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Sample records for joule heating term

  1. Discretization of the Joule heating term for plasma discharge fluid models in unstructured meshes

    SciTech Connect

    Deconinck, T.; Mahadevan, S.; Raja, L.L.

    2009-07-01

    The fluid (continuum) approach is commonly used for simulation of plasma phenomena in electrical discharges at moderate to high pressures (>10's mTorr). The description comprises governing equations for charged and neutral species transport and energy equations for electrons and the heavy species, coupled to equations for the electromagnetic fields. The coupling of energy from the electrostatic field to the plasma species is modeled by the Joule heating term which appears in the electron and heavy species (ion) energy equations. Proper numerical discretization of this term is necessary for accurate description of discharge energetics; however, discretization of this term poses a special problem in the case of unstructured meshes owing to the arbitrary orientation of the faces enclosing each cell. We propose a method for the numerical discretization of the Joule heating term using a cell-centered finite volume approach on unstructured meshes with closed convex cells. The Joule heating term is computed by evaluating both the electric field and the species flux at the cell center. The dot product of these two vector quantities is computed to obtain the Joule heating source term. We compare two methods to evaluate the species flux at the cell center. One is based on reconstructing the fluxes at the cell centers from the fluxes at the face centers. The other recomputes the flux at the cell center using the common drift-diffusion approximation. The reconstructed flux scheme is the most stable method and yields reasonably accurate results on coarse meshes.

  2. Joule heating in nanowires

    NASA Astrophysics Data System (ADS)

    Fangohr, Hans; Chernyshenko, Dmitri S.; Franchin, Matteo; Fischbacher, Thomas; Meier, Guido

    2011-08-01

    We study the effect of Joule heating from electric currents flowing through ferromagnetic nanowires on the temperature of the nanowires and on the temperature of the substrate on which the nanowires are grown. The spatial current density distribution, the associated heat generation, and diffusion of heat are simulated within the nanowire and the substrate. We study several different nanowire and constriction geometries as well as different substrates: (thin) silicon nitride membranes, (thick) silicon wafers, and (thick) diamond wafers. The spatially resolved increase in temperature as a function of time is computed. For effectively three-dimensional substrates (where the substrate thickness greatly exceeds the nanowire length), we identify three different regimes of heat propagation through the substrate: regime (i), where the nanowire temperature increases approximately logarithmically as a function of time. In this regime, the nanowire temperature is well described analytically by You [Appl. Phys. Lett.APPLAB0003-695110.1063/1.2399441 89, 222513 (2006)]. We provide an analytical expression for the time tc that marks the upper applicability limit of the You model. After tc, the heat flow enters regime (ii), where the nanowire temperature stays constant while a hemispherical heat front carries the heat away from the wire and into the substrate. As the heat front reaches the boundary of the substrate, regime (iii) is entered, where the nanowire and substrate temperature start to increase rapidly. For effectively two-dimensional substrates (where the nanowire length greatly exceeds the substrate thickness), there is only one regime in which the temperature increases logarithmically with time for large times, before the heat front reaches the substrate boundary. We provide an analytical expression, valid for all pulse durations, that allows one to accurately compute this temperature increase in the nanowire on thin substrates.

  3. Joule heating at high latitudes

    NASA Technical Reports Server (NTRS)

    Foster, J. C.; St.-Maurice, J.-P.; Abreu, V. J.

    1983-01-01

    Calculations based on simultaneous observations of the electric field magnitude, and individual measurements of ion drift velocity and particle precipitation, over the lifetime of the AE-C satellite, are used to determine high latitude Joule heating. Conductivities produced by an averaged seasonal illumination were included with those calculated from particle precipitation. It is found that high latitude Joule heating occurs in an approximately oval pattern, and consists of dayside cleft, dawn and dusk sunward convection, and night sector heating regions. On average, heating in the cleft and dawn-dusk regions contributes the largest heat input, and there is no apparent difference between hemispheres for similar seasons. Joule heat input is 50 percent greater in summer than in winter, due primarily to the greater conductivity caused by solar production.

  4. Joule heating in electrokinetic flow.

    PubMed

    Xuan, Xiangchun

    2008-01-01

    Electrokinetic flow is an efficient means to manipulate liquids and samples in lab-on-a-chip devices. It has a number of significant advantages over conventional pressure-driven flow. However, there exists inevitable Joule heating in electrokinetic flow, which is known to cause temperature variations in liquids and draw disturbances to electric, flow and concentration fields via temperature-dependent material properties. Therefore, both the throughput and the resolution of analytic studies performed in microfluidic devices are affected. This article reviews the recent progress on the topic of Joule heating and its effect in electrokinetic flow, particularly the theoretical and experimental accomplishments from the aspects of fluid mechanics and heat/mass transfer. The primary focus is placed on the temperature-induced flow variations and the accompanying phenomena at the whole channel or chip level.

  5. Reduced Joule heating in nanowires

    NASA Astrophysics Data System (ADS)

    Léonard, François

    2011-03-01

    The temperature distribution in nanowires due to Joule heating is studied analytically using a continuum model and a Green's function approach. We show that the temperatures reached in nanowires can be much lower than that predicted by bulk models of Joule heating, due to heat loss at the nanowire surface that is important at nanoscopic dimensions, even when the thermal conductivity of the environment is relatively low. In addition, we find that the maximum temperature in the nanowire scales weakly with length, in contrast to the bulk system. A simple criterion is presented to assess the importance of these effects. The results have implications for the experimental measurements of nanowire thermal properties, for thermoelectric applications, and for controlling thermal effects in nanowire electronic devices.

  6. Numerical Modeling of Electroacoustic Logging Including Joule Heating

    NASA Astrophysics Data System (ADS)

    Plyushchenkov, Boris D.; Nikitin, Anatoly A.; Turchaninov, Victor I.

    It is well known that electromagnetic field excites acoustic wave in a porous elastic medium saturated with fluid electrolyte due to electrokinetic conversion effect. Pride's equations describing this process are written in isothermal approximation. Update of these equations, which allows to take influence of Joule heating on acoustic waves propagation into account, is proposed here. This update includes terms describing the initiation of additional acoustic waves excited by thermoelastic stresses and the heat conduction equation with right side defined by Joule heating. Results of numerical modeling of several problems of propagation of acoustic waves excited by an electric field source with and without consideration of Joule heating effect in their statements are presented. From these results, it follows that influence of Joule heating should be taken into account at the numerical simulation of electroacoustic logging and at the interpretation of its log data.

  7. Joule-Thomson expander and heat exchanger

    NASA Technical Reports Server (NTRS)

    Norman, R. H.

    1976-01-01

    The Joule-Thomson Expander and Heat Exchanger Program was initiated to develop an assembly (JTX) which consists of an inlet filter, counterflow heat exchanger, Joule-Thomson expansion device, and a low pressure jacket. The program objective was to develop a JTX which, when coupled to an open cycle supercritical helium refrigerating system (storage vessel), would supply superfluid helium (He II) at 2 K or less for cooling infrared detectors.

  8. Remote Joule heating by a carbon nanotube.

    PubMed

    Baloch, Kamal H; Voskanian, Norvik; Bronsgeest, Merijntje; Cumings, John

    2012-04-08

    Minimizing Joule heating remains an important goal in the design of electronic devices. The prevailing model of Joule heating relies on a simple semiclassical picture in which electrons collide with the atoms of a conductor, generating heat locally and only in regions of non-zero current density, and this model has been supported by most experiments. Recently, however, it has been predicted that electric currents in graphene and carbon nanotubes can couple to the vibrational modes of a neighbouring material, heating it remotely. Here, we use in situ electron thermal microscopy to detect the remote Joule heating of a silicon nitride substrate by a single multiwalled carbon nanotube. At least 84% of the electrical power supplied to the nanotube is dissipated directly into the substrate, rather than in the nanotube itself. Although it has different physical origins, this phenomenon is reminiscent of induction heating or microwave dielectric heating. Such an ability to dissipate waste energy remotely could lead to improved thermal management in electronic devices.

  9. Joule heating in the high-latitude mesosphere

    NASA Technical Reports Server (NTRS)

    Banks, P. M.

    1979-01-01

    The contribution made by Joule dissipation to heating of the daytime high-latitude upper mesosphere is discussed. During solar proton precipitation events in regions of large electric fields, Joule dissipation can be substantially larger than the local solar heating rate. Altitude profiles of Joule dissipation are presented for the polar cleft region for the August 4, 1972, solar proton event.

  10. Joule heating effects on electroosmotic entry flow.

    PubMed

    Prabhakaran, Rama Aravind; Zhou, Yilong; Patel, Saurin; Kale, Akshay; Song, Yongxin; Hu, Guoqing; Xuan, Xiangchun

    2017-03-01

    Electroosmotic flow is the transport method of choice in microfluidic devices over traditional pressure-driven flow. To date, however, studies on electroosmotic flow have been almost entirely limited to inside microchannels. This work presents the first experimental study of Joule heating effects on electroosmotic fluid entry from the inlet reservoir (i.e., the well that supplies fluids and samples) to the microchannel in a polymer-based microfluidic chip. Electrothermal fluid circulations are observed at the reservoir-microchannel junction, which grow in size and strength with the increasing alternating current to direct current voltage ratio. Moreover, a 2D depth-averaged numerical model is developed to understand the effects of Joule heating on fluid temperature and flow fields in electrokinetic microfluidic chips. This model overcomes the problems encountered in previous unrealistic 2D and costly 3D models, and is able to predict the observed electroosmotic entry flow patterns with a good agreement.

  11. Nanowire transformation and annealing by Joule heating.

    PubMed

    Hummelgård, Magnus; Zhang, Renyun; Carlberg, Torbjörn; Vengust, Damjan; Dvorsek, Damjan; Mihailovic, Dragan; Olin, Håkan

    2010-04-23

    Joule heating of bundles of Mo(6)S(3)I(6) nanowires, in real time, was studied using in situ TEM probing. TEM imaging, electron diffraction, and conductivity measurements showed a complete transformation of Mo(6)S(3)I(6) into Mo via thermal decomposition. The resulting Mo nanowires had a conductivity that was 2-3 orders higher than the starting material. The conductivity increased even further, up to 1.8 x 10(6) S m( - 1), when the Mo nanowires went through annealing phases. These results suggest that Joule heating might be a general way to transform or anneal nanowires, pointing to applications such as metal nanowire fabrication, novel memory elements based on material transformation, or in situ improvement of field emitters.

  12. Optimal joule heating of the subsurface

    DOEpatents

    Berryman, J.G.; Daily, W.D.

    1994-07-05

    A method for simultaneously heating the subsurface and imaging the effects of the heating is disclosed. This method combines the use of tomographic imaging (electrical resistance tomography or ERT) to image electrical resistivity distribution underground, with joule heating by electrical currents injected in the ground. A potential distribution is established on a series of buried electrodes resulting in energy deposition underground which is a function of the resistivity and injection current density. Measurement of the voltages and currents also permits a tomographic reconstruction of the resistivity distribution. Using this tomographic information, the current injection pattern on the driving electrodes can be adjusted to change the current density distribution and thus optimize the heating. As the heating changes conditions, the applied current pattern can be repeatedly adjusted (based on updated resistivity tomographs) to affect real time control of the heating.

  13. Optimal joule heating of the subsurface

    DOEpatents

    Berryman, James G.; Daily, William D.

    1994-01-01

    A method for simultaneously heating the subsurface and imaging the effects of the heating. This method combines the use of tomographic imaging (electrical resistance tomography or ERT) to image electrical resistivity distribution underground, with joule heating by electrical currents injected in the ground. A potential distribution is established on a series of buried electrodes resulting in energy deposition underground which is a function of the resistivity and injection current density. Measurement of the voltages and currents also permits a tomographic reconstruction of the resistivity distribution. Using this tomographic information, the current injection pattern on the driving electrodes can be adjusted to change the current density distribution and thus optimize the heating. As the heating changes conditions, the applied current pattern can be repeatedly adjusted (based on updated resistivity tomographs) to affect real time control of the heating.

  14. An analytical model of joule heating in piezoresistive microcantilevers.

    PubMed

    Ansari, Mohd Zahid; Cho, Chongdu

    2010-01-01

    The present study investigates Joule heating in piezoresistive microcantilever sensors. Joule heating and thermal deflections are a major source of noise in such sensors. This work uses analytical and numerical techniques to characterise the Joule heating in 4-layer piezoresistive microcantilevers made of silicon and silicon dioxide substrates but with the same U-shaped silicon piezoresistor. A theoretical model for predicting the temperature generated due to Joule heating is developed. The commercial finite element software ANSYS Multiphysics was used to study the effect of electrical potential on temperature and deflection produced in the cantilevers. The effect of piezoresistor width on Joule heating is also studied. Results show that Joule heating strongly depends on the applied potential and width of piezoresistor and that a silicon substrate cantilever has better thermal characteristics than a silicon dioxide cantilever.

  15. Effect of Joule heating on electrokinetic transport.

    PubMed

    Cetin, Barbaros; Li, Dongqing

    2008-03-01

    The Joule heating (JH) is a ubiquitous phenomenon in electrokinetic flow due to the presence of electrical potential gradient and electrical current. JH may become pronounced for applications with high electrical potential gradients or with high ionic concentration buffer solutions. In this review, an in-depth look at the effect of JH on electrokinetic processes is provided. Theoretical modeling of EOF and electrophoresis (EP) with the presence of JH is presented and the important findings from the previous studies are examined. A numerical study of a fused-silica capillary PCR reactor powered by JH is also presented to extend the discussion of favorable usage of JH.

  16. Carbon Welding by Ultrafast Joule Heating.

    PubMed

    Yao, Yonggang; Fu, Kun Kelvin; Zhu, Shuze; Dai, Jiaqi; Wang, Yanbin; Pastel, Glenn; Chen, Yanan; Li, Tian; Wang, Chengwei; Li, Teng; Hu, Liangbing

    2016-11-09

    Carbon nanomaterials exhibit outstanding electrical and mechanical properties, but these superior properties are often compromised as nanomaterials are assembled into bulk structures. This issue of scaling limits the use of carbon nanostructures and can be attributed to poor physical contacts between nanostructures. To address this challenge, we propose a novel technique to build a 3D interconnected carbon matrix by forming covalent bonds between carbon nanostructures. High temperature Joule heating was applied to bring the carbon nanofiber (CNF) film to temperatures greater than 2500 K at a heating rate of 200 K/min to fuse together adjacent carbon nanofibers with graphitic carbon bonds, forming a 3D continuous carbon network. The bulk electrical conductivity of the carbon matrix increased four orders of magnitude to 380 S/cm with a sheet resistance of 1.75 Ω/sq. The high temperature Joule heating not only enables fast graphitization of carbon materials at high temperature, but also provides a new strategy to build covalently bonded graphitic carbon networks from amorphous carbon source. Because of the high electrical conductivity, good mechanical structures, and anticorrosion properties, the 3D interconnected carbon membrane shows promising applications in energy storage and electrocatalysis fields.

  17. The global joule heat production rate and the AE index

    NASA Technical Reports Server (NTRS)

    Wei, S.; Ahn, B.-H.; Akasofu, S.-I.

    1985-01-01

    The degree of accuracy with which the AE index may be used as a measure of the joule heat production rate is evaluated for a typical substorm event on March 18, 1978, by estimating the global joule heat production rate as a function of time on the basis of data obtained from the IMS's six meridian chains. It is found that, although the AE index is statistically linearly related to the global joule heat production rate, caution is required when one assumes that details of AE index time variations during individual events are representative of those of the joule heat production rate.

  18. Welding dissimilar metal microwires by Joule heating

    NASA Astrophysics Data System (ADS)

    Sunagawa, Takuya; Tohmyoh, Hironori

    2015-06-01

    In this paper we report on the Joule heat welding of dissimilar metal microwires. The current required for successful welding was investigated. Various combinations of 25 µm diameter Cu, Au and Al microwires were welded together using this technique. The welded dissimilar metal wire systems were then cut by supplying a higher current, and it was found that the position at which the wires cut was not at the midpoint, i.e., the position of the weld, of the wire system. This is because the temperature distributions formed in the dissimilar metal systems were asymmetrical. The positions at which the wires cut were in good agreement with those predicted by a heat conduction model. The lower limit for successful welding of the dissimilar metal microwire system was found to be determined by the lower of the two currents required to cut microwires of the individual materials.

  19. Joule heating during solid tissue electroporation.

    PubMed

    Pliquett, U

    2003-03-01

    The application of high-voltage pulses to biological tissue causes not only electroporation, a non-thermal phenomenon of pore creation within a lipid membrane due to an elevated electric field, but also significant heating. Once a biological membrane is porated, the current density increases several times, causing Joule heating. A combined experimental and theoretical study is reported. The theoretical temperature rise for a 1.25 kV cm(-1), 6 ms pulse is about 11.2 K for a tissue conductivity of 0.5 S m(-1) (i.e. myocardial tissue) during high-voltage application. Owing to the inhomogeneous electric field obtained with the use of needle electrodes, the temperature rises first at the electrodes, where the field strength reaches a maximum. Only for highly conductive tissue such as muscle was a temperature effect primarily observed in the bulk. Even if the temperature effect is biologically insignificant, it can affect the creation of stabile aqueous pathways by electroporation. The calculation of temperature distribution during high-voltage application, taking the electric field strength and the heat transfer into account, can be a useful tool for electrode optimisation.

  20. Observations of joule and particle heating in the auroral zone

    NASA Technical Reports Server (NTRS)

    Banks, P. M.

    1977-01-01

    Observational data from the Chatanika, Alaska incoherent scatter radar have been used to deduce atmospheric heating rates associated with particle precipitation and joule dissipation. During periods when Chatanika is in the vicinity of the auroral oval the height-integrated heat input to the lower thermosphere can be as large as 100 ergs per sq cm per sec with joule and particle heating rates of comparable magnitude. Altitude profiles of these heat inputs are also obtained, showing that the energy liberated by joule dissipation tends to peak at a substantially higher altitude (about 130 km) than that due to particles (100-120 km). As a consequence, it follows that joule heating can be expected to provide a rapid means for creating thermospheric disturbances. It is also pointed out that joule and particle heating are permanent features of the auroral oval and polar cap. As such, expansion of the auroral oval leads to an increase in the total global heating and, hence, to the close relationship between magnetic disturbances and thermospheric perturbation.

  1. Non-joule heating of ice in an electric field.

    PubMed

    Petrenko, Victor F; Ryzhkin, Ivan A

    2011-06-16

    We theoretically predict and calculate non-Joule heating/cooling caused by a direct electric current in ordinary crystalline ice Ih. The cause of this effect is related to partial ordering/disordering occurring in the proton subsystem of ice when protons either drift or diffuse in the ice. Depending on relative directions of the electric current and the configuration vector of ice, the non-Joule effect can be either positive, that is, heat generation, or negative, that is, heat absorption, and its absolute magnitude is usually comparable with that of normal Joule heating. The magnitude of this phenomenon is also approximately inversely proportional to the ice temperature and, thus, is more pronounced at low temperatures.

  2. Global and local Joule heating effects seen by DE 2

    NASA Technical Reports Server (NTRS)

    Heelis, R. A.; Coley, W. R.

    1988-01-01

    In the altitude region between 350 and 550 km, variations in the ion temperature principally reflect similar variations in the local frictional heating produced by a velocity difference between the ions and the neutrals. Here, the distribution of the ion temperature in this altitude region is shown, and its attributes in relation to previous work on local Joule heating rates are discussed. In addition to the ion temperature, instrumentation on the DE 2 satellite also provides a measure of the ion velocity vector representative of the total electric field. From this information, the local Joule heating rate is derived. From an estimate of the height-integrated Pedersen conductivity it is also possible to estimate the global (height-integrated) Joule heating rate. Here, the differences and relationships between these various parameters are described.

  3. Strongly coupled radiative transfer and Joule heating in the cathode of an arc heater

    NASA Technical Reports Server (NTRS)

    Durgapal, P.; Palmer, Grant E.

    1993-01-01

    Radiation and Joule heating in the electrode region of an arc heater are discussed. Radiative transport equations for a true axisymmetric geometry are used. A subsonic code is developed to numerically solve the fluid equations with strongly coupled radiation and Joule heating representative of a high pressure and high current arc heater. Analytic expression for the divergence of radiative heat flux derived previously is used. Jacobians of the radiation term are derived. The Joule heating term is computed using a previously developed code. The equilibrium gas model consists of seven species. The fluxes are differenced using Van Leer flux splitting. Using this code, the effects of radiative cooling on the thermodynamic parameters of the arc core are discussed.

  4. Electroosmotic flow and Joule heating in preparative continuous annular electrochromatography.

    PubMed

    Laskowski, René; Bart, Hans-Jörg

    2015-09-01

    An openFOAM "computational fluid dynamic" simulation model was developed for the description of local interaction of hydrodynamics and Joule heating in annular electrochromatography. A local decline of electrical conductivity of the background eluent is caused by an electrokinetic migration of ions resulting in higher Joule heat generation. The model equations consider the Navier-Stokes equation for incompressible fluids, the energy equation for stationary temperature fields, and the mass transfer equation for the electrokinetic flow. The simulations were embedded in commercial ANSYS Fluent software and in open-source environment openFOAM. The annular gap (1 mm width) contained an inorganic C8 reverse-phase monolith as stationary phase prepared by an in situ sol-gel process. The process temperature generated by Joule heating was determined by thermal camera system. The local hydrodynamics in the prototype was detected by a gravimetric contact-free measurement method and experimental and simulated values matched quite well.

  5. Dynamical response of nanostructures and Joule heat release.

    PubMed

    Gurevich, V L; Kozub, V I; Muradov, M I

    2011-10-12

    We consider Joule heat release in a quantum wire joining two classical reservoirs under the action of a nonstationary periodic electric field. The rate of heat generation and its spatial distribution is discussed. The heat is spread over the lengths of electron mean free paths in the reservoirs. We find that the total rates of heat generation in both reservoirs that are joined by the nanostructure are the same.

  6. Nonlinear phenomena in multiferroic nanocapacitor: Joule heating and electromechanical effects

    SciTech Connect

    Kim, Yunseok; Kumar, Amit; Tselev, Alexander; Kravchenko, Ivan I; Kalinin, Sergei V; Jesse, Stephen

    2011-01-01

    We demonstrate an approach for probing nonlinear electromechanical responses in BiFeO3 thin film nanocapacitors using half-harmonic band excitation piezoresponse force microscopy (PFM). Nonlinear PFM images of nanocapacitor arrays show clearly visible clusters of capacitors associated with variations of local leakage current through the BiFeO3 film. Strain spectroscopy measurements and finite element modeling point to significance of the Joule heating and show that the thermal effects caused by the Joule heating can provide nontrivial contributions to the nonlinear electromechanical responses in ferroic nanostructures. This approach can be further extended to unambiguous mapping of electrostatic signal contributions to PFM and related techniques.

  7. Nonlinear phenomena in multiferroic nanocapacitors: joule heating and electromechanical effects.

    PubMed

    Kim, Yunseok; Kumar, Amit; Tselev, Alexander; Kravchenko, Ivan I; Han, Hee; Vrejoiu, Ionela; Lee, Woo; Hesse, Dietrich; Alexe, Marin; Kalinin, Sergei V; Jesse, Stephen

    2011-11-22

    We demonstrate an approach for probing nonlinear electromechanical responses in BiFeO(3) thin film nanocapacitors using half-harmonic band excitation piezoresponse force microscopy (PFM). Nonlinear PFM images of nanocapacitor arrays show clearly visible clusters of capacitors associated with variations of local leakage current through the BiFeO(3) film. Strain spectroscopy measurements and finite element modeling point to significance of the Joule heating and show that the thermal effects caused by the Joule heating can provide nontrivial contributions to the nonlinear electromechanical responses in ferroic nanostructures. This approach can be further extended to unambiguous mapping of electrostatic signal contributions to PFM and related techniques.

  8. Diffusion, Fluxes, Friction Forces, and Joule Heating in Two-Temperature Multicomponent Magnetohydrodynamics

    NASA Technical Reports Server (NTRS)

    Chang, C. H.

    1999-01-01

    The relationship between Joule heating, diffusion fluxes, and friction forces has been studied for both total and electron thermal energy equations, using general expressions for multicomponent diffusion in two-temperature plasmas with the velocity dependent Lorentz force acting on charged species in a magnetic field. It is shown that the derivation of Joule heating terms requires both diffusion fluxes and friction between species which represents the resistance experienced by the species moving at different relative velocities. It is also shown that the familiar Joule heating term in the electron thermal energy equation includes artificial effects produced by switching the convective velocity from the species velocity to the mass-weighted velocity, and thus should not be ignored even when there is no net energy dissipation.

  9. Joule heating and runaway electron acceleration in a solar flare

    NASA Technical Reports Server (NTRS)

    Holman, Gordon D.; Kundu, Mukul R.; Kane, Sharad R.

    1989-01-01

    The hard and soft x ray and microwave emissions from a solar flare (May 14, 1980) were analyzed and interpreted in terms of Joule heating and runaway electron acceleration in one or more current sheets. It is found that all three emissions can be generated with sub-Dreicer electric fields. The soft x ray emitting plasma can only be heated by a single current sheet if the resistivity in the sheet is well above the classical, collisional resistivity of 10(exp 7) K, 10(exp 11)/cu cm plasma. If the hard x ray emission is from thermal electrons, anomalous resistivity or densities exceeding 3 x 10(exp 12)/cu cm are required. If the hard x ray emission is from nonthermal electrons, the emissions can be produced with classical resistivity in the current sheets if the heating rate is approximately 4 times greater than that deduced from the soft x ray data (with a density of 10(exp 10)/cu cm in the soft x ray emitting region), if there are at least 10(exp 4) current sheets, and if the plasma properties in the sheets are characteristic of the superhot plasma observed in some flares by Lin et al., and with Hinotori. Most of the released energy goes directly into bulk heating, rather than accelerated particles.

  10. Joule Heating Effects on Electrokinetic Flow Instabilities in Ferrofluids

    NASA Astrophysics Data System (ADS)

    Brumme, Christian; Shaw, Ryan; Zhou, Yilong; Prabhakaran, Rama; Xuan, Xiangchun

    We have demonstrated in our earlier work that the application of a tangential electric field can draw fluid instabilities at the interface of a ferrofluid/water co-flow. These electrokinetic flow instabilities are produced primarily by the mismatch of electric conductivities of the two fluids. We demonstrate in this talk that the Joule heating induced fluid temperature rises and gradients can significantly suppress the electrokinetic flow instabilities. We also develop a two-dimensional depth-averaged numerical model to predict the fluid temperature, flow and concentration fields in the two-fluid system with the goal to understand the Joule heating effects on electric field-driven ferrofluid flow instabilities. This work was supported by the Honors and Creative Inquiry programs at Clemson University.

  11. Joule heating in packed capillaries used in capillary electrochromatography.

    PubMed

    Rathore, Anurag S; Reynolds, Kimberly J; Colón, Luis A

    2002-09-01

    Effective heat dissipation is critical for reproducible and efficient separations in electrically driven separation systems. Flow rate, retention kinetics, and analyte diffusion rates are some of the characteristics that are affected by variation in the temperature of the mobile phase inside the column. In this study, we examine the issue of Joule heating in packed capillary columns used in capillary electrochromatography (CEC). As almost all commonly used CEC packings are poor thermal conductors, it is assumed that the packing particles do not conduct heat and heat transfer is solely through the mobile phase flowing through the system. The electrical conductivity of various mobile phases was measured at different temperatures by a conductivity meter and the temperature coefficient for each mobile phase was calculated. This was followed by measurement of the electrical current at several applied voltages to calculate the conductivity of the solution within the column as a function of the applied voltage. An overall increase in the conductivity is attributed to Joule heating within the column, while a constant conductivity means good heat dissipation. A plot of conductivity versus applied voltage was used as the indicator of poor heat dissipation. Using theories that have been proposed earlier for modeling of Joule heating effects in capillary electrophoresis (CE), we estimated the temperature within CEC columns. Under mobile and stationary phase conditions typically used in CEC, heat dissipation was found to be not always efficient. Elevated temperatures within the columns in excess of 23 degrees C above ambient temperature were calculated for packed columns, and about 35 degrees C for an open column, under a given set of conditions. The results agree with recently published experimental findings with nuclear magnetic resonance (NMR) thermometry, and Raman spectroscopic measurements.

  12. Joule Heating Investigations Using the Sondrestrom Radar and DMSP Satellites

    DTIC Science & Technology

    1990-06-01

    in particular, to validate Joule heating rates inferred from satellite data while the satellite was moving through the field of view of the...auroral arc around 75* which slowly moved to the north. The SSF Pedersen conductance curve shows a corresponding peak at 75* and a slight enhancement...covered with radar operation while moving through the Sondrestrom field of view. Under favorable conditions such an experiment could provide a

  13. Miniature Joule - Thomson liquefier with sintered heat exchanger

    NASA Astrophysics Data System (ADS)

    Eugeniusz, Bodio; Maciej, Chorowski; Marta, Wilczek; Arkadiusz, Bozek

    Conventional Joule-Thomson refrigerators are made with finned, capillary tubing for the heat exchanger and a throttling valve for reducing the pressure [1]. A new kind of recuperative miniature heat-exchanger can be developed if a powder metallurgy technology is used. A high pressure capillary tube is sintered with metal powder. The grains of metal should be ball shaped or similar. In result of sintering process a good thermal contact between an outside tube surface and powder grains is achieved. The heat exchange surface is well developed and a porous sinter acts as a low pressure gas canal.

  14. The Joule heating problem in silver nanowire transparent electrodes.

    PubMed

    Khaligh, H H; Xu, L; Khosropour, A; Madeira, A; Romano, M; Pradére, C; Tréguer-Delapierre, M; Servant, L; Pope, M A; Goldthorpe, I A

    2017-10-20

    Silver nanowire transparent electrodes have shown considerable potential to replace conventional transparent conductive materials. However, in this report we show that Joule heating is a unique and serious problem with these electrodes. When conducting current densities encountered in organic solar cells, the average surface temperature of indium tin oxide (ITO) and silver nanowire electrodes, both with sheet resistances of 60 ohms/square, remains below 35 °C. However, in contrast to ITO, the temperature in the nanowire electrode is very non-uniform, with some localized points reaching temperatures above 250 °C. These hotspots accelerate nanowire degradation, leading to electrode failure after 5 days of continuous current flow. We show that graphene, a commonly used passivation layer for these electrodes, slows nanowire degradation and creates a more uniform surface temperature under current flow. However, the graphene does not prevent Joule heating in the nanowires and local points of high temperature ultimately shift the failure mechanism from nanowire degradation to melting of the underlying plastic substrate. In this paper, surface temperature mapping, lifetime testing under current flow, post-mortem analysis, and modelling illuminate the behaviour and failure mechanisms of nanowires under extended current flow and provide guidelines for managing Joule heating.

  15. The Joule heating problem in silver nanowire transparent electrodes

    NASA Astrophysics Data System (ADS)

    Khaligh, H. H.; Xu, L.; Khosropour, A.; Madeira, A.; Romano, M.; Pradére, C.; Tréguer-Delapierre, M.; Servant, L.; Pope, M. A.; Goldthorpe, I. A.

    2017-10-01

    Silver nanowire transparent electrodes have shown considerable potential to replace conventional transparent conductive materials. However, in this report we show that Joule heating is a unique and serious problem with these electrodes. When conducting current densities encountered in organic solar cells, the average surface temperature of indium tin oxide (ITO) and silver nanowire electrodes, both with sheet resistances of 60 ohms/square, remains below 35 °C. However, in contrast to ITO, the temperature in the nanowire electrode is very non-uniform, with some localized points reaching temperatures above 250 °C. These hotspots accelerate nanowire degradation, leading to electrode failure after 5 days of continuous current flow. We show that graphene, a commonly used passivation layer for these electrodes, slows nanowire degradation and creates a more uniform surface temperature under current flow. However, the graphene does not prevent Joule heating in the nanowires and local points of high temperature ultimately shift the failure mechanism from nanowire degradation to melting of the underlying plastic substrate. In this paper, surface temperature mapping, lifetime testing under current flow, post-mortem analysis, and modelling illuminate the behaviour and failure mechanisms of nanowires under extended current flow and provide guidelines for managing Joule heating.

  16. Joule heating and anomalous resistivity in the solar corona

    NASA Astrophysics Data System (ADS)

    Spangler, S. R.

    2009-06-01

    Recent radioastronomical observations of Faraday rotation in the solar corona can be interpreted as evidence for coronal currents, with values as large as 2.5×109 Amperes (Spangler, 2007). These estimates of currents are used to develop a model for Joule heating in the corona. It is assumed that the currents are concentrated in thin current sheets, as suggested by theories of two dimensional magnetohydrodynamic turbulence. The Spitzer result for the resistivity is adopted as a lower limit to the true resistivity. The calculated volumetric heating rate is compared with an independent theoretical estimate by Cranmer et al. (2007). This latter estimate accounts for the dynamic and thermodynamic properties of the corona at a heliocentric distance of several solar radii. Our calculated Joule heating rate is less than the Cranmer et al estimate by at least a factor of 3×105. The currents inferred from the observations of Spangler (2007) are not relevant to coronal heating unless the true resistivity is enormously increased relative to the Spitzer value. However, the same model for turbulent current sheets used to calculate the heating rate also gives an electron drift speed which can be comparable to the electron thermal speed, and larger than the ion acoustic speed. It is therefore possible that the coronal current sheets are unstable to current-driven instabilities which produce high levels of waves, enhance the resistivity and thus the heating rate.

  17. Acceleration of runaway electrons and Joule heating in solar flares

    NASA Technical Reports Server (NTRS)

    Holman, G. D.

    1985-01-01

    The electric field acceleration of electrons out of a thermal plasma and the simultaneous Joule heating of the plasma are studied. Acceleration and heating timescales are derived and compared, and upper limits are obtained on the acceleration volume and the rate at which electrons can be accelerated. These upper limits, determined by the maximum magnetic field strength observed in flaring regions, place stringent restrictions upon the acceleration process. The role of the plasma resistivity in these processes is examined, and possible sources of anomalous resistivity are summarized. The implications of these results for the microwave and hard X-ray emission from solar flares are examined.

  18. Joule heating in ferromagnetic nanowires: Prediction and observation

    NASA Astrophysics Data System (ADS)

    Kim, Kab-Jin; Lee, Jae-Chul; Choe, Sug-Bong; Shin, Kyung-Ho

    2008-05-01

    We present an analytic theory of the Joule heating in metallic nanowires. The steady state is calculated for heat conduction through the insulation layer and then the transient state is considered from the thermodynamics law. The temperature is predicted to exhibit a quick exponential decay to a steady state within a few tens of nanoseconds. The decay time is linearly dependent on the temperature coefficient and both increase to saturation values with the increasing wire width. The validity of the theory is experimentally confirmed by the in situ measurement of the temperature-dependent electric resistance.

  19. Joule heating of Io's ionosphere by unipolar induction currents

    NASA Technical Reports Server (NTRS)

    Herbert, F.; Lichtenstein, B. R.

    1980-01-01

    Electrical induction in Io's ionosphere, due to the corotating plasma bound to the Jovian magnetosphere, is one possible source for the attainment of the high temperatures suggested by the large scale height of Io's ionosphere. Unipolar induction models are constructed to calculate ionospheric joule heating numerically, whose heating rates lie between 10 to the -9th and 10 to the -8th W/cu m. The binding and coupling of the ionosphere is due to the dense, and possibly ionized, neutral SO2 atmosphere, and there appears to be no need to postulate the existence of an intrinsic Ionian magnetic field in order to retain the observed ionnosphere.

  20. Acceleration of runaway electrons and Joule heating in solar flares

    NASA Technical Reports Server (NTRS)

    Holman, G. D.

    1984-01-01

    The electric field acceleration of electrons out of a thermal plasma and the simultaneous Joule heating of the plasma are studied. Acceleration and heating timescales are derived and compared, and upper limits are obtained on the acceleration volume and the rate at which electrons can be accelerated. These upper limits, determined by the maximum magnetic field strength observed in flaring regions, place stringent restrictions upon the acceleration process. The role of the plasma resistivity in these processes is examined, and possible sources of anomalous resistivity are summarized. The implications of these results for the microwave and hard X-ray emission from solar flares are examined.

  1. Acceleration of runaway electrons and Joule heating in solar flares

    NASA Technical Reports Server (NTRS)

    Holman, G. D.

    1985-01-01

    The electric field acceleration of electrons out of a thermal plasma and the simultaneous Joule heating of the plasma are studied. Acceleration and heating timescales are derived and compared, and upper limits are obtained on the acceleration volume and the rate at which electrons can be accelerated. These upper limits, determined by the maximum magnetic field strength observed in flaring regions, place stringent restrictions upon the acceleration process. The role of the plasma resistivity in these processes is examined, and possible sources of anomalous resistivity are summarized. The implications of these results for the microwave and hard X-ray emission from solar flares are examined.

  2. Joule heating of Io's ionosphere by unipolar induction currents

    SciTech Connect

    Herbert, F.; Lichtenstein, B.R.

    1980-01-01

    Electrical induction in Io's ionosphere, due to the corotating plasma bound to the Jovian magnetosphere, is one possible source for the attainment of the high temperatures suggested by the large scale height of Io's ionosphere. Unipolar induction models are constructed to calculate ionospheric joule heating numerically, whose heating rates lie between 10 to the -9th and 10 to the -8th W/cu m. The binding and coupling of the ionosphere is due to the dense, and possibly ionized, neutral SO2 atmosphere, and there appears to be no need to postulate the existence of an intrinsic Ionian magnetic field in order to retain the observed ionnosphere.

  3. Stabilization of Joule Heating in the Electropyroelectric Method

    NASA Astrophysics Data System (ADS)

    Ivanov, R.; Hernández, M.; Marín, E.; Araujo, C.; Alaniz, D.; Araiza, M.; Martínez-Ordoñez, E. I.

    2012-11-01

    Recently the so-called electropyroelectric technique for thermal characterization of liquids has been proposed (Ivanov et al., J. Phys. D: Appl. Phys. 43, 225501 (2010)). In this method a pyroelectric sensor, in good thermal contact with the investigated sample, is heated by passing an amplitude-modulated electrical current through the electrical contacts. As a result of the heat dissipated to the sample, the pyroelectric signal measured as a voltage drop across the electrical contacts changes in a periodical way. The amplitude and phase of this signal can be measured by lock-in detection as a function of the electrical current modulation frequency. Because the signal amplitude and phase depend on the thermal properties of the sample, these can be determined straightforwardly by fitting the experimental data to a theoretical model based on the solution of the heat diffusion equation with proper boundary conditions. In general, the experimental conditions are selected so that the thermal effusivity becomes the measured magnitude. The technique has the following handicap. As the result of heating and wear of the metal coating layers (previously etched to achieve a serpentine form) with time, their electrical resistance changes with time, so that the heat power dissipated by the Joule effect can vary, and thermal effusivity measurement can become inaccurate. To avoid this problem in this study, a method is proposed that allows maintaining stable the Joule dissipated power. An electronic circuit is designed whose stability and characteristics are investigated and discussed.

  4. Physical and numerical modeling of Joule-heated melters

    NASA Astrophysics Data System (ADS)

    Eyler, L. L.; Skarda, R. J.; Crowder, R. S., III; Trent, D. S.; Reid, C. R.; Lessor, D. L.

    1985-10-01

    The Joule-heated ceramic-lined melter is an integral part of the high level waste immobilization process under development by the US Department of Energy. Scaleup and design of this waste glass melting furnace requires an understanding of the relationships between melting cavity design parameters and the furnace performance characteristics such as mixing, heat transfer, and electrical requirements. Developing empirical models of these relationships through actual melter testing with numerous designs would be a very costly and time consuming task. Additionally, the Pacific Northwest Laboratory (PNL) has been developing numerical models that simulate a Joule-heated melter for analyzing melter performance. This report documents the method used and results of this modeling effort. Numerical modeling results are compared with the more conventional, physical modeling results to validate the approach. Also included are the results of numerically simulating an operating research melter at PNL. Physical Joule-heated melters modeling results used for qualiying the simulation capabilities of the melter code included: (1) a melter with a single pair of electrodes and (2) a melter with a dual pair (two pairs) of electrodes. The physical model of the melter having two electrode pairs utilized a configuration with primary and secondary electrodes. The principal melter parameters (the ratio of power applied to each electrode pair, modeling fluid depth, electrode spacing) were varied in nine tests of the physical model during FY85. Code predictions were made for five of these tests. Voltage drops, temperature field data, and electric field data varied in their agreement with the physical modeling results, but in general were judged acceptable.

  5. Physical and numerical modeling of Joule-heated melters

    SciTech Connect

    Eyler, L.L.; Skarda, R.J.; Crowder, R.S. III; Trent, D.S.; Reid, C.R.; Lessor, D.L.

    1985-10-01

    The Joule-heated ceramic-lined melter is an integral part of the high level waste immobilization process under development by the US Department of Energy. Scaleup and design of this waste glass melting furnace requires an understanding of the relationships between melting cavity design parameters and the furnace performance characteristics such as mixing, heat transfer, and electrical requirements. Developing empirical models of these relationships through actual melter testing with numerous designs would be a very costly and time consuming task. Additionally, the Pacific Northwest Laboratory (PNL) has been developing numerical models that simulate a Joule-heated melter for analyzing melter performance. This report documents the method used and results of this modeling effort. Numerical modeling results are compared with the more conventional, physical modeling results to validate the approach. Also included are the results of numerically simulating an operating research melter at PNL. Physical Joule-heated melters modeling results used for qualiying the simulation capabilities of the melter code included: (1) a melter with a single pair of electrodes and (2) a melter with a dual pair (two pairs) of electrodes. The physical model of the melter having two electrode pairs utilized a configuration with primary and secondary electrodes. The principal melter parameters (the ratio of power applied to each electrode pair, modeling fluid depth, electrode spacing) were varied in nine tests of the physical model during FY85. Code predictions were made for five of these tests. Voltage drops, temperature field data, and electric field data varied in their agreement with the physical modeling results, but in general were judged acceptable. 14 refs., 79 figs., 17 tabs.

  6. Super-Joule heating in graphene and silver nanowire network

    NASA Astrophysics Data System (ADS)

    Maize, Kerry; Das, Suprem R.; Sadeque, Sajia; Mohammed, Amr M. S.; Shakouri, Ali; Janes, David B.; Alam, Muhammad A.

    2015-04-01

    Transistors, sensors, and transparent conductors based on randomly assembled nanowire networks rely on multi-component percolation for unique and distinctive applications in flexible electronics, biochemical sensing, and solar cells. While conduction models for 1-D and 1-D/2-D networks have been developed, typically assuming linear electronic transport and self-heating, the model has not been validated by direct high-resolution characterization of coupled electronic pathways and thermal response. In this letter, we show the occurrence of nonlinear "super-Joule" self-heating at the transport bottlenecks in networks of silver nanowires and silver nanowire/single layer graphene hybrid using high resolution thermoreflectance (TR) imaging. TR images at the microscopic self-heating hotspots within nanowire network and nanowire/graphene hybrid network devices with submicron spatial resolution are used to infer electrical current pathways. The results encourage a fundamental reevaluation of transport models for network-based percolating conductors.

  7. Flash Joule heating for ductilization of metallic glasses.

    PubMed

    Okulov, I V; Soldatov, I V; Sarmanova, M F; Kaban, I; Gemming, T; Edström, K; Eckert, J

    2015-07-29

    Metallic glasses (MGs) inherit their amorphous structure from the liquid state, which predetermines their ability to withstand high loads approaching the theoretical limit. However, the absence of slip systems makes them very sensitive to the type of loading and extremely brittle in tension. The latter can be improved by precipitation of ductile crystals, which suppress a catastrophic propagation of shear bands in a glassy matrix. Here we report a novel approach to obtain MG-matrix composites with tensile ductility by flash Joule heating applied to Cu47.5Zr47.5Al5 (at.%) metallic glass. This homogeneous, volumetric and controllable rapid heat treatment allows achieving uniformly distributed metastable B2 CuZr crystals in the glassy matrix. It results in a significant tensile strain of 6.8±0.5%. Moreover, optimized adjustment of the heat-treatment conditions enables tuning of microstructure to achieve desired mechanical properties.

  8. Joule heating effects on reservoir-based dielectrophoresis.

    PubMed

    Kale, Akshay; Patel, Saurin; Qian, Shizhi; Hu, Guoqing; Xuan, Xiangchun

    2014-03-01

    Reservoir-based dielectrophoresis (rDEP) is a recently developed technique that exploits the inherent electric field gradients at a reservoir-microchannel junction to focus, trap, and sort particles. However, the locally amplified electric field at the junction is likely to induce significant Joule heating effects that are not considered in previous studies. This work investigates experimentally and numerically these effects on particle transport and control in rDEP processes in PDMS/PDMS microchips. It is found that Joule heating effects can reduce rDEP focusing considerably and may even disable rDEP trapping. This is caused by the fluid temperature rise at the reservoir-microchannel junction, which significantly increases the local particle velocity due to fluid flow and particle electrophoresis while has a weak impact on the particle velocity due to rDEP. The numerical predictions of particle stream width and electric current, which are the respective indicators of rDEP manipulation and fluid temperature, are demonstrated to both match the experimental measurements with a good accuracy.

  9. Selective surface functionalization of silicon nanowires via nanoscale joule heating.

    PubMed

    Park, Inkyu; Li, Zhiyong; Pisano, Albert P; Williams, R Stanley

    2007-10-01

    In this letter, we report a novel approach to selectively functionalize the surface of silicon nanowires located on silicon-based substrates. This method is based upon highly localized nanoscale Joule heating along silicon nanowires under an applied electrical bias. Numerical simulation shows that a high-temperature (>800 K) with a large thermal gradient can be achieved by applying an appropriate electrical bias across silicon nanowires. This localized heating effect can be utilized to selectively ablate a protective polymer layer from a region of the chosen silicon nanowire. The exposed surface, with proper postprocessing, becomes available for surface functionalization with chemical linker molecules, such as 3-mercaptopropyltrimethoxysilanes, while the surrounding area is still protected by the chemically inert polymer layer. This approach is successfully demonstrated on silicon nanowire arrays fabricated on SOI wafers and visualized by selective attachment of gold nanoparticles.

  10. Marangoni mixed convection flow with Joule heating and nonlinear radiation

    SciTech Connect

    Hayat, Tasawar; Shaheen, Uzma; Shafiq, Anum; Alsaedi, Ahmed; Asghar, Saleem

    2015-07-15

    Marangoni mixed convective flow of Casson fluid in a thermally stratified medium is addressed. Flow analysis has been carried out in presence of inclined magnetic field. Heat transfer analysis is discussed in the presence of viscous dissipation, Joule heating and nonlinear thermal radiation. The governing nonlinear partial differential equations are first converted into ordinary differential systems and then developed the convergent series solutions. Flow pattern with the influence of pertinent parameters namely the magnetic parameter, Casson fluid parameter, temperature ratio parameter, stratification parameter, Prandtl number, Eckert number and radiation parameter is investigated. Expression of local Nusselt number is computed and analyzed. It is found that the Nusselt number decreases by increasing magnetic parameter, temperature ratio parameter, angle of inclination and stratification parameter. Moreover the effect of buoyancy parameter on the velocity distribution is opposite in both the opposing and assisting flow phenomena. Thermal field and associated layer thickness are enhanced for larger radiation parameter.

  11. Reliable electrophoretic mobilities free from Joule heating effects using CE.

    PubMed

    Evenhuis, Christopher J; Hruska, Vlastimil; Guijt, Rosanne M; Macka, Miroslav; Gas, Bohuslav; Marriott, Philip J; Haddad, Paul R

    2007-10-01

    Ionic electrophoretic mobilities determined by means of CE experiments are sometimes different when compared to generally accepted values based on limiting ionic conductance measurements. While the effect of ionic strength on electrophoretic mobility has been long understood, the increase in the mobility that results from Joule heating (the resistive heating that occurs when a current passes through an electrolyte) has been largely overlooked. In this work, a simple method for obtaining reliable and reproducible values of electrophoretic mobility is described. The electrophoretic mobility is measured over a range of driving powers and the extrapolation to zero power dissipation is employed to eliminate the effect of Joule heating. These extrapolated values of electrophoretic mobility can then be used to calculate limiting ionic mobilities by making a correction for ionic strength; this somewhat complicated calculation is conveniently performed by using the freeware program PeakMaster 5. These straightforward procedures improve the agreement between experimentally determined and literature values of limiting ionic mobility by at least one order of magnitude. Using Tris-chromate BGE with a value of conductivity 0.34 S/m and ionic strength 59 mM at a modest dissipated power per unit length of 2.0 W/m, values of mobility for inorganic anions were increased by an average of 12.6% relative to their values free from the effects of Joule heating. These increases were accompanied by a reduction in mobilities due to the ionic strength effect, which was 11% for univalent and 28% for divalent inorganic ions compared to their limiting ionic mobilities. Additionally, it was possible to determine the limiting ionic mobility for a number of aromatic anions by using PeakMaster 5 to perform an ionic strength correction. A major significance of this work is in being able to use CE to obtain reliable and accurate values of electrophoretic mobilities with all its benefits, including

  12. Electro-osmotic infusion for joule heating soil remediation techniques

    DOEpatents

    Carrigan, Charles R.; Nitao, John J.

    1999-01-01

    Electro-osmotic infusion of ground water or chemically tailored electrolyte is used to enhance, maintain, or recondition electrical conductivity for the joule heating remediation technique. Induced flows can be used to infuse electrolyte with enhanced ionic conductivity into the vicinity of the electrodes, maintain the local saturation of near-electrode regions and resaturate a partially dried out zone with groundwater. Electro-osmotic infusion can also tailor the conductivity throughout the target layer by infusing chemically modified and/or heated electrolyte to improve conductivity contrast of the interior. Periodic polarity reversals will prevent large pH changes at the electrodes. Electro-osmotic infusion can be used to condition the electrical conductivity of the soil, particularly low permeability soil, before and during the heating operation. Electro-osmotic infusion is carried out by locating one or more electrodes adjacent the heating electrodes and applying a dc potential between two or more electrodes. Depending on the polarities of the electrodes, the induced flow will be toward the heating electrodes or away from the heating electrodes. In addition, electrodes carrying a dc potential may be located throughout the target area to tailor the conductivity of the target area.

  13. The role of Joule heating in dispersive mixing effects in electrophoretic cells: hydrodynamic considerations.

    PubMed

    Bosse, M A; Arce, P

    2000-03-01

    The analysis described in this contribution is focused on the effect of Joule heating generation on the hydrodynamics of batch electrophoretic cells (i.e., cells that do not display a forced convective term in the motion equation). The hydrodynamics of these cells is controlled by the viscous forces and by the buoyancy force caused by the temperature gradients due to the Joule heating generation. The analysis is based on differential models that lead to analytical and/or asymptotic solutions for the temperature and velocity profiles of the cell. The results are useful in determining the characteristics of the temperature and velocity profiles inside the cell. Furthermore, the results are excellent tools to be used in the analysis of the dispersive-mixing of solute when Joule heating generation must be accounted for. The analysis is performed by identifying two sequentially coupled problems. Thus, the "carrier fluid problem" and the "solute problem" are outlined. The former is associated with all the factors affecting the velocity profile and the latter is related to the convective-diffusion aspects that control the spreading of the solute inside the cell. The analysis of this contribution is centered on the discussion of the "carrier fluid problem" only. For the boundary conditions selected in the contribution, the study leads to the derivation of an analytical temperature and a "universal" velocity profile that feature the Joule heating number. The Grashof number is a scaling factor of the actual velocity profile. Several characteristics of these profiles are studied and some numerical illustrations have been included.

  14. On the Role of Hall and Pedersen Conductivities in Determination of Ionospheric Joule Heating

    NASA Astrophysics Data System (ADS)

    Ceren Kalafatoglu, Emine; Kaymaz, Zerefsan

    2013-04-01

    Ionospheric Joule heating is defined as the frictional heating which results from the collisions between the neutrals and charged particles at the ionospheric heights. These collisional processes gain importance around 120 km in the E and F regions of the ionosphere where there are more neutral atoms, and particularly at the auroral altitudes, where Hall and Pedersen conductivities are comparable to each other. The most conventional ways of calculating ionospheric Joule heating relies on the relationship between electric field and Pedersen conductivity. The role of Hall conductivity in the calculation of Joule heating still remains unclear, and in general its contribution is accepted to be minor when compared to the Pedersen currents at the first approximation. However, results from the MHD simulations show that Joule heating is reduced in the regions where Hall conductivity is close to or higher than Pedersen conductivity. These local variations also modify the global Joule heating pattern and distribution. MHD models take into account the magnetosphere and ionosphere interaction and incorporate with the ionospheric modules which include the interaction between the neutral winds and charged paricles. In this study, we have selected two isolated substorm events that occurred in March, 2008 to investigate the effects of Hall conductivity on the Joule heating. We run NASA/CCMC MHD models, e.g. SWMF/BATSRUS, during these times under concurrent solar wind and IMF conditions. The outputs from the models will be used to calculate Joule heating with the Hall conductivity effects properly included. In this presentation, we will show our preliminary results on the Joule heating rates from the models, quantify the degree of Pedersen and Hall conductivity contributions on the Joule heating, and address on their contributions on the global distribution of the Joule heating. We will also compare and discuss our findings with those available in the literature.

  15. Refractory electrodes for joule heating and methods of using same

    DOEpatents

    Lamar, D.A.; Chapman, C.C.; Elliott, M.L.

    1998-05-12

    A certain group of electrically conductive refractory materials presently known for use in high temperature applications as throat constructions, melter sidewalls, forehearth, stacks, port sills, hot face lining for slagging coal gasifiers, slag runners, and linings for nuclear waste encapsulation furnaces may be used as electrodes permitting joule heating at temperatures in excess of 1,200 C in excess of about 4400 hours even in the presence of transition group element(s). More specifically, the invention is an electrode for melting earthen materials, wherein the electrode is made from an electrically conductive refractory material, specifically at least one metal oxide wherein the metal is selected from the group consisting of chrome, ruthenium, rhodium, tin and combinations thereof. 2 figs.

  16. Refractory electrodes for joule heating and methods of using same

    DOEpatents

    Lamar, David A.; Chapman, Chris C.; Elliott, Michael L.

    1998-01-01

    A certain group of electrically conductive refractory materials presently known for use in high temperature applications as throat constructions, melter sidewalls, forehearth, stacks, port sills, hot face lining for slagging coal gasifiers, slag runners, and linings for nuclear waste encapsulation furnaces may be used as electrodes permitting joule heating at temperatures in excess of 1200 C. in excess of about 4400 hours even in the presence of transition group element(s). More specifically, the invention is an electrode for melting earthen materials, wherein the electrode is made from an electrically conductive refractory material, specifically at least one metal oxide wherein the metal is selected from the group consisting of chrome, ruthenium, rhodium, tin and combinations thereof.

  17. Fluid flow and heat transfer in Joule-Thomson coolers coupled with infrared detectors

    NASA Astrophysics Data System (ADS)

    Du, Bingyan; Jia, Weimin

    2011-08-01

    Joule-Thomson coolers have been widely used in infrared detectors with respect to compact, light and low cost. For self-regulating Joule-Thomson cooler, its performance is required to be improved with the development of higher mass and larger diameter of focal plane infrared detectors. Self-regulating Joule-Thomson coolers use a limited supply of high pressure gas to support the cooling of infrared detectors. In order to develop Joule-Thomson coolers with a given volume of stored gas, it is important to study on fluid flow and heat transfer of Joule-Thomson coolers coupled with infrared detectors, especially the starting time of Joule-Thomson coolers. A serial of experiments of Joule-Thomson coolers coupled with 128×128 focal plane infrared detectors have been carried out. The exchanger of coolers are made of a d=0.5mm capillary finned with a copper wire. The coolers are self-regulated by bellows and the diameters are about 8mm. Nitrogen is used as working gas. The effect of pressure of working gas has been studied. The relation between starting time and pressure of working gas is proved to fit exponential decay. Error analysis has also been carried. It is crucial to study the performance of Joule-Thomson coolers coupled with infrared detectors. Deeper research on Joule-Thomson coolers will be carried on to improve the Joule-Thomson coolers for infrared detectors.

  18. ULF wave electromagnetic energy flux into the ionosphere: Joule heating implications

    NASA Astrophysics Data System (ADS)

    Hartinger, M. D.; Moldwin, M. B.; Zou, S.; Bonnell, J. W.; Angelopoulos, V.

    2015-01-01

    Ultralow-frequency (ULF) waves—in particular, Alfvén waves-transfer energy into the Earth's ionosphere via Joule heating, but it is unclear how much they contribute to global and local heating rates relative to other energy sources. In this study we use Time History of Events and Macroscale Interactions during Substorms satellite data to investigate the spatial, frequency, and geomagnetic activity dependence of the ULF wave Poynting vector (electromagnetic energy flux) mapped to the ionosphere. We use these measurements to estimate Joule heating rates, covering latitudes at or below the nominal auroral oval and below the open/closed field line boundary. We find ULF wave Joule heating rates (integrated over 3-30 mHz frequency band) typically range from 0.001 to 1 mW/m2. We compare these rates to empirical models of Joule heating associated with large-scale, static (on ULF wave timescales) current systems, finding that ULF waves nominally contribute little to the global, integrated Joule heating rate. However, there are extreme cases with ULF wave Joule heating rates of ≥10 mW/m2—in these cases, which are more likely to occur when Kp ≥ 3, ULF waves make significant contributions to the global Joule heating rate. We also find ULF waves routinely make significant contributions to local Joule heating rates near the noon and midnight local time sectors, where static current systems nominally contribute less to Joule heating; the most important contributions come from lower frequency (<7 mHz) waves.

  19. ULF Wave Electromagnetic Energy Flux into the Ionosphere: Joule Heating Implications

    NASA Astrophysics Data System (ADS)

    Hartinger, M.; Moldwin, M.; Zou, S.; Bonnell, J. W.; Angelopoulos, V.

    2014-12-01

    Ultra Low Frequency (ULF) waves - such as standing Alfven waves - are one mechanism for coupling the inner magnetosphere to the Earth's ionosphere. For example, they transfer energy from the solar wind or ring current into the Earth's ionosphere via Joule heating. In this study, we use NASA Time History of Events and Macroscale Interactions during Substorms (THEMIS) satellite data to investigate the spatial, frequency, and geomagnetic activity dependence of the ULF wave Poynting vector (electromagnetic energy flux) mapped to the ionosphere. We use these measurements to estimate Joule heating rates. We compare these rates to empirical models of Joule heating associated with large scale, static (on ULF wave timescales) current systems, finding that ULF waves usually contribute little to the global, integrated Joule heating rate. However, there are extreme cases when ULF waves make significant contributions to global Joule heating. Finally, we find ULF waves routinely make significant contributions to local Joule heating rates near the noon and midnight local time sectors, where static current systems nominally contribute less to Joule heating; the most important contributions come from lower frequency (<7 mHz) waves.

  20. Joule Heating Resistance Can Differ from Ohmic Resistance.

    NASA Astrophysics Data System (ADS)

    Saslow, Wayne M.

    1998-03-01

    For slow, steady discharge of a voltaic cell with more than one active charge-carrier, the cell's Joule heating resistance RJ differs from its Ohmic resistance R. Here RJ is determined by volume integration over the local rate of heating, J_1^2/σ1 + J_2^2/σ2 +dots (J1 is the part of the electric current due to carrier #1, σ1 is its conductivity). RJ involves only the current-carrying ions, whereas R=Δ V/I involves all of the ions because all ions contribute to the electric field and voltage Δ V across the cell. We explicitly study a well-charged lead-acid cell(W.M.Saslow, Phys.Rev.Lett. 76), 4849 (1996) and a Zn-Cu cell.(See Sect.8.1 of manuscript at http://physics.tamu.edu/ )saslow R/RJ can be greater than or less than unity.

  1. Magnetospheric structure and atmospheric Joule heating of habitable planets orbiting M-dwarf stars

    SciTech Connect

    Cohen, O.; Drake, J. J.; Garraffo, C.; Poppenhaeger, K.; Glocer, A.; Ridley, A. J.; Gombosi, T. I.

    2014-07-20

    We study the magnetospheric structure and the ionospheric Joule Heating of planets orbiting M-dwarf stars in the habitable zone using a set of magnetohydrodynamic models. The stellar wind solution is used to drive a model for the planetary magnetosphere, which is coupled with a model for the planetary ionosphere. Our simulations reveal that the space environment around close-in habitable planets is extreme, and the stellar wind plasma conditions change from sub- to super-Alfvénic along the planetary orbit. As a result, the magnetospheric structure changes dramatically with a bow shock forming in the super-Alfvénic sectors, while no bow shock forms in the sub-Alfvénic sectors. The planets reside most of the time in the sub-Alfvénic sectors with poor atmospheric protection. A significant amount of Joule Heating is provided at the top of the atmosphere as a result of the intense stellar wind. For the steady-state solution, the heating is about 0.1%-3% of the total incoming stellar irradiation, and it is enhanced by 50% for the time-dependent case. The significant Joule Heating obtained here should be considered in models for the atmospheres of habitable planets in terms of the thickness of the atmosphere, the top-side temperature and density, the boundary conditions for the atmospheric pressure, and particle radiation and transport. Here we assume constant ionospheric Pedersen conductance similar to that of the Earth. The conductance could be greater due to the intense EUV radiation leading to smaller heating rates. We plan to quantify the ionospheric conductance in future study.

  2. Destabilization of a liquid metal by nonuniform Joule heating

    NASA Astrophysics Data System (ADS)

    Renaudière de Vaux, Sébastien; Zamansky, Rémi; Bergez, Wladimir; Tordjeman, Philippe; Haquet, Jean-François

    2017-09-01

    We study the effect of an impressing AC magnetic field at the bottom of a liquid metal layer of thickness h . In this situation the fluid is set in motion by the buoyancy forces caused by internal heat sources. The heat sources, caused by the Joule effect induced by the AC field, present an exponentially decaying profile, with characteristic length δ . As the magnetic field is horizontal, the Lorentz force has no influence on the dynamics of the system since it contributes only to the magnetic pressure. We propose an analysis of both the transient and fully developed regimes using linear stability analysis (LSA) and direct numerical simulations (DNSs). The transient period is governed by the temporal evolution of the temperature field as well as the development of the convective instability, which can be concomitant and therefore requires adopting a transient LSA algorithm to track these two effects. The DNSs have been performed for various distributions of the heat sources and various total heat input. This corresponds to independently varying δ /h in the range 0.04 ≤δ /h ≤0.45 and a Rayleigh number 1.1 ×104≤Ra≤1.2 ×105 . We observe the relaxation of the temperature up to the steady conductive profile before the transition to the nonlinear regime when Ra is small, whereas for larger Ra, nonlinear effects appear during the relaxation of the temperature profile. The unsteadiness of the temperature field significantly alters the development of the instability because of a much smaller growth rate. Surprisingly, we observe that δ /h has only a limited influence on averaged quantities as well as on the patterns for both the linear and nonlinear regimes. This comes with the fact that the profiles present an apparent reflectional symmetry, despite the asymmetry of the governing equations.

  3. Acceleration of runaway electrons and Joule heating in solar flares

    SciTech Connect

    Holman, G.D.

    1985-06-15

    The electric-field acceleration of electrons out of a thermal plasma and the simultaneous Joule heating of the plasma are studied. Acceleration and heating time scales are derived and compared, and upper limits are obtained on the acceleration volume and the rate at which electrons can be accelerated. These upper limits, determined by the maximum magnetic-field strength observed in flaring regions, place stringent restrictions on the acceleration process. The implications of these results for the microwave and hard X-ray emission from solar flares are examined. The major conclusions are: (1) The simple electric-field acceleration of electrons is found, in agreement with Spicer, to be incapable of producing a large enough electron flux to explain the bulk of the observed hard X-ray emission from solar flares as nonthermal bremsstrahlung. For the bulk of the X-ray emission to be nonthermal, at least 10/sup 4/ oppositely directed current channels are required, or an acceleration mechanism that does not result in a net current in the acceleration region is required. (2) lf the bulk of the X-ray emission is thermal, a single current sheet can yield the required heating and acceleration time scales and the required electron energies for the microwave emission. This is accomplished with an electric field that is much smaller than the Dreicer field (E/sub D//Eroughly-equal10--50). (3) The rise time of the nonthermal emission is determined by the time needed to generate the required number of runaway electrons rather than by the time needed to accelerate the electrons to the required energies, which is generally a much shorter time scale. (4) The acceleration of enough electrons to produce a microwave flare requires the resupply of electrons to both the current sheet and the runaway region of velocity space.

  4. Toward reversing Joule heating with a phonon-absorbing heterobarrier

    NASA Astrophysics Data System (ADS)

    Shin, Seungha; Kaviany, Massoud

    2015-02-01

    Using a graded heterobarrier placed along an electron channel, phonons emitted in Joule heating are recycled in situ by increasing the entropy of phonon-absorbing electrons. The asymmetric electric potential distribution created by alloy grading separates the phonon absorption and emission regions, and emission in the larger effective-mass region causes momentum relaxation with smaller electron kinetic energy loss. These lead to smaller overall phonon emission and simultaneous potential-gain and self-cooling effects. Larger potential is gained with lower current and higher optical-phonon temperature. The self-consistent Monte Carlo simulations complying with the lateral momentum conservation combined with the entropy analysis are applied to a GaAs:Al electron channel with a graded heterobarrier, and under ideal lateral thermal isolation from surroundings, the phonon recycling efficiency reaches 25% of the reversible limit at 350 K, and it increases with temperature. The lateral momentum contributes to the transmission across the barrier, so partially nonconserving lateral momentum electron scattering (rough interface) can improve efficiency.

  5. Coherent radar estimates of average high-latitude ionospheric Joule heating

    SciTech Connect

    Kosch, M.J.; Nielsen, E.

    1995-07-01

    The Scandinavian Twin Auroral Radar Experiment (STARE) and Sweden and Britain Radar Experiment (SABRE) bistatic coherent radar systems have been employed to estimate the spatial and temporal variation of the ionospheric Joule heating in the combined geographic latitude range 63.8 deg - 72.6 deg (corrected geomagnetic latitude 61.5 deg - 69.3 deg) over Scandinavia. The 173 days of good observations with all four radars have been analyzed during the period 1982 to 1986 to estimate the average ionospheric electric field versus time and latitude. The AE dependent empirical model of ionospheric Pedersen conductivity of Spiro et al. (1982) has been used to calculate the Joule heating. The latitudinal and diurnal variation of Joule heating as well as the estimated mean hemispherical heating of 1.7 x 10(exp 11) W are in good agreement with earlier results. Average Joule heating was found to vary linearly with the AE, AU, and AL indices and as a second-order power law with Kp. The average Joule heating was also examined as a function of the direction and magnitude of the interplanetary magnetic field. It has been shown for the first time that the ionospheric electric field magnitude as well as the Joule heating increase with increasingly negative (southward) Bz.

  6. Heat, work and subtle fluids: a commentary on Joule (1850) 'On the mechanical equivalent of heat'.

    PubMed

    Young, John

    2015-04-13

    James Joule played the major role in establishing the conservation of energy, or the first law of thermodynamics, as a universal, all-pervasive principle of physics. He was an experimentalist par excellence and his place in the development of thermodynamics is unarguable. This article discusses Joule's life and scientific work culminating in the 1850 paper, where he presented his detailed measurements of the mechanical equivalent of heat using his famous paddle-wheel apparatus. Joule's long series of experiments in the 1840s leading to his realisation that the conservation of energy was probably of universal validity is discussed in context with the work of other pioneers, notably Sadi Carnot, who effectively formulated the principle of the second law of thermodynamics a quarter of a century before the first law was accepted. The story of Joule's work is a story of an uphill struggle against a critical scientific establishment unwilling to accept the mounting evidence until it was impossible to ignore. His difficulties in attracting funding and publishing in reputable journals despite the quality of his work will resonate with many young scientists and engineers of the present day. This commentary was written to celebrate the 350th anniversary of the journal Philosophical Transactions of the Royal Society.

  7. Assessment of ionospheric Joule heating by GUMICS-4 MHD simulation, AMIE, and satellite-based statistics: towards a synthesis

    NASA Astrophysics Data System (ADS)

    Palmroth, M.; Janhunen, P.; Pulkkinen, T. I.; Aksnes, A.; Lu, G.; Østgaard, N.; Watermann, J.; Reeves, G. D.; Germany, G. A.

