 μm, which results in a large hysteresis in the bulk thermal expansion behavior. Hot pressing at 1273 K under a uniaxial pressure of 25 MPa results in a fine-grained (2-5 μm) ceramic. Glazing the ceramic prevents moisture pick up and a linear thermal expansion over the entire temperature range 1100-300 K and an average linear thermal expansion co-efficient of -9.65 x 10 -6 /K is observed. The effect of water on the thermal expansion behavior of this system is discussed
Noncommutative solitons: moduli spaces, quantization, finite θ effects and stability
Hadasz, Leszek; Rocek, Martin; Lindström, Ulf; von Unge, Rikard
2001-06-01
We find the N-soliton solution at infinite θ, as well as the metric on the moduli space corresponding to spatial displacements of the solitons. We use a perturbative expansion to incorporate the leading θ-1 corrections, and find an effective short range attraction between solitons. We study the stability of various solutions. We discuss the finite θ corrections to scattering, and find metastable orbits. Upon quantization of the two-soliton moduli space, for any finite θ, we find an s-wave bound state.
The moduli and gravitino (non)-problems in models with strongly stabilized moduli
International Nuclear Information System (INIS)
Evans, Jason L.; Olive, Keith A.; Garcia, Marcos A.G.
2014-01-01
In gravity mediated models and in particular in models with strongly stabilized moduli, there is a natural hierarchy between gaugino masses, the gravitino mass and moduli masses: m 1/2 << m 3/2 << m φ . Given this hierarchy, we show that 1) moduli problems associated with excess entropy production from moduli decay and 2) problems associated with moduli/gravitino decays to neutralinos are non-existent. Placed in an inflationary context, we show that the amplitude of moduli oscillations are severely limited by strong stabilization. Moduli oscillations may then never come to dominate the energy density of the Universe. As a consequence, moduli decay to gravitinos and their subsequent decay to neutralinos need not overpopulate the cold dark matter density
Brane Gas-Driven Bulk Expansion as a Precursor Stage to Brane Inflation
International Nuclear Information System (INIS)
Shuhmaher, Natalia; Brandenberger, Robert
2006-01-01
We propose a new way of obtaining slow-roll inflation in the context of higher dimensional models motivated by string and M theory. In our model, all extra spatial dimensions are orbifolded. The initial conditions are taken to be a hot dense bulk brane gas which drives an initial phase of isotropic bulk expansion. This phase ends when a weak potential between the orbifold fixed planes begins to dominate. For a wide class of potentials, a period during which the bulk dimensions decrease sufficiently slowly to lead to slow-roll inflation of the three dimensions parallel to the orbifold fixed planes will result. Once the separation between the orbifold fixed planes becomes of the string scale, a repulsive potential due to string effects takes over and leads to a stabilization of the radion modes. The conversion of bulk branes into radiation during the phase of bulk contraction leads to reheating
Mirror symmetry and the moduli space for generic hypersurfaces in toric varieties
Berglund, P; Klemm, A D
1995-01-01
The moduli dependence of (2,2) superstring compactifications based on Calabi--Yau hypersurfaces in weighted projective space has so far only been investigated for Fermat-type polynomial constraints. These correspond to Landau-Ginzburg orbifolds with c=9 whose potential is a sum of A-type singularities. Here we consider the generalization to arbitrary quasi-homogeneous singularities at c=9. We use mirror symmetry to derive the dependence of the models on the complexified K\\"ahler moduli and check the expansions of some topological correlation functions against explicit genus zero and genus one instanton calculations. As an important application we give examples of how non-algebraic (``twisted'') deformations can be mapped to algebraic ones, hence allowing us to study the full moduli space. We also study how moduli spaces can be nested in each other, thus enabling a (singular) transition from one theory to another. Following the recent work of Greene, Morrison and Strominger we show that this corresponds to bla...
High-pressure X-ray diffraction study of bulk- and nanocrystalline GaN
DEFF Research Database (Denmark)
Jorgensen, J.E.; Jakobsen, J.M.; Jiang, Jianzhong
2003-01-01
Bulk- and nanocrystalline GaN have been studied by high-pressure energy-dispersive X-ray diffraction. Pressure-induced structural phase transitions from the wurtzite to the NaCl phase were observed in both materials. The transition pressure was found to be 40 GPa for the bulk-crystalline GaN, while...... the wurtzite phase was retained up to 60 GPa in the case of nanocrystalline GaN. The bulk moduli for the wurtzite phases were determined to be 187 ( 7) and 319 ( 10) GPa for the bulk- and nanocrystalline phases, respectively, while the respective NaCl phases were found to have very similar bulk moduli [ 208...
Pressure derivatives of elastic moduli of fused quartz to 10 kb
Peselnick, L.; Meister, R.; Wilson, W.H.
1967-01-01
Measurements of the longitudinal and shear moduli were made on fused quartz to 10 kb at 24??5??C. The anomalous behavior of the bulk modulus K at low pressure, ???K ???P 0, at higher pressures. The pressure derivative of the rigidity modulus ???G ???P remains constant and negative for the pressure range covered. A 15-kb hydrostatic pressure vessel is described for use with ultrasonic pulse instrumentation for precise measurements of elastic moduli and density changes with pressure. The placing of the transducer outside the pressure medium, and the use of C-ring pressure seals result in ease of operation and simplicity of design. ?? 1967.
International Nuclear Information System (INIS)
Sun Xiaowei; Liu Zijiang; Chen Qifeng; Chu Yandong; Wang Chengwei
2006-01-01
The thermal expansivity and bulk modulus of ZnO with NaCl-type cubic structure were estimated by using the constant temperature and pressure molecular dynamics technique with effective pair potentials which consist of the Coulomb, dispersion, and repulsion interaction at high pressures and temperatures. It is shown that the calculated thermodynamic parameters including linear thermal expansion coefficient, isothermal bulk modulus and its pressure derivative are in good agreement with the available experimental data and the latest theoretical results. At an extended pressure and temperature ranges, linear thermal expansion coefficient and isothermal bulk modus have also been predicted. The thermodynamic properties of ZnO with NaCl-type cubic structure are summarized in the pressure 0-150 GPa ranges and the temperature up to 3000 K
Numerical solution of the ekpyrotic scenario in the moduli space approximation
International Nuclear Information System (INIS)
Soerensen, Torquil MacDonald
2005-01-01
A numerical solution to the equations of motion for the ekpyrotic bulk brane scenario in the moduli space approximation is presented. The visible universe brane has positive tension, and we use a potential that goes to zero exponentially at large distance, and also goes to zero at small distance. In the case considered, no bulk brane, visible brane collision occurs in the solution. This property and the general behavior of the solution is qualitatively the same when the visible brane tension is negative, and for many different parameter choices
Heterotic moduli stabilization
International Nuclear Information System (INIS)
Cicoli, M.; De Alwis, S.; Colorado Univ., Boulder, CO; Westphal, A.
2013-04-01
We perform a systematic analysis of moduli stabilization for weakly coupled heterotic string theory compactified on smooth Calabi-Yau three-folds. We focus on both supersymmetric and supersymmetry breaking vacua of generic (0,2) compactifications obtained by minimising the total (F+D)-term scalar potential. After reviewing how to stabilise all the geometric moduli in a supersymmetric way by including fractional fluxes, non-perturbative and threshold effects, we show that the inclusion of α' corrections leads to new de Sitter or nearly Minkowski vacua which break supersymmetry spontaneously. The minimum lies at moderately large volumes of all the geometric moduli, at perturbative values of the string coupling and at the right phenomenological value of the GUT gauge coupling. However the structure of the heterotic 3-form flux used for complex structure moduli stabilization does not contain enough freedom to tune the superpotential. This results in the generic prediction of high-scale supersymmetry breaking around the GUT scale. We finally provide a dynamical derivation of anisotropic compactifications with stabilized moduli which allow for perturbative gauge coupling unification around 10 16 GeV.
Heterotic moduli stabilization
Energy Technology Data Exchange (ETDEWEB)
Cicoli, M. [Bologna Univ. (Italy). Dipt. Fisica ed Astronomia; INFN, Bologna (Italy); Adbus Salam ICTP, Trieste (Italy); De Alwis, S. [Adbus Salam ICTP, Trieste (Italy); Colorado Univ., Boulder, CO (United States). UCB 390 Physics Dept.; Westphal, A. [DESY Hamburg (Germany). Theory Group
2013-04-15
We perform a systematic analysis of moduli stabilization for weakly coupled heterotic string theory compactified on smooth Calabi-Yau three-folds. We focus on both supersymmetric and supersymmetry breaking vacua of generic (0,2) compactifications obtained by minimising the total (F+D)-term scalar potential. After reviewing how to stabilise all the geometric moduli in a supersymmetric way by including fractional fluxes, non-perturbative and threshold effects, we show that the inclusion of {alpha}' corrections leads to new de Sitter or nearly Minkowski vacua which break supersymmetry spontaneously. The minimum lies at moderately large volumes of all the geometric moduli, at perturbative values of the string coupling and at the right phenomenological value of the GUT gauge coupling. However the structure of the heterotic 3-form flux used for complex structure moduli stabilization does not contain enough freedom to tune the superpotential. This results in the generic prediction of high-scale supersymmetry breaking around the GUT scale. We finally provide a dynamical derivation of anisotropic compactifications with stabilized moduli which allow for perturbative gauge coupling unification around 10{sup 16} GeV.
Experimental and theoretical investigation of the elastic moduli of silicate glasses and crystals
Philipps, Katharina; Stoffel, Ralf Peter; Dronskowski, Richard; Conradt, Reinhard
2017-02-01
A combined quantum-mechanical and thermodynamic approach to the mechanical properties of multicomponent silicate glasses is presented. Quantum chemical calculations based on density-functional theory (DFT) on various silicate systems were performed to explore the crystalline polymorphs existing for a given chemical composition. These calculations reproduced the properties of known polymorphs even in systems with extensive polymorphism, like MgSiO3. Properties resting on the atomic and electronic structure, i.e., molar volumes (densities) and bulk moduli were predicted correctly. The theoretical data (molar equilibrium volumes, bulk moduli) were then used to complement the available experimental data. In a phenomenological evaluation, experimental data of bulk moduli, a macroscopic property resting on phononic structure, were found to linearly scale with the ratios of atomic space demand to actual molar volume in a universal way. Silicates ranging from high-pressure polymorphs to glasses were represented by a single master line. This suggests that above the Debye limit (in practice: above room temperature), the elastic waves probe the short range order coordination polyhedra and their next-neighbor linkage only, while the presence or absence of an extended translational symmetry is irrelevant. As a result, glasses can be treated - with respect to the properties investigated - as commensurable members of polymorphic series. Binary glasses fit the very same line as their one-component end-members, again both in the crystalline and glassy state. Finally, it is shown that the macroscopic properties of multicomponent glasses also are linear superpositions of the properties of their constitutional phases (as determined from phase diagrams or by thermochemical calculations) taken in their respective glassy states. This is verified experimentally for heat capacities and Young’s moduli of industrial glass compositions. It can be concluded, that the combined quantum
On bulk viscosity and moduli decay
International Nuclear Information System (INIS)
Laine, Mikko
2010-01-01
This pedagogically intended lecture, one of four under the header 'Basics of thermal QCD', reviews an interesting relationship, originally pointed out by Boedeker, that exists between the bulk viscosity of Yang-Mills theory (of possible relevance to the hydrodynamics of heavy ion collision experiments) and the decay rate of scalar fields coupled very weakly to a heat bath (appearing in some particle physics inspired cosmological scenarios). This topic serves, furthermore, as a platform on which a number of generic thermal field theory concepts are illustrated. The other three lectures (on the QCD equation of state and the rates of elastic as well as inelastic processes experienced by heavy quarks) are recapitulated in brief encyclopedic form. (author)
Explicitly broken supersymmetry with exactly massless moduli
Energy Technology Data Exchange (ETDEWEB)
Dong, Xi [Stanford Institute for Theoretical Physics, Department of Physics, Stanford University,Stanford, CA 94305 (United States); Freedman, Daniel Z. [Stanford Institute for Theoretical Physics, Department of Physics, Stanford University,Stanford, CA 94305 (United States); Center for Theoretical Physics and Department of Mathematics,Massachusetts Institute of Technology,Cambridge, MA 02139 (United States); Zhao, Yue [Stanford Institute for Theoretical Physics, Department of Physics, Stanford University,Stanford, CA 94305 (United States)
2016-06-16
The AdS/CFT correspondence is applied to an analogue of the little hierarchy problem in three-dimensional supersymmetric theories. The bulk is governed by a supergravity theory in which a U(1) × U(1) R-symmetry is gauged by Chern-Simons fields. The bulk theory is deformed by a boundary term quadratic in the gauge fields. It breaks SUSY completely and sources an exactly marginal operator in the dual CFT. SUSY breaking is communicated by gauge interactions to bulk scalar fields and their spinor superpartners. The bulk-to-boundary propagator of the Chern-Simons fields is a total derivative with respect to the bulk coordinates. Integration by parts and the Ward identity permit evaluation of SUSY breaking effects to all orders in the strength of the deformation. The R-charges of scalars and spinors differ so large SUSY breaking mass shifts are generated. Masses of R-neutral particles such as scalar moduli are not shifted to any order in the deformation strength, despite the fact that they may couple to R-charged fields running in loops. We also obtain a universal deformation formula for correlation functions under an exactly marginal deformation by a product of holomorphic and anti-holomorphic U(1) currents.
Moduli mediation without moduli-induced gravitino problem
Energy Technology Data Exchange (ETDEWEB)
Akita, Kensuke [Department of Physics, Waseda University, Tokyo, 169-8555 (Japan); Kobayashi, Tatsuo [Department of Physics, Hokkaido University,Sapporo, 060-0810 (Japan); Oikawa, Akane; Otsuka, Hajime [Department of Physics, Waseda University, Tokyo, 169-8555 (Japan)
2016-05-30
We study the moduli-induced gravitino problem within the framework of the phenomenologically attractive mirage mediations. The huge amount of gravitino generated by the moduli decay can be successfully diluted by introducing an extra light modulus field which does not induce the supersymmetry breaking. Since the lifetime of extra modulus field becomes longer than usually considered modulus field, our proposed mechanism is applied to both the low- and high-scale supersymmetry breaking scenarios. We also point out that such an extra modulus field appears in the flux compactification of type II string theory.
Structures and Elastic Moduli of Polymer Nanocomposite Thin Films
Yuan, Hongyi; Karim, Alamgir; University of Akron Team
2014-03-01
Polymeric thin films generally possess unique mechanical and thermal properties due to confinement. In this study we investigated structures and elastic moduli of polymer nanocomposite thin films, which can potentially find wide applications in diverse areas such as in coating, permeation and separation. Conventional thermoplastics (PS, PMMA) and biopolymers (PLA, PCL) were chosen as polymer matrices. Various types of nanoparticles were used including nanoclay, fullerene and functionalized inorganic particles. Samples were prepared by solvent-mixing followed by spin-coating or flow-coating. Film structures were characterized using X-ray scattering and transmission electron microscopy. Elastic moduli were measured by strain-induced elastic buckling instability for mechanical measurements (SIEBIMM), and a strengthening effect was found in certain systems due to strong interaction between polymers and nanoparticles. The effects of polymer structure, nanoparticle addition and film thickness on elastic modulus will be discussed and compared with bulk materials.
Special geometry on the moduli space for the two-moduli non-Fermat Calabi–Yau
Directory of Open Access Journals (Sweden)
Konstantin Aleshkin
2018-01-01
Full Text Available We clarify the recently proposed method for computing a special Kähler metric on a Calabi–Yau complex structure moduli space using the fact that the moduli space is a subspace of a particular Frobenius manifold. We use this method to compute a previously unknown special Kähler metric in a two-moduli non-Fermat model.
Special geometry on the moduli space for the two-moduli non-Fermat Calabi-Yau
Aleshkin, Konstantin; Belavin, Alexander
2018-01-01
We clarify the recently proposed method for computing a special Kähler metric on a Calabi-Yau complex structure moduli space using the fact that the moduli space is a subspace of a particular Frobenius manifold. We use this method to compute a previously unknown special Kähler metric in a two-moduli non-Fermat model.
Anti-D3 branes and moduli in non-linear supergravity
Garcia del Moral, Maria P.; Parameswaran, Susha; Quiroz, Norma; Zavala, Ivonne
2017-10-01
Anti-D3 branes and non-perturbative effects in flux compactifications spontaneously break supersymmetry and stabilise moduli in a metastable de Sitter vacua. The low energy 4D effective field theory description for such models would be a supergravity theory with non-linearly realised supersymmetry. Guided by string theory modular symmetry, we compute this non-linear supergravity theory, including dependence on all bulk moduli. Using either a constrained chiral superfield or a constrained vector field, the uplifting contribution to the scalar potential from the anti-D3 brane can be parameterised either as an F-term or Fayet-Iliopoulos D-term. Using again the modular symmetry, we show that 4D non-linear supergravities that descend from string theory have an enhanced protection from quantum corrections by non-renormalisation theorems. The superpotential giving rise to metastable de Sitter vacua is robust against perturbative string-loop and α' corrections.
The Hilbert Series of the One Instanton Moduli Space
Benvenuti, Sergio; Mekareeya, Noppadol; 10.1007
2010-01-01
The moduli space of k G-instantons on R^4 for a classical gauge group G is known to be given by the Higgs branch of a supersymmetric gauge theory that lives on Dp branes probing D(p + 4) branes in Type II theories. For p = 3, these (3 + 1) dimensional gauge theories have N = 2 supersymmetry and can be represented by quiver diagrams. The F and D term equations coincide with the ADHM construction. The Hilbert series of the moduli spaces of one instanton for classical gauge groups is easy to compute and turns out to take a particularly simple form which is previously unknown. This allows for a G invariant character expansion and hence easily generalisable for exceptional gauge groups, where an ADHM construction is not known. The conjectures for exceptional groups are further checked using some new techniques like sewing relations in Hilbert Series. This is applied to Argyres-Seiberg dualities.
International Nuclear Information System (INIS)
Page, L.; Heard, H.C.
1981-01-01
Young's modulus (E), bulk modulus (K), and the coefficient of thermal linear expansion (α) have been determined for Climax quartz monzonite to 500 0 C and pressures (P) to 55 MPa and for Sudbury gabbro to 300 0 C and 55 MPa. For each rock, both E and K decreased with T and increased with P in a nonlinear manner. In the monzonite, E and K decreased by up to 60% as P decreased from 55.2 to 6.9 MPa isothermally, while the gabbro indicated a decrease up to 70% over the same pressure range. As T increased isobarically, E and K for the monzonite decreased by up to a factor of approx. 80% from 19 to 500 0 C. The moduli of the gabbro decreased by as much as 70% from 19 to 300 0 C. α for the monzonite increased with T and decreased with P in a nonmonotonic fashion, with most measured values for α greater than values calculated for the crack-free aggregate. Depending on P, α in the monzonite increased from 8 to 11.10 -6 0 C -1 at 40 0 C to 22 to 25.10 -6 C -1 at 475 0 C. For the gabbro, α also generally decreased with increasing P. Values ranged from 6 to 11.10 -6 0 C -1 , showing a nonlinear trend and very little net increas over the T range from 19 to 300 0 C. Calculated permeability of these rocks based on the α determinations indicated that permeabilities may increase by up to a factor of 3 over the temperature interval 19 to 300 0 C, and the permeability of the monzonite is inferred to increase by up to a factor of 8 by 500 0 C. In both rocks, most measurements are consistent with microcracks controlling the thermoelastic response by opening with T and closing with sigma and P
Moduli of weighted hyperplane arrangements
Lahoz, Martí; Macrí, Emanuele; Stellari, Paolo
2015-01-01
This book focuses on a large class of geometric objects in moduli theory and provides explicit computations to investigate their families. Concrete examples are developed that take advantage of the intricate interplay between Algebraic Geometry and Combinatorics. Compactifications of moduli spaces play a crucial role in Number Theory, String Theory, and Quantum Field Theory – to mention just a few. In particular, the notion of compactification of moduli spaces has been crucial for solving various open problems and long-standing conjectures. Further, the book reports on compactification techniques for moduli spaces in a large class where computations are possible, namely that of weighted stable hyperplane arrangements.
The moduli problem for plane branches
Zariski, Oscar
2006-01-01
Moduli problems in algebraic geometry date back to Riemann's famous count of the 3g-3 parameters needed to determine a curve of genus g. In this book, Zariski studies the moduli space of curves of the same equisingularity class. After setting up and reviewing the basic material, Zariski devotes one chapter to the topology of the moduli space, including an explicit determination of the rare cases when the space is compact. Chapter V looks at specific examples where the dimension of the generic component can be determined through rather concrete methods. Zariski's last chapter concerns the application of deformation theory to the moduli problem, including the determination of the dimension of the generic component for a particular family of curves. An appendix by Bernard Teissier reconsiders the moduli problem from the point of view of deformation theory. He gives new proofs of some of Zariski's results, as well as a natural construction of a compactification of the moduli space.
Supersymmetric moduli stabilization and high-scale inflation
International Nuclear Information System (INIS)
Buchmueller, Wilfried; Wieck, Clemens; Winkler, Martin Wolfgang
2014-04-01
We study the back-reaction of moduli fields on the inflaton potential in generic models of F-term inflation. We derive the moduli corrections as a power series in the ratio of Hubble scale and modulus mass. The general result is illustrated with two examples, hybrid inflation and chaotic inflation. We find that in both cases the decoupling of moduli dynamics and inflation requires moduli masses close to the scale of grand unification. For smaller moduli masses the CMB observables are strongly affected.
Moduli stabilization in non-geometric backgrounds
International Nuclear Information System (INIS)
Becker, Katrin; Becker, Melanie; Vafa, Cumrun; Walcher, Johannes
2007-01-01
Type II orientifolds based on Landau-Ginzburg models are used to describe moduli stabilization for flux compactifications of type II theories from the world-sheet CFT point of view. We show that for certain types of type IIB orientifolds which have no Kaehler moduli and are therefore intrinsically non-geometric, all moduli can be explicitly stabilized in terms of fluxes. The resulting four-dimensional theories can describe Minkowski as well as anti-de Sitter vacua. This construction provides the first string vacuum with all moduli frozen and leading to a 4D Minkowski background
String moduli stabilization at the conifold
Energy Technology Data Exchange (ETDEWEB)
Blumenhagen, Ralph; Herschmann, Daniela; Wolf, Florian [Max-Planck-Institut für Physik (Werner-Heisenberg-Institut),Föhringer Ring 6, 80805 München (Germany)
2016-08-18
We study moduli stabilization for type IIB orientifolds compactified on Calabi-Yau threefolds in the region close to conifold singularities in the complex structure moduli space. The form of the periods implies new phenomena like exponential mass hierarchies even in the regime of negligible warping. Integrating out the heavy conic complex structure modulus leads to an effective flux induced potential for the axio-dilaton and the remaining complex structure moduli containing exponentially suppressed terms that imitate non-perturbative effects. It is shown that this scenario can be naturally combined with the large volume scenario so that all moduli are dynamically stabilized in the dilute flux regime. As an application of this moduli stabilization scheme, a string inspired model of aligned inflation is designed that features a parametrically controlled hierarchy of mass scales.
Energy Technology Data Exchange (ETDEWEB)
Ishiwata, Koji; Jeong, Kwang Sik [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Takahashi, Fuminobu [Tohoku Univ., Sendai (Japan). Dept. of Physics; Tokyo Univ., Kashiwa (Japan). Kavli IPMU, TODIAS
2013-12-15
We study a scenario for baryogenesis in modular cosmology and discuss its implications for the moduli stabilization mechanism and the supersymmetry (SUSY) breaking scale. If moduli fields dominate the Universe and decay into the standard model particles through diatonic couplings, the right amount of baryon asymmetry can be generated through CP violating decay of gluino into quark and squark followed by baryon-number violating squark decay. We find that, in the KKLT-type moduli stabilization, at least two non-perturbative terms are required to obtain a sizable CP phase, and that the successful baryogenesis is possible for the soft SUSY breaking mass heavier than O(1) TeV. A part of the parameter space for successful baryogenesis can be probed at the collider experiments, dinucleon decay search experiment, and the measurements of electric dipole moments of neutron and electron. It is also shown that similar baryogenesis works in the case of the gravitino- or the saxion-dominated Universe.
Note on moduli stabilization, supersymmetry breaking and axiverse
Energy Technology Data Exchange (ETDEWEB)
Higaki, Tetsutaro [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Kobayashi, Tatsuo [Kyoto Univ. (Japan). Dept. of Physics
2011-06-15
We study properties of moduli stabilization in the four dimensional N=1 supergravity theory with heavy moduli and would-be saxion-axion multiplets including light string-theoretic axions. We give general formulation for the scenario that heavy moduli and saxions are stabilized while axions remain light, assuming that moduli are stabilized near the supersymmetric solution. One can find stable vacuum, i.e. nontachyonic saxions, in the non-supersymmetric Minkowski vacua. We also discuss the cases, where the moduli are coupled to the supersymmetry breaking sector and/or moduli have contributions to supersymmetry breaking. Furthermore we study the models with axions originating from matter-like fields. Our analysis on moduli stabilization is applicable even if there are not light axion multiplets. (orig.)
Moduli determination of continuous fiber ceramic composites (CFCCs)
International Nuclear Information System (INIS)
Liaw, P.K.; Hsu, D.K.; Miriyala, N.; Snead, L.L.; McHargue, C.J.
1995-01-01
Nicalon TM /silicon carbide composites were fabricated by the Forced Chemical Vapor Infiltration (FCVI) method. Both through-thickness and in-plane (fiber fabric plane) moduli were determined using ultrasonic techniques. The through-thickness elastic constants (moduli) were found to be much less than the in-plane moduli. Increased porosity significantly decreased both in-plane and through-thickness moduli. A periodic model using a homogenization method was formulated to predict the effect of porosity on the moduli of woven fabric composites. The predicted moduli were found to be in reasonably good agreement with the experimental results. ((orig.))
Moduli fields as quintessence and the chameleon
International Nuclear Information System (INIS)
Brax, Philippe; Martin, Jerome
2007-01-01
We consider models where moduli fields are not stabilized and play the role of quintessence. In order to evade gravitational tests, we investigate the possibility that moduli behave as chameleon fields. We find that, for realistic moduli superpotentials, the chameleon effect is not strong enough, implying that moduli quintessence models are gravitationally ruled out. More generally, we state a no-go theorem for quintessence in supergravity whereby models either behave like a pure cosmological constant or violate gravitational tests
Instanton counting, Macdonald function and the moduli space of D-branes
International Nuclear Information System (INIS)
Awata, Hidetoshi; Kanno, Hiroaki
2005-01-01
We argue the connection of Nekrasov's partition function in the Ω background and the moduli space of D-branes, suggested by the idea of geometric engineering and Gopakumar-Vafa invariants. In the instanton expansion of N = 2 SU(2) Yang-Mills theory the Nakrasov's partition function with equivariant parameters ε 1 ,ε 2 of toric action on C 2 factorizes correctly as the character of SU(2) L x SU(2) R spin representation. We show that up to two instantons the spin contents are consistent with the Lefschetz action on the moduli space of D2-branes on (local) F 0 . We also present an attempt at constructing a refined topological vertex in terms of the Macdonald function. The refined topological vertex with two parameters of T 2 action allows us to obtain the generating functions of equivariant χ y and elliptic genera of the Hilbert scheme of n points on C 2 by the method of topological vertex
O'Grady, Kieran G
2016-01-01
The author studies the GIT quotient of the symplectic grassmannian parametrizing lagrangian subspaces of \\bigwedge^3{\\mathbb C}^6 modulo the natural action of \\mathrm{SL}_6, call it \\mathfrak{M}. This is a compactification of the moduli space of smooth double EPW-sextics and hence birational to the moduli space of HK 4-folds of Type K3^{[2]} polarized by a divisor of square 2 for the Beauville-Bogomolov quadratic form. The author will determine the stable points. His work bears a strong analogy with the work of Voisin, Laza and Looijenga on moduli and periods of cubic 4-folds.
Moduli spaces in algebraic geometry
International Nuclear Information System (INIS)
Goettsche, L.
2000-01-01
This volume of the new series of lecture notes of the Abdus Salam International Centre for Theoretical Physics contains the lecture notes of the School on Algebraic Geometry which took place at the Abdus Salam International Centre for Theoretical Physics from 26 July to 13 August 1999. The school consisted of 2 weeks of lecture courses and one week of conference. The topic of the school was moduli spaces. More specifically the lectures were divided into three subtopics: principal bundles on Riemann surfaces, moduli spaces of vector bundles and sheaves on projective varieties, and moduli spaces of curves
The Linear Thermal Expansion of Bulk Nanocrystalline Ingot Iron from Liquid Nitrogen to 300 K.
Wang, S G; Mei, Y; Long, K; Zhang, Z D
2009-09-17
The linear thermal expansions (LTE) of bulk nanocrystalline ingot iron (BNII) at six directions on rolling plane and conventional polycrystalline ingot iron (CPII) at one direction were measured from liquid nitrogen temperature to 300 K. Although the volume fraction of grain boundary and residual strain of BNII are larger than those of CPII, LTE of BNII at the six measurement directions were less than those of CPII. This phenomenon could be explained with Morse potential function and the crystalline structure of metals. Our LTE results ruled out that the grain boundary and residual strain of BNII did much contribution to its thermal expansion. The higher interaction potential energy of atoms, the less partial derivative of interaction potential energy with respect to temperature T and the porosity free at the grain boundary of BNII resulted in less LTE in comparison with CPII from liquid nitrogen temperature to 300 K. The higher LTE of many bulk nanocrystalline materials resulted from the porosity at their grain boundaries. However, many authors attributed the higher LTE of many nanocrystalline metal materials to their higher volume fraction of grain boundaries.
The Linear Thermal Expansion of Bulk Nanocrystalline Ingot Iron from Liquid Nitrogen to 300 K
Directory of Open Access Journals (Sweden)
Mei Y
2009-01-01
Full Text Available Abstract The linear thermal expansions (LTE of bulk nanocrystalline ingot iron (BNII at six directions on rolling plane and conventional polycrystalline ingot iron (CPII at one direction were measured from liquid nitrogen temperature to 300 K. Although the volume fraction of grain boundary and residual strain of BNII are larger than those of CPII, LTE of BNII at the six measurement directions were less than those of CPII. This phenomenon could be explained with Morse potential function and the crystalline structure of metals. Our LTE results ruled out that the grain boundary and residual strain of BNII did much contribution to its thermal expansion. The higher interaction potential energy of atoms, the less partial derivative of interaction potential energy with respect to temperature T and the porosity free at the grain boundary of BNII resulted in less LTE in comparison with CPII from liquid nitrogen temperature to 300 K. The higher LTE of many bulk nanocrystalline materials resulted from the porosity at their grain boundaries. However, many authors attributed the higher LTE of many nanocrystalline metal materials to their higher volume fraction of grain boundaries.
Ridge regression for predicting elastic moduli and hardness of calcium aluminosilicate glasses
Deng, Yifan; Zeng, Huidan; Jiang, Yejia; Chen, Guorong; Chen, Jianding; Sun, Luyi
2018-03-01
It is of great significance to design glasses with satisfactory mechanical properties predictively through modeling. Among various modeling methods, data-driven modeling is such a reliable approach that can dramatically shorten research duration, cut research cost and accelerate the development of glass materials. In this work, the ridge regression (RR) analysis was used to construct regression models for predicting the compositional dependence of CaO-Al2O3-SiO2 glass elastic moduli (Shear, Bulk, and Young’s moduli) and hardness based on the ternary diagram of the compositions. The property prediction over a large glass composition space was accomplished with known experimental data of various compositions in the literature, and the simulated results are in good agreement with the measured ones. This regression model can serve as a facile and effective tool for studying the relationship between the compositions and the property, enabling high-efficient design of glasses to meet the requirements for specific elasticity and hardness.
Moduli stabilization in higher dimensional brane models
International Nuclear Information System (INIS)
Flachi, Antonino; Pujolas, Oriol; Garriga, Jaume; Tanaka, Takahiro
2003-01-01
We consider a class of warped higher dimensional brane models with topology M x Σ x S 1 /Z 2 , where Σ is a D2 dimensional manifold. Two branes of co-dimension one are embedded in such a bulk space-time and sit at the orbifold fixed points. We concentrate on the case where an exponential warp factor (depending on the distance along the orbifold) accompanies the Minkowski M and the internal space Σ line elements. We evaluate the moduli effective potential induced by bulk scalar fields in these models, and we show that generically this can stabilize the size of the extra dimensions. As an application, we consider a scenario where supersymmetry is broken not far below the cutoff scale, and the hierarchy between the electroweak and the effective Planck scales is generated by a combination of redshift and large volume effects. The latter is efficient due to the shrinking of Σ at the negative tension brane, where matter is placed. In this case, we find that the effective potential can stabilize the size of the extra dimensions (and the hierarchy) without fine tuning, provided that the internal space Σ is flat. (author)
Moduli stabilization in higher dimensional brane models
Energy Technology Data Exchange (ETDEWEB)
Flachi, Antonino; Pujolas, Oriol [IFAE, Campus UAB, 08193 Bellaterra, Barcelona (Spain)]. E-mail: pujolas@ifae.es; Garriga, Jaume [IFAE, Campus UAB, 08193 Bellaterra, Barcelona (Spain); Departament de Fisica Fonamental and C.E.R. en Astrofisica, Fisica de Particules i Cosmologia Universitat de Barcelona, Marti i Franques 1, 08028 Barcelona (Spain); Tanaka, Takahiro [Institute of Cosmology, Department of Physics and Astronomy, Tufts University, Medford MA 02155 (United States); Yukawa Institute for Theoretical Physics, Kyoto University, Kyoto 606-8502 (Japan)
2003-08-01
We consider a class of warped higher dimensional brane models with topology M x {sigma} x S{sup 1}/Z{sub 2}, where {sigma} is a D2 dimensional manifold. Two branes of co-dimension one are embedded in such a bulk space-time and sit at the orbifold fixed points. We concentrate on the case where an exponential warp factor (depending on the distance along the orbifold) accompanies the Minkowski M and the internal space {sigma} line elements. We evaluate the moduli effective potential induced by bulk scalar fields in these models, and we show that generically this can stabilize the size of the extra dimensions. As an application, we consider a scenario where supersymmetry is broken not far below the cutoff scale, and the hierarchy between the electroweak and the effective Planck scales is generated by a combination of redshift and large volume effects. The latter is efficient due to the shrinking of {sigma} at the negative tension brane, where matter is placed. In this case, we find that the effective potential can stabilize the size of the extra dimensions (and the hierarchy) without fine tuning, provided that the internal space {sigma} is flat. (author)
Moduli spaces of convex projective structures on surfaces
DEFF Research Database (Denmark)
Fock, V. V.; Goncharov, A. B.
2007-01-01
We introduce explicit parametrisations of the moduli space of convex projective structures on surfaces, and show that the latter moduli space is identified with the higher Teichmüller space for defined in [V.V. Fock, A.B. Goncharov, Moduli spaces of local systems and higher Teichmüller theory, math.......AG/0311149]. We investigate the cluster structure of this moduli space, and define its quantum version....
Quantum scattering in two black hole moduli space
International Nuclear Information System (INIS)
Sakamoto, Kenji; Shiraishi, Kiyoshi
2003-01-01
We discuss the quantum scattering process in a moduli space consisting of two maximally charged dilaton black holes. The black hole moduli space geometry has different structures for arbitrary dimensions and various values of the dilaton coupling. We study the quantum effects of the different moduli space geometries with scattering process. Then, it is found that there is a resonance state on certain moduli spaces
International Nuclear Information System (INIS)
Sewell, Thomas D.; Bennett, Carl M.
2000-01-01
Isothermal-isobaric Monte Carlo calculations were used to obtain predictions of the elastic coefficients and derived engineering moduli and Poisson ratios for crystalline hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX). The elastic coefficients were computed using the strain fluctuation formula due to Rahman and Parrinello [J. Chem. Phys. 76, 2662 (1982)]. Calculations were performed as a function of temperature (218 K≤T≤333 K) and hydrostatic pressure (0 GPa≤p≤4 GPa). The predicted values of the moduli and Poisson ratios under ambient conditions are in accord with general expectations for molecular crystals and with a very recent, unpublished determination for RDX. The moduli exhibit a sensitive pressure dependence whereas the Poisson ratios are relatively independent of pressure. The temperature dependence of the moduli is comparable to the precision of the results. However, the crystal does exhibit thermal softening for most pressures. An additional product of the calculations is information about the pressure-volume-temperature (pVT) equation of state. We obtain near-quantitative agreement with experiment for the case of hydrostatic compression and reasonable, but not quantitative, correspondence for thermal expansion. The results indicate a significant dependence of the thermal expansion coefficients on hydrostatic pressure. (c) 2000 American Institute of Physics
Metastable SUSY breaking, de Sitter moduli stabilisation and Kaehler moduli inflation
International Nuclear Information System (INIS)
Krippendorf, Sven; Quevedo, Fernando
2009-01-01
We study the influence of anomalous U(1) symmetries and their associated D-terms on the vacuum structure of global field theories once they are coupled to N = 1 supergravity and in the context of string compactifications with moduli stabilisation. In particular, we focus on a IIB string motivated construction of the ISS scenario and examine the influence of one additional U(1) symmetry on the vacuum structure. We point out that in the simplest one-Kaehler modulus compactification, the original ISS vacuum gets generically destabilised by a runaway behaviour of the potential in the modulus direction. In more general compactifications with several Kaehler moduli, we find a novel realisation of the LARGE volume scenario with D-term uplifting to de Sitter space and both D-term and F-term supersymmetry breaking. The structure of soft supersymmetry breaking terms is determined in the preferred scenario where the standard model cycle is not stabilised non-perturbatively and found to be flavour universal. Our scenario also provides a purely supersymmetric realisation of Kaehler moduli (blow-up and fibre) inflation, with similar observational properties as the original proposals but without the need to include an extra (non-SUSY) uplifting term.
Sheath and bulk expansion induced by RF bias in atmospheric pressure microwave plasma
Lee, Jimo; Nam, Woojin; Lee, Jae Koo; Yun, Gunsu
2017-10-01
A large axial volume expansion of microwave-driven plasma at atmospheric pressure is achieved by applying a low power radio frequency (RF) bias at an axial location well isolated from the original plasma bulk. The evolution of the plasma plume visualized by high speed ICCD imaging suggest that the free electrons drifting toward the bias electrode cause the prodigious expansion of the sheath, creating a stable plasma stream channel between the microwave and the RF electrodes. For argon plasma in ambient air, enhanced emissions of OH and N2 spectral lines are measured in the extended plume region, supporting the acceleration of electrons and subsequent generation of radical species. The coupling of RF bias with microwave provides an efficient way of enlarging the plasma volume and enhancing the production of radicals. Work supported by the National Research Foundation of Korea under BK21+ program and Grant No. 2015R1D1A1A01061556 (Ministry of Education).
String moduli inflation. An overview
Energy Technology Data Exchange (ETDEWEB)
Cicoli, Michele [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Quevedo, Fernando [Cambridge Univ. (United Kingdom). DAMTP/CMS; Abdus Salam International Centre for Theoretical Physics, Trieste (Italy)
2011-06-15
We present an overview of inflationary models derived from string theory focusing mostly on closed string moduli as inflatons. After a detailed discussion of the {eta}-problem and different approaches to address it, we describe possible ways to obtain a de Sitter vacuum with all closed string moduli stabilised. We then look for inflationary directions and present some of the most promising scenarios where the inflatons are either the real or the imaginary part of Kaehler moduli. We pay particular attention on extracting potential observable implications, showing how most of the scenarios predict negligible gravitational waves and could therefore be ruled out by the Planck satellite. We conclude by briefly mentioning some open challenges in string cosmology beyond deriving just inflation. (orig.)
String moduli inflation. An overview
International Nuclear Information System (INIS)
Cicoli, Michele; Quevedo, Fernando
2011-06-01
We present an overview of inflationary models derived from string theory focusing mostly on closed string moduli as inflatons. After a detailed discussion of the η-problem and different approaches to address it, we describe possible ways to obtain a de Sitter vacuum with all closed string moduli stabilised. We then look for inflationary directions and present some of the most promising scenarios where the inflatons are either the real or the imaginary part of Kaehler moduli. We pay particular attention on extracting potential observable implications, showing how most of the scenarios predict negligible gravitational waves and could therefore be ruled out by the Planck satellite. We conclude by briefly mentioning some open challenges in string cosmology beyond deriving just inflation. (orig.)
Temperature- and thickness-dependent elastic moduli of polymer thin films
Directory of Open Access Journals (Sweden)
Ao Zhimin
2011-01-01
Full Text Available Abstract The mechanical properties of polymer ultrathin films are usually different from those of their counterparts in bulk. Understanding the effect of thickness on the mechanical properties of these films is crucial for their applications. However, it is a great challenge to measure their elastic modulus experimentally with in situ heating. In this study, a thermodynamic model for temperature- (T and thickness (h-dependent elastic moduli of polymer thin films Ef(T,h is developed with verification by the reported experimental data on polystyrene (PS thin films. For the PS thin films on a passivated substrate, Ef(T,h decreases with the decreasing film thickness, when h is less than 60 nm at ambient temperature. However, the onset thickness (h*, at which thickness Ef(T,h deviates from the bulk value, can be modulated by T. h* becomes larger at higher T because of the depression of the quenching depth, which determines the thickness of the surface layer δ.
Energy Technology Data Exchange (ETDEWEB)
Avelino, Arturo; Nucamendi, Ulises, E-mail: avelino@ifm.umich.mx, E-mail: ulises@ifm.umich.mx [Instituto de Física y Matemáticas, Universidad Michoacana de San Nicolás de Hidalgo, Edificio C-3, Ciudad Universitaria, CP. 58040, Morelia, Michoacán (Mexico)
2010-08-01
We explore the viability of a bulk viscous matter-dominated Universe to explain the present accelerated expansion of the Universe. The model is composed by a pressureless fluid with bulk viscosity of the form ζ = ζ{sub 0}+ζ{sub 1}H where ζ{sub 0} and ζ{sub 1} are constants and H is the Hubble parameter. The pressureless fluid characterizes both the baryon and dark matter components. We study the behavior of the Universe according to this model analyzing the scale factor as well as some curvature scalars and the matter density. On the other hand, we compute the best estimated values of ζ{sub 0} and ζ{sub 1} using the type Ia Supernovae (SNe Ia) probe. We find that from all the possible scenarios for the Universe, the preferred one by the best estimated values of (ζ{sub 0},ζ{sub 1}) is that of an expanding Universe beginning with a Big-Bang, followed by a decelerated expansion at early times, and with a smooth transition in recent times to an accelerated expansion epoch that is going to continue forever. The predicted age of the Universe is a little smaller than the mean value of the observational constraint coming from the oldest globular clusters but it is still inside of the confidence interval of this constraint. A drawback of the model is the violation of the local second law of thermodynamics in redshifts z∼>1. However, when we assume ζ{sub 1} = 0, the simple model ζ = ζ{sub 0} evaluated at the best estimated value for ζ{sub 0} satisfies the local second law of thermodynamics, the age of the Universe is in perfect agreement with the constraint of globular clusters, and it also has a Big-Bang, followed by a decelerated expansion with the smooth transition to an accelerated expansion epoch in late times, that is going to continue forever.
Gravitational Particle Production and the Moduli Problem
Felder, G; Linde, Andrei D; Felder, Gary; Kofman, Lev; Linde, Andrei
2000-01-01
A theory of gravitational production of light scalar particles during and after inflation is investigated. We show that in the most interesting cases where long-wavelength fluctuations of light scalar fields can be generated during inflation, these fluctuations rather than quantum fluctuations produced after inflation give the dominant contribution to particle production. In such cases a simple analytical theory of particle production can be developed. Application of our results to the theory of quantum creation of moduli fields demonstrates that if the moduli mass is smaller than the Hubble constant then these fields are copiously produced during inflation. This gives rise to the cosmological moduli problem even if there is no homogeneous component of the classical moduli field in the universe. To avoid this version of the moduli problem it is necessary for the Hubble constant H during the last stages of inflation and/or the reheating temperature T_R after inflation to be extremely small.
Farkas, Gavril; Geer, Gerard
2016-01-01
This book provides an overview of the latest developments concerning the moduli of K3 surfaces. It is aimed at algebraic geometers, but is also of interest to number theorists and theoretical physicists, and continues the tradition of related volumes like “The Moduli Space of Curves” and “Moduli of Abelian Varieties,” which originated from conferences on the islands Texel and Schiermonnikoog and which have become classics. K3 surfaces and their moduli form a central topic in algebraic geometry and arithmetic geometry, and have recently attracted a lot of attention from both mathematicians and theoretical physicists. Advances in this field often result from mixing sophisticated techniques from algebraic geometry, lattice theory, number theory, and dynamical systems. The topic has received significant impetus due to recent breakthroughs on the Tate conjecture, the study of stability conditions and derived categories, and links with mirror symmetry and string theory. At the same time, the theory of irred...
International Nuclear Information System (INIS)
Pokropivny, V. V.; Bekenev, V. L.
2006-01-01
The energy-band structure, density of states, electron density distribution, equation of state, and bulk moduli of three boron-nitride fulborenite crystals, i.e., B 12 N 12 with diamond lattice and B 24 N 24 , B 12 N 12 with simple cubic lattice, whose sites contain fulborene B 12 N 12 and B 24 N 24 molecules, are calculated for the first time using the full-potential linearized augmented plane wave method. The following hyperdiamond B 12 N 12 parameters were obtained: the equilibrium lattice parameter a = 1.1191 nm, the B-N bond length a BN = 0.1405 nm, the number of atoms per unit cell Z = 192, the density ρ = 2.823 g/cm 3 , the bulk modulus B 0 = 658 GPa, and the band gap ΔE g = 3.05 eV. This is a previously unknown unique light superhard semiconductor faujasite with a recorded bulk modulus higher than that of diamond. There are reasons to assume that it is a E phase. The characteristics of B 24 N 24 with simple cubic lattice are as follows: the equilibrium lattice parameter a = 0.7346 nm, the B-N bond length a BN = 0.1521 nm, the number of atoms per unit cell Z = 48, the density ρ = 2.495 g/cm 3 , the bulk modulus B 0 = 367 GPa, and the band gap ΔE g = 3.76 eV. This material is a heteropolar semiconductor or insulator with a bulk modulus comparable with that of cubic boron nitride, as well as a new boron-nitride zeolite with channel diameter of 0.46 nm. B 12 N 12 with simple cubic lattice is a molecular semimetal
Evaluation of mechanical properties of Dy123 bulk superconductors by 3-point bending tests
International Nuclear Information System (INIS)
Katagiri, K.; Hatakeyama, Y.; Sato, T.; Kasaba, K.; Shoji, Y.; Murakami, A.; Teshima, H.; Hirano, H.
2006-01-01
In order to evaluate the mechanical properties, such as Young's modulus and strength, of Dy123 bulk superconductors and those with 10 wt.% Ag 2 O, we performed 3-point bending tests at room (RT) and liquid nitrogen temperatures (LNT) using specimens cut from the bulks. The Young's modulus and the bending strength increased with decrease in temperature. In the tests loading in the direction of c-axis and ones perpendicular to it, Young's moduli were almost comparable at both RT and LNT. Although the strengths for both orientations were also comparable at LNT, those at RT were different. Young's moduli loaded in the direction of c-axis for Ag 2 O added bulk specimens, 127 GPa in average at RT, were almost comparable to those without Ag 2 O, and 134 GPa at LNT, were slightly lower than those without Ag 2 O. On the other hand, the strengths at both RT and LNT were enhanced by 20% by the Ag addition. The mechanical properties of Dy123 bulks without Ag 2 O were compared with those of Y123 bulks obtained previously. The Young's modulus for loading in the direction of c-axis was slightly lower, and the strength was comparable to those in Y123 bulks, respectively
On D-brane dynamics and moduli stabilization
Kitazawa, Noriaki
2017-09-01
We discuss the effect of the dynamics of D-branes on moduli stabilization in type IIB string theory compactifications, with reference to a concrete toy model of T6/Z 3 orientifold compactification with fractional D3-branes and anti-D3-branes at orbifold fixed points. The resulting attractive forces between anti-D3-branes and D3-branes, together with the repulsive forces between anti-D3-branes and O3-planes, can affect the stability of the compact space. There are no complex structure moduli in T6/Z 3 orientifold, which should thus capture some generic features of more general settings where all complex structure moduli are stabilized by three-form fluxes. The simultaneous presence of branes and anti-branes brings along the breaking of supersymmetry. Non-BPS combinations of this type are typical of “brane supersymmetry breaking” and are a necessary ingredient in the KKLT scenario for stabilizing the remaining Kähler moduli. The conclusion of our analysis is that, while mutual D-brane interactions sometimes help Kähler moduli stabilization, this is not always the case.
Moduli stabilization in type IIB orientifolds
International Nuclear Information System (INIS)
Schulgin, W.
2007-01-01
This thesis deals with the stabilization of the moduli fields in the compactifications of the type IIB string theory on orientifolds. A concrete procedure for the construction of solutions, in which all moduli fields are fixed, yields the KKLT scenario. We study, on which models the scenario can be applied, if approximations of the original KKLT work are abandoned. We find that in a series of models, namely such without complex-structure moduli the construction of the consistent solutions in the framework of the KKLT scenario is not possible. The nonperturbative effects, like D3 instantons and gaugino condensates are a further component of the KKLT scenario. They lead to the stabilization of the Kaehler moduli. We present criteria for the generation of the superpotential due to the D3 instantons at a Calaby-Yau manifold in presence of fluxes. Furthermore we show that although the presence of the nonperturbative superpotential in the equations of motions is correlated with the switching on of all ISD and IASD fluxes, the deciding criterium for the generation of the nonperturbative superpotential depends only on the fluxes of the type (2,1). Thereafter we discuss two models, in which we stabilize all moduli fields. Thereby it deals with Calabi-Yau orientifolds which have been obtained by a blow-up procedure from the Z 6-II and Z 2 x Z 4 orientifolds
Moduli space of torsional manifolds
International Nuclear Information System (INIS)
Becker, Melanie; Tseng, L.-S.; Yau, S.-T.
2007-01-01
We characterize the geometric moduli of non-Kaehler manifolds with torsion. Heterotic supersymmetric flux compactifications require that the six-dimensional internal manifold be balanced, the gauge bundle be Hermitian Yang-Mills, and also the anomaly cancellation be satisfied. We perform the linearized variation of these constraints to derive the defining equations for the local moduli. We explicitly determine the metric deformations of the smooth flux solution corresponding to a torus bundle over K3
Singular points in moduli spaces of Yang-Mills fields
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Ticciati, R.
1984-01-01
This thesis investigates the metric dependence of the moduli spaces of Yang-Mills fields of an SU(2) principal bundle P with chern number -1 over a four-dimensional, simply-connected, oriented, compact smooth manifold M with positive definite intersection form. The purpose of this investigation is to suggest that the surgery class of the moduli space of irreducible connections is, for a generic metric, a Z 2 topological invariant of the smooth structure on M. There are three main parts. The first two parts are local analysis of singular points in the moduli spaces. The last part is global. The first part shows that the set of metrics for which the moduli space of irreducible connections has only non-degenerate singularities has codimension at least one in the space of all metrics. The second part shows that, for a one-parameter family of moduli spaces in a direction transverse to the set of metrics for which the moduli spaces have singularities, passing through a non-degenerate singularity of the simplest type changes the moduli space by a cobordism. The third part shows that generic one-parameter families of metrics give rise to six-dimensional manifolds, the corresponding family of moduli spaces of irreducible connections. It is shown that when M is homeomorphic to S 4 the six-dimensional manifold is a proper cobordism, thus establishing the independence of the surgery class of the moduli space on the metric on M
Moduli space of Chern-Simons gravity
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Soda, Jiro; Yamanaka, Yuki
1990-09-01
Conformally invariant (2+1)-dimensional gravity, Chern-Shimons gravity, is studied. Its solution space, moduli space, is investigated using the linearization method. The dimension of moduli space is determined as 18g - 18 for g > 1,6 for g = 1 and 0 for g = 0. We discuss the geometrical meaning of our investigation. (author)
Moduli stabilization and the pattern of sparticle spectra
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Choi, Kiwoon
2008-01-01
We discuss the pattern of low energy sparticle spectra which appears in some class of moduli stabilization scenario. In case that light moduli are stabilized by non-perturbative effects encoded in the superpotential and a phenomenologically viable de Sitter vacuum is obtained by a sequestered supersymmetry breaking sector, the anomaly-mediated soft terms become comparable to the moduli-mediated ones, leading to a quite distinctive pattern of low energy spacticle masses dubbed the mirage mediation pattern. We also discuss low energy sparticle masses in more general mixed-mediation scenario which includes a comparable size of gauge mediation in addition to the moduli and anomaly mediations.
Thermodynamics and elastic moduli of fluids with steeply repulsive potentials
Heyes, D. M.
1997-08-01
Analytic expressions for the thermodynamic properties and elastic moduli of molecular fluids interacting with steeply repulsive potentials are derived using Rowlinson's hard-sphere perturbation treatment which employs a softness parameter, λ specifying the deviation from the hard-sphere potential. Generic potentials of this form might be used to represent the interactions between near-hard-sphere stabilized colloids. Analytic expressions for the equivalent hard-sphere diameter of inverse power [ɛ(σ/r)n where ɛ sets the energy scale and σ the distance scale] exponential and logarithmic potential forms are derived using the Barker-Henderson formula. The internal energies in the hard-sphere limit are predicted essentially exactly by the perturbation approach when compared against molecular dynamics simulation data using the same potentials. The elastic moduli are similarly accurately predicted in the hard-sphere limit, as they are trivially related to the internal energy. The compressibility factors from the perturbation expansion do not compare as favorably with simulation data, and in this case the Carnahan-Starling equation of state prediction using the analytic effective hard-sphere diameter would appear to be a preferable route for this thermodynamic property. A more refined state point dependent definition for the effective hard-sphere diameter is probably required for this property.
International Nuclear Information System (INIS)
Pandya, Tushar C; Bhatt, Apoorva D; Thakar, Nilesh A
2012-01-01
In the present paper an attempt has been made for the comparative study of different equations of state for silicon (Phase-1, cubic diamond structure) in the pressure range of 0-11 GPa. We compare the results of different equations of state (EOS) with available experimental data. The Kwon and Kim EOS is found to give far better agreement with the available experimental data. Results obtained by Poirier-Tarantola, Vinet, Tait and Suzuki's equations of state are not giving satisfactory agreement with the available experimental data. In the present study simple methods based on thermodynamic functions are presented to investigate the temperature dependence of thermal expansivity and bulk modulus for silicon. The results are reported for silicon. The calculated values of thermal expansivity are in good agreement with experimental data.
Singular moduli and Arakelov intersection
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Weng Lin.
1994-05-01
The value of the modular function j(τ) at imaginary quadratic arguments τ in the upper half plane is usually called singular moduli. In this paper, we use Arakelov intersection to give the prime factorizations of a certain combination of singular moduli, coming from the Hecke correspondence. Such a result may be considered as the degenerate one of Gross and Zagier on Heegner points and derivatives of L-series in their paper [GZ1], and is parallel to the result in [GZ2]. (author). 2 refs
Cordell, Jacqueline M; Vogl, Michelle L; Wagoner Johnson, Amy J
2009-10-01
While recognized as a promising bone substitute material, hydroxyapatite (HA) has had limited use in clinical settings because of its inherent brittle behavior. It is well established that macropores ( approximately 100 microm) in a HA implant, or scaffold, are required for bone ingrowth, but recent research has shown that ingrowth is enhanced when scaffolds also contain microporosity. HA is sensitive to synthesis and processing parameters and therefore characterization for specific applications is necessary for transition to the clinic. To that end, the mechanical behavior of bulk microporous HA and HA scaffolds with multi-scale porosity (macropores between rods in the range of 250-350 microm and micropores within the rods with average size of either 5.96 microm or 16.2 microm) was investigated in order to determine how strength and reliability were affected by micropore size (5.96 microm versus 16.2 microm). For the bulk microporous HA, strength increased with decreasing micropore size in both bending (19 MPa to 22 MPa) and compression (71 MPa to 110 MPa). To determine strength reliability, the Weibull moduli for the bulk microporous HA were determined. The Weibull moduli for bending increased (became more reliable) with decreasing pore size (7 to 10) while the Weibull moduli for compression decreased (became less reliable) with decreasing pore size (9 to 6). Furthermore, the elastic properties of the bulk microporous HA (elastic modulus of 30 GPa) and the compressive strengths of the HA scaffolds with multi-scale porosity (8 MPa) did not vary with pore size. The mechanisms responsible for the trends observed were discussed.
On moduli spaces in AdS{sub 4} supergravity
Energy Technology Data Exchange (ETDEWEB)
Alwis, Senarath de [Colorado Univ., Boulder, CO (United States). Dept. of Physics; Louis, Jan [Hamburg Univ. (Germany). Fachbereich 12 - Physik; Hamburg Univ. (Germany). Zentrum fuer Mathematische Physik; McAllister, Liam [Cornell Univ., Ithaca, NY (United States). Dept. of Physics; Triendl, Hagen [CERN, Geneva (Switzerland). Theory Division, Physics Dept.; Westphal, Alexander [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany). Gruppe Theorie
2013-12-15
We study the structure of the supersymmetric moduli spaces of N=1 and N=2 supergravity theories in AdS{sub 4} backgrounds. In the N=1 case, the moduli space cannot be a complex submanifold of the Kaehler field space, but is instead real with respect to the inherited complex structure. In N=2 supergravity the same result holds for the vector multiplet moduli space, while the hypermultiplet moduli space is a Kaehler submanifold of the quaternionic-Kaehler field space. These findings are in agreement with AdS/CFT considerations.
Accidental Kähler moduli inflation
International Nuclear Information System (INIS)
Maharana, Anshuman; Rummel, Markus; Sumitomo, Yoske
2015-01-01
We study a model of accidental inflation in type IIB string theory where inflation occurs near the inflection point of a small Kähler modulus. A racetrack structure helps to alleviate the known concern that string-loop corrections may spoil Kähler Moduli Inflation unless having a significant suppression via the string coupling or a special brane setup. Also, the hierarchy of gauge group ranks required for the separation between moduli stabilization and inflationary dynamics is relaxed. The relaxation becomes more significant when we use the recently proposed D-term generated racetrack model
Successfully combining SUGRA hybrid inflation and moduli stabilisation
International Nuclear Information System (INIS)
Davis, S.C.
2008-01-01
Inflation and moduli stabilisation mechanisms work well independently, and many string-motivated supergravitymodels have been proposed for them. However a complete theory will contain both, and there will be (gravitational) interactions between the two sectors. These give corrections to the inflaton potential, which generically ruin inflation. This holds true even for fine-tuned moduli stabilisation schemes. We show that a viable combined model can be obtained if it is the Kaehler functions (G=K+ln vertical stroke W vertical stroke 2 ) of the two sectors that are added, rather than the superpotentials (as is usually done). Interaction between the two sectors does still impose some restrictions on the moduli stabilisation mechanism, which are derived. Significantly, we find that the (post-inflation) moduli stabilisation scale no longer needs to be above the inflationary energy scale. (orig.)
Geometry and quantization of moduli spaces
Andersen, Jørgen; Riera, Ignasi
2016-01-01
This volume is based on four advanced courses held at the Centre de Recerca Matemàtica (CRM), Barcelona. It presents both background information and recent developments on selected topics that are experiencing extraordinary growth within the broad research area of geometry and quantization of moduli spaces. The lectures focus on the geometry of moduli spaces which are mostly associated to compact Riemann surfaces, and are presented from both classical and quantum perspectives.
The topology of moduli space and quantum field theory
International Nuclear Information System (INIS)
Montano, D.; Sonnenschein, J.
1989-01-01
We show how an SO(2,1) gauge theory with a fermionic symmetry may be used to describe the topology of the moduli space of curves. The observables of the theory correspond to the generators of the cohomology of moduli space. This is an extension of the topological quantum field theory introduced by Witten to investigate the cohomology of Yang-Mills instanton moduli space. We explore the basic structure of topological quantum field theories, examine a toy U(1) model, and then realize a full theory of moduli space topology. We also discuss why a pure gravity theory, as attempted in previous work, could not succeed. (orig.)
Tripathy, Haraprasanna; Hajra, Raj Narayan; Sudha, C.; Raju, S.; Saibaba, Saroja
2018-04-01
The Young's modulus (E) and Shear modulus (G) of an indigenously developed 18Cr-9Ni-0.1C-2.95 Cu-0.58Nb (wt %) austenitic stainless steel has been evaluated in the temperature range 298 K to 1273 K (25 °C to 1000 °C), using Impulse excitation technique (IET). The Bulk modulus (K) and the poison's ratio have been estimated from the measured values of E and G. It is observed that the elastic constants (E, G and K) are found to decrease in a nonlinear fashion with increase in temperature. The Cu precipitation is found to influence the elastic moduli of the steel in the cooling cycle. The observed elastic moduli are fitted to 3rd order polynomial equations in order to describe the temperature dependence of E, G, K moduli in the temperature range 298-1273 K (25 °C to 1000 °C). The room temperature values of E,G and K moduli is found to be 207, 82 and 145 GPa respectively for the present steel.
