Derivation of governing equation for predicting thermal conductivity of composites with spherical inclusions and its applications

International Nuclear Information System (INIS)

Lee, Jae-Kon; Kim, Jin-Gon

2011-01-01

A governing differential equation for predicting the effective thermal conductivity of composites with spherical inclusions is shown to be simply derived by using the result of the generalized self-consistent model. By applying the equation to composites including spherical inclusions such as graded spherical inclusions, microballoons, mutiply-coated spheres, and spherical inclusions with an interphase, their effective thermal conductivities are easily predicted. The results are compared with those in the literatures to be consistent. It can be stated from the investigations that the effective thermal conductivity of composites with spherical inclusions can be estimated as long as their conductivities are expressed as a function of their radius. -- Highlights: → We derive equation for predicting the effective thermal conductivity of composites. → The equation is derived using the results of the generalized self-consistent model. → The inclusions are graded sphere, microballoons, and mutiply-coated spheres.

Kinematic equations for resolved-rate control of an industrial robot arm

Science.gov (United States)

Barker, L. K.

1983-01-01

An operator can use kinematic, resolved-rate equations to dynamically control a robot arm by watching its response to commanded inputs. Known resolved-rate equations for the control of a particular six-degree-of-freedom industrial robot arm and proceeds to simplify the equations for faster computations are derived. Methods for controlling the robot arm in regions which normally cause mathematical singularities in the resolved-rate equations are discussed.

Non-equilibrium reaction rates in chemical kinetic equations

Science.gov (United States)

Gorbachev, Yuriy

2018-05-01

Within the recently proposed asymptotic method for solving the Boltzmann equation for chemically reacting gas mixture, the chemical kinetic equations has been derived. Corresponding one-temperature non-equilibrium reaction rates are expressed in terms of specific heat capacities of the species participate in the chemical reactions, bracket integrals connected with the internal energy transfer in inelastic non-reactive collisions and energy transfer coefficients. Reactions of dissociation/recombination of homonuclear and heteronuclear diatomic molecules are considered. It is shown that all reaction rates are the complex functions of the species densities, similarly to the unimolecular reaction rates. For determining the rate coefficients it is recommended to tabulate corresponding bracket integrals, additionally to the equilibrium rate constants. Correlation of the obtained results with the irreversible thermodynamics is established.

Decay Rates of Interactive Hyperbolic-Parabolic PDE Models with Thermal Effects on the Interface

International Nuclear Information System (INIS)

Lasiecka, I.; Lebiedzik, C.

2000-01-01

We consider coupled PDE systems comprising of a hyperbolic and a parabolic-like equation with an interface on a portion of the boundary. These models are motivated by structural acoustic problems. A specific prototype consists of a wave equation defined on a three-dimensional bounded domain Ω coupled with a thermoelastic plate equation defined on Γ 0 -a flat surface of the boundary Ω. Thus, the coupling between the wave and the plate takes place on the interface Γ 0 . The main issue studied here is that of uniform stability of the overall interactive model. Since the original (uncontrolled) model is only strongly stable, but not uniformly stable, the question becomes: what is the 'minimal amount' of dissipation necessary to obtain uniform decay rates for the energy of the overall system? Our main result states that boundary nonlinear dissipation placed only on a suitable portion of the part of the boundary which is complementary to Γ 0 , suffices for the stabilization of the entire structure. This result is new with respect to the literature on several accounts: (i) thermoelasticity is accounted for in the plate model; (ii) the plate model does not account for any type of mechanical damping, including the structural damping most often considered in the literature; (iii) there is no mechanical damping placed on the interface Γ 0 ; (iv) the boundary damping is nonlinear without a prescribed growth rate at the origin; (v) the undamped portions of the boundary partial Ω are subject to Neumann (rather than Dirichlet) boundary conditions, which is a recognized difficulty in the context of stabilization of wave equations, due to the fact that the strong Lopatinski condition does not hold. The main mathematical challenge is to show how the thermal energy is propagated onto the hyperbolic component of the structure. This is achieved by using a recently developed sharp theory of boundary traces corresponding to wave and plate equations, along with the analytic

Connecting Related Rates and Differential Equations

Science.gov (United States)

Brandt, Keith

2012-01-01

This article points out a simple connection between related rates and differential equations. The connection can be used for in-class examples or homework exercises, and it is accessible to students who are familiar with separation of variables.

Theory of nanolaser devices: Rate equation analysis versus microscopic theory

DEFF Research Database (Denmark)

Lorke, Michael; Skovgård, Troels Suhr; Gregersen, Niels

2013-01-01

A rate equation theory for quantum-dot-based nanolaser devices is developed. We show that these rate equations are capable of reproducing results of a microscopic semiconductor theory, making them an appropriate starting point for complex device simulations of nanolasers. The input...

Nonlinear fluctuations-induced rate equations for linear birth-death processes

Science.gov (United States)

Honkonen, J.

2008-05-01

The Fock-space approach to the solution of master equations for one-step Markov processes is reconsidered. It is shown that in birth-death processes with an absorbing state at the bottom of the occupation-number spectrum and occupation-number independent annihilation probability of occupation-number fluctuations give rise to rate equations drastically different from the polynomial form typical of birth-death processes. The fluctuation-induced rate equations with the characteristic exponential terms are derived for Mikhailov’s ecological model and Lanchester’s model of modern warfare.

Nonlinear fluctuation-induced rate equations for linear birth-death processes

International Nuclear Information System (INIS)

Honkonen, J.

2008-01-01

The Fock-space approach to the solution of master equations for the one-step Markov processes is reconsidered. It is shown that in birth-death processes with an absorbing state at the bottom of the occupation-number spectrum and occupation-number independent annihilation probability occupation-number fluctuations give rise to rate equations drastically different from the polynomial form typical of birth-death processes. The fluctuation-induced rate equations with the characteristic exponential terms are derived for Mikhailov's ecological model and Lanchester's model of modern warfare

Constitutional equations of thermal stresses of particle-reinforced composite

International Nuclear Information System (INIS)

Asakawa, Atsushi; Noda, Naotake; Tohgo, Keiichiro; Tsuji, Tomoaki.

1994-01-01

Functionally gradient materials (FGM) have been developed as ultrahigh-heat-resistant materials in aircraft, space engineering and nuclear fields. In the heat-resistant FGM which contain particles (ceramics) in the matrix (metal), the matrix will be subjected to plastic deformation, particles will be debonded, and finally cracks will be generated. The constitutive equations of FGM which take into account the damage process and change in temperature are necessary in order to solve these phenomena. In this paper, the constitutive equations of particle-reinforced composites with consideration of the damage process and change in temperature are estimated by the equivalent inclusion method in terms of elastoplasticity. The stress-strain relations and the coefficients of linear thermal expansion of the composites (Al-PSZ and Ti-PSZ) are calculated in ultrahigh temperature. (author)

Standard Test Method for Determining Thermal Neutron Reaction Rates and Thermal Neutron Fluence Rates by Radioactivation Techniques

CERN Document Server

American Society for Testing and Materials. Philadelphia

2008-01-01

1.1 The purpose of this test method is to define a general procedure for determining an unknown thermal-neutron fluence rate by neutron activation techniques. It is not practicable to describe completely a technique applicable to the large number of experimental situations that require the measurement of a thermal-neutron fluence rate. Therefore, this method is presented so that the user may adapt to his particular situation the fundamental procedures of the following techniques. 1.1.1 Radiometric counting technique using pure cobalt, pure gold, pure indium, cobalt-aluminum, alloy, gold-aluminum alloy, or indium-aluminum alloy. 1.1.2 Standard comparison technique using pure gold, or gold-aluminum alloy, and 1.1.3 Secondary standard comparison techniques using pure indium, indium-aluminum alloy, pure dysprosium, or dysprosium-aluminum alloy. 1.2 The techniques presented are limited to measurements at room temperatures. However, special problems when making thermal-neutron fluence rate measurements in high-...

Thermal transport property of Ge34 and d-Ge investigated by molecular dynamics and the Slack's equation

International Nuclear Information System (INIS)

Han-Fu, Wang; Wei-Guo, Chu; Yan-Jun, Guo; Hao, Jin

2010-01-01

In this study, we evaluate the values of lattice thermal conductivity κ L of type II Ge clathrate (Ge 34 ) and diamond phase Ge crystal (d-Ge) with the equilibrium molecular dynamics (EMD) method and the Slack's equation. The key parameters of the Slack's equation are derived from the thermodynamic properties obtained from the lattice dynamics (LD) calculations. The empirical Tersoff's potential is used in both EMD and LD simulations. The thermal conductivities of d-Ge calculated by both methods are in accordance with the experimental values. The predictions of the Slack's equation are consistent with the EMD results above 250 K for both Ge 34 and d-Ge. In a temperature range of 200–1000 K, the κ L value of d-Ge is about several times larger than that of Ge 34 . (condensed matter: structure, thermal and mechanical properties)

A unified momentum equation approach for computing thermal residual stresses during melting and solidification

Science.gov (United States)

Yeo, Haram; Ki, Hyungson

2018-03-01

In this article, we present a novel numerical method for computing thermal residual stresses from a viewpoint of fluid-structure interaction (FSI). In a thermal processing of a material, residual stresses are developed as the material undergoes melting and solidification, and liquid, solid, and a mixture of liquid and solid (or mushy state) coexist and interact with each other during the process. In order to accurately account for the stress development during phase changes, we derived a unified momentum equation from the momentum equations of incompressible fluids and elastoplastic solids. In this approach, the whole fluid-structure system is treated as a single continuum, and the interaction between fluid and solid phases across the mushy zone is naturally taken into account in a monolithic way. For thermal analysis, an enthalpy-based method was employed. As a numerical example, a two-dimensional laser heating problem was considered, where a carbon steel sheet was heated by a Gaussian laser beam. Momentum and energy equations were discretized on a uniform Cartesian grid in a finite volume framework, and temperature-dependent material properties were used. The austenite-martensite phase transformation of carbon steel was also considered. In this study, the effects of solid strains, fluid flow, mushy zone size, and laser heating time on residual stress formation were investigated.

Diffusion equations and the time evolution of foreign exchange rates

Energy Technology Data Exchange (ETDEWEB)

Figueiredo, Annibal; Castro, Marcio T. de [Institute of Physics, Universidade de Brasília, Brasília DF 70910-900 (Brazil); Fonseca, Regina C.B. da [Department of Mathematics, Instituto Federal de Goiás, Goiânia GO 74055-110 (Brazil); Gleria, Iram, E-mail: iram@fis.ufal.br [Institute of Physics, Federal University of Alagoas, Brazil, Maceió AL 57072-900 (Brazil)

2013-10-01

We investigate which type of diffusion equation is most appropriate to describe the time evolution of foreign exchange rates. We modify the geometric diffusion model assuming a non-exponential time evolution and the stochastic term is the sum of a Wiener noise and a jump process. We find the resulting diffusion equation to obey the Kramers–Moyal equation. Analytical solutions are obtained using the characteristic function formalism and compared with empirical data. The analysis focus on the first four central moments considering the returns of foreign exchange rate. It is shown that the proposed model offers a good improvement over the classical geometric diffusion model.

Diffusion equations and the time evolution of foreign exchange rates

Science.gov (United States)

Figueiredo, Annibal; de Castro, Marcio T.; da Fonseca, Regina C. B.; Gleria, Iram

2013-10-01

We investigate which type of diffusion equation is most appropriate to describe the time evolution of foreign exchange rates. We modify the geometric diffusion model assuming a non-exponential time evolution and the stochastic term is the sum of a Wiener noise and a jump process. We find the resulting diffusion equation to obey the Kramers-Moyal equation. Analytical solutions are obtained using the characteristic function formalism and compared with empirical data. The analysis focus on the first four central moments considering the returns of foreign exchange rate. It is shown that the proposed model offers a good improvement over the classical geometric diffusion model.

Diffusion equations and the time evolution of foreign exchange rates

International Nuclear Information System (INIS)

Figueiredo, Annibal; Castro, Marcio T. de; Fonseca, Regina C.B. da; Gleria, Iram

2013-01-01

We investigate which type of diffusion equation is most appropriate to describe the time evolution of foreign exchange rates. We modify the geometric diffusion model assuming a non-exponential time evolution and the stochastic term is the sum of a Wiener noise and a jump process. We find the resulting diffusion equation to obey the Kramers–Moyal equation. Analytical solutions are obtained using the characteristic function formalism and compared with empirical data. The analysis focus on the first four central moments considering the returns of foreign exchange rate. It is shown that the proposed model offers a good improvement over the classical geometric diffusion model.

Empirical rate equation model and rate calculations of hydrogen generation for Hanford tank waste

International Nuclear Information System (INIS)

HU, T.A.

1999-01-01

Empirical rate equations are derived to estimate hydrogen generation based on chemical reactions, radiolysis of water and organic compounds, and corrosion processes. A comparison of the generation rates observed in the field with the rates calculated for twenty eight tanks shows agreement within a factor of two to three

ECONOMETRIC APPROACH TO DIFFERENCE EQUATIONS MODELING OF EXCHANGE RATES CHANGES

Directory of Open Access Journals (Sweden)

Josip Arnerić

2010-12-01

Full Text Available Time series models that are commonly used in econometric modeling are autoregressive stochastic linear models (AR and models of moving averages (MA. Mentioned models by their structure are actually stochastic difference equations. Therefore, the objective of this paper is to estimate difference equations containing stochastic (random component. Estimated models of time series will be used to forecast observed data in the future. Namely, solutions of difference equations are closely related to conditions of stationary time series models. Based on the fact that volatility is time varying in high frequency data and that periods of high volatility tend to cluster, the most successful and popular models in modeling time varying volatility are GARCH type models and their variants. However, GARCH models will not be analyzed because the purpose of this research is to predict the value of the exchange rate in the levels within conditional mean equation and to determine whether the observed variable has a stable or explosive time path. Based on the estimated difference equation it will be examined whether Croatia is implementing a stable policy of exchange rates.

Oral L-menthol reduces thermal sensation, increases work-rate and extends time to exhaustion, in the heat at a fixed rating of perceived exertion.

Science.gov (United States)

Flood, T R; Waldron, M; Jeffries, O

2017-07-01

The study investigated the effect of a non-thermal cooling agent, L-menthol, on exercise at a fixed subjective rating of perceived exertion (RPE) in a hot environment. Eight male participants completed two trials at an exercise intensity between 'hard' and 'very hard', equating to 16 on the RPE scale at ~35 °C. Participants were instructed to continually adjust their power output to maintain an RPE of 16 throughout the exercise trial, stopping once power output had fallen by 30%. In a randomized crossover design, either L-menthol or placebo mouthwash was administered prior to exercise and at 10 min intervals. Power output, [Formula: see text]O 2 , heart rate, core and skin temperature was monitored, alongside thermal sensation and thermal comfort. Isokinetic peak power sprints were conducted prior to and immediately after the fixed RPE trial. Exercise time was greater (23:23 ± 3:36 vs. 21:44 ± 2:32 min; P = 0.049) and average power output increased (173 ± 24 vs. 167 ± 24 W; P = 0.044) in the L-menthol condition. Peak isokinetic sprint power declined from pre-post trial in the L-menthol l (9.0%; P = 0.015) but not in the placebo condition (3.4%; P = 0.275). Thermal sensation was lower in the L-menthol condition (P = 0.036), despite no changes in skin or core temperature (P > 0.05). These results indicate that a non-thermal cooling mouth rinse lowered thermal sensation, resulting in an elevated work rate, which extended exercise time in the heat at a fixed RPE.

Analysis of equations of state and temperature dependence of thermal expansivity and bulk modulus for silicon

International Nuclear Information System (INIS)

Pandya, Tushar C; Bhatt, Apoorva D; Thakar, Nilesh A

2012-01-01

In the present paper an attempt has been made for the comparative study of different equations of state for silicon (Phase-1, cubic diamond structure) in the pressure range of 0-11 GPa. We compare the results of different equations of state (EOS) with available experimental data. The Kwon and Kim EOS is found to give far better agreement with the available experimental data. Results obtained by Poirier-Tarantola, Vinet, Tait and Suzuki's equations of state are not giving satisfactory agreement with the available experimental data. In the present study simple methods based on thermodynamic functions are presented to investigate the temperature dependence of thermal expansivity and bulk modulus for silicon. The results are reported for silicon. The calculated values of thermal expansivity are in good agreement with experimental data.

Numerical solution of conservation equations in the transient model for the system thermal - hydraulics in the Korsar computer code

International Nuclear Information System (INIS)

Yudov, Y.V.

2001-01-01

The functional part of the KORSAR computer code is based on the computational unit for the reactor system thermal-hydraulics and other thermal power systems with water cooling. The two-phase flow dynamics of the thermal-hydraulic network is modelled by KORSAR in one-dimensional two-fluid (non-equilibrium and nonhomogeneous) approximation with the same pressure of both phases. Each phase is characterized by parameters averaged over the channel sections, and described by the conservation equations for mass, energy and momentum. The KORSAR computer code relies upon a novel approach to mathematical modelling of two-phase dispersed-annular flows. This approach allows a two-fluid model to differentiate the effects of the liquid film and droplets in the gas core on the flow characteristics. A semi-implicit numerical scheme has been chosen for deriving discrete analogs the conservation equations in KORSAR. In the semi-implicit numerical scheme, solution of finite-difference equations is reduced to the problem of determining the pressure field at a new time level. For the one-channel case, the pressure field is found from the solution of a system of linear algebraic equations by using the tri-diagonal matrix method. In the branched network calculation, the matrix of coefficients in the equations describing the pressure field is no longer tri-diagonal but has a sparseness structure. In this case, the system of linear equations for the pressure field can be solved with any of the known classical methods. Such an approach is implemented in the existing best-estimate thermal-hydraulic computer codes (TRAC, RELAP5, etc.) For the KORSAR computer code, we have developed a new non-iterative method for calculating the pressure field in the network of any topology. This method is based on the tri-diagonal matrix method and performs well when solving the thermal-hydraulic network problems. (author)

Lyapunov stability and poisson structure of the thermal TDHF and RPA equations

International Nuclear Information System (INIS)

Balian, R.; Veneroni, M.

1989-01-01

The thermal TDHF equation is analyzed in the Liouville representation of quantum mechanics, where the matrix elements of the single-particle (s.p) density ρ behave as classical dynamical variables. By introducing the Lie--Poisson bracket associated with the unitary group of the s.p. Hilbert space, we show that TDHF has a Hamiltonian, but non-canonical, classical form. Within this Poisson structure, either the s.p. energy or the s.p. grand potential Ω(ρ) act as a Hamilton function. The Lyapunov stability of both the TDHF and RPA equations around a HF state then follows, since the HF approximation for thermal equilibrium is determined by minimizing Ω(ρ). The RPA matrix in the Liouville space is expressed as the product of the Poisson tensor with the HF stability matrix, interpreted as a metric tensor generated by the entropy. This factorization displays the roles of the energy and entropy terms arising from Ω(ρ) in the RPA dynamics, and it helps to construct the RPA modes. Several extensions are considered. copyright 1989 Academic Press, Inc

Lyapunov stability and Poisson structure of the thermal TDHF and RPA equations

International Nuclear Information System (INIS)

Veneroni, M.; Balian, R.

1989-01-01

The thermal TDHF equation is analyzed in the Liouville representation of quantum mechanics, where the matrix elements of the single-particle (s.p.) density ρ behave as classical dynamical variables. By introducing the Lie-Poisson bracket associated with the unitary group of the s.p. Hilbert space, we show that TDHF has a hamiltonian, but non-canonical, classical form. Within this Poisson structure, either the s.p. energy or the s.p. grand potential Ω(ρ) act as a Hamilton function. The Lyapunov stability of both the TDHF and RPA equations around a HF state then follows, since the HF approximation for thermal equilibrium is determined by minimizing Ω(ρ). The RPA matrix in the Liouville space is expressed as the product of the Poisson tensor with the HF stability matrix, interpreted as a metric tensor generated by the entropy. This factorization displays the roles of the energy and entropy terms arising from Ω(ρ) in the RPA dynamics, and it helps to construct the RPA modes. Several extensions are considered

Modelling of thermal transport using Fokker-Planck equations in laser produced plasma

International Nuclear Information System (INIS)

Nakarmi, J.J.; Jha, L.N.

1996-12-01

The kinetic equation with Fokker-Planck collision term has been presented to obtain the distribution function in the corona of inertial confinement fusion, in the presence of the self generated magnetic field. The resulting distribution has non-local form with the convolution in Maxwellian. An expression for thermal flux with self generated magnetic field is obtained. (author). 22 refs

General particle transport equation. Final report

International Nuclear Information System (INIS)

Lafi, A.Y.; Reyes, J.N. Jr.

1994-12-01

The general objectives of this research are as follows: (1) To develop fundamental models for fluid particle coalescence and breakage rates for incorporation into statistically based (Population Balance Approach or Monte Carlo Approach) two-phase thermal hydraulics codes. (2) To develop fundamental models for flow structure transitions based on stability theory and fluid particle interaction rates. This report details the derivation of the mass, momentum and energy conservation equations for a distribution of spherical, chemically non-reacting fluid particles of variable size and velocity. To study the effects of fluid particle interactions on interfacial transfer and flow structure requires detailed particulate flow conservation equations. The equations are derived using a particle continuity equation analogous to Boltzmann's transport equation. When coupled with the appropriate closure equations, the conservation equations can be used to model nonequilibrium, two-phase, dispersed, fluid flow behavior. Unlike the Eulerian volume and time averaged conservation equations, the statistically averaged conservation equations contain additional terms that take into account the change due to fluid particle interfacial acceleration and fluid particle dynamics. Two types of particle dynamics are considered; coalescence and breakage. Therefore, the rate of change due to particle dynamics will consider the gain and loss involved in these processes and implement phenomenological models for fluid particle breakage and coalescence

Rate equation modelling of the optically pumped spin-exchange source

International Nuclear Information System (INIS)

Stenger, J.; Rith, K.

1995-01-01

Sources for spin polarized hydrogen or deuterium, polarized via spin-exchange of a laser optically pumped alkali metal, can be modelled by rate equations. The rate equations for this type of source, operated either with hydrogen or deuterium, are given explicitly with the intention of providing a useful tool for further source optimization and understanding. Laser optical pumping of alkali metal, spin-exchange collisions of hydrogen or deuterium atoms with each other and with alkali metal atoms are included, as well as depolarization due to flow and wall collisions. (orig.)

Practical Application and Obstacles of AVHRR Thermal Data for Estimation of Effusion Rates at Tolbachik Volcano, Kamchatka Peninsula, Russian Federation

Science.gov (United States)

McAlpin, D. B.; Meyer, F. J.; Webley, P. W.

2017-12-01

Using thermal data from Advanced Very High Resolution Radiometer (AVHRR) sensors, we investigated algorithms to estimate the effusive volume of lava flows from the 2012-13 eruption of Tolbachik Volcano with high temporal resolution. AVHRR are polar orbiting, radiation detection instruments that provide reflectance and radiance data in six spectral bands with a ground resolution of 1.1 km². During the Tolbachik eruption of 2012-13, active AVHRR instruments were available aboard four polar orbiting platforms. Although the primary purpose of the instruments is climate and ocean studies, their multiple platforms provide global coverage at least twice daily, with data for all regions of the earth no older than six hours. This frequency makes the AVHRR instruments particularly suitable for the study of volcanic activity. While methods for deriving effusion rates from thermal observations have been previously published, a number of topics complicate their practical application. In particular, these include (1) unknown material parameters used in the estimation process; (2) relatively coarse resolution of thermal sensors; (3) optimizing a model to describe the number of thermal regimes within each pixel and (4) frequent saturation issues in thermal channels. We present ongoing investigations into effusion rate estimation from AVHRR data using the 2012-13 eruption of Tolbachik Volcano as a test event. For this eruption we studied approaches for coping with issues (1) - (4) to pave the way to a more operational implementation of published techniques. To address (1), we used Monte Carlo simulations to understand the sensitivity of effusion rate estimates to changes in material parameters. To study (2) and (3) we compared typical two-component (exposed lava on ambient background) and three-component models (exposed lava, cooled crust, ambient background) for their relative performance. To study issue (4), we compared AVHRR-derived effusion rates to reference data derived from

Rate equation analysis and non-Hermiticity in coupled semiconductor laser arrays

Science.gov (United States)

Gao, Zihe; Johnson, Matthew T.; Choquette, Kent D.

2018-05-01

Optically coupled semiconductor laser arrays are described by coupled rate equations. The coupled mode equations and carrier densities are included in the analysis, which inherently incorporate the carrier-induced nonlinearities including gain saturation and amplitude-phase coupling. We solve the steady-state coupled rate equations and consider the cavity frequency detuning and the individual laser pump rates as the experimentally controlled variables. We show that the carrier-induced nonlinearities play a critical role in the mode control, and we identify gain contrast induced by cavity frequency detuning as a unique mechanism for mode control. Photon-mediated energy transfer between cavities is also discussed. Parity-time symmetry and exceptional points in this system are studied. Unbroken parity-time symmetry can be achieved by judiciously combining cavity detuning and unequal pump rates, while broken symmetry lies on the boundary of the optical locking region. Exceptional points are identified at the intersection between broken symmetry and unbroken parity-time symmetry.

Creatinine Clearance Is Not Equal to Glomerular Filtration Rate and Cockcroft-Gault Equation Is Not Equal to CKD-EPI Collaboration Equation.

Science.gov (United States)

Fernandez-Prado, Raul; Castillo-Rodriguez, Esmeralda; Velez-Arribas, Fernando Javier; Gracia-Iguacel, Carolina; Ortiz, Alberto

2016-12-01

Direct oral anticoagulants (DOACs) may require dose reduction or avoidance when glomerular filtration rate is low. However, glomerular filtration rate is not usually measured in routine clinical practice. Rather, equations that incorporate different variables use serum creatinine to estimate either creatinine clearance in mL/min or glomerular filtration rate in mL/min/1.73 m 2 . The Cockcroft-Gault equation estimates creatinine clearance and incorporates weight into the equation. By contrast, the Modification of Diet in Renal Disease and Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations estimate glomerular filtration rate and incorporate ethnicity but not weight. As a result, an individual patient may have very different renal function estimates, depending on the equation used. We now highlight these differences and discuss the impact on routine clinical care for anticoagulation to prevent embolization in atrial fibrillation. Pivotal DOAC clinical trials used creatinine clearance as a criterion for patient enrollment, and dose adjustment and Federal Drug Administration recommendations are based on creatinine clearance. However, clinical biochemistry laboratories provide CKD-EPI glomerular filtration rate estimations, resulting in discrepancies between clinical trial and routine use of the drugs. Copyright © 2016 Elsevier Inc. All rights reserved.

MURLI, 1-D Flux, Reaction Rate in Cylindrical Geometry Thermal Reactor Lattice by Transport

International Nuclear Information System (INIS)

Huria, H.C.

1985-01-01

1 - Description of problem or function: MURLI is an integral transport theory code to calculate fluxes and reaction rates in one- dimensional cylindrical geometry lattice cells of a thermal reactor. For a specified buckling, it computes k-effective using few-group diffusion theory and a few-group collapsed set of Cross sections. The code can optionally be used to solve a first order differential equation for the number density of fissile, fertile and fission product nuclei as a function of time, and to recalculate fluxes, reaction rates and k-effective at different stages of burnup. A 27-group cross section data library is included. There are four pseudo-fission products each associated with the decay chains of plutonium and uranium isotopes in addition to Rh-105, Xe-135, Np-239, U-236, Am-241, Am-242 and Am-243. There is also data for one lumped pseudo-fission product. 2 - Method of solution: Multiple collision probabilities and escape probabilities are calculated for each cylindrical shell region assuming protons are born uniformly and isotropically over the entire region volume. The equations of integral transport theory can then be solved for neutron flux. The first order differential burnup equation is solved by a fourth order Runge-Kutta method. 3 - Restrictions on the complexity of the problem: There are maxima of 8 fissionable elements, 8 resonant elements, and 20 spatial regions

Coupled force-balance and particle-occupation rate equations for high-field electron transport

International Nuclear Information System (INIS)

Lei, X. L.

2008-01-01

It is pointed out that in the framework of balance-equation approach, the coupled force-balance and particle-occupation rate equations can be used as a complete set of equations to determine the high-field transport of semiconductors in both strong and weak electron-electron interaction limits. We call to attention that the occupation rate equation conserves the total particle number and maintains the energy balance of the relative electron system, and there is no need to introduce any other term in it. The addition of an energy-drift term in the particle-occupation rate equation [Phys. Rev. B 71, 195205 (2005)] is physically inadequate for the violation of the total particle-number conservation and the energy balance. It may lead to a substantial unphysical increase of the total particle number by the application of a dc electric field

Wearable Sweat Rate Sensors for Human Thermal Comfort Monitoring.

Science.gov (United States)

Sim, Jai Kyoung; Yoon, Sunghyun; Cho, Young-Ho

2018-01-19

We propose watch-type sweat rate sensors capable of automatic natural ventilation by integrating miniaturized thermo-pneumatic actuators, and experimentally verify their performances and applicability. Previous sensors using natural ventilation require manual ventilation process or high-power bulky thermo-pneumatic actuators to lift sweat rate detection chambers above skin for continuous measurement. The proposed watch-type sweat rate sensors reduce operation power by minimizing expansion fluid volume to 0.4 ml through heat circuit modeling. The proposed sensors reduce operation power to 12.8% and weight to 47.6% compared to previous portable sensors, operating for 4 hours at 6 V batteries. Human experiment for thermal comfort monitoring is performed by using the proposed sensors having sensitivity of 0.039 (pF/s)/(g/m 2 h) and linearity of 97.9% in human sweat rate range. Average sweat rate difference for each thermal status measured in three subjects shows (32.06 ± 27.19) g/m 2 h in thermal statuses including 'comfortable', 'slightly warm', 'warm', and 'hot'. The proposed sensors thereby can discriminate and compare four stages of thermal status. Sweat rate measurement error of the proposed sensors is less than 10% under air velocity of 1.5 m/s corresponding to human walking speed. The proposed sensors are applicable for wearable and portable use, having potentials for daily thermal comfort monitoring applications.

Exact and approximate solutions for the decades-old Michaelis-Menten equation: Progress-curve analysis through integrated rate equations.

Science.gov (United States)

Goličnik, Marko

2011-01-01

The Michaelis-Menten rate equation can be found in most general biochemistry textbooks, where the time derivative of the substrate is a hyperbolic function of two kinetic parameters (the limiting rate V, and the Michaelis constant K(M) ) and the amount of substrate. However, fundamental concepts of enzyme kinetics can be difficult to understand fully, or can even be misunderstood, by students when based only on the differential form of the Michaelis-Menten equation, and the variety of methods available to calculate the kinetic constants from rate versus substrate concentration "textbook data." Consequently, enzyme kinetics can be confusing if an analytical solution of the Michaelis-Menten equation is not available. Therefore, the still rarely known exact solution to the Michaelis-Menten equation is presented here through the explicit closed-form equation in terms of the Lambert W(x) function. Unfortunately, as the W(x) is not available in standard curve-fitting computer programs, the practical use of this direct solution is limited for most life-science students. Thus, the purpose of this article is to provide analytical approximations to the equation for modeling Michaelis-Menten kinetics. The elementary and explicit nature of these approximations can provide students with direct and simple estimations of kinetic parameters from raw experimental time-course data. The Michaelis-Menten kinetics studied in the latter context can provide an ideal alternative to the 100-year-old problems of data transformation, graphical visualization, and data analysis of enzyme-catalyzed reactions. Hence, the content of the course presented here could gradually become an important component of the modern biochemistry curriculum in the 21st century. Copyright © 2011 Wiley Periodicals, Inc.

A Multiparameter Thermal Conductivity Equation for 1,1-Difluoroethane (R152a) with an Optimized Functional Form

Science.gov (United States)

Scalabrin, G.; Marchi, P.; Finezzo, F.

2006-11-01

The application of an optimization technique to the available experimental data has led to the development of a new multiparameter equation λ = λ ( T,ρ ) for the representation of the thermal conductivity of 1,1-difluoroethane (R152a). The region of validity of the proposed equation covers the temperature range from 220 to 460 K and pressures up to 55 MPa, including the near-critical region. The average absolute deviation of the equation with respect to the selected 939 primary data points is 1.32%. The proposed equation represents therefore a significant improvement with respect to the literature conventional equation. The density value required by the equation is calculated at the chosen temperature and pressure conditions using a high accuracy equation of state for the fluid.

Computation of point reactor dynamics equations with thermal feedback via weighted residue method

International Nuclear Information System (INIS)

Suo Changan; Liu Xiaoming

1986-01-01

Point reactor dynamics equations with six groups of delayed neutrons have been computed via weighted-residual method in which the delta function was taken as a weighting function, and the parabolic with or without exponential factor as a trial function respectively for an insertion of large or smaller reactivity. The reactivity inserted into core can be varied with time, including insertion in forms of step function, polynomials up to second power and sine function. A thermal feedback of single flow channel model was added in. The thermal equations concerned were treated by use of a backward difference technique. A WRK code has been worked out, including implementation of an automatic selection of time span based on an input of error requirement and of an automatic change between computation with large reactivity and that with smaller one. On the condition of power varied slowly and without feedback, the results are not sensitive to the selection of values of time span. At last, the comparison of relevant results has shown that the agreement is quite well

Laser Rate Equation Based Filtering for Carrier Recovery in Characterization and Communication

DEFF Research Database (Denmark)

Piels, Molly; Iglesias Olmedo, Miguel; Xue, Weiqi

2015-01-01

We formulate a semiconductor laser rate equationbased approach to carrier recovery in a Bayesian filtering framework. Filter stability and the effect of model inaccuracies (unknown or un-useable rate equation coefficients) are discussed. Two potential application areas are explored: laser...... characterization and carrier recovery in coherent communication. Two rate equation based Bayesian filters, the particle filter and extended Kalman filter, are used in conjunction with a coherent receiver to measure frequency noise spectrum of a photonic crystal cavity laser with less than 20 nW of fiber...

Population decay time and distribution of exciton states analyzed by rate equations based on theoretical phononic and electron-collisional rate coefficients

Science.gov (United States)

Oki, Kensuke; Ma, Bei; Ishitani, Yoshihiro

2017-11-01

Population distributions and transition fluxes of the A exciton in bulk GaN are theoretically analyzed using rate equations of states of the principal quantum number n up to 5 and the continuum. These rate equations consist of the terms of radiative, electron-collisional, and phononic processes. The dependence of the rate coefficients on temperature is revealed on the basis of the collisional-radiative model of hydrogen plasma for the electron-collisional processes and theoretical formulation using Fermi's "golden rule" for the phononic processes. The respective effects of the variations in electron, exciton, and lattice temperatures are exhibited. This analysis is a base of the discussion on nonthermal equilibrium states of carrier-exciton-phonon dynamics. It is found that the exciton dissociation is enhanced even below 150 K mainly by the increase in the lattice temperature. When the thermal-equilibrium temperature increases, the population fluxes between the states of n >1 and the continuum become more dominant. Below 20 K, the severe deviation from the Saha-Boltzmann distribution occurs owing to the interband excitation flux being higher than the excitation flux from the 1 S state. The population decay time of the 1 S state at 300 K is more than ten times longer than the recombination lifetime of excitons with kinetic energy but without the upper levels (n >1 and the continuum). This phenomenon is caused by a shift of population distribution to the upper levels. This phonon-exciton-radiation model gives insights into the limitations of conventional analyses such as the ABC model, the Arrhenius plot, the two-level model (n =1 and the continuum), and the neglect of the upper levels.

The compressive behaviour and constitutive equation of polyimide foam in wide strain rate and temperature

Directory of Open Access Journals (Sweden)

Yoshimoto Akifumi

2015-01-01

Full Text Available These days, polymer foams, such as polyurethane foam and polystyrene foam, are used in various situations as a thermal insulator or shock absorber. In general, however, their strength is insufficient in high temperature environments because of their low glass transition temperature. Polyimide is a polymer which has a higher glass transition temperature and high strength. Its mechanical properties do not vary greatly, even in low temperature environments. Therefore, polyimide foam is expected to be used in the aerospace industry. Thus, the constitutive equation of polyimide foam that can be applied across a wide range of strain rates and ambient temperature is very useful. In this study, a series of compression tests at various strain rates, from 10−3 to 103 s−1 were carried out in order to examine the effect of strain rate on the compressive properties of polyimide foam. The flow stress of polyimide foam increased rapidly at dynamic strain rates. The effect of ambient temperature on the properties of polyimide foam was also investigated at temperature from − 190 °C to 270°∘C. The flow stress decreased with increasing temperature.

A paradox: The thermal rate coefficient for the H+DCl → HCl+D exchange reaction

International Nuclear Information System (INIS)

Thompson, D.L.; Suzukawa, H.H. Jr.; Raff, L.M.

1975-01-01

Previously reported photolysis experiments indicate that the frequency factors associated with the hydrogen-exchange reactions H+DCl → HCl+D and D+HCl → DCl+H are on the order of 10 10 cm 3 /molcenter-dotsec. A series of unadjusted, quasiclassical trajectory calculations were been carried out to compute the thermal rate coefficients and activation parameters for a series of 13 thermal processes of the type A+BC → AB+C, where A=H, D, or Cl and BC=H 2 , D 2 , HCl, DCl, or Cl 2 . In addition, hot-atom yield ratios have been computed from the IRP equation for the reactions D*+DCl → D 2 +Cl, D*+Cl 2 → DCl + Cl as a function of the initial D* laboratory energy. The computations yield (1) hot-atom DCl/D 2 yield ratios within a factor of 2 of the experimental values; (2) thermal activation energies in satisfactory agreement with experiment for all processes investigated; and (3) frequency factors in reasonable accord with experiment for all the reactions except the hydrogen exchange reactions

Filtering of sound from the Navier-Stokes equations. [An approximation for describing thermal convection in a compressible fluid

Energy Technology Data Exchange (ETDEWEB)

Paolucci, S.

1982-12-01

An approximation leading to anelastic equations capable of describing thermal convection in a compressible fluid is given. These equations are more general than the Oberbeck-Boussinesq equations and different than the standard anelastic equations in that they can be used for the computation of convection in a fluid with large density gradients present. We show that the equations do not contain acoustic waves, while at the same time they can still describe the propagation of internal waves. Throughout we show that the filtering of acoustic waves, within the limits of the approximation, does not appreciably alter the description of the physics.

Modeling of thermal conductivity of nanofluids by modifying Maxwell’s equation using cell model approach

International Nuclear Information System (INIS)

Mehta, Siddharth; Chauhan, K. Prashanth; Kanagaraj, S.

2011-01-01

Nanofluid is an innovative heat transfer fluid with superior potential for enhancing the heat transfer performance of conventional fluids. Though many attempts have been made to investigate the abnormal high thermal conductivity of nanofluids, the existing models cannot precisely predict the same. An attempt has been made to develop a model for predicting the thermal conductivity of different types of nanofluids. The model presented here is derived based on the fact that thermal conductivity of nanofluids depends on thermal conductivity of particle and fluid as well as micro-convective heat transfer due to Brownian motion of nanoparticles. Novelty of the article lies in giving a unique equation which predicts thermal conductivity of nanofluids for different concentrations and particle sizes which also correctly predicts the trends observed in experimental data over a wide range of particle sizes, temperatures, and particle concentrations.

Generalized rate-equation analysis of excitation exchange between silicon nanoclusters and erbium ions

International Nuclear Information System (INIS)

Kenyon, A. J.; Wojdak, M.; Ahmad, I.; Loh, W. H.; Oton, C. J.

2008-01-01

We discuss the use of rate equations to analyze the sensitization of erbium luminescence by silicon nanoclusters. In applying the general form of second-order coupled rate-equations to the Si nanocluster-erbium system, we find that the photoluminescence dynamics cannot be described using a simple rate equation model. Both rise and fall times exhibit a stretched exponential behavior, which we propose arises from a combination of a strongly distance-dependent nanocluster-erbium interaction, along with the finite size distribution and indirect band gap of the silicon nanoclusters. Furthermore, the low fraction of erbium ions that can be excited nonresonantly is a result of the small number of ions coupled to nanoclusters

Proposition of Regression Equations to Determine Outdoor Thermal Comfort in Tropical and Humid Environment

Directory of Open Access Journals (Sweden)

Sangkertadi Sangkertadi

2012-05-01

Full Text Available This study is about field experimentation in order to construct regression equations of perception of thermalcomfort for outdoor activities under hot and humid environment. Relationships between thermal-comfort perceptions, micro climate variables (temperatures and humidity and body parameters (activity, clothing, body measure have been observed and analyzed. 180 adults, men, and women participated as samples/respondents. This study is limited for situation where wind velocity is about 1 m/s, which touch the body of the respondents/samples. From questionnaires and field measurements, three regression equations have been developed, each for activity of normal walking, brisk walking, and sitting.

Rate equation simulation of temporal characteristics of a pulsed dye ...

Indian Academy of Sciences (India)

-dependent, two-dimensional (in space) rate equation model of a .... fluorescence band of the dye is divided into ten wavelength segments of variable sizes. ... qualitative and reasonably good quantitative agreement with experimental results.

Improved decay rates for solutions for a multidimensional generalized Benjamin-Bona-Mahony equation

KAUST Repository

Said-Houari, Belkacem

2014-01-01

In this paper, we study the decay rates of solutions for the generalized Benjamin-Bona-Mahony equation in multi-dimensional space. For initial data in some L1-weighted spaces, we prove faster decay rates of the solutions. More precisely, using the Fourier transform and the energy method, we show the global existence and the convergence rates of the solutions under the smallness assumption on the initial data and we give better decay rates of the solutions. This result improves early works in J. Differential Equations 158(2) (1999), 314-340 and Nonlinear Anal. 75(7) (2012), 3385-3392. © 2014-IOS Press.

Accelerated thermal and radiative ageing of hydrogenated NBR for DRC

International Nuclear Information System (INIS)

Mares, G.; Notingher, P.

1996-01-01

The accelerated thermal and gamma radiation ageing of HNBR carbon black-T80 has been studied by measuring the residual deformation under constant deflection -- DRC, in air, using a relevant equation for the relaxation phenomena. The residual deformation under constant deflection during the process of accelerated ageing is increasing but the structure of polymer answers in the proper manner to the mechanical stress. The degradation equations were obtained, using Alfrey model for the relaxation polymer subject to compression and an Arrhenius dependence for the chemical reaction rate. The inverted relaxation time for the thermal degradation is depending on the chemical reaction rate and the dose rate of gamma radiation

Validity of Saha's equation of thermal ionization for negatively charged spherical particles in complex plasmas in thermal equilibrium

International Nuclear Information System (INIS)

Sodha, M. S.; Mishra, S. K.

2011-01-01

The authors have discussed the validity of Saha's equation for the charging of negatively charged spherical particles in a complex plasma in thermal equilibrium, even when the tunneling of the electrons, through the potential energy barrier surrounding the particle is considered. It is seen that the validity requires the probability of tunneling of an electron through the potential energy barrier surrounding the particle to be independent of the direction (inside to outside and vice versa) or in other words the Born's approximation should be valid.

Validation of resting metabolic rate prediction equations for teenagers

Directory of Open Access Journals (Sweden)

Paulo Henrique Santos da Fonseca

2007-09-01

Full Text Available The resting metabolic rate (RMR can be defi ned as the minimum rate of energy spent and represents the main component of the energetic outlay. The purpose of this study is to validate equations to predict the resting metabolic rate in teenagers (103 individuals, being 51 girls and 52 boys, with age between 10 and 17 years from Florianópolis – SC – Brazil. It was measured: the body weight, body height, skinfolds and obtained the lean and body fat mass through bioimpedance. The nonproteic RMR was measured by Weir’s equation (1949, utilizing AeroSport TEEM-100 gas analyzer. The studied equations were: Harry and Benedict (1919, Schofi eld (1985, WHO/FAO/UNU (1985, Henry and Rees (1991, Molnár et al. (1998, Tverskaya et al. (1998 and Müller et al. (2004. In order to study the cross-validation of the RMR prediction equations and its standard measure (Weir 1949, the following statistics procedure were calculated: Pearson’s correlation (r ≥ 0.70, the “t” test with the signifi cance level of p0.05 in relation to the standard measure, with exception of the equations suggested for Tverskaya et al. (1998, and the two models of Müller et al (2004. Even though there was not a signifi cant difference, only the models considered for Henry and Rees (1991, and Molnár et al. (1995 had gotten constant error variation under 5%. All the equations analyzed in the study in girls had not reached criterion of correlation values of 0.70 with the indirect calorimetry. Analyzing the prediction equations of RMR in boys, all of them had moderate correlation coeffi cients with the indirect calorimetry, however below 0.70. Only the equation developed for Tverskaya et al. (1998 presented differences (p ABSTRACT0,05 em relação à medida padrão (Weir 1949, com exceção das equações sugeridas por Tverskaya et al. (1998 e os dois modelos de Müller et al (2004. Mesmo não havendo diferença signifi cativa, somente os modelos propostos por Henry e Rees (1991

Equations to Estimate Creatinine Excretion Rate : The CKD Epidemiology Collaboration

NARCIS (Netherlands)

Ix, Joachim H.; Wassel, Christina L.; Stevens, Lesley A.; Beck, Gerald J.; Froissart, Marc; Navis, Gerjan; Rodby, Roger; Torres, Vicente E.; Zhang, Yaping (Lucy); Greene, Tom; Levey, Andrew S.

Background and objectives Creatinine excretion rate (CER) indicates timed urine collection accuracy. Although equations to estimate CER exist, their bias and precision are untested and none simultaneously include age, sex, race, and weight. Design, setting, participants, & measurements Participants

Accurate and approximate thermal rate constants for polyatomic chemical reactions

International Nuclear Information System (INIS)

Nyman, Gunnar

2007-01-01

In favourable cases it is possible to calculate thermal rate constants for polyatomic reactions to high accuracy from first principles. Here, we discuss the use of flux correlation functions combined with the multi-configurational time-dependent Hartree (MCTDH) approach to efficiently calculate cumulative reaction probabilities and thermal rate constants for polyatomic chemical reactions. Three isotopic variants of the H 2 + CH 3 → CH 4 + H reaction are used to illustrate the theory. There is good agreement with experimental results although the experimental rates generally are larger than the calculated ones, which are believed to be at least as accurate as the experimental rates. Approximations allowing evaluation of the thermal rate constant above 400 K are treated. It is also noted that for the treated reactions, transition state theory (TST) gives accurate rate constants above 500 K. TST theory also gives accurate results for kinetic isotope effects in cases where the mass of the transfered atom is unchanged. Due to neglect of tunnelling, TST however fails below 400 K if the mass of the transferred atom changes between the isotopic reactions

Stochastic substitute for coupled rate equations in the modeling of highly ionized transient plasmas

International Nuclear Information System (INIS)

Eliezer, S.; Falquina, R.; Minguez, E.

1994-01-01

Plasmas produced by intense laser pulses incident on solid targets often do not satisfy the conditions for local thermodynamic equilibrium, and so cannot be modeled by transport equations relying on equations of state. A proper description involves an excessively large number of coupled rate equations connecting many quantum states of numerous species having different degrees of ionization. Here we pursue a recent suggestion to model the plasma by a few dominant states perturbed by a stochastic driving force. The driving force is taken to be a Poisson impulse process, giving a Langevin equation which is equivalent to a Fokker-Planck equation for the probability density governing the distribution of electron density. An approximate solution to the Langevin equation permits calculation of the characteristic relaxation rate. An exact stationary solution to the Fokker-Planck equation is given as a function of the strength of the stochastic driving force. This stationary solution is used, along with a Laplace transform, to convert the Fokker-Planck equation to one of Schroedinger type. We consider using the classical Hamiltonian formalism and the WKB method to obtain the time-dependent solution

Loss and thermal model for power semiconductors including device rating information

DEFF Research Database (Denmark)

Ma, Ke; Bahman, Amir Sajjad; Beczkowski, Szymon

2014-01-01

The electrical loading and device rating are both important factors that determine the loss and thermal behaviors of power semiconductor devices. In the existing loss and thermal models, only the electrical loadings are focused and treated as design variables, while the device rating is normally...

On the structure of the master equation for a two-level system coupled to a thermal bath

International Nuclear Information System (INIS)

Vega, Inés de

2015-01-01

We derive a master equation from the exact stochastic Liouville–von-Neumann (SLN) equation (Stockburger and Grabert 2002 Phys. Rev. Lett. 88 170407). The latter depends on two correlated noises and describes exactly the dynamics of an oscillator (which can be either harmonic or present an anharmonicity) coupled to an environment at thermal equilibrium. The newly derived master equation is obtained by performing analytically the average over different noise trajectories. It is found to have a complex hierarchical structure that might be helpful to explain the convergence problems occurring when performing numerically the stochastic average of trajectories given by the SLN equation (Koch et al 2008 Phys. Rev. Lett. 100 230402, Koch 2010 PhD thesis Fakultät Mathematik und Naturwissenschaften der Technischen Universitat Dresden). (paper)

On the structure of the master equation for a two-level system coupled to a thermal bath

Science.gov (United States)

de Vega, Inés

2015-04-01

We derive a master equation from the exact stochastic Liouville-von-Neumann (SLN) equation (Stockburger and Grabert 2002 Phys. Rev. Lett. 88 170407). The latter depends on two correlated noises and describes exactly the dynamics of an oscillator (which can be either harmonic or present an anharmonicity) coupled to an environment at thermal equilibrium. The newly derived master equation is obtained by performing analytically the average over different noise trajectories. It is found to have a complex hierarchical structure that might be helpful to explain the convergence problems occurring when performing numerically the stochastic average of trajectories given by the SLN equation (Koch et al 2008 Phys. Rev. Lett. 100 230402, Koch 2010 PhD thesis Fakultät Mathematik und Naturwissenschaften der Technischen Universitat Dresden).

Systematic approach to thermal leptogenesis

Energy Technology Data Exchange (ETDEWEB)

Frossard, T.; Kartavtsev, A. [Max-Planck-Institut fuer Kernphysik, Heidelberg (Germany); Garny, M. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Hohenegger, A. [Ecole Polytechnique Federale de Lausanne, LPPC, BSP (Switzerland); Mitrouskas, D. [Muenchen Univ. (Germany)

2012-11-15

In this work we study thermal leptogenesis using non-equilibrium quantum field theory. Starting from fundamental equations for correlators of the quantum fields we describe the steps necessary to obtain quantum kinetic equations for quasiparticles. These can easily be compared to conventional results and overcome conceptional problems inherent in the canonical approach. Beyond CP-violating decays we include also those scattering processes which are tightly related to the decays in a consistent approximation of fourth order in the Yukawa couplings. It is demonstrated explicitly how the S-matrix elements for the scattering processes in the conventional approach are related to two- and three-loop contributions to the effective action. We derive effective decay and scattering amplitudes taking medium corrections and thermal masses into account. In this context we also investigate CP-violating Higgs decay within the same formalism. From the kinetic equations we derive rate equations for the lepton asymmetry improved in that they include quantum-statistical effects and medium corrections to the quasiparticle properties.

Validity of predictive equations for basal metabolic rate in Japanese adults.