    2005-09-01

    We investigate the Northern Hemisphere Joule heating from several observational and computational sources with the purpose of calibrating a previously identified functional dependence between solar wind parameters and ionospheric total energy consumption computed from a global magnetohydrodynamic (MHD) simulation (Grand Unified Magnetosphere Ionosphere Coupling Simulation, GUMICS-4). In this paper, the calibration focuses on determining the amount and temporal characteristics of Northern Hemisphere Joule heating. Joule heating during a substorm is estimated from global observations, including electric fields provided by Super Dual Auroral Network (SuperDARN) and Pedersen conductances given by the ultraviolet (UV) and X-ray imagers on board the Polar satellite. Furthermore, Joule heating is assessed from several activity index proxies, large statistical surveys, assimilative data methods (AMIE), and the global MHD simulation GUMICS-4. We show that the temporal and spatial variation of the Joule heating computed from the GUMICS-4 simulation is consistent with observational and statistical methods. However, the different observational methods do not give a consistent estimate for the magnitude of the global Joule heating. We suggest that multiplying the GUMICS-4 total Joule heating by a factor of 10 approximates the observed Joule heating reasonably well. The lesser amount of Joule heating in GUMICS-4 is essentially caused by weaker Region 2 currents and polar cap potentials. We also show by theoretical arguments that multiplying independent measurements of averaged electric fields and Pedersen conductances yields an overestimation of Joule heating. Keywords. Ionosphere (Auroral ionosphere; Modeling and forecasting; Electric fields and currents)

  8. Decoupling electrocaloric effect from Joule heating in a solid state cooling device

    NASA Astrophysics Data System (ADS)

    Quintero, M.; Ghivelder, L.; Gomez-Marlasca, F.; Parisi, F.

    2011-12-01

    We report a heat dynamics analysis of the electrocaloric effect (ECE) in commercial multilayer capacitors based on BaTiO3 dielectric, a promising candidate for applications as a solid state cooling device. Direct measurements of the time evolution of the sample's temperature changes under different applied voltages allow us to decouple the contributions from Joule heating and from the ECE. Heat balance equations were used to model the thermal coupling between different parts of the system. Fingerprints of Joule heating and the ECE could be resolved at different time scales. We argue that Joule heating and the thermal coupling of the device to the environment must be carefully taken in to account in future developments of refrigeration technologies employing the ECE.

  9. Hybrid joule heating/electro-osmosis process for extracting contaminants from soil layers

    SciTech Connect

    Carrigan, Charles R.; Nitao, John J.

    2003-06-10

    Joule (ohmic) heating and electro-osmosis are combined in a hybrid process for removal of both water-soluble contaminants and non-aqueous phase liquids from contaminated, low-permeability soil formations that are saturated. Central to this hybrid process is the partial desaturation of the formation or layer using electro-osmosis to remove a portion of the pore fluids by induction of a ground water flow to extraction wells. Joule heating is then performed on a partially desaturated formation. The joule heating and electro-osmosis operations can be carried out simultaneously or sequentially if the desaturation by electro-osmosis occurs initially. Joule heating of the desaturated formation results in a very effective transfer or partitioning of liquid state contaminants to the vapor phase. The heating also substantially increases the vapor phase pressure in the porous formation. As a result, the contaminant laden vapor phase is forced out into soil layers of a higher permeability where other conventional removal processes, such as steam stripping or ground water extraction can be used to capture the contaminants. This hybrid process is more energy efficient than joule heating or steam stripping for cleaning low permeability formations and can share electrodes to minimize facility costs.

  10. Influence of moderate Joule heating on electroosmotic flow velocity, retention, and efficiency in capillary electrochromatography.

    PubMed

    Chen, Guofang; Tallarek, Ulrich; Seidel-Morgenstern, Andreas; Zhang, Yukui

    2004-07-30

    The influence of Joule heating on electroosmotic flow velocity, the retention factor of neutral analytes, and separation efficiency in capillary electrochromatography was investigated theoretically and experimentally. A plot of electrical current against the applied electrical field strength was used to evaluate the Joule heating effect. When the mobile phase concentration of Tris buffer exceeded 5.0 mM in the studied capillary electrochromatography systems using particulate and monolithic columns (with an accompanying power level of heat dissipation higher than 0.35 W/m), the Joule heating effect became clearly noticeable. Theoretical models for describing the variation of electroosmotic flow velocity with increasing applied field strength and the change of retention factors for neutral analytes with electrical field strength at higher Tris buffer concentrations were analyzed to explain consequences of Joule heating in capillary electrochromatography. Qualitative agreement between experimental data and implications of the theoretical model analysis was observed. The decrease of separation efficiency in capillary electrochromatography with macroporous octadecylsilica particles at high buffer concentration can be also attributed to Joule heating mainly via the increased axial diffusion of the analyte molecules and dispersion of solute bands by a nonuniform electroosmotic flow profile over the column cross-section. However, within a moderate temperature range, the contribution of the macroscopic velocity profile in the column arising from radial temperature gradients is insignificant.

  11. Numerical modeling of the Joule heating effect on electrokinetic flow focusing.

    PubMed

    Huang, Kuan-Da; Yang, Ruey-Jen

    2006-05-01

    In electrokinetically driven microfluidic systems, the driving voltage applied during operation tends to induce a Joule heating effect in the buffer solution. This heat source alters the solution's characteristics and changes both the electrical potential field and the velocity field during the transport process. This study performs a series of numerical simulations to investigate the Joule heating effect and analyzes its influence on the electrokinetic focusing performance. The results indicate that the Joule heating effect causes the diffusion coefficient of the sample to increase, the potential distribution to change, and the flow velocity field to adopt a nonuniform profile. These variations are particularly pronounced under tighter focusing conditions and at higher applied electrical intensities. In numerical investigations, it is found that the focused bandwidth broadens because thermal diffusion effect is enhanced by Joule heating. The variation in the potential distribution induces a nonuniform flow field and causes the focused bandwidth to tighten and broaden alternately as a result of the convex and concave velocity flow profiles, respectively. The present results confirm that the Joule heating effect exerts a considerable influence on the electrokinetic focusing ratio.

  12. Calculating Hemispheric Power and Joule Heating using Defense Meteorological Satellite Program (DMSP) F13 data

    NASA Astrophysics Data System (ADS)

    Khan, M.; Emery, B. A.; Maute, A. I.

    2013-12-01

    Thermosphere Ionosphere Electrodynamics General Circulation Model (TIEGCM) simulates the thermosphere-ionosphere with self consistent electrodynamics. The Weimer 2005 ion convection model can be used with a parameterized model of the aurora based on the electron auroral hemispheric power. The spatial location and radius of the auroral model is adjusted with respect to the Weimer 2005 boundary for zero electric potential, but the resulting Joule heating may be an under or over estimation of the real magnetosphere-ionosphere energy transfer. To improve the auroral model so that the resulting Joule heating is relatively realistic is the ultimate aim of this project. To this end, we achieve a number of sub-goals using data from the DMSP-F13, which is in a dawn-dusk orbit. We use data from the Ion Drift Meter (IDM) to quantify the relative positions of the convection reversal boundary (CRB), the cross-track ion drift (Vy) sunward peaks, and the equatorward boundary of zero velocities (or zero electric potential) and compare them to Weimer 2005 positions for the same orbits. The electric field is estimated only from the cross-track ion velocity Vy in the dawn-dusk orbits, while the along-track ion velocity Vx is ignored. We also calculate auroral Pederson conductance using the auroral electron energy flux and mean electron energy measurements from the DMSP Special Sensor Precipitating Electron and Ion Spectrometer (SSJ/4). The hemispheric power is estimated from the electron energy flux. The Joule heating is approximately the product of the Pedersen conductance and the square of the electric field, where we include Pedersen conductance from EUV and from the aurora to estimate EUV Joule heating and particle Joule heating. Our results for a range of Bz Interplanetary Magnetic Fields (IMF Bz) values show that the hemispheric power is largest in the morning sector where the aurora is widest. The aurora mostly lies in the sunward ion flow region and thus the integrated

  13. Estimation of Joule heating effect on temperature and pressure distribution in electrokinetic-driven microchannel flows.

    PubMed

    Chein, Reiyu; Yang, Yeong Chin; Lin, Yushan

    2006-02-01

    In this study we present simple analytical models that predict the temperature and pressure variations in electrokinetic-driven microchannel flow under the Joule heating effect. For temperature prediction, a simple model shows that the temperature is related to the Joule heating parameter, autothermal Joule heating parameter, external cooling parameter, Peclet number, and the channel length to channel hydraulic diameter ratio. The simple model overpredicted the thermally developed temperature compared with the full numerical simulation, but in good agreement with the experimental measurements. The factors that affect the external cooling parameters, such as the heat transfer coefficient, channel configuration, and channel material are also examined based on this simple model. Based on the mass conservation, a simple model is developed that predicts the pressure variations, including the temperature effect. An adverse pressure gradient is required to satisfy the mass conservation requirement. The temperature effect on the pressure gradient is via the temperature-dependent fluid viscosity and electroosmotic velocity.

  14. Role of Joule heating on the free convection process in a batch electrophoretic cell

    NASA Astrophysics Data System (ADS)

    Bosse Fuenzalida, Maria Angelica

    1998-12-01

    The problem of the effect of Joule heating generation on the hydrodynamic profiles and on solute transport found in electrophoretic devices has been studied in this thesis. The research has been focused on the following two problems: The first one is centered around the effect of the Joule heating on the hydrodynamic velocity profile only, and it is referred to as 'The Carrier Fluid Problem'. The other problem is related to the effect of the Joule heating on the solute transport inside electrophoretic cells, and it has been referred to as 'The Solute Problem'. The two problems identified above are sequentially coupled and, therefore, the carrier fluid problem was investigated first to yield the velocity profiles required in the analysis of the solute transport problem. The carrier fluid problem has been studied for both the Newtonian and the non-Newtonian fluids. To this end, the power-law model was used to study the effect of the rheology of the material in conjunction with the effect of Joule heating generation inside batch electrophoretic devices. The velocity profiles obtained in this study are all analytical results for both cases. This aspect of the research is then effectively used to study the effect of the Joule heating generation on the motion of solutes (such as macromolecules) under the influence of both type of carriers, mainly the Newtonian and the non Newtonian fluids described above. The study was performed by using an area-averaging approach that yielded analytical results for the effective diffusivity of the device.

  15. Joule Heating as a Signature of Magnetosphere-Ionosphere-Thermosphere Coupling

    NASA Astrophysics Data System (ADS)

    Ceren Kalafatoglu Eyiguler, Emine; Kaymaz, Zerefsan

    2016-07-01

    Since its first proposal by Birkeland in the early 1900s, the link between magnetosphere and ionosphere (M-I) has been immensely studied but there are still great variety of unsolved problems ranging from how to correctly balance the field aligned current (FAC) closure in the ionosphere to the resulting interactions between ions and neutrals in the ionosphere, and how the ionospheric conductivity and neutral wind control the M-I feedback to the mapping of the ionospheric regions to the magnetotail. It is now well known that during magnetically disturbed periods, the energy deposited to the magnetosphere by the solar wind is partitioned mainly between three domains: the ring current, ionosphere (via auroral particle precipitation and Joule heating) and the plasmoid release in the magnetotail. It is previously found that large part of this transferred energy is in the form of Joule heating which is the increase in ion-neutral collisions due to the increased energy input. However, Joule heating is also affected by the enhanced neutral wind motion during geomagnetic storms and substorms. Thus, it is one of the key manifestations of the M-I-T coupling. In this talk, we first give a through review of the present studies and recent advancements in the M-I-T research area then show the link between the magnetosphere and ionosphere by investigating the activity-time Joule heating variations as well as paying special attention to the neutral wind effects on Joule heating.

  16. Analytical and numerical study of Joule heating effects on electrokinetically pumped continuous flow PCR chips.

    PubMed

    Gui, Lin; Ren, Carolyn L

    2008-03-18

    Joule heating is an inevitable phenomenon for microfluidic chips involving electrokinetic pumping, and it becomes a more important issue when chips are made of polymeric materials because of their low thermal conductivities. Therefore, it is very important to develop methods for evaluating Joule heating effects in microfluidic chips in a relatively easy manner. To this end, two analytical models have been established and solved using the Green's function for evaluating Joule heating effects on the temperature distribution in a microfluidic-based PCR chip. The first simplified model focuses on the understanding of Joule heating effects by ignoring the influences of the boundary conditions. The second model aims to consider practical experimental conditions. The analytical solutions to the two models are particularly useful in providing guidance for microfluidic chip design and operation prior to expensive chip fabrication and characterization. To validate the analytical solutions, a 3-D numerical model has also been developed and the simultaneous solution to this model allows the temperature distribution in a microfluidic PCR chip to be obtained, which is used to compare with the analytical results. The developed numerical model has been applied for parametric studies of Joule heating effects on the temperature control of microfluidic chips.

  17. Incorporation of the Joule Heating of highly conducting materials into the Truchas code via an asymptotic approach

    SciTech Connect

    Akcay, Cihan; Haut, Terry Scot; Carlson, Neil N.

    2016-05-21

    The EM module of the Truchas code currently lacks the capability to model the Joule (Ohmic) heating of highly conducting materials that are inserted into induction furnaces from time to time to change the heating profile. This effect is difficult to simulate directly because of the requirement to resolve the extremely thin skin depth of good conductors, which is computationally costly. For example, copper has a skin depth, δ ~ 1 mm, for an oscillation frequency of tens of kHz. The industry is interested in determining what fraction of the heating power is lost to the Joule heating of these good conductors inserted inside the furnaces. The approach presented in this document is one of asymptotics where the leading order (unperturbed) solution is taken as that which emerges from solving the EM problem for a perfectly conducting insert. The conductor is treated as a boundary of the domain. The perturbative correction enters as a series expansion in terms of the dimensionless skin depth δ/L, where L is the characteristic size of the EM system. The correction at each order depends on the previous. This means that the leading order correction only depends on the unperturbed solution, in other words, it does not require Truchas to perform an additional EM field solve. Thus, the Joule heating can be captured by a clever leveraging of the existing tools in Truchas with only slight modifications.

  18. Remote joule heating assisted carrier transport in MWCNTs probed at nanosecond time scale.

    PubMed

    Mishra, Abhishek; Shrivastava, Mayank

    2016-10-19

    Quantum model of joule heating relies on electron-phonon scattering in the high field region (hot side contact), which locally increases phonon population and forms hot spots. Hot spots in the high field region are known to suffer carrier transport. In this work, for the first time we report remote joule heating of the cold side contact, i.e. zero electric field region, through multi-walled CNTs (MWCNTs), which is discovered to assist in carrier transport through the MWCNT channels. To precisely capture the dynamics of remote joule heating assisted carrier transport, MWCNTs are probed at nanosecond time scales. This leverages investigations at time scales comparable to characteristic thermal diffusion times and allows electron-phonon interactions and the nature of carrier transport to be probed under non-equilibrium conditions.

  19. Measuring Joule heating and strain induced by electrical current with Moire interferometry

    SciTech Connect

    Chen Bicheng; Basaran, Cemal

    2011-04-01

    This study proposes a new method to locate and measure the temperature of the hot spots caused by Joule Heating by measuring the free thermal expansion in-plane strain. It is demonstrated that the hotspot caused by the Joule heating in a thin metal film/plate structure can be measured by Phase shifting Moire interferometry with continuous wavelet transform (PSMI/CWT) at the microscopic scale. A demonstration on a copper film is conducted to verify the theory under different current densities. A correlation between the current density and strain in two orthogonal directions (one in the direction of the current flow) is proposed. The method can also be used for the measurement of the Joule heating in the microscopic solid structures in the electronic packaging devices. It is shown that a linear relationship exists between current density squared and normal strains.

  20. Manipulation and Joule heat welding of Ag nanowires prepared by atomic migration

    NASA Astrophysics Data System (ADS)

    Tohmyoh, Hironori; Fukui, Satoru

    2012-09-01

    Ag nanowires (NWs) with diameters of about 200 nm and length of 2-7 μm are prepared on a substrate by an atomic migration called stress-induced migration and are picked up from the substrate with electrostatic forces. The Ag NWs are then offered for the welding experiment in a scanning electron microscope and successfully welded together using Joule heating introduced into the NWs by supplying the constant direct current. It is discovered that the welding of Ag NWs is achieved under the current supply in a self-completed manner. The conditions for successful Joule heat welding are analyzed by the parameter that governs the melting phenomenon at the nanocontacts of two NWs. From the experiment and the analysis, electromigration, i.e., another type of atomic migration due to higher electron flow, is found to be occurred during the welding and this is considered to enhance the welding performance of two NWs with Joule heat.

  1. Residual resistance of 2D and 3D structures and Joule heat release.

    PubMed

    Gurevich, V L; Kozub, V I

    2011-06-22

    We consider a residual resistance and Joule heat release in 2D nanostructures as well as in ordinary 3D conductors. We assume that elastic scattering of conduction electrons by lattice defects is predominant. Within a rather intricate situation in such systems we discuss in detail two cases. (1) The elastic scattering alone (i.e. without regard of inelastic mechanisms of scattering) leads to a transition of the mechanical energy (stored by the electrons under the action of an electric field) into heat in a traditional way. This process can be described by the Boltzmann equation where it is possible to do the configuration averaging over defect positions in the electron-impurity collision term. The corresponding conditions are usually met in metals. (2) The elastic scattering can be considered with the help of the standard electron-impurity collision integral only in combination with some additional averaging procedure (possibly including inelastic scattering or some mechanisms of electron wavefunction phase destruction). This situation is typical for degenerate semiconductors with a high concentration of dopants and conduction electrons. Quite often, heat release can be observed via transfer of heat to the lattice, i.e. via inelastic processes of electron-phonon collisions and can take place at distances much larger than the size of the device. However, a direct heating of the electron system can be registered too by, for instance, local measurements of the current noise or direct measurement of an electron distribution function.

  2. Hall and ion slip effects on peristaltic flow of Jeffrey nanofluid with Joule heating

    NASA Astrophysics Data System (ADS)

    Hayat, T.; Shafique, Maryam; Tanveer, A.; Alsaedi, A.

    2016-06-01

    This paper addresses mixed convective peristaltic flow of Jeffrey nanofluid in a channel with complaint walls. The present investigation includes the viscous dissipation, thermal radiation and Joule heating. Hall and ion slip effects are also taken into account. Related problems through long wavelength and low Reynolds number are examined for stream function, temperature and concentration. Impacts of thermal radiation, Hartman number, Brownian motion parameter, thermophoresis, Joule heating, Hall and ion slip parameters are investigated in detail. It is observed that velocity increases and temperature decreases with Hall and ion slip parameters. Further the thermal radiation on temperature has qualitatively similar role to that of Hall and ion slip effects.

  3. Radiative Peristaltic Flow of Jeffrey Nanofluid with Slip Conditions and Joule Heating

    PubMed Central

    Hayat, Tasawar; Shafique, Maryam; Tanveer, Anum; Alsaedi, Ahmed

    2016-01-01

    Mixed convection peristaltic flow of Jeffrey nanofluid in a channel with compliant walls is addressed here. The present investigation includes the viscous dissipation, thermal radiation and Joule heating. Whole analysis is performed for velocity, thermal and concentration slip conditions. Related problems through long wavelength and low Reynolds number are examined for stream function, temperature and concentration. Impacts of thermal radiation, Hartman number, Brownian motion parameter, thermophoresis, Joule heating and slip parameters are explored in detail. Clearly temperature is a decreasing function of Hartman number and radiation parameter. PMID:26886919

  4. Selective domain wall depinning by localized Oersted fields and Joule heating

    NASA Astrophysics Data System (ADS)

    Ilgaz, Dennis; Kläui, Mathias; Heyne, Lutz; Boulle, Olivier; Zinser, Fabian; Krzyk, Stephen; Fonin, Mikhail; Rüdiger, Ulrich; Backes, Dirk; Heyderman, Laura J.

    2008-09-01

    Using low temperature magnetoresistance measurements, the possibility to selectively move a domain wall locally by applying current pulses through a Au nanowire adjacent to a permalloy element is studied. We find that the domain wall depinning field is drastically modified with increasing current density due to the Joule heating and the Oersted field of the current, and controlled motion due to the Oersted field without any externally applied fields is achieved. By placing the domain wall at various distances from the Au wire, we determine the range of the Joule heating and the Oersted field and both effects can be separated.

  5. Joule heating effects and the experimental determination of temperature during CE.

    PubMed

    Evenhuis, Christopher J; Haddad, Paul R

    2009-03-01

    Joule heating is ubiquitous in electrokinetic separations. This review is in two major parts. The first part documents the effects of Joule heating on the physical properties of the electrolyte and efficiency of separations and the second part focuses on advances in the determination of electrolyte temperatures that have been described in the literature over the past 5 years. The focus is on methods that can be applied by practitioners without the need for elaborate experimental requirements. Although the emphasis is on CE, many of the conclusions also apply to microfluidic formats.

  6. Radiative Peristaltic Flow of Jeffrey Nanofluid with Slip Conditions and Joule Heating.

    PubMed

    Hayat, Tasawar; Shafique, Maryam; Tanveer, Anum; Alsaedi, Ahmed

    2016-01-01

    Mixed convection peristaltic flow of Jeffrey nanofluid in a channel with compliant walls is addressed here. The present investigation includes the viscous dissipation, thermal radiation and Joule heating. Whole analysis is performed for velocity, thermal and concentration slip conditions. Related problems through long wavelength and low Reynolds number are examined for stream function, temperature and concentration. Impacts of thermal radiation, Hartman number, Brownian motion parameter, thermophoresis, Joule heating and slip parameters are explored in detail. Clearly temperature is a decreasing function of Hartman number and radiation parameter.

  7. Controlled Formation of Zigzag and Armchair Edges in Graphene Nanoribbons by Joule Heating

    SciTech Connect

    Sumpter, Bobby G; Dresselhaus, M; Terrones Maldonado, Mauricio; Meunier, Vincent; Romo Herrera, Jose M; Jia, Xiaoting; Hofmann, Mario; Campos-Delgado, Jessica; Reina, Alfonso; Kong, Jing; Hsieh, Ya-Ping; Son, Hyungbin

    2009-01-01

    We demonstrate and monitor an efficient edge reconstruction process, at the atomic scale, for graphite nanoribbons by Joule heating inside an integrated transmission electron microscope equipped with a scanning tunneling stage STM (TEM-STM system). During Joule annealing, sharp edges and step-edge arrays are formed, mostly with either zigzag or armchair edge configurations. Their formation is driven by both thermal and electric field related mechanisms. Model calculations show that the dominant annealing mechanisms involve point defect annealing and edge reconstruction. Joule heating is thus shown to provide an effective way to produce clean zigzag and armchair edges, which could be useful for both fundamental studies of edge reactivity, magnetism, and could provide a route for increasing carrier mobility and for the development of future electronics applications.

  8. Seebeck effect influence on joule heat evolution in electrically conductive silicate materials

    NASA Astrophysics Data System (ADS)

    Fiala, Lukáš; Medved, Igor; Maděra, Jiří; Černý, Robert

    2016-07-01

    In general, silicate building materials are non-conductive matters that are not able to evolve heat when they are subjected to an external voltage. However, the electrical conductivity can be increased by addition of electrically conductive admixtures in appropriate amount which leads to generation of conductive paths in materials matrix. Such enhanced materials can evolve Joule heat and are utilizable as a core of self-heating or snow-melting systems. In this paper, Joule heat evolution together with Seebeck effect in electrically conductive silicate materials was taken into consideration and the model based on heat equation with included influence of DC electric field was proposed. Besides, a modeling example of heating element was carried out on FEM basis and time development of temperature in chosen surface points was expressed in order to declare ability of such system to be applicable.

  9. Analytical study of Joule heating effects on electrokinetic transportation in capillary electrophoresis.

    PubMed

    Xuan, Xiangchun; Li, Dongqing

    2005-02-04

    Electric fields are often used to transport fluids (by electroosmosis) and separate charged samples (by electrophoresis) in microfluidic devices. However, there exists inevitable Joule heating when electric currents are passing through electrolyte solutions. Joule heating not only increases the fluid temperature, but also produces temperature gradients in cross-stream and axial directions. These temperature effects make fluid properties non-uniform, and hence alter the applied electric potential field and the flow field. The mass species transport is also influenced. In this paper we develop an analytical model to study Joule heating effects on the transport of heat, electricity, momentum and mass species in capillary-based electrophoresis. Close-form formulae are derived for the temperature, applied electrical potential, velocity, and pressure fields at steady state, and the transient concentration field as well. Also available are the compact formulae for the electric current and the volume flow rate through the capillary. It is shown that, due to the thermal end effect, sharp temperature drops appear close to capillary ends, where sharp rises of electric field are required to meet the current continuity. In order to satisfy the mass continuity, pressure gradients have to be induced along the capillary. The resultant curved fluid velocity profile and the increase of molecular diffusion both contribute to the dispersion of samples. However, Joule heating effects enhance the sample transport velocity, reducing the analysis time in capillary electrophoretic separations.

  10. Effect of Joule heating on isoelectric focusing of proteins in a microchannel

    PubMed Central

    Yoo, Kisoo; Shim, Jaesool; Dutta, Prashanta

    2014-01-01

    Electric field-driven separation and purification techniques, such as isoelectric focusing (IEF) and isotachophoresis, generate heat in the system that can affect the performance of the separation process. In this study, a new mathematical model is presented for IEF that considers the temperature rise due to Joule heating. We used the model to study focusing phenomena and separation performance in a microchannel. A finite volume-based numerical technique is developed to study temperature-dependent IEF. Numerical simulation for narrow range IEF (6 < pH < 10) is performed in a straight microchannel for 100 ampholytes and two model proteins: staphylococcal nuclease and pancreatic ribonuclease. Separation results of the two proteins are obtained with and without considering the temperature rise due to Joule heating in the system for a nominal electric field of 100 V/cm. For the no Joule heating case, constant properties are used, while for the Joule heating case, temperature-dependent titration curves and thermo-physical properties are used. Our numerical results show that the temperature change due to Joule heating has a significant impact on the final focusing points of proteins, which can lower the separation performance considerably. In the absence of advection and any active cooling mechanism, the temperature increase is the highest at the mid-section of a microchannel. We also found that the maximum temperature in the system is a strong function of the ΔpK  value of the carrier ampholytes. Simulation results are also obtained for different values of applied electric fields in order to find the optimum working range considering the simulation time and buffer temperature. Moreover, the model is extended to study IEF in a straight microchip where pH is formed by supplying H+ and OH−, and the thermal analysis shows that the heat generation is negligible in ion supplied IEF. PMID:25553199

  11. Effect of Joule heating on isoelectric focusing of proteins in a microchannel.

    PubMed

    Yoo, Kisoo; Shim, Jaesool; Dutta, Prashanta

    2014-11-01

    Electric field-driven separation and purification techniques, such as isoelectric focusing (IEF) and isotachophoresis, generate heat in the system that can affect the performance of the separation process. In this study, a new mathematical model is presented for IEF that considers the temperature rise due to Joule heating. We used the model to study focusing phenomena and separation performance in a microchannel. A finite volume-based numerical technique is developed to study temperature-dependent IEF. Numerical simulation for narrow range IEF (6 < pH < 10) is performed in a straight microchannel for 100 ampholytes and two model proteins: staphylococcal nuclease and pancreatic ribonuclease. Separation results of the two proteins are obtained with and without considering the temperature rise due to Joule heating in the system for a nominal electric field of 100 V/cm. For the no Joule heating case, constant properties are used, while for the Joule heating case, temperature-dependent titration curves and thermo-physical properties are used. Our numerical results show that the temperature change due to Joule heating has a significant impact on the final focusing points of proteins, which can lower the separation performance considerably. In the absence of advection and any active cooling mechanism, the temperature increase is the highest at the mid-section of a microchannel. We also found that the maximum temperature in the system is a strong function of the [Formula: see text] value of the carrier ampholytes. Simulation results are also obtained for different values of applied electric fields in order to find the optimum working range considering the simulation time and buffer temperature. Moreover, the model is extended to study IEF in a straight microchip where pH is formed by supplying H(+) and OH(-), and the thermal analysis shows that the heat generation is negligible in ion supplied IEF.

  12. Joule-heating power dissipation in a type-II superconductor tube.

    NASA Technical Reports Server (NTRS)

    Urban, E. W.

    1972-01-01

    The theoretical analysis of the Joule-heating power density in a specific hollow cylinder of a NbZr superconductor is presented. It is seen that the power density, which is the primary source of internal heating neglecting localized annihilation heating, can have a very complicated behavior, especially in the circular region. Rough estimates of the relative temperature changes are made, and the locations at which instabilities are more likely to initiate are considered.

  13. Interaction of magnetization and heat dynamics for pulsed domain wall movement with Joule heating

    NASA Astrophysics Data System (ADS)

    Lepadatu, Serban

    2016-10-01

    Pulsed domain wall movement is studied here in Ni80Fe20 nanowires on SiO2, using a fully integrated electrostatic, thermoelectric, and micromagnetics solver based on the Landau-Lifshitz-Bloch equation, including Joule heating, anisotropic magneto-resistance, and Oersted field contributions. During the applied pulse, the anisotropic magneto-resistance of the domain wall generates a dynamic heat gradient, which increases the current-driven velocity by up to 15%. Using a temperature-dependent conductivity, significant differences are found between the constant voltage-pulsed and constant current-pulsed domain wall movement: constant voltage pulses are shown to be more efficient at displacing domain walls whilst minimizing the increase in temperature, with the total domain wall displacement achieved over a fixed pulse duration having a maximum with respect to the driving pulse strength.

  14. Ionospheric Joule heating and Poynting flux in quasi-static approximation

    NASA Astrophysics Data System (ADS)

    VanhamäKi, H.; Yoshikawa, A.; Amm, O.; Fujii, R.

    2012-08-01

    Energy flow is an important aspect of magnetosphere-ionosphere coupling. Electromagnetic energy is transported as Poynting flux from the magnetosphere to the ionosphere, where it is dissipated as Joule heating. Recently Richmond derived an "Equipotential Boundary Poynting Flux (EBPF) theorem", that the Poynting flux within a flux tube whose boundary is an equipotential curve is dissipated inside the ionospheric foot point of the flux tube. In this article we study Richmond's EBPF theorem more closely by considering the curl-free and divergence-free parts as well as the Hall and Pedersen parts of the ionospheric current system separately. Our main findings are that i) divergence-free currents are on average dissipationless, ii) the curl-free Pedersen current is responsible for the whole ionospheric Joule heating and iii) pointwise match between vertical Poynting flux and ionospheric Joule heating is broken by gradients of Hall and Pedersen conductances. Results i) and ii) hold when integrated over the whole ionosphere or any area bounded by an equipotential curve. The present study is limited to quasi-static phenomena. The more general topic of electrodynamic Joule heating and Poynting flux, including inductive effects, will be addressed in a future study.

  15. A JOULE-HEATED MELTER TECHNOLOGY FOR THE TREATMENT AND IMMOBILIZATION OF LOW-ACTIVITY WASTE

    SciTech Connect

    KELLY SE

    2011-04-07

    This report is one of four reports written to provide background information regarding immobilization technologies remaining under consideration for supplemental immobilization of Hanford's low-activity waste. This paper provides the reader a general understanding of joule-heated ceramic lined melters and their application to Hanford's low-activity waste.

  16. Investigation of Neutral Wind Effects on the Global Joule Heating Rate Using MHD and TI Models

    NASA Astrophysics Data System (ADS)

    Kalafatoglu, E.; Kaymaz, Z.

    2013-12-01

    Precise calculation of global Joule heating rate is a long standing question in thermosphere-ionosphere coupling processes. The absence of the complete and direct, in-situ measurements of the parameters involved in the calculation of Joule heating such as the conductivity of the medium, small-scale variations of electric fields, and neutral winds at the ionospheric heights poses a great uncertainty in its determination. In this work, we study the effects of the neutral wind on the global Joule heating rate. Most of the time, owing to above mentioned difficulties the effects of the neutral wind have been neglected in the calculations. We investigate their effects using BATSRUS MHD model, TIEGCM and GITM. Using horizontal current density, Cowling conductivity, and Pedersen conductivities from the MHD model, we calculate the joule heating rate with and without the neutral wind contribution. We apply the procedure for March 2008 magnetospheric substorm events and quantify the differences to show the neutral wind contribution. We compare the results with those obtained using neutral wind velocities from TIEGCM and GITM models. This way while we compare and demonstrate the discrepancies between the models, we also provide an assessment for the integration of thermospheric and magnetospheric models.

  17. Local temperature redistribution and structural transition during joule-heating-driven conductance switching in VO2.

    PubMed

    Kumar, Suhas; Pickett, Matthew D; Strachan, John Paul; Gibson, Gary; Nishi, Yoshio; Williams, R Stanley

    2013-11-13

    Joule-heating induced conductance-switching is studied in VO2 , a Mott insulator. Complementary in situ techniques including optical characterization, blackbody microscopy, scanning transmission X-ray microscopy (STXM) and numerical simulations are used. Abrupt redistribution in local temperature is shown to occur upon conductance-switching along with a structural phase transition, at the same current.

  18. Chatanika radar observations relating to the latitudinal and local time variations of Joule heating

    NASA Technical Reports Server (NTRS)

    Banks, P. M.; Foster, J. C.; Doupnik, J. R.

    1981-01-01

    Observations of plasma convection made with the Chatanika incoherent scatter radar have been analyzed to give latitude/local time plots of the electric field contribution (E squared) to thermospheric Joule heating. The data, which plan the invariant latitude range 56 deg to 75 deg, show the presence of strong heating throughout the auroral regions. Of special interest are brief interludes of intense heating (greater than 50 mW/sq m) that are observed at nearly all local times and latitudes in response to magnetospheric disturbances. Further, there seem to be particular regions of the auroral oval where Joule heating seems to be continually enhanced above the broad background. The results of six 24-hour experiments are presented to illustrate summer and winter conditions. A shorter eight hour experiment is also given to show the characteristics of cleft heating, insofar as they are visible to the Chatanika radar.

  19. Experimental evidence in support of Joule heating associated with geomagnetic activity

    NASA Technical Reports Server (NTRS)

    Devries, L. L.

    1971-01-01

    High resolution accelerometer measurements in the altitude region 140 to 300 km from a satellite in a near-polar orbit during a period of extremely high geomagnetic activity indicate that Joule heating is the primary source of energy for atmospheric heating associated with geomagnetic activity. This conclusion is supported by the following observational evidence: (1) There is an atmospheric response in the auroral zone which is nearly simulataneous with the onset of geomagnetic activity, with no significant response in the equatorial region until several hours later; (2) The maximum heating occurs at geographic locations near the maximum current of the auroral electrojet; and (3) There is evidence of atmospheric waves originating near the auroral zone at altitudes where Joule heating would be expected to occur. An analysis of atmospheric response time to this heat shows time delays are apparently independent of altitude but are strongly dependent upon geomagnetic latitude.

  20. GEM-CEDAR Challenge: Poynting Flux at DMSP and Modeled Joule Heat

    NASA Technical Reports Server (NTRS)

    Rastaetter, Lutz; Shim, Ja Soon; Kuznetsova, Maria M.; Kilcommons, Liam M.; Knipp, Delores J.; Codrescu, Mihail; Fuller-Rowell, Tim; Emery, Barbara; Weimer, Daniel R.; Cosgrove, Russell; Wiltberger, Michael; Raeder, Joachim; Li, Wenhui; Toth, Gabor; Welling, Daniel

    2016-01-01

    Poynting flux into the ionosphere measures the electromagnetic energy coming from the magnetosphere. This energy flux can vary greatly between quiet times and geomagnetic active times. As part of the Geospace Environment Modeling-coupling energetics and dynamics of atmospheric regions modeling challenge, physics-based models of the 3-D ionosphere and ionospheric electrodynamics solvers of magnetosphere models that specify Joule heat and empirical models specifying Poynting flux were run for six geomagnetic storm events of varying intensity. We compared model results with Poynting flux values along the DMSP-15 satellite track computed from ion drift meter and magnetic field observations. Although being a different quantity, Joule heat can in practice be correlated to incoming Poynting flux because the energy is dissipated primarily in high latitudes where Poynting flux is being deposited. Within the physics-based model group, we find mixed results with some models overestimating Joule heat and some models agreeing better with observed Poynting flux rates as integrated over auroral passes. In contrast, empirical models tend to underestimate integrated Poynting flux values. Modeled Joule heat or Poynting flux patterns often resemble the observed Poynting flux patterns on a large scale, but amplitudes can differ by a factor of 2 or larger due to the highly localized nature of observed Poynting flux deposition that is not captured by the models. In addition, the positioning of modeled patterns appear to be randomly shifted against the observed Poynting flux energy input. This study is the first to compare Poynting flux and Joule heat in a large variety of models of the ionosphere.

  1. GEM-CEDAR Challenge: Poynting Flux at DMSP and Modeled Joule Heat

    NASA Technical Reports Server (NTRS)

    Rastaetter, Lutz; Shim, Ja Soon; Kuznetsova, Maria M.; Kilcommons, Liam M.; Knipp, Delores J.; Codrescu, Mihail; Fuller-Rowell, Tim; Emery, Barbara; Weimer, Daniel R.; Cosgrove, Russell; hide

    2016-01-01

    Poynting flux into the ionosphere measures the electromagnetic energy coming from the magnetosphere. This energy flux can vary greatly between quiet times and geomagnetic active times. As part of the Geospace Environment Modeling-coupling energetics and dynamics of atmospheric regions modeling challenge, physics-based models of the 3-D ionosphere and ionospheric electrodynamics solvers of magnetosphere models that specify Joule heat and empirical models specifying Poynting flux were run for six geomagnetic storm events of varying intensity. We compared model results with Poynting flux values along the DMSP-15 satellite track computed from ion drift meter and magnetic field observations. Although being a different quantity, Joule heat can in practice be correlated to incoming Poynting flux because the energy is dissipated primarily in high latitudes where Poynting flux is being deposited. Within the physics-based model group, we find mixed results with some models overestimating Joule heat and some models agreeing better with observed Poynting flux rates as integrated over auroral passes. In contrast, empirical models tend to underestimate integrated Poynting flux values. Modeled Joule heat or Poynting flux patterns often resemble the observed Poynting flux patterns on a large scale, but amplitudes can differ by a factor of 2 or larger due to the highly localized nature of observed Poynting flux deposition that is not captured by the models. In addition, the positioning of modeled patterns appear to be randomly shifted against the observed Poynting flux energy input. This study is the first to compare Poynting flux and Joule heat in a large variety of models of the ionosphere.

  2. Joule heating hot spot at high latitudes in the afternoon sector

    NASA Astrophysics Data System (ADS)

    Cai, L.; Aikio, A. T.; Milan, S. E.

    2016-07-01

    The afternoon Joule heating hot spot has been studied statistically by using the EISCAT Svalbard Radar (ESR) measurements at 75.4° Corrected Geomagnetic latitude (CGMLAT) and the OMNI solar wind data base. For a small subset of events, the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) field-aligned current distributions have been available. The main results are as follows. Afternoon Joule heating hot spots are associated with high values of ionospheric electric fields and slightly enhanced Pedersen conductances. The Joule heating hot spot values are larger in summer than in winter, which can be explained by the higher Pedersen conductances during summer than winter. The afternoon Joule heating hot spots are located close to the reversals of the large-scale field-aligned current systems. The most common location is close to the Region 1/Region 2 boundary and those events are associated with sunward convecting F region plasma. In a few cases, the hot spots take place close to the Region 1/Region 0 boundary and then the ionospheric plasma is convecting antisunward. The hot spots may occur both during slow (<450 km/s) and high (>450 km/s) speed solar wind conditions. During slow-speed solar wind events, the dominant interplanetary magnetic field (IMF) direction is southward, which is the general requirement for the low-latitude magnetic merging at the dayside magnetopause. During high-speed solar wind, also northward IMF conditions appear, but those are associated with large values of the IMF |By| component, making again the dayside magnetopause merging possible. Finally, the measured afternoon hot spot Joule heating rates are not a linear function of the solar wind energy coupling function.

  3. GEM-CEDAR challenge: Poynting flux at DMSP and modeled Joule heat

    NASA Astrophysics Data System (ADS)

    Rastätter, Lutz; Shim, Ja Soon; Kuznetsova, Maria M.; Kilcommons, Liam M.; Knipp, Delores J.; Codrescu, Mihail; Fuller-Rowell, Tim; Emery, Barbara; Weimer, Daniel R.; Cosgrove, Russell; Wiltberger, Michael; Raeder, Joachim; Li, Wenhui; Tóth, Gábor; Welling, Daniel

    2016-02-01

    Poynting flux into the ionosphere measures the electromagnetic energy coming from the magnetosphere. This energy flux can vary greatly between quiet times and geomagnetic active times. As part of the Geospace Environment Modeling-coupling energetics and dynamics of atmospheric regions modeling challenge, physics-based models of the 3-D ionosphere and ionospheric electrodynamics solvers of magnetosphere models that specify Joule heat and empirical models specifying Poynting flux were run for six geomagnetic storm events of varying intensity. We compared model results with Poynting flux values along the DMSP-15 satellite track computed from ion drift meter and magnetic field observations. Although being a different quantity, Joule heat can in practice be correlated to incoming Poynting flux because the energy is dissipated primarily in high latitudes where Poynting flux is being deposited. Within the physics-based model group, we find mixed results with some models overestimating Joule heat and some models agreeing better with observed Poynting flux rates as integrated over auroral passes. In contrast, empirical models tend to underestimate integrated Poynting flux values. Modeled Joule heat or Poynting flux patterns often resemble the observed Poynting flux patterns on a large scale, but amplitudes can differ by a factor of 2 or larger due to the highly localized nature of observed Poynting flux deposition that is not captured by the models. In addition, the positioning of modeled patterns appear to be randomly shifted against the observed Poynting flux energy input. This study is the first to compare Poynting flux and Joule heat in a large variety of models of the ionosphere.

  4. Joule heat generation in thermionic cathodes of high-pressure arc discharges

    SciTech Connect

    Benilov, M. S.; Cunha, M. D.

    2013-02-14

    The nonlinear surface heating model of plasma-cathode interaction in high-pressure arcs is extended to take into account the Joule effect inside the cathode body. Calculation results are given for different modes of current transfer to tungsten cathodes of different configurations in argon plasmas of atmospheric or higher pressures. Special attention is paid to analysis of energy balances of the cathode and the near-cathode plasma layer. In all the cases, the variation of potential inside the cathode is much smaller than the near-cathode voltage drop. However, this variation can be comparable to the volt equivalent of the energy flux from the plasma to the cathode and then the Joule effect is essential. Such is the case of the diffuse and mixed modes on rod cathodes at high currents, where the Joule heating causes a dramatic change of thermal and electrical regimes of the cathode. The Joule heating has virtually no effect over characteristics of spots on rod and infinite planar cathodes.

  5. Rotating ferro-nanofluid over stretching plate under the effect of hall current and joule heating

    NASA Astrophysics Data System (ADS)

    Abdel-Wahed, Mohamed S.

    2017-05-01

    The behavior of boundary layer over a stretching plate filled with ferromagnetic Fe3O4 nanoparticles and subjected to magnetic field with hall current, joule heating and nonlinear thermal radiation has been investigated. The modeling based on nonlinear partial differential equations due to continuity, momentum and heat equations, these equations transformed to a system of nonlinear ordinary differential equations using similarity transformation technique then solved numerically. The effect of hall current, joule heating and thermal radiation on the physical quantities such as surface shear stress and heat flux have been investigated and discussed. Moreover, the velocities and temperature profiles of the boundary layer under the influence of the presented external forces plotted and discussed.

  6. Micro-scale heat-exchangers for Joule-Thomson cooling.

    SciTech Connect

    Gross, Andrew John

    2014-01-01

    This project focused on developing a micro-scale counter flow heat exchangers for Joule-Thomson cooling with the potential for both chip and wafer scale integration. This project is differentiated from previous work by focusing on planar, thin film micromachining instead of bulk materials. A process will be developed for fabricating all the devices mentioned above, allowing for highly integrated micro heat exchangers. The use of thin film dielectrics provides thermal isolation, increasing efficiency of the coolers compared to designs based on bulk materials, and it will allow for wafer-scale fabrication and integration. The process is intended to implement a CFHX as part of a Joule-Thomson cooling system for applications with heat loads less than 1mW. This report presents simulation results and investigation of a fabrication process for such devices.

  7. Low-power concentration and separation using temperature gradient focusing via Joule heating.

    PubMed

    Kim, Sun Min; Sommer, Greg J; Burns, Mark A; Hasselbrink, Ernest F

    2006-12-01

    We present an experimental study of temperature gradient focusing (TGF) exploiting an inherent Joule heating phenomenon. A simple variable-width PDMS device delivers rapid and repeatable focusing of model analytes using significantly lower power than conventional TGF techniques. High electric potential applied to the device induces a temperature gradient within the microchannel due to the channel's variable width, and the temperature-dependent mobility of the analytes causes focusing at a specific location. The PDMS device also shows simultaneous separation and concentration capability of a mixture of two sample analytes in less than 10 min. An experiment combining Joule heating with external heating/cooling further supports the hypothesis that temperature is indeed the dominant factor in achieving focusing with this technique.

  8. Joule heating and determination of temperature in capillary electrophoresis and capillary electrochromatography columns.

    PubMed

    Rathore, Anurag S

    2004-05-28

    This article reviews the progress that has taken place in the past decade on the topic of estimation of Joule heating and temperature inside an open or packed capillary in electro-driven separation techniques of capillary electrophoresis (CE) and capillary electrochromatography (CEC), respectively. Developments in theoretical modeling of the heat transfer in the capillary systems have focused on attempts to apply the existing models on newer techniques such as CEC and chip-based CE. However, the advent of novel analytical tools such as pulsed magnetic field gradient nuclear magnetic resonance (NMR), NMR thermometry, and Raman spectroscopy, have led to a revolution in the area of experimental estimation of Joule heating and temperature inside the capillary via the various noninvasive techniques. This review attempts to capture the major findings that have been reported in the past decade.

  9. Breakdown of Richardson's Law in Electron Emission from Individual Self-Joule-Heated Carbon Nanotubes

    PubMed Central

    Wei, Xianlong; Wang, Sheng; Chen, Qing; Peng, Lianmao

    2014-01-01

    Probing the validity of classical macroscopic physical laws at the nanoscale is important for nanoscience research. Herein, we report on experimental evidence that electron emission from individual hot carbon nanotubes (CNTs) heated by self-Joule-heating does not obey Richardson's law of thermionic emission. By using an in-situ multi-probe measurement technique, electron emission density (J) and temperature (T) of individual self-Joule-heated CNTs are simultaneously determined. Experimental ln(J/T2) − 1/T plots are found to exhibit an upward bending feature deviating from the straight lines in Richardson plots, and the measured electron emission density is more than one order of magnitude higher than that predicted by Richardson's law. The breakdown of Richardson's law implies a much better electron emission performance of individual CNTs as compared to their macroscopic allotropes and clusters, and the need of new theoretical descriptions of electron emission from individual low-dimensional nanostructures. PMID:24869719

  10. The effect of DC Joule-heating on magnetic structure of conventional amorphous wires

    NASA Astrophysics Data System (ADS)

    Aştefănoaei, Iordana; Stancu, Alexandru; Chiriac, Horia

    2007-09-01

    In this paper, we determined the effect of DC Joule-heating on magnetic structure of conventional amorphous wires starting from the stresses that appear during preparation process. For a specified value of applied electrical DC current to some amorphous wires, we have analyzed the thermal stresses that appear during the thermal treatment and we calculated the radius of axial magnetic domain (cylindrical inner core) that results after the preparation and annealing processes. We have obtained that: (a) the total stresses (owing to the successive heating, crystallization and cooling) depend strongly on the applied electrical DC current and the radius of the wires; (b) the axial magnetic domain is bigger for the wire having a bigger radius; (c) the cylindrical inner core enlarges significantly after DC Joule-heating; and (d) smaller internal stresses are obtained at smaller values of the wire's radius.

  11. Implantable polymer/metal thin film structures for the localized treatment of cancer by Joule heating

    NASA Astrophysics Data System (ADS)

    Kan-Dapaah, Kwabena; Rahbar, Nima; Theriault, Christian; Soboyejo, Wole

    2015-04-01

    This paper presents an implantable polymer/metal alloy thin film structure for localized post-operative treatment of breast cancer. A combination of experiments and models is used to study the temperature changes due to Joule heating by patterned metallic thin films embedded in poly-dimethylsiloxane. The heat conduction within the device and the surrounding normal/cancerous breast tissue is modeled with three-dimensional finite element method (FEM). The FEM simulations are used to explore the potential effects of device geometry and Joule heating on the temperature distribution and lesion (thermal dose). The FEM model is validated using a gel model that mimics biological media. The predictions are also compared to prior results from in vitro studies and relevant in vivo studies in the literature. The implications of the results are discussed for the potential application of polymer/metal thin film structures in hyperthermic treatment of cancer.

  12. Breakdown of Richardson's law in electron emission from individual self-Joule-heated carbon nanotubes.

    PubMed

    Wei, Xianlong; Wang, Sheng; Chen, Qing; Peng, Lianmao

    2014-05-29

    Probing the validity of classical macroscopic physical laws at the nanoscale is important for nanoscience research. Herein, we report on experimental evidence that electron emission from individual hot carbon nanotubes (CNTs) heated by self-Joule-heating does not obey Richardson's law of thermionic emission. By using an in-situ multi-probe measurement technique, electron emission density (J) and temperature (T) of individual self-Joule-heated CNTs are simultaneously determined. Experimental ln(J/T(2)) - 1/T plots are found to exhibit an upward bending feature deviating from the straight lines in Richardson plots, and the measured electron emission density is more than one order of magnitude higher than that predicted by Richardson's law. The breakdown of Richardson's law implies a much better electron emission performance of individual CNTs as compared to their macroscopic allotropes and clusters, and the need of new theoretical descriptions of electron emission from individual low-dimensional nanostructures.

  13. Modeling Joule Heating Effect on Lunar O2 Generation via Electrolytic Reduction.

    NASA Technical Reports Server (NTRS)

    Dominquez, Jesus; Poizeau, Sophie; Sibille, Laurent

    2009-01-01

    Kennedy Space Center is leading research work on lunar O2 generation via electrolytic reduction of regolith; the metal oxide present in the regolith is dissociated in oxygen anions and metal cations leading to the generation of gaseous oxygen at the anode and liquid metal at the cathode. Electrical resistance of molten regolith is high, leading to heating of the melt when electrical current is applied between the electrodes (Joule heating). The authors have developed a 3D model using a rigorous approach for two coupled physics (thermal and electrical potential) to not only study the effect of Joule heating on temperature distribution throughout the molten regolith but also to evaluate and optimize the design of the electrolytic cells. This paper presents the results of the thermal analysis performed on the model and used to validate the design of the electrolytic cell.

  14. Passivation of organic light emitting diode anode grid lines by pulsed Joule heating

    NASA Astrophysics Data System (ADS)

    Janka, M.; Gierth, R.; Rubingh, J.-E.; Abendroth, M.; Eggert, M.; Moet, D. J. D.; Lupo, D.

    2015-09-01

    We report the self-aligned passivation of a current distribution grid for an organic light emitting diode (OLED) anode using a pulsed Joule heating method to align the passivation layer accurately on the metal grid. This method involves passing an electric current through the grid to cure a polymer dielectric. Uncured polymer is then rinsed away, leaving a patterned dielectric layer that conforms to the shape of the grid lines. To enhance the accuracy of the alignment, heat conduction into the substrate and the transparent electrode is limited by using short current pulses instead of a constant current. Excellent alignment accuracy of the dielectric layer on printed metal grid lines has been achieved, with a typical 4-μm dielectric overhang. In addition to good accuracy, pulsed Joule heating significantly cuts down process time and energy consumption compared to heating with a constant current. The feasibility of using a printed current distribution grid and Joule heating was demonstrated in an OLED device.

  15. Jupiter Thermospheric General Circulation Model (JTGCM): Global Structure and Dynamics Driven by Auroral and Joule Heating

    NASA Technical Reports Server (NTRS)

    Bougher, S. W.; J. Il. Waite, Jr.; Majeed, T.

    2005-01-01

    A growing multispectral database plus recent Galileo descent measurements are being used to construct a self-consistent picture of the Jupiter thermosphere/ionosphere system. The proper characterization of Jupiter s upper atmosphere, embedded ionosphere, and auroral features requires the examination of underlying processes, including the feedbacks of energetics, neutral-ion dynamics, composition, and magnetospheric coupling. A fully 3-D Jupiter Thermospheric General Circulation Model (JTGCM) has been developed and exercised to address global temperatures, three-component neutral winds, and neutral-ion species distributions. The domain of this JTGCM extends from 20-microbar (capturing hydrocarbon cooling) to 1.0 x 10(exp -4) nbar (including aurora/Joule heating processes). The resulting JTGCM has been fully spun-up and integrated for greater than or equal to40 Jupiter rotations. Results from three JTGCM cases incorporating moderate auroral heating, ion drag, and moderate to strong Joule heating processes are presented. The neutral horizontal winds at ionospheric heights vary from 0.5 km/s to 1.2 km/s, atomic hydrogen is transported equatorward, and auroral exospheric temperatures range from approx.1200-1300 K to above 3000 K, depending on the magnitude of Joule heating. The equatorial temperature profiles from the JTGCM are compared with the measured temperature structure from the Galileo AS1 data set. The best fit to the Galileo data implies that the major energy source for maintaining the equatorial temperatures is due to dynamical heating induced by the low-latitude convergence of the high-latitude-driven thermospheric circulation. Overall, the Jupiter thermosphere/ionosphere system is highly variable and is shown to be strongly dependent on magnetospheric coupling which regulates Joule heating.

  16. Jupiter Thermospheric General Circulation Model (JTGCM): Global Structure and Dynamics Driven by Auroral and Joule Heating

    NASA Technical Reports Server (NTRS)

    Bougher, S. W.; J. Il. Waite, Jr.; Majeed, T.

    2005-01-01

    A growing multispectral database plus recent Galileo descent measurements are being used to construct a self-consistent picture of the Jupiter thermosphere/ionosphere system. The proper characterization of Jupiter s upper atmosphere, embedded ionosphere, and auroral features requires the examination of underlying processes, including the feedbacks of energetics, neutral-ion dynamics, composition, and magnetospheric coupling. A fully 3-D Jupiter Thermospheric General Circulation Model (JTGCM) has been developed and exercised to address global temperatures, three-component neutral winds, and neutral-ion species distributions. The domain of this JTGCM extends from 20-microbar (capturing hydrocarbon cooling) to 1.0 x 10(exp -4) nbar (including aurora/Joule heating processes). The resulting JTGCM has been fully spun-up and integrated for greater than or equal to40 Jupiter rotations. Results from three JTGCM cases incorporating moderate auroral heating, ion drag, and moderate to strong Joule heating processes are presented. The neutral horizontal winds at ionospheric heights vary from 0.5 km/s to 1.2 km/s, atomic hydrogen is transported equatorward, and auroral exospheric temperatures range from approx.1200-1300 K to above 3000 K, depending on the magnitude of Joule heating. The equatorial temperature profiles from the JTGCM are compared with the measured temperature structure from the Galileo AS1 data set. The best fit to the Galileo data implies that the major energy source for maintaining the equatorial temperatures is due to dynamical heating induced by the low-latitude convergence of the high-latitude-driven thermospheric circulation. Overall, the Jupiter thermosphere/ionosphere system is highly variable and is shown to be strongly dependent on magnetospheric coupling which regulates Joule heating.

  17. Simulations of joule effect heating in a bulge test

    NASA Astrophysics Data System (ADS)

    Demazel, Nathan; Laurent, Hervé; Carin, Muriel; Coër, Jérémy; Le Masson, Philippe; Favero, Jérôme; Canivenc, Romain; Graveleau, Stéphane

    2016-10-01

    This work focuses on the integration of an electrical conduction heating of circular blank in a bulge test device. This device will be used to characterize the thermomechanical behaviour of Usibor®1500 under biaxial deformation at very high temperature (to 930°C). First a thermoelectric model using COMSOL Multiphysics® was developed to study the heating of a rectangular blank. This model is validated by comparing the calculated temperatures with thermocouples measurements. Secondly electrical field optimization is approached to obtain a fast and uniform heating of a circular blank.

  18. Influence of Joule heating on current-induced domain wall depinning

    SciTech Connect

    Moretti, Simone Raposo, Victor; Martinez, Eduardo

    2016-06-07

    The domain wall depinning from a notch in a Permalloy nanostrip on top of a SiO{sub 2}/Si substrate is studied theoretically under application of static magnetic fields and the injection of short current pulses. The influence of Joule heating on current-induced domain wall depinning is explored self-consistently by coupling the magnetization dynamics in the ferromagnetic strip to the heat transport throughout the system. Our results indicate that Joule heating plays a remarkable role in these processes, resulting in a reduction in the critical depinning field and/or in a temporary destruction of the ferromagnetic order for typically injected current pulses. In agreement with experimental observations, similar pinning-depinning phase diagrams can be deduced for both current polarities when the Joule heating is taken into account. These observations, which are incompatible with the sole contribution of spin transfer torques, provide a deeper understanding of the physics underlying these processes and establish the real scope of the spin transfer torque. They are also relevant for technological applications based on current-induced domain-wall motion along soft strips.

  19. Joule heating in the mesosphere and thermosphere during the July 13, 1982, solar proton event

    NASA Technical Reports Server (NTRS)

    Roble, R. G.; Emery, B. A.; Garcia, R. R.; Killeen, T. L.; Hays, P. B.; Reid, G. C.; Solomon, S.; Evans, D. S.; Spencer, N. W.; Brace, L. H.

    1987-01-01

    The solar proton event of July 13, 1982 produced considerable ionization in the polar-cap mesosphere. Energetic solar proton fluxes were measured by the NOAA-6 satellite. The DE-2 satellite measured the low-energy electrons, the ion drift velocity, and other atmospheric and ionospheric properties during the event in the region of the measured maximum electric field (189 mV/m at 2215 UT near 60 deg N), a Joule heating rate of 1-3 K/day is calculated between 70 and 80 km, exceeding the heating due to ozone absorption at noon in the summer hemisphere in that altitude range. The Joule heating rate above 90 km greatly exceeded 20 K/day. The calculated height-integrated Joule heating rate above 100 km in the same region exceeded 400 ergs/sq cm sec, and DE-2 near 350 km measured neutral winds of nearly 1000 m/s and neutral gas temperatures of over 2000 K. The overall ionospheric structure calculated below the DE-2 satellite is described.

  20. Joule heating in the mesosphere and thermosphere during the July 13, 1982, solar proton event

    NASA Technical Reports Server (NTRS)

    Roble, R. G.; Emery, B. A.; Garcia, R. R.; Killeen, T. L.; Hays, P. B.; Reid, G. C.; Solomon, S.; Evans, D. S.; Spencer, N. W.; Brace, L. H.

    1987-01-01

    The solar proton event of July 13, 1982 produced considerable ionization in the polar-cap mesosphere. Energetic solar proton fluxes were measured by the NOAA-6 satellite. The DE-2 satellite measured the low-energy electrons, the ion drift velocity, and other atmospheric and ionospheric properties during the event in the region of the measured maximum electric field (189 mV/m at 2215 UT near 60 deg N), a Joule heating rate of 1-3 K/day is calculated between 70 and 80 km, exceeding the heating due to ozone absorption at noon in the summer hemisphere in that altitude range. The Joule heating rate above 90 km greatly exceeded 20 K/day. The calculated height-integrated Joule heating rate above 100 km in the same region exceeded 400 ergs/sq cm sec, and DE-2 near 350 km measured neutral winds of nearly 1000 m/s and neutral gas temperatures of over 2000 K. The overall ionospheric structure calculated below the DE-2 satellite is described.

  1. Incorporating Cold Cap Behavior in a Joule-heated Waste Glass Melter Model

    SciTech Connect

    Varija Agarwal; Donna Post Guillen

    2013-08-01

    In this paper, an overview of Joule-heated waste glass melters used in the vitrification of high level waste (HLW) is presented, with a focus on the cold cap region. This region, in which feed-to-glass conversion reactions occur, is critical in determining the melting properties of any given glass melter. An existing 1D computer model of the cold cap, implemented in MATLAB, is described in detail. This model is a standalone model that calculates cold cap properties based on boundary conditions at the top and bottom of the cold cap. Efforts to couple this cold cap model with a 3D STAR-CCM+ model of a Joule-heated melter are then described. The coupling is being implemented in ModelCenter, a software integration tool. The ultimate goal of this model is to guide the specification of melter parameters that optimize glass quality and production rate.

  2. Initial Determinations of Ionospheric Electric Fields and Joule Heating from MAVEN Observations

    NASA Astrophysics Data System (ADS)

    Fillingim, M. O.; Fogle, A. L.; Aleryani, O.; Dunn, P.; Lillis, R. J.; McFadden, J. P.; Connerney, J. E. P.; Mahaffy, P. R.; Andersson, L.; Ergun, R.

    2015-12-01

    MAVEN provides in-situ measurements of the neutral and ion species as well as the magnetic field throughout the ionosphere of Mars. By combining these measurements, we are able to calculate both the ionospheric currents and the ionospheric conductivity. It is then straightforward to determine the electric field in the collisional ionosphere from a simplified Ohm's law. In addition, we can also estimate the amount of Joule heating in the ionosphere from j · E. Here, we show initial determinations of both ionospheric electric fields and Joule heating using MAVEN data. The electric fields are highly variable from orbit-to-orbit suggesting that the ionospheric electrodynamics can change on timescales of several hours. These changes may be driven by changes in the upstream solar wind and IMF or may result from dynamical variations of thermospheric neutral winds.

  3. Joule heating effects on particle immobilization in insulator-based dielectrophoretic devices

    PubMed Central

    Gallo-Villanueva, Roberto C.; Sano, Michael B.; Lapizco-Encinas, Blanca H.; Davalos, Rafael V.

    2014-01-01

    In this work, the temperature effects due to Joule heating obtained by application of a DC electric potential were investigated for a microchannel with cylindrical insulating posts employed for insulator based dielectrophoresis (iDEP). The conductivity of the suspending medium, the local electric field, and the gradient of the squared electric field, which directly affect the magnitude of the dielectrophoretic force exerted on particles, were computationally simulated employing COMSOL Multiphysics. It was observed that a temperature gradient is formed along the microchannel which redistributes the conductivity of the suspending medium leading to an increase of the dielectrophoretic force towards the inlet of the channel while decreasing towards the outlet. Experimental results are in good agreement with simulations on the particle trapping zones anticipated. This study demonstrates the importance of considering Joule heating effects when designing iDEP systems. PMID:24002905

  4. Residual resistance and Joule heat generation in bulk samples and nanostructures

    SciTech Connect

    Gurevich, V. L.

    2008-08-15

    The Joule heat generation under residual resistance conditions in bulk samples of metals and degenerate semiconductors is discussed. We assume that the conductance of the system is determined by elastic scattering of conduction electrons and consider the Ohmic regime. We come to conclusion that the amount of Joule heat generated in such a system is determined by the residual resistance provided that the length of phase coherence of the electron wave functions is smaller than the dimensions of the sample. For a quantum well, this condition is imposed on its lateral dimensions and does not concern its width. It is indicated that this is only a suf-ficient condition that can be relaxed by further investigations.

  5. Joule heating effects on particle immobilization in insulator-based dielectrophoretic devices.

    PubMed

    Gallo-Villanueva, Roberto C; Sano, Michael B; Lapizco-Encinas, Blanca H; Davalos, Rafael V

    2014-02-01

    In this work, the temperature effects due to Joule heating obtained by application of a direct current electric potential were investigated for a microchannel with cylindrical insulating posts employed for insulator-based dielectrophoresis. The conductivity of the suspending medium, the local electric field, and the gradient of the squared electric field, which directly affect the magnitude of the dielectrophoretic force exerted on particles, were computationally simulated employing COMSOL Multiphysics. It was observed that a temperature gradient is formed along the microchannel, which redistributes the conductivity of the suspending medium leading to an increase of the dielectrophoretic force toward the inlet of the channel while decreasing toward the outlet. Experimental results are in good agreement with simulations on the particle-trapping zones anticipated. This study demonstrates the importance of considering Joule heating effects when designing insulator-based dielectrophoresis systems.

  6. Energetics and the resistive tearing mode - Effects of Joule heating and radiation

    NASA Technical Reports Server (NTRS)

    Steinolfson, R. S.

    1983-01-01

    The contribution of energy flux to the dynamics of magnetic field reconnection is analytically studied in order to determine the influence of Joule heating and radiation on the linear development of the tearing instability in slab geometry. A temperature-dependent Coulomb-like resistivity is used to provide the coupling between the dynamics and the energy equation. Analytical expressions are derived for the growth rates utilizing constant-psi and long-wavelength approximations. The solutions indicate the occurrence of several modes in addition to the usual tearing mode, several of which have relatively slow, complex growth rates. At large values of the magnetic Reynolds number, there are at least two modes with purely exponential growth when the radiative loss decreases with increasing temperature. If the radiation is neglected, the Joule heating alone also results in two modes with real, positive growth at large S. Below a particular value of S, all the modes are generally stabilized.

  7. Direct imaging of Joule heating dynamics and temperature profiling inside a carbon nanotube interconnect.

    PubMed

    Costa, Pedro M F J; Gautam, Ujjal K; Bando, Yoshio; Golberg, Dmitri

    2011-08-09

    Understanding resistive (or Joule) heating in fundamental nanoelectronic blocks, such as carbon nanotubes, remains a major challenge, particularly in regard to their structural and thermal variations during prolonged periods of electrical stress. Here we show real-time imaging of the associated effects of Joule heating in the channel of carbon nanotube interconnects. First, electrical contacts to nanotubes entirely filled with a sublimable material are made inside a transmission electron microscope. On exposure to a high current density, resistive hotspots are identified on (or near) the contact points. These later migrate and expand along the carbon nanotube, as indicated by the localized sublimation of the encapsulated material. Using the hotspot edges as markers, it is possible to estimate the internal temperature profiles of the nanotube. Simple and direct, our method provides remarkable spatial and temporal insights into the dynamics of resistive hotspots and millisecond-paced thermal variations occurring inside nanoscaled tubular interconnects.

  8. Super-Joule heating in graphene and silver nanowire network

    SciTech Connect

    Maize, Kerry; Das, Suprem R.; Sadeque, Sajia; Mohammed, Amr M. S.; Shakouri, Ali E-mail: alam@purdue.edu; Janes, David B.; Alam, Muhammad A. E-mail: alam@purdue.edu

    2015-04-06

    Transistors, sensors, and transparent conductors based on randomly assembled nanowire networks rely on multi-component percolation for unique and distinctive applications in flexible electronics, biochemical sensing, and solar cells. While conduction models for 1-D and 1-D/2-D networks have been developed, typically assuming linear electronic transport and self-heating, the model has not been validated by direct high-resolution characterization of coupled electronic pathways and thermal response. In this letter, we show the occurrence of nonlinear “super-Joule” self-heating at the transport bottlenecks in networks of silver nanowires and silver nanowire/single layer graphene hybrid using high resolution thermoreflectance (TR) imaging. TR images at the microscopic self-heating hotspots within nanowire network and nanowire/graphene hybrid network devices with submicron spatial resolution are used to infer electrical current pathways. The results encourage a fundamental reevaluation of transport models for network-based percolating conductors.

  9. Restrictions on linear heat capacities from Joule-Brayton maximum-work cycle efficiency

    NASA Astrophysics Data System (ADS)

    Angulo-Brown, F.; Gonzalez-Ayala, Julian; Arias-Hernandez, L. A.

    2014-02-01

    This paper discusses the possibility of using the Joule-Brayton cycle to determine the accessible value range for the coefficients a and b of the heat capacity at constant pressure Cp, expressed as Cp=a+bT (with T the absolute temperature) by using the Carnot theorem. This is made for several gases which operate as the working fluids. Moreover, the landmark role of the Curzon-Ahlborn efficiency for this type of cycle is established.

  10. Solar Wind Effect on Joule Heating in the High-Latitude Ionosphere

    NASA Astrophysics Data System (ADS)

    Cai, L.; Aikio, A. T.; Nygren, T. J.