Successfully combining SUGRA hybrid inflation and moduli stabilisation
Energy Technology Data Exchange (ETDEWEB)
Davis, S.C. [CEA Centre d' Etudes de Saclay, 91 - Gif-sur-Yvette (France). Service de Physique Theorique; Postma, M. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)]|[Nationaal Inst. voor Kernfysica en Hoge-Energiefysica (NIKHEF), Amsterdam (Netherlands)
2008-01-15
Inflation and moduli stabilisation mechanisms work well independently, and many string-motivated supergravitymodels have been proposed for them. However a complete theory will contain both, and there will be (gravitational) interactions between the two sectors. These give corrections to the inflaton potential, which generically ruin inflation. This holds true even for fine-tuned moduli stabilisation schemes. We show that a viable combined model can be obtained if it is the Kaehler functions (G=K+ln vertical stroke W vertical stroke {sup 2}) of the two sectors that are added, rather than the superpotentials (as is usually done). Interaction between the two sectors does still impose some restrictions on the moduli stabilisation mechanism, which are derived. Significantly, we find that the (post-inflation) moduli stabilisation scale no longer needs to be above the inflationary energy scale. (orig.)
Energy Technology Data Exchange (ETDEWEB)
Ghosh, G., E-mail: g-ghosh@northwestern.edu [Department of Materials Science and Engineering, Robert R. McCormick School of Engineering and Applied Science, Northwestern University, 2220 Campus Drive, Evanston, IL 60208-3108 (United States)
2015-08-15
A comprehensive computational study of elastic properties of cementite (Fe{sub 3}C) and its alloyed counterparts (M{sub 3}C (M = Al, Co, Cr, Cu, Fe, Hf, Mn, Mo, Nb, Ni, Si, Ta, Ti, V, W, Zr, Cr{sub 2}FeC and CrFe{sub 2}C) having the crystal structure of Fe{sub 3}C is carried out employing electronic density-functional theory (DFT), all-electron PAW pseudopotentials and the generalized gradient approximation for the exchange-correlation energy (GGA). Specifically, as a part of our systematic study of cohesive properties of solids and in the spirit of materials genome, following properties are calculated: (i) single-crystal elastic constants, C{sub ij}, of above M{sub 3}Cs; (ii) anisotropies of bulk, Young’s and shear moduli, and Poisson’s ratio based on calculated C{sub ij}s, demonstrating their extreme anisotropies; (iii) isotropic (polycrystalline) elastic moduli (bulk, shear, Young’s moduli and Poisson’s ratio) of M{sub 3}Cs by homogenization of calculated C{sub ij}s; and (iv) acoustic Debye temperature, θ{sub D}, of M{sub 3}Cs based on calculated C{sub ij}s. We provide a critical appraisal of available data of polycrystalline elastic properties of alloyed cementite. Calculated single crystal properties may be incorporated in anisotropic constitutive models to develop and test microstructure-processing-property-performance links in multi-phase materials where cementite is a constituent phase.
International Nuclear Information System (INIS)
Du, Y.L.; Sun, Z.M.; Hashimoto, H.; Barsoum, M.W.
2009-01-01
We have performed theoretical studies on the elastic and thermodynamic properties of the solid solution: Ti 2 AlC 0.5 N 0.5 . The lattice parameters, elastic constants, bulk, shear, Young's moduli, Poisson's ratio and Debye temperature were calculated and compared with those of the end members, Ti 2 AlC and Ti 2 AlN. The temperature dependence of the bulk moduli, thermal expansion coefficient and specific heats of Ti 2 AlC 0.5 N 0.5 were obtained from the quasi-harmonic Debye model. The calculated elastic and thermodynamic properties were compared with experimental data.
Elastic Moduli of Carbon Nanohorns
Directory of Open Access Journals (Sweden)
Dinesh Kumar
2011-01-01
Full Text Available Carbon nanotube is a special case of carbon nanohorns or carbon nanocones with zero apex angle. Research into carbon nanohorns started almost at the same time as the discovery of nanotubes in 1991. Most researchers focused on the investigation of nanotubes, and the exploration of nanohorns attracted little attention. To model the carbon nanohorns, we make use of a more reliable second-generation reactive empirical bond-order potential by Brenner and coworkers. We investigate the elastic moduli and conclude that these nanohorns are equally strong and require in-depth investigation. The values of Young's and Shear moduli decrease with apex angle.
Moduli vacuum misalignment and precise predictions in string inflation
Energy Technology Data Exchange (ETDEWEB)
Cicoli, Michele [Dipartimento di Fisica ed Astronomia, Università di Bologna,via Irnerio 46, 40126 Bologna (Italy); INFN sezione di Bologna,viale Berti Pichat 6/2, 40127 Bologna (Italy); Abdus Salam ICTP,Strada Costiera 11, Trieste 34014 (Italy); Dutta, Koushik [Theory Division, Saha Institute of Nuclear Physics,1/AF Salt Lake, Kolkata 700064 (India); Maharana, Anshuman [Harish Chandra Research Intitute,Chattnag Road, Jhunsi, Allahabad 211019 (India); Quevedo, Fernando [Abdus Salam ICTP,Strada Costiera 11, Trieste 34014 (Italy); DAMTP, University of Cambridge,Wilberforce Road, Cambridge, CB3 0WA (United Kingdom)
2016-08-03
The predictions for all the cosmological observables of any inflationary model depend on the number of e-foldings which is sensitive to the post-inflationary history of the universe. In string models the generic presence of light moduli leads to a late-time period of matter domination which lowers the required number of e-foldings and, in turn, modifies the exact predictions of any inflationary model. In this paper we compute exactly the shift of the number of e-foldings in Kähler moduli inflation which is determined by the magnitude of the moduli initial displacement caused by vacuum misalignment and the moduli decay rates. We find that the preferred number of e-foldings gets reduced from 50 to 45, causing a modification of the spectral index at the percent level. Our results illustrate the importance of understanding the full post-inflationary evolution of the universe in order to derive precise predictions in string inflation. To perform this task it is crucial to work in a setting where there is good control over moduli stabilisation.
Moduli vacuum misalignment and precise predictions in string inflation
International Nuclear Information System (INIS)
Cicoli, Michele; Dutta, Koushik; Maharana, Anshuman; Quevedo, Fernando
2016-01-01
The predictions for all the cosmological observables of any inflationary model depend on the number of e-foldings which is sensitive to the post-inflationary history of the universe. In string models the generic presence of light moduli leads to a late-time period of matter domination which lowers the required number of e-foldings and, in turn, modifies the exact predictions of any inflationary model. In this paper we compute exactly the shift of the number of e-foldings in Kähler moduli inflation which is determined by the magnitude of the moduli initial displacement caused by vacuum misalignment and the moduli decay rates. We find that the preferred number of e-foldings gets reduced from 50 to 45, causing a modification of the spectral index at the percent level. Our results illustrate the importance of understanding the full post-inflationary evolution of the universe in order to derive precise predictions in string inflation. To perform this task it is crucial to work in a setting where there is good control over moduli stabilisation.
de Jong, Maarten; Chen, Wei; Notestine, Randy; Persson, Kristin; Ceder, Gerbrand; Jain, Anubhav; Asta, Mark; Gamst, Anthony
2016-10-03
Materials scientists increasingly employ machine or statistical learning (SL) techniques to accelerate materials discovery and design. Such pursuits benefit from pooling training data across, and thus being able to generalize predictions over, k-nary compounds of diverse chemistries and structures. This work presents a SL framework that addresses challenges in materials science applications, where datasets are diverse but of modest size, and extreme values are often of interest. Our advances include the application of power or Hölder means to construct descriptors that generalize over chemistry and crystal structure, and the incorporation of multivariate local regression within a gradient boosting framework. The approach is demonstrated by developing SL models to predict bulk and shear moduli (K and G, respectively) for polycrystalline inorganic compounds, using 1,940 compounds from a growing database of calculated elastic moduli for metals, semiconductors and insulators. The usefulness of the models is illustrated by screening for superhard materials.
Physical factors controlling the ductility of bulk metallic glasses
Energy Technology Data Exchange (ETDEWEB)
Liu, Y. [Central South University, China; Liu, Chain T [ORNL; Zhang, Z. [University of Tennessee, Knoxville (UTK); Keppens, V. [University of Tennessee, Knoxville (UTK)
2008-01-01
In order to identify key physical factor controlling the deformation and fracture behavior of bulk metallic glasses (BMGs), we compiled and analyzed the elastic moduli and compressive ductility for BMGs. In addition, new modulus data were generated in the critical ranges in order to facilitate the analysis. We have found that the intrinsic ductility of BMGs can be correlated with the bulk-to-shear modulus ratio B/G according to Pugh's [Philos. Mag. 45, 823 (1954) ] rule. In some individual BMG systems, for example, Fe based, the relationship seems to be very clear. The physical meaning of this correlation is discussed in terms of atomic bonding and connectivity.
Higgs, moduli problem, baryogenesis and large volume compactifications
Energy Technology Data Exchange (ETDEWEB)
Higaki, Tetsutaro [RIKEN Nishina Center, Saitama (Japan). Mathematical Physics Lab.; Kamada, Kohei [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Takahashi, Fuminobu [Tohoku Univ., Sendai (Japan). Dept. of Physics
2012-07-15
We consider the cosmological moduli problem in the context of high-scale supersymmetry breaking suggested by the recent discovery of the standard-model like Higgs boson. In order to solve the notorious moduli-induced gravitino problem, we focus on the LARGE volume scenario, in which the modulus decay into gravitinos can be kinematically forbidden. We then consider the Affleck-Dine mechanism with or without an enhanced coupling with the inflaton, taking account of possible Q-ball formation. We show that the baryon asymmetry of the present Universe can be generated by the Affleck-Dine mechanism in LARGE volume scenario, solving the moduli and gravitino problems.
Higgs, moduli problem, baryogenesis and large volume compactifications
International Nuclear Information System (INIS)
Higaki, Tetsutaro; Takahashi, Fuminobu
2012-07-01
We consider the cosmological moduli problem in the context of high-scale supersymmetry breaking suggested by the recent discovery of the standard-model like Higgs boson. In order to solve the notorious moduli-induced gravitino problem, we focus on the LARGE volume scenario, in which the modulus decay into gravitinos can be kinematically forbidden. We then consider the Affleck-Dine mechanism with or without an enhanced coupling with the inflaton, taking account of possible Q-ball formation. We show that the baryon asymmetry of the present Universe can be generated by the Affleck-Dine mechanism in LARGE volume scenario, solving the moduli and gravitino problems.
Moduli of Parabolic Higgs Bundles and Atiyah Algebroids
DEFF Research Database (Denmark)
Logares, Marina; Martens, Johan
2010-01-01
In this paper we study the geometry of the moduli space of (non-strongly) parabolic Higgs bundles over a Riemann surface with marked points. We show that this space possesses a Poisson structure, extending the one on the dual of an Atiyah algebroid over the moduli space of parabolic vector bundle...
Metastable SUSY Breaking, de Sitter Moduli Stabilisation and Kähler Moduli Inflation
Krippendorf, Sven
2009-01-01
We study the influence of anomalous U(1) symmetries and their associated D-terms on the vacuum structure of global field theories once they are coupled to N=1 supergravity and in the context of string compactifications with moduli stabilisation. In particular, we focus on a IIB string motivated construction of the ISS scenario and examine the influence of one additional U(1) symmetry on the vacuum structure. We point out that in the simplest one-Kahler modulus compactification, the original ISS vacuum gets generically destabilised by a runaway behaviour of the potential in the modulus direction. In more general compactifications with several Kahler moduli, we find a novel realisation of the LARGE volume scenario with D-term uplifting to de Sitter space and both D-term and F-term supersymmetry breaking. The structure of soft supersymmetry breaking terms is determined in the preferred scenario where the standard model cycle is not stabilised non-perturbatively and found to be flavour universal. Our scenario als...
DEFF Research Database (Denmark)
Jakobsen, Bo; Hecksher, Tina; Christensen, Tage Emil
2012-01-01
The frequency-dependent dielectric constant, shear and adiabatic bulk moduli, longitudinal thermal expansion coefficient, and longitudinal specific heat have been measured for two van der Waals glass-forming liquids, tetramethyl-tetraphenyl-trisiloxane (DC704) and 5-polyphenyl-4-ether. Within the...
International Nuclear Information System (INIS)
Li Ying; Qiu Xinming; Yin Yajun; Yang Fan; Fan Qinshan
2009-01-01
Under hydrostatic pressure, the equivalent elastic moduli of a zigzag single-walled carbon nanotube (SWNT) are analytically determined by energy conservation, with the consideration of the covalent bond deformation. The theoretical predictions on the transverse mechanical properties of a zigzag SWNT agree reasonably well with those given by the molecular structures mechanics simulations and also the ab initio calculations. From the simple geometry calculation, the circumferential strain is about 2-3 times of the axial strain of a zigzag SWNT under hydrostatic pressure. The bulk modulus of a zigzag SWNT is found to be 3/7 times of its radial Young's modulus.
The universal connection and metrics on moduli spaces
International Nuclear Information System (INIS)
Massamba, Fortune; Thompson, George
2003-11-01
We introduce a class of metrics on gauge theoretic moduli spaces. These metrics are made out of the universal matrix that appears in the universal connection construction of M. S. Narasimhan and S. Ramanan. As an example we construct metrics on the c 2 = 1 SU(2) moduli space of instantons on R 4 for various universal matrices. (author)
The output least-squares approach to estimating Lamé moduli
Gockenbach, Mark S.
2007-12-01
The Lamé moduli of a heterogeneous, isotropic, planar membrane can be estimated by observing the displacement of the membrane under a known edge traction, and choosing estimates of the moduli that best predict the observed displacement under a finite-element simulation. This algorithm converges to the exact moduli given pointwise measurements of the displacement on an increasingly fine mesh. The error estimates that prove this convergence also show the instability of the inverse problem.
Aspects of Moduli Stabilization in Type IIB String Theory
Directory of Open Access Journals (Sweden)
Shaaban Khalil
2016-01-01
Full Text Available We review moduli stabilization in type IIB string theory compactification with fluxes. We focus on KKLT and Large Volume Scenario (LVS. We show that the predicted soft SUSY breaking terms in KKLT model are not phenomenological viable. In LVS, the following result for scalar mass, gaugino mass, and trilinear term is obtained: m0=m1/2=-A0=m3/2, which may account for Higgs mass limit if m3/2~O(1.5 TeV. However, in this case, the relic abundance of the lightest neutralino cannot be consistent with the measured limits. We also study the cosmological consequences of moduli stabilization in both models. In particular, the associated inflation models such as racetrack inflation and Kähler inflation are analyzed. Finally, the problem of moduli destabilization and the effect of string moduli backreaction on the inflation models are discussed.
On rationality of moduli spaces of vector bundles on real Hirzebruch ...
Indian Academy of Sciences (India)
Introduction. Moduli spaces of semistable vector bundles on a smooth projective variety are studied from various points of view. One of the questions that is often addressed is the birational type of the moduli space, more precisely, the question of rationality. It is known that the moduli space of semistable vector bundles of ...
Lectures on moduli of principal G-bundles over algebraic curves
International Nuclear Information System (INIS)
Sorger, C.
2000-01-01
These notes are supposed to be an introduction to the moduli of G-bundles on curves. Therefore I will lay stress on ideas in order to make these notes more readable. In the last years the moduli spaces of G-bundles over algebraic curves have attracted some attention from various subjects like from conformal field theory or Beilinson and Drinfeld's geometric Langlands program. In both subjects it turned out that the 'stacky' point of view is more convenient and as the basic motivation of these notes is to introduce to the latter subject our moduli spaces will be moduli stacks (and not coarse moduli spaces). As people may feel uncomfortable with stacks I have included a small introduction to them. Actually there is a forthcoming book of Laumon and Moret-Bailly based on their preprint and my introduction merely does the step -1, i.e. explains why we are forced to use them here and recalls the basic results I need later. So here is the plan of the lectures: after some generalities on G-bundles, I will classify them topologically. Actually the proof is more interesting than the result as it will give a flavor of the basic theorem on G-bundles which describes the moduli stack as a double quotient of loop-groups. This 'uniformization theorem', which goes back to A. Weil as a bijection on sets, will be proved in the section following the topological classification. Then I will introduce two line bundles on the moduli stack: the determinant and the paffian bundle. The first one can be used to describe the canonical bundle on the moduli stack and the second to define a square-root of it. Unless G is simply connected the square root depends on the choice of a theta-characteristic. This square root plays an important role in the geometric Langlands program. Actually, in order to get global differential operators on the moduli stack one has to consider twisted differential operators with values in these square-roots. The rest of the lectures will be dedicated to describe the
Structure and properties of cerium oxides in bulk and nanoparticulate forms
International Nuclear Information System (INIS)
Gangopadhyay, Shruba; Frolov, Dmitry D.; Masunov, Artëm E.; Seal, Sudipta
2014-01-01
The experimental and computational studies on the cerium oxide nanoparticles, as well as stoichiometric phases of bulk ceria are reviewed. Based on structural similarities of these phases in hexagonal aspect, electroneutral and non-polar pentalayers are identified as building blocks of type A sesquioxide structure. The idealized core/shell structure of the ceria nanoparticles is described as dioxide core covered by a single pentalayer of sesquioxide, which explains the exceptional stability of subsurface vacancies in nanoceria. The density functional theory (DFT) predictions of the lattice parameters and elastic moduli for the Ce(IV) and Ce(III) oxides at the hybrid DFT level are also presented. The calculated values for both compounds agree with available experimental data and allow predicting changes in the lattice parameter with decreasing size of the nanoparticles. The lattice parameter is calculated as equilibrium between contraction of sesquioxide structure in the core, and expansion of dioxide structure in the shell of the nanoparticle. This is consistent with available XRD data on ceria NPs obtained in mild aqueous conditions. The core/shell model, however, breaks down when applied to the size dependence of lattice parameter in NPs obtained by the laser ablation techniques
Moduli Backreaction on Inflationary Attractors
Roest, Diederik; Werkman, Pelle
2016-01-01
We investigate the interplay between moduli dynamics and inflation, focusing on the KKLT-scenario and cosmological $\\alpha$-attractors. General couplings between these sectors can induce a significant backreaction and potentially destroy the inflationary regime; however, we demonstrate that this generically does not happen for $\\alpha$-attractors. Depending on the details of the superpotential, the volume modulus can either be stable during the entire inflationary trajectory, or become tachyonic at some point and act as a waterfall field, resulting in a sudden end of inflation. In the latter case there is a universal supersymmetric minimum where the scalars end up, preventing the decompactification scenario. The observational predictions conform to the universal value of attractors, fully compatible with the Planck data, with possibly a capped number of e-folds due to the interplay with moduli.
Bounds on Masses of Bulk Fields in String Compactifications
Energy Technology Data Exchange (ETDEWEB)
Kachru, Shamit; McGreevy, John; Svrcek, Peter; /Stanford U., Phys. Dept. /SLAC
2006-02-13
In string compactification on a manifold X, in addition to the string scale and the normal scales of low-energy particle physics, there is a Kaluza-Klein scale 1/R associated with the size of X. We present an argument that generic string models with low-energy supersymmetry have, after moduli stabilization, bulk fields with masses which are parametrically lighter than 1/R. We discuss the implications of these light states for anomaly mediation and gaugino mediation scenarios.
Fei-Ran Shen; Hao Kuang; Feng-Xia Hu; Hui Wu; Qing-Zhen Huang; Fei-Xiang Liang; Kai-Ming Qiao; Jia Li; Jing Wang; Yao Liu; Lei Zhang; Min He; Ying Zhang; Wen-Liang Zuo; Ji-Rong Sun
2017-01-01
Materials with zero thermal expansion (ZTE) or precisely tailored thermal expansion are in urgent demand of modern industries. However, the overwhelming majority of materials show positive thermal expansion. To develop ZTE or negative thermal expansion (NTE) materials as compensators has become an important challenge. Here, we present the evidence for the realization of ultra-low thermal expansion in Mn–Co–Ge–In particles. The bulk with the Ni2In-type hexagonal structure undergoes giant NTE o...
Moduli spaces of unitary conformal field theories
International Nuclear Information System (INIS)
Wendland, K.
2000-08-01
We investigate various features of moduli spaces of unitary conformal field theories. A geometric characterization of rational toroidal conformal field theories in arbitrary dimensions is presented and discussed in relation to singular tori and those with complex multiplication. We study the moduli space M 2 of unitary two-dimensional conformal field theories with central charge c = 2. All the 26 non-exceptional non-isolated irreducible components of M 2 are constructed that may be obtained by an orbifold procedure from toroidal theories. The parameter spaces and partition functions are calculated explicitly. All multicritical points and lines are determined, such that all but three of these 26 components are directly or indirectly connected to the space of toroidal theories in M 2 . Relating our results to those by Dixon, Ginsparg, Harvey on the classification of c = 3/2 superconformal field theories, we give geometric interpretations to all non-isolated orbifolds discussed by them and correct their statements on multicritical points within the moduli space of c = 3/2 superconformal field theories. In the main part of this work, we investigate the moduli space M of N = (4, 4) superconformal field theories with central charge c = 6. After a slight emendation of its global description we give generic partition functions for models contained in M. We explicitly determine the locations of various known models in the component of M associated to K3 surfaces
The Infinitesimal Moduli Space of Heterotic G 2 Systems
de la Ossa, Xenia; Larfors, Magdalena; Svanes, Eirik E.
2018-06-01
Heterotic string compactifications on integrable G 2 structure manifolds Y with instanton bundles {(V,A), (TY,\\tilde{θ})} yield supersymmetric three-dimensional vacua that are of interest in physics. In this paper, we define a covariant exterior derivative D and show that it is equivalent to a heterotic G 2 system encoding the geometry of the heterotic string compactifications. This operator D acts on a bundle Q}=T^*Y \\oplus End(V) \\oplus End(TY)} and satisfies a nilpotency condition \\check{{D^2=0} , for an appropriate projection of D. Furthermore, we determine the infinitesimal moduli space of these systems and show that it corresponds to the finite-dimensional cohomology group H^1_{D}(Q). We comment on the similarities and differences of our result with Atiyah's well-known analysis of deformations of holomorphic vector bundles over complex manifolds. Our analysis leads to results that are of relevance to all orders in the {α'} expansion.
Vortex-strings in N=2 SQCD and bulk-string decoupling
Gerchkovitz, Efrat; Karasik, Avner
2018-02-01
We study vortex-strings in four-dimensional N=2 supersymmetric SU( N c ) × U(1) gauge theories with N f hypermultiplets in the fundamental representation of SU( N c ) and general U(1) charges. If N f > N c , the vacuum is not gapped and the low-energy theory contains both the vacuum massless excitations and the string zero-modes. The question we address in this work is whether the vacuum and the string moduli decouple at low energies, allowing a description of the low-energy dynamics in terms of a two-dimensional theory on the string worldsheet. We find a simple condition controlling the bulk-string coupling: if there exist two flavors such that the product of their U(1) charge difference with the magnetic flux carried by the string configuration is not an integer multiple of 2 π, the string has zero-modes that decay slower than 1 /r, where r is the radial distance from the string core. These modes are coupled to the vacuum massless excitations even at low energies. If, however, all such products are integer multiples of 2 π, long-range modes of this type do not exist and the string moduli decouple from the bulk at low energies. This condition turns out to coincide with the condition of trivial Aharonov-Bohm phases for the particles in the spectrum. In addition to a derivation of the bulk-string decoupling criterion using classical analysis of the string zero-modes, we provide a non-perturbative derivation of the criterion, which uses supersymmetric localization techniques.
Natural inflation and moduli stabilization in heterotic orbifolds
International Nuclear Information System (INIS)
Ruehle, Fabian; Wieck, Clemens
2015-03-01
We study moduli stabilization in combination with inflation in heterotic orbifold compactifications in the light of a large Hubble scale and the favored tensor-to-scalar ratio r∼0.05. To account for a trans-Planckian field range we implement aligned natural inflation. Although there is only one universal axion in heterotic constructions, further axions from the geometric moduli can be used for alignment and inflation. We argue that such an alignment is rather generic on orbifolds, since all non-perturbative terms are determined by modular weights of the involved fields and the Dedekind η function. We present two setups inspired by the mini-landscape models of the Z 6-II orbifold which realize aligned inflation and stabilization of the relevant moduli. One has a supersymmetric vacuum after inflation, while the other includes a gaugino condensate which breaks supersymmetry at a high scale.
Accelerating universes driven by bulk particles
International Nuclear Information System (INIS)
Brito, F.A.; Cruz, F.F.; Oliveira, J.F.N.
2005-01-01
We consider our universe as a 3d domain wall embedded in a 5d dimensional Minkowski space-time. We address the problem of inflation and late time acceleration driven by bulk particles colliding with the 3d domain wall. The expansion of our universe is mainly related to these bulk particles. Since our universe tends to be permeated by a large number of isolated structures, as temperature diminishes with the expansion, we model our universe with a 3d domain wall with increasing internal structures. These structures could be unstable 2d domain walls evolving to fermi-balls which are candidates to cold dark matter. The momentum transfer of bulk particles colliding with the 3d domain wall is related to the reflection coefficient. We show a nontrivial dependence of the reflection coefficient with the number of internal dark matter structures inside the 3d domain wall. As the population of such structures increases the velocity of the domain wall expansion also increases. The expansion is exponential at early times and polynomial at late times. We connect this picture with string/M-theory by considering BPS 3d domain walls with structures which can appear through the bosonic sector of a five-dimensional supergravity theory
Morphology and linear-elastic moduli of random network solids.
Nachtrab, Susan; Kapfer, Sebastian C; Arns, Christoph H; Madadi, Mahyar; Mecke, Klaus; Schröder-Turk, Gerd E
2011-06-17
The effective linear-elastic moduli of disordered network solids are analyzed by voxel-based finite element calculations. We analyze network solids given by Poisson-Voronoi processes and by the structure of collagen fiber networks imaged by confocal microscopy. The solid volume fraction ϕ is varied by adjusting the fiber radius, while keeping the structural mesh or pore size of the underlying network fixed. For intermediate ϕ, the bulk and shear modulus are approximated by empirical power-laws K(phi)proptophin and G(phi)proptophim with n≈1.4 and m≈1.7. The exponents for the collagen and the Poisson-Voronoi network solids are similar, and are close to the values n=1.22 and m=2.11 found in a previous voxel-based finite element study of Poisson-Voronoi systems with different boundary conditions. However, the exponents of these empirical power-laws are at odds with the analytic values of n=1 and m=2, valid for low-density cellular structures in the limit of thin beams. We propose a functional form for K(ϕ) that models the cross-over from a power-law at low densities to a porous solid at high densities; a fit of the data to this functional form yields the asymptotic exponent n≈1.00, as expected. Further, both the intensity of the Poisson-Voronoi process and the collagen concentration in the samples, both of which alter the typical pore or mesh size, affect the effective moduli only by the resulting change of the solid volume fraction. These findings suggest that a network solid with the structure of the collagen networks can be modeled in quantitative agreement by a Poisson-Voronoi process. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Moduli backreaction on inflationary attractors
International Nuclear Information System (INIS)
Roest, Diederik; Werkman, Pelle
2016-07-01
We investigate the interplay between moduli dynamics and inflation, focusing on the KKLT- scenario and cosmological α-attractors. General couplings between these sectors can induce a significant backreaction and potentially destroy the inflationary regime; however, we demonstrate that this generically does not happen for α-attractors. Depending on the details of the superpotential, the volume modulus can either be stable during the entire inflationary trajectory, or become tachyonic at some point and act as a waterfall field, resulting in a sudden end of inflation. In the latter case there is a universal supersymmetric minimum where the scalars end up, preventing the decompactification scenario. The gravitino mass is independent from the inflationary scale with no fine-tuning of the parameters. The observational predictions conform to the universal value of attractors, fully compatible with the Planck data, with possibly a capped number of e-folds due to the interplay with moduli.
Young's moduli of cables for high field superconductive dipole magnet
International Nuclear Information System (INIS)
Yamada, Shunji; Shintomi, Takakazu.
1983-01-01
Superconductive dipole magnets for big accelerators are subjected to enormous electro-magnetic force, when they are operated with high field such as 10 Tesla. They should be constructed by means of superconductive cables, which have high Young's modulus, to obtain good performance. To develop such cables we measured the Young's moduli of cables for practical use of accelerator magnets. They are monolithic and compacted strand cables. We measured also Young's moduli of monolithic copper and brass cables for comparison. The obtained data showed the Young's moduli of 35 and 15 GPa for the monolithic and compacted strand cables, respectively. (author)
On the possibility of large axion moduli spaces
Energy Technology Data Exchange (ETDEWEB)
Rudelius, Tom [Jefferson Physical Laboratory, Harvard University,Cambridge, MA 02138 (United States)
2015-04-28
We study the diameters of axion moduli spaces, focusing primarily on type IIB compactifications on Calabi-Yau three-folds. In this case, we derive a stringent bound on the diameter in the large volume region of parameter space for Calabi-Yaus with simplicial Kähler cone. This bound can be violated by Calabi-Yaus with non-simplicial Kähler cones, but additional contributions are introduced to the effective action which can restrict the field range accessible to the axions. We perform a statistical analysis of simulated moduli spaces, finding in all cases that these additional contributions restrict the diameter so that these moduli spaces are no more likely to yield successful inflation than those with simplicial Kähler cone or with far fewer axions. Further heuristic arguments for axions in other corners of the duality web suggest that the difficulty observed in http://dx.doi.org/10.1088/1475-7516/2003/06/001 of finding an axion decay constant parametrically larger than M{sub p} applies not only to individual axions, but to the diagonals of axion moduli space as well. This observation is shown to follow from the weak gravity conjecture of http://dx.doi.org/10.1088/1126-6708/2007/06/060, so it likely applies not only to axions in string theory, but also to axions in any consistent theory of quantum gravity.
Explicit Gromov-Hausdorff compactifications of moduli spaces of Kähler-Einstein Fano manifolds
DEFF Research Database (Denmark)
Spotti, Cristiano; Sun, Song
We exhibit the first non-trivial concrete examples of Gromov-Hausdorff compactifications of moduli spaces of Kähler-Einstein Fano manifolds in all complex dimensions bigger than two (Fano K-moduli spaces). We also discuss potential applications to explicit study of moduli spaces of K-stable Fano...
Bulk moduli and high pressure phases of ThX compounds. Pt. 2
International Nuclear Information System (INIS)
Staun Olsen, J.; Gerward, L.; Benedict, U.; Luo, H.; Vogt, O.
1989-01-01
The high-pressure crystal structures of the members of the ThX series, where X = S, Se and Te, have been studied using synchrotron X-ray diffraction in the pressure range up to about 60 GPa. A distorted fcc structure is observed for ThS above 20 GPa. These transforms to the CsCl structure at 15 GPa. has the CsCl structure already at atmospheric pressure and no further phase transition has been observed. A log-log plot of bulk modulus versus specific volume gives a straight line with slope -1.85. (orig.)
On elastic moduli and elastic anisotropy in polycrystalline martensitic NiTi
International Nuclear Information System (INIS)
Qiu, S.; Clausen, B.; Padula, S.A.; Noebe, R.D.; Vaidyanathan, R.
2011-01-01
A combined experimental and computational effort was undertaken to provide insight into the elastic response of B19' martensitic NiTi variants as they exist in bulk, polycrystalline aggregate form during monotonic tensile and compressive loading. The experimental effort centered on using in situ neutron diffraction during loading to measure elastic moduli in several directions along with an average Young's modulus and a Poisson's ratio. The measurements were compared with predictions from a 30,000 variant, self-consistent polycrystalline deformation model that accounted for the elastic intergranular constraint, and also with predictions of single crystal behavior from previously published ab initio studies. Variant conversion and detwinning processes that influenced the intergranular constraint occurred even at stresses where the macroscopic stress-strain response appeared linear. Direct evidence of these processes was revealed in changes in texture, which were captured in inverse pole figures constructed from the neutron diffraction measurements.
On a new compactification of the moduli of vector bundles on a surface
International Nuclear Information System (INIS)
Timofeeva, N V
2008-01-01
A new compactification of the moduli scheme of Gieseker-stable vector bundles with prescribed Hilbert polynomial on a smooth projective polarized surface (S,H) defined over a field k=k-bar of characteristic zero is constructed. The families of locally free sheaves on the surface S are completed by locally free sheaves on surfaces that are certain modifications of S. The new moduli space has a birational morphism onto the Gieseker-Maruyama moduli space. The case when the Gieseker-Maruyama space is a fine moduli space is considered. Bibliography: 12 titles.
Czech Academy of Sciences Publication Activity Database
Guirao, A. J.; Hájek, Petr Pavel
2007-01-01
Roč. 135, č. 10 (2007), s. 3233-3240 ISSN 0002-9939 R&D Projects: GA AV ČR IAA100190502 Institutional research plan: CEZ:AV0Z10190503 Keywords : Banach spaces * moduli of convexity * uniformly rotund norms Subject RIV: BA - General Mathematics Impact factor: 0.520, year: 2007
Evaluation of Procedures for Backcalculation of Airfield Pavement Moduli
2015-08-01
ER D C/ G SL T R -1 5 -3 1 Evaluation of Procedures for Backcalculation of Airfield Pavement Moduli G eo te ch n ic al a n d S tr u...August 2015 Evaluation of Procedures for Backcalculation of Airfield Pavement Moduli Lucy P. Priddy and Carlos R. Gonzalez Geotechnical and...USAF’s) airfield pavement structural evaluation procedures. Determining the structural integrity of airfield pavement relies on the analysis of
Structure and bulk modulus of Ln-doped UO{sub 2} (Ln = La, Nd) at high pressure
Energy Technology Data Exchange (ETDEWEB)
Rittman, Dylan R., E-mail: drittman@stanford.edu [Department of Geological Sciences, Stanford University, Stanford, CA 94305 (United States); Park, Sulgiye; Tracy, Cameron L. [Department of Geological Sciences, Stanford University, Stanford, CA 94305 (United States); Zhang, Lei [Peter A. Rock Thermochemistry Laboratory and NEAT ORU, University of California Davis, Davis, CA 95616 (United States); Department of Chemical Engineering and Materials Science, University of California Davis, Davis, CA 95616 (United States); Palomares, Raul I.; Lang, Maik [Department of Nuclear Engineering, University of Tennessee, Knoxville, TN 37996 (United States); Navrotsky, Alexandra [Peter A. Rock Thermochemistry Laboratory and NEAT ORU, University of California Davis, Davis, CA 95616 (United States); Department of Chemical Engineering and Materials Science, University of California Davis, Davis, CA 95616 (United States); Mao, Wendy L. [Department of Geological Sciences, Stanford University, Stanford, CA 94305 (United States); Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, CA 94025 (United States); Ewing, Rodney C. [Department of Geological Sciences, Stanford University, Stanford, CA 94305 (United States)
2017-07-15
The structure of lanthanide-doped uranium dioxide, Ln{sub x}U{sub 1-x}O{sub 2-0.5x+y} (Ln = La, Nd), was investigated at pressures up to ∼50–55 GPa. Samples were synthesized with different lanthanides at different concentrations (x ∼ 0.2 and 0.5), and all were slightly hyperstoichiometric (y ∼ 0.25–0.4). In situ high-pressure synchrotron X-ray diffraction was used to investigate their high-pressure phase behavior and determine their bulk moduli. All samples underwent a fluorite-to-cotunnite phase transformation with increasing pressure. The pressure of the phase transformation increased with increasing hyperstoichiometry, which is consistent with results from previous computational simulations. Bulk moduli are inversely proportional to both the ionic radius of the lanthanide and its concentration, as quantified using a weighted cationic radius ratio. This trend was found to be consistent with the behavior of other elastic properties measured for Ln-doped UO{sub 2}, such as Young's modulus. - Highlights: •Ln-doped UO{sub 2} transforms from fluorite to cotunnite at high pressure. •Transition pressure increases with increasing hyperstoichiometry. •Bulk modulus decreases with increasing Ln-dopant radius and concentration.
Moduli Potentials in Type IIA Compactifications with RR and NS Flux
Energy Technology Data Exchange (ETDEWEB)
Kachru, S.
2004-12-01
We describe a simple class of type IIA string compactifications on Calabi-Yau manifolds where background fluxes generate a potential for the complex structure moduli, the dilaton, and the Kaehler moduli. This class of models corresponds to gauged {Nu} = 2 supergravities, and the potential is completely determined by a choice of gauging and by data of the {Nu} = 2 Calabi-Yau model--the prepotential for vector multiplets and the quaternionic metric on the hypermultiplet moduli space. Using mirror symmetry, one can determine many (though not all) of the quantum corrections which are relevant in these models.
On elastic moduli and elastic anisotropy in polycrystalline martensitic NiTi
Energy Technology Data Exchange (ETDEWEB)
Qiu, S. [Advanced Materials Processing and Analysis Center (AMPAC), Mechanical, Materials and Aerospace Engineering Department, University of Central Florida, Orlando, FL 32816 (United States); Clausen, B. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Padula, S.A.; Noebe, R.D. [NASA Glenn Research Center, Cleveland, OH 44135 (United States); Vaidyanathan, R., E-mail: raj@mail.ucf.edu [Advanced Materials Processing and Analysis Center (AMPAC), Mechanical, Materials and Aerospace Engineering Department, University of Central Florida, Orlando, FL 32816 (United States)
2011-08-15
A combined experimental and computational effort was undertaken to provide insight into the elastic response of B19' martensitic NiTi variants as they exist in bulk, polycrystalline aggregate form during monotonic tensile and compressive loading. The experimental effort centered on using in situ neutron diffraction during loading to measure elastic moduli in several directions along with an average Young's modulus and a Poisson's ratio. The measurements were compared with predictions from a 30,000 variant, self-consistent polycrystalline deformation model that accounted for the elastic intergranular constraint, and also with predictions of single crystal behavior from previously published ab initio studies. Variant conversion and detwinning processes that influenced the intergranular constraint occurred even at stresses where the macroscopic stress-strain response appeared linear. Direct evidence of these processes was revealed in changes in texture, which were captured in inverse pole figures constructed from the neutron diffraction measurements.
International Nuclear Information System (INIS)
Avelino, Arturo; Nucamendi, Ulises
2009-01-01
We test a cosmological model which the only component is a pressureless fluid with a constant bulk viscosity as an explanation for the present accelerated expansion of the universe. We classify all the possible scenarios for the universe predicted by the model according to their past, present and future evolution and we test its viability performing a Bayesian statistical analysis using the SCP ''Union'' data set (307 SNe Ia), imposing the second law of thermodynamics on the dimensionless constant bulk viscous coefficient ζ-tilde and comparing the predicted age of the universe by the model with the constraints coming from the oldest globular clusters. The best estimated values found for ζ-tilde and the Hubble constant H 0 are: ζ-tilde = 1.922±0.089 and H 0 = 69.62±0.59 (km/s)Mpc −1 with a χ 2 min = 314 (χ 2 d.o.f = 1.031). The age of the universe is found to be 14.95±0.42 Gyr. We see that the estimated value of H 0 as well as of χ 2 d.o.f are very similar to those obtained from ΛCDM model using the same SNe Ia data set. The estimated age of the universe is in agreement with the constraints coming from the oldest globular clusters. Moreover, the estimated value of ζ-tilde is positive in agreement with the second law of thermodynamics (SLT). On the other hand, we perform different forms of marginalization over the parameter H 0 in order to study the sensibility of the results to the way how H 0 is marginalized. We found that it is almost negligible the dependence between the best estimated values of the free parameters of this model and the way how H 0 is marginalized in the present work. Therefore, this simple model might be a viable candidate to explain the present acceleration in the expansion of the universe
International Nuclear Information System (INIS)
Le, Hung M; Pham, Tan-Tien; Dat, Vo Duy; Kawazoe, Yoshiyuki
2017-01-01
The ferrocyanide structures of transition metals (M) Ti 2+ , Cr 2+ , Mn 2+ , or Co 2+ are investigated using a first-principles modeling approach. The crystal structure of cobalt ferrocyanide is found to resemble previous experimental data with good accuracy (∼1% error). The considered porous structures possess magnetic moments of 8.00 µ B /cell, 8.00 µ B /cell, 4.00 µ B /cell, and 4.00 µ B /cell given by the [TiFe(CN) 6 ] 2− , [CrFe(CN) 6 ] 2− , [MnFe(CN) 6 ] 2− , and [CoFe(CN) 6 ] 2− frameworks, respectively. There is only one spin-state occupation at the Fermi level, which leads to the conclusion of semi-metallicity of the four structures. To verify the reliability of the electronic and magnetic properties, linear-response DFT + U calculations are performed and establish excellent agreement with the conventional DFT calculations. Then, the mechanical strength is evaluated by estimating the bulk moduli of the four structures, which fall in the range of 114 GPa–133 GPa. Upon the consideration of one C ≡ N − linker defect, the magnetic moments of cobalt ferrocyanide and manganese ferrocyanide rise dramatically to 8 µ B /cell, while that of the titanium structure drops to 6 µ B /cell. In light of the electronic structure evidence, we believe that the low-spin Fe cation nearby the C ≡ N − defect has an indirect effect on spin polarization of the four Co cations in the unit cell. (paper)
Elastic properties of Pd40Cu30Ni10P20 bulk glass in supercooled liquid region
DEFF Research Database (Denmark)
Nishiyama, N.; Inoue, A.; Jiang, Jianzhong
2001-01-01
In situ ultrasonic measurements for the Pd40Cu30Ni10P20 bulk glass in three states: Glassy solid, supercooled liquid, and crystalline, have been performed. It is found that velocities of both longitudinal and transverse waves and elastic moduli (shear modulus, bulk modulus, Young's modulus......, and Lame parameter), together with Debye temperature, gradually decrease with increasing temperature through the glass transition temperature as the Poisson's ratio increases. The behavior of the velocity of transverse wave vs. temperature in the supercooled liquid region could be explained by viscosity...
Moduli Spaces for Linear Differential Equations and the Painlevé Equations
Put, Marius van der; Saito, Masa-Hiko
2009-01-01
A systematic construction of isomonodromic families of connections of rank two on the Riemarm sphere is obtained by considering the analytic Riemann-Hilbert map RH : M -> R, where M is a moduli space of connections and 72, the monodromy space, is a moduli space for analytic data (i.e., ordinary
Size-dependent elastic moduli and vibrational properties of fivefold twinned copper nanowires
Zheng, Y. G.; Zhao, Y. T.; Ye, H. F.; Zhang, H. W.
2014-08-01
Based on atomistic simulations, the elastic moduli and vibration behaviors of fivefold twinned copper nanowires are investigated in this paper. Simulation results show that the elastic (i.e., Young’s and shear) moduli exhibit size dependence due to the surface effect. The effective Young’s modulus is found to decrease slightly whereas the effective shear modulus increases slightly with the increase in the wire radius. Both moduli tend to approach certain values at a larger radius and can be suitably described by core-shell composite structure models. Furthermore, we show by comparing simulation results and continuum predictions that, provided the effective Young’s and shear moduli are used, classic elastic theory can be applied to describe the small-amplitude vibration of fivefold twinned copper nanowires. Moreover, for the transverse vibration, the Timoshenko beam model is more suitable because shear deformation becomes apparent.
Size-dependent elastic moduli and vibrational properties of fivefold twinned copper nanowires
International Nuclear Information System (INIS)
Zheng, Y G; Zhao, Y T; Ye, H F; Zhang, H W
2014-01-01
Based on atomistic simulations, the elastic moduli and vibration behaviors of fivefold twinned copper nanowires are investigated in this paper. Simulation results show that the elastic (i.e., Young’s and shear) moduli exhibit size dependence due to the surface effect. The effective Young’s modulus is found to decrease slightly whereas the effective shear modulus increases slightly with the increase in the wire radius. Both moduli tend to approach certain values at a larger radius and can be suitably described by core-shell composite structure models. Furthermore, we show by comparing simulation results and continuum predictions that, provided the effective Young’s and shear moduli are used, classic elastic theory can be applied to describe the small-amplitude vibration of fivefold twinned copper nanowires. Moreover, for the transverse vibration, the Timoshenko beam model is more suitable because shear deformation becomes apparent. (paper)
A flux-scaling scenario for high-scale moduli stabilization in string theory
Directory of Open Access Journals (Sweden)
Ralph Blumenhagen
2015-08-01
Full Text Available Tree-level moduli stabilization via geometric and non-geometric fluxes in type IIB orientifolds on Calabi–Yau manifolds is investigated. The focus is on stable non-supersymmetric minima, where all moduli are fixed except for some massless axions. The scenario includes the purely axionic orientifold-odd moduli. A set of vacua allowing for parametric control over the moduli vacuum expectation values and their masses is presented, featuring a specific scaling with the fluxes. Uplift mechanisms and supersymmetry breaking soft masses on MSSM-like D7-branes are discussed as well. This scenario provides a complete effective framework for realizing the idea of F-term axion monodromy inflation in string theory. It is argued that, with all masses close to the Planck and GUT scales, one is confronted with working at the threshold of controlling all mass hierarchies.
A flux-scaling scenario for high-scale moduli stabilization in string theory
Energy Technology Data Exchange (ETDEWEB)
Blumenhagen, Ralph [Max-Planck-Institut für Physik (Werner-Heisenberg-Institut), Föhringer Ring 6, 80805 München (Germany); Font, Anamaría [Max-Planck-Institut für Physik (Werner-Heisenberg-Institut), Föhringer Ring 6, 80805 München (Germany); Arnold Sommerfeld Center for Theoretical Physics, LMU, Theresienstr. 37, 80333 München (Germany); Fuchs, Michael [Max-Planck-Institut für Physik (Werner-Heisenberg-Institut), Föhringer Ring 6, 80805 München (Germany); Herschmann, Daniela, E-mail: herschma@mpp.mpg.de [Max-Planck-Institut für Physik (Werner-Heisenberg-Institut), Föhringer Ring 6, 80805 München (Germany); Plauschinn, Erik [Dipartimento di Fisica e Astronomia “Galileo Galilei”, Università di Padova, Via Marzolo 8, 35131 Padova (Italy); INFN, Sezione di Padova, Via Marzolo 8, 35131 Padova (Italy); Sekiguchi, Yuta; Wolf, Florian [Max-Planck-Institut für Physik (Werner-Heisenberg-Institut), Föhringer Ring 6, 80805 München (Germany); Arnold Sommerfeld Center for Theoretical Physics, LMU, Theresienstr. 37, 80333 München (Germany)
2015-08-15
Tree-level moduli stabilization via geometric and non-geometric fluxes in type IIB orientifolds on Calabi–Yau manifolds is investigated. The focus is on stable non-supersymmetric minima, where all moduli are fixed except for some massless axions. The scenario includes the purely axionic orientifold-odd moduli. A set of vacua allowing for parametric control over the moduli vacuum expectation values and their masses is presented, featuring a specific scaling with the fluxes. Uplift mechanisms and supersymmetry breaking soft masses on MSSM-like D7-branes are discussed as well. This scenario provides a complete effective framework for realizing the idea of F-term axion monodromy inflation in string theory. It is argued that, with all masses close to the Planck and GUT scales, one is confronted with working at the threshold of controlling all mass hierarchies.
CP violation and moduli stabilization in heterotic models
International Nuclear Information System (INIS)
Giedt, Joel
2002-01-01
The role of moduli stabilization in predictions for CP violation is examined in the context of four-dimensional effective supergravity models obtained from the weakly coupled heterotic string. They point out that while stabilization of compactification moduli has been studied extensively, the determination of background values for other scalar by dynamical means has not been subjected to the same degree of scrutiny. These other complex scalars are important potential sources of CP violation and they show in a simple model how their background values (including complex phases) may be determined from the minimization of the supergravity scalar potential, subject to the constraint of vanishing cosmological constant
The Coulomb Branch Formula for Quiver Moduli Spaces
Manschot, Jan; Sen, Ashoke
2014-01-01
In recent series of works, by translating properties of multi-centered supersymmetric black holes into the language of quiver representations, we proposed a formula that expresses the Hodge numbers of the moduli space of semi-stable representations of quivers with generic superpotential in terms of a set of invariants associated to `single-centered' or `pure-Higgs' states. The distinguishing feature of these invariants is that they are independent of the choice of stability condition. Furthermore they are uniquely determined by the $\\chi_y$-genus of the moduli space. Here, we provide a self-contained summary of the Coulomb branch formula, spelling out mathematical details but leaving out proofs and physical motivations.
International Nuclear Information System (INIS)
Bodryakov, V.Yu.; Povzner, A.A.
2000-01-01
The correlation between the temperature dependence of elastic moduli and the Debye temperature of paramagnetic metal is analyzed in neglect of the temperature dependence of the Poison coefficient σ within the frames of the Debye-Grueneisen presentations. It is shown, that namely the temperature dependence of the elastic moduli determines primarily the temperature dependence of the Debye temperature Θ(T). On the other hand, the temperature dependence Θ(T) very weakly effects the temperature dependence of the elastic moduli. The later made it possible to formulate the self-consistent approach to calculation of the elastic moduli temperature dependence. The numerical estimates of this dependence parameters are conducted by the example of the all around compression modulus of the paramagnetic lutetium [ru
Measurements of Young's and shear moduli of rail steel at elevated temperatures.
Bao, Yuanye; Zhang, Haifeng; Ahmadi, Mehdi; Karim, Md Afzalul; Felix Wu, H
2014-03-01
The design and modelling of the buckling effect of Continuous Welded Rail (CWR) requires accurate material constants, especially at elevated temperatures. However, such material constants have rarely been found in literature. In this article, the Young's moduli and shear moduli of rail steel at elevated temperatures are determined by a new sonic resonance method developed in our group. A network analyser is used to excite a sample hanged inside a furnace through a simple tweeter type speaker. The vibration signal is picked up by a Polytec OFV-5000 Laser Vibrometer and then transferred back to the network analyser. Resonance frequencies in both the flexural and torsional modes are measured, and the Young's moduli and shear moduli are determined through the measured resonant frequencies. To validate the measured elastic constants, the measurements have been repeated by using the classic sonic resonance method. The comparisons of obtained moduli from the two methods show an excellent consistency of the results. In addition, the material elastic constants measured are validated by an ultrasound test based on a pulse-echo method and compared with previous published results at room temperature. The measured material data provides an invaluable reference for the design of CWR to avoid detrimental buckling failure. Copyright © 2013 Elsevier B.V. All rights reserved.
On a new compactification of moduli of vector bundles on a surface. III: Functorial approach
International Nuclear Information System (INIS)
Timofeeva, Nadezhda V
2011-01-01
A new compactification for the scheme of moduli for Gieseker-stable vector bundles with prescribed Hilbert polynomial on the smooth projective polarized surface (S,L) is constructed. We work over the field k=k-bar of characteristic zero. Families of locally free sheaves on the surface S are completed with locally free sheaves on schemes which are modifications of S. The Gieseker-Maruyama moduli space has a birational morphism onto the new moduli space. We propose the functor for families of pairs 'polarized scheme-vector bundle' with moduli space of such type. Bibliography: 16 titles.
REDUCED ISOTROPIC CRYSTAL MODEL WITH RESPECT TO THE FOURTH-ORDER ELASTIC MODULI
Directory of Open Access Journals (Sweden)
O. Burlayenko
2018-04-01
Full Text Available Using a reduced isotropic crystal model the relationship between the fourth-order elastic moduli of an isotropic medium and the independent components of the fourth-order elastic moduli tensor of real crystals of various crystal systems is found. To calculate the coefficients of these relations, computer algebra systems Redberry and Mathematica for working with high order tensors in the symbolic and explicit form were used, in light of the overly complex computation. In an isotropic medium, there are four independent fourth order elastic moduli. This is due to the presence of four invariants for an eighth-rank tensor in the three-dimensional space, that has symmetries over the pairs of indices. As an example, the moduli of elasticity of an isotropic medium corresponding to certain crystals of cubic system are given (LiF, NaCl, MgO, CaF2. From the obtained results it can be seen that the reduced isotropic crystal model can be most effectively applied to high-symmetry crystal systems.
Directory of Open Access Journals (Sweden)
Yi Yang
2017-07-01
Full Text Available In order to reveal the differences and conversion relations between the tensile, compressive and flexural moduli of cement stabilized macadam, in this paper, we develop a new test method for measuring three moduli simultaneously. By using the materials testing system, we test three moduli of the cement stabilized macadam under different loading rates, propose a flexural modulus calculation formula which considers the shearing effect, reveal the change rules of the tensile, compression and flexural moduli with the loading rate and establish the conversion relationships between the three moduli. The results indicate that: three moduli become larger with the increase of the loading rate, showing a power function pattern; with the shear effect considered, the flexural modulus is increased by 47% approximately over that in the current test method; the tensile and compression moduli of cement stabilized macadam are significantly different. Therefore, if only the compression modulus is used as the structural design parameter of asphalt pavement, there will be a great deviation in the analysis of the load response. In order to achieve scientific design and calculation, the appropriate design parameters should be chosen based on the actual stress state at each point inside the pavement structure.
Moduli, Scalar Charges, and the First Law of Black Hole Thermodynamics
International Nuclear Information System (INIS)
Gibbons, G.; Kallosh, R.; Kol, B.
1996-01-01
We show that under variation of moduli fields φ the first law of black hole thermodynamics becomes dM=κdA/8π +ΩdJ+ψdq+χdp-Σdφ, where Σ are the scalar charges. Also the ADM mass is extremized at fixed A, J, (p,q) when the moduli fields take the fixed value φ fix (p,q) which depend only on electric and magnetic charges. Thus the double-extreme black hole minimizes the mass for fixed conserved charges. We can now explain the fact that extreme black holes fix the moduli fields at the horizon φ=φ fix (p,q): φ fix is such that the scalar charges vanish: Σ(φ fix ,(p,q))=0. copyright 1996 The American Physical Society
Chaotic inflation in no-scale supergravity with string inspired moduli stabilization
International Nuclear Information System (INIS)
Li, Tianjun; Li, Zhijin; Nanopoulos, Dimitri V.
2015-01-01
The simple chaotic inflation is highly consistent with the BICEP2 experiment, and no-scale supergravity can be realized naturally in various string compactifications. Thus, we construct a chaotic inflation model in no-scale supergravity inspired from Type IIB string compactification with an anomalous U(1) X gauged symmetry. We introduce two moduli T 1 and T 2 which transform non-trivially under U(1) X , and some pairs of fundamental quarks charged under the SU(N) x U(1) X gauge group. The non-trivial transformations of moduli under U(1) X lead to a moduli-dependent Fayet-Iliopoulos (FI) term. The modulus T 2 and the real component of T 1 are stabilized by the non-perturbative effect from quark condensation and the U(1) X D-term. In particular, the stabilization from the anomalous U(1) X D-term with moduli-dependent FI term is crucial for inflation since it gives heavy mass to the real component of the modulus T 1 while keeping its axionic part light. Choosing the proper parameters, we obtain a global Minkowski vacuum where the imaginary part of T 1 has a quadratic potential for chaotic inflation. (orig.)
Shen, Fei-Ran; Kuang, Hao; Hu, Feng-Xia; Wu, Hui; Huang, Qing-Zhen; Liang, Fei-Xiang; Qiao, Kai-Ming; Li, Jia; Wang, Jing; Liu, Yao; Zhang, Lei; He, Min; Zhang, Ying; Zuo, Wen-Liang; Sun, Ji-Rong; Shen, Bao-Gen
2017-10-01
Materials with zero thermal expansion (ZTE) or precisely tailored thermal expansion are in urgent demand of modern industries. However, the overwhelming majority of materials show positive thermal expansion. To develop ZTE or negative thermal expansion (NTE) materials as compensators has become an important challenge. Here, we present the evidence for the realization of ultra-low thermal expansion in Mn-Co-Ge-In particles. The bulk with the Ni2In-type hexagonal structure undergoes giant NTE owing to a martensitic magnetostructural transition. The major finding is that the thermal expansion behavior can be totally controlled by modulating the crystallinity degree and phase transition from atomic scale. Self-compensation effect leads to ultra-low thermal expansion with a linear expansion coefficient as small as +0.68 × 10-6/K over a wide temperature range around room temperature. The present study opens an avenue to reach ZTE particularly from the large class of giant NTE materials based on phase transition.
Directory of Open Access Journals (Sweden)
Fei-Ran Shen
2017-10-01
Full Text Available Materials with zero thermal expansion (ZTE or precisely tailored thermal expansion are in urgent demand of modern industries. However, the overwhelming majority of materials show positive thermal expansion. To develop ZTE or negative thermal expansion (NTE materials as compensators has become an important challenge. Here, we present the evidence for the realization of ultra-low thermal expansion in Mn–Co–Ge–In particles. The bulk with the Ni2In-type hexagonal structure undergoes giant NTE owing to a martensitic magnetostructural transition. The major finding is that the thermal expansion behavior can be totally controlled by modulating the crystallinity degree and phase transition from atomic scale. Self-compensation effect leads to ultra-low thermal expansion with a linear expansion coefficient as small as +0.68 × 10−6/K over a wide temperature range around room temperature. The present study opens an avenue to reach ZTE particularly from the large class of giant NTE materials based on phase transition.
Elasticity moduli, thermal expansion coefficients and Debye temperature of titanium alloys
International Nuclear Information System (INIS)
Beletskij, V.M.; Glej, V.A.; Maksimyuk, P.A.; Tabachnik, V.I.; Opanasenko, V.F.
1979-01-01
Studied are the characteristics of titanium alloys which reflect best the bonding forces for atoms in a crystal lattice: elastic modules, their temperature dependences, thermal expansion coefficient and Debye temperatures. For the increase of the accuracy of measuring modules and especially their changes with temperature an ultrasonic echo-impulse method of superposition has been used. The temperature dependences of Young modulus of the VT1-0, VT16 and VT22 titanium alloys are plotted. The Young module and its change with temperature depend on the content of alloying elements. The Young module decrease with temperature may be explained within the framework of the inharmonic effect theory. The analysis of the results obtained permits to suppose that alloying of titanium alloys with aluminium results in an interatomic interaction increase that may be one of the reasons of their strength increase
Moduli evolution in the presence of thermal corrections
International Nuclear Information System (INIS)
Barreiro, Tiago; Carlos, Beatriz de; Copeland, Edmund J.; Nunes, Nelson J.
2008-01-01
We study the effect of thermal corrections on the evolution of moduli in effective supergravity models. This is motivated by previous results in the literature suggesting that these corrections could alter and even erase the presence of a minimum in the zero temperature potential, something that would have disastrous consequences in these particular models. We show that, in a representative sample of flux compactification constructions, this need not be the case, although we find that the inclusion of thermal corrections can dramatically decrease the region of initial conditions for which the moduli are stabilized. Moreover, the bounds on the reheating temperature coming from demanding that the full, finite temperature potential, has a minimum can be considerably relaxed given the slow pace at which the evolution proceeds.
Dimensional reduction for D3-brane moduli
International Nuclear Information System (INIS)
Cownden, Brad; Frey, Andrew R.; Marsh, M.C. David; Underwood, Bret
2016-01-01
Warped string compactifications are central to many attempts to stabilize moduli and connect string theory with cosmology and particle phenomenology. We present a first-principles derivation of the low-energy 4D effective theory from dimensional reduction of a D3-brane in a warped Calabi-Yau compactification of type IIB string theory with imaginary self-dual 3-form flux, including effects of D3-brane motion beyond the probe approximation, and find the metric on the moduli space of brane positions, the universal volume modulus, and axions descending from the 4-form potential. As D3-branes may be considered as carrying either electric or magnetic charges for the self-dual 5-form field strength, we present calculations in both duality frames. Our results are consistent with, but extend significantly, earlier results on the low-energy effective theory arising from D3-branes in string compactifications.
On natural inflation and moduli stabilisation in string theory
Energy Technology Data Exchange (ETDEWEB)
Palti, Eran [Institut für Theoretische Physik, Ruprecht-Karls-Universität, Philosophenweg 19, Heidelberg, 69120 (Germany)
2015-10-28
Natural inflation relies on the existence of an axion decay constant which is super-Planckian. In string theory only sub-Planckian axion decay constants have been found in any controlled regime. However in field theory it is possible to generate an enhanced super-Planckian decay constant by an appropriate aligned mixing between axions with individual sub-Planckian decay constants. We study the possibility of such a mechanism in string theory. In particular we construct a new realisation of an alignment scenario in type IIA string theory compactifications on a Calabi-Yau where the alignment is induced through fluxes. Within field theory the original decay constants are taken to be independent of the parameters which induce the alignment. In string theory however they are moduli dependent quantities and so interact gravitationally with the physics responsible for the mixing. We show that this gravitational effect of the fluxes on the moduli can precisely cancel any enhancement of the effective decay constant. This censorship of an effective super-Planckian decay constant depends on detailed properties of Calabi-Yau moduli spaces and occurs for all the examples and classes that we study. We expand these results to a general superpotential assuming only that the axion superpartners are fixed supersymmetrically and are able to show for a large class of Calabi-Yau manifolds, but not all, that the cancellation effect occurs and is independent of the superpotential. We also study simple models where the moduli are fixed non-supersymmetrically and find that similar cancellation behaviour can emerge. Finally we make some comments on a possible generalisation to axion monodromy inflation models.
