Thermo field dynamics in the treatment of the nuclear pairing problem at finite temperature
International Nuclear Information System (INIS)
Civitarese, O.; DePaoli, A.L.
1993-01-01
The use of the thermo field dynamics, in dealing with the study of nuclear properties at finite temperature, is discussed for the case of a nuclear Hamiltonian which includes a single-particle term and a monopole pairing residual two-body interaction. The rules of the thermo fields dynamics are applied to double the Hilbert space, thus accounting for the thermal occupation of single-particle states, and to construct dual spaces, both for single-particle (BCS) and collective (RPA) degrees of freedom. It is shown that the rules of the thermo field dynamics yield to a temperature dependence of the equations describing quasiparticle and phonon excitations which is similar to the one found in the more conventional finite temperature Wick's theorem approach, namely: By dealing with thermal averages. (orig.)
International Nuclear Information System (INIS)
Kulich, N.V.; Nemtsev, V.A.
1986-01-01
The analytical solution to the problem on the stationary temperature field in an infinite structural element of rectangular profile characteristic of the conjugation points of a vessel and a tube sheet of a heat exchanger (or of a finned surface) at the third-kind boundary conditions has been obtained by the methods of the complex variable function theory. With the help of the obtained analytical dependences the calculations of the given element of the design and the comparison with the known data have been conducted. The proposed analytical solution can be effectively used in calculations of temperature fields in finned surfaces and structural elements of the power equipment of the considered profile and the method is applied for solution of the like problems
Correlation Models for Temperature Fields
North, Gerald R.
2011-05-16
This paper presents derivations of some analytical forms for spatial correlations of evolving random fields governed by a white-noise-driven damped diffusion equation that is the analog of autoregressive order 1 in time and autoregressive order 2 in space. The study considers the two-dimensional plane and the surface of a sphere, both of which have been studied before, but here time is introduced to the problem. Such models have a finite characteristic length (roughly the separation at which the autocorrelation falls to 1/e) and a relaxation time scale. In particular, the characteristic length of a particular temporal Fourier component of the field increases to a finite value as the frequency of the particular component decreases. Some near-analytical formulas are provided for the results. A potential application is to the correlation structure of surface temperature fields and to the estimation of large area averages, depending on how the original datastream is filtered into a distribution of Fourier frequencies (e.g., moving average, low pass, or narrow band). The form of the governing equation is just that of the simple energy balance climate models, which have a long history in climate studies. The physical motivation provided by the derivation from a climate model provides some heuristic appeal to the approach and suggests extensions of the work to nonuniform cases.
Energy Technology Data Exchange (ETDEWEB)
Gavrina, T.Ye.; Polyachenko, A.L.
1984-01-01
An integral transforms method is used to find solution to one of the basic direct problems in the theory of nonstationary well thermometry, that is, the problem about restoring the initial distribution of temperature in the well after disrupting the thermal equilibrium. Both the length of the effects, as well as the heterogeneity of the mediums in thermophysical properties are considered in the well and stratum system. The time asymptotic distribution of temperature in the well is acquired.
Estimation of complete temperature fields from measured temperatures
International Nuclear Information System (INIS)
Clegg, S.T.; Roemer, R.B.
1984-01-01
In hyperthermia treatments, it is desirable to be able to predict complete tissue temperature fields from sampled temperatures taken at a few locations. This is a difficult problem in hyperthermia treatments since the tissue blood perfusion is unknown. An initial attempt to do this automatically using unconstrained optimization techniques to minimize the differences between steady state temperatures measured during a treatment and temperatures (at the same locations) predicted from treatment simulations has been previously reported. A second technique using transient temperatures following a step decrease in power has been developed. This technique, which appears to be able to better predict complete temperature fields is presented and both it and the steady state technique are applied to data from both simulated and experimental hyperthermia treatments. The results of applying the two techniques are compared for one-dimensional situations. One particularly important problem which the transient technique can solve (and the steady state technique does not seem to be able to do as well) is that of predicting the complete temperature field in situations where the true maximum and/or minimum temperatures present are not measured by the available instrumentation
Electromagnetic Field Theory A Collection of Problems
Mrozynski, Gerd
2013-01-01
After a brief introduction into the theory of electromagnetic fields and the definition of the field quantities the book teaches the analytical solution methods of Maxwell’s equations by means of several characteristic examples. The focus is on static and stationary electric and magnetic fields, quasi stationary fields, and electromagnetic waves. For a deeper understanding, the many depicted field patterns are very helpful. The book offers a collection of problems and solutions which enable the reader to understand and to apply Maxwell’s theory for a broad class of problems including classical static problems right up to waveguide eigenvalue problems. Content Maxwell’s Equations - Electrostatic Fields - Stationary Current Distributions – Magnetic Field of Stationary Currents – Quasi Stationary Fields: Eddy Currents - Electromagnetic Waves Target Groups Advanced Graduate Students in Electrical Engineering, Physics, and related Courses Engineers and Physicists Authors Professor Dr.-Ing. Gerd Mrozynski...
Potential problems with interpolating fields
Energy Technology Data Exchange (ETDEWEB)
Birse, Michael C. [The University of Manchester, Theoretical Physics Division, School of Physics and Astronomy, Manchester (United Kingdom)
2017-11-15
A potential can have features that do not reflect the dynamics of the system it describes but rather arise from the choice of interpolating fields used to define it. This is illustrated using a toy model of scattering with two coupled channels. A Bethe-Salpeter amplitude is constructed which is a mixture of the waves in the two channels. The potential derived from this has a strong repulsive core, which arises from the admixture of the closed channel in the wave function and not from the dynamics of the model. (orig.)
Obstacle mean-field game problem
Gomes, Diogo A.
2015-01-01
In this paper, we introduce and study a first-order mean-field game obstacle problem. We examine the case of local dependence on the measure under assumptions that include both the logarithmic case and power-like nonlinearities. Since the obstacle operator is not differentiable, the equations for first-order mean field game problems have to be discussed carefully. Hence, we begin by considering a penalized problem. We prove this problem admits a unique solution satisfying uniform bounds. These bounds serve to pass to the limit in the penalized problem and to characterize the limiting equations. Finally, we prove uniqueness of solutions. © European Mathematical Society 2015.
Stream temperature investigations: field and analytic methods
Bartholow, J.M.
1989-01-01
This document provides guidance to the user of the U.S. Fish and Wildlife Service’s Stream Network Temperature Model (SNTEMP). Planning a temperature study is discussed in terms of understanding the management objectives and ensuring that the questions will be accurately answered with the modeling approach being used. A sensitivity analysis of SNTEMP is presented to illustrate which input variables are most important in predicting stream temperatures. This information helps prioritize data collection activities, highlights the need for quality control, focuses on which parameters can be estimated rather than measured, and offers a broader perspective on management options in terms of knowing where the biggest temperature response will be felt. All of the major input variables for stream geometry, meteorology, and hydrology are discussed in detail. Each variable is defined, with guidance given on how to measure it, what kind of equipment to use, where to obtain it from another agency, and how to calculate it if the data are in a form other than that required by SNTEMP. Examples are presented for the various forms in which water temperature, discharge, and meteorological data are commonly found. Ranges of values for certain input variables that are difficult to measure of estimate are given. Particular attention is given to those variables not commonly understood by field biologists likely to be involved in a stream temperature study. Pertinent literature is cited for each variable, with emphasis on how other people have treated particular problems and on results they have found.
Common Group Problems: A Field Study.
Weinberg, Sanford B.; And Others
1981-01-01
A field study of a naturally functioning group (N=125) was conducted to identify common group problems. Trained observers attended group meetings and described the problems encountered. Difficulties of cohesion, leadership, sub-group formation, and personality conflict were identified. (RC)
Radiological field survey problems and solutions
International Nuclear Information System (INIS)
Deming, E.J.; Boerner, A.J.
1986-01-01
Situations often arise during radiological field surveys which require the health physicist to improvise and/or make spot decisions. At times these situations can be humorous, but they can also present hazards more serious than normal radiological considerations. This presentation will depict various problematic situations encountered by Oak Ridge Associated Universities Radiological Site Assessment Program in the course of performing field environmental surveys. Detailing these potential hazards can alert other field survey groups to problems they may encounter
Compton scattering at finite temperature: thermal field dynamics approach
International Nuclear Information System (INIS)
Juraev, F.I.
2006-01-01
Full text: Compton scattering is a classical problem of quantum electrodynamics and has been studied in its early beginnings. Perturbation theory and Feynman diagram technique enables comprehensive analysis of this problem on the basis of which famous Klein-Nishina formula is obtained [1, 2]. In this work this problem is extended to the case of finite temperature. Finite-temperature effects in Compton scattering is of practical importance for various processes in relativistic thermal plasmas in astrophysics. Recently Compton effect have been explored using closed-time path formalism with temperature corrections estimated [3]. It was found that the thermal cross section can be larger than that for zero-temperature by several orders of magnitude for the high temperature realistic in astrophysics [3]. In our work we use a main tool to account finite-temperature effects, a real-time finite-temperature quantum field theory, so-called thermofield dynamics [4, 5]. Thermofield dynamics is a canonical formalism to explore field-theoretical processes at finite temperature. It consists of two steps, doubling of Fock space and Bogolyubov transformations. Doubling leads to appearing additional degrees of freedom, called tilded operators which together with usual field operators create so-called thermal doublet. Bogolyubov transformations make field operators temperature-dependent. Using this formalism we treat Compton scattering at finite temperature via replacing in transition amplitude zero-temperature propagators by finite-temperature ones. As a result finite-temperature extension of the Klein-Nishina formula is obtained in which differential cross section is represented as a sum of zero-temperature cross section and finite-temperature correction. The obtained result could be useful in quantum electrodynamics of lasers and for relativistic thermal plasma processes in astrophysics where correct account of finite-temperature effects is important. (author)
On electromagnetic field problems in inhomogeneous media
Mohsen, A.
1973-01-01
Analysis of electromagnetic fields in inhomogeneous media is of practical interest in general scattering and propagation problems and in the study of lenses. For certain types of inhomogeneities, the fields may be represented in terms of two scalars. In a general orthogonal coordinate system, these potentials satisfy second order differential equations. Exact solutions of these equations are known only for a few particular cases and in general, an approximate or numerical technique must be employed. The present work reviews and generalizes some of the main methods of attack of the problem. The results are presented in a form appropriate for numerical computation.
Temperature field for radiative tomato peeling
International Nuclear Information System (INIS)
Cuccurullo, G; Giordano, L
2017-01-01
Nowadays peeling of tomatoes is performed by using steam or lye, which are expensive and polluting techniques, thus sustainable alternatives are searched for dry peeling and, among that, radiative heating seems to be a fairly promising method. This paper aims to speed up the prediction of surface temperatures useful for realizing dry-peeling, thus a 1D-analytical model for the unsteady temperature field in a rotating tomato exposed to a radiative heating source is presented. Since only short times are of interest for the problem at hand, the model involves a semi-infinite slab cooled by convective heat transfer while heated by a pulsating heat source. The model being linear, the solution is derived following the Laplace Transform method. A 3D finite element model of the rotating tomato is introduced as well in order to validate the analytical solution. A satisfactory agreement is attained. Therefore, two different ways to predict the onset of the peeling conditions are available which can be of help for proper design of peeling plants. Particular attention is paid to study surface temperature uniformity, that being a critical parameter for realizing an easy tomato peeling. (paper)
Finite-temperature field theory
International Nuclear Information System (INIS)
Kapusta, J.I.; Landshoff, P.V.
1989-01-01
Particle number is not conserved in relativistic theories although both lepton and baryon number are. Therefore when discussing the thermodynamics of a quantum field theory one uses the grand canonical formalism. The entropy S is maximised, keeping fixed the ensemble averages E and N of energy and lepton number. Two lagrange multipliers are introduced. (author)
Field Problems in the South Bronx.
Madrigal, Stasia, Ed.
1983-01-01
Articles in this issue of the bulletin of the Hispanic Research Center focus on the problems of collecting demographic and social data in the South Bronx. The introductory article summarizes the contents of this issue. The second (by Lloyd H. Rogler, Osvaldo Barreras, and Rosemary Santana Cooney) is based on the experiences of field workers…
Aleph Field Solver Challenge Problem Results Summary
Energy Technology Data Exchange (ETDEWEB)
Hooper, Russell [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Moore, Stan Gerald [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
2015-01-01
Aleph models continuum electrostatic and steady and transient thermal fields using a finite-element method. Much work has gone into expanding the core solver capability to support enriched modeling consisting of multiple interacting fields, special boundary conditions and two-way interfacial coupling with particles modeled using Aleph's complementary particle-in-cell capability. This report provides quantitative evidence for correct implementation of Aleph's field solver via order- of-convergence assessments on a collection of problems of increasing complexity. It is intended to provide Aleph with a pedigree and to establish a basis for confidence in results for more challenging problems important to Sandia's mission that Aleph was specifically designed to address.
Thermo field dynamics: a quantum field theory at finite temperature
International Nuclear Information System (INIS)
Mancini, F.; Marinaro, M.; Matsumoto, H.
1988-01-01
A brief review of the theory of thermo field dynamics (TFD) is presented. TFD is introduced and developed by Umezawa and his coworkers at finite temperature. The most significant concept in TFD is that of a thermal vacuum which satisfies some conditions denoted as thermal state conditions. The TFD permits to reformulate theories at finite temperature. There is no need in an additional principle to determine particle distributions at T ≠ 0. Temperature and other macroscopic parameters are introduced in the definition of the vacuum state. All operator formalisms used in quantum field theory at T=0 are preserved, although the field degrees of freedom are doubled. 8 refs
Nonstationary temperature field in the fuel element
International Nuclear Information System (INIS)
Vehauc, A.; Spasojevic, D.
1970-03-01
Nonstationary temperature field in the fuel element was examined for spatial and time distribution of the specific power generated in the fuel element. Analytical method was developed for calculating the temperature variation in the fuel element of a nuclear reactor for a typical shape of the heat generation function. The method is based on series expansion of the temperature field by self functions and application of Laplace transformation in time coordinate. For numerical calculation of the temperature distribution a computer code was developed based on the proposed method and applied on the ZUSE-Z-23 computer [sr
Mean field canonical treatments at finite temperature
International Nuclear Information System (INIS)
Rossignoli, R.
1990-01-01
A method is proposed to make mean field and higher order canonical treatments at finite temperature. Definite improvements are made over the usual Hartree-Fock thermal (great canonical) treatment. (Author). 10 refs., 3 figs
General temperature field measurement by digital holography
Czech Academy of Sciences Publication Activity Database
Doleček, Roman; Psota, Pavel; Lédl, Vít; Vít, Tomáš; Václavík, Jan; Kopecký, V.
2013-01-01
Roč. 52, č. 1 (2013), A319-A325 ISSN 1559-128X Institutional support: RVO:61389021 Keywords : digital holography * temperature field measurement * tomography Subject RIV: BH - Optics, Masers, Lasers Impact factor: 1.649, year: 2013
Low frequency electromagnetic fields and health problems
International Nuclear Information System (INIS)
Zahedi, A.; Cosic, I.
1996-01-01
Full text: Electromagnetic fields developed around the electric circuits are considered as magnetic pollution and these fields are produced wherever electric appliances or machinery are used at home as well as at workplace. Electric fields and magnetic fields around the home are produced by anything with electric current flowing through it including: the street power lines, the home wiring system, electric ovens, refrigerators, washing machines, electric clothes dryers, vacuum cleaners, television sets, video cassette recorders, toasters, light bulbs, clock radios, electric blankets, mobile phones, etc. In the workplace they would be produced by: nearby power lines, factory machinery, computers/video display units, lights, photocopiers, electrical cabling etc. As one can see, human life is strongly dependent on using-electric appliance. A large number of studies have been undertaken to find out the correlation between electromagnetic fields and health problems. The following significant results have been reported [Lerner E.J., IEEE Spectrum, 57-67, May 1984]: (a) Induction of chromosomal defects in mice spermatogenetic cells following microwave radiation in the Ghz range; (b) Changes in the calcium balance of living cats' brains exposed to microwaves modulated at extremely low frequencies; (c) Alternation of nerve and bone cells exposed to extremely low frequency fields; (d) Decreased activity of the immune cells of mice exposed to modulated microwaves; (e) Apparent increase in deformed foetuses among miniature swine exposed to intense power-line frequency fields. The mostly investigated effect is the effect of electromagnetic irradiation in particular one produced by power lines, and cancer. More than 100 epidemiological studies have been reported but no conclusive result was achieved. A number of studies with laboratory animals were also inconclusive. However, some of these experiments have shown improvements in immune system and tumour suppression when
Infrared problems in field perturbation theory
International Nuclear Information System (INIS)
David, Francois.
1982-12-01
The work presented mainly covers questions related to the presence of ''infrared'' divergences in perturbation expansions of the Green functions of certain massless field theories. It is important to determine the mathematical status of perturbation expansions in field theory in order to define the region in which they are valid. Renormalization and the symmetry of a theory are important factors in infrared problems. The main object of this thesis resides in the mathematical techniques employed: integral representations of the Feynman amplitudes; methods for desingularization, regularization and dimensional renormalization. Nonlinear two dimensional space-time sigma models describing Goldstone's low energy boson dynamics associated with a breaking of continuous symmetry are studied. Random surface models are then investigated followed by infrared divergences in super-renormalizable theories. Finally, nonperturbation effects in massless theories are studied by expanding the two-dimensional nonlinear sigma model in 1/N [fr
Topics on field theories at finite temperature
International Nuclear Information System (INIS)
Eboli, O.J.P.
1985-01-01
The dynamics of a first order phase transition through the study of the decay rate of the false vacuum in the high temperature limit are analysed. An alternative approach to obtain the phase diagram of a field theory which is based on the study of the free energy of topological defects, is developed the behavior of coupling constants with the help of the Dyson-Schwinger equations at finite temperature, is evaluated. (author) [pt
Problems of vector Lagrangians in field theories
International Nuclear Information System (INIS)
Krivsky, I.Yu.; Simulik, V.M.
1997-01-01
A vector Lagrange approach to the Dirac spinor field and the relationship between the vector Lagrangians for the spinor and electromagnetic fields are considered. A vector Lagrange approach for the system of interacting electromagnetic B=(B μ υ)=(E-bar,H-bar) and spinor Ψ fields is constructed. New Lagrangians (scalar and vector) for electromagnetic field in terms of field strengths are found. The foundations of two new QED models are formulated
MODELING OF TEMPERATURE FIELDS IN A SOLID HEAT ACCUMULLATORS
Directory of Open Access Journals (Sweden)
S. S. Belimenko
2016-10-01
Full Text Available Purpose. Currently, one of the priorities of energy conservation is a cost savings for heating in commercial and residential buildings by the stored thermal energy during the night and its return in the daytime. Economic effect is achieved due to the difference in tariffs for the cost of electricity in the daytime and at night. One of the most common types of devices that allow accumulating and giving the resulting heat are solid heat accumulators. The main purpose of the work: 1 software development for the calculation of the temperature field of a flat solid heat accumulator, working due to the heat energy accumulation in the volume of thermal storage material without phase transition; 2 determination the temperature distribution in its volumes at convective heat transfer. Methodology. To achieve the study objectives a heat transfer theory and Laplace integral transform were used. On its base the problems of determining the temperature fields in the channels of heat accumulators, having different cross-sectional shapes were solved. Findings. Authors have developed the method of calculation and obtained solutions for the determination of temperature fields in channels of the solid heat accumulator in conditions of convective heat transfer. Temperature fields over length and thickness of channels were investigated. Experimental studies on physical models and industrial equipment were conducted. Originality. For the first time the technique of calculating the temperature field in the channels of different cross-section for the solid heat accumulator in the charging and discharging modes was proposed. The calculation results are confirmed by experimental research. Practical value. The proposed technique is used in the design of solid heat accumulators of different power as well as full-scale production of them was organized.
To the problem of electron temperature control in plasma
International Nuclear Information System (INIS)
Galechyan, G.A.; Anna, P.R.
1995-01-01
One of the main problems in low temperature plasma is control plasma parameters at fixed values of current and gas pressure in the discharge. It is known that an increase in the intensity of sound wave directed along the positive column to values in excess of a definite threshold leads to essential rise of the temperature of electrons. However, no less important is the reduction of electron temperature in the discharge down to the value less than that in plasma in the absence external influence. It is known that to reduce the electron temperature in the plasma of CO 2 laser, easily ionizable admixture are usually introduced in the discharge area with the view of increasing the overpopulation. In the present work we shall show that the value of electron temperature can be reduced by varying of sound wave intensity at its lower values. The experiment was performed on an experimental setup consisted of the tube with length 52 cm and diameter 9.8 cm, two electrodes placed at the distance of 27 cm from each other. An electrodynamical radiator of sound wave was fastened to one of tube ends. Fastened to the flange at the opposite end was a microphone for the control of sound wave parameters. The studies were performed in range of pressures from 40 to 180 Torr and discharge currents from 40 to 110 mA. The intensity of sound wave was varied from 74 to 92 dB. The measurement made at the first resonance frequency f = 150 Hz of sound in the discharge tube, at which a quarter of wave length keep within the length of the tube. The measurement of longitudinal electric field voltage in plasma of positive column was conducted with the help of two probes according to the compensation method. Besides, the measurement of gas temperature in the discharge were taken. Two thermocouple sensors were arranged at the distance of 8 cm from the anode, one of them being installed on the discharge tube axis, the second-fixed the tube wall
To the problem of electron temperature control in plasma
Energy Technology Data Exchange (ETDEWEB)
Galechyan, G.A. [Institute of Applied Problem of Physics, Yerevan (Armenia); Anna, P.R. [Raritan Valley Community College, Somerville, NJ (United States)
1995-12-31
One of the main problems in low temperature plasma is control plasma parameters at fixed values of current and gas pressure in the discharge. It is known that an increase in the intensity of sound wave directed along the positive column to values in excess of a definite threshold leads to essential rise of the temperature of electrons. However, no less important is the reduction of electron temperature in the discharge down to the value less than that in plasma in the absence external influence. It is known that to reduce the electron temperature in the plasma of CO{sub 2} laser, easily ionizable admixture are usually introduced in the discharge area with the view of increasing the overpopulation. In the present work we shall show that the value of electron temperature can be reduced by varying of sound wave intensity at its lower values. The experiment was performed on an experimental setup consisted of the tube with length 52 cm and diameter 9.8 cm, two electrodes placed at the distance of 27 cm from each other. An electrodynamical radiator of sound wave was fastened to one of tube ends. Fastened to the flange at the opposite end was a microphone for the control of sound wave parameters. The studies were performed in range of pressures from 40 to 180 Torr and discharge currents from 40 to 110 mA. The intensity of sound wave was varied from 74 to 92 dB. The measurement made at the first resonance frequency f = 150 Hz of sound in the discharge tube, at which a quarter of wave length keep within the length of the tube. The measurement of longitudinal electric field voltage in plasma of positive column was conducted with the help of two probes according to the compensation method. Besides, the measurement of gas temperature in the discharge were taken. Two thermocouple sensors were arranged at the distance of 8 cm from the anode, one of them being installed on the discharge tube axis, the second-fixed the tube wall.
Two problems in thermal field theory
Indian Academy of Sciences (India)
Abstract. In this talk, I review recent progress made in two areas of thermal ﬁeld theory. In particular, I discuss various approaches for the calculation of the quark gluon plasma thermodynamical properties, and the problem of its photon production rate.
Two problems in thermal field theory
Indian Academy of Sciences (India)
F can be calculated perturbatively as a sum of vacuum ... F / F id eal d c b a. Figure 4. Results of the screened perturbative expansion for the free energy as a func- tion of the coupling constant in scalar field theory [8]. (a) and (b): first ... for the pressure of a SU(3) Yang–Mills gas just by introducing a mass in the propagator.
Electron temperature diagnostics in the RFX reversed field pinch experiment
International Nuclear Information System (INIS)
Bartiromo, R.; Carraro, L.; Marrelli, L.; Murari, A.; Pasqualotto, R.; Puiatti, M.E.; Scarin, P.; Valisa, M.; Franz, P.; Martin, P.; Zabeo, L.
2000-01-01
The paper presents an integrated approach to the problem of electron temperature diagnostics of the plasma in a reversed field pinch. Three different methods, sampling different portions of the electron distribution function, are adopted, namely Thomson scattering, soft X-ray spectroscopy by pulse-height analysis and filtered soft X-ray intensity ratio. A careful analysis of the different sources of systematic errors is performed and a novel statistical approach is adopted to mutually validate the three independent measurements. A satisfactory agreement is obtained over a large range of experimental conditions, indicating that in the plasma core the energy distribution function is well represented by a maxwellian. (author)
Field Response Prediction: Framing the problem.
Energy Technology Data Exchange (ETDEWEB)
Cabrera-Palmer, Belkis [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
2017-06-01
Predicting the performance of radiation detection systems at field sites based on measured performance acquired under controlled conditions at test locations, e.g., the Nevada National Security Site (NNSS), remains an unsolved and standing issue within DNDO’s testing methodology. Detector performance can be defined in terms of the system’s ability to detect and/or identify a given source or set of sources, and depends on the signal generated by the detector for the given measurement configuration (i.e., source strength, distance, time, surrounding materials, etc.) and on the quality of the detection algorithm. Detector performance is usually evaluated in the performance and operational testing phases, where the measurement configurations are selected to represent radiation source and background configurations of interest to security applications.
Benhamou, Mabrouk; Kassou-Ou-Ali, Ahmed
We extend to finite-temperature field theories, involving charged scalar or nonvanishing spin particles, the α parametrization of field theories at zero temperature. This completes a previous work concerning the scalar theory. As there, a function θ, which contains all temperature dependence, appears in the α integrand. The function θ is an extension of the usual theta function. The implications of the α parametrization for the renormalization problem are discussed.
Analysis of the high-temperature particulate collection problem
Energy Technology Data Exchange (ETDEWEB)
Razgaitis, R.
1977-10-01
Particulate agglomeration and separation at high temperatures and pressures are examined, with particular emphasis on the unique features of the direct-cycle application of fluidized-bed combustion. The basic long-range mechanisms of aerosol separation are examined, and the effects of high temperature and high pressure on usable collection techniques are assessed. Primary emphasis is placed on those avenues that are not currently attracting widespread research. The high-temperature, particulate-collection problem is surveyed, together with the peculiar requirements associated with operation of turbines with particulate-bearing gas streams. 238 references.
Benchmark problems for numerical implementations of phase field models
International Nuclear Information System (INIS)
Jokisaari, A. M.; Voorhees, P. W.; Guyer, J. E.; Warren, J.; Heinonen, O. G.
2016-01-01
Here, we present the first set of benchmark problems for phase field models that are being developed by the Center for Hierarchical Materials Design (CHiMaD) and the National Institute of Standards and Technology (NIST). While many scientific research areas use a limited set of well-established software, the growing phase field community continues to develop a wide variety of codes and lacks benchmark problems to consistently evaluate the numerical performance of new implementations. Phase field modeling has become significantly more popular as computational power has increased and is now becoming mainstream, driving the need for benchmark problems to validate and verify new implementations. We follow the example set by the micromagnetics community to develop an evolving set of benchmark problems that test the usability, computational resources, numerical capabilities and physical scope of phase field simulation codes. In this paper, we propose two benchmark problems that cover the physics of solute diffusion and growth and coarsening of a second phase via a simple spinodal decomposition model and a more complex Ostwald ripening model. We demonstrate the utility of benchmark problems by comparing the results of simulations performed with two different adaptive time stepping techniques, and we discuss the needs of future benchmark problems. The development of benchmark problems will enable the results of quantitative phase field models to be confidently incorporated into integrated computational materials science and engineering (ICME), an important goal of the Materials Genome Initiative.
Modeling of the temperature field of the casting ladle lining
Zabolotsky, A. V.
2011-03-01
We propose a method for calculating the temperature field of the casting ladle lining by a modified relaxation method. Given such initial data as the metal temperature in the ladle, the ambient temperature, and the lining structure, this method permits calculating the stationary temperature fields both inside the lining and on the surface of the ladle jacket. The model was tested by comparing experimentally measured temperature values on the surface of the ladle jacket with calculated temperatures. A satisfactory agreement between calculated and experimental temperature values of the ladle surface has been obtained.
Field of Temperature Measurement by Virtual Instrumentation
Directory of Open Access Journals (Sweden)
Libor HARGAŠ
2009-01-01
Full Text Available This paper introduces about temperature determination for given dot of picture through image analysis. Heat transfer is the transition of thermal energy from a heated item to a cooler item. Main method of measurement of temperature in image is Pattern Matching, color scale detection and model detection. We can measure temperature dependency at time for selected point of thermo vision images. This measurement gives idea about the heat transfer at time dependences.
Iterative solution of field problems with a varying physical parameter
Tijhuis, A.G.; Beurden, M.C. van; Zwamborn, A.P.M.
2002-01-01
In this paper, linear field problems with a varying physical parameter are solved with the conjugate-gradient FFT method and a dedicated extrapolation procedure for generating the initial estimate. The scheme is formulated and illustrated for two simple example problems. The importance of the choice
Wall deffects in field theories at finite temperature
International Nuclear Information System (INIS)
Bazeia Filho, D.
1985-01-01
We discuss the effect of restauration of simmetry in field theories at finite temperature and its relation with wall deffects which appear as consequence of the instability of the constant field configuration. (M.W.O.) [pt
Problems with ink skin markings for radiation field setups
International Nuclear Information System (INIS)
Endoh, Masaru; Saeki, Mituaki; Ishida, Yusei
1982-01-01
Ink skin markings are used in radiation therapy to aid in reproduction of treatment field setups or to indelibly outline field markings or tumors. We reported two cases of indelible ink skin for radiation field septa with minimal discomfort and dermatitis have been experienced for 6 months and above since end of radiotherapy. These indelible ink skin markings look like tattoo that will be big problems in the case of young female. We improved these problems by using of 10 percent silver nitrate instead of habitual skin ink. (author)
Tolman temperature gradients in a gravitational field
Santiago, Jessica; Visser, Matt
2018-01-01
Tolman's relation for the temperature gradient in an equilibrium self-gravitating general relativistic fluid is broadly accepted within the general relativity community. However, the concept of temperature gradients in thermal equilibrium continues to cause confusion in other branches of physics, since it contradicts naive versions of the laws of classical thermodynamics. In this paper we discuss the crucial role of the universality of free fall, and how thermodynamics emphasises the great di...
Pattern recognition in the satellite temperature retrieval problem
Thompson, O. E.; Goldberg, M. D.; Dazlich, D. A.
1985-01-01
Pattern recognition procedures have been developed in order to improve the first-guess fields for satellite temperature retrievals. The first procedure is used to select one or more historical radiosonde temperature profiles as analog estimates of ambient thermal structure. The second procedure is used to organize a priori data into shape-coherent pattern libraries using structural information inherent in the data itself. On the basis of independent tests of about 800 temperature retrievals, it was found that: (1) the pattern recognition techniques reduced first-guess profile errors by nearly 50 percent in comparison with traditional partitioning schemes; and (2) with regression and physical-iterative retrieval algorithms, however, the effect of pattern recognition on temperature retrieval error was insignificant. Analysis of individual retrieval errors showed that poor retrievals may outweigh the potential benefits of both pattern recognition techniques.
Causality in finite temperature quantum field theory
International Nuclear Information System (INIS)
Paz, J.P.
1991-01-01
Some properties of various 'real time' formalisms are examined. The authors discuss conceptual (and sometimes very important) differences between the Niemi-Semmenoff method, the Closed Time Path formalism, and Thermo Field Dynamics. (author). 15 refs
Effect of a background electric field on the Hagedorn temperature
International Nuclear Information System (INIS)
Ferrer, E.J.; Incera, V. de la; Fradkin, E.S.
1990-07-01
We compute the one-loop free energy of the open neutral string gas in a constant electromagnetic background. Starting from this result we show that the Hagedorn temperature of this hot string gas depends on the background electric field. The larger the electric field, the lower the Hagedorn temperature is. (author). 13 refs
Stochastic thermoelastic problem of a functionally graded plate under random temperature load
Energy Technology Data Exchange (ETDEWEB)
Chiba, R. [Miyagi National College of Technology, Department of Mechanical Engineering, Natori (Japan); Sugano, Y. [Iwate University, Department of Mechanical Engineering, Morioka (Japan)
2007-04-15
This study attempts to derive the statistics of temperature and thermal stress in functionally graded material (FGM) plates exposed to random external temperatures. The thermomechanical properties of the FGM plates are assumed to vary arbitrarily only in the plate thickness direction. The external temperatures are expressed as random functions with respect to time. The transient temperature field in the FGM plate is determined by solving a nonhomogeneous heat conduction problem for a multilayered plate with linear nonhomogeneous thermal conductivity and different homogeneous heat capacity in each layer. The autocorrelations and power spectrum densities (PSDs) of temperature and thermal stress are derived analytically. These statistics for FGM plates composed of partially stabilised zirconia (PSZ) and austenitic stainless steel (SUS304) are computed under the condition that the fluctuation in the external temperature can be considered as white noise or a stationary Markov process. (orig.)
Dynamic reconstruction algorithm of temperature field based on Kalman filter
Li, Yanqiu; Liu, Shi; Han, Ren
2017-05-01
Development of temperature reconstruction algorithm plays an important role in the application of temperature field measurement by acoustic tomography. A dynamic model of temperature field reconstruction by acoustic tomography is established. A dynamic reconstruction algorithm based on Kalman Filter (KF) is proposed considering both acoustic measurement and the dynamic evolution information. An objective function fusing space constrain with dynamic evolution information is designed. Simulation results of three temperature field distribution models show that the reconstruction quality of dynamic reconstruction method based on KF is better than those of static reconstruction methods.
El-Kaddah, N.; Szekely, J.
1982-01-01
A mathematical representation was developed for the electromagnetic force field, the flow field, the temperature field (and for transport controlled kinetics), in a levitation melted metal droplet. The technique of mutual inductances was employed for the calculation of the electromagnetic force field, while the turbulent Navier - Stokes equations and the turbulent convective transport equations were used to represent the fluid flow field, the temperature field and the concentration field. The governing differential equations, written in spherical coordinates, were solved numerically. The computed results were in good agreement with measurements, regarding the lifting force, and the average temperature of the specimen and carburization rates, which were transport controlled.
Problems of a transformer with high-temperature superconductors
International Nuclear Information System (INIS)
Mueller, W.
1989-01-01
Fundamental reflections are made on the demands which have to be made on the short-circuit current limitation in the network on the one hand and on the admissible magnetic boundary field strengths of high-temperature superconduction on the other hand. The aim to develop mechanically self-supporting windings led for conventional core-type transformer designs to the construction of concentric-lay winding arrangements with magnetic stray field strengths, which seem to be realizable with regard to material development. Due to the further aim of avoiding core losses, a design study on a coreless high-temperature superconduction transformer was drawn up the windings of which are united in a coaxial cable which is wound up to a toroidal coil. The factors of influence which are relevant for the rating, operating characteristics and the application of a transformer like this are discussed. (orig.) [de
TEMPERATURE FIELDS IN THE ZONE OF CONNECTION BETWEEN WINDOW AND BUILDING ENVELOPE
V. V. Ivanov; A. N. Butenko; L. V. Karaseva
2011-01-01
Problem statement. To determine additional heat losses through window opening slopes, it is ne-cessary to calculate temperature fields of a wall in the zone of connection between window and building envelope. Two types of building envelopes are considered: solid brick wall and two-layer-wall of bricks and fiber foam concrete block interlayered with air.Results. The results obtained show the influence of a window on the temperature field of wall opening. Different types of wall structures are ...
Factors Influencing Temperature Fields during Combustion Reactions
2014-05-20
nanothermite reaction. A review of the recent work in nanothermite temperature measurement techniques and advances is provided in Ref. [25]. Optical pyrometry...III : Coupling Pyrometer and IR Data For each nanothermite, the thermal image with the maxi- mum amount of radiance was identified. From each of...D. Frost, J. Levine, Optical Pyrometry of Fireballs of Metalized Explosives, Propellants Explos. Pyrotech. 2006, 31, 169. [10] M. Zachariah
Supersymmetric field theories at finite temperature
International Nuclear Information System (INIS)
Dicus, D.A.; Tata, X.R.
1983-01-01
We show by explicit calculations to second and third order in perturbation theory, that finite temperature effects do not break the supersymmetry Ward-Takahashi identities of the Wess-Zumino model. Moreover, it is argued that this result is true to all orders in perturbation theory, and further, true for a wide class of supersymmetric theories. We point out, however, that these identities can be broken in the course of a phase transition that restores an originally broken internal symmetry
An implementation problem for boson fields and quantum Girsanov transform
Energy Technology Data Exchange (ETDEWEB)
Ji, Un Cig, E-mail: uncigji@chungbuk.ac.kr [Department of Mathematics, Research Institute of Mathematical Finance, Chungbuk National University, Cheongju 361-763 (Korea, Republic of); Obata, Nobuaki, E-mail: obata@math.is.tohoku.ac.jp [Graduate School of Information Sciences, Tohoku University, Sendai 980-8579 (Japan)
2016-08-15
We study an implementation problem for quadratic functions of annihilation and creation operators on a boson field in terms of quantum white noise calculus. The implementation problem is shown to be equivalent to a linear differential equation for white noise operators containing quantum white noise derivatives. The solution is explicitly obtained and turns out to form a class of white noise operators including generalized Fourier–Gauss and Fourier–Mehler transforms, Bogoliubov transform, and a quantum extension of the Girsanov transform.
An implementation problem for boson fields and quantum Girsanov transform
International Nuclear Information System (INIS)
Ji, Un Cig; Obata, Nobuaki
2016-01-01
We study an implementation problem for quadratic functions of annihilation and creation operators on a boson field in terms of quantum white noise calculus. The implementation problem is shown to be equivalent to a linear differential equation for white noise operators containing quantum white noise derivatives. The solution is explicitly obtained and turns out to form a class of white noise operators including generalized Fourier–Gauss and Fourier–Mehler transforms, Bogoliubov transform, and a quantum extension of the Girsanov transform.
Sound field reproduction as an equivalent acoustical scattering problem.
Fazi, Filippo Maria; Nelson, Philip A
2013-11-01
Given a continuous distribution of acoustic sources, the determination of the source strength that ensures the synthesis of a desired sound field is shown to be identical to the solution of an equivalent acoustic scattering problem. The paper begins with the presentation of the general theory that underpins sound field reproduction with secondary sources continuously arranged on the boundary of the reproduction region. The process of reproduction by a continuous source distribution is modeled by means of an integral operator (the single layer potential). It is then shown how the solution of the sound reproduction problem corresponds to that of an equivalent scattering problem. Analytical solutions are computed for two specific instances of this problem, involving, respectively, the use of a secondary source distribution in spherical and planar geometries. The results are shown to be the same as those obtained with analyses based on High Order Ambisonics and Wave Field Synthesis, respectively, thus bringing to light a fundamental analogy between these two methods of sound reproduction. Finally, it is shown how the physical optics (Kirchhoff) approximation enables the derivation of a high-frequency simplification for the problem under consideration, this in turn being related to the secondary source selection criterion reported in the literature on Wave Field Synthesis.
Nonlinear boundary value problems in quantum field theory
International Nuclear Information System (INIS)
Schrader, R.
1989-01-01
We discuss the general structure of a quantum field theory which is free in the interior of a bounded set B of R n . It is shown how to recover the field theory in the interior of B from a certain quantum field theory on the boundary. With an application to string theory in mind, we discuss the example where B equals an interval and the boundary value problem is given in terms of a euclidean functional integral with a P(var phi) interaction restricted to the boundary. copyright 1989 Academic Press, Inc
Cauchy's problem for field equations with arbitrary spin
International Nuclear Information System (INIS)
Wuensch, V.
1983-01-01
We discuss Cauchy's problem and Huygens' principle for relativistic higher spin and non-zero mass equations, which are internally consistent in an arbitrary curved space-time. A representation theorem for the solution and conditions for the validity of Huygens' principle are given. The space-times on which these field equations satisfy Huygens' principle are determined explicitly [fr
Multiphysics field analysis and multiobjective design optimization: a benchmark problem
Czech Academy of Sciences Publication Activity Database
di Barba, P.; Doležel, Ivo; Karban, P.; Kůs, P.; Mach, F.; Mognaschi, M. E.; Savini, A.
2014-01-01
Roč. 22, č. 7 (2014), s. 1214-1225 ISSN 1741-5977 R&D Projects: GA ČR(CZ) GAP102/11/0498 Institutional support: RVO:61388998 Keywords : coupled-field problems * finite-element analysis * hp-FEM adaptation Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 0.868, year: 2014
Towards quantum gravity via quantum field theory. Problems and perspectives
Energy Technology Data Exchange (ETDEWEB)
Fredenhagen, Klaus [II. Institut fuer Theoretische Physik, Universitaet Hamburg (Germany)
2016-07-01
General Relativity is a classical field theory; the standard methods for constructing a corresponding quantum field theory, however, meet severe difficulties, in particular perturbative non-renormalizability and the problem of background independence. Nevertheless, modern approaches to quantum field theory have significantly lowered these obstacles. On the side of non-renormalizability, this is the concept of effective theories, together with indications for better non-perturbative features of the renormalization group flow. On the side of background independence the main progress comes from an improved understanding of quantum field theories on generic curved spacetimes. Combining these informations, a promising approach to quantum gravity is an expansion around a classical solution which then is a quantum field theory on a given background, augmented by an identity which expresses independence against infinitesimal shifts of the background. The arising theory is expected to describe small corrections to classical general relativity. Inflationary cosmology is expected to arise as a lowest order approximation.
Temperature dependency of silicon structures for magnetic field gradient sensing
Dabsch, Alexander; Rosenberg, Christoph; Stifter, Michael; Keplinger, Franz
2018-02-01
This work describes the temperature dependence of two sensors for magnetic field gradient sensors and demonstrates a structure to compensate for the drift of resonance frequency over a wide temperature range. The temperature effect of the sensing element is based on internal stresses induced by the thermal expansion of material, therefore FEM is used to determine the change of the eigenvalues of the sensing structure. The experimental setup utilizes a Helmholtz coil system to generate the magnetic field and to excite the MEMS structure with Lorentz forces. The MEMS structure is placed on a plate heated with resistors and cooled by a Peltier element to control the plate temperature. In the second part, we describe how one can exploit temperature sensitivity for temperature measurements and we show the opportunity to include the temperature effect to increase the sensitivity of single-crystal silicon made flux density gradient sensors.
Problem-based, interdisciplinary field-based courses
DEFF Research Database (Denmark)
Hill, Trevor; Birch-Thomsen, Torben; Traynor, Catherine
2008-01-01
the context of their learning better and have a greater appreciation of their own personal development. The process calls for long-term commitment to the communities with whom one works closely, the recognition of sometimes having to 'think on one's feet', being prepared to make mistakes and use frustration......Student field courses at Universities are increasingly incorporating problem-based interdisciplinary approaches to enhance learning opportunities. This paper reports upon seven field-based, problem-oriented, interdisciplinary courses held within southern Africa concerning natural resource...... management and sustainable land use. The SLUSE (Sustainable Land Use and Natural Resource Management) project, under which these courses were devised, is introduced and the process of field-course implementation is described. The SLUSE approach is discussed in terms of management issues, levels...
Low-temperature field evaporation of Nb3Sn compound
International Nuclear Information System (INIS)
Ksenofontov, V.A.; Kul'ko, V.B.; Kutsenko, P.A.
1986-01-01
Investigation results on field evaporation of superconducting Nb 3 Sn compound wth A15 lattice are presented. Compound evaporation is shown to proceed in two stages. Evaporation field and ionic composition of evaporating material are determined. It is found out that in strong electric fields compound surface represents niobium skeleton, wich does not form regular image. Comparison of ion-microscopic and calculated images formed by low-temperature field evaporation indicates to possibility of sample surface reconstruction after preferable tin evaporation
Rigid format alter packets for the analysis of electromagnetic field problems
Spreeuw, E.; Reefman, R. J. B.
1975-01-01
The computer program NASTRAN is used to solve electromagnetic field problems. The diffusion equation and the boundary conditions valid for problems of these kinds together with a replacing potential energy function are given. The extent to which an analogy with finite element displacement and temperature approaches holds is indicated. The outputting of complex quantities is made possible after adjustment of standard rigid format 1 input data blocks to module SDR2. The applications made involve the study of the proximity effect in a system of three parallel conductors and the analysis of the magnetic field in the vicinity of the points of contact in circuit breakers.
Simulation of Temperature Field in HDPE Pipe Thermal Welding
Directory of Open Access Journals (Sweden)
LIU Li-jun
2017-04-01
Full Text Available For high density polyethylene pipe connection，welding technology is the key of the high density engineering plastic pressure pipe safety. And the temperature distribution in the welding process has a very important influence on the welding quality. Polyethylene pipe weld joints of one dimensional unsteady overall heat transfer model is established by MARC software and simulates temperature field and stress field distribution of the welding process，and the thermocouple temperature automatic acquisition system of welding temperature field changes were detected，and compared by simulation and experiment .The results show that，at the end of the heating，the temperature of the pipe does not reach the maximum，but reached the maximum at 300 s，which indicates that the latent heat of phase change in the process of pressure welding. In the process of pressure welding， the axial stress of the pipe is gradually changed from tensile stress to compressive stress.
Creativity of Field-dependent and Field-independent Students in Posing Mathematical Problems
Azlina, N.; Amin, S. M.; Lukito, A.
2018-01-01
This study aims at describing the creativity of elementary school students with different cognitive styles in mathematical problem-posing. The posed problems were assessed based on three components of creativity, namely fluency, flexibility, and novelty. The free-type problem posing was used in this study. This study is a descriptive research with qualitative approach. Data collections were conducted through written task and task-based interviews. The subjects were two elementary students. One of them is Field Dependent (FD) and the other is Field Independent (FI) which were measured by GEFT (Group Embedded Figures Test). Further, the data were analyzed based on creativity components. The results show thatFD student’s posed problems have fulfilled the two components of creativity namely fluency, in which the subject posed at least 3 mathematical problems, and flexibility, in whichthe subject posed problems with at least 3 different categories/ideas. Meanwhile,FI student’s posed problems have fulfilled all three components of creativity, namely fluency, in which thesubject posed at least 3 mathematical problems, flexibility, in which thesubject posed problems with at least 3 different categories/ideas, and novelty, in which the subject posed problems that are purely the result of her own ideas and different from problems they have known.
Effect of electric field (at different temperatures) on germination of ...
African Journals Online (AJOL)
Chickpea (Cicer arietinum) seeds were exposed to electric field from zero to 1300 V for 15 min at three different temperatures (13, 16 and 19°C). It was found that the exposure of chickpea seeds to the electric field caused a change in water uptake capacity (and its coefficient) as compared to control. A new theoretical model ...
Probing High Temperature Superconductors with Magnetometry in Ultrahigh Magnetic Fields
Energy Technology Data Exchange (ETDEWEB)
Li, Lu [Univ. of Michigan, Ann Arbor, MI (United States)
2017-07-26
The objective of this research is to investigate the high-field magnetic properties of high temperature superconductors, materials that conduct electricity without loss. A technique known as high-resolution torque magnetometry that was developed to directly measure the magnetization of high temperature superconductors. This technique was implemented using the 65 Tesla pulsed magnetic field facility that is part of the National High Magnetic Field Laboratory at Los Alamos National Laboratory. This research addressed unanswered questions about the interplay between magnetism and superconductivity, determine the electronic structure of high temperature superconductors, and shed light on the mechanism of high temperature superconductivity and on potential applications of these materials in areas such as energy generation and power transmission. Further applications of the technology resolve the novel physical phenomena such as correlated topological insulators, and spin liquid state in quantum magnets.
Variability of surface temperature in agricultural fields of central California
Hatfield, J. L.; Millard, J. P.; Goettelman, R. C.
1982-01-01
In an attempt to evaluate the relationship between hand-held infrared thermometers and aircraft thermal scanners in near-level terrain and to quantify the variability of surface temperatures within individual fields, ground-based and aircraft thermal sensor measurements were made along a 50-km transect on 3 May 1979 and a 20-km transect on 7 August 1980. These comparisons were made on fields near Davis, California. Agreement was within 1 C for fields covered with vegetation and 3.6 C for bare, dry fields. The variability within fields was larger for bare, dry fields than for vegetatively covered fields. In 1980, with improvements in the collection of ground truth data, the agreement was within 1 C for a variety of fields.
Sprites, lightning, cloudtop temperatures and mesospheric electric field
São Sabbas, F.; Sentman, D.; Taylor, M.; Wescott, E.; Stenbaek-Nielsen, H.
2003-04-01
Sprites are one of the optical manifestations of electrical energy deposition in the mesosphere by lightning activity in the troposphere. Observations obtained from the Space Shuttle, and during ground and aircraft campaigns conducted in the U.S., Peru, Central America, Australia, Japan, Europe, Taiwan, and Brazil have confirmed the global aspect these phenomena. In order to better understand the mechanism and implications of energy deposition in the mesosphere, detailed studies of the characteristics of spatial and temporal relationship between sprites and lightning, and the characteristics of the generating meteorological system and of the surrounding atmosphere at the locations where sprites have been observed are necessary. The full problem includes consideration of both the source (lightning) characteristics, as well as the ambient medium where sprite ignition occurs. This paper summarizes results of a PhD thesis that examines (1) the observed relationships between the distribution of distance and time delays between the sprites and underlying causative lightning, (2) the correlations between sprites, lightning and cloudtop temperatures extracted from IR satellite images, and (3) the structure of electric fields in an inhomogeneous conductivity distribution at sprite initiation altitudes 75-85 km. The results suggest that conductivity inhomogeneities in the mesosphere may play an important role in determining the locations where sprite ignition occurs above a thunderstorm.
Topology Optimization of a High-Temperature Superconducting Field Winding of a Synchronous Machine
DEFF Research Database (Denmark)
Pozzi, Matias; Mijatovic, Nenad; Jensen, Bogi Bech
2013-01-01
This paper presents topology optimization (TO) of the high-temperature superconductor (HTS) field winding of an HTS synchronous machine. The TO problem is defined in order to find the minimum HTS material usage for a given HTS synchronous machine design. Optimization is performed using a modified...
Dual mean field search for large scale linear and quadratic knapsack problems
Banda, Juan; Velasco, Jonás; Berrones, Arturo
2017-07-01
An implementation of mean field annealing to deal with large scale linear and non linear binary optimization problems is given. Mean field annealing is based on the analogy between combinatorial optimization and interacting physical systems at thermal equilibrium. Specifically, a mean field approximation of the Boltzmann distribution given by a Lagrangian that encompass the objective function and the constraints is calculated. The original discrete task is in this way transformed into a continuous variational problem. In our version of mean field annealing, no temperature parameter is used, but a good starting point in the dual space is given by a ;thermodynamic limit; argument. The method is tested in linear and quadratic knapsack problems with sizes that are considerably larger than those used in previous studies of mean field annealing. Dual mean field annealing is capable to find high quality solutions in running times that are orders of magnitude shorter than state of the art algorithms. Moreover, as may be expected for a mean field theory, the solutions tend to be more accurate as the number of variables grow.
Measurement of critical temperature as a function of field
McInturff, A. D.; Ishibashi, K.; Heard, G. D.
The critical temperature has been measured for various magnet conductors as a function of the perpendicular applied magnetic field. The isothermal environment was provided by a variable temperature cryostat which fits into the bore of a 10 telsa solenoid. The temperature gradient across the sample volume was measured to be less than 25 millikelvins. The superconducting to normal state transition was measured resistively, using sample current densities from 0.01 to 2 A cm -2. The maximum applied magnetic field was 10 T and varied less than 0.5% in the sample volume. The critical transport current range of the samples measured from tens to thousands of amperes in the presence of a 10 T perpendicular magnetic field at 4.2 K.
Electron holography for fields in solids: Problems and progress
International Nuclear Information System (INIS)
Lichte, Hannes; Börrnert, Felix; Lenk, Andreas; Lubk, Axel; Röder, Falk; Sickmann, Jan; Sturm, Sebastian; Vogel, Karin; Wolf, Daniel
2013-01-01
Electron holography initially was invented by Dennis Gabor for solving the problems raised by the aberrations of electron lenses in Transmission Electron Microscopy. Nowadays, after hardware correction of aberrations allows true atomic resolution of the structure, for comprehensive understanding of solids, determination of electric and magnetic nanofields is the most challenging task. Since fields are phase objects in the TEM, electron holography is the unrivaled method of choice. After more than 40 years of experimental realization and steady improvement, holography is increasingly contributing to these highly sophisticated and essential questions in materials science, as well to the understanding of electron waves and their interaction with matter. - Highlights: • We review the development of the method of electron holography. • We outline the role of information content as guideline. • We outline the improvements of the method. • We sketch the future instrumental development. • We summarize the still existing problems to solve
The external field dependence of the BCS critical temperature
DEFF Research Database (Denmark)
Frank, Rupert L.; Hainzl, Christian; Seiringer, Robert
2016-01-01
We consider the Bardeen-Cooper-Schrieffer free energy functional for particles interacting via a two-body potential on a microscopic scale and in the presence of weak external fields varying on a macroscopic scale. We study the influence of the external fields on the critical temperature. We show...... that in the limit where the ratio between the microscopic and macroscopic scale tends to zero, the next to leading order of the critical temperature is determined by the lowest eigenvalue of the linearization of the Ginzburg-Landau equation....
Infrared-temperature variability in a large agricultural field
Millard, J. P.; Goettelman, R. C.; Leroy, M. J.
1981-01-01
Dunnigan Agro-Meteorological Experiment airborne thermal scanner images of a large varying-terrain barley field are acquired and analyzed. Temperature variability that may occur within instantaneous fields of view (IFOV) is defined (coefficient of variation: standard deviation/mean temperature in degrees C), and the percentage of the area within various IFOV's within + or - 1, 2, 3, and 5 degrees of the mean is determined. With the exception of very rugged terrain, over 80% of the area within 4, 16, 65 and 258 ha cells was at temperatures within + or - 3 C of the mean cell temperature. Remote measurements of field temperature appeared to be slightly influenced by pixel size in the range 4 ha to 259 ha, and the area percentage within any pixel which contributes within + or - 1, 2, 3, and 5 degrees C of the mean, is nominally the same. In conclusion, no great advantage is found in utilizing a small IFOV instead of a large one for remote sensing of crop temperature.
Real-time temperature field measurement based on acoustic tomography
International Nuclear Information System (INIS)
Bao, Yong; Jia, Jiabin; Polydorides, Nick
2017-01-01
Acoustic tomography can be used to measure the temperature field from the time-of-flight (TOF). In order to capture real-time temperature field changes and accurately yield quantitative temperature images, two improvements to the conventional acoustic tomography system are studied: simultaneous acoustic transmission and TOF collection along multiple ray paths, and an offline iteration reconstruction algorithm. During system operation, all the acoustic transceivers send modulated and filtered wideband Kasami sequences simultaneously to facilitate fast and accurate TOF measurements using cross-correlation detection. For image reconstruction, the iteration process is separated and executed offline beforehand to shorten computation time for online temperature field reconstruction. The feasibility and effectiveness of the developed methods are validated in the simulation study. The simulation results demonstrate that the proposed method can reduce the processing time per frame from 160 ms to 20 ms, while the reconstruction error remains less than 5%. Hence, the proposed method has great potential in the measurement of rapid temperature change with good temporal and spatial resolution. (paper)
Thermocouple based method of temperature and velocity field mapping
Czech Academy of Sciences Publication Activity Database
Gregor, J.; Jakubová, I.; Mendl, T.; Šenk, J.; Kopecký, Vladimír
2002-01-01
Roč. 52, supplement D (2002), s. 596-600 ISSN 0011-4626. [Symposium on Plasma Physics and Technology/20th./. Prague, 10.06.2002-13.06.2002] Institutional research plan: CEZ:AV0Z2043910 Keywords : determination of temperature, velocity field Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 0.311, year: 2002
Temperature fields in a growing solar silicon crystal
Directory of Open Access Journals (Sweden)
Kondrik A. I.
2012-06-01
Full Text Available The optimal thermal terms for growing by Czochralski method Si single-crystals, suitable for making photoelectric energy converters, has been defined by the computer simulation method. Dependences of temperature fields character and crystallization front form on the diameter of the crystal, stage and speed of growing, and also on correlation between diameter and height of the crystal has been studied.
Field emission behavior of carbon nanotube field emitters after high temperature thermal annealing
Directory of Open Access Journals (Sweden)
Yuning Sun
2014-07-01
Full Text Available The carbon nanotube (CNT field emitters have been fabricated by attaching a CNT film on a graphite rod using graphite adhesive material. The CNT field emitters showed much improved field emission properties due to increasing crystallinity and decreasing defects in CNTs after the high temperature thermal annealing at 900 °C in vacuum ambient. The CNT field emitters showed the low turn-on electric field of 1.15 V/μm, the low threshold electric field of 1.62 V/μm, and the high emission current of 5.9 mA which corresponds to a current density of 8.5 A/cm2. In addition, the CNT field emitters indicated the enhanced field emission properties due to the multi-stage effect when the length of the graphite rod increases. The CNT field emitter showed good field emission stability after the high temperature thermal annealing. The CNT field emitter revealed a focused electron beam spot without any focusing electrodes and also showed good field emission repeatability.
Temperature rising characteristics of ammonium diurante in microwave fields
International Nuclear Information System (INIS)
Liu Bingguo; Peng JinHui; Huang Daifu; Zhang Libo; Hu Jinming; Zhuang Zebiao; Kong Dongcheng; Guo Shenghui; Li Chunxiang
2010-01-01
The temperature rising characteristics of ammonium diurante, triuranium octaoxide (U 3 O 8 ), and their mixture were investigated under microwave irradiation, aiming at exploring newly theoretical foundation for advanced metallurgical methods. The temperature rising curves showed that ammonium diurante had weak capability to absorb microwave energy, while triuranium octaoxide had the very strong absorption capability. The temperature of mixture containing 20% of U 3 O 8 could rise from room temperature to 1171 K within 280 s. The ability to absorb microwave energy for the mixture with different ratios increased with the increase in the amount of U 3 O 8 . These are in good agreement with the results of Maxwell-Garnett effective medium theory. It is feasible to calcine ammonium diurante by adding of small amounts of U 3 O 8 in microwave fields.
Study on the temperature field of large-sized sapphire single crystal furnace
Zhai, J. P.; Jiang, J. W.; Liu, K. G.; Peng, X. B.; Jian, D. L.; Li, I. L.
2018-01-01
In this paper, the temperature field of large-sized (120kg, 200kg and 300kg grade) sapphire single crystal furnace was simulated. By keeping the crucible diameter ratio and the insulation system unchanged, the power consumption, axial and radial temperature gradient, solid-liquid surface shape, stress distribution and melt flow were studied. The simulation results showed that with the increase of the single crystal furnace size, the power consumption increased, the temperature field insulation effect became worse, the growth stress value increased and the stress concentration phenomenon occurred. To solve these problems, the middle and bottom insulation system should be enhanced during designing the large-sized sapphire single crystal furnace. The appropriate radial and axial temperature gradient was favorable to reduce the crystal stress and prevent the occurrence of cracking. Expanding the interface between the seed and crystal was propitious to avoid the stress accumulation phenomenon.