    2014-12-01

    The interplanetary magnetic field (IMF) carried by solar wind affects strongly several key parameters in the high-latitude ionosphere. In this study, the solar wind effect on those parameters especially on Joule heating is conducted statistically based on the simultaneous measurements by the EISCAT radars in Tromsø (TRO, 66.6° cgmLat, mainly within the auroral oval on the nightside), and on Svalbard (ESR, 75.4º cgmLat, mostly within the polar cap). The most important findings are as follows: (i) At TRO, the decrease in Joule heating in the afternoon-evening sector due to neutral winds reported by Aikio et al. [2012] requires southward IMF conditions and a sufficiently high solar wind electric field. The increase in the morning sector takes place for all IMF directions within a region where the upper-E neutral wind has a large equatorward component and the F-region plasma flow is directed eastward. (ii) At ESR, an afternoon hot spot of joule heating centred typically at 14-15 MLT is observed during all IMF conditions. Enhanced Pedersen conductances within the hot spot region are observed only for the IMF Bz+/By- conditions, and the corresponding convection electric field values within the hot spot are smaller than during the other IMF conditions. Hence, the hot spot represents a region of persistent magnetopsheric electromagnetic energy input. (iii) For the southward IMF conditions, the MLT-integrated Joule heating rate without neutral winds for By- is twice the value for By+ at TRO. This can plausibly be explained by the higher average solar wind electric field values for By-.

  11. In situ transmission electron microscopy of individual carbon nanotetrahedron/nanoribbon structures in Joule heating

    SciTech Connect

    Masuda, Yusuke; Yoshida, Hideto; Takeda, Seiji; Kohno, Hideo

    2014-08-25

    Collapse of a carbon nanotube results in the formation of a nanoribbon, and a switching of the collapse direction yields a nanotetrahedron in the middle of a nanoribbon. Here, we report in-situ transmission electron microscopy observations of the behavior of carbon nanotetrahedron/nanoribbon structures during Joule heating to reveal their thermal stability. In addition, we propose that the observed process is related to the formation process of the structure.

  12. Restrictions on linear heat capacities from Joule-Brayton maximum-work cycle efficiency.

    PubMed

    Angulo-Brown, F; Gonzalez-Ayala, Julian; Arias-Hernandez, L A

    2014-02-01

    This paper discusses the possibility of using the Joule-Brayton cycle to determine the accessible value range for the coefficients a and b of the heat capacity at constant pressure C(p), expressed as C(p) = a + bT (with T the absolute temperature) by using the Carnot theorem. This is made for several gases which operate as the working fluids. Moreover, the landmark role of the Curzon-Ahlborn efficiency for this type of cycle is established.

  13. Programmable mechanical resonances in MEMS by localized joule heating of phase change materials.

    PubMed

    Manca, Nicola; Pellegrino, Luca; Kanki, Teruo; Yamasaki, Syouta; Tanaka, Hidekazu; Siri, Antonio Sergio; Marré, Daniele

    2013-11-26

    A programmable micromechanical resonator based on a VO2 thin film is reported. Multiple mechanical eigenfrequency states are programmed using Joule heating as local power source, gradually driving the phase transition of VO2 around its Metal-Insulator transition temperature. Phase coexistence of domains is used to tune the stiffness of the device via local control of internal stresses and mechanical properties. This study opens perspectives for developing mechanically configurable nanostructure arrays.

  14. Literature review of arc/plasma, combustion, and joule-heated melter vitrification systems

    SciTech Connect

    Freeman, C.J.; Abrigo, G.P.; Shafer, P.J.; Merrill, R.A.

    1995-07-01

    This report provides reviews of papers and reports for three basic categories of melters: arc/plasma-heated melters, combustion-heated melters, and joule-heated melters. The literature reviewed here represents those publications which may lend insight to phase I testing of low-level waste vitrification being performed at the Hanford Site in FY 1995. For each melter category, information from those papers and reports containing enough information to determine steady-state mass balance data is tabulated at the end of each section. The tables show the composition of the feed processed, the off-gas measured via decontamination factors, gross energy consumptions, and processing rates, among other data.

  15. Joule Heating and Thermal Denaturation of Proteins in Nano-ESI Theta Tips

    NASA Astrophysics Data System (ADS)

    Zhao, Feifei; Matt, Sarah M.; Bu, Jiexun; Rehrauer, Owen G.; Ben-Amotz, Dor; McLuckey, Scott A.

    2017-07-01

    Electro-osmotically induced Joule heating in theta tips and its effect on protein denaturation were investigated. Myoglobin, equine cytochrome c, bovine cytochrome c, and carbonic anhydrase II solutions were subjected to electro-osmosis in a theta tip and all of the proteins were denatured during the process. The extent of protein denaturation was found to increase with the applied square wave voltage and electrolyte concentration. The solution temperature at the end of a theta tip was measured directly by Raman spectroscopy and shown to increase with the square wave voltage, thereby demonstrating the effect of Joule heating through an independent method. The electro-osmosis of a solution comprised of myoglobin, bovine cytochrome c, and ubiquitin demonstrated that the magnitude of Joule heating that causes protein denaturation is positively correlated with protein melting temperature. This allows for a quick determination of a protein's relative thermal stability. This work establishes a fast, novel method for protein conformation manipulation prior to MS analysis and provides a temperature-controllable platform for the study of processes that take place in solution with direct coupling to mass spectrometry.

  16. Joule Heating and Thermal Denaturation of Proteins in Nano-ESI Theta Tips

    NASA Astrophysics Data System (ADS)

    Zhao, Feifei; Matt, Sarah M.; Bu, Jiexun; Rehrauer, Owen G.; Ben-Amotz, Dor; McLuckey, Scott A.

    2017-10-01

    Electro-osmotically induced Joule heating in theta tips and its effect on protein denaturation were investigated. Myoglobin, equine cytochrome c, bovine cytochrome c, and carbonic anhydrase II solutions were subjected to electro-osmosis in a theta tip and all of the proteins were denatured during the process. The extent of protein denaturation was found to increase with the applied square wave voltage and electrolyte concentration. The solution temperature at the end of a theta tip was measured directly by Raman spectroscopy and shown to increase with the square wave voltage, thereby demonstrating the effect of Joule heating through an independent method. The electro-osmosis of a solution comprised of myoglobin, bovine cytochrome c, and ubiquitin demonstrated that the magnitude of Joule heating that causes protein denaturation is positively correlated with protein melting temperature. This allows for a quick determination of a protein's relative thermal stability. This work establishes a fast, novel method for protein conformation manipulation prior to MS analysis and provides a temperature-controllable platform for the study of processes that take place in solution with direct coupling to mass spectrometry. [Figure not available: see fulltext.

  17. Improved Ionospheric Electrodynamic Models and Application to Calculating Joule Heating Rates

    NASA Technical Reports Server (NTRS)

    Weimer, D. R.

    2004-01-01

    Improved techniques have been developed for empirical modeling of the high-latitude electric potentials and magnetic field aligned currents (FAC) as a function of the solar wind parameters. The FAC model is constructed using scalar magnetic Euler potentials, and functions as a twin to the electric potential model. The improved models have more accurate field values as well as more accurate boundary locations. Non-linear saturation effects in the solar wind-magnetosphere coupling are also better reproduced. The models are constructed using a hybrid technique, which has spherical harmonic functions only within a small area at the pole. At lower latitudes the potentials are constructed from multiple Fourier series functions of longitude, at discrete latitudinal steps. It is shown that the two models can be used together in order to calculate the total Poynting flux and Joule heating in the ionosphere. An additional model of the ionospheric conductivity is not required in order to obtain the ionospheric currents and Joule heating, as the conductivity variations as a function of the solar inclination are implicitly contained within the FAC model's data. The models outputs are shown for various input conditions, as well as compared with satellite measurements. The calculations of the total Joule heating are compared with results obtained by the inversion of ground-based magnetometer measurements. Like their predecessors, these empirical models should continue to be a useful research and forecast tools.

  18. Temperature measurement of Joule heated silicon micro/nanowires using selectively decorated quantum dots

    NASA Astrophysics Data System (ADS)

    Yun, Jeonghoon; Ahn, Jae-Hyuk; Lee, Bong Jae; Moon, Dong-Il; Choi, Yang-Kyu; Park, Inkyu

    2016-12-01

    We developed a novel method to measure local temperature at micro/nano-scale regions using selective deposition of quantum dots (QDs) as a sensitive temperature probe and measured the temperature of Joule heated silicon microwires (SiMWs) and silicon nanowires (SiNWs) by this method. The QDs are selectively coated only on the surface of the SiMWs and SiNWs by a sequential process composed of selective opening of a polymethyl methacrylate layer via Joule heating, covalent bonding of QDs, and lift-off process. The temperatures of the Joule-heated SiMWs and SiNWs can be measured by characterizing the temperature-dependent shift of photoluminescence peak of the selectively deposited QDs even with far-field optics. The validity of the extracted temperature has been also confirmed by comparing with numerical simulation results. The proposed method can potentially provide micro/nanoscale measurement of localized temperatures for a wide range of electrical and optical devices.

  19. Joule heating effects on electroosmotic flow in insulator-based dielectrophoresis.

    PubMed

    Sridharan, Sriram; Zhu, Junjie; Hu, Guoqing; Xuan, Xiangchun

    2011-09-01

    Insulator-based dielectrophoresis (iDEP) is an emerging technology that has been successfully used to manipulate a variety of particles in microfluidic devices. However, due to the locally amplified electric field around the in-channel insulator, Joule heating often becomes an unavoidable issue that may disturb the electroosmotic flow and affect the particle motion. This work presents the first experimental study of Joule heating effects on electroosmotic flow in a typical iDEP device, e.g., a constriction microchannel, under DC-biased AC voltages. A numerical model is also developed to simulate the observed flow pattern by solving the coupled electric, energy, and fluid equations in a simplified two-dimensional geometry. It is observed that depending on the magnitude of the DC voltage, a pair of counter-rotating fluid circulations can occur at either the downstream end alone or each end of the channel constriction. Moreover, the pair at the downstream end appears larger in size than that at the upstream end due to DC electroosmotic flow. These fluid circulations, which are reasonably simulated by the numerical model, form as a result of the action of the electric field on Joule heating-induced fluid inhomogeneities in the constriction region.

  20. Improved Ionospheric Electrodynamic Models and Application to Calculating Joule Heating Rates

    NASA Technical Reports Server (NTRS)

    Weimer, D. R.

    2004-01-01

    Improved techniques have been developed for empirical modeling of the high-latitude electric potentials and magnetic field aligned currents (FAC) as a function of the solar wind parameters. The FAC model is constructed using scalar magnetic Euler potentials, and functions as a twin to the electric potential model. The improved models have more accurate field values as well as more accurate boundary locations. Non-linear saturation effects in the solar wind-magnetosphere coupling are also better reproduced. The models are constructed using a hybrid technique, which has spherical harmonic functions only within a small area at the pole. At lower latitudes the potentials are constructed from multiple Fourier series functions of longitude, at discrete latitudinal steps. It is shown that the two models can be used together in order to calculate the total Poynting flux and Joule heating in the ionosphere. An additional model of the ionospheric conductivity is not required in order to obtain the ionospheric currents and Joule heating, as the conductivity variations as a function of the solar inclination are implicitly contained within the FAC model's data. The models outputs are shown for various input conditions, as well as compared with satellite measurements. The calculations of the total Joule heating are compared with results obtained by the inversion of ground-based magnetometer measurements. Like their predecessors, these empirical models should continue to be a useful research and forecast tools.

  1. Temperature measurement of Joule heated silicon micro/nanowires using selectively decorated quantum dots.

    PubMed

    Yun, Jeonghoon; Ahn, Jae-Hyuk; Lee, Bong Jae; Moon, Dong-Il; Choi, Yang-Kyu; Park, Inkyu

    2016-12-16

    We developed a novel method to measure local temperature at micro/nano-scale regions using selective deposition of quantum dots (QDs) as a sensitive temperature probe and measured the temperature of Joule heated silicon microwires (SiMWs) and silicon nanowires (SiNWs) by this method. The QDs are selectively coated only on the surface of the SiMWs and SiNWs by a sequential process composed of selective opening of a polymethyl methacrylate layer via Joule heating, covalent bonding of QDs, and lift-off process. The temperatures of the Joule-heated SiMWs and SiNWs can be measured by characterizing the temperature-dependent shift of photoluminescence peak of the selectively deposited QDs even with far-field optics. The validity of the extracted temperature has been also confirmed by comparing with numerical simulation results. The proposed method can potentially provide micro/nanoscale measurement of localized temperatures for a wide range of electrical and optical devices.

  2. Selectively Tuning a Buckled Si/SiO2 Membrane MEMS through Joule Heating Actuation and Mechanical Restriction

    DTIC Science & Technology

    2014-03-01

    SELECTIVELY TUNING A BUCKLED SI/SIO2 MEMBRANE MEMS THROUGH JOULE HEATING ACTUATION AND MECHANICAL RESTRICTION THESIS Kyle K...A BUCKLED SI/SIO2 MEMBRANE MEMS THROUGH JOULE HEATING ACTUATION AND MECHANICAL RESTRICTION I. Introduction Background Springs are a well-known...investigated a buckled beam structure as a switching mechanism for several years [9]. This concept will be discussed comprehensively in this research

  3. Joule-Heated Molten Regolith Electrolysis Reactor Concepts for Oxygen and Metals Production on the Moon and Mars

    NASA Technical Reports Server (NTRS)

    Sibille, Laurent; Dominques, Jesus A.

    2012-01-01

    The maturation of Molten Regolith Electrolysis (MRE) as a viable technology for oxygen and metals production on explored planets relies on the realization of the self-heating mode for the reactor. Joule heat generated during regolith electrolysis creates thermal energy that should be able to maintain the molten phase (similar to electrolytic Hall-Heroult process for aluminum production). Self-heating via Joule heating offers many advantages: (1) The regolith itself is the crucible material, it protects the vessel walls (2) Simplifies the engineering of the reactor (3) Reduces power consumption (no external heating) (4) Extends the longevity of the reactor. Predictive modeling is a tool chosen to perform dimensional analysis of a self-heating reactor: (1) Multiphysics modeling (COMSOL) was selected for Joule heat generation and heat transfer (2) Objective is to identify critical dimensions for first reactor prototype.

  4. Liquid film dewetting induced by impulsive Joule heating

    NASA Astrophysics Data System (ADS)

    Mayer, H. C.; Krechetnikov, R.

    2017-09-01

    Motivated by the need for understanding the boiling processes in three-phase microscopic systems, the present work aims to uncover the physics of forced dewetting of a liquid film initially attached to a metal wire frame, which is heated with a rate up to O (108) K s-1 by discharging a capacitor impulsively. Depending on the corresponding heat flux ≤O (1011) J m-2 , there are several key dewetting regimes—no detachment, nonuniform detachment, and uniform detachment of a film—differentiated by boiling transitions in the film Plateau borders. Transitions between these regimes prove to occur, for various wire diameters and frame sizes, around the same values of the capacitor energy per unit wire volume. Also, an intrinsic transverse instability manifesting itself in the formation of fingers along the detached liquid film rim is discovered and analyzed in detail.

  5. A 3D reconstruction solution to ultrasound Joule heat density tomography based on acousto-electric effect: a simulation study

    NASA Astrophysics Data System (ADS)

    Yang, R.; Song, A.; Li, X. D.; Lu, Y.; Yan, R.; Xu, B.; Li, X.

    2014-10-01

    A 3D reconstruction solution to ultrasound Joule heat density tomography based on acousto-electric effect by deconvolution is proposed for noninvasive imaging of biological tissue. Compared with ultrasound current source density imaging, ultrasound Joule heat density tomography doesn't require any priori knowledge of conductivity distribution and lead fields, so it can gain better imaging result, more adaptive to environment and with wider application scope. For a general 3D volume conductor with broadly distributed current density field, in the AE equation the ultrasound pressure can't simply be separated from the 3D integration, so it is not a common modulation and basebanding (heterodyning) method is no longer suitable to separate Joule heat density from the AE signals. In the proposed method the measurement signal is viewed as the output of Joule heat density convolving with ultrasound wave. As a result, the internal 3D Joule heat density can be reconstructed by means of Wiener deconvolution. A series of computer simulations set for breast cancer imaging applications, with consideration of ultrasound beam diameter, noise level, conductivity contrast, position dependency and size of simulated tumors, have been conducted to evaluate the feasibility and performance of the proposed reconstruction method. The computer simulation results demonstrate that high spatial resolution 3D ultrasound Joule heat density imaging is feasible using the proposed method, and it has potential applications to breast cancer detection and imaging of other organs.

  6. Assessment of Joule heating and its effects on electroosmotic flow and electrophoretic transport of solutes in microfluidic channels.

    PubMed

    Tang, Gongyue; Yan, Deguang; Yang, Chun; Gong, Haiqing; Chai, John Chee; Lam, Yee Cheong

    2006-02-01

    Joule heating is inevitable when an electric field is applied across a conducting medium. It would impose limitations on the performance of electrokinetic microfluidic devices. This article presents a 3-D mathematical model for Joule heating and its effects on the EOF and electrophoretic transport of solutes in microfluidic channels. The governing equations were numerically solved using the finite-volume method. Experiments were carried out to investigate the Joule heating associated phenomena and to verify the numerical models. A rhodamine B-based thermometry technique was employed to measure the solution temperature distributions in microfluidic channels. The microparticle image velocimetry technique was used to measure the velocity profiles of EOF under the influence of Joule heating. The numerical solutions were compared with experimental results, and reasonable agreement was found. It is found that with the presence of Joule heating, the EOF velocity deviates from its normal "plug-like" profile. The numerical simulations show that Joule heating not only accelerates the sample transport but also distorts the shape of the sample band.

  7. Testing of a scanning adiabatic calorimeter with Joule effect heating of the sample.

    PubMed

    Barreiro-Rodríguez, G; Yáñez-Limón, J M; Contreras-Servin, C A; Herrera-Gomez, A

    2008-01-01

    We evaluated a scanning adiabatic resistive calorimeter (SARC) developed to measure the specific enthalpy of viscous and gel-type materials. The sample is heated employing the Joule effect. The cell is constituted by a cylindrical jacket and two pistons, and the sample is contained inside the jacket between the two pistons. The upper piston can slide to allow for thermal expansion and to keep the pressure constant. The pistons also function as electrodes for the sample. While the sample is heated through the Joule effect, the electrodes and the jacket are independently heated to the same temperature of the sample using automatic control. This minimizes the heat transport between the sample and its surroundings. The energy to the sample is supplied by applying to the electrodes an ac voltage in the kilohertz range, establishing a current in the sample and inducing electric dissipation. This energy can be measured with enough exactitude to determine the heat capacity. This apparatus also allows for the quantification of the thermal conductivity by reproducing the evolution of the temperature as heat is introduced only to one of the pistons. To this end, the system was modeled using finite element calculations. This dual capability proved to be very valuable for correction in the determination of the specific enthalpy. The performance of the SARC was evaluated by comparing the heat capacity results to those obtained by differential scanning calorimetry measurements using a commercial apparatus. The analyzed samples were zeolite, bauxite, hematite, bentonite, rice flour, corn flour, and potato starch.

  8. Testing of a scanning adiabatic calorimeter with Joule effect heating of the sample

    NASA Astrophysics Data System (ADS)

    Barreiro-Rodríguez, G.; Yáñez-Limón, J. M.; Contreras-Servin, C. A.; Herrera-Gomez, A.

    2008-01-01

    We evaluated a scanning adiabatic resistive calorimeter (SARC) developed to measure the specific enthalpy of viscous and gel-type materials. The sample is heated employing the Joule effect. The cell is constituted by a cylindrical jacket and two pistons, and the sample is contained inside the jacket between the two pistons. The upper piston can slide to allow for thermal expansion and to keep the pressure constant. The pistons also function as electrodes for the sample. While the sample is heated through the Joule effect, the electrodes and the jacket are independently heated to the same temperature of the sample using automatic control. This minimizes the heat transport between the sample and its surroundings. The energy to the sample is supplied by applying to the electrodes an ac voltage in the kilohertz range, establishing a current in the sample and inducing electric dissipation. This energy can be measured with enough exactitude to determine the heat capacity. This apparatus also allows for the quantification of the thermal conductivity by reproducing the evolution of the temperature as heat is introduced only to one of the pistons. To this end, the system was modeled using finite element calculations. This dual capability proved to be very valuable for correction in the determination of the specific enthalpy. The performance of the SARC was evaluated by comparing the heat capacity results to those obtained by differential scanning calorimetry measurements using a commercial apparatus. The analyzed samples were zeolite, bauxite, hematite, bentonite, rice flour, corn flour, and potato starch.

  9. Measurements and Electrical Equivalent Model of Polymer PTC as a Function of Joule Heating Energy

    NASA Astrophysics Data System (ADS)

    Abubaker, Zawam; Maeyama, Mitsuaki

    In this paper, experiments were conducted to study the electrical I-V characteristics of the polymer Positive Temperature Coefficient (PTC)resistor as a function of joule heating due to I2R. More than 80short-circuit tests were carried out on four samples (rated 60V/40A), and the results show that all PTC samples tripped when the thresholdinput energy nearly equaled 20 J. We propose a new mathematical modelfor the PTC in the fault current condition, a PTC-TACS (Transient Analysis of Control Systems) model, by using the Electro-Magnetic Transient Program (EMTP), which is a function of the input joule heatingenergy. A comparison between the experimental results and EMTPsimulation results has shown that the PTC-TACS model is valid and veryeffective to investigate the PTC under fault current conditions inelectrical circuits and to design an over-current limiter based on PTCmaterials for industrial applications. In the discussion about radiationpower loss in case that the applied voltage is greater than 50V or thetripped time is less than 4ms, it is shown that the radiation powerloss can be neglected and the PTC resistance can be expressed only bythe input joule heating energy.

  10. Joule heating and field-aligned currents: Preliminary results from DE-2

    NASA Technical Reports Server (NTRS)

    Sugiura, M.

    1986-01-01

    There are three main processes by which energy is transferred from the magnetosphere to the thermosphere: (1) charge exchange of the ring current particles; (2) precipitation of charged particles; and (3) joule dissipation by the magnetosphere-ionosphere current systems. The importance of this last process has been recognized and the rate of joule heating has been estimated by many workers. Observations of the electric (E) and magnetic (B) fields from Dynamics Explorer Satellite 2 are providing a new set of data on field-aligned currents. One of the remarkable features found in these observations is the high correlation between an orthogonal pair of the E and B field components. In recent years, observational data have accrued concerning the relationship between the interplanetary magnetic field and the size of the polar cap and also about the evolution of a substorm or a magnetic storm. It is suggested that these findings be incorporated in future model calculations.

  11. Revisit of Joule heating in CE: the contribution of surface conductance.

    PubMed

    Xuan, Xiangchun

    2007-08-01

    We present in this short communication the true form of Joule heating in CE which considers the contribution of surface conductance. This increased conductivity of electrolyte solution within electrical double layer has never been discussed in previous studies. The resultant intensive heat generation near the capillary wall is demonstrated using numerical simulation to produce not a locally strong temperature rise, but an additional temperature elevation in the whole solution compared to the model neglecting surface conductance. The latter effect is, however, negligible in typical CE while it might become significant in very small channels.

  12. MHD Flow with Hall current and Joule Heating Effects over an Exponentially Stretching Sheet

    NASA Astrophysics Data System (ADS)

    Srinivasacharya, D.; Jagadeeshwar, P.

    2017-06-01

    The aim of the present paper is to study the influence of Hall current and Joule heating on flow, heat and mass transfer over an exponentially stretching sheet in a viscous fluid. Using similarity transformations the governing nonlinear coupled equations are converted into ordinary differential equations. These equations are linearized using the successive linearization method and then solved using the Chebyshev pseudo spectral method. The influence of magnetic parameter, Hall parameter, suction/injection parameter and slip parameter on the physical quantities are presented graphically. The obtained results are compared with the previously published results for special cases.

  13. Imaging Joule Heating in an 80 nm Wide Titanium Nanowire by Thermally Modulated Fluorescence

    NASA Astrophysics Data System (ADS)

    Saïdi, E.; Labéguerie-Egéa, J.; Billot, L.; Lesueur, J.; Mortier, M.; Aigouy, L.

    2013-09-01

    A fluorescent erbium/ytterbium co-doped fluoride nanocrystal glued at the end of a sharp atomic force microscope tungsten tip was used as a nanoscale thermometer. The thermally induced fluorescence quenching enabled observation of the heating and measurement of the temperature distribution in a Joule-heated 80 nm wide and 2 μm long titanium nanowire fabricated on an oxidized silicon substrate. The measurements have been carried out in an alternating heating mode by applying a modulated current on the device at low frequency. The heating is found to be inhomogeneous along the wire, and the temperature in its center increases quadratically with the applied current. Heat appears to be confined mainly along the wire, with weak lateral diffusion along the substrate and in the lateral metallic pads. The lateral resolution of this thermal measurement technique is better than 250 nm. It could also be used to study thermally induced defects in nanodevices.

  14. Effect of Joule heating and current crowding on electromigration in mobile technology

    NASA Astrophysics Data System (ADS)

    Tu, K. N.; Liu, Yingxia; Li, Menglu

    2017-03-01

    In the present era of big data and internet of things, the use of microelectronic products in all aspects of our life is manifested by the ubiquitous presence of mobile devices as i-phones and wearable i-products. These devices are facing the need for higher power and greater functionality applications such as in i-health, yet they are limited by physical size. At the moment, software (Apps) is much ahead of hardware in mobile technology. To advance hardware, the end of Moore's law in two-dimensional integrated circuits can be extended by three-dimensional integrated circuits (3D ICs). The concept of 3D ICs has been with us for more than ten years. The challenge in 3D IC technology is dense packing by using both vertical and horizontal interconnections. Mass production of 3D IC devices is behind schedule due to cost because of low yield and uncertain reliability. Joule heating is serious in a dense structure because of heat generation and dissipation. A change of reliability paradigm has advanced from failure at a specific circuit component to failure at a system level weak-link. Currently, the electronic industry is introducing 3D IC devices in mainframe computers, where cost is not an issue, for the purpose of collecting field data of failure, especially the effect of Joule heating and current crowding on electromigration. This review will concentrate on the positive feedback between Joule heating and electromigration, resulting in an accelerated system level weak-link failure. A new driving force of electromigration, the electric potential gradient force due to current crowding, will be reviewed critically. The induced failure tends to occur in the low current density region.

  15. Thermographic NDT based on transient temperature field under Joule effect heating

    SciTech Connect

    Sakagami, Takahide; Ogura, Keiji

    1994-12-31

    The thermographic NDT based on the transient temperature distribution under the Joule effect heating by an electric current was discussed. Two different types of inspection methods, i.e., the singular method and the insulation method were examined. The singular method based on the heat concentration at the crack tip was successfully applied to the identification of the through-thickness and surface cracks embedded in steel plates. The resolution of the crack identification by the singular method was examined by the current intensity factor and the thermal diffusion length. The insulation method based on the temperature turbulence appears on the sample surface due to the thermal insulation of the defect was tested for the identification of the delaminated defect in CFRP. Two methods of the Joule effect heating, the direct current application and the induction heating, were successfully applied for the thermographic NDT of the delaminated defects in CFRP samples. The thermographic NDT developed in this study was found to be applicable to nondestructive flaw- and defect-inspection both in metallic and composite materials.

  16. Simple and strong: twisted silver painted nylon artificial muscle actuated by Joule heating

    NASA Astrophysics Data System (ADS)

    Mirvakili, Seyed M.; Rafie Ravandi, Ali; Hunter, Ian W.; Haines, Carter S.; Li, Na; Foroughi, Javad; Naficy, Sina; Spinks, Geoffrey M.; Baughman, Ray H.; Madden, John D. W.

    2014-03-01

    Highly oriented nylon and polyethylene fibres shrink in length when heated and expand in diameter. By twisting and then coiling monofilaments of these materials to form helical springs, the anisotropic thermal expansion has recently been shown to enable tensile actuation of up to 49% upon heating. Joule heating, by passing a current through a conductive coating on the surface of the filament, is a convenient method of controlling actuation. In previously reported work this has been done using highly flexible carbon nanotube sheets or commercially available silver coated fibres. In this work silver paint is used as the Joule heating element at the surface of the muscle. Up to 29% linear actuation is observed with energy and power densities reaching 840 kJ m-3 (528 J kg-1) and 1.1 kW kg-1 (operating at 0.1 Hz, 4% strain, 1.4 kg load). This simple coating method is readily accessible and can be applied to any polymer filament. Effective use of this technique relies on uniform coating to avoid temperature gradients.

  17. A new flaw inspection technique based on infrared thermal images under Joule effect heating

    NASA Astrophysics Data System (ADS)

    Sakagami, Takahide; Ogura, Keiji

    1992-11-01

    A new nondestructive inspection technique using infrared thermography was proposed, in which the thermal image of the surface temperature on a heated sample was used to identify flaws and defects. Joule effect heating by an electric current was employed to heat the sample instantaneously. Both numerical and experimental studies were conducted on the resolution and the availability in the detection of the through-thickness and surface cracks embedded in steel plates. The results showed that a singular concentration was observed at the crack tips in the surface temperature field in the transient stage of heat conduction, and the cracks were found to be sensitively detected from such a singular temperature field in the early transient stage. This technique was also applied to the inspection of the delamination defect in carbon-fiber reinforced plastics.

  18. Solar wind effect on Joule heating in the high-latitude ionosphere

    NASA Astrophysics Data System (ADS)

    Cai, L.; Aikio, A. T.; Nygrén, T.

    2014-12-01

    The effect of solar wind on several electrodynamic parameters, measured simultaneously by the European Incoherent Scatter (EISCAT) radars in Tromsø (TRO, 66.6° cgmLat) and on Svalbard (ESR, 75.4° cgmLat), has been evaluated statistically. The main emphasis is on Joule heating rate QJ, which has been estimated by taking into account the neutral wind. In addition, a generally used proxy QE, which is the Pedersen conductance times the electric field squared, has been calculated. The most important findings are as follows. (i) The decrease in Joule heating in the afternoon-evening sector due to winds reported by Aikio et al. (2012) requires southward interplanetary magnetic field (IMF) conditions and a sufficiently high solar wind electric field. The increase in the morning sector takes place for all IMF directions within a region where the upper E neutral wind has a large equatorward component and the F region plasma flow is directed eastward. (ii) At ESR, an afternoon hot spot of Joule heating centered typically at 14-15 magnetic local time (MLT) is observed during all IMF conditions. Enhanced Pedersen conductances within the hot spot region are observed only for the IMF Bz + /By- conditions, and the corresponding convection electric field values within the hot spot are smaller than during the other IMF conditions. Hence, the hot spot represents a region of persistent magnetospheric electromagnetic energy input, and the median value is about 3 mW/m2. (iii) For the southward IMF conditions, the MLT-integrated QE for By- is twice the value for By+ at TRO. This can plausibly be explained by the higher average solar wind electric field values for By-.

  19. MHD stagnation point flow over a stretching cylinder with variable thermal conductivity and joule heating

    NASA Astrophysics Data System (ADS)

    Jahan, Shah; Sakidin, Hamzah; Nazar, Roslinda Mohd

    2016-11-01

    The behavior of magnetohydrodynamics (MHD) flow of viscous fluid near the stagnation point over a stretching cylinder with variable thermal conductivity is analyzed. Thermal conductivity is assumed to be linearly related with temperature. The joule heating effects due to magnetic field is also encountered here. Analytical solutions are developed for both momentum and energy equations by using the homotopy analysis method (HAM). The variations of different parameters on the velocity and temperature distributions along with the skin friction coefficient and local Nusselt number are displayed graphically. Numerical values for the skin friction coefficient are calculated and discussed

  20. Nanoscale dynamics of Joule heating and bubble nucleation in a solid-state nanopore

    NASA Astrophysics Data System (ADS)

    Levine, Edlyn V.; Burns, Michael M.; Golovchenko, Jene A.

    2016-01-01

    We present a mathematical model for Joule heating of an electrolytic solution in a nanopore. The model couples the electrical and thermal dynamics responsible for rapid and extreme superheating of the electrolyte within the nanopore. The model is implemented numerically with a finite element calculation, yielding a time and spatially resolved temperature distribution in the nanopore region. Temperatures near the thermodynamic limit of superheat are predicted to be attained just before the explosive nucleation of a vapor bubble is observed experimentally. Knowledge of this temperature distribution enables the evaluation of related phenomena including bubble nucleation kinetics, relaxation oscillation, and bubble dynamics.

  1. Circulation in the high-latitude thermosphere due to electric fields and Joule heating

    NASA Technical Reports Server (NTRS)

    Heaps, M. G.; Megill, L. R.

    1975-01-01

    Electric fields in the earth's upper atmosphere are capable of setting the neutral atmosphere in motion via ion-neutral collisions as well as pressure gradients from resultant Joule heating. By means of simple models for the high-latitude thermosphere and electric fields a simplified set of coupled equations is solved which show that moderate electric fields, when present for a period of several hours, are capable of displacing the neutral atmosphere of the order of 50 km in the vertical, a few hundred kilometers in the north-south direction and over 1000 km in the east-west direction.

  2. Circulation in the high-latitude thermosphere due to electric fields and Joule heating

    NASA Technical Reports Server (NTRS)

    Heaps, M. G.; Megill, L. R.

    1975-01-01

    Electric fields in the earth's upper atmosphere are capable of setting the neutral atmosphere in motion via ion-neutral collisions as well as pressure gradients from resultant Joule heating. By means of simple models for the high-latitude thermosphere and electric fields a simplified set of coupled equations is solved which show that moderate electric fields, when present for a period of several hours, are capable of displacing the neutral atmosphere of the order of 50 km in the vertical, a few hundred kilometers in the north-south direction and over 1000 km in the east-west direction.

  3. Nanoscale dynamics of Joule heating and bubble nucleation in a solid-state nanopore.

    PubMed

    Levine, Edlyn V; Burns, Michael M; Golovchenko, Jene A

    2016-01-01

    We present a mathematical model for Joule heating of an electrolytic solution in a nanopore. The model couples the electrical and thermal dynamics responsible for rapid and extreme superheating of the electrolyte within the nanopore. The model is implemented numerically with a finite element calculation, yielding a time and spatially resolved temperature distribution in the nanopore region. Temperatures near the thermodynamic limit of superheat are predicted to be attained just before the explosive nucleation of a vapor bubble is observed experimentally. Knowledge of this temperature distribution enables the evaluation of related phenomena including bubble nucleation kinetics, relaxation oscillation, and bubble dynamics.

  4. A study of Joule heating-induced breakdown of carbon nanotube interconnects.

    PubMed

    Santini, C A; Vereecken, P M; Volodin, A; Groeseneken, G; De Gendt, S; Haesendonck, C Van

    2011-09-30

    We investigate breakdown of carbon nanotube (CNT) interconnects induced by Joule heating in air and under high vacuum conditions (10(-5) mbar). A CNT with a diameter of 18 nm, which is grown by chemical vapor deposition to connect opposing titanium nitride (TiN) electrodes, is able to carry an electrical power up to 0.6 mW before breaking down under vacuum, with a corresponding maximum current density up to 8 × 10(7) A cm(-2) (compared to 0.16 mW and 2 × 10(7) A cm(-2) in air). Decoration with electrochemically deposited Ni particles allows protection of the CNT interconnect against oxidation and improvement of the heat release through the surrounding environment. A CNT decorated with Ni particles is able to carry an increased electrical power of about 1.5 mW before breaking down under vacuum, with a corresponding maximum current density as high as 1.2 × 10(8) A cm(-2). The Joule heating produced along the current carrying CNT interconnect is able to melt the Ni particles and promotes the formation of titanium carbon nitride which improves the electrical contact between the CNT and the TiN electrodes.

  5. Numerical modeling of Joule heating effects in insulator-based dielectrophoresis microdevices.

    PubMed

    Kale, Akshay; Patel, Saurin; Hu, Guoqing; Xuan, Xiangchun

    2013-03-01

    Insulator-based DEP (iDEP) has been established as a powerful tool for manipulating particles in microfluidic devices. However, Joule heating may become an issue in iDEP microdevices due to the local amplification of electric field around the insulators. This results in an electrothermal force that can manifest itself in the flow field in the form of circulations, thus affecting the particle motion. We develop herein a transient, 3D, full-scale numerical model to study Joule heating and its effects on the coupled transport of charge, heat, and fluid in an iDEP device with a rectangular constriction microchannel. This model is validated by comparing the simulation results with the experimentally obtained fluid flow patterns and particle images that were reported in our recent works. It identifies a significant difference in the time scales of the electric, temperature, and flow fields in iDEP microdevices. It also predicts the locations of electrothermal flow circulations in different halves of the channel at the upstream and downstream of the constriction.

  6. Particle and Joule heating of the neutral polar thermosphere in cusp region using atmosphere Explorer-C satellite measurements

    NASA Technical Reports Server (NTRS)

    Griffis, M.; Nisbet, J. S.; Bleuler, E.

    1981-01-01

    It is pointed out that thermospheric heating in the auroral zone and polar cap is of great importance to the variations in the high-latitude neutral wind and the resulting global temperature and densities. The considered investigation is concerned with relating in a quantitative manner the energy inputs from the Joule heating and particle inputs with the thermospheric responses, taking into account the cusp region, and the region of the eastward auroral electrojet. The data used in the investigation were obtained by the Atmosphere Explorer C satellite in late December 1974. Attention is given to electric fields derived from ion drift measurements, electric field strength and particle energy flux measured by the low energy electron experiment for AE-C orbit 4708, electron density contours, Joule heating contours, and height integrated Joule heating and particle energy flux.

  7. One type of hydrodynamic instability in joule heating of a fluid near an ion-selective surface

    NASA Astrophysics Data System (ADS)

    Nikitin, N. V.; Khasmatulina, N. Yu.; Ganchenko, G. S.; Kalaidin, E. N.; Kiriy, V. A.; Demekhin, E. A.

    2016-06-01

    The stability of the equilibrium state of an electrolyte in a horizontal microgap between two ionselective surfaces in an electric field is studied with the Joule heating of the fluid taken into account. It is established that the Joule heating can lead to instability at the potential differences, which are several times smaller than those in the isothermal case. The effects of microscale thermal instability differ from the Rayleigh-Benard thermal convection: the destabilization occurs upon heating in the upper part of the gap.

  8. Mixed Convective Peristaltic Flow of Water Based Nanofluids with Joule Heating and Convective Boundary Conditions.

    PubMed

    Hayat, Tasawar; Nawaz, Sadaf; Alsaedi, Ahmed; Rafiq, Maimona

    2016-01-01

    Main objective of present study is to analyze the mixed convective peristaltic transport of water based nanofluids using five different nanoparticles i.e. (Al2O3, CuO, Cu, Ag and TiO2). Two thermal conductivity models namely the Maxwell's and Hamilton-Crosser's are used in this study. Hall and Joule heating effects are also given consideration. Convection boundary conditions are employed. Furthermore, viscous dissipation and heat generation/absorption are used to model the energy equation. Problem is simplified by employing lubrication approach. System of equations are solved numerically. Influence of pertinent parameters on the velocity and temperature are discussed. Also the heat transfer rate at the wall is observed for considered five nanofluids using the two phase models via graphs.

  9. Mixed Convective Peristaltic Flow of Water Based Nanofluids with Joule Heating and Convective Boundary Conditions

    PubMed Central

    Hayat, Tasawar; Nawaz, Sadaf; Alsaedi, Ahmed; Rafiq, Maimona

    2016-01-01

    Main objective of present study is to analyze the mixed convective peristaltic transport of water based nanofluids using five different nanoparticles i.e. (Al2O3, CuO, Cu, Ag and TiO2). Two thermal conductivity models namely the Maxwell's and Hamilton-Crosser's are used in this study. Hall and Joule heating effects are also given consideration. Convection boundary conditions are employed. Furthermore, viscous dissipation and heat generation/absorption are used to model the energy equation. Problem is simplified by employing lubrication approach. System of equations are solved numerically. Influence of pertinent parameters on the velocity and temperature are discussed. Also the heat transfer rate at the wall is observed for considered five nanofluids using the two phase models via graphs. PMID:27104596

  10. Modulation calorimetry in diamond anvil cells. II. Joule-heating design and prototypes

    NASA Astrophysics Data System (ADS)

    Geballe, Zachary M.; Struzhkin, Viktor V.; Townley, Andrew; Jeanloz, Raymond

    2017-04-01

    Part I shows that quantitative measurements of heat capacity are theoretically possible inside diamond anvil cells via high-frequency Joule heating (100 kHz-10 MHz), opening up the possibility of new methods to detect and characterize transformations at high-pressure such as the glass transitions, melting, magnetic orderings, and the onset of superconductivity. Here, we test the possibility outlined in Part I, using prototypes and detailed numerical models. First, a coupled electrical-thermal numerical model shows that specific heat of metals inside diamond cells can be measured directly using ˜1 MHz frequency, with <10 % accuracy. Second, we test physical models of high-pressure experiments, i.e., diamond-cell mock-ups. Metal foils of 2-6 μm-thickness are clamped between glass insulation inside diamond anvil cells. Fitting data from 10 Hz to ˜30 kHz, we infer the specific heat capacities of Fe, Pt, and Ni with ±20%-30% accuracy. The electrical test equipment generates -80 dBc spurious harmonics, which overwhelm the thermally induced harmonics at higher frequencies, disallowing the high precision expected from numerical models. An alternative Joule-heating calorimetry experiment, on the other hand, does allow absolute measurements with <10 % accuracy, despite the -80 dBc spurious harmonics: the measurement of thermal effusivity, √{ρc k } (ρ, c, and k being density, specific heat, and thermal conductivity), of the insulation surrounding a thin-film heater. Using a ˜50 nm-thick Pt heater surrounded by glass and 10 Hz-300 kHz frequency, we measure thermal effusivity with ±6 % accuracy inside the sample chamber of a diamond anvil cell.

  11. Impact of Joule Heating and pH on Biosolids Electro-Dewatering.

    PubMed

    Navab-Daneshmand, Tala; Beton, Raphaël; Hill, Reghan J; Frigon, Dominic

    2015-05-05

    Electro-dewatering (ED) is a novel technology to reduce the overall costs of residual biosolids processing, transport, and disposal. In this study, we investigated Joule heating and pH as parameters controlling the dewaterability limit, dewatering rate, and energy efficiency. Temperature-controlled electrodes revealed that Joule heating enhances water removal by increasing evaporation and electro-osmotic flow. High temperatures increased the dewatering rate, but had little impact on the dewaterability limit and energy efficiency. Analysis of horizontal layers after 15-min ED suggests electro-osmotic flow reversal, as evidenced by a shifting of the point of minimum moisture content from the anode toward the cathode. This flow reversal was also confirmed by the pH at the anode being below the isoelectric point, as ascertained by pH titration. The important role of pH on ED was further studied by adding acid/base solutions to biosolids prior to ED. An acidic pH reduced the biosolids charge while simultaneously increasing the dewatering efficiency. Thus, process optimization depends on trade-offs between speed and efficiency, according to physicochemical properties of the biosolids microstructure.

  12. Role of Joule heating in dispersive mixing effects in electrophoretic cells: convective-diffusive transport aspects.

    PubMed

    Bosse, M A; Arce, P

    2000-03-01

    This contribution addresses the problem of solute dispersion in a free convection electrophoretic cell for the batch mode of operation, caused by the Joule heating generation. The problem is analyzed by using the two-problem approach originally proposed by Bosse and Arce (Electrophoresis 2000, 21, 1018-1025). The approach identifies the carrier fluid problem and the solute problem. This contribution is focused on the latter. The strategy uses a sequential coupling between the energy, momentum and mass conservation equations and, based on geometrical and physical assumptions for the system, leads to the derivation of analytical temperature and velocity profiles inside the cell. These results are subsequently used in the derivation of the effective dispersion coefficient for the cell by using the method of area averaging. The result shows the first design equation that relates the Joule heating effect directly to the solute dispersion in the cell. Some illustrative results are presented and discussed and their implication to the operation and design of the device is addressed. Due to the assumptions made, the equation may be viewed as an upper boundary for applications such as free flow electrophoresis.

  13. Joule-Heating-Induced Damage in Cu-Al Wedge Bonds Under Current Stressing

    NASA Astrophysics Data System (ADS)

    Yang, Tsung-Han; Lin, Yu-Min; Ouyang, Fan-Yi

    2014-01-01

    Copper wires are increasingly used to replace gold wires in wire-bonding technology owing to their better electrical properties and lower cost. However, not many studies have been conducted on electromigration-induced failure of Cu wedge bonds on Al metallization. In this study, we investigated the failure mechanism of Cu-Al wedge bonds under high current stressing from 4 × 104 A/cm2 to 1 × 105 A/cm2 at ambient temperature of 175°C. The resistance evolution of samples during current stressing and the microstructure of the joint interface between the Cu wire and Al-Si bond pad were examined. The results showed that abnormal crack formation accompanying significant intermetallic compound growth was observed at the second joint of the samples, regardless of the direction of electric current for both current densities of 4 × 104 A/cm2 and 8 × 104 A/cm2. We propose that this abnormal crack formation at the second joint is mainly due to the higher temperature induced by the greater Joule heating at the second joint for the same current stressing, because of its smaller bonded area compared with the first joint. The corresponding fluxes induced by the electric current and chemical potential difference between Cu and Al were calculated and compared to explain the failure mechanism. For current density of 1 × 105 A/cm2, the Cu wire melted within 0.5 h owing to serious Joule heating.

  14. Nanoscale Joule heating and electromigration enhanced ripening of silver nanowire contacts.

    PubMed

    Song, Tze-Bin; Chen, Yu; Chung, Choong-Heui; Yang, Yang Michael; Bob, Brion; Duan, Hsin-Sheng; Li, Gang; Tu, King-Ning; Huang, Yu; Yang, Yang

    2014-03-25

    Solution-processed metallic nanowire thin film is a promising candidate to replace traditional indium tin oxide as the next-generation transparent and flexible electrode. To date however, the performance of these electrodes is limited by the high contact resistance between contacting nanowires; so improving the point contacts between these nanowires remains a major challenge. Existing methods for reducing the contact resistance require either a high processing power, long treatment time, or the addition of chemical reagents, which could lead to increased manufacturing cost and damage the underlying substrate or device. Here, a nanoscale point reaction process is introduced as a fast and low-power-consumption way to improve the electrical contact properties between metallic nanowires. This is achieved via current-assisted localized joule heating accompanied by electromigration. Localized joule heating effectively targets the high-resistance contact points between nanowires, leading to the automatic removal of surface ligands, welding of contacting nanowires, and the reshaping of the contact pathway between the nanowires to form a more desirable geometry of low resistance for interwire conduction. This result shows the interplay between thermal and electrical interactions at the highly reactive nanocontacts and highlights the control of the nanoscale reaction as a simple and effective way of turning individual metallic nanowires into a highly conductive interconnected nanowire network. The temperature of the adjacent device layers can be kept close to room temperature during the process, making this method especially suitable for use in devices containing thermally sensitive materials such as polymer solar cells.

  15. MHD Mixed Convective Peristaltic Motion of Nanofluid with Joule Heating and Thermophoresis Effects

    PubMed Central

    Shehzad, Sabir Ali; Abbasi, Fahad Munir; Hayat, Tasawar; Alsaadi, Fuad

    2014-01-01

    The primary objective of present investigation is to introduce the novel aspect of thermophoresis in the mixed convective peristaltic transport of viscous nanofluid. Viscous dissipation and Joule heating are also taken into account. Problem is modeled using the lubrication approach. Resulting system of equations is solved numerically. Effects of sundry parameters on the velocity, temperature, concentration of nanoparticles and heat and mass transfer rates at the wall are studied through graphs. It is noted that the concentration of nanoparticles near the boundaries is enhanced for larger thermophoresis parameter. However reverse situation is observed for an increase in the value of Brownian motion parameter. Further, the mass transfer rate at the wall significantly decreases when Brownian motion parameter is assigned higher values. PMID:25391147

  16. MHD mixed convective peristaltic motion of nanofluid with Joule heating and thermophoresis effects.

    PubMed

    Shehzad, Sabir Ali; Abbasi, Fahad Munir; Hayat, Tasawar; Alsaadi, Fuad

    2014-01-01

    The primary objective of present investigation is to introduce the novel aspect of thermophoresis in the mixed convective peristaltic transport of viscous nanofluid. Viscous dissipation and Joule heating are also taken into account. Problem is modeled using the lubrication approach. Resulting system of equations is solved numerically. Effects of sundry parameters on the velocity, temperature, concentration of nanoparticles and heat and mass transfer rates at the wall are studied through graphs. It is noted that the concentration of nanoparticles near the boundaries is enhanced for larger thermophoresis parameter. However reverse situation is observed for an increase in the value of Brownian motion parameter. Further, the mass transfer rate at the wall significantly decreases when Brownian motion parameter is assigned higher values.

  17. Nanoscale Joule heating, Peltier cooling and current crowding at graphene-metal contacts

    NASA Astrophysics Data System (ADS)

    Grosse, Kyle L.; Bae, Myung-Ho; Lian, Feifei; Pop, Eric; King, William P.

    2011-05-01

    The performance and scaling of graphene-based electronics is limited by the quality of contacts between the graphene and metal electrodes. However, the nature of graphene-metal contacts remains incompletely understood. Here, we use atomic force microscopy to measure the temperature distributions at the contacts of working graphene transistors with a spatial resolution of ~10 nm (refs 5, , , 8), allowing us to identify the presence of Joule heating, current crowding and thermoelectric heating and cooling. Comparison with simulation enables extraction of the contact resistivity (150-200 Ω µm2) and transfer length (0.2-0.5 µm) in our devices; these generally limit performance and must be minimized. Our data indicate that thermoelectric effects account for up to one-third of the contact temperature changes, and that current crowding accounts for most of the remainder. Modelling predicts that the role of current crowding will diminish and the role of thermoelectric effects will increase as contacts improve.

  18. Nanoscale Joule heating, Peltier cooling and current crowding at graphene-metal contacts.

    PubMed

    Grosse, Kyle L; Bae, Myung-Ho; Lian, Feifei; Pop, Eric; King, William P

    2011-05-01

    The performance and scaling of graphene-based electronics is limited by the quality of contacts between the graphene and metal electrodes. However, the nature of graphene-metal contacts remains incompletely understood. Here, we use atomic force microscopy to measure the temperature distributions at the contacts of working graphene transistors with a spatial resolution of ~ 10 nm (refs 5-8), allowing us to identify the presence of Joule heating, current crowding and thermoelectric heating and cooling. Comparison with simulation enables extraction of the contact resistivity (150-200 Ω µm²) and transfer length (0.2-0.5 µm) in our devices; these generally limit performance and must be minimized. Our data indicate that thermoelectric effects account for up to one-third of the contact temperature changes, and that current crowding accounts for most of the remainder. Modelling predicts that the role of current crowding will diminish and the role of thermoelectric effects will increase as contacts improve.

  19. Highly Stable and Conductive Microcapsules for Enhancement of Joule Heating Performance

    PubMed Central

    2016-01-01

    Nanocarbons show great promise for establishing the next generation of Joule heating systems, but suffer from the limited maximum temperature due to precociously convective heat dissipation from electrothermal system to surrounding environment. Here we introduce a strategy to eliminate such convective heat transfer by inserting highly stable and conductive microcapsules into the electrothermal structures. The microcapsule is composed of encapsulated long-chain alkanes and graphene oxide/carbon nanotube hybrids as core and shell material, respectively. Multiform carbon nanotubes in the microspheres stabilize the capsule shell to resist volume-change-induced rupture during repeated heating/cooling process, and meanwhile enhance the thermal conductance of encapsulated alkanes which facilitates an expeditious heat exchange. The resulting microcapsules can be homogeneously incorporated in the nanocarbon-based electrothermal structures. At a dopant of 5%, the working temperature can be enhanced by 30% even at a low voltage and moderate temperature, which indicates a great value in daily household applications. Therefore, the stable and conductive microcapsule may serve as a versatile and valuable dopant for varieties of heat generation systems. PMID:27002594

  20. Microchannel heat exchanger for two-phase Mixed Refrigerant Joule Thomson process

    NASA Astrophysics Data System (ADS)

    Baek, Seungwhan; Lee, Jisung; Lee, Cheonkyu; Jeong, Sangkwon

    2014-01-01

    Mixed Refrigerant Joule Thomson (MR-JT) refrigerators are widely used in various kinds of cryogenic systems these days. Printed Circuit Heat Exchanger (PCHE) is one of the promising cryogenic compact recuperators for MR-JT refrigerators due to its compactness, high NTU and robustness. However, PCHE composed with microchannel bundles can cause flow mal-distribution, and it can cause the degradation of thermal performance of the system. To mitigate the flow mal-distribution problem, the cross link (or intra-layer bypass) can be adapted to parallel microchannels. Two heat exchangers are fabricated in this study; one has straight channels, and the other one has intra-layer bypass structure between channels to enhance the flow distribution. The MR-JT refrigerators are operated with these two heat exchanger and the no-load temperatures are compared. The lower no load temperature achieved with the intra-layer bypass structured heat exchanger. The results indicate that the flow mal-distribution in the microchannel heat exchanger can be mitigated with intra-layer bypass structure, and relaxation of flow mal-distribution in the heat exchanger guarantee the MR-JT refrigerator's performance.

  1. Highly Stable and Conductive Microcapsules for Enhancement of Joule Heating Performance.

    PubMed

    Zheng, Zhaoliang; Jin, Jidong; Xu, Guang-Kui; Zou, Jianli; Wais, Ulrike; Beckett, Alison; Heil, Tobias; Higgins, Sean; Guan, Lunhui; Wang, Ying; Shchukin, Dmitry

    2016-04-26

    Nanocarbons show great promise for establishing the next generation of Joule heating systems, but suffer from the limited maximum temperature due to precociously convective heat dissipation from electrothermal system to surrounding environment. Here we introduce a strategy to eliminate such convective heat transfer by inserting highly stable and conductive microcapsules into the electrothermal structures. The microcapsule is composed of encapsulated long-chain alkanes and graphene oxide/carbon nanotube hybrids as core and shell material, respectively. Multiform carbon nanotubes in the microspheres stabilize the capsule shell to resist volume-change-induced rupture during repeated heating/cooling process, and meanwhile enhance the thermal conductance of encapsulated alkanes which facilitates an expeditious heat exchange. The resulting microcapsules can be homogeneously incorporated in the nanocarbon-based electrothermal structures. At a dopant of 5%, the working temperature can be enhanced by 30% even at a low voltage and moderate temperature, which indicates a great value in daily household applications. Therefore, the stable and conductive microcapsule may serve as a versatile and valuable dopant for varieties of heat generation systems.

  2. Considerable different frequency dependence of dynamic tensile modulus between self-heating (Joule heat) and external heating for polymer--nickel-coated carbon fiber composites.

    PubMed

    Zhang, Rong; Bin, Yuezhen; Dong, Enyuan; Matsuo, Masaru

    2014-06-26

    Dynamic tensile moduli of polyethylene--nickel-coated carbon fiber (NiCF) composites with 10 and 4 vol % NiCF contents under electrical field were measured by a homemade instrument in the frequency range of 100--0.01 Hz. The drastic descent of the storage modulus of the composite with 10 vol % was verified in lower frequency range with elevating surface temperature (T(s)) by self-heating (Joule heat). The composite was cut when T(s) was beyond 108 °C. On the other hand, the measurement of the composite with 4 vol % beyond 88 °C was impossible, since T(s) did not elevate because of the disruption of current networks. Incidentally, the dynamic tensile moduli by external heating could be measured up to 130 and 115 °C for 10 and 4 vol %, respectively, but the two composites could be elongated beyond the above temperatures. Such different properties were analyzed in terms of crystal dispersions, electrical treeing, and thermal fluctuation-induced tunneling effect.

  3. Influence of Newtonian Heating on Three Dimensional MHD Flow of Couple Stress Nanofluid with Viscous Dissipation and Joule Heating

    PubMed Central

    Ramzan, Muhammad

    2015-01-01

    The present exploration discusses the influence of Newtonian heating on the magnetohydrodynamic (MHD) three dimensional couple stress nanofluid past a stretching surface. Viscous dissipation and Joule heating effects are also considered. Moreover, the nanofluid model includes the combined effects of thermophoresis and Brownian motion. Using an appropriate transformation, the governing non linear partial differential equations are converted into nonlinear ordinary differential equations. Series solutions using Homotopy Analysis method (HAM) are computed. Plots are presented to portrait the arising parameters in the problem. It is seen that an increase in conjugate heating parameter results in considerable increase in the temperature profile of the stretching wall. Skin friction coefficient, local Nusselt and local Sherwood numbers tabulated and analyzed. Higher values of conjugate parameter, Thermophoresis parameter and Brownian motion parameter result in enhancement of temperature distribution. PMID:25874800

  4. Influence of Newtonian heating on three dimensional MHD flow of couple stress nanofluid with viscous dissipation and Joule heating.

    PubMed

    Ramzan, Muhammad

    2015-01-01

    The present exploration discusses the influence of Newtonian heating on the magnetohydrodynamic (MHD) three dimensional couple stress nanofluid past a stretching surface. Viscous dissipation and Joule heating effects are also considered. Moreover, the nanofluid model includes the combined effects of thermophoresis and Brownian motion. Using an appropriate transformation, the governing non linear partial differential equations are converted into nonlinear ordinary differential equations. Series solutions using Homotopy Analysis method (HAM) are computed. Plots are presented to portrait the arising parameters in the problem. It is seen that an increase in conjugate heating parameter results in considerable increase in the temperature profile of the stretching wall. Skin friction coefficient, local Nusselt and local Sherwood numbers tabulated and analyzed. Higher values of conjugate parameter, Thermophoresis parameter and Brownian motion parameter result in enhancement of temperature distribution.

  5. Simultaneous effects of slip and wall properties on MHD peristaltic motion of nanofluid with Joule heating

    NASA Astrophysics Data System (ADS)

    Hayat, T.; Nisar, Z.; Ahmad, B.; Yasmin, H.

    2015-12-01

    This paper is devoted to the magnetohydrodynamic (MHD) peristaltic transport of nanofluid in a channel with wall properties. Flow analysis is addressed in the presence of viscous dissipation, partial slip and Joule heating effects. Mathematical modelling also includes the salient features of Brownian motion and thermophoresis. Both analytic and numerical solutions are provided. Comparison between the solutions is shown in a very good agreement. Attention is focused to the Brownian motion parameter, thermophoresis parameter, Hartman number, Eckert number and Prandtl number. Influences of various parameters on skin friction coefficient, Nusselt and Sherwood numbers are also investigated. It is found that both the temperature and nanoparticles concentration are increasing functions of Brownian motion and thermophoresis parameters.

  6. Ozone generation by negative corona discharge: the effect of Joule heating

    NASA Astrophysics Data System (ADS)

    Yanallah, K.; Pontiga, F.; Fernández-Rueda, A.; Castellanos, A.; Belasri, A.

    2008-10-01

    Ozone generation in pure oxygen using a wire-to-cylinder corona discharge reactor is experimentally and numerically investigated. Ozone concentration is determined by means of direct UV spectroscopy and the effects of Joule heating and ozone decomposition on the electrodes are analysed for different discharge gaps. The numerical model combines the physical processes in the corona discharge with the chemistry of ozone formation and destruction. The chemical kinetics model and the electrical model are coupled through Poisson's equation, and the current-voltage (CV) characteristic measured in experiments is used as input data to the numerical simulation. The numerical model is able to predict the radial distributions of electrons, ions, atoms and molecules for each applied voltage of the CV characteristic. In particular, the evolution of ozone density inside the discharge cell has been investigated as a function of current intensity and applied voltage.

  7. The role of Joule heating in the formation of nanogaps by electromigration

    NASA Astrophysics Data System (ADS)

    Trouwborst, M. L.; van der Molen, S. J.; van Wees, B. J.

    2006-06-01

    We investigate the formation of nanogaps in gold wires due to electromigration. We show that the breaking process will not start until a local temperature of typically 400 K is reached by Joule heating. This value is rather independent of the temperature of the sample environment (4.2-295 K). Furthermore, we demonstrate that the breaking dynamics can be controlled by minimizing the total series resistance of the system. In this way, the local temperature rise just before breakdown is limited and melting effects are prevented. Hence, electrodes with gaps <2 nm are easily made, without the need of active feedback. For optimized samples, we observe quantized conductance steps prior to the gap formation.

  8. The voltage limitation for phase coherence experiments: non-equilibrium effects versus Joule heating

    NASA Astrophysics Data System (ADS)

    Linke, H.; Omling, P.; Xu, Hongqi; Lindelof, P. E.

    1996-12-01

    The breaking of phase coherence of electrons by a finite bias voltage is studied in a quasi-one-dimensional electron gas. Although the wire is longer than the energy relaxation length we find that Joule heating in the wire is not important for dephasing of non-equilibrium electrons. Instead, phase breaking occurs by electron-electron interaction due to the excess energy of the injected electrons with respect to the Fermi energy. The relevant limiting parameter for phase coherence is, therefore, the bias voltage, rather than the dissipated power. A model calculation suggests that our results are of general relevance for coherence experiments in one-dimensional geometry on length scales of the same order of magnitude as the energy relaxation length.

  9. Thermomigration in Pb-Sn solder joints under joule heating during electric current stressing

    NASA Astrophysics Data System (ADS)

    Ye, Hua; Basaran, Cemal; Hopkins, Douglas

    2003-02-01

    Electromigration of solder joint under high dc current density is known as a reliability concern for the future high-density flip chip packaging and power packaging. Biased mass diffusion within solder joint from cathode to anode under high dc current density is observed in these experiments. In this letter, the experiments on flip chip solder joints under dc current stressing are conducted and thermomigration due to the thermal gradient in the solder joint caused by joule heating is reported. A three-dimensional coupled electric thermal finite-element (FE) simulation of a realistic flip chip module shows the existence of thermal gradient in the solder joint which is high enough to trigger thermomigration.

  10. In situ monitoring of Joule heating effects in germanium nanowires by μ-Raman spectroscopy.

    PubMed

    Lugstein, Alois; Mijić, Mario; Burchhart, Thomas; Zeiner, Clemens; Langegger, Rupert; Schneider, Michael; Schmid, Ulrich; Bertagnolli, Emmerich

    2013-02-15

    We explored a noninvasive optical method to determine the Joule heating of individual germanium nanowires. Using confocal μ-Raman spectroscopy, variations in the optical phonon frequency, in detail the downshifting of the first-order Stokes Raman band, are correlated to the temperature increase of vapor-liquid-solid grown germanium nanowires under an applied electrical bias. The germanium nanowires were found to handle high threshold current densities of more than 10(6) A cm(-2) before sustaining immediate deterioration. Failure of single crystalline germanium nanowires was directly observed when the applied electric field reached the breakdown point of 1.25 × 10(5) V cm(-1).

  11. Composites of Graphene Nanoribbon Stacks and Epoxy for Joule Heating and Deicing of Surfaces.

    PubMed

    Raji, Abdul-Rahman O; Varadhachary, Tanvi; Nan, Kewang; Wang, Tuo; Lin, Jian; Ji, Yongsung; Genorio, Bostjan; Zhu, Yu; Kittrell, Carter; Tour, James M

    2016-02-10

    A conductive composite of graphene nanoribbon (GNR) stacks and epoxy is fabricated. The epoxy is filled with the GNR stacks, which serve as a conductive additive. The GNR stacks are on average 30 nm thick, 250 nm wide, and 30 μm long. The GNR-filled epoxy composite exhibits a conductivity >100 S/m at 5 wt % GNR content. This permits application of the GNR-epoxy composite for deicing of surfaces through Joule (voltage-induced) heating generated by the voltage across the composite. A power density of 0.5 W/cm(2) was delivered to remove ∼1 cm-thick (14 g) monolith of ice from a static helicopter rotor blade surface in a -20 °C environment.

  12. Numerical analysis of the electrical failure of a metallic nanowire mesh due to Joule heating.

    PubMed

    Li, Yuan; Tsuchiya, Kaoru; Tohmyoh, Hironori; Saka, Masumi

    2013-08-30

    To precisely examine the electrical failure behavior of a metallic nanowire mesh induced by Joule heating (i.e., melting), a previously developed numerical method was modified with regard to the maximum temperature in the mesh and the electrical resistivity of the nanowire. A sample case of an Ag nanowire mesh under specific working conditions was analyzed with highly accurate numerical results. By monitoring the temperature in the mesh, the current required to trigger the melting of a mesh segment (i.e., the melting current) could be obtained. The melting process of a mesh equipped with a current source during actual operation was predicted on the basis of the obtained relationship between the melting current and the corresponding melting voltage in the numerical melting process. Local unstable and stable melting could be precisely identified for both the current-controlled and voltage-controlled current sources in the present example.

  13. Consistent melting behavior induced by Joule heating between Ag microwire and nanowire meshes.

    PubMed

    Tsuchiya, Kaoru; Li, Yuan; Saka, Masumi

    2014-01-01

    The melting behavior of an Ag microwire mesh induced by Joule heating was numerically investigated and compared with that of the corresponding Ag nanowire mesh with the same structure but different geometrical and physical properties of the wire itself. According to the relationship of melting current and melting voltage during the melting process, a similar repetitive zigzag pattern in melting behavior was discovered in both meshes. On this basis, a dimensionless parameter defined as figure of merit was proposed to characterize the current-carrying ability of the mesh. The consistent feature of figure of merit in both meshes indicates that the melting behavior of the Ag nanowire mesh can be predicted from the present results of the corresponding Ag microwire mesh with the same structure but made from a different wire (e.g., different size, different material) through simple conversion. The present findings can provide fundamental insight into the reliability analysis on the metallic nanowire mesh-based transparent conductive electrode.

  14. Nanoscale Dynamics of Joule heating and Bubble Nucleation in a Solid-State Nanopore

    PubMed Central

    Levine, Edlyn V.; Burns, Michael M.; Golovchenko, Jene A.

    2016-01-01

    We present a mathematical model for Joule heating of an electrolytic solution in a nanopore. The model couples the electrical and thermal dynamics responsible for rapid and extreme superheating of the electrolyte within the nanopore. The model is implemented numerically with a finite element calculation, yielding a time and spatially resolved temperature distribution in the nanopore region. Temperatures near the thermodynamic limit of superheat are predicted to be attained just before the explosive nucleation of a vapor bubble is observed experimentally. Knowledge of this temperature distribution enables the evaluation of related phenomena including bubble nucleation kinetics, relaxation oscillation, and bubble dynamics. PACS numbers 47.55.dp, 47.55.db, 85.35.-p, 05.70Fh PMID:26871171

  15. Joule heating induced transient temperature field and its effects on electroosmosis in a microcapillary packed with microspheres.

    PubMed

    Kang, Y; Yang, C; Huang, X

    2005-08-02

    The Joule heating induced transient temperature field and its effect on the electroosmotic flow in a capillary packed with microspheres is analyzed numerically using the control-volume-based finite difference method. The model incorporates the coupled momentum equation for the electroosmotic velocity, the energy equations for the Joule heating induced temperature distributions in both the packed column and the capillary wall, and the mass and electric current continuity equations. The temperature-dependent physical properties of the electrolyte solution are taken into consideration. The characteristics of the Joule heating induced transient development of temperature and electroosmotic flow fields are studied. Specifically, the simulation shows that the presence of Joule heating causes a noticeable axial temperature gradient in the thermal entrance region and elevates a significant temperature increment inside the microcapillary. The temperature changes in turn greatly affect the electroosmotic velocity by means of the temperature-dependent fluid viscosity, dielectric constant, and local electric field strength. Furthermore, the model predicts an induced pressure gradient to counterbalance the axial variation of the electroosmotic velocity so as to maintain the fluid mass continuity. In addition, under specific conditions, the present model is validated by comparing with the existing analytical model and experimental data from the literature.

  16. Efficiency and output power of thermoelectric module by taking into account corrected Joule and Thomson heat

    NASA Astrophysics Data System (ADS)

    Kim, Hee Seok; Liu, Weishu; Ren, Zhifeng

    2015-09-01

    The maximum conversion efficiency of a thermoelectric module composed of p- and n-type materials has been widely calculated using a constant property model since the 1950s, but this conventional model is only valid in limited conditions and no Thomson heat is accounted for. Since Thomson heat causes the efficiency under- or over-rated depending on the temperature dependence of Seebeck coefficient, it cannot be ignored especially in large temperature difference between the hot and cold sides. In addition, incorrect Joule heat is taken into consideration for heat flux evaluation of a thermoelectric module at thermal boundaries due to the assumption of constant properties in the conventional model. For this reason, more practical predictions for efficiency and output power and its corresponding optimum conditions of p- and n-type materials need to be revisited. In this study, generic formulae are derived based on a cumulative temperature dependence model including Thomson effect. The formulae reliably predict the maximum efficiency and output power of a thermoelectric module at a large temperature.