String loop moduli stabilisation and cosmology in IIB flux compactifications
International Nuclear Information System (INIS)
Cicoli, M.
2010-01-01
We present a detailed review of the moduli stabilisation mechanism and possible cosmological implications of the LARGE Volume Scenario (LVS) that emerges naturally in the context of type IIB Calabi-Yau flux compactifications. After a quick overview of physics beyond the Standard Model, we present string theory as the most promising candidate for a consistent theory of quantum gravity. We then give a pedagogical introduction to type IIB compactifications on Calabi-Yau orientifolds where most of the moduli are stabilised by turning on background fluxes. However in order to fix the Kaehler moduli one needs to consider several corrections beyond the leading order approximations. After presenting a survey of all the existing solutions to this problem, we derive the topological conditions on an arbitrary Calabi-Yau to obtain the LVS since it requires no fine-tuning of the fluxes and provides a natural solution of the hierarchy problem. After performing a systematic study of the behaviour of string loop corrections for general type IIB compactifications, we show how they play a crucial role to achieve full Kaehler moduli stabilisation in the LVS. Before examining the possible cosmological implication of these scenarios, we present a broad overview of string cosmology. We then notice how, in the case of K3-fibrations, string loop corrections give rise naturally to an inflationary model which yields observable gravity waves. We finally study the finite-temperature behaviour of the LVS and discuss prospects for future work. (Abstract Copyright [2010], Wiley Periodicals, Inc.)
Bohr--Sommerfeld Lagrangians of moduli spaces of Higgs bundles
DEFF Research Database (Denmark)
Biswas, Indranil; Gammelgaard, Niels Leth; Logares, Marina
Let $X$ be a compact connected Riemann surface of genus at least two. Let $M_H(r,d)$ denote the moduli space of semistable Higgs bundles on $X$ of rank $r$ and degree $d$. We prove that the compact complex Bohr-Sommerfeld Lagrangians of $M_H(r,d)$ are precisely the irreducible components of the n......Let $X$ be a compact connected Riemann surface of genus at least two. Let $M_H(r,d)$ denote the moduli space of semistable Higgs bundles on $X$ of rank $r$ and degree $d$. We prove that the compact complex Bohr-Sommerfeld Lagrangians of $M_H(r,d)$ are precisely the irreducible components...
Compositional dependence of Young's moduli for amorphous FeCo-SiO2 thin films
International Nuclear Information System (INIS)
Zhang, L.; Xie, J. L.; Deng, L. J.; Guo, Q.; Zhu, Z. W.; Bi, L.
2011-01-01
Systematic force-deflection measurements with microcantilevers and a combinatorial-deposition method have been used to investigate the Young's moduli of amorphous composite FeCo-SiO 2 thin films as a function of film composition, with high compositional resolution. It is found that the modulus decreases monotonically with increasing FeCo content. Such a trend can be explained in terms of the metalloid atoms having a significant effect on the Young's moduli of metal-metalloid composites, which is associated with the strong chemical interaction between the metalloid and themetallic atoms rather than that between the metallic components themselves. This work provides an efficient and effective method to study the moduli of magnetic thin films over a largecomposition coverage, and to compare the relative magnitudes of moduli for differentcompositions at high compositional resolution.
Moduli and (un)attractor black hole thermodynamics
Astefanesei, D.; Goldstein, K.D.; Mahapatra, S.
2008-01-01
We investigate four-dimensional spherically symmetric black hole solutions in gravity theories with massless, neutral scalars non-minimally coupled to gauge fields. In the non-extremal case, we explicitly show that, under the variation of the moduli, the scalar charges appear in the first law of
No-scale D-term inflation with stabilized moduli
Energy Technology Data Exchange (ETDEWEB)
Buchmueller, Wilfried; Domcke, Valerie; Wieck, Clemens
2013-09-15
We study the consistency of hybrid inflation and moduli stabilization, using the Kallosh- Linde model as an example for the latter. We find that F-term hybrid inflation is not viable since inflationary trajectories are destabilized by tachyonic modes. On the other hand, D-term hybrid inflation is naturally compatible with moduli stabilization due to the absence of a large superpotential term during the inflationary phase. Our model turns out to be equivalent to superconformal D-term inflation and it therefore successfully accounts for the CMB data in the large-field regime. Supersymmetry breaking can be incorporated via an O'Raifeartaigh model. For GUT-scale inflation one obtains a stringent bound on the gravitino mass. A rough estimate yields m{sub 3/2}>or similar 10{sup 5} GeV, contrary to naive expectation.
No-scale D-term inflation with stabilized moduli
International Nuclear Information System (INIS)
Buchmueller, Wilfried; Domcke, Valerie; Wieck, Clemens
2013-09-01
We study the consistency of hybrid inflation and moduli stabilization, using the Kallosh- Linde model as an example for the latter. We find that F-term hybrid inflation is not viable since inflationary trajectories are destabilized by tachyonic modes. On the other hand, D-term hybrid inflation is naturally compatible with moduli stabilization due to the absence of a large superpotential term during the inflationary phase. Our model turns out to be equivalent to superconformal D-term inflation and it therefore successfully accounts for the CMB data in the large-field regime. Supersymmetry breaking can be incorporated via an O'Raifeartaigh model. For GUT-scale inflation one obtains a stringent bound on the gravitino mass. A rough estimate yields m 3/2 >or similar 10 5 GeV, contrary to naive expectation.
Quantum moduli spaces of N=1 string theories
International Nuclear Information System (INIS)
Banks, T.; Dine, M.
1996-01-01
Generically, string models with N=1 supersymmetry are not expected to have moduli beyond perturbation theory; stringy nonperturbative effects as well as low energy field-theoretic phenomena such as gluino condensation will lift any flat directions. In this work, we describe models where some subspace of the moduli space survives nonperturbatively. Discrete R symmetries forbid any inherently stringy effects, and dynamical considerations control the field-theoretic effects. The surviving subspace is a space of high symmetry; the system is attracted to this subspace by a potential which we compute. Models of this type may be useful for considerations of duality and raise troubling cosmological questions about string theory. Our considerations also suggest a mechanism for fixing the expectation value of the dilaton. copyright 1996 The American Physical Society
A minicourse on moduli of curves
International Nuclear Information System (INIS)
Looijenga, E.
2000-01-01
These are notes that accompany a short course given at the School on Algebraic Geometry 1999 at the ICTP, Trieste. A major goal is to outline various approaches to moduli spaces of curves. In the last part I discuss the algebraic classes that naturally live on these spaces; these can be thought of as the characteristic classes for bundles of curves. (author)
IMPA-ICTP School on Moduli of Curves
Ciliberto, Ciro; Esteves, Eduardo; Melo, Margarida; Voisin, Claire
2017-01-01
Providing a timely description of the present state of the art of moduli spaces of curves and their geometry, this volume is written in a way which will make it extremely useful both for young people who want to approach this important field, and also for established researchers, who will find references, problems, original expositions, new viewpoints, etc. The book collects the lecture notes of a number of leading algebraic geometers and in particular specialists in the field of moduli spaces of curves and their geometry. This is an important subject in algebraic geometry and complex analysis which has seen spectacular developments in recent decades, with important applications to other parts of mathematics such as birational geometry and enumerative geometry, and to other sciences, including physics. The themes treated are classical but with a constant look to modern developments (see Cascini, Debarre, Farkas, and Sernesi's contributions), and include very new material, such as Bridgeland stability (see M...
Symplectic geometry on moduli spaces of holomorphic bundles over complex surfaces
Khesin, Boris; Rosly, Alexei
2000-01-01
We give a comparative description of the Poisson structures on the moduli spaces of flat connections on real surfaces and holomorphic Poisson structures on the moduli spaces of holomorphic bundles on complex surfaces. The symplectic leaves of the latter are classified by restrictions of the bundles to certain divisors. This can be regarded as fixing a "complex analogue of the holonomy" of a connection along a "complex analogue of the boundary" in analogy with the real case.
Picard-Fuchs equations and the moduli space of superconformal field theories
International Nuclear Information System (INIS)
Cadavid, A.C.; Ferrara, S.
1991-01-01
We derive simple techniques which allow us to relate Picard-Fuchs differential equations for the periods of holomorphic p-forms on certain complex manifolds, to their moduli space and its modular group (target space duality). For Calabi-Yau manifolds the special geometry of moduli space gives the Zamolodchikov metric and the Yukawa couplings in terms of the periods. For general N=2 superconformal theories these equations exactly determine perturbed correlation functions of the chiral rings of primary fields. (orig.)
Candelas, Philip; de la Ossa, Xenia; McOrist, Jock
2017-12-01
Heterotic vacua of string theory are realised, at large radius, by a compact threefold with vanishing first Chern class together with a choice of stable holomorphic vector bundle. These form a wide class of potentially realistic four-dimensional vacua of string theory. Despite all their phenomenological promise, there is little understanding of the metric on the moduli space of these. What is sought is the analogue of special geometry for these vacua. The metric on the moduli space is important in phenomenology as it normalises D-terms and Yukawa couplings. It is also of interest in mathematics, since it generalises the metric, first found by Kobayashi, on the space of gauge field connections, to a more general context. Here we construct this metric, correct to first order in {α^{\\backprime}}, in two ways: first by postulating a metric that is invariant under background gauge transformations of the gauge field, and also by dimensionally reducing heterotic supergravity. These methods agree and the resulting metric is Kähler, as is required by supersymmetry. Checking the metric is Kähler is intricate and the anomaly cancellation equation for the H field plays an essential role. The Kähler potential nevertheless takes a remarkably simple form: it is the Kähler potential of special geometry with the Kähler form replaced by the {α^{\\backprime}}-corrected hermitian form.
The homology groups of moduli spaces on non-classical Klein surfaces
International Nuclear Information System (INIS)
Zaw, Myint
2001-08-01
We describe the moduli space M-vector±(g,c) of non-classical directed Klein surfaces of genus g=h-c-1 with c≥0 distinguished points as a configuration space B ± (h,c) of classes h-slit pairs in C. Based on this model, we prove that M-vector ± (g,c) is non-orientable for any g and c and we compute the homology groups of the moduli spaces M-vector ± (g,c) for g≤2. (author)
BCFT moduli space in level truncation
Czech Academy of Sciences Publication Activity Database
Kudrna, Matěj; Maccaferri, C.
2016-01-01
Roč. 2016, č. 4 (2016), 1-33, č. článku 057. ISSN 1029-8479 R&D Projects: GA ČR(CZ) GA14-31689S Institutional support: RVO:68378271 Keywords : deformation: marginal * field theory: string * tachyon: potential * string: open * moduli space * effective potential * nonperturbative * toy model Subject RIV: BF - Elementary Particles and High Energy Physics Impact factor: 6.063, year: 2016
Moduli stabilisation for chiral global models
International Nuclear Information System (INIS)
Cicoli, Michele; Mayrhofer, Christoph; Valandro, Roberto
2011-10-01
We combine moduli stabilisation and (chiral) model building in a fully consistent global set-up in Type IIB/F-theory. We consider compactifications on Calabi-Yau orientifolds which admit an explicit description in terms of toric geometry. We build globally consistent compactifications with tadpole and Freed-Witten anomaly cancellation by choosing appropriate brane set-ups and world-volume fluxes which also give rise to SU(5)- or MSSM-like chiral models. We fix all the Kaehler moduli within the Kaehler cone and the regime of validity of the 4D effective field theory. This is achieved in a way compatible with the local presence of chirality. The hidden sector generating the non-perturbative effects is placed on a del Pezzo divisor that does not have any chiral intersections with any other brane. In general, the vanishing D-term condition implies the shrinking of the rigid divisor supporting the visible sector. However, we avoid this problem by generating r< n D-term conditions on a set of n intersecting divisors. The remaining (n-r) flat directions are fixed by perturbative corrections to the Kaehler potential. We illustrate our general claims in an explicit example. We consider a K3-fibred Calabi-Yau with four Kaehler moduli, that is an hypersurface in a toric ambient space and admits a simple F-theory up-lift. We present explicit choices of brane set-ups and fluxes which lead to three different phenomenological scenarios: the first with GUT-scale strings and TeV-scale SUSY by fine-tuning the background fluxes; the second with an exponentially large value of the volume and TeV-scale SUSY without fine-tuning the background fluxes; and the third with a very anisotropic configuration that leads to TeV-scale strings and two micron-sized extra dimensions. The K3 fibration structure of the Calabi-Yau three-fold is also particularly suitable for cosmological purposes. (orig.)
Moduli stabilisation for chiral global models
Energy Technology Data Exchange (ETDEWEB)
Cicoli, Michele [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Abdus Salam International Centre for Theoretical Physics, Trieste (Italy); Mayrhofer, Christoph [Heidelberg Univ. (Germany). Inst. fuer Theoretische Physik; Valandro, Roberto [Hamburg Univ. (Germany). 2. Inst. fuer Theoretische Physik
2011-10-15
We combine moduli stabilisation and (chiral) model building in a fully consistent global set-up in Type IIB/F-theory. We consider compactifications on Calabi-Yau orientifolds which admit an explicit description in terms of toric geometry. We build globally consistent compactifications with tadpole and Freed-Witten anomaly cancellation by choosing appropriate brane set-ups and world-volume fluxes which also give rise to SU(5)- or MSSM-like chiral models. We fix all the Kaehler moduli within the Kaehler cone and the regime of validity of the 4D effective field theory. This is achieved in a way compatible with the local presence of chirality. The hidden sector generating the non-perturbative effects is placed on a del Pezzo divisor that does not have any chiral intersections with any other brane. In general, the vanishing D-term condition implies the shrinking of the rigid divisor supporting the visible sector. However, we avoid this problem by generating r
Moduli evolution in the presence of flux compactifications
International Nuclear Information System (INIS)
Barreiro, Tiago; Carlos, Beatriz de; Copeland, Ed; Nunes, Nelson J.
2005-01-01
We study the cosmological evolution of the volume moduli in a class of recently proposed inflationary universe models of Kachru et al. arising out of Type IIB string theory, where a number of the moduli fields have been stabilized through flux compactifications. Developing an approach introduced by some of us earlier, we show, in agreement with Brustein et al., how the presence of extra sources of matter act so as to provide additional friction, slowing the modulus field as it evolves down its potential, thereby vastly increasing the region of parameter space which leads to the eventual stabilization of these fields. Extending the case to include both the real and imaginary parts of the volume modulus, we show how the parameter space of initial conditions is modified and comment on the impact for these inflationary models arising out of flux type compactifications
Instantons from geodesics in AdS moduli spaces
Ruggeri, Daniele; Trigiante, Mario; Van Riet, Thomas
2018-03-01
We investigate supergravity instantons in Euclidean AdS5 × S5/ℤk. These solutions are expected to be dual to instantons of N = 2 quiver gauge theories. On the supergravity side the (extremal) instanton solutions are neatly described by the (lightlike) geodesics on the AdS moduli space for which we find the explicit expression and compute the on-shell actions in terms of the quantised charges. The lightlike geodesics fall into two categories depending on the degree of nilpotency of the Noether charge matrix carried by the geodesic: for degree 2 the instantons preserve 8 supercharges and for degree 3 they are non-SUSY. We expect that these findings should apply to more general situations in the sense that there is a map between geodesics on moduli-spaces of Euclidean AdS vacua and instantons with holographic counterparts.
Elastic Moduli of Permanently Densified Silica Glasses
Deschamps, T.; Margueritat, J.; Martinet, C.; Mermet, A.; Champagnon, B.
2014-01-01
Modelling the mechanical response of silica glass is still challenging, due to the lack of knowledge concerning the elastic properties of intermediate states of densification. An extensive Brillouin Light Scattering study on permanently densified silica glasses after cold compression in diamond anvil cell has been carried out, in order to deduce the elastic properties of such glasses and to provide new insights concerning the densification process. From sound velocity measurements, we derive phenomenological laws linking the elastic moduli of silica glass as a function of its densification ratio. The found elastic moduli are in excellent agreement with the sparse data extracted from literature, and we show that they do not depend on the thermodynamic path taken during densification (room temperature or heating). We also demonstrate that the longitudinal sound velocity exhibits an anomalous behavior, displaying a minimum for a densification ratio of 5%, and highlight the fact that this anomaly has to be distinguished from the compressibility anomaly of a-SiO2 in the elastic domain. PMID:25431218
Probing the moduli dependence of refined topological amplitudes
Directory of Open Access Journals (Sweden)
I. Antoniadis
2015-12-01
Full Text Available With the aim of providing a worldsheet description of the refined topological string, we continue the study of a particular class of higher derivative couplings Fg,n in the type II string effective action compactified on a Calabi–Yau threefold. We analyse first order differential equations in the anti-holomorphic moduli of the theory, which relate the Fg,n to other component couplings. From the point of view of the topological theory, these equations describe the contribution of non-physical states to twisted correlation functions and encode an obstruction for interpreting the Fg,n as the free energy of the refined topological string theory. We investigate possibilities of lifting this obstruction by formulating conditions on the moduli dependence under which the differential equations simplify and take the form of generalised holomorphic anomaly equations. We further test this approach against explicit calculations in the dual heterotic theory.
How to define the storage and loss moduli for a rheologically nonlinear material?
Argatov, Ivan; Iantchenko, Alexei; Kocherbitov, Vitaly
2017-11-01
A large amplitude oscillatory shear (LAOS) is considered in the strain-controlled regime, and the interrelation between the Fourier transform and the stress decomposition approaches is established. Several definitions of the generalized storage and loss moduli are examined in a unified conceptual scheme based on the Lissajous-Bowditch plots. An illustrative example of evaluating the generalized moduli from a LAOS flow is given.
Moduli Dark Matter and the Search for Its Decay Line using Suzaku X-Ray Telescope
Kusenko, Alexander; Loewenstein, Michael; Yanagida, Tsutomu T.
2013-01-01
Light scalar fields called moduli arise from a variety of different models involving supersymmetry and/or string theory; thus their existence is a generic prediction of leading theories for physics beyond the standard model. They also present a formidable, long-standing problem for cosmology. We argue that an anthropic solution to the moduli problem exists in the case of small moduli masses and that it automatically leads to dark matter in the form of moduli. The recent discovery of the 125 GeV Higgs boson implies a lower bound on the moduli mass of about a keV. This form of dark matter is consistent with the observed properties of structure formation, and it is amenable to detection with the help of x-ray telescopes. We present the results of a search for such dark matter particles using spectra extracted from the first deep x-ray observations of the Draco and Ursa Minor dwarf spheroidal galaxies, which are darkmatter- dominated systems with extreme mass-to-light ratios and low intrinsic backgrounds. No emission line is positively detected, and we set new constraints on the relevant new physics.
On the Young's moduli of Ti-6Al-4V alloys
International Nuclear Information System (INIS)
Fan, Zhongyun
1993-01-01
In this paper, the authors will present an iterative approach to Young's modulus of multi-phase composites developed by Fan et al. The iterative approach will then be applied to Ti-6Al-4V alloys to predict their effective Young's moduli. It is hoped that the theoretical predictions will offer a quantitative explanation to the peculiar shape of the E c -f β curve and will shed some light on controlling the Young's moduli of Ti-6Al-4V alloys by choosing the proper heat treatment procedure
Transverse thermal expansion of carbon fiber/epoxy matrix composites
Helmer, J. F.; Diefendorf, R. J.
1983-01-01
Thermal expansion coefficients and moduli of elasticity have been determined experimentally for a series of epoxy-matrix composites reinforced with carbon and Kevlar fibers. It is found that in the transverse direction the difference between the properties of the fiber and the matrix is not as pronounced as in the longitudinal direction, where the composite properties are fiber-dominated. Therefore, the pattern of fiber packing tends to affect transverse composite properties. The transverse properties of the composites tested are examined from the standpoint of the concept of homogeneity defined as the variation of packing (or lack thereof) throughout a sample.
Moduli destabilization via gravitational collapse
Energy Technology Data Exchange (ETDEWEB)
Hwang, Dong-il [Sogang Univ., Seoul (Korea, Republic of). Center for Quantum Spacetime; Pedro, Francisco G. [Deutsches Elektronen-Synchrotron DESY, Hamburg (Germany). Theory Group; Yeom, Dong-han [Sogang Univ., Seoul (Korea, Republic of). Center for Quantum Spacetime; Kyoto Univ. (Japan). Yukawa Inst. for Theoretical Physics
2013-06-15
We examine the interplay between gravitational collapse and moduli stability in the context of black hole formation. We perform numerical simulations of the collapse using the double null formalism and show that the very dense regions one expects to find in the process of black hole formation are able to destabilize the volume modulus. We establish that the effects of the destabilization will be visible to an observer at infinity, opening up a window to a region in spacetime where standard model's couplings and masses can differ significantly from their background values.
Thermal expansion: Metallic elements and alloys. [Handbook
Touloukian, Y. S.; Kirby, R. K.; Taylor, R. E.; Desai, P. D.
1975-01-01
The introductory sections of the work are devoted to the theory of thermal expansion of solids and to methods for the measurement of the linear thermal expansion of solids (X-ray methods, high speed methods, interferometry, push-rod dilatometry, etc.). The bulk of the work is devoted to numerical data on the thermal linear expansion of all the metallic elements, a large number of intermetallics, and a large number of binary alloy systems and multiple alloy systems. A comprehensive bibliography is provided along with an index to the materials examined.
International Nuclear Information System (INIS)
Kogan, I.I.
1991-01-01
The quantum geometrodynamics of the open topological membrane is described in terms of 2+1 topologically massive gravity (TMG) where the inverse graviton mass is proportional to the 2D central charge and thus is the measure of the off-criticality. The hamiltonian quantization of TMG on Riemann surfaces is considered and the moduli space appears as the subspace of the quantum-mechanical configuration space containing, besides the moduli, the first-order time derivatives of half of the moduli. The appearance of the first-order time derivatives as coordinates, not momenta, is due to the third-order derivative in the TMG lagrangian. The hamiltonian for the latter leads us to the discrete levels picture which looks like the topologically massive gauge theory (TMGT) case, where we also get the Landau levels picture and the lowest Landau level corresponds to the Hilbert space of the Chern-Simons theory (CST). The connection between the positivity of the energy and the complex structure on the moduli space is discussed. (orig.)
On the compactification of the moduli space of branched minimal immersions of S2 into S4
International Nuclear Information System (INIS)
Loo, B.
1992-01-01
We study the natural compactification of the moduli space of branched minimal immersions of S 2 into S 4 . We prove that the (compactified) moduli space M d is a connected projective variety of dimension 2d+4. It is irreducible when d=1,2, and it has two irreducible components when d ≥ 3. We discuss the bubbling phenomenon at the boundary of the moduli space. (author). 26 refs, 3 figs
Frequency-dependent complex modulus at the glass transition in Pd40Ni10Cu30P20 bulk amorphous alloys
International Nuclear Information System (INIS)
Lee, M.L.; Li, Y.; Feng, Y.P.; Carter, W.C.
2003-01-01
We report frequency-dependent measurements of the dynamic elastic modulus of a Pd 40 Cu 30 Ni 10 P 20 bulk amorphous phase near its glass transition temperature. The storage and loss moduli exhibit a structural relaxation similar to those observed by other characterization techniques. Parameters obtained by fitting to the Vogel-Fulcher-Tamman equation and the Kohlrausch-Williams-Watts model exhibit similar behaviors to those other methods
QUANTITATIVE NON-DESTRUCTIVE EVALUATION (QNDE) OF THE ELASTIC MODULI OF POROUS TIAL ALLOYS
International Nuclear Information System (INIS)
Yeheskel, O.
2008-01-01
The elastic moduli of γ-TiA1 were studied in porous samples consolidated by various techniques e.g. cold isostatic pressing (CIP), pressure-less sintering, or hot isostatic pressing (HIP). Porosity linearly affects the dynamic elastic moduli of samples. The results indicate that the sound wave velocities and the elastic moduli affected by the processing route and depend not only on the attained density but also on the consolidation temperature. In this paper we show that there is linear correlation between the shear and the longitudinal sound velocities in porous TiA1. This opens the way to use a single sound velocity as a tool for quantitative non-destructive evaluation (QNDE) of porous TiA1 alloys. Here we demonstrate the applicability of an equation derived from the elastic theory and used previously for porous cubic metals
The temperature dependence of the isothermal bulk modulus at 1 bar pressure
International Nuclear Information System (INIS)
Garai, J.; Laugier, A.
2007-01-01
It is well established that the product of the volume coefficient of thermal expansion and the bulk modulus is nearly constant at temperatures higher than the Debye temperature. Using this approximation allows predicting the values of the bulk modulus. The derived analytical solution for the temperature dependence of the isothermal bulk modulus has been applied to ten substances. The good correlations to the experiments indicate that the expression may be useful for substances for which bulk modulus data are lacking
Preparation and elastic moduli of germanate glass containing lead and bismuth.
Sidek, Hj A A; Bahari, Hamid R; Halimah, Mohamed K; Yunus, Wan M M
2012-01-01
This paper reports the rapid melt quenching technique preparation for the new family of bismuth-lead germanate glass (BPG) systems in the form of (GeO(2))(60)-(PbO)(40-) (x)-(½Bi(2)O(3))(x) where x = 0 to 40 mol%. Their densities with respect of Bi(2)O(3) concentration were determined using Archimedes' method with acetone as a floatation medium. The current experimental data are compared with those of bismuth lead borate (B(2)O(3))(20)-(PbO)(80-) (x)-(Bi(2)O(3))(x). The elastic properties of BPG were studied using the ultrasonic pulse-echo technique where both longitudinal and transverse sound wave velocities have been measured in each glass samples at a frequency of 15 MHz and at room temperature. Experimental data shows that all the physical parameters of BPG including density and molar volume, both longitudinal and transverse velocities increase linearly with increasing of Bi(2)O(3) content in the germanate glass network. Their elastic moduli such as longitudinal, shear and Young's also increase linearly with addition of Bi(2)O(3) but the bulk modulus did not. The Poisson's ratio and fractal dimensionality are also found to vary linearly with the Bi(2)O(3) concentration.
Preparation and Elastic Moduli of Germanate Glass Containing Lead and Bismuth
Directory of Open Access Journals (Sweden)
Wan M. M. Yunus
2012-04-01
Full Text Available This paper reports the rapid melt quenching technique preparation for the new family of bismuth-lead germanate glass (BPG systems in the form of (GeO260–(PbO40−x–(½Bi2O3x where x = 0 to 40 mol%. Their densities with respect of Bi2O3 concentration were determined using Archimedes’ method with acetone as a floatation medium. The current experimental data are compared with those of bismuth lead borate (B2O320–(PbO80−x–(Bi2O3x. The elastic properties of BPG were studied using the ultrasonic pulse-echo technique where both longitudinal and transverse sound wave velocities have been measured in each glass samples at a frequency of 15 MHz and at room temperature. Experimental data shows that all the physical parameters of BPG including density and molar volume, both longitudinal and transverse velocities increase linearly with increasing of Bi2O3 content in the germanate glass network. Their elastic moduli such as longitudinal, shear and Young’s also increase linearly with addition of Bi2O3 but the bulk modulus did not. The Poisson’s ratio and fractal dimensionality are also found to vary linearly with the Bi2O3 concentration.
Quantum-induced interactions in the moduli space of degenerate BPS domain walls
International Nuclear Information System (INIS)
Alonso-Izquierdo, A.; Guilarte, J. Mateos
2014-01-01
In this paper quantum effects are investigated in a very special two-scalar field model having a moduli space of BPS topological defects. In a (1+1)-dimensional space-time the defects are classically degenerate in mass kinks, but in (3+1) dimensions the kinks become BPS domain walls, all of them sharing the same surface tension at the classical level. The heat kernel/zeta function regularization method will be used to control the divergences induced by the quantum kink and domain wall fluctuations. A generalization of the Gilkey-DeWitt-Avramidi heat kernel expansion will be developed in order to accommodate the infrared divergences due to zero modes in the spectra of the second-order kink and domain wall fluctuation operators, which are respectively N=2×N=2 matrix ordinary or partial differential operators. Use of these tools in the spectral zeta function associated with the Hessian operators paves the way to obtain general formulas for the one-loop kink mass and domain wall tension shifts in any (1+1)- or (3+1)-dimensional N-component scalar field theory model. Application of these formulae to the BPS kinks or domain walls of the N=2 model mentioned above reveals the breaking of the classical mass or surface tension degeneracy at the quantum level. Because the main parameter distinguishing each member in the BPS kink or domain wall moduli space is essentially the distance between the centers of two basic kinks or walls, the breaking of the degeneracy amounts to the surge in quantum-induced forces between the two constituent topological defects. The differences in surface tension induced by one-loop fluctuations of BPS walls give rise mainly to attractive forces between the constituent walls except if the two basic walls are very far apart. Repulsive forces between two close walls only arise if the coupling approaches the critical value from below
The information metric on the moduli space of instantons with global symmetries
Directory of Open Access Journals (Sweden)
Emanuel Malek
2016-02-01
Full Text Available In this note we revisit Hitchin's prescription [1] of the Fisher metric as a natural measure on the moduli space of instantons that encodes the space–time symmetries of a classical field theory. Motivated by the idea of the moduli space of supersymmetric instantons as an emergent space in the sense of the gauge/gravity duality, we extend the prescription to encode also global symmetries of the underlying theory. We exemplify our construction with the instanton solution of the CPN sigma model on R2.
Canonical generators of the cohomology of moduli of parabolic bundles on curves
International Nuclear Information System (INIS)
Biswas, I.; Raghavendra, N.
1994-11-01
We determine generators of the rational cohomology algebras of moduli spaces of parabolic vector bundles on a curve, under some 'primality' conditions on the parabolic datum. These generators are canonical in a precise sense. Our results are new even for usual vector bundles (i.e., vector bundles without parabolic structure) whose rank is greater than 2 and is coprime to the degree; in this case, they are generalizations of a theorem of Newstead on the moduli of vector bundles of rank 2 and odd degree. (author). 11 refs
Energy Technology Data Exchange (ETDEWEB)
Hamed, Elham [University of Illinois at Urbana-Champaign, Department of Mechanical Science and Engineering, 1206 West Green Street, Urbana, IL 61801 (United States); Novitskaya, Ekaterina, E-mail: eevdokim@ucsd.edu [University of California, San Diego, Department of Mechanical and Aerospace Engineering, Materials Science and Engineering Program, 9500 Gilman Dr., La Jolla, CA 92093 (United States); Li, Jun; Jasiuk, Iwona [University of Illinois at Urbana-Champaign, Department of Mechanical Science and Engineering, 1206 West Green Street, Urbana, IL 61801 (United States); McKittrick, Joanna [University of California, San Diego, Department of Mechanical and Aerospace Engineering, Materials Science and Engineering Program, 9500 Gilman Dr., La Jolla, CA 92093 (United States)
2015-09-01
The elastic moduli of trabecular bone were modeled using an analytical multiscale approach. Trabecular bone was represented as a porous nanocomposite material with a hierarchical structure spanning from the collagen–mineral level to the trabecular architecture level. In parallel, compression testing was done on bovine femoral trabecular bone samples in two anatomical directions, parallel to the femoral neck axis and perpendicular to it, and the measured elastic moduli were compared with the corresponding theoretical results. To gain insights on the interaction of collagen and minerals at the nanoscale, bone samples were deproteinized or demineralized. After such processing, the treated samples remained as self-standing structures and were tested in compression. Micro-computed tomography was used to characterize the hierarchical structure of these three bone types and to quantify the amount of bone porosity. The obtained experimental data served as inputs to the multiscale model and guided us to represent bone as an interpenetrating composite material. Good agreement was found between the theory and experiments for the elastic moduli of the untreated, deproteinized, and demineralized trabecular bone. - Highlights: • A multiscale model was used to predict the elastic moduli of trabecular bone. • Samples included demineralized, deproteinized and untreated bone. • The model portrays bone as a porous, interpenetrating two phase composite. • The experimental elastic moduli for trabecular bone fell between theoretical bounds.
International Nuclear Information System (INIS)
Hamed, Elham; Novitskaya, Ekaterina; Li, Jun; Jasiuk, Iwona; McKittrick, Joanna
2015-01-01
The elastic moduli of trabecular bone were modeled using an analytical multiscale approach. Trabecular bone was represented as a porous nanocomposite material with a hierarchical structure spanning from the collagen–mineral level to the trabecular architecture level. In parallel, compression testing was done on bovine femoral trabecular bone samples in two anatomical directions, parallel to the femoral neck axis and perpendicular to it, and the measured elastic moduli were compared with the corresponding theoretical results. To gain insights on the interaction of collagen and minerals at the nanoscale, bone samples were deproteinized or demineralized. After such processing, the treated samples remained as self-standing structures and were tested in compression. Micro-computed tomography was used to characterize the hierarchical structure of these three bone types and to quantify the amount of bone porosity. The obtained experimental data served as inputs to the multiscale model and guided us to represent bone as an interpenetrating composite material. Good agreement was found between the theory and experiments for the elastic moduli of the untreated, deproteinized, and demineralized trabecular bone. - Highlights: • A multiscale model was used to predict the elastic moduli of trabecular bone. • Samples included demineralized, deproteinized and untreated bone. • The model portrays bone as a porous, interpenetrating two phase composite. • The experimental elastic moduli for trabecular bone fell between theoretical bounds
Holographic bulk reconstruction with α' corrections
Roy, Shubho R.; Sarkar, Debajyoti
2017-10-01
We outline a holographic recipe to reconstruct α' corrections to anti-de Sitter (AdS) (quantum) gravity from an underlying CFT in the strictly planar limit (N →∞ ). Assuming that the boundary CFT can be solved in principle to all orders of the 't Hooft coupling λ , for scalar primary operators, the λ-1 expansion of the conformal dimensions can be mapped to higher curvature corrections of the dual bulk scalar field action. Furthermore, for the metric perturbations in the bulk, the AdS /CFT operator-field isomorphism forces these corrections to be of the Lovelock type. We demonstrate this by reconstructing the coefficient of the leading Lovelock correction, also known as the Gauss-Bonnet term in a bulk AdS gravity action using the expression of stress-tensor two-point function up to subleading order in λ-1.
Infinite Grassmannian and moduli space of G-bundles
International Nuclear Information System (INIS)
Kumar, S.; Ramanathan, A.
1993-03-01
Let C be a smooth irreducible projective curve and G a simply connected simple affine algebraic group of C. We study in this paper the relationship between the space of vacua defined in Conformal Field Theory and the space of sections of a line bundle on the moduli space of G-bundles over C. (author). 33 refs
Locality, bulk equations of motion and the conformal bootstrap
Energy Technology Data Exchange (ETDEWEB)
Kabat, Daniel [Department of Physics and Astronomy, Lehman College, City University of New York,250 Bedford Park Blvd. W, Bronx NY 10468 (United States); Lifschytz, Gilad [Department of Mathematics, Faculty of Natural Science, University of Haifa,199 Aba Khoushy Ave., Haifa 31905 (Israel)
2016-10-18
We develop an approach to construct local bulk operators in a CFT to order 1/N{sup 2}. Since 4-point functions are not fixed by conformal invariance we use the OPE to categorize possible forms for a bulk operator. Using previous results on 3-point functions we construct a local bulk operator in each OPE channel. We then impose the condition that the bulk operators constructed in different channels agree, and hence give rise to a well-defined bulk operator. We refer to this condition as the “bulk bootstrap.” We argue and explicitly show in some examples that the bulk bootstrap leads to some of the same results as the regular conformal bootstrap. In fact the bulk bootstrap provides an easier way to determine some CFT data, since it does not require knowing the form of the conformal blocks. This analysis clarifies previous results on the relation between bulk locality and the bootstrap for theories with a 1/N expansion, and it identifies a simple and direct way in which OPE coefficients and anomalous dimensions determine the bulk equations of motion to order 1/N{sup 2}.
On the reconstruction of a unitary matrix from its moduli. Existence of continuous ambiguities
International Nuclear Information System (INIS)
Auberson, G.
1989-01-01
It is shown that, for an n x n unitary matrix with n ≥ 4, the knowledge of the moduli of its elements is not always sufficient to determine this matrix up to 'trivial' or 'discrete' ambiguities. Using a parametrization a la Kobayashi-Maskawa in the case n=4, we exhibit various configurations of the moduli for which a continuous ambiguity appears (i.e., some non-trivial phase remains free). (orig.)
The Picard group of the moduli space of r-Spin Riemann surfaces
DEFF Research Database (Denmark)
Randal-Williams, Oscar
2012-01-01
An r-Spin Riemann surface is a Riemann surface equipped with a choice of rth root of the (co)tangent bundle. We give a careful construction of the moduli space (orbifold) of r-Spin Riemann surfaces, and explain how to establish a Madsen–Weiss theorem for it. This allows us to prove the “Mumford...... conjecture” for these moduli spaces, but more interestingly allows us to compute their algebraic Picard groups (for g≥10, or g≥9 in the 2-Spin case). We give a complete description of these Picard groups, in terms of explicitly constructed line bundles....
Supersymmetric SU(5) GUT with Stabilized Moduli
Antoniadis, Ignatios; Panda, Binata
2008-01-01
We construct a minimal example of a supersymmetric grand unified model in a toroidal compactification of type I string theory with magnetized D9-branes. All geometric moduli are stabilized in terms of the background internal magnetic fluxes which are of "oblique" type (mutually non-commuting). The gauge symmetry is just SU(5) and the gauge non-singlet chiral spectrum contains only three families of quarks and leptons transforming in the $10+{\\bar 5}$ representations.
In Silico Measurement of Elastic Moduli of Nematic Liquid Crystals
Sidky, Hythem; de Pablo, Juan J.; Whitmer, Jonathan K.
2018-03-01
Experiments on confined droplets of the nematic liquid crystal 5CB have questioned long-established bounds imposed on the elastic free energy of nematic systems. This elasticity, which derives from molecular alignment within nematic systems, is quantified through a set of moduli which can be difficult to measure experimentally and, in some cases, can only be probed indirectly. This is particularly true of the surfacelike saddle-splay elastic term, for which the available experimental data indicate values on the cusp of stability, often with large uncertainties. Here, we demonstrate that all nematic elastic moduli, including the saddle-splay elastic constant k24, may be calculated directly from atomistic molecular simulations. Importantly, results obtained through in silico measurements of the 5CB elastic properties demonstrate unambiguously that saddle-splay elasticity alone is unable to describe the observed confined morphologies.
Wunderman, Irwin; Siegel, Edward Carl-Ludwig; Lewis, Thomas; Young, Frederic; Smith, Adolph; Dresschhoff-Zeller, Gieselle
2013-03-01
SHMUTZ: ``wet-graphite''Scheike-....[Adv.Mtls.(7/16/12)]hyper/super-SCHMUTZ-conductor(S!!!) = ``wet''(?)-``graphite''(?) = ``graphene''(?) = water(?) = hydrogen(?) =ultra-heavy proton-bands(???) = ...(???) claimed room/high-Tc/high-Jc superconductOR ``p''-``wave''/ BAND(!!!) superconductIVITY and actualized/ instantiated MgB2 high-Tc superconductors and their BCS- superconductivity: Tc Siegel[ICMAO(77);JMMM 7,190(78)] connection to SiegelJ.Nonxline-Sol.40,453(80)] disorder/amorphous-superconductivity in nano-powders mechanical bulk/shear(?)-moduli/hardness: proton-irradiated diamond, powders TiB2, TiC,{Siegel[Semis. & Insuls.5:39,47, 62 (79)])-...``VS''/concommitance with Siegel[Phys.Stat.Sol.(a)11,45(72)]-Dempsey [Phil.Mag. 8,86,285(63)]-Overhauser-(Little!!!)-Seitz-Smith-Zeller-Dreschoff-Antonoff-Young-...proton-``irradiated''/ implanted/ thermalized-in-(optimal: BOTH heat-capacity/heat-sink & insulator/maximal dielectric-constant) diamond: ``VS'' ``hambergite-borate-mineral transformable to Overhauser optimal-high-Tc-LiBD2 in Overhauser-(NW-periodic-table)-Land: CO2/CH4-ETERNAL-sequestration by-product: WATER!!!: physics lessons from
Realistic D-brane models on warped throats: Fluxes, hierarchies and moduli stabilization
International Nuclear Information System (INIS)
Cascales, J.F.G.; Garcia del Moral, M.P.; Quevedo, F.; Uranga, A.
2004-01-01
We describe the construction of string theory models with semirealistic spectrum in a sector of (anti) D3-branes located at an orbifold singularity at the bottom of a highly warped throat geometry, which is a generalisation of the Klebanov-Strassler deformed conifold. These models realise the Randall-Sundrum proposal to naturally generate the Planck/electroweak hierarchy in a concrete string theory embedding, and yielding interesting chiral open string spectra. We describe examples with Standard Model gauge group (or left-right symmetric extensions) and three families of SM fermions, with correct quantum numbers including hypercharge. The dilaton and complex structure moduli of the geometry are stabilised by the 3-form fluxes required to build the throat. We describe diverse issues concerning the stabilisation of geometric Kahler moduli, like blow-up modes of the orbifold singularities, via D term potentials and gauge theory non-perturbative effects, like gaugino condensation. This local geometry, once embedded in a full compactification, could give rise to models with all moduli stabilised, and with the potential to lead to de Sitter vacua. Issues of gauge unification, proton stability, supersymmetry breaking and Yukawa couplings are also discussed. (author)
Moduli space for endomorphisms of finite dimension vector spaces
International Nuclear Information System (INIS)
Kanarek, H.
1990-12-01
Consider the set (End n ) of endomorphisms of vector spaces of dimension n n ). What we present here is a decomposition of (End n ) in which each element has a fine moduli space and one of them is composed by the semisimple endomorphisms as D. Mumford shows. (author). 2 refs
Stability of Picard Bundle Over Moduli Space of Stable Vector ...
Indian Academy of Sciences (India)
Abstract. Answering a question of [BV] it is proved that the Picard bundle on the moduli space of stable vector bundles of rank two, on a Riemann surface of genus at least three, with fixed determinant of odd degree is stable.
Moduli for decorated tuples of sheaves and representation spaces ...
Indian Academy of Sciences (India)
R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22
We extend the scope of a former paper to vector bundle problems involving ... the machinery of algebraic geometry to the gauge theoretic moduli space for the pairs ... A nice example of a classification problem which can be formulated in our ... Numerous famous special cases of this construction have been studied in the ...
Micromechanical modeling of tungsten-based bulk metallic glass matrix composites
Energy Technology Data Exchange (ETDEWEB)
Li Hao [Department of Mechanical Engineering-Engineering Mechanics, Michigan Technological University, 1400 Townsend Drive, Houghton, MI 49931 (United States); Li Ke [Department of Mechanical Engineering, Texas A and M University, TAMU 3123, College Station, TX 77843 (United States)]. E-mail: keli@tamu.edu; Subhash, Ghatu [Department of Mechanical Engineering-Engineering Mechanics, Michigan Technological University, 1400 Townsend Drive, Houghton, MI 49931 (United States); Kecskes, Laszlo J. [Weapons and Materials Research Directorate, US Army Research Laboratory, Aberdeen Proving Ground, MD 21005 (United States); Dowding, Robert J. [Weapons and Materials Research Directorate, US Army Research Laboratory, Aberdeen Proving Ground, MD 21005 (United States)
2006-08-15
Micromechanics models are developed for tungsten (W)-based bulk metallic glass (BMG) matrix composites employing the Voronoi tessellation technique and the finite element (FE) method. The simulation results indicate that the computed elastic moduli are close to those measured in the experiments. The predicted stress-strain curves agree well with their experimentally obtained counterparts in the early stage of the plastic deformation. An increase in the W volume fraction leads to a decrease in the yield stress and an increase in the Young's modulus of the composite. In addition, contours of equivalent plastic strain for increasing applied strains provide an explanation why shear bands were observed in the glassy phase, along the W/BMG interface, and in the W phase of failed W/BMG composite specimens.
Gauge and moduli hierarchy in a multiply warped braneworld scenario
International Nuclear Information System (INIS)
Das, Ashmita; SenGupta, Soumitra
2013-01-01
Discovery of Higgs-like boson near the mass scale ∼126 Gev generates renewed interest to the gauge hierarchy problem in the standard model related to the stabilisation of the Higgs mass within Tev scale without any unnatural fine tuning. One of the successful attempts to resolve this problem has been the Randall–Sundrum warped geometry model. Subsequently this 5-dimensional model was extended to a doubly warped 6-dimensional (or higher) model which can offer a geometric explanation of the fermion mass hierarchy in the standard model of elementary particles (D. Choudhury and S. SenGupta, 2007 [1]). In an attempt to address the dark energy issue, we in this work extend such 6-dimensional warped braneworld model to include non-flat 3-branes at the orbifold fixed points such that a small but non-vanishing brane cosmological constant is induced in our observable brane. We show that the requirements of a Planck to Tev scale warping along with a vanishingly small but non-zero cosmological constant on the visible brane with non-hierarchical moduli, each with scale close to Planck length, lead to a scenario where the 3-branes can have energy scales either close to Tev or close to Planck scale. Such a scenario can address both the gauge hierarchy as well as fermion mass hierarchy problem in standard model without introducing hierarchical scales between the two moduli. Thus simultaneous resolutions to the gauge hierarchy problem, fermion mass hierarchy problem and non-hierarchical moduli problem are closely linked with the near flatness condition of our universe.
Biļešu tirdzniecības risinājuma zāles plāna modulis
Bušs, Jēkabs
2015-01-01
Biļešu tirdzniecības risinājuma zāles plāna modulis, ir daļa no biļešu tirdzniecības programmprodukta. Modulis sniedz iespēju iestādes klientiem ērti aplūkot zāles plānojumu, kā arī iestādes darbiniekiem izmantot to kā zāles plānojuma administrēšanas un tirdzniecības galveno rīku. Modulis sniedz iespēju apskatīt konkrētos datus par attiecīgām izrādēm, sniedz iespēju apskatīt un uzstādīt attiecīgo izrāžu bloķētās vietas, bet pats galvenais, modulis sniedz iespēju iestādes darbiniekiem ar g...
On the L2-metric of vortex moduli spaces
Baptista, J.M.
2011-01-01
We derive general expressions for the Kähler form of the L2-metric in terms of standard 2-forms on vortex moduli spaces. In the case of abelian vortices in gauged linear sigma-models, this allows us to compute explicitly the Kähler class of the L2-metric. As an application we compute the total
Arithmetic fundamental groups and moduli of curves
International Nuclear Information System (INIS)
Makoto Matsumoto
2000-01-01
This is a short note on the algebraic (or sometimes called arithmetic) fundamental groups of an algebraic variety, which connects classical fundamental groups with Galois groups of fields. A large part of this note describes the algebraic fundamental groups in a concrete manner. This note gives only a sketch of the fundamental groups of the algebraic stack of moduli of curves. Some application to a purely topological statement, i.e., an obstruction to the subjectivity of Johnson homomorphisms in the mapping class groups, which comes from Galois group of Q, is explained. (author)
Non-minimal gauge mediation and moduli stabilization
International Nuclear Information System (INIS)
Jelinski, T.; Lalak, Z.; Pawelczyk, J.
2010-01-01
In this Letter we consider U(1) A -gauged Polonyi model with two spurions coupled to a twisted closed string modulus. This offers a consistent setup for metastable SUSY breakdown which allows for moduli stabilization and naturally leads to gauge or hybrid gauge/gravitational mediation mechanism. Due to the presence of the second spurion one can arrange for a solution of the μ and B μ problems in a version of modified Giudice-Masiero mechanism, which works both in the limit of pure gauge mediation and in the mixed regime of hybrid mediation.
Thermal expansion accompanying the glass-liquid transition and crystallization
Directory of Open Access Journals (Sweden)
M. Q. Jiang
2015-12-01
Full Text Available We report the linear thermal expansion behaviors of a Zr-based (Vitreloy 1 bulk metallic glass in its as-cast, annealed and crystallized states. Accompanying the glass-liquid transition, the as-cast Vitreloy 1 shows a continuous decrease in the thermal expansivity, whereas the annealed glass shows a sudden increase. The crystallized Vitreloy 1 exhibits an almost unchanged thermal expansivity prior to its melting. Furthermore, it is demonstrated that the nucleation of crystalline phases can induce a significant thermal shrinkage of the supercooled liquid, but with the growth of these nuclei, the thermal expansion again dominates. These results are explained in the framework of the potential energy landscape, advocating that the configurational and vibrational contributions to the thermal expansion of the glass depend on both, structure and temperature.
Influence of seed layer moduli on FEM based modulus backcalculation results
CSIR Research Space (South Africa)
Matsui, K
2006-01-01
Full Text Available This paper presents recentupdates of DBALM (Dynamic Back Analysis for Layer Moduli) software whose solver is based on exi-symmetric FEM and was first developed in 1993. Examples of airfield pavement application are also presented. The results...
Accelerated and decelerated expansion in a causal dissipative cosmology
Cruz, Miguel; Cruz, Norman; Lepe, Samuel
2017-12-01
In this work we explore a new cosmological solution for an universe filled with one dissipative fluid, described by a barotropic equation of state (EoS) p =ω ρ , in the framework of the full Israel-Stewart theory. The form of the bulk viscosity has been assumed of the form ξ =ξ0ρ1 /2. The relaxation time is taken to be a function of the EoS, the bulk viscosity and the speed of bulk viscous perturbations, cb. The solution presents an initial singularity, where the curvature scalar diverges as the scale factor goes to zero. Depending on the values for ω , ξ0, cb accelerated and decelerated cosmic expansion can be obtained. In the case of accelerated expansion, the viscosity drives the effective EoS to be of quintessence type, for the single fluid with positive pressure. Nevertheless, we show that only the solution with decelerated expansion satisfies the thermodynamics conditions d S /d t >0 (growth of the entropy) and d2S /d t2<0 (convexity condition). We show that an exact stiff matter EoS is not allowed in the framework of the full causal thermodynamic approach; and in the case of a EoS very close to the stiff matter regime, we found that dissipative effects becomes negligible so the entropy remains constant. Finally, we show numerically that the solution is stable under small perturbations.
N=2 topological gauge theory, the Euler characteristic of moduli spaces, and the Casson invariant
International Nuclear Information System (INIS)
Blau, M.; Thompson, G.
1991-11-01
Gauge theory with a topological N=2 symmetry is discussed. This theory captures the de Rahm complex and Riemannian geometry of some underlying moduli space M and the partition function equals the Euler number χ (M) of M. Moduli spaces of instantons and of flat connections in 2 and 3 dimensions are explicitly dealt with. To motivate the constructions the relation between the Mathai-Quillen formalism and supersymmetric quantum mechanics are explained and a new kind of supersymmetric quantum mechanics is introduced, based on the Gauss-Codazzi equations. The gauge theory actions are interpreted from the Atiyah-Jeffrey point of view and related to super-symmetric quantum mechanics on spaces of connections. As a consequence of these considerations the Euler number χ (M) of the moduli space of flat connections as a generalization to arbitrary three-manifolds of the Casson invariant. The possibility of constructing a topological version of the Penner matrix model is also commented. (author). 63 refs
The moduli space of instantons on an ALE space from 3d $\\mathcal{N}=4$ field theories
Mekareeya, Noppadol
2015-01-01
The moduli space of instantons on an ALE space is studied using the moduli space of $\\mathcal{N}=4$ field theories in three dimensions. For instantons in a simple gauge group $G$ on $\\mathbb{C}^2/\\mathbb{Z}_n$, the Hilbert series of such an instanton moduli space is computed from the Coulomb branch of the quiver given by the affine Dynkin diagram of $G$ with flavour nodes of unitary groups attached to various nodes of the Dynkin diagram. We provide a simple prescription to determine the ranks and the positions of these flavour nodes from the order of the orbifold $n$ and from the residual subgroup of $G$ that is left unbroken by the monodromy of the gauge field at infinity. For $G$ a simply laced group of type $A$, $D$ or $E$, the Higgs branch of such a quiver describes the moduli space of instantons in projective unitary group $PU(n) \\cong U(n)/U(1)$ on orbifold $\\mathbb{C}^2/\\hat{G}$, where $\\hat{G}$ is the discrete group that is in McKay correspondence to $G$. Moreover, we present the quiver whose Coulomb ...
Strong moduli stabilization and phenomenology
Dudas, Emilian; Mambrini, Yann; Mustafayev, Azar; Olive, Keith A
2013-01-01
We describe the resulting phenomenology of string theory/supergravity models with strong moduli stabilization. The KL model with F-term uplifting, is one such example. Models of this type predict universal scalar masses equal to the gravitino mass. In contrast, A-terms receive highly suppressed gravity mediated contributions. Under certain conditions, the same conclusion is valid for gaugino masses, which like A-terms, are then determined by anomalies. In such models, we are forced to relatively large gravitino masses (30-1000 TeV). We compute the low energy spectrum as a function of m_{3/2}. We see that the Higgs masses naturally takes values between 125-130 GeV. The lower limit is obtained from the requirement of chargino masses greater than 104 GeV, while the upper limit is determined by the relic density of dark matter (wino-like).
Moduli/inflaton mixing with supersymmetry breaking field
Energy Technology Data Exchange (ETDEWEB)
Endo, M.; Takahashi, F. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)]|[Tokyo Univ. (Japan). Inst. for Cosmic Ray Research; Hamaguchi, K. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)]|[Tokyo Univ. (Japan). Dept. of Physics
2006-05-15
A heavy scalar field such as moduli or an inflaton generally mixes with a field responsible for the supersymmetry breaking. We study the scalar decay into the standard model particles and their superpartners, gravitinos, and the supersymmetry breaking sector, particularly paying attention to decay modes that proceed via the mixing between the scalar and the supersymmetry breaking field. The impacts of the new decay processes on cosmological scenarios are also discussed; the modulus field generically produces too much gravitinos, and most of the inflation models tend to result in too high reheating temperature and/or gravitino overproduction. (Orig.)
Biophysical constraints on leaf expansion in a tall conifer.
Fredrick C. Meinzer; Barbara J. Bond; Jennifer A. Karanian
2008-01-01
The physiological mechanisms responsible for reduced extension growth as trees increase in height remain elusive. We evaluated biophysical constraints on leaf expansion in old-growth Douglas-fir (Psuedotsuga menziesii (Mirb.) Franco) trees. Needle elongation rates, plastic and elastic extensibility, bulk leaf water, (L...
International Nuclear Information System (INIS)
Schneider, Jochen M.; Music, Denis; Sun Zhimei
2005-01-01
We have studied the effect of the valence electron concentration, on the bulk modulus and the chemical bonding in Ta 2 AC and Zr 2 AC (A=Al, Si, and P) by means of ab initio calculations. Our equilibrium volume and the hexagonal ratio (c/a) agree well (within 2.7% and 1.2%, respectively) with previously published experimental data for Ta 2 AlC. The bulk moduli of both Ta 2 AC and Zr 2 AC increase as Al is substituted with Si and P by 13.1% and 20.1%, respectively. This can be understood since the substitution is associated with an increased valence electron concentration, resulting in band filling and an extensive increase in cohesion
Porous composite with negative thermal expansion obtained by photopolymer additive manufacturing
Directory of Open Access Journals (Sweden)
Akihiro Takezawa
2015-07-01
Full Text Available Additive manufacturing (AM could be a novel method of fabricating composite and porous materials having various effective performances based on mechanisms of their internal geometries. Materials fabricated by AM could rapidly be used in industrial application since they could easily be embedded in the target part employing the same AM process used for the bulk material. Furthermore, multi-material AM has greater potential than usual single-material AM in producing materials with effective properties. Negative thermal expansion is a representative effective material property realized by designing a composite made of two materials with different coefficients of thermal expansion. In this study, we developed a porous composite having planar negative thermal expansion by employing multi-material photopolymer AM. After measurement of the physical properties of bulk photopolymers, the internal geometry was designed by topology optimization, which is the most effective structural optimization in terms of both minimizing thermal stress and maximizing stiffness. The designed structure was converted to a three-dimensional stereolithography (STL model, which is a native digital format of AM, and assembled as a test piece. The thermal expansions of the specimens were measured using a laser scanning dilatometer. Negative thermal expansion corresponding to less than −1 × 10−4 K−1 was observed for each test piece of the N = 3 experiment.
GUT scale extra dimensions and light moduli in supergravity and cosmology
Energy Technology Data Exchange (ETDEWEB)
Moeller, Jan
2010-05-15
We study the dynamical properties of geometric moduli in five- and six-dimensional supergravity compactified on flat orbifolds, focusing on the impact of the Kaehler potential. In both cases, the Kaehler potential exhibits no-scale structure at tree level. In five dimensions, the volume modulus (radion) can be stabilized by means of perturbative Kaehler corrections. In six dimensions, the same holds for size and shape of the extra dimensions, only if the dilaton can be stabilized in a Minkowski vacuum by nonperturbative effects. We develop a systematic description of almost no-scale models and derive a model independent formula for the radion mass. The radion mass is suppressed compared to the gravitino mass. The supression factor reflects the hierarchy between the Planck and the compactification scale. We analyze a specific example, where the compactification scale is determined by Fayet-Iliopoulos terms of a locally anomalous Abelian gauge group, which are O(M{sub GUT}). In a scenario with gravitino dark matter, this leads to a radion mass of 1-10 MeV. In this mass range, the radion is cosmologically stable and contributes to the dark matter density. Based on galactic gamma ray data, we derive a tight bound on the initial displacement of the field value from its low energy vacuum. We also investigate implications of typical moduli Kaehler potentials on the cosmological evolution of the scalar fields. In particular, we discuss a class of models with steep exponential potentials and non-canonical kinetic terms, motivated by our radion example. We consider the overshooting problem of cosmological moduli dynamics, and the possibility of slow-roll solutions despite the steepness of the scalar potential. (orig.)
GUT scale extra dimensions and light moduli in supergravity and cosmology
International Nuclear Information System (INIS)
Moeller, Jan
2010-05-01
We study the dynamical properties of geometric moduli in five- and six-dimensional supergravity compactified on flat orbifolds, focusing on the impact of the Kaehler potential. In both cases, the Kaehler potential exhibits no-scale structure at tree level. In five dimensions, the volume modulus (radion) can be stabilized by means of perturbative Kaehler corrections. In six dimensions, the same holds for size and shape of the extra dimensions, only if the dilaton can be stabilized in a Minkowski vacuum by nonperturbative effects. We develop a systematic description of almost no-scale models and derive a model independent formula for the radion mass. The radion mass is suppressed compared to the gravitino mass. The supression factor reflects the hierarchy between the Planck and the compactification scale. We analyze a specific example, where the compactification scale is determined by Fayet-Iliopoulos terms of a locally anomalous Abelian gauge group, which are O(M GUT ). In a scenario with gravitino dark matter, this leads to a radion mass of 1-10 MeV. In this mass range, the radion is cosmologically stable and contributes to the dark matter density. Based on galactic gamma ray data, we derive a tight bound on the initial displacement of the field value from its low energy vacuum. We also investigate implications of typical moduli Kaehler potentials on the cosmological evolution of the scalar fields. In particular, we discuss a class of models with steep exponential potentials and non-canonical kinetic terms, motivated by our radion example. We consider the overshooting problem of cosmological moduli dynamics, and the possibility of slow-roll solutions despite the steepness of the scalar potential. (orig.)
Charge-density-shear-moduli relationships in aluminum-lithium alloys.
Eberhart, M
2001-11-12
Using the first principles full-potential linear-augmented-Slater-type orbital technique, the energies and charge densities of aluminum and aluminum-lithium supercells have been computed. The experimentally observed increase in aluminum's shear moduli upon alloying with lithium is argued to be the result of predictable changes to aluminum's total charge density, suggesting that simple rules may allow the alloy designer to predict the effects of dilute substitutional elements on alloy elastic response.
Von Neuman representations on self-dual Hilbert W* moduli
International Nuclear Information System (INIS)
Frank, M.
1987-01-01
Von Neumann algebras M of bounded operators on self-dual Hilbert W* moduli H possessing a cyclic-separating element x-bar in H are considered. The close relation of them to certain real subspaces of H is established. Under the supposition that the underlying W*-algebra is commutative, a Tomita-Takesaki type theorem is stated. The natural cone in H arising from the pair (M, x-bar) is investigated and its properties are obtained
Moduli spaces for linear differential equations and the Painlev'e equations
Put, Marius van der; Saito, Masa-Hiko
2009-01-01
In this paper, we give a systematic construction of ten isomonodromic families of connections of rank two on P1 inducing Painlev´e equations. The classification of ten families is given by considering the Riemann-Hilbert morphism from a moduli space of connections with certain type of regular and
Colossal negative thermal expansion in reduced layered ruthenate.
