Variable mass diffusion effects on free convection flow past an impulsively started infinite vertical plate

NASA Astrophysics Data System (ADS)

Rushi Kumar, B.; Jayakar, R.; Vijay Kumar, A. G.

2017-11-01

An exact analysis of the problem of free convection flow of a viscous incompressible chemically reacting fluid past an infinite vertical plate with the flow due to impulsive motion of the plate with Newtonian heating in the presence of thermal radiation and variable mass diffusion is performed. The resulting governing equations were tackled by Laplace transform technique. Finally the effects of pertinent flow parameters such as the radiation parameter, chemical reaction parameter, buoyancy ratio parameter, thermal Grashof number, Schmidt number, Prandtl number and time on the velocity, temperature, concentration and skin friction for both aiding and opposing flows were examined in detail when Pr=0.71(conducting air) and Pr=7.0(water).

Infinitely robust order and local order-parameter tulips in Apollonian networks with quenched disorder

NASA Astrophysics Data System (ADS)

Kaplan, C. Nadir; Hinczewski, Michael; Berker, A. Nihat

2009-06-01

For a variety of quenched random spin systems on an Apollonian network, including ferromagnetic and antiferromagnetic bond percolation and the Ising spin glass, we find the persistence of ordered phases up to infinite temperature over the entire range of disorder. We develop a renormalization-group technique that yields highly detailed information, including the exact distributions of local magnetizations and local spin-glass order parameters, which turn out to exhibit, as function of temperature, complex and distinctive tulip patterns.

Correlation effects during liquid infiltration into hydrophobic nanoporous media

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

Borman, V. D., E-mail: vdborman@mephi.ru; Belogorlov, A. A.; Byrkin, V. A.

To explain the thermal effects observed during the infiltration of a nonwetting liquid into a disordered nanoporous medium, we have constructed a model that includes correlation effects in a disordered medium. It is based on analytical methods of the percolation theory. The infiltration of a porous medium is considered as the infiltration of pores in an infinite cluster of interconnected pores. Using the model of randomly situated spheres (RSS), we have been able to take into account the correlation effect of the spatial arrangement and connectivity of pores in the medium. The other correlation effect of the mutual arrangement ofmore » filled and empty pores on the shell of an infinite percolation cluster of filled pores determines the infiltration fluctuation probability. This probability has been calculated analytically. Allowance for these correlation effects during infiltration and defiltration makes it possible to suggest a physical mechanism of the contact angle hysteresis and to calculate the dependences of the contact angles on the degree of infiltration, porosity of the medium, and temperature. Based on the suggested model, we have managed to describe the temperature dependences of the infiltration and defiltration pressures and the thermal effects that accompany the absorption of energy by disordered porous medium-nonwetting liquid systems with various porosities in a unified way.« less

Analytical YORP torques model with an improved temperature distribution function

NASA Astrophysics Data System (ADS)

Breiter, S.; Vokrouhlický, D.; Nesvorný, D.

2010-01-01

Previous models of the Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effect relied either on the zero thermal conductivity assumption, or on the solutions of the heat conduction equations assuming an infinite body size. We present the first YORP solution accounting for a finite size and non-radial direction of the surface normal vectors in the temperature distribution. The new thermal model implies the dependence of the YORP effect in rotation rate on asteroids conductivity. It is shown that the effect on small objects does not scale as the inverse square of diameter, but rather as the first power of the inverse.

MD simulation study of the diffusion and local structure of n-alkanes in liquid and supercritical methanol at infinite dilution.

PubMed

Feng, Huajie; Gao, Wei; Su, Li; Sun, Zhenfan; Chen, Liuping

2017-06-01

The diffusion coefficients of 14 n-alkanes (ranging from methane to n-tetradecane) in liquid and supercritical methanol at infinite dilution (at a pressure of 10.5 MPa and at temperatures of 299 K and 515 K) were deduced via molecular dynamics simulations. Values for the radial distribution function, coordination number, and number of hydrogen bonds were then calculated to explore the local structure of each fluid. The flexibility of the n-alkane (as characterized by the computed dihedral distribution, end-to-end distance, and radius of gyration) was found to be a major influence and hydrogen bonding to be a minor influence on the local structure. Hydrogen bonding reduces the flexibility of the n-alkane, whereas increasing the temperature enhances its flexibility, with temperature having a greater effect than hydrogen bonding on flexibility. Graphical abstract The flexibility of the alkane is a major influence and the hydrogen bonding is a minor influence on the first solvation shell; the coordination numbers of long-chain n-alkanes in the first solvation shell are rather low.

Interuniversal entanglement in a cyclic multiverse

NASA Astrophysics Data System (ADS)

Robles-Pérez, Salvador; Balcerzak, Adam; Dąbrowski, Mariusz P.; Krämer, Manuel

2017-04-01

We study scenarios of parallel cyclic multiverses which allow for a different evolution of the physical constants, while having the same geometry. These universes are classically disconnected, but quantum-mechanically entangled. Applying the thermodynamics of entanglement, we calculate the temperature and the entropy of entanglement. It emerges that the entropy of entanglement is large at big bang and big crunch singularities of the parallel universes as well as at the maxima of the expansion of these universes. The latter seems to confirm earlier studies that quantum effects are strong at turning points of the evolution of the universe performed in the context of the timeless nature of the Wheeler-DeWitt equation and decoherence. On the other hand, the entropy of entanglement at big rip singularities is going to zero despite its presumably quantum nature. This may be an effect of total dissociation of the universe structures into infinitely separated patches violating the null energy condition. However, the temperature of entanglement is large/infinite at every classically singular point and at maximum expansion and seems to be a better measure of quantumness.

An analytical investigation of transient effects on rewetting of heated thin flat plates

NASA Technical Reports Server (NTRS)

Platt, J. A.

1993-01-01

The rewetting of a hot surface is a problem of prime importance in the microgravity application of heat pipe technology, where rewetting controls the time before operations can be re-established following depriming of a heat pipe. Rewetting is also important in the nuclear industry (in predicting behavior during loss-of-coolant accidents), as well as in the chemical and petrochemical industries. Recently Chan and Zhang have presented a closed-form solution for the determination of the rewetting speed of a liquid film flowing over a finite (but long) hot plate subject to uniform heating. Unfortunately, their physically unreasonable initial conditions preclude a meaningful analysis of start-up transient behavior. A new nondimensionalization and closed-form solution for an infinitely-long, uniformly-heated plate is presented. Realistic initial conditions (step change in temperature across the wetting front) and boundary conditions (no spatial temperature gradients infinitely far from the wetting front) are employed. The effects of parametric variation on the resulting simpler closed-form solution are presented and compared with the predictions of a 'quasi-steady' model. The time to reach steady-state rewetting is found to be a strong function of the initial dry-region plate temperature. For heated plates it is found that in most cases the effect of the transient response terms cannot be neglected, even for large times.

Experimental Identification and Simulation of Time and/or Rate Dependent Reversible and Irreversible Deformation Regions for both a Titanium and Nickel Alloy

NASA Technical Reports Server (NTRS)

Arnold, Steven M.; Lerch, Bradley A.; Sellers, Cory

2013-01-01

In this paper time and/or rate dependent deformation regions are experimentally mapped out as a function of temperature. It is clearly demonstrated that the concept of a threshold stress (a stress that delineate reversible and irreversible behavior) is valid and necessary at elevated temperatures and corresponds to the classical yield stress at lower temperatures. Also the infinitely slow modulus, (Es) i.e. the elastic modulus of the material if it was loaded at an infinitely slow strain rate, and the "dynamic modulus", modulus, Ed, which represents the modulus of the material if it is loaded at an infinitely fast rate are used to delineate rate dependent from rate independent regions. As demonstrated at elevated temperatures there is a significant difference between the two modulus values, thus indicating both significant time-dependence and rate dependence. In the case of the nickel-based super alloy, ME3, this behavior is also shown to be grain size specific. Consequently, at higher temperatures viscoelastic behavior exist below k (i.e., the threshold stress) and at stresses above k the behavior is viscoplastic. Finally a multi-mechanism, stress partitioned viscoelastic model, capable of being consistently coupled to a viscoplastic model is characterized over the full temperature range investigated for Ti-6-4 and ME3.

Gas chromatographic measurements of activity coefficients at infinite dilution for refrigerants with a polyol ester oil as a stationary phase

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

Stryjek, R.; Bobbo, S.; Camporese, R.

1999-05-01

Activity coefficients at infinite dilution have been measured by gas chromatography for 14 refrigerants (R12, R22, R32, R124, R125, R134a, R142b, R143a, RE170, R236ea, R290, R600, R600a, and R236fa) as solutes, using a polyol ester oil (POE), EMKARATE by ICI, as a stationary phase (solvent). Instrumental analysis (NMR, IR) showed that the main components of the oil are pentaerithritol esters of carboxylic acids, and electrospray ionization spectrometry revealed an average molecular mass of the POE of 618 g/mol. The measurements were performed within a temperature range of 244 K to 313 K, but a specific temperature range for each refrigerantmore » was adopted depending on its retention data. The experimental findings are well-represented by the equation: ln {gamma}{sub i}{sup {infinity}} = a{sub i} {minus} b{sub i}/T. Some refrigerants, i.e., R22, R124, R125, R236ea, and R236fa, show quite a considerable positive temperature dependence of their activity coefficients at infinite dilution, which can be attributed to hydrogen bonding with the POE, unlike other refrigerants that show a small, either positive or negative temperature dependence. To the authors` knowledge, there are no data in the literature on activity coefficients at infinite dilution for refrigerant and oil (lubricant) systems, and details on the solubility of refrigerants in oils are also extremely scarce.« less

A Large Deviations Analysis of Certain Qualitative Properties of Parallel Tempering and Infinite Swapping Algorithms

DOE PAGES

Doll, J.; Dupuis, P.; Nyquist, P.

2017-02-08

Parallel tempering, or replica exchange, is a popular method for simulating complex systems. The idea is to run parallel simulations at different temperatures, and at a given swap rate exchange configurations between the parallel simulations. From the perspective of large deviations it is optimal to let the swap rate tend to infinity and it is possible to construct a corresponding simulation scheme, known as infinite swapping. In this paper we propose a novel use of large deviations for empirical measures for a more detailed analysis of the infinite swapping limit in the setting of continuous time jump Markov processes. Usingmore » the large deviations rate function and associated stochastic control problems we consider a diagnostic based on temperature assignments, which can be easily computed during a simulation. We show that the convergence of this diagnostic to its a priori known limit is a necessary condition for the convergence of infinite swapping. The rate function is also used to investigate the impact of asymmetries in the underlying potential landscape, and where in the state space poor sampling is most likely to occur.« less

On steady two-dimensional Carreau fluid flow over a wedge in the presence of infinite shear rate viscosity

NASA Astrophysics Data System (ADS)

Khan, Masood; Sardar, Humara

2018-03-01

This paper investigates the steady two-dimensional flow over a moving/static wedge in a Carreau viscosity model with infinite shear rate viscosity. Additionally, heat transfer analysis is performed. Using suitable transformations, nonlinear partial differential equations are transformed into ordinary differential equations and solved numerically using the Runge-Kutta Fehlberg method coupled with the shooting technique. The effects of various physical parameters on the velocity and temperature distributions are displayed graphically and discussed qualitatively. A comparison with the earlier reported results has been made with an excellent agreement. It is important to note that the increasing values of the wedge angle parameter enhance the fluid velocity while the opposite trend is observed for the temperature field for both shear thinning and thickening fluids. Generally, our results reveal that the velocity and temperature distributions are marginally influenced by the viscosity ratio parameter. Further, it is noted that augmented values of viscosity ratio parameter thin the momentum and thermal boundary layer thickness in shear thickening fluid and reverse is true for shear thinning fluid. Moreover, it is noticed that the velocity in case of moving wedge is higher than static wedge.

Flow adjustment inside large finite-size wind farms approaching the infinite wind farm regime

NASA Astrophysics Data System (ADS)

Wu, Ka Ling; Porté-Agel, Fernando

2017-04-01

Due to the increasing number and the growing size of wind farms, the distance among them continues to decrease. Thus, it is necessary to understand how these large finite-size wind farms and their wakes could interfere the atmospheric boundary layer (ABL) dynamics and adjacent wind farms. Fully-developed flow inside wind farms has been extensively studied through numerical simulations of infinite wind farms. The transportation of momentum and energy is only vertical and the advection of them is neglected in these infinite wind farms. However, less attention has been paid to examine the length of wind farms required to reach such asymptotic regime and the ABL dynamics in the leading and trailing edges of the large finite-size wind farms. Large eddy simulations are performed in this study to investigate the flow adjustment inside large finite-size wind farms in conventionally-neutral boundary layer with the effect of Coriolis force and free-atmosphere stratification from 1 to 5 K/km. For the large finite-size wind farms considered in the present work, when the potential temperature lapse rate is 5 K/km, the wind farms exceed the height of the ABL by two orders of magnitude for the incoming flow inside the farms to approach the fully-developed regime. An entrance fetch of approximately 40 times of the ABL height is also required for such flow adjustment. At the fully-developed flow regime of the large finite-size wind farms, the flow characteristics match those of infinite wind farms even though they have different adjustment length scales. The role of advection at the entrance and exit regions of the large finite-size wind farms is also examined. The interaction between the internal boundary layer developed above the large finite-size wind farms and the ABL under different potential temperature lapse rates are compared. It is shown that the potential temperature lapse rate plays a role in whether the flow inside the large finite-size wind farms adjusts to the fully-developed flow regime. The flow characteristics of the wake of these large finite-size wind farms are reported to forecast the effect of large finite-size wind farms on adjacent wind farms. A power deficit as large as 8% is found at a distance of 10 km downwind from the large finite-size wind farms.

Generalized thermoelastic problem of an infinite body with a spherical cavity under dual-phase-lags

NASA Astrophysics Data System (ADS)

Karmakar, R.; Sur, A.; Kanoria, M.

2016-07-01

The aim of the present contribution is the determination of the thermoelastic temperatures, stress, displacement, and strain in an infinite isotropic elastic body with a spherical cavity in the context of the mechanism of the two-temperature generalized thermoelasticity theory (2TT). The two-temperature Lord-Shulman (2TLS) model and two-temperature dual-phase-lag (2TDP) model of thermoelasticity are combined into a unified formulation with unified parameters. The medium is assumed to be initially quiescent. The basic equations are written in the form of a vector matrix differential equation in the Laplace transform domain, which is then solved by the state-space approach. The expressions for the conductive temperature and elongation are obtained at small times. The numerical inversion of the transformed solutions is carried out by using the Fourier-series expansion technique. A comparative study is performed for the thermoelastic stresses, conductive temperature, thermodynamic temperature, displacement, and elongation computed by using the Lord-Shulman and dual-phase-lag models.

Linear stability of compressible Taylor-Couette flow

NASA Technical Reports Server (NTRS)

Kao, Kai-Hsiung; Chow, Chuen-Yen

1992-01-01

A temporal stability analysis of compressible Taylor-Couette flow is presented. The viscous flow studied in this paper is contained between two concentric cylinders of infinite length, which are rotating with different angular velocities and are kept at different surface temperatures. The effects of differential rotation and temperature difference on the stability of Taylor-Couette flow are contrasted for a range of Mach numbers ranging from incompressible to Mach 3.0. The relative motion of the cylinders dramatically affects the characteristics of the Couette flow at the onset of instability. The flow is stabilized or destabilized depending upon the temperature ratio and speeds of the two cylinders. Independent of Mach number and temperature ratio, increasing Reynolds number generally promotes a destabilizing effect, indicating the inviscid nature of the Taylor-Couette flow.

Dynamics of hot random quantum spin chains: from anyons to Heisenberg spins

NASA Astrophysics Data System (ADS)

Parameswaran, Siddharth; Potter, Andrew; Vasseur, Romain

2015-03-01

We argue that the dynamics of the random-bond Heisenberg spin chain are ergodic at infinite temperature, in contrast to the many-body localized behavior seen in its random-field counterpart. First, we show that excited-state real-space renormalization group (RSRG-X) techniques suffer from a fatal breakdown of perturbation theory due to the proliferation of large effective spins that grow without bound. We repair this problem by deforming the SU (2) symmetry of the Heisenberg chain to its `anyonic' version, SU(2)k , where the growth of effective spins is truncated at spin S = k / 2 . This enables us to construct a self-consistent RSRG-X scheme that is particularly simple at infinite temperature. Solving the flow equations, we compute the excited-state entanglement and show that it crosses over from volume-law to logarithmic scaling at a length scale ξk ~eαk3 . This reveals that (a) anyon chains have random-singlet-like excited states for any finite k; and (b) ergodicity is restored in the Heisenberg limit k --> ∞ . We acknowledge support from the Quantum Materials program of LBNL (RV), the Gordon and Betty Moore Foundation (ACP), and UC Irvine startup funds (SAP).

Effect of Differential Diffusion in Two-Component Media

NASA Astrophysics Data System (ADS)

Ingel', L. Kh.

2017-03-01

Examples are presented of an exact solution of a nonstationary problem on the development of convection in a binary mixture (seawater) near an infinite vertical surface in which the buoyancy disturbances are determined both by the temperature and by the disturbances of the impurity (salt) concentration. Consideration is given to the development of convection in a homogeneous medium near an infinite vertical surface at whose boundary specification is made of constant (after ″switching on″ at the initial moment) heat fluxes and impurities or variations of these substances, i.e., problems with boundary conditions of 1st and 2nd kind are considered. The obtained analytical solutions demonstrate the possibility of a nontrivial effect associated with the difference in the values of the coefficients of transfer of two substances: the inflows of positive buoyancy may lead, contrary to intuitive notions, to the origination of descending motion of the medium rather than the ascending one. Clarification is provided for the physical meaning of such effects, which can be substantial, for example, in melting of sea ice.

Effects of Shapes of Solute Molecules on Diffusion: A Study of Dependences on Solute Size, Solvent, and Temperature.

PubMed

Chan, T C; Li, H T; Li, K Y

2015-12-24

Diffusivities of basically linear, planar, and spherical solutes at infinite dilution in various solvents are studied to unravel the effects of solute shapes on diffusion. On the basis of the relationship between the reciprocal of diffusivity and the molecular volume of solute molecules with similar shape in a given solvent at constant temperature, the diffusivities of solutes of equal molecular volume but different shapes are evaluated and the effects due to different shapes of two equal-sized solute molecules on diffusion are determined. It is found that the effects are dependent on the size of the solute pairs studied. Evidence of the dependence of the solute-shape effects on solvent properties is also demonstrated and discussed. Here, some new diffusion data of aromatic compounds in methanol at different temperatures are reported. The result for methanol in this study indicates that the effects of solute shape on diffusivity are only weakly dependent on temperature.

Infinitely Robust Order and Local Order-Parameter Tulips in Apollonian Networks with Quenched Disorder

NASA Astrophysics Data System (ADS)

Nadir Kaplan, C.; Hinczewski, Michael; Berker, A. Nihat

2009-03-01

For a variety of quenched random spin systems on an Apollonian network, including ferromagnetic and antiferromagnetic bond percolation and the Ising spin glass, we find the persistence of ordered phases up to infinite temperature over the entire range of disorder.[1] We develop a renormalization-group technique that yields highly detailed information, including the exact distributions of local magnetizations and local spin-glass order parameters, which turn out to exhibit, as function of temperature, complex and distinctive tulip patterns. [1] C.N. Kaplan, M. Hinczewski, and A.N. Berker, arXiv:0811.3437v1 [cond-mat.dis-nn] (2008).

Low Temperature Analysis of Correlation Functions of the Blume-Emery-Griffiths Model at the Antiquadrupolar-Disordered Interface

NASA Astrophysics Data System (ADS)

Lima, Paulo C.

2016-11-01

We show that at low temperatures the d dimensional Blume-Emery-Griffiths model in the antiquadrupolar-disordered interface has all its infinite volume correlation functions < prod _{iin A}σ _i^{n_i}rangle _{τ }, where Asubset Z^d is finite and sum _{iin A}n_i is odd, equal zero, regardless of the boundary condition τ . In particular, the magnetization < σ _irangle _{τ } is zero, for all τ . We also show that the infinite volume mean magnetization lim _{Λ → ∞}Big < 1/|Λ |sum _{iin Λ }σ _iBig rangle _{Λ ,τ } is zero, for all τ.

Comparison of infinite and wedge fringe settings in Mach Zehnder interferometer for temperature field measurement

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

Haridas, Divya; P, Vibin Antony; Sajith, V.

2014-10-15

Interferometric method, which utilizes the interference of coherent light beams, is used to determine the temperature distribution in the vicinity of a vertical heater plate. The optical components are arranged so as to obtain wedge fringe and infinite fringe patterns and isotherms obtained in each case were compared. In wedge fringe setting, image processing techniques has been used for obtaining isotherms by digital subtraction of initial parallel fringe pattern from deformed fringe pattern. The experimental results obtained are compared with theoretical correlations. The merits and demerits of the fringe analysis techniques are discussed on the basis of the experimental results.

Comparison principle for impulsive functional differential equations with infinite delays and applications

NASA Astrophysics Data System (ADS)

Li, Xiaodi; Shen, Jianhua; Akca, Haydar; Rakkiyappan, R.

2018-04-01

We introduce the Razumikhin technique to comparison principle and establish some comparison results for impulsive functional differential equations (IFDEs) with infinite delays, where the infinite delays may be infinite time-varying delays or infinite distributed delays. The idea is, under the help of Razumikhin technique, to reduce the study of IFDEs with infinite delays to the study of scalar impulsive differential equations (IDEs) in which the solutions are easy to deal with. Based on the comparison principle, we study the qualitative properties of IFDEs with infinite delays , which include stability, asymptotic stability, exponential stability, practical stability, boundedness, etc. It should be mentioned that the developed results in this paper can be applied to IFDEs with not only infinite delays but also persistent impulsive perturbations. Moreover, even for the special cases of non-impulsive effects or/and finite delays, the criteria prove to be simpler and less conservative than some existing results. Finally, two examples are given to illustrate the effectiveness and advantages of the proposed results.

Boundary layer flow of MHD generalized Maxwell fluid over an exponentially accelerated infinite vertical surface with slip and Newtonian heating at the boundary

NASA Astrophysics Data System (ADS)

Imran, M. A.; Riaz, M. B.; Shah, N. A.; Zafar, A. A.

2018-03-01

The aim of this article is to investigate the unsteady natural convection flow of Maxwell fluid with fractional derivative over an exponentially accelerated infinite vertical plate. Moreover, slip condition, radiation, MHD and Newtonian heating effects are also considered. A modern definition of fractional derivative operator recently introduced by Caputo and Fabrizio has been used to formulate the fractional model. Semi analytical solutions of the dimensionless problem are obtained by employing Stehfest's and Tzou's algorithms in order to find the inverse Laplace transforms for temperature and velocity fields. Temperature and rate of heat transfer for non-integer and integer order derivatives are computed and reduced to some known solutions from the literature. Finally, in order to get insight of the physical significance of the considered problem regarding velocity and Nusselt number, some graphical illustrations are made using Mathcad software. As a result, in comparison between Maxwell and viscous fluid (fractional and ordinary) we found that viscous (fractional and ordinary) fluids are swiftest than Maxwell (fractional and ordinary) fluids.

Sweeprate and temperature effects on crackling noise

NASA Astrophysics Data System (ADS)

White, Robert Allen

Crackling noise, defined as separate bursts characterized by power law behavior of the frequency histograms over many decades, is observed in many driven systems far from equilibrium. Examples of such systems pepper a remarkable range of length and energy scales from jerky domain wall motion of disordered magnets, to the sometimes devastating crackling of the earth to the bursty release of energy in the photosphere of the sun dwarfing that of our most horrible WMD. Typically, crackling noise is modeled in the infinitely slow driving rate limit at zero temperature. In this dissertation I investigate the effects of relaxing these limits. First I consider the crackling system at zero temperature and finite sweeprate. I discuss how the temporal overlap of power law bursts can account for a wide range of scaling behavior and provide a criterion for sweeprate controlled exponents based on exponents obtained in the infinitely slowly driven limit. I also discuss scaling arguments for hitherto unexplained results in the power spectrum of crackling response in disordered magnets, commonly referred to as Barkhausen noise. Scaling arguments and numerical results are compared to Barkhausen noise measurements in two materials representing distinct adiabatically driven universality classes. Relaxation of the zero temperature constraint cannot be done without considering finite sweeprates due to global relaxation timescales that arise at finite temperatures. We investigate the connection between sweeprate and thermal fluctuations in the far from equilibrium limit typical of crackling systems. Again, using scaling arguments and numerical simulations of the random field Ising model near a disorder-induced critical point we analyze interesting crossover phenomena in the power spectra which are also observed in Barkhausen noise but have yet to be explained.

Thermodynamic analysis of journal bearings operating under steady state loading in laminar regime. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Khonsari, M. M.

1983-01-01

Thermohydrodynamic effects in journal bearings operating under steady load in laminar regime are investigated. An analytical model for the finite and infinitely long journal bearings is formulated. The model includes correction factors for the cavitation effects in the unloaded region of the bearing and the mixing of the recirculating oil and supply oil at the oil inlet. A finite difference computer program is developed to numerically solve the governing equations of the continuity, Reynolds, energy, Laplace heat conduction, and a viscosity-temperature relation simultaneously. The program includes a numerical technique for obtaining an isothermal shaft temperature. The numerical results of temperature distribution and the heat effects on the bearing load carrying capacity agree closely with those of experimental findings. Several different sets of simpler boundary conditions for the energy equation are studied.

Assessment of the Thermodynamic Properties of DL-p-Mentha-1,8-diene, 4-Isopropyl-1-Methylcyclohexene (DL-limonene) by Inverse Gas Chromatography (IGC).

PubMed

Farshchi, Negin; Abbasian, Ali; Larijani, Kambiz

2018-05-10

Limonene is a colorless liquid hydrocarbon and had been investigated as a plasticizer for many plastics. Prediction of solubility between different materials is an advantage in many ways, one of the most convenient ways to know the compatibility of materials is to determine the degree of solubility of them in each other. The concept of "solubility parameter" can help practitioners in this way.In this study, inverse gas chromatography (IGC) method at infinite dilution was used for determination of the thermodynamic properties of DL-p-mentha-1,8-diene, 4-Isopropyl-1-methylcyclohexene (DL-limonene). The interaction between DL-limonene and 13 solvents were examined in the temperature range of 63-123°C through the assessment of the thermodynamic sorption parameters, the parameters of mixing at infinite dilution, the weight fraction activity coefficient and the Flory-Huggins interaction parameters. Additionally, the solubility parameter for DL-limonene and the temperature dependence of these parameters was investigated as well.Results show that there is a temperature dependence in solubility parameter, which increases by decreasing temperature. However, there were no specific dependence between interaction parameters and temperature, but chemical structure appeared to have a significant effect on them as well as on the type and strength of intermolecular interactions between DL-limonene and investigated solvents. The solubility parameter δ2 of DL-limonene determined to be 19.20 (J/cm3)0.5 at 25°C.

Second cluster integral from the spectrum of an infinite XXZ spin chain

NASA Astrophysics Data System (ADS)

Bibikov, P. N.

2015-03-01

First and second terms of the low-temperature cluster expansion for the free energy density of a magnetically polarized XXZ spin chain is obtained within the propagator approach suggested by E.W. Montroll and J.C. Ward. All the calculations employ only one- and two-magnon infinite-chain spectrums. In the XXX-point the result reproduces the well known S. Katsura's formula obtained 50 years ago by finite-chain calculations.

Effects of the regularization on the restoration of chiral and axial symmetries

NASA Astrophysics Data System (ADS)

Costa, P.; Ruivo, M. C.; de Sousa, C. A.

2008-05-01

The effects of a type of regularization for finite temperatures on the restoration of chiral and axial symmetries are investigated within the SU(3) Nambu-Jona-Lasinio model. The regularization consists in using an infinite cutoff in the integrals that are convergent at finite temperature, a procedure that allows one to take into account the effects of high momentum quarks at high temperatures. It is found that the critical temperature for the phase transition is closer to lattice results than the one obtained with the conventional regularization, and the restoration of chiral and axial symmetries, signaled by the behavior of several observables, occurs simultaneously and at a higher temperature. The restoration of the axial symmetry appears as a natural consequence of the full recovering of the chiral symmetry that was dynamically broken. By using an additional ansatz that simulates instanton suppression effects, by means of a convenient temperature dependence of the anomaly coefficient, we found that the restoration of U(2) symmetry is shifted to lower values, but the dominant effect at high temperatures comes from the new regularization that enhances the decrease of quark condensates, especially in the strange sector.

Resonant Vibrations and Vibrational Heating of Physically Nonlinear Viscoelastic Shells and Their Damping Using Piezoelectric Sensor and Actuator

NASA Astrophysics Data System (ADS)

Kirichok, I. F.

2017-09-01

Forced axisymmetric resonant vibrations and vibrational heating of viscoelastic, physically nonlinear, closed, spherical, and infinitely long cylindrical shells and ring with piezoelectric sensor and actuator are considered. The effect of physical nonlinearity of passive material on the vibration amplitude and vibrational heating temperature is studied. The possibility of active damping of vibrations by piezoelectric sensors and actuators is demonstrated.

Hawking radiation, entanglement, and teleportation in the background of an asymptotically flat static black hole

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

Pan Qiyuan; Jing Jiliang

2008-09-15

The effect of the Hawking temperature on the entanglement and teleportation for the scalar field in a most general, static, and asymptotically flat black hole with spherical symmetry has been investigated. It has been shown that the same 'initial entanglement' for the state parameter {alpha} and its 'normalized partners'{radical}(1-{alpha}{sup 2}) will be degraded by the Hawking effect with increasing Hawking temperature along two different trajectories except for the maximally entangled state. In the infinite Hawking temperature limit, corresponding to the case of the black hole evaporating completely, the state no longer has distillable entanglement for any {alpha}. It is interestingmore » to note that the mutual information in this limit is equal to just half of the 'initially mutual information'. It has also been demonstrated that the fidelity of teleportation decreases as the Hawking temperature increases, which indicates the degradation of entanglement.« less

Computationally efficient thermal-mechanical modelling of selective laser melting

NASA Astrophysics Data System (ADS)

Yang, Yabin; Ayas, Can

2017-10-01

The Selective laser melting (SLM) is a powder based additive manufacturing (AM) method to produce high density metal parts with complex topology. However, part distortions and accompanying residual stresses deteriorates the mechanical reliability of SLM products. Modelling of the SLM process is anticipated to be instrumental for understanding and predicting the development of residual stress field during the build process. However, SLM process modelling requires determination of the heat transients within the part being built which is coupled to a mechanical boundary value problem to calculate displacement and residual stress fields. Thermal models associated with SLM are typically complex and computationally demanding. In this paper, we present a simple semi-analytical thermal-mechanical model, developed for SLM that represents the effect of laser scanning vectors with line heat sources. The temperature field within the part being build is attained by superposition of temperature field associated with line heat sources in a semi-infinite medium and a complimentary temperature field which accounts for the actual boundary conditions. An analytical solution of a line heat source in a semi-infinite medium is first described followed by the numerical procedure used for finding the complimentary temperature field. This analytical description of the line heat sources is able to capture the steep temperature gradients in the vicinity of the laser spot which is typically tens of micrometers. In turn, semi-analytical thermal model allows for having a relatively coarse discretisation of the complimentary temperature field. The temperature history determined is used to calculate the thermal strain induced on the SLM part. Finally, a mechanical model governed by elastic-plastic constitutive rule having isotropic hardening is used to predict the residual stresses.

Global Well-Posedness of the NLS System for Infinitely Many Fermions

NASA Astrophysics Data System (ADS)

Chen, Thomas; Hong, Younghun; Pavlović, Nataša

2017-04-01

In this paper, we study the mean field quantum fluctuation dynamics for a system of infinitely many fermions with delta pair interactions in the vicinity of an equilibrium solution (the Fermi sea) at zero temperature, in dimensions d = 2, 3, and prove global well-posedness of the corresponding Cauchy problem. Our work extends some of the recent important results obtained by Lewin and Sabin in [33,34], who addressed this problem for more regular pair interactions.

Hall effects on unsteady MHD flow of second grade fluid through porous medium with ramped wall temperature and ramped surface concentration

NASA Astrophysics Data System (ADS)

VeeraKrishna, M.; Chamkha, Ali J.

2018-05-01

The heat generation/absorption and thermo-diffusion on an unsteady free convective MHD flow of radiating and chemically reactive second grade fluid near an infinite vertical plate through a porous medium and taking the Hall current into account have been studied. Assume that the bounding plate has a ramped temperature with a ramped surface concentration and isothermal temperature with a ramped surface concentration. The analytical solutions for the governing equations are obtained by making use of the Laplace transforms technique. The velocity, temperature, and concentration profiles are discussed through graphs. We also found that velocity, temperature, and concentration profiles in the case of ramped temperature with ramped surface concentrations are less than those of isothermal temperature with ramped surface concentrations. Also, the expressions of the skin friction, Nusselt number, and Sherwood number are obtained and represented computationally through a tabular form.

Finite grid radius and thickness effects on retarding potential analyzer measured suprathermal electron density and temperature

NASA Technical Reports Server (NTRS)

Knudsen, William C.

1992-01-01

The effect of finite grid radius and thickness on the electron current measured by planar retarding potential analyzers (RPAs) is analyzed numerically. Depending on the plasma environment, the current is significantly reduced below that which is calculated using a theoretical equation derived for an idealized RPA having grids with infinite radius and vanishingly small thickness. A correction factor to the idealized theoretical equation is derived for the Pioneer Venus (PV) orbiter RPA (ORPA) for electron gasses consisting of one or more components obeying Maxwell statistics. The error in density and temperature of Maxwellian electron distributions previously derived from ORPA data using the theoretical expression for the idealized ORPA is evaluated by comparing the densities and temperatures derived from a sample of PV ORPA data using the theoretical expression with and without the correction factor.

Application of mass spectrometer-inverse gas chromatography to study polymer-solvent diffusivity and solubility.

PubMed

Galdámez, J Román; Danner, Ronald P; Duda, J Larry

2007-07-20

The application of a mass spectrometer detector in capillary column inverse gas chromatography is shown to be a valuable tool in the measurement of diffusion and solubility in polymer-solvent systems. The component specific detector provides excellent results for binary polymer-solvent systems, but it is particularly valuable because it can be readily applied to multicomponent systems. Results for a number of infinitely dilute solvents in poly(vinyl acetate) (PVAc) are reported over a range of temperature from 60 to 150 degrees C. Results are also reported for finite concentrations of toluene and methanol in PVAc from 60 to 110 degrees C. Finally, the technique was applied to study the effect of finite concentrations of toluene on the diffusion coefficients of THF and cyclohexane in PVAc. The experimental data compare well with literature values for both infinite and finite concentrations, indicating that the experimental protocol described in this work is sound.

Frozen into stripes: fate of the critical Ising model after a quench.

PubMed

Blanchard, T; Picco, M

2013-09-01

In this article we study numerically the final state of the two-dimensional ferromagnetic critical Ising model after a quench to zero temperature. Beginning from equilibrium at T_{c}, the system can be blocked in a variety of infinitely long lived stripe states in addition to the ground state. Similar results have already been obtained for an infinite temperature initial condition and an interesting connection to exact percolation crossing probabilities has emerged. Here we complete this picture by providing an example of stripe states precisely related to initial crossing probabilities for various boundary conditions. We thus show that this is not specific to percolation but rather that it depends on the properties of spanning clusters in the initial state.

Effect of electric field and temperature gradient on orientational dynamics of nematics encapsulated in a hallow cylindrical cavity

NASA Astrophysics Data System (ADS)

Zakharov, A. V.; Maslennikov, P. V.

2018-05-01

We have considered a homogeneously oriented liquid crystal (HOLC) microvolume, confined between two infinitely long horizontal coaxial cylinders subjected to both a temperature gradient ∇T and a radially applied electric field E . We have investigated dynamic field pumping, i.e. studied the interactions between director, velocity, electric fields, as well as a radially applied temperature gradient, where the inner cylinder is kept at a lower temperature than the outer one. In order to elucidate the role of ∇T and E in producing hydrodynamic flow, we have carried out a numerical study of a system of hydrodynamic equations including director reorientation, fluid flow, and temperature redistribution across the HOLC cavity. Calculations show that, under the effect of the named perturbations and at high curvature of the inner cylinder, the HOLC microvolume settles down to a nonstandard pumping regime with maximum flow in the vicinity of the cooler inner cylinder.

Analytical and numerical solutions for heat transfer and effective thermal conductivity of cracked media

NASA Astrophysics Data System (ADS)

Tran, A. B.; Vu, M. N.; Nguyen, S. T.; Dong, T. Q.; Le-Nguyen, K.

2018-02-01

This paper presents analytical solutions to heat transfer problems around a crack and derive an adaptive model for effective thermal conductivity of cracked materials based on singular integral equation approach. Potential solution of heat diffusion through two-dimensional cracked media, where crack filled by air behaves as insulator to heat flow, is obtained in a singular integral equation form. It is demonstrated that the temperature field can be described as a function of temperature and rate of heat flow on the boundary and the temperature jump across the cracks. Numerical resolution of this boundary integral equation allows determining heat conduction and effective thermal conductivity of cracked media. Moreover, writing this boundary integral equation for an infinite medium embedding a single crack under a far-field condition allows deriving the closed-form solution of temperature discontinuity on the crack and particularly the closed-form solution of temperature field around the crack. These formulas are then used to establish analytical effective medium estimates. Finally, the comparison between the developed numerical and analytical solutions allows developing an adaptive model for effective thermal conductivity of cracked media. This model takes into account both the interaction between cracks and the percolation threshold.

Estimation of Solvation Quantities from Experimental Thermodynamic Data: Development of the Comprehensive CompSol Databank for Pure and Mixed Solutes

NASA Astrophysics Data System (ADS)

Moine, Edouard; Privat, Romain; Sirjean, Baptiste; Jaubert, Jean-Noël

2017-09-01

The Gibbs energy of solvation measures the affinity of a solute for its solvent and is thus a key property for the selection of an appropriate solvent for a chemical synthesis or a separation process. More fundamentally, Gibbs energies of solvation are choice data for developing and benchmarking molecular models predicting solvation effects. The Comprehensive Solvation—CompSol—database was developed with the ambition to propose very large sets of new experimental solvation chemical-potential, solvation entropy, and solvation enthalpy data of pure and mixed components, covering extended temperature ranges. For mixed compounds, the solvation quantities were generated in infinite-dilution conditions by combining experimental values of pure-component and binary-mixture thermodynamic properties. Three types of binary-mixture properties were considered: partition coefficients, activity coefficients at infinite dilution, and Henry's-law constants. A rigorous methodology was implemented with the aim to select data at appropriate conditions of temperature, pressure, and concentration for the estimation of solvation data. Finally, our comprehensive CompSol database contains 21 671 data associated with 1969 pure species and 70 062 data associated with 14 102 binary mixtures (including 760 solvation data related to the ionic-liquid class of solvents). On the basis of the very large amount of experimental data contained in the CompSol database, it is finally discussed how solvation energies are influenced by hydrogen-bonding association effects.

The interaction of evaporative and convective instabilities

NASA Astrophysics Data System (ADS)

Ozen, O.

Evaporative convection arises in a variety of natural and industrial processes, such as drying of lakebeds, heat pipe technology and dry-eye syndrome. The phenomenon of evaporative convection leads to an interfacial instability where an erstwhile flat surface becomes undulated as a control variable, such as temperature drop, exceeds a critical value. This instability has been investigated by others assuming that the vapor phase is infinitely deep and passive, i.e. vapor fluid dynamics has been ignored. However, when we look at some engineering processes, such as distillation columns, heat pipes and drying technologies where phase change takes place we might imagine that the assumption of an infinitely deep vapor layer or at least that of a passive vapor is inappropriate. Previous work on convection in bilayer systems with no phase-change suggests that active vapor layers play a major role in determining the stability of an interface. Hence, for the case of convection with phase-change, we will address this issue and try to answer the question whether the infinitely deep and passive vapor layer is a valid assumption. We have also investigated, theoretically, the gravity and surface tension gradient-driven instabilities occurring during the evaporation of a liquid into its own vapor taking into account the fluid dynamics of both phases and the finiteness of the domains of each phase, i.e. the liquid and its vapor are assumed to be confined between two horizontal plates, and different heating arrangements are applied. The effects of fluid layer depths, the evaporation rate and the temperature gradient applied across the fluids on the stability of the interface are studied. The modes of the flow pattern are determined for each scenario. The physics of the instability are explained and a comparison is made with the results of similar, yet physically different problems.

A notable difference between ideal gas and infinite molar volume limit of van der Waals gas

NASA Astrophysics Data System (ADS)

Liu, Q. H.; Shen, Y.; Bai, R. L.; Wang, X.

2010-05-01

The van der Waals equation of state does not sufficiently represent a gas unless a thermodynamic potential with two proper and independent variables is simultaneously determined. The limiting procedures under which the behaviour of the van der Waals gas approaches that of an ideal gas are letting two van der Waals coefficients be zero rather than letting the molar volume become infinitely large; otherwise, the partial derivative of internal energy with respect to pressure at a fixed temperature does not vanish.

A Study of Chemically Reactive Species and Thermal Radiation Effects on an Unsteady MHD Free Convection Flow Through a Porous Medium Past a Flat Plate with Ramped Wall Temperature

NASA Astrophysics Data System (ADS)

Pandit, K. K.; Sarma, D.; Singh, S. I.

2017-12-01

An investigation of the effects of a chemical reaction and thermal radiation on unsteady MHD free convection heat and mass transfer flow of an electrically conducting, viscous, incompressible fluid past a vertical infinite flat plate embedded in a porous medium is carried out. The flow is induced by a general time-dependent movement of the vertical plate, and the cases of ramped temperature and isothermal plates are studied. An exact solution of the governing equations is obtained in closed form by the Laplace Transform technique. Some applications of practical interest for different types of plate motions are discussed. The numerical values of fluid velocity, temperature and species concentration are displayed graphically whereas the numerical values of skin friction, Nusselt number and Sherwood number are presented in a tabular form for various values of pertinent flow parameters for both ramped temperature and isothermal plates.

Dodecahedral space topology as an explanation for weak wide-angle temperature correlations in the cosmic microwave background.

PubMed

Luminet, Jean-Pierre; Weeks, Jeffrey R; Riazuelo, Alain; Lehoucq, Roland; Uzan, Jean-Philippe

2003-10-09

The current 'standard model' of cosmology posits an infinite flat universe forever expanding under the pressure of dark energy. First-year data from the Wilkinson Microwave Anisotropy Probe (WMAP) confirm this model to spectacular precision on all but the largest scales. Temperature correlations across the microwave sky match expectations on angular scales narrower than 60 degrees but, contrary to predictions, vanish on scales wider than 60 degrees. Several explanations have been proposed. One natural approach questions the underlying geometry of space--namely, its curvature and topology. In an infinite flat space, waves from the Big Bang would fill the universe on all length scales. The observed lack of temperature correlations on scales beyond 60 degrees means that the broadest waves are missing, perhaps because space itself is not big enough to support them. Here we present a simple geometrical model of a finite space--the Poincaré dodecahedral space--which accounts for WMAP's observations with no fine-tuning required. The predicted density is Omega(0) approximately 1.013 > 1, and the model also predicts temperature correlations in matching circles on the sky.

Control of single-photon routing in a T-shaped waveguide by another atom

NASA Astrophysics Data System (ADS)

Huang, Jin-Song; Wang, Jing-Wen; Wang, Yan; Li, Yan-Ling; Huang, You-Wen

2018-04-01

Quantum routers with a high routing rate of much more than 0.5 are of great importance for quantum networks. We provide a scheme to perform bidirectional high routing-rate transfer in a T-shaped coupled-resonator waveguide (CRW), which extends a recent unidirectional scheme proposed by Lu et al. (Opt Express 23:22955, 2015). By locating an extra two-level atom in the infinite CRW channel of the T-shaped CRW with a three-level system, an effective potential is generated. Our numerical results show that high routing capability from the infinite CRW channel to the semi-infinite channel can be achieved, and routing capability from the semi-infinite CRW channel to the infinite channel can also be significantly enhanced, with the help of the effective potential. Therefore, the proposed double-atom configuration could be utilized as a bidirectional quantum routing controller to implement high transfer rate routing of single photons.

Numerical investigation of velocity slip and temperature jump effects on unsteady flow over a stretching permeable surface

NASA Astrophysics Data System (ADS)

Hosseini, E.; Loghmani, G. B.; Heydari, M.; Rashidi, M. M.

2017-02-01

In this paper, the boundary layer flow and heat transfer of unsteady flow over a porous accelerating stretching surface in the presence of the velocity slip and temperature jump effects are investigated numerically. A new effective collocation method based on rational Bernstein functions is applied to solve the governing system of nonlinear ordinary differential equations. This method solves the problem on the semi-infinite domain without truncating or transforming it to a finite domain. In addition, the presented method reduces the solution of the problem to the solution of a system of algebraic equations. Graphical and tabular results are presented to investigate the influence of the unsteadiness parameter A , Prandtl number Pr, suction parameter fw, velocity slip parameter γ and thermal slip parameter φ on the velocity and temperature profiles of the fluid. The numerical experiments are reported to show the accuracy and efficiency of the novel proposed computational procedure. Comparisons of present results are made with those obtained by previous works and show excellent agreement.

Experimental study of thermocapillary flows in a thin liquid layer with heat fluxes imposed on the free surface

NASA Technical Reports Server (NTRS)

Lai, Chun-Liang; Greenberg, Paul S.; Chai, An-Ti

1988-01-01

To study thermocapillary flows in a two-dimensional thin liquid layer with heat fluxes imposed on the free surface experimentally, a long tray configuration was employed to simulate the infinite layer. The surface temperature distribution due to thermocapillary convective for different flow regimes was measured and compared with theoretical predictions. A short tray configuration was also employed to study the end wall effects (insulating or conducting). The results show that for a strong convection flow with an insulating wall as the boundary the surface temperature distribution became quite uniform. Consequently, the thermocapillary driving force was greatly reduced. On the other hand, a strong fluid motion always existed adjacent to the conducting wall because of the large surface temperature gradient near the wall.

Localization in covariance matrices of coupled heterogenous Ornstein-Uhlenbeck processes

NASA Astrophysics Data System (ADS)

Barucca, Paolo

2014-12-01

We define a random-matrix ensemble given by the infinite-time covariance matrices of Ornstein-Uhlenbeck processes at different temperatures coupled by a Gaussian symmetric matrix. The spectral properties of this ensemble are shown to be in qualitative agreement with some stylized facts of financial markets. Through the presented model formulas are given for the analysis of heterogeneous time series. Furthermore evidence for a localization transition in eigenvectors related to small and large eigenvalues in cross-correlations analysis of this model is found, and a simple explanation of localization phenomena in financial time series is provided. Finally we identify both in our model and in real financial data an inverted-bell effect in correlation between localized components and their local temperature: high- and low-temperature components are the most localized ones.

Hall effects on unsteady MHD reactive flow of second grade fluid through porous medium in a rotating parallel plate channel

NASA Astrophysics Data System (ADS)

Krishna, M. Veera; Swarnalathamma, B. V.

2017-07-01

We considered the transient MHD flow of a reactive second grade fluid through porous medium between two infinitely long horizontal parallel plates when one of the plate is set into uniform accelerated motion in the presence of a uniform transverse magnetic field under Arrhenius reaction rate. The governing equations are solved by Laplace transform technique. The effects of the pertinent parameters on the velocity, temperature are discussed in detail. The shear stress and Nusselt number at the plates are also obtained analytically and computationally discussed with reference to governing parameters.

Exact low-temperature series expansion for the partition function of the zero-field Ising model on the infinite square lattice.

PubMed

Siudem, Grzegorz; Fronczak, Agata; Fronczak, Piotr

2016-10-10

In this paper, we provide the exact expression for the coefficients in the low-temperature series expansion of the partition function of the two-dimensional Ising model on the infinite square lattice. This is equivalent to exact determination of the number of spin configurations at a given energy. With these coefficients, we show that the ferromagnetic-to-paramagnetic phase transition in the square lattice Ising model can be explained through equivalence between the model and the perfect gas of energy clusters model, in which the passage through the critical point is related to the complete change in the thermodynamic preferences on the size of clusters. The combinatorial approach reported in this article is very general and can be easily applied to other lattice models.

Exact low-temperature series expansion for the partition function of the zero-field Ising model on the infinite square lattice

PubMed Central

Siudem, Grzegorz; Fronczak, Agata; Fronczak, Piotr

2016-01-01

In this paper, we provide the exact expression for the coefficients in the low-temperature series expansion of the partition function of the two-dimensional Ising model on the infinite square lattice. This is equivalent to exact determination of the number of spin configurations at a given energy. With these coefficients, we show that the ferromagnetic–to–paramagnetic phase transition in the square lattice Ising model can be explained through equivalence between the model and the perfect gas of energy clusters model, in which the passage through the critical point is related to the complete change in the thermodynamic preferences on the size of clusters. The combinatorial approach reported in this article is very general and can be easily applied to other lattice models. PMID:27721435

Effective conductivity of a periodic dilute composite with perfect contact and its series expansion

NASA Astrophysics Data System (ADS)

Pukhtaievych, Roman

2018-06-01

We study the asymptotic behavior of the effective thermal conductivity of a periodic two-phase dilute composite obtained by introducing into an infinite homogeneous matrix a periodic set of inclusions of a different material, each of them of size proportional to a positive parameter ɛ . We assume a perfect thermal contact at constituent interfaces, i.e., a continuity of the normal component of the heat flux and of the temperature. For ɛ small, we prove that the effective conductivity can be represented as a convergent power series in ɛ and we determine the coefficients in terms of the solutions of explicit systems of integral equations.

Emergent interparticle interactions in thermal amorphous solids

NASA Astrophysics Data System (ADS)

Gendelman, Oleg; Lerner, Edan; Pollack, Yoav G.; Procaccia, Itamar; Rainone, Corrado; Riechers, Birte

2016-11-01

Amorphous media at finite temperatures, be them liquids, colloids, or glasses, are made of interacting particles that move chaotically due to thermal energy, continuously colliding and scattering off each other. When the average configuration in these systems relaxes only at long times, one can introduce effective interactions that keep the mean positions in mechanical equilibrium. We introduce a framework to determine the effective force laws that define an effective Hessian that can be employed to discuss stability properties and the density of states of the amorphous system. We exemplify the approach with a thermal glass of hard spheres; these experience zero forces when not in contact and infinite forces when they touch. Close to jamming we recapture the effective interactions that at temperature T depend on the gap h between spheres as T /h [C. Brito and M. Wyart, Europhys. Lett. 76, 149 (2006), 10.1209/epl/i2006-10238-x]. For hard spheres at lower densities or for systems whose binary bare interactions are longer ranged (at any density), the emergent force laws include ternary, quaternary, and generally higher-order many-body terms, leading to a temperature-dependent effective Hessian.

Alternative dimensional reduction via the density matrix

NASA Astrophysics Data System (ADS)

de Carvalho, C. A.; Cornwall, J. M.; da Silva, A. J.

2001-07-01

We give graphical rules, based on earlier work for the functional Schrödinger equation, for constructing the density matrix for scalar and gauge fields in equilibrium at finite temperature T. More useful is a dimensionally reduced effective action (DREA) constructed from the density matrix by further functional integration over the arguments of the density matrix coupled to a source. The DREA is an effective action in one less dimension which may be computed order by order in perturbation theory or by dressed-loop expansions; it encodes all thermal matrix elements. We term the DREA procedure alternative dimensional reduction, to distinguish it from the conventional dimensionally reduced field theory (DRFT) which applies at infinite T. The DREA is useful because it gives a dimensionally reduced theory usable at any T including infinity, where it yields the DRFT, and because it does not and cannot have certain spurious infinities which sometimes occur in the density matrix itself or the conventional DRFT; these come from ln T factors at infinite temperature. The DREA can be constructed to all orders (in principle) and the only regularizations needed are those which control the ultraviolet behavior of the zero-T theory. An example of spurious divergences in the DRFT occurs in d=2+1φ4 theory dimensionally reduced to d=2. We study this theory and show that the rules for the DREA replace these ``wrong'' divergences in physical parameters by calculable powers of ln T; we also compute the phase transition temperature of this φ4 theory in one-loop order. Our density-matrix construction is equivalent to a construction of the Landau-Ginzburg ``coarse-grained free energy'' from a microscopic Hamiltonian.

Rare events in finite and infinite dimensions

NASA Astrophysics Data System (ADS)

Reznikoff, Maria G.

Thermal noise introduces stochasticity into deterministic equations and makes possible events which are never seen in the zero temperature setting. The driving force behind the thesis work is a desire to bring analysis and probability to bear on a class of relevant and intriguing physical problems, and in so doing, to allow applications to drive the development of new mathematical theory. The unifying theme is the study of rare events under the influence of small, random perturbations, and the manifold mathematical problems which ensue. In the first part, we apply large deviation theory and prefactor estimates to a coherent rotation micromagnetic model in order to analyze thermally activated magnetic switching. We consider recent physical experiments and the mathematical questions "asked" by them. A stochastic resonance type phenomenon is discovered, leading to the definition of finite temperature astroids. Non-Arrhenius behavior is discussed. The analysis is extended to ramped astroids. In addition, we discover that for low damping and ultrashort pulses, deterministic effects can override thermal effects, in accord with very recent ultrashort pulse experiments. Even more interesting, perhaps, is the study of large deviations in the infinite dimensional context, i.e. in spatially extended systems. Inspired by recent numerical investigations, we study the stochastically perturbed Allen Cahn and Cahn Hilliard equations. For the Allen Cahn equation, we study the action minimization problem (a deterministic variational problem) and prove the action scaling in four parameter regimes, via upper and lower bounds. The sharp interface limit is studied. We formally derive a reduced action functional which lends insight into the connection between action minimization and curvature flow. For the Cahn Hilliard equation, we prove upper and lower bounds for the scaling of the energy barrier in the nucleation and growth regime. Finally, we consider rare events in large or infinite domains, in one spatial dimension. We introduce a natural reference measure through which to analyze the invariant measure of stochastically perturbed, nonlinear partial differential equations. Also, for noisy reaction diffusion equations with an asymmetric potential, we discover how to rescale space and time in order to map the dynamics in the zero temperature limit to the Poisson Model, a simple version of the Johnson-Mehl-Avrami-Kolmogorov model for nucleation and growth.

Photothermal waves for two temperature with a semiconducting medium under using a dual-phase-lag model and hydrostatic initial stress

NASA Astrophysics Data System (ADS)

Lotfy, Kh.

2017-07-01

The dual-phase-lag (DPL) model with two different time translations and Lord-Shulman (LS) theory with one relaxation time are applied to study the effect of hydrostatic initial stress on medium under the influence of two temperature parameter(a new model will be introduced using two temperature theory) and photothermal theory. We solved the thermal loading at the free surface in the semi-infinite semiconducting medium-coupled plasma waves with the effect of mechanical force during a photothermal process. The exact expressions of the considered variables are obtained using normal mode analysis also the two temperature coefficient ratios were obtained analytically. Numerical results for the field quantities are given in the physical domain and illustrated graphically under the effects of several parameters. Comparisons are made between the results of the two different models with and without two temperature parameter, and for two different values of the hydrostatic initial stress. A comparison is carried out between the considered variables as calculated from the generalized thermoelasticity based on the DPL model and the LS theory in the absence and presence of the thermoelastic and thermoelectric coupling parameters.

Do `negative' temperatures exist?

NASA Astrophysics Data System (ADS)

Lavenda, B. H.

1999-06-01

A modification of the second law is required for a system with a bounded density of states and not the introduction of a `negative' temperature scale. The ascending and descending branches of the entropy versus energy curve describe particle and hole states, having thermal equations of state that are given by the Fermi and logistic distributions, respectively. Conservation of energy requires isentropic states to be isothermal. The effect of adiabatically reversing the field is entirely mechanical because the only difference between the two states is their energies. The laws of large and small numbers, leading to the normal and Poisson approximations, characterize statistically the states of infinite and zero temperatures, respectively. Since the heat capacity also vanishes in the state of maximum disorder, the third law can be generalized in systems with a bounded density of states: the entropy tends to a constant as the temperature tends to either zero or infinity.

Axi-symmetric generalized thermoelastic diffusion problem with two-temperature and initial stress under fractional order heat conduction

NASA Astrophysics Data System (ADS)

Deswal, Sunita; Kalkal, Kapil Kumar; Sheoran, Sandeep Singh

2016-09-01

A mathematical model of fractional order two-temperature generalized thermoelasticity with diffusion and initial stress is proposed to analyze the transient wave phenomenon in an infinite thermoelastic half-space. The governing equations are derived in cylindrical coordinates for a two dimensional axi-symmetric problem. The analytical solution is procured by employing the Laplace and Hankel transforms for time and space variables respectively. The solutions are investigated in detail for a time dependent heat source. By using numerical inversion method of integral transforms, we obtain the solutions for displacement, stress, temperature and diffusion fields in physical domain. Computations are carried out for copper material and displayed graphically. The effect of fractional order parameter, two-temperature parameter, diffusion, initial stress and time on the different thermoelastic and diffusion fields is analyzed on the basis of analytical and numerical results. Some special cases have also been deduced from the present investigation.

A Dynamical Systems Explanation of the Hurst Effect and Atmospheric Low-Frequency Variability

PubMed Central

Franzke, Christian L. E.; Osprey, Scott M.; Davini, Paolo; Watkins, Nicholas W.

2015-01-01

The Hurst effect plays an important role in many areas such as physics, climate and finance. It describes the anomalous growth of range and constrains the behavior and predictability of these systems. The Hurst effect is frequently taken to be synonymous with Long-Range Dependence (LRD) and is typically assumed to be produced by a stationary stochastic process which has infinite memory. However, infinite memory appears to be at odds with the Markovian nature of most physical laws while the stationarity assumption lacks robustness. Here we use Lorenz's paradigmatic chaotic model to show that regime behavior can also cause the Hurst effect. By giving an alternative, parsimonious, explanation using nonstationary Markovian dynamics, our results question the common belief that the Hurst effect necessarily implies a stationary infinite memory process. We also demonstrate that our results can explain atmospheric variability without the infinite memory previously thought necessary and are consistent with climate model simulations. PMID:25765880

Entangled state teleportation through a couple of quantum channels composed of XXZ dimers in an Ising- XXZ diamond chain

NASA Astrophysics Data System (ADS)

Rojas, M.; de Souza, S. M.; Rojas, Onofre

2017-02-01

The quantum teleportation plays an important role in quantum information process, in this sense, the quantum entanglement properties involving an infinite chain structure is quite remarkable because real materials could be well represented by an infinite chain. We study the teleportation of an entangled state through a couple of quantum channels, composed by Heisenberg dimers in an infinite Ising-Heisenberg diamond chain, the couple of chains are considered sufficiently far away from each other to be ignored the any interaction between them. To teleporting a couple of qubits through the quantum channel, we need to find the average density operator for Heisenberg spin dimers, which will be used as quantum channels. Assuming the input state as a pure state, we can apply the concept of fidelity as a useful measurement of teleportation performance of a quantum channel. Using the standard teleportation protocol, we have derived an analytical expression for the output concurrence, fidelity, and average fidelity. We study in detail the effects of coupling parameters, external magnetic field and temperature dependence of quantum teleportation. Finally, we explore the relations between entanglement of the quantum channel, the output entanglement and the average fidelity of the system. Through a kind of phase diagram as a function of Ising-Heisenberg diamond chain model parameters, we illustrate where the quantum teleportation will succeed and a region where the quantum teleportation could fail.

The effect of gravity modulation on thermosolutal convection

NASA Technical Reports Server (NTRS)

Saunders, Bonita V.; Murray, Bruce T.; Mcfadden, G. B.; Coriell, S. R.; Wheeler, A. A.

1992-01-01

In a gravitational field, the opposing effects of components of different diffusivities, for example, temperature and solute, in the density profile in a fluid may produce convective instabilities that exhibit a broad range of dynamical behavior. The effect of time periodic vertical gravity modulation on the onset of these instabilities in an infinite horizontal layer with stress free boundaries is examined. This work is viewed as a first step in expanding previous results in solidification to the full problem of characterizing the effects of gravity modulation in thermosolutal convection during the directional solidification of binary alloys. Calculations carried out both with and without steady background acceleration are presented, the latter results being relevant to microgravity conditions.

Quasineutral plasma expansion into infinite vacuum as a model for parallel ELM transport

NASA Astrophysics Data System (ADS)

Moulton, D.; Ghendrih, Ph; Fundamenski, W.; Manfredi, G.; Tskhakaya, D.

2013-08-01

An analytic solution for the expansion of a plasma into vacuum is assessed for its relevance to the parallel transport of edge localized mode (ELM) filaments along field lines. This solution solves the 1D1V Vlasov-Poisson equations for the adiabatic (instantaneous source), collisionless expansion of a Gaussian plasma bunch into an infinite space in the quasineutral limit. The quasineutral assumption is found to hold as long as λD0/σ0 ≲ 0.01 (where λD0 is the initial Debye length at peak density and σ0 is the parallel length of the Gaussian filament), a condition that is physically realistic. The inclusion of a boundary at x = L and consequent formation of a target sheath is found to have a negligible effect when L/σ0 ≳ 5, a condition that is physically plausible. Under the same condition, the target flux densities predicted by the analytic solution are well approximated by the ‘free-streaming’ equations used in previous experimental studies, strengthening the notion that these simple equations are physically reasonable. Importantly, the analytic solution predicts a zero heat flux density so that a fluid approach to the problem can be used equally well, at least when the source is instantaneous. It is found that, even for JET-like pedestal parameters, collisions can affect the expansion dynamics via electron temperature isotropization, although this is probably a secondary effect. Finally, the effect of a finite duration, τsrc, for the plasma source is investigated. As is found for an instantaneous source, when L/σ0 ≳ 5 the presence of a target sheath has a negligible effect, at least up to the explored range of τsrc = L/cs (where cs is the sound speed at the initial temperature).