Communication Problems in Requirements Engineering: A Field Study
Al-Rawas, Amer; Easterbrook, Steve
1996-01-01
The requirements engineering phase of software development projects is characterized by the intensity and importance of communication activities. During this phase, the various stakeholders must be able to communicate their requirements to the analysts, and the analysts need to be able to communicate the specifications they generate back to the stakeholders for validation. This paper describes a field investigation into the problems of communication between disparate communities involved in the requirements specification activities. The results of this study are discussed in terms of their relation to three major communication barriers: (1) ineffectiveness of the current communication channels; (2) restrictions on expressiveness imposed by notations; and (3) social and organizational barriers. The results confirm that organizational and social issues have great influence on the effectiveness of communication. They also show that in general, end-users find the notations used by software practitioners to model their requirements difficult to understand and validate.
Electron holography for fields in solids: problems and progress.
Lichte, Hannes; Börrnert, Felix; Lenk, Andreas; Lubk, Axel; Röder, Falk; Sickmann, Jan; Sturm, Sebastian; Vogel, Karin; Wolf, Daniel
2013-11-01
Electron holography initially was invented by Dennis Gabor for solving the problems raised by the aberrations of electron lenses in Transmission Electron Microscopy. Nowadays, after hardware correction of aberrations allows true atomic resolution of the structure, for comprehensive understanding of solids, determination of electric and magnetic nanofields is the most challenging task. Since fields are phase objects in the TEM, electron holography is the unrivaled method of choice. After more than 40 years of experimental realization and steady improvement, holography is increasingly contributing to these highly sophisticated and essential questions in materials science, as well to the understanding of electron waves and their interaction with matter. © 2013 Elsevier B.V. All rights reserved.
Zhang, Senfu
2018-03-29
Magnetic skyrmions are topologically protected nanoscale spin textures exhibiting fascinating physical behaviors. Recent observations of room temperature skyrmions in sputtered multilayer films are an important step towards their use in ultra-low power devices. Such practical applications prefer skyrmions to be stable at zero magnetic fields and room temperature. Here, we report the creation of skyrmion lattices in Pt/Co/Ta multilayers by a scanning local field using magnetic force microscopy tips. We also show that those newly created skyrmion lattices are stable at both room temperature and zero fields. Lorentz transmission electron microscopy measurements reveal that the skyrmions in our films are of Néel-type. To gain a deeper understanding of the mechanism behind the creation of a skyrmion lattice by the scanning of local fields, we perform micromagnetic simulations and find the experimental results to be in agreement with our simulation data. This study opens another avenue for the creation of skyrmion lattices in thin films.
Research of the Border Mobility Influence on the Half-Space Temperature Field Under Heat Flux
Directory of Open Access Journals (Sweden)
P. A. Vlasov
2014-01-01
Full Text Available Among the problems of unsteady heat conduction, tasks that can be solved in analytical closedform hold a special place. This species can be used both for parametric optimization of thermal protection of structures and for testing of computational algorithms.The previous paper presented an analytical solution of the problem to find the half-space temperature field with the uniformly moving boundary, which was under the external heat flux of constant power. In this paper we consider a similar problem, but the law of the moving boundary is assumed to be arbitrary nondecreasing, and the power of the heat flux can vary over time.An analytical dependence of the problem solution on the temperature of a moving boundary was obtained by using the Fourier transformation in the spatial variable. To determine the temperature of moving boundary, Volterra integral equation of the second kind was drawn. The solution of this equation was numerically conducted using a specially developed computational algorithm.The obtained representation was used to research the most characteristic features of the process to form the temperature field in studied area when implementing the various laws of boundaries motion and different operating conditions for the external heat flux influence. Using computational experiments allowed us to find that the asymptotic nature of this dependence confirms the results obtained in previous work. It has been established that the nonlinear character of both the boundary motion law and the external heat flux power variation law mainly affect the specifics of the transition process.
Numerical solution of a model for a superconductor field problem
International Nuclear Information System (INIS)
Alsop, L.E.; Goodman, A.S.; Gustavson, F.G.; Miranker, W.L.
1979-01-01
A model of a magnetic field problem occurring in connection with Josephson junction devices is derived, and numerical solutions are obtained. The model is of mathematical interest, because the magnetic vector potential satisfies inhomogeneous Helmholtz equations in part of the region, i.e., the superconductors, and the Laplace equation elsewhere. Moreover, the inhomogeneities are the guage constants for the potential, which are different for each superconductor, and their magnitudes are proportional to the currents flowing in the superconductors. These constants are directly related to the self and mutual inductances of the superconducting elements in the device. The numerical solution is obtained by the iterative use of a fast Poisson solver. Chebyshev acceleration is used to reduce the number of iterations required to obtain a solution. A typical problem involves solving 100,000 simultaneous equations, which the algorithm used with this model does in 20 iterations, requiring three minutes of CPU time on an IBM VM/370/168. Excellent agreement is obtained between calculated and observed values for the inductances
Infinitely long cylinder in a sinusoidal field (Problem 2)
International Nuclear Information System (INIS)
Ida, N.
1986-01-01
The results presented here were obtained with a 2-D (and axisymmetric) eddy current program called EDDYNDT. The program uses the magnetic vector potential formulation and was specifically designed for the calculation of coil impedances in NDT applications. For normal applications, flux densities, forces, eddy current densities and stored and dissipated energies are not calculated. The program required minor modifications to calculated these quantities form the magnetic vector potential. In its present form, program EDDYNDT cannot handle flux normal boundary conditions. To avoid this, half the cylinder was modeled as opposed to the quarter cylinder in the mesh recommended in the problem outline. This increased the number of elements and nodes but did not change their density or location. Both a solution without the cylinder and a solution with the cylinder are presented. The fields presented are calculated at the center of each element. For this reason, the values presented are interpolated between neighboring elements. This creates a problem, particularly at discontinuities where the errors are largest
Perturbative algebraic quantum field theory at finite temperature
Energy Technology Data Exchange (ETDEWEB)
Lindner, Falk
2013-08-15
We present the algebraic approach to perturbative quantum field theory for the real scalar field in Minkowski spacetime. In this work we put a special emphasis on the inherent state-independence of the framework and provide a detailed analysis of the state space. The dynamics of the interacting system is constructed in a novel way by virtue of the time-slice axiom in causal perturbation theory. This method sheds new light in the connection between quantum statistical dynamics and perturbative quantum field theory. In particular it allows the explicit construction of the KMS and vacuum state for the interacting, massive Klein-Gordon field which implies the absence of infrared divergences of the interacting theory at finite temperature, in particular for the interacting Wightman and time-ordered functions.
Control of colloids with gravity, temperature gradients, and electric fields
Sullivan, M; Harrison, C; Austin, R H; Megens, M; Hollingsworth, A; Russel, W B; Cheng Zhen; Mason, T; Chaikin, P M
2003-01-01
We have used a variety of different applied fields to control the density, growth, and structure of colloidal crystals. Gravity exerts a body force proportional to the buoyant mass and in equilibrium produces a height-dependent concentration profile. A similar body force can be obtained with electric fields on charged particles (electrophoresis), a temperature gradient on all particles, or an electric field gradient on uncharged particles (dielectrophoresis). The last is particularly interesting since its magnitude and sign can be changed by tuning the applied frequency. We study these effects in bulk (making 'dielectrophoretic bottles' or traps), to control concentration profiles during nucleation and growth and near surfaces. We also study control of non-spherical and optically anisotropic particles with the light field from laser tweezers.
Organ preservation at low temperature: a physical and biological problem
Aussedat, J.; Boutron, P.; Coquilhat, P.; Descotes, J. L.; Faure, G.; Ferrari, M.; Kay, L.; Mazuer, J.; Monod, P.; Odin, J.; Ray, A.
1993-02-01
Before reporting the preliminary results obtained by our group, we first review the main problems to be solved in the preservation of organs at very low temperature, before being transplanted. This cryopreservation is being presently explored in order to increase the preservation tiine of transplants and to contribute to a better control of the donor recipient compatibility. We recall that, for the isolated cells to be preserved at nitrogen liquid temperatures, as now successfully performed at industrial scale, it is necessary to immerse the cells in a solution containing more or less t,oxical additives (so-called cryopro tect ants). Furthermore cooling and warming rates must be specific of each type of cells. We then show that cryo preservation could be extrapolated to whole organs by means of vitrification, the only way to avoid any ice crystallization. This vitrification will be the result of two directions of research, the one on the elaboration of cryoprotective solutions, the least toxic possible, the other on the obtention of high enough and homogeneous cooling and warming rates. After having briefly summarized the state of research on the heart and kidneys of small mammals, we present the first results that we have obtained on perfusion at 4 ^{circ}C and the auto-transplantation of rabbit kidneys, on the toxicity of a new cryoprotectant, 2,3-butanediol, on the heart rate, and on the cooling of experimental models of organs. Avant de présenter les résultats préliminaires obtenus par notre groupe, nous passons d'abord en revue les principaux problèmes à résoudre pour conserver à très basse température des organes en vue de leur transplantation. Cette cryopréservation est une voie de recherche actuellement explorée pour augmenter la durée de conservation des greffons et permettre ainsi de mieux contrôler la compatibilité donneur-receveur. Nous rappelons que la conservation des cellules isolées à la température de l'azote liquide, actuellement
The Temperature - Magnetic Field Relation in Observed and Simulated Sunspots
Sobotka, Michal; Rezaei, Reza
2017-12-01
Observations of the relation between continuum intensity and magnetic field strength in sunspots have been made for nearly five decades. This work presents full-Stokes measurements of the full-split (g = 3) line Fe i 1564.85 nm with a spatial resolution of 0.5^'' obtained with the GREGOR Infrared Spectrograph in three large sunspots. The continuum intensity is corrected for instrumental scattered light, and the brightness temperature is calculated. Magnetic field strength and inclination are derived directly from the line split and the ratio of Stokes components. The continuum intensity (temperature) relations to the field strength are studied separately in the umbra, light bridges, and penumbra. The results are consistent with previous studies, and it was found that the scatter of values in the relations increases with increasing spatial resolution thanks to resolved fine structures. The observed relations show trends common for the umbra, light bridges, and the inner penumbra, while the outer penumbra has a weaker magnetic field than the inner penumbra at equal continuum intensities. This fact can be interpreted in terms of the interlocking comb magnetic structure of the penumbra. A comparison with data obtained from numerical simulations was made. The simulated data generally have a stronger magnetic field and a weaker continuum intensity than the observations, which may be explained by stray light and limited spatial resolution of the observations, and also by photometric inaccuracies of the simulations.
Sun, W.; Liu, H. L.; Cai, Y. G.; Li, Y. L.; Zhou, H. Y.; Zhou, Y.
2018-01-01
The temperature field distribution in the medium-voltage vacuum interrupter decides the thermal stability of it. In this paper, the simulation model of a kind of 12kV/3150A/40kA medium-voltage vacuum interrupter is constructed, and conductive bridge model is used. This paper simulates current contraction and Joule heating between contacts, and solves relevant problems using the function of the thermal-electrical coupling in the finite element software ANSYS. Steady-state temperature rise of vacuum interrupter at rated current and transient temperature rise of vacuum interrupter at short-time withstand current are calculated. Influence of the contact situation on vacuum interrupter temperature rise is analyzed. Steady-state temperature rise experiments for the interrupter are carried out, and experiment results verify the accuracy of simulation results. The results are useful in the designing and optimizing of medium-voltage vacuum interrupter.
Imulation of temperature field in swirl pulverized coal boiler
Lv, Wei; Wu, Weifeng; Chen, Chen; Chen, Weifeng; Qi, Guoli; Zhang, Songsong
2018-02-01
In order to achieve the goal of energy saving and emission reduction and energy efficient utilization, taking a 58MW swirl pulverized coal boiler as the research object, the three-dimensional model of the rotor is established. According to the principle of CFD, basic assumptions and boundary conditions are selected, the temperature field in the furnace of 6 kinds of working conditions is numerically solved, and the temperature distribution in the furnace is analyzed. The calculation results show that the temperature of the working condition 1 is in good agreement with the experimental data, and the error is less than 10%,the results provide a theoretical basis for the following calculation. Through the comparison of the results of the 6 conditions, it is found that the working condition 3 is the best operating condition of the pulverized coal boiler.
ESTIMATION OF THE CONCRETE PAVEMENT TEMPERATURE FIELDS AND THEIR GRADIENTS
Directory of Open Access Journals (Sweden)
M. K. Pshembaev
2015-01-01
Full Text Available The heat fluxes impact on the road-dressing concrete surfacing under different regions climatic conditions of the construction and maintenance dramatically degrades their solidity, corroding-, shiftingand frost-resistance, and ultimately – the service durability. The source of deformation processes is the character of the gradient temperature fields in the road dressing materials developing with both protracted (static and short run (dynamic heat-and-mass impacts that forward destruction of the pavement surface layers being in contact with free air. In addition, pulsating hydrodynamic pressures appear in the pores of moisture-laden pavement as a result of the vehicular traffic that foster material structure disruption of the surface layers leading to irreversible deformation incipiency (cracks etc.. The authors report of developing a С++ computer program for temperature and gradient fields engineering evaluations of the road dressings made of materials with various surfacing and free-air thermophysical characteristics in line with boundary conditions of the 3rd kind for semi-bounded body. The paper presents the evaluation results in form of graphical curves of the temperature allocation along the surfacing thickness as function of its initial temperature and thermophysical characteristics of the concrete.
Shape Design of Unsteady Forced Heat-convection Fields to Control Temperature Distribution History
Katamine, Eiji; Okada, Naoya
2017-11-01
This paper presents a numerical solution to shape design of unsteady forced heat-convection fields to control temperature to a prescribed distribution. The square error integral between the actual temperature distributions and the prescribed temperature distributions on the prescribed sub-domains during the specified period of time is used as the objective functional. Shape gradient of the shape design problem is derived theoretically using the Lagrange multiplier method, adjoint variable method, and the formulae of the material derivative. Reshaping is carried out by the traction method proposed as an approach to solving shape optimization problems. Numerical analyses program for the shape design is developed based on FreeFem++, and the validity of proposed method is confirmed by results of 2D numerical analyses.
Quasi-Stationary Temperature Field of Two-Layer Half-Space with Moving Boundary
Directory of Open Access Journals (Sweden)
P. A. Vlasov
2015-01-01
Full Text Available Due to intensive introduction of mathematical modeling methods into engineering practice, analytical methods for solving problems of heat conduction theory along with computational methods become increasingly important. Despite the well-known limitations of the analytical method applicability, this trend is caused by many reasons. In particular, solutions of the appropriate problems presented in analytically closed form can be used to test the new efficient computational algorithms, to carry out a parametric study of the temperature field of the analyzed system and to explore specific features of its formation, to formulate and solve optimization problems. In addition, these solutions allow us to explore the possibility for simplifying mathematical model with retaining its adequacy to the studied process.The main goal of the conducted research is to provide an analytically closed-form solution to the problem of finding the quasi-stationary temperature field of the system, which is simulated by isotropic half-space with isotropic coating of constant thickness. The outer boundary of this system is exposed to the Gaussian-type heat flux and uniformly moves in parallel with itself.A two-dimensional mathematical model that takes into account the axial symmetry of the studied process has been used. After the transition to a moving coordinate system rigidly associated with a moving boundary the Hankel integral transform of zero order (with respect to the radial variable and the Laplace transform (with respect to the temporal variable were used. Next, the image of the Hankel transform for the stationary temperature field of the system with respect to the moving coordinate system was found using a limit theorem of operational calculus. This allowed representing the required quasi-stationary field in the form of an improper integral of the first kind, which depends on the parameters. This result obtained can be used to conduct a parametric study and solve
In-orbit Calibration and Local Gravity Field Continuation Problem
Pail, R.
In the course of the GOCE data processing many calibration tasks have to be per- formed. Towards the final part of the data stream, an absolute calibration and vali- dation of the gradiometer signal is required. One of the most promising methods for such an in-orbit calibration is the use of well-surveyed areas on the Earth's surface, where the accuracy of the known gravity field information is high enough to meet the mission requirements. For this purpose ground gravity data have to be continued upward to the GOCE satellite altitude of approximately 250 km, where a comparison with the actual observations is performed. Since there are only very few regions on the globe which fulfil the accuracy requirements, the corresponding gravity information is extremely locally bounded, dismissing standard global continuation strategies and simultaneously resulting in edge effect and windowing problems. Based on a synthetic gravity test environment providing in addition to statistical er- ror information also absolute error estimates several upward continuation methods, e.g. least squares collocation, equivalent source techniques using point masses or area density distributions defined on a spherical surface section, are described, assessed and compared. It turns out that all these strictly local approaches fail to work suffi- ciently accurate. Consequently, a combined solution strategy is proposed, supporting the high-quality gravity field information within the well-surveyed test area with a low accuracy, but globally defined Earth model. Under quite realistic assumptions the upward continuation is performed with rms errors of gravity gradients in the order of 1 mE. The most crucial limiting factor of this method is spectral leakage in the course of an adequate representation of the initial gravity information. We will particularly focus on the consequences and effects of the different approaches on the accuracy of GOCE level 1b and 2 products. In order to demonstrate
Temperature field in concrete when in contact with hot liquids
International Nuclear Information System (INIS)
Andrade Lima, F.R. de.
1981-09-01
In an HCDA (Hypothetical Core Disruptive Accident) it is postulated that liquid metal coolants and core materials come in contact with the retaining concrete structure. A mathematical model and an associated computer program was previously developed to describle the transient heat and mass transfer in the concrete. Implementations on the original program-USINT- are included to consider the variations of the thermal conductivity as a function of the temperature. Also a subroutine - PLOTTI - is incorporated to the program for the plotting of the results. The new program - USINTG - is used to calculate the temperature and pressure fields and the water released from concrete structures during a sodium leak simulation and with the concrete structures in contact with liquid sodium. No consideration about chemical reactions involving the sodium when in contact with concrete is considered. (Author) [pt
Mathematics of thermal diffusion in an exponential temperature field
Zhang, Yaqi; Bai, Wenyu; Diebold, Gerald J.
2018-04-01
The Ludwig-Soret effect, also known as thermal diffusion, refers to the separation of gas, liquid, or solid mixtures in a temperature gradient. The motion of the components of the mixture is governed by a nonlinear, partial differential equation for the density fractions. Here solutions to the nonlinear differential equation for a binary mixture are discussed for an externally imposed, exponential temperature field. The equation of motion for the separation without the effects of mass diffusion is reduced to a Hamiltonian pair from which spatial distributions of the components of the mixture are found. Analytical calculations with boundary effects included show shock formation. The results of numerical calculations of the equation of motion that include both thermal and mass diffusion are given.
Stochastic analysis of temperature fields in frozen foundation soils
Burkov, Pyotr; Konan, Eme Cesar; Burkov, Vladimir; Burkova, Svetlana; Kolesov, Aleks
2017-01-01
One of the most crucial issues of compressor stations engineering and construction is to provide foundation stability and robustness of such stations in permafrost conditions. To date, one of the most used protection methods for compressor stations in permafrost conditions is thermal stabilization of soil. This paper is focused on calculation of the temperature stabilizing foundation based on the mathematical model of stochastic analysis and the forecast of temperature field impacts. Thermotechnical calculations can be used to provide the best estimate of the standard values of strength and deformation parameters of permafrost soils subjected to shear stress and pile foot pressure. The best estimate will be useful for optimization of engineering solutions in terms of support and foundation structures.
Modelling of the temperature field that accompanies friction stir welding
Directory of Open Access Journals (Sweden)
Nosal Przemysław
2017-01-01
Full Text Available The thermal modelling of the Friction Stir Welding process allows for better recognition and understanding of phenomena occurring during the joining process of different materials. It is of particular importance considering the possibilities of process technology parameters, optimization and the mechanical properties of the joint. This work demonstrates the numerical modelling of temperature distribution accompanying the process of friction stir welding. The axisymmetric problem described by Fourier’s type equation with internal heat source is considered. In order to solve the diffusive initial value problem a fully implicit scheme of the finite difference method is applied. The example under consideration deals with the friction stir welding of a plate (0.7 cm thick made of Al 6082-T6 by use of a tool made of tungsten alloy, whereas the material subjected to welding was TiC powder. Obtained results confirm both quantitatively and qualitatively experimental observations that the superior temperature corresponds to the zone where the pin joints the shoulder.
Temperature-field phase diagram of extreme magnetoresistance.
Fallah Tafti, Fazel; Gibson, Quinn; Kushwaha, Satya; Krizan, Jason W; Haldolaarachchige, Neel; Cava, Robert Joseph
2016-06-21
The recent discovery of extreme magnetoresistance (XMR) in LaSb introduced lanthanum monopnictides as a new platform to study this effect in the absence of broken inversion symmetry or protected linear band crossing. In this work, we report XMR in LaBi. Through a comparative study of magnetotransport effects in LaBi and LaSb, we construct a temperature-field phase diagram with triangular shape that illustrates how a magnetic field tunes the electronic behavior in these materials. We show that the triangular phase diagram can be generalized to other topological semimetals with different crystal structures and different chemical compositions. By comparing our experimental results to band structure calculations, we suggest that XMR in LaBi and LaSb originates from a combination of compensated electron-hole pockets and a particular orbital texture on the electron pocket. Such orbital texture is likely to be a generic feature of various topological semimetals, giving rise to their small residual resistivity at zero field and subject to strong scattering induced by a magnetic field.
Pretest Calculations of Temperature Changes for Field Thermal Conductivity Tests
International Nuclear Information System (INIS)
N.S. Brodsky
2002-01-01
A large volume fraction of the potential monitored geologic repository at Yucca Mountain may reside in the Tptpll (Tertiary, Paintbrush Group, Topopah Spring Tuff, crystal poor, lower lithophysal) lithostratigraphic unit. This unit is characterized by voids, or lithophysae, which range in size from centimeters to meters. A series of thermal conductivity field tests are planned in the Enhanced Characterization of the Repository Block (ECRB) Cross Drift. The objective of the pretest calculation described in this document is to predict changes in temperatures in the surrounding rock for these tests for a given heater power and a set of thermal transport properties. The calculation can be extended, as described in this document, to obtain thermal conductivity, thermal capacitance (density x heat capacity, J · m -3 · K -1 ), and thermal diffusivity from the field data. The work has been conducted under the ''Technical Work Plan For: Testing and Monitoring'' (BSC 2001). One of the outcomes of this analysis is to determine the initial output of the heater. This heater output must be sufficiently high that it will provide results in a reasonably short period of time (within several weeks or a month) and be sufficiently high that the heat increase is detectable by the instruments employed in the test. The test will be conducted in stages and heater output will be step increased as the test progresses. If the initial temperature is set too high, the experiment will not have as many steps and thus fewer thermal conductivity data points will result
Evaluation of random temperature fluctuation problems with frequency response approach
International Nuclear Information System (INIS)
Lejeail, Yves; Kasahara, Naoto
2000-01-01
Since thermal striping is a coupled thermohydraulic and thermomechanical phenomenon, sodium mock-up tests were usually required to confirm structural integrity. Authors have developed the frequency response function to establish design-by-analysis methodology for this phenomenon. Applicability of this method to sinusoidal fluctuation was validated through two benchmark problems with FAENA and TIFFSS facilities under EJCC contract. This report describes the extension of the frequency response method to random fluctuations. As an example of application, fatigue strength of a Tee junction of PHENIX secondary piping system was investigated. (author)
A new computer method for temperature measurement based on an optimal control problem
Damean, N.; Houkes, Z.; Regtien, Paulus P.L.
1996-01-01
A new computer method to measure extreme temperatures is presented. The method reduces the measurement of the unknown temperature to the solving of an optimal control problem, using a numerical computer. Based on this method, a new device for temperature measurement is built. It consists of a
Directory of Open Access Journals (Sweden)
Scott N. Williamson
2014-01-01
Full Text Available Spatially continuous satellite infrared temperature measurements are essential for understanding the consequences and drivers of change, at local and regional scales, especially in northern and alpine environments dominated by a complex cryosphere where in situ observations are scarce. We describe two methods for producing daily temperature fields using MODIS “clear-sky” day-time Land Surface Temperatures (LST. The Interpolated Curve Mean Daily Surface Temperature (ICM method, interpolates single daytime Terra LST values to daily means using the coincident diurnal air temperature curves. The second method calculates daily mean LST from daily maximum and minimum LST (MMM values from MODIS Aqua and Terra. These ICM and MMM models were compared to daily mean air temperatures recorded between April and October at seven locations in southwest Yukon, Canada, covering characteristic alpine land cover types (tundra, barren, glacier at elevations between 1,408 m and 2,319 m. Both methods for producing mean daily surface temperatures have advantages and disadvantages. ICM signals are strongly correlated with air temperature (R2 = 0.72 to 0.86, but have relatively large variability (RMSE = 4.09 to 4.90 K, while MMM values had a stronger correlation to air temperature (R2 = 0.90 and smaller variability (RMSE = 2.67 K. Finally, when comparing 8-day LST averages, aggregated from the MMM method, to air temperature, we found a high correlation (R2 = 0.84 with less variability (RMSE = 1.54 K. Where the trend was less steep and the y-intercept increased by 1.6 °C compared to the daily correlations. This effect is likely a consequence of LST temperature averages being differentially affected by cloud cover over warm and cold surfaces. We conclude that satellite infrared skin temperature (e.g., MODIS LST, which is often aggregated into multi-day composites to mitigate data reductions caused by cloud cover, changes in its relationship to air temperature
Gao, Zhiwen; Zheng, Zhiye; Li, Xueyi
2015-12-01
To analyze the fracture problem of the nonhomogeneous high temperature superconductor (HTS) slab under electromagnetic force, we derive the real fundamental solutions based on eigenvalue and eigenvector analyses. The superconductor E-J constitutive law is characterized by the Bean model where the critical current density is independent of the flux density. Fracture analysis is performed by the methods of singular integral equations which are solved numerically by Lobatto-Chybeshev collocation method. Numerical results of the stress intensity factor (SIF) are obtained. Moreover, the crack opening displacement (COD) can be obtained by numerical integration dislocation density functions. The effects of the thickness ratio, HTS material nonhomogeneous parameters, applied magnetic field and critical current density on SIF and COD are discussed. The present work could theoretically provide quantitative predictions of the fracture mechanism of the nonhomogeneous HTS.
Problems related to macroscopic electric fields in the magnetosphere
International Nuclear Information System (INIS)
Faelthammar, C.
1977-01-01
The macroscopic electric fields in the magnetosphere originate from internal as well as external sources. The fields are intimately coupled with the dynamics of magnetospheric plasma convection. They also depend on the complicated electrical properties of the hot collisionless plasma. Macroscopic electric fields are responsible for some important kinds of energization of charged particles that take place in the magnetosphere and affect not only particles of auroral energy but also, by multistep processes, trapped high-energy particles. A particularly interesting feature of magnetospheric electric fields is that they can have substantial components along the geomagnetic field, as has recently been confirmed by observations. Several physical mechanisms have been identified by which such electric fields can be supported even when collisions between particles are negligible. Comments are made on the magnetic mirror effect, anomalous resistivity, the collisionless thermoelectric effect, and electric double layers, emphasizing key features and differences and their significance in the light of recent observational data
Measuring surface temperature of isolated neutron stars and related problems
Teter, Marcus Alton
New and exciting results for measuring neutron star surface temperatures began with the successful launch of the Chandra X-ray observatory. Among these results are new detections of neutron star surface temperatures which have made it possible to seriously test neutron star thermal evolution theories. The important new temperature determination of the Vela pulsar (Pavlov, et al., 2001a) requires a non-standard cooling scenario to explain it. Apart from this result, we have measured PSR B1055-52's surface temperature in this thesis, determining that it can be explained by standard cooling with heating. Our spectral fit of the combined data from ROSAT and Chandra have shown that a three component model, two thermal blackbodies and an non-thermal power-law, is required to explain the data. Furthermore, our phase resolved spectroscopy has begun to shed light on the geometry of the hot spot on PSR B1055-52's surface as well as the structure of the magnetospheric radiation. Also, there is strong evidence for a thermal distribution over its surface. Most importantly, the fact that PSR B1055-52 does not have a hydrogen atmosphere has been firmly established. To reconcile these two key observations, on the Vela pulsar and PSR B1055-52, we tested neutron star cooling with neutrino processes including the Cooper pair neutrino emission process. Overall, it has been found that a phase change associated with pions being present in the cores of more massive neutron stars explains all current of the data. A transition from neutron matter to pion condensates in the central stellar core explains the difference between standard and non-standard cooling scenarios, because the superfluid suppression of pion cooling will reduce the emissivity of the pion direct URCA process substantially. A neutron star with a mass of [Special characters omitted.] with a medium stiffness equation of state and a T72 type neutron superfluid models the standard cooling case well. A neutron star of [Special
Many-body problems in high temperature superconductivity
International Nuclear Information System (INIS)
Yu Lu.
1991-10-01
In this brief review the basic experimental facts about high T c superconductors are outlined. The superconducting properties of these superconductors are not very different from those of the ordinary superconductors. However, their normal state properties cannot be described by the standard Fermi liquid (FL) theory. Our current understanding of the strongly correlated models is summarized. In one dimension these systems behave like a ''Luttinger liquid'', very much distinct from the FL. In spite of the enormous efforts made in two-dimensional studies, the question of FL vs non-FL behaviour is still open. The numerical results as well as various approximation schemes are discussed. Both the single hole problem in a quantum antiferromagnet and finite doping regime are considered. (author). 104 refs, 9 figs
Directory of Open Access Journals (Sweden)
S. G. Tikhomirov
2015-01-01
Full Text Available In the article discussed the mathematical formulation and numerical algorithm for solving the problem of calculating the temperature field in the process vulcanizing of the product, whose the thermal characteristics are depended on the temperature. As a mathematical model considered the system of differential equations of heat conduction, taking into account the change in the coefficients of thermal conductivity and heat density in multilayer product of the temperature. The system of equations is solved for a given initial distribution of temperature and for a given (time-dependent temperatures on the border of the product to the press-mold and to the diaphragm. On the border of the contacts of adjacent layers are given the condition of continuity of temperature and heat flux. Change of the thermal conductivity from the time is approximated by linear functions. The activation energy of the vulcanization process is determined on the basis of experimental data obtained in the control test samples using a reometer. Considering the function representing the corresponding integrals of the thermal conductivity, the original system of differential equations is transformed to an equivalent system of differential equations convenient for constructing numerical algorithms for solving the problem. The resulting system of partial differential equations derived using the method of finite-difference approximation is replaced by a system of algebraic equations. Solution of the system of algebraic equations is carried out under the scheme explicit difference approximation. In the article calculated the temperature field for the tire at given initial and boundary conditions. Stability and accuracy of the numerical algorithm for solving the problem is demonstrated by the calculations performed with different sampling step along the time and space coordinates. Assessment of the degree of completion of the process is carried out by calculated equivalent time for
Directory of Open Access Journals (Sweden)
Esther Müller
2012-01-01
Full Text Available Temperature has been shown to play an important role in the life cycles of insects. Early season feeders in Palaearctic regions profit by the high nutritional quality of their host plants early in the year, but face the problem of having to develop at low average springtime temperatures. This study examines the influence of short periods of heating in the field on larval development and on mortality with the model system Galeruca tanaceti L. (Coleoptera: Chrysomelidae, an early season feeder, that hatches at low springtime temperatures. Field and laboratory experiments under different constant and variable temperature regimes were performed. While in the field, the average daily temperature was close to the lower developmental threshold of the species of 10.9°C; maximum temperatures of above 30°C were sometimes reached. Larvae developed significantly faster, and pupae were heavier, in the field and in an assay with short periods of heating than at the same average temperature under constant conditions in the laboratory. We conclude that larvae profit substantially from short periods of heating and temperature variation in the field and that intervals of high temperature enable insect survival and exploitation of nutrient-rich food resources at early times in the season.
Solution of reverse problems in nuclear geophysics (equivalent field method)
Energy Technology Data Exchange (ETDEWEB)
Barenbaum, A.A.; Polyachenko, A.L.; Yakubson, K.I.
1982-06-01
The approach to the solution of reverse problems in nuclear geophysics based on special integration of two nuclear methods of near similar physical nature is theoretically substantiated. Taking into account the required accuracy of the reverse problem solution such an approach substantially simplifies the interpretation algorithm. The effectiveness of the approach is illustrated by numerical calculations on the example of several complexes of nuclear methods.
A code for calculating force and temperature of a bitter plate type toroidal field coil system
International Nuclear Information System (INIS)
Christensen, U.
1989-01-01
To assist the design effort of the TF coils for CIT, a set of programs was developed to calculate the transient spatial distribution of the current density, the temperature and the forces in the TF coil conductor region. The TF coils are of the Bitter (disk) type design and therefore have negligible variation of current density in the toroidal direction. During the TF pulse, voltages are induced which cause the field and current to diffuse in the minor radial direction. This penetration, combined with the increase of resistance due to the temperature rise determines the distribution of the current. After the current distribution has been determined, the in-plane (TF-TF) and the out-of-plane (TF-PF) forces in the conductor are computed. The predicted currents and temperatures have been independently corroborated using the SPARK code which has been modified for this type of problem. 6 figs
Self-interacting scalar fields at high-temperature
Energy Technology Data Exchange (ETDEWEB)
Deur, Alexandre [University of Virginia, Charlottesville, VA (United States)
2017-06-15
We study two self-interacting scalar field theories in their high-temperature limit using path integrals on a lattice. We first discuss the formalism and recover known potentials to validate the method. We then discuss how these theories can model, in the high-temperature limit, the strong interaction and General Relativity. For the strong interaction, the model recovers the known phenomenology of the nearly static regime of heavy quarkonia. The model also exposes a possible origin for the emergence of the confinement scale from the approximately conformal Lagrangian. Aside from such possible insights, the main purpose of addressing the strong interaction here - given that more sophisticated approaches already exist - is mostly to further verify the pertinence of the model in the more complex case of General Relativity for which non-perturbative methods are not as developed. The results have important implications on the nature of Dark Matter. In particular, non-perturbative effects naturally provide flat rotation curves for disk galaxies, without need for non-baryonic matter, and explain as well other observations involving Dark Matter such as cluster dynamics or the dark mass of elliptical galaxies. (orig.)
Energy Technology Data Exchange (ETDEWEB)
Claesson, J.; Probert, T. [Lund Univ. (Sweden). Dept. of Building Physics and Mathematical Physics
1996-01-01
The temperature field in rock due to a large rectangular grid of heat releasing canisters containing nuclear waste is studied. The solution is by superposition divided into different parts. There is a global temperature field due to the large rectangular canister area, while a local field accounts for the remaining heat source problem. The global field is reduced to a single integral. The local field is also solved analytically using solutions for a finite line heat source and for an infinite grid of point sources. The local solution is reduced to three parts, each of which depends on two spatial coordinates only. The temperatures at the envelope of a canister are given by a single thermal resistance, which is given by an explicit formula. The results are illustrated by a few numerical examples dealing with the KBS-3 concept for storage of nuclear waste. 8 refs.
The ''INVERSE PROBLEM'' to the evaluation of magnetic fields
International Nuclear Information System (INIS)
Caspi, S.; Helm, M.; Laslett, L.J.
1996-01-01
In the design of superconducting magnet elements, such as may be required to guide and focus ions in a particle accelerator, one frequently premises some particular current distribution and then proceeds to compute the consequent magnetic field through use of the laws of Biot and Savart or of Ampere. When working in this manner one of course may need to revise frequently the postulated current distribution before arriving at a resulting magnetic field of acceptable field quality. It therefore is of interest to consider an alternative (inverse) procedure in which one specifies a desired character for the field required in the region interior to the winding and undertakes then to evaluate the current distribution on the specified winding surface that would provide this desired field. By evaluating the specified potential in the region interior to the winding along the interface, the authors have determined that a relaxation solution to the potential in the region outside the winding can be converged and used to calculate wire location. They have demonstrated this method by applying a slightly modified version of the program POISSON to a periodic alternating sinusoidal quadrupole field
Development of high temperature superconductors for magnetic field applications
International Nuclear Information System (INIS)
Larbalestier, D.C.
1991-01-01
The key requirement for magnetic field applications of high temperature superconductor (HTS) materials is to have conductors with high transport critical current density available for magnet builders. After 3 or 4 years of being without any such object, conductor makers have had recent success in producing simple conductor prototypes. These have permitted the construction of simple HTS magnets having self fields exceeding 1 tesla at 4K. Thus the scientific feasibility of making powerful HTS magnets has been demonstrated. Attention to the technological aspects of making HTS conductors for magnets with strong flux pinning and reduced superconducting granularity is now sensible and attractive. However, extrinsic defects such as filament sausaging, cracking, misaligned grains and other perturbations to long range current flow must be controlled at a low level if the benefit of intrinsic improvements to the critical current density is to be maintained in the conductor form. Due to the great complexity of HTS materials, there is sometimes confusion as to whether a given sample has an intrinsically or extrinsically limited critical current density. Systematic microstructure variation experiments and resistive transition analysis are shown to be particularly helpful in this phase of conductor development
Directory of Open Access Journals (Sweden)
A. V. Livshits
2014-01-01
Full Text Available The article is devoted to non-stationary temperature field blanks from aluminum alloys during heat treatment. It consists of the introduction and two smaller paragraphs. In the introduction the author concerns the influence of residual stresses arising in the manufacturing process of details, on the strength of the whole aircraft construction and, consequently, on their technical and economic parameters, such as weight, reliability, efficiency, and cost. He also notes that the residual stresses appeared during the production of parts change their location, size and direction under the influence of the elastic deformations that occur during the exploitation of aircraft. Redistributed residual stresses may have a chaotic distribution that may cause overlap of these stresses on the stresses caused by the impact of workload of constructions and destruction or damage of aircraft components.The first paragraph is devoted to the existing methods and techniques for determining the residual stresses. The presented methods and techniques are analyzed to show the advantages and disadvantages of each of them. The conclusion is drawn that the method to determine the residual stresses is necessary, its cost is less than those of existing ones, and an error does not exceed 10%.In the second section, the author divides the problem of determining the residual stresses into two parts, and describes the solution methods of the first one. The first problem is to define the temperature field of the work piece. The author uses a Fourier equation with the definition of initial and boundary conditions to describe a mathematical model of the heat cycle of work piece cooling. He draws special attention here to the fact that it is complicated to determine the heat transfer coefficient, which characterizes the process of cooling the work piece during hardening because of its dependence on a number of factors, such as changing temperature-dependent material properties of
Postharvest problems of tomato production in Ghana - Field studies ...
African Journals Online (AJOL)
The farmers carry out neither on-farm nor off-farm storage of the fresh tomato fruits. The major postharvest problems of the farmers are the need for permanent purchasing outlets and the stabilization of the unit price per box of tomato. This calls for a significant look at the distribution system for tomatoes. JOURNAL OF THE ...
Experimental Problem Solving: An Instructional Improvement Field Experiment.
Ross, John A.; Maynes, Florence J.
1983-01-01
An instructional program based on expert-novice differences in experimental problem-solving performance was taught to grade six students (N=265). Performance was assessed with multiple-choice and open-ended measures of specific transfer. Between-group comparisons using pretest scores as covariate showed treatment condition students consistently…
T-->0 mean-field population dynamics approach for the random 3-satisfiability problem.
Zhou, Haijun
2008-06-01
During the past decade, phase-transition phenomena in the random 3-satisfiability ( 3 -SAT) problem has been intensively studied by statistical physics methods. In this work, we study the random 3 -SAT problem by the mean-field first-step replica-symmetry-broken cavity theory at the limit of temperature T-->0 . The reweighting parameter y of the cavity theory is allowed to approach infinity together with the inverse temperature beta with fixed ratio r=ybeta . Focusing on the system's space of satisfiable configurations, we carry out extensive population dynamics simulations using the technique of importance sampling, and we obtain the entropy density s(r) and complexity Sigma(r) of zero-energy clusters at different r values. We demonstrate that the population dynamics may reach different fixed points with different types of initial conditions. By knowing the trends of s(r) and Sigma(r) with r , we can judge whether a certain type of initial condition is appropriate at a given r value. This work complements and confirms the results of several other very recent theoretical studies.
Rapid high temperature field test method for evaluation of geothermal calcite scale inhibitors
Energy Technology Data Exchange (ETDEWEB)
Asperger, R.G.
1982-08-01
A test method is described which allows the rapid field testing of calcite scale inhibitors in high- temperature geothermal brines. Five commercial formulations, chosen on the basis of laboratory screening tests, were tested in brines with low total dissolved solids at ca 500 F. Four were found to be effective; of these, 2 were found to be capable of removing recently deposited scale. One chemical was tested in the full-flow brine line for 6 wks. It was shown to stop a severe surface scaling problem at the well's control valve, thus proving the viability of the rapid test method. (12 refs.)
A Mixed Enthalpy-Temperature Finite Element Method For Generalized Phase-Change Problems
DEFF Research Database (Denmark)
krabbenhøft, Kristian; Damkilde, Lars
2003-01-01
In a large number of problems of engineering interest the transition of the material from one phase to another is of vital importance in describing the overall physical behaviour. Common applications include metal casting, freezing and thawing of foodstuffs and other biological materials, ground...... freezing and solar energy storage. The phase-change problem is characterized by an abrupt change in enthalpy per unit temperature in a narrow temperature range around the freezing point....
Mean Field Approach to the Giant Wormhole Problem
Gamba, A.; Kolokolov, I.; Martellini, M.
We introduce a gaussian probability density for the space-time distribution of worm-holes, thus taking effectively into account wormhole interaction. Using a mean-field approximation for the free energy, we show that giant wormholes are probabilistically suppressed in a homogenous isotropic “large” universe.
Directory of Open Access Journals (Sweden)
S. M. Zhuchkov
2007-01-01
Full Text Available The calculation methods of the temperature field of the breakdown, being rolled in lines of the modern high-speed wire mill, is developed on the basis of solving of problem of the contact exchange of hot metal with cold rollers.
OPTIMIZATION OF INHOMOGENEOUS THICK-WALLED SPHERICAL SHELL IN THE TEMPERATURE FIELD
Directory of Open Access Journals (Sweden)
Andreev Vladimir Igorevich
2012-12-01
Full Text Available The authors consider the central symmetric problem of the theory of elasticity of inhomogeneous bodies for thick-walled spheres exposed to the external pressure in a stationary temperature field. The essence of the inverse problem lies in the identification of such dependence of the elastic modulus on the radius whereby the stress state of the sphere is the same as the pre-set one. Maximal stresses in thick-walled shells exposed to internal or external pressures occur in the proximity to the internal contour. Thus, destruction in this area is initiated upon the achievement of the limit state, while the rest of the shell is underused. The essence of the problem solved in the paper is the following. The problems are solved using the simultaneous exposure to forces and temperature loads.The two theories of strength are considered at once: a maximum normal stress theory and a maximum shear stress theory. It is proven that according to the first theory maximum stresses in an inhomogeneous shell are 1.35 times smaller than those in the homogeneous shell. The stress reduction rate equals to 2.5, if the maximum shear stress theory is employed. Thus, the introduction of artificial inhomogeneity leads to the optimization of shells by reducing their thickness or increasing loads.
Energy Technology Data Exchange (ETDEWEB)
Gao, Zhiwen, E-mail: gaozhw@lzu.edu.cn; Zheng, Zhiye; Li, Xueyi
2015-12-15
Highlights: • We studied firstly nonhomogeneity fracture in HTS base on real fundamental solutions. • The SIF of nonhomogeneity HTS decrease with nonhomogeneity parameters increasing. • The greater the applied field, the higher the SIF value. • The greater critical current density of the nonhomogeneity HTS is, the smaller values of the SIF. - Abstract: To analyze the fracture problem of the nonhomogeneous high temperature superconductor (HTS) slab under electromagnetic force, we derive the real fundamental solutions based on eigenvalue and eigenvector analyses. The superconductor E-J constitutive law is characterized by the Bean model where the critical current density is independent of the flux density. Fracture analysis is performed by the methods of singular integral equations which are solved numerically by Lobatto–Chybeshev collocation method. Numerical results of the stress intensity factor (SIF) are obtained. Moreover, the crack opening displacement (COD) can be obtained by numerical integration dislocation density functions. The effects of the thickness ratio, HTS material nonhomogeneous parameters, applied magnetic field and critical current density on SIF and COD are discussed. The present work could theoretically provide quantitative predictions of the fracture mechanism of the nonhomogeneous HTS.
Directory of Open Access Journals (Sweden)
Gongfa Li
2015-06-01
Full Text Available With the development of metallurgical industry and the improvement of kiln technology, the processing properties of kiln equipment are being paid more attention. The rotary kiln is one of the most representatives of the furnace equipment; higher requirements of the rotary kiln are put forward in response to the call of the national energy saving and emission reduction. That is, the new designed equipment has the characteristics of the optimal energy consumption and stable performance. In order to analyze the energy consumption of the rotary kiln, it is necessary to study the heat transfer process of the rotary kilns. The three-dimensional numerical model of the rotary kiln is set up by using the finite element technology. After analyzing the data, it is found that different thicknesses of the kiln crust and different working conditions have certain influence on the rotary kiln’s temperature field and stress field. After analyzing the result of the simulation, the temperature of the rotary kiln’s outer wall has an approximate linear relationship with the thickness of the kiln crust. Changing the thickness of the kiln crust will not only alter the value of the maximum stress but also have influence on the position of maximum stress. The increase in the thickness of the kiln crust can reduce the extreme value of stress. When the wind speed of induce fan inside the kiln is larger, the temperature of each layer will be relatively high as well, and the temperature curve is softer, and the temperature variation is more stable. It has also been found that when the comprehensive coefficient of heat exchange outside the kiln surface is larger, the thermal stress created by the body of kiln is smaller. The phenomenon of excessive thermal stress can be improved by changing the outer surface ventilation conditions of the rotary kiln. In order to ensure that the high temperature of the kiln wall has no influence on working wheels, and make sure the
Electron temperature control by an external magnetic field in solenoidal inductive discharge
International Nuclear Information System (INIS)
Lee, Min-Hyong; Ku, Ju-Hwan; Hwang, Kwang-Tae; Chung, Chin-Wook
2009-01-01
Electron temperature control is performed by controlling the external magnetic field strength in a solenoidal inductive discharge. As the magnetic field strength increases, the electron temperature of the plasma bulk decreases. The temperature at the discharge center falls from 3.1 to 1.5 eV when a 52 G dc magnetic field is applied. This decrease in the temperature is accompanied by a decrease in the plasma density. The change in temperature by the magnetic field is caused by both the electron confinement and the restriction of electron transport by the magnetic field in solenoidal inductive discharge.
Numerical solution of electromagnetic field problems in two and three dimensions
International Nuclear Information System (INIS)
Trowbridge, C.W.
1981-01-01
Recent developments in algorithms for solving electromagnetic field problems carried out at Rutherford Appleton Laboratory (RAL) are reviewed. The interaction of electric and magnetic fields provides many examples of coupled problems which have been solved by the Finite Element method. This paper concentrates on static and low frequency problems using the differential operator approach. The status of computation for 2D fields is discussed. The use of scalar potentials for 3D static fields for economy is emphasised and the importance of selecting potential types carefully to minimise numerical cancellation errors is also discussed. Some formulations for the vector 3D field problem for eddy current fields are derived with analytic and experimental field measurement comparisons. Results using software packages built at RAL are presented to illustrate the methods. (author)
Investigation of field temperature in moulds of foamed plaster
Directory of Open Access Journals (Sweden)
M. Pawlak
2007-12-01
Full Text Available Plaster moulds used in precision foundry are characterized by a very low permeability which, in the case of classic plaster moulds, equals to about 0,01÷0,02 m2/(MPa·s. One of the most effective methods for increasing the permeability is a foaming treatment. Another characteristic feature of plaster is its very good insulating power which has influence on the process of solidification and cooling of a cast and also on a knock-out property. This insulating power is a function of thermophysical properties of plaster which, in turn, depend mainly on the mineralogical composition of the mould material, its bulk density as well as on the temperature of the pouring alloy. In the case of a foamed plaster mould an increase of the degree of foaming increases its porosity which causes a change in its thermophysical properties, thereby increasing susceptibility of the mass to overheating. The susceptibility of the plaster layer surrounding the cast to overheating is favorable because it makes it easier to knock-out of the cast by immersing the hot mould in cold water. Thermal and phase tensions that are created during this process cause fast destruction of plaster. This paper describes our investigations aimed at the determination of the dependence of the mould temperature field on the time of the cast stay in the mould, as recorded in a process of an unsteady heat flow. The determined data were planned to be used for estimation of the technological properties of the plaster mould. The tests were carried out using the plaster α-Supraduro and Alkanol XC (foaming agent. The test mould had a diameter of Ø 120 mm with centrally situated mould cavity of Ø 30 mm. Plaster moulds with a degree of foaming 20; 32,5 and 45% and comparatively from non-foaming plaster were tested and their temperatures were measured at the distance x=2; 9; 21; 25;27; 30 mm from the mould cavity within 25 min. Analysis of the results leads to the conclusion, that the highest
Seeing is believing -- SpyJack system investigates field problems
International Nuclear Information System (INIS)
O'Meara, D.
1998-01-01
The SpyJack Remote Monitoring System, a stand-alone, single-site remote well monitoring system that works off its own embedded controller is described. The supervisory control and data acquisition (SCADA) unit, developed by CORE Technologies Inc., has an integrated voice/alarm system, monitoring sensors installed at remote well sites continuously 24 hours a day with a digital camera, with 300 degrees of visual confirmation capability. It can also be used as a surveillance tool against terrorism as has been shown in the case of some recent debilitating attacks on remote wells in Alberta. SpyJack monitors flow rates and pressures, pumpjack stroke rates, sucker rod temperature, load cell and engine shut-off relay, as well as ambient temperature, tank levels, and motion detection. At the office, SpyJack Well Management Interface uses nine drop-down screens to take users through the remote monitoring and control of each site. The screens include production sensors, line sensors, dyno chart, environmental/safety sensors and sensor information and set up. Currently under development is the unsolicited dial-out capability. When implemented the system will send out information at pre-determined times, such as every four hours, or at specific times during the day. Compressing images to enable speedier downloading is also being planned
Applications of satellite data relay to problems of field seismology
Webster, W. J., Jr.; Miller, W. H.; Whitley, R.; Allenby, R. J.; Dennison, R. T.
1980-01-01
A seismic signal processor was developed and tested for use with the NOAA-GOES satellite data collection system. Performance tests on recorded, as well as real time, short period signals indicate that the event recognition technique used is nearly perfect in its rejection of cultural signals and that data can be acquired in many swarm situations with the use of solid state buffer memories. Detailed circuit diagrams are provided. The design of a complete field data collection platform is discussed and the employment of data collection platforms in seismic network is reviewed.
A Boundary Element Solution to the Problem of Interacting AC Fields in Parallel Conductors
Directory of Open Access Journals (Sweden)
Einar M. Rønquist
1984-04-01
Full Text Available The ac fields in electrically insulated conductors will interact through the surrounding electromagnetic fields. The pertinent field equations reduce to the Helmholtz equation inside each conductor (interior problem, and to the Laplace equation outside the conductors (exterior problem. These equations are transformed to integral equations, with the magnetic vector potential and its normal derivative on the boundaries as unknowns. The integral equations are then approximated by sets of algebraic equations. The interior problem involves only unknowns on the boundary of each conductor, while the exterior problem couples unknowns from several conductors. The interior and the exterior problem are coupled through the field continuity conditions. The full set of equations is solved by standard Gaussian elimination. We also show how the total current and the dissipated power within each conductor can be expressed as boundary integrals. Finally, computational results for a sample problem are compared with a finite difference solution.
Determining the field emitter temperature during laser irradiation in the pulsed laser atom probe
International Nuclear Information System (INIS)
Kellogg, G.L.
1981-01-01
Three methods are discussed for determining the field emitter temperature during laser irradiation in the recently developed Pulsed Laser Atom Probe. A procedure based on the reduction of the lattice evaporation field with increasing emitter temperature is found to be the most convenient and reliable method between 60 and 500 K. Calibration curves (plots of the evaporation field versus temperature) are presented for dc and pulsed field evaporation of W, Mo, and Rh. These results show directly the important influence of the evaporation rate on the temperature dependence of the evaporation field. The possibility of a temperature calibration based on the ionic charge state distribution of field evaporated lattice atoms is also discussed. The shift in the charge state distributions which occurs when the emitter temperature is increased and the applied field strength is decreased at a constant rate of evaporation is shown to be due to the changing field and not the changing temperature. Nevertheless, the emitter temperature can be deduced from the charge state distribution for a specified evaporation rate. Charge state distributions as a function of field strength and temperature are presented for the same three materials. Finally, a preliminary experiment is reported which shows that the emitter temperature can be determined from field ion microscope observations of single atom surface diffusion over low index crystal planes. This last calibration procedure is shown to be very useful at higher temperatures (>600 K) where the other two methods become unreliable
Energy Technology Data Exchange (ETDEWEB)
Gupta, Ramesh; Scanlan, Ronald; Ghosh, Arup K.; Weggel, Robert J.; Palmer, Robert; Anerella, Michael D.; Schmalzle, Jesse
2017-10-17
A dipole-magnet system and method for producing high-magnetic-fields, including an open-region located in a radially-central-region to allow particle-beam transport and other uses, low-temperature-superconducting-coils comprised of low-temperature-superconducting-wire located in radially-outward-regions to generate high magnetic-fields, high-temperature-superconducting-coils comprised of high-temperature-superconducting-tape located in radially-inward-regions to generate even higher magnetic-fields and to reduce erroneous fields, support-structures to support the coils against large Lorentz-forces, a liquid-helium-system to cool the coils, and electrical-contacts to allow electric-current into and out of the coils. The high-temperature-superconducting-tape may be comprised of bismuth-strontium-calcium-copper-oxide or rare-earth-metal, barium-copper-oxide (ReBCO) where the rare-earth-metal may be yttrium, samarium, neodymium, or gadolinium. Advantageously, alignment of the large-dimension of the rectangular-cross-section or curved-cross-section of the high-temperature-superconducting-tape with the high-magnetic-field minimizes unwanted erroneous magnetic fields. Alignment may be accomplished by proper positioning, tilting the high-temperature-superconducting-coils, forming the high-temperature-superconducting-coils into a curved-cross-section, placing nonconducting wedge-shaped-material between windings, placing nonconducting curved-and-wedge-shaped-material between windings, or by a combination of these techniques.
Energetic consequences of field body temperatures in the green iguana
Lichtenbelt, WDVM; Wesselingh, RA
We investigated body temperatures of free-ranging green iguanas (Iguana iguana) on Curacao (Netherlands Antilles), and how metabolic costs and benefits of food processing affect body temperatures. Body temperatures of free-living iguanas were measured by radio telemetry. We also used a model, with
Estimating relic magnetic fields from CMB temperature correlations
Giovannini, Massimo
2009-01-01
The temperature and polarization inhomogeneities of the Cosmic Microwave Background might bear the mark of pre-decoupling magnetism. The parameters of a putative magnetized background are hereby estimated from the observed temperature autocorrelation as well as from the measured temperature-polarization cross-correlation.
Symmetries, causality problems and neutrino fields in antipode universes
International Nuclear Information System (INIS)
Sasse, F.D.
1986-01-01
The S 3 xR and H 3 xR Lie groups are characterized, and using continuous deformations of S 3 and H 3 subgroups algebra, Lorentz space-time metrics with g E left invariance and g D right invariance are introduced. The topology of sections of these space-time is investigated and its relation with global causality problems is shown. In the search of g E and g D isometries, it is shown that in the class of metrics associated to H 3 xR topology, there is a particular case which accepts a G 7 group of isometries. It is shown that the g E and g D metrics characterize universes which vortices of cosmological fluid (when it is present), in relation to the inertial compass, are opposite. In the particular coordinate system, that is used, these metrics differs only by a coordinate inversion transformation. Neutrinos interacting with the geometry of these spaces times is considered. It is shown that the physical transformation which consists in to reverse the universe rotation and to reverse a determined component of neutrino momentum, leads the universe with g E (g D ) metric containing neutrinos, with determined helicity, to another one with g D (g E )metric containing neutrinos, with opposite helicity from the original. Thus, neutrinos can be used to distinguish physically these two universes, supposing that in a given universe neutrinos there is always a type of helicity. (M.C.K.) [pt
On the problems of the Litija ore field
Directory of Open Access Journals (Sweden)
Ivan Mlakar
1994-12-01
Full Text Available All available information on the now inaccessible Pb-Zb-Ba deposits Litija, Zavrstnik, Zagorica, Maljek, Hrastarija and Štriglovec was critically evaluated. Data were completed and numerous earlier unsolved questions were answered.In the studied area the existence of a Middle Triassic tectonic-erosional phase was proved, the Old Tertiary overthrust structure analyzed and the relative ages of various neotectonic fault systems established.Special attention was attributed to the Litija, or Sitarjevec, deposit. On the ground of data on position of thick shale intercalations within Carboniferous sandstone the geological structure of the deposit was reconstructed, proofs on the conforming or unconforming position of orebodies collected, and certain relati¬onships between the pre-ore and post-ore tectonics clarified. With geochemical investigations the presence of an extensive dispersion halo was proved, in which the anomalies produced by Pb, Hg and Ba are the best expressed.Also the position of other deposits in space and in stratigraphic column was defined. At the end also the author's views on genesis and age of mineralization are presented. Orebodies are hydrothermal. subvertical, epignetic and predominantly discordant, with poorly expressed vertical zoning.The work is a synthesis of understanding of geological structure and mineralization in the Litija ore field.
Zero field entanglement in dipolar coupling spin system at negative temperatures
Furman, Gregory B.; Meerovich, Victor M.; Sokolovsky, Vladimir L.
2013-01-01
A dipolar coupled spin system can achieve internal thermodynamic equilibrium states at negative absolute temperature. We study analytically and numerically the temperature dependence of the concurrence in a dipolar coupled spin-1/2 system in both non-zero and zero fields and show that, at negative temperatures, entangled states can exist even in zero magnetic field.
Some problems on rf breakdown in room temperature accelerator structure, a possible criterion
International Nuclear Information System (INIS)
Wang, J.W.
1986-04-01
The discussion is confined to high gradient, room-temperature accelerators which have clean well-finished cavity surfaces and good vacuum conditions. Breakdown-initiating mechanisms due to ''cold'' field electron emission occurring at isolated sites on broad-area cavity surfaces, where the field is enhanced, are described. The influences of an alternating field and transition time tunneling are taken into account. The thermal instability resulting in vacuum voltage breakdown is hypothesized to derive a new criterion for room-temperature accelerator structure. 18 refs., 5 figs
Yaparova, N.