Science.gov (United States)

Miyake, Rieko; Tanaka, Shigeho; Ohkawara, Kazunori; Ishikawa-Takata, Kazuko; Hikihara, Yuki; Taguri, Emiko; Kayashita, Jun; Tabata, Izumi

2011-01-01

Many predictive equations for basal metabolic rate (BMR) based on anthropometric measurements, age, and sex have been developed, mainly for healthy Caucasians. However, it has been reported that many of these equations, used widely, overestimate BMR not only for Asians, but also for Caucasians. The present study examined the accuracy of several predictive equations for BMR in Japanese subjects. In 365 healthy Japanese male and female subjects, aged 18 to 79 y, BMR was measured in the post-absorptive state using a mask and Douglas bag. Six predictive equations were examined. Total error was used as an index of the accuracy of each equation's prediction. Predicted BMR values by Dietary Reference Intakes for Japanese (Japan-DRI), Adjusted Dietary Reference Intakes for Japanese (Adjusted-DRI), and Ganpule equations were not significantly different from the measured BMR in either sex. On the other hand, Harris-Benedict, Schofield, and Food and Agriculture Organization of the United Nations/World Health Organization/United Nations University equations were significantly higher than the measured BMR in both sexes. The prediction error by Japan-DRI, Adjusted-DRI, and Harris-Benedict equations was significantly correlated with body weight in both sexes. Total error using the Ganpule equation was low in both males and females (125 and 99 kcal/d, respectively). In addition, total error using the Adjusted-DRI equation was low in females (95 kcal/d). Thus, the Ganpule equation was the most accurate in predicting BMR in our healthy Japanese subjects, because the difference between the predicted and measured BMR was relatively small, and body weight had no effect on the prediction error.

Nuclear fission with a Langevin equation

International Nuclear Information System (INIS)

Boilley, D.; Suraud, E.; Abe, Yasuhisa

1992-01-01

A microscopically derived Langevin equation is applied to thermally induced nuclear fission. An important memory effect is pointed out and discussed. A strong friction coefficient, estimated from microscopic quantities, tends to decrease the stationary limit of the fission rate and to increase the transient time. The calculations are performed with a collective mass depending on the collective variable and with a constant mass. Fission rates calculated at different temperatures are shown and compared with previous available results. (author) 23 refs.; 7 figs

Kinetic parameters, collision rates, energy exchanges and transport coefficients of non-thermal electrons in premixed flames at sub-breakdown electric field strengths

KAUST Repository

Bisetti, Fabrizio

2014-01-02

The effects of an electric field on the collision rates, energy exchanges and transport properties of electrons in premixed flames are investigated via solutions to the Boltzmann kinetic equation. The case of high electric field strength, which results in high-energy, non-thermal electrons, is analysed in detail at sub-breakdown conditions. The rates of inelastic collisions and the energy exchange between electrons and neutrals in the reaction zone of the flame are characterised quantitatively. The analysis includes attachment, ionisation, impact dissociation, and vibrational and electronic excitation processes. Our results suggest that Townsend breakdown occurs for E/N = 140 Td. Vibrational excitation is the dominant process up to breakdown, despite important rates of electronic excitation of CO, CO2 and N2 as well as impact dissociation of O2 being apparent from 50 Td onwards. Ohmic heating in the reaction zone is found to be negligible (less than 2% of peak heat release rate) up to breakdown field strengths for realistic electron densities equal to 1010 cm-3. The observed trends are largely independent of equivalence ratio. In the non-thermal regime, electron transport coefficients are insensitive to mixture composition and approximately constant across the flame, but are highly dependent on the electric field strength. In the thermal limit, kinetic parameters and transport coefficients vary substantially across the flame due to the spatially inhomogeneous concentration of water vapour. A practical approach for identifying the plasma regime (thermal versus non-thermal) in studies of electric field effects on flames is proposed. © 2014 Taylor & Francis.

Method and apparatus for obtaining enhanced production rate of thermal chemical reactions

Science.gov (United States)

Tonkovich, Anna Lee Y [Pasco, WA; Wang, Yong [Richland, WA; Wegeng, Robert S [Richland, WA; Gao, Yufei [Kennewick, WA

2003-04-01

The present invention is a method and apparatus (vessel) for providing a heat transfer rate from a reaction chamber through a wall to a heat transfer chamber substantially matching a local heat transfer rate of a catalytic thermal chemical reaction. The key to the invention is a thermal distance defined on a cross sectional plane through the vessel inclusive of a heat transfer chamber, reaction chamber and a wall between the chambers. The cross sectional plane is perpendicular to a bulk flow direction of the reactant stream, and the thermal distance is a distance between a coolest position and a hottest position on the cross sectional plane. The thermal distance is of a length wherein the heat transfer rate from the reaction chamber to the heat transfer chamber substantially matches the local heat transfer rate.

Theoretical Time Dependent Thermal Neutron Spectra and Reaction Rates in H2O and D2O

International Nuclear Information System (INIS)

Purohit, S.N.

1966-04-01

The early theoretical and experimental time dependent neutron thermalization studies were limited to the study of the transient spectrum in the diffusion period. The recent experimental measurements of the time dependent thermal neutron spectra and reaction rates, for a number of moderators, have generated considerable interest in the study of the time dependent Boltzmann equation. In this paper we present detailed results for the time dependent spectra and the reaction rates for resonance detectors using several scattering models of H 2 O and D 2 O. This study has been undertaken in order to interpret the integral time dependent neutron thermalization experiments in liquid moderators which have been performed at the AB Atomenergi. The proton gas and the deuteron gas models are inadequate to explain the measured reaction rates in H 2 O and D 2 O. The bound models of Nelkin for H 2 O and of Butler for D 2 O give much better agreement with the experimental results than the gas models. Nevertheless, some disagreement between theoretical and experimental results still persists. This study also indicates that the bound model of Butler and the effective mass 3. 6 gas model of Brown and St. John give almost identical reaction rates. It is also surprising to note that the calculated reaction rate for Cd for the Butler model appears to be in better agreement with the experimental results of D 2 O than of the Nelkin model with H 2 O experiments. The present reaction rate studies are sensitive enough so as to distinguish between the gas model and the bound model of a moderator. However, to investigate the details of a scattering law (such as the effect of the hindered rotations in H 2 O and D 2 O and the weights of different dynamical modes) with the help of these studies would require further theoretical as well as experimental investigations. Theoretical results can be further improved by improving the source for thermal neutrons, the group structure and the scattering

A simple algebraic cancer equation: calculating how cancers may arise with normal mutation rates

Directory of Open Access Journals (Sweden)

Shibata Darryl

2010-01-01

Full Text Available Abstract Background The purpose of this article is to present a relatively easy to understand cancer model where transformation occurs when the first cell, among many at risk within a colon, accumulates a set of driver mutations. The analysis of this model yields a simple algebraic equation, which takes as inputs the number of stem cells, mutation and division rates, and the number of driver mutations, and makes predictions about cancer epidemiology. Methods The equation [p = 1 - (1 - (1 - (1 - udkNm ] calculates the probability of cancer (p and contains five parameters: the number of divisions (d, the number of stem cells (N × m, the number of critical rate-limiting pathway driver mutations (k, and the mutation rate (u. In this model progression to cancer "starts" at conception and mutations accumulate with cell division. Transformation occurs when a critical number of rate-limiting pathway mutations first accumulates within a single stem cell. Results When applied to several colorectal cancer data sets, parameter values consistent with crypt stem cell biology and normal mutation rates were able to match the increase in cancer with aging, and the mutation frequencies found in cancer genomes. The equation can help explain how cancer risks may vary with age, height, germline mutations, and aspirin use. APC mutations may shorten pathways to cancer by effectively increasing the numbers of stem cells at risk. Conclusions The equation illustrates that age-related increases in cancer frequencies may result from relatively normal division and mutation rates. Although this equation does not encompass all of the known complexity of cancer, it may be useful, especially in a teaching setting, to help illustrate relationships between small and large cancer features.

Mixed Convection Flow along a Stretching Cylinder in a Thermally Stratified Medium

Directory of Open Access Journals (Sweden)

Swati Mukhopadhyay

2012-01-01

Full Text Available An analysis for the axisymmetric laminar boundary layer mixed convection flow of a viscous and incompressible fluid towards a stretching cylinder immersed in a thermally stratified medium is presented in this paper. Similarity transformation is employed to convert the governing partial differential equations into highly nonlinear ordinary differential equations. Numerical solutions of these equations are obtained by a shooting method. It is found that the heat transfer rate at the surface is lower for flow in a thermally stratified medium compared to that of an unstratified medium. Moreover, both the skin friction coefficient and the heat transfer rate at the surface are larger for a cylinder compared to that for a flat plate.

Study on thermal wave based on the thermal mass theory

Institute of Scientific and Technical Information of China (English)

无

2009-01-01

The conservation equations for heat conduction are established based on the concept of thermal mass.We obtain a general heat conduction law which takes into account the spatial and temporal inertia of thermal mass.The general law introduces a damped thermal wave equation.It reduces to the well-known CV model when the spatial inertia of heat flux and temperature and the temporal inertia of temperature are neglected,which indicates that the CV model only considers the temporal inertia of heat flux.Numerical simulations on the propagation and superposition of thermal waves show that for small thermal perturbation the CV model agrees with the thermal wave equation based on the thermal mass theory.For larger thermal perturbation,however,the physically impossible phenomenon pre-dicted by CV model,i.e.the negative temperature induced by the thermal wave superposition,is eliminated by the general heat conduction law,which demonstrates that the present heat conduction law based on the thermal mass theory is more reasonable.

Study on thermal wave based on the thermal mass theory

Institute of Scientific and Technical Information of China (English)

HU RuiFeng; CAO BingYang

2009-01-01

The conservation equations for heat conduction are established based on the concept of thermal mass. We obtain a general heat conduction law which takes into account the spatial and temporal inertia of thermal mass. The general law introduces a damped thermal wave equation. It reduces to the well-known CV model when the spatial inertia of heat flux and temperature and the temporal inertia of temperature are neglected, which indicates that the CV model only considers the temporal inertia of heat flux. Numerical simulations on the propagation and superposition of thermal waves show that for small thermal perturbation the CV model agrees with the thermal wave equation based on the thermal mass theory. For larger thermal perturbation, however, the physically impossible phenomenon pre-dicted by CV model, i.e. the negative temperature induced by the thermal wave superposition, is eliminated by the general heat conduction law, which demonstrates that the present heat conduction law based on the thermal mass theory is more reasonable.

Surface hopping, transition state theory, and decoherence. II. Thermal rate constants and detailed balance

Energy Technology Data Exchange (ETDEWEB)

Jain, Amber; Subotnik, Joseph E., E-mail: subotnik@sas.upenn.edu [Department of Chemistry, University of Pennsylvania, 231 South 34th Street, Philadelphia, Pennsylvania 19104 (United States)

2015-10-07

We investigate a simple approach to compute a non-adiabatic thermal rate constant using the fewest switches surface hopping (FSSH) dynamics. We study the effects of both decoherence (using our augmented-FSSH (A-FSSH) algorithm) and forbidden hops over a large range of parameters, including high and low friction regimes, and weak and strong electronic coupling regimes. Furthermore, when possible, we benchmark our results against exact hierarchy equations of motion results, where we usually find a maximum error of roughly a factor of two (at reasonably large temperatures). In agreement with Hammes-Schiffer and Tully, we find that a merger of transition state theory and surface hopping can be both accurate and efficient when performed correctly. We further show that detailed balance is followed approximately by A-FSSH dynamics.

Constraining Non-thermal and Thermal properties of Dark Matter

Directory of Open Access Journals (Sweden)

Bhupal eDev

2014-05-01

Full Text Available We describe the evolution of Dark Matter (DM abundance from the very onset of its creation from inflaton decay under the assumption of an instantaneous reheating. Based on the initial conditions such as the inflaton mass and its decay branching ratio to the DM species, the reheating temperature, and the mass and interaction rate of the DM with the thermal bath, the DM particles can either thermalize (fully/partially with the primordial bath or remain non-thermal throughout their evolution history. In the thermal case, the final abundance is set by the standard freeze-out mechanism for large annihilation rates, irrespective of the initial conditions. For smaller annihilation rates, it can be set by the freeze-in mechanism which also does not depend on the initial abundance, provided it is small to begin with. For even smaller interaction rates, the DM decouples while being non-thermal, and the relic abundance will be essentially set by the initial conditions. We put model-independent constraints on the DM mass and annihilation rate from over-abundance by exactly solving the relevant Boltzmann equations, and identify the thermal freeze-out, freeze-in and non-thermal regions of the allowed parameter space. We highlight a generic fact that inflaton decay to DM inevitably leads to an overclosure of the Universe for a large range of DM parameter space, and thus poses a stringent constraint that must be taken into account while constructing models of DM. For the thermal DM region, we also show the complementary constraints from indirect DM search experiments, Big Bang Nucleosynthesis, Cosmic Microwave Background, Planck measurements, and theoretical limits due to the unitarity of S-matrix. For the non-thermal DM scenario, we show the allowed parameter space in terms of the inflaton and DM masses for a given reheating temperature, and compute the comoving free-streaming length to identify the hot, warm and cold DM regimes.

Subjective thermal sensation and human body exergy consumption rate: analysis and correlation

DEFF Research Database (Denmark)

Simone, Angela; Dovjak, M.; Kolarik, Jakub

2011-01-01

, it is reasonable to consider both the exergy flows in building and those within the human body. There is a need to verify the human-body exergy model with the Thermal-Sensation (TS) response of subjects exposed to different combinations of indoor climate parameters (temperature, humidity, etc.). First results...... available on the relation between human-body exergy consumption rates and subjectively assessed thermal sensation showed that the minimum human body exergy consumption rate is associated with thermal sensation votes close to thermal neutrality, tending to slightly cool side of thermal sensation. By applying...... the exergy concept to the built indoor environment, additional results are going to be explored. By using the data available so far of operative temperature (to), the human body exergy consumption rates increase as to increases above 24°C or decreases below 22°C at relative humidity (RH) lower than 50...

How "Hot Precursors" Modify Island Nucleation: A Rate-Equation Model

Science.gov (United States)

Morales-Cifuentes, Josue R.; Einstein, T. L.; Pimpinelli, A.

2014-12-01

We propose a novel island nucleation and growth model explicitly including transient (ballistic) mobility of the monomers deposited at rate F , assumed to be in a hot precursor state before thermalizing. In limiting regimes, corresponding to fast (diffusive) and slow (ballistic) thermalization, the island density N obeys scaling N ∝Fα . In between is found a rich, complex behavior, with various distinctive scaling regimes, characterized by effective exponents αeff and activation energies that we compute exactly. Application to N (F ,T ) of recent organic-molecule deposition experiments yields an excellent fit.

On Regularly Varying and History-Dependent Convergence Rates of Solutions of a Volterra Equation with Infinite Memory

Directory of Open Access Journals (Sweden)

Appleby JohnAD

2010-01-01

Full Text Available We consider the rate of convergence to equilibrium of Volterra integrodifferential equations with infinite memory. We show that if the kernel of Volterra operator is regularly varying at infinity, and the initial history is regularly varying at minus infinity, then the rate of convergence to the equilibrium is regularly varying at infinity, and the exact pointwise rate of convergence can be determined in terms of the rate of decay of the kernel and the rate of growth of the initial history. The result is considered both for a linear Volterra integrodifferential equation as well as for the delay logistic equation from population biology.

The thermal coupling constant and the gap equation in the λ φ 4D model

International Nuclear Information System (INIS)

Ananos, G.N.J.; Malbouisson, A.P.C.; Svaiter, N.F.

1998-05-01

By the concurrent use of two different resummation methods, the composite operator formalism and the Dyson-Schwinger equation, we re-examine the behaviour at finite temperature of the O(N)-symmetric λψ 4 model in a generic D-dimensional Euclidean space. In the cases D = 3 and D = 4, an analysis of the thermal behaviour of the renormalized squared mass and coupling constant are done for all temperatures. It results that the thermal renormalized squared mass is positive and increases monotonically with the temperature. The behavior of the thermal coupling constant is quite different in odd or even dimensional space. In D = 3, the thermal coupling constant decreases up to a minimum value different from zero and ten grows up monotonically as the temperature increases. In the case D = 4, it is found that the thermal renormalized coupling constant tends in the high temperature limit to a constant asymptotic value. Also for general D-dimensional Euclidean space, we are able to obtain a formula for the critical temperature of the second order phase transition. This formula agrees with previous known values at D = 3 and D 4. (author)

A relation between calculated human body exergy consumption rate and subjectively assessed thermal sensation

DEFF Research Database (Denmark)

Simone, Angela; Kolarik, Jakub; Iwamatsu, Toshiya

2011-01-01

occupants, it is reasonable to consider both the exergy flows in building and those within the human body. Until now, no data have been available on the relation between human-body exergy consumption rates and subjectively assessed thermal sensation. The objective of the present work was to relate thermal...... sensation data, from earlier thermal comfort studies, to calculated human-body exergy consumption rates. The results show that the minimum human body exergy consumption rate is associated with thermal sensation votes close to thermal neutrality, tending to the slightly cool side of thermal sensation....... Generally, the relationship between air temperature and the exergy consumption rate, as a first approximation, shows an increasing trend. Taking account of both convective and radiative heat exchange between the human body and the surrounding environment by using the calculated operative temperature, exergy...

Dynamic pathways to mediate reactions buried in thermal fluctuations. I. Time-dependent normal form theory for multidimensional Langevin equation.

Science.gov (United States)

Kawai, Shinnosuke; Komatsuzaki, Tamiki

2009-12-14

We present a novel theory which enables us to explore the mechanism of reaction selectivity and robust functions in complex systems persisting under thermal fluctuation. The theory constructs a nonlinear coordinate transformation so that the equation of motion for the new reaction coordinate is independent of the other nonreactive coordinates in the presence of thermal fluctuation. In this article we suppose that reacting systems subject to thermal noise are described by a multidimensional Langevin equation without a priori assumption for the form of potential. The reaction coordinate is composed not only of all the coordinates and velocities associated with the system (solute) but also of the random force exerted by the environment (solvent) with friction constants. The sign of the reaction coordinate at any instantaneous moment in the region of a saddle determines the fate of the reaction, i.e., whether the reaction will proceed through to the products or go back to the reactants. By assuming the statistical properties of the random force, one can know a priori a well-defined boundary of the reaction which separates the full position-velocity space in the saddle region into mainly reactive and mainly nonreactive regions even under thermal fluctuation. The analytical expression of the reaction coordinate provides the firm foundation on the mechanism of how and why reaction proceeds in thermal fluctuating environments.

Effect of thermal fluctuations in spin-torque driven magnetization dynamics

International Nuclear Information System (INIS)

Bonin, R.; Bertotti, G.; Serpico, C.; Mayergoyz, I.D.; D'Aquino, M.

2007-01-01

Nanomagnets with uniaxial symmetry driven by an external field and spin-polarized currents are considered. Anisotropy, applied field, and spin polarization are all aligned along the symmetry axis. Thermal fluctuations are described by adding a Gaussian white noise stochastic term to the Landau-Lifshitz-Gilbert equation for the deterministic dynamics. The corresponding Fokker-Planck equation is derived. It is shown that deterministic dynamics, thermal relaxation, and transition rate between stable states are governed by an effective potential including the effect of current injection

Effect of thermal fluctuations in spin-torque driven magnetization dynamics

Energy Technology Data Exchange (ETDEWEB)

Bonin, R. [INRiM, I-10135 Turin (Italy)]. E-mail: bonin@inrim.it; Bertotti, G. [INRiM, I-10135 Turin (Italy); Serpico, C. [Dipartimento di Ingegneria Elettrica, Universita di Napoli ' Federico II' I-80125 Naples (Italy); Mayergoyz, I.D. [Department of Electrical and Computer Engineering, University of Maryland, College Park, MD 20742 (United States); D' Aquino, M. [Dipartimento per le Tecnologie, Universita di Napoli ' Parthenope' , I-80133 Naples (Italy)

2007-09-15

Nanomagnets with uniaxial symmetry driven by an external field and spin-polarized currents are considered. Anisotropy, applied field, and spin polarization are all aligned along the symmetry axis. Thermal fluctuations are described by adding a Gaussian white noise stochastic term to the Landau-Lifshitz-Gilbert equation for the deterministic dynamics. The corresponding Fokker-Planck equation is derived. It is shown that deterministic dynamics, thermal relaxation, and transition rate between stable states are governed by an effective potential including the effect of current injection.

Fixation of waste materials in grouts: Part 3, Equation for critical flow rate

International Nuclear Information System (INIS)

Tallent, O.K.; McDaniel, E.W.; Spence, R.D.; Godsey, T.T.; Dodson, K.E.

1986-12-01

Critical flow rate data for grouts prepared from three distinctly different nuclear waste materials have been correlated. The wastes include Oak Ridge National Laboratory (ORNL) low-level waste (LLW) solution, Hanford Facility waste (HFW) solution, and cladding removal waste (CRW) slurry. Data for the three wastes have been correlated with a 0.96 coefficient of correlation by the following equation: log V/sub E/ = 0.289 + 0.707 log μ/sub E/, where V/sub E/ and μ/sub E/ denote critical flow rate in m 3 /min and apparent viscosity in Pa.s, respectively. The equation may be used to estimate critical flow rate for grouts prepared within the compositional range of the investigation. 5 refs., 4 figs., 7 tabs

Cell membrane temperature rate sensitivity predicted from the Nernst equation.

Science.gov (United States)

Barnes, F S

1984-01-01

A hyperpolarized current is predicted from the Nernst equation for conditions of positive temperature derivatives with respect to time. This ion current, coupled with changes in membrane channel conductivities, is expected to contribute to a transient potential shift across the cell membrane for silent cells and to a change in firing rate for pacemaker cells.

Thermal history regulates methylbutenol basal emission rate in Pinus ponderosa.

Science.gov (United States)

Gray, Dennis W; Goldstein, Allen H; Lerdau, Manuel T

2006-07-01

Methylbutenol (MBO) is a 5-carbon alcohol that is emitted by many pines in western North America, which may have important impacts on the tropospheric chemistry of this region. In this study, we document seasonal changes in basal MBO emission rates and test several models predicting these changes based on thermal history. These models represent extensions of the ISO G93 model that add a correction factor C(basal), allowing MBO basal emission rates to change as a function of thermal history. These models also allow the calculation of a new emission parameter E(standard30), which represents the inherent capacity of a plant to produce MBO, independent of current or past environmental conditions. Most single-component models exhibited large departures in early and late season, and predicted day-to-day changes in basal emission rate with temporal offsets of up to 3 d relative to measured basal emission rates. Adding a second variable describing thermal history at a longer time scale improved early and late season model performance while retaining the day-to-day performance of the parent single-component model. Out of the models tested, the T(amb),T(max7) model exhibited the best combination of day-to-day and seasonal predictions of basal MBO emission rates.

Rate equation modelling of erbium luminescence dynamics in erbium-doped silicon-rich-silicon-oxide

Energy Technology Data Exchange (ETDEWEB)

Shah, Miraj, E-mail: m.shah@ee.ucl.ac.uk [Department of Electronic and Electrical Engineering, UCL, Torrington Place, London WC1E 7JE (United Kingdom); Wojdak, Maciej; Kenyon, Anthony J. [Department of Electronic and Electrical Engineering, UCL, Torrington Place, London WC1E 7JE (United Kingdom); Halsall, Matthew P.; Li, Hang; Crowe, Iain F. [Photon Science Institute and School of Electrical and Electronic Engineering, University of Manchester, Sackville St Building, Manchester M13 9PL (United Kingdom)

2012-12-15

Erbium doped silicon-rich silica offers broad band and very efficient excitation of erbium photoluminescence (PL) due to a sensitization effect attributed to silicon nanocrystals (Si-nc), which grow during thermal treatment. PL decay lifetime measurements of sensitised Er{sup 3+} ions are usually reported to be stretched or multi exponential, very different to those that are directly excited, which usually show a single exponential decay component. In this paper, we report on SiO{sub 2} thin films doped with Si-nc's and erbium. Time resolved PL measurements reveal two distinct 1.54 {mu}m Er decay components; a fast microsecond component, and a relatively long lifetime component (10 ms). We also study the structural properties of these samples through TEM measurements, and reveal the formation of Er clusters. We propose that these Er clusters are responsible for the fast {mu}s decay component, and we develop rate equation models that reproduce the experimental transient observations, and can explain some of the reported transient behaviour in previously published literature.

Numerical study for enhancing the thermal conductivity of phase change material (PCM) storage using high thermal conductivity porous matrix

International Nuclear Information System (INIS)

Mesalhy, Osama; Lafdi, Khalid; Elgafy, Ahmed; Bowman, Keith

2005-01-01

In this paper, the melting process inside an irregular geometry filled with high thermal conductivity porous matrix saturated with phase change material PCM is investigated numerically. The numerical model is resting on solving the volume averaged conservation equations for mass, momentum and energy with phase change (melting) in the porous medium. The convection motion of the liquid phase inside the porous matrix is solved considering the Darcy, Brinkman and Forchiemer effects. A local thermal non-equilibrium assumption is considered due to the large difference in thermal properties between the solid matrix and PCM by applying a two energy equation model. The numerical code shows good agreement for pure PCM melting with another published numerical work. Through this study it is found that the presence of the porous matrix has a great effect on the heat transfer and melting rate of the PCM energy storage. Decreasing the porosity of the matrix increases the melting rate, but it also damps the convection motion. It is also found that the best technique to enhance the response of the PCM storage is to use a solid matrix with high porosity and high thermal conductivity

Thermal energy storages analysis for high temperature in air solar systems

International Nuclear Information System (INIS)

Andreozzi, Assunta; Buonomo, Bernardo; Manca, Oronzio; Tamburrino, Salvatore

2014-01-01

In this paper a high temperature thermal storage in a honeycomb solid matrix is numerically investigated and a parametric analysis is accomplished. In the formulation of the model it is assumed that the system geometry is cylindrical, the fluid and the solid thermo physical properties are temperature independent and radiative heat transfer is taken into account whereas the effect of gravity is neglected. Air is employed as working fluid and the solid material is cordierite. The evaluation of the fluid dynamic and thermal behaviors is accomplished assuming the honeycomb as a porous medium. The Brinkman–Forchheimer–extended Darcy model is used in the governing equations and the local thermal non equilibrium is assumed. The commercial CFD Fluent code is used to solve the governing equations in transient regime. Numerical simulations are carried out with storage medium for different mass flow rates of the working fluid and different porosity values. Results in terms of temperature profiles, temperatures fields and stored thermal energy as function of time are presented. The effects of storage medium, different porosity values and mass flow rate on stored thermal energy and storage time are shown. - Highlights: • HTTES in a honeycomb solid matrix is numerically investigated. • The numerical analysis is carried out assuming the honeycomb as a porous medium. • The Brinkman–Forchheimer–extended Darcy model is used in the governing equations. • Results are carried out for different mass flow rates and porosity values. • The main effect is due to the porosity which set the thermal energy storage value

The contribution of thermal radiation to the thermal conductivity of porous UO2

International Nuclear Information System (INIS)

Bakker, K.; Kwast, H.; Cordfunke, E.H.P.

1994-09-01

The influence of cylindrical, spherical and ellipsoidal inclusions on the overall thermal conductivity was computed with the finite element technique. The results of these calculations were compared with equations that describe the effect of inclusions on the overall thermal conductivity. The analytical equation of Schulz that describes the effect of inclusions on the overall thermal conductivity is in good agreement with the results of the finite element computations. This good agreement shows that among a variety of porosity correction formulas, the equation of Schulz gives the best description of the effect of inclusions on the overall thermal conductivity. This equation and the results of finite element calculations allow us to compute the contribution of radiation to the overall thermal conductivity of UO 2 with oblate ellipsoidal porosity. The present radiation calculations show that Hayes and Peddicord overestimated the contribution of thermal radiation to the thermal conductivity. (orig.)

Rate equation description of quantum noise in nanolasers with few emitters

DEFF Research Database (Denmark)

Mørk, Jesper; Lippi, G. L.

2018-01-01

Rate equations for micro- and nanocavity lasers are formulated which take account of the finite number of emitters, Purcell effects as well as stochastic effects of spontaneous emission quantum noise. Analytical results are derived for the intensity noise and intensity correlation properties, g(2...

A relation between calculated human body exergy consumption rate and subjectively assessed thermal sensation

Energy Technology Data Exchange (ETDEWEB)

Simone, Angela; Kolarik, Jakub; Olesen, Bjarne W. [ICIEE/BYG, Technical University of Denmark (Denmark); Iwamatsu, Toshiya [Faculty of Urban Environmental Science, Tokyo Metropolitan University (Japan); Asada, Hideo [Architech Consulting Co., Tokyo (Japan); Dovjak, Mateja [Faculty of Civil and Geodetic Engineering, University of Ljubljana (Slovenia); Schellen, Lisje [Eindhoven University of Technology, Faculty of Architecture Building and Planning (Netherlands); Shukuya, Masanori [Laboratory of Building Environment, Tokyo City University, Yokohama (Japan)

2011-01-15

Application of the exergy concept to research on the built environment is a relatively new approach. It helps to optimize climate conditioning systems so that they meet the requirements of sustainable building design. As the building should provide a healthy and comfortable environment for its occupants, it is reasonable to consider both the exergy flows in building and those within the human body. Until now, no data have been available on the relation between human-body exergy consumption rates and subjectively assessed thermal sensation. The objective of the present work was to relate thermal sensation data, from earlier thermal comfort studies, to calculated human-body exergy consumption rates. The results show that the minimum human body exergy consumption rate is associated with thermal sensation votes close to thermal neutrality, tending to the slightly cool side of thermal sensation. Generally, the relationship between air temperature and the exergy consumption rate, as a first approximation, shows an increasing trend. Taking account of both convective and radiative heat exchange between the human body and the surrounding environment by using the calculated operative temperature, exergy consumption rates increase as the operative temperature increases above 24 C or decreases below 22 C. With the data available so far, a second-order polynomial relationship between thermal sensation and the exergy consumption rate was established. (author)

The specification of cross exchange rate equations used to test Purchasing Power Parity

OpenAIRE

Hunter, J; Simpson, M

2004-01-01

The Article considers the speciÞcation of models used to test Pur- chasing Power Parity when applied to cross exchange rates. SpeciÞcally, conventional dynamic models used to test stationarity of the real exchange rate are likely to be misspeciÞed, except when the parameters of each ex- change rate equation are the same

The contribution of thermal radiation to the thermal conductivity of porous UO2

International Nuclear Information System (INIS)

Bakker, K.; Kwast, H.; Cordfunke, E.H.P.

1995-01-01

The influence of cylindrical, spherical and ellipsoidal inclusions on the overall thermal conductivity was computed with the finite element technique. The results of these calculations were compared with equations that describe the effect of inclusions on the overall thermal conductivity. The analytical equation of Schulz [B. Schulz, KfK-1988 (1974)] that describes the effect of inclusions on the overall thermal conductivity is in good agreement with the results of the finite element computations. This good agreement shows that among a variety of porosity correction formulas, the equation of Schulz gives the best description of the effect of inclusions on the overall thermal conductivity. This equation and the results of finite element calculations allow us to compute the contribution of radiation to the overall thermal conductivity of UO 2 with oblate ellipsoidal porosity. The present radiation calculations show that Hayes and Peddicord [S.L. Hayes and K.L. Peddicord, J. Nucl. Mater. 202 (1993) 87] overestimated the contribution of thermal radiation to the thermal conductivity. ((orig.))

Thermal conductance and basal metabolic rate are part of a coordinated system for heat transfer regulation

Science.gov (United States)

Naya, Daniel E.; Spangenberg, Lucía; Naya, Hugo; Bozinovic, Francisco

2013-01-01

Thermal conductance measures the ease with which heat leaves or enters  an organism's body. Although the analysis of this physiological variable in relation to climatic and ecological factors can be traced to studies by Scholander and colleagues, only small advances have occurred ever since. Here, we analyse the relationship between minimal thermal conductance estimated during summer (Cmin) and several ecological, climatic and geographical factors for 127 rodent species, in order to identify the exogenous factors that have potentially affected the evolution of thermal conductance. In addition, we evaluate whether there is compensation between Cmin and basal metabolic rate (BMR)—in such a way that a scale-invariant ratio between both variables is equal to one—as could be expected from the Scholander–Irving model of heat transfer. Our major findings are (i) annual mean temperature is the best single predictor of mass-independent Cmin. (ii) After controlling for the effect of body mass, there is a strong positive correlation between log10 (Cmin) and log10 (BMR). Further, the slope of this correlation is close to one, indicating an almost perfect compensation between both physiological variables. (iii) Structural equation modelling indicated that Cmin values are adjusted to BMR values and not the other way around. Thus, our results strongly suggest that BMR and thermal conductance integrate a coordinated system for heat regulation in endothermic animals and that summer conductance values are adjusted (in an evolutionary sense) to track changes in BMRs. PMID:23902915

Thermal conductance and basal metabolic rate are part of a coordinated system for heat transfer regulation.

Science.gov (United States)

Naya, Daniel E; Spangenberg, Lucía; Naya, Hugo; Bozinovic, Francisco

2013-09-22

Thermal conductance measures the ease with which heat leaves or enters an organism's body. Although the analysis of this physiological variable in relation to climatic and ecological factors can be traced to studies by Scholander and colleagues, only small advances have occurred ever since. Here, we analyse the relationship between minimal thermal conductance estimated during summer (Cmin) and several ecological, climatic and geographical factors for 127 rodent species, in order to identify the exogenous factors that have potentially affected the evolution of thermal conductance. In addition, we evaluate whether there is compensation between Cmin and basal metabolic rate (BMR)-in such a way that a scale-invariant ratio between both variables is equal to one-as could be expected from the Scholander-Irving model of heat transfer. Our major findings are (i) annual mean temperature is the best single predictor of mass-independent Cmin. (ii) After controlling for the effect of body mass, there is a strong positive correlation between log10 (Cmin) and log10 (BMR). Further, the slope of this correlation is close to one, indicating an almost perfect compensation between both physiological variables. (iii) Structural equation modelling indicated that Cmin values are adjusted to BMR values and not the other way around. Thus, our results strongly suggest that BMR and thermal conductance integrate a coordinated system for heat regulation in endothermic animals and that summer conductance values are adjusted (in an evolutionary sense) to track changes in BMRs.

Complete Loss and Thermal Model of Power Semiconductors Including Device Rating Information

DEFF Research Database (Denmark)

Ma, Ke; Bahman, Amir Sajjad; Beczkowski, Szymon

2015-01-01

Thermal loading of power devices are closely related to the reliability performance of the whole converter system. The electrical loading and device rating are both important factors that determine the loss and thermal behaviors of power semiconductor devices. In the existing loss and thermal...

Validation of estimated glomerular filtration rate equations for Japanese children.

Science.gov (United States)

Gotoh, Yoshimitsu; Uemura, Osamu; Ishikura, Kenji; Sakai, Tomoyuki; Hamasaki, Yuko; Araki, Yoshinori; Hamda, Riku; Honda, Masataka

2018-01-25

The gold standard for evaluation of kidney function is renal inulin clearance (Cin). However, the methodology for Cin is complicated and difficult, especially for younger children and/or patients with bladder dysfunction. Therefore, we developed a simple and easier method for obtaining the estimated glomerular filtration rate (eGFR) using equations and values for several biomarkers, i.e., serum creatinine (Cr), serum cystatin C (cystC), serum beta-2 microglobulin (β 2 MG), and creatinine clearance (Ccr). The purpose of the present study was to validate these equations with a new data set. To validate each equation, we used data of 140 patients with CKD with clinical need for Cin, using the measured GFR (mGFR). We compared the results for each eGFR equation with the mGFR using mean error (ME), root mean square error (RMSE), P 30 , and Bland-Altman analysis. The ME of Cr, cystC, β 2 MG, and Ccr based on eGFR was 15.8 ± 13.0, 17.2 ± 16.5, 15.4 ± 14.3, and 10.6 ± 13.0 ml/min/1.73 m 2 , respectively. The RMSE was 29.5, 23.8, 20.9, and 16.7, respectively. The P 30 was 79.4, 71.1, 69.5, and 92.9%, respectively. The Bland-Altman bias analysis showed values of 4.0 ± 18.6, 5.3 ± 16.8, 12.7 ± 17.0, and 2.5 ± 17.2 ml/min/1.73 m 2 , respectively, for these parameters. The bias of each eGFR equation was not large. Therefore, each eGFR equation could be used.

Ablation, Thermal Response, and Chemistry Program for Analysis of Thermal Protection Systems

Science.gov (United States)

Milos, Frank S.; Chen, Yih-Kanq

2010-01-01

In previous work, the authors documented the Multicomponent Ablation Thermochemistry (MAT) and Fully Implicit Ablation and Thermal response (FIAT) programs. In this work, key features from MAT and FIAT were combined to create the new Fully Implicit Ablation, Thermal response, and Chemistry (FIATC) program. FIATC is fully compatible with FIAT (version 2.5) but has expanded capabilities to compute the multispecies surface chemistry and ablation rate as part of the surface energy balance. This new methodology eliminates B' tables, provides blown species fractions as a function of time, and enables calculations that would otherwise be impractical (e.g. 4+ dimensional tables) such as pyrolysis and ablation with kinetic rates or unequal diffusion coefficients. Equations and solution procedures are presented, then representative calculations of equilibrium and finite-rate ablation in flight and ground-test environments are discussed.

Existing creatinine-based equations overestimate glomerular filtration rate in Indians.

Science.gov (United States)

Kumar, Vivek; Yadav, Ashok Kumar; Yasuda, Yoshinari; Horio, Masaru; Kumar, Vinod; Sahni, Nancy; Gupta, Krishan L; Matsuo, Seiichi; Kohli, Harbir Singh; Jha, Vivekanand

2018-02-01

Accurate estimation of glomerular filtration rate (GFR) is important for diagnosis and risk stratification in chronic kidney disease and for selection of living donors. Ethnic differences have required correction factors in the originally developed creatinine-based GFR estimation equations for populations around the world. Existing equations have not been validated in the vegetarian Indian population. We examined the performance of creatinine and cystatin-based GFR estimating equations in Indians. GFR was measured by urinary clearance of inulin. Serum creatinine was measured using IDMS-traceable Jaffe's and enzymatic assays, and cystatin C by colloidal gold immunoassay. Dietary protein intake was calculated by measuring urinary nitrogen appearance. Bias, precision and accuracy were calculated for the eGFR equations. A total of 130 participants (63 healthy kidney donors and 67 with CKD) were studied. About 50% were vegetarians, and the remainder ate meat 3.8 times every month. The average creatinine excretion were 14.7 mg/kg/day (95% CI: 13.5 to 15.9 mg/kg/day) and 12.4 mg/kg/day (95% CI: 11.2 to 13.6 mg/kg/day) in males and females, respectively. The average daily protein intake was 46.1 g/day (95% CI: 43.2 to 48.8 g/day). The mean mGFR in the study population was 51.66 ± 31.68 ml/min/1.73m 2 . All creatinine-based eGFR equations overestimated GFR (p < 0.01 for each creatinine based eGFR equation). However, eGFR by CKD-EPI Cys was not significantly different from mGFR (p = 0.38). The CKD-EPI Cys exhibited lowest bias [mean bias: -3.53 ± 14.70 ml/min/1.73m 2 (95% CI: -0.608 to -0.98)] and highest accuracy (P 30 : 74.6%). The GFR in the healthy population was 79.44 ± 20.19 (range: 41.90-134.50) ml/min/1.73m 2 . Existing creatinine-based GFR estimating equations overestimate GFR in Indians. An appropriately powered study is needed to develop either a correction factor or a new equation for accurate assessment of kidney function in the

Time-dependent integral transport equation kernels, leakage rates and collision rates for plane and spherical geometry

International Nuclear Information System (INIS)

Henderson, D.L.

1987-01-01

Time-dependent integral transport equation flux and current kernels for plane and spherical geometry are derived for homogeneous media. Using the multiple collision formalism, isotropic sources that are delta distributions in time are considered for four different problems. The plane geometry flux kernel is applied to a uniformly distributed source within an infinite medium and to a surface source in a semi-infinite medium. The spherical flux kernel is applied to a point source in an infinite medium and to a point source at the origin of a finite sphere. The time-dependent first-flight leakage rates corresponding to the existing steady state first-flight escape probabilities are computed by the Laplace transform technique assuming a delta distribution source in time. The case of a constant source emitting neutrons over a time interval, Δt, for a spatially uniform source is obtained for a slab and a sphere. Time-dependent first-flight leakage rates are also determined for the general two region spherical medium problem for isotropic sources with a delta distribution in time uniformly distributed throughout both the inner and outer regions. The time-dependent collision rates due to the uncollided neutrons are computed for a slab and a sphere using the time-dependent first-flight leakage rates and the time-dependent continuity equation. The case of a constant source emitting neutrons over a time interval, Δt, is also considered

Spent-fuel pool thermal hydraulics: The evaporation question

International Nuclear Information System (INIS)

Yilmaz, T.P.; Lai, J.C.

1996-01-01

Many nuclear power plants are currently using dense fuel arrangements that increase the number of spent fuel elements stored in their spent-fuel pools (SFPs). The denser spent-fuel storage results in higher water temperatures, especially when certain event scenarios are analyzed. In some of these event scenarios, it is conservative to maximize the evaporation rate, while in other circumstances it is required to minimize the evaporation rates for conservatism. Evaporation is such a fundamental phenomenon that many branches of engineering developed various equations based on theory and experiments. The evaporation rates predicted by existing equations present a wide range of variation, especially at water temperatures >40 degrees C. Furthermore, a study on which equations provide the highest and lowest evaporation rates has not been done until now. This study explores the sensitivity of existing evaporation equations to various parameters and recommends the limiting evaporation equations for use in the solution of SFP thermal problems. Note that the results of this study may be applicable to a much wider range of applications from irrigation ponds, cooling lakes, and liquid-waste management to calculating adequate air exchange rate for swimming pools and health spas

Exact Solutions of Fragmentation Equations with General Fragmentation Rates and Separable Particles Distribution Kernels

Directory of Open Access Journals (Sweden)

S. C. Oukouomi Noutchie

2014-01-01

Full Text Available We make use of Laplace transform techniques and the method of characteristics to solve fragmentation equations explicitly. Our result is a breakthrough in the analysis of pure fragmentation equations as this is the first instance where an exact solution is provided for the fragmentation evolution equation with general fragmentation rates. This paper is the key for resolving most of the open problems in fragmentation theory including “shattering” and the sudden appearance of infinitely many particles in some systems with initial finite particles number.

Numerical Analysis Of Hooke Jeeves-Runge Kutta To Determine Reaction Rate Equation In Pyrrole Polymerization

International Nuclear Information System (INIS)

Gunawan, Indra; Sulistyo, Harry; Rochmad

2001-01-01

The numerical analysis of Hooke Jeeves Methods combined with Runge Kutta Methods is used to determine the exact model of reaction rate equation of pyrrole polymerization. Chemical polymerization of pyrrole was conducted with FeCI 3 / pyrrole solution at concentration ratio of 1.62 mole / mole and 2.18 mole / mole with varrying temperature of 28, 40, 50, and 60 o C. FeCl 3 acts as an oxidation agent to form pyrrole cation that will polymerize. The numerical analysis was done to examine the exact model of reaction rate equation which is derived from reaction equation of initiation, propagation, and termination. From its numerical analysis, it is found that the pyrrole polymerization follows third order of pyrrole cation concentration

An effective rate equation approach to reaction kinetics in small volumes: theory and application to biochemical reactions in nonequilibrium steady-state conditions.

Science.gov (United States)

Grima, R

2010-07-21

Chemical master equations provide a mathematical description of stochastic reaction kinetics in well-mixed conditions. They are a valid description over length scales that are larger than the reactive mean free path and thus describe kinetics in compartments of mesoscopic and macroscopic dimensions. The trajectories of the stochastic chemical processes described by the master equation can be ensemble-averaged to obtain the average number density of chemical species, i.e., the true concentration, at any spatial scale of interest. For macroscopic volumes, the true concentration is very well approximated by the solution of the corresponding deterministic and macroscopic rate equations, i.e., the macroscopic concentration. However, this equivalence breaks down for mesoscopic volumes. These deviations are particularly significant for open systems and cannot be calculated via the Fokker-Planck or linear-noise approximations of the master equation. We utilize the system-size expansion including terms of the order of Omega(-1/2) to derive a set of differential equations whose solution approximates the true concentration as given by the master equation. These equations are valid in any open or closed chemical reaction network and at both the mesoscopic and macroscopic scales. In the limit of large volumes, the effective mesoscopic rate equations become precisely equal to the conventional macroscopic rate equations. We compare the three formalisms of effective mesoscopic rate equations, conventional rate equations, and chemical master equations by applying them to several biochemical reaction systems (homodimeric and heterodimeric protein-protein interactions, series of sequential enzyme reactions, and positive feedback loops) in nonequilibrium steady-state conditions. In all cases, we find that the effective mesoscopic rate equations can predict very well the true concentration of a chemical species. This provides a useful method by which one can quickly determine the

[Estimating glomerular filtration rate in 2012: which adding value for the CKD-EPI equation?].

Science.gov (United States)

Delanaye, Pierre; Mariat, Christophe; Moranne, Olivier; Cavalier, Etienne; Flamant, Martin

2012-07-01

Measuring or estimating glomerular filtration rate (GFR) is still considered as the best way to apprehend global renal function. In 2009, the new Chronic Kidney Disease Epidemiology (CKD-EPI) equation has been proposed as a better estimator of GFR than the Modification of Diet in Renal Disease (MDRD) study equation. This new equation is supposed to underestimate GFR to a lesser degree in higher GFR levels. In this review, we will present and deeply discuss the performances of this equation. Based on articles published between 2009 and 2012, this review will underline advantages, notably the better knowledge of chronic kidney disease prevalence, but also limitations of this new equation, especially in some specific populations. We eventually insist on the fact that all these equations are estimations and nephrologists should remain cautious in their interpretation. Copyright © 2012 Association Société de néphrologie. Published by Elsevier SAS. All rights reserved.

Theoretical Time Dependent Thermal Neutron Spectra and Reaction Rates in H{sub 2}O and D{sub 2}O

Energy Technology Data Exchange (ETDEWEB)

Purohit, S N

1966-04-15

The early theoretical and experimental time dependent neutron thermalization studies were limited to the study of the transient spectrum in the diffusion period. The recent experimental measurements of the time dependent thermal neutron spectra and reaction rates, for a number of moderators, have generated considerable interest in the study of the time dependent Boltzmann equation. In this paper we present detailed results for the time dependent spectra and the reaction rates for resonance detectors using several scattering models of H{sub 2}O and D{sub 2}O. This study has been undertaken in order to interpret the integral time dependent neutron thermalization experiments in liquid moderators which have been performed at the AB Atomenergi. The proton gas and the deuteron gas models are inadequate to explain the measured reaction rates in H{sub 2}O and D{sub 2}O. The bound models of Nelkin for H{sub 2}O and of Butler for D{sub 2}O give much better agreement with the experimental results than the gas models. Nevertheless, some disagreement between theoretical and experimental results still persists. This study also indicates that the bound model of Butler and the effective mass 3. 6 gas model of Brown and St. John give almost identical reaction rates. It is also surprising to note that the calculated reaction rate for Cd for the Butler model appears to be in better agreement with the experimental results of D{sub 2}O than of the Nelkin model with H{sub 2}O experiments. The present reaction rate studies are sensitive enough so as to distinguish between the gas model and the bound model of a moderator. However, to investigate the details of a scattering law (such as the effect of the hindered rotations in H{sub 2}O and D{sub 2}O and the weights of different dynamical modes) with the help of these studies would require further theoretical as well as experimental investigations. Theoretical results can be further improved by improving the source for thermal neutrons, the

Comment on 'A Forecasting Equation for the Canada-US Dollar Real Exchange Rate'

OpenAIRE

Kollmann, Robert

1993-01-01

This paper is a comment on the paper 'A Forecasting Equation for the Canada-US Dollar Exchange Rate' (Robert Amano and Simon van Norden, Bank of Canada). The comment was published in: The Exchange Rate and the Economy, Proceedings of 1992 Bank of Canada Conference; Bank of Canada, 1993, Ottawa (ISBN 0-660-15195-2), pp. 266-271.

Crossover behavior of the thermal conductance and Kramers’ transition rate theory

Science.gov (United States)

Velizhanin, Kirill A.; Sahu, Subin; Chien, Chih-Chun; Dubi, Yonatan; Zwolak, Michael

2015-12-01

Kramers’ theory frames chemical reaction rates in solution as reactants overcoming a barrier in the presence of friction and noise. For weak coupling to the solution, the reaction rate is limited by the rate at which the solution can restore equilibrium after a subset of reactants have surmounted the barrier to become products. For strong coupling, there are always sufficiently energetic reactants. However, the solution returns many of the intermediate states back to the reactants before the product fully forms. Here, we demonstrate that the thermal conductance displays an analogous physical response to the friction and noise that drive the heat current through a material or structure. A crossover behavior emerges where the thermal reservoirs dominate the conductance at the extremes and only in the intermediate region are the intrinsic properties of the lattice manifest. Not only does this shed new light on Kramers’ classic turnover problem, this result is significant for the design of devices for thermal management and other applications, as well as the proper simulation of transport at the nanoscale.

Thermal expansion

International Nuclear Information System (INIS)

Yun, Y.

2015-01-01

Thermal expansion of fuel pellet is an important property which limits the lifetime of the fuels in reactors, because it affects both the pellet and cladding mechanical interaction and the gap conductivity. By fitting a number of available measured data, recommended equations have been presented and successfully used to estimate thermal expansion coefficient of the nuclear fuel pellet. However, due to large scatter of the measured data, non-consensus data have been omitted in formulating the equations. Also, the equation is strongly governed by the lack of appropriate experimental data. For those reasons, it is important to develop theoretical methodologies to better describe thermal expansion behaviour of nuclear fuel. In particular, first-principles and molecular dynamics simulations have been certainly contributed to predict reliable thermal expansion without fitting the measured data. Furthermore, the two theoretical techniques have improved on understanding the change of fuel dimension by describing the atomic-scale processes associated with lattice expansion in the fuels. (author)

Transport and relaxation properties of superfluid 3He. I. Kinetic equation and Bogoliubov quasiparticle relaxation rate

International Nuclear Information System (INIS)

Einzel, D.; Woelfle, P.

1978-01-01

The kinetic equation for Bogoliubov quasiparticles for both the A and B phases of superfluid 3 He is derived from the general matrix kinetic equation. A condensed expression for the exact spin-symmetric collision integral is given. The quasiparticle relaxation rate is calculated for the BW state using the s--p approximation for the quasiparticle scattering amplitude. By using the results for the quasiparticle relaxation rate, the mean free path of Bogoliubov quasiparticles is calculated for all temperatures

Current use of equations for estimating glomerular filtration rate in Spanish laboratories.