A remark on the phase transitions of modified action spin and gauge models

NASA Astrophysics Data System (ADS)

Seiberg, Nathan; Solomon, Sorin

1983-06-01

We consider the phase diagrams of modified action gauge and spin models and concentrate on their periphery - infinitely far from their origins (zero temperature - β-1 = 0). In this limit the exact positions of the phase transitions are found by looking for the global minimum of the single plaquette action (for a spin system - the single link energy). As the parameters of the model are varied, the position of such a global minimum is in general changed. When this changed is non-analytic, a phase transition takes place. The phase structure for finite β is clearly similar, but not identical to the infinite β one. We discuss several finite β corrections that should be applied to the exactly known infinite β picture. We confront our analysis for infinite β2 = ∑ iβ2i with the Monte Carlo simulations for two four-dimensional gauge systems: an SU(3) gauge model with action S=-Re∑ p( β1tr Up+ β2(tr Up) 2) and an SU(2) model with S=- Re Σ p[β 1{1}/{2}trU p+β 2( {1}/{2}trU p) 2+β 3( {1}/{2}trU p) 3] .

Coupled Electronic and Magnetic Phase Transition in the Infinite-Layer Phase LaSrNiRuO4.

PubMed

Patino, Midori Amano; Zeng, Dihao; Bower, Ryan; McGrady, John E; Hayward, Michael A

2016-09-06

Topochemical reduction of the ordered double perovskite LaSrNiRuO6 with CaH2 yields LaSrNiRuO4, an extended oxide phase containing infinite sheets of apex-linked, square-planar Ni(1+)O4 and Ru(2+)O4 units ordered in a checkerboard arrangement. At room temperature the localized Ni(1+) (d(9), S = (1)/2) and Ru(2+) (d(6), S = 1) centers behave paramagnetically. However, on cooling below 250 K the system undergoes a cooperative phase transition in which the nickel spins align ferromagnetically, while the ruthenium cations appear to undergo a change in spin configuration to a diamagnetic spin state. Features of the low-temperature crystal structure suggest a symmetry lowering Jahn-Teller distortion could be responsible for the observed diamagnetism of the ruthenium centers.

Comptonization of X-rays by low-temperature electrons. [photon wavelength redistribution in cosmic sources

NASA Technical Reports Server (NTRS)

Illarionov, A.; Kallman, T.; Mccray, R.; Ross, R.

1979-01-01

A method is described for calculating the spectrum that results from the Compton scattering of a monochromatic source of X-rays by low-temperature electrons, both for initial-value relaxation problems and for steady-state spatial diffusion problems. The method gives an exact solution of the inital-value problem for evolution of the spectrum in an infinite homogeneous medium if Klein-Nishina corrections to the Thomson cross section are neglected. This, together with approximate solutions for problems in which Klein-Nishina corrections are significant and/or spatial diffusion occurs, shows spectral structure near the original photon wavelength that may be used to infer physical conditions in cosmic X-ray sources. Explicit results, shown for examples of time relaxation in an infinite medium and spatial diffusion through a uniform sphere, are compared with results obtained by Monte Carlo calculations and by solving the appropriate Fokker-Planck equation.

Infinite charge mobility in muscovite at 300 K

NASA Astrophysics Data System (ADS)

Russell, F. Michael; Archilla, Juan F. R.; Frutos, Fabian; Medina-Carrasco, Santiago

2017-11-01

Evidence is presented for infinite charge mobility in natural crystals of muscovite mica at room temperature. Muscovite has a basic layered structure containing a flat monatomic sheet of potassium sandwiched between mirror silicate layers. It is an excellent electrical insulator. Studies of defects in muscovite crystals indicated that positive charge could propagate over great distances along atomic chains in the potassium sheets in the absence of an applied electric potential. The charge moved in association with anharmonic lattice excitations that moved at about sonic speed and created by nuclear recoil of the radioactive isotope 40K. This was verified by measuring currents passing through crystals when irradiated with energetic alpha particles at room temperature. The charge propagated more than 1000 times the range of the alpha particles of average energy and 250 times the range of channelling particles of maximum energy. The range is limited only by size of the crystal.

Elementary solutions of coupled model equations in the kinetic theory of gases

NASA Technical Reports Server (NTRS)

Kriese, J. T.; Siewert, C. E.; Chang, T. S.

1974-01-01

The method of elementary solutions is employed to solve two coupled integrodifferential equations sufficient for determining temperature-density effects in a linearized BGK model in the kinetic theory of gases. Full-range completeness and orthogonality theorems are proved for the developed normal modes and the infinite-medium Green's function is constructed as an illustration of the full-range formalism. The appropriate homogeneous matrix Riemann problem is discussed, and half-range completeness and orthogonality theorems are proved for a certain subset of the normal modes. The required existence and uniqueness theorems relevant to the H matrix, basic to the half-range analysis, are proved, and an accurate and efficient computational method is discussed. The half-space temperature-slip problem is solved analytically, and a highly accurate value of the temperature-slip coefficient is reported.

Universal Broadening of the Light Cone in Low-Temperature Transport

NASA Astrophysics Data System (ADS)

Bertini, Bruno; Piroli, Lorenzo; Calabrese, Pasquale

2018-04-01

We consider the low-temperature transport properties of critical one-dimensional systems that can be described, at equilibrium, by a Luttinger liquid. We focus on the prototypical setting where two semi-infinite chains are prepared in two thermal states at small but different temperatures and suddenly joined together. At large distances x and times t , conformal field theory characterizes the energy transport in terms of a single light cone spreading at the sound velocity v . Energy density and current take different constant values inside the light cone, on its left, and on its right, resulting in a three-step form of the corresponding profiles as a function of ζ =x /t . Here, using a nonlinear Luttinger liquid description, we show that for generic observables this picture is spoiled as soon as a nonlinearity in the spectrum is present. In correspondence of the transition points x /t =±v , a novel universal region emerges at infinite times, whose width is proportional to the temperatures on the two sides. In this region, expectation values have a different temperature dependence and show smooth peaks as a function of ζ . We explicitly compute the universal function describing such peaks. In the specific case of interacting integrable models, our predictions are analytically recovered by the generalized hydrodynamic approach.

The formation of topological defects in phase transitions

NASA Technical Reports Server (NTRS)

Hodges, Hardy M.

1989-01-01

It was argued, and fought through numerical work that the results of non-dynamical Monte Carlo computer simulations cannot be applied to describe the formation of topological defects when the correlation length at the Ginzburg temperature is significantly smaller than the horizon size. To test the current hypothesis that infinite strings at formation are essentially described by Brownian walks of size the correlation length at the Ginzburg temperature, fields at the Ginzburg temperature were equilibrated. Infinite structure do not exist in equilibrium for reasonable definitions of the Ginzburg temperature, and horizons must be included in a proper treatment. A phase transition, from small-scale to large-scale string or domain wall structure, is found to occur very close to the Ginzburg temperature, in agreement with recent work. The formation process of domain walls and global strings were investigated through the breaking of initially ordered states. To mimic conditions in the early Universe, cooling times are chosen so that horizons exist in the sample volume when topological structure formation occurs. The classical fields are evolved in real-time by the numerical solution of Langevin equations of motion on a three dimensional spatial lattice. The results indicate that it is possible for most of the string energy to be in small loops, rather than in long strings, at formation.

Blood flow analysis with considering nanofluid effects in vertical channel

NASA Astrophysics Data System (ADS)

Noreen, S.; Rashidi, M. M.; Qasim, M.

2017-06-01

Manipulation of heat convection of copper particles in blood has been considered peristaltically. Two-phase flow model is used in a channel with insulating walls. Flow analysis has been approved by assuming small Reynold number and infinite length of wave. Coupled equations are solved. Numerical solution are computed for the pressure gradient, axial velocity function and temperature. Influence of attention-grabbing parameters on flow entities has been analyzed. This study can be considered as mathematical representation to the vibrance of physiological systems/tissues/organs provided with medicine.

Vacuum Polarization by a Magnetic Flux Tube at Finite Temperature in the Cosmic String Space-Time

NASA Astrophysics Data System (ADS)

Spinelly, J.; Bezerra de Mello, E. R.

In this paper, we analyze the effect produced by the temperature in the vacuum polarization associated with a charged massless scalar field in the presence of a magnetic flux tube in the cosmic string space-time. Three different configurations of magnetic fields are taken into account: (i) a homogeneous field inside the tube, (ii) a field proportional to 1/r, and (iii) a cylindrical shell with δ-function. In these three cases, the axis of the infinitely long tube of radius R coincides with the cosmic string. Because of the complexity of this analysis in the region inside the tube, we consider the thermal effect in the region outside. In order to develop this analysis, we construct the thermal Green function associated with this system for the three above-mentioned situations considering points in the region outside the tube. We explicitly calculate, in the high-temperature limit, the thermal average of the field square and the energy-momentum tensor.

Boundary effect on the elastic field of a semi-infinite solid containing inhomogeneities

PubMed Central

Liu, Y. J.; Song, G.; Yin, H. M.

2015-01-01

The boundary effect of one inhomogeneity embedded in a semi-infinite solid at different depths has firstly been investigated using the fundamental solution for Mindlin's problem. Expanding the eigenstrain in a polynomial form and using the Eshelby's equivalent inclusion method, one can calculate the eigenstrain and thus obtain the elastic field. When the inhomogeneity is far from the boundary, the solution recovers Eshelby's solution. The method has been extended to a many-particle system in a semi-infinite solid, which is first demonstrated by the cases of two spheres. The comparison of the asymptotic form solution with the finite-element results shows the accuracy and capability of this method. The solution has been used to illustrate the boundary effects on its effective material behaviour of a semi-infinite simple cubic lattice particulate composite. The local field of a semi-infinite composite has been calculated at different volume fractions. A representative unit cell has been taken with different depths to the surface. The average stress and strain of the unit cell have been calculated under uniform loading conditions of normal or shear force on the surface, respectively. The effective elastic moduli of the unit cell not only depend on the material proportion, but also on its distance to the surface. The present model can be extended to other types of particle distribution and ellipsoidal particles. PMID:26345084

Boundary effect on the elastic field of a semi-infinite solid containing inhomogeneities.

PubMed

Liu, Y J; Song, G; Yin, H M

2015-07-08

The boundary effect of one inhomogeneity embedded in a semi-infinite solid at different depths has firstly been investigated using the fundamental solution for Mindlin's problem. Expanding the eigenstrain in a polynomial form and using the Eshelby's equivalent inclusion method, one can calculate the eigenstrain and thus obtain the elastic field. When the inhomogeneity is far from the boundary, the solution recovers Eshelby's solution. The method has been extended to a many-particle system in a semi-infinite solid, which is first demonstrated by the cases of two spheres. The comparison of the asymptotic form solution with the finite-element results shows the accuracy and capability of this method. The solution has been used to illustrate the boundary effects on its effective material behaviour of a semi-infinite simple cubic lattice particulate composite. The local field of a semi-infinite composite has been calculated at different volume fractions. A representative unit cell has been taken with different depths to the surface. The average stress and strain of the unit cell have been calculated under uniform loading conditions of normal or shear force on the surface, respectively. The effective elastic moduli of the unit cell not only depend on the material proportion, but also on its distance to the surface. The present model can be extended to other types of particle distribution and ellipsoidal particles.

SQDFT: Spectral Quadrature method for large-scale parallel O(N) Kohn-Sham calculations at high temperature

NASA Astrophysics Data System (ADS)

Suryanarayana, Phanish; Pratapa, Phanisri P.; Sharma, Abhiraj; Pask, John E.

2018-03-01

We present SQDFT: a large-scale parallel implementation of the Spectral Quadrature (SQ) method for O(N) Kohn-Sham Density Functional Theory (DFT) calculations at high temperature. Specifically, we develop an efficient and scalable finite-difference implementation of the infinite-cell Clenshaw-Curtis SQ approach, in which results for the infinite crystal are obtained by expressing quantities of interest as bilinear forms or sums of bilinear forms, that are then approximated by spatially localized Clenshaw-Curtis quadrature rules. We demonstrate the accuracy of SQDFT by showing systematic convergence of energies and atomic forces with respect to SQ parameters to reference diagonalization results, and convergence with discretization to established planewave results, for both metallic and insulating systems. We further demonstrate that SQDFT achieves excellent strong and weak parallel scaling on computer systems consisting of tens of thousands of processors, with near perfect O(N) scaling with system size and wall times as low as a few seconds per self-consistent field iteration. Finally, we verify the accuracy of SQDFT in large-scale quantum molecular dynamics simulations of aluminum at high temperature.

Large-scale behaviour of local and entanglement entropy of the free Fermi gas at any temperature

NASA Astrophysics Data System (ADS)

Leschke, Hajo; Sobolev, Alexander V.; Spitzer, Wolfgang

2016-07-01

The leading asymptotic large-scale behaviour of the spatially bipartite entanglement entropy (EE) of the free Fermi gas infinitely extended in multidimensional Euclidean space at zero absolute temperature, T = 0, is by now well understood. Here, we present and discuss the first rigorous results for the corresponding EE of thermal equilibrium states at T> 0. The leading large-scale term of this thermal EE turns out to be twice the first-order finite-size correction to the infinite-volume thermal entropy (density). Not surprisingly, this correction is just the thermal entropy on the interface of the bipartition. However, it is given by a rather complicated integral derived from a semiclassical trace formula for a certain operator on the underlying one-particle Hilbert space. But in the zero-temperature limit T\\downarrow 0, the leading large-scale term of the thermal EE considerably simplifies and displays a {ln}(1/T)-singularity which one may identify with the known logarithmic enhancement at T = 0 of the so-called area-law scaling. birthday of the ideal Fermi gas.

Viscous dissipation impact on MHD free convection radiating fluid flow past a vertical porous plate

NASA Astrophysics Data System (ADS)

Raju, R. Srinivasa; Reddy, G. Jithender; Kumar, M. Anil

2018-05-01

An attempt has been made to study the radiation effects on unsteady MHD free convective flow of an incompressible fluid past an infinite vertical porous plate in the presence of viscous dissipation. The governing partial differential equations are solved numerically by using Galerkin finite element method. Computations were performed for a wide range of governing flow parameters viz., Magnetic Parameter, Schmidt number, Thermal radiation, Prandtl number, Eckert number and Permeability parameter. The effects of these flow parameters on velocity, temperature are shown graphically. In addition the local values of the Skin friction coefficient are shown in tabular form.

Plasma Modes

NASA Astrophysics Data System (ADS)

Dubin, D. H. E.

This chapter explores several aspects of the linear electrostatic normal modes of oscillation for a single-species non-neutral plasma in a Penning trap. Linearized fluid equations of motion are developed, assuming the plasma is cold but collisionless, which allow derivation of the cold plasma dielectric tensor and the electrostatic wave equation. Upper hybrid and magnetized plasma waves in an infinite uniform plasma are described. The effect of the plasma surface in a bounded plasma system is considered, and the properties of surface plasma waves are characterized. The normal modes of a cylindrical plasma column are discussed, and finally, modes of spheroidal plasmas, and finite temperature effects on the modes, are briefly described.

Asymptotic expansions of solutions of the heat conduction equation in internally bounded cylindrical geometry

USGS Publications Warehouse

Ritchie, R.H.; Sakakura, A.Y.

1956-01-01

The formal solutions of problems involving transient heat conduction in infinite internally bounded cylindrical solids may be obtained by the Laplace transform method. Asymptotic series representing the solutions for large values of time are given in terms of functions related to the derivatives of the reciprocal gamma function. The results are applied to the case of the internally bounded infinite cylindrical medium with, (a) the boundary held at constant temperature; (b) with constant heat flow over the boundary; and (c) with the "radiation" boundary condition. A problem in the flow of gas through a porous medium is considered in detail.

The Effect of MHD on Free Convection with Periodic Temperature and Concentration in the Presence of Thermal Radiation and Chemical Reaction

NASA Astrophysics Data System (ADS)

Zigta, B.; Koya, P. R.

2017-12-01

This paper studies the effect of magneto hydrodynamics on unsteady free convection between a pair of infinite vertical Couette plates. The temperature of the plates and concentration between the plates vary with time. Convection between the plates is considered in the presence of thermal radiation and chemical reaction. The solution is obtained using perturbation techniques. These techniques are used to transform nonlinear coupled partial differential equations to a system of ordinary differential equations. The resulting equations are solved analytically. The solution is expressed in terms of power series with some small parameter. The effect of various parameters, viz., velocity, temperature and concentration, has been discussed. Mat lab code simulation study is carried out to support the theoretical results. The result shows that as the thermal radiation parameter R increases, the temperature decreases near the moving porous plate while it approaches to a zero in the region close to the boundary layer of the stationary plate. Moreover, as the modified Grashof number, i.e., based on concentration difference, increases, the velocity of the fluid flow increases hence the concentration decreases. An increase in both the chemical reaction parameter and Schmidt number results in decreased concentration.

On The Stability Of Model Flows For Chemical Vapour Deposition

NASA Astrophysics Data System (ADS)

Miller, Robert

2016-11-01

The flow in a chemical vapour deposition (CVD) reactor is assessed. The reactor is modelled as a flow over an infinite-radius rotating disk, where the mean flow and convective instability of the disk boundary layer are measured. Temperature-dependent viscosity and enforced axial flow are used to model the steep temperature gradients present in CVD reactors and the pumping of the gas towards the disk, respectively. Increasing the temperature-dependence parameter of the fluid viscosity (ɛ) results in an overall narrowing of the fluid boundary layer. Increasing the axial flow strength parameter (Ts) accelerates the fluid both radially and axially, while also narrowing the thermal boundary layer. It is seen that when both effects are imposed, the effects of axial flow generally dominate those of the viscosity temperature dependence. A local stability analysis is performed and the linearized stability equations are solved using a Galerkin projection in terms of Chebyshev polynomials. The neutral stability curves are then plotted for a range of ɛ and Ts values. Preliminary results suggest that increasing Ts has a stabilising effect on both type I and type II stationary instabilities, while small increases in ɛ results in a significant reduction to the critical Reynolds number.

Constraints on black hole remnants

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

Giddings, S.B.

1994-01-15

One possible fate of information lost to black holes is its preservation in black hole remnants. It is argued that a type of effective field theory describes such remnants (generically referred to as informons). The general structure of such a theory is investigated and the infinite pair production problem is revisited. A toy model for remnants clarifies some of the basic issues; in particular, infinite remnant production is not suppressed simply by the large internal volumes as proposed in cornucopion scenarios. Criteria for avoiding infinite production are stated in terms of couplings in the effective theory. Such instabilities remain amore » problem barring what would be described in that theory as a strong coupling conspiracy. The relation to Euclidean calculations of cornucopion production is sketched, and potential flaws in that analysis are outlined. However, it is quite plausible that pair production of ordinary black holes (e.g., Reissner-Noerdstrom or others) is suppressed due to strong effective couplings. It also remains an open possibility that a microsopic dynamics can be found yielding an appropriate strongly coupled effective theory of neutral informons without infinite pair production.« less

Thermodynamics of a periodically driven qubit

NASA Astrophysics Data System (ADS)

Donvil, Brecht

2018-04-01

We present a new approach to the open system dynamics of a periodically driven qubit in contact with a temperature bath. We are specifically interested in the thermodynamics of the qubit. It is well known that by combining the Markovian approximation with Floquet theory it is possible to derive a stochastic Schrödinger equation in for the state of the qubit. We follow here a different approach. We use Floquet theory to embed the time-non autonomous qubit dynamics into time-autonomous yet infinite dimensional dynamics. We refer to the resulting infinite dimensional system as the dressed-qubit. Using the Markovian approximation we derive the stochastic Schrödinger equation for the dressed-qubit. The advantage of our approach is that the jump operators are ladder operators of the Hamiltonian. This simplifies the formulation of the thermodynamics. We use the thermodynamics of the infinite dimensional system to recover the thermodynamical description for the driven qubit. We compare our results with the existing literature and recover the known results.

Integrated Sachs-Wolfe effect in massive bigravity

NASA Astrophysics Data System (ADS)

Enander, Jonas; Akrami, Yashar; Mörtsell, Edvard; Renneby, Malin; Solomon, Adam R.

2015-04-01

We study the integrated Sachs-Wolfe (ISW) effect in ghost-free, massive bigravity. We focus on the infinite-branch bigravity (IBB) model which exhibits viable cosmic expansion histories and stable linear perturbations, while the cosmological constant is set to zero and the late-time accelerated expansion of the Universe is due solely to the gravitational interaction terms. The ISW contribution to the CMB auto-correlation power spectrum is predicted, as well as the cross-correlation between the CMB temperature anisotropies and large-scale structure. We use ISW amplitudes as inferred from the WMAP 9-year temperature data together with galaxy and AGN data provided by the WISE mission in order to compare the theoretical predictions to the observations. The ISW amplitudes in IBB are found to be larger than the corresponding ones in the standard Λ CDM model by roughly a factor of 1.5, but are still consistent with the observations.

Comparative study of bolometric and non-bolometric switching elements for microwave phase shifters

NASA Technical Reports Server (NTRS)

Tabib-Azar, Massood; Bhasin, Kul B.; Romanofsky, Robert R.

1991-01-01

The performance of semiconductor and high critical temperature superconductor switches is compared as they are used in delay-line-type microwave and millimeter-wave phase shifters. Such factors as their ratios of the off-to-on resistances, parasitic reactances, power consumption, speed, input-to-output isolation, ease of fabrication, and physical dimensions are compared. Owing to their almost infinite off-to-on resistance ratio and excellent input-to-output isolation, bolometric superconducting switches appear to be quite suitable for use in microwave phase shifters; their only drawbacks are their speed and size. The SUPERFET, a novel device whose operation is based on the electric field effect in high critical temperature ceramic superconductors is also discussed. Preliminary results indicate that the SUPERFET is fast and that it can be scaled; therefore, it can be fabricated with dimensions comparable to semiconductor field-effect transistors.

Landau-de Gennes theory of surface-enhanced ordering in smectic films.

PubMed

Shalaginov, A N; Sullivan, D E

2001-03-01

A Landau theory for surface-enhanced ordering in smectic-A free-standing films is described, based on a generalization of de Gennes' model for a "presmectic" fluid confined between two walls. According to the theory, smectic ordering in free-standing films heated above the bulk smectic melting temperature is due to an intrinsic surface contribution rather than an external field. The theory yields a persistent finite-size effect, in that the film melting temperatures do not tend to the bulk transition temperature in the limit of infinite film thickness. It also predicts that a continuous transition from (N+1)- to N-layer films is impossible without an external field. The theory closely fits existing experimental data on layer-thinning transitions in compounds which exhibit a bulk smectic-A to nematic phase transition. Possible origins of the intrinsic surface contribution are discussed.

Fractional Order Two-Temperature Dual-Phase-Lag Thermoelasticity with Variable Thermal Conductivity

PubMed Central

Mallik, Sadek Hossain; Kanoria, M.

2014-01-01

A new theory of two-temperature generalized thermoelasticity is constructed in the context of a new consideration of dual-phase-lag heat conduction with fractional orders. The theory is then adopted to study thermoelastic interaction in an isotropic homogenous semi-infinite generalized thermoelastic solids with variable thermal conductivity whose boundary is subjected to thermal and mechanical loading. The basic equations of the problem have been written in the form of a vector-matrix differential equation in the Laplace transform domain, which is then solved by using a state space approach. The inversion of Laplace transforms is computed numerically using the method of Fourier series expansion technique. The numerical estimates of the quantities of physical interest are obtained and depicted graphically. Some comparisons of the thermophysical quantities are shown in figures to study the effects of the variable thermal conductivity, temperature discrepancy, and the fractional order parameter. PMID:27419210

Collisional excitation of interstellar methyl cyanide

NASA Technical Reports Server (NTRS)

Green, Sheldon

1986-01-01

Theoretical calculations are used to determine the collisional excitation rates of methyl cyanide under interstellar molecular cloud conditions. The required Q(L,M) as a function of kinetic temperature were determined by averaging fixed energy IOS (infinite order sudden) results over appropriate Boltzmann distributions of collision energies. At a kinetic temperature of 40 K, rates within a K ladder were found to be accurate to generally better than about 30 percent.

Optimal performance of heat engines with a finite source or sink and inequalities between means.

PubMed

Johal, Ramandeep S

2016-07-01

Given a system with a finite heat capacity and a heat reservoir, and two values of initial temperatures, T_{+} and T_{-}(

Effect of zone size on the convergence of exact solutions for diffusion in single phase systems with planar, cylindrical or spherical geometry

NASA Technical Reports Server (NTRS)

Unnam, J.; Tenney, D. R.

1981-01-01

Exact solutions for diffusion in single phase binary alloy systems with constant diffusion coefficient and zero-flux boundary condition have been evaluated to establish the optimum zone size of applicability. Planar, cylindrical and spherical interface geometry, and finite, singly infinite, and doubly infinite systems are treated. Two solutions are presented for each geometry, one well suited to short diffusion times, and one to long times. The effect of zone-size on the convergence of these solutions is discussed. A generalized form of the diffusion solution for doubly infinite systems is proposed.

A simple model for closure temperature of a trace element in cooling bi-mineralic systems

NASA Astrophysics Data System (ADS)

Liang, Yan

2015-09-01

Closure temperature is defined as the lower temperature limit at which the element of interest effectively ceases diffusive exchange with its surrounding medium during cooling. Here we generalize the classic equation of Dodson (1973) for cooling mono-mineralic systems to cooling bi-mineralic aggregates by considering diffusive exchange of a trace element between the two minerals in a closed system. We present a simple analytical model that includes key parameters affecting the closure temperature of a trace element in cooling bi-mineralic systems: cooling rate, temperature-dependent diffusion coefficients for the trace element in the two minerals, temperature-dependent partition coefficient of the trace element between the two minerals, effective grain sizes of the two minerals, and volume proportions of the minerals in the system. We show that closure temperatures of a trace element in cooling bi-mineralic systems are bounded by the closure temperatures of the trace element in the two mono-mineralic systems and that our generalized model reduces to Dodson's equation when one of the mineral serves as "an effective infinite" reservoir to the other mineral. Application to closure temperatures of REE in orthopyroxene and clinopyroxene bi-mineralic systems highlights the importance of REE diffusion and partitioning in the pyroxenes as well as clinopyroxene modal abundance and grain size in the systems. Closure temperatures for REE in two-pyroxene bearing equigranular rocks are controlled primarily by diffusion in orthopyroxene unless the modal abundance of clinopyroxene is very small. This has important bearings on the interpretation of temperatures derived from the REE-in-two-pyroxene thermometer.

Wave packet dynamics for a system with position and time-dependent effective mass in an infinite square well

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

Vubangsi, M.; Tchoffo, M.; Fai, L. C.

The problem of a particle with position and time-dependent effective mass in a one-dimensional infinite square well is treated by means of a quantum canonical formalism. The dynamics of a launched wave packet of the system reveals a peculiar revival pattern that is discussed. .

Low temperature structures of dCpG-proflavine. Conformational and hydration effects.

PubMed Central

Schneider, B; Ginell, S L; Berman, H M

1992-01-01

The structure of the complex of dCpG with proflavine was determined using x-ray data taken at -130 degrees C (low temperature) and at -2 degrees C (cold temperature) and compared with the structure of the complex determined previously at room temperature (Shieh, H. S., H. M. Berman, M. Dabrow, and S. Neidle. 1980. Nucleic Acids Res. 8:85-97). Low temperature was refined with 5,125 reflections between 8.0 and 0.93 A, Anisotropically modeled temperature factors were used for DNA/drug atoms and isotropic ones for water oxygens to R factor of 12.2% in P2(1)2(1)2; a = 32.853, b = 21.760, c = 13.296 A. Cold temperature was refined isotropically with 2,846 reflections 8.0-0.89 A to R = 15.1% in P2(1)2(1)2; a = 32.867, b = 22.356, c = 13.461 A. Both structures are very similar to the room temperature one, though some important differences were observed: one guanine sugar moiety is disordered and additional water molecules have been located that give rise to infinite polyhedral hydration networks. Images FIGURE 2 PMID:1489914

Rigorous theory of graded thermoelectric converters including finite heat transfer coefficients

NASA Astrophysics Data System (ADS)

Gerstenmaier, York Christian; Wachutka, Gerhard

2017-11-01

Maximization of thermoelectric (TE) converter performance with an inhomogeneous material and electric current distribution has been investigated in previous literature neglecting thermal contact resistances to the heat reservoirs. The heat transfer coefficients (HTCs), defined as inverse thermal contact resistances per unit area, are thus infinite, whereas in reality, always parasitic thermal resistances, i.e., finite HTCs, are present. Maximization of the generated electric power and of cooling power in the refrigerator mode with respect to Seebeck coefficients and heat conductivity for a given profile of the material's TE figure of merit Z are mathematically ill-posed problems in the presence of infinite HTCs. As will be shown in this work, a fully self consistent solution is possible for finite HTCs, and in many respects, the results are fundamentally different. A previous theory for 3D devices will be extended to include finite HTCs and is applied to 1D devices. For the heat conductivity profile, an infinite number of solutions exist leading to the same device performance. Cooling power maximization for finite HTCs in 1D will lead to a strongly enhanced corresponding efficiency (coefficient of performance), whereas results with infinite HTCs lead to a non-monotonous temperature profile and coefficient of performance tending to zero for the prescribed heat conductivities. For maximized generated electric power, the corresponding generator efficiency is nearly a constant independent from the finite HTC values. The maximized efficiencies in the generator and cooling mode are equal to the efficiencies for the infinite HTC, provided that the corresponding powers approach zero. These and more findings are condensed in 4 theorems in the conclusions.

Realizing the Potential of the Effective Area Model: Refining the Software and Incorporating Recent Advances to Maximize Usefulness on Military Installations

DTIC Science & Technology

2010-07-01

list(e0 = -0.3, Dmax = 50, D0 = 20) > d <- seq(params$Dmax * 1.1) > plot(d, sapply(d, point.edge.effect, params), type = "l", lwd = 2, + xlab...infinite.edge.effect(): > params$k = 50 > plot(d, sapply(d, infinite.edge.effect, params), type = "l", + lwd = 2, xlab = "distance", ylab = "z", main = "effect of

Evolution of superclusters and delocalized states in GaAs1-xNx

NASA Astrophysics Data System (ADS)

Fluegel, B.; Alberi, K.; Beaton, D. A.; Crooker, S. A.; Ptak, A. J.; Mascarenhas, A.

2012-11-01

The evolution of individual nitrogen cluster bound states into an extended state infinite supercluster in dilute GaAs1-xNx was probed through temperature and intensity-dependent, time-resolved and magnetophotoluminescence (PL) measurements. Samples with compositions less than 0.23% N exhibit PL behavior that is consistent with emission from the extended states of the conduction band. Near a composition of 0.23% N, a discontinuity develops between the extended state PL peak energy and the photoluminescence excitation absorption edge. The existence of dual localized/delocalized state behavior near this composition signals the formation of an N supercluster just below the conduction band edge. The infinite supercluster is fully developed by 0.32% N.

The Hartree Equation for Infinitely Many Particles I. Well-Posedness Theory

NASA Astrophysics Data System (ADS)

Lewin, Mathieu; Sabin, Julien

2015-02-01

We show local and global well-posedness results for the Hartree equation where γ is a bounded self-adjoint operator on , ρ γ ( x) = γ( x, x) and w is a smooth short-range interaction potential. The initial datum γ(0) is assumed to be a perturbation of a translation-invariant state γ f = f(-Δ) which describes a quantum system with an infinite number of particles, such as the Fermi sea at zero temperature, or the Fermi-Dirac and Bose-Einstein gases at positive temperature. Global well-posedness follows from the conservation of the relative (free) energy of the state γ( t), counted relatively to the stationary state γ f . We indeed use a general notion of relative entropy, which allows us to treat a wide class of stationary states f(-Δ). Our results are based on a Lieb-Thirring inequality at positive density and on a recent Strichartz inequality for orthonormal functions, which are both due to Frank, Lieb, Seiringer and the first author of this article.

Hydrostatic Adjustment in Vertically Stratified Atmospheres

NASA Technical Reports Server (NTRS)

Duffy, Dean G.

2000-01-01

Hydrostatic adjustment due to diabatic heat in two nonisothermal atmospheres is examined. In the first case the temperature stratification is continuous; in the second case the atmosphere is composed of a warm, isothermal troposphere and a colder, isothermal semi-infinitely deep stratosphere.In both cases hydrostatic adjustment, to a good approximation, follows the pattern found in the Lamb problem (semi-infinitely deep. isothermal atmosphere): Initially we have acoustic waves with the kinetic energy increasing or decreasing at the expense of available elastic energy. After this initial period the acoustic waves evolve into acoustic-gravity waves with the kinetic, available potential and available elastic energies interacting with each other. Relaxation to hydrostatic balance occurs within a few oscillations. Stratification in an atmosphere with a continuous temperature profile affects primarily the shape and amplitude of the disturbances. In the two-layer atmosphere, a certain amount of energy is trapped in the tropospheric waveguide as disturbances reflect off the tropopause and back into the troposphere. With each internal reflection a portion of this trapped energy escapes and radiates to infinity.

[Determination of solubility parameters of high density polyethylene by inverse gas chromatography].

PubMed

Wang, Qiang; Chen, Yali; Liu, Ruiting; Shi, Yuge; Zhang, Zhengfang; Tang, Jun

2011-11-01

Inverse gas chromatographic (IGC) technology was used to determine the solubility parameters of high density polyethylene (HDPE) at the absolute temperatures from 303.15 to 343.15 K. Six solvents were applied as test probes including hexane (n-C6), heptane (n-C7), octane (n-C8), nonane (n-C9), chloroform (CHCl3) and ethyl acetate (EtAc). Some thermodynamic parameters were obtained by IGC data analysis such as the specific retention volumes of the solvents (V(0)(g)), the molar enthalpy of sorption (delta H(S)(1)), the partial molar enthalpy of mixing at infinite dilution (delta H(1)(infinity)), the molar enthalpy of vaporization (delta H(v)), the activity coefficients at infinite dilution (omega (1)(infinity)), and Flow-Huggins interaction parameters (X(1,2)(infinity)) between HDPE and probe solvents. The results showed that the above six probes are poor solvents for HDPE. The solubility parameter of HDPE at room temperature (298.15 K) was also derived as 19.00 (J/cm3)(0.5).

Asymptotic solution of Fokker-Planck equation for plasma in Paul traps

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

Shah, Kushal

2010-05-15

An exact analytic solution of the Vlasov equation for the plasma distribution in a Paul trap is known to be a Maxwellian and thus, immune to collisions under the assumption of infinitely fast relaxation [K. Shah and H. S. Ramachandran, Phys. Plasmas 15, 062303 (2008)]. In this paper, it is shown that even for a more realistic situation of finite time relaxation, solutions of the Fokker-Planck equation lead to an equilibrium solution of the form of a Maxwellian with oscillatory temperature. This shows that the rf heating observed in Paul traps cannot be caused due to collisional effects alone.

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

Ferrario, Lorenzo, E-mail: lorenzo.ferrario@polimi.it; Little, Justin M., E-mail: jml@princeton.edu; Choueiri, Edgar Y., E-mail: choueiri@princeton.edu

The plasma flow in a finite-electron-temperature magnetic nozzle, under the influence of an applied azimuthal current at the throat, is modeled analytically to assess its propulsive performance. A correction to the nozzle throat boundary conditions is derived by modifying the radial equilibrium of a magnetized infinite two-population cylindrical plasma column with the insertion of an external azimuthal body force for the electrons. Inclusion of finite-temperature effects, which leads to a modification of the radial density profile, is necessary for calculating the propulsive performance, which is represented by nozzle divergence efficiency and thrust coefficient. The solutions show that the application ofmore » the azimuthal current enhances all the calculated performance parameters through the narrowing of the radial density profile at the throat, and that investing power in this beam focusing effect is more effective than using the same power to pre-heat the electrons. The results open the possibility for the design of a focusing stage between the plasma source and the nozzle that can significantly enhance the propulsive performance of electron-driven magnetic nozzles.« less

SQDFT: Spectral Quadrature method for large-scale parallel O ( N ) Kohn–Sham calculations at high temperature

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

Suryanarayana, Phanish; Pratapa, Phanisri P.; Sharma, Abhiraj

We present SQDFT: a large-scale parallel implementation of the Spectral Quadrature (SQ) method formore » $$\\mathscr{O}(N)$$ Kohn–Sham Density Functional Theory (DFT) calculations at high temperature. Specifically, we develop an efficient and scalable finite-difference implementation of the infinite-cell Clenshaw–Curtis SQ approach, in which results for the infinite crystal are obtained by expressing quantities of interest as bilinear forms or sums of bilinear forms, that are then approximated by spatially localized Clenshaw–Curtis quadrature rules. We demonstrate the accuracy of SQDFT by showing systematic convergence of energies and atomic forces with respect to SQ parameters to reference diagonalization results, and convergence with discretization to established planewave results, for both metallic and insulating systems. Here, we further demonstrate that SQDFT achieves excellent strong and weak parallel scaling on computer systems consisting of tens of thousands of processors, with near perfect $$\\mathscr{O}(N)$$ scaling with system size and wall times as low as a few seconds per self-consistent field iteration. Finally, we verify the accuracy of SQDFT in large-scale quantum molecular dynamics simulations of aluminum at high temperature.« less

Validation of the SINDA/FLUINT code using several analytical solutions

NASA Technical Reports Server (NTRS)

Keller, John R.

1995-01-01

The Systems Improved Numerical Differencing Analyzer and Fluid Integrator (SINDA/FLUINT) code has often been used to determine the transient and steady-state response of various thermal and fluid flow networks. While this code is an often used design and analysis tool, the validation of this program has been limited to a few simple studies. For the current study, the SINDA/FLUINT code was compared to four different analytical solutions. The thermal analyzer portion of the code (conduction and radiative heat transfer, SINDA portion) was first compared to two separate solutions. The first comparison examined a semi-infinite slab with a periodic surface temperature boundary condition. Next, a small, uniform temperature object (lumped capacitance) was allowed to radiate to a fixed temperature sink. The fluid portion of the code (FLUINT) was also compared to two different analytical solutions. The first study examined a tank filling process by an ideal gas in which there is both control volume work and heat transfer. The final comparison considered the flow in a pipe joining two infinite reservoirs of pressure. The results of all these studies showed that for the situations examined here, the SINDA/FLUINT code was able to match the results of the analytical solutions.

Laser depth profiling studies of helium diffusion in Durango fluorapatite

NASA Astrophysics Data System (ADS)

van Soest, Matthijs C.; Monteleone, Brian D.; Hodges, Kip V.; Boyce, Jeremy W.

2011-05-01

Ultraviolet lasers coupled with sensitive mass spectrometers provide a useful way to measure laboratory-induced noble gas diffusion profiles in minerals, thus enabling the calculation of diffusion parameters. We illustrate this laser ablation depth profiling (LADP) technique for a previously well-studied mineral-isotopic system: 4He in Durango fluorapatite. LADP studies were conducted on oriented, polished slabs from a single crystal that were heated under vacuum to a variety of temperatures between 300 and 450 °C for variable times. The resolved 4He profiles exhibited error-function loss as predicted by previous bulk 4He diffusion studies. All of the slabs, regardless of crystallographic orientation, yielded modeled diffusivities that are statistically co-linear on an Arrhenius diagram, suggesting no diffusional anisotropy of 4He in this material. The data indicate an activation energy of 142.2 ± 5.0 (2 σ) kJ/mol and diffusivity at infinite temperature - reported as ln( D0) - of -4.71 ± 0.94 (2 σ) m 2/s. These values imply a bulk closure temperature for 4He in Durango fluorapatite of 74 °C for a 50 μm radius grain, infinite cylinder geometry, and a cooling rate of 10 °C/Myr.

SQDFT: Spectral Quadrature method for large-scale parallel O ( N ) Kohn–Sham calculations at high temperature

DOE PAGES

Suryanarayana, Phanish; Pratapa, Phanisri P.; Sharma, Abhiraj; ...

2017-12-07

We present SQDFT: a large-scale parallel implementation of the Spectral Quadrature (SQ) method formore » $$\\mathscr{O}(N)$$ Kohn–Sham Density Functional Theory (DFT) calculations at high temperature. Specifically, we develop an efficient and scalable finite-difference implementation of the infinite-cell Clenshaw–Curtis SQ approach, in which results for the infinite crystal are obtained by expressing quantities of interest as bilinear forms or sums of bilinear forms, that are then approximated by spatially localized Clenshaw–Curtis quadrature rules. We demonstrate the accuracy of SQDFT by showing systematic convergence of energies and atomic forces with respect to SQ parameters to reference diagonalization results, and convergence with discretization to established planewave results, for both metallic and insulating systems. Here, we further demonstrate that SQDFT achieves excellent strong and weak parallel scaling on computer systems consisting of tens of thousands of processors, with near perfect $$\\mathscr{O}(N)$$ scaling with system size and wall times as low as a few seconds per self-consistent field iteration. Finally, we verify the accuracy of SQDFT in large-scale quantum molecular dynamics simulations of aluminum at high temperature.« less

Floquet-Magnus theory and generic transient dynamics in periodically driven many-body quantum systems

NASA Astrophysics Data System (ADS)

Kuwahara, Tomotaka; Mori, Takashi; Saito, Keiji

2016-04-01

This work explores a fundamental dynamical structure for a wide range of many-body quantum systems under periodic driving. Generically, in the thermodynamic limit, such systems are known to heat up to infinite temperature states in the long-time limit irrespective of dynamical details, which kills all the specific properties of the system. In the present study, instead of considering infinitely long-time scale, we aim to provide a general framework to understand the long but finite time behavior, namely the transient dynamics. In our analysis, we focus on the Floquet-Magnus (FM) expansion that gives a formal expression of the effective Hamiltonian on the system. Although in general the full series expansion is not convergent in the thermodynamics limit, we give a clear relationship between the FM expansion and the transient dynamics. More precisely, we rigorously show that a truncated version of the FM expansion accurately describes the exact dynamics for a certain time-scale. Our theory reveals an experimental time-scale for which non-trivial dynamical phenomena can be reliably observed. We discuss several dynamical phenomena, such as the effect of small integrability breaking, efficient numerical simulation of periodically driven systems, dynamical localization and thermalization. Especially on thermalization, we discuss a generic scenario on the prethermalization phenomenon in periodically driven systems.

Thermographic Phosphor Measurements of Shock-Shock Interactions on a Swept Cylinder

NASA Technical Reports Server (NTRS)

Jones, Michelle L.; Berry, Scott A.

2013-01-01

The effects of fin leading-edge radius and sweep angle on peak heating rates due to shock-shock interactions were investigated in the NASA Langley Research Center 20-inch Mach 6 Air Tunnel. The fin model leading edges, which represent cylindrical leading edges or struts on hypersonic vehicles, were varied from 0.25 inches to 0.75 inches in radius. A 9deg wedge generated a planar oblique shock at 16.7deg to the flow that intersected the fin bow shock, producing a shock-shock interaction that impinged on the fin leading edge. The fin angle of attack was varied from 0deg (normal to the free-stream) to 15deg and 25deg swept forward. Global temperature data was obtained from the surface of the fused silica fins using phosphor thermography. Metal oil flow models with the same geometries as the fused silica models were used to visualize the streamline patterns for each angle of attack. High-speed zoom-schlieren videos were recorded to show the features and temporal unsteadiness of the shock-shock interactions. The temperature data were analyzed using one-dimensional semi-infinite as well as one- and two-dimensional finite-volume methods to determine the proper heat transfer analysis approach to minimize errors from lateral heat conduction due to the presence of strong surface temperature gradients induced by the shock interactions. The general trends in the leading-edge heat transfer behavior were similar for the three shock-shock interactions, respectively, between the test articles with varying leading-edge radius. The dimensional peak heat transfer coefficient augmentation increased with decreasing leading-edge radius. The dimensional peak heat transfer output from the two-dimensional code was about 20% higher than the value from a standard, semi-infinite onedimensional method.

Experimental Investigation of Shock-Shock Interactions Over a 2-D Wedge at M=6

NASA Technical Reports Server (NTRS)

Jones, Michelle L.

2013-01-01

The effects of fin-leading-edge radius and sweep angle on peak heating rates due to shock-shock interactions were investigated in the NASA Langley Research Center 20-inch Mach 6 Air Tunnel. The fin model leading edges, which represent cylindrical leading edges or struts on hypersonic vehicles, were varied from 0.25 inches to 0.75 inches in radius. A 9deg wedge generated a planar oblique shock at 16.7deg to the flow that intersected the fin bow shock, producing a shock-shock interaction that impinged on the fin leading edge. The fin angle of attack was varied from 0deg (normal to the free-stream) to 15deg and 25deg swept forward. Global temperature data was obtained from the surface of the fused silica fins through phosphor thermography. Metal oil flow models with the same geometries as the fused silica models were used to visualize the streamline patterns for each angle of attack. High-speed zoom-schlieren videos were recorded to show the features and temporal unsteadiness of the shock-shock interactions. The temperature data were analyzed using one-dimensional semi-infinite as well as one- and two-dimensional finite-volume methods to determine the proper heat transfer analysis approach to minimize errors from lateral heat conduction due to the presence of strong surface temperature gradients induced by the shock interactions. The general trends in the leading-edge heat transfer behavior were similar for the three shock-shock interactions, respectively, between the test articles with varying leading-edge radius. The dimensional peak heat transfer coefficient augmentation increased with decreasing leading-edge radius. The dimensional peak heat transfer output from the two-dimensional code was about 20% higher than the value from a standard, semi-infinite one-dimensional method.

2.5D Finite/infinite Element Approach for Simulating Train-Induced Ground Vibrations

NASA Astrophysics Data System (ADS)

Yang, Y. B.; Hung, H. H.; Kao, J. C.

2010-05-01

The 2.5D finite/infinite element approach for simulating the ground vibrations by surface or underground moving trains will be briefly summarized in this paper. By assuming the soils to be uniform along the direction of the railway, only a two-dimensional profile of the soil perpendicular to the railway need be considered in the modeling. Besides the two in-plane degrees of freedom (DOFs) per node conventionally used for plane strain elements, an extra DOF is introduced to account for the out-of-plane wave transmission. The profile of the half-space is divided into a near field and a semi-infinite far field. The near field containing the train loads and irregular structures is simulated by the finite elements, while the far field covering the soils with infinite boundary by the infinite elements, by which due account is taken of the radiation effects for the moving loads. Enhanced by the automated mesh expansion procedure proposed previously by the writers, the far field impedances for all the lower frequencies are generated repetitively from the mesh created for the highest frequency considered. Finally, incorporated with a proposed load generation mechanism that takes the rail irregularity and dynamic properties of trains into account, an illustrative case study was performed. This paper investigates the vibration isolation effect of the elastic foundation that separates the concrete slab track from the underlying soil or tunnel structure. In addition, the advantage of the 2.5D approach was clearly demonstrated in that the three-dimensional wave propagation effect can be virtually captured using a two-dimensional finite/infinite element mesh. Compared with the conventional 3D approach, the present approach appears to be simple, efficient and generally accurate.

Effect of electric field and temperature gradient on the orientational dynamics of liquid crystals in a microvolume cylindrical cavity.

PubMed

Zakharov, A V; Vakulenko, A A; Romano, Silvano

2009-10-28

We have considered a homogeneously aligned liquid crystal (HALC) microvolume confined between two infinitely long horizontal coaxial cylinders and investigated dynamic field pumping, i.e., studied the interactions between director, velocity, and electric E fields as well as a radially applied temperature gradient inverted Delta T, where the inner cylinder is kept at a lower temperature than the outer one. In order to elucidate the role of inverted Delta T in producing hydrodynamic flow u, we have carried out a numerical study of a system of hydrodynamic equations including director reorientation, fluid flow, and temperature redistribution across the HALC cavity. Calculations show that only under the influence of inverted Delta T does the initially quiescent HALC sample settle down to a stationary flow regime with horizontal component of velocity u(eq)(r). The effects of inverted Delta T and of the size of the HALC cavity on magnitude and direction of u(eq)(r) have been investigated for a number of hydrodynamic regimes. Calculations also showed that E influences only the director redistribution across the HALC but not the magnitude of the velocity u(eq)(r).

Energy and Momentum Relaxation Times of 2D Electrons Due to Near Surface Deformation Potential Scattering

NASA Astrophysics Data System (ADS)

Pipa, Viktor; Vasko, Fedor; Mitin, Vladimir

1997-03-01

The low temperature energy and momentum relaxation rates of 2D electron gas placed near the free or clamped surface of a semi-infinit sample are calculated. To describe the electron-acoustic phonon interaction with allowance of the surface effect the method of elasticity theory Green functions was used. This method allows to take into account the reflection of acoustic waves from the surface and related mutual conversion of LA and TA waves. It is shown that the strength of the deformation potential scattering at low temperatures substantially depends on the mechanical conditions at the surface: relaxation rates are suppressed for the free surface while for the rigid one the rates are enhanced. The dependence of the conductivity on the distance between the 2D layer and the surface is discussed. The effect is most pronounced in the range of temperatures 2 sl pF < T < (2 hbar s_l)/d, where pF is the Fermi momentum, sl is the velocity of LA waves, d is the width of the quantum well.

Understanding the impact of the central atom on the ionic liquid behavior: phosphonium vs ammonium cations.

PubMed

Carvalho, Pedro J; Ventura, Sónia P M; Batista, Marta L S; Schröder, Bernd; Gonçalves, Fernando; Esperança, José; Mutelet, Fabrice; Coutinho, João A P

2014-02-14

The influence of the cation's central atom in the behavior of pairs of ammonium- and phosphonium-based ionic liquids was investigated through the measurement of densities, viscosities, melting temperatures, activity coefficients at infinite dilution, refractive indices, and toxicity against Vibrio fischeri. All the properties investigated are affected by the cation's central atom nature, with ammonium-based ionic liquids presenting higher densities, viscosities, melting temperatures, and enthalpies. Activity coefficients at infinite dilution show the ammonium-based ionic liquids to present slightly higher infinite dilution activity coefficients for non-polar solvents, becoming slightly lower for polar solvents, suggesting that the ammonium-based ionic liquids present somewhat higher polarities. In good agreement these compounds present lower toxicities than the phosphonium congeners. To explain this behavior quantum chemical gas phase DFT calculations were performed on isolated ion pairs at the BP-TZVP level of theory. Electronic density results were used to derive electrostatic potentials of the identified minimum conformers. Electrostatic potential-derived CHelpG and Natural Population Analysis charges show the P atom of the tetraalkylphosphonium-based ionic liquids cation to be more positively charged than the N atom in the tetraalkylammonium-based analogous IL cation, and a noticeable charge delocalization occurring in the tetraalkylammonium cation, when compared with the respective phosphonium congener. It is argued that this charge delocalization is responsible for the enhanced polarity observed on the ammonium based ionic liquids explaining the changes in the thermophysical properties observed.

Understanding the impact of the central atom on the ionic liquid behavior: Phosphonium vs ammonium cations

NASA Astrophysics Data System (ADS)

Carvalho, Pedro J.; Ventura, Sónia P. M.; Batista, Marta L. S.; Schröder, Bernd; Gonçalves, Fernando; Esperança, José; Mutelet, Fabrice; Coutinho, João A. P.

2014-02-01

The influence of the cation's central atom in the behavior of pairs of ammonium- and phosphonium-based ionic liquids was investigated through the measurement of densities, viscosities, melting temperatures, activity coefficients at infinite dilution, refractive indices, and toxicity against Vibrio fischeri. All the properties investigated are affected by the cation's central atom nature, with ammonium-based ionic liquids presenting higher densities, viscosities, melting temperatures, and enthalpies. Activity coefficients at infinite dilution show the ammonium-based ionic liquids to present slightly higher infinite dilution activity coefficients for non-polar solvents, becoming slightly lower for polar solvents, suggesting that the ammonium-based ionic liquids present somewhat higher polarities. In good agreement these compounds present lower toxicities than the phosphonium congeners. To explain this behavior quantum chemical gas phase DFT calculations were performed on isolated ion pairs at the BP-TZVP level of theory. Electronic density results were used to derive electrostatic potentials of the identified minimum conformers. Electrostatic potential-derived CHelpG and Natural Population Analysis charges show the P atom of the tetraalkylphosphonium-based ionic liquids cation to be more positively charged than the N atom in the tetraalkylammonium-based analogous IL cation, and a noticeable charge delocalization occurring in the tetraalkylammonium cation, when compared with the respective phosphonium congener. It is argued that this charge delocalization is responsible for the enhanced polarity observed on the ammonium based ionic liquids explaining the changes in the thermophysical properties observed.

Tomograms for open quantum systems: In(finite) dimensional optical and spin systems

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

Thapliyal, Kishore, E-mail: tkishore36@yahoo.com; Banerjee, Subhashish, E-mail: subhashish@iitj.ac.in; Pathak, Anirban, E-mail: anirban.pathak@gmail.com

Tomograms are obtained as probability distributions and are used to reconstruct a quantum state from experimentally measured values. We study the evolution of tomograms for different quantum systems, both finite and infinite dimensional. In realistic experimental conditions, quantum states are exposed to the ambient environment and hence subject to effects like decoherence and dissipation, which are dealt with here, consistently, using the formalism of open quantum systems. This is extremely relevant from the perspective of experimental implementation and issues related to state reconstruction in quantum computation and communication. These considerations are also expected to affect the quasiprobability distribution obtained frommore » experimentally generated tomograms and nonclassicality observed from them. -- Highlights: •Tomograms are constructed for open quantum systems. •Finite and infinite dimensional quantum systems are studied. •Finite dimensional systems (phase states, single & two qubit spin states) are studied. •A dissipative harmonic oscillator is considered as an infinite dimensional system. •Both pure dephasing as well as dissipation effects are studied.« less

Poro-mechanical coupling influences on potential for rainfall-induced shallow landslides in unsaturated soils

NASA Astrophysics Data System (ADS)

Wu, L. Z.; Selvadurai, A. P. S.; Zhang, L. M.; Huang, R. Q.; Huang, Jinsong

2016-12-01

Rainfall-induced landslides are a common occurrence in terrain with steep topography and soils that have degradable strength. Rainfall infiltration into a partially saturated slope of infinite extent can lead to either a decrease or complete elimination of soil suction, compromising the slopes' stability. In this research the rainfall infiltration coupled with deformation of a partially saturated soil slope during rainfall infiltration is analyzed. The limit equilibrium conditions and the shear strength relationship of a partially saturated soil are employed to develop an analytical solution for calculating the stability of an infinite partially saturated slope due to rainfall infiltration. The analytical solutions are able to consider the influence of the coupled effects on the stability of the slope. The factors that affect the safety of a partially saturated slope of infinite extent are discussed. The results indicate that the poro-mechanical coupling of water infiltration and deformation has an important effect on the stability of the infinite unsaturated slope.

Infinite variance in fermion quantum Monte Carlo calculations.

PubMed

Shi, Hao; Zhang, Shiwei

2016-03-01

For important classes of many-fermion problems, quantum Monte Carlo (QMC) methods allow exact calculations of ground-state and finite-temperature properties without the sign problem. The list spans condensed matter, nuclear physics, and high-energy physics, including the half-filled repulsive Hubbard model, the spin-balanced atomic Fermi gas, and lattice quantum chromodynamics calculations at zero density with Wilson Fermions, and is growing rapidly as a number of problems have been discovered recently to be free of the sign problem. In these situations, QMC calculations are relied on to provide definitive answers. Their results are instrumental to our ability to understand and compute properties in fundamental models important to multiple subareas in quantum physics. It is shown, however, that the most commonly employed algorithms in such situations have an infinite variance problem. A diverging variance causes the estimated Monte Carlo statistical error bar to be incorrect, which can render the results of the calculation unreliable or meaningless. We discuss how to identify the infinite variance problem. An approach is then proposed to solve the problem. The solution does not require major modifications to standard algorithms, adding a "bridge link" to the imaginary-time path integral. The general idea is applicable to a variety of situations where the infinite variance problem may be present. Illustrative results are presented for the ground state of the Hubbard model at half-filling.

Mathematical model of a smoldering log.

Treesearch

Fernando de Souza Costa; David Sandberg

2004-01-01

A mathematical model is developed describing the natural smoldering of logs. It is considered the steady one dimensional propagation of infinitesimally thin fronts of drying, pyrolysis, and char oxidation in a horizontal semi-infinite log. Expressions for the burn rates, distribution profiles of temperature, and positions of the drying, pyrolysis, and smoldering fronts...

Reports of investigations on: Derivation of an infinite-dilution activity coefficient model and application to two-component vapor/liquid equilibria data: Final report

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

Roper, V.P.; Kobayashi, R.

1988-02-01

Infinite-dilution fugacity coefficients were obtained for the system fluorene/phenanthrene at thirteen temperatures by fitting total pressure across the entire mole fraction range by a computer routine. A thermodynamically consistent routine, that allowed for both positive and negative pressure deviations from the ideal values, was used to correlate data over the full mole fraction range from 0 to 1. The four-suffix Margules activity coefficient model without modification essentially served this purpose since total pressures and total pressure derivatives with respect to mole fraction were negligible compared to pressure measurement precision. The water/ethanol system and binary systems comprised of aniline, chlorobenzene, acetonitrilemore » and other polar compounds were fit for total pressure across the entire mole fraction range for binary Vapor-Liquid-Equilbria (VLE) using the rigorous, thermodynamically consistent Gibbs-Duhem Relation derived by Ibl and Dodge. Data correlation was performed using a computer least squares procedure. Infinite-dilution fugacity coefficients were obtained using a modified Margules activity coefficient model.« less

Applications of stochastic mechanics to polyatomic lattices

NASA Astrophysics Data System (ADS)

Beumée, J. G. B.; Vilallonga, E.; Rabitz, H.

1990-03-01

Stochastic quantization in the sense of Nelson provides an alternative interpretation of some aspects of quantum mechanics in the coordinate representation, and it was combined recently with the Ford, Kac, and Mazur (FKM) approximation [J. Math. Phys. 6, 504 (1965)] for large lattices to construct a quantum analog to the Brownian motion process. In this paper a similar approach is applied to model the effect of temperature fluctuations in a one-dimensional ordered chain of atoms with nearest-neighbor linear forces. However, we do not make use of the FKM approximation, and as a consequence the statistical properties of the involved processes are exactly determined by the lattice force field. In particular, we evaluate the covariance matrix for the fluctuations, and we examine its high- and low-temperature behavior. Because of the translation invariance of the interaction potential, the covariance matrix for the fluctuations becomes singular implying that the associated probability density has equal density along the zero eigenvector of the interaction matrix. This behavior is readily interpreted in terms of the motion of the center of mass of the system, which corresponds to a stochastically perturbed translation, while all other modes are bounded with a probability of 1. As is well known, the transformation to internal (bondlength) coordinates leads to a Hamiltonian specified by a nonsingular interaction matrix. We examine the variance of the fluctuations for the internal coordinates, and we show that in the high-temperature limit the result agrees with that of classical statistical mechanics. Both the position and bondlength of the surface atom decrease with time as is expected for a semi-infinite lattice. However, the position of the surface atom is less dependent on substrate-atom positions than is the surface bondlength on substrate bondlengths. Finally, the autocorrelation function of the surface bondlength in the case of a semi-infinite lattice limit is investigated for low- and high-temperature limits.

Signals of strong electronic correlation in ion scattering processes

NASA Astrophysics Data System (ADS)

Bonetto, F.; Gonzalez, C.; Goldberg, E. C.

2016-05-01

Previous measurements of neutral atom fractions for S r+ scattered by gold polycrystalline surfaces show a singular dependence with the target temperature. There is still not a theoretical model that can properly describe the magnitude and the temperature dependence of the neutralization probabilities found. Here, we applied a first-principles quantum-mechanical theoretical formalism to describe the time-dependent scattering process. Three different electronic correlation approaches consistent with the system analyzed are used: (i) the spinless approach, where two charge channels are considered (S r0 and S r+ ) and the spin degeneration is neglected; (ii) the infinite-U approach, with the same charge channels (S r0 and S r+ ) but considering the spin degeneration; and (iii) the finite-U approach, where the first ionization and second ionization energy levels are considered very, but finitely, separated. Neutral fraction magnitudes and temperature dependence are better described by the finite-U approach, indicating that e -correlation plays a significant role in charge-transfer processes. However, none of them is able to explain the nonmonotonous temperature dependence experimentally obtained. Here, we suggest that small changes in the surface work function introduced by the target heating, and possibly not detected by experimental standard methods, could be responsible for that singular behavior. Additionally, we apply the same theoretical model using the infinite-U approximation for the Mg-Au system, obtaining an excellent description of the experimental neutral fractions measured.

Determination of gas-liquid partition coefficients of several organic solutes in trihexyl(tetradecyl)phosphonium bromide using capillary gas chromatography columns.

PubMed

Ronco, Nicolás R; Menestrina, Fiorella; Romero, Lílian M; Castells, Cecilia B

2017-06-09

In this paper, we report gas-liquid partition constants for thirty-five volatile organic solutes in the room temperature ionic liquid trihexyl(tetradecyl)phosphonium bromide measured by gas-liquid chromatography using capillary columns. The relative contribution of gas-liquid partition and interfacial adsorption to retention was evaluated through the use of columns with different the phase ratio. Four capillary columns with exactly known phase ratios were constructed and employed to measure the solute retention factors at four temperatures between 313.15 and 343.15K. The partition coefficients were calculated from the slopes of the linear regression between solute retention factors and the reciprocal of phase ratio at a given temperature according to the gas-liquid chromatographic theory. Gas-liquid interfacial adsorption was detected for a few solutes and it has been considered for the calculations of partition coefficient. Reliable solute's infinite dilution activity coefficients can be obtained when retention data are determined by a unique partitioning mechanism. The partial molar excess enthalpies at infinite dilution have been estimated from the dependence of experimental values of solute activity coefficients with the column temperature. A thorough discussion of the uncertainties of the experimental measurements and the main advantages of the use of capillary columns to acquire the aforementioned relevant thermodynamic information was performed. Copyright © 2017 Elsevier B.V. All rights reserved.