Takenaka, Koshi; Okamoto, Yoshihiko; Shinoda, Tsubasa; Katayama, Naoyuki; Sakai, Yuki
2017-01-10
Large negative thermal expansion (NTE) has been discovered during the last decade in materials of various kinds, particularly materials associated with a magnetic, ferroelectric or charge-transfer phase transition. Such NTE materials have attracted considerable attention for use as thermal-expansion compensators. Here, we report the discovery of giant NTE for reduced layered ruthenate. The total volume change related to NTE reaches 6.7% in dilatometry, a value twice as large as the largest volume change reported to date. We observed a giant negative coefficient of linear thermal expansion α=-115 × 10 -6 K -1 over 200 K interval below 345 K. This dilatometric NTE is too large to be attributable to the crystallographic unit-cell volume variation with temperature. The highly anisotropic thermal expansion of the crystal grains might underlie giant bulk NTE via microstructural effects consuming open spaces in the sintered body on heating.
Yukawa unification in moduli-dominant SUSY breaking
International Nuclear Information System (INIS)
Khalil, S.; Tatsuo Kobayashi
1997-07-01
We study Yukawa in string models with moduli-dominant SUSY breaking. This type of SUSY breaking in general leads to non-universal soft masses, i.e. soft scalar masses and gaugino masses. Such non-universality is important for phenomenological aspects of Yukawa unification, i.e., successful electroweak breaking, SUSY corrections to the bottom mass and the branching ratio of b → sγ. We show three regions in the whole parameter space which lead to successful electroweak breaking and allow small SUSY corrections to the bottom mass. For these three regions we investigated the b → sγ decay and mass spectra. (author). 26 refs, 6 figs
Properties of Bulk Sintered Silver As a Function of Porosity
Energy Technology Data Exchange (ETDEWEB)
Wereszczak, Andrew A [ORNL; Vuono, Daniel J [ORNL; Wang, Hsin [ORNL; Ferber, Mattison K [ORNL; Liang, Zhenxian [ORNL
2012-06-01
This report summarizes a study where various properties of bulk-sintered silver were investigated over a range of porosity. This work was conducted within the National Transportation Research Center's Power Device Packaging project that is part of the DOE Vehicle Technologies Advanced Power Electronics and Electric Motors Program. Sintered silver, as an interconnect material in power electronics, inherently has porosity in its produced structure because of the way it is made. Therefore, interest existed in this study to examine if that porosity affected electrical properties, thermal properties, and mechanical properties because any dependencies could affect the intended function (e.g., thermal transfer, mechanical stress relief, etc.) or reliability of that interconnect layer and alter how its performance is modeled. Disks of bulk-sintered silver were fabricated using different starting silver pastes and different sintering conditions to promote different amounts of porosity. Test coupons were harvested out of the disks to measure electrical resistivity and electrical conductivity, thermal conductivity, coefficient of thermal expansion, elastic modulus, Poisson's ratio, and yield stress. The authors fully recognize that the microstructure of processed bulk silver coupons may indeed not be identical to the microstructure produced in thin (20-50 microns) layers of sintered silver. However, measuring these same properties with such a thin actual structure is very difficult, requires very specialized specimen preparation and unique testing instrumentation, is expensive, and has experimental shortfalls of its own, so the authors concluded that the herein measured responses using processed bulk sintered silver coupons would be sufficient to determine acceptable values of those properties. Almost all the investigated properties of bulk sintered silver changed with porosity content within a range of 3-38% porosity. Electrical resistivity, electrical conductivity
A family of metrics on the moduli space of CP2 instantons
International Nuclear Information System (INIS)
Habermann, L.
1992-01-01
A family of Riemannian metrics on the moduli space of irreducible self-dual connections of instanton number k=1 over CP 2 is considered. We find explicit formulas for these metrics and deduce conclusions concerning the geometry of the instant space. (orig.)
Compressibility and thermal expansion of cubic silicon nitride
DEFF Research Database (Denmark)
Jiang, Jianzhong; Lindelov, H.; Gerward, Leif
2002-01-01
The compressibility and thermal expansion of the cubic silicon nitride (c-Si3N4) phase have been investigated by performing in situ x-ray powder-diffraction measurements using synchrotron radiation, complemented with computer simulations by means of first-principles calculations. The bulk...... compressibility of the c-Si3N4 phase originates from the average of both Si-N tetrahedral and octahedral compressibilities where the octahedral polyhedra are less compressible than the tetrahedral ones. The origin of the unit cell expansion is revealed to be due to the increase of the octahedral Si-N and N-N bond...
Quantitative determination of optical trapping strength and viscoelastic moduli inside living cells
International Nuclear Information System (INIS)
Mas, Josep; Berg-Sørensen, Kirstine; Richardson, Andrew C; Reihani, S Nader S; Oddershede, Lene B
2013-01-01
With the success of in vitro single-molecule force measurements obtained in recent years, the next step is to perform quantitative force measurements inside a living cell. Optical traps have proven excellent tools for manipulation, also in vivo, where they can be essentially non-invasive under correct wavelength and exposure conditions. It is a pre-requisite for in vivo quantitative force measurements that a precise and reliable force calibration of the tweezers is performed. There are well-established calibration protocols in purely viscous environments; however, as the cellular cytoplasm is viscoelastic, it would be incorrect to use a calibration procedure relying on a viscous environment. Here we demonstrate a method to perform a correct force calibration inside a living cell. This method (theoretically proposed in Fischer and Berg-Sørensen (2007 J. Opt. A: Pure Appl. Opt. 9 S239)) takes into account the viscoelastic properties of the cytoplasm and relies on a combination of active and passive recordings of the motion of the cytoplasmic object of interest. The calibration procedure allows us to extract absolute values for the viscoelastic moduli of the living cell cytoplasm as well as the force constant describing the optical trap, thus paving the way for quantitative force measurements inside the living cell. Here, we determine both the spring constant of the optical trap and the elastic contribution from the cytoplasm, influencing the motion of naturally occurring tracer particles. The viscoelastic moduli that we find are of the same order of magnitude as moduli found in other cell types by alternative methods. (paper)
On Rationality of Moduli Spaces of Vector Bundles on Real ...
Indian Academy of Sciences (India)
Let be a real form of a Hirzebruch surface. Let M H ( r , c 1 , c 2 ) be the moduli space of vector bundles on . Under some numerical conditions on r , c 1 and c 2 , we identify those M H ( r , c 1 , c 2 ) that are rational. Author Affiliations. Indranil Biswas1 Ronnie Sebastian2. School of Mathematics, Tata Institute of ...
Shape, size and temperature dependency of thermal expansion ...
Indian Academy of Sciences (India)
M GOYAL
2018-05-19
May 19, 2018 ... Oriental J. Chem.32(4), 2193 (2016), is extended in the present study using Qi and Wang model [Mater. Chem. Phys. ... Nanomaterials; shape factor; size effect; thermal expansion; equation of state. ... als are different from that of their bulk material. ..... and 1c along with the present calculated results. It is.
Moduli of Riemann surfaces, transcendental aspects
International Nuclear Information System (INIS)
Hain, R.
2000-01-01
These notes are an informal introduction to moduli spaces of compact Riemann surfaces via complex analysis, topology and Hodge Theory. The prerequisites for the first lecture are just basic complex variables, basic Riemann surface theory up to at least the Riemann-Roch formula, and some algebraic topology, especially covering space theory. The first lecture covers moduli in genus 0 and genus 1 as these can be understood using relatively elementary methods, but illustrate many of the points which arise in higher genus. The notes cover more material than was covered in the lectures, and sometimes the order of topics in the notes differs from that in the lectures. We have seen in genus 1 case that M 1 is the quotient Γ 1 /X 1 of a contractible complex manifold X 1 = H by a discrete group Γ 1 = SL 2 (Z). The action of Γ 1 on X 1 is said to be virtually free - that is, Γ 1 has a finite index subgroup which acts (fixed point) freely on X 1 . In this section we will generalize this to all g >= 1 - we will sketch a proof that there is a contractible complex manifold Xg, called Teichmueller space, and a group Γ g , called the mapping class group, which acts virtually freely on X g . The moduli space of genus g compact Riemann surfaces is the quotient: M g = Γ g /X g . This will imply that M g has the structure of a complex analytic variety with finite quotient singularities. Teichmueller theory is a difficult and technical subject. Because of this, it is only possible to give an overview. In this lecture, we compute the orbifold Picard group of M g for all g >= 1. Recall that an orbifold line bundle over M g is a holomorphic line bundle L over Teichmueller space X g together with an action of the mapping class group Γ g on it such that the projection L → X g is Γ g -equivariant. An orbifold section of this line bundle is a holomorphic Γ g -equivariant section X g → L of L. This is easily seen to be equivalent to fixing a level l>= 3 and considering holomorphic
Determination of static moduli in fractured rocks by T-matrix model
Czech Academy of Sciences Publication Activity Database
Chalupa, F.; Vilhelm, J.; Petružálek, Matěj; Bukovská, Z.
2017-01-01
Roč. 22, č. 1 (2017), s. 22-31 ISSN 1335-1788 Institutional support: RVO:67985831 Keywords : fractured rocks * dynamic and static moduli * T-matrix model * elastic wave velocity * well logging Subject RIV: DB - Geology ; Mineralogy OBOR OECD: Geology Impact factor: 0.769, year: 2016 http://actamont.tuke.sk/pdf/2017/n1/3chalupa.pdf
Oh, Jae Eun
2011-11-01
Crystalline zeolitic materials, such as hydroxycancrinite, hydroxysodalite, herschelite and nepheline, are often synthesized from geopolymerization using fly-ash and solutions of NaOH at high temperatures. Comprised mainly of 6-membered aluminosilicate rings that act as basic building units, their crystal structures may provide insight into the reaction products formed in NaOH-activated fly ash-based geopolymers. Recent research indicates that the hydroxycancrinite and hydroxysodalite may play an important role as possible analogues of zeolitic precursor in geopolymers. Herein is reported a high pressure synchrotron study of the behavior of hydroxycancrinite exposed to pressures up to 6.1 GPa in order to obtain its bulk modulus. A refined equation of state for hydroxycancrinite yielded a bulk modulus of Ko = 46 ± 5 GPa (assuming Ko′ = 4.0) for a broad range of applied pressure. When low pressure values are excluded from the fit and only the range of 2.5 and 6.1 GPa is considered, the bulk modulus of hydroxycancrinite was found to be Ko = 46.9 ± 0.9 GPa (Ko′ = 4.0 ± 0.4, calculated). Comparison with the literature shows that all zeolitic materials possessing single 6-membered rings (i.e., hydroxycancrinite, sodalite and nepheline) have similar bulk moduli. © 2011 Elsevier Ltd. All rights reserved.
International Nuclear Information System (INIS)
Lu Xiaogang; Selleby, Malin; Sundman, Bo
2007-01-01
The thermal expansivities and heat capacities of MX (M = Ti, Zr, Hf, V, Nb, Ta; X = C, N) carbides and nitrides with NaCl structure were calculated using the Debye-Grueneisen model combined with ab initio calculations. Two different approximations for the Grueneisen parameter γ were used in the Debye-Grueneisen model, i.e. the expressions proposed by Slater and by Dugdale and MacDonald. The thermal electronic contribution was evaluated from ab initio calculations of the electronic density of states. The calculated results were compared with CALPHAD assessments and experimental data. It was found that the calculations using the Dugdale-MacDonald γ can account for most of the experimental data. By fitting experimental heat capacity and thermal expansivity data below the Debye temperatures, an estimation of Poisson's ratio was obtained and Young's and shear moduli were evaluated. In order to reach a reasonable agreement with experimental data, it was necessary to use the logarithmic averaged mass of the constituent atoms. The agreements between the calculated and the experimental values for the bulk and Young's moduli are generally better than the agreement for shear modulus
Bigravity from gradient expansion
International Nuclear Information System (INIS)
Yamashita, Yasuho; Tanaka, Takahiro
2016-01-01
We discuss how the ghost-free bigravity coupled with a single scalar field can be derived from a braneworld setup. We consider DGP two-brane model without radion stabilization. The bulk configuration is solved for given boundary metrics, and it is substituted back into the action to obtain the effective four-dimensional action. In order to obtain the ghost-free bigravity, we consider the gradient expansion in which the brane separation is supposed to be sufficiently small so that two boundary metrics are almost identical. The obtained effective theory is shown to be ghost free as expected, however, the interaction between two gravitons takes the Fierz-Pauli form at the leading order of the gradient expansion, even though we do not use the approximation of linear perturbation. We also find that the radion remains as a scalar field in the four-dimensional effective theory, but its coupling to the metrics is non-trivial.
Helgerud, M.B.; Waite, W.F.; Kirby, S.H.; Nur, A.
2009-01-01
We used ultrasonic pulse transmission to measure compressional, P, and shear, S, wave speeds in laboratory-formed polycrystalline ice Ih, si methane hydrate, and sll methane-ethane hydrate. From the wave speed's linear dependence on temperature and pressure and from the sample's calculated density, we derived expressions for bulk, shear, and compressional wave moduli and Poisson's ratio from -20 to 15??C and 22.4 to 32.8 MPa for ice Ih, -20 to 15??C and 30.5 to 97.7 MPa for si methane hydrate, and -20 to 10??C and 30.5 to 91.6 MPa for sll methane-ethane hydrate. All three materials had comparable P and S wave speeds and decreasing shear wave speeds with increasing applied pressure. Each material also showed evidence of rapid intergranular bonding, with a corresponding increase in wave speed, in response to pauses in sample deformation. There were also key differences. Resistance to uniaxial compaction, indicated by the pressure required to compact initially porous samples, was significantly lower for ice Ih than for either hydrate. The ice Ih shear modulus decreased with increasing pressure, in contrast to the increase measured in both hydrates ?? 2009.
Moduli of mathematical instanton vector bundles with odd c2 on projective space
International Nuclear Information System (INIS)
Tikhomirov, Aleksandr S
2012-01-01
We study the moduli space I n of mathematical instanton vector bundles of rank 2 with second Chern class n≥1 on the projective space P 3 , and prove the irreducibility of I n for arbitrary odd n≥1.
Hurwitz numbers, moduli of curves, topological recursion, Givental's theory and their relations
Spitz, L.
2014-01-01
The study of curves is an important area of research in algebraic geometry and mathematical physics. In my thesis I study so-called moduli spaces of curves; these are spaces that parametrize all curves with some specified properties. In particular, I study maps from curves to other spaces, recursive
Elastic moduli of biological fibers in a coarse-grained model: crystalline cellulose and β-amyloids.
Poma, Adolfo B; Chwastyk, Mateusz; Cieplak, Marek
2017-10-25
We study the mechanical response of cellulose and β-amyloid microfibrils to three types of deformation: tensile, indentational, and shear. The cellulose microfibrils correspond to the allomorphs Iα or Iβ whereas the β-amyloid microfibrils correspond to the polymorphs of either two- or three-fold symmetry. This response can be characterized by three elastic moduli, namely, Y L , Y T , and S. We use a structure-based coarse-grained model to analyze the deformations in a unified manner. We find that each of the moduli is almost the same for the two allomorphs of cellulose but Y L is about 20 times larger than Y T (140 GPa vs. 7 GPa), indicating the existence of significant anisotropy. For cellulose we note that the anisotropy results from the involvement of covalent bonds in stretching. For β-amyloid, the sense of anisotropy is opposite to that of cellulose. In the three-fold symmetry case, Y L is about half of Y T (3 vs. 7) whereas for two-fold symmetry the anisotropy is much larger (1.6 vs. 21 GPa). The S modulus is derived to be 1.2 GPa for three-fold symmetry and one half of it for the other symmetry and 3.0 GPa for cellulose. The values of the moduli reflect deformations in the hydrogen-bond network. Unlike in our theoretical approach, no experiment can measure all three elastic moduli with the same apparatus. However, our theoretical results are consistent with various measured values: typical Y L for cellulose Iβ ranges from 133 to 155 GPa, Y T from 2 to 25 GPa, and S from 1.8 to 3.8 GPa. For β-amyloid, the experimental values of S and Y T are about 0.3 GPa and 3.3 GPa respectively, while the value of Y L has not been reported.
International Nuclear Information System (INIS)
Ullemeyer, K; Keppler, R; Lokajíček, T; Vasin, R N; Behrmann, J H
2015-01-01
The elastic anisotropy of bulk rock depends on the mineral textures, the crack fabric and external parameters like, e.g., confining pressure. The texture-related contribution to elastic anisotropy can be predicted from the mineral textures, the largely sample-dependent contribution of the other parameters must be determined experimentally. Laboratory measurements of the elastic wave velocities are mostly limited to pressures of the intermediate crust. We describe a method, how the elastic wave velocity trends and, by this means, the elastic constants can be extrapolated to the pressure conditions of the lower crust. The extrapolated elastic constants are compared to the texture-derived ones. Pronounced elastic anisotropy is evident for phyllosilicate minerals, hence, the approach is demonstrated for two phyllosilicate-rich gneisses with approximately identical volume fractions of the phyllosilicates but different texture types. (paper)
Using Ultrasonic Lamb Waves To Measure Moduli Of Composites
Kautz, Harold E.
1995-01-01
Measurements of broad-band ultrasonic Lamb waves in plate specimens of ceramic-matrix/fiber and metal-matrix/fiber composite materials used to determine moduli of elasticity of materials. In one class of potential applications of concept, Lamb-wave responses of specimens measured and analyzed at various stages of thermal and/or mechanical processing to determine effects of processing, without having to dissect specimens. In another class, structural components having shapes supporting propagation of Lamb waves monitored ultrasonically to identify signs of deterioration and impending failure.
Temperature dependence of bulk modulus and second-order elastic constants
International Nuclear Information System (INIS)
Singh, P.P.; Kumar, Munish
2004-01-01
A simple theoretical model is developed to investigate the temperature dependence of the bulk modulus and second order elastic constants. The method is based on the two different approaches viz. (i) the theory of thermal expansivity formulated by Suzuki, based on the Mie-Gruneisen equation of state, (ii) the theory of high-pressure-high-temperature equation of state formulated by Kumar, based on thermodynamic analysis. The results obtained for a number of crystals viz. NaCl, KCl, MgO and (Mg, Fe) 2 SiO 4 are discussed and compared with the experimental data. It is concluded that the Kumar formulation is far better that the Suzuki theory of thermal expansivity
Misra, Aalok
2008-01-01
We consider issues of moduli stabilization and "area codes" for type II flux compactifications, and the "Inverse Problem" and "Fake Superpotentials" for extremal (non)supersymmetric black holes in type II compactifications on (orientifold of) a compact two-parameter Calabi-Yau expressed as a degree-18 hypersurface in WCP^4[1,1,1,6,9] which has multiple singular loci in its moduli space. We argue the existence of extended "area codes" [1] wherein for the same set of large NS-NS and RR fluxes, one can stabilize all the complex structure moduli and the axion-dilaton modulus (to different sets of values) for points in the moduli space away as well as near the different singular conifold loci leading to the existence of domain walls. By including non-perturbative alpha' and instanton corrections in the Kaehler potential and superpotential [2], we show the possibility of getting a large-volume non-supersymmetric (A)dS minimum. Further, using techniques of [3] we explicitly show that given a set of moduli and choice...
Quantum triangulations moduli space, quantum computing, non-linear sigma models and Ricci flow
Carfora, Mauro
2017-01-01
This book discusses key conceptual aspects and explores the connection between triangulated manifolds and quantum physics, using a set of case studies ranging from moduli space theory to quantum computing to provide an accessible introduction to this topic. Research on polyhedral manifolds often reveals unexpected connections between very distinct aspects of mathematics and physics. In particular, triangulated manifolds play an important role in settings such as Riemann moduli space theory, strings and quantum gravity, topological quantum field theory, condensed matter physics, critical phenomena and complex systems. Not only do they provide a natural discrete analogue to the smooth manifolds on which physical theories are typically formulated, but their appearance is also often a consequence of an underlying structure that naturally calls into play non-trivial aspects of representation theory, complex analysis and topology in a way that makes the basic geometric structures of the physical interactions involv...
Elastic Moduli of Nanoparticle-Polymer Composite Thin Films via Buckling on Elastomeric Substrates
Yuan, Hongyi; Karim, Alamgir; University of Akron Team
2011-03-01
Polymeric thin films find applications in diverse areas such as coatings, barriers and packaging. The dispersion of nanoparticles into the films was proven to be an effective method to generate tunable properties, particularly mechanical strength. However, there are very few methods for mechanical characterization of the composite thin films with high accuracy. In this study, nanometric polystyrene and polyvinyl alcohol films with uniformly dispersed cobalt and Cloisite nanoparticles at varying concentrations were synthesized via flow-coating and then transferred to crosslinked polydimethylsiloxane (PDMS) flexible substrates. The technique of Strain-Induced Elastic Buckling Instability for Mechanical Measurements (SIEBIMM) was employed to determine the elastic moduli of the films, which were calculated from the buckling patterns generated by applying compressive stresses. Results on moduli of films as a function of the concentrations of nanoparticles and the thicknesses of the composite films will be presented. *Corresponding author: alamgir@uakron.edu
International Nuclear Information System (INIS)
Omar, M.S.
2012-01-01
Graphical abstract: Three models are derived to explain the nanoparticles size dependence of mean bonding length, melting temperature and lattice thermal expansion applied on Sn, Si and Au. The following figures are shown as an example for Sn nanoparticles indicates hilly applicable models for nanoparticles radius larger than 3 nm. Highlights: ► A model for a size dependent mean bonding length is derived. ► The size dependent melting point of nanoparticles is modified. ► The bulk model for lattice thermal expansion is successfully used on nanoparticles. -- Abstract: A model, based on the ratio number of surface atoms to that of its internal, is derived to calculate the size dependence of lattice volume of nanoscaled materials. The model is applied to Si, Sn and Au nanoparticles. For Si, that the lattice volume is increases from 20 Å 3 for bulk to 57 Å 3 for a 2 nm size nanocrystals. A model, for calculating melting point of nanoscaled materials, is modified by considering the effect of lattice volume. A good approach of calculating size-dependent melting point begins from the bulk state down to about 2 nm diameter nanoparticle. Both values of lattice volume and melting point obtained for nanosized materials are used to calculate lattice thermal expansion by using a formula applicable for tetrahedral semiconductors. Results for Si, change from 3.7 × 10 −6 K −1 for a bulk crystal down to a minimum value of 0.1 × 10 −6 K −1 for a 6 nm diameter nanoparticle.
Energy Technology Data Exchange (ETDEWEB)
Omar, M.S., E-mail: dr_m_s_omar@yahoo.com [Department of Physics, College of Science, University of Salahaddin-Erbil, Arbil, Kurdistan (Iraq)
2012-11-15
Graphical abstract: Three models are derived to explain the nanoparticles size dependence of mean bonding length, melting temperature and lattice thermal expansion applied on Sn, Si and Au. The following figures are shown as an example for Sn nanoparticles indicates hilly applicable models for nanoparticles radius larger than 3 nm. Highlights: ► A model for a size dependent mean bonding length is derived. ► The size dependent melting point of nanoparticles is modified. ► The bulk model for lattice thermal expansion is successfully used on nanoparticles. -- Abstract: A model, based on the ratio number of surface atoms to that of its internal, is derived to calculate the size dependence of lattice volume of nanoscaled materials. The model is applied to Si, Sn and Au nanoparticles. For Si, that the lattice volume is increases from 20 Å{sup 3} for bulk to 57 Å{sup 3} for a 2 nm size nanocrystals. A model, for calculating melting point of nanoscaled materials, is modified by considering the effect of lattice volume. A good approach of calculating size-dependent melting point begins from the bulk state down to about 2 nm diameter nanoparticle. Both values of lattice volume and melting point obtained for nanosized materials are used to calculate lattice thermal expansion by using a formula applicable for tetrahedral semiconductors. Results for Si, change from 3.7 × 10{sup −6} K{sup −1} for a bulk crystal down to a minimum value of 0.1 × 10{sup −6} K{sup −1} for a 6 nm diameter nanoparticle.
High-pressure high-temperature stability of hcp-Ir_{x}Os_{1-x} (x = 0.50 and 0.55) alloys
Energy Technology Data Exchange (ETDEWEB)
Yusenko, Kirill V.; Bykova, Elena; Bykov, Maxim; Gromilov, Sergey A.; Kurnosov, Alexander V.; Prescher, Clemens; Prakapenka, Vitali B.; Crichton, Wilson A.; Hanfland, Michael; Margadonna, Serena; Dubrovinsky, Leonid S.
2016-12-23
Hcp-Ir_{0.55}Os_{0.45} and hcp-Ir_{0.50}Os_{0.50} alloys were synthesised by thermal decomposition of single-source precursors in hydrogen atmosphere. Both alloys correspond to a miscibility gap in the Ir–Os binary phase diagram and therefore are metastable at ambient conditions. An in situ powder X-ray diffraction has been used for a monitoring a formation of hcp-Ir0.55Os0.45 alloy from (NH_{4})_{2}[Ir_{0.55}Os_{0.45}Cl_{6}] precursor. A crystalline intermediate compound and nanodimentional metallic particles with a large concentration of defects has been found as key intermediates in the thermal decomposition process in hydrogen flow. High-temperature stability of titled hcp-structured alloys has been investigated upon compression up to 11 GPa using a multi-anvil press and up to 80 GPa using laser-heated diamond-anvil cells to obtain a phase separation into fcc + hcp mixture. Compressibility curves at room temperature as well as thermal expansion at ambient pressure and under compression up to 80 GPa were collected to obtain thermal expansion coefficients and bulk moduli. hcp-Ir_{0.55}Os_{0.45} alloy shows bulk moduli B0 = 395 GPa. Thermal expansion coefficients were estimated as α = 1.6·10^{-5} K^{-1} at ambient pressure and α = 0.3·10^{-5} K^{-1} at 80 GPa. Obtained high-pressure high-temperature data allowed us to construct the first model for pressure-dependent Ir–Os phase diagram.
Glass transition and thermal expansivity of polystyrene thin films
International Nuclear Information System (INIS)
Inoue, R.; Kanaya, T.; Miyazaki, T.; Nishida, K.; Tsukushi, I.; Shibata, K.
2006-01-01
We have studied glass transition temperature and thermal expansivity of polystyrene thin films supported on silicon substrate using X-ray reflectivity and inelastic neutron scattering techniques. In annealing experiments, we have found that the reported apparent negative expansivity of polymer thin films is caused by unrelaxed structure due to insufficient annealing. Using well-annealed films, we have evaluated glass transition temperature T g and thermal expansivity as a function of film thickness. The glass transition temperature decreases with film thickness and is constant below about 10 nm, suggesting the surface glass transition temperature of 355 K, which is lower than that in bulk. We have also found that the thermal expansivity in the glassy state decreases with film thickness even after annealing. The decrease has been attributed to hardening of harmonic force constant arising from chain confinement in a thin film. This idea has been confirmed in the inelastic neutron scattering measurements
Glass transition and thermal expansivity of polystyrene thin films
Energy Technology Data Exchange (ETDEWEB)
Inoue, R. [Institute for Chemical Research, Kyoto University, Uji, Kyoto-fu 611-0011 (Japan); Kanaya, T. [Institute for Chemical Research, Kyoto University, Uji, Kyoto-fu 611-0011 (Japan)]. E-mail: kanaya@scl.kyoto-u.ac.jp; Miyazaki, T. [Nitto Denko Corporation, 1-1-2 Shimohozumi, Ibaraki, Osaka-fu 567-8680 (Japan); Nishida, K. [Institute for Chemical Research, Kyoto University, Uji, Kyoto-fu 611-0011 (Japan); Tsukushi, I. [Chiba Institute of Technology, Narashino, Chiba-ken 275-0023 (Japan); Shibata, K. [Japan Atomic Energy Research Institute, Tokai, Ibaraki-ken 319-1195 (Japan)
2006-12-20
We have studied glass transition temperature and thermal expansivity of polystyrene thin films supported on silicon substrate using X-ray reflectivity and inelastic neutron scattering techniques. In annealing experiments, we have found that the reported apparent negative expansivity of polymer thin films is caused by unrelaxed structure due to insufficient annealing. Using well-annealed films, we have evaluated glass transition temperature T {sub g} and thermal expansivity as a function of film thickness. The glass transition temperature decreases with film thickness and is constant below about 10 nm, suggesting the surface glass transition temperature of 355 K, which is lower than that in bulk. We have also found that the thermal expansivity in the glassy state decreases with film thickness even after annealing. The decrease has been attributed to hardening of harmonic force constant arising from chain confinement in a thin film. This idea has been confirmed in the inelastic neutron scattering measurements.
Global D-brane models with stabilised moduli and light axions
Cicoli, Michele
2014-03-01
We review recent attempts to try to combine global issues of string compactifications, like moduli stabilisation, with local issues, like semi-realistic D-brane constructions. We list the main problems encountered, and outline a possible solution which allows globally consistent embeddings of chiral models. We also argue that this stabilisation mechanism leads to an axiverse. We finally illustrate our general claims in a concrete example where the Calabi-Yau manifold is explicitly described by toric geometry.
Bulk renormalization and particle spectrum in codimension-two brane worlds
International Nuclear Information System (INIS)
Salvio, Alberto
2013-01-01
We study the Casimir energy due to bulk loops of matter fields in codimension-two brane worlds and discuss how effective field theory methods allow us to use this result to renormalize the bulk and brane operators. In the calculation we explicitly sum over the Kaluza-Klein (KK) states with a new convenient method, which is based on a combined use of zeta function and dimensional regularization. Among the general class of models we consider we include a supersymmetric example, 6D gauged chiral supergravity. Although much of our discussion is more general, we treat in some detail a class of compactifications, where the extra dimensions parametrize a rugby ball shaped space with size stabilized by a bulk magnetic flux. The rugby ball geometry requires two branes, which can host the Standard Model fields and carry both tension and magnetic flux (of the bulk gauge field), the leading terms in a derivative expansion. The brane properties have an impact on the KK spectrum and therefore on the Casimir energy as well as on the renormalization of the brane operators. A very interesting feature is that when the two branes carry exactly the same amount of flux, one half of the bulk supersymmetries survives after the compactification, even if the brane tensions are large. We also discuss the implications of these calculations for the natural value of the cosmological constant when the bulk has two large extra dimensions and the bulk supersymmetry is partially preserved (or completely broken).
Young's moduli of carbon materials investigated by various classical molecular dynamics schemes
Gayk, Florian; Ehrens, Julian; Heitmann, Tjark; Vorndamme, Patrick; Mrugalla, Andreas; Schnack, Jürgen
2018-05-01
For many applications classical carbon potentials together with classical molecular dynamics are employed to calculate structures and physical properties of such carbon-based materials where quantum mechanical methods fail either due to the excessive size, irregular structure or long-time dynamics. Although such potentials, as for instance implemented in LAMMPS, yield reasonably accurate bond lengths and angles for several carbon materials such as graphene, it is not clear how accurate they are in terms of mechanical properties such as for instance Young's moduli. We performed large-scale classical molecular dynamics investigations of three carbon-based materials using the various potentials implemented in LAMMPS as well as the EDIP potential of Marks. We show how the Young's moduli vary with classical potentials and compare to experimental results. Since classical descriptions of carbon are bound to be approximations it is not astonishing that different realizations yield differing results. One should therefore carefully check for which observables a certain potential is suited. Our aim is to contribute to such a clarification.
The moduli space of two U(1) instantons on noncommutative $R^4$ and $R^3\\times S^1$
Lee, Kimyeong; Tong, David; Yi, Sangheon
2000-01-01
We employ the ADHM method to derive the moduli space of two instantons in U(1) gauge theory on a noncommutative space. We show by an explicit hyperK\\"ahler quotient construction that the relative metric of the moduli space of two instantons on $R^4$ is the Eguchi-Hanson metric and find a unique threshold bound state. For two instantons on $R^3\\times S^1$, otherwise known as calorons, we give the asymptotic metric and conjecture a completion. We further discuss the relationship of caloron modu...
Functional Apparent Moduli (FAMs) as Predictors of Oral Implant Osseointegration Dynamics
Chang, Po-Chun; Seol, Yang-Jo; Kikuchi, Noboru; Goldstein, Steven A.; Giannobile, William V.
2010-01-01
At present, limited functional data exists regarding the application and use of biomechanical and imaging technologies for oral implant osseointegration assessment. The objective of this investigation was to determine the functional apparent moduli (FAMs) that could predict the dynamics of oral implant osseointegration. Using an in vivo dental implant osseous healing model, two FAMs, functional bone apparent modulus (FBAM) and composite tissue apparent modulus (FCAM), of the selected peri-imp...
International Nuclear Information System (INIS)
Park, Kwan Soo; Lee, Sam Sun; Huh, Kyung Hoe; Yi, Wan Jin; Heo, Min Suk; Choi, Soon Chul
2008-01-01
To investigate the relationship between 3D bone architectural parameters and direction-related elastic moduli of cancellous bone of mandibular condyle. Two micro-pigs (Micro-pigR, PWG Genetics Korea) were used. Each pig was about 12 months old and weighing around 44 kg. 31 cylindrical bone specimen were obtained from cancellous bone of condyles for 3D analysis and measured by micro-computed tomography. Six parameters were trabecular thickness (Tb.Th), bone specific surface (BS/BV), percent bone volume (BV/TV), structure model index (SMI), degree of anisotropy (DA) and 3-dimensional fractal dimension (3DFD). Elastic moduli of three orthogonal directions (superiorinferior (SI), medial-lateral (ML), andterior-posterior (AP) direction) were calculated through finite element analysis. Elastic modulus of superior-inferior direction was higher than those of other directions. Elastic moduli of 3 orthogonal directions showed different correlation with 3D architectural parameters. Elastic moduli of SI and ML directions showed significant strong to moderate correlation with BV/TV, SMI and 3DFD. Elastic modulus of cancellous bone of pig mandibular condyle was highest in the SI direction and it was supposed that the change into plate-like structure of trabeculae was mainly affected by increase of trabeculae of SI and ML directions.
Higher-Derivative Supergravity and Moduli Stabilization
International Nuclear Information System (INIS)
Ciupke, David; Westphal, Alexander; Louis, Jan; Hamburg Univ.
2015-05-01
We review the ghost-free four-derivative terms for chiral superfields in N=1 supersymmetry and supergravity. These terms induce cubic polynomial equations of motion for the chiral auxiliary fields and correct the scalar potential. We discuss the different solutions and argue that only one of them is consistent with the principles of effective field theory. Special attention is paid to the corrections along flat directions which can be stabilized or destabilized by the higher-derivative terms. We then compute these higher-derivative terms explicitly for the type IIB string compactified on a Calabi-Yau orientifold with fluxes via Kaluza-Klein reducing the (α') 3 R 4 corrections in ten dimensions for the respective N=1 Kaehler moduli sector. We prove that together with flux and the known (α') 3 -corrections the higher-derivative term stabilizes all Calabi-Yau manifolds with positive Euler number, provided the sign of the new correction is negative.
The fine structure of the moduli space of abelian differentials in genus 3
Looijenga, Eduard; Gabriele, Mondello
2014-01-01
The moduli space of curves endowed with a nonzero abelian differential admits a natural stratification according to the configuration of its zeroes. We give a description of these strata for genus 3 in terms of root system data. For each non-open stratum we obtain a presentation of its orbifold
Moduli stabilization and uplifting with dynamically generated F-terms
International Nuclear Information System (INIS)
Dudas, Emilian; Papineau, Chloe; Pokorski, Stefan
2007-01-01
We use the F-term dynamical supersymmetry breaking models with metastable vacua in order to uplift the vacuum energy in the KKLT moduli stabilization scenario. The main advantage compared to earlier proposals is the manifest supersymmetric treatment and the natural coexistence of a TeV gravitino mass with a zero cosmological constant. We argue that it is generically difficult to avoid anti de-Sitter supersymmetric minima, however the tunneling rate from the metastable vacuum with zero vacuum energy towards them can be very suppressed. We briefly comment on the properties of the induced soft terms in the observable sector
Moduli stabilization and uplifting with dynamically generated F-terms
Energy Technology Data Exchange (ETDEWEB)
Dudas, Emilian [CERN Theory Division, CH-1211, Geneva 23 (Switzerland); Papineau, Chloe [CPhT, Ecole Polytechnique, F-91128 Palaiseau Cedex (France); Pokorski, Stefan [Institute of Theoretical Physics, Univ. of Warsaw, 00-681 Warsaw (Poland)
2007-02-15
We use the F-term dynamical supersymmetry breaking models with metastable vacua in order to uplift the vacuum energy in the KKLT moduli stabilization scenario. The main advantage compared to earlier proposals is the manifest supersymmetric treatment and the natural coexistence of a TeV gravitino mass with a zero cosmological constant. We argue that it is generically difficult to avoid anti de-Sitter supersymmetric minima, however the tunneling rate from the metastable vacuum with zero vacuum energy towards them can be very suppressed. We briefly comment on the properties of the induced soft terms in the observable sector.
Mechanical heterogeneity in ionic liquids
Veldhorst, Arno A.; Ribeiro, Mauro C. C.
2018-05-01
Molecular dynamics (MD) simulations of five ionic liquids based on 1-alkyl-3-methylimidazolium cations, [CnC1im]+, have been performed in order to calculate high-frequency elastic moduli and to evaluate heterogeneity of local elastic moduli. The MD simulations of [CnC1im][NO3], n = 2, 4, 6, and 8, assessed the effect of domain segregation when the alkyl chain length increases, and [C8C1im][PF6] assessed the effect of strength of anion-cation interaction. Dispersion curves of excitation energies of longitudinal and transverse acoustic, LA and TA, modes were obtained from time correlation functions of mass currents at different wavevectors. High-frequency sound velocity of LA modes depends on the alkyl chain length, but sound velocity for TA modes does not. High-frequency bulk and shear moduli, K∞ and G∞, depend on the alkyl chain length because of a density effect. Both K∞ and G∞ are strongly dependent on the anion. The calculation of local bulk and shear moduli was accomplished by performing bulk and shear deformations of the systems cooled to 0 K. The simulations showed a clear connection between structural and elastic modulus heterogeneities. The development of nano-heterogeneous structure with increasing length of the alkyl chain in [CnC1im][NO3] implies lower values for local bulk and shear moduli in the non-polar domains. The mean value and the standard deviations of distributions of local elastic moduli decrease when [NO3]- is replaced by the less coordinating [PF6]- anion.
Digitally controlled measurement of sonic elastic moduli and internal friction by phase analysis
International Nuclear Information System (INIS)
O'Brien, M.H.; Hunter, O. Jr.; Rasmussen, M.D.; Skank, H.D.
1983-01-01
An automated system is described for measuring internal friction and elastic moduli using sonic resonance techniques. This mirocomputer-controlled device does phase angle analysis in addition to traditional decay and peak-width internal friction measurement. The apparatus may be programmed to make measurements at any sequence of temperatures between room temperature and 1600 0 C
Third-order elastic moduli for alkali-halide crystals possessing the sodium chloride structure
International Nuclear Information System (INIS)
Ray, U.
2010-01-01
The values of third-order elastic moduli for alkali halides, having NaCl-type crystal structure are calculated according to the Born-Mayer potential model, considering the repulsive interactions up to the second nearest neighbours and calculating the values of the potential parameters for each crystal, independently, from the compressibility data. This work presents the first published account of the calculation of the third-order elastic moduli taking the actual value of the potential parameter unlike the earlier works. Third-order elastic constants have been computed for alkali halides at 0 and 300 K. The results of the third-order elastic constants are compared with the available experimental and theoretical data. Very good agreement between experimental and theoretical third-order elastic constant data (except C 123 ) is found. We have also computed the values of the pressure derivatives of second-order elastic constants and Anderson-Grueneisen parameter for alkali halides, which agree reasonably well with the experimental values, indicating the satisfactory nature of our computed data for third-order elastic constants.
Mechanical properties of non-centrosymmetric CePt3Si and CePt3B
Rogl, G.; Legut, D.; Sýkora, R.; Müller, P.; Müller, H.; Bauer, E.; Puchegger, S.; Zehetbauer, M.; Rogl, P.
2017-05-01
Elastic moduli, hardness (both at room temperature) and thermal expansion (4.2-670 K) have been experimentally determined for polycrystalline CePt3Si and its prototype compound CePt3B as well as for single-crystalline CePt3Si. Resonant ultrasound spectroscopy was used to determine elastic properties (Young’s modulus E and Poisson’s ratio ν) via the eigenfrequencies of the sample and the knowledge of sample mass and dimensions. Bulk and shear moduli were calculated from E and ν, and the respective Debye temperatures were derived. In addition, ab initio DFT calculations were carried out for both compounds. A comparison of parameters evaluated from DFT with those of experiments revealed, in general, satisfactory agreement. Positive and negative thermal expansion values obtained from CePt3Si single crystal data are fairly well explained in terms of the crystalline electric field model, using CEF parameters derived recently from inelastic neutron scattering. DFT calculations, in addition, demonstrate that the atomic vibrations keep almost unaffected by the antisymmetric spin-orbit coupling present in systems with crystal structures having no inversion symmetry. This is opposite to electronic properties, where the antisymmetric spin-orbit interaction has shown to distinctly influence features like the superconducting condensate of CePt3Si.
Directory of Open Access Journals (Sweden)
Chengbo Yu
2016-02-01
Full Text Available The generalized mixture rule (GMR is used to provide a unified framework for describing Young's (E, shear (G and bulk (K moduli, Lame parameter (λ, and P- and S-wave velocities (Vp and Vs as a function of porosity in various isotropic materials such as metals, ceramics and rocks. The characteristic J values of the GMR for E, G, K and λ of each material are systematically different and display consistent correlations with the Poisson's ratio of the nonporous material (ν0. For the materials dominated by corner-shaped pores, the fixed point at which the effective Poisson's ratio (ν remains constant is at ν0 = 0.2, and J(G > J(E > J(K > J(λ and J(G 0.2 and ν0 J(Vp and J(Vs 0.2 and ν0 0.2 and ν0 = 0.2, respectively. For natural rocks containing thin-disk-shaped pores parallel to mineral cleavages, grain boundaries and foliation, however, the ν fixed point decreases nonlinearly with decreasing pore aspect ratio (α: width/length. With increasing depth or pressure, cracks with smaller α values are progressively closed, making the ν fixed point rise and finally reach to the point at ν0 = 0.2.
Anomaly matching conditions and the moduli space of supersymmetric gauge theories
International Nuclear Information System (INIS)
Dotti, G.; Manohar, A.V.
1998-01-01
The structure of the moduli space of N=1 supersymmetric gauge theories is analyzed from an algebraic geometric viewpoint. The connection between the fundamental fields of the ultraviolet theory, and the gauge-invariant composite fields of the infrared theory is explained in detail. The results are then used to prove an anomaly matching theorem. The theorem is used to study anomaly matching for supersymmetric QCD, and can explain all the known anomaly matching results for this case. (orig.)
2012-12-01
Backcalculation of pavement moduli has been an intensively researched subject for more than four decades. Despite the existence of many backcalculation programs employing different backcalculation procedures and algorithms, accurate inverse of the la...
Fixing All Moduli in a Simple F-Theory Compactification
International Nuclear Information System (INIS)
Denef, F.
2005-01-01
We discuss a simple example of an F-theory compactification on a Calabi-Yau fourfold where background fluxes, together with nonperturbative effects from Euclidean D3 instantons and gauge dynamics on D7 branes, allow us to fix all closed and open string moduli. We explicitly check that the known higher order corrections to the potential, which we neglect in our leading approximation, only shift the results by a small amount. In our exploration of the model, we encounter interesting new phenomena, including examples of transitions where D7 branes absorb O3 planes, while changing topology to preserve the net D3 charge
Thermal expansion studies on Inconel-600[reg] by high temperature X-ray diffraction
International Nuclear Information System (INIS)
Raju, S.; Sivasubramanian, K.; Divakar, R.; Panneerselvam, G.; Banerjee, A.; Mohandas, E.; Antony, M.P.
2004-01-01
The lattice thermal expansion characteristics of Inconel-600[reg] have been studied by high temperature X-ray diffraction (HT-XRD) technique in the temperature range 298-1200 K. Altogether four experimental runs were conducted on thin foils of about 75-100 μm thickness. The diffraction profiles have been accurately calibrated to offset the shift in 2θ values introduced by sample buckling at elevated temperatures. The corrected lattice parameter data have been used to estimate the instantaneous and mean linear thermal expansion coefficients as a function of temperature. The thermal expansion values estimated in the present study show a fair degree of agreement with other existing dilatometer based bulk thermal expansion estimates. The lattice parameter for this alloy at 300 K is found to be 0.3549(1) nm. The mean linear thermal expansivity is found to be 11.4 x 10 -6 K -1
Effect of rotation on the elastic moduli of solid 4He
Tsuiki, T.; Takahashi, D.; Murakawa, S.; Okuda, Y.; Kono, K.; Shirahama, K.
2018-02-01
We report measurements of elastic moduli of hcp solid 4He down to 15 mK when the samples are rotated unidirectionally. Recent investigations have revealed that the elastic behavior of solid 4He is dominated by gliding of dislocations and pinning of them by 3He impurities, which move in the solidlike Bloch waves (impuritons). Motivated by the recent controversy of torsional oscillator studies, we have performed direct measurements of shear and Young's moduli of annular solid 4He using pairs of quarter-circle-shape piezoelectric transducers (PZTs) while the whole apparatus is rotated with angular velocity Ω up to 4 rad/s. We have found that shear modulus μ is suppressed by rotation below 80 mK, when shear strain applied by PZT exceeds a critical value, above which μ decreases because the shear strain unbinds dislocations from 3He impurities. The rotation-induced decrement of μ at Ω =4 rad/s is about 14.7(12.3)% of the total change of temperature dependent μ for solid samples of pressure 3.6(5.4) MPa. The decrements indicate that the probability of pinning of 3He on dislocation segment G decreases by several orders of magnitude. We propose that the motion of 3He impuritons under rotation becomes strongly anisotropic by the Coriolis force, resulting a decrease in G for dislocation lines aligning parallel to the rotation axis.
Effect of Pore Size, Morphology and Orientation on the Bulk Stiffness of a Porous Ti35Nb4Sn Alloy
Torres-Sanchez, Carmen; McLaughlin, John; Bonallo, Ross
2018-04-01
The metal foams of a titanium alloy were designed to study porosity as well as pore size and shape independently. These were manufactured using a powder metallurgy/space-holder technique that allowed a fine control of the pore size and morphology; and then characterized and tested against well-established models to predict a relationship between porosity, pore size and shape, and bulk stiffness. Among the typically used correlations, existing power-law models were found to be the best fit for the prediction of macropore morphology against compressive elastic moduli, outperforming other models such as exponential, polynomial or binomial. Other traditional models such as linear ones required of updated coefficients to become relevant to metal porous sintered macrostructures. The new coefficients reported in this study contribute toward a design tool that allows the tailoring of mechanical properties through porosity macrostructure. The results show that, for the same porosity range, pore shape and orientation have a significant effect on mechanical performance and that they can be predicted. Conversely, pore size has only a mild impact on bulk stiffness.
DEFF Research Database (Denmark)
Hecksher, Tina; Olsen, Niels Boye; Nelson, Keith Adam
2013-01-01
We present dynamic shear and bulk modulus measurements of supercooled tetraphenyl-tetramethyl-trisiloxane (DC704) and 5-phenyl-4-ether over a range of temperatures close to their glass transition. The data are analyzed and compared in terms of time-temperature superposition (TTS), the relaxation ...
International Nuclear Information System (INIS)
Lindstad, Haakon; Jullumstrø, Egil; Sandaas, Inge
2013-01-01
Historically, fuel costs have been small compared with the fixed costs of a bulk vessel, its crewing and management. Today, however, fuel accounts for more than 50% of the total costs. In combination with an introduction of stricter energy efficiency requirements for new vessels, this might make design improvement a necessity for all new bulk vessels. This is in contradiction to traditional bulk vessel designs, where the focus has been on maximizing the cargo-carrying capacity at the lowest possible building cost and not on minimizing the energy consumption. Moreover, the Panama Canal has historically been an important design criterion, while the new canal locks from 2014 will significantly increase the maximum size of vessels that can pass. The present paper provides an assessment of cost and emissions as a function of alternative bulk vessel designs with focus on a vessel's beam, length and hull slenderness, expressed by the length displacement ratio for three fuel price scenarios. The result shows that with slenderer hull forms the emissions drop. With today's fuel price of 600 USD per ton of fuel, emissions can thus be reduced by up to 15–25% at a negative abatement cost. - Highlights: • We have assessed cost and emissions as a function of alternative bulk vessel designs. • The design focus has been on vessel beam, length, hull slenderness and bow section length. • The assessment has taken into account three different fuel price scenarios. • When the block coefficient is reduced and the hull becomes more slender the emissions drop. • With a fuel price of 600 USD/t, emissions can be reduced by up to 15–25% at a negative abatement cost
Anisotropic elastic and thermal properties of titanium borides by first-principles calculations
Energy Technology Data Exchange (ETDEWEB)
Sun, Liang; Gao, Yimin [State Key Laboratory for Mechanical Behavior of Materials, Xi’an Jiaotong University, Xi’an 710049 (China); Xiao, Bing [Department of Physics and Quantum Theory Group, School of Science and Engineering, Tulane University, New Orleans, LA 70118 (United States); Li, Yefei, E-mail: yefeili@126.com [State Key Laboratory for Mechanical Behavior of Materials, Xi’an Jiaotong University, Xi’an 710049 (China); Wang, Guoliang [State Key Laboratory for Mechanical Behavior of Materials, Xi’an Jiaotong University, Xi’an 710049 (China)
2013-12-05
Highlights: •Elastic properties of titanium borides are calculated by first principles calculation. •Thermodynamical stability of titanium borides is analyzed. •Heat capacity and thermal expansion coefficient for titanium borides are calculated and compared. •Grüneisen parameters of titanium borides are calculated. -- Abstract: The anisotropic elastic and thermal expansions of the titanium borides (TiB{sub 2}, Ti{sub 3}B{sub 4}, TiB{sub P}nma and TiB{sub F}m3{sup ¯}m) are calculated from first-principles using density functional theory. All borides show different anisotropic elastic properties; the bulk, shear and Young’s moduli are consistent with those determined experimentally. The temperature dependence of thermal expansions is mainly caused by the restoration of thermal energy due to phonon excitations at low temperature. When the temperature is higher than 500 K, the volumetric coefficient is increased linearly by increasing temperature. Meanwhile, the heat capacities of titanium borides are obtained based on the knowledge of thermal expansion coefficient and the elasticity, the calculations are in good agreement with the experiments.
Exact moduli space metrics for hyperbolic vortex polygons
International Nuclear Information System (INIS)
Krusch, S.; Speight, J. M.
2010-01-01
Exact metrics on some totally geodesic submanifolds of the moduli space of static hyperbolic N-vortices are derived. These submanifolds, denoted as Σ n,m , are spaces of C n -invariant vortex configurations with n single vortices at the vertices of a regular polygon and m=N-n coincident vortices at the polygon's center. The geometric properties of Σ n,m are investigated, and it is found that Σ n,n-1 is isometric to the hyperbolic plane of curvature -(3πn) -1 . The geodesic flow on Σ n,m and a geometrically natural variant of geodesic flow recently proposed by Collie and Tong ['The dynamics of Chern-Simons vortices', Phys. Rev. D Part. Fields Gravit. Cosmol. 78, 065013 (2008);e-print arXiv:hep-th/0805.0602] are analyzed in detail.
Distribution of flux vacua around singular points in Calabi-Yau moduli space
International Nuclear Information System (INIS)
Eguchi, Tohru; Tachikawa, Yuji
2006-01-01
We study the distribution of type-IIB flux vacua in the moduli space near various singular loci, e.g. conifolds, ADE singularities on P 1 , Argyres-Douglas point etc, using the Ashok-Douglas density det (R+ω). We find that the vacuum density is integrable around each of them, irrespective of the type of the singularities. We study in detail an explicit example of an Argyres-Douglas point embedded in a compact Calabi-Yau manifold
Stability of Picard bundle over moduli space of stable vector bundles ...
Indian Academy of Sciences (India)
Springer Verlag Heidelberg #4 2048 1996 Dec 15 10:16:45
Since the morphism ϕ is given by the universal property of the moduli space, the pullback of the universal bundle E on X × M to X × P by the map idX × ϕ is isomorphic (up to a twist by a line bundle coming from P) to ˜E. In other words, there is an integer k such that. 0 −→ (idX × ϕ)∗E −→ W ⊠ OP (k) −→ Ox×P (k + 1) −→ 0.
In vitro behaviors of rat mesenchymal stem cells on bacterial celluloses with different moduli
International Nuclear Information System (INIS)
Taokaew, Siriporn; Phisalaphong, Muenduen; Zhang Newby, Bi-min
2014-01-01
Compressive moduli of bacteria-synthesized cellulose (BC) were altered by two drying techniques: ambient-air drying and freeze drying. While no significant differences in dry weight were found, their cross-sectional structures and thickness varied greatly. Freeze dried BCs had loose cross-sectional structures and a thickness of ∼ 4.7 mm, whereas air dried BCs had more compacted cross-sectional structures and a thickness of ∼ 0.1 mm. The compressive moduli of the rehydrated freeze dried and rehydrated air dried BCs were measured to be 21.06 ± 0.22 kPa and 90.09 ± 21.07 kPa, respectively. When rat mesenchymal stem cells (rMSCs) were seeded on these BCs, they maintained a round morphology in the first 3 days of cultivation. More spread-out morphology and considerable proliferation on freeze dried BCs were observed in 7 days, but not on air-dried BCs. The cells were further grown for 3 weeks in the absence and presence of differentiation agents. Without using any differentiation agents, no detectable differentiation was noticed for rMSCs further cultivated on both types of BC. With differentiation inducing agents, chondrogenic differentiation, visualized by histological staining, was observed in some area of the rehydrated freeze dried BCs; while osteogenic differentiation was noticed on the stiffer rehydrated air dried BCs. - Graphical abstract: In the presence of induction agents, rat mesenchymal stem cells (rMSCs) preferentially differentiated into osteocytes on stiffer air dried BC films. - Highlights: • Bacterial cellulose (BC) sheets with different moduli generated by drying differently • Air-dried BC exhibited a modulus similar to that of bone. • Freeze-dried BC showed a modulus in the range of that of muscle. • Air-dried BC promoted the differentiation of rMSCs into osteocytes. • Freeze-dried BC promoted the differentiation of rMSCs into chondrocytes
In vitro behaviors of rat mesenchymal stem cells on bacterial celluloses with different moduli
Energy Technology Data Exchange (ETDEWEB)
Taokaew, Siriporn [Department of Chemical Engineering, Faculty of Engineering, Chulalongkorn University, Bangkok 10330 (Thailand); Department of Chemical and Biomolecular Engineering, The University of Akron, Akron, OH 44325-3906 (United States); Phisalaphong, Muenduen [Department of Chemical Engineering, Faculty of Engineering, Chulalongkorn University, Bangkok 10330 (Thailand); Zhang Newby, Bi-min, E-mail: bimin@uakron.edu [Department of Chemical and Biomolecular Engineering, The University of Akron, Akron, OH 44325-3906 (United States)
2014-05-01
Compressive moduli of bacteria-synthesized cellulose (BC) were altered by two drying techniques: ambient-air drying and freeze drying. While no significant differences in dry weight were found, their cross-sectional structures and thickness varied greatly. Freeze dried BCs had loose cross-sectional structures and a thickness of ∼ 4.7 mm, whereas air dried BCs had more compacted cross-sectional structures and a thickness of ∼ 0.1 mm. The compressive moduli of the rehydrated freeze dried and rehydrated air dried BCs were measured to be 21.06 ± 0.22 kPa and 90.09 ± 21.07 kPa, respectively. When rat mesenchymal stem cells (rMSCs) were seeded on these BCs, they maintained a round morphology in the first 3 days of cultivation. More spread-out morphology and considerable proliferation on freeze dried BCs were observed in 7 days, but not on air-dried BCs. The cells were further grown for 3 weeks in the absence and presence of differentiation agents. Without using any differentiation agents, no detectable differentiation was noticed for rMSCs further cultivated on both types of BC. With differentiation inducing agents, chondrogenic differentiation, visualized by histological staining, was observed in some area of the rehydrated freeze dried BCs; while osteogenic differentiation was noticed on the stiffer rehydrated air dried BCs. - Graphical abstract: In the presence of induction agents, rat mesenchymal stem cells (rMSCs) preferentially differentiated into osteocytes on stiffer air dried BC films. - Highlights: • Bacterial cellulose (BC) sheets with different moduli generated by drying differently • Air-dried BC exhibited a modulus similar to that of bone. • Freeze-dried BC showed a modulus in the range of that of muscle. • Air-dried BC promoted the differentiation of rMSCs into osteocytes. • Freeze-dried BC promoted the differentiation of rMSCs into chondrocytes.
International Nuclear Information System (INIS)
Niranjan, Manish K
2015-01-01
We present a comparative study of the anisotropy in the elastic properties of the C49, C54 and C40 phases of TiSi 2 , as well as orthorhombic TiSi and hexagonal Ti 5 Si 3 . The elastic constants, elastic moduli, Debye temperature and sound velocities are computed within the framework of density functional theory. The computed values of the elastic constants and moduli are found to be in excellent agreement with available experimental values. The average elastic moduli, such as Young’s modulus, shear modulus, bulk modulus and Poisson’s ratio, of polycrystalline aggregates are computed using the computed elastic constants of single crystals. The anisotropy in elastic properties is analyzed using estimates of shear anisotropic factors, bulk modulus anisotropic factors and variations in Young’s and bulk moduli in different crystallographic directions. Among the Ti–Si phases, the computed directional Young’s modulus profiles of C49 TiSi 2 and C40 TiSi 2 are found to be quite similar to those of bulk Si and Ti, respectively. In addition to the elastic properties, the electronic structure of five Ti–Si phases is studied. The density of states and planar charge density profiles reveal mixed covalent–metallic bonding in all Ti–Si phases. (paper)
Energy Technology Data Exchange (ETDEWEB)
Min, Young Jae; Yun, Gyeong Won; Kim, Kyung Min; Roh, Yuji; Kim, Young H. [Applied Acoustics Lab, Korea Science Academy of KAIST, Busan (Korea, Republic of)
2016-02-15
Single crystalline silicon wafers having (100), (110), and (111) directions are employed as specimens for obtaining slowness profiles. Leaky Lamb waves (LLW) from immersed wafers were detected by varying the incident angles of the specimens and rotating the specimens. From an analysis of LLW signals for different propagation directions and phase velocities of each specimen, slowness profiles were obtained, which showed a unique symmetry with different symmetric axes. Slowness profiles were compared with elastic moduli of each wafer. They showed the same symmetries as crystal structures. In addition, slowness profiles showed expected patterns and values that can be inferred from elastic moduli. This implies that slowness profiles can be used to examine crystal structures of anisotropic solids.
Directory of Open Access Journals (Sweden)
A. KH. Alassafee
2017-11-01
Full Text Available The modified DebyeâEinstein approximation model is used to calculate nanoscale size-dependent values of Gruneisen parameters and lattice specific heat capacity for Si nanowires. All parameters forming the model, including Debye temperatures, bulk moduli, the lattice thermal expansion and the lattice volume, are calculated according to their nanoscale size dependence. Values for lattice volume Gruneisen parameters increase with the decrease of the nanowiresâ diameter, while all other parameters decrease. The nanosize dependence of lattice thermal parameters agree with other reported theoretical results. Keywords: Lattice specific heat capacity, Gruneisen parameter, DebyeâEinstein model, Si nanowires
Molecular dynamics study of the thermal expansion coefficient of silicon
Energy Technology Data Exchange (ETDEWEB)
Nejat Pishkenari, Hossein, E-mail: nejat@sharif.edu; Mohagheghian, Erfan; Rasouli, Ali
2016-12-16
Due to the growing applications of silicon in nano-scale systems, a molecular dynamics approach is employed to investigate thermal properties of silicon. Since simulation results rely upon interatomic potentials, thermal expansion coefficient (TEC) and lattice constant of bulk silicon have been obtained using different potentials (SW, Tersoff, MEAM, and EDIP) and results indicate that SW has a better agreement with the experimental observations. To investigate effect of size on TEC of silicon nanowires, further simulations are performed using SW potential. To this end, silicon nanowires of different sizes are examined and their TEC is calculated by averaging in different directions ([100], [110], [111], and [112]) and various temperatures. Results show that as the size increases, due to the decrease of the surface effects, TEC approaches its bulk value. - Highlights: • MD simulations of TEC and lattice constant of bulk silicon. • Effects of four potentials on the results. • Comparison to experimental data. • Investigating size effect on TEC of silicon nanowires.