Science.gov (United States)

Gràcia-Garcia, Sílvia; Montañés-Bermúdez, Rosario; Morales-García, Luis J; Díez-de Los Ríos, M José; Jiménez-García, Juan Á; Macías-Blanco, Carlos; Martínez-López, Rosalina; Ruiz-Altarejos, Joaquín; Ruiz-Martín, Guadalupe; Sanz-Hernández, Sonia; Ventura-Pedret, Salvador

2012-07-17

In 2006 the Spanish Society of Clinical Biochemistry and Molecular Pathology (SEQC) and the Spanish Society of Nephrology (S.E.N.) developed a consensus document in order to facilitate the diagnosis and monitoring of chronic kidney disease with the incorporation of equations for estimating glomerular filtration rate (eGFR) into laboratory reports. The current national prevalence of eGFR reporting and the degree of adherence to these recommendations among clinical laboratories is unknown. We administered a national survey in 2010-11 to Spanish clinical laboratories. The survey was through e-mail or telephone to laboratories that participated in the SEQC’s Programme for External Quality Assurance, included in the National Hospitals Catalogue 2010, including both primary care and private laboratories. A total of 281 laboratories answered to the survey. Of these, 88.2% reported on the eGFR, with 61.9% reporting on the MDRD equation and 31.6% using the MDRD-IDMS equation. A total of 42.5% of laboratories always reported serum creatinine values, and other variables only when specifically requested. Regarding the way results were presented, 46.2% of laboratories reported the exact numerical value only when the filtration rate was below 60mL/min/1.73m2, while 50.6% reported all values regardless. In 56.3% of the cases reporting eGFR, an interpretive commentary of it was enclosed. Although a high percentage of Spanish laboratories have added eGFR in their reports, this metric is not universally used. Moreover, some aspects, such as the equation used and the correct expression of eGFR results, should be improved.

Numerical Study of Thermal Radiation Effect on Confined Turbulent Free Triangular Jets

Directory of Open Access Journals (Sweden)

Kiyan Parham

2013-01-01

Full Text Available The present study investigates the effects of thermal radiation on turbulent free triangular jets. Finite volume method is applied for solving mass, momentum, and energy equations simultaneously. Discrete ordinate method is used to determine radiation transfer equation (RTE. Results are presented in terms of velocity, kinetic energy, and its dissipation rate fields. Results show that thermal radiation speeds the development of velocity on the jet axis and enhances kinetic energy; therefore, when radiation is added to free jet its mixing power, due to extra kinetic energy, increases.

Variability of glomerular filtration rate estimation equations in elderly Chinese patients with chronic kidney disease

Directory of Open Access Journals (Sweden)

Liu X

2012-10-01

Full Text Available Xun Liu,1,2,* Mu-hua Cheng,3,* Cheng-gang Shi,1 Cheng Wang,1 Cai-lian Cheng,1 Jin-xia Chen,1 Hua Tang,1 Zhu-jiang Chen,1 Zeng-chun Ye,1 Tan-qi Lou11Division of Nephrology, Department of Internal Medicine, The Third Affiliated Hospital of Sun Yet-sun University, Guangzhou, China; 2College of Biology Engineering, South China University of Technology, Guangzhou, China; 3Department of Nuclear Medicine, The Third Affiliated Hospital of Sun Yet-sun University, Guangzhou, China *These authors contributed equally to this paperBackground: Chronic kidney disease (CKD is recognized worldwide as a public health problem, and its prevalence increases as the population ages. However, the applicability of formulas for estimating the glomerular filtration rate (GFR based on serum creatinine (SC levels in elderly Chinese patients with CKD is limited.Materials and methods: Based on values obtained with the technetium-99m diethylenetriaminepentaacetic acid (99mTc-DTPA renal dynamic imaging method, 319 elderly Chinese patients with CKD were enrolled in this study. Serum creatinine was determined by the enzymatic method. The GFR was estimated using the Cockroft–Gault (CG equation, the Modification of Diet in Renal Disease (MDRD equations, the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI equation, the Jelliffe-1973 equation, and the Hull equation.Results: The median of difference ranged from −0.3–4.3 mL/min/1.73 m2. The interquartile range (IQR of differences ranged from 13.9–17.6 mL/min/1.73 m2. Accuracy with a deviation less than 15% ranged from 27.6%–32.9%. Accuracy with a deviation less than 30% ranged from 53.6%–57.7%. Accuracy with a deviation less than 50% ranged from 74.9%–81.5%. None of the equations had accuracy up to the 70% level with a deviation less than 30% from the standard glomerular filtration rate (sGFR. Bland–Altman analysis demonstrated that the mean difference ranged from −3.0–2.4 mL/min/1.73 m2. However, the

Determination and Analysis of Ar-41 Dose Rate Characteristic at Thermal Column of Kartini Reactor

International Nuclear Information System (INIS)

Widarto; Sardjono, Y.

2007-01-01

Determination and Analysis of Ar-41 activity dose rate at the thermal column after shutdown of Kartini reactor has been done. Based on evaluation and analysis concluded that external dose rate is D = 1.606x10 -6 Sv/second and internal dose rate is 3.429x10 -1 1 Sv/second. It means that if employee work at the column thermal area for 15 minutes a day, 5 days a week, in a year will be 0.376 Sv still under dose rate limit i.e. 0.5 Sv, so that the column thermal facility is safely area. (author)

Proportional and Integral Thermal Control System for Large Scale Heating Tests

Science.gov (United States)

Fleischer, Van Tran

2015-01-01

The National Aeronautics and Space Administration Armstrong Flight Research Center (Edwards, California) Flight Loads Laboratory is a unique national laboratory that supports thermal, mechanical, thermal/mechanical, and structural dynamics research and testing. A Proportional Integral thermal control system was designed and implemented to support thermal tests. A thermal control algorithm supporting a quartz lamp heater was developed based on the Proportional Integral control concept and a linearized heating process. The thermal control equations were derived and expressed in terms of power levels, integral gain, proportional gain, and differences between thermal setpoints and skin temperatures. Besides the derived equations, user's predefined thermal test information generated in the form of thermal maps was used to implement the thermal control system capabilities. Graphite heater closed-loop thermal control and graphite heater open-loop power level were added later to fulfill the demand for higher temperature tests. Verification and validation tests were performed to ensure that the thermal control system requirements were achieved. This thermal control system has successfully supported many milestone thermal and thermal/mechanical tests for almost a decade with temperatures ranging from 50 F to 3000 F and temperature rise rates from -10 F/s to 70 F/s for a variety of test articles having unique thermal profiles and test setups.

Best-fitting prediction equations for basal metabolic rate: informing obesity interventions in diverse populations.

Science.gov (United States)

Sabounchi, N S; Rahmandad, H; Ammerman, A

2013-10-01

Basal metabolic rate (BMR) represents the largest component of total energy expenditure and is a major contributor to energy balance. Therefore, accurately estimating BMR is critical for developing rigorous obesity prevention and control strategies. Over the past several decades, numerous BMR formulas have been developed targeted to different population groups. A comprehensive literature search revealed 248 BMR estimation equations developed using diverse ranges of age, gender, race, fat-free mass, fat mass, height, waist-to-hip ratio, body mass index and weight. A subset of 47 studies included enough detail to allow for development of meta-regression equations. Utilizing these studies, meta-equations were developed targeted to 20 specific population groups. This review provides a comprehensive summary of available BMR equations and an estimate of their accuracy. An accompanying online BMR prediction tool (available at http://www.sdl.ise.vt.edu/tutorials.html) was developed to automatically estimate BMR based on the most appropriate equation after user-entry of individual age, race, gender and weight.

Numerical modelling of tools steel hardening. A thermal phenomena and phase transformations

Directory of Open Access Journals (Sweden)

T. Domański

2010-01-01

Full Text Available This paper the model hardening of tool steel takes into considerations of thermal phenomena and phase transformations in the solid state are presented. In the modelling of thermal phenomena the heat equations transfer has been solved by Finite Elements Method. The graph of continuous heating (CHT and continuous cooling (CCT considered steel are used in the model of phase transformations. Phase altered fractions during the continuous heating austenite and continuous cooling pearlite or bainite are marked in the model by formula Johnson-Mehl and Avrami. For rate of heating >100 K/s the modified equation Koistinen and Marburger is used. Modified equation Koistinen and Marburger identify the forming fraction of martensite.

Translational control of a graphically simulated robot arm by kinematic rate equations that overcome elbow joint singularity

Science.gov (United States)

Barker, L. K.; Houck, J. A.; Carzoo, S. W.

1984-01-01

An operator commands a robot hand to move in a certain direction relative to its own axis system by specifying a velocity in that direction. This velocity command is then resolved into individual joint rotational velocities in the robot arm to effect the motion. However, the usual resolved-rate equations become singular when the robot arm is straightened. To overcome this elbow joint singularity, equations were developed which allow continued translational control of the robot hand even though the robot arm is (or is nearly) fully extended. A feature of the equations near full arm extension is that an operator simply extends and retracts the robot arm to reverse the direction of the elbow bend (difficult maneuver for the usual resolved-rate equations). Results show successful movement of a graphically simulated robot arm.

Evolution of a Network of Vortex Loops in He-II: Exact Solution of the Rate Equation

International Nuclear Information System (INIS)

Nemirovskii, Sergey K.

2006-01-01

The evolution of a network of vortex loops in He-II due to the fusion and breakdown of vortex loops is studied. We perform investigation on the base of the ''rate equation'' for the distribution function n(l) of number of loops of length l. By use of the special ansatz we have found the exact powerlike solution of the rate equation in a stationary case. That solution is the famous equilibrium distribution n(l)∝l -5/2 obtained earlier from thermodynamic arguments. Our result, however, is not equilibrium; it describes the state with two mutual fluxes of the length (or energy) in l space. Analyzing this solution we drew several results on the structure and dynamics of the vortex tangle in the superfluid turbulent helium. In particular, we obtained that the mean radius of the curvature is of the order of interline space and that the decay of the vortex tangle obeys the Vinen equation. We also evaluated the full rate of reconnection

Evolution of a network of vortex loops in He-II: exact solution of the rate equation.

Science.gov (United States)

Nemirovskii, Sergey K

2006-01-13

The evolution of a network of vortex loops in He-II due to the fusion and breakdown of vortex loops is studied. We perform investigation on the base of the "rate equation" for the distribution function n(l) of number of loops of length l. By use of the special ansatz we have found the exact power-like solution of the rate equation in a stationary case. That solution is the famous equilibrium distribution n(l) proportional l(-5/2) obtained earlier from thermodynamic arguments. Our result, however, is not equilibrium; it describes the state with two mutual fluxes of the length (or energy) in l space. Analyzing this solution we drew several results on the structure and dynamics of the vortex tangle in the superfluid turbulent helium. In particular, we obtained that the mean radius of the curvature is of the order of interline space and that the decay of the vortex tangle obeys the Vinen equation. We also evaluated the full rate of reconnection.

Unsteady-state human-body exergy consumption rate and its relation to subjective assessment of dynamic thermal environments

DEFF Research Database (Denmark)

Schweiker, Marcel; Kolarik, Jakub; Dovjak, Mateja

2016-01-01

of the present study confirmed previously indicated trends that lowest human body exergy consumption rate is associated with thermal sensation close to neutrality. Moreover, higher acceptability was in general associated with lower human body exergy consumption rate. (C) 2016 Elsevier B.V. All rights reserved.......Few examples studied applicability of exergy analysis on human thermal comfort. These examples relate the human-body exergy consumption rate with subjectively obtained thermal sensation votes and had been based on steady-state calculation methods. However, humans are rarely exposed to steady...... between the human-body exergy consumption rate and subjective assessment of thermal environment represented by thermal sensation as well as to extend the investigation towards thermal acceptability votes. Comparison of steady-state and unsteady-state model showed that results from both models were...

Predicting fractional bed load transport rates: Application of the Wilcock‐Crowe equations to a regulated gravel bed river

Science.gov (United States)

Gaeuman, David; Andrews, E.D.; Krause, Andreas; Smith, Wes

2009-01-01

Bed load samples from four locations in the Trinity River of northern California are analyzed to evaluate the performance of the Wilcock‐Crowe bed load transport equations for predicting fractional bed load transport rates. Bed surface particles become smaller and the fraction of sand on the bed increases with distance downstream from Lewiston Dam. The dimensionless reference shear stress for the mean bed particle size (τ*rm) is largest near the dam, but varies relatively little between the more downstream locations. The relation between τ*rm and the reference shear stresses for other size fractions is constant across all locations. Total bed load transport rates predicted with the Wilcock‐Crowe equations are within a factor of 2 of sampled transport rates for 68% of all samples. The Wilcock‐Crowe equations nonetheless consistently under‐predict the transport of particles larger than 128 mm, frequently by more than an order of magnitude. Accurate prediction of the transport rates of the largest particles is important for models in which the evolution of the surface grain size distribution determines subsequent bed load transport rates. Values of τ*rm estimated from bed load samples are up to 50% larger than those predicted with the Wilcock‐Crowe equations, and sampled bed load transport approximates equal mobility across a wider range of grain sizes than is implied by the equations. Modifications to the Wilcock‐Crowe equation for determining τ*rm and the hiding function used to scale τ*rm to other grain size fractions are proposed to achieve the best fit to observed bed load transport in the Trinity River.

Stochastic approaches to dynamics of heavy ion collisions, the case of thermal fission

International Nuclear Information System (INIS)

Boilley, D.; Abe, Y.

1994-01-01

In order to study the influence of fluctuations on various phenomena linked to heavy ion collisions, a Langevin equation has been derived from a microscopic model. Parameters entering this equation are completely determined from microscopic quantities characterizing nuclear matter. This equation has been applied to various phenomena at intermediate energies. This paper focuses on large amplitude motions and especially thermal fission. Fission rate is calculated and compared to experimental results

Effect of the thermal evaporation rate of Al cathodes on organic light emitting diodes

International Nuclear Information System (INIS)

Shin, Hee Young; Suh, Min Chul

2014-01-01

Graphical abstract: - Highlights: • The TOF-SIMS analysis to investigate cathode diffusion during evaporation process. • Performance change of OLEDs prepared with different evaporation rate of Al cathode. • Change of electron transport behavior during thermal evaporation process. - Abstract: The relationship between the thermal evaporation rate of Al cathodes and the device performance of organic light-emitting diodes (OLEDs) was investigated to clarify the source of leakage current. Time-of-flight secondary ion mass spectrometry was applied to identify the diffusion of Li and Al fragments into the underlying organic layer during the thermal evaporation process. We prepared various OLEDs by varying the evaporation rates of the Al cathode to investigate different device performance. Interestingly, the leakage current level decreased when the evaporation rate reached ∼25 Å/s. In contrast, the best efficiency and operational lifetime was obtained when the evaporation rate was 5 Å/s

Kraus operator solutions to a fermionic master equation describing a thermal bath and their matrix representation

Science.gov (United States)

Xiang-Guo, Meng; Ji-Suo, Wang; Hong-Yi, Fan; Cheng-Wei, Xia

2016-04-01

We solve the fermionic master equation for a thermal bath to obtain its explicit Kraus operator solutions via the fermionic state approach. The normalization condition of the Kraus operators is proved. The matrix representation for these solutions is obtained, which is incongruous with the result in the book completed by Nielsen and Chuang [Quantum Computation and Quantum Information, Cambridge University Press, 2000]. As especial cases, we also present the Kraus operator solutions to master equations for describing the amplitude-decay model and the diffusion process at finite temperature. Project supported by the National Natural Science Foundation of China (Grant No. 11347026), the Natural Science Foundation of Shandong Province, China (Grant Nos. ZR2013AM012 and ZR2012AM004), and the Research Fund for the Doctoral Program and Scientific Research Project of Liaocheng University, Shandong Province, China.

Effect of high heating rate on thermal decomposition behaviour of ...

Indian Academy of Sciences (India)

the thermal decomposition behaviour of the aforementioned powder at high heating rates was taken into considera- ... does not change the process of releasing hydrogen from titanium hydride ... from titanium hydride in a sequence of steps.

Characteristics of quantum dash laser under the rate equation model framework

KAUST Repository

Khan, Mohammed Zahed Mustafa

2010-09-01

The authors present a numerical model to study the carrier dynamics of InAs/InP quantum dash (QDash) lasers. The model is based on single-state rate equations, which incorporates both, the homogeneous and the inhomogeneous broadening of lasing spectra. The numerical technique also considers the unique features of the QDash gain medium. This model has been applied successfully to analyze the laser spectra of QDash laser. ©2010 IEEE.

Effect of high heating rate on thermal decomposition behaviour of ...

Indian Academy of Sciences (India)

Effect of high heating rate on thermal decomposition behaviour of titanium hydride ... hydride powder, while switching it from internal diffusion to chemical reaction. ... TiH phase and oxides form on the powder surface, controlling the process.

Modeling ground thermal regime of an ancient buried ice body in Beacon Valley, Antarctica using a 1-D heat equation with latent heat effect

Science.gov (United States)

Liu, L.; Sletten, R. S.; Hallet, B.; Waddington, E. D.; Wood, S. E.

2013-12-01

An ancient massive ice body buried under several decimeters of debris in Beacon Valley, Antarctica is believed to be over one million years old, making it older than any known glacier or ice cap. It is fundamentally important as a reservoir of water, proxy for climatic information, and an expression of the periglacial landscape. It is also one of Earth's closest analog for widespread, near-surface ice found in Martian soils and ice-cored landforms. We are interested in understanding controls on how long this ice may persist since our physical model of sublimation suggests it should not be stable. In these models, the soil temperatures and the gradient are important because it determines the direction and magnitude of the vapor flux, and thus sublimation rates. To better understand the heat transfer processes and constrain the rates of processes governing ground ice stability, a model of the thermal behavior of the permafrost is applied to Beacon Valley, Antarctica. It calculates soil temperatures based on a 1-D thermal diffusion equation using a fully implicit finite volume method (FVM). This model is constrained by soil physical properties and boundary conditions of in-situ ground surface temperature measurements (with an average of -23.6oC, a maximum of 20.5oC and a minimum of -54.3oC) and ice-core temperature record at ~30 m. Model results are compared to in-situ temperature measurements at depths of 0.10 m, 0.20 m, 0.30 m, and 0.45 m to assess the model's ability to reproduce the temperature profile for given thermal properties of the debris cover and ice. The model's sensitivity to the thermal diffusivity of the permafrost and the overlaying debris is also examined. Furthermore, we incorporate the role of ice condensation/sublimation which is calculated using our vapor diffusion model in the 1-D thermal diffusion model to assess potential latent heat effects that in turn affect ground ice sublimation rates. In general, the model simulates the ground thermal

Adjoint Sensitivity Analysis of Radiative Transfer Equation: Temperature and Gas Mixing Ratio Weighting Functions for Remote Sensing of Scattering Atmospheres in Thermal IR

Science.gov (United States)

Ustinov, E.

1999-01-01

Sensitivity analysis based on using of the adjoint equation of radiative transfer is applied to the case of atmospheric remote sensing in the thermal spectral region with non-negligeable atmospheric scattering.

Transient three-dimensional thermal-hydraulic analysis of nuclear reactor fuel rod arrays: general equations and numerical scheme

International Nuclear Information System (INIS)

Wnek, W.J.; Ramshaw, J.D.; Trapp, J.A.; Hughes, E.D.; Solbrig, C.W.

1975-11-01

A mathematical model and a numerical solution scheme for thermal-hydraulic analysis of fuel rod arrays are given. The model alleviates the two major deficiencies associated with existing rod array analysis models, that of a correct transverse momentum equation and the capability of handling reversing and circulatory flows. Possible applications of the model include steady state and transient subchannel calculations as well as analysis of flows in heat exchangers, other engineering equipment, and porous media

Correction factor determination on failure rate equation of MacLaurin series for low and high mode application

Directory of Open Access Journals (Sweden)

Totok R. Biyanto

2016-06-01

Full Text Available Safety Instrumented Function (SIF is implemented on the system to prevent hazard in process industry. In general, most of SIF implementation in process industry works in low demand condition. Safety valuation of SIF that works in low demand can be solved by using quantitative method. The quantitative method is a simplified exponential equation form of MacLaurin series, which can be called simplified equation. Simplified equation used in high demand condition will generate a higher Safety Integrity Level (SIL and it will affect the higher safety cost. Therefore, the value of low or high demand rate limit should be determined to prevent it. The result of this research is a first order equation that can fix the error of SIL, which arises from the usage of simplified equation, without looking the demand rate limit for low and high demand. This equation is applied for SIL determination on SIF with 1oo1 vote. The new equation from this research is λ = 0.9428 λMC + 1.062E−04 H/P, with 5% average of error, where λMC is a value of λ from the simplified equation, Hazardous event frequency (H is a probabilistic frequency of hazard event and P is Probability of Failure on Demand (PFD in Independent Protection Layers (IPLs. The equation generated from this research could correct SIL of SIF in various H and P. Therefore, SIL design problem could be solved and it provides an appropriate SIL.

Rate concept and retarded master equations for dissipative tight-binding models

International Nuclear Information System (INIS)

Egger, R.; Mak, C.H.; Weiss, U.

1994-01-01

Employing a ''noninteracting-cluster approximation,'' the dynamics of multistate dissipative tight-binding models has been formulated in terms of a set of generalized retarded master equations. The rates for the various pathways are expressed as power series in the intersite couplings. We apply this to the superexchange mechanism, which is relevant for bacterial photosynthesis and bridged electron transfer systems. This approach provides a general and unified description of both incoherent and coherent transport

A Globally Convergent Matrix-Free Method for Constrained Equations and Its Linear Convergence Rate

Directory of Open Access Journals (Sweden)

Min Sun

2014-01-01

Full Text Available A matrix-free method for constrained equations is proposed, which is a combination of the well-known PRP (Polak-Ribière-Polyak conjugate gradient method and the famous hyperplane projection method. The new method is not only derivative-free, but also completely matrix-free, and consequently, it can be applied to solve large-scale constrained equations. We obtain global convergence of the new method without any differentiability requirement on the constrained equations. Compared with the existing gradient methods for solving such problem, the new method possesses linear convergence rate under standard conditions, and a relax factor γ is attached in the update step to accelerate convergence. Preliminary numerical results show that it is promising in practice.

Solution of the stellar structure equations in Eulerian coordinates

International Nuclear Information System (INIS)

Deupree, R.G.

1976-01-01

The equations of hydrostatic and thermal equilibrium, assuming only radiative energy transport and spherical symmetry, are solved in Eulerian coordinates by a suitable modification of the Henyey method. An Eulerian approach may possibly be more suitably extended to more spatial dimensions than the usual Lagrangian procedure. The principle advantage of this method is that the equations of hydrostatic and thermal equilibrium and Poisson's equation may be solved simultaneously

Theoretical study of flow in a thermal countercurrent centrifuge

International Nuclear Information System (INIS)

Durivault, Jean; Louvet, Pierre.

1976-03-01

This paper deals with the flow calculation in a thermal countercurrent centrifuge at total reflux. Matched asymptotic expansions are used to find approximate solutions of Navier-Stokes equations which are assumed to be valid in the whole domaine. Convection and viscous dissipation disappear because of linearization, but compressibility is taken into account. Let epsilon be the Ekman number. The equations are solved in the inviscid core, in the horizontal Ekman layers of thickness 0 (epsilonsup(1/2) and in the Stewartson layer of thickness 0 (epsilonsup(1/3)), parallel to the axis. As the thermal convection is neglected, the Stewartson layer of thickness 0 (epsilon sup(1/4)) does not occur. The results show the importance of the recirculating mass-flow rate of order 0 (epsilonsup(1/3)) in front of the countercurrent mass-flow rate of order 0 (epsilonsup(1/2)). The temperature profile rules the pattern and the intensity of the recirculating flow [fr

Heart rate variation and electroencephalograph--the potential physiological factors for thermal comfort study.

Science.gov (United States)

Yao, Y; Lian, Z; Liu, W; Jiang, C; Liu, Y; Lu, H

2009-04-01

Human thermal comfort researches mainly focus on the relation between the environmental factors (e.g. ambient temperature, air humidity, and air velocity, etc.) and the thermal comfort sensation based on a large amount of subjective field investigations. Although some physiological factors, such as skin temperature and metabolism were used in many thermal comfort models,they are not enough to establish a perfect thermal comfort model. In this paper,another two physiological factors, i.e. heart rate variation (HRV) and electroencephalograph (EEG), are explored for the thermal comfort study. Experiments were performed to investigate how these physiological factors respond to the environmental temperatures, and what is the relationship between HRV and EEG and thermal comfort. The experimental results indicate that HRV and EEG may be related to thermal comfort, and they may be useful to understand the mechanism of thermal comfort.

Semiempirical equations for modeling solid-state kinetics based on a Maxwell-Boltzmann distribution of activation energies: applications to a polymorphic transformation under crystallization slurry conditions and to the thermal decomposition of AgMnO4 crystals.

Science.gov (United States)

Skrdla, Peter J; Robertson, Rebecca T

2005-06-02

Many solid-state reactions and phase transformations performed under isothermal conditions give rise to asymmetric, sigmoidally shaped conversion-time (x-t) profiles. The mathematical treatment of such curves, as well as their physical interpretation, is often challenging. In this work, the functional form of a Maxwell-Boltzmann (M-B) distribution is used to describe the distribution of activation energies for the reagent solids, which, when coupled with an integrated first-order rate expression, yields a novel semiempirical equation that may offer better success in the modeling of solid-state kinetics. In this approach, the Arrhenius equation is used to relate the distribution of activation energies to a corresponding distribution of rate constants for the individual molecules in the reagent solids. This distribution of molecular rate constants is then correlated to the (observable) reaction time in the derivation of the model equation. In addition to providing a versatile treatment for asymmetric, sigmoidal reaction curves, another key advantage of our equation over other models is that the start time of conversion is uniquely defined at t = 0. We demonstrate the ability of our simple, two-parameter equation to successfully model the experimental x-t data for the polymorphic transformation of a pharmaceutical compound under crystallization slurry (i.e., heterogeneous) conditions. Additionally, we use a modification of this equation to model the kinetics of a historically significant, homogeneous solid-state reaction: the thermal decomposition of AgMnO4 crystals. The potential broad applicability of our statistical (i.e., dispersive) kinetic approach makes it a potentially attractive alternative to existing models/approaches.

Evaluation of Instrumentation and Dynamic Thermal Ratings for Overhead Lines

Energy Technology Data Exchange (ETDEWEB)

Phillips, A. [New York Power Authority, White Plains, NY (United States)

2013-01-31

In 2010, a project was initiated through a partnership between the Department of Energy (DOE) and the New York Power Authority (NYPA) to evaluate EPRI's rating technology and instrumentation that can be used to monitor the thermal states of transmission lines and provide the required real-time data for real-time rating calculations. The project included the installation and maintenance of various instruments at three 230 kV line sites in northern New York. The instruments were monitored, and data collection and rating calculations were performed for about a three year period.

New equations for density, entropy, heat capacity, and potential temperature of a saline thermal fluid

Science.gov (United States)

Sun, Hongbing; Feistel, Rainer; Koch, Manfred; Markoe, Andrew

2008-10-01

A set of fitted polynomial equations for calculating the physical variables density, entropy, heat capacity and potential temperature of a thermal saline fluid for a temperature range of 0-374 °C, pressure range of 0.1-100 MPa and absolute salinity range of 0-40 g/kg is established. The freshwater components of the equations are extracted from the recently released tabulated data of freshwater properties of Wagner and Pruß [2002. The IAPWS formulation 1995 for the thermodynamic properties of ordinary water substance for general and scientific use. Journal of Physical and Chemical Reference Data 31, 387-535]. The salt water component of the equation is based on the near-linear relationship between density, salinity and specific heat capacity and is extracted from the data sets of Feistel [2003. A new extended Gibbs thermodynamic potential of seawater. Progress in Oceanography 58, 43-114], Bromley et al. [1970. Heat capacities and enthalpies of sea salt solutions to 200 °C. Journal of Chemical and Engineering Data 15, 246-253] and Grunberg [1970. Properties of sea water concentrates. In: Third International Symposium on Fresh Water from the Sea, vol. 1, pp. 31-39] in a temperature range 0-200 °C, practical salinity range 0-40, and varying pressure and is also calibrated by the data set of Millero et al. [1981. Summary of data treatment for the international high pressure equation of state for seawater. UNESCO Technical Papers in Marine Science 38, 99-192]. The freshwater and salt water components are combined to establish a workable multi-polynomial equation, whose coefficients were computed through standard linear regression analysis. The results obtained in this way for density, entropy and potential temperature are comparable with those of existing models, except that our new equations cover a wider temperature—(0-374 °C) than the traditional (0-40 °C) temperature range. One can apply these newly established equations to the calculation of in-situ or

Evaluating of air flow movements and thermal comfort in a model room with Euler equation: Two dimensional study

Energy Technology Data Exchange (ETDEWEB)

Chafi, Fatima Zohra; Halle, Stephane [Mechanical engineering department, Ecole de technologie superieure, Quebec university, 1100 rue Notre-Dame Ouest, Montreal, Quebec H3C 1K3 (Canada)

2011-02-15

This paper presents the results of a study that consists of estimating the temperature distribution and air flow movement in a model room with a numerical model based on the Euler equations. Numerical results obtained for two scenarios of ventilation and heating are compared with the predictions of a Navier-Stokes model, as well as with experimental results. A comparison of the local thermal comfort indices PMV and PPD obtained experimentally and numerically is also presented. Results show that the Euler model is capable of properly estimating the temperature distribution, the air movement and the comfort indices in the room. Furthermore, the use of Euler equations allows a reduction of computational time in the order of 30% compared to the Navier-Stokes modeling. (author)

Alternative solution algorithm for coupled thermal-hydraulic problems

International Nuclear Information System (INIS)

Farnsworth, D.A.; Rice, J.G.

1986-01-01

A thermal-hydraulic system involves flow of a fluid for which a combined solution of the continuity, momentum, and energy equations is required. When the solutions of the energy and momentum fields are dependent on each other, the system is said to be thermally coupled. A common problem encountered in the numerical solution of strongly coupled thermal-hydraulic problems is a very slow rate of convergence or a complete lack of convergence. Many times this degradation in convergence is due to the lack of true coupling between the energy and momentum fields during the iteration process. In the most widely used solution algorithms - such as the SIMPLE algorithm and its many variants - a sequential solution technique is required. That is, the solution process alternates between the flow and energy fields until a converged solution is obtained. This approach allows only implicit energy-momentum coupling. To improve the convergence rate for strongly coupled problems, a practical solution algorithm that can accommodate true energy-momentum coupling terms was developed. A complete simultaneous (versus sequential) solution of the governing conservation equations utilizing a line-by-line solution was developed and direct coupling terms between the momentum and energy fields were added utilizing a modified Newton-Raphson technique

Charge exchange of muons in gases. Kinetic equations

International Nuclear Information System (INIS)

Turner, R.E.

1983-01-01

Kinetic equations for the spin-density operators of the diamagnetic and paramagnetic states of the positive muon are obtained for the description of the slowing-down process encountered when high-energy muons thermalize in a single-component gas. The motion of this two-species system is generated by the Liouville superoperators associated with the diamagnetic and paramagnetic spin Hamiltonians and by time-dependent rate superoperators which depict the probabilities per collision that an electron is captured or lost. These rates are translational averages of the appropriate Boltzmann collision operators. That is, they are momentum and position integrals of the product of either the electron capture or loss total cross section with the single-particle translational density operators for the muon (or muonium) and a gas particle. These rates are time dependent because the muon (or muonium) translational density operator is time dependent. The initial amplitudes and phases of the observed thermal spin polarization in muon-spin-rotation (μSR) experiments are then obtained in terms of the spin-density operators emerging from the stopping regime

Energy cascade with small-scale thermalization, counterflow metastability, and anomalous velocity of vortex rings in Fourier-truncated Gross-Pitaevskii equation

International Nuclear Information System (INIS)

Krstulovic, Giorgio; Brachet, Marc

2011-01-01

The statistical equilibria of the (conservative) dynamics of the Gross-Pitaevskii equation (GPE) with a finite range of spatial Fourier modes are characterized using a new algorithm, based on a stochastically forced Ginzburg-Landau equation (SGLE), that directly generates grand-canonical distributions. The SGLE-generated distributions are validated against finite-temperature GPE-thermalized states and exact (low-temperature) results obtained by steepest descent on the (grand-canonical) partition function. A standard finite-temperature second-order λ transition is exhibited. A mechanism of GPE thermalization through a direct cascade of energy is found using initial conditions with mass and energy distributed at large scales. A long transient with partial thermalization at small scales is observed before the system reaches equilibrium. Vortices are shown to disappear as a prelude to final thermalization and their annihilation is related to the contraction of vortex rings due to mutual friction. Increasing the amount of dispersion at the truncation wave number is shown to slow thermalization and vortex annihilation. A bottleneck that produces spontaneous effective self-truncation with partial thermalization is characterized in the limit of large dispersive effects. Metastable counterflow states, with nonzero values of momentum, are generated using the SGLE algorithm. Spontaneous nucleation of the vortex ring is observed and the corresponding Arrhenius law is characterized. Dynamical counterflow effects on vortex evolution are investigated using two exact solutions of the GPE: traveling vortex rings and a motionless crystal-like lattice of vortex lines. Longitudinal effects are produced and measured on the crystal lattice. A dilatation of vortex rings is obtained for counterflows larger than their translational velocity. The vortex ring translational velocity has a dependence on temperature that is an order of magnitude above that of the crystal lattice, an effect

The Thermal Entropy Density of Spacetime

Directory of Open Access Journals (Sweden)

Rongjia Yang

2013-01-01

Full Text Available Introducing the notion of thermal entropy density via the first law of thermodynamics and assuming the Einstein equation as an equation of thermal state, we obtain the thermal entropy density of any arbitrary spacetime without assuming a temperature or a horizon. The results confirm that there is a profound connection between gravity and thermodynamics.

Testing thermal gradient driving force for grain boundary migration using molecular dynamics simulations

International Nuclear Information System (INIS)

Bai, Xian-Ming; Zhang, Yongfeng; Tonks, Michael R.

2015-01-01

Strong thermal gradients in low-thermal-conductivity ceramics may drive extended defects, such as grain boundaries and voids, to migrate in preferential directions. In this work, molecular dynamics simulations are conducted to study thermal gradient driven grain boundary migration and to verify a previously proposed thermal gradient driving force equation, using uranium dioxide as a model system. It is found that a thermal gradient drives grain boundaries to migrate up the gradient and the migration velocity increases under a constant gradient owing to the increase in mobility with temperature. Different grain boundaries migrate at very different rates due to their different intrinsic mobilities. The extracted mobilities from the thermal gradient driven simulations are compared with those calculated from two other well-established methods and good agreement between the three different methods is found, demonstrating that the theoretical equation of the thermal gradient driving force is valid, although a correction of one input parameter should be made. The discrepancy in the grain boundary mobilities between modeling and experiments is also discussed.

The impact of thermal wave characteristics on thermal dose distribution during thermal therapy: A numerical study

International Nuclear Information System (INIS)

Shih, T.-C.; Kou, H.-S.; Liauh, C.-T.; Lin, W.-L.

2005-01-01

The aim of this study was to investigate the effects of the propagation speed of a thermal wave in terms of the thermal relaxation time on the temperature/thermal dose distributions in living tissue during thermal therapies. The temperature field in tissue was solved by the finite difference method, and the thermal dose was calculated from the formulation proposed by Sapareto and Dewey [Int. J. Radiat. Oncol. Biol. Phys. 10, 787-800 (1984)]. Under the same total deposited energy, for a rapid heating process the time lagging behavior of the peak temperature became pronounced and the level of the peak temperature was decreased with increasing the thermal relaxation time. When the heating duration was longer than the thermal relaxation time of tissues, there was no significant difference between the thermal dose distributions with/without considering the effect of the thermal relaxation time. In other words, when the heating duration is comparable to or shorter than the thermal relaxation time of tissue, the results of the wave bioheat transfer equation (WBHTE) are fully different from that of the Pennes' bioheat transfer equation (PBHTE). Besides, for a rapid heating process the dimension of thermal lesion was still significantly affected by perfusion, because this is what is predicted by the WBHTE but not by the PBHTE, i.e., the wave feature of the temperature field cannot fully be predicted by the PBHTE

The rate of thermal expansion of a thin metallic slab of arbitrary shape.

Science.gov (United States)

Lee, Y C

2009-08-12

In a previous paper the rate of thermal expansion of a long, slender insulating bar has been worked out. Our present aim is to extend that work to the thermal expansion rate of not only a long metallic bar, but to further generalize it to a thin metallic slab of arbitrary shape. Assuming that the thickness of the slab is small compared to the linear dimension of its area we again take advantage of the two distinct, disparate timescales to turn the familiar problem of thermal expansion into a time-dependent problem of the rate of the expansion. Based on the previously established finite physical momentum of an acoustic phonon when translational invariance is broken, we show that the combined pressure of the phonons and the free electrons due to their outward momenta would suffer a Doppler reduction as the specimen expands upon heating. This Doppler reduction gives rise to damping of the expanding motion, thus yielding as a first result the time of thermal expansion of a long slender metal bar. The generalization to the important case of a thin metallic slab of any shape is then worked out in detail before a concluding section containing a long physical discussion and summary.

The extended Price equation quantifies species selection on mammalian body size across the Palaeocene/Eocene Thermal Maximum.

Science.gov (United States)

Rankin, Brian D; Fox, Jeremy W; Barrón-Ortiz, Christian R; Chew, Amy E; Holroyd, Patricia A; Ludtke, Joshua A; Yang, Xingkai; Theodor, Jessica M

2015-08-07

Species selection, covariation of species' traits with their net diversification rates, is an important component of macroevolution. Most studies have relied on indirect evidence for its operation and have not quantified its strength relative to other macroevolutionary forces. We use an extension of the Price equation to quantify the mechanisms of body size macroevolution in mammals from the latest Palaeocene and earliest Eocene of the Bighorn and Clarks Fork Basins of Wyoming. Dwarfing of mammalian taxa across the Palaeocene/Eocene Thermal Maximum (PETM), an intense, brief warming event that occurred at approximately 56 Ma, has been suggested to reflect anagenetic change and the immigration of small bodied-mammals, but might also be attributable to species selection. Using previously reconstructed ancestor-descendant relationships, we partitioned change in mean mammalian body size into three distinct mechanisms: species selection operating on resident mammals, anagenetic change within resident mammalian lineages and change due to immigrants. The remarkable decrease in mean body size across the warming event occurred through anagenetic change and immigration. Species selection also was strong across the PETM but, intriguingly, favoured larger-bodied species, implying some unknown mechanism(s) by which warming events affect macroevolution. © 2015 The Author(s).

Thermal Death Kinetics of Conogethes Punctiferalis (Lepidoptera: Pyralidae) as Influenced by Heating Rate and Life Stage.

Science.gov (United States)

Hou, Lixia; Du, Yanli; Johnson, Judy A; Wang, Shaojin

2015-10-01

Thermal death kinetics of Conogethes punctiferalis (Guenée) (Lepidoptera: Pyralidae) at different life stages, heating rate, and temperature is essential for developing postharvest treatments to control pests in chestnuts. Using a heating block system (HBS), the most heat-tolerant life stage of C. punctiferalis and the effects of heating rate (0.1, 0.5, 1, 5, and 10°C/min) on insect mortality were determined. The thermal death kinetic data of fifth-instar C. punctiferalis were obtained at temperatures between 44 and 50°C at a heating rate of 5°C/min. The results showed that the relative heat tolerance of C. punctiferalis was found to be fifth instars>pupae> third instars> eggs. To avoid the enhanced thermal tolerance of C. punctiferalis at low heating rates (0.1 or 0.5°C/min), a high heating rate of 5°C/min was selected to simulate the fast radio frequency heating in chestnuts and further determine the thermal death kinetic data. Thermal death curves of C. punctiferalis followed a 0th-order kinetic reaction model. The minimum exposure time to achieve 100% mortality was 55, 12, 6, and 3 min at 44, 46, 48, and 50°C, respectively. The activation energy for controlling C. punctiferalis was 482.15 kJ/mol with the z value of 4.09°C obtained from the thermal death-time curve. The information provided by thermal death kinetics for C. punctiferalis is useful in developing effective postharvest thermal treatment protocols for disinfesting chestnuts. © The Authors 2015. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Effect of heating rate on thermal cracking characteristics and kinetics of Xinjiang oil sand bitumen by TG-FTIR

Science.gov (United States)

Hao, Junhui; Zhang, Jinhong; Qiao, Yingyun; Tian, Yuanyu

2017-08-01

This work was aimed to investigate effects of heating rate on thermal cracking behaviors, distribution of gaseous products and activation energy of the thermal cracking process of Xinjiang oil sand bitumen (OSB). The thermal cracking experiments of Xinjiang OSB were performed by using thermogravimetric analyzer (TGA) at various heating rates of 10, 20, 50, 80 and 120 K/min. The evolving characteristic of gaseous products produced from the thermal cracking process was evaluated by the Fourier transform infrared spectrometry (FTIR) connected with TG. The kinetic parameters of the thermal cracking process of Xinjiang OSB at each of heating rate were determined by the Coats-Redfern model. The result show that the temperature intervals of DE volatilization stage and main reaction stage, the ((dw/dt) max and Tmax in thermal cracking process of Xinjiang OSB all increased with the increasing heating rate. While the heating rate has not obvious effect on the coke yield of Xinjiang OSB. Furthermore, the maximum absorbance of gaseous products and corresponding temperature became larger as the heating rate increases. The activation energy of this two stage both presented increasing trend with the rising heating rate, while the increasing content of that of DE volatilization stage was weaker compared to that of main reaction stage.

Measured Thermal and Fast Neutron Fluence Rates for ATF-1 Holders During ATR Cycle 157D

Energy Technology Data Exchange (ETDEWEB)

Smith, Larry Don [Idaho National Lab. (INL), Idaho Falls, ID (United States); Miller, David Torbet [Idaho National Lab. (INL), Idaho Falls, ID (United States)

2016-03-01

This report contains the thermal (2200 m/s) and fast (E>1MeV) neutron fluence rate data for the ATF-1 holders located in core for ATR Cycle 157D which were measured by the Radiation Measurements Laboratory (RML) as requested by the Power Reactor Programs (ATR Experiments) Radiation Measurements Work Order. This report contains measurements of the fluence rates corresponding to the particular elevations relative to the 80-ft. core elevation. The data in this report consist of (1) a table of the ATR power history and distribution, (2) a hard copy listing of all thermal and fast neutron fluence rates, and (3) plots of both the thermal and fast neutron fluence rates. The fluence rates reported are for the average power levels given in the table of power history and distribution.

Neutron fluence rate and energy spectrum in SPRR-300 reactor thermal column

International Nuclear Information System (INIS)

Dou Haifeng; Dai Junlong

2006-01-01

In order to modify the simple one-dimension model, the neutron fluence rate distribution calculated with ANISN code ws checked with that calculated with MCNP code. To modify the error caused by ignoring the neutron landscape orientation leaking, the reflector that can't be modeled in a simple one-dimension model was dealt by extending landscape orientation scale. On this condition the neutron fluence rate distribution and the energy spectrum in the thermal column of SPRR-300 reactor were calculated with one-dimensional code ANISN, and the results of Cd ratio are well accorded with the experimental results. The deviation between them is less than 5% and it isn't above 10% in one or two special positions. It indicates that neutron fluence rate distribution and energy spectrum in the thermal column can be well calculated with one-dimensional code ANISN. (authors)

Ion thermal and dispersion effects in Farley-Buneman instabilities

International Nuclear Information System (INIS)

Litt, S. K.; Smolyakov, A. I.; Hassan, E.; Horton, W.

2015-01-01

Farley-Buneman modes are an example of the collisional instability, which is thought to be the dominant mechanism for the irregularities in low ionosphere region. Despite high collisionality due to electron-neutral and ion-neutral collisions, the kinetic effects associated with finite temperature are important for determination of the mode frequencies and growth rate. This is especially important for ion component that is largely unmagnetized due to low ion cyclotron frequency. The ion thermal effects are strongly pronounced for shorter wavelengths and are crucial for the growth rate cut-off at high wavenumbers. We develop an extended fluid model for ion dynamics to incorporate the effects of ion thermal motion. The model is based on the extended MHD model that includes the evolution equations for higher order moments such as ion viscosity and ion heat flux. We also develop the generalized Chapman-Enskog closure model that provides exact linear closures based on the linearized kinetic equation. The results of these models are compared and tested against the linear kinetic model. The dispersion of Farley-Buneman modes and growth rate behavior are investigated in the short wavelength region

A High Temperature Kinetic Study for the Thermal Unimolecular Decomposition of Diethyl Carbonate

KAUST Repository

Alabbad, Mohammed

2017-07-08

Thermal unimolecular decomposition of diethyl carbonate (DEC) was investigated in a shock tube by measuring ethylene concentration with a CO2 gas laser over 900 - 1200 K and 1.2 – 2.8 bar. Rate coefficients were extracted using a simple kinetic scheme comprising of thermal decomposition of DEC as initial step followed by rapid thermal decomposition of the intermediate ethyl-hydrogen-carbonate. Our results were further analysed using ab initio and master equation calculations to obtain pressure- and temperature- dependence of rate coefficients. Similar to alkyl esters, unimolecular decomposition of DEC is found to undergo six-center retro-ene elimination of ethylene in a concerted manner.

A High Temperature Kinetic Study for the Thermal Unimolecular Decomposition of Diethyl Carbonate

KAUST Repository

Alabbad, Mohammed; Giri, Binod; Szőri, Milan; Viskolcz, Bé la; Farooq, Aamir

2017-01-01

Thermal unimolecular decomposition of diethyl carbonate (DEC) was investigated in a shock tube by measuring ethylene concentration with a CO2 gas laser over 900 - 1200 K and 1.2 – 2.8 bar. Rate coefficients were extracted using a simple kinetic scheme comprising of thermal decomposition of DEC as initial step followed by rapid thermal decomposition of the intermediate ethyl-hydrogen-carbonate. Our results were further analysed using ab initio and master equation calculations to obtain pressure- and temperature- dependence of rate coefficients. Similar to alkyl esters, unimolecular decomposition of DEC is found to undergo six-center retro-ene elimination of ethylene in a concerted manner.

Efficient models for photoionization produced by non-thermal gas discharges in air based on radiative transfer and the Helmholtz equations

International Nuclear Information System (INIS)

Bourdon, A; Pasko, V P; Liu, N Y; Celestin, S; Segur, P; Marode, E

2007-01-01

This paper presents formulation of computationally efficient models of photoionization produced by non-thermal gas discharges in air based on three-group Eddington and improved Eddington (SP 3 ) approximations to the radiative transfer equation, and on effective representation of the classic integral model for photoionization in air developed by Zheleznyak et al (1982) by a set of three Helmholtz differential equations. The reported formulations represent extensions of ideas advanced recently by Segur et al (2006) and Luque et al (2007), and allow fast and accurate solution of photoionization problems at different air pressures for the range 0.1 O 2 O 2 is the partial pressure of molecular oxygen in air in units of Torr ( p O 2 = 150 Torr) at atmospheric pressure) and R in cm is an effective geometrical size of the physical system of interest. The presented formulations can be extended to other gases and gas mixtures subject to availability of related emission, absorption and photoionization coefficients. The validity of the developed models is demonstrated by performing direct comparisons of the results from these models and results obtained from the classic integral model. Specific validation comparisons are presented for a set of artificial sources of photoionizing radiation with different Gaussian dimensions, and for a realistic problem involving development of a double-headed streamer at ground pressure. The reported results demonstrate the importance of accurate definition of the boundary conditions for the photoionization production rate for the solution of second order partial differential equations involved in the Eddington, SP 3 and the Helmholtz formulations. The specific algorithms derived from the classic photoionization model of Zheleznyak et al (1982), allowing accurate calculations of boundary conditions for differential equations involved in all three new models described in this paper, are presented. It is noted that the accurate formulation of

Quantum adiabatic Markovian master equations

International Nuclear Information System (INIS)

Albash, Tameem; Zanardi, Paolo; Boixo, Sergio; Lidar, Daniel A

2012-01-01

We develop from first principles Markovian master equations suited for studying the time evolution of a system evolving adiabatically while coupled weakly to a thermal bath. We derive two sets of equations in the adiabatic limit, one using the rotating wave (secular) approximation that results in a master equation in Lindblad form, the other without the rotating wave approximation but not in Lindblad form. The two equations make markedly different predictions depending on whether or not the Lamb shift is included. Our analysis keeps track of the various time and energy scales associated with the various approximations we make, and thus allows for a systematic inclusion of higher order corrections, in particular beyond the adiabatic limit. We use our formalism to study the evolution of an Ising spin chain in a transverse field and coupled to a thermal bosonic bath, for which we identify four distinct evolution phases. While we do not expect this to be a generic feature, in one of these phases dissipation acts to increase the fidelity of the system state relative to the adiabatic ground state. (paper)

Ion Streaming Instabilities in Pair Ion Plasma and Localized Structure with Non-Thermal Electrons

Science.gov (United States)

Nasir Khattak, M.; Mushtaq, A.; Qamar, A.

2015-12-01

Pair ion plasma with a fraction of non-thermal electrons is considered. We investigate the effects of the streaming motion of ions on linear and nonlinear properties of unmagnetized, collisionless plasma by using the fluid model. A dispersion relation is derived, and the growth rate of streaming instabilities with effect of streaming motion of ions and non-thermal electrons is calculated. A qausi-potential approach is adopted to study the characteristics of ion acoustic solitons. An energy integral equation involving Sagdeev potential is derived during this process. The presence of the streaming term in the energy integral equation affects the structure of the solitary waves significantly along with non-thermal electrons. Possible application of the work to the space and laboratory plasmas are highlighted.

Ion streaming instabilities in pair ion plasma and localized structure with non-thermal electrons

Energy Technology Data Exchange (ETDEWEB)

Khattak, M. Nasir; Qamar, A., E-mail: mnnasirphysics@gmail.com [Department of Physics, University of Peshawar (Pakistan); Mushtaq, A. [Department of Physics, Abdul Wali Khan University Mardan, National Center for Physics, Mardan (Pakistan)

2015-12-15

Pair ion plasma with a fraction of non-thermal electrons is considered. We investigate the effects of the streaming motion of ions on linear and nonlinear properties of unmagnetized, collisionless plasma by using the fluid model. A dispersion relation is derived, and the growth rate of streaming instabilities with effect of streaming motion of ions and non-thermal electrons is calculated. A quasi-potential approach is adopted to study the characteristics of ion acoustic solitons. An energy integral equation involving Sagdeev potential is derived during this process. The presence of the streaming term in the energy integral equation affects the structure of the solitary waves significantly along with non-thermal electrons. Possible application of the work to the space and laboratory plasmas are highlighted. (author)

Effect of Cattaneo-Christov heat flux on Jeffrey fluid flow with variable thermal conductivity

Science.gov (United States)

Hayat, Tasawar; Javed, Mehwish; Imtiaz, Maria; Alsaedi, Ahmed

2018-03-01

This paper presents the study of Jeffrey fluid flow by a rotating disk with variable thickness. Energy equation is constructed by using Cattaneo-Christov heat flux model with variable thermal conductivity. A system of equations governing the model is obtained by applying boundary layer approximation. Resulting nonlinear partial differential system is transformed to ordinary differential system. Homotopy concept leads to the convergent solutions development. Graphical analysis for velocities and temperature is made to examine the influence of different involved parameters. Thermal relaxation time parameter signifies that temperature for Fourier's heat law is more than Cattaneo-Christov heat flux. A constitutional analysis is made for skin friction coefficient and heat transfer rate. Effects of Prandtl number on temperature distribution and heat transfer rate are scrutinized. It is observed that larger Reynolds number gives illustrious temperature distribution.