  17. Using an empirical model of Joule heating in thermosphere-ionosphere coupled models

    NASA Astrophysics Data System (ADS)

    Weimer, Daniel

    The interaction of the solar wind and the embedded Interplanetary Magnetic Field (IMF) with the Earth's magnetic field produces auroral currents that heat the ionosphere at high-latitudes. Coupling between the ionosphere and thermosphere results in significant heating of the ther-mosphere. During major geomagnetic storms the temperature changes in the thermosphere are significant, causing the neutral atmosphere to expand upward, which in turn causes satellites in low-Earth orbit to experience a higher drag force and decreased orbital velocity. There is a real need to model and predict these variations in the thermosphere. The Weimer 2005 model of ionospheric electric potentials and field-aligned currents can be used to help solve this problem. This presentation will describe the model and how it derives the ionospheric Joule heating rates. Comparisons with neutral density derived from CHAMP and GRACE satellite measurements will also be shown. This comparison is facilitated through use of the "global nighttime minimum exospheric temperature" (Tc) in the Jacchia-Bowman 2008 (JB2008) model. It is shown that the empirical model of auroral heating can be used to quite accurately predict orbit-averaged perturbations to Tc as a function of time, given measurements of the IMF. The empirical model can also be used as a driver in physics-based, numerical Thermosphere-Ionosphere Coupled Models; present and future uses in such programs will be covered.

  18. Joule heating a palladium nanowire sensor for accelerated response and recovery to hydrogen gas.

    PubMed

    Yang, Fan; Taggart, David K; Penner, Reginald M

    2010-07-05

    The properties of a single heated palladium (Pd) nanowire for the detection of hydrogen gas (H(2)) are explored. In these experiments, a Pd nanowire, 48-98 microm in length, performs three functions in parallel: 1) Joule self-heating is used to elevate the nanowire temperature by up to 128 K, 2) the 4-contact wire resistance in the absence of H(2) is used to measure its temperature, and 3) the nanowire resistance in the presence of H(2) is correlated with its concentration, allowing it to function as a H(2) sensor. Compared with the room-temperature response of a Pd nanowire, the response of the heated nanowire to hydrogen is altered in two ways: First, the resistance change (DeltaR/R(0)) induced by H(2) exposure at any concentration is reduced by a factor of up to 30 and second, the rate of the resistance change - observed at the beginning ("response") and at the end ("recovery") of a pulse of H(2) - is increased by more than a factor of 50 at some H(2) concentrations. Heating nearly eliminates the retardation of response and recovery seen from 1-2% H(2), caused by the alpha --> beta phase transition of PdH(x), a pronounced effect for nanowires at room temperature. The activation energies associated with sensor response and recovery are measured and interpreted.

  19. MHD Stagnation-Point Flow and Heat Transfer with Effects of Viscous Dissipation, Joule Heating and Partial Velocity Slip

    NASA Astrophysics Data System (ADS)

    Mat Yasin, Mohd Hafizi; Ishak, Anuar; Pop, Ioan

    2015-12-01

    The steady two-dimensional stagnation-point flow and heat transfer past a permeable stretching/shrinking sheet with effects of viscous dissipation, Joule heating and partial velocity slip in the presence of a magnetic field is investigated. The partial differential equations are reduced to nonlinear ordinary differential equations by using a similarity transformation, before being solved numerically by shooting technique. Results indicate that the skin friction coefficient and the local Nusselt number increase as magnetic parameter increases. It is found that for the stretching sheet the solution is unique while for the shrinking sheet there exist nonunique solutions (dual solutions) in certain range of parameters. The stability analysis shows that the upper branch solution is stable while the lower branch solution is unstable.

  20. MHD Stagnation-Point Flow and Heat Transfer with Effects of Viscous Dissipation, Joule Heating and Partial Velocity Slip

    PubMed Central

    Mat Yasin, Mohd Hafizi; Ishak, Anuar; Pop, Ioan

    2015-01-01

    The steady two-dimensional stagnation-point flow and heat transfer past a permeable stretching/shrinking sheet with effects of viscous dissipation, Joule heating and partial velocity slip in the presence of a magnetic field is investigated. The partial differential equations are reduced to nonlinear ordinary differential equations by using a similarity transformation, before being solved numerically by shooting technique. Results indicate that the skin friction coefficient and the local Nusselt number increase as magnetic parameter increases. It is found that for the stretching sheet the solution is unique while for the shrinking sheet there exist nonunique solutions (dual solutions) in certain range of parameters. The stability analysis shows that the upper branch solution is stable while the lower branch solution is unstable. PMID:26647651

  1. MHD Stagnation-Point Flow and Heat Transfer with Effects of Viscous Dissipation, Joule Heating and Partial Velocity Slip.

    PubMed

    Yasin, Mohd Hafizi Mat; Ishak, Anuar; Pop, Ioan

    2015-12-09

    The steady two-dimensional stagnation-point flow and heat transfer past a permeable stretching/shrinking sheet with effects of viscous dissipation, Joule heating and partial velocity slip in the presence of a magnetic field is investigated. The partial differential equations are reduced to nonlinear ordinary differential equations by using a similarity transformation, before being solved numerically by shooting technique. Results indicate that the skin friction coefficient and the local Nusselt number increase as magnetic parameter increases. It is found that for the stretching sheet the solution is unique while for the shrinking sheet there exist nonunique solutions (dual solutions) in certain range of parameters. The stability analysis shows that the upper branch solution is stable while the lower branch solution is unstable.

  2. Transmission electron microscopy assisted in-situ joule heat dissipation study of individual InAs nanowires

    SciTech Connect

    Xu, T. T.; Wei, X. L. E-mail: qingchen@pku.edu.cn; Shu, J. P.; Chen, Q. E-mail: qingchen@pku.edu.cn

    2013-11-04

    Managing heat transport at nanoscale is an important and challenging task for nanodevice applications and nanostructure engineering. Herein, through in-situ engineering nanowire (NW)-electrode contacts with electron beam induced carbon deposition in a transmission electron microscope, Joule heat dissipation along individual suspended Indium Arsenide NWs is well managed to obtain pre-designed temperature profiles along NWs. The temperature profiles are experimentally determined by the breakdown site of NWs under Joule heating and breakdown temperature measurement. A model with NW-electrode contacts being well considered is proposed to describe heat transport along a NW. By fitting temperature profiles with the model, thermal conductance at NW-electrode contacts is obtained. It is found that, the temperature profile along a specific NW is mainly governed by the relative thermal conductance at the two NW-electrode contacts, which is engineered in experiments.

  3. Joule heating monitoring in a microfluidic channel by observing the Brownian motion of an optically trapped microsphere.

    PubMed

    Brans, Toon; Strubbe, Filip; Schreuer, Caspar; Vandewiele, Stijn; Neyts, Kristiaan; Beunis, Filip

    2015-09-01

    Electric fields offer a variety of functionalities to Lab-on-a-Chip devices. The use of these fields often results in significant Joule heating, affecting the overall performance of the system. Precise knowledge of the temperature profile inside a microfluidic device is necessary to evaluate the implications of heat dissipation. This article demonstrates how an optically trapped microsphere can be used as a temperature probe to monitor Joule heating in these devices. The Brownian motion of the bead at room temperature is compared with the motion when power is dissipated in the system. This gives an estimate of the temperature increase at a specific location in a microfluidic channel. We demonstrate this method with solutions of different ionic strengths, and establish a precision of 0.9 K and an accuracy of 15%. Furthermore, it is demonstrated that transient heating processes can be monitored with this technique, albeit with a limited time resolution.

  4. Influence of radiation on MHD peristaltic blood flow through a tapered channel in presence of slip and joule heating

    NASA Astrophysics Data System (ADS)

    Ahamad, N. Ameer; Ravikumar, S.; Govindaraju, Kalimuthu

    2017-07-01

    The aim of the present attempt was to investigate an effect of slip and joule heating on MHD peristaltic Newtonian fluid through an asymmetric vertical tapered channel under influence of radiation. The Mathematical modeling is investigated by utilizing long wavelength and low Reynolds number assumptions. The effects of Hartmann number, porosity parameter, volumetric flow rate, radiation parameter, non uniform parameter, shift angle, Prandtl number, Brinkman number, heat source/sink parameter on temperature characteristics are presented graphically and discussed in detail.

  5. Combating Frosting with Joule-Heated Liquid-Infused Superhydrophobic Coatings.

    PubMed

    Elsharkawy, Mohamed; Tortorella, Domenico; Kapatral, Shreyas; Megaridis, Constantine M

    2016-05-03

    Frost formation is omnipresent when suitable environmental conditions are met. A good portion of research on combating frost formation has revolved around the passive properties of superhydrophobic (SHPO) and slippery lubricant-impregnated porous (SLIP) surfaces. Despite much progress, the need for surfaces that can effectively combat frost formation over prolonged periods still remains. In this work, we report, for the first time, the use of electrically conductive SHPO/SLIP surfaces for active mitigation of frost formation. First, we demonstrate the failure of these surfaces to passively avert prolonged (several hours) frosting. Next, we make use of their electroconductive property for active Joule heating, which results in the removal of any formed frost. We study the role of the impregnating lubricant in the heat transfer across the interface, the surface, and the ambient. We show that, even though the thermal properties of the impregnating lubricant may vary drastically, the lubricant type does not noticeably affect the defrosting behavior of the surface. We attribute this outcome to the dominant thermal resistance of the thick frost layer formed on the cooled surface. We support this claim by drawing parallels between the present system and heat transfer through a one-dimensional (1D) composite medium, and solving the appropriate transient transport equations. Lastly, we propose periodic thermal defrosting for averting frost formation altogether. This methodology utilizes the coating's passive repellent capabilities, while eliminating the dominant effect of thick deposited frost layers. The periodic heating approach takes advantage of lubricants with higher thermal conductivities, which effectively enhance heat transfer through the porous multiphase surface that forms the first line of defense against frosting.

  6. James Joule and meteors

    NASA Astrophysics Data System (ADS)

    Hughes, David W.

    1989 was the hundredth anniversary of the death of James Prescott Joule, the Prescott being his mother's family name and the Joule, rhyming with cool, originating from the Derbyshire village of Youlgreave. Joule is rightly famous for his experimental efforts to establish the law of conservation of energy, and for the fact that J, the symbol known as the mechanical equivalent of heat, is named after him. Astronomically his "light has been hidden under a bushel". James Joule had a major influence on the physics of meteors.

  7. Joule-Heated Molten Regolith Electrolysis Reactor Concepts for Oxygen and Metals Production on the Moon and Mars

    NASA Technical Reports Server (NTRS)

    Sibille, Laurent; Dominguez, Jesus A.

    2012-01-01

    The technology of direct electrolysis of molten lunar regolith to produce oxygen and molten metal alloys has progressed greatly in the last few years. The development of long-lasting inert anodes and cathode designs as well as techniques for the removal of molten products from the reactor has been demonstrated. The containment of chemically aggressive oxide and metal melts is very difficult at the operating temperatures ca. 1600 C. Containing the molten oxides in a regolith shell can solve this technical issue and can be achieved by designing a Joule-heated (sometimes called 'self-heating') reactor in which the electrolytic currents generate enough Joule heat to create a molten bath. Solutions obtained by multiphysics modeling allow the identification of the critical dimensions of concept reactors.

  8. Effect of concurrent joule heat and charge trapping on RESET for NbAlO fabricated by atomic layer deposition

    PubMed Central

    2013-01-01

    The RESET process of NbAlO-based resistive switching memory devices fabricated by atomic layer deposition is investigated at low temperatures from 80 to 200 K. We observed that the conduction mechanism of high resistance state changed from hopping conduction to Frenkel-Poole conduction with elevated temperature. It is found that the conductive filament rupture in RRAM RESET process can be attributed not only to the Joule heat generated by internal current flow through a filament but also to the charge trap/detrapping effect. The RESET current decreases upon heating. Meanwhile, the energy consumption also decreases exponentially. This phenomenon indicates the temperature-related charge trap/detrapping process which contributes to the RESET besides direct Joule heat. PMID:23421401

  9. Effect of concurrent joule heat and charge trapping on RESET for NbAlO fabricated by atomic layer deposition.

    PubMed

    Zhou, Peng; Ye, Li; Sun, Qing Qing; Wang, Peng Fei; Jiang, An Quan; Ding, Shi Jin; Zhang, David Wei

    2013-02-19

    The RESET process of NbAlO-based resistive switching memory devices fabricated by atomic layer deposition is investigated at low temperatures from 80 to 200 K. We observed that the conduction mechanism of high resistance state changed from hopping conduction to Frenkel-Poole conduction with elevated temperature. It is found that the conductive filament rupture in RRAM RESET process can be attributed not only to the Joule heat generated by internal current flow through a filament but also to the charge trap/detrapping effect. The RESET current decreases upon heating. Meanwhile, the energy consumption also decreases exponentially. This phenomenon indicates the temperature-related charge trap/detrapping process which contributes to the RESET besides direct Joule heat.

  10. Polar thermospheric Joule heating, and redistribution of recombination energy in the upper mesosphere

    NASA Technical Reports Server (NTRS)

    Mayr, H. G.; Harris, I.; Dube, M.

    1990-01-01

    Kellogg (1961), suggested that transport of atomic oxygen from the summer into the winter hemisphere and subsequent release of energy by three body recombination, O+O+N2 yields O2+N2+E, may contribute significantly to the so-called mesopause temperature anomaly. Earlier model calculations have shown that Kellogg's mechanism produces about a 10-percent increase in the temperature from summer to winter at 90 km. This process, however, is partly compensated by differential heating from absorption of UV radiation associated with dissociation of O2. In the auroral region of the thermosphere, there is a steady energy dissipation by Joule heating causing a redistribution and depletion of atomic oxygen due to wind-induced diffusion. With the removal of O, latent chemical energy normally released by three body recombination is also removed, and the result is that the temperature decreases by almost 2 percent near 90 km. Through dynamic feedback, this process reduces the depletion of atomic oxygen by about 25 percent and the temperature perturbation in the exosphere from 10 to 7 percent at polar latitudes. Under the influence of the internal dynamo interaction, the prevailing zonal circulation in the upper thermosphere changes direction when the redistribution of recombination energy is considered.

  11. Joule heat-induced breakdown of organic thin-film devices under pulse operation

    NASA Astrophysics Data System (ADS)

    Yoshida, Kou; Matsushima, Toshinori; Shiihara, Yu; Kuwae, Hiroyuki; Mizuno, Jun; Adachi, Chihaya

    2017-05-01

    We investigated the influence of the substrate's thermal conductivities (k) and the widths of the electrical pulses (τpulse) on the maximum current densities (Jmax) in organic thin-film devices. We also estimated the temperature rise (ΔT) inside devices under the pulse operation using numerical calculations to interpret the observed differences in Jmax. For a long τpulse of 5 μs, Jmax is higher for devices with high-k sapphire substrates (around 1.2 kA/cm2) than devices with low-k plastic substrates (around 0.4 kA/cm2). This is because high-k sapphire substrates can work as heat sinks to relax ΔT for such a long τpulse. Operation of devices with high-k sapphire substrates for a short τpulse of 70 ns resulted in further relaxation of ΔT, leading to an increase of Jmax to around 5 kA/cm2. Interestingly, for such a short τpulse, devices with high-k sapphire and low-k plastic substrates showed similar Jmax and ΔT values, the reason for which may be that it is difficult for the generated Joule heat to travel to the substrate across a low-k organic layer within this short time.

  12. Polar thermospheric Joule heating, and redistribution of recombination energy in the upper mesosphere

    NASA Technical Reports Server (NTRS)

    Mayr, H. G.; Harris, I.; Dube, M.

    1990-01-01

    Kellogg (1961), suggested that transport of atomic oxygen from the summer into the winter hemisphere and subsequent release of energy by three body recombination, O+O+N2 yields O2+N2+E, may contribute significantly to the so-called mesopause temperature anomaly. Earlier model calculations have shown that Kellogg's mechanism produces about a 10-percent increase in the temperature from summer to winter at 90 km. This process, however, is partly compensated by differential heating from absorption of UV radiation associated with dissociation of O2. In the auroral region of the thermosphere, there is a steady energy dissipation by Joule heating causing a redistribution and depletion of atomic oxygen due to wind-induced diffusion. With the removal of O, latent chemical energy normally released by three body recombination is also removed, and the result is that the temperature decreases by almost 2 percent near 90 km. Through dynamic feedback, this process reduces the depletion of atomic oxygen by about 25 percent and the temperature perturbation in the exosphere from 10 to 7 percent at polar latitudes. Under the influence of the internal dynamo interaction, the prevailing zonal circulation in the upper thermosphere changes direction when the redistribution of recombination energy is considered.

  13. Local and transient structural changes in stratum corneum at high electric fields: contribution of Joule heating.

    PubMed

    Pliquett, U; Gallo, S; Hui, S W; Gusbeth, Ch; Neumann, E

    2005-09-01

    Electroporation of skin is accompanied by local heating, such that thermally induced structural changes of the stratum corneum (SC) accompany the field effect. Comparing on the time scale, the local changes in structure, temperature and conductance of the SC, during and after the pulse, it is seen that Joule heating also facilitates the subsequent molecular transport. It is found that the transport of medium-sized, ionic molecules occurs through localized transport regions (LTR). The size of a LTR increases with the pulse length, whereas the density of the LTRs increases with increasing voltage, for instance at U(SC=)80 V, the LTR cover approximately 0.02--1% of the surface area. The state of low resistance within the LTR is long-lived. During high voltage application, the center of the LTR is heated above the phase transition temperature of the SC lipids (70 degrees C) and the heat front propagates outwards. Inside the SC, the pulse causes aggregates of small-sized vesicles. At a higher temperature, the aggregate formation and their disappearance are delayed. Multiple pulses with the applied voltage of U(appl)=80 V induce the formation of long-lasting vesicle aggregates with a diameter of slashed circle=1--30 microm, covering 0.05--0.5% of the total sample area. The electric energy dissipated within the LTR during high voltage application is apparently sufficient to raise the temperature well above the phase transition temperature of the lipids of the SC, accounting for the conformational changes from the multi-lamella to the vesicular structures.

  14. Joule-heated graphene-wrapped sponge enables fast clean-up of viscous crude-oil spill.

    PubMed

    Ge, Jin; Shi, Lu-An; Wang, Yong-Chao; Zhao, Hao-Yu; Yao, Hong-Bin; Zhu, Yin-Bo; Zhang, Ye; Zhu, Hong-Wu; Wu, Heng-An; Yu, Shu-Hong

    2017-04-03

    The clean-up of viscous crude-oil spills is a global challenge. Hydrophobic and oleophilic oil sorbents have been demonstrated as promising candidates for oil-spill remediation. However, the sorption speeds of these oil sorbents for viscous crude oil are rather limited. Herein we report a Joule-heated graphene-wrapped sponge (GWS) to clean-up viscous crude oil at a high sorption speed. The Joule heat of the GWS reduced in situ the viscosity of the crude oil, which prominently increased the oil-diffusion coefficient in the pores of the GWS and thus speeded up the oil-sorption rate. The oil-sorption time was reduced by 94.6% compared with that of non-heated GWS. Besides, the oil-recovery speed was increased because of the viscosity decrease of crude oil. This in situ Joule self-heated sorbent design will promote the practical application of hydrophobic and oleophilic oil sorbents in the clean-up of viscous crude-oil spills.

  15. A parameter governing the melting induced at the micrometer level in a dissimilar metal wire system by Joule heating

    NASA Astrophysics Data System (ADS)

    Tohmyoh, Hironori; Sunagawa, Takuya

    2015-06-01

    In this paper, we deal with the phenomenon of melting at the point of contact between dissimilar metals by Joule heating. A heat conduction model for this dissimilar metal wire system is considered and the current required to sever the wire system by Joule heating is determined. The position at which the wire system severs depends on the ratio of the lengths of the two wires. Whereas this dependency is discontinuous, the current required to sever the wire is found to be continuous with respect to the ratio of the wire lengths, and the behaviors of the position and the current for severing the wire system are found to be classified into three regions. Based on these findings, a parameter that governs the melting phenomenon at the micrometer level for different ratios of wire lengths is proposed. Attempts were made to weld 25 μm thick Cu and Al wires of various lengths together by Joule heating. Moreover, the conditions for stably welding dissimilar metal wires together can be found quantitatively using the parameter proposed in this paper. It is noted that the welding condition described by the proposed parameter is independent with respect to the ratio of the lengths of the two wires in the respective regions.

  16. Joule-heated graphene-wrapped sponge enables fast clean-up of viscous crude-oil spill

    NASA Astrophysics Data System (ADS)

    Ge, Jin; Shi, Lu-An; Wang, Yong-Chao; Zhao, Hao-Yu; Yao, Hong-Bin; Zhu, Yin-Bo; Zhang, Ye; Zhu, Hong-Wu; Wu, Heng-An; Yu, Shu-Hong

    2017-05-01

    The clean-up of viscous crude-oil spills is a global challenge. Hydrophobic and oleophilic oil sorbents have been demonstrated as promising candidates for oil-spill remediation. However, the sorption speeds of these oil sorbents for viscous crude oil are rather limited. Herein we report a Joule-heated graphene-wrapped sponge (GWS) to clean-up viscous crude oil at a high sorption speed. The Joule heat of the GWS reduced in situ the viscosity of the crude oil, which prominently increased the oil-diffusion coefficient in the pores of the GWS and thus speeded up the oil-sorption rate. The oil-sorption time was reduced by 94.6% compared with that of non-heated GWS. Besides, the oil-recovery speed was increased because of the viscosity decrease of crude oil. This in situ Joule self-heated sorbent design will promote the practical application of hydrophobic and oleophilic oil sorbents in the clean-up of viscous crude-oil spills.

  17. Heat, work and subtle fluids: a commentary on Joule (1850) ‘On the mechanical equivalent of heat’

    PubMed Central

    Young, John

    2015-01-01

    James Joule played the major role in establishing the conservation of energy, or the first law of thermodynamics, as a universal, all-pervasive principle of physics. He was an experimentalist par excellence and his place in the development of thermodynamics is unarguable. This article discusses Joule's life and scientific work culminating in the 1850 paper, where he presented his detailed measurements of the mechanical equivalent of heat using his famous paddle-wheel apparatus. Joule's long series of experiments in the 1840s leading to his realisation that the conservation of energy was probably of universal validity is discussed in context with the work of other pioneers, notably Sadi Carnot, who effectively formulated the principle of the second law of thermodynamics a quarter of a century before the first law was accepted. The story of Joule's work is a story of an uphill struggle against a critical scientific establishment unwilling to accept the mounting evidence until it was impossible to ignore. His difficulties in attracting funding and publishing in reputable journals despite the quality of his work will resonate with many young scientists and engineers of the present day. This commentary was written to celebrate the 350th anniversary of the journal Philosophical Transactions of the Royal Society. PMID:25750152

  18. Joule Heating-Induced Metal-Insulator Transition in Epitaxial VO2/TiO2 Devices.

    PubMed

    Li, Dasheng; Sharma, Abhishek A; Gala, Darshil K; Shukla, Nikhil; Paik, Hanjong; Datta, Suman; Schlom, Darrell G; Bain, James A; Skowronski, Marek

    2016-05-25

    DC and pulse voltage-induced metal-insulator transition (MIT) in epitaxial VO2 two terminal devices were measured at various stage temperatures. The power needed to switch the device to the ON-state decrease linearly with increasing stage temperature, which can be explained by the Joule heating effect. During transient voltage induced MIT measurement, the incubation time varied across 6 orders of magnitude. Both DC I-V characteristic and incubation times calculated from the electrothermal simulations show good agreement with measured values, indicating Joule heating effect is the cause of MIT with no evidence of electronic effects. The width of the metallic filament in the ON-state of the device was extracted and simulated within the thermal model.

  19. Joule-heating-supported plasma filamentation and branching during subcritical microwave irradiation

    NASA Astrophysics Data System (ADS)

    Takahashi, Masayuki; Kageyama, Yoshiaki; Ohnishi, Naofumi

    2017-05-01

    Breakdown physics induced by a subcritical microwave was numerically reproduced by using a two-dimensional effective diffusion model for plasma transport and combining it with Maxwell's equations and a neutral gas dynamics equation. A discrete plasma structure was obtained when E0,rms/Ec ≧0.69 , where E0,rms is the root-mean-square of the incident electric field and Ec is the breakdown threshold, because an overcritical field that exceeded the breakdown threshold was formed in a region away from the bulk plasma by the wave reflection when the plasma reflectivity was increased by joule heating. However, a continuous plasma structure with a branching pattern was formed when E0,rms/Ec <0.69 because the enhanced electric-field region away from the bulk plasma never exceeded the breakdown threshold even when the plasma reflectivity increased. The propagation speed of the plasma front drastically decreased when E0,rms/Ec <0.69 because the plasma propagation was sustained by strong gas expansion, which required more time than wave-reflection and ionization processes.

  20. Effect of Joule heating in current-driven domain wall motion

    NASA Astrophysics Data System (ADS)

    Yamaguchi, A.; Nasu, S.; Tanigawa, H.; Ono, T.; Miyake, K.; Mibu, K.; Shinjo, T.

    2005-01-01

    It was found that high current density needed for the current-driven domain wall motion results in the Joule heating of the sample. The sample temperature, when the current-driven domain wall motion occurred, was estimated by measuring the sample resistance during the application of a pulsed current. The sample temperature was 750 K for the threshold current density of 6.7×1011A/m2 in a 10-nm-thick Ni81Fe19 wire with a width of 240 nm on thermally oxidized silicon substrate. The temperature was raised to 830 K for the current density of 7.5×1011A/m2, which is very close to the Curie temperature of bulk Ni81Fe19. When the current density exceeded 7.5×1011A/m2, an appearance of a multidomain structure in the wire was observed by magnetic force microscopy, suggesting that the sample temperature exceeded the Curie temperature.

  1. Precipitation and dissolution of Co granules in CuCo alloys: Reverse effects of Joule heating

    NASA Astrophysics Data System (ADS)

    da Silva, F. C. S.; Ferrari, E. F.; Knobel, M.

    1999-12-01

    Measurements of resistance R versus electrical current I were performed during annealing of melt-spun pure Cu and Cu90Co10 ribbons using linearly varying current Joule heating. Typical results of Cu90Co10 samples show three characteristic stages. For low applied currents (I<4.0 A), a metallic behavior is observed and compared with pure Cu samples. Precipitation is the dominant process for intermediate currents (5.0 A9.0 A). Competition between precipitation and dissolution of Co granules depends also on the cooling rates, and we observed that it is possible to freeze high temperature off-equilibrium configurations down to room temperature after an appropriate quenching. Experimental annealing conditions were simulated using the Monte Carlo-Metropolis method, with Kawasaki dynamics of diffusing atoms, to study the kinetics of transformations in the Cu-Co system. Simulations show that precipitation and re-solution competition occurs as functions of both temperature and time. A relationship between simulated Co atoms configuration and resistance measurements is made

  2. A dynamic molecular probe to investigate catalytic effects and Joule heating in enantioselective MEKC.

    PubMed

    Trapp, Oliver

    2007-02-01

    Enantiomerization of ferroin [tris(1,10-phenanthroline)-iron(II)-complex] was investigated by enantioselective dynamic micellar EKC. The enantiomer separation was performed in an aqueous 50 mM sodium borate/sodium dihydrogenphosphate buffer at pH 8.0 in the presence of the chiral surfactant sodium cholate. The unified equation of dynamic chromatography was employed to determine reaction rate constants from the electropherograms featured with distinct plateau formation. Activation parameters DeltaH( not equal) = 124.0 +/- 0.5 kJ/mol and DeltaS( not equal) = 121 +/- 1 J.K(-1)mol(-1) were calculated from temperature-dependent measurements between 10.0 and 27.5 degrees C in 2.5 K steps. Considering the data obtained by polarimetry of enantiomeric pure ferroin in water, it was found that enantiomerization rate in the micelle is accelerated by a factor of 12. Because of the highly positive activation entropy DeltaS( not equal), ferroin was used as a temperature-sensitive dynamic molecular probe to determine temperature deviations caused by Joule heating.

  3. Consistent melting behavior induced by Joule heating between Ag microwire and nanowire meshes

    PubMed Central

    2014-01-01

    The melting behavior of an Ag microwire mesh induced by Joule heating was numerically investigated and compared with that of the corresponding Ag nanowire mesh with the same structure but different geometrical and physical properties of the wire itself. According to the relationship of melting current and melting voltage during the melting process, a similar repetitive zigzag pattern in melting behavior was discovered in both meshes. On this basis, a dimensionless parameter defined as figure of merit was proposed to characterize the current-carrying ability of the mesh. The consistent feature of figure of merit in both meshes indicates that the melting behavior of the Ag nanowire mesh can be predicted from the present results of the corresponding Ag microwire mesh with the same structure but made from a different wire (e.g., different size, different material) through simple conversion. The present findings can provide fundamental insight into the reliability analysis on the metallic nanowire mesh-based transparent conductive electrode. PMID:24910578

  4. Probing charge trapping and joule heating in graphene field-effect transistors by transient pulsing

    NASA Astrophysics Data System (ADS)

    Ramamoorthy, H.; Somphonsane, R.; Radice, J.; He, G.; Nathawat, J.; Kwan, C.-P.; Zhao, M.; Bird, J. P.

    2017-08-01

    We use pulsed electrical studies to investigate the various processes that limit the current carrying capacity of graphene high frequency transistors. By investigating the transient response of these devices over a time scale that spans some twelve orders of magnitude, we identify the presence of four distinct processes that degrade the current: (1) charge injection into deep traps within the interior of the oxide; (2) Joule heating of the transistor substrate by hot carriers in the graphene channel; (3) equilibration of interfacial-state filling in response to voltage transients, and; (4) leakage of captured charge from the deep traps, once the pulsed voltage is removed. The time scale associated with these processes ranges from nanoseconds to hours, with process (1) being the fastest and process (4) the slowest. By pulsing the transistors on time intervals as short as a few nanoseconds, we therefore demonstrate how it is possible to obtain output characteristics from them that are essentially free from the influence of these different mechanisms. Under such conditions, the hot-carrier drift velocity is shown to saturate at the large values expected for intrinsic graphene. Beyond graphene, this approach of pulsed characterization of transistor performance should be broadly applicable to studies of other two-dimensional semiconductors, including transition-metal dichalcogenides, black phosphorous, silicene, and topological insulators.

  5. Joule heating effects on separation efficiency in capillary zone electrophoresis with an initial voltage ramp.

    PubMed

    Xuan, Xiangchun; Hu, Guoqing; Li, Dongqing

    2006-08-01

    An analytical model is developed to quantify the Joule heating effects on the separation efficiency in CZE with an initial voltage ramp. This model considers the temporal variations of nonuniform temperature and flow fields in the course of voltage ramping. The temperature dependence of electrical conductivity, dynamic viscosity, and mass density of the fluid is also taken into account. We demonstrate that the application of an initial voltage ramp delays the development of pressure-driven flows induced passively by the axial temperature gradients. The thermal dispersion is thus significantly reduced, resulting in a higher theoretical plate number in CZE. Such improvement in the separation efficiency is apparent in noncoated capillaries at high electric fields with an appropriate voltage ramp-up time. These predictions are consistent with previous observations in both aqueous and nonaqueous CZE that took place in uncoated capillaries. In coated capillaries where the EOF is suppressed, however, our model predicts a lower plate number in the presence of an initial voltage ramp.

  6. Influence of thermal radiation and Joule heating in the Eyring-Powell fluid flow with the Soret and Dufour effects

    NASA Astrophysics Data System (ADS)

    Hayat, T.; Ali, Sh.; Alsaedi, A.; Alsulami, H. H.

    2016-11-01

    A two-dimensional magnetohydrodynamic boundary layer flow of the Eyring-Powell fluid on a stretching surface in the presence of thermal radiation and Joule heating is analyzed. The Soret and Dufour effects are taken into account. Partial differential equations are reduced to a system of ordinary differential equations, and series solutions of the resulting system are derived. Velocity, temperature, and concentration profiles are obtained. The skin friction coefficient and the local Nusselt and Sherwood numbers are computed and analyzed.

  7. Hall current and Joule heating effects on peristaltic flow of viscous fluid in a rotating channel with convective boundary conditions

    NASA Astrophysics Data System (ADS)

    Hayat, Tasawar; Zahir, Hina; Alsaedi, Ahmed; Ahmad, Bashir

    The present article has been arranged to study the Hall current and Joule heating effects on peristaltic flow of viscous fluid in a channel with flexible walls. Both fluid and channel are in a state of solid body rotation. Convective conditions for heat transfer in the formulation are adopted. Viscous dissipation in energy expression is taken into account. Resulting differential systems after invoking small Reynolds number and long wavelength considerations are numerically solved. Runge-Kutta scheme of order four is implemented for the results of axial and secondary velocities, temperature and heat transfer coefficient. Comparison with previous limiting studies is shown. Outcome of new parameters of interest is analyzed.

  8. Using simultaneous particle and field observations on a low-altitude satellite to estimate Joule heat energy flow into the high-latitude ionosphere

    SciTech Connect

    Rich, F.J.; Gussenhoven, M.S.; Greenspan, M.E.

    1987-06-01

    This report describes the background, the algorithm for calculating, and the early results of a survey of the Joule heat deposited in the high-latitude ionosphere. The algorithm is based upon data obtained with the polar-orbiting DMSP/F7 spacecraft. A significant portion of the energy input to the high-latitude ionosphere and thermosphere is transmitted from the magnetosphere to the ionosphere via precipitation of electrons and ions and via Joule heat. Several earlier spacecraft of the Defense Meteorological Satellite Program (DMSP) have carried sensors to measure the particle contribution to the energy low. The contribution from the precipitating particles has been extensively surveyed and reported. The DMSP/F7 is the first spacecraft of this series to carry sensors that allow the measurement of parameters which can be used to calculate the Joule heat input. This report is the beginning of a survey of the Joule heat.

  9. Towards high concentration enhancement of microfluidic temperature gradient focusing of sample solutes using combined AC and DC field induced Joule heating.

    PubMed

    Ge, Zhengwei; Wang, Wei; Yang, Chun

    2011-04-07

    It is challenging to continuously concentrate sample solutes in microfluidic channels. We present an improved electrokinetic technique for enhancing microfluidic temperature gradient focusing (TGF) of sample solutes using combined AC and DC field induced Joule heating effects. The introduction of an AC electric field component services dual functions: one is to produce Joule heat for generating temperature gradient; the other is to suppress electroosmotic flow. Consequently the required DC voltages for achieving sample concentration by Joule heating induced TGF are reduced, thereby leading to smaller electroosmotic flow (EOF) and thus backpressure effects. As a demonstration, the proposed technique can lead to concentration enhancement of sample solutes of more than 2500-fold, which is much higher than the existing literature reported microfluidic concentration enhancement by utilizing the Joule heating induced TGF technique.

  10. Modified data analysis for thermal conductivity measurements of polycrystalline silicon microbridges using a steady state Joule heating technique.

    PubMed

    Sayer, Robert A; Piekos, Edward S; Phinney, Leslie M

    2012-12-01

    Accurate knowledge of thermophysical properties is needed to predict and optimize the thermal performance of microsystems. Thermal conductivity is experimentally determined by measuring quantities such as voltage or temperature and then inferring a thermal conductivity from a thermal model. Thermal models used for data analysis contain inherent assumptions, and the resultant thermal conductivity value is sensitive to how well the actual experimental conditions match the model assumptions. In this paper, a modified data analysis procedure for the steady state Joule heating technique is presented that accounts for bond pad effects including thermal resistance, electrical resistance, and Joule heating. This new data analysis method is used to determine the thermal conductivity of polycrystalline silicon (polysilicon) microbridges fabricated using the Sandia National Laboratories SUMMiT V™ micromachining process over the temperature range of 77-350 K, with the value at 300 K being 71.7 ± 1.5 W/(m K). It is shown that making measurements on beams of multiple lengths is useful, if not essential, for inferring the correct thermal conductivity from steady state Joule heating measurements.

  11. Modified data analysis for thermal conductivity measurements of polycrystalline silicon microbridges using a steady state Joule heating technique

    NASA Astrophysics Data System (ADS)

    Sayer, Robert A.; Piekos, Edward S.; Phinney, Leslie M.

    2012-12-01

    Accurate knowledge of thermophysical properties is needed to predict and optimize the thermal performance of microsystems. Thermal conductivity is experimentally determined by measuring quantities such as voltage or temperature and then inferring a thermal conductivity from a thermal model. Thermal models used for data analysis contain inherent assumptions, and the resultant thermal conductivity value is sensitive to how well the actual experimental conditions match the model assumptions. In this paper, a modified data analysis procedure for the steady state Joule heating technique is presented that accounts for bond pad effects including thermal resistance, electrical resistance, and Joule heating. This new data analysis method is used to determine the thermal conductivity of polycrystalline silicon (polysilicon) microbridges fabricated using the Sandia National Laboratories SUMMiT V™ micromachining process over the temperature range of 77-350 K, with the value at 300 K being 71.7 ± 1.5 W/(m K). It is shown that making measurements on beams of multiple lengths is useful, if not essential, for inferring the correct thermal conductivity from steady state Joule heating measurements.

  12. Rapid concentration of deoxyribonucleic acid via Joule heating induced temperature gradient focusing in poly-dimethylsiloxane microfluidic channel.

    PubMed

    Ge, Zhengwei; Wang, Wei; Yang, Chun

    2015-02-09

    This paper reports rapid microfluidic electrokinetic concentration of deoxyribonucleic acid (DNA) with the Joule heating induced temperature gradient focusing (TGF) by using our proposed combined AC and DC electric field technique. A peak of 480-fold concentration enhancement of DNA sample is achieved within 40s in a simple poly-dimethylsiloxane (PDMS) microfluidic channel of a sudden expansion in cross-section. Compared to a sole DC field, the introduction of an AC field can reduce DC field induced back-pressure and produce sufficient Joule heating effects, resulting in higher concentration enhancement. Within such microfluidic channel structure, negative charged DNA analytes can be concentrated at a location where the DNA electrophoretic motion is balanced with the bulk flow driven by DC electroosmosis under an appropriate temperature gradient field. A numerical model accounting for a combined AC and DC field and back-pressure driven flow effects is developed to describe the complex Joule heating induced TGF processes. The experimental observation of DNA concentration phenomena can be explained by the numerical model.

  13. Thermodynamic optimization of mixed refrigerant Joule- Thomson systems constrained by heat transfer considerations

    NASA Astrophysics Data System (ADS)

    Hinze, J. F.; Klein, S. A.; Nellis, G. F.

    2015-12-01

    Mixed refrigerant (MR) working fluids can significantly increase the cooling capacity of a Joule-Thomson (JT) cycle. The optimization of MRJT systems has been the subject of substantial research. However, most optimization techniques do not model the recuperator in sufficient detail. For example, the recuperator is usually assumed to have a heat transfer coefficient that does not vary with the mixture. Ongoing work at the University of Wisconsin-Madison has shown that the heat transfer coefficients for two-phase flow are approximately three times greater than for a single phase mixture when the mixture quality is between 15% and 85%. As a result, a system that optimizes a MR without also requiring that the flow be in this quality range may require an extremely large recuperator or not achieve the performance predicted by the model. To ensure optimal performance of the JT cycle, the MR should be selected such that it is entirely two-phase within the recuperator. To determine the optimal MR composition, a parametric study was conducted assuming a thermodynamically ideal cycle. The results of the parametric study are graphically presented on a contour plot in the parameter space consisting of the extremes of the qualities that exist within the recuperator. The contours show constant values of the normalized refrigeration power. This ‘map’ shows the effect of MR composition on the cycle performance and it can be used to select the MR that provides a high cooling load while also constraining the recuperator to be two phase. The predicted best MR composition can be used as a starting point for experimentally determining the best MR.

  14. Effect of Channel Sidewalls on Joule Heating Induced Sample Dispersion in Rectangular Ducts

    PubMed Central

    Dutta, Debashis

    2015-01-01

    In this article, we analyze the effect of channel sidewalls on the broadening of analyte bands resulting from Joule heating during their electrokinetic migration through a rectangular conduit. A method-of-moments formulation has been used to numerically evaluate the Taylor-Aris dispersivity of sample zones under these conditions for thin electrical double layers applicable to a majority of microfluidic assays. Our analysis shows that the larger surface area to volume ratio around the side regions of a rectangular channel causes these corners to stay cooler than the rest of the conduit. While such a thermal profile does not modify the electroosmotic flow in the system for a fixed temperature at the channel walls, it reduces the electrophoretic transport rate by about 10% for small temperature differentials across the channel cross-section (<10°C). The effect of these thermal gradients on the hydrodynamic dispersion of analyte bands is more significant however, increasing such band broadening by nearly an order of magnitude in large aspect ratio designs. Our analyses further show that the trends noted above are magnified when a fixed heat transfer coefficient is assumed at the channel walls, in which case, the temperature along this boundary is no longer constant. The non-isothermal channel walls combined with the temperature dependence of zeta potential and other material properties in this situation leads to a non-uniform electroosmotic slip velocity in the system modifying both fluid and analyte transport rates. Again, while the resulting solute flow profile reduces the migration velocity of sample zones only to a moderate extent, it is found to increase the hydrodynamic dispersion of analyte bands by several orders of magnitude in large aspect ratio rectangular channels. PMID:26597437

  15. Effect of Channel Sidewalls on Joule Heating Induced Sample Dispersion in Rectangular Ducts.

    PubMed

    Dutta, Debashis

    2016-02-01

    In this article, we analyze the effect of channel sidewalls on the broadening of analyte bands resulting from Joule heating during their electrokinetic migration through a rectangular conduit. A method-of-moments formulation has been used to numerically evaluate the Taylor-Aris dispersivity of sample zones under these conditions for thin electrical double layers applicable to a majority of microfluidic assays. Our analysis shows that the larger surface area to volume ratio around the side regions of a rectangular channel causes these corners to stay cooler than the rest of the conduit. While such a thermal profile does not modify the electroosmotic flow in the system for a fixed temperature at the channel walls, it reduces the electrophoretic transport rate by about 10% for small temperature differentials across the channel cross-section (<10°C). The effect of these thermal gradients on the hydrodynamic dispersion of analyte bands is more significant however, increasing such band broadening by nearly an order of magnitude in large aspect ratio designs. Our analyses further show that the trends noted above are magnified when a fixed heat transfer coefficient is assumed at the channel walls, in which case, the temperature along this boundary is no longer constant. The non-isothermal channel walls combined with the temperature dependence of zeta potential and other material properties in this situation leads to a non-uniform electroosmotic slip velocity in the system modifying both fluid and analyte transport rates. Again, while the resulting solute flow profile reduces the migration velocity of sample zones only to a moderate extent, it is found to increase the hydrodynamic dispersion of analyte bands by several orders of magnitude in large aspect ratio rectangular channels.

  16. Polar tongue of ionization (TOI) and associated Joule heating intensification investigated during the magnetically disturbed period of 1-2 October 2001

    NASA Astrophysics Data System (ADS)

    Horvath, Ildiko; Lovell, Brian C.

    2016-06-01

    We investigate storm-enhanced density (SED) and polar tongue of ionization (TOI) over North America under southward Interplanetary Magnetic Field conditions. We focus on the 30 September to 1 October 2001 medium magnetic storm's recovery phase (Period 1) and on the last substorm (Period 2) of the following 2 October substorm series. We aim to study the SED-TOI structure in the time frame of solar wind energy input to the magnetosphere-ionosphere system and in terms of Joule heating. We utilize GPS total electron content maps tracking SED plume and polar TOI, and spectrogram images detecting polar rain and precipitation void and thus evidencing dayside merging. The variations of merging electric (E) field (EM) and its mapped-down polar equivalent (EP), energy input efficiency (EIeff), and modeled Joule heating rate (QJoule) are monitored. Results show multiple Joule heating intensification points implying multiple energy deposition points at high latitudes where the magnetic pole was one of the preferred locations. During the higher EIeff (~1.5%) Period 2, the polar TOI was associated with a well-defined strong QJoule intensification and with polar rain (or void) on the dayside (or nightside). During the lower EIeff (~0.5%) Period 1, only weak QJoule intensification occurred in the absence of both polar TOI and polar rain. We highlight the polar TOI's potential impact on the thermosphere. We conclude that (i) strong (EM ≈ 5 mV/m during Period 2) or weak (EM ≈ 0.5-2 mV/m during Period 1) EM facilitated energy deposition close to the magnetic pole and (ii) EIeff could be used as a diagnostic of the polar TOI's intensity.

  17. Hall and Joule heating effects on peristaltic flow of Powell-Eyring liquid in an inclined symmetric channel

    NASA Astrophysics Data System (ADS)

    Hayat, T.; Aslam, Naseema; Rafiq, M.; Alsaadi, Fuad E.

    This article is intended to investigate the influence of Hall current on peristaltic transport of conducting Eyring-Powell fluid in an inclined symmetric channel. Energy equation is modeled by taking Joule heating effect into consideration. Velocity and thermal slip conditions are imposed. Lubrication approximation is considered for the analysis. Fundamental equations are non-linear due to fluid parameter A. Regular perturbation technique is employed to find the solution of systems of equations. The key roles of different embedded parameters on velocity, temperature and heat transfer coefficient in the problem are discussed graphically. Trapping phenomenon is analyzed carefully.

  18. Auroral ionosphere Joule heating as a reason of the upper thermosphere overheating in the Jupiter and Saturn systems

    NASA Astrophysics Data System (ADS)

    Alexeev, Igor; Belenkaya, Elena; Khodachenko, Maxim; Grigoryan, Maria

    All giant planets in the Solar System and particularly Saturn and Jupiter are known to have an upper neutral atmosphere far hotter than it is expected from solar extreme ultraviolet heating alone. While the measured exospheric temperatures on Saturn and Jupiter are close to 500 K and to 1100 K - 2000 K, respectively, the solar heating alone can provide an exospheric temperature only about 200 K. Two main energy deposition mechanisms are discussed in the literature to resolve this contradictions: (1) the gravitation wave dissipation in the upper atmosphere, and (2) the auroral thermosphere Joule heating by the Pedersen ionospheric currents. The ionospheric currents are associated with the field-aligned currents generated due to the magnetosphere-ionosphere slipping. Here we focus on the second mechanism. To improve the accuracy of the numerical estimations we derived the analytic formulas, which describe the dependence of the auroral energy flux on the planetary magnetic field strength, as well as on the solar wind plasma ram pressure, and on the breaking of magnetospheric plasma corotation. The last effect is essential for Jupiter, where the main oval is driven internally at Alvenic radius. We pay attention to the general physical phenomena, which may be only slightly influenced/modified by the specific atmospheric composition and photochemical ionospheric reactions. One of the most important energy inputs to the polar upper atmosphere is Joule heating by the ionospheric Pedersen currents. We estimate it to be ~3.0 TW for Saturn and about 1000 times more (3500 TW) for Jupiter. That represents a significant energy input to Saturn’s and Jupiter’s thermospheres. It is more than an order of magnitude larger as compared to the globally averaged solar input. Therefore, Joule heating may be reasonably appealed for the explanation of the observed high thermosphere temperatures by Saturn (~400-600 K) and Jupiter (1200 K).

  19. Joule-Thomson valves for long term service in space cryocoolers

    NASA Technical Reports Server (NTRS)

    Lester, J. M.; Benedict, B.

    1985-01-01

    Joule-Thomson valves for small cryocoolers have throttling passages on the order of 0.1 millimeter in diameter. Consequently, they can become plugged easily and stop the operation of the cooler. Plugging can be caused by solid particles, liquids or gases. Plugging is usually caused by the freezing of contaminant gases from the process stream. In small open loop coolers and in closed loop coolers where periodic maintenance is allowed, the problem is overcome by using careful assembly techniques, pure process gases, warm filters and cold adsorbers. A more thorough approach is required for closed loop cryocoolers which must operate unattended for long periods. This paper presents the results of an effort to solve this problem. The causes of plugging are examined, and various ways to eliminate plugging are discussed. Finally, the development of a J-T defroster is explained. It is concluded that a combination of preventive measures and a defroster will reduce the chance of cooler failure by plugging to such a degree that J-T coolers can be used for long term space missions.

  20. Joule heating effects on unsteady natural convection flow near a moving semi-infinite vertical plate with variable heat flux and mass transfer

    NASA Astrophysics Data System (ADS)

    Narahari, Marneni; Raju, S. Suresh Kumar; Nagarani, P.

    2016-11-01

    The unsteady MHD free convective boundary-layer flow along an impulsively started semi-infinite vertical plate with variable heat flux and mass transfer have been investigated numerically. The effects of chemical reaction, thermal radiation and Joule heating are incorporated in the governing equations. Crank-Nicolson finite-difference method is used to solve the governing coupled non-linear partial differential equations. The influence of thermal radiation, chemical reaction and Joule heating on flow characteristics are presented graphically and discussed in detailed. To validate the present numerical results, a comparison study has been performed with the previously published results and found that the results are in excellent agreement. It is found that the local Nusselt and Sherwood numbers decreases with the intensification of magnetic field and the local Sherwood number slightly decreases with the increase of radiation parameter.

  1. A self-heated silicon nanowire array: selective surface modification with catalytic nanoparticles by nanoscale Joule heating and its gas sensing applications.

    PubMed

    Yun, Jeonghoon; Jin, Chun Yan; Ahn, Jae-Hyuk; Jeon, Seokwoo; Park, Inkyu

    2013-08-07

    We demonstrated novel methods for selective surface modification of silicon nanowire (SiNW) devices with catalytic metal nanoparticles by nanoscale Joule heating and local chemical reaction. The Joule heating of a SiNW generated a localized heat along the SiNW and produced endothermic reactions such as hydrothermal synthesis of nanoparticles or thermal decomposition of polymer thin films. In the first method, palladium (Pd) nanoparticles could be selectively synthesized and directly coated on a SiNW by the reduction of the Pd precursor via Joule heating of the SiNW. In the second method, a sequential process composed of thermal decomposition of a polymer, evaporation of a Pd thin film, and a lift-off process was utilized. The selective decoration of Pd nanoparticles on SiNW was successfully accomplished by using both methods. Finally, we demonstrated the applications of SiNWs decorated with Pd nanoparticles as hydrogen detectors. We also investigated the effect of self-heating of the SiNW sensor on its sensing performance.

  2. Joule-Thomson effect and internal convection heat transfer in turbulent He II flow

    NASA Astrophysics Data System (ADS)

    Walstrom, P. L.

    1988-03-01

    The temperature rise in highly turbulent He II flowing in tubing was measured in the temperature range 1.6-2.1 K. The effect of internal convection heat transport on the predicted temperature profiles is calculated from the two-fluid model with mutual friction. The model predictions are in good agreement with the measurements, provided that the pressure gradient term is retained in the expression for internal convection heat flow.

  3. Joule-Thomson effect and internal convection heat transfer in turbulent He II flow

    NASA Technical Reports Server (NTRS)

    Walstrom, P. L.

    1988-01-01

    The temperature rise in highly turbulent He II flowing in tubing was measured in the temperature range 1.6-2.1 K. The effect of internal convection heat transport on the predicted temperature profiles is calculated from the two-fluid model with mutual friction. The model predictions are in good agreement with the measurements, provided that the pressure gradient term is retained in the expression for internal convection heat flow.

  4. MHD effects and heat transfer for the UCM fluid along with Joule heating and thermal radiation using Cattaneo-Christov heat flux model

    NASA Astrophysics Data System (ADS)

    Shah, S.; Hussain, S.; Sagheer, M.

    2016-08-01

    Present study examines the numerical analysis of MHD flow of Maxwell fluid with thermal radiation and Joule heating by considering the recently developed Cattaneo-Christov heat flux model which explains the time relaxation characteristics for the heat flux. The objective is to analyze the governing parameters such as viscoelastic fluid parameter, Magnetic parameter, Eckert and Prandtl number's impact on the velocity and temperature profiles through graphs and tables. Suitable similarity transformations have been used to reduce the formulated PDEs into a system of coupled non-linear ODEs. Shooting technique has been invoked for finding the numerical solutions of the dimensionless velocity and temperature profiles. Additionally, the MATLAB built-in routine bvp4c has also been used to verify and strengthen the results obtained by shooting method. From some special cases of the present work, a comparison with the previously published results has been presented.

  5. MHD effects and heat transfer for the UCM fluid along with Joule heating and thermal radiation using Cattaneo-Christov heat flux model

    SciTech Connect

    Shah, S. Hussain, S.; Sagheer, M.

    2016-08-15

    Present study examines the numerical analysis of MHD flow of Maxwell fluid with thermal radiation and Joule heating by considering the recently developed Cattaneo-Christov heat flux model which explains the time relaxation characteristics for the heat flux. The objective is to analyze the governing parameters such as viscoelastic fluid parameter, Magnetic parameter, Eckert and Prandtl number’s impact on the velocity and temperature profiles through graphs and tables. Suitable similarity transformations have been used to reduce the formulated PDEs into a system of coupled non-linear ODEs. Shooting technique has been invoked for finding the numerical solutions of the dimensionless velocity and temperature profiles. Additionally, the MATLAB built-in routine bvp4c has also been used to verify and strengthen the results obtained by shooting method. From some special cases of the present work, a comparison with the previously published results has been presented.

  6. High Latitude Precipitating Energy Flux and Joule Heating During Geomagnetic Storms Determined from AMPERE Field-aligned Currents

    NASA Astrophysics Data System (ADS)

    Robinson, R. M.; Zanetti, L. J.; Anderson, B. J.; Korth, H.; Samara, M.; Michell, R.; Grubbs, G. A., II; Hampton, D. L.; Dropulic, A.

    2016-12-01

    A high latitude conductivity model based on field-aligned currents measured by the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) provides the means for complete specification of electric fields and currents at high latitudes. Based on coordinated measurements made by AMPERE and the Poker Flat Incoherent Scatter Radar, the model determines the most likely value of the ionospheric conductance from the direction, magnitude, and magnetic local time of the field-aligned current. A conductance model driven by field-aligned currents ensures spatial and temporal consistency between the calculated electrodynamic parameters. To validate the results, the Pedersen and Hall conductances were used to calculate the energy flux associated with the energetic particle precipitation. When integrated over the entire hemisphere, the total energy flux compares well with the Hemispheric Power Index derived from the OVATION-PRIME model. The conductances were also combined with the field-aligned currents to calculate the self-consistent electric field, which was then used to compute horizontal currents and Joule heating. The magnetic perturbations derived from the currents replicate most of the variations observed in ground-based magnetograms. The model was used to study high latitude particle precipitation, currents, and Joule heating for 24 magnetic storms. In most cases, the total energy input from precipitating particles and Joule heating exhibits a sharply-peaked maximum at the times of local minima in Dst, suggesting a close coupling between the ring current and the high latitude currents driven by the Region 2 field-aligned currents. The rapid increase and decrease of the high latitude energy deposition suggests an explosive transfer of energy from the magnetosphere to the ionosphere just prior to storm recovery.

  7. In-line application of electric field in capillary separation systems: Joule heating, pH and conductivity.

    PubMed

    Eriksson, Björn O; Skuland, Inger Lill; Marlin, Nicola D; Andersson, Magnus B O; Blomberg, Lars G

    2008-03-15

    This study concerns the technique electric field-assisted capillary liquid chromatography. In this technique, an electric field is applied over the separation capillary in order to provide an additional selectivity. In this technique, the electric field is applied in-line in the separation capillary and here the electric current is the factor limiting the magnitude of applied electric field. The influence of Joule heating and other factors on the current in such systems has been investigated. The temperature in the capillary was first measured within a standard CE set-up, as function of effect per unit of length. Then the same cooling system was applied to an in-line set-up, to replicate the conditions between the two systems, and thus the temperature. Thus Joule heating effects could then be calculated within the in-line system. It was found that for systems applying an electric field in line, the direct influence from Joule heating was only relatively small. The pH in the capillary was measured in the in-line set-up using cresol red/TRIS solutions as pH probe. Significant changes in pH were observed and the results suggested that electrolysis of water is the dominant electrode reaction in the in-line system. In summary, the observed conductivity change in in-line systems was found to be mainly due to the pH change by hydrolysis of water, but primarily not due the temperature change in the capillary column.

  8. Effect of Joule heating on current-induced asymmetries and breakdown of the quantum Hall effect in narrow Hall bars

    NASA Astrophysics Data System (ADS)

    Gerhardts, Rolf R.

    2017-01-01

    Recent low-temperature scanning-force-microscopy experiments on narrow Hall bars, under the conditions of the integer quantum Hall effect (IQHE) and its breakdown, have revealed an interesting position dependence of the Hall potential, which changes drastically with the applied magnetic field and the strength of the imposed current through the sample. The present paper shows, that inclusion of Joule heating into an existing self-consistent theory of screening and magneto-transport, which assumes translation invariant Hall bars with a homogeneous background charge due to doping, can explain the experimental results on the breakdown of the IQHE in the so called edge-dominated regime.

  9. Heat and mass transfer in magneto-biofluid flow through a non-Darcian porous medium with Joule effect

    NASA Astrophysics Data System (ADS)

    Sharma, B. K.; Mishra, A.; Gupta, S.

    2013-07-01

    In the present study, a mathematical model for the hydromagnetic non-Newtonian biofluid flow in the non-Darcy porous medium with Joule effect is proposed. A uniform magnetic field acts perpendicularly to the porous surface. The governing nonlinear partial differential equations are transformed into linear ones which are solved numerically by applying the explicit finite difference method. The effects of various parameters, like Reynolds number and hydro-magnetic, Forchheimer, and Darcian parameters, Prandtl, Eckert, and Schmidt numbers, on the velocity, temperature, and concentration are presented graphically. The results of the study can find applications in surgical operations, industrial material processing, and various heat transfer processes.

  10. Influence of Thermal Boundary Effects on the Process of Creating Recovery Stresses in a SMA Wire Activated by Joule Heating

    NASA Astrophysics Data System (ADS)

    Debska, Aleksandra; Balandraud, Xavier; Destrebecq, Jean-François; Gwozdziewicz, Piotr; Seruga, Andrzej

    2017-07-01

    The study deals with the influence of thermal boundary effects on the process of creating recovery stresses in a SMA wire activated by Joule heating, during a thermal cycle (up to the return to ambient temperature). First, a thermal characterization is performed using infrared thermography for temperature profile measurements along the wire in a steady-state regime. Second, recovery stress tests are performed using a uniaxial testing machine. Finally, tests are analyzed using a thermomechanical model, taking the inhomogeneous temperature distribution along the wire into account. The influence of the initial distribution of martensite (before thermal activation of the memory effect) is discussed, as well as the influence of the wire length. It is shown that the thermal boundary effects at the contact with the grips of the testing machine significantly influence the response of the wire. For instance, during the heating of the wire, an austenite-to-martensite transformation may occur in the zones near the wire ends (where the temperature remains close to ambient) due to the increased stress. A length of influence of the thermal boundary effects on the overall wire response is defined, and a condition to neglect this influence is proposed. The study highlights the importance of taking thermal boundary effects into account for practical applications of SMAs based on Joule heating.

  11. Three-dimensional noninvasive ultrasound Joule heat tomography based on the acousto-electric effect using unipolar pulses: a simulation study.

    PubMed

    Yang, Renhuan; Li, Xu; Song, Aiguo; He, Bin; Yan, Ruqiang

    2012-11-21

    Electrical properties of biological tissues are highly sensitive to their physiological and pathological status. Thus it is of importance to image electrical properties of biological tissues. However, spatial resolution of conventional electrical impedance tomography (EIT) is generally poor. Recently, hybrid imaging modalities combining electric conductivity contrast and ultrasonic resolution based on the acousto-electric effect has attracted considerable attention. In this study, we propose a novel three-dimensional (3D) noninvasive ultrasound Joule heat tomography (UJHT) approach based on the acousto-electric effect using unipolar ultrasound pulses. As the Joule heat density distribution is highly dependent on the conductivity distribution, an accurate and high-resolution mapping of the Joule heat density distribution is expected to give important information that is closely related to the conductivity contrast. The advantages of the proposed ultrasound Joule heat tomography using unipolar pulses include its simple inverse solution, better performance than UJHT using common bipolar pulses and its independence of a priori knowledge of the conductivity distribution of the imaging object. Computer simulation results show that using the proposed method, it is feasible to perform a high spatial resolution Joule heat imaging in an inhomogeneous conductive media. Application of this technique on tumor scanning is also investigated by a series of computer simulations.

  12. Estimation of Joule heating and its role in nonlinear electrical response of Tb0.5Sr0.5MnO3 single crystal

    NASA Astrophysics Data System (ADS)

    Nhalil, Hariharan; Elizabeth, Suja

    2016-12-01

    Highly non-linear I-V characteristics and apparent colossal electro-resistance were observed in non-charge ordered manganite Tb0.5Sr0.5MnO3 single crystal in low temperature transport measurements. Significant changes were noticed in top surface temperature of the sample as compared to its base while passing current at low temperature. By analyzing these variations, we realize that the change in surface temperature (ΔTsur) is too small to have caused by the strong negative differential resistance. A more accurate estimation of change in the sample temperature was made by back-calculating the sample temperature from the temperature variation of resistance (R-T) data (ΔTcal), which was found to be higher than ΔTsur. This result indicates that there are large thermal gradients across the sample. The experimentally derived ΔTcal is validated with the help of a simple theoretical model and estimation of Joule heating. Pulse measurements realize substantial reduction in Joule heating. With decrease in sample thickness, Joule heating effect is found to be reduced. Our studies reveal that Joule heating plays a major role in the nonlinear electrical response of Tb0.5Sr0.5MnO3. By careful management of the duty cycle and pulse current I-V measurements, Joule heating can be mitigated to a large extent.

  13. Application of High-Speed Infrared Imaging to Study Transient Joule Heating in Station Class Zinc Oxide Surge Arresters

    SciTech Connect

    Dinwiddie, R. B.; Wang, H.; Johnnerfelt, B.

    2004-03-15

    Zinc Oxide based surge arresters are widely used to safeguard and improve reliability of the electrical power delivering and transmission systems. The primary application of surge arresters is to protect valuable components such as transformers from lightning strikes and switching transients in the transmission lines. Metal-oxide-varistor blocks (MOV, e.g. ZnO) are used in surge arrester assemblies. ORNL has developed an advanced infrared imaging technique to monitor the joule heating during transient heating of small varistors. In a recent short-term R&D effort, researchers from ABB and ORNL have expanded the use of IR imaging to larger station-class arrester blocks. An on-site visit to the ABB facility demonstrated that the use of IR imaging is not only feasible but also has the potential to improve arrester quality and reliability. The ASEA Brown Bower (ABB) Power and Technology & Development Company located at Greensburg PA having benefited from collaborative R&D cooperation with ORNL. ABB has decided a follow-on CRADA project is very important. While the previous efforts to study surge arresters included broader studies of IR imaging and computer modeling, ABB has recognized the potential of IR imaging, decided to focus on this particular area. ABB plans to use this technique to systematically study the possible defects in the arrester fabrication process. ORNL will improve the real-time monitoring capability and provide analysis of the infrared images. More importantly, the IR images will help us understand transient heating in a ceramic material from the scientific standpoint. With the improved IR imaging ABB and ORNL will employ the IR system to visualize manufacturing defects that could not be detected otherwise. The proposed on-site tests at ABB Power Technology & Development processing facility will identify the defects and also allow quick adjustments to be made since the resulting products can be inspected immediately. ABB matched the DOE $50K funding

  14. Short Time-Scale Enhancements to the Global Thermosphere Temperature and Nitric Oxide Content Resulting From Ionospheric Joule Heating

    NASA Astrophysics Data System (ADS)

    Weimer, D. R.; Mlynczak, M. G.; Hunt, L. A.; Sutton, E. K.

    2014-12-01

    The total Joule heating in the polar ionosphere can be derived from an empirical model of the electric fields and currents, using input measurements of the solar wind velocity and interplanetary magnetic field (IMF). In the thermosphere, measurements of the neutral density from accelerometers on the CHAMP and GRACE satellites are used to derive exospheric temperatures, showing that enhanced ionospheric energy dissipation produces elevated temperatures with little delay.Using the total ionospheric heating, changes in the global mean exosphere temperature as a function of time can be calculated with a simple differential equation. The results compare very well with the CHAMP and GRACE measurement. A critical part of the calculation is the rate at which the thermosphere cools after the ionospheric heating is reduced. It had been noted previously that events with significant levels of heating subsequently cool at a faster rate, and this cooling was attributed to enhanced nitric oxide emissions. This correlation with nitric oxide has been confirmed with very high correlations with measurements of nitric oxide emissions in the thermosphere, from the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument on the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite. These measurements were used in a recent improvement in the equations that calculate the thermosphere temperature. The global nitric oxide cooling rates are included in this calculation, and the predicted levels of nitric oxide, derived from the ionosphere heating model, match the SABER measurements very well, having correlation coefficients on the order of 0.9.These calculations are used to govern the sorting of measurements CHAMP and GRACE measurements, on the basis of the global temperature enhancements due to Joule heating, as well as various solar indices, and season. Global maps of the exospheric temperature are produced from these sorted data.

  15. Conjugated Effect of Joule Heating and Magnetohydrodynamic on Laminar Convective Heat Transfer of Nanofluids Inside a Concentric Annulus in the Presence of Slip Condition

    NASA Astrophysics Data System (ADS)

    Moshizi, S. A.; Pop, I.

    2016-07-01

    In the current study, the conjugated effect of Joule heating and magnetohydrodynamics (MHD) on the forced convective heat transfer of fully developed laminar nanofluid flows inside annular pipes, under the influence of MHD field, has been investigated. The temperature and nanoparticle distributions at both the inner and outer walls are assumed to vary in the direction of the fluid. Furthermore, owing to the nanoparticle migrations in the fluid, a slip condition becomes far more important than the no-slip condition of the fluid-solid interface, which appropriately represents the non-equilibrium region near the interface. The governing equations—obtained by employing the Buongiorno's model for nanofluid in cylindrical coordinates—are converted into two-point ordinary boundary value differential equations and solved numerically. The effects of various controlling parameters on the flow characteristics, the average Nusselt number and the average Sherwood number have been assessed in detail. Additionally, the effect of the inner to outer diameter ratio on the heat and mass transfer rate has been studied. The results obtained indicate that, in the presence of a magnetic field when the fluid is electrically conductive, heat transfer will be reduced significantly due to the influences of Joule heating, while the average mass transfer rate experiences an opposite trend. Moreover, the increase in the slip velocity on both the walls causes the average heat transfer to rise and the average mass transfer to decrease.

  16. Influence of Joule heating on magnetostriction and giant magnetoimpedance effect in a glass covered CoFeSiB microwire

    NASA Astrophysics Data System (ADS)

    Kraus, L.; Knobel, M.; Kane, S. N.; Chiriac, H.

    1999-04-01

    The influence of annealing parameters (time ta, current Ia, and applied stress σa) on magnetic properties of Joule heated amorphous Co68.15Fe4.35Si12.5B15 glass covered microwire (13 μm) was investigated. Annealing under applied stress induces additional anisotropy which is proportional to σa and can be removed by subsequent heating without stress. The magnetoimpedance, measured on the sample with the lowest anisotropy field (HK≈120 Am-1), shows sharp maxima at H=±HK. For driving currents higher than 0.2 mA nonlinear behavior is observed, and the magnitude of giant magnetoimpedance significantly decreases. The maximum relative change of impedance (60%), observed for the highest frequency, 900 kHz, compares well with the values reported on conventional wires.

  17. Localized joule heating as a mask-free technique for the local synthesis of ZnO nanowires on silicon nanodevices.

    PubMed

    Chen, C C; Lin, Y S; Sang, C H; Sheu, J-T

    2011-11-09

    We report a mask-free technique for the local synthesis of ZnO nanowires (NWs) on polysilicon nanobelts and polysilicon NW devices. First, we used localized joule heating to generate a poly(methyl methacrylate) (PMMA) nanotemplate, allowing the rapid and self-aligned ablation of PMMA within a short period of time (ca. 5 μs). Next, we used ion-beam sputtering to prepare an ultrathin Au film and a ZnO seed layer; a subsequent lift-off process left the seed layers selectively within the PMMA nanotemplate. Gold nanoparticles and ZnO NWs were formed selectively in the localized joule heating region.

  18. Measurement and simulation of Joule heating during treatment of B-16 melanoma tumors in mice with nanosecond pulsed electric fields.