Thermal behaviors of liquid La-based bulk metallic glasses
Energy Technology Data Exchange (ETDEWEB)
Zhang, D. W.; Wang, X. D., E-mail: wangxd@zju.edu.cn, E-mail: jiangjz@zju.edu.cn; Lou, H. B.; Cao, Q. P.; Jiang, J. Z., E-mail: wangxd@zju.edu.cn, E-mail: jiangjz@zju.edu.cn [International Center for New-Structured Materials (ICNSM), Laboratory of New-Structured Materials, State Key Laboratory of Silicon Materials, and Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China); Wang, L. W. [Institute of Materials Science and Engineering, Lanzhou University, Lanzhou 730000 (China); Zhang, D. X. [State Key Laboratory of Modern Optical Instrumentation, Zhejiang University, Hangzhou 310027 (China)
2014-12-14
Thermal behaviors of liquid La-based bulk metallic glasses have been measured by using the dilatometer with a self-sealed sample cell. It is demonstrated that the strong glass forming liquid not only has the small thermal expansion coefficient but also shows the slow variation rate. Moreover, the strong glass former has relatively dense atomic packing and also small density change in the liquid state. The results suggest that the high glass forming ability of La-based metallic glasses would be closely related to the slow atomic rearrangements in liquid melts.
N=2→0 super no-scale models and moduli quantum stability
Directory of Open Access Journals (Sweden)
Costas Kounnas
2017-06-01
Full Text Available We consider a class of heterotic N=2→0 super no-scale Z2-orbifold models. An appropriate stringy Scherk–Schwarz supersymmetry breaking induces tree level masses to all massless bosons of the twisted hypermultiplets and therefore stabilizes all twisted moduli. At high supersymmetry breaking scale, the tachyons that occur in the N=4→0 parent theories are projected out, and no Hagedorn-like instability takes place in the N=2→0 models (for small enough marginal deformations. At low supersymmetry breaking scale, the stability of the untwisted moduli is studied at the quantum level by taking into account both untwisted and twisted contributions to the 1-loop effective potential. The latter depends on the specific branch of the gauge theory along which the background can be deformed. We derive its expression in terms of all classical marginal deformations in the pure Coulomb phase, and in some mixed Coulomb/Higgs phases. In this class of models, the super no-scale condition requires having at the massless level equal numbers of untwisted bosonic and twisted fermionic degrees of freedom. Finally, we show that N=1→0 super no-scale models are obtained by implementing a second Z2 orbifold twist on N=2→0 super no-scale Z2-orbifold models.
Temperature dependence of the interband critical points of bulk Ge and strained Ge on Si
Fernando, Nalin S.; Nunley, T. Nathan; Ghosh, Ayana; Nelson, Cayla M.; Cooke, Jacqueline A.; Medina, Amber A.; Zollner, Stefan; Xu, Chi; Menendez, Jose; Kouvetakis, John
2017-11-01
Epitaxial Ge layers on a Si substrate experience a tensile biaxial stress due to the difference between the thermal expansion coefficients of the Ge epilayer and the Si substrate, which can be measured using asymmetric X-ray diffraction reciprocal space maps. This stress depends on temperature and affects the band structure, interband critical points, and optical spectra. This manuscripts reports careful measurements of the temperature dependence of the dielectric function and the interband critical point parameters of bulk Ge and Ge epilayers on Si using spectroscopic ellipsometry from 80 to 780 K and from 0.8 to 6.5 eV. The authors find a temperature-dependent redshift of the E1 and E1 + Δ1 critical points in Ge on Si (relative to bulk Ge). This redshift can be described well with a model based on thermal expansion coefficients, continuum elasticity theory, and the deformation potential theory for interband transitions. The interband transitions leading to E0‧ and E2 critical points have lower symmetry and therefore are not affected by the stress.
Effect of TeO2 on the elastic moduli of sodium borate glasses
International Nuclear Information System (INIS)
Saddeek, Y.B.; Abd El Latif, Lamia
2004-01-01
Sodium borate glass containing tellurite as Te x Na 2-2x B 4-4x O 7-5x with x=0, 0.05, 0.15, 0.25 and 0.35 have been prepared by rapid quenching. Ultrasonic velocity (both longitudinal and shear) measurements have been made using a transducer operated at the fundamental frequency of 4 MHz at room temperature. The density was measured by the conventional Archimedes method. The elastic moduli, the Debye temperature, Poisson's ratio, and the parameters derived from the Makishima-Mackenzie model and the bond compression model have been obtained as a function of TeO 2 content. The monotonic decrease in the velocities and the elastic moduli, and the increase in the ring diameter and the ratio K bc /K e as a function of TeO 2 modifier content reveals the loose packing structure, which is attributed to the increase in the molar volume and the reduction in the vibrations of the borate lattice. The observed results confirm that the addition of TeO 2 changes the rigid character of Na 2 B 4 O 7 to a matrix of ionic behaviour bonds (NBOs). This is due to the creation of more and more discontinuities and defects in the glasses, thus breaking down the borax structure
A new method for evaluating structural stability of bulk metallic glasses
Energy Technology Data Exchange (ETDEWEB)
Zhao, Lei; Jia, Haoling [Key Laboratory of Aerospace Materials and Performance, Ministry of Education, School of Materials Science and Engineering, Beihang University, Beijing 100191 (China); Xie, Shenghui; Zeng, Xierong [College of Materials Science and Engineering, Shenzhen University and Shenzhen Key Laboratory of Special Functional Materials, ShenZhen 518060 (China); Zhang, Tao [Key Laboratory of Aerospace Materials and Performance, Ministry of Education, School of Materials Science and Engineering, Beihang University, Beijing 100191 (China); Ma, Chaoli, E-mail: machaoli@buaa.edu.c [Key Laboratory of Aerospace Materials and Performance, Ministry of Education, School of Materials Science and Engineering, Beihang University, Beijing 100191 (China)
2010-08-15
This paper proposed a new method for evaluating the structural stability of bulk metallic glasses (BMGs) based on dilatometric measurements. During heating in the dilatometric experiments, the BMGs expanded continuously with increasing temperature. When the temperature reached the glass transition temperature (T{sub g}), viscous shrinkage occurred due to the viscosity of material becoming lower. Since the inhomogeneous nature of the metallic glasses at atomic level, the processes of rigid expansion and the viscous shrinkage co-exist in a certain temperature region. The expansion stopped completely at a temperature (named T{sub p} here) beyond T{sub g}. The values of the temperature region, {Delta}T{sub gp} = T{sub p} - T{sub g}, and the corresponding time interval ({Delta}t{sub gp}) and the activation energy (E{sub p}) corresponding to the expansion processes, are the reflection of the structural stability of BMGs. Investigating the co-existing processes kinetically and thermodynamically, we can make an insight into the structural stability of metallic glasses. Based on this idea, the thermal expansion behaviors of Mg-, Pd-, Zr-, Ti- and Fe-based BMG were studied, and their structural stability was evaluated by the parameters of {Delta}T{sub gp}, {Delta}t{sub gp} and E{sub p}.
Elastic moduli of a Brownian colloidal glass former
Fritschi, S.; Fuchs, M.
2018-01-01
The static, dynamic and flow-dependent shear moduli of a binary mixture of Brownian hard disks are studied by an event-driven molecular dynamics simulation. Thereby, the emergence of rigidity close to the glass transition encoded in the static shear modulus G_∞ is accessed by three methods. Results from shear stress auto-correlation functions, elastic dispersion relations, and the elastic response to strain deformations upon the start-up of shear flow are compared. This enables one to sample the time-dependent shear modulus G(t) consistently over several decades in time. By that a very precise specification of the glass transition point and of G_∞ is feasible. Predictions by mode coupling theory of a finite shear modulus at the glass transition, of α-scaling in fluid states close to the transition, and of shear induced decay in yielding glass states are tested and broadly verified.
Emergence and expansion of cosmic space as due to M0-branes
Energy Technology Data Exchange (ETDEWEB)
Sepehri, Alireza, E-mail: alireza.sepehri@uk.ac.ir [Faculty of Physics, Shahid Bahonar University, P.O. Box 76175, Kerman (Iran, Islamic Republic of); Research Institute for Astronomy and Astrophysics of Maragha (RIAAM), P.O. Box 55134-441, Maragha (Iran, Islamic Republic of); Setare, Mohammad Reza, E-mail: rezakord@ipm.ir [Department of Science, University of Kurdistan, Campus of Bijar, Bijar (Iran, Islamic Republic of); Capozziello, Salvatore, E-mail: capozziello@na.infn.it [Dipartimento di Fisica, Universita di Napoli Federico II, 80126, Naples (Italy); INFN Sez. di Napoli, Compl. Univ. di Monte S. Angelo, Edificio G, 80126, Naples (Italy); Gran Sasso Science Institute (INFN), Viale F. Crispi, 7, 67100, L’Aquila (Italy)
2015-12-29
Recently, Padmanabhan discussed that the difference between the number of degrees of freedom on the boundary surface and the number of degrees of freedom in a bulk region causes the accelerated expansion of the universe. The main question arising is: what is the origin of this inequality between the surface degrees of freedom and the bulk degrees of freedom? We answer this question in M-theory. In our model, first M0-branes are compactified on one circle and ND0-branes are created. Then ND0-branes join each other, grow, and form one D5-branes. Next, the D5-brane is compactified on two circles and our universe’s D3-brane, two D1-branes and some extra energies are produced. After that, one of the D1-branes, which is closer to the universe’s brane, gives its energy into it, and this leads to an increase in the difference between the numbers of degrees of freedom and the occurring inflation era. With the disappearance of this D1-brane, the number of degrees of freedom of boundary surface and bulk region become equal and inflation ends. At this stage, extra energies that are produced due to the compactification cause an expansion of the universe and deceleration epoch. Finally, another D1-brane dissolves in our universe’s brane, leads to an inequality between degrees of freedom, and there occurs a new phase of acceleration.
Emergence and expansion of cosmic space as due to M0-branes
International Nuclear Information System (INIS)
Sepehri, Alireza; Setare, Mohammad Reza; Capozziello, Salvatore
2015-01-01
Recently, Padmanabhan discussed that the difference between the number of degrees of freedom on the boundary surface and the number of degrees of freedom in a bulk region causes the accelerated expansion of the universe. The main question arising is: what is the origin of this inequality between the surface degrees of freedom and the bulk degrees of freedom? We answer this question in M-theory. In our model, first M0-branes are compactified on one circle and ND0-branes are created. Then ND0-branes join each other, grow, and form one D5-branes. Next, the D5-brane is compactified on two circles and our universe’s D3-brane, two D1-branes and some extra energies are produced. After that, one of the D1-branes, which is closer to the universe’s brane, gives its energy into it, and this leads to an increase in the difference between the numbers of degrees of freedom and the occurring inflation era. With the disappearance of this D1-brane, the number of degrees of freedom of boundary surface and bulk region become equal and inflation ends. At this stage, extra energies that are produced due to the compactification cause an expansion of the universe and deceleration epoch. Finally, another D1-brane dissolves in our universe’s brane, leads to an inequality between degrees of freedom, and there occurs a new phase of acceleration
Topological recursion for chord diagrams, RNA complexes, and cells in moduli spaces
DEFF Research Database (Denmark)
Andersen, Jørgen Ellegaard; Chekhov, Leonid O.; Penner, Robert
2013-01-01
and free energies are convergent for small t and all s as a perturbation of the Gaussian potential, which arises for st=0. This perturbation is computed using the formalism of the topological recursion. The corresponding enumeration of chord diagrams gives at once the number of RNA complexes of a given...... topology as well as the number of cells in Riemann's moduli spaces for bordered surfaces. The free energies are computed here in principle for all genera and explicitly for genera less than four....
International Nuclear Information System (INIS)
Nicula, R.; Crisan, O.; Crisan, A.D.; Mercioniu, I.; Stir, M.; Vasiliu, F.
2015-01-01
Highlights: • Formation of the L10 FePt hard-magnetic phase (>90%) directly in the as-cast state. • Specific alternating hard/soft nanostructure is stable to 600 °C without grain growth. • Anisotropic and non-linear thermal expansion effects. • The FePtAgB alloy behaves like a single magnetic phase (full exchange coupling). - Abstract: Rare-earth free (RE-free) exchange coupling nanocomposite magnets are intensively studied nowadays due to their potential use in applications demanding stable high-temperature operation and corrosion resistance. In this respect, the FePt alloy system is one of the most actively addressed potential permanent magnet solutions. In FePt alloys, promising magnetic features arise from the co-existence of hard magnetic L1 0 FePt and soft magnetic L1 2 Fe 3 Pt phases emerged from the same metastable precursor. The present work deals with an in-situ temperature-resolved synchrotron radiation study of the thermal stability, thermal expansion and microstructure evolution in exchange-coupled FePtAgB alloys. The as-cast microstructural state as well as the optimized magnetic behavior are given as reference and correlated to the observed microstructural evolution with temperature. The melt-spun Fe 48 Pt 28 Ag 6 B 18 alloy ribbons were examined in situ by synchrotron X-ray powder diffraction from ambient temperature up to 600 °C. The FePt-Fe 3 Pt exchange-coupled microstructure achieved by rapid solidification is not significantly altered during the high temperature exposure. The thermal expansion of the FePt L1 0 unit cell has been found to be strongly anisotropic, being essentially an in-plane expansion which may be seen as an anisotropic invar effect. For the FePt L1 0 phase, a significant deviation from linear thermal expansion is observed at the Curie temperature T C = 477 °C. This non-linear behavior above T C is tentatively linked to a diffusion/segregation mechanism of Ag. The promising hard magnetic properties as well as the
Bohr-Sommerfeld orbits in the moduli space of flat connections and the Verlinde dimension formula
International Nuclear Information System (INIS)
Jeffrey, L.C.; Weitsman, J.
1992-01-01
We show how the moduli space of flat SU(2) connections on a two-manifold can be quantized. The dimension of the quantization, given by the number of integral fibres of the polarization, matches the Verlinde formula, which is known to give the dimension of the quantization of this space in a Kaehler polarization. (orig./HSI)
Bulk viscous matter and recent acceleration of the universe
Energy Technology Data Exchange (ETDEWEB)
Sasidharan, Athira; Mathew, Titus K. [Cochin University of Science and Technology, Department of Physics, Kochi (India)
2015-07-15
We consider a cosmological model dominated by bulk viscous matter with a total bulk viscosity coefficient proportional to the velocity and acceleration of the expansion of the universe in such a way that ζ = ζ{sub 0} + ζ{sub 1}(a)/(a) + ζ{sub 2}(a)/(a). We show that there exist two limiting conditions in the bulk viscous coefficients (ζ{sub 0}, ζ{sub 1}, ζ{sub 2}) which correspond to a universe having a Big Bang at the origin, followed by an early decelerated epoch and then making a smooth transition into an accelerating epoch. We have constrained the model using the type Ia Supernovae data, evaluated the best estimated values of all the bulk viscous parameters and the Hubble parameter corresponding to the two limiting conditions. We found that even though the evolution of the cosmological parameters are in general different for the two limiting cases, they show identical behavior for the best estimated values of the parameters from both limiting conditions. A recent acceleration would occur if ζ{sub 0} + ζ{sub 1} > 1 for the first limiting conditions and if ζ{sub 0} + ζ{sub 1} < 1 for the second limiting conditions. The age of the universe predicted by this model is found to be less than that predicted from the oldest galactic globular clusters. The total bulk viscosity seems to be negative in the past and becomes positive when z ≤ 0.8. So the model violates the local second law of thermodynamics. However, the model satisfies the generalized second law of thermodynamics at the apparent horizon throughout the evolution of the universe. We also made a statefinder analysis of the model and found that it is distinguishably different from the standard ΛCDM model at present, but it shows a de Sitter type behavior in the far future of the evolution. (orig.)
On Type IIB moduli stabilization and N=4,8 supergravities
Energy Technology Data Exchange (ETDEWEB)
Aldazabal, Gerardo [Centro Atomico Bariloche, Instituto Balseiro (CNEA-UNC) and CONICET, 8400 S.C. de Bariloche (Argentina); Marques, Diego [Institut de Physique Theorique, CEA/ Saclay, 91191 Gif-sur-Yvette Cedex (France); Nunez, Carmen, E-mail: carmen@iafe.uba.a [Instituto de Astronomia y Fisica del Espacio (CONICET-UBA) and Departamento de Fisica, FCEN, Universidad de Buenos Aires, C.C. 67 - Suc. 28, 1428 Buenos Aires (Argentina); Rosabal, Jose A. [Centro Atomico Bariloche, Instituto Balseiro (CNEA-UNC) and CONICET, 8400 S.C. de Bariloche (Argentina)
2011-08-01
We analyze D=4 compactifications of Type IIB theory with generic, geometric and non-geometric, dual fluxes turned on. In particular, we study N=1 toroidal orbifold compactifications that admit an embedding of the untwisted sector into gauged N=4,8 supergravities. Truncations, spontaneous breaking of supersymmetry and the inclusion of sources are discussed. The algebraic identities satisfied by the supergravity gaugings are used to implement the full set of consistency constraints on the background fluxes. This allows to perform a generic study of N=1 vacua and identify large regions of the parameter space that do not admit complete moduli stabilization. Illustrative examples of AdS and Minkowski vacua are presented.
Piezooptic behavior of certain fluids
International Nuclear Information System (INIS)
Weiss, J.D.
1985-01-01
In this paper we present an analysis of pressure--volume data for certain optical fluids, which characterizes them by two parameters: their bulk moduli and the pressure derivative of their bulk moduli, both evaluated at zero pressure. We then relate their refractive-index changes to density and pressure using this analysis and the Lorentz-Lorenz equation with a density-dependent polarizability. An example of the use of such fluids in a fiber-optic pressure gauge being developed at Sandia is also discussed
International Nuclear Information System (INIS)
Cheng, Chao-Lin; Fang, Weileun; Tsai, Ming-Han
2015-01-01
Many standard CMOS processes, provided by existing foundries, are available. These standard CMOS processes, with stacking of various metal and dielectric layers, have been extensively applied in integrated circuits as well as micro-electromechanical systems (MEMS). It is of importance to determine the material properties of the metal and dielectric films to predict the performance and reliability of micro devices. This study employs an existing approach to determine the coefficients of thermal expansion (CTEs) of metal and dielectric films for standard CMOS processes. Test cantilevers with different stacking of metal and dielectric layers for standard CMOS processes have been designed and implemented. The CTEs of standard CMOS films can be determined from measurements of the out-of-plane thermal deformations of the test cantilevers. To demonstrate the feasibility of the present approach, thin films prepared by the Taiwan Semiconductor Manufacture Company 0.35 μm 2P4M CMOS process are characterized. Eight test cantilevers with different stacking of CMOS layers and an auxiliary Si cantilever on a SOI wafer are fabricated. The equivalent elastic moduli and CTEs of the CMOS thin films including the metal and dielectric layers are determined, respectively, from the resonant frequency and static thermal deformation of the test cantilevers. Moreover, thermal deformations of cantilevers with stacked layers different to those of the test beams have been employed to verify the measured CTEs and elastic moduli. (paper)
A model for the parabolic slices Per1(e2πip/q) in moduli space of quadratic rational maps
DEFF Research Database (Denmark)
Uhre, Eva
2010-01-01
The notion of relatedness loci in the parabolic slices Per1(e2πip/q) in moduli space of quadratic rational maps is introduced. They are counterparts of the disconnectedness or escape locus in the slice of quadratic polynomials. A model for these loci is presented, and a strategy of proof of the f......The notion of relatedness loci in the parabolic slices Per1(e2πip/q) in moduli space of quadratic rational maps is introduced. They are counterparts of the disconnectedness or escape locus in the slice of quadratic polynomials. A model for these loci is presented, and a strategy of proof...... of the faithfulness of the model is given....
Effective moduli of high volume fraction particulate composites
International Nuclear Information System (INIS)
Kwon, P.; Dharan, C.K.H.
1995-01-01
Predictions using current micromechanics theories for the effective moduli of particulate-reinforced composites tend to break down at high volume fractions of the reinforcing phase. The predictions are usually well below experimentally measured values of the Young's modulus for volume fractions exceeding about 0.6. In this paper, the concept of contiguity, which is a measure of phase continuity, is applied to Mori-Tanaka micromechanics theory. It is shown that contiguity of the second phase increases with volume fraction, leading eventually to a reversal in the roles of the inclusion and matrix. In powder metallurgy practice, it is well known that at high volume fractions, sintering and consolidation of the reinforcement make it increasingly continuous and more like the matrix phase, while the former matrix tends to become more like the inclusion phase. The concept of contiguity applied to micromechanics theory results in very good agreement between the predicted Young's modulus and experimental data on tungsten carbide particulate-reinforced cobalt
New holographic dark energy model with constant bulk viscosity in modified f(R,T) gravity theory
Srivastava, Milan; Singh, C. P.
2018-06-01
The aim of this paper is to study new holographic dark energy (HDE) model in modified f(R,T) gravity theory within the framework of a flat Friedmann-Robertson-Walker model with bulk viscous matter content. It is thought that the negative pressure caused by the bulk viscosity can play the role of dark energy component, and drive the accelerating expansion of the universe. This is the motive of this paper to observe such phenomena with bulk viscosity. In the specific model f(R,T)=R+λ T, where R is the Ricci scalar, T the trace of the energy-momentum tensor and λ is a constant, we find the solution for non-viscous and viscous new HDE models. We analyze new HDE model with constant bulk viscosity, ζ =ζ 0= const. to explain the present accelerated expansion of the universe. We classify all possible scenarios (deceleration, acceleration and their transition) with possible positive and negative ranges of λ over the constraint on ζ 0 to analyze the evolution of the universe. We obtain the solutions of scale factor and deceleration parameter, and discuss the evolution of the universe. We observe the future finite-time singularities of type I and III at a finite time under certain constraints on λ . We also investigate the statefinder and Om diagnostics of the viscous new HDE model to discriminate with other existing dark energy models. In late time the viscous new HDE model approaches to Λ CDM model. We also discuss the thermodynamics and entropy of the model and find that it satisfies the second law of thermodynamics.
Simultaneous measurement of field dependence of elastic moduli by laser interferometry
Bayon, A; Salazar, F
2000-01-01
A methodology is applied which allows the simultaneous determination of Young's modulus and the shear modulus to evaluate elastic moduli variations with the magnetic field (DELTA E and DELTA G). The method employed is based on the simultaneous detection of the transverse and torsional natural frequencies of a slender magnetic bar located within a solenoid. The resultant vibration is detected via a heterodyne interferometric optical system with a broad bandwidth. The vibration detection and excitation systems do not interact with the sample. The applicability of the method is demonstrated by characterizing 10-mm-diameter nickel bars. The results are compared with those obtained from longitudinal vibrations.
Dynamics of moduli and gaugino condensates in an expanding universe
International Nuclear Information System (INIS)
Papineau, C.; Ramos-Sanchez, S.; Postma, M.
2009-08-01
We study dynamical moduli stabilization driven by gaugino condensation in supergravity. In the presence of background radiation, there exists a region of initial conditions leading to successful stabilization. We point out that most of the allowed region corresponds to initial Hubble rate H close to the scale of condensation Λ, which is the natural cutoff of the effective theory. We first show that including the condensate dynamics sets a strong bound on the initial conditions. We then find that (complete) decoupling of the condensate happens at H about two orders of magnitude below Λ. This bound implies that in the usual scenario with the condensate integrated out, only the vicinity of the minimum leads to stabilization. Finally, we discuss the effects of thermal corrections. (orig.)
Emergence and expansion of cosmic space as due to M0-branes
Energy Technology Data Exchange (ETDEWEB)
Sepehri, Alireza [Shahid Bahonar University, Faculty of Physics, Kerman (Iran, Islamic Republic of); Research Institute for Astronomy and Astrophysics of Maragha (RIAAM), Maragha (Iran, Islamic Republic of); Setare, Mohammad Reza [University of Kurdistan, Department of Science, Bijar (Iran, Islamic Republic of); Capozziello, Salvatore [Universita di Napoli Federico II, Dipartimento di Fisica, Naples (Italy); Complutense Univ. di Monte S. Angelo, Naples (Italy); Gran Sasso Science Institute (INFN), L' Aquila (Italy); INFN Sezione di Napoli, Naples (Italy)
2015-12-15
Recently, Padmanabhan (arXiv:1206.4916 [hepth]) discussed that the difference between the number of degrees of freedom on the boundary surface and the number of degrees of freedom in a bulk region causes the accelerated expansion of the universe. The main question arising is: what is the origin of this inequality between the surface degrees of freedom and the bulk degrees of freedom? We answer this question in M-theory. In our model, first M0-branes are compactified on one circle and N D0-branes are created. Then N D0-branes join each other, grow, and form one D5-branes. Next, the D5-brane is compactified on two circles and our universe's D3-brane, two D1-branes and some extra energies are produced. After that, one of the D1-branes, which is closer to the universe's brane, gives its energy into it, and this leads to an increase in the difference between the numbers of degrees of freedom and the occurring inflation era. With the disappearance of this D1-brane, the number of degrees of freedom of boundary surface and bulk region become equal and inflation ends. At this stage, extra energies that are produced due to the compactification cause an expansion of the universe and deceleration epoch. Finally, another D1-brane dissolves in our universe's brane, leads to an inequality between degrees of freedom, and there occurs a new phase of acceleration. (orig.)
Moduli dynamics as a predictive tool for thermal maximally supersymmetric Yang-Mills at large N
Energy Technology Data Exchange (ETDEWEB)
Morita, Takeshi [Department of Physics, Shizuoka University,836 Ohya, Suruga-ku, Shizuoka 422-8529 (Japan); Department of Physics and Astronomy, University of Kentucky,Lexington, KY 40506 (United States); Shiba, Shotaro [Maskawa Institute for Science and Culture, Kyoto Sangyo University,Kamigamo-Motoyama, Kita-ku, Kyoto 603-8555 (Japan); Wiseman, Toby [Theoretical Physics Group, Blackett Laboratory, Imperial College,Exhibition Road, London SW7 2AZ (United Kingdom); Withers, Benjamin [Mathematical Sciences and STAG Research Centre, University of Southampton,Highfield, Southampton SO17 1BJ (United Kingdom)
2015-07-09
Maximally supersymmetric (p+1)-dimensional Yang-Mills theory at large N and finite temperature, with possibly compact spatial directions, has a rich phase structure. Strongly coupled phases may have holographic descriptions as black branes in various string duality frames, or there may be no gravity dual. In this paper we provide tools in the gauge theory which give a simple and unified picture of the various strongly coupled phases, and transitions between them. Building on our previous work we consider the effective theory describing the moduli of the gauge theory, which can be computed precisely when it is weakly coupled far out on the Coulomb branch. Whilst for perturbation theory naive extrapolation from weak coupling to strong gives little information, for this moduli theory naive extrapolation from its weakly to its strongly coupled regime appears to encode a surprising amount of information about the various strongly coupled phases. We argue it encodes not only the parametric form of thermodynamic quantities for these strongly coupled phases, but also certain transcendental factors with a geometric origin, and allows one to deduce transitions between the phases. We emphasise it also gives predictions for the behaviour of other observables in these phases.
Moduli dynamics as a predictive tool for thermal maximally supersymmetric Yang-Mills at large N
International Nuclear Information System (INIS)
Morita, Takeshi; Shiba, Shotaro; Wiseman, Toby; Withers, Benjamin
2015-01-01
Maximally supersymmetric (p+1)-dimensional Yang-Mills theory at large N and finite temperature, with possibly compact spatial directions, has a rich phase structure. Strongly coupled phases may have holographic descriptions as black branes in various string duality frames, or there may be no gravity dual. In this paper we provide tools in the gauge theory which give a simple and unified picture of the various strongly coupled phases, and transitions between them. Building on our previous work we consider the effective theory describing the moduli of the gauge theory, which can be computed precisely when it is weakly coupled far out on the Coulomb branch. Whilst for perturbation theory naive extrapolation from weak coupling to strong gives little information, for this moduli theory naive extrapolation from its weakly to its strongly coupled regime appears to encode a surprising amount of information about the various strongly coupled phases. We argue it encodes not only the parametric form of thermodynamic quantities for these strongly coupled phases, but also certain transcendental factors with a geometric origin, and allows one to deduce transitions between the phases. We emphasise it also gives predictions for the behaviour of other observables in these phases.
International Nuclear Information System (INIS)
Asta, M.; Foiles, S.M.; Quong, A.A.
1998-01-01
The configurational thermodynamic properties of fcc-based Al-Sc alloys and coherent Al/Al 3 Sc interphase-boundary interfaces have been calculated from first principles. The computational approach used in this study combines the results of pseudopotential total-energy calculations with a cluster-expansion description of the alloy energetics. Bulk and interface configurational-thermodynamic properties are computed using a low-temperature-expansion technique. Calculated values of the {100} and {111} Al/Al 3 Sc interfacial energies at zero temperature are, respectively, 192 and 226mJ/m 2 . The temperature dependence of the calculated interfacial free energies is found to be very weak for {100} and more appreciable for {111} orientations; the primary effect of configurational disordering at finite temperature is to reduce the degree of crystallographic anisotropy associated with calculated interfacial free energies. The first-principles-computed solid-solubility limits for Sc in bulk fcc Al are found to be underestimated significantly in comparison with experimental measurements. It is argued that this discrepancy can be largely attributed to nonconfigurational contributions to the entropy which have been neglected in the present thermodynamic calculations. copyright 1998 The American Physical Society
Iron phosphate glasses: Bulk properties and atomic scale structure
Energy Technology Data Exchange (ETDEWEB)
Joseph, Kitheri; Stennett, Martin C.; Hyatt, Neil C.; Asuvathraman, R.; Dube, Charu L.; Gandy, Amy S.; Govindan Kutty, K. V.; Jolley, Kenny; Vasudeva Rao, P. R.; Smith, Roger
2017-10-01
Bulk properties such as glass transition temperature, density and thermal expansion of iron phosphate glass compositions, with replacement of Cs by Ba, are investigated as a surrogate for the transmutation of 137Cs to 137Ba, relevant to the immobilisation of Cs in glass. These studies are required to establish the appropriate incorporation rate of 137Cs in iron phosphate glass. Density and glass transition temperature increases with the addition of BaO indicating the shrinkage and reticulation of the iron phosphate glass network. The average thermal expansion coefficient reduces from 19.8 × 10-6 K-1 to 13.4 × 10-6 K-1, when 25 wt. % of Cs2O was replaced by 25 wt. % of BaO in caesium loaded iron phosphate glass. In addition to the above bulk properties, the role of Ba as a network modifier in the structure of iron phosphate glass is examined using various spectroscopic techniques. The FeII content and average coordination number of iron in the glass network was estimated using Mössbauer spectroscopy. The FeII content in the un-doped iron phosphate glass and barium doped iron phosphate glasses was 20, 21 and 22 ± 1% respectively and the average Fe coordination varied from 5.3 ± 0.2 to 5.7 ± 0.2 with increasing Ba content. The atomic scale structure was further probed by Fe K-edge X-ray absorption spectroscopy. The average coordination number provided by extended X-ray absorption fine structure spectroscopy and X-ray absorption near edge structure was in good agreement with that given by the Mössbauer data.
Grain bulk density measurement based on wireless network
Directory of Open Access Journals (Sweden)
Wu Fangming
2017-01-01
Full Text Available To know the accurate quantity of stored grain, grain density sensors must be used to measure the grain’s bulk density. However, multi-sensors should be inserted into the storage facility, to quickly collect data during the inventory checking of stored grain. In this study, the ZigBee and Wi-Fi coexistence network’s ability to transmit data collected by density sensors was investigated. A system consisting of six sensor nodes, six router nodes, one gateway and one Android Pad was assembled to measure the grain’s bulk density and calculate its quantity. The CC2530 chip with ZigBee technology was considered as the core of the information processing, and wireless nodes detection in sensor, and router nodes. ZigBee worked in difference signal channel with Wi-Fi to avoid interferences and connected with Wi-Fi module by UART serial communications interfaces in gateway. The Android Pad received the measured data through the gateway and processed this data to calculate quantity. The system enabled multi-point and real-time parameter detection inside the grain storage. Results show that the system has characteristics of good expansibility, networking flexibility and convenience.
feet of the uppermost Kayenta sandstone unit at the Mixed Company site, for which the in situ elastic moduli are determined to be as follows: C11...and plastic anisotropic properties of Kayenta sandstone from the Mixed Company site are in poor agreement with newly generated data. (Author)
Czech Academy of Sciences Publication Activity Database
Poživilová, Alena; Plešek, Jiří
2005-01-01
Roč. 482, č. 482 (2005), s. 327-330 ISSN 0255-5476 R&D Projects: GA ČR(CZ) GA101/03/0331; GA ČR(CZ) GP106/03/D038 Institutional research plan: CEZ:AV0Z20760514 Keywords : acoustoelasticity * large strains * third order elastic moduli Subject RIV: JG - Metallurgy Impact factor: 0.399, year: 2005
International Nuclear Information System (INIS)
Zhou Mu; Wang Feng; Zheng Zhou; Liu Xiankun; Jiang Tao
2013-01-01
The elastic and thermodynamic properties of UO 2 under extreme physical condition are studied by using the density functional theory and quasi-harmonic Debye model. Results show that UO 2 is still stable ionic crystal under high temperatures, and pressures. Tetragonal shear constant is steady under high pressures and temperatures, while elastic constant C 44 is stable under high temperatures, but rises with pressure sharply. Bulk modulus, shear modulus and Young's modulus increase with pressure rapidly, but temperature would not cause evident debasement of the moduli, all of which indicate that UO 2 has excellent mechanical properties. Heat capacity of different pressures increases with temperature and is close to the Dulong-Petit limit near 1000 K. Debye temperature decreases with temperature, and increases with pressure. Under low pressure, thermal expansion coefficient raises with temperature rapidly, and then gets slow at higher pressure and temperature. Besides, the thermal expansion coefficient of UO 2 is much lower than that of other nuclear materials. (authors)
Løken, Andreas; Haugsrud, Reidar; Bjørheim, Tor S
2016-11-16
Differentiating chemical and thermal expansion is virtually impossible to achieve experimentally. While thermal expansion stems from a softening of the phonon spectra, chemical expansion depends on the chemical composition of the material. In the present contribution, we, for the first time, completely decouple thermal and chemical expansion through first principles phonon calculations on BaCeO 3 , providing new fundamental insights to lattice expansion. We assess the influence of defects on thermal expansion, and how this in turn affects the interpretation of chemical expansion and defect thermodynamics. The calculations reveal that the linear thermal expansion coefficient is lowered by the introduction of oxygen vacancies being 10.6 × 10 -6 K -1 at 300 K relative to 12.2 × 10 -6 K -1 for both the protonated and defect-free bulk lattice. We further demonstrate that the chemical expansion coefficient upon hydration varies with temperature, ranging from 0.070 to 0.115 per mole oxygen vacancy. Ultimately, we find that, due to differences in the thermal expansion coefficients under dry and wet conditions, the chemical expansion coefficients determined experimentally are grossly underestimated - around 55% lower in the case of 10 mol% acceptor doped BaCeO 3 . Lastly, we evaluate the effect of these volume changes on the vibrational thermodynamics.
Models for the brane-bulk interaction: Toward understanding braneworld cosmological perturbations
Binétruy, Pierre; Bucher, Martin; Carvalho, Carla
2004-08-01
Using some simple toy models, we explore the nature of the brane-bulk interaction for cosmological models with a large extra dimension. We are in particular interested in understanding the role of the bulk gravitons, which from the point of view of an observer on the brane will appear to generate dissipation and nonlocality, effects that cannot be incorporated into an effective (3+1)-dimensional Lagrangian field theoretic description. We explicitly work out the dynamics of several discrete systems consisting of a finite number of degrees of freedom on the boundary coupled to a (1+1)-dimensional field theory subject to a variety of wave equations. Systems both with and without time translation invariance are considered and moving boundaries are discussed as well. The models considered contain all the qualitative features of quantized linearized cosmological perturbations for a Randall-Sundrum universe having an arbitrary expansion history, with the sole exception of gravitational gauge invariance, which will be treated in a later paper.
Gandhi, Saurabh; Yurtsev, Eugene; Korolev, Kirill; Gore, Jeff
Range expansions are becoming more frequent due to environmental changes and rare long distance dispersal, often facilitated by anthropogenic activities. Simple models in theoretical ecology explain many emergent properties of range expansions, such as a constant expansion velocity, in terms of organism-level properties such as growth and dispersal rates. Testing these quantitative predictions in natural populations is difficult because of large environmental variability. Here, we used a controlled microbial model system to study range expansions of populations with and without intra-specific cooperativity. For non-cooperative growth, the expansion dynamics were dominated by population growth at the low-density front, which pulled the expansion forward. We found these expansions to be in close quantitative agreement with the classical theory of pulled waves by Fisher and Skellam, suitably adapted to our experimental system. However, as cooperativity increased, the expansions transitioned to being pushed, i.e. controlled by growth in the bulk as well as in the front. Although both pulled and pushed waves expand at a constant velocity and appear otherwise similar, their distinct dynamics leads to very different evolutionary consequences. Given the prevalence of cooperative growth in nature, understanding the effects of cooperativity is essential to managing invading species and understanding their evolution.
Exploring Lovelock theory moduli space for Schrödinger solutions
Directory of Open Access Journals (Sweden)
Dileep P. Jatkar
2016-09-01
Full Text Available We look for Schrödinger solutions in Lovelock gravity in D>4. We span the entire parameter space and determine parametric relations under which the Schrödinger solution exists. We find that in arbitrary dimensions pure Lovelock theories have Schrödinger solutions of arbitrary radius, on a co-dimension one locus in the Lovelock parameter space. This co-dimension one locus contains the subspace over which the Lovelock gravity can be written in the Chern–Simons form. Schrödinger solutions do not exist outside this locus and on this locus they exist for arbitrary dynamical exponent z. This freedom in z is due to the degeneracy in the configuration space. We show that this degeneracy survives certain deformation away from the Lovelock moduli space.
Exploring Lovelock theory moduli space for Schrödinger solutions
Jatkar, Dileep P.; Kundu, Nilay
2016-09-01
We look for Schrödinger solutions in Lovelock gravity in D > 4. We span the entire parameter space and determine parametric relations under which the Schrödinger solution exists. We find that in arbitrary dimensions pure Lovelock theories have Schrödinger solutions of arbitrary radius, on a co-dimension one locus in the Lovelock parameter space. This co-dimension one locus contains the subspace over which the Lovelock gravity can be written in the Chern-Simons form. Schrödinger solutions do not exist outside this locus and on this locus they exist for arbitrary dynamical exponent z. This freedom in z is due to the degeneracy in the configuration space. We show that this degeneracy survives certain deformation away from the Lovelock moduli space.
Fujishiro, H.; Takahashi, K.; Naito, T.; Yanagi, Y.; Itoh, Y.; Nakamura, T.
2018-07-01
We have proposed new reinforcement structures using an aluminum alloy ring to the annular REBaCuO bulks applicable to compact and cryogen-free 400 MHz (9.4 T) nuclear magnetic resonance (NMR) spectrometer using a numerical simulation of mechanical stress. The thermal compressive stress, σθcool, which was applied to the annular bulks during cooling due to the difference of thermal expansion coefficient between bulk and aluminum alloy, became fairly enhanced at the surface of the uppermost bulk for the new reinforcement structures, compared to the conventional reinforcement with the same height as the annular bulk, in which the compressive σθcool value was reduced. During field-cooled magnetization (FCM), the electromagnetic hoop stress, σθFCM, became the maximum at the innermost edge of the uppermost ring bulk at intermediate time step. The actual total hoop stress, σθ (= σθcool + σθFCM), due to both cooling and FCM processes was also analyzed and the new ring structures are fairly effective to reduce the σθ value and became lower than the fracture strength of the bulk. The new reinforcement structures have a possibility to avoid the fracture of the bulks and to realize a 400 MHz NMR spectrometer.
U(N) instantons on N=(1/2) superspace: Exact solution and geometry of moduli space
International Nuclear Information System (INIS)
Britto, Ruth; Feng Bo; Lunin, Oleg; Rey, Soo-Jong
2004-01-01
We construct the exact solution of one (anti-)instanton in N=(1/2) super Yang-Mills theory defined on non(anti-)commutative superspace. We first identify N=(1/2) superconformal invariance as maximal spacetime symmetry. For the gauge group U(2), the SU(2) part of the solution is given by the standard (anti-)instanton, but the U(1) field strength also turns out to be nonzero. The solution is SO(4) rotationally symmetric. For the gauge group U(N), in contrast with the U(2) case, we show that the entire U(N) part of the solution is deformed by non(anti-)commutativity and fermion zero modes. The solution is no longer rotationally symmetric; it is polarized into an axially symmetric configuration because of the underlying non(anti-)commutativity. We compute the 'information metric' of one (anti-)instanton. We find that the moduli space geometry is deformed from the hyperbolic space H 5 (Euclidean anti-de Sitter space) in a way anticipated from reduced spacetime symmetry. Remarkably, the volume measure of the moduli space turns out to be independent of the non(anti-)commutativity. Implications for D branes in the Ramond-Ramond flux background and the gauge-gravity correspondence are discussed
Thermal expansion properties of Bi-2212 in Ag or an Ag-alloy matrix
International Nuclear Information System (INIS)
Tenbrink, J.; Krauth, H.
1994-01-01
The thermal expansion properties of polycrystalline Bi 2 Sr 2 Ca 1 Cu 2 O 8+x melt-processed bulk specimens, and Bi 2 Sr 2 Ca 1 Cu 2 O 8+x monocore as well as multifilamentary round wires in Ag or Ag-alloy matrix have been investigated over the temperature range from -150 to 800 degrees C. Although the thermal expansion of Bi 2 Sr 2 Ca 1 Cu 2 O 8+x is distinctly lower compared with Ag, the thermal expansion properties of the Bi 2 Sr 2 Ca 1 Cu 2 O 8+x -Ag or AgNiMg-alloy composite conductors are essentially governed by the matrix material. The thermal expansion of the encountered oxide-dispersion-strengthened AgNiMg alloys is only slightly lower compared with that of pure Ag. Therefore the thermal expansion of all investigated Bi 2 Sr 2 Ca 1 Cu 2 O 8+x -Ag or Ag-alloy composite wires was found to be close to that of pure Ag. The reason for this striking behaviour is shown to be related to a surprisingly low elastic modulus of the polycrystalline Bi-2212 wire cores of the order of 10 to a maximum 40 GPa. (author)
Mapping Thermal Expansion Coefficients in Freestanding 2D Materials at the Nanometer Scale
Hu, Xuan; Yasaei, Poya; Jokisaari, Jacob; Öǧüt, Serdar; Salehi-Khojin, Amin; Klie, Robert F.
2018-02-01
Two-dimensional materials, including graphene, transition metal dichalcogenides and their heterostructures, exhibit great potential for a variety of applications, such as transistors, spintronics, and photovoltaics. While the miniaturization offers remarkable improvements in electrical performance, heat dissipation and thermal mismatch can be a problem in designing electronic devices based on two-dimensional materials. Quantifying the thermal expansion coefficient of 2D materials requires temperature measurements at nanometer scale. Here, we introduce a novel nanometer-scale thermometry approach to measure temperature and quantify the thermal expansion coefficients in 2D materials based on scanning transmission electron microscopy combined with electron energy-loss spectroscopy to determine the energy shift of the plasmon resonance peak of 2D materials as a function of sample temperature. By combining these measurements with first-principles modeling, the thermal expansion coefficients (TECs) of single-layer and freestanding graphene and bulk, as well as monolayer MoS2 , MoSe2 , WS2 , or WSe2 , are directly determined and mapped.
MPL-A program for computations with iterated integrals on moduli spaces of curves of genus zero
Bogner, Christian
2016-06-01
We introduce the Maple program MPL for computations with multiple polylogarithms. The program is based on homotopy invariant iterated integrals on moduli spaces M0,n of curves of genus 0 with n ordered marked points. It includes the symbol map and procedures for the analytic computation of period integrals on M0,n. It supports the automated computation of a certain class of Feynman integrals.
Structural and thermomechanical properties of the zinc-blende AlX (X = P, As, Sb) compounds
Ha, Vu Thi Thanh; Hung, Vu Van; Hanh, Pham Thi Minh; Nguyen, Viet Tuyen; Hieu, Ho Khac
2017-08-01
The structural and thermomechanical properties of zinc-blende aluminum class of III-V compounds have been studied based on the statistical moment method (SMM) in quantum statistical mechanics. Within the SMM scheme, we derived the analytical expressions of the nearest-neighbor distance, thermal expansion coefficient, atomic mean-square displacement and elastic moduli (Young’s modulus, bulk modulus and shear modulus). Numerical calculations have been performed for zinc-blende AlX (X = As, P, Sb) at ambient conditions up to the temperature of 1000 K. Our results are in good and reasonable agreements with earlier measurements and can provide useful references for future experimental and theoretical works. This research presents a systematic approach to investigate the thermodynamic and mechanical properties of materials.
Liu, Gang; Zhou, Jian; Wang, Hui
2017-06-14
Based on Grüneisen's theory, the elastic properties and thermal expansion of bulk SnSe with the Pnma phase are investigated by using first-principles calculations. Our numerical results indicate that the linear thermal expansion coefficient along the a direction is smaller than the one along the b direction, while the one along the c direction shows a significant negative value, even at high temperature. The numerical results are in good accordance with experimental results. In addition, generalized and macroscopic Grüneisen parameters are also presented. It is also found that SnSe possesses negative Possion's ratio. The contributions of different phonon modes to NTE along the c direction are investigated, and it is found that the two modes which make the most important contributions to NTE are transverse vibrations perpendicular to the c direction. Finally, we analyze the relation of elastic constants to negative thermal expansion, and demonstrate that negative thermal expansion can also occur even with all positive macroscopic Grüneisen parameters.
Bogan, Sam
2001-01-01
The first year included a study of the non-visible damage of composite overwrapped pressure vessels with B. Poe of the Materials Branch of Nasa-Langley. Early determinations showed a clear reduction in non-visible damage for thin COPVs when partially pressurized rather than unpressurized. Literature searches on Thicker-wall COPVs revealed surface damage but clearly visible. Analysis of current Analytic modeling indicated that that current COPV models lacked sufficient thickness corrections to predict impact damage. After a comprehensive study of available published data and numerous numerical studies based on observed data from Langley, the analytic framework for modeling the behavior was determined lacking and both Poe and Bogan suggested any short term (3yr) result for Jove would be overly ambitious and emphasis should be placed on transverse shear moduli studies. Transverse shear moduli determination is relevant to the study of fatigue, fracture and aging effects in composite structures. Based on the techniques developed by Daniel & Tsai, Bogan and Gates determined to verify the results for K3B and 8320. A detailed analytic and experimental plan was established and carried out that included variations in layup, width, thickness, and length. As well as loading rate variations to determine effects and relaxation moduli. The additional axial loads during the torsion testing were studied as was the placement of gages along the composite specimen. Of the proposed tasks, all of tasks I and 2 were completed with presentations given at Langley, SEM conferences and ASME/AIAA conferences. Sensitivity issues with the technique associated with the use of servohydraulic test systems for applying the torsional load to the composite specimen limited the torsion range for predictable and repeatable transverse shear properties. Bogan and Gates determined to diverge on research efforts with Gates continuing the experimental testing at Langley and Bogan modeling the apparent non
Mechanical reliability of bulk high Tc superconductors
International Nuclear Information System (INIS)
Freiman, S.W.
1990-01-01
Most prospective applications for high T c superconductors in bulk form, e.g. magnets, motors, will require appreciable mechanical strength. Work at NIST [National Institute of Standards and Technology] has begun to address issues related to mechanical reliability. For example, recent studies on Ba-Y-Cu-O have shown that the intrinsic crack growth resistance, K IC , of crystals of this material is even smaller than was first reported, less than that of window glass, and is sensitive to moisture. Processing conditions, particularly sintering and annealing atmosphere, have been shown to have a major influence on microstructure and internal stresses in the material. Large internal stresses result from the tetragonal to orthorhombic phase transformation as well as the thermal expansion anisotropy in the grains of the ceramic. Because stress relief is absent, microcracks form which have a profound influence on strength
A proof that Witten's open string theory gives a single cover of moduli space
International Nuclear Information System (INIS)
Zwiebach, B.; Massachusetts Inst. of Tech., Cambridge
1991-01-01
We show that Witten's open string diagrams are surfaces with metrics of minimal area under the condition that all nontrivial open Jordan curves be longer or equal to π. The minimal area property is used together with a mini-max problem to establish a new existence and uniqueness theorem for quadratic differentials in open Riemann surfaces with or without punctures on the boundaries. This theorem implies that the Feynman rules of open string theory give a single cover of the moduli of open Riemann surfaces. (orig.)
International Nuclear Information System (INIS)
Gough, N.
1993-01-01
The Institute Bulk Oil Clauses produced by the London market and the American SP-13c Clauses are examined in detail in this article. The duration and perils covered are discussed, and exclusions, adjustment clause 15 of the Institute Bulk Oil Clauses, Institute War Clauses (Cargo), and Institute Strikes Clauses (Bulk Oil) are outlined. (UK)
Thermal diffusivity of samarium-gadolinium zirconate solid solutions
International Nuclear Information System (INIS)
Pan, W.; Wan, C.L.; Xu, Q.; Wang, J.D.; Qu, Z.X.
2007-01-01
We synthesized samarium-gadolinium zirconate solid solutions and determined their thermal diffusivities, Young's moduli and thermal expansion coefficients, which are very important for their application in thermal barrier coatings. Samarium-gadolinium zirconate solid solutions have extremely low thermal diffusivity between 20 and 600 deg. C. The solid solutions have lower Young's moduli and higher thermal expansion coefficients than those of pure samarium and gadolinium zirconates. This combination of characteristics is promising for the application of samarium and gadolinium zirconates in gas turbines. The mechanism of phonon scattering by point defects is discussed
Yuan, J. H.; Shi, Y.; Pharr, M.; Feng, X.; Rogers, John A.; Huang, Yonggang
2016-01-01
A mechanics model is developed for the encapsulated piezoelectric thin-film actuators/sensors system imperfectly bonded to the human skin to simultaneously determine the Young's moduli of the epidermis and dermis as well as the thickness of epidermis. PMID:27330219
DEFF Research Database (Denmark)
Benetti, Ana Raquel; Havndrup-Pedersen, Cæcilie; Honoré, Daniel
2015-01-01
the restorative procedure. The aim of this study, therefore, was to compare the depth of cure, polymerization contraction, and gap formation in bulk-fill resin composites with those of a conventional resin composite. To achieve this, the depth of cure was assessed in accordance with the International Organization...... for Standardization 4049 standard, and the polymerization contraction was determined using the bonded-disc method. The gap formation was measured at the dentin margin of Class II cavities. Five bulk-fill resin composites were investigated: two high-viscosity (Tetric EvoCeram Bulk Fill, SonicFill) and three low......-viscosity (x-tra base, Venus Bulk Fill, SDR) materials. Compared with the conventional resin composite, the high-viscosity bulk-fill materials exhibited only a small increase (but significant for Tetric EvoCeram Bulk Fill) in depth of cure and polymerization contraction, whereas the low-viscosity bulk...
Effect of graphene nanoplatelets on coefficient of thermal expansion of polyetherimide composite
International Nuclear Information System (INIS)
Wu, Huang; Drzal, Lawrence T.
2014-01-01
Thermal expansion is one of the major concerns for polymer composites. In this research, graphene nanoplatelets (GNPs) were added to polyetherimide (PEId) thermoplastic polymer in order to reduce the coefficient of thermal expansion (CTE) of the injection molded composite. First, the coefficient of linear thermal expansion (LTE) was measured in three directions in the anisotropic coupon: 0°, 90° and the out of plane Z direction. It is found that the GNP particles are very effective in terms of reducing the LTE in 0° direction due to high degree of alignment. After annealing above glass transition temperature, significant increase of 0° LTE and decrease of Z° LTE were observed. The bulk CTE was calculated by adding up the LTEs in all three directions and is found to be independent of annealing. Second, several models were applied to predict both CTE and LTE. It is found that Schapery's lower limit model fits the experimental CTE very well. Chow's model was applied for LTEs in three directions. The behavior of GNP-5/PEId composites is explained by the combination of Chow's model and morphology obtained by scanning electron microscope (SEM). - Highlights: • Coefficient of thermal expansion (CTE) of polymer composite is characterized. • Reduction of linear thermal expansion depends on filler orientation. • Filler orientation is characterized based on the location of the specimen. • Filler orientation is changed by annealing, causing subsequent change in CTE. • CTE and linear thermal expansion coefficient are modeled
Quantum triangulations. Moduli spaces, strings, and quantum computing
Energy Technology Data Exchange (ETDEWEB)
Carfora, Mauro; Marzouli, Annalisa [Univ. degli Studi di Pavia (Italy). Dipt. Fisica Nucleare e Teorica; Istituto Nazionale di Fisica Nucleare e Teorica, Pavia (Italy)
2012-07-01
Research on polyhedral manifolds often points to unexpected connections between very distinct aspects of Mathematics and Physics. In particular triangulated manifolds play quite a distinguished role in such settings as Riemann moduli space theory, strings and quantum gravity, topological quantum field theory, condensed matter physics, and critical phenomena. Not only do they provide a natural discrete analogue to the smooth manifolds on which physical theories are typically formulated, but their appearance is rather often a consequence of an underlying structure which naturally calls into play non-trivial aspects of representation theory, of complex analysis and topology in a way which makes manifest the basic geometric structures of the physical interactions involved. Yet, in most of the existing literature, triangulated manifolds are still merely viewed as a convenient discretization of a given physical theory to make it more amenable for numerical treatment. The motivation for these lectures notes is thus to provide an approachable introduction to this topic, emphasizing the conceptual aspects, and probing, through a set of cases studies, the connection between triangulated manifolds and quantum physics to the deepest. This volume addresses applied mathematicians and theoretical physicists working in the field of quantum geometry and its applications. (orig.)
Directory of Open Access Journals (Sweden)
Basilios Tsikouras
2016-08-01
Full Text Available Representative perlite bulk rock samples from two areas of Milos Island, Greece were collected and the expansion properties of their industrial product were investigated. Coarse crude perlite from Tsigrado exhibits better expansibility, which is assigned to the presence of coarser crystallites in its bulk parent rock. During thermal treatment, the finer crystallites of the coarse crude perlite from Trachilas are entrapped in the groundmass and lead to overheating, which inhibits expansion and eventually results in shrinkage. Geochemical modification of the expanded perlites relative to their crude precursors were investigated, using the isocon method. Volatilisation of crystalline water is the main factor controlling mass reduction of the expanded perlites. Other elements, during the adequate expansion of the Tsigrado perlite, can be classified into three categories. The elements that participate preferentially in crystals decrease in the expanded material at amounts higher than the total mass loss of the rock, due to their escape controlled mainly by the removal of the crystalline phases. The elements equally participating in crystals and the groundmass show losses equivalent to the total mass loss of the rocks, as they escaped in the crystalline phases and airborne particles from the groundmass during thermal treatment. Decrease of highly incompatible elements, which mostly participate in the groundmass, in the expanded products is less than the total mass loss, as they escaped mainly in the airborne particles. The inadequate expansion and burst of the Trachilas perlite did not allow for a similar categorisation, due to random and unpredictable escape of the elements. We propose the application of this method to an artificial system to predict unexpandable mineral phases in bulk perlite, as well as elements that are most likely to participate in the amorphous perlite phase, which cannot be determined from a regular industrial production line
Instanton transition in thermal and moduli deformed de Sitter cosmology
International Nuclear Information System (INIS)
Kounnas, Costas; Partouche, Herve
2008-01-01
We consider the de Sitter cosmology deformed by the presence of a thermal bath of radiation and/or time-dependent moduli fields. Depending on the parameters, either a first or second-order phase transition can occur. In the first case, an instanton allows a double analytic continuation. It induces a probability to enter the inflationary evolution by tunnel effect from another cosmological solution. The latter starts with a big bang and, in the case the transition does not occur, ends with a big crunch. A temperature duality exchanges the two cosmological branches. In the limit where the pure de Sitter universe is recovered, the tunnel effect reduces to a 'creation from nothing', due to the vanishing of the big bang branch. However, the latter may be viable in some range of the deformation parameter. In the second case, there is a smooth evolution from a big bang to the inflationary phase
Interface effects on effective elastic moduli of nanocrystalline materials
International Nuclear Information System (INIS)
Wang Gangfeng; Feng Xiqiao; Yu Shouwen; Nan Cewen
2003-01-01
Interfaces often play a significant role in many physical properties and phenomena of nanocrystalline materials (NcMs). In the present paper, the interface effects on the effective elastic property of NcMs are investigated. First, an atomic potential method is suggested for estimating the effective elastic modulus of an interface phase. Then, the Mori-Tanaka effective field method is employed to determine the overall effective elastic moduli of a nanocrystalline material, which is regarded as a binary composite consisting of a crystal or inclusion phase with regular lattice connected by an amorphous-like interface or matrix phase. Finally, the stiffening effects of strain gradients are examined on the effective elastic property by using the strain gradient theory to analyze a representative unit cell. Our analysis shows two physical mechanisms of interfaces that influence the effective stiffness and other mechanical properties of materials. One is the softening effect due to the distorted atomic structures and the increased atomic spacings in interface regions, and another is the baffling effect due to the existence of boundary layers between the interface phase and the crystalline phase
Nonlinear elastic properties of bulk metallic glasses Zr52.5Ti5Cu17.9Ni14.6Al10 and Pd40Cu30Ni10P20
International Nuclear Information System (INIS)
Kobelev, N.P.; Kolyvanov, E.L.; Khonik, V.A.
2005-01-01
The influence of uniaxial compression on the propagation of ultrasonic vibrations in Zr 52.5 Ti 5 Cu 17.9 Ni 14.6 Al 10 and Pd 40 Cu 30 Ni 10 P 20 bulk metallic glasses produced by melt quenching at a rate of 100 K/s is investigated. Elastic deformation was realized by compression of the samples along their long axis up to strains of about 1 GPa. Deriving of major ratios used during the calculation of the third-order elastic moduli of the glasses is described in brief, the results of the calculations being provided. A qualitative agreement between the calculated results and available data on the influence of the uniform pressure on the sound wave propagation rate was obtained [ru
Atomistic Calculation of Elastic Moduli in Strained Silicon
National Research Council Canada - National Science Library
Zhu, Richard; Pan, Ernian; Chung, Peter W; Cai, Xinli; Liew, Kim M; Buldum, Alper
2007-01-01
.... Using our approach, the bulk modulus, effective elastic stiffnesses C11, C12, and C44 of the strained silicon, including also the effective Young's modulus and Poisson's ratio, are all calculated...
Nanopatterned bulk metallic glass-based biomaterials modulate macrophage polarization.
Shayan, Mahdis; Padmanabhan, Jagannath; Morris, Aaron H; Cheung, Bettina; Smith, Ryan; Schroers, Jan; Kyriakides, Themis R
2018-06-01
Polarization of macrophages by chemical, topographical and mechanical cues presents a robust strategy for designing immunomodulatory biomaterials. Here, we studied the ability of nanopatterned bulk metallic glasses (BMGs), a new class of metallic biomaterials, to modulate murine macrophage polarization. Cytokine/chemokine analysis of IL-4 or IFNγ/LPS-stimulated macrophages showed that the secretion of TNF-α, IL-1α, IL-12, CCL-2 and CXCL1 was significantly reduced after 24-hour culture on BMGs with 55 nm nanorod arrays (BMG-55). Additionally, under these conditions, macrophages increased phagocytic potential and exhibited decreased cell area with multiple actin protrusions. These in vitro findings suggest that nanopatterning can modulate biochemical cues such as IFNγ/LPS. In vivo evaluation of the subcutaneous host response at 2 weeks demonstrated that the ratio of Arg-1 to iNOS increased in macrophages adjacent to BMG-55 implants, suggesting modulation of polarization. In addition, macrophage fusion and fibrous capsule thickness decreased and the number and size of blood vessels increased, which is consistent with changes in macrophage responses. Our study demonstrates that nanopatterning of BMG implants is a promising technique to selectively polarize macrophages to modulate the immune response, and also presents an effective tool to study mechanisms of macrophage polarization and function. Implanted biomaterials elicit a complex series of tissue and cellular responses, termed the foreign body response (FBR), that can be influenced by the polarization state of macrophages. Surface topography can influence polarization, which is broadly characterized as either inflammatory or repair-like. The latter has been linked to improved outcomes of the FBR. However, the impact of topography on macrophage polarization is not fully understood, in part, due to a lack of high moduli biomaterials that can be reproducibly processed at the nanoscale. Here, we studied
Ab initio modelling of methane hydrate thermophysical properties.
Jendi, Z M; Servio, P; Rey, A D
2016-04-21
The key thermophysical properties of methane hydrate were determined using ab initio modelling. Using density functional theory, the second-order elastic constants, heat capacity, compressibility, and thermal expansion coefficient were calculated. A wide and relevant range of pressure-temperature conditions were considered, and the structures were assessed for stability using the mean square displacement and radial distribution functions. Methane hydrate was found to be elastically isotropic with a linear dependence of the bulk modulus on pressure. Equally significant, multi-body interactions were found to be important in hydrates, and water-water interactions appear to strongly influence compressibility like in ice Ih. While the heat capacity of hydrate was found to be higher than that of ice, the thermal expansion coefficient was significantly lower, most likely due to the lower rigidity of hydrates. The mean square displacement gave important insight into stability, heat capacity, and elastic moduli, and the radial distribution functions further confirmed stability. The presented results provide a much needed atomistic thermoelastic characterization of methane hydrates and are essential input for the large-scale applications of hydrate detection and production.