Unsteady boundary layer flow and heat transfer of a Casson fluid past an oscillating vertical plate with Newtonian heating.

PubMed

Hussanan, Abid; Zuki Salleh, Mohd; Tahar, Razman Mat; Khan, Ilyas

2014-01-01

In this paper, the heat transfer effect on the unsteady boundary layer flow of a Casson fluid past an infinite oscillating vertical plate with Newtonian heating is investigated. The governing equations are transformed to a systems of linear partial differential equations using appropriate non-dimensional variables. The resulting equations are solved analytically by using the Laplace transform method and the expressions for velocity and temperature are obtained. They satisfy all imposed initial and boundary conditions and reduce to some well-known solutions for Newtonian fluids. Numerical results for velocity, temperature, skin friction and Nusselt number are shown in various graphs and discussed for embedded flow parameters. It is found that velocity decreases as Casson parameters increases and thermal boundary layer thickness increases with increasing Newtonian heating parameter.

First- and second-order metal-insulator phase transitions and topological aspects of a Hubbard-Rashba system

NASA Astrophysics Data System (ADS)

Marcelino, Edgar

2017-05-01

This paper considers a model consisting of a kinetic term, Rashba spin-orbit coupling and short-range Coulomb interaction at zero temperature. The Coulomb interaction is decoupled by a mean-field approximation in the spin channel using field theory methods. The results feature a first-order phase transition for any finite value of the chemical potential and quantum criticality for vanishing chemical potential. The Hall conductivity is also computed using the Kubo formula in a mean-field effective Hamiltonian. In the limit of infinite mass the kinetic term vanishes and all the phase transitions are of second order; in this case the spontaneous symmetry-breaking mechanism adds a ferromagnetic metallic phase to the system and features a zero-temperature quantization of the Hall conductivity in the insulating one.

Couette flow of an incompressible fluid in a porous channel with mass transfer

NASA Astrophysics Data System (ADS)

Niranjana, N.; Vidhya, M.; Govindarajan, A.

2018-04-01

The present discussion deals with the study of couette flow through a porous medium of a viscous incompressible fluid between two infinite horizontal parallel porous flat plates with heat and mass transfer. The stationary plate and the plate in uniform motion are subjected to transverse sinusoidal injection and uniform suction of the fluid. Due to this type of injection velocity, the flow becomes three dimensional. The analytical solutions of the nonlinear partial differential equations of this problem are obtained by using perturbation technique. Expressions for the velocity, temperature fields and the rate of heat and mass transfers are obtained. Effects of the following parameters Schmidt number (Sc), Modified Grashof number (Gm) on the velocity, temperature and concentration fields are obtained numerically and depicted through graphs. The rate of heat and mass transfer are also analyzed.

Thermal mirror spectrometry: An experimental investigation of optical glasses

NASA Astrophysics Data System (ADS)

Zanuto, V. S.; Herculano, L. S.; Baesso, M. L.; Lukasievicz, G. V. B.; Jacinto, C.; Malacarne, L. C.; Astrath, N. G. C.

2013-03-01

The Thermal mirror technique relies on measuring laser-induced nanoscale surface deformation of a solid sample. The amplitude of the effect is directly dependent on the optical absorption and linear thermal expansion coefficients, and the time evolution depends on the heat diffusion properties of the sample. Measurement of transient signals provide direct access to thermal, optical and mechanical properties of the material. The theoretical models describing this effect can be formulated for very low optical absorbing and for absorbing materials. In addition, the theories describing the effect apply for semi-infinite and finite samples. In this work, we apply the Thermal mirror technique to measure physical properties of optical glasses. The semi-infinite and finite models are used to investigate very low optical absorbing glasses. The thickness limit for which the semi-infinite model retrieves the correct values of the thermal diffusivity and amplitude of the transient is obtained using the finite description. This procedure is also employed on absorbing glasses, and the semi-infinite Beer-Lambert law model is used to analyze the experimental data. The experimental data show the need to use the finite model for samples with very low bulk absorption coefficients and thicknesses L < 1.5 mm. This analysis helped to establish limit values of thickness for which the semi-infinite model for absorbing materials could be used, L > 1.0 mm in this case. In addition, the physical properties of the samples were calculated and absolute values derived.

Rotating metric in nonsingular infinite derivative theories of gravity

NASA Astrophysics Data System (ADS)

Cornell, Alan S.; Harmsen, Gerhard; Lambiase, Gaetano; Mazumdar, Anupam

2018-05-01

In this paper, we will provide a nonsingular rotating spacetime metric for a ghost-free infinite derivative theory of gravity in a linearized limit. We will provide the predictions for the Lense-Thirring effect for a slowly rotating system, and how it is compared with that from general relativity.

Effects of the temperature and pressure on the electronic and optical properties of an exciton in GaAs/Ga1-xAlxAs quantum ring

NASA Astrophysics Data System (ADS)

El-Bakkari, K.; Sali, A.; Iqraoun, E.; Rezzouk, A.; Es-Sbai, N.; Ouazzani Jamil, M.

2018-06-01

Using a variational approach, we have calculated the binding energies (E1s,2sb) and interband emission energy (Eph) of an exciton confined in GaAs / Ga1 - x Alx As quantum rings (QRs) structures under effects of the temperature and pressure, in the effective mass approximation. We have taken into consideration the difference in the effective masses of the charge carriers in two materials, well and barrier. The results that we have obtained show clearly that E1s,2sb and Eph are influenced by the structure geometries of QR (height H, radial thickness Δ R and potential barrier), the temperature and pressure. Indeed, with a smaller geometric parameter, E1s,2sb and Eph become higher due to the improvement in confinement of the charge carriers. We have also observed that for a given value of the temperature, the pressure leads to an increasing of the E1s,2sb and Eph , and the latter quantities are decreasing with temperature. In addition, these variations of the E1s,2sb and Eph under the external perturbations are more remarkable in small H for fixed Δ R , and for larger Δ R for a given value of the H, because for the choice of a finite height of the barrier in the z direction and an infinite confinement in ρ direction.

Unsteady magnetohydrodynamic free convection flow of a second grade fluid in a porous medium with ramped wall temperature.

PubMed

Samiulhaq; Ahmad, Sohail; Vieru, Dumitru; Khan, Ilyas; Shafie, Sharidan

2014-01-01

Magnetic field influence on unsteady free convection flow of a second grade fluid near an infinite vertical flat plate with ramped wall temperature embedded in a porous medium is studied. It has been observed that magnitude of velocity as well as skin friction in case of ramped temperature is quite less than the isothermal temperature. Some special cases namely: (i) second grade fluid in the absence of magnetic field and porous medium and (ii) Newtonian fluid in the presence of magnetic field and porous medium, performing the same motion are obtained. Finally, the influence of various parameters is graphically shown.

Pressure distribution with surface roughness for effect between porous infinitely long rectangular plates with MHD couple stress squeeze film lubrication

NASA Astrophysics Data System (ADS)

Sangeetha, S.; Kesavan, Sundarammal

2018-04-01

This investigation is an analysis of MHD couple stress squeeze film performance with a rough surface between porous infinitely long rectangular plates. The pressure equation for the magnetic field is mathematically derived using Christensen’s stochastic equation. Therefore, the upshot of this magnetic effect reveals the enhanced performance of the pressure which is compared to the Newtonian instance.

Propagation of SH waves in an infinite/semi-infinite piezoelectric/piezomagnetic periodically layered structure.

PubMed

Pang, Yu; Liu, Yu-Shan; Liu, Jin-Xi; Feng, Wen-Jie

2016-04-01

In this paper, SH bulk/surface waves propagating in the corresponding infinite/semi-infinite piezoelectric (PE)/piezomagnetic (PM) and PM/PE periodically layered composites are investigated by two methods, the stiffness matrix method and the transfer matrix method. For a semi-infinite PE/PM or PM/PE medium, the free surface is parallel to the layer interface. Both PE and PM materials are assumed to be transversely isotropic solids. Dispersion equations are derived by the stiffness/transfer matrix methods, respectively. The effects of electric-magnetic (ME) boundary conditions at the free surface and the layer thickness ratios on dispersion curves are considered in detail. Numerical examples show that the results calculated by the two methods are the same. The dispersion curves of SH surface waves are below the bulk bands or inside the frequency gaps. The ratio of the layer thickness has an important effect not only on the bulk bands but also on the dispersion curves of SH surface waves. Electric and magnetic boundary conditions, respectively, determine the dispersion curves of SH surface waves for the PE/PM and PM/PE semi-infinite structures. The band structures of SH bulk waves are consistent for the PE/PM and PM/PE structures, however, the dispersive behaviors of SH surface waves are indeed different for the two composites. The realization of the above-mentioned characteristics of SH waves will make it possible to design PE/PM acoustic wave devices with periodical structures and achieve the better performance. Copyright © 2016 Elsevier B.V. All rights reserved.

Single file diffusion into a semi-infinite tube.

PubMed

Farrell, Spencer G; Brown, Aidan I; Rutenberg, Andrew D

2015-11-23

We investigate single file diffusion (SFD) of large particles entering a semi-infinite tube, such as luminal diffusion of proteins into microtubules or flagella. While single-file effects have no impact on the evolution of particle density, we report significant single-file effects for individually tracked tracer particle motion. Both exact and approximate ordering statistics of particles entering semi-infinite tubes agree well with our stochastic simulations. Considering initially empty semi-infinite tubes, with particles entering at one end starting from an initial time t = 0, tracked particles are initially super-diffusive after entering the system, but asymptotically diffusive at later times. For finite time intervals, the ratio of the net displacement of individual single-file particles to the average displacement of untracked particles is reduced at early times and enhanced at later times. When each particle is numbered, from the first to enter (n = 1) to the most recent (n = N), we find good scaling collapse of this distance ratio for all n. Experimental techniques that track individual particles, or local groups of particles, such as photo-activation or photobleaching of fluorescently tagged proteins, should be able to observe these single-file effects. However, biological phenomena that depend on local concentration, such as flagellar extension or luminal enzymatic activity, should not exhibit single-file effects.

Periodically driven ergodic and many-body localized quantum systems

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

Ponte, Pedro; Department of Physics and Astronomy, University of Waterloo, ON N2L 3G1; Chandran, Anushya

2015-02-15

We study dynamics of isolated quantum many-body systems whose Hamiltonian is switched between two different operators periodically in time. The eigenvalue problem of the associated Floquet operator maps onto an effective hopping problem. Using the effective model, we establish conditions on the spectral properties of the two Hamiltonians for the system to localize in energy space. We find that ergodic systems always delocalize in energy space and heat up to infinite temperature, for both local and global driving. In contrast, many-body localized systems with quenched disorder remain localized at finite energy. We support our conclusions by numerical simulations of disorderedmore » spin chains. We argue that our results hold for general driving protocols, and discuss their experimental implications.« less

Magnetic fields end-face effect investigation of HTS bulk over PMG with 3D-modeling numerical method

NASA Astrophysics Data System (ADS)

Qin, Yujie; Lu, Yiyun

2015-09-01

In this paper, the magnetic fields end-face effect of high temperature superconducting (HTS) bulk over a permanent magnetic guideway (PMG) is researched with 3D-modeling numerical method. The electromagnetic behavior of the bulk is simulated using finite element method (FEM). The framework is formulated by the magnetic field vector method (H-method). A superconducting levitation system composed of one rectangular HTS bulk and one infinite long PMG is successfully investigated using the proposed method. The simulation results show that for finite geometrical HTS bulk, even the applied magnetic field is only distributed in x-y plane, the magnetic field component Hz which is along the z-axis can be observed interior the HTS bulk.

Thermal diffusion effect on MHD mixed convective flow along a vertically inclined plate: A casson fluid flow

NASA Astrophysics Data System (ADS)

Prasad, D. V. V. Krishna; Chaitanya, G. S. Krishna; Raju, R. Srinivasa

2018-05-01

The nature of Casson fluid on MHD free convective flow of over an impulsively started infinite vertically inclined plate in presence of thermal diffusion (Soret), thermal radiation, heat and mass transfer effects is studied. The basic governing nonlinear coupled partial differential equations are solved numerically using finite element method. The relevant physical parameters appearing in velocity, temperature and concentration profiles are analyzed and discussed through graphs. Finally, the results for velocity profiles and the reduced Nusselt and Sherwood numbers are obtained and compared with previous results in the literature and are found to be in excellent agreement. Applications of the present study would be useful in magnetic material processing and chemical engineering systems.

Thermal analysis of the vertical bridgman semiconductor crystal growth technique. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Jasinski, T. J.

1982-01-01

The quality of semiconductor crystals grown by the vertical Bridgman technique is strongly influenced by the axial and radial variations of temperature within the charge. The relationship between the thermal parameters of the vertical Bridgman system and the thermal behavior of the charge are examined. Thermal models are developed which are capable of producing results expressable in analytical form and which can be used without recourse to extensive computer work for the preliminary thermal design of vertical Bridgman crystal growth systems. These models include the effects of thermal coupling between the furnace and the charge, charge translation rate, charge diameter, thickness and thermal conductivity of the confining crucible, thermal conductivity change and liberation of latent heat at the growth interface, and infinite charge length. The hot and cold zone regions, considered to be at spatially uniform temperatures, are separated by a gradient control region which provides added thermal design flexibility for controlling the temperature variations near the growth interface.

Is Bare Band Description of Carrier Transport Appropriate in Pentacene?

NASA Astrophysics Data System (ADS)

Andersen, John D.; Giuggioli, Luca; Kenkre, V. M.

2002-03-01

Experiments on injected charges in pentacene single crystals reveal mobilities typical of inorganic semiconductors and temperature dependence (for T<430K) suggesting bandlike behavior.(J. H. Schon, C. Kloc, and B. Batlogg, Phys. Rev. Lett. 86, 3843 (2001)) Polaronic bands, particularly their narrowing with increasing temperature, were invoked(V. M. Kenkre, John D. Andersen, D.H. Dunlap, and C.B. Duke, Phys. Rev. Lett. 62, 1165 (1989)) in the related naphthalene problem.(L. B. Schein, C. B. Duke, and A.R. McGhie, Phys. Rev. Lett. 40, 197 (1978); L. B. Schein, W. Warta, and N. Karl, Chem. Phys. Lett. 100, 34 (1983)) Because the low temperature mobility values in pentacene suggest moderately large bandwidths, we address two questions. Does a bare wide (effectively infinite) band description work for pentacene for T<400K? And, is a bare finite band description compatible with those data? These questions are answered by modifications of a theory originally constructed for inorganic materials and a newly developed mobility theory.

Heat Diffusion in Gases, Including Effects of Chemical Reaction

NASA Technical Reports Server (NTRS)

Hansen, C. Frederick

1960-01-01

The diffusion of heat through gases is treated where the coefficients of thermal conductivity and diffusivity are functions of temperature. The diffusivity is taken proportional to the integral of thermal conductivity, where the gas is ideal, and is considered constant over the temperature interval in which a chemical reaction occurs. The heat diffusion equation is then solved numerically for a semi-infinite gas medium with constant initial and boundary conditions. These solutions are in a dimensionless form applicable to gases in general, and they are used, along with measured shock velocity and heat flux through a shock reflecting surface, to evaluate the integral of thermal conductivity for air up to 5000 degrees Kelvin. This integral has the properties of a heat flux potential and replaces temperature as the dependent variable for problems of heat diffusion in media with variable coefficients. Examples are given in which the heat flux at the stagnation region of blunt hypersonic bodies is expressed in terms of this potential.

Current collection in an anisotropic plasma

NASA Technical Reports Server (NTRS)

Li, Wei-Wei

1990-01-01

A general method is given to derive the current-potential relations in anisotropic plasmas. Orbit limit current is assumed. The collector is a conductive sphere or an infinite cylinder. Any distribution which is an arbitrary function of the velocity vector can be considered as a superposition of many mono-energetic beams whose current-potential relations are known. The results for two typical pitch angle distributions are derived and discussed in detail. The general properties of the current potential relations are very similar to that of a Maxwellian plasma except for an effective temperature which varies with the angle between the magnetic field and the charging surface. The conclusions are meaningful to generalized geometries.

Transient temperature distributions in simple conducting bodies steadily heated through a laminar boundary layer

NASA Technical Reports Server (NTRS)

Parker, Hermon M

1953-01-01

An analysis is made of the transient heat-conduction effects in three simple semi-infinite bodies: the flat insulated plate, the conical shell, and the slender solid cone. The bodies are assumed to have constant initial temperatures and, at zero time, to begin to move at a constant speed and zero angle of attack through a homogeneous atmosphere. The heat input is taken as that through a laminar boundary layer. Radiation heat transfer and transverse temperature gradients are assumed to be zero. The appropriate heat-conduction equations are solved by an iteration method, the zeroeth-order terms describing the situation in the limit of small time. The method is presented and the solutions are calculated to three orders which are sufficient to give reasonably accurate results when the forward edge has attained one-half the total temperature rise (nose half-rise time). Flight Mach number and air properties occur as parameters in the result. Approximate expressions for the extent of the conduction region and nose half-rise times as functions of the parameters of the problem are presented. (author)

Finite Volume Numerical Methods for Aeroheating Rate Calculations from Infrared Thermographic Data

NASA Technical Reports Server (NTRS)

Daryabeigi, Kamran; Berry, Scott A.; Horvath, Thomas J.; Nowak, Robert J.

2003-01-01

The use of multi-dimensional finite volume numerical techniques with finite thickness models for calculating aeroheating rates from measured global surface temperatures on hypersonic wind tunnel models was investigated. Both direct and inverse finite volume techniques were investigated and compared with the one-dimensional semi -infinite technique. Global transient surface temperatures were measured using an infrared thermographic technique on a 0.333-scale model of the Hyper-X forebody in the Langley Research Center 20-Inch Mach 6 Air tunnel. In these tests the effectiveness of vortices generated via gas injection for initiating hypersonic transition on the Hyper-X forebody were investigated. An array of streamwise orientated heating striations were generated and visualized downstream of the gas injection sites. In regions without significant spatial temperature gradients, one-dimensional techniques provided accurate aeroheating rates. In regions with sharp temperature gradients due to the striation patterns two-dimensional heat transfer techniques were necessary to obtain accurate heating rates. The use of the one-dimensional technique resulted in differences of 20% in the calculated heating rates because it did not account for lateral heat conduction in the model.

Thermoelastic stress in oceanic lithosphere due to hotspot reheating

NASA Technical Reports Server (NTRS)

Zhu, Anning; Wiens, Douglas A.

1991-01-01

The effect of hotspot reheating on the intraplate stress field is investigated by modeling the three-dimensional thermal stress field produced by nonuniform temperature changes in an elastic plate. Temperature perturbations are calculated assuming that the lithosphere is heated by a source in the lower part of the thermal lithosphere. A thermal stress model for the elastic lithosphere is calculated by superposing the stress fields resulting from temperature changes in small individual elements. The stress in an elastic plate resulting from a temperature change in each small element is expressed as an infinite series, wherein each term is a source or an image modified from a closed-from half-space solution. The thermal stress solution is applied to midplate swells in oceanic lithosphere with various thermal structures and plate velocities. The results predict a stress field with a maximum deviatoric stress on the order of 100 MPa covering a broad area around the hotspot plume. The predicted principal stress orientations show a complicated geographical pattern, with horizontal extension perpendicular to the hotspot track at shallow depths and compression along the track near the bottom of the elastic lithosphere.

The Perfect Glass Paradigm: Disordered Hyperuniform Glasses Down to Absolute Zero

NASA Astrophysics Data System (ADS)

Zhang, G.; Stillinger, F. H.; Torquato, S.

2016-11-01

Rapid cooling of liquids below a certain temperature range can result in a transition to glassy states. The traditional understanding of glasses includes their thermodynamic metastability with respect to crystals. However, here we present specific examples of interactions that eliminate the possibilities of crystalline and quasicrystalline phases, while creating mechanically stable amorphous glasses down to absolute zero temperature. We show that this can be accomplished by introducing a new ideal state of matter called a “perfect glass”. A perfect glass represents a soft-interaction analog of the maximally random jammed (MRJ) packings of hard particles. These latter states can be regarded as the epitome of a glass since they are out of equilibrium, maximally disordered, hyperuniform, mechanically rigid with infinite bulk and shear moduli, and can never crystallize due to configuration-space trapping. Our model perfect glass utilizes two-, three-, and four-body soft interactions while simultaneously retaining the salient attributes of the MRJ state. These models constitute a theoretical proof of concept for perfect glasses and broaden our fundamental understanding of glass physics. A novel feature of equilibrium systems of identical particles interacting with the perfect-glass potential at positive temperature is that they have a non-relativistic speed of sound that is infinite.

The Perfect Glass Paradigm: Disordered Hyperuniform Glasses Down to Absolute Zero.

PubMed

Zhang, G; Stillinger, F H; Torquato, S

2016-11-28

Rapid cooling of liquids below a certain temperature range can result in a transition to glassy states. The traditional understanding of glasses includes their thermodynamic metastability with respect to crystals. However, here we present specific examples of interactions that eliminate the possibilities of crystalline and quasicrystalline phases, while creating mechanically stable amorphous glasses down to absolute zero temperature. We show that this can be accomplished by introducing a new ideal state of matter called a "perfect glass". A perfect glass represents a soft-interaction analog of the maximally random jammed (MRJ) packings of hard particles. These latter states can be regarded as the epitome of a glass since they are out of equilibrium, maximally disordered, hyperuniform, mechanically rigid with infinite bulk and shear moduli, and can never crystallize due to configuration-space trapping. Our model perfect glass utilizes two-, three-, and four-body soft interactions while simultaneously retaining the salient attributes of the MRJ state. These models constitute a theoretical proof of concept for perfect glasses and broaden our fundamental understanding of glass physics. A novel feature of equilibrium systems of identical particles interacting with the perfect-glass potential at positive temperature is that they have a non-relativistic speed of sound that is infinite.

The Perfect Glass Paradigm: Disordered Hyperuniform Glasses Down to Absolute Zero

PubMed Central

Zhang, G.; Stillinger, F. H.; Torquato, S.

2016-01-01

Rapid cooling of liquids below a certain temperature range can result in a transition to glassy states. The traditional understanding of glasses includes their thermodynamic metastability with respect to crystals. However, here we present specific examples of interactions that eliminate the possibilities of crystalline and quasicrystalline phases, while creating mechanically stable amorphous glasses down to absolute zero temperature. We show that this can be accomplished by introducing a new ideal state of matter called a “perfect glass”. A perfect glass represents a soft-interaction analog of the maximally random jammed (MRJ) packings of hard particles. These latter states can be regarded as the epitome of a glass since they are out of equilibrium, maximally disordered, hyperuniform, mechanically rigid with infinite bulk and shear moduli, and can never crystallize due to configuration-space trapping. Our model perfect glass utilizes two-, three-, and four-body soft interactions while simultaneously retaining the salient attributes of the MRJ state. These models constitute a theoretical proof of concept for perfect glasses and broaden our fundamental understanding of glass physics. A novel feature of equilibrium systems of identical particles interacting with the perfect-glass potential at positive temperature is that they have a non-relativistic speed of sound that is infinite. PMID:27892452

Dynamic behavior of the bray-liebhafsky oscillatory reaction controlled by sulfuric acid and temperature

NASA Astrophysics Data System (ADS)

Pejić, N.; Vujković, M.; Maksimović, J.; Ivanović, A.; Anić, S.; Čupić, Ž.; Kolar-Anić, Lj.

2011-12-01

The non-periodic, periodic and chaotic regimes in the Bray-Liebhafsky (BL) oscillatory reaction observed in a continuously fed well stirred tank reactor (CSTR) under isothermal conditions at various inflow concentrations of the sulfuric acid were experimentally studied. In each series (at any fixed temperature), termination of oscillatory behavior via saddle loop infinite period bifurcation (SNIPER) as well as some kind of the Andronov-Hopf bifurcation is presented. In addition, it was found that an increase of temperature, in different series of experiments resulted in the shift of bifurcation point towards higher values of sulfuric acid concentration.

Hierarchical Freezing in a Lattice Model

NASA Astrophysics Data System (ADS)

Byington, Travis W.; Socolar, Joshua E. S.

2012-01-01

A certain two-dimensional lattice model with nearest and next-nearest neighbor interactions is known to have a limit-periodic ground state. We show that during a slow quench from the high temperature, disordered phase, the ground state emerges through an infinite sequence of phase transitions. We define appropriate order parameters and show that the transitions are related by renormalizations of the temperature scale. As the temperature is decreased, sublattices with increasingly large lattice constants become ordered. A rapid quench results in a glasslike state due to kinetic barriers created by simultaneous freezing on sublattices with different lattice constants.

[Determination of the solubility parameter of organosolv lignin by inverse gas chromatography].

PubMed

Yu, Yachen; Li, Kunlan; Ma, Yingchong; Wei, Ligang

2013-02-01

An inverse gas chromatographic (IGC) method has been used to measure the solubility parameters (delta2) of organosolv lignin at the absolute temperatures from 333.15 K to 373.15 K. The test probe solvents were n-octane (n-C8), n-decane (n-C10), n-dodecane (n-C12), and n-tetradecane (n-C14). The specific retention volumes of the solvents (Vg0), the molar enthalpy of sorption (deltaH1S), the partial molar enthalpy of mixing at infinite dilution (deltaH1infinity), the molar enthalpy of vaporization (deltaHv), the activity coefficients at infinite dilution (Omega1- infinity), and Flory-Huggins inter action parameters (chi12infinity) between organosolv lignin and probe solvents were obtained. The results showed that the above four probes are poor solvents for organosolv lignin; at the same temperature, the chi12infinity reduced with the increase of the carbon number of probe solvents. The average solubility parameter of organosolv lignin was determined as 19.03 (J x cm(-3))1/2.

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

Korneeva, Anna; Shaydurov, Vladimir

In the paper, the data analysis is considered for thin-film thermoresistors coated on to a radio-electronic printed circuit board to determine possible zones of its overheating. A mathematical model consists in an underdetermined system of linear algebraic equations with an infinite set of solutions. For computing a more real solution, two additional conditions are used: the smoothness of a solution and the positiveness of an increase of temperature during overheating. Computational experiments demonstrate that an overheating zone is determined exactly with a tolerable accuracy of temperature in it.

An investigation of the critical liquid-vapor properties of dilute KCl solutions

USGS Publications Warehouse

Potter, R.W.; Babcock, R.S.; Czamanske, G.K.

1976-01-01

The three parameters that define the critical point, temperature, pressure, and volume have been experimentally determined by means of filling studies in a platinum-lined system for five KCl solutions ranging from 0.006 to 0.568 m. The platinum-lined vessels were used to overcome the problems with corrosion experienced by earlier workers. The critical temperature (tc), pressure (Pc), and volume (Vc) were found to fit the equations {Mathematical expression} from infinite dilution to 1.0 m. ?? 1976 Plenum Publishing Corporation.

A Computer Simulation Study of Vntr Population Genetics: Constrained Recombination Rules Out the Infinite Alleles Model

PubMed Central

Harding, R. M.; Boyce, A. J.; Martinson, J. J.; Flint, J.; Clegg, J. B.

1993-01-01

Extensive allelic diversity in variable numbers of tandem repeats (VNTRs) has been discovered in the human genome. For population genetic studies of VNTRs, such as forensic applications, it is important to know whether a neutral mutation-drift balance of VNTR polymorphism can be represented by the infinite alleles model. The assumption of the infinite alleles model that each new mutant is unique is very likely to be violated by unequal sister chromatid exchange (USCE), the primary process believed to generate VNTR mutants. We show that increasing both mutation rates and misalignment constraint for intrachromosomal recombination in a computer simulation model reduces simulated VNTR diversity below the expectations of the infinite alleles model. Maximal constraint, represented as slippage of single repeats, reduces simulated VNTR diversity to levels expected from the stepwise mutation model. Although misalignment rule is the more important variable, mutation rate also has an effect. At moderate rates of USCE, simulated VNTR diversity fluctuates around infinite alleles expectation. However, if rates of USCE are high, as for hypervariable VNTRs, simulated VNTR diversity is consistently lower than predicted by the infinite alleles model. This has been observed for many VNTRs and accounted for by technical problems in distinguishing alleles of neighboring size classes. We use sampling theory to confirm the intrinsically poor fit to the infinite alleles model of both simulated VNTR diversity and observed VNTR polymorphisms sampled from two Papua New Guinean populations. PMID:8293988

A computer simulation study of VNTR population genetics: constrained recombination rules out the infinite alleles model.

PubMed

Harding, R M; Boyce, A J; Martinson, J J; Flint, J; Clegg, J B

1993-11-01

Extensive allelic diversity in variable numbers of tandem repeats (VNTRs) has been discovered in the human genome. For population genetic studies of VNTRs, such as forensic applications, it is important to know whether a neutral mutation-drift balance of VNTR polymorphism can be represented by the infinite alleles model. The assumption of the infinite alleles model that each new mutant is unique is very likely to be violated by unequal sister chromatid exchange (USCE), the primary process believed to generate VNTR mutants. We show that increasing both mutation rates and misalignment constraint for intrachromosomal recombination in a computer simulation model reduces simulated VNTR diversity below the expectations of the infinite alleles model. Maximal constraint, represented as slippage of single repeats, reduces simulated VNTR diversity to levels expected from the stepwise mutation model. Although misalignment rule is the more important variable, mutation rate also has an effect. At moderate rates of USCE, simulated VNTR diversity fluctuates around infinite alleles expectation. However, if rates of USCE are high, as for hypervariable VNTRs, simulated VNTR diversity is consistently lower than predicted by the infinite alleles model. This has been observed for many VNTRs and accounted for by technical problems in distinguishing alleles of neighboring size classes. We use sampling theory to confirm the intrinsically poor fit to the infinite alleles model of both simulated VNTR diversity and observed VNTR polymorphisms sampled from two Papua New Guinean populations.

A computer simulation study of VNTR population genetics: Constrained recombination rules out the infinite alleles model

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

Harding, R.M.; Martinson, J.J.; Flint, J.

1993-11-01

Extensive allelic diversity in variable numbers of tandem repeats (VNTRs) has been discovered in the human genome. For population genetic studies of VNTRs, such as forensic applications, it is important to know whether a neutral mutation-drift balance of VNTR polymorphism can be represented by the infinite alleles model. The assumption of the infinite alleles model that each new mutant is unique is very likely to be violated by unequal sister chromatid exchange (USCE), the primary process believed to generate VNTR mutants. The authors show that increasing both mutation rates and misalignment constraint for intrachromosomal recombination in a computer simulation modelmore » reduces simulated VNTR diversity below the expectations of the infinite alleles model. Maximal constraint, represented as slippage of single repeats, reduces simulated VNTR diversity to levels expected from the stepwise mutation model. Although misalignment rule is the more important variable, mutation rate also has an effect. At moderate rates of USCE, simulated VNTR diversity fluctuates around infinite alleles expectation. However, if rates of USCE are high, as for hypervariable VNTRs, simulated VNTR diversity is consistently lower than predicted by the infinite alleles model. This has been observed for many VNTRs and accounted for by technical problems in distinguishing alleles of neighboring size classes. The authors use sampling theory to confirm the intrinsically poor fit to the infinite model of both simulated VNTR diversity and observed VNTR polymorphisms sampled from two Papua New Guinean populations. 25 refs., 20 figs., 4 tabs.« less

HUFF, a One-Dimensional Hydrodynamics Code for Strong Shocks

DTIC Science & Technology

1978-12-01

results for two sample problems. The first problem discussed is a one-kiloton nuclear burst in infinite sea level air. The second problem is the one...of HUFF as an effective first order hydro- dynamic computer code. 1 KT Explosion The one-kiloton nuclear explosion in infinite sea level air was

Mirror Numbers and Wigner's ``Unreasonable Effectiveness''

NASA Astrophysics Data System (ADS)

Berezin, Alexander

2006-04-01

Wigner's ``unreasonable effectiveness of mathematics in physics'' can be augmented by concept of mirror number (MN). It is defined as digital string infinite in both directions. Example is ()5141327182() where first 5 digits is Pi ``spelled'' backward (``mirrored'') and last 5 digits is the beginning of decimal exp1 string. Let MN be constructed from two different transcendental (or algebraically irrational) numbers, set of such MNs is Cantor-uncountable. Most MNs have contain any finite digital sequence repeated infinitely many times. In spirit of ``Contact'' (C.Sagan) each normal MN contains ``Library of Babel'' of all possible texts and patterns (J.L.Borges). Infinite at both ends, MN do not have any numerical values and, contrary to numbers written in positional systems, all digits in MNs have equal weight -- sort of ``numerological democracy''. In Pythagorean-Platonic models (space-time and physical world originating from pure numbers) idea of MN resolves paradox of ``beginning'' (or ``end'') of time. Because in MNs all digits have equal status, (quantum) randomness leads to more uniform and fully ergodic phase trajectories (cf. F.Dyson, Infinite in All Directions) .

Heat treatment effect on the electronic and magnetic structures of nanographene sheets investigated through electron spectroscopy and conductance measurements.

PubMed

Takashiro, Jun-ichi; Kudo, Yasuhiko; Kaneko, Satoshi; Takai, Kazuyuki; Ishii, Takafumi; Kyotani, Takashi; Enoki, Toshiaki; Kiguchi, Manabu

2014-04-28

The heat treatment effect on the electronic and magnetic structures of a disordered network of nanographene sheets has been investigated by in situ measurements of X-ray photoemission spectroscopy, near-edge X-ray absorption fine structure (NEXAFS), and electrical conductance, together with temperature-programmed desorption measurements. Oxygen-containing functional groups bonded to nanographene edges in the pristine sample are almost completely decomposed under heat treatment up to 1300-1500 K, resulting in the formation of edges primarily terminated by hydrogen. The removal of the oxygen-containing groups enhances the conductance owing to the decrease in the electron transport barriers between nanographene sheets. Heat treatment above 1500 K removes also the hydrogen atoms from the edges, promoting the successive fusion of nanographene sheets at the expense of edges. The decrease in the π* peak width in NEXAFS indicates the progress of the fusion reaction, that is, the extension of the π-conjugation, which agrees with the increase in the orbital susceptibility previously reported. The fusion leads to the formation of local π/sp(2) bridges between nanographene sheets and brings about an insulator-to-metal transition at 1500-1600 K, at which the bridge network becomes infinite. As for the magnetism, the intensity of the edge state peak in NEXAFS, which corresponds to the number of the spin-polarized edge states, decreases above 1500 K, though the effective edge-state spin density per edge state starts decreasing at approximately 200 K lower than the temperature of the edge state peak change. This disagreement indicates the development of antiferromagnetic short range ordering as a precursor of a spin glass state near the insulator-metal transition, at which the random network of inter-nanographene-sheet exchange interactions strengthened with the formation of the π/sp(2) bridges becomes infinite.

Slanted-edge MTF testing for establishing focus alignment at infinite conjugate of space optical systems with gravity sag effects

NASA Astrophysics Data System (ADS)

Newswander, T.; Riesland, David W.; Miles, Duane; Reinhart, Lennon

2017-09-01

For space optical systems that image extended scenes such as earth-viewing systems, modulation transfer function (MTF) test data is directly applicable to system optical resolution. For many missions, it is the most direct metric for establishing the best focus of the instrument. Additionally, MTF test products can be combined to predict overall imaging performance. For fixed focus instruments, finding the best focus during ground testing is critical to achieving good imaging performance. The ground testing should account for the full-imaging system, operational parameters, and operational environment. Testing the full-imaging system removes uncertainty caused by breaking configurations and the combination of multiple subassembly test results. For earth viewing, the imaging system needs to be tested at infinite conjugate. Operational environment test conditions should include temperature and vacuum. Optical MTF testing in the presence of operational vibration and gravity release is less straightforward and may not be possible on the ground. Gravity effects are mitigated by testing in multiple orientations. Many space telescope systems are designed and built to have optimum performance in a gravity-free environment. These systems can have imaging performance that is dominated by aberration including astigmatism. This paper discusses how the slanted edge MTF test is applied to determine the best focus of a space optical telescope in ground testing accounting for gravity sag effects. Actual optical system test results and conclusions are presented.

Wave-vortex interactions in the nonlinear Schrödinger equation

NASA Astrophysics Data System (ADS)

Guo, Yuan; Bühler, Oliver

2014-02-01

This is a theoretical study of wave-vortex interaction effects in the two-dimensional nonlinear Schrödinger equation, which is a useful conceptual model for the limiting dynamics of superfluid quantum condensates at zero temperature. The particular wave-vortex interaction effects are associated with the scattering and refraction of small-scale linear waves by the straining flows induced by quantized point vortices and, crucially, with the concomitant nonlinear back-reaction, the remote recoil, that these scattered waves exert on the vortices. Our detailed model is a narrow, slowly varying wavetrain of small-amplitude waves refracted by one or two vortices. Weak interactions are studied using a suitable perturbation method in which the nonlinear recoil force on the vortex then arises at second order in wave amplitude, and is computed in terms of a Magnus-type force expression for both finite and infinite wavetrains. In the case of an infinite wavetrain, an explicit asymptotic formula for the scattering angle is also derived and cross-checked against numerical ray tracing. Finally, under suitable conditions a wavetrain can be so strongly refracted that it collapses all the way onto a zero-size point vortex. This is a strong wave-vortex interaction by definition. The conditions for such a collapse are derived and the validity of ray tracing theory during the singular collapse is investigated.

QCD equation of state with almost physical quark masses

NASA Astrophysics Data System (ADS)

Cheng, M.; Christ, N. H.; Datta, S.; van der Heide, J.; Jung, C.; Karsch, F.; Kaczmarek, O.; Laermann, E.; Mawhinney, R. D.; Miao, C.; Petreczky, P.; Petrov, K.; Schmidt, C.; Soeldner, W.; Umeda, T.

2008-01-01

We present results on the equation of state in QCD with two light quark flavors and a heavier strange quark. Calculations with improved staggered fermions have been performed on lattices with temporal extent Nτ=4 and 6 on a line of constant physics with almost physical quark mass values; the pion mass is about 220 MeV, and the strange quark mass is adjusted to its physical value. High statistics results on large lattices are obtained for bulk thermodynamic observables, i.e. pressure, energy and entropy density, at vanishing quark chemical potential for a wide range of temperatures, 140MeV≤T≤800MeV. We present a detailed discussion of finite cutoff effects which become particularly significant for temperatures larger than about twice the transition temperature. At these high temperatures we also performed calculations of the trace anomaly on lattices with temporal extent Nτ=8. Furthermore, we have performed an extensive analysis of zero temperature observables including the light and strange quark condensates and the static quark potential at zero temperature. These are used to set the temperature scale for thermodynamic observables and to calculate renormalized observables that are sensitive to deconfinement and chiral symmetry restoration and become order parameters in the infinite and zero quark mass limits, respectively.

Stability of the quantum Sherrington-Kirkpatrick spin glass model

NASA Astrophysics Data System (ADS)

Young, A. P.

2017-09-01

I study in detail the quantum Sherrington-Kirkpatrick (SK) model, i.e., the infinite-range Ising spin glass in a transverse field, by solving numerically the effective one-dimensional model that the quantum SK model can be mapped to in the thermodynamic limit. I find that the replica symmetric solution is unstable down to zero temperature, in contrast to some previous claims, and so there is not only a line of transitions in the (longitudinal) field-temperature plane (the de Almeida-Thouless, AT, line) where replica symmetry is broken, but also a quantum de Almeida-Thouless (QuAT) line in the transverse field-longitudinal field plane at T =0 . If the QuAT line also occurs in models with short-range interactions its presence might affect the performance of quantum annealers when solving spin glass-type problems with a bias (i.e., magnetic field).

Performance Optimization of Irreversible Air Heat Pumps Considering Size Effect

NASA Astrophysics Data System (ADS)

Bi, Yuehong; Chen, Lingen; Ding, Zemin; Sun, Fengrui

2018-06-01

Considering the size of an irreversible air heat pump (AHP), heating load density (HLD) is taken as thermodynamic optimization objective by using finite-time thermodynamics. Based on an irreversible AHP with infinite reservoir thermal-capacitance rate model, the expression of HLD of AHP is put forward. The HLD optimization processes are studied analytically and numerically, which consist of two aspects: (1) to choose pressure ratio; (2) to distribute heat-exchanger inventory. Heat reservoir temperatures, heat transfer performance of heat exchangers as well as irreversibility during compression and expansion processes are important factors influencing on the performance of an irreversible AHP, which are characterized with temperature ratio, heat exchanger inventory as well as isentropic efficiencies, respectively. Those impacts of parameters on the maximum HLD are thoroughly studied. The research results show that HLD optimization can make the size of the AHP system smaller and improve the compactness of system.

Thermodynamic properties of the S =1 /2 twisted triangular spin tube

NASA Astrophysics Data System (ADS)

Ito, Takuya; Iino, Chihiro; Shibata, Naokazu

2018-05-01

Thermodynamic properties of the twisted three-leg spin tube under magnetic field are studied by the finite-T density-matrix renormalization group method. The specific heat, spin, and chiral susceptibilities of the infinite system are calculated for both the original and its low-energy effective models. The obtained results show that the presence of the chirality is observed as a clear peak in the specific heat at low temperature and the contribution of the chirality dominates the low-temperature part of the specific heat as the exchange coupling along the spin tube decreases. The peak structures in the specific heat, spin, and chiral susceptibilities are strongly modified near the quantum phase transition where the critical behaviors of the spin and chirality correlations change. These results confirm that the chirality plays a major role in characteristic low-energy behaviors of the frustrated spin systems.

Inter-Diffusion in the Presence of Free Convection

NASA Technical Reports Server (NTRS)

Gupta, Prabhat K.

1999-01-01

Because of their technological importance, establishment of the precise values of interdiffusion coefficients is important in multicomponent fluid systems. Such values are not available because diffusion is influenced by free convection due to compositionally induced density variations. In this project, earth based diffusion experiments are being performed in a viscous fluid system PbO-SiO2 at temperatures between 500-1000 C. This system is chosen because it shows a large variation in density with small changes in composition and is expected to show a large free convection effect. Infinite diffusion couples at different temperatures and times are being studied with different orientations with respect to gravity. Composition fields will be measured using an Electron Microprobe Analyzer and will be compared with the results of a complementary modeling study to extract the values of the true diffusion coefficient from the measured diffusion profiles.

Axisymmetric Eigenmodes of Spheroidal Pure Electron Plasmas

NASA Astrophysics Data System (ADS)

Kawai, Yosuke; Saitoh, Haruhiko; Yoshida, Zensho; Kiwamoto, Yasuhito

2010-11-01

The axisymmetric electrostatic eigenmodes of spheroidal pure electron plasmas have been studied experimentally. It is confirmed that the observed spheroidal plasma attains a theoretically expected equilibrium density distribution, with the exception of a low-density halo distribution surrounding the plasma. When the eigenmode frequency observed for the plasma is compared with the frequency predicted by the dispersion relation derived under ideal conditions wherein the temperature is zero and the boundary is located at an infinite distance from the plasma, it is observed that the absolute value of the observed frequency is systematically higher than the theoretical prediction. Experimental examinations and numerical calculations indicate that the upward shift of the eigenmode frequency cannot be accounted for solely by the finite temperature effect, but is significantly affected by image charges induced on the conducting boundary and the resulting distortion of the density profile from the theoretical expectation.

The infinite range Heisenberg model and high temperature superconductivity

NASA Astrophysics Data System (ADS)

Tahir-Kheli, Jamil

1992-01-01

The thesis deals with the theory of high temperature superconductivity from the standpoint of three-band Hubbard models.Chapter 1 of the thesis proposes a strongly coupled variational wavefunction that has the three-spin system of an oxygen hole and its two neighboring copper spins in a doublet and the background Cu spins in an eigenstate of the infinite range antiferromagnet. This wavefunction is expected to be a good "zeroth order" wavefunction in the superconducting regime of dopings. The three-spin polaron is stabilized by the hopping terms rather than the copper-oxygen antiferromagnetic coupling Jpd. Considering the effect of the copper-copper antiferromagnetic coupling Jdd, we show that the three-spin polaron cannot be pure Emery (Dg), but must have a non-negligible amount of doublet-u (Du) character for hopping stabilization. Finally, an estimate is made for the magnitude of the attractive coupling of oxygen holes.Chapter 2 presents an exact solution to a strongly coupled Hamiltonian for the motion of oxygen holes in a 1-D Cu-O lattice. The Hamiltonian separates into two pieces: one for the spin degrees of freedom of the copper and oxygen holes, and the other for the charge degrees of freedom of the oxygen holes. The spinon part becomes the Heisenberg antiferromagnet in 1-D that is soluble by the Bethe Ansatz. The holon piece is also soluble by a Bethe Ansatz with simple algebraic relations for the phase shifts.Finally, we show that the nearest neighbor Cu-Cu spin correlation increases linearly with doping and becomes positive at x [...] 0.70.

X-ray photoemission study of the infinite-layer cuprate superconductor Sr(0.9) La (0.1) CuO(2)

NASA Technical Reports Server (NTRS)

Vasquez, R. P.; Jung, C. U.; Kim, J. Y.; Kim, M. S.; Lee, S. Y.; Lee, S. I.

2001-01-01

The electron-doped infinite-layer superconductor Sr(0.9)La(0.1) CuO(2) is studied with x-ray photoemission spectroscopy (XPS). A nonaqueous chemical etchant is shown to effectively remove contaminants and to yield surfaces from which signals intrinsic to the superconductor dominate.

The Interface between Neighborhood Density and Optional Infinitives: Normal Development and Specific Language Impairment

ERIC Educational Resources Information Center

Hoover, Jill R.; Storkel, Holly L.; Rice, Mabel L.

2012-01-01

The effect of neighborhood density on optional infinitives was evaluated for typically developing (TD) children and children with Specific Language Impairment (SLI). Forty children, twenty in each group, completed two production tasks that assessed third person singular production. Half of the sentences in each task presented a dense verb, and…

Thermodynamic properties of hyperbranched polymer, Boltorn U3000, using inverse gas chromatography.

PubMed

Domańska, Urszula; Zołek-Tryznowska, Zuzanna

2009-11-19

Mass-fraction activity coefficients at infinite dilution (Omega13(infinity)) of alkanes (C5-C10), cycloalkanes (C5-C8), alkenes (C5-C8), alkynes (C5-C8), aromatic hydrocarbons (benzene, toluene, ethylbenzene, o-, m-, p-xylene, thiophene), alcohols (C1-C5), water, ethers (tetrahydrofuran (THF), methyl-tert-butylether (MTBE), diethyl-, di-n-propyl-, di-n-butyl ether), and ketones (propanone, 2-pentanone, 3-pentanone, 2-hexanone, 3-hexanone, cyclopentanone) in the hyperbranched polymer, Boltorn U3000 (B-U3000), have been determined by inverse gas chromatography (IGC) using the polymer as the stationary phase. The measurements were carried out at different temperatures between 308.15 and 348.15 K. The density and thermophysical properties of polymer were described. The specific retention volume (V(g)), the Flory-Huggins interaction parameter (chi13(infinity)), the molar enthalpy of sorption (the partial molar enthalpies of solute dissolution) (Delta(s)H), the partial molar excess enthalpy at infinite dilution of the solute and polymer (DeltaH1(E,infinity)), the partial molar Gibbs excess energy at infinite dilution (DeltaG1(E,infinity)), and the solubility parameter (delta3) were calculated.

Efficient Geometry and Data Handling for Large-Scale Monte Carlo - Thermal-Hydraulics Coupling

NASA Astrophysics Data System (ADS)

Hoogenboom, J. Eduard

2014-06-01

Detailed coupling of thermal-hydraulics calculations to Monte Carlo reactor criticality calculations requires each axial layer of each fuel pin to be defined separately in the input to the Monte Carlo code in order to assign to each volume the temperature according to the result of the TH calculation, and if the volume contains coolant, also the density of the coolant. This leads to huge input files for even small systems. In this paper a methodology for dynamical assignment of temperatures with respect to cross section data is demonstrated to overcome this problem. The method is implemented in MCNP5. The method is verified for an infinite lattice with 3x3 BWR-type fuel pins with fuel, cladding and moderator/coolant explicitly modeled. For each pin 60 axial zones are considered with different temperatures and coolant densities. The results of the axial power distribution per fuel pin are compared to a standard MCNP5 run in which all 9x60 cells for fuel, cladding and coolant are explicitly defined and their respective temperatures determined from the TH calculation. Full agreement is obtained. For large-scale application the method is demonstrated for an infinite lattice with 17x17 PWR-type fuel assemblies with 25 rods replaced by guide tubes. Again all geometrical detailed is retained. The method was used in a procedure for coupled Monte Carlo and thermal-hydraulics iterations. Using an optimised iteration technique, convergence was obtained in 11 iteration steps.

Stress and strain concentration at a circular hole in an infinite plate

NASA Technical Reports Server (NTRS)

Stowell, Elbridge Z

1950-01-01

The theory of elasticity shows that the maximum stress at a circular hole in an infinite plate in tension is three times the applied stress when the material remains elastic. The effect of plasticity of the material is to lower this ratio. This paper considers the theoretical problem of the stress distribution in an infinitely large sheet with a circular hole for the general case where the material may have any stress-strain curve. The plate is assumed to be under uniform tension at a large distance from the hole. The material is taken to be isotropic and incompressible. (author)

Prediction of the interaction between a simple moving vehicle and an infinite periodically supported rail - Green's functions approach

NASA Astrophysics Data System (ADS)

Mazilu, Traian

2010-09-01

This paper herein describes the interaction between a simple moving vehicle and an infinite periodically supported rail, in order to signalise the basic features of the vehicle/track vibration behaviour in general, and wheel/rail vibration, in particular. The rail is modelled as an infinite Timoshenko beam resting on semi-sleepers via three-directional rail pads and ballast. The time-domain analysis was performed applying Green's matrix of the track method. This method allows taking into account the nonlinearities of the wheel/rail contact and the Doppler effect. The numerical analysis is dedicated to the wheel/rail response due to two types of excitation: the steady-state interaction and rail irregularities. The study points out to certain aspects regarding the parametric resonance, the amplitude-modulated vibration due to corrugation and the Doppler effect.

The Effect of Composition on Diffusion of Au in Fe and Fe-Ni Alloys

NASA Astrophysics Data System (ADS)

Johanesen, K. E.; Watson, H. C.; Fei, Y.

2005-12-01

Understanding siderophile element diffusion in Fe-Ni alloys will lead to tighter constraints on processes such as meteoritic body cooling rates, and inner core-outer core communication. Recent studies have determined the effect of temperature and pressure on diffusion in this system, but the effect of composition has not yet been explored adequately. The effect of Ni content on Au diffusion in an Fe-Ni system was explored for Fe-Ni alloys with concentrations of 0, 20, and 30 wt. % Ni. Diffusion couple experiments were conducted using a piston cylinder press at 1 GPa and temperatures ranging from 1150°C to 1400°C. Concentration profiles were measured by electron microprobe and were fitted to the linear diffusion solution for an semi-infinite diffusion couple to extract diffusion coefficients (D) using a non-linear least squares fit routine. As predicted, D increases with Ni content and also with temperature. The diffusivities ranged from 2.06×10-9 at 1150°C to 5.76×10-8 at 1350°C for 0 wt. % Ni; 5.17×10-9 at 1150° C to 1.93×10-7 at 1400°C for 20 wt. % Ni; and 2.41×10-8 at 1150°C to 2.13×10-7 at 1400°C for 30 wt. % Ni. As temperature increases, the effect of Ni on diffusion rates increases, implying a possible change in diffusion mechanism between 1250°C and 1300°C. Ni appears to have a negligible effect at lower temperatures, which would indicate that Ni may not need to be considered when modeling siderophile trace element diffusion rates in iron meteorites.

Hydrodynamic and Thermal Slip Effect on Double-Diffusive Free Convective Boundary Layer Flow of a Nanofluid Past a Flat Vertical Plate in the Moving Free Stream

PubMed Central

Khan, Waqar A.; Uddin, Md Jashim; Ismail, A. I. Md.

2013-01-01

The effects of hydrodynamic and thermal slip boundary conditions on the double-diffusive free convective flow of a nanofluid along a semi-infinite flat solid vertical plate are investigated numerically. It is assumed that free stream is moving. The governing boundary layer equations are non-dimensionalized and transformed into a system of nonlinear, coupled similarity equations. The effects of the controlling parameters on the dimensionless velocity, temperature, solute and nanofluid concentration as well as on the reduced Nusselt number, reduced Sherwood number and the reduced nanoparticle Sherwood number are investigated and presented graphically. To the best of our knowledge, the effects of hydrodynamic and thermal slip boundary conditions have not been investigated yet. It is found that the reduced local Nusselt, local solute and the local nanofluid Sherwood numbers increase with hydrodynamic slip and decrease with thermal slip parameters. PMID:23533566

Infinite slope stability under steady unsaturated seepage conditions

USGS Publications Warehouse

Lu, Ning; Godt, Jonathan W.

2008-01-01

We present a generalized framework for the stability of infinite slopes under steady unsaturated seepage conditions. The analytical framework allows the water table to be located at any depth below the ground surface and variation of soil suction and moisture content above the water table under steady infiltration conditions. The framework also explicitly considers the effect of weathering and porosity increase near the ground surface on changes in the friction angle of the soil. The factor of safety is conceptualized as a function of the depth within the vadose zone and can be reduced to the classical analytical solution for subaerial infinite slopes in the saturated zone. Slope stability analyses with hypothetical sandy and silty soils are conducted to illustrate the effectiveness of the framework. These analyses indicate that for hillslopes of both sandy and silty soils, failure can occur above the water table under steady infiltration conditions, which is consistent with some field observations that cannot be predicted by the classical infinite slope theory. A case study of shallow slope failures of sandy colluvium on steep coastal hillslopes near Seattle, Washington, is presented to examine the predictive utility of the proposed framework.

Thermodynamic study of quercetin and rutin mixtures with alcohols

NASA Astrophysics Data System (ADS)

Szymczyk, Katarzyna; Taraba, Anna

2018-04-01

The paper presents interactions between quercetin (3,3‧,4‧,5,7-pentahydroxyflavone) and its glycoside, rutin with short chain alcohols, methanol, ethanol and 1-propanol studied by the surface tension measurements. An attempt was made to investigate the effect of flavonoid and alcohol concentrations as well as temperature on the thermodynamic parameters of alcohols adsorption at the water-air interface that is the standard free enthalpy, enthalpy and entropy of adsorption as well as the infinite dilution activity coefficient. The obtained results show that the mixtures of quercetin with methanol and rutin with ethanol are characterized by the best adsorption properties but all studied systems become less structured after adsorption.

Procesos físicos en mezclas gaseosas

NASA Astrophysics Data System (ADS)

Milone, L. A.; Merlo, D. C.

In gaseous mixtures of different compositions (solar, metal poor, Helium-rich and Helium metal poor), we analyze chemical abundances (free electrons, neutral atoms, ions, negative ions and moleculae) as function of temperature and electronic pressures. At relative lower temperatures and higher electronic pressures, we obtain unreachable physical conditions if molecular formation of H2 and C2 are not included (the relations log (Pg) vs log (Pe) tend to infinite); this divergence disappears if molecular formation is taken into account. Finally, we analyze and explain the causes of this phenomena using accuracy numerical calculations.

The Finite-Size Scaling Relation for the Order-Parameter Probability Distribution of the Six-Dimensional Ising Model

NASA Astrophysics Data System (ADS)

Merdan, Ziya; Karakuş, Özlem

2016-11-01

The six dimensional Ising model with nearest-neighbor pair interactions has been simulated and verified numerically on the Creutz Cellular Automaton by using five bit demons near the infinite-lattice critical temperature with the linear dimensions L=4,6,8,10. The order parameter probability distribution for six dimensional Ising model has been calculated at the critical temperature. The constants of the analytical function have been estimated by fitting to probability function obtained numerically at the finite size critical point.

The early universe history from contraction-deformation of the Standard Model

NASA Astrophysics Data System (ADS)

Gromov, N. A.

2017-03-01

The elementary particles evolution in the early Universe from Plank time up to several milliseconds is presented. The developed theory is based on the high-temperature (high-energy) limit of the Standard Model which is generated by the contractions of its gauge groups. At the infinite temperature all particles lose masses. Only massless neutral -bosons, massless Z-quarks, neutrinos and photons are survived in this limit. The weak interactions become long-range and are mediated by neutral currents, quarks have only one color degree of freedom.

Work distributions for random sudden quantum quenches

NASA Astrophysics Data System (ADS)

Łobejko, Marcin; Łuczka, Jerzy; Talkner, Peter

2017-05-01

The statistics of work performed on a system by a sudden random quench is investigated. Considering systems with finite dimensional Hilbert spaces we model a sudden random quench by randomly choosing elements from a Gaussian unitary ensemble (GUE) consisting of Hermitian matrices with identically, Gaussian distributed matrix elements. A probability density function (pdf) of work in terms of initial and final energy distributions is derived and evaluated for a two-level system. Explicit results are obtained for quenches with a sharply given initial Hamiltonian, while the work pdfs for quenches between Hamiltonians from two independent GUEs can only be determined in explicit form in the limits of zero and infinite temperature. The same work distribution as for a sudden random quench is obtained for an adiabatic, i.e., infinitely slow, protocol connecting the same initial and final Hamiltonians.

On Condensation Properties of Bethe Roots Associated with the XXZ Chain

NASA Astrophysics Data System (ADS)

Kozlowski, Karol K.

2018-02-01

I prove that the Bethe roots describing either the ground state or a certain class of "particle-hole" excited states of the XXZ spin-1/2 chain in any sector with magnetisation m \\in [0;1/2] exist, are uniquely defined, and form, in the infinite volume limit, a dense distribution on a subinterval of R. The results hold for any value of the anisotropy {Δ ≥ -1}. In fact, I establish an even stronger result, namely the existence of an all order asymptotic expansion of the counting function associated with such roots. As a corollary, these results allow one to prove the existence and form of the infinite volume limit of various observables attached to the model -the excitation energy, momentum, the zero temperature correlation functions, so as to name a few- that were argued earlier in the literature.

A selection principle for Benard-type convection

NASA Technical Reports Server (NTRS)

Knightly, G. H.; Sather, D.

1985-01-01

In a Benard-type convection problem, the stationary flows of an infinite layer of fluid lying between two rigid horizontal walls and heated uniformly from below are determined. As the temperature difference across the layer increases beyond a certain value, other convective motions appear. These motions are often cellular in character in that their streamlines are confined to certain well-defined cells having, for example, the shape of rolls or hexagons. A selection principle that explains why hexagonal cells seem to be preferred for certain ranges of the parameters is formulated. An operator-theoretical formulation of one generalized Bernard problem is given. The infinite dimensional problem is reduced to one of solving a finite dimensional system of equations, namely, the selection equations. These equations are solved and a linearized stability analysis of the resultant stationary flows is presented.

Heat and Mass Transfer on MHD Free convective flow of Second grade fluid through Porous medium over an infinite vertical plate

NASA Astrophysics Data System (ADS)

Dastagiri Babu, D.; Venkateswarlu, S.; Keshava Reddy, E.

2017-08-01

In this paper, we have considered the unsteady free convective two dimensional flow of a viscous incompressible electrically conducting second grade fluid over an infinite vertical porous plate under the influence of uniform transverse magnetic field with time dependent permeability, oscillatory suction. The governing equations of the flow field are solved by a regular perturbation method for small amplitude of the permeability. The closed form solutions for the velocity, temperature and concentration have been derived analytically and also its behavior is computationally discussed with reference to different flow parameters with the help of profiles. The skin fiction on the boundary, the heat flux in terms of the Nusselt number and rate of mass transfer in terms of Sherwood number are also obtained and their behavior computationally discussed.

Bath-induced correlations in an infinite-dimensional Hilbert space

NASA Astrophysics Data System (ADS)

Nizama, Marco; Cáceres, Manuel O.

2017-09-01

Quantum correlations between two free spinless dissipative distinguishable particles (interacting with a thermal bath) are studied analytically using the quantum master equation and tools of quantum information. Bath-induced coherence and correlations in an infinite-dimensional Hilbert space are shown. We show that for temperature T> 0 the time-evolution of the reduced density matrix cannot be written as the direct product of two independent particles. We have found a time-scale that characterizes the time when the bath-induced coherence is maximum before being wiped out by dissipation (purity, relative entropy, spatial dispersion, and mirror correlations are studied). The Wigner function associated to the Wannier lattice (where the dissipative quantum walks move) is studied as an indirect measure of the induced correlations among particles. We have supported the quantum character of the correlations by analyzing the geometric quantum discord.

A selection principle in Benard-type convection

NASA Technical Reports Server (NTRS)

Knightly, G. H.; Sather, D.

1983-01-01

In a Benard-type convection problem, the stationary flows of an infinite layer of fluid lying between two rigid horizontal walls and heated uniformly from below are determined. As the temperature difference across the layer increases beyond a certain value, other convective motions appear. These motions areoften cellular in character in that their streamlines are confined to certain well-defined cells having, for example, the shape of rolls or hexagons. A selection principle that explains why hexagonal cells seem to be preferred for certain ranges of the parameters is formulated. An operator-theoretical formulation of one generalized Bernard problem is given. The infinite dimensional problem is reduced to one of solving a finite dimensional system of equations, namely, the selection equations. These equations are solved and a linearized stability analysis of the resultant stationary flows is presented.