Quantum thermal rectification to design thermal diodes and transistors

Energy Technology Data Exchange (ETDEWEB)

Joulain, Karl; Ezzahri, Younes; Ordonez-Miranda, Jose [Univ. de Poitiers, Futuroscope Chasseneuil (France). Inst. Pprime, CNRS

2017-05-01

We study in this article how heat can be exchanged between two-level systems, each of them being coupled to a thermal reservoir. Calculations are performed solving a master equation for the density matrix using the Born-Markov approximation. We analyse the conditions for which a thermal diode and a thermal transistor can be obtained as well as their optimisation.

Analysis of the Effects of Thermal Environment on Optical Systems for Navigation Guidance and Control in Supersonic Aircraft Based on Empirical Equations.

Science.gov (United States)

Cheng, Xuemin; Yang, Yikang; Hao, Qun

2016-10-17

The thermal environment is an important factor in the design of optical systems. This study investigated the thermal analysis technology of optical systems for navigation guidance and control in supersonic aircraft by developing empirical equations for the front temperature gradient and rear thermal diffusion distance, and for basic factors such as flying parameters and the structure of the optical system. Finite element analysis (FEA) was used to study the relationship between flying and front dome parameters and the system temperature field. Systematic deduction was then conducted based on the effects of the temperature field on the physical geometry and ray tracing performance of the front dome and rear optical lenses, by deriving the relational expressions between the system temperature field and the spot size and positioning precision of the rear optical lens. The optical systems used for navigation guidance and control in supersonic aircraft when the flight speed is in the range of 1-5 Ma were analysed using the derived equations. Using this new method it was possible to control the precision within 10% when considering the light spot received by the four-quadrant detector, and computation time was reduced compared with the traditional method of separately analysing the temperature field of the front dome and rear optical lens using FEA. Thus, the method can effectively increase the efficiency of parameter analysis and computation in an airborne optical system, facilitating the systematic, effective and integrated thermal analysis of airborne optical systems for navigation guidance and control.

Validation of predictive equations for glomerular filtration rate in the Saudi population

Directory of Open Access Journals (Sweden)

Al Wakeel Jamal

2009-01-01

Full Text Available Predictive equations provide a rapid method of assessing glomerular filtration rate (GFR. To compare the various predictive equations for the measurement of this parameter in the Saudi population, we measured GFR by the Modification of Diet in Renal Disease (MDRD and Cockcroft-Gault formulas, cystatin C, reciprocal of cystatin C, creatinine clearance, reciprocal of creatinine, and inulin clearance in 32 Saudi subjects with different stages of renal disease. We com-pared GFR measured by inulin clearance and the estimated GFR by the equations. The study included 19 males (59.4% and 13 (40.6% females with a mean age of 42.3 ± 15.2 years and weight of 68.6 ± 17.7 kg. The mean serum creatinine was 199 ± 161 μmol/L. The GFR measured by inulin clearance was 50.9 ± 33.5 mL/min, and the estimated by Cockcroft-Gault and by MDRD equations was 56.3 ± 33.3 and 52.8 ± 32.0 mL/min, respectively. The GFR estimated by MDRD revealed the strongest correlation with the measured inulin clearance (r= 0.976, P= 0.0000 followed by the GFR estimated by Cockcroft-Gault, serum cystatin C, and serum creatinine (r= 0.953, P= 0.0000 (r= 0.787, P= 0.0001 (r= -0.678, P= 0.001, respectively. The reciprocal of cystatin C and serum creatinine revealed a correlation coefficient of 0.826 and 0.93, respectively. Cockroft-Gault for-mula overestimated the GFR by 5.40 ± 10.3 mL/min in comparison to the MDRD formula, which exhibited the best correlation with inulin clearance in different genders, age groups, body mass index, renal transplant recipients, chronic kidney disease stages when compared to other GFR predictive equations.

Integral equation hierarchy for continuum percolation

International Nuclear Information System (INIS)

Given, J.A.

1988-01-01

In this thesis a projection operator technique is presented that yields hierarchies of integral equations satisfied exactly by the n-point connectedness functions in a continuum version of the site-bond percolation problem. The n-point connectedness functions carry the same structural information for a percolation problem as then-point correlation functions do for a thermal problem. This method extends the Potts model mapping of Fortuin and Kastelyn to the continuum by exploiting an s-state generalization of the Widom-Rowlinson model, a continuum model for phase separation. The projection operator technique is used to produce an integral equation hierarchy for percolation similar to the Born-Green heirarchy. The Kirkwood superposition approximation (SA) is extended to percolation in order to close this hierarchy and yield a nonlinear integral equation for the two-point connectedness function. The fact that this function, in the SA, is the analytic continuation to negative density of the two-point correlation function in a corresponding thermal problem is discussed. The BGY equation for percolation is solved numerically, both by an expansion in powers of the density, and by an iterative technique due to Kirkwood. It is argued both analytically and numerically, that the BYG equation for percolation, unlike its thermal counterpart, shows non-classical critical behavior, with η = 1 and γ = 0.05 ± .1. Finally a sequence of refinements to the superposition approximations based in the theory of fluids by Rice and Lekner is discussed

Charge exchange of muons in gases: I. Kinetic equations

International Nuclear Information System (INIS)

Turner, R.E.

1983-06-01

Kinetic equations for the spin density operators of the diamagnetic and paramagnetic states of the positive muon are obtained for the description of the slowing-down process encountered when high energy muons thermalize in a single component gas. The motion of this two species system is generated by the Liouville superoperators associated with the diamagnetic and paramagnetic spin Hamiltonians and by time-dependent rate superoperators which depict the probabilities per collision that an electron is captured or lost. These rates are translational averages of the appropriate Boltzmann collision operators. That is, they are momentum and position integrals of the product of either the electron capture or loss total cross section with the single particle translational density operators for the muon (or muonium) and a gas particle. These rates are time dependent because the muon (or muonium) translational density operator is time dependent. The initial amplitudes and phases of the observed thermal spin polarization in μSR experiments are then obtained in terms of the spin density operators emerging from the stopping regime

Thermal sensation models: a systematic comparison.

Science.gov (United States)

Koelblen, B; Psikuta, A; Bogdan, A; Annaheim, S; Rossi, R M

2017-05-01

Thermal sensation models, capable of predicting human's perception of thermal surroundings, are commonly used to assess given indoor conditions. These models differ in many aspects, such as the number and type of input conditions, the range of conditions in which the models can be applied, and the complexity of equations. Moreover, the models are associated with various thermal sensation scales. In this study, a systematic comparison of seven existing thermal sensation models has been performed with regard to exposures including various air temperatures, clothing thermal insulation, and metabolic rate values after a careful investigation of the models' range of applicability. Thermo-physiological data needed as input for some of the models were obtained from a mathematical model for human physiological responses. The comparison showed differences between models' predictions for the analyzed conditions, mostly higher than typical intersubject differences in votes. Therefore, it can be concluded that the choice of model strongly influences the assessment of indoor spaces. The issue of comparing different thermal sensation scales has also been discussed. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Thermal Dehydration Kinetics of Gypsum and Borogypsum under Non-isothermal Conditions

Institute of Scientific and Technical Information of China (English)

I.Y.Elbeyli; S.Piskin

2004-01-01

Thermal dehydration of gypsum and borogypsum was investigated under nonisothermal conditions in air by using simultaneous thermogravimetric-differential thermal analyzer. Nonisothermal experiments were carried out at various linear heating rates. Kinetics of dehydration in the temperature range of 373-503 K were evaluated from the DTA (differential thermal analysis)-TGA (thermogravimetric analysis) data by means of Coats-Redfern,Kissinger and Doyle Equations. Values of the activation energy and the pre-exponential factor of the dehydration were calculated. The results of thermal experiments and kinetic parameters indicated that borogypsum is similar to gypsum from dehydration mechanism point of view although it consists of boron and small amount of alkali metal oxides.

Nonlinear electrostatic wave equations for magnetized plasmas - II

DEFF Research Database (Denmark)

Dysthe, K. B.; Mjølhus, E.; Pécseli, H. L.

1985-01-01

For pt.I see ibid., vol.26, p.443-7 (1984). The problem of extending the high frequency part of the Zakharov equations for nonlinear electrostatic waves to magnetized plasmas, is considered. Weak electromagnetic and thermal effects are retained on an equal footing. Direction dependent (electrosta......For pt.I see ibid., vol.26, p.443-7 (1984). The problem of extending the high frequency part of the Zakharov equations for nonlinear electrostatic waves to magnetized plasmas, is considered. Weak electromagnetic and thermal effects are retained on an equal footing. Direction dependent...... (electrostatic) cut-off implies that various cases must be considered separately, leading to equations with rather different properties. Various equations encountered previously in the literature are recovered as limiting cases....

Utility rate equations of group population dynamics in biological and social systems.

Directory of Open Access Journals (Sweden)

Vyacheslav I Yukalov

Full Text Available We present a novel system of equations to describe the evolution of self-organized structured societies (biological or human composed of several trait groups. The suggested approach is based on the combination of ideas employed in the theory of biological populations, system theory, and utility theory. The evolution equations are defined as utility rate equations, whose parameters are characterized by the utility of each group with respect to the society as a whole and by the mutual utilities of groups with respect to each other. We analyze in detail the cases of two groups (cooperators and defectors and of three groups (cooperators, defectors, and regulators and find that, in a self-organized society, neither defectors nor regulators can overpass the maximal fractions of about [Formula: see text] each. This is in agreement with the data for bee and ant colonies. The classification of societies by their distance from equilibrium is proposed. We apply the formalism to rank the countries according to the introduced metric quantifying their relative stability, which depends on the cost of defectors and regulators as well as their respective population fractions. We find a remarkable concordance with more standard economic ranking based, for instance, on GDP per capita.

Utility Rate Equations of Group Population Dynamics in Biological and Social Systems

Science.gov (United States)

Yukalov, Vyacheslav I.; Yukalova, Elizaveta P.; Sornette, Didier

2013-01-01

We present a novel system of equations to describe the evolution of self-organized structured societies (biological or human) composed of several trait groups. The suggested approach is based on the combination of ideas employed in the theory of biological populations, system theory, and utility theory. The evolution equations are defined as utility rate equations, whose parameters are characterized by the utility of each group with respect to the society as a whole and by the mutual utilities of groups with respect to each other. We analyze in detail the cases of two groups (cooperators and defectors) and of three groups (cooperators, defectors, and regulators) and find that, in a self-organized society, neither defectors nor regulators can overpass the maximal fractions of about each. This is in agreement with the data for bee and ant colonies. The classification of societies by their distance from equilibrium is proposed. We apply the formalism to rank the countries according to the introduced metric quantifying their relative stability, which depends on the cost of defectors and regulators as well as their respective population fractions. We find a remarkable concordance with more standard economic ranking based, for instance, on GDP per capita. PMID:24386163

EFFECT OF FINITE LARMOR RADIUS CORRECTIONS ON THE THERMAL INSTABILITY OF THERMALLY CONDUCTING VISCOUS PLASMA WITH HALL CURRENT AND ELECTRON INERTIA

Energy Technology Data Exchange (ETDEWEB)

Jain, Shweta; Sharma, Prerana [Physics Department, Ujjain Engineering College, Ujjain, MP-456010 (India); Kaothekar, Sachin [Physics Department, Mahakal Institute of Technology, Ujjain, MP-456664 (India); Chhajlani, R. K., E-mail: sackaothekar@gmail.com [Retired, School of Studies in Physics, Vikram University Ujjain, MP-456010 (India)

2016-10-01

The thermal instability of an infinite homogeneous, thermally conducting, and rotating plasma, incorporating finite electrical resistivity, finite electron inertia, and an arbitrary radiative heat-loss function in the presence of finite Larmor radius corrections and Hall current, has been studied. Analysis has been made with the help of linearized magnetohydrodynamics (MHD) equations. A general dispersion relation is obtained using the normal mode analysis method, and the dispersion relation is discussed for longitudinal propagation and transverse propagation separately. The dispersion relation has been solved numerically to obtain the dependence of the growth rate on the various parameters involved. The conditions of modified thermal instability and stability are discussed in the different cases of interest.

Exponential decay rate of the power spectrum for solutions of the Navier--Stokes equations

International Nuclear Information System (INIS)

Doering, C.R.; Titi, E.S.

1995-01-01

Using a method developed by Foias and Temam [J. Funct. Anal. 87, 359 (1989)], exponential decay of the spatial Fourier power spectrum for solutions of the incompressible Navier--Stokes equations is established and explicit rigorous lower bounds on a small length scale defined by the exponential decay rate are obtained

An estimator for the relative entropy rate of path measures for stochastic differential equations

Energy Technology Data Exchange (ETDEWEB)

Opper, Manfred, E-mail: manfred.opper@tu-berlin.de

2017-02-01

We address the problem of estimating the relative entropy rate (RER) for two stochastic processes described by stochastic differential equations. For the case where the drift of one process is known analytically, but one has only observations from the second process, we use a variational bound on the RER to construct an estimator.

Effect of warming rate on the critical thermal maxima of crabs, shrimp and fish

OpenAIRE

Vinagre, Catarina; Leal, Inês; Mendonça, Vanessa; Flores, Augusto Alberto Valero

2015-01-01

he threat of global warming has prompted numerous recent studies on the thermal tolerance of marine species. A widely used method to determine the upper thermal limit has been the Critical Thermal Maximum (CTMax), a dynamic method, meaning that temperature is increased gradually until a critical point is reached. This method presents several advantages over static methods, however, there is one main issue that hinders interpretation and comparison of CTMax results: the rate at which the tempe...

Estimation of respiratory rate from thermal videos of preterm infants.

Science.gov (United States)

Pereira, Carina Barbosa; Heimann, Konrad; Venema, Boudewijn; Blazek, Vladimir; Czaplik, Michael; Leonhardt, Steffen

2017-07-01

Studies have demonstrated that respiratory rate (RR) is a good predictor of the patient condition as well as an early marker of patient deterioration and physiological distress. However, it is also referred as "the neglected vital parameter". This is mainly due to shortcoming of current monitoring techniques. Moreover, in preterm infants, the removal of adhesive electrodes cause epidermal stripping, skin disruption, and with it pain. This paper proposes a new algorithm for estimation of RR in thermal videos of moderate preterm infants. It uses the temperature modulation around the nostrils over the respiratory cycle to extract this vital parameter. To compensate movement artifacts the approach incorporates a tracking algorithm. In addition, a new reliable and accurate algorithm for robust estimation of local (breath-to-breath) intervals was included. To evaluate the performance of this approach, thermal recordings of four moderate preterm infants were acquired. Results were compared with RR derived from body surface electrocardiography. The results showed an excellent agreement between thermal imaging and gold standard. On average, the relative error between both monitoring techniques was 3.42%. In summary, infrared thermography may be a clinically relevant alternative to conventional sensors, due to its high thermal resolution and outstanding characteristics.

Analysis of the Effects of Thermal Environment on Optical Systems for Navigation Guidance and Control in Supersonic Aircraft Based on Empirical Equations

Directory of Open Access Journals (Sweden)

Xuemin Cheng

2016-10-01

Full Text Available The thermal environment is an important factor in the design of optical systems. This study investigated the thermal analysis technology of optical systems for navigation guidance and control in supersonic aircraft by developing empirical equations for the front temperature gradient and rear thermal diffusion distance, and for basic factors such as flying parameters and the structure of the optical system. Finite element analysis (FEA was used to study the relationship between flying and front dome parameters and the system temperature field. Systematic deduction was then conducted based on the effects of the temperature field on the physical geometry and ray tracing performance of the front dome and rear optical lenses, by deriving the relational expressions between the system temperature field and the spot size and positioning precision of the rear optical lens. The optical systems used for navigation guidance and control in supersonic aircraft when the flight speed is in the range of 1–5 Ma were analysed using the derived equations. Using this new method it was possible to control the precision within 10% when considering the light spot received by the four-quadrant detector, and computation time was reduced compared with the traditional method of separately analysing the temperature field of the front dome and rear optical lens using FEA. Thus, the method can effectively increase the efficiency of parameter analysis and computation in an airborne optical system, facilitating the systematic, effective and integrated thermal analysis of airborne optical systems for navigation guidance and control.

A validated disease specific prediction equation for resting metabolic rate in underweight patients with COPD

Directory of Open Access Journals (Sweden)

Anita Nordenson

2010-09-01

Full Text Available Anita Nordenson2, Anne Marie Grönberg1,2, Lena Hulthén1, Sven Larsson2, Frode Slinde11Department of Clinical Nutrition, Sahlgrenska Academy at University of Gothenburg, Göteborg, Sweden; 2Department of Internal Medicine/Respiratory Medicine and Allergology, Sahlgrenska Academy at University of Gothenburg, SwedenAbstract: Malnutrition is a serious condition in chronic obstructive pulmonary disease (COPD. Successful dietary intervention calls for calculations of resting metabolic rate (RMR. One disease-specific prediction equation for RMR exists based on mainly male patients. To construct a disease-specific equation for RMR based on measurements in underweight or weight-losing women and men with COPD, RMR was measured by indirect calorimetry in 30 women and 11 men with a diagnosis of COPD and body mass index <21 kg/m2. The following variables, possibly influencing RMR were measured: length, weight, middle upper arm circumference, triceps skinfold, body composition by dual energy x-ray absorptiometry and bioelectrical impedance, lung function, and markers of inflammation. Relations between RMR and measured variables were studied using univariate analysis according to Pearson. Gender and variables that were associated with RMR with a P value <0.15 were included in a forward multiple regression analysis. The best-fit multiple regression equation included only fat-free mass (FFM: RMR (kJ/day = 1856 + 76.0 FFM (kg. To conclude, FFM is the dominating factor influencing RMR. The developed equation can be used for prediction of RMR in underweight COPD patients.Keywords: pulmonary disease, chronic obstructive, basal metabolic rate, malnutrition, body composition

Applicability of the Schwartz Equation and the Chronic Kidney Disease in Children Bedside Equation for Estimating Glomerular Filtration Rate in Overweight Children.

Science.gov (United States)

Lewis, Teresa V; Harrison, Donald L; Gildon, Brooke L; Carter, Sandra M; Turman, Martin A

2016-06-01

To determine if significant correlations exist between glomerular filtration rate (GFR) prediction equation values, derived by using the original Schwartz equation and the Chronic Kidney Disease in Children (CKiD) bedside equation with a 24-hour urine creatinine clearance (Clcr ) value normalized to a body surface area of 1.73 m(2) in overweight and obese children. Prospective analysis (20 patients) and retrospective analysis (43 patients). Pediatric inpatient ward and pediatric nephrology clinic at a comprehensive academic medical center. Sixty-three pediatric patients (aged 5-17 years), of whom 27 were overweight (body mass index [BMI] at the 85th percentile or higher) and 36 were not overweight (BMI lower than the 85th percentile [controls]) between 2007 and 2012. Data from the overweight patients were compared with nonoverweight controls. GFR values were calculated by using the original Schwartz equation and the CKiD bedside equation. Each patient's 24-hour urine Clcr value normalized to a body surface area of 1.73 m(2) served as the index value. A Pearson correlation coefficient model was used to determine association between the 24-hour urine Clcr value (index value) with the Schwartz and CKiD GFR estimations. Significant correlation was found to exist between the Schwartz and CKiD bedside GFR estimations relative to the 24-hour urine Clcr in the control subjects (r = 0.85, poverweight subjects (r = 0.86, poverweight children with a kidney disorder. The CKiD bedside GFR estimations were not significantly different compared with 24-hour urine Clcr values for the overweight group with kidney disorder (p=0.85). The Schwartz and CKiD bedside estimations of GFR correlated with 24-hour urine Clcr values in both overweight and nonoverweight children. Compared with the Schwartz equation, which tended to overestimate renal function, the CKiD bedside equation appeared to approximate 24-hour urine Clcr more closely in overweight children with kidney disorder. © 2016

Thermal stress in UO2 during sintering as a possible cause of cracking

International Nuclear Information System (INIS)

Aragones, M.A.; Tobias, E.; Tulli, I.; Naquid, C.

1980-01-01

Thermal stresses arising during sintering of UO 2 pellets are evaluated numerically by the solution of coupled equations for heat transfer through the sample. Results are compared with those of a semiempirical approach reported in the literature. Better insight into the heat transfer process is obtained from the solution of the coupled equations rather than from the empirical approach. The two approaches give different results for the thermal stresses arising during sintering. The use of heating and cooling rates of approximately 0.5 0 Cs -1 is found to prevent the possibility of cracking in UO 2 pellets of radii varying from 0.6 cm to 1 cm during sintering in hydrogen or argon-hydrogen atmospheres. (author)

Measured thermal and fast neutron fluence rates ATR Cycle 101-B, October 11, 1993--November 27, 1993

International Nuclear Information System (INIS)

Murray, R.K.; Rogers, J.W.

1994-01-01

This report contains the thermal (2200 m/s) and fast (E>lMeV) neutron fluence rate data for ATR Cycle 101-B which were measured by the Radiation Measurements Laboratory (RML) as requested by the Power Reactor Programs (ATR Experiments) Radiation Measurements Work Order. This report contains fluence rate values corresponding to the particular elevations (relative to the 80 ft. core elevation) where the measurements were taken. The data in this report consists of (1) a table of the ATR power history and distribution, (2) a hard copy listing of all thermal and fast neutron fluence rates, (3) plots of both the thermal and fast neutron fluence rates, and (4) a magnetic record (3.5 inch diskette) containing a listing of only the fast neutron fluence rates, their assigned elevations proper header identification of all monitor positions contained herein

Isomorph invariance of Couette shear flows simulated by the SLLOD equations of motion

DEFF Research Database (Denmark)

Separdar, Leila; Bailey, Nicholas; Schrøder, Thomas

2013-01-01

fluctuations of virial and potential energy. Such systems have good isomorphs (curves in the thermodynamic phase diagram along which structural, dynamical, and some thermodynamic quantities are invariant when expressed in reduced units). The SLLOD equations of motion were used to simulate Couette shear flows......Non-equilibrium molecular dynamics simulations were performed to study the thermodynamic, structural, and dynamical properties of the single-component Lennard-Jones and the Kob-Andersen binary Lennard-Jones liquids. Both systems are known to have strong correlations between equilibrium thermal...... of the two systems. We show analytically that these equations are isomorph invariant provided the reduced strain rate is fixed along the isomorph. Since isomorph invariance is generally only approximate, a range of strain rates were simulated to test for the predicted invariance, covering both the linear...

An Implementation of Interfacial Transport Equation into the CUPID code

Energy Technology Data Exchange (ETDEWEB)

Park, Ik Kyu; Cho, Heong Kyu; Yoon, Han Young; Jeong, Jae Jun

2009-11-15

A component scale thermal hydraulic analysis code, CUPID (Component Unstructured Program for Interfacial Dynamics), is being developed for the analysis of components for a nuclear reactor, such as reactor vessel, steam generator, containment, etc. It adopted a three-dimensional, transient, two phase and three-field model. In order to develop the numerical schemes for the three-field model, various numerical schemes have been examined including the SMAS, semi-implicit ICE, SIMPLE. The governing equations for a 2-phase flow are composed of mass, momentum, and energy conservation equations for each phase. These equation sets are closed by the interfacial transfer rate of mass, momentum, and energy. The interfacial transfer of mass, momentum, and energy occurs through the interfacial area, and this area plays an important role in the transfer rate. The flow regime based correlations are used for calculating the interracial area in the traditional style 2-phase flow model. This is dependent upon the flow regime and is limited to the fully developed 2-phase flow region. Its application to the multi-dimensional 2-phase flow has some limitation because it adopts the measured results of 2-phase flow in the 1-dimensional tube. The interfacial area concentration transport equation had been suggested in order to calculate the interfacial area without the interfacial area correlations. The source terms to close the interfacial area transport equation should be further developed for a wide ranger usage of it. In this study, the one group interfacial area concentration transport equation has been implemented into the CUPID code. This interfacial area concentration transport equation can be used instead of the interfacial area concentration correlations for the bubbly flow region.

An Implementation of Interfacial Transport Equation into the CUPID code

International Nuclear Information System (INIS)

Park, Ik Kyu; Cho, Heong Kyu; Yoon, Han Young; Jeong, Jae Jun

2009-11-01

A component scale thermal hydraulic analysis code, CUPID (Component Unstructured Program for Interfacial Dynamics), is being developed for the analysis of components for a nuclear reactor, such as reactor vessel, steam generator, containment, etc. It adopted a three-dimensional, transient, two phase and three-field model. In order to develop the numerical schemes for the three-field model, various numerical schemes have been examined including the SMAS, semi-implicit ICE, SIMPLE. The governing equations for a 2-phase flow are composed of mass, momentum, and energy conservation equations for each phase. These equation sets are closed by the interfacial transfer rate of mass, momentum, and energy. The interfacial transfer of mass, momentum, and energy occurs through the interfacial area, and this area plays an important role in the transfer rate. The flow regime based correlations are used for calculating the interracial area in the traditional style 2-phase flow model. This is dependent upon the flow regime and is limited to the fully developed 2-phase flow region. Its application to the multi-dimensional 2-phase flow has some limitation because it adopts the measured results of 2-phase flow in the 1-dimensional tube. The interfacial area concentration transport equation had been suggested in order to calculate the interfacial area without the interfacial area correlations. The source terms to close the interfacial area transport equation should be further developed for a wide ranger usage of it. In this study, the one group interfacial area concentration transport equation has been implemented into the CUPID code. This interfacial area concentration transport equation can be used instead of the interfacial area concentration correlations for the bubbly flow region

Temperature waves and the Boltzmann kinetic equation for phonons

International Nuclear Information System (INIS)

Urushev, D.; Borisov, M.; Vavrek, A.

1988-01-01

The ordinary parabolic equation for thermal conduction based on the Fourier empiric law as well as the generalized thermal conduction equation based on the Maxwell law have been derived from the Boltzmann equation for the phonons within the relaxation time approximation. The temperature waves of the so-called second sound in crystals at low temperatures are transformed into Fourier waves at low frequencies with respect to the characteristic frequency of the U-processes. These waves are transformed into temperature waves similar to the second sound waves in He II at frequences higher than the U-processes characteristic. 1 fig., 19 refs

A lumped model of venting during thermal runaway in a cylindrical Lithium Cobalt Oxide lithium-ion cell

Science.gov (United States)

Coman, Paul T.; Rayman, Sean; White, Ralph E.

2016-03-01

This paper presents a mathematical model built for analyzing the intricate thermal behavior of a 18650 LCO (Lithium Cobalt Oxide) battery cell during thermal runaway when venting of the electrolyte and contents of the jelly roll (ejecta) is considered. The model consists of different ODEs (Ordinary Differential Equations) describing reaction rates and electrochemical reactions, as well as the isentropic flow equations for describing electrolyte venting. The results are validated against experimental findings from Golubkov et al. [1] [Andrey W. Golubkov, David Fuchs, Julian Wagner, Helmar Wiltsche, Christoph Stangl, Gisela Fauler, Gernot Voitice Alexander Thaler and Viktor Hacker, RSC Advances, 4:3633-3642, 2014] for two cases - with flow and without flow. The results show that if the isentropic flow equations are not included in the model, the thermal runaway is triggered prematurely at the point where venting should occur. This shows that the heat dissipation due to ejection of electrolyte and jelly roll contents has a significant contribution. When the flow equations are included, the model shows good agreement with the experiment and therefore proving the importance of including venting.

On Regularly Varying and History-Dependent Convergence Rates of Solutions of a Volterra Equation with Infinite Memory

OpenAIRE

John A. D. Appleby

2010-01-01

We consider the rate of convergence to equilibrium of Volterra integrodifferential equations with infinite memory. We show that if the kernel of Volterra operator is regularly varying at infinity, and the initial history is regularly varying at minus infinity, then the rate of convergence to the equilibrium is regularly varying at infinity, and the exact pointwise rate of convergence can be determined in terms of the rate of decay of the kernel and the rate of growth of the initial history. ...

DETERMINATION OF TEMPERATURE DISTRIBUTION FOR ANNULAR FINS WITH TEMPERATURE DEPENDENT THERMAL CONDUCTIVITY BY HPM

Directory of Open Access Journals (Sweden)

Davood Domairry Ganji

2011-01-01

Full Text Available In this paper, homotopy perturbation method has been used to evaluate the temperature distribution of annular fin with temperature-dependent thermal conductivity and to determine the temperature distribution within the fin. This method is useful and practical for solving the nonlinear heat transfer equation, which is associated with variable thermal conductivity condition. The homotopy perturbation method provides an approximate analytical solution in the form of an infinite power series. The annular fin heat transfer rate with temperature-dependent thermal conductivity has been obtained as a function of thermo-geometric fin parameter and the thermal conductivity parameter describing the variation of the thermal conductivity.

Accelerated thermal and radiation-oxidation combined degradation of electric cable insulation materials

International Nuclear Information System (INIS)

Yagi, Toshiaki; Seguchi, Tadao; Yoshida, Kenzo

1986-03-01

For the development of accelerated testing methodology to estimate the life time of electric cable, which is installed in radiation field such as a nuclear reactor containment vessel, radiation and thermal combined degradation of cable insulation and jacketing materials was studied. The materials were two types of formulated polyethylene, ethylene-propylene rubber, Hypalon, and Neoprene. With Co-60 γ-rays the materials were irradiated up to 0.5 MGy under vacuum and in oxygen under pressure, then exposed to thermal aging at elevated temperature in oxygen. The degradation was investigated by the tensile test, gelfraction, and swelling measurements. The thermal degradation rate for each sample increases with increase of oxygen concentration, i.e. oxygen pressure, during the aging, and tends to saturate above 0.2 MPa of oxygen pressure. Then, the effects of irradiation and the temperature on the thermal degradation rate were investigated at the oxygen pressure of 0.2 MPa in the temperature range from 110 deg C to 150 deg C. For all of samples irradiated in oxygen, the following thermal degradation rate was accelerated by several times comparing with unirradiated samples, while the rate of thermal degradation for the sample except Neoprene irradiated under vacuum was nearly equal to that of unirradiated one. By the analysis of thermal degradation rate against temperature using Arrhenius equation, it was found that the activation energy tends to decrease for the samples irradiated in oxidation condition. (author)

Consistency in thermophysical properties: enthalpy, heat capacity, thermal conductivity and thermal diffusivity of solid UO2

International Nuclear Information System (INIS)

Fink, J.K.; Chasanov, M.G.; Leibowitz, L.

Equations have been derived for the enthalpy, heat capacity, thermal conductivity, and thermal diffusivity of UO 2 . In selection of these equations, we considered the traditional criterion of lowest relative standard deviation between experimental data and the function chosen to fit these data as well as consistency between the thermophysical properties. In the latter case, we considered consistency in (1) thermodynamic relations among properties, (2) the choice of physical phenomena on which to base the theoretical formulation of the equations, and (3) the existence and temperature of phase transitions

Some contributions to the high strain rate deformation of solids and the thermally activated deformation of wood

International Nuclear Information System (INIS)

Ferguson, W George

2009-01-01

The behaviour of metals as a function of rate of loading, strain rate, and temperature is discussed in terms of previous work by the author. Strain rates range from 10 -3 s -1 , obtained in a standard tensile testing machine, to 10 2 s -1 obtained in a hydraulic piston driven machine and up to 10 4 s -1 , very high strain rates with a Kolsky split Hopkinson bar using shear type loading. At rates less 10 3 s -1 the strength is a function of strain rate and temperature, is thermally activated and governed by the stress-assisted thermal activation of dislocations across short-range barriers in the crystal. At very high strain rates however the behaviour is controlled by interaction of dislocations with either phonons or electrons, giving a strength proportional to strain rate. The compressive strength of small clear samples of wood, Pinus radiata and Kahikatea, determined over the strain rate range 10 -3 s -1 to 10 3 s -1 as a function of strain rate, temperature and moisture content shows the behaviour to again be thermally activated with the strength a function of stain rate, temperature and moisture content. A rate theory of deformation is developed where the yield behaviour of wood is assumed to result from the stress-assisted thermally activated motion of elementary fibrils over short-range barriers. The moisture is assumed to affect the bond energy between elementary fibrils and the barrier energy is taken to be a linear decreasing function of increasing moisture content and the moisture to act like a plasticiser in separating the elementary fibrils. The theory more than adequately explains the observed behaviour.

The Application of Structural Equation Modeling to Maternal Ratings of Twins' Behavior and Emotional Problems.

Science.gov (United States)

Silberg, Judy L.; And Others

1994-01-01

Applied structural equation modeling to twin data to assess impact of genetic and environmental factors on children's behavioral and emotional functioning. Applied models to maternal ratings of behavior of 515 monozygotic and 749 dizygotic twin pairs. Importance of genetic, shared, and specific environmental factors for explaining variation was…

Non-equilibrium effects upon the non-Markovian Caldeira-Leggett quantum master equation

International Nuclear Information System (INIS)

Bolivar, A.O.

2011-01-01

Highlights: → Classical Brownian motion described by a non-Markovian Fokker-Planck equation. → Quantization process. → Quantum Brownian motion described by a non-Markovian Caldeira-Leggett equation. → A non-equilibrium quantum thermal force is predicted. - Abstract: We obtain a non-Markovian quantum master equation directly from the quantization of a non-Markovian Fokker-Planck equation describing the Brownian motion of a particle immersed in a generic environment (e.g. a non-thermal fluid). As far as the especial case of a heat bath comprising of quantum harmonic oscillators is concerned, we derive a non-Markovian Caldeira-Leggett master equation on the basis of which we work out the concept of non-equilibrium quantum thermal force exerted by the harmonic heat bath upon the Brownian motion of a free particle. The classical limit (or dequantization process) of this sort of non-equilibrium quantum effect is scrutinized, as well.

Heat transport in two-dimensional materials by directly solving the phonon Boltzmann equation under Callaway's dual relaxation model

Science.gov (United States)

Guo, Yangyu; Wang, Moran

2017-10-01

The single mode relaxation time approximation has been demonstrated to greatly underestimate the lattice thermal conductivity of two-dimensional materials due to the collective effect of phonon normal scattering. Callaway's dual relaxation model represents a good approximation to the otherwise ab initio solution of the phonon Boltzmann equation. In this work we develop a discrete-ordinate-method (DOM) scheme for the numerical solution of the phonon Boltzmann equation under Callaway's model. Heat transport in a graphene ribbon with different geometries is modeled by our scheme, which produces results quite consistent with the available molecular dynamics, Monte Carlo simulations, and experimental measurements. Callaway's lattice thermal conductivity model with empirical boundary scattering rates is examined and shown to overestimate or underestimate the direct DOM solution. The length convergence of the lattice thermal conductivity of a rectangular graphene ribbon is explored and found to depend appreciably on the ribbon width, with a semiquantitative correlation provided between the convergence length and the width. Finally, we predict the existence of a phonon Knudsen minimum in a graphene ribbon only at a low system temperature and isotope concentration so that the average normal scattering rate is two orders of magnitude stronger than the intrinsic resistive one. The present work will promote not only the methodology for the solution of the phonon Boltzmann equation but also the theoretical modeling and experimental detection of hydrodynamic phonon transport in two-dimensional materials.

The modified CKD-EPI equation may be not more accurate than CKD-EPI equation in determining glomerular filtration rate in Chinese patients with chronic kidney disease.

Science.gov (United States)

Xie, Peng; Huang, Jian-Min; Li, Ying; Liu, Huai-Jun; Qu, Yan

2017-06-01

To investigate the application of the new modified Chronic Kidney Disease Epidemiology Collaboration (mCKD-EPI) equation developed by Liu for the measurement of glomerular filtration rate (GFR) in Chinese patients with chronic kidney disease (CKD) and to evaluate whether this modified form is more accurate than the original one in clinical practice. GFR was determined simultaneously by 3 methods: (a) 99m Tc-diethylene triamine pentaacetic acid ( 99m Tc-DTPA) dual plasma sample clearance method (mGFR), which was used as the reference standard; (b) CKD-EPI equation (eGFRckdepi); (c) modified CKD-EPI equation (eGFRmodified). Concordance correlation and Passing-Bablok regression were used to compare the validity of eGFRckdepi and eGFRmodified. Bias, precision and accuracy were compared to identify which equation showed the better performance in determining GFR. A total of 170 patients were enrolled. Both eGFRckdepi and eGFRmodified correlated well with mGFR (concordance correlation coefficient 0.90 and 0.74, respectively) and the Passing-Bablok regression equation of eGFRckdepi and eGFRmodified against mGFR was mGFR = 0.37 + 1.04 eGFRckdepi and -49.25 + 1.74 eGFRmodified, respectively. In terms of bias, precision and 30 % accuracy, eGFRmodified showed a worse performance compared to eGFRckdepi, in the whole cohort. The new modified CKD-EPI equation cannot replace the original CKD-EPI equation in determining GFR in Chinese patients with CKD.

Tracer kinetics: Modelling by partial differential equations of inhomogeneous compartments with age-dependent elimination rates. Pt. 1

International Nuclear Information System (INIS)

Winkler, E.

1991-01-01

Mathematical models in tracer kinetics are usually based on ordinary differential equations which correspond to a system of kinetically homogeneous compartments (standard compartments). A generalization is possible by the admission of inhomogeneities in the behaviour of the elements belonging to a compartment. The important special case of the age-dependence of elimination rates is treated in its deterministic version. It leads to partial different equations (i.e., systems with distributed coefficients) with the 'age' or the 'residence time' of an element of the compartment as a variable additional to 'time'. The basic equations for one generalized compartment and for systems of such compartments are given together with their general solutions. (orig.) [de

Computing generalized Langevin equations and generalized Fokker-Planck equations.

Science.gov (United States)

Darve, Eric; Solomon, Jose; Kia, Amirali

2009-07-07

The Mori-Zwanzig formalism is an effective tool to derive differential equations describing the evolution of a small number of resolved variables. In this paper we present its application to the derivation of generalized Langevin equations and generalized non-Markovian Fokker-Planck equations. We show how long time scales rates and metastable basins can be extracted from these equations. Numerical algorithms are proposed to discretize these equations. An important aspect is the numerical solution of the orthogonal dynamics equation which is a partial differential equation in a high dimensional space. We propose efficient numerical methods to solve this orthogonal dynamics equation. In addition, we present a projection formalism of the Mori-Zwanzig type that is applicable to discrete maps. Numerical applications are presented from the field of Hamiltonian systems.

Comparing the measured basal metabolic rates in patients with chronic disorders of consciousness to the estimated basal metabolic rate calculated from common predictive equations.

Science.gov (United States)

Xiao, Guizhen; Xie, Qiuyou; He, Yanbin; Wang, Ziwen; Chen, Yan; Jiang, Mengliu; Ni, Xiaoxiao; Wang, Qinxian; Murong, Min; Guo, Yequn; Qiu, Xiaowen; Yu, Ronghao

2017-10-01

Accurately predicting the basal metabolic rate (BMR) of patients in a vegetative state (VS) or minimally conscious state (MCS) is critical to proper nutritional therapy, but commonly used equations have not been shown to be accurate. Therefore, we compared the BMR measured by indirect calorimetry (IC) to BMR values estimated using common predictive equations in VS and MCS patients. Body composition variables were measured using the bioelectric impedance analysis (BIA) technique. BMR was measured by IC in 82 patients (64 men and 18 women) with VS or MCS. Patients were classified by body mass index as underweight (BMR was estimated for each group using the Harris-Benedict (H-B), Schofield, or Cunningham equations and compared to the measured BMR using Bland-Altman analyses. For the underweight group, there was a significant difference between the measured BMR values and the estimated BMR values calculated using the H-B, Schofield, and Cunningham equations (p BMR values estimated using the H-B and Cunningham equations were different significantly from the measured BMR (p BMR in the normal-weight group. The Schofield equation showed the best concordance (only 41.5%) with the BMR values measured by IC. None of the commonly used equations to estimate BMR were suitable for the VS or MCS populations. Indirect calorimetry is the preferred way to avoid either over or underestimate of BMR values. Copyright © 2016. Published by Elsevier Ltd.

Tap density equations of granular powders based on the rate process theory and the free volume concept.

Science.gov (United States)

Hao, Tian

2015-02-28

The tap density of a granular powder is often linked to the flowability via the Carr index that measures how tight a powder can be packed, under an assumption that more easily packed powders usually flow poorly. Understanding how particles are packed is important for revealing why a powder flows better than others. There are two types of empirical equations that were proposed to fit the experimental data of packing fractions vs. numbers of taps in the literature: the inverse logarithmic and the stretched exponential. Using the rate process theory and the free volume concept under the assumption that particles will obey similar thermodynamic laws during the tapping process if the "granular temperature" is defined in a different way, we obtain the tap density equations, and they are reducible to the two empirical equations currently widely used in literature. Our equations could potentially fit experimental data better with an additional adjustable parameter. The tapping amplitude and frequency, the weight of the granular materials, and the environmental temperature are grouped into this parameter that weighs the pace of the packing process. The current results, in conjunction with our previous findings, may imply that both "dry" (granular) and "wet" (colloidal and polymeric) particle systems are governed by the same physical mechanisms in term of the role of the free volume and how particles behave (a rate controlled process).

Quantum decoherence in electronic current flowing through carbon nanotubes induced by thermal atomic vibrations

Science.gov (United States)

Ishizeki, Keisuke; Sasaoka, Kenji; Konabe, Satoru; Souma, Satofumi; Yamamoto, Takahiro

2018-06-01

We theoretically investigate quantum decoherence in electronic currents flowing through metallic carbon nanotubes caused by thermal atomic vibrations using the time-dependent Schrödinger equation for an open system. We reveal that the quantum coherence of conduction electrons decays exponentially with tube length at a fixed temperature, and that the decay rate increases with temperature. We also find that the phase relaxation length due to the thermal atomic vibrations is inversely proportional to temperature.

Thermal degradation of deoxynivalenol during maize bread baking.

Science.gov (United States)

Numanoglu, E; Gökmen, V; Uygun, U; Koksel, H

2012-01-01

The thermal degradation of deoxynivalenol (DON) was determined at isothermal baking conditions within the temperature range of 100-250°C, using a crust-like model, which was prepared with naturally contaminated maize flour. No degradation was observed at 100°C. For the temperatures of 150, 200 and 250°C, thermal degradation rate constants (k) were calculated and temperature dependence of DON degradation was observed by using Arrhenius equation. The degradation of DON obeyed Arrhenius law with a regression coefficient of 0.95. A classical bread baking operation was also performed at 250°C for 70 min and the rate of DON degradation in the bread was estimated by using the kinetic data derived from the model study. The crust and crumb temperatures recorded during bread baking were used to calculate the thermal degradation rate constants (k) and partial DON degradations at certain time intervals. Using these data, total degradation at the end of the entire baking process was predicted for both crust and crumb. This DON degradation was consistent with the experimental degradation data, confirming the accuracy of kinetic constants determined by means of the crust-like model.

Micromagnetic simulation of thermally activated switching in fine particles

International Nuclear Information System (INIS)

Scholz, Werner; Schrefl, Thomas; Fidler, J.

2001-01-01

Effects of thermal activation are included in micromagnetic simulations by adding a random thermal field to the effective magnetic field. As a result, the Landau-Lifshitz equation is converted into a stochastic differential equation of Langevin type with multiplicative noise. The Stratonovich interpretation of the stochastic Landau-Lifshitz equation leads to the correct thermal equilibrium properties. The proper generalization of Taylor expansions to stochastic calculus gives suitable time integration schemes. For a single rigid magnetic moment the thermal equilibrium properties are investigated. It is found, that the Heun scheme is a good compromise between numerical stability and computational complexity. Small cubic and spherical ferromagnetic particles are studied

Behavior of quenched and tempered steels under high strain rate compression loading

International Nuclear Information System (INIS)

Meyer, L.W.; Seifert, K.; Abdel-Malek, S.

1997-01-01

Two quenched and tempered steels were tested under compression loading at strain rates of ε = 2.10 2 s -1 and ε = 2.10 3 s -1 . By applying the thermal activation theory, the flow stress at very high strain rates of 10 5 to 10 6 s -1 is derived from low temperature and high strain rate tests. Dynamic true stress - true strain behaviour presents, that stress increases with increasing strain until a maximum, then it decreases. Because of the adiabatic process under dynamic loading the maximum flow stress will occur at a lower strain if the strain rate is increased. Considering strain rate, strain hardening, strain rate hardening and strain softening, a constitutive equation with different additive terms is successfully used to describe the behaviour of material under dynamic compression loading. Results are compared with other models of constitutive equations. (orig.)

Tracer kinetics: Modelling by partial differential equations of inhomogeneous compartments with age-dependent elimination rates. Pt. 2

International Nuclear Information System (INIS)

Winkler, E.

1991-01-01

The general theory of inhomogeneous compartments with age-dependent elimination rates is illustrated by examples. Mathematically, it turns out that models consisting of partial differential equations include ordinary, delayed and integro-differential equations, a general fact which is treated here in the context of linear tracer kinetics. The examples include standard compartments as a degenerate case, systems of standard compartments (compartment blocks), models resulting in special residence time distributions, models with pipes, and systems with heterogeneous particles. (orig./BBR) [de

Coupled energy-drift and force-balance equations for high-field hot-carrier transport

International Nuclear Information System (INIS)

Huang, Danhong; Alsing, P.M.; Apostolova, T.; Cardimona, D.A.

2005-01-01

Coupled energy-drift and force-balance equations that contain a frictional force for the center-of-mass motion of electrons are derived for hot-electron transport under a strong dc electric field. The frictional force is found to be related to the net rate of phonon emission, which takes away the momentum of a phonon from an electron during each phonon-emission event. The net rate of phonon emission is determined by the Boltzmann scattering equation, which depends on the distribution of electrons interacting with phonons. The work done by the frictional force is included into the energy-drift equation for the electron-relative scattering motion and is found to increase the thermal energy of the electrons. The importance of the hot-electron effect in the energy-drift term under a strong dc field is demonstrated in reducing the field-dependent drift velocity and mobility. The Doppler shift in the energy conservation of scattering electrons interacting with impurities and phonons is found to lead to an anisotropic distribution of electrons in the momentum space along the field direction. The importance of this anisotropic distribution is demonstrated through a comparison with the isotropic energy-balance equation, from which we find that defining a state-independent electron temperature becomes impossible. To the leading order, the energy-drift equation is linearized with a distribution function by expanding it into a Fokker-Planck-type equation, along with the expansions of both the force-balance equation and the Boltzmann scattering equation for hot phonons

Thermal stratification effects on MHD radiative flow of nanofluid over nonlinear stretching sheet with variable thickness

Directory of Open Access Journals (Sweden)

Yahaya Shagaiya Daniel

2018-04-01

Full Text Available The combined effects of thermal stratification, applied electric and magnetic fields, thermal radiation, viscous dissipation and Joules heating are numerically studied on a boundary layer flow of electrical conducting nanofluid over a nonlinearly stretching sheet with variable thickness. The governing equations which are partial differential equations are converted to a couple of ordinary differential equations with suitable similarity transformation techniques and are solved using implicit finite difference scheme. The electrical conducting nanofluid particle fraction on the boundary is passively rather than actively controlled. The effects of the emerging parameters on the electrical conducting nanofluid velocity, temperature, and nanoparticles concentration volume fraction with skin friction, heat transfer characteristics are examined with the aids of graphs and tabular form. It is observed that the variable thickness enhances the fluid velocity, temperature, and nanoparticle concentration volume fraction. The heat and mass transfer rate at the surface increases with thermal stratification resulting to a reduction in the fluid temperature. Electric field enhances the nanofluid velocity which resolved the sticking effects caused by a magnetic field which suppressed the profiles. Radiative heat transfer and viscous dissipation are sensitive to an increase in the fluid temperature and thicker thermal boundary layer thickness. Comparison with published results is examined and presented. Keywords: MHD nanofluid, Variable thickness, Thermal radiation, Similarity solution, Thermal stratification

A Modified Eyring Equation for Modeling Yield and Flow Stresses of Metals at Strain Rates Ranging from 10−5 to 5 × 104 s−1

Directory of Open Access Journals (Sweden)

Ramzi Othman

2015-01-01

Full Text Available In several industrial applications, metallic structures are facing impact loads. Therefore, there is an important need for developing constitutive equations which take into account the strain rate sensitivity of their mechanical properties. The Johnson-Cook equation was widely used to model the strain rate sensitivity of metals. However, it implies that the yield and flow stresses are linearly increasing in terms of the logarithm of strain rate. This is only true up to a threshold strain rate. In this work, a three-constant constitutive equation, assuming an apparent activation volume which decreases as the strain rate increases, is applied here for some metals. It is shown that this equation fits well the experimental yield and flow stresses for a very wide range of strain rates, including quasi-static, high, and very high strain rates (from 10−5 to 5 × 104 s−1. This is the first time that a constitutive equation is showed to be able to fit the yield stress over a so large strain rate range while using only three material constants.

Nonlinear coupled equations for electrochemical cells as developed by the general equation for nonequilibrium reversible-irreversible coupling.

Science.gov (United States)

Bedeaux, Dick; Kjelstrup, Signe; Öttinger, Hans Christian

2014-09-28

We show how the Butler-Volmer and Nernst equations, as well as Peltier effects, are contained in the general equation for nonequilibrium reversible and irreversible coupling, GENERIC, with a unique definition of the overpotential. Linear flux-force relations are used to describe the transport in the homogeneous parts of the electrochemical system. For the electrode interface, we choose nonlinear flux-force relationships. We give the general thermodynamic basis for an example cell with oxygen electrodes and electrolyte from the solid oxide fuel cell. In the example cell, there are two activated chemical steps coupled also to thermal driving forces at the surface. The equilibrium exchange current density obtains contributions from both rate-limiting steps. The measured overpotential is identified at constant temperature and stationary states, in terms of the difference in electrochemical potential of products and reactants. Away from these conditions, new terms appear. The accompanying energy flux out of the surface, as well as the heat generation at the surface are formulated, adding to the general thermodynamic basis.

Nonlinear coupled equations for electrochemical cells as developed by the general equation for nonequilibrium reversible-irreversible coupling

Science.gov (United States)

Bedeaux, Dick; Kjelstrup, Signe; Öttinger, Hans Christian

2014-09-01

We show how the Butler-Volmer and Nernst equations, as well as Peltier effects, are contained in the general equation for nonequilibrium reversible and irreversible coupling, GENERIC, with a unique definition of the overpotential. Linear flux-force relations are used to describe the transport in the homogeneous parts of the electrochemical system. For the electrode interface, we choose nonlinear flux-force relationships. We give the general thermodynamic basis for an example cell with oxygen electrodes and electrolyte from the solid oxide fuel cell. In the example cell, there are two activated chemical steps coupled also to thermal driving forces at the surface. The equilibrium exchange current density obtains contributions from both rate-limiting steps. The measured overpotential is identified at constant temperature and stationary states, in terms of the difference in electrochemical potential of products and reactants. Away from these conditions, new terms appear. The accompanying energy flux out of the surface, as well as the heat generation at the surface are formulated, adding to the general thermodynamic basis.

Thermal conductivity and thermal diffusivity of solid UO2

International Nuclear Information System (INIS)

Fink, J.K.; Chasanov, M.G.; Leibowitz, L.

1981-06-01

New equations for the thermal conductivity of solid UO 2 were derived based upon a nonlinear least squares fit of the data available in the literature. In the development of these equations, consideration was given to their thermodynamic consistency with heat capacity and density and theoretical consistency with enthalpy and heat capacity. Consistent with our previous treatment of enthalpy and heat capacity, 2670 K was selected as the temperature of a phase transition. A nonlinear equation, whose terms represent contributions due to phonons and electrons, was selected for the temperature region below 2670 K. Above 2670 K, the data were fit by a linear equation

Benchmark calculations of thermal reaction rates. I - Quantal scattering theory

Science.gov (United States)

Chatfield, David C.; Truhlar, Donald G.; Schwenke, David W.