    PubMed

    Pliquett, Uwe; Nuccitelli, Richard

    2014-12-01

    Experimental evidence shows that nanosecond pulsed electric fields (nsPEF) trigger apoptosis in skin tumors. We have postulated that the energy delivered by nsPEF is insufficient to impart significant heating to the treated tissue. Here we use both direct measurements and theoretical modeling of the Joule heating in order to validate this assumption. For the temperature measurement, thermo-sensitive liquid crystals (TLC) were used to determine the surface temperature while a micro-thermocouple (made from 30 μm wires) was used for measuring the temperature inside the tissue. The calculation of the temperature distribution used an asymptotic approach with the repeated calculation of the electric field, Joule heating and heat transfer, and the subsequent readjustment of the electrical tissue conductivity. This yields a temperature distribution both in space and time. It can be shown that for the measured increase in temperature an unexpectedly high electrical conductivity of the tissue would be required, which was indeed found by using voltage and current monitoring during the experiment. Using impedance measurements within t(after)=50 μs after the pulse revealed a fast decline of the high conductivity state when the electric field ceases. The experimentally measured high conductance of a skin fold (mouse) between plate electrodes was about 5 times higher than those of the maximally expected conductance due to fully electroporated membrane structures (G(max)/G(electroporated))≈5. Fully electroporated membrane structure assumes that 100% of the membranes are conductive which is estimated from an impedance measurement at 10 MHz where membranes are capacitively shorted. Since the temperature rise in B-16 mouse melanoma tumors due to equally spaced (Δt=2 s) 300 ns-pulses with E=40 kV/cm usually does not exceed ΔΤ=3 K at all parts of the skin fold between the electrodes, a hyperthermic effect on the tissue can be excluded.

  19. Numerical analyses of fluid flow in Joule-heated cavity of low-Prandtl number fluid

    NASA Astrophysics Data System (ADS)

    Xiaohui, Zhang; Mingjie, Zhang; Qigang, Zhong

    2012-09-01

    The aim of present investigation is to verify SGSD scheme by von-Neumann method. The stability condition of Courant number and diffusion number are proved in implicit and explicit discretization of the convection and diffusion terms for advection-diffusion equation in engineering fluid flow and heat transfer. Then, a series of numerical simulation of fluid flow and heat transfer based on two-dimensional unsteady state model has been studied. In the present numerical study, the fluid is in a rectangular cavity with an aspect ratio of 2, and the direct current is applied for heating the process medium by a pair of plate electrodes. The top wall is cooled with atmosphere and all other walls are kept thermally insulated. for the fluid of Pr=0.01, even we use SGSD scheme and IDEAL algorithm it is found that periodic oscillation flow evolves, which can significantly affect the fluid flow and heat transfer. Iteration convergence cannot be obtained. This means that oscillation is due to the physical nonlinear system. These transient characteristics of velocity are presented graphically.

  20. Electro-osmotic flow of power-law fluid and heat transfer in a micro-channel with effects of Joule heating and thermal radiation

    NASA Astrophysics Data System (ADS)

    Shit, G. C.; Mondal, A.; Sinha, A.; Kundu, P. K.

    2016-11-01

    A mathematical model has been developed for studying the electro-osmotic flow and heat transfer of bio-fluids in a micro-channel in the presence of Joule heating effects. The flow of bio-fluid is governed by the non-Newtonian power-law fluid model. The effects of thermal radiation and velocity slip condition have been examined in the case of hydrophobic channel. The Poisson-Boltzmann equation governing the electrical double layer field and a body force generated by the applied electric potential field are taken into consideration. The results presented here pertain to the case where the height of the channel is much greater than the thickness of electrical double layer comprising the Stern and diffuse layers. The expressions for flow characteristics such as velocity, temperature, shear stress and Nusselt number have been derived analytically under the purview of the present model. The results estimated on the basis of the data available in the existing scientific literatures are presented graphically. The effects of thermal radiation have an important bearing on the therapeutic procedure of hyperthermia, particularly in understanding the heat transfer in micro-channel in the presence of electric potential. The dimensionless Joule heating parameter has a reducing impact on Nusselt number for both pseudo-plastic and dilatant fluids, nevertheless its impact on Nusselt number is more pronounced for dilatant fluid. Furthermore, the effect of viscous dissipation has a significant role in controlling heat transfer and should not be neglected.

  1. Joule heating effects on MHD mixed convection of a Jeffrey fluid over a stretching sheet with power law heat flux: A numerical study

    NASA Astrophysics Data System (ADS)

    Babu, D. Harish; Narayana, P. V. Satya

    2016-08-01

    An analysis has been carried out to study the Joule heating effect on MHD heat transfer of an incompressible Jeffrey fluid due to a stretching porous sheet with power law heat flux and heat source. A constant magnetic field is applied normal to the stretching surface. The basic governing equations are reduced into the coupled nonlinear ordinary differential equations by using similarity transformations. The resulting equations are then solved numerically by shooting method with fourth order Runge-Kutta scheme. The effects of various physical parameters entering into the problem on dimensionless velocity and temperature distribution are discussed through graphs and tables. The results reveal that the momentum and thermal boundary layer thickness are significantly influenced by Deborah number (β), ratio of relaxation and retardation times parameter (λ), heat generation parameter (β*), Eckert number (Ec) and magnetic field parameter (M). A comparison with the previously published works shows excellent agreement.

  2. Effects of high-latitude ionospheric electric field variability on the estimation of global thermospheric Joule heating

    NASA Astrophysics Data System (ADS)

    Matsuo, Tomoko

    One of the outstanding problems in modeling of the magnetosphere-ionosphere-thermosphere system is the quantitative bias systematically seen in simulated thermosphere and ionosphere responses to magnetospheric forcing. This systematic bias is considered to be attributed largely to insufficient Joule heating. In this study, effects of high-latitude ionospheric electric field variability on the estimation of Joule heating are investigated by incorporating the characteristics of electric field variability derived from observations into the forcing of a thermosphere-ionosphere-electrodynamic general circulation model (TIEGCM). First, the magnitude of the variability is quantified as the sample standard deviation of plasma drift measurements from the Dynamics Explorer (DE-2) satellite. The spatial distribution of the standard deviation over the area poleward of 45° magnetic latitude and its climatological behavior with respect to the magnitude and orientation of the interplanetary magnetic field (IMF) and the dipole tilt angle (season) are examined. In general, the magnitude of the standard deviation exceeds the strength of the mean electric field in most of the polar area, especially under northward IMF conditions. The analysis reveals that electric field variability varies with magnetic-latitude, magnetic-local-time, IMF, and season in a manner distinct from that of the climatological electric field. Second, we characterize dominant modes of high-latitude electric field variability as a set of two-dimensional empirical orthogonal functions (EOFs), based on a sequential non-linear regression analysis of the electric field derived from DE-2 data. Together with the mean fields, 11 EOFs are capable of representing 68% of the squared electric field, leaving only a fairly random component as a residual. Third, the temporal coherence of electric field variability whose spatial coherence can be represented in the form of EOFs is estimated for the storm period of January 9

  3. Effect of Joule heating on efficiency and performance for microchip-based and capillary-based electrophoretic separation systems: a closer look.

    PubMed

    Petersen, Nickolaj J; Nikolajsen, Rikke P H; Mogensen, Klaus B; Kutter, Jörg P

    2004-01-01

    An attempt is made to revisit the main theoretical considerations concerning temperature effects ("Joule heating") in electro-driven separation systems, in particular lab-on-a-chip systems. Measurements of efficiencies in microfabricated devices under different Joule heating conditions are evaluated and compared to both theoretical models and measurements performed on conventional capillary systems. The widely accepted notion that planar microdevices are less susceptible to Joule heating effects is largely confirmed. The heat dissipation from a nonthermostatically controlled glass microdevice was found to be comparable to that from a liquid-cooled-fused silica capillary. Using typically dimensioned glass and glass/silicon microdevices, the experimental results indicate that 5-10 times higher electric field strengths can be applied than on conventional capillaries, before detrimental effects on the separation efficiency occur. The main influence of Joule heating on efficiency is via the establishment of a radial temperature profile across the lumen of the capillary or channel. An overall temperature increase of the buffer solution has only little influence on the quality of the separation. Still, active temperature control (cooling, thermostatting) can help prevent boiling of the buffer and increase the reproducibility of the results.

  4. Heat treatment of whole milk by the direct joule effect--experimental and numerical approaches to fouling mechanisms.

    PubMed

    Fillaudeau, L; Winterton, P; Leuliet, J C; Tissier, J P; Maury, V; Semet, F; Debreyne, P; Berthou, M; Chopard, F

    2006-12-01

    The development of alternative technologies such as the direct Joule effect to pasteurize and sterilize food products is of great scientific and industrial interest. Our objective was 1) to gain insight into the ability to ensure ultra-high-temperature treatment of milk and 2) to investigate the links among thermal, hydraulic, and electrical phenomena in relation to fouling in a direct Joule effect heater. The ohmic heater [OH; E perpendicular to v (where E is the electrical field and v is the velocity); P (power) = 15 kW] was composed of 5 flat rectangular cells [e (space between the plate and electrode) = 15 mm, w (wall) = 76 mm, and L (length of the plate in plate heat exchanger or electrode) = 246 mm]--3 active cells to ensure heating and 2 (at the extremities) for electrical insulation and the recovery of leakage currents. In the first step, the thermal performance of the OH was investigated vs. the flow regimen [50 < Re (Reynolds number) < 5,000], supplied power (0 < P < 15 kW), and electrical conductivity of fluids (0.1 < sigma(20 degrees C) < 2 S/m) under clean conditions with model fluids. This protocol enabled a global thermal approach (thermal and electrical balance, modeling of the temperature profile of a fluid) and local analysis of the wall temperature of the electrode. An empirical correlation was established to estimate the temperature gradient, T(w)-T(b) (where T(w) is the wall temperature and T(b) is the product temperature) under clean conditions (without fouling) and was used to define operating conditions for pure-volume and direct-resistance heating. In the second step, the ability of OH to ensure the ultra-high-temperature treatment of whole milk was investigated and compared with a plate heat exchanger. Special care was taken to investigate the heat transfer phenomena occurring over a range of temperatures from 105 to 138 degrees C. This temperature range corresponds to the part of the process made critical by protein and mineral fouling

  5. Joule Heating Effect on Field-Free Magnetization Switching by Spin-Orbit Torque in Exchange-Biased Systems

    NASA Astrophysics Data System (ADS)

    Razavi, Seyed Armin; Wu, Di; Yu, Guoqiang; Lau, Yong-Chang; Wong, Kin L.; Zhu, Weihua; He, Congli; Zhang, Zongzhi; Coey, J. M. D.; Stamenov, Plamen; Khalili Amiri, Pedram; Wang, Kang L.

    2017-02-01

    Switching of magnetization via spin-orbit torque provides an efficient alternative for nonvolatile memory and logic devices. However, to achieve deterministic switching of perpendicular magnetization, an external magnetic field collinear with the current is usually required, which makes these devices inappropriate for practical applications. In this work, we examine the current-induced magnetization switching in a perpendicularly magnetized exchange-biased Pt /CoFe /IrMn system. A magnetic field annealing technique is used to introduce in-plane exchange biases, which are quantitatively characterized. Under proper conditions, field-free current-driven switching is achieved. We study the Joule heating effect, and we show how it can decrease the in-plane exchange bias and degrade the field-free switching. Furthermore, we discuss that the exchange-bias training effect can have similar effects.

  6. Bulk SmCo5/α-Fe nanocomposite permanent magnets fabricated by mould-free Joule-heating compaction

    NASA Astrophysics Data System (ADS)

    Rong, Chuanbing; Zhang, Ying; Poudyal, Narayan; Wang, Dapeng; Kramer, M. J.; Liu, J. Ping

    2011-04-01

    Bulk SmCo5/α-Fe nanocomposite magnets have been prepared using a Joule-heating compaction technique. Nearly fully dense bulk magnets are obtained by compacting the milled powders under a pressure of 2 GPa at temperatures above 400 °C. Structural analysis shows that the grain size of both the SmCo5 and the α-Fe phases is in the range of 10 to 15 nm when the compaction temperature is lower than 500 °C, which ensures effective interphase exchange coupling. A further increase in compaction temperature leads to significant grain growth and deterioration of magnetic properties. A maximum energy product of about 18.5 MGOe was obtained in the bulk SmCo5/α-Fe nanocomposite magnets, which is 90% higher than that of the single-phase counterpart prepared under the same conditions.

  7. Joule heating and spin-transfer torque investigated on the atomic scale using a spin-polarized scanning tunneling microscope.

    PubMed

    Krause, S; Herzog, G; Schlenhoff, A; Sonntag, A; Wiesendanger, R

    2011-10-28

    The influence of a high spin-polarized tunnel current onto the switching behavior of a superparamagnetic nanoisland on a nonmagnetic substrate is investigated by means of spin-polarized scanning tunneling microscopy. A detailed lifetime analysis allows for a quantification of the effective temperature rise of the nanoisland and the modification of the activation energy barrier for magnetization reversal, thereby using the nanoisland as a local thermometer and spin-transfer torque analyzer. Both the Joule heating and spin-transfer torque are found to scale linearly with the tunnel current. The results are compared to experiments performed on lithographically fabricated magneto-tunnel junctions, revealing a very high spin-transfer torque switching efficiency in our experiments.

  8. Experimental evaluation of an adaptive Joule-Thomson cooling system including silicon-microfabricated heat exchanger and microvalve components.

    PubMed

    Zhu, Weibin; Park, Jong M; White, Michael J; Nellis, Gregory F; Gianchandani, Yogesh B

    2011-03-01

    This article reports the evaluation of a Joule-Thomson (JT) cooling system that combines two custom micromachined components-a Si/glass-stack recuperative heat exchanger and a piezoelectrically actuated expansion microvalve. With the microvalve controlling the flow rate, this system can modulate cooling to accommodate varying refrigeration loads. The perforated plate Si/glass heat exchanger is fabricated with a stack of alternating silicon plates and Pyrex glass spacers. The microvalve utilizes a lead zirconate titanate actuator to push a Si micromachined valve seat against a glass plate, thus modulating the flow passing through the gap between the valve seat and the glass plate. The fabricated heat exchanger has a footprint of 1 × 1 cm(2) and a length of 35 mm. The size of the micromachined piezoelectrically actuated valve is about 1 × 1 × 1 cm(3). In JT cooling tests, the temperature of the system was successfully controlled by adjusting the input voltage of the microvalve. When the valve was fully opened (at an input voltage of -30 V), the system cooled down to a temperature as low as 254.5 K at 430 kPa pressure difference between inlet and outlet at steady state and 234 K at 710 kPa in a transient state. The system provided cooling powers of 75 mW at 255 K and 150 mW at 258 K. Parasitic heat loads at 255 K are estimated at approximately 700 mW.

  9. Joule heating effect on a continuously moving thin needle in MHD Sakiadis flow with thermophoresis and Brownian moment

    NASA Astrophysics Data System (ADS)

    Sulochana, C.; Ashwinkumar, G. P.; Sandeep, N.

    2017-09-01

    In the current study, we investigated the impact of thermophoresis and Brownian moment on the boundary layer 2D forced convection flow of a magnetohydrodynamic nanofluid along a persistently moving horizontal needle with frictional heating effect. The various pertinent parameters are taken into account in the present analysis, namely, the thermophoresis and Brownian moment, uneven heat source/sink, Joule heating and frictional heating effects. To check the variation in the boundary layer behavior, we considered two distinct nanoparticles namely Al50Cu50 (alloy with 50% alumina and 50% copper) and Cu with water as base liquid. Numerical solutions are derived for the reduced system of governing PDEs by employing the shooting process. Computational results of the flow, energy and mass transport are interpreted with the support of tables and graphical illustrations. The obtained results indicate that the increase in the needle size significantly reduces the flow and thermal fields. In particular, the velocity field of the Cu-water nanofluid is highly affected when compared with the Al50Cu50 -water nanofluid. Also, we showed that the thermophoresis and Brownian moment parameters are capable of enhancing the thermal conductivity to a great extent.

  10. Cycling Joule Thomson refrigerator

    NASA Technical Reports Server (NTRS)

    Tward, E. (Inventor)

    1983-01-01

    A symmetrical adsorption pump/compressor system having a pair of mirror image legs and a Joule Thomson expander, or valve, interposed between the legs thereof for providing a, efficient refrigeration cycle is described. The system further includes a plurality of gas operational heat switches adapted selectively to transfer heat from a thermal load and to transfer or discharge heat through a heat projector, such as a radiator or the like. The heat switches comprise heat pressurizable chambers adapted for alternate pressurization in response to adsorption and desorption of a pressurizing gas confined therein.

  11. Joule Thomson refrigerator

    NASA Technical Reports Server (NTRS)

    Chan, Chung K. (Inventor); Gatewood, John R. (Inventor)

    1988-01-01

    A bi-directional Joule Thomson refrigerator is described, which is of simple construction at the cold end of the refrigerator. Compressed gas flowing in either direction through the Joule Thomson expander valve and becoming liquid, is captured in a container in direct continuous contact with the heat load. The Joule Thomson valve is responsive to the temperature of the working fluid near the valve, to vary the flow resistance through the valve so as to maintain a generally constant flow mass between the time that the refrigerator is first turned on and the fluid is warm, and the time when the refrigerator is near its coldest temperature and the fluid is cold. The valve is operated by differences in thermal coefficients of expansion of materials to squeeze and release a small tube which acts as the expander valve.

  12. Influence of nonlinear thermal radiation and viscous dissipation on three-dimensional flow of Jeffrey nano fluid over a stretching sheet in the presence of Joule heating

    NASA Astrophysics Data System (ADS)

    Ganesh Kumar, K.; Rudraswamy, N. G.; Gireesha, B. J.; Krishnamurthy, M. R.

    2017-09-01

    Present exploration discusses the combined effect of viscous dissipation and Joule heating on three dimensional flow and heat transfer of a Jeffrey nanofluid in the presence of nonlinear thermal radiation. Here the flow is generated over bidirectional stretching sheet in the presence of applied magnetic field by accounting thermophoresis and Brownian motion of nanoparticles. Suitable similarity transformations are employed to reduce the governing partial differential equations into coupled nonlinear ordinary differential equations. These nonlinear ordinary differential equations are solved numerically by using the Runge-Kutta-Fehlberg fourth-fifth order method with shooting technique. Graphically results are presented and discussed for various parameters. Validation of the current method is proved by comparing our results with the existing results under limiting situations. It can be concluded that combined effect of Joule and viscous heating increases the temperature profile and thermal boundary layer thickness.

  13. Off-gas characteristics of defense waste vitrification using liquid-fed Joule-heated ceramic melters

    SciTech Connect

    Goles, R.W.; Sevigny, G.J.

    1983-09-01

    Off-gas and effluent characterization studies have been established as part of a PNL Liquid-Fed Ceramic Melter development program supporting the Savannah River Laboratory Defense Waste Processing Facility (SRL-DWPF). The objectives of these studies were to characterize the gaseous and airborne emission properties of liquid-fed joule-heated melters as a function of melter operational parameters and feed composition. All areas of off-gas interest and concern including effluent characterization, emission control, flow rate behavior and corrosion effects have been studied using alkaline and formic-acid based feed compositions. In addition, the behavioral patterns of gaseous emissions, the characteristics of melter-generated aerosols and the nature and magnitude of melter effluent losses have been established under a variety of feeding conditions with and without the use of auxiliary plenum heaters. The results of these studies have shown that particulate emissions are responsible for most radiologically important melter effluent losses. Melter-generated gases have been found to be potentially flammable as well as corrosive. Hydrogen and carbon monoxide present the greatest flammability hazard of the combustibles produced. Melter emissions of acidic volatile compounds of sulfur and the halogens have been responsible for extensive corrosion observed in melter plenums and in associated off-gas lines and processing equipment. The use of auxiliary plenum heating has had little effect upon melter off-gas characteristics other than reducing the concentrations of combustibles.

  14. Joule heating-induced coexisted spin Seebeck effect and spin Hall magnetoresistance in the platinum/Y{sub 3}Fe{sub 5}O{sub 12} structure

    SciTech Connect

    Wang, W. X.; Wang, S. H.; Zou, L. K.; Cai, J. W.; Sun, J. R. E-mail: sun-zg@whut.edu.cn; Sun, Z. G.

    2014-11-03

    Spin Seebeck effect (SSE) and spin Hall magnetoresistance (SMR) are observed simultaneously in the Pt/Y{sub 3}Fe{sub 5}O{sub 12} hybrid structure when thermal gradient is produced by Joule heating. According to their dependences on applied current, these two effects can be separated. Their dependence on heating power and magnetic field is systematically studied. With the increase of heating power, the SSE enhances linearly, whereas the SMR decreases slowly. The origin of the spin currents is further analyzed. The heating power dependences of the spin currents associated with the SSE and the SMR are found to be different.

  15. Joule heating effects on electromagnetohydrodynamic flow through a peristaltically induced micro-channel with different zeta potential and wall slip

    NASA Astrophysics Data System (ADS)

    Ranjit, N. K.; Shit, G. C.

    2017-09-01

    This paper aims to develop a mathematical model for magnetohydrodynamic flow of biofluids through a hydrophobic micro-channel with periodically contracting and expanding walls under the influence of an axially applied electric field. The velocity slip effects have been taken into account at the channel walls by employing different slip lengths due to hydrophobic gating. Different temperature jump factors have also been used to investigate the thermomechanical interactions at the fluid-solid interface. The electromagnetohydrodynamic flow in a microchannel is simplified under the framework of Debye-Hückel linearization approximation. We have derived the closed-form solutions for the linearized dimensionless boundary value problem under the assumptions of long wave length and low Reynolds number. The axial velocity, temperature, pressure distribution, stream function, wall shear stress and the Nusselt number have been appraised for diverse values of the parameters approaching into the problem. Our main focus is to determine the effects of different zeta potential on the axial velocity and temperature distribution under electromagnetic environment. This study puts forward an important observation that the different zeta potential plays an important role in controlling fluid velocity. The study further reveals that the temperature increases significantly with the Joule heating parameter and the Brinkman number (arises due to the dissipation of energy).

  16. Effects of temperature dependence of electrical and thermal conductivities on the Joule heating of a one dimensional conductor

    NASA Astrophysics Data System (ADS)

    Antoulinakis, F.; Chernin, D.; Zhang, Peng; Lau, Y. Y.

    2016-10-01

    We examine the effects of temperature dependence of the electrical and thermal conductivities on Joule heating of a one-dimensional conductor by solving the coupled non-linear steady state electrical and thermal conduction equations. The spatial temperature distribution and the maximum temperature and its location within the conductor are evaluated for four cases: (i) constant electrical conductivity and linear temperature dependence of thermal conductivity, (ii) linear temperature dependence of both electrical and thermal conductivities, (iii) the Wiedemann-Franz relation for metals, and (iv) polynomial fits to measured data for carbon nanotube fibers and for copper. For (i) and (ii), it is found that there are conditions under which no steady state solution exists, which may indicate the possibility of thermal runaway. For (i), analytical solutions are constructed, from which explicit expressions for the parameter bounds for the existence of steady state solutions are obtained. The shifting of these bounds due to the introduction of linear temperature dependence of electrical conductivity (case (ii)) is studied numerically. These results may provide guidance in the design of circuits and devices in which the effects of coupled thermal and electrical conduction are important.

  17. Joule heating investigations using the Sondrestrom radar and DMSP satellites. Final report, 10 December 1989-9 May 1990

    SciTech Connect

    Watermann, J.; de la Beaujardiere, O.

    1991-01-01

    The objective of our study was to cross-validate Joule heating rates derived from Defense Meteorological Satellite Program (DMSP) F7 observations through comparison with incoherent scatter radar measurements from Sondre Stromfjord, Greenland, In spite of obvious difficulties encountered within localized and dynamic structures such as discrete auroral arcs, where electric field and Pederson current estimates did not match, good agreement was found within relatively stable structures like the poleward edge of the diffuse aurora. Unrelated to spatial and temporal ambiguity problems, a systematic discrepancy in a summer daytime Pedersen conductance calculations from spacecraft and radar data was found. Although the conditions for comparison were generally not optimal because the temporal and spatial coincidences between spacecraft and radar measurements were not perfect, 50% of the cases examined were in good agreement. Possible error source for the remaining cases of disagreement are identified and explanations for the disagreement are offered. The necessity of further efforts to cross validate measurements of ionospheric parameters is emphasized and ways for improvements of the comparison method are suggested.

  18. One-Step Sub-micrometer-Scale Electrohydrodynamic Inkjet Three-Dimensional Printing Technique with Spontaneous Nanoscale Joule Heating.

    PubMed

    Zhang, Bin; Seong, Baekhoon; Lee, Jaehyun; Nguyen, VuDat; Cho, Daehyun; Byun, Doyoung

    2017-09-06

    A one-step sub-micrometer-scale electrohydrodynamic (EHD) inkjet three-dimensional (3D)-printing technique that is based on the drop-on-demand (DOD) operation for which an additional postsintering process is not required is proposed. Both the numerical simulation and the experimental observations proved that nanoscale Joule heating occurs at the interface between the charged silver nanoparticles (Ag-NPs) because of the high electrical contact resistance during the printing process; this is the reason why an additional postsintering process is not required. Sub-micrometer-scale 3D structures were printed with an above-35 aspect ratio via the use of the proposed printing technique; furthermore, it is evident that the designed 3D structures such as a bridge-like shape can be printed with the use of the proposed printing technique, allowing for the cost-effective fabrication of a 3D touch sensor and an ultrasensitive air flow-rate sensor. It is believed that the proposed one-step printing technique may replace the conventional 3D conductive-structure printing techniques for which a postsintering process is used because of its economic efficiency.

  19. Polypyrrole/silver coaxial nanowire aero-sponges for temperature-independent stress sensing and stress-triggered Joule heating.

    PubMed

    He, Weina; Li, Guangyong; Zhang, Shangquan; Wei, Yong; Wang, Jin; Li, Qingwen; Zhang, Xuetong

    2015-04-28

    To obtain ideal sensing materials with nearly zero temperature coefficient resistance (TCR) for self-temperature-compensated pressure sensors, we proposed an Incipient Network Conformal Growth (INCG) technology to prepare hybrid and elastic porous materials: the nanoparticles (NPs) are first dispersed in solvent to form an incipient network, another component is then introduced to coat the incipient network conformally via wet chemical route. The conformal coatings not only endow NPs with high stability but also offer them additional structural elasticity, meeting requirements for future generations of portable, compressive and flexible devices. The resultant polypyrrole/silver coaxial nanowire hybrid aero-sponges prepared via INCG technology have been processed into a piezoresistive sensor with highly sensing stability (low TCR 0.86 × 10(-3)/°C), sensitivity (0.33 kPa(-1)), short response time (1 ms), minimum detectable pressure (4.93 Pa) after suffering repeated stimuli, temperature change and electric heating. Moreover, a stress-triggered Joule heater can be also fabricated mainly by the PPy-Ag NW hybrid aero-sponges with nearly zero temperature coefficient.

  20. Verification of Joule heat evolution model for silicate building materials with electrically conductive admixtures

    NASA Astrophysics Data System (ADS)

    Fiala, Lukáš; Maděra, Jiří; Černý, Robert

    2017-07-01

    Silicate building materials naturally exhibit electrically non-conductive behavior. However, a sufficient amount of electrically conductive admixtures leads to a significant increase of the electrical conductivity. This fact can be utilized in several practical ways, such as for development of self-sensing, electromagnetically-shielding or self-heating materials. In this paper, self-heating ability of chosen silicate material was tested and previously developed heating model was verified by means of comparison of calculated temperature evolution in time data with those experimentally determined by thermocouples placed on lateral sides. Sufficiently electrically conductive mixture with carbon black (CB) in amount of 8.89 % was used for DC experiment. Theoretical data were obtained by subsequent FEM calculations conducted on 3D model of the tested sample.

  1. The effect of the transformation of point defects under Joule heating on efficiency of LEDs with InGaN/GaN quantum wells

    NASA Astrophysics Data System (ADS)

    Bochkareva, N. I.; Ivanov, A. M.; Klochkov, A. V.; Tarala, V. A.; Shreter, Yu. G.

    2016-11-01

    It is shown that a short-time Joule heating of the active region of light-emitting diodes with InGaN/GaN quantum wells up to 125°C at a current density of 150 A/cm2 stimulates changes in the energy spectrum of defect states in the energy gap of GaN and leads to an increase in the quantum efficiency.

  2. Global effect of auroral particle and Joule heating in the undisturbed thermosphere

    NASA Technical Reports Server (NTRS)

    Hinton, B. B.

    1978-01-01

    From the compositional variations observed with the neutral atmosphere composition experiment on OGO 6 and a simplified model of thermospheric dynamics, global average values of non-EUV heating are deduced. These are 0.19-0.25 mW/sq m for quiet days and 0.44-0.58 mW/sq m for ordinary days.

  3. A Virial Treatment of the Joule and Joule-Thomson Coefficients.

    ERIC Educational Resources Information Center

    Rybolt, Thomas R.

    1981-01-01

    Provides background information designed to aid a physical chemistry student in using the virial equation of state in deriving expressions for other thermodynamic properties, such as writing the Joule and Joule-Thomson coefficients in terms of virial expansions. (CS)

  4. Effect of current crowding and Joule heating on electromigration-induced failure in flip chip composite solder joints tested at room temperature

    SciTech Connect

    Nah, J.W.; Suh, J.O.; Tu, K.N.

    2005-07-01

    The electromigration of flip chip solder joints consisting of 97Pb-3Sn and 37Pb-63Sn composite solders was studied under high current densities at room temperature. The mean time to failure and failure modes were found to be strongly dependent on the change in current density. The composite solder joints did not fail after 1 month stressed at 4.07x10{sup 4} A/cm{sup 2}, but failed after just 10 h of current stressing at 4.58x10{sup 4} A/cm{sup 2}. At a slightly higher current stressing of 5.00x10{sup 4} A/cm{sup 2}, the composite solder joints failed after only 0.6 h due to melting. Precipitation and growth of Cu{sub 6}Sn{sub 5} at the cathode caused the Cu under bump metallurgy to be quickly consumed and resulted in void formation at the contact area. The void reduced the contact area and displaced the electrical path, affecting the current crowding and Joule heating inside the solder bump. Significant Joule heating inside solder bumps can cause melting of the solder and quick failure. The effect of void propagation on current crowding and Joule heating was confirmed by simulation.

  5. Domain structure in Joule-heated CoFeSiB glass-covered amorphous microwires probed by magnetoimpedance and ferromagnetic resonance

    NASA Astrophysics Data System (ADS)

    da Silva, R. B.; Carara, M.; de Andrade, A. M. H.; Severino, A. M.; Sommer, R. L.

    2003-10-01

    Impedance spectra (100 kHz⩽f⩽1.8 GHz) were measured at different magnetic fields, and magnetoimpedance and magnetization measurements were performed in as-produced and Joule-heated Co70.4Fe4.6Si10B15 glass-covered amorphous microwires. From the magnetization curves and ferromagnetic resonance features obtained from the impedance spectra, it was possible to propose a domain structure in the as-produced microwires, as well as to follow its evolution with the annealing current. The inner core and outer shell domain structure were observed. The outer shell domains evolve from a circumferential, in the as-cast sample, to a helical structure in the case of the annealed samples. On the other hand, the inner core evolves from a domain structure typical of a radial anisotropy to a longitudinal one. This domain structure evolution is explained in terms of the combined effects of the stress, promoted by the annealing temperature, and the magnetic field caused by the annealing current.

  6. Preparative isoelectric focusing and Joule effect: a purification cell that contains a heat exchanger.

    PubMed

    Araque, A; Jaugey, J; Javet, P

    1996-01-01

    Reproducibility in protein purification by preparative isoelectric focusing depends greatly on temperature control during the separation process. A preparative apparatus is described, including a heat exchanger between compartments with isoelectric membranes. The selectivity of the isoelectric membranes was optimized as a function of isoelectric points of the separated proteins. At 2500 V and 60 W, 0.3 g of horse heart myoglobin from 0.2 g of whale skeletal muscle myoglobin could be separated in 1 h. At a total load of 2 g protein, 97% of bovine hemoglobin (2% initial concentration) was purified from bovine serum albumin (0.15%).

  7. Effect of Joule Heating and Thermal Radiation in Flow of Third Grade Fluid over Radiative Surface

    PubMed Central

    Hayat, Tasawar; Shafiq, Anum; Alsaedi, Ahmed

    2014-01-01

    This article addresses the boundary layer flow and heat transfer in third grade fluid over an unsteady permeable stretching sheet. The transverse magnetic and electric fields in the momentum equations are considered. Thermal boundary layer equation includes both viscous and Ohmic dissipations. The related nonlinear partial differential system is reduced first into ordinary differential system and then solved for the series solutions. The dependence of velocity and temperature profiles on the various parameters are shown and discussed by sketching graphs. Expressions of skin friction coefficient and local Nusselt number are calculated and analyzed. Numerical values of skin friction coefficient and Nusselt number are tabulated and examined. It is observed that both velocity and temperature increases in presence of electric field. Further the temperature is increased due to the radiation parameter. Thermal boundary layer thickness increases by increasing Eckert number. PMID:24454694

  8. Effect of Joule heating and thermal radiation in flow of third grade fluid over radiative surface.

    PubMed

    Hayat, Tasawar; Shafiq, Anum; Alsaedi, Ahmed

    2014-01-01

    This article addresses the boundary layer flow and heat transfer in third grade fluid over an unsteady permeable stretching sheet. The transverse magnetic and electric fields in the momentum equations are considered. Thermal boundary layer equation includes both viscous and Ohmic dissipations. The related nonlinear partial differential system is reduced first into ordinary differential system and then solved for the series solutions. The dependence of velocity and temperature profiles on the various parameters are shown and discussed by sketching graphs. Expressions of skin friction coefficient and local Nusselt number are calculated and analyzed. Numerical values of skin friction coefficient and Nusselt number are tabulated and examined. It is observed that both velocity and temperature increases in presence of electric field. Further the temperature is increased due to the radiation parameter. Thermal boundary layer thickness increases by increasing Eckert number.

  9. Iron Phosphate Glass for Vitrifying Hanford AZ102 LAW in Joule Heated and Cold Crucible Induction Melters

    SciTech Connect

    Day, Delbert E.; Brow, R. K.; Ray, C. S.; Kim, Cheol-Woon; Reis, Signo T.; Vienna, John D.; Peeler, David K.; Johnson, Fabienne; Hansen, E. K.; Sevigny, Gary J.; Soelberg, Nicolas R.; Pegg, Ian L.; Gan, Hao

    2012-01-05

    An iron phosphate composition for vitrifying a high sulfate (~17 wt%) and high alkali (~80 wt%) low activity Hanford waste, known as AZ102 LAW, has been developed for processing in a Joule Heated Melter (JHM) or a Cold Crucible Induction Melter (CCIM). This composition produced a glass waste form, designated as MS26AZ102F-2, with a waste loading of 26 wt% of the AZ102 which corresponded to a total alkali and sulfate (SO3) content of 21 and 4.2 wt%, respectively. A slurry (7M Na) of MS26AZ102F-2 simulant was melted continuously at temperatures between 1030 and 1090°C for 10 days in a small JHM at PNNL and for 7 days in a CCIM at INL. The as-cast glasses produced in both melters and in trial laboratory experiments along with their CCC-treated counterparts met the DOE LAW requirements for the Product Consistency Test (PCT) and the Vapor Hydration Test (VHT). These glass waste forms retained up to 77 % of the SO3 (3.3 wt%), 100% of the Cesium, and 33 to 44% of the rhenium, surrogate for Tc-99, all of which either exceeded or were comparable to the retention limit for these species in borosilicate glass nuclear waste form. Analyses of commercial K-3 refractory lining and the Inconel 693 metal electrodes used in JHM indicated only minimum corrosion of these components by the iron phosphate glass. This is the first time that an iron phosphate composition (slurry feed) was melted continuously in the JHM and CCIM, thereby, demonstrating that iron phosphate glasses can be used as alternative hosts for vitrifying nuclear waste.

  10. Impact of Joule heating, roughness, and contaminants on the relative hardness of polycrystalline gold.

    PubMed

    Freeze, Christopher R; Ji, Xiaoyin; Kingon, Angus I; Irving, Douglas L

    2013-11-27

    Asperities play a central role in the mechanical and electrical properties of contacting surfaces. Changes in trends of uniaxial compression of an asperity tip in contact with a polycrystalline substrate as a function of substrate geometry, compressive stress and applied voltage are investigated here by implementation of a coupled continuum and atomistic approach. Surprisingly, an unmodified Au polycrystalline substrate is found to be softer than one containing a void for conditions of high stress and an applied voltage of 0.2 V. This is explained in terms of the temperature distribution and weakening of Au as a function of temperature. The findings in this communication are important to the design of materials for electrical contacts because applied conditions may play a role in reversing relative hardness of the materials for conditions experienced during operation.

  11. Dynamically tracking the joule heating effect on the voltage induced metal-insulator transition in VO2 crystal film

    NASA Astrophysics Data System (ADS)

    Liao, G. M.; Chen, S.; Fan, L. L.; Chen, Y. L.; Wang, X. Q.; Ren, H.; Zhang, Z. M.; Zou, C. W.

    2016-04-01

    Insulator to metal phase transitions driven by external electric field are one of the hottest topics in correlated oxide study. While this electric triggered phenomena always mixes the electric field switching effect and joule thermal effect together, which are difficult to clarify the intrinsic mechanism. In this paper, we investigate the dynamical process of voltage-triggered metal-insulator transition (MIT) in a VO2 crystal film and observe the temperature dependence of the threshold voltages and switching delay times, which can be explained quite well based on a straightforward joule thermal model. By conducting the voltage controlled infrared transmittance measurement, the delayed infrared transmission change is also observed, further confirming the homogeneous switching process for a large-size film. All of these results show strong evidences that joule thermal effect plays a dominated role in electric-field-induced switching of VO2 crystal.

  12. Separation of Joule Heating and Peltier Cooling via Time-Resolved X-Ray Di?raction in Si/SiGe Superlattice

    NASA Astrophysics Data System (ADS)

    Kozina, Michael; Fuchs, Matthias; Chen, Jian; Jiang, Mason; Chen, Pice; Evans, Paul; Vermeersch, Bjorn; Bahk, Je-Hyeong; Shakouri, Ali; Brewe, Dale; Reis, David

    2012-02-01

    We present detailed measurements of the thermal pro?le in a pulsed current SiGe-based thermoelectric micro-cooler. The evolution of heat ?ow in thermoelectric materials has been previously studied using time-domain thermore?ectance imaging; however, such methods are typically only sensitive to the surface temperature of the device, and the heat ?ow into the material remains hidden. Using time-resolved x-ray di?raction, we probe the transient temperature change in both the surface gold electrode and the underlying Si/SiGe superlattice using the shift in diffraction pattern caused by thermal expansion. We are also able to resolve Joule heating vs. Peltier cooling taking place in the gold through separation of timescales made possible by the relatively short duration (100ps) of the Advanced Photon Source.

  13. Numerical investigation of MHD stagnation point flow and heat transfer over a permeable shrinking sheet with external magnetic field, viscous dissipation and Joule heating

    NASA Astrophysics Data System (ADS)

    Jafar, Khamisah; Nazar, Roslinda; Ishak, Anuar; Pop, Ioan

    2012-05-01

    The present study considers the steady laminar magnetohydrodynamic (MHD) boundary layer flow of a viscous and incompressible electrically conducting fluid near the stagnation point on a horizontal continuously shrinking surface, with variable wall temperature and a constant magnetic field applied normal to the surface of the sheet. The surface is assumed to be permeable, allowing either suction or injection at the wall. By introducing an appropriate similarity transformation, the governing system of partial differential equations is first transformed into a system of ordinary differential equations, which is then solved numerically using an implicit finite-difference scheme known as the Keller-box method for some values of the selected parameters. The effects of the governing parameters, namely the shrinking parameter λ, the suction parameter f0 and the magnetic parameter M on the skin friction coefficient, the local Nusselt number as well as the velocity and temperature profiles are determined and discussed. For the present study, the analysis is limited to the case where the Prandtl number is fixed at unity, i.e. Pr = 1 and the Eckert number, Ec = 0.5. It is found that solutions for the shrinking sheet only exist when the magnitude of the shrinking parameter is less than some limiting critical value λc. Where solutions do exist, they are either a unique solution or dual solutions, and for large enough suction at the wall, there may even be triple solutions. For the shrinking sheet, in the presence of viscous dissipation and Joule heating, the magnetic field increases the surface shear stress and slightly increases the surface heat transfer rate.

  14. On the Evolution From Micrometer-Scale Inhomogeneity to Global Overheated Structure During the Intense Joule Heating of a z-Pinch Rod

    DOE PAGES

    Awe, T. J.; Yu, E. P.; Yates, K. C.; ...

    2017-02-21

    Ultrafast optical microscopy of metal z-pinch rods pulsed with megaampere current is contributing new data and critical insight into what provides the fundamental seed for the magneto-Rayleigh-Taylor (MRT) instability. A two-frame near infrared/visible intensified-charge-coupled device gated imager with 2-ns temporal resolution and 3-μm spatial resolution captured emissions from the nonuniformly Joule heated surfaces of ultrasmooth aluminum (Al) rods. Nonuniform surface emissions are consistently first observed from discrete, 10-μm scale, subelectronvolt spots. Aluminum 6061 alloy, with micrometer-scale nonmetallic resistive inclusions, forms several times more spots than 99.999% pure Al 5N; 5-10 ns later, azimuthally stretched elliptical spots and distinct strata (40-100more » μm wide by 10 μm tall) are observed on Al 6061, but not on Al 5N. In such overheat strata, aligned parallel to the magnetic field, we find that they are highly effective seeds for MRT instability growth. Our data give credence to the hypothesis that early nonuniform Joule heating, such as the electrothermal instability, may provide the dominant seed for MRT.« less

  15. Electrokinetically driven continuous-flow enrichment of colloidal particles by Joule heating induced temperature gradient focusing in a convergent-divergent microfluidic structure.

    PubMed

    Zhao, Cunlu; Ge, Zhengwei; Song, Yongxin; Yang, Chun

    2017-09-07

    Enrichment of colloidal particles in continuous flow has not only numerous applications but also poses a great challenge in controlling physical forces that are required for achieving particle enrichment. Here, we for the first time experimentally demonstrate the electrokinetically-driven continuous-flow enrichment of colloidal particles with Joule heating induced temperature gradient focusing (TGF) in a microfluidic convergent-divergent structure. We consider four mechanisms of particle transport, i.e., advection due to electroosmosis, electrophoresis, dielectrophoresis and, and further clarify their roles in the particle enrichment. It is experimentally determined and numerically verified that the particle thermophoresis plays dominant roles in enrichment of all particle sizes considered in this study and the combined effect of electroosmosis-induced advection and electrophoresis is mainly to transport particles to the zone of enrichment. Specifically, the enrichment of particles is achieved with combined DC and AC voltages rather than a sole DC or AC voltage. A numerical model is formulated with consideration of the abovementioned four mechanisms, and the model can rationalize the experimental observations. Particularly, our analysis of numerical and experimental results indicates that thermophoresis which is usually an overlooked mechanism of material transport is crucial for the successful electrokinetic enrichment of particles with Joule heating induced TGF.

  16. Effect of the Joule heating and of the material voids on free-convective transport in porous or fibrous media with applied electrical fields.

    PubMed

    Erdmann, Eleonora; Oyanader, Mario A; Arce, Pedro

    2005-08-01

    The effect of the geometry of the soil in electrokinetic application has been studied by using capillary models of annular geometry. The Joule heating generation has been included as a primary effect of temperature development leading to buoyancy flows. The heat transfer model has been formulated for conduction-dominated regime. The results of this model have been coupled with the motion equation to obtain the analytical hydrodynamic velocity profile. Numerical illustrations, demonstrating the effect of the cross-sectional area of the annular region on the velocity field, have been included. It is observed that a substantial effect on the magnitude of such velocity field for different parameters of the system. The results are useful to obtain better understanding of the role of the soil geometry in potential soil cleaning field operations.

  17. Joule Unlimited Technologies Approval

    EPA Pesticide Factsheets

    This March 29 letter from EPA approves the petition from Joule Unlimited Technologies, Inc. regarding ethanol produced through the Joule Helioculture Process under the Clean Air Act for renewable fuel [D-code 5] RINs under the RFS program.

  18. Iron Phosphate Glass for Vitrifying Hanford AZ102 LAW in Joule Heated and Cold Crucible Induction Melters - 12240

    SciTech Connect

    Day, Delbert E.; Brow, Richard K.; Ray, Chandra S.; Reis, Signo T.; Kim, Cheol-Woon; Vienna, John D.; Sevigny, Gary; Peeler, David; Johnson, Fabienne C.; Hansen, Eric K.; Soelberg, Nick; Pegg, Ian L.; Gan, Hao

    2012-07-01

    An iron phosphate composition for vitrifying a high sulfate (∼17 wt%) and high alkali (∼80 wt%) Hanford low activity waste (LAW), known as AZ-102 LAW, has been developed for processing in a Joule Heated Melter (JHM) or a Cold Crucible Induction Melter (CCIM). This composition produced a glass waste form, designated as MS26AZ102F-2, with a waste loading of 26 wt% of the AZ-102 which corresponded to a total alkali and sulfate (represented as SO{sub 3}) content of 21 and 4.4 wt%, respectively. A slurry (7 M Na{sup +}) of MS26AZ102F-2 simulant was melted continuously at temperatures between 1030 and 1090 deg. C for 10 days in a small JHM at PNNL and for 70 hours in a CCIM at INL. The as-cast glasses produced in both melters and in trial laboratory experiments along with their canister centerline cooled (CCC) counterparts met the requirements for the Product Consistency Test (PCT) and the Vapor Hydration Test (VHT) responses in the Hanford Tank Waste Treatment and Immobilization Plant (WTP) Contract. These glass waste forms retained up to 77 % of the SO{sub 3} (3.3 wt%), 100% of the Cesium, and 33 to 44% of the rhenium (used as a surrogate for Tc) all of which either exceeded or were comparable to the retention limit for these species in borosilicate glass nuclear waste form. Analyses of commercial K-3 refractory lining and the Inconel 693 metal electrodes used in JHM indicated only minimum corrosion of these components by the iron phosphate glass. This is the first time that an iron phosphate composition was melted continuously in a slurry fed JHM and in the US, thereby, demonstrating that iron phosphate glasses can be used as alternative hosts for vitrifying nuclear waste. The following conclusions are drawn from the results of the present work. (1) An iron phosphate composition, designated as MS26AZ102F-2, containing 26 wt% of the simulated high sulfate (17 wt%), high alkali (80 wt%) Hanford AZ-102 LAW meets all the criteria for processing in a JHM and CCIM. This

  19. Joule heating effect on oxide whisker growth induced by current stressing in Cu/Sn-58Bi/Cu solder joint

    NASA Astrophysics Data System (ADS)

    He, Hongwen; Cao, Liqiang; Wan, Lixi; Zhao, Haiyan; Xu, Guangchen; Guo, Fu

    2012-08-01

    The electromigration test was conducted in Cu/Sn-58Bi/Cu solder joint with high current density of 104 A/ cm2. Results showed that a large number of whiskers with natural weed appearance were observed at the cathode side in such a short current stressing time. Furthermore, some secondary whiskers were attached to the primary whiskers, which has never been reported before. We presumed the vapor-solid (VS) mechanism to explain the oxide whiskers growth, which was quite different from the traditional theory that the compressive stress took on the driving force. In conclusion, due to the over-Joule heating effect, the metal oxide whiskers were synthesized in bulk quantities by thermal evaporation of Sn oxide and Bi oxide.

  20. Effect of superconductive destruction in YBa{sub 2}Cu{sub 3}O{sub 7-{sigma}} bulk bridges under the action of strong Joule self heating

    SciTech Connect

    Morgoon, V.N.; Rodrigues, D.

    1996-02-01

    Transition from superconductive to normal state and back into superconductive state in bulk single crystal YBaCuO bridges with twins induced by a strong transport current has been investigated. The current voltage characteristics (CVC), the temperature and magnetic field dependences of resistance [resistive transition (RT)] in the regime of fixed current near T{sub c} were studied in detail. A sharp dynamic superconductive transition or switching over effect, nonlinear CVC, and hysteresis were observed. The CVC and RT characteristics can be explained by the thermal bistability phenomena at strong Joule self-heating of bridges, in particular, in the presence of internal local inhomogeneities in superconductor. Electrical characteristics of bridges which can be used as nonlinear elements for cryogenic electronics were obtained.

  1. Temperature increase due to Joule heating in a nanostructured MgO-based magnetic tunnel junction over a wide current-pulse range.

    PubMed

    Jeong, Boram; Lim, Sang Ho

    2011-07-01

    The temperature increase due to Joule heating in a nanopillar of a magnetic tunnel junction sandwiched by top and bottom electrodes was calculated by the finite element method. The results for the critical condition for the current-induced magnetization switching measured over a wide current-pulse range were taken from the literature. At long pulse widths, the temperature increase was solely dependent on the magnitude of the critical current density. However, no saturation in the temperature increase occurred for short pulse widths. In this case, the temperature increase additionally depended on the pulse width, so that a broad maximum occurred in the pulse width (or the critical current density) dependence of the temperature increase. The original results for the critical condition were corrected by accounting for the temperature increase and these corrected results, together with the Slonczewski equation, were used to extract an accurate value for the thermal stability factor.

  2. A governing parameter for the melting phenomenon at nanocontacts by Joule heating and its application to joining together two thin metallic wires

    SciTech Connect

    Tohmyoh, Hironori

    2009-01-01

    For cutting and joining extremely thin metallic wires, the issue of Joule heating in the wires is considered. The middle of a section of a thin Pt wire with a diameter of about 800 nm was melted locally by a direct current supply, and the wire was cut at a predetermined point by applying a force to shear the molten part of the wire. Furthermore, a constant current was applied to a system in which the free ends of two Pt wires were contacted, and the wires were joined together. A parameter, which governs the melting phenomenon at the point of contact of very thin wires, is proposed. It was verified that the conditions required for joining thin wires were able to be determined by the parameter that depends on the applied current, the length and cross sectional area of the wires, and a function of the geometrical quantities for calibrating the thermal conditions.

  3. Direct evidence of molecular aggregation and degradation mechanism of organic light-emitting diodes under joule heating: an STM and photoluminescence study.

    PubMed

    Gong, Jian-Ru; Wan, Li-Jun; Lei, Sheng-Bin; Bai, Chun-Li; Zhang, Xiao-Hong; Lee, Shuit-Tong

    2005-02-10

    The Joule heating effect on electroluminescent efficiency is important in the degradation origin of organic light-emitting diodes (OLED). Scanning tunneling microscopy (STM) and photoluminescence (PL) measurements were performed on the guest molecule BT (1,4-bis(benzothiazole-vinyl) benzene), host molecule TPBI (2, 2',2' '-(1,3,5-phenylene)tris-[1-phenyl-1H-benzimidazole]), and their mixture deposited on an HOPG surface to study the OLED degradation mechanism due to thermal heating. At room temperature, BT and TPBI in the mixed layer show good compatibility and high PL intensity, but at higher temperatures, they show phase separation and aggregation into their own domains and a concomitant decrease in PL intensity. The PL intensity loss suggests ineffective energy transfer from TPBI to BT due to phase separation, which may cause OLED degradation. Scanning tunneling spectroscopy (STS) results show that the band gaps of TPBI and BT remain unchanged with the annealing temperature, suggesting that the heat-induced decay of OLED is related to the interfacial structural change rather than the respective molecular band gap. The results provide direct evidence showing how the molecular structures of the mixed layer vary and affect the PL intensity due to temperature.

  4. Investigation of MHD effects and heat transfer for the upper-convected Maxwell (UCM-M) micropolar fluid with Joule heating and thermal radiation using a hyperbolic heat flux equation

    NASA Astrophysics Data System (ADS)

    Khan, Sabeel M.; Hammad, M.; Batool, S.; Kaneez, H.

    2017-04-01

    In this article, we investigate MHD flow of micropolar upper-convected Maxwell (UCM) fluid with the application of a recently proposed hyperbolic heat flux equation thus allowing explaining the time relaxation characteristics for heat flux. The aim is to incorporate microstructural effects in the upper-convected Maxwell fluid with Joule heating and thermal radiation. In this respect, microrotation of the fluid particles is taken into account and as a result the angular-momentum balance equation is obtained. The resulting governing flow equations are transformed into their respective system of ODEs by using suitable similarity transformations. As a consequence two non-dimensional parameters arise thus accounting for microstructural effects in the UCM fluid. Effects of these microstructural parameters on macroscopic velocity, microrotations and temperature profiles are examined. Moreover, different other physical parameters for instance, Magnetic parameter, Eckert number, Prandtl number, fluid and thermal relaxation time affecting the velocities and temperature profiles are also studied and discussed in case of both classical and micropolar fluid flow. The accuracy of the numerical solution obtained by the shooting method is shown by comparing the skin friction coefficient values in the case of classical fluid flow with existing results in the literature.

  5. On the effectiveness of viscous dissipation and Joule heating on steady Magnetohydrodynamic heat and mass transfer flow over an inclined radiate isothermal permeable surface in the presence of thermophoresis

    NASA Astrophysics Data System (ADS)

    Alam, M. S.; Rahman, M. M.; Sattar, M. A.

    2009-05-01

    The combined effect of viscous dissipation and joule heating on steady Magnetohydrodynamic heat and mass transfer flow of viscous incompressible fluid over an inclined radiate isothermal permeable surface in the presence of thermophoresis is studied. Numerical results for the dimensionless velocity, temperature and concentration profiles as well as the local skin-friction coefficient, the local Nusselt number and the local Stanton number are displayed graphically for various physical parameters. Comparisons with previously published work are performed and the results are found to be in very good agreement. Results show that rate of heat transfer is sensitive for increasing angle of inclination parameter for the case of fluid injection and it decreases with the increase of magnetic field parameter and Eckert number.

  6. The Mayer-Joule Principle: The Foundation of the First Law of Thermodynamics

    NASA Astrophysics Data System (ADS)

    Newburgh, Ronald; Leff, Harvey S.

    2011-11-01

    To most students today the mechanical equivalent of heat, called the Mayer-Joule principle, is simply a way to convert from calories to joules and vice versa. However, in linking work and heat—once thought to be disjointed concepts—it goes far beyond unit conversion. Heat had eluded understanding for two centuries after Galileo Galilei constructed an early thermometer. Independently, Julius Robert Mayer and James Prescott Joule found the connection between heat and work, the Mayer-Joule principle.

  7. Steady State and Dynamics of Joule Heating in Magnetic Tunnel Junctions Observed via the Temperature Dependence of RKKY Coupling

    NASA Astrophysics Data System (ADS)

    Chavent, A.; Ducruet, C.; Portemont, C.; Vila, L.; Alvarez-Hérault, J.; Sousa, R.; Prejbeanu, I. L.; Dieny, B.

    2016-09-01

    Understanding quantitatively the heating dynamics in magnetic tunnel junctions submitted to current pulses is very important in the context of spin-transfer-torque magnetic random-access memory development. Here we provide a method to probe the heating of magnetic tunnel junctions using the Ruderman-Kittel-Kasuya-Yoshida coupling of a synthetic ferrimagnetic storage layer as a thermal sensor. The temperature increase versus applied bias voltage is measured thanks to the decrease of the spin-flop field with temperature. This method allows distinguishing spin-transfer torque effects from the influence of temperature on the switching field. The heating dynamics is then studied in real time by probing the conductance variation due to spin-flop rotation during heating. This approach provides a method for measuring fast heating in spintronic devices, particularly magnetic random-access memory using thermally assisted or spin-transfer torque writing.

  8. Comparison of a Joule effect calibration system using Kanthal wire and a laser diode as heat sources

    NASA Astrophysics Data System (ADS)

    Maldonado, Blas A.; Bárcena-Soto, Maximiliano; Casillas, Norberto; Flores, Jorge L.

    2009-09-01

    Here it is presented a comparison of two calibration techniques applied to a thermistor element used in a surface microcalorimeter which operates under Isoperibol conditions. Usually surface microcalorimeters employ a thermistor as a temperature sensing element, whose heat capacity requires to be evaluated before they can be used. One alternative method to estimate its heat capacity is by supplying a known amount of energy and detecting its temperature changes. Thus, surface heating can be achieved by different techniques; one of them is by supplying energy to the thermistor by passing current through a Ni-Cr coil wined around the glass bulb thermistor. A rather different and more convenient technique consists of directly illuminating a small well-defined thermistor area with an infrared 1550 nm wavelength laser beam, while detecting the thermistor temperature changes. Both procedures are thoroughly compared and the heat capacities obtained by both methods are presented.

  9. Exciton quenching by diffusion of 2,3,5,6-tetrafluoro-7,7',8,8'-tetra cyano quino dimethane and its consequences on joule heating and lifetime of organic light-emitting diodes.

    PubMed

    Tyagi, Priyanka; Kumar, Arunandan; Giri, Lalat Indu; Dalai, Manas Kumar; Tuli, Suneet; Kamalasanan, M N; Srivastava, Ritu

    2013-10-01

    In this Letter, the effect of F(4)-TCNQ insertion at the anode/hole transport layer (HTL) interface was studied on joule heating and the lifetime of organic light-emitting diodes (OLEDs). Joule heating was found to reduce significantly (pixel temperature decrease by about 10 K at a current density of 40 mA/cm(2)) by this insertion. However, the lifetime was found to reduce significantly with a 1 nm thick F(4)-TCNQ layer, and it improved by increasing the thickness of this layer. Thermal diffusion of F(4)-TCNQ into HTL leads to F(4)-TCNQ ionization by charge transfer, and drift of these molecules into the emissive layer caused faster degradation of the OLEDs. This drift was found to reduce with an increase in the thickness of F(4)-TCNQ.

  10. Joule heating induced thermomigration failure in un-powered microbumps due to thermal crosstalk in 2.5D IC technology

    SciTech Connect

    Li, Menglu; Tu, K. N.; Kim, Dong Wook; Gu, Sam; Parkinson, Dilworth Y.; Barnard, Harold

    2016-08-21

    Thermal-crosstalk induced thermomigration failure in un-powered microbumps has been found in 2.5D integrated circuit (IC) circuit. In 2.5D IC, a Si interposer was used between a polymer substrate and a device chip which has transistors. The interposer has no transistors. If transistors are added to the interposer chip, it becomes 3D IC. In our test structure, there are two Si chips placed horizontally on a Si interposer. The vertical connections between the interposer and the Si chips are through microbumps. We powered one daisy chain of the microbumps under one Si chip; however, the un-powered microbumps in the neighboring chip are failed with big holes in the solder layer. We find that Joule heating from the powered microbumps is transferred horizontally to the bottom of the neighboring un-powered microbumps, and creates a large temperature gradient, in the order of 1000 °C/cm, through the un-powered microbumps in the neighboring chip, so the latter failed by thermomigration. In addition, we used synchrotron radiation tomography to compare three sets of microbumps in the test structure: microbumps under electromigration, microbumps under thermomigration, and microbumps under a constant temperature thermal annealing. The results show that the microbumps under thermomigration have the largest damage. Furthermore, simulation of temperature distribution in the test structure supports the finding of thermomigration.

  11. Joule heating induced thermomigration failure in un-powered microbumps due to thermal crosstalk in 2.5D IC technology

    NASA Astrophysics Data System (ADS)

    Li, Menglu; Kim, Dong Wook; Gu, Sam; Parkinson, Dilworth Y.; Barnard, Harold; Tu, K. N.

    2016-08-01

    Thermal-crosstalk induced thermomigration failure in un-powered microbumps has been found in 2.5D integrated circuit (IC) circuit. In 2.5D IC, a Si interposer was used between a polymer substrate and a device chip which has transistors. The interposer has no transistors. If transistors are added to the interposer chip, it becomes 3D IC. In our test structure, there are two Si chips placed horizontally on a Si interposer. The vertical connections between the interposer and the Si chips are through microbumps. We powered one daisy chain of the microbumps under one Si chip; however, the un-powered microbumps in the neighboring chip are failed with big holes in the solder layer. We find that Joule heating from the powered microbumps is transferred horizontally to the bottom of the neighboring un-powered microbumps, and creates a large temperature gradient, in the order of 1000 °C/cm, through the un-powered microbumps in the neighboring chip, so the latter failed by thermomigration. In addition, we used synchrotron radiation tomography to compare three sets of microbumps in the test structure: microbumps under electromigration, microbumps under thermomigration, and microbumps under a constant temperature thermal annealing. The results show that the microbumps under thermomigration have the largest damage. Furthermore, simulation of temperature distribution in the test structure supports the finding of thermomigration.

  12. Minimizing the impact of Joule heating as a prerequisite for the reliable analysis of metal-protein complexes by capillary electrophoresis.

    PubMed

    Nowak, Paweł Mateusz; Śpiewak, Klaudyna; Woźniakiewicz, Michał; Kościelniak, Paweł

    2017-04-28

    Herein we report on a drastic release of metal ions from the Fe-bound transferrin, and Fe- or Mn-bound lactoferrin, observed upon the increase in the separation voltage during CE-based analysis. To verify whether this process is caused directly by electric field, we developed an Isothermal Voltage Increase approach (IVI), which is the extension of methods reported by Krylov et al. IVI ensures isothermal conditions while increasing separation voltage by a hydrodynamic pushing of the injected sample to the actively cooled capillary section, combined with a rationale choice of cooling temperature, dependent on the value of current. Interestingly, the application of IVI revealed that the previously observed effect was caused solely by the insufficient dissipation of Joule heating - the saturation of each protein remained unchanged despite a significant rise in the electric field. This outcome demonstrates how crucial is to ensure an effective temperature control for preventing systematic errors in the analysis of biomolecular complexes. IVI seems also to be a simple and useful tool for discovering new potential processes that may be stimulated directly by electric field. Copyright © 2017 Elsevier B.V. All rights reserved.

  13. Influence of viscous dissipation and Joule heating on MHD bio-convection flow over a porous wedge in the presence of nanoparticles and gyrotactic microorganisms.

    PubMed

    Khan, Umar; Ahmed, Naveed; Mohyud-Din, Syed Tauseef

    2016-01-01

    The flow over a porous wedge, in the presence of viscous dissipation and Joule heating, has been investigated. The wedge is assumed to be saturated with nanofluid containing gyrotactic microorganisms. For the flow, magneto-hydrodynamic effects are also taken into consideration. The problem is formulated by using the passive control model. The partial differential equations, governing the flow, are transformed into a set of ordinary differential equations by employing some suitable similarity transformations. A numerical scheme, called Runge-Kutta-Fehlberg method, has been used to obtain the local similarity solutions for the system. Variations in the velocity, temperature, concentration and motile micro-organisms density profiles are highlighted with the help of graphs. The expressions for skin friction coefficient, Nusselt number, Sherwood number and motile micro-organisms density number are obtained and plotted accordingly. For the validity of the obtained results, a comparison with already existing results (special cases) is also presented. The magnetic field increases the velocity of the fluid. Injection at the walls can be used to reduce the velocity boundary layer thickness. Thermal boundary layer thickness can be reduced by using the magnetic field and the suction at the wall. The motile microorganisms density profile is an increasing function of the bioconvection Pecket number and bioconvection constant. The same is a decreasing function of m, M and Le. The skin friction coefficient increases with increasing m and [Formula: see text]. Nusselt number and the density number of motile microorganisms are higher for the case of suction as compared to the injection case. The density number of motile microorganisms is an increasing function for all the involved parameters.

  14. The Joule-Thomson effect in confined fluids

    NASA Astrophysics Data System (ADS)

    Schoen, Martin

    1999-08-01

    The Joule-Thomson effect is discussed for a fluid composed of spherically symmetric Lennard-Jones(12,6) molecules (of “diameter” σ) confined between two planar, rigid, structureless solid substrates separated by sz=10 and 20 σ. The effect of “strong” and “weak” of the substrate is studied by employing fluid-substrate potentials with and without attractive interactions, respectively. The focal point of this study is the confinement-induced depression of the inversion temperature Tinv with respect to the bulk value. It is defined such that during a Joule-Thomson expansion the temperature of a (confined or bulk) gas remains constant. In the limit of vanishing gas density, Tinv is computed from the second virial coefficient defined through a density expansion of the transverse stress T∥ in the gas. For higher densities Tinv is computed from the (transverse) expansion coefficient α∥ which is accessible through density and enthalpy fluctuations in mixed stress-strain ensemble Monte Carlo simulations. Results of these simulations are analyzed in terms of a mean-field theory which provides a qualitatively correct description of the Joule-Thomson effect in confined fluids. The smaller sz the more depressed (with respect to the bulk) is Tinv. The density dependence of Tinv is different for “strong” and “weak” substrates. Without attractive fluid-fluid interactions Tinv does not exist and the confined gas is always heated during a Joule-Thomson expansion. In this case α∥ is independent of the substrate material.

  15. Watt and joule balances

    NASA Astrophysics Data System (ADS)

    Robinson, Ian A.

    2014-04-01

    The time is fast approaching when the SI unit of mass will cease to be based on a single material artefact and will instead be based upon the defined value of a fundamental constant—the Planck constant—h . This change requires that techniques exist both to determine the appropriate value to be assigned to the constant, and to measure mass in terms of the redefined unit. It is important to ensure that these techniques are accurate and reliable to allow full advantage to be taken of the stability and universality provided by the new definition and to guarantee the continuity of the world's mass measurements, which can affect the measurement of many other quantities such as energy and force. Up to now, efforts to provide the basis for such a redefinition of the kilogram were mainly concerned with resolving the discrepancies between individual implementations of the two principal techniques: the x-ray crystal density (XRCD) method [1] and the watt and joule balance methods which are the subject of this special issue. The first three papers report results from the NRC and NIST watt balance groups and the NIM joule balance group. The result from the NRC (formerly the NPL Mk II) watt balance is the first to be reported with a relative standard uncertainty below 2 × 10-8 and the NIST result has a relative standard uncertainty below 5 × 10-8. Both results are shown in figure 1 along with some previous results; the result from the NIM group is not shown on the plot but has a relative uncertainty of 8.9 × 10-6 and is consistent with all the results shown. The Consultative Committee for Mass and Related Quantities (CCM) in its meeting in 2013 produced a resolution [2] which set out the requirements for the number, type and quality of results intended to support the redefinition of the kilogram and required that there should be agreement between them. These results from NRC, NIST and the IAC may be considered to meet these requirements and are likely to be widely debated

  16. Joule heating scanning structure system.

    PubMed

    Moya, J A

    2016-08-01

    A method and its system to study the structural evolution on soft magnetic amorphous and nanocrystalline ribbon shaped alloys are presented. With only one sample, a complete set of magnetic and electric data at room and at high temperature are obtained in a relatively short period of time, allowing us to elucidate the structural changes occurring in the alloy and to determine the optimal soft magnetic properties annealing conditions.

  17. Joule-Heated Ceramic-Lined Melter to Vitrify Liquid Radioactive Wastes Containing Am241 Generated From MOX Fuel Fabrication in Russia

    SciTech Connect

    Smith, E C; Bowan II, B W; Pegg, I; Jardine, L J

    2004-11-16

    americium it contains. Silver is widely used as an additive in glass making. However, its solubility is known to be limited in borosilicate glasses. Further, silver, which is present as a nitrate salt in the waste, can be easily reduced to molten silver in the melting process. Molten silver, if formed, would be difficult to reintroduce into the glass matrix and could pose operating difficulties for the glass melter. This will place a limitation on the waste loading of the melter feed material to prevent the separation of silver from the waste within the melter. If the silver were recovered in the MOx fabrication process, which is currently under consideration, the composition of the glass would likely be limited only by the thermal heat load from the incorporated {sup 241}Am. The resulting mass of glass used to encapsulate the waste could then be reduced by a factor of approximately three. The vitrification process used to treat the waste stream is proposed to center on a joule-heated ceramic lined slurry fed melter. Glass furnaces of this type are used in the United States to treat high-level waste (HLW) at the: Defense Waste Processing Facility, West Valley Demonstration Project, and to process the Hanford tank waste. The waste will initially be blended with glass-forming chemicals, which are primarily sand and boric acid. The resulting slurry is pumped to the melter for conversion to glass. The melter is a ceramic lined metal box that contains a molten glass pool heated by passing electric current through the glass. Molten glass from the melter is poured into canisters to cool and solidify. They are then sealed and decontaminated to form the final waste disposal package. Emissions generated in the melter from the vitrification process are treated by an off-gas system to remove radioactive contamination and destroy nitrogen oxides (NOx).

  18. The Mayer-Joule Principle: The Foundation of the First Law of Thermodynamics

    ERIC Educational Resources Information Center

    Newburgh, Ronald; Leff, Harvey S.