Interplay between bulk medium evolution and (D)GLV energy loss
International Nuclear Information System (INIS)
Molnar, Denes; Sun, Deke
2014-01-01
We study the consistency between high-p T nuclear suppression (R AA ) and elliptic flow (v 2 ) using Gyulassy–Levai–Vitev (GLV) energy loss or a simpler power-law dE/dL formula, for a variety of bulk evolution models. The results generally confirm our earlier work [1] that found suppressed elliptic flow for transversely expanding media. One exception is the set of hydrodynamic solutions used recently [2] by Betz and Gyulassy, which give significantly higher v 2 but unfortunately assume unrealistic bag-model equation of state. On the other hand, we show that covariant treatment of energy loss introduces an interplay between jet direction and hydrodynamic flow of the medium, which largely counteracts elliptic flow suppression caused by transverse expansion
Cramer, Ashley D; Dong, Wen-Fei; Benbow, Natalie L; Webber, Jessie L; Krasowska, Marta; Beattie, David A; Ferri, James K
2017-09-13
We studied the interfacial mechanical properties of polyelectrolyte multilayer assemblies of poly(diallylamine hydrochloride) (PAH) and poly(4-styrenesulfonate)sodium salt (PSS) at the air-water interface using axisymmetric drop shape analysis (ADSA) during hydrostatic inflation as a function of aqueous salt concentration and two different polyanion molecular weights (M w ∼ 13 and 70 kDa). Surface elastic moduli (G s ) ranged from 50 to 300 mN m -1 . Using the measured film thickness, the bulk moduli (G) ranged from 10 to 90 MPa consistent with elastomeric solids. This solid-like interface was evidenced by a systematic departure of the inflated shape from the Young-Laplace equation, which assumes a liquid-like interface. Surface elastic moduli increased and bulk elastic moduli decreased with increasing nanomembrane transverse dimension, and multilayers with the lower molecular weight anion were more transversely compact than those of higher molecular weight and displayed a larger elastic modulus. The bulk moduli of both types of multilayer assemblies asymptotically approach a constant value for films with more than two bilayers of polyelectrolyte, consistent with the observed transition from a 'glassy' to 'rubbery' state. Both types of multilayer assemblies displayed plasticization with increasing sodium chloride concentration in the adjoining aqueous phase, i.e. saloplasticity, and exhibited a transition from elastic to plastic response to deformation. The restored mobility of the polyelectrolyte resulting from the shift from intrinsic to extrinsic charge complexation, restores fluidity to the interface and is evidenced by experimental observation of a liquid-like interface when loaded. The higher molecular weight polyanion multilayers plasticized at lower salt concentrations suggesting that the lower melting point of the higher molecular weight polyanion assembly is attributable to a lesser extent of electrostatic cross-linking underscoring the unconventional
DEFF Research Database (Denmark)
Sørensen, Morten Kanne; Fabricius, Ida Lykke
2017-01-01
The elastic bulk modulus of a sandstone is affected by the fluid saturation as compression induces a pressure in the fluid thus increasing the bulk modulus of the sandstone as a whole. Assuming a uniform induced pressure and no interaction between the saturating fluid and the solid rock the fluid...... contribution to the elastic bulk modulus is quantified by Gassmann's equations. Experimental measurements of the fluid contribution to the elastic moduli are, however often much larger than predicted within the assumptions of Gassmann. Clay-rich low-mobility sandstones are especially prone to having elastic...... moduli highly sensitive to the fluid saturation. The presence of clay in a sandstone can affect two of the underlying assumptions to Gassmann's equations: decreased fluid mobility can cause pressure gradients and fluid-clay interactions are common. The elastic and petrophysical properties of clay...
International Nuclear Information System (INIS)
Ansari, R.; Ajori, S.; Rouhi, S.
2016-01-01
Synthesizing polyphenylene polymer, a two-dimensional hydrocarbon known as porous graphene, has led to the initiation of a new age in nanoscience. In this investigation, molecular dynamics (MD) simulations are carried out to study the mechanical properties of porous graphene such as Young's modulus, Poisson's ratio, bulk modulus and ultimate strength and strain. The fracture initiation and propagation pattern of porous graphene are also considered in this study. The results show that Young's and bulk moduli of porous graphene are lower than those of graphene, graphene and graphyne. Unlikely, it is also observed that its Poisson's ratio is considerably more than that of graphene, graphene and graphyne. Furthermore, it is found out that Young's and bulk moduli as well as fracture strain and ultimate stress are extremely size-dependent and also the porous graphene can be considered as an isotropic material.
Wu, H. I.; Spence, R. D.; Sharpe, P. J.; Goeschl, J. D.
1985-01-01
The traditional bulk elastic modulus approach to plant cell pressure-volume relations is inconsistent with its definition. The relationship between the bulk modulus and Young's modulus that forms the basis of their usual application to cell pressure-volume properties is demonstrated to be physically meaningless. The bulk modulus describes stress/strain relations of solid, homogeneous bodies undergoing small deformations, whereas the plant cell is best described as a thin-shelled, fluid-filled structure with a polymer base. Because cell walls possess a polymer structure, an alternative method of mechanical analysis is presented using polymer elasticity principles. This initial study presents the groundwork of polymer mechanics as would be applied to cell walls and discusses how the matrix and microfibrillar network induce nonlinear stress/strain relationships in the cell wall in response to turgor pressure. In subsequent studies, these concepts will be expanded to include anisotropic expansion as regulated by the microfibrillar network.
Energy Technology Data Exchange (ETDEWEB)
Subramanian, Raju, E-mail: sraju@igcar.gov.in [Metallurgy & Materials Group, Indira Gandhi Centre for Atomic Research (IGCAR), Kalpakkam 603102 (India); Tripathy, Haraprasanna; Rai, Arun Kumar; Hajra, Raj Narayan; Saibaba, Saroja; Jayakumar, Tammana [Metallurgy & Materials Group, Indira Gandhi Centre for Atomic Research (IGCAR), Kalpakkam 603102 (India); Rajendra Kumar, Ellappan [TBM Division, Institute for Plasma Research (IPR), Gandhi Nagar (India)
2015-04-15
Highlights: • Lattice & bulk thermal expansion of RAFM steel characterized by HTXRD and dilatometry. • Mean thermal expansion of α-ferrite is 1.48 × 10{sup −5} K{sup −1}; that of γ-austenite, 2.4 × 10{sup −5} K{sup −1}. • Magnetism makes a small negative contribution to overall thermal expansion. - Abstract: The lattice and bulk thermal expansion behavior of an Indian version of reduced activation ferritic–martensitic (INRAFM) steel has been quantified using high temperature X-ray diffraction and dilatometry. The lattice parameter of tempered α-ferrite phase exhibited a smooth quadratic increase with temperature, while that of γ-austenite remained fairly linear up to 1273 K. The results suggest that α-ferrite + Carbides → γ-austenite transformation occurs upon continuous heating in the temperature range, 1146 ⩽ T ⩽ 1173 K. Further, this transformation is found to be accompanied by a reduction in average atomic volume. The mean linear thermal expansion coefficients of tempered α-ferrite and γ-austenite phases are estimated to be about 1.48 × 10{sup −5} and 2.4 × 10{sup −5} K{sup −1} respectively. The magnetic contribution to relative thermal dilatation (Δl/l{sub 298}){sub mag} is found to be small and negative, as compared to phonon contribution.
Atomic Resolution Imaging of Nanoscale Chemical Expansion in PrxCe1-xO2-δ during In Situ Heating.
Swallow, Jessica G; Lee, Ja Kyung; Defferriere, Thomas; Hughes, Gareth M; Raja, Shilpa N; Tuller, Harry L; Warner, Jamie H; Van Vliet, Krystyn J
2018-02-27
Thin film nonstoichiometric oxides enable many high-temperature applications including solid oxide fuel cells, actuators, and catalysis. Large concentrations of point defects (particularly, oxygen vacancies) enable fast ionic conductivity or gas exchange kinetics in these materials but also manifest as coupling between lattice volume and chemical composition. This chemical expansion may be either detrimental or useful, especially in thin film devices that may exhibit enhanced performance through strain engineering or decreased operating temperatures. However, thin film nonstoichiometric oxides can differ from bulk counterparts in terms of operando defect concentrations, transport properties, and mechanical properties. Here, we present an in situ investigation of atomic-scale chemical expansion in Pr x Ce 1-x O 2-δ (PCO), a mixed ionic-electronic conducting oxide relevant to electrochemical energy conversion and high-temperature actuation. Through a combination of electron energy loss spectroscopy and transmission electron microscopy with in situ heating, we characterized chemical strains and changes in oxidation state in cross sections of PCO films grown on yttria-stabilized zirconia (YSZ) at temperatures reaching 650 °C. We quantified, both statically and dynamically, the nanoscale chemical expansion induced by changes in PCO redox state as a function of position and direction relative to the film-substrate interface. Additionally, we observed dislocations at the film-substrate interface, as well as reduced cation localization to threading defects within PCO films. These results illustrate several key aspects of atomic-scale structure and mechanical deformation in nonstoichiometric oxide films that clarify distinctions between films and bulk counterparts and that hold several implications for operando chemical expansion or "breathing" of such oxide films.
Kanoun, Mohammed; Hermet, Patrick; Goumri-Said, Souraya
2012-01-01
On the basis of recent experiments, the solid solution transition-metal diborides were proposed to be new ultra-incompressible hard materials. We investigate using density functional theory based methods the structural and mechanical properties, electronic structure, and hardness of Os 1-xRu xB 2 solid solutions. A difference in chemical bonding occurs between OsB 2 and RuB 2 diborides, leading to significantly different elastic properties: a large bulk, shear moduli, and hardness for Os-rich diborides and relatively small bulk, shear moduli, and hardness for Ru-rich diborides. The electronic structure and bonding characterization are also analyzed as a function of Ru-dopant concentration in the OsB 2 lattice. © 2012 American Chemical Society.
Kanoun, Mohammed
2012-05-31
On the basis of recent experiments, the solid solution transition-metal diborides were proposed to be new ultra-incompressible hard materials. We investigate using density functional theory based methods the structural and mechanical properties, electronic structure, and hardness of Os 1-xRu xB 2 solid solutions. A difference in chemical bonding occurs between OsB 2 and RuB 2 diborides, leading to significantly different elastic properties: a large bulk, shear moduli, and hardness for Os-rich diborides and relatively small bulk, shear moduli, and hardness for Ru-rich diborides. The electronic structure and bonding characterization are also analyzed as a function of Ru-dopant concentration in the OsB 2 lattice. © 2012 American Chemical Society.
Issa, Yaser; Watts, David C; Boyd, Daniel; Price, Richard B
2016-04-01
To determine the nanohardness and elastic moduli of two bulk-fill resin based composites (RBCs) at increasing depths from the surface and increasing distances laterally from the center after light curing. Two bulk-fill dental RBCs: Tetric EvoCeram Bulk Fill (TECBF) and Filtek Bulk Fill Flowable (FBFF) were light cured in a metal mold with a 6mm diameter and a 10mm long semi-circular notch. The RBCs were photo-polymerized for 10s using a light emitting diode (LED) Bluephase Style curing light, with the original light probe that lacked the homogenizer. This light has two blue light and one violet light LED emitters. By changing the probe orientation over the mold, the light output from only two LEDs reached the RBC. Measurements were made using: (i) the light from one violet and one blue LED, and (ii) the light from the two blue LEDs. Five specimens of each RBC were made using each LED orientation (total 20 specimens). Specimens were then stored in the dark at 37°C for 24h. Fifty indents were made using an Agilent G200 nanoindentor down to 4mm from the surface and 2.5mm right and left of the centerline. The results were analyzed (alpha=0.05) using multiple paired-sample t-tests, ANOVA, Bonferroni post-hoc tests, and Pearson correlations. The elastic modulus and nanohardness varied according to the depth and the distance from the centerline. For TECBF, no significant difference was found between the spatial variations in the elastic modulus or hardness values when violet-blue or blue-blue LEDs were used. For FBFF, the elastic modulus and nanohardness on the side exposed to the violet emitter were significantly less than the side exposed to the blue emitter. A strong correlation between nanohardness and elastic modulus was found in all groups (r(2)=0.9512-0.9712). Resin polymerization was not uniform throughout the RBC. The nanohardness and elastic modulus across two RBC materials were found to decline differently according to the orientation of the violet and blue
Liu, X Sherry; Sajda, Paul; Saha, Punam K; Wehrli, Felix W; Bevill, Grant; Keaveny, Tony M; Guo, X Edward
2008-02-01
Trabecular plates and rods are important microarchitectural features in determining mechanical properties of trabecular bone. A complete volumetric decomposition of individual trabecular plates and rods was used to assess the orientation and morphology of 71 human trabecular bone samples. The ITS-based morphological analyses better characterize microarchitecture and help predict anisotropic mechanical properties of trabecular bone. Standard morphological analyses of trabecular architecture lack explicit segmentations of individual trabecular plates and rods. In this study, a complete volumetric decomposition technique was developed to segment trabecular bone microstructure into individual plates and rods. Contributions of trabecular type-associated morphological parameters to the anisotropic elastic moduli of trabecular bone were studied. Seventy-one human trabecular bone samples from the femoral neck (FN), tibia, and vertebral body (VB) were imaged using muCT or serial milling. Complete volumetric decomposition was applied to segment trabecular bone microstructure into individual plates and rods. The orientation of each individual trabecula was determined, and the axial bone volume fractions (aBV/TV), axially aligned bone volume fraction along each orthotropic axis, were correlated with the elastic moduli. The microstructural type-associated morphological parameters were derived and compared with standard morphological parameters. Their contributions to the anisotropic elastic moduli, calculated by finite element analysis (FEA), were evaluated and compared. The distribution of trabecular orientation suggested that longitudinal plates and transverse rods dominate at all three anatomic sites. aBV/TV along each axis, in general, showed a better correlation with the axial elastic modulus (r(2) = 0.95 approximately 0.99) compared with BV/TV (r(2) = 0.93 approximately 0.94). The plate-associated morphological parameters generally showed higher correlations with the
Explaining the electroweak scale and stabilizing moduli in M theory
International Nuclear Information System (INIS)
Acharya, Bobby S.; Bobkov, Konstantin; Kane, Gordon L.; Kumar, Piyush; Shao Jing
2007-01-01
In a recent paper [B. Acharya, K. Bobkov, G. Kane, P. Kumar, and D. Vaman, Phys. Rev. Lett. 97, 191601 (2006).] it was shown that in fluxless M theory vacua with at least two hidden sectors undergoing strong gauge dynamics and a particular form of the Kaehler potential, all moduli are stabilized by the effective potential and a stable hierarchy is generated, consistent with standard gauge unification. This paper explains the results of [B. Acharya, K. Bobkov, G. Kane, P. Kumar, and D. Vaman, Phys. Rev. Lett. 97, 191601 (2006).] in more detail and generalizes them, finding an essentially unique de Sitter vacuum under reasonable conditions. One of the main phenomenological consequences is a prediction which emerges from this entire class of vacua: namely, gaugino masses are significantly suppressed relative to the gravitino mass. We also present evidence that, for those vacua in which the vacuum energy is small, the gravitino mass, which sets all the superpartner masses, is automatically in the TeV-100 TeV range
Yu, Denis Y. W.; Hoster, Harry E.; Batabyal, Sudip K.
2014-01-01
Nanomaterials as anode for lithium-ion batteries (LIB) have gained widespread interest in the research community. However, scaling up and processibility are bottlenecks to further commercialization of these materials. Here, we report that bulk antimony sulfide with a size of 10–20 μm exhibits a high capacity and stable cycling of 800 mAh g−1. Mechanical and chemical stabilities of the electrodes are ensured by an optimal electrode-electrolyte system design, with a polyimide-based binder together with fluoroethylene carbonate in the electrolyte. The polyimide binder accommodates the volume expansion during alloying process and fluoroethylene carbonate suppresses the increase in charge transfer resistance of the electrodes. We observed that particle size is not a major factor affecting the charge-discharge capacities, rate capability and stability of the material. Despite the large particle size, bulk antimony sulfide shows excellent rate performance with a capacity of 580 mAh g−1 at a rate of 2000 mA g−1. PMID:24691396
International Nuclear Information System (INIS)
Schoen, M.
1995-01-01
In this article the Taylor-expansion method is introduced by which Monte Carlo (MC) simulations in the canonical ensemble can be speeded up significantly, Substantial gains in computational speed of 20-40% over conventional implementations of the MC technique are obtained over a wide range of densities in homogeneous bulk phases. The basic philosophy behind the Taylor-expansion method is a division of the neighborhood of each atom (or molecule) into three different spatial zones. Interactions between atoms belonging to each zone are treated at different levels of computational sophistication. For example, only interactions between atoms belonging to the primary zone immediately surrounding an atom are treated explicitly before and after displacement. The change in the configurational energy contribution from secondary-zone interactions is obtained from the first-order term of a Taylor expansion of the configurational energy in terms of the displacement vector d. Interactions with atoms in the tertiary zone adjacent to the secondary zone are neglected throughout. The Taylor-expansion method is not restricted to the canonical ensemble but may be employed to enhance computational efficiency of MC simulations in other ensembles as well. This is demonstrated for grand canonical ensemble MC simulations of an inhomogeneous fluid which can be performed essentially on a modern personal computer
The Witten-Reshetikhin-Turaev invariants of finite order mapping tori II
DEFF Research Database (Denmark)
Andersen, Jørgen Ellegaard; Himpel, Benjamin
2012-01-01
We identify the leading order term of the asymptotic expansion of the Witten–Reshetikhin–Turaev invariants for finite order mapping tori with classical invariants for all simple and simply-connected compact Lie groups. The square root of the Reidemeister torsion is used as a density on the moduli...... space of flat connections and the leading order term is identified with the integral over this moduli space of this density weighted by a certain phase for each component of the moduli space. We also identify this phase in terms of classical invariants such as Chern–Simons invariants, eta invariants...
Energy Technology Data Exchange (ETDEWEB)
Ansari, R.; Ajori, S. [Department of Mechanical Engineering, University of Guilan, P.O. Box 3756, Rasht (Iran, Islamic Republic of); Rouhi, S., E-mail: s_rouhi@iaul.ac.ir [Young Researchers and Elite Club, Langroud Branch, Islamic Azad University, Langroud, Guilan (Iran, Islamic Republic of)
2016-01-15
Synthesizing polyphenylene polymer, a two-dimensional hydrocarbon known as porous graphene, has led to the initiation of a new age in nanoscience. In this investigation, molecular dynamics (MD) simulations are carried out to study the mechanical properties of porous graphene such as Young's modulus, Poisson's ratio, bulk modulus and ultimate strength and strain. The fracture initiation and propagation pattern of porous graphene are also considered in this study. The results show that Young's and bulk moduli of porous graphene are lower than those of graphene, graphene and graphyne. Unlikely, it is also observed that its Poisson's ratio is considerably more than that of graphene, graphene and graphyne. Furthermore, it is found out that Young's and bulk moduli as well as fracture strain and ultimate stress are extremely size-dependent and also the porous graphene can be considered as an isotropic material.
International Nuclear Information System (INIS)
Benson, A.K.; Wu, J.
2000-01-01
Two of the needed elastic parameters for predicting velocities in porous, fluid-filled rocks, the bulk modulus of the empty, porous rock and the shear modulus of the rock, are very difficult to obtain in situ. A novel modeling approach is developed by inverting the Biot-Geertsma-Gassmann (BGG) and shear-wave equations to generate values for the bulk and shear moduli, respectively, by using available velocity and porosity data obtained from borehole logs and/or cores from water/brine-saturated rocks. These values of bulk and shear moduli, along with reasonable in-situ estimates of rock-matrix and fluid parameters generated from the Batzle-Wang formulation, are then used to predict compressional and shear-wave velocities, compressional-shear wave ratios, and reflection coefficients at the interfaces between host rocks and fluid-saturated rocks, either fully or partially saturated with hydrocarbons or water, as a function of depth and/or porosity
Young's modulus of a copper-stabilized niobium-titanium superconductive wire
International Nuclear Information System (INIS)
Ledbetter, H.M.; Moulder, J.C.; Austin, M.W.
1980-01-01
Young's modulus was determined for a 0.6-mm-dia niobium-titanium superconductive wire. Two methods were used: continuous-wave-resonance and laser-pulse-excitation. Young's moduli were also determined for the components - copper and Nb-Ti - in both wire and bulk forms. Some mechanical-deformation effects on Young's modulus were also measured. From the component' elastic moduli, that of the composite was predicted accurately by a simple rule-of-mixtures relationship
Holographic currents in first order Gravity and finite Fefferman-Graham expansions
International Nuclear Information System (INIS)
Banados, Maximo; Miskovic, Olivera; Theisen, Stefan
2006-01-01
We study the holographic currents associated to Chern-Simons theories. We start with an example in three dimensions and find the holographic representations of vector and chiral currents reproducing the correct expression for the chiral anomaly. In five dimensions, Chern-Simons theory for AdS group describes first order gravity and we show that there exists a gauge fixing leading to a finite Fefferman-Graham expansion. We derive the corresponding holographic currents, namely, the stress tensor and spin current which couple to the metric and torsional degrees of freedom at the boundary, respectively. We obtain the correct Ward identities for these currents by looking at the bulk constraint equations
International Nuclear Information System (INIS)
Panneerselvam, G.; Antony, M.P.; Srinivasan, T.G.; Vasudeva Rao, P.R.
2010-01-01
Full text: Thorium-praseodymium mixed oxide solid solutions containing 15, 25, 40 and 55 mole percent of praseodymia were synthesized by mixing the solutions of thorium nitrate in water and praseodymium oxide (Pr 6 O 11 ) in conc. HNO 3 . Subsequently, their hydroxides were co-precipitated by the addition of aqueous ammonia. Further the precipitate was dried at 50 deg C, calcined at 600 deg C for 4 hours and sintered at 1200 deg C for 6 h in air. X-ray diffraction measurements were performed for phase identification and lattice parameter derivation. Single-phase fluorite structure was observed for all the compositions. Bulk and theoretical densities of solid solutions were also determined by immersion and X-ray techniques. Thermal expansion coefficients and percentage linear thermal expansion of the solid solutions were determined using high temperature X-ray diffraction technique in the temperature range 300 to 1700 K for the first time. The room temperature lattice constants estimated for above compositions are 0.5578, 0.5565, 0.5545 and 0.5526 nm, respectively. The mean linear thermal expansion coefficients for the solid solutions are 15.48 x 10 -6 K -1 , 18.35 x 10 -6 K -1 , 22.65 x 10 -6 K -1 and 26.95 x 10 -6 K -1 , respectively. The percentage linear thermal expansions in this temperature range are 1.68, 1.89, 2.21 and 2.51 respectively. It is seen that the solid solutions are stable up to 1700 K. It is also seen that the effect and nature of the dopant are the important parameters influencing the thermal expansion of the ThO 2 . The lattice parameter of the solid solutions exhibited a decreasing trend with respect to praseodymia addition. The percentage linear thermal expansion of the solid solutions increases steadily with increasing temperature
International Nuclear Information System (INIS)
Yun, Y.
2015-01-01
Thermal expansion of fuel pellet is an important property which limits the lifetime of the fuels in reactors, because it affects both the pellet and cladding mechanical interaction and the gap conductivity. By fitting a number of available measured data, recommended equations have been presented and successfully used to estimate thermal expansion coefficient of the nuclear fuel pellet. However, due to large scatter of the measured data, non-consensus data have been omitted in formulating the equations. Also, the equation is strongly governed by the lack of appropriate experimental data. For those reasons, it is important to develop theoretical methodologies to better describe thermal expansion behaviour of nuclear fuel. In particular, first-principles and molecular dynamics simulations have been certainly contributed to predict reliable thermal expansion without fitting the measured data. Furthermore, the two theoretical techniques have improved on understanding the change of fuel dimension by describing the atomic-scale processes associated with lattice expansion in the fuels. (author)
Transferable Force Field for Metal–Organic Frameworks from First-Principles: BTW-FF
2014-01-01
We present an ab-initio derived force field to describe the structural and mechanical properties of metal–organic frameworks (or coordination polymers). The aim is a transferable interatomic potential that can be applied to MOFs regardless of metal or ligand identity. The initial parametrization set includes MOF-5, IRMOF-10, IRMOF-14, UiO-66, UiO-67, and HKUST-1. The force field describes the periodic crystal and considers effective atomic charges based on topological analysis of the Bloch states of the extended materials. Transferable potentials were developed for the four organic ligands comprising the test set and for the associated Cu, Zn, and Zr metal nodes. The predicted materials properties, including bulk moduli and vibrational frequencies, are in agreement with explicit density functional theory calculations. The modal heat capacity and lattice thermal expansion are also predicted. PMID:25574157
Low-temperature thermal expansion
International Nuclear Information System (INIS)
Collings, E.W.
1986-01-01
This chapter discusses the thermal expansion of insulators and metals. Harmonicity and anharmonicity in thermal expansion are examined. The electronic, magnetic, an other contributions to low temperature thermal expansion are analyzed. The thermodynamics of the Debye isotropic continuum, the lattice-dynamical approach, and the thermal expansion of metals are discussed. Relative linear expansion at low temperatures is reviewed and further calculations of the electronic thermal expansion coefficient are given. Thermal expansions are given for Cu, Al and Ti. Phenomenologic thermodynamic relationships are also discussed
Thermodynamic properties of bulk and confined water
Energy Technology Data Exchange (ETDEWEB)
Mallamace, Francesco, E-mail: francesco.mallamace@unime.it [Dipartimento di Fisica e Scienza della Terra Università di Messina and CNISM, I-98168 Messina (Italy); Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Center for Polymer Studies and Department of Physics, Boston University, Boston, Massachusetts 02215 (United States); Corsaro, Carmelo [Dipartimento di Fisica e Scienza della Terra Università di Messina and CNISM, I-98168 Messina (Italy); Mallamace, Domenico [Dipartimento di Scienze dell' Ambiente, della Sicurezza, del Territorio, degli Alimenti e della Salute, Università di Messina, I-98166 Messina (Italy); Vasi, Sebastiano; Vasi, Cirino [IPCF-CNR, I-98166 Messina (Italy); Stanley, H. Eugene [Center for Polymer Studies and Department of Physics, Boston University, Boston, Massachusetts 02215 (United States)
2014-11-14
The thermodynamic response functions of water display anomalous behaviors. We study these anomalous behaviors in bulk and confined water. We use nuclear magnetic resonance (NMR) to examine the configurational specific heat and the transport parameters in both the thermal stable and the metastable supercooled phases. The data we obtain suggest that there is a behavior common to both phases: that the dynamics of water exhibit two singular temperatures belonging to the supercooled and the stable phase, respectively. One is the dynamic fragile-to-strong crossover temperature (T{sub L} ≃ 225 K). The second, T{sup *} ∼ 315 ± 5 K, is a special locus of the isothermal compressibility K{sub T}(T, P) and the thermal expansion coefficient α{sub P}(T, P) in the P–T plane. In the case of water confined inside a protein, we observe that these two temperatures mark, respectively, the onset of protein flexibility from its low temperature glass state (T{sub L}) and the onset of the unfolding process (T{sup *})
Nanoscale Electromechanics To Measure Thermal Conductivity, Expansion, and Interfacial Losses.
Mathew, John P; Patel, Raj; Borah, Abhinandan; Maliakkal, Carina B; Abhilash, T S; Deshmukh, Mandar M
2015-11-11
We study the effect of localized Joule heating on the mechanical properties of doubly clamped nanowires under tensile stress. Local heating results in systematic variation of the resonant frequency; these frequency changes result from thermal stresses that depend on temperature dependent thermal conductivity and expansion coefficient. The change in sign of the linear expansion coefficient of InAs is reflected in the resonant response of the system near a bath temperature of 20 K. Using finite element simulations to model the experimentally observed frequency shifts, we show that the thermal conductivity of a nanowire can be approximated in the 10-60 K temperature range by the empirical form κ = bT W/mK, where the value of b for a nanowire was found to be b = 0.035 W/mK(2), significantly lower than bulk values. Also, local heating allows us to independently vary the temperature of the nanowire relative to the clamping points pinned to the bath temperature. We suggest a loss mechanism (dissipation ~10(-4)-10(-5)) originating from the interfacial clamping losses between the metal and the semiconductor nanostructure.
Microhardness of bulk-fill composite materials
Kelić, Katarina; Matić, Sanja; Marović, Danijela; Klarić, Eva; Tarle, Zrinka
2016-01-01
The aim of the study was to determine microhardness of high- and low-viscosity bulk-fill composite resins and compare it with conventional composite materials. Four materials of high-viscosity were tested, including three bulk-fills: QuiXfi l (QF), x-tra fil (XTF) and Tetric EvoCeram Bulk Fill (TEBCF), while nanohybrid composite GrandioSO (GSO) served as control. The other four were low-viscosity composites, three bulk-fill materials: Smart Dentin Replacement (SDR), Venus Bulk Fill (VBF) and ...
Gravity mediated supersymmetry breaking in six dimensions
International Nuclear Information System (INIS)
Falkowski, Adam; Lee, Hyun Min; Luedeling, Christoph
2005-01-01
We study gravity mediated supersymmetry breaking in four-dimensional effective theories derived from six-dimensional brane-world supergravity. Using the Noether method we construct a locally supersymmetric action for a bulk-brane system consisting of the minimal six-dimensional supergravity coupled to vector and chiral multiplets located at four-dimensional branes. Couplings of the bulk moduli to the brane are uniquely fixed, in particular, they are flavour universal. We compactify this system on T 2 /Z 2 and derive the four-dimensional effective supergravity. The tree-level effective Kaehler potential is not of the sequestered form, therefore gravity mediation may occur at tree-level. We identify one scenario of moduli stabilization in which the soft scalar masses squared are positive
Explaining the electroweak scale and stabilizing moduli in M theory
Acharya, Bobby S.; Bobkov, Konstantin; Kane, Gordon L.; Kumar, Piyush; Shao, Jing
2007-12-01
In a recent paper [B. Acharya, K. Bobkov, G. Kane, P. Kumar, and D. Vaman, Phys. Rev. Lett. 97, 191601 (2006).PRLTAO0031-900710.1103/PhysRevLett.97.191601] it was shown that in fluxless M theory vacua with at least two hidden sectors undergoing strong gauge dynamics and a particular form of the Kähler potential, all moduli are stabilized by the effective potential and a stable hierarchy is generated, consistent with standard gauge unification. This paper explains the results of [B. Acharya, K. Bobkov, G. Kane, P. Kumar, and D. Vaman, Phys. Rev. Lett. 97, 191601 (2006).PRLTAO0031-900710.1103/PhysRevLett.97.191601] in more detail and generalizes them, finding an essentially unique de Sitter vacuum under reasonable conditions. One of the main phenomenological consequences is a prediction which emerges from this entire class of vacua: namely, gaugino masses are significantly suppressed relative to the gravitino mass. We also present evidence that, for those vacua in which the vacuum energy is small, the gravitino mass, which sets all the superpartner masses, is automatically in the TeV 100 TeV range.
Non-minimal derivative coupling scalar field and bulk viscous dark energy
Energy Technology Data Exchange (ETDEWEB)
Mostaghel, Behrang [Shahid Beheshti University, Department of Physics, Tehran (Iran, Islamic Republic of); Moshafi, Hossein [Institute for Advanced Studies in Basic Sciences, Department of Physics, Zanjan (Iran, Islamic Republic of); Movahed, S.M.S. [Shahid Beheshti University, Department of Physics, Tehran (Iran, Islamic Republic of); Institute for Research in Fundamental Sciences (IPM), School of Physics, Tehran (Iran, Islamic Republic of)
2017-08-15
Inspired by thermodynamical dissipative phenomena, we consider bulk viscosity for dark fluid in a spatially flat two-component Universe. Our viscous dark energy model represents phantom-crossing which avoids big-rip singularity. We propose a non-minimal derivative coupling scalar field with zero potential leading to accelerated expansion of the Universe in the framework of bulk viscous dark energy model. In this approach, the coupling constant, κ, is related to viscosity coefficient, γ, and the present dark energy density, Ω{sub DE}{sup 0}. This coupling is bounded as κ element of [-1/9H{sub 0}{sup 2}(1 - Ω{sub DE}{sup 0}), 0]. We implement recent observational data sets including a joint light-curve analysis (JLA) for SNIa, gamma ray bursts (GRBs) for most luminous astrophysical objects at high redshifts, baryon acoustic oscillations (BAO) from different surveys, Hubble parameter from HST project, Planck CMB power spectrum and lensing to constrain model free parameters. The joint analysis of JLA + GRBs + BAO + HST shows that Ω{sub DE}{sup 0} = 0.696 ± 0.010, γ = 0.1404 ± 0.0014 and H{sub 0} = 68.1 ± 1.3. Planck TT observation provides γ = 0.32{sup +0.31}{sub -0.26} in the 68% confidence limit for the viscosity coefficient. The cosmographic distance ratio indicates that current observed data prefer to increase bulk viscosity. The competition between phantom and quintessence behavior of the viscous dark energy model can accommodate cosmological old objects reported as a sign of age crisis in the ΛCDM model. Finally, tension in the Hubble parameter is alleviated in this model. (orig.)
Negative thermal expansion materials: technological key for control of thermal expansion
Koshi Takenaka
2012-01-01
Most materials expand upon heating. However, although rare, some materials contract upon heating. Such negative thermal expansion (NTE) materials have enormous industrial merit because they can control the thermal expansion of materials. Recent progress in materials research enables us to obtain materials exhibiting negative coefficients of linear thermal expansion over −30 ppm K−1. Such giant NTE is opening a new phase of control of thermal expansion in composites. Specifically examining pra...
Bulk electric system reliability evaluation incorporating wind power and demand side management
Huang, Dange
correlations and the interactive effects of wind power and load forecast uncertainty on system reliability are examined. The concept of the security cost associated with operating in the marginal state in the well-being framework is incorporated in the economic analyses associated with system expansion planning including wind power and load forecast uncertainty. Overall reliability cost/worth analyses including security cost concepts are applied to select an optimal wind power injection strategy in a bulk electric system. The effects of the various demand side management measures on system reliability are illustrated using the system, load point, and well-being indices, and the reliability index probability distributions. The reliability effects of demand side management procedures in a bulk electric system including wind power and load forecast uncertainty considerations are also investigated. The system reliability effects due to specific demand side management programs are quantified and examined in terms of their reliability benefits.
Hamedi-Sangsari, Adrien; Chinipardaz, Zahra; Carrasco, Lee
2017-10-01
The aim of this study was to compare outcome measurements of skeletal and dental expansion with bone-borne (BB) versus tooth-borne (TB) appliances after surgically assisted rapid palatal expansion (SARPE). This study was performed to provide quantitative measurements that will help the oral surgeon and orthodontist in selecting the appliance with, on average, the greatest amount of skeletal expansion and the least amount of dental expansion. A computerized database search was performed using PubMed, EBSCO, Cochrane, Scopus, Web of Science, and Google Scholar on publications in reputable oral surgery and orthodontic journals. A systematic review and meta-analysis was completed with the predictor variable of expansion appliance (TB vs BB) and outcome measurement of expansion (in millimeters). Of 487 articles retrieved from the 6 databases, 5 articles were included, 4 with cone-beam computed tomographic (CBCT) data and 1 with non-CBCT 3-dimensional cast data. There was a significant difference in skeletal expansion (standardized mean difference [SMD], 0.92; 95% confidence interval [CI], 0.54-1.30; P appliances. However, there was no significant difference in dental expansion (SMD, 0.05; 95% CI, -0.24 to 0.34; P = .03). According to the literature, to achieve more effective skeletal expansion and minimize dental expansion after SARPE, a BB appliance should be favored. Copyright © 2017 American Association of Oral and Maxillofacial Surgeons. Published by Elsevier Inc. All rights reserved.
Two-fold origin of the deformation-induced ferromagnetism in bulk Fe60Al40 (at.%) alloys
International Nuclear Information System (INIS)
Menendez, E; Surinach, S; Baro, M D; Sort, J; Liedke, M O; Fassbender, J; Nogues, J
2008-01-01
The transition from the atomically ordered B2-phase to the chemically disordered A2-phase and the concomitant deformation-induced ferromagnetism have been investigated in bulk polycrystalline Fe 60 Al 40 (at.%) alloys subjected to compression processes. A detailed correlation between structural, magnetic and mechanical properties reveals that the generated ferromagnetism depends on the stress level but is virtually independent of the loading rate. The mechanisms governing the induced ferromagnetism also vary as the stress level is increased. Namely, in the low-stress regime both lattice cell expansion and atomic intermixing play a role in the induced ferromagnetic behavior. Conversely, lattice expansion seems to become the main mechanism contributing to the generated ferromagnetism in the high-stress regime. Furthermore, a correlation is also observed between the order-disorder transition and the mechanical hardness. Hence, a combination of magnetic and mechanical measurements can be used, in synergetic manner, to investigate this deformation-induced phase transition.
Large area bulk superconductors
Miller, Dean J.; Field, Michael B.
2002-01-01
A bulk superconductor having a thickness of not less than about 100 microns is carried by a polycrystalline textured substrate having misorientation angles at the surface thereof not greater than about 15.degree.; the bulk superconductor may have a thickness of not less than about 100 microns and a surface area of not less than about 50 cm.sup.2. The textured substrate may have a thickness not less than about 10 microns and misorientation angles at the surface thereof not greater than about 15.degree.. Also disclosed is a process of manufacturing the bulk superconductor and the polycrystalline biaxially textured substrate material.
Anisotropic Bulk Viscous String Cosmological Model in a Scalar-Tensor Theory of Gravitation
Directory of Open Access Journals (Sweden)
D. R. K. Reddy
2013-01-01
Full Text Available Spatially homogeneous, anisotropic, and tilted Bianchi type-VI0 model is investigated in a new scalar-tensor theory of gravitation proposed by Saez and Ballester (1986 when the source for energy momentum tensor is a bulk viscous fluid containing one-dimensional cosmic strings. Exact solution of the highly nonlinear field equations is obtained using the following plausible physical conditions: (i scalar expansion of the space-time which is proportional to the shear scalar, (ii the barotropic equations of state for pressure and energy density, and (iii a special law of variation for Hubble’s parameter proposed by Berman (1983. Some physical and kinematical properties of the model are also discussed.
International Nuclear Information System (INIS)
Ding Shouguo; Xie Yu; Yang Ping; Weng Fuzhong; Liu Quanhua; Baum, Bryan; Hu Yongxiang
2009-01-01
The bulk-scattering properties of dust aerosols and clouds are computed for the community radiative transfer model (CRTM) that is a flagship effort of the Joint Center for Satellite Data Assimilation (JCSDA). The delta-fit method is employed to truncate the forward peaks of the scattering phase functions and to compute the Legendre expansion coefficients for re-constructing the truncated phase function. Use of more terms in the expansion gives more accurate re-construction of the phase function, but the issue remains as to how many terms are necessary for different applications. To explore this issue further, the bidirectional reflectances associated with dust aerosols, water clouds, and ice clouds are simulated with various numbers of Legendre expansion terms. To have relative numerical errors smaller than 5%, the present analyses indicate that, in the visible spectrum, 16 Legendre polynomials should be used for dust aerosols, while 32 Legendre expansion terms should be used for both water and ice clouds. In the infrared spectrum, the brightness temperatures at the top of the atmosphere are computed by using the scattering properties of dust aerosols, water clouds and ice clouds. Although small differences of brightness temperatures compared with the counterparts computed with 4, 8, 128 expansion terms are observed at large viewing angles for each layer, it is shown that 4 terms of Legendre polynomials are sufficient in the radiative transfer computation at infrared wavelengths for practical applications.
International Nuclear Information System (INIS)
Li, J H; Dai, X D; Wang, T L; Liu, B X
2007-01-01
We propose a two-parameter binomial truncation function for the second-moment approximation of the tight-binding (TB-SMA) interatomic potential and illustrate in detail the procedure of constructing the potentials for binary and ternary transition metal systems. For the ternary Ni-Hf-Ti system, the lattice constants, cohesion energies, elastic constants and bulk moduli of six binary compounds, i.e. L1 2 Ni 3 Hf, NiHf 3 , Ni 3 Ti, NiTi 3 , Hf 3 Ti and HfTi 3 , are firstly acquired by ab initio calculations and then employed to derive the binomial-truncated TB-SMA Ni-Hf-Ti potential. Applying the ab initio derived Ni-Hf-Ti potential, the lattice constants, cohesive energy, elastic constants and bulk moduli of another six binary compounds, i.e. D0 3 NiHf 3 , NiTi 3 HfTi 3 , and B2 NiHf, NiTi, HfTi, and two ternary compounds, i.e. C1 b NiHfTi, L2 1 Ni 2 HfTi, are calculated, respectively. It is found that, for the eight binary compounds studied, the calculated lattice constants and cohesion energies are in excellent agreement with those directly acquired from ab initio calculations and that the elastic constants and bulk moduli calculated from the potential are also qualitatively consistent with the results from ab initio calculations
Fabrication of Fe1.1Se0.5Te0.5 bulk by a high energy ball milling technique
Liu, Jixing; Li, Chengshan; Zhang, Shengnan; Feng, Jianqing; Zhang, Pingxiang; Zhou, Lian
2017-11-01
Fe1.1Se0.5Te0.5 superconducting bulks were successfully synthesized by a high energy ball milling (HEBM) aided sintering technique. Two advantages of this new technique have been revealed compared with traditional solid state sintering method. One is greatly increased the density of sintered bulks. It is because the precursor powders with β-Fe(Se, Te) and δ-Fe(Se, Te) were obtained directly by the HEBM process and without formation of liquid Se (and Te), which could avoid the huge volume expansion. The other is the obvious decrease of sintering temperature and dwell time due to the effective shortened length of diffusion paths. The superconducting critical temperature Tc of 14.2 K in our sample is comparable with those in previous reports, and further optimization of chemical composition is on the way.
An ab-initio investigation on SrLa intermetallic compound
Kumar, S. Ramesh; Jaiganesh, G.; Jayalakshmi, V.
2018-05-01
The electronic, elastic and thermodynamic property of CsCl-type SrLa are investigated through density functional theory. The energy-volume relation for this compound has been obtained. The band structure, density of states and charge density in (110) plane are also examined. The elastic constants (C11, C12 and C44) of SrLa is computed, then, using these elastic constants, the bulk moduli, shear moduli, Young's moduli and Poisson's ratio are also derived. The calculated results showed that CsCl-type SrLa is ductile at ambient conditions. The thermodynamic quantities such as free energy, entropy and heat capacity as a function of temperature are estimated and the results obtained are discussed.
International Nuclear Information System (INIS)
Dvinskikh, S.V.; Furo, I.; Neretnieks, I.
2010-01-01
Document available in extended abstract form only. Compacted bentonite clay is currently attracting attention as a promising 'self-sealing' buffer material to build in-ground barriers for the encapsulation of radioactive waste. It is expected to fill up the space between waste canister and surrounding ground by swelling and thus delay flow and migration from the host rock to the canister. Evaluation and understanding of the swelling properties of pre-compacted bentonite are of uttermost importance for designing such buffers. The major goal of our studies was to provide, in a non-invasive manner, a quantitative measure of bentonite distribution in extended samples during different physical processes in an aqueous environment such as swelling, dissolution, and sedimentation on the time scale from minutes to years. The propagation of the swelling front during clay expansion depending on the geometry of the confining space was also studied. To characterize the state of colloids that form after/during clay swelling the water self-diffusion coefficient was measured on a spatially resolved manner. The distribution and displacement within the bentonite systems of foreign particles, either natural ones (sand or quartz) or artificially admixed model particles of controlled size were also monitored. Both natural montmorillonites and purified and ion-exchanged montmorillonite clays were investigated. The primary variables were clay composition and water ionic strength. Magnetic resonance imaging and nuclear magnetic resonance spectroscopy were adapted and used as main experimental techniques. With this approach, spatially resolved movement of the clay/water interface as well as clay particle distributions in gel phase can be monitored. Bulk samples with swelling in a vertical tube and in a horizontal channel were investigated and clay content distribution profiles in the concentration range over five orders of magnitude and with sub-millimetre spatial resolution were
Ni, Jennifer E.; Case, Eldon D.; Schmidt, Robert D.; Wu, Chun-I.; Hogan, Timothy P.; Trejo, Rosa M.; Lara-Curzio, Edgar; Kanatzidis, Mercouri G.
2013-12-01
Twenty-six (Pb0.95Sn0.05Te)0.92(PbS)0.08-0.055% PbI2-SiC nanoparticle (SiCnp) composite thermoelectric specimens were either hot pressed or pulsed electric current sintered (PECS). Bloating (a thermally induced increase in porosity, P, for as-densified specimens) was observed during annealing at temperatures >603 K for hot-pressed specimens and PECS-processed specimens from wet milled powders, but in contrast seven out of seven specimens densified by PECS from dry milled powders showed no observable bloating following annealing at temperatures up to 936 K. In this study, bloating in the specimens was accessed via thermal annealing induced changes in (i) porosity measured by scanning electron microscopy on fractured specimen surfaces, (ii) specimen volume and (iii) elastic moduli. The moduli were measured by resonant ultrasound spectroscopy. SiCnp additions (1-3.5 vol.%) changed the fracture mode from intergranular to transgranular, inhibited grain growth, and limited bloating in the wet milled PECS specimens. Inhibition of bloating likely occurs due to cleaning of contamination from powder particle surfaces via PECS processing which has been reported previously in the literature.
Bandyopadhyay, Rebanta; Selbo, Jon; Amidon, Gregory E; Hawley, Michael
2005-11-01
This study investigates the effects of crystal lattice deformation on the powder X-ray diffraction (PXRD) patterns of compressed polycrystalline specimen (compacts/tablets) made from molecular, crystalline powders. The displacement of molecules and the corresponding adjustment of interplanar distances (d-spacings) between diffracting planes of PNU-288034 and PNU-177553, which have crystal habits with a high aspect ratio favoring preferred orientation during tableting, are demonstrated by shifts in the diffracted peak positions. The direction of shift in diffracted peak positions suggests a reduction of interplanar d-spacing in the crystals of PNU-288034 and PNU-177553 following compaction. There is also a general reduction of peak intensities following compression at the different compressive loads. The lattice strain representing the reduction in d-spacing is proportional to the original d-spacing of the uncompressed sample suggesting that, as with systems that obey a simple Hooke's law relationship, the further apart the planes of atoms/molecules within the lattice are, the easier it is for them to approach each other under compressive stresses. For a third model compound comprising more equant-shaped crystals of PNU-141659, the shift in diffracted peak positions are consistent with an expansion of lattice spacing after compression. This apparent anomaly is supported by the PXRD studies of the bulk powder consisting of fractured crystals where also, the shift in peak position suggests expansion of the lattice planes. Thus the crystals of PNU-141659 may be fracturing under the compressive loads used to produce the compacts. Additional studies are underway to relate the PXRD observations with the bulk tableting properties of these model compounds.
Mechanical, Thermodynamic and Electronic Properties of Wurtzite and Zinc-Blende GaN Crystals
Luan, Xinghe; Feng, Chuang; Yang, Daoguo; Zhang, Guoqi
2017-01-01
For the limitation of experimental methods in crystal characterization, in this study, the mechanical, thermodynamic and electronic properties of wurtzite and zinc-blende GaN crystals were investigated by first-principles calculations based on density functional theory. Firstly, bulk moduli, shear moduli, elastic moduli and Poisson’s ratios of the two GaN polycrystals were calculated using Voigt and Hill approximations, and the results show wurtzite GaN has larger shear and elastic moduli and exhibits more obvious brittleness. Moreover, both wurtzite and zinc-blende GaN monocrystals present obvious mechanical anisotropic behavior. For wurtzite GaN monocrystal, the maximum and minimum elastic moduli are located at orientations [001] and , respectively, while they are in the orientations and for zinc-blende GaN monocrystal, respectively. Compared to the elastic modulus, the shear moduli of the two GaN monocrystals have completely opposite direction dependences. However, different from elastic and shear moduli, the bulk moduli of the two monocrystals are nearly isotropic, especially for the zinc-blende GaN. Besides, in the wurtzite GaN, Poisson’s ratios at the planes containing [001] axis are anisotropic, and the maximum value is 0.31 which is located at the directions vertical to [001] axis. For zinc-blende GaN, Poisson’s ratios at planes (100) and (111) are isotropic, while the Poisson’s ratio at plane (110) exhibits dramatically anisotropic phenomenon. Additionally, the calculated Debye temperatures of wurtzite and zinc-blende GaN are 641.8 and 620.2 K, respectively. At 300 K, the calculated heat capacities of wurtzite and zinc-blende are 33.6 and 33.5 J mol−1 K−1, respectively. Finally, the band gap is located at the G point for the two crystals, and the band gaps of wurtzite and zinc-blende GaN are 3.62 eV and 3.06 eV, respectively. At the G point, the lowest energy of conduction band in the wurtzite GaN is larger, resulting in a wider band gap
Mechanical, Thermodynamic and Electronic Properties of Wurtzite and Zinc-Blende GaN Crystals
Directory of Open Access Journals (Sweden)
Hongbo Qin
2017-12-01
Full Text Available For the limitation of experimental methods in crystal characterization, in this study, the mechanical, thermodynamic and electronic properties of wurtzite and zinc-blende GaN crystals were investigated by first-principles calculations based on density functional theory. Firstly, bulk moduli, shear moduli, elastic moduli and Poisson’s ratios of the two GaN polycrystals were calculated using Voigt and Hill approximations, and the results show wurtzite GaN has larger shear and elastic moduli and exhibits more obvious brittleness. Moreover, both wurtzite and zinc-blende GaN monocrystals present obvious mechanical anisotropic behavior. For wurtzite GaN monocrystal, the maximum and minimum elastic moduli are located at orientations [001] and <111>, respectively, while they are in the orientations <111> and <100> for zinc-blende GaN monocrystal, respectively. Compared to the elastic modulus, the shear moduli of the two GaN monocrystals have completely opposite direction dependences. However, different from elastic and shear moduli, the bulk moduli of the two monocrystals are nearly isotropic, especially for the zinc-blende GaN. Besides, in the wurtzite GaN, Poisson’s ratios at the planes containing [001] axis are anisotropic, and the maximum value is 0.31 which is located at the directions vertical to [001] axis. For zinc-blende GaN, Poisson’s ratios at planes (100 and (111 are isotropic, while the Poisson’s ratio at plane (110 exhibits dramatically anisotropic phenomenon. Additionally, the calculated Debye temperatures of wurtzite and zinc-blende GaN are 641.8 and 620.2 K, respectively. At 300 K, the calculated heat capacities of wurtzite and zinc-blende are 33.6 and 33.5 J mol−1 K−1, respectively. Finally, the band gap is located at the G point for the two crystals, and the band gaps of wurtzite and zinc-blende GaN are 3.62 eV and 3.06 eV, respectively. At the G point, the lowest energy of conduction band in the wurtzite GaN is larger
Mechanical, Thermodynamic and Electronic Properties of Wurtzite and Zinc-Blende GaN Crystals.
Qin, Hongbo; Luan, Xinghe; Feng, Chuang; Yang, Daoguo; Zhang, Guoqi
2017-12-12
For the limitation of experimental methods in crystal characterization, in this study, the mechanical, thermodynamic and electronic properties of wurtzite and zinc-blende GaN crystals were investigated by first-principles calculations based on density functional theory. Firstly, bulk moduli, shear moduli, elastic moduli and Poisson's ratios of the two GaN polycrystals were calculated using Voigt and Hill approximations, and the results show wurtzite GaN has larger shear and elastic moduli and exhibits more obvious brittleness. Moreover, both wurtzite and zinc-blende GaN monocrystals present obvious mechanical anisotropic behavior. For wurtzite GaN monocrystal, the maximum and minimum elastic moduli are located at orientations [001] and , respectively, while they are in the orientations and for zinc-blende GaN monocrystal, respectively. Compared to the elastic modulus, the shear moduli of the two GaN monocrystals have completely opposite direction dependences. However, different from elastic and shear moduli, the bulk moduli of the two monocrystals are nearly isotropic, especially for the zinc-blende GaN. Besides, in the wurtzite GaN, Poisson's ratios at the planes containing [001] axis are anisotropic, and the maximum value is 0.31 which is located at the directions vertical to [001] axis. For zinc-blende GaN, Poisson's ratios at planes (100) and (111) are isotropic, while the Poisson's ratio at plane (110) exhibits dramatically anisotropic phenomenon. Additionally, the calculated Debye temperatures of wurtzite and zinc-blende GaN are 641.8 and 620.2 K, respectively. At 300 K, the calculated heat capacities of wurtzite and zinc-blende are 33.6 and 33.5 J mol -1 K -1 , respectively. Finally, the band gap is located at the G point for the two crystals, and the band gaps of wurtzite and zinc-blende GaN are 3.62 eV and 3.06 eV, respectively. At the G point, the lowest energy of conduction band in the wurtzite GaN is larger, resulting in a wider band gap. Densities of
Vaziri Yazdi Pin, Mohammad
Electric power distribution systems are the last high voltage link in the chain of production, transport, and delivery of the electric energy, the fundamental goals of which are to supply the users' demand safely, reliably, and economically. The number circuit miles traversed by distribution feeders in the form of visible overhead or imbedded underground lines, far exceed those of all other bulk transport circuitry in the transmission system. Development and expansion of the distribution systems, similar to other systems, is directly proportional to the growth in demand and requires careful planning. While growth of electric demand has recently slowed through efforts in the area of energy management, the need for a continued expansion seems inevitable for the near future. Distribution system and expansions are also independent of current issues facing both the suppliers and the consumers of electrical energy. For example, deregulation, as an attempt to promote competition by giving more choices to the consumers, while it will impact the suppliers' planning strategies, it cannot limit the demand growth or the system expansion in the global sense. Curiously, despite presence of technological advancements and a 40-year history of contributions in the area, many of the major utilities still relay on experience and resort to rudimentary techniques when planning expansions. A comprehensive literature review of the contributions and careful analyses of the proposed algorithms for distribution expansion, confirmed that the problem is a complex, multistage and multiobjective problem for which a practical solution remains to be developed. In this research, based on the 15-year experience of a utility engineer, the practical expansion problem has been clearly defined and the existing deficiencies in the previous work identified and analyzed. The expansion problem has been formulated as a multistage planning problem in line with a natural course of development and industry
Clay squirt: Local flow dispersion in shale-bearing sandstones
DEFF Research Database (Denmark)
Sørensen, Morten Kanne; Fabricius, Ida Lykke
2017-01-01
Dispersion of elastic-wave velocity is common in sandstone and larger in shaly sandstone than in clean sandstone. Dispersion in fluid-saturated shaly sandstone often exceeds the level expected from the stress-dependent elastic moduli of dry sandstone. The large dispersion has been coined clay...... squirt and is proposed to originate from a pressure gradient between the clay microporosity and the effective porosity. We have formulated a simple model that quantifies the clay-squirt effect on bulk moduli of sandstone with homogeneously distributed shale laminae or dispersed shale. The model...... predictions were compared with the literature data. For sandstones with dispersed shale, agreement was found, whereas other sandstones have larger fluid-saturated bulk modulus, possibly due to partially load-bearing shales or heterogeneous shale distribution. The data that agree with the clay-squirt model...
Negative thermal expansion materials
International Nuclear Information System (INIS)
Evans, J.S.O.
1997-01-01
The recent discovery of negative thermal expansion over an unprecedented temperature range in ZrW 2 O 8 (which contracts continuously on warming from below 2 K to above 1000 K) has stimulated considerable interest in this unusual phenomenon. Negative and low thermal expansion materials have a number of important potential uses in ceramic, optical and electronic applications. We have now found negative thermal expansion in a large new family of materials with the general formula A 2 (MO 4 ) 3 . Chemical substitution dramatically influences the thermal expansion properties of these materials allowing the production of ceramics with negative, positive or zero coefficients of thermal expansion, with the potential to control other important materials properties such as refractive index and dielectric constant. The mechanism of negative thermal expansion and the phase transitions exhibited by this important new class of low-expansion materials will be discussed. (orig.)
Non-repeatability of large plasticity for Fe-based bulk metallic glasses
Energy Technology Data Exchange (ETDEWEB)
Yang, Weiming [State Key Laboratory for Geomechanics and Deep Underground Engineering, School of Mechanics and Civil Engineering, School of Sciences, China University of Mining and Technology, Xuzhou 221116 (China); Sun, Baoan [Department of Mechanical and Biomedical Engineering, City University of Hong Kong (Hong Kong); Zhao, Yucheng, E-mail: zhaoyc1972@163.com [State Key Laboratory for Geomechanics and Deep Underground Engineering, School of Mechanics and Civil Engineering, School of Sciences, China University of Mining and Technology, Xuzhou 221116 (China); Li, Qiang [School of Physics Science and Technology, Xinjiang University, Urumqi, Xinjiang 830046 (China); Hou, Long; Luo, Ning [State Key Laboratory for Geomechanics and Deep Underground Engineering, School of Mechanics and Civil Engineering, School of Sciences, China University of Mining and Technology, Xuzhou 221116 (China); Dun, Chaochao [Department of Physics, Wake Forest University, Winston Salem, NC 27109 (United States); Zhao, Chengliang [Key Laboratory of Magnetic Materials and Devices, Ningbo Institute of Materials Technology & Engineering, Chinese Academy of Sciences, Ningbo 315201 (China); Ma, Zhanguo [State Key Laboratory for Geomechanics and Deep Underground Engineering, School of Mechanics and Civil Engineering, School of Sciences, China University of Mining and Technology, Xuzhou 221116 (China); Liu, Haishun, E-mail: liuhaishun@126.com [State Key Laboratory for Geomechanics and Deep Underground Engineering, School of Mechanics and Civil Engineering, School of Sciences, China University of Mining and Technology, Xuzhou 221116 (China); Shen, Baolong [School of Materials Science and Engineering, Southeast University, Nanjing 211189 (China)
2016-08-15
Serrated flow is an essential characteristic of the plastic deformation of metallic glasses. Under restricted loading conditions, the formation and expansion of shear bands act as the serrated flow of stress-strain curves in metallic glasses. In this work, serrated flows in Fe{sub 50}Ni{sub 30}P{sub 13}C{sub 7} glassy samples with different plasticity were studied. The distribution histogram shows a monotonically decreasing trend during the initial deformation stage (i.e., the plastic deformation in the range of 0–8%), whereas in the following deformation stage (i.e., a plastic deformation of 8–14%), the stress drop frequency distribution presents both a monotonically decreasing distribution and a peak shape similar to chaotic dynamics. It is shown that the spatial evolution behavior of shear bands in Fe{sub 50}Ni{sub 30}P{sub 13}C{sub 7} metallic glasses evolved from self-organized critical to chaotic dynamics in the form of serrated flow, which reveals the origin of discrete plasticity of Fe-based bulk metallic glasses. This study has potential applications for understanding the plastic deformation mechanism. - Highlights: • Two-stage deformation mechanism in Fe-based bulk metallic glasses. • Distribution of the stress drop amplitude is significantly different at two stages. • The stages are related to multiple shear bands and discrete plasticity.
Non-repeatability of large plasticity for Fe-based bulk metallic glasses
International Nuclear Information System (INIS)
Yang, Weiming; Sun, Baoan; Zhao, Yucheng; Li, Qiang; Hou, Long; Luo, Ning; Dun, Chaochao; Zhao, Chengliang; Ma, Zhanguo; Liu, Haishun; Shen, Baolong
2016-01-01
Serrated flow is an essential characteristic of the plastic deformation of metallic glasses. Under restricted loading conditions, the formation and expansion of shear bands act as the serrated flow of stress-strain curves in metallic glasses. In this work, serrated flows in Fe_5_0Ni_3_0P_1_3C_7 glassy samples with different plasticity were studied. The distribution histogram shows a monotonically decreasing trend during the initial deformation stage (i.e., the plastic deformation in the range of 0–8%), whereas in the following deformation stage (i.e., a plastic deformation of 8–14%), the stress drop frequency distribution presents both a monotonically decreasing distribution and a peak shape similar to chaotic dynamics. It is shown that the spatial evolution behavior of shear bands in Fe_5_0Ni_3_0P_1_3C_7 metallic glasses evolved from self-organized critical to chaotic dynamics in the form of serrated flow, which reveals the origin of discrete plasticity of Fe-based bulk metallic glasses. This study has potential applications for understanding the plastic deformation mechanism. - Highlights: • Two-stage deformation mechanism in Fe-based bulk metallic glasses. • Distribution of the stress drop amplitude is significantly different at two stages. • The stages are related to multiple shear bands and discrete plasticity.
Developing bulk exchange spring magnets
Mccall, Scott K.; Kuntz, Joshua D.
2017-06-27
A method of making a bulk exchange spring magnet by providing a magnetically soft material, providing a hard magnetic material, and producing a composite of said magnetically soft material and said hard magnetic material to make the bulk exchange spring magnet. The step of producing a composite of magnetically soft material and hard magnetic material is accomplished by electrophoretic deposition of the magnetically soft material and the hard magnetic material to make the bulk exchange spring magnet.