Infinite-range Heisenberg model and high-temperature superconductivity

NASA Astrophysics Data System (ADS)

Tahir-Kheli, Jamil; Goddard, William A., III

1993-11-01

A strongly coupled variational wave function, the doublet spin-projected Néel state (DSPN), is proposed for oxygen holes in three-band models of high-temperature superconductors. This wave function has the three-spin system of the oxygen hole plus the two neighboring copper atoms coupled in a spin-1/2 doublet. The copper spins in the neighborhood of a hole are in an eigenstate of the infinite-range Heisenberg antiferromagnet (SPN state). The doublet three-spin magnetic polaron or hopping polaron (HP) is stabilized by the hopping terms tσ and tτ, rather than by the copper-oxygen antiferromagnetic coupling Jpd. Although, the HP has a large projection onto the Emery (Dg) polaron, a non-negligible amount of doublet-u (Du) character is required for optimal hopping stabilization. This is due to Jdd, the copper-copper antiferromagnetic coupling. For the copper spins near an oxygen hole, the copper-copper antiferromagnetic coupling can be considered to be almost infinite ranged, since the copper-spin-correlation length in the superconducting phase (0.06-0.25 holes per in-plane copper) is approximately equal to the mean separation of the holes (between 2 and 4 lattice spacings). The general DSPN wave function is constructed for the motion of a single quasiparticle in an antiferromagnetic background. The SPN state allows simple calculations of various couplings of the oxygen hole with the copper spins. The energy minimum is found at symmetry (π/2,π/2) and the bandwidth scales with Jdd. These results are in agreement with exact computations on a lattice. The coupling of the quasiparticles leads to an attraction of holes and its magnitude is estimated.

Effect of vacuum annealing and substrate temperature on structural and optical properties of ZnIn2Se4 thin films

NASA Astrophysics Data System (ADS)

El-Nahass, M. M.; Attia, A. A.; Salem, G. F.; Ali, H. A. M.; Ismail, M. I.

2013-09-01

Zinc indium selenide (ZnIn2Se4) thin films were prepared by the thermal evaporation technique with high deposition rate. The effect of thermal annealing in vacuum on the crystallinity of the as-deposited films was studied at different temperatures (523, 573 and 623 K). The effect of substrate temperature (623 K) for different thickness values (173, 250, 335 and 346 nm) on the optical parameters of ZnIn2Se4 was also studied. The structural studies showed nanocrystalline nature of the room temperature (300 K) deposited films with crystallite size of about a few nanometers. The crystallite size increased up to 31 nm with increasing the annealing temperature in vacuum. From the reflection and transmission data, the refractive index n and the extinction coefficient k were estimated for ZnIn2Se4 thin films and they were found to be independent of film thickness. Analysis of the absorption coefficient data of the as-deposited films revealed the existence of allowed direct and indirect transitions with optical energy gaps of 2.21 eV and 1.71 eV, respectively. These values decreased with increasing annealing temperature. At substrate temperature of 623 K, the direct band gap increased to 2.41 eV whereas the value of indirect band gap remained nearly unchanged. The dispersion analysis showed that the values of the oscillator energy Eo, dispersion energy Ed, dielectric constant at infinite frequency ε∞, and lattice dielectric constant εL were changed appreciably under the effect of annealing and substrate temperature. The covalent nature of structure was studied as a function of the annealing and substrate temperature using an empirical relation for the dispersion energy Ed. Generalized Miller's rule and linear refractive index were used to estimate the nonlinear susceptibility and nonlinear refractive index of the thin films.

Determination of thermodynamic properties of poly (cyclohexyl methacrylate) by inverse gas chromatography.

PubMed

Kaya, Ismet; Pala, Cigdem Yigit

2014-07-01

In this work, some thermodynamic properties of poly (cyclohexyl methacrylate) were studied by inverse gas chromatography (IGC). For this purpose, the polymeric substance was coated on Chromosorb W and which was filled into a glass column. The retention times (t(r)) of the probes were determined from the interactions of poly (cyclohexyl methacrylate) with n-pentane, n-hexane, n-heptane, n-octane, n-decane, methanol, ethanol, 2-propanol, butanol, acetone, ethyl methyl ketone, benzene, toluene and o-xylene by IGC technique. Then, the specific volume (Vg(0)) was determined for each probe molecule. By using (1/T; lnVg(0)) graphics, the glass transition temperature of poly (cyclohexyl methacrylate) was found to be 373 K. The adsorption heat under the glass transition temperature (deltaH(a)), and partial molar heat of sorption above the glass transition (deltaH1(S)), partial molar free energy of sorption (deltaG1(S)) and partial molar entropy of sorption (deltaS1(S)) belonging to sorption for every probe were calculated. The partial molar heat of mixing at infinite dilution (deltaH1(infinity)), partial molar free energy of mixing at infinite dilution (deltaG1(infinity)), Flory-Huggins interaction parameter (chi12(infinity)) and weight fraction activity coefficient (a1/w1)(infinity) values of polymer-solute systems were calculated at different column temperatures. The solubility parameters (delta2) of the polymer were obtained by IGC technique.

Global Aeroheating Measurements of Shock-Shock Interactions on a Swept Cylinder

NASA Technical Reports Server (NTRS)

Mason, Michelle L.; Berry, Scott A.

2015-01-01

The effects of fin leading-edge radius and sweep angle on peak heating rates due to shock-shock interactions were investigated in the NASA Langley Research Center 20-Inch Mach 6 Air Tunnel. The cylindrical leading-edge fin models, with radii varied from 0.25 to 0.75 inches, represent wings or struts on hypersonic vehicles. A 9deg wedge generated a planar oblique shock at 16.7deg. to the flow that intersected the fin bow shock, producing a shock-shock interaction that impinged on the fin leading edge. The fin sweep angle was varied from 0deg (normal to the free-stream) to 15deg and 25deg swept forward. These cases were chosen to explore three characterized shock-shock interaction types. Global temperature data were obtained from the surface of the fused silica fins using phosphor thermography. Metal oil flow models with the same geometries as the fused silica models were used to visualize the streamline patterns for each angle of attack. High-speed zoom-schlieren videos were recorded to show the features and any temporal unsteadiness of the shock-shock interactions. The temperature data were analyzed using a one-dimensional semi-infinite method, as well as one- and two-dimensional finite-volume methods. These results were compared to determine the proper heat transfer analysis approach to minimize errors from lateral heat conduction due to the presence of strong surface temperature gradients induced by the shock interactions. The general trends in the leading-edge heat transfer behavior were similar for each explored shock-shock interaction type regardless of the leading-edge radius. However, the dimensional peak heat transfer coefficient augmentation increased with decreasing leading-edge radius. The dimensional peak heat transfer output from the two-dimensional code was about 20% higher than the value from a standard, semi-infinite one-dimensional method.

Ultrasound thermography: A new temperature reconstruction model and in vivo results

NASA Astrophysics Data System (ADS)

Bayat, Mahdi; Ballard, John R.; Ebbini, Emad S.

2017-03-01

The recursive echo strain filter (RESF) model is presented as a new echo shift-based ultrasound temperature estimation model. The model is shown to have an infinite impulse response (IIR) filter realization of a differentitor-integrator operator. This model is then used for tracking sub-therapeutic temperature changes due to high intensity focused ultrasound (HIFU) shots in the hind limb of the Copenhagen rats in vivo. In addition to the reconstruction filter, a motion compensation method is presented which takes advantage of the deformation field outside the region of interest to correct the motion errors during temperature tracking. The combination of the RESF model and motion compensation algorithm is shown to greatly enhance the accuracy of the in vivo temperature estimation using ultrasound echo shifts.

Proposal for Universality in the Viscosity of Metallic Liquids

DOE PAGES

Blodgett, M. E.; Egami, Takeshi; Nussinov, Z.; ...

2015-09-09

The range of magnitude of the liquid viscosity, η, as a function of temperature is one of the most impressive of any physical property, changing by approximately 17 orders of magnitude from its extrapolated value at infinite temperature (η o) to that at the glass transition temperature, T g. We present experimental measurements of containerlessly processed metallic liquids that suggest that log(η/η o) as a function of T A/T is a potentially universal scaled curve. In stark contrast to previous approaches, the scaling requires only two fitting parameters, which are on average predictable. The temperature T A corresponds to themore » onset of cooperative motion and is strongly correlated with T g, suggesting that the processes underlying the glass transition first appear in the high temperature liquid.« less

Computational analysis of non-Newtonian boundary layer flow of nanofluid past a semi-infinite vertical plate with partial slip

NASA Astrophysics Data System (ADS)

Amanulla, C. H.; Nagendra, N.; Suryanarayana Reddy, M.

2018-03-01

An analysis of this paper is examined, two-dimensional, laminar with heat and mass transfer of natural convective nanofluid flow past a semi-infinite vertical plate surface with velocity and thermal slip effects are studied theoretically. The coupled governing partial differential equations are transformed to ordinary differential equations by using non-similarity transformations. The obtained ordinary differential equations are solved numerically by a well-known method named as Keller Box Method (KBM). The influences of the emerging parameters i.e. Casson fluid parameter (β), Brownian motion parameter (Nb), thermophoresis parameter (Nt), Buoyancy ratio parameter (N), Lewis number (Le), Prandtl number (Pr), Velocity slip factor (Sf) and Thermal slip factor (ST) on velocity, temperature and nano-particle concentration distributions is illustrated graphically and interpreted at length. The major sources of nanoparticle migration in Nanofluids are Thermophoresis and Brownian motion. A suitable agreement with existing published literature is made and an excellent agreement is observed for the limiting case and also validation of solutions with a Nakamura tridiagonal method has been included. It is observed that nanoparticle concentrations on surface decreases with an increase in slip parameter. The study is relevant to enrobing processes for electric-conductive nano-materials, of potential use in aerospace and other industries.

Counting statistics for genetic switches based on effective interaction approximation

NASA Astrophysics Data System (ADS)

Ohkubo, Jun

2012-09-01

Applicability of counting statistics for a system with an infinite number of states is investigated. The counting statistics has been studied a lot for a system with a finite number of states. While it is possible to use the scheme in order to count specific transitions in a system with an infinite number of states in principle, we have non-closed equations in general. A simple genetic switch can be described by a master equation with an infinite number of states, and we use the counting statistics in order to count the number of transitions from inactive to active states in the gene. To avoid having the non-closed equations, an effective interaction approximation is employed. As a result, it is shown that the switching problem can be treated as a simple two-state model approximately, which immediately indicates that the switching obeys non-Poisson statistics.

Density functional theory study of the conformational space of an infinitely long polypeptide chain

NASA Astrophysics Data System (ADS)

Ireta, Joel; Scheffler, Matthias

2009-08-01

The backbone conformational space of infinitely long polyalanine is investigated with density-functional theory and mapping the potential energy surface in terms of (L, θ) cylindrical coordinates. A comparison of the obtained (L, θ) Ramachandran-like plot with results from an extended set of protein structures shows excellent conformity, with the exception of the polyproline II region. It is demonstrated the usefulness of infinitely long polypeptide models for investigating the influence of hydrogen bonding and its cooperative effect on the backbone conformations. The results imply that hydrogen bonding together with long-range electrostatics is the main actuator for most of the structures assumed by protein residues.

Solute-solvent interactions in 2,4-dihydroxyacetophenone isonicotinoylhydrazone solutions in N, N-dimethylformamide and dimethyl sulfoxide at 298-313 K on ultrasonic and viscometric data

NASA Astrophysics Data System (ADS)

Dikkar, A. B.; Pethe, G. B.; Aswar, A. S.

2016-02-01

The speed of sound ( u), density (ρ), and viscosity (η) of 2,4-dihydroxyacetophenone isonicotinoylhydrazone (DHAIH) have been measured in N, N-dimethyl formamide and dimethyl sulfoxide at equidistance temperatures 298.15, 303.15, 308.15, and 313.15 K. These data were used to calculate some important ultrasonic and thermodynamic parameters such as apparent molar volume ( V ϕ s st ), apparent molar compressibility ( K ϕ), partial molar volume ( V ϕ 0 ) and partial molar compressibility ( K ϕ 0 ), were estimated by using the values of ( V ϕ 0 ) and ( K ϕ), at infinite dilution. Partial molar expansion at infinite dilution, (ϕ E 0 ) has also been calculated from temperature dependence of partial molar volume V ϕ 0 . The viscosity data have been analyzed using the Jones-Dole equation, and the viscosity, B coefficients are calculated. The activation free energy has been calculated from B coefficients and partial molar volume data. The results have been discussed in the term of solute-solvent interaction occurring in solutions and it was found that DHAIH acts as a structure maker in present systems.

Application of finite inverse gas chromatography in hypromellose acetate succinate-water-acetone systems.

PubMed

Chiu, Sheng-Wei; Sturm, Derek R; Moser, Justin D; Danner, Ronald P

2016-09-30

A modification of a GC was developed to investigate both infinitely dilute and finite concentrations of solvents in polymers. Thermodynamic properties of hypromellose acetate succinate (HPMCAS-L)-acetone-water systems are important for the optimization of spray-drying processes used in pharmaceutical manufacturing of solid dispersion formulations. These properties, at temperatures below the glass transition temperature, were investigated using capillary column inverse gas chromatography (CCIGC). Water was much less soluble in the HPMCAS-L than acetone. Experiments were also conducted at infinitely dilute concentrations of one of the solvents in HPMCAS-L that was already saturated with the other solvent. Overall the partitioning of the water was not significantly affected by the presence of either water or acetone in the polymer. The acetone partition coefficient decreased as either acetone or water was added to the HPMCAS-L. A representation of the HPMCAS-L structure in terms of UNIFAC groups has been developed. With these groups, the UNIFAC-vdw-FV model did a reasonable job of predicting the phase equilibria in the binary and ternary systems. The Flory-Huggins correlation with fitted interaction parameters represented the data well. Copyright © 2016 Elsevier B.V. All rights reserved.

Analytical solution of the transient temperature profile in gain medium of passively Q-switched microchip laser.

PubMed

Han, Xiahui; Li, Jianlang

2014-11-01

The transient temperature evolution in the gain medium of a continuous wave (CW) end-pumped passively Q-switched microchip (PQSM) laser is analyzed. By approximating the time-dependent population inversion density as a sawtooth function of time and treating the time-dependent pump absorption of a CW end-pumped PQSM laser as the superposition of an infinite series of short pumping pulses, the analytical expressions of transient temperature evolution and distribution in the gain medium for four- and three-level laser systems, respectively, are given. These analytical solutions are applied to evaluate the transient temperature evolution and distribution in the gain medium of CW end-pumped PQSM Nd:YAG and Yb:YAG lasers.

Novel Infrared Dynamics of Cold Atoms on Hot Graphene

NASA Astrophysics Data System (ADS)

Sengupta, Sanghita; Kotov, Valeri; Clougherty, Dennis

The low-energy dynamics of cold atoms interacting with macroscopic graphene membranes exhibits severe infrared divergences when treated perturbatively. These infrared problems are even more pronounced at finite temperature due to the (infinitely) many flexural phonons excited in graphene. We have devised a technique to take account (resummation) of such processes in the spirit of the well-known exact solution of the independent boson model. Remarkably, there is also similarity to the infrared problems and their treatment (via the Bloch-Nordsieck scheme) in finite temperature ``hot'' quantum electrodynamics and chromodynamics due to the long-range, unscreened nature of gauge interactions. The method takes into account correctly the strong damping provided by the many emitted phonons at finite temperature. In our case, the inverse membrane size plays the role of an effective low-energy scale, and, unlike the above mentioned field theories, there remains an unusual, highly nontrivial dependence on that scale due to the 2D nature of the problem. We present detailed results for the sticking (atomic damping rate) rate of cold atomic hydrogen as a function of the membrane temperature and size. We find that the rate is very strongly dependent on both quantities.

Phase-tunable temperature amplifier

NASA Astrophysics Data System (ADS)

Paolucci, F.; Marchegiani, G.; Strambini, E.; Giazotto, F.

2017-06-01

Coherent caloritronics, the thermal counterpart of coherent electronics, has drawn growing attention since the discovery of heat interference in 2012. Thermal interferometers, diodes, transistors and nano-valves have been theoretically proposed and experimentally demonstrated by exploiting the quantum phase difference between two superconductors coupled through a Josephson junction. So far, the quantum-phase modulator has been realized in the form of a superconducting quantum interference device (SQUID) or a superconducting quantum interference proximity transistor (SQUIPT). Thence, an external magnetic field is necessary in order to manipulate the heat transport. Here, we theoretically propose the first on-chip fully thermal caloritronic device: the phase-tunable temperature amplifier (PTA). Taking advantage of a recently discovered thermoelectric effect in spin-split superconductors coupled to a spin-polarized system, we generate the magnetic flux controlling the transport through a temperature-biased SQUIPT by applying a temperature gradient. We simulate the behavior of the device and define a number of figures of merit in full analogy with voltage amplifiers. Notably, our architecture ensures almost infinite input thermal impedance, maximum gain of about 11 and efficiency reaching the 95%. This concept paves the way for applications in radiation sensing, thermal logics and quantum information.

Finite Volume Numerical Methods for Aeroheating Rate Calculations from Infrared Thermographic Data

NASA Technical Reports Server (NTRS)

Daryabeigi, Kamran; Berry, Scott A.; Horvath, Thomas J.; Nowak, Robert J.

2006-01-01

The use of multi-dimensional finite volume heat conduction techniques for calculating aeroheating rates from measured global surface temperatures on hypersonic wind tunnel models was investigated. Both direct and inverse finite volume techniques were investigated and compared with the standard one-dimensional semi-infinite technique. Global transient surface temperatures were measured using an infrared thermographic technique on a 0.333-scale model of the Hyper-X forebody in the NASA Langley Research Center 20-Inch Mach 6 Air tunnel. In these tests the effectiveness of vortices generated via gas injection for initiating hypersonic transition on the Hyper-X forebody was investigated. An array of streamwise-orientated heating striations was generated and visualized downstream of the gas injection sites. In regions without significant spatial temperature gradients, one-dimensional techniques provided accurate aeroheating rates. In regions with sharp temperature gradients caused by striation patterns multi-dimensional heat transfer techniques were necessary to obtain more accurate heating rates. The use of the one-dimensional technique resulted in differences of 20% in the calculated heating rates compared to 2-D analysis because it did not account for lateral heat conduction in the model.

Effect of platykurtic and leptokurtic distributions in the random-field Ising model: mean-field approach.

PubMed

Duarte Queirós, Sílvio M; Crokidakis, Nuno; Soares-Pinto, Diogo O

2009-07-01

The influence of the tail features of the local magnetic field probability density function (PDF) on the ferromagnetic Ising model is studied in the limit of infinite range interactions. Specifically, we assign a quenched random field whose value is in accordance with a generic distribution that bears platykurtic and leptokurtic distributions depending on a single parameter tau<3 to each site. For tau<5/3, such distributions, which are basically Student-t and r distribution extended for all plausible real degrees of freedom, present a finite standard deviation, if not the distribution has got the same asymptotic power-law behavior as a alpha-stable Lévy distribution with alpha=(3-tau)/(tau-1). For every value of tau, at specific temperature and width of the distribution, the system undergoes a continuous phase transition. Strikingly, we impart the emergence of an inflexion point in the temperature-PDF width phase diagrams for distributions broader than the Cauchy-Lorentz (tau=2) which is accompanied with a divergent free energy per spin (at zero temperature).

Metallurgical Effects of Shunting Current on Resistance Spot-Welded Joints of AA2219 Sheets

NASA Astrophysics Data System (ADS)

Jafari Vardanjani, M.; Araee, A.; Senkara, J.; Jakubowski, J.; Godek, J.

2016-08-01

Shunting effect is the loss of electrical current via the secondary circuit provided due to the existence of previous nugget in a series of welding spots. This phenomenon influences on metallurgical aspects of resistance spot-welded (RSW) joints in terms of quality and performance. In this paper RSW joints of AA2219 sheets with 1 mm thickness are investigated metallurgically for shunted and single spots. An electro-thermal finite element analysis is performed on the RSW process of shunted spot and temperature distribution and variation are obtained. These predictions are then compared with experimental micrographs. Three values of 5 mm, 20 mm, and infinite (i.e., single spot) are assumed for welding distance. Numerical and experimental results are matching each other in terms of nugget and HAZ geometry as increasing distance raised nugget size and symmetry of HAZ. In addition, important effect of shunting current on nugget thickness, microstructure, and Copper segregation on HAZ grain boundaries were discovered. A quantitative analysis is also performed about the influence of welding distance on important properties including ratio of nugget thickness and diameter ( r t), ratio of HAZ area on shunted and free side of nugget ( r HA), and ratio of equivalent segregated and total amount of Copper, measured in sample ( r Cu) on HAZ. Increasing distance from 5 mm to infinite, indicated a gain of 111.04, -45.55, and -75.15% in r t, r HA, and r Cu, respectively, while obtained ratios for 20 mm welding distance was suitable compared to single spot.

Thermal Casimir and Casimir–Polder interactions in N parallel 2D Dirac materials

NASA Astrophysics Data System (ADS)

Khusnutdinov, Nail; Kashapov, Rashid; Woods, Lilia M.

2018-07-01

The Casimir and Casimir–Polder interactions are investigated in a stack of equally spaced graphene layers. The optical response of the individual graphene is taken into account using gauge invariant components of the polarization tensor extended to the whole complex frequency plane. The planar symmetry for the electromagnetic boundary conditions is further used to obtain explicit forms for the Casimir energy stored in the stack and the Casimir–Polder energy between an atom above the stack. Our calculations show that these fluctuation induced interactions experience strong thermal effects due to the graphene Dirac-like energy spectrum. The spatial dispersion and temperature dependence in the optical response are also found to be important for enhancing the interactions especially at smaller separations. Analytical expressions for low and high temperature limits and their comparison with corresponding expressions for an infinitely conducting planar stack are further used to expand our understanding of Casimir and Casimir–Polder energies in Dirac materials. Our results may be useful to experimentalists as new ways to probe thermal effects at the nanoscale in such universal interactions.

Two-level system in spin baths: Non-adiabatic dynamics and heat transport

NASA Astrophysics Data System (ADS)

Segal, Dvira

2014-04-01

We study the non-adiabatic dynamics of a two-state subsystem in a bath of independent spins using the non-interacting blip approximation, and derive an exact analytic expression for the relevant memory kernel. We show that in the thermodynamic limit, when the subsystem-bath coupling is diluted (uniformly) over many (infinite) degrees of freedom, our expression reduces to known results, corresponding to the harmonic bath with an effective, temperature-dependent, spectral density function. We then proceed and study the heat current characteristics in the out-of-equilibrium spin-spin-bath model, with a two-state subsystem bridging two thermal spin-baths of different temperatures. We compare the behavior of this model to the case of a spin connecting boson baths, and demonstrate pronounced qualitative differences between the two models. Specifically, we focus on the development of the thermal diode effect, and show that the spin-spin-bath model cannot support it at weak (subsystem-bath) coupling, while in the intermediate-strong coupling regime its rectifying performance outplays the spin-boson model.

Three-state Potts model on non-local directed small-world lattices

NASA Astrophysics Data System (ADS)

Ferraz, Carlos Handrey Araujo; Lima, José Luiz Sousa

2017-10-01

In this paper, we study the non-local directed Small-World (NLDSW) disorder effects in the three-state Potts model as a form to capture the essential features shared by real complex systems where non-locality effects play a important role in the behavior of these systems. Using Monte Carlo techniques and finite-size scaling analysis, we estimate the infinite lattice critical temperatures and the leading critical exponents in this model. In particular, we investigate the first- to second-order phase transition crossover when NLDSW links are inserted. A cluster-flip algorithm was used to reduce the critical slowing down effect in our simulations. We find that for a NLDSW disorder densities p

A mathematical model for mixed convective flow of chemically reactive Oldroyd-B fluid between isothermal stretching disks

NASA Astrophysics Data System (ADS)

Hashmi, M. S.; Khan, N.; Ullah Khan, Sami; Rashidi, M. M.

In this study, we have constructed a mathematical model to investigate the heat source/sink effects in mixed convection axisymmetric flow of an incompressible, electrically conducting Oldroyd-B fluid between two infinite isothermal stretching disks. The effects of viscous dissipation and Joule heating are also considered in the heat equation. The governing partial differential equations are converted into ordinary differential equations by using appropriate similarity variables. The series solution of these dimensionless equations is constructed by using homotopy analysis method. The convergence of the obtained solution is carefully examined. The effects of various involved parameters on pressure, velocity and temperature profiles are comprehensively studied. A graphical analysis has been presented for various values of problem parameters. The numerical values of wall shear stress and Nusselt number are computed at both upper and lower disks. Moreover, a graphical and tabular explanation for critical values of Frank-Kamenetskii regarding other flow parameters.

Surface tension of droplets and Tolman lengths of real substances and mixtures from density functional theory

NASA Astrophysics Data System (ADS)

Rehner, Philipp; Gross, Joachim

2018-04-01

The curvature dependence of interfacial properties has been discussed extensively over the last decades. After Tolman published his work on the effect of droplet size on surface tension, where he introduced the interfacial property now known as Tolman length, several studies were performed with varying results. In recent years, however, some consensus has been reached about the sign and magnitude of the Tolman length of simple model fluids. In this work, we re-examine Tolman's equation and how it relates the Tolman length to the surface tension and we apply non-local classical density functional theory (DFT) based on the perturbed chain statistical associating fluid theory (PC-SAFT) to characterize the curvature dependence of the surface tension of real fluids as well as mixtures. In order to obtain a simple expression for the surface tension, we use a first-order expansion of the Tolman length as a function of droplet radius Rs, as δ(Rs) = δ0 + δ1/Rs, and subsequently expand Tolman's integral equation for the surface tension, whereby a second-order expansion is found to give excellent agreement with the DFT result. The radius-dependence of the surface tension of increasingly non-spherical substances is studied for n-alkanes, up to icosane. The infinite diameter Tolman length is approximately δ0 = -0.38 Å at low temperatures. For more strongly non-spherical substances and for temperatures approaching the critical point, however, the infinite diameter Tolman lengths δ0 turn positive. For mixtures, even if they contain similar molecules, the extrapolated Tolman length behaves strongly non-ideal, implying a qualitative change of the curvature behavior of the surface tension of the mixture.

Surface tension of droplets and Tolman lengths of real substances and mixtures from density functional theory.

PubMed

Rehner, Philipp; Gross, Joachim

2018-04-28

The curvature dependence of interfacial properties has been discussed extensively over the last decades. After Tolman published his work on the effect of droplet size on surface tension, where he introduced the interfacial property now known as Tolman length, several studies were performed with varying results. In recent years, however, some consensus has been reached about the sign and magnitude of the Tolman length of simple model fluids. In this work, we re-examine Tolman's equation and how it relates the Tolman length to the surface tension and we apply non-local classical density functional theory (DFT) based on the perturbed chain statistical associating fluid theory (PC-SAFT) to characterize the curvature dependence of the surface tension of real fluids as well as mixtures. In order to obtain a simple expression for the surface tension, we use a first-order expansion of the Tolman length as a function of droplet radius R s , as δ(R s ) = δ 0 + δ 1 /R s , and subsequently expand Tolman's integral equation for the surface tension, whereby a second-order expansion is found to give excellent agreement with the DFT result. The radius-dependence of the surface tension of increasingly non-spherical substances is studied for n-alkanes, up to icosane. The infinite diameter Tolman length is approximately δ 0 = -0.38 Å at low temperatures. For more strongly non-spherical substances and for temperatures approaching the critical point, however, the infinite diameter Tolman lengths δ 0 turn positive. For mixtures, even if they contain similar molecules, the extrapolated Tolman length behaves strongly non-ideal, implying a qualitative change of the curvature behavior of the surface tension of the mixture.

Effects of temperature and surface orientation on migration behaviours of helium atoms near tungsten surfaces

NASA Astrophysics Data System (ADS)

Wang, Xiaoshuang; Wu, Zhangwen; Hou, Qing

2015-10-01

Molecular dynamics simulations were performed to study the dependence of migration behaviours of single helium atoms near tungsten surfaces on the surface orientation and temperature. For W{100} and W{110} surfaces, He atoms can quickly escape out near the surface without accumulation even at a temperature of 400 K. The behaviours of helium atoms can be well-described by the theory of continuous diffusion of particles in a semi-infinite medium. For a W{111} surface, the situation is complex. Different types of trap mutations occur within the neighbouring region of the W{111} surface. The trap mutations hinder the escape of He atoms, resulting in their accumulation. The probability of a He atom escaping into vacuum from a trap mutation depends on the type of the trap mutation, and the occurrence probabilities of the different types of trap mutations are dependent on the temperature. This finding suggests that the escape rate of He atoms on the W{111} surface does not show a monotonic dependence on temperature. For instance, the escape rate at T = 1500 K is lower than the rate at T = 1100 K. Our results are useful for understanding the structural evolution and He release on tungsten surfaces and for designing models in other simulation methods beyond molecular dynamics.

Steady-state and dynamic evaluation of the electric propulsion system test bed vehicle on a road load simulator

NASA Technical Reports Server (NTRS)

Dustin, M. O.

1983-01-01

The propulsion system of the Lewis Research Center's electric propulsion system test bed vehicle was tested on the road load simulator under the DOE Electric and Hybrid Vehicle Program. This propulsion system, consisting of a series-wound dc motor controlled by an infinitely variable SCR chopper and an 84-V battery pack, is typical of those used in electric vehicles made in 1976. Steady-state tests were conducted over a wide range of differential output torques and vehicle speeds. Efficiencies of all of the components were determined. Effects of temperature and voltage variations on the motor and the effect of voltage changes on the controller were examined. Energy consumption and energy efficiency for the system were determined over the B and C driving schedules of the SAE J227a test procedure.

Approximate analysis of the formation of a buoyant solid sphere in a supercooled melt

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

Solomon, A.D.; Wilson, D.G.; Alexiades, V.

1986-03-01

A mathematical model is presented for the idealized formation and development of a buoyant sphere solidifying in an infinite pool of supercooled liquid. The solid and liquid are of the same pure material and the solid is less dense than the liquid. Initially the liquid is at a uniform temperature that is below its equilibrium freezing temperature, T/sub cr/, but above the so called hypercooled temperature, T/sub cr/ - H/c/sub L/. Here H and c/sub L/ are the latent heat of solidification and the specific heat of the liquid, respectively. An approximate solution is derived based on the Megerlin approximationmore » method. 11 refs.« less

Emittance Theory for Cylindrical Fiber Selective Emitter

NASA Technical Reports Server (NTRS)

Chubb, Donald L.

1998-01-01

A fibrous rare earth selective emitter is approximated as an infinitely long cylinder. The spectral emittance, epsilon(lambda), is obtained by solving the radiative transfer equations with appropriate boundary conditions and uniform temperature. For optical depths, Kappa(R) = alpha(lambda)R, where alpha(lambda) is the extinction coefficient and R is the cylinder radius, greater than 1 the spectral emittance is nearly at its maximum value. There is an optimum cylinder radius, R(opt), for maximum emitter efficiency, eta(E). Values for R(opt) are strongly dependent on the number of emission bands of the material. The optimum radius decreases slowly with increasing emitter temperature, while the maximum efficiency and useful radiated power increase rapidly with increasing temperature.

Research of the rotation effect upon the hydrodynamics and heat and mass transport in a chemical reactor

NASA Astrophysics Data System (ADS)

Gicheva, Natalia I.

2017-11-01

The subject of this research is a chemical reactor for producing tungsten. A physical and mathematical model of fluid motion and heat and mass transfer in a vortex chamber of the chemical reactor under forced and free convection has been described and simulated using two methods. The numerical simulation was carried out in «vortex - stream functions and «velocity - pressure» variables. The velocity field, the mass and the temperature distributions in the reactor were obtained. The influence of a rotation effect upon the hydrodynamics and heat and mass transport was showed. The rotation is important for more uniform distribution of temperature and matter in the vortex chamber. Parametric studies on effects of the Reynolds, Prandtl and Rossbi criteria on the flow characteristics were also performed. Reliability of the calculations was verified by comparing the results obtained by the methods mentioned above. Also, the created model was applied for numerically solving of the classical test problem of the velocity distribution in an annular channel and that of a rotating infinite disk in a stationary liquid. The study findings showed a good agreement with the exact solutions.

Study the effect of chemical reaction and variable viscosity on free convection MHD radiating flow over an inclined plate bounded by porous medium

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

Ali, M., E-mail: ali.mehidi93@gmail.com; Department of Mathematics, Chittagong University of Engineering and Technology, Chittagong-4349; Alim, M. A., E-mail: maalim@math.buet.ac.bd

An analysis is performed to study the free convection heat and mass transfer flow of an electrically conducting incompressible viscous fluid about a semi-infinite inclined porous plate under the action of radiation, chemical reaction in presence of magnetic field with variable viscosity. The dimensionless governing equations are steady, two-dimensional coupled and non-linear ordinary differential equation. Nachtsgeim-Swigert shooting iteration technique along with Runge-Kutta integration scheme is used to solve the non-dimensional governing equations. The effects of magnetic parameter, viscosity parameter and chemical reaction parameter on velocity, temperature and concentration profiles are discussed numerically and shown graphically. Therefore, the results of velocitymore » profile decreases for increasing values of magnetic parameter and viscosity parameter but there is no effect for reaction parameter. The temperature profile decreases in presence of magnetic parameter, viscosity parameter and Prandtl number but increases for radiation parameter. Also, concentration profile decreases for the increasing values of magnetic parameter, viscosity parameter and reaction parameter. All numerical calculations are done with respect to salt water and fixed angle of inclination of the plate.« less

Infinite coherence time of edge spins in finite-length chains

NASA Astrophysics Data System (ADS)

Maceira, Ivo A.; Mila, Frédéric

2018-02-01

Motivated by the recent observation that exponentially long coherence times can be achieved for edge spins in models with strong zero modes, we study the impact of level crossings in finite-length spin chains on the dynamics of the edge spins. Focusing on the X Y spin-1 /2 chain with a transverse or longitudinal magnetic field, two models relevant to understanding recent experimental results on cobalt adatoms, we show that the edge spins can remain coherent for an infinite time even for a finite-length chain if the magnetic field is tuned to a value at which there is a level crossing. Furthermore, we show that the edge spins remain coherent for any initial state for the integrable case of a transverse field because all states have level crossings at the same value of the field, while the coherence time is increasingly large for lower temperatures in the case of a longitudinal field, which is nonintegrable.

Quantum Black Hole Model and HAWKING’S Radiation

NASA Astrophysics Data System (ADS)

Berezin, Victor

The black hole model with a self-gravitating charged spherical symmetric dust thin shell as a source is considered. The Schroedinger-type equation for such a model is derived. This equation appeared to be a finite differences equation. A theory of such an equation is developed and general solution is found and investigated in details. The discrete spectrum of the bound state energy levels is obtained. All the eigenvalues appeared to be infinitely degenerate. The ground state wave functions are evaluated explicitly. The quantum black hole states are selected and investigated. It is shown that the obtained black hole mass spectrum is compatible with the existence of Hawking’s radiation in the limit of low temperatures both for large and nearly extreme Reissner-Nordstrom black holes. The above mentioned infinite degeneracy of the mass (energy) eigenvalues may appeared helpful in resolving the well known information paradox in the black hole physics.

A thermodynamic study of the amphiphilic phenothiazine drug thioridazine hydrochloride in water/ethanol solvent

NASA Astrophysics Data System (ADS)

Cheema, Mohammad Arif; Barbosa, Silvia; Taboada, Pablo; Castro, Emilio; Siddiq, Mohammad; Mosquera, Víctor

2006-09-01

The thermodynamic properties of aqueous solutions of the tricyclic antidepressant amphiphilic phenothiazine drug thioridazine hydrochloride in the temperature range 20-50 °C and in the presence of ethanol have been measured. The phenothiazine tranquillizing drugs have interesting association characteristics that derive from their rigid, tricyclic hydrophobic groups. Thioridazine hydrochloride is a drug used in treatment of mental illness that shows side effects. Therefore, it is interesting to study the change of its physico-chemical properties with temperature and with the surrounding environment to understand the action mechanism of the drug. Densities, conductivities, and surface tension were measured to obtain surface and bulk solution properties. Critical concentrations, cc, at different temperatures and in the presence of ethanol, and partition coefficients, K, have been calculated, the latter using an indirect method based in the pseudophase model with the help of apparent molar volume data. This method has the advantage that allows calculating the distribution coefficients at solubilizate concentrations below the saturation. Conductivity data show two critical concentrations. The second critical concentration is not clear by density data. The effect of the alcohol is to decrease the first critical concentration due to a decrease in headgroup repulsion. The molar apparent volumes at infinite dilution and in the aggregate in water and in presence of ethanol have been also obtained.

Dynamic Temperature and Pressure Measurements in the Core of a Propulsion Engine

NASA Technical Reports Server (NTRS)

Schuster, Bill; Gordon, Grant; Hultgren, Lennart S.

2015-01-01

Dynamic temperature and pressure measurements were made in the core of a TECH977 propulsion engine as part of a NASA funded investigation into indirect combustion noise. Dynamic temperature measurements were made in the combustor, the inter-turbine duct, and the mixer using ten two-wire thermocouple probes. Internal dynamic pressure measurements were made at the same locations using piezoresistive transducers installed in semi-infinite coils. Measurements were acquired at four steady state operating conditions covering the range of aircraft approach power settings. Fluctuating gas temperature spectra were computed from the thermocouple probe voltage measurements using a compensation procedure that was developed under previous NASA test programs. A database of simultaneously acquired dynamic temperature and dynamic pressure measurements was produced. Spectral and cross-spectral analyses were conducted to explore the characteristics of the temperature and pressure fluctuations inside the engine, with a particular focus on attempting to identify the presence of indirect combustion noise.

Microelectronic bioinstrumentation systems

NASA Technical Reports Server (NTRS)

Ko, W. H.; Hynecek, J.

1975-01-01

The possibility of using RF fields to power biologically implanted transmitters used in biomedical experiments was investigated. This approach would be especially useful when animal subjects are strapped in chairs or confined in cages. A telemetry system using an external source of energy has the additional advantage of not being limited in operation by battery lifetime and can therefore operate for virtually infinite lengths of time. A description of a system based on this principle is given. Progress in the development of battery-driven transmitters is also reported, including an ingestible temperature telemetry system and a resistance-to-pulse frequency convertor for implantable temperature telemetry systems.

Viscous Dissipation in One-Dimensional Quantum Liquids

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

Matveev, K. A.; Pustilnik, M.

We develop a theory of viscous dissipation in one-dimensional single-component quantum liquids at low temperatures. Such liquids are characterized by a single viscosity coefficient, the bulk viscosity. We show that for a generic interaction between the constituent particles this viscosity diverges in the zerotemperature limit. In the special case of integrable models, the viscosity is infinite at any temperature, which can be interpreted as a breakdown of the hydrodynamic description. In conclusion, our consideration is applicable to all single-component Galilean- invariant one-dimensional quantum liquids, regardless of the statistics of the constituent particles and the interaction strength.

Exact solution for the layered convection of a viscous incompressible fluid at specified temperature gradients and tangential forces on the free boundary

NASA Astrophysics Data System (ADS)

Burmasheva, N. V.; Prosviryakov, E. Yu.

2017-12-01

A new exact analytical solution of a system of thermal convection equations in the Boussinesq approximation describing layered flows in an incompressible viscous fluid is obtained. A fluid flow in an infinite layer is considered. Convection in the fluid is induced by tangential stresses specified on the upper non-deformable boundary. At the fixed lower boundary, the no-slip condition is satisfied. Temperature corrections are given on the both boundaries of the fluid layer. The possibility of physical field stratification is investigated.

Viscous Dissipation in One-Dimensional Quantum Liquids

DOE PAGES

Matveev, K. A.; Pustilnik, M.

2017-07-20

We develop a theory of viscous dissipation in one-dimensional single-component quantum liquids at low temperatures. Such liquids are characterized by a single viscosity coefficient, the bulk viscosity. We show that for a generic interaction between the constituent particles this viscosity diverges in the zerotemperature limit. In the special case of integrable models, the viscosity is infinite at any temperature, which can be interpreted as a breakdown of the hydrodynamic description. In conclusion, our consideration is applicable to all single-component Galilean- invariant one-dimensional quantum liquids, regardless of the statistics of the constituent particles and the interaction strength.

ENGINEERING APPLICATIONS OF ANALOG COMPUTERS

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

Bryant, L.T.; Janicke, M.J.; Just, L.C.

1963-10-31

Six experiments from the fields of reactor engineering, heat transfer, and dynamics are presented to illustrate the engineering applications of analog computers. The steps required for producing the analog solution are shown, as well as complete information for duplicating the solution. Graphical results are provided. The experiments include: deceleration of a reactor control rod, pressure variations through a packed bed, reactor kinetics over many decades with thermal feedback, a vibrating system with two degrees of freedom, temperature distribution in a radiating fin, temperature distribution in an infinite slab considering variable thermal properties, and iodine -xenon buildup in a reactor. (M.C.G.)

Edge effect on a vacancy state in semi-infinite graphene

NASA Astrophysics Data System (ADS)

Deng, Hai-Yao; Wakabayashi, Katsunori

2014-09-01

The edge effect on a single vacancy state of semi-infinite graphene (SIG) has been studied using Green's function method within the tight-binding model. In the case of infinite graphene, it is known that a vacancy induces a zero-energy resonance state, whose wave function decays inversely with distance (R) from the vacancy and is not normalizable. However, for SIG with an armchair edge, we find that the corresponding wave function decays as R-2 and hence becomes normalizable owing to the intervalley interference caused by the armchair edge. For SIG with a zigzag edge, the vacancy state depends on the sublattice of the vacancy. When the vacancy and the edge belong to different sublattices, the vacancy has no effect on the zero-energy vacancy state. In contrast, when the vacancy is located on the same sublattice as the edge, the resonance state disappears but the wave function at zero energy is strongly distorted near the vacancy. Our results reveal that the presence of edges crucially changes the vacancy state in graphene, and thus such a state can be used to probe the edge structure.

Qualitative breakdown of the noncrossing approximation for the symmetric one-channel Anderson impurity model at all temperatures

NASA Astrophysics Data System (ADS)

Sposetti, C. N.; Manuel, L. O.; Roura-Bas, P.

2016-08-01

The Anderson impurity model is studied by means of the self-consistent hybridization expansions in its noncrossing (NCA) and one-crossing (OCA) approximations. We have found that for the one-channel spin-1 /2 particle-hole symmetric Anderson model, the NCA results are qualitatively wrong for any temperature, even when the approximation gives the exact threshold exponents of the ionic states. Actually, the NCA solution describes an overscreened Kondo effect, because it is the same as for the two-channel infinite-U single-level Anderson model. We explicitly show that the NCA is unable to distinguish between these two very different physical systems, independently of temperature. Using the impurity entropy as an example, we show that the low-temperature values of the NCA entropy for the symmetric case yield the limit Simp(T =0 ) →ln√{2 }, which corresponds to the zero temperature entropy of the overscreened Kondo model. Similar pathologies are predicted for any other thermodynamic property. On the other hand, we have found that the OCA approach lifts the artificial mapping between the models and restores correct properties of the ground state, for instance, a vanishing entropy at low enough temperatures Simp(T =0 ) →0 . Our results indicate that the very well known NCA should be used with caution close to the symmetric point of the Anderson model.

Micromechanics of Size Effect in Failure Due to Distributed Cracking

DTIC Science & Technology

1990-02-26

Eshelby’s theorem for eigenstrains in elliptical inclusions in an infinite elastic solid. The special cases of localization of strain into a spherical...into an ellipsoidal region in an infinite solid. The Department at Civil Engineering, solution exploits Eshelby’s theorem for eigenstrains in...band does not represent an exact solution because the strain eO (the eigenstrain ) in order to fit into the hole perfectly boundary conditions cannot be

Transient Effects in Planar Solidification of Dilute Binary Alloys

NASA Technical Reports Server (NTRS)

Mazuruk, Konstantin; Volz, Martin P.

2008-01-01

The initial transient during planar solidification of dilute binary alloys is studied in the framework of the boundary integral method that leads to the non-linear Volterra integral governing equation. An analytical solution of this equation is obtained for the case of a constant growth rate which constitutes the well-known Tiller's formula for the solute transient. The more physically relevant, constant ramping down temperature case has been studied both numerically and analytically. In particular, an asymptotic analytical solution is obtained for the initial transient behavior. A numerical technique to solve the non-linear Volterra equation is developed and the solution is obtained for a family of the governing parameters. For the rapid solidification condition, growth rate spikes have been observed even for the infinite kinetics model. When recirculating fluid flow is included into the analysis, the spike feature is dramatically diminished. Finally, we have investigated planar solidification with a fluctuating temperature field as a possible mechanism for frequently observed solute trapping bands.

Option pricing for stochastic volatility model with infinite activity Lévy jumps

NASA Astrophysics Data System (ADS)

Gong, Xiaoli; Zhuang, Xintian

2016-08-01

The purpose of this paper is to apply the stochastic volatility model driven by infinite activity Lévy processes to option pricing which displays infinite activity jumps behaviors and time varying volatility that is consistent with the phenomenon observed in underlying asset dynamics. We specially pay attention to three typical Lévy processes that replace the compound Poisson jumps in Bates model, aiming to capture the leptokurtic feature in asset returns and volatility clustering effect in returns variance. By utilizing the analytical characteristic function and fast Fourier transform technique, the closed form formula of option pricing can be derived. The intelligent global optimization search algorithm called Differential Evolution is introduced into the above highly dimensional models for parameters calibration so as to improve the calibration quality of fitted option models. Finally, we perform empirical researches using both time series data and options data on financial markets to illustrate the effectiveness and superiority of the proposed method.

Solution of Eshelby's inclusion problem with a bounded domain and Eshelby's tensor for a spherical inclusion in a finite spherical matrix based on a simplified strain gradient elasticity theory

NASA Astrophysics Data System (ADS)

Gao, X.-L.; Ma, H. M.

2010-05-01

A solution for Eshelby's inclusion problem of a finite homogeneous isotropic elastic body containing an inclusion prescribed with a uniform eigenstrain and a uniform eigenstrain gradient is derived in a general form using a simplified strain gradient elasticity theory (SSGET). An extended Betti's reciprocal theorem and an extended Somigliana's identity based on the SSGET are proposed and utilized to solve the finite-domain inclusion problem. The solution for the disturbed displacement field is expressed in terms of the Green's function for an infinite three-dimensional elastic body in the SSGET. It contains a volume integral term and a surface integral term. The former is the same as that for the infinite-domain inclusion problem based on the SSGET, while the latter represents the boundary effect. The solution reduces to that of the infinite-domain inclusion problem when the boundary effect is not considered. The problem of a spherical inclusion embedded concentrically in a finite spherical elastic body is analytically solved by applying the general solution, with the Eshelby tensor and its volume average obtained in closed forms. This Eshelby tensor depends on the position, inclusion size, matrix size, and material length scale parameter, and, as a result, can capture the inclusion size and boundary effects, unlike existing Eshelby tensors. It reduces to the classical Eshelby tensor for the spherical inclusion in an infinite matrix if both the strain gradient and boundary effects are suppressed. Numerical results quantitatively show that the inclusion size effect can be quite large when the inclusion is very small and that the boundary effect can dominate when the inclusion volume fraction is very high. However, the inclusion size effect is diminishing as the inclusion becomes large enough, and the boundary effect is vanishing as the inclusion volume fraction gets sufficiently low.

Quantitative photothermal heating and cooling measurements of engineered nanoparticles in an optical trap

NASA Astrophysics Data System (ADS)

Roder, Paden Bernard

Laser tweezers and optical trapping has provided scientists and engineers a unique way to study the wealth of phenomena that materials exhibit at the micro- and nanoscale, much of which remains mysterious. Of particular interest is the interplay between light absorption and subsequent heat generation of laser-irradiated materials, especially due to recent interest in developing nanoscale materials for use as agents for photothermal cancer treatments. An introduction to optical trapping physics and laser tweezers are given in Chapter 1 and 2 of this thesis, respectively. The remaining chapters, summarized below, describe the theoretical basis of laser heating of one-dimensional nanostructures and experiments in which optically-trapped nanostructures are studied using techniques developed for a laser tweezer. In Chapter 3, we delve into the fundamentals of laser heating of one-dimensional materials by developing an analytical model of pulsed laser heating of uniform and tapered supported nanowires and compare calculations with experimental data to comment on the effects that the material's physical, optical, and thermal parameters have on its heating and cooling rates. We then consider closed-form analytical solutions for the temperature rise within infinite circular cylinders with nanometer-scale diameters irradiated at right angles by TM-polarized continuous-wave laser sources, which allows for analysis of laser-heated nanowires in a solvated environment. The infinite nanowire analysis will then be extended to the optical heating of laser-irradiated finite nanowires in the framework of a laser tweezer, which enables predictive capabilities and direct comparison with laser trapping experiments. An effective method for determining optically-trapped particle temperatures as well as the temperature gradient in the surrounding medium will be discussed in Chapter 4. By combining laser tweezer calibration techniques, forward-scattered light power spectrum analysis, and hot Brownian motion theory, we attempt to measure realistic temperatures at the surface of an optically-trapped particle while properly accounting for inhomogeneous temperature fields generated by the optical trap. In Chapter 5, this technique is then applied to measure the temperature of engineered gold- and silicon-implanted silicon nanowires to rigorously study the effect ion implantation has on silicon nanowire photothermal efficiencies. Silicon nanowire photothermal efficiencies are shown to drastically increase by implanting with gold ions and cause superheating of water of over 200 C at the trap site, suggesting potential application as agents for photothermal cancer therapies. Chapter 6 describes the hydrothermal synthesis and optical trapping of engineered YLF nanoparticles doped with Yb(III) ions. Laser tweezer experiments using the developed temperature extraction techniques and hot Brownian motion analysis show the first observation of particles undergoing recently hypothesized cold Brownian motion and local laser refrigeration in a condensed phase via anti-Stokes photoluminescence. Furthermore, YLF nanoparticles codoped with Er(III) and Yb(III) ions are also developed and their intense visible upconversion of the NIR trapping laser is used to monitor its internal lattice temperature using ratiometric thermography. The results suggest the potential of these materials to investigate kinetics and temperature sensitivity of basic cellular processes, or to act as simultaneous theranostic-hypothermia agents to identify and treat cancerous tissues. Finally, Chapter 7 presents a summary of the salient conclusions of the reported studies. The chapter concludes with a short discussion of my personal experience with being a member of a new research group and setting up the Pauzauskie laboratory.

Fermionic entanglement that survives a black hole

NASA Astrophysics Data System (ADS)

Martín-Martínez, Eduardo; León, Juan

2009-10-01

We introduce an arbitrary number of accessible modes when analyzing bipartite entanglement degradation due to Unruh effect between two partners Alice and Rob. Under the single mode approximation (SMA) a fermion field only had a few accessible levels due to Pauli exclusion principle conversely to bosonic fields which had an infinite number of excitable levels. This was argued to justify entanglement survival in the fermionic case in the SMA infinite acceleration limit. Here we relax SMA. Hence, an infinite number of modes are excited as the observer Rob accelerates, even for a fermion field. We will prove that, despite this analogy with the bosonic case, entanglement loss is limited. We will show that this comes from fermionic statistics through the characteristic structure it imposes on the infinite dimensional density matrix for Rob. Surprisingly, the surviving entanglement is independent of the specific maximally entangled state chosen, the kind of fermionic field analyzed, and the number of accessible modes considered. We shall discuss whether this surviving entanglement goes beyond the purely statistical correlations, giving insight concerning the black hole information paradox.

On beam shaping of the field radiated by a line source coupled to finite or infinite photonic crystals.

PubMed

Ceccuzzi, Silvio; Jandieri, Vakhtang; Baccarelli, Paolo; Ponti, Cristina; Schettini, Giuseppe

2016-04-01

Comparison of the beam-shaping effect of a field radiated by a line source, when an ideal infinite structure constituted by two photonic crystals and an actual finite one are considered, has been carried out by means of two different methods. The lattice sums technique combined with the generalized reflection matrix method is used to rigorously investigate the radiation from the infinite photonic crystals, whereas radiation from crystals composed of a finite number of rods along the layers is analyzed using the cylindrical-wave approach. A directive radiation is observed with the line source embedded in the structure. With an increased separation distance between the crystals, a significant edge diffraction appears that provides the main radiation mechanism in the finite layout. Suitable absorbers are implemented to reduce the above-mentioned diffraction and the reflections at the boundaries, thus obtaining good agreement between radiation patterns of a localized line source coupled to finite and infinite photonic crystals, when the number of periods of the finite structure is properly chosen.

Viscous/potential flow about multi-element two-dimensional and infinite-span swept wings: Theory and experiment

NASA Technical Reports Server (NTRS)

Olson, L. E.; Dvorak, F. A.

1975-01-01

The viscous subsonic flow past two-dimensional and infinite-span swept multi-component airfoils is studied theoretically and experimentally. The computerized analysis is based on iteratively coupled boundary layer and potential flow analysis. The method, which is restricted to flows with only slight separation, gives surface pressure distribution, chordwise and spanwise boundary layer characteristics, lift, drag, and pitching moment for airfoil configurations with up to four elements. Merging confluent boundary layers are treated. Theoretical predictions are compared with an exact theoretical potential flow solution and with experimental measures made in the Ames 40- by 80-Foot Wind Tunnel for both two-dimensional and infinite-span swept wing configurations. Section lift characteristics are accurately predicted for zero and moderate sweep angles where flow separation effects are negligible.

Propagation and radiation of sound from flanged circular ducts with circumferentially varying wall admittances. I Semi-infinite ducts. II - Finite ducts with sources

NASA Technical Reports Server (NTRS)

Fuller, C. R.

1984-01-01

Sound propagation in infinite, semiinfinite, and finite circular ducts with circumferentially varying wall admittances is investigated analytically. The infinite case is considered, and an example demonstrates the effects of wall-admittance distribution on dispersion characteristics and mode shapes. An exact solution is obtained for the semiinfinite case, a circular duct with a flanged opening: sidelobe suppression and circumferential-mode energy scattering leading to radiated-field asymmetry are found. A finite duct system with specified hard-walled pressure sources is examined in detail, evaluating reflection coefficients, transmission losses, and radiated-field directivity. Graphs and diagrams are provided, and the implications of the results obtained for the design of aircraft-turbofan inlet liners are discussed.

Competition and the Reference Pricing Scheme for pharmaceuticals.

PubMed

Ghislandi, Simone

2011-12-01

By introducing n (>1) firms with infinite cross-price elasticity (i.e. generic drugs), we explore the effects of competition on the optimal pricing strategies under a Reference Pricing Scheme (RPS). A two-stage model repeated infinite number of times is presented. When stage 1 is competitive, the equilibrium in pure strategies exists and is efficient only if the reference price (R) does not depend on the price of the branded product. When generics collude, the way R is designed is crucial for both the stability of the cartel among generics and the collusive prices in equilibrium. An optimally designed RPS must set R as a function only of the infinitely elastic side of the market and should provide the right incentives for competition. Copyright © 2011 Elsevier B.V. All rights reserved.

Nuclear data libraries assessment for modelling a small fluoride salt-cooled, high-temperature reactor

NASA Astrophysics Data System (ADS)

Mohamed, Hassan; Lindley, Benjamin; Parks, Geoffrey

2017-01-01

Nuclear data consists of measured or evaluated probabilities of various fundamental physical interactions involving the nuclei of atoms and their properties. Most fluoride salt-cooled high-temperature reactor (FHR) studies that were reviewed do not give detailed information on the data libraries used in their assessments. Therefore, the main objective of this data libraries comparison study is to investigate whether there are any significant discrepancies between main data libraries, namely ENDF/B-VII, JEFF-3.1 and JEF-2.2. Knowing the discrepancies, especially its magnitude, is important and relevant for readers as to whether further cautions are necessary for any future verification or validation processes when modelling an FHR. The study is performed using AMEC's reactor physics software tool, WIMS. The WIMS calculation is simply a 2-D infinite lattice of fuel assembly calculation. The comparison between the data libraries in terms of infinite multiplication factor, kinf and pin power map are presented. Results show that the discrepancy between JEFF-3.1 and ENDF/B-VII libraries is reasonably small but increases as the fuel depletes due to the data libraries uncertainties that are accumulated at each burnup step. Additionally, there are large discrepancies between JEF-2.2 and ENDF/B-VII because of the inadequacy of the JEF-2.2 library.

On Kronecker-Capelli type theorems for infinite systems

NASA Astrophysics Data System (ADS)

Fedorov, Foma M.; Potapova, Sargylana V.

2017-11-01

On the basis of the new concept of the decrement of an infinite matrices and determinants, we studied the inconsistency of a general infinite systems of linear algebraic equations. We proved the theorem on inconsistency of a infinite system when the decrement of its matrix is nonzero.

Magneto-hydrodynamic simulations of Heavy Ion Collisions with ECHO-QGP

NASA Astrophysics Data System (ADS)

Inghirami, G.; Del Zanna, L.; Beraudo, A.; Haddadi Moghaddam, M.; Becattini, F.; Bleicher, M.

2018-05-01

It is believed that very strong magnetic fields may induce many interesting physical effects in the Quark Gluon Plasma, like the Chiral Magnetic Effect, the Chiral Separation Effect, a modification of the critical temperature or changes in the collective flow of the emitted particles. However, in the hydrodynamic numerical simulations of Heavy Ion Collisions the magnetic fields have been either neglected or considered as external fields which evolve independently from the dynamics of the fluid. To address this issue, we recently modified the ECHO-QGP code, including for the first time the effects of electromagnetic fields in a consistent way, although in the limit of an infinite electrical conductivity of the plasma (ideal magnetohydrodynamics). In this proceedings paper we illustrate the underlying 3+1 formalisms of the current version of the code and we present the results of its basic preliminary application in a simple case. We conclude with a brief discussion of the possible further developments and future uses of the code, from RHIC to FAIR collision energies.

Gelfand-type problem for two-phase porous media

PubMed Central

Gordon, Peter V.; Moroz, Vitaly

2014-01-01

We consider a generalization of the Gelfand problem arising in Frank-Kamenetskii theory of thermal explosion. This generalization is a natural extension of the Gelfand problem to two-phase materials, where, in contrast to the classical Gelfand problem which uses a single temperature approach, the state of the system is described by two different temperatures. We show that similar to the classical Gelfand problem the thermal explosion occurs exclusively owing to the absence of stationary temperature distribution. We also show that the presence of interphase heat exchange delays a thermal explosion. Moreover, we prove that in the limit of infinite heat exchange between phases the problem of thermal explosion in two-phase porous media reduces to the classical Gelfand problem with renormalized constants. PMID:24611025

Temperature Effect on Rheological Behavior of Silicone Oils. A Model for the Viscous Heating.

PubMed

Romano, Mario R; Cuomo, Francesca; Massarotti, Nicola; Mauro, Alessandro; Salahudeen, Mohamed; Costagliola, Ciro; Ambrosone, Luigi

2017-07-27

The rheological behavior of silicone oils, (CH 3 ) 3 SiO-[Si(CH 3 ) 2 O] n -Si(CH 3 ) 3 , and their mixtures is studied. Shear-stress measurements, in the temperature range of 293-313 K, reveal that this polymer family is a group of shear-thinning liquids with a yield stress below which no flow occurs. Experimental diagrams, i.e., shear stress versus shear rate, are satisfactorily described by the Casson fluid model over a wide range of shear rates. In order to monitor the effect of temperature on fluid properties, Casson's rheological model is reformulated using the fictitious shear rate, γ̇ f , and the infinite-shear viscosity, η ∞ , as constitutive parameters. Due to low intermolecular forces and high chain flexibility, γ̇ f varies very little when the temperature increases. For this reason, the apparent material viscosity depends on temperature only through η ∞ , which exponentially decreases until high shear rates are reached, and there is more alignment possible. Interestingly, the temperature sensitivity of this pseudoplastic behavior is the same for all of the silicone oils investigated; therefore, they can be classified according to their tendency to emulsify. Experimental results are then used to model the flow of silicone oils in a cylindrical pipe and estimate the temperature increase due to viscous heating. Numerical results show that the normalized temperature, i.e., ratio of fluid temperature to wall temperature, increases approximately 23%, and the apparent viscosity decreases drastically, going toward the center of the tube. The non-Newtonian nature of fluid is reflected in the presence of a critical region. In this region, the velocity and temperature gradients vanish. Since silicon oil is a surgical tool, we hope that the acquired physicochemical information can provide help to facilitate the removal of this material during surgical procedures.

Organ and effective dose rate coefficients for submersion exposure in occupational settings

DOE PAGES

Veinot, K. G.; Y-12 National Security Complex, Oak Ridge, TN; Dewji, S. A.; ...

2017-08-24

External dose coefficients for environmental exposure scenarios are often computed using assumption on infinite or semi-infinite radiation sources. For example, in the case of a person standing on contaminated ground, the source is assumed to be distributed at a given depth (or between various depths) and extending outwards to an essentially infinite distance. In the case of exposure to contaminated air, the person is modeled as standing within a cloud of infinite, or semi-infinite, source distribution. However, these scenarios do not mimic common workplace environments where scatter off walls and ceilings may significantly alter the energy spectrum and dose coefficients.more » In this study, dose rate coefficients were calculated using the International Commission on Radiological Protection (ICRP) reference voxel phantoms positioned in rooms of three sizes representing an office, laboratory, and warehouse. For each room size calculations using the reference phantoms were performed for photons, electrons, and positrons as the source particles to derive mono-energetic dose rate coefficients. Since the voxel phantoms lack the resolution to perform dose calculations at the sensitive depth for the skin, a mathematical phantom was developed and calculations were performed in each room size with the three source particle types. Coefficients for the noble gas radionuclides of ICRP Publication 107 (e.g., Ne, Ar, Kr, Xe, and Rn) were generated by folding the corresponding photon, electron, and positron emissions over the mono-energetic dose rate coefficients. Finally, results indicate that the smaller room sizes have a significant impact on the dose rate per unit air concentration compared to the semi-infinite cloud case. For example, for Kr-85 the warehouse dose rate coefficient is 7% higher than the office dose rate coefficient while it is 71% higher for Xe-133.« less

Parallel Ellipsoidal Perfectly Matched Layers for Acoustic Helmholtz Problems on Exterior Domains

DOE PAGES

Bunting, Gregory; Prakash, Arun; Walsh, Timothy; ...