1991-01-01

The thermal rate coefficient for the prototype reaction H + H2 yields H2 + H with zero total angular momentum is calculated by summing, averaging, and numerically integrating state-to-state reaction probabilities calculated by time-independent quantum-mechanical scattering theory. The results are very carefully converged with respect to all numerical parameters in order to provide high-precision benchmark results for confirming the accuracy of new methods and testing their efficiency.

Localized states in an unbounded neural field equation with smooth firing rate function: a multi-parameter analysis.

Science.gov (United States)

Faye, Grégory; Rankin, James; Chossat, Pascal

2013-05-01

The existence of spatially localized solutions in neural networks is an important topic in neuroscience as these solutions are considered to characterize working (short-term) memory. We work with an unbounded neural network represented by the neural field equation with smooth firing rate function and a wizard hat spatial connectivity. Noting that stationary solutions of our neural field equation are equivalent to homoclinic orbits in a related fourth order ordinary differential equation, we apply normal form theory for a reversible Hopf bifurcation to prove the existence of localized solutions; further, we present results concerning their stability. Numerical continuation is used to compute branches of localized solution that exhibit snaking-type behaviour. We describe in terms of three parameters the exact regions for which localized solutions persist.

Injection molding of ceramic filled polypropylene: The effect of thermal conductivity and cooling rate on crystallinity

International Nuclear Information System (INIS)

Suplicz, A.; Szabo, F.; Kovacs, J.G.

2013-01-01

Highlights: • BN, talc and TiO 2 in 30 vol% were compounded with polypropylene matrix. • According to the DSC measurements, the fillers are good nucleating agents. • The thermal conductivity of the fillers influences the cooling rate of the melt. • The higher the cooling rate is, the lower the crystallinity in the polymer matrix. - Abstract: Three different nano- and micro-sized ceramic powders (boron-nitride (BN), talc and titanium-dioxide (TiO 2 )) in 30 vol% have been compounded with a polypropylene (PP) matrix. Scanning electron microscopy (SEM) shows that the particles are dispersed smoothly in the matrix and larger aggregates cannot be discovered. The cooling gradients and the cooling rate in the injection-molded samples were estimated with numerical simulations and finite element analysis software. It was proved with differential scanning calorimetry (DSC) measurements that the cooling rate has significant influence on the crystallinity of the compounds. At a low cooling rate BN works as a nucleating agent so the crystallinity of the compound is higher than that of unfilled PP. On the other hand, at a high cooling rate, the crystallinity of the compound is lower than that of unfilled PP because of its higher thermal conductivity. The higher the thermal conductivity is, the higher the real cooling rate in the material, which influences the crystallization kinetics significantly

The Boltzmann equation in the difference formulation

Energy Technology Data Exchange (ETDEWEB)

Szoke, Abraham [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Brooks III, Eugene D. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

2015-05-06

First we recall the assumptions that are needed for the validity of the Boltzmann equation and for the validity of the compressible Euler equations. We then present the difference formulation of these equations and make a connection with the time-honored Chapman - Enskog expansion. We discuss the hydrodynamic limit and calculate the thermal conductivity of a monatomic gas, using a simplified approximation for the collision term. Our formulation is more consistent and simpler than the traditional derivation.

Simplified equations for transient heat transfer problems at low Fourier numbers

DEFF Research Database (Denmark)

Christensen, Martin Gram; Adler-Nissen, Jens

2015-01-01

and validated for infinite slabs, infinite cylinders and spheres and by an industrial application example, covering the center temperature and the volume average temperature. The approach takes ground in the residual difference between a 1 term series solution and a 100 term solution to the Fourier equation...... of the thermal response for solids subjected to convective heat transfer. By representing the residual thermal response as a function of the Biot number and the first eigenvalue, the new approach enables the description of the thermal response in the whole Fourier regime. The presented equation is simple...

An estimation of reactor thermal power uncertainty using UFM-based feedwater flow rate in nuclear power plants

International Nuclear Information System (INIS)

Byung Ryul Jung; Ho Cheol Jang; Byung Jin Lee; Se Jin Baik; Woo Hyun Jang

2005-01-01

Most of Pressurized Water Reactors (PWRs) utilize the venturi meters (VMs) to measure the feedwater (FW) flow rate to the steam generator in the calorimetric measurement, which is used in the reactor thermal power (RTP) estimation. However, measurement drifts have been experienced due to some anomalies on the venturi meter (generally called the venturi meter fouling). The VM's fouling tends to increase the measured pressure drop across the meter, which results in indication of increased feedwater flow rate. Finally, the reactor thermal power is overestimated and the actual reactor power is to be reduced to remain within the regulatory limits. To overcome this VM's fouling problem, the Ultrasonic Flow Meter (UFM) has recently been gaining attention in the measurement of the feedwater flow rate. This paper presents the applicability of a UFM based feedwater flow rate in the estimation of reactor thermal power uncertainty. The FW and RTP uncertainties are compared in terms of sensitivities between the VM- and UFM-based feedwater flow rates. Data from typical Optimized Power Reactor 1000 (OPR1000) plants are used to estimate the uncertainty. (authors)

Splitting of the rate matrix as a definition of time reversal in master equation systems

International Nuclear Information System (INIS)

Liu Fei; Le, Hong

2012-01-01

Motivated by recent progress in nonequilibrium fluctuation relations, we present a generalized time reversal for stochastic master equation systems with discrete states, which is defined as a splitting of the rate matrix into irreversible and reversible parts. An immediate advantage of this definition is that a variety of fluctuation relations can be attributed to different matrix splittings. Additionally, we find that the accustomed total entropy production formula and conditions of the detailed balance must be modified appropriately to account for the reversible rate part, which was previously ignored. (paper)

Stochastic porous media equations

CERN Document Server

Barbu, Viorel; Röckner, Michael

2016-01-01

Focusing on stochastic porous media equations, this book places an emphasis on existence theorems, asymptotic behavior and ergodic properties of the associated transition semigroup. Stochastic perturbations of the porous media equation have reviously been considered by physicists, but rigorous mathematical existence results have only recently been found. The porous media equation models a number of different physical phenomena, including the flow of an ideal gas and the diffusion of a compressible fluid through porous media, and also thermal propagation in plasma and plasma radiation. Another important application is to a model of the standard self-organized criticality process, called the "sand-pile model" or the "Bak-Tang-Wiesenfeld model". The book will be of interest to PhD students and researchers in mathematics, physics and biology.

Thermal Analysis On The Kinetics Of Magnesium-Aluminum Layered Double Hydroxides In Different Heating Rates

Directory of Open Access Journals (Sweden)

Hongbo Y.

2015-06-01

Full Text Available The thermal decomposition of magnesium-aluminum layered double hydroxides (LDHs was investigated by thermogravimetry analysis and differential scanning calorimetry (DSC methods in argon environment. The influence of heating rates (including 2.5, 5, 10, 15 and 20K/min on the thermal behavior of LDHs was revealed. By the methods of Kissinger and Flynn-Wall-Ozawa, the thermal kinetic parameters of activation energy and pre-exponential factor for the exothermic processes under non-isothermal conditions were calculated using the analysis of corresponding DSC curves.

Thermal behaviour of solar air heater with compound parabolic concentrator

International Nuclear Information System (INIS)

Tchinda, Rene

2008-01-01

A mathematical model for computing the thermal performance of an air heater with a truncated compound parabolic concentrator having a flat one-sided absorber is presented. A computer code that employs an iterative solution procedure is constructed to solve the governing energy equations and to estimate the performance parameters of the collector. The effects of the air mass flow rate, the wind speed and the collector length on the thermal performance of the present air heater are investigated. Predictions for the performance of the solar heater also exhibit reasonable agreement, with experimental data with an average error of 7%

Experimental study of the surface thermal signature of gravity currents: application to the assessment of lava flow effusion rate

Science.gov (United States)

Garel, F.; Kaminski, E.; Tait, S.; Limare, A.

2011-12-01

During an effusive volcanic eruption, the crisis management is mainly based on the prediction of lava flows advance and its velocity. As the spreading of lava flows is mainly controlled by its rheology and the eruptive mass flux, the key question is how to evaluate them during the eruption (rather than afterwards.) A relationship between the heat flux lost by the lava at its surface and the eruption rate is likely to exist, based on the first-order argument that higher eruption rates should correspond to larger power radiated by a lava flow. The semi-empirical formula developed by Harris and co-workers (e.g. Harris et al., Bull. Volc. 2007) is currently used to estimate lava flow rate from satellite surveys yielding the surface temperatures and area of the lava flow field. However, this approach is derived from a static thermal budget of the lava flow and does not explicitly model the time-evolution of the surface thermal signal. Here we propose laboratory experiments and theoretical studies of the cooling of a viscous axisymmetric gravity current fed at constant flux rate. We first consider the isoviscous case, for which the spreading is well-know. The experiments using silicon oil and the theoretical model both reveal the establishment of a steady surface thermal structure after a transient time. The steady state is a balance between surface cooling and heat advection in the flow. The radiated heat flux in the steady regime, a few days for a basaltic lava flow, depends mainly on the effusion rate rather than on the viscosity. In this regime, one thermal survey of the radiated power could provide a consistent estimate of the flow rate if the external cooling conditions (wind) are reasonably well constrained. We continue to investigate the relationship between the thermal radiated heat flux and the effusion rate by using in the experiments fluids with temperature-dependent viscosity (glucose syrup) or undergoing solidification while cooling (PEG wax). We observe a

Thermal-mechanical deformation modelling of soft tissues for thermal ablation.

Science.gov (United States)

Li, Xin; Zhong, Yongmin; Jazar, Reza; Subic, Aleksandar

2014-01-01

Modeling of thermal-induced mechanical behaviors of soft tissues is of great importance for thermal ablation. This paper presents a method by integrating the heating process with thermal-induced mechanical deformations of soft tissues for simulation and analysis of the thermal ablation process. This method combines bio-heat transfer theories, constitutive elastic material law under thermal loads as well as non-rigid motion dynamics to predict and analyze thermal-mechanical deformations of soft tissues. The 3D governing equations of thermal-mechanical soft tissue deformation are discretized by using the finite difference scheme and are subsequently solved by numerical algorithms. Experimental results show that the proposed method can effectively predict the thermal-induced mechanical behaviors of soft tissues, and can be used for the thermal ablation therapy to effectively control the delivered heat energy for cancer treatment.

Exact evaluation of the rates of electrostatic decay and scattering off thermal ions for an unmagnetized Maxwellian plasma

Energy Technology Data Exchange (ETDEWEB)

Layden, B.; Cairns, Iver H.; Robinson, P. A. [School of Physics, University of Sydney, Sydney, NSW 2006 (Australia)

2013-08-15

Electrostatic decay of Langmuir waves into Langmuir and ion sound waves (L→L′+S) and scattering of Langmuir waves off thermal ions (L+i→L′+i′, also called “nonlinear Landau damping”) are important nonlinear weak-turbulence processes. The rates for these processes depend on the quadratic longitudinal response function α{sup (2)} (or, equivalently, the quadratic longitudinal susceptibility χ{sup (2)}), which describes the second-order response of a plasma to electrostatic wave fields. Previous calculations of these rates for an unmagnetized Maxwellian plasma have relied upon an approximate form for α{sup (2)} that is valid where two of the wave fields are fast (i.e., v{sub φ}=ω/k≫V{sub e} where ω is the angular frequency, k is the wavenumber, and V{sub e} is the electron thermal speed) and one is slow (v{sub φ}≪V{sub e}). Recently, an exact expression was derived for α{sup (2)} that is valid for any phase speeds of the three waves in an unmagnetized Maxwellian plasma. Here, this exact α{sup (2)} is applied to the calculation of the three-dimensional rates for electrostatic decay and scattering off thermal ions, and the resulting exact rates are compared with the approximate rates. The calculations are performed using previously derived three-dimensional rates for electrostatic decay given in terms of a general α{sup (2)}, and newly derived three-dimensional rates for scattering off thermal ions; the scattering rate is derived assuming a Maxwellian ion distribution, and both rates are derived assuming arc distributions for the wave spectra. For most space plasma conditions, the approximate rate is found to be accurate to better than 20%; however, for sufficiently low Langmuir phase speeds (v{sub φ}/V{sub e}≈3) appropriate to some spatial domains of the foreshock regions of planetary bow shocks and type II solar radio bursts, the use of the exact rate may be necessary for accurate calculations. The relative rates of electrostatic decay

BREIT code: Analytical solution of the balance rate equations for charge-state evolutions of heavy-ion beams in matter

Energy Technology Data Exchange (ETDEWEB)

Winckler, N., E-mail: n.winckler@gsi.de [GSI Helmholtzzentrum für Schwerionenforschung GmbH, 64291 Darmstadt (Germany); Rybalchenko, A. [GSI Helmholtzzentrum für Schwerionenforschung GmbH, 64291 Darmstadt (Germany); Shevelko, V.P. [P.N. Lebedev Physical Institute, 119991 Moscow (Russian Federation); Al-Turany, M. [GSI Helmholtzzentrum für Schwerionenforschung GmbH, 64291 Darmstadt (Germany); CERN, European Organization for Nuclear Research, 1211 Geneve 23 (Switzerland); Kollegger, T. [GSI Helmholtzzentrum für Schwerionenforschung GmbH, 64291 Darmstadt (Germany); Stöhlker, Th. [GSI Helmholtzzentrum für Schwerionenforschung GmbH, 64291 Darmstadt (Germany); Helmholtz-Institute Jena, D-07743 Jena (Germany); Institut für Optik und Quantenelektronik, Friedrich-Schiller-Universität, D-07743 Jena (Germany)

2017-02-01

A detailed description of a recently developed BREIT computer code (Balance Rate Equations of Ion Transportation) for calculating charge-state fractions of ion beams passing through matter is presented. The code is based on the analytical solutions of the differential balance equations for the charge-state fractions as a function of the target thickness and can be used for calculating the ion evolutions in gaseous, solid and plasma targets. The BREIT code is available on-line and requires the charge-changing cross sections and initial conditions in the input file. The eigenvalue decomposition method, applied to obtain the analytical solutions of the rate equations, is described in the paper. Calculations of non-equilibrium and equilibrium charge-state fractions, performed by the BREIT code, are compared with experimental data and results of other codes for ion beams in gaseous and solid targets. Ability and limitations of the BREIT code are discussed in detail.

Cancellation of infrared and mass singularities in the thermal di-lepton rate

International Nuclear Information System (INIS)

Altherr, T.; Becherrawy, T.

1989-03-01

We give a rigorous proof that, at first order in α s , the thermal di-lepton rate is free of infrared and mass singularities. The calculation is performed for massive quarks in the real-time formalism with the n-dimensional regularization scheme. The cancellation is shown to occur within each topology

Nanoscale thermal transport

Science.gov (United States)

Cahill, David G.; Ford, Wayne K.; Goodson, Kenneth E.; Mahan, Gerald D.; Majumdar, Arun; Maris, Humphrey J.; Merlin, Roberto; Phillpot, Simon R.

2003-01-01

Rapid progress in the synthesis and processing of materials with structure on nanometer length scales has created a demand for greater scientific understanding of thermal transport in nanoscale devices, individual nanostructures, and nanostructured materials. This review emphasizes developments in experiment, theory, and computation that have occurred in the past ten years and summarizes the present status of the field. Interfaces between materials become increasingly important on small length scales. The thermal conductance of many solid-solid interfaces have been studied experimentally but the range of observed interface properties is much smaller than predicted by simple theory. Classical molecular dynamics simulations are emerging as a powerful tool for calculations of thermal conductance and phonon scattering, and may provide for a lively interplay of experiment and theory in the near term. Fundamental issues remain concerning the correct definitions of temperature in nonequilibrium nanoscale systems. Modern Si microelectronics are now firmly in the nanoscale regime—experiments have demonstrated that the close proximity of interfaces and the extremely small volume of heat dissipation strongly modifies thermal transport, thereby aggravating problems of thermal management. Microelectronic devices are too large to yield to atomic-level simulation in the foreseeable future and, therefore, calculations of thermal transport must rely on solutions of the Boltzmann transport equation; microscopic phonon scattering rates needed for predictive models are, even for Si, poorly known. Low-dimensional nanostructures, such as carbon nanotubes, are predicted to have novel transport properties; the first quantitative experiments of the thermal conductivity of nanotubes have recently been achieved using microfabricated measurement systems. Nanoscale porosity decreases the permittivity of amorphous dielectrics but porosity also strongly decreases the thermal conductivity. The

A fast iterative scheme for the linearized Boltzmann equation

Science.gov (United States)

Wu, Lei; Zhang, Jun; Liu, Haihu; Zhang, Yonghao; Reese, Jason M.

2017-06-01

Iterative schemes to find steady-state solutions to the Boltzmann equation are efficient for highly rarefied gas flows, but can be very slow to converge in the near-continuum flow regime. In this paper, a synthetic iterative scheme is developed to speed up the solution of the linearized Boltzmann equation by penalizing the collision operator L into the form L = (L + Nδh) - Nδh, where δ is the gas rarefaction parameter, h is the velocity distribution function, and N is a tuning parameter controlling the convergence rate. The velocity distribution function is first solved by the conventional iterative scheme, then it is corrected such that the macroscopic flow velocity is governed by a diffusion-type equation that is asymptotic-preserving into the Navier-Stokes limit. The efficiency of this new scheme is assessed by calculating the eigenvalue of the iteration, as well as solving for Poiseuille and thermal transpiration flows. We find that the fastest convergence of our synthetic scheme for the linearized Boltzmann equation is achieved when Nδ is close to the average collision frequency. The synthetic iterative scheme is significantly faster than the conventional iterative scheme in both the transition and the near-continuum gas flow regimes. Moreover, due to its asymptotic-preserving properties, the synthetic iterative scheme does not need high spatial resolution in the near-continuum flow regime, which makes it even faster than the conventional iterative scheme. Using this synthetic scheme, with the fast spectral approximation of the linearized Boltzmann collision operator, Poiseuille and thermal transpiration flows between two parallel plates, through channels of circular/rectangular cross sections and various porous media are calculated over the whole range of gas rarefaction. Finally, the flow of a Ne-Ar gas mixture is solved based on the linearized Boltzmann equation with the Lennard-Jones intermolecular potential for the first time, and the difference

Formal derivation of a 6 equation macro scale model for two-phase flows - link with the 4 equation macro scale model implemented in Flica 4; Etablissement formel d'un modele diphasique macroscopique a 6 equations - lien avec le modele macroscopique a 4 equations flica 4

Energy Technology Data Exchange (ETDEWEB)

Gregoire, O

2008-07-01

In order to simulate nuclear reactor cores, we presently use the 4 equation model implemented within FLICA4 code. This model is complemented with 2 algebraic closures for thermal disequilibrium and relative velocity between phases. Using such closures, means an 'a priori' knowledge of flows calculated in order to ensure that modelling assumptions apply. In order to improve the degree of universality to our macroscopic modelling, we propose in the report to derive a more general 6 equation model (balance equations for mass, momentum and enthalpy for each phase) for 2-phase flows. We apply the up-scaling procedure (Whitaker, 1999) classically used in porous media analysis to the statistically averaged equations (Aniel-Buchheit et al., 2003). By doing this, we apply the double-averaging procedure (Pedras and De Lemos, 2001 and Pinson et al. 2006): statistical and spatial averages. Then, using weighted averages (analogous to Favre's average) we extend the spatial averaging concept to variable density and 2-phase flows. This approach allows the global recovering of the structure of the systems of equations implemented in industrial codes. Supplementary contributions, such as dispersion, are also highlighted. Mechanical and thermal exchanges between solids and fluid are formally derived. Then, thanks to realistic simplifying assumptions, we show how it is possible to derive the original 4 equation model from the full 6 equation model. (author)

Using random walk in models specified by stochastic differential equations to determine the best expression for the bacterial growth rate

DEFF Research Database (Denmark)

method allows us to develop a new expression for the growth rate. The method is based on the stochastic continuous-discrete time state-space model, with a continuous-time state equation (a stochastic differential equation, SDE) combined with a discrete-time measurement equation. In our study the SDE...... described by Kristensen et. al [2]. The resulting time series allows us graphically to inspect the functional dependence of the growth rate on the substrate content. From the method described above we find three new plausible expressions for μ(S). Therefore we apply the likelihood-ratio test to compare...... for the Monod expression. Thus, the method was applied to successfully determine a significant better expression for the substrate dependent growth expression, and we find the method generally applicable for model development. References [1] Kristensen NR, Madsen H, Jørgensen, SB (2004) A method for systematic...

Response, thermal regulatory threshold and thermal breakdown threshold of restrained RF-exposed mice at 905 MHz

Energy Technology Data Exchange (ETDEWEB)

Ebert, S [Swiss Federal Institute of Technology (ETH), Zurich, 8092 Zurich (Switzerland); Eom, S J [Swiss Federal Institute of Technology (ETH), Zurich, 8092 Zurich (Switzerland); Schuderer, J [Foundation for Research on Information Technologies in Society (IT' IS), Zeughausstrasse 43, 8004 Zurich (Switzerland); Apostel, U [Fraunhofer Institute for Toxicology and Experimental Medicine, Nicolai-Fuchs-Strasse 1, 30625 Hannover (Germany); Tillmann, T [Fraunhofer Institute for Toxicology and Experimental Medicine, Nicolai-Fuchs-Strasse 1, 30625 Hannover (Germany); Dasenbrock, C [Fraunhofer Institute for Toxicology and Experimental Medicine, Nicolai-Fuchs-Strasse 1, 30625 Hannover (Germany); Kuster, N [Swiss Federal Institute of Technology (ETH), Zurich, 8092 Zurich (Switzerland)

2005-11-07

The objective of this study was the determination of the thermal regulatory and the thermal breakdown thresholds for in-tube restrained B6C3F1 and NMRI mice exposed to radiofrequency electromagnetic fields at 905 MHz. Different levels of the whole-body averaged specific absorption rate (SAR 0, 2, 5, 7.2, 10, 12.6 and 20 W kg{sup -1}) have been applied to the mice inside the 'Ferris Wheel' exposure setup at 22 {+-} 2 {sup 0}C and 30-70% humidity. The thermal responses were assessed by measurement of the rectal temperature prior, during and after the 2 h exposure session. For B6C3F1 mice, the thermal response was examined for three different weight groups (20 g, 24 g, 29 g), both genders and for pregnant mice. Additionally, NMRI mice with a weight of 36 g were investigated for an interstrain comparison. The thermal regulatory threshold of in-tube restrained mice was found at SAR levels between 2 W kg{sup -1} and 5 W kg{sup -1}, whereas the breakdown of regulation was determined at 10.1 {+-} 4.0 W kg{sup -1}(K = 2) for B6C3F1 mice and 7.7 {+-} 1.6 W kg{sup -1}(K = 2) for NMRI mice. Based on a simplified power balance equation, the thresholds show a clear dependence upon the metabolic rate and weight. NMRI mice were more sensitive to thermal stress and respond at lower SAR values with regulation and breakdown. The presented data suggest that the thermal breakdown for in-tube restrained mice, whole-body exposed to radiofrequency fields, may occur at SAR levels of 6 W kg{sup -1}(K = 2) at laboratory conditions.

Effects of Heating Rate on the Dynamic Tensile Mechanical Properties of Coal Sandstone during Thermal Treatment

Directory of Open Access Journals (Sweden)

Ming Li

2017-01-01

Full Text Available The effects of coal layered combustion and the heat injection rate on adjacent rock were examined in the process of underground coal gasification and coal-bed methane mining. Dynamic Brazilian disk tests were conducted on coal sandstone at 800°C and slow cooling from different heating rates by means of a Split Hopkinson Pressure Bar (SHPB test system. It was discovered that thermal conditions had significant effects on the physical and mechanical properties of the sandstone including longitudinal wave velocity, density, and dynamic linear tensile strength; as the heating rates increased, the thermal expansion of the sandstone was enhanced and the damage degree increased. Compared with sandstone at ambient temperature, the fracture process of heat-treated sandstone was more complicated. After thermal treatment, the specimen had a large crack in the center and cracks on both sides caused by loading; the original cracks grew and mineral particle cracks, internal pore geometry, and other defects gradually appeared. With increasing heating rates, the microscopic fracture mode transformed from ductile fracture to subbrittle fracture. It was concluded that changes in the macroscopic mechanical properties of the sandstone were result from changes in the composition and microstructure.

High strain rates spallation phenomena with relation to the equation of state

International Nuclear Information System (INIS)

Dekel, E.

1997-11-01

Theoretical spall strength, defined as the stress needed to separate a material along a plane surface instantaneously, is one order of magnitude larger then the measured spell strength at strain rates up to 10 6 s -1 . The discrepancy is explained by material initial flaws and cavities which grow and coalesce under stress and weaken the material. Measurements of spall strength of materials shocked by a high power laser shows a rapid increase in the spall strength with the strain rate at strain rates of about 10 7 s -1 . This indicates that the initial flaws does not have time to coalesce and the interatomic forces become dominant. In order to break the material more cavities must be created. This cavities are characterized by the interatomic forces and are created statistically: material under tensile stress is in a metastable condition and due to thermal fluctuations cavities are formed. Cavities larger than a certain critical size grow due to the stress. They grow until the material disintegrates at the spall plane. The theoretical results predict the increase in spall strength at high strain rates, as observed experimentally. (authors)

THERMAL CONSOLIDATION OF LAYERED POROUS HALF-SPACE TO VARIABLE THERMAL LOADING

Institute of Scientific and Technical Information of China (English)

BAI Bing

2006-01-01

An analytical method was derived for the thermal consolidation of layered,saturated porous half-space to variable thermal loading with time. In the coupled governing equations of linear thermoelastic media, the influences of thermo-osmosis effect and thermal filtration effect were introduced. Solutions in Laplace transform space were first obtained and then numerically inverted. The responses of a double-layered porous space subjected to exponential decaying thermal loading were studied. The influences of the differences between the properties of the two layers (e.g., the coefficient of thermal consolidation, elastic modulus) on thermal consolidation were discussed. The studies show that the coupling effects of displacement and stress fields on temperature field can be completely neglected, however, thc thermo-osmosis effect has an obvious influence on thermal responses.

Structural Equation Modeling (SEM) for Satisfaction and Dissatisfaction Ratings; Multiple Group Invariance Analysis across Scales with Different Response Format

Science.gov (United States)

Mazaheri, Mehrdad; Theuns, Peter

2009-01-01

The current study evaluates three hypothesized models on subjective well-being, comprising life domain ratings (LDR), overall satisfaction with life (OSWL), and overall dissatisfaction with life (ODWL), using structural equation modeling (SEM). A sample of 1,310 volunteering students, randomly assigned to six conditions, rated their overall life…

Kinetic equation solution by inverse kinetic method

International Nuclear Information System (INIS)

Salas, G.

1983-01-01

We propose a computer program (CAMU) which permits to solve the inverse kinetic equation. The CAMU code is written in HPL language for a HP 982 A microcomputer with a peripheral interface HP 9876 A ''thermal graphic printer''. The CAMU code solves the inverse kinetic equation by taking as data entry the output of the ionization chambers and integrating the equation with the help of the Simpson method. With this program we calculate the evolution of the reactivity in time for a given disturbance

Asymptotics of steady states of a selection–mutation equation for small mutation rate

KAUST Repository

Calsina, Àngel

2013-12-01

We consider a selection-mutation equation for the density of individuals with respect to a continuous phenotypic evolutionary trait. We assume that the competition term for an individual with a given trait depends on the traits of all the other individuals, therefore giving an infinite-dimensional nonlinearity. Mutations are modelled by means of an integral operator. We prove existence of steady states and show that, when the mutation rate goes to zero, the asymptotic profile of the population is a Cauchy distribution. © Royal Society of Edinburgh 2013.

Asymptotics of steady states of a selection–mutation equation for small mutation rate

KAUST Repository

Calsina, À ngel; Cuadrado, Sí lvia; Desvillettes, Laurent; Raoul, Gaë l

2013-01-01

We consider a selection-mutation equation for the density of individuals with respect to a continuous phenotypic evolutionary trait. We assume that the competition term for an individual with a given trait depends on the traits of all the other individuals, therefore giving an infinite-dimensional nonlinearity. Mutations are modelled by means of an integral operator. We prove existence of steady states and show that, when the mutation rate goes to zero, the asymptotic profile of the population is a Cauchy distribution. © Royal Society of Edinburgh 2013.

Fluctuation and thermal energy balance for drift-wave turbulence

International Nuclear Information System (INIS)

Kim, Chang-Bae; Horton, W.

1990-05-01

Energy conservation for the drift-wave system is shown to be separated into the wave-energy power balance equation and an ambient thermal-energy transport equation containing the anomalous transport fluxes produced by the fluctuations. The wave energy equation relates the wave energy density and wave energy flux to the anomalous transport flux and the dissipation of the fluctuations. The thermal balance equation determines the evolution of the temperature profiles from the divergence of the anomalous heat flux, the collisional heating and cooling mechanisms and the toroidal pumping effect. 16 refs., 1 tab

Fluctuation and thermal energy balance for drift-wave turbulence

International Nuclear Information System (INIS)

Changbae Kim; Horton, W.

1991-01-01

Energy conservation for the drift-wave system is shown to be separated into the wave-energy power balance equation and an ambient thermal-energy transport equation containing the anomalous transport fluxes produced by the fluctuations. The wave energy equation relates the wave energy density and wave energy flux to the anomalous transport flux and the dissipation of the fluctuations. The thermal balance equation determines the evolution of the temperature profiles from the divergence of the anomalous heat flux, the collisional heating and cooling mechanisms and the toroidal pumping effect. (author)

Non-thermal escape rates of atmospheric H and D from Mars using MAVEN data

Science.gov (United States)

Gacesa, M.; Zahnle, K. J.

2017-12-01

Geological evidence suggests that an ocean of liquid water existed on Mars until at least middle to late Noachian era (4.1 to 3.8 Ga) and possibly, at least episodically, as late as Hesperian. Between 67% and 87% of the total primordial amount of water, equal to about 70 to 110 meters equivalent (spread over the entire Mars' surface), is believed to have escape to space, while about 35 meters remains on or beneath the surface as water ice. Establishing better constraints on these numbers and identifying the responsible atmospheric loss processes remains the major objective of NASA's Mars Atmosphere and Volatile EvolutioN (MAVEN) mission. The ratio of atmospheric Deuterium and Hydrogen (D/H) on Mars is one of the best indicators of water loss to space. While majority of H and D escape through thermal Jeans escape, up to 10% of D can escape to space via non-thermal mechanisms, such as collisions with superthermal neutral atoms. In this study, we present new estimates of non-thermal escape rates of light molecules of interest to the water evolution, including H2, HD, OH, and OD, based on recent measurements of atmospheric density and temperature profiles by MAVEN. The escape mechanisms considered include photochemical sources of hot O, as well as collisions with energetic neutral atoms produced in charge-exchange of solar wind ions with atmospheric gases1,2. Energy transport and escape rates are modeled using quantum reactive scattering formalism3 and seasonal variations are illustrated. Finally, a simple estimate of the role of the non-thermal escape mechanisms in previous eras is given. We conclude that D escape rates can be affected by the non-thermal processes with consequences on the estimates of primordial water inventory based on the D/H ratio. [1] N. Lewkow and V. Kharchenko, Astroph. J., 790, 98 (2014) [2] M. Gacesa, N. Lewkow, V. Kharchenko, Icarus 284, 90 (2017) [3] M. Gacesa and V. Kharchenko, Geophys. Res. Lett., 39, L10203 (2012)

Macroscopic balance equations for two-phase flow models

International Nuclear Information System (INIS)

Hughes, E.D.

1979-01-01

The macroscopic, or overall, balance equations of mass, momentum, and energy are derived for a two-fluid model of two-phase flows in complex geometries. These equations provide a base for investigating methods of incorporating improved analysis methods into computer programs, such as RETRAN, which are used for transient and steady-state thermal-hydraulic analyses of nuclear steam supply systems. The equations are derived in a very general manner so that three-dimensional, compressible flows can be analysed. The equations obtained supplement the various partial differential equation two-fluid models of two-phase flow which have recently appeared in the literature. The primary objective of the investigation is the macroscopic balance equations. (Auth.)

Estimating glomerular filtration rate using the new CKD-EPI equation and other equations in patients with autosomal dominant polycystic kidney disease

DEFF Research Database (Denmark)

Orskov, Bjarne; Borresen, Malene L; Feldt-Rasmussen, Bo

2010-01-01

(CKD-EPI) equation, the Cockcroft-Gault equation adjusted for body surface area and the MDRD equation with cystatin C. Performance was evaluated by mean bias, precision and accuracy. RESULTS: The MDRD equation with cystatin C had 97% of GFR estimates within 30% of measured GFR (accuracy). Both the CKD-EPI....... The CKD-EPI or the Cockcroft-Gault equations showed better performance compared to the 4-variable MDRD equation....

Mathematical modeling and the two-phase constitutive equations

International Nuclear Information System (INIS)

Boure, J.A.

1975-01-01

The problems raised by the mathematical modeling of two-phase flows are summarized. The models include several kinds of equations, which cannot be discussed independently, such as the balance equations and the constitutive equations. A review of the various two-phase one-dimensional models proposed to date, and of the constitutive equations they imply, is made. These models are either mixture models or two-fluid models. Due to their potentialities, the two-fluid models are discussed in more detail. To avoid contradictions, the form of the constitutive equations involved in two-fluid models must be sufficiently general. A special form of the two-fluid models, which has particular advantages, is proposed. It involves three mixture balance equations, three balance equations for slip and thermal non-equilibriums, and the necessary constitutive equations [fr

Modification of the Kolmogorov-Johnson-Mehl-Avrami rate equation for non-isothermal experiments and its analytical solution

OpenAIRE

Farjas, Jordi; Roura, Pere

2008-01-01

Avrami's model describes the kinetics of phase transformation under the assumption of spatially random nucleation. In this paper we provide a quasi-exact analytical solution of Avrami's model when the transformation takes place under continuous heating. This solution has been obtained with different activation energies for both nucleation and growth rates. The relation obtained is also a solution of the so-called Kolmogorov-Johnson-Mehl-Avrami transformation rate equation. The corresponding n...

Efficient quantum-classical method for computing thermal rate constant of recombination: application to ozone formation.

Science.gov (United States)

Ivanov, Mikhail V; Babikov, Dmitri

2012-05-14

Efficient method is proposed for computing thermal rate constant of recombination reaction that proceeds according to the energy transfer mechanism, when an energized molecule is formed from reactants first, and is stabilized later by collision with quencher. The mixed quantum-classical theory for the collisional energy transfer and the ro-vibrational energy flow [M. Ivanov and D. Babikov, J. Chem. Phys. 134, 144107 (2011)] is employed to treat the dynamics of molecule + quencher collision. Efficiency is achieved by sampling simultaneously (i) the thermal collision energy, (ii) the impact parameter, and (iii) the incident direction of quencher, as well as (iv) the rotational state of energized molecule. This approach is applied to calculate third-order rate constant of the recombination reaction that forms the (16)O(18)O(16)O isotopomer of ozone. Comparison of the predicted rate vs. experimental result is presented.

Metabolic rate and thermal conductance of lemmings from high-arctic Canada and Siberia

NARCIS (Netherlands)

Klaassen, M.R.J.; Agrell, J.; Lindström, A.

2002-01-01

The arctic climate places high demands on the energy metabolism of its inhabitants. We measured resting (RMR) and basal metabolic rates (BMR), body temperatures, and dry and wet thermal conductances in summer morphs of the lemmings Dicrostonyx groenlandicus and Lemmus trimucronatus in arctic Canada,

Relationship between dynamic infrared thermal images and blood perfusion rate of the tongue in anaemia patients

Science.gov (United States)

Xie, Haiwei; Zhang, Yan

2018-03-01

The relationship between dynamic infrared (IR) thermal images and blood perfusion rate of the tongues of anaemia patients was investigated. Blood perfusion rates at multiple locations on the tongues of 62 anaemia patients and 70 control subjects were measured. For both groups of subjects, dynamic IR thermal images were also recorded within 16 s after the mouth opened. The results showed that the blood perfusion rates at different sites (apex, middle, left side and right side) on the tongues in anaemia patients (3.49, 3.71, 3.85 and 3.77 kg/s m-3) were significantly lower than those at the corresponding sites in control subjects (4.45, 4.66, 4.81 and 4.70 kg/s m-3). After the mouth opened, the tongue temperature decreased more rapidly in anaemia patients than in control subjects. To analyse the heat transfer mechanism, a transient heat transfer model of the tongue was developed. The tongue temperatures in anaemia patients and control subjects were calculated using this model and compared to the tongue temperatures measured by the IR thermal imager. The relationship between the tongue surface temperature and the tongue blood perfusion rate was analysed. The simulation results indicated that the low blood perfusion rate and the correlated changes in anaemia patients can cause faster temperature decreases of the tongue surface.

Allometric equations for maximum filtration rate in blue mussels Mytilus edulis and importance of condition index

DEFF Research Database (Denmark)

Riisgård, Hans Ulrik; Larsen, Poul Scheel; Pleissner, Daniel

2014-01-01

rate (F, l h-1), W (g), and L (mm) as described by the equations: FW = aWb and FL = cLd, respectively. This is done by using available and new experimental laboratory data on M. edulis obtained by members of the same research team using different methods and controlled diets of cultivated algal cells...

Modification of the Hottel-Whillier-Bliss equation for cover absorption effects in solar collectors

Energy Technology Data Exchange (ETDEWEB)

Wijeysundera, N E

1981-01-01

The effects of solar radiation absorption and the thermal resistance of a solar collector cover system on the various factors which occur in the Hottel-Whillier-Bliss (HWB) equation are considered. It is shown that by extending the thermal network analogy to systems with distributed heat sources, the heat transfer analysis of the collector can be done with little computational effort. The analysis also leads to a simple form of the HWB equation, with additional factors to account for the source distribution and the thermal resistance of the cover system, and it is applicable to conventional flat plate collectors and to other thermal trap collectors. A series of calculations for multilayer systems is presented to show the relative importance of the various factors in the modified HWB equation for different cover configurations.

Is the Chronic Kidney Disease Epidemiology Collaboration creatinine–cystatin C equation useful for glomerular filtration rate estimation in the elderly?

Directory of Open Access Journals (Sweden)

Liu X

2013-10-01

Full Text Available Xun Liu,1,2,* Huijuan Ma,1,* Hui Huang,3 Cheng Wang,1 Hua Tang,1 Ming Li,1 Yanni Wang,1 Tanqi Lou1 1Division of Nephrology, Department of Internal Medicine, The Third Affiliated Hospital of Sun Yat-sen University, 2College of Biology Engineering, South China University of Technology, 3Department of Cardiology, Sun Yat-sen Memorial Hospital of Sun Yat-sen University, Guangzhou, People's Republic of China*These authors contributed equally to the paperBackground: We aimed to evaluate the performance of the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI creatinine–cystatin C equation in a cohort of elderly Chinese participants.Materials and methods: Glomerular filtration rate (GFR was measured in 431 elderly Chinese participants by the technetium-99m diethylene-triamine-penta-acetic acid (99mTc-DTPA renal dynamic imaging method, and was calibrated equally to the dual plasma sample 99mTc-DTPA-GFR. Performance of the CKD-EPI creatinine–cystatin C equation was compared with the Cockroft–Gault equation, the re-expressed 4-variable Modification of Diet in Renal Disease (MDRD equation, and the CKD-EPI creatinine equation.Results: Although the bias of the CKD-EPI creatinine–cystatin C equation was greater than with the other equations (median difference, 5.7 mL/minute/1.73 m2 versus a range from 0.4–2.5 mL/minute/1.73 m2; P<0.001 for all, the precision was improved with the CKD-EPI creatinine–cystatin C equation (interquartile range for the difference, 19.5 mL/minute/1.73 m2 versus a range from 23.0–23.6 mL/minute/1.73 m2; P<0.001 for all comparisons, leading to slight improvement in accuracy (median absolute difference, 10.5 mL/minute/1.73 m2 versus 12.2 and 11.4 mL/minute/1.73 m2 for the Cockcroft–Gault equation and the re-expressed 4-variable MDRD equation, P=0.04 for both; 11.6 mL/minute/1.73 m2 for the CKD-EPI creatinine equation, P=0.11, as the optimal scores of performance (6.0 versus a range from 1.0–2.0 for the other

Determine variation of poisson ratios and thermal creep stresses and strain rates in an isotropic disc

Directory of Open Access Journals (Sweden)

Gupta Nishi

2016-01-01

Full Text Available Seth's transition theory is applied to the problem of thermal creep transition stresses and strain rates in a thin rotating disc with shaft having variable density by finite deformation. Neither the yield criterion nor the associated flow rule is assumed here. The results obtained here are applicable to compressible materials. If the additional condition of incompressibility is imposed, then the expression for stresses corresponds to those arising from Tresca yield condition. Thermal effect decreased value of radial stress at the internal surface of the rotating isotropic disc made of compressible material as well as incompressible material and this value of radial stress further much increases with the increase in angular speed. With the introduction of thermal effects, the maximum value of strain rates further increases at the internal surface for compressible materials as compare to incompressible material.

Thermal transport properties of helium, helium--air mixtures, water, and tubing steel used in the CACHE program to compute HTGR auxiliary heat exchanger performance

International Nuclear Information System (INIS)

Tallackson, J.R.

1976-02-01

A description is presented of the thermal transport properties of the materials involved in digital computer calculations of heat transfer rates by the core auxiliary heat exchangers in large HTGR nuclear steam supply systems. These materials are pure helium, mixtures of helium with common gases having molecular weights in the range of 28 to 32, alloy steel tubing, and water. For use in programmed computations the viscosity, thermal conductivity, and specific heat are represented primarily by equations augmented by curves and tabulations. Materials supporting the development and selection of the property equations are included

Effect of thermal effluents from the Savannah River Plant on leaf decomposition rates in onsite creeks and the Savannah River

International Nuclear Information System (INIS)

Sadowski, P.W.; Matthews, R.A.

1986-06-01

Sweet gum and sycamore leaf packs were packs were placed in a thermally stressed, a post-thermal, and an ambient stream located on the Savannah River Plant, South Carolina, and in the Savannah River below the mouth of each stream. Processing rates for the leaf packs were determined over a 77-day period from December 1982 to March 1983. Due to inundation of the sampling sites by river flooding, temperatures in the stream receiving thermal effluent were reduced after day 24. Sweet gum leaves decomposed considerably faster than did sycamore leaves, particularly in the thermal creek. An exponential decay model was used to demonstrate significant differences in loss of ash-free dry weight from leaf packs in thermally stressed and nonthermal creeks. Differences in leaf processing rates between creek sites were greatest during periods of therma stress. Within each leaf species, leaf processing rates were not significantly different between nonthermal sites, nor between sites in the Savannah River

Thermal sensation and comfort with transient metabolic rates

DEFF Research Database (Denmark)

Goto, Tomonobu; Toftum, Jørn; Dear, R. d.

2002-01-01

This study investigated the effect on thermal perceptions and preferences of controlled metabolic excursions of various intensities (20%, 40%, 60% relative work load) and durations (3-30 min) imposed on subjects that alternated between sedentary activity and exercise on a treadmill. The thermal...... environment was held constant at a temperature corresponding to PMV=0 at sedentary activity. Even low activity changes of short duration (1 min at 20% relative work load) affected thermal perceptions. However, after circa 15 min of constant activity, subjective thermal responses approximated the steady...

Radar equations for modern radar

CERN Document Server

Barton, David K

2012-01-01

Based on the classic Radar Range-Performance Analysis from 1980, this practical volume extends that work to ensure applicability of radar equations to the design and analysis of modern radars. This unique book helps you identify what information on the radar and its environment is needed to predict detection range. Moreover, it provides equations and data to improve the accuracy of range calculations. You find detailed information on propagation effects, methods of range calculation in environments that include clutter, jamming and thermal noise, as well as loss factors that reduce radar perfo

Dose rate effect on the yield of radiation induced response with thermal fading

International Nuclear Information System (INIS)

Chernov, V.; Rogalev, B.; Barboza-Flores, M.

2005-01-01

A model describing the dependences of the accumulation of thermally unstable radiation induced defects on the dose and dose rate is proposed. The model directly takes into account the track nature of the ionizing radiation represented as accumulation processes of defects in tracks averaged over a crystal volume considering various degrees of overlapping in space and time. The accumulation of the defects in the tracks is phenomenologically described. General expressions are obtained that allows radiation yield simulation of defects involving known creation and transformation processes. The cases considered, of linear accumulation (constant increment of the defects in tracks) and accumulation with saturation (complete saturation of the defects in one track), lead to a set of linear dose dependences with saturation, which are routinely used in luminescence and ESR dating. The accumulation, with increase of sensitivity in regions overlapped by two or more tracks, gave a set of dose dependences, from linear-sublinear-linear-saturation, distinctive of quartz up to linear-supralinear-linear-saturation. It is shown that the effect of the dose rate on dose dependences is determined by a dimensionless parameter a=Pτ/D0, where P is the dose rate, τ is the defect lifetime and D0 is the track dose. At a-bar 1 the dose rate influences basically the accumulation of thermally unstable defects. In the reverse case the dose dependences did not seems to be influenced by the dose rate

A study on the characteristics of the decay heat removal capacity for a large thermal rated LMR design

International Nuclear Information System (INIS)

Uh, J. H.; Kim, E. K.; Kim, S. O.

2003-01-01

The design characteristics and the decay heat removal capacity according to the type of DHR (Decay Heat Removal) system in LMR are quantitatively analyzed, and the general relationship between the rated core thermal power and decay heat removal capacity is created in this study. Based on these analyses results, a feasibility of designing a larger thermal rating KALIMER plant is investigated in view of decay heat removal capacity, and DRC (Direct Reactor Cooling) type DHR system which rejects heat from the reactor pool to air is proper to satisfy the decay heat removal capacity for a large thermal rating plant above 1,000 MWth. Some defects, however, including the heat loss under normal plant operation and the lack of reliance associated with system operation should be resolved in order to adopt the total passive concept. Therefore, the new concept of DHR system for a larger thermal rating KALIMER design, named as PDRC (passive decay heat removal circuit), is established in this study. In the newly established concept of PDRC, the Na-Na heat exchanger is located above the sodium cold pool and is prevented from the direct sodium contact during normal operation. This total passive feature has the superiority in the aspect of the minimizing the normal heat loss and the increasing the operation reliance of DHR system by removing either any operator action or any external operation signal associated with system operation. From this study, it is confirmed that the new concept of PDRC is useful to the designing of a large thermal rating power plant of KALIMER-600 in view of decay heat removal capability

Thermal performance of a multiple PCM thermal storage unit for free cooling

International Nuclear Information System (INIS)

Mosaffa, A.H.; Infante Ferreira, C.A.; Talati, F.; Rosen, M.A.

2013-01-01

Highlights: ► Numerical analysis on the performance of a thermal storages as free cooling system. ► Employing multiple PCMs to enhance heat transfer rate in thermal storages. ► Using an effective heat capacity method, the phase change parameters are determined. ► The effect of the slabs size and air channel thickness on COP is investigated. - Abstract: As demand for refrigeration and air conditioning increased during the last decade, the opportunities have expanded for using thermal energy storage (TES) systems in an economically advantageous manner in place of conventional cooling plants. Many cool storage systems use phase change materials (PCMs) and achieve peak load shifting in buildings. This work presents numerical investigations of the performance enhancement of a free cooling system using a TES unit employing multiple PCMs. The TES unit is composed of a number of rectangular channels for the flowing heat transfer fluid, separated by PCM slabs. Using the effective heat capacity method, the melting and solidification of the PCM is solved. The forced convective heat transfer inside the channels is analyzed by solving the energy equation, which is coupled with the heat conduction equation in the container wall. The effect of design parameters such as PCM slab length, thickness and fluid passage gap on the storage performance is also investigated using an energy based optimization. The results show that a system which can guarantee comfort conditions for the climate of Tabriz, Iran has an optimum COP of 7.0. This could be achieved by a combination of CaCl 2 ·6H 2 O with RT25 with the optimum air channel thickness of 3.2 mm, length of 1.3 m and PCM slab thickness of 10 mm

submitter BREIT code: Analytical solution of the balance rate equations for charge-state evolutions of heavy-ion beams in matter

CERN Document Server

Winckler, N; Shevelko, V P; Al-Turany, M; Kollegger, T; Stöhlker, Th

2017-01-01

A detailed description of a recently developed BREIT computer code (Balance Rate Equations of Ion Transportation) for calculating charge-state fractions of ion beams passing through matter is presented. The code is based on the analytical solutions of the differential balance equations for the charge-state fractions as a function of the target thickness and can be used for calculating the ion evolutions in gaseous, solid and plasma targets. The BREIT code is available on-line and requires the charge-changing cross sections and initial conditions in the input file. The eigenvalue decomposition method, applied to obtain the analytical solutions of the rate equations, is described in the paper. Calculations of non-equilibrium and equilibrium charge-state fractions, performed by the BREIT code, are compared with experimental data and results of other codes for ion beams in gaseous and solid targets. Ability and limitations of the BREIT code are discussed in detail.

[Consensus document: recommendations for the use of equations to estimate glomerular filtration rate in children].

Science.gov (United States)

Montañés Bermúdez, R; Gràcia Garcia, S; Fraga Rodríguez, G M; Escribano Subias, J; Diez de Los Ríos Carrasco, M J; Alonso Melgar, A; García Nieto, V

2014-05-01

The appearance of the K/DOQI guidelines in 2002 on the definition, evaluation and staging of chronic kidney disease (CKD) have led to a major change in how to assess renal function in adults and children. These guidelines, recently updated, recommended that the study of renal function is based, not only on measuring the serum creatinine concentration, but this must be accompanied by the estimation of glomerular filtration rate (GFR) obtained by an equation. However, the implementation of this recommendation in the clinical laboratory reports in the paediatric population has been negligible. Numerous studies have appeared in recent years on the importance of screening and monitoring of patients with CKD, the emergence of new equations for estimating GFR, and advances in clinical laboratories regarding the methods for measuring plasma creatinine and cystatin C, determined by the collaboration between the departments of paediatrics and clinical laboratories to establish recommendations based on the best scientific evidence on the use of equations to estimate GFR in this population. The purpose of this document is to provide recommendations on the evaluation of renal function and the use of equations to estimate GFR in children from birth to 18 years of age. The recipients of these recommendations are paediatricians, nephrologists, clinical biochemistry, clinical analysts, and all health professionals involved in the study and evaluation of renal function in this group of patients. Copyright © 2013 Asociación Española de Pediatría. Published by Elsevier Espana. All rights reserved.