Negative thermal expansion materials: technological key for control of thermal expansion.
Takenaka, Koshi
2012-02-01
Most materials expand upon heating. However, although rare, some materials contract upon heating. Such negative thermal expansion (NTE) materials have enormous industrial merit because they can control the thermal expansion of materials. Recent progress in materials research enables us to obtain materials exhibiting negative coefficients of linear thermal expansion over -30 ppm K -1 . Such giant NTE is opening a new phase of control of thermal expansion in composites. Specifically examining practical aspects, this review briefly summarizes materials and mechanisms of NTE as well as composites containing NTE materials, based mainly on activities of the last decade.
Negative thermal expansion materials: technological key for control of thermal expansion
Directory of Open Access Journals (Sweden)
Koshi Takenaka
2012-01-01
Full Text Available Most materials expand upon heating. However, although rare, some materials contract upon heating. Such negative thermal expansion (NTE materials have enormous industrial merit because they can control the thermal expansion of materials. Recent progress in materials research enables us to obtain materials exhibiting negative coefficients of linear thermal expansion over −30 ppm K−1. Such giant NTE is opening a new phase of control of thermal expansion in composites. Specifically examining practical aspects, this review briefly summarizes materials and mechanisms of NTE as well as composites containing NTE materials, based mainly on activities of the last decade.
Negative thermal expansion materials: technological key for control of thermal expansion
International Nuclear Information System (INIS)
Takenaka, Koshi
2012-01-01
Most materials expand upon heating. However, although rare, some materials contract upon heating. Such negative thermal expansion (NTE) materials have enormous industrial merit because they can control the thermal expansion of materials. Recent progress in materials research enables us to obtain materials exhibiting negative coefficients of linear thermal expansion over −30 ppm K −1 . Such giant NTE is opening a new phase of control of thermal expansion in composites. Specifically examining practical aspects, this review briefly summarizes materials and mechanisms of NTE as well as composites containing NTE materials, based mainly on activities of the last decade. (topical review)
Elasticity, electronic properties and hardness of MoC investigated by first principles calculations
International Nuclear Information System (INIS)
Liu, YangZhen; Jiang, YeHua; Feng, Jing; Zhou, Rong
2013-01-01
The crystal structure, cohesive energy, formation enthalpy, mechanical anisotropy, electronic properties and hardness of α−MoC, β−MoC and γ−MoC are investigated by the first-principles calculations. The elastic constants and the bulk moduli, shear moduli, Young's moduli are calculated. The Young's modulus values of α−MoC, β−MoC and γ−MoC are 395.6 GPa, 551.2 GPa and 399.5 GPa, respectively. The surface constructions of Young's moduli identify the mechanical anisotropy of molybdenum carbide, and the results show that anisotropy of α−MoC is stronger than others. The electronic structure indicates that the bonding behaviors of MoC are the combinations of covalent and metallic bonds. The hardness of β−MoC is obviously higher than those of α−MoC and γ−MoC
Mechanical and thermal properties of bulk ZrB{sub 2}
Energy Technology Data Exchange (ETDEWEB)
Nakamori, Fumihiro [Graduate School of Engineering, Osaka University (Japan); Ohishi, Yuji, E-mail: ohishi@ms.see.eng.osaka-u.ac.jp [Graduate School of Engineering, Osaka University (Japan); Muta, Hiroaki; Kurosaki, Ken [Graduate School of Engineering, Osaka University (Japan); Fukumoto, Ken-ichi [Research Institute of Nuclear Engineering, University of Fukui (Japan); Yamanaka, Shinsuke [Graduate School of Engineering, Osaka University (Japan); Research Institute of Nuclear Engineering, University of Fukui (Japan)
2015-12-15
ZrB{sub 2} appears to have formed in the fuel debris at the Fukushima Daiichi nuclear disaster site, through the reaction between Zircaloy cladding materials and the control rod material B{sub 4}C. Since ZrB{sub 2} has a high melting point of 3518 K, the ceramic has been widely studied as a heat-resistant material. Although various studies on the thermochemical and thermophysical properties have been performed for ZrB{sub 2}, significant differences exist in the data, possibly due to impurities or the porosity within the studied samples. In the present study, we have prepared a ZrB{sub 2} bulk sample with 93.1% theoretical density by sintering ZrB{sub 2} powder. On this sample, we have comprehensively examined the thermal and mechanical properties of ZrB{sub 2} by the measurement of specific heat, ultrasonic sound velocities, thermal diffusivity, and thermal expansion. Vickers hardness and fracture toughness were also measured and found to be 13–23 GPa and 1.8–2.8 MPa m{sup 0.5}, respectively. The relationships between these properties were carefully examined in the present study. - Highlights: • A ZrB{sub 2} bulk sample with 93.1% theoretical density was prepared by sintering ZrB{sub 2} powder. • We have evaluated mechanical and thermal properties such as Vickers hardness, fracture toughness and thermal conductivity. • The relationships between these properties were carefully examined.
Modelling of bulk superconductor magnetization
International Nuclear Information System (INIS)
Ainslie, M D; Fujishiro, H
2015-01-01
This paper presents a topical review of the current state of the art in modelling the magnetization of bulk superconductors, including both (RE)BCO (where RE = rare earth or Y) and MgB 2 materials. Such modelling is a powerful tool to understand the physical mechanisms of their magnetization, to assist in interpretation of experimental results, and to predict the performance of practical bulk superconductor-based devices, which is particularly important as many superconducting applications head towards the commercialization stage of their development in the coming years. In addition to the analytical and numerical techniques currently used by researchers for modelling such materials, the commonly used practical techniques to magnetize bulk superconductors are summarized with a particular focus on pulsed field magnetization (PFM), which is promising as a compact, mobile and relatively inexpensive magnetizing technique. A number of numerical models developed to analyse the issues related to PFM and optimise the technique are described in detail, including understanding the dynamics of the magnetic flux penetration and the influence of material inhomogeneities, thermal properties, pulse duration, magnitude and shape, and the shape of the magnetization coil(s). The effect of externally applied magnetic fields in different configurations on the attenuation of the trapped field is also discussed. A number of novel and hybrid bulk superconductor structures are described, including improved thermal conductivity structures and ferromagnet–superconductor structures, which have been designed to overcome some of the issues related to bulk superconductors and their magnetization and enhance the intrinsic properties of bulk superconductors acting as trapped field magnets. Finally, the use of hollow bulk cylinders/tubes for shielding is analysed. (topical review)
Thermal expansion of coking coals
Energy Technology Data Exchange (ETDEWEB)
Orlik, M.; Klimek, J. (Vyzkumny a Zkusebni Ustav Nova Hut, Ostrava (Czechoslovakia))
1992-12-01
Analyzes expansion of coal mixtures in coke ovens during coking. Methods for measuring coal expansion on both a laboratory and pilot plant scale are comparatively evaluated. The method, developed, tested and patented in Poland by the Institute for Chemical Coal Processing in Zabrze (Polish standard PN-73/G-04522), is discussed. A laboratory device developed by the Institute for measuring coal expansion is characterized. Expansion of black coal from 10 underground mines in the Ostrava-Karvina coal district and from 9 coal mines in the Upper Silesia basin in Poland is comparatively evaluated. Investigations show that coal expansion reaches a maximum for coal types with a volatile matter ranging from 20 to 25%. With increasing volatile matter in coal, its expansion decreases. Coal expansion increases with increasing swelling index. Coal expansion corresponds with coal dilatation. With increasing coal density its expansion increases. Coal mixtures should be selected in such a way that their expansion does not cause a pressure exceeding 40 MPa. 11 refs.
Mining the bulk positron lifetime
International Nuclear Information System (INIS)
Aourag, H.; Guittom, A.
2009-01-01
We introduce a new approach to investigate the bulk positron lifetimes of new systems based on data-mining techniques. Through data mining of bulk positron lifetimes, we demonstrate the ability to predict the positron lifetimes of new semiconductors on the basis of available semiconductor data already studied. Informatics techniques have been applied to bulk positron lifetimes for different tetrahedrally bounded semiconductors in order to discover computational design rules. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)
Gassmann Theory Applies to Nanoporous Media
Gor, Gennady Y.; Gurevich, Boris
2018-01-01
Recent progress in extraction of unconventional hydrocarbon resources has ignited the interest in the studies of nanoporous media. Since many thermodynamic and mechanical properties of nanoscale solids and fluids differ from the analogous bulk materials, it is not obvious whether wave propagation in nanoporous media can be described using the same framework as in macroporous media. Here we test the validity of Gassmann equation using two published sets of ultrasonic measurements for a model nanoporous medium, Vycor glass, saturated with two different fluids, argon, and n-hexane. Predictions of the Gassmann theory depend on the bulk and shear moduli of the dry samples, which are known from ultrasonic measurements and the bulk moduli of the solid and fluid constituents. The solid bulk modulus can be estimated from adsorption-induced deformation or from elastic effective medium theory. The fluid modulus can be calculated according to the Tait-Murnaghan equation at the solvation pressure in the pore. Substitution of these parameters into the Gassmann equation provides predictions consistent with measured data. Our findings set up a theoretical framework for investigation of fluid-saturated nanoporous media using ultrasonic elastic wave propagation.
Tate, Stephen James
2013-10-01
In the 1960s, the technique of using cluster expansion bounds in order to achieve bounds on the virial expansion was developed by Lebowitz and Penrose (J. Math. Phys. 5:841, 1964) and Ruelle (Statistical Mechanics: Rigorous Results. Benjamin, Elmsford, 1969). This technique is generalised to more recent cluster expansion bounds by Poghosyan and Ueltschi (J. Math. Phys. 50:053509, 2009), which are related to the work of Procacci (J. Stat. Phys. 129:171, 2007) and the tree-graph identity, detailed by Brydges (Phénomènes Critiques, Systèmes Aléatoires, Théories de Jauge. Les Houches 1984, pp. 129-183, 1986). The bounds achieved by Lebowitz and Penrose can also be sharpened by doing the actual optimisation and achieving expressions in terms of the Lambert W-function. The different bound from the cluster expansion shows some improvements for bounds on the convergence of the virial expansion in the case of positive potentials, which are allowed to have a hard core.
Maas, Michael; Bodnar, Pedro Marcus; Hess, Ulrike; Treccani, Laura; Rezwan, Kurosch
2013-10-01
The synthesis of porous hydroxyapatite scaffolds is essential for biomedical applications such as bone tissue engineering and replacement. One way to induce macroporosity, which is needed to support bone in-growth, is to use protein additives as foaming agents. Another reason to use protein additives is the potential to introduce a specific biofunctionality to the synthesized scaffolds. In this work, we study the rheological properties of a hydroxyapatite suspension system with additions of the proteins bovine serum albumin (BSA), lysozyme (LSZ) and fibrinogen (FIB). Both the rheology of the bulk phase as well as the interfacial shear rheology are studied. The bulk rheological data provides important information on the setting behavior of the thixotropic suspension, which we find to be faster with the addition of FIB and LSZ and much slower with BSA. Foam bubble stabilization mechanisms can be rationalized via interfacial shear rheology and we show that it depends on the growth of interfacial films at the suspension/air interface. These interfacial films support the stabilization of bubbles within the ceramic matrix and thereby introduce macropores. Due to the weak interaction of the protein molecules with the hydroxyapatite particles of the suspension, we find that BSA forms the most stable interfacial films, followed by FIB. LSZ strongly interacts with the hydroxyapatite particles and thus only forms thin films with very low elastic moduli. In summary, our study provides fundamental rheological insights which are essential for tailoring hydroxyapatite/protein suspensions in order to synthesize scaffolds with controlled porosities. Copyright © 2013 Elsevier Inc. All rights reserved.
International Nuclear Information System (INIS)
Bindi, Luca
2009-01-01
The crystal structure of empressite, AgTe, a rare silver telluride, has been investigated by in situ X-ray single-crystal diffraction methods within the temperature range 298-463 K. AgTe remains orthorhombic, space group Pmnb (Pnma as standard), and shows only normal thermal expansion over the entire temperature range. The unit-cell parameters show a gradual increase with the increase of temperature. Slight adjustments in the geometry of Ag-tetrahedra and in the crystal-chemical environment of tellurium atoms occur in a continuous way without abrupt structural changes. The coefficients of thermal expansion along various axes are: α a = 1.5 x 10 -5 K -1 , α b = 3.0 x 10 -5 K -1 , α c = 2.2 x 10 -5 K -1 , and the bulk thermal expansion coefficient α V is 5.4 x 10 -5 K -1 for the temperature range 298-463 K
International Nuclear Information System (INIS)
Bud'ko, A.B.; Velikovich, A.L.; Liberman, M.A.; Felber, F.S.
1989-01-01
A solution is derived for the problem of the initial, linear stage of the growth of small perturbations in the course of the cylindrically symmetric compression and expansion of a plasma liner and a Z-pinch with a sharp boundary. In these systems, Rayleigh-Taylor instabilities localized near the plasma boundaries are the most dangerous. Bulk convective instabilities develop in addition to these Rayleigh-Taylor instabilities. The various instability modes, including local and global Rayleigh-Taylor modes, which grown in an accelerated plasma with distributed profiles of hydrodynamic variables, are classified. The spectra of the instability growth rates are calculated for plasma liners and Z-pinches. The shape of these spectra reveals an explanation of the stratification and filamentation of the plasma observed experimentally in pinches and liners. The imposition of a longitudinal magnetic field gives rise to a stability window in the space of the flow parameters. In this window, the Rayleigh-Taylor modes are suppressed completely by magnetic shear, while the bulk convective modes are suppressed to a significant extent
Handling of bulk solids theory and practice
Shamlou, P A
1990-01-01
Handling of Bulk Solids provides a comprehensive discussion of the field of solids flow and handling in the process industries. Presentation of the subject follows classical lines of separate discussions for each topic, so each chapter is self-contained and can be read on its own. Topics discussed include bulk solids flow and handling properties; pressure profiles in bulk solids storage vessels; the design of storage silos for reliable discharge of bulk materials; gravity flow of particulate materials from storage vessels; pneumatic transportation of bulk solids; and the hazards of solid-mater
Ferromagnetic bulk glassy alloys
International Nuclear Information System (INIS)
Inoue, Akihisa; Makino, Akihiro; Mizushima, Takao
2000-01-01
This paper deals with the review on the formation, thermal stability and magnetic properties of the Fe-based bulk glassy alloys in as-cast bulk and melt-spun ribbon forms. A large supercooled liquid region over 50 K before crystallization was obtained in Fe-(Al, Ga)-(P, C, B, Si), Fe-(Cr, Mo, Nb)-(Al, Ga)-(P, C, B) and (Fe, Co, Ni)-Zr-M-B (M=Ti, Hf, V, Nb, Ta, Cr, Mo and W) systems and bulk glassy alloys were produced in a thickness range below 2 mm for the Fe-(Al, Ga)-(P, C, B, Si) system and 6 mm for the Fe-Co-(Zr, Nb, Ta)-(Mo, W)-B system by copper-mold casting. The ring-shaped glassy Fe-(Al, Ga)-(P, C, B, Si) alloys exhibit much better soft magnetic properties as compared with the ring-shaped alloy made from the melt-spun ribbon because of the formation of the unique domain structure. The good combination of high glass-forming ability and good soft magnetic properties indicates the possibility of future development as a new bulk glassy magnetic material
Oliveira, Laís Rani Sales; Braga, Stella Sueli Lourenço; Bicalho, Aline Arêdes; Ribeiro, Maria Tereza Hordones; Price, Richard Bengt; Soares, Carlos José
2018-07-01
To describe a method of measuring the molar cusp deformation using micro-computed tomography (micro-CT), the propagation of enamel cracks using transillumination, and the effects of hygroscopic expansion after incremental and bulk-filling resin composite restorations. Twenty human molars received standardized Class II mesio-occlusal-distal cavity preparations. They were restored with either a bulk-fill resin composite, X-tra fil (XTRA), or a conventional resin composite, Filtek Z100 (Z100). The resin composites were tested for post-gel shrinkage using a strain gauge method. Cusp deformation (CD) was evaluated using the images obtained using a micro-CT protocol and using a strain-gauge method. Enamel cracks were detected using transillumination. The post-gel shrinkage of Z100 was higher than XTRA (P cracks than XTRA (P = 0.012). Micro-CT was an effective method for evaluating the cusp deformation. Transillumination was effective for detecting enamel cracks. There were fewer negative effects of polymerization shrinkage in bulk-fill resin restorations using XTRA than for the conventional incremental filling technique using conventional composite resin Z100. Shrinkage and cusp deformation are directly related to the formation of enamel cracks. Cusp deformation and crack propagation may increase the risk of tooth fracture. Copyright © 2018 Elsevier Ltd. All rights reserved.
Lee, Scott; Richards, Zachary
2015-03-01
The section modulus of a bone is a measure of its ability to resist bending torques. Carnivorous dinosaurs presumably had strong arm bones to hold struggling prey during hunting. Some theropods are believed to have become herbivorous and such animals would not have needed such strong arms. In this work, the section moduli of the humerus bones of bipedal theropod dinosaurs (from Microvenator celer to Tyrannosaurus rex) are studied to determine the maximum bending loads their arms could withstand. The results show that bending strength is not of uniform importance to these magnificent animals. The predatory theropods had strong arms for use in hunting. In contrast, the herbivorous dinosaurs had weaker arms.
International Nuclear Information System (INIS)
Gathers, G.R.; Shaner, J.W.; Hodgson, W.M.
1978-01-01
Results of isobaric expansion measurements for platinum are presented, including simultaneous values for enthalpy, specific volume, temperature and electrical resistivity in tabular form as well as numerical fits up to 7500 K. The specific heat for the liquid is C/sub p/ = 5.85 +- 0.30 R and is essentially constant up to 7500 K. The bulk thermal expansion coefficient increases from approx. 7.5 x 10 -5 K -1 at melt to approx. 1.03 x 10 -4 K -1 at 7500 K. The heat of fusion observed is Δh = 0.14 +- 0.03 MJ/kg and the melting point slope with pressure is estimated to be dT/sub m//dp =31 +- 10 K/GPa. The estimated critical parameters are T/sub c/ = 9285 K, P/sub c/ = 0.9492 GPa, v/sub c/ = 2.120 x 10 -4 m 3 /kg, and z/sub c/ = 0.5085. Preliminary results of a new sound velocity technique are discussed for lead. This technique will allow determination of specific heat c/sub v/, isothermal compressibility K/sub T/ and the constant temperature volume derivatives of entropy and internal energy, as well as the Gruneisen parameter γ/sub G/
Thermal expansion of granite rocks
International Nuclear Information System (INIS)
Stephansson, O.
1978-04-01
The thermal expansion of rocks is strongly controlled by the thermal expansion of the minerals. The theoretical thermal expansion of the Stripa Granite is gound to be 21 . 10 -6 [deg C] -1 at 25 deg C and 38 . 10 -6 [deg C] -1 at 400 deg C. The difference in expansion for the rock forming minerals causes micro cracking at heating. The expansion due to micro cracks is found to be of the same order as the mineral expansion. Most of the micro cracks will close at pressures of the order of 10 - 20 MPa. The thermal expansion of a rock mass including the effect of joints is determined in the pilot heater test in the Stripa Mine
Directory of Open Access Journals (Sweden)
Nicola H. Perry
2016-10-01
Full Text Available Mixed conducting perovskite oxides and related structures serving as electrodes for electrochemical oxygen incorporation and evolution in solid oxide fuel and electrolysis cells, respectively, play a significant role in determining the cell efficiency and lifetime. Desired improvements in catalytic activity for rapid surface oxygen exchange, fast bulk transport (electronic and ionic, and thermo-chemo-mechanical stability of oxygen electrodes will require increased understanding of the impact of both bulk and surface chemistry on these properties. This review highlights selected work at the International Institute for Carbon-Neutral Energy Research (I2CNER, Kyushu University, set in the context of work in the broader community, aiming to characterize and understand relationships between bulk and surface composition and oxygen electrode performance. Insights into aspects of bulk point defect chemistry, electronic structure, crystal structure, and cation choice that impact carrier concentrations and mobilities, surface exchange kinetics, and chemical expansion coefficients are emerging. At the same time, an understanding of the relationship between bulk and surface chemistry is being developed that may assist design of electrodes with more robust surface chemistries, e.g., impurity tolerance or limited surface segregation. Ion scattering techniques (e.g., secondary ion mass spectrometry, SIMS, or low energy ion scattering spectroscopy, LEIS with high surface sensitivity and increasing lateral resolution are proving useful for measuring surface exchange kinetics, diffusivity, and corresponding outer monolayer chemistry of electrodes exposed to typical operating conditions. Beyond consideration of chemical composition, the use of strain and/or a high density of active interfaces also show promise for enhancing performance.
Elastic anisotropy and low-temperature thermal expansion in the shape memory alloy Cu-Al-Zn.
Kuruvilla, Santhosh Potharay; Menon, C S
2008-04-01
Cu-based shape memory alloys are known for their technologically important pseudo-elastic and shapememory properties, which are intimately associated with the martensitic transformation. A combination of deformation theory and finite-strain elasticity theory has been employed to arrive at the expressions for higher order elastic constants of Cu-Al-Zn based on Keating's approach. The second- and third-order elastic constants are in good agreement with the measurements. The aggregate elastic properties like bulk modulus, pressure derivatives, mode Grüneisen parameters of the elastic waves, low temperature limit of thermal expansion, and the Anderson-Grüneisen parameter are also presented.
Gromnitskaya, E. L.; Danilov, I. V.; Lyapin, A. G.; Brazhkin, V. V.
2015-10-01
We present a low-temperature and high-pressure ultrasonic study of elastic properties of isotopic H2O-D2O solid solutions, comparing their properties with those of the isotopically pure H2O and D2O ices. Measurements were carried out for solid state amorphization (SSA) from 1h to high-density amorphous (HDA) ice upon compression up to 1.8 GPa at 77 K and for the temperature-induced (77 -190 K ) u-HDA (unrelaxed HDA) → e-HDA (expanded HDA) → low-density amorphous (LDA )→1 c cascade of ice transformations near room pressure. There are many similarities in the elasticity behaviour of H2O ,D2O , and H2O-D2O solid solutions, including the softening of the shear elastic modulus as a precursor of SSA and the HDA →LDA transition. We have found significant isotopic effects during H/D substitution, including elastic softening of H2O -D2O solid solutions with respect to the isotopically pure ices in the case of the bulk moduli of ices 1c and 1h and for both bulk and shear elastic moduli of HDA ice at high pressures (>1 GPa ) . This softening is related to the configurational isotopic disorder in the solid solutions. At low pressures, the isotope concentration dependence of the elastic moduli of u-HDA ice changes remarkably and becomes monotonic with pronounced change of the bulk modulus (≈20 %) .
International Nuclear Information System (INIS)
Czél, Gergely; Takács, Dénes
2015-01-01
A new material property determination method is presented for the calculation of effective elastic moduli of non-circular ring specimens cut from filament wound oval profile polymer composite sewer liner pipes. The hoop direction elastic moduli was determined using the test results obtained from ring compression tests, which is a very basic setup, and requires no special equipment. Calculations were executed for many different oval profiles, and diagrams were constructed, from which the cross section dependent C_e_f_f constants can be taken. The new method was validated by the comparison of tests and finite element analysis results. The calculation method and the diagrams are essential design tools for engineers, and a big step forward in sizing non-circular profile liner pipes. - Highlights: • A simple modulus measurement method is presented for non-circular ring specimens. • The evaluation method is validated against a finite element model. • Profile shape dependent constants are presented for a wide range of cross-sections. • A set of charts with the constants are provided to aid design engineers.
Misra, A
2008-01-01
We consider two sets of issues in this paper. The first has to do with moduli stabilization, existence of “area codes” [A. Giryavets, New attractors and area codes, JHEP 0603 (2006) 020, hep-th/0511215] and the possibility of getting a non-supersymmetric dS minimum without the addition of -branes as in KKLT for type II flux compactifications. The second has to do with the “inverse problem” [K. Saraikin, C. Vafa, Non-supersymmetric black holes and topological strings, hep-th/0703214] and “fake superpotentials” [A. Ceresole, G. Dall'Agata, Flow equations for non-BPS extremal black holes, JHEP 0703 (2007) 110, hep-th/0702088] for extremal (non-)supersymmetric black holes in type II compactifications. We use (orientifold of) a “Swiss cheese” Calabi–Yau [J.P. Conlon, F. Quevedo, K. Suruliz, Large-volume flux compactifications: Moduli spectrum and D3/D7 soft supersymmetry breaking, JHEP 0508 (2005) 007, hep-th/0505076] expressed as a degree-18 hypersurface in WCP4[1,1,1,6,9] in the “large-volume...
Gupta, Manoj; Gupta, T C
2017-10-01
The present study aims to accurately estimate inertial, physical, and dynamic parameters of human body vibratory model consistent with physical structure of the human body that also replicates its dynamic response. A 13 degree-of-freedom (DOF) lumped parameter model for standing person subjected to support excitation is established. Model parameters are determined from anthropometric measurements, uniform mass density, elastic modulus of individual body segments, and modal damping ratios. Elastic moduli of ellipsoidal body segments are initially estimated by comparing stiffness of spring elements, calculated from a detailed scheme, and values available in literature for same. These values are further optimized by minimizing difference between theoretically calculated platform-to-head transmissibility ratio (TR) and experimental measurements. Modal damping ratios are estimated from experimental transmissibility response using two dominant peaks in the frequency range of 0-25 Hz. From comparison between dynamic response determined form modal analysis and experimental results, a set of elastic moduli for different segments of human body and a novel scheme to determine modal damping ratios from TR plots, are established. Acceptable match between transmissibility values calculated from the vibratory model and experimental measurements for 50th percentile U.S. male, except at very low frequencies, establishes the human body model developed. Also, reasonable agreement obtained between theoretical response curve and experimental response envelop for average Indian male, affirms the technique used for constructing vibratory model of a standing person. Present work attempts to develop effective technique for constructing subject specific damped vibratory model based on its physical measurements.
Entanglement, holography and causal diamonds
de Boer, Jan; Haehl, Felix M.; Heller, Michal P.; Myers, Robert C.
2016-08-01
We argue that the degrees of freedom in a d-dimensional CFT can be reorganized in an insightful way by studying observables on the moduli space of causal diamonds (or equivalently, the space of pairs of timelike separated points). This 2 d-dimensional space naturally captures some of the fundamental nonlocality and causal structure inherent in the entanglement of CFT states. For any primary CFT operator, we construct an observable on this space, which is defined by smearing the associated one-point function over causal diamonds. Known examples of such quantities are the entanglement entropy of vacuum excitations and its higher spin generalizations. We show that in holographic CFTs, these observables are given by suitably defined integrals of dual bulk fields over the corresponding Ryu-Takayanagi minimal surfaces. Furthermore, we explain connections to the operator product expansion and the first law of entanglemententropy from this unifying point of view. We demonstrate that for small perturbations of the vacuum, our observables obey linear two-derivative equations of motion on the space of causal diamonds. In two dimensions, the latter is given by a product of two copies of a two-dimensional de Sitter space. For a class of universal states, we show that the entanglement entropy and its spin-three generalization obey nonlinear equations of motion with local interactions on this moduli space, which can be identified with Liouville and Toda equations, respectively. This suggests the possibility of extending the definition of our new observables beyond the linear level more generally and in such a way that they give rise to new dynamically interacting theories on the moduli space of causal diamonds. Various challenges one has to face in order to implement this idea are discussed.
Entanglement, holography and causal diamonds
Energy Technology Data Exchange (ETDEWEB)
Boer, Jan de [Institute of Physics, Universiteit van Amsterdam,Science Park 904, 1090 GL Amsterdam (Netherlands); Haehl, Felix M. [Centre for Particle Theory & Department of Mathematical Sciences, Durham University,South Road, Durham DH1 3LE (United Kingdom); Heller, Michal P.; Myers, Robert C. [Perimeter Institute for Theoretical Physics,31 Caroline Street North, Waterloo, Ontario N2L 2Y5 (Canada)
2016-08-29
We argue that the degrees of freedom in a d-dimensional CFT can be re-organized in an insightful way by studying observables on the moduli space of causal diamonds (or equivalently, the space of pairs of timelike separated points). This 2d-dimensional space naturally captures some of the fundamental nonlocality and causal structure inherent in the entanglement of CFT states. For any primary CFT operator, we construct an observable on this space, which is defined by smearing the associated one-point function over causal diamonds. Known examples of such quantities are the entanglement entropy of vacuum excitations and its higher spin generalizations. We show that in holographic CFTs, these observables are given by suitably defined integrals of dual bulk fields over the corresponding Ryu-Takayanagi minimal surfaces. Furthermore, we explain connections to the operator product expansion and the first law of entanglement entropy from this unifying point of view. We demonstrate that for small perturbations of the vacuum, our observables obey linear two-derivative equations of motion on the space of causal diamonds. In two dimensions, the latter is given by a product of two copies of a two-dimensional de Sitter space. For a class of universal states, we show that the entanglement entropy and its spin-three generalization obey nonlinear equations of motion with local interactions on this moduli space, which can be identified with Liouville and Toda equations, respectively. This suggests the possibility of extending the definition of our new observables beyond the linear level more generally and in such a way that they give rise to new dynamically interacting theories on the moduli space of causal diamonds. Various challenges one has to face in order to implement this idea are discussed.
Dispersion in poroelastic systems
International Nuclear Information System (INIS)
Berryman, James G.; Wang, Herbert F.
2001-01-01
We address one key source of the known discrepancies between theory and experiment in poroelasticity, i.e., the fact that Gassmann's equations for the bulk and shear moduli predict that the shear modulus is independent of the saturating fluid properties, whereas it is observed on the contrary that at high enough frequencies the shear modulus can in fact depend on the fluid's elastic properties in many porous materials. One clue to understanding this behavior comes from effective medium theory, which shows that the shear modulus does depend on the fluid properties in many circumstances. In comparison to values predicted by effective medium theory, Gassmann's equations predict different, smaller values for both the effective bulk and shear moduli of porous media. Sorting through these apparent (but not actual) disagreements among theory and theory, and theory and experiment is the main thrust of the paper
Compliance characteristics of cracked UO2 pellets
International Nuclear Information System (INIS)
Williford, R.E.; Mohr, C.L.; Lanning, D.D.
1981-01-01
The thermally induced cracking of UO 2 fuel pellets causes simultaneous reductions of the bulk (extrinsic) fuel thermal conductivity and elastic moduli to values significantly less than those for solid pellets. The magnitude of these bulk properly reductions was found to be primarily dependent on the amount of crack area in the transverse plane of the fuel. The model described herein uses a simple description of the crack geometry to couple the fuel rod thermal and mechanical behaviors by relating in-reactor data to Hooke's Law and a crack compliance model. Data from the NRC/PNL Halden experiment IFA-432 show that for a typical helium-filled BWR-design rod at 30 kW/m, the effective thermal conductivity and elastic moduli of the cracked fuel are 4/5 and 1/40 of that for solid pellets, respectively
Takahashi, T.
2017-12-01
The static Young's modulus (deformability) of a rock is indispensable for designing and constructing tunnels, dams and underground caverns in civil engineering. Static Young's modulus which is an elastic modulus at large strain level is usually obtained with the laboratory tests of rock cores sampled in boreholes drilled in a rock mass. A deformability model of the entire rock mass is then built by extrapolating the measurements based on a rock mass classification obtained in geological site characterization. However, model-building using data obtained from a limited number of boreholes in the rock mass, especially a complex rock mass, may cause problems in the accuracy and reliability of the model. On the other hand, dynamic Young's modulus which is the modulus at small strain level can be obtained from seismic velocity. If dynamic Young's modulus can be rationally converted to static one, a seismic velocity model by the seismic method can be effectively used to build a deformability model of the rock mass. In this study, we have, therefore, developed a rock physics model (Mavko et al., 2009) to estimate static Young's modulus from dynamic one for sedimentary rocks. The rock physics model has been generally applied to seismic properties at small strain level. In the proposed model, however, the sandy shale model, one of rock physics models, is extended for modeling the static Young's modulus at large strain level by incorporating the mixture of frictional and frictionless grain contacts into the Hertz-Mindlin model. The proposed model is verified through its application to the dynamic Young's moduli derived from well log velocities and static Young's moduli measured in the tri-axial compression tests of rock cores sampled in the same borehole as the logs were acquired. This application proves that the proposed rock physics model can be possibly used to estimate static Young's modulus (deformability) which is required in many types of civil engineering applications
Compressibility of Ir-Os alloys under high pressure
International Nuclear Information System (INIS)
Yusenko, Kirill V.; Bykova, Elena; Bykov, Maxim; Gromilov, Sergey A.; Kurnosov, Alexander V.; Prescher, Clemens; Prakapenka, Vitali B.; Hanfland, Michael; Smaalen, Sander van; Margadonna, Serena; Dubrovinsky, Leonid S.
2015-01-01
Highlights: • fcc- and hcp-Ir-Os alloys were prepared from single-source precursors. • Their atomic volumes measured at ambient conditions using powder X-ray diffraction follow nearly linear dependence. • Compressibility of alloys have been studied up to 30 GPa at room temperature in diamond anvil cells. • Their bulk moduli increase with increasing osmium content. - Abstract: Several fcc- and hcp-structured Ir-Os alloys were prepared from single-source precursors in hydrogen atmosphere at 873 K. Their atomic volumes measured at ambient conditions using powder X-ray diffraction follow nearly linear dependence as a function of composition. Alloys have been studied up to 30 GPa at room temperature by means of synchrotron-based X-ray powder diffraction in diamond anvil cells. Their bulk moduli increase with increasing osmium content and show a deviation from linearity. Bulk modulus of hcp-Ir 0.20 Os 0.80 is identical to that of pure Os (411 GPa) within experimental errors. Peculiarities on fcc-Ir 0.80 Os 0.20 compressibility curve indicate possible changes of its electronic properties at ∼20 GPa
Growth of Rayleigh-Taylor and bulk convective instabilities in dynamics of plasma liners and pinches
International Nuclear Information System (INIS)
Bud'ko, A.B.; Velikovich, A.L.; Liberman, M.A.; Felber, F.S.
1989-01-01
Perturbation growth is studied for the initial, linear stage of an instability development in the course of a cylindrically-symmetric compression and expansion of plasma liners and Z-pinches with a sharp boundary. The hydrodynamic instabilities are Rayleigh-Taylor and bulk convective ones, the former being the most dengerous. Classification of the instability modes developing in accelerated plasmas, inclusing the local and global Rayleigh-Taylor modes, is given. The spectra of the instability growth rates are calculated for plasma liners and Z-pinches. The properties of the spectra appear to explain the filamentation and stratification of plasmas observed in the experiments with liners and Z-pinches. An axial magnetic field is shown to create a window of stability in the space of the flow parameters, where th Rayleigh-Taylor modes are fully suppressed by the magnetic shear, and the bulk convective ones - to a considerable extent. The axial magnetic field required to stabilize the implosion of a liner is estimated as B z0 =(10-30 kG)I(MA)/R 0 (cm), where I is the average current, R 0 - the initial radius of the liner
Gravity mediation in 6d brane-world supergravity
International Nuclear Information System (INIS)
Lee, H.M.
2005-09-01
We consider the gravity-mediated SUSY breaking within the effective theory of six-dimensional brane-world supergravity. We construct the supersymmetric bulk-brane action by Noether method and find the nontrivial moduli coupling of the brane F- and D-terms. We find that the low energy Kaehler potential is not of sequestered form, so gravity mediation may occur at tree level. In moduli stabilization with anomaly effects included, the scalar soft mass squared can be positive at tree level and it can be comparable to the anomaly mediation. (orig.)
Coupling brane fields to bulk supergravity
Energy Technology Data Exchange (ETDEWEB)
Parameswaran, Susha L. [Uppsala Univ. (Sweden). Theoretical Physics; Schmidt, Jonas [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)
2010-12-15
In this note we present a simple, general prescription for coupling brane localized fields to bulk supergravity. We illustrate the procedure by considering 6D N=2 bulk supergravity on a 2D orbifold, with brane fields localized at the fixed points. The resulting action enjoys the full 6D N=2 symmetries in the bulk, and those of 4D N=1 supergravity at the brane positions. (orig.)
Energy Technology Data Exchange (ETDEWEB)
Bindi, Luca [Museo di Storia Naturale, sez. di Mineralogia, Universita di Firenze, Via La Pira 4, I-50121 Firenze (Italy)], E-mail: luca.bindi@unifi.it
2009-04-03
The crystal structure of empressite, AgTe, a rare silver telluride, has been investigated by in situ X-ray single-crystal diffraction methods within the temperature range 298-463 K. AgTe remains orthorhombic, space group Pmnb (Pnma as standard), and shows only normal thermal expansion over the entire temperature range. The unit-cell parameters show a gradual increase with the increase of temperature. Slight adjustments in the geometry of Ag-tetrahedra and in the crystal-chemical environment of tellurium atoms occur in a continuous way without abrupt structural changes. The coefficients of thermal expansion along various axes are: {alpha}{sub a} = 1.5 x 10{sup -5} K{sup -1}, {alpha}{sub b} = 3.0 x 10{sup -5} K{sup -1}, {alpha}{sub c} = 2.2 x 10{sup -5} K{sup -1}, and the bulk thermal expansion coefficient {alpha}{sub V} is 5.4 x 10{sup -5} K{sup -1} for the temperature range 298-463 K.
International Nuclear Information System (INIS)
Lind, P.
1993-02-01
The completeness properties of the discrete set of bound state, virtual states and resonances characterizing the system of a single nonrelativistic particle moving in a central cutoff potential is investigated. From a completeness relation in terms of these discrete states and complex scattering states one can derive several Resonant State Expansions (RSE). It is interesting to obtain purely discrete expansion which, if valid, would significantly simplify the treatment of the continuum. Such expansions can be derived using Mittag-Leffler (ML) theory for a cutoff potential and it would be nice to see if one can obtain the same expansions starting from an eigenfunction theory that is not restricted to a finite sphere. The RSE of Greens functions is especially important, e.g. in the continuum RPA (CRPA) method of treating giant resonances in nuclear physics. The convergence of RSE is studied in simple cases using square well wavefunctions in order to achieve high numerical accuracy. Several expansions can be derived from each other by using the theory of analytic functions and one can the see how to obtain a natural discretization of the continuum. Since the resonance wavefunctions are oscillating with an exponentially increasing amplitude, and therefore have to be interpreted through some regularization procedure, every statement made about quantities involving such states is checked by numerical calculations.Realistic nuclear wavefunctions, generated by a Wood-Saxon potential, are used to test also the usefulness of RSE in a realistic nuclear calculation. There are some fundamental differences between different symmetries of the integral contour that defines the continuum in RSE. One kind of symmetry is necessary to have an expansion of the unity operator that is idempotent. Another symmetry must be used if we want purely discrete expansions. These are found to be of the same form as given by ML. (29 refs.)
Bulk viscosity of spin-one color superconductors
Energy Technology Data Exchange (ETDEWEB)
Sa' d, Basil A.
2009-08-27
The bulk viscosity of several quark matter phases is calculated. It is found that the effect of color superconductivity is not trivial, it may suppress, or enhance the bulk viscosity depending on the critical temperature and the temperature at which the bulk viscosity is calculated. Also, is it found that the effect of neutrino-emitting Urca processes cannot be neglected in the consideration of the bulk viscosity of strange quark matter. The results for the bulk viscosity of strange quark matter are used to calculate the r-mode instability window of quark stars with several possible phases. It is shown that each possible phase has a different structure for the r-mode instability window. (orig.)
Bulk viscosity of spin-one color superconductors
International Nuclear Information System (INIS)
Sa'd, Basil A.
2009-01-01
The bulk viscosity of several quark matter phases is calculated. It is found that the effect of color superconductivity is not trivial, it may suppress, or enhance the bulk viscosity depending on the critical temperature and the temperature at which the bulk viscosity is calculated. Also, is it found that the effect of neutrino-emitting Urca processes cannot be neglected in the consideration of the bulk viscosity of strange quark matter. The results for the bulk viscosity of strange quark matter are used to calculate the r-mode instability window of quark stars with several possible phases. It is shown that each possible phase has a different structure for the r-mode instability window. (orig.)
Mechanical, thermodynamic and electronic properties of wurtzite and zinc-blende GaN crystals
Qin, Hongbo; Luan, Xinghe; Feng, Chuang; Yang, Daoguo; Zhang, G.Q.
2017-01-01
For the limitation of experimental methods in crystal characterization, in this study, the mechanical, thermodynamic and electronic properties of wurtzite and zinc-blende GaN crystals were investigated by first-principles calculations based on density functional theory. Firstly, bulk moduli,
Isotropic Negative Thermal Expansion Metamaterials.
Wu, Lingling; Li, Bo; Zhou, Ji
2016-07-13
Negative thermal expansion materials are important and desirable in science and engineering applications. However, natural materials with isotropic negative thermal expansion are rare and usually unsatisfied in performance. Here, we propose a novel method to achieve two- and three-dimensional negative thermal expansion metamaterials via antichiral structures. The two-dimensional metamaterial is constructed with unit cells that combine bimaterial strips and antichiral structures, while the three-dimensional metamaterial is fabricated by a multimaterial 3D printing process. Both experimental and simulation results display isotropic negative thermal expansion property of the samples. The effective coefficient of negative thermal expansion of the proposed models is demonstrated to be dependent on the difference between the thermal expansion coefficient of the component materials, as well as on the circular node radius and the ligament length in the antichiral structures. The measured value of the linear negative thermal expansion coefficient of the three-dimensional sample is among the largest achieved in experiments to date. Our findings provide an easy and practical approach to obtaining materials with tunable negative thermal expansion on any scale.
International Nuclear Information System (INIS)
Cook, W.H.; Kennedy, C.R.; Eatherly, W.P.
1975-01-01
The characterization of property changes in various grades of near-isotropic, ''binderless'' grades of graphite as functions of fluence accumulated at 715 0 C from 0 to 42 x 10 21 neutrons/cm 2 (E greater than 50 keV) was made. Generally, the average coefficients of thermal expansion (CTE) from 20 to 600 0 C and the room-temperature values for strengths, fracture strains, Young's moduli, shear moduli, and calculated figures of merit (FOM) for resistance to thermal shock all ultimately decreased with fluence. (U.S.)
International Nuclear Information System (INIS)
Wang, Yonggang; Wen, Ting; Park, Changyong; Kenney-Benson, Curtis; Pravica, Michael; Zhao, Yusheng; Yang, Wenge
2016-01-01
The structure stability under high pressure and thermal expansion behavior of Na 3 OBr and Na 4 OI 2 , two prototypes of alkali-metal-rich antiperovskites, were investigated by in situ synchrotron X-ray diffraction techniques under high pressure and low temperature. Both are soft materials with bulk modulus of 58.6 GPa and 52.0 GPa for Na 3 OBr and Na 4 OI 2 , respectively. The cubic Na 3 OBr structure and tetragonal Na 4 OI 2 with intergrowth K 2 NiF 4 structure are stable under high pressure up to 23 GPa. Although being a characteristic layered structure, Na 4 OI 2 exhibits nearly isotropic compressibility. Negative thermal expansion was observed at low temperature range (20–80 K) in both transition-metal-free antiperovskites for the first time. The robust high pressure structure stability was examined and confirmed by first-principles calculations among various possible polymorphisms qualitatively. The results provide in-depth understanding of the negative thermal expansion and robust crystal structure stability of these antiperovskite systems and their potential applications
Pentoney, Christopher; Harwell, Jeff; Leroy, Gondy
2014-01-01
Searching for medical information online is a common activity. While it has been shown that forming good queries is difficult, Google's query suggestion tool, a type of query expansion, aims to facilitate query formation. However, it is unknown how this expansion, which is based on what others searched for, affects the information gathering of the online community. To measure the impact of social-based query expansion, this study compared it with content-based expansion, i.e., what is really in the text. We used 138,906 medical queries from the AOL User Session Collection and expanded them using Google's Autocomplete method (social-based) and the content of the Google Web Corpus (content-based). We evaluated the specificity and ambiguity of the expansion terms for trigram queries. We also looked at the impact on the actual results using domain diversity and expansion edit distance. Results showed that the social-based method provided more precise expansion terms as well as terms that were less ambiguous. Expanded queries do not differ significantly in diversity when expanded using the social-based method (6.72 different domains returned in the first ten results, on average) vs. content-based method (6.73 different domains, on average).
Ha, Vu Thi Thanh; Hung, Vu Van; Hanh, Pham Thi Minh; Tuyen, Nguyen Viet; Hai, Tran Thi; Hieu, Ho Khac
2018-03-01
The thermodynamic and mechanical properties of III-V zinc-blende AlP, InP semiconductors and their alloys have been studied in detail from statistical moment method taking into account the anharmonicity effects of the lattice vibrations. The nearest neighbor distance, thermal expansion coefficient, bulk moduli, specific heats at the constant volume and constant pressure of the zincblende AlP, InP and AlyIn1-yP alloys are calculated as functions of the temperature. The statistical moment method calculations are performed by using the many-body Stillinger-Weber potential. The concentration dependences of the thermodynamic quantities of zinc-blende AlyIn1-yP crystals have also been discussed and compared with those of the experimental results. Our results are reasonable agreement with earlier density functional theory calculations and can provide useful qualitative information for future experiments. The moment method then can be developed extensively for studying the atomistic structure and thermodynamic properties of nanoscale materials as well.
Thermodynamic properties of bcc crystals at high temperatures: The transition metals
International Nuclear Information System (INIS)
MacDonald, R.A.; Shukla, R.C.
1985-01-01
The second-neighbor central-force model of a bcc crystal, previously used in lowest-order anharmonic perturbation theory to calculate the thermodynamic properties of the alkali metals, is here applied to the transition metals V, Nb, Ta, Mo, and W. The limitations of the model are apparent in the thermal-expansion results, which fall away from the experimental trend above about 1800 K. The specific heat similarly fails to exhibit the sharp rise that is observed at higher temperatures. A static treatment of vacancies cannot account for the difference between theory and experiment. The electrons have been taken into account by using a model that specifically includes d-band effects in the electron ground-state energy. The results thus obtained for the bulk moduli are quite satisfactory. In the light of these results, we discuss the prerequisites for a better treatment of metals when the electrons play an important role in determining the thermodynamic properties
Bulk viscous matter and recent acceleration of the universe based on causal viscous theory
Energy Technology Data Exchange (ETDEWEB)
Mohan, N.D.J.; Sasidharan, Athira; Mathew, Titus K. [Cochin University of Science and Technology, Department of Physics, Kochi (India)
2017-12-15
The evolution of the bulk viscous matter dominated universe has been analysed using the full causal theory for the evolution of the viscous pressure in the context of the recent acceleration of the universe. The form of the viscosity is taken as ξ = αρ{sup 1/2}. We obtained analytical solutions for the Hubble parameter and scale factor of the universe. The model parameters have been computed using the observational data. The evolution of the prominent cosmological parameters was obtained. The age of the universe for the best estimated model parameters is found to be less than observational value. The viscous matter behaves like a stiff fluid in the early phase and evolves to a negative pressure fluid in the later phase. The equation of state is found to be stabilised with value ω > -1. The local as well as generalised second law of thermodynamics is satisfied. The statefinder diagnostic shows that this model is distinct from the standard ΛCDM. One of the marked deviations seen in this model to be compared with the corresponding model using the Eckart approach is that in this model the bulk viscosity decreases with the expansion of the universe, while in the Eckart formalism it increases from negative values in the early universe towards positive values. (orig.)
Bulk viscous matter and recent acceleration of the universe based on causal viscous theory
International Nuclear Information System (INIS)
Mohan, N.D.J.; Sasidharan, Athira; Mathew, Titus K.
2017-01-01
The evolution of the bulk viscous matter dominated universe has been analysed using the full causal theory for the evolution of the viscous pressure in the context of the recent acceleration of the universe. The form of the viscosity is taken as ξ = αρ 1/2 . We obtained analytical solutions for the Hubble parameter and scale factor of the universe. The model parameters have been computed using the observational data. The evolution of the prominent cosmological parameters was obtained. The age of the universe for the best estimated model parameters is found to be less than observational value. The viscous matter behaves like a stiff fluid in the early phase and evolves to a negative pressure fluid in the later phase. The equation of state is found to be stabilised with value ω > -1. The local as well as generalised second law of thermodynamics is satisfied. The statefinder diagnostic shows that this model is distinct from the standard ΛCDM. One of the marked deviations seen in this model to be compared with the corresponding model using the Eckart approach is that in this model the bulk viscosity decreases with the expansion of the universe, while in the Eckart formalism it increases from negative values in the early universe towards positive values. (orig.)
Directory of Open Access Journals (Sweden)
Farahat F
2016-09-01
Full Text Available Statement of Problem: For many years, application of the composite restoration with a thickness less than 2 mm for achieving the minimum polymerization contraction and stress has been accepted as a principle. But through the recent development in dental material a group of resin based composites (RBCs called Bulk Fill is introduced whose producers claim the possibility of achieving a good restoration in bulks with depths of 4 or even 5 mm. Objectives: To evaluate the effect of irradiation times and bulk depths on the degree of cure (DC of a bulk fill composite and compare it with the universal type. Materials and Methods: This study was conducted on two groups of dental RBCs including Tetric N Ceram Bulk Fill and Tetric N Ceram Universal. The composite samples were prepared in Teflon moulds with a diameter of 5 mm and height of 2, 4 and 6 mm. Then, half of the samples in each depth were cured from the upper side of the mould for 20s by LED light curing unit. The irradiation time for other specimens was 40s. After 24 hours of storage in distilled water, the microhardness of the top and bottom of the samples was measured using a Future Tech (Japan- Model FM 700 Vickers hardness testing machine. Data were analyzed statistically using the one and multi way ANOVAand Tukey’s test (p = 0.050. Results: The DC of Tetric N Ceram Bulk Fill in defined irradiation time and bulk depth was significantly more than the universal type (p < 0.001. Also, the DC of both composites studied was significantly (p < 0.001 reduced by increasing the bulk depths. Increasing the curing time from 20 to 40 seconds had a marginally significant effect (p ≤ 0.040 on the DC of both bulk fill and universal studied RBC samples. Conclusions: The DC of the investigated bulk fill composite was better than the universal type in all the irradiation times and bulk depths. The studied universal and bulk fill RBCs had an appropriate DC at the 2 and 4 mm bulk depths respectively and
The rate of beneficial mutations surfing on the wave of a range expansion.
Directory of Open Access Journals (Sweden)
Rémi Lehe
Full Text Available Many theoretical and experimental studies suggest that range expansions can have severe consequences for the gene pool of the expanding population. Due to strongly enhanced genetic drift at the advancing frontier, neutral and weakly deleterious mutations can reach large frequencies in the newly colonized regions, as if they were surfing the front of the range expansion. These findings raise the question of how frequently beneficial mutations successfully surf at shifting range margins, thereby promoting adaptation towards a range-expansion phenotype. Here, we use individual-based simulations to study the surfing statistics of recurrent beneficial mutations on wave-like range expansions in linear habitats. We show that the rate of surfing depends on two strongly antagonistic factors, the probability of surfing given the spatial location of a novel mutation and the rate of occurrence of mutations at that location. The surfing probability strongly increases towards the tip of the wave. Novel mutations are unlikely to surf unless they enjoy a spatial head start compared to the bulk of the population. The needed head start is shown to be proportional to the inverse fitness of the mutant type, and only weakly dependent on the carrying capacity. The precise location dependence of surfing probabilities is derived from the non-extinction probability of a branching process within a moving field of growth rates. The second factor is the mutation occurrence which strongly decreases towards the tip of the wave. Thus, most successful mutations arise at an intermediate position in the front of the wave. We present an analytic theory for the tradeoff between these factors that allows to predict how frequently substitutions by beneficial mutations occur at invasion fronts. We find that small amounts of genetic drift increase the fixation rate of beneficial mutations at the advancing front, and thus could be important for adaptation during species invasions.
Jedrzejowska, Agnieszka; Grzybowski, Andrzej; Paluch, Marian
2017-07-19
In this paper, we report the nontrivial results of our investigations of dynamic and thermodynamic moduli in search of invariants for viscous liquids in the density scaling regime by using selected supercooled van der Waals liquids as representative materials. Previously, the dynamic modulus M p-T (defined in the pressure-temperature representation by the ratio of isobaric activation energy and activation volume) as well as the ratio B T /M p-T (where B T is the thermodynamic modulus defined as the inverse isothermal compressibility) have been suggested as some kinds of material constants. We have established that they are not valid in the explored wide range of temperatures T over a dozen decades of structural relaxation times τ. The temperature dependences of M p-T and B T /M p-T have been elucidated by comparison with the well-known measure of the relative contribution of temperature and density fluctuations to molecular dynamics near the glass transition, i.e., the ratio of isochoric and isobaric activation energies. Then, we have implemented an idea to transform the definition of the dynamic modulus M p-T from the p-T representation to the V-T one. This idea relied on the disentanglement of combined temperature and density fluctuations involved in isobaric parameters and has resulted in finding an invariant for viscous liquids in the density scaling regime, which is the ratio of thermodynamic and dynamic moduli, B T /M V-T . In this way, we have constituted a characteristic of thermodynamics and molecular dynamics, which remains unchanged in the supercooled liquid state for a given material, the molecular dynamics of which obeys the power density scaling law.
2013-12-04
.... FDA-2013-N-1525] List of Bulk Drug Substances That May Be Used in Pharmacy Compounding; Bulk Drug... proposed rule to list bulk drug substances used in pharmacy compounding and preparing to develop a list of... Formulary monograph, if a monograph exists, and the United States Pharmacopoeia chapter on pharmacy...
To clone or not to clone? Induced pluripotent stem cells can be generated in bulk culture.
Willmann, Charlotte A; Hemeda, Hatim; Pieper, Lisa A; Lenz, Michael; Qin, Jie; Joussen, Sylvia; Sontag, Stephanie; Wanek, Paul; Denecke, Bernd; Schüler, Herdit M; Zenke, Martin; Wagner, Wolfgang
2013-01-01
Induced pluripotent stem cells (iPSCs) are usually clonally derived. The selection of fully reprogrammed cells generally involves picking of individual colonies with morphology similar to embryonic stem cells (ESCs). Given that fully reprogrammed cells are highly proliferative and escape from cellular senescence, it is conceivable that they outgrow non-pluripotent and partially reprogrammed cells during culture expansion without the need of clonal selection. In this study, we have reprogrammed human dermal fibroblasts (HDFs) with episomal plasmid vectors. Colony frequency was higher and size was larger when using murine embryonic fibroblasts (MEFs) as stromal support instead of HDFs or human mesenchymal stromal cells (MSCs). We have then compared iPSCs which were either clonally derived by manual selection of a single colony, or derived from bulk-cultures of all initial colonies. After few passages their morphology, expression of pluripotency markers, and gene expression profiles did not reveal any significant differences. Furthermore, clonally-derived and bulk-cultured iPSCs revealed similar in vitro differentiation potential towards the three germ layers. Therefore, manual selection of individual colonies does not appear to be necessary for the generation of iPSCs - this is of relevance for standardization and automation of cell culture procedures.
Bulk viscosity in holographic Lifshitz hydrodynamics
International Nuclear Information System (INIS)
Hoyos, Carlos; Kim, Bom Soo; Oz, Yaron
2014-01-01
We compute the bulk viscosity in holographic models dual to theories with Lifshitz scaling and/or hyperscaling violation, using a generalization of the bulk viscosity formula derived in arXiv:1103.1657 from the null focusing equation. We find that only a class of models with massive vector fields are truly Lifshitz scale invariant, and have a vanishing bulk viscosity. For other holographic models with scalars and/or massless vector fields we find a universal formula in terms of the dynamical exponent and the hyperscaling violation exponent
Determination of the elastic constants of portlandite by Brillouin spectroscopy
Speziale, S.; Reichmann, H.J.; Schilling, F.R.; Wenk, H.R.; Monteiro, P.J.M.
2008-01-01
The single crystal elastic constants Cij and the shear and adiabatic bulk modulus of a natural portlandite (Ca(OH)2) crystal were determined by Brillouin spectroscopy at ambient conditions. The elastic constants, expressed in GPa, are: C11 = 102.0(± 2.0), C12 = 32.1(± 1.0), C13 = 8.4(± 0.4), C14 = 4.5(± 0.2), C33 = 33.6(± 0.7), C44 = 12.0(± 0.3), C66 = (C11-C12)/2 = 35.0(± 1.1), where the numbers in parentheses are 1σ standard deviations. The Reuss bounds of the adiabatic bulk and shear moduli are K0S = 26.0(± 0.3) GPa and G0 = 17.5(± 0.4) GPa, respectively, while the Voigt bounds of these moduli are K0S = 37.3(± 0.4) GPa and G0 = 24.4(± 0.3) GPa. The Reuss and Voigt bounds for the aggregate Young's modulus are 42.8(± 1.0) GPa and 60.0(± 0.8) GPa respectively, while the aggregate Poisson's ratio is equal to 0.23(± 0.01). Portlandite exhibits both large compressional elastic anisotropy with C11/C33 = 3.03(± 0.09) equivalent to that of the isostructural hydroxide brucite (Mg(OH)2), and large shear anisotropy with C66/C44 = 2.92(± 0.12) which is 11% larger than brucite. The comparison between the bulk modulus of portlandite and that of lime (CaO) confirms a systematic linear relationship between the bulk moduli of brucite-type simple hydroxides and the corresponding NaCl-type oxides. © 2008 Elsevier Ltd. All rights reserved.
Determination of the elastic constants of portlandite by Brillouin spectroscopy
Speziale, S.
2008-10-01
The single crystal elastic constants Cij and the shear and adiabatic bulk modulus of a natural portlandite (Ca(OH)2) crystal were determined by Brillouin spectroscopy at ambient conditions. The elastic constants, expressed in GPa, are: C11 = 102.0(± 2.0), C12 = 32.1(± 1.0), C13 = 8.4(± 0.4), C14 = 4.5(± 0.2), C33 = 33.6(± 0.7), C44 = 12.0(± 0.3), C66 = (C11-C12)/2 = 35.0(± 1.1), where the numbers in parentheses are 1σ standard deviations. The Reuss bounds of the adiabatic bulk and shear moduli are K0S = 26.0(± 0.3) GPa and G0 = 17.5(± 0.4) GPa, respectively, while the Voigt bounds of these moduli are K0S = 37.3(± 0.4) GPa and G0 = 24.4(± 0.3) GPa. The Reuss and Voigt bounds for the aggregate Young\\'s modulus are 42.8(± 1.0) GPa and 60.0(± 0.8) GPa respectively, while the aggregate Poisson\\'s ratio is equal to 0.23(± 0.01). Portlandite exhibits both large compressional elastic anisotropy with C11/C33 = 3.03(± 0.09) equivalent to that of the isostructural hydroxide brucite (Mg(OH)2), and large shear anisotropy with C66/C44 = 2.92(± 0.12) which is 11% larger than brucite. The comparison between the bulk modulus of portlandite and that of lime (CaO) confirms a systematic linear relationship between the bulk moduli of brucite-type simple hydroxides and the corresponding NaCl-type oxides. © 2008 Elsevier Ltd. All rights reserved.
Longitudinal and bulk viscosities of expanded rubidium
International Nuclear Information System (INIS)
Zaheri, Ali Hossein Mohammad; Srivastava, Sunita; Tankeshwar, K
2003-01-01
First three non-vanishing sum rules for the bulk and longitudinal stress auto-correlation functions have been evaluated for liquid Rb at six thermodynamic states along the liquid-vapour coexistence curve. The Mori memory function formalism and the frequency sum rules have been used to calculate bulk and longitudinal viscosities. The results thus obtained for the ratio of bulk viscosity to shear viscosity have been compared with experimental and other theoretical predictions wherever available. The values of the bulk viscosity have been found to be more than the corresponding values of the shear viscosity for all six thermodynamic states investigated here
Directory of Open Access Journals (Sweden)
Pereira, A. H. A.
2012-06-01
Full Text Available The work herein verifies the changes of the elastic moduli, damping and modulus of rupture (MOR of a high alumina refractory castable due to heating, cooling and heating-cooling thermal shock damage. Twelve prismatic specimens were prepared for the tests and divided into four groups. The thermal shocks were performed on three groups, each containing three specimens having abrupt temperature changes of 1100°C during heating in the first group, during cooling in the second and during heating followed by cooling in the third group. The fourth group, which was taken as a reference did not receive any thermal shock. The elastic moduli were measured after each thermal shock cycle. After 10 cycles, the MOR, the damping and the damping dependence on excitation amplitude were measured at room temperature for all specimens.
The elastic moduli showed a similar decrease and the damping a similar increase due to the cooling and heating-cooling thermal shocks. The heating thermal shocks caused no significant changes on the elastic moduli and damping. However, the MOR appeared to be sensitive to the heating thermal shock. This work also shows that the damping for the studied refractory castable is non-linear (i.e., amplitude of excitation sensitive and that this non-linearity increases when the damage level rises.