2018-01-26

Exterior acoustic problems occur in a wide range of applications, making the finite element analysis of such problems a common practice in the engineering community. Various methods for truncating infinite exterior domains have been developed, including absorbing boundary conditions, infinite elements, and more recently, perfectly matched layers (PML). PML are gaining popularity due to their generality, ease of implementation, and effectiveness as an absorbing boundary condition. PML formulations have been developed in Cartesian, cylindrical, and spherical geometries, but not ellipsoidal. In addition, the parallel solution of PML formulations with iterative solvers for the solution of the Helmholtz equation, and howmore » this compares with more traditional strategies such as infinite elements, has not been adequately investigated. In this study, we present a parallel, ellipsoidal PML formulation for acoustic Helmholtz problems. To faciliate the meshing process, the ellipsoidal PML layer is generated with an on-the-fly mesh extrusion. Though the complex stretching is defined along ellipsoidal contours, we modify the Jacobian to include an additional mapping back to Cartesian coordinates in the weak formulation of the finite element equations. This allows the equations to be solved in Cartesian coordinates, which is more compatible with existing finite element software, but without the necessity of dealing with corners in the PML formulation. Herein we also compare the conditioning and performance of the PML Helmholtz problem with infinite element approach that is based on high order basis functions. On a set of representative exterior acoustic examples, we show that high order infinite element basis functions lead to an increasing number of Helmholtz solver iterations, whereas for PML the number of iterations remains constant for the same level of accuracy. Finally, this provides an additional advantage of PML over the infinite element approach.« less

Parallel Ellipsoidal Perfectly Matched Layers for Acoustic Helmholtz Problems on Exterior Domains

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

Bunting, Gregory; Prakash, Arun; Walsh, Timothy

Exterior acoustic problems occur in a wide range of applications, making the finite element analysis of such problems a common practice in the engineering community. Various methods for truncating infinite exterior domains have been developed, including absorbing boundary conditions, infinite elements, and more recently, perfectly matched layers (PML). PML are gaining popularity due to their generality, ease of implementation, and effectiveness as an absorbing boundary condition. PML formulations have been developed in Cartesian, cylindrical, and spherical geometries, but not ellipsoidal. In addition, the parallel solution of PML formulations with iterative solvers for the solution of the Helmholtz equation, and howmore » this compares with more traditional strategies such as infinite elements, has not been adequately investigated. In this study, we present a parallel, ellipsoidal PML formulation for acoustic Helmholtz problems. To faciliate the meshing process, the ellipsoidal PML layer is generated with an on-the-fly mesh extrusion. Though the complex stretching is defined along ellipsoidal contours, we modify the Jacobian to include an additional mapping back to Cartesian coordinates in the weak formulation of the finite element equations. This allows the equations to be solved in Cartesian coordinates, which is more compatible with existing finite element software, but without the necessity of dealing with corners in the PML formulation. Herein we also compare the conditioning and performance of the PML Helmholtz problem with infinite element approach that is based on high order basis functions. On a set of representative exterior acoustic examples, we show that high order infinite element basis functions lead to an increasing number of Helmholtz solver iterations, whereas for PML the number of iterations remains constant for the same level of accuracy. Finally, this provides an additional advantage of PML over the infinite element approach.« less

Organ and effective dose rate coefficients for submersion exposure in occupational settings

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

Veinot, K. G.; Y-12 National Security Complex, Oak Ridge, TN; Dewji, S. A.

External dose coefficients for environmental exposure scenarios are often computed using assumption on infinite or semi-infinite radiation sources. For example, in the case of a person standing on contaminated ground, the source is assumed to be distributed at a given depth (or between various depths) and extending outwards to an essentially infinite distance. In the case of exposure to contaminated air, the person is modeled as standing within a cloud of infinite, or semi-infinite, source distribution. However, these scenarios do not mimic common workplace environments where scatter off walls and ceilings may significantly alter the energy spectrum and dose coefficients.more » In this study, dose rate coefficients were calculated using the International Commission on Radiological Protection (ICRP) reference voxel phantoms positioned in rooms of three sizes representing an office, laboratory, and warehouse. For each room size calculations using the reference phantoms were performed for photons, electrons, and positrons as the source particles to derive mono-energetic dose rate coefficients. Since the voxel phantoms lack the resolution to perform dose calculations at the sensitive depth for the skin, a mathematical phantom was developed and calculations were performed in each room size with the three source particle types. Coefficients for the noble gas radionuclides of ICRP Publication 107 (e.g., Ne, Ar, Kr, Xe, and Rn) were generated by folding the corresponding photon, electron, and positron emissions over the mono-energetic dose rate coefficients. Finally, results indicate that the smaller room sizes have a significant impact on the dose rate per unit air concentration compared to the semi-infinite cloud case. For example, for Kr-85 the warehouse dose rate coefficient is 7% higher than the office dose rate coefficient while it is 71% higher for Xe-133.« less

Frequency response of a thermocouple wire: Effects of axial conduction

NASA Technical Reports Server (NTRS)

Forney, L. J.; Fralick, G. C.

1990-01-01

Theoretical expressions are derived for the steady-state frequency response of a thermocouple wire. In particular, the effects of axial heat conduction are demonstrated for both a uniform thermocouple wire and a nonuniform wire with unequal material properties and wire diameters across the junction. For the case of a uniform wire, the amplitude ratio and phase angle compare favorably with the series solution of Scadron and Warshawsky (1952) except near the ends of the wire. For the case of a non-uniform wire, the amplitude ratio at low frequency omega yields 0 agrees with the results of Scadron and Warshawsky for a steady-state temperature distribution. Moreover, the frequency response for a non-uniform wire in the limit of infinite length l yields infinity is shown to reduce to a simple expression that is analogous to the classic first order solution for a thermocouple wire with uniform properties.

Regimes of heating and dynamical response in driven many-body localized systems

NASA Astrophysics Data System (ADS)

Gopalakrishnan, Sarang; Knap, Michael; Demler, Eugene

2016-09-01

We explore the response of many-body localized (MBL) systems to periodic driving of arbitrary amplitude, focusing on the rate at which they exchange energy with the drive. To this end, we introduce an infinite-temperature generalization of the effective "heating rate" in terms of the spread of a random walk in energy space. We compute this heating rate numerically and estimate it analytically in various regimes. When the drive amplitude is much smaller than the frequency, this effective heating rate is given by linear response theory with a coefficient that is proportional to the optical conductivity; in the opposite limit, the response is nonlinear and the heating rate is a nontrivial power law of time. We discuss the mechanisms underlying this crossover in the MBL phase. We comment on implications for the subdiffusive thermal phase near the MBL transition, and for response in imperfectly isolated MBL systems.

Effect of instantaneous and continuous quenches on the density of vibrational modes in model glasses.

PubMed

Lerner, Edan; Bouchbinder, Eran

2017-08-01

Computational studies of supercooled liquids often focus on various analyses of their "underlying inherent states"-the glassy configurations at zero temperature obtained by an infinitely fast (instantaneous) quench from equilibrium supercooled states. Similar protocols are also regularly employed in investigations of the unjamming transition at which the rigidity of decompressed soft-sphere packings is lost. Here we investigate the statistics and localization properties of low-frequency vibrational modes of glassy configurations obtained by such instantaneous quenches. We show that the density of vibrational modes grows as ω^{β} with β depending on the parent temperature T_{0} from which the glassy configurations were instantaneously quenched. For quenches from high temperature liquid states we find β≈3, whereas β appears to approach the previously observed value β=4 as T_{0} approaches the glass transition temperature. We discuss the consistency of our findings with the theoretical framework of the soft potential model, and contrast them with similar measurements performed on configurations obtained by continuous quenches at finite cooling rates. Our results suggest that any physical quench at rates sufficiently slower than the inverse vibrational time scale-including all physically realistic quenching rates of molecular or atomistic glasses-would result in a glass whose density of vibrational modes is universally characterized by β=4.

Effect of instantaneous and continuous quenches on the density of vibrational modes in model glasses

NASA Astrophysics Data System (ADS)

Lerner, Edan; Bouchbinder, Eran

2017-08-01

Computational studies of supercooled liquids often focus on various analyses of their "underlying inherent states"—the glassy configurations at zero temperature obtained by an infinitely fast (instantaneous) quench from equilibrium supercooled states. Similar protocols are also regularly employed in investigations of the unjamming transition at which the rigidity of decompressed soft-sphere packings is lost. Here we investigate the statistics and localization properties of low-frequency vibrational modes of glassy configurations obtained by such instantaneous quenches. We show that the density of vibrational modes grows as ωβ with β depending on the parent temperature T0 from which the glassy configurations were instantaneously quenched. For quenches from high temperature liquid states we find β ≈3 , whereas β appears to approach the previously observed value β =4 as T0 approaches the glass transition temperature. We discuss the consistency of our findings with the theoretical framework of the soft potential model, and contrast them with similar measurements performed on configurations obtained by continuous quenches at finite cooling rates. Our results suggest that any physical quench at rates sufficiently slower than the inverse vibrational time scale—including all physically realistic quenching rates of molecular or atomistic glasses—would result in a glass whose density of vibrational modes is universally characterized by β =4 .

Hard-sphere mixture excess free energy at infinite size ratio

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

Tukur, N.M.; Hamad, E.Z.; Mansoori, G.A.

1999-02-01

This article presents the exact limiting value of the derivative of the excess Helmholtz energy, A{sup E}, with respect to molecular size at constant temperature, density and composition for a binary mixture of hard spheres with an infinite size ratio ({sigma}{sub 11}/{sigma}{sub 22}{r_arrow}{infinity}); i.e., lim{sub {sigma}{sub 22}{r_arrow}0}[({partial_derivative}A{sub hs}{sup E}/RT)/{partial_derivative}{sigma}{sub 22}]{sub T,{rho},x,{sigma}{sub 11}}=({pi}/2){rho}x{sub 1}x{sub 2}{sigma}{sub 11}{sup 2}/(1{minus}({pi}/6){rho}x{sub 1}{sigma}{sub 11}{sup 3}). This limiting value is compared with the Mansoori{endash}Carnahan{endash}Starling{endash}Leland (MCSL) and also used to test the limits of some commonly used models in estimating the excess free energy of solvents in mixtures or polymer solutions. The models evaluated include the van Laar,more » Wilson, Edmond{endash}Ogston, Flory{endash}Huggins, Lacome{endash}Sanchez, Scott{endash}Magat, and Chen {ital et al.} It is shown that while the MCSL equation of state produces the same limiting value as the exact value reported here the other mixture models deviate from the exact value. This expression may be utilized to correct the mixture theories at their infinite size ratio limits. {copyright} {ital 1999 American Institute of Physics.}« less

Linear Rayleigh-Taylor instability in an accelerated Newtonian fluid with finite width

NASA Astrophysics Data System (ADS)

Piriz, S. A.; Piriz, A. R.; Tahir, N. A.

2018-04-01

The linear theory of Rayleigh-Taylor instability is developed for the case of a viscous fluid layer accelerated by a semi-infinite viscous fluid, considering that the top interface is a free surface. Effects of the surface tensions at both interfaces are taken into account. When viscous effects dominate on surface tensions, an interplay of two mechanisms determines opposite behaviors of the instability growth rate with the thickness of the heavy layer for an Atwood number AT=1 and for sufficiently small values of AT. In the former case, viscosity is a less effective stabilizing mechanism for the thinnest layers. However, the finite thickness of the heavy layer enhances its viscous effects that, in general, prevail on the viscous effects of the semi-infinite medium.

Modality, Infinitives, and Finite Bare Verbs in Dutch and English Child Language

ERIC Educational Resources Information Center

Blom, Elma

2007-01-01

This article focuses on the meaning of nonfinite clauses ("root infinitives") in Dutch and English child language. I present experimental and naturalistic data confirming the claim that Dutch root infinitives are more often modal than English root infinitives. This cross-linguistic difference is significantly smaller than previously assumed,…

Cluster properties of the one-dimensional lattice gas: the microscopic meaning of grand potential.

PubMed

Fronczak, Agata

2013-02-01

Using a concrete example, we demonstrate how the combinatorial approach to a general system of particles, which was introduced in detail in an earlier paper [Fronczak, Phys. Rev. E 86, 041139 (2012)], works and where this approach provides a genuine extension of results obtained through more traditional methods of statistical mechanics. We study the cluster properties of a one-dimensional lattice gas with nearest-neighbor interactions. Three cases (the infinite temperature limit, the range of finite temperatures, and the zero temperature limit) are discussed separately, yielding interesting results and providing alternative proof of known results. In particular, the closed-form expression for the grand partition function in the zero temperature limit is obtained, which results in the nonanalytic behavior of the grand potential, in accordance with the Yang-Lee theory.

Overcoming the sign problem at finite temperature: Quantum tensor network for the orbital eg model on an infinite square lattice

NASA Astrophysics Data System (ADS)

Czarnik, Piotr; Dziarmaga, Jacek; Oleś, Andrzej M.

2017-07-01

The variational tensor network renormalization approach to two-dimensional (2D) quantum systems at finite temperature is applied to a model suffering the notorious quantum Monte Carlo sign problem—the orbital eg model with spatially highly anisotropic orbital interactions. Coarse graining of the tensor network along the inverse temperature β yields a numerically tractable 2D tensor network representing the Gibbs state. Its bond dimension D —limiting the amount of entanglement—is a natural refinement parameter. Increasing D we obtain a converged order parameter and its linear susceptibility close to the critical point. They confirm the existence of finite order parameter below the critical temperature Tc, provide a numerically exact estimate of Tc, and give the critical exponents within 1 % of the 2D Ising universality class.

A new leakage measurement method for damaged seal material

NASA Astrophysics Data System (ADS)

Wang, Shen; Yao, Xue Feng; Yang, Heng; Yuan, Li; Dong, Yi Feng

2018-07-01

In this paper, a new leakage measurement method based on the temperature field and temperature gradient field is proposed for detecting the leakage location and measuring the leakage rate in damaged seal material. First, a heat transfer leakage model is established, which can calculate the leakage rate based on the temperature gradient field near the damaged zone. Second, a finite element model of an infinite plate with a damaged zone is built to calculate the leakage rate, which fits the simulated leakage rate well. Finally, specimens in a tubular rubber seal with different damage shapes are used to conduct the leakage experiment, validating the correctness of this new measurement principle for the leakage rate and the leakage position. The results indicate the feasibility of the leakage measurement method for damaged seal material based on the temperature gradient field from infrared thermography.

Scalable L-infinite coding of meshes.

PubMed

Munteanu, Adrian; Cernea, Dan C; Alecu, Alin; Cornelis, Jan; Schelkens, Peter

2010-01-01

The paper investigates the novel concept of local-error control in mesh geometry encoding. In contrast to traditional mesh-coding systems that use the mean-square error as target distortion metric, this paper proposes a new L-infinite mesh-coding approach, for which the target distortion metric is the L-infinite distortion. In this context, a novel wavelet-based L-infinite-constrained coding approach for meshes is proposed, which ensures that the maximum error between the vertex positions in the original and decoded meshes is lower than a given upper bound. Furthermore, the proposed system achieves scalability in L-infinite sense, that is, any decoding of the input stream will correspond to a perfectly predictable L-infinite distortion upper bound. An instantiation of the proposed L-infinite-coding approach is demonstrated for MESHGRID, which is a scalable 3D object encoding system, part of MPEG-4 AFX. In this context, the advantages of scalable L-infinite coding over L-2-oriented coding are experimentally demonstrated. One concludes that the proposed L-infinite mesh-coding approach guarantees an upper bound on the local error in the decoded mesh, it enables a fast real-time implementation of the rate allocation, and it preserves all the scalability features and animation capabilities of the employed scalable mesh codec.

Viscous effects on the Rayleigh-Taylor instability with background temperature gradient

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

Gerashchenko, Sergiy; Livescu, Daniel

Here we studied the growth rate of the compressible Rayleigh-Taylor instability in the presence of a background temperature gradient, Θ, using a normal mode analysis. The effect of Θ variation is examined for three interface types corresponding to the combinations of the viscous properties of the fluids (inviscid-inviscid, viscous-viscous, and viscous-inviscid) at different Atwood numbers, At, and when at least one of the fluids' viscosity is non-zero, as a function of the Grashof number. For the general case, the resulting ordinary differential equations are solved numerically; however, dispersion relations for the growth rate are presented for several limiting cases. Anmore » analytical solution is found for the inviscid-inviscid interface and the corresponding dispersion equation for the growth rate is obtained in the limit of large Θ. For the viscous-inviscid case, a dispersion relation is derived in the incompressible limit and Θ=0. Compared to Θ=0 case, the role of Θ<0 (hotter light fluid) is destabilizing and becomes stabilizing when Θ>0 (colder light fluid). The most pronounced effect of Θ ≠ 0 is found at low At and/or at large perturbation wavelengths relative to the domain size for all interface types. On the other hand, at small perturbation wavelengths relative to the domain size, the growth rate for the Θ<0 case exceeds the infinite domain incompressible constant density result. The results are applied to two practical examples, using sets of parameters relevant to Inertial Confinement Fusion coasting stage and solar corona plumes. The role of viscosity on the growth rate reduction is discussed together with highlighting the range of wavenumbers most affected by viscosity. The viscous effects further increase in the presence of background temperature gradient, when the viscosity is temperature dependent.« less

Viscous effects on the Rayleigh-Taylor instability with background temperature gradient

DOE PAGES

Gerashchenko, Sergiy; Livescu, Daniel

2016-07-28

Here we studied the growth rate of the compressible Rayleigh-Taylor instability in the presence of a background temperature gradient, Θ, using a normal mode analysis. The effect of Θ variation is examined for three interface types corresponding to the combinations of the viscous properties of the fluids (inviscid-inviscid, viscous-viscous, and viscous-inviscid) at different Atwood numbers, At, and when at least one of the fluids' viscosity is non-zero, as a function of the Grashof number. For the general case, the resulting ordinary differential equations are solved numerically; however, dispersion relations for the growth rate are presented for several limiting cases. Anmore » analytical solution is found for the inviscid-inviscid interface and the corresponding dispersion equation for the growth rate is obtained in the limit of large Θ. For the viscous-inviscid case, a dispersion relation is derived in the incompressible limit and Θ=0. Compared to Θ=0 case, the role of Θ<0 (hotter light fluid) is destabilizing and becomes stabilizing when Θ>0 (colder light fluid). The most pronounced effect of Θ ≠ 0 is found at low At and/or at large perturbation wavelengths relative to the domain size for all interface types. On the other hand, at small perturbation wavelengths relative to the domain size, the growth rate for the Θ<0 case exceeds the infinite domain incompressible constant density result. The results are applied to two practical examples, using sets of parameters relevant to Inertial Confinement Fusion coasting stage and solar corona plumes. The role of viscosity on the growth rate reduction is discussed together with highlighting the range of wavenumbers most affected by viscosity. The viscous effects further increase in the presence of background temperature gradient, when the viscosity is temperature dependent.« less

On the stability of an infinite swept attachment line boundary layer

NASA Technical Reports Server (NTRS)

Hall, P.; Mallik, M. R.; Poll, D. I. A.

1984-01-01

The instability of an infinite swept attachment line boundary layer is considered in the linear regime. The basic three dimensional flow is shown to be susceptible to travelling wave disturbances which propagate along the attachment line. The effect of suction on the instability is discussed and the results suggest that the attachment line boundary layer on a swept wing can be significantly stabilized by extremely small amounts of suction. The results obtained are in excellent agreement with the available experimental observations.

Inequivalent coherent state representations in group field theory

NASA Astrophysics Data System (ADS)

Kegeles, Alexander; Oriti, Daniele; Tomlin, Casey

2018-06-01

In this paper we propose an algebraic formulation of group field theory and consider non-Fock representations based on coherent states. We show that we can construct representations with an infinite number of degrees of freedom on compact manifolds. We also show that these representations break translation symmetry. Since such representations can be regarded as quantum gravitational systems with an infinite number of fundamental pre-geometric building blocks, they may be more suitable for the description of effective geometrical phases of the theory.

Infrared thermography applied to the study of heated and solar pavement: from numerical modeling to small scale laboratory experiments

NASA Astrophysics Data System (ADS)

Le Touz, N.; Toullier, T.; Dumoulin, J.

2017-05-01

The present study addresses the thermal behaviour of a modified pavement structure to prevent icing at its surface in adverse winter time conditions or overheating in hot summer conditions. First a multi-physic model based on infinite elements method was built to predict the evolution of the surface temperature. In a second time, laboratory experiments on small specimen were carried out and the surface temperature was monitored by infrared thermography. Results obtained are analyzed and performances of the numerical model for real scale outdoor application are discussed. Finally conclusion and perspectives are proposed.

Study on the Equilibrium Between Liquid Iron and Calcium Vapor

NASA Astrophysics Data System (ADS)

Berg, Martin; Lee, Jaewoo; Sichen, Du

2017-06-01

The solubility of calcium in liquid iron at 1823 K and 1873 K (1550 °C and 1600 °C) as a function of calcium potential was studied experimentally. The measurements were performed using a closed molybdenum holder in which liquid calcium and liquid iron were held at different temperatures. The results indicate a linear relationship between the activity of calcium, relative to pure liquid calcium, and the mole fraction of dissolved calcium in liquid iron, with a negligible temperature dependency in the ranges studied. The activity coefficient of calcium in liquid iron at infinite dilution, γ_{Ca(l0°, was calculated as 1551.

ab initio calculation of the rate of vibrational relaxation and thermal dissociation of hydrogen by helium at high temperatures

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

Dove, J.E.; Raynor, S.

The master equation for the thermal dissociation of para-H/sub 2/ infinitely dilute in He, was solved for temperatures of 1000 to 10,000/sup 0/K. Transition probabilities, used in the master equation, were obtained, in the case of energy transfer transitions, from distorted wave and quasi-classical trajectory calculations and, for dissociative processes, from trajectory calculations alone. An ab initio potential was used. From the solution, values of the dissociation rate constant, vibrational relaxation times, and incubation times for dissociation and vibrational relaxation were calculated. The sensitivity of the calculated results to variations in the transition probabilities was examined. Vibrational relaxation is mostmore » sensitive to simultaneous transitions in vibration and rotation (VRT processes); pure rotational (RT) transitions also have a substantial effect. Dissociation is most strongly affected by RT processes, but changes in VRT and groups of dissociative transitions also have a significant effect. However complete suppression of all dissociative transitions except those from levels immediately next to the continuum lowers the dissociation rates only by a factor of about 2. The location of the dissociation ''bottleneck'' is discussed. 5 figures, 3 tables.« less

Numerical experiments with flows of elongated granules

NASA Technical Reports Server (NTRS)

Elrod, Harold G.; Brewe, David E.

1992-01-01

Theory and numerical results are given for a program simulating two dimensional granular flow (1) between two infinite, counter-moving, parallel, roughened walls, and (2) for an infinitely wide slider. Each granule is simulated by a central repulsive force field ratcheted with force restitution factor to introduce dissipation. Transmission of angular momentum between particles occurs via Coulomb friction. The effect of granular hardness is explored. Gaps from 7 to 28 particle diameters are investigated, with solid fractions ranging from 0.2 to 0.9. Among features observed are: slip flow at boundaries, coagulation at high densities, and gross fluctuation in surface stress. A videotape has been prepared to demonstrate the foregoing effects.

Density-matrix renormalization group method for the conductance of one-dimensional correlated systems using the Kubo formula

NASA Astrophysics Data System (ADS)

Bischoff, Jan-Moritz; Jeckelmann, Eric

2017-11-01

We improve the density-matrix renormalization group (DMRG) evaluation of the Kubo formula for the zero-temperature linear conductance of one-dimensional correlated systems. The dynamical DMRG is used to compute the linear response of a finite system to an applied ac source-drain voltage; then the low-frequency finite-system response is extrapolated to the thermodynamic limit to obtain the dc conductance of an infinite system. The method is demonstrated on the one-dimensional spinless fermion model at half filling. Our method is able to replicate several predictions of the Luttinger liquid theory such as the renormalization of the conductance in a homogeneous conductor, the universal effects of a single barrier, and the resonant tunneling through a double barrier.

Axisymmetric deformation in a micropolar thermoelastic medium under fractional order theory of thermoelasticity

NASA Astrophysics Data System (ADS)

Kumar, Rajneesh; Singh, Kulwinder; Pathania, Devinder Singh

2017-07-01

The purpose of this paper is to study the variations in temperature, radial and normal displacement, normal stress, shear stress and couple stress in a micropolar thermoelastic solid in the context of fractional order theory of thermoelasticity. Eigen value approach together with Laplace and Hankel transforms are employed to obtain the general solution of the problem. The field variables corresponding to different fractional order theories of thermoelasticity have been obtained in the transformed domain. The general solution is applied to an infinite space subjected to a concentrated load at the origin. To obtained solution in the physical domain numerical inversion technique has been applied and numerically computed results are depicted graphically to analyze the effects of fractional order parameter on the field variables.

Quantum Griffiths singularity of superconductor-metal transition in Ga thin films.

PubMed

Xing, Ying; Zhang, Hui-Min; Fu, Hai-Long; Liu, Haiwen; Sun, Yi; Peng, Jun-Ping; Wang, Fa; Lin, Xi; Ma, Xu-Cun; Xue, Qi-Kun; Wang, Jian; Xie, X C

2015-10-30

The Griffiths singularity in a phase transition, caused by disorder effects, was predicted more than 40 years ago. Its signature, the divergence of the dynamical critical exponent, is challenging to observe experimentally. We report the experimental observation of the quantum Griffiths singularity in a two-dimensional superconducting system. We measured the transport properties of atomically thin gallium films and found that the films undergo superconductor-metal transitions with increasing magnetic field. Approaching the zero-temperature quantum critical point, we observed divergence of the dynamical critical exponent, which is consistent with the Griffiths singularity behavior. We interpret the observed superconductor-metal quantum phase transition as the infinite-randomness critical point, where the properties of the system are controlled by rare large superconducting regions. Copyright © 2015, American Association for the Advancement of Science.

Similarity solutions for unsteady free-convection flow from a continuous moving vertical surface

NASA Astrophysics Data System (ADS)

Abd-El-Malek, Mina B.; Kassem, Magda M.; Mekky, Mohammad L.

2004-03-01

The transformation group theoretic approach is applied to present an analysis of the problem of unsteady free convection flow over a continuous moving vertical sheet in an ambient fluid. The thermal boundary layer induced within a vertical semi-infinite layer of Boussinseq fluid by a constant heated bounding plate. The application of two-parameter groups reduces the number of independent variables by two, and consequently the system of governing partial differential equations with the boundary conditions reduces to a system of ordinary differential equations with appropriate boundary conditions. The obtained ordinary differential equations are solved analytically for the temperature and numerically for the velocity using the shooting method. Effect of Prandtl number on the thermal boundary-layer and velocity boundary-layer are studied and plotted in curves.

Infinite Multiplets

DOE R&D Accomplishments Database

Nambu, Y.

1967-01-01

The main ingredients of the method of infinite multiplets consist of: 1) the use of wave functions with an infinite number of components for describing an infinite tower of discrete states of an isolated system (such as an atom, a nucleus, or a hadron), 2) the use of group theory, instead of dynamical considerations, in determining the properties of the wave functions.

Boundary Conditions for Infinite Conservation Laws

NASA Astrophysics Data System (ADS)

Rosenhaus, V.; Bruzón, M. S.; Gandarias, M. L.

2016-12-01

Regular soliton equations (KdV, sine-Gordon, NLS) are known to possess infinite sets of local conservation laws. Some other classes of nonlinear PDE possess infinite-dimensional symmetries parametrized by arbitrary functions of independent or dependent variables; among them are Zabolotskaya-Khokhlov, Kadomtsev-Petviashvili, Davey-Stewartson equations and Born-Infeld equation. Boundary conditions were shown to play an important role for the existence of local conservation laws associated with infinite-dimensional symmetries. In this paper, we analyze boundary conditions for the infinite conserved densities of regular soliton equations: KdV, potential KdV, Sine-Gordon equation, and nonlinear Schrödinger equation, and compare them with boundary conditions for the conserved densities obtained from infinite-dimensional symmetries with arbitrary functions of independent and dependent variables.

Assessment of the thermodynamic properties of poly(2,2,2-trifluoroethyl methacrylate) by inverse gas chromatography.

PubMed

Papadopoulou, Stella K; Panayiotou, Costas

2014-01-10

The thermodynamic properties of poly(2,2,2-trifluoroethyl methacrylate) (PTFEMA) were determined by the aid of the inverse gas chromatography technique (IGC), at infinite dilution. The interactions between the polymer and 15 solvents were examined in the temperature range of 120-150 °C via the estimation of the thermodynamic sorption parameters, the parameters of mixing at infinite dilution, the weight fraction activity coefficients and the Flory-Huggins interaction parameters. Additionally, the total and the partial solubility parameters of PTFEMA were estimated. The findings of this work indicate that the type and strength of the intermolecular interactions between the polymer and the solvents are strongly depended on the functional groups of the polymer and the solvents. The proton acceptor character of the polymer is responsible for the preferential solubility of PTFEMA in chloroform which acts as a proton donor solvent. The results also reveal that the polymer is insoluble in alkanes and alcohols whereas it presents good miscibility with polar solvents, especially with 2-butanone, 2-pentanone and 1,4-dioxane. Furthermore, the total and dispersive solubility parameters appear diminishing upon temperature rise, whereas the opposite behavior is noticed for the polar and hydrogen bonding solubility parameters. The latter increase with temperature, probably, due to conformational changes of the polymer on the solid support. Finally, comparison of the solubilization profiles of fluorinated methacrylic polymers studied by IGC, leads to the conclusion that PTFEMA is more soluble compared to polymers with higher fluorine content. Copyright © 2013 Elsevier B.V. All rights reserved.

A CTRW-based model of time-resolved fluorescence lifetime imaging in a turbid medium

NASA Astrophysics Data System (ADS)

Chernomordik, Victor; Gandjbakhche, Amir H.; Hassan, Moinuddin; Pajevic, Sinisa; Weiss, George H.

2010-12-01

We develop an analytic model of time-resolved fluorescent imaging of photons migrating through a semi-infinite turbid medium bounded by an infinite plane in the presence of a single stationary point fluorophore embedded in the medium. In contrast to earlier models of fluorescent imaging in which photon motion is assumed to be some form of continuous diffusion process, the present analysis is based on a continuous-time random walk (CTRW) on a simple cubic lattice, the objective being to estimate the position and lifetime of the fluorophore. This can provide information related to local variations in pH and temperature with potential medical significance. Aspects of the theory were tested using time-resolved measurements of the fluorescence from small inclusions inside tissue-like phantoms. The experimental results were found to be in good agreement with theoretical predictions provided that the fluorophore was not located too close to the planar boundary, a common problem in many diffusive systems.

Synthesis, Structure and bonding Analysis of the Polar Intermetallic Phase Ca2Pt2Cd

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

Samal, Saroj L.; Corbett, John D.

The polar intermetallic phase Ca2Pt2Cd was discovered during explorations of the Ca-Pt-Cd system. The compound was synthesized by high temperature reactions, and its structure refined by single-crystal X-ray diffraction as orthorhombic, Immm, a = 4.4514(5), b = 5.8415(6), c = 8.5976(9) Å, Z = 2. The structure formally contains infinite, planar networks of [Pt2Cd]4– along the ab plane, which can be described as tessellation of six and four-member rings of the anions, with cations stuffed between the anion layers. The infinite condensed platinum chains show a substantial long–short distortion of 0.52 Å, an appreciable difference between Ca2Pt2Cd (26 valence electrons)more » and the isotypic but regular Ca2Cu2Ga (29 VE). The relatively large cation proportion diminishes the usual dominance of polar (Pt–Cd) and 5d–5d (Pt–Pt) contributions to the total Hamilton populations.« less

Electronic transport close to semi-infinite 2D systems and their interfaces

NASA Astrophysics Data System (ADS)

Xia, Fanbing; Wang, Jian; Jian Wang's research Group Team

Transport properties of 2D materials especially close to their boundary has received much attention after the successful fabrication of Graphene. While most previous work is devoted to the conventional lead-device-lead setup with a finite size center area, this project investigates real space transport properties of infinite and semi-infinite 2D systems under the framework of Non-equilibrium Green's function. The commonly used method of calculating Green's function by inverting matrices in the real space can be unstable in dealing with large systems as sometimes it gives non-converging result. By transforming from the real space to momentum space, the author managed to replace the matrix inverting process by Brillouin Zone integral which can be greatly simplified by the application of contour integral. Combining this methodology with Dyson equations, we are able to calculate transport properties of semi-infinite graphene close to its zigzag boundary and its combination with other material including s-wave superconductor. Interference pattern of transmitted and reflected electrons, Graphene lensing effects and difference between Specular Andreev reflection and normal Andreev reflection are verified. We also generalize how to apply this method to a broad range of 2D materials. The University of Hong Kong.

Modeling solubility of CO2/hydrocarbon gas in ionic liquid ([emim][FAP]) using Aspen Plus simulations.

PubMed

Bagchi, Bishwadeep; Sati, Sushmita; Shilapuram, Vidyasagar

2017-08-01

The Peng-Robinson equation of state with quadratic van der Waals (vdW) mixing rule model was chosen to perform the thermodynamic calculations in Flash3 column of Aspen Plus to predict the solubility of CO 2 or any one of the hydrocarbons (HCs) among methane, ethane, propane, and butane in an ionic liquid 1-ethyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate ([emim][FAP]). Bubble point pressure, solubility, bubble point temperature, fugacity, and partial molar volume at infinite dilution were obtained from the simulations, and enthalpy of absorption, Gibbs free energy of solvation, and entropy change of absorption were estimated by thermodynamic relations. Results show that carbon chain length has a significant effect on the bubble point pressure. Methane has the highest bubble point pressure among all the considered HCs and CO 2 . The bubble point pressure and fugacity variation with temperature is different for CO 2 as compared to HCs for mole fractions above 0.2. Two different profiles are noticed for enthalpy of absorption when plotted as a function of mole fraction of gas soluble in IL. Partial molar volume of CO 2 decreases with increase in temperature in [emim][FAP], while it is increased for HCs. Bubble point temperature decreases with increase in the mole fraction of the solute. Entropy of solvation increases with temperature till a particular value followed by a decrease with further increase in temperature. Gibbs free energy change of solvation showed that the process of solubility was spontaneous.

The effect of a uniform magnetic field on the onset of steady Benard-Marangoni convection in a layer of conducting fluid

NASA Astrophysics Data System (ADS)

Wilson, S. K.

1993-05-01

Analytical and numerical techniques are used to analyze the effect of a uniform vertical magnetic field on the onset of steady Benard-Marangoni convection in a horizontal layer of quiescent, electrically conducting fluid subject to a uniform vertical temperature gradient. Marangoni numbers for the onset of steady convection are found to be critically dependent on the nondimensional Crispation and Bond numbers. Two different asymptotic limits of strong surface tension and strong magnetic field are analyzed. Data obtained indicate that the presence of the magnetic field always has a stabilizing effect on the layer. Assuming that the Marangoni number is a critical parameter, it is shown that, if the free surface is nondeformable, then any particular disturbance can be stabilized with a sufficiently strong magnetic field. If the free surface is deformable and gravity waves are excluded, then the layer is always unstable to infinitely long wavelength disturbances with or without a magnetic field.

Auto-ignition of methane-air mixtures flowing along an array of thin catalytic plates

NASA Astrophysics Data System (ADS)

Treviño, C.

2010-12-01

In this paper, the heterogeneous ignition of a methane-air mixture flowing along an infinite array of catalytic parallel plates has been studied by inclusion of gas expansion effects and the finite heat conduction on the plates. The system of equations considers the full compressible Navier-Stokes equations coupled with the energy equations of the plates. The gas expansion effects which arise from temperature changes have been considered. The heterogeneous kinetics considers the adsorption and desorption reactions for both reactants. The limits of large and small longitudinal thermal conductance of the plate material are analyzed and the critical conditions for ignition are obtained in closed form. The governing equations are solved numerically using finite differences. The results show that ignition is more easily produced as the longitudinal wall thermal conductance increases, and the effects of the gas expansion on the catalytic ignition process are rather small due to the large value of the activation energy of the desorption reaction of adsorbed oxygen atoms.

Emittance Theory for Cylindrical Fiber Selective Emitter

NASA Technical Reports Server (NTRS)

Chubb, Donald L.

1998-01-01

A fibrous rare earth selective emitter is approximated as an infinitely long, cylinder. The spectral emittance, e(sub x), is obtained L- by solving the radiative transfer equations with appropriate boundary conditions and uniform temperature. For optical depth, K(sub R), where alpha(sub lambda), is the extinction coefficient and R is the cylinder radius, greater than 1 the spectral emittance depths, K(sub R) alpha(sub lambda)R, is nearly at its maximum value. There is an optimum cylinder radius, R(sub opt) for maximum emitter efficiency, n(sub E). Values for R(sub opt) are strongly dependent on the number of emission bands of the material. The optimum radius decreases slowly with increasing emitter temperature, while the maximum efficiency and useful radiated power increase rapidly with increasing, temperature.

The electronic and optical properties of quantum nano-structures

NASA Astrophysics Data System (ADS)

Ham, Heon

In semiconducting quantum nano-structures, the excitonic effects play an important role when we fabricate opto-electronic devices, such as lasers, diodes, detectors, etc. To gain a better understanding of the excitonic effects in quantum nano-structures, we investigated the exciton binding energy, oscillator strength, and linewidth in quantum nano-structures using both the infinite and finite well models. We investigated also the hydrogenic impurity binding energy and the photoionization cross section of the hydrogenic impurity in a spherical quantum dot. In our work, the variational approach is used in all calculations, because the Hamiltonian of the system is not separable, due to the different symmetries of the Coulomb and confining potentials. In the infinite well model of the semiconducting quantum nanostructures, the binding energy of the exciton increases with decreasing width of the potential barriers due to the increase in the effective strength of the Coulomb interaction between the electron and hole. In the finite well model, the exciton binding energy reaches a peak value, and the binding energy decreases with further decrease in the width of the potential barriers. The exciton linewidth in the infinite well model increases with decreasing wire radius, because the scattering rate of the exciton increases with decreasing wire radius. In the finite well model, the exciton linewidth in a cylindrical quantum wire reaches a peak value and the exciton linewidth decreases with further decrease in the wire radius, because the exciton is not well confined at very smaller wire radii. The binding energy of the hydrogenic impurity in a spherical quantum dot has also calculated using both the infinite and the finite well models. The binding energy of the hydrogenic impurity was calculated for on center and off center impurities in the spherical quantum dots. With decreasing radii of the dots, the binding energy of the hydrogenic impurity increases in the infinite well model. The binding energy of the hydrogenic impurity in the finite well model reaches a peak value and decreases with further decrease in the dot radii for both on center and off center impurities. We have calculated the photoionization cross section as a function of the radius and the frequency using both the infinite and finite well models. The photoionizaton cross section has a peak value at a frequency where the photon energy equals the difference between the final and initial state energies of the impurity. The behavior of the cross section with dot radius depends upon the location of the impurity and the polarization of the electromagnetic field.

Input Sources of Third Person Singular –s Inconsistency in Children with and without Specific Language Impairment*

PubMed Central

Leonard, Laurence B.; Fey, Marc E.; Deevy, Patricia; Bredin-Oja, Shelley L.

2015-01-01

We tested four predictions based on the assumption that optional infinitives can be attributed to properties of the input whereby children inappropriately extract nonfinite subject-verb sequences (e.g. the girl run) from larger input utterances (e.g. Does the girl run? Let’s watch the girl run). Thirty children with specific language impairment (SLI) and 30 typically developing children heard novel and familiar verbs that appeared exclusively either in utterances containing nonfinite subject-verb sequences or in simple sentences with the verb inflected for third person singular –s. Subsequent testing showed strong input effects, especially for the SLI group. The results provide support for input-based factors as significant contributors not only to the optional infinitive period in typical development, but also to the especially protracted optional infinitive period seen in SLI. PMID:25076070

Can increasing the viscosity of formulations be used to reduce the human skin penetration of the sunscreen oxybenzone?

PubMed

Cross, S E; Jiang, R; Benson, H A; Roberts, M S

2001-07-01

The effect of adding thickening agents on the penetration of a sunscreen benzophenone-3 through epidermal and a high-density polyethylene membrane was studied using both very thick (infinite dose) and thin (in use) applications. Contradictory results were obtained. Thickening agents retard skin penetration, in a manner consistent with a diffusional resistance in the formulation, when applied as an infinite dose. In contrast, when applied as in thin (in use) doses, thickening agents promote penetration, most likely through greater stratum corneum diffusivity arising from an enhanced hydration by the thicker formulations. The two key implications from this work are (i) a recognition of the danger in the potential extrapolation of infinite dosing to in use situations, and (ii) to recognize that thicker formulations may sometimes enhance the penetration of other topical agents when applied "in use".

Dynamic Infinite Mixed-Membership Stochastic Blockmodel.

PubMed

Fan, Xuhui; Cao, Longbing; Xu, Richard Yi Da

2015-09-01

Directional and pairwise measurements are often used to model interactions in a social network setting. The mixed-membership stochastic blockmodel (MMSB) was a seminal work in this area, and its ability has been extended. However, models such as MMSB face particular challenges in modeling dynamic networks, for example, with the unknown number of communities. Accordingly, this paper proposes a dynamic infinite mixed-membership stochastic blockmodel, a generalized framework that extends the existing work to potentially infinite communities inside a network in dynamic settings (i.e., networks are observed over time). Additional model parameters are introduced to reflect the degree of persistence among one's memberships at consecutive time stamps. Under this framework, two specific models, namely mixture time variant and mixture time invariant models, are proposed to depict two different time correlation structures. Two effective posterior sampling strategies and their results are presented, respectively, using synthetic and real-world data.

Experimental and theoretical aspects of studying themodynamics and mass transport in polymer-solvent systems

NASA Astrophysics Data System (ADS)

Davis, Peter Kennedy

Mass transport and thermodynamics in polymer-solvent systems are two key areas of importance to the polymer industry. Numerous processes including polymerization reactors, membrane separations, foam production, devolatilization processes, film and coating drying, supercritical extractions, drug delivery, and even nano-technology require fundamental phase equilibria and diffusion information. Although such information is vital in equipment design and optimization, acquisition and modeling of these data are still in the research and development stages. This thesis is rather diverse as it addresses many realms of this broad research area. From high pressure to low pressure, experimental to theoretical, and infinite dilution to finite concentration, the thesis covers a wide range of topics that are of current importance to the industrial and academic polymer community. Chapter 1 discusses advances in the development of a new volumetric sorption pressure decay technique to make phase equilibrium and diffusion measurements in severe temperature-pressure environments. Chapter 2 provides the derivations and results of a new completely predictive Group Contribution Lattice Fluid Equation of State for multi-component polymer-solvent systems. The remaining four chapters demonstrate advances in the modeling of inverse gas chromatography (IGC) experiments. IGC has been used extensively of the last 50 years to make low pressure sorption and diffusion measurements at infinitely dilute and finite solvent concentrations. Chapter 3 proposes a new IGC experiment capable of obtaining ternary vapor-liquid equilibria in polymer-solvent-solvent systems. Also in that chapter, an extensive derivation is provided for a continuum model capable of describing the results of such an experiment. Chapter 4 presents new data collected on a packed column IGC experiment and a new model that can be used with those experimental data to obtain diffusion and partition coefficients. Chapter 5 addresses a rather controversial topic about IGC experiments near the polymer glass transition temperature. Using a new IGC model capable of describing both bulk absorption and surface adsorption, IGC behavior around the glass transition was able to be better understood. Finally, Chapter 6 presents an IGC model that can be used to separate bulk effects from surface effects in capillary column IGC experiments.

Magnetism and structural chemistry of ternary borides RE2MB 6 ( RE = rare earth, M = Ru, Os)

NASA Astrophysics Data System (ADS)

Hiebl, K.; Rogl, P.; Nowotny, H.

1984-10-01

The magnetic behavior of the ternary borides RE2RuB 6 and RE2OsB 6 ( RE = Y, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) was studied in the temperature range 1.5 K < T < 1100 K. All compounds crystallize with the Y 2ReB 6-type structure and are characterized by direct RE- RE contacts and the formation of planar infinite two-dimensional rigid boron nets. The magnetic properties reveal a typical Van Vleck paramagnetism of free RE3+-ions at temperatures higher than 200 K with ferromagnetic interaction in the low-temperature range T < 55 K. The ferromagnetic ordering temperatures vary with the De Gennes factor. There is no indication for a magnetic contribution from the Ru(Os)-sublattice. Above 1.8 K none of the samples were found to be superconducting.

Practical deviations from Henry`s law for water/air partitioning of volatile organic compounds

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

Schabron, J.F.; Rovani, J.F. Jr.

A study was conducted to define parameters relating to the use of a down hole submersible photoionization detector (PID) probe to measure volatile organic compounds (VOCs) in an artificial headspace. The partitioning of toluene and trichloroethylene between water and air was studied as a function of analyte concentration and water temperature. The Henry`s law constant governing this partitioning represents an ideal condition at infinite dilution for a particular temperature. The results show that in practice. this partitioning is far from ideal. Conditions resulting in apparent, practical deviations from Henry`s law include temperature and VOC concentration. Thus, a single value ofmore » Henry`s law constant for a particular VOC such as toluene can provide only an approximation of concentration in the field. Detector response in saturated humidity environments as a function of water temperature and analyte concentration was studied also.« less

Convective flow in the solid rotation of a viscous incompressible fluid

NASA Astrophysics Data System (ADS)

Gorshkov, A. V.; Prosviryakov, E. Yu.

2017-12-01

The analytical solution of the Ekman convective stationary flow of a viscous incompressible fluid in an infinite layer is obtained. A solution to an overdetermined system of the Oberbeck-Boussinesq equations is considered. It is shown that the structure of the solution allows one to preserve the advective derivative in the heat equation; this makes it possible to model the delamination of the temperature and pressure fields and to describe backflow in the ocean.

Dynamical conductivity at the dirty superconductor-metal quantum phase transition.

PubMed

Del Maestro, Adrian; Rosenow, Bernd; Hoyos, José A; Vojta, Thomas

2010-10-01

We study the transport properties of ultrathin disordered nanowires in the neighborhood of the superconductor-metal quantum phase transition. To this end we combine numerical calculations with analytical strong-disorder renormalization group results. The quantum critical conductivity at zero temperature diverges logarithmically as a function of frequency. In the metallic phase, it obeys activated scaling associated with an infinite-randomness quantum critical point. We extend the scaling theory to higher dimensions and discuss implications for experiments.

Multiscale implementation of infinite-swap replica exchange molecular dynamics.

PubMed

Yu, Tang-Qing; Lu, Jianfeng; Abrams, Cameron F; Vanden-Eijnden, Eric

2016-10-18

Replica exchange molecular dynamics (REMD) is a popular method to accelerate conformational sampling of complex molecular systems. The idea is to run several replicas of the system in parallel at different temperatures that are swapped periodically. These swaps are typically attempted every few MD steps and accepted or rejected according to a Metropolis-Hastings criterion. This guarantees that the joint distribution of the composite system of replicas is the normalized sum of the symmetrized product of the canonical distributions of these replicas at the different temperatures. Here we propose a different implementation of REMD in which (i) the swaps obey a continuous-time Markov jump process implemented via Gillespie's stochastic simulation algorithm (SSA), which also samples exactly the aforementioned joint distribution and has the advantage of being rejection free, and (ii) this REMD-SSA is combined with the heterogeneous multiscale method to accelerate the rate of the swaps and reach the so-called infinite-swap limit that is known to optimize sampling efficiency. The method is easy to implement and can be trivially parallelized. Here we illustrate its accuracy and efficiency on the examples of alanine dipeptide in vacuum and C-terminal β-hairpin of protein G in explicit solvent. In this latter example, our results indicate that the landscape of the protein is a triple funnel with two folded structures and one misfolded structure that are stabilized by H-bonds.

Electric and magnetic microfields inside and outside space-limited configurations of ions and ionic currents

NASA Astrophysics Data System (ADS)

Romanovsky, M. Yu; Ebeling, W.; Schimansky-Geier, L.

2005-01-01

The problem of electric and magnetic microfields inside finite spherical systems of stochastically moving ions and outside them is studied. The first possible field of applications is high temperature ion clusters created by laser fields [1]. Other possible applications are nearly spherical liquid systems at room-temperature containing electrolytes. Looking for biological applications we may also think about a cell which is a complicated electrolytic system or even a brain which is a still more complicated system of electrolytic currents. The essential model assumption is the random character of charges motion. We assume in our basic model that we have a finite nearly spherical system of randomly moving charges. Even taking into account that this is at best a caricature of any real system, it might be of interest as a limiting case, which admits a full theoretical treatment. For symmetry reasons, a random configuration of moving charges cannot generate a macroscopic magnetic field, but there will be microscopic fluctuating magnetic fields. Distributions for electric and magnetic microfields inside and outside such space- limited systems are calculated. Spherical systems of randomly distributed moving charges are investigated. Starting from earlier results for infinitely large systems, which lead to Holtsmark- type distributions, we show that the fluctuations in finite charge distributions are larger (in comparison to infinite systems of the same charge density).

Structural properties and magic structures in hydrogenated finite and infinite silicon nanowires

NASA Astrophysics Data System (ADS)

Zdetsis, A. D.; Koukaras, E. N.; Garoufalis, C. S.

2007-11-01

Unusual effects such as bending and "canting," related with the stability, have been identified by ab initio real-space calculations for hydrogenated silicon nanowires. We have examined in detail the electronic and structural properties of finite and infinite nanowires as a function of length (and width) and have developed stability and bending rules, demonstrating that "magic" wires do not bend. Reconstructed 2×1 nanowires are practically as stable as the magic ones. Our calculations are in good agreement with the experimental data of Ma et al. [Science 299, 1874 (2003).].

Resonant frequency of microstrip antennas calculated from TE-excitation of an infinite strip embedded in a grounded dielectric slab

NASA Technical Reports Server (NTRS)

Bailey, M. C.

1979-01-01

The calculation of currents induced by a plane wave normally incident upon an infinite strip embedded in a grounded dielectric slab is used to infer the resonant width (or frequency) of rectangular microstrip antennas. By placing the strip inside the dielectric, the effect of a dielectric cover of the same material as the substrate can be included in the calculation of resonant frequency. A comparison with measured results indicated agreement of 1 percent or better for rectangular microstrip antennas constructed on Teflon-fiberglass substrate.

Determination of thermodynamic properties of isotactic poly(1-butene) at infinite dilution using density and inverse gas chromatography.

PubMed

Kozłowska, Marta Karolina; Domańska, Urszula; Lempert, Małgorzata; Rogalski, Marek

2005-03-18

The partial molar volumes, V1(M), and the molar volume of isotactic crystalline low-molecular-weight poly(1-butene), iPBu-1, V1, have been calculated from the measured density of {iPBu-1 + solvent (n-hexane, n-heptane, n-nonane, n-decane, p-xylene, cyclohexane and chloroform)} systems. Some of the thermodynamic quantities were also obtained for the iPBu-1 with eight hydrocarbons (n-octane, n-decane, n-undecane, n-dodecane, n-tridecane, o-xylene, m-xylene, p-xylene) by the method of inverse gas chromatography at various temperatures. The weight fraction activity coefficients of the solvent at infinite dilution, omega2(infinity) and the Flory-Huggins thermodynamic interaction parameters, chi21(infinity), between polymer and solvents were determined. The partial molar free energy, deltaG2(infinity), the partial molar heat of mixing, deltaH2(infinity), at infinite dilution and the polymer solubility parameter, delta1, were calculated. Additionally, the (solid + liquid) binary mixtures equilibria, SLE, of iPBu-1 with three hydrocarbons (n-octane, n-decane and m-xylene) were studied by a dynamic method. By performing these experiments over a large concentration range, the T-x phase diagrams of the polymer-solvent systems were constructed. The excess Gibbs energy models were used to describe the nonideal behaviour of the liquid phase. The omega2(infinity) were determined from the solubility measurements and were predicted by using the UNIFAC FV model.

A model of freezing foods with liquid nitrogen using special functions

NASA Astrophysics Data System (ADS)

Rodríguez Vega, Martín.

2014-05-01

A food freezing model is analyzed analytically. The model is based on the heat diffusion equation in the case of cylindrical shaped food frozen by liquid nitrogen; and assuming that the thermal conductivity of the cylindrical food is radially modulated. The model is solved using the Laplace transform method, the Bromwich theorem, and the residue theorem. The temperature profile in the cylindrical food is presented as an infinite series of special functions. All the required computations are performed with computer algebra software, specifically Maple. Using the numeric values of the thermal and geometric parameters for the cylindrical food, as well as the thermal parameters of the liquid nitrogen freezing system, the temporal evolution of the temperature in different regions in the interior of the cylindrical food is presented both analytically and graphically. The duration of the liquid nitrogen freezing process to achieve the specified effect on the cylindrical food is computed. The analytical results are expected to be of importance in food engineering and cooking engineering. As a future research line, the formulation and solution of freezing models with thermal memory is proposed.

The generation of thermal stress and strain during quenching

NASA Astrophysics Data System (ADS)

Soomro, A. B.

A viscoelastic-plastic mathematical model was used to calculate the thermal stress and strain generated during the quenching of an infinite plate of high hardenability steel (835M30) in water, oil and Polymer. In the present work the mathematical model was modified to include the effect of initial stress on the rate of stress relaxation, which has been found to be significant. The data required to incorporate this effect into the calculations, were obtained experimentally during the-.present investigation. The effect of an applied stress during transformation (transformation plasticity) was also introduced in the mathematical model. The new model produced a marked improvement in the degree of agreement between the calculated and experimental residual stress, although the corresponding level of agreement in the case of residual strain was less good. In particular, strains after water quenching agreed less well with experiment as a consequence of the change in the model, although this drawback was not found after oil and polymer quenching. The new mathematical model was used to investigate the effect of martempering, section size and transformation temperature range on the generation of thermal stress and strain. A salt bath treatment above the Ms temperature followed by air cooling prevented residual stress development, but an oil quench after the salt bath treatment generated a level of residual stress at the end of cooling that was similar to that obtained after a direct oil quench from 850°C. Neither martempering process was successful in reducing residual strain.With.an increase in section size a reduction in the residual stress and an increase in the distortions was obtained after a water quench. However, after oil quenching the overall effect of section size on residual stress and strain was small. The effect of variation in the transformation temperature range was found to be small in the case of residual stress but an increase in Ms temperature produced a significant increase in the level of residual strain.

Testing density-dependent groundwater models: Two-dimensional steady state unstable convection in infinite, finite and inclined porous layers

USGS Publications Warehouse

Weatherill, D.; Simmons, C.T.; Voss, C.I.; Robinson, N.I.

2004-01-01

This study proposes the use of several problems of unstable steady state convection with variable fluid density in a porous layer of infinite horizontal extent as two-dimensional (2-D) test cases for density-dependent groundwater flow and solute transport simulators. Unlike existing density-dependent model benchmarks, these problems have well-defined stability criteria that are determined analytically. These analytical stability indicators can be compared with numerical model results to test the ability of a code to accurately simulate buoyancy driven flow and diffusion. The basic analytical solution is for a horizontally infinite fluid-filled porous layer in which fluid density decreases with depth. The proposed test problems include unstable convection in an infinite horizontal box, in a finite horizontal box, and in an infinite inclined box. A dimensionless Rayleigh number incorporating properties of the fluid and the porous media determines the stability of the layer in each case. Testing the ability of numerical codes to match both the critical Rayleigh number at which convection occurs and the wavelength of convection cells is an addition to the benchmark problems currently in use. The proposed test problems are modelled in 2-D using the SUTRA [SUTRA-A model for saturated-unsaturated variable-density ground-water flow with solute or energy transport. US Geological Survey Water-Resources Investigations Report, 02-4231, 2002. 250 p] density-dependent groundwater flow and solute transport code. For the case of an infinite horizontal box, SUTRA results show a distinct change from stable to unstable behaviour around the theoretical critical Rayleigh number of 4??2 and the simulated wavelength of unstable convection agrees with that predicted by the analytical solution. The effects of finite layer aspect ratio and inclination on stability indicators are also tested and numerical results are in excellent agreement with theoretical stability criteria and with numerical results previously reported in traditional fluid mechanics literature. ?? 2004 Elsevier Ltd. All rights reserved.

Pressure-induced stable BeN4 as a high-energy density material

NASA Astrophysics Data System (ADS)

Zhang, Shoutao; Zhao, Ziyuan; Liu, Lulu; Yang, Guochun

2017-10-01

Polynitrogens are the ideal rocket fuels or propellants. Due to strong triple N≡N bond in N2, the direct polymerization of nitrogen is rather difficult (i.e. extreme high temperature and high pressure). However, the use of nitrides as precursors or the reaction of N2 with other elements has been proved to be an effective way to obtain polynitrogens. Here, with assistance of the advanced first-principles swarm-intelligence structure searches, we found that P 1 bar -BeN4, containing infinite zigzag-like polymeric nitrogen chains, can be synthesized by compressing the mixture of Be3N2 and N2 at 25.4 GPa, which is greatly lower than 110 GPa for synthesizing cubic gauche nitrogen and other polynitrogen compounds (e.g. bulk CNO at 52 GPa and SN4 at 49 GPa). Its structural stability can be attributed to the coexistence of ionic Be-N and covalent N-N bonds. Intriguingly, this phase has high kinetic stability and remains metastable at ambient pressure. The exceptional properties, including high energy density (3.60 kJ g-1), high nitrogen content (86.1%), high dynamical stability, and low polymerization pressure, make P 1 bar -structured BeN4 a promising high energy material. Infinite nitrogen chains in P 1 bar -BeN4 transform to N10 rings network in P21/c phase at 115.1 GPa. P 1 bar -BeN4 is metallic, while P21/c-BeN4 is an insulator.

Gas-liquid coexistence for the boson square-well fluid and the (4)He binodal anomaly.

PubMed

Fantoni, Riccardo

2014-08-01

The binodal of a boson square-well fluid is determined as a function of the particle mass through a quantum Gibbs ensemble Monte Carlo algorithm devised by R. Fantoni and S. Moroni [J. Chem. Phys. (to be published)]. In the infinite mass limit we recover the classical result. As the particle mass decreases, the gas-liquid critical point moves at lower temperatures. We explicitly study the case of a quantum delocalization de Boer parameter close to the one of (4)He. For comparison, we also determine the gas-liquid coexistence curve of (4)He for which we are able to observe the binodal anomaly below the λ-transition temperature.

Electromagnetic Scattering by Multiple Cavities Embedded in the Infinite 2D Ground Plane

DTIC Science & Technology

2014-07-01

Electromagnetic Scattering by Multiple Cavities Embedded in the Infinite 2D Ground Plane Peijun Li 1 and Aihua W. Wood 2 1 Department of...of the electromagnetic wave scattering by multiple open cavities, which are embedded in an infinite two-dimensional ground plane . By introducing a...equation, variational formulation. I. INTRODUCTION A cavity is referred to as a local perturbation of the infinite ground plane . Given the cavity

Floquet–Magnus theory and generic transient dynamics in periodically driven many-body quantum systems

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

Kuwahara, Tomotaka, E-mail: tomotaka.phys@gmail.com; WPI, Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577; Mori, Takashi

2016-04-15

This work explores a fundamental dynamical structure for a wide range of many-body quantum systems under periodic driving. Generically, in the thermodynamic limit, such systems are known to heat up to infinite temperature states in the long-time limit irrespective of dynamical details, which kills all the specific properties of the system. In the present study, instead of considering infinitely long-time scale, we aim to provide a general framework to understand the long but finite time behavior, namely the transient dynamics. In our analysis, we focus on the Floquet–Magnus (FM) expansion that gives a formal expression of the effective Hamiltonian onmore » the system. Although in general the full series expansion is not convergent in the thermodynamics limit, we give a clear relationship between the FM expansion and the transient dynamics. More precisely, we rigorously show that a truncated version of the FM expansion accurately describes the exact dynamics for a certain time-scale. Our theory reveals an experimental time-scale for which non-trivial dynamical phenomena can be reliably observed. We discuss several dynamical phenomena, such as the effect of small integrability breaking, efficient numerical simulation of periodically driven systems, dynamical localization and thermalization. Especially on thermalization, we discuss a generic scenario on the prethermalization phenomenon in periodically driven systems. -- Highlights: •A general framework to describe transient dynamics for periodically driven systems. •The theory is applicable to generic quantum many-body systems including long-range interacting systems. •Physical meaning of the truncation of the Floquet–Magnus expansion is rigorously established. •New mechanism of the prethermalization is proposed. •Revealing an experimental time-scale for which non-trivial dynamical phenomena can be reliably observed.« less

Asymmetrical effects of mesophyll conductance on fundamental photosynthetic parameters and their relationships estimated from leaf gas exchange measurements.