    2011-01-01

    To most students today the mechanical equivalent of heat, called the Mayer-Joule principle, is simply a way to convert from calories to joules and vice versa. However, in linking work and heat--once thought to be disjointed concepts--it goes far beyond unit conversion. Heat had eluded understanding for two centuries after Galileo Galilei…

  19. The Mayer-Joule Principle: The Foundation of the First Law of Thermodynamics

    ERIC Educational Resources Information Center

    Newburgh, Ronald; Leff, Harvey S.

    2011-01-01

    To most students today the mechanical equivalent of heat, called the Mayer-Joule principle, is simply a way to convert from calories to joules and vice versa. However, in linking work and heat--once thought to be disjointed concepts--it goes far beyond unit conversion. Heat had eluded understanding for two centuries after Galileo Galilei…

  20. Cascade Joule-Thomson refrigerators

    NASA Technical Reports Server (NTRS)

    Tward, E.; Steyert, W. A.

    1983-01-01

    The design criteria for cascade Joule-Thomson refrigerators for cooling in the temperature range from 300 K to 4.2 K were studied. The systems considered use three or four refrigeration stages with various working gases to achieve the low temperatures. Each stage results in cooling to a progressively lower temperature and provides cooling at intermediate temperatures to remove the substantial amount of parasitic heat load encountered in a typical dewar. With careful dewar design considerable cooling can be achieved with moderate gas flows. For many applications, e.g., in the cooling of sensitive sensors, the fact that the refrigerator contains no moving parts and may be remotely located from the gas source is of considerable advantage. A small compressor suitable for providing the gas flows required was constructed.

  1. Joule-Thomson Expander Without Check Valves

    NASA Technical Reports Server (NTRS)

    Chan, C. K.; Gatewood, J. R.

    1989-01-01

    Cooling effected by bidirectional, reciprocating flow of gas. Type of Joule-Thomson (J-T) expander for cryogenic cooling requires no check valves to prevent reverse flow of coolant. More reliable than conventional J-T expander, containing network of check valves, each potential source of failure. Gas flows alternately from left to right and right to left. Heat load cooled by evaporation of liquid from left or right compartment, whichever at lower pressure.

  2. On spectral relaxation method approach for steady von Kármán flow of a Reiner-Rivlin fluid with Joule heating, viscous dissipation and suction/injection

    NASA Astrophysics Data System (ADS)

    Motsa, Sandile S.; Makukula, Zodwa G.

    2013-03-01

    In this study we use the spectral relaxation method (SRM) for the solution of the steady von Kármán flow of a Reiner-Rivlin fluid with Joule heating and viscous dissipation. The spectral relaxation method is a new Chebyshev spectral collocation based iteration method that is developed from the Gauss-Seidel idea of decoupling systems of equations. In this work, we investigate the applicability of the method in solving strongly nonlinear boundary value problems of von Kármán flow type. The SRM results are validated against previous results present in the literature and with those obtained using the bvp4c, a MATLAB inbuilt routine for solving boundary value problems. The study highlights the accuracy and efficiency of the proposed SRM method in solving highly nonlinear boundary layer type equations.

  3. Joule Heating Induced Nonlinear Behavior in the Phase-Separated System (La0.73Bi0.27)0.67Ca0.33MnO3

    NASA Astrophysics Data System (ADS)

    Wu, Yuying; Li, Haina; Xia, Zhengcai; Zhang, Gufei; Vanacken, Johan; Moshchalkov, Victor V.

    2011-05-01

    A conduction mechanism has been investigated in the phase-separated compound (La0.73Bi0.27)0.67Ca0.33MnO3 at various temperatures below and above the ferromagnetic-paramagnetic (FM-PM) transition temperature T c . When a high current density applied, a strong nonlinear behavior with negative differential resistance (NDR) was observed. The application of an external magnetic field inhibits the appearance of NDR. Usually, the experiments strongly suggest that the electric field has an important effect on the nonlinear conduction behavior of the sample. However, our experiment shows that, instead of the electric field effect (that is electroresistance), the observed nonlinear behavior results mainly from the Joule heating effect. Thus, we should exercise extreme caution when interpreting the nonlinear conduction behavior of the phase-separated system.

  4. Memoir of James Prescott Joule

    NASA Astrophysics Data System (ADS)

    Reynolds, Osborne

    2011-06-01

    1. Introduction; 2. Parentage and early life; 3. Joule's first research; 4. Second research; 5. Third research; 6. Efforts to convince the scientific world; 7. The year 1847; 8. Joule's views accepted by Thomson, Rankine, and Clausius; 9. Middle life; 10. Later life; Appendix to page 18; Note A to page 88; Index.

  5. Multicomponent gas sorption Joule-Thomson refrigeration

    NASA Technical Reports Server (NTRS)

    Jones, Jack A. (Inventor); Petrick, S. Walter (Inventor); Bard, Steven (Inventor)

    1991-01-01

    The present invention relates to a cryogenic Joule-Thomson refrigeration capable of pumping multicomponent gases with a single stage sorption compressor system. Alternative methods of pumping a multicomponent gas with a single stage compressor are disclosed. In a first embodiment, the sorbent geometry is such that a void is defined near the output of the sorption compressor. When the sorbent is cooled, the sorbent primarily adsorbs the higher boiling point gas such that the lower boiling point gas passes through the sorbent to occupy the void. When the sorbent is heated, the higher boiling point gas is desorbed at high temperature and pressure and thereafter propels the lower boiling point gas out of the sorption compressor. A mixing chamber is provided to remix the constituent gases prior to expansion of the gas through a Joule-Thomson valve. Other methods of pumping a multicomponent gas are disclosed. For example, where the sorbent is porous and the low boiling point gas does not adsorb very well, the pores of the sorbent will act as a void space for the lower boiling point gas. Alternatively, a mixed sorbent may be used where a first sorbent component physically adsorbs the high boiling point gas and where the second sorbent component chemically absorbs the low boiling point gas.

  6. Steady-state analytical model of suspended p-type 3C-SiC bridges under consideration of Joule heating

    NASA Astrophysics Data System (ADS)

    Balakrishnan, Vivekananthan; Dinh, Toan; Phan, Hoang-Phuong; Kozeki, Takahiro; Namazu, Takahiro; Viet Dao, Dzung; Nguyen, Nam-Trung

    2017-07-01

    This paper reports an analytical model and its validation for a released microscale heater made of 3C-SiC thin films. A model for the equivalent electrical and thermal parameters was developed for the two-layer multi-segment heat and electric conduction. The model is based on a 1D energy equation, which considers the temperature-dependent resistivity and allows for the prediction of voltage-current and power-current characteristics of the microheater. The steady-state analytical model was validated by experimental characterization. The results, in particular the nonlinearity caused by temperature dependency, are in good agreement. The low power consumption of the order of 0.18 mW at approximately 310 K indicates the potential use of the structure as thermal sensors in portable applications.

  7. Long-term evolution of anthropogenic heat fluxes into a subsurface urban heat island.

    PubMed

    Menberg, Kathrin; Blum, Philipp; Schaffitel, Axel; Bayer, Peter

    2013-09-03

    Anthropogenic alterations in urban areas influence the thermal environment causing elevated atmospheric and subsurface temperatures. The subsurface urban heat island effect is observed in several cities. Often shallow urban aquifers exist with thermal anomalies that spread laterally and vertically, resulting in the long-term accumulation of heat. In this study, we develop an analytical heat flux model to investigate possible drivers such as increased ground surface temperatures (GSTs) at artificial surfaces and heat losses from basements of buildings, sewage systems, subsurface district heating networks, and reinjection of thermal wastewater. By modeling the anthropogenic heat flux into the subsurface of the city of Karlsruhe, Germany, in 1977 and 2011, we evaluate long-term trends in the heat flux processes. It revealed that elevated GST and heat loss from basements are dominant factors in the heat anomalies. The average total urban heat flux into the shallow aquifer in Karlsruhe was found to be ∼759 ± 89 mW/m(2) in 1977 and 828 ± 143 mW/m(2) in 2011, which represents an annual energy gain of around 1.0 × 10(15) J. However, the amount of thermal energy originating from the individual heat flux processes has changed significantly over the past three decades.

  8. Comparison between GITM simulation and JOULE rocket observation

    NASA Astrophysics Data System (ADS)

    Deng, Y.; Ridley, A. J.; Zhan, T.; Larsen, M.; Pfaff, R.

    2006-12-01

    The JOULE sounding rocket experiment was carried out at the Poker Flat Research Range in Alaska on March 27, 2003. Two instrumented rockets and one chemical tracer rocket were lauched around 12:00UT, which followed many hours of geomagnetically active conditions. They measured the in-situ small-scale electric field, ion velocity and electric density in the upper mesosphere and low thermosphere. From the released trimethyl aluminum (TMA) trails, neutral wind profiles were provided. Since the Global Ionosphere Thermosphere Model (GITM) has a flexible grid structure, sub-degree resolution around the JOULE rocket position can be applied and relatively reasonable results in such a small-scale can be achived. Not only will the simulation results be compared with JOULE observations, but also the comparsion between simulations using different high-latitude drivers will be conducted. It will be shown that using AMIE results produces more accurate neutral wind patterns than empirical models, although the auroral precipitation pattern may be too wide in AMIE, producing too much E- region electron density within GITM. In order to show the significance of spatial variability, GITM will also be run with different resolutions. This study will help us validate the GITM model and understand the significance of small-scale structure to the Joule heating.

  9. Joule heating in spin Hall geometry

    NASA Astrophysics Data System (ADS)

    Taniguchi, Tomohiro

    2016-07-01

    The theoretical formula for the entropy production rate in the presence of spin current is derived using the spin-dependent transport equation and thermodynamics. This theory is applicable regardless of the source of the spin current, for example, an electric field, a temperature gradient, or the Hall effect. It reproduces the result in a previous work on the dissipation formula when the relaxation time approximation is applied to the spin relaxation rate. By using the developed theory, it is found that the dissipation in the spin Hall geometry has a contribution proportional to the square of the spin Hall angle.

  10. Electroosmotic Entry Flow with Joule Heating Effects

    NASA Astrophysics Data System (ADS)

    Prabhakaran, Rama; Kale, Akshay; Xuan, Xiangchun

    Electrokinetic flow, which transports liquids by electroosmosis and samples by electrophoresis, is the transport method of choice in microfluidic chips over traditional pressure-driven flows. Studies on electrokinetic flows have so far been almost entirely limited to inside microchannels. Very little work has been done on the electroosmotic fluid entry from a reservoir to a microchannel, which is the origin of all fluid and sample motions in microchips. We demonstrate in this talk that strong vortices of opposite circulating directions can be generated in electroosmotic entry flows. We also develop a two-dimensional depth-averaged numerical model of the entire microchip to predict and understand the fluid temperature and flow fields at the reservoir-microchannel junction.

  11. Comment on ``Long-Term Global Heating From Energy Use''

    NASA Astrophysics Data System (ADS)

    Fleming, James R.

    2008-12-01

    In a prominent article published in Tellus in 1969, Mikhail I. Budyko, with the Main Geophysical Observatory, Leningrad, Soviet Union, wrote that ``all the energy used by man is transformed into heat, the main portion of this energy being an additional source of heat as compared to the present radiation gain'' [Budyko, 1969, p. 618]. He pointed out that this heating was over and above any climate forcing from anthropogenic greenhouse gases and-since energy use was growing geometrically-it was likely to result in the retreat of the cryosphere, accompanied by excessive and potentially damaging global warming, perhaps in 200 years or less. Eric J. Chaisson, in Eos (``Long-Term Global Heating From Energy Use,'' 89(28), 253-254, 2008), does not acknowledge Budyko's research. Chaisson cites cosmic history and the history of the human species, but he provides no references to the conceptual history of the idea that human energy use could result in global heating. Budyko first published on the Earth's heat budget in 1948 and in 1998 received the Blue Planet Prize, sponsored by the Asahi Glass Foundation, for his lifetime accomplishments in quantitative climatology. His work on the energy budget of the Earth and anthropogenic influences really should have been cited (see a selection of key articles in the online National Science Digital Library, at http://wiki.nsdl.org/index.php/PALE:ClassicArticles/GlobalWarming).

  12. "Joule" Enjoy Using This Metric Unit.

    ERIC Educational Resources Information Center

    Rayner-Canham, Geoffrey

    1984-01-01

    Discusses advantages of using the joule as the focus of a teaching strategy to unify the concept of energy. Includes applications to various energy forms and use of the joule in converting constants. A set of worked problems, using relationships discussed in the article, are available from the author. (JM)

  13. Cryogenic characterization of low-cost Joule-Thomson coolers

    NASA Astrophysics Data System (ADS)

    Guichard, Jerome; Cottereau, Alain; Chazot, Dominique

    2000-12-01

    This paper highlights two main achievements which were performed by AIR LIQUIDE during the last decade in the field of low cost Joule-Thomson coolers. On one hand, in order to comply with new geometrical requirements, AIR LIQUIDE is able to propose a flat cooler. This compact geometry is enabled by a new, cheap, type of heat exchanger. It offers a better resistance to external vibrations. On the other hand AIR LIQUIDE has developed, in the frame of a commercial program, a complete cryogenic cooling system, composed of a dual flow Joule-Thomson cooler, a pressurized gas capacity equipped with a manifold block and a pyrotechnic actuator, and the requested pipes and connectors. The dual flow is enabled by flexion of a washer made of shape memory alloy.

  14. Near-Term Laser Launch Capability: The Heat Exchanger Thruster

    NASA Astrophysics Data System (ADS)

    Kare, Jordin T.

    2003-05-01

    The heat exchanger (HX) thruster concept uses a lightweight (up to 1 MW/kg) flat-plate heat exchanger to couple laser energy into flowing hydrogen. Hot gas is exhausted via a conventional nozzle to generate thrust. The HX thruster has several advantages over ablative thrusters, including high efficiency, design flexibility, and operation with any type of laser. Operating the heat exchanger at a modest exhaust temperature, nominally 1000 C, allows it to be fabricated cheaply, while providing sufficient specific impulse (~600 seconds) for a single-stage vehicle to reach orbit with a useful payload; a nominal vehicle design is described. The HX thruster is also comparatively easy to develop and test, and offers an extremely promising route to near-term demonstration of laser launch.

  15. Long-term predictions of minewater geothermal systems heat resources

    NASA Astrophysics Data System (ADS)

    Harcout-Menou, Virginie; de ridder, fjo; laenen, ben; ferket, helga

    2014-05-01

    Abandoned underground mines usually flood due to the natural rise of the water table. In most cases the process is relatively slow giving the mine water time to equilibrate thermally with the the surrounding rock massif. Typical mine water temperature is too low to be used for direct heating, but is well suited to be combined with heat pumps. For example, heat extracted from the mine can be used during winter for space heating, while the process could be reversed during summer to provide space cooling. Altough not yet widely spread, the use of low temperature geothermal energy from abandoned mines has already been implemented in the Netherlands, Spain, USA, Germany and the UK. Reliable reservoir modelling is crucial to predict how geothermal minewater systems will react to predefined exploitation schemes and to define the energy potential and development strategy of a large-scale geothermal - cold/heat storage mine water systems. However, most numerical reservoir modelling software are developed for typical environments, such as porous media (a.o. many codes developed for petroleum reservoirs or groundwater formations) and cannot be applied to mine systems. Indeed, mines are atypical environments that encompass different types of flow, namely porous media flow, fracture flow and open pipe flow usually described with different modelling codes. Ideally, 3D models accounting for the subsurface geometry, geology, hydrogeology, thermal aspects and flooding history of the mine as well as long-term effects of heat extraction should be used. A new modelling approach is proposed here to predict the long-term behaviour of Minewater geothermal systems in a reactive and reliable manner. The simulation method integrates concepts for heat and mass transport through various media (e.g., back-filled areas, fractured rock, fault zones). As a base, the standard software EPANET2 (Rossman 1999; 2000) was used. Additional equations for describing heat flow through the mine (both

  16. SIGNAL MEDIATORS AT INDUCTION OF HEAT RESISTANCE OF WHEAT PLANTLETS BY SHORT-TERM HEATING.

    PubMed

    Karpets, Yu V; Kolupaev, Yu E; Yastreb, T O

    2015-01-01

    The effects of functional interplay of calcium ions, reactive oxygen species (ROS) and nitric oxide (NO) in the cells of wheat plantlets roots (Triticum aestivum L.) at the induction of their heat resistance by a short-term influence of hyperthermia (heating at the temperature of 42 degrees C during 1 minute) have been investigated. The transitional increase of NO and H2O2 content, invoked by heating, was suppressed by the treatment of plantlets with the antagonists of calcium EGTA (chelator of exocellular calcium), lanthanum chloride (blocker of calcium channels of various types) and neomycin (inhibitor of phosphatidylinositol-dependent phospholipase C). The rise of hydrogen peroxide content, caused by hardening, was partially suppressed by the action of inhibitors of nitrate reductase (sodium wolframate) and NO-synthase (N(G)-nitro-L-arginine methyl ester--L-NAME), and the increasing of nitric oxide content was suppressed by the treatment of plants with the antioxidant ionol and with the scavenger of hydrogen peroxide (dimethylthiourea). These compounds and antagonists of calcium also partially removed the effect of the rise of plantlets' heat resistance, invoked by hardening heating. The conclusion on calcium's role in the activation of enzymatic systems, generating reactive oxygen species and nitric oxide, and on the functional interplay of these signal mediators at the induction of heat resistance of plantlets by hardening heating is made.

  17. From Joule to Caratheodory and Born: A Conceptual Evolution of the First Law of Thermodynamics

    ERIC Educational Resources Information Center

    Rosenberg, Robert M.

    2010-01-01

    In the years after Joule's experiment on the equivalence of heat and work, it was taken for granted that heat and work could be independently defined and that the change in energy for a change of state is the sum of the heat and the work. Only with the work of Caratheodory and Born did it become clear that heat cannot be measured independently,…

  18. From Joule to Caratheodory and Born: A Conceptual Evolution of the First Law of Thermodynamics

    ERIC Educational Resources Information Center

    Rosenberg, Robert M.

    2010-01-01

    In the years after Joule's experiment on the equivalence of heat and work, it was taken for granted that heat and work could be independently defined and that the change in energy for a change of state is the sum of the heat and the work. Only with the work of Caratheodory and Born did it become clear that heat cannot be measured independently,…

  19. A miniature Joule-Thomson cooler for optical detectors in space.

    PubMed

    Derking, J H; Holland, H J; Tirolien, T; ter Brake, H J M

    2012-04-01

    The utilization of single-stage micromachined Joule-Thomson (JT) coolers for cooling small optical detectors is investigated. A design of a micromachined JT cold stage-detector system is made that focuses on the interface between a JT cold stage and detector, and on the wiring of the detector. Among various techniques, adhesive bonding is selected as most suitable technique for integrating the detector with the JT cold stage. Also, the optimum wiring of the detector is discussed. In this respect, it is important to minimize the heat conduction through the wiring. Therefore, each wire should be optimized in terms of acceptable impedance and thermal heat load. It is shown that, given a certain impedance, the conductive heat load of electrically bad conducting materials is about twice as high as that of electrically good conducting materials. A micromachined JT cold stage is designed and integrated with a dummy detector. The JT cold stage is operated at 100 K with nitrogen as the working fluid and at 140 K with methane. Net cooling powers of 143 mW and 117 mW are measured, respectively. Taking into account a radiative heat load of 40 mW, these measured values make the JT cold stage suitable for cooling a photon detector with a power dissipation up to 50 mW, allowing for another 27 to 53 mW heat load arising from the electrical leads.

  20. A miniature Joule-Thomson cooler for optical detectors in space

    NASA Astrophysics Data System (ADS)

    Derking, J. H.; Holland, H. J.; Tirolien, T.; ter Brake, H. J. M.

    2012-04-01

    The utilization of single-stage micromachined Joule-Thomson (JT) coolers for cooling small optical detectors is investigated. A design of a micromachined JT cold stage-detector system is made that focuses on the interface between a JT cold stage and detector, and on the wiring of the detector. Among various techniques, adhesive bonding is selected as most suitable technique for integrating the detector with the JT cold stage. Also, the optimum wiring of the detector is discussed. In this respect, it is important to minimize the heat conduction through the wiring. Therefore, each wire should be optimized in terms of acceptable impedance and thermal heat load. It is shown that, given a certain impedance, the conductive heat load of electrically bad conducting materials is about twice as high as that of electrically good conducting materials. A micromachined JT cold stage is designed and integrated with a dummy detector. The JT cold stage is operated at 100 K with nitrogen as the working fluid and at 140 K with methane. Net cooling powers of 143 mW and 117 mW are measured, respectively. Taking into account a radiative heat load of 40 mW, these measured values make the JT cold stage suitable for cooling a photon detector with a power dissipation up to 50 mW, allowing for another 27 to 53 mW heat load arising from the electrical leads.

  1. Shock-Wave Compression and Joule-Thomson Expansion

    NASA Astrophysics Data System (ADS)

    Hoover, Wm. G.; Hoover, Carol G.; Travis, Karl P.

    2014-04-01

    Structurally stable atomistic one-dimensional shock waves have long been simulated by injecting fresh cool particles and extracting old hot particles at opposite ends of a simulation box. The resulting shock profiles demonstrate tensor temperature, Txx≠Tyy and Maxwell's delayed response, with stress lagging strain rate and heat flux lagging temperature gradient. Here this same geometry, supplemented by a short-ranged external "plug" field, is used to simulate steady Joule-Kelvin throttling flow of hot dense fluid through a porous plug, producing a dilute and cooler product fluid.

  2. Shock-wave compression and Joule-Thomson expansion.

    PubMed

    Hoover, Wm G; Hoover, Carol G; Travis, Karl P

    2014-04-11

    Structurally stable atomistic one-dimensional shock waves have long been simulated by injecting fresh cool particles and extracting old hot particles at opposite ends of a simulation box. The resulting shock profiles demonstrate tensor temperature, Txx≠Tyy and Maxwell's delayed response, with stress lagging strain rate and heat flux lagging temperature gradient. Here this same geometry, supplemented by a short-ranged external "plug" field, is used to simulate steady Joule-Kelvin throttling flow of hot dense fluid through a porous plug, producing a dilute and cooler product fluid.

  3. Joule-Thomson expansion of the charged AdS black holes

    NASA Astrophysics Data System (ADS)

    Ökcü, Özgür; Aydıner, Ekrem

    2017-01-01

    In this paper, we study Joule-Thomson effects for charged AdS black holes. We obtain inversion temperatures and curves. We investigate similarities and differences between van der Waals fluids and charged AdS black holes for the expansion. We obtain isenthalpic curves for both systems in the T- P plane and determine the cooling-heating regions.

  4. Direct observation of nanometer-scale Joule and Peltier effects in phase change memory devices

    NASA Astrophysics Data System (ADS)

    Grosse, Kyle L.; Xiong, Feng; Hong, Sungduk; King, William P.; Pop, Eric

    2013-05-01

    We measure power dissipation in phase change memory (PCM) devices by scanning Joule expansion microscopy (SJEM) with ˜50 nm spatial and 0.2 K temperature resolution. The temperature rise in the Ge2Sb2Te5 (GST) is dominated by Joule heating, but at the GST-TiW contacts it is a combination of Peltier and current crowding effects. Comparison of SJEM and electrical measurements with simulations of the PCM devices uncovers a thermopower of ˜350 μV K-1 and a contact resistance of ˜2.0 × 10-8 Ω m2 (to TiW) for 25 nm thick films of face centered-cubic crystalline GST. Knowledge of such nanometer-scale Joule, Peltier, and current crowding effects is essential for energy-efficient design of future PCM technology.

  5. Sensitivity of Micromachined Joule-Thomson Cooler to Clogging Due to Moisture

    NASA Astrophysics Data System (ADS)

    Cao, H. S.; Vanapalli, S.; Holland, H. J.; Vermeer, C. H.; ter Brake, H. J. M.

    A major issue in long-term operation of micromachined Joule-Thomson coolers is the clogging of the microchannels and/or the restriction due to the deposition of water molecules present in the working fluid. In this study, we present the performance of a microcooler operated with nitrogen gas with different moisture levels. Relatively low-purity nitrogen gas (5.0) is supplied from a gas bottle and led through a filter to control the moisture level. The filter consists of a tube-in-tube counter flow heat exchanger (CFHX) and a heat exchanger that is stabilized at a certain temperature by using a Stirling cooler. The set-point temperature determines the moisture level at the exit of the heat exchanger. It is found that the moisture level has influence on the mass-flow rate during the cool down. Once the microcooler reaches the set cold-end temperature, the main deposition area shifts into the CFHX and the moisture level at the restriction is almost independent on the inlet moisture level of the microcooler. The moisture level at the restriction increases with the increasing cold-end temperature when the cold-end temperature is lower than the saturation temperature of the water in the nitrogen gas. Higher cold-end temperature results in higher clogging rate.

  6. Performance analysis of small capacity liquid nitrogen generator based on Joule-Thomson refrigerator coupled with air separation membrane

    NASA Astrophysics Data System (ADS)

    Piotrowska-Hajnus, Agnieszka; Chorowski, Maciej

    2012-06-01

    Joule - Thomson small capacity refrigerators supplied with gas mixture are studied theoretically and experimentally for a variety of applications. They can be especially promising when coupled with membrane air separators. We present liquid nitrogen generation system based on Joule - Thomson cooler joined with air separation membrane. Hollow fiber membrane is used for nitrogen separation from compressed and purified atmospheric air. Joule-Thomson refrigerator operates with a dedicated nitrogen - hydrocarbons mixture and provides a cooling power used for the separated nitrogen liquefaction. Special attention has been paid to a heat exchanger coupling the Joule- Thomson refrigerator with the membrane air separator. This paper describes the system design, the procedure of its working parameters optimization and tests results.

  7. Dynamical Behavior of Discrete Bubble and Heat Transfer of Nucleate Pool Boiling in Short-Term Microgravity

    NASA Astrophysics Data System (ADS)

    Zhao, Jian-Fu

    2012-07-01

    Boiling in microgravity is an increasing significant subject of investigation. Motivation for the study comes not only from many potential space applications due to its high efficiency to transfer high heat flux with liquid-vapor phase change, but also from powerful platform of microgravity to reveal the mechanism of heat transfer underneath the phenomenon of boiling. In the present paper, the growth of a discrete bubble during nucleate pool boiling and heat transfer in short-term microgravity is studied experimentally utilizing the drop tower Beijing. A P-doped N-type square silicon chip with the dimensions of 10x10x0.5 mm ^{3} was used as the heater. Two 0.25-mm diameters copper wires for power supply was soldered to the side surfaces of the chip at the opposite ends. The normal resistant of the chip is 75 Ω. The chip was heated by using Joule effect. A D.C. power supply of constant current was used to input energy to the heater element. A 0.12-mm diameter, T-type thermocouple adhered on the centre of the backside of the chip was used for the measurement of wall temperature, while two other T-type thermocouples were used for the bulk liquid temperature. FC-72 was used as working fluid. The concentration of air was determined by using Henry law as 0.0046 moles gas/mole liquid. The pressure and the bulk liquid temperature in the boiling chamber were nominally 102.0 kPa and 12.0 °C, respectively. The shapes of the bubbles were recorded using a high speed camera at a speed of 250 fps with a shutter speed of 1/2000 s. Based on the image manipulation, the effective diameter of the discrete bubble is obtained. The experiments were conducted utilizing the drop tower Beijing, which can provide a short-term microgravity condition. The residual gravity of 10 ^{-2 ... -3} g _{0} can be maintained throughout the short duration of 3.6 s. To avoid the influence of natural convection in normal gravity environment, the heating switched on at the release of the drop capsule

  8. Magnus: A New Resistive MHD Code with Heat Flow Terms

    NASA Astrophysics Data System (ADS)

    Navarro, Anamaría; Lora-Clavijo, F. D.; González, Guillermo A.

    2017-07-01

    We present a new magnetohydrodynamic (MHD) code for the simulation of wave propagation in the solar atmosphere, under the effects of electrical resistivity—but not dominant—and heat transference in a uniform 3D grid. The code is based on the finite-volume method combined with the HLLE and HLLC approximate Riemann solvers, which use different slope limiters like MINMOD, MC, and WENO5. In order to control the growth of the divergence of the magnetic field, due to numerical errors, we apply the Flux Constrained Transport method, which is described in detail to understand how the resistive terms are included in the algorithm. In our results, it is verified that this method preserves the divergence of the magnetic fields within the machine round-off error (˜ 1× {10}-12). For the validation of the accuracy and efficiency of the schemes implemented in the code, we present some numerical tests in 1D and 2D for the ideal MHD. Later, we show one test for the resistivity in a magnetic reconnection process and one for the thermal conduction, where the temperature is advected by the magnetic field lines. Moreover, we display two numerical problems associated with the MHD wave propagation. The first one corresponds to a 3D evolution of a vertical velocity pulse at the photosphere-transition-corona region, while the second one consists of a 2D simulation of a transverse velocity pulse in a coronal loop.

  9. Statistical thermodynamics of aerosols and the gas-solid Joule-Thomson effect

    NASA Astrophysics Data System (ADS)

    Pierotti, Robert A.; Rybolt, Thomas R.

    1984-04-01

    Due to the adsorption of a gas by a solid, it is expected that an aerosol created by dispersing a fine powder in a gas would have unique thermodynamic properties not found in pure or mixed gases. The virial equation of state associated with an aerosol dusty gas is obtained from statistical thermodynamic considerations. In the theoretical model presented here, the aerosol is considered to be a two component fluid made up of solid particles and gas molecules. The aerosol virial equation of state is used to derive an expression for the Joule-Thomson effect associated with a gas-solid dispersion. The magnitude of the gas-solid Joule-Thomson effect is expressed in terms of gas and gas-solid virial coefficients. Previous adsorption data for an argon-porous carbon system is used to obtain gas-solid virial coefficients and to predict the magnitude of the gas-solid Joule-Thomson effect. A significant enhancement of the Joule-Thomson effect is predicted for gas-solid systems which display a strong interaction. For example, at a temperature of 300 K an argon-Saran 746 porous carbon aerosol system at a concentration of (0.4 g of powder/l of gas) is predicted to have a gas-solid Joule-Thomson coefficient of 3.6 K/atm which is ten times greater than the effect for pure argon.

  10. Long-Term Global Heating From Energy Usage

    NASA Astrophysics Data System (ADS)

    Chaisson, Eric J.

    2008-07-01

    Even if civilization on Earth stops polluting the biosphere with greenhouse gases, humanity could eventually be awash in too much heat, namely, the dissipated heat by-product generated by any nonrenewable energy source. Apart from the Sun's natural aging-which causes an approximately 1% luminosity rise for each 108 years and thus about 1°C increase in Earth's surface temperature-well within 1000 years our technological society could find itself up against a fundamental limit to growth: an unavoidable global heating of roughly 3°C dictated solely by the second law of thermodynamics, a biogeophysical effect often ignored when estimating future planetary warming scenarios.

  11. Control of variation of properties of maraging chromium-nickel steels in long-term heating

    NASA Astrophysics Data System (ADS)

    Tarasenko, L. V.; Titov, V. I.; Elyutina, L. A.

    2010-11-01

    Variation of the phase composition and mechanical properties of maraging steels of the Fe - Cr - Ni - Mo - Ti system after heat treatment (hardening and aging) and long-term heating for up to 1500 h at a temperature of 400 - 450°C is studied. It is shown that the degree of variation of the properties of steels with different contents of titanium after long-term heating can be regulated by changing the mode of the aging.

  12. Application of vanadium hydride compressors for Joule-Thomson cryocoolers

    NASA Astrophysics Data System (ADS)

    Bowman, R. C., Jr.; Freeman, B. D.; Phillips, J. R.

    The Joule-Thomson expansion of hydrogen gas offers efficient and reliable cryocoolers to produce temperatures between 10 and 50 K. A critical component to the development of these devices is the metal hydride storage bed that provides a nonmechanical method to compress hydrogen gas via the reversible absorption by appropriate metals or alloys. A thermodynamic model has been used to calculate the impact of operational parameters such as input/output pressure ratios and bed temperature on energy balance and system efficiency. Detailed comparisons are reported for a compressor which utilizes vanadium metal as the sorbent for either hydrogen or deuterium where the unusually large isotope differences between the phase diagrams and thermal properties for VH(x) and VD(x) have been considered. The sensitivity of heat input requirements to the uncertainties in primary variables are described.

  13. Manganese Nitride Sorption Joule-Thomson Refrigerator

    NASA Technical Reports Server (NTRS)

    Jones, Jack A.; Phillips, Wayne M.

    1992-01-01

    Proposed sorption refrigeration system of increased power efficiency combines MnxNy sorption refrigeration stage with systems described in "Regenerative Sorption Refrigerator" (NPO-17630). Measured pressure-vs-composition isotherms for reversible chemisorption of N2 in MnxNy suggest feasibility to incorporate MnxNy chemisorption stage in Joule-Thomson cryogenic system. Discovery represents first known reversible nitrogen chemisorption compression system. Has potential in nitrogen-isotope separation, nitrogen purification, or contamination-free nitrogen compression.

  14. Studies on solar heating systems with long-term heat storage for northern high latitudes

    NASA Astrophysics Data System (ADS)

    Lund, P.

    The feasibility of liquid-based solar heating systems with seasonal heat storage for cold climates is addressed using thermal performance studies. The thermal analyses are based on several new computer models comprising three different types of seasonal storage: duct storage, rock caverns, and solar ponds. These are employed in a community solar heating system and are mainly charged by solar energy. Simulation models are used to investigate the effects of the system dimensioning on the thermal performance. Different methods used to study the feasibility of a district solar heating system for the Finnish climate are presented. Finally, the computer models are used to determine the expected performance of the first Finnish community solar heating system with seasonal heat storage, the Kerava solar village. Preliminary measurement results from the village are given.

  15. Size effects in long-term quasistatic heat transport.

    PubMed

    Panasyuk, George Y; Yerkes, Kirk L

    2013-06-01

    We consider finite-size effects on heat transfer between thermal reservoirs mediated by a quantum system, where the number of modes in each reservoir is finite. Our approach is based on the generalized quantum Langevin equation and the thermal reservoirs are described as ensembles of oscillators within the Drude-Ullersma model. A general expression for the heat current between the thermal reservoirs in the long-time quasistatic regime, when an observation time is of the order of Δ(-1) and Δ is the mode spacing constant of a thermal reservoir, is obtained. The resulting equations that govern the long-time relaxation for the mode temperatures and the average temperatures of the reservoirs are derived and approximate analytical solutions are found. The obtained time dependencies of the temperatures and the resulting heat current reveal peculiarities at t=2πm/Δ with non-negative integers m and the heat current vanishes nonmonotonically when t→∞. The validity of Fourier's law for a chain of finite-size macroscopic subsystems is considered. As is shown, for characteristic times of the order of Δ(-1) the temperatures of subsystems' modes deviate from each other and the validity of Fourier's law cannot be established. In a case when deviations of initial temperatures of the subsystems from their average value are small, t→∞ asymptotic values for the mode temperatures do not depend on a mode's number and are the same as if Fourier's law were valid for all times.

  16. Size effects in long-term quasistatic heat transport

    NASA Astrophysics Data System (ADS)

    Panasyuk, George Y.; Yerkes, Kirk L.

    2013-06-01

    We consider finite-size effects on heat transfer between thermal reservoirs mediated by a quantum system, where the number of modes in each reservoir is finite. Our approach is based on the generalized quantum Langevin equation and the thermal reservoirs are described as ensembles of oscillators within the Drude-Ullersma model. A general expression for the heat current between the thermal reservoirs in the long-time quasistatic regime, when an observation time is of the order of Δ-1 and Δ is the mode spacing constant of a thermal reservoir, is obtained. The resulting equations that govern the long-time relaxation for the mode temperatures and the average temperatures of the reservoirs are derived and approximate analytical solutions are found. The obtained time dependencies of the temperatures and the resulting heat current reveal peculiarities at t=2πm/Δ with non-negative integers m and the heat current vanishes nonmonotonically when t→∞. The validity of Fourier's law for a chain of finite-size macroscopic subsystems is considered. As is shown, for characteristic times of the order of Δ-1 the temperatures of subsystems' modes deviate from each other and the validity of Fourier's law cannot be established. In a case when deviations of initial temperatures of the subsystems from their average value are small, t→∞ asymptotic values for the mode temperatures do not depend on a mode's number and are the same as if Fourier's law were valid for all times.

  17. Long-term heating to improve receiver performance

    NASA Astrophysics Data System (ADS)

    Glatzmaier, Greg C.; Cable, Robert; Newmarker, Marc

    2017-06-01

    The buildup of hydrogen in the heat transfer fluid (HTF) that circulates through components of parabolic trough power plants decreases receiver thermal efficiency, and ultimately, it decreases plant performance and electricity output. The generation and occurrence of hydrogen in the HTF provides the driving force for hydrogen to permeate from the HTF through the absorber tube wall and into the receiver annulus. Getters adsorb hydrogen from the annulus volume until they saturate and are no longer able to maintain low hydrogen pressure. The increase in hydrogen pressure within the annulus significantly degrades thermal performance of the receiver and decreases overall power-plant efficiency. NREL and Acciona Energy North America (Acciona) are developing a method to control the levels of dissolved hydrogen in the circulating HTF. The basic approach is to remove hydrogen from the expansion tanks of the HTF subsystem at a rate that maintains hydrogen in the circulating HTF to a target level. Full-plant steady-state models developed by the National Renewable Energy Laboratory (NREL) predict that if hydrogen is removed from the HTF within the expansion tanks, the HTF that circulates through the collector field remains essentially free of hydrogen until the HTF returns to the power block in the hot headers. One of the key findings of our modeling is the prediction that hydrogen will reverse-permeate out of the receiver annulus if dissolved hydrogen in the HTF is kept sufficiently low. To test this prediction, we performed extended heating of an in-service receiver that initially had high levels of hydrogen in its annulus. The heating was performed using NREL's receiver test stand. Results of our testing showed that receiver heat loss steadily decreased with daily heating, resulting in a corresponding improvement in receiver thermal efficiency.

  18. Performance analysis of a miniature Joule-Thomson cryocooler with and without the distributed J-T effect

    NASA Astrophysics Data System (ADS)

    Damle, Rashmin; Atrey, Milind

    2015-12-01

    Cryogenic temperatures are obtained with Joule-Thomson (J-T) cryocoolers in an easier way as compared to other cooling techniques. Miniature J-T cryocoolers are often employed for cooling of infrared sensors, cryoprobes, biological samples, etc. A typical miniature J-T cryocooler consists of a storage reservoir/compressor providing the high pressure gas, a finned tube recuperative heat exchanger, an expansion valve/orifice, and the cold end. The recuperative heat exchanger is indispensable for attaining cryogenic temperatures. The geometrical parameters and the operating conditions of the heat exchanger drastically affect the cryocooler performance in terms of cool down time and cooling effect. In the literature, the numerical models for the finned recuperative heat exchanger have neglected the distributed J-T effect. The distributed J-T effect accounts for the changes in enthalpy of the fluid due to changes of pressure in addition to those due to changes of temperature. The objective of this work is to explore the distributed J-T effect and study the performance of a miniature J-T cryocooler with and without the distributed J-T effect. A one dimensional transient model is employed for the numerical analysis of the cryocooler. Cases with different operating conditions are worked out with argon and nitrogen as working fluids.

  19. Joule-Thomson Cooler Produces Nearly Constant Temperature

    NASA Technical Reports Server (NTRS)

    Bard, Steven; Wu, Jiunn-Jeng; Trimble, Curtis A.

    1992-01-01

    Improved Joule-Thomson cooler maintains nearly constant temperature. Absolute-pressure relief valve helps stabilize temperature of cold head despite variations in atmospheric pressure. Feedback-controlled electrical heater provides additional stabilization. Demand-flow Joule-Thomson valve requires less nitrogen than fixed-orifice Joule-Thomson valve providing same amount of cooling. Provides stable low temperatures required for operation of such devices as tunable diode lasers in laboratory and balloon-borne instruments detecting contaminants in atmosphere.

  20. Ultra-high temperature stability Joule-Thomson cooler with capability to accomodate pressure variations

    NASA Technical Reports Server (NTRS)

    Bard, Steven (Inventor); Wu, Jiunn-Jeng (Inventor); Trimble, Curtis A. (Inventor)

    1992-01-01

    A Joule-Thomson cryogenic refrigeration system capable of achieving high temperature stabilities in the presence of varying temperature, atmospheric pressure, and heat load is provided. The Joule-Thomson cryogenic refrigeration system includes a demand flow Joule-Thomson expansion valve disposed in a cryostat of the refrigeration system. The expansion valve has an adjustable orifice that controls the flow of compressed gas therethrough and induces cooling and partial liquefaction of the gas. A recuperative heat exchanger is disposed in the cryostat and coupled to the expansion valve. A thermostatically self-regulating mechanism is disposed in the cryostat and coupled to the J-T expansion valve. The thermostatically self-regulating mechanism automatically adjusts the cross sectional area of the adjustable valve orifice in response to environmental temperature changes and changes in power dissipated at a cold head. A temperature sensing and adjusting mechanism is coupled to a cold head for adjusting the temperature of the cold head in response to the change in heat flow in the cold head. The temperature sensing and adjusting mechanism comprises a temperature sensitive diode, a wound wire heater, and an electrical feedback control circuit coupling the diode to the heater. An absolute pressure relief valve is interposed between the output of the cryostat and an exhaust port for maintaining a constant exhaust temperature in the refrigerating system, independent of the changes in atmospheric pressure.

  1. Improving Control in a Joule-Thomson Refrigerator

    NASA Technical Reports Server (NTRS)

    Borders, James; Pearson, David; Prina, Mauro

    2005-01-01

    A report discusses a modified design of a Joule-Thomson (JT) refrigerator under development to be incorporated into scientific instrumentation aboard a spacecraft. In most other JT refrigerators (including common household refrigerators), the temperature of the evaporator (the cold stage) is kept within a desired narrow range by turning a compressor on and off as needed. This mode of control is inadequate for the present refrigerator because a JT-refrigerator compressor performs poorly when the flow from its evaporator varies substantially, and this refrigerator is required to maintain adequate cooling power. The proposed design modifications include changes in the arrangement of heat exchangers, addition of a clamp that would afford a controlled heat leak from a warmer to a cooler stage to smooth out temperature fluctuations in the cooler stage, and incorporation of a proportional + integral + derivative (PID) control system that would regulate the heat leak to maintain the temperature of the evaporator within a desired narrow range while keeping the amount of liquid in the evaporator within a very narrow range in order to optimize the performance of the compressor. Novelty lies in combining the temperature- and cooling-power-regulating controls into a single control system.

  2. Short term post-partum heat stress in dairy cows

    NASA Astrophysics Data System (ADS)

    Fuquay, J. W.; Chapin, L. T.; Brown, W. H.

    1980-06-01

    Since many dairy cows calve during late summer, the objective was to determine if heat stress immediately post-partum would (1) alter metabolism, thus, increasing susceptibility to metabolic disorders, (2) affect lactation and/or (3) affect reproduction. Forty four cows, calving during late summer, were paired with one member of each pair stressed (HS) for the first 10 post-partum days in a hot barn. Controls (CC) were kept in a cooled section of the barn. Plasma drawn weekly for 7 weeks was analyzed in an autoanalyzer for calcium, inor. phosphorus, protein, glucose and cholesterol and by radioimmunoassay for cortisol and progesterone. Ovaries and uteri were palpated weekly. Rectal temperatures were significant higher for HS during the first 10 post-partum days. No significant effects on plasma constituents were observed during the 10-day treatment period. For the 7-week period, glucose and cholesterol were lower in HS, as were cyclic peaks of progesterone and cortisol. Both calcium and inorganic phosphorus remained clinically low for the 7 weeks, but no treatment effects were seen. Uteri of HS involuted more rapidly than the CC. Treatment did not affect reproductive efficiency. Lactation milk yields did not differ, but milk fat percent was lower in HS. Heat stress immediately post-partum altered lipid metabolism, but the animal's compensatory mechanisms prevented reduction in milk production or reproductive efficiency.

  3. Mega-joule experiment area study, 1989

    SciTech Connect

    Slaughter, D.; Oirth, C.; Woodworth, J.

    1995-03-09

    This document contains Chapters 3 and 4 from the Mega-Joule Experiment Area Study, 1989. Water frost on the first containment wall is studied in detail in Chapter 3. Considered topics are the computer modeling of frost ablation and shock propagation and the experimental characterization of water frost. The latter is broken down into: frost crystal morphology, experiment configuration, growth rate results, density results, thermal conductivity, crush strength of frost, frost integrity, frost response to simulated soft x-rays. Chapter 4 presents information on surrounding shielding and structures to include: cryogenic spheres for first wall and coolant containment; shield tank concerning primary neutron and gamma ray shielding; and secondary shielding.

  4. Spring-Loaded Joule-Thomson Valve

    NASA Technical Reports Server (NTRS)

    Jones, J. A.; Britcliffe, M. J.

    1986-01-01

    Improved design reduces clogging and maintains constant pressure drop as flow rate varies. Spring-Loaded Joule-Thomson Valve pressure drop regulated by spring pushing stainless-steel ball against soft brass seat. Pressure drop remains nearly constant, regardless of helium flow rate and of any gas contaminants frozen on valve seat. Because springloaded J-T valve maintains constant pressure drop, upstream roomtemperature throttle valve adjusts flow rate precisely for any given upstream pressure. In addition, new valve relatively invulnerable to frozen gas contaminants, which clog fixed-orifice J-T valves.

  5. Short-Term Energy Outlook Model Documentation: Regional Residential Heating Oil Price Model

    EIA Publications

    2009-01-01

    The regional residential heating oil price module of the Short-Term Energy Outlook (STEO) model is designed to provide residential retail price forecasts for the 4 census regions: Northeast, South, Midwest, and West.

  6. Short-Term Energy Outlook Model Documentation: Regional Residential Heating Oil Price Model

    EIA Publications

    2009-01-01

    The regional residential heating oil price module of the Short-Term Energy Outlook (STEO) model is designed to provide residential retail price forecasts for the 4 census regions: Northeast, South, Midwest, and West.

  7. Nanometer-scale temperature imaging for independent observation of Joule and Peltier effects in phase change memory devices

    SciTech Connect

    Grosse, Kyle L.; Pop, Eric; King, William P.

    2014-09-15

    This paper reports a technique for independent observation of nanometer-scale Joule heating and thermoelectric effects, using atomic force microscopy (AFM) based measurements of nanometer-scale temperature fields. When electrical current flows through nanoscale devices and contacts the temperature distribution is governed by both Joule and thermoelectric effects. When the device is driven by an electrical current that is both periodic and bipolar, the temperature rise due to the Joule effect is at a different harmonic than the temperature rise due to the Peltier effect. An AFM tip scanning over the device can simultaneously measure all of the relevant harmonic responses, such that the Joule effect and the Peltier effect can be independently measured. Here we demonstrate the efficacy of the technique by measuring Joule and Peltier effects in phase change memory devices. By comparing the observed temperature responses of these working devices, we measure the device thermopower, which is in the range of 30 ± 3 to 250 ± 10 μV K{sup −1}. This technique could facilitate improved measurements of thermoelectric phenomena and properties at the nanometer-scale.

  8. Nanometer-scale temperature imaging for independent observation of Joule and Peltier effects in phase change memory devices

    NASA Astrophysics Data System (ADS)

    Grosse, Kyle L.; Pop, Eric; King, William P.

    2014-09-01

    This paper reports a technique for independent observation of nanometer-scale Joule heating and thermoelectric effects, using atomic force microscopy (AFM) based measurements of nanometer-scale temperature fields. When electrical current flows through nanoscale devices and contacts the temperature distribution is governed by both Joule and thermoelectric effects. When the device is driven by an electrical current that is both periodic and bipolar, the temperature rise due to the Joule effect is at a different harmonic than the temperature rise due to the Peltier effect. An AFM tip scanning over the device can simultaneously measure all of the relevant harmonic responses, such that the Joule effect and the Peltier effect can be independently measured. Here we demonstrate the efficacy of the technique by measuring Joule and Peltier effects in phase change memory devices. By comparing the observed temperature responses of these working devices, we measure the device thermopower, which is in the range of 30 ± 3 to 250 ± 10 μV K-1. This technique could facilitate improved measurements of thermoelectric phenomena and properties at the nanometer-scale.

  9. Nanometer-scale temperature imaging for independent observation of Joule and Peltier effects in phase change memory devices.

    PubMed

    Grosse, Kyle L; Pop, Eric; King, William P

    2014-09-01

    This paper reports a technique for independent observation of nanometer-scale Joule heating and thermoelectric effects, using atomic force microscopy (AFM) based measurements of nanometer-scale temperature fields. When electrical current flows through nanoscale devices and contacts the temperature distribution is governed by both Joule and thermoelectric effects. When the device is driven by an electrical current that is both periodic and bipolar, the temperature rise due to the Joule effect is at a different harmonic than the temperature rise due to the Peltier effect. An AFM tip scanning over the device can simultaneously measure all of the relevant harmonic responses, such that the Joule effect and the Peltier effect can be independently measured. Here we demonstrate the efficacy of the technique by measuring Joule and Peltier effects in phase change memory devices. By comparing the observed temperature responses of these working devices, we measure the device thermopower, which is in the range of 30 ± 3 to 250 ± 10 μV K(-1). This technique could facilitate improved measurements of thermoelectric phenomena and properties at the nanometer-scale.

  10. Turbulent resistive heating of solar coronal arches

    NASA Technical Reports Server (NTRS)

    Benford, G.

    1983-01-01

    The possibility that coronal heating occurs by means of anomalous Joule heating by electrostatic ion cyclotron waves is examined, with consideration given to currents running from foot of a loop to the other. It is assumed that self-fields generated by the currents are absent and currents follow the direction of the magnetic field, allowing the plasma cylinder to expand radially. Ion and electron heating rates are defined within the cylinder, together with longitudinal conduction and convection, radiation and cross-field transport, all in terms of Coulomb and turbulent effects. The dominant force is identified as electrostatic ion cyclotron instability, while ion acoustic modes remain stable. Rapid heating from an initial temperature of 10 eV to 100-1000 eV levels is calculated, with plasma reaching and maintaining a temperature in the 100 eV range. Strong heating is also possible according to the turbulent Ohm's law and by resistive heating.

  11. Isothermic and fixed intensity heat acclimation methods induce similar heat adaptation following short and long-term timescales.

    PubMed

    Gibson, Oliver R; Mee, Jessica A; Tuttle, James A; Taylor, Lee; Watt, Peter W; Maxwell, Neil S

    2015-01-01

    Heat acclimation requires the interaction between hot environments and exercise to elicit thermoregulatory adaptations. Optimal synergism between these parameters is unknown. Common practise involves utilising a fixed workload model where exercise prescription is controlled and core temperature is uncontrolled, or an isothermic model where core temperature is controlled and work rate is manipulated to control core temperature. Following a baseline heat stress test; 24 males performed a between groups experimental design performing short term heat acclimation (STHA; five 90 min sessions) and long term heat acclimation (LTHA; STHA plus further five 90 min sessions) utilising either fixed intensity (50% VO2peak), continuous isothermic (target rectal temperature 38.5 °C for STHA and LTHA), or progressive isothermic heat acclimation (target rectal temperature 38.5 °C for STHA, and 39.0 °C for LTHA). Identical heat stress tests followed STHA and LTHA to determine the magnitude of adaptation. All methods induced equal adaptation from baseline however isothermic methods induced adaptation and reduced exercise durations (STHA = -66% and LTHA = -72%) and mean session intensity (STHA = -13% VO2peak and LTHA = -9% VO2peak) in comparison to fixed (p < 0.05). STHA decreased exercising heart rate (-10 b min(-1)), core (-0.2 °C) and skin temperature (-0.51 °C), with sweat losses increasing (+0.36 Lh(-1)) (p<0.05). No difference between heat acclimation methods, and no further benefit of LTHA was observed (p > 0.05). Only thermal sensation improved from baseline to STHA (-0.2), and then between STHA and LTHA (-0.5) (p<0.05). Both the continuous and progressive isothermic methods elicited exercise duration, mean session intensity, and mean T(rec) analogous to more efficient administration for maximising adaptation. Short term isothermic methods are therefore optimal for individuals aiming to achieve heat adaptation most economically, i.e. when integrating heat acclimation into

  12. Basics of Joule-Thomson Liquefaction and JT Cooling

    NASA Astrophysics Data System (ADS)

    de Waele, A. T. A. M.

    2017-01-01

    This paper describes the basic operation of Joule-Thomson liquefiers and Joule-Thomson coolers. The discussion is based on the first law of thermodynamics mainly using hT-diagrams. It is limited to single-component fluids. A nitrogen liquefier and a helium cooler are discussed as important examples.

  13. Basics of Joule-Thomson Liquefaction and JT Cooling

    NASA Astrophysics Data System (ADS)

    de Waele, A. T. A. M.

    2017-03-01

    This paper describes the basic operation of Joule-Thomson liquefiers and Joule-Thomson coolers. The discussion is based on the first law of thermodynamics mainly using hT-diagrams. It is limited to single-component fluids. A nitrogen liquefier and a helium cooler are discussed as important examples.

  14. Analysis of two-stage Joule-Thomson expansion

    NASA Astrophysics Data System (ADS)

    Narasaki, Katsuhiro

    2016-03-01

    To cool far infrared detectors for infrared observation or superconductor-insulator-superconductor (SIS) mixers for atmospheric observation, 1 K-class and 4 K-class coolers have been developed. These coolers consist of a two-stage Stirling cooler for pre-cooling and a Joule-Thomson (JT) cooler with a single JT valve. This paper presents descriptions of theoretical analyses based on enthalpy balance to elucidate the benefits of a two-stage JT valve type compared with those of a single JT valve type in a JT cooler. First, relational expressions for heat balance analysis of enthalpy for single-stage JT expansion are introduced. Then similar relational expressions for two-stage JT expansion are introduced under some assumptions. Results of heat balance analyses using several parameters demonstrated that, using two-stage JT expansion, the cooling capacity for a 1 K-class cooler is improved by 100%; that of a 4 K-class cooler is improved by about 30%.

  15. Performance Analysis of Joule-Thomson Cooler Supplied with Gas Mixtures

    NASA Astrophysics Data System (ADS)

    Piotrowska, A.; Chorowski, M.; Dorosz, P.

    2017-02-01

    Joule-Thomson (J-T) cryo-coolers working in closed cycles and supplied with gas mixtures are the subject of intensive research in different laboratories. The replacement of pure nitrogen by nitrogen-hydrocarbon mixtures allows to improve both thermodynamic parameters and economy of the refrigerators. It is possible to avoid high pressures in the heat exchanger and to use standard refrigeration compressor instead of gas bottles or high-pressure oil free compressor. Closed cycle and mixture filled Joule-Thomson cryogenic refrigerator providing 10-20 W of cooling power at temperature range 90-100 K has been designed and manufactured. Thermodynamic analysis including the optimization of the cryo-cooler mixture has been performed with ASPEN HYSYS software. The paper describes the design of the cryo-cooler and provides thermodynamic analysis of the system. The test results are presented and discussed.

  16. Compact laser through improved heat conductance

    NASA Technical Reports Server (NTRS)

    Yang, L. C.

    1975-01-01

    A 16-joule-pulse laser has been developed in which a boron nitride heat-conductor enclosure is used to remove heat from the elements. Enclosure is smaller and lighter than systems in which cooling fluids are used.

  17. Current and projected state of Joule-Thomson cooling technology

    NASA Astrophysics Data System (ADS)

    Hansen, Robert G.

    1996-06-01

    The cooling of infrared sensors and electro-optical devices by Joule-Thomson cryostats has been a viable systems option for electro optical systems since the 1960's. Currently, other options such as thermal electric coolers, closed cycle coolers and non-cooled detector technology are available and present alternatives for the system designer. In specific applications, Joule-Thomson cryostats still prove to be the option of choice. This paper will discuss the current and projected applications for Joule-Thomson cryostats as well as define and discuss the advantages of Joule-Thomson cooling technology. The importance of contamination control, reliability, and `Total Quality Management' in the manufacturing of Joule-Thomson cryostats will be emphasized.

  18. Near-term viability of solar heat applications for the federal sector

    NASA Astrophysics Data System (ADS)

    Williams, T. A.

    1991-12-01

    Solar thermal technologies are capable of providing heat across a wide range of temperatures, making them potentially attractive for meeting energy requirements for industrial process heat applications and institutional heating. The energy savings that could be realized by solar thermal heat are quite large, potentially several quads annually. Although technologies for delivering heat at temperatures above 100 C currently exist within industry, only a fairly small number of commercial systems have been installed to date. The objective of this paper is to investigate and discuss the prospects for near term solar heat sales to federal facilities as a mechanism for providing an early market niche to the aid the widespread development and implementation of the technology. The specific technical focus is on mid-temperature (100 to 350 C) heat demands that could be met with parabolic trough systems. Federal facilities have several features relative to private industry that may make them attractive for solar heat applications relative to other sectors. Key features are specific policy mandates for conserving energy, a long term planning horizon with well defined decision criteria, and prescribed economic return criteria for conservation and solar investments that are generally less stringent than the investment criteria used by private industry. Federal facilities also have specific difficulties in the sale of solar heat technologies that are different from those of other sectors, and strategies to mitigate these difficulties will be important. For the baseline scenario developed in this paper, the solar heat application was economically competitive with heat provided by natural gas. The system levelized energy cost was $5.9/MBtu for the solar heat case, compared to $6.8/MBtu for the life cycle fuel cost of a natural gas case. A third-party ownership would also be attractive to federal users, since it would guarantee energy savings and would not need initial federal funds.

  19. Minimal Joule dissipation models of magnetospheric convection

    NASA Astrophysics Data System (ADS)

    Barbosa, D. D.

    This paper gives a topical review of theoretical models of magnetospheric convection based on the concept of minimal Joule dissipation. A two-dimensional slab model of the ionosphere featuring an enhanced conductivity auroral oval is used to compute high-latitude electric fields and currents. Mathematical methods used in the modeling include Fourier analysis, fast Fourier transforms, and variational calculus. Also, conformal transformations are introduced in the analysis, which enable the auroral oval to be represented as a nonconcentric, crescent-shaped figure. Convection patterns appropriate to geomagnetic quiet and disturbed conditions are computed, the differentiating variable being the relative amount of power dissipated in the magnetospheric ring current. When ring current dissipation is small, the convection electric field is restricted to high latitudes (shielding regime), and when it is large, a significant penetration of the field to low latitudes occurs, accompanied by an increase in the ratio of the region I current to the region 2 current.

  20. Minimal Joule dissipation models of magnetospheric convection

    NASA Technical Reports Server (NTRS)

    Barbosa, D. D.

    1988-01-01

    This paper gives a topical review of theoretical models of magnetospheric convection based on the concept of minimal Joule dissipation. A two-dimensional slab model of the ionosphere featuring an enhanced conductivity auroral oval is used to compute high-latitude electric fields and currents. Mathematical methods used in the modeling include Fourier analysis, fast Fourier transforms, and variational calculus. Also, conformal transformations are introduced in the analysis, which enable the auroral oval to be represented as a nonconcentric, crescent-shaped figure. Convection patterns appropriate to geomagnetic quiet and disturbed conditions are computed, the differentiating variable being the relative amount of power dissipated in the magnetospheric ring current. When ring current dissipation is small, the convection electric field is restricted to high latitudes (shielding regime), and when it is large, a significant penetration of the field to low latitudes occurs, accompanied by an increase in the ratio of the region I current to the region 2 current.

  1. On the integral Joule-Thomson effect

    NASA Astrophysics Data System (ADS)

    Maytal, B.-Z.; Shavit, A.

    In this paper, the integral inversion curve concept is developed, involving the locus of all points with a vanishing integral Joule-Thomson (J-T) effect ΔTh and isothermal enthalpy change. The structure of the ΔhT surface over the plane of ( pr,T r) is explored. The maximum isothermal J-T effect ΔhT is related to the normal boiling temperature of the gas. The correlation of the integral effect based on real gas data with a low acentric factor is compared with Van der Waals' equation of state closed form predictions. The maximum integral isenthalpic J-T effect ΔTh which does not undergo a phase change during the expansion, is studied via Van der Waals' equation of state.

  2. Effect of the Long-Term Warming Since the Last Glacial Maximum on Terrestrial Heat Flow

    NASA Astrophysics Data System (ADS)

    Huang, S.; Duan, W.; Wang, H.

    2013-12-01

    Terrestrial heat flow is a geophysical parameter enumerating the outward energy flux from the interior of Earth. It is conventionally measured in boreholes as the product of thermal conductivity of rocks and geothermal gradient, which is subject to the influence from the variations in ground surface temperature condition. As such, on the one hand variation of heat flow density with depth is a direct temperature record of paleoclimate change; on the other hand ground surface temperature history imposes transient perturbation on a heat flow measurement. The assessment of the paleoclimate effect on a heat flow measurement requires a good understanding of the paleoclimate history. In this study, we evaluate the transient effect of the long-term warming since the last glacial maximum on the continental heat flow with both forward and inversion approaches. With the forward approach, we calculate the subsurface temperature response to climate change based on the latest reconstruction of the last 30,000 year paleoclimate history. We then translate the thermal response to the perturbation to a heat flow measurement. With the inversion approach, we use a set of 6,144 qualified data selected from more than 13,000 reported continental heat flow measurements to synthesize a global profile of heat flow versus depth. We then invert this synthesized profile for a paleoclimate history and a steady-state heat flow profile. Our result shows that continental heat flow measurements within the depths down to around 2000 m are systematically lower than the steady state heat flow because of the effect of the last deglacial warming. If this transient perturbation is leaved uncorrected, the mean continental heat flow could be underestimated by as much as twenty percents. This study is supported by the NSF Grant 1202673 and Grant SKLLQG1201 of the Institute of Earth Environment, Chinese Academy of Sciences.

  3. Multiple pollutant removal using the condensing heat exchanger. Task 3, Long term testing at the ECTC

    SciTech Connect

    Schulze, K.H.

    1996-01-01

    The objective of this task is to demonstrate long term operation of a condensing heat exchanger for coal-fired conditions. A small condensing heat exchanger will be installed at the Environmental Control Technology Center in Barker, New York. It will be installed downstream of the flue gas particulate removal system. The test will determine the amount of wear, if any, on the Teflon{trademark} covered internals of the heat exchanger. Visual inspection and measurements will be obtained for the Teflon{trademark} covered tubes during the test. The material wear study will conducted over a one year calendar period, and the CHX equipment will be operated to the fullest extent allowable.

  4. Joule-Thompson effect in a disperse medium

    NASA Astrophysics Data System (ADS)

    Tolmachev, E. M.

    1980-05-01

    An expression for the Joule-Thompson coefficient of a polydisperse medium subject to throttling is derived in the relaxation approximation of thermodynamics of irreversible processes, with both temperature and velocity relaxation in the phases taken into account.

  5. The Joule-Thomson expansion coefficient by formula manipulation

    SciTech Connect

    Hirose, Y.; Kitazawa, T. ); Yoshida, T. . Faculty of Engineering)

    1990-07-01

    By use of formula manipulation, practical programs used to estimate the Joule-Thomson coefficients are presented in this paper. The available equations of state used include the following: van der Waals, Virial, BWR, RK, and SRK. The Joule-Thomson coefficients for nitrogen and ethane are estimated by the proposed programs, and their ability to reproduce experimental values is tested. It is found that the RK equation yields the best results for nitrogen and ethane despite its simplicity.

  6. Long-term statistical analysis on hot days and heat wave in Mongolia

    NASA Astrophysics Data System (ADS)

    Erdenebat, E.; Sato, T.

    2014-12-01

    In this study, 40 years of hot day and heat wave in Mongolia is investigated. Hot days carry difficulties and losses for Mongolian economy and daily life, such as people and livestock fell unfavorable (ill affected), agriculture losses, drying small rivers and lakes, causing steppe fires and etc. The hot day is one of the severe weather extreme in Mongolia, and their frequency and intensity have been increasing and becoming more severe. Intensive and longer-lasted hot days break out a heat wave event. Therefore, a monitoring of hot day and heat wave's occurrence and its long-term change are in nationwide scale. Longer prolonged heat wave may one of the causes for drought initiation while occurrence of drought has noticeably increased since last decade, which it is consistent with the heat wave occurrence. We analyzed maximum air temperature and precipitation data at 12 stations obtained from National Agency for Meteorology and Environment Monitoring (NAMEM) of Mongolia. Definition of the hot day is calculated by each station from reference period (1971-2000) and the heat wave is defined by when the daily maximum air temperature is 5K higher than the daily climatology of the reference period and lasted more than 4 consecutive days. Spatial distribution of long-term mean heat wave occurrence suggests that two areas, in Siberia and Mongolia, show high frequency. Those two areas are separated each other. Time series analysis indicates that the frequency kept similar level in 1970s and 1980s. In last two decade, however, heat wave was increased in central Mongolia in 1990s and northern half of Mongolia in 2000s as well as Western and Eastern Siberia.

  7. Mixed refrigerant Joule-Thomson sorption cryocoolers

    NASA Astrophysics Data System (ADS)

    Tzabar, Nir; Grossman, Gershon

    2014-01-01

    Joule-Thomson (JT) sorption cryocooling is the most mature technology for cooling from a normal Room-Temperature (RT) down to temperatures below 100 K in the absence of moving parts. Therefore, high reliability and no vibrations are attainable, in comparison with other cryocoolers. Cooling to 80 - 100 K with JT cryocoolers is often implemented with pure nitrogen. Alternatively, mixed refrigerants have been suggested for reducing the operating pressures to enable closed cycle cryocooling. There is a variety of publications describing nitrogen sorption cryocoolers with different configurations of sorption compressors. In the present research we suggest a novel sorption JT cryocooler that operates with a mixed refrigerant. Merging of sorption cryocooling and a mixed refrigerant enables the use of a simple, single stage compressor for cooling to 80 - 100 K, lower operating temperatures of the sorption cycle, and thus - reduced power consumption. In previous studies we have analyzed sorption compressors for mixed gases and mixed refrigerants for JT cryocoolers, separately. In this paper the option of mixed refrigerant sorption JT cryocoolers is explored. The considerations for developing mixed refrigerants to be driven by sorption compressors and to be utilized with JT cryocoolers are provided. It appears that, unlike with pure nitrogen, mixed refrigerants can be suitable for JT cryocooling with a single stage sorption compressor.

  8. Final Report on the Joule-Scale Experimental Demonstration

    SciTech Connect

    Shverdin, M

    2008-10-01

    We describe the final results of the High Power Laser Pulse Recirculation project. We have developed and implementing a novel technique for picosecond, Joule-class laser pulse recirculation inside a passive cavity. The aim of this project was to develop technology compatible with increasing the efficiency of Compton based light sources by more than an order of magnitude. In year 1 of the project, we achieved a greater than 40 times average power enhancement of the mJ-scale laser pulses inside a passive cavity with internal focus. In year 2, we demonstrated recirculation of lasers pulses with energies up to 191 mJ at 532 nm, at a repetition rate of 10 Hz, and a pulse duration of 20 ps. In this high energy regime, we achieved up to 14 times average power enhancement inside the cavity. This enhancement factor is compatible with the new X-band based mono-energetic gamma-ray machine, Velociraptor, being constructed at LLNL. The demonstrated cavity enhancement is primarily limited by the poor spatial beam quality of the high power laser beam. We expect a nearly diffraction limited laser beam to achieve 40 times or better cavity enhancement, as demonstrated in low energy experiments in FY-07. The two primary obstacles to higher average brightness and conversion efficiency of laser pulse energy to gamma-rays are the relatively small Compton scattering cross-section and the typically low repetition rates of Joule-class interaction lasers (10 Hz). Only a small fraction (10{sup -10}) of the available laser photons is converted to gamma-rays, while the rest is discarded. To significantly reduce the average power requirements of the laser and increase the overall system efficiency, we can recirculate laser light for repeated interactions with electron bunches. Our pulse recirculation scheme is based on nonlinear frequency conversion, termed recirculation injection by nonlinear gating (RING), inside a passive cavity. The main objectives of the two year project were: (1) Validate

  9. Gene expression profiles during short-term heat stress in the red sea coral Stylophora pistillata.

    PubMed

    Maor-Landaw, Keren; Karako-Lampert, Sarit; Waldman Ben-Asher, Hiba; Goffredo, Stefano; Falini, Giuseppe; Dubinsky, Zvy; Levy, Oren

    2014-10-01

    During the past several decades, corals worldwide have been affected by severe bleaching events leading to wide-spread coral mortality triggered by global warming. The symbiotic Red Sea coral Stylophora pistillata from the Gulf of Eilat is considered an opportunistic 'r' strategist. It can thrive in relatively unstable environments and is considered a stress-tolerant species. Here, we used a S. pistillata custom microarray to examine gene expression patterns and cellular pathways during short-term (13-day) heat stress. The results allowed us to identify a two-step reaction to heat stress, which intensified significantly as the temperature was raised to a 32 °C threshold, beyond which, coping strategies failed at 34 °C. We identified potential 'early warning genes' and 'severe heat-related genes'. Our findings suggest that during short-term heat stress, S. pistillata may divert cellular energy into mechanisms such as the ER-unfolded protein response (UPR) and ER-associated degradation (ERAD) at the expense of growth and biomineralization processes in an effort to survive and subsequently recover from the stress. We suggest a mechanistic theory for the heat stress responses that may explain the success of some species which can thrive under a wider range of temperatures relative to others. © 2014 John Wiley & Sons Ltd.