En este trabajo se investigaron las alteraciones de los módulos elásticos dinámicos, del amortiguamiento y del módulo de rotura (MOR de un material refractario moldeable de alta alúmina después de recibir choques térmicos de calentamiento, enfriamiento y calentamiento seguido de enfriamiento (calentamiento-enfriamiento. Para ello se prepararon doce cuerpos prismáticos dividiéndolos en cuatro grupos. Los choques térmicos se le aplicaron a sólo tres grupos, cada uno con tres muestras. Al primer grupo se le aplicó un cambio brusco de temperatura de 1100 °C en calentamiento, en enfriamiento al segundo grupo y calentamiento seguido
Multi-Regge kinematics and the moduli space of Riemann spheres with marked points
Energy Technology Data Exchange (ETDEWEB)
Duca, Vittorio Del [Institute for Theoretical Physics, ETH Zürich,Hönggerberg, 8093 Zürich (Switzerland); Druc, Stefan; Drummond, James [School of Physics & Astronomy, University of Southampton,Highfield, Southampton, SO17 1BJ (United Kingdom); Duhr, Claude [Theoretical Physics Department, CERN,Route de Meyrin, CH-1211 Geneva 23 (Switzerland); Center for Cosmology, Particle Physics and Phenomenology (CP3),Université catholique de Louvain,Chemin du Cyclotron 2, 1348 Louvain-La-Neuve (Belgium); Dulat, Falko [SLAC National Accelerator Laboratory, Stanford University,Stanford, CA 94309 (United States); Marzucca, Robin [Center for Cosmology, Particle Physics and Phenomenology (CP3),Université catholique de Louvain,Chemin du Cyclotron 2, 1348 Louvain-La-Neuve (Belgium); Papathanasiou, Georgios [SLAC National Accelerator Laboratory, Stanford University,Stanford, CA 94309 (United States); Verbeek, Bram [Center for Cosmology, Particle Physics and Phenomenology (CP3),Université catholique de Louvain,Chemin du Cyclotron 2, 1348 Louvain-La-Neuve (Belgium)
2016-08-25
We show that scattering amplitudes in planar N=4 Super Yang-Mills in multi-Regge kinematics can naturally be expressed in terms of single-valued iterated integrals on the moduli space of Riemann spheres with marked points. As a consequence, scattering amplitudes in this limit can be expressed as convolutions that can easily be computed using Stokes’ theorem. We apply this framework to MHV amplitudes to leading-logarithmic accuracy (LLA), and we prove that at L loops all MHV amplitudes are determined by amplitudes with up to L+4 external legs. We also investigate non-MHV amplitudes, and we show that they can be obtained by convoluting the MHV results with a certain helicity flip kernel. We classify all leading singularities that appear at LLA in the Regge limit for arbitrary helicity configurations and any number of external legs. Finally, we use our new framework to obtain explicit analytic results at LLA for all MHV amplitudes up to five loops and all non-MHV amplitudes with up to eight external legs and four loops.
Non-Abelian flux tubes in N=1 SQCD: Supersizing world-sheet supersymmetry
International Nuclear Information System (INIS)
Shifman, M.; Yung, A.
2005-01-01
We consider non-Abelian 1/2 Bogomol'nyi-Prasad-Sommerfield (BPS) flux tubes (strings) in a deformed N=2 supersymmetric gauge theory, with mass terms μ 1,2 of the adjoint fields breaking N=2 down to N=1. The main feature of the non-Abelian strings is the occurrence of orientational moduli associated with the possibility of rotations of their color fluxes inside a global SU(N) group. The bulk four-dimensional theory has four supercharges; half-criticality of the non-Abelian strings would imply then N=1 supersymmetry on the world sheet, i.e. two supercharges. In fact, superalgebra of the reduced moduli space has four supercharges. Internal dynamics of the orientational moduli are described by a two-dimensional CP(N-1) model on the string world sheet. We focus mainly on the SU(2) case, i.e. CP(1) world-sheet theory. We show that non-Abelian BPS strings exist for all values of μ 1,2 . The low-energy theory of moduli is indeed CP(1), with four supercharges, in a wide region of breaking parameters μ 1,2 . Only in the limit of very large μ 1,2 , above some critical value does the N=2 world-sheet supersymmetry break down to N=1. We observe 'supersymmetry emergence' for the flux-tube junction (confined monopole): The kink-monopole is half-critical considered from the standpoint of the world-sheet CP(1) model (i.e. two supercharges conserved), while in the bulk N=1 theory there is no monopole central charge at all
Synthesis, characterization and thermal expansion studies on ThO2-SmO1.5 solid solutions
International Nuclear Information System (INIS)
Panneerselvam, G.; Antony, M.P.
2008-01-01
Full text: A highly homogeneous Th 1-x Sm x O 2 ; 0 ≤ x ≤ 0.8 solid solutions were synthesized by co-precipitation technique and the co-precipitated samples were sintered at 1473 K. Compositions of the solid solutions were characterized by standard wet-chemical analysis. X-ray diffraction measurements were performed in the sintered pellets for structural analysis, lattice parameter calculation and determination of solid solubility of SmO 1.5 in ThO 2 matrix. Bulk and theoretical densities of solid solutions were also determined. A fluorite structure was observed for ThO 2 -SmO 1.5 solid solutions with 0-55.2 mol % SmO 1.5 . Their thermal expansion coefficients were measured using high temperature X-ray diffraction technique. The mean linear thermal expansivity, αm for ThO 2 -SmO 1.5 solid solutions containing 17.9, 41.7 and 52.0 mole percent of SmO 1.5 were determined in the temperature range 298 to 2000 K for the first time. The mean linear thermal expansion coefficients for ThO 2 -SmO 1.5 solid solutions are 10.47x10 -6 K -1 , 11.16x10 -6 K -1 and 11.45x10 -6 K -1 , respectively. The percentage linear thermal expansion in this temperature range, for ThO 2 -SmO 1.5 solid solutions containing 17.9, 41.7 and 52.0 mol % SmO 1.5 are 1.82,1.94 and 1.99 respectively. It is suggested that the solid solutions are stable up to 2000 K. It is also suggested that the effect and nature of the dopant are the important parameters influenced in the thermal expansion of the ThO 2
International Nuclear Information System (INIS)
Zhao Wei; Yu Niann-i
1998-01-01
Estimation of the elastic modulus is important in engineering design. One difference between CFCCs (continuous fiber-reinforced ceramic-matrix composites), and CMCs (whisker, particulate, or short fiber-reinforced ceramic-matrix composites), is that the anisotropic behavior of CFCCs plays an important role in affecting their mechanical behavior. This feature may also contribute to the variation of elastic properties and strengths of CFCC. In this paper, a Fortran program is developed to quantify the lamina stacking sequence effect on the effective elastic moduli of the laminated CFCCs. The material for modeling is a plain-weave Nicalon fiber-reinforced silicon carbide (Nicalon/SiC) CFCCs. Results show that various stacking sequences within the CFCC (a [0/30/60] lay-up) will give different effective elastic moduli of the CFCCs. This trend leads to a variation of the slope of the linear portion on the flexural stress-strain curve, i.e., changing the position of the starting point of the non-linear portion, and the shape of the whole curve, which gives a different value of the peak stress in the curve. (orig.)
Energy expansion planning by considering electrical and thermal expansion simultaneously
International Nuclear Information System (INIS)
Abbasi, Ali Reza; Seifi, Ali Reza
2014-01-01
Highlights: • This paper focused on the expansion planning optimization of energy systems. • Employing two form of energy: the expansion of electrical and thermal energies. • The main objective is to minimize the costs. • A new Modified Honey Bee Mating Optimization (MHBMO) algorithm is applied. - Abstract: This study focused on the expansion planning optimization of energy systems employing two forms of energy: the expansion of electrical and thermal energies simultaneously. The main objective of this investigation is confirming network adequacy by adding new equipment to the network, over a given planning horizon. The main objective of the energy expansion planning (EEP) is to minimize the real energy loss, voltage deviation and the total cost of installation equipments. Since the objectives are different and incommensurable, it is difficult to solve the problem by the conventional approaches that may optimize a single objective. So, the meta-heuristic algorithm is applied to this problem. Here, Honey Bee Mating Optimization algorithm (HBMO) as a new evolutionary optimization algorithm is utilized. In order to improve the total ability of HBMO for the global search and exploration, a new modification process is suggested such a way that the algorithm will search the total search space globally. Also, regarding the uncertainties of the new complicated energy systems, in this paper for the first time, the EEP problem is investigated in a stochastic environment by the use of probabilistic load flow technique based on Point Estimate Method (PEM). In order to evaluate the feasibility and effectiveness of the proposed algorithm, two modified test systems are used as case studies
Bulk temperature measurement in thermally striped pipe flows
International Nuclear Information System (INIS)
Lemure, N.; Olvera, J.R.; Ruggles, A.E.
1995-12-01
The hot leg flows in some Pressurized Water Reactor (PWR) designs have a temperature distribution across the pipe cross-section. This condition is often referred to as a thermally striped flow. Here, the bulk temperature measurement of pipe flows with thermal striping is explored. An experiment is conducted to examine the feasibility of using temperature measurements on the external surface of the pipe to estimate the bulk temperature of the flow. Simple mixing models are used to characterize the development of the temperature profile in the flow. Simple averaging techniques and Backward Propagating Neural Net are used to predict bulk temperature from the external temperature measurements. Accurate bulk temperatures can be predicted. However, some temperature distributions in the flow effectively mask the bulk temperature from the wall and cause significant error in the bulk temperature predicted using this technique
Transfer points of belt conveyors operating with unfavorable bulk
Energy Technology Data Exchange (ETDEWEB)
Goehring, H [Technische Universitaet, Dresden (German Democratic Republic)
1989-06-01
Describes design of belt conveyor chutes that transfer bulk of surface mines from one conveyor to another. Conveyor belt velocity is a significant parameter. Unfavorable chute design may lead to bulk flow congestion, bulk velocity losses etc. The bulk flow process is analyzed, bulk flow velocities, belt inclinations and bulk feeding from 2 conveyors into one chute are taken into account. Conventional chutes have parabolic belt impact walls. An improved version with divided impact walls is proposed that maintains a relatively high bulk velocity, reduces friction at chute walls and decreases wear and dirt build-up. Design of the improved chute is explained. It is built to adapt to existing structures without major modifications. The angle between 2 belt conveyors can be up to 90 degrees, the best bulk transfer is noted at conveyor angles below 60 degrees. Various graphs and schemes are provided. 6 refs.
International Nuclear Information System (INIS)
Dzenus, M.; Hundhausen, W.; Jansing, W.
1980-01-01
This discourse recounts efforts put into the SNR-2 project; specifically the development of compensation devices. The various prototypes of these compensation devices are described and the state of the development reviewed. Large Na (sodium)-heat transfer systems require a lot of valuable space if the component lay-out does not include compensation devices. So, in order to condense the spatial requirement as much as possible, expansion joints must be integrated into the pipe system. There are two basic types to suit the purpose: axial expansion joints and angular expansion joints. The expansion joints were developed on the basis of specific design criteria whereby differentiation is made between expansion joints of small and large nominal diameter. Expansion joints for installation in the sodium-filled primary piping are equipped with safety bellows in addition to the actual working bellows. Expansion joints must be designed and mounted in a manner to completely withstand seismic forces. The design must exclude any damage to the bellows during intermittent operations, that is, when sodium is drained the bellows' folds must be completely empty; otherwise residual solidified sodium could destroy the bellows when restarting. The expansion joints must be engineered on the basis of the following design data for the secondary system of the SNR project: working pressure: 16 bar; failure mode pressure: 5 events; failure mode: 5 sec., 28.5 bar, 520 deg. C; working temperature: 520 deg. C; temperature transients: 30 deg. C/sec.; service life: 200,000 h; number of load cycles: 10 4 ; material: 1.4948 or 1.4919; layer thickness of folds: 0.5 mm; angular deflection (DN 800): +3 deg. C or; axial expansion absorption (DN 600): ±80 mm; calculation: ASME class. The bellows' development work is not handled within this scope. The bellows are supplied by leading manufacturers, and warrant highest quality. Multiple bellows were selected on the basis of maximum elasticity - a property
Energy Technology Data Exchange (ETDEWEB)
Dzenus, M.; Hundhausen, W.; Jansing, W.
1979-10-15
This discourse recounts efforts put into the SNR-2 project; specifically the development of compensation devices. The various prototypes of these compensation devices are described and the state of development reviewed. The expansion joints were developed on the basis of specific design criteria whereby differentiation is made between expansion joints of small and large nominal diameter. Expansion joints for installation in the sodium-filled primary piping are equipped with safety bellows in addition to the actual working bellows.
Virtual thermal expansion coefficient of Cu precipitated in the Fe95Cu5 alloy
International Nuclear Information System (INIS)
Koeszegi, L.; Somogyvari, Z.
1999-01-01
Complete text of publication follows. Precipitations on grain boundaries play very important role in the formation of material's characteristics like embrittlement, durability etc. It was already shown [1] that Cu precipitations are under different stress conditions than the bulk material. The situation is more complicated in the case when a construction is exposed to temperature changes as well. In that case not only the residual stresses during the fabrication but the different thermal expansion coefficients can produce additional problems. This situation was modelled using Fe 95 Cu 5 alloy where Cu precipitates on the grain boundaries. The alloy was produced by high-frequency melting and an extra heat treatment was used to produce a quasi-equilibrium state. Pure Cu was also measured to compare the behaviours. Cu(111) Bragg peak was measured at different temperatures by high resolution neutron diffraction. The measurements were carried out on the G5-2 spectrometer at LLB in Saclay. Measurements show that not only residual stress can be recognised on the Cu precipitates but the thermal expansion coefficient of these precipitates definitly differ from the ones of pure Cu. (author)
Elastic properties of gamma-Pu by resonant ultrasound spectroscopy
Energy Technology Data Exchange (ETDEWEB)
Migliori, Albert [Los Alamos National Laboratory; Betts, J [Los Alamos National Laboratory; Trugman, A [Los Alamos National Laboratory; Mielke, C H [Los Alamos National Laboratory; Mitchell, J N [Los Alamos National Laboratory; Ramos, M [Los Alamos National Laboratory; Stroe, I [WORXESTER, MA
2009-01-01
Despite intense experimental and theoretical work on Pu, there is still little understanding of the strange properties of this metal. We used resonant ultrasound spectroscopy method to investigate the elastic properties of pure polycrystalline Pu at high temperatures. Shear and longitudinal elastic moduli of the {gamma}-phase of Pu were determined simultaneously and the bulk modulus was computed from them. A smooth linear and large decrease of all elastic moduli with increasing temperature was observed. We calculated the Poisson ratio and found that it increases from 0.242 at 519K to 0.252 at 571K.
High Temperature Energy Storage – HTES project: Geotechnics and Gelogy section
DEFF Research Database (Denmark)
Paci, Laura; Rocchi, Irene; Fabricius, Ida Lykke
and erosion of Zealand during the Neogene. The results shown were obtained calculating the maximum effective stress based on the burial anomaly as studied by Japsen (1998). In addition, the elastic moduli were calculated using the bulk density and the elastic P‐wave velocity log data by means of the iso......‐frame model proposed by Fabricius (2003). The model allows us to estimate the elastic moduli by comparing the elastic modulus obtained by elastic P‐wave measurements with the theoretical one obtained under the assumptions of either particles in suspension or cemented particles constituting a frame....
Influence of Young's moduli in 3D fluid-structure coupled models of the human cochlea
Böhnke, Frank; Semmelbauer, Sebastian; Marquardt, Torsten
2015-12-01
The acoustic wave propagation in the human cochlea was studied using a tapered box-model with linear assumptions respective to all mechanical parameters. The discretisation and evaluation is conducted by a commercial finite element package (ANSYS). The main difference to former models of the cochlea was the representation of the basilar membrane by a 3D elastic solid. The Young's moduli of this solid were modified to study their influence on the travelling wave. The lymph in the scala vestibuli and scala tympani was represented by a viscous and nearly incompressible fluid finite element approach. Our results show the maximum displacement for f = 2kHz at half of the length of the cochlea in accordance with former experiments. For low frequencies f <200 Hz nearly zero phase shifts were found, whereas for f =1 kHz it reaches values up to -12 cycles depending on the degree of orthotropy.
ANALISIS KESELAMATAN TERMOHIDROLIK BULK SHIELDING REAKTOR KARTINI
Directory of Open Access Journals (Sweden)
Azizul Khakim
2015-10-01
Full Text Available ABSTRAK ANALISIS KESELAMATAN TERMOHIDROLIK BULK SHIELDING REAKTOR KARTINI. Bulk shielding merupakan fasilitas yang terintegrasi dengan reaktor Kartini yang berfungsi sebagai penyimpanan sementara bahan bakar bekas. Fasilitas ini merupakan fasilitas yang termasuk dalam struktur, sistem dan komponen (SSK yang penting bagi keselamatan. Salah satu fungsi keselamatan dari sistem penanganan dan penyimpanan bahan bakar adalah mencegah kecelakaan kekritisan yang tak terkendali dan membatasi naiknya temperatur bahan bakar. Analisis keselamatan paling kurang harus mencakup analisis keselamatan dari sisi neutronik dan termo hidrolik Bulk shielding. Analisis termo hidrolik ditujukan untuk memastikan perpindahan panas dan proses pendinginan bahan bakar bekas berjalan baik dan tidak terjadi akumulasi panas yang mengancam integritas bahan bakar. Code tervalidasi PARET/ANL digunakan untuk analisis pendinginan dengan mode konveksi alam. Hasil perhitungan menunjukkan bahwa mode pendinginan konvekasi alam cukup memadai dalam mendinginkan panas sisa tanpa mengakibatkan kenaikan temperatur bahan bakar yang signifikan. Kata kunci: Bulk shielding, bahan bakar bekas, konveksi alam, PARET. ABSTRACT THERMAL HYDRAULIC SAFETY ANALYSIS OF BULK SHIELDING KARTINI REACTOR. Bulk shielding is an integrated facility to Kartini reactor which is used for temporary spent fuels storage. The facility is one of the structures, systems and components (SSCs important to safety. Among the safety functions of fuel handling and storage are to prevent any uncontrolable criticality accidents and to limit the fuel temperature increase. Safety analyses should, at least, cover neutronic and thermal hydraulic calculations of the bulk shielding. Thermal hydraulic analyses were intended to ensure that heat removal and the process of the spent fuels cooling takes place adequately and no heat accumulation that challenges the fuel integrity. Validated code, PARET/ANL was used for analysing the
Expansions for Coulomb wave functions
Boersma, J.
1969-01-01
In this paper we derive a number of expansions for Whittaker functions, regular and irregular Coulomb wave functions. The main result consists of a new expansion for the irregular Coulomb wave functions of orders zero and one in terms of regular Coulomb wave functions. The latter expansions are
Superductile bulk metallic glass
International Nuclear Information System (INIS)
Yao, K.F.; Ruan, F.; Yang, Y.Q.; Chen, N.
2006-01-01
Usually, monolithic bulk metallic glasses undergo inhomogeneous plastic deformation and exhibit poor ductility (<2%) at room temperature. We report a newly developed Pd-Si binary bulk metallic glass, which exhibits a uniform plastic deformation and a large plastic engineering strain of 82% and a plastic true strain of 170%, together with initial strain hardening, slight strain softening and final strain hardening characteristics. The uniform shear deformation and the ultrahigh plasticity are mainly attributed to strain hardening, which results from the nanoscale inhomogeneity due to liquid phase separation. The formed nanoscale inhomogeneity will hinder, deflect, and bifurcate the propagation of shear bands
Bulk viscosity of molecular fluids
Jaeger, Frederike; Matar, Omar K.; Müller, Erich A.
2018-05-01
The bulk viscosity of molecular models of gases and liquids is determined by molecular simulations as a combination of a dilute gas contribution, arising due to the relaxation of internal degrees of freedom, and a configurational contribution, due to the presence of intermolecular interactions. The dilute gas contribution is evaluated using experimental data for the relaxation times of vibrational and rotational degrees of freedom. The configurational part is calculated using Green-Kubo relations for the fluctuations of the pressure tensor obtained from equilibrium microcanonical molecular dynamics simulations. As a benchmark, the Lennard-Jones fluid is studied. Both atomistic and coarse-grained force fields for water, CO2, and n-decane are considered and tested for their accuracy, and where possible, compared to experimental data. The dilute gas contribution to the bulk viscosity is seen to be significant only in the cases when intramolecular relaxation times are in the μs range, and for low vibrational wave numbers (<1000 cm-1); This explains the abnormally high values of bulk viscosity reported for CO2. In all other cases studied, the dilute gas contribution is negligible and the configurational contribution dominates the overall behavior. In particular, the configurational term is responsible for the enhancement of the bulk viscosity near the critical point.
Unified bulk-boundary correspondence for band insulators
Rhim, Jun-Won; Bardarson, Jens H.; Slager, Robert-Jan
2018-03-01
The bulk-boundary correspondence, a topic of intensive research interest over the past decades, is one of the quintessential ideas in the physics of topological quantum matter. Nevertheless, it has not been proven in all generality and has in certain scenarios even been shown to fail, depending on the boundary profiles of the terminated system. Here, we introduce bulk numbers that capture the exact number of in-gap modes, without any such subtleties in one spatial dimension. Similarly, based on these 1D bulk numbers, we define a new 2D winding number, which we call the pole winding number, that specifies the number of robust metallic surface bands in the gap as well as their topological character. The underlying general methodology relies on a simple continuous extrapolation from the bulk to the boundary, while tracking the evolution of Green's function's poles in the vicinity of the bulk band edges. As a main result we find that all the obtained numbers can be applied to the known insulating phases in a unified manner regardless of the specific symmetries. Additionally, from a computational point of view, these numbers can be effectively evaluated without any gauge fixing problems. In particular, we directly apply our bulk-boundary correspondence construction to various systems, including 1D examples without a traditional bulk-boundary correspondence, and predict the existence of boundary modes on various experimentally studied graphene edges, such as open boundaries and grain boundaries. Finally, we sketch the 3D generalization of the pole winding number by in the context of topological insulators.
46 CFR 148.04-23 - Unslaked lime in bulk.
2010-10-01
... 46 Shipping 5 2010-10-01 2010-10-01 false Unslaked lime in bulk. 148.04-23 Section 148.04-23... HAZARDOUS MATERIALS IN BULK Special Additional Requirements for Certain Material § 148.04-23 Unslaked lime in bulk. (a) Unslaked lime in bulk must be transported in unmanned, all steel, double-hulled barges...
Conformal expansions and renormalons
Energy Technology Data Exchange (ETDEWEB)
Rathsman, J.
2000-02-07
The coefficients in perturbative expansions in gauge theories are factorially increasing, predominantly due to renormalons. This type of factorial increase is not expected in conformal theories. In QCD conformal relations between observables can be defined in the presence of a perturbative infrared fixed-point. Using the Banks-Zaks expansion the authors study the effect of the large-order behavior of the perturbative series on the conformal coefficients. The authors find that in general these coefficients become factorially increasing. However, when the factorial behavior genuinely originates in a renormalon integral, as implied by a postulated skeleton expansion, it does not affect the conformal coefficients. As a consequence, the conformal coefficients will indeed be free of renormalon divergence, in accordance with previous observations concerning the smallness of these coefficients for specific observables. The authors further show that the correspondence of the BLM method with the skeleton expansion implies a unique scale-setting procedure. The BLM coefficients can be interpreted as the conformal coefficients in the series relating the fixed-point value of the observable with that of the skeleton effective charge. Through the skeleton expansion the relevance of renormalon-free conformal coefficients extends to real-world QCD.
Bearing-Mounting Concept Accommodates Thermal Expansion
Nespodzany, Robert; Davis, Toren S.
1995-01-01
Pins or splines allow radial expansion without slippage. Design concept for mounting rotary bearing accommodates differential thermal expansion between bearing and any structure(s) to which bearing connected. Prevents buildup of thermal stresses by allowing thermal expansion to occur freely but accommodating expansion in such way not to introduce looseness. Pin-in-slot configuration also maintains concentricity.
Local elastic properties of nano-confined fluids: A density functional study
Energy Technology Data Exchange (ETDEWEB)
Sun, Zongli, E-mail: zongli_sun@163.com [Science and Technology College, North China Electric Power University, Baoding 071051 (China); Kang, Yanshuang [College of Science, Agriculture University of Hebei, Baoding 071001 (China)
2014-05-01
The understanding of mechanical properties of confined fluids is essential for modeling and manipulating of nano-scaled systems. Unlike the uniform phase, the confined fluids usually display different features in structure and related properties. Due to the presence of the confining geometry, the density profile and many physical and chemical properties may be position-dependent. The aim of our research is to derive an expression for the local elastic property by using the classical elastic theory. Both the bulk and shear moduli are expressed as functional of density of particle. The theoretical result derived is applied to the Lennard-Jones fluids confined in nano-cavity. Comparison of our numerical result and the simulation result is made and qualitative agreement is observed. Further, influence of bulk density, temperature and external potential on moduli is calculated and the physical mechanism is analyzed. Relationship between contact modulus and the interfacial tension is also calculated. Their opposite trend with temperature is observed.
Local elastic properties of nano-confined fluids: A density functional study
International Nuclear Information System (INIS)
Sun, Zongli; Kang, Yanshuang
2014-01-01
The understanding of mechanical properties of confined fluids is essential for modeling and manipulating of nano-scaled systems. Unlike the uniform phase, the confined fluids usually display different features in structure and related properties. Due to the presence of the confining geometry, the density profile and many physical and chemical properties may be position-dependent. The aim of our research is to derive an expression for the local elastic property by using the classical elastic theory. Both the bulk and shear moduli are expressed as functional of density of particle. The theoretical result derived is applied to the Lennard-Jones fluids confined in nano-cavity. Comparison of our numerical result and the simulation result is made and qualitative agreement is observed. Further, influence of bulk density, temperature and external potential on moduli is calculated and the physical mechanism is analyzed. Relationship between contact modulus and the interfacial tension is also calculated. Their opposite trend with temperature is observed.
Structural and electronic properties of AlX (X = P, As, Sb) nanowires: Ab initio study
International Nuclear Information System (INIS)
Srivastava, Anurag; Tyagi, Neha
2012-01-01
Present paper discusses the structural stability and electronic properties of AlX (X = P, As and Sb) nanowires in its linear, zigzag, ladder, square and hexagonal type atomic configurations. The structural optimization has been performed in self consistence manner by using generalized gradient approximation with revised Perdew, Burke and Ernzerhof type parameterization. The study observes that in all the three nanowires, the square shaped atomic configuration is the most stable one. The calculated electronic band structures and density of states profile confirms the semiconducting behaviour of linear and zigzag shaped nanowires of AlP, whereas for AlAs and AlSb nanowires are metallic. The ground state properties have also been analysed in terms of bond length, bulk modulus and pressure derivative for all the nanowires along with their bulk counterpart. The lower bulk modulus of all the linear shaped geometries of AlX nanowires in comparison to its bulk counterpart indicates softening of the material at reduced dimension. -- Graphical abstract: Figure-Electronic band structure of zigzag shaped AlP nanowire. The present electronic band structures of zigzag and linear shaped AlP nanowires are showing a clear band gap at Γ point, however others (AlAs and AlSb) in zigzag as well as in linear shape show metallic behaviour. Highlights: ► Stability analysis of five geometries of AlX (X = P, As and Sb) nanowires studied. ► Square shaped geometry of AlX nanowires is most stable. ► Linear and zigzag shaped AlP nanowires are semiconducting. ► Bulk moduli of all the linear nanowires are lower than their bulk counterpart. ► Lower bulk moduli defends the softening of material.
Deformations, moduli stabilisation and gauge couplings at one-loop
Energy Technology Data Exchange (ETDEWEB)
Honecker, Gabriele; Koltermann, Isabel [PRISMA Cluster of Excellence, MITP & Institut für Physik (WA THEP),Johannes Gutenberg-Universität,Staudingerweg 9, 55128 Mainz (Germany); Staessens, Wieland [Instituto de Física Teórica UAM-CSIC, Universidad Autónoma de Madrid Cantoblanco,Calle de Nicolás Cabrera 13-15, 28049 Madrid (Spain); Departamento de Física Teórica, Universidad Autónoma de Madrid Cantoblanco,Calle de Nicolás Cabrera 13-15, 28049 Madrid (Spain)
2017-04-05
We investigate deformations of ℤ{sub 2} orbifold singularities on the toroidal orbifold T{sup 6}/(ℤ{sub 2}×ℤ{sub 6}) with discrete torsion in the framework of Type IIA orientifold model building with intersecting D6-branes wrapping special Lagrangian cycles. To this aim, we employ the hypersurface formalism developed previously for the orbifold T{sup 6}/(ℤ{sub 2}×ℤ{sub 2}) with discrete torsion and adapt it to the (ℤ{sub 2}×ℤ{sub 6}×ΩR) point group by modding out the remaining ℤ{sub 3} subsymmetry and the orientifold projection ΩR. We first study the local behaviour of the ℤ{sub 3}×ΩR invariant deformation orbits under non-zero deformation and then develop methods to assess the deformation effects on the fractional three-cycle volumes globally. We confirm that D6-branes supporting USp(2N) or SO(2N) gauge groups do not constrain any deformation, while deformation parameters associated to cycles wrapped by D6-branes with U(N) gauge groups are constrained by D-term supersymmetry breaking. These features are exposed in global prototype MSSM, Left-Right symmetric and Pati-Salam models first constructed in (DOI: 10.1016/j.nuclphysb.2015.10.009; 10.1002/prop.201400066), for which we here count the number of stabilised moduli and study flat directions changing the values of some gauge couplings. Finally, we confront the behaviour of tree-level gauge couplings under non-vanishing deformations along flat directions with the one-loop gauge threshold corrections at the orbifold point and discuss phenomenological implications, in particular on possible LARGE volume scenarios and the corresponding value of the string scale M{sub string}, for the same global D6-brane models.
Bulk solitary waves in elastic solids
Samsonov, A. M.; Dreiden, G. V.; Semenova, I. V.; Shvartz, A. G.
2015-10-01
A short and object oriented conspectus of bulk solitary wave theory, numerical simulations and real experiments in condensed matter is given. Upon a brief description of the soliton history and development we focus on bulk solitary waves of strain, also known as waves of density and, sometimes, as elastic and/or acoustic solitons. We consider the problem of nonlinear bulk wave generation and detection in basic structural elements, rods, plates and shells, that are exhaustively studied and widely used in physics and engineering. However, it is mostly valid for linear elasticity, whereas dynamic nonlinear theory of these elements is still far from being completed. In order to show how the nonlinear waves can be used in various applications, we studied the solitary elastic wave propagation along lengthy wave guides, and remarkably small attenuation of elastic solitons was proven in physical experiments. Both theory and generation for strain soliton in a shell, however, remained unsolved problems until recently, and we consider in more details the nonlinear bulk wave propagation in a shell. We studied an axially symmetric deformation of an infinite nonlinearly elastic cylindrical shell without torsion. The problem for bulk longitudinal waves is shown to be reducible to the one equation, if a relation between transversal displacement and the longitudinal strain is found. It is found that both the 1+1D and even the 1+2D problems for long travelling waves in nonlinear solids can be reduced to the Weierstrass equation for elliptic functions, which provide the solitary wave solutions as appropriate limits. We show that the accuracy in the boundary conditions on free lateral surfaces is of crucial importance for solution, derive the only equation for longitudinal nonlinear strain wave and show, that the equation has, amongst others, a bidirectional solitary wave solution, which lead us to successful physical experiments. We observed first the compression solitary wave in the
Module 13: Bulk Packaging Shipments by Highway
International Nuclear Information System (INIS)
Przybylski, J.L.
1994-07-01
The Hazardous Materials Modular Training Program provides participating United States Department of Energy (DOE) sites with a basic, yet comprehensive, hazardous materials transportation training program for use onsite. This program may be used to assist individual program entities to satisfy the general awareness, safety training, and function specific training requirements addressed in Code of Federal Regulation (CFR), Title 49, Part 172, Subpart H -- ''Training.'' Module 13 -- Bulk Packaging Shipments by Highway is a supplement to the Basic Hazardous Materials Workshop. Module 13 -- Bulk Packaging Shipments by Highway focuses on bulk shipments of hazardous materials by highway mode, which have additional or unique requirements beyond those addressed in the ten module core program. Attendance in this course of instruction should be limited to those individuals with work experience in transporting hazardous materials utilizing bulk packagings and who have completed the Basic Hazardous Materials Workshop or an equivalent. Participants will become familiar with the rules and regulations governing the transportation by highway of hazardous materials in bulk packagings and will demonstrate the application of these requirements through work projects and examination
27 CFR 20.191 - Bulk articles.
2010-04-01
... 27 Alcohol, Tobacco Products and Firearms 1 2010-04-01 2010-04-01 false Bulk articles. 20.191... Users of Specially Denatured Spirits Operations by Users § 20.191 Bulk articles. Users who convey articles in containers exceeding one gallon may provide the recipient with a photocopy of subpart G of this...
Henley, R.W.; Berger, B.R.
2011-01-01
Large bulk-tonnage high-sulfidation gold deposits, such as Yanacocha, Peru, are the surface expression of structurally-controlled lode gold deposits, such as El Indio, Chile. Both formed in active andesite-dacite volcanic terranes. Fluid inclusion, stable isotope and geologic data show that lode deposits formed within 1500. m of the paleo-surface as a consequence of the expansion of low-salinity, low-density magmatic vapor with very limited, if any, groundwater mixing. They are characterized by an initial 'Sulfate' Stage of advanced argillic wallrock alteration ?? alunite commonly with intense silicification followed by a 'Sulfide' Stage - a succession of discrete sulfide-sulfosalt veins that may be ore grade in gold and silver. Fluid inclusions in quartz formed during wallrock alteration have homogenization temperatures between 100 and over 500 ??C and preserve a record of a vapor-rich environment. Recent data for El Indio and similar deposits show that at the commencement of the Sulfide Stage, 'condensation' of Cu-As-S sulfosalt melts with trace concentrations of Sb, Te, Bi, Ag and Au occurred at > 600 ??C following pyrite deposition. Euhedral quartz crystals were simultaneously deposited from the vapor phase during crystallization of the vapor-saturated melt occurs to Fe-tennantite with progressive non-equilibrium fractionation of heavy metals between melt-vapor and solid. Vugs containing a range of sulfides, sulfosalts and gold record the changing composition of the vapor. Published fluid inclusion and mineralogical data are reviewed in the context of geological relationships to establish boundary conditions through which to trace the expansion of magmatic vapor from source to surface and consequent alteration and mineralization. Initially heat loss from the vapor is high resulting in the formation of acid condensate permeating through the wallrock. This Sulfate Stage alteration effectively isolates the expansion of magmatic vapor in subsurface fracture arrays
Bulk metallic glass matrix composites
International Nuclear Information System (INIS)
Choi-Yim, H.; Johnson, W.L.
1997-01-01
Composites with a bulk metallic glass matrix were synthesized and characterized. This was made possible by the recent development of bulk metallic glasses that exhibit high resistance to crystallization in the undercooled liquid state. In this letter, experimental methods for processing metallic glass composites are introduced. Three different bulk metallic glass forming alloys were used as the matrix materials. Both ceramics and metals were introduced as reinforcement into the metallic glass. The metallic glass matrix remained amorphous after adding up to a 30 vol% fraction of particles or short wires. X-ray diffraction patterns of the composites show only peaks from the second phase particles superimposed on the broad diffuse maxima from the amorphous phase. Optical micrographs reveal uniformly distributed particles in the matrix. The glass transition of the amorphous matrix and the crystallization behavior of the composites were studied by calorimetric methods. copyright 1997 American Institute of Physics
Physico-chemical properties of (U,Ce)O2
International Nuclear Information System (INIS)
Yamada, K.; Yamanaka, S.; Katsura, M.
1998-01-01
The high-temperature X-ray diffraction analysis of (U,Ce)O 2 with CeO 2 contents ranging from 0 to 20 mol.% CeO 2 was performed to obtain the variation of the linear thermal expansion coefficient with the CeO 2 content. Ultrasonic pulse-echo measurements were also carried out from room temperature to 673 K to estimate the change in the mechanical properties of (U,Ce)O 2 with the CeO 2 content. The variation in the linear thermal expansion coefficient at the low CeO 2 content region is more steep than that expected from the linear thermal expansion coefficient of UO 2 and CeO 2 . The Young's and shear moduli of all (U,Ce)O 2 were found to decrease with rising temperature. This was due to the increase of the bond length accompanied by the thermal expansion. Although the lattice parameter decreased with CeO 2 content, the moduli of (U,Ce)O 2 were found to decrease with increasing CeO 2 content at room temperature. These results show that in the range from 0 to 20 mol.% of CeO 2 , as CeO 2 content increases, the bottom of the potential energy in (U,Ce)O 2 is shallower and broader. (orig.)
δ expansion applied to quantum electrodynamics
International Nuclear Information System (INIS)
Bender, C.M.; Boettcher, S.; Milton, K.A.
1992-01-01
A recently proposed technique known as the δ expansion provides a nonperturbative treatment of a quantum field theory. The δ-expansion approach can be applied to electrodynamics in such a way that local gauge invariance is preserved. In this paper it is shown that for electrodynamic processes involving only external photon lines and no external electron lines the δ expansion is equivalent to a fermion loop expansion. That is, the coefficient of δ n in the δ expansion is precisely the sum of all n-electron-loop Feynman diagrams in a conventional weak-coupling approximation. This equivalence does not extend to processes having external electron lines. When external electron lines are present, the δ expansion is truly nonperturbative and does not have a simple interpretation as a resummation of conventional Feynman diagrams. To illustrate the nonperturbative character of the δ expansion we perform a speculative calculation of the fermion condensate in the massive Schwinger model in the limit of large coupling constant
Directory of Open Access Journals (Sweden)
Shamshad Ul Haq
2016-01-01
Full Text Available Expressed sequence tags (ESTs are important resource for gene discovery, gene expression and its regulation, molecular marker development, and comparative genomics. We procured 10000 ESTs and analyzed 267 EST-SSRs markers through computational approach. The average density was one SSR/10.45 kb or 6.4% frequency, wherein trinucleotide repeats (66.74% were the most abundant followed by di- (26.10%, tetra- (4.67%, penta- (1.5%, and hexanucleotide (1.2% repeats. Functional annotations were done and after-effect newly developed 63 EST-SSRs were used for cross transferability, genetic diversity, and bulk segregation analysis (BSA. Out of 63 EST-SSRs, 42 markers were identified owing to their expansion genetics across 20 different plants which amplified 519 alleles at 180 loci with an average of 2.88 alleles/locus and the polymorphic information content (PIC ranged from 0.51 to 0.93 with an average of 0.83. The cross transferability ranged from 25% for wheat to 97.22% for Schlerostachya, with an average of 55.86%, and genetic relationships were established based on diversification among them. Moreover, 10 EST-SSRs were recognized as important markers between bulks of pooled DNA of sugarcane cultivars through BSA. This study highlights the employability of the markers in transferability, genetic diversity in grass species, and distinguished sugarcane bulks.
Structural control of elastic moduli in ferrogels and the importance of non-affine deformations
Pessot, Giorgio; Cremer, Peet; Borin, Dmitry Y.; Odenbach, Stefan; Löwen, Hartmut; Menzel, Andreas M.
2014-09-01
One of the central appealing properties of magnetic gels and elastomers is that their elastic moduli can reversibly be adjusted from outside by applying magnetic fields. The impact of the internal magnetic particle distribution on this effect has been outlined and analyzed theoretically. In most cases, however, affine sample deformations are studied and often regular particle arrangements are considered. Here we challenge these two major simplifications by a systematic approach using a minimal dipole-spring model. Starting from different regular lattices, we take into account increasingly randomized structures, until we finally investigate an irregular texture taken from a real experimental sample. On the one hand, we find that the elastic tunability qualitatively depends on the structural properties, here in two spatial dimensions. On the other hand, we demonstrate that the assumption of affine deformations leads to increasingly erroneous results the more realistic the particle distribution becomes. Understanding the consequences of the assumptions made in the modeling process is important on our way to support an improved design of these fascinating materials.
Institute of Scientific and Technical Information of China (English)
C.C.Roach; Y.C.Lu
2017-01-01
Nanocomposites enhanced with two-dimensional,layered graphene fillers are a new class of engineering materials that exhibit superior properties and characteristics to composites with conventional fillers.However,the roles of "interlayers" in layered graphene fillers have yet to be fully explored.This paper examines the effect of interlayers on mechanical properties of layered graphene polymer composites.As an effective filler,the fundamental properties (in-plane Young's modulus EL1,out-of-plane Young's modulus EL2;shear modulus GL12,major Poisson's ratio 1L12) of the layered graphene were computed by using the Arridge's lamellar model.The effects of interlayers on effective moduli of layered graphene epoxy composites were examined through the Tandon-Weng model.The properties of the interlayer show noticeable impact on elastic properties of the composites,particular the out-of-plane properties (Young's modulus E2 and shear modulus G12).The interlayer spacing is seen to have much great influence on properties of the composites.As the interlayer spacing increases from 0.34 nm to 2 nm,all elastic properties of the composites have been greatly decreased.
Bulk-viscosity-driven asymmetric inflationary universe
International Nuclear Information System (INIS)
Waga, I.; Lima, J.A.S.; Portugal, R.
1987-01-01
A primordial net bosinic charge is introduced in the context of the bulk-viscosity-driven inflationary models. The analysis is carried through a macroscopic point of view in the framework of the causal thermodynamic theory. The conditions for having exponetial and generalized inflation are obtained. A phenomenological expression for the bulk viscosity coefficient is also derived. (author) [pt
Crystal structure and thermal expansion of a CsCe{sub 2}Cl{sub 7} scintillator
Energy Technology Data Exchange (ETDEWEB)
Zhuravleva, M., E-mail: mzhuravl@utk.edu [Scintillation Materials Research Center, University of Tennessee, Knoxville, TN (United States); Department of Materials Science and Engineering, University of Tennessee, Knoxville, TN (United States); Lindsey, A. [Scintillation Materials Research Center, University of Tennessee, Knoxville, TN (United States); Department of Materials Science and Engineering, University of Tennessee, Knoxville, TN (United States); Chakoumakos, B.C. [Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, TN 37996 (United States); Custelcean, R. [Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN (United States); Meilleur, F. [Biology and Soft Matter Division, Oak Ridge National Laboratory, Oak Ridge, TN (United States); Hughes, R.W.; Kriven, W.M. [Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL (United States); Melcher, C.L. [Scintillation Materials Research Center, University of Tennessee, Knoxville, TN (United States); Department of Materials Science and Engineering, University of Tennessee, Knoxville, TN (United States)
2015-07-15
We used single-crystal X-ray diffraction data to determine crystal structure of CsCe{sub 2}Cl{sub 7}. It crystallizes in a P112{sub 1}/b space group with a=19.352(1) Å, b=19.352(1) Å, c=14.838(1) Å, γ=119.87(2)°, and V=4818.6(5) Å{sup 3}. Differential scanning calorimetry measurements combined with the structural evolution of CsCe{sub 2}Cl{sub 7} via X-ray diffractometry over a temperature range from room temperature to the melting point indicates no obvious intermediate solid–solid phase transitions. The anisotropy in the average linear coefficient of thermal expansion of the a axis (21.3×10{sup –6}/°C) with respect to the b and c axes (27.0×10{sup –6}/°C) was determined through lattice parameter refinement of the temperature dependent diffraction patterns. These findings suggest that the reported cracking behavior during melt growth of CsCe{sub 2}Cl{sub 7} bulk crystals using conventional Bridgman and Czochralski techniques may be largely attributed to the anisotropy in thermal expansion. - Graphical abstract: Three-dimensional quadric surface of thermal expansion coefficient of CsCe{sub 2}Cl{sub 7} at room temperature (sphere – isotropic) and near melting point (ellipsoid – anisotropic). - Highlights: • Crystal structure of CsCe{sub 2}Cl{sub 7} was solved through X-ray diffraction. • Linear coefficients of thermal expansion were determined from in-situ XRD in 25–650 °C. • Anisotropy of the a axis with respect to b and c axes (21.3 vs 27.0×10{sup –6}/°C) was found. • No solid–solid phase transitions were observed via XRD and thermal analysis.
Accelerating the loop expansion
International Nuclear Information System (INIS)
Ingermanson, R.
1986-01-01
This thesis introduces a new non-perturbative technique into quantum field theory. To illustrate the method, I analyze the much-studied phi 4 theory in two dimensions. As a prelude, I first show that the Hartree approximation is easy to obtain from the calculation of the one-loop effective potential by a simple modification of the propagator that does not affect the perturbative renormalization procedure. A further modification then susggests itself, which has the same nice property, and which automatically yields a convex effective potential. I then show that both of these modifications extend naturally to higher orders in the derivative expansion of the effective action and to higher orders in the loop-expansion. The net effect is to re-sum the perturbation series for the effective action as a systematic ''accelerated'' non-perturbative expansion. Each term in the accelerated expansion corresponds to an infinite number of terms in the original series. Each term can be computed explicitly, albeit numerically. Many numerical graphs of the various approximations to the first two terms in the derivative expansion are given. I discuss the reliability of the results and the problem of spontaneous symmetry-breaking, as well as some potential applications to more interesting field theories. 40 refs
International Nuclear Information System (INIS)
Taylor, D.
1984-01-01
This paper gives regression data for a modified second order polynomial fitted to the expansion data of, and percentage expansions for dioxides with (a) the fluorite and antifluorite structure: AmO 2 , BkO 2 , CeO 2 , CmO 2 , HfO 2 , Li 2 O, NpO 2 , PrO 2 , PuO 2 , ThO 2 , UO 2 , ZrO 2 , and (b) the rutile structure: CrO 2 , GeO 2 , IrO 2 , MnO 2 , NbO 2 , PbO 2 , SiO 2 , SnO 2 , TeO 2 , TiO 2 and VO 2 . Reduced expansion curves for the dioxides showed only partial grouping into iso-electronic series for the fluorite structures and showed that the 'law of corresponding states' did not apply to the rutile structures. (author)
DEFF Research Database (Denmark)
Kanchana, V.; Vaitheeswaran, G.; Ma, Yanming
2009-01-01
agree well with the experimental values. The elastic constants of Fe2VAl and Fe2VGa are predicted. From the elastic constants the shear modulus, Young's modulus, Poisson's ratio, sound velocities, and Debye temperatures are obtained. By analyzing the ratio between the bulk and shear moduli, we conclude...
High-pressure structural study of yttrium monochalcogenides from experiment and theory
DEFF Research Database (Denmark)
Vaitheeswaran, G.; Kanchana, V.; Svane, A.
2011-01-01
High-pressure powder x-ray diffraction experiments using synchrotron radiation are performed on the yttrium monochalcogenides YS, YSe, and YTe up to a maximum pressure of 23 GPa. The ambient NaCl structure is stable throughout the pressure range covered. The bulk moduli are determined to be 93, 82...
Lectures on Hilbert modular varieties and modular forms
Goren, Eyal Z
2001-01-01
This book is devoted to certain aspects of the theory of p-adic Hilbert modular forms and moduli spaces of abelian varieties with real multiplication. The theory of p-adic modular forms is presented first in the elliptic case, introducing the reader to key ideas of N. M. Katz and J.-P. Serre. It is re-interpreted from a geometric point of view, which is developed to present the rudiments of a similar theory for Hilbert modular forms. The theory of moduli spaces of abelian varieties with real multiplication is presented first very explicitly over the complex numbers. Aspects of the general theory are then exposed, in particular, local deformation theory of abelian varieties in positive characteristic. The arithmetic of p-adic Hilbert modular forms and the geometry of moduli spaces of abelian varieties are related. This relation is used to study q-expansions of Hilbert modular forms, on the one hand, and stratifications of moduli spaces on the other hand. The book is addressed to graduate students and non-exper...
Bulk velocity extraction for nano-scale Newtonian flows
Energy Technology Data Exchange (ETDEWEB)
Zhang, Wenfei, E-mail: zwenfei@gmail.com [Key Laboratory of Mechanical Reliability for Heavy Equipments and Large Structures of Hebei Province, Yanshan University, Qinhuangdao 066004 (China); Sun, Hongyu [Key Laboratory of Mechanical Reliability for Heavy Equipments and Large Structures of Hebei Province, Yanshan University, Qinhuangdao 066004 (China)
2012-04-16
The conventional velocity extraction algorithm in MDS method has difficulty to determine the small flow velocity. This study proposes a new method to calculate the bulk velocity in nano-flows. Based on the Newton's law of viscosity, according to the calculated viscosities and shear stresses, the flow velocity can be obtained by numerical integration. This new method can overcome the difficulty existed in the conventional MDS method and improve the stability of the computational process. Numerical results show that this method is effective for the extraction of bulk velocity, no matter the bulk velocity is large or small. -- Highlights: ► Proposed a new method to calculate the bulk velocity in nano-flows. ► It is effective for the extraction of small bulk velocity. ► The accuracy, convergence and stability of the new method is good.
Bulk velocity extraction for nano-scale Newtonian flows
International Nuclear Information System (INIS)
Zhang, Wenfei; Sun, Hongyu
2012-01-01
The conventional velocity extraction algorithm in MDS method has difficulty to determine the small flow velocity. This study proposes a new method to calculate the bulk velocity in nano-flows. Based on the Newton's law of viscosity, according to the calculated viscosities and shear stresses, the flow velocity can be obtained by numerical integration. This new method can overcome the difficulty existed in the conventional MDS method and improve the stability of the computational process. Numerical results show that this method is effective for the extraction of bulk velocity, no matter the bulk velocity is large or small. -- Highlights: ► Proposed a new method to calculate the bulk velocity in nano-flows. ► It is effective for the extraction of small bulk velocity. ► The accuracy, convergence and stability of the new method is good.
Thermal expansion of beryllium oxide
International Nuclear Information System (INIS)
Solodukhin, A.V.; Kruzhalov, A.V.; Mazurenko, V.G.; Maslov, V.A.; Medvedev, V.A.; Polupanova, T.I.
1987-01-01
Precise measurements of temperature dependence of the coefficient of linear expansion in the 22-320 K temperature range on beryllium oxide monocrystals are conducted. A model of thermal expansion is suggested; the range of temperature dependence minimum of the coefficient of thermal expansion is well described within the frames of this model. The results of the experiment may be used for investigation of thermal stresses in crystals
Brane Lorentz symmetry from Lorentz breaking in the bulk
Energy Technology Data Exchange (ETDEWEB)
Bertolami, O [Departamento de Fisica, Instituto Superior Tecnico, Avenida Rovisco Pais 1, 1049-001 Lisbon (Portugal); Carvalho, C [Departamento de Fisica, Instituto Superior Tecnico, Avenida Rovisco Pais 1, 1049-001 Lisbon (Portugal)
2007-05-15
We propose the mechanism of spontaneous symmetry breaking of a bulk vector field as a way to generate the selection of bulk dimensions invisible to the standard model confined to the brane. By assigning a nonvanishing vacuum value to the vector field, a direction is singled out in the bulk vacuum, thus breaking the bulk Lorentz symmetry. We present the condition for induced Lorentz symmetry on the brane, as phenomenologically required.
Convergence of mayer expansions
International Nuclear Information System (INIS)
Brydges, D.C.
1986-01-01
The tree graph bound of Battle and Federbush is extended and used to provide a simple criterion for the convergence of (iterated) Mayer expansions. As an application estimates on the radius of convergence of the Mayer expansion for the two-dimensional Yukawa gas (nonstable interaction) are obtained
Large-scale HTS bulks for magnetic application
Werfel, Frank N.; Floegel-Delor, Uta; Riedel, Thomas; Goebel, Bernd; Rothfeld, Rolf; Schirrmeister, Peter; Wippich, Dieter
2013-01-01
ATZ Company has constructed about 130 HTS magnet systems using high-Tc bulk magnets. A key feature in scaling-up is the fabrication of YBCO melts textured multi-seeded large bulks with three to eight seeds. Except of levitation, magnetization, trapped field and hysteresis, we review system engineering parameters of HTS magnetic linear and rotational bearings like compactness, cryogenics, power density, efficiency and robust construction. We examine mobile compact YBCO bulk magnet platforms cooled with LN2 and Stirling cryo-cooler for demonstrator use. Compact cryostats for Maglev train operation contain 24 pieces of 3-seed bulks and can levitate 2500-3000 N at 10 mm above a permanent magnet (PM) track. The effective magnetic distance of the thermally insulated bulks is 2 mm only; the stored 2.5 l LN2 allows more than 24 h operation without refilling. 34 HTS Maglev vacuum cryostats are manufactured tested and operate in Germany, China and Brazil. The magnetic levitation load to weight ratio is more than 15, and by group assembling the HTS cryostats under vehicles up to 5 t total loads levitated above a magnetic track is achieved.
Characterisation of bulk solids
Energy Technology Data Exchange (ETDEWEB)
D. McGlinchey [Glasgow Caledonian University, Glasgow (United Kingdom). Centre for Industrial Bulk Solids Handling
2005-07-01
Handling of powders and bulk solids is a critical industrial technology across a broad spectrum of industries, including minerals processing. With contributions from leading authors in their respective fields, this book provides the reader with a sound understanding of the techniques, importance and application of particulate materials characterisation. It covers the fundamental characteristics of individual particles and bulk particulate materials, and includes discussion of a wide range of measurement techniques, and the use of material characteristics in design and industrial practice. Contents: Characterising particle properties; Powder mechanics and rheology; Characterisation for hopper and stockpile design; Fluidization behaviour; Characterisation for pneumatic conveyor design; Explosiblility; 'Designer' particle characteristics; Current industrial practice; and Future trends. 130 ills.
Bulk viscosity and cosmological evolution
International Nuclear Information System (INIS)
Beesham, A.
1996-01-01
In a recent interesting paper, Pimentel and Diaz-Rivera (Nuovo Cimento B, 109(1994) 1317) have derived several solutions with bulk viscosity in homogeneous and isotropic cosmological models. They also discussed the properties of these solutions. In this paper the authors relate the solutions of Pimentel and Diaz-Rivera by simple transformations to previous solutions published in the literature, showing that all the solutions can be derived from the known existing ones. Drawbacks to these approaches of studying bulk viscosity are pointed out, and better approaches indicated
Directory of Open Access Journals (Sweden)
Hui Niu
2012-09-01
Full Text Available Systematic first-principles calculations based on density functional theory were performed on a wide range of Ln2TiO5 compositions (Ln = La, Ce, Pr, Nd, Sm, Gd, Tb, Dy and Y in order to investigate their structural, elastic, electronic, and thermal properties. At low temperature, these compounds crystallize in orthorhombic structures with a Pnma symmetry, and the calculated equilibrium structural parameters agree well with experimental results. A complete set of elastic parameters including elastic constants, Hill's bulk moduli, Young's moduli, shear moduli and Poisson's ratio were calculated. All Ln2TiO5 are ductile in nature. Analysis of densities of states and charge densities and electron localization functions suggests that the oxide bonds are highly ionic with some degree of covalency in the Ti-O bonds. Thermal properties including the mean sound velocity, Debye temperature, and minimum thermal conductivity were obtained from the elastic constants.
Energy Flow Exciting Field-Aligned Current at Substorm Expansion Onset
Ebihara, Y.; Tanaka, T.
2017-12-01
At substorm expansion onset, upward field-aligned currents (FACs) increase abruptly, and a large amount of electromagnetic energy starts to consume in the polar ionosphere. A question arises as to where the energy comes from. Based on the results obtained by the global magnetohydrodynamics simulation, we present energy flow and energy conversion associated with the upward FACs that manifest the onset. Our simulations show that the cusp/mantle region transmits electromagnetic energy to almost the entire region of the magnetosphere when the interplanetary magnetic field is southward. Integral curve of the Poynting flux shows a spiral moving toward the ionosphere, probably suggesting the pathway of electromagnetic energy from the cusp/mantle dynamo to the ionosphere. The near-Earth reconnection initiates three-dimensional redistribution of the magnetosphere. Flow shear in the near-Earth region results in the generation of the near-Earth dynamo and the onset FACs. The onset FACs are responsible to transport the electromagnetic energy toward the Earth. In the near-Earth region, the electromagnetic energy coming from the cusp/mantle dynamo is converted to the kinetic energy (known as bursty bulk flow) and the thermal energy (associated with high-pressure region in the inner magnetosphere). Then, they are converted to the electromagnetic energy associated with the onset FACs. A part of electromagnetic energy is stored in the lobe region during the growth phase. The release of the stored energy, together with the continuously supplied energy from the cusp/mantle dynamo, contributes to the energy supply to the ionosphere during the expansion phase.
Directory of Open Access Journals (Sweden)
Xi Liu
2016-12-01
Full Text Available The compressibility of the spinel solid solutions, (Mg1−xMnxCr2O4 with x = 0.00 (0, 0.20 (0, 0.44 (2, 0.61 (2, 0.77 (2 and 1.00 (0, has been investigated by using a diamond-anvil cell coupled with synchrotron X-ray radiation up to ∼10 GPa (ambient T. The second-order Birch–Murnaghan equation of state was used to fit the PV data, yielding the following values for the isothermal bulk moduli (KT, 198.2 (36, 187.8 (87, 176.1 (32, 168.7 (52, 192.9 (61 and 199.2 (61 GPa, for the spinel solid solutions with x = 0.00 (0, 0.20 (0, 0.44 (2, 0.61 (2, 0.77 (2 and 1.00 (0, respectively (KT′ fixed as 4. The KT value of the MgCr2O4 spinel is in good agreement with existing experimental determinations and theoretical calculations. The correlation between the KT and x is not monotonic, with the KT values similar at both ends of the binary MgCr2O4MnCr2O4, but decreasing towards the middle. This non-monotonic correlation can be described by two equations, KT = −49.2 (11x + 198.0 (4 (x ≤ ∼0.6 and KT = 92 (41x + 115 (30 (x ≥ ∼0.6, and can be explained by the evolution of the average bond lengths of the tetrahedra and octahedra of the spinel solid solutions. Additionally, the relationship between the thermal expansion coefficient and composition is correspondingly reinterpreted, the continuous deformation of the oxygen array is demonstrated, and the evolution of the component polyhedra is discussed for this series of spinel solid solutions. Our results suggest that the correlation between the KT and composition of a solid solution series may be complicated, and great care should be paid while estimating the KT of some intermediate compositions from the KT of the end-members.
Fu, Qiang; Xiong, Yucheng; Zhang, Wenhua; Xu, Dongyan
2017-09-01
This paper presents a setup for measuring the Seebeck coefficient and the electrical resistivity of bulk thermoelectric materials. The sample holder was designed to have a compact structure and can be directly mounted in a standard cryostat system for temperature-dependent measurements. For the Seebeck coefficient measurement, a thin bar-shaped sample is mounted bridging two copper bases; and two ceramic heaters are used to generate a temperature gradient along the sample. Two type T thermocouples are used to determine both temperature and voltage differences between two widely separated points on the sample. The thermocouple junction is flattened into a disk and pressed onto the sample surface by using a spring load. The flexible fixation method we adopted not only simplifies the sample mounting process but also prevents thermal contact deterioration due to the mismatch of thermal expansion coefficients between the sample and other parts. With certain modifications, the sample holder can also be used for four-probe electrical resistivity measurements. High temperature measurements are essential for thermoelectric power generation. The experimental system we developed is capable of measuring the Seebeck coefficient and the electrical resistivity of bulk thermoelectric materials in a wide temperature range from 80 to 500 K, which can be further extended to even higher temperatures. Measurements on two standard materials, constantan and nickel, confirmed the accuracy and the reliability of the system.
Nonhomogeneous morphology and the elastic modulus of aligned carbon nanotube films
International Nuclear Information System (INIS)
Won, Yoonjin; Gao, Yuan; Kenny, Thomas W; Goodson, Kenneth E; Guzman de Villoria, Roberto; Wardle, Brian L; Xiang, Rong; Maruyama, Shigeo
2015-01-01
Carbon nanotube (CNT) arrays offer the potential to develop nanostructured materials that leverage their outstanding physical properties. Vertically aligned carbon nanotubes (VACNTs), also named CNT forests, CNT arrays, or CNT turfs, can provide high heat conductivity and sufficient mechanical compliance to accommodate thermal expansion mismatch for use as thermal interface materials (TIMs). This paper reports measurements of the in-plane moduli of vertically aligned, single-walled CNT (SWCNT) and multi-walled CNT (MWCNT) films. The mechanical response of these films is related to the nonhomogeneous morphology of the grown nanotubes, such as entangled nanotubes of a top crust layer, aligned CNTs in the middle region, and CNTs in the bottom layer. To investigate how the entanglements govern the overall mechanical moduli of CNT films, we remove the crust layer consisting of CNT entanglements by etching the CNT films from the top. A microfabricated cantilever technique shows that crust removal reduces the resulting moduli of the etched SWCNT films by as much as 40%, whereas the moduli of the etched MWCNT films do not change significantly, suggesting a minimal crust effect on the film modulus for thick MWCNT films (>90 μm). This improved understanding will allow us to engineer the mechanical moduli of CNT films for TIMs or packaging applications. (paper)