PubMed

Sun, Ying; Gu, Lianhong; Dickinson, Robert E; Pallardy, Stephen G; Baker, John; Cao, Yonghui; DaMatta, Fábio Murilo; Dong, Xuejun; Ellsworth, David; Van Goethem, Davina; Jensen, Anna M; Law, Beverly E; Loos, Rodolfo; Martins, Samuel C Vitor; Norby, Richard J; Warren, Jeffrey; Weston, David; Winter, Klaus

2014-04-01

Worldwide measurements of nearly 130 C3 species covering all major plant functional types are analysed in conjunction with model simulations to determine the effects of mesophyll conductance (g(m)) on photosynthetic parameters and their relationships estimated from A/Ci curves. We find that an assumption of infinite g(m) results in up to 75% underestimation for maximum carboxylation rate V(cmax), 60% for maximum electron transport rate J(max), and 40% for triose phosphate utilization rate T(u) . V(cmax) is most sensitive, J(max) is less sensitive, and T(u) has the least sensitivity to the variation of g(m). Because of this asymmetrical effect of g(m), the ratios of J(max) to V(cmax), T(u) to V(cmax) and T(u) to J(max) are all overestimated. An infinite g(m) assumption also limits the freedom of variation of estimated parameters and artificially constrains parameter relationships to stronger shapes. These findings suggest the importance of quantifying g(m) for understanding in situ photosynthetic machinery functioning. We show that a nonzero resistance to CO2 movement in chloroplasts has small effects on estimated parameters. A non-linear function with gm as input is developed to convert the parameters estimated under an assumption of infinite gm to proper values. This function will facilitate gm representation in global carbon cycle models. © 2013 John Wiley & Sons Ltd.

Solute atmospheres at dislocations

DOE PAGES

Hirth, John P.; Barnett, David M.; Hoagland, Richard G.

2017-06-01

In this study, a two-dimensional plane strain elastic solution is determined for the Cottrell solute atmosphere around an edge dislocation in an infinitely long cylinder of finite radius (the matrix), in which rows of solutes are represented by cylindrical rods with in-plane hydrostatic misfit (axial misfit is also considered). The periphery of the matrix is traction-free, thus introducing an image solute field which generates a solute-solute interaction energy that has not been considered previously. The relevant energy for the field of any distribution of solutes coexistent with a single edge dislocation along the (matrix) cylinder axis is determined, and coherencymore » effects are discussed and studied. Monte Carlo simulations accounting for all pertinent interactions over a range of temperatures are found to yield solute distributions different from classical results, namely, (1) Fermi-Dirac condensations at low temperatures at the free surface, (2) the majority of the atmosphere lying within an unexpectedly large non-linear interaction region near the dislocation core, and (3) temperature-dependent asymmetrical solute arrangements that promote bending. The solute distributions at intermediate temperatures show a 1/r dependence in agreement with previous linearized approximations. With a standard state of solute corresponding to a mean concentration, c 0, the relevant interaction energy expression presented in this work is valid when extended to large concentrations for which Henry's Law and Vegard's Law do not apply.« less

Solute atmospheres at dislocations

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

Hirth, John P.; Barnett, David M.; Hoagland, Richard G.

In this study, a two-dimensional plane strain elastic solution is determined for the Cottrell solute atmosphere around an edge dislocation in an infinitely long cylinder of finite radius (the matrix), in which rows of solutes are represented by cylindrical rods with in-plane hydrostatic misfit (axial misfit is also considered). The periphery of the matrix is traction-free, thus introducing an image solute field which generates a solute-solute interaction energy that has not been considered previously. The relevant energy for the field of any distribution of solutes coexistent with a single edge dislocation along the (matrix) cylinder axis is determined, and coherencymore » effects are discussed and studied. Monte Carlo simulations accounting for all pertinent interactions over a range of temperatures are found to yield solute distributions different from classical results, namely, (1) Fermi-Dirac condensations at low temperatures at the free surface, (2) the majority of the atmosphere lying within an unexpectedly large non-linear interaction region near the dislocation core, and (3) temperature-dependent asymmetrical solute arrangements that promote bending. The solute distributions at intermediate temperatures show a 1/r dependence in agreement with previous linearized approximations. With a standard state of solute corresponding to a mean concentration, c 0, the relevant interaction energy expression presented in this work is valid when extended to large concentrations for which Henry's Law and Vegard's Law do not apply.« less

Inviscid spatial stability of a compressible mixing layer. II - The flame sheet model

NASA Technical Reports Server (NTRS)

Jackson, T. L.; Grosch, C. E.

1990-01-01

The results of an inviscid spatial calculation for a compressible reacting mixing layer are reported. The limit of infinitive activation energy is taken and the diffusion flame is approximated by a flame sheet. Results are reported for the phase speeds of the neutral waves and maximum growth rates of the unstable waves as a function of the parameters of the problem: the ratio of the temperature of the stationary stream to that of the moving stream, the Mach number of the moving streams, the heat release per unit mass fraction of the reactant, the equivalence ratio of the reaction, and the frequency of the disturbance. These results are compared to the phase speeds and growth rates of the corresponding nonreacting mixing layer. We show that the addition of combustion has important and complex effects on the flow stability.

Partial Molar Volumes of 15-Crown-5 Ether in Mixtures of N,N-Dimethylformamide with Water.

PubMed

Tyczyńska, Magdalena; Jóźwiak, Małgorzata

2014-01-01

The density of 15-crown-5 ether (15C5) solutions in the mixtures of N,N -dimethylformamide (DMF) and water (H 2 O) was measured within the temperature range 293.15-308.15 K using an Anton Paar oscillatory U-tube densimeter. The results were used to calculate the apparent molar volumes ( V Φ ) of 15C5 in the mixtures of DMF + H 2 O over the whole concentration range. Using the apparent molar volumes and Redlich and Mayer equation, the standard partial molar volumes of 15-crown-5 were calculated at infinite dilution ([Formula: see text]). The limiting apparent molar expansibilities ( α ) were also calculated. The data are discussed from the point of view of the effect of concentration changes on interactions in solution.

Thermocapillary convection in two immiscible liquid layers with free surface

NASA Technical Reports Server (NTRS)

Doi, Takao; Koster, Jean N.

1993-01-01

Thermocapillary convection is studied in two immiscible liquid layers with one free surface, one liquid/liquid interface, and differential heating applied parallel to the interfaces. An analytical solution is introduced for infinite horizontal layers. The defining parameter for the flow pattern is lambda, the ratio of the temperature coefficient of the interfacial tension to that of the surface tension. Four different flow patterns exist under zero gravity conditions. 'Halt' conditions which halt the fluid motion in the lower encapsulated liquid layer have been found. A numerical experiment is carried out to study effects of vertical end walls on the double layer convection in a 2D cavity. The halt condition obtained from the analytical study is found to be valid in the limit of small Reynolds numbers. The flow in the encapsulated liquid layer can be suppressed substantially.

Accelerated sampling by infinite swapping of path integral molecular dynamics with surface hopping

NASA Astrophysics Data System (ADS)

Lu, Jianfeng; Zhou, Zhennan

2018-02-01

To accelerate the thermal equilibrium sampling of multi-level quantum systems, the infinite swapping limit of a recently proposed multi-level ring polymer representation is investigated. In the infinite swapping limit, the ring polymer evolves according to an averaged Hamiltonian with respect to all possible surface index configurations of the ring polymer and thus connects the surface hopping approach to the mean-field path-integral molecular dynamics. A multiscale integrator for the infinite swapping limit is also proposed to enable efficient sampling based on the limiting dynamics. Numerical results demonstrate the huge improvement of sampling efficiency of the infinite swapping compared with the direct simulation of path-integral molecular dynamics with surface hopping.

The infinite limit as an eliminable approximation for phase transitions

NASA Astrophysics Data System (ADS)

Ardourel, Vincent

2018-05-01

It is generally claimed that infinite idealizations are required for explaining phase transitions within statistical mechanics (e.g. Batterman 2011). Nevertheless, Menon and Callender (2013) have outlined theoretical approaches that describe phase transitions without using the infinite limit. This paper closely investigates one of these approaches, which consists of studying the complex zeros of the partition function (Borrmann et al., 2000). Based on this theory, I argue for the plausibility for eliminating the infinite limit for studying phase transitions. I offer a new account for phase transitions in finite systems, and I argue for the use of the infinite limit as an approximation for studying phase transitions in large systems.

Characterization of thermal cut-off mechanisms in prismatic lithium-ion batteries

NASA Astrophysics Data System (ADS)

Venugopal, Ganesh

Lithium-ion (Li-ion) cells that are subjected to electrical abuse, overcharge and external short-circuit in particular, exhibit a rapid increase in cell temperature that could potentially lead to catastrophic disassembly of the cell. For this reason these cells are integrated or combined with one or more safety components that are designed to restrict or even prevent current flow through the cell under abusive conditions. In this work, the characteristics of these components in several prismatic Li-ion cells are studied by monitoring the impedance ( Z) at 1 kHz and the open circuit voltage (OCV) of the discharged cells as a function of temperature. All the cells studied were found to use polyethylene-based shutdown (SD) separators that were irreversibly activated within a narrow temperature range between 130 and 135°C. In some cells irreversible cut-off was also provided by a current interrupt device (CID) or a thermal fuse. Both these devices had a circuit-breaker effect, causing the impedance of the cell to rise infinitely and the OCV to drop to zero. In addition to these irreversible cut-off mechanisms, some cells also contained internal or external positive-temperature-coefficient (PTC) devices that could provide current-limiting capability over a very wide temperature range. The interdependence of the thermal behavior of these components on each other and on other thermally dependant processes like cell venting, separator meltdown and weld joint failure are also discussed.

Analysis of transitional separation bubbles on infinite swept wings

NASA Technical Reports Server (NTRS)

Davis, R. L.; Carter, J. E.

1986-01-01

A previously developed two-dimensional local inviscid-viscous interaction technique for the analysis of airfoil transitional separation bubbles, ALESEP (Airfoil Leading Edge Separation), has been extended for the calculation of transitional separation bubbles over infinite swept wings. As part of this effort, Roberts' empirical correlation, which is interpreted as a separated flow empirical extension of Mack's stability theory for attached flows, has been incorporated into the ALESEP procedure for the prediction of the transition location within the separation bubble. In addition, the viscous procedure used in the ALESEP techniques has been modified to allow for wall suction. A series of two-dimensional calculations is presented as a verification of the prediction capability of the interaction techniques with the Roberts' transition model. Numerical tests have shown that this two-dimensional natural transition correlation may also be applied to transitional separation bubbles over infinite swept wings. Results of the interaction procedure are compared with Horton's detailed experimental data for separated flow over a swept plate which demonstrates the accuracy of the present technique. Wall suction has been applied to a similar interaction calculation to demonstrate its effect on the separation bubble. The principal conclusion of this paper is that the prediction of transitional separation bubbles over two-dimensional or infinite swept geometries is now possible using the present interacting boundary layer approach.

On information loss in AdS 3/CFT 2

DOE PAGES

Fitzpatrick, A. Liam; Kaplan, Jared; Li, Daliang; ...

2016-05-18

We discuss information loss from black hole physics in AdS 3, focusing on two sharp signatures infecting CFT 2 correlators at large central charge c: ‘forbidden singularities’ arising from Euclidean-time periodicity due to the effective Hawking temperature, and late-time exponential decay in the Lorentzian region. We study an infinite class of examples where forbidden singularities can be resolved by non-perturbative effects at finite c, and we show that the resolution has certain universal features that also apply in the general case. Analytically continuing to the Lorentzian regime, we find that the non-perturbative effects that resolve forbidden singularities qualitatively change themore » behavior of correlators at times t ~S BH, the black hole entropy. This may resolve the exponential decay of correlators at late times in black hole backgrounds. By Borel resumming the 1/c expansion of exact examples, we explicitly identify ‘information-restoring’ effects from heavy states that should correspond to classical solutions in AdS 3. Lastly, our results suggest a line of inquiry towards a more precise formulation of the gravitational path integral in AdS 3.« less

Universality of entropy scaling in one dimensional gapless models.

PubMed

Korepin, V E

2004-03-05

We consider critical models in one dimension. We study the ground state in the thermodynamic limit (infinite lattice). We are interested in an entropy of a subsystem. We calculate the entropy of a part of the ground state from a space interval (0,x). At zero temperature it describes the entanglement of the part of the ground state from this interval with the rest of the ground state. We obtain an explicit formula for the entropy of the subsystem at any temperature. At zero temperature our formula reproduces a logarithmic formula, discovered by Vidal, Latorre, Rico, and Kitaev for spin chains. We prove our formula by means of conformal field theory and the second law of thermodynamics. Our formula is universal. We illustrate it for a Bose gas with a delta interaction and for the Hubbard model.

Dynamical conductivity at the dirty superconductor-metal quantum phase transition

NASA Astrophysics Data System (ADS)

Hoyos, J. A.; Del Maestro, Adrian; Rosenow, Bernd; Vojta, Thomas

2011-03-01

We study the transport properties of ultrathin disordered nanowires in the neighborhood of the superconductor-metal quantum phase transition. To this end we combine numerical calculations with analytical strong-disorder renormalization group results. The quantum critical conductivity at zero temperature diverges logarithmically as a function of frequency. In the metallic phase, it obeys activated scaling associated with an infinite-randomness quantum critical point. We extend the scaling theory to higher dimensions and discuss implications for experiments. Financial support: Fapesp, CNPq, NSF, and Research Corporation.

A Monte Carlo-finite element model for strain energy controlled microstructural evolution - 'Rafting' in superalloys

NASA Technical Reports Server (NTRS)

Gayda, J.; Srolovitz, D. J.

1989-01-01

This paper presents a specialized microstructural lattice model, MCFET (Monte Carlo finite element technique), which simulates microstructural evolution in materials in which strain energy has an important role in determining morphology. The model is capable of accounting for externally applied stress, surface tension, misfit, elastic inhomogeneity, elastic anisotropy, and arbitrary temperatures. The MCFET analysis was found to compare well with the results of analytical calculations of the equilibrium morphologies of isolated particles in an infinite matrix.

Experimental Investigations, Modeling, and Analyses of High-Temperature Devices for Space Applications. Part 1

DTIC Science & Technology

1999-01-01

Cylinder and Another Interior Shell of Different Length (Reid and Tennant 1973) 429 C. 1.19. View Factors between Two Infinitely-Long Parallel and Opposed...by Another Parallel Cylinder of Different Radius 433 X C. 1.21. View Factor between Two Parallel and Opposed Cylinders of Unequal Radii and Equal...Length (Juul 1982) 435 C. 1.22. View Factor between Two Parallel Cylindrical Sections at Different Levels and of Different Length 439 C.2 CALCULATION OF

Explicit expressions of self-diffusion coefficient, shear viscosity, and the Stokes-Einstein relation for binary mixtures of Lennard-Jones liquids

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

Ohtori, Norikazu, E-mail: ohtori@chem.sc.niigata-u.ac.jp; Ishii, Yoshiki

Explicit expressions of the self-diffusion coefficient, D{sub i}, and shear viscosity, η{sub sv}, are presented for Lennard-Jones (LJ) binary mixtures in the liquid states along the saturated vapor line. The variables necessary for the expressions were derived from dimensional analysis of the properties: atomic mass, number density, packing fraction, temperature, and the size and energy parameters used in the LJ potential. The unknown dependence of the properties on each variable was determined by molecular dynamics (MD) calculations for an equimolar mixture of Ar and Kr at the temperature of 140 K and density of 1676 kg m{sup −3}. The scalingmore » equations obtained by multiplying all the single-variable dependences can well express D{sub i} and η{sub sv} evaluated by the MD simulation for a whole range of compositions and temperatures without any significant coupling between the variables. The equation for D{sub i} can also explain the dual atomic-mass dependence, i.e., the average-mass and the individual-mass dependence; the latter accounts for the “isotope effect” on D{sub i}. The Stokes-Einstein (SE) relation obtained from these equations is fully consistent with the SE relation for pure LJ liquids and that for infinitely dilute solutions. The main differences from the original SE relation are the presence of dependence on the individual mass and on the individual energy parameter. In addition, the packing-fraction dependence turned out to bridge another gap between the present and original SE relations as well as unifying the SE relation between pure liquids and infinitely dilute solutions.« less

Analysis of semiclassical approximations in the framework of quantumhadrodynamics

NASA Astrophysics Data System (ADS)

Speicher, C.; Engel, E.; Dreizler, R. M.

1993-10-01

We examine the importance of gradient corrections to the Thomas-Fermi (TF) approximation for the description of semi-infinite nuclear matter and nuclei within the framework of quantumhadrodynamics. The discussion of semi-infinite nuclear matter exhibits most clearly how surface properties depend on the parametrisation of the effective interaction. In agreement with earlier studies it is found that for parametrisations with low effective mass the original extended TF (ETF) equations cannot be solved. We present a scheme to overcome this problem which is very much in the spirit of the semiclassical approach and allows for a solution in any situation. For the case of nuclei the results of the TF and ETF approximations are compared to those of Hartree calculations which serve as a standard in this context. In accordance with the sensitivity of semi-infinite nuclear matter results to the specific parametrisation, ETF does not yield a consistent improvement over TF for all parametrisations. However, by examining a larger number of parametrisations it is shown that those cases where TF results are closer to Hartree data have to be regarded as fortuitous and that on average the agreement between ETF and Hartree results is clearly better.

First-principles calculations for XAS of infinite-layer iron oxides

NASA Astrophysics Data System (ADS)

Kodera, Mitsuru; Shishidou, Tatsuya; Oguchi, Tamio

2011-03-01

The oxygen defect perovskite SrFe O3 - x shows various properties such as the giant magnetoresistance effect and the thermoelectric effect. It had been believed that the oxygen content in SrFe O3 - x changes up to x = 0.5 . Recently, Tsujimoto et al . have succeeded in synthesizing the infinite-layer iron oxide SrFe O2 . SrFe O2 has a square-planar oxygen coordination, while the iron oxides usually have the tetrahedral and octahedral coordination. CaFe O2 has also infinite layer structure and the same magnetic ordering as SrFe O2 . However, it is suggested that the oxygen coordination of CaFe O2 is different from that of SrFe O2 . In order to investigate the electronic structure of iron in (Ca, Sr) Fe O2 , the x-ray absorption spectroscopy (XAS) spectrum has been measured. In this work, we perform the calculation for XAS spectrum near the Fe-K edge of (Ca, Sr) Fe O2 using the first-principles calculations. We compare the results with the experiment and discuss the electronic structure of iron in (Ca, Sr) Fe O2 .

Characterization of undulatory locomotion in granular media

NASA Astrophysics Data System (ADS)

Peng, Zhiwei; Pak, On Shun; Elfring, Gwynn

2015-11-01

Undulatory locomotion is ubiquitous in nature, from the swimming of flagellated microorganisms in biological fluids, to the slithering of snakes on land, or the locomotion of sandfish lizards in sand. Analysis of locomotion in granular materials is relatively less developed compared with fluids partially due to a lack of validated force models but a recently proposed resistive force theory (RFT) in granular media has been shown useful in studying the locomotion of a sand-swimming lizard. Here we employ this model to investigate the swimming characteristics of an undulating slender filament of both finite and infinite length. For infinite swimmers, similar to results in viscous fluids, the sawtooth waveform is found to be optimal for propulsion speed at a given power consumption. We also compare the swimming characteristics of sinusoidal and sawtooth swimmers with swimming in viscous fluids. More complex swimming dynamics emerge when the assumption of an infinite swimmer is removed. In particular, we characterize the effects of drifting and pitching in terms of propulsion speed and efficiency for a finite sinusoidal swimmer. The results complement our understanding of undulatory locomotion and provide insights into the effective design of locomotive systems in granular media.

Extremely correlated Fermi liquid theory of the t-J model in 2 dimensions: low energy properties

NASA Astrophysics Data System (ADS)

Shastry, B. Sriram; Mai, Peizhi

2018-01-01

Low energy properties of the metallic state of the two-dimensional t-J model are presented for second neighbor hopping with hole-doping (t\\prime ≤slant 0) and electron-doping (t\\prime > 0), with various superexchange energy J. We use a closed set of equations for the Greens functions obtained from the extremely correlated Fermi liquid theory. These equations reproduce the known low energies features of the large U Hubbard model in infinite dimensions. The density and temperature dependent quasiparticle weight, decay rate and the peak spectral heights over the Brillouin zone are calculated. We also calculate the resistivity, Hall conductivity, Hall number and cotangent Hall angle. The spectral features display high thermal sensitivity at modest T for density n≳ 0.8, implying a suppression of the effective Fermi-liquid temperature by two orders of magnitude relative to the bare bandwidth. The cotangent Hall angle exhibits a T 2 behavior at low T, followed by an interesting kink at higher T. The Hall number exhibits strong renormalization due to correlations. Flipping the sign of t\\prime changes the curvature of the resistivity versus T curves between convex and concave. Our results provide a natural route for understanding the observed difference in the temperature dependent resistivity of strongly correlated electron-doped and hole-doped matter.

Quantizing and sampling considerations in digital phased-locked loops

NASA Technical Reports Server (NTRS)

Hurst, G. T.; Gupta, S. C.

1974-01-01

The quantizer problem is first considered. The conditions under which the uniform white sequence model for the quantizer error is valid are established independent of the sampling rate. An equivalent spectral density is defined for the quantizer error resulting in an effective SNR value. This effective SNR may be used to determine quantized performance from infinitely fine quantized results. Attention is given to sampling rate considerations. Sampling rate characteristics of the digital phase-locked loop (DPLL) structure are investigated for the infinitely fine quantized system. The predicted phase error variance equation is examined as a function of the sampling rate. Simulation results are presented and a method is described which enables the minimum required sampling rate to be determined from the predicted phase error variance equations.

A nomogram for interpreting slope stability of fine-grained deposits in modern and ancient-marine environments.

USGS Publications Warehouse

Booth, J.S.; Sangrey, D.A.; Fugate, J.K.

1985-01-01

This nomogram was designed to aid in interpreting the causes of mass movement in modern and ancient settings, to provide a basis for evaluating and predicting slope stability under given conditions and to further the understanding of the relationships among the several key factors that control slope stability. Design of the nomogram is based on effective stress and combines consolidation theory as applicable to depositional environments with the infinite-slope model of slope-stability analysis. If infinite-slope conditions are assumed to exist, the effective overburden stress can be used to derive a factor of safety against static slope failure by using the angle of internal friction and the slope angle. -from Authors

A correlation method to predict the surface pressure distribution on an infinite plate from which a jet is issuing. [effects of a lifting jet

NASA Technical Reports Server (NTRS)

Perkins, S. C., Jr.; Menhall, M. R.

1978-01-01

A correlation method to predict pressures induced on an infinite plate by a jet issuing from the plate into a subsonic free stream was developed. The complete method consists of an analytical method which models the blockage and entrainment properties of the jet and a correlation which accounts for the effects of separation. The method was developed for jet velocity ratios up to ten and for radial distances up to five diameters from the jet. Correlation curves and data comparisons are presented for jets issuing normally from a flat plate with velocity ratios one to twelve. Also, a list of references which deal with jets in a crossflow is presented.

Quantum transverse-field Ising model on an infinite tree from matrix product states

NASA Astrophysics Data System (ADS)

Nagaj, Daniel; Farhi, Edward; Goldstone, Jeffrey; Shor, Peter; Sylvester, Igor

2008-06-01

We give a generalization to an infinite tree geometry of Vidal’s infinite time-evolving block decimation (iTEBD) algorithm [G. Vidal, Phys. Rev. Lett. 98, 070201 (2007)] for simulating an infinite line of quantum spins. We numerically investigate the quantum Ising model in a transverse field on the Bethe lattice using the matrix product state ansatz. We observe a second order phase transition, with certain key differences from the transverse field Ising model on an infinite spin chain. We also investigate a transverse field Ising model with a specific longitudinal field. When the transverse field is turned off, this model has a highly degenerate ground state as opposed to the pure Ising model whose ground state is only doubly degenerate.

How the Hawking radiation affect quantum Fisher information of Dirac particles in the background of a Schwarzschild black hole

NASA Astrophysics Data System (ADS)

Huang, ChunYu; Ma, Wen-chao; Wang, Dong; Ye, Liu

2018-01-01

In this work, the effect of Hawking radiation on the quantum Fisher information (QFI) of Dirac particles is investigated in the background of a Schwarzschild black hole. Interestingly, it has been verified that the QFI with respect to the weight parameter θ of a target state is always independent of the Hawking temperature T. This implies that if we encode the information on the weight parameter, then we can affirm that the corresponding accuracy of the parameter estimation will be immune to the Hawking effect. Besides, it reveals that the QFI with respect to the phase parameter φ exhibits a decay behavior with the increase in the Hawking temperature T and converges to a nonzero value in the limit of infinite Hawking temperature T. Remarkably, it turns out that the function F_φ on θ =π \\big /4 symmetry was broken by the influence of the Hawking radiation. Finally, we generalize the case of a three-qubit system to a case of a N-qubit system, i.e., |ψ > _{1,2,3,\\ldots ,N} =(cos θ | 0 > ^{⊗ N}+sin θ e^{iφ }| 1 > ^{⊗ N}) and obtain an interesting result: the number of particles in the initial state does not affect the QFI F_θ , nor the QFI F_φ . However, with the increasing number of particles located near the event horizon, F_φ will be affected by Hawking radiation to a large extent, while F_θ is still free from disturbance resulting from the Hawking effects.

High frequency thermal emission from the lunar surface and near surface temperature of the Moon from Chang’E-2 microwave radiometer

NASA Astrophysics Data System (ADS)

Fang, Tuo; Fa, Wenzhe

2014-04-01

Near surface temperature of the Moon and thermal behaviors of the lunar regolith can provide important information for constraining thermal and magmatic evolution models of the Moon and engineering constrains for in situ lunar exploration system. In this study, China’s Chang’E-2 (CE-2) microwave radiometer (MRM) data at high frequency channels are used to investigate near surface temperature of the Moon given the penetration ability of microwave into the desiccated and porous lunar regolith. Factors that affect high frequency brightness temperature (TB), such as surface slope, solar albedo and dielectric constant, are analyzed first using a revised Racca’s temperature model. Radiative transfer theory is then used to model thermal emission from a semi-infinite regolith medium, with considering dielectric constant and temperature profiles within the regolith layer. To decouple the effect of diurnal temperature variation in the uppermost lunar surface, diurnal averaged brightness temperatures at high frequency channels are used to invert mean diurnal surface and subsurface temperatures based on their bilinear profiles within the regolith layer. Our results show that, at the scale of the spatial resolution of CE-2 MRM, surface slope of crater wall varies typically from about 20° to 30°, and this causes a variation in TB about 10-15 K. Solar albedo can give rise to a TB difference of about 5-10 K between maria and highlands, whereas a ∼2-8 K difference can be compensated by the dielectric constant on the other hand. Inversion results indicate that latitude (ϕ) variations of the mean diurnal surface and subsurface temperatures follow simple rules as cos0.30ϕ and cos0.36ϕ, respectively. The inverted mean diurnal temperature profiles at the Apollo 15 and 17 landing sites are also compared with the Apollo heat flow experiment data, showing an inversion uncertainty <4 K for surface temperature and <1 K for subsurface temperature.

Infinity: The Twilight Zone of Mathematics.

ERIC Educational Resources Information Center

Love, William P.

1989-01-01

The theorems and proofs presented are designed to enhance student understanding of the theory of infinity as developed by Cantor and others. Three transfinite numbers are defined to express the cardinality of infinite algebraic sets, infinite sets of geometric points and infinite sets of functions. (DC)

Generalized analytic solutions and response characteristics of magnetotelluric fields on anisotropic infinite faults

NASA Astrophysics Data System (ADS)

Bing, Xue; Yicai, Ji

2018-06-01

In order to understand directly and analyze accurately the detected magnetotelluric (MT) data on anisotropic infinite faults, two-dimensional partial differential equations of MT fields are used to establish a model of anisotropic infinite faults using the Fourier transform method. A multi-fault model is developed to expand the one-fault model. The transverse electric mode and transverse magnetic mode analytic solutions are derived using two-infinite-fault models. The infinite integral terms of the quasi-analytic solutions are discussed. The dual-fault model is computed using the finite element method to verify the correctness of the solutions. The MT responses of isotropic and anisotropic media are calculated to analyze the response functions by different anisotropic conductivity structures. The thickness and conductivity of the media, influencing MT responses, are discussed. The analytic principles are also given. The analysis results are significant to how MT responses are perceived and to the data interpretation of the complex anisotropic infinite faults.

Effect of capillary forces on the nonstationary fall of a drop in an infinite fluid

NASA Astrophysics Data System (ADS)

Antanovskii, L. K.

1991-12-01

An explicit solution is presented for the linear problem concerning the motion of a drop in an infinite fluid in the presence of any number of surfactants (chemical reactions are not considered in the first approximation). It is shown that the behavior of the system considered is consistent with the Le Chatelier principle. The reactivity of the capillary forces is directly related to the fundamental principles of thermodynamics, which makes it possible to write equations of surfactant thermodiffusion in symmetric form and obtain a relatively simple solution to the linearized problem.

Crack problems for a rectangular plate and an infinite strip

NASA Technical Reports Server (NTRS)

Civelek, M. B.; Erdogan, F.

1980-01-01

The general plane problem for an infinite strip containing multiple cracks perpendicular to its boundaries is considered. The problem is reduced to a system of singular integral equations. Two specific problems of practical interest are then studied in detail. The first problem explores the interaction effect of multiple edge cracks in a plate or beam under tension or bending. The second problem is that of a rectangular plate containing an arbitrarily oriented crack in the plane of symmetry. Particular emphasis is placed on the problem of a plate containing an edge crack and subjected to concentrated forces.

Determination of drying kinetics and convective heat transfer coefficients of ginger slices

NASA Astrophysics Data System (ADS)

Akpinar, Ebru Kavak; Toraman, Seda

2016-10-01

In the present work, the effects of some parametric values on convective heat transfer coefficients and the thin layer drying process of ginger slices were investigated. Drying was done in the laboratory by using cyclone type convective dryer. The drying air temperature was varied as 40, 50, 60 and 70 °C and the air velocity is 0.8, 1.5 and 3 m/s. All drying experiments had only falling rate period. The drying data were fitted to the twelve mathematical models and performance of these models was investigated by comparing the determination of coefficient ( R 2), reduced Chi-square ( χ 2) and root mean square error between the observed and predicted moisture ratios. The effective moisture diffusivity and activation energy were calculated using an infinite series solution of Fick's diffusion equation. The average effective moisture diffusivity values and activation energy values varied from 2.807 × 10-10 to 6.977 × 10-10 m2/s and 19.313-22.722 kJ/mol over the drying air temperature and velocity range, respectively. Experimental data was used to evaluate the values of constants in Nusselt number expression by using linear regression analysis and consequently, convective heat transfer coefficients were determined in forced convection mode. Convective heat transfer coefficient of ginger slices showed changes in ranges 0.33-2.11 W/m2 °C.

Low-temperature transport in out-of-equilibrium XXZ chains

NASA Astrophysics Data System (ADS)

Bertini, Bruno; Piroli, Lorenzo

2018-03-01

We study the low-temperature transport properties of out-of-equilibrium XXZ spin-1/2 chains. We consider the protocol where two semi-infinite chains are prepared in two thermal states at small but different temperatures and suddenly joined together. We focus on the qualitative and quantitative features of the profiles of local observables, which at large times t and distances x from the junction become functions of the ratio \\zeta=x/t . By means of the generalized hydrodynamic equations, we analyse the rich phenomenology arising by considering different regimes of the phase diagram. In the gapped phases, variations of the profiles are found to be exponentially small in the temperatures, but described by non-trivial functions of ζ. We provide analytical formulae for the latter, which give accurate results also for small but finite temperatures. In the gapless regime, we show how the three-step conformal predictions for the profiles of energy density and energy current are naturally recovered from the hydrodynamic equations. Moreover, we also recover the recent non-linear Luttinger liquid predictions for low-temperature transport: universal peaks of width \

Improving the Instruction of Infinite Series

ERIC Educational Resources Information Center

Lindaman, Brian; Gay, A. Susan

2012-01-01

Calculus instructors struggle to teach infinite series, and students have difficulty understanding series and related concepts. Four instructional strategies, prominently used during the calculus reform movement, were implemented during a 3-week unit on infinite series in one class of second-semester calculus students. A description of each…

Ice Ih anomalies: Thermal contraction, anomalous volume isotope effect, and pressure-induced amorphization.

PubMed

Salim, Michael A; Willow, Soohaeng Yoo; Hirata, So

2016-05-28

Ice Ih displays several anomalous thermodynamic properties such as thermal contraction at low temperatures, an anomalous volume isotope effect (VIE) rendering the volume of D2O ice greater than that of H2O ice, and a pressure-induced transition to the high-density amorphous (HDA) phase. Furthermore, the anomalous VIE increases with temperature, despite its quantum-mechanical origin. Here, embedded-fragment ab initio second-order many-body perturbation (MP2) theory in the quasiharmonic approximation (QHA) is applied to the Gibbs energy of an infinite, proton-disordered crystal of ice Ih at wide ranges of temperatures and pressures. The quantum effect of nuclei moving in anharmonic potentials is taken into account from first principles without any empirical or nonsystematic approximation to either the electronic or vibrational Hamiltonian. MP2 predicts quantitatively correctly the thermal contraction at low temperatures, which is confirmed to originate from the volume-contracting hydrogen-bond bending modes (acoustic phonons). It qualitatively reproduces (but underestimates) the thermal expansion at higher temperatures, caused by the volume-expanding hydrogen-bond stretching (and to a lesser extent librational) modes. The anomalous VIE is found to be the result of subtle cancellations among closely competing isotope effects on volume from all modes. Consequently, even ab initio MP2 with the aug-cc-pVDZ and aug-cc-pVTZ basis sets has difficulty reproducing this anomaly, yielding qualitatively varied predictions of the sign of the VIE depending on such computational details as the choice of the embedding field. However, the temperature growth of the anomalous VIE is reproduced robustly and is ascribed to the librational modes. These solid-state MP2 calculations, as well as MP2 Born-Oppenheimer molecular dynamics, find a volume collapse and a loss of symmetry and long-range order in ice Ih upon pressure loading of 2.35 GPa or higher. Concomitantly, rapid softening of acoustic phonons is observed starting around 2 GPa. They constitute a computational detection of a mechanical instability in ice Ih and the resulting pressure-induced amorphization to HDA.

Ice Ih anomalies: Thermal contraction, anomalous volume isotope effect, and pressure-induced amorphization

NASA Astrophysics Data System (ADS)

Salim, Michael A.; Willow, Soohaeng Yoo; Hirata, So

2016-05-01

Ice Ih displays several anomalous thermodynamic properties such as thermal contraction at low temperatures, an anomalous volume isotope effect (VIE) rendering the volume of D2O ice greater than that of H2O ice, and a pressure-induced transition to the high-density amorphous (HDA) phase. Furthermore, the anomalous VIE increases with temperature, despite its quantum-mechanical origin. Here, embedded-fragment ab initio second-order many-body perturbation (MP2) theory in the quasiharmonic approximation (QHA) is applied to the Gibbs energy of an infinite, proton-disordered crystal of ice Ih at wide ranges of temperatures and pressures. The quantum effect of nuclei moving in anharmonic potentials is taken into account from first principles without any empirical or nonsystematic approximation to either the electronic or vibrational Hamiltonian. MP2 predicts quantitatively correctly the thermal contraction at low temperatures, which is confirmed to originate from the volume-contracting hydrogen-bond bending modes (acoustic phonons). It qualitatively reproduces (but underestimates) the thermal expansion at higher temperatures, caused by the volume-expanding hydrogen-bond stretching (and to a lesser extent librational) modes. The anomalous VIE is found to be the result of subtle cancellations among closely competing isotope effects on volume from all modes. Consequently, even ab initio MP2 with the aug-cc-pVDZ and aug-cc-pVTZ basis sets has difficulty reproducing this anomaly, yielding qualitatively varied predictions of the sign of the VIE depending on such computational details as the choice of the embedding field. However, the temperature growth of the anomalous VIE is reproduced robustly and is ascribed to the librational modes. These solid-state MP2 calculations, as well as MP2 Born-Oppenheimer molecular dynamics, find a volume collapse and a loss of symmetry and long-range order in ice Ih upon pressure loading of 2.35 GPa or higher. Concomitantly, rapid softening of acoustic phonons is observed starting around 2 GPa. They constitute a computational detection of a mechanical instability in ice Ih and the resulting pressure-induced amorphization to HDA.

Ice Ih anomalies: Thermal contraction, anomalous volume isotope effect, and pressure-induced amorphization

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

Salim, Michael A.; Willow, Soohaeng Yoo; Hirata, So, E-mail: sohirata@illinois.edu

Ice Ih displays several anomalous thermodynamic properties such as thermal contraction at low temperatures, an anomalous volume isotope effect (VIE) rendering the volume of D{sub 2}O ice greater than that of H{sub 2}O ice, and a pressure-induced transition to the high-density amorphous (HDA) phase. Furthermore, the anomalous VIE increases with temperature, despite its quantum-mechanical origin. Here, embedded-fragment ab initio second-order many-body perturbation (MP2) theory in the quasiharmonic approximation (QHA) is applied to the Gibbs energy of an infinite, proton-disordered crystal of ice Ih at wide ranges of temperatures and pressures. The quantum effect of nuclei moving in anharmonic potentials ismore » taken into account from first principles without any empirical or nonsystematic approximation to either the electronic or vibrational Hamiltonian. MP2 predicts quantitatively correctly the thermal contraction at low temperatures, which is confirmed to originate from the volume-contracting hydrogen-bond bending modes (acoustic phonons). It qualitatively reproduces (but underestimates) the thermal expansion at higher temperatures, caused by the volume-expanding hydrogen-bond stretching (and to a lesser extent librational) modes. The anomalous VIE is found to be the result of subtle cancellations among closely competing isotope effects on volume from all modes. Consequently, even ab initio MP2 with the aug-cc-pVDZ and aug-cc-pVTZ basis sets has difficulty reproducing this anomaly, yielding qualitatively varied predictions of the sign of the VIE depending on such computational details as the choice of the embedding field. However, the temperature growth of the anomalous VIE is reproduced robustly and is ascribed to the librational modes. These solid-state MP2 calculations, as well as MP2 Born–Oppenheimer molecular dynamics, find a volume collapse and a loss of symmetry and long-range order in ice Ih upon pressure loading of 2.35 GPa or higher. Concomitantly, rapid softening of acoustic phonons is observed starting around 2 GPa. They constitute a computational detection of a mechanical instability in ice Ih and the resulting pressure-induced amorphization to HDA.« less

Large Black Holes in the Randall-Sundrum II Model

NASA Astrophysics Data System (ADS)

Yaghoobpour Tari, Shima

The Einstein equation with a negative cosmological constant ! in the five dimensions for the Randall-Sundrum II model, which includes a black hole, has been solved numerically. We have constructed an AdS5-CFT 4 solution numerically, using a spectral method to minimize the integral of the square of the error of the Einstein equation, with 210 parameters to be determined by optimization. This metric is conformal to the Schwarzschild metric at an AdS5 boundary with an infinite scale factor. So, we consider this solution as an infinite-mass black hole solution. We have rewritten the infinite-mass black hole in the Fefferman-Graham form and obtained the numerical components of the CFT energy-momentum tensor. Using them, we have perturbed the metric to relocate the brane from infinity and obtained a large static black hole solution for the Randall- Sundrum II model. The changes of mass, entropy, temperature and area of the large black hole from the Schwarzschild metric are studied up to the first order for the perturbation parameter 1/(-Λ5M 2). The Hawking temperature and entropy for our large black hole have the same values as the Schwarzschild metric with the same mass, but the horizon area is increased by about 4.7/(-Λ5). Figueras, Lucietti, and Wiseman found an AdS5-CFT4 solution using an independent and different method from us, called the Ricci-DeTurck-flow method. Then, Figueras and Wiseman perturbed this solution in a same way as we have done and obtained the solution for the large black hole in the Randall-Sundrum II model. These two numerical solutions are the first mathematical proofs for having a large black hole in the Randall-Sundrum II. We have compared their results with ours for the CFT energy-momentum tensor components and the perturbed metric. We have shown that the results are closely in agreement, which can be considered as evidence that the solution for the large black hole in the Randall-Sundrum II model exists.

Number of revolutions of a particle around a black hole: Is it infinite or finite?

NASA Astrophysics Data System (ADS)

Pavlov, Yuri V.; Zaslavskii, Oleg B.

2018-01-01

We consider a particle falling into a rotating black hole. Such a particle makes an infinite number of revolutions n from the viewpoint of a remote observer who uses the Boyer-Lindquist type of coordinates. We examine the behavior of n when it is measured with respect to a local reference frame that also rotates due to dragging effect of spacetime. The crucial point consists here in the observation that for a nonextremal black hole, the leading contributions to n from a particle itself and the reference frame have the same form being in fact universal, so that divergences mutually cancel. As a result, the relative number of revolutions turns out to be finite. For the extremal black hole this is not so, n can be infinite. Different choices of the local reference frame are considered, the results turn out to be the same qualitatively. For illustration, we discuss two explicit examples—rotation in the flat spacetime and in the Kerr metric.

Pattern Formation and Complexity Emergence

NASA Astrophysics Data System (ADS)

Berezin, Alexander A.

2001-03-01

Success of nonlinear modelling of pattern formation and self-organization encourages speculations on informational and number theoretical foundations of complexity emergence. Pythagorean "unreasonable effectiveness of integers" in natural processes is perhaps extrapolatable even to universal emergence "out-of-nothing" (Leibniz, Wheeler). Because rational numbers (R = M/N) are everywhere dense on real axis, any digital string (hence any "book" from "Library of Babel" of J.L.Borges) is "recorded" infinitely many times in arbitrary many rationals. Furthermore, within any arbitrary small interval there are infinitely many Rs for which (either or both) integers (Ms and Ns) "carry" any given string of any given length. Because any iterational process (such as generation of fractal features of Mandelbrot Set) is arbitrary closely approximatable with rational numbers, the infinite pattern of integers expresses itself in generation of complexity of the world, as well as in emergence of the world itself. This "tunnelling" from Platonic World ("Platonia" of J.Barbour) to a real (physical) world is modern recast of Leibniz's motto ("for deriving all from nothing there suffices a single principle").

The Effect of Finite Thickness Extent on Estimating Depth to Basement from Aeromagnetic Data

NASA Astrophysics Data System (ADS)

Blakely, R. J.; Salem, A.; Green, C. M.; Fairhead, D.; Ravat, D.

2014-12-01

Depth to basement estimation methods using various components of the spectral content of magnetic anomalies are in common use by geophysicists. Examples of these are the Tilt-Depth and SPI methods. These methods use simple models having the base of the magnetic body at infinity. Recent publications have shown that this 'infinite depth' assumption causes underestimation of the depth to the top of sources, especially in areas where the bottom of the magnetic layer is shallow, as would occur in high heat-flow regions. This error has been demonstrated in both model studies and using real data with seismic or well control. To overcome the limitation of infinite depth this contribution presents the mathematics for a finite depth contact body in the Tilt depth and SPI methods and applies it to the central Red Sea where the Curie isotherm and Moho are shallow. The difference in the depth estimation between the infinite and finite contacts is such a case is significant and can exceed 200%.

Maximal near-field radiative heat transfer between two plates

NASA Astrophysics Data System (ADS)

Nefzaoui, Elyes; Ezzahri, Younès; Drévillon, Jérémie; Joulain, Karl

2013-09-01

Near-field radiative transfer is a promising way to significantly and simultaneously enhance both thermo-photovoltaic (TPV) devices power densities and efficiencies. A parametric study of Drude and Lorentz models performances in maximizing near-field radiative heat transfer between two semi-infinite planes separated by nanometric distances at room temperature is presented in this paper. Optimal parameters of these models that provide optical properties maximizing the radiative heat flux are reported and compared to real materials usually considered in similar studies, silicon carbide and heavily doped silicon in this case. Results are obtained by exact and approximate (in the extreme near-field regime and the electrostatic limit hypothesis) calculations. The two methods are compared in terms of accuracy and CPU resources consumption. Their differences are explained according to a mesoscopic description of nearfield radiative heat transfer. Finally, the frequently assumed hypothesis which states a maximal radiative heat transfer when the two semi-infinite planes are of identical materials is numerically confirmed. Its subsequent practical constraints are then discussed. Presented results enlighten relevant paths to follow in order to choose or design materials maximizing nano-TPV devices performances.

The Green's functions for peridynamic non-local diffusion.

PubMed

Wang, L J; Xu, J F; Wang, J X

2016-09-01

In this work, we develop the Green's function method for the solution of the peridynamic non-local diffusion model in which the spatial gradient of the generalized potential in the classical theory is replaced by an integral of a generalized response function in a horizon. We first show that the general solutions of the peridynamic non-local diffusion model can be expressed as functionals of the corresponding Green's functions for point sources, along with volume constraints for non-local diffusion. Then, we obtain the Green's functions by the Fourier transform method for unsteady and steady diffusions in infinite domains. We also demonstrate that the peridynamic non-local solutions converge to the classical differential solutions when the non-local length approaches zero. Finally, the peridynamic analytical solutions are applied to an infinite plate heated by a Gauss source, and the predicted variations of temperature are compared with the classical local solutions. The peridynamic non-local diffusion model predicts a lower rate of variation of the field quantities than that of the classical theory, which is consistent with experimental observations. The developed method is applicable to general diffusion-type problems.

Divergence of activity expansions: Is it actually a problem?

NASA Astrophysics Data System (ADS)

Ushcats, M. V.; Bulavin, L. A.; Sysoev, V. M.; Ushcats, S. Yu.

2017-12-01

For realistic interaction models, which include both molecular attraction and repulsion (e.g., Lennard-Jones, modified Lennard-Jones, Morse, and square-well potentials), the asymptotic behavior of the virial expansions for pressure and density in powers of activity has been studied taking power terms of high orders into account on the basis of the known finite-order irreducible integrals as well as the recent approximations of infinite irreducible series. Even in the divergence region (at subcritical temperatures), this behavior stays thermodynamically adequate (in contrast to the behavior of the virial equation of state with the same set of irreducible integrals) and corresponds to the beginning of the first-order phase transition: the divergence yields the jump (discontinuity) in density at constant pressure and chemical potential. In general, it provides a statistical explanation of the condensation phenomenon, but for liquid or solid states, the physically proper description (which can turn the infinite discontinuity into a finite jump of density) still needs further study of high-order cluster integrals and, especially, their real dependence on the system volume (density).

A-priori testing of sub-grid models for chemically reacting nonpremixed turbulent shear flows

NASA Technical Reports Server (NTRS)

Jimenez, J.; Linan, A.; Rogers, M. M.; Higuera, F. J.

1996-01-01

The beta-assumed-pdf approximation of (Cook & Riley 1994) is tested as a subgrid model for the LES computation of nonpremixed turbulent reacting flows, in the limit of cold infinitely fast chemistry, for two plane turbulent mixing layers with different degrees of intermittency. Excellent results are obtained for the computation of integrals properties such as product mass fraction, and the model is applied to other quantities such as powers of the temperature and the pdf of the scalar itself. Even in these cases the errors are small enough to be useful in practical applications. The analysis is extended to slightly out of equilibrium problems such as the generation of radicals, and formulated in terms of the pdf of the scalar gradients. It is shown that the conditional gradient distribution is universal in a wide range of cases whose limits are established. Within those limits, engineering approximations to the radical concentration are also possible. It is argued that the experiments in this paper are essentially in the limit of infinite Reynolds number.

Envisioning the Infinite by Projecting Finite Properties

ERIC Educational Resources Information Center

Ely, Robert

2011-01-01

We analyze interviews with 24 post-secondary students as they reason about infinite processes in the context of the tricky Tennis Ball Problem. By metaphorically projecting various properties from the finite states such as counting and indexing, participants envisioned widely varying final states for the infinite process. Depending on which…

Understanding the Behaviour of Infinite Ladder Circuits

ERIC Educational Resources Information Center

Ucak, C.; Yegin, K.

2008-01-01

Infinite ladder circuits are often encountered in undergraduate electrical engineering and physics curricula when dealing with series and parallel combination of impedances, as a part of filter design or wave propagation on transmission lines. The input impedance of such infinite ladder circuits is derived by assuming that the input impedance does…

Low temperature structures of dCpG-proflavine.

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

Schneider, B.; Ginell, S. L.; Berman, H. M.

1992-12-01

The structure of the complex of dCpG with proflavine was determined using x-ray data taken at -130 degrees C (low temperature) and at -2 degrees C (cold temperature) and compared with the structure of the complex determined previously at room temperature (Shieh, H. S., H. M. Berman, M. Dabrow, and S. Neidle. 1980. Nucleic Acids Res. 8:85-97). Low temperature was refined with 5,125 reflections between 8.0 and 0.93 A, Anisotropically modeled temperature factors were used for DNA/drug atoms and isotropic ones for water oxygens to R factor of 12.2% in P2(1)2(1)2; a = 32.853, b = 21.760, c = 13.296more » A. Cold temperature was refined isotropically with 2,846 reflections 8.0-0.89 A to R = 15.1% in P2(1)2(1)2; a = 32.867, b = 22.356, c = 13.461 A. Both structures are very similar to the room temperature one, though some important differences were observed: one guanine sugar moiety is disordered and additional water molecules have been located that give rise to infinite polyhedral hydration networks.« less

AlGaInAs EML having high extinction ratios fabricated by identical epitaxial layer technique

NASA Astrophysics Data System (ADS)

Deng, Qiufang; Guo, Lu; Liang, Song; Sun, Siwei; Xie, Xiao; Zhu, Hongliang; Wang, Wei

2018-04-01

AlGaInAs electroabsorption-modulated lasers (EMLs) fabricated by identical epitaxial layer technique are demonstrated. The EML device shows an infinite characteristic temperature when the temperature ranges from 20 oC to 30 oC. The integrated modulator has static extinction ratios of larger than 20 dB at a reverse bias voltage of - 2 V. The small signal modulation bandwidth of the modulator is larger than 11 GHz. At 10 Gb/s data modulation, the dynamic extinction ratio is about 9.5 dB in a back to back test configuration. Because only a simple fabrication procedure is needed, our EMLs are promising low cost light sources for optical fiber transmission applications.

Effects of selected materials and geometries on the beta dose equivalent rate in a tissue equivalent phantom immersed in infinite clouds of 133Xe

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

Piltingsrud, H.V.; Gels, G.L.

1986-06-01

Most calculations of dose equivalent (D.E.) rates at 70-micron tissue depths in tissue equivalent (T.E.) phantoms from infinite clouds (radius exceeds maximum beta range in air) of /sup 133/Xe do not consider the possible effects of clothing overlays. Consequently, a series of measurements were made using a 1-mm-thick plastic scintillation detector assembly mounted in a tissue equivalent (T.E.) phantom with an overlay of 70 micron of T.E. material. This assembly was placed in an infinite cloud containing a known concentration of /sup 133/Xe. Material samples were placed at selected distances from the detector phantom, both individually and in various combinations.more » Pulse-height spectra resulting from beta radiations were converted to relative D.E. rates at a 70-micron tissue depth. The relative D.E. rates were reduced from values with no clothing cover by as little as 45% when placing a single thin nylon cloth 1 cm from the phantom, to 94% for a T-shirt material plus wool material plus denim placed 1/2, 1 and 3 cm, respectively, from the phantom. The results indicate that even loosely fitting clothing can have an important effect on reducing the D.E. rate. Close-fitting clothing appears to provide better protection.« less

Density functional study of the 13C NMR chemical shifts in small-to-medium-diameter infinite single-walled carbon nanotubes.

PubMed

Zurek, Eva; Pickard, Chris J; Walczak, Brian; Autschbach, Jochen

2006-11-02

NMR chemical shifts were calculated for semiconducting (n,0) single-walled carbon nanotubes (SWNTs) with n ranging from 7 to 17. Infinite isolated SWNTs were calculated using a gauge-including projector-augmented plane-wave (GIPAW) approach with periodic boundary conditions and density functional theory (DFT). In order to minimize intertube interactions in the GIPAW computations, an intertube distance of 8 A was chosen. For the infinite tubes, we found a chemical shift range of over 20 ppm for the systems considered here. The SWNT family with lambda = mod(n, 3) = 0 has much smaller chemical shifts compared to the other two families with lambda = 1 and lambda = 2. For all three families, the chemical shifts decrease roughly inversely proportional to the tube's diameter. The results were compared to calculations of finite capped SWNT fragments using a gauge-including atomic orbital (GIAO) basis. Direct comparison of the two types of calculations could be made if benzene was used as the internal (computational) reference. The NMR chemical shifts of finite SWNTs were found to converge very slowly, if at all, to the infinite limit, indicating that capping has a strong effect (at least for the (9,0) tubes) on the calculated properties. Our results suggest that (13)C NMR has the potential for becoming a useful tool in characterizing SWNT samples.

A general derivation and quantification of the third law of thermodynamics.

PubMed

Masanes, Lluís; Oppenheim, Jonathan

2017-03-14

The most accepted version of the third law of thermodynamics, the unattainability principle, states that any process cannot reach absolute zero temperature in a finite number of steps and within a finite time. Here, we provide a derivation of the principle that applies to arbitrary cooling processes, even those exploiting the laws of quantum mechanics or involving an infinite-dimensional reservoir. We quantify the resources needed to cool a system to any temperature, and translate these resources into the minimal time or number of steps, by considering the notion of a thermal machine that obeys similar restrictions to universal computers. We generally find that the obtainable temperature can scale as an inverse power of the cooling time. Our results also clarify the connection between two versions of the third law (the unattainability principle and the heat theorem), and place ultimate bounds on the speed at which information can be erased.

A general derivation and quantification of the third law of thermodynamics

PubMed Central

Masanes, Lluís; Oppenheim, Jonathan

2017-01-01

The most accepted version of the third law of thermodynamics, the unattainability principle, states that any process cannot reach absolute zero temperature in a finite number of steps and within a finite time. Here, we provide a derivation of the principle that applies to arbitrary cooling processes, even those exploiting the laws of quantum mechanics or involving an infinite-dimensional reservoir. We quantify the resources needed to cool a system to any temperature, and translate these resources into the minimal time or number of steps, by considering the notion of a thermal machine that obeys similar restrictions to universal computers. We generally find that the obtainable temperature can scale as an inverse power of the cooling time. Our results also clarify the connection between two versions of the third law (the unattainability principle and the heat theorem), and place ultimate bounds on the speed at which information can be erased. PMID:28290452

Densities, Ultrasonic Speeds, and Excess Properties of Binary Mixtures of Diethylene Glycol with 1-Butanol, 2-Butanol, and 1,4-Butanediol at Different Temperatures

NASA Astrophysics Data System (ADS)

Ali, Anwar; Ansari, Sana; Uzair, Sahar; Tasneem, Shadma; Nabi, Firdosa

2015-11-01

Densities ρ and ultrasonic speeds u for pure diethylene glycol, 1-butanol, 2-butanol, and 1,4-butanediol and for their binary mixtures over the entire composition range were measured at 298.15 K, 303.15 K, 308.15 K, and 313.15 K. Using these data, the excess molar volumes, VE_m, deviations in isentropic compressibilities, {\\varDelta }ks, apparent molar volumes, V_{φi} , partial molar volumes, overline{V}_{m,i} , and excess partial molar volumes, overline{V}_{m,i}^E , have been calculated over the entire composition range, and also the excess partial molar volumes of the components at infinite dilution, overline{V}_{m,i}^{E,infty } have been calculated. The excess functions have been correlated using the Redlich-Kister equation at different temperatures. The variations of these derived parameters with composition and temperature are presented graphically.

Finite-temperature dynamic structure factor of the spin-1 XXZ chain with single-ion anisotropy

NASA Astrophysics Data System (ADS)

Lange, Florian; Ejima, Satoshi; Fehske, Holger

2018-02-01

Improving matrix-product state techniques based on the purification of the density matrix, we are able to accurately calculate the finite-temperature dynamic response of the infinite spin-1 XXZ chain with single-ion anisotropy in the Haldane, large-D , and antiferromagnetic phases. Distinct thermally activated scattering processes make a significant contribution to the spectral weight in all cases. In the Haldane phase, intraband magnon scattering is prominent, and the on-site anisotropy causes the magnon to split into singlet and doublet branches. In the large-D phase response, the intraband signal is separated from an exciton-antiexciton continuum. In the antiferromagnetic phase, holons are the lowest-lying excitations, with a gap that closes at the transition to the Haldane state. At finite temperatures, scattering between domain-wall excitations becomes especially important and strongly enhances the spectral weight for momentum transfer π .

Non-Fermi glasses: fractionalizing electrons at finite energy density

NASA Astrophysics Data System (ADS)

Parameswaran, Siddharth; Gopalakrishnan, Sarang

Non-Fermi liquids are metals that cannot be adiabatically deformed into free fermion states. We argue for the existence of ``non-Fermi glasses,'' which are phases of interacting disordered fermions that are fully many-body localized, yet cannot be deformed into an Anderson insulator without an eigenstate phase transition. We explore the properties of such non-Fermi glasses, focusing on a specific solvable example. At high temperature, non-Fermi glasses have qualitatively similar spectral features to Anderson insulators. We identify a diagnostic, based on ratios of correlation functions, that sharply distinguishes between the two phases even at infinite temperature. We argue that our results and diagnostic should generically apply to the high-temperature behavior of the many-body localized descendants of fractionalized phases. S.A.P. is supported by NSF Grant DMR-1455366 and a UC President's Research Catalyst Award CA-15-327861, and S.G. by the Burke Institute at Caltech.

Similar solutions for the compressible laminar boundary layer with heat transfer and pressure gradient

NASA Technical Reports Server (NTRS)

Cohen, Clarence B; Reshotko, Eli

1956-01-01

Stewartson's transformation is applied to the laminar compressible boundary-layer equations and the requirement of similarity is introduced, resulting in a set of ordinary nonlinear differential equations previously quoted by Stewartson, but unsolved. The requirements of the system are Prandtl number of 1.0, linear viscosity-temperature relation across the boundary layer, an isothermal surface, and the particular distributions of free-stream velocity consistent with similar solutions. This system admits axial pressure gradients of arbitrary magnitude, heat flux normal to the surface, and arbitrary Mach numbers. The system of differential equations is transformed to integral system, with the velocity ratio as the independent variable. For this system, solutions are found by digital computation for pressure gradients varying from that causing separation to the infinitely favorable gradient and for wall temperatures from absolute zero to twice the free-stream stagnation temperature. Some solutions for separated flows are also presented.

Students' Conception of Infinite Series

ERIC Educational Resources Information Center

Martinez-Planell, Rafael; Gonzalez, Ana Carmen; DiCristina, Gladys; Acevedo, Vanessa

2012-01-01

This is a report of a study of students' understanding of infinite series. It has a three-fold purpose: to show that students may construct two essentially different notions of infinite series, to show that one of the constructions is particularly difficult for students, and to examine the way in which these two different constructions may be…

Viscous effects on the Rayleigh-Taylor instability with background temperature gradient

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

Gerashchenko, S.; Livescu, D., E-mail: livescu@lanl.gov

The growth rate of the compressible Rayleigh-Taylor instability is studied in the presence of a background temperature gradient, Θ, using a normal mode analysis. The effect of Θ variation is examined for three interface types corresponding to the combinations of the viscous properties of the fluids (inviscid-inviscid, viscous-viscous, and viscous-inviscid) at different Atwood numbers, At, and when at least one of the fluids' viscosity is non-zero, as a function of the Grashof number. For the general case, the resulting ordinary differential equations are solved numerically; however, dispersion relations for the growth rate are presented for several limiting cases. An analyticalmore » solution is found for the inviscid-inviscid interface and the corresponding dispersion equation for the growth rate is obtained in the limit of large Θ. For the viscous-inviscid case, a dispersion relation is derived in the incompressible limit and Θ = 0. Compared to Θ = 0 case, the role of Θ < 0 (hotter light fluid) is destabilizing and becomes stabilizing when Θ > 0 (colder light fluid). The most pronounced effect of Θ ≠ 0 is found at low At and/or at large perturbation wavelengths relative to the domain size for all interface types. On the other hand, at small perturbation wavelengths relative to the domain size, the growth rate for the Θ < 0 case exceeds the infinite domain incompressible constant density result. The results are applied to two practical examples, using sets of parameters relevant to Inertial Confinement Fusion coasting stage and solar corona plumes. The role of viscosity on the growth rate reduction is discussed together with highlighting the range of wavenumbers most affected by viscosity. The viscous effects further increase in the presence of background temperature gradient, when the viscosity is temperature dependent.« less

Fluctuations around equilibrium laws in ergodic continuous-time random walks.

PubMed

Schulz, Johannes H P; Barkai, Eli

2015-06-01

We study occupation time statistics in ergodic continuous-time random walks. Under thermal detailed balance conditions, the average occupation time is given by the Boltzmann-Gibbs canonical law. But close to the nonergodic phase, the finite-time fluctuations around this mean are large and nontrivial. They exhibit dual time scaling and distribution laws: the infinite density of large fluctuations complements the Lévy-stable density of bulk fluctuations. Neither of the two should be interpreted as a stand-alone limiting law, as each has its own deficiency: the infinite density has an infinite norm (despite particle conservation), while the stable distribution has an infinite variance (although occupation times are bounded). These unphysical divergences are remedied by consistent use and interpretation of both formulas. Interestingly, while the system's canonical equilibrium laws naturally determine the mean occupation time of the ergodic motion, they also control the infinite and Lévy-stable densities of fluctuations. The duality of stable and infinite densities is in fact ubiquitous for these dynamics, as it concerns the time averages of general physical observables.

Propagation and damping of Alfvén waves in low solar atmosphere

NASA Astrophysics Data System (ADS)

Ryu, Chang-Mo; Huynh, Cong Tuan

2017-10-01

Propagation and damping of Alfvén waves in the inner solar corona are studied using a 2D magnetohydrodynamics (MHD) simulation code with realistic density and temperature profiles in a uniform background magnetic field. A linear wave is launched by ascribing a sinusoidal fluid motion at about 1000 km from the surface of the Sun, which is shown to generate Alfvénic wave motions along the height. The 2D MHD simulation shows that for B0 ≈ 3 G, Alfvén waves of about 10-2 Hz with an infinite horizontal length-scale can penetrate into the corona, transferring about 90 per cent their energies. This raises the possibility that the wave can be dissipated by various physical processes. The results show that the propagating wave can effectively damp via viscosity in the lower region of the corona, if a horizontal scale of granular size is incorporated.