2017-10-01
We consider the problem of heating a cylindrical body with an internal thermal source when the main characteristics of the material such as specific heat, thermal conductivity and material density depend on the temperature at each point of the body. We can control the surface temperature and the heat flow from the surface inside the cylinder, but it is impossible to measure the temperature on axis and the initial temperature in the entire body. This problem is associated with the temperature measurement challenge and appears in non-destructive testing, in thermal monitoring of heat treatment and technical diagnostics of operating equipment. The mathematical model of heating is represented as nonlinear parabolic PDE with the unknown initial condition. In this problem, both the Dirichlet and Neumann boundary conditions are given and it is required to calculate the temperature values at the internal points of the body. To solve this problem, we propose the numerical method based on using of finite-difference equations and a regularization technique. The computational scheme involves solving the problem at each spatial step. As a result, we obtain the temperature function at each internal point of the cylinder beginning from the surface down to the axis. The application of the regularization technique ensures the stability of the scheme and allows us to significantly simplify the computational procedure. We investigate the stability of the computational scheme and prove the dependence of the stability on the discretization steps and error level of the measurement results. To obtain the experimental temperature error estimates, computational experiments were carried out. The computational results are consistent with the theoretical error estimates and confirm the efficiency and reliability of the proposed computational scheme.
Ma, Hongjun; Liu, Huajun; Liu, Fang; Zhang, Huahui; Ci, Lu; Shi, Yi; Lei, Lei
2018-01-01
High-Temperature Superconductors (HTS) are potential materials for high-field magnets, low-loss transmission cables, and Superconducting Magnetic Energy Storage (SMES) due to their high upper critical magnetic field (Hc2) and critical temperature (Tc). The critical current (Ic) of HTS, which is one of the most important parameters for superconductor application, depends strongly on the magnetic fields and temperatures. A new Ic measurement system that can carry out accurate Ic measurement for HTS short samples with various temperatures (4.2-80 K), magnetic fields (0-14 T), and angles of the magnetic field (0°-90°) has been developed. The Ic measurement system mainly consists of a measurement holder, temperature-control system, background magnet, test cryostat, data acquisition system, and DC power supply. The accuracy of temperature control is better than ±0.1 K over the 20-80 K range and ±0.05 K when measured below 20 K. The maximum current is over 1000 A with a measurement uncertainty of 1%. The system had been successfully used for YBa2Cu3O7-x(YBCO) tapes Ic determination with different temperatures and magnetic fields.
Dust in fusion devices-a multi-faceted problem connecting high- and low-temperature plasma physics
International Nuclear Information System (INIS)
Winter, J
2004-01-01
Small particles with sizes between a few nanometers and a few 10 μm (dust) are formed in fusion devices by plasma-surface interaction processes. Though it is not a major problem today, dust is considered a problem that could arise in future long pulse fusion devices. This is primarily due to its radioactivity and due to its very high chemical reactivity. Dust formation is particularly pronounced when carbonaceous wall materials are used. Dust particles can be transported in the tokamak over significant distances. Radioactivity leads to electrical charging of dust and to its interaction with plasmas and electric fields. This may cause interference with the discharge but may also result in options for particle removal. This paper discusses some of the multi-faceted problems using information both from fusion research and from low-temperature dusty plasma work
Aspects of the SO(5) symmetry and the problem of high temperature superconductivity
Demler, Eugene A.
This dissertation reviews several aspects of the SO(5) theory, that unifies superconductivity and antiferromagnetism and that has recently been suggested in connection with the problem of high temperature superconductivity. Microscopic analysis of the pi operators (generators of the SO(5) symmetry) is given for the t-J and Hubbard models and it is argued that pseudo-Goldstone bosons that correspond to these operators produce resonant peaks observed in neutron scattering experiments on YBCO. Microscopic models with exact SO(5) symmetry are considered and the nature of the AF/SC transition in these systems is discussed. Analysis of a non-Abelian SU(2) holonomy of the SO (5) spinor states is presented, the SO(5) Berry's phase is shown to be related to the second Hopf map and described by a Yang monopole at the degeneracy point. These results are used to show that fermionic excitations in models with exact SO(5) symmetry may be described as four component Dirac fermions coupled to SU(2) gauge fields in 2 + 1 dimensions. Finally some experimental tests of the SO(5) model are suggested.
Analysis of the temperature field around salt diapirs
DEFF Research Database (Denmark)
Jensen, Peter Klint
1990-01-01
heat flux should be higher over 3D structures. On the other hand the areal extent of the temperature anomaly around the salt structures is less in the 3D case. Calculation examples indicate that low temperature geothermal energy exploitation of the formations around the top of a salt diapir can...
Analysis, approximation, and computation of a coupled solid/fluid temperature control problem
Gunzburger, Max D.; Lee, Hyung C.
1993-01-01
An optimization problem is formulated motivated by the desire to remove temperature peaks, i.e., 'hot spots', along the bounding surfaces of containers of fluid flows. The heat equation of the solid container is coupled to the energy equations for the fluid. Heat sources can be located in the solid body, the fluid, or both. Control is effected by adjustments to the temperature of the fluid at the inflow boundary. Both mathematical analyses and computational experiments are given.
International Nuclear Information System (INIS)
Ziegler, K.
1982-01-01
The examples given show the quality and use of manufacturers' data for a series of behaviour criteria for strain gages in the high temperature region. These results should not only be regarded critically. The manufacturer must appreciate that the very costly programme of investigations on the users' side represents a product development for large parts for the manufacturer of the strain gauges. It would therefore be desirable if these considerations were to initiate investigations on the manufacturer's part, in order to clear up the problematic are of the use of strain gages in the high temperature field, in order to provide the customer with more reliable and better strain gage characteristics for very expensive high temperature strain measurements. (orig.) [de
International Nuclear Information System (INIS)
Anzai, Toshio; Shibata, Keiichi
1992-01-01
The materials for high temperature facilities are usually determined by the heat resistant strength except special corrosive environment. High temperature corrosion has been considered in the case of using low quality fuel which is avoided recently. Even though fuel is clean, high temperature corrosion occurs due to the rise of design temperature and the intake of sea salt particles. There is also one more high temperature corrosion problem on process side that consumes heat energy. The research on high temperature corrosion is important for realizing new energy system such as molten carbonate type fuel cell, pulverized coal-firing supercritical power generation and high temperature gas-cooled nuclear reactor. In this report, the examples experienced actually in a chemical plant are examined, and the possibility of material technology against high temperature corrosion is reviewed. Corrosion phenomena in high temperature environment, the examples of corrosion in the high temperature facilities in a chemical plant and the material technology as the countermeasures for corrosion prevention are reported. (K.I.)
Applications of Markov random field models for inversion problems in geosciences
Kuwatani, T.; Nagata, K.; Okada, M.; Toriumi, M.
2012-12-01
Recently, a variety of spatial and temporal data sets can be obtained thanks to technological advances of measurement and observation in geosciences. It is very important to inverse spatial or temporal physical variables from these imaging data sets. The Markov random field (MRF) model is a stochastic model using Markov chains that is often applied for image restoration and pattern recognition in information science. In the MRF model, the spatial or temporal variations of physical properties are assumed to be relatively small compared to the observational noise and analytical uncertainty. By the Bayesian approach, the MRF model appropriately filters out high-frequency noise, and we can obtain accurate spatial distributions or time series of physical properties. Furthermore, it has the potential advantage of the incorporation of prior geophysical and geological information through the evaluation function. The purpose of this study is to develop the MRF model in order to apply it to various inversion problems in geosciences. Based on the Bayesian inference, we incorporated the nonlinear generation process of observational data sets into the MRF model. The Markov chain Monte Carlo (MCMC) algorithm was implemented to estimate hyperparameters and optimize target variables. Furthermore, it's important for inversion problems in geosciences to understand discontinuous behavior of physical variables, for example, detection of fault planes and lithospheric boundaries in the earth's interior. By introducing Potts spins as latent variables to the MRF model, we can simultaneously estimate the distributions of continuous and discontinuous variables. For examples of applications, we will introduce two inversion problems: one is a pressure-temperature inversion from compositional data of zoned minerals, and the other is an inversion of fluid distributions from observed seismic velocity structure. Based on these examples, we will discuss effectiveness and broad applicability of the
Wainwright, Carroll L.
2012-09-01
I present a numerical package (CosmoTransitions) for analyzing finite-temperature cosmological phase transitions driven by single or multiple scalar fields. The package analyzes the different vacua of a theory to determine their critical temperatures (where the vacuum energy levels are degenerate), their supercooling temperatures, and the bubble wall profiles which separate the phases and describe their tunneling dynamics. I introduce a new method of path deformation to find the profiles of both thin- and thick-walled bubbles. CosmoTransitions is freely available for public use.Program summaryProgram Title: CosmoTransitionsCatalogue identifier: AEML_v1_0Program summary URL: http://cpc.cs.qub.ac.uk/summaries/AEML_v1_0.htmlProgram obtainable from: CPC Program Library, Queen's University, Belfast, N. IrelandLicensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.htmlNo. of lines in distributed program, including test data, etc.: 8775No. of bytes in distributed program, including test data, etc.: 621096Distribution format: tar.gzProgramming language: Python.Computer: Developed on a 2009 MacBook Pro. No computer-specific optimization was performed.Operating system: Designed and tested on Mac OS X 10.6.8. Compatible with any OS with Python installed.RAM: Approximately 50 MB, mostly for loading plotting packages.Classification: 1.9, 11.1.External routines: SciPy, NumPy, matplotLibNature of problem: I describe a program to analyze early-Universe finite-temperature phase transitions with multiple scalar fields. The goal is to analyze the phase structure of an input theory, determine the amount of supercooling at each phase transition, and find the bubble-wall profiles of the nucleated bubbles that drive the transitions.Solution method: To find the bubble-wall profile, the program assumes that tunneling happens along a fixed path in field space. This reduces the equations of motion to one dimension, which can then be solved using the overshoot
The linearized Boltzmann equation: a concise and accurate solution of the temperature-jump problem
Siewert, C E
2003-01-01
Polynomial expansion procedures, along with an analytical discrete-ordinates method, are used to solve the temperature-jump problem based on a rigorous version of the linearized Boltzmann equation for rigid-sphere interactions. In particular, the temperature and density perturbations and the temperature-jump coefficient are obtained (essentially) analytically in terms of a modern version of the discrete-ordinates method. The developed algorithms are implemented for general values of the accommodation coefficient to yield numerical results that can be considered a new standard of reference.
Song, Li-qiang; Wang, Qi-ming
2016-10-01
The thermal problem is one of the important research contents of the design and operation about giant radio antenna. This kind of influence to the antenna has been concerned in the astronomy field. Due to the instantaneous temperature load and uncertainty, it is difficult to accurately analysis and effectively control about its effect. It has important significance to analyze the thermal problem of giant radio antenna to its design and operation. The research of solar cookers and temperature field on Five-hundred-meter Aperture Spherical radio Telescope (FAST) were preceded in detail. The tests of temperature distribute about 30 meters antenna in Mi-yun observatory station were performed. The research work including the parameters related to the sun, the flow algorithm of telescope site, mathematical model of solar cooker, analysis results of temperature field and corresponding control strategy, the temperature distribution test of 30 meters model. The results showed that: solar cookers could be weakened and controlled effectively of FAST. This work will provide a reference to design and operation of the FAST and same big antenna. It has certain theory significance, engineering significance and application value.
Energy Technology Data Exchange (ETDEWEB)
Ek-In, Surapat; Ruffolo, David [Department of Physics, Faculty of Science, Mahidol University, Bangkok (Thailand); Malakit, Kittipat [Department of Physics, Faculty of Science and Techonology, Thammasat University, Pathum Thani (Thailand); Shay, Michael A. [Department of Physics and Astronomy, University of Delaware, Newark, DE (United States); Cassak, Paul A., E-mail: kmalakit@gmail.com [Department of Physics and Astronomy, West Virginia University, Morgantown, WV (United States)
2017-08-20
We perform the first study of the properties of the Larmor electric field (LEF) in collisionless asymmetric magnetic reconnection in the presence of an out-of-plane (guide) magnetic field for different sets of representative upstream parameters at Earth’s dayside magnetopause with an ion temperature greater than the electron temperature (the ion-to-electron temperature ratio fixed at 2) using two-dimensional particle-in-cell simulations. We show that the LEF does persist in the presence of a guide field. We study how the LEF thickness and strength change as a function of guide field and the magnetospheric temperature and reconnecting magnetic field strength. We find that the thickness of the LEF structure decreases, while its magnitude increases when a guide field is added to the reconnecting magnetic field. The added guide field makes the Larmor radius smaller, so the scaling with the magnetospheric ion Larmor radius is similar to that reported for the case without a guide field. Note, however, that the physics causing the LEF is not well understood, so future work in other parameter regimes is needed to fully predict the LEF for arbitrary conditions. We also find that a previously reported upstream electron temperature anisotropy arises in the vicinity of the LEF region both with and without a guide field. We argue that the generation of the anisotropy is linked to the existence of the LEF. The LEF can be used in combination with the electron temperature anisotropy as a signature to effectively identify dayside reconnection sites in observations.
Analysis of the temperature field around salt diapirs
DEFF Research Database (Denmark)
Jensen, Peter Klint
1990-01-01
heat flux should be higher over 3D structures. On the other hand the areal extent of the temperature anomaly around the salt structures is less in the 3D case. Calculation examples indicate that low temperature geothermal energy exploitation of the formations around the top of a salt diapir can...... be favoured by a reduced drilling depth of 30% compared with the diapir-free case. It is further concluded thatsurface heat flow measurements in profiles across the diapir may be used in distinguishing between salt and shale diapirs....
Akinyemi, Olukayode D.; Mendes, Nathan
2007-03-01
Knowledge about the dynamics of soil moisture and heat, especially at the surface, provides important insights into the physical processes governing their interactions with the atmosphere, thereby improving the understanding of patterns of climate dynamics. In this context the paper presents the numerical and field experimental results of temperature and moisture evolution, which were measured on the surface of a sandy soil at Abeokuta, south-western Nigeria. An unconditionally stable numerical method was used, which linearizes the vapour concentration driving-potential term giving the moisture exchanged at the boundaries in terms of temperature and moisture content, and simultaneously solves the governing equations for each time step. The model avoids stability problems and limitations to low moisture contents and the usual assumption of constant thermal conductivity. Instantaneous temperature measurements were made at the surface using a thermocouple, while the gravimetric method was employed to determine the volumetric water contents at some specific hours of the experimental period. The observed experimental data compared fairly well with the predicted values, with both having correlation coefficients greater than 0.9 and consequently following a common diurnal trend. The sensitivity of the model was very high to the choice of simulation parameters, especially grid size refinement and time step. While the model underestimated the soil moisture content at 6 a.m. and 10 p.m., the measured temperatures were however overestimated. When compared to moisture content, average errors for temperature were low resulting in a minimal absolute difference in amplitude of 0.81 °C.
Modern field courses and problem-based learning; a comparison between industry and academia
Hesthammer, Jonny; Fossen, Haakon
2006-01-01
Problem-based learning (PBL) can provide an attractive learning situation in relation to field courses. Combined with information technology, the learning effect can be enhanced compared with more traditional courses that use lecture-based learning and no advanced technological aids. However, the use of information technology in field courses requires the consideration of fundamental pedagogic principles. In May 2003, two separate geological field courses were run at locations ...
Temperature dependence of critical magnetic fields for the Abelian Higgs model
International Nuclear Information System (INIS)
Magpantay, J.; Mukku, C.; Sayed, W.A.
1981-05-01
One loop temperature and external electromagnetic field effects on the Abelian Higgs model are studied using the momentum space heat kernel. We obtain expressions for the critical fields necessary for symmetry restoration at some finite temperature and display the critical B vs. T curve separating the broken and restored phases in the B-T plane. (author)
International Nuclear Information System (INIS)
Russenschuck, S.; Tortschanoff, T.; Ijspeert, A.; Perin, R.; Siegel, N.
1994-01-01
After measuring the magnetic field of a model or prototype superconducting magnet for the Large Hadron Collider (LHC) an inverse field problem is formulated in order to explain the origin of the content of unwanted multipole terms. The inverse problem solving is done by means of a least-squares minimization using the Levenberg-Marquard algorithm. Although the uniqueness of the results remains uncertain, useful insights into the causes of measured field imperfections can be deduced. A model dipole magnet, a main quadrupole prototype and a combined dipole-sextupole corrector magnet are given as examples
Non-uniform Solar Temperature Field on Large Aperture, Fully ...
Indian Academy of Sciences (India)
In this study, a 110-m fully steerable radio telescope was used as an analysis platform and the integral parametric finite element model of the antenna structure was built in the ANSYS thermal analysis module. The boundary conditions of periodic air temperature, solar radiation, long-wave radiation shadows of the ...
Non-uniform Solar Temperature Field on Large Aperture, Fully ...
Indian Academy of Sciences (India)
C. The solar cooker effect distribution in the time-history and rotation operation ranges represents a valuable reference for the design of the secondary reflector. In order to avoid loss of effectiveness or burn-out at extremely high temperatures and to ensure optimal structure performance, it is necessary to adopt materials that.
Directory of Open Access Journals (Sweden)
V. N. Vasilenko
2014-01-01
Full Text Available Summary. Improvement of the theory and methods of calculation of extrusion equipment is a problem whose solution provides the optimal design of its components in order to obtain the desired product quality. As the quality of the extrudate , extrusion machine performance is largely determined by the mode of pre matrix zone worm , article considers the mathematical model of the extrusion process for this particular zone of the extruder. Using co-extrusion will greatly expand the range of multicomponent products , balanced chemical composition and with programmable features. In their manufacture the inner layer is formed from fatvitamin fillings and an outer shell - of the extrusion obtained cereal-based . To ensure the stability of the co-extrusion process forming head channels must be designed so that the pressure generated therein is sufficient to distribute the material and the residence time therein of the extrudate is minimized. Solution of this problem requires an accurate description of the flow of materials in the form of channels . This article contains a mathematical description of the process of co-extrusion feed mixtures in the channel matrix of the extruder. The analytical determination of the distribution of temperature fields in fat-vitamin stuffing. A method for selecting the diameter of the dispensing nozzle to the desired value of the ratio of volumetric flow rates of the extrudate and fillings is proposed. The analysis of the flow of heat-labile non-Newtonian fluids in channels extruder with allowance for dissipative phenomena and nonisothermal is conducted. Analytical determination of the distribution of temperature fields in fat-vitamine filling extrudates was conducted for the sites from the pump outlet to the extruder housing ,in the pre matrix zone and co-extrusion head shape . The resulting mathematical model can be easily adapted to other areas of the extruder.
Field evaporation of the compound emitters at the various temperatures
International Nuclear Information System (INIS)
Golubev, O.L.
2010-01-01
Field evaporation process of the compounds emitters, which consist the elements with the various values of the ionization potentials I n has complicated nature. According to classical theory of a field evaporation of metals, the atoms with various I n must be evaporated at various evaporation fields F ev and the atoms with large I n must be accumulated on an emitter surface. But according to experiments a field evaporation of the compound emitters leads to an evaporation of the elements at the same value F ev , the atoms are evaporated as atomic or cluster ions and an accumulation of the atoms with large I n is not observed. The evaporation mechanism for the atomic ions may be explained as follows, an evaporation of the easy ionized elements leads to decrease of a binding energy of the hard ionized elements and to decrease their values of F ev . The explanation may be problematical for the more complicated mechanism of the cluster field evaporation. (authors)
Measuring system for magnetic field and temperature with digital signal processing
Directory of Open Access Journals (Sweden)
Druzhinin A. A.
2013-10-01
Full Text Available The measuring system for the magnetic field and temperature using silicon whiskers p-type conductivity as a primary device has been developed. The developed system allows the measurement of the magnetic field and temperature in the temperature range 4,2—77 K, as well as to measure the temperature under the influence of magnetic fields in the range of 100—300 K. It is shown that this system is suitable for the conversion of small signals using a programmable gain amplifier and analog-to-digital converter with high resolution.
Suwono, Hadi; Wibowo, Agung
2018-01-01
Biology learning emphasizes problem-based learning as a learning strategy to develop students ability in identifying and solving problems in the surrounding environment. Problem identification skills are closely correlated with questioning skills. By holding this skill, students tend to deliver a procedural question instead of the descriptive one. Problem-based learning through field investigation is an instruction model which directly exposes the students to problems or phenomena that occur in the environment, and then the students design the field investigation activities to solve these problems. The purpose of this research was to describe the improvement of undergraduate biology students on questioning skills, biological literacy, and academic achievement through problem-based learning through field investigation (PBFI) compared with the lecture-based instruction (LBI). This research was a time series quasi-experimental design. The research was conducted on August - December 2015 and involved 26 undergraduate biology students at the State University of Malang on the Freshwater Ecology course. The data were collected during the learning with LBI and PBFI, in which questioning skills, biological literacy, and academic achievement were collected 3 times in each learning model. The data showed that the procedural correlative and causal types of questions are produced by the students to guide them in conducting investigations and problem-solving in PBFI. The biological literacy and academic achievement of the students at PBFI are significantly higher than those at LBI. The results show that PBFI increases the questioning skill, biological literacy, and the academic achievement of undergraduate biology students.
Electric field and temperature effects in irradiated MOSFETs
Energy Technology Data Exchange (ETDEWEB)
Silveira, M. A. G., E-mail: marcilei@fei.edu.br; Santos, R. B. B.; Leite, F. G.; Araújo, N. E.; Cirne, K. H.; Melo, M. A. A.; Rallo, A. [Centro Universitário da FEI, São Bernardo do Campo, S.P. (Brazil); Aguiar, Vitor A. P.; Aguirre, F.; Macchione, E. L. A.; Added, N.; Medina, N. H. [Instituto de Física da USP, São Paulo, S.P. (Brazil)
2016-07-07
Electronic devices exposed to ionizing radiation exhibit degradation on their electrical characteristics, which may compromise the functionality of the device. Understanding the physical phenomena responsible for radiation damage, which may be specific to a particular technology, it is of extreme importance to develop methods for testing and recovering the devices. The aim of this work is to check the influence of thermal annealing processes and electric field applied during irradiation of Metal Oxide Semiconductor Field Effect Transistors (MOSFET) in total ionizing dose experiments analyzing the changes in the electrical parameters in these devices.
Schwinger α-PARAMETRIC Representation of Finite Temperature Field Theories:. Renormalization
Benhamou, M.; Kassou-Ou-Ali, A.
We present the extension of the zero temperature Schwinger α-representation to the finite temperature scalar field theories. We give, in a compact form, the α-integrand of Feynman amplitudes of these theories. Using this representation, we analyze short-range divergences, and recover in a simple way the known result that the counterterms are temperature-independent.
High temperature study of flexible silicon-on-insulator fin field-effect transistors
Diab, Amer El Hajj
2014-09-29
We report high temperature electrical transport characteristics of a flexible version of the semiconductor industry\\'s most advanced architecture: fin field-effect transistor on silicon-on-insulator with sub-20 nm fins and high-κ/metal gate stacks. Characterization from room to high temperature (150 °C) was completed to determine temperature dependence of drain current (Ids), gate leakage current (Igs), transconductance (gm), and extracted low-field mobility (μ0). Mobility degradation with temperature is mainly caused by phonon scattering. The other device characteristics show insignificant difference at high temperature which proves the suitability of inorganic flexible electronics with advanced device architecture.
Bullock, S. Ray; Myers, R. M.
1994-01-01
Applied-field magnetoplasmadynamic (MPD) thruster performance is below levels required for primary propulsion missions. While MPD thruster performance has been found to increase with the magnitude of the applied-field strength, there is currently little understanding of the impact of applied-field shape on thruster performance. The results of a study in which a single applied-field thruster was operated using three solenoidal magnets with diameters of 12.7, 15.2, and 30.4-cm are presented. Thruster voltage and anode power deposition were measured for each applied field shape over a range of field strengths. Plume electron number density and temperature distributions were measured using a Langmuir probe in an effort to determine the effect of field shape on plume confinement by the diverging magnetic-field for each of the three magnetic field shapes. Results show that the dependence of the measured thruster characteristics on field shape were non-monotonic and that the field shape had a significant effect on the plume density and temperature profiles.
Coaxial monitoring of temperature field in selective pulsed laser melting
Liu, Che; Chen, Zhongyun; Cao, Hongzhong; Zhou, Jianhong
2017-10-01
Selective Laser Melting is a rapid manufacturing technology which produces complex parts layer by layer. The presence of thermal stress and thermal strain in the forming process often leads to defects in the formed parts. In order to detect fabricate errors and avoid failure which caused by thermal gradient in time. An infrared thermal imager and a high speed CCD camera were applied to build a coaxial optical system for real-time monitoring the temperature distribution and changing trend of laser affected zone in SLM forming process. Molten tracks were fabricated by SLM under different laser parameters such as frequency, pulse width. And the relationship between the laser parameters and the temperature distribution were all obtained and analyzed.
Field Test of Boiler Primary Loop Temperature Controller
Energy Technology Data Exchange (ETDEWEB)
Glanville, P. [Partnership for Advanced Residential Retrofit, Des Plaines, IL (United States); Rowley, P. [Partnership for Advanced Residential Retrofit, Des Plaines, IL (United States); Schroeder, D. [Partnership for Advanced Residential Retrofit, Des Plaines, IL (United States); Brand, L. [Partnership for Advanced Residential Retrofit, Des Plaines, IL (United States)
2014-09-01
Beyond these initial system efficiency upgrades are an emerging class of Advanced Load Monitoring (ALM) aftermarket controllers that dynamically respond to the boiler load, with claims of 10% to 30% of fuel savings over a heating season. For hydronic boilers specifically, these devices perform load monitoring, with continuous measurement of supply and, in some cases, return water temperatures. Energy savings from these ALM controllers are derived from dynamic management of the boiler differential, where a microprocessor with memory of past boiler cycles prevents the boiler from firing for a period of time, to limit cycling losses and inefficient operation during perceived low load conditions. These differ from OTR controllers, which vary boiler setpoint temperatures with ambient conditions while maintaining a fixed differential.
Numerical Analysis of the Temperature Field in Luminaires
Directory of Open Access Journals (Sweden)
J. Murín
2004-01-01
Full Text Available This paper contains a calculation of the thermal field caused by electro-heat in lighting devices. After specifying the heat sources, a thermal analysis is make using the finite element method and the equivalent thermal scheme method. The calculated results have been verified experimentally.
Directory of Open Access Journals (Sweden)
Sergey V. Fedosov
2017-09-01
Full Text Available Applications of foam glass is currently quite wide. This material is applied directly to construction and other human activities. Recent years the attention of scientists aimed at modeling the thermal processes in the production of foamed glass. Appear works in which the developed mathematical model allows to predict the distribution of temperature fields in the foam glass material at various stages of heat treatment of the material. The emergence of these models reveals a number of promising directions in the improvement of technology of producing foamed glass. Within the phenomenological formulation of the problem it is necessary to consider three-dimensional temperature field in the charge of foam-glass and inside the metal mold for foaming. It is necessary to consider the nonstationarity of the process and dynamics of change in macrovisiontm values. It is also worth noting that in the conditions of heat treatment of charge materials occurs difficult the heat transfer. The distribution of temperature fields in the foam glass material is from near-surface regions of the charge to the center. The first objective of the study is to find and describe the distribution of temperature fields in the volume of the foam glass of the charge to reflect changes in microphysically parameters in foam glass batch due to the gradual formation of porosity of the material of the charge from the periphery to the center. The second task is to find conditions for the uniform formation of the pore volume of the material. The paper presents a boundaryvalue problem of heat transfer in foam glass material for the metal mold on the x coordinate. This illustration of temperature field distribution inside the metal mold for foaming.
Random-field Ising model: Insight from zero-temperature simulations
Directory of Open Access Journals (Sweden)
P.E. Theodorakis
2014-12-01
Full Text Available We enlighten some critical aspects of the three-dimensional (d=3 random-field Ising model (RFIM from simulations performed at zero temperature. We consider two different, in terms of the field distribution, versions of model, namely a Gaussian RFIM and an equal-weight trimodal RFIM. By implementing a computational approach that maps the ground-state of the system to the maximum-flow optimization problem of a network, we employ the most up-to-date version of the push-relabel algorithm and simulate large ensembles of disorder realizations of both models for a broad range of random-field values and systems sizes V=LxLxL, where L denotes linear lattice size and Lmax=156. Using as finite-size measures the sample-to-sample fluctuations of various quantities of physical and technical origin, and the primitive operations of the push-relabel algorithm, we propose, for both types of distributions, estimates of the critical field hmax and the critical exponent ν of the correlation length, the latter clearly suggesting that both models share the same universality class. Additional simulations of the Gaussian RFIM at the best-known value of the critical field provide the magnetic exponent ratio β/ν with high accuracy and clear out the controversial issue of the critical exponent α of the specific heat. Finally, we discuss the infinite-limit size extrapolation of energy- and order-parameter-based noise to signal ratios related to the self-averaging properties of the model, as well as the critical slowing down aspects of the algorithm.
A few categories of electromagnetic field problems treated through Fuzzy Logic
Lolea, M. S.; Dzitac, S.
2018-01-01
The paper deals with the problems of fuzzy logic applied in the field of electromagnetism. In the first part, there are presented some theoretical aspects regarding the characteristics and the application of the fuzzy logic in the general case. Are presented then, some categories of electromagnetic field problems treated by fuzzy logic. The accent is on the effects of exposure to the electromagnetic field on the human body. For this approach is dedicated a paragraph at the end of the paper. There is an application on how to treat by fuzzy logic the effects of electric field exposure. For this purpose, the fuzzy toolbox existing in the Matlab software and the results of some electric field strength measurements into a power substation are used. The results of the study and its conclusions are analyzed and exposed at the end of the paper.
Some problems on materials tests in high temperature hydrogen base gas mixture
International Nuclear Information System (INIS)
Shikama, Tatsuo; Tanabe, Tatsuhiko; Fujitsuka, Masakazu; Yoshida, Heitaro; Watanabe, Ryoji
1980-01-01
Some problems have been examined on materials tests (creep rupture tests and corrosion tests) in high temperature mixture gas of hydrogen (80%H 2 + 15%CO + 5%CO 2 ) simulating the reducing gas for direct steel making. H 2 , CO, CO 2 and CH 4 in the reducing gas interact with each other at elevated temperature and produce water vapor (H 2 O) and carbon (soot). Carbon deposited on the walls of retorts and the water condensed at pipings of the lower temperature gas outlet causes blocking of gas flow. The gas reactions have been found to be catalyzed by the retort walls, and appropriate selection of the materials for retorts has been found to mitigate the problems caused by water condensation and carbon deposition. Quartz has been recognized to be one of the most promising materials for minimizing the gas reactions. And ceramic coating, namely, BN (born nitride) on the heat resistant superalloy, MO-RE II, has reduced the amounts of water vapor and deposited carbon (sooting) produced by gas reactions and has kept dew points of outlet gas below room temperature. The well known emf (thermo-electromotive force) deterioration of Alumel-Chromel thermocouples in the reducing gases at elevated temperatures has been also found to be prevented by the ceramic (BN) coating. (author)
The Temperature - Magnetic Field Relation in Observed and Simulated Sunspots
Czech Academy of Sciences Publication Activity Database
Sobotka, Michal; Rezaei, R.
2017-01-01
Roč. 292, č. 12 (2017), 188/1-188/12 ISSN 0038-0938 R&D Projects: GA ČR(CZ) GA14-04338S; GA MŠk(CZ) 7E13003 EU Projects: European Commission(XE) 312495 - SOLARNET Institutional support: RVO:67985815 Keywords : sunspots * magnetic fields * comparison Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics OBOR OECD: Astronomy (including astrophysics,space science) Impact factor: 2.682, year: 2016
International Nuclear Information System (INIS)
Gavrilov, S.P.; Gitman, D.M.; Fradkin, E.S.
1987-01-01
A generating functional for expectation values is found for QED at a finite temperature with an external field which destroys the stability of the vacuum. The equations for connected Green functions and the effective action for the mean field are written out. Their representation is obtained in the form of an integral over the proper time for the Green function taking into account temperature effects in a constant uniform field. By means of this representation the polarization operator for the mean field in an external constant uniform field has been calculated
International Nuclear Information System (INIS)
Gavrilov, S.P.; Gitman, D.M.; Fradkin, E.S.
1987-01-01
A functional generating expectation values is obtained for QED at a finite temperature in presence of an external field violating the vacuum stability. Equations for connected Green's functions and the effective action for the mean field are derived. The Green function is obtained as an integral with respect of the proper time; the representation takes into account temperature effects in a constant homogeneous field. The polarization operator for the mean field in an external constant homogeneous field is calculated by means of the integral representation
Field Test of Boiler Primary Loop Temperature Controller
Energy Technology Data Exchange (ETDEWEB)
Glanville, P.; Rowley, P.; Schroeder, D.; Brand, L.
2014-09-01
Beyond these initial system efficiency upgrades are an emerging class of Advanced Load Monitoring (ALM) aftermarket controllers that dynamically respond to the boiler load, with claims of 10% to 30% of fuel savings over a heating season. For hydronic boilers specifically, these devices perform load monitoring, with continuous measurement of supply and in some cases return water temperatures. Energy savings from these ALM controllers are derived from dynamic management of the boiler differential, where a microprocessor with memory of past boiler cycles prevents the boiler from firing for a period of time, to limit cycling losses and inefficient operation during perceived low load conditions. These differ from OTR controllers, which vary boiler setpoint temperatures with ambient conditions while maintaining a fixed differential. PARR installed and monitored the performance of one type of ALM controller, the M2G from Greffen Systems, at multifamily sites in the city of Chicago and its suburb Cary, IL, both with existing OTR control. Results show that energy savings depend on the degree to which boilers are over-sized for their load, represented by cycling rates. Also savings vary over the heating season with cycling rates, with greater savings observed in shoulder months. Over the monitoring period, over-sized boilers at one site showed reductions in cycling and energy consumption in line with prior laboratory studies, while less over-sized boilers at another site showed muted savings.
Generic problems with Li2O breeders and tritium control in high-temperature fusion reactors
International Nuclear Information System (INIS)
Hickman, R.G.
1982-01-01
Within the past year, major reactor design studies have been performed using Li 2 O as a breeder material. These are the INTOR and STARFIRE/DEMO projects. We in our studies on fusion/synfuels are embarking on another, but our blanket will operate at significantly higher temperatures than these two. Some of the problems inherent in using this material are aggravated and some are diminished by operating at higher temperatures. For the conditions of the above two design studies many of the problems were mentioned in the respective references. This report reviews the available data, the educated guesses about unavailable data, and the design options that have been and are being chosen. The review of this information is a needed part for our proposed use of Li 2 O as a breeder in a fusion/synfuel reactor blanket. Further details will be available in various appropriate sections of our FY82 project report
Some tests of flat plate photovoltaic module cell temperatures in simulated field conditions
Griffith, J. S.; Rathod, M. S.; Paslaski, J.
1981-01-01
The nominal operating cell temperature (NOCT) of solar photovoltaic (PV) modules is an important characteristic. Typically, the power output of a PV module decreases 0.5% per deg C rise in cell temperature. Several tests were run with artificial sun and wind to study the parametric dependencies of cell temperature on wind speed and direction and ambient temperature. It was found that the cell temperature is extremely sensitive to wind speed, moderately so to wind direction and rather insensitive to ambient temperature. Several suggestions are made to obtain data more typical of field conditions.
Modeling and Numerical Simulation of the Grinding Temperature Field with Nanoparticle Jet of MQL
Directory of Open Access Journals (Sweden)
C. H. Li
2013-01-01
Full Text Available In this research, the heat transfer model of surface grinding temperature field with nanoparticle jet flow of MQL as well as the proportionality coefficient model of energy input workpiece was established, respectively. The numerical simulation of surface grinding temperature field of three workpiece materials was conducted. The results present that, in the workpiece, the surface temperature was significantly higher than the subsurface temperature, presenting relatively large temperature gradient along the direction of workpiece thickness. The impact of the grinding depth on grinding temperature was significant. With the increase of the cut depth, peak values of the grinding temperature rocketed. Distribution rules of the temperature field of 2Cr13 in four cooling and lubrication approaches were the same. Based on the excellent heat transfer property of nanofluids, the output heat through the grinding medium acquired an increasingly high proportion, leading to the drop of the temperature in the grinding zone. For the same cooling and lubrication conditions, grinding temperature presented insignificant changes along the direction of grinding width. Yet, under different cooling conditions, the temperature variation was significant. MQL grinding conditions with additive nanoparticles demonstrated great impact on the weakening of temperature effect on the grinding zone.
arXiv Spin models in complex magnetic fields: a hard sign problem
de Forcrand, Philippe
2018-01-01
Coupling spin models to complex external fields can give rise to interesting phenomena like zeroes of the partition function (Lee-Yang zeroes, edge singularities) or oscillating propagators. Unfortunately, it usually also leads to a severe sign problem that can be overcome only in special cases; if the partition function has zeroes, the sign problem is even representation-independent at these points. In this study, we couple the N-state Potts model in different ways to a complex external magnetic field and discuss the above mentioned phenomena and their relations based on analytic calculations (1D) and results obtained using a modified cluster algorithm (general D) that in many cases either cures or at least drastically reduces the sign-problem induced by the complex external field.
Renormalizability of the nuclear many-body problem with the Skyrme interaction beyond mean field
Yang, C. J.; Grasso, M.; Moghrabi, K.; van Kolck, U.
2017-05-01
Phenomenological effective interactions like Skyrme forces are currently used in mean-field calculations in nuclear physics. Mean-field models have strong analogies with the first order of the perturbative many-body problem and the currently used effective interactions are adjusted at the mean-field level. In this work, we analyze the renormalizability of the nuclear many-body problem in the case where the effective Skyrme interaction is employed in its standard form and the perturbative problem is solved up to second order. We focus on symmetric nuclear matter and its equation of state, which can be calculated analytically at this order. It is shown that only by applying specific density dependence and constraints to the interaction parameters can renormalizability be guaranteed in principle. This indicates that the standard Skyrme interaction does not in general lead to a renormalizable theory. To achieve renormalizability, other terms should be added to the interaction and employed perturbatively only at first order.
Zhang, Lan; Seagren, Eric A; Davis, Allen P; Karns, Jeffrey S
2012-06-01
Microbial activities are significantly influenced by temperature. This study investigated the effects of temperature on the capture and destruction of bacteria from urban stormwater runoff in bioretention media using 2-year field evaluations coupled with controlled laboratory column studies. Field data from two bioretention cells show that the concentration of indicator bacteria (fecal coliforms and Escherichia coli) was reduced during most storm events, and that the probability of meeting specific water quality criteria in the discharge was increased. Indicator bacteria concentration in the input flow typically increased with higher daily temperature. Although bacterial removal efficiency was independent of temperature in the field and laboratory, column tests showed that bacterial decay coefficients in conventional bioretention media (CBM) increase exponentially with elevated temperature. Increases in levels of protozoa and heterotrophic bacteria associated with increasing temperature appear to contribute to faster die-off of trapped E. coli in CBM via predation and competition.
2d Model Field Theories at Finite Temperature and Density
Schoen, Verena; Thies, Michael
2000-01-01
In certain 1+1 dimensional field theoretic toy models, one can go all the way from microscopic quarks via the hadron spectrum to the properties of hot and dense baryonic matter in an essentially analytic way. This "miracle" is illustrated through case studies of two popular large N models, the Gross-Neveu and the 't Hooft model - caricatures of the Nambu-Jona-Lasinio model and real QCD, respectively. The main emphasis will be on aspects related to spontaneous symmetry breaking (discrete or co...
Energy Technology Data Exchange (ETDEWEB)
Hollinger, Greg L. [Idaho National Lab. (INL), Idaho Falls, ID (United States)
2014-06-01
Background: The current rules in the nuclear section of the ASME Boiler and Pressure Vessel (B&PV) Code , Section III, Subsection NH for the evaluation of strain limits and creep-fatigue damage using simplified methods based on elastic analysis have been deemed inappropriate for Alloy 617 at temperatures above 1200F (650C)1. To address this issue, proposed code rules have been developed which are based on the use of elastic-perfectly plastic (E-PP) analysis methods and which are expected to be applicable to very high temperatures. The proposed rules for strain limits and creep-fatigue evaluation were initially documented in the technical literature 2, 3, and have been recently revised to incorporate comments and simplify their application. The revised code cases have been developed. Task Objectives: The goal of the Sample Problem task is to exercise these code cases through example problems to demonstrate their feasibility and, also, to identify potential corrections and improvements should problems be encountered. This will provide input to the development of technical background documents for consideration by the applicable B&PV committees considering these code cases for approval. This task has been performed by Hollinger and Pease of Becht Engineering Co., Inc., Nuclear Services Division and a report detailing the results of the E-PP analyses conducted on example problems per the procedures of the E-PP strain limits and creep-fatigue draft code cases is enclosed as Enclosure 1. Conclusions: The feasibility of the application of the E-PP code cases has been demonstrated through example problems that consist of realistic geometry (a nozzle attached to a semi-hemispheric shell with a circumferential weld) and load (pressure; pipe reaction load applied at the end of the nozzle, including axial and shear forces, bending and torsional moments; through-wall transient temperature gradient) and design and operating conditions (Levels A, B and C).
Research on early-warning index of the spatial temperature field in concrete dams.
Yang, Guang; Gu, Chongshi; Bao, Tengfei; Cui, Zhenming; Kan, Kan
2016-01-01
Warning indicators of the dam body's temperature are required for the real-time monitoring of the service conditions of concrete dams to ensure safety and normal operations. Warnings theories are traditionally targeted at a single point which have limitations, and the scientific warning theories on global behavior of the temperature field are non-existent. In this paper, first, in 3D space, the behavior of temperature field has regional dissimilarity. Through the Ward spatial clustering method, the temperature field was divided into regions. Second, the degree of order and degree of disorder of the temperature monitoring points were defined by the probability method. Third, the weight values of monitoring points of each regions were explored via projection pursuit. Forth, a temperature entropy expression that can describe degree of order of the spatial temperature field in concrete dams was established. Fifth, the early-warning index of temperature entropy was set up according to the calculated sequential value of temperature entropy. Finally, project cases verified the feasibility of the proposed theories. The early-warning index of temperature entropy is conducive to the improvement of early-warning ability and safety management levels during the operation of high concrete dams.
Huang, Ying; Wu, Siyu; Li, Ruiqi; Yang, Qinghua; Zhang, Yugang; Liu, Caixia
2013-10-01
This paper presents a novel temperature sensor array by dispensing conductive composites on a flexible printed circuit board which is able to acquire the ambient temperature. The flexible temperature sensor array was fabricated by using carbon fiber-filled silicon rubber based composites on a flexible polyimide circuit board, which can both ensure their high flexibility. It found that CF with 12 wt% could be served as the best conductive filler for higher temperature sensitivity and better stability comparing with some other proportion for dynamic range from 30&° to 90°. The preparation of the temperature sensitive material has also been described in detail. Connecting the flexible sensor array with a data acquisition card and a personal computer (PC), some heat sources with different shapes were loaded on the sensor array; the detected results were shown in the interface by LabVIEW software. The measured temperature contours are in good agreement with the shapes and amplitudes of different heat sources. Furthermore, in consideration of the heat dissipation in the air, the relationship between the resistance and the distance of heat sources with sensor array was also detected to verify the accuracy of the sensor array, which is also a preparation for our future work. Experimental results demonstrate the effectiveness and accuracy of the developed flexible sensor array, and it can be used as humanoid artificial skin for sensation system of robots.
International Nuclear Information System (INIS)
Zhukov, A.V.; Ivanov, E.Ph.; Kuznetsov, I.A.; Sorokin, A.P.; Ushakov, P.A.
1994-01-01
Failure conditions due to dangerous increasing in power or flow rate drop are the most hazardous in terms of the rise of thermal stresses. Initial rise in temperature may run to 100 C and more. Sodium temperature at the subassembly inlet is varied according to definite time constant which is equal to fuel pin time constant (about 2 sec), that is below the time constant for massive part of subassembly head (4-10 sec). Thus, variations in sodium temperature are, for subassembly head, almost momentary and bring about maximal thermal stresses. Experiments on transient temperature behavior in subassembly head under thermal impact conditions have been performed on the model. Magnitude of temperature has been measured in two cross sections by chromel-alumel thermocouples bond in the middle of the wall, at its outer surface and in the coolant flow for distance of 3 mm from the wall. To measure temperature difference between middle of the wall and its surface fast differential thermocouples chromel-sodium-potassium have been used
High Temperature Corrosion Problem of Boiler Components in presence of Sulfur and Alkali based Fuels
Ghosh, Debashis; Mitra, Swapan Kumar
2011-04-01
Material degradation and ageing is of particular concern for fossil fuel fired power plant components. New techniques/approaches have been explored in recent years for Residual Life assessment of aged components and material degradation due to different damage mechanism like creep, fatigue, corrosion and erosion etc. Apart from the creep, the high temperature corrosion problem in a fossil fuel fired boiler is a matter of great concern if the fuel contains sulfur, chlorine sodium, potassium and vanadium etc. This paper discusses the material degradation due to high temperature corrosion in different critical components of boiler like water wall, superheater and reheater tubes and also remedial measures to avoid the premature failure. This paper also high lights the Residual Life Assessment (RLA) methodology of the components based on high temperature fireside corrosion. of different critical components of boiler.
Research on the characteristics of temperature field of asphalt pavement in seasonal frozen region
International Nuclear Information System (INIS)
Qiao, Jiangang; Liu, Weizheng
2014-01-01
The characteristics of climate in seasonal frozen area are low temperature and a large range of temperature variation between day and night in winter. These characteristics often lead to problems of asphalt pavement, especially transverse cracks. To reduce the problems of asphalt pavement, it is necessary to examine the distribution of the temperature range of asphalt pavement. A three-dimensional finite element model was used, taking the SMA asphalt pavement as an example with solid70 and plane55 unit features of ANSYS software. It can obtain the relationship between temperature gradient and time and the relationship between temperature gradient and depth. In addition, a function relation model of stress and time was also established. It can provide a theoretical basis for the prevention and treatment of problems of asphalt pavement in seasonal frozen area. Moreover, it has an important significance for improving asphalt pavement design
Numerical simulation of temperature field in K9 glass irradiated by ultraviolet pulse laser
Wang, Xi; Fang, Xiaodong
2015-10-01
The optical component of photoelectric system was easy to be damaged by irradiation of high power pulse laser, so the effect of high power pulse laser irradiation on K9 glass was researched. A thermodynamic model of K9 glass irradiated by ultraviolet pulse laser was established using the finite element software ANSYS. The article analyzed some key problems in simulation process of ultraviolet pulse laser damage of K9 glass based on ANSYS from the finite element models foundation, meshing, loading of pulse laser, setting initial conditions and boundary conditions and setting the thermal physical parameters of material. The finite element method (FEM) model was established and a numerical analysis was performed to calculate temperature field in K9 glass irradiated by ultraviolet pulse laser. The simulation results showed that the temperature of irradiation area exceeded the melting point of K9 glass, while the incident laser energy was low. The thermal damage dominated in the damage mechanism of K9 glass, the melting phenomenon should be much more distinct.
Directory of Open Access Journals (Sweden)
Nikolić Radovan H.
2014-01-01
Full Text Available This paper is the result of research and operation modeling of the new systems for cooling of cutting tools based on thermoelectric module. A copper inlay with thermoelectric module on the back side was added to a standard turning tool for metal processing. For modeling and simulating the operation of thermoelectric module, finite element method was used as a method for successful solving the problems of inhomogeneous transient temperature field on the cutting tip of lathe knives. Developed mathematical model is implemented in the software package PAK-T through which numerical results are obtained. Experimental research was done in different conditions of thermoelectric module operation. Cooling of the hot module side was done by a heat exchanger based on fluid using automatic temperature regulator. After the calculation is done, numerical results are in good agreement with experimental. It can be concluded that developed mathematical model can be used successfully for modeling of cooling of cutting tools. [Projekat Ministarstva nauke Republike Srbije, br. TR32036
The quantum N-body problem in the mean-field and semiclassical regime.
Golse, François
2018-04-28
The present work discusses the mean-field limit for the quantum N -body problem in the semiclassical regime. More precisely, we establish a convergence rate for the mean-field limit which is uniform as the ratio of Planck constant to the action of the typical single particle tends to zero. This convergence rate is formulated in terms of a quantum analogue of the quadratic Monge-Kantorovich or Wasserstein distance. This paper is an account of some recent collaboration with C. Mouhot, T. Paul and M. Pulvirenti.This article is part of the themed issue 'Hilbert's sixth problem'. © 2018 The Author(s).
Analysis of non-stationary temperature field in reactor fuel element
International Nuclear Information System (INIS)
Vehauc, A.; Spasojevic, D.
1970-01-01
Starting from time and space distribution of power generation determined previously stationary analysis of fuel element, a method was developed for non-stationary conditions. It is based on development of temperature field by eigenfunctions and application of Laplace transformation for calculating transfer function of power variation in time and space distribution of temperature field in the fuel element. Dynamic behaviour of fuel element in non-stationary regime and frequency analysis of the transfer function was done. Transfer function of temperature field is given in the form of amplitude and frequency characteristics
Potential high temperature corrosion problems due to co-firing of biomass and fossil fuels
DEFF Research Database (Denmark)
Montgomery, Melanie; Vilhelmsen, T.; Jensen, S.A.
2007-01-01
Over the past years, considerable high temperature corrosion problems have been encountered when firing biomass in power plants due to the high content of potassium chloride in the deposits. Therefore to combat chloride corrosion problems co-firing of biomass with a fossil fuel has been undertaken...... significant corrosion attack was due to sulphidation attack at the grain boundaries of 18-8 steel after 3 years exposure. The corrosion mechanisms and corrosion rates are compared with biomass firing and coal firing. Potential corrosion problems due to co-firing biomass and fossil fuels are discussed....... appear such as sulphidation and hot corrosion due to sulphate deposits. At Studstrup power plant Unit 4, based on trials with exposure times of 3000 hours using 0-20% straw co-firing with coal, the plant now runs with a fuel of 10% straw + coal. After three years exposure in this environment...
Potential high temperature corrosion problems due to co-firing of biomass and fossil fuels
DEFF Research Database (Denmark)
Montgomery, Melanie; Vilhelmsen, T.; Jensen, S.A.
2008-01-01
Over the past few years, considerable high temperature corrosion problems have been encountered when firing biomass in power plants due to the high content of potassium chloride in the deposits. Therefore, to combat chloride corrosion problems cofiring of biomass with a fossil fuel has been....... However, the most significant corrosion attack was sulphidation attack at the grain boundaries of 18-8 steel after 3 years exposure. The corrosion mechanisms and corrosion rates are compared with biomass firing and coal firing. Potential corrosion problems due to co-firing biomass and fossil fuels...... corrosion mechanisms appear such as sulphidation and hot corrosion due to sulphate deposits. At Studstrup power plant Unit 4, based on trials with exposure times of 3000 h using 0–20% straw co-firing with coal, the plant now runs with a fuel mix of 10% strawþcoal. Based on results from a 3 years exposure...
Samkharadze, N; Kumar, A; Manfra, M J; Pfeiffer, L N; West, K W; Csáthy, G A
2011-05-01
We fabricated a He-3 immersion cell for transport measurements of semiconductor nanostructures at ultra low temperatures and in strong magnetic fields. We have a new scheme of field-independent thermometry based on quartz tuning fork Helium-3 viscometry which monitors the local temperature of the sample's environment in real time. The operation and measurement circuitry of the quartz viscometer is described in detail. We provide evidence that the temperature of two-dimensional electron gas confined to a GaAs quantum well follows the temperature of the quartz viscometer down to 4 mK.
Directory of Open Access Journals (Sweden)
Roald TAYMANOV
2009-03-01
Full Text Available The paper examines some problems that concern terminology in the field of measuring instruments which include sensors and elements of artificial intelligence. At present, a "common language" in this area does not exist. It is shown that application of an evolutionary method helps to systematize the concepts and creates a basis facilitating understanding of the relations between terms. Proposals on terms and their definitions in the field considered are given.
International Nuclear Information System (INIS)
Schultze, Volkmar; IJsselsteijn, Rob; May, Torsten; Meyer, Hans-Georg
2003-01-01
We developed a gradiometer system based on a single-layer high-temperature superconductor dc superconducting quantum interference device (SQUID), which can be freely moved within the Earth's magnetic field during measurement. The problem of circumferential shielding currents in the parallel gradiometer pick-up loop is solved by the use of an appropriately designed magnetometer SQUID integrated on the gradiometer chip. The magnetometer's feedback coil of the flux-locked loop is laid out as a small Helmholtz coil pair, thus keeping the homogeneous magnetic field constant for both the magnetometer and the gradiometer. Therefore, the balance of the directly coupled gradiometer SQUID is enhanced from 100 up to 3800. The noise limited magnetic field gradient resolution of 45 pT m -1 Hz -1/2 is preserved down to frequencies of several Hz even after strong motion in the Earth's magnetic field
Cloud microphysical characteristics versus temperature for three Canadian field projects
Directory of Open Access Journals (Sweden)
I. Gultepe
2002-11-01
Full Text Available The purpose of this study is to better understand how cloud microphysical characteristics such as liquid water content (LWC and droplet number concentration (Nd change with temperature (T. The in situ observations were collected during three research projects including: the Radiation, Aerosol, and Cloud Experiment (RACE which took place over the Bay of Fundy and Central Ontario during August 1995, the First International Regional Arctic Cloud Experiment (FIRE.ACE which took place in the Arctic Ocean during April 1998, and the Alliance Icing Research Study (AIRS which took place in the Ontario region during the winter of 1999–2000. The RACE, FIRE.ACE, and AIRS projects represent summer mid-latitude clouds, Arctic clouds, and mid-latitude winter clouds, respectively. A LWC threshold of 0.005 g m-3 was used for this study. Similar to other studies, LWC was observed to decrease with decreasing T. The LWC-T relationship was similar for all projects, although the range of T conditions for each project was substantially different, and the variability of LWC within each project was considerable. Nd also decreased with decreasing T, and a parameterization for Nd versus T is suggested that may be useful for modeling studies.Key words. Atmospheric composition and structure (cloud physics and chemistry – Meteorology and atmospheric dynamics (climatology; general circulation
Analytical Methods for Temperature Field and Temperature Stress of Column Pier under Solar Radiation
Directory of Open Access Journals (Sweden)
Yin-hui Wang
2015-01-01
Full Text Available Based on the previous research work, a new idea is proposed for analyzing the impact of solar radiation on the substructure of bridges. Investigation is conducted in the thermodynamic phenomena and temperature stress of a dual-column pier. Research is led to the thermal conductivity of concrete structure and the values of the environmental parameters under solar radiation. An analytical code is written for the thermal analysis of the dual-column pier using the parametric modeling function of FE software, by means of which the temperature distribution of the bridge structure is computed under solar radiation. Using the thermal analytical results, the temperature stress of the dual-column pier is further calculated. The results tell that the temperature gradient distribution curve inside the concrete of the pier fits favorably the curve defined in the design specification and coincides quite well with real situation, which verifies the new idea proposed in this paper. Under the solar radiation which is a time-variable nonlinear temperature load to the bridge, the maximum principal stress is found at the corner of the pier with the sign of negative, which is believed to threaten the safety of the substructure of bridge and is necessary to arouse emphasis.
Directory of Open Access Journals (Sweden)
Hui Wang
2013-01-01
Full Text Available The boundary-type hybrid finite element formulation coupling the Kirchhoff transformation is proposed for the two-dimensional nonlinear heat conduction problems in solids with or without circular holes, and the thermal conductivity of material is assumed to be in terms of temperature change. The Kirchhoff transformation is firstly used to convert the nonlinear partial differential governing equation into a linear one by introducing the Kirchhoff variable, and then the new linear system is solved by the present hybrid finite element model, in which the proper fundamental solutions associated with some field points are used to approximate the element interior fields and the conventional shape functions are employed to approximate the element frame fields. The weak integral functional is developed to link these two fields and establish the stiffness equation with sparse and symmetric coefficient matrix. Finally, the algorithm is verified on several examples involving various expressions of thermal conductivity and existence of circular hole, and numerical results show good accuracy and stability.
Silicon junctionless field effect transistors as room temperature terahertz detectors
Marczewski, J.; Knap, W.; Tomaszewski, D.; Zaborowski, M.; Zagrajek, P.
2015-09-01
Terahertz (THz) radiation detection by junctionless metal-oxide-semiconductor field-effect transistors (JL MOSFETs) was studied and compared with THz detection using conventional MOSFETs. It has been shown that in contrast to the behavior of standard transistors, the junctionless devices have a significant responsivity also in the open channel (low resistance) state. The responsivity for a photolithographically defined JL FET was 70 V/W and the noise equivalent power 460 pW/√Hz. Working in the open channel state may be advantageous for THz wireless and imaging applications because of its low thermal noise and possible high operating speed or large bandwidth. It has been proven that the junctionless MOSFETs can also operate in a zero gate bias mode, which enables simplification of the THz array circuitry. Existing models of THz detection by MOSFETs were considered and it has been demonstrated that the process of detection by these junctionless devices cannot be explained within the framework of the commonly accepted models and therefore requires a new theoretical approach.
Huang, Ya-Yi; Huang, Ching-Yi; Lin, Shiu-Mei; Wu, Shu-Chuan
2006-08-01
Increased morbidity and mortality has been associated with neonates admitted with body temperatures below 36 degrees C. We employed an experimental design in a randomized control trial to compare the effectiveness of using early kangaroo care (KC) for extrauterine temperature adaptation against that of using radiant warmers. Trial subjects included 78 consecutive cesarean newborn infants with hypothermia problems. The KC group received skin-to-skin contact with their mothers in the post-operative room, while infants in the control group received routine care under radiant warmers. The mean temperature of the KC group was slightly higher than that of the control group (36.29 degrees C vs. 36.22 degrees C, p = .044). After four hours, 97.43% of KC group infants had reached normal body temperatures, compared with 82.05% in the radiant warmer group. Results demonstrate the positive effects of KC for extrauterine temperature adaptation in hypothermia infants. In the course of evidence-based practice, KC could be incorporated into the standard care regimen in order to improve hypothermia care.