Thermal Fluctuations in Smooth Dissipative Particle Dynamics simulation of mesoscopic thermal systems

Science.gov (United States)

Gatsonis, Nikolaos; Yang, Jun

2013-11-01

The SDPD-DV is implemented in our work for arbitrary 3D wall bounded geometries. The particle position and momentum equations are integrated with a velocity-Verlet algorithm and the entropy equation is integrated with a Runge-Kutta algorithm. Simulations of nitrogen gas are performed to evaluate the effects of timestep and particle scale on temperature, self-diffusion coefficient and shear viscosity. The hydrodynamic fluctuations in temperature, density, pressure and velocity from the SDPD-DV simulations are evaluated and compared with theoretical predictions. Steady planar thermal Couette flows are simulated and compared with analytical solutions. Simulations cover the hydrodynamic and mesocopic regime and show thermal fluctuations and their dependence on particle size.

Flavored quantum Boltzmann equations

International Nuclear Information System (INIS)

Cirigliano, Vincenzo; Lee, Christopher; Ramsey-Musolf, Michael J.; Tulin, Sean

2010-01-01

We derive from first principles, using nonequilibrium field theory, the quantum Boltzmann equations that describe the dynamics of flavor oscillations, collisions, and a time-dependent mass matrix in the early universe. Working to leading nontrivial order in ratios of relevant time scales, we study in detail a toy model for weak-scale baryogenesis: two scalar species that mix through a slowly varying time-dependent and CP-violating mass matrix, and interact with a thermal bath. This model clearly illustrates how the CP asymmetry arises through coherent flavor oscillations in a nontrivial background. We solve the Boltzmann equations numerically for the density matrices, investigating the impact of collisions in various regimes.

Theory of transformation thermal convection for creeping flow in porous media: Cloaking, concentrating, and camouflage

Science.gov (United States)

Dai, Gaole; Shang, Jin; Huang, Jiping

2018-02-01

Heat can transfer via thermal conduction, thermal radiation, and thermal convection. All the existing theories of transformation thermotics and optics can treat thermal conduction and thermal radiation, respectively. Unfortunately, thermal convection has seldom been touched in transformation theories due to the lack of a suitable theory, thus limiting applications associated with heat transfer through fluids (liquid or gas). Here, we develop a theory of transformation thermal convection by considering the convection-diffusion equation, the equation of continuity, and the Darcy law. By introducing porous media, we get a set of equations keeping their forms under coordinate transformation. As model applications, the theory helps to show the effects of cloaking, concentrating, and camouflage. Our finite-element simulations confirm the theoretical findings. This work offers a transformation theory for thermal convection, thus revealing novel behaviors associated with potential applications; it not only provides different hints on how to control heat transfer by combining thermal conduction, thermal convection, and thermal radiation, but also benefits mass diffusion and other related fields that contain a set of equations and need to transform velocities at the same time.

Power balance equation in electron beam evaporation process

International Nuclear Information System (INIS)

Blumenfeld, L.; Soubbaramayer.

1994-01-01

The aim of the paper is to solve the equation giving the total power of the gun, used in the electron beam evaporation process, in terms of the power used to generated the vapor stream and the three main power losses due to three parasite phenomena: turbulent thermal convection in the molten pool, electron back scattering and heat radiation from the vapor emitting surface. Scaling laws are first reviewed and results are given with the example of the evaporation of aluminium with a 5 kW axisymmetric gun working in steady state mode. The influence of an applied magnetic field on the evaporation rate is also examined. 5 refs., 3 figs., 1 tab

Stability and decay rates of nonisotropic attractive Bose-Einstein condensates

International Nuclear Information System (INIS)

Huepe, C.; Tuckerman, L. S.; Metens, S.; Brachet, M. E.

2003-01-01

Nonisotropic attractive Bose-Einstein condensates are investigated numerically with Newton and inverse Arnoldi methods. The stationary solutions of the Gross-Pitaevskii equation and their linear stability are computed. Bifurcation diagrams are calculated and used to find the condensate decay rates corresponding to macroscopic quantum tunneling, two-three-body inelastic collisions, and thermally induced collapse. Isotropic and nonisotropic condensates are compared. The effect of anisotropy on the bifurcation diagram and the decay rates is discussed. Spontaneous isotropization of the condensates is found to occur. The influence of isotropization on the decay rates is characterized near the critical point

Cool-down flow-rate limits imposed by thermal stresses in LNG pipelines

Science.gov (United States)

Novak, J. K.; Edeskuty, F. J.; Bartlit, J. R.

Warm cryogenic pipelines are usually cooled to operating temperature by a small, steady flow of the liquid cryogen. If this flow rate is too high or too low, undesirable stresses will be produced. Low flow-rate limits based on avoidance of stratified two-phase flow were calculated for pipelines cooled with liquid hydrogen or nitrogen. High flow-rate limits for stainless steel and aluminum pipelines cooled by liquid hydrogen or nitrogen were determined by calculating thermal stress in thick components vs flow rate and then selecting some reasonable stress limits. The present work extends these calculations to pipelines made of AISI 304 stainless steel, 6061 aluminum, or ASTM A420 9% nickel steel cooled by liquid methane or a typical natural gas. Results indicate that aluminum and 9% nickel steel components can tolerate very high cool-down flow rates, based on not exceeding the material yield strength.

Unsteady natural convection flow past an accelerated vertical plate in a thermally stratified fluid

Directory of Open Access Journals (Sweden)

Deka Rudra Kt.

2009-01-01

Full Text Available An exact solution to one-dimensional unsteady natural convection flow past an infinite vertical accelerated plate, immersed in a viscous thermally stratified fluid is investigated. Pressure work term and the vertical temperature advection are considered in the thermodynamic energy equation. The dimensionless governing equations are solved by Laplace Transform techniques for the Prandtl number unity. The velocity and temperature profiles as well as the skin-friction and the rate of heat transfer are presented graphically and discussed the effects of the Grashof number Gr, stratification parameter S at various times t.

Thermal behaviour of a solar air heater with a compound parabolic concentrator

International Nuclear Information System (INIS)

Tchinda, R.

2005-11-01

A mathematical model for computing the thermal performance of an air heater with a truncated compound parabolic concentrator having a flat one-sided absorber is presented. A computed code that employs an iterative solution procedure is constructed to solve the governing energy equations and to estimate the performance parameters of the collector. The effects of the air mass flow rate, the wind speed and the collector length on the thermal performance of the present air heater are investigated. Prediction for the performance of the solar heater also exhibits reasonable agreement with experimental data with an average error of 7%. (author)

Scaling analysis and instantons for thermally assisted tunneling and quantum Monte Carlo simulations

Science.gov (United States)

Jiang, Zhang; Smelyanskiy, Vadim N.; Isakov, Sergei V.; Boixo, Sergio; Mazzola, Guglielmo; Troyer, Matthias; Neven, Hartmut

2017-01-01

We develop an instantonic calculus to derive an analytical expression for the thermally assisted tunneling decay rate of a metastable state in a fully connected quantum spin model. The tunneling decay problem can be mapped onto the Kramers escape problem of a classical random dynamical field. This dynamical field is simulated efficiently by path-integral quantum Monte Carlo (QMC). We show analytically that the exponential scaling with the number of spins of the thermally assisted quantum tunneling rate and the escape rate of the QMC process are identical. We relate this effect to the existence of a dominant instantonic tunneling path. The instanton trajectory is described by nonlinear dynamical mean-field theory equations for a single-site magnetization vector, which we solve exactly. Finally, we derive scaling relations for the "spiky" barrier shape when the spin tunneling and QMC rates scale polynomially with the number of spins N while a purely classical over-the-barrier activation rate scales exponentially with N .

Controlling Thermal Conduction by Graded Materials

Science.gov (United States)

Ji, Qin; Huang, Ji-Ping

2018-04-01

Manipulating thermal conductivities are fundamentally important for controlling the conduction of heat at will. Thermal cloaks and concentrators, which have been extensively studied recently, are actually graded materials designed according to coordinate transformation approaches, and their effective thermal conductivity is equal to that of the host medium outside the cloak or concentrator. Here we attempt to investigate a more general problem: what is the effective thermal conductivity of graded materials? In particular, we perform a first-principles approach to the analytic exact results of effective thermal conductivities of materials possessing either power-law or linear gradation profiles. On the other hand, by solving Laplace’s equation, we derive a differential equation for calculating the effective thermal conductivity of a material whose thermal conductivity varies along the radius with arbitrary gradation profiles. The two methods agree with each other for both external and internal heat sources, as confirmed by simulation and experiment. This work provides different methods for designing new thermal metamaterials (including thermal cloaks and concentrators), in order to control or manipulate the transfer of heat. Support by the National Natural Science Foundation of China under Grant No. 11725521, by the Science and Technology Commission of Shanghai Municipality under Grant No. 16ZR1445100

Polymer degradation rate control of hybrid rocket combustion

Science.gov (United States)

Stickler, D. B.; Ramohalli, K. N. R.

1970-01-01

Polymer degradation to small fragments is treated as a rate controlling step in hybrid rocket combustion. Both numerical and approximate analytical solutions of the complete energy and polymer chain bond conservation equations for the condensed phase are obtained. Comparison with inert atmosphere data is very good. It is found that the intersect of curves of pyrolysis rate versus interface temperature for hybrid combustors, with the thermal degradation theory, falls at a pyrolysis rate very close to that for which a pressure dependence begins to be observable. Since simple thermal degradation cannot give sufficient depolymerization at higher pyrolysis rates, it is suggested that oxidative catalysis of the process occurs at the surface, giving a first order dependence on reactive species concentration at the wall. Estimates of the ratio of this activation energy and interface temperature are in agreement with best fit procedures for hybrid combustion data. Requisite active species concentrations and flux are shown to be compatible with turbulent transport. Pressure dependence of hybrid rocket fuel regression rate is thus shown to be describable in a consistent manner in terms of reactive species catalysis of polymer degradation.

3-D thermal weight function method and multiple virtual crack extension technique for thermal shock problems

International Nuclear Information System (INIS)

Lu Yanlin; Zhou Xiao; Qu Jiadi; Dou Yikang; He Yinbiao

2005-01-01

An efficient scheme, 3-D thermal weight function (TWF) method, and a novel numerical technique, multiple virtual crack extension (MVCE) technique, were developed for determination of histories of transient stress intensity factor (SIF) distributions along 3-D crack fronts of a body subjected to thermal shock. The TWF is a universal function, which is dependent only on the crack configuration and body geometry. TWF is independent of time during thermal shock, so the whole history of transient SIF distributions along crack fronts can be directly calculated through integration of the products of TWF and transient temperatures and temperature gradients. The repeated determinations of the distributions of stresses (or displacements) fields for individual time instants are thus avoided in the TWF method. An expression of the basic equation for the 3-D universal weight function method for Mode I in an isotropic elastic body is derived. This equation can also be derived from Bueckner-Rice's 3-D WF formulations in the framework of transformation strain. It can be understood from this equation that the so-called thermal WF is in fact coincident with the mechanical WF except for some constants of elasticity. The details and formulations of the MVCE technique are given for elliptical cracks. The MVCE technique possesses several advantages. The specially selected linearly independent VCE modes can directly be used as shape functions for the interpolation of unknown SIFs. As a result, the coefficient matrix of the final system of equations in the MVCE method is a triple-diagonal matrix and the values of the coefficients on the main diagonal are large. The system of equations has good numerical properties. The number of linearly independent VCE modes that can be introduced in a problem is unlimited. Complex situations in which the SIFs vary dramatically along crack fronts can be numerically well simulated by the MVCE technique. An integrated system of programs for solving the

Derivation of simplified basic equations of gas-liquid two-phase dispersed flow based on two-fluid model

International Nuclear Information System (INIS)

Kataoka, Isao; Tomiyama, Akio

2004-01-01

The simplified and physically reasonable basic equations for the gas-liquid dispersed flow were developed based on some appropriate assumptions and the treatment of dispersed phase as isothermal rigid particles. Based on the local instant formulation of mass, momentum and energy conservation of the dispersed flow, time-averaged equations were obtained assuming that physical quantities in the dispersed phase are uniform. These assumptions are approximately valid when phase change rate and/or chemical reaction rate are not so large at gas-liquid interface and there is no heat generation in within the dispersed phase. Detailed discussions were made on the characteristics of obtained basic equations and physical meanings of terms consisting the basic equations. It is shown that, in the derived averaged momentum equation, the terms of pressure gradient and viscous momentum diffusion do not appear and, in the energy equation, the term of molecular thermal diffusion heat flux does not appear. These characteristics of the derived equations were shown to be very consistent concerning the physical interpretation of the gas-liquid dispersed flow. Furthermore, the obtained basic equations are consistent with experiments for the dispersed flow where most of averaged physical quantities are obtained assuming that the distributions of those are uniform within the dispersed phase. Investigation was made on the problem whether the obtained basic equations are well-posed or ill-posed for the initial value problem. The eigenvalues of the simplified mass and momentum equations are calculated for basic equations obtained here and previous two-fluid basic equations with one pressure model. Well-posedness and ill-posedness are judged whether the eigenvalues are real or imaginary. The result indicated the newly developed basic equations always constitute the well-posed initial value problem while the previous two-fluid basic equations based on one pressure model constitutes ill

Thermal Properties of Beryllium Metal

International Nuclear Information System (INIS)

Cho, Tae Won; Baek, Je Kyun; Jeong, Gwan Yoon; Kim, Ji Hyeon; Sohn, Dong Seong

2013-01-01

It is known that the presence of as-fabricated porosity largely affect thermal conductivity of beryllium. Therefore, in this paper we will suggest a new thermal conductivity equation which consider volume fraction and discuss how this can be applied to irradiation induced degradation of thermal conductivity later. This study was performed to develop a new correlation of thermal conductivity of Beryllium. Although there are many factors like BeO contents, impurity level, grain size, and porosity, we assumed porosity will be the dominant factor for thermal conductivity. Therefore, a new correlation which consider volume fraction by applying Maxwell-Eucken equation is developed and this is consistent to some degrees. However, increasing impurity level and decreasing grain size will decrease thermal conductivity. Therefore, we need to consider their effects although we assume BeO contents, impurity, and grain size do not make noticeable effects in the future. Furthermore, thermal conductivity degradation by neutron irradiation should be considered afterward. There are two main factors for the thermal conductivity degradation: the one is defects formed by neutron collisions and the other is helium generated by transmutation of Be. It is known that they make a considerable degradation of conductivity. Beryllium is known there are considerable volume increases by helium accumulation. Therefore, we anticipate our suggested model can be applicable if it has been developed furthermore considering irradiation induced swelling

Direct quantum mechanical calculation of the F + H{sub 2} {yields} HF + H thermal rate constant

Energy Technology Data Exchange (ETDEWEB)

Moix, Marc [Computer Simulation and Modeling (COSMO) Lab, Parc Cientific de Barcelona, Josep Samitier 5, 08028 Barcelona (Spain); Institut de Quimica Teorica i Computacional de la UB (IQTCUB), Universitat de Barcelona (Spain); Huarte-Larranaga, Fermin [Computer Simulation and Modeling (COSMO) Lab, Parc Cientific de Barcelona, Josep Samitier 5, 08028 Barcelona (Spain); Institut de Quimica Teorica i Computacional de la UB (IQTCUB), Universitat de Barcelona (Spain)], E-mail: fhuarte@pcb.ub.es

2008-07-03

Accurate full-dimensional quantum mechanical thermal rate constant values have been calculated for the F+H{sub 2}{yields}HF+H reaction on the Stark-Werner ab initio potential energy surface. These calculations are based on a flux correlation functions and employ a rigorous statistical sampling scheme to account for the overall rotation and the MCTDH scheme for the wave packet propagation. Our results shed some light on discrepancies on the thermal rate found for previous flux correlation based calculations with respect to accurate reactive scattering results. The resonance pattern of the all-J cumulative reaction probability is analyzed in terms of the partial wave contributions.

Nonlinear heat conduction equations with memory: Physical meaning and analytical results

Science.gov (United States)

Artale Harris, Pietro; Garra, Roberto

2017-06-01

We study nonlinear heat conduction equations with memory effects within the framework of the fractional calculus approach to the generalized Maxwell-Cattaneo law. Our main aim is to derive the governing equations of heat propagation, considering both the empirical temperature-dependence of the thermal conductivity coefficient (which introduces nonlinearity) and memory effects, according to the general theory of Gurtin and Pipkin of finite velocity thermal propagation with memory. In this framework, we consider in detail two different approaches to the generalized Maxwell-Cattaneo law, based on the application of long-tail Mittag-Leffler memory function and power law relaxation functions, leading to nonlinear time-fractional telegraph and wave-type equations. We also discuss some explicit analytical results to the model equations based on the generalized separating variable method and discuss their meaning in relation to some well-known results of the ordinary case.

Effects of Covalent Functionalization of MWCNTs on the Thermal Properties and Non-Isothermal Crystallization Behaviors of PPS Composites

Directory of Open Access Journals (Sweden)

Myounguk Kim

2017-09-01

Full Text Available In this study, a PPS/MWCNTs composite was prepared with poly(phenylene sulfide (PPS, as well as pristine and covalent functionalized multi-walled carbon nanotubes (MWCNTs via melt-blending techniques. Moreover, the dispersion of the MWCNTs on the PPS matrix was improved by covalent functionalization as can be seen from a Field-Emission Scanning Electron Microscope (FE-SEM images. The thermal properties of the PPS/MWCNTs composites were characterized using a thermal conductivity analyzer, and a differential scanning calorimeter (DSC. To analyze the crystallization behavior of polymers under conditions similar with those in industry, the non-isothermal crystallization behaviors of the PPS/MWCNTs composites were confirmed using various kinetic equations, such as the modified Avrami equation and Avrami-Ozawa combined equation. The crystallization rate of PPS/1 wt % pristine MWCNTs composite (PPSP1 was faster because of the intrinsic nucleation effect of the MWCNTs. However, the crystallization rates of the composites containing covalently-functionalized MWCNTs were slower than PPSP1 because of the destruction of the MWCNTs graphitic structure via covalent functionalization. Furthermore, the activation energies calculated by Kissinger’s method were consistently decreased by covalent functionalization.

Application of a mechanism-based rate equation to black liquor gasification rate data

Energy Technology Data Exchange (ETDEWEB)

Overacker, N.L.; Waag, K.J.; Frederick, W.J. [Oregon State University, OR (United States). Dept. of Chemical Engineering; Whitty, K.J.

1995-09-01

There is growing interest worldwide to develop alternate chemical recovery processes for paper mills which are cheaper, safer, more efficient and more environmentally sound than traditional technology. Pressurized gasification of black liquor is the basis for many proposed schemes and offers the possibility to double the amount of electricity generated per unit of dry black liquor solids. Such technology also has capital, safety and environmental advantages. One of the most important considerations regarding this emerging technology is the kinetics of the gasification reaction. This has been studied empirically at Aabo Akademi University for the pressurized gasification with carbon dioxide and steam. For the purposes of reactor modeling and scale-up, however, a thorough understanding of the mechanism behind the reaction is desirable. This report discusses the applicability of a mechanism-based rate equation to gasification of black liquor. The mechanism considered was developed for alkali-catalyzed gasification of carbon and is tested using black liquor gasification data obtained during simultaneous reaction with H{sub 2}O and CO. Equilibrium considerations and the influence of the water-gas shift reaction are also discussed. The work presented here is a cooperative effort between Aabo Akademi University and Oregon State University. The experimental work and some of the data analysis was performed at Aabo Akademi University. Development of the models and consideration of their applicability was performed primarily at Oregon State University

First-order partial differential equations

CERN Document Server

Rhee, Hyun-Ku; Amundson, Neal R

2001-01-01

This first volume of a highly regarded two-volume text is fully usable on its own. After going over some of the preliminaries, the authors discuss mathematical models that yield first-order partial differential equations; motivations, classifications, and some methods of solution; linear and semilinear equations; chromatographic equations with finite rate expressions; homogeneous and nonhomogeneous quasilinear equations; formation and propagation of shocks; conservation equations, weak solutions, and shock layers; nonlinear equations; and variational problems. Exercises appear at the end of mo

Including gauge corrections to thermal leptogenesis

International Nuclear Information System (INIS)

Huetig, Janine

2013-01-01

This thesis provides the first approach of a systematic inclusion of gauge corrections to leading order to the ansatz of thermal leptogenesis. We have derived a complete expression for the integrated lepton number matrix including all resummations needed. For this purpose, a new class of diagram has been invented, namely the cylindrical diagram, which allows diverse investigations into the topic of leptogenesis such as the case of resonant leptogenesis. After a brief introduction of the topic of the baryon asymmetry in the universe and a discussion of its most promising solutions as well as their advantages and disadvantages, we have presented our framework of thermal leptogenesis. An effective model was described as well as the associated Feynman rules. The basis for using nonequilibrium quantum field theory has been built in chapter 3. At first, the main definitions have been presented for equilibrium thermal field theory, afterwards we have discussed the Kadanoff-Baym equations for systems out of equilibrium using the example of the Majorana neutrino. The equations have also been solved in the context of leptogenesis in chapter 4. Since gauge corrections play a crucial role throughout this thesis, we have also repeated the naive ansatz by replacing the free equilibrium propagator by propagators including thermal damping rates due to the Standard Model damping widths for lepton and Higgs fields. It is shown that this leads to a comparable result to the solutions of the Boltzmann equations for thermal leptogenesis. Thus it becomes obvious that Standard Model corrections are not negligible for thermal leptogenesis and therefore need to be included systematically from first principles. In order to achieve this we have started discussing the calculation of ladder rung diagrams for Majorana neutrinos using the HTL and the CTL approach in chapter 5. All gauge corrections are included in this framework and thus it has become the basis for the following considerations

Including gauge corrections to thermal leptogenesis

Energy Technology Data Exchange (ETDEWEB)

Huetig, Janine

2013-05-17

This thesis provides the first approach of a systematic inclusion of gauge corrections to leading order to the ansatz of thermal leptogenesis. We have derived a complete expression for the integrated lepton number matrix including all resummations needed. For this purpose, a new class of diagram has been invented, namely the cylindrical diagram, which allows diverse investigations into the topic of leptogenesis such as the case of resonant leptogenesis. After a brief introduction of the topic of the baryon asymmetry in the universe and a discussion of its most promising solutions as well as their advantages and disadvantages, we have presented our framework of thermal leptogenesis. An effective model was described as well as the associated Feynman rules. The basis for using nonequilibrium quantum field theory has been built in chapter 3. At first, the main definitions have been presented for equilibrium thermal field theory, afterwards we have discussed the Kadanoff-Baym equations for systems out of equilibrium using the example of the Majorana neutrino. The equations have also been solved in the context of leptogenesis in chapter 4. Since gauge corrections play a crucial role throughout this thesis, we have also repeated the naive ansatz by replacing the free equilibrium propagator by propagators including thermal damping rates due to the Standard Model damping widths for lepton and Higgs fields. It is shown that this leads to a comparable result to the solutions of the Boltzmann equations for thermal leptogenesis. Thus it becomes obvious that Standard Model corrections are not negligible for thermal leptogenesis and therefore need to be included systematically from first principles. In order to achieve this we have started discussing the calculation of ladder rung diagrams for Majorana neutrinos using the HTL and the CTL approach in chapter 5. All gauge corrections are included in this framework and thus it has become the basis for the following considerations

Cavitation and thermal dilepton production in QGP

International Nuclear Information System (INIS)

Bhatt, Jitesh R.; Mishra, Hiranmaya; Sreekanth, V.

2012-01-01

We study the effects of bulk and shear viscosities on both hydrodynamical evolution and thermal dilepton emission rate from the QGP phase at RHIC energies. We use lattice QCD inspired parametrization for the bulk viscosity and trace anomaly (equation of state) to describe behavior of the system near the critical temperature T c . Ratio of the shear viscosity to entropy density is taken to be η/s∼1/4π. We calculate the corrections on the dilepton production rates due to modification in the distribution function, arising due to the presence of the bulk and shear viscosities. It is shown that when the system temperature evolves close to T c the effect of the bulk viscosity on the dilepton emission rates cannot be ignored. It is demonstrated that the bulk viscosity can suppress the thermal dilepton spectra where as the effect of the shear viscosity is to enhance it. Further we show that the bulk viscosity driven fragmentation or cavitation can set in very early during the hydrodynamical evolution and this in turn would make the hydrodynamical treatment invalid beyond the cavitation time. We find that even though the finite bulk viscosity corrections and the onset of the cavitation reduce the production rates, the effect of the minimal η/s=1/4π can enhance the dilepton production rates significantly in the regime p T ⩾2 GeV.

Stagnation point flow on bioconvection nanofluid over a stretching/shrinking surface with velocity and thermal slip effects

Science.gov (United States)

Chan, Sze Qi; Aman, Fazlina; Mansur, Syahira

2017-09-01

Nanofluid containing nanometer sized particles has become an ideal thermal conductivity medium for the flow and heat transfer in many industrial and engineering applications due to their high rate of heat transfer. However, swimming microorganisms are imposed into the nanofluid to overcome the instability of nanoparticles due to a bioconvection phenomenon. This paper investigates the stagnation point flow on bioconvection heat transfer of a nanofluid over a stretching/shrinking surface containing gyrotactic microorganisms. Velocity and thermal slip effects are the two conditions incorporated into the model. Similarity transformation is applied to reduce the governing nonlinear partial differential equations into the nonlinear ordinary differential equations. The transformed equations are then solved numerically. The results are displayed in the form of graphs and tables. The effects of these governing parameters on the skin friction coefficient, local Nusselt number, local Sherwood number and the local density of the motile microorganisms are analysed and discussed in details.

A nonlinear wave equation in nonadiabatic flame propagation

International Nuclear Information System (INIS)

Booty, M.R.; Matalon, M.; Matkowsky, B.J.

1988-01-01

The authors derive a nonlinear wave equation from the diffusional thermal model of gaseous combustion to describe the evolution of a flame front. The equation arises as a long wave theory, for values of the volumeric heat loss in a neighborhood of the extinction point (beyond which planar uniformly propagating flames cease to exist), and for Lewis numbers near the critical value beyond which uniformly propagating planar flames lose stability via a degenerate Hopf bifurcation. Analysis of the equation suggests the possibility of a singularity developing in finite time

An Equation-of-State Compositional In-Situ Combustion Model: A Study of Phase Behavior Sensitivity

DEFF Research Database (Denmark)

Kristensen, Morten Rode; Gerritsen, M. G.; Thomsen, Per Grove

2009-01-01

phase behavior sensitivity for in situ combustion, a thermal oil recovery process. For the one-dimensional model we first study the sensitivity to numerical discretization errors and provide grid density guidelines for proper resolution of in situ combustion behavior. A critical condition for success...... to ignition. For a particular oil we show that the simplified approach overestimates the required air injection rate for sustained front propagation by 17% compared to the equation of state-based approach....

Determining the spill flow discharge of combined sewer overflows using rating curves based on computational fluid dynamics instead of the standard weir equation.

Science.gov (United States)

Fach, S; Sitzenfrei, R; Rauch, W

2009-01-01

It is state of the art to evaluate and optimise sewer systems with urban drainage models. Since spill flow data is essential in the calibration process of conceptual models it is important to enhance the quality of such data. A wide spread approach is to calculate the spill flow volume by using standard weir equations together with measured water levels. However, these equations are only applicable to combined sewer overflow (CSO) structures, whose weir constructions correspond with the standard weir layout. The objective of this work is to outline an alternative approach to obtain spill flow discharge data based on measurements with a sonic depth finder. The idea is to determine the relation between water level and rate of spill flow by running a detailed 3D computational fluid dynamics (CFD) model. Two real world CSO structures have been chosen due to their complex structure, especially with respect to the weir construction. In a first step the simulation results were analysed to identify flow conditions for discrete steady states. It will be shown that the flow conditions in the CSO structure change after the spill flow pipe acts as a controlled outflow and therefore the spill flow discharge cannot be described with a standard weir equation. In a second step the CFD results will be used to derive rating curves which can be easily applied in everyday practice. Therefore the rating curves are developed on basis of the standard weir equation and the equation for orifice-type outlets. Because the intersection of both equations is not known, the coefficients of discharge are regressed from CFD simulation results. Furthermore, the regression of the CFD simulation results are compared with the one of the standard weir equation by using historic water levels and hydrographs generated with a hydrodynamic model. The uncertainties resulting of the wide spread use of the standard weir equation are demonstrated.

Thermal Characterization of Edible Oils by Using Photopyroelectric Technique

Science.gov (United States)

Lara-Hernández, G.; Suaste-Gómez, E.; Cruz-Orea, A.; Mendoza-Alvarez, J. G.; Sánchez-Sinéncio, F.; Valcárcel, J. P.; García-Quiroz, A.

2013-05-01

Thermal properties of several edible oils such as olive, sesame, and grape seed oils were obtained by using the photopyroelectric technique. The inverse photopyroelectric configuration was used in order to obtain the thermal effusivity of the oil samples. The theoretical equation for the photopyroelectric signal in this configuration, as a function of the incident light modulation frequency, was fitted to the experimental data in order to obtain the thermal effusivity of these samples. Also, the back photopyroelectric configuration was used to obtain the thermal diffusivity of these oils; this thermal parameter was obtained by fitting the theoretical equation for this configuration, as a function of the sample thickness (called the thermal wave resonator cavity), to the experimental data. All measurements were done at room temperature. A complete thermal characterization of these edible oils was achieved by the relationship between the obtained thermal diffusivities and thermal effusivities with their thermal conductivities and volumetric heat capacities. The obtained results are in agreement with the thermal properties reported for the case of the olive oil.

Stress relaxation of thermally bowed fuel pins

International Nuclear Information System (INIS)

Crossland, I.G.; Speight, M.V.

1983-01-01

The presence of cross-pin temperature gradients in nuclear reactor fuel pins produces differential thermal expansion which, in turn, causes the fuel pin to bow elastically. If the pin is restrained in any way, such thermal bowing causes the pin to be stressed. At high temperatures these stresses can relax by creep and it is shown here that this causes the pin to suffer an additional permanent deflection, so that when the cross-pin temperature difference is removed the pin remains bowed. By representing the cylindrical pin by an equivalent I-beam, the present work examines this effect when it takes place by secondary creep. Two restraint systems are considered, and it is demonstrated that the rate of relaxation depends mainly upon the creep equation, and hence the temperature, and also the magnitude of the initial stresses. (author)

A correct enthalpy relationship as thermal comfort index for livestock.

Science.gov (United States)

Rodrigues, Valéria Cristina; da Silva, Iran José Oliveira; Vieira, Frederico Márcio Corrêa; Nascimento, Sheila Tavares

2011-05-01

Researchers working with thermal comfort have been using enthalpy to measure thermal energy inside rural facilities, establishing indicator values for many situations of thermal comfort and heat stress. This variable turned out to be helpful in analyzing thermal exchange in livestock systems. The animals are exposed to an environment which is decisive for the thermoregulatory process, and, consequently, the reactions reflect states of thermal comfort or heat stress, the last being responsable for problems of sanity, behavior and productivity. There are researchers using enthalpy as a qualitative indicator of thermal environment of livestock such as poultry, cattle and hogs in tropical regions. This preliminary work intends to check different enthalpy equations using information from classical thermodynamics, and proposes a direct equation as thermal comfort index for livestock systems.

Design Considerations for Thermally Insulating Structural Sandwich Panels for Hypersonic Vehicles

Science.gov (United States)

Blosser, Max L.

2016-01-01

Simplified thermal/structural sizing equations were derived for the in-plane loading of a thermally insulating structural sandwich panel. Equations were developed for the strain in the inner and outer face sheets of a sandwich subjected to uniaxial mechanical loads and differences in face sheet temperatures. Simple equations describing situations with no viable solution were developed. Key design parameters, material properties, and design principles are identified. A numerical example illustrates using the equations for a preliminary feasibility assessment of various material combinations and an initial sizing for minimum mass of a sandwich panel.

Energy intake underreporting of adults in a household survey: the impact of using a population specific basal metabolic rate equation

Directory of Open Access Journals (Sweden)

Danielle Ribeiro de Souza

2015-04-01

Full Text Available The purpose of the present study was to identify energy intake (EI underreporting and to estimate the impact of using a population specific equation for the basal metabolic rate (BMR in a probability sample of adults from Niterói, Rio de Janeiro State, Brazil. A sample of 1,726 subjects participated in the study. EI was assessed by a 24-hour dietary recall and EI/BMR was computed with BMR estimated using internationally recommended equations as well as specific equations developed for the adult population of Niterói. Mean EI was 1,570.9 and 2,188.8kcal.day-1 for women and men, respectively. EI decreased with increasing age in both men and women. BMR estimated by the Brazilian equation was significantly lower than the values estimated by the international equation for all age, sex and nutritional status groups. In general, EI underreporting was found in at least 50% of the population, higher in women, and increased with increasing age and body mass index (BMI. The results of the present study confirm that EI is underreported, even when BMR is estimated using population-specific equations.

Musculoskeletal Disorders study in damming construction workers by Fox equation and measurement heart rate at work

Directory of Open Access Journals (Sweden)

L. Gheibi

2008-04-01

Full Text Available Background and aims   Musculoskeletal Disorders are prevalent in construction workers in comparison to other working groups. These workers in damming construction worked at awkward  postures for long times, so ergonomic assessment of jobs was important.   Methods   This is a descriptive-analytical cross sectional study that conducted in 2008 on a random sample of workers of damming construction in Takab city (110 men who were assessed by Nordic Musculoskeletal questionnaire and digital indicator for heart measurement. To estimate  Vo2max consumption Fox equation was used and data were analyzed by SPSS software.   Results   The average of total time of worked was 36.6 86.8 months. Results showed that the  most prevalent (%55.5 MSDs was low back pain which was positively related with type of job,  the number of standing and sitting posotions at work, total time of work, age, smoking, level of   education, weight,Vo2max that estimated by Fox Equation, and heart rate at working (P<0.05.   Conclusion   The results of this study reveal that prevalence rate of musculoskeletal disorders are high among damming construction workers, and heart rate and Vo2max consumption increases with increase in work load. Therefore, optimal physiological conditions should be considered  and physical capacity be measured. Prior to employment of workers approperiate corrections are  warranted      

Finger tapping movements of Parkinson's disease patients automatically rated using nonlinear delay differential equations.

Science.gov (United States)

Lainscsek, C; Rowat, P; Schettino, L; Lee, D; Song, D; Letellier, C; Poizner, H

2012-03-01

Parkinson's disease is a degenerative condition whose severity is assessed by clinical observations of motor behaviors. These are performed by a neurological specialist through subjective ratings of a variety of movements including 10-s bouts of repetitive finger-tapping movements. We present here an algorithmic rating of these movements which may be beneficial for uniformly assessing the progression of the disease. Finger-tapping movements were digitally recorded from Parkinson's patients and controls, obtaining one time series for every 10 s bout. A nonlinear delay differential equation, whose structure was selected using a genetic algorithm, was fitted to each time series and its coefficients were used as a six-dimensional numerical descriptor. The algorithm was applied to time-series from two different groups of Parkinson's patients and controls. The algorithmic scores compared favorably with the unified Parkinson's disease rating scale scores, at least when the latter adequately matched with ratings from the Hoehn and Yahr scale. Moreover, when the two sets of mean scores for all patients are compared, there is a strong (r = 0.785) and significant (p<0.0015) correlation between them.

Stability of thermal HFB and dissipative thermal RPA

CERN Document Server

Tanabe, K

1999-01-01

It is shown that, as for a Nilsson + pairing model, the extended stability condition of the thermal Hartree-Fock-Bogoliubov (THFB) solution coincides with the one of the thermal RPA (TRPA) solution unless the pairing constant G is too large. As possible extensions of the TRPA equation in alternative ways describing thermal fluctuation effect, the extended TRPA (ETRPA) and the dissipative TRPA (DTRPA) are discussed. Furthermore, the general microscopic framework of the TRPA predicts the saturation and decrease of giant resonance width in high temperature limit, i.e. the fragmentation width GAMMA sub f propor to(kT) sup ( sup - sup 3 sup ( sup 2 sup ) sup ) and the spreading width GAMMA suparrow down propor to(kT) sup ( sup - sup 1 sup ( sup 2 sup ) sup ).

Proposal of the penalty factor equations considering weld strength over-match

International Nuclear Information System (INIS)

Kim, Jong Sung; Jeong, Jae Wook; Lee, Kang Yong

2017-01-01

This paper proposes penalty factor equations that take into consideration the weld strength over-match given in the classified form similar to the revised equations presented in the Code Case N-779 via cyclic elastic-plastic finite element analysis. It was found that the Ke analysis data reflecting elastic follow-up can be consolidated by normalizing the primary-plus-secondary stress intensity ranges excluding the nonlinear thermal stress intensity component, S_n to over-match degree of yield strength, M_F. For the effect of over-match on K_n × K_v_"1, dispersion of the Kn × K_v analysis data can be sharply reduced by dividing total stress intensity range, excluding local thermal stresses, S_p_-_l_t by M_F. Finally, the proposed equations were applied to the weld between the safe end and the piping of a pressurizer surge nozzle in pressurized water reactors in order to calculate a cumulative usage factor. The cumulative usage factor was then compared with those derived by the previous K_e factor equations. The result shows that application of the proposed equations can significantly reduce conservatism of fatigue assessment using the previous K_e factor equations

Proposal of the Penalty Factor Equations Considering Weld Strength Over-Match

Directory of Open Access Journals (Sweden)

Jong-Sung Kim

2017-06-01

Full Text Available This paper proposes penalty factor equations that take into consideration the weld strength over-match given in the classified form similar to the revised equations presented in the Code Case N-779 via cyclic elastic-plastic finite element analysis. It was found that the Ke analysis data reflecting elastic follow-up can be consolidated by normalizing the primary-plus-secondary stress intensity ranges excluding the nonlinear thermal stress intensity component, Sn to over-match degree of yield strength, MF. For the effect of over-match on Kn × Κν, dispersion of the Kn × Κν analysis data can be sharply reduced by dividing total stress intensity range, excluding local thermal stresses, Sp-lt by MF. Finally, the proposed equations were applied to the weld between the safe end and the piping of a pressurizer surge nozzle in pressurized water reactors in order to calculate a cumulative usage factor. The cumulative usage factor was then compared with those derived by the previous Ke factor equations. The result shows that application of the proposed equations can significantly reduce conservatism of fatigue assessment using the previous Ke factor equations.

Constitutive equations for two-phase flows

International Nuclear Information System (INIS)

Boure, J.A.

1974-12-01

The mathematical model of a system of fluids consists of several kinds of equations complemented by boundary and initial conditions. The first kind equations result from the application to the system, of the fundamental conservation laws (mass, momentum, energy). The second kind equations characterize the fluid itself, i.e. its intrinsic properties and in particular its mechanical and thermodynamical behavior. They are the mathematical model of the particular fluid under consideration, the laws they expressed are so called the constitutive equations of the fluid. In practice the constitutive equations cannot be fully stated without reference to the conservation laws. Two classes of model have been distinguished: mixture model and two-fluid models. In mixture models, the mixture is considered as a single fluid. Besides the usual friction factor and heat transfer correlations, a single constitutive law is necessary. In diffusion models, the mixture equation of state is replaced by the phasic equations of state and by three consitutive laws, for phase change mass transfer, drift velocity and thermal non-equilibrium respectively. In the two-fluid models, the two phases are considered separately; two phasic equations of state, two friction factor correlations, two heat transfer correlations and four constitutive laws are included [fr

Load rate dependence of the mechanical properties of thermal barrier coating systems

Energy Technology Data Exchange (ETDEWEB)

Zotov, Nikolay; Eggeler, Gunther [Institut fuer Werkstoffe, Ruhr Universitaet Bochum, 44780 Bochum (Germany); Bartsch, Marion [Institut fuer Werkstoff-Forschung, DLR Koeln, 51147 Koeln (Germany)

2009-07-01

Thermal barrier coatings (TBC), composed of yttrium-stabilized zirconia (YSZ) ceramic top coat (TC) and intermetallic NiCoCrAlY bond coat (BC) are commonly used as protective coatings of Ni-based high temperature gas engine components. Nanoindentation techniques are increasingly applied for determining the TBC mechanical properties on a nanometre scale. However, little is known about the load-rate dependence of the mechanical properties, which is important for better understanding of cyclic thermal fatigue experiments. Nanoindentations with different load rates omega were performed on polished cross-sections of TBC, deposited by EB-PVD on IN625 substrates (S), using a XP Nanoindenter (MTS) equipped with Berkovich diamond tip. The Young's modulus (E) of the TC is independent of omega, while E for the BC and the S decreases with omega. The hardness (H) of the TC and the BC increases, while H for the S decreases with omega. From the dependence of H on omega, creep power-law exponents c = 0.24(11) and c = 0.023(6) for the TC and the BC were determined. For all TBC components, a decrease with omega of the power-law exponents n and m, describing the loading and unloading nanoindentation curves, is observed.

A thermal engine for underwater glider driven by ocean thermal energy

International Nuclear Information System (INIS)

Yang, Yanan; Wang, Yanhui; Ma, Zhesong; Wang, Shuxin

2016-01-01

Highlights: • Thermal engine with a double-tube structure is developed for underwater glider. • Isostatic pressing technology is effective to increase volumetric change rate. • Actual volumetric change rate reaches 89.2% of the theoretical value. • Long term sailing of 677 km and 27 days is achieved by thermal underwater glider. - Graphical Abstract: - Abstract: Underwater glider is one of the most popular platforms for long term ocean observation. Underwater glider driven by ocean thermal energy extends the duration and range of underwater glider powered by battery. Thermal engine is the core device of underwater glider to harvest ocean thermal energy. In this paper, (1) model of thermal engine was raised by thermodynamics method and the performance of thermal engine was investigated, (2) thermal engine with a double-tube structure was developed and isostatic pressing technology was applied to improve the performance for buoyancy driven, referencing powder pressing theory, (3) wall thickness of thermal engine was optimized to reduce the overall weight of thermal engine, (4) material selection and dimension determination were discussed for a faster heat transfer design, by thermal resistance analysis, (5) laboratory test and long term sea trail were carried out to test the performance of thermal engine. The study shows that volumetric change rate is the most important indicator to evaluating buoyancy-driven performance of a thermal engine, isostatic pressing technology is effective to improve volumetric change rate, actual volumetric change rate can reach 89.2% of the theoretical value and the average power is about 124 W in a typical diving profile. Thermal engine developed by Tianjin University is a superior thermal energy conversion device for underwater glider. Additionally, application of thermal engine provides a new solution for miniaturization of ocean thermal energy conversion.

Subchannel analysis program for boiling water reactor fuel bundles based on five conservation equations of two-phase flow

International Nuclear Information System (INIS)

Bessho, Y.; Uchikawa, S.

1985-01-01

A subchannel analysis program, MENUETT, is developed for evaluation of thermal-hydraulic characteristics in boiling water reactor fuel bundles. This program is based on five conservation equations of two-phase flow with the drift-flux correlation. The cross flows are calculated separately for liquid and vapor phases from the lateral momentum conservation equation. The effects of turbulent mixing and void drift are accounted for in the program. The conservation equations are implicitly differentiated with the convective terms by the donor-cell method, and are solved iteratively in the axial and lateral directions. Data of the 3 X 3 rod bundle experiments are used for program verification. The lateral distributions of equilibrium quality and mass flow rate at the bundle exit calculated by the program compare satisfactorily with the experimental results

Measured thermal and fast neutron fluence rates ATR Cycle 99-A, November 23, 1992--January 23, 1993

International Nuclear Information System (INIS)

Murray, R.K.; Rogers, J.W.

1993-03-01

This report contains the thermal (2200 m/s) and fast (E>me) neutron fluence rate data for ATR Cycle 99-A which were measured by the Radiation Measurements Laboratory (RML) as requested by the Power ReactorPrograms (ATR Experiments) Radiation Measurements Work Order. This report contains fluence rate values corresponding to the particular elevations (relative to the 80 ft. core elevation) where the measurements were taken. The data in this report consists of (1) a table of the ATR power history and distribution, (2) a hard copy listing of all thermal and fast neutron fluence rates, (3) plots of both the thermal and fast neutron fluence rates, and (4) a magnetic record (3.5 inch diskette) containing a listing of only the fast neutron fluence rates, their assigned elevations and proper header identification of all monitor positions contained herein. The fluence rates reported are for the average power levels given in the table of power history and distribution. All ''H'' holder monitor wires for this cycle are 54 inches long. All ''SR'' holder monitor wires for this cycle are 55 inches long. This length allows measurement of the full core region and makes the first count elevation 24.73 inches above core midplane. Due to the safety rod problems in the west lobe, ''BR'' holders were used in the W-1, 2, 3, and 4 positions. All ''BR'' holder monitor wires for this cycle are 56.25 inches long. The distance from the end of the wires to the first count position was 4.25 inches for all wires counted from this cycle

A comparison of the eigenvalue equations in kappa, α, lambda and γ in reactor theory. Application to fast and thermal systems in unreflected and reflected configurations

International Nuclear Information System (INIS)

Velarde, G.; Ahnert, C.; Aragones, J.M.

1977-01-01

A comparative study of the eigenvalue transport in kappa, lambda, γ and α is made. The neutronic fluxes obtained by solving the transport equation in the four eigenvalue types are compared numerically for fast and thermal systems in unreflected and reflected configurations. Important conclusions will be obtained about the appropiate use of each eigenvalue depending on the calculation type to be performed. (author)

Comparison between a serum creatinine-and a cystatin C-based glomerular filtration rate equation in patients receiving amphotericin B.

Science.gov (United States)

Karimzadeh, Iman; Khalili, Hossein

2016-06-06

Serum cystatin C (Cys C) has a number of advantages over serum creatinine in the evaluation of kidney function. Apart from Cys C level itself, several formulas have also been introduced in different clinical settings for the estimation of glomerular filtration rate (GFR) based upon serum Cys C level. The aim of the present study was to compare a serum Cys C-based equation with Cockcroft-Gault serum creatinine-based formula, both used in the calculation of GFR, in patients receiving amphotericin B. Fifty four adult patients with no history of acute or chronic kidney injury having been planned to receive conventional amphotericin B for an anticipated duration of at least 1 week for any indication were recruited. At three time points during amphotericin B treatment, including days 0, 7, and 14, serum cystatin C as well as creatinine levels were measured. GFR at the above time points was estimated by both creatinine (Cockcroft-Gault) and serum Cys C based equations. There was significant correlation between creatinine-based and Cys C-based GFR values at days 0 (R = 0.606, P = 0.001) and 7 (R = 0.714, P creatinine-and a cystatin C-based glomerular filtration rate equation in patients receiving amphotericin B.

Effect of brine flow rate on the performance of a spiral-jacketed thermal storage tank used for SDHW systems: A computational fluid dynamics study

International Nuclear Information System (INIS)

Baek, Seung Man; Nam, Jin Hyun; Hong, Hiki; Kim, Charn-Jung

2011-01-01

This study numerically investigates the effect of the brine flow rate on the thermal performance of a spiral-jacketed thermal storage tank (TST) installed in a solar domestic hot water (SDHW) system. The spiral-jacketed TST is a TST with a mantle heat exchanger, consisting of a vertical, cylindrical water tank for energy storage and a spiral brine flow path attached to the tank wall for heat transfer. A computational fluid dynamics (CFD) model was constructed based on the actual geometry of a spiral-jacketed TST. In addition, the boundary conditions were defined by considering solar radiation and ambient temperature data that were measured during experimental operation of the SDHW system. The numerical results demonstrated that an increase in the brine flow rate enhances the thermal efficiency of the TST due to higher heat transfer coefficients in the spiral path, and also leads to reduced thermal stratification in the TST. On the other hand, a lower brine flow rate increased the heat transfer rate at the inlet of the spiral path near the top of the TST, which resulted in enhanced thermal stratification. The optimal range for the rate of brine flow rate is discussed with respect to the thermal efficiency of the TST and the required pumping power for brine circulation in the spiral flow path. - Highlights: → A CFD model was developed for a spiral-jacketed thermal storage tank (TST) installed in a solar domestic hot water (SDHW) system. → Effects of brine flow rate on the overall performance of the spiral-jacketed TST were numerically investigated. → Higher brine flow rates slightly increased the solar energy acquired by the TST, but it also increased the pump power required to circulate the brine. → Lower brine flow rates were found to be a better option for the spiral-jacketed TST, by maximizing the exergy of the SDHW system.

Application of heat-balance integral method to conjugate thermal explosion

Directory of Open Access Journals (Sweden)

Novozhilov Vasily

2009-01-01

Full Text Available Conjugate thermal explosion is an extension of the classical theory, proposed and studied recently by the author. The paper reports application of heat-balance integral method for developing phase portraits for systems undergoing conjugate thermal explosion. The heat-balance integral method is used as an averaging method reducing partical differential equation problem to the set of first-order ordinary differential equations. The latter reduced problem allows natural interpretation in appropriately chosen phase space. It is shown that, with the help of heat-balance integral technique, conjugate thermal explosion problem can be described with a good accuracy by the set of non-linear first-order differential equations involving complex error function. Phase trajectories are presented for typical regimes emerging in conjugate thermal explosion. Use of heat-balance integral as a spatial averaging method allows efficient description of system evolution to be developed.

Combining several thermal indices to generate a unique heat comfort assessment methodology

Directory of Open Access Journals (Sweden)

Wissam EL Hachem

2015-11-01

Full Text Available Purpose: The proposed methodology hopes to provide a systematic multi-disciplinary approach to assess the thermal environment while minimizing unneeded efforts. Design/methodology/approach: Different factors affect the perception of the human thermal experience: metabolic rate (biology, surrounding temperatures (heat balance and environmental factors and cognitive treatment (physiology.This paper proposes a combination of different multidisciplinary variables to generate a unique heat comfort assessment methodology. The variables at stake are physiological, biological, and environmental. Our own heat analysis is thoroughly presented and all relevant equations are described. Findings: Most companies are oblivious about potential dangers of heat stress accidents and thus about methods to monitor and prevent them. This methodology enables the company or the concerned individual to conduct a preliminary assessment with minimal wasted resources and time in unnecessary steps whilst providing a guideline for a detailed study with minimal error rates if needed. More so, thermal comfort is an integral part of sound ergonomics practices, which in turn are decisive for the success of any lean six sigma initiative. Research limitations/implications: This methodology requires several full implementations to finalize its design. Originality/value: Most used heat comfort models are inherently uncertain and tiresome to apply. An extensive literature review confirms the need for a uniform assessment methodology that combines the different thermal comfort models such as the Fanger comfort model (PMV, PPD and WGBT since high error rates coupled with tiresome calculations often hinder the thermal assessment process.

Analyses of glass transition phenomena by solving differential equation with delay effect

International Nuclear Information System (INIS)

Takeuchi, A.; Inoue, A.

2007-01-01

A linear differential equation for the analyses of glass transition phenomena has been proposed by taking into account the delay effect due to the change in transportation of atoms near the glass transition temperature (T g ). Under the condition maintaining the order of the differential equation as the second, the non-linear differential equation proposed by Van Den Beukel and Sietsma is modified to obtain the analytic solution for a linear equation by introducing the following points: the delay effect which is described with a term of Mackey-Glass model, a concept of effective free volume (x fe eff ) and its concentration expression (C fe eff ) which correspond to the equilibrium, and an additional term associated with C fe eff . In analyzing the linear equation, Doyle's p-function was used for the integral of reaction rate with respect to temperature (T). It is found that the linear equation proposed in the present study can describe the changes in free volume (x) with increasing temperature in the dx/dT-T chart, the sharp increase in free volume at T g , and over shooting phenomena of free volume slightly above the T g , as experimentally in thermal analyses for metallic glasses. The linear solution obtained in the present study is of great importance for the analyses of the glass transition because the change in free volume with increasing temperature on heating is described with fundamental functions

Detailed Balance of Thermalization Dynamics in Rydberg-Atom Quantum Simulators.