Inviscid spatial stability of a compressible mixing layer. Part 2: The flame sheet model

NASA Technical Reports Server (NTRS)

Jackson, T. L.; Grosch, C. E.

1989-01-01

The results of an inviscid spatial calculation for a compressible reacting mixing layer are reported. The limit of infinitive activation energy is taken and the diffusion flame is approximated by a flame sheet. Results are reported for the phase speeds of the neutral waves and maximum growth rates of the unstable waves as a function of the parameters of the problem: the ratio of the temperature of the stationary stream to that of the moving stream, the Mach number of the moving streams, the heat release per unit mass fraction of the reactant, the equivalence ratio of the reaction, and the frequency of the disturbance. These results are compared to the phase speeds and growth rates of the corresponding nonreacting mixing layer. We show that the addition of combustion has important, and complex effects on the flow stability.

Impact of New Nuclear Data Libraries on Small Sized Long Life CANDLE HTGR Design Parameters

NASA Astrophysics Data System (ADS)

Liem, Peng Hong; Hartanto, Donny; Tran, Hoai Nam

2017-01-01

The impact of new evaluated nuclear data libraries (JENDL-4.0, ENDF/B-VII.0 and JEFF-3.1) on the core characteristics of small-sized long-life CANDLE High Temperature Gas-Cooled Reactors (HTGRs) with uranium and thorium fuel cycles was investigated. The most important parameters of the CANDLE core characteristics investigated here covered (1) infinite multiplication factor of the fresh fuel containing burnable poison, (2) the effective multiplication factor of the equilibrium core, (3) the moving velocity of the burning region, (4) the attained discharge burnup, and (5) the maximum power density. The reference case was taken from the current JENDL-3.3 results. For the uranium fuel cycle, the impact of the new libraries was small, while significant impact was found for thorium fuel cycle. The findings indicated the needs of more accurate nuclear data libraries for nuclides involved in thorium fuel cycle in the future.

On the Induction of the First-Order Phase Magnetic Transitions by Acoustic Vibrations in MnSi

NASA Astrophysics Data System (ADS)

Pikin, S. A.

2017-12-01

The main result of the paper contains the conclusion that the magnetic phase transition in MnSi always remains first order at any temperature and magnetic field. In these aims, a model of coupling of an order parameter with other degrees of freedom is used. The coupling of magnetic order parameters with long-wave acoustic phonons, in the presence of the nonsingular parts of the bulk and shear moduli, a first-order transition occurs, participle near the transition the heat capacity and the compressibility remain finite, if the heat capacity becomes infinite in the system disregarding the acoustic phonons. The role of the Frenkel heterophase fluctuations is discussed. The impurity effect shows that, for some phases, the heat capacity of the system remains continuous and finite at the transition point. It is supposed that the transition is progressively smoothed by these fluctuations at the application of the magnetic field.

On the induction of the first-order phase magnetic transitions by acoustic vibrations in MnSi

NASA Astrophysics Data System (ADS)

Pikin, S. A.

2017-12-01

The main result of the paper contains the conclusion that the magnetic phase transition in MnSi always remains first order at any temperature and magnetic field. In these aims, a model of coupling of an order parameter with other degrees of freedom is used. The coupling of magnetic order parameters with longwave acoustic phonons, in the presence of the nonsingular parts of the bulk and shear moduli, a first-order transition occurs, participle near the transition the heat capacity and the compressibility remain finite, if in the system without allowance of the acoustic phonons the heat capacity becomes infinite. The role of the Frenkel heterophase fluctuations is discussed. The impurity effect shows that, for some phases, the heat capacity of the system remains continuous and finite at the transition point. It is supposed that the transition is progressively smoothed by these fluctuations at the application of the magnetic field.

Analysis of the axisymmetric indentation of a semi-infinite piezoelectric material: The evaluation of the contact stiffness and the effective piezoelectric constant

NASA Astrophysics Data System (ADS)

Yang, Fuqian

2008-04-01

A general solution of the axisymmetric indentation is obtained in the closed form for a semi-infinite, transverse isotropic piezoelectric material by a rigid-conducting indenter of arbitrary-axisymmetric profile. Explicit relationships are derived for dependences of the indentation depth and the indentation-induced charge on indentation force and applied electrical potential. Simple formulas are obtained for contact stiffness and effective piezoelectric constant, which can be used in indentation test and piezoresponse force microscopy to analyze the elastic and piezoelectric responses of piezoelectric materials. Depending on the direction of electric field (the potential difference), the electric field can either increase or suppress indentation deformation. The corresponding results are given for cylindrical, conical, and paraboloidal indenters.

Effect of gravity modulation on thermosolutal convection in an infinite layer of fluid

NASA Astrophysics Data System (ADS)

Saunders, B. V.; Murray, B. T.; McFadden, G. B.; Coriell, S. R.; Wheeler, A. A.

1991-10-01

The effect of time-periodic vertical gravity modulation on the onset of thermosolutal convection in an infinite horizontal layer with stress free boundaries is studied using Floquet theory for the linear stability analysis. Situations are considered for which the fluid layer is stably stratified in either the fingering or diffusive regimes of double diffusive convection. Results are presented both with and without steady background acceleration. Modulation may stabilize an unstable base solution or destabilize a stable base solution. In addition to synchronous and subharmonic response to the modulation frequency, instability in the double diffusive system can occur via a complex conjugate mode. In the diffusive regime, where oscillatory onset occurs in the unmodulated system, regions of resonant instability occur and exhibit strong coupling with the unmodulated oscillatory frequency.

Love-type wave propagation in a pre-stressed viscoelastic medium influenced by smooth moving punch

NASA Astrophysics Data System (ADS)

Singh, A. K.; Parween, Z.; Chatterjee, M.; Chattopadhyay, A.

2015-04-01

In the present paper, a mathematical model studying the effect of smooth moving semi-infinite punch on the propagation of Love-type wave in an initially stressed viscoelastic strip is developed. The dynamic stress concentration due to the punch for the force of a constant intensity has been obtained in the closed form. Method based on Weiner-hopf technique which is indicated by Matczynski has been employed. The study manifests the significant effect of various affecting parameters viz. speed of moving punch associated with Love-type wave speed, horizontal compressive/tensile initial stress, vertical compressive/tensile initial stress, frequency parameter, and viscoelastic parameter on dynamic stress concentration due to semi-infinite punch. Moreover, some important peculiarities have been traced out and depicted by means of graphs.

Effect of injection screen slot geometry on hydraulic conductivity tests

NASA Astrophysics Data System (ADS)

Klammler, Harald; Nemer, Bassel; Hatfield, Kirk

2014-04-01

Hydraulic conductivity and its spatial variability are important hydrogeological parameters and are typically determined through injection tests at different scales. For injection test interpretation, shape factors are required to account for injection screen geometry. Shape factors act as proportionality constants between hydraulic conductivity and observed ratios of injection flow rate and injection head at steady-state. Existing results for such shape factors assume either an ideal screen (i.e., ignoring effects of screen slot geometry) or infinite screen length (i.e., ignoring effects of screen extremes). In the present work, we investigate the combined effects of circumferential screen slot geometry and finite screen length on injection shape factors. This is done in terms of a screen entrance resistance by solving a steady-state potential flow mixed type boundary value problem in a homogeneous axi-symmetric flow domain using a semi-analytical solution approach. Results are compared to existing analytical solutions for circumferential and longitudinal slots on infinite screens, which are found to be identical. Based on an existing approximation, an expression is developed for a dimensionless screen entrance resistance of infinite screens, which is a function of the relative slot area only. For anisotropic conditions, e.g., when conductivity is smaller in the vertical direction than in the horizontal, screen entrance losses for circumferential slots increase, while they remain unaffected for longitudinal slots. This work is not concerned with investigating the effects of (possibly turbulent) head losses inside the injection device including the passage through the injection slots prior to entering the porous aquifer.

Consideration of some factors affecting low-frequency fuselage noise transmission for propeller aircraft

NASA Technical Reports Server (NTRS)

Mixson, J. S.; Roussos, L. A.

1986-01-01

Possible reasons for disagreement between measured and predicted trends of sidewall noise transmission at low frequency are investigated using simplified analysis methods. An analytical model combining incident plane acoustic waves with an infinite flat panel is used to study the effects of sound incidence angle, plate structural properties, frequency, absorption, and the difference between noise reduction and transmission loss. Analysis shows that these factors have significant effects on noise transmission but they do not account for the differences between measured and predicted trends at low frequencies. An analytical model combining an infinite flat plate with a normally incident acoustic wave having exponentially decaying magnitude along one coordinate is used to study the effect of a localized source distribution such as is associated with propeller noise. Results show that the localization brings the predicted low-frequency trend of noise transmission into better agreement with measured propeller results. This effect is independent of low-frequency stiffness effects that have been previously reported to be associated with boundary conditions.

Finite volume effects on the electric polarizability of neutral hadrons in lattice QCD

NASA Astrophysics Data System (ADS)

Lujan, M.; Alexandru, A.; Freeman, W.; Lee, F. X.

2016-10-01

We study the finite volume effects on the electric polarizability for the neutron, neutral pion, and neutral kaon using eight dynamically generated two-flavor nHYP-clover ensembles at two different pion masses: 306(1) and 227(2) MeV. An infinite volume extrapolation is performed for each hadron at both pion masses. For the neutral kaon, finite volume effects are relatively mild. The dependence on the quark mass is also mild, and a reliable chiral extrapolation can be performed along with the infinite volume extrapolation. Our result is αK0 phys=0.356 (74 )(46 )×10-4 fm3 . In contrast, for neutron, the electric polarizability depends strongly on the volume. After removing the finite volume corrections, our neutron polarizability results are in good agreement with chiral perturbation theory. For the connected part of the neutral pion polarizability, the negative trend persists, and it is not due to finite volume effects but likely sea quark charging effects.

Lyapunov exponents for infinite dimensional dynamical systems

NASA Technical Reports Server (NTRS)

Mhuiris, Nessan Mac Giolla

1987-01-01

Classically it was held that solutions to deterministic partial differential equations (i.e., ones with smooth coefficients and boundary data) could become random only through one mechanism, namely by the activation of more and more of the infinite number of degrees of freedom that are available to such a system. It is only recently that researchers have come to suspect that many infinite dimensional nonlinear systems may in fact possess finite dimensional chaotic attractors. Lyapunov exponents provide a tool for probing the nature of these attractors. This paper examines how these exponents might be measured for infinite dimensional systems.

Role of switching-on and -off effects in the vacuum instability

NASA Astrophysics Data System (ADS)

Adorno, T. C.; Ferreira, R.; Gavrilov, S. P.; Gitman, D. M.

2018-04-01

We find exact differential mean numbers of fermions and bosons created from the vacuum due to a composite electric field of special configuration. This configuration imitates a finite switching-on and -off regime and consists of fields that switch on exponentially from the infinitely remote past, remains constant during a certain interval T and switch off exponentially to the infinitely remote future. We show that calculations in the slowly varying field approximation are completely predictable in the framework of a locally constant field approximation. Beyond the slowly varying field approximation, we study effects of fast switching on and off in a number of cases when the size of the dimensionless parameter eET is either close or exceeds the threshold value that determines the transition from a regime sensitive to on-off parameters to the slowly varying regime for which these effects are secondary.

Effects of relaxation of gluten network on rehydration kinetics of pasta.

PubMed

Ogawa, Takenobu; Hasegawa, Ayako; Adachi, Shuji

2014-01-01

The aim of this study was to investigate the effects of the relaxation of the gluten network on pasta rehydration kinetics. The moisture content of pasta, under conditions where the effects of the diffusion of water on the moisture content were negligible, was estimated by extrapolating the average moisture content of pasta of various diameters to 0 mm. The moisture content of imaginary, infinitely thin pasta did not reach equilibrium even after 1 h of rehydration. The rehydration of pasta made of only gluten was also measured. The rate constants estimated by the Long and Richman equation for both the pasta indicated that the rehydration kinetics of infinitely thin pasta were similar to those of gluten pasta. These results suggest that the swelling of starch by fast gelatinization was restricted by the honeycomb structural network of gluten and the relaxation of the gluten network controlled pasta rehydration kinetics.

Maximally random discrete-spin systems with symmetric and asymmetric interactions and maximally degenerate ordering

NASA Astrophysics Data System (ADS)

Atalay, Bora; Berker, A. Nihat

2018-05-01

Discrete-spin systems with maximally random nearest-neighbor interactions that can be symmetric or asymmetric, ferromagnetic or antiferromagnetic, including off-diagonal disorder, are studied, for the number of states q =3 ,4 in d dimensions. We use renormalization-group theory that is exact for hierarchical lattices and approximate (Migdal-Kadanoff) for hypercubic lattices. For all d >1 and all noninfinite temperatures, the system eventually renormalizes to a random single state, thus signaling q ×q degenerate ordering. Note that this is the maximally degenerate ordering. For high-temperature initial conditions, the system crosses over to this highly degenerate ordering only after spending many renormalization-group iterations near the disordered (infinite-temperature) fixed point. Thus, a temperature range of short-range disorder in the presence of long-range order is identified, as previously seen in underfrustrated Ising spin-glass systems. The entropy is calculated for all temperatures, behaves similarly for ferromagnetic and antiferromagnetic interactions, and shows a derivative maximum at the short-range disordering temperature. With a sharp immediate contrast of infinitesimally higher dimension 1 +ɛ , the system is as expected disordered at all temperatures for d =1 .

Densities and apparent molar volumes of atmospherically important electrolyte solutions. 1. The solutes H2SO4, HNO3, HCl, Na2SO4, NaNO3, NaCl, (NH4)2SO4, NH4NO3, and NH4Cl from 0 to 50 °C, including extrapolations to very low temperature and to the pure liquid state, and NaHSO4, NaOH, and NH3 at 25 °C.

PubMed

Clegg, S L; Wexler, A S

2011-04-21

Calculations of the size and density of atmospheric aerosols are complicated by the fact that they can exist at concentrations highly supersaturated with respect to dissolved salts and supercooled with respect to ice. Densities and apparent molar volumes of solutes in aqueous solutions containing the solutes H(2)SO(4), HNO(3), HCl, Na(2)SO(4), NaNO(3), NaCl, (NH(4))(2)SO(4), NH(4)NO(3), and NH(4)Cl have been critically evaluated and represented using fitted equations from 0 to 50 °C or greater and from infinite dilution to concentrations saturated or supersaturated with respect to the dissolved salts. Using extrapolated densities of high-temperature solutions and melts, the relationship between density and concentration is extended to the hypothetical pure liquid solutes. Above a given reference concentration of a few mol kg(-1), it is observed that density increases almost linearly with decreasing temperature, and comparisons with available data below 0 °C suggest that the fitted equations for density can be extrapolated to very low temperatures. As concentration is decreased below the reference concentration, the variation of density with temperature tends to that of water (which decreases as temperature is reduced below 3.98 °C). In this region below the reference concentration, and below 0 °C, densities are calculated using extrapolated apparent molar volumes which are constrained to agree at the reference concentrations with an equation for the directly fitted density. Calculated volume properties agree well with available data at low temperatures, for both concentrated and dilute solutions. Comparisons are made with literature data for temperatures of maximum density. Apparent molar volumes at infinite dilution are consistent, on a single ion basis, to better than ±0.1 cm(3) mol(-1) from 0 to 50 °C. Volume properties of aqueous NaHSO(4), NaOH, and NH(3) have also been evaluated, at 25 °C only. In part 2 of this work (ref 1 ) an ion interaction (Pitzer) model has been used to calculate apparent molar volumes of H(2)SO(4) in 0-3 mol kg(-1) aqueous solutions of the pure acid and to represent directly the effect of the HSO(4)(-) ↔ H(+) + SO(4)(2-) reaction. The results are incorporated into the treatment of aqueous H(2)SO(4) density described here. Densities and apparent molar volumes from -20 to 50 °C, and from 0 to 100 wt % of solute, are tabulated for the electrolytes listed in the title and have also been incorporated into the extended aerosol inorganics model (E-AIM, http://www.aim.env.uea.ac.uk/aim/aim.php) together with densities of the solid salts and hydrates.

A statics-dynamics equivalence through the fluctuation–dissipation ratio provides a window into the spin-glass phase from nonequilibrium measurements

PubMed Central

Baity-Jesi, Marco; Calore, Enrico; Cruz, Andres; Fernandez, Luis Antonio; Gil-Narvión, José Miguel; Gordillo-Guerrero, Antonio; Iñiguez, David; Maiorano, Andrea; Marinari, Enzo; Martin-Mayor, Victor; Monforte-Garcia, Jorge; Muñoz Sudupe, Antonio; Navarro, Denis; Parisi, Giorgio; Perez-Gaviro, Sergio; Ricci-Tersenghi, Federico; Ruiz-Lorenzo, Juan Jesus; Schifano, Sebastiano Fabio; Tarancón, Alfonso; Tripiccione, Raffaele; Yllanes, David

2017-01-01

We have performed a very accurate computation of the nonequilibrium fluctuation–dissipation ratio for the 3D Edwards–Anderson Ising spin glass, by means of large-scale simulations on the special-purpose computers Janus and Janus II. This ratio (computed for finite times on very large, effectively infinite, systems) is compared with the equilibrium probability distribution of the spin overlap for finite sizes. Our main result is a quantitative statics-dynamics dictionary, which could allow the experimental exploration of important features of the spin-glass phase without requiring uncontrollable extrapolations to infinite times or system sizes. PMID:28174274

Acquisition of Inertia by a Moving Crack

NASA Astrophysics Data System (ADS)

Goldman, Tamar; Livne, Ariel; Fineberg, Jay

2010-03-01

We experimentally investigate the dynamics of “simple” tensile cracks. Within an effectively infinite medium, a crack’s dynamics perfectly correspond to inertialess behavior predicted by linear elastic fracture mechanics. Once a crack interacts with waves that it generated at earlier times, this description breaks down. Cracks then acquire inertia and sluggishly accelerate. Crack inertia increases with crack speed v and diverges as v approaches its limiting value. We show that these dynamics are in excellent accord with an equation of motion derived in the limit of an infinite strip [M. Marder, Phys. Rev. Lett. 66, 2484 (1991)PRLTAO0031-900710.1103/PhysRevLett.66.2484].

Time-space modal logic for verification of bit-slice circuits

NASA Astrophysics Data System (ADS)

Hiraishi, Hiromi

1996-03-01

The major goal of this paper is to propose a new modal logic aiming at formal verification of bit-slice circuits. The new logic is called as time-space modal logic and its major feature is that it can handle two transition relations: one for time transition and the other for space transition. As for a verification algorithm, a symbolic model checking algorithm of the new logic is shown. This could be applicable to verification of bit-slice microprocessor of infinite bit width and 1D systolic array of infinite length. A simple benchmark result shows the effectiveness of the proposed approach.

Grid-free density functional calculations on periodic systems.

PubMed

Varga, Stefan

2007-09-21

Density fitting scheme is applied to the exchange part of the Kohn-Sham potential matrix in a grid-free local density approximation for infinite systems with translational periodicity. It is shown that within this approach the computational demands for the exchange part scale in the same way as for the Coulomb part. The efficiency of the scheme is demonstrated on a model infinite polymer chain. For simplicity, the implementation with Dirac-Slater Xalpha exchange functional is presented only. Several choices of auxiliary basis set expansion coefficients were tested with both Coulomb and overlap metric. Their effectiveness is discussed also in terms of robustness and norm preservation.

Grid-free density functional calculations on periodic systems

NASA Astrophysics Data System (ADS)

Varga, Štefan

2007-09-01

Density fitting scheme is applied to the exchange part of the Kohn-Sham potential matrix in a grid-free local density approximation for infinite systems with translational periodicity. It is shown that within this approach the computational demands for the exchange part scale in the same way as for the Coulomb part. The efficiency of the scheme is demonstrated on a model infinite polymer chain. For simplicity, the implementation with Dirac-Slater Xα exchange functional is presented only. Several choices of auxiliary basis set expansion coefficients were tested with both Coulomb and overlap metric. Their effectiveness is discussed also in terms of robustness and norm preservation.

The University as an Infinite Game: Revitalising Activism in the Academy

ERIC Educational Resources Information Center

Harré, Niki; Grant, Barbara M.; Locke, Kirsten; Sturm, Sean

2017-01-01

We offer here a metaphor of the university as an "infinite game" in which we bring to life insight, imagination, and radical inclusion; and resist the "finite games" that can lead us astray. We suggest that keeping the infinite game alive within universities is a much-needed form of academic activism. We offer four vignettes…

Orthogonality preserving infinite dimensional quadratic stochastic operators

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

Akın, Hasan; Mukhamedov, Farrukh

In the present paper, we consider a notion of orthogonal preserving nonlinear operators. We introduce π-Volterra quadratic operators finite and infinite dimensional settings. It is proved that any orthogonal preserving quadratic operator on finite dimensional simplex is π-Volterra quadratic operator. In infinite dimensional setting, we describe all π-Volterra operators in terms orthogonal preserving operators.

Inspiring Examples in Rearrangements of Infinite Products

ERIC Educational Resources Information Center

Ramasinghe, W.

2007-01-01

It is well known that simple examples are really encouraging in the understanding of rearrangements of infinite series. In this paper a similar role is played by simple examples in the case of infinite products. Iterated products of double products seem to have a similar spirit of rearrangements of products, although they are not the same.…

The Transition from Comparison of Finite to the Comparison of Infinite Sets: Teaching Prospective Teachers.

ERIC Educational Resources Information Center

Tsamir, Pessia

1999-01-01

Describes a course in Cantorian Set Theory relating to prospective secondary mathematics teachers' tendencies to overgeneralize from finite to infinite sets. Indicates that when comparing the number of elements in infinite sets, teachers who took the course were more successful and more consistent in their use of single method than those who…

Certain approximation problems for functions on the infinite-dimensional torus: Lipschitz spaces

NASA Astrophysics Data System (ADS)

Platonov, S. S.

2018-02-01

We consider some questions about the approximation of functions on the infinite-dimensional torus by trigonometric polynomials. Our main results are analogues of the direct and inverse theorems in the classical theory of approximation of periodic functions and a description of the Lipschitz spaces on the infinite-dimensional torus in terms of the best approximation.

Analytical study of nozzle performance for nuclear thermal rockets

NASA Technical Reports Server (NTRS)

Davidian, Kenneth O.; Kacynski, Kenneth J.

1991-01-01

Nuclear propulsion has been identified as one of the key technologies needed for human exploration of the Moon and Mars. The Nuclear Thermal Rocket (NTR) uses a nuclear reactor to heat hydrogen to a high temperature followed by expansion through a conventional convergent-divergent nozzle. A parametric study of NTR nozzles was performed using the Rocket Engine Design Expert System (REDES) at the NASA Lewis Research Center. The REDES used the JANNAF standard rigorous methodology to determine nozzle performance over a range of chamber temperatures, chamber pressures, thrust levels, and different nozzle configurations. A design condition was set by fixing the propulsion system exit radius at five meters and throat radius was varied to achieve a target thrust level. An adiabatic wall was assumed for the nozzle, and its length was assumed to be 80 percent of a 15 degree cone. The results conclude that although the performance of the NTR, based on infinite reaction rates, looks promising at low chamber pressures, finite rate chemical reactions will cause the actual performance to be considerably lower. Parameters which have a major influence on the delivered specific impulse value include the chamber temperature and the chamber pressures in the high thrust domain. Other parameters, such as 2-D and boundary layer effects, kinetic rates, and number of nozzles, affect the deliverable performance of an NTR nozzle to a lesser degree. For a single nozzle, maximum performance of 930 seconds and 1030 seconds occur at chamber temperatures of 2700 and 3100 K, respectively.

Finite Feedback Cycling in Structural Equation Models

ERIC Educational Resources Information Center

Hayduk, Leslie A.

2009-01-01

In models containing reciprocal effects, or longer causal loops, the usual effect estimates assume that any effect touching a loop initiates an infinite cycling of effects around that loop. The real world, in contrast, might permit only finite feedback cycles. I use a simple hypothetical model to demonstrate that if the world permits only a few…

Magnetism of californium metal

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

Nave, S.E.; Moore, J.R.; Spaar, M.T.

1984-01-01

Magnetic susceptibility measurements have been made on samples of californium-249 metal having the dhcp crystal structure. At temperatures between 100K and 300K and at fields up to 50 kilogauss, the samples exhibit Curie-Weiss behavior with 3 samples giving a magnetic moment per atom of ..mu../sub eff/ = 10.6 +- 0.2 ..mu../sub B/ and paramagnetic Weiss temperatures, theta/sub p/, in the range of -2K to -41K. These values of ..mu../sub eff/ are in good agreement with the value expected (10.62..mu../sub B/) for a free-ion 5f/sup 9/ configuration based on an L-S coupling scheme and Hund's Rule. A fourth sample gives themore » values ..mu../sub eff/ = 9.7 +- 0.2..mu../sub B/ and theta/sub p/ = -41K. At low temperatures the samples exhibit an ordered magnetic transition to a state with a saturated moment of 6.1 ..mu../sub B//atom when extrapolated to infinitely-high field. The low temperature ordered phase exists at temperatures below T/sub c/ = 51 +- 2K as determined from constant magnetization plots. 2 references, 3 figures.« less

Matrix theory interpretation of discrete light cone quantization string worldsheets

PubMed

Grignani; Orland; Paniak; Semenoff

2000-10-16

We study the null compactification of type-IIA string perturbation theory at finite temperature. We prove a theorem about Riemann surfaces establishing that the moduli spaces of infinite-momentum-frame superstring worldsheets are identical to those of branched-cover instantons in the matrix-string model conjectured to describe M theory. This means that the identification of string degrees of freedom in the matrix model proposed by Dijkgraaf, Verlinde, and Verlinde is correct and that its natural generalization produces the moduli space of Riemann surfaces at all orders in the genus expansion.

Proceedings of the 1987 Scientific Conference on Obscuration and Aerosol Research

DTIC Science & Technology

1988-10-01

anodized aluminum plate on the other, is intended to simulate a semi-infinite medium. The mirrors M1 and M2, aperture, and lens L3 collect the light... OXIDATION OF SULFUR DIOXIDE WITH OH RADICAL IN THE PRESENCE OF WATER VAPOUR AND AMMlONIA TO FORM CONDENSATION NUCLEI Patrick M. Nolan and James P. Friend...determined from the relation p pRT Aao 2D,Mf ý_t where temperature, Dg is the gas phase diffusion coefficient, and Mw is the molecular weight of the

Black hole evaporation in conformal gravity

NASA Astrophysics Data System (ADS)

Bambi, Cosimo; Modesto, Leonardo; Porey, Shiladitya; Rachwał, Lesław

2017-09-01

We study the formation and the evaporation of a spherically symmetric black hole in conformal gravity. From the collapse of a spherically symmetric thin shell of radiation, we find a singularity-free non-rotating black hole. This black hole has the same Hawking temperature as a Schwarzschild black hole with the same mass, and it completely evaporates either in a finite or in an infinite time, depending on the ensemble. We consider the analysis both in the canonical and in the micro-canonical statistical ensembles. Last, we discuss the corresponding Penrose diagram of this physical process.

Iterative adaption of the bidimensional wall of the French T2 wind tunnel around a C5 axisymmetrical model: Infinite variation of the Mach number at zero incidence and a test at increased incidence

NASA Technical Reports Server (NTRS)

Archambaud, J. P.; Dor, J. B.; Payry, M. J.; Lamarche, L.

1986-01-01

The top and bottom two-dimensional walls of the T2 wind tunnel are adapted through an iterative process. The adaptation calculation takes into account the flow three-dimensionally. This method makes it possible to start with any shape of walls. The tests were performed with a C5 axisymmetric model at ambient temperature. Comparisons are made with the results of a true three-dimensional adaptation.

A TBA approach to thermal transport in the XXZ Heisenberg model

NASA Astrophysics Data System (ADS)

Zotos, X.

2017-10-01

We show that the thermal Drude weight and magnetothermal coefficient of the 1D easy-plane Heisenberg model can be evaluated by an extension of the Bethe ansatz thermodynamics formulation by Takahashi and Suzuki (1972 Prog. Theor. Phys. 48 2187). They have earlier been obtained by the quantum transfer matrix method (Klümper 1999 Z. Phys. B 91 507). Furthermore, this approach can be applied to the study of the far-out of equilibrium energy current generated at the interface between two semi-infinite chains held at different temperatures.

Linear-to-λ-Shape P-O-P Bond Transmutation in Polyphosphates with Infinite (PO3)∞ Chain.

PubMed

Wang, Ying; Li, Lin; Han, Shujuan; Lei, Bing-Hua; Abudoureheman, Maierhaba; Yang, Zhihua; Pan, Shilie

2017-09-05

A new metal polyphosphate, α-CsBa 2 (PO 3 ) 5 , exhibiting the first example of a linear P-O-P bond angle in a one-dimensional (PO 3 ) ∞ chain has been reported. Interestingly, α → β phase transition occurs in CsBa 2 (PO 3 ) 5 along with the P-O-P bonds varying from linear to λ-shape, suggesting that α-CsBa 2 (PO 3 ) 5 with unfavorable linear P-O-P bonds is more stable at ambient temperature.

Black hole evaporation in conformal gravity

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

Bambi, Cosimo; Rachwał, Lesław; Modesto, Leonardo

We study the formation and the evaporation of a spherically symmetric black hole in conformal gravity. From the collapse of a spherically symmetric thin shell of radiation, we find a singularity-free non-rotating black hole. This black hole has the same Hawking temperature as a Schwarzschild black hole with the same mass, and it completely evaporates either in a finite or in an infinite time, depending on the ensemble. We consider the analysis both in the canonical and in the micro-canonical statistical ensembles. Last, we discuss the corresponding Penrose diagram of this physical process.

Infinite index extensions of local nets and defects

NASA Astrophysics Data System (ADS)

Del Vecchio, Simone; Giorgetti, Luca

The subfactor theory provides a tool to analyze and construct extensions of Quantum Field Theories, once the latter are formulated as local nets of von Neumann algebras. We generalize some of the results of [62] to the case of extensions with infinite Jones index. This case naturally arises in physics, the canonical examples are given by global gauge theories with respect to a compact (non-finite) group of internal symmetries. Building on the works of Izumi-Longo-Popa [44] and Fidaleo-Isola [30], we consider generalized Q-systems (of intertwiners) for a semidiscrete inclusion of properly infinite von Neumann algebras, which generalize ordinary Q-systems introduced by Longo [58] to the infinite index case. We characterize inclusions which admit generalized Q-systems of intertwiners and define a braided product among the latter, hence we construct examples of QFTs with defects (phase boundaries) of infinite index, extending the family of boundaries in the grasp of [7].

Self-consistent elastic continuum theory of degenerate, equilibrium aperiodic solids.

PubMed

Bevzenko, Dmytro; Lubchenko, Vassiliy

2014-11-07

We show that the vibrational response of a glassy liquid at finite frequencies can be described by continuum mechanics despite the vast degeneracy of the vibrational ground state; standard continuum elasticity assumes a unique ground state. The effective elastic constants are determined by the bare elastic constants of individual free energy minima of the liquid, the magnitude of built-in stress, and temperature, analogously to how the dielectric response of a polar liquid is determined by the dipole moment of the constituent molecules and temperature. In contrast with the dielectric constant--which is enhanced by adding polar molecules to the system--the elastic constants are down-renormalized by the relaxation of the built-in stress. The renormalization flow of the elastic constants has three fixed points, two of which are trivial and correspond to the uniform liquid state and an infinitely compressible solid, respectively. There is also a nontrivial fixed point at the Poisson ratio equal to 1/5, which corresponds to an isospin-like degeneracy between shear and uniform deformation. The present description predicts a discontinuous jump in the (finite frequency) shear modulus at the crossover from collisional to activated transport, consistent with the random first order transition theory.

Chemistry and structure of coal-derived asphaltenes, Phase III. Quarterly progress report, January--March 1978

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

Yen, T. F.

1978-01-01

The solubility limits of Synthoil and PAMCO asphaltenes have been measured as a function of Hildebrand solubility parameters and hydrogen bonding. Solvents with moderate hydrogen bonding capacity such as dioxane, ethyl benzoate and dibutyl phthalate were found to be most effective in dissolving asphaltenes over the widest range of solubility parameters. VPO molecular weight studies of coal liquid derived carbenes, as a function of concentration in the solvent THF, indicate that these fractions are more strongly self-associated than the corresponding asphaltenes, and generally afford high infinite dilution number average molecular weights: Synthoil, 861; HRI H-Coal, 1156; Cat. Inc. SRC, 1228;more » PAMCO SRC, 1054. The variable ESR temperature dependence of the spin intensity for a Synthoil asphaltene-I/sub 2/ charge transfer followed a 1/T (Curie--Weiss) dependence over the temperature range from 25/sup 0/ to -114/sup 0/C suggesting that independent, non-interacting donor and acceptor doublets were formed. Weight percent OH values, determined from 'H NMR analysis of silylated asphaltenes, were found to provide a reasonably linear correlation with the absorbance of the monomeric OH infrared stretching bands of the asphaltenes.« less

Introduction to the theory of infinite systems. Theory and practices

NASA Astrophysics Data System (ADS)

Fedorov, Foma M.

2017-11-01

A review of the author's work is given, which formed the basis for a new theory of general infinite systems. The Gaussian elimination and Cramer's rule have been extended to infinite systems. A special particular solution is obtained, it is called a strictly particular solution. Necessary and sufficient conditions for existence of the nontrivial solutions of homogeneous systems are given.

Confusing Aspects in the Calculation of the Electrostatic Potential of an Infinite Line of Charge

ERIC Educational Resources Information Center

Jimenez, J. L.; Campos, I.; Roa-Neri, J. A. E.

2012-01-01

In this work we discuss the trick of eliminating infinite potential of reference arguing that it corresponds to a constant of integration, in the problem of determining the electrostatic potential of an infinite line of charge with uniform density, and show how the problem must be tackled properly. The usual procedure is confusing for most…

Functors of White Noise Associated to Characters of the Infinite Symmetric Group

NASA Astrophysics Data System (ADS)

Bożejko, Marek; Guţă, Mădălin

The characters of the infinite symmetric group are extended to multiplicative positive definite functions on pair partitions by using an explicit representation due to Veršik and Kerov. The von Neumann algebra generated by the fields with f in an infinite dimensional real Hilbert space is infinite and the vacuum vector is not separating. For a family depending on an integer N< - 1 an ``exclusion principle'' is found allowing at most ``identical particles'' on the same state: The algebras are type factors. Functors of white noise are constructed and proved to be non-equivalent for different values of N.

Regular Gleason Measures and Generalized Effect Algebras

NASA Astrophysics Data System (ADS)

Dvurečenskij, Anatolij; Janda, Jiří

2015-12-01

We study measures, finitely additive measures, regular measures, and σ-additive measures that can attain even infinite values on the quantum logic of a Hilbert space. We show when particular classes of non-negative measures can be studied in the frame of generalized effect algebras.

Hybrid Defect Phase Transition: Renormalization Group and Monte Carlo Analysis

NASA Astrophysics Data System (ADS)

Kaufman, Miron; Diep, H. T.

2010-03-01

For the q-state Potts model with 2 < q <= 4 on the square lattice with a defect line, the order parameter on the defect line jumps discontinuously from zero to a nonzero value while the defect energy varies continuously with the temperature at the critical temperature. Monte-Carlo simulations (H. T. Diep, M. Kaufman, Phys Rev E 2009) of the q-state Potts model on a square lattice with a line of defects verify the renormalization group prediction (M. Kaufman, R. B. Griffiths, Phys Rev B 1982) on the occurrence of the hybrid transition on the defect line. This is interesting since for those q values the bulk transition is continuous. This hybrid (continuous - discontinuous) defect transition is induced by the infinite range correlations at the bulk critical point.

Existence of negative differential thermal conductance in one-dimensional diffusive thermal transport

NASA Astrophysics Data System (ADS)

Hu, Jiuning; Chen, Yong P.

2013-06-01

We show that in a finite one-dimensional (1D) system with diffusive thermal transport described by the Fourier's law, negative differential thermal conductance (NDTC) cannot occur when the temperature at one end is fixed and there are no abrupt junctions. We demonstrate that NDTC in this case requires the presence of junction(s) with temperature-dependent thermal contact resistance (TCR). We derive a necessary and sufficient condition for the existence of NDTC in terms of the properties of the TCR for systems with a single junction. We show that under certain circumstances we even could have infinite (negative or positive) differential thermal conductance in the presence of the TCR. Our predictions provide theoretical basis for constructing NDTC-based devices, such as thermal amplifiers, oscillators, and logic devices.

Electrophoresis of fd-virus particles: experiments and an analysis of the effect of finite rod lengths.

PubMed

Buitenhuis, Johan

2012-09-18

The electrophoretic mobility of rodlike fd viruses is measured and compared to theory, with the theoretical calculations performed according to Stigter (Stigter, D. Charged Colloidal Cylinder with a Gouy Double-Layer. J. Colloid Interface Sci. 1975, 53, 296-306. Stigter, D. Electrophoresis of Highly Charged Colloidal Cylinders in Univalent Salt- Solutions. 1. Mobility in Transverse Field. J. Phys. Chem. 1978, 82, 1417-1423. Stigter, D. Electrophoresis of Highly Charged Colloidal Cylinders in Univalent Salt Solutions. 2. Random Orientation in External Field and Application to Polyelectrolytes. J. Phys. Chem. 1978, 82, 1424-1429. Stigter, D. Theory of Conductance of Colloidal Electrolytes in Univalent Salt Solutions. J. Phys. Chem. 1979, 83, 1663-1670), who describes the electrophoretic mobility of infinite cylinders including relaxation effects. Using the dissociation constants of the ionizable groups on the surfaces of the fd viruses, we can calculate the mobility without any adjustable parameter (apart from the possible Stern layer thickness). In addition, the approximation in the theoretical description of Stigter (and others) of using a model of infinitely long cylinders, which consequently is independent of the aspect ratio, is examined by performing more elaborate numerical calculations for finite cylinders. It is shown that, although the electrophoretic mobility of cylindrical particles in the limit of low ionic strength depends on the aspect ratio much more than "end effects", at moderate and high ionic strengths the finite and infinite cylinder models differ only to a degree that can be attributed to end effects. Furthermore, the range of validity of the Stokes regime is systematically calculated.

Mean Green operators of deformable fiber networks embedded in a compliant matrix and property estimates

NASA Astrophysics Data System (ADS)

Franciosi, Patrick; Spagnuolo, Mario; Salman, Oguz Umut

2018-04-01

Composites comprising included phases in a continuous matrix constitute a huge class of meta-materials, whose effective properties, whether they be mechanical, physical or coupled, can be selectively optimized by using appropriate phase arrangements and architectures. An important subclass is represented by "network-reinforced matrices," say those materials in which one or more of the embedded phases are co-continuous with the matrix in one or more directions. In this article, we present a method to study effective properties of simple such structures from which more complex ones can be accessible. Effective properties are shown, in the framework of linear elasticity, estimable by using the global mean Green operator for the entire embedded fiber network which is by definition through sample spanning. This network operator is obtained from one of infinite planar alignments of infinite fibers, which the network can be seen as an interpenetrated set of, with the fiber interactions being fully accounted for in the alignments. The mean operator of such alignments is given in exact closed form for isotropic elastic-like or dielectric-like matrices. We first exemplify how these operators relevantly provide, from classic homogenization frameworks, effective properties in the case of 1D fiber bundles embedded in an isotropic elastic-like medium. It is also shown that using infinite patterns with fully interacting elements over their whole influence range at any element concentration suppresses the dilute approximation limit of these frameworks. We finally present a construction method for a global operator of fiber networks described as interpenetrated such bundles.

Analytical Proof That There is no Effect of Confinement or Curvature on the Maxwell-Boltzmann Collision Frequency

NASA Astrophysics Data System (ADS)

Carnio, Brett N.; Elliott, Janet A. W.

2014-08-01

The number of Maxwell-Boltzmann particles that hit a flat wall in infinite space per unit area per unit time is a well-known result. As new applications are arising in micro and nanotechnologies there are a number of situations in which a rarefied gas interacts with either a flat or curved surface in a small confined geometry. Thus, it is necessary to prove that the Maxwell-Boltzmann collision frequency result holds even if a container's dimensions are on the order of nanometers and also that this result is valid for both a finite container with flat walls (a rectangular container) and a finite container with a curved wall (a cylindrical container). An analytical proof confirms that the Maxwell-Boltzmann collision frequencies for either a finite rectangular container or a finite cylindrical container are both equal to the well-known result obtained for a flat wall in infinite space. A major aspect of this paper is the introduction of a mathematical technique to solve the arising infinite sum of integrals whose integrands depend on the Maxwell-Boltzmann velocity distribution.

Progressive phase trends in plates with embedded acoustic black holes.

PubMed

Conlon, Stephen C; Feurtado, Philip A

2018-02-01

Acoustic black holes (ABHs) have been explored and demonstrated to be effective passive treatments for broadband noise and vibration control. Performance metrics for assessing damping concepts are often focused on maximizing structural damping loss factors. Optimally performing damping treatments can reduce the resonant response of a driven system well below the direct field response. This results in a finite structure whose vibration input-output response follows that of an infinite structure. The vibration mobility transfer functions between locations on a structure can be used to assess the structure's vibration response phase, and compare its phase response characteristics to those of idealized systems. This work experimentally explores the phase accumulation in finite plates, with and without embedded grids of ABHs. The measured results are compared and contrasted with theoretical results for finite and infinite uniform plates. Accumulated phase characteristics, their spatial dependence and limits, are examined for the plates and compared to theoretical estimates. The phase accumulation results show that the embedded acoustic black hole treatments can significantly enhance the damping of the plates to the point that their phase accumulation follows that of an infinite plate.

Ideas of Flat and Curved Space in History of Physics

NASA Astrophysics Data System (ADS)

Berezin, Alexander A.

2006-04-01

Since ``everything which is not prohibited is compulsory'' (assigned to Gell-Mann) we can postulate infinite flat Cartesian N-dimensional (N: any integer) space-time (ST) as embedding for any curved ST. Ergodicity raises quest of whether total number of inflationary and/or Everett bubbles (mini-verses) is finite, countably infinite (aleph-zero) or uncountably infinite (aleph-one). Are these bubbles form Gaussian distribution or form some non-random subsetting? Perhaps, communication between mini-verses (idea of D.Deutsch) can be facilitated by a kind of minimax non-local dynamics akin to Fermat principle? (Minimax Principle in Bubble Cosmology). Even such classical effects as magnetism and polarization have some non-local features. Can we go below the Planck length to perhaps Compton wavelength of our ``Hubble's bubble'' (h/Mc = 10 to minus 95 m, if M = 10 to 54 kg)? When talking about time loops and ergodicity (eternal return paradigm) is there some hysterisis in the way quantum states are accessed in ``forward'' or ``reverse'' direction? (reverse direction implies backward causality of J.Wheeler and/or Aristotelian final causation).

Using infinite-volume, continuum QED and lattice QCD for the hadronic light-by-light contribution to the muon anomalous magnetic moment

NASA Astrophysics Data System (ADS)

Blum, Thomas; Christ, Norman; Hayakawa, Masashi; Izubuchi, Taku; Jin, Luchang; Jung, Chulwoo; Lehner, Christoph

2017-08-01

In our previous work, Blum et al. [Phys. Rev. Lett. 118, 022005 (2017), 10.1103/PhysRevLett.118.022005], the connected and leading disconnected hadronic light-by-light contributions to the muon anomalous magnetic moment (g -2 ) have been computed using lattice QCD ensembles corresponding to physical pion mass generated by the RBC/UKQCD Collaboration. However, the calculation is expected to suffer from a significant finite-volume error that scales like 1 /L2 where L is the spatial size of the lattice. In this paper, we demonstrate that this problem is cured by treating the muon and photons in infinite-volume, continuum QED, resulting in a weighting function that is precomputed and saved with affordable cost and sufficient accuracy. We present numerical results for the case when the quark loop is replaced by a muon loop, finding the expected exponential approach to the infinite volume limit and consistency with the known analytic result. We have implemented an improved weighting function which reduces both discretization and finite-volume effects arising from the hadronic part of the amplitude.

Initial condition-dependent dynamics and transient period in memristor-based hypogenetic jerk system with four line equilibria

NASA Astrophysics Data System (ADS)

Bao, Han; Wang, Ning; Bao, Bocheng; Chen, Mo; Jin, Peipei; Wang, Guangyi

2018-04-01

Memristor-based nonlinear dynamical system easily presents the initial condition-dependent dynamical phenomenon of extreme multistability, i.e., coexisting infinitely many attractors, which has been received much attention in recent years. By introducing an ideal and active flux-controlled memristor into an existing hypogenetic chaotic jerk system, an interesting memristor-based chaotic system with hypogenetic jerk equation and circuit forms is proposed. The most striking feature is that this system has four line equilibria and exhibits the extreme multistability phenomenon of coexisting infinitely many attractors. Stability of these line equilibria are analyzed, and coexisting infinitely many attractors' behaviors with the variations of the initial conditions are investigated by bifurcation diagrams, Lyapunov exponent spectra, attraction basins, and phased portraits, upon which the forming mechanism of extreme multistablity in the memristor-based hypogenetic jerk system is explored. Specially, unusual transition behavior of long term transient period with steady chaos, completely different from the phenomenon of transient chaos, can be also found for some initial conditions. Moreover, a hardware circuit is design and fabricated and its experimental results effectively verify the truth of extreme multistablity.

Using infinite-volume, continuum QED and lattice QCD for the hadronic light-by-light contribution to the muon anomalous magnetic moment

DOE PAGES

Blum, Thomas; Christ, Norman; Hayakawa, Masashi; ...

2017-08-22

In our previous work, the connected and leading disconnected hadronic light-by-light contributions to the muon anomalous magnetic moment (g — 2) have been computed using lattice QCD ensembles corresponding to physical pion mass generated by the RBC/UKQCD Collaboration. However, the calculation is expected to suffer from a significant finite-volume error that scales like 1/L 2 where L is the spatial size of the lattice. In this paper, we demonstrate that this problem is cured by treating the muon and photons in infinite-volume, continuum QED, resulting in a weighting function that is precomputed and saved with affordable cost and sufficient accuracy.more » We present numerical results for the case when the quark loop is replaced by a muon loop, finding the expected exponential approach to the infinite volume limit and consistency with the known analytic result. Here, we have implemented an improved weighting function which reduces both discretization and finite-volume effects arising from the hadronic part of the amplitude.« less

Using infinite-volume, continuum QED and lattice QCD for the hadronic light-by-light contribution to the muon anomalous magnetic moment

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

Blum, Thomas; Christ, Norman; Hayakawa, Masashi

In our previous work, the connected and leading disconnected hadronic light-by-light contributions to the muon anomalous magnetic moment (g — 2) have been computed using lattice QCD ensembles corresponding to physical pion mass generated by the RBC/UKQCD Collaboration. However, the calculation is expected to suffer from a significant finite-volume error that scales like 1/L 2 where L is the spatial size of the lattice. In this paper, we demonstrate that this problem is cured by treating the muon and photons in infinite-volume, continuum QED, resulting in a weighting function that is precomputed and saved with affordable cost and sufficient accuracy.more » We present numerical results for the case when the quark loop is replaced by a muon loop, finding the expected exponential approach to the infinite volume limit and consistency with the known analytic result. Here, we have implemented an improved weighting function which reduces both discretization and finite-volume effects arising from the hadronic part of the amplitude.« less

Elastic guided waves in a layered plate with rectangular cross section.

PubMed

Mukdadi, O M; Desai, Y M; Datta, S K; Shah, A H; Niklasson, A J

2002-11-01

Guided waves in a layered elastic plate of rectangular cross section (finite width and thickness) has been studied in this paper. A semianalytical finite element method in which the deformation of the cross section is modeled by two-dimensional finite elements and analytical representation of propagating waves along the length of the plate has been used. The method is applicable to arbitrary number of layers and general anisotropic material properties of each layer, and is similar to the stiffness method used earlier to study guided waves in a laminated composite plate of infinite width. Numerical results showing the effect of varying the width of the plate on the dispersion of guided waves are presented and are compared with those for an infinite plate. In addition, effect of thin anisotropic coating or interface layers on the guided waves is investigated.

Non-pairwise additivity of the leading-order dispersion energy

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

Hollett, Joshua W., E-mail: j.hollett@uwinnipeg.ca

2015-02-28

The leading-order (i.e., dipole-dipole) dispersion energy is calculated for one-dimensional (1D) and two-dimensional (2D) infinite lattices, and an infinite 1D array of infinitely long lines, of doubly occupied locally harmonic wells. The dispersion energy is decomposed into pairwise and non-pairwise additive components. By varying the force constant and separation of the wells, the non-pairwise additive contribution to the dispersion energy is shown to depend on the overlap of density between neighboring wells. As well separation is increased, the non-pairwise additivity of the dispersion energy decays. The different rates of decay for 1D and 2D lattices of wells is explained inmore » terms of a Jacobian effect that influences the number of nearest neighbors. For an array of infinitely long lines of wells spaced 5 bohrs apart, and an inter-well spacing of 3 bohrs within a line, the non-pairwise additive component of the leading-order dispersion energy is −0.11 kJ mol{sup −1} well{sup −1}, which is 7% of the total. The polarizability of the wells and the density overlap between them are small in comparison to that of the atomic densities that arise from the molecular density partitioning used in post-density-functional theory (DFT) damped dispersion corrections, or DFT-D methods. Therefore, the nonadditivity of the leading-order dispersion observed here is a conservative estimate of that in molecular clusters.« less

Knudsen pump inspired by Crookes radiometer with a specular wall

NASA Astrophysics Data System (ADS)

Baier, Tobias; Hardt, Steffen; Shahabi, Vahid; Roohi, Ehsan

2017-03-01

A rarefied gas is considered in a channel consisting of two infinite parallel plates between which an evenly spaced array of smaller plates is arranged normal to the channel direction. Each of these smaller plates is assumed to possess one ideally specularly reflective and one ideally diffusively reflective side. When the temperature of the small plates differs from the temperature of the sidewalls of the channel, these boundary conditions result in a temperature profile around the edges of each small plate that breaks the reflection symmetry along the channel direction. This in turn results in a force on each plate and a net gas flow along the channel. The situation is analyzed numerically using the direct simulation Monte Carlo method and compared with analytical results where available. The influence of the ideally specularly reflective wall is assessed by comparing with simulations using a finite accommodation coefficient at the corresponding wall. The configuration bears some similarity to a Crookes radiometer, where a nonsymmetric temperature profile at the radiometer vanes is generated by different temperatures on each side of the vane, resulting in a motion of the rotor. The described principle may find applications in pumping gas on small scales driven by temperature gradients.

The effective theory of shift-symmetric cosmologies

NASA Astrophysics Data System (ADS)

Finelli, Bernardo; Goon, Garrett; Pajer, Enrico; Santoni, Luca

2018-05-01

A shift symmetry is a ubiquitous ingredient in inflationary models, both in effective constructions and in UV-finite embeddings such as string theory. It has also been proposed to play a key role in certain Dark Energy and Dark Matter models. Despite the crucial role it plays in cosmology, the observable, model independent consequences of a shift symmetry are yet unknown. Here, assuming an exact shift symmetry, we derive these consequences for single-clock cosmologies within the framework of the Effective Field Theory of Inflation. We find an infinite set of relations among the otherwise arbitrary effective coefficients, which relate non-Gaussianity to their time dependence. For example, to leading order in derivatives, these relations reduce the infinitely many free functions in the theory to just a single one. Our Effective Theory of shift-symmetric cosmologies describes, among other systems, perfect and imperfect superfluids coupled to gravity and driven superfluids in the decoupling limit. Our results are the first step to determine observationally whether a shift symmetry is at play in the laws of nature and whether it is broken by quantum gravity effects.

Negative refraction, surface modes, and superlensing effect via homogenization near resonances for a finite array of split-ring resonators.

PubMed

Farhat, M; Guenneau, S; Enoch, S; Movchan, A B

2009-10-01

We present a theoretical and numerical analysis of liquid surface waves (LSWs) localized at the boundary of a phononic crystal consisting of split-ring resonators (SRRs). We first derive the homogenized parameters of the fluid-filled structure using a three-scale asymptotic expansion in the linearized Navier-Stokes equations. In the limit when the wavelength of the LSW is much larger than the typical heterogeneity size of the phononic crystal, we show that it behaves as an artificial fluid with an anisotropic effective shear modulus and a dispersive effective-mass density. We then analyze dispersion diagrams associated with LSW propagating within an infinite array of SRR, for which eigensolutions are sought in the form of Floquet-Bloch waves. The main emphasis is given to the study of localized modes within such a periodic fluid-filled structure and to the control of low-frequency stop bands associated with resonances of SRRs. Considering a macrocell, we are able to compute the dispersion of LSW supported by a semi-infinite phononic crystal of SRRs. We find that the dispersion of this evanescent mode nearly sits within the first stop band of the doubly periodic structure. We further discover that it is linked to the frequency at which the effective-mass density of the homogenized phononic crystal becomes negative. We demonstrate that this surface mode displays the hallmarks of all-angle negative refraction and it leads to a superlensing effect. Last, we note that our homogenization results for the velocity potential can be applied mutatis mutandis to designs of electromagnetic and acoustic superlenses for transverse electric waves propagating in arrays of infinite conducting SRRs and antiplane shear waves in arrays of cracks shaped as SRRs.

Effect of vegetative canopy architecture on vertical transport of massless particles

USDA-ARS?s Scientific Manuscript database

A series of large-eddy simulations were performed to examine the effect of canopy architecture on particle dispersion. A heterogeneous canopy geometry was simulated that consists of a set of infinitely repeating vegetation rows. Simulations in which row structure was approximately resolved were comp...

Hydrodynamic theory of diffusion in two-temperature multicomponent plasmas

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

Ramshaw, J.D.; Chang, C.H.

Detailed numerical simulations of multicomponent plasmas require tractable expressions for species diffusion fluxes, which must be consistent with the given plasma current density J{sub q} to preserve local charge neutrality. The common situation in which J{sub q} = 0 is referred to as ambipolar diffusion. The use of formal kinetic theory in this context leads to results of formidable complexity. We derive simple tractable approximations for the diffusion fluxes in two-temperature multicomponent plasmas by means of a generalization of the hydrodynamical approach used by Maxwell, Stefan, Furry, and Williams. The resulting diffusion fluxes obey generalized Stefan-Maxwell equations that contain drivingmore » forces corresponding to ordinary, forced, pressure, and thermal diffusion. The ordinary diffusion fluxes are driven by gradients in pressure fractions rather than mole fractions. Simplifications due to the small electron mass are systematically exploited and lead to a general expression for the ambipolar electric field in the limit of infinite electrical conductivity. We present a self-consistent effective binary diffusion approximation for the diffusion fluxes. This approximation is well suited to numerical implementation and is currently in use in our LAVA computer code for simulating multicomponent thermal plasmas. Applications to date include a successful simulation of demixing effects in an argon-helium plasma jet, for which selected computational results are presented. Generalizations of the diffusion theory to finite electrical conductivity and nonzero magnetic field are currently in progress.« less

Macroscopic descriptions of rarefied gases from the elimination of fast variables

NASA Astrophysics Data System (ADS)

Dellar, Paul J.

2007-10-01

The Boltzmann equation describing a dilute monatomic gas is equivalent to an infinite hierarchy of evolution equations for successive moments of the distribution function. The five moments giving the macroscopic mass, momentum, and energy densities are unaffected by collisions between atoms, while all other moments naturally evolve on a fast collisional time scale. We show that the macroscopic equations of Chen, Rao, and Spiegel [Phys. Lett. A 271, 87 (2000)], like the familiar Navier-Stokes-Fourier equations, emerge from using a systematic procedure to eliminate the higher moments, leaving closed evolution equations for the five moments unaffected by collisions. The two equation sets differ through their treatment of contributions from the temperature to the momentum and energy fluxes. Using moment equations offers a definitive treatment of the Prandtl number problem using model collision operators, greatly reduces the labor of deriving equations for different collision operators, and clarifies the role of solvability conditions applied to the distribution function. The original Chen-Rao-Spiegel approach offers greatly improved agreement with experiments for the phase speed of ultrasound, but when corrected to match the Navier-Stokes-Fourier equations at low frequencies, it then underestimates the phase speed at high frequencies. Our introduction of a translational temperature, as in the kinetic theory of polyatomic gases, motivates a distinction in the energy flux between advection of internal energy and the work done by the pressure. Exploiting this distinction yields macroscopic equations that offer further improvement in agreement with experimental data, and arise more naturally as an approximation to the infinite hierarchy of evolution equations for moments.

Concurrent Solution and Adsorption of Hydrocarbons in Gas Chromatographic Columns Packed with Different Loadings of 3-Methylsydnone on Chromosorb P

PubMed

Castells; Romero; Nardillo

1997-08-01

Thermodynamic properties of solution in 3-methylsydnone (3MS) and of adsorption at the nitrogen/3MS interface were gas chromatographically measured for a group of fifteen hydrocarbons at infinite dilution conditions. Retention volumes were measured at five temperatures within the range 37-52°C in six columns containing different loadings of 3MS on Chromosorb P AW. Partition and adsorption coefficients were calculated and from their temperature dependence the corresponding enthalpies were obtained, although with considerable error; infinite dilution activity coefficients of the hydrocarbons in the bulk and in the surface phases demonstrated a strong correlation. Bulk activity coefficients in 3MS were very much smaller than those previously measured for the same solutes in formamide (FA) and in ethyleneglycol (EG), and were also smaller than what could be predicted on account of 3MS cohesive energy density as estimated from the quotient sigma/v1/3 (sigma, surface tension; v, molar volume). There was not such a large difference between the surface activity coefficients in the three solvents; furthermore, the quotients (surface activity coefficient/bulk activity coefficient) for a given solute in 3MS were twice as large as in FA and about three times larger than in EG. These results make evident the difficulties inherent in the prediction of surface phase properties from those in the bulk and cast doubts on the pertinency of employing the surface tension to compare cohesive energy densities of polar solvents with important chemical differences.

Determination of heat transfer parameters by use of finite integral transform and experimental data for regular geometric shapes

NASA Astrophysics Data System (ADS)

Talaghat, Mohammad Reza; Jokar, Seyyed Mohammad

2017-12-01

This article offers a study on estimation of heat transfer parameters (coefficient and thermal diffusivity) using analytical solutions and experimental data for regular geometric shapes (such as infinite slab, infinite cylinder, and sphere). Analytical solutions have a broad use in experimentally determining these parameters. Here, the method of Finite Integral Transform (FIT) was used for solutions of governing differential equations. The temperature change at centerline location of regular shapes was recorded to determine both the thermal diffusivity and heat transfer coefficient. Aluminum and brass were used for testing. Experiments were performed for different conditions such as in a highly agitated water medium ( T = 52 °C) and in air medium ( T = 25 °C). Then, with the known slope of the temperature ratio vs. time curve and thickness of slab or radius of the cylindrical or spherical materials, thermal diffusivity value and heat transfer coefficient may be determined. According to the method presented in this study, the estimated of thermal diffusivity of aluminum and brass is 8.395 × 10-5 and 3.42 × 10-5 for a slab, 8.367 × 10-5 and 3.41 × 10-5 for a cylindrical rod and 8.385 × 10-5 and 3.40 × 10-5 m2/s for a spherical shape, respectively. The results showed there is close agreement between the values estimated here and those already published in the literature. The TAAD% is 0.42 and 0.39 for thermal diffusivity of aluminum and brass, respectively.

Superconducting spin switch with infinite magnetoresistance induced by an internal exchange field.

PubMed

Li, Bin; Roschewsky, Niklas; Assaf, Badih A; Eich, Marius; Epstein-Martin, Marguerite; Heiman, Don; Münzenberg, Markus; Moodera, Jagadeesh S

2013-03-01

A theoretical prediction by de Gennes suggests that the resistance in a FI/S/FI (where FI is a ferromagnetic insulator, and S is a superconductor) structure will depend on the magnetization direction of the two FI layers. We report a magnetotransport measurement in a EuS/Al/EuS structure, showing that an infinite magnetoresistance can be produced by tuning the internal exchange field at the FI/S interface. This proximity effect at the interface can be suppressed by an Al(2)O(3) barrier as thin as 0.3 nm, showing the extreme confinement of the interaction to the interface giving rise to the demonstrated phenomena.

Finite horizon optimum control with and without a scrap value

NASA Astrophysics Data System (ADS)

Neck, R.; Blueschke-Nikolaeva, V.; Blueschke, D.

2017-06-01

In this paper, we study the effects of scrap values on the solutions of optimal control problems with finite time horizon. We show how to include a scrap value, either for the state variables or for the state and the control variables, in the OPTCON2 algorithm for the optimal control of dynamic economic systems. We ask whether the introduction of a scrap value can serve as a substitute for an infinite horizon in economic policy optimization problems where the latter option is not available. Using a simple numerical macroeconomic model, we demonstrate that the introduction of a scrap value cannot induce control policies which can be expected for problems with an infinite time horizon.

A statistical model of a metallic inclusion in semiconducting media

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

Shikin, V. B., E-mail: shikin@issp.ac.ru

The properties of an isolated multicharged atom embedded into a semiconducting medium are discussed. The analysis generalizes the results of the known Thomas–Fermi theory for a multicharged (Z ≫ 1) atom in vacuum when it is immersed into an electron–hole gas of finite temperature. The Thomas–Fermi–Debye (TFD) atom problem is directly related to the properties of donors in low-doped semiconductors and is alternative in its conclusions to the ideal scenario of dissociation of donors. In the existing ideal statistics, an individual donor under infinitely low doping is completely ionized (a charged center does not hold its neutralizing counter-ions). A Thomas–Fermi–Debyemore » atom (briefly, a TFD donor) remains a neutral formation that holds its screening “coat” even for infinitely low doping level, i.e., in the region of n{sub d}λ{sub 0}{sup 3} ≪ 1, where n{sub d} is the concentration of the doping impurity and λ{sub 0} is the Debye length with the parameters of intrinsic semiconductor. Various observed consequences in the behavior of a TFD donor are discussed that allow one to judge the reality of the implications of the TFD donor model.« less

Exactly solvable model of the two-dimensional electrical double layer.