International Nuclear Information System (INIS)
Liu, Sha; Liu, Shi; Tong, Guowei
2017-01-01
In industrial areas, temperature distribution information provides a powerful data support for improving system efficiency, reducing pollutant emission, ensuring safety operation, etc. As a noninvasive measurement technology, acoustic tomography (AT) has been widely used to measure temperature distribution where the efficiency of the reconstruction algorithm is crucial for the reliability of the measurement results. Different from traditional reconstruction techniques, in this paper a two-phase reconstruction method is proposed to ameliorate the reconstruction accuracy (RA). In the first phase, the measurement domain is discretized by a coarse square grid to reduce the number of unknown variables to mitigate the ill-posed nature of the AT inverse problem. By taking into consideration the inaccuracy of the measured time-of-flight data, a new cost function is constructed to improve the robustness of the estimation, and a grey wolf optimizer is used to solve the proposed cost function to obtain the temperature distribution on the coarse grid. In the second phase, the Adaboost.RT based BP neural network algorithm is developed for predicting the temperature distribution on the refined grid in accordance with the temperature distribution data estimated in the first phase. Numerical simulations and experiment measurement results validate the superiority of the proposed reconstruction algorithm in improving the robustness and RA. (paper)
International Nuclear Information System (INIS)
Kuroyanagi, Toshiyuki
1983-07-01
Based on an idea that surface conditions should be a reflection of interior temperature and interior heat flux variation as inverse as interior conditions has been determined completely by the surface temperature and/on surface heat flux as boundary conditions, a method is presented for determining the surface temperature and the surface heat flux of a solid when the temperature and heat flux at an interior point are a prescribed function of time. The method is developed by the integration of Duhumels' integral which has unknown temperature or unknown heat flux in its integrand. Specific forms of surface condition determination are developed for a sample inverse problem: slab. Ducussing the effect of a degree of avairable informations at an interior point due to damped system and the effect of variation of surface conditions on those formulations, it is shown that those formulations are capable of representing the unknown surface conditions except for small time interval followed by discontinuous change of surface conditions. The small un-resolved time interval is demonstrated by a numerical example. An evaluation method of heat flux at an interior point, which is requested by those formulations, is discussed. (author)
Liu, Sha; Liu, Shi; Tong, Guowei
2017-11-01
In industrial areas, temperature distribution information provides a powerful data support for improving system efficiency, reducing pollutant emission, ensuring safety operation, etc. As a noninvasive measurement technology, acoustic tomography (AT) has been widely used to measure temperature distribution where the efficiency of the reconstruction algorithm is crucial for the reliability of the measurement results. Different from traditional reconstruction techniques, in this paper a two-phase reconstruction method is proposed to ameliorate the reconstruction accuracy (RA). In the first phase, the measurement domain is discretized by a coarse square grid to reduce the number of unknown variables to mitigate the ill-posed nature of the AT inverse problem. By taking into consideration the inaccuracy of the measured time-of-flight data, a new cost function is constructed to improve the robustness of the estimation, and a grey wolf optimizer is used to solve the proposed cost function to obtain the temperature distribution on the coarse grid. In the second phase, the Adaboost.RT based BP neural network algorithm is developed for predicting the temperature distribution on the refined grid in accordance with the temperature distribution data estimated in the first phase. Numerical simulations and experiment measurement results validate the superiority of the proposed reconstruction algorithm in improving the robustness and RA.
Ultrafast Electric Field Pulse Control of Giant Temperature Change in Ferroelectrics
Qi, Y.; Liu, S.; Lindenberg, A. M.; Rappe, A. M.
2018-01-01
There is a surge of interest in developing environmentally friendly solid-state-based cooling technology. Here, we point out that a fast cooling rate (≈1011 K /s ) can be achieved by driving solid crystals to a high-temperature phase with a properly designed electric field pulse. Specifically, we predict that an ultrafast electric field pulse can cause a giant temperature decrease up to 32 K in PbTiO3 occurring on few picosecond time scales. We explain the underlying physics of this giant electric field pulse-induced temperature change with the concept of internal energy redistribution: the electric field does work on a ferroelectric crystal and redistributes its internal energy, and the way the kinetic energy is redistributed determines the temperature change and strongly depends on the electric field temporal profile. This concept is supported by our all-atom molecular dynamics simulations of PbTiO3 and BaTiO3 . Moreover, this internal energy redistribution concept can also be applied to understand electrocaloric effect. We further propose new strategies for inducing giant cooling effect with ultrafast electric field pulse. This Letter offers a general framework to understand electric-field-induced temperature change and highlights the opportunities of electric field engineering for controlled design of fast and efficient cooling technology.
Directory of Open Access Journals (Sweden)
Avilov Alex
2017-01-01
Full Text Available The purpose of this paper is to estimate the dynamic characteristics of the heating process of thin plates during polishing with a free abrasive. A mathematical model of the temperature field distribution in space and time according to the plate thickness is based on Lagrange equation of the second kind in the thermodynamics of irreversible processes (variation principle Bio. The research results of thermo elasticity of thin plates (membranes will allow to correct the modes of polishing with a free abrasive to receive the exact reflecting surfaces of satellites reflector, to increase temperature stability and the ability of radio signal reflection, satellite precision guidance. Calculations of temperature fields in thin plates of different thicknesses (membranes is held in the Excel, a graphical characteristics of temperature fields in thin plates (membranes show non-linearity of temperature distribution according to the thickness of thin plates (membranes.
Measurement of temperature fields in specimens of quartz ceramic during surface ablation
Frolov, G. A.; Pasichnyi, V. V.; Suzdal'Tsev, E. I.; Tsyganenko, V. S.
1989-08-01
The authors propose a method of mounting thermocouples and have obtained temperature fields within specimens of pure and doped quartz ceramic. The linearity of the dependenceΔ * = fleft( {sqrt tau } right) for deep isotherms has been proved experimentally.
Temperature-Dependent Coercive Field Measured by a Quantum Dot Strain Gauge.
Chen, Yan; Zhang, Yang; Keil, Robert; Zopf, Michael; Ding, Fei; Schmidt, Oliver G
2017-12-13
Coercive fields of piezoelectric materials can be strongly influenced by environmental temperature. We investigate this influence using a heterostructure consisting of a single crystal piezoelectric film and a quantum dots containing membrane. Applying electric field leads to a physical deformation of the piezoelectric film, thereby inducing strain in the quantum dots and thus modifying their optical properties. The wavelength of the quantum dot emission shows butterfly-like loops, from which the coercive fields are directly derived. The results suggest that coercive fields at cryogenic temperatures are strongly increased, yielding values several tens of times larger than those at room temperature. We adapt a theoretical model to fit the measured data with very high agreement. Our work provides an efficient framework for predicting the properties of ferroelectric materials and advocating their practical applications, especially at low temperatures.
Directory of Open Access Journals (Sweden)
Druzhinin A. A.
2017-12-01
Full Text Available Sensitive element of multifunctional sensor for measuring temperature, strain and magnetic field induction has been developed based on the studies of electrical conductivity and magnetoresistance of silicon and germanium microcrystals in the temperature range 4.2—70 K, strain ±1.5*10–3 rel.un. and magnetic fields of 0—14 T. The feature of the sensitive element is the using of the p- and n-type conductivity germanium microcrystals as mechanical and magnetic field sensors, respectively, and the p-type silicon microcrystal — as temperature sensor. That allows providing the compensation of temperature influence on piezoresistance and on sensitivity to the magnetic field.
Effect of temperature field on solidification structure of pure Al under pulse magneto-oscillation
Directory of Open Access Journals (Sweden)
Li Bo
2011-05-01
Full Text Available This article discusses the effect of temperature field on the Pulse Magneto-Oscillation (PMO induced solidification refinement of pure aluminium to provide more information for the industrial application of the PMO solidification technology. The temperature field is altered mainly by applied variable cooling conditions and pulse parameters. Experimental results show that the refinement effect in the case of full sand mould applied is weakened with the decreasing of cooling rate, however, in the alternative case, the sand mould whose sand bottom was replaced by a graphite block is favorable to the survival of equiaxed nucleus. The refinement mechanism is discussed in terms of the relationship between temperature field and the formation process of solidified structure. The formation or survival of nucleus depends on both temperature field and Joule heat produced by PMO, both low pulse frequency and high pulse current were experimentally confirmed to be effective; and PMO was demonstrated high potential in industrial application.
Bolemon, Jay S.; Etzold, David J.
1974-01-01
Discusses the use of a small computer to solve self-consistent field problems of one-dimensional systems of two or more interacting particles in an elementary quantum mechanics course. Indicates that the calculation can serve as a useful introduction to the iterative technique. (CC)
A Two-Mode Mean-Field Optimal Switching Problem for the Full Balance Sheet
Directory of Open Access Journals (Sweden)
Boualem Djehiche
2014-01-01
a two-mode optimal switching problem of mean-field type, which can be described by a system of Snell envelopes where the obstacles are interconnected and nonlinear. The main result of the paper is a proof of a continuous minimal solution to the system of Snell envelopes, as well as the full characterization of the optimal switching strategy.
Kinetic approach to the initial value problem in quantum field theory
International Nuclear Information System (INIS)
Lin Chi Yong; Toledo Piza, A.F.R. de.
1989-06-01
Time-dependente projection techniques developed to derive kinetic equations in the context of the quantum many-body problem are applied to φ 4 field theory. The approach is illustrated by working out the 0+1 dimensional case explicitly, including numerical solutions of the kinetic equations. Extension to higher dimensions is briefly discussed. (author) [pt
On the inverse problem of the calculus of variations in field theory
International Nuclear Information System (INIS)
Henneaux, M.
1984-01-01
The inverse problem of the calculus of variations is investigated in the case of field theory. Uniqueness of the action principle is demonstrated for the vector Laplace equation in a non-decomposable Riemannian space, as well as for the harmonic map equation. (author)
Rocket to Creativity: A Field Experience in Problem-Based and Project-Based Learning
Dole, Sharon F.; Bloom, Lisa A.; Doss, Kristy Kowalske
2016-01-01
This article reports the impact of a field experience in problem-based (PBL) and project-based learning (PjBL) on in-service teachers' conceptions of experiential learning. Participants had been enrolled in a hybrid class that included an online component in which they learned about PBL and PjBL, and an experiential component in which they…
Effect of temperature on Acoustic Evaluation of standing trees and logs: Part 2: Field Investigation
Shan Gao; Xiping Wang; Lihai Wang; R. Bruce Allison
2013-01-01
The objectives of this study were to investigate the effect of seasonal temperature changes on acoustic velocity measured on standing trees and green logs and to develop models for compensating temperature differences because acoustic measurements are performed in different climates and seasons. Field testing was conducted on 20 red pine (Pinus resinosa...
On the possibility of multiplicity of temperature fields in a microwave ...
African Journals Online (AJOL)
We investigate a steady temperature dependent perfusion during a cancer therapy. We show how the choice of perfusion could lead to more than one temperature fields which could lead to an undesired result. Journal of the Nigerian Association of Mathematical Physics Vol. 10 2006: pp. 499-502.
Effect of temperature on composition of the methanotrophic community in rice field and forest soil
Mohanty, S.R.; Bodelier, P.L.E.; Conrad, R.
2007-01-01
Temperature change affects methane consumption in soil. However, there is no information on possible temperature control of methanotrophic bacterial populations. Therefore, we studied CH4 consumption and populations of methanotrophs in an upland forest soil and a rice field soil incubated at
Correlation Properties of the Backscattered Field in a Nonstationary Statistical Problem
Gulin, O. É.; Yaroshchuk, I. O.
2001-11-01
The statistical problem of the scattering of wideband pulses by a random layered medium at normal incidence is considered in the framework of the wave approach in the space—time domain. Simulated correlation functions and power spectral densities of the backscattered field are presented. They extend the earlier findings concerning the backscattered field formation and also confirm and refine a number of conclusions drawn earlier from the behavior of the field’s statistical moments. The simulation technique is free from approximations commonly used in the statistical analysis of the propagation problems and can be used to study the statistical properties of the scattered field in a wide range of time intervals, as well as to find the limits of applicability of the approximate methods.
Influence of Non-uniform Temperature Field on Spectra of Fibre Bragg Grating
International Nuclear Information System (INIS)
Yan, Zhou; Xing-Fang, He; Xiao-Yong, Fang; Jie, Yuan; Li-Qun, Yin; Mao-Sheng, Cao
2009-01-01
We simulate the spectrum characteristics of fibre Bragg grating (FBG) with non-uniform temperature using the transmission matrix method, and the results are analysed. It is found that firstly the modulated coefficient of average refractive index is a very important parameter that influences the spectrum characteristic of the fibre Bragg grating, and secondly the spectrum curves are different in different temperature fields at the same parameter. Hence, we can determine the metrical temperature by analysing the spectrum of fibre Bragg grating
Energy Technology Data Exchange (ETDEWEB)
Ju, Benxiang, E-mail: jubenxiang@qq.com [National Instrument Functional Materials Engineering Technology Research Center, Chongqing 400707 (China); Tang, Rui; Zhang, Dengyou; Yang, Bailian [National Instrument Functional Materials Engineering Technology Research Center, Chongqing 400707 (China); Yu, Miao; Liao, Changrong [College of Optoelectronic Engineering, Chongqing University, Chongqing 400044 (China)
2015-01-15
Both anisotropic and isotropic magnetorheological elastomer (MRE) samples were fabricated by using as-prepared polyurethane (PU) matrix and carbonyl iron particles. Temperature-dependent dynamic mechanical properties of MRE were investigated and analyzed. Due to the unique structural features of as-prepared matrix, temperature has a greater impact on the properties of as-prepared MRE, especially isotropic MRE. With increasing of temperature and magnetic field, MR effect of isotropic MRE can reach up to as high as 4176.5% at temperature of 80 °C, and the mechanism of the temperature-dependent in presence of magnetic field was discussed. These results indicated that MRE is a kind of temperature-dependent material, and can be cycled between MRE and MR plastomer (MRP) by varying temperature. - Highlights: • Both anisotropic and isotropic MRE were fabricated by using as-prepared matrix. • Temperature-dependent properties of MRE under magnetic field were investigated. • As-prepared MRE can transform MRE to MRP by adjusting temperature.
Wang, S.L.; Son, P.C. van; Wees, B.J. van; Klapwijk, T.M.
1992-01-01
The conductance of ballistic point contacts in high-mobility Si-inversion layers has been studied at several temperatures between 75 and 600 mK both without and in a magnetic field (up to 12T). When the width of constriction is varied in zero magnetic field, step-like features at multiples of 4e2/h
Integrated passive and wireless sensor for magnetic fields, temperature and humidity
Li, Bodong
2013-11-01
This paper presents a surface acoustic wave-based passive and wireless sensor that can measure magnetic field, temperature and humidity. A thin film giant magnetoimpedance sensor, a thermally sensitive LiNbO3 substrate and a humidity sensitive hydrogel are integrated together with a surface acoustic wave transducer to realize the multifunctional sensor. The device is characterized using a network analyzer under sequentially changing humidity, temperature and magnetic field conditions. The first hand results show the sensor response to all three sensing parameters with small temperature interference on the magnetic signals. © 2013 IEEE.
A numerical simulation of soil temperature and moisture variations for a bare field
Schieldge, J. P.; Kahle, A. B.; Alley, R. E.
1982-01-01
The diurnal variations of soil temperature and moisture content were simulated for a bare agricultural field in the San Joaquin Valley in California. The simulation pertained to the first 72 hours of drying, from saturation, of a sandy, clay loam soil. The results were compared with measurements of soil temperature and moisture content made at the field. Calculated and measured values of soil temperature trends agreed in general, but model results of moisture trends did not replicate observed diurnal effects evident at depths 4 centimeters or more below the surface.
Installation for microwave investigations of high-temperature superconductivity in magnetic field
Akhvlediani, I G; Mamniashvili, G I; Chigvinadze, D G
2002-01-01
Paper describes advanced EPR-spectrometer RE 1306 designed to investigate into structure of magnetic flux in high-temperature superconductors (HTSC). To measure in low fields one uses power source generating current within 0-600 mA limits and 10-500 Gauss field. To ensure temperature studies of HTSC within up to approx 15 K range one used helium and nitrogen cold steam blowing through resonator of EPR-spectrometer. To stabilize specimen temperature prior to cold steams enter double tube one fixed one more heater
Modeling of Temperature Field Evolution During Multilayered Direct Laser Metal Deposition
Zhang, DongYun; Feng, Zhe; Wang, ChengJie; Liu, Zhen; Dong, DongDong; Zhou, Yan; Wu, Rui
2017-06-01
It is of great importance to thoroughly explore the evolving temperature fields of direct laser metal deposition (abbreviated as LMD) in vertical thin wall manufacturing. It is helpful to control the temperature gradient, and even to adjust to forming microstructures and accumulation of residual stress. In this paper, a comprehensive three-dimensional transient model is developed for evolving temperature fields. The manufactured material is DS superalloy Rene80. The laser-powder interaction during the powder flowing process is simulated first, and its possible effect on the temperature field of the melting pool is analyzed. Then a 3D numerical simulation for the evolving temperature field is carried out based on considering transport phenomena during LMD such as the change in phase, powder injection and liquid flow. The applied deposition parameters are derived from experimental investigation with optimized vertical wall manufacturing. The simulated results explain why a balance between heat input and dissipation could form inside the vertical thin wall. These reconstruct the instability at an early phase of the building process without any temperature control unit and exhibit the influence of parameters such as laser power, deposition velocity and laser beam deposition pattern. The simulation results of temperature evolution are consistent with experimental investigation.
Temperature- and field-induced structural transitions in magnetic colloidal clusters
Hernández-Rojas, J.; Calvo, F.
2018-02-01
Magnetic colloidal clusters can form chain, ring, and more compact structures depending on their size. In the present investigation we examine the combined effects of temperature and external magnetic field on these configurations by means of extensive Monte Carlo simulations and a dedicated analysis based on inherent structures. Various thermodynamical, geometric, and magnetic properties are calculated and altogether provide evidence for possibly multiple structural transitions at low external magnetic field. Temperature effects are found to overcome the ordering effect of the external field, the melted stated being associated with low magnetization and a greater compactness. Tentative phase diagrams are proposed for selected sizes.
Energy Technology Data Exchange (ETDEWEB)
Grimaldi, G; Leo, A; Cirillo, C; Attanasio, C; Nigro, A; Pace, S [CNR-INFM Laboratorio Regionale SuperMat, Via Salvador Allende, I-84081 Baronissi (Italy)], E-mail: grimaldi@sa.infn.it
2009-06-24
We study the vortex dynamics in the instability regime induced by high dissipative states well above the critical current in Nb superconducting strips. The magnetic field and temperature behavior of the critical vortex velocity corresponding to the observed dynamic instability is ascribed to intrinsic non-equilibrium phenomena. The Larkin-Ovchinnikov (LO) theory of electronic instability in high velocity vortex motion has been applied to interpret the temperature dependence of the critical vortex velocity. The magnetic field dependence of the vortex critical velocity shows new features in the low-field regime not predicted by LO.
Comparison of velocity and temperature fields for two types of spacers in an annular channel
Directory of Open Access Journals (Sweden)
Lávička David
2012-04-01
Full Text Available The paper deals with measurement of flow field using a modern laser method (PIV in an annular channel of very small dimension - a fuel cell model. The velocity field was measured in several positions and plains around the spacer. The measurement was extended also to record temperatures by thermocouples soldered into stainless-steel tube wall. The measurement was focused on cooling process of the preheated fuel cell tube model, where the tube was very slowly flooded with water. Main result of the paper is comparison of two spacer's designs with respect to measured velocity and temperature fields.
Effect of inhomogeneous temperature fields on acoustic streaming structures in resonators.
Červenka, Milan; Bednařík, Michal
2017-06-01
Acoustic streaming in 2D rectangular resonant channels filled with a fluid with a spatial temperature distribution is studied within this work. An inertial force is assumed for driving the acoustic field; the temperature inhomogeneity is introduced by resonator walls with prescribed temperature distribution. The method of successive approximations is employed to derive linear equations for calculation of primary acoustic and time-averaged secondary fields including the streaming velocity. The model equations have a standard form which allows their numerical integration using a universal solver; in this case, COMSOL Multiphysics was employed. The numerical results show that fluid temperature variations in the direction perpendicular to the resonator axis influence strongly the streaming field if the ratio of the channel width and the viscous boundary layer thickness is big enough; the streaming in the Rayleigh vortices can be supported as well as opposed, which can ultimately lead to the appearance of additional vortices.
Infrared-temperature variability in a large agricultural field. [Dunnigan, California
Millard, J. P.; Goettelman, R. C.; Leroy, M. L. (Principal Investigator)
1980-01-01
The combined effect of water carved gullies, varying soil color, moisture state of the soil and crop, nonuniform phenology, and bare spots was measured for commercially grown barley planted on varying terrain. For all but the most rugged terrain, over 80% of the area within 4, 16, 65, and 259 ha cells was at temperatures within 3 C of the mean cell temperature. The result of using relatively small, 4 ha instantaneous field of views for remote sensing applications is that either the worst or the best of conditions is often observed. There appears to be no great advantage in utilizing a small instantaneous field of view instead of a large one for remote sensing of crop canopy temperatures. The two alternatives for design purposes are then either a very high spatial resolution, of the order of a meter or so, where the field is very accurately temperature mapped, or a low resolution, where the actual size seems to make little difference.
Measurement of the fluctuating temperature field in a heated swirling jet with BOS tomography
Lang, Henning M.; Oberleithner, Kilian; Paschereit, C. Oliver; Sieber, Moritz
2017-07-01
This work investigates the potential of background-oriented schlieren tomography (3D-BOS) for the temperature field reconstruction in a non-isothermal swirling jet undergoing vortex breakdown. The evaluation includes a quantitative comparison of the mean and phase-averaged temperature field with thermocouple and fast-response resistance thermometer as well as a qualitative comparison between the temperature field and the flow field obtained from particle image velocimetry (PIV). Compared to other temperature-measuring techniques, 3D-BOS enables non-invasive capturing of the entire three-dimensional temperature field. In contrast to previous 3D-BOS applications, the present investigation makes use of the special character of the flow, which provides a global instability that leads to a rotational symmetry of the jet. Additionally, the rotational motion of the jet is used to obtain a tomographic reconstruction from a single camera. The quality of 3D-BOS results with respect to the physical setup as well as the numerical procedure is analyzed and discussed. Furthermore, a new approach for the treatment of thin occluding objects in the field of view is presented.
Wang, J.; Emile-Geay, J.; Vaccaro, A.; Guillot, D.; Rajaratnam, B.
2013-12-01
updated multi-proxy network and produce a new 2000-year-long global temperature reconstruction. The network expands upon the existing M08 network by screening tree-ring proxies for the 'divergence problem' [D'Arrigo et al., 2008] and adds 58 non tree-ring proxies, of which 28 are located in the tropics and 11 are available within at least the past 1500 years. Overall, considerable differences are still evident among reconstructions using different CFR methods. Yet such differences are smaller using the updated proxy network compared with using the M08 network, consistent with pseudoproxy studies [Wang et al, 2013]. Our results collectively highlight the fragility of reconstructed patterns in the current state of proxy networks and CFR methods. We conclude that dynamical interpretations of such patterns are premature until these technical aspects are resolved. Reference: Wang, J., Emile-Geay, J., Guillot, D., Smerdon, J. E., and Rajaratnam, B.: Evaluating climate field reconstruction techniques using improved emulations of real-world conditions, Clim. Past Discuss., 9, 3015-3060, doi:10.5194/cpd-9-3015-2013, 2013.
Application of Abaqus to analysis of the temperature field in elements heated by moving heat sources
Directory of Open Access Journals (Sweden)
W. Piekarska
2010-10-01
Full Text Available Numerical analysis of thermal phenomena occurring during laser beam heating is presented in this paper. Numerical models of surface andvolumetric heat sources were presented and the influence of different laser beam heat source power distribution on temperature field wasanalyzed. Temperature field was obtained by a numerical solution the transient heat transfer equation with activity of inner heat sources using finite element method. Temperature distribution analysis in welded joint was performed in the ABAQUS/Standard solver. The DFLUXsubroutine was used for implementation of the movable welding heat source model. Temperature-depended thermophysical properties for steelwere assumed in computer simulations. Temperature distribution in laser beam surface heated and butt welded plates was numericallyestimated.
DEFF Research Database (Denmark)
Bharuth-Ram, K.; Hansen, Mikkel Fougt; Mørup, Steen
2001-01-01
at temperatures of 300 K and 80 K, in zero field and in an external field of 0.60 T, on the metallic inclusions in these grits. The Mossbauer spectra of the inclusions are rather complex, reflecting the contributions of several different magnetic phases. Our results show that the temperature variation......Mossbauer spectroscopy of the metallic inclusions in diamond grits produced in high-temperature high-pressure synthesis have revealed varying but interesting results. The MDAS(1) grits synthesized with Fe/Ni solvent-catalysts show Mossbauer spectra that vary with grit size, with the ferromagnetic...... of the Mossbauer spectra is not due to superparamagnetic relaxation of ferromagnetic inclusions but rather to magnetic ordering temperatures of the order of room temperature. Based on the spectral lineshapes and elemental analyses, we suggest the inclusions in the 63-75 mum grits contain iron mainly in Fe...
Energy Technology Data Exchange (ETDEWEB)
Morreeuw, J.P.; Dubroca, B. [CEA Centre d' Etudes Scientifiques et Techniques d' Aquitaine, 33 - Le Barp (France); Sangam, A.; Dubroca, B.; Charrier, P.; Tikhonchuk, V.T. [Bordeaux-1 Univ., CELIA, 33 - Talence (France); Sangam, A.; Dubroca, B.; Charrier, P. [Bordeaux-1 Univ., MAB, 33 - Talence (France)
2006-06-15
The laser interaction with an underdense plasma leads to an anisotropic laser heating of electrons. This temperature anisotropy gradient in turn is the source of an early magnetic field, which has an important effect on the plasma evolution, due to the thermal flux reduction. We describe the temperature anisotropy by an evolution equation including the anisotropy-magnetic field coupling and observe a rather efficient magnetic field generation. However at high anisotropy levels, a small-scale instability emerges, leading to a serious problem in numerical calculations. We introduce the kinetics effects, which fix the problem by the anisotropy diffusion through the heat flux tensor. A constant-coefficient Fokker-Planck model in the 2-dimensional geometry allows us to derive an anisotropy diffusion term. The diffusion coefficient is fitted from the kinetic theory of the collisional anisotropic (Weibel) instability growth rate. Such an anisotropy diffusion term wipes out the unphysical instability without any undesirable smoothing. This diffusion along with the viscosity term leads also to a quite good restitution of the Weibel instability growth rate and to the short wavelength cutoff, even in a weakly collisional situation. This allows us to use such a model to predict the emergence of the Weibel instability as well as its saturation. (authors)
Gauge fields in the separation of rotations and internal motions in the n-body problem
International Nuclear Information System (INIS)
Littlejohn, R.G.; Reinsch, M.
1997-01-01
The problem of separating rotations from internal motions in systems such as macroscopic flexible bodies, atoms, molecules, nuclei, and solar systems is an old one, with many applications in physics, chemistry, and engineering. A new element, however, which has not been appreciated until fairly recently, is the existence of certain gauge fields on the reduced configuration space for such systems. These (non-Abelian) gauge fields arise in the open-quotes falling catclose quotes problem, in which changes in shape induce changes in external orientation; but they also have a dynamical significance, and enter as gauge potentials in the Lagrangian or Hamiltonian describing the internal or reduced dynamics. Physically these gauge fields represent Coriolis effects. This review concentrates on the case of nonrelativistic, n-body systems not subject to external torques, and develops the gauge theory of rotations and internal motions in detail. Both classical and quantum treatments are given. The gauge theory is developed from the standpoint of classical, coordinate-based tensor analysis; more abstract mathematical notation is generally not used, although the basic geometrical ideas of fiber-bundle theory are developed as needed. Certain old results, such as the Wilson-Howard-Watson Hamiltonian of molecular physics, are examined from a gauge-theoretical standpoint; and several new results are presented, including field equations of the Kaluza-Klein type satisfied by the gauge fields, and geometrical interpretations of the Eckart frame. copyright 1997 The American Physical Society
Directory of Open Access Journals (Sweden)
V. M. Mikhailov
2017-12-01
Full Text Available Purpose. Testing of numerical solution algorithm for integral equation for calculation of plane meridian magnetostatic field source distribution at interfaces of piecewise homogeneous magnetized medium by means of electrostatic analogy. Methodology. The piecewise homogeneous medium consists of three regions with different magnetic permeabilities: the shell of arbitrary meridian section, external unlimited medium outside the shell, and the medium inside the shell. For testing external homogeneous magnetic field effect on spherical shell is considered. The analytical solution of this problem on the basis of electrostatic analogy from the solution of the problem uniform electrostatic field effect on dielectric shell is obtained. We have compared results of numerical solution of integral equation with the data obtained by means of analytical solution at the variation of magnetic permeabilities of regions of medium. Results. Integral equation and the algorithm of its numerical solution for calculation of source field distribution at the boundaries of piecewise homogeneous medium is validated. Testing of integral equations correctness for calculation of fictitious magnetic charges distribution on axisymmetric boundaries of piecewise homogeneous magnetized medium and algorithms of their numerical solutions can be carried out by means of analytical solutions of problems of homogeneous electrostatic field effect analysis on piecewise homogeneous dielectric medium with central symmetry of boundaries – single-layer and multilayer spherical shells. In the case of spherical shell in wide range of values of the parameter λk, including close to ± 1, numerical solution of integral equation is stable, and relative error in calculating of fictitious magnetic charges surface density and magnetic field intensity inside the shell is from tenths of a percent up to several percent except for the cases of very small values of these quantities. Originality. The use
Kamenshchik, A. Yu.
2018-03-01
We investigate particular cosmological models, based either on tachyon fields or on perfect fluids, for which soft future singularities arise in a natural way. Our main result is the description of a smooth crossing of the soft singularity in models with an anti-Chaplygin gas or with a particular tachyon field in the presence of dust. Such a crossing is made possible by certain transformations of matter properties. We discuss and compare also different approaches to the problem of crossing of the Big Bang-Big Crunch singularities.
Agustan, S.; Juniati, Dwi; Yuli Eko Siswono, Tatag
2017-10-01
Nowadays, reflective thinking is one of the important things which become a concern in learning mathematics, especially in solving a mathematical problem. The purpose of this paper is to describe how the student used reflective thinking when solved an algebra problem. The subject of this research is one female student who has field independent cognitive style. This research is a descriptive exploratory study with data analysis using qualitative approach to describe in depth reflective thinking of prospective teacher in solving an algebra problem. Four main categories are used to analyse the reflective thinking in solving an algebra problem: (1) formulation and synthesis of experience, (2) orderliness of experience, (3) evaluating the experience and (4) testing the selected solution based on the experience. The results showed that the subject described the problem by using another word and the subject also found the difficulties in making mathematical modelling. The subject analysed two concepts used in solving problem. For instance, geometry related to point and line while algebra is related to algebra arithmetic operation. The subject stated that solution must have four aspect to get effective solution, specifically the ability to (a) understand the meaning of every words; (b) make mathematical modelling; (c) calculate mathematically; (d) interpret solution obtained logically. To test the internal consistency or error in solution, the subject checked and looked back related procedures and operations used. Moreover, the subject tried to resolve the problem in a different way to compare the answers which had been obtained before. The findings supported the assertion that reflective thinking provides an opportunity for the students in improving their weakness in mathematical problem solving. It can make a grow accuracy and concentration in solving a mathematical problem. Consequently, the students will get the right and logic answer by reflective thinking.
Khan, Ambreen Asfar; Zaman, Akbar; Yaseen, Sundas
2018-03-01
In this article, two models of the generalized thermo-elastic theory are used to see the influence on the refraction and reflection of the plane waves at the interface under a constant magnetic field. The elasticity modulus depends on the reference temperature. The elasticity modulus is considered as a linear function of reference temperature. The resulting problem is solved by using the boundary conditions at the interface. The matrix equations have been solved numerically.
Calculation of induced modes of magnetic field in the geodynamo problem
International Nuclear Information System (INIS)
Yokoyama, Yukiko; Yukutake, Takesi
1989-01-01
In the dynamo problem, the calculation of induced modes is of vital importance, because the interaction of fluid motions with the magnetic field induces specific types of fields which are, in many cases, different either from the type of velocity field or from the original magnetic field. This special induction relationship, known as 'selection rules', has so far been derived by calculating Adams-Gaunt integrals and Elsasser integrals. In this paper, we calculate the induced modes in a more direct way, expressing the magnetic fields and the velocity in a spherical harmonic series. By linearizing the product terms of spherical harmonic functions, which appear in interaction terms between the velocity and the magnetic field, into a simple spherical harmonic series, we have derived the induced magnetic modes in a simple general form. When the magnetic field and the velocity are expressed by toroidal and poloidal modes, four kinds of interaction are conceivable between the velocity and the magnetic field. By each interaction, two modes, the poloidal and toroidal, are induced, except in the interaction of the toroidal velocity with the toroidal magnetic field, which induces only the toroidal mode. In spite of the diversity of interaction processes, the induced modes have been found to be expressed simply by two types. For a velocity of degree l and order k interacting with a magnetic field of degree n and order m, one type is the mode with degree and order of n+l-2t, |m±k| for an integer t, and the other with n+l-2t-1, |m±k|. (author)
Agustan, S.; Juniati, Dwi; Siswono, Tatag Yuli Eko
2017-08-01
Reflective thinking is an important component in the world of education, especially in professional education of teachers. In learning mathematics, reflective thinking is one way to solve mathematical problem because it can improve student's curiosity when student faces a mathematical problem. Reflective thinking is also a future competence that should be taught to students to face the challenges and to respond of demands of the 21st century. There are many factors which give impact toward the student's reflective thinking when student solves mathematical problem. One of them is cognitive style. For this reason, reflective thinking and cognitive style are important things in solving contextual mathematical problem. This research paper describes aspect of reflective thinking in solving contextual mathematical problem involved solution by using some mathematical concept, namely linear program, algebra arithmetic operation, and linear equations of two variables. The participant, in this research paper, is a male-prospective teacher who has Field Dependent. The purpose of this paper is to describe aspect of prospective teachers' reflective thinking in solving contextual mathematical problem. This research paper is a descriptive by using qualitative approach. To analyze the data, the researchers focus in four main categories which describe prospective teacher's activities using reflective thinking, namely; (a) formulation and synthesis of experience, (b) orderliness of experience, (c) evaluating the experience and (d) testing the selected solution based on the experience.
Solar cooker effect test and temperature field simulation of radio telescope subreflector
International Nuclear Information System (INIS)
Chen, Deshen; Wang, Huajie; Qian, Hongliang; Zhang, Gang; Shen, Shizhao
2016-01-01
Highlights: • Solar cooker effect test of a telescope subreflector is conducted for the first time. • The cause and temperature distribution regularities are analyzed contrastively. • Simulation methods are proposed using light beam segmentation and tracking methods. • The validity of simulation methods is evaluated using the test results. - Abstract: The solar cooker effect can cause a local high temperature of the subreflector and can directly affect the working performance of the radio telescope. To study the daily temperature field and solar cooker effect of a subreflector, experimental studies are carried out with a 3-m-diameter radio telescope model for the first time. Initially, the solar temperature distribution rules, especially the solar cooker effect, are summarized according to the field test results under the most unfavorable conditions. Then, a numerical simulation for the solar temperature field of the subreflector is studied by light beam segmentation and tracking methods. Finally, the validity of the simulation methods is evaluated using the test results. The experimental studies prove that the solar cooker effect really exists and should not be overlooked. In addition, simulation methods for the subreflector temperature field proposed in this paper are effective. The research methods and conclusions can provide valuable references for thermal design, monitoring and control of similar high-precision radio telescopes.
Directory of Open Access Journals (Sweden)
Rudowicz Czesław
2015-07-01
Full Text Available The interface between optical spectroscopy, electron magnetic resonance (EMR, and magnetism of transition ions forms the intricate web of interrelated notions. Major notions are the physical Hamiltonians, which include the crystal field (CF (or equivalently ligand field (LF Hamiltonians, and the effective spin Hamiltonians (SH, which include the zero-field splitting (ZFS Hamiltonians as well as to a certain extent also the notion of magnetic anisotropy (MA. Survey of recent literature has revealed that this interface, denoted CF (LF ↔ SH (ZFS, has become dangerously entangled over the years. The same notion is referred to by three names that are not synonymous: CF (LF, SH (ZFS, and MA. In view of the strong need for systematization of nomenclature aimed at bringing order to the multitude of different Hamiltonians and the associated quantities, we have embarked on this systematization. In this article, we do an overview of our efforts aimed at providing a deeper understanding of the major intricacies occurring at the CF (LF ↔ SH (ZFS interface with the focus on the EMR-related problems for transition ions.
International electromagnetic workshop. Problem 2: Infinitely long cylinder in a sinusoidal field
International Nuclear Information System (INIS)
Morisue, T.
1986-01-01
In this report, Problem 2 is solved using the magnetic vector potential and integral equation method. The computing process consists of two phases: in Phase 1 the boundary values of the vector potential and its normal derivative are calculated, and in Phase 2 the magnetic field and eddy current at the specified points are computed using the finite difference method (in the cylinder) and the integral equation method (both inside and outside the cylinder). The results coincide well with the analytical solution
International Nuclear Information System (INIS)
Calkins, Mathew; Gates, D.E.A.; Gates, S. James Jr.; Golding, William M.
2015-01-01
Starting with valise supermultiplets obtained from 0-branes plus field redefinitions, valise adinkra networks, and the “Garden Algebra,” we discuss an architecture for algorithms that (starting from on-shell theories and, through a well-defined computation procedure), search for off-shell completions. We show in one dimension how to directly attack the notorious “off-shell auxiliary field” problem of supersymmetry with algorithms in the adinkra network-world formulation.
Gulin, O. E.; Yaroshchuk, I. O.
2001-10-01
Within the framework of an exact wave approach in the spatial-time domain, the one-dimensional stochastic problem of sound pulse scattering by a layered random medium is considered. On the basis of a unification of methods which has been developed by the authors, previously applied to the investigation of non-stationary deterministic wave problems and stochastic stationary wave problems, an analytical-numerical simulation of the behaviour of the backscattered field stochastic characteristics was carried out. Several forms of incident pulses and signals are analysed. We assume that random fluctuations of a medium are described by virtue of the Gaussian Markov process with an exponential correlation function. The most important parameters appearing in the problem are discussed; namely, the time scales of diffusion, pulse durations, the medium layer thickness or the largest observation time scale in comparison with the time scale of one correlation length for the case of a half-space. An exact pattern of the pulse backscattering processes is obtained. It is illustrated by the behaviour of the backscattered field statistical moments for all observation times which are of interest. It is shown that during the time interval when the main part of the pulse energy leaves the medium, the backscattered field is a substantially non-stationary process, having a non-zero mean value and an average intensity that decays according to a power law. There are various power indices for the different duration incident pulses, however, they are not the same as those of previous papers, which were obtained on the basis of an approximate and asymptotic analysis. We have also verified that the Gaussian law is valid for the probability density function of the backscattered field in the case of any incident pulse duration.
Carrier, J
1999-01-01
This paper presents field research on the major ethical problems in the study of male homosexuality in Mexico from 1968 up to the present and describes a solution to these problems. Ethical concerns about the psychological and social well-being of respondents are heightened in when the focus of a study is on a highly private, sensitive and sanctioned human behavior such as sexual relations. The ethics of a gay man conducting participant observation studies of male homosexuality tend particularly to be open to special scrutiny and suspicion. Most of the major ethical concerns about the study of male homosexuality are related to 1) the methods used by the researcher to collect participant-observation and interview data and 2) the possibility that the dissemination of study findings by the researcher to the outside world may lead to unwanted adverse effects on project respondents and on the population they represent. The use of the participant-observer in gathering of data in the field presents a serious ethical problem that must be addressed by sex researchers. Thus, future researchers contemplating ethnographic participant observation studies in the field must take into account the reality that it is extremely unlikely that they will be able to separate their private sex lives completely from their research.
Analytic Solution to the Problem of Aircraft Electric Field Mill Calibration
Koshak, W. J.
2003-12-01
It is by no means a simple task to retrieve storm electric fields from an aircraft instrumented with electric field mill sensors. The presence of the aircraft distorts the ambient field in a complicated way. Before retrievals of the storm field can be made, the field mill measurement system must be "calibrated". In other words, a relationship between impressed (i.e., ambient) electric field and mill output must be established. If this relationship can be determined, it is mathematically inverted so that ambient field can be inferred from the mill outputs. Previous studies have primarily focused on linear theories where the "relationship" between ambient field and mill output is described by a "calibration matrix" M. Each element of the matrix describes how a particular component of the ambient field is enhanced by the aircraft. For example the product MixEx is the contribution of the Ex field to the ith mill output. Similarly, net aircraft charge (described by a "charge field component" Eq) contributes an amount MiqEq to the output of the ith sensor. The central difficulty in obtaining M stems from the fact that the impressed field (Ex, Ey, Ez, Eq) is not known but is instead estimated. Typically, the aircraft is flown through a series of roll and pitch maneuvers in fair weather, and the values of the fair weather field and aircraft charge are estimated at each point along the aircraft trajectory. These initial estimates are often highly inadequate, but several investigators have improved the estimates by implementing various (ad hoc) iterative methods. Though numerical tests show that some of the iterative methods do improve the initial estimates, none of the iterative methods guarantee absolute convergence to the true values, or even to values reasonably close to the true values when measurement errors are present. In this work, the mathematical problem is solved directly by analytic means. For m mills installed on an arbitrary aircraft, it is shown that it is
Thomas, Silke; Heinrich, Sabine; von Kries, Rüdiger; Radon, Katja
2010-02-01
Only few studies have so far investigated possible health effects of radio-frequency electromagnetic fields (RF EMF) in children and adolescents, although experts discuss a potential higher vulnerability to such fields. We aimed to investigate a possible association between measured exposure to RF EMF fields and behavioural problems in children and adolescents. 1,498 children and 1,524 adolescents were randomly selected from the population registries of four Bavarian (South of Germany) cities. During an Interview data on participants' mental health, socio-demographic characteristics and potential confounders were collected. Mental health behaviour was assessed using the German version of the Strengths and Difficulties Questionnaire (SDQ). Using a personal dosimeter, we obtained radio-frequency EMF exposure profiles over 24 h. Exposure levels over waking hours were expressed as mean percentage of the reference level. Overall, exposure to radiofrequency electromagnetic fields was far below the reference level. Seven percent of the children and 5% of the adolescents showed an abnormal mental behaviour. In the multiple logistic regression analyses measured exposure to RF fields in the highest quartile was associated to overall behavioural problems for adolescents (OR 2.2; 95% CI 1.1-4.5) but not for children (1.3; 0.7-2.6). These results are mainly driven by one subscale, as the results showed an association between exposure and conduct problems for adolescents (3.7; 1.6-8.4) and children (2.9; 1.4-5.9). As this is one of the first studies that investigated an association between exposure to mobile telecommunication networks and mental health behaviour more studies using personal dosimetry are warranted to confirm these findings.
International Nuclear Information System (INIS)
Thomas, Silke; Heinrich, Sabine; Kries, Ruediger von; Radon, Katja
2010-01-01
Only few studies have so far investigated possible health effects of radio-frequency electromagnetic fields (RF EMF) in children and adolescents, although experts discuss a potential higher vulnerability to such fields. We aimed to investigate a possible association between measured exposure to RF EMF fields and behavioural problems in children and adolescents. 1,498 children and 1,524 adolescents were randomly selected from the population registries of four Bavarian (South of Germany) cities. During an Interview data on participants' mental health, socio-demographic characteristics and potential confounders were collected. Mental health behaviour was assessed using the German version of the Strengths and Difficulties Questionnaire (SDQ). Using a personal dosimeter, we obtained radio-frequency EMF exposure profiles over 24 h. Exposure levels over waking hours were expressed as mean percentage of the reference level. Overall, exposure to radiofrequency electromagnetic fields was far below the reference level. Seven percent of the children and 5% of the adolescents showed an abnormal mental behaviour. In the multiple logistic regression analyses measured exposure to RF fields in the highest quartile was associated to overall behavioural problems for adolescents (OR 2.2; 95% CI 1.1-4.5) but not for children (1.3; 0.7-2.6). These results are mainly driven by one subscale, as the results showed an association between exposure and conduct problems for adolescents (3.7; 1.6-8.4) and children (2.9; 1.4-5.9). As this is one of the first studies that investigated an association between exposure to mobile telecommunication networks and mental health behaviour more studies using personal dosimetry are warranted to confirm these findings.
Chen, Ruirun; Yang, Yaohua; Gong, Xue; Guo, Jingjie; Su, Yanqing; Ding, Hongsheng; Fu, Hengzhi
2017-12-01
The electromagnetic cold crucible (EMCC) technique is an effective method to melt and directionally solidify reactive and high-temperature materials without contamination. The temperature field and fluid flow induced by the electromagnetic field are very important for melting and controlling the microstructure. In this article, a 3D EMCC model for calculating the magnetic field in the charges (TiAl alloys) using the T-Ω finite element method was established and verified. Magnetic fields in the charge under different electrical parameters, positions and dimensions of the charge were calculated and analyzed. The calculated results show that the magnetic field concentrates in the skin layer, and the magnetic flux density ( B) increases with increasing of the frequency, charge diameter and current. The maximum B in the charge is affected by the position of the charge in EMCC ( h 1) and the charge height ( h 2), which emerges at the middle of coils ( h c) when the relationship of h c < h 1 + h 2 < h c + δ is satisfied. Lower frequency and smaller charge diameter can improve the uniformity of the magnetic field in the charge. Consequently, the induced uniform electromagnetic stirring weakens the turbulence and improves temperature uniformity in the vicinity of the solid/liquid (S/L) interface, which is beneficial to forming a planar S/L interface during directional solidification. Based on the above conclusions, the TiAlNb alloy was successfully melted with lower power consumption and directionally solidified by the square EMCC.
Room-temperature deposition of diamond-like carbon field emitter on flexible substrates
International Nuclear Information System (INIS)
Chen, H.; Iliev, M.N.; Liu, J.R.; Ma, K.B.; Chu, W.-K.; Badi, N.; Bensaoula, A.; Svedberg, E.B.
2006-01-01
Room-temperature fabrication of diamond-like carbon electron field emitters on flexible polyimide substrate is reported. These thin film field emitters are made using an Ar gas cluster ion beam assisted C 6 vapor deposition method. The bond structure of the as-deposited diamond-like carbon film was studied using Raman spectroscopy. The field emission characteristics of the deposited films were also measured. Electron current densities over 15 mA/cm 2 have been recorded under an electrical field of about 65 V/μm. These diamond-like carbon field emitters are easy and inexpensive to fabricate. The results are promising for flexible field-emission fabrication without the need of complex patterning and tip shaping as compared to the Spindt-type field emitters
The Gribov problem in presence of background field for SU(2 Yang–Mills theory
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Fabrizio Canfora
2016-12-01
Full Text Available The Gribov problem in the presence of a background field is analyzed: in particular, we study the Gribov copies equation in the Landau–De Witt gauge as well as the semi-classical Gribov gap equation. As background field, we choose the simplest non-trivial one which corresponds to a constant gauge potential with non-vanishing component along the Euclidean time direction. This kind of constant non-Abelian background fields is very relevant in relation with (the computation of the Polyakov loop but it also appears when one considers the non-Abelian Schwinger effect. We show that the Gribov copies equation is affected directly by the presence of the background field, constructing an explicit example. The analysis of the Gribov gap equation shows that the larger the background field, the smaller the Gribov mass parameter. These results strongly suggest that the relevance of the Gribov copies (from the path integral point of view decreases as the size of the background field increases.
Test fields on compact spacetimes: Problems, some partial results and speculations
International Nuclear Information System (INIS)
Yurtsever, U.
1989-09-01
In this paper we study some basic aspects of (Lorentzian) field theory on compact Lorentz manifolds. All compact spacetimes are acausal, i.e. possess closed timelike curves; this makes them a useful testbed in analyzing some new notions of causality that we will introduce for more general acausal spacetimes. In addition, studying compact spacetimes in their own right raises a wide range of fascinating mathematical problems some of which we will explore. We will see that it is reasonable to expect Lorentzian field theory on a compact spacetime to provide information on the topology of the underlying manifold; if this is true, then this information is likely to be ''orthogonal'' (or complementary) to the information obtained through the study of Euclidean field theory. (author). 45 refs, 2 figs
Nigam, Kaushal; Pandey, Sunil; Kondekar, P. N.; Sharma, Dheeraj
2016-09-01
The conventional tunnel field-effect transistors (TFETs) have shown potential to scale down in sub-22 nm regime due to its lower sub-threshold slope and robustness against short-channel effects (SCEs), however, sensitivity towards temperature variation is a major concern. Therefore, for the first time, we investigate temperature sensitivity analysis of a polarity controlled electrostatically doped tunnel field-effect transistor (ED-TFET). Different performance metrics and analog/RF figure-of-merits were considered and compared for both devices, and simulations were performed using Silvaco ATLAS device tool. We found that the variation in ON-state current in ED-TFET is almost temperature independent due to electrostatically doped mechanism, while, it increases in conventional TFET at higher temperature. Above room temperature, the variation in ION, IOFF, and SS sensitivity in ED-TFET are only 0.11%/K, 2.21%/K, and 0.63%/K, while, in conventional TFET the variations are 0.43%/K, 2.99%/K, and 0.71%/K, respectively. However, below room temperature, the variation in ED-TFET ION is 0.195%/K compared to 0.27%/K of conventional TFET. Moreover, it is analysed that the incomplete ionization effect in conventional TFET severely affects the drive current and the threshold voltage, while, ED-TFET remains unaffected. Hence, the proposed ED-TFET is less sensitive towards temperature variation and can be used for cryogenics as well as for high temperature applications.
Zhao, J.; Ai, X.; Li, Y. Z.
2007-10-01
This paper presents analyses of the transient temperature fields in an infinite plate, an infinite solid cylinder and a solid sphere made of functionally graded materials (FGMs) under convective boundary conditions. The composition and the thermo-physical properties of the infinite FGM plate, the infinite FGM solid cylinder and the FGM solid sphere are of planar symmetric, axially symmetric and spherically symmetric distributions, respectively. The analytical formulae of the one-dimensional transient temperature fields for the three FGM solids are obtained respectively by using the separation-of-variables method and the variable substitution method. Numerical results reveal that the transient temperature fields of the FGM components exhibit similar shape effect to that of homogeneous components. The present work provides valuable basis for the investigation of the thermal shock resistance of FGMs with various shapes.
International Nuclear Information System (INIS)
Schmidt, W.F.
1977-01-01
A survey is given on the mobility of excess electrons in liquid hydrocarbons and related compounds. It was found that the mobility is strongly influenced by the molecular structure of the liquid, by the temperature, and by the electric field strength. The mobility in hydrocarbons increases as the shape of the molecule approaches a sphere. The temperature coefficient is positive in most liquids over a limited temperature although exceptions have been observed in liquid methane. The field dependence of the mobility in high mobility liquids (>10 cm 2 V -1 s -1 ) showed a decrease of the mobility at higher field strengths while in low mobility liquids ( 2 V -1 s -1 ) it showed an increase. These results are discussed on the basis of the extended and the localized electron models. The predictions of these theories are compared with the experimental results and conclusions on the validity of the underlying assumptions are drawn. (author)
Schmidt, R. F.
1982-01-01
A transition from the antenna noise temperature formulation for extended noise sources in the far-field or Fraunhofer-region of an antenna to one of the intermediate near field or Fresnel-region is discussed. The effort is directed toward microwave antenna simulations and high-speed digital computer analysis of radiometric sounding units used to obtain water vapor and temperature profiles of the atmosphere. Fresnel-region fields are compared at various distances from the aperture. The antenna noise temperature contribution of an annular noise source is computed in the Fresnel-region (D squared/16 lambda) for a 13.2 cm diameter offset-paraboloid aperture at 60 GHz. The time-average Poynting vector is used to effect the computation.
International Nuclear Information System (INIS)
Jee, Madan; Prasad, Vijay; Singh, Amita
1995-01-01
The electrical resistivity, Hall coefficient and electronic mobility of n-type and p-type crystals of indium antimonide have been measured from 25 degC-100 degC temperature range. It has been found by this measurement that indium antimonide is a compound semiconductor with a high mobility 10 6 cm 2 /V.S. The Hall coefficient R H was measured as a function of magnetic field strength H for a number of samples of both p and n-type using fields up to 12 kilo gauss. The Hall coefficient R h decreases with increasing magnetic fields as well as with increase in temperature of the sample. The electric field is more effective on samples with high mobilities and consequently the deviations from linearity are manifested at comparatively low values of the electric field. The measurement of R H in weak and strong magnetic fields makes it possible to determine the separate concentration of heavy and light holes. Measured values of Hall coefficient and electrical resistivity show that there is a little variation of ρ and R h with temperatures as well as with magnetic fields. (author). 12 refs., 5 tabs
International Nuclear Information System (INIS)
Vachutka, J; Grec, P; Mornstein, V; Caruana, C J
2008-01-01
The heating of tissues by diagnostic ultrasound can pose a significant hazard particularly in the imaging of the unborn child. The demonstration of the temperature field in tissue is therefore an important objective in the teaching of biomedical physics to healthcare professionals. The temperature field in a soft tissue model was made visible and measured using thermography. Temperature data from the images were used to investigate the dependence of temperature increase within the model on ultrasound exposure time and distance from the transducer. The experiment will be used within a multi-professional biomedical physics teaching laboratory for enhancing learning regarding the principles of thermography and the thermal effects of ultrasound to medical and healthcare students and also for demonstrating the quantitative use of thermographic imaging to students of biophysics, medical physics and medical technology
International Nuclear Information System (INIS)
Surducan, V.; Surducan, E.; Dadarlat, D.
2013-01-01
Microwave induced heating is widely used in medical treatments, scientific and industrial applications. The temperature field inside a microwave heated sample is often inhomogenous, therefore multiple temperature sensors are required for an accurate result. Nowadays, non-contact (Infra Red thermography or microwave radiometry) or direct contact temperature measurement methods (expensive and sophisticated fiber optic temperature sensors transparent to microwave radiation) are mainly used. IR thermography gives only the surface temperature and can not be used for measuring temperature distributions in cross sections of a sample. In this paper we present a very simple experimental method for temperature distribution highlighting inside a cross section of a liquid sample, heated by a microwave radiation through a coaxial applicator. The method proposed is able to offer qualitative information about the heating distribution, using a temperature sensitive liquid crystal sheet. Inhomogeneities as smaller as 1°-2°C produced by the symmetry irregularities of the microwave applicator can be easily detected by visual inspection or by computer assisted color to temperature conversion. Therefore, the microwave applicator is tuned and verified with described method until the temperature inhomogeneities are solved
Responses of track and field coaches to athletes with eating problems.
Plateau, C R; Arcelus, J; McDermott, H J; Meyer, C
2015-04-01
This study aimed to explore how track and field coaches respond to athletes with eating problems. Eleven experienced coaches participated in semi-structured interviews exploring their responses to, and challenges faced when, working with athletes with eating problems. The analysis revealed three themes relating to the strategies employed by coaches. The first theme indicated a supportive approach, where coaches were proactive in seeking support and in reducing training at the early stages of an eating problem. The second theme outlined an avoidant approach, characterized by coach reluctance to be involved in managing eating problems, and a lack of confidence in their knowledge of eating disorders. The third theme involved a confrontational approach, where coaches employed strict rules and engaged in coercion to persuade athletes to seek treatment. All of the coaches reported facing challenges in persuading athletes to seek treatment and were frustrated by the lack of available support. The study highlights the importance of providing resources and support services where coaches can seek advice. Coach-education packages can utilize the findings to highlight the strengths and limitations of different coach strategies, and to reinforce the importance of their role in identification and intervention when eating problems in athletes are suspected. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.
Pressure and temperature fields and water released by concrete submitted to high heat fluxes
International Nuclear Information System (INIS)
Andrade Lima, F.R. de
1982-01-01
Inovations are introduced in the original program USINT considering thermal conductivity variations with the temperature. A subroutine - PLOTTI - is incorporate to the program aiming to obtain a graphic for results. The new program - USINTG - is used for calculating the field of pressure and temperature and the water released from the concrete structure during a simulation of sodium leak. The theoretical results obtained with USINTG are in good agreement with the experimental results previously obtained. (E.G.) [pt
On the calculation of finite-temperature effects in field theories
International Nuclear Information System (INIS)
Brandt, F.T.; Frenkel, J.; Taylor, J.C.
1991-03-01
We discuss an alternative method for computing finite-temperature effects in field theories, within the framework of the imaginary-time formalism. Our approach allows for a systematic calculation of the high temperature expansion in terms of Riemann Zeta functions. The imaginary-time result is analytically continued to the complex plane. We are able to obtain the real-time limit of the real and the imaginary parts of the Green functions. (author)
International Nuclear Information System (INIS)
Ovcharova, A.; Kolev, N.; Nedkov, N.
2005-01-01
The aims of the present study were connected with evaluation of the basic soil properties, distribution of thermal, hydrological and electronic soil properties and criteria for minimization of the measurement points, obtained in the cotton non-irrigated field of the Institute of durum wheat and cotton near Chirpan. It were measured crop temperature of cotton field and soil surface temperature distribution during the main vegetative stages. Using the energy balance equation and soil water balance equation was calculated the intensity of evapotranspiration during the days of measurements
Bernier, Maxime; Gaborit, Gwenaël; Duvillaret, Lionel; Paupert, Alain; Lasserre, Jean-Louis
2008-05-01
We present pigtailed electro-optic probes that allow a simultaneous measurement of high frequency electric fields and temperature using a unique laser probe beam. This has been achieved by the development of a novel probe design associated with a fully automated servo-controlled optical bench, initially developed to stabilize the electric field sensor response. The developed electro-optic probes present a stable response in outdoors conditions over a time duration exceeding 1 h, a frequency bandwidth from kHz to tens of GHz with a sensitivity of 0.7 Vm(-1)Hz(-(1/2)), and a temperature accuracy of 40 mK.
International Nuclear Information System (INIS)
Kim, Dong-Hyun; Lee, Se-Ho; Kim, Kyoung-Nam; Kim, Kwang-Mahn; Shim, In-Bo; Lee, Yong-Keun
2005-01-01
Various ferrites (Fe-, Li-, Ni/Zn/Cu-, Co-, Co/Ni, Ba- and Sr-ferrites) were investigated with respect to their application for hyperthermia. Temperature changes under an alternating magnetic field were observed. The area of hysteresis loop was much larger in the Ba- and Sr-ferrites than for that of the Fe-, Ni/Zn/Cu-, Li-, Co- and Co/Ni-ferrites. Co-ferrite exhibited the most applicable temperature change ΔT=19.25K (29.62W/gs), in distilled water when the field was 110A/m
Tang, Yundong; Flesch, Rodolfo C. C.; Jin, Tao
2018-01-01
Magnetic nanoparticle (MNP) hyperthermia ablates malignant cells by heating the region of interest when MNPs are subjected to an external alternating magnetic field. The energy density to be dissipated into heat, and consequently the temperature profile during treatment, depends on the distribution of MNPs within the tumoral region. This paper uses numerical models to evaluate the temporal and spatial temperature distributions inside a tumor when intratumoral injection of MNPs is considered. To this end, the theories of mass transfer and diffusion in interstitial tissue are combined with Rosensweig’s theory and Pennes bio-heat transfer equation, and the finite element method is used for analyzing the temperature field under different scenarios. Simulation results demonstrate that the treatment temperature field strongly depends on factors, such as the injection method, particle size, injection concentration and injection dose. However, the maximal temperature reached during hyperthermia and the effective treatment area are difficult to control. In order to obtain better treatment effects, this paper investigates a solution that uses a kind of material with low Curie temperature and the results show that the effective treatment area of hyperthermia can be significantly improved using this type of MNP.
Effects of the temperature and magnetic-field dependent coupling on the properties of QCD matter
Yang, Li; Wen, Xin-Jian
2017-09-01
To reflect the asymptotic freedom in the thermal direction, a temperature-dependent coupling was proposed in the literature. We investigate its effect on QCD matter with and without strong magnetic fields. Compared with the fixed coupling constant, the running coupling leads to a drastic change in the dynamical quark mass, entropy density, sound velocity, and specific heat. The crossover transition of QCD matter at finite temperature is characterized by the pseudocritical temperature Tpc , which is generally determined by the peak of the derivative of the quark condensate with respect to the temperature d ϕ /d T , or equivalently, by the derivative of the quark dynamical mass d M /d T . In a strong magnetic field, the temperature- and magnetic-field-dependent coupling G (e B ,T ) was recently introduced to account for inverse magnetic catalysis. We propose an analytical relation between the two criteria d ϕ /d T and d M /d T and show a discrepancy between them in finding the pseudocritical temperature. The magnitude of the discrepancy depends on the behavior of d G /d T .
