Sample records for wall temperature fluctuations

  1. Inverse heat conduction estimation of inner wall temperature fluctuations under turbulent penetration (United States)

    Guo, Zhouchao; Lu, Tao; Liu, Bo


    Turbulent penetration can occur when hot and cold fluids mix in a horizontal T-junction pipe at nuclear plants. Caused by the unstable turbulent penetration, temperature fluctuations with large amplitude and high frequency can lead to time-varying wall thermal stress and even thermal fatigue on the inner wall. Numerous cases, however, exist where inner wall temperatures cannot be measured and only outer wall temperature measurements are feasible. Therefore, it is one of the popular research areas in nuclear science and engineering to estimate temperature fluctuations on the inner wall from measurements of outer wall temperatures without damaging the structure of the pipe. In this study, both the one-dimensional (1D) and the two-dimensional (2D) inverse heat conduction problem (IHCP) were solved to estimate the temperature fluctuations on the inner wall. First, numerical models of both the 1D and the 2D direct heat conduction problem (DHCP) were structured in MATLAB, based on the finite difference method with an implicit scheme. Second, both the 1D IHCP and the 2D IHCP were solved by the steepest descent method (SDM), and the DHCP results of temperatures on the outer wall were used to estimate the temperature fluctuations on the inner wall. Third, we compared the temperature fluctuations on the inner wall estimated by the 1D IHCP with those estimated by the 2D IHCP in four cases: (1) when the maximum disturbance of temperature of fluid inside the pipe was 3°C, (2) when the maximum disturbance of temperature of fluid inside the pipe was 30°C, (3) when the maximum disturbance of temperature of fluid inside the pipe was 160°C, and (4) when the fluid temperatures inside the pipe were random from 50°C to 210°C.

  2. Primary collector wall local temperature fluctuations in the area of water-steam phase boundary

    Energy Technology Data Exchange (ETDEWEB)

    Matal, O.; Klinga, J.; Simo, T. [Energovyzkum Ltd., Brno (Switzerland)


    A limited number of temperature sensors could be installed at the primary collector surface in the area of water - steam phase boundary. The surface temperatures as well WWER 440 steam generator process data were measured and stored for a long time and off-line evaluated. Selected results are presented in the paper. (orig.). 2 refs.

  3. Attenuation of Temperature Fluctuations on an External Surface of the Wall by a Phase Change Material-Activated Layer

    Directory of Open Access Journals (Sweden)

    Dariusz Heim


    Full Text Available Periodical changes of temperature on an external surface of building envelope, e.g., thermal stress or excessive heat gains, is often an undesirable phenomenon. The idea proposed and described in the following paper is to stabilize the external surface temperature in a period of significant heat gains by the originally developed, novel composite modified by phase change material (PCM and applied as an external, thin finishing plaster layer. The PCM composite is made from porous, granulated perlite soaked with paraffin wax (Tm = 25 °C and macro-encapsulated by synthetic resin. The effect of temperature attenuation was estimated for two designated periods of time—the heat gains season (HGS and the heat losses season (HLS. The attenuation coefficient (AC was proposed as evaluation parameter of isothermal storage of heat gains determining the reduction of temperature fluctuations. The maximum registered temperature of an external surface for a standard insulation layer was around 20 K higher than for the case modified by PCM. The calculated values of AC were relatively constant during HGS and around two times lower for PCM case. The obtained results confirmed that the proposed modification of an external partition by equipped with additional PCM layer can be effectively used to minimize temperature variations and heat flux in the heat gains season.

  4. temperature fluctuation inside inert atmosphere silos

    African Journals Online (AJOL)


    TEMPERATURE FLUCTUATION INSIDE INERT ATMOSPHERE SILOS. E. S. Ajayi, et al. Nigerian Journal of Technology. Vol. 35, No. 3, July 2016. 643 also resist heat flow from solar radiation from outside. This is usually achieved by painting the silo wall with white paint. Some of the advantages of inert atmosphere storage ...

  5. Fuel Temperature Fluctuations During Storage (United States)

    Levitin, R. E.; Zemenkov, Yu D.


    When oil and petroleum products are stored, their temperature significantly impacts how their properties change. The paper covers the problem of determining temperature fluctuations of hydrocarbons during storage. It provides results of the authors’ investigations of the stored product temperature variations relative to the ambient temperature. Closeness and correlation coefficients between these values are given. Temperature variations equations for oil and petroleum products stored in tanks are deduced.

  6. Quantum entanglement and temperature fluctuations. (United States)

    Ourabah, Kamel; Tribeche, Mouloud


    In this paper, we consider entanglement in a system out of equilibrium, adopting the viewpoint given by the formalism of superstatistics. Such an approach yields a good effective description for a system in a slowly fluctuating environment within a weak interaction between the system and the environment. For this purpose, we introduce an alternative version of the formalism within a quantum mechanical picture and use it to study entanglement in the Heisenberg XY model, subject to temperature fluctuations. We consider both isotropic and anisotropic cases and explore the effect of different temperature fluctuations (χ^{2}, log-normal, and F distributions). Our results suggest that particular fluctuations may enhance entanglement and prevent it from vanishing at higher temperatures than those predicted for the same system at thermal equilibrium.

  7. temperature fluctuation inside inert atmosphere silos

    African Journals Online (AJOL)

    This research was conducted to study temperature fluctuation inside the inert atmosphere silos loaded with wheat, compare the temperature fluctuation across the top, middle and bottom part of the silo in relation to the ambient temperature. Temperature readings of the ambient and at the top, middle and bottom part of the ...

  8. Response of Fusarium solani to Fluctuating Temperatures (United States)

    Keith F. Jensen; Phillip E. Reynolds; Phillip E. Reynolds


    The purpose of this study was to measure growth under a range of constant temperatures and under a series of fluctuating temperature regimes, and to determine if growth in the fluctuating temperiture regimes could be predicted satisfactorily from the growth data collected in the constant temperature experiments. Growth was measured on both agar and liquid culture to...

  9. Toward models for fluctuating wall quantities in incompressible turbulent flows (United States)

    Towne, Aaron; Yang, Xiang; Moin, Parviz


    Wall models for large-eddy simulation have been developed that provide accurate estimates of mean wall quantities such as shear stress, heat transfer, and pressure. However, these models typically do not deliver accurate predictions of the space-time fluctuations of these quantities. In this presentation, we describe some first steps toward constructing new wall models that predict the spatiotemporal properties of wall quantities by taking advantage of recent advances in our ability to identify and model the coherent structures that are known to play a central role in the near-wall dynamics. We first analyze data from a direct numerical simulation of a channel at Reτ = 1000 using spectral estimation techniques to isolate the contribution from different scales to fluctuating wall quantities and correlation analysis to link different spatial locations. Then, we explore how modes obtained via singular value decomposition of the resolvent operator, which is obtained from the linearized flow equations, could be used to model these fluctuations. This analysis provides a starting point for leveraging these model reduction ideas to improve the prediction of near-wall fluctuations using wall-modelled large-eddy simulation. Funded by NASA Grant No. NNX15AU93A and PSAAPII Grant No. DE-NA0002373.

  10. temperature fluctuation inside inert atmosphere silos

    African Journals Online (AJOL)


    This research was conducted to study temperature fluctuation inside the inert atmosphere silos loaded with wheat, compare ... gases most especially carbondioxide (CO2) is due to safety of ... even to agriculture and resistance of pests to some.

  11. Classical and quantum temperature fluctuations via holography

    Energy Technology Data Exchange (ETDEWEB)

    Balatsky, Alexander V. [KTH Royal Inst. of Technology, Stockholm (Sweden); Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Gudnason, Sven Bjarke [KTH Royal Inst. of Technology, Stockholm (Sweden); Thorlacius, Larus [KTH Royal Inst. of Technology, Stockholm (Sweden); University of Iceland, Reykjavik (Iceland); Zarembo, Konstantin [KTH Royal Inst. of Technology, Stockholm (Sweden); Inst. of Theoretical and Experimental Physics (ITEP), Moscow (Russian Federation); Uppsala Univ. (Sweden); Krikun, Alexander [KTH Royal Inst. of Technology, Stockholm (Sweden); Inst. of Theoretical and Experimental Physics (ITEP), Moscow (Russian Federation); Kedem, Yaron [KTH Royal Inst. of Technology, Stockholm (Sweden)


    We study local temperature fluctuations in a 2+1 dimensional CFT on the sphere, dual to a black hole in asymptotically AdS space-time. The fluctuation spectrum is governed by the lowest-lying hydrodynamic sound modes of the system whose frequency and damping rate determine whether temperature fluctuations are thermal or quantum. We calculate numerically the corresponding quasinormal frequencies and match the result with the hydrodynamics of the dual CFT at large temperature. As a by-product of our analysis we determine the appropriate boundary conditions for calculating low-lying quasinormal modes for a four-dimensional Reissner-Nordstrom black hole in global AdS.

  12. Effect of programmed circadian temperature fluctuations on ...

    African Journals Online (AJOL)

    Effect of programmed circadian temperature fluctuations on population dynamics of. Biomphalaria pfeifferi (Krauss). K.N. de Kock and J.A. van Eeden. Snail Research Unit, Medical Research Council, Potchefstroom University for Christian Higher Education,. Potchefstroom. Until now all life-table studies on freshwater snails.

  13. temperature fluctuation inside inert atmosphere silos

    African Journals Online (AJOL)


    foreigners and involves the use of sophisticated gadgets that cannot be easily adopted by farmer [3]. The factors affecting temperature of grains in store includes the bin or silo size, wall insulation, shading of the bin or silo complex, heat generation by the grain and the surrounding, material of construction and grain agitation ...

  14. Refractive-index and absorption fluctuations in the infrared caused by temperature, humidity, and pressure fluctuations (United States)

    Hill, R. J.; Clifford, S. F.; Lawrence, R. S.


    The dependence of fluctuations in atmospheric absorption and refraction upon fluctuations in temperature, humidity, and pressure is found for infrared frequencies. This dependence has contributions from line and continuum absorption and from anomalous refraction by water vapor. The functions that relate these fluctuations are necessary for evaluating degradation of electromagnetic radiation by turbulence. They are computed for a given choice of mean atmospheric conditions and graphed as functions of frequency in the wavelength range 5.7 microns to radio waves. It is found that turbulent fluctuations in total pressure give a negligible contribution to absorption and refraction fluctuations. Humidity fluctuations dominate absorption fluctuations, but contributions by temperature and humidity affect refraction fluctuations. Sufficiently strong humidity fluctuations can dominate the refraction fluctuations for some infrared frequencies but not for visible frequencies. The variance of log amplitude is examined for scintillation of infrared light to determine whether absorption or refraction fluctuations dominate under several conditions.

  15. ECE imaging of electron temperature and electron temperature fluctuations (invited)

    NARCIS (Netherlands)

    Deng, B.H.; Domier, C.W.; N C Luhmann Jr.,; Brower, D.L.; Cima, G.; Donne, A. J. H.; Oyevaar, T.; van de Pol, M.J.


    Electron cyclotron emission imaging (ECE imaging or ECEI) is a novel plasma diagnostic technique for the study of electron temperature profiles and fluctuations in magnetic fusion plasma devices. Instead of a single receiver located in the tokamak midplane as in conventional ECE radiometers, ECEI

  16. Probing thermodynamic fluctuations in high temperature superconductors (United States)

    Vidal, Felix; Veira, J. A.; Maza, J.; Miguélez, F.; Morán, E.; Alario, M. A.


    We probe thermodynamic fluctuations in HTSC by measuring the excess electrical conductivity, Δσ, abovr T c in single-phase (within 4%) Ba 2LnCu 3O 7-δ compounds, with LnY, Ho and Sm. As expected, the measured relative effect, Δσ / σ (300 K), is much more important in HTSC than for low-temperature superconductors (at least one order of magnitude). In the reduced temperature region -5=-0.47 ± 0.06. This result confirms an universal critical behaviour of Δσ in HTSC, and the value of agrees with that predicted by the Aslamazov-Larkin (AL) theory for three-dimensional BCS superconductivity. However, A shows a normal conductivity dependence which is not accounted for by the AL theory.

  17. Modelling wall pressure fluctuations under a turbulent boundary layer (United States)

    Doisy, Yves


    The derivation of the wave vector-frequency (w-f) spectrum of wall pressure fluctuations below a turbulent boundary layer developed over a rigid flat plate is re-considered. The Lighthill's equation for pressure fluctuations is derived in a frame of reference fix with respect to the plate, at low Mach numbers, and transformed into the convected frame moving with the flow. To model the source terms of the Lighthill equation, it is assumed that in the inertial range, the turbulence is locally isotropic in the convected frame. The w-f spectrum of isotropic turbulence is obtained from symmetry considerations by extending the isotropy to space time, based on the concept of sweeping velocity. The resulting solution for the pressure w-f spectrum contains a term (the mean shear-turbulence term) which does not fulfill the Kraichnan Philipps theorem, due to the form of the selected turbulent velocity spectrum. The viscous effects are accounted for by a cut-off depending on wall distance; this procedure allows extending the model beyond the inertial range contribution. The w-f pressure spectrum is derived and compared to the experimental low wavenumber data of Farabee and Geib (1991) [8] and Bonness et al. (2010) [5], for which a good agreement is obtained. The derived expression is also compared to Chase theoretical model Chase (1987) [6] and found to agree well in the vicinity of the convective ridge of the subsonic domain and to differ significantly both in supersonic and subsonic low wavenumber limits. The pressure spectrum derived from the model and its scaling are discussed and compared to experimental data and to the empirical model of Goody (2002) [23], which results from the compilation of a large set of experimental data. Very good agreement is obtained, except at vanishing frequencies where it is claimed that the experimental results lack of significance due to the limited size of the experimental facilities. This hypothesis supported by the results obtained from

  18. Wall shear stress fluctuations: Mixed scaling and their effects on velocity fluctuations in a turbulent boundary layer (United States)

    Diaz-Daniel, Carlos; Laizet, Sylvain; Vassilicos, J. Christos


    The present work investigates numerically the statistics of the wall shear stress fluctuations in a turbulent boundary layer (TBL) and their relation to the velocity fluctuations outside of the near-wall region. The flow data are obtained from a Direct Numerical Simulation (DNS) of a zero pressure-gradient TBL using the high-order flow solver Incompact3D [S. Laizet and E. Lamballais, "High-order compact schemes for incompressible flows: A simple and efficient method with quasi-spectral accuracy," J. Comput. Phys. 228(16), 5989 (2009)]. The maximum Reynolds number of the simulation is R e𝜃≈2000 , based on the free-stream velocity and the momentum thickness of the boundary layer. The simulation data suggest that the root-mean-squared fluctuations of the streamwise and spanwise wall shear-stress components τx and τz follow a logarithmic dependence on the Reynolds number, consistent with the empirical correlation of Örlü and Schlatter [R. Örlü and P. Schlatter, "On the fluctuating wall-shear stress in zero pressure-gradient turbulent boundary layer flows," Phys. Fluids 23, 021704 (2011)]. These functional dependencies can be used to estimate the Reynolds number dependence of the wall turbulence dissipation rate in good agreement with reference DNS data. Our results suggest that the rare negative events of τx can be associated with the extreme values of τz and are related to the presence of coherent structures in the buffer layer, mainly quasi-streamwise vortices. We also develop a theoretical model, based on a generalisation of the Townsend-Perry hypothesis of wall-attached eddies, to link the statistical moments of the filtered wall shear stress fluctuations and the second order structure function of fluctuating velocities at a distance y from the wall. This model suggests that the wall shear stress fluctuations may induce a higher slope in the turbulence energy spectra of streamwise velocities than the one predicted by the Townsend-Perry attached