PubMed

Samaj, L; Bajnok, Z

2005-12-01

We consider equilibrium statistical mechanics of a simplified model for the ideal conductor electrode in an interface contact with a classical semi-infinite electrolyte, modeled by the two-dimensional Coulomb gas of pointlike unit charges in the stability-against-collapse regime of reduced inverse temperatures 0< or = beta < 2. If there is a potential difference between the bulk interior of the electrolyte and the grounded electrode, the electrolyte region close to the electrode (known as the electrical double layer) carries some nonzero surface charge density. The model is mappable onto an integrable semi-infinite sine-Gordon theory with Dirichlet boundary conditions. The exact form-factor and boundary state information gained from the mapping provide asymptotic forms of the charge and number density profiles of electrolyte particles at large distances from the interface. The result for the asymptotic behavior of the induced electric potential, related to the charge density via the Poisson equation, confirms the validity of the concept of renormalized charge and the corresponding saturation hypothesis. It is documented on the nonperturbative result for the asymptotic density profile at a strictly nonzero beta that the Debye-Hückel beta-->0 limit is a delicate issue.

Diffusion coefficients of phenylbutazone in supercritical CO2 and in ethanol.

PubMed

Kong, Chang Yi; Watanabe, Kou; Funazukuri, Toshitaka

2013-03-01

The diffusion coefficients D(12) of phenylbutazone at infinite dilution in supercritical CO(2) were measured by the chromatographic impulse response (CIR) method. The measurements were carried out over the temperature range from 308.2 to 343.2 K at pressures up to 40.0 MPa. In addition, the D(12) data of phenylbutazone at infinite dilution in ethanol were also measured by the Taylor dispersion method at 298.2-333.2K and at atmospheric pressure. The D(12) value of phenylbutazone increased from 4.45×10(-10) m(2) s(-1) at 298.2 K and 0.1 MPa in ethanol to about 1.43×10(-8) m(2) s(-1) at 343.2 K and 14.0 MPa in supercritical CO(2). It was found that all diffusion data of phenylbutazone measured in this study in supercritical CO(2) and in ethanol can be satisfactorily represented by the hydrodynamic equation over a wide range of fluid viscosity from supercritical state to liquid state with average absolute relative deviation of 5.4% for 112 data points. Copyright © 2013 Elsevier B.V. All rights reserved.

Multiple equilibria, bifurcations and selection scenarios in cosymmetric problem of thermal convection in porous medium

NASA Astrophysics Data System (ADS)

Govorukhin, Vasily N.; Shevchenko, Igor V.

2017-12-01

We study convection in a two-dimensional container of porous material saturated with fluid and heated from below. This problem belongs to the class of dynamical systems with nontrivial cosymmetry. The cosymmetry gives rise to a hidden parameter in the system and continuous families of infinitely many equilibria, and leads to non-trivial bifurcations. In this article we present our numerical studies that demonstrate nonlinear phenomena resulting from the existence of cosymmetry. We give a comprehensive picture of different bifurcations which occur in cosymmetric dynamical systems and in the convection problem. It includes internal and external (as an invariant set) bifurcations of one-parameter families of equilibria, as well as bifurcations leading to periodic, quasiperiodic and chaotic behaviour. The existence of infinite number of stable steady-state regimes begs the important question as to which of them can realize in physical experiments. In this paper, this question (known as the selection problem) is studied in detail. In particular, we show that the selection scenarios strongly depend on the initial temperature distribution of the fluid. The calculations are carried out by the global cosymmetry-preserving Galerkin method, and numerical methods used to analyse cosymmetric systems are also described.

Forming of AHSS using Servo-Presses

NASA Astrophysics Data System (ADS)

Groseclose, Adam Richard

Stamping of Advanced High Strength Steel (AHSS) alloys poses several challenges due to the material's higher strength and low formability compared to conventional steels and other problems such as (a) inconsistency of incoming material properties, (b) ductile fracture during forming, (c) higher contact pressure and temperature rise during forming, (d) higher die wear leading to reduced tool life, (e) higher forming load/press capacity, and (f) large springback leading to dimensional inaccuracy in the formed part. [Palaniswamy et. al., 2007]. The use of AHSS has been increasing steadily in automotive stamping. New AHSS alloys (TRIP, TWIP) may replace some of the Hot Stamping applications. Stamping of AHSS alloys, especially higher strength materials, 780 MPa and higher, present new challenges in obtaining good part definition (corner and fillet radii), formability (fracture and resulting scrap) and in reducing springback. Servo-drive presses, having the capability to have infinitely variable and adjustable ram speed and dwell at BDC, offer a potential improvement in quality, part definition, and springback reduction especially when the infinitely adjustable slide motion is used in combination with a CNC hydraulic cushion. Thus, it is desirable to establish a scientific/engineering basis for improving the stamping conditions in forming AHSS using a servo-drive press.

The Green’s functions for peridynamic non-local diffusion

PubMed Central

Wang, L. J.; Xu, J. F.

2016-01-01

In this work, we develop the Green’s function method for the solution of the peridynamic non-local diffusion model in which the spatial gradient of the generalized potential in the classical theory is replaced by an integral of a generalized response function in a horizon. We first show that the general solutions of the peridynamic non-local diffusion model can be expressed as functionals of the corresponding Green’s functions for point sources, along with volume constraints for non-local diffusion. Then, we obtain the Green’s functions by the Fourier transform method for unsteady and steady diffusions in infinite domains. We also demonstrate that the peridynamic non-local solutions converge to the classical differential solutions when the non-local length approaches zero. Finally, the peridynamic analytical solutions are applied to an infinite plate heated by a Gauss source, and the predicted variations of temperature are compared with the classical local solutions. The peridynamic non-local diffusion model predicts a lower rate of variation of the field quantities than that of the classical theory, which is consistent with experimental observations. The developed method is applicable to general diffusion-type problems. PMID:27713658

Automated Assume-Guarantee Reasoning for Omega-Regular Systems and Specifications

NASA Technical Reports Server (NTRS)

Chaki, Sagar; Gurfinkel, Arie

2010-01-01

We develop a learning-based automated Assume-Guarantee (AG) reasoning framework for verifying omega-regular properties of concurrent systems. We study the applicability of non-circular (AGNC) and circular (AG-C) AG proof rules in the context of systems with infinite behaviors. In particular, we show that AG-NC is incomplete when assumptions are restricted to strictly infinite behaviors, while AG-C remains complete. We present a general formalization, called LAG, of the learning based automated AG paradigm. We show how existing approaches for automated AG reasoning are special instances of LAG.We develop two learning algorithms for a class of systems, called infinite regular systems, that combine finite and infinite behaviors. We show that for infinity-regular systems, both AG-NC and AG-C are sound and complete. Finally, we show how to instantiate LAG to do automated AG reasoning for infinite regular, and omega-regular, systems using both AG-NC and AG-C as proof rules

Optimal feedback control infinite dimensional parabolic evolution systems: Approximation techniques

NASA Technical Reports Server (NTRS)

Banks, H. T.; Wang, C.

1989-01-01

A general approximation framework is discussed for computation of optimal feedback controls in linear quadratic regular problems for nonautonomous parabolic distributed parameter systems. This is done in the context of a theoretical framework using general evolution systems in infinite dimensional Hilbert spaces. Conditions are discussed for preservation under approximation of stabilizability and detectability hypotheses on the infinite dimensional system. The special case of periodic systems is also treated.

Identities of Finitely Generated Algebras Over AN Infinite Field

NASA Astrophysics Data System (ADS)

Kemer, A. R.

1991-02-01

It is proved that for each finitely generated associative PI-algebra U over an infinite field F, there is a finite-dimensional F-algebra C such that the ideals of identities of the algebras U and C coincide. This yields a positive solution to the local problem of Specht for algebras over an infinite field: A finitely generated free associative algebra satisfies the maximum condition for T-ideals.

Chain of point-like potentials in Script R3 and infiniteness of the number of bound states

NASA Astrophysics Data System (ADS)

Boitsev, A. A.; Popov, I. Yu; Sokolov, O. V.

2014-10-01

Infinite chain of point-like potentials having the Hamiltonian with infinite number of eigenvalues below the continuous spectrum is constructed. The background of the model is the theory of self-adjoint extensions of symmetric operators in the Hilbert space. The analogous example of the Hamiltonian is obtained for the system of three-dimensional waveguides coupled through point-like windows.

Stationary temperature profiles in a liquid nanochannel: Comparisons between molecular-dynamics simulation and classical hydrostatics

NASA Astrophysics Data System (ADS)

Okumura, Hisashi; Heyes, David M.

2006-12-01

We compare the results of three-dimensional molecular-dynamics (MD) simulations of a Lennard-Jones (LJ) liquid with a hydrostatic (HS) solution of a high temperature liquid channel which is surrounded by a fluid at lower temperature. The maximum temperature gradient, dT/dx , between the two temperature regions ranged from ∞ (step function) to dT/dx=0.1 (in the usual LJ units). Because the systems were in stationary-nonequilibrium states with no fluid flow, both MD simulation and the HS solution gave flat profiles for the normal pressure in all temperature-gradient cases. However, the other quantities showed differences between the two methods. The MD-derived density was found to oscillate over the length of ca. 8 LJ particle diameters from the boundary plane in the system with the infinite temperature gradient, while the HS-derived density showed simply a stepwise profile. The MD simulation also showed another anomaly near the boundary in potential energy. We have found systems in which the HS treatment works well and those where the HS approach breaks down, and therefore established the minimum length scale for the HS treatment to be valid. We also compare the kinetic temperature and the configurational temperature in these systems, and show that these can differ in the transition zone between the two temperatures.

Stationary temperature profiles in a liquid nanochannel: comparisons between molecular-dynamics simulation and classical hydrostatics.

PubMed

Okumura, Hisashi; Heyes, David M

2006-12-01

We compare the results of three-dimensional molecular-dynamics (MD) simulations of a Lennard-Jones (LJ) liquid with a hydrostatic (HS) solution of a high temperature liquid channel which is surrounded by a fluid at lower temperature. The maximum temperature gradient, dT/dx , between the two temperature regions ranged from infinity (step function) to dT/dx=0.1 (in the usual LJ units). Because the systems were in stationary-nonequilibrium states with no fluid flow, both MD simulation and the HS solution gave flat profiles for the normal pressure in all temperature-gradient cases. However, the other quantities showed differences between the two methods. The MD-derived density was found to oscillate over the length of ca. 8 LJ particle diameters from the boundary plane in the system with the infinite temperature gradient, while the HS-derived density showed simply a stepwise profile. The MD simulation also showed another anomaly near the boundary in potential energy. We have found systems in which the HS treatment works well and those where the HS approach breaks down, and therefore established the minimum length scale for the HS treatment to be valid. We also compare the kinetic temperature and the configurational temperature in these systems, and show that these can differ in the transition zone between the two temperatures.

Full Angular Profile of the Coherent Polarization Opposition Effect

NASA Technical Reports Server (NTRS)

Mishchenko, Michael I.; Luck, Jean-Marc; Nieuwenhuizen, Theo M.

1999-01-01

We use the rigorous vector theory of weak photon localization for a semi-infinite medium composed of nonabsorbing Rayleigh scatterers to compute the full angular profile of the polarization opposition effect. The latter is caused by coherent backscattering of unpolarized incident light and accompanies the renowned backscattering intensity peak.

Buckling Behavior of Long Anisotropic Plates Subjected to Fully Restrained Thermal Expansion

NASA Technical Reports Server (NTRS)

Nemeth, Michael P.

2003-01-01

An approach for synthesizing buckling results and behavior for thin, balanced and unbalanced symmetric laminates that are subjected to uniform heating or cooling and which are fully-restrained against thermal expansion or contraction is presented. This approach uses a nondimensional analysis for infinitely long, flexurally anisotropic plates that are subjected to combined mechanical loads and is based on useful nondimensional parameters. In addition, stiffness-weighted laminate thermal-expansion parameters are derived and used to determine critical temperature changes in terms of physically intuitive mechanical buckling coefficients. The effects of membrane orthotropy and anisotropy are included. Many results are presented for some common laminates that are intended to facilitate a structural designer's transition to the use of the generic buckling design curves that are presented in the paper. Several generic buckling design curves are presented that provide physical insight into buckling response and provide useful design data. Examples are presented that demonstrate the use of generic design curves. The analysis approach and generic results indicate the effects and characteristics of laminate thermal expansion, membrane orthotropy and anisotropy, and flexural orthotropy and anisotropy in a very general, unifying manner.

Singular perturbations with boundary conditions and the Casimir effect in the half space

NASA Astrophysics Data System (ADS)

Albeverio, S.; Cognola, G.; Spreafico, M.; Zerbini, S.

2010-06-01

We study the self-adjoint extensions of a class of nonmaximal multiplication operators with boundary conditions. We show that these extensions correspond to singular rank 1 perturbations (in the sense of Albeverio and Kurasov [Singular Perturbations of Differential Operaters (Cambridge University Press, Cambridge, 2000)]) of the Laplace operator, namely, the formal Laplacian with a singular delta potential, on the half space. This construction is the appropriate setting to describe the Casimir effect related to a massless scalar field in the flat space-time with an infinite conducting plate and in the presence of a pointlike "impurity." We use the relative zeta determinant (as defined in the works of Müller ["Relative zeta functions, relative determinants and scattering theory," Commun. Math. Phys. 192, 309 (1998)] and Spreafico and Zerbini ["Finite temperature quantum field theory on noncompact domains and application to delta interactions," Rep. Math. Phys. 63, 163 (2009)]) in order to regularize the partition function of this model. We study the analytic extension of the associated relative zeta function, and we present explicit results for the partition function and for the Casimir force.

Numerical analysis of MHD Casson Navier's slip nanofluid flow yield by rigid rotating disk

NASA Astrophysics Data System (ADS)

Rehman, Khalil Ur; Malik, M. Y.; Zahri, Mostafa; Tahir, M.

2018-03-01

An exertion is perform to report analysis on Casson liquid equipped above the rigid disk for z bar > 0 as a semi-infinite region. The flow of Casson liquid is achieve through rotation of rigid disk with constant angular frequency Ω bar . Magnetic interaction is consider by applying uniform magnetic field normal to the axial direction. The nanosized particles are suspended in the Casson liquid and rotation of disk is manifested with Navier's slip condition, heat generation/absorption and chemical reaction effects. The obtain flow narrating differential equations subject to MHD Casson nanofluid are transformed into ordinary differential system. For this purpose the Von Karman way of scheme is executed. To achieve accurate trends a computational algorithm is develop rather than to go on with usual build-in scheme. The effects logs of involved parameters, namely magnetic field parameter, Casson fluid parameter, slip parameter, thermophoresis and Brownian motion parameters on radial, tangential velocities, temperature, nanoparticles concentration, Nusselt and Sherwood numbers are provided by means of graphical and tabular structures. It is observed that both tangential and radial velocities are decreasing function of Casson fluid parameter.

Decoherence and lead-induced interdot coupling in nonequilibrium electron transport through interacting quantum dots: A hierarchical quantum master equation approach

NASA Astrophysics Data System (ADS)

Härtle, R.; Cohen, G.; Reichman, D. R.; Millis, A. J.

2013-12-01

The interplay between interference effects and electron-electron interactions in electron transport through an interacting double quantum dot system is investigated using a hierarchical quantum master equation approach which becomes exact if carried to infinite order and converges well if the temperature is not too low. Decoherence due to electron-electron interactions is found to give rise to pronounced negative differential resistance, enhanced broadening of structures in current-voltage characteristics, and an inversion of the electronic population. Dependence on gate voltage is shown to be a useful method of distinguishing decoherence-induced phenomena from effects induced by other mechanisms such as the presence of a blocking state. Comparison of results obtained by the hierarchical quantum master equation approach to those obtained from the Born-Markov approximation to the Nakajima-Zwanzig equation and from the noncrossing approximation to the nonequilibrium Green's function reveals the importance of an interdot coupling that originates from the energy dependence of the conduction bands in the leads and the need for a systematic perturbative expansion.

User's manual for the one-dimensional hypersonic experimental aero-thermodynamic (1DHEAT) data reduction code

NASA Technical Reports Server (NTRS)

Hollis, Brian R.

1995-01-01

A FORTRAN computer code for the reduction and analysis of experimental heat transfer data has been developed. This code can be utilized to determine heat transfer rates from surface temperature measurements made using either thin-film resistance gages or coaxial surface thermocouples. Both an analytical and a numerical finite-volume heat transfer model are implemented in this code. The analytical solution is based on a one-dimensional, semi-infinite wall thickness model with the approximation of constant substrate thermal properties, which is empirically corrected for the effects of variable thermal properties. The finite-volume solution is based on a one-dimensional, implicit discretization. The finite-volume model directly incorporates the effects of variable substrate thermal properties and does not require the semi-finite wall thickness approximation used in the analytical model. This model also includes the option of a multiple-layer substrate. Fast, accurate results can be obtained using either method. This code has been used to reduce several sets of aerodynamic heating data, of which samples are included in this report.

On radiative heat transfer in stagnation point flow of MHD Carreau fluid over a stretched surface

NASA Astrophysics Data System (ADS)

Khan, Masood; Sardar, Humara; Mudassar Gulzar, M.

2018-03-01

This paper investigates the behavior of MHD stagnation point flow of Carreau fluid in the presence of infinite shear rate viscosity. Additionally heat transfer analysis in the existence of non-linear radiation with convective boundary condition is performed. Moreover effects of Joule heating is observed and mathematical analysis is presented in the presence of viscous dissipation. The suitable transformations are employed to alter the leading partial differential equations to a set of ordinary differential equations. The subsequent non-straight common ordinary differential equations are solved numerically by an effective numerical approach specifically Runge-Kutta Fehlberg method alongside shooting technique. It is found that the higher values of Hartmann number (M) correspond to thickening of the thermal and thinning of momentum boundary layer thickness. The analysis further reveals that the fluid velocity is diminished by increasing the viscosity ratio parameter (β∗) and opposite trend is observed for temperature profile for both hydrodynamic and hydromagnetic flows. In addition the momentum boundary layer thickness is increased with velocity ratio parameter (α) and opposite is true for thermal boundary layer thickness.

An algorithm for the estimation of bounds on the emissivity and temperatures from thermal multispectral airborne remotely sensed data

NASA Technical Reports Server (NTRS)

Jaggi, S.; Quattrochi, D.; Baskin, R.

1992-01-01

The effective flux incident upon the detectors of a thermal sensor, after it has been corrected for atmospheric effects, is a function of a non-linear combination of the emissivity of the target for that channel and the temperature of the target. The sensor system cannot separate the contribution from the emissivity and the temperature that constitute the flux value. A method that estimates the bounds on these temperatures and emissivities from thermal data is described. This method is then tested with remotely sensed data obtained from NASA's Thermal Infrared Multispectral Scanner (TIMS) - a 6 channel thermal sensor. Since this is an under-determined set of equations i.e. there are 7 unknowns (6 emissivities and 1 temperature) and 6 equations (corresponding to the 6 channel fluxes), there exist theoretically an infinite combination of values of emissivities and temperature that can satisfy these equations. Using some realistic bounds on the emissivities, bounds on the temperature are calculated. These bounds on the temperature are refined to estimate a tighter bound on the emissivity of the source. An error analysis is also carried out to quantitatively determine the extent of uncertainty introduced in the estimate of these parameters. This method is useful only when a realistic set of bounds can be obtained for the emissivities of the data. In the case of water the lower and upper bounds were set at 0.97 and 1.00 respectively. Five flights were flown in succession at altitudes of 2 km (low), 6 km (mid), 12 km (high), and then back again at 6 km and 2 km. The area selected with the Ross Barnett reservoir near Jackson, Mississippi. The mission was flown during the predawn hours of 1 Feb. 1992. Radiosonde data was collected for that duration to profile the characteristics of the atmosphere. Ground truth temperatures using thermometers and radiometers were also obtained over an area of the reservoir. The results of two independent runs of the radiometer data averaged 7.03 plus or minus .70 for the first run and 7.31 plus or minus .88 for the second run. The results of the algorithm yield a temperature of 7.68 for the low altitude data to 8.73 for the high altitude data.

Lau phase interferometer for the measurement of the temperature and temperature profile of a gaseous flame

NASA Astrophysics Data System (ADS)

Shakher, Chandra; Thakur, Madhuri

2001-05-01

In this paper we have investigated the utility of Lau phase interferometer with white light source and circular gratings to measure temperature and temperature profile of an axisymmetric flame. In Lau phase interferometer the two gratings are separated by infinite distance. The third grating is placed at a distance Z equals n.p2(lambda) , (where n is an integer, d is the pitch of the grating and (lambda) is the wavelength of the white light source). The sensitivity of the system is determined by the pitch 'p' of the grating and the distance Z between the gratings. If the distance Z between the two gratings is increased to enhance the sensitivity, the accuracy of measurement is reduced because of the reduction in the fringe contrast. In white light Lau phase interferometer the fringe contrast can be improved by optimizing the self-image plane and the pitch of the grating. From the recorded interferogram the angle of deflection ((phi) ) is measured and temperature at a different point of the flame is calculated. The temperature measured using Lau phase interferometer is in good agreement with the temperature measured by thermocouple and dataloger. Details of the theoretical analysis and experimental results are presented.

Infinite product expansion of the Fokker-Planck equation with steady-state solution.

PubMed

Martin, R J; Craster, R V; Kearney, M J

2015-07-08

We present an analytical technique for solving Fokker-Planck equations that have a steady-state solution by representing the solution as an infinite product rather than, as usual, an infinite sum. This method has many advantages: automatically ensuring positivity of the resulting approximation, and by design exactly matching both the short- and long-term behaviour. The efficacy of the technique is demonstrated via comparisons with computations of typical examples.

Nonlocal Theory for Fracturing of Quasibrittle Materials.

DTIC Science & Technology

1994-03-01

eigenstrain e* be applied to an ellipsoidal domain 0J contained * in this infinite body. The values of the cigenstrain t* are such that the stress is...affecting its stresses and deformation. Thus, the change of potential energy of the infinite body caused by the applied eigenstrain is the same as the...infinite body is subjected to external forces alone or eigenstrain a* alone, respectively. If plane-strain cases are considered, the ellipsoid becomes an

Infinite product expansion of the Fokker–Planck equation with steady-state solution

PubMed Central

Martin, R. J.; Craster, R. V.; Kearney, M. J.

2015-01-01

We present an analytical technique for solving Fokker–Planck equations that have a steady-state solution by representing the solution as an infinite product rather than, as usual, an infinite sum. This method has many advantages: automatically ensuring positivity of the resulting approximation, and by design exactly matching both the short- and long-term behaviour. The efficacy of the technique is demonstrated via comparisons with computations of typical examples. PMID:26346100

Classical simulation of infinite-size quantum lattice systems in two spatial dimensions.

PubMed

Jordan, J; Orús, R; Vidal, G; Verstraete, F; Cirac, J I

2008-12-19

We present an algorithm to simulate two-dimensional quantum lattice systems in the thermodynamic limit. Our approach builds on the projected entangled-pair state algorithm for finite lattice systems [F. Verstraete and J. I. Cirac, arxiv:cond-mat/0407066] and the infinite time-evolving block decimation algorithm for infinite one-dimensional lattice systems [G. Vidal, Phys. Rev. Lett. 98, 070201 (2007)10.1103/PhysRevLett.98.070201]. The present algorithm allows for the computation of the ground state and the simulation of time evolution in infinite two-dimensional systems that are invariant under translations. We demonstrate its performance by obtaining the ground state of the quantum Ising model and analyzing its second order quantum phase transition.

Graph determined symbolic dynamics and hybrid systems

NASA Astrophysics Data System (ADS)

Ayers, Kimberly Danielle

In this paper we explore the concept of symbolic dynamical systems whose structure is determined by a directed graph, and then discrete-continuous hybrid systems that arise from such dynamical systems. Typically, symbolic dynamics involve the study of a left shift of a bi-infinite sequence. We examine the case when the bi-infinite system is dictated by a graph; that is, the sequence is a bi-infinite path of a directed graph. We then use the concept to study a system of dynamical systems all on the same compact space M, where "switching" between the systems occurs as given by the bi-infinite sequence in question. The concepts of limit sets, chain recurrent sets, chaos, and Morse sets for these systems are explored.

Assessing Compliance-Effect Bias in the Two Stage Least Squares Estimator

ERIC Educational Resources Information Center

Reardon, Sean; Unlu, Fatih; Zhu, Pei; Bloom, Howard

2011-01-01

The proposed paper studies the bias in the two-stage least squares, or 2SLS, estimator that is caused by the compliance-effect covariance (hereafter, the compliance-effect bias). It starts by deriving the formula for the bias in an infinite sample (i.e., in the absence of finite sample bias) under different circumstances. Specifically, it…

The effect of magnetic nanoparticle concentration on the structure organisation of a microferrogel

NASA Astrophysics Data System (ADS)

Ryzhkov, A. V.; Melenev, P. V.; Balasoiu, M.; Raikher, Yu L.

2018-03-01

Coarse-grained molecular dynamics simulation is applied to study the structural response of micro-sized magnetopolymer objects – microferrogels (MFG). The results for MFGs with different magnetic properties and concentrations of magnetic filler nanoparticles are analysed to detect the transition between non-aggregated configurations and the states with pronounced chains. The nanoparticles are assumed to be either magnetically isotropic or to possess infinite magnetic anisotropy. It is shown that, depending on the type of the particle anisotropy, an applied field in rather different ways affects the MFG structure and shape. Diagrams describing the degree of aggregation as a function of the parameter of the interparticle magnetodipolar interaction and concentration are presented. In particular, it is found that in the case of infinitely anisotropic nanoparticles the aggregation transitions undergoes via a non-trivial scenario. The effect of the structure transformations on the volume change of the MFG objects is studied as well.

Uncovering low dimensional macroscopic chaotic dynamics of large finite size complex systems

NASA Astrophysics Data System (ADS)

Skardal, Per Sebastian; Restrepo, Juan G.; Ott, Edward

2017-08-01

In the last decade, it has been shown that a large class of phase oscillator models admit low dimensional descriptions for the macroscopic system dynamics in the limit of an infinite number N of oscillators. The question of whether the macroscopic dynamics of other similar systems also have a low dimensional description in the infinite N limit has, however, remained elusive. In this paper, we show how techniques originally designed to analyze noisy experimental chaotic time series can be used to identify effective low dimensional macroscopic descriptions from simulations with a finite number of elements. We illustrate and verify the effectiveness of our approach by applying it to the dynamics of an ensemble of globally coupled Landau-Stuart oscillators for which we demonstrate low dimensional macroscopic chaotic behavior with an effective 4-dimensional description. By using this description, we show that one can calculate dynamical invariants such as Lyapunov exponents and attractor dimensions. One could also use the reconstruction to generate short-term predictions of the macroscopic dynamics.

Structural versus electrical properties of an organic-inorganic hybrid material based on sulfate

NASA Astrophysics Data System (ADS)

Ben Rached, Asma; Guionneau, Philippe; Lebraud, Eric; Mhiri, Tahar; Elaoud, Zakaria

2017-01-01

A new organo-sulfate compound is obtained by slow evaporation at room temperature and is characterized by powder and single-crystal X-ray diffraction (XRD) at variable temperatures. The benzylammonium monohydrogenosulfate of formula C6H5CH2NH3+. HSO4-, denoted (BAS), crystallizes in the monoclinic system P21/c space group with the following parameters at room temperature: a=5.623(5)Å, b=20.239(5) Å, c=8.188(5)Å, β=94.104(5)°. The crystal structure consists of infinite parallel two-dimensional planes built by HSO4- anions and C6H5CH2NH3+ cations interconnected by strong O-H….. O and N-H….. O hydrogen bonds. A phase transition is detected at 350 K by differential scanning calorimetry (DSC) and confirmed by powder XRD. Conductivity measurements using the impedance spectroscopy technique allow to determine the conductivity relaxation parameters associated with the H+ conduction from an analysis of the M"/M"max spectrum measured in a wide temperature range. Transport properties of this material appear to be due to an H+ ion hopping mechanism.

Temperature field for radiative tomato peeling

NASA Astrophysics Data System (ADS)

Cuccurullo, G.; Giordano, L.

2017-01-01

Nowadays peeling of tomatoes is performed by using steam or lye, which are expensive and polluting techniques, thus sustainable alternatives are searched for dry peeling and, among that, radiative heating seems to be a fairly promising method. This paper aims to speed up the prediction of surface temperatures useful for realizing dry-peeling, thus a 1D-analytical model for the unsteady temperature field in a rotating tomato exposed to a radiative heating source is presented. Since only short times are of interest for the problem at hand, the model involves a semi-infinite slab cooled by convective heat transfer while heated by a pulsating heat source. The model being linear, the solution is derived following the Laplace Transform method. A 3D finite element model of the rotating tomato is introduced as well in order to validate the analytical solution. A satisfactory agreement is attained. Therefore, two different ways to predict the onset of the peeling conditions are available which can be of help for proper design of peeling plants. Particular attention is paid to study surface temperature uniformity, that being a critical parameter for realizing an easy tomato peeling.

Model for calorimetric measurements in an open quantum system

NASA Astrophysics Data System (ADS)

Donvil, Brecht; Muratore-Ginanneschi, Paolo; Pekola, Jukka P.; Schwieger, Kay

2018-05-01

We investigate the experimental setup proposed in New J. Phys. 15, 115006 (2013), 10.1088/1367-2630/15/11/115006 for calorimetric measurements of thermodynamic indicators in an open quantum system. As a theoretical model we consider a periodically driven qubit coupled with a large yet finite electron reservoir, the calorimeter. The calorimeter is initially at equilibrium with an infinite phonon bath. As time elapses, the temperature of the calorimeter varies in consequence of energy exchanges with the qubit and the phonon bath. We show how under weak-coupling assumptions, the evolution of the qubit-calorimeter system can be described by a generalized quantum jump process including as dynamical variable the temperature of the calorimeter. We study the jump process by numeric and analytic methods. Asymptotically with the duration of the drive, the qubit-calorimeter attains a steady state. In this same limit, we use multiscale perturbation theory to derive a Fokker-Planck equation governing the calorimeter temperature distribution. We inquire the properties of the temperature probability distribution close and at the steady state. In particular, we predict the behavior of measurable statistical indicators versus the qubit-calorimeter coupling constant.

Diffusion of a particle in the spatially correlated exponential random energy landscape: Transition from normal to anomalous diffusion.

PubMed

Novikov, S V

2018-01-14

Diffusive transport of a particle in a spatially correlated random energy landscape having exponential density of states has been considered. We exactly calculate the diffusivity in the nondispersive quasi-equilibrium transport regime for the 1D transport model and found that for slow decaying correlation functions the diffusivity becomes singular at some particular temperature higher than the temperature of the transition to the true non-equilibrium dispersive transport regime. It means that the diffusion becomes anomalous and does not follow the usual ∝ t 1/2 law. In such situation, the fully developed non-equilibrium regime emerges in two stages: first, at some temperature there is the transition from the normal to anomalous diffusion, and then at lower temperature the average velocity for the infinite medium goes to zero, thus indicating the development of the true dispersive regime. Validity of the Einstein relation is discussed for the situation where the diffusivity does exist. We provide also some arguments in favor of conservation of the major features of the new transition scenario in higher dimensions.

Phase equilibrium measurements on twelve binary mixtures

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

Giles, N.F.; Wilson, H.L.; Wilding, W.V.

1996-11-01

Phase equilibrium measurements have been performed on twelve binary mixtures. The PTx method was used to obtain vapor-liquid equilibrium data for the following binary systems at two temperatures each: ethanethiol + propylene; nitrobenzene + methanol; pyridine + ethyl acetate; octane + tert-amyl methyl ether; diisopropyl ether + butane; 1,3-dichloro-2-propanol + epichlorohydrin; 2,3-dichloro-1-propanol + epichlorohydrin; 2,3-epoxy-1-propanol + epichlorohydrin; 3-chloro-1,2-propanediol + epichlorohydrin; methanol + hydrogen cyanide. For these systems, equilibrium vapor and liquid phase compositions were derived from the PTx data using the Soave equation of state to represent the vapor phase and the Wilson, NRTL, or Redlich-Kister activity coefficient model tomore » represent the liquid phase. The infinite dilution activity coefficient of methylamine in N-methyl-2-pyrrolidone was determined at three temperatures by performing PTx measurements on the N-methyl-2-pyrrolidone was determined at three temperatures by performing PTx measurements on the N-methyl-2-pyrrolidone-rich half of the binary. Liquid-liquid equilibrium studies were made on the triethylene glycol + 1-pentene system at two temperatures by directly analyzing samples taken from each liquid phase.« less

Conformation transitions of a single polyelectrolyte chain in a poor solvent: a replica-exchange lattice Monte-Carlo study.

PubMed

Wang, Lang; Wang, Zheng; Jiang, Run; Yin, Yuhua; Li, Baohui

2017-03-15

The thermodynamic behaviors of a strongly charged polyelectrolyte chain in a poor solvent are studied using replica-exchange Monte-Carlo simulations on a lattice model, focusing on the effects of finite chain length and the solvent quality on the chain conformation and conformation transitions. The neutralizing counterions and solvent molecules are considered explicitly. The thermodynamic quantities that vary continuously with temperature over a wide range are computed using the multiple histogram reweighting method. Our results suggest that the strength of the short-range hydrophobic interaction, the chain length, and the temperature of the system, characterized by ε, N, and T, respectively, are important parameters that control the conformations of a charged chain. When ε is moderate, the competition between the electrostatic energy and the short-range hydrophobic interaction leads to rich conformations and conformation transitions for a longer chain with a fixed length. Our results have unambiguously demonstrated the stability of the n-pearl-necklace structures, where n has a maximum value and decreases with decreasing temperature. The maximum n value increases with increasing chain length. Our results have also demonstrated the first-order nature of the conformation transitions between the m-pearl and the (m-1)-pearl necklaces. With the increase of ε, the transition temperature increases and the first-order feature becomes more pronounced. It is deduced that at the thermodynamic limit of infinitely long chain length, the conformational transitions between the m-pearl and the (m-1)-pearl necklaces may remain first order when ε > 0 and m = 2 or 3. Pearl-necklace conformations cannot be observed when either ε is too large or N is too small. To observe a pearl-necklace conformation, the T value needs to be carefully chosen for simulations performed at only a single temperature.

Quantum Bath Refrigeration towards Absolute Zero: Challenging the Unattainability Principle

NASA Astrophysics Data System (ADS)

Kolář, M.; Gelbwaser-Klimovsky, D.; Alicki, R.; Kurizki, G.

2012-08-01

A minimal model of a quantum refrigerator, i.e., a periodically phase-flipped two-level system permanently coupled to a finite-capacity bath (cold bath) and an infinite heat dump (hot bath), is introduced and used to investigate the cooling of the cold bath towards absolute zero (T=0). Remarkably, the temperature scaling of the cold-bath cooling rate reveals that it does not vanish as T→0 for certain realistic quantized baths, e.g., phonons in strongly disordered media (fractons) or quantized spin waves in ferromagnets (magnons). This result challenges Nernst’s third-law formulation known as the unattainability principle.

Al(0.5)Nb(1.5)(PO(4))(3).

PubMed

Zhao, Dan; Liang, Peng; Su, Ling; Chang, Huan; Yan, Shi

2011-02-12

Single crystals of the title compound, aluminium niobium triphosphate, Al(0.5)Nb(1.5)(PO(4))(3), have been synthesized by a high-temperature reaction in a platinium crucible. The Al(III) and Nb(V) atoms occupy the same site on the axis, with disorder in the ratio of 1:3. The fundamental building units of the title structure are isolated Al/NbO(6) octa-hedra and PO(4) tetra-hedra (. 2 symmetry), which are further inter-locked by corner-sharing O atoms, leading to a three-dimensional framework structure with infinite channels along the a axis.

Multi-Functional Composite Fatigue

NASA Technical Reports Server (NTRS)

Minnetyan, Levon; Chamis, Christos C.

2008-01-01

Damage and fracture of composites subjected to monotonically increasing static, tension-tension cyclic, pressurization, and flexural cyclic loading are evaluated via a recently developed composite mechanics code that allows the user to focus on composite response at infinitely small scales. Constituent material properties, stress and strain limits are scaled up to the laminate level to evaluate the overall damage and durability. Results show the number of cycles to failure at different temperatures. A procedure is outlined for use of computational simulation data in the assessment of damage tolerance, determination of sensitive parameters affecting fracture, and interpretation of results with insight for design decisions.

Microstates of black holes in expanding universe from interacting branes

NASA Astrophysics Data System (ADS)

Shiba, Shotaro

2017-05-01

Thermodynamics of the near extremal black p-branes can be described by collective motions of gravitationally interacting branes. This proposal is called the p-soup model. In this paper, we check this proposal in the case of black brane system which is asymptotically Friedmann-Lemaître-Robertson-Walker universe in an infinite distance. As a result, we can show that the gravitationally interacting branes explain free energy, entropy, temperature and other physical quantities in these systems. This implies that the microstates of this kind of brane system can be also understood in the p-soup model.

Quantum bath refrigeration towards absolute zero: challenging the unattainability principle.

PubMed

Kolář, M; Gelbwaser-Klimovsky, D; Alicki, R; Kurizki, G

2012-08-31

A minimal model of a quantum refrigerator, i.e., a periodically phase-flipped two-level system permanently coupled to a finite-capacity bath (cold bath) and an infinite heat dump (hot bath), is introduced and used to investigate the cooling of the cold bath towards absolute zero (T=0). Remarkably, the temperature scaling of the cold-bath cooling rate reveals that it does not vanish as T→0 for certain realistic quantized baths, e.g., phonons in strongly disordered media (fractons) or quantized spin waves in ferromagnets (magnons). This result challenges Nernst's third-law formulation known as the unattainability principle.

Comment on "Similarity between quantum mechanics and thermodynamics: Entropy, temperature, and Carnot cycle".

PubMed

González-Díaz, L A; Díaz-Solórzano, S

2015-05-01

In the paper by Abe and Okuyama [Phys. Rev. E 83, 021121 (2011)], the quantum Carnot cycle of a simple two-state model of a particle confined in a one-dimensional infinite potential well is discussed. It is claimed that the state at the beginning of the quantum Carnot cycle is pure. After that, it is apparently transmuted to a mixed state if Clausius equality is imposed. We prove that this statement is incorrect. In particular, we prove that the state at the beginning of the cycle is mixed due to the process of measuring energy.

Quantum Monte Carlo study of spin correlations in the one-dimensional Hubbard model

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

Sandvik, A.W.; Scalapino, D.J.; Singh, C.

1993-07-15

The one-dimensional Hubbard model is studied at and close to half-filling using a generalization of Handscomb's quantum Monte Carlo method. Results for spin-correlation functions and susceptibilities are presented for systems of up to 128 sites. The spin-correlation function at low temperature is well described by a recently introduced formula relating the correlation function of a finite periodic system to the corresponding [ital T]=0 correlation function of the infinite system. For the [ital T][r arrow]0 divergence of the [ital q]=2[ital k][sub [ital F

Thermo-Mechanical Effect on Poly Crystalline Boron Nitride Tool Life During Friction Stir Welding (Dwell Period)

NASA Astrophysics Data System (ADS)

Almoussawi, M.; Smith, A. J.

2018-05-01

Poly Crystalline Boron Nitride (PCBN) tool wear during the friction stir welding of high melting alloys is an obstacle to commercialize the process. This work simulates the friction stir welding process and tool wear during the plunge/dwell period of 14.8 mm EH46 thick plate steel. The Computational Fluid Dynamic (CFD) model was used for simulation and the wear of the tool is estimated from temperatures and shear stress profile on the tool surface. Two sets of tool rotational speeds were applied including 120 and 200 RPM. Seven plunge/dwell samples were prepared using PCBN FSW tool, six thermocouples were also embedded around each plunge/dwell case in order to record the temperatures during the welding process. Infinite focus microscopy technique was used to create macrographs for each case. The CFD result has been shown that a shear layer around the tool shoulder and probe-side denoted as thermo-mechanical affected zone (TMAZ) was formed and its size increase with tool rotational speed increase. Maximum peak temperature was also found to increase with tool rotational speed increase. PCBN tool wear under shoulder was found to increase with tool rotational speed increase as a result of tool's binder softening after reaching to a peak temperature exceeds 1250 °C. Tool wear also found to increase at probe-side bottom as a result of high shear stress associated with the decrease in the tool rotational speed. The amount of BN particles revealed by SEM in the TMAZ were compared with the CFD model.

Elementary particles in the early Universe

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

Gromov, N.A., E-mail: gromov@dm.komisc.ru

The high-temperature limit of the Standard Model generated by the contractions of gauge groups is discussed. Contraction parameters of gauge group SU(2) of the Electroweak Model and gauge group SU(3) of Quantum Chromodynamics are taken identical and tending to zero when the temperature increases. Properties of the elementary particles change drastically at the infinite temperature limit: all particles lose masses, all quarks are monochromatic. Electroweak interactions become long-range and are mediated by neutral currents. Particles of different kind do not interact. It looks like some stratification with only one sort of particles in each stratum. The Standard Model passes inmore » this limit through several stages, which are distinguished by the powers of the contraction parameter. For any stage intermediate models are constructed and the exact expressions for the respective Lagrangians are presented. The developed approach describes the evolution of the Standard Model in the early Universe from the Big Bang up to the end of several nanoseconds.« less

Thermodynamic entanglement of magnonic condensates

NASA Astrophysics Data System (ADS)

Yuan, H. Y.; Yung, Man-Hong

2018-02-01

Over the past decade, significant progress has been achieved to create Bose-Einstein condensates (BECs) of magnetic excitations, i.e., magnons, at room temperature, which is a novel quantum many-body system with a strong spin-spin correlation, and contains potential applications in magnonic spintronics. For quantum information science, the magnonic condensates can become an attractive source of quantum entanglement, which plays a central role in most of the quantum information processing tasks. Here we theoretically study the entanglement properties of a magnon gas above and below the condensation temperature. We show that the thermodynamic entanglement of the spins is a manifestation of the off-diagonal long-range order; the entanglement of the condensate does not vanish, even if the spins are separated by an infinitely long distance, which is fundamentally distinct from the normal magnetic ordering below the Curie temperature. In addition, the phase-transition point occurs when the derivative of the entanglement changes abruptly. These results provide a theoretical foundation for a future investigation of the magnon BEC in terms of quantum entanglement.

Solubility of HFCs in pentaerythritol tetraalkyl esters

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

Wahlstroem, A.; Vamling, L.

2000-02-01

The solubilities of difluoromethane (HFC32), 1,1,1,2,2-pentafluoroethane (HFC125), 1,1,1,2-tetrafluoroethane (HFC134a), 1,1,1-trifluoroethane (HFC143a) and 1,1-difluoroethane (HFC152a) in pentaerythritol tetranonanoate, pentaerythritol tetra-2-ethylbutanoate, and pentaerythritol tetra-2-ethylhexanoate have been measured at temperatures between 303 and 363 K and pressures between 0.07 and 2.1 MPa. Henry's constant and the activity coefficient for HFCs at infinite dilution were derived for measurements below 0.34 MPa. The measurements were made by an isochoric method with an uncertainty of <2% for Henry's constant and <3% at high pressure. Within the investigated temperature range, solubilities for HFCs in pentaerythritol tetraalkyl esters decrease in the following order: HFC152a > HFC134a > HFC32more » > HFC125 > HFC143a. The experimental data have been correlated with a Flory-Huggins model with an extended temperature dependence, which is able to describe the data with a deviation from measured data of <2.7%.« less

Modelling of Strains During SAW Surfacing Taking into Heat of the Weld in Temperature Field Description and Phase Transformations

NASA Astrophysics Data System (ADS)

Winczek, J.; Makles, K.; Gucwa, M.; Gnatowska, R.; Hatala, M.

2017-08-01

In the paper, the model of the thermal and structural strain calculation in a steel element during single-pass SAW surfacing is presented. The temperature field is described analytically assuming a bimodal volumetric model of heat source and a semi-infinite body model of the surfaced (rebuilt) workpiece. The electric arc is treated physically as one heat source. Part of the heat is transferred by the direct impact of the electric arc, while another part of the heat is transferred to the weld by the melted material of the electrode. Kinetics of phase transformations during heating is limited by temperature values at the beginning and at the end of austenitic transformation, while the progress of phase transformations during cooling is determined on the basis of TTT-welding diagramand JMA-K law for diffusive transformations, and K-M law for martensitic transformation. Totalstrains equal to the sum ofthermaland structuralstrainsinduced by phasetransformationsin weldingcycle.

A Riemann-Hilbert formulation for the finite temperature Hubbard model

NASA Astrophysics Data System (ADS)

Cavaglià, Andrea; Cornagliotto, Martina; Mattelliano, Massimo; Tateo, Roberto

2015-06-01

Inspired by recent results in the context of AdS/CFT integrability, we reconsider the Thermodynamic Bethe Ansatz equations describing the 1D fermionic Hubbard model at finite temperature. We prove that the infinite set of TBA equations are equivalent to a simple nonlinear Riemann-Hilbert problem for a finite number of unknown functions. The latter can be transformed into a set of three coupled nonlinear integral equations defined over a finite support, which can be easily solved numerically. We discuss the emergence of an exact Bethe Ansatz and the link between the TBA approach and the results by Jüttner, Klümper and Suzuki based on the Quantum Transfer Matrix method. We also comment on the analytic continuation mechanism leading to excited states and on the mirror equations describing the finite-size Hubbard model with twisted boundary conditions.

Lee-Wick black holes

NASA Astrophysics Data System (ADS)

Bambi, Cosimo; Modesto, Leonardo; Wang, Yixu

2017-01-01

We derive and study an approximate static vacuum solution generated by a point-like source in a higher derivative gravitational theory with a pair of complex conjugate ghosts. The gravitational theory is local and characterized by a high derivative operator compatible with Lee-Wick unitarity. In particular, the tree-level two-point function only shows a pair of complex conjugate poles besides the massless spin two graviton. We show that singularity-free black holes exist when the mass of the source M exceeds a critical value Mcrit. For M >Mcrit the spacetime structure is characterized by an outer event horizon and an inner Cauchy horizon, while for M =Mcrit we have an extremal black hole with vanishing Hawking temperature. The evaporation process leads to a remnant that approaches the zero-temperature extremal black hole state in an infinite amount of time.

Emergent kinetic constraints, ergodicity breaking, and cooperative dynamics in noisy quantum systems

NASA Astrophysics Data System (ADS)

Everest, B.; Marcuzzi, M.; Garrahan, J. P.; Lesanovsky, I.

2016-11-01

Kinetically constrained spin systems play an important role in understanding key properties of the dynamics of slowly relaxing materials, such as glasses. Recent experimental studies have revealed that manifest kinetic constraints govern the evolution of strongly interacting gases of highly excited atoms in a noisy environment. Motivated by this development we explore which types of kinetically constrained dynamics can generally emerge in quantum spin systems subject to strong noise and show how, in this framework, constraints are accompanied by conservation laws. We discuss an experimentally realizable case of a lattice gas, where the interplay between those and the geometry of the lattice leads to collective behavior and time-scale separation even at infinite temperature. This is in contrast to models of glass-forming substances which typically rely on low temperatures and the consequent suppression of thermal activation.

Small-scale modification to the lensing kernel

NASA Astrophysics Data System (ADS)

Hadzhiyska, Boryana; Spergel, David; Dunkley, Joanna

2018-02-01

Calculations of the cosmic microwave background (CMB) lensing power implemented into the standard cosmological codes such as camb and class usually treat the surface of last scatter as an infinitely thin screen. However, since the CMB anisotropies are smoothed out on scales smaller than the diffusion length due to the effect of Silk damping, the photons which carry information about the small-scale density distribution come from slightly earlier times than the standard recombination time. The dominant effect is the scale dependence of the mean redshift associated with the fluctuations during recombination. We find that fluctuations at k =0.01 Mpc-1 come from a characteristic redshift of z ≈1090 , while fluctuations at k =0.3 Mpc-1 come from a characteristic redshift of z ≈1130 . We then estimate the corrections to the lensing kernel and the related power spectra due to this effect. We conclude that neglecting it would result in a deviation from the true value of the lensing kernel at the half percent level at small CMB scales. For an all-sky, noise-free experiment, this corresponds to a ˜0.1 σ shift in the observed temperature power spectrum on small scales (2500 ≲l ≲4000 ).

Polydisperse sphere packing in high dimensions, a search for an upper critical dimension

NASA Astrophysics Data System (ADS)

Morse, Peter; Clusel, Maxime; Corwin, Eric

2012-02-01

The recently introduced granocentric model for polydisperse sphere packings has been shown to be in good agreement with experimental and simulational data in two and three dimensions. This model relies on two effective parameters that have to be estimated from experimental/simulational results. The non-trivial values obtained allow the model to take into account the essential effects of correlations in the packing. Once these parameters are set, the model provides a full statistical description of a sphere packing for a given polydispersity. We investigate the evolution of these effective parameters with the spatial dimension to see if, in analogy with the upper critical dimension in critical phenomena, there exists a dimension above which correlations become irrelevant and the model parameters can be fixed a priori as a function of polydispersity. This would turn the model into a proper theory of polydisperse sphere packings at that upper critical dimension. We perform infinite temperature quench simulations of frictionless polydisperse sphere packings in dimensions 2-8 using a parallel algorithm implemented on a GPGPU. We analyze the resulting packings by implementing an algorithm to calculate the additively weighted Voronoi diagram in arbitrary dimension.

A new method of field MRTD test

NASA Astrophysics Data System (ADS)

Chen, Zhibin; Song, Yan; Liu, Xianhong; Xiao, Wenjian

2014-09-01

MRTD is an important indicator to measure the imaging performance of infrared camera. In the traditional laboratory test, blackbody is used as simulated heat source which is not only expensive and bulky but also difficult to meet field testing requirements of online automatic infrared camera MRTD. To solve this problem, this paper introduces a new detection device for MRTD, which uses LED as a simulation heat source and branded plated zinc sulfide glass carved four-bar target as a simulation target. By using high temperature adaptability cassegrain collimation system, the target is simulated to be distance-infinite so that it can be observed by the human eyes to complete the subjective test, or collected to complete objective measurement by image processing. This method will use LED to replace blackbody. The color temperature of LED is calibrated by thermal imager, thereby, the relation curve between the LED temperature controlling current and the blackbody simulation temperature difference is established, accurately achieved the temperature control of the infrared target. Experimental results show that the accuracy of the device in field testing of thermal imager MRTD can be limited within 0.1K, which greatly reduces the cost to meet the project requirements with a wide application value.

Free vibration analysis of elastic structures submerged in an infinite or semi-infinite fluid domain by means of a coupled FE-BE solver

NASA Astrophysics Data System (ADS)

Zheng, Chang-Jun; Bi, Chuan-Xing; Zhang, Chuanzeng; Gao, Hai-Feng; Chen, Hai-Bo

2018-04-01

The vibration behavior of thin elastic structures can be noticeably influenced by the surrounding water, which represents a kind of heavy fluid. Since the feedback of the acoustic pressure onto the structure cannot be neglected in this case, a strong coupled scheme between the structural and fluid domains is usually required. In this work, a coupled finite element and boundary element (FE-BE) solver is developed for the free vibration analysis of structures submerged in an infinite fluid domain or a semi-infinite fluid domain with a free water surface. The structure is modeled by the finite element method (FEM). The compressibility of the fluid is taken into account, and hence the Helmholtz equation serves as the governing equation of the fluid domain. The boundary element method (BEM) is employed to model the fluid domain, and a boundary integral formulation with a half-space fundamental solution is used to satisfy the Dirichlet boundary condition on the free water surface exactly. The resulting nonlinear eigenvalue problem (NEVP) is converted into a small linear one by using a contour integral method. Adequate modifications are suggested to improve the efficiency of the contour integral method and avoid missing the eigenfrequencies of interest. The Burton-Miller method is used to filter out the fictitious eigenfrequencies of the boundary integral formulations. Numerical examples are given to demonstrate the accuracy and applicability of the developed eigensolver, and also show that the fluid-loading effect strongly depends on both the water depth and the mode shapes.

Labelled Execution Systems

DTIC Science & Technology

2012-05-07

executions are all the executions of the first except the single infinite execution stuttering around s0. And because of this exception, s0 is not bisimilar...maximal paths in the diagram, and that whose executions are all the executions of the first system except the infinite execution stuttering around s0. s...advance to s1, from where on it behaves just like the first one. What sets the behaviour of the two processes apart is, of course, the infinite stuttering

Acoustic plane wave diffraction from a truncated semi-infinite cone in axial irradiation

NASA Astrophysics Data System (ADS)

Kuryliak, Dozyslav; Lysechko, Victor

2017-11-01

The diffraction problem of the plane acoustic wave on the semi-infinite truncated soft and rigid cones in the case of axial incidence is solved. The problem is formulated as a boundary-value problem in terms of Helmholtz equation, with Dirichlet and Neumann boundary conditions, for scattered velocity potential. The incident field is taken to be the total field of semi-infinite cone, the expression of which is obtained by solving the auxiliary diffraction problem by the use of Kontorovich-Lebedev integral transformation. The diffracted field is sought via the expansion in series of the eigenfunctions for subdomains of the Helmholtz equation taking into account the edge condition. The corresponding diffraction problem is reduced to infinite system of linear algebraic equations (ISLAE) making use of mode matching technique and orthogonality properties of the Legendre functions. The method of analytical regularization is applied in order to extract the singular part in ISLAE, invert it exactly and reduce the problem to ISLAE of the second kind, which is readily amenable to calculation. The numerical solution of this system relies on the reduction method; and its accuracy depends on the truncation order. The case of degeneration of the truncated semi-infinite cone into an aperture in infinite plane is considered. Characteristic features of diffracted field in near and far fields as functions of cone's parameters are examined.

Thermodynamic properties, melting temperature and viscosity of the mantles of Super Earths

NASA Astrophysics Data System (ADS)

Stamenkovic, V.; Spohn, T.; Breuer, D.

2010-12-01

The recent dicscovery of extrasolar planets with radii of about twice the Earth radius and masses of several Earth masses such as e.g., Corot-7b (approx 5Mearth and 1.6Rearth, Queloz et al. 2009) has increased the interest in the properties of rock at extremely high pressures. While the pressure at the Earth’s core-mantle boundary is about 135GPa, pressures at the base of the mantles of extraterrestrial rocky planets - if these are at all differentiated into mantles and cores - may reach Tera Pascals. Although the properties and the mineralogy of rock at extremely high pressure is little known there have been speculations about mantle convection, plate tectonics and dynamo action in these “Super-Earths”. We assume that the mantles of these planets can be thought of as consisting of perovskite but we discuss the effects of the post-perovskite transition and of MgO. We use the Keane equation of state and the Slater relation (see e.g., Stacey and Davies 2004) to derive an infinite pressure value for the Grüneisen parameter of 1.035. To derive this value we adopted the infinite pressure limit for K’ (pressure derivative of the bulk modulus) of 2.41 as derived by Stacey and Davies (2004) by fitting PREM. We further use the Lindeman law to calculate the melting curve. We gauge the melting curve using the available experimental data for pressures up to 120GPa. The melting temperature profile reaches 6000K at 135GPa and increases to temperatures between 12,000K and 24,000K at 1.1TPa with a preferred value of 21,000K. We find the adiabatic temperature increase to reach 2,500K at 135GPa and 5,400K at 1.1TPa. To calculate the pressure dependence of the viscosity we assume that the rheology is diffusion controlled and calculate the partial derivative with respect to pressure of the activation enthalpy. We cast the partial derivative in terms of an activation volume and use the semi-empirical homologous temperature scaling (e.g., Karato 2008). We find that the activation volume decreases from 2.4cm^3/mol at 135GPa to 1.6cm^3/mol at 1.1TPa. An estimate of the viscosity increase across the mantle to a pressure of 1.1TPa using the adiabat calculated above results in an increase of the viscosity of 19 orders of magnitude. This value raises questions about the differentiation of these planets, heat transfer in their deep interiors, and magnetic field generation.(Ref.: Karato, S. 2008. Deformation of Earth Materials, Cambridge University Press.; Stacey, F.D., Davies, P.M. 2004. PEPI 142: 137; Queloz, D. et al., 2009. Astronomy and Astrophysics 506: 303.)

Casimir interaction of rodlike particles in a two-dimensional critical system.

PubMed

Eisenriegler, E; Burkhardt, T W

2016-09-01

We consider the fluctuation-induced interaction of two thin, rodlike particles, or "needles," immersed in a two-dimensional critical fluid of Ising symmetry right at the critical point. Conformally mapping the plane containing the needles onto a simpler geometry in which the stress tensor is known, we analyze the force and torque between needles of arbitrary length, separation, and orientation. For infinite and semi-infinite needles we utilize the mapping of the plane bounded by the needles onto the half plane, and for two needles of finite length we use the mapping onto an annulus. For semi-infinite and infinite needles the force is expressed in terms of elementary functions, and we also obtain analytical results for the force and torque between needles of finite length with separation much greater than their length. Evaluating formulas in our approach numerically for several needle geometries and surface universality classes, we study the full crossover from small to large values of the separation to length ratio. In these two limits the numerical results agree with results for infinitely long needles and with predictions of the small-particle operator expansion, respectively.

Field-incidence noise transmission loss of general aviation aircraft double wall configurations

NASA Astrophysics Data System (ADS)

Grosveld, F. W.

1984-01-01

Theoretical formulations have been developed to describe the transmission of reverberant sound through an infinite, semi-infinite and a finite double panel structure. The model incorporates the fundamental resonance frequencies of each of the panels, the mass-air-mass resonances of the structure, the standing wave resonances in the cavity between the panels and finally the coincidence resonance regions, where the exciting sound pressure wave and flexural waves of each of the panels coincide. It is shown that phase cancellation effects of pressure waves reflected from the cavity boundaries back into the cavity allows the transmission loss of a finite double panel structure to be approximated by a finite double panel mounted in an infinite baffle having no cavity boundaries. Comparison of the theory with high quality transmission loss data yields good agreement in the mass-controlled frequency region. It is shown that the application of acoustic blankets to the double panel structure does not eliminate the mass-air-mass resonances if those occur at low frequencies. It is concluded that this frequency region of low noise transmission loss is a potential interior noise problem area for propeller driven aircraft having a double panel fuselage construction.

Interaction between moving tandem wheels and an infinite rail with periodic supports - Green's matrices of the track method in stationary reference frame

NASA Astrophysics Data System (ADS)

Mazilu, Traian

2017-08-01

This paper approaches the issue of the interaction between moving tandem wheels and an infinite periodically supported rail and points out at the basic characteristics in the steady-state interaction behaviour and in the interaction in the presence of the rail random irregularity. The rail is modelled as an infinite Timoshenko beam resting on supports which are discretely modelling the inertia of the sleepers and ballast and also the viscoelastic features of the rail pads, the ballast and the subgrade. Green‧s matrices of the track method in stationary reference frame were applied so as to conduct the time-domain analysis. This method allows to consider the nonlinearities of the wheel/rail contact and the Doppler effect. The study highlights certain aspects regarding the influence of the wheel base on the wheels/rail contact forces, particularly at the parametric resonance, due to the coincidence between the wheel/rail natural frequency and the passing frequency and also when the rail surface exhibits random irregularity. It has been shown that the wheel/rail dynamic behaviour is less intense when the wheel base equals integer multiple of the sleeper bay.

Effect of debond growth on stress-intensity factors in a cracked orthotropic sheet stiffened by a semi-infinite orthotropic sheet

NASA Technical Reports Server (NTRS)

Bigelow, C. A.

1986-01-01

Stress-intensity factors are determined for a cracked infinite sheet adhesively bonded to a stringer, and debonding of the adhesive layer is predicted. The stringer is modeled as a semi-infinite sheet. Adhesive nonlinearity is also included. Both the sheet and stringer are treated as homogeneous, orthotropic materials. A set of integral equations is formulated and solved to obtain the adhesive shear stresses and crack-tip stress-intensity factors. Adhesive debonding is predicted using a rupture criterion based on the combined adhesive stresses. When the crack is not under the stringer, the debond extends along the edge of the stringer. When the crack tip is beneath the stringer, the debond grows to the end of the crack, then along the edge of the stringer. Stress levels required for debond initiation decrease as the crack tip is moved beneath the stringer. With a nonlinear adhesive, the debond initiates at higher applied stress levels than in linear adhesive cases. Compared with the linear adhesive solution, modeling a nonlinear adhesive causes the stress-intensity factor to increase when the bond is assumed to remain intact but causes the stress-intensity factor to decrease when debonding is included.

Panels with low-Q-factor resonators with theoretically infinite sound-proofing ability at a single frequency

NASA Astrophysics Data System (ADS)

Lazarev, L. A.

2015-07-01

An infinite panel with two types of resonators regularly installed on it is theoretically considered. Each resonator is an air-filled cavity hermetically closed by a plate, which executes piston vibrations. The plate and air inside the cavity play the roles of mass and elasticity, respectively. Every other resonator is reversed. At a certain ratio between the parameters of the resonators at the tuning frequency of the entire system, the acoustic-pressure force that directly affects the panel can be fully compensated by the action forces of the resonators. In this case, the sound-proofing ability (transmission loss) tends to infinity. The presented calculations show that a complete transmission-loss effect can be achieved even with low- Q resonators.