Science.gov (United States)

Kim, Hyosub; Park, YeJe; Kim, Kyungtae; Sim, H-S; Ahn, Jaewook

2018-05-04

Dynamics of large complex systems, such as relaxation towards equilibrium in classical statistical mechanics, often obeys a master equation that captures essential information from the complexities. Here, we find that thermalization of an isolated many-body quantum state can be described by a master equation. We observe sudden quench dynamics of quantum Ising-like models implemented in our quantum simulator, defect-free single-atom tweezers in conjunction with Rydberg-atom interaction. Saturation of their local observables, a thermalization signature, obeys a master equation experimentally constructed by monitoring the occupation probabilities of prequench states and imposing the principle of the detailed balance. Our experiment agrees with theories and demonstrates the detailed balance in a thermalization dynamics that does not require coupling to baths or postulated randomness.

Detailed Balance of Thermalization Dynamics in Rydberg-Atom Quantum Simulators

Science.gov (United States)

Kim, Hyosub; Park, YeJe; Kim, Kyungtae; Sim, H.-S.; Ahn, Jaewook

2018-05-01

Dynamics of large complex systems, such as relaxation towards equilibrium in classical statistical mechanics, often obeys a master equation that captures essential information from the complexities. Here, we find that thermalization of an isolated many-body quantum state can be described by a master equation. We observe sudden quench dynamics of quantum Ising-like models implemented in our quantum simulator, defect-free single-atom tweezers in conjunction with Rydberg-atom interaction. Saturation of their local observables, a thermalization signature, obeys a master equation experimentally constructed by monitoring the occupation probabilities of prequench states and imposing the principle of the detailed balance. Our experiment agrees with theories and demonstrates the detailed balance in a thermalization dynamics that does not require coupling to baths or postulated randomness.

Adaptive radiation along a thermal gradient: preliminary results of habitat use and respiration rate divergence among whitefish morphs.

Directory of Open Access Journals (Sweden)

Kimmo Kalevi Kahilainen

Full Text Available Adaptive radiation is considered an important mechanism for the development of new species, but very little is known about the role of thermal adaptation during this process. Such adaptation should be especially important in poikilothermic animals that are often subjected to pronounced seasonal temperature variation that directly affects metabolic function. We conducted a preliminary study of individual lifetime thermal habitat use and respiration rates of four whitefish (Coregonus lavaretus (L. morphs (two pelagic, one littoral and one profundal using stable carbon and oxygen isotope values of otolith carbonate. These morphs, two of which utilized pelagic habitats, one littoral and one profundal recently diverged via adaptive radiation to exploit different major niches in a deep and thermally stratified subarctic lake. We found evidence that the morphs used different thermal niches. The profundal morph had the most distinct thermal niche and consistently occupied the coldest thermal habitat of the lake, whereas differences were less pronounced among the shallow water pelagic and littoral morphs. Our results indicated ontogenetic shifts in thermal niches: juveniles of all whitefish morphs inhabited warmer ambient temperatures than adults. According to sampling of the otolith nucleus, hatching temperatures were higher for benthic compared to pelagic morphs. Estimated respiration rate was the lowest for benthivorous profundal morph, contrasting with the higher values estimated for the other morphs that inhabited shallower and warmer water. These preliminary results suggest that physiological adaptation to different thermal habitats shown by the sympatric morphs may play a significant role in maintaining or strengthening niche segregation and divergence in life-history traits, potentially contributing to reproductive isolation and incipient speciation.

Thermally induced pressure locking of gate valves: A survey of valve bonnet pressurization rates

International Nuclear Information System (INIS)

Ezekoye, L.I.; Moore, W.E.

1996-01-01

Closed, water filled gate valves run the risk of becoming pressurized due to heat input from the environment or from adjacent connected piping. Thermal pressurization of gate valve bonnets may lead to the valves failing to open on demand and can even induce structural failure of valves. This paper presents an analytical prediction of the pressurization rate of a closed pressure vessel subject to uniform heating which may be considered as an upper bound to the pressurization rate that may occur in the field. Then actual valve experiences described in the literature are reviewed to determine the expected pressurization rate in existing hardware designs. A statistical approach is applied to reconcile the differing pressurization rates reported in the literature and determine a rate that can be applied in valve evaluations. The limitations of the reconciled rate are discussed

METHOD FOR DETERMINATION OF THERMAL CHARACTERISTICS OF THE LAYER OF GRANULAR MEDIA WITH ELEMENTS OF PULSED THERMAL NDT

Directory of Open Access Journals (Sweden)

Y. V. Shokina

2015-01-01

Full Text Available At the Department of Food Production of Murmansk State Technical University (MSTU was developed a method of producing smoke fuel using infrared energy supply. The method provides a stable temperature pyrolysis of wood fuel is less than 400 ° C. Kinetic of the heating layer of fuel (wooden chips is affected by chip's density and moisture content. The method of calculating of the optimum modes of smoke produce, which is based on a system of differential equations of heat and mass transfer in the IR smoke generator, was previously proposed. The system of equations includes thermal characteristics (TC of the fuel layer (e.g. specific heat, thermal conductivity, thermal diffusivity. The exact definition of these characteristics affect the accuracy of the experimental calculation of optimal process conditions with use of the developed software. A definition of layer's TC by a method with elements of pulsed thermal NDT. The use of thermal imager is proposed for measuring the temperature of the irritated surface of the porous wooden chip's lawyer.

Thermal Equation of State of Natural Ti-Bearing Clinohumite

Science.gov (United States)

Qin, Fei; Wu, Xiang; Zhang, Dongzhou; Qin, Shan; Jacobsen, Steven D.

2017-11-01

The natural occurrence of clinohumite in metabasalts and hydrothermally altered peridotites provides a source of water-rich minerals in subducted slabs, making knowledge of their phase relations and crystal chemistry under high pressure-temperature (P-T) conditions important for understating volatile recycling and geodynamic process in the Earth's mantle. Here we present a synchrotron-based, single-crystal X-ray diffraction study on two natural Ti-bearing clinohumites up to 28 GPa and 750 K in order to simulate conditions within subducted slabs. No phase transition occurs in clinohumite over this P-T range. Pressure-volume relationships of both compositions at room temperature were fitted to a third-order Birch-Murnaghan equation of state (EoS) with V0 = 650.4(3) Å3, KT0 = 141(4) GPa, and KT0' = 4.0(6) for Ti-poor clinohumite (0.07 Ti per formula unit, pfu) and V0 = 650.8(3) Å3, KT0 = 144(4) GPa, and KT0' = 3.6(7) for Ti-rich clinohumite (0.21 Ti pfu). Both clinohumites exhibit anisotropic compression with βb > βc > βa. We also refined P-V-T equation of state parameters using the high-temperature Birch-Murnaghan EoS, yielding (∂KT0/∂T)P = -0.040(10) GPa/K and αT = 5.1(6) × 10-5 K-1 for Ti-poor clinohumite and (∂KT0/∂T)P = -0.045(11) GPa/K and αT = 5.7(6) × 10-5 K-1 for Ti-rich clinohumite. Ti-poor and Ti-rich clinohumites display similar equations of state but are 20% more incompressible than Mg-pure clinohumite and display 5% higher bulk sound velocity than olivine at upper mantle conditions. Our results provide constraints for modeling geodynamic process related to the subduction and transport of potentially water-rich slabs in the mantle.

Comparative Thermal Degradation Patterns of Natural Yellow Colorants Used in Foods.

Science.gov (United States)

Giménez, Pedro J; Fernández-López, José A; Angosto, José M; Obón, José M

2015-12-01

There is a great interest in natural yellow colorants due to warnings issued about certain yellow food colorings of synthetic origin. However, no comparative studies have been reported of their thermal stability. For this reason, the thermal stabilities of six natural yellow colorants used in foods--lutein, riboflavin, curcumin, ß-carotene, gardenia yellow and Opuntia betaxanthins--were studied in simple solutions over a temperature range 30-90 °C. Spectral properties and visual color were investigated during 6 h of heat treatment. Visual color was monitored from the CIEL*a*b* parameters. The remaining absorbance at maximum wavelength and the total color difference were used to quantify color degradation. The rate of color degradation increased as the temperature rose. The results showed that the thermal degradation of the colorants followed a first-order reaction kinetics. The reaction rate constants and half-life periods were determined as being central to understanding the color degradation kinetics. The temperature-dependent degradation was adequately modeled on the Arrhenius equation. Activation energies ranged from 3.2 kJmol(-1) (lutein) to 43.7 kJmol(-1) (Opuntia betaxanthins). ß-carotene and lutein exhibited high thermal stability, while betaxanthins and riboflavin degraded rapidly as temperature increased. Gardenia yellow and curcumin were in an intermediate position.

Characterization and modeling of thermal diffusion and aggregation in nanofluids.

Energy Technology Data Exchange (ETDEWEB)

Gharagozloo, Patricia E.; Goodson, Kenneth E. (Stanford University, Stanford, CA)

2010-05-01

Fluids with higher thermal conductivities are sought for fluidic cooling systems in applications including microprocessors and high-power lasers. By adding high thermal conductivity nanoscale metal and metal oxide particles to a fluid the thermal conductivity of the fluid is enhanced. While particle aggregates play a central role in recent models for the thermal conductivity of nanofluids, the effect of particle diffusion in a temperature field on the aggregation and transport has yet to be studied in depth. The present work separates the effects of particle aggregation and diffusion using parallel plate experiments, infrared microscopy, light scattering, Monte Carlo simulations, and rate equations for particle and heat transport in a well dispersed nanofluid. Experimental data show non-uniform temporal increases in thermal conductivity above effective medium theory and can be well described through simulation of the combination of particle aggregation and diffusion. The simulation shows large concentration distributions due to thermal diffusion causing variations in aggregation, thermal conductivity and viscosity. Static light scattering shows aggregates form more quickly at higher concentrations and temperatures, which explains the increased enhancement with temperature reported by other research groups. The permanent aggregates in the nanofluid are found to have a fractal dimension of 2.4 and the aggregate formations that grow over time are found to have a fractal dimension of 1.8, which is consistent with diffusion limited aggregation. Calculations show as aggregates grow the viscosity increases at a faster rate than thermal conductivity making the highly aggregated nanofluids unfavorable, especially at the low fractal dimension of 1.8. An optimum nanoparticle diameter for these particular fluid properties is calculated to be 130 nm to optimize the fluid stability by reducing settling, thermal diffusion and aggregation.

Comparison of the performance of the updated Schwartz, combined Schwartz and the Grubb glomerular filtration rate equations in a general pediatric population

Directory of Open Access Journals (Sweden)

Alaleh Gheissari

2014-01-01

Full Text Available To determine the performance of the updated Schwartz, combined Schwartz and Grubb glomerular filtration rate (GFR equations in a relatively large number of healthy children with no known renal disease, we studied 712 students aged between seven and 18 years from the Isfahan province of Iran by random cluster sampling between 2009 and 2010. Blood investigations included blood urea nitrogen, creatinine and cystatin C. For each participant, GFR was calculated based on the three equations. We used Bland-Altman plots and weighted kappa statistics to compare the performance of the study equations. The mean age of the children was 12.2 ± 2.4 years. A high concordance in estimating GFR (mean difference: 0 ± 12.7 mL/min/1.73 m 2 and a very good agreement in defining chronic kidney disease (CKD and non-CKD individuals (weighted kappa: 0.85; 95% confidence intervals: 0.69-1 were observed between the updated Schwartz and the combined Schwartz equations. Poor agreement was observed between the Grubb equation and two Schwartz equations in estimating GFR and defining CKD. There was no systematic deviation between the updated Schwartz and the combined Schwartz equations in children with normal renal function. The Grubb equation was highly inconsistent with both Schwartz equations in this population. We conclude that the updated Schwartz equation is simpler and more accessible than the combined Schwartz equation in daily clinical practice and CKD screening programs.

State-dependent neutral delay equations from population dynamics.

Science.gov (United States)

Barbarossa, M V; Hadeler, K P; Kuttler, C

2014-10-01

A novel class of state-dependent delay equations is derived from the balance laws of age-structured population dynamics, assuming that birth rates and death rates, as functions of age, are piece-wise constant and that the length of the juvenile phase depends on the total adult population size. The resulting class of equations includes also neutral delay equations. All these equations are very different from the standard delay equations with state-dependent delay since the balance laws require non-linear correction factors. These equations can be written as systems for two variables consisting of an ordinary differential equation (ODE) and a generalized shift, a form suitable for numerical calculations. It is shown that the neutral equation (and the corresponding ODE--shift system) is a limiting case of a system of two standard delay equations.

Thermodynamic consistency of viscoplastic material models involving external variable rates in the evolution equations for the internal variables

International Nuclear Information System (INIS)

Malmberg, T.

1993-09-01

The objective of this study is to derive and investigate thermodynamic restrictions for a particular class of internal variable models. Their evolution equations consist of two contributions: the usual irreversible part, depending only on the present state, and a reversible but path dependent part, linear in the rates of the external variables (evolution equations of ''mixed type''). In the first instance the thermodynamic analysis is based on the classical Clausius-Duhem entropy inequality and the Coleman-Noll argument. The analysis is restricted to infinitesimal strains and rotations. The results are specialized and transferred to a general class of elastic-viscoplastic material models. Subsequently, they are applied to several viscoplastic models of ''mixed type'', proposed or discussed in the literature (Robinson et al., Krempl et al., Freed et al.), and it is shown that some of these models are thermodynamically inconsistent. The study is closed with the evaluation of the extended Clausius-Duhem entropy inequality (concept of Mueller) where the entropy flux is governed by an assumed constitutive equation in its own right; also the constraining balance equations are explicitly accounted for by the method of Lagrange multipliers (Liu's approach). This analysis is done for a viscoplastic material model with evolution equations of the ''mixed type''. It is shown that this approach is much more involved than the evaluation of the classical Clausius-Duhem entropy inequality with the Coleman-Noll argument. (orig.) [de

Slip effects on MHD boundary layer flow over an exponentially stretching sheet with suction/blowing and thermal radiation

Directory of Open Access Journals (Sweden)

Swati Mukhopadhyay

2013-09-01

Full Text Available The boundary layer flow and heat transfer towards a porous exponential stretching sheet in presence of a magnetic field is presented in this analysis. Velocity slip and thermal slip are considered instead of no-slip conditions at the boundary. Thermal radiation term is incorporated in the temperature equation. Similarity transformations are used to convert the partial differential equations corresponding to the momentum and energy equations into non-linear ordinary differential equations. Numerical solutions of these equations are obtained by shooting method. It is found that the horizontal velocity decreases with increasing slip parameter as well as with the increasing magnetic parameter. Temperature increases with the increasing values of magnetic parameter. Temperature is found to decrease with an increase of thermal slip parameter. Thermal radiation enhances the effective thermal diffusivity and the temperature rises.

Proposal of the penalty factor equations considering weld strength over-match

Energy Technology Data Exchange (ETDEWEB)

Kim, Jong Sung [Dept. of Nuclear Engineering, Sejong University, Seoul (Korea, Republic of); Jeong, Jae Wook [Korea Hydro and Nuclear Power Co., Ltd., Gyeongju (Korea, Republic of); Lee, Kang Yong [State Key Laboratory of Structural Analysis for Industrial Equipment, Dept. of Engineering Mechanics, Dalian University of Technology, Dalian (China)

2017-06-15

This paper proposes penalty factor equations that take into consideration the weld strength over-match given in the classified form similar to the revised equations presented in the Code Case N-779 via cyclic elastic-plastic finite element analysis. It was found that the Ke analysis data reflecting elastic follow-up can be consolidated by normalizing the primary-plus-secondary stress intensity ranges excluding the nonlinear thermal stress intensity component, S{sub n} to over-match degree of yield strength, M{sub F}. For the effect of over-match on K{sub n} × K{sub v{sup 1}}, dispersion of the Kn × K{sub v} analysis data can be sharply reduced by dividing total stress intensity range, excluding local thermal stresses, S{sub p-lt} by M{sub F}. Finally, the proposed equations were applied to the weld between the safe end and the piping of a pressurizer surge nozzle in pressurized water reactors in order to calculate a cumulative usage factor. The cumulative usage factor was then compared with those derived by the previous K{sub e} factor equations. The result shows that application of the proposed equations can significantly reduce conservatism of fatigue assessment using the previous K{sub e} factor equations.

Exact solutions to the Mo-Papas and Landau-Lifshitz equations

Science.gov (United States)

Rivera, R.; Villarroel, D.

2002-10-01

Two exact solutions of the Mo-Papas and Landau-Lifshitz equations for a point charge in classical electrodynamics are presented here. Both equations admit as an exact solution the motion of a charge rotating with constant speed in a circular orbit. These equations also admit as an exact solution the motion of two identical charges rotating with constant speed at the opposite ends of a diameter. These exact solutions allow one to obtain, starting from the equation of motion, a definite formula for the rate of radiation. In both cases the rate of radiation can also be obtained, with independence of the equation of motion, from the well known fields of a point charge, that is, from the Maxwell equations. The rate of radiation obtained from the Mo-Papas equation in the one-charge case coincides with the rate of radiation that comes from the Maxwell equations; but in the two-charge case the results do not coincide. On the other hand, the rate of radiation obtained from the Landau-Lifshitz equation differs from the one that follows from the Maxwell equations in both the one-charge and two-charge cases. This last result does not support a recent statement by Rohrlich in favor of considering the Landau-Lifshitz equation as the correct and exact equation of motion for a point charge in classical electrodynamics.

Exact solutions to the Mo-Papas and Landau-Lifshitz equations

International Nuclear Information System (INIS)

Rivera, R.; Villarroel, D.

2002-01-01

Two exact solutions of the Mo-Papas and Landau-Lifshitz equations for a point charge in classical electrodynamics are presented here. Both equations admit as an exact solution the motion of a charge rotating with constant speed in a circular orbit. These equations also admit as an exact solution the motion of two identical charges rotating with constant speed at the opposite ends of a diameter. These exact solutions allow one to obtain, starting from the equation of motion, a definite formula for the rate of radiation. In both cases the rate of radiation can also be obtained, with independence of the equation of motion, from the well known fields of a point charge, that is, from the Maxwell equations. The rate of radiation obtained from the Mo-Papas equation in the one-charge case coincides with the rate of radiation that comes from the Maxwell equations; but in the two-charge case the results do not coincide. On the other hand, the rate of radiation obtained from the Landau-Lifshitz equation differs from the one that follows from the Maxwell equations in both the one-charge and two-charge cases. This last result does not support a recent statement by Rohrlich in favor of considering the Landau-Lifshitz equation as the correct and exact equation of motion for a point charge in classical electrodynamics

Comparison of measured and predicted thermal mixing tests using improved finite difference technique

International Nuclear Information System (INIS)

Hassan, Y.A.; Rice, J.G.; Kim, J.H.

1983-01-01

The numerical diffusion introduced by the use of upwind formulations in the finite difference solution of the flow and energy equations for thermal mixing problems (cold water injection after small break LOCA in a PWR) was examined. The relative importance of numerical diffusion in the flow equations, compared to its effect on the energy equation was demonstrated. The flow field equations were solved using both first order accurate upwind, and second order accurate differencing schemes. The energy equation was treated using the conventional upwind and a mass weighted skew upwind scheme. Results presented for a simple test case showed that, for thermal mixing problems, the numerical diffusion was most significant in the energy equation. The numerical diffusion effect in the flow field equations was much less significant. A comparison of predictions using the skew upwind and the conventional upwind with experimental data from a two dimensional thermal mixing text are presented. The use of the skew upwind scheme showed a significant improvement in the accuracy of the steady state predicted temperatures. (orig./HP)

The plasma wake field excitation: Recent developments from thermal to quantum regime

Science.gov (United States)

Fedele, Renato; Tanjia, Fatema; de Nicola, Sergio; Jovanović, Dušan; Jovanović

2013-12-01

To describe the transverse nonlinear and collective self-consistent interaction of a long relativistic electron or positron beam with an unmagnetized plasma, a pair of coupled nonlinear differential equations were proposed by Fedele and Shukla in 1992 (Fedele, R. and Shukla, P. K. 1992a Phys. Rev. A 45, 4045). They were obtained within the quantum-like description provided by the thermal wave model and the theory of plasma wake field excitation. The pair of equations comprises a 2D Schrödinger-like equation for a complex wave function (whose squared modulus is proportional to beam density) and a Poisson-like equation for the plasma wake potential. The dispersion coefficient of the Schrödinger-like equation is proportional to the beam thermal emittance. More recently, Fedele-Shukla equations have been further applied to magnetized plasmas, and solutions were found in the form of nonlinear vortex states and ring solitons. They have been also applied to plasma focusing problems and extended from thermal to quantum regimes. We present here a review of the original approach, and subsequent developments.

Identification of strain-rate and thermal sensitive material model with an inverse method

Directory of Open Access Journals (Sweden)

Peroni M.

2010-06-01

Full Text Available This paper describes a numerical inverse method to extract material strength parameters from the experimental data obtained via mechanical tests at different strainrates and temperatures. It will be shown that this procedure is particularly useful to analyse experimental results when the stress-strain fields in the specimen cannot be correctly described via analytical models. This commonly happens in specimens with no regular shape, in specimens with a regular shape when some instability phenomena occur (for example the necking phenomena in tensile tests that create a strongly heterogeneous stress-strain fields or in dynamic tests (where the strain-rate field is not constant due to wave propagation phenomena. Furthermore the developed procedure is useful to take into account thermal phenomena generally affecting high strain-rate tests due to the adiabatic overheating related to the conversion of plastic work. The method presented requires strong effort both from experimental and numerical point of view, anyway it allows to precisely identify the parameters of different material models. This could provide great advantages when high reliability of the material behaviour is necessary. Applicability of this method is particularly indicated for special applications in the field of aerospace engineering, ballistic, crashworthiness studies or particle accelerator technologies, where materials could be submitted to strong plastic deformations at high-strain rate in a wide range of temperature. Thermal softening effect has been investigated in a temperature range between 20°C and 1000°C.

Numerical Analysis of a Paraffin/Metal Foam Composite for Thermal Storage

Science.gov (United States)

Di Giorgio, P.; Iasiello, M.; Viglione, A.; Mameli, M.; Filippeschi, S.; Di Marco, P.; Andreozzi, A.; Bianco, N.

2017-01-01

In the last decade, the use of Phase Change Materials (PCMs) as passive thermal energy storage has been widely studied both analytically and experimentally. Among the PCMs, paraffins show many advantages, such as having a high latent heat, a low vapour pressure, being chemically inert, stable and non-toxic. But, their thermal conductivity is very low with a high volume change during the melting process. An efficient way to increase their poor thermal conductivity is to couple them with open cells metallic foams. This paper deals with a theoretical analysis of paraffin melting process inside an aluminum foam. A mathematical model is developed by using the volume-averaged governing equations for the porous domain, made up by the PCM embedded into the metal foam. Non-Darcian and buoyancy effects are considered in the momentum equation, while the energy equations are modelled with the Local Thermal Non-Equilibrium (LTNE) approach. The PCM liquefaction is treated with the apparent heat capacity method and the governing equations are solved with a finite-element scheme by COMSOL Multiphysics®. A new method to calculate the coupling coefficients needed for the thermal model has been developed and the results obtained have been validated comparing them to experimental data in literature.

Calculating lattice thermal conductivity: a synopsis

Science.gov (United States)

Fugallo, Giorgia; Colombo, Luciano

2018-04-01

We provide a tutorial introduction to the modern theoretical and computational schemes available to calculate the lattice thermal conductivity in a crystalline dielectric material. While some important topics in thermal transport will not be covered (including thermal boundary resistance, electronic thermal conduction, and thermal rectification), we aim at: (i) framing the calculation of thermal conductivity within the general non-equilibrium thermodynamics theory of transport coefficients, (ii) presenting the microscopic theory of thermal conduction based on the phonon picture and the Boltzmann transport equation, and (iii) outlining the molecular dynamics schemes to calculate heat transport. A comparative and critical addressing of the merits and drawbacks of each approach will be discussed as well.

Thermal conductivity analysis of SiC ceramics and fully ceramic microencapsulated fuel composites

International Nuclear Information System (INIS)

Lee, Hyeon-Geun; Kim, Daejong; Lee, Seung Jae; Park, Ji Yeon; Kim, Weon-Ju

2017-01-01

Highlights: • Thermal conductivity of SiC ceramics and FCM pellets was measured and discussed. • Thermal conductivity of FCM pellets was analyzed by the Maxwell-Eucken equation. • Effective thermal conductivity of TRISO particles applied in this study was assumed. - Abstract: The thermal conductivity of SiC ceramics and FCM fuel composites, consisting of a SiC matrix and TRISO coated particles, was measured and analyzed. SiC ceramics and FCM pellets were fabricated by hot press sintering with Al_2O_3 and Y_2O_3 sintering additives. Several factors that influence thermal conductivity, specifically the content of sintering additives for SiC ceramics and the volume fraction of TRISO particles and the matrix thermal conductivity of FCM pellets, were investigated. The thermal conductivity values of samples were analyzed on the basis of their microstructure and the arrangement of TRISO particles. The thermal conductivity of the FCM pellets was compared to that predicted by the Maxwell-Eucken equation and the thermal conductivity of TRISO coated particles was calculated. The thermal conductivity of FCM pellets in various sintering conditions was in close agreement to that predicted by the Maxwell-Eucken equation with the fitted thermal conductivity value of TRISO particles.

Darcy-Forchheimer flow of Maxwell nanofluid flow with nonlinear thermal radiation and activation energy

Directory of Open Access Journals (Sweden)

T. Sajid

2018-03-01

Full Text Available The present article is about the study of Darcy-Forchheimer flow of Maxwell nanofluid over a linear stretching surface. Effects like variable thermal conductivity, activation energy, nonlinear thermal radiation is also incorporated for the analysis of heat and mass transfer. The governing nonlinear partial differential equations (PDEs with convective boundary conditions are first converted into the nonlinear ordinary differential equations (ODEs with the help of similarity transformation, and then the resulting nonlinear ODEs are solved with the help of shooting method and MATLAB built-in bvp4c solver. The impact of different physical parameters like Brownian motion, thermophoresis parameter, Reynolds number, magnetic parameter, nonlinear radiative heat flux, Prandtl number, Lewis number, reaction rate constant, activation energy and Biot number on Nusselt number, velocity, temperature and concentration profile has been discussed. It is viewed that both thermophoresis parameter and activation energy parameter has ascending effect on the concentration profile.

Fundamental processes in the production of thermally stimulated luminescence

International Nuclear Information System (INIS)

McKeever, S.W.S.; Markey, B.G.; Lewandowski, A.C.

1993-01-01

We introduce two new functions, known as the q(T) and Q(T) functions, which describe how close a system is to quasi-equilibrium during the production of thermally stimulated conductivity (TSC) and thermoluminescence (TL). These functions are related to physically meaningful quantities (i.e. the various rates of recombination, excitation and retrapping) and are closely related to the kinetic-order function, P(T). From a numerical analysis of the rate equations describing the flow of charge carriers between various energy levels in a simple model for TL and TSC we demonstrate that the usual equation for describing TL emission is related to the actual TL peak by the Q(T) function, for first-order kinetics. The use of the simplified function to analyze TL and TSC data leads to errors which can be directly traced to the departure of the system from quasi-equilibrium. We show how the q(T) function can be obtained experimentally and we present arguments to demonstrate that first-order kinetics are likely to be the most common in nature. (author)

Simulation of Thermal Transients using CSMP

International Nuclear Information System (INIS)

Konuk, A.A.

1981-01-01

A mathematical model has been developed to simulate thermal transientes for the Hellum Loop of the 'Instituto de Pesquisas Energeticas e Nuleares', Sao Paulo. The model is based on the energy equation applied to the various components of the loop. The non-linear system of first order ordinary differential equation and algebraic equations has been solved using IBM'S 'System/360-Continuous System Modeling Program-CSMP'. The model has been tested satisfactory with experimental results. (Author) [pt

Technical note: Use of a simplified equation for estimating glomerular filtration rate in beef cattle.

Science.gov (United States)

Murayama, I; Miyano, A; Sasaki, Y; Hirata, T; Ichijo, T; Satoh, H; Sato, S; Furuhama, K

2013-11-01

This study was performed to clarify whether a formula (Holstein equation) based on a single blood sample and the isotonic, nonionic, iodine contrast medium iodixanol in Holstein dairy cows can apply to the estimation of glomerular filtration rate (GFR) for beef cattle. To verify the application of iodixanol in beef cattle, instead of the standard tracer inulin, both agents were coadministered as a bolus intravenous injection to identical animals at doses of 10 mg of I/kg of BW and 30 mg/kg. Blood was collected 30, 60, 90, and 120 min after the injection, and the GFR was determined by the conventional multisample strategies. The GFR values from iodixanol were well consistent with those from inulin, and no effects of BW, age, or parity on GFR estimates were noted. However, the GFR in cattle weighing less than 300 kg, aged<1 yr old, largely fluctuated, presumably due to the rapid ruminal growth and dynamic changes in renal function at young adult ages. Using clinically healthy cattle and those with renal failure, the GFR values estimated from the Holstein equation were in good agreement with those by the multisample method using iodixanol (r=0.89, P=0.01). The results indicate that the simplified Holstein equation using iodixanol can be used for estimating the GFR of beef cattle in the same dose regimen as Holstein dairy cows, and provides a practical and ethical alternative.

Thermal Marangoni convection in two-phase flow of dusty Casson fluid

Science.gov (United States)

Mahanthesh, B.; Gireesha, B. J.

2018-03-01

This paper deals with the thermal Marangoni convection effects in magneto-Casson liquid flow through suspension of dust particles. The transpiration cooling aspect is accounted. The surface tension is assumed to be fluctuating linearly with temperature. The fluid and dust particle's temperature of the interface is chosen as a quadratic function of interface arc length. The governing problem is modelled by conservation laws of mass, momentum and energy for fluid and dust particle phase. Stretching transformation technique is utilized to form ordinary differential equations from the partial differential equations. Later, the numerical solutions based on Runge-Kutta-Fehlberg method are established. The momentum and heat transport distributions are focused on the outcome of distinct governing parameters. The results of Nusselt number is also presented and discussed. It is established that the heat transfer rate is higher in the case of dusty non-Newtonian fluid than dusty Newtonian fluid. The rate of heat transfer can be enhanced by suspending dust particles in a base liquid.

Transport of thermal water from well to thermal baths

Science.gov (United States)

Montegrossi, Giordano; Vaselli, Orlando; Tassi, Franco; Nocentini, Matteo; Liccioli, Caterina; Nisi, Barbara

2013-04-01

The main problem in building a thermal bath is having a hot spring or a thermal well located in an appropriate position for customer access; since Roman age, thermal baths were distributed in the whole empire and often road and cities were built all around afterwards. Nowadays, the perspectives are changed and occasionally the thermal resource is required to be transported with a pipeline system from the main source to the spa. Nevertheless, the geothermal fluid may show problems of corrosion and scaling during transport. In the Ambra valley, central Italy, a geothermal well has recently been drilled and it discharges a Ca(Mg)-SO4, CO2-rich water at the temperature of 41 °C, that could be used for supplying a new spa in the surrounding areas of the well itself. The main problem is that the producing well is located in a forest tree ca. 4 km far away from the nearest structure suitable to host the thermal bath. In this study, we illustrate the pipeline design from the producing well to the spa, constraining the physical and geochemical parameters to reduce scaling and corrosion phenomena. The starting point is the thermal well that has a flow rate ranging from 22 up to 25 L/sec. The thermal fluid is heavily precipitating calcite (50-100 ton/month) due to the calcite-CO2 equilibrium in the reservoir, where a partial pressure of 11 bar of CO2 is present. One of the most vexing problems in investigating scaling processed during the fluid transport in the pipeline is that there is not a proper software package for multiphase fluid flow in pipes characterized by such a complex chemistry. As a consequence, we used a modified TOUGHREACT with Pitzer database, arranged to use Darcy-Weisbach equation, and applying "fictitious" material properties in order to give the proper y- z- velocity profile in comparison to the analytical solution for laminar fluid flow in pipes. This investigation gave as a result the lowest CO2 partial pressure to be kept in the pipeline (nearly 2

Comparative analysis of turbulent effects on thermal plasma characteristics inside the plasma torches with rod- and well-type cathodes

International Nuclear Information System (INIS)

Hur, Min; Hong, Sang Hee

2002-01-01

The thermal plasma characteristics inside the two non-transferred plasma torches with rod-type cathode (RTC) and well-type cathode (WTC) are analysed in conjunction with turbulent effects on them in the atmospheric-pressure conditions. A control volume method and a modified semi-implicit pressure linked equations revised algorithm are used for solving the governing equations, i.e. conservation equations of mass, momentum, and energy together with a current continuity equation for arc discharge. A cold flow analysis is introduced to find the cathode spot position in the WTC torch, and both the laminar and turbulent models are employed to gain a physical insight into the turbulent effects on the thermal plasma characteristics produced inside the two torches. The numerical analysis for an RTC torch shows that slightly different values of plasma temperature and velocity between the laminar and turbulent calculations occur and the radial temperature profiles are constricted at the axis with increasing the gas flow rate, and that the large turbulent viscosities appear mostly near the anode wall. These calculated results indicate that the turbulent effects on the thermal plasma characteristics are very weak in the whole discharge region inside the RTC torch. On the other hand, the calculated results of the two numerical simulations for a WTC torch present that the significantly different values of plasma characteristics between the two models appear in the whole torch region and the plasma temperatures decrease with increasing the gas flow rate because the relatively strong turbulent effects are prevailing in the entire interior region of the WTC torch. From the comparisons of plasma net powers calculated and measured in this work, the turbulent modelling turns out to provide the more accurately calculated results close to the measured ones compared with the laminar one, especially for the torch with WTC. This is because the turbulent effects are considerably strong in

From hard thermal loops to Langevin dynamics

International Nuclear Information System (INIS)

Boedeker, Dietrich

1999-01-01

In hot non-Abelian gauge theories, processes characterized by the momentum scale g 2 T (such as electroweak baryon number violation in the very early universe) are non-perturbative. An effective theory for the soft (vertical bar p vertical bar ∼ g 2 T) field modes is obtained by integrating out momenta larger than than g 2 T. Starting from the hard thermal loop effective theory, which is the result of integrating out the scale T, it is shown how to integrate out the scale gT in an expansion in the gauge coupling g. At leading order in g, one obtains Vlasov-Boltzmann equations for the soft field modes, which contain a Gaussian noise and a collision term. The 2-point function of the noise and the collision term are explicitly calculated in a leading logarithmic approximation. In this approximation the Boltzmann equation is solved. The resulting effective theory for the soft field modes is described by a Langevin equation. It determines the parametric form of the hot baryon number violation rate as Γ = κg 10 log(1/g)gT 4 , and it allows for a calculation for κ on the lattice

Thermal performance analysis of heat exchanger for closed wet cooling tower using heat and mass transfer analogy

International Nuclear Information System (INIS)

Yoo, Seong Yeon; Han, Kyu Hyun; Kim, Jin Hyuck

2010-01-01

In closed wet cooling towers, the heat transfer between the air and external tube surfaces can be composed of the sensible heat transfer and the latent heat transfer. The heat transfer coefficient can be obtained from the equation for external heat transfer of tube banks. According to experimental data, the mass transfer coefficient was affected by the air velocity and spray water flow rate. This study provides the correlation equation for mass transfer coefficient based on the analogy of the heat and mass transfer and the experimental data. The results from this correlation equation showed fairly good agreement with experimental data. The cooling capacity and thermal efficiency of the closed wet cooling tower were calculated from the correlation equation to analyze the performance of heat exchanger for the tower

Entropy Generation in Thermal Radiative Loading of Structures with Distinct Heaters

Directory of Open Access Journals (Sweden)

Mohammad Yaghoub Abdollahzadeh Jamalabadi

2017-09-01

Full Text Available Thermal loading by radiant heaters is used in building heating and hot structure design applications. In this research, characteristics of the thermal radiative heating of an enclosure by a distinct heater are investigated from the second law of thermodynamics point of view. The governing equations of conservation of mass, momentum, and energy (fluid and solid are solved by the finite volume method and the semi-implicit method for pressure linked equations (SIMPLE algorithm. Radiant heaters are modeled by constant heat flux elements, and the lower wall is held at a constant temperature while the other boundaries are adiabatic. The thermal conductivity and viscosity of the fluid are temperature-dependent, which leads to complex partial differential equations with nonlinear coefficients. The parameter study is done based on the amount of thermal load (presented by heating number as well as geometrical configuration parameters, such as the aspect ratio of the enclosure and the radiant heater number. The results present the effect of thermal and geometrical parameters on entropy generation and the distribution field. Furthermore, the effect of thermal radiative heating on both of the components of entropy generation (viscous dissipation and heat dissipation is investigated.

Deriving Langevin equations in curved spacetime

International Nuclear Information System (INIS)

Ramos, Rudnei O.; Tavares, Romulo F.

2013-01-01

Full text: Warm inflation is an inflationary scenario where the interactions between the inflaton and other degrees of freedom are considered. The effective equation of motion for the inflaton is in general of the form of a Langevin equation, that includes both quantum and thermal effects and where these effects manifest in the form of dissipation and stochastic noise terms, which are related by a generalized fluctuation-dissipation relation. The dissipation term is related to the interactions of the inflaton with other degrees of freedom of the thermal bath that can be obtained from the appropriate Feynman propagators. As the inflaton evolves into an expanding metric, these effects have to be taken into account when calculating the Green functions and consequently the Feynman propagators. In this work we present the considerations that must be made to calculate the Green functions in curved space (expanding metric) and in the presence of radiation in order to proper derive the effective evolution of the inflaton in the warm-inflation scenario. (author)

Design and development of a linear thermal actuator

Science.gov (United States)

Bush, G.; Osborne, D.

1985-01-01

The design and development of a linear thermal actuator (LTA) for space applications is described. The actuator is driven by thermal energy and utilizes the property of thermal expansion to do work. Equations to predict performance are developed and used to optimize the design of the development model LTA. Design details and test results are presented and discussed.

Analysis of thermally induced magnetization dynamics in spin-transfer nano-oscillators

Energy Technology Data Exchange (ETDEWEB)

D' Aquino, M., E-mail: daquino@uniparthenope.it [Department of Technology, University of Naples ' Parthenope' , 80143 Naples (Italy); Serpico, C. [Department of Engineering, University of Naples Federico II, 80125 Naples (Italy); Bertotti, G. [Istituto Nazionale di Ricerca Metrologica 10135 Torino (Italy); Bonin, R. [Politecnico di Torino - Sede di Verres, 11029 Verres (Aosta) (Italy); Mayergoyz, I.D. [ECE Department and UMIACS, University of Maryland, College Park, MD 20742 (United States)

2012-05-01

The thermally induced magnetization dynamics in the presence of spin-polarized currents injected into a spin-valve-like structure used as microwave spin-transfer nano-oscillator (STNO) is considered. Magnetization dynamics is described by the stochastic Landau-Lifshitz-Slonczewski (LLS) equation. First, it is shown that, in the presence of thermal fluctuations, the spectrum of the output signal of the STNO exhibits multiple peaks at low and high frequencies. This circumstance is associated with the occurrence of thermally induced transitions between stationary states and magnetization self-oscillations. Then, a theoretical approach based on the separation of time-scales is developed to obtain a stochastic dynamics only in the slow state variable, namely the energy. The stationary distribution of the energy and the aforementioned transition rates are analytically computed and compared with the results of direct integration of the LLS dynamics, showing very good agreement.

Boundary-integral equation formulation for time-dependent inelastic deformation in metals

Energy Technology Data Exchange (ETDEWEB)

Kumar, V; Mukherjee, S

1977-01-01

The mathematical structure of various constitutive relations proposed in recent years for representing time-dependent inelastic deformation behavior of metals at elevated temperatues has certain features which permit a simple formulation of the three-dimensional inelasticity problem in terms of real time rates. A direct formulation of the boundary-integral equation method in terms of rates is discussed for the analysis of time-dependent inelastic deformation of arbitrarily shaped three-dimensional metallic bodies subjected to arbitrary mechanical and thermal loading histories and obeying constitutive relations of the kind mentioned above. The formulation is based on the assumption of infinitesimal deformations. Several illustrative examples involving creep of thick-walled spheres, long thick-walled cylinders, and rotating discs are discussed. The implementation of the method appears to be far easier than analogous BIE formulations that have been suggested for elastoplastic problems.

The validity of quantum-classical multi-channel diffusion equations describing interlevel transitions in the condensed phase. The adiabatic representation

CERN Document Server

Basilevsky, M V

2002-01-01

We develop an approach for derivation of quantum-classical relaxation equations for a two-channel problem. The treatment is based on the adiabatic channel wavefunctions and the system-bath coupling is modelled as a bilinear interaction in momentum representation. In the quantum-classical limit we obtain Liouville equations with the relaxation operator containing diffusion terms diagonal in Liouvillian space and the off-diagonal part which is responsible for thermal interlevel transitions. The high-frequency interlevel quantum beats are fully taken into account in this relaxation term. In the framework of the present formulation and as a consequence of the momentum-dependent interaction the Smoluchovsky diffusion limit can be reached without invoking Fokker-Planck equations as an intermediate step. The inherent property of equations so obtained is that the partial rates of interlevel transitions obey the principle of detailed balance. This result could not be gained in earlier treatments of the two-level diffu...

Age-Predicted Maximal Heart Rate in Recreational Marathon Runners: A Cross-Sectional Study on Fox's and Tanaka's Equations

Science.gov (United States)

Nikolaidis, Pantelis T.; Rosemann, Thomas; Knechtle, Beat

2018-01-01

Age-based prediction equations of maximal heart rate (HRmax), such as the popular formulas Fox's 220-age, or Tanaka's 208-0.7 × age, have been widely used in various populations. Surprisingly, so far these equations have not been validated in marathon runners, despite the importance of the role of HRmax for training purposes in endurance running. The aim of the present study was to examine the validity of Fox and Tanaka equations in a large sample of women and men recreational marathon runners. Participants (n = 180, age 43.2 ± 8.5 years, VO2max 46.8 mL/min/kg, finishers in at least one marathon during the last year) performed a graded exercise test on a treadmill, where HRmax was measured. Measured HRmax correlated largely with age in the total sample (r = −0.50, p marathon runners. In addition, exercise physiologists and sport scientists should consider the observed differences among various assessment methods when performing exercise testing or prescribing training program relying on HR. PMID:29599724

Age-Predicted Maximal Heart Rate in Recreational Marathon Runners: A Cross-Sectional Study on Fox's and Tanaka's Equations.

Science.gov (United States)

Nikolaidis, Pantelis T; Rosemann, Thomas; Knechtle, Beat

2018-01-01

Age-based prediction equations of maximal heart rate (HR max ), such as the popular formulas Fox's 220-age, or Tanaka's 208-0.7 × age, have been widely used in various populations. Surprisingly, so far these equations have not been validated in marathon runners, despite the importance of the role of HR max for training purposes in endurance running. The aim of the present study was to examine the validity of Fox and Tanaka equations in a large sample of women and men recreational marathon runners. Participants ( n = 180, age 43.2 ± 8.5 years, VO 2max 46.8 mL/min/kg, finishers in at least one marathon during the last year) performed a graded exercise test on a treadmill, where HR max was measured. Measured HR max correlated largely with age in the total sample ( r = -0.50, p marathon runners. In addition, exercise physiologists and sport scientists should consider the observed differences among various assessment methods when performing exercise testing or prescribing training program relying on HR.

Transient thermal driven bubble's surface and its potential ultrasound-induced damage

Science.gov (United States)

Movahed, Pooya; Freund, Jonathan B.

2017-11-01

Ultrasound-induced bubble activity in soft tissues is well-known to be a potential injury mechanism in therapeutic ultrasound treatments. We consider damage by transient thermal effects, including a hypothetical mechanism based on transient thermal phenomena, including viscous dissipation. A spherically symmetric compressible Navier-Stokes discretization is developed to solve the full governing equations, both inside and outside of the bubble, without the usual simplifications in the Rayleigh-Plesset bubble dynamics approach. Equations are solved in the Lagrangian framework, which provides a sharp and accurate representation of the interface as well as the viscous dissipation and thermal transport effects, which preclude reduction to the usual Rayleigh-Plesset ordinary differential equation. This method is used to study transient thermal effects at different frequencies and pressure amplitudes relevant to therapeutic ultrasound treatments. High temperatures achieved in the surrounding medium during the violent bubble collapse phase due to the viscous dissipation in the surrounding medium and thermal conduction from the bubble are expected to cause damage. This work was supported by NIH NIDDK Grant P01-DK043881.

Impact of momentum anisotropy and turbulent chromo-fields on thermal particle production in quark-gluon-plasma medium

Energy Technology Data Exchange (ETDEWEB)

Chandra, Vinod [Indian Institute of Technology Gandhinagar, Gandhinagar, Gujarat (India); Sreekanth, V. [Indian Institute of Science, Centre for High Energy Physics, Bangalore (India)

2017-06-15

Momentum anisotropy present during the hydrodynamic evolution of the Quark-Gluon Plasma (QGP) in RHIC may lead to the chromo-Weibel instability and turbulent chromo-fields.The dynamics of the quark and gluon momentum distributions in this case is governed by an effective diffusive Vlasov equation (linearized). The solution of this linearized transport equation for the modified momentum distribution functions lead to the mathematical form of non-equilibrium momentum distribution functions of quarks/antiquarks and gluons. The modifications to these distributions encode the physics of turbulent color fields and momentum anisotropy. In the present manuscript, we employ these distribution functions to estimate the thermal dilepton production rate in the QGP medium. The production rate is seen to have appreciable sensitivity to the strength of the anisotropy. (orig.)

An investigation on the assessed thermal sensation and human body exergy consumption rate

DEFF Research Database (Denmark)

Simone, Angela; Kolarik, Jakub; Iwamatsu, Toshiya

2010-01-01

perception of the indoor environment is rare. As the building should provide healthy and comfortable environment for its occupants, it is reasonable to consider both the exergy flows in the building and within the human body. A relatively new approach of the relation between the exergy concept and the built......-environment research has been explored in the present work. The relationship of subjectively assessed thermal sensation data, from earlier thermal comfort studies, to the calculated human-body exergy consumption has been analysed. The results show that the minimum human body exergy consumption rate was related......The exergy concept helps to optimize indoor climate conditioning systems to meet the requirements of sustainable building design. While the exergy approach to design and operation of indoor climate conditioning systems is relatively well established, its exploitation in connection to human...

Application of an analytical method for solution of thermal hydraulic conservation equations

Energy Technology Data Exchange (ETDEWEB)

Fakory, M.R. [Simulation, Systems & Services Technologies Company (S3 Technologies), Columbia, MD (United States)

1995-09-01

An analytical method has been developed and applied for solution of two-phase flow conservation equations. The test results for application of the model for simulation of BWR transients are presented and compared with the results obtained from application of the explicit method for integration of conservation equations. The test results show that with application of the analytical method for integration of conservation equations, the Courant limitation associated with explicit Euler method of integration was eliminated. The results obtained from application of the analytical method (with large time steps) agreed well with the results obtained from application of explicit method of integration (with time steps smaller than the size imposed by Courant limitation). The results demonstrate that application of the analytical approach significantly improves the numerical stability and computational efficiency.

Numerical Analysis on the Influence of Thermal Effects on Oil Flow Characteristic in High-Pressure Air Injection (HPAI Process

Directory of Open Access Journals (Sweden)

Hu Jia

2012-01-01

Full Text Available In previous laboratory study, we have shown the thermal behavior of Keke Ya light crude oil (Tarim oilfield, branch of CNPC for high-pressure air injection (HPAI application potential study. To clarify the influences of thermal effects on oil production, in this paper, we derived a mathematical model for calculating oil flow rate, which is based on the heat conduction property in porous media from the combustion tube experiment. Based on remarkably limited knowledge consisting of very global balance arguments and disregarding all the details of the mechanisms in the reaction zone, the local governing equations are formulated in a dimensionless form. We use finite difference method to solve this model and address the study by way of qualitative analysis. The time-space dimensionless oil flow rate (qD profiles are established for comprehensive studies on the oil flow rate characteristic affected by thermal effects. It also discusses how these findings will impact HPAI project performances, and several guidelines are suggested.

Variable Thermal Conductivity on Compressible Boundary Layer ...

African Journals Online (AJOL)

In this paper, variable thermal conductivity on heat transfer over a circular cylinder is presented. The concept of assuming constant thermal conductivity on materials is however not efficient. Hence, the governing partial differential equation is reduced using non-dimensionless variables into a system of coupled non-linear ...

Generalized heat-transport equations: parabolic and hyperbolic models

Science.gov (United States)

Rogolino, Patrizia; Kovács, Robert; Ván, Peter; Cimmelli, Vito Antonio

2018-03-01

We derive two different generalized heat-transport equations: the most general one, of the first order in time and second order in space, encompasses some well-known heat equations and describes the hyperbolic regime in the absence of nonlocal effects. Another, less general, of the second order in time and fourth order in space, is able to describe hyperbolic heat conduction also in the presence of nonlocal effects. We investigate the thermodynamic compatibility of both models by applying some generalizations of the classical Liu and Coleman-Noll procedures. In both cases, constitutive equations for the entropy and for the entropy flux are obtained. For the second model, we consider a heat-transport equation which includes nonlocal terms and study the resulting set of balance laws, proving that the corresponding thermal perturbations propagate with finite speed.

Thermal rectification based on phonon hydrodynamics and thermomass theory

Directory of Open Access Journals (Sweden)

Dong Yuan

2016-06-01

Full Text Available The thermal diode is the fundamental device for phononics. There are various mechanisms for thermal rectification, e.g. different temperature dependent thermal conductivity of two ends, asymmetric interfacial resistance, and nonlocal behavior of phonon transport in asymmetric structures. The phonon hydrodynamics and thermomass theory treat the heat conduction in a fluidic viewpoint. The phonon gas flowing through the media is characterized by the balance equation of momentum, like the Navier-Stokes equation for fluid mechanics. Generalized heat conduction law thereby contains the spatial acceleration (convection term and the viscous (Laplacian term. The viscous term predicts the size dependent thermal conductivity. Rectification appears due to the MFP supersession of phonons. The convection term also predicts rectification because of the inertia effect, like a gas passing through a nozzle or diffuser.

Parameters identification in strain-rate and thermal sensitive visco-plastic material model for an alumina dispersion strengthened copper

CERN Document Server

Scapin, M; Peroni, M

2011-01-01

The main objective of this paper is getting strain-hardening, thermal and strain-rate parameters for a material model in order to correctly reproduce the deformation process that occurs in high strain-rate scenario, in which the material reaches also high levels of plastic deformation and temperature. In particular, in this work the numerical inverse method is applied to extract material strength parameters from experimental data obtained via mechanical tests at different strain-rates (from quasi-static loading to high strain-rate) and temperatures (between 20 C and 1000 C) for an alumina dispersion strengthened copper material, which commercial name is GLIDCOP. Thanks to its properties GLIDCOP finds several applications in particle accelerator technologies, where problems of thermal management, combined with structural requirements, play a key role. Currently, it is used for the construction of structural and functional parts of the particle beam collimation system. Since the extreme condition in which the m...