  19. Minute Temperature Fluctuations Detected in Eta Bootis (United States)


    periods around 20 minutes. These periods are longer than those of the Sun, as expected for a star that is larger and heavier than the Sun. The figure accompanying this Press Release shows these oscillations in the form of a "power spectrum", i.e., the amount of temperature change at different values of the period. Most of the highest peaks correspond to the real oscillations in the star. The changes (fluctuations) of the temperature of Eta Bootis vary with the oscillation mode and, at the time of these observations, were mostly between 0.03 and 0.08 degrees. This diagramme provides the first strong evidence ever for solar-type oscillations in a star other than the Sun. An article with the detailed results will soon appear in the "Astronomical Journal". Agreement with Stellar Theory The measured periods of the main oscillation modes give important information about the interior of Eta Bootis. Theoretical models of the star have now been compared with these observations and the astronomers were pleased to find that the agreement is excellent, implying that current stellar theory is remarkably good. This shows that we apparently understand stars quite well, but there is of course still much to be learned. Future observations of this kind, with ground-based telescopes and possibly in a more distant future also from space, promise to open up a new and exciting way of studying stars. From now on, we will be able "to look inside" stars in great detail. Appendix: Spectral Analysis Dark spectral lines were first seen in the solar spectrum by the German physicist Johann Fraunhofer in 1814. Later, in the mid-nineteenth century, such lines were also seen in the spectra of other stars. It is now known that they are due to the upper, cooler layers in the solar and stellar atmospheres, whose atoms and molecules absorb the radiation from the hotter, deeper layers at specific wavelengths. These wavelengths serve as "footprints" of these atoms and molecules and allow astronomers to

  20. Interaction of Mean Temperature and Daily Fluctuation Influences Dengue Incidence in Dhaka, Bangladesh

    National Research Council Canada - National Science Library

    Sharmin, Sifat; Glass, Kathryn; Viennet, Elvina; Harley, David


    .... In addition to the significant associations of mean temperature and temperature fluctuation with dengue incidence, we found interaction of mean and temperature fluctuation significantly influences...

  1. Determination of surface stress anisotropy from domain wall fluctuations

    NARCIS (Netherlands)

    Zandvliet, Henricus J.W.; Poelsema, Bene


    The thermally induced meandering of domain walls between (2×1) and c(4×2) regions on Ge(001) is analyzed with a scanning tunneling microscope in order to extract the anisotropy of the surface stress tensor. On small length scales the domain walls exhibit random walker behavior, whereas on larger

  2. Numerical simulation of long-period fluid temperature fluctuation at a mixing tee for the thermal fatigue problem

    Energy Technology Data Exchange (ETDEWEB)

    Utanohara, Yoichi, E-mail: [Institute of Nuclear Safety System, Inc., 64 Sata, Mihama-cho, Mikata-gun, Fukui 919-1205 (Japan); Nakamura, Akira, E-mail: [Institute of Nuclear Safety System, Inc., 64 Sata, Mihama-cho, Mikata-gun, Fukui 919-1205 (Japan); Miyoshi, Koji, E-mail: [Institute of Nuclear Safety System, Inc., 64 Sata, Mihama-cho, Mikata-gun, Fukui 919-1205 (Japan); Kasahara, Naoto, E-mail: [University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan)


    Highlights: • A large eddy simulation of a mixing tee was carried out. • Fluid temperature fluctuation could be predicted qualitatively. • Grid convergence was almost attained and the simulation continued until 100 s. • A longer-period temperature fluctuation than the well-known St = 0.2 appeared. • Prediction of long-period temperature fluctuations improves the thermal fatigue assessment. - Abstract: Thermal fatigue cracks may be initiated at mixing tees where high and low temperature fluids flow in and mix. According to a previous study, damage by thermal fatigue depends on the frequency of the fluid temperature fluctuation near the wall surface. Structures have the time constant of structural response that depends on physical properties of the structure and the gain of the frequency response tends to become maximum at the frequency lower than the typical frequency of fluid temperature fluctuation. Hence the effect of the lower frequency, that is, long-period temperature fluctuation is important for the thermal fatigue assessment. The typical frequency of fluid temperature fluctuation is about St = 0.2 (nearly 6 Hz), where St is Strouhal number and means non-dimensional frequency. In the experimental study by Miyoshi et al. (2014), a longer-period fluctuation than St = 0.2 was also observed. Results of a fluid–structure coupled analysis by Kamaya et al. (2011) showed this long-period temperature fluctuation causes severer damage to piping. In the present study, a large eddy simulation was carried out to investigate the predictive performance of the long-period fluid temperature fluctuation more quantitatively. Numerical simulation was conducted for the WATLON experiment which was the water experiment of a mixing tee performed at the Japan Atomic Energy Agency. Four computational grids were used to confirm grid convergence. In the short time (9 s) simulations, tendencies of time-averaged and fluctuated velocities could be followed. Time

  3. Spin motive forces and current fluctuations due to Brownian motion of domain walls

    NARCIS (Netherlands)

    Lucassen, M.E.|info:eu-repo/dai/nl/314406913; Duine, R.A.|info:eu-repo/dai/nl/304830127


    We compute the power spectrum of the noise in the current due to spin motive forces by a fluctuating domain wall. We find that the power spectrum of the noise in the current is colored and depends on the Gilbert damping, the spin transfer torque parameter beta, and the domain-wall pinning potential

  4. Analysis of heat exchanger network for temperature fluctuation

    Directory of Open Access Journals (Sweden)

    Jin Zunlong


    Full Text Available Subject to temperature disturbance, exchangers in heat exchanger network will interact. It is necessary to evaluate the degree of temperature fluctuation in the network. There is inherently linear relationship between output and inlet temperatures of heat exchanger network. Based on this, the concept of temperature-change sensitivity coefficient was put forward. Quantitative influence of temperature fluctuation in the network was carried out in order to examine transmission character of temperature fluctuation in the system. And the information was obtained for improving the design quality of heat exchanger network. Favorable results were obtained by the introduced method compared with the experimental results. These results will assist engineers to distinguish primary and secondary influencing factors, which can be used in observing and controlling influencing factors accurately.

  5. Log-layer mismatch and modeling of the fluctuating wall stress in wall-modeled large-eddy simulations (United States)

    Yang, Xiang I. A.; Park, George Ilhwan; Moin, Parviz


    Log-layer mismatch refers to a chronic problem found in wall-modeled large-eddy simulation (WMLES) or detached-eddy simulation, where the modeled wall-shear stress deviates from the true one by approximately 15 % . Many efforts have been made to resolve this mismatch. The often-used fixes, which are generally ad hoc, include modifying subgrid-scale stress models, adding a stochastic forcing, and moving the LES-wall-model matching location away from the wall. An analysis motivated by the integral wall-model formalism suggests that log-layer mismatch is resolved by the built-in physics-based temporal filtering. In this work we investigate in detail the effects of local filtering on log-layer mismatch. We show that both local temporal filtering and local wall-parallel filtering resolve log-layer mismatch without moving the LES-wall-model matching location away from the wall. Additionally, we look into the momentum balance in the near-wall region to provide an alternative explanation of how LLM occurs, which does not necessarily rely on the numerical-error argument. While filtering resolves log-layer mismatch, the quality of the wall-shear stress fluctuations predicted by WMLES does not improve with our remedy. The wall-shear stress fluctuations are highly underpredicted due to the implied use of LES filtering. However, good agreement can be found when the WMLES data are compared to the direct numerical simulation data filtered at the corresponding WMLES resolutions.

  6. Global and hemispheric temperature reconstruction from glacier length fluctuations

    NARCIS (Netherlands)

    Leclercq, P.W.|info:eu-repo/dai/nl/339579951; Oerlemans, J.|info:eu-repo/dai/nl/06833656X


    Temperature reconstructions for recent centuries provide a historical context for the warming over the twentieth century. We reconstruct annual averaged surface temperatures of the past 400 years on hemispherical and global scale from glacier length fluctuations. We use the glacier length records of

  7. Force fluctuations on a wall in interaction with a granular lid-driven cavity flow (United States)

    Kneib, François; Faug, Thierry; Nicolet, Gilles; Eckert, Nicolas; Naaim, Mohamed; Dufour, Frédéric


    The force fluctuations experienced by a boundary wall subjected to a lid-driven cavity flow are investigated by means of numerical simulations based on the discrete-element method. The time-averaged dynamics inside the cavity volume and the resulting steady force on the wall are governed by the boundary macroscopic inertial number, the latter being derived from the shearing velocity and the confinement pressure imposed at the top. The force fluctuations are quantified through measuring both the autocorrelation of force time series and the distributions of grain-wall forces, at distinct spatial scales from particle scale to wall scale. A key result is that the grain-wall force distributions are entirely driven by the boundary macroscopic inertial number, whatever the spatial scale considered. In particular, when the wall scale is considered, the distributions are found to evolve from nearly exponential to nearly Gaussian distributions by decreasing the macroscopic inertial number. The transition from quasistatic to dense inertial flow is well identified through remarkable changes in the shapes of the distributions of grain-wall forces, accompanied by a loss of system memory in terms of the mesoscale force transmitted toward the wall.

  8. Global and hemispheric temperature reconstruction from glacier length fluctuations

    Energy Technology Data Exchange (ETDEWEB)

    Leclercq, Paul Willem; Oerlemans, Johannes [Universiteit Utrecht, IMAU, Utrecht (Netherlands)


    Temperature reconstructions for recent centuries provide a historical context for the warming over the twentieth century. We reconstruct annual averaged surface temperatures of the past 400 years on hemispherical and global scale from glacier length fluctuations. We use the glacier length records of 308 glaciers. The reconstruction is a temperature proxy with decadal resolution that is completely independent of other temperature records. Temperatures are derived from glacier length changes using a linear response equation and an analytical glacier model that is calibrated on numerical model results. The global and hemispherical temperatures reconstructed from glacier length fluctuations are in good agreement with the instrumental record of the last century. Furthermore our results agree with existing multi-proxy reconstructions of temperature in the pre-instrumental period. The temperature record obtained from glacier fluctuations confirms the pronounced warming of the twentieth century, giving a global cumulative warming of 0.94 {+-} 0.31 K over the period 1830-2000 and a cumulative warming of 0.84 {+-} 0.35 K over the period 1600-2000. (orig.)

  9. Fatty acid compostion and extreme temperature tolerance following exposure to fluctuating temperatures in a soil arthropod

    NARCIS (Netherlands)

    Dooremalen, van C.; Suring, W.; Ellers, J.


    Ectotherms commonly adjust their lipid composition to ambient temperature to counteract detrimental thermal effects on lipid fluidity. However, the extent of lipid remodeling and the associated fitness consequences under continuous temperature fluctuations are not well-described. The objective of

  10. Fluctuating wall shear stress and velocity measurements in a turbulent boundary layer (United States)

    Pabon, Rommel; Ukeiley, Lawrence; Barnard, Casey; Sheplak, Mark


    Knowledge of mean wall shear stress on a surface can shed light on important performance parameters, but the fluctuating shear, even in simple flows, has not been as easily measured, and can be of interest in fundamental boundary layer research. Experiments on a flat plate model were performed to investigate the relationship between the wall shear stress and large scale events in the turbulent boundary layer. A MEMS based differential capacitance shear stress system with 1 mm × 1 mm floating element which can measure the fluctuating and static components of shear simultaneously, coupled with a hot wire anemometer were used for characterizing the turbulent boundary layer. Velocity profiles and turbulence statistics approaching the wall characterized the two dimensionality of the flat plate, and a trailing edge flap was used to impose a zero pressure gradient. The mean streamwise velocity profile was scaled by the friction velocity using the measured shear stress and independently compared to classical fits. Correlations between the fluctuating shear and measured velocities were used to elucidate the large scale events and to compare with previous fluctuating shear measurements for validation.


    Directory of Open Access Journals (Sweden)

    A. E. Zakharevich


    Full Text Available The investigation of indoor air temperature fluctuations within the occupied zone (habitable zone induced by the periodic changes of outdoor air temperature was carried out with the use of numerical simulation of heat transfer processes in the heated room. The developed and programme-implemented two-dimensional physical and mathematical model takes into account unsteady nature of the complex conjugate heat transfer in building envelopes and indoor air spaces when using different types of heating devices. The design features of building structures and windows are considered. The model includes the equations of radiative heat transfer between indoor surfaces, window panes and outdoor environment. In the study, the harmonic changes of outside temperature are specified by the cosine law with the twenty-four-hour period. Two types of heaters are examined: radiator and underfloor heating. Heating output of the devices is specified time-invariable according to the thermal balance defined by the traditional method. Simulations are performed for the three combinations of heat-transfer properties of building structures. The quantitative characteristics of the induced indoor air temperature fluctuations within the occupied zone depending on the building envelope thermal inertia and the type of used heater were found out. The analysis of results yielded the following conclusions. Reducing inertia of glazing leads to more rapid penetration of outdoor temperature wave into the room. While the amplitude of the indoor air temperature fluctuations within the occupied zone remains constant by reason of the unchanged thermal inertia of the main building structures. The significant increase in the amplitude of harmonic changes of indoor air temperature within the occupied zone is observed when reducing inertia of walls and floors whereas the delay with respect to outside air temperature fluctuations remains almost invariable.

  12. Quantum-gravity fluctuations and the black-hole temperature

    Energy Technology Data Exchange (ETDEWEB)

    Hod, Shahar [The Ruppin Academic Center, Emeq Hefer (Israel); The Hadassah Institute, Jerusalem (Israel)


    Bekenstein has put forward the idea that, in a quantum theory of gravity, a black hole should have a discrete energy spectrum with concomitant discrete line emission. The quantized black-hole radiation spectrum is expected to be very different from Hawking's semi-classical prediction of a thermal black-hole radiation spectrum. One naturally wonders: Is it possible to reconcile the discrete quantum spectrum suggested by Bekenstein with the continuous semi-classical spectrum suggested by Hawking? In order to address this fundamental question, in this essay we shall consider the zero-point quantum-gravity fluctuations of the black-hole spacetime. In a quantum theory of gravity, these spacetime fluctuations are closely related to the characteristic gravitational resonances of the corresponding black-hole spacetime. Assuming that the energy of the black-hole radiation stems from these zero-point quantum-gravity fluctuations of the black-hole spacetime, we derive the effective temperature of the quantized black-hole radiation spectrum. Remarkably, it is shown that this characteristic temperature of the discrete (quantized) black-hole radiation agrees with the well-known Hawking temperature of the continuous (semi-classical) black-hole spectrum. (orig.)

  13. Fluctuations of local electric field and dipole moments in water between metal walls


    Takae, Kyohei; Onuki, Akira


    We examine the thermal fluctuations of the local electric field $E_k^{\\rm loc}$ and the dipole moment $\\mu_k$ in liquid water at $T=298$ K between metal walls in electric field applied in the perpendicular direction. We use analytic theory and molecular dynamics simulation. In this situation, there is a global electrostatic coupling between the surface charges on the walls and the polarization in the bulk. Then, the correlation function of the polarization density $p_z(r)$ along the applied f...

  14. Influence of temperature fluctuations on equilibrium ice sheet volume

    Directory of Open Access Journals (Sweden)

    T. B. Mikkelsen


    Full Text Available Forecasting the future sea level relies on accurate modeling of the response of the Greenland and Antarctic ice sheets to changing temperatures. The surface mass balance (SMB of the Greenland Ice Sheet (GrIS has a nonlinear response to warming. Cold and warm anomalies of equal size do not cancel out and it is therefore important to consider the effect of interannual fluctuations in temperature. We find that the steady-state volume of an ice sheet is biased toward larger size if interannual temperature fluctuations are not taken into account in numerical modeling of the ice sheet. We illustrate this in a simple ice sheet model and find that the equilibrium ice volume is approximately 1 m SLE (meters sea level equivalent smaller when the simple model is forced with fluctuating temperatures as opposed to a stable climate. It is therefore important to consider the effect of interannual temperature fluctuations when designing long experiments such as paleo-spin-ups. We show how the magnitude of the potential bias can be quantified statistically. For recent simulations of the Greenland Ice Sheet, we estimate the bias to be 30 Gt yr−1 (24–59 Gt yr−1, 95 % credibility for a warming of 3 °C above preindustrial values, or 13 % (10–25, 95 % credibility of the present-day rate of ice loss. Models of the Greenland Ice Sheet show a collapse threshold beyond which the ice sheet becomes unsustainable. The proximity of the threshold will be underestimated if temperature fluctuations are not taken into account. We estimate the bias to be 0.12 °C (0.10–0.18 °C, 95 % credibility for a recent estimate of the threshold. In light of our findings it is important to gauge the extent to which this increased variability will influence the mass balance of the ice sheets.

  15. Glacier fluctuations, global temperature and sea-level change (United States)

    Leclercq, P. W.


    The current world-wide glacier retreat is a clear sign of global warming. In addition, glaciers contribute to sea-level rise as a consequence of the current retreat. In this thesis we use records of past glacier fluctuations to reconstruct past climate variations and the glacier contribution to sea-level change. Firstly, a coherent data set of world-wide glacier fluctuations over the past centuries is compiled. Most available information of glacier fluctuations concerns glacier length fluctuations. There is currently a large number of sources available, varying from field observations, satellite images and aerial photography to reconstructions from historical documents and geological evidence. The data set, resulting from the compilation of available data, contains 374 length records of glaciers from all continents and is described in Chapter 2. In Chapter 3, a climatic interpretation of the length fluctuations of Glaciar Frías is presented. This glacier in North Patagonia has the longest detailed length record in southern South America. The glacier behaviour is modelled with a simplified mass balance model that is coupled with a flow line model. A warming of North Patagonian climate with 1.16 °Csince the mid 17th century, or a decrease in precipitation of 34%, would best explain the observed retreat since 1639. Driving the glacier model with existing climate reconstructions shows that the uncertainties in these reconstructions are rather large. In addition, it appears that the length fluctuations are mainly driven by variations in temperature rather than variations in precipitation. The development of such detailed models is not feasible for all glaciers in the length fluctuations data set. In the next chapter a simplified approach is used to reconstruct global and hemispheric temperature for the period 1600-2000 from world-wide glacier length fluctuations. The reconstructions show that global temperature was more or less constant from 1600 until the middle of

  16. Global and quantum risks of extreme temperature fluctuations in Moscow

    Directory of Open Access Journals (Sweden)

    Mogiljuk Zhanna


    Full Text Available The article discusses topical problems of legal support for construction activities in relation to global climate change. Therefore, the results of high-resolution studies were treated. These studies tracked the pattern of fluctuation intensity changes of maximum and minimum temperatures in Moscow in the period of 1973 to 2009. The article highlights methodology elements for the statistical analysis of technical risks for implementing extreme temperature loads. A quantitative predictive risk assessment of extreme high and low temperatures and thawing risks for the entire life cycle of buildings are given. These estimates are intended to take account of the thermal loads on the ecological systems of urban areas as well as to design buildings and engineering systems that form microclimate of premises. The paper presents for the first time the obtained by the authors and previously unknown quantum regularities of the air temperature variations in the surface layer of the atmosphere. It also contains graphic materials for statistical studies of the fluctuation intensity evolution of maximum and minimum daily temperatures in the city of Moscow.

  17. Wall-attached structures of streamwise velocity fluctuations in turbulent boundary layer (United States)

    Hwang, Jinyul; Sung, Hyung Jin


    The wall-attached structures of streamwise velocity fluctuations (u) are explored using direct numerical simulation data of turbulent boundary layer at Reτ = 1000 . We identify the structures of u, which are extended close to the wall. Their height (ly) ranges from the near-wall region to the edge of turbulent boundary layer. They are geometrically self-similar in a sense that the length and width of the structures are proportional to the distance from the wall. The population density of the attached structures shows that the tall attached structures (290 attached eddies addressed by Perry and coworkers. The streamwise turbulent intensity of these tall attached structures follows the logarithmic distribution with the distance from the wall. The wall-attached structures of u identified in the present work are a proper candidate for Townsend's attached eddy hypothesis and these structures exist in the low Reynolds number turbulent boundary layer. This work was supported by the Creative Research Initiatives (No. 2017-013369) program of the National Research Foundation of Korea (MSIP) and supported by the Supercomputing Center (KISTI).

  18. Suppression of Temperature Fluctuations and Energy Barrier Generation by Velocity Shear (United States)

    Boedo, J. A.; Terry, P. W.; Gray, D.; Ivanov, R. S.; Conn, R. W.; Jachmich, S.; van Oost, G.; Textor Team


    First measurements of temperature fluctuations in a region of high velocity shear show that absolute and normalized fluctuation levels are reduced across the shear layer, a result that is consistent with weak parallel electron thermal conduction in the electron temperature dynamics. The concomitant reduction of temperature, density, and electric field fluctuations reduces the anomalous conducted and convected heat fluxes.

  19. Simulation of Temperature Fluctuations in Stirling Engine Regenerator Matrices

    DEFF Research Database (Denmark)

    Andersen, Stig Kildegaard; Carlsen, Henrik; Thomsen, Per Grove


    The objective of this study has been to create a model for studying the effects of fluctuations in regenerator matrix temperatures on Stirling engine performance. A one-dimensional model with axial discretisation of engine components has been formulated using the balance equations for mass, energy...... an idealised model. Steady state periodic solutions to the model are found using a custom built shooting method that finds solutions that simultaneously satisfy cyclic boundary conditions and integral conditions. It has been found that true steady state periodic solutions to the model can be reliably...

  20. Temperature-independent, seasonal fluctuations in immune function of the Mojave Desert Tortoise (Gopherus agassizii)

    National Research Council Canada - National Science Library

    Horn, K.R; Sandmeier, F.C; Tracy, C.R


    .... agassizii at a controlled, constant ambient temperature, we quantified predominantly temperature-independent, seasonal fluctuations in innate immune function and circulating leukocytes in a reptile...

  1. Estimating local heat transfer coefficients from thin wall temperature measurements (United States)

    Gazizov, I. M.; Davletshin, I. A.; Paereliy, A. A.


    An approach to experimental estimation of local heat transfer coefficient on a plane wall has been described. The approach is based on measurements of heat-transfer fluid and wall temperatures during some certain time of wall cooling. The wall was a thin plate, a printed circuit board, made of composite epoxy material covered with a copper layer. The temperature field can be considered uniform across the plate thickness when heat transfer is moderate and thermal resistance of the plate in transversal direction is low. This significantly simplifies the heat balance written for the wall sections that is used to estimate the heat transfer coefficient. The copper layer on the plate etched to form a single strip acted as resistance thermometers that measured the local temperature of the wall.

  2. Temperature fluctuations driven by magnetorotational instability in protoplanetary disks

    Energy Technology Data Exchange (ETDEWEB)

    McNally, Colin P. [Niels Bohr International Academy, Niels Bohr Institute, Blegdamsvej 17, DK-2100 Copenhagen Ø (Denmark); Hubbard, Alexander; Low, Mordecai-Mark Mac [Department of Astrophysics, American Museum of Natural History, New York, NY 10024-5192 (United States); Yang, Chao-Chin, E-mail:, E-mail:, E-mail:, E-mail: [Lund Observatory, Department of Astronomy and Theoretical Physics, Lund University, Box 43, SE-22100 Lund (Sweden)


    The magnetorotational instability (MRI) drives magnetized turbulence in sufficiently ionized regions of protoplanetary disks, leading to mass accretion. The dissipation of the potential energy associated with this accretion determines the thermal structure of accreting regions. Until recently, the heating from the turbulence has only been treated in an azimuthally averaged sense, neglecting local fluctuations. However, magnetized turbulence dissipates its energy intermittently in current sheet structures. We study this intermittent energy dissipation using high resolution numerical models including a treatment of radiative thermal diffusion in an optically thick regime. Our models predict that these turbulent current sheets drive order-unity temperature variations even where the MRI is damped strongly by Ohmic resistivity. This implies that the current sheet structures where energy dissipation occurs must be well-resolved to correctly capture the flow structure in numerical models. Higher resolutions are required to resolve energy dissipation than to resolve the magnetic field strength or accretion stresses. The temperature variations are large enough to have major consequences for mineral formation in disks, including melting chondrules, remelting calcium-aluminum-rich inclusions, and annealing silicates; and may drive hysteresis: current sheets in MRI active regions could be significantly more conductive than the remainder of the disk.

  3. Temperature measurements in a wall stabilized steady flame using CARS

    KAUST Repository

    Sesha Giri, Krishna


    Flame quenching by heat loss to a surface continues to be an active area of combustion research. Close wall temperature measurements in an isothermal wall-stabilized flame are reported in this work. Conventional N-vibrational Coherent Anti-Stokes Raman Scattering (CARS) thermometry as close as 275 μm to a convex wall cooled with water has been carried out. The standard deviation of mean temperatures is observed to be ~6.5% for high temperatures (>2000K) and ~14% in the lower range (<500K). Methane/air and ethylene/air stoichiometric flames for various global strain rates based on exit bulk velocities are plotted and compared. CH* chemiluminescence is employed to determine the flame location relative to the wall. Flame locations are shown to move closer to the wall with increasing strain rates in addition to higher near-wall temperatures. Peak temperatures for ethylene are considerably higher (~250-300K) than peak temperatures for methane. Preheat zone profiles are similar for different strain rates across fuels. This work demonstrates close wall precise temperature measurments using CARS.

  4. Glacier fluctuations, global temperature and sea-level change


    P. W. Leclercq


    The current world-wide glacier retreat is a clear sign of global warming. In addition, glaciers contribute to sea-level rise as a consequence of the current retreat. In this thesis we use records of past glacier fluctuations to reconstruct past climate variations and the glacier contribution to sea-level change. Firstly, a coherent data set of world-wide glacier fluctuations over the past centuries is compiled. Most available information of glacier fluctuations concerns glacier length fluctua...

  5. Fluctuations of local electric field and dipole moments in water between metal walls. (United States)

    Takae, Kyohei; Onuki, Akira


    We examine the thermal fluctuations of the local electric field Ek (loc) and the dipole moment μk in liquid water at T = 298 K between metal walls in electric field applied in the perpendicular direction. We use analytic theory and molecular dynamics simulation. In this situation, there is a global electrostatic coupling between the surface charges on the walls and the polarization in the bulk. Then, the correlation function of the polarization density pz(r) along the applied field contains a homogeneous part inversely proportional to the cell volume V. Accounting for the long-range dipolar interaction, we derive the Kirkwood-Fröhlich formula for the polarization fluctuations when the specimen volume v is much smaller than V. However, for not small v/V, the homogeneous part comes into play in dielectric relations. We also calculate the distribution of Ek (loc) in applied field. As a unique feature of water, its magnitude |Ek (loc)| obeys a Gaussian distribution with a large mean value E0 ≅ 17 V/nm, which arises mainly from the surrounding hydrogen-bonded molecules. Since |μk|E0 ∼ 30kBT, μk becomes mostly parallel to Ek (loc). As a result, the orientation distributions of these two vectors nearly coincide, assuming the classical exponential form. In dynamics, the component of μk(t) parallel to Ek (loc)(t) changes on the time scale of the hydrogen bonds ∼5 ps, while its smaller perpendicular component undergoes librational motions on time scales of 0.01 ps.

  6. Finite Temperature Qcd With Domain Wall Fermions

    CERN Document Server

    Fleming, G T


    Domain wall fermions are a new lattice fermion formulation which preserves the full chiral symmetry of the continuum at finite lattice spacing, up to terms exponentially small in an extra parameter. We discuss the main features of the formulation and its application to study of QCD with two light fermions of equal mass. We also present numerical studies of the two flavor QCD thermodynamics with aT = 1/4.

  7. Controllable effects of quantum fluctuations on spin free-induction decay at room temperature (United States)

    Liu, Gang-Qin; Pan, Xin-Yu; Jiang, Zhan-Feng; Zhao, Nan; Liu, Ren-Bao


    Fluctuations of local fields cause decoherence of quantum objects. Usually at high temperatures, thermal noises are much stronger than quantum fluctuations unless the thermal effects are suppressed by certain techniques such as spin echo. Here we report the discovery of strong quantum-fluctuation effects of nuclear spin baths on free-induction decay of single electron spins in solids at room temperature. We find that the competition between the quantum and thermal fluctuations is controllable by an external magnetic field. These findings are based on Ramsey interference measurement of single nitrogen-vacancy center spins in diamond and numerical simulation of the decoherence, which are in excellent agreement. PMID:22666535

  8. Fluctuation-induced heat release from temperature-quenched nuclear spins near a quantum critical point. (United States)

    Kim, Y H; Kaur, N; Atkins, B M; Dalal, N S; Takano, Y


    At a quantum critical point (QCP)--a zero-temperature singularity in which a line of continuous phase transition terminates--quantum fluctuations diverge in space and time, leading to exotic phenomena that can be observed at nonzero temperatures. Using a quantum antiferromagnet, we present calorimetric evidence that nuclear spins frozen in a high-temperature nonequilibrium state by temperature quenching are annealed by quantum fluctuations near the QCP. This phenomenon, with readily detectable heat release from the nuclear spins as they are annealed, serves as an excellent marker of a quantum critical region around the QCP and provides a probe of the dynamics of the divergent quantum fluctuations.

  9. Thermal fluctuations affect the transcriptome through mechanisms independent of average temperature. (United States)

    Sørensen, Jesper Givskov; Schou, Mads Fristrup; Kristensen, Torsten Nygaard; Loeschcke, Volker


    Terrestrial ectotherms are challenged by variation in both mean and variance of temperature. Phenotypic plasticity (thermal acclimation) might mitigate adverse effects, however, we lack a fundamental understanding of the molecular mechanisms of thermal acclimation and how they are affected by fluctuating temperature. Here we investigated the effect of thermal acclimation in Drosophila melanogaster on critical thermal maxima (CTmax) and associated global gene expression profiles as induced by two constant and two ecologically relevant (non-stressful) diurnally fluctuating temperature regimes. Both mean and fluctuation of temperature contributed to thermal acclimation and affected the transcriptome. The transcriptomic response to mean temperatures comprised modification of a major part of the transcriptome, while the response to fluctuations affected a much smaller set of genes, which was highly independent of both the response to a change in mean temperature and to the classic heat shock response. Although the independent transcriptional effects caused by fluctuations were relatively small, they are likely to contribute to our understanding of thermal adaptation. We provide evidence that environmental sensing, particularly phototransduction, is a central mechanism underlying the regulation of thermal acclimation to fluctuating temperatures. Thus, genes and pathways involved in phototransduction are likely of importance in fluctuating climates.

  10. Glacier fluctuations, global temperature and sea-level change

    NARCIS (Netherlands)

    Leclercq, P.W.


    The current world-wide glacier retreat is a clear sign of global warming. In addition, glaciers contribute to sea-level rise as a consequence of the current retreat. In this thesis we use records of past glacier fluctuations to reconstruct past climate variations and the glacier contribution to

  11. How two types of fluctuating temperature affect the growth of Fusarium solani (United States)

    Keith F. Jensen; Phillip E. Reynolds


    Growth of six isolates of Fusarium solani on potato dextrose agar was determined with (1) continually changing temperature programs, (2) programs consisting of two alternating constant temperatures, and (3) a constant temperature program. All programs had a mean of 70º F. Growth increased with an increase in temperature fluctuation of 10 or...

  12. Time evolution of temperature fluctuation in a non-equilibrated system

    Energy Technology Data Exchange (ETDEWEB)

    Bhattacharyya, Trambak; Garg, Prakhar; Sahoo, Raghunath [Indian Institute of Technology Indore, Discipline of Physics, School of Basic Sciences, Simrol (India); Samantray, Prasant [Indian Institute of Technology Indore, Centre of Astronomy, School of Basic Sciences, Simrol (India)


    The evolution equation for inhomogeneous and anisotropic temperature fluctuation inside a medium is derived within the ambit of Boltzmann Transport Equation (BTE) for a hot gas of massless particles. Also, specializing to a situation created after a heavy-ion collision (HIC), we analyze the Fourier space variation of temperature fluctuation of the medium using its temperature profile. The effect of viscosity on the variation of fluctuations in the latter case is investigated and possible implications for early universe cosmology, and its connection with HICs are also explored. (orig.)

  13. Current-Fluctuation Mechanism of Field Emitters Using Metallic Single-Walled Carbon Nanotubes with High Crystallinity

    Directory of Open Access Journals (Sweden)

    Norihiro Shimoi


    Full Text Available Field emitters can be used as a cathode electrode in a cathodoluminescence device, and single-walled carbon nanotubes (SWCNTs that are synthesized by arc discharge are expected to exhibit good field emission (FE properties. However, a cathodoluminescence device that uses field emitters radiates rays whose intensity considerably fluctuates at a low frequency, and the radiant fluctuation is caused by FE current fluctuation. To solve this problem, is very important to obtain a stable output for field emitters in a cathodoluminescence device. The authors consider that the electron-emission fluctuation is caused by Fowler–Nordheim electron tunneling and that the electrons in the Fowler–Nordheim regime pass through an inelastic potential barrier. We attempted to develop a theoretical model to analyze the power spectrum of the FE current fluctuation using metallic SWCNTs as field emitters, owing to their electrical conductivity by determining their FE properties. Field emitters that use metallic SWCNTs with high crystallinity were successfully developed to achieve a fluctuating FE current from field emitters at a low frequency by employing inelastic electron tunneling. This paper is the first report of the successful development of an inelastic-electron-tunneling model with a Wentzel–Kramers–Brillouin approximation for metallic SWCNTs based on the evaluation of FE properties.

  14. Daily Temperature Fluctuations Alter Interactions between Closely Related Species of Marine Nematodes.

    Directory of Open Access Journals (Sweden)

    Nele De Meester

    Full Text Available In addition to an increase in mean temperature, climate change models predict decreasing amplitudes of daily temperature fluctuations. In temperate regions, where daily and seasonal fluctuations are prominent, such decreases in daily temperature fluctuations can have a pronounced effect on the fitness of species and on the outcome of species interactions. In this study, the effect of a temperature regime with daily fluctuations versus a constant temperature on the fitness and interspecific interactions of three cryptic species of the marine nematode species complex of Litoditis marina (Pm I, Pm III and Pm IV were investigated. In a lab experiment, different combinations of species (monospecific treatment: Pm I and Pm IV and Pm III alone; two-species treatment: Pm I + Pm IV; three-species treatment: Pm I + Pm IV + Pm III were subjected to two different temperature regimes: one constant and one fluctuating temperature. Our results showed that fluctuating temperature had minor or no effects on the population fitness of the three species in monocultures. In contrast, interspecific interactions clearly influenced the fitness of all three species, both positively and negatively. Temperature regime did have a substantial effect on the interactions between the species. In the two-species treatment, temperature regime altered the interaction from a sort of mutualism to commensalism. In addition, the strength of the interspecific interactions changed depending on the temperature regime in the three-species treatment. This experiment confirms that interactions between the species can change depending on the abiotic environment; these results show that it is important to incorporate the effect of fluctuations on interspecific interactions to predict the effect of climate change on biodiversity.

  15. Impact of diurnal temperature fluctuations on larval settlement and growth of the reef coral Pocillopora damicornis

    Directory of Open Access Journals (Sweden)

    L. Jiang


    Full Text Available Diurnal fluctuations in seawater temperature are ubiquitous on tropical reef flats. However, the effects of such dynamic temperature variations on the early stages of corals are poorly understood. In this study, we investigated the responses of larvae and new recruits of Pocillopora damicornis to two constant temperature treatments (29 and 31 °C and two diurnally fluctuating treatments (28–31 and 30–33 °C with daily means of 29 and 31 °C, respectively simulating the 3 °C diel oscillations at 3 m depth on the Luhuitou fringing reef (Sanya, China. Results showed that the thermal stress on settlement at 31 °C was almost negated by the fluctuating treatment. Further, neither elevated temperature nor temperature fluctuations caused bleaching responses in recruits, while the maximum excitation pressure over photosystem II (PSII was reduced under fluctuating temperatures. Although early growth and development were highly stimulated at 31 °C, oscillations of 3 °C had little effects on budding and lateral growth at either mean temperature. Nevertheless, daytime encounters with the maximum temperature of 33 °C in fluctuating 31 °C elicited a notable reduction in calcification compared to constant 31 °C. These results underscore the complexity of the effects caused by diel temperature fluctuations on early stages of corals and suggest that ecologically relevant temperature variability could buffer warming stress on larval settlement and dampen the positive effects of increased temperatures on coral growth.

  16. Forecasting temperature fluctuations of brake discs on a hoisting machine

    Energy Technology Data Exchange (ETDEWEB)

    Barecki, Z.; Jankowski, A.


    Evaluates a method for forecasting temperature of brake discs on hoists used in underground coal mines. Formulae describing the following phenomena are derived: energy of mechanical braking, density of energy stream absorbed by the friction liners on disc brakes, temperature increase of a disc brake caused by braking, disc cooling intensity, disc temperature during repeated braking, minimum disc mass and surface. Use of the forecasting formulae is explained with the example of disc brake operation on 2 hoists. Temperature increase on disc surface and temperature increase of disc volume are treated as 2 basic indices characterizing disc brake operation. 11 refs.

  17. Heat transfer and wall temperature effects in shock wave turbulent boundary layer interactions

    CERN Document Server

    Bernardini, Matteo; Pirozzoli, Sergio; Grasso, Francesco


    Direct numerical simulations are carried out to investigate the effect of the wall temperature on the behavior of oblique shock-wave/turbulent boundary layer interactions at freestream Mach number $2.28$ and shock angle of the wedge generator $\\varphi = 8^{\\circ}$. Five values of the wall-to-recovery-temperature ratio ($T_w/T_r$) are considered, corresponding to cold, adiabatic and hot wall thermal conditions. We show that the main effect of cooling is to decrease the characteristic scales of the interaction in terms of upstream influence and extent of the separation bubble. The opposite behavior is observed in the case of heating, that produces a marked dilatation of the interaction region. The distribution of the Stanton number shows that a strong amplification of the heat transfer occurs across the interaction, and the maximum values of thermal and dynamic loads are found in the case of cold wall. The analysis reveals that the fluctuating heat flux exhibits a strong intermittent behavior, characterized by ...

  18. FDNS code to predict wall heat fluxes or wall temperatures in rocket nozzles (United States)

    Karr, Gerald R.


    This report summarizes the findings on the NASA contract NAG8-212, Task No. 3. The overall project consists of three tasks, all of which have been successfully completed. In addition, some supporting supplemental work, not required by the contract, has been performed and is documented herein. Task 1 involved the modification of the wall functions in the code FDNS to use a Reynolds Analogy-based method. Task 2 involved the verification of the code against experimentally available data. The data chosen for comparison was from an experiment involving the injection of helium from a wall jet. Results obtained in completing this task also show the sensitivity of the FDNS code to unknown conditions at the injection slot. Task 3 required computation of the flow of hot exhaust gases through the P&W 40K subscale nozzle. Computations were performed both with and without film coolant injection. The FDNS program tends to overpredict heat fluxes, but, with suitable modeling of backside cooling, may give reasonable wall temperature predictions. For film cooling in the P&W 40K calorimeter subscale nozzle, the average wall temperature is reduced from 1750 R to about 1050 R by the film cooling. The average wall heat flux is reduced by a factor of three.

  19. Effects of temperature fluctuations on cuttlebone formation of cuttlefish Sepia esculenta (United States)

    Lei, Shuhan; Zhang, Xiumei; Liu, Songlin; Chen, Siqing


    The morphological characteristics and the cuttlebone formation of Sepia esculenta exposed to different water temperature fluctuations were investigated under laboratory conditions. Temperature fluctuation cycles (15 cycles, 60 d in total) consisted of the following three regimes of 4 d duration: keeping water temperature in 26°C for 3 d (Group A), 2 d (Group B), 0 d (Group C, control); then keeping water temperature in 16°C for the next 1, 2, 4 d. No significant difference in the survival rate was observed between the control and temperature fluctuation groups ( P >0.05). Lamellar depositions in a temperature fluctuation cycle were 2.45±0.02 for Group A, 2.00±0.02 for Group B, and 1.78±0.02 for Group C ( P< 0.05). The relationship between age and number of lamellas in the cuttlebone of S. esculenta under each water temperature fluctuation could be described as the linear model and the number of lamellas in the cuttlebone did not correspond to actual age. Group A had the highest cuttlebone growth index (CGI), the lowest locular index (LI), and inter-streak distances comparing with those of control group. However, the number of lamellas and LI or CGI showed a quadratic relationship for each temperature fluctuation group. In addition, temperature fluctuations caused the breakage of cuttlebone dark rings, which was considered a thermal mark. The position of the breakage in the dark rings was random. This thermal mark can be used as supplementary information for marking and releasing techniques.

  20. Growth and survival of Apache Trout under static and fluctuating temperature regimes (United States)

    Recsetar, Matthew S.; Bonar, Scott A.; Feuerbacher, Olin


    Increasing stream temperatures have important implications for arid-region fishes. Little is known about effects of high water temperatures that fluctuate over extended periods on Apache Trout Oncorhynchus gilae apache, a federally threatened species of southwestern USA streams. We compared survival and growth of juvenile Apache Trout held for 30 d in static temperatures (16, 19, 22, 25, and 28°C) and fluctuating diel temperatures (±3°C from 16, 19, 22 and 25°C midpoints and ±6°C from 19°C and 22°C midpoints). Lethal temperature for 50% (LT50) of the Apache Trout under static temperatures (mean [SD] = 22.8 [0.6]°C) was similar to that of ±3°C diel temperature fluctuations (23.1 [0.1]°C). Mean LT50 for the midpoint of the ±6°C fluctuations could not be calculated because survival in the two treatments (19 ± 6°C and 22 ± 6°C) was not below 50%; however, it probably was also between 22°C and 25°C because the upper limb of a ±6°C fluctuation on a 25°C midpoint is above critical thermal maximum for Apache Trout (28.5–30.4°C). Growth decreased as temperatures approached the LT50. Apache Trout can survive short-term exposure to water temperatures with daily maxima that remain below 25°C and midpoint diel temperatures below 22°C. However, median summer stream temperatures must remain below 19°C for best growth and even lower if daily fluctuations are high (≥12°C).

  1. Interaction of Mean Temperature and Daily Fluctuation Influences Dengue Incidence in Dhaka, Bangladesh.

    Directory of Open Access Journals (Sweden)

    Sifat Sharmin

    Full Text Available Local weather influences the transmission of the dengue virus. Most studies analyzing the relationship between dengue and climate are based on relatively coarse aggregate measures such as mean temperature. Here, we include both mean temperature and daily fluctuations in temperature in modelling dengue transmission in Dhaka, the capital of Bangladesh. We used a negative binomial generalized linear model, adjusted for rainfall, anomalies in sea surface temperature (an index for El Niño-Southern Oscillation, population density, the number of dengue cases in the previous month, and the long term temporal trend in dengue incidence. In addition to the significant associations of mean temperature and temperature fluctuation with dengue incidence, we found interaction of mean and temperature fluctuation significantly influences disease transmission at a lag of one month. High mean temperature with low fluctuation increases dengue incidence one month later. Besides temperature, dengue incidence was also influenced by sea surface temperature anomalies in the current and previous month, presumably as a consequence of concomitant anomalies in the annual rainfall cycle. Population density exerted a significant positive influence on dengue incidence indicating increasing risk of dengue in over-populated Dhaka. Understanding these complex relationships between climate, population, and dengue incidence will help inform outbreak prediction and control.

  2. Survival of Apache Trout eggs and alevins under static and fluctuating temperature regimes (United States)

    Recsetar, Matthew S.; Bonar, Scott A.


    Increased stream temperatures due to global climate change, livestock grazing, removal of riparian cover, reduction of stream flow, and urbanization will have important implications for fishes worldwide. Information exists that describes the effects of elevated water temperatures on fish eggs, but less information is available on the effects of fluctuating water temperatures on egg survival, especially those of threatened and endangered species. We tested the posthatch survival of eyed eggs and alevins of Apache Trout Oncorhynchus gilae apache, a threatened salmonid, in static temperatures of 15, 18, 21, 24, and 27°C, and also in treatments with diel fluctuations of ±3°C around those temperatures. The LT50 for posthatch survival of Apache Trout eyed eggs and alevins was 17.1°C for static temperatures treatments and 17.9°C for the midpoints of ±3°C fluctuating temperature treatments. There was no significant difference in survival between static temperatures and fluctuating temperatures that shared the same mean temperature, yet there was a slight difference in LT50s. Upper thermal tolerance of Apache Trout eyed eggs and alevins is much lower than that of fry to adult life stages (22–23°C). Information on thermal tolerance of early life stages (eyed egg and alevin) will be valuable to those restoring streams or investigating thermal tolerances of imperiled fishes.

  3. Experimental study on the wall jet over a riblet surface. ; Measurement of mean and fluctuating velocities and estimation of drag reduction. Riburetto men ni sou hekimen funryu ni kansuru jikkenteki kenkyu. ; Heikin-hendo sokudoba to teiko gensho no hyoka

    Energy Technology Data Exchange (ETDEWEB)

    Yamashita, S. (Gifu Univ., Gifu (Japan). Faculty of Engineering); Hayashimoto, H. (Gifu Univ., Gifu (Japan). Graduate School); Inoue, Y. (Suzuka National College of Technology, Mie (Japan)); Iwakami, Y.


    A wall-jet has a wide range of application such as to control of the boundary layer of a wing of an aeroplane, control of temperature of the vanes of a gas turbine and flow inside a fluid control device. This field of flow comprises a wall layer on the wall side having the characteristics of a boundary layer and an outer layer on the external side which is like a free jet, the two layers being separated by a boundary where the flow is at a maximum speed. This study was carried out to clarify the effect of riblets experimentally using as a base jet a wall jet which was one of basic shearing flows. In particular, studied were the degrees of change in the mean and fluctuating velocities near the wall surface and reduction of drag. The following results were obtained. A significant difference was recognized in the vicinity of the wall in the mean velocity distribution between the mean velocities on the riblet surface and on the smooth surface. The fluctuating velocity component in the x direction on the riblet surface decreased by about a maximum of 20% when compared with that on the smooth surface. In contrast, the fluctuating velocity in the y direction and Reynolds shearing stress both on the riblet and smooth surfaces were substantially in agreement with each other within the range of this experiment. 28 refs., 12 figs., 1 tab.

  4. Measurement of Temperature Fluctuations and Microscopic Growth Rates in a Silicon Floating Zone and Microgravity (United States)

    Schweizer, Markus; Croell, Arne


    A silicon crystal growth experiment has been accomplished using the floating-zone technique under microgravity on a sounding rocket (TEXUS 36). Measurements of temperature fluctuations in the silicon melt zone due to time dependent thermocapillary convection (Marangoni convection) and an observation of the microscopic growth rate were simultaneously performed during the experiment. Temperature fluctuations of about 0.5 - 0.7 C with a frequency range growth rate fluctuates considerably around the average growth rate of 1 mm/min: Growth rates up to 3 to 4mm/min, close to zero mm/min, as well as negative values (backmelting) were observed. Dopant striations are clearly visible in the Sb-doped crystal. They were characterized by Spreading Resistance measurements and Differential Interference Contrast microscopy. The frequencies of temperature fluctuations, microscopic growth rates, and the dopant inhomogeneities correspond quite well, with main frequencies between 0.1 and 0.3 Hz. 3D numerical simulations were performed to predict the optimum position of the temperature sensor, and the characteristic temperature amplitudes and frequencies. At a position 3.4mm above the interface and 1.4mm inside the melt, equivalent to the sensor tip position in the experiment, temperature fluctuations up to 1.8 C and frequencies ? 0.25Hz were found in the simulations.

  5. Coupling of infraslow fluctuations in autonomic and central vigilance markers: Skin temperature, EEG beta power and ERP P300 latency

    NARCIS (Netherlands)

    Ramautar, J.R.; Romeijn, N.; Gomez-Herrero, G.; Piantoni, G.; van Someren, E.J.W.


    Even under thermoneutral conditions, skin temperature fluctuates spontaneously, most prominently at distal parts of the body. These fluctuations were shown to be associated with fluctuations in vigilance: mild manipulation of skin temperature during nocturnal sleep affects sleep depth and the power

  6. Statistical Analysis of Thomson Scattering Measurements for High-Frequency Temperature Fluctuations (United States)

    Morton, Lucas; den Hartog, Daniel; Parke, Eli; Duff, James; Lin, Liang


    The MST Thomson Scattering (TS) Diagnostic is used to study electron temperature (Te) fluctuations at frequencies (lasers can fire 4-5 pulses at repetition rate of 12.5 kHz. Adjusting the time delay between the lasers (as low as 1 μs) allows probing of high-frequency (up to 1 MHz) fluctuations by autocorrelating the resulting Te measurements. This technique's effectiveness is demonstrated by comparing its results to those of tearing-mode-correlation studies. In 400 kA standard MST discharges, the dominant tearing modes have associated Te fluctuations of up to 25 +/- 5eV in the core. The TS autocorrelation measures total fluctuations of 42 +/- 5eV, indicating that tearing comprises much of the core Te fluctuations. With improved laser alignment, we investigate 400 kA improved confinement (PPCD) plasmas where global tearing activity is reduced and electrostatic turbulence may dominate electron thermal transport and fluctuation power. We also find no significant Te fluctuation (<5eV) correlated with edge-localized density fluctuations seen by the FIR interferometer in 200kA PPCD plasmas. This work supported by the US DOE and NSF.

  7. Temperature dependence of universal conductance fluctuation due to development of weak localization in graphene (United States)

    Terasawa, D.; Fukuda, A.; Fujimoto, A.; Ohno, Y.; Matsumoto, K.


    The temperature effect of quantum interference on resistivity is examined in monolayer graphene, with experimental results showing that the amplitude of the conductance fluctuation increases as temperature decreases. We find that this behavior can be attributed to the decrease in the inelastic scattering (dephasing) rate, which enhances the weak localization (WL) correction to resistivity. Following a previous report that explained the relationship between the universal conductance fluctuation (UCF) and WL regarding the gate voltage dependence (Terasawa et al., 2017) [19], we propose that the temperature dependence of the UCF in monolayer graphene can be interpreted by the WL theory.

  8. The effects of fluctuating temperature regimes on the embryonic development of lake whitefish (Coregonus clupeaformis). (United States)

    Lim, Michael Y-T; Manzon, Richard G; Somers, Christopher M; Boreham, Douglas R; Wilson, Joanna Y


    Fluctuating incubation temperatures may have significant effects on fish embryogenesis; yet most laboratory-based studies use constant temperatures. For species that experience large, natural seasonal temperature changes during embryogenesis, such as lake whitefish (Coregonus clupeaformis), seasonal temperature regimes are likely optimal for development. Anthropogenic activities can increase average and/or variability of natural incubation temperatures over large (e.g. through climate change) or smaller (e.g. thermal effluent discharge) geographic scales. To investigate this, we incubated lake whitefish embryos under constant (2, 5, or 8°C) and fluctuating temperature regimes. Fluctuating temperature regimes had a base temperature of 2°C with: 1) seasonal temperature changes that modeled natural declines/inclines; 2) tri-weekly +3°C, 1h temperature spikes; or 3) both seasonal temperature changes and temperature spikes. We compared mortality to hatch, morphometrics, and heart rate at three developmental stages. Mortality rate was similar for embryos incubated at constant 2°C, constant 5°C, or with seasonal temperatures, but was significantly greater at constant 8°C. Embryos incubated constantly at >2°C had reduced body growth and yolk consumption compared to embryos incubated with seasonal temperature changes. When measured at the common base temperature of 2°C, embryos incubated at constant 2°C had lower heart rates than embryos incubated with both seasonal temperature changes and temperature spikes. Our study suggests that incubating lake whitefish embryos with constant temperatures may significantly alter development, growth, and heart rate compared to incubating with seasonal temperature changes, emphasizing the need to include seasonal temperature changes in laboratory-based studies. Copyright © 2017 Elsevier Inc. All rights reserved.

  9. Development of analytical model for evaluating temperature fluctuation in coolant. 12. Investigation of stationary random temperature fluctuation characteristics in frequency domain

    Energy Technology Data Exchange (ETDEWEB)

    Muramatsu, Toshiharu [Power Reactor and Nuclear Fuel Development Corp., Oarai, Ibaraki (Japan). Oarai Engineering Center


    Thermal striping phenomena characterized by stationary random temperature fluctuations are observed in the region immediately above the core exit of liquid-metal-cooled fast breeder reactors (LMFBRs) due to the interactions of cold sodium flowing out of a control rod (C/R) assembly and hot sodium flowing out of adjacent fuel assemblies (F/As). Therefore the in-vessel components located in the core outlet region, such as upper core structure (UCS), flow guide tube, C/R upper guide tube, etc., must be protected against the stationary random thermal process which might induce high-cycle fatigue. In this study, frequency characteristics of stationary random temperature fluctuations were investigated by the use of the time-series data from parallel impinging jet experiments, TIFFSS-I. (J.P.N.)

  10. Temperature fluctuation of the Iceland mantle plume through time


    Spice, Holly E.; Fitton, John; Kirstein, Linda


    The newly developed Al-in-olivine geothermometer was used to find the olivine-Cr-spinel crystallization temperatures of a suite of picrites spanning the spatial and temporal extent of the North Atlantic Igneous Province (NAIP), which is widely considered to be the result of a deep-seated mantle plume. Our data confirm that start-up plumes are associated with a pulse of anomalously hot mantle over a large spatial area before becoming focused into a narrow upwelling. We find that the thermal an...

  11. Physical modelling of temperature fluctuations in a high aspect ratio model of the Czochralski crystal growth (United States)

    Pal, J.; Cramer, A.; Grants, I.; Eckert, S.; Gerbeth, G.


    A low temperature liquid metal model of the Czochralski (CZ) crystal growth process is considered experimentally for a high aspect ratio. Temperature fluctuations close to the edge of the model crystal are studied under the action of a rotating magnetic field (RMF) and/or rotation of the model crystal. A rotation of thermal structures is observed which loses its periodicity at sufficiently high strengths of the RMF. This finding is in qualitative agreement with previous findings in Rayleigh-Bénard (RB) cells. Opposing to that more generic case, the remaining amplitude of the temperature fluctuations stays significantly higher. I.e., the suppression of the fluctuations, which are detrimental to the growth of a mono-crystal, is weaker in the model under investigation.

  12. The effect of temperature fluctuations of reaction rate constants in turbulent reacting flows (United States)

    Chinitz, W.; Antaki, P. J.; Kassar, G. M.


    Current models of turbulent reacting flows frequently use Arrhenius reaction rate constants obtained from static or laminar flow theory and/or experiments, or from best fits of static, laminar, and turbulent data. By treating the reaction rate constant as a continuous random variable which is temperature-dependent, the present study assesses the effect of turbulent temperature fluctuations on the reaction rate constant. This model requires that a probability density function (PDF) describing the nature of the fluctuations be specified. Three PDFs are examined: the clipped Gaussian, the beta PDF, and the ramp model. All the models indicate that the reaction rate constant is greater in a turbulent flow field than in an equivalent laminar flow. In addition, an amplification ratio, which is the ratio of the turbulent rate constant to the laminar rate constant, is defined and its behavior as a function of the mean temperature fluctuations is described

  13. Biodegradation of Toluene Under Seasonal and Diurnal Fluctuations of Soil-Water Temperature.

    KAUST Repository

    Yadav, Brijesh K


    An increasing interest in bioremediation of hydrocarbon polluted sites raises the question of the influence of seasonal and diurnal changes on soil-water temperature on biodegradation of BTEX, a widespread group of (sub)-surface contaminants. Therefore, we investigated the impact of a wide range of varying soil-water temperature on biodegradation of toluene under aerobic conditions. To see the seasonal impact of temperature, three sets of batch experiments were conducted at three different constant temperatures: 10°C, 21°C, and 30°C. These conditions were considered to represent (1) winter, (2) spring and/or autumn, and (3) summer seasons, respectively, at many polluted sites. Three additional sets of batch experiments were performed under fluctuating soil-water temperature cases (21<>10°C, 30<>21°C, and 10<>30°C) to mimic the day-night temperature patterns expected during the year. The batches were put at two different temperatures alternatively to represent the day (high-temperature) and night (low-temperature) times. The results of constant- and fluctuating-temperature experiments show that toluene degradation is strongly dependent on soil-water temperature level. An almost two-fold increase in toluene degradation time was observed for every 10°C decrease in temperature for constant-temperature cases. Under fluctuating-temperature conditions, toluene degraders were able to overcome the temperature stress and continued thriving during all considered weather scenarios. However, a slightly longer time was taken compared to the corresponding time at daily mean temperature conditions. The findings of this study are directly useful for bioremediation of hydrocarbon-polluted sites having significant diurnal and seasonal variations of soil-water temperature.

  14. Temperature fluctuations underneath the ice in Diamond Lake, Hennepin County, Minnesota (United States)

    Kletetschka, Gunther; Fischer, Tomas; Mls, Jiří; DěDeček, Petr


    Diamond Lake in Minnesota is covered every winter with ice and snow providing a modified thermal insulation between water and air. Autonomous temperature sensors, data loggers, were placed in this lake so that hourly measurements could be obtained from the snow-covered ice and water. The sensors that became frozen measured damped and delayed thermal response from the air-temperature fluctuation. Those sensors that were deeper within the snow-covered ice measured continuous, almost constant, temperature values near freezing. Several of them were within the liquid water and responded with a fluctuation of 24 h periods of amplitudes up to 0.2°C. Our analysis of the vertical temperature profiles suggested that the source of periodic water heating comes from the lake bottom. Because of the absence of daily temperature variations of the snow-covered ice, the influence of the air-temperature fluctuation can be ruled out. We attribute the heating process to the periodic inflow of groundwater to the lake and the cooling to the heat diffusion to the overlying ice cover. The periodic groundwater inflow is interpreted due to solid Earth tides, which cause periodic fluctuations of the groundwater pressure head.

  15. Effects of ion temperature fluctuations on the stability of resistive ballooning modes

    Energy Technology Data Exchange (ETDEWEB)

    Singh, R. [Inst. for Plasma Research, Bhat, Gandhinagar (India); Nordman, H.; Jarmen, A.; Weiland, J. [Chalmers Univ. of Technology, Goeteborg (Sweden). Inst. for Electromagnetic Field Theory and Plasma Physics


    The influence of ion temperature fluctuations on the stability of resistive drift- and ballooning-modes is investigated using a two-fluid model. The Eigenmode equations are derived and solved analytically in a low beta model equilibrium. Parameters relevant to L-mode edge plasmas from the Texas Experimental Tokamak are used. The resistive modes are found to be destabilized by ion temperature fluctuations over a broad range of mode numbers. The scaling of the growth rate with magnetic shear and mode number is elucidated. 13 refs, 4 figs.

  16. Delay time for fine particle ignition within gas with fluctuating temperature (United States)

    Derevich, I. V.; Galdina, D. D.


    The Pontryagin equation was applied to calculating the average time for the random process escaping the assign interval: this gives the average delay time for waiting of particle ignition moment in a turbulent flow of gas. A direct numerical simulation method was developed for gas temperature fluctuations with assigned autocorrelation function and particle temperature fluctuations due to exothermal chemical reaction. The method was based on numerical solution of a system of stochastic differential equations. Results of direct simulation were validated through comparing with the analytical solution available for particles without exothermal reaction. Analytical calculations and results of direct numerical simulation for the delay time of particle ignition are in agreement.

  17. Fluctuation induced diamagnetism in the zero magnetic field limit in a low temperature superconducting alloy. (United States)

    Mosqueira, J; Carballeira, C; Vidal, F


    By using a Pb-18 at. % In alloy, the fluctuation induced diamagnetism was measured in the zero magnetic field limit, never observed until now in a low-T(C) superconductor. This allows us to disentangle the dynamic and the nonlocal electrodynamic effects from the short-wavelength fluctuation effects. The latter may be explained on the grounds of the Gaussian-Ginzburg-Landau approach by introducing a total energy cutoff in the fluctuation spectrum, which strongly suggests the existence of a well-defined temperature in the normal state above which all fluctuating modes vanish. This conclusion may also have implications when describing the superconducting state formation of the high-T(C) cuprates.

  18. Fine-scale temperature fluctuation and modulation of Dirofilaria immitis larval development in Aedes aegypti. (United States)

    Ledesma, Nicholas; Harrington, Laura


    We evaluated degree-day predictions of Dirofilaria immitis development (HDU) under constant and fluctuating temperature treatments of equal average daily temperature. Aedes aegypti mosquitoes were infected with D. immitis microfilariae and parasite development was recorded at set time points in dissected mosquitoes. Time to L3 development in Malpighian tubules and detection in mosquito heads was shorter for larvae experiencing a daily regime of 19±9°C than larvae at constant 19°C; larval development rate in Malpighian tubules was slower in fluctuating regimes maintained above the 14°C developmental threshold than larvae under constant temperatures. We showed that hourly temperature modeling more accurately predicted D. immitis development to infective L3 stage. Development time differed between fluctuating and constant temperature treatments spanning the 14°C development threshold, implicating a physiological basis for these discrepancies. We conclude that average daily temperature models underestimate L3 development-and consequently dog heartworm transmission risk-at colder temperatures, and spatiotemporal models of D. immitis transmission risk should use hourly temperature data when analyzing high daily temperature ranges spanning 14°C. Copyright © 2015 The Authors. Published by Elsevier B.V. All rights reserved.

  19. Fluctuations at a low mean temperature accelerate dengue virus transmission by Aedes aegypti.

    Directory of Open Access Journals (Sweden)

    Lauren B Carrington

    Full Text Available BACKGROUND: Environmental factors such as temperature can alter mosquito vector competence for arboviruses. Results from recent studies indicate that daily fluctuations around an intermediate mean temperature (26°C reduce vector competence of Aedes aeygpti for dengue viruses (DENV. Theoretical predictions suggest that the mean temperature in combination with the magnitude of the diurnal temperature range (DTR mediate the direction of these effects. METHODOLOGY/PRINCIPAL FINDINGS: We tested the effect of temperature fluctuations on Ae. aegypti vector competence for DENV serotype-1 at high and low mean temperatures, and confirmed this theoretical prediction. A small DTR had no effect on vector competence around a high (30°C mean, but a large DTR at low temperature (20°C increased the proportion of infected mosquitoes with a disseminated infection by 60% at 21 and 28 days post-exposure compared to a constant 20°C. This effect resulted from a marked shortening of DENV extrinsic incubation period (EIP in its mosquito vector; i.e., a decrease from 29.6 to 18.9 days under the fluctuating vs. constant temperature treatment. CONCLUSIONS: Our results indicate that Ae. aegypti exposed to large fluctuations at low temperatures have a significantly shorter virus EIP than under constant temperature conditions at the same mean, leading to a considerably greater potential for DENV transmission. These results emphasize the value of accounting for daily temperature variation in an effort to more accurately understand and predict the risk of mosquito-borne pathogen transmission, provide a mechanism for sustained DENV transmission in endemic areas during cooler times of the year, and indicate that DENV transmission could be more efficient in temperate regions than previously anticipated.

  20. Effects of fluctuating temperature and food availability on reproduction and lifespan. (United States)

    Schwartz, Tonia S; Pearson, Phillip; Dawson, John; Allison, David B; Gohlke, Julia M


    Experimental studies on energetics and aging often remove two major factors that in part regulate the energy budget in a normal healthy individual: reproduction and fluctuating environmental conditions that challenge homeostasis. Here we use the cyclical parthenogenetic Daphnia pulex to evaluate the role of a fluctuating thermal environment on both reproduction and lifespan across six food concentrations. We test the hypotheses that (1) caloric restriction extends lifespan; (2) maximal reproduction will come with a cost of shortened lifespan; and (3) at a given food concentration, relative to a metabolically equivalent constant temperature environment a diel fluctuating thermal environment will alter the allocation of energy to reproduction and lifespan to maintain homeostasis. We did not identify a level of food concentration that extended lifespan in response to caloric restriction, and we found no cost of reproduction in terms of lifespan. Rather, the individuals at the highest food levels generally had the highest reproductive output and the longest lifespans, the individuals at the intermediate food level decreased reproduction and maintained lifespan, and the individuals at the three lower food concentrations had a decrease in reproduction and lifespan as would be predicted with increasing levels of starvation. Fluctuating temperature had no effect on lifespan at any food concentration, but delayed time to reproductive maturity and decreased early reproductive output at all food concentrations. This suggests that a fluctuating temperature regimen activates molecular pathways that alter energy allocation. The costs of fluctuating temperature on reproduction were not consistent across the lifespan. Statistical interactions for age of peak reproduction and lifetime fecundity suggest that senescence of the reproductive system may vary between temperature regimens at the different food concentrations. Copyright © 2016 Elsevier Inc. All rights reserved.

  1. Measurement of Temperature Fluctuations and Microscopic Growth Rates in a Silicon Floating Zone Under Microgravity (United States)

    Croell, Arne; Schweizer, Markus; Dold, P.; Kaiser, T.; Lichtensteiger, M.; Benz, K. W.


    USA Several microgravity experiments on sounding rockets and the Space Shuttle have shown that time-dependent thermocapillary (Marangoni) convection is the major cause for the formation of dopant striations in floating-zone grown semiconductor crystals, at least in small-scale systems not employing RF heating. To quantify this correlation, a silicon floating-zone experiment was performed during the TEXUS36 flight (February 7, 1998) in the monoellipsoid mirror furnace TEM02-ELLI. During the experiment, temperature fluctuations in the silicon melt zone and the microscopic growth rate were simultaneously measured. Temperature fluctuations of 0.5 C - 0.7 C with main frequencies between 0.1 Hz and 0.3 Hz were detectable. The microscopic growth rate fluctuated considerably around the average growth rate of 1 mm/min: rates from 4 mm/min to negative values (backmelting) were observed. Dopant striations are clearly visible in the Sb-doped crystal. They were characterized by Spreading Resistance measurements and Differential Interference Contrast microscopy. The frequencies associated with the dopant inhomogeneities correspond quite well with those of the temperature fluctuations and microscopic growth rates. 3D numerical simulations were performed to predict the optimum position of the temperature sensor, to evaluate characteristic temperature amplitudes and frequencies, and to give insight into the instability mechanisms of Marangoni convection in this configuration. The simulations were in good agreement with the experimental values, showing temperature fluctuations with frequencies ? 0.25 Hz and amplitudes up to 1.8 C at a position equivalent to that of the sensor tip in the experiment.

  2. Single Wall Carbon Nanotubes Based Cryogenic Temperature Sensor Platforms. (United States)

    Monea, Bogdan Florian; Ionete, Eusebiu Ilarian; Spiridon, Stefan Ionut; Leca, Aurel; Stanciu, Anda; Petre, Emil; Vaseashta, Ashok


    We present an investigation consisting of single walled carbon nanotubes (SWCNTs) based cryogenic temperature sensors, capable of measuring temperatures in the range of 2-77 K. Carbon nanotubes (CNTs) due to their extremely small size, superior thermal and electrical properties have suggested that it is possible to create devices that will meet necessary requirements for miniaturization and better performance, by comparison to temperature sensors currently available on the market. Starting from SWCNTs, as starting material, a resistive structure was designed. Employing dropcast method, the carbon nanotubes were deposited over pairs of gold electrodes and in between the structure electrodes from a solution. The procedure was followed by an alignment process between the electrodes using a dielectrophoretic method. Two sensor structures were tested in cryogenic field down to 2 K, and the resistance was measured using a standard four-point method. The measurement results suggest that, at temperatures below 20 K, the temperature coefficient of resistance average for sensor 1 is 1.473%/K and for sensor 2 is 0.365%/K. From the experimental data, it can be concluded that the dependence of electrical resistance versus temperature can be approximated by an exponential equation and, correspondingly, a set of coefficients are calculated. It is further concluded that the proposed approach described here offers several advantages, which can be employed in the fabrication of a microsensors for cryogenic applications.

  3. The use of spontaneous voltage fluctuations for the measurement of low temperatures

    NARCIS (Netherlands)

    Endt, P.M.


    A discussion is given of the method proposed by Lawson and Long to use the noise across a resistance as a measure of its absolute temperature. The statistical fluctuations in the measured noise are calculated, taking into account the bandwidth of the amplifier. This calculation shows that is not

  4. Effects of rapid temperature fluctuations prior to breeding on reproductive efficiency in replacement gilts (United States)

    Recently, we determined that rapidly cooling pigs after acute heat stress (HS) resulted in a pathological condition, and because rapid temperature fluctuations are often associated with reduced reproductive success in sows it lends itself to the hypothesis that these conditions may be linked. Study ...

  5. The height dependence of quiet-sun photospheric temperature fluctuations in observations and simulations

    NARCIS (Netherlands)

    Koza, J.|info:eu-repo/dai/nl/304847704; Kucera, A.; Rybák, J.; Wöhl, H.


    We derive rms temperature fluctuations as a function of height throughout the solar photosphere for the non-magnetic photosphere and a small area of enhanced magnetic activity, through semi-empirical inversion based on response functions of a 15-minute time sequence of 118″-long slit spectrograms

  6. Thermal fluctuations affect the transcriptome through mechanisms independent of average temperature


    Jesper Givskov Sørensen; Mads Fristrup Schou; Torsten Nygaard Kristensen; Volker Loeschcke


    Terrestrial ectotherms are challenged by variation in both mean and variance of temperature. Phenotypic plasticity (thermal acclimation) might mitigate adverse effects, however, we lack a fundamental understanding of the molecular mechanisms of thermal acclimation and how they are affected by fluctuating temperature. Here we investigated the effect of thermal acclimation in Drosophila melanogaster on critical thermal maxima (CTmax) and associated global gene expression profiles as induced by ...

  7. Long-range correlations in rectal temperature fluctuations of healthy infants during maturation.

    Directory of Open Access Journals (Sweden)

    Georgette Stern

    Full Text Available BACKGROUND: Control of breathing, heart rate, and body temperature are interdependent in infants, where instabilities in thermoregulation can contribute to apneas or even life-threatening events. Identifying abnormalities in thermoregulation is particularly important in the first 6 months of life, where autonomic regulation undergoes critical development. Fluctuations in body temperature have been shown to be sensitive to maturational stage as well as system failure in critically ill patients. We thus aimed to investigate the existence of fractal-like long-range correlations, indicative of temperature control, in night time rectal temperature (T(rec patterns in maturing infants. METHODOLOGY/PRINCIPAL FINDINGS: We measured T(rec fluctuations in infants every 4 weeks from 4 to 20 weeks of age and before and after immunization. Long-range correlations in the temperature series were quantified by the correlation exponent, alpha using detrended fluctuation analysis. The effects of maturation, room temperature, and immunization on the strength of correlation were investigated. We found that T(rec fluctuations exhibit fractal long-range correlations with a mean (SD alpha of 1.51 (0.11, indicating that T(rec is regulated in a highly correlated and hence deterministic manner. A significant increase in alpha with age from 1.42 (0.07 at 4 weeks to 1.58 (0.04 at 20 weeks reflects a change in long-range correlation behavior with maturation towards a smoother and more deterministic temperature regulation, potentially due to the decrease in surface area to body weight ratio in the maturing infant. alpha was not associated with mean room temperature or influenced by immunization CONCLUSIONS: This study shows that the quantification of long-range correlations using alpha derived from detrended fluctuation analysis is an observer-independent tool which can distinguish developmental stages of night time T(rec pattern in young infants, reflective of maturation of

  8. A large temperature fluctuation may trigger an epidemic erythromelalgia outbreak in China (United States)

    Liu, Tao; Zhang, Yonghui; Lin, Hualiang; Lv, Xiaojuan; Xiao, Jianpeng; Zeng, Weilin; Gu, Yuzhou; Rutherford, Shannon; Tong, Shilu; Ma, Wenjun


    Although erythromelalgia (EM) has been documented in the literature for almost 150 years, it is still poorly understood. To overcome this limitation, we examined the spatial distribution of epidemic EM, and explored the association between temperature fluctuation and epidemic EM outbreaks in China. We searched all peer-reviewed literature on primary epidemic EM outbreaks in China. A two-stage model was used to characterize the relationship between temperature fluctuation and epidemic EM outbreaks. We observed that epidemic EM outbreaks were reported from 13 provinces during 1960-2014 and they mainly occurred between February and March in southern China. The majority of EM cases were middle school students, with a higher incidence rate in female and resident students. The major clinical characteristics of EM cases included burning, sharp, tingling and/or stinging pain in toes, soles and/or dorsum of feet, fever, erythema and swelling. A large ``V''-shaped fluctuation of daily average temperature (TM) observed during the epidemic EM outbreaks was significantly associated with the number of daily EM cases (β = 1.22, 95%CI: 0.66 ~ 1.79), which indicated that this ``V''-shaped fluctuation of TM probably triggered the epidemic EM outbreaks.

  9. Local wall heat flux/temperature meter for convective flow and method of utilizing same (United States)

    Boyd, Ronald D. (Inventor); Ekhlassi, Ali (Inventor); Cofie, Penrose (Inventor)


    According to one embodiment of the invention, a method includes providing a conduit having a fluid flowing therethrough, disposing a plurality of temperature measurement devices inside a wall of the conduit, positioning at least some of the temperature measurement devices proximate an inside surface of the wall of the conduit, positioning at least some of the temperature measurement devices at different radial positions at the same circumferential location within the wall, measuring a plurality of temperatures of the wall with respective ones of the temperature measurement devices to obtain a three-dimensional temperature topology of the wall, determining the temperature dependent thermal conductivity of the conduit, and determining a multi-dimensional thermal characteristic of the inside surface of the wall of the conduit based on extrapolation of the three-dimensional temperature topology and the temperature dependent thermal conductivities.

  10. Lagrangian temperature and vertical velocity fluctuations due to gravity waves in the lower stratosphere (United States)

    Podglajen, Aurélien; Hertzog, Albert; Plougonven, Riwal; Legras, Bernard


    Wave-induced Lagrangian fluctuations of temperature and vertical velocity in the lower stratosphere are quantified using measurements from superpressure balloons (SPBs). Observations recorded every minute along SPB flights allow the whole gravity wave spectrum to be described and provide unprecedented information on both the intrinsic frequency spectrum and the probability distribution function of wave fluctuations. The data set has been collected during two campaigns coordinated by the French Space Agency in 2010, involving 19 balloons over Antarctica and 3 in the deep tropics. In both regions, the vertical velocity distributions depart significantly from a Gaussian behavior. Knowledge on such wave fluctuations is essential for modeling microphysical processes along Lagrangian trajectories. We propose a new simple parameterization that reproduces both the non-Gaussian distribution of vertical velocities (or heating/cooling rates) and their observed intrinsic frequency spectrum.

  11. The effect of fluctuating temperatures during development on fitness-related traits of Scatophaga stercoraria (Diptera: Scathophagidae). (United States)

    Kjærsgaard, Anders; Pertoldi, Cino; Loeschcke, Volker; Blanckenhorn, Wolf U


    Development of ectotherms is highly temperature dependent. Studies using variable thermal environments can improve ecological relevance of data because organisms naturally face day-to-day stochastic temperature fluctuations as well as seasonal changes in the amplitude of such daily fluctuations. The objective of this study was to investigate if, and to what extent, the use of constant temperatures is justified in studies of the model species, yellow dung fly, Scatophaga stercoraria (L.). We examined the effect of temperature fluctuation on the expression of several life history traits and the effect on subsequent adult longevity. We used two fluctuating temperature treatments with the same mean but different amplitudes (15/21°C, 12/24°C; 12/12 h), and three constant temperature treatments spanning the wide temperature range faced in the wild (12, 18, and 24°C). Large temperature fluctuation was mostly detrimental (lower juvenile survival, slower growth, smaller body size, and longer development), whereas moderate temperature fluctuation usually gave responses similar to the constant regime. When developing in fluctuating temperatures, adult longevity (no effect), body size (lower), and wing shape (narrower wings) deviated from the expectations based on the constant temperature reaction norms, presumably because of acclimation responses. Contrary to some studies no obvious beneficial effects of moderate temperature fluctuation were observed. Instead, yellow dung flies seem to canalize development in the face of temperature fluctuation up to a point when detrimental effects become unavoidable. The relatively greater effects of extreme constant developmental temperatures question their biological relevance in experiments.

  12. Comparing density, electron temperature, and magnetic fluctuations with gyrokinetic simulations using new synthetic diagnostics (United States)

    Ernst, D. R.; Bergerson, W.; Ennever, P.; Greenwald, M.; Hubbard, A.; Irby, J.; Phillips, P.; Porkolab, M.; Rowan, W.; Terry, J. L.; Xu, P.; Alcator C-Mod Team


    Three new synthetic turbulence diagnostics are implemented in GS2 and compared with measurements: phase contrast imaging, polarimetry, and electron-cyclotron (ECE) emission. Our new synthetic diagnostic framework is based on transforming to a real-space annulus in Cartesian coordinates. This allows straightforward convolution with diagnostic point-spread functions, or integration over viewing chords. Wavenumber spectra and fluctuation amplitudes, as well as transport fluxes, are compared with measurements. Both phase contrast imaging and newly observed ECE electron temperature fluctuations, closely follow the electron temperature in an internal transport barrier during on-axis heating pulses, consistent with the role of TEM turbulence. New C-Mod polarimetry measurements, showing strong broadband core magnetic fluctuations, will also be examined against gyrokinetic simulations. The new framework is readily extended to other fluctuation measurements such as two-color interferometry, beam emission spectroscopy, Doppler back-scattering, ECE imaging, and microwave imaging reflectometry. Supported by U.S. DoE awards DE-FC02-08ER54966, DE-FC02-99ER54512, DE-FG03-96ER54373.

  13. Temperature reconstruction from the length fluctuations of small glaciers in the eastern Alps (northeastern Italy) (United States)

    Zecchetto, Stefano; Serandrei-Barbero, Rossana; Donnici, Sandra


    In this study, a linear model computing the air temperature fluctuations from the measured glacier snout fluctuations has been applied, for the first time, to three small glaciers in the western Tauern Alps (eastern Alps) in the period 1929-2011. The considered glaciers, with areas between 0.2 and 1.3 km^2, are characterized by relevant time variations of their morphology, length and slope. The model requires the knowledge of two parameters: the glacier climate sensitivity C_s and the glacier response time τ, both depending on the glacier morphological characteristics and on the precipitation. Applied to the glaciers assuming C_s and τ as in the original formulation, it underestimates the temperature increase of {≈ } 1.8°C derived over the whole period from the in situ data. Given the characteristics of these small glaciers, these parameters have been recalibrated by means of a non-linear least-square regression using an independent set of glaciers. Their mean value is of about 210 m/K and 3.8 years respectively. With the recalibrated values of the new glacier climate sensitivity C^*_s and response time τ ^*, the temperature fluctuations derived by the model reproduce well those obtained from the observed temperatures computed over the hydrological year, with linear correlations between 0.8 and 0.9. The increase of the modeled mean temperature over the whole period fits in with that derived from observed temperature. Considering that the length fluctuations of these small glaciers affect significantly their slope and length, we tested the impact in the model of a time dependent formulation of C_s and τ: the results indicate slight improvements both in the values of the correlation between the reconstructed and the observed temperature fluctuations and in the global temperature increase. Given the above value of climate sensitivity, the large retreat of the small alpine glaciers threatens their survival within a few decades, but the morphological changes in

  14. Does incubation temperature fluctuation influence hatchling phenotypes in reptiles? A test using parthenogenetic geckos. (United States)

    Andrewartha, Sarah J; Mitchell, Nicola J; Frappell, Peter B


    Many lineages of parthenogenetic organisms have persisted through significant environmental change despite the constraints imposed by their fixed genotype and limited evolutionary potential. The ability of parthenogens to occur sympatrically with sexual relatives may in part be due to phenotypic plasticity in their responses to their environment, especially with respect to incubation temperature--a maternally selected trait. Here we measured the incubation temperatures selected by two lineages of triploid parthenogenic geckos in the Heteronotia binoei complex by allowing them to deposit clutches along a thermal gradient. The average nest temperature selected was 28.4 degrees C, with no significant differences between parthenogenic races or individual clones. To investigate the effect of nest-temperature variability on physiological and morphological traits, we incubated eggs from different races at one of four incubation regimes (32 degrees +/- 0 degrees, +/- 3 degrees , +/- 5 degrees , or +/- 9 degrees C). Embryos incubated at constant 32 degrees C developed faster than embryos reared under increasing extremes of diel temperature fluctuation (+/- 3 degrees , +/- 5 degrees C), and incubation at 32 degrees +/- 9 degrees C was unsuccessful. Incubation regime had no effect on the body size, preferred substrate temperature, or mass-specific .V(O2) of hatchlings. However, parthenogenic race had a significant effect on egg mass, tail length, snout-to-vent length, total length, and .V(O2) . We conclude that developmental traits are strongly influenced by clonal genotypes in this parthenogenic complex but are well buffered against fluctuations in incubation temperature.

  15. Response of New zealand mudsnails Potamopyrgus antipodarum to freezing and near freezing fluctuating water temperatures (United States)

    Moffitt, Christine M.; James, Christopher A.


    We explored the resilience of the invasive New Zealand mudsnail Potamopyrgus antipodarum to fluctuating winter freezing and near-freezing temperature cycles in laboratory tests. Our goal was to provide data to confirm field observations of mortality and presumed mortality in stream habitats with fluctuating freezing to near-freezing temperatures. We tested individuals from 2 locations with distinctly different thermal regimes and population densities. One location had low snail densities and water temperatures with strong diel and seasonal water variation. The other location had high snail densities and nearly constant water temperatures. Groups of individuals from both locations were tested in each of 3 laboratory-created diel thermal cycles around nominal temperatures of 0, 2, or 4°C. Mortality occurred in cycles around 0°C in both populations, and little to no mortality occurred at temperatures >0°C. Individuals from both sources held in diel 0°C cycles for 72 h showed 100% mortality. Our findings support observations from published field studies that survival was limited in infested habitats subject to freezing temperatures.

  16. Analysis of Numerical Simulation Database for Pressure Fluctuations Induced by High-Speed Turbulent Boundary Layers (United States)

    Duan, Lian; Choudhari, Meelan M.


    Direct numerical simulations (DNS) of Mach 6 turbulent boundary layer with nominal freestream Mach number of 6 and Reynolds number of Re(sub T) approximately 460 are conducted at two wall temperatures (Tw/Tr = 0.25, 0.76) to investigate the generated pressure fluctuations and their dependence on wall temperature. Simulations indicate that the influence of wall temperature on pressure fluctuations is largely limited to the near-wall region, with the characteristics of wall-pressure fluctuations showing a strong temperature dependence. Wall temperature has little influence on the propagation speed of the freestream pressure signal. The freestream radiation intensity compares well between wall-temperature cases when normalized by the local wall shear; the propagation speed of the freestream pressure signal and the orientation of the radiation wave front show little dependence on the wall temperature.

  17. Measurements of density, temperature, and their fluctuations in turbulent supersonic flow using UV laser spectroscopy (United States)

    Fletcher, Douglas G.; Mckenzie, R. L.


    Nonintrusive measurements of density, temperature, and their turbulent fluctuation levels were obtained in the boundary layer of an unseeded, Mach 2 wind tunnel flow. The spectroscopic technique that was used to make the measurements is based on the combination of laser-induced oxygen fluorescence and Raman scattering by oxygen and nitrogen from the same laser pulse. Results from this demonstration experiment are compared with previous measurements obtained in the same facility using conventional probes and an earlier spectroscopic technique. Densities and temperatures measured with the current technique agree with the previous surveys to within 3 percent and 2 percent, respectively. The fluctuation amplitudes for both variables agree with the measurements obtained using the earlier spectroscopic technique and show evidence of an unsteady, weak shock wave that perturbs the boundary layer.

  18. Measurement of turbulent electron temperature fluctuations on the ASDEX Upgrade tokamak using correlated electron cyclotron emission

    Energy Technology Data Exchange (ETDEWEB)

    Freethy, S. J., E-mail: [Max Planck Institute for Plasma Physics, 85748 Garching (Germany); Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Conway, G. D.; Happel, T.; Köhn, A. [Max Planck Institute for Plasma Physics, 85748 Garching (Germany); Classen, I.; Vanovac, B. [FOM Institute DIFFER, 5612 AJ Eindhoven (Netherlands); Creely, A. J.; White, A. E. [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)


    Turbulent temperature fluctuations are measured on the ASDEX Upgrade tokamak using pairs of closely spaced, narrow-band heterodyne radiometer channels and a standard correlation technique. The pre-detection spacing and bandwidth of the radiometer channel pairs is chosen such that they are physically separated less than a turbulent correlation length, but do not overlap. The radiometer has 4 fixed filter frequency channels and two tunable filter channels for added flexibility in the measurement position. Relative temperature fluctuation amplitudes are observed in a helium plasma to be δT/T = (0.76 ± 0.02)%, (0.67 ± 0.02)%, and (0.59 ± 0.03)% at normalised toroidal flux radius of ρ{sub tor} = 0.82, 0.75, and 0.68, respectively.

  19. Metabolic rate and oxidative stress in insects exposed to low temperature thermal fluctuations. (United States)

    Lalouette, L; Williams, C M; Hervant, F; Sinclair, B J; Renault, D


    Fluctuating temperatures are a predominant feature of the natural environment but their effects on ectotherm physiology are not well-understood. The warm periods of fluctuating thermal regimes (FTRs) provide opportunities for repair leading to increased survival, but there are also indications of negative effects of warm exposure. In this study, we examined respiration and oxidative stress in adult Alphitobius diaperinus exposed to FTRs and to constant low temperatures. We hypothesized that cold exposure will cause oxidative stress and that FTRs would reduce the amount of chill injuries, via activation of the antioxidant system. We measured V˙CO2, activities of super oxide dismutase (SOD), amounts of total (GSHt) and oxidized glutathione (GSSG) during cold and warm periods of FTRs. Increased severity of cold exposure caused a decrease in the glutathione pool. SOD levels increased during the recovery period in the more severe FTR. The antioxidant response was sufficient to counter the reactive oxygen species production, as the GSH:GSSG ratio increased. We conclude that cold stress causes oxidative damage in these beetles, and that a warm recovery period activates the antioxidant system allowing repair of cold-induced damage, leading to the increased survival previously noted in beetles exposed to fluctuating versus constant temperatures. Copyright © 2010 Elsevier Inc. All rights reserved.

  20. Thermal fluctuations of haemoglobin from different species: adaptation to temperature via conformational dynamics (United States)

    Stadler, A. M.; Garvey, C. J.; Bocahut, A.; Sacquin-Mora, S.; Digel, I.; Schneider, G. J.; Natali, F.; Artmann, G. M.; Zaccai, G.


    Thermodynamic stability, configurational motions and internal forces of haemoglobin (Hb) of three endotherms (platypus, Ornithorhynchus anatinus; domestic chicken, Gallus gallus domesticus and human, Homo sapiens) and an ectotherm (salt water crocodile, Crocodylus porosus) were investigated using circular dichroism, incoherent elastic neutron scattering and coarse-grained Brownian dynamics simulations. The experimental results from Hb solutions revealed a direct correlation between protein resilience, melting temperature and average body temperature of the different species on the 0.1 ns time scale. Molecular forces appeared to be adapted to permit conformational fluctuations with a root mean square displacement close to 1.2 Å at the corresponding average body temperature of the endotherms. Strong forces within crocodile Hb maintain the amplitudes of motion within a narrow limit over the entire temperature range in which the animal lives. In fully hydrated powder samples of human and chicken, Hb mean square displacements and effective force constants on the 1 ns time scale showed no differences over the whole temperature range from 10 to 300 K, in contrast to the solution case. A complementary result of the study, therefore, is that one hydration layer is not sufficient to activate all conformational fluctuations of Hb in the pico- to nanosecond time scale which might be relevant for biological function. Coarse-grained Brownian dynamics simulations permitted to explore residue-specific effects. They indicated that temperature sensing of human and chicken Hb occurs mainly at residues lining internal cavities in the β-subunits. PMID:22696485

  1. Rapid fluctuations of the air and surface temperature in the city of Bucharest (Romania) (United States)

    Cheval, Sorin; Dumitrescu, Alexandru; Hustiu, Mihaita-Cristinel


    Urban areas derive significant changes of the ambient temperature generating specific challenges for society and infrastructure. Extreme temperature events, heat and cold waves affect the human comfort, increase the health risk, and require specific building regulations and emergency preparedness, strongly related to the magnitude and frequency of the thermal hazards. Rapid changes of the temperature put a particular stress for the urban settlements, and the topic has been approached constantly in the scientific literature. Due to its geographical position in a plain area with a temperate climate and noticeable continental influence, the city of Bucharest (Romania) deals with high seasonal and daily temperature variations. However, rapid fluctuations also occur at sub-daily scale caused by cold or warm air advections or by very local effects (e.g. radiative heat exchange, local precipitation). For example, in the area of Bucharest, the cold fronts of the warm season may trigger temperature decreasing up to 10-15 centigrades / hour, while warm advections lead to increasing of 1-2 centigrades / hour. This study focuses on the hourly and sub-hourly temperature variations over the period November 2014 - February 2016, using air temperature data collected from urban sensors and meteorological stations of the national network, and land surface temperature data obtained from satellite remote sensing. The analysis returns different statistics, such as magnitude, intensity, frequency, simultaneous occurrence and areal coverage of the rapid temperature fluctuations. Furthermore, the generating factors for each case study are assessed, and the results are used to define some preliminary patterns and enhance the urban temperature forecast at fine scale. The study was funded by the Romanian Programme Partnership in Priority Domains, PN - II - PCCA - 2013 - 4 - 0509 - Reducing UHI effects to improve urban comfort and balance energy consumption in Bucharest (REDBHI).

  2. Temperature dependence of the single photon emission from interface-fluctuation GaN quantum dots. (United States)

    Le Roux, F; Gao, K; Holmes, M; Kako, S; Arita, M; Arakawa, Y


    The temperature dependent single photon emission statistics of interface-fluctuation GaN quantum dots are reported. Quantum light emission is confirmed at temperatures up to ~77 K, by which point the background emission degrades the emission purity and results in a measured g(2) (0) in excess of 0.5. A discussion on the extent of the background contamination is also given through comparison to extensive data taken under various ambient and experimental conditions, revealing that the quantum dots themselves are emitting single photons with high purity.

  3. The Effect of Fluctuating Temperatures During Development on Fitness-Related Traits of Scatophaga stercoraria (Diptera: Scathophagidae)


    Kjærsgaard, Anders; Pertoldi, Cino; Loeschcke, Volker; Wolf U. Blanckenhorn


    Development of ectotherms is highly temperature dependent. Studies using variable thermal environments can improve ecological relevance of data because organisms naturally face day-to-day stochastic temperature fluctuations as well as seasonal changes in the amplitude of such daily fluctuations. The objective of this study was to investigate if, and to what extent, the use of constant temperatures is justified in studies of the model species, yellow dung fly, Scatophaga stercoraria (L.). We e...

  4. Limits to the thermal tolerance of corals adapted to a highly fluctuating, naturally extreme temperature environment (United States)

    Schoepf, Verena; Stat, Michael; Falter, James L.; McCulloch, Malcolm T.


    Naturally extreme temperature environments can provide important insights into the processes underlying coral thermal tolerance. We determined the bleaching resistance of Acropora aspera and Dipsastraea sp. from both intertidal and subtidal environments of the naturally extreme Kimberley region in northwest Australia. Here tides of up to 10 m can cause aerial exposure of corals and temperatures as high as 37 °C that fluctuate daily by up to 7 °C. Control corals were maintained at ambient nearshore temperatures which varied diurnally by 4-5 °C, while treatment corals were exposed to similar diurnal variations and heat stress corresponding to ~20 degree heating days. All corals hosted Symbiodinium clade C independent of treatment or origin. Detailed physiological measurements showed that these corals were nevertheless highly sensitive to daily average temperatures exceeding their maximum monthly mean of ~31 °C by 1 °C for only a few days. Generally, Acropora was much more susceptible to bleaching than Dipsastraea and experienced up to 75% mortality, whereas all Dipsastraea survived. Furthermore, subtidal corals, which originated from a more thermally stable environment compared to intertidal corals, were more susceptible to bleaching. This demonstrates that while highly fluctuating temperatures enhance coral resilience to thermal stress, they do not provide immunity to extreme heat stress events.

  5. Thermal analysis of optical reference cavities for low sensitivity to environmental temperature fluctuations. (United States)

    Dai, Xiaojiao; Jiang, Yanyi; Hang, Chao; Bi, Zhiyi; Ma, Longsheng


    The temperature stability of optical reference cavities is significant in state-of-the-art ultra-stable narrow-linewidth laser systems. In this paper, the thermal time constant and thermal sensitivity of reference cavities are analyzed when reference cavities respond to environmental perturbations via heat transfer of thermal conduction and thermal radiation separately. The analysis as well as simulation results indicate that a reference cavity enclosed in multiple layers of thermal shields with larger mass, higher thermal capacity and lower emissivity is found to have a larger thermal time constant and thus a smaller sensitivity to environmental temperature perturbations. The design of thermal shields for reference cavities may vary according to experimentally achievable temperature stability and the coefficient of thermal expansion of reference cavities. A temperature fluctuation-induced length instability of reference cavities as low as 6 × 10(-16) on a day timescale can be achieved if a two-layer thermal shield is inserted between a cavity with the coefficient of thermal expansion of 1 × 10(-10) /K and an outer vacuum chamber with temperature fluctuation amplitude of 1 mK and period of 24 hours.

  6. The spoilage of air-packaged broiler meat during storage at normal and fluctuating storage temperatures. (United States)

    Zhang, Q Q; Han, Y Q; Cao, J X; Xu, X L; Zhou, G H; Zhang, W Y


    Bacterial diversity and the major flora present on air-packaged broiler meat during storage at normal (4°C) and fluctuating storage temperatures (0-4°C and 4-10°C) were investigated using culture-dependent and culture-independent approaches. Culture-dependent analysis revealed that the growth of microflora was retarded when broiler meat was stored at lower temperatures (0-4°C). Denaturing gradient gel electrophoresis profiles showed that Staphylococcus spp., Pseudomonas spp., Acinetobacter spp., Carnobacterium spp., Aeromonas spp., and Weissella spp. were the dominant bacteria throughout all storage conditions. Enterobacteriaceae only appeared in samples subjected to storage with high temperature abuse, whereas Shewanella spp. and Psychrobacter spp. were only detected in samples stored below 4°C. Our results provide evidence that, compared with storage at a standard fixed temperature (4°C), fluctuations in temperatures induce a more complex bacterial diversity in the air-packaged broiler.

  7. Effects of non-equilibrium angle fluctuation on F1-ATPase kinetics induced by temperature increase. (United States)

    Tamiya, Yuji; Watanabe, Rikiya; Noji, Hiroyuki; Li, Chun-Biu; Komatsuzaki, Tamiki


    F 1 -ATPase (F 1 ) is an efficient rotary protein motor, whose reactivity is modulated by the rotary angle to utilize thermal fluctuation. In order to elucidate how its kinetics are affected by the change in the fluctuation, we have extended the reaction-diffusion formalism [R. Watanabe et al., Biophys. J., 2013, 105, 2385] applicable to a wider range of temperatures based on experimental data analysis of F 1 derived from thermophilic Bacillus under high ATP concentration conditions. Our simulation shows that the rotary angle distribution manifests a stronger non-equilibrium feature as the temperature increases, because ATP hydrolysis and P i release are more accelerated compared with the timescale of rotary angle relaxation. This effect causes the rate coefficient obtained from dwell time fitting to deviate from the Arrhenius relation in P i release, which has been assumed in the previous activation thermodynamic quantities estimation using linear Arrhenius fitting. Larger negative correlation is also found between hydrolysis and P i release waiting time in a catalytic dwell with the increase in temperature. This loss of independence between the two successive reactions at the catalytic dwell sheds doubt on the conventional dwell time fitting to obtain rate coefficients with a double exponential function at temperatures higher than 65 °C, which is close to the physiological temperature of the thermophilic Bacillus.

  8. Effects of rf power on electron density and temperature, neutral temperature, and Te fluctuations in an inductively coupled plasma (United States)

    Camparo, James; Fathi, Gilda


    Atomic clocks that fly on global-navigation satellites such as global positioning system (GPS) and Galileo employ light from low-temperature, inductively coupled plasmas (ICPs) for atomic signal generation and detection (i.e., alkali/noble-gas rf-discharge lamps). In this application, the performance of the atomic clock and the capabilities of the navigation system depend sensitively on the stability of the ICP's optical emission. In order to better understand the mechanisms that might lead to instability in these rf-discharge lamps, and hence the satellite atomic clocks, we studied the optical emission from a Rb/Xe ICP as a function of the rf power driving the plasma. Surprisingly, we found that the electron density in the plasma was essentially independent of increases in rf power above its nominal value (i.e., "rf-power gain") and that the electron temperature was only a slowly varying function of rf-power gain. The primary effect of rf power was to increase the temperature of the neutrals in the plasma, which was manifested by an increase in Rb vapor density. Interestingly, we also found evidence for electron temperature fluctuations (i.e., fluctuations in the plasma's high-energy electron content). The variance of these fluctuations scaled inversely with the plasma's mean electron temperature and was consistent with a simple model that assumed that the total electron density in the discharge was independent of rf power. Taken as a whole, our results indicate that the electrons in alkali/noble-gas ICPs are little affected by slight changes in rf power and that the primary effect of such changes is to heat the plasma's neutral species.

  9. Quasi-optical design for systems to diagnose the electron temperature and density fluctuations on EAST

    Energy Technology Data Exchange (ETDEWEB)

    Cao, Qifo; Liu, Yong; Zhao, Hailin, E-mail:; Zhou, Tianfu; Ti, Ang; Hu, Liqun [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China)


    A system to simultaneously diagnose the electron temperature and density fluctuations is proposed for Experimental Advanced Superconducting Tokamak device. This system includes a common quasi-optical antenna, a correlation electron cyclotron emission (CECE) system that is used to measure the electron temperature fluctuations and a Doppler backscattering (DBS) system that is used to measure the electron density fluctuations. The frequency range of the proposed CECE system is 108-120 GHz, and this corresponds to a radial coverage of normalized radius ((R − R{sub 0})/a, R{sub 0} = 1850 mm, a = 450 mm) from 0.2 to 0.67 for the plasma operation with a toroidal magnetic field of 2.26 T. This paper focuses on the design of the quasi-optical antenna and aims at optimizing the poloidal resolution for different frequency bands. An optimum result gives the beam radius for the CECE system of 13-15 mm and this corresponds to a wave number range of k{sub θ} < 2.4 cm{sup −1}. The beam radius is 20-30 mm for V band (50-75 GHz) and 15-20 mm for W band (75-110 GHz).

  10. Survival of rapidly fluctuating natural low winter temperatures by High Arctic soil invertebrates

    DEFF Research Database (Denmark)

    Convey, Peter; Abbandonato, Holly; Bergan, Frode


    The extreme polar environment creates challenges for its resident invertebrate communities and the stress tolerance of some of these animals has been examined over many years. However, although it is well appreciated that standard air temperature records often fail to describe accurately conditio...... polar soil invertebrate community may be robust to at least one important predicted consequence of projected climate change....... may insulate terrestrial habitats from extreme air temperature fluctuations. Further, climate projections suggest large changes in precipitation will occur in the polar regions, with the greatest changes expected during the winter period and, hence, implications for the insulation of overwintering...... microhabitats. To assess survival of natural High Arctic soil invertebrate communities contained in soil and vegetation cores to natural winter temperature variations, the overwintering temperatures they experienced were manipulated by deploying cores in locations with varying snow accumulation: No Snow...

  11. Nest temperature fluctuations in a cavity nester, the southern ground-hornbill. (United States)

    Combrink, L; Combrink, H J; Botha, A J; Downs, C T


    Southern ground-hornbills Bucorvus leadbeateri inhabit savanna and bushveld regions of South Africa. They nest in the austral summer, which coincides with the wet season and hottest daytime temperatures in the region. They are secondary cavity nesters and typically nest in large cavities in trees, cliffs and earth banks, but readily use artificial nest boxes. Southern ground-hornbills are listed as Endangered in South Africa, with reintroductions into suitable areas highlighted as a viable conservation intervention for the species. Nest microclimate, and the possible implications this may have for the breeding biology of southern ground-hornbills, have never been investigated. We used temperature dataloggers to record nest cavity temperature and ambient temperature for one artificial and 11 natural southern ground-hornbill tree cavity nests combined, spanning two breeding seasons. Mean hourly nest temperature, as well as mean minimum and mean maximum nest temperature, differed significantly between southern ground-hornbill nests in both breeding seasons. Mean nest temperature also differed significantly from mean ambient temperature for both seasons. Natural nest cavities provided a buffer against the ambient temperature fluctuations. The artificial nest provided little insulation against temperature extremes, being warmer and cooler than the maximum and minimum local ambient temperatures, respectively. Nest cavity temperature was not found to have an influence on the breeding success of the southern ground-hornbill groups investigated in this study. These results have potentially important implications for southern ground-hornbill conservation and artificial nest design, as they suggest that the birds can tolerate greater nest cavity temperature extremes than previously thought. Copyright © 2017 Elsevier Ltd. All rights reserved.

  12. Survival of rapidly fluctuating natural low winter temperatures by High Arctic soil invertebrates. (United States)

    Convey, Peter; Abbandonato, Holly; Bergan, Frode; Beumer, Larissa Teresa; Biersma, Elisabeth Machteld; Bråthen, Vegard Sandøy; D'Imperio, Ludovica; Jensen, Christina Kjellerup; Nilsen, Solveig; Paquin, Karolina; Stenkewitz, Ute; Svoen, Mildrid Elvik; Winkler, Judith; Müller, Eike; Coulson, Stephen James


    The extreme polar environment creates challenges for its resident invertebrate communities and the stress tolerance of some of these animals has been examined over many years. However, although it is well appreciated that standard air temperature records often fail to describe accurately conditions experienced at microhabitat level, few studies have explicitly set out to link field conditions experienced by natural multispecies communities with the more detailed laboratory ecophysiological studies of a small number of 'representative' species. This is particularly the case during winter, when snow cover may insulate terrestrial habitats from extreme air temperature fluctuations. Further, climate projections suggest large changes in precipitation will occur in the polar regions, with the greatest changes expected during the winter period and, hence, implications for the insulation of overwintering microhabitats. To assess survival of natural High Arctic soil invertebrate communities contained in soil and vegetation cores to natural winter temperature variations, the overwintering temperatures they experienced were manipulated by deploying cores in locations with varying snow accumulation: No Snow, Shallow Snow (30 cm) and Deep Snow (120 cm). Air temperatures during the winter period fluctuated frequently between +3 and -24 °C, and the No Snow soil temperatures reflected this variation closely, with the extreme minimum being slightly lower. Under 30 cm of snow, soil temperatures varied less and did not decrease below -12 °C. Those under deep snow were even more stable and did not decline below -2 °C. Despite these striking differences in winter thermal regimes, there were no clear differences in survival of the invertebrate fauna between treatments, including oribatid, prostigmatid and mesostigmatid mites, Araneae, Collembola, Nematocera larvae or Coleoptera. This indicates widespread tolerance, previously undocumented for the Araneae, Nematocera or Coleoptera, of

  13. Determination of humidity and temperature fluctuations based on MOZAIC data and parametrisation of persistent contrail coverage for general circulation models

    Directory of Open Access Journals (Sweden)

    K. M. Gierens


    Full Text Available Humidity and temperature fluctuations at pressure levels between 166 and 290 hPa on the grid scale of general circulation models for a region covered by the routes of airliners, mainly over the Atlantic, have been determined by evaluation of the data obtained with almost 2000 flights within the MOZAIC programme. It is found that the distributions of the fluctuations cannot be modelled by Gaussian distributions, because large fluctuations appear with a relatively high frequency. Lorentz distributions were used for the analytical representation of the fluctuation distributions. From these a joint probability distribution has been derived for simultaneous temperature and humidity fluctuations. This function together with the criteria for the formation and persistence of contrails are used to derive the maximum possible fractional coverage of persistent contrails in a grid cell of a GCM. This can be employed in a statistical formulation of contrail appearance in a climate model.

  14. Determination of humidity and temperature fluctuations based on MOZAIC data and parametrisation of persistent contrail coverage for general circulation models

    Directory of Open Access Journals (Sweden)

    K. M. Gierens

    Full Text Available Humidity and temperature