Variations in geomagnetic field and temperature in Spain during the past millennium
Nachasova, I. E.; Burakov, K. S.; Pilipenko, O. V.; Markov, G. P.
2015-07-01
The archaeomagnetic studies are conducted for the collection of coated ceramic samples from the Albarracin archaeological monument in Spain dated to the 10-20th centuries A.D. The pattern of variations in geomagnetic field intensity during this time interval is identified. The behavior of geomagnetic intensity is dominated by a decreasing trend (from ˜80 to 40 μT). The variation with a characteristic time of a few hundred years is the most striking one. Investigation of the material from this collection by the method of rehydroxylation provided the temperature estimates for this region of Spain for the time interval of pottery production. The temperature variations generally tend to increase, while the main trend in the variations of geomagnetic intensity is decreasing. The time series of temperature and intensity of the main magnetic field contain variations with close characteristic times shifted in time so that the changes in temperature go somewhat ahead of the changes in the geomagnetic field. It was previously suggested to improve the accuracy and resolution of the obtained variations in the past magnetic field using the method of archaeomagnetic dating of the material from archaeological monuments. The method was tested by dating the pottery kiln material from the El Molon monument, Spain, with the use of the virtual geomagnetic pole curve based on the past magnetic field in the East Europe. The method proved to be quite efficient and promising for dating the archaeological material from all over Europe.
Anisotropic temperature dependence of the magnetic-field penetration in superconducting UPt3
International Nuclear Information System (INIS)
Broholm, C.; Aeppli, G.; Kleiman, R.N.; Harshman, D.R.; Bishop, D.J.; Bucher, E.; Williams, D.L.; Ansaldo, E.J.; Heffner, R.H.
1990-01-01
The anisotropy and temperature dependence of the magnetic-field penetration in superconducting UPt 3 have been measured by muon spin relaxation. The extrapolated zero-temperature values for the penetration depths parallel and perpendicular to the c axis are λ parallel =7070±30 A and λ perpendicular =7820±30 A, respectively. The temperature dependences of λ parallel and λ perpendicular are different and can both be accounted for by a superconducting gap function with a line of nodes in the basal plane and axial point nodes
Numerical Analysis of Temperature Field in a Disc Brake at Different Cover Angle of the Pad
Directory of Open Access Journals (Sweden)
Grześ Piotr
2014-12-01
Full Text Available In the paper an influence of the cover angle of the pad on temperature fields of the components of the disc brake is studied. A three-dimensional finite element (FE model of the pad-disc system was developed at the condition of equal temperatures on the contacting surfaces. Calculations were carried out for a single braking process at constant deceleration assuming that the contact pressure corresponds with the cover angle of the pad so that the moment of friction is equal in each case analysed. Evolutions and distributions of temperature both for the contact surface of the pad and the disc were computed and shown.
Rocket to Creativity: A Field Experience in Problem-Based and Project-Based Learning
Directory of Open Access Journals (Sweden)
Sharon F. Dole
2016-11-01
Full Text Available The purpose of this article is to examine the impact of a field experience in problem-based (PBL and project-based learning (PjBL on pre-service and in-service teachers’ conceptions of experiential learning. In our study, participants had been enrolled in a hybrid class that included an online component in which they learned about PBL and PjBL and an experiential component in which they facilitated PBL and PjBL with children in grades 1-9 during a one-week field experience on a university campus. The goal of the field experience is for teachers to change their practice from didactic to inquiry and to promote critical and creative thinking in their students. We used a case study method that involved data derived from six different sources: online structured interviews, follow-up telephone interviews, discussion board posts, reflections, course feedback, and observations. The main theme that emerged from the data analysis was the critical role the field experience played in applying theory to practice. Sub-themes included understanding the process of implementing PBL and PjBL, mastering the logistics of PBL and PjBL, becoming facilitators, and collaborating with partners. Results showed that the field experience gave the teachers the “courage” to experiment with a student-centered methodology.
International Nuclear Information System (INIS)
Ida, Katsumi
2001-01-01
The structure of the radial electric field and toroidal/poloidal flow is discussed for the high temperature plasma in toroidal systems, tokamak and Heliotron type magnetic configurations. The spontaneous toroidal and poloidal flows are observed in the plasma with improved confinement. The radial electric field is mainly determined by the poloidal flow, because the contribution of toroidal flow to the radial electric field is small. The jump of radial electric field and poloidal flow are commonly observed near the plasma edge in the so-called high confinement mode (H-mode) plasmas in tokamaks and electron root plasma in stellarators including Heliotrons. In general the toroidal flow is driven by the momentum input from neutral beam injected toroidally. There is toroidal flow not driven by neutral beam in the plasma and it will be more significant in the plasma with large electric field. The direction of these spontaneous toroidal flows depends on the symmetry of magnetic field. The spontaneous toroidal flow driven by the ion temperature gradient is in the direction to increase the negative radial electric field in tokamak. The direction of spontaneous toroidal flow in Heliotron plasmas is opposite to that in tokamak plasma because of the helicity of symmetry of the magnetic field configuration. (author)
Temperature field downstream of an heated bundle mock-up results for different power distribution
International Nuclear Information System (INIS)
Girard, J.P.; Buravand, Y.
1982-10-01
The aim of these peculiar experiments performed on the ML4 loop in ISPRA is to evaluate the characteristics of the temperature field over a length of 20 to 30 dias downstream of a rod bundle for different temperatures profiles at the bundle outlet. The final purpose of this work will be to establish either directly or through models whether it is possible or not to detect subassembly failures using suitable of the subassembly outlet temperature signal. 15 hours of digital and analog recording were taped for five different power distributions in the bundle. The total power dissipation remained constant during the whole run. Two flow rates and seven axial location were investigated. It is shown that the different temperature profiles produce slight differences in the variance and skewness of the temperature signal measured along the axis of the pipe over 20 dias
Nugraheni, L.; Budayasa, I. K.; Suwarsono, S. T.
2018-01-01
The study was designed to discover examine the profile of metacognition of vocational high school student of the Machine Technology program that had high ability and field independent cognitive style in mathematical problem solving. The design of this study was exploratory research with a qualitative approach. This research was conducted at the Machine Technology program of the vocational senior high school. The result revealed that the high-ability student with field independent cognitive style conducted metacognition practices well. That involved the three types of metacognition activities, consisting of planning, monitoring, and evaluating at metacognition level 2 or aware use, 3 or strategic use, 4 or reflective use in mathematical problem solving. The applicability of the metacognition practices conducted by the subject was never at metacognition level 1 or tacit use. This indicated that the participant were already aware, capable of choosing strategies, and able to reflect on their own thinking before, after, or during the process at the time of solving mathematical problems.That was very necessary for the vocational high school student of Machine Technology program.
Quantum brachistochrone problem for a spin-1 system in a magnetic field
Frydryszak, A. M.; Tkachuk, V. M.
2008-01-01
We study the quantum brachistochrone problem for a spin-1 system in a magnetic field of constant absolute value. Such a system gives us the possibility to examine in detail the statement that the state vectors realizing evolution with the minimal time of passage evolve along the subspace spanned by the initial and final state vectors [Carlini , Phys. Rev. Lett. 96, 060503 (2006); Brody and Hook, J. Phys. A 39, L167 (2006)]. Considering an explicit example, we show the existence of a quantum brachistochrone with the minimal possible time; however, the state vector we study leaves the subspace spanned by the initial and final state vectors during evolution. This is the result of our choice of a more constrained Hamiltonian than the one assumed in the general quantum brachistochrone problem. It is worth noting that such an evolution, being more complicated, is time optimal but with larger time than in the general case. This might be important for experiments, where a general Hamiltonian with all the allowed parameters is difficult to implement, but a constrained one, depending on the magnetic field, can be realized. However, for the preconstrained Hamiltonian not all final states are accessible. The present result does not contradict the general statement of the quantum brachistochrone problem, but gives additional insight into possible realization of the time-optimal passage.
Energy Technology Data Exchange (ETDEWEB)
Tupek, Michael R. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
2016-06-30
In recent years there has been a proliferation of modeling techniques for forward predictions of crack propagation in brittle materials, including: phase-field/gradient damage models, peridynamics, cohesive-zone models, and G/XFEM enrichment techniques. However, progress on the corresponding inverse problems has been relatively lacking. Taking advantage of key features of existing modeling approaches, we propose a parabolic regularization of Barenblatt cohesive models which borrows extensively from previous phase-field and gradient damage formulations. An efficient explicit time integration strategy for this type of nonlocal fracture model is then proposed and justified. In addition, we present a C++ computational framework for computing in- put parameter sensitivities efficiently for explicit dynamic problems using the adjoint method. This capability allows for solving inverse problems involving crack propagation to answer interesting engineering questions such as: 1) what is the optimal design topology and material placement for a heterogeneous structure to maximize fracture resistance, 2) what loads must have been applied to a structure for it to have failed in an observed way, 3) what are the existing cracks in a structure given various experimental observations, etc. In this work, we focus on the first of these engineering questions and demonstrate a capability to automatically and efficiently compute optimal designs intended to minimize crack propagation in structures.
The Chamber for Studying Rice Response to Elevated Nighttime Temperature in Field
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Song Chen
2013-01-01
Full Text Available An in situ temperature-controlled field chamber was developed for studying a large population of rice plant under different nighttime temperature treatments while maintaining conditions similar to those in the field during daytime. The system consists of a pipe hoop shed-type chamber with manually removable covers manipulated to provide a natural environment at daytime and a relatively stable and accurate temperature at night. Average air temperatures of 22.4 ± 0.3°C at setting of 22°C, 27.6 ± 0.4°C at 27°C, and 23.8 ± 0.7°C ambient conditions were maintained with the system. No significant horizontal and vertical differences in temperature were found and only slight changes in water temperatures were observed between the chambers and ambient conditions at 36 days after transplanting. A slight variation in CO2 concentration was observed at the end of the treatment during the day, but the 10-μmol CO2 mol−1 difference was too small to alter plant response. The present utilitarian system, which only utilizes an air conditioner/heater, is suitable for studying the effect of nighttime temperature on plant physiological responses with minimal perturbation of other environmental factors. At the same time, it will enable in situ screening of many rice genotypes.
Finite-State Mean-Field Games, Crowd Motion Problems, and its Numerical Methods
Machado Velho, Roberto
2017-09-10
In this dissertation, we present two research projects, namely finite-state mean-field games and the Hughes model for the motion of crowds. In the first part, we describe finite-state mean-field games and some applications to socio-economic sciences. Examples include paradigm shifts in the scientific community and the consumer choice behavior in a free market. The corresponding finite-state mean-field game models are hyperbolic systems of partial differential equations, for which we propose and validate a new numerical method. Next, we consider the dual formulation to two-state mean-field games, and we discuss numerical methods for these problems. We then depict different computational experiments, exhibiting a variety of behaviors, including shock formation, lack of invertibility, and monotonicity loss. We conclude the first part of this dissertation with an investigation of the shock structure for two-state problems. In the second part, we consider a model for the movement of crowds proposed by R. Hughes in [56] and describe a numerical approach to solve it. This model comprises a Fokker-Planck equation coupled with an Eikonal equation with Dirichlet or Neumann data. We first establish a priori estimates for the solutions. Next, we consider radial solutions, and we identify a shock formation mechanism. Subsequently, we illustrate the existence of congestion, the breakdown of the model, and the trend to the equilibrium. We also propose a new numerical method for the solution of Fokker-Planck equations and then to systems of PDEs composed by a Fokker-Planck equation and a potential type equation. Finally, we illustrate the use of the numerical method both to the Hughes model and mean-field games. We also depict cases such as the evacuation of a room and the movement of persons around Kaaba (Saudi Arabia).
Sensing Properties of a Novel Temperature Sensor Based on Field Assisted Thermal Emission
Directory of Open Access Journals (Sweden)
Zhigang Pan
2017-02-01
Full Text Available The existing temperature sensors using carbon nanotubes (CNTs are limited by low sensitivity, complicated processes, or dependence on microscopy to observe the experimental results. Here we report the fabrication and successful testing of an ionization temperature sensor featuring non-self-sustaining discharge. The sharp tips of nanotubes generate high electric fields at relatively low voltages, lowering the work function of electrons emitted by CNTs, and thereby enabling the safe operation of such sensors. Due to the temperature effect on the electron emission of CNTs, the collecting current exhibited an exponential increase with temperature rising from 20 °C to 100 °C. Additionally, a higher temperature coefficient of 0.04 K−1 was obtained at 24 V voltage applied on the extracting electrode, higher than the values of other reported CNT-based temperature sensors. The triple-electrode ionization temperature sensor is easy to fabricate and converts the temperature change directly into an electrical signal. It shows a high temperature coefficient and good application potential.
Sensing Properties of a Novel Temperature Sensor Based on Field Assisted Thermal Emission.
Pan, Zhigang; Zhang, Yong; Cheng, Zhenzhen; Tong, Jiaming; Chen, Qiyu; Zhang, Jianpeng; Zhang, Jiaxiang; Li, Xin; Li, Yunjia
2017-02-27
The existing temperature sensors using carbon nanotubes (CNTs) are limited by low sensitivity, complicated processes, or dependence on microscopy to observe the experimental results. Here we report the fabrication and successful testing of an ionization temperature sensor featuring non-self-sustaining discharge. The sharp tips of nanotubes generate high electric fields at relatively low voltages, lowering the work function of electrons emitted by CNTs, and thereby enabling the safe operation of such sensors. Due to the temperature effect on the electron emission of CNTs, the collecting current exhibited an exponential increase with temperature rising from 20 °C to 100 °C. Additionally, a higher temperature coefficient of 0.04 K -1 was obtained at 24 V voltage applied on the extracting electrode, higher than the values of other reported CNT-based temperature sensors. The triple-electrode ionization temperature sensor is easy to fabricate and converts the temperature change directly into an electrical signal. It shows a high temperature coefficient and good application potential.
Inverse scattering problem for a magnetic field in the Glauber approximation
International Nuclear Information System (INIS)
Bogdanov, I.V.
1985-01-01
New results in the general theory of scattering are obtained. An inverse problem at fixed energy for an axisymmetric magnetic field is formulated and solved within the frames of the quantum-mechanical Glauber approximation. The solution is found in quadratures in the form of an explicit inversion algorithm reproducing a vector potential by the angular dependence of the scattering amplitude. Extreme transitions from the eikonal inversion method to the classical and Born ones are investigated. Integral and differential equations are derived for the eikonal amplitude that ensure the real value of the vector potential and its energy independence. Magnetoelectric analogies the existence of equivalent axisymmetric electric and magnetic fields scattering charged particles in the same manner both in the Glauber and Born approximation are established. The mentioned analogies permit to simulate ion-potential scattering by potential one that is of interest from the practical viewpoint. Three-dimensional (excentral) eikonal inverse problems for the electric and magnetic fields are discussed. The results of the paper can be used in electron optics
Directory of Open Access Journals (Sweden)
Christine Yao-Yun Chang
2015-03-01
Full Text Available Climate change will increase autumn air temperature, while photoperiod decrease will remain unaffected. We assessed the effect of increased autumn air temperature on timing and development of cold acclimation and freezing resistance in Eastern white pine (EWP, Pinus strobus under field conditions. For this purpose we simulated projected warmer temperatures for southern Ontario in a Temperature Free-Air-Controlled Enhancement (T-FACE experiment and exposed EWP seedlings to ambient (Control or elevated temperature (ET, +1.5°C/+3°C during day/night. Photosynthetic gas exchange, chlorophyll fluorescence, photoprotective pigments, leaf non-structural carbohydrates (NSC, and cold hardiness were assessed over two consecutive autumns. Nighttime temperature below 10°C and photoperiod below 12h initiated downregulation of assimilation in both treatments. When temperature further decreased to 0°C and photoperiod became shorter than 10h, downregulation of the light reactions and upregulation of photoprotective mechanisms occurred in both treatments. While ET seedlings did not delay the timing of the downregulation of assimilation, stomatal conductance in ET seedlings was decreased by 20-30% between August and early October. In both treatments leaf NSC composition changed considerably during autumn but differences between Control and ET seedlings were not significant. Similarly, development of freezing resistance was induced by exposure to low temperature during autumn, but the timing was not delayed in ET seedlings compared to Control seedlings. Our results indicate that EWP is most sensitive to temperature changes during October and November when downregulation of photosynthesis , enhancement of photoprotection, synthesis of cold-associated NSCs and development of freezing resistance occur. However, we also conclude that the timing of the development of freezing resistance in EWP seedlings is not affected by moderate temperature increases used in our
Sala, Juan E.; Pisoni, Juan P.; Quintana, Flavio
2017-04-01
Temperature is a primary determinant of biogeographic patterns and ecosystem processes. Standard techniques to study the ocean temperature in situ are, however, particularly limited by their time and spatial coverage, problems which might be partially mitigated by using marine top predators as biological platforms for oceanographic sampling. We used small archival tags deployed on 33 Magellanic penguins (Spheniscus magellanicus), and obtained 21,070 geo-localized profiles of water temperature, during late spring of 2008, 2011, 2012 and 2013; in a region of the North Patagonian Sea with limited oceanographic records in situ. We compared our in situ data of sea surface temperature (SST) with those available from satellite remote sensing; to describe the three-dimensional temperature fields around the area of influence of two important tidal frontal systems; and to study the inter-annual variation in the three-dimensional temperature fields. There was a strong positive relationship between satellite- and animal-derived SST data although there was an overestimation by remote-sensing by a maximum difference of +2 °C. Little inter-annual variability in the 3-dimensional temperature fields was found, with the exception of 2012 (and to a lesser extent in 2013) where the SST was significantly higher. In 2013, we found weak stratification in a region which was unexpected. In addition, during the same year, a warm small-scale vortex is indicated by the animal-derived temperature data. This allowed us to describe and better understand the dynamics of the water masses, which, so far, have been mainly studied by remote sensors and numerical models. Our results highlight again the potential of using marine top predators as biological platforms to collect oceanographic data, which will enhance and accelerate studies on the Southwest Atlantic Ocean. In a changing world, threatened by climate change, it is urgent to fill information gaps on the coupled ocean-atmosphere system
Dowling, N A; Merkouris, S S; Lorains, F K
2016-07-01
Despite significant psychiatric comorbidity in problem gambling, there is little evidence on which to base treatment recommendations for subpopulations of problem gamblers with comorbid psychiatric disorders. This mini-review draws on two separate systematic searches to identify possible interventions for comorbid problem gambling and psychiatric disorders, highlight the gaps in the currently available evidence base, and stimulate further research in this area. In this mini-review, only 21 studies that have conducted post-hoc analyses to explore the influence of psychiatric disorders or problem gambling subtypes on gambling outcomes from different types of treatment were identified. The findings of these studies suggest that most gambling treatments are not contraindicated by psychiatric disorders. Moreover, only 6 randomized studies comparing the efficacy of interventions targeted towards specific comorbidity subgroups with a control/comparison group were identified. The results of these studies provide preliminary evidence for modified dialectical behavior therapy for comorbid substance use, the addition of naltrexone to cognitive-behavioral therapy (CBT) for comorbid alcohol use problems, and the addition of N-acetylcysteine to tobacco support programs and imaginal desensitisation/motivational interviewing for comorbid nicotine dependence. They also suggest that lithium for comorbid bipolar disorder, escitalopram for comorbid anxiety disorders, and the addition of CBT to standard drug treatment for comorbid schizophrenia may be effective. Future research evaluating interventions sequenced according to disorder severity or the functional relationship between the gambling behavior and comorbid symptomatology, identifying psychiatric disorders as moderators of the efficacy of problem gambling interventions, and evaluating interventions matched to client comorbidity could advance this immature field of study. Copyright © 2016 Elsevier Ltd. All rights reserved.
Directory of Open Access Journals (Sweden)
Qiu Hongbo
2017-06-01
Full Text Available At present, the drivers with different control methods are used in most of permanent magnet synchronous motors (PMSM. A current outputted by a driver contains a large number of harmonics that will cause the PMSM torque ripple, winding heating and rotor temperature rise too large and so on. In this paper, in order to determine the influence of the current harmonics on the motor performance, different harmonic currents were injected into the motor armature. Firstly, in order to study the influence of the current harmonic on the motor magnetic field, a novel decoupling method of the motor magnetic field was proposed. On this basis, the difference of harmonic content in an air gap magnetic field was studied, and the influence of a harmonic current on the air gap flux density was obtained. Secondly, by comparing the fluctuation of the motor torque in the fundamental and different harmonic currents, the influence of harmonic on a motor torque ripple was determined. Then, the influence of different current harmonics on the eddy current loss of the motor was compared and analyzed, and the influence of the drive harmonic on the eddy current loss was obtained. Finally, by using a finite element method (FEM, the motor temperature distribution with different harmonics was obtained.
Casimir problem of spherical dielectrics: quantum statistical and field theoretical approaches.
Høye, J S; Brevik, I; Aarseth, J B
2001-05-01
The Casimir free energy for a system of two dielectric concentric nonmagnetic spherical bodies is calculated with use of a quantum statistical mechanical method, at arbitrary temperature. By means of this rather novel method, which turns out to be quite powerful (we have shown this to be true in other situations also), we consider first an explicit evaluation of the free energy for the static case, corresponding to zero Matsubara frequency (n=0). Thereafter, the time-dependent case is examined. For comparison we consider the calculation of the free energy with use of the more commonly known field theoretical method, assuming for simplicity metallic boundary surfaces.
Basic Properties and Problem Fields of Scientific-Innovation Space of the Region
Directory of Open Access Journals (Sweden)
Alexey Aleksandrovich Rumyantsev
2013-06-01
Full Text Available Increasing scale of the scientific-innovative activity in administrative-territorial units, complicating structure of the regional scientific-innovative complexes and development of inter-regional horizontal and vertical ties expand the space of the scientific and innovation activity research of which primarily involves the development of theoretical and methodological provisions. Basing on the philosophical category «space», the paper describes main properties of the scientific-innovative space of the region and the factors causing them. The author identified problem fields as the direction of possible transformation of scientific-innovative space of the region. The analysis allowed defining some features of the scientific and innovation space and problems of development. The obtained results show the feasibility of study of the scientific-innovative activity in the spatial dimension
Energy Technology Data Exchange (ETDEWEB)
Balakirev, Fedor F [Los Alamos National Laboratory; Migliori, A [MPA-NHMFL; Riggs, S [NHMFL-FSU; Hunte, F [NHMFL-FSU; Gurevich, A [NHMFL-FSU; Larbalestier, D [NHMFL-FSU; Boebinger, G [NHMFL-FSU; Jaroszynski, J [NHMFL-FSU; Ren, Z [CHINA; Lu, W [CHINA; Yang, J [CHINA; Shen, X [CHINA; Dong, X [CHINA; Zhao, Z [CHINA; Jin, R [ORNL; Sefat, A [ORNL; Mcguire, M [ORNL; Sales, B [ORNL; Christen, D [ORNL; Mandrus, D [ORNL
2008-01-01
We compare magnetotransport of the three iron-arsenide-based compounds ReFeAsO (Re=La, Sm, Nd) in very high DC and pulsed magnetic fields up to 45 and 54 T, respectively. Each sample studied exhibits a superconducting transition temperature near the maximum reported to date for that particular compound. While high magnetic fields do not suppress the superconducting state appreciably, the resistivity, Hall coefficient, and critical magnetic fields, taken together, suggest that the phenomenology and superconducting parameters of the oxypnictide superconductors bridges the gap between MgB{sub 2} and YBCO.
Experimental study of thermoacoustic effects on a single plate. Pt. 1. Temperature fields
Energy Technology Data Exchange (ETDEWEB)
Wetzel, M.; Herman, C. [Johns Hopkins Univ., Baltimore, MD (USA). Dept. of Mech. Eng.
2000-03-01
The thermal interaction between a heated solid plate and the acoustically driven working fluid was investigated by visualizing and quantifying the temperature fields in the neighbourhood of the solid plate. A combination of holographic interferometry and high-speed cinematography was applied in the measurements. A better knowledge of these temperature fields is essential to develop systematic design methodologies for heat exchangers in oscillatory flows. The difference between heat transfer in oscillatory flows with zero mean velocity and steady-state flows is demonstrated in the paper. Instead of heat transfer from a heated solid surface to the colder bulk fluid, the visualized temperature fields indicated that heat was transferred from the working fluid into the stack plate at the edge of the plate. In the experiments, the thermoacoustic effect was visualized through the temperature measurements. A novel evaluation procedure that accounts for the influence of the acoustic pressure variations on the refractive index was applied to accurately reconstruct the high-speed, two-dimensional oscillating temperature distributions. (orig.)
A broadband microwave Corbino spectrometer at ³He temperatures and high magnetic fields.
Liu, Wei; Pan, LiDong; Armitage, N P
2014-09-01
We present the technical details of a broadband microwave spectrometer for measuring the complex conductance of thin films covering the range from 50 MHz up to 16 GHz in the temperature range 300 mK-6 K and at applied magnetic fields up to 8 T. We measure the complex reflection from a sample terminating a coaxial transmission line and calibrate the signals with three standards with known reflection coefficients. Thermal isolation of the heat load from the inner conductor is accomplished by including a section of NbTi superconducting cable (transition temperature around 8-9 K) and hermetic seal glass bead adapters. This enables us to stabilize the base temperature of the sample stage at 300 mK. However, the inclusion of this superconducting cable complicates the calibration procedure. We document the effects of the superconducting cable on our calibration procedure and the effects of applied magnetic fields and how we control the temperature with great repeatability for each measurement. We have successfully extracted reliable data in this frequency, temperature, and field range for thin superconducting films and highly resistive graphene samples.
Directory of Open Access Journals (Sweden)
Marković Miloš D.
2016-01-01
Full Text Available The Research in this paper considered the temperatures fields as the consequently influenced effects appeared by plastic deformation, in the explosively forming process aimed to design Explosively Formed Projectiles (henceforth EFP. As the special payloads of the missiles, used projectiles are packaged as the metal liners, joined with explosive charges, to design explosive propulsion effect. Their final form and velocity during shaping depend on distributed temperatures in explosively driven plastic deformation process. Developed simulation model consider forming process without metal cover of explosive charge, in aim to discover liner’s dynamical correlations of effective plastic strains and temperatures in the unconstrained detonation environment made by payload construction. The temperature fields of the liner’s copper material are considered in time, as the consequence of strain/stress displacements driven by explosion environmental thermodynamically fields of pressures and temperatures. Achieved final velocities and mass loses as the expected EFP performances are estimated regarding their dynamical shaping and thermal gradients behavior vs. effective plastic strains. Performances and parameters are presented vs. process time, numerically simulated by the Autodyne software package. [Projekat Ministarstva nauke Republike Srbije, br. III-47029
A surface acoustic wave passive and wireless sensor for magnetic fields, temperature, and humidity
Li, Bodong
2015-01-01
In this paper, we report an integrated single-chip surface acoustic wave sensor with the capability of measuring magnetic field, temperature, and humidity. The sensor is fabricated using a thermally sensitive LiNbO3 substrate, a humidity sensitive hydrogel coating, and a magnetic field sensitive impedance load. The sensor response to individually and simultaneously changing magnetic field, temperature and humidity is characterized by connecting a network analyzer directly to the sensor. Analytical models for each measurand are derived and used to compensate noise due to cross sensitivities. The results show that all three measurands can be monitored in parallel with sensitivities of 75 ppm/°C, 0.13 dB/%R.H. (at 50%R.H.), 0.18 dB/Oe and resolutions of 0.1 °C, 0.4%R.H., 1 Oe for temperature, humidity and magnetic field, respectively. A passive wireless measurement is also conducted on a current line using, which shows the sensors capability to measure both temperature and current signals simultaneously.
Electric field and temperature in a target induced by a plasma jet imaged using Mueller polarimetry
Slikboer, Elmar; Sobota, Ana; Guaitella, Olivier; Garcia-Caurel, Enric
2018-01-01
Mueller polarimetry is used to investigate the behavior of an electro optic target (BSO crystal) under exposure of guided ionization waves produced by an atmospheric pressure plasma jet. For the first time, this optical technique is time resolved to obtain the complete Mueller matrix of the sample right before and after the impact of the discharges. By analyzing the induced birefringence, the spatial profiles and local values are obtained of both the electric field and temperature in the sample. Electric fields are generated due to deposited surface charges and a temperature profile is present, due to the heat transferred by the plasma jet. The study of electric field dynamics and local temperature increase at the target, due to the plasma jet is important for biomedical applications, as well as surface functionalization. This work shows how Mueller polarimetry can be used as a novel diagnostic to simultaneously acquire the spatial distribution and local values of both the electric field and temperature, by coupling the external source of anisotropy to the measured induced birefringence via the symmetry point group of the examined material.
CSIR Research Space (South Africa)
Mudau, AE
2010-11-01
Full Text Available blackbody located 450 m away in the field. In this paper we present the temperatures measured on the blackbody using Jade infrared imager, namely medium wave infrared (MWIR) imager operating in the 3-5 micron, band and a Fluke 574 precision handheld infrared...
Athletic field paint color impacts transpiration and canopy temperature in bermudagrass
Athletic field paints have varying impacts on turfgrass health which have been linked to their ability to alter photosynthetically active radiation (PAR) and photosynthesis based on color. It was further hypothesized they may also alter transpiration and canopy temperature by disrupting gas exchange...
Field tests reveal genetic variation for performance atlow temperatures in Drosophila melanogaster
DEFF Research Database (Denmark)
Overgaard, Johannes; Sørensen, Jesper Givskov; Jensen, Louise Toft
2010-01-01
investigated a population of Drosophila melanogaster for performance at low temperature conditions in the field using release recapture assays and in the laboratory using standard cold resistance assays. The aim of the study was to get a better understanding of the nature and underlying mechanisms of the trait...
Extension of PIV for measuring granular temperature field in dense fluidized beds.
Dijkhuizen, W.; Bokkers, G.A.; Deen, N.G.; van Sint Annaland, M.; Kuipers, J.A.M.
2007-01-01
In this work a particle image velocimetry (PIV) technique has been extended to enable the simultaneous measurement of the instantaneous velocity and granular temperature fields. The PIV algorithm has been specifically optimized for dense granular systems and has been thoroughly tested with
Inverse problem for the mean-field monomer-dimer model with attractive interaction
International Nuclear Information System (INIS)
Contucci, Pierluigi; Luzi, Rachele; Vernia, Cecilia
2017-01-01
The inverse problem method is tested for a class of monomer-dimer statistical mechanics models that contain also an attractive potential and display a mean-field critical point at a boundary of a coexistence line. The inversion is obtained by analytically identifying the parameters in terms of the correlation functions and via the maximum-likelihood method. The precision is tested in the whole phase space and, when close to the coexistence line, the algorithm is used together with a clustering method to take care of the underlying possible ambiguity of the inversion. (paper)
The Riemann monodromy problem and conformal field theories on the torus
International Nuclear Information System (INIS)
Blok, B.
1989-01-01
We generalize the Riemann monodromy problem approach to the investigation of conformal field theories on a higher genus Riemann surface. In particular, we discuss the associated differential equations for the correlators. This approach reveals the connection between the s-point correlation function on a genus-g Riemann surface and the (s-2)-point function on a genus-(g+1) Riemann surface. For the case of the torus we show how this approach gives the Samir, Mukhi and Sen differential equations. (orig.)
Inverse problem for the mean-field monomer-dimer model with attractive interaction
Contucci, Pierluigi; Luzi, Rachele; Vernia, Cecilia
2017-05-01
The inverse problem method is tested for a class of monomer-dimer statistical mechanics models that contain also an attractive potential and display a mean-field critical point at a boundary of a coexistence line. The inversion is obtained by analytically identifying the parameters in terms of the correlation functions and via the maximum-likelihood method. The precision is tested in the whole phase space and, when close to the coexistence line, the algorithm is used together with a clustering method to take care of the underlying possible ambiguity of the inversion.
Numerical simulation of velocity and temperature fields in natural circulation loop
Sukomel, L. A.; Kaban’kov, O. N.
2017-11-01
Low flow natural circulation regimes are realized in many practical applications and the existence of the reliable engineering and design calculation methods of flows driven exclusively by buoyancy forces is an actual problem. In particular it is important for the analysis of start up regimes of passive safety systems of nuclear power plants. In spite of a long year investigations of natural circulation loops no suitable predicting recommendations for heat transfer and friction for the above regimes have been proposed for engineering practice and correlations for forced flow are commonly used which considerably overpredicts the real flow velocities. The 2D numerical simulation of velocity and temperature fields in circular tubes for laminar flow natural circulation with reference to the laboratory experimental loop has been carried out. The results were compared with the 1D modified model and experimental data obtained on the above loop. The 1D modified model was still based on forced flow correlations, but in these correlations the physical properties variability and the existence of thermal and hydrodynamic entrance regions are taken into account. The comparison of 2D simulation, 1D model calculations and the experimental data showed that even subject to influence of liquid properties variability and entrance regions on heat transfer and friction the use of 1D model with forced flow correlations do not improve the accuracy of calculations. In general, according to 2D numerical simulation the wall shear stresses are mainly affected by the change of wall velocity gradient due to practically continuous velocity profiles deformation along the whole heated zone. The form of velocity profiles and the extent of their deformation in its turn depend upon the wall heat flux density and the hydraulic diameter.
The stochastic mechanics of fields in a general relativistic context: Problems and perspectives
International Nuclear Information System (INIS)
De Falco, D.
1987-01-01
The problem of a formulation of Nelson's stochastic mechanics of scalar fields in the context of general relativity is considered. The simple example of the scalar field in the Wightman vacuum state on the Rindler wedge is examined, the stochastic counterpart of the Fulling ambiguity of canonical quantization is formulated, and the role of the stochastic quantization is formulated, and the role of the stochastic mechanics of thermal mixtures, as formulated by Guerra and Loffredo, is analyzed in the solution, in the spirit of Davies and Unruh, of the above ambiguity. An overall picture emerges which, both in the explicit example considered here and in its straightforward generalizations to static submanifolds of more general space-times, confirms Smolin's point of view that stochastic quantization is a very natural conceptual frame in which to study the general non covariance of the distinction between quantum and thermal fluctuations. (orig.)
Dual origin of room temperature sub-terahertz photoresponse in graphene field effect transistors
Bandurin, D. A.; Gayduchenko, I.; Cao, Y.; Moskotin, M.; Principi, A.; Grigorieva, I. V.; Goltsman, G.; Fedorov, G.; Svintsov, D.
2018-04-01
Graphene is considered as a promising platform for detectors of high-frequency radiation up to the terahertz (THz) range due to its superior electron mobility. Previously, it has been shown that graphene field effect transistors (FETs) exhibit room temperature broadband photoresponse to incoming THz radiation, thanks to the thermoelectric and/or plasma wave rectification. Both effects exhibit similar functional dependences on the gate voltage, and therefore, it was difficult to disentangle these contributions in previous studies. In this letter, we report on combined experimental and theoretical studies of sub-THz response in graphene field-effect transistors analyzed at different temperatures. This temperature-dependent study allowed us to reveal the role of the photo-thermoelectric effect, p-n junction rectification, and plasmonic rectification in the sub-THz photoresponse of graphene FETs.
International Nuclear Information System (INIS)
Eab, C. H.; Lim, S. C.; Teo, L. P.
2007-01-01
This paper studies the Casimir effect due to fractional massless Klein-Gordon field confined to parallel plates. A new kind of boundary condition called fractional Neumann condition which involves vanishing fractional derivatives of the field is introduced. The fractional Neumann condition allows the interpolation of Dirichlet and Neumann conditions imposed on the two plates. There exists a transition value in the difference between the orders of the fractional Neumann conditions for which the Casimir force changes from attractive to repulsive. Low and high temperature limits of Casimir energy and pressure are obtained. For sufficiently high temperature, these quantities are dominated by terms independent of the boundary conditions. Finally, validity of the temperature inversion symmetry for various boundary conditions is discussed
Energy Technology Data Exchange (ETDEWEB)
Jung, Hyeyun [Department of Chemistry, Brown University, Providence, RI 02912 (United States); Gusev, Vitalyi E. [Universite du Maine, av. Messiaen, 72085 Le Mans Cedex 09 (France); Baek, Hyoungsu [Department of Applied Mathematics, Brown University, Providence, RI 02912 (United States); Wang, Yaqi [Department of Chemistry, Brown University, Providence, RI 02912 (United States); Diebold, Gerald J., E-mail: Gerald_Diebold@Brown.ed [Department of Chemistry, Brown University, Providence, RI 02912 (United States)
2011-05-09
The Ludwig-Soret effect, also known as thermal diffusion, describes the separation of mixtures in the presence of a temperature gradient. Here, a solution to the nonlinear differential equation that describes the motion of components of a binary mixture in a linear temperature field is given for long times, when the distribution of the components in space becomes time independent. A new experimental method based on the use of a scanning confocal microscope to monitor the spatial distribution of fluorescence from fluorescein labelled nanoparticles in water in a linear temperature field is described. - Highlights: We give a steady state solution to the Ludwig-Soret equation. We give a method of finding Soret parameters based on terminal spatial distributions. We introduce a new experimental method based on probing with a confocal microscope. The method is applied to studying fluorescent nanoparticles suspended in water.
Energy Technology Data Exchange (ETDEWEB)
Hauet, T.; Gunther, C.M.; Pfau, B.; Eisebitt, S.; Fischer, P.; Rick, R. L.; Thiele, J.-U.; Hellwig, O.; Schabes, M.E.
2007-07-01
Dipolar interactions in a soft/Pd/hard [CoNi/Pd]{sub 30}/Pd/[Co/Pd]{sub 20} multilayer system, where a thick Pd layer between two ferromagnetic units prevents direct exchange coupling, are directly revealed by combining magnetometry and state-of-the-art layer resolving soft x-ray imaging techniques with sub-100-nm spatial resolution. The domains forming in the soft layer during external magnetic field reversal are found to match the domains previously trapped in the hard layer. The low Curie temperature of the soft layer allows varying its intrinsic parameters via temperature and thus studying the competition with dipolar fields due to the domains in the hard layer. Micromagnetic simulations elucidate the role of [CoNi/Pd] magnetization, exchange, and anisotropy in the duplication process. Finally, thermally driven domain replication in remanence during temperature cycling is demonstrated.
Temperature and velocity measurement fields of fluids using a schlieren system.
Martínez-González, Adrian; Guerrero-Viramontes, J A; Moreno-Hernández, David
2012-06-01
This paper proposes a combined method for two-dimensional temperature and velocity measurements in liquid and gas flow using a schlieren system. Temperature measurements are made by relating the intensity level of each pixel in a schlieren image to the corresponding knife-edge position measured at the exit focal plane of the schlieren system. The same schlieren images were also used to measure the velocity of the fluid flow. The measurement is made by using particle image velocimetry (PIV). The PIV software used in this work analyzes motion between consecutive schlieren frames to obtain velocity fields. The proposed technique was applied to measure the temperature and velocity fields in the natural convection of water provoked by a heated rectangular plate.
Capobianco, Christopher J.; Jones, John H.; Drake, Michael J.
1993-01-01
Low-temperature metal-silicate partition coefficients are extrapolated to magma ocean temperatures. If the low-temperature chemistry data is found to be applicable at high temperatures, an important assumption, then the results indicate that high temperature alone cannot account for the excess siderophile element problem of the upper mantle. For most elements, a rise in temperature will result in a modest increase in siderophile behavior if an iron-wuestite redox buffer is paralleled. However, long-range extrapolation of experimental data is hazardous when the data contains even modest experimental errors. For a given element, extrapolated high-temperature partition coefficients can differ by orders of magnitude, even when data from independent studies is consistent within quoted errors. In order to accurately assess siderophile element behavior in a magma ocean, it will be necessary to obtain direct experimental measurements for at least some of the siderophile elements.
Directory of Open Access Journals (Sweden)
Gongfa Li
2015-04-01
Full Text Available With the development of metallurgical industry and the improvement of continuous casting technology, the processing properties of casting technology equipment are being paid more attention. Ladle is one of the most representatives of the furnace equipment; higher requirements of ladle are put forward in response to the call for national energy-saving and emission reduction. According to the requirements of actual operator and working condition, a lining structure of a new type of ladle with nanometer adiabatic material is put forward. Based on heat transfer theory and finite element technology, the three-dimensional finite element model of a new type of ladle is established. Temperature field and stress field of the new type of ladle with the nanometer adiabatic material in lining structure after baking are analyzed. The results indicate that the distributions of temperature and thermal stress level of working layer, permanent layer, and nanometer heat insulating layer are similar, and they are in the permissible stress and temperature range of each material for the new type of ladle. Especially heat preservation effect of nanometer adiabatic material is excellent. Furthermore, the maximum temperature of shell for the new type of ladle drops to 114°C than the traditional ladle, and the maximum stress of shell for the new type of ladle is lower than the traditional ladle, that is, 114 MPa. It can provide reliable theory for energy-saving and emission reduction of metallurgy industry, which also points out the right direction for the future development of the iron and steel industry.
International Nuclear Information System (INIS)
Zhou, Dayu; Guan, Yan; Vopson, Melvin M.; Xu, Jin; Liang, Hailong; Cao, Fei; Dong, Xianlin; Mueller, Johannes; Schenk, Tony; Schroeder, Uwe
2015-01-01
HfO 2 -based binary lead-free ferroelectrics show promising properties for non-volatile memory applications, providing that their polarization reversal behavior is fully understood. In this work, temperature-dependent polarization hysteresis measured over a wide applied field range has been investigated for Si-doped HfO 2 ferroelectric thin films. Our study indicates that in the low and medium electric field regimes (E < twofold coercive field, 2E c ), the reversal process is dominated by the thermal activation on domain wall motion and domain nucleation; while in the high-field regime (E > 2E c ), a non-equilibrium nucleation-limited-switching mechanism dominates the reversal process. The optimum field for ferroelectric random access memory (FeRAM) applications was determined to be around 2.0 MV/cm, which translates into a 2.0 V potential applied across the 10 nm thick films
Einecke, S.; Schulz, C.; Sick, V.
2000-11-01
A technique based on planar laser-induced fluorescence of 3-pentanone, for measurements of absolute concentration, temperature and fuel/air equivalence ratios in turbulent, high-pressure combustion systems such as an internal combustion engine is presented. Quasi-simultaneous excitation with 248 nm and 308 nm of 3-pentanone that is used as a fluorescence tracer doped to iso-octane, yields pairs of strongly temperature-dependent fluorescence images. Previous investigations have resulted in information on temperature and pressure dependence of absorption cross-sections and fluorescence quantum yields. Using these data the ratio of corresponding fluorescence images can be converted to temperature images. Instantaneous temperature distribution fields in the compression stroke and in the unburned end-gas of an SI engine were measured. The temperature fields obtained from the two-line technique are used to correct the original tracer-LIF images in order to evaluate quantitative fuel distributions in terms of number densities and fuel/air equivalence ratio.
Simulation on Temperature Field of Radiofrequency Lesions System Based on Finite Element Method
International Nuclear Information System (INIS)
Xiao, D; Qian, Z; Li, W; Qian, L
2011-01-01
This paper mainly describes the way to get the volume model of damaged region according to the simulation on temperature field of radiofrequency ablation lesion system in curing Parkinson's disease based on finite element method. This volume model reflects, to some degree, the shape and size of the damaged tissue during the treatment with all tendencies in different time or core temperature. By using Pennes equation as heat conduction equation of radiofrequency ablation of biological tissue, the author obtains the temperature distribution field of biological tissue in the method of finite element for solving equations. In order to establish damage models at temperature points of 60 deg. C, 65 deg. C, 70 deg. C, 75 deg. C, 80 deg. C, 85 deg. C and 90 deg. C while the time points are 30s, 60s, 90s and 120s, Parkinson's disease model of nuclei is reduced to uniform, infinite model with RF pin at the origin. Theoretical simulations of these models are displayed, focusing on a variety of conditions about the effective lesion size on horizontal and vertical. The results show the binary complete quadratic non-linear joint temperature-time models of the maximum damage diameter and maximum height. The models can comprehensively reflect the degeneration of target tissue caused by radio frequency temperature and duration. This lay the foundation for accurately monitor of clinical RF treatment of Parkinson's disease in the future.
International Nuclear Information System (INIS)
Hernandez, O.
1997-01-01
We have studied with neutron scattering techniques betaine calcium chloride dihydrate (BCCD), a dielectric aperiodic crystal which displays a Devil's staircase type phase diagram made up of several incommensurate and commensurate phases, having a range of stability very sensitive to temperature, electric field and hydrostatic pressure. We have measured a global hysteresis of δ(T) of about 2-3 K in the two incommensurate phases. A structural study of the modulated commensurate phases 1/4 and 1/5 allows us to evidence that the atomic modulation functions are anharmonic. The relevance of the modelization of the modulated structure by polar Ising pseudo-spins is then directly established. On the basis of group theory calculation in the four dimensional super-space, we interpret this anharmonic modulation as a soliton regime with respect to the lowest-temperature non modulated ferroelectric phase. The continuous character of the transition to the lowest-temperature non modulated phase and the diffuse scattering observed in this phase are accounted for the presence of ferroelectric domains separated by discommensurations. Furthermore, we have shown that X-rays induce in BCCD a strong variation with time of irradiation of the intensity of satellite peaks, and more specifically for third order ones. This is why the 'X-rays' structural model is found more harmonic than the 'neutron' one. Under electric field applied along the vector b axis, we confirm that commensurate phases with δ = even/odd are favoured and hence are polar along this direction. We have evidenced at 10 kV / cm two new higher order commensurate phases in the phase INC2, corroborating the idea of a 'complete' Devil's air-case phase diagram. A phenomenon of generalized coexistence of phases occurs above 5 kV / cm. We have characterized at high field phase transitions between 'coexisting' phases, which are distinguishable from classical lock-in transitions. Under hydrostatic pressure, our results contradict
Siswono, T. Y. E.; Kohar, A. W.; Rosyidi, A. H.; Hartono, S.; Masriyah
2018-01-01
Designing problem like in PISA is known as a challenging activity for teachers particularly as the use of authentic context within that type of problem. This paper aims to describe the experiences of secondary mathematics teachers in designing PISA-like problems within an innovative training program focusing on building teachers’ understanding on the concept of mathematical literacy. The teachers were engaged in a set of problem-solving and problem-posing activities using PISA-based problem within indoor and outdoor field experiences. Within indoor field experience, the teachers worked collaboratively in groups on designing PISA-like problems with a given context through problem generation and reformulation techniques. Within outdoor field experience, they worked on designing PISA-like problems with self-chosen context from the place where the outdoor field experience took place. Our analysis indicates that there were improvements on the PISA-like problems designed by teachers based on its level use of context from indoor to outdoor experience. Also, the teachers were relatively successful with creating appropriate and motivating contexts by harnessing a variety of context consisting of personal, occupational, societal, and scientific contexts. However, they still experienced difficulties in turning these contexts into an appropriate problem satisfying PISA framework such as regarding authenticity of context use, language structure, and PISA task profile.
Smoleński, T.; Kazimierczuk, T.; Goryca, M.; Molas, M. R.; Nogajewski, K.; Faugeras, C.; Potemski, M.; Kossacki, P.
2018-01-01
Optical orientation of localized/bound excitons is shown to be effectively enhanced by the application of magnetic fields as low as 20 mT in monolayer WS2. At low temperatures, the evolution of the polarization degree of different emission lines of monolayer WS2 with increasing magnetic fields is analyzed and compared to similar results obtained on a WSe2 monolayer. We study the temperature dependence of this effect up to T=60 K for both materials, focusing on the dynamics of the valley pseudospin relaxation. A rate equation model is used to analyze our data and from the analysis of the width of the polarization dip in magnetic field we conclude that the competition between the dark exciton pseudospin relaxation and the decay of the dark exciton population into the localized states are rather different in these two materials which are representative of the two extreme cases for the ratio of relaxation rate and depolarization rate.
Yin, Shengyong; Miao, Xudong; Zhang, Xueming; Chen, Xinhua; Wen, Hao
2018-02-01
Nanosecond pulsed electric field (nsPEF) is a novel non-thermal tumor ablation technique. However, how nsPEF affect cell physiology at different environmental temperature is still kept unknown. But this issue is of critical clinical practice relevance. This work aim to investigate how nsPEF treated cancer cells react to different environmental temperatures (0, 4, 25, and 37°C). Their cell viability, apoptosis, mitochondrial membrane potential, and reactive oxygen species (ROS) were examined. Lower temperature resulted in higher apoptosis rate, decreased mitochondria membrane potential, and increased ROS levels. Sucrose and N-acetylcysteine (NAC) pre-incubation inhibit ROS generation and increase cell survival, protecting nsPEF-treated cells from low temperature-caused cell death. This work provides an experimental basis for hypothermia and fluid transfusion during nsPEF ablation with anesthesia. © 2017 Wiley Periodicals, Inc.
Cosmological dynamics of D-BIonic and DBI scalar field and coincidence problem of dark energy
Panpanich, Sirachak; Maeda, Kei-ichi; Mizuno, Shuntaro
2017-05-01
We study the cosmological dynamics of a D-BIonic and Dirac-Born-Infeld scalar field, which is coupled to matter fluid. For the exponential potential and the exponential couplings, we find a new analytic scaling solution yielding the accelerated expansion of the Universe. Since it is shown to be an attractor for some range of the coupling parameters, the density parameter of matter fluid can be the observed value, as in the coupled quintessence with a canonical scalar field. Contrary to the usual coupled quintessence, where the value of the matter coupling giving the observed density parameter is too large to satisfy the observational constraint from the cosmic microwave background, we show that the D-BIonic theory can give a similar solution with a much smaller value of matter coupling. As a result, together with the fact that the D-BIonic theory has a screening mechanism, the D-BIonic theory can solve the so-called coincidence problem as well as the dark energy problem.
New approaches of the potential field for QPSO algorithm applied to nuclear reactor reload problem
International Nuclear Information System (INIS)
Nicolau, Andressa dos Santos; Schirru, Roberto
2015-01-01
Recently quantum-inspired version of the Particle Swarm Optimization (PSO) algorithm, Quantum Particle Swarm Optimization (QPSO) was proposed. The QPSO algorithm permits all particles to have a quantum behavior, where some sort of 'quantum motion' is imposed in the search process. When the QPSO is tested against a set of benchmarking functions, it showed superior performances as compared to classical PSO. The QPSO outperforms the classical one most of the time in convergence speed and achieves better levels for the fitness functions. The great advantage of QPSO algorithm is that it uses only one parameter control. The critical step or QPSO algorithm is the choice of suitable attractive potential field that can guarantee bound states for the particles moving in the quantum environment. In this article, one version of QPSO algorithm was tested with two types of potential well: delta-potential well harmonic oscillator. The main goal of this study is to show with of the potential field is the most suitable for use in QPSO in a solution of the Nuclear Reactor Reload Optimization Problem, especially in the cycle 7 of a Brazilian Nuclear Power Plant. All result were compared with the performance of its classical counterpart of the literature and shows that QPSO algorithm are well situated among the best alternatives for dealing with hard optimization problems, such as NRROP. (author)
An investigation of methods for neutron dose measurement in high temperature irradiation fields
Energy Technology Data Exchange (ETDEWEB)
Kosako, Toshisou; Sugiura, Nobuyuki [Tokyo Univ. (Japan); Kudo, Kazuhiko [Kyushu Univ., Fukuoka (Japan)] [and others
2000-10-01
The Japan Atomic Energy Research Institute (JAERI) has been conducting the innovative basic research on high temperature since 1994, which is a series of high temperature irradiation studies using the High Temperature Engineering Test Reactor (HTTR). 'The Task Group for Evaluation of Irradiation Dose under High Temperature Radiation' was founded in the HTTR Utilization Research Committee, which is the promoting body of the innovative basic research. The present report is a summary of investigation which has been made by the Task Group on the present status and subjects of research and development of neutron detectors in high temperature irradiation fields, in view of contributing to high temperature irradiation research using the HTTR. Detectors investigated here in the domestic survey are the following five kinds of in-core detectors: 1) small fission counter, 2) small fission chamber, 3) self-powered detector, 4) activation detector, and 5) optical fiber. In addition, the research and development status in Russia has been investigated. The present report will also be useful as nuclear instrumentation of high temperature gas-cooled reactors. (author)
Dynamic temperature fields under Mars landing sites and implications for supporting microbial life.
Ulrich, Richard; Kral, Tim; Chevrier, Vincent; Pilgrim, Robert; Roe, Larry
2010-01-01
While average temperatures on Mars may be too low to support terrestrial life-forms or aqueous liquids, diurnal peak temperatures over most of the planet can be high enough to provide for both, down to a few centimeters beneath the surface for some fraction of the time. A thermal model was applied to the Viking 1, Viking 2, Pathfinder, Spirit, and Opportunity landing sites to demonstrate the dynamic temperature fields under the surface at these well-characterized locations. A benchmark temperature of 253 K was used as a lower limit for possible metabolic activity, which corresponds to the minimum found for specific terrestrial microorganisms. Aqueous solutions of salts known to exist on Mars can provide liquid solutions well below this temperature. Thermal modeling has shown that 253 K is reached beneath the surface at diurnal peak heating for at least some parts of the year at each of these landing sites. Within 40 degrees of the equator, 253 K beneath the surface should occur for at least some fraction of the year; and, within 20 degrees , it will be seen for most of the year. However, any life-form that requires this temperature to thrive must also endure daily excursions to far colder temperatures as well as periods of the year where 253 K is never reached at all.
Large low-field magnetoresistance of Fe3O4 nanocrystal at room temperature
International Nuclear Information System (INIS)
Mi, Shu; Liu, Rui; Li, Yuanyuan; Xie, Yong; Chen, Ziyu
2017-01-01
Superparamagnetic magnetite (Fe 3 O 4 ) nanoparticles with an average size of 6.5 nm and good monodispersion were synthesized and investigated by X-ray diffraction, Raman spectrometer, transmission electron microscopy and vibrating sample magnetometer. Corresponding low-field magnetoresistance (LFMR) was tested by physical property measurement system. A quite high LFMR has been observed at room temperature. For examples, at a field of 3000 Oe, the LFMR is −3.5%, and when the field increases to 6000 Oe, the LFMR is up to −5.1%. The electron spin polarization was estimated at 25%. This result is superior to the previous reports showing the LFMR of no more than 2% at room temperature. The conduction mechanism is proposed to be the tunneling of conduction electrons between adjacent grains considering that the monodisperse nanocrystals may supply more grain boundaries increasing the tunneling probability, and consequently enhancing the overall magnetoresistance. - Highlights: • Superparamagnetic Fe3O4 nanoparticles with small size were synthesized. • A quite high LFMR has been observed at room temperature. • The more grain boundaries increase the tunneling probability and enlarge the MR. • The fast response of the sample increase the MR at a low field.
International Nuclear Information System (INIS)
Saleh, P.M.
2000-01-01
Critical current measurements on state of the art practical high temperature superconductors are presented. Bi 2 Sr 2 CaCu 2 O silver-alloy matrix powder-in-tube and silver-alloy substrate dip-coated tapes, formed into various geometries, have been tested in pulsed magnetic fields of various pulse lengths. These measurements have been compared to tests performed in continuous magnetic fields. A distinct discrepancy between pulsed and continuous measurements has been observed in these silver-alloy, high temperature superconductor composites. The critical current measured in pulsed fields is depressed compared to those measured in continuous fields. Evidence is provided to strongly suggest that eddy current heating in the silver-alloy substrate/sheath of the conductor is responsible for this discrepancy. A model is presented to predict the temperature rise due to eddy current heating. This model shows good agreement with observations. In order to perform measurements on Bi 2 Sr 2 Ca 2 Cu 3 O silver-alloy matrix powder-in-tube conductor, a novel split pulsed magnet has been designed and constructed. This has allowed the first measurements of this kind to be performed on these materials, the results of which are presented in this thesis. The split magnet project itself is presented as a unique engineering project. The design models are compared to magnet test data. Suggestions for possible future improvements of the technique are presented, including a innovative design of a 100ms pulsed magnet solenoid. (author)
Stress analysis in high-temperature superconductors under pulsed field magnetization
Wu, Haowei; Yong, Huadong; Zhou, Youhe
2018-04-01
Bulk high-temperature superconductors (HTSs) have a high critical current density and can trap a large magnetic field. When bulk superconductors are magnetized by the pulsed field magnetization (PFM) technique, they are also subjected to a large electromagnetic stress, and the resulting thermal stress may cause cracking of the superconductor due to the brittle nature of the sample. In this paper, based on the H-formulation and the law of heat transfer, we can obtain the distributions of electromagnetic field and temperature, which are in qualitative agreement with experiment. After that, based on the dynamic equilibrium equations, the mechanical response of the bulk superconductor is determined. During the PFM process, the change in temperature has a dramatic effect on the radial and hoop stresses, and the maximum radial and hoop stress are 24.2 {{MPa}} and 22.6 {{MPa}}, respectively. The mechanical responses of a superconductor for different cases are also studied, such as the peak value of the applied field and the size of bulk superconductors. Finally, the stresses are also presented for different magnetization methods.
Saleh, P M
2000-01-01
including a innovative design of a 100ms pulsed magnet solenoid. Critical current measurements on state of the art practical high temperature superconductors are presented. Bi sub 2 Sr sub 2 CaCu sub 2 O silver-alloy matrix powder-in-tube and silver-alloy substrate dip-coated tapes, formed into various geometries, have been tested in pulsed magnetic fields of various pulse lengths. These measurements have been compared to tests performed in continuous magnetic fields. A distinct discrepancy between pulsed and continuous measurements has been observed in these silver-alloy, high temperature superconductor composites. The critical current measured in pulsed fields is depressed compared to those measured in continuous fields. Evidence is provided to strongly suggest that eddy current heating in the silver-alloy substrate/sheath of the conductor is responsible for this discrepancy. A model is presented to predict the temperature rise due to eddy current heating. This model shows good agreement with observations. ...