On the fluid-dynamical approximation to the Boltzmann equation at the level of the Navier-Stokes equation

International Nuclear Information System (INIS)

Kawashima, S.; Matsumara, A.; Nishida, T.

1979-01-01

The compressible and heat-conductive Navier-Stokes equation obtained as the second approximation of the formal Chapman-Enskog expansion is investigated on its relations to the original nonlinear Boltzmann equation and also to the incompressible Navier-Stokes equation. The solutions of the Boltzmann equation and the incompressible Navier-Stokes equation for small initial data are proved to be asymptotically equivalent (mod decay rate tsup(-5/4)) as t → + infinitely to that of the compressible Navier-Stokes equation for the corresponding initial data. (orig.) 891 HJ/orig. 892 MKO

Evaluation of thermal conductivity for liquid lead lithium alloys at various Li concentrations based on measurement and evaluation of density, thermal diffusivity and specific heat of alloys

Energy Technology Data Exchange (ETDEWEB)

Kondo, Masatoshi, E-mail: kondo.masatoshi@nr.titech.ac.jp [Tokyo Institute of Technology, 2-12-1, 2-12-1 O-okayama, Meguro-ku, Tokyo 152-8550 (Japan); Nakajima, Yuu; Tsuji, Mitsuyo [Tokai University, 4-1-1 Kitakaname, Hiratsuka-shi, Kanagawa 259-1292 (Japan); Nozawa, Takashi [Japan Atomic Energy Agency, Rokkasyo-mura, Kamikita-gun, Aomori 039-3212 (Japan)

2016-11-01

Graphical abstract: Thermal diffusivities and thermal conductivities of liquid Pb–Li alloys (Pb–5Li, Pb–11Li and Pb–17Li). - Highlights: • The densities and specific heats of liquid Pb–Li alloys are evaluated based on the previous studies, and mathematically expressed in the equations with the functions of temperature and Li concentration. • The thermal diffusivities of liquid Pb–Li alloys (i.e., Pb–5Li, Pb–11Li and Pb–17Li) are obtained by laser flash method, and mathematically expressed in the equations with the functions of temperature and Li concentration. • The thermal conductivities of liquid Pb–Li alloys were evaluated and mathematically expressed in the equations with the functions of temperature and Li concentration. - Abstract: The thermophysical properties of lead lithium alloy (Pb–Li) are essential for the design of liquid Pb–Li blanket system. The purpose of the present study is to make clear the density, the thermal diffusivity and the heat conductivity of the alloys as functions of temperature and Li concentration. The densities of the solid alloys were measured by means of the Archimedean method. The densities of the alloys at 300 K as a function of Li concentration (0 at% < χ{sub Li} < 28 at%) were obtained in the equation as ρ{sub (300} {sub K)} [g/cm{sup 3}] = −6.02 × 10{sup −2} × χ{sub Li} + 11.3. The density of the liquid alloys was formulated as functions of temperature and Li concentration (0 at% < χ{sub Li} < 30 at%), and expressed in the equation as ρ [g/cm{sup 3}] = (9.00 × 10{sup −6} × T − 7.01 × 10{sup −2}) × χ{sub Li} + 11.4 − 1.19 × 10{sup −3}T. The thermal diffusivity of Pb, Pb–5Li, Pb–11Li and Pb–17Li were measured by means of laser flash method. The thermal diffusivity of Pb–17Li was obtained in the equation as α{sub Pb–17Li} [cm{sup 2}/s] = 3.46 × 10{sup −4}T + 1.05 × 10{sup −1} for the temperature range between 573 K and 773 K. The thermal conductivity of

Diffusion phenomenon for linear dissipative wave equations

KAUST Repository

Said-Houari, Belkacem

2012-01-01

In this paper we prove the diffusion phenomenon for the linear wave equation. To derive the diffusion phenomenon, a new method is used. In fact, for initial data in some weighted spaces, we prove that for {equation presented} decays with the rate {equation presented} [0,1] faster than that of either u or v, where u is the solution of the linear wave equation with initial data {equation presented} [0,1], and v is the solution of the related heat equation with initial data v 0 = u 0 + u 1. This result improves the result in H. Yang and A. Milani [Bull. Sci. Math. 124 (2000), 415-433] in the sense that, under the above restriction on the initial data, the decay rate given in that paper can be improved by t -γ/2. © European Mathematical Society.

Approach to chemical equilibrium in thermal models

International Nuclear Information System (INIS)

Boal, D.H.

1984-01-01

The experimentally measured (μ - , charged particle)/(μ - ,n) and (p,n/p,p') ratios for the emission of energetic nucleons are used to estimate the time evolution of a system of secondary nucleons produced in a direct interaction of a projectile or captured muon. The values of these ratios indicate that chemical equilibrium is not achieved among the secondary nucleons in noncomposite induced reactions, and this restricts the time scale for the emission of energetic nucleons to be about 0.7 x 10 -23 sec. It is shown that the reason why thermal equilibrium can be reached so rapidly for a particular nucleon species is that the sum of the particle spectra produced in multiple direct reactions looks surprisingly thermal. The rate equations used to estimate the reaction times for muon and nucleon induced reactions are then applied to heavy ion collisions, and it is shown that chemical equilibrium can be reached more rapidly, as one would expect

Measured thermal and fast neutron fluence rates for ATF-1 holders during ATR cycle 160A

International Nuclear Information System (INIS)

Walker, B. J.; Miller, D. T.

2017-01-01

This report contains the thermal (2200 m/s) and fast (E>1MeV) neutron fluence rate data for the ATF-1 holders located in core for ATR Cycle 160A which were measured by the Radiation Measurements Laboratory (RML).

Measured thermal and fast neutron fluence rates for ATF-1 holders during ATR cycle 160A

Energy Technology Data Exchange (ETDEWEB)

Walker, B. J. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Miller, D. T. [Idaho National Lab. (INL), Idaho Falls, ID (United States)

2017-06-06

This report contains the thermal (2200 m/s) and fast (E>1MeV) neutron fluence rate data for the ATF-1 holders located in core for ATR Cycle 160A which were measured by the Radiation Measurements Laboratory (RML).

Development of interfacial area transport equation

International Nuclear Information System (INIS)

Kim, Seung Jin; Ishii, Mamoru; Kelly, Joseph

2005-01-01

The interfacial area transport equation dynamically models the changes in interfacial structures along the flow field by mechanistically modeling the creation and destruction of dispersed phase. Hence, when employed in the numerical thermal-hydraulic system analysis codes, it eliminates artificial bifurcations stemming from the use of the static flow regime transition criteria. Accounting for the substantial differences in the transport mechanism for various sizes of bubbles, the transport equation is formulated for two characteristic groups of bubbles. The group 1 equation describes the transport of small-dispersed bubbles, whereas the group 2 equation describes the transport of large cap, slug or churn-turbulent bubbles. To evaluate the feasibility and reliability of interfacial area transport equation available at present, it is benchmarked by an extensive database established in various two-phase flow configurations spanning from bubbly to churn-turbulent flow regimes. The geometrical effect in interfacial area transport is examined by the data acquired in vertical air-water two-phase flow through round pipes of various sizes and a confined flow duct, and by those acquired in vertical co-current downward air-water two-phase flow through round pipes of two different sizes

COMTA - a computer code for fuel mechanical and thermal analysis

International Nuclear Information System (INIS)

Basu, S.; Sawhney, S.S.; Anand, A.K.; Anantharaman, K.; Mehta, S.K.

1979-01-01

COMTA is a generalized computer code for integrity analysis of the free standing fuel cladding, with natural UO 2 or mixed oxide fuel pellets. Thermal and Mechanical analysis is done simultaneously for any power history of the fuel pin. For analysis, the fuel cladding is assumed to be axisymmetric and is subjected to axisymmetric load due to contact pressure, gas pressure, coolant pressure and thermal loads. Axial variation of load is neglected and creep and plasticity are assumed to occur at constant volume. The pellet is assumed to be made of concentric annuli. The fission gas release integral is dependent on the temperature and the power produced in each annulus. To calculate the temperature distribution in the fuel pin, the variation of bulk coolant temperature is given as an input to the code. Gap conductance is calculated at every time step, considering fuel densification, fuel relocation and gap closure, filler gas dilution by released fission gas, gap closure by expansion and irradiation swelling. Overall gap conductance is contributed by heat transfer due to the three modes; conduction convection and radiation as per modified Ross and Stoute model. Equilibrium equations, compatibility equations, stress strain relationships (including thermal strains and permanent strains due to creep and plasticity) are used to obtain triaxial stresses and strains. Thermal strain is assumed to be zero at hot zero power conditions. The boundary conditions are obtained for radial stresses at outside and inside surfaces by making these equal to coolant pressure and internal pressure respectively. A multi-mechanism creep model which accounts for thermal and irradiation creep is used to calculate the overall creep rate. Effective plastic strain is a function of effective stress and material constants. (orig.)

Rapid estimation of glucosinolate thermal degradation rate constants in leaves of Chinese kale and broccoli (Brassica oleracea) in two seasons.

Science.gov (United States)

Hennig, Kristin; Verkerk, Ruud; Bonnema, Guusje; Dekker, Matthijs

2012-08-15

Kinetic modeling was used as a tool to quantitatively estimate glucosinolate thermal degradation rate constants. Literature shows that thermal degradation rates differ in different vegetables. Well-characterized plant material, leaves of broccoli and Chinese kale plants grown in two seasons, was used in the study. It was shown that a first-order reaction is appropriate to model glucosinolate degradation independent from the season. No difference in degradation rate constants of structurally identical glucosinolates was found between broccoli and Chinese kale leaves when grown in the same season. However, glucosinolate degradation rate constants were highly affected by the season (20-80% increase in spring compared to autumn). These results suggest that differences in glucosinolate degradation rate constants can be due to variation in environmental as well as genetic factors. Furthermore, a methodology to estimate rate constants rapidly is provided to enable the analysis of high sample numbers for future studies.

Measured thermal and fast neutron fluence rates, ATR Cycle 102-A, 11/28/93 thru 1/16/94

International Nuclear Information System (INIS)

Murray, R.K.; Rogers, J.W.

1994-02-01

This report contains the thermal (2,200 m/s) and fast (E > 1MeV) neutron fluence rate data for ATR Cycle 102-A which were measured by the Radiation Measurements Laboratory (RML) as requested by the Power Reactor Programs (ATR Experiments) Radiation Measurements Work Order. This report contains fluence rate values corresponding to the particular elevations (relative to the 80 ft. core elevation) where the measurements were taken. The data in this report consists of (1) a table of the ATR power history and distribution, (2) a hard copy listing of all thermal and fast neutron fluence rates, (3) plots of both the thermal and fast neutron fluence rates, and (4) a magnetic record (3.5 inch diskette) containing a listing of only the fast neutron fluence rates, their assigned elevations and proper header identification of all monitor positions contained herein. The fluence rates reported are for the average power levels given in the table of power history and distribution. All ''H'' holder monitoring wires for this cycle are 54 inches long. All ''SR'' holder monitor wires for this cycle are 55 inches long. This length allows measurement of the full core region and makes the first count elevation 24.73 inches above core midplane. Due to the safety rod problems in the west lobe, ''BR'' holders were used in the W-1, 2, 3, and 4 positions. All ''BR'' holder monitor wires for this cycle are 56.25 inches long. The distance from the end of the wires to the first count position was 4.25 inches for all wires counted from this cycle

Thermal conductivity as influenced by the temperature and apparent viscosity of dairy products.

Science.gov (United States)

Gonçalves, B J; Pereira, C G; Lago, A M T; Gonçalves, C S; Giarola, T M O; Abreu, L R; Resende, J V

2017-05-01

This study aimed to evaluate the rheological behavior and thermal conductivity of dairy products, composed of the same chemical components but with different formulations, as a function of temperature. Subsequently, thermal conductivity was related to the apparent viscosity of yogurt, fermented dairy beverage, and fermented milk. Thermal conductivity measures and rheological tests were performed at 5, 10, 15, 20, and 25°C using linear probe heating and an oscillatory rheometer with concentric cylinder geometry, respectively. The results were compared with those calculated using the parallel, series, and Maxwell-Eucken models as a function of temperature, and the discrepancies in the results are discussed. Linear equations were fitted to evaluate the influence of temperature on the thermal conductivity of the dairy products. The rheological behavior, specifically apparent viscosity versus shear rate, was influenced by temperature. Herschel-Bulkley, power law, and Newton's law models were used to fit the experimental data. The Herschel-Bulkley model best described the adjustments for yogurt, the power law model did so for fermented dairy beverages, and Newton's law model did so for fermented milk and was then used to determine the rheological parameters. Fermented milk showed a Newtonian trend, whereas yogurt and fermented dairy beverage were shear thinning. Apparent viscosity was correlated with temperature by the Arrhenius equation. The formulation influenced the effective thermal conductivity. The relationship between the 2 properties was established by fixing the temperature and expressing conductivity as a function of apparent viscosity. Thermal conductivity increased with viscosity and decreased with increasing temperature. Copyright © 2017 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Coupled double-distribution-function lattice Boltzmann method for the compressible Navier-Stokes equations.

Science.gov (United States)

Li, Q; He, Y L; Wang, Y; Tao, W Q

2007-11-01

A coupled double-distribution-function lattice Boltzmann method is developed for the compressible Navier-Stokes equations. Different from existing thermal lattice Boltzmann methods, this method can recover the compressible Navier-Stokes equations with a flexible specific-heat ratio and Prandtl number. In the method, a density distribution function based on a multispeed lattice is used to recover the compressible continuity and momentum equations, while the compressible energy equation is recovered by an energy distribution function. The energy distribution function is then coupled to the density distribution function via the thermal equation of state. In order to obtain an adjustable specific-heat ratio, a constant related to the specific-heat ratio is introduced into the equilibrium energy distribution function. Two different coupled double-distribution-function lattice Boltzmann models are also proposed in the paper. Numerical simulations are performed for the Riemann problem, the double-Mach-reflection problem, and the Couette flow with a range of specific-heat ratios and Prandtl numbers. The numerical results are found to be in excellent agreement with analytical and/or other solutions.

Effect of creatinine assay calibration on glomerular filtration rate prediction by MDRD equation

Directory of Open Access Journals (Sweden)

Débora Spessatto

2009-01-01

Full Text Available Background: The evaluation of renal function should be performed with glomerular filtration rate (GFR estimation employing the Modification of Diet in Renal Disease (MDRD study equation, which includes age, gender, ethnicity and serum creatinine. However, creatinine methods require traceability with standardized methods. Objective: To analyse the impact of creatinine calibration on MDRD calculated GFR. Methods: 140 samples of plasma with creatinine values <2,0 mg/dl were analysed by Jaffé’s reaction with Creatinina Modular P (Roche ®; method A; reference and Creatinina Advia 1650 (Bayer ®; method B; non-standardized. The results with the different methods were compared and aligned with standardized method through a conversion formula. MDRD GFR was estimated. Results: Values were higher for method B (1.03 ± 0.29 vs. 0.86 ± 0.32 mg/dl, P<0.001. This difference declined when methods were aligned with the equation y=1.07x -0.249, and the aligned values were 0,9 ± 0,31 mg/dl. Non-traceable creatinine methods misclassificaed chronic kidney disease in 10% more (false positive. This disagreement disappeared after the regression alignment. Conclusion: Creatinine method calibration has a large impact over the final results of serum creatinine and GFR. The alignment of the non-standardized results through conversion formulas is a reasonable alternative to harmonize serum creatinine results while waiting for the full implementation of international  standardization programs.

Basal Metabolic Rate of Adolescent Modern Pentathlon Athletes: Agreement between Indirect Calorimetry and Predictive Equations and the Correlation with Body Parameters.

Directory of Open Access Journals (Sweden)

Luiz Lannes Loureiro

Full Text Available The accurate estimative of energy needs is crucial for an optimal physical performance among athletes and the basal metabolic rate (BMR equations often are not well adjusted for adolescent athletes requiring the use of specific methods, such as the golden standard indirect calorimetry (IC. Therefore, we had the aim to analyse the agreement between the BMR of adolescents pentathletes measured by IC and estimated by commonly used predictive equations.Twenty-eight athletes (17 males and 11 females were evaluated for BMR, using IC and the predictive equations Harris and Benedict (HB, Cunningham (CUN, Henry and Rees (HR and FAO/WHO/UNU (FAO. Body composition was obtained using DXA and sexual maturity data were retrieved through validated questionnaires. The correlations among anthropometric variables an IC were analysed by T-student test and ICC, while the agreement between IC and the predictive equations was analysed according to Bland and Altman and by survival-agreement plotting.The whole sample average BMR measured by IC was significantly different from the estimated by FAO (p<0.05. Adjusting data by gender FAO and HR equations were statistically different from IC (p <0.05 among males, while female differed only for the HR equation (p <0.05.The FAO equation underestimated athletes' BMR when compared with IC (T Test. When compared to the golden standard IC, using Bland and Altman, ICC and Survival-Agreement, the equations underestimated the energy needs of adolescent pentathlon athletes up to 300kcal/day. Therefore, they should be used with caution when estimating individual energy requirements in such populations.

Neutronics methods for thermal radiative transfer

International Nuclear Information System (INIS)

Larsen, E.W.

1988-01-01

The equations of thermal radiative transfer are time discretized in a semi-implicit manner, yielding a linear transport problem for each time step. The governing equation in this problem has the form of a neutron transport equation with fission but no scattering. Numerical methods are described, whose origins lie in neutron transport, and that have been successfully adapted to this new problem. Acceleration methods that have been developed specifically for the radiative transfer problem, but may have generalizations applicable in neutronics problems, are also discussed

Heat transfer and thermal stress analysis in grooved tubes

Indian Academy of Sciences (India)

ANSYS (1997) computer code has been used to analyse the thermal ... The numerical method is used succesfully to solve the governing equations ... thermal stress is an important criterion for consideration in the design of new compact heat.

Thermal conductivity and heat transfer in superlattices

Energy Technology Data Exchange (ETDEWEB)

Chen, G; Neagu, M; Borca-Tasciuc, T

1997-07-01

Understanding the thermal conductivity and heat transfer processes in superlattice structures is critical for the development of thermoelectric materials and devices based on quantum structures. This work reports progress on the modeling of thermal conductivity of superlattice structures. Results from the models established based on the Boltzmann transport equation could explain existing experimental results on the thermal conductivity of semiconductor superlattices in both in plane and cross-plane directions. These results suggest the possibility of engineering the interfaces to further reduce thermal conductivity of superlattice structures.

HERESY, 2-D Few-Group Static Eigenvalues Calculation for Thermal Reactor

International Nuclear Information System (INIS)

Finch, D.R.

1965-01-01

1 - Description of problem or function: HERESY3 solves the two- dimensional, few-group, static reactor eigenvalue problem using the heterogeneous (source-sink or Feinburg-Galanin) formalism. The solution yields the reactor k-effective and absorption reaction rates for each rod normalized to the most absorptive rod in the thermal level. Epithermal fissions are allowed at each resonance level, and lattice-averaged values of thermal utilization, resonance escape probability, thermal and resonance eta values, and the fast fission factor are calculated. Kernels in the calculation are based on age-diffusion theory. Both finite reactor lattices and infinitely repeating reactor super-cells may be calculated. Rod parameters may be calculated by several internal options, and a direct interface is provided to a HAMMER system (NESC Abstract 277) lattice library tape to obtain cell parameters. Criticality searches are provided on thermal utilization, thermal eta, and axial leakage buckling. 2 - Method of solution: Direct power iteration on matrix form of the heterogeneous critical equation is used. 3 - Restrictions on the complexity of the problem: Maxima of - 50 flux/geometry symmetry positions; 20 physically different assemblies; 9 resonance levels; 5000 rod coordinate positions

Applications of Lie-group methods to the equations of magnetohydrodynamics

International Nuclear Information System (INIS)

Mandrekas, J.

1987-01-01

The invariance properties of various sets of magnetohydrodynamic (MHD) equations are studied using techniques from the theory of differential forms. Equations considered include the ideal MHD equations in different geometries and with different magnetic field configurations, the MHD equations in the presence of gravitational forces due to self-attraction or external fields, and the MHD equations including finite thermal conductivity and magnetic viscosity. The knowledge of the group structure of these equations is then used to introduce similarity variables to these equations. For each choice of similarity variables, the original set of partial differential equations is transformed into a set of ordinary differential equations and the most general form of the initial conditions is determined. Three cases are studied in detail and the corresponding sets of ordinary differential equations are solved numerically: the problem of a blast wave in an inhomogeneous atmosphere, the problem of a piston moving according to a power law in time, and the problem of a piston moving according to an exponential law in time

Calculation of momentum distribution function of a non-thermal fermionic dark matter

Energy Technology Data Exchange (ETDEWEB)

Biswas, Anirban; Gupta, Aritra, E-mail: anirbanbiswas@hri.res.in, E-mail: aritra@hri.res.in [Harish-Chandra Research Institute, Chhatnag Road, Jhunsi, Allahabad 211 019 (India)

2017-03-01

The most widely studied scenario in dark matter phenomenology is the thermal WIMP scenario. Inspite of numerous efforts to detect WIMP, till now we have no direct evidence for it. A possible explanation for this non-observation of dark matter could be because of its very feeble interaction strength and hence, failing to thermalise with the rest of the cosmic soup. In other words, the dark matter might be of non-thermal origin where the relic density is obtained by the so-called freeze-in mechanism. Furthermore, if this non-thermal dark matter is itself produced substantially from the decay of another non-thermal mother particle, then their distribution functions may differ in both size and shape from the usual equilibrium distribution function. In this work, we have studied such a non-thermal (fermionic) dark matter scenario in the light of a new type of U(1){sub B−L} model. The U(1){sub B−L} model is interesting, since, besides being anomaly free, it can give rise to neutrino mass by Type II see-saw mechanism. Moreover, as we will show, it can accommodate a non-thermal fermionic dark matter as well. Starting from the collision terms, we have calculated the momentum distribution function for the dark matter by solving a coupled system of Boltzmann equations. We then used it to calculate the final relic abundance, as well as other relevant physical quantities. We have also compared our result with that obtained from solving the usual Boltzmann (or rate) equations directly in terms of comoving number density, Y . Our findings suggest that the latter approximation is valid only in cases where the system under study is close to equilibrium, and hence should be used with caution.

Effects of microwave heating on the thermal states of biological tissues

African Journals Online (AJOL)

A mathematical analysis of microwave heating equations in one-dimensional multi-layer model has been discussed. Maxwell's equations and transient bioheat transfer equation were numerically calculated by using finite difference method to predict the effects of thermal physical properties on the transient temperature of ...

Quantification of Gains and Risks of Static Thermal Rating Based on Typical Meteorological Year

Czech Academy of Sciences Publication Activity Database

Heckenbergerová, Jana; Musílek, P.; Filimonenkov, K.

2013-01-01

Roč. 44, č. 1 (2013), s. 227-235 ISSN 0142-0615 R&D Projects: GA MŠk LD12009 Grant - others:GA AV ČR(CZ) M100300904 Institutional support: RVO:67985807 Keywords : Overhead power transmission lines * Conductor ampacity * Probabilistic static thermal rating * Typical meteorological year * Risk tolerance * Energy throughput Subject RIV: JE - Non-nuclear Energetics, Energy Consumption ; Use Impact factor: 3.432, year: 2012

Estimation of fuel burning rate and heating value with highly variable properties for optimum combustion control

International Nuclear Information System (INIS)

Hsi, C.-L.; Kuo, J.-T.

2008-01-01

Estimating solid residue gross burning rate and heating value burning in a power plant furnace is essential for adequate manipulation to achieve energy conversion optimization and plant performance. A model based on conservation equations of mass and thermal energy is established in this work to calculate the instantaneous gross burning rate and lower heating value of solid residue fired in a combustion chamber. Comparing the model with incineration plant control room data indicates that satisfactory predictions of fuel burning rates and heating values can be obtained by assuming the moisture-to-carbon atomic ratio (f/a) within the typical range from 1.2 to 1.8. Agreement between mass and thermal analysis and the bed-chemistry model is acceptable. The model would be useful for furnace fuel and air control strategy programming to achieve optimum performance in energy conversion and pollutant emission reduction

The flow behavior and constitutive equation in isothermal compression of FGH4096-GH4133B dual alloy

International Nuclear Information System (INIS)

Liu, Yanhui; Yao, Zekun; Ning, Yongquan; Nan, Yang; Guo, Hongzhen; Qin, Chun; Shi, Zhifeng

2014-01-01

Highlights: • Hot compression behaviors of the FGH4096-GH4133B dual alloy were investigated. • Constitutive equation also represented deformation behavior of a dual alloy. • The effects of deformation activation energy on the microstructures were discussed. • Constitutive equation represented an accurate and precise estimate of flow stress. - Abstract: The electron beam welding of superalloy FGH4096 and GH4133B was conducted, and the cylindrical compression specimens were machined from the central part of the electron beam weldments. Isothermal compression tests were carried out on electron beam weldments FGH4096-GH4133B alloy at the temperatures of 1020–11140 °C (the nominal γ′-transus temperature is about 1080 °C) and the strain rates of 0.001–1.0 s −1 with the height reduction of 50%. True stress–true strain curves are sensitive to the deformation temperature and strain rate, and the flow stress decreases with the increasing deformation temperature and the decreasing strain rate. The true stress–true strain curves can indicate the intrinsic relationship between the flow stress and the thermal-dynamic behavior. The apparent activation energy of deformation at the strain of 0.6 was calculated to be 550 kJ/mol, and the apparent activation energy has a great effect on the microstructure. The constitutive equation that describes the flow stress as a function of strain rate and deformation temperature was proposed for modeling the hot deformation process of FGH4096-GH4133B electron beam weldments. The constitutive equation at the strain of 0.6 was established using the hyperbolic law. The relationship between the strain and the values of parameters was studied, and the cubic functions were built. The constitutive equation during the whole process can be obtained based on the parameters under different strains. Comparing the experimental flow stress and the calculated flow stress, the constitutive equation obtained in this paper can be very good

Hard thermal loops, static response, and the composite effective action

International Nuclear Information System (INIS)

Jackiw, R.; Liu, Q.; Lucchesi, C.

1994-01-01

First, we investigate the static non-Abelian Kubo equation. We prove that it does not possess finite energy solutions; thereby we establish that gauge theories do not support hard thermal solitons. This general result is verified by a numerical solution of the equations. A similar argument shows that ''static'' instantons are absent. In addition, we note that the static equations reproduce the expected screening of the non-Abelian electric field by a gauge-invariant Debye mass m=gT √(N+N F /2)/3 . Second, we derive the non-Abelian Kubo equation from the composite effective action. This is achieved by showing that the requirement of stationarity of the composite effective action is equivalent, within a kinematical approximation scheme, to the condition of gauge invariance for the generating functional of hard thermal loops

Dynamic characteristics of rotating pretwisted clamped-clamped beam under thermal stress

International Nuclear Information System (INIS)

Zhang, Bo; Li, Yueming; Lu, Wei Zhen

2016-01-01

Effects of thermal stress on the vibration characteristics, buckling limit and critical speed of a rotating pretwisted beam clamped to rigid hub at a stagger angle were investigated. By considering the work done by thermal stress, the thermal influence on stiffness matrix was introduced in the dynamic model. The motion equations were derived based on Lagrange equation by employing three pure Cartesian deformation variables combined with nonlinear von Karman strain formula. Numerical investigations studied the modal characteristics of the beam. Numerical results calculated from a commercial finite element code and obtained with the present modeling method were in good agreement with the previous results reported in the literature. The combined softening effects due to the thermal stress and the rotation motion were observed. Furthermore, it is shown that the inclusion of thermal stress is necessary for blades operating under a high temperature field. Buckling thermal loads and the critical rotating speed were calculated through solving the corresponding nonlinear equations numerically, and some pertinent conclusions are outlined. It is also found that the peak value position of the first mode shape approaches to the tip of blade with the increment of rotating speed and hub radius. However, the variation in the environment temperature causes only a slight alteration in the mode shape

Dynamic characteristics of rotating pretwisted clamped-clamped beam under thermal stress

Energy Technology Data Exchange (ETDEWEB)

Zhang, Bo; Li, Yueming [State Key Laboratory for Strength and Vibration of Mechanical Structures, Shaanxi Key Laboratory of Environment and Control for Flight Vehicle, School of Aerospace, Xi' an Jiaotong UniversityXi' an (China); Lu, Wei Zhen [Dept. of Civil and Architectural Engineering, City University of Hong Kong, Hong Kong (China)

2016-09-15

Effects of thermal stress on the vibration characteristics, buckling limit and critical speed of a rotating pretwisted beam clamped to rigid hub at a stagger angle were investigated. By considering the work done by thermal stress, the thermal influence on stiffness matrix was introduced in the dynamic model. The motion equations were derived based on Lagrange equation by employing three pure Cartesian deformation variables combined with nonlinear von Karman strain formula. Numerical investigations studied the modal characteristics of the beam. Numerical results calculated from a commercial finite element code and obtained with the present modeling method were in good agreement with the previous results reported in the literature. The combined softening effects due to the thermal stress and the rotation motion were observed. Furthermore, it is shown that the inclusion of thermal stress is necessary for blades operating under a high temperature field. Buckling thermal loads and the critical rotating speed were calculated through solving the corresponding nonlinear equations numerically, and some pertinent conclusions are outlined. It is also found that the peak value position of the first mode shape approaches to the tip of blade with the increment of rotating speed and hub radius. However, the variation in the environment temperature causes only a slight alteration in the mode shape.

Fractional Bhatnagar-Gross-Krook kinetic equation

Science.gov (United States)

Goychuk, Igor

2017-11-01

The linear Boltzmann equation (LBE) approach is generalized to describe fractional superdiffusive transport of the Lévy walk type in external force fields. The time distribution between scattering events is assumed to have a finite mean value and infinite variance. It is completely characterized by the two scattering rates, one fractional and a normal one, which defines also the mean scattering rate. We formulate a general fractional LBE approach and exemplify it with a particularly simple case of the Bohm and Gross scattering integral leading to a fractional generalization of the Bhatnagar, Gross and Krook (BGK) kinetic equation. Here, at each scattering event the particle velocity is completely randomized and takes a value from equilibrium Maxwell distribution at a given fixed temperature. We show that the retardation effects are indispensable even in the limit of infinite mean scattering rate and argue that this novel fractional kinetic equation provides a viable alternative to the fractional Kramers-Fokker-Planck (KFP) equation by Barkai and Silbey and its generalization by Friedrich et al. based on the picture of divergent mean time between scattering events. The case of divergent mean time is also discussed at length and compared with the earlier results obtained within the fractional KFP. Also a phenomenological fractional BGK equation without retardation effects is proposed in the limit of infinite scattering rates. It cannot be, however, rigorously derived from a scattering model, being rather clever postulated. It this respect, this retardationless equation is similar to the fractional KFP by Barkai and Silbey. However, it corresponds to the opposite, much more physical limit and, therefore, also presents a viable alternative.

Thixoforming of Steel: New Tools Conception to Analyse Thermal Exchanges and Strain Rate Effects

International Nuclear Information System (INIS)

Cezard, P.; Bigot, R.; Becker, E.; Mathieu, S.; Pierret, J. C.; Rassili, A.

2007-01-01

Through different papers, authors shown that the influence of thermal exchanges was a first order parameter on the semi-solid steel behaviour, and certainly for every semi-solid metallic materials. These thermal exchanges hide other parameters effect like, for example, the strain rate influence. This paper tries to determine the influence of these two parameters by using a new extrusion device on a hydraulic press. This new tools conception annihilated the influence of the decrease of the punch speed before stopping and permitted to have a constant speed during the experiment. This work also deals with the homogeneous flow during thixoforming of steel and shows the importance to couple initial temperature of the slug with punch speed. This paper presents different conditions which permitted to have a homogeneous flow by keeping a low load

Continuous surface force based lattice Boltzmann equation method for simulating thermocapillary flow

International Nuclear Information System (INIS)

Zheng, Lin; Zheng, Song; Zhai, Qinglan

2016-01-01

In this paper, we extend a lattice Boltzmann equation (LBE) with continuous surface force (CSF) to simulate thermocapillary flows. The model is designed on our previous CSF LBE for athermal two phase flow, in which the interfacial tension forces and the Marangoni stresses as the results of the interface interactions between different phases are described by a conception of CSF. In this model, the sharp interfaces between different phases are separated by a narrow transition layers, and the kinetics and morphology evolution of phase separation would be characterized by an order parameter via Cahn–Hilliard equation which is solved in the frame work of LBE. The scalar convection–diffusion equation for temperature field is resolved by thermal LBE. The models are validated by thermal two layered Poiseuille flow, and two superimposed planar fluids at negligibly small Reynolds and Marangoni numbers for the thermocapillary driven convection, which have analytical solutions for the velocity and temperature. Then thermocapillary migration of two/three dimensional deformable droplet are simulated. Numerical results show that the predictions of present LBE agreed with the analytical solution/other numerical results. - Highlights: • A CSF LBE to thermocapillary flows. • Thermal layered Poiseuille flows. • Thermocapillary migration.

Continuous surface force based lattice Boltzmann equation method for simulating thermocapillary flow

Energy Technology Data Exchange (ETDEWEB)

Zheng, Lin, E-mail: lz@njust.edu.cn [School of Energy and Power Engineering, Nanjing University of Science and Technology, Nanjing 210094 (China); Zheng, Song [School of Mathematics and Statistics, Zhejiang University of Finance and Economics, Hangzhou 310018 (China); Zhai, Qinglan [School of Economics Management and Law, Chaohu University, Chaohu 238000 (China)

2016-02-05

In this paper, we extend a lattice Boltzmann equation (LBE) with continuous surface force (CSF) to simulate thermocapillary flows. The model is designed on our previous CSF LBE for athermal two phase flow, in which the interfacial tension forces and the Marangoni stresses as the results of the interface interactions between different phases are described by a conception of CSF. In this model, the sharp interfaces between different phases are separated by a narrow transition layers, and the kinetics and morphology evolution of phase separation would be characterized by an order parameter via Cahn–Hilliard equation which is solved in the frame work of LBE. The scalar convection–diffusion equation for temperature field is resolved by thermal LBE. The models are validated by thermal two layered Poiseuille flow, and two superimposed planar fluids at negligibly small Reynolds and Marangoni numbers for the thermocapillary driven convection, which have analytical solutions for the velocity and temperature. Then thermocapillary migration of two/three dimensional deformable droplet are simulated. Numerical results show that the predictions of present LBE agreed with the analytical solution/other numerical results. - Highlights: • A CSF LBE to thermocapillary flows. • Thermal layered Poiseuille flows. • Thermocapillary migration.

A Well-Posed Two Phase Flow Model and its Numerical Solutions for Reactor Thermal-Fluids Analysis

Energy Technology Data Exchange (ETDEWEB)

Kadioglu, Samet Y. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Berry, Ray [Idaho National Lab. (INL), Idaho Falls, ID (United States); Martineau, Richard [Idaho National Lab. (INL), Idaho Falls, ID (United States)

2016-08-01

A 7-equation two-phase flow model and its numerical implementation is presented for reactor thermal-fluids applications. The equation system is well-posed and treats both phases as compressible flows. The numerical discretization of the equation system is based on the finite element formalism. The numerical algorithm is implemented in the next generation RELAP-7 code (Idaho National Laboratory (INL)’s thermal-fluids code) built on top of an other INL’s product, the massively parallel multi-implicit multi-physics object oriented code environment (MOOSE). Some preliminary thermal-fluids computations are presented.

A Well-Posed Two Phase Flow Model and its Numerical Solutions for Reactor Thermal-Fluids Analysis

International Nuclear Information System (INIS)

Kadioglu, Samet Y.; Berry, Ray; Martineau, Richard

2016-01-01

A 7-equation two-phase flow model and its numerical implementation is presented for reactor thermal-fluids applications. The equation system is well-posed and treats both phases as compressible flows. The numerical discretization of the equation system is based on the finite element formalism. The numerical algorithm is implemented in the next generation RELAP-7 code (Idaho National Laboratory (INL)'s thermal-fluids code) built on top of an other INL's product, the massively parallel multi-implicit multi-physics object oriented code environment (MOOSE). Some preliminary thermal-fluids computations are presented.

Effect of thermal phonons on the superconducting transition temperature

International Nuclear Information System (INIS)

Leavens, C.R.; Talbot, E.

1983-01-01

There is no consensus in the literature on whether or not thermal phonons depress the superconducting transition temperature T/sub c/. In this paper it is shown by accurate numerical solution of the real-frequency Eliashberg equations for the pairing self-energy phi and renormalization function Z that thermal phonons in the kernel for phi raise T/sub c/ but those in Z lower it by a larger amount so that the net effect is to depress T/sub c/. (A previous calculation which ignored the effect of thermal phonons in phi overestimated the suppression of T/sub c/ by at least a factor of 3.) It is shown how to switch off the thermal phonons in the imaginary-frequency Eliashberg equations, exactly for Z and approximately for phi. The real-frequency and approximate imaginary-frequency results for the depression of T/sub c/ by thermal phonons are in very satisfactory agreement. Thermal phonons are found to depress the transition temperature of Nb 3 Sn by only 2%. It is estimated that the suppression of T/sub c/ by thermal phonons saturates at about 50% in the limit of very strong electron-phonon coupling

Specificity Switching Pathways in Thermal and Mass Evaporation of Multicomponent Hydrocarbon Droplets: A Mesoscopic Observation.

Science.gov (United States)

Nasiri, Rasoul; Luo, Kai H

2017-07-10

For well over one century, the Hertz-Knudsen equation has established the relationship between thermal - mass transfer coefficients through a liquid - vapour interface and evaporation rate. These coefficients, however, have been often separately estimated for one-component equilibrium systems and their simultaneous influences on evaporation rate of fuel droplets in multicomponent systems have yet to be investigated at the atomic level. Here we first apply atomistic simulation techniques and quantum/statistical mechanics methods to understand how thermal and mass evaporation effects are controlled kinetically/thermodynamically. We then present a new development of a hybrid method of quantum transition state theory/improved kinetic gas theory, for multicomponent hydrocarbon systems to investigate how concerted-distinct conformational changes of hydrocarbons at the interface affect the evaporation rate. The results of this work provide an important physical concept in fundamental understanding of atomistic pathways in topological interface transitions of chain molecules, resolving an open problem in kinetics of fuel droplets evaporation.

Solution methods for large systems of linear equations in BACCHUS

International Nuclear Information System (INIS)

Homann, C.; Dorr, B.

1993-05-01

The computer programme BACCHUS is used to describe steady state and transient thermal-hydraulic behaviour of a coolant in a fuel element with intact geometry in a fast breeder reactor. In such computer programmes generally large systems of linear equations with sparse matrices of coefficients, resulting from discretization of coolant conservation equations, must be solved thousands of times giving rise to large demands of main storage and CPU time. Direct and iterative solution methods of the systems of linear equations, available in BACCHUS, are described, giving theoretical details and experience with their use in the programme. Besides use of a method of lines, a Runge-Kutta-method, for solution of the partial differential equation is outlined. (orig.) [de

Money market rates and implied CCAPM rates: some international evidence

OpenAIRE

Yamin Ahmad

2004-01-01

New Neoclassical Synthesis models equate the instrument of monetary policy to the implied CCAPM rate arising from an Euler equation. This paper identifies monetary policy shocks within six of the G7 countries and examines the movement of money market and implied CCAPM rates. The key result is that an increase in the nominal interest rate leads to a fall in the implied CCAPM rate. Incorporating habit still yields the same result. The findings suggest that the movement of these two rates implie...

Evaluation of Energy Consumption in the Mercury Treatment of Phosphor Powder from Spent Fluorescent Lamps Using a Thermal Process

Directory of Open Access Journals (Sweden)

Yong Choi

2017-11-01

Full Text Available In a pilot-plant-scale thermal mercury treatment of phosphor powder from spent fluorescent lamps, energy consumption was estimated to control mercury content by the consideration of reaction kinetics. Mercury content was analyzed as a function of treatment temperature and time. The initial mercury content of the phosphor powder used in the thermal process was approximately 3500 mg/kg. The target mercury content in the phosphor powder thermal process of the phosphor powder was 5 mg/kg or less at 400 °C or higher because the target mercury content was recommended by Minamata Convention and Basel Convention. During thermal processing, the reaction rate was represented by a first order reaction with the Arrhenius equation. The reaction rate constant increased with temperature from 0.0112 min−1 at 350 °C to 0.0558 min−1 at 600 °C. The frequency factor was 2.51 min−1, and the activation energy was 6509.11 kcal/kg. Reaction rate constants were used to evaluate the treatment time required to reduce mercury content in phosphor powder to be less than 5 mg/kg. The total energy consumption in a pilot-plant-scale thermal process was evaluated to determine the optimal temperature for removing mercury in phosphor powder.

Implementation and verification of a coupled fire model as a thermal boundary condition within P3/THERMAL

International Nuclear Information System (INIS)

Hensinger, D.M.; Gritzo, L.A.; Koski, J.A.

1996-01-01

A user-defined boundary condition subroutine has been implemented within P3/THERMAL to represent the heat flux between a noncombusting object and an engulfing fire. The heat flux calculations includes a simple 2D fire model in which energy and radiative heat transport equations are solved to produce estimates of the heat fluxes at the fire-object interface. These estimates reflect radiative coupling between a cold object and the flow of hot combustion gases which has been observed in fire experiments. The model uses a database of experimental pool fire measurements for far field boundary conditions and volumetric heat release rates. Taking into account the coupling between a structure and the fire is an improvement over the σT 4 approximation frequently used as a boundary condition for engineered system response and is the preliminary step in the development of a fire model with a predictive capability. This paper describes the implementation of the fire model as a P3/THERMAL boundary condition and presents the results of a verification calculation carried out using the model

Measured thermal and fast neutron fluence rates, ATR Cycle 100-BC, April 23, 1993--May 13, 1993

International Nuclear Information System (INIS)

Smith, L.D.; Murray, R.K.; Rogers, J.W.

1993-07-01

This report contains the thermal (2200 m/s) and fast (E>1MeV) neutron fluence rate data for ATR Cycle 100-BC which were measured by the Radiation Measurements Laboratory (RML) as requested by the Power Reactor Programs (ATR Experiments) Radiation Measurements Work Order. This report contains fluence rate values corresponding to the particular elevations (relative to the 80 ft. core elevation) where the measurements were taken. The data in this report consists of (1) a table of the ATR power history and distribution, (2) a hard copy listing of all thermal and fast neutron fluence rates, (3) plots of both the thermal and fast neutron fluence rates, and (4) a magnetic record (3.5 inch diskette) containing a listing of only the fast neutron fluence rates, their assigned elevations and proper header identification of all monitor positions contained herein. The fluence rates reported are for the average power levels given in the table of power history and distribution. All open-quotes Hclose quotes holder monitor wires for this cycle are 54 inches long. All open-quotes SRclose quotes holder monitor wires for this cycle are 55 inches long. This length allows measurement of the full core region and makes the first count elevation 24.73 inches above core midplane. Due to the safety rod problems in the west lobe, open-quotes BRclose quotes holders were used in the W-1, 2, 3, and 4 positions. All open-quotes BRclose quotes holder monitor wires for this cycle are 56.25 inches long. The distance from the end of the wires to the first count position was 4.25 inches for all wires counted from this cycle. The results from the measurements in the W-1, 2, 3, 4 monitor positions indicate that the safety rod followers were rotated to a different azimuthal orientation relative to the normal orientation. The results indicate that the rotation was counterclockwise from their normal orientation. This is the same condition observed starting with Cycle 99-B

Improving thermal efficiency and increasing production rate in the double moving beds thermally coupled reactors by using differential evolution (DE) technique

International Nuclear Information System (INIS)

Karimi, Mohsen; Rahimpour, Mohammad Reza; Rafiei, Razieh; Shariati, Alireza; Iranshahi, Davood

2016-01-01

Highlights: • Double moving bed thermally coupled reactor is modeled in two dimensions. • The required heat of naphtha process is attained with nitrobenzene hydrogenation. • DE optimization method is applied to optimize operating conditions. • Hydrogen, aromatic and aniline productions increase in the proposed configuration. - Abstract: According to the global requirements for energy saving and the control of global warming, multifunctional auto-thermal reactors as a novel concept in the process integration (PI) have risen up in the recent years. In the novel modification presented in this study, the required heat of endothermic naphtha reforming process has been supplied by nitrobenzene hydrogenation reaction. In addition, the enhancement of reactor performance, such as the increase of production rate, has become a key issue in the diverse industries. Thus, Differential Evolution (DE) technique is applied to optimize the operating conditions (temperature and pressure) and designing parameters of a thermally coupled reactor with double moving beds. Ultimately, the obtained results of the proposed model are compared with non-optimized and conventional model. This model results in noticeable reduction in the operational costs as well as enhancement of the net profit of the plant. The increase in the hydrogen and aromatic production shows the superiority of the proposed model.

Analysis of internal ablation for the thermal control of aerospace vehicles

Science.gov (United States)

Camberos, Jose A.; Roberts, Leonard

1989-01-01

A new method of thermal protection for transatmospheric vehicles is introduced. The method involves the combination of radiation, ablation and transpiration cooling. By placing an ablating material behind a fixed-shape, porous outer shield, the effectiveness of transpiration cooling is made possible while retaining the simplicity of a passive mechanism. A simplified one-dimensional approach is used to derive the governing equations. Reduction of these equations to non-dimensional form yields two parameters which characterize the thermal protection effectiveness of the shield and ablator combination for a given trajectory. The non-dimensional equations are solved numerically for a sample trajectory corresponding to glide re-entry. Four typical ablators are tested and compared with results obtained by using the thermal properties of water. For the present level of analysis, the numerical computations adequately support the analytical model.

Determination of the in-core power and the average core temperature of low power research reactors using gamma dose rate measurements

International Nuclear Information System (INIS)

Osei Poku, L.

2012-01-01

Most reactors incorporate out-of-core neutron detectors to monitor the reactor power. An accurate relationship between the powers indicated by these detectors and actual core thermal power is required. This relationship is established by calibrating the thermal power. The most common method used in calibrating the thermal power of low power reactors is neutron activation technique. To enhance the principle of multiplicity and diversity of measuring the thermal neutron flux and/or power and temperature difference and/or average core temperature of low power research reactors, an alternative and complimentary method has been developed, in addition to the current method. Thermal neutron flux/Power and temperature difference/average core temperature were correlated with measured gamma dose rate. The thermal neutron flux and power predicted using gamma dose rate measurement were in good agreement with the calibrated/indicated thermal neutron fluxes and powers. The predicted data was also good agreement with thermal neutron fluxes and powers obtained using the activation technique. At an indicated power of 30 kW, the gamma dose rate measured predicted thermal neutron flux of (1* 10 12 ± 0.00255 * 10 12 ) n/cm 2 s and (0.987* 10 12 ± 0.00243 * 10 12 ) which corresponded to powers of (30.06 ± 0.075) kW and (29.6 ± 0.073) for both normal level of the pool water and 40 cm below normal levels respectively. At an indicated power of 15 kW, the gamma dose rate measured predicted thermal neutron flux of (5.07* 10 11 ± 0.025* 10 11 ) n/cm 2 s and (5.12 * 10 11 ±0.024* 10 11 ) n/cm 2 s which corresponded to power of (15.21 ± 0.075) kW and (15.36 ± 0.073) kW for both normal levels of the pool water and 40 cm below normal levels respectively. The power predicted by this work also compared well with power obtained from a three-dimensional neutronic analysis for GHARR-1 core. The predicted power also compares well with calculated power using a correlation equation obtained from

Nonequlibrium dynamics of scalar fields in a thermal bath

International Nuclear Information System (INIS)

Anisimov, A.; Buchmueller, W.; Drewes, M.; Mendizabal, S.

2008-12-01

We study the approach to equilibrium for a scalar field which is coupled to a large thermal bath. Our analysis of the initial value problem is based on Kadanoff-Baym equations which are shown to be equivalent to a stochastic Langevin equation. The interaction with the thermal bath generates a temperature-dependent spectral density, either through decay and inverse decay processes or via Landau damping. In equilibrium, energy density and pressure are determined by the Bose-Einstein distribution function evaluated at a complex quasi-particle pole. The time evolution of the statistical propagator is compared with solutions of the Boltzmann equations for particles as well as quasi-particles. The dependence on initial conditions and the range of validity of the Boltzmann approximation are determined. (orig.)

Solar thermal barometer

International Nuclear Information System (INIS)

Anon.

2004-01-01

After the bad year of 2002, the european solar thermal market returned to double-digit growth rate in 2003: 22%. Nevertheless, the sector still has not recovered the growth rate it had in the early 2000 and European Commission targets are still far from being reached. This paper presents the thermal solar industry barometer. Data on the evolution of annually installed surfaces in the european union since 1993, the cumulated capacity of thermal collectors installed in the European Union, the estimation of the annual energy production associated to european solar thermal capacities and the main companies of the European Union thermal solar sector are presented and discussed. (A.L.B.)

Factors Associated with Asthma ED Visit Rates among Medicaid-enrolled Children: A Structural Equation Modeling Approach

Directory of Open Access Journals (Sweden)

Luceta McRoy

2017-02-01

Full Text Available Background: Asthma is one of the leading causes of emergency department visits and school absenteeism among school-aged children in the United States, but there is significant local-area variation in emergency department visit rates, as well as significant differences across racial-ethnic groups. Analysis: We first calculated emergency department (ED visit rates among Medicaid-enrolled children age 5–12 with asthma using a multi-state dataset. We then performed exploratory factor analysis using over 226 variables to assess whether they clustered around three county-level conceptual factors (socioeconomic status, healthcare capacity, and air quality thought to be associated with variation in asthma ED visit rates. Measured variables (including ED visit rate as the outcome of interest were then standardized and tested in a simple conceptual model through confirmatory factor analysis. Results: County-level (contextual variables did cluster around factors declared a priori in the conceptual model. Structural equation models connecting the ED visit rates to socioeconomic status, air quality, and healthcare system professional capacity factors (consistent with our conceptual framework converged on a solution and achieved a reasonable goodness of fit on confirmatory factor analysis. Conclusion: Confirmatory factor analysis offers an approach for quantitatively testing conceptual models of local-area variation and racial disparities in asthma-related emergency department use.

Integration of a Multizone Airflow Model into a Thermal simulation Program

DEFF Research Database (Denmark)

Jensen, Rasmus Lund; Sørensen, Karl Grau; Heiselberg, Per

2007-01-01

An existing computer model for dynamic hygrothermal analysis of buildings has been extended with a multizone airflow model based on loop equations to account for the coupled thermal and airflow in natural and hybrid ventilated buildings.......An existing computer model for dynamic hygrothermal analysis of buildings has been extended with a multizone airflow model based on loop equations to account for the coupled thermal and airflow in natural and hybrid ventilated buildings....

TEMPEST-2, Thermalization Program for Neutron Spectra and Multigroup Cross-Sections

International Nuclear Information System (INIS)

Gowins, G.

1984-01-01

Description of problem or function: TEMPEST2 is a neutron thermalization program based upon the Wigner-Wilkins approximation for light moderators and the Wilkins approximation for heavy moderators. A Maxwellian distribution may also be used. The model used may be selected as a function of energy. The second-order differential equations are integrated directly rather than transformed to the Riccati equation. The program provides microscopic and macroscopic cross-section averages over the thermal neutron spectrum