  10. Development of Solar Wind Model Driven by Empirical Heat Flux and Pressure Terms

    NASA Technical Reports Server (NTRS)

    Sittler, Edward C., Jr.; Ofman, L.; Selwa, M.; Kramar, M.

    2008-01-01

    We are developing a time stationary self-consistent 2D MHD model of the solar corona and solar wind as suggested by Sittler et al. (2003). Sittler & Guhathakurta (1999) developed a semiempirical steady state model (SG model) of the solar wind in a multipole 3-streamer structure, with the model constrained by Skylab observations. Guhathakurta et al. (2006) presented a more recent version of their initial work. Sittler et al. (2003) modified the SG model by investigating time dependent MHD, ad hoc heating term with heat conduction and empirical heating solutions. Next step of development of 2D MHD models was performed by Sittler & Ofman (2006). They derived effective temperature and effective heat flux from the data-driven SG model and fit smooth analytical functions to be used in MHD calculations. Improvements of the Sittler & Ofman (2006) results now show a convergence of the 3-streamer topology into a single equatorial streamer at altitudes > 2 R(sub S). This is a new result and shows we are now able to reproduce observations of an equatorially confined streamer belt. In order to allow our solutions to be applied to more general applications, we extend that model by using magnetogram data and PFSS model as a boundary condition. Initial results were presented by Selwa et al. (2008). We choose solar minimum magnetogram data since during solar maximum the boundary conditions are more complex and the coronal magnetic field may not be described correctly by PFSS model. As the first step we studied the simplest 2D MHD case with variable heat conduction, and with empirical heat input combined with empirical momentum addition for the fast solar wind. We use realistic magnetic field data based on NSO/GONG data, and plan to extend the study to 3D. This study represents the first attempt of fully self-consistent realistic model based on real data and including semi-empirical heat flux and semi-empirical effective pressure terms.

  11. Heat shock protein 72 (Hsp72) improves long term recovery after focal cerebral ischemia in mice.

    PubMed

    Xu, Lijun; Xiong, Xiaoxing; Ouyang, Yibing; Barreto, George; Giffard, Rona

    2011-01-25

    Many brain protective strategies have been tested over short survival intervals, but few have been examined for long term benefit. The inducible member of the Heat shock protein 70 (Hsp70) family, Heat shock protein 72 (Hsp72), has been widely found to reduce ischemic injury. Here we assessed outcome in Hsp72 transgenic overexpressing mice and wild type littermates for one month following transient focal ischemia. Hsp72 reduced infarct area lost and improved behavioral outcome on rotarod and foot fault at one month. Thus protection by Hsp72 overexpression is long lasting, and includes improved recovery of motor function over one month.

  12. Effect of short-term exercise-heat acclimation on ventilatory and cerebral blood flow responses to passive heating at rest in humans.

    PubMed

    Fujii, Naoto; Tsuji, Bun; Honda, Yasushi; Kondo, Narihiko; Nishiyasu, Takeshi

    2015-09-01

    Hyperthermia induces hyperventilation and cerebral hypoperfusion in resting humans. We tested the hypothesis that short-term exercise-heat acclimation would alleviate those effects. Twenty healthy male subjects were divided into two groups that performed exercise training in the heat (TR-HEAT, n = 10) or cold (TR-COLD, n = 10). Before and after the training, the subjects in both groups participated in passive-heat tests at rest. Training was performed at 37°C (TR-HEAT) or 10°C (TR-COLD) and entailed four 20-min bouts of cycling at 50% peak oxygen uptake separated by 10-min recoveries daily for 6 consecutive days. After TR-HEAT, esophageal temperature was lowered when measured before and during passive heating, as was the esophageal temperature threshold for cutaneous active vasodilation, whereas plasma volume was increased (all P < 0.05). These traditional indices of successful heat acclimation were not all induced by TR-COLD (all P > 0.05). TR-HEAT had no significant effect on passive heating-induced increases in minute ventilation, even when evaluated as the esophageal temperature threshold for increases in minute ventilation and the slope relating minute ventilation to esophageal temperature (all P > 0.05). By contrast, TR-HEAT attenuated the passive heating-induced reduction in the cerebral vascular conductance index (middle cerebral artery mean blood velocity/mean arterial pressure) (all P < 0.05). TR-COLD did not attenuate the increase in minute ventilation or the decrease in the cerebral vascular conductance index observed during passive heating (all P > 0.05). These data suggest that in resting heated humans, short-term heat acclimation achieved through moderate-intensity exercise training (i.e., 50% peak oxygen uptake) in the heat does not influence hyperthermia-induced hyperventilation, but it does potentially attenuate cerebral hypoperfusion.

  13. Short-term heat acclimation is effective and may be enhanced rather than impaired by dehydration.

    PubMed

    Garrett, A T; Goosens, N G; Rehrer, N J; Patterson, M J; Harrison, J; Sammut, I; Cotter, J D

    2014-01-01

    Most heat acclimation data are from regimes longer than 1 week, and acclimation advice is to prevent dehydration. We hypothesized that (i) short-term (5-day) heat acclimation would substantially improve physiological strain and exercise tolerance under heat stress, and (ii) dehydration would provide a thermally independent stimulus for adaptation. Nine aerobically fit males heat acclimated using controlled-hyperthermia (rectal temperature 38.5°C) for 90 min on 5 days; once euhydrated (EUH) and once dehydrated (DEH) during acclimation bouts. Exercising heat stress tests (HSTs) were completed before and after acclimations (90-min cycling in Ta 35°C, 60% RH). During acclimation bouts, [aldosterone]plasma rose more across DEH than EUH (95%CI for difference between regimes: 40-411 pg ml(-1); P = 0.03; n = 5) and was positively related to plasma volume expansion (r = 0.65; P = 0.05), which tended to be larger in DEH (CI: -1 to 10%; P = 0.06; n = 9). In HSTs, resting forearm perfusion increased more in DEH (by 5.9 ml 100 tissue ml(-1) min(-1): -11.5 to -1.0; P = 0.04) and end-exercise cardiac frequency fell to a greater extent (by 11 b min(-1): -1 to 22; P = 0.05). Hydration-related effects on other endocrine, cardiovascular, and psychophysical responses to HSTs were unclear. Rectal temperature was unchanged at rest but was 0.3°C lower at end exercise (P < 0.01; interaction: P = 0.52). Short-term (5-day) heat acclimation induced effective adaptations, some of which were more pronounced after fluid-regulatory strain from permissive dehydration, and not attributable to dehydration effects on body temperature. Copyright © 2014 Wiley Periodicals, Inc.

  14. Communication: Ab initio Joule-Thomson inversion data for argon

    NASA Astrophysics Data System (ADS)

    Wiebke, Jonas; Senn, Florian; Pahl, Elke; Schwerdtfeger, Peter

    2013-02-01

    The Joule-Thomson coefficient μH(P, T) is computed from the virial equation of state up to seventh-order for argon obtained from accurate ab initio data. Higher-order corrections become increasingly more important to fit the low-temperature and low-pressure regime and to avoid the early onset of divergence in the Joule-Thomson inversion curve. Good agreement with experiment is obtained for temperatures T > 250 K. The results also illustrate the limitations of the virial equation in regions close to the critical temperature.

  15. Program For Joule-Thomson Analysis Of Mixed Cryogens

    NASA Technical Reports Server (NTRS)

    Jones, Jack A.; Lund, Alan

    1994-01-01

    JTMIX computer program predicts ideal and realistic properties of mixed gases at temperatures between 65 and 80 K. Performs Joule-Thomson analysis of any gaseous mixture of neon, nitrogen, various hydrocarbons, argon, oxygen, carbon monoxide, carbon dioxide, and hydrogen sulfide. When used in conjunction with DDMIX computer program of National Institute of Standards and Technology (NIST), JTMIX accurately predicts order-of-magnitude increases in Joule-Thomson cooling capacities occuring when various hydrocarbons added to nitrogen. Also predicts boiling temperature of nitrogen depressed from normal value to as low as 60 K upon addition of neon. Written in Turbo C.

  16. Communication: Ab initio Joule-Thomson inversion data for argon.

    PubMed

    Wiebke, Jonas; Senn, Florian; Pahl, Elke; Schwerdtfeger, Peter

    2013-02-21

    The Joule-Thomson coefficient μ(H)(P, T) is computed from the virial equation of state up to seventh-order for argon obtained from accurate ab initio data. Higher-order corrections become increasingly more important to fit the low-temperature and low-pressure regime and to avoid the early onset of divergence in the Joule-Thomson inversion curve. Good agreement with experiment is obtained for temperatures T > 250 K. The results also illustrate the limitations of the virial equation in regions close to the critical temperature.

  17. Physiological and molecular evidence of differential short-term heat tolerance in Mediterranean seagrasses

    PubMed Central

    Marín-Guirao, Lazaro; Ruiz, Juan M.; Dattolo, Emanuela; Garcia-Munoz, Rocio; Procaccini, Gabriele

    2016-01-01

    The increase in extreme heat events associated to global warming threatens seagrass ecosystems, likely by affecting key plant physiological processes such as photosynthesis and respiration. Understanding species’ ability to acclimate to warming is crucial to better predict their future trends. Here, we study tolerance to warming in two key Mediterranean seagrasses, Posidonia oceanica and Cymodocea nodosa. Stress responses of shallow and deep plants were followed during and after short-term heat exposure in mesocosms by coupling photo-physiological measures with analysis of expression of photosynthesis and stress-related genes. Contrasting tolerance and capacity to heat acclimation were shown by shallow and deep P. oceanica ecotypes. While shallow plants acclimated through respiratory homeostasis and activation of photo-protective mechanisms, deep ones experienced photosynthetic injury and impaired carbon balance. This suggests that P. oceanica ecotypes are thermally adapted to local conditions and that Mediterranean warming will likely diversely affect deep and shallow meadow stands. On the other hand, contrasting mechanisms of heat-acclimation were adopted by the two species. P. oceanica regulates photosynthesis and respiration at the level of control plants while C. nodosa balances both processes at enhanced rates. These acclimation discrepancies are discussed in relation to inherent attributes of the two species. PMID:27345831

  18. Physiological and molecular evidence of differential short-term heat tolerance in Mediterranean seagrasses

    NASA Astrophysics Data System (ADS)

    Marín-Guirao, Lazaro; Ruiz, Juan M.; Dattolo, Emanuela; Garcia-Munoz, Rocio; Procaccini, Gabriele

    2016-06-01

    The increase in extreme heat events associated to global warming threatens seagrass ecosystems, likely by affecting key plant physiological processes such as photosynthesis and respiration. Understanding species’ ability to acclimate to warming is crucial to better predict their future trends. Here, we study tolerance to warming in two key Mediterranean seagrasses, Posidonia oceanica and Cymodocea nodosa. Stress responses of shallow and deep plants were followed during and after short-term heat exposure in mesocosms by coupling photo-physiological measures with analysis of expression of photosynthesis and stress-related genes. Contrasting tolerance and capacity to heat acclimation were shown by shallow and deep P. oceanica ecotypes. While shallow plants acclimated through respiratory homeostasis and activation of photo-protective mechanisms, deep ones experienced photosynthetic injury and impaired carbon balance. This suggests that P. oceanica ecotypes are thermally adapted to local conditions and that Mediterranean warming will likely diversely affect deep and shallow meadow stands. On the other hand, contrasting mechanisms of heat-acclimation were adopted by the two species. P. oceanica regulates photosynthesis and respiration at the level of control plants while C. nodosa balances both processes at enhanced rates. These acclimation discrepancies are discussed in relation to inherent attributes of the two species.

  19. Modeling heat exchange characteristics of long term space operations: Role of skin wettedness and exercise

    NASA Technical Reports Server (NTRS)

    Gonzalez, Richard R.

    1994-01-01

    The problems of heat exchange during rest and exercise during long term space operations are covered in this report. Particular attention is given to the modeling and description of the consequences of requirement to exercise in a zero-g atmosphere during Space Shuttle flights, especially long term ones. In space environments, there exists no free convection therefore only forced convection occurring by movement, such as pedalling on a cycle ergometer, augments required heat dissipation necessary to regulate body temperature. The requirement to exercise at discrete periods of the day is good practice in order to resist the deleterious consequences of zero-gravity problems and improve distribution of body fluids. However, during exercise (ca. 180 to 250W), in zero-g environments, the mass of eccrine sweating rests as sheets on the skin surface and the sweat cannot evaporate readily. The use of exercise suits with fabrics that have hydrophobic or outwicking properties somewhat distributes the mass of sweat to a larger surface from which to evaporate. However, with no free convection, increased skin wettedness throughout the body surface induces increasing thermal discomfort, particularly during continuous exercise. This report presents several alternatives to aid in this problem: use of intermittent exercise, methods to quantify local skin wettedness, and introduction of a new effective temperature that integrates thermal stress and heat exchange avenues in a zero-g atmosphere.

  20. Clogging in micromachined Joule-Thomson coolers: Mechanism and preventive measures

    NASA Astrophysics Data System (ADS)

    Cao, H. S.; Vanapalli, S.; Holland, H. J.; Vermeer, C. H.; ter Brake, H. J. M.

    2013-07-01

    Micromachined Joule-Thomson coolers can be used for cooling small electronic devices. However, a critical issue for long-term operation of these microcoolers is the clogging caused by the deposition of water that is present as impurity in the working fluid. We present a model that describes the deposition process considering diffusion and kinetics of water molecules. In addition, the deposition and sublimation process was imaged, and the experimental observation fits well to the modeling predictions. By changing the temperature profile along the microcooler, the operating time of the microcooler under test at 105 K extends from 11 to 52 h.

  1. Short-term heat acclimation improves the determinants of endurance performance and 5-km running performance in the heat.

    PubMed

    James, Carl A; Richardson, Alan J; Watt, Peter W; Willmott, Ashley G B; Gibson, Oliver R; Maxwell, Neil S

    2017-03-01

    This study investigated the effect of 5 days of controlled short-term heat acclimation (STHA) on the determinants of endurance performance and 5-km performance in runners, relative to the impairment afforded by moderate heat stress. A control group (CON), matched for total work and power output (2.7 W·kg(-1)), differentiated thermal and exercise contributions of STHA on exercise performance. Seventeen participants (10 STHA, 7 CON) completed graded exercise tests (GXTs) in cool (13 °C, 50% relative humidity (RH), pre-training) and hot conditions (32 °C, 60% RH, pre- and post-training), as well as 5-km time trials (TTs) in the heat, pre- and post-training. STHA reduced resting (p = 0.01) and exercising (p = 0.04) core temperature alongside a smaller change in thermal sensation (p = 0.04). Both groups improved the lactate threshold (LT, p = 0.021), lactate turnpoint (LTP, p = 0.005) and velocity at maximal oxygen consumption (vV̇O2max; p = 0.031) similarly. Statistical differences between training methods were observed in TT performance (STHA, -6.2(5.5)%; CON, -0.6(1.7)%, p = 0.029) and total running time during the GXT (STHA, +20.8(12.7)%; CON, +9.8(1.2)%, p = 0.006). There were large mean differences in change in maximal oxygen consumption between STHA +4.0(2.2) mL·kg(-1)·min(-1) (7.3(4.0)%) and CON +1.9(3.7) mL·kg(-1)·min(-1) (3.8(7.2)%). Running economy (RE) deteriorated following both training programmes (p = 0.008). Similarly, RE was impaired in the cool GXT, relative to the hot GXT (p = 0.004). STHA improved endurance running performance in comparison with work-matched normothermic training, despite equality of adaptation for typical determinants of performance (LT, LTP, vV̇O2max). Accordingly, these data highlight the ergogenic effect of STHA, potentially via greater improvements in maximal oxygen consumption and specific thermoregulatory and associated thermal perception adaptations absent in normothermic training.

  2. Ceramic 3D printed Joule Thomson mini cryocooler intended for HOT IR detectors

    NASA Astrophysics Data System (ADS)

    Shapiro, A.; Fraiman, L.; Parahovnik, A.

    2017-05-01

    Joule Thomson (JT) Cryocooler is a well-known technology which is widely used in research and industry. The cooling effect is achieved by isenthalpic expansion of the cooling gas in an orifice. A JT cooler has two basic components: a counter flow heat exchanger and an orifice. Due to the fact that the cooler has no moving parts and contains relatively simple components it is a great candidate for miniaturization, and realization with the new additive manufacturing technologies. In the current work we discuss the implementation of 3D ceramic printing as a possible fabrication technology for a JT cooler intended for cooling IR detectors operated at temperature of about 150K. In this paper we present a comprehensive analysis including coolant considerations, heat transfer calculations and realization of the cooler.

  3. Quantitative thermal imaging of single-walled carbon nanotube devices by scanning Joule expansion microscopy.

    PubMed

    Xie, Xu; Grosse, Kyle L; Song, Jizhou; Lu, Chaofeng; Dunham, Simon; Du, Frank; Islam, Ahmad E; Li, Yuhang; Zhang, Yihui; Pop, Eric; Huang, Yonggang; King, William P; Rogers, John A

    2012-11-27

    Electrical generation of heat in single-walled carbon nanotubes (SWNTs) and subsequent thermal transport into the surroundings can critically affect the design, operation, and reliability of electronic and optoelectronic devices based on these materials. Here we investigate such heat generation and transport characteristics in perfectly aligned, horizontal arrays of SWNTs integrated into transistor structures. We present quantitative assessments of local thermometry at individual SWNTs in these arrays, evaluated using scanning Joule expansion microscopy. Measurements at different applied voltages reveal electronic behaviors, including metallic and semiconducting responses, spatial variations in diameter or chirality, and localized defect sites. Analytical models, validated by measurements performed on different device structures at various conditions, enable accurate, quantitative extraction of temperature distributions at the level of individual SWNTs. Using current equipment, the spatial resolution and temperature precision are as good as ∼100 nm and ∼0.7 K, respectively.

  4. Formation of laves phase in a refractory austenitic steel due to long-term heating

    NASA Astrophysics Data System (ADS)

    Tarasenko, L. V.; Shal'kevich, A. B.

    2011-07-01

    Steels of the Fe - Cr - Ni -Mo - Nb - Al - C system are studied by methods of phase physicochemical analysis and electron microscopy with the aim to determine the causes of changes in mechanical properties after long-term heating at a temperature of 600 - 700°C. Grain-boundary formation of particles of a Laves phase is shown to cause decrease in the impact toughness and transformation of particles of γ'-phase under conditions of creep. The effect of alloying elements on the chemical composition of the multicomponent Laves phase is studied depending on the temperatures of hardening, aging, and subsequent heating. Concentration correspondence between the chemical composition of the austenite and the intermetallic tcp phase formed in aging is discovered. A computational scheme for predicting the possibility of formation of Laves phases in multicomponent alloys is suggested.

  5. Long-term effect of volcanic forcing on ocean heat content

    NASA Astrophysics Data System (ADS)

    Gregory, J. M.

    2010-11-01

    Explosive volcanic eruptions cause episodic negative radiative forcing of the climate system. Using coupled atmosphere-ocean general circulation models (AOGCMs) subjected to historical forcing since the late nineteenth century, previous authors have shown that each large volcanic eruption is associated with a sudden drop in ocean heat content and sea-level from which the subsequent recovery is slow. Here we show that this effect may be an artefact of experimental design, caused by the AOGCMs not having been spun up to a steady state with volcanic forcing before the historical integrations begin. Because volcanic forcing has a long-term negative average, a cooling tendency is thus imposed on the ocean in the historical simulation. We recommend that an extra experiment be carried out in parallel to the historical simulation, with constant time-mean historical volcanic forcing, in order to correct for this effect and avoid misinterpretation of ocean heat content changes.

  6. Long-Term Monitoring of Mini-Split Ductless Heat Pumps in the Northeast

    SciTech Connect

    Ueno, K.; Loomis, H.

    2015-06-01

    Transformations, Inc. has extensive experience building their high performance housing at a variety of Massachusetts locations, in both a production and custom home setting. The majority of their construction uses mini-split heat pumps (MSHPs) for space conditioning. This research covered the long-term performance of MSHPs in Zone 5A; it is the culmination of up to 3 years' worth of monitoring in a set of eight houses. This research examined electricity use of MSHPs, distributions of interior temperatures and humidity when using simplified (two-point) heating systems in high-performance housing, and the impact of open-door/closed-door status on temperature distributions. The use of simplified space conditioning distribution (through use of MSHPs) provides significant first cost savings, which are used to offset the increased investment in the building enclosure.

  7. GEM-CEDAR Study of Ionospheric Energy Input and Joule Dissipation

    NASA Technical Reports Server (NTRS)

    Rastaetter, Lutz; Kuznetsova, Maria M.; Shim, Jasoon

    2012-01-01

    We are studying ionospheric model performance for six events selected for the GEM-CEDAR modeling challenge. DMSP measurements of electric and magnetic fields are converted into Poynting Flux values that estimate the energy input into the ionosphere. Models generate rates of ionospheric Joule dissipation that are compared to the energy influx. Models include the ionosphere models CTIPe and Weimer and the ionospheric electrodynamic outputs of global magnetosphere models SWMF, LFM, and OpenGGCM. This study evaluates the model performance in terms of overall balance between energy influx and dissipation and tests the assumption that Joule dissipation occurs locally where electromagnetic energy flux enters the ionosphere. We present results in terms of skill scores now commonly used in metrics and validation studies and we can measure the agreement in terms of temporal and spatial distribution of dissipation (i.e, location of auroral activity) along passes of the DMSP satellite with the passes' proximity to the magnetic pole and solar wind activity level.

  8. James Prescott Joule and the idea of energy

    NASA Astrophysics Data System (ADS)

    Cardwell, Donald

    1989-05-01

    To commemorate the centenary of Joule's death, this article offers a brief account of the origins and development of his ideas and their incorporation into mainstream physics. The scientific, technological and social importance of his work is explained and he is shown to be a quintessential physicist.

  9. The similarity law for the Joule-Thomson inversion line.

    PubMed

    Apfelbaum, E M; Vorob'ev, V S

    2014-10-23

    We show that the expression for the Joule-Thomson inversion temperature following from the van der Waals equation and recorded in a form reduced to the Boyle values has a universal character and can be applied to many real substances and model systems.

  10. Mixed-Gas Sorption Joule-Thomson Refrigerator

    NASA Technical Reports Server (NTRS)

    Jones, Jack A.; Petrick, S. Walter; Bard, Steven

    1991-01-01

    Proposed mixed-gas sorption Joule-Thomson refrigerator provides cooling down to temperature of 70 K. Includes only one stage and no mechanical compressor. Simpler, operates without vibrating, and consumes less power in producing same amount of cooling. Same sorption principle of operation applicable in compressor that chemisorbs oxygen or hydrogen from mixture with helium, neon, and/or other nonreactive gases.

  11. Long-term heat stress induces the inflammatory response in dairy cows revealed by plasma proteome analysis.

    PubMed

    Min, Li; Zheng, Nan; Zhao, Shengguo; Cheng, Jianbo; Yang, Yongxin; Zhang, Yangdong; Yang, Hongjian; Wang, Jiaqi

    2016-03-04

    In this work we employed a comparative proteomic approach to evaluate seasonal heat stress and investigate proteomic alterations in plasma of dairy cows. Twelve lactating Holstein dairy cows were used and the treatments were: heat stress (n = 6) in hot summer (at the beginning of the moderate heat stress) and no heat stress (n = 6) in spring natural ambient environment, respectively. Subsequently, heat stress treatment lasted 23 days (at the end of the moderate heat stress) to investigate the alterations of plasma proteins, which might be employed as long-term moderate heat stress response in dairy cows. Changes in plasma proteins were analyzed by two-dimensional electrophoresis (2-DE) combined with mass spectrometry. Analysis of the properties of the identified proteins revealed that the alterations of plasma proteins were related to inflammation in long-term moderate heat stress. Furthermore, the increase in plasma tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) directly demonstrated that long-term moderate heat stress caused an inflammatory response in dairy cows.

  12. How specialized volatiles respond to chronic and short-term physiological and shock heat stress in Brassica nigra.

    PubMed

    Kask, Kaia; Kännaste, Astrid; Talts, Eero; Copolovici, Lucian; Niinemets, Ülo

    2016-09-01

    Brassicales release volatile glucosinolate breakdown products upon tissue mechanical damage, but it is unclear how the release of glucosinolate volatiles responds to abiotic stresses such as heat stress. We used three different heat treatments, simulating different dynamic temperature conditions in the field to gain insight into stress-dependent changes in volatile blends and photosynthetic characteristics in the annual herb Brassica nigra (L.) Koch. Heat stress was applied by either heating leaves through temperature response curve measurements from 20 to 40 °C (mild stress), exposing plants for 4 h to temperatures 25-44 °C (long-term stress) or shock-heating leaves to 45-50 °C. Photosynthetic reduction through temperature response curves was associated with decreased stomatal conductance, while the reduction due to long-term stress and collapse of photosynthetic activity after heat shock stress were associated with non-stomatal processes. Mild stress decreased constitutive monoterpene emissions, while long-term stress and shock stress resulted in emissions of the lipoxygenase pathway and glucosinolate volatiles. Glucosinolate volatile release was more strongly elicited by long-term stress and lipoxygenase product released by heat shock. These results demonstrate that glucosinolate volatiles constitute a major part of emission blend in heat-stressed B. nigra plants, especially upon chronic stress that leads to induction responses.

  13. Heat stress increases long-term human migration in rural Pakistan

    NASA Astrophysics Data System (ADS)

    Mueller, V.; Gray, C.; Kosec, K.

    2014-03-01

    Human migration attributable to climate events has recently received significant attention from the academic and policy communities . Quantitative evidence on the relationship between individual, permanent migration and natural disasters is limited . A 21-year longitudinal survey conducted in rural Pakistan (1991-2012) provides a unique opportunity to understand the relationship between weather and long-term migration. We link individual-level information from this survey to satellite-derived measures of climate variability and control for potential confounders using a multivariate approach. We find that flooding--a climate shock associated with large relief efforts--has modest to insignificant impacts on migration. Heat stress, however--which has attracted relatively little relief--consistently increases the long-term migration of men, driven by a negative effect on farm and non-farm income. Addressing weather-related displacement will require policies that both enhance resilience to climate shocks and lower barriers to welfare-enhancing population movements.

  14. Nanofocus of tenth of joules and a portable plasma focus of few joules for field applications

    SciTech Connect

    Soto, Leopoldo; Pavez, Cristian; Moreno, Jose; Tarifeno, Ariel; Pedreros, Jose; Altamirano, Luis

    2009-01-21

    A repetitive pinch plasma focus that works with stored energy less than 1 J per shot has be developed at the Chilean Nuclear Energy Commission. The main features of this device, repetitive Nanofocus, are 5 nF of capacity, 5 nH of inductance, 5-10 kV charging voltage, 60-250 mJ stored energy, 5-10 kA current peak, per shot. The device has been operated at 20 Hz in hydrogen and deuterium. X-ray radiographs of materials of different thickness were obtained. Neutrons were detected using a system based upon {sup 3}He proportional counter in chare integrated mode. However, the reproducibility of this miniaturized device is low and several technological subjects have to be previously solved in order to produce neutrons for periods greater than minutes. Further studies in the Nanofocus are being carried out. In addition, a device with a stored energy of a few joules is being explored. A preliminary compact, low weight (3 kg), portable PF device (25 cmx5 cmx5 cm) for field applications has been designed. This device was designed to operate with few kilovolts (10 kV or less) with a stored energy of 2 J and a repetition rate of 10 Hz without cooling. A neutron flux of the order of 10{sup 4}-10{sup 5} n/s is expected.

  15. Development of novel short-term heating angioplasty: thermal denaturation dynamics of collagen in artery wall

    NASA Astrophysics Data System (ADS)

    Shimazaki, N.; Tokunaga, H.; Katou, Y.; Hayashi, T.; Arai, T.

    2009-02-01

    We have studied to develop the new thermal angioplasty methodology, photo-thermo dynamic balloon angioplasty (PTDBA), which provides artery dilatation with short-term (<15s) and uniform heating through the balloon by the combination of the efficient laser driven heat generation and fluid perfusion. Thermal denaturation degree of the collagen in artery media may be the important factor to attain sufficient artery dilatation for the PTDBA. In order to predict the optimum heating condition i.e. the balloon temperature and heating duration, we investigated the thermal denaturation dynamics of artery collagen in ex vivo. The extracted fresh porcine carotid artery was used. The temperature-dependent light scattering property and mechanical property of the artery specimen were simultaneously measured during artery temperature rising by specially made setup to assess the denaturation of arterial collagen. The change rate of the backscattered light intensity from the artery specimen; I(T)/I0 with 633nm was measured to evaluate the artery scattering property change with the thermal denaturation. The artery specimen was heated from 25°C to 80°C with constant temperature rising rate of 3°C/min. The measured I(T)/I0 was suddenly increased over 48°C. This boundary temperature might be the initiation temperature of the arterial collagen denaturation. We defined the variation of the I(T)/I0 as the collagen denaturation ratio, and calculated the reactive enthalpy by the chemical equilibrium theory. Since the calculated enthalpy was similar to the enthalpy in literature report, the variety of I(T)/I0 during the temperature rising might be attributed to the collagen conformational change due to the denaturation. In terms of the artery internal force measurement, the artery force was decreased with increasing of the artery temperature up to 65°C (i.e. softening), and increased over 65°C (i.e. shrinkage). We confirmed that the changes of the backscattered light (at 633nm in

  16. Effect of radiant heat on head temperature gradient in term infants.

    PubMed

    Gunn, A J; Gunn, T R

    1996-05-01

    To test the hypothesis that external radiant heating might lead to significant fluctuations in superficial and core head temperatures in newborn infants. In an observation group of 14 term infants nursed under a radiant heater, servo-controlled to the abdominal skin, changes in rectal, core head, and scalp temperatures with heater activation were examined. In a further intervention group of six infants the effect of a reflective head shield on the fluctuations of scalp temperature was also tested. In the observation group, when the heater had been off for 30 minutes, the rectal and scalp temperatures were 36.7 (SD 0.6) and 35.6 (0.6) degrees C, respectively, a difference of 1.2 (0.2) degrees C. After 30 minutes with the radiant heater on this fell to 0.2 (0.5) degrees C. The core head temperature, however, remained similar to the rectal temperature throughout. In the intervention group a reflective shield prevented the loss of the rectal-scalp gradient. Overhead heater activation is associated with loss of the core to scalp temperature gradient, but no change in core head temperature in term infants. The clinical relevance of this superficial heating in vulnerable infants warrants further study.

  17. Joule-Thomson coefficient of ideal anyons within fractional exclusion statistics

    SciTech Connect

    Qin Fang; Chen Jisheng

    2011-02-15

    The analytical expressions of the Joule-Thomson coefficient for homogeneous and harmonically trapped three-dimensional ideal anyons which obey Haldane fractional exclusion statistics are derived. For an ideal Fermi gas, the Joule-Thomson coefficient is negative, which means that there is no maximum Joule-Thomson inversion temperature. With careful study, it is found that there exists a Joule-Thomson inversion temperature in the fractional exclusion statistics model. Furthermore, the relations between the Joule-Thomson inversion temperature and the statistical parameter g are investigated.

  18. Joule-Thomson coefficient of ideal anyons within fractional exclusion statistics.

    PubMed

    Qin, Fang; Chen, Ji-sheng

    2011-02-01

    The analytical expressions of the Joule-Thomson coefficient for homogeneous and harmonically trapped three-dimensional ideal anyons which obey Haldane fractional exclusion statistics are derived. For an ideal Fermi gas, the Joule-Thomson coefficient is negative, which means that there is no maximum Joule-Thomson inversion temperature. With careful study, it is found that there exists a Joule-Thomson inversion temperature in the fractional exclusion statistics model. Furthermore, the relations between the Joule-Thomson inversion temperature and the statistical parameter g are investigated.

  19. A simple indicator to rapidly assess the short-term impact of heat waves on mortality within the French heat warning system.

    PubMed

    Antics, Annamaria; Pascal, Mathilde; Laaidi, Karine; Wagner, Vérène; Corso, Magali; Declercq, Christophe; Beaudeau, Pascal

    2013-01-01

    We propose a simple method to provide a rapid and robust estimate of the short-term impacts of heat waves on mortality, to be used for communication within a heat warning system. The excess mortality during a heat wave is defined as the difference between the observed mortality over the period and the observed mortality over the same period during the N preceding years. This method was tested on 19 French cities between 1973 and 2007. In six cities, we compared the excess mortality to that obtained using a modelling of the temperature-mortality relationship. There was a good agreement between the excess mortalities estimated by the simple indicator and by the models. Major differences were observed during the most extreme heat waves, in 1983 and 2003, and after the implementation of the heat prevention plan in 2006. Excluding these events, the mean difference between the estimates obtained by the two methods was of 13 deaths [1:45]. A comparison of mortality with the previous years provides a simple estimate of the mortality impact of heat waves. It can be used to provide early and reliable information to stakeholders of the heat prevention plan, and to select heat waves that should be further investigated.

  20. Modelling Long-Term Changes of the Heat Budget and Chemistry near the Mesopause

    NASA Astrophysics Data System (ADS)

    Chabrillat, S.; Brasseur, G.; Fonteyn, D.

    Modelling studies have evaluated that the standard scenario of doubling CO2 has an important impact on the radiative budget of the mesosphere/lower thermosphere region (MLT) and could induce temperature changes comparable in magnitude to the effect of the 11-year solar cycle. Long-term observations of stratospheric water vapor and methane exhibit trends which should also influence the MLT. This effect is difficult to evaluate, because these trends in H2 O and CH4 can not be explained by current models of the middle atmosphere. Using SOCRATES, an interactive 2 D- model extending from the surface to the lower thermosphere, we study the sensitivity of the MLT region to each of these changes (CO2 , CH4 , H2 O, solar cycle) and to their combined effects.The focus is on the mesopause level, which coincides with a secondary maximum in ozone abundance. In order to quantify the transient response of the MLT to these changes, we run very long (100-year) simulations with long-term trends of the natural and anthropogenic forcings. D e to the currentu limitations in middle atmosphere modelling, we suppose that the dynamical forcing due to wave breaking remains constant from year to year, and we use stratospheric abundances of methane and water vapor based on observations. We discuss the estimated long-term change in ozone, heating and temperature at the mesopause, paying special attention to the trends at summer solstice and to the variations in the annual amplitudes of the seasonal cycles.

  1. Laser driven short-term thermal angioplasty: enhancement of drug delivery performance by heating with tension

    NASA Astrophysics Data System (ADS)

    Suganuma, Kao; Homma, Rie; Shimazaki, Natsumi; Ogawa, Emiyu; Arai, Tsunenori

    2017-02-01

    To enhance drug delivery performance of drug eluting balloon (DEB) against re-stenosis, we have proposed a heating drug delivery during balloon dilatation using our laser driven short-term thermal angioplasty which may realize to suppress surrounding thermal injury. We studied an influence of vessel dilatation parameters on the heating drug delivery. These parameters were classified into two different forces, that is, circumferential tension and inter-luminal pressure. We think these parameters were not able to determine only by balloon pressure. The circumferential tension with 0-30 mN/mm2 was added to a porcine carotid artery using an automatic stage. Various temperature solutions with 37, and 70°C of hydrophobic fluorescent Rhodamine B with 3 μg/ml in concentration were dropped on pig carotid wall. We measured a defined drug delivery amount as well as delivery depth by a microscopic fluorescence measurement on the cross section of the solution delivered vessel. In the case of 37°C, we found the intima surface drug amount with 7 mN/mm2 was increased as 10-20 times as other tension cases. On the other hand, at 70°C, we found the optimum tension with 30 mN/mm2. We found the drug delivery enhancement might be related to the change of super microscopic surface structure of the vessel. We predict that the collagen thermal denaturation of the vessel wall might play important role to the drug delivery.

  2. Design of a valved moving magnet type linear compressor for a Joule-Thomson cryocooler

    NASA Astrophysics Data System (ADS)

    Wang, W. W.; Wang, L. Y.; Gan, Z. H.

    2014-01-01

    For temperatures around 4-6 K, Joule-Thomson (J-T) cryocoolers can achieve a higher efficiency than Stirling or pulse tube cryocoolers thus have been widely used in space. It is crucial for a J-T compressor to obtain a relatively high pressure ratio. With this concept, a valved moving magnet type linear compressor has been designed. This paper describes the design method and component structure of the linear compressor in detail. The electromagnetic force of linear motor, stiffness and stress distribution of flexure springs were calculated based on finite element method (FEM). System resonance was specially considered to achieve a high efficiency, and system vibration and heat dissipation problems were discussed. The design goal of the linear compressor is to achieve an efficiency of 80% and a lifetime longer than 5 years.

  3. Gifford-McMahon/Joule-Thomson Refrigerator Cools to 2.5 K

    NASA Technical Reports Server (NTRS)

    Britcliffe, Michael; Fernandez, Jose; Hanson, Theodore

    2005-01-01

    A compact refrigerator designed specifically for cooling a microwave maser low-noise amplifier is capable of removing heat at a continuous rate of 180 mW at a temperature of 2.5 K. This refrigerator is a combination of (1) a commercial Gifford-McMahon (GM) refrigerator nominally rated for cooling to 4 K and (2) a Joule-Thomson (J-T) circuit. The GM refrigerator pre-cools the J-T circuit, which provides the final stage of cooling. The refrigerator is compact and capable of operating in any orientation. Moreover, in comparison with a typical refrigerator heretofore used to cool a maser to 4.5 K, this refrigerator is simpler and can be built at less than half the cost.

  4. Transparent Pd Wire Network-Based Areal Hydrogen Sensor with Inherent Joule Heater.

    PubMed

    Walia, Sunil; Gupta, Ritu; Rao, K D M; Kulkarni, Giridhar U

    2016-09-07

    A high degree of transparency in devices is considered highly desirable for futuristic technology. This demands that both the active material and the electrodes are made of transparent materials. In this work, a transparent Pd wire network (∼1 cm(2)), fabricated using crackle lithography technique with sheet resistance and transmittance of ∼200 Ohm per square and ∼80%, respectively, serves multiple roles; besides being an electrode, it acts as an active material for H2 sensing as well as an in-built electrothermal heater. The sensor works over a wide range of hydrogen (H2) concentration down to 0.02% with a response time of ∼41 s, which could be improved to ∼13 s by in situ Joule heating to ∼75 °C. Importantly, the device has the potential of scale-up to a window size transparent panel and to be flexible when desired.

  5. Comparative Exergetic Analysis of Joule-Thomson Liquefiers

    NASA Astrophysics Data System (ADS)

    Chorowski, Maciej

    2004-06-01

    The Joule-Thomson microliquefiers are very reliable and noiseless cryocoolers, specially well fitted for cryostating small electronic devices, IR detectors or cryosurgical probes. Their essential drawback is low thermodynamic efficiency imposing high supply gas pressure, usually above 10 MPa. An exergetic analysis of the microliquefier has been performed and exergy-loss sources identified. Some of the losses can be avoided if a pure gas is replaced with a proper gas mixture and in result the supply gas pressure can be lowered significantly. The efficiencies and working parameters of Joule-Thomson microliquefier fed with pure N2 and the mixtures N2 - CH4 and N2 - R13 have been estimated and measured. The mixture properties have been calculated using the Peng-Robinson equation of state. The possibility to use a liquid-solid phase transition in a cooling-power "on-off" control loop has been observed.

  6. Numerical Investigation of Influence of Electrode Immersion Depth on Heat Transfer and Fluid Flow in Electroslag Remelting Process

    NASA Astrophysics Data System (ADS)

    Wang, Qiang; Cai, Hui; Pan, Liping; He, Zhu; Liu, Shuang; Li, Baokuan

    2016-12-01

    The influence of the electrode immersion depth on the electromagnetic, flow and temperature fields, as well as the solidification progress in an electroslag remelting furnace have been studied by a transient three-dimensional coupled mathematical model. Maxwell's equations were solved by the electrical potential approach. The Lorentz force and Joule heating were added into the momentum and energy conservation equations as a source term, respectively, and were updated at each time step. The volume of fluid method was invoked to track the motion of the metal droplet and slag-metal interface. The solidification was modeled by an enthalpy-porosity formulation. An experiment was carried out to validate the model. The total amount of Joule heating decreases from 2.13 × 105 W to 1.86 × 105 W when the electrode immersion depth increases from 0.01 m to 0.03 m. The variation law of the slag temperature is different from that of the Joule heating. The volume average temperature rises from 1856 K to 1880 K when the immersion depth increases from 0.01 m to 0.02 m, and then drops to 1869 K if the immersion depth continuously increases to 0.03 m. As a result, the deepest metal pool, which is around 0.03 m, is formed when the immersion depth is 0.02 m.

  7. The first determination of the Planck constant with the joule balance NIM-2

    NASA Astrophysics Data System (ADS)

    Li, Zhengkun; Zhang, Zhonghua; Lu, Yunfeng; Hu, Pengcheng; Liu, Yongmeng; Xu, Jinxin; Bai, Yang; Zeng, Tao; Wang, Gang; You, Qiang; Wang, Dawei; Li, Shisong; He, Qing; Tan, Jiubin

    2017-10-01

    The National Institute of Metrology (NIM, China) proposed a joule balance method to measure the Planck constant in 2006, and built the first prototype NIM-1 to verify its principle with a relative uncertainty of 8.9  ×  10–6 by 2013. Since 2013, a new joule balance NIM-2 has been designed, with a series of improvements to reduce the measurement uncertainty. By April 2017, NIM-2 has been constructed and can be employed to measure the Planck constant in vacuum. A first measurement on NIM-2 yields a determination of the Planck constant is 6.626 069 2(16)  ×  10–34 Js with a relative uncertainty of 2.4  ×  10–7. The determination differs in relative terms by  ‑1.27  ×  10–7 from the CODATA 2014 value. Further improvement of NIM-2 is still in progress towards 10–8 level uncertainty in the future.

  8. Neural progenitor cell proliferation in the hypothalamus is involved in acquired heat tolerance in long-term heat-acclimated rats.

    PubMed

    Matsuzaki, Kentaro; Katakura, Masanori; Sugimoto, Naotoshi; Hara, Toshiko; Hashimoto, Michio; Shido, Osamu

    2017-01-01

    Constant exposure to moderate heat facilitates progenitor cell proliferation and neuronal differentiation in the hypothalamus of heat-acclimated (HA) rats. In this study, we investigated neural phenotype and responsiveness to heat in HA rats' hypothalamic newborn cells. Additionally, the effect of hypothalamic neurogenesis on heat acclimation in rats was evaluated. Male Wistar rats (5 weeks old) were housed at an ambient temperature (Ta) of 32°C for 6 days (STHA) or 40 days (LTHA), while control (CN) rats were kept at a Ta of 24°C for 6 days (STCN) or 40 days (LTCN). Bromodeoxyuridine (BrdU) was intraperitoneally injected daily for five consecutive days (50 mg/kg/day) after commencing heat exposure. The number of hypothalamic BrdU-immunopositive (BrdU+) cells in STHA and LTHA rats was determined immunohistochemically in brain samples and found to be significantly greater than those in respective CN groups. In LTHA rats, approximately 32.6% of BrdU+ cells in the preoptic area (POA) of the anterior hypothalamus were stained by GAD67, a GABAergic neuron marker, and 15.2% of BrdU+ cells were stained by the glutamate transporter, a glutamatergic neuron marker. In addition, 63.2% of BrdU+ cells in the POA were immunolabeled with c-Fos. Intracerebral administration of the mitosis inhibitor, cytosine arabinoside (AraC), interfered with the proliferation of neural progenitor cells and acquired heat tolerance in LTHA rats, whereas the selected ambient temperature was not changed. These results demonstrate that heat exposure generates heat responsive neurons in the POA, suggesting a pivotal role in autonomic thermoregulation in long-term heat-acclimated rats.

  9. Frequency-dependent stability of CNT Joule heaters in ionizable media and desalination processes

    NASA Astrophysics Data System (ADS)

    Dudchenko, Alexander V.; Chen, Chuxiao; Cardenas, Alexis; Rolf, Julianne; Jassby, David

    2017-07-01

    Water shortages and brine waste management are increasing challenges for coastal and inland regions, with high-salinity brines presenting a particularly challenging problem. These high-salinity waters require the use of thermally driven treatment processes, such as membrane distillation, which suffer from high complexity and cost. Here, we demonstrate how controlling the frequency of an applied alternating current at high potentials (20 Vpp) to a porous thin-film carbon nanotube (CNT)/polymer composite Joule heating element can prevent CNT degradation in ionizable environments such as high-salinity brines. By operating at sufficiently high frequencies, these porous thin-films can be directly immersed in highly ionizable environments and used as flow-through heating elements. We demonstrate that porous CNT/polymer composites can be used as self-heating membranes to directly heat high-salinity brines at the water/vapour interface of the membrane distillation element, achieving high single-pass recoveries that approach 100%, far exceeding standard membrane distillation recovery limits.

  10. Frequency-dependent stability of CNT Joule heaters in ionizable media and desalination processes.

    PubMed

    Dudchenko, Alexander V; Chen, Chuxiao; Cardenas, Alexis; Rolf, Julianne; Jassby, David

    2017-07-01

    Water shortages and brine waste management are increasing challenges for coastal and inland regions, with high-salinity brines presenting a particularly challenging problem. These high-salinity waters require the use of thermally driven treatment processes, such as membrane distillation, which suffer from high complexity and cost. Here, we demonstrate how controlling the frequency of an applied alternating current at high potentials (20 Vpp) to a porous thin-film carbon nanotube (CNT)/polymer composite Joule heating element can prevent CNT degradation in ionizable environments such as high-salinity brines. By operating at sufficiently high frequencies, these porous thin-films can be directly immersed in highly ionizable environments and used as flow-through heating elements. We demonstrate that porous CNT/polymer composites can be used as self-heating membranes to directly heat high-salinity brines at the water/vapour interface of the membrane distillation element, achieving high single-pass recoveries that approach 100%, far exceeding standard membrane distillation recovery limits.

  11. The long-term corrosion performance of Alloy 22 in heated brine solutions

    DOE PAGES

    Enos, D. G.; Bryan, C. R.

    2015-02-13

    Long-term corrosion experiments have been performed on Alloy 22 (UNS N06022), in a series of heated brines formulated to represent evaporatively concentrated ground water, to evaluate the long-term corrosion performance of the material. These solutions included 0.5 M NaCl, in addition to two simulated concentrated ground water solutions. Under conditions where Alloy 22 was anticipated to be passive, the corrosion rate was found to be vanishingly small (i.e., below the resolution of the weight-loss technique used to quantify corrosion in this study). However, under low pH conditions where Alloy 22 was anticipated to be active, or more specifically, where themore » chromium oxide passive film was not thermodynamically stable, the corrosion rate was appreciable. Furthermore, under such conditions the corrosion rate was observed to be a strong function of temperature, with an activation energy of 72.9±1.8 kJ/mol. Time of Flight-Secondary Ion Mass Spectroscopy analysis of the oxide layer revealed that, while sulfur was present within the oxide for all test conditions, no accumulation was observed at or near the metal/oxide interface. Furthermore, these observations confirm that inhibition of passive film formation via sulfur accumulation does not occur during the corrosion of Alloy 22.« less

  12. The long-term corrosion performance of Alloy 22 in heated brine solutions

    SciTech Connect

    Enos, D. G.; Bryan, C. R.

    2015-02-13

    Long-term corrosion experiments have been performed on Alloy 22 (UNS N06022), in a series of heated brines formulated to represent evaporatively concentrated ground water, to evaluate the long-term corrosion performance of the material. These solutions included 0.5 M NaCl, in addition to two simulated concentrated ground water solutions. Under conditions where Alloy 22 was anticipated to be passive, the corrosion rate was found to be vanishingly small (i.e., below the resolution of the weight-loss technique used to quantify corrosion in this study). However, under low pH conditions where Alloy 22 was anticipated to be active, or more specifically, where the chromium oxide passive film was not thermodynamically stable, the corrosion rate was appreciable. Furthermore, under such conditions the corrosion rate was observed to be a strong function of temperature, with an activation energy of 72.9±1.8 kJ/mol. Time of Flight-Secondary Ion Mass Spectroscopy analysis of the oxide layer revealed that, while sulfur was present within the oxide for all test conditions, no accumulation was observed at or near the metal/oxide interface. Furthermore, these observations confirm that inhibition of passive film formation via sulfur accumulation does not occur during the corrosion of Alloy 22.

  13. Long Term Thermal Stability In Air Of Ionic Liquid Based Alternative Heat Transfer Fluids For Clean Energy Production

    SciTech Connect

    Fox, Elise B; Kendrick, Sarah E.; Visser, Ann E.; Bridges, Nicholas J.

    2012-10-15

    The purpose of this study was to investigate the effect of long-term aging on the thermal stability and chemical structure of seven different ILs so as to explore their suitability for use as a heat transfer fluid. This was accomplished by heating the ILs for 15 weeks at 200°C in an oxidizing environment and performing subsequent analyses on the aged chemicals.

  14. Wear, creep, and frictional heating of femoral implant articulating surfaces and the effect on long-term performance--Part II, Friction, heating, and torque.

    PubMed

    Davidson, J A; Schwartz, G; Lynch, G; Gir, S

    1988-04-01

    In Part I, (J.A. Davidson and G. Schwartz, "Wear, creep, and frictional heating of femoral implant articulating surfaces and the effect on long-term performance--Part I, A review," J. Biomed. Mater. Res., 21, 000-000 (1987) it was shown that lubrication of the artificial hip joint was complex and that long-term performance is governed by the combined wear, creep, and to a lesser extent, oxidation degradation of the articulating materials. Importantly, it was shown that a tendency for heating exists during articulation in the hip joint and that elevated temperatures can increase the wear, creep, and oxidation degradation rate of UHMWPE. The present study was performed to examine closely the propensity to generate heat during articulation in a hip joint simulator. The systems investigated were polished Co-Cr-Mo alloy articulating against UHMWPE, polished alumina ceramic against UHMWPE, and polished alumina against itself. Frictional torque was also evaluated for each system at various levels of applied loads. A walking load history was used in both the frictional heating and torque tests. The majority of tests were performed with 5 mL of water lubricant. However, the effect of various concentrations of hyaluronic acid was also evaluated. Results showed frictional heating to occur in all three systems, reaching an equilibrium after roughly 30 min articulation time. Ceramic systems showed reduced levels of heating compared to the cobalt alloy-UHMWPE system. The level of frictional torque for each system ranked similar to their respective tendencies to generate heat. Hyaluronic acid had little effect, while dry conditions and the presence of small quantities of bone cement powder in water lubricant significantly increased frictional torque.

  15. Short term effect of air pollution, noise and heat waves on preterm births in Madrid (Spain).

    PubMed

    Arroyo, Virginia; Díaz, Julio; Ortiz, Cristina; Carmona, Rocío; Sáez, Marc; Linares, Cristina

    2016-02-01

    these, heat temperatures at Lag 1 (RR: 1.055; 95% CI:( (1.018 1.092)) on preterm births in Madrid City during the studied period. In the model adjusted for preterm births, similar RR was obtained for the same environmental variables. Especially PM2.5, diurnal noise levels and O3 have a short-term impact on total births and heat temperatures on preterm births in Madrid City during the studied period. Our results suggest that, given the widespread exposure of the population to the environmental factors analyzed and the possible effects on long-term health associated to low birth weight. There is a clear need to minimize this exposure through the decrease of air pollution and noise levels and through the behavior modification of the mothers. Copyright © 2015 Elsevier Inc. All rights reserved.

  16. Effect of long-term administration of zinc after scrotal heating on mice spermatozoa and subsequent offspring quality.

    PubMed

    Ghasemi, N; Babaei, H; Azizallahi, S; Kheradmand, A

    2009-08-01

    This study was set to investigate whether the adverse effects of heat on spermatozoa and subsequent foetuses could be prevented by long-term zinc administration. The scrotums of animals were immersed in water at either 43 degrees C (heat group) or 23 degrees C (control group). Half of the heat and control mice were given 10 mg kg(-1) zinc every other day for 60 days and the others received sterile saline instead of zinc. Heat stress significantly reduced sperm motility, concentration, hypoosmotic swelling-water test (HOS-WT) positive and chromomycin A(3) (CMA(3)) negative spermatozoa at the first 15 days, and the greatest decrease occurred at 30 days (P < 0.05). Sperm motility, concentration and HOS-WT positive spermatozoa were also reduced initially in the zinc administered group, but we did not observe any further decrease in the above mentioned parameters on day 30 (P < 0.05). The weight of foetuses obtained from the females mated with paternal heat treatment males was significantly lower than that of the control group (P < 0.05) and long-term zinc therapy caused a partial recovery (P > 0.05). This study demonstrates that the adverse effects of hyperthermia on semen parameters may be prevented by zinc therapy. Likewise, long-term administration of zinc could improve quality of litter obtained from the females mated with scrotal heat treatment males.

  17. Microstructure Changing of P91 Heat Resistant Steel during Short-Term Creep at 873K

    NASA Astrophysics Data System (ADS)

    Jiaqiang, Gao; Qijiang, Wang; Yedong, Zhou

    The working temperature of main steam pipe in (ultra-)supercritical power generating units is 873K, and creep behavior of P91 was tested under this temperature with the stress of 140MPa for 5534h, and the minimum creep rate was 0.2μm/h. Then creep test for short period were conducted for 100h and 1800h, and samples considered as primary creep stage and steady-state creep stage respectively. These samples as well as initial state and creep ruptured samples were observed by transmission electronic microscope(TEM) mainly under scanning mode(STEM). The precipitates in P91 heat resistant steel at different states were studied in detail with two methods: carbon extraction replica and twin-jet thin foil. It was shown that microstructure of P91 heat resistant steel after creep was degraded, especially for accelerated stage. That means the density of dislocation decrease, and the width of martensitic lath as well as the size of sub-grain were coarsen. It can be seen that the mean size of precipitates was coarsen slightly too. There were Laves phases in sample of steady-state creep stage with the size of 150nm. While it was coarse easily to large size more than 500nm in creep-ruptured samples. It would exert strengthening effect by precipitating along lath boundaries and sub-grain boundaries in early stage of creep. But Laves phases were prone to coarsen, which would weaken their strengthening effect and become detrimental to long term creep.

  18. Long-term evolution of tidal heating and surface temperature on extrasolar planets

    NASA Astrophysics Data System (ADS)

    Kanova, Michaela; Behounkova, Marie

    2015-04-01

    Increasing number of detected extrasolar planets provides a unique statistical set that may help us to improve our knowledge about planetary evolution. Indirect detection methods employed in search for exoplanets are most sensitive to objects orbiting close to their host star and this criterion gets particularly important in the case of low-mass terrestrial planets. Here, we focus on long-term orbital and thermal evolution of a single planet subjected to stellar tides. Our approach combines evaluation of surface temperature as well as numerical computation of tidal effects on planetary orbit and internal heating. By calculating the tidal evolution of the orbit [1], we analyze the effect of initial orbital parameters (eccentricity, semi-major axis and rotational frequency) on secular changes in surface temperature and tidal dissipation. The maximum surface temperature and temperature gradient is computed during the process and it evolves together with the semi-major axis, the eccentricity and the ratio of spin and orbital frequency. Significant increase in the surface temperature is observed when the planet encounters a spin-orbit resonance. We solve the heat diffusion equation numerically for both 1D and 3D geometry in a thin spherical shell corresponding to a subsurface layer (see e.g. [2]), where the upper boundary condition is given by energy equilibrium and is strongly non-linear in temperature due to Stefan-Boltzmann law. Additionally, we solve the viscoelastic response to the tidal loading during orbital evolution. Following the method of [3,4], the tidal heating is evaluated for Maxwell or Andrade rheology in the time domain. We study disturbing potential caused by the body's deformation, the time dependence of phase lag and time lag during one orbit and compare our results with traditionally used constant tidal lag models (e.g. [1,5]). The effect of a 3D internal structure on the disturbing potential is investigated as well. This study is our first step

  19. Nonlinear feedback in a six-dimensional Lorenz model: impact of an additional heating term

    NASA Astrophysics Data System (ADS)

    Shen, B.-W.

    2015-12-01

    In this study, a six-dimensional Lorenz model (6DLM) is derived, based on a recent study using a five-dimensional (5-D) Lorenz model (LM), in order to examine the impact of an additional mode and its accompanying heating term on solution stability. The new mode added to improve the representation of the streamfunction is referred to as a secondary streamfunction mode, while the two additional modes, which appear in both the 6DLM and 5DLM but not in the original LM, are referred to as secondary temperature modes. Two energy conservation relationships of the 6DLM are first derived in the dissipationless limit. The impact of three additional modes on solution stability is examined by comparing numerical solutions and ensemble Lyapunov exponents of the 6DLM and 5DLM as well as the original LM. For the onset of chaos, the critical value of the normalized Rayleigh number (rc) is determined to be 41.1. The critical value is larger than that in the 3DLM (rc ~ 24.74), but slightly smaller than the one in the 5DLM (rc ~ 42.9). A stability analysis and numerical experiments obtained using generalized LMs, with or without simplifications, suggest the following: (1) negative nonlinear feedback in association with the secondary temperature modes, as first identified using the 5DLM, plays a dominant role in providing feedback for improving the solution's stability of the 6DLM, (2) the additional heating term in association with the secondary streamfunction mode may destabilize the solution, and (3) overall feedback due to the secondary streamfunction mode is much smaller than the feedback due to the secondary temperature modes; therefore, the critical Rayleigh number of the 6DLM is comparable to that of the 5DLM. The 5DLM and 6DLM collectively suggest different roles for small-scale processes (i.e., stabilization vs. destabilization), consistent with the following statement by Lorenz (1972): "If the flap of a butterfly's wings can be instrumental in generating a tornado, it can

  20. On the possible cycles via the unified perspective of cryocoolers. Part A: The Joule-Thomson cryocooler

    SciTech Connect

    Maytal, Ben-Zion; Pfotenhauer, John M.

    2014-01-29

    Joule-Thomson (JT) cryocoolers possess a self adjusting effect, which preserves the state of the returning stream from the evaporator as a saturated vapor. The heat load can be entirely absorbed at constant temperature by evaporation even for different sized heat exchangers. It is not possible for the steady state flow resulting from a gradual cool down to penetrate 'deeper' into the two-phase dome, and produce a two phase return flow even with a heat exchanger of unlimited size. Such behavior was implicitly taken for granted in the literature but never clearly stated nor questioned and therefore never systematically proven. The discussion provided below provides such a proof via the unified model of cryocoolers. This model portrays all cryocoolers as magnifiers of their respective elementary temperature reducing mechanism through the process of 'interchanging'.

  1. Hydrogen evolution in nickel-water heat pipes.

    NASA Technical Reports Server (NTRS)

    Anderson, W. T.

    1973-01-01

    A study was made of the evolution of hydrogen gas in nickel-water heat pipes for the purpose of investigating methods of accelerated life testing. The data were analyzed in terms of a phenomenological corrosion model of heat pipe degradation which incorporates corrosion and oxidation theory and contains parameters which can be determined by experiment. The gas was evolved with a linear time dependence and an exponential temperature dependence with an activation energy of 1.03 x 10 to the minus 19th joules. A flow-rate dependence of the gas evolution was found in the form of a threshold. The results were used to predict usable lifetimes of heat pipes operated at normal operating conditions from results taken under accelerated operating conditions.

  2. AMNIOTIC FLUID HEAT SHOCK PROTEIN 70 CONCENTRATION IN HISTOLOGIC CHORIOAMNIONITIS, TERM AND PRETERM PARTURITION

    PubMed Central

    Chaiworapongsa, Tinnakorn; Erez, Offer; Kusanovic, Juan Pedro; Vaisbuch, Edi; Mazaki-Tovi, Shali; Gotsch, Francesca; Than, Nandor Gabor; Mittal, Pooja; Kim, Yeon Mee; Camacho, Natalia; Edwin, Samuel; Gomez, Ricardo; Hassan, Sonia S.; Romero, Roberto

    2008-01-01

    Objective Heat shock protein (HSP) 70, a conserved member of the stress protein family, is produced in almost all cell types in response to a wide range of stressful stimuli and their production has a survival value. Evidence suggests that extra-cellular HSP70 is involved in the activation of the innate and adaptive immune response. Furthermore, increased mRNA expression of HSP 70 was observed in human fetal membranes following endotoxin stimulation. This study was conducted to determine the changes in amniotic fluid HSP70 concentrations during pregnancy, term and preterm parturition, intra-amniotic infection (IAI), and histologic chorioamnionitis. Study design A cross-sectional study was conducted in 376 pregnant women in the following groups: 1) women with a normal pregnancy that were classified in the following categories: a) women in the mid-trimester (14–18 weeks) who underwent amniocentesis for genetic indications and delivered normal infants at term (n=72); b) women at term not in labor (n=23); and c) those at term in labor (n=48); 2) women with spontaneous preterm labor and intact membranes that were subdivided into the following categories: a) preterm labor who delivered at term without IAI (n=42), b) preterm labor who delivered preterm without IAI (n=57), and c) preterm labor and delivery with IAI (n=30); and 3) women with preterm prelabor rupture of membranes (PROM) with (n=50) and without (n=54) IAI. Among patients with preterm labor with intact membranes and preterm PROM who delivered within 72 hours of amniocentesis, placenta, umbilical cord and chorioamniotic membranes were collected and assessed for the presence or absence of acute inflammatory lesions in the extra-placental membranes (histologic chorioamnionitis) and/or umbilical cords (funisitis). HSP70 concentrations in amniotic fluid were determined using a sensitive and specific immunoassay. Non-parametric statistics were used for analysis. A p value <0.05 was considered statistically

  3. Heat Loss in a Laser-Driven, Magnetized, X-Ray Source with Thermoelectric Terms

    NASA Astrophysics Data System (ADS)

    Giuliani, J. L.; Velikovich, A. L.; Kemp, G. E.; Colvin, J. D.; Koning, J.; Fournier, K. B.

    2016-10-01

    The efficiency of laser-driven K-shell radiation sources, i.e., pipes containing a gas or a metal foam, may be improved by using an axial magnetic field to thermally insulate the pipe wall from the hot interior. A planar, self-similar solution for the magnetic and thermal diffusion is developed to model the near wall physics that includes the thermoelectric Nernst and Ettingshausen effects. This solution extends previous work for the MagLIF concept to include the full dependence of the transport coefficients on the electron Hall parameter. The analytic solution assumes a constant pressure. This case is matched with a 1D MHD code, which is then applied to the case allowing for pressure gradients. These numerical solutions are found to evolve toward the self-similar ones. The variation of the time integrated heat loss with and without the thermoelectric terms will be examined. The present work provides a verification test for general MHD codes that use Braginskii's or Epperlein-Haines' transport model to account for thermoelectric effects. NRL supported by the DOE/NNSA. LLNL work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract No. DE-AC52-07NA27344.

  4. Physiological and production responses to feeding schedule in lactating dairy cows exposed to short-term, moderate heat stress.

    PubMed

    Ominski, K H; Kennedy, A D; Wittenberg, K M; Moshtaghi Nia, S A

    2002-04-01

    The objective of this research was to characterize the production responses of lactating dairy cows during and after short-term, moderate heat exposure, and to determine whether evening (p.m.) feeding would alleviate the associated production losses. In a two-period, cross-over design, eight mature lactating cows were fed a total mixed ration at either 0830 or 2030 h. Each 15-d period consisted of a 5-d thermoneutral phase, a 5-d heat stress phase and a 5-d thermoneutral recovery phase. Mean daily vaginal temperature and respiration rate increased by 0.6 +/- 0.04 degrees C and 27 +/- 1.3 breaths/min, respectively, during short-term heat exposure. Daily dry matter intake, milk yield and solids-not-fat were depressed by 1.4 +/- 0.13 kg, 1.7 +/- 0.32 kg and 0.07 +/- 0.023%, respectively, during heat exposure. During the recovery phase, dry matter intake remained depressed, milk protein declined by 0.05 +/- 0.020%, and daily milk yield exhibited a further decline of 1.2 +/- 0.32 kg. Time of feeding had no effect on vaginal temperature, respiration rate, dry matter intake, water intake, milk yield, fat-corrected milk, protein percent, solids-non-fat percent or somatic cell count during heat exposure or during the recovery period that followed. Fat percent was, however, significantly lower in p.m.-fed animals. These data indicate that short-term, moderate heat stress, which occurs during the spring and summer months in Canada and the Northern United States, will significantly decrease production in the lactating cow. Shifting from morning to evening feeding did not alleviate production losses associated with this type of heat stress.

  5. Mi-1-mediated nematode resistance in tomatoes is broken by short-term heat stress but recovers over time

    USDA-ARS?s Scientific Manuscript database

    In tomato (Solanum lycopersicum Mill.), the only available genomic resource of resistance to root-knot nematodes (RKN; Meloidogyne incognita, M. javanica and M. arenaria), which are considered among the most devastating crop pests worldwide, is a single dominant gene termed Mi-1. Heat stress is thou...