Temperature and cooling field dependent exchange coupling in [Cr/Gd]{sub 5} multilayers
Energy Technology Data Exchange (ETDEWEB)
Jiao, Z.W.; Chen, H.J.; Jiang, W.D.; Wang, J.F.; Yu, S.J. [Department of Physics, China Jiliang University, Hangzhou (China); Hou, Y.L.; Lu, B.; Ye, Q.L. [Department of Physics, Hangzhou Normal University, Hangzhou (China)
2016-09-15
Exchange coupling has been investigated in the [Cr/Gd]{sub 5} multilayers deposited at 25, 200, and 400 C, where the Neel temperature (T{sub N}) of antiferromagnetic Cr is slightly higher than the Curie temperature (T{sub C}) of ferromagnetic Gd. It was found that the exchange coupling existed not only at T{sub C} < T < T{sub N}, but also above the temperature (T{sub N}) of antiferromagnetic orderings with incommensurate spin-density wave structures transiting to paramagnetic state. These results can be discussed in terms of the crucial role played by the antiferromagnetic spins of Cr with commensurate spin-density wave structures in the vicinity of the Cr/Gd interfaces. Moreover, the exchange coupling of the multilayers grown at different temperatures exhibited different dependencies on the measuring temperature and the cooling field, respectively. Positive exchange bias was observed in the multilayers grown at 200 and 400 C. The interfacial roughness, grain size, and the antiferromagnetic orderings of Cr may be responsible for the anomalous exchange coupling of the multilayers. In addition, the competition between the exchange coupling at Cr/Gd interfaces and the external field-Cr surface magnetic coupling can explain the appearance of negative or positive exchange bias. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
Du, Yongxing; Zhang, Lingze; Sang, Lulu; Wu, Daocheng
2016-04-29
In this paper, an Archimedean planar spiral antenna for the application of thermotherapy was designed. This type of antenna was chosen for its compact structure, flexible application and wide heating area. The temperature field generated by the use of this Two-armed Spiral Antenna in a muscle-equivalent phantom was simulated and subsequently validated by experimentation. First, the specific absorption rate (SAR) of the field was calculated using the Finite Element Method (FEM) by Ansoft's High Frequency Structure Simulation (HFSS). Then, the temperature elevation in the phantom was simulated by an explicit finite difference approximation of the bioheat equation (BHE). The temperature distribution was then validated by a phantom heating experiment. The results showed that this antenna had a good heating ability and a wide heating area. A comparison between the calculation and the measurement showed a fair agreement in the temperature elevation. The validated model could be applied for the analysis of electromagnetic-temperature distribution in phantoms during the process of antenna design or thermotherapy experimentation.
Flynn, Casey L.; Vogt, Marissa F.; Withers, Paul; Andersson, Laila; England, Scott; Liu, Guiping
2017-11-01
Mars lacks a global magnetic field but possesses concentrated regions of crustal magnetic field that influence the planet's interaction with the solar wind and the structure of the Martian ionosphere. In this study we survey 17 months of MAVEN Langmuir Probe and Waves dayside electron density and temperature measurements to study how these quantities are affected in regions with strong crustal magnetic fields. Above 200 km altitude, we find that regions of strong crustal magnetic fields feature cooler electron temperatures and enhanced electron densities compared to regions with little or no crustal magnetic field. Neutral densities and temperatures are not significantly affected. Closed field lines on which electrons can be trapped are more prevalent in strong crustal field regions than elsewhere. Trapped on closed field lines, electrons are protected against loss processes involving the solar wind. This would lead to longer plasma lifetimes, higher densities, and lower temperatures.
ABOUT TEMPERATURE FIELDS AND CONDITIONS OF GASEOUS CONDENSATION OF NEBULAES IN THE PLANETARY VORTEX
Directory of Open Access Journals (Sweden)
L. V. Klyuchinskaya
2014-01-01
Full Text Available New exact solution of the spherically-axissymmetric Eiler's equations, called as planetary vortex, is applied to the problem of formation in planetary nebula germs of planets due to the condensation of gases in the areas of vortex instability which calls the rings of planetary vortex. It is shown that the vortex perturbations causes changes in preassure and temperature at which the gases of nebula condense themselves, forming the germs of the planets.
Directory of Open Access Journals (Sweden)
Zarei S
2015-05-01
Full Text Available Background: Nowadays, mothers are continuously exposed to different sources of electromagnetic fields before and even during pregnancy. It has recently been shown that exposure to mobile phone radiation during pregnancy may lead to adverse effects on the brain development in offspring and cause hyperactivity. Researchers have shown that behavioral problems in laboratory animals which have a similar appearance to ADHD are caused by intrauterine exposure to mobile phones. Objective: The purpose of this study was to investigate whether the maternal exposure to different sources of electromagnetic fields affect on the rate and severity of speech problems in their offspring. Methods: In this study, mothers of 35 healthy 3-5 year old children (control group and 77 children and diagnosed with speech problems who had been referred to a speech treatment center in Shiraz, Iran were interviewed. These mothers were asked whether they had exposure to different sources of electromagnetic fields such as mobile phones, mobile base stations, Wi-Fi, cordless phones, laptops and power lines. Results: We found a significant association between either the call time (P=0.002 or history of mobile phone use (months used and speech problems in the offspring (P=0.003. However, other exposures had no effect on the occurrence of speech problems. To the best of our knowledge, this is the first study to investigate a possible association between maternal exposure to electromagnetic field and speech problems in the offspring. Although a major limitation in our study is the relatively small sample size, this study indicates that the maternal exposure to common sources of electromagnetic fields such as mobile phones can affect the occurrence of speech problems in the offspring.
Self propagating high temperature synthesis of metal oxides. Reactions in external magnetic fields
Aguas, M D
2001-01-01
The preparation of metal oxides by Self-Propagating High-Temperature Synthesis is reported. The reactions are started with a point source of ignition; typically a hot wire. A synthesis wave is observed moving out from the point source and reactions terminate in seconds. Products obtained can be classified into ferrites (magnetic applications) and stannates (gas sensing applications). Ferrites were synthesised under variable external magnetic fields. The synthesis wave is hotter in the presence of an external magnetic field for hard ferrite synthesis. For spinel ferrites the opposite was observed. Materials synthesised in the field show differences in their bulk magnetic properties (coercivity and saturation magnetisation), structures and microstructures. Combustion reactions in large fields revealed changes in unit cell volume (shrinkage was observed for hard ferrites while expansion was observed for spinel ferrites). SHS synthesised hard ferrites show two distinct components; one has large grain structure co...
Enhanced field emission of ZnO nanoneedle arrays via solution etching at room temperature
DEFF Research Database (Denmark)
Ma, Huanming; Qin, Zhiwei; Wang, Zaide
2017-01-01
ZnO nanoneedle arrays (ZnO nns) were synthesized by a facile two-step solution-phase method based on the etching of pre-synthesized ZnO nanowire arrays (ZnO nws) with flat ends at room temperature. Field emission measurement results showed that the turn-on electronic fields of ZnO nns and nws wer...... 2.7 and 5.3 V μm−1 at a current density of 10 μA cm−2, and the field enhancement factors were 4939.3 for ZnO nns and 1423.6 for ZnO nws. The enhanced field emission properties in ZnO nns were ascribed to the sharp tip geometry....
Temperature dependence of the electric field gradient in AgPd and AgPt alloys
International Nuclear Information System (INIS)
Krolas, K.
1977-07-01
The measurements of temperature dependence of the electric field gradient (EFG) on 111 Cd nuclei in AgPd and AgPt alloys were performed using the time dependent perturbed angular correlation method. The EFG caused by impurities distributed in further coordination shells decrease stronaer with increasing temperature than the EFG due to single impurity being the nearest neighbour of the probe atom. These results were explained assuming different modes of thermal vibrations of single impurity atoms and impurity complexes in silver host lattice. (author)
Ion Temperature Measurements in the Tore Supra Scrape-Off Layer Using a Retarding Field Analyzer
International Nuclear Information System (INIS)
Kocan, M.; Gunn, J.P.; Pascal, J.Y.; Gauthier, E.
2010-01-01
The retarding field analyzer (RFA) is one of the only widely accepted diagnostics for measuring the ion temperature T i )in the tokamak scrape-off layer. An overview of the outstanding RFA performance over ten years of operation in Tore Supra tokamak is given and the validation of T i measurements is addressed. The RFA measurements in Tore Supra are found to be well reproducible. The ion-to-electron temperature ratio is higher than one at low-to-moderate ion-electron collisionality regime and converges to unity at high collisionality regime. (authors)
Temperature dependent properties of InSb and InAs nanowire field-effect transistors
Nilsson, Henrik A.; Caroff, Philippe; Thelander, Claes; Lind, Erik; Karlström, Olov; Wernersson, Lars-Erik
2010-04-01
We present temperature dependent electrical measurements on InSb and InAs nanowire field-effect transistors (FETs). The FETs are fabricated from InAs/InSb heterostructure nanowires, where one complete transistor is defined within each of the two segments. Both the InSb and the InAs FETs are n-type with good current saturation and low voltage operation. The off-current for the InSb FET shows a strong temperature dependence, which we attribute to a barrier lowering due to an increased band-to-band tunneling in the drain part of the channel.
Blaen, Phillip J.; Brekenfeld, Nicolai; Comer-Warner, Sophie; Krause, Stefan
2017-11-01
The use of multitracer field fluorometry is increasing in the hydrological sciences. However, obtaining high-quality fluorescence measurements is challenging given the variability in environmental conditions within stream ecosystems. Here, we conducted a series of stream tracer tests to examine the degree to which multitracer field fluorometry produces reliable estimates of tracer concentrations under realistic field conditions. Using frequently applied examples of conservative (Uranine) and reactive (Resazurin-Resorufin) fluorescent tracers, we show that in situ measurements of tracer breakthrough curves can deviate markedly from corresponding samples analyzed under laboratory conditions. To investigate the effects of key environmental variables on fluorescence measurements, we characterized the response of field fluorometer measurements to changes in temperature, turbidity, and tracer concentration. Results showed pronounced negative log-linear effects of temperature on fluorescence measurements for all tracers, with stronger effects observed typically at lower tracer concentrations. We also observed linear effects of turbidity on fluorescence measurements that varied predictably with tracer concentration. Based on our findings, we present methods to correct field fluorometer measurements for variation in these parameters. Our results show how changing environmental conditions can introduce substantial uncertainties in the analysis of fluorescent tracer breakthrough curves, and highlight the importance of accounting for these changes to prevent incorrect inferences being drawn regarding the physical and biogeochemical processes underpinning observed patterns.
Room-temperature near-field reflection spectroscopy of single quantum wells
DEFF Research Database (Denmark)
Langbein, Wolfgang Werner; Hvam, Jørn Marcher; Madsen, Steen
1997-01-01
. This technique suppresses efficiently the otherwise dominating far-field background and reduces topographic artifacts. We demonstrate its performance on a thin, strained near-surface CdS/ZnS single quantum well at room temperature. The optical structure of these topographically flat samples is due to Cd......We report on a novel optical near-field technique to measure the local polarizability of a topographically flat sample with a spatial resolution better than 100 nm. Using an uncoated fiber probe, we implement a cross-polarization detection of the optical signal at the fiber dither frequency...
Effects of multiple-helicity fields on ion temperature gradient modes
Energy Technology Data Exchange (ETDEWEB)
Kuroda, T. [National Inst. for Fusion Science, Toki, Gifu (Japan); Sugama, H. [Graduate Univ. for Advanced Studies, Toki, Gigu (Japan)
2001-04-01
Effects of multiple-helicity magnetic fields on ion temperature gradient (ITG) modes in toroidal helical systems like the Large Helical Device (LHD) are studied by means of the linear gyrokinetic theory. Especially, dependence of the real frequency, growth rate, and the eigenfunction of the ITG mode on sideband-helicity fields added to the main helical component is investigated. Comparison between multiple-helicity effects on the ITG mode with those on the neoclassical ripple transport is presented, and optimization of the magnetic configuration for better plasma confinement is discussed. (author)
Directory of Open Access Journals (Sweden)
Gorbunov A.D.
2016-08-01
Full Text Available Existing solutions of radiant and convective heating (cooling body problems at the initial stage at unsteady heat transfer coefficients and temperatures are rather cumbersome. The purpose of this work is getting simpler dependencies. Decisions are based on the analysis of relations between the cause (heat flow and the effect (surface temperature in the initial period of heating. Two simple and effective engineering methods of calculation of unsteady temperature fields, and axial thermal stresses at the initial stage of heating (cooling of body of canonical form for both convection and radiation heat transfer at variable ambient temperature and environmental factors have been developed. Some of the solutions are generic in nature, which allows significantly reducing the number of variables and thus using the graphical method of problem solving. The formulas for calculating the bulk and central temperature in the initial stage are provided; other researchers of nonlinear heat conduction problems did not usually do this. It has been found that the axial thermal stresses are determined entirely by the heat flow on the surface. The adequacy of the developed techniques is based on five cases of calculation of heating (cooling plates under various conditions of its thermal loading. It is shown that the error in determining the surface temperature does not exceed 6%, and that the developed method can be used up to Fourier numbers Fo<0.4
DEFF Research Database (Denmark)
Rizzi, G.; Lundtoft, N.C.; Østerberg, F.W.
2012-01-01
We investigate the changes of planar Hall effect bridge magnetic field sensors upon exposure to temperatures between 25° C and 90°C. From analyses of the sensor response vs. magnetic fields we extract the exchange bias field Hex, the uniaxial anisotropy field HK and the anisotropic magnetoresista...
Deriving Deep Ocean Temperature Changes From the Ambient Acoustic Noise Field
Sambell, K.; Evers, L. G.; Snellen, M.
2016-12-01
Passively deriving the deep ocean temperature is a challenge. However, knowledge about changes in the deep ocean temperature are important in relation to climate change. In-situ observations are are and satellite observations are hardly applicable. Low-frequency sound waves of a few hertz can penetrate the deep oceans over long distances. As their propagation is temperature dependent, these waves contain valuable information that can be used for temperature monitoring. In this study, the use of interferometry is demonstrated by applying this technique to ambient noise measured at two hydrophone arrays located near Robinson Crusoe Island in the South Pacific Ocean. The arrays are separated by 40 km and are located at a depth of 800 m. Both arrays consist of three hydrophones with an interstation distance of 2 km. It is shown that the acoustic velocity, and with this the temperature variation, can be derived from measured hydro-acoustic data. Furthermore, the findings are supported by ocean models that describe the propagation of sound between the hydrophone arrays. This study shows the potential of using the ambient noise field for temperature monitoring in the deep ocean.
Temperature and microwave near field imaging by thermo-elastic optical indicator microscopy
Lee, Hanju; Arakelyan, Shant; Friedman, Barry; Lee, Kiejin
2016-12-01
A high resolution imaging of the temperature and microwave near field can be a powerful tool for the non-destructive testing of materials and devices. However, it is presently a very challenging issue due to the lack of a practical measurement pathway. In this work, we propose and demonstrate experimentally a practical method resolving the issue by using a conventional CCD-based optical indicator microscope system. The present method utilizes the heat caused by an interaction between the material and an electromagnetic wave, and visualizes the heat source distribution from the measured photoelastic images. By using a slide glass coated by a metal thin film as the indicator, we obtain optically resolved temperature, electric, and magnetic microwave near field images selectively with a comparable sensitivity, response time, and bandwidth of existing methods. The present method provides a practical way to characterize the thermal and electromagnetic properties of materials and devices under various environments.
Origin of temperature and field dependence of magnetic skyrmion size in ultrathin nanodots
Tomasello, R.; Guslienko, K. Y.; Ricci, M.; Giordano, A.; Barker, J.; Carpentieri, M.; Chubykalo-Fesenko, O.; Finocchio, G.
2018-02-01
Understanding the physical properties of magnetic skyrmions is important for fundamental research with the aim to develop new spintronic device paradigms where both logic and memory can be integrated at the same level. Here, we show a universal model based on the micromagnetic formalism that can be used to study skyrmion stability as a function of magnetic field and temperature. We consider ultrathin, circular ferromagnetic magnetic dots. Our results show that magnetic skyrmions with a small radius—compared to the dot radius—are always metastable, while large radius skyrmions form a stable ground state. The change of energy profile determines the weak (strong) size dependence of the metastable (stable) skyrmion as a function of temperature and/or field.
Low-magnetic field, room-temperature colossal magnetoresistance in manganite thin films
Robson, Marcia Christine
The manganese (Mn) based perovskite oxide materials (manganites), of the chemical form T1--xDxMnO3, display a large magnetic field induced decrease in their resistivity, termed colossal magnetoresistance. Typically, colossal magnetoresistance in the manganite samples is observed at low temperatures and high magnetic fields (>1 Tesla). However, an enhanced magnetoresistance at low magnetic fields and room temperature in these manganite samples would be technologically useful. In an effort to characterize this low magnetic field, room temperature magnetoresistance, the role of several different physical parameters has been explored in this thesis. These physical parameters include lattice mismatch strain, which originates from the epitaxial growth of single layer manganite thin films, the application of different radiation probes, such as microwave radiation, and the introduction of artificial grain boundaries in the form of interfaces in manganite multilayers. Lattice mismatch strain originates from the difference in the lattice constants of the manganite thin film and the crystalline substrate. The nature of the effect of the lattice mismatch strain on these transport properties for La0.7Ba0.3MnO3 thin films has been studied by varying the degree of lattice mismatch strain in the thin film. Variation of the lattice mismatch strain was achieved by varying the thickness of the manganite thin films, by annealing the manganite thin films in oxygen, and by buffering the manganite films with a lattice matched buffer layer. Each of these approaches relaxed the lattice mismatch strain, resulting in an increase of the low magnetic field, room temperature magnetoresistance. Microwave radiation probes determine the magnetic homogeneity of the manganite thin films and the effect of this magnetic homogeneity on the low magnetic field, room temperature magnetoresistance. La0.7Ba 0.3MnO3 thin films showed no gross magnetic homogeneitiese. The magnetic homogeneity increased in the
A first look at Quasi-Monte Carlo for lattice field theory problems
Energy Technology Data Exchange (ETDEWEB)
Jansen, K. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC; Leovey, H.; Griewank, A. [Humboldt-Universitaet, Berlin (Germany). Inst. fuer Mathematik; Nube, A. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC; Humboldt-Universitaet, Berlin (Germany). Inst. fuer Physik; Mueller-Preussker, M. [Humboldt-Universitaet, Berlin (Germany). Inst. fuer Physik
2012-11-15
In this project we initiate an investigation of the applicability of Quasi-Monte Carlo methods to lattice field theories in order to improve the asymptotic error behavior of observables for such theories. In most cases the error of an observable calculated by averaging over random observations generated from an ordinary Monte Carlo simulation behaves like N{sup -1/2}, where N is the number of observations. By means of Quasi-Monte Carlo methods it is possible to improve this behavior for certain problems to up to N{sup -1}. We adapted and applied this approach to simple systems like the quantum harmonic and anharmonic oscillator and verified an improved error scaling.
Controlling the sign problem in finite-density quantum field theory
Energy Technology Data Exchange (ETDEWEB)
Garron, Nicolas; Langfeld, Kurt [University of Liverpool, Theoretical Physics Division, Department of Mathematical Sciences, Liverpool (United Kingdom)
2017-07-15
Quantum field theories at finite matter densities generically possess a partition function that is exponentially suppressed with the volume compared to that of the phase quenched analog. The smallness arises from an almost uniform distribution for the phase of the fermion determinant. Large cancellations upon integration is the origin of a poor signal to noise ratio. We study three alternatives for this integration: the Gaussian approximation, the ''telegraphic'' approximation, and a novel expansion in terms of theory-dependent moments and universal coefficients. We have tested the methods for QCD at finite densities of heavy quarks. We find that for two of the approximations the results are extremely close - if not identical - to the full answer in the strong sign-problem regime. (orig.)
Problem of diagnostics of motive capabilities of man in the field of mass physical culture
Directory of Open Access Journals (Sweden)
Khor'yakov V.A.
2012-11-01
Full Text Available The problem of diagnostics of motive functions of man is examined in the field of mass physical culture. In research 246 girls and 180 youths took part in age 17 - 19 years. For them determined the quickness of motions; «explosive» force of muscles - extensor of feet and hands; co-ordinating capabilities; absolute force; static, dynamic and speed endurance; physical ability and mobility in a rachis. The test program of estimation of psychomotor functions of man is offered on the different stages of ontogenesis. Rotined necessity of measuring of power and capacity of mechanisms of energy-supply on each of the stages and estimation of ability of individual to the management motions in space and time. It is suggested to decide optimum program of testing development exceptionally from biological positions, taking into account conformities to the law of development and involution of motive functions on each of the stages of ontogenesis.
A first look at quasi-Monte Carlo for lattice field theory problems
International Nuclear Information System (INIS)
Jansen, K; Nube, A; Leovey, H; Griewank, A; Mueller-Preussker, M
2013-01-01
In this project we initiate an investigation of the applicability of Quasi-Monte Carlo methods to lattice field theories in order to improve the asymptotic error behavior of observables for such theories. In most cases the error of an observable calculated by averaging over random observations generated from an ordinary Monte Carlo simulation behaves like N −1/2 , where N is the number of observations. By means of Quasi-Monte Carlo methods it is possible to improve this behavior for certain problems to up to N −1 . We adapted and applied this approach to simple systems like the quantum harmonic and anharmonic oscillator and verified an improved error scaling
Kiloampere, Variable-Temperature, Critical-Current Measurements of High-Field Superconductors.
Goodrich, L F; Cheggour, N; Stauffer, T C; Filla, B J; Lu, X F
2013-01-01
K to those measured on the same specimen in flowing helium gas ("gas" or I c gas) at the same temperature. These comparisons indicate the temperature control is effective over the superconducting wire length between the voltage taps, and this condition is valid for all types of sample investigated, including Nb-Ti, Nb3Sn, and MgB2 wires. The liquid/gas comparisons are used to study the variable-temperature measurement protocol that was necessary to obtain the "correct" critical current, which was assumed to be the I c liq. We also calibrated the magnetoresistance effect of resistive thermometers for temperatures from 4 K to 35 K and magnetic fields from 0 T to 16 T. This calibration reduces systematic errors in the variable-temperature data, but it does not affect the liquid/gas comparison since the same thermometers are used in both cases.
International Nuclear Information System (INIS)
Piskunov, N.E.
1985-01-01
Mathematical formulation of the inverse problem of determination of magnetic field geometry from the polarization profiles of spectral lines is gven. The solving algorithm is proposed. A set of model calculations has shown the effectiveness of the algorithm, the high precision of magnetic star model parameters obtained and also the advantages of the inverse problem method over the commonly used method of interpretation of effective field curves
Studies in the derivative expansion and finite temperature quantum field theory
International Nuclear Information System (INIS)
Karev, A.
1987-01-01
The real time formalism of the finite temperature quantum field theories is discussed. It is then applied to calculate the Witten index in supersymmetric quantum mechanics. The Witten index is an order parameter of supersymmetry breaking. The author calculation of the Witten index shows that supersymmetry is spontaneously broken at finite temperature, reinstating the conclusions of earlier studies. The derivative expansion is a useful technique for studying low energy effective theories. We use this method in two space-time dimensions and show how the solubility of certain theories arises in this approach. We further apply this technique to show the temperature independence of the Abelian chiral anomaly, particularly in the context of the Schwinger model
Energy Technology Data Exchange (ETDEWEB)
Kansal, Anuj Kumar, E-mail: akansal@barc.gov.in [Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Joshi, Jyeshtharaj B., E-mail: jbjoshi@gmail.com [Homi Bhabha National Institute, Anushaktinagar, Mumbai 400094 (India); Maheshwari, Naresh Kumar, E-mail: nmahesh@barc.gov.in [Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Vijayan, Pallippattu Krishnan, E-mail: vijayanp@barc.gov.in [Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India)
2015-06-15
Highlights: • 3D CFD of vertical calandria vessel. • Spatial distribution of volumetric heat generation. • Effect of Archimedes number. • Non-dimensional analysis. - Abstract: Three dimensional computational fluid dynamics (CFD) analysis has been performed for the moderator flow and temperature fields inside a vertical calandria vessel of nuclear reactor under normal operating condition using OpenFOAM CFD code. OpenFOAM is validated by comparing the predicted results with the experimental data available in literature. CFD model includes the calandria vessel, calandria tubes, inlet header and outlet header. Analysis has been performed for the cases of uniform and spatial distribution of volumetric heat generation. Studies show that the maximum temperature in moderator is lower in the case of spatial distribution of heat generation as compared to that in the uniform heat generation in calandria. In addition, the effect of Archimedes number on maximum and average moderator temperature was investigated.
Measurement of flow field in the pebble bed type high temperature gas-cooled reactor
International Nuclear Information System (INIS)
Lee, Sa Ya; Lee, Jae Young
2008-01-01
In this study, flow field measurement of the Pebble Bed Reactor(PBR) for the High Temperature Gascooled Reactor(HTGR) was performed. Large number of pebbles in the core of PBR provides complicated flow channel. Due to the complicated geometries, numerical analysis has been intensively made rather than experimental observation. However, the justification of computational simulation by the experimental study is crucial to develop solid analysis of design method. In the present study, a wind tunnel installed with pebbles stacked was constructed and equipped with the Particle Image Velocimetry(PIV). We designed the system scaled up to realize the room temperature condition according to the similarity. The PIV observation gave us stagnation points, low speed region so that the suspected high temperature region can be identified. With the further supplementary experimental works, the present system may produce valuable data to justify the Computational Fluid Dynamics(CFD) simulation method
Wang, Daoming; Zi, Bin; Zeng, Yishan; Qian, Sen; Qian, Jun
2017-09-01
The unpredictable power fluctuation due to severe heating has been demonstrated to be a critical bottleneck technique restricting the application of magnetorheological (MR) clutches in vehicle industry. The aim of this study is to introduce a low-cost transient simulation approach for evaluating the heat build-up and dissipation of a liquid-cooled MR vehicle clutch. This paper firstly performs a detailed description of the developed MR clutch in terms of operation principle, material selection and configuration. Subsequently, transient temperature simulations are carried out under various conditions to reveal the distribution, variation and impact factors of the transient temperature field. Following these, an experimental setup is established for heating tests of the clutch prototype. Experimental results concerning the temperature variation of magnetorheological fluids and the maximum allowable transient slip power of the clutch prototype are presented, which in return verify the correctness and feasibility of the simulation.
International Nuclear Information System (INIS)
Catapano, F.; Zimbardo, G.; Artemyev, A. V.; Vasko, I. Y.
2015-01-01
We develop current sheet models which allow to regulate the level of plasma temperature and density inhomogeneities across the sheet. These models generalize the classical Harris model via including two current-carrying plasma populations with different temperature and the background plasma not contributing to the current density. The parameters of these plasma populations allow regulating contributions of plasma density and temperature to the pressure balance. A brief comparison with spacecraft observations demonstrates the model applicability for describing the Earth magnetotail current sheet. We also develop a two dimensional (2D) generalization of the proposed model. The interesting effect found for 2D models is the nonmonotonous profile (along the current sheet) of the magnetic field component perpendicular to the current sheet. Possible applications of the model are discussed
DEFF Research Database (Denmark)
Bharuth-Ram, K.; Hansen, Mikkel Fougt; Mørup, Steen
2001-01-01
order observed in the larger grits collapsing as one went to smaller grit sizes. Two sets of De Beers MDAS diamond grits of US mesh size 400-500 (d=30-38 mum) and 200-230 (d=63-75 mum) were selected for temperature- and field-dependent investigations. Transmission Mossbauer measurements were made...... of the Mossbauer spectra is not due to superparamagnetic relaxation of ferromagnetic inclusions but rather to magnetic ordering temperatures of the order of room temperature. Based on the spectral lineshapes and elemental analyses, we suggest the inclusions in the 63-75 mum grits contain iron mainly in Fe......-Ni alloys with composition in the vicinity of 70 at.% Fe, and those in the 30-38 mum grits contain, in addition to Fe-Ni alloys, a phase with hyperfine parameters close to those of a Fe-Co alloy....
Labram, John G; Fabini, Douglas H; Perry, Erin E; Lehner, Anna J; Wang, Hengbin; Glaudell, Anne M; Wu, Guang; Evans, Hayden; Buck, David; Cotta, Robert; Echegoyen, Luis; Wudl, Fred; Seshadri, Ram; Chabinyc, Michael L
2015-09-17
While recent improvements in the reported peak power conversion efficiency (PCE) of hybrid organic-inorganic perovskite solar cells have been truly astonishing, there are many fundamental questions about the electronic behavior of these materials. Here we have studied a set of electronic devices employing methylammonium lead iodide ((MA)PbI3) as the active material and conducted a series of temperature-dependent measurements. Field-effect transistor, capacitor, and photovoltaic cell measurements all reveal behavior consistent with substantial and strongly temperature-dependent polarization susceptibility in (MA)PbI3 at temporal and spatial scales that significantly impact functional behavior. The relative PCE of (MA)PbI3 photovoltaic cells is observed to reduce drastically with decreasing temperature, suggesting that such polarization effects could be a prerequisite for high-performance device operation.
Renormalisation of a self-consistent scheme in quantum field theories at finite temperature
International Nuclear Information System (INIS)
Reinosa, Urko
2003-01-01
In this thesis, we study the renormalisation of a self-consistent technique in quantum field theory at finite temperature. The so-called two-particle-irreducible scheme is useful to deal with strongly interacting quantum systems where the fluctuations are however soft enough to distribute the main interactions among quasiparticle degrees of freedom. Numerous non-relativistic systems follow this quasiparticle picture but also relativistic ones such as the quark gluon plasma (high temperature phase of Quantum Chromodynamics). The success of such techniques stems essentially from the fact that these are non-perturbative methods. This is however the source of a certain number of difficulties in particular in the framework of quantum field theories since ultraviolet divergences have to be eliminated in a non-perturbative context. This thesis shows how to proceed with the renormalisation of this scheme in the case of a scalar theory with φ 4 interaction, at finite temperature. We also discuss the independence of the counterterms with respect to temperature, which is a crucial question when defining trustworthy physical quantities. (author) [fr
Numerical evaluation of multipass welding temperature field in API 5L X80 steel welded joints
Directory of Open Access Journals (Sweden)
J Nóbrega
2016-10-01
Full Text Available Many are the metallurgical changes suffered by materials when subjected to welding thermal cycle, promoting a considerable influence on the welded structures thermo mechanical properties. In project phase, one alternative for evaluating the welding cycle variable, would be the employment of computational methods through simulation. So, this paper presents an evaluation of the temperature field in a multipass welding of API 5L X80 steel used for oil and gas transportation, using the ABAQUS ® software, based on Finite Elements Method (FEM. During the simulation complex phenomena are considerable including: Variation in physical and mechanical properties of materials as a function of temperature, welding speed and the different mechanisms of heat exchange with the environment (convection and radiation were used. These considerations allow a more robust mathematical modeling for the welding process. An analytical heat source proposed by Goldak, to model the heat input in order to characterize the multipass welding through the GTAW (Gas Tungsten Arc Welding process on root and the SMAW (Shielded Metal Arc Welding process for the filling passes were used. So, it was possible to evaluate the effect of each welding pass on the welded joint temperature field, through the temperature peaks and cooling rates values during the welding process.
Applications of the renormalization group approach to problems in quantum field theory
International Nuclear Information System (INIS)
Renken, R.L.
1985-01-01
The presence of fluctuations at many scales of length complicates theories of quantum fields. However, interest is often focused on the low-energy consequences of a theory rather than the short distance fluctuations. In the renormalization-group approach, one takes advantage of this by constructing an effective theory with identical low-energy behavior, but without short distance fluctuations. Three problems of this type are studied here. In chapter 1, an effective lagrangian is used to compute the low-energy consequences of theories of technicolor. Corrections to weak-interaction parameters are found to be small, but conceivably measurable. In chapter 2, the renormalization group approach is applied to second order phase transitions in lattice gauge theories such as the deconfining transition in the U(1) theory. A practical procedure for studying the critical behavior based on Monte Carlo renormalization group methods is described in detail; no numerical results are presented. Chapter 3 addresses the problem of computing the low-energy behavior of atoms directly from Schrodinger's equation. A straightforward approach is described, but is found to be impractical
STATE AND PROBLEMS TRAINING, ADVANCED TRAINING AND RETRAINING IN THE FIELD OF LAND PLANNING
Directory of Open Access Journals (Sweden)
Tretiak A.
2016-05-01
Full Text Available Scientific and technological progress and improve land relations, land use and organization of work makes the need for systematic improvement of forms and methods of preparation, training and retraining in the land. Training in the land - is the formation of staff knowledge and skills in a particular professional field, that training people who want to get a profession in the field of land relations and the use and protection of land and other natural resources. In this connection the question the quality of the professionals who work in the system of land and land management enterprises. So in recent years, the system of land worked by 25 thousand. People .. to 28 thousand. People. The number of employees of DerzhzemahenstvaUkraine(and today DerzhheokadastruUkraine ranged from 9.5 - 10 thousand. People. Thus, in stateenterprisesLandManagement Institute, Centre of state land cadastre and land management of private enterprises and entrepreneurs are about 18 thousand. People. In the system of fixed services is almost 90% of workers with higher education. But of these, only about about 70% have higher education universities III-IV accreditation levels, and only about 50% - land management. Managers and professionals who have land management and land use close to education up together with the Bachelor education only 64% of the total number of employees. Thus, the problem of professional education in the field of land is very relevant. It is necessary to consider further training of land-management education for integrated communities. The article is justification for expanding areas of training in the field of land management and the introduction of new professions (specializations and the management of natural areas. According to Article 66 of the Law of Ukraine "On Land Management" of 22.05.2003 number 858-IV, professional activities in the field of land may engage citizens with special higher education levels and appropriate professional
Magnetic hyperfine field at a Cd impurity diluted in RCo{sub 2} at finite temperatures
Energy Technology Data Exchange (ETDEWEB)
Oliveira, A.L. de, E-mail: alexandre.oliveira@ifrj.edu.br [Instituto Federal de Educação, Ciência e Tecnologia do Rio de Janeiro, Campus Nilópolis – RJ (Brazil); Chaves, C.M., E-mail: cmch@cbpf.br [Centro Brasileiro de Pesquisas Físicas, Rio de Janeiro (Brazil); Oliveira, N.A. de [Instituto de Física Armando Dias Tavares, Universidade do Estado do Rio de Janeiro, Rio de Janeiro (Brazil); Troper, A. [Centro Brasileiro de Pesquisas Físicas, Rio de Janeiro (Brazil)
2015-06-15
The local magnetic moments and the magnetic hyperfine fields at an s–p Cd impurity diluted in inter-metallic Laves phase compounds RCo{sub 2} (R=Gd, Tb) at finite temperatures are calculated. For other rare earth elements (light or heavy) the pure compounds display a magnetic first order transition and are not describable by our formalism. The host has two coupled lattices (R and Co) both having itinerant d electrons but only the rare earth lattice has localized f electrons. They all contribute to the magnetization of the host and also to the local moment and to the magnetic hyperfine field at the impurity. The investigation of magnetic hyperfine field in these materials then provides valuable information on the d-itinerant electrons and also on the localized (4f) magnetic moments. For the d–d electronic interaction we use the Hubbard–Stratonovich identity thus allowing the employment of functional integral in the static saddle point approximation. Our model reproduces quite well the experimental data. - Highlights: • A functional integral method in the static limit, producing site disorder, is used. • The site disorder is treated with the coherent potential approximation (CPA) • A Friedel sum rule gives a self-consistency condition for the impurity energy. • The experimental curve of hyperfine fields×temperature is very well reproduced.
Böttger, B.; Eiken, J.; Apel, M.
2009-10-01
Performing microstructure simulation of technical casting processes suffers from the strong interdependency between latent heat release due to local microstructure formation and heat diffusion on the macroscopic scale: local microstructure formation depends on the macroscopic heat fluxes and, in turn, the macroscopic temperature solution depends on the latent heat release, and therefore on the microstructure formation, in all parts of the casting. A self-consistent homoenthalpic approximation to this micro-macro problem is proposed, based on the assumption of a common enthalpy-temperature relation for the whole casting which is used for the description of latent heat production on the macroscale. This enthalpy-temperature relation is iteratively obtained by phase-field simulations on the microscale, thus taking into account the specific morphological impact on the latent heat production. This new approach is discussed and compared to other approximations for the coupling of the macroscopic heat flux to complex microstructure models. Simulations are performed for the binary alloy Al-3at%Cu, using a multiphase-field solidification model which is coupled to a thermodynamic database. Microstructure formation is simulated for several positions in a simple model plate casting, using a one-dimensional macroscopic temperature solver which can be directly coupled to the microscopic phase-field simulation tool.
International Nuclear Information System (INIS)
Boettger, B.; Eiken, J.; Apel, M.
2009-01-01
Performing microstructure simulation of technical casting processes suffers from the strong interdependency between latent heat release due to local microstructure formation and heat diffusion on the macroscopic scale: local microstructure formation depends on the macroscopic heat fluxes and, in turn, the macroscopic temperature solution depends on the latent heat release, and therefore on the microstructure formation, in all parts of the casting. A self-consistent homoenthalpic approximation to this micro-macro problem is proposed, based on the assumption of a common enthalpy-temperature relation for the whole casting which is used for the description of latent heat production on the macroscale. This enthalpy-temperature relation is iteratively obtained by phase-field simulations on the microscale, thus taking into account the specific morphological impact on the latent heat production. This new approach is discussed and compared to other approximations for the coupling of the macroscopic heat flux to complex microstructure models. Simulations are performed for the binary alloy Al-3at%Cu, using a multiphase-field solidification model which is coupled to a thermodynamic database. Microstructure formation is simulated for several positions in a simple model plate casting, using a one-dimensional macroscopic temperature solver which can be directly coupled to the microscopic phase-field simulation tool.
Vasyutin, M. A.; Kuz'michev, N. D.; Shilkin, D. A.
2018-02-01
The effect of the fractality of the cluster interfaces in the normal phase of a copper-oxide high-temperature superconductor YBCO on the magnetic creep has been studied. The model of a magnetic field dependence of voltage induced by the flux creep for different transport currents has been suggested. The experimental dependences have been approximated using an exponent-hyperbolic function with a current parameter. The empiric magnetic field dependence of the fractal dimensionality of the interfaces of YBCO clusters has been registered. The magnitudes of the magnetic field intensity and fractal dimensionality at which the vortices start to penetrate the granules of the samples have been determined. The connective index of paths of the vortex quench at the percolation threshold has been calculated.
Directory of Open Access Journals (Sweden)
Fenglong Wang
2016-11-01
Full Text Available Herein, we experimentally investigate the effect of temperature on the electric field tunable ferromagnetic resonance (FMR in a ferroelectric/ferromagnetic heterostructure, and demonstrate the tuning of abnormal change in FMR using the polarization of the ferroelectric layer above 200 K. The FMR was found to be almost unchanged under different electric field strength at 100 K owing to frozen polarization, which causes extremely weak magnetoelectric coupling. More interestingly, negative effective linewidth was observed when an electric field greater than 10 kV/cm was applied above 220 K. The simultaneous electrical control of magnetization and its damping via FMR based on linear magnetoelectric coupling are directly relevant to use of composite multiferroics for a wide range of devices.
Motional Stark Effect measurements of the local magnetic field in high temperature fusion plasmas
Wolf, R. C.; Bock, A.; Ford, O. P.; Reimer, R.; Burckhart, A.; Dinklage, A.; Hobirk, J.; Howard, J.; Reich, M.; Stober, J.
2015-10-01
The utilization of the Motional Stark Effect (MSE) experienced by the neutral hydrogen or deuterium injected into magnetically confined high temperature plasmas is a well established technique to infer the internal magnetic field distribution of fusion experiments. In their rest frame, the neutral atoms experience a Lorentz electric field, EL = v × B, which results in a characteristic line splitting and polarized line emission. The different properties of the Stark multiplet allow inferring, both the magnetic field strength and the orientation of the magnetic field vector. Besides recording the full MSE spectrum, several types of polarimeters have been developed to measure the polarization direction of the Stark line emission. To test physics models of the magnetic field distribution and dynamics, the accuracy requirements are quite demanding. In view of these requirements, the capabilities and issues of the different techniques are discussed, including the influence of the Zeeman Effect and the sensitivity to radial electric fields. A newly developed Imaging MSE system, which has been tested on the ASDEX Upgrade tokamak, is presented. The sensitivity allows to resolve sawtooth oscillations. A shorter version of this contribution is due to be published in PoS at: 1st EPS conference on Plasma Diagnostics
Mixing of charged and neutral Bose condensates at nonzero temperature and magnetic field
Directory of Open Access Journals (Sweden)
Haber Alexander
2017-01-01
Full Text Available It is expected that in the interior of compact stars a proton superconductor coexists with and couples to a neutron superfluid. Starting from a field-theoretical model for two complex scalar fields – one of which is electrically charged – we derive a Ginzburg-Landau potential which includes entrainment between the two fluids and temperature effects from thermal excitations of the two scalar fields and the gauge field. The Ginzburg-Landau description is then used for an analysis of the phase structure in the presence of an external magnetic field. In particular, we study the effect of the superfluid on the flux tube phase by computing the various critical magnetic fields and deriving an approximation for the flux tube interaction. As a result, we point out differences to the naive expectations from an isolated superconductor, for instance the existence of a first-order flux tube onset, resulting in a more complicated phase structure in the region between type-I and type-II superconductivity.
Influence of Magnetic Field on Electric Charge Transport in Holomiun Thin Films at Low Temperatures
Directory of Open Access Journals (Sweden)
Jan Dudas
2005-01-01
Full Text Available Holmium thin films were prepared by evaporation in ultrahigh vacuum (UHV and high precision electrical resistance measurements were performed on them as well as on holomium bulk sample in the wide temperature range from 4,2 K up to the room temperature. Electric charge transport is profoundly influenced by the magnetic structure at low temperatures and a "knee-like" resistance anomaly was observed near the transportation from paramagnetic state to basal-plane spiral structure in bulk with the Neel temperature TN=128,9 K and below ~ 122 K in thin Ho films in a thickness range from 98 nm to 215 nm. Unexpected resistance minimum at ~ 9 K and a slope´s charge of the R vs. T curve near ~ 170 K was observed in 215 nm thin film. Application of magnetic field parallel to the substrate and thin film plane for temperatures below ~ 150 K caused the decrease of resistence value with increasing magnetic flux density. Increasing suppression of the TN value up to ~ 5 K with increasing flux density value up to 5 T was observed in Ho films.
Non-uniform Solar Temperature Field on Large Aperture, Fully-Steerable Telescope Structure
Liu, Yan
2016-09-01
In this study, a 110-m fully steerable radio telescope was used as an analysis platform and the integral parametric finite element model of the antenna structure was built in the ANSYS thermal analysis module. The boundary conditions of periodic air temperature, solar radiation, long-wave radiation shadows of the surrounding environment, etc. were computed at 30 min intervals under a cloudless sky on a summer day, i.e., worstcase climate conditions. The transient structural temperatures were then analyzed under a period of several days of sunshine with a rational initial structural temperature distribution until the whole set of structural temperatures converged to the results obtained the day before. The non-uniform temperature field distribution of the entire structure and the main reflector surface RMS were acquired according to changes in pitch and azimuth angle over the observation period. Variations in the solar cooker effect over time and spatial distributions in the secondary reflector were observed to elucidate the mechanism of the effect. The results presented here not only provide valuable realtime data for the design, construction, sensor arrangement and thermal deformation control of actuators but also provide a troubleshooting reference for existing actuators.
Ambient-temperature incubation for the field detection of Escherichia coli in drinking water.
Brown, J; Stauber, C; Murphy, J L; Khan, A; Mu, T; Elliott, M; Sobsey, M D
2011-04-01
Escherichia coli is the pre-eminent microbiological indicator used to assess safety of drinking water globally. The cost and equipment requirements for processing samples by standard methods may limit the scale of water quality testing in technologically less developed countries and other resource-limited settings, however. We evaluate here the use of ambient-temperature incubation in detection of E. coli in drinking water samples as a potential cost-saving and convenience measure with applications in regions with high (>25°C) mean ambient temperatures. This study includes data from three separate water quality assessments: two in Cambodia and one in the Dominican Republic. Field samples of household drinking water were processed in duplicate by membrane filtration (Cambodia), Petrifilm™ (Cambodia) or Colilert® (Dominican Republic) on selective media at both standard incubation temperature (35–37°C) and ambient temperature, using up to three dilutions and three replicates at each dilution. Matched sample sets were well correlated with 80% of samples (n = 1037) within risk-based microbial count strata (E. coli CFU 100 ml−1 counts of 1000), and a pooled coefficient of variation of 17% (95% CI 15–20%) for paired sample sets across all methods. These results suggest that ambient-temperature incubation of E. coli in at least some settings may yield sufficiently robust data for water safety monitoring where laboratory or incubator access is limited.
On the Lauwerier formulation of the temperature field problem in oil strata
Directory of Open Access Journals (Sweden)
Lyubomir Boyadjiev
2005-01-01
equation is solved by means of the Caputo differintegration operator D∗(α of order 0<α≤1 and the Laplace transform. The solution is obtained in an integral form, where the integrand is expressed in terms of a convolution of two special functions of Wright type.
García, Guillermo A; Dreccer, M Fernanda; Miralles, Daniel J; Serrago, Román A
2015-11-01
Warm nights are a widespread predicted feature of climate change. This study investigated the impact of high night temperatures during the critical period for grain yield determination in wheat and barley crops under field conditions, assessing the effects on development, growth and partitioning crop-level processes driving grain number per unit area (GN). Experiments combined: (i) two contrasting radiation and temperature environments: late sowing in 2011 and early sowing in 2013, (ii) two well-adapted crops with similar phenology: bread wheat and two-row malting barley and (iii) two temperature regimes: ambient and high night temperatures. The night temperature increase (ca. 3.9 °C in both crops and growing seasons) was achieved using purpose-built heating chambers placed on the crop at 19:000 hours and removed at 7:00 hours every day from the third detectable stem node to 10 days post-flowering. Across growing seasons and crops, the average minimum temperature during the critical period ranged from 11.2 to 17.2 °C. Wheat and barley grain yield were similarly reduced under warm nights (ca. 7% °C(-1) ), due to GN reductions (ca. 6% °C(-1) ) linked to a lower number of spikes per m(2) . An accelerated development under high night temperatures led to a shorter critical period duration, reducing solar radiation capture with negative consequences for biomass production, GN and therefore, grain yield. The information generated could be used as a starting point to design management and/or breeding strategies to improve crop adaptation facing climate change. © 2015 John Wiley & Sons Ltd.
Agarwal, Shilpi; Kumar, Varun; Shakher, Chandra
2018-03-01
This paper presents the effect of magnetic field (upward decreasing, uniform and upward increasing) on wick stabilized micro diffusion flame by using digital holographic interferometry (DHI). The investigations reveal that under the influence of upward decreasing and uniform magnetic field temperature inside the micro flame increases in comparison to temperature inside micro flame without magnetic field. This is in contrary to normal diffusion flame, where uniform magnetic field has a little or no effect on the temperature. DHI is inherently more accurate more precise and is having better spatial resolution. DHI is ideally suited to study micro flame.
Naohito, NAKAZAWA; Research Institute for Theoretical Physics Hiroshima University
1985-01-01
We formulate a field-theoretical method at finite temperature to calculate a thermal energy-momentum tensor in arbitrary curved space-times using a momentum-space representation of the thermal Green's function in terms of Riemann normal coordinates. In particular, the thermal energy-momentum tensor for a massive scalar field is calculated by the high-temperature expansion. A locally observed temperature is obtained by requiring the conservation law of the thermal energy-momentum tensor.
Energy Technology Data Exchange (ETDEWEB)
Verma, S.P. [Laboratorio de Energia Solar, Temixco, UNAM (Mexico); Rodriguez-Gonzalez, U. [Facultad de Ciencias de la Tierra, Linares, UANL (Mexico)
1997-02-01
The temperature field distribution in La Primavera geothermal area, Jalisco, located in the western part of the Mexican Volcanic Belt (MVB), has been simulated from cooling of a shallow magma chamber (assumed as the primary heat source) during the entire volcanic history of the caldera. Similar to the other two geothermal fields of the MVB (Los Humeros and Los Azufres), it is considered that the evolution of the magma chamber is controlled by the processes of fractional crystallization as well as magma recharge. Besides these processes, heat contribution is also taken into account from decay of natural radioactive elements, U, Th, and K, present in all geological materials. In some models presented in this work, convection in the geothermal reservoir is simulated by assigning higher values of thermal conductivities (up to 20 times the rock conductivities) to respective geologic units. The heat transfer equation has been solved by a finite element implicit method. The results of temperature simulations from the magma chamber are compared with undisturbed formation temperatures in three drill wells. (author)
International Nuclear Information System (INIS)
Zeitz, W.D.
1974-01-01
Hyperfine field investigations were made to determine the critical exponent β in Nickel metals as in pure 63 NiNi system as in two systems 66 CuNi and 67 ZnNi. The experimental method was the time-differential observation of the perturbed angular correlation of gammas after a nuclear reaction. The isomeric states 63 Ni: 5/2 - for 87.2 keV, tau = 2.49 μs, g = 0.301; 66 Cu: 6 - for 1154.1 keV, tau = 860 ns, g = 0.1733; 67 Zn: 9/2 + for 605 keV, tau = 480 ns, g = 0.243 were excited in (d,p), ( 3 He,p) and (α,n) nuclear reactions on the isotope rich 62 Ni and 64 Ni. A new developed fast electron beam heating cared for a sufficient temperature stability in the range up to 1 0 below the Curie point. (orig./WL) [de
Field measurements of temperature profile for floatovoltaic dryer in the tropics
Osman, F. A.; Ya'acob, M. E.; Iskandar, A. Noor
2017-09-01
Most of the equator region in a tropical climate zone experiences hot and humid weather but sometimes heavy rain and thunderstorms which occur stochastically in monsoon season. Sunlight which is the energy source can be harvested approximately 8 hours (on average basis) daily throughout the year which leads to the promotion of Solar PV technologies. This works projects the field performance for a new Floatovoltaic Dryer prototype with flexible PV roofing structures covering the top of the dryer system. The field measurements are collected on the lake of Engineering Faculty, UPM supported with 4-parameter weather station. Temperature profile with RH measurements inside the Floatovoltaic Dryer compartments as compared to direct-sun drying mechanism are the main contributions of this work and it projects more than 12 W of convection heat energy could be harvested by using the clean system. The field measurements imply various points of thermocouple and humidity sensor throughout the experiment. Temperature and humidity will be the main elements recorded to analyze the differences under monocrystalline PV panel as compared to natural drying.
Probing α -RuCl3 Beyond Magnetic Order: Effects of Temperature and Magnetic Field
Winter, Stephen M.; Riedl, Kira; Kaib, David; Coldea, Radu; Valentí, Roser
2018-02-01
Recent studies have brought α -RuCl3 to the forefront of experimental searches for materials realizing Kitaev spin-liquid physics. This material exhibits strongly anisotropic exchange interactions afforded by the spin-orbit coupling of the 4 d Ru centers. We investigate the dynamical response at finite temperature and magnetic field for a realistic model of the magnetic interactions in α -RuCl3 . These regimes are thought to host unconventional paramagnetic states that emerge from the suppression of magnetic order. Using exact diagonalization calculations of the quantum model complemented by semiclassical analysis, we find a very rich evolution of the spin dynamics as the applied field suppresses the zigzag order and stabilizes a quantum paramagnetic state that is adiabatically connected to the fully polarized state at high fields. At finite temperature, we observe large redistributions of spectral weight that can be attributed to the anisotropic frustration of the model. These results are compared to recent experiments and provide a road map for further studies of these regimes.
Influence of the temperature-dependent viscosity on convective flow in the radial force field.
Travnikov, Vadim; Zaussinger, Florian; Beltrame, Philippe; Egbers, Christoph
2017-08-01
The numerical investigation of convective flows in the radial force field caused by an oscillating electric field between spherical surfaces has been performed. A temperature difference (T_{1}>T_{2}) as well as a radial force field triggers a fluid flow similar to the Rayleigh-Bénard convection. The onset of convective flow has been studied by means of the linear stability analysis as a function of the radius ratio η=R_{1}/R_{2}. The influence of the temperature-dependent viscosity has been investigated in detail. We found that a varying viscosity contrast β=ν(T_{2})/ν(T_{1}) between β=1 (constant viscosity) and β=50 decreases the critical Rayleigh number by a factor of 6. Additionally, we perform a bifurcation analysis based on numerical simulations which have been calculated using a modified pseudospectral code. Numerical results have been compared with the GeoFlow experiment which is located on the International Space Station (ISS). Nonturbulent three-dimensional structures are found in the numerically predicted parameter regime. Furthermore, we observed multiple stable solutions in both experiments and numerical simulations, respectively.
Effect of temperature and magnetic field on disorder in semiconductor structures
Energy Technology Data Exchange (ETDEWEB)
Agrinskaya, N. V., E-mail: nina.agrins@mail.ioffe.ru; Kozub, V. I. [Russian Academy of Sciences, Ioffe Physical–Technical Institute (Russian Federation)
2017-02-15
We present the results of consistent theoretical analysis of various factors that may lead to influence of temperature and external magnetic field on disorder in semiconductor structures. Main attention is paid to quantum well (QW) structures in which only QWs or both QW and barriers are doped (the doping level is assumed to be close to the value corresponding to the metal–insulator transition). The above factors include (i) ionization of localized states to the region of delocalized states above the mobility edge, which is presumed to exist in the impurity band; (ii) the coexistence in the upper and lower Hubbard bands (upon doping of QWs as well as barriers); in this case, in particular, the external magnetic field determines the relative contribution of the upper Hubbard band due to spin correlations at doubly filled sites; and (iii) the contribution of the exchange interaction at pairs of sites, in which the external magnetic field can affect the relation between ferromagnetic and antiferromagnetic configurations. All these factors, which affect the structure and degree of disorder, lead to specific features in the temperature dependence of resistivity and determine specific features of the magnetoresistance. Our conclusions are compared with available experimental data.
Pion propagator in relativistic quantum field theories of the nuclear many-body problem
International Nuclear Information System (INIS)
Matsui, T.; Serot, B.D.
1982-01-01
Pion interactions in the nuclear medium are studied using renormalizable relativistic quantum field theories. Previous studies using pseudoscalar πN coupling encountered difficulties due to the large strength of the πNN vertex. We therefore formulate renormalizable field theories with pseudovector πN coupling using techniques introduced by Weinberg and Schwinger. Calculations are performed for two specific models; the scalar-vector theory of Walecka, extended to include π and rho mesons in a non-chiral fashion, and the linear sigma-model with an additional neutral vector meson. Both models qualitatively reproduce low-energy πN phenomenology and lead to nuclear matter saturation in the relativistic Hartree formalism, which includes baryon vacuum fluctuations. The pions propagator is evaluated in the one-nucleon-loop approximation, which corresponds to a relativistic random-phase approximation built on the Hartree ground state. Virtual NN-bar loops are included, and suitable renormalization techniques are illustrated. The local-density approximation is used to compare the threshold pion self-energy to the s-wave pion-nucleus optical potential. In the non-chiral model, s-wave pion-nucleus scattering is too large in both pseudoscalar and pseudovector calculations, indicating that additional constraints must be imposed on the Lagrangian. In the chiral model, the threshold self-energy vanishes automatically in the pseudovector case, but does so for pseudoscalar coupling only if the baryon effective mass is chosen self-consistently Since extrapolation from free space to nuclear density can lead to large effects, pion propagation in the medium can determine which πN coupling is more suitable for the relativistic nuclear many-body problem. Conversely, pion interactions constrain the model Lagrangian and the nuclear matter equation of state. An approximately chiral model with pseudovector coupling is favored
International Nuclear Information System (INIS)
Jirous, F.; Klik, F.; Janeba, B.; Daliba, J.; Delis, J.
1989-01-01
Experimentally determined were coolant temperature and velocity fields at the inlet of the WWER-440 reactor core. The accuracy estimate is presented of temperature measurements and the relation is given for determining the resulting measurement error. An estimate is also made of the accuracy of solution of the system of equations for determining coefficients B kn using the method of the least square fit. Coefficients B kn represent the relative contribution of the mass flow of the k-th fuel assembly from the n-th loop and allow the calculation of coolant temperatures at the inlet of the k-th fuel assembly, when coolant temperatures in loops at reactor inlet are known. A comparison is made of the results of measurements on a hydrodynamic model of a WWER-440 reactor with results of measurements made at unit 4 of the Dukovany nuclear power plant. Full agreement was found for 32 model measurements and 6 reactor measurements. It may be assumed that the results of other model measurements obtained for other operating variants will also apply for an actual reactor. Their applicability may, however, only be confirmed by repeating the experiment on other WWER-440 reactors. (Z.M.). 5 figs., 7 refs
The effect of magnetic field and high temperature on the properties of blanket ceramics
International Nuclear Information System (INIS)
Kizane, Gunta; Tiliks, Juris; Vitins, Aigars; Kolodinska, Elina
2004-01-01
This study had the following task: 1) To estimate the magnetic field (MF, 7-9 T) effect on the formation of radiation-induced defects and products of radiolysis of ceramic breeder materials (Li 4 SiO 4 , Li 2 TiO 3 ). 2) To estimate the MF effect on the parameters of tritium release from the ceramics under conditions if high-temperature radiolysis. 3) To test the MF effect for the Li 4 SiO 4 pebbles irradiated under the real condition (HFR Petten-EXOTIC-8). The MF facilitates the location of tritium in the matrix of ceramics at the irradiation at temperature below 900 K, forming additional (20 - 25 %) radiation induced defects as tritium scavenging centers. No MF effect of this kind takes place at the higher temperature. At present, there is now information about the MF effect on the formation of colloid lithium and other radiolysis. The MF decreases the parameters of tritium release, increasing the diffusion path of charged tritium particles in the grain volume of the ceramic. This is proportional to the MF intensity and the grain size of ceramics. Irradiation at a high temperature facilitates the grain growth of the ceramics enhancing the retarding effect of the MF on the tritium release. (Y. Tanaka)
Directory of Open Access Journals (Sweden)
Ali Naderi
2012-01-01
Full Text Available By developing a two-dimensional (2D full quantum simulation, the attributes of carbon nanotube field-effect transistors (CNTFETs in different temperatures have been comprehensively investigated. Simulations have been performed by employing the self-consistent solution of 2D Poisson-Schrödinger equations within the nonequilibrium Green's function (NEGF formalism. Principal characteristics of CNTFETs such as current capability, drain conductance, transconductance, and subthreshold swing (SS have been investigated. Simulation results present that as temperature raises from 250 to 500 K, the drain conductance and on-current of the CNTFET improved; meanwhile the on-/off-current ratio deteriorated due to faster growth in off-current. Also the effects of temperature on short channel effects (SCEs such as drain-induced barrier lowering (DIBL and threshold voltage roll-off have been studied. Results show that the subthreshold swing and DIBL parameters are almost linearly correlated, so the degradation of these parameters has the same origin and can be perfectly influenced by the temperature.
Impact of Brake Pad Structure on Temperature and Stress Fields of Brake Disc
Directory of Open Access Journals (Sweden)
Guoshun Wang
2013-01-01
Full Text Available Utilizing ABAQUS finite element software, the study established the relationship between a brake pad structure and distributions of temperature and thermal stress on brake disc. By introducing radial structure factor and circular structure factor concepts, the research characterized the effect of friction block radial and circumferential arrangement on temperature field of the brake disc. A method was proposed for improving heat flow distribution of the brake disc through optimizing the position of the friction block of the brake pad. Structure optimization was conducted on brake pads composed of 5 or 7 circular friction blocks. The result shows that, with the same overall contact area of friction pair, an appropriate brake pad structure can make the friction energy distribute evenly and therefore lowers peak temperature and stress of the brake disc. Compared with a brake pad of 7 friction blocks, an optimized brake pad of 5 friction blocks lowered the peak temperature of the corresponding brake disc by 4.9% and reduced the highest stress by 10.7%.
Beyond mean-field properties of binary dipolar Bose mixtures at low temperatures
Pastukhov, Volodymyr
2017-02-01
We rigorously analyze the low-temperature properties of homogeneous three-dimensional two-component Bose mixture with dipole-dipole interaction. For such a system the effective hydrodynamic action that governs the behavior of low-energy excitations is derived. The infrared structure of the exact single-particle Green's functions is obtained in terms of macroscopic parameters, namely the inverse compressibility and the superfluid density matrices. Within the one-loop approximation we calculate some of the most relevant observable quantities and give the beyond mean-field stability condition for the binary dipolar Bose gas in the dilute limit. A brief variational derivation of the coupled equations that describe macroscopic hydrodynamics of the system in the external nonuniform potential at zero temperature is presented.
Sharma, V. K.; Chattopadhyay, M. K.; Khandelwal, A.; Roy, S. B.
2010-11-01
A near room-temperature martensitic transition is observed in the ferromagnetic austenite state of Ni50Mn34In16 alloy with 2% Cu substitution at the Ni site. Application of magnetic field in the martensite state induces a reverse martensitic transition in this alloy. dc magnetization, magnetoresistance and strain measurements in this alloy reveal that associated with this martensitic transition there exist a large magnetocaloric effect, a large magnetoresitance and a magnetic-field temperature-induced strain. This NiMnIn alloy system thus is an example of an emerging class of magnetic materials whose physical properties can be tuned by suitable chemical substitutions, to achieve magnetic-field and temperature-induced multifunctional properties at and around room temperature
Quasi-direct numerical simulation of a pebble bed configuration, Part-II: Temperature field analysis
International Nuclear Information System (INIS)
Shams, A.; Roelofs, F.; Komen, E.M.J.; Baglietto, E.
2013-01-01
Highlights: ► Quasi direct numerical simulations (q-DNSs) of a pebble bed configuration have been performed. ► This q-DNS database may serve as a reference for the validation of different turbulence modeling approaches. ► A wide range of qualitative and quantitative data throughout the computational domain has been generated. ► Results for mean, RMS of temperature and respective turbulent heat fluxes are extensively reported in this paper. -- Abstract: Good prediction of the flow and heat transfer phenomena in the pebble bed core of a high temperature reactor (HTR) is a challenge for available turbulence models, which still require to be validated. While experimental data are generally desirable in this validation process, due to the complex geometric configuration and measurement difficulties, a very limited amount of data is currently available. On the other hand, direct numerical simulation (DNS) is considered an accurate simulation technique, which may serve as an alternative for validating turbulence models. In the framework of the present study, quasi-direct numerical simulation (q-DNS) of a single face cubic centered pebble bed is performed, which will serve as a reference for the validation of different turbulence modeling approaches in order to perform calculations for a randomly arranged pebble bed. These simulations were performed at a Reynolds number of 3088, based on pebble diameter, with a porosity level of 0.42. Results related to flow field (mean, RMS and covariance of velocity) have been presented in Part-I, whereas, in the present article, we focus our attention to the analysis of the temperature field. A wide range of qualitative and quantitative data for the thermal field (mean, RMS and turbulent heat flux) has been generated
Xia, Ji; Xu, Xiao; Miyake, Atsushi; Kimura, Yuta; Omori, Toshihiro; Tokunaga, Masashi; Kainuma, Ryosuke
2017-12-01
Stress-induced and magnetic-field-induced martensitic transformation behaviors at low temperatures were investigated for Fe-Mn-Al-Ni alloys. The magnetic-field-induced reverse martensitic transformation was directly observed by in situ optical microscopy. Magnetization measurements under pulsed magnetic fields up to 50 T were carried out at temperatures between 4.2 and 125 K on a single-crystal sample; full magnetic-field-induced reverse martensitic transformation was confirmed at all tested temperatures. Compression tests from 10 to 100 K were conducted on a single-crystal sample; full shape recovery was obtained at all tested temperatures. It was found that the temperature dependence of both the critical stress and critical magnetic field is small and that the transformation hysteresis is less sensitive to temperature even at cryogenic temperatures. The temperature dependence of entropy change during martensitic transformation up to 100 K was then derived using the Clausius-Clapeyron relation with critical stresses and magnetic fields.
Reineke, Kai; Schottroff, Felix; Meneses, Nicolas; Knorr, Dietrich
2015-01-01
The intention of this study was to investigate the inactivation of endospores by a combined thermal and pulsed electric field (PEF) treatment. Therefore, self-cultivated spores of Bacillus subtilis and commercial Geobacillus stearothermophilus spores with certified heat resistance were utilized. Spores of both strains were suspended in saline water (5.3 mS cm(-1)), skim milk (0.3% fat; 5.3 mS cm(-1)) and fresh prepared carrot juice (7.73 mS cm(-1)). The combination of moderate preheating (70-90°C) and an insulated PEF-chamber, combined with a holding tube (65 cm) and a heat exchanger for cooling, enabled a rapid heat up to 105-140°C (measured above the PEF chamber) within 92.2-368.9 μs. To compare the PEF process with a pure thermal inactivation, each spore suspension was heat treated in thin glass capillaries and D-values from 90 to 130°C and its corresponding z-values were calculated. For a comparison of the inactivation data, F-values for the temperature fields of both processes were calculated by using computational fluid dynamics (CFD). A preheating of saline water to 70°C with a flow rate of 5 l h(-1), a frequency of 150 Hz and an energy input of 226.5 kJ kg(-1), resulted in a measured outlet temperature of 117°C and a 4.67 log10 inactivation of B. subtilis. The thermal process with identical F-value caused only a 3.71 log10 inactivation. This synergism of moderate preheating and PEF was even more pronounced for G. stearothermophilus spores in saline water. A preheating to 95°C and an energy input of 144 kJ kg(-1) resulted in an outlet temperature of 126°C and a 3.28 log10 inactivation, whereas nearly no inactivation (0.2 log10) was achieved during the thermal treatment. Hence, the PEF technology was evaluated as an alternative ultra-high temperature process. However, for an industrial scale application of this process for sterilization, optimization of the treatment chamber design is needed to reduce the occurring inhomogeneous temperature fields.
FIELD SURVEYS OF OZONE SYMPTOMS IN EUROPE. PROBLEMS, RELIABILITY AND SIGNIFICANCE FOR ECOSYSTEMS
Directory of Open Access Journals (Sweden)
F. Bussotti
2015-04-01
Full Text Available The ICP-Forest program for the monitoring of forest conditions includes the assessment of ozone symptoms in the European forests. This contribute to discussion points out the problems related to the recognition of such symptoms, with a special focus on the difficulties to extend the results obtained in experimental conditions to woody plant species growing in the field. Non specific symptoms (such as reddening, yellowing, early senescence and leaf loss, and the concurrent action of modifying factors (high light, drought, nutrient deficiency, pest attack and fungi make the recognition elusive. In these cases, the action of ozone cannot be proven or excluded with “ad hoc” experiments. Apparently “good” bioindicators (Rubus sp. Cornus sp. pl., Prunus sp. pl., Viburnum sp. pl. etc. are not suitable to assess the impact of ozone on vegetation. Symptoms are not necessarily related to the ozone dose taken up by stomata, and don’t are reliable indicator for biomass and productivity losses. Symptoms can be considered an epiphenomenon of more complex ecosystem processes.
The dose-volume constraint satisfaction problem for inverse treatment planning with field segments
International Nuclear Information System (INIS)
Michalski, Darek; Xiao, Ying; Censor, Yair; Galvin, James M
2004-01-01
The prescribed goals of radiation treatment planning are often expressed in terms of dose-volume constraints. We present a novel formulation of a dose-volume constraint satisfaction search for the discretized radiation therapy model. This approach does not rely on any explicit cost function. Inverse treatment planning uses the aperture-based approach with predefined, according to geometric rules, segmental fields. The solver utilizes the simultaneous version of the cyclic subgradient projection algorithm. This is a deterministic iterative method designed for solving the convex feasibility problems. A prescription is expressed with the set of inequalities imposed on the dose at the voxel resolution. Additional constraint functions control the compliance with selected points of the expected cumulative dose-volume histograms. The performance of this method is tested on prostate and head-and-neck cases. The relationships with other models and algorithms of similar conceptual origin are discussed. The demonstrated advantages of the method are: the equivalence of the algorithmic and prescription parameters, the intuitive setup of free parameters, and the improved speed of the method as compared to similar iterative as well as other techniques. The technique reported here will deliver approximate solutions for inconsistent prescriptions
A gradient stable scheme for a phase field model for the moving contact line problem
Gao, Min
2012-02-01
In this paper, an efficient numerical scheme is designed for a phase field model for the moving contact line problem, which consists of a coupled system of the Cahn-Hilliard and Navier-Stokes equations with the generalized Navier boundary condition [1,2,4]. The nonlinear version of the scheme is semi-implicit in time and is based on a convex splitting of the Cahn-Hilliard free energy (including the boundary energy) together with a projection method for the Navier-Stokes equations. We show, under certain conditions, the scheme has the total energy decaying property and is unconditionally stable. The linearized scheme is easy to implement and introduces only mild CFL time constraint. Numerical tests are carried out to verify the accuracy and stability of the scheme. The behavior of the solution near the contact line is examined. It is verified that, when the interface intersects with the boundary, the consistent splitting scheme [21,22] for the Navier Stokes equations has the better accuracy for pressure. © 2011 Elsevier Inc.
Temperature Fields in Soft Tissue during LPUS Treatment: Numerical Prediction and Experiment Results
International Nuclear Information System (INIS)
Kujawska, Tamara; Wojcik, Janusz; Nowicki, Andrzej
2010-01-01
Recent research has shown that beneficial therapeutic effects in soft tissues can be induced by the low power ultrasound (LPUS). For example, increasing of cells immunity to stress (among others thermal stress) can be obtained through the enhanced heat shock proteins (Hsp) expression induced by the low intensity ultrasound. The possibility to control the Hsp expression enhancement in soft tissues in vivo stimulated by ultrasound can be the potential new therapeutic approach to the neurodegenerative diseases which utilizes the known feature of cells to increase their immunity to stresses through the Hsp expression enhancement. The controlling of the Hsp expression enhancement by adjusting of exposure level to ultrasound energy would allow to evaluate and optimize the ultrasound-mediated treatment efficiency. Ultrasonic regimes are controlled by adjusting the pulsed ultrasound waves intensity, frequency, duration, duty cycle and exposure time. Our objective was to develop the numerical model capable of predicting in space and time temperature fields induced by a circular focused transducer generating tone bursts in multilayer nonlinear attenuating media and to compare the numerically calculated results with the experimental data in vitro. The acoustic pressure field in multilayer biological media was calculated using our original numerical solver. For prediction of temperature fields the Pennes' bio-heat transfer equation was employed. Temperature field measurements in vitro were carried out in a fresh rat liver using the 15 mm diameter, 25 mm focal length and 2 MHz central frequency transducer generating tone bursts with the spatial peak temporal average acoustic intensity varied between 0.325 and 1.95 W/cm 2 , duration varied from 20 to 500 cycles at the same 20% duty cycle and the exposure time varied up to 20 minutes. The measurement data were compared with numerical simulation results obtained under experimental boundary conditions. Good agreement between the
Determination of Ground Heat Exchangers Temperature Field in Geothermal Heat Pumps
Zhurmilova, I.; Shtym, A.
2017-11-01
For the heating and cooling supply of buildings and constructions geothermal heat pumps using low-potential ground energy are applied by means of ground exchangers. The process of heat transfer in a system of ground exchangers is a phenomenon of complex heat transfer. The paper presents a mathematical modeling of heat exchange processes, the temperature fields are built which are necessary for the determination of the ground array that ensures an adequate supply of low potential energy excluding the freezing of soil around the pipes in the ground heat exchangers and guaranteeing a reliable operation of geothermal heat pumps.
Correspondence between imaginary-time and real-time finite-temperature field theory
International Nuclear Information System (INIS)
Kobes, R.
1990-01-01
It is known that one-particle-irreducible graphs found using the imaginary-time formalism of finite-temperature field theory differ in general with those of the real-time formalism. Here it is shown that within the real-time formalism one can consider a sum of graphs, motivated by causality arguments, which at least in a number of simple examples agree with the corresponding analytically continued imaginary-time result. The occurrence of multiple statistical factors in this sum of graphs is discussed
Directory of Open Access Journals (Sweden)
Weiguo Li
2011-01-01
Full Text Available Taking the hafnium diboride ceramic as an example, the effects of heating rate, cooling rate, thermal shock initial temperature, and external constraint on the thermal shock resistance (TSR of ultra-high temperature ceramics (UHTCs were studied through numerical simulation in this paper. The results show that the external constraint has an approximately linear influence on the critical rupture temperature difference of UHTCs. The external constraint prepares a compressive stress field in the structure because of the predefined temperature field, and this compressive stress field relieves the tension stress in the structure when it is cooled down and then it improves the TSR of UHTCs. As the thermal shock initial temperature, a danger heating rate (or cooling rate exists where the critical temperature difference is the lowest.
Eremin, V V; Verbitskaya, E
2002-01-01
This study presents the results on the modeling of the electric field distribution, which is controlled by injection and trapping of non- equilibrium carriers, in Si detectors irradiated by high neutron fluences. Analytical calculation of the electric field distribution in detectors irradiated by neutron fluences of H-10**1**4 to 5-10**1**5 cm**-**2 has been performed, which shows possibility of full depletion voltage reduction at low operational temperatures with hole injection. All calculations are focused on the improvement of charge collection efficiency and prediction for detector behavior in LHC experiments. Comparison of the results of calculations to the experimental data published earlier shows a good qualitative agreement. 10 Refs.
Swartz, M.; Allkofer, Y.; Bortoletto, D.; Cremaldi, L.; Cucciarelli, S.; Dorokhov, A.; Hoermann, C.; Kim, D.; Konecki, M.; Kotlinski, D.; Prokofiev, Kirill; Regenfus, Christian; Rohe, T.; Sanders, D.A.; Son, S.; Speer, T.
2006-01-01
We show that doubly peaked electric fields are necessary to describe grazing-angle charge collection measurements of irradiated silicon pixel sensors. A model of irradiated silicon based upon two defect levels with opposite charge states and the trapping of charge carriers can be tuned to produce a good description of the measured charge collection profiles in the fluence range from 0.5x10^{14} Neq/cm^2 to 5.9x10^{14} Neq/cm^2. The model correctly predicts the variation in the profiles as the temperature is changed from -10C to -25C. The measured charge collection profiles are inconsistent with the linearly-varying electric fields predicted by the usual description based upon a uniform effective doping density. This observation calls into question the practice of using effective doping densities to characterize irradiated silicon.
Graphene field-effect transistors as room-temperature terahertz detectors
Vicarelli, L.; Vitiello, M. S.; Coquillat, D.; Lombardo, A.; Ferrari, A. C.; Knap, W.; Polini, M.; Pellegrini, V.; Tredicucci, A.
2012-10-01
The unique optoelectronic properties of graphene make it an ideal platform for a variety of photonic applications, including fast photodetectors, transparent electrodes in displays and photovoltaic modules, optical modulators, plasmonic devices, microcavities, and ultra-fast lasers. Owing to its high carrier mobility, gapless spectrum and frequency-independent absorption, graphene is a very promising material for the development of detectors and modulators operating in the terahertz region of the electromagnetic spectrum (wavelengths in the hundreds of micrometres), still severely lacking in terms of solid-state devices. Here we demonstrate terahertz detectors based on antenna-coupled graphene field-effect transistors. These exploit the nonlinear response to the oscillating radiation field at the gate electrode, with contributions of thermoelectric and photoconductive origin. We demonstrate room temperature operation at 0.3 THz, showing that our devices can already be used in realistic settings, enabling large-area, fast imaging of macroscopic samples.
Distributions of temperature and stress fields on penetration assembly during multi-pass welding
International Nuclear Information System (INIS)
Li Hong; Li Li
2010-01-01
Welding is a fundamental manufacturing technique used to join metal components. They cause errors during the assembly of the structure and reduce the strength of the structure. Based on an elastic-plastic-model, a three-dimensional finite element numerical simulation of a stainless steel penetration assembly during multi-pass welding with girth welds is carried out in this paper. And then the transient temperature field and the real-time dynamic stresses field of the structure are obtained. The heat source is modeled as a moving heat flux along girth welds following a double ellipsoid distribution. The 'birth and death' element method is applied to simulate the gradual growth of welding pass metal. The way of predicting the residual stresses in this paper can prepare an error-minimizing guide at design stage and can be used in accuracy management.
Three-dimensionality of field-induced magnetism in a high-temperature superconductor
DEFF Research Database (Denmark)
Lake, B.; Lefmann, K.; Christensen, N.B.
2005-01-01
Many physical properties of high-temperature superconductors are two-dimensional phenomena derived from their square-planar CuO(2) building blocks. This is especially true of the magnetism from the copper ions. As mobile charge carriers enter the CuO(2) layers, the antiferromagnetism of the parent...... insulators, where each copper spin is antiparallel to its nearest neighbours(1), evolves into a fluctuating state where the spins show tendencies towards magnetic order of a longer periodicity. For certain charge-carrier densities, quantum fluctuations are sufficiently suppressed to yield static long......-period order(2-6), and external magnetic fields also induce such order(7-12). Here we show that, in contrast to the chemically controlled order in superconducting samples, the field-induced order in these same samples is actually three-dimensional, implying significant magnetic linkage between the CuO(2...
Elzouka, Mahmoud
This dissertation investigates Near-Field Thermal Radiation (NFTR) applied to MEMS-based concentrated solar thermophotovoltaics (STPV) energy conversion and thermal memory and logics. NFTR is the exchange of thermal radiation energy at nano/microscale; when separation between the hot and cold objects is less than dominant radiation wavelength (˜1 mum). NFTR is particularly of interest to the above applications due to its high rate of energy transfer, exceeding the blackbody limit by orders of magnitude, and its strong dependence on separation gap size, surface nano/microstructure and material properties. Concentrated STPV system converts solar radiation to electricity using heat as an intermediary through a thermally coupled absorber/emitter, which causes STPV to have one of the highest solar-to-electricity conversion efficiency limits (85.4%). Modeling of a near-field concentrated STPV microsystem is carried out to investigate the use of STPV based solid-state energy conversion as high power density MEMS power generator. Numerical results for In 0.18Ga0.82Sb PV cell illuminated with tungsten emitter showed significant enhancement in energy transfer, resulting in output power densities as high as 60 W/cm2; 30 times higher than the equivalent far-field power density. On thermal computing, this dissertation demonstrates near-field heat transfer enabled high temperature NanoThermoMechanical memory and logics. Unlike electronics, NanoThermoMechanical memory and logic devices use heat instead of electricity to record and process data; hence they can operate in harsh environments where electronics typically fail. NanoThermoMechanical devices achieve memory and thermal rectification functions through the coupling of near-field thermal radiation and thermal expansion in microstructures, resulting in nonlinear heat transfer between two temperature terminals. Numerical modeling of a conceptual NanoThermoMechanical is carried out; results include the dynamic response under
International Nuclear Information System (INIS)
Russo, A.; Speranza, A.; DELIA, R.; ANTOLINI, R.; FERRARI, P.; FILIPPI, M.
2006-01-01
The Physics Department of Trento University (Italy), in collaboration with Bruker Biospin decided to set up a 4 T MR system for research in the neurological field as well as on the biological effects of high field MRI. Nowadays the number of similar apparatus set up in the world is very low, several of these operate in the USA, some in Australia and one in Israel. Due to the very low diffusion of these equipments and to the few knowledge today available about the biological effects by clinical application of high field MRI, the problems related to the installation of the apparatus from the safety point of view are not well standardized. Therefore, in Trento, it has been necessary to deal with many problems regarding the set up of the MRI apparatus, taking also into account the current law in Italy with respect the safety and protection in MRI applications. In the present paper the Authors show the carried out studies and analyses, in relation to the organization of the safety aspects. These studies have resulted in arranging specific guidelines for: working in controlled way; emergency procedures for the patient advanced life support; procedures for the protocol of patient protection; rules for the safety of the operators, patients and general public. The carried out analyses have mainly taken into account the danger identification and the risk evaluation. For this reason it was set up a test protocol regarding:the performing tests, the very detailed test modalities for their periodic performance and the test sequence. For the patient safety and protection it has been necessary to put care, in the first step of the survey, to the subjects in critical situations, due to: working activity, clinical history, health conditions of the patient at the moment of the examination. So it has been necessary to set up an anamnesis questionnaire for the patient, finalized to spot: (1) the patients with particular contraindications for the MR examination; (2) the patients which
Energy Technology Data Exchange (ETDEWEB)
Russo, A.; Speranza, A. [National Research Council, Institute of Bioimaging and Biostructures- Dep.of Biomorphological and Functional Sciences - University Federico II, Napoli (Italy); DELIA, R. [University of Rome - Medicine and Surgery Faculty - La Sapienza Sez. Rieti (Italy); ANTOLINI, R. [University of Trento - Department of Physics, Trento (Italy); FERRARI, P. [University of Trento - Direction of Polo di Rovereto, Trento (Italy); FILIPPI, M. [University of Trento Prevention and Protection Service, Trento (Italy)
2006-07-01
The Physics Department of Trento University (Italy), in collaboration with Bruker Biospin decided to set up a 4 T MR system for research in the neurological field as well as on the biological effects of high field MRI. Nowadays the number of similar apparatus set up in the world is very low, several of these operate in the USA, some in Australia and one in Israel. Due to the very low diffusion of these equipments and to the few knowledge today available about the biological effects by clinical application of high field MRI, the problems related to the installation of the apparatus from the safety point of view are not well standardized. Therefore, in Trento, it has been necessary to deal with many problems regarding the set up of the MRI apparatus, taking also into account the current law in Italy with respect the safety and protection in MRI applications. In the present paper the Authors show the carried out studies and analyses, in relation to the organization of the safety aspects. These studies have resulted in arranging specific guidelines for: working in controlled way; emergency procedures for the patient advanced life support; procedures for the protocol of patient protection; rules for the safety of the operators, patients and general public. The carried out analyses have mainly taken into account the danger identification and the risk evaluation. For this reason it was set up a test protocol regarding:the performing tests, the very detailed test modalities for their periodic performance and the test sequence. For the patient safety and protection it has been necessary to put care, in the first step of the survey, to the subjects in critical situations, due to: working activity, clinical history, health conditions of the patient at the moment of the examination. So it has been necessary to set up an anamnesis questionnaire for the patient, finalized to spot: (1) the patients with particular contraindications for the MR examination; (2) the patients which
The onset of dissipation in high-temperature superconductors: Self-field experiments
Talantsev, E. F.; Strickland, N. M.; Wimbush, S. C.; Crump, W. P.
2017-12-01
The transport critical current, Ic, is usually defined in terms of a threshold electric field criterion, Ec, with the convention Ec = 1 μV/cm chosen somewhat arbitrarily to provide "reasonably small" electric power dissipation in practical devices. Thus Ic is not fundamentally determined. However, recently it has been shown that the self-field critical current of thin-film superconductors is indeed a fundamental property governed only by the London penetration depth of the material. Here we reconsider the definition of the critical current and resolve this apparent contradiction. We measure the field distribution across the width of both first-generation and second-generation high-temperature superconducting tapes as the transport current is increased from zero to Ic. We identify a threshold current, Ic,surfB, at which the local surface magnetic flux density, Bsurf, abruptly crosses over from a non-linear to a linear dependence on the transport current, as measured at any point on the superconductor surface. This results from the current distribution across the tape width transitioning from non-uniform to uniform. This coincides with the onset of dissipation and immediately precedes the appearance of a measureable electric field. In the present examples Ic,surfB is 12-15% lower than an Ic determined by the Ec criterion. We propose the transition of Bsurf(I) from non-linear to linear as a more fundamental criterion for determining transport critical currents.
In situ correction of field errors induced by temperature gradient in cryogenic undulators
Directory of Open Access Journals (Sweden)
Takashi Tanaka
2009-12-01
Full Text Available A new technique of undulator field correction for cryogenic permanent magnet undulators (CPMUs is proposed to correct the phase error induced by temperature gradient. This technique takes advantage of two important instruments: one is the in-vacuum self-aligned field analyzer with laser instrumentation system to precisely measure the distribution of the magnetic field generated by the permanent magnet arrays placed in vacuum, and the other is the differential adjuster to correct the local variation of the magnet gap. The details of the two instruments are described together with the method of how to analyze the field measurement data and deduce the gap variation along the undulator axis. The correction technique was applied to the CPMU with a length of 1.7 m and a magnetic period of 14 mm. It was found that the phase error induced during the cooling process was attributable to local gap variations of around 30 μm, which were then corrected by the differential adjuster.
Borradaile, Graham J.; Lagroix, France; Trimble, Dale
2001-09-01
Conventional alternating field (AF) demagnetization of the magnetite-bearing claystone foundations of a Saxon or late medieval lime kiln in Lincolnshire, England fail to isolate stable characteristic remanences, or remanences compatible with possible contemporary geomagnetic field orientations. Consolidation of the material prevented thermal demagnetization. When low temperature demagnetization (LTD) precedes AF demagnetization, however, the vector plots show a stable characteristic (primary) component. Magnetic anisotropy measurements show that the LTD did not significantly disturb the mineral fabric of the claystone, that the mineral fabric did not deflect the palaeofield, and that AF demagnetization did not induce a field-impressed anisotropy during the experiments. Anisotropy of low-field magnetic susceptibility (AMS) is affected by all minerals, and therefore the anisotropy of the magnetite was isolated by measuring anisotropy of anhysteretic remanence (AARM); this is of more relevance in evaluating the potential for palaeofield deflection. Thus, we conclude that LTD preceding AF demagnetization is responsible for improving the isolation of a characteristic remanence, which then favours a late medieval age for the kiln foundation.
Research, Development, and Field Testing of Thermochemical Recuperation for High Temperature Furnace
Energy Technology Data Exchange (ETDEWEB)
Kurek, Harry; Kozlov, Aleksandr
2014-03-31
potential performance of TCR. • Phase II: Conduct research and development to take the validated technology concept from Phase I to a developmental state for a Phase 3, prototype field test. • Phase III: Design, fabricate, and prototype field testing of the TCR unit close coupled to an existing high temperature reheat furnace at a steel company for evaluation under industrial conditions The project was initiated on September 30, 2008. The report of Phase I results and conclusions was issued on October 30, 2009. The findings were reviewed by the project partners and the collective recommendation was to proceed with Phase II. Upon the work-conclusion, the Phase II report was issued on March 5, 2012. The scope of work involved the physical testing of a laboratory scale Recuperative Reformer (RR) to validate predicted performances from the feasibility study in Phase I (26% fuel reduction). Although the testing was a successful validation (21% fuel reduction mode), a technical issue 5 arose, namely a Methane Reforming Rate (MRR) roll off or non-sustaining of the methane reforming rate. GTI’s preliminary conclusions were that mechanism(s) producing the methane reforming rate reduction were not entirely known or understood and the chemical kinetics that triggered the roll off mechanism and/or other mechanisms needed to be further evaluated. GTI developed a plan to uncover the reason(s) for not sustaining a satisfactory Methane Reforming Rate (MRR) of the laboratory scale recuperator reformer (RR). The extended testing program consisted primarily of four tasks based on expected outcomes at that time. The project partners reviewed the proposal and recommended the proposed work extension to proceed and suspension of Phase III pending further review of the results of this work identified as Task 2.5. Additional Temperature Threshold Testing was undertaken by GTI and simultaneously independent analysis was carried out by the University of California Davis. Upon completion of the
Analysis of flow fields, temperatures and ruthenium transport in the test facility
International Nuclear Information System (INIS)
Kaerkelae, T.; Pyykoenen, J.; Auvinen, A.; Jokiniemi, J.
2008-03-01
Ruthenium transport experiments were conducted at VTT during years 2002- 2006. Experiments gave information about ruthenium behaviour in air ingress accident conditions. This study complements those experiments with an analysis of the flows and thermal fields in the test system. Temperature profiles were measured at the walls of the experimental facility. Computational fluid dynamics (CFD) simulations used the measured profiles and provided predictions of flows and temperatures inside the furnace. Ruthenium transport was also modelled with CFD. Thermal characterisation of the reactor demonstrated that buoyancy has a significant role during the cooling after the furnace. A hypothesis of the dominant role of RuO2 and RuO3 condensation on reactor walls gave simulation results that are in accordance with radiotracer measurements of deposition in experiments conducted with furnace at 1500K. Actually, RuO3 does not condensate, but it thermal decomposes to RuO2. This does not seem to have effect on result. Particle formation around the furnace exit could be detected from the comparison of modelling results with the measured profiles. In several other experiments ruthenium behaviour is dominated by other issues. These are related to the complex ruthenium chemistry that includes various surface reactions. Thermal equilibrium indicates significant gaseous RuO4 concentration around 1300 K. It seems that seed particles decreased the catalytic decomposition activity of RuO4 to RuO2 around this temperature pushing the gas concentration towards the equilibrium, and further give rise to gaseous RuO4 transport to low temperatures. At higher temperature increasing mass flow rate of RuO2 particles is likely to catalyse (decomposition) reaction of RuO4 to RuO2. (au)
Steiss, Janet E; Wright, James C
2008-10-01
To determine whether Labrador Retrievers participating in field trials develop respiratory alkalosis and hypocapnia primarily in conditions of high ambient temperatures. 16 Labrador Retrievers. At each of 5 field trials, 5 to 10 dogs were monitored during a test (retrieval of birds over a variable distance on land [1,076 to 2,200 m]; 36 assessments); ambient temperatures ranged from 2.2 degrees to 29.4 degrees C. For each dog, rectal temperature was measured and a venous blood sample was collected in a heparinized syringe within 5 minutes of test completion. Blood samples were analyzed on site for Hct; pH; sodium, potassium, ionized calcium, glucose, lactate, bicarbonate, and total CO2 concentrations; and values of PvO2 and PvCO2. Scatterplots of each variable versus ambient temperature were reviewed. Regression analysis was used to evaluate the effect of ambient temperature ( 21 degrees C) on each variable. Compared with findings at ambient temperatures 21 degrees C; rectal temperature did not differ. Two dogs developed signs of heat stress in 1 test at an ambient temperature of 29 degrees C; their rectal temperatures were higher and PvCO2 values were lower than findings in other dogs. When running distances frequently encountered at field trials, healthy Labrador Retrievers developed hyperthermia regardless of ambient temperature. Dogs developed respiratory alkalosis and hypocapnia at ambient temperatures > 21 degrees C.
On the mixing model for calculating the temperature fields in nuclear reactor fuel assemblies
International Nuclear Information System (INIS)
Mikhin, V.I.; Zhukov, A.V.
1985-01-01
One of the alternatives of the mixing model applied for calculating temperature fields in nuclear reactor fuel assemblies,including the fuel assemblies with nonequilibrium energy-release in fuel element cross section, is consistently described. The equations for both constant and variable values of coolant density and heat capacity are obtained. The mixing model is based on a set of mass, heat and longitudinal momentum balance equations. This set is closed by the ratios connecting the unknown values for gaps between fuel elements with the averaged values for neighbouring channels. The ratios to close momentum and heat balance equations, explaining, in particular, the nonequivalent heat and mass, momentum and mass transfer coefficients, are suggested. The balance equations with variable coolant density and heat capacity are reduced to the form coinciding with those of the similar equations with constant values of these parameters. Application of one of the main ratios of the mixing model relating the coolant transverse overflow in the gaps between fuel elements to the averaged coolant rates (flow rates) in the neighbouring channels is mainly limited by the coolant stabilized flow in the fuel assemblies with regular symmetrical arrangement of elements. Mass transfer coefficients for these elements are experimentally determined. The ratio in the paper is also applicable for calculation of fuel assembly temperature fields with a small relative shift of elements
Pielke, R.A.; Stohlgren, T.; Schell, L.; Parton, W.; Doesken, N.; Redmond, K.; Moeny, J.; McKee, T.; Kittel, T.G.F.
2002-01-01
We evaluated long-term trends in average maximum and minimum temperatures, threshold temperatures, and growing season in eastern Colorado, USA, to explore the potential shortcomings of many climate-change studies that either: (1) generalize regional patterns from single stations, single seasons, or a few parameters over short duration from averaging dissimilar stations: or (2) generalize an average regional pattern from coarse-scale general circulation models. Based on 11 weather stations, some trends were weakly regionally consistent with previous studies of night-time temperature warming. Long-term (80 + years) mean minimum temperatures increased significantly (P days per year with temperatures ??? - 17.8 ??C (???0??F). However, spatial and temporal variation in the direction of change was enormous for all the other weather parameters tested, and, in the majority of tests, few stations showed significant trends (even at P summer, four stations had significant increases and three stations had significant decreases in minimum temperatures, producing a strongly mixed regional signal. Trends in maximum temperature varied seasonally and geographically, as did trends in threshold temperature days ???32.2??C (???90??F) or days ???37.8??C (???100??F). There was evidence of a subregional cooling in autumn's maximum temperatures, with five stations showing significant decreasing trends. There were many geographic anomalies where neighbouring weather stations differed greatly in the magnitude of change or where they had significant and opposite trends. We conclude that sub-regional spatial and seasonal variation cannot be ignored when evaluating the direction and magnitude of climate change. It is unlikely that one or a few weather stations are representative of regional climate trends, and equally unlikely that regionally projected climate change from coarse-scale general circulation models will accurately portray trends at sub-regional scales. However, the assessment of a
Li, Jiexiang; Sagoe, Gideon; Yang, Guang; Lu, Guoping
2018-02-01
Classical geothermometers are useful tools for estimating reservoir temperatures of geothermal systems. However, their application to low-medium temperature reservoirs is limited because large variations of temperatures calculated by different classical geothermometers are usually observed. In order to help choose the most appropriate classical geothermometer for calculating the temperatures of low-medium temperature reservoirs, this study evaluated the mineral-aqueous equilibria of typical low-medium temperature felsic reservoirs in the Yangbajing geothermal field and Guangdong geothermal fields. The findings of this study support that reservoirs in the Guangdong geothermal fields have no direct magma influence. Also, natural reservoirs may represent the intermediate steady state before reaching full equilibrium, which rarely occurs. For the low-medium temperature geothermal systems without the influence of magma, even with seawater intrusion, the process of minerals reaching mineral-aqueous equilibrium is sequential: chlorite and chalcedony are the first, then followed by K-feldspar, kaolinite and K-mica. Chlorite may reach equilibrium at varying activity values, and the equilibrium between K-feldspar and kaolinite or K-feldspar and K-mica can fix the contents of K and Al in the solutions. Although the SiO2 and Al attain equilibrium state, albite and laumontite remain unsaturated and thus may affect low-medium temperature calculations. In this study, the chalcedony geothermometer was found to be the most suitable geothermometer for low-medium temperature reservoirs. The results of K-Mg geothermometer may be useful to complement that of the chalcedony geothermometer in low-medium temperature reservoir systems. Na-K geothermometer will give unreliable results at low-medium temperatures; and Na-K-Ca will also be unsuitable to calculate reservoir temperatures lower than 180 °C, probably caused by the chemical imbalance of laumontite.
Failure to reach the optimal temperature during cryoablation due to refrigerant cylinder problem.
Kumar, Narendra; Dinh, Trang; Magdi Abbas, Mohamed; Phan, Kevin; Manusama, Randolph; Philippens, Suzanne; Maessen, Jos; Timmermans, Carl
2015-02-01
Pulmonary vein (PV) isolation is considered as a key to atrial fibrillation (AF) treatment. Cryoballoon ablation is an effective therapy for PV isolation for AF with minimal side effects and was approved by the US Food and Drug Administration (FDA) several years ago. Successful isolation of PVs during cryoablation depends on the balloon temperature and helps in early identification of noneffective cryoballoon applications. A lower balloon temperature has been associated with long-term success in isolation of PVs. At the start of the procedure, the cryoconsole displayed "low refrigerant level". After a few cycles of successful cryoballoon applications, for a fresh application for a new PV, the optimal temperature was not obtained in spite of obtaining good grade of occlusion and ostial positioning for right inferior pulmonary vein (RIPV). Later, immediately after changing the refrigerant cylinder, suitable temperature was obtained. We faced this situation thrice in a span of eight months. Low refrigerant level may cause nonoptimal temperature during cryoablation, which can be resolved by premature change of a gas cylinder.
Rasmussen, Laura Helene; Zhang, Wenxin; Hollesen, Jørgen; Cable, Stefanie; Hvidtfeldt Christiansen, Hanne; Jansson, Per-Erik; Elberling, Bo
2017-04-01
Permafrost affected areas in Greenland are expected to experience a marked temperature increase within decades. Most studies have considered near-surface permafrost sensitivity, whereas permafrost temperatures below the depths of zero annual amplitude is less studied despite being closely related to changes in near-surface conditions, such as changes in active layer thermal properties, soil moisture and snow depth. In this study, we measured the sensitivity of thermal conductivity (TC) to gravimetric water content (GWC) in frozen and thawed permafrost sediments from fine-sandy and gravelly deltaic and fine-sandy alluvial deposits in the Zackenberg valley, NE Greenland. We further calibrated a coupled heat and water transfer model, the "CoupModel", for one central delta sediment site with average snow depth and further forced it with meteorology from a nearby delta sediment site with a topographic snow accumulation. With the calibrated model, we simulated deep permafrost thermal dynamics in four 20-year scenarios with changes in surface temperature and active layer (AL) soil moisture: a) 3 °C warming and AL water table at 0.5 m depth; b) 3 °C warming and AL water table at 0.1 m depth; c) 6 °C warming and AL water table at 0.5 m depth and d) 6 °C warming and AL water table at 0.1 m depth. Our results indicate that frozen sediments have higher TC than thawed sediments. All sediments show a positive linear relation between TC and soil moisture when frozen, and a logarithmic one when thawed. Gravelly delta sediments were highly sensitive, but never reached above 12 % GWC, indicating a field effect of water retention capacity. Alluvial sediments are less sensitive to soil moisture than deltaic (fine and coarse) sediments, indicating the importance of unfrozen water in frozen sediment. The deltaic site with snow accumulation had 1 °C higher mean annual ground temperature than the average snow depth site. Permafrost temperature at the depth of 18 m increased with 1
Michael, L.; Nikiforakis, N.
2018-02-01
This work is concerned with the effect of cavity collapse in non-ideal explosives as a means of controlling their sensitivity. The main objective is to understand the origin of localised temperature peaks (hot spots) which play a leading order role at the early stages of ignition. To this end, we perform two- and three-dimensional numerical simulations of shock-induced single gas-cavity collapse in liquid nitromethane. Ignition is the result of a complex interplay between fluid dynamics and exothermic chemical reaction. In order to understand the relative contribution between these two processes, we consider in this first part of the work the evolution of the physical system in the absence of chemical reactions. We employ a multi-phase mathematical formulation which can account for the large density difference across the gas-liquid material interface without generating spurious temperature peaks. The mathematical and physical models are validated against experimental, analytic, and numerical data. Previous inert studies have identified the impact of the upwind (relative to the direction of the incident shock wave) side of the cavity wall to the downwind one as the main reason for the generation of a hot spot outside of the cavity, something which is also observed in this work. However, it is also apparent that the topology of the temperature field is more complex than previously thought and additional hot spot locations exist, which arise from the generation of Mach stems rather than jet impact. To explain the generation mechanisms and topology of the hot spots, we carefully follow the complex wave patterns generated in the collapse process and identify specifically the temperature elevation or reduction generated by each wave. This enables tracking each hot spot back to its origins. It is shown that the highest hot spot temperatures can be more than twice the post-incident shock temperature of the neat material and can thus lead to ignition. By comparing two
International Nuclear Information System (INIS)
Dino, Wilson Agerico; Kasai, Hideaki; Rodulfo, Emmanuel Tapas; Nishi, Mayuko
2006-01-01
Manifestations of the Kondo effect on an atomic length scale on and around a magnetic atom adsorbed on a nonmagnetic surface differ depending on the spectroscopic mode of operation of the scanning tunneling microscope. Two prominent signatures of the Kondo effect that can be observed at surfaces are the development of a sharp resonance (Yosida-Kondo resonance) at the Fermi level, which broadens with increasing temperature, and the splitting of this sharp resonance upon application of an external magnetic field. Until recently, observing the temperature and magnetic field dependence has been a challenge, because the experimental conditions strongly depend on the system's critical temperature, the so-called Kondo temperature T K . In order to clearly observe the temperature dependence, one needs to choose a system with a large T K . One can thus perform the experiments at temperatures T K . However, because the applied external magnetic field necessary to observe the magnetic field dependence scales with T K , one needs to choose a system with a very small T K . This in turn means that one should perform the experiments at very low temperatures, e.g., in the mK range. Here we discuss the temperature and magnetic field dependence of the Yosida-Kondo resonance for a single magnetic atom on a metal surface, in relation to recent experimental developments
Luukko, P. J. J.; Räsänen, E.
2013-03-01
We present a code for solving the single-particle, time-independent Schrödinger equation in two dimensions. Our program utilizes the imaginary time propagation (ITP) algorithm, and it includes the most recent developments in the ITP method: the arbitrary order operator factorization and the exact inclusion of a (possibly very strong) magnetic field. Our program is able to solve thousands of eigenstates of a two-dimensional quantum system in reasonable time with commonly available hardware. The main motivation behind our work is to allow the study of highly excited states and energy spectra of two-dimensional quantum dots and billiard systems with a single versatile code, e.g., in quantum chaos research. In our implementation we emphasize a modern and easily extensible design, simple and user-friendly interfaces, and an open-source development philosophy. Catalogue identifier: AENR_v1_0 Program summary URL: http://cpc.cs.qub.ac.uk/summaries/AENR_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: GNU General Public License version 3 No. of lines in distributed program, including test data, etc.: 11310 No. of bytes in distributed program, including test data, etc.: 97720 Distribution format: tar.gz Programming language: C++ and Python. Computer: Tested on x86 and x86-64 architectures. Operating system: Tested under Linux with the g++ compiler. Any POSIX-compliant OS with a C++ compiler and the required external routines should suffice. Has the code been vectorised or parallelized?: Yes, with OpenMP. RAM: 1 MB or more, depending on system size. Classification: 7.3. External routines: FFTW3 (http://www.fftw.org), CBLAS (http://netlib.org/blas), LAPACK (http://www.netlib.org/lapack), HDF5 (http://www.hdfgroup.org/HDF5), OpenMP (http://openmp.org), TCLAP (http://tclap.sourceforge.net), Python (http://python.org), Google Test (http://code.google.com/p/googletest/) Nature of problem: Numerical calculation
Shi, Y.; Jiang, G.; Hu, S.
2017-12-01
Daqing, as the largest oil field of China with more than 50 years of exploration and production history for oil and gas, its geothermal energy utilization was started in 2000, with a main focus on district heating and direct use. In our ongoing study, data from multiple sources are collected, including BHT, DST, steady state temperature measurements in deep wells and thermophysical properties of formations. Based on these measurements, an elaborate investigation of the temperature field of Daqing Oilfield is made. Moreover, through exploration for oil and gas, subsurface geometry, depth, thickness and properties of the stratigraphic layers have been extensively delineated by well logs and seismic profiles. A 3D model of the study area is developed incorporating the information of structure, stratigraphy, basal heat flow, and petrophysical and thermophysical properties of strata. Based on the model, a simulation of the temperature field of Daqing Oilfield is generated. A purely conductive regime is presumed, as demonstrated by measured temperature log in deep wells. Wells W1, W2 and SK2 are used as key wells for model calibration. Among them, SK2, as part of the International Continental Deep Drilling Program, has a designed depth of 6400m, the steady state temperature measurement in the borehole has reached the depth of 4000m. The results of temperature distribution generated from simulation and investigation are compared, in order to evaluate the potential of applying the method to other sedimentary basins with limited borehole temperature measurements but available structural, stratigraphic and thermal regime information.
Czech Academy of Sciences Publication Activity Database
Doležel, Ivo; Kropík, P.; Ulrych, B.
2013-01-01
Roč. 219, č. 13 (2013), s. 7159-7169 ISSN 0096-3003 R&D Projects: GA ČR GA102/09/1305 Grant - others:GA MŠk(CZ) MEB051041 Institutional support: RVO:61388998 Keywords : induction heating * electric field * temperature field Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 1.600, year: 2013 http://www.sciencedirect.com/science/article/pii/S0096300311010824
Ivanov, Martin; Warrach-Sagi, Kirsten; Wulfmeyer, Volker
2018-04-01
A new approach for rigorous spatial analysis of the downscaling performance of regional climate model (RCM) simulations is introduced. It is based on a multiple comparison of the local tests at the grid cells and is also known as "field" or "global" significance. New performance measures for estimating the added value of downscaled data relative to the large-scale forcing fields are developed. The methodology is exemplarily applied to a standard EURO-CORDEX hindcast simulation with the Weather Research and Forecasting (WRF) model coupled with the land surface model NOAH at 0.11 ∘ grid resolution. Monthly temperature climatology for the 1990-2009 period is analysed for Germany for winter and summer in comparison with high-resolution gridded observations from the German Weather Service. The field significance test controls the proportion of falsely rejected local tests in a meaningful way and is robust to spatial dependence. Hence, the spatial patterns of the statistically significant local tests are also meaningful. We interpret them from a process-oriented perspective. In winter and in most regions in summer, the downscaled distributions are statistically indistinguishable from the observed ones. A systematic cold summer bias occurs in deep river valleys due to overestimated elevations, in coastal areas due probably to enhanced sea breeze circulation, and over large lakes due to the interpolation of water temperatures. Urban areas in concave topography forms have a warm summer bias due to the strong heat islands, not reflected in the observations. WRF-NOAH generates appropriate fine-scale features in the monthly temperature field over regions of complex topography, but over spatially homogeneous areas even small biases can lead to significant deteriorations relative to the driving reanalysis. As the added value of global climate model (GCM)-driven simulations cannot be smaller than this perfect-boundary estimate, this work demonstrates in a rigorous manner the
Sharifi, Reza; Moore, Farid; Mohammadi, Zargham; Keshavarzi, Behnam
2016-01-01
Chemical analyses of water samples from 19 hot and cold springs are used to characterize Takab geothermal field, west of Iran. The springs are divided into two main groups based on temperature, host rock, total dissolved solids (TDS), and major and minor elements. TDS, electrical conductivity (EC), Cl(-), and SO4 (2-) concentrations of hot springs are all higher than in cold springs. Higher TDS in hot springs probably reflect longer circulation and residence time. The high Si, B, and Sr contents in thermal waters are probably the result of extended water-rock interaction and reflect flow paths and residence time. Binary, ternary, and Giggenbach diagrams were used to understand the deeper mixing conditions and locations of springs in the model system. It is believed that the springs are heated either by mixing of deep geothermal fluid with cold groundwater or low conductive heat flow. Mixing ratios are evaluated using Cl, Na, and B concentrations and a mass balance approach. Calculated quartz and chalcedony geothermometer give lower reservoir temperatures than cation geothermometers. The silica-enthalpy mixing model predicts a subsurface reservoir temperature between 62 and 90 °C. The δ(18)O and δD (δ(2)H) are used to trace and determine the origin and movement of water. Both hot and cold waters plot close to the local meteoric line, indicating local meteoric origin.
Temperature dependence of magnetic anisotropy and magnetostriction: Beyond the mean-field theory
International Nuclear Information System (INIS)
Millev, Y.; Faehnle, M.
1994-05-01
The first nonvanishing magnetic anisotropy coefficient is calculated as a function of temperature for any spin quantum number and all temperatures below the Curie temperature for the case of face-centred cubic symmetry within the random-phase approximation (RPA). A detailed and instructive comparison between the mean-field and the RPA predictions is carried out. The RPA magnetization curves are also given for the first time for spins S>1/2. Most of the theoretical considerations are quite general as regard lattice type and even decoupling scheme and can thus be applied straightforwardly to other cases of interest. The progress reported here has been attained with the help of a new simplified and improved parametric approach and of a recent calculation of the average occupation number of magnons within the RPA. In particular, the new approach makes unnecessary the solving of integral equations so that the proposed procedure is especially simple and practically versatile in applications to any particular anisotropic material. (author). Refs, 6 figs
Cooling profiles of laser induced temperature fields for superconducting vanadium nitrate products
Emetere, Moses Eterigho
2016-01-01
The flexibility of vanadium nitrate makes it a good constituent for emerging superconductors. Its thermal instability engenders a disordered structure when doped by insulating constituents. The physics of the heat source i.e. the probe laser was theoretical derived to avoid deficiency of the superconducting material at low laser energy density. The mathematical experimentation was accomplished by queering the energy balance and heat conductivity of the individual constituents of the reagent. In-depth analysis of the layered distribution of laser induced temperature fields was carried out by cooling the compound via the forced convective cooling technique to about 150 °C. The material was gradual heated via the laser probe to its superconducting state. The structural defect which explained different state of the thermal outcomes were explained and proven to correspond with experimental outcomes. The temperature distribution under the irradiating laser intensity (0.45 W) shows an effective decay rate probability density function which is peculiar to the concept of photoluminescence. The dynamics of the electronic structure of thermally-excited superconducting materials is hinged on the complementary stoichiometry signatures, thermal properties amongst others. The maximum possible critical temperatures of the inter-layer were calculated to be about 206 K.
Jung, Jin-Oh; Choi, Seokhwan; Lee, Yeonghoon; Kim, Jinwoo; Son, Donghyeon; Lee, Jhinhwan
2017-10-01
We have built a variable temperature scanning probe microscope (SPM) that covers 4.6 K-180 K and up to 7 T whose SPM head fits in a 52 mm bore magnet. It features a temperature-controlled sample stage thermally well isolated from the SPM body in good thermal contact with the liquid helium bath. It has a 7-sample-holder storage carousel at liquid helium temperature for systematic studies using multiple samples and field emission targets intended for spin-polarized spectroscopic-imaging scanning tunneling microscopy (STM) study on samples with various compositions and doping conditions. The system is equipped with a UHV sample preparation chamber and mounted on a two-stage vibration isolation system made of a heavy concrete block and a granite table on pneumatic vibration isolators. A quartz resonator (qPlus)-based non-contact atomic force microscope (AFM) sensor is used for simultaneous STM/AFM operation for research on samples with highly insulating properties such as strongly underdoped cuprates and strongly correlated electron systems.
Basic thermo-fluid dynamic problems in high temperature heat exchangers
International Nuclear Information System (INIS)
McEligot, D.M.
1986-01-01
The authors consider high temperature heat exchangers to be ones where the heat transfer coefficients cannot be predicted confidently by classical analyses for pure forced convection with constant fluid properties. Alternatively, one could consider heat exchangers operating above some arbitrary temperature, say 1000F or 600C perhaps, to be at high temperature conditions. In that case, most common working fluids will be superheated vapors or gases. While some liquid metal heat exchangers are designed to operate in this range, the heat transfer coefficients of liquid metals are usually sufficiently high that the dominant thermal resistance would be due to the second fluid. This paper concentrates on convective heat transfer with gases. Typical applications include modular gas cooled nuclear reactors, proposed nuclear propulsion systems and space power plants, and superheaters in Rankine steam cycles
A light touch: application of optics and lasers to temperature control problems
CSIR Research Space (South Africa)
Forbes, A
2010-11-01
Full Text Available is by definition a non-contact measurement process; there is not physical contact with the object under study, and the light we use for our measurement is light that is being ?released? or emitted from the object due to its temperature. Bodies radiate energy... Around one hundred years ago, physicists discovered the na-ture of blackbodies: objects that exhibit a particular trait that the light they emit is dependent on the temperature of the body itself. The most well known example of a blackbody is our Sun...
Narita, Fumio; Fox, Marina; Mori, Kotaro; Takeuchi, Hiroki; Kobayashi, Takuya; Omote, Kenji
2017-11-01
This paper studies the energy harvesting characteristics of piezoelectric laminates consisting of barium titanate (BaTiO3) and copper (Cu) from room temperature to cryogenic/high temperatures both experimentally and numerically. First, the output voltages of the piezoelectric BaTiO3/Cu laminates were measured from room temperature to a cryogenic temperature (77 K). The output power was evaluated for various values of load resistance. The results showed that the maximum output power density is approximately 2240 nW cm‑3. The output voltages of the BaTiO3/Cu laminates were also measured from room temperature to a higher temperature (333 K). To discuss the output voltages of the BaTiO3/Cu laminates due to temperature changes, phase field and finite element simulations were combined. A phase field model for grain growth was used to generate grain structures. The phase field model was then employed for BaTiO3 polycrystals, coupled with the time-dependent Ginzburg–Landau theory and the oxygen vacancies diffusion, to calculate the temperature-dependent piezoelectric coefficient and permittivity. Using these properties, the output voltages of the BaTiO3/Cu laminates from room temperature to both 77 K and 333 K were analyzed by three dimensional finite element methods, and the results are presented for several grain sizes and oxygen vacancy densities. It was found that electricity in the BaTiO3 ceramic layer is generated not only through the piezoelectric effect caused by a thermally induced bending stress but also by the temperature dependence of the BaTiO3 piezoelectric coefficient and permittivity.
Current Problems and Possible Solutions in High-Temperature Lead-Free Soldering
Czech Academy of Sciences Publication Activity Database
Kroupa, Aleš; Andersson, D.; Hoo, N.; Pearce, J.; Watson, A.; Dinsdale, A.; Mucklejohn, S.
2012-01-01
Roč. 21, č. 5 (2012), s. 629-637 ISSN 1059-9495 Institutional support: RVO:68081723 Keywords : lead-free soldering , * materials for high-temperature LF * new technologies for HT lead-free soldering Subject RIV: BJ - Thermodynamics Impact factor: 0.915, year: 2012
Broken symmetries at high temperatures and the problem of baryon excess of the universe
Mohapatra, Rabindra N
1979-01-01
We discuss a class of gauge theories, where spontan- eously broken symmetries, instead of being restored, persist as the temperature is increased. Applying these ideas to the specific case of the soft CP- viola tion in grand unified theories, we discuss a mechanism to generate the baryon to entropy ratio of the universe.
On a non-linear problem posed by the temperature determination in an electrically heated plate
International Nuclear Information System (INIS)
Gerber, R.
1958-01-01
Let us consider a flat plate, electrically heated, with one face thermally insulated and the other face isothermal. It is shown that a two-dimensional perturbation of the insulated face has no influence on the temperature of this face. (author) [fr
Karachev, I I
1989-10-01
Maximum allowable electromagnetic field levels produced by teletransmitting stations and differentiated by frequency have been described. The prospects of further studies on the improvement of hygienic standardization of electromagnetic fields have been set forth.
Lim, Mikyung; Song, Jaeman; Kim, Jihoon; Lee, Seung S.; Lee, Ikjin; Lee, Bong Jae
2018-05-01
The present work successfully achieves a strong enhancement in performance of a near-field thermophotovoltaic (TPV) system operating at low temperature and large-vacuum-gap width by introducing a hyperbolic-metamaterial (HMM) emitter, multilayered graphene, and an Au-backside reflector. Design variables for the HMM emitter and the multilayered-graphene-covered TPV cell are optimized for maximizing the power output of the near-field TPV system with the genetic algorithm. The near-field TPV system with the optimized configuration results in 24.2 times of enhancement in power output compared with that of the system with a bulk emitter and a bare TPV cell. Through the analysis of the radiative heat transfer together with surface-plasmon-polariton (SPP) dispersion curves, it is found that coupling of SPPs generated from both the HMM emitter and the multilayered-graphene-covered TPV cell plays a key role in a substantial increase in the heat transfer even at a 200-nm vacuum gap. Further, the backside reflector at the bottom of the TPV cell significantly increases not only the conversion efficiency, but also the power output by generating additional polariton modes which can be readily coupled with the existing SPPs of the HMM emitter and the multilayered-graphene-covered TPV cell.
Felder, Thomas C.; Gambogi, William J.; Phillips, Nancy; MacMaster, Steven W.; Yu, Bao-Ling; Trout, T. John
2017-08-01
The need for faster PV qualification tests that more accurately match field observations is leading to tests with higher acceleration levels, and validating the new tests through comparison to field data is an important step. We have tested and compared a wide panel of backsheets according to a proposed new backsheet UV exposure qualification standard from the International Electrotechnical Commission (IEC). Weathering Technical Standard IEC 62788-7-2 specifies higher irradiance and higher black panel temperature UV Xenon exposures. We tested PVF, PVDF, PET, PA and FEVEbased backsheets in glass laminates and simple backsheet coupons in UV exposure condition A3 (0.8W/sqmnm@340nm and 90° C BPT) We find mild yellowing with no mechanical loss in the original lower intensity ASTM G155 0.55 W/sqm-nm 70C BPT exposure condition. The new A3 exposures creates mechanical loss in sensitive backsheets, with no effect on known durable backsheets. Results from the new exposure are closer to field mechanical loss data.
Numerical analysis of air-flow and temperature field in a passenger car compartment
Kamar, Haslinda Mohamed; Kamsah, Nazri; Mohammad Nor, Ahmad Miski
2012-06-01
This paper presents a numerical study on the temperature field inside a passenger's compartment of a Proton Wira saloon car using computational fluid dynamics (CFD) method. The main goal is to investigate the effects of different glazing types applied onto the front and rear windscreens of the car on the distribution of air-temperature inside the passenger compartment in the steady-state conditions. The air-flow condition in the passenger's compartment is also investigated. Fluent CFD software was used to develop a three-dimensional symmetrical model of the passenger's compartment. Simplified representations of the driver and one rear passenger were incorporated into the CFD model of the passenger's compartment. Two types of glazing were considered namely clear insulated laminated tint (CIL) with a shading coefficient of 0.78 and green insulated laminate tint (GIL) with a shading coefficient of 0.5. Results of the CFD analysis were compared with those obtained when the windscreens are made up of clear glass having a shading coefficient of 0.86. Results of the CFD analysis show that for a given glazing material, the temperature of the air around the driver is slightly lower than the air around the rear passenger. Also, the use of GIL glazing material on both the front and rear windscreens significantly reduces the air temperature inside the passenger's compartment of the car. This contributes to a better thermal comfort condition to the occupants. Swirling air flow condition occurs in the passenger compartment. The air-flow intensity and velocity are higher along the side wall of the passenger's compartment compared to that along the middle section of the compartment. It was also found that the use of glazing materials on both the front and rear windscreen has no significant effects on the air-flow condition inside the passenger's compartment of the car.
Temperature dataloggers as stove use monitors (SUMs): Field methods and signal analysis
Ruiz-Mercado, Ilse; Canuz, Eduardo; Smith, Kirk R.
2013-01-01
We report the field methodology of a 32-month monitoring study with temperature dataloggers as Stove Use Monitors (SUMs) to quantify usage of biomass cookstoves in 80 households of rural Guatemala. The SUMs were deployed in two stoves types: a well-operating chimney cookstove and the traditional open-cookfire. We recorded a total of 31,112 days from all chimney cookstoves, with a 10% data loss rate. To count meals and determine daily use of the stoves we implemented a peak selection algorithm based on the instantaneous derivatives and the statistical long-term behavior of the stove and ambient temperature signals. Positive peaks with onset and decay slopes exceeding predefined thresholds were identified as “fueling events”, the minimum unit of stove use. Adjacent fueling events detected within a fixed-time window were clustered in single “cooking events” or “meals”. The observed means of the population usage were: 89.4% days in use from all cookstoves and days monitored, 2.44 meals per day and 2.98 fueling events. We found that at this study site a single temperature threshold from the annual distribution of daily ambient temperatures was sufficient to differentiate days of use with 0.97 sensitivity and 0.95 specificity compared to the peak selection algorithm. With adequate placement, standardized data collection protocols and careful data management the SUMs can provide objective stove-use data with resolution, accuracy and level of detail not possible before. The SUMs enable unobtrusive monitoring of stove-use behavior and its systematic evaluation with stove performance parameters of air pollution, fuel consumption and climate-altering emissions. PMID:25225456
Michael, L.; Nikiforakis, N.
2018-02-01
two- and three-dimensional simulations to examine the change in topology, temperatures, and reactive strength of the hot spots by the third dimension. It is apparent that belated ignition times can be avoided by the use of three-dimensional simulations. The effect of the chemical reactions on the topology and strength of the hot spots in the timescales considered is also studied, in a comparison between inert and reactive simulations where maximum temperature fields and their growth rates are examined.
Yang, Zhibo; Zhang, Zhen; Liu, Aiju; Liu, Shian
2017-01-01
To solve problems in dressings for metal-bonded super-hard abrasive wheels, such as low efficiency and rapid wear, this article introduces a laser-assisted ultrasonic vibration dressing technique. Firstly, finite-element simulations were conducted on the dressing process of a bronze-bonded diamond wheel, and the wheel's temperature field distributions under different laser parameters were simulated. By analysing the simulation results of temperature fields and the melting point of the bronze bond, the laser parameters for laser-assisted ultrasonic vibration dressing tests were optimized, and then actual tests were carried out on the bronze-bonded diamond wheel. Results showed that, with appropriate technology parameters, the laser-assisted ultrasonic vibration dressing technique achieved desirable dressing results; specifically, the dressing force was low, the abrasive particles had high protrusions and the wheel had a large chip space and favourable surface topography.
A Mixed Enthalpy-Temperature Finite Element Method For Generalized Phase-Change Problems
DEFF Research Database (Denmark)
krabbenhøft, Kristian; Damkilde, Lars
2003-01-01
In a large number of problems of engineering interest the transition of the material from one phase to another is of vital importance in describing the overall physical behaviour. Common applications include metal casting, freezing and thawing of foodstuffs and other biological materials, ground ...
International Nuclear Information System (INIS)
Fujisawa, Nobuyuki; Abe, Takao; Yamagata, Takayuki; Tomidokoro, Hirofumi
2014-01-01
Highlights: • Flickering characteristics and temperature field of premixed methane/air flame are studied in co-flow. • The temperature is measured by improved flame reaction technique by correcting the number density of metal atoms. • The temperature calibration is conducted by sodium D-line reversal method. • The oscillation amplitude of flame decreases and the frequency increases with co-flow velocity. • The oscillation amplitude increases with equivalence ratio. - Abstract: The flickering characteristics and the temperature field of an axisymmetric premixed methane/air flame under the influence of co-flow are studied experimentally using the image analysis and the flame reaction technique. The premixed flame is visualized by the alkali metal solution of sodium (Na) for characterizing the flickering characteristics. The temperature measurement of the flame is carried out using the flame reaction technique combined with the relationship between the local intensity of the flame and the temperature from the sodium D-line reversal method, and the influence of the number density distribution of Na on the measured temperature field is corrected by the measurement integrated analysis of the flame with the iterative procedure. This technique is validated by the local temperature measurement in the steady flame under the influence of co-flow using the thermocouple calibrated by the sodium D-line reversal method. The flame visualization and temperature measurement in the flickering flame of the premixed methane/air flame indicates that the flame contour and the temperature field oscillate periodically with the flickering frequency due to the Kelvin–Helmholtz instability of the flame. The oscillation amplitude decreases and the frequency increases gradually with the co-flow velocity increases similar to the observation in the diffusion flame in literature, while the oscillation amplitude grows with the equivalence ratio increases. These changes in the flickering
International Nuclear Information System (INIS)
Cheah, C Y; Jaurigue, L C; Kaiser, A B; Gómez-Navarro, C
2013-01-01
We report an analysis of low-temperature measurements of the conductance of partially disordered reduced graphene oxide, finding that the data follow a simple crossover scenario. At room temperature, the conductance is dominated by two-dimensional (2D) electric field-assisted, thermally driven (Pollak–Riess) variable-range hopping (VRH) through highly disordered regions. However, at lower temperatures T, we find a smooth crossover to follow the exp(−E 0 /E) 1/3 field-driven (Shklovskii) 2D VRH conductance behaviour when the electric field E exceeds a specific crossover value E C (T) 2D =(E a E 0 1/3 /3) 3/4 determined by the scale factors E 0 and E a for the high-field and intermediate-field regimes respectively. Our crossover scenario also accounts well for experimental data reported by other authors for three-dimensional disordered carbon networks, suggesting wide applicability. (paper)
International Nuclear Information System (INIS)
Chen, Deshen; Qian, Hongliang; Wang, Huajie; Zhang, Gang; Fan, Feng; Shen, Shizhao
2017-01-01
Highlights: • Solar non-uniform temperature field test of a telescope’s reflector is conducted initially. • Time-varying distribution regularities are analyzed contrastively. • Simulation methods are proposed involving environmental factors and self-shadowing. • Refined discrimination method for the shadow distribution is put forward. • Validity of simulation methods is evaluated with the experimental data. - Abstract: To improve the ability of deep-space exploration, many astronomers around the world are actively engaged in the construction of large-aperture and high-precision radio telescopes. The temperature effect is one of three main factors affecting the reflector accuracy of radio telescopes. To study the daily non-uniform temperature field of the main reflector, experimental studies are first carried out with a 3-m-aperture radio telescope model. According to the test results for 16 working conditions, the distribution rule and time-varying regularity of the daily temperature field are summarized initially. Next, theoretical methods for the temperature field of the main reflector are studied considering multiple environmental parameters and self-shadows. Finally, the validity of the theoretical methods is evaluated with test results. The experimental study demonstrates that the non-uniform temperature distribution of the main reflector truly exists and should not be overlooked, and that the theoretical methods for the reflector temperature field proposed in this paper are effective. The research methods and conclusions can provide valuable references for thermal design, monitoring and control of similar high-precision radio telescopes.
Temperature and Magnetic Field Driven Modifications in the I-V Features of Gold-DNA-Gold Structure
Directory of Open Access Journals (Sweden)
Nadia Mahmoudi Khatir
2014-10-01
Full Text Available The fabrication of Metal-DNA-Metal (MDM structure-based high sensitivity sensors from DNA micro-and nanoarray strands is a key issue in their development. The tunable semiconducting response of DNA in the presence of external electromagnetic and thermal fields is a gift for molecular electronics. The impact of temperatures (25–55 °C and magnetic fields (0–1200 mT on the current-voltage (I-V features of Au-DNA-Au (GDG structures with an optimum gap of 10 μm is reported. The I-V characteristics acquired in the presence and absence of magnetic fields demonstrated the semiconducting diode nature of DNA in GDG structures with high temperature sensitivity. The saturation current in the absence of magnetic field was found to increase sharply with the increase of temperature up to 45 °C and decrease rapidly thereafter. This increase was attributed to the temperature-assisted conversion of double bonds into single bond in DNA structures. Furthermore, the potential barrier height and Richardson constant for all the structures increased steadily with the increase of external magnetic field irrespective of temperature variations. Our observation on magnetic field and temperature sensitivity of I-V response in GDG sandwiches may contribute towards the development of DNA-based magnetic sensors.
Directory of Open Access Journals (Sweden)
Kai eReineke
2015-05-01
Full Text Available The intention of this study was to investigate the inactivation of endospores by a combined thermal and pulsed electric field (PEF treatment. Therefore, self-cultivated spores of Bacillus subtilis and commercial Geobacillus stearothermophilus spores with certified heat resistance were utilized. Spores of both strains were suspended in saline water (5.3 mS cm-1, skim milk (0.3% fat; 5.3 mS cm-1 and fresh prepared carrot juice (7.73 mS cm-1. The combination of moderate preheating (70-90 °C and an insulated PEF-chamber, combined with a holding tube (65 cm and a heat exchanger for cooling, enabled a rapid heat up to 105-140 °C (measured above the PEF chamber within 92.2-368.9 µs. To compare the PEF process with a pure thermal inactivation, each spore suspension was heat treated in thin glass capillaries and D-values from 90 to 130°C and its corresponding z-values were calculated. For a comparison of the inactivation data, F-values for the temperature fields of both processes were calculated by using Comsol Multiphysics combined with a Matlab routine.A preheating of saline water to 70 °C with a flow rate of 5 l h-1, a frequency of 150 Hz and an energy input of 226.5 kJ kg-1, resulted in a measured outlet temperature of 117 °C and a 4.67 log10 inactivation of Bacillus subtilis. The thermal process with identical F-value caused only a 3.71 log10 inactivation. This synergism of moderate preheating and PEF was even more pronounced for Geobacillus stearothermophilus spores in saline water. A preheating to 95 °C and an energy input of 144 kJ kg-1 resulted in an outlet temperature of 126 °C and a 3.28 log10 inactivation, whereas nearly no inactivation (0.2 log10 was achieved during the thermal treatment.Hence, the PEF technology was evaluated as an alternative ultra-high temperature process. However, for an industrial scale application of this process for sterilization, optimization of the treatment chamber design is needed to reduce the occurring
Directory of Open Access Journals (Sweden)
Huang Can
2014-08-01
Full Text Available In the present paper, a numerical model combining radiation and conduction for porous materials is developed based on the finite volume method. The model can be used to investigate high-temperature thermal insulations which are widely used in metallic thermal protection systems on reusable launch vehicles and high-temperature fuel cells. The effective thermal conductivities (ECTs which are measured experimentally can hardly be used separately to analyze the heat transfer behaviors of conduction and radiation for high-temperature insulation. By fitting the effective thermal conductivities with experimental data, the equivalent radiation transmittance, absorptivity and reflectivity, as well as a linear function to describe the relationship between temperature and conductivity can be estimated by an inverse problems method. The deviation between the calculated and measured effective thermal conductivities is less than 4%. Using the material parameters so obtained for conduction and radiation, the heat transfer process in multilayer thermal insulation (MTI is calculated and the deviation between the calculated and the measured transient temperatures at a certain depth in the multilayer thermal insulation is less than 6.5%.
International Nuclear Information System (INIS)
Oizumi, T.; Laakso, I.; Hirata, A.; Fujiwara, O.; Watanabe, S.; Taki, M.; Kojima, M.; Sasaki, H.; Sasaki, K.
2013-01-01
The eye is said to be one of the most sensitive organs to microwave heating. According to previous studies, the possibility of microwave-induced cataract formation has been experimentally investigated in rabbit and monkey eyes, but not for the human eye due to ethical reasons. In the present study, the temperature elevation in the lens, the skin around the eye and the core temperature of numerical human and rabbit models for far-field and near-field exposures at 2.45 GHz are investigated. The temperature elevations in the human and rabbit models were compared with the threshold temperatures for inducing cataracts, thermal pain in the skin and reversible health effects such as heat exhaustion or heat stroke. For plane-wave exposure, the core temperature elevation is shown to be essential both in the human and in the rabbit models as suggested in the international guidelines and standards. For localised exposure of the human eye, the temperature elevation of the skin was essential, and the lens temperature did not reach its threshold for thermal pain. On the other hand, the lens temperature elevation was found to be dominant for the rabbit eye. (authors)
Directory of Open Access Journals (Sweden)
Dae Won Ji
2017-05-01
Full Text Available The strain changes during temperature rise of a poled lead titanate zirconate rectangular parallelepiped switched by electric field at room temperature are obtained by integrating thermal expansion coefficients that are measured using an invar-specimen. By estimating and analyzing pyroelectric and thermal expansion coefficients, first-order differential equations are constructed for polarization and strain changes during temperature increase. The solutions to the differential equations are found and used to calculate the high temperature behavior of the materials. It is shown that the predictions are well compared with measured responses. Finally, the developed formulae are applied to calculate strain butterfly loops from a polarization hysteresis loop at a high temperature.
International Nuclear Information System (INIS)
Cheng, M C; Yan, B P; Lee, K H; Ma, Q Y; Yang, E S
2005-01-01
High temperature superconductor (HTS) thin films have been applied in making a low loss RF receiver coil for improving magnetic resonance imaging image quality. However, the application of these coils is severely limited by their limited field of view (FOV). Stringent fabrication environment requirements and high cost are further limitations. In this paper, we propose a simpler method for designing and fabricating HTS coils. Using industrial silver alloy sheathed Bi (2-x) Pb x Sr 2 Ca 2 Cu 3 O 10 (Bi-2223) HTS tapes, a five-inch single-turn HTS solenoid coil has been developed, and human wrist images have been acquired with this coil. The HTS tape coil has demonstrated an enhanced FOV over a six-inch YBCO thin film surface coil at 77 K with comparable signal-to-noise ratio
International Nuclear Information System (INIS)
Holford, D.J.; Fayer, M.J.
1990-08-01
Protective barriers are being considered for use at the Hanford Site to enhance the isolation of radioactive wastes from water, plant, and animal intrusion. Lysimeters were constructed to evaluate the performance of asphalt barrier formulations under natural environmental conditions. These lysimeters were constructed of 1.7-m lengths of PVC pipe that have a diameter of 30 cm. The lysimeters were filled with layers of gravel, coarse sand, and asphalt. The sand and gravel placed under the asphalt barrier were wet when installed. TOUGH was used to conduct simulations to assess the effect of temperature variations on moisture and vapor movement beneath the asphalt layer in field test lysimeters. All variables in TOUGH were converted to double precision so that simulations could be run on a Sun-4 UNIX workstation. A radially symmetric grid was used to simulate the lysimeter. 8 refs., 9 figs
Unusual angular and temperature dependence of the upper critical field in UPt/sub 3/
Energy Technology Data Exchange (ETDEWEB)
Shivaram, B.S.; Rosenbaum, T.F.; Hinks, D.G.
1986-06-01
We report measurements of the upper critical field, H/sub c2/, inclined at various angles with respect to the c-axis in the heavy fermion superconductor UPt/sub 3/. The angular anisotropy observed near T/sub c/ = 0.53K cannot be explained quantitatively by presently available theoretical expressions which consider either isotropic or anisotropic pairing. In addition, we find that the anisotropy apparently disappears at T /approximately/200 mK, only to reemerge at lower temperatures with an opposite sense. We have also studied H/sub c2/ in the basal lane of this hexagonal crystal and find no angular dependence within the limits of our measurements. 15 refs., 4 figs., 1 tab.
Study of Temperature Fields at Sprinkled Smooth and Sandblasted Tube Bundle
Directory of Open Access Journals (Sweden)
Kracík Petr
2014-03-01
Full Text Available The paper focuses on the influence of sprinkled tube surface on distribution of temperature fields, i.e. the heat transfer coefficient on the tubes surface. Two types of tubes have been tested, a smooth one and a sandblasted one in particular. A tube bundle comprises of thirteen copper tubes divided into two rows and it is located in a low pressure chamber where vacuum is generated using an exhauster via ejector. The liquid tested was water at an absolute pressure in a chamber in between 97 kPa up to 10 kPa and a thermal gradient 55 to 30 °C. The flow of the falling film liquid ranged between zero and 17 litres per minute.
Optimization of lift gas allocation in a gas lifted oil field as non-linear optimization problem
Directory of Open Access Journals (Sweden)
Roshan Sharma
2012-01-01
Full Text Available Proper allocation and distribution of lift gas is necessary for maximizing total oil production from a field with gas lifted oil wells. When the supply of the lift gas is limited, the total available gas should be optimally distributed among the oil wells of the field such that the total production of oil from the field is maximized. This paper describes a non-linear optimization problem with constraints associated with the optimal distribution of the lift gas. A non-linear objective function is developed using a simple dynamic model of the oil field where the decision variables represent the lift gas flow rate set points of each oil well of the field. The lift gas optimization problem is solved using the emph'fmincon' solver found in MATLAB. As an alternative and for verification, hill climbing method is utilized for solving the optimization problem. Using both of these methods, it has been shown that after optimization, the total oil production is increased by about 4. For multiple oil wells sharing lift gas from a common source, a cascade control strategy along with a nonlinear steady state optimizer behaves as a self-optimizing control structure when the total supply of lift gas is assumed to be the only input disturbance present in the process. Simulation results show that repeated optimization performed after the first time optimization under the presence of the input disturbance has no effect in the total oil production.
Methodology for high-throughput field phenotyping of canopy temperature using airborne thermography
Directory of Open Access Journals (Sweden)
David Matthew Deery
2016-12-01
Full Text Available Lower canopy temperature (CT, resulting from increased stomatal conductance, has been associated with increased yield in wheat. Historically, CT has been measured with hand-held infrared thermometers. Using the hand-held CT method on large field trials is problematic, mostly because measurements are confounded by temporal weather changes during the time requiredto measure all plots. The hand-held CT method is laborious and yet the resulting heritability low, thereby reducing confidence in selection in large scale breeding endeavours.We have developed a reliable and scalable crop phenotyping method for assessing CT in large field experiments. The method involves airborne thermography from a manned helicopter using a radiometrically-calibrated thermal camera. Thermal image data is acquired from large experiments in the order of seconds, thereby enabling simultaneous measurement of CT on potentially 1,000s of plots. Effects of temporal weather variation when phenotyping large experiments using hand-held infrared thermometers are therefore reduced. The method is designed for cost-effective and large-scale use by the non-technical user and includes custom-developed software for data processing to obtain CT data on a single-plot basis for analysis.Broad-sense heritability was routinely greater than 0.50, and as high as 0.79, for airborne thermography CT measured near anthesis on a wheat experiment comprising 768 plots of size 2 x 6 m. Image analysis based on the frequency distribution of temperature pixels to remove the possible influence of background soil did not improve broad-sense heritability. Total imageacquisition and processing time was ca. 25 min and required only one person (excluding the helicopter pilot. The results indicate the potential to phenotype CT on large populations in genetics studies or for selection within a plant breeding program.
International Nuclear Information System (INIS)
Yung Moo Huh
2001-01-01
Thermodynamics has been studied systematically for the high temperature cuprate superconductor La 2-x Sr x CuO 4-δ , La-214, in the entire superconductive region from strongly underdoped to strongly overdoped regimes. Magnetization studies with H(parallel)c have been made in order to investigate the changes in free energy of the system as the number of carriers is reduced. Above the superconducting transition temperature, the normal-state magnetization exhibits a two-dimensional Heisenberg antiferromagnetic behavior. Below T c , magnetization data are thermodynamically reversible over large portions of the H-T plane, so the free energy is well defined in these regions. As the Sr concentration is varied over the wide range from 0.060 (strongly underdoped) to 0.234 (strongly overdoped), the free energy change goes through a maximum at the optimum doped in a manner similar to the T c0 vs. x curve. The density of states, N(0), remains nearly constant in the overdoped and optimum doped regimes, taking a broad maximum around x = 0.188, and then drops abruptly towards zero in the underdoped regime. The La 2-x Sr x CuO 4 (La-214) system displays the fluctuating vortex behavior with the characteristic of either 2D or 3D fluctuations as indicated by clearly identifiable crossing points T* close to T c . The dimensional character of the fluctuations depends on both applied magnetic fields and the density of charge carriers. The dimensional crossover from 2D to 3D occurs in the strongly underdoped regime when the c-axis coherence distance ζ c becomes comparable to the spacing between adjacent CuO 2 layers s at sufficiently high magnetic fields near H c2
International Nuclear Information System (INIS)
Finnemore, Douglas K.
2001-01-01
Thermodynamics has been studied systematically for the high temperature cuprate superconductor La 2-x Sr x CuO 4-δ , La-214, in the entire superconductive region from strongly underdoped to strongly overdoped regimes. Magnetization studies with H (parallel) c have been made in order to investigate the changes in free energy of the system as the number of carriers is reduced. Above the superconducting transition temperature, the normal-state magnetization exhibits a two-dimensional Heisenberg antiferromagnetic behavior. Below T c , magnetization data are thermodynamically reversible over large portions of the H-T plane, so the free energy is well defined in these regions. As the Sr concentration is varied over the wide range from 0.060 (strongly underdoped) to 0.234 (strongly overdoped), the free energy change goes through a maximum at the optimum doped in a manner similar to the T c0 vs. x curve. The density of states, N(0), remains nearly constant in the overdoped and optimum doped regimes, taking a broad maximum around x = 0.188, and then drops abruptly towards zero in the underdoped regime. The La 2-x Sr x CuO 4 (La-214) system displays the fluctuating vortex behavior with the characteristic of either 2D or 3D fluctuations as indicated by clearly identifiable crossing points T* close to T c . The dimensional character of the fluctuations depends on both applied magnetic fields and the density of charge carriers. The dimensional crossover from 2D to 3D occurs in the strongly underdoped regime when the c-axis coherence distance ξ c becomes comparable to the spacing between adjacent CuO 2 layers s at sufficiently high magnetic field near H c2
Energy Technology Data Exchange (ETDEWEB)
Finnemore, Douglas K. [Iowa State Univ., Ames, IA (United States)
2001-01-01
Thermodynamics has been studied systematically for the high temperature cuprate superconductor La_{2-x}Sr_{x}CuO_{4-δ}, La-214, in the entire superconductive region from strongly underdoped to strongly overdoped regimes. Magnetization studies with H $\\parallel$ c have been made in order to investigate the changes in free energy of the system as the number of carriers is reduced. Above the superconducting transition temperature, the normal-state magnetization exhibits a two-dimensional Heisenberg antiferromagnetic behavior. Below T_{c}, magnetization data are thermodynamically reversible over large portions of the H-T plane, so the free energy is well defined in these regions. As the Sr concentration is varied over the wide range from 0.060 (strongly underdoped) to 0.234 (strongly overdoped), the free energy change goes through a maximum at the optimum doped in a manner similar to the T_{c0} vs. x curve. The density of states, N(0), remains nearly constant in the overdoped and optimum doped regimes, taking a broad maximum around x = 0.188, and then drops abruptly towards zero in the underdoped regime. The La_{2-x}Sr_{x}CuO_{4} (La-214) system displays the fluctuating vortex behavior with the characteristic of either 2D or 3D fluctuations as indicated by clearly identifiable crossing points T* close to T_{c}. The dimensional character of the fluctuations depends on both applied magnetic fields and the density of charge carriers. The dimensional crossover from 2D to 3D occurs in the strongly underdoped regime when the c-axis coherence distance ξ_{c} becomes comparable to the spacing between adjacent CuO_{2} layers s at sufficiently high magnetic field near H_{c2}.
Methodology for High-Throughput Field Phenotyping of Canopy Temperature Using Airborne Thermography
Deery, David M.; Rebetzke, Greg J.; Jimenez-Berni, Jose A.; James, Richard A.; Condon, Anthony G.; Bovill, William D.; Hutchinson, Paul; Scarrow, Jamie; Davy, Robert; Furbank, Robert T.
2016-01-01
Lower canopy temperature (CT), resulting from increased stomatal conductance, has been associated with increased yield in wheat. Historically, CT has been measured with hand-held infrared thermometers. Using the hand-held CT method on large field trials is problematic, mostly because measurements are confounded by temporal weather changes during the time required to measure all plots. The hand-held CT method is laborious and yet the resulting heritability low, thereby reducing confidence in selection in large scale breeding endeavors. We have developed a reliable and scalable crop phenotyping method for assessing CT in large field experiments. The method involves airborne thermography from a manned helicopter using a radiometrically-calibrated thermal camera. Thermal image data is acquired from large experiments in the order of seconds, thereby enabling simultaneous measurement of CT on potentially 1000s of plots. Effects of temporal weather variation when phenotyping large experiments using hand-held infrared thermometers are therefore reduced. The method is designed for cost-effective and large-scale use by the non-technical user and includes custom-developed software for data processing to obtain CT data on a single-plot basis for analysis. Broad-sense heritability was routinely >0.50, and as high as 0.79, for airborne thermography CT measured near anthesis on a wheat experiment comprising 768 plots of size 2 × 6 m. Image analysis based on the frequency distribution of temperature pixels to remove the possible influence of background soil did not improve broad-sense heritability. Total image acquisition and processing time was ca. 25 min and required only one person (excluding the helicopter pilot). The results indicate the potential to phenotype CT on large populations in genetics studies or for selection within a plant breeding program. PMID:27999580
Amosova, E. V.; Shishkin, A. V.
2017-11-01
This article introduces the result of studying the heat exchange in the fuel element of the nuclear reactor fuel magazine. Fuel assemblies are completed as a bundle of cylindrical fuel elements located at the tops of a regular triangle. Uneven distribution of fuel rods in a nuclear reactor’s core forms the inhomogeneity of temperature fields. This article describes the developed method for heat exchange calculation with the account for impact of an inhomogeneous temperature field on the thermal-physical properties of materials and unsteady effects. The acquired calculation results are used for evaluating the tolerable temperature levels in protective case materials.
Quasi-static evolution of sheared force-free fields and the solar flare problem
Aly, J. J.
1985-01-01
Some new results are given showing the possible evolution of a two-dimensional force-free field in the half-space z greater than 0 toward an open field. This evolution is driven by shearing motions applied to the feet of the field lines on the boundary z = 0. The consequences of these results for a model of the two-ribbon solar flare are discussed.
Diliberto, Iole; Cappuzzo, Santo; Inguaggiato, Salvatore; Cosenza, Paolo
2014-05-01
We present an instrumental system to measure and to map the space variation of the surface temperature in volcanic fields. The system is called Pirogips, its essential components are a Pyrometer and a Global Position System but also other devices useful to obtain a good performance of the operating system have been included. In the framework of investigation to define and interpret volcanic scenarios, the long-term monitoring of gas geochemistry can improve the resolution of the scientific approaches by other specific disciplines. Indeed the fluid phase is released on a continuous mode from any natural system which produces energy in excess respect to its geological boundaries. This is the case of seismic or magmatic active areas where the long-term geochemical monitoring is able to highlight, and to follow in real time, changes in the rate of energy release and/or in the feeding sources of fluids, thus contributing to define the actual behaviour of the investigated systems (e.g. Paonita el al., 2013; 2002; Taran, 2011; Zettwood and Tazieff, 1973). The demand of pirogips starts from the personal experience in long term monitoring of gas geochemistry (e.g. Diliberto I.S, 2013; 2011; et al., 2002; Inguaggiato et al.,2012a, 2012b). Both space and time variation of surface temperature highlight change of energy and mass release from the deep active system, they reveal the upraise of deep and hot fluid and can be easily detected. Moreover a detailed map of surface temperature can be very useful for establishing a network of sampling points or installing a new site for geochemical monitoring. Water is commonly the main component of magmatic or hydrothermal fluid release and it can reach the ground surface in the form of steam, as in the high and low temperature fumaroles fields, or it can even condense just below the ground surface. In this second case the water disperses in pores or circulates in the permeable layers while the un-condensable gases reach the surface (e
Analysis of temperature field in the Banderas Bay Region between June 2009 to June 2012
Carrillo-Gonzalez, F. M.; Cornejo-Lopez, V. M.; Morales-Hernández, J. C.
2012-12-01
We present the spatial and temporary analysis of temperature fields monitored hourly and monthly throughout the year in the Banderas Bay region between the period June 2009 to June 2011. The study area is the atmospheric basin of Banderas Bay, between of Puerto Vallarta Jal. and Puerto Vallarta New Nay., in 20.66381 N,-105.20574W. The data used was obtained from the Atmospheric Monitoring Network in the Banderas Bay region, which comprises of at least 10 automatic weather stations distributed heterogeneously throughout the study area, which provide data on major meteorological variables at 10 minute intervals. It has been observed that the behavior throughout the year of major weather variables are determined by local processes (valley and breeze circulation) primarily and macro-scale phenomena (presence of the North Pacific anticyclone and trade winds). Greater thermal amplitude in the mountain regions of the River Ameca Valley, compared to coastal zones, with the latter influenced by the sea surface temperature. We registered small heat islands in urbane areas, which gives background information for future studies on pollution, health, prevention of natural disasters etc.
Fall field crickets did not acclimate to simulated seasonal changes in temperature.
Niehaus, Amanda C; Wilson, Robbie S; Storm, Jonathan J; Angilletta, Michael J
2012-02-01
In nature, many organisms alter their developmental trajectory in response to environmental variation. However, studies of thermal acclimation have historically involved stable, unrealistic thermal treatments. In our study, we incorporated ecologically relevant treatments to examine the effects of environmental stochasticity on the thermal acclimation of the fall field cricket (Gryllus pennsylvanicus). We raised crickets for 5 weeks at either a constant temperature (25°C) or at one of three thermal regimes mimicking a seasonal decline in temperature (from 25 to 12°C). The latter three treatments differed in their level of thermal stochasticity: crickets experienced either no diel cycle, a predictable diel cycle, or an unpredictable diel cycle. Following these treatments, we measured several traits considered relevant to survival or reproduction, including growth rate, jumping velocity, feeding rate, metabolic rate, and cold tolerance. Contrary to our predictions, the acclimatory responses of crickets were unrelated to the magnitude or type of thermal variation. Furthermore, acclimation of performance was not ubiquitous among traits. We recommend additional studies of acclimation in fluctuating environments to assess the generality of these findings.
Mildaziene, Vida; Pauzaite, Giedre; Malakauskiene, Asta; Zukiene, Rasa; Nauciene, Zita; Filatova, Irina; Azharonok, Viktor; Lyushkevich, Veronika
2016-08-30
Radiofrequency (5.28 MHz) electromagnetic radiation and low-temperature plasma were applied as short-term (2-15 min) seed treatments to two perennial woody plant species, including Smirnov's rhododendron (Rhododendron smirnowii Trautv.) and black mulberry (Morus nigra L.). Potential effects were evaluated using germination indices and morphometry. The results suggest that treatment with electromagnetic field stimulated germination of freshly harvested R. smirnowii seeds (increased germination percentage up to 70%), but reduced germination of fresh M. nigra seeds (by 24%). Treatment with low-temperature plasma negatively affected germination for R. smirnowii, and positively for M. nigra. The treatment-induced changes in germination depended on seed dormancy state. Longer-term observations revealed that the effects persisted for more than a year; however, even negative effects on germination came out as positive effects on plant morphometric traits over time. Treatments characterized as distressful based on changes in germination and seedling length increased growth of R. smirnowii after 13 months. Specific changes included stem and root branching, as well as increased leaf count and surface area. These findings imply that longer-term patterns of response to seed stressors may be complex, and therefore, commonly used stressor-effects estimates, such as germination rate or seedling morphology, may be insufficient for qualifying stress response. Bioelectromagnetics. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.
Liu, Yongfeng; Zhang, You-tong; Gou, Chenhua; Tian, Hongsen
2008-12-01
Temperature laser- induced- fluorescence (LIF) 2-D imaging measurements using a new multi-spectral detection strategy are reported for high pressure flames in high-speed diesel engine. Schematic of the experimental set-up is outlined and the experimental data on the diesel engine is summarized. Experiment injection system is a third generation Bosch high-pressure common rail featuring a maximum pressure of 160 MPa. The injector is equipped with a six-hole nozzle, where each hole has a diameter of 0.124 mm. and slightly offset (by 1.0 mm) to the center of the cylinder axis to allow a better cooling of the narrow bridge between the exhaust valves. The measurement system includes a blower, which supplied the intake flow rate, and a prototype single-valve direct injection diesel engine head modified to lay down the swirled-type injector. 14-bit digital CCD cameras are employed to achieve a greater level of accuracy in comparison to the results of previous measurements. The temperature field spatial distributions in the cylinder for different crank angle degrees are carried out in a single direct-injection diesel engine.
2D temperature field measurement in a direct-injection engine using LIF technology
Liu, Yongfeng; Tian, Hongsen; Yang, Jianwei; Sun, Jianmin; Zhu, Aihua
2011-12-01
A new multi-spectral detection strategy for temperature laser- induced- fluorescence (LIF) 2-D imaging measurements is reported for high pressure flames in high-speed diesel engine. Schematic of the experimental set-up is outlined and the experimental data on the diesel engine is summarized. Experiment injection system is a third generation Bosch high-pressure common rail featuring a maximum pressure of 160MPa. The injector is equipped with a six-hole nozzle, where each hole has a diameter of 0.124 mm. and slightly offset to the center of the cylinder axis to allow a better cooling of the narrow bridge between the exhaust valves. The measurement system includes a blower, which supplied the intake flow rate, and a prototype single-valve direct injection diesel engine head modified to lay down the swirled-type injector. 14-bit digital CCD cameras are employed to achieve a greater level of accuracy in comparison to the results of previous measurements. The temperature field spatial distributions in the cylinder for different crank angle degrees are carried out in a single direct-injection diesel engine.
Energy Technology Data Exchange (ETDEWEB)
Cottingham, Patrick, E-mail: pcotting@usc.edu [Department of Chemistry, University of Southern California, 3620 McClintock Avenue, Los Angeles, CA 90089 (United States); Morey, Jennifer R. [Department of Chemistry, Johns Hopkins University, 3400 N. Charles St., Baltimore, MD 21218 (United States); Institute for Quantum Matter, Department of Physics and Astronomy, Johns Hopkins University, 3400 N. Charles St., Baltimore, MD 21218 (United States); Lemire, Amanda [SPF Technologies, 390 Medford St., Somerville, MA 02145 (United States); Lemire, Penny [Department of Materials Science and Engineering, Johns Hopkins University, 3400 N. Charles St., Baltimore, MD 21218 (United States); McQueen, Tyrel M. [Department of Chemistry, Johns Hopkins University, 3400 N. Charles St., Baltimore, MD 21218 (United States); Institute for Quantum Matter, Department of Physics and Astronomy, Johns Hopkins University, 3400 N. Charles St., Baltimore, MD 21218 (United States); Department of Materials Science and Engineering, Johns Hopkins University, 3400 N. Charles St., Baltimore, MD 21218 (United States)
2016-10-15
We report instrumentation for photovoltage and photocurrent spectroscopy over a larger continuous range of wavelengths, temperatures, and applied magnetic fields than other instruments described in the literature: 350 nm≤λ≤1700 nm, 1.8 K≤T≤300 K, and B≤9 T. This instrument uses a modulated monochromated incoherent light source with total power<30 μW in combination with an LED in order to probe selected regions of non-linear responses while maintaining low temperatures and avoiding thermal artifacts. The instrument may also be used to measure a related property, the photomagnetoresistance. We demonstrate the importance of normalizing measured responses for variations in light power and describe a rigorous process for performing these normalizations. We discuss several circuits suited to measuring different types of samples and provide analysis for converting measured values into physically relevant properties. Uniform approaches to measurement of these photoproperties are essential for reliable quantitative comparisons between emerging new materials with energy applications. - Highlights: • A novel instrument for measuring photoconductivity and photocurrents of materials and devices. • Continuous parameter space: 350 nm≤λ≤1700, 1.8 K≤T≤300 K, and B≤9 T. • Methodology for treating non-linear responses and variable lamp intensity. • Mathematical detail for extracting properties of materials from measured values is provided.
Kannan, M. T. Senthil; Kumar, Bharat; Balasubramaniam, M.; Agrawal, B. K.; Patra, S. K.
2017-06-01
For the first time, we apply the temperature-dependent relativistic mean-field (TRMF) model to study the ternary fragmentation of heavy nuclei using the level density approach. The relative fragmentation probability of a particular fragment is obtained by evaluating the convolution integrals that employ the excitation energy and the level density parameter for a given temperature calculated within the TRMF formalism. To illustrate, we have considered the ternary fragmentations in 252Cf, 242Pu, and 236U with a fixed third fragment A3=48Ca , 20O, and 16O, respectively. The relative fragmentation probabilities are studied for the temperatures T =1 , 2, and 3 MeV. For the comparison, the relative fragmentation probabilities are also calculated from the single-particle energies of the finite range droplet model (FRDM). In general, the larger phase space for the ternary fragmentation is observed indicating that such fragmentations are most probable ones. For T =2 and 3 MeV, Sn +Ni +Ca is the most probable combination for the nucleus 252Cf. However, for the nuclei 242Pu and 236U, the maximum fragmentation probabilities at T =2 MeV differ from those at T =3 MeV. For T =3 MeV, the closed shell (Z =8 ) light-mass fragment with its corresponding partners has larger scission point probabilities. But, at T =2 MeV, Si, P, and S are favorable fragments with the corresponding partners. It is noticed that the symmetric binary fragmentation along with the fixed third fragment for 242Pu and 236U is also favored at T =1 MeV.
Full Scale Field Trial of the Low Temperature Mercury Capture Process
Energy Technology Data Exchange (ETDEWEB)
Locke, James [CONSOL Energy Inc., South Park, PA (United States); Winschel, Richard [CONSOL Energy Inc., South Park, PA (United States)
2012-05-21
CONSOL Energy Inc., with partial funding from the Department of Energy (DOE) National Energy Technology Laboratory, designed a full-scale installation for a field trial of the Low-Temperature Mercury Control (LTMC) process, which has the ability to reduce mercury emissions from coal-fired power plants by over 90 percent, by cooling flue gas temperatures to approximately 230°F and absorbing the mercury on the native carbon in the fly ash, as was recently demonstrated by CONSOL R&D on a slip-stream pilot plant at the Allegheny Energy Mitchell Station with partial support by DOE. LTMC has the potential to remove over 90 percent of the flue gas mercury at a cost at least an order of magnitude lower (on a $/lb mercury removed basis) than activated carbon injection. The technology is suitable for retrofitting to existing and new plants, and, although it is best suited to bituminous coal-fired plants, it may have some applicability to the full range of coal types. Installation plans were altered and moved from the original project host site, PPL Martins Creek plant, to a second host site at Allegheny Energy's R. Paul Smith plant, before installation actually occurred at the Jamestown (New York) Board of Public Utilities (BPU) Samuel A. Carlson (Carlson) Municipal Generating Station Unit 12, where the LTMC system was operated on a limited basis. At Carlson, over 60% mercury removal was demonstrated by cooling the flue gas to 220-230°F at the ESP inlet via humidification. The host unit ESP operation was unaffected by the humidification and performed satisfactorily at low temperature conditions.
Shivanian, Elyas; Hosseini Ghoncheh, S. J.
2017-02-01
In this paper, the nonlinear fin problem with temperature-dependent thermal conductivity and heat transfer coefficient is revisited. In this problem, it has been assumed that the heat transfer coefficient is expressed in a power-law form and the thermal conductivity is a linear function of temperature. A method based on the traditional shooting method and the homotopy analysis method is applied, the so-called shooting homotopy analysis method (SHHAM), to the governing nonlinear differential equation. In this technique, more high-order approximate solutions are computable and multiple solutions are easily searched and discovered due to being free of the symbolic variable. It is found that the solution might be empty, unique or dual depending on the values of the parameters of the model. Furthermore, corresponding fin efficiencies with high accuracy are computed. As a consequence, a new branch solution for this nonlinear problem by a new proposed method, based on the traditional shooting method and the homotopy analysis method, is obtained.
International Nuclear Information System (INIS)
Qi, J.A.; Leung, C.W.; Wong, W.O.; Probert, S.D.
2006-01-01
Reference-beam interferometry (RBI) was applied to study the axisymmetric temperature fields of a small-scale, low Reynolds-number, low-pressure and fuel-rich premixed butane/air circular-flame jet, when it was impinging vertically upwards onto a horizontal copper plate. By maintaining a Reynolds number, Re, of 500 and an equivalence ratio, φ, of 1.8, interferograms of the impinging-flame jet were obtained for various nozzle-to-plate-distances. Temperature fields of the flame were then determined using the inverse Abel transformation from the obtained interferograms. Temperatures at several locations were measured experimentally with a T-type thermocouple: they were used as a reference to help in the determination as well as the validation. In the present study, a non-contact method has been successfully developed to measure the temperature fields of a circular impinging gas-fired flame jet
DEFF Research Database (Denmark)
Walker, Julian; Ursic, Hana; Bencan, Andreja
2016-01-01
The rare-earth (RE)-modified bismuth ferrite (BiFeO3 or BFO) family of ferroelectrics have uncomplicated lead-free chemistries and simple perovskite structures. Due to the high Curie transition temperature of the parent BiFeO3 perovskite (similar to 830 °C), they are promising piezoelectric...... materials for use at elevated temperatures. However, the influence of the specific RE species on the electromechanical behavior at high temperatures and above the coercive electric-field is not widely reported. Here, structural analysis over multiple length scales using X-ray diffraction, transmission......, there are qualitative differences in the field-induced strain and electric current behavior as a function of electric-field cycling and the materials exhibit an electrical-history dependent behavior. Bi0.91Dy0.09FeO3 possesses an improved d33 stability as a function of temperature relative to the parent BFO perovskite...
Field and temperature scaling of the critical current density in commercial REBCO coated conductors
Senatore, Carmine; Bonura, Marco; Kulich, Miloslav; Mondonico, Giorgio
2016-01-01
Scaling relations describing the electromagnetic behaviour of coated conductors (CCs) greatly simplify the design of REBCO-based devices. The performance of REBCO CCs is strongly influenced by fabrication route, conductor architecture and materials, and these parameters vary from one manufacturer to the others. In the present work we have examined the critical surface for the current density, Jc(T,B,θ ), of coated conductors from six different manufacturers: American Superconductor Co. (US), Bruker HTS GmbH (Germany), Fujikura Ltd. (Japan), SuNAM Co. Ltd. (Korea), SuperOx ZAO (Russia) and SuperPower Inc. (US). Electrical transport and magnetic measurements were performed at temperatures between 4.2 K and 77 K and in magnetic field up to 19 T. Experiments were conducted at three different orientations of the field with respect to the crystallographic c-axis of the REBCO layer, θ = 0deg , 45deg and 90deg , in order to probe the angular anisotropy of Jc. In spite of the large variability of CCs performance, ...
International Nuclear Information System (INIS)
Gelis, Francois
1998-12-01
The general framework of this work is thermal field theory, and more precisely the perturbative calculation of thermal Green's functions. In a first part, I consider the problems closely related to the formalism itself. After two introductory chapters devoted to set up the framework and the notations used afterwards, a chapter is dedicated to a clarification of certain aspects of the justification of the Feynman rules of the real time formalism. Then, I consider in the chapter 4 the problem of cutting rules in the real time formalisms. In particular, after solving a controversy on this subject, I generalize these cutting rules to the 'retarded-advanced' version of this formalism. Finally, the last problem considered in this part is that of the pion decay into two photons in a thermal bath. I show that the discrepancies found in the literature are due to peculiarities of the analytical properties of the thermal Green's functions. The second part deals with the calculations of the photons or dilepton (virtual photon) production rate by a quark gluon plasma. The framework of this study is the effective theory based on the resummation of hard thermal loops. The first aspects of this study is related to the production of virtual photons, where we show that important contributions arise at two loops, completing the result already known at one loop. In the case of real photon production, we show that extremely strong collinear singularities make two loop contributions dominant compared to one loop ones. In both cases, the importance of two loop contributions can be interpreted as weaknesses of the hard thermal loop approximation. (author)
The Major Field Test in Business: A Solution to the Problem of Assurance of Learning Assessment?
Green, Jeffrey J.; Stone, Courtenay Clifford; Zegeye, Abera
2014-01-01
Colleges and universities are being asked by numerous sources to provide assurance of learning assessments of their students and programs. Colleges of business have responded by using a plethora of assessment tools, including the Major Field Test in Business. In this article, the authors show that the use of the Major Field Test in Business for…
DEFF Research Database (Denmark)
Rizzi, G.; Lundtoft, N.C.; Østerberg, F.W.
2012-01-01
We investigate the changes of planar Hall effect bridge magnetic field sensors upon exposure to temperatures between 25° C and 90°C. From analyses of the sensor response vs. magnetic fields we extract the exchange bias field Hex, the uniaxial anisotropy field HK and the anisotropic...... magnetoresistance (AMR) of the exchange biased thin film at a given temperature and by comparing measurements carried out at elevated temperatures T with measurements carried out at 25° C after exposure to T, we can separate the reversible from the irreversible changes of the sensor. The results are not only...... relevant for sensor applications but also demonstrate the method as a useful tool for characterizing exchange-biased thin films....
Zhang, Zhenyu
This thesis is written to summarize investigations of the mechanisms that underlie the kinetics of diatomic ligand rebinding to the iron atom of the heme group, which is chelated inside heme proteins. The family of heme proteins is a major object of studies for several branches of scientific research activity. Understanding the ligand binding mechanisms and pathways is one of the major goals for biophysics. My interests mainly focus on the physics of this ligand binding process. Therefore, to investigate the problem, isolated from the influence of the protein matrix, Fe-protophorphyrin IX is chosen as the prototype system in my studies. Myoglobin, the most extensively and intensively studied protein, is another ideal system that allows coupling the protein polypeptide matrix into the investigation. A technique to synchro-lock two laser pulse trains electronically is applied to our pump-probe spectroscopic studies. Based on this technique, a two color, fs/ps pump-probe system is developed which extends the temporal window for our investigation to 13ns and fills a gap existing in previous pump-probe investigations. In order to apply this newly-developed pump-probe laser system to implement systematic studies on the kinetics of diatomic ligand (NO, CO, O2) rebinding to heme and heme proteins, several experimental setups are utilized. In Chapter 1, the essential background knowledge, which helps to understand the iron-ligand interaction, is briefly described. In Chapter 2, in addition to a description of the preparation protocols of protein samples and details of the method for data analysis, three home-made setups are described, which include: a picosecond laser regenerative amplifier, a pump-probe application along the bore (2-inch in diameter) of a superconducting magnet and a temperature-controllable cryostat for spinning sample cell. Chapter 3 presents high magnetic field studies of several heme-ligand or protein-ligand systems. Pump-probe spectroscopy is used to
Liu, Yan; Lin, Zhao-Jun; Yang, Ming; Luan, Chong-Biao; Wang, Yu-Tang; Lv, Yuan-Jie; Feng, Zhi-Hong
2016-12-01
The electron mobility of the AlGaN/AlN/GaN heterostructure field-effect transistors (HFETs) with the ratio of the gate length to the drain-to-source distance being less than 1/2 has been studied in the temperature range 100 ˜ 300 K. The measured electron mobility at each testing temperature is obtained by using the capacitance-voltage (C-V) and current-voltage (I-V) characteristics measured at the corresponding temperature, and the theoretically calculated temperature-dependent electron mobility is determined by Matthiessen’s law, which includes five kinds of important scattering mechanisms. For the prepared sample, the measured electron mobility with respect to the two-dimensional electron gas (2DEG) density was observed to increase to a peak point first and then decrease at each testing temperature. By comparing the measured electron mobility with the theoretically calculated value, the changing trend of the electron mobility at each testing temperature was found to be mainly determined by polarization Coulomb field (PCF) scattering. Particularly at lower temperature, PCF scattering plays a more significant role in the changing trend of the electron mobility.
International Nuclear Information System (INIS)
Cheng, Tai-Min; Ma, Yan-Ming; Ge, Chong-Yuan; Sun, Shu-Sheng; Jia, Wei-Ye; Li, Qing-Yun; Shi, Xiao-Fei; Li, Lin; Zhu, Lin
2013-01-01
The elementary excitation spectra of a one-dimensional ferrimagnetic diamond chain in the spin-1/2 XY model at low temperatures have been calculated by using an invariant eigen-operator (IEO) method, the energies of elementary excitations in different specific cases are discussed, and the analytic solutions of three critical magnetic field intensities (H C1 , H C2 , and H peak ) are given. The magnetization versus external magnetic field curve displays a 1/3 magnetization plateau at low temperatures, in which H C1 is the critical magnetic field intensity from the disappearance of the 1/3 magnetization plateau to spin-flop states, H C2 is the critical magnetic field intensity from spin-flop states to the saturation magnetization, and H peak is the critical magnetic field intensity when the temperature magnetization shows a peak in the external magnetic field. The temperature dependences of the magnetic susceptibility and the specific heat show a double peak structure. The entropy and the magnetic susceptibility versus external magnetic field curves also exhibit a double peak structure, and the positions of the two peaks correspond to H C1 and H C2 , respectively. This derives from the competition among different types of energies: the temperature-dependent thermal disorder energy, the potential energy of the spin magnetic moment, the ferromagnetic exchange interaction energy, and the anti-ferromagnetic exchange interaction energy. However at low temperatures, the specific heat as a function of external magnetic field curve exhibits minima at the above two critical points (H C1 and H C2 ). The origins of the above phenomena are discussed in detail.
Directory of Open Access Journals (Sweden)
Tarzia Domingo Alberto
2017-01-01
Full Text Available We obtain for the two-phase Lamé-Clapeyron-Stefan problem for a semi-infinite material an equivalence between the temperature and convective boundary conditions at the fixed face in the case that an inequality for the convective transfer coefficient is satisfied. Moreover, an inequality for the coefficient which characterizes the solid-liquid interface of the classical Neumann solution is also obtained. This inequality must be satisfied for data of any phase-change material, and as a consequence the result given in Tarzia, Quart. Appl. Math., 39 (1981, 491-497 is also recovered when a heat flux condition was imposed at the fixed face.
Yin, Haihong; Yu, Ke; Song, Changqing; Wang, Zhiliang; Zhu, Ziqiang
2014-09-01
VO2 nanostructures are attractive materials because of their reversible metal-insulator transition (MIT) and wide applications in devices. When they are used as field emitters, a new type of temperature-controlled field emission device can be fabricated. Vapor transport methods used to synthesize traditional VO2 nanostructures are energy-intensive, low yield, and produce simple morphology (quasi-1D) that exhibits substrate clamping; thus they are not suitable for field emission applications. To overcome these limitations, ZnO nanotetrapods were used as templates, and patterned core-shell VO2@ZnO nanotetrapods were successfully grown on an ITO/glass substrate via a low-temperature CVD synthesis. SEM, TEM, EDX, XPS analyses and X-ray diffraction revealed that the cores and shells of these nanotetrapods were single crystal wurtzite-type ZnO and polycrystalline VO2, respectively. The VO2@ZnO nanotetrapods show strongly MIT-related FE properties, the emission current density at low temperature is significantly enhanced in comparison with pure VO2 nanostructures, and the emission current density increased by about 20 times as the ambient temperature increased from 25 to 105 °C at a fixed field of 5 V μm-1. Although the VO2@ZnO nanotetrapods show a worse FE performance at low temperatures compared with pure ZnO nanotetrapods, the FE performance was substantially improved at high temperatures, which was attributed to the MIT-related band bending near the interface and the abrupt resistance change across the MIT.
Paleomagnetism of the moon and the problem of planetary dynamo fields
International Nuclear Information System (INIS)
Dolginov, S.S.
1986-01-01
It is shown within the scope of the precessional dynamo model that satellites of the moon, which, as has been proposed, existed in equatorial orbits 4-3.8 Gyr ago and whose fall to the surface relates to the formation of the maria (14) and a change in position of the axis of rotation of the moon (15), could have determined the generation of a strong dynamo field of 10 -4 T in which the ancient lunar rocks acquired thermoremanent magnetization. The strong dynamo field attenuated with the fall of the satellites to the surface of the moon, but a moderate dynamo field could have been generated with the precession of the moon under the perturbing effect of the gravitational field of the earth. This field also attenuated with the recession of the moon from the earth and its acquisition of synchronous rotation. If the distribution of the paleofields over the entire surface of the moon, which one can hope will be established, confirms the assumption of uniform magnetization of the lunar crest by a field of internal origin, then the planetary precessional dynamo model gets additional proof of the established cause-effect relation: If the source inducing the precessional motion disappears, then the magnetic field disappears
Problems of the protection of bioresources development ofthe Bovanenkovo gas condensate field
Directory of Open Access Journals (Sweden)
Vladimir Dmitrievich Bogdanov
2012-12-01
Full Text Available The data on the fish fauna and fish food resources in the Bovanenkovo gas field are presented. The estimation of fishery and fishery potential of water bodies, hydrobiological characteristics of water bodies in the studied area are given. It is shown that the arrangement of the gas field leads to overfishing BGKM fish and change the state of aquatic ecosystems associated with the violation of runoff, backfilling flood waters, crossing streams communications, water diversion, pollution, sand mining. Thehydrobionts reaction to anthropogenic influence in the area of the gas field developmentis identified and recommendations to reduce the impact on aquatic ecosystems in the period of construction are given
Xiong, Qing; Xu, Le; Wang, Xia; Xiong, Lin; Huang, Qinghua; Chen, Qiang; Wang, Jingang; Peng, Wenxiong; Li, Jiarui
2018-03-01
Gas temperature is an important basic parameter for both fundamental research and applications of plasmas. In this work, efforts were made to visualize the full spatial field of gas temperature (T g) in a microdischarge with sharp T g gradients by a method of calibrated Schlieren (CS) photography. Compared to other two typical diagnostic approaches, optical emission spectroscopy (OES) and Rayleigh scattering, the proposed CS method exhibits the ability to capture the whole field of gas temperature using a single Schlieren image, even the discharge is of non-luminous zones like Faraday dark space (FDS). The image shows that the T g field in the studied micro-glow air discharge expands quickly with the increase of discharge currents, especially in the cathode region. The two-dimensional maps of gas temperature display a ‘W-shape’ with sharp gradients in both areas of negative and positive glows, slightly arched distributions in the positive column, and cooling zones in the FDS. The obtained T g fields show similar patterns to that of the discharge luminance. With an increase in discharge currents, more electric energy is dissipated by heating air gas and inducing constriction of the low-temperature FDS. Except in the vicinities of electrode boundaries, due to the interference from optical diffraction, the estimated gas temperature distributions are of acceptable accuracy, confirmed by the approaches of OES and UV Rayleigh scattering.
Directory of Open Access Journals (Sweden)
H. P. Jagadish
2013-01-01
Full Text Available Squeeze film dampers are novel rotor dynamic devices used to alleviate small amplitude, large force vibrations and are used in conjunction with antifriction bearings in aircraft jet engine bearings to provide external damping as these possess very little inherent damping. Electrorheological (ER fluids are controllable fluids in which the rheological properties of the fluid, particularly viscosity, can be controlled in accordance with the requirements of the rotor dynamic system by controlling the intensity of the applied electric field and this property can be utilized in squeeze film dampers, to provide variable stiffness and damping at a particular excitation frequency. The paper investigates the effect of temperature and electric field on the apparent viscosity and dynamic (stiffness and damping characteristics of ER fluid (suspension of diatomite in transformer oil using the available literature. These characteristics increase with the field as the viscosity increases with the field. However, these characteristics decrease with increase in temperature and shear strain rate as the viscosity of the fluid decreases with temperature and shear strain rate. The temperature is an important parameter as the aircraft jet engine rotors are located in a zone of high temperature gradients and the damper fluid is susceptible to large variations in temperature.
Directory of Open Access Journals (Sweden)
V. S. Zarubin
2016-01-01
dependence of the absorption factor on the local intensity of this radiation. Furthermore, it can be a significant dependence of this factor on the local value of the material temperature, reflecting the above-mentioned relationship between the absorption of electromagnetic wave energy and the excitation of material microparticles. This process can be described by Boltzmann distribution function that comprises the energy to activate microparticles and the local value of temperature.This paper presents a variational formulation of the nonlinear problem of stationary heat conduction in a plate for the case when the radiation reduction factor in relation to the Bouguer law depends on the local temperature. This formulation includes a functional that can have several fixed points corresponding to different steady states of the plate temperature. Analysis of the properties of this functional enabled us to identify the stationary points, which correspond to the realized temperature distribution in the plate.
International Nuclear Information System (INIS)
Zhang, Shiping; Shen, Guoqing; An, Liansuo; Niu, Yuguang
2015-01-01
Online monitoring of the temperature field is crucial to optimally adjust combustion within a boiler. In this paper, acoustic computed tomography (CT) technology was used to obtain the temperature profile of a furnace cross-section. The physical principles behind acoustic CT, acoustic signals and time delay estimation were studied. Then, the technique was applied to a domestic 600-MW coal-fired boiler. Acoustic CT technology was used to monitor the temperature field of the cross-section in the boiler furnace, and the temperature profile was reconstructed through ART iteration. The linear sweeping frequency signal was adopted as the sound source signal, whose sweeping frequency ranged from 500 to 3000 Hz with a sweeping cycle of 0.1 s. The generalized cross-correlation techniques with PHAT and ML were used as the time delay estimation method when the boiler was in different states. Its actual operation indicated that the monitored images accurately represented the combustion state of the boiler, and the acoustic CT system was determined to be accurate and reliable. - Highlights: • An online monitoring approach to monitor temperature field in a boiler furnace. • The paper provides acoustic CT technology to obtain the temperature profile of a furnace cross-section. • The temperature profile was reconstructed through ART iteration. • The technique is applied to a domestic 600-MW coal-fired boiler. • The monitored images accurately represent the combustion state of the boiler
Inverse estimation of the temperature field within a gas-filled duct section by use of acoustic data
International Nuclear Information System (INIS)
Kim, Tae-Kyoon; Ih, Jeong-Guon
2015-01-01
Knowledge of the temperature distribution of an in-duct gaseous medium is essential in the monitoring of combustion status. To obtain the temperature distribution, an inverse relationship based on the Radon transform is formulated by using the measured time retardation data from a set of acoustic sensors and actuators. The entire spatial distribution can be obtained by interpolating the estimated discrete temperature data using either a path-based or spaced-based method. An interpolation method then determines the precision of the final imaging result. The characteristics and performance of two interpolation methods are investigated in a simulation study by reconstructing the temperature distribution of a rectangular cross-section. To calculate the temperature field, the path-based interpolation method adopts a direct expression of temperature variation along the propagation path, whereas the space-based interpolation method uses data obtained at predetermined points deployed inside the field. The average reconstruction accuracy of the space-based interpolation for temperature fields with 1 and 4 local maxima is 22% and 183% better than that of path-based interpolation, respectively. Also, the space-based interpolation method is more robust with regard to measurement noise than the path-based interpolation method. (paper)
Mi, Yan; Rui, Shaoqin; Li, Chengxiang; Yao, Chenguo; Xu, Jin; Bian, Changhao; Tang, Xuefeng
2017-07-01
High-frequency nanosecond-pulsed electric fields were recently introduced for tumor or abnormal tissue ablation to solve some problems of conventional electroporation. However, it is necessary to study the thermal effects of high-field-intensity nanosecond pulses inside tissues. The multi-parametric analysis performed here is based on a finite element model of liver tissue with a tumor that has been punctured by a pair of needle electrodes. The pulse voltage used in this study ranges from 1 to 4 kV, the pulse width ranges from 50 to 500 ns, and the repetition frequency is between 100 kHz and 1 MHz. The total pulse length is 100 μs, and the pulse burst repetition frequency is 1 Hz. Blood flow and metabolic heat generation have also been considered. Results indicate that the maximum instantaneous temperature at 100 µs can reach 49 °C, with a maximum instantaneous temperature at 1 s of 40 °C, and will not cause thermal damage during single pulse bursts. By parameter fitting, we can obtain maximum instantaneous temperature at 100 µs and 1 s for any parameter values. However, higher temperatures will be achieved and may cause thermal damage when multiple pulse bursts are applied. These results provide theoretical basis of pulse parameter selection for future experimental researches.