  6. A Positive Feedback Loop between HEAT SHOCK PROTEIN101 and HEAT STRESS-ASSOCIATED 32-KD PROTEIN Modulates Long-Term Acquired Thermotolerance Illustrating Diverse Heat Stress Responses in Rice Varieties1[W][OPEN

    PubMed Central

    Lin, Meng-yi; Chai, Kuo-hsing; Ko, Swee-suak; Kuang, Lin-yun; Lur, Huu-Sheng; Charng, Yee-yung

    2014-01-01

    Heat stress is an important factor that has a negative impact on rice (Oryza sativa) production. To alleviate this problem, it is necessary to extensively understand the genetic basis of heat tolerance and adaptability to heat stress in rice. Here, we report the molecular mechanism underlying heat acclimation memory that confers long-term acquired thermotolerance (LAT) in this monocot plant. Our results showed that a positive feedback loop formed by two heat-inducible genes, HEAT SHOCK PROTEIN101 (HSP101) and HEAT STRESS-ASSOCIATED 32-KD PROTEIN (HSA32), at the posttranscriptional level prolongs the effect of heat acclimation in rice seedlings. The interplay between HSP101 and HSA32 also affects basal thermotolerance of rice seeds. These findings are similar to those reported for the dicot plant Arabidopsis (Arabidopsis thaliana), suggesting a conserved function in plant heat stress response. Comparison between two rice cultivars, japonica Nipponbare and indica N22 showed opposite performance in basal thermotolerance and LAT assays. ‘N22’ seedlings have a higher basal thermotolerance level than cv Nipponbare and vice versa at the LAT level, indicating that these two types of thermotolerance can be decoupled. The HSP101 and HSA32 protein levels were substantially higher in cv Nipponbare than in cv N22 after a long recovery following heat acclimation treatment, at least partly explaining the difference in the LAT phenotype. Our results point out the complexity of thermotolerance diversity in rice cultivars, which may need to be taken into consideration when breeding for heat tolerance for different climate scenarios. PMID:24520156

  7. Factors controlling short-term soil microbial response after laboratory heating. Preliminary results

    NASA Astrophysics Data System (ADS)

    Jiménez-Compán, Elizabeth; Jiménez-Morillo, Nicasio; Jordán, Antonio; Bárcenas-Moreno, Gema

    2015-04-01

    Soil microbial response after fire is controlled by numerous variables which conclude with a mosaic of results depending on organic carbon alterations or pH fire-induced changes. This fact has complicated the studies focused on post-fire microbial response, compiling high variability of opposite result in the bibliography. Soil laboratory heating cannot emulate a real wildfire effect on soil but lead us the possibility to control several variables and it is a valid tool to clarify the relative weight of different factors controlling microbial response after soil heating. In this preliminary study different heated treatments were applied to unaltered forest soil samples, obtaining 4 different heating treatments to simulate a range of fire intensities: unaltered-control (UH), and soil heated at 300, 450 and 500 °C. In order to isolate possible nutrient availability or pH heating-induced changes, different culture media were prepared using soil:water extract from each heating treatments and adding different supplements to obtain the total of 11 different culture media: unheated soil without supplements (UH-N-), unheated soil with nutrient supplement (UH-N+), soil heated at 300 °C without supplements (300-N-), soil heated at 300 °C with nutrient supplement (300-N+), soil heated at 300 °C with nutrient supplement and pH-buffered (300-N+pH); soil heated at 450 °C without supplements (450-N-), soil heated at 450 °C with nutrient supplement (450-N+), soil heated at 450 °C with nutrient supplement and pH-buffered (450-N+); soil heated at 500 °C without supplements (500-N-), soil heated at 500 °C with nutrient supplement (500-N+), soil heated at 500 °C with nutrient supplement and pH-buffered (500-N+). Each media was inoculated with different dilutions of a microbial suspension from the original unaltered soil, and the abundance of viable and cultivable microorganisms were measured by plate count method. In addition, the analysis of heating-induced soil organic

  8. FY 2009 Annual Report of Joule Software Metric SC GG 3.1/2.5.2, Improve Computational Science Capabilities

    SciTech Connect

    Kothe, Douglas B; Roche, Kenneth J; Kendall, Ricky A

    2010-01-01

    The Joule Software Metric for Computational Effectiveness is established by Public Authorizations PL 95-91, Department of Energy Organization Act, and PL 103-62, Government Performance and Results Act. The U.S. Office of Management and Budget (OMB) oversees the preparation and administration of the President s budget; evaluates the effectiveness of agency programs, policies, and procedures; assesses competing funding demands across agencies; and sets the funding priorities for the federal government. The OMB has the power of audit and exercises this right annually for each federal agency. According to the Government Performance and Results Act of 1993 (GPRA), federal agencies are required to develop three planning and performance documents: 1.Strategic Plan: a broad, 3 year outlook; 2.Annual Performance Plan: a focused, 1 year outlook of annual goals and objectives that is reflected in the annual budget request (What results can the agency deliver as part of its public funding?); and 3.Performance and Accountability Report: an annual report that details the previous fiscal year performance (What results did the agency produce in return for its public funding?). OMB uses its Performance Assessment Rating Tool (PART) to perform evaluations. PART has seven worksheets for seven types of agency functions. The function of Research and Development (R&D) programs is included. R&D programs are assessed on the following criteria: Does the R&D program perform a clear role? Has the program set valid long term and annual goals? Is the program well managed? Is the program achieving the results set forth in its GPRA documents? In Fiscal Year (FY) 2003, the Department of Energy Office of Science (DOE SC-1) worked directly with OMB to come to a consensus on an appropriate set of performance measures consistent with PART requirements. The scientific performance expectations of these requirements reach the scope of work conducted at the DOE national laboratories. The Joule system

  9. Long-term variability of heat waves in Argentina and recurrence probability of the severe 2008 heat wave in Buenos Aires

    NASA Astrophysics Data System (ADS)

    Rusticucci, Matilde; Kyselý, Jan; Almeira, Gustavo; Lhotka, Ondřej

    2016-05-01

    Heat waves are one of the main concerns related to the impacts of climate change, because their frequency and severity are projected to increase in a future climate. The objectives of this work are to study the long-term variability of heat waves over Argentina and to estimate recurrence probability of the most severe 2008 heat wave in Buenos Aires. We used three definitions of heat waves that were based on (1) daily maximum temperature above the 90th percentile (MaxTHW), (2) daily minimum temperature above the 90th percentile (MinTHW) and (3) both maximum and minimum temperatures above the corresponding 90th percentiles (EHW). The minimum length of a heat wave was 3 days, and the analysis was performed over the October-March period. Decadal values in Buenos Aires experienced clear increases in heat waves according to MinTHW and EHW, with the highest frequency for both in the 2001-2010 decade, but at other stations, combinations of different trends and decadal variability resulted in some cases in a decrease of extreme heat waves. In the north-western part of the country, a strong positive change in the last decade was found, mainly due to the increment in the persistence of MinTHW but also accompanied by increases in MaxTHW. In general, other stations show a clear positive trend in MinTHW and decadal variability in MaxTHW, with the largest EHW cases in the last decade. We also estimated recurrence probability of the longest and most severe heat wave in Buenos Aires (over 1909-2010, according to intensity measured by the cumulative excess of maximum daily temperature above the 90th percentile) that occurred from 3 to 14 November 2008, by means of simulations with a stochastic first-order autoregressive model. The recurrence probability of such long and severe heat wave is small in the present climate but it is likely to increase substantially in the near future even under a moderate warming trend.

  10. Regional differences in sweat rate response of steers to short-term heat stress.

    PubMed

    Scharf, B; Wax, L E; Aiken, G E; Spiers, D E

    2008-11-01

    Six Angus steers (319 +/- 8.5 kg) were assigned to one of two groups (hot or cold exposure) of three steers each, and placed into two environmental chambers initially maintained at 16.5-18.8 degrees C air temperature (Ta). Cold chamber Ta was lowered to 8.4 degrees C, while Ta within the hot chamber was increased to 32.7 degrees C over a 24-h time period. Measurements included respiration rate, and air and body (rectal and skin) temperatures. Skin temperature was measured at shoulder and rump locations, with determination of sweat rate using a calibrated moisture sensor. Rectal temperature did not change in cold or hot chambers. However, respiration rate nearly doubled in the heat (P < 0.05), increasing when Ta was above 24 degrees C. Skin temperatures at the two locations were highly correlated (P < 0.05) with each other and with Ta. In contrast, sweat rate showed differences at rump and shoulder sites. Sweat rate of the rump exhibited only a small increase with Ta. However, sweat rate at the shoulder increased more than four-fold with increasing Ta. Increased sweat rate in this region is supported by an earlier report of a higher density of sweat glands in the shoulder compared to rump regions. Sweat rate was correlated with several thermal measurements to determine the best predictor. Fourth-order polynomial expressions of short-term rectal and skin temperature responses to hot and cold exposures produced r values of 0.60, 0.84, and 0.98, respectively. These results suggest that thermal inputs other than just rectal or skin temperature drive the sweat response in cattle.

  11. Regional differences in sweat rate response of steers to short-term heat stress

    NASA Astrophysics Data System (ADS)

    Scharf, B.; Wax, L. E.; Aiken, G. E.; Spiers, D. E.

    2008-11-01

    Six Angus steers (319 ± 8.5 kg) were assigned to one of two groups (hot or cold exposure) of three steers each, and placed into two environmental chambers initially maintained at 16.5-18.8°C air temperature ( T a). Cold chamber T a was lowered to 8.4°C, while T a within the hot chamber was increased to 32.7°C over a 24-h time period. Measurements included respiration rate, and air and body (rectal and skin) temperatures. Skin temperature was measured at shoulder and rump locations, with determination of sweat rate using a calibrated moisture sensor. Rectal temperature did not change in cold or hot chambers. However, respiration rate nearly doubled in the heat ( P < 0.05), increasing when T a was above 24°C. Skin temperatures at the two locations were highly correlated ( P < 0.05) with each other and with T a. In contrast, sweat rate showed differences at rump and shoulder sites. Sweat rate of the rump exhibited only a small increase with T a. However, sweat rate at the shoulder increased more than four-fold with increasing T a. Increased sweat rate in this region is supported by an earlier report of a higher density of sweat glands in the shoulder compared to rump regions. Sweat rate was correlated with several thermal measurements to determine the best predictor. Fourth-order polynomial expressions of short-term rectal and skin temperature responses to hot and cold exposures produced r values of 0.60, 0.84, and 0.98, respectively. These results suggest that thermal inputs other than just rectal or skin temperature drive the sweat response in cattle.

  12. Analysis of burns caused by long-term exposure to a heating pad.

    PubMed

    Diller, K R

    1991-01-01

    The potential for creating a second-degree burn by extended exposure to an electric heating pad was evaluated in a simple model. Extrapolation of empirical results from experiments in thermal burns and in hyperthermia indicated that a heating pad at the low power setting can produce a burn within a threshold time of approximately 12 to 20 hours.

  13. Subcritical convection in an internally heated layer

    NASA Astrophysics Data System (ADS)

    Xiang, Linyan; Zikanov, Oleg

    2017-06-01

    Thermal convection in a horizontal layer with uniform internal heating and stress-free constant-temperature boundaries is analyzed numerically. The work is motivated by the questions arising in the development of liquid metal batteries, in which convection is induced by the Joule heating of electrolyte. It is demonstrated that three-dimensional convection cells exist at subcritical Rayleigh numbers.

  14. Expression of HSPs: an adaptive mechanism during long-term heat stress in goats ( Capra hircus)

    NASA Astrophysics Data System (ADS)

    Dangi, Satyaveer Singh; Gupta, Mahesh; Dangi, Saroj K.; Chouhan, Vikrant Singh; Maurya, V. P.; Kumar, Puneet; Singh, Gyanendra; Sarkar, Mihir

    2015-08-01

    Menacing global rise in surface temperature compelled more focus of research over understanding heat stress response mechanism of animals and mitigation of heat stress. Twenty-four goats divided into four groups ( n = 6) such as NHS (non-heat-stressed), HS (heat-stressed), HS + VC (heat-stressed administered with vitamin C), and HS + VE + Se (heat-stressed administered with vitamin E and selenium). Except NHS group, other groups were exposed to repeated heat stress (42 °C) for 6 h on 16 consecutive days. Blood samples were collected at the end of heat exposure on days 1, 6, 11, and 16. When groups compared between days, expression of all heat shock proteins (HSPs) showed a similar pattern as first peak on day 1, reached to basal level on the sixth day, and followed by second peak on day 16. The relative messenger RNA (mRNA) and protein expression of HSP 60, HSP70, and HSP90 was observed highest ( P < 0.05) in HS group, followed by antioxidant-administered group on days 1 and 16, which signifies that antioxidants have dampening effect on HSP expression. HSP105/110 expression was highest ( P < 0.05) on day 16. We conclude that HSP expression pattern is at least two-peak phenomenon, i.e., primary window of HSP protection on the first day followed by second window of protection on day 16. HSP60, HSP70, and HSP90 play an important role during the initial phase of heat stress acclimation whereas HSP105/110 joins this cascade at later phase. Antioxidants may possibly attenuate the HSP expression by reducing the oxidative stress.

  15. Expression of HSPs: an adaptive mechanism during long-term heat stress in goats (Capra hircus).

    PubMed

    Dangi, Satyaveer Singh; Gupta, Mahesh; Dangi, Saroj K; Chouhan, Vikrant Singh; Maurya, V P; Kumar, Puneet; Singh, Gyanendra; Sarkar, Mihir

    2015-08-01

    Menacing global rise in surface temperature compelled more focus of research over understanding heat stress response mechanism of animals and mitigation of heat stress. Twenty-four goats divided into four groups (n = 6) such as NHS (non-heat-stressed), HS (heat-stressed), HS + VC (heat-stressed administered with vitamin C), and HS + VE + Se (heat-stressed administered with vitamin E and selenium). Except NHS group, other groups were exposed to repeated heat stress (42 °C) for 6 h on 16 consecutive days. Blood samples were collected at the end of heat exposure on days 1, 6, 11, and 16. When groups compared between days, expression of all heat shock proteins (HSPs) showed a similar pattern as first peak on day 1, reached to basal level on the sixth day, and followed by second peak on day 16. The relative messenger RNA (mRNA) and protein expression of HSP 60, HSP70, and HSP90 was observed highest (P < 0.05) in HS group, followed by antioxidant-administered group on days 1 and 16, which signifies that antioxidants have dampening effect on HSP expression. HSP105/110 expression was highest (P < 0.05) on day 16. We conclude that HSP expression pattern is at least two-peak phenomenon, i.e., primary window of HSP protection on the first day followed by second window of protection on day 16. HSP60, HSP70, and HSP90 play an important role during the initial phase of heat stress acclimation whereas HSP105/110 joins this cascade at later phase. Antioxidants may possibly attenuate the HSP expression by reducing the oxidative stress.

  16. Mi-1-Mediated Nematode Resistance in Tomatoes is Broken by Short-Term Heat Stress but Recovers Over Time

    PubMed Central

    Marques de Carvalho, Luciana; Benda, Nicole D.; Vaughan, Martha M.; Cabrera, Ana R.; Hung, Kaddie; Cox, Thomas; Abdo, Zaid; Allen, L. Hartwell; Teal, Peter E. A.

    2015-01-01

    Tomato (Solanum lycopersicum L.) is among the most valuable agricultural products, but Meloidogyne spp. (root-knot nematode) infestations result in serious crop losses. In tomato, resistance to root-knot nematodes is controlled by the gene Mi-1, but heat stress interferes with Mi-1-associated resistance. Inconsistent results in published field and greenhouse experiments led us to test the effect of short-term midday heat stress on tomato susceptibility to Meloidogyne incognita race 1. Under controlled day/night temperatures of 25°C/21°C, ‘Amelia’, which was verified as possessing the Mi-1 gene, was deemed resistant (4.1 ± 0.4 galls/plant) and Rutgers, which does not possess the Mi-1 gene, was susceptible (132 ± 9.9 galls/plant) to M. incognita infection. Exposure to a single 3 hr heat spike of 35°C was sufficient to increase the susceptibility of ‘Amelia’ but did not affect Rutgers. Despite this change in resistance, Mi-1 gene expression was not affected by heat treatment, or nematode infection. The heat-induced breakdown of Mi-1 resistance in ‘Amelia’ did recover with time regardless of additional heat exposures and M. incognita infection. These findings would aid in the development of management strategies to protect the tomato crop at times of heightened M. incognita susceptibility. PMID:26170475

  17. Mathematical model of induction heating

    NASA Astrophysics Data System (ADS)

    Rak, Josef

    2017-07-01

    One of mathematical models of induction heating can be described by a parabolic differential equation with the specific Joule looses in the body. Advantage of this method is that the detailed knowledge of the 3D-magnetic field is not necessary and move of the body or the inductor can be easily implemented. The specific Joule looses can computed by solving the Fredholm integral equation of the second kind for the eddy current of density by the Nyström method with the singularity subtraction.

  18. Lunar heat-flow experiment: Long term temperature observations on the lunar surface at Apollo sites 15 and 17

    NASA Technical Reports Server (NTRS)

    Peters, K.

    1975-01-01

    Several investigators of the Apollo lunar experiments have observed gradual increases in the mean temperatures recorded by various surface thermometers. Similar effects were noticed in the temperatures of the thermometers of the Apollo 15 and 17 Heat Flow Experiments. An analysis of the long term temperature histories of the heat flow experiment thermometers is presented. These data show that no change in mean surface temperature at the Apollo 15 and 17 sites has occurred, and suggest that the slow increase in mean temperatures of thermometers in the electronics housing are due to changes in radiative properties of the housing's surfaces.

  19. The effects of single versus twice daily short term heat acclimation on heat strain and 3000m running performance in hot, humid conditions.

    PubMed

    Willmott, A G B; Gibson, O R; Hayes, M; Maxwell, N S

    2016-02-01

    Endurance performances are impaired under conditions of elevated heat stress. Short term heat acclimation (STHA) over 4-6 days can evoke rapid adaptation, which mitigate decrements in performance and alleviate heat strain. This study investigated the efficacy of twice daily heat acclimation (TDHA) compared to single session per day heat acclimation (SDHA) and normothermic training, at inducing heat acclimation phenotype and its impact upon running performance in hot, humid conditions. Twenty one, moderately trained males were matched and assigned to three groups; SDHA (mean±SD) (peak oxygen consumption [V̇O2peak] 45.8±6.1mLkg(-1)min(-1), body mass 81.3±16.0kg, stature 182±3cm), TDHA (46.1±7.0mLkg(-1)min(-1), 80.1±11.9kg, 178±4cm) or control (CON) (47.1±3.5mLkg(-1)min(-1), 78.6±16.7kg, 178±4cm). Interventions consisted of 45min cycling at 50% V̇O2peak, once daily for 4d (SDHA) and twice daily for 2d (TDHA), in 35°C, 60% relative humidity (RH), and once daily for 4 days (CON) in 21°C, 40% RH. Participants completed a pre- and post-intervention 5km treadmill run trial in 30°C, 60% RH, where the first 2km were fixed at 40% V̇O2peak and the final 3km was self-paced. No statistically significant interaction effects occurred within- or between-groups over the 2-4 days intervention. While within-group differences were found in physiological and perceptual measures during the fixed intensity trial post-intervention, they did not statistically differ between-groups. Similarly, TDHA (-36±34s [+3.5%]) and SDHA (-26±28s [+2.8%]) groups improved 3km performances (p=0.35), but did not differ from CON (-6±44s [+0.6%]). This is the first study to investigate the effects of HA twice daily and compare it with traditional single session per day STHA. These STHA protocols may have the ability to induce partial adaptive responses to heat stress and possibly enhance performance in environmentally challenging conditions, however, future development is warranted to

  20. JouleLabs Cooperative Research and Development Agreement: Cooperative Research and Development Final Report, CRADA Number CRD-08-00301

    SciTech Connect

    Bilello, D.

    2010-08-01

    The National Renewable Energy Laboratory (NREL) and Joule Labs Inc. (Joule Labs) will collaborate on creating a software platform for the development and distribution of renewable energy and energy efficiency analysis tools.

  1. Ice Accretion on Wires and Anti-Icing Induced by Joule Effect.

    NASA Astrophysics Data System (ADS)

    Personne, P.; Gayet, J.-F.

    1988-02-01

    This study concerns both the formation of ice accreted around wires due to rotation from gravitational and aerodynamic forces, and the anti-icing induced by the Joule effect. The experiments have been carried out in an instrumented wind tunnel operating in natural conditions. The results show that the growth rate increases with the ice deposit thickness. Because of low airspeed and small cloud droplets, the total collection efficiency is less than 0.2. The discrepancies between the observed collection efficiencies and those predicted by Langmuir and Biodgett's theory increase with time and consequently with the ice thickness. This may be due to the complex shape of the deposit which is noncircular and presents a rough surface. These results point out the difficulties in modeling the detail of such ice profiles in this range of conditions. The air temperature plays a significant role in the rotation angle of the wire and in the ice growth rates. The surface temperature of wires is measured in order to validate the heat balance of the heated wires; this gives a proposed estimation of the current to prevent the wire from icing.

  2. Escherichia coli Heat Shock Protein DnaK: Production and Consequences in Terms of Monitoring Cooking

    PubMed Central

    Seyer, Karine; Lessard, Martin; Piette, Gabriel; Lacroix, Monique; Saucier, Linda

    2003-01-01

    Through use of commercially available DnaK proteins and anti-DnaK monoclonal antibodies, a competitive enzyme-linked immunosorbent assay was developed to quantify this heat shock protein in Escherichia coli ATCC 25922 subjected to various heating regimens. For a given process lethality (F7010 of 1, 3, and 5 min), the intracellular concentration of DnaK in E. coli varied with the heating temperature (50 or 55°C). In fact, the highest DnaK concentrations were found after treatments at the lower temperature (50°C) applied for a longer time. Residual DnaK after heating was found to be necessary for cell recovery, and additional DnaK was produced during the recovery process. Overall, higher intracellular concentrations of DnaK tended to enhance cell resistance to a subsequent lethal stress. Indeed, E. coli cells that had undergone a sublethal heat shock (105 min at 55°C, F7010 = 3 min) accompanied by a 12-h recovery (containing 76,786 ± 25,230 molecules/cell) resisted better than exponentially growing cells (38,500 ± 6,056 molecules/cell) when later heated to 60°C for 50 min (F7010 = 5 min). Results reported here suggest that using stress protein to determine cell adaptation and survival, rather than cell counts alone, may lead to more efficient heat treatment. PMID:12788720

  3. Self-heating induced instability of oxide thin film transistors under dynamic stress

    NASA Astrophysics Data System (ADS)

    Kise, Kahori; Fujii, Mami N.; Urakawa, Satoshi; Yamazaki, Haruka; Kawashima, Emi; Tomai, Shigekazu; Yano, Koki; Wang, Dapeng; Furuta, Mamoru; Ishikawa, Yasuaki; Uraoka, Yukiharu

    2016-01-01

    Degradation caused by Joule heating of transparent amorphous oxide semiconductor thin-film transistors (TFTs) is an important issue for display technology. Deep understanding of the mechanism of self-heating degradation generated by driving pulse voltage will pave the way for the development of highly reliable flexible displays. In this work, by using a pseudo interval measurement method, we examined the relationship of the highest and the lowest heating temperature in pulse 1 cycle and frequency. These self-heating converged to a constant temperature under pulse voltage applied at 1 kHz. Moreover, the long-term reliability under positive-bias stress voltage at 1 kHz of low converged temperature condition was improved relative to that of the stress voltage at 10 Hz of dynamic temperature change condition. We discussed the degradation mechanism of oxide TFTs generated by pulse voltage, and clarified that the degradation was accelerated by thermionic emission which occurred at low frequency.

  4. Effect of short- and long-term heat stress on the conception risk of dairy cows under natural service and artificial insemination breeding programs.

    PubMed

    Schüller, L-K; Burfeind, O; Heuwieser, W

    2016-04-01

    The objectives of this retrospective study were to examine the effect of heat stress on natural service and artificial insemination (AI) breeding methods. We investigated the influence of short- and long-term heat stress on the conception risk (CR) of dairy cows bred by natural service or by AI with frozen-thawed or fresh semen. In addition, the relationship between breeding method and parity was determined. Cows bred by AI with frozen-thawed semen exposed to long-term heat stress (mean temperature-humidity index ≥73 in the period 21d before breeding) were 63% less likely to get pregnant compared with cows not exposed to heat stress. Cows bred by AI with fresh semen were 80% less likely to get pregnant during periods of short-term heat stress than during periods without heat stress. Furthermore, multiparous cows bred by AI with frozen-thawed or fresh semen were 22 and 67% less likely to get pregnant, respectively, than primiparous cows. No influence of heat stress or parity was noted on the CR of cows bred by natural service. The present study indicates that the likelihood of dairy cows becoming pregnant is reduced by short- and long-term heat stress depending on the type of semen employed. In particular, CR of cows inseminated with fresh semen is negatively affected by short-term heat stress and CR of cows inseminated with frozen-thawed semen is negatively affected by long-term heat stress.

  5. Development of heat sink concept for near-term fusion power plant divertor

    NASA Astrophysics Data System (ADS)

    Rimza, Sandeep; Khirwadkar, Samir; Velusamy, Karupanna

    2017-04-01

    Development of an efficient divertor concept is an important task to meet in the scenario of the future fusion power plant. The divertor, which is a vital part of the reactor has to discharge the considerable fraction of the total fusion thermal power (∼15%). Therefore, it has to survive very high thermal fluxes (∼10 MW/m2). In the present paper, an efficient divertor heat exchanger cooled by helium is proposed for the fusion tokamak. The Plasma facing surface of divertor made-up of several modules to overcome the stresses caused by high heat flux. The thermal hydraulic performance of one such module is numerically investigated in the present work. The result shows that the proposed design is capable of handling target heat flux values of 10 MW/m2. The computational model has been validated against high-heat flux experiments and a satisfactory agreement is noticed between the present simulation and the reported results.

  6. Effects of Short-Term Thermal Alteration on Organic Matter in Experimentally-Heated Tagish Lake Observed by Raman Spectroscopy

    NASA Technical Reports Server (NTRS)

    Chan, Q. H. S.; Nakato, A.; Zolensky, M. E.; Nakamura, T.; Kebukawa, Y.

    2007-01-01

    Carbonaceous chondrites exhibit a wide range of aqueous and thermal alteration characteristics. Examples of the thermally metamorphosed carbonaceous chondrites (TMCCs) include the C2-ung/CM2TIVs Belgica (B)-7904 and Yamato (Y) 86720. The alteration extent is the most complete in these meteorites and thus they are considered typical end-members of TMCCs exhibiting complete dehydration of matrix phyllosilicates [1, 2]. The estimated heating conditions are 10 to 10(sup 3) days at 700 C to 1 to 100 hours at 890 C, i.e. short-term heating induced by impact and/or solar radiation [3]. The chemical and bulk oxygen isotopic compositions of the matrix of the carbonate (CO3)-poor lithology of the Tagish Lake (hereafter Tag) meteorite bears similarities to these TMCCs [4]. We investigated the experimentally-heated Tag with the use of Raman spectroscopy to understand how short-term heating affects the maturity of insoluble organic matter (IOM) in aqueously altered meteorites.

  7. An integrated environmental perfusion chamber and heating system for long-term, high resolution imaging of living cells.

    PubMed

    Hing, W A; Poole, C A; Jensen, C G; Watson, M

    2000-08-01

    This communication presents the design and application of an integrated environmental perfusion chamber and stage heating blanket suitable for time-lapse video microscopy of living cells. The system consists of two independently regulated components: a perfusion chamber suitable for the maintenance of cell viability and the variable delivery of environmental factors, and a separate heating blanket to control the temperature of the microscope stage and limit thermal conduction from the perfusion chamber. Two contrasting experiments are presented to demonstrate the versatility of the system. One long-term sequence illustrates the behaviour of cells exposed to ceramic fibres. The other shows the shrinking response of cultured articular cartilage chondrons under dynamic hyper-osmotic conditions designed to simulate joint loading. The chamber is simple in design, economical to produce and permits long-term examination of dynamic cellular behaviour while satisfying the fundamental requirements for the maintenance of environmental factors that influence cell viability.

  8. Mild heat treatments induce long-term changes in metabolites associated with energy metabolism in Drosophila melanogaster.

    PubMed

    Sarup, Pernille; Petersen, Simon Metz Mariendal; Nielsen, Niels Chr; Loeschcke, Volker; Malmendal, Anders

    2016-11-01

    Heat-induced hormesis, the beneficial effect of mild heat-induced stress, increases the average lifespan of many organisms. Yet little is known about the mechanisms underlying this effect. We used nuclear magnetic resonance spectroscopy to investigate the long-term effects of repeated mild heat treatments on the metabolome of male Drosophila melanogaster. 10 days after the heat treatment, metabolic aging appears to be slowed down, and a treatment response with 40 % higher levels of alanine and lactate and lower levels of aspartate and glutamate were measured. All treatment effects had disappeared 16 days later. Metabolic reprogramming has been associated with the life extending effects of dietary restriction. The metabolite changes induced by the hormetic treatment suggest that the positive effects might not be limited to the repair pathways induced, but that there also is a change in energy metabolism. A possible direct link between changes in energy metabolism and heat induced increase in Hsp70 expression is discussed.

  9. Agar-Silica-Gel Heating Phantom May Be Suitable for Long-Term Quality Assurance of MRgHIFU

    NASA Astrophysics Data System (ADS)

    Partanen, Ari

    2009-04-01

    In MRgHIFU, the purpose of frequent quality assurance is to detect changes in system performance to prevent adverse effects during treatments. Due to high ultrasound intensities in MRgHIFU, it is essential to assure that the procedure is safe and efficacious and that image-based guidance of the treatment is reliable. We aimed to develop a guideline for MRgHIFU QA by acquiring MR temperature maps during ultrasonic heating of an agar-silica-gel phantom over a four month-period using three separate MRgHIFU uterine leiomyoma treatment systems. From this data, the stability of the maximum temperature elevation, the targeting accuracy, and the dimensions of the heated volume were analyzed. Additionally, we studied the sensitivity of these parameters to reveal hypothetical decrease in HIFU performance. After calibration, the mean targeting offsets of the heated volume were observed to be less than 2 mm in the three orthogonal directions. The measured maximum temperature elevation and the length and the width of the heated volume remained consistent throughout the four-month period. Furthermore, it was found that the parameters under investigation were sensitive to reveal the decreased HIFU performance. We conclude that an agar-silica -based phantom is suitable for targeting accuracy and heating properties QA of MRgHIFU system even in long-term use. Moreover, this simple QA method may be used to reveal small changes in HIFU performance assuring consistent functionality and safety of the MRgHIFU system.

  10. Long term climatology and trends of heat and cold waves over southern Bihar, India

    NASA Astrophysics Data System (ADS)

    Mahdi, S. Sheraz; Dhekale, B. S.

    2016-12-01

    The purpose of this paper is to analyse the trends and variability in extreme temperature indices. We examined climatological distribution of heat and cold waves of two important agro-climatic zones (South Bihar Alluvial Zone-IIIA and B), which is part of the middle Indo-Gangetic Basin and comprising 17 densely populated (1108 persons/km 2) districts of Bihar state. We used series of daily maximum and minimum temperature data from 1969 to 2013 of seven stations to calculate temperature indices, from which the trend, occurrence, duration and severity of heat and cold waves were estimated. Results revealed that, in a period of 45 years, zone-IIIA and B has experienced 251/182 and 337/140 average number of heat and cold events, respectively. Although the zone-IIIA on average is experiencing ≥8 heat and cold wave days per season, both these high frequency temperature extremes are decreasing at the rate 0.15 and 0.17 per year, respectively, with significance at 95% confidence level. Zone-IIIB on average is experiencing ≤5 heat and cold days per season, but heat waves have been found increasing at the rate 0.11 per year, whereas, a non-significant decreasing rate of 0.04/year was observed in cold waves. The study also inferred that heat waves of the month of May in zone-IIIA and of June in zone-IIIB are more frequent, hotter and longer than other months of hot weather period under study, whereas, the cold waves of month January are more frequent and longer, in both zones.

  11. Temperature and heat capacity of atomic clusters as estimated in terms of kinetic-energy release of atomic evaporation

    NASA Astrophysics Data System (ADS)

    Fujii, Mikiya; Takatsuka, Kazuo

    2007-11-01

    The temperature and heat capacity of isolated atomic clusters are studied in terms of an ab initio statistical theory of kinetic energy distribution by atomic evaporation. Two definitions of canonical temperature are examined and numerically compared: One is based on the most probable kinetic energy release (KER), whereas the other is determined with use of the entire distribution of the KER. The mutual relationship and their advantages are discussed.

  12. Stability improvement for coil position locking of joule balance

    NASA Astrophysics Data System (ADS)

    Bai, Yang; Liu, Yongmeng; Lu, Yunfeng; Hu, Pengcheng; Wang, Dawei; Li, Zhengkun; Tan, Jiubin; Zhang, Zhonghua

    2017-08-01

    The relative vertical position locking precision between the exciting and suspended coils is an important uncertainty for the Planck constant traceability in joule balance. In order to improve the relative vertical position locking precision, several stability experiments are conducted. The stability characteristics of the suspended and exciting coils are measured using a six-axis laser interferometer system; meanwhile, the effectiveness of the active vibration isolation table is measured using a vibration measurement sensor. The piezoelectric ceramic actuators with PID controller are used to compensate the relative vertical displacement drifts while a six-axis laser interferometer system is used to measure the positions of two coils. Experimental results show that the relative vertical position is stably locked.

  13. Ohm's Law, Fick's Law, Joule's Law, and Ground Water Flow

    SciTech Connect

    Narasimhan, T.N.

    1999-02-01

    Starting from the contributions of Ohm, Fick and Joule during the nineteenth century, an integral expression is derived for a steady-state groundwater flow system. In general, this integral statement gives expression to the fact that the steady-state groundwater system is characterized by two dependent variables, namely, flow geometry and fluid potential. As a consequence, solving the steady-state flow problem implies the finding of optimal conditions under which flow geometry and the distribution of potentials are compatible with each other, subject to the constraint of least action. With the availability of the digital computer and powerful graphics software, this perspective opens up possibilities of understanding the groundwater flow process without resorting to the traditional differential equation. Conceptual difficulties arise in extending the integral expression to a transient groundwater flow system. These difficulties suggest that the foundations of groundwater hydraulics deserve to be reexamined.

  14. One Joule per GFlop for BLAS2 Now!

    NASA Astrophysics Data System (ADS)

    Keller, Vincent; Gruber, Ralf

    2010-09-01

    Energy consumption is today one of the major topics that the HPC community tries to tackle. In this paper, the authors present a thought experiment aiming at building a node of a supercomputer based on a GPU (Nvidia GTX280). The paper concentrate on BLAS2 operations that dominate many scientific applications. They show that it is already possible today to build a node that is able to perform one GFlop while consuming only one Joule. This corresponds to an energy reduction by one to two orders of magnitude. Technical limitations imposed by computer manufacturers hinder the realisation of such ecological resources. In a second part of the paper a new FLOPS-driven governor is presented aiming at boosting the CPU performance for applications that are not main memory access bound, and showing results on an Intel mobile processor.

  15. Joule-Thomson cryogenic cooler with extremely high thermal stability

    NASA Technical Reports Server (NTRS)

    Bard, Steven; Wu, J. J.; Trimble, Curt

    1991-01-01

    An 80-K Joule-Thomson (J-T) cooling system designed for the Probe Infrared Laser Spectrometer (PIRLS) proposed for the Huygens Titan Probe of the Cassini Saturn orbiter mission is presented. The cryogenic cooling requirements of the PIRLS instrument are listed, and the cooler system design including details of a J-T cryostat, cold head, and dewar design is described along with the results of a thermal modeling effort and lab cooler performance testing. It is shown that by using active feedback temperature control of the cold head in combination with the self-regulating action of the J-T cryostat, a temperature stability of less than 0.1 mK/min is achieved by the cooler weighting 1.8 kg.

  16. Joule-Thomson cryogenic cooler with extremely high thermal stability

    NASA Technical Reports Server (NTRS)

    Bard, Steven; Wu, J. J.; Trimble, Curt

    1991-01-01

    An 80-K Joule-Thomson (J-T) cooling system designed for the Probe Infrared Laser Spectrometer (PIRLS) proposed for the Huygens Titan Probe of the Cassini Saturn orbiter mission is presented. The cryogenic cooling requirements of the PIRLS instrument are listed, and the cooler system design including details of a J-T cryostat, cold head, and dewar design is described along with the results of a thermal modeling effort and lab cooler performance testing. It is shown that by using active feedback temperature control of the cold head in combination with the self-regulating action of the J-T cryostat, a temperature stability of less than 0.1 mK/min is achieved by the cooler weighting 1.8 kg.

  17. Fluorescence imaging of heat-stress induced mitochondrial long-term depolarization in breast cancer cells.

    PubMed

    Dressler, Cathrin; Beuthan, Juergen; Mueller, Gerhard; Zabarylo, Urszula; Minet, Olaf

    2006-09-01

    Various thermotherapies are based on the induction of lethal heat in target tissues. Spatial and temporal instabilities of elevated temperatures induced in therapy targets require optimized treatment protocols and reliable temperature control methods during thermotherapies. Heat-stress induced effects on mitochondrial transmembrane potentials were analyzed in breast cancer cells, species MX1, using the potential sensor JC-1 (Molecular Probes, Invitrogen, Germany). Potential dependant labeling of heat-stressed cells was imaged and evaluated by fluorescence microscopy and compared with control cells. JC-1 stains mitochondria in cells with high mitochondrial potentials by forming orange-red fluorescent J-aggregates while in cells with depolarized or damaged mitochondria the sensor dye exists as green fluorescent monomers. In MX1 cells orange-red and green fluorescence intensities were correlated with each other after various heat-stress treatments and states of mitochondrial membrane potentials were deduced from the image data. With increasing stress temperatures the intensity of red fluorescent J-aggregates decreased while the green fluorescence intensity of JC-1 monomers increased. This heat-stress response happened in a nonlinear manner with increasing temperatures resulting in a nonlinear increase of red/green fluorescence ratios. These data indicated that mitochondria in MX1 cells were increasingly depolarized in response to increasing ambient temperatures.

  18. Integrated Heat Switch/Oxide Sorption Compressor

    NASA Technical Reports Server (NTRS)

    Bard, Steven

    1989-01-01

    Thermally-driven, nonmechanical compressor uses container filled with compressed praseodymium cerium oxide powder (PrCeOx) to provide high-pressure flow of oxygen gas for driving closed-cycle Joule-Thomson-expansion refrigeration unit. Integrated heat switch/oxide sorption compressor has no moving parts except check valves, which control flow of oxygen gas between compressor and closed-cycle Joule-Thomson refrigeration system. Oxygen expelled from sorbent at high pressure by evacuating heat-switch gap and turning on heater.

  19. An electrical-heating and self-sensing shape memory polymer composite incorporated with carbon fiber felt

    NASA Astrophysics Data System (ADS)

    Gong, Xiaobo; Liu, Liwu; Liu, Yanju; Leng, Jinsong

    2016-03-01

    Shape memory polymers (SMPs) have the ability to adjust their stiffness, lock a temporary shape, and recover the permanent shape upon imposing an appropriate stimulus. They have found their way into the field of morphing structures. The electrically Joule resistive heating of the conductive composite can be a desirable stimulus to activate the shape memory effect of SMPs without external heating equipment. Electro-induced SMP composites incorporated with carbon fiber felt (CFF) were explored in this work. The CFF is an excellent conductive filler which can easily spread throughout the composite. It has a huge advantage in terms of low cost, simple manufacturing process, and uniform and tunable temperature distribution while heating. A continuous and compact conductive network made of carbon fibers and the overlap joints among them was observed from the microscopy images, and this network contributes to the high conductive properties of the CFF/SMP composites. The CFF/SMP composites can be electrical-heated rapidly and uniformly, and its’ shape recovery effect can be actuated by the electrical resistance Joule heating of the CFF without an external heater. The CFF/SMP composite get higher modulus and higher strength than the pure SMP without losing any strain recovery property. The high dependence of temperature and strain on the electrical resistance also make the composite a good self-sensing material. In general, the CFF/SMP composite shows great prospects as a potential material for the future morphing structures.

  20. Acute effects of short-term intimal heating by laser-heated thermal balloon angioplasty in canine stenotic femoral arteries in vivo

    NASA Astrophysics Data System (ADS)

    Miyamoto, Akira; Sakurada, Masami; Arai, Tsunenori; Mizuno, Kyoichi; Sugiyabu, Yasunori; Kurita, Akira; Nakamura, Haruo; Kikuchi, Makoto; Watanabe, Tamishige; Utsumi, Atsushi; Akai, Yoshiro; Takeuchi, Kiyoshi

    1993-06-01

    Short-term intimal heating may be effective to improve luminal geometry without deep medial injury which can induce restenosis. We developed a new laser-heated thermal balloon catheter which can quickly raise and lower the balloon temperature. To investigate the acute effect of short-term thermal balloon angioplasty (STBA) for stenotic lesions, we performed STBA following balloon angioplasty (BA) in 8 canine stenotic femoral arteries. Cw Nd:YAG laser delivery (10 W, 15 s) induced the maximum temperature of 83 degree(s)C on average. Angiography and angioscopy were performed at pre-BA, post-BA and post-STBA. The angiographical mean stenotic diameter was 1.8 mm at pre-BA, 2.2 mm* at post-BA, 2.9 mm** at post-STBA (*:p < 0.05 pre-BA vs post-BA, **:p < 0.05 pre- and post-BA vs post-STBA). The angioscopic observation revealed intimal flaps and tears in 7 lesions after BA. The luminal geometry after STBA was symmetrically expanded. However, the intimal injury was still observed although the intimal flaps were partly sealed by STBA. These results suggested that the dilatation mechanism of STBA for stenotic lesions might be attributed to preventing elastic recoil rather than to sealing intimal fragments induced by BA.

  1. Analysis of fluid flow in Joule-Thomson coolers coupled with infrared detector

    NASA Astrophysics Data System (ADS)

    Du, Bingyan; Hu, Yin; Wang, Zhan; Li, Xiuqiang

    2014-11-01

    Joule-Thomson cooler have its unique advantages with respect to compact, light and low cost. Joule-Thomson coolers have been widely used in HgCdTe infrared detectors, InSb infrared detectors and InAs/GaSb superlattice infrared detectors. The performance of Joule-Thomson coolers is required to be improved with the development of higher mass and larger diameter focal plane infrared detectors. Joule-Thomson coolers use a limited supply of high pressure gas to support the cooling of infrared detectors. In order to maximize the usage time and minimize the cooling down time for a given volume of stored gas for Joule-Thomson coolers, it is important to study on fluid flow of Joule-Thomson coolers. Experiments were carried out to focus on the performance of Joule-Thomson coolers coupled with infrared detectors. The effect of ambient temperature, the state of supply gas pressure is considered. The relationship between volume rates and supply gas pressure was proved to fit some regulates while the other parameters are fixed. Moreover, the effects of ambient temperature are analyzed.

  2. Joule-Thomson Cooling Due to CO2 Injection into Natural GasReservoirs

    SciTech Connect

    Oldenburg, Curtis M.

    2006-04-21

    Depleted natural gas reservoirs are a promising target for Carbon Sequestration with Enhanced Gas Recovery (CSEGR). The focus of this study is on evaluating the importance of Joule-Thomson cooling during CO2 injection into depleted natural gas reservoirs. Joule-Thomson cooling is the adiabatic cooling that accompanies the expansion of a real gas. If Joule-Thomson cooling were extreme, injectivity and formation permeability could be altered by the freezing of residual water,formation of hydrates, and fracturing due to thermal stresses. The TOUGH2/EOS7C module for CO2-CH4-H2O mixtures is used as the simulation analysis tool. For verification of EOS7C, the classic Joule-Thomson expansion experiment is modeled for pure CO2 resulting in Joule-Thomson coefficients in agreement with standard references to within 5-7 percent. For demonstration purposes, CO2 injection at constant pressure and with a large pressure drop ({approx}50 bars) is presented in order to show that cooling by more than 20 C can occur by this effect. Two more-realistic constant-rate injection cases show that for typical systems in the Sacramento Valley, California, the Joule-Thomson cooling effect is minimal. This simulation study shows that for constant-rate injections into high-permeability reservoirs, the Joule-Thomson cooling effect is not expected to create significant problems for CSEGR.

  3. Changes in antioxidants are critical in determining cell responses to short- and long-term heat stress.

    PubMed

    Sgobba, Alessandra; Paradiso, Annalisa; Dipierro, Silvio; De Gara, Laura; de Pinto, Maria Concetta

    2015-01-01

    Heat stress can have deleterious effects on plant growth by impairing several physiological processes. Plants have several defense mechanisms that enable them to cope with high temperatures. The synthesis and accumulation of heat shock proteins (HSPs), as well as the maintenance of an opportune redox balance play key roles in conferring thermotolerance to plants. In this study changes in redox parameters, the activity and/or expression of reactive oxygen species (ROS) scavenging enzymes and the expression of two HSPs were studied in tobacco Bright Yellow-2 (TBY-2) cells subjected to moderate short-term heat stress (SHS) and long-term heat stress (LHS). The results indicate that TBY-2 cells subjected to SHS suddenly and transiently enhance antioxidant systems, thus maintaining redox homeostasis and avoiding oxidative damage. The simultaneous increase in HSPs overcomes the SHS and maintains the metabolic functionality of cells. In contrast the exposure of cells to LHS significantly reduces cell growth and increases cell death. In the first phase of LHS, cells enhance antioxidant systems to prevent the formation of an oxidizing environment. Under prolonged heat stress, the antioxidant systems, and particularly the enzymatic ones, are inactivated. As a consequence, an increase in H2 O2 , lipid peroxidation and protein oxidation occurs. This establishment of oxidative stress could be responsible for the increased cell death. The rescue of cell growth and cell viability, observed when TBY-2 cells were pretreated with galactone-γ-lactone, the last precursor of ascorbate, and glutathione before exposure to LHS, highlights the crucial role of antioxidants in the acquisition of basal thermotolerance.

  4. Mixed-refrigerant Joule-Thomson (MR JT) mini-cryocoolers

    NASA Astrophysics Data System (ADS)

    Tzabar, Nir

    2014-01-01

    This paper presents the progress in our ongoing research on Mixed-Refrigerant (MR) Joule-Thomson (JT) cryocoolers. The research begun by exploring different MRs and testing various compressors: oil-lubricated and oil-free, reciprocating and linear, custom-made and commercial. Closed-cycle JT cryocoolers benefit from the fact that the compressor might be located far from the cold-end and thus there are no moving parts, no vibrations, and no heat emission near the cold-end. As a consequence, the compressor may be located where there are no severe size limitations, its heat can be conveniently removed, and it can be easily maintained. However, in some applications there is still a demand for a small compressor to drive a JT cryocooler although it is located far from the cooled device. Recently, we have developed a miniature oil-free compressor for MR JT cryocoolers that weighs about 700 g and its volume equals about 300 cc. The cryocooler operates with a MR that contains Ne, N2, and Hydrocarbons. This MR has been widely investigated with different compressors and varying operating conditions and proved to be stable. The current research investigates the performances of MR JT mini-cryocooler operating with the MR mentioned above, driven with our miniature compressor, and a cold-finger prototype. A Dewar with heat load of about 230 mW is cooled to about 80 K at ambient temperatures between 0°C and 40°C. The experimental results obtained are stable and demonstrate the ability to control the cooling temperature by changing the rotation speed of the compressor.

  5. [Sports and extreme conditions. Cardiovascular incidence in long term exertion and extreme temperatures (heat, cold)].

    PubMed

    Melin, B; Savourey, G

    2001-06-30

    During ultra-endurance exercise, both increase in body temperature and dehydration due to sweat losses, lead to a decrease in central blood volume. The heart rate drift allows maintaining appropriate cardiac output, in order to satisfy both muscle perfusion and heat transfer requirements by increasing skin blood flow. The resulting dehydration can impair thermal regulation and increase the risks of serious accidents as heat stroke. Endurance events, lasting more than 8 hours, result in large sweat sodium chloride losses. Thus, ingestion of large amounts of water with poor salt intake can induce symptomatic hyponatremia (plasma sodium < 130 mEq/L) which is also a serious accident. Heat environment increases the thermal constraint and when the air humidity is high, evaporation of sweat is compromise. Thus, thermal stress becomes uncompensable which increases the risk of cardiovascular collapse. Cold exposure induces physiological responses to maintain internal temperature by both limiting thermal losses and increasing metabolic heat production. Cold can induce accidental hypothermia and local frost-bites; moreover, it increases the risk of arrhythmia during exercise. Some guidelines (cardiovascular fitness, water and electrolyte intakes, protective clothing) are given for each extreme condition.

  6. Short-Term, Low-Volume Training Improves Heat Acclimatization in an Operational Context

    PubMed Central

    Charlot, Keyne; Tardo-Dino, Pierre-Emmanuel; Buchet, Jean-François; Koulmann, Nathalie; Bourdon, Stéphanie; Lepetit, Benoit; Roslonski, Martin; Jousseaume, Loïc; Malgoyre, Alexandra

    2017-01-01

    Personnel who travel to areas with a hot climate (WBGT > 27°C) may suffer from the heat (physiological strain, thermal discomfort, increased probability of heat illness), making them partially or fully inoperative. Performing physical activities during heat acclimatization is known to improve this process (i.e., improve measures of acclimatization for the same duration of acclimation). However, it is unknown whether such training would be efficient in an operative context, characterized by a high volume of work-related physical activity. Thirty French soldiers (Training group, T) performed a short (5 days), progressive, moderate (from three to five 8-min running sets at 50% of the speed at VO2max for 32–56 min) aerobic training program upon arriving at their base in United Arab Emirates (~40°C and 12% RH). A control group (30 soldiers; No Training, NT) continued to perform their usual outdoor military activities (~6 h.d−1). A field heat stress test (HST; three 8-min running sets at 50% of the speed at VO2max) was performed, before and after the heat acclimatization period, to assess physiological and subjective changes. Rectal temperature, heart rate (HR), thermal discomfort at rest and at the end of exercise, rates of perceived exertion (RPE), and sweat loss and osmolality decreased following heat acclimatization in both groups. However, the decreases in the T group were larger than those in the NT group for HR at the end of exercise (−20 ± 13 vs. −13 ± 6 bpm, respectively, p = 0.044), thermal discomfort at rest (−2.6 ± 2.7 vs. −1.4 ± 2.1 cm, respectively, p = 0.013) and at the end of exercise (−2.6 ± 1.9 vs. −1.6 ± 1.7 cm, respectively, p = 0.037) and RPE (−2.3 ± 1.8 vs. −1.3 ± 1.7, respectively, p = 0.035). Thus, we showed that adding short (<60 min), daily, moderate-intensity training sessions during a professional mission in a hot and dry environment accelerated several heat-acclimatization-induced changes at rest and during

  7. The 30 MHz imaging radar observations of auroral irregularities during the JOULE campaign

    NASA Astrophysics Data System (ADS)

    Bahcivan, H.; Hysell, D. L.; Larsen, M. F.; Pfaff, R. F.

    2005-05-01

    Coherent backscatter from the auroral electrojet was observed by a 30 MHz imaging radar in Anchorage during the Joint Observations of Upper Latitude Electrodynamics (JOULE) campaign conducted from the Poker Flat Research Range in the spring of 2003. The observations were made at the same time that ionospheric electric fields and plasma number densities were measured in situ by instruments on sounding rockets. Neutral wind profiles were also measured during the campaign from triangulation of chemiluminescent trails from rocket releases. Aperture synthesis radar imaging techniques permit the sorting of the coherent backscatter into small azimuth and range bins and the determination of the scattering altitude. Individual Doppler spectra could thereby be unambiguously associated with in situ electric field measurements in the same small volume. We find that the Doppler shifts of the auroral echoes correspond to the ion acoustic speed times the cosine of the flow angle, where the former is predicted according to an empirical wave heating law. Type I echoes are only observed for very small flow angles regardless of the convection speed.

  8. Joule-Thomson cryocooler with neon and nitrogen mixture using commercial air-conditioning compressors

    NASA Astrophysics Data System (ADS)

    Lee, Jisung; Oh, Haejin; Baek, Seungwhan; Lee, Cheonkyu; Jeong, Sangkwon

    2014-01-01

    A 2-stage mixed refrigerant (MR) Joule-Thomson (JT) cryocooler was designed for cooling high temperature superconducting cable below 70 K. The low temperature cycle was to operate with neon-nitrogen mixture, and the required compression ratio was approximately 24 when the suction pressure was 100 kPa. The high compression ratio of 24, the low pressure of 100 kPa at compressor suction, and the working fluid with high heat of compression were challenging issues to existing typical compression systems. We developed an innovative compression system with commercial oil-lubricated air-conditioning compressors. They were 2-stage rotary compressors originally designed for R410Aand connected in series. The compressors were modified to accommodate effective intercooling at every stage to alleviate compressor overheating problem. Additionally, fine-grade three-stage oil filters, an adsorber, and driers were installed at the discharge line to avoid a potential clogging problem from oil mist and moisture at low temperature sections. The present compression system was specifically demonstrated with a neon-nitrogen MR JT cryocooler. The operating pressure ratio was able to meet the designed specifications, and the recorded no-load mini mum temperature was 63.5 K . Commercial air-conditioning compressors were successfully applied to the high-c ompression ratio MR JT cryocooler with adequate modification using off-the-shelf components.

  9. Clogging of Joule-Thomson Devices in Liquid Hydrogen-Lunar Lander Descent Stage Operating Regime

    NASA Astrophysics Data System (ADS)

    Jurns, J. M.

    2010-04-01

    Joule-Thomson (J-T) devices have been identified as critical components for future space exploration missions. The NASA Constellation Program lunar architecture considers LOX/LH2 propulsion for the lunar lander descent stage main engine an enabling technology, ensuring the cryogenic propellants are available at the correct conditions for engine operation. This cryogenic storage system may utilize a Thermodynamic Vent System (TVS) that includes J-T devices to maintain tank fluid pressure and temperature. Previous experimental investigations have indicated that J-T devices may become clogged when flowing LH2 while operating at a temperature range from 20.5 K to 24.4 K. It has been proposed that clogging is due to a trace amount of metastable, supercooled liquid neon in the regular LH2 supply. In time, flow blockage occurs from accretion of solid neon on the orifice. This clogging poses a realistic threat to spacecraft propulsion systems utilizing J-T devices in cryogenic pressure control systems. TVS failure due to J-T clogging would prevent removal of environmental heat from the propellant and potential loss of mission. This report describes J-T clogging tests performed with LH2. Tests were performed in the expected Lunar Lander operating regime, and several methods were evaluated to determine the optimum approach to mitigating the potential risk of J-T clogging.

  10. Do older firefighters show long-term adaptations to work in the heat?

    PubMed

    Wright, Heather E; Larose, Joanie; McLellan, Tom M; Miller, Scott; Boulay, Pierre; Kenny, Glen P

    2013-01-01

    Older experienced firefighters may show signs of heat adaptation, and thus reduced physiological strain, due to repeated occupational heat stress exposure. The aim was to examine physiological and perceptual strain, and hydration, responses to intermittent exercise in the heat in 12 older Non-Firefighter (Non-FF) and experienced Firefighter (FF) males, pair matched for age (Group mean ± SE: Non-FF = 51.7 ± 1.5, FF = 49.8 ± 1.1 years), VO(2peak) (Non-FF = 39.4 ± 2.2, FF = 40.7 ± 1.8 mL·kg(-1)·min(-1)), body surface area (Non-FF = 1.94 ± 0.04, FF = 2.03 ± 0.03 m(2)), and percent body fat (Non-FF = 24.4 ± 2.3, FF = 19.3 ± 1.8%). Rectal (Tre) and mean skin (MT(sk)) temperatures, heart rate (HR), local sweat rate (LSR), hydration indices, and ratings of thermal sensation and perceived exertion were measured during 4 ×15-min (rest 15-min) moderate-to-heavy cycling bouts (400 W heat production) in Dry and Humid heat (35°C, ∼20 and ∼60% relative humidity, respectively). No differences were observed between the Non-FF and FF for T(re), T(re) change, MT(sk), HR,% max HR, LSR, physiological strain index (PhSI), or % plasma volume change. Plasma protein concentration was reduced at baseline for the Non-FF (7.6 ± 0.1 g·100 mL(-1)) than FF (8.0 ± 0.1 g·100 mL(-1)). The Perceptual Strain Index overestimated PhSI for Non-FF and FF in both thermal conditions. At the end of exercise, the Non-FF showed a greater Tre difference between thermal conditions (0.27 ± 0.05°C) compared to the FF (0.10 ± 0.09°C). Although the Non-Firefighters and Firefighters demonstrate similar cardiovascular and hydration responses during moderate-to-heavy intensity exercise within each of the thermal conditions, the attenuated thermal effects between the two heat stress conditions in the Firefighters suggests a protective adaptation.

  11. Long-Term Acclimation to Different Thermal Regimes Affects Molecular Responses to Heat Stress in a Freshwater Clam Corbicula Fluminea

    PubMed Central

    Falfushynska, Halina I.; Phan, Tuan; Sokolova, Inna M.

    2016-01-01

    Global climate change (GCC) can negatively affect freshwater ecosystems. However, the degree to which freshwater populations can acclimate to long-term warming and the underlying molecular mechanisms are not yet fully understood. We used the cooling water discharge (CWD) area of a power plant as a model for long-term warming. Survival and molecular stress responses (expression of molecular chaperones, antioxidants, bioenergetic and protein synthesis biomarkers) to experimental warming (20–41 °C, +1.5 °C per day) were assessed in invasive clams Corbicula fluminea from two pristine populations and a CWD population. CWD clams had considerably higher (by ~8–12 °C) lethal temperature thresholds than clams from the pristine areas. High thermal tolerance of CWD clams was associated with overexpression of heat shock proteins HSP70, HSP90 and HSP60 and activation of protein synthesis at 38 °C. Heat shock response was prioritized over the oxidative stress response resulting in accumulation of oxidative lesions and ubiquitinated proteins during heat stress in CWD clams. Future studies should determine whether the increase in thermal tolerance in CWD clams are due to genetic adaptation and/or phenotypic plasticity. Overall, our findings indicate that C. fluminea has potential to survive and increase its invasive range during warming such as expected during GCC. PMID:27995990

  12. Long-Term Acclimation to Different Thermal Regimes Affects Molecular Responses to Heat Stress in a Freshwater Clam Corbicula Fluminea.

    PubMed

    Falfushynska, Halina I; Phan, Tuan; Sokolova, Inna M

    2016-12-20

    Global climate change (GCC) can negatively affect freshwater ecosystems. However, the degree to which freshwater populations can acclimate to long-term warming and the underlying molecular mechanisms are not yet fully understood. We used the cooling water discharge (CWD) area of a power plant as a model for long-term warming. Survival and molecular stress responses (expression of molecular chaperones, antioxidants, bioenergetic and protein synthesis biomarkers) to experimental warming (20-41 °C, +1.5 °C per day) were assessed in invasive clams Corbicula fluminea from two pristine populations and a CWD population. CWD clams had considerably higher (by ~8-12 °C) lethal temperature thresholds than clams from the pristine areas. High thermal tolerance of CWD clams was associated with overexpression of heat shock proteins HSP70, HSP90 and HSP60 and activation of protein synthesis at 38 °C. Heat shock response was prioritized over the oxidative stress response resulting in accumulation of oxidative lesions and ubiquitinated proteins during heat stress in CWD clams. Future studies should determine whether the increase in thermal tolerance in CWD clams are due to genetic adaptation and/or phenotypic plasticity. Overall, our findings indicate that C. fluminea has potential to survive and increase its invasive range during warming such as expected during GCC.

  13. Long-Term Acclimation to Different Thermal Regimes Affects Molecular Responses to Heat Stress in a Freshwater Clam Corbicula Fluminea

    NASA Astrophysics Data System (ADS)

    Falfushynska, Halina I.; Phan, Tuan; Sokolova, Inna M.

    2016-12-01

    Global climate change (GCC) can negatively affect freshwater ecosystems. However, the degree to which freshwater populations can acclimate to long-term warming and the underlying molecular mechanisms are not yet fully understood. We used the cooling water discharge (CWD) area of a power plant as a model for long-term warming. Survival and molecular stress responses (expression of molecular chaperones, antioxidants, bioenergetic and protein synthesis biomarkers) to experimental warming (20–41 °C, +1.5 °C per day) were assessed in invasive clams Corbicula fluminea from two pristine populations and a CWD population. CWD clams had considerably higher (by ~8–12 °C) lethal temperature thresholds than clams from the pristine areas. High thermal tolerance of CWD clams was associated with overexpression of heat shock proteins HSP70, HSP90 and HSP60 and activation of protein synthesis at 38 °C. Heat shock response was prioritized over the oxidative stress response resulting in accumulation of oxidative lesions and ubiquitinated proteins during heat stress in CWD clams. Future studies should determine whether the increase in thermal tolerance in CWD clams are due to genetic adaptation and/or phenotypic plasticity. Overall, our findings indicate that C. fluminea has potential to survive and increase its invasive range during warming such as expected during GCC.

  14. Effects of long-term thermal aging on the tensile and creep properties of commercially heat-treated alloy 718

    SciTech Connect

    Booker, M.K.

    1984-01-01

    Alloy 718 is a structure material widely used in elevated-temperature applications. In particular, it was extensively used in the design of the upper internal system and control rod drive line of the proposed Clinch River Breeder Reactor. Its popularity is due to several excellent behavioral features, including high creep and creep-rupture strength, good oxidation resistance, and exceptional high-cycle fatigue strength. However, alloy 718 is extremely complex, and its microstructure can be significantly modified by thermal treatment. The stability of the alloy in long-term elevated-temperature service is therefore a substantial concern in any such application. This report presents tensile and creep data obtained on three heats of alloy 718 after thermal aging for up to 27,000 h from 593 to 76{degree}C. Implications of these results in terms of long-term stability of the alloy are discussed. 5 refs., 13 figs., 6 tabs.

  15. Short-term exposure to heat stress attenuates appetite and intestinal integrity in growing pigs.

    PubMed

    Pearce, S C; Sanz-Fernandez, M V; Hollis, J H; Baumgard, L H; Gabler, N K

    2014-12-01

    Acute heat stress (HS) and heat stroke can be detrimental to the health, well-being, and performance of mammals such as swine. Therefore, our objective was to chronologically characterize how a growing pig perceives and initially copes with a severe heat load. Crossbred gilts (n=32; 63.8±2.9 kg) were subjected to HS conditions (37°C and 40% humidity) with ad libitum intake for 0, 2, 4, or 6 h (n=8/time point). Rectal temperature (Tr), respiration rates (RR), and feed intake were determined every 2 h. Pigs were euthanized at each time point and fresh ileum and colon samples were mounted into modified Ussing chambers to assess ex vivo intestinal integrity and function. Transepithelial electrical resistance (TER) and fluorescein isothiocyanate-labeled dextran (FD4) permeability were assessed. As expected, Tr increased linearly over time (P<0.001) with the highest temperature observed at 6 h of HS. Compared to the 0-h thermal-neutral (TN) pigs, RR increased (230%; P<0.001) in the first 2 h and remained elevated over the 6 h of HS (P<0.05). Feed intake was dramatically reduced due to HS and this corresponded with significant changes in plasma glucose, ghrelin, and glucose-dependent insulinotropic peptide (P<0.050). At as early as 2 h of HS, ileum TER linearly decreased (P<0.01), while FD4 linearly increased with time (P<0.05). Colon TER and FD4 changed due to HS in quadratic responses over time (P=0.050) similar to the ileum but were less pronounced. In response to HS, ileum and colon heat shock protein (HSP) 70 mRNA and protein abundance increased linearly over time (P<0.050). Altogether, these data indicated that a short duration of HS (2-6 h) compromised feed intake and intestinal integrity in growing pigs.

  16. On the Causes of and Long Term Changes in Eurasian Heat Waves

    NASA Technical Reports Server (NTRS)

    Schubert, Siegfried; Wang, Hailan; Koster, Randal; Suarez, Max

    2012-01-01

    The MERRA reanalysis, other observations, and the GEOS-S model have been used to diagnose the causes of Eurasian heat waves including the recent extreme events that occurred in Europe during 2003 and in Russia during 2010. The results show that such extreme events are an amplification of natural patterns of atmospheric variability (in this case a particular large-scale atmospheric planetary wave) that develop over the Eurasian continent as a result of internal atmospheric forcing. The amplification occurs when the wave occasionally becomes locked in place for several weeks to months resulting in extreme heat and drying with the location depending on the phase of the upper atmospheric wave. Model experiments suggest that forcing from both the ocean (SST) and land playa role phase-locking the waves. An ensemble of very long GEOS-S model simulations (spanning the 20th century) forced with observed SST and greenhouse gases show that the model is capable of generating very similar heat waves, and that they have become more extreme in the last thirty years as a result of the overall warming of the Asian continent.

  17. Effects of Short-Term Thermal Alteration on Organic Matter in Experimentally-Heated Tagish Lake Observed by Raman Spectroscopy

    NASA Technical Reports Server (NTRS)

    Chan, Q. H. S.; Nakato, A.; Zolensky, M. E.; Nakamura, T.; Kebukawa, Y.; Maisano, J.; Colbert, M.; Martinez, J. E.

    2017-01-01

    Carbonaceous chondrites exhibit a wide range of aqueous and thermal alteration characteristics, while some are known to demonstrate mineralogical and petrologic evidence of having been thermally metamorphosed after aqueous alteration. This group of meteorites are commonly referred as thermally met-amorphosed carbonaceous chondrites (TMCCs), and their reflectance spectra show resemblances to that of C-type asteroids which typically have low albedos. This suggests that the surfaces of the C-type asteroids are also composed of both hydrous and dehydrated minerals, and thus TMCCs are among the best samples that can be studied in laboratory to reveal the true nature of the C-type asteroids. Although TMCCs are usually meteorites that were previously categorized as CI and CM chondrites, they are not strictly CI/CM because they exhibit isotopic and petrographic characteristics that significantly deviate from typical CI/CM. More appropriately, they are called CI-like and/or CM-like chondrites. Typical examples of TMCCs include the C2-ung/CM2TIV Belgica (B)-7904 and Yamato (Y) 86720. Thermal alteration is virtually complete in these meteorites and thus they are considered typical end-members of TMCCs exhibiting complete dehydration of matrix phyllosilicates. The estimated heating conditions are 10 to 103 days at 700 C to 1 to 100 hours at 890 C, i.e. short-term heating induced by impact and/or solar radiation. While the petrology and chemistry of TMCCs have only recently been extensively characterized, we have just begun to study in detail their organic contents. In order to understand how short-term heating affects the maturity of insoluble organic matter (IOM) in hydrous chondrites, we investigated experimentally-heated Tagish Lake meteorite using Raman spectroscopy, as the chemical and bulk oxygen isotopic compositions of the matrix of the carbonate (CO3)-poor lithology of the Tagish Lake (hereafter Tag) meteorite bears similarities to the TMCCs.

  18. Short-term heat stress exposure limits based on wet bulb globe temperature adjusted for clothing and metabolic rate.

    PubMed

    Bernard, Thomas E; Ashley, Candi D

    2009-10-01

    Most heat stress exposure assessments based on wet bulb globe temperature (WBGT) consider the environmental conditions, metabolic demands, and clothing requirements, and the exposure limit is for extended work periods (e.g., a typical workday). The U.S. Navy physiological heat exposure limit (PHEL) curves and rational models of heat stress also consider time as a job risk factor so that there is a limiting time for exposures above a conventional WBGT exposure limit. The PHEL charts have not been examined for different clothing and the rational models require personal computers. The current study examined the role of clothing in short-term (time limited) exposures and proposed a relationship between a Safe Exposure Time and WBGT adjusted for clothing and metabolic rate. Twelve participants worked at a metabolic rate of 380 W in three clothing ensembles [clothing adjustment factors]: (1) work clothes (0 degrees C-WBGT), (2) NexGen microporous coveralls (2.5 degrees C-WBGT), and (2) vapor-barrier coveralls (6.5 degrees C-WBGT) at five levels of heat stress (approximately at the clothing adjusted TLV plus 7.0, 8.0, 9.5, 11.5 and 15.0 degrees C-WBGT). The combinations of metabolic rate, clothing, and environment were selected in anticipation that the participants would reach a physiological limit in less than 120 min. WBGT-based clothing adjustment factors were used to account for different clothing ensembles, and no differences were found for ensemble, which meant that the clothing adjustment factor can be used in WBGT-based time limited exposures. An equation was proposed to recommend a Safe Exposure Time for exposures under 120 min. The recommended times were longer than the PHEL times or times from a rational model of heat stress.

  19. On the Sensitivity of Atmospheric Model Implied Ocean Heat Transport to the Dominant Terms of the Surface Energy Balance

    SciTech Connect

    Gleckler, P J

    2004-11-03

    The oceanic meridional heat transport (T{sub o}) implied by an atmospheric General Circulation Model (GCM) can help evaluate a model's readiness for coupling with an ocean GCM. In this study we examine the T{sub o} from benchmark experiments of the Atmospheric Model Intercomparison Project, and evaluate the sensitivity of T{sub o} to the dominant terms of the surface energy balance. The implied global ocean TO in the Southern Hemisphere of many models is equatorward, contrary to most observationally-based estimates. By constructing a hybrid (model corrected by observations) T{sub o}, an earlier study demonstrated that the implied heat transport is critically sensitive to the simulated shortwave cloud radiative effects, which have been argued to be principally responsible for the Southern Hemisphere problem. Systematic evaluation of one model in a later study suggested that the implied T{sub o} could be equally as sensitive to a model's ocean surface latent heat flux. In this study we revisit the problem with more recent simulations, making use of estimates of ocean surface fluxes to construct two additional hybrid calculations. The results of the present study demonstrate that indeed the implied T{sub o} of an atmospheric model is very sensitive to problems in not only the surface net shortwave, but the latent heat flux as well. Many models underestimate the shortwave radiation reaching the surface in the low latitudes, and overestimate the latent heat flux in the same region. The additional hybrid transport calculations introduced here could become useful model diagnostic tests as estimates of implied ocean surface fluxes are improved.

  20. Effect of Anode Change on Heat Transfer and Magneto-hydrodynamic Flow in Aluminum Reduction Cell

    NASA Astrophysics Data System (ADS)

    Wang, Qiang; Li, Baokuan; Fafard, Mario

    2016-02-01

    In order to explore the impact of anode replacement on heat transfer and magneto-hydrodynamic flow in aluminum smelting cells, a transient three-dimensional coupled mathematical model has been developed. With a steady state magnetic field, an electrical potential approach was used to obtain electromagnetic fields. Joule heating and Lorentz force, which were the source terms in the energy and momentum equations, were updated at each iteration. The phase change of molten electrolyte (bath) was modeled by an enthalpy-based technique in which the mushy zone was treated as a porous medium with porosity equal to the liquid fraction. A reasonable agreement between the test data and simulated results was achieved. Under normal conditions, the bath at the middle of the cell is hotter, while becoming colder at the four corners. Due to the heat extracted from the bath, the temperature of the new cold anode increases over time. The temperature of the bath under the new cold anode therefore quickly drops, resulting in a decrease of the electrical conductivity. More Joule effect is created. In addition, the bath under the new cold anode gradually freezes and flows more slowly. The temperature of the new anode located at the middle of the cell rises faster because of the warmer bath. It is easier to eliminate the effect of anode change when it occurs in the middle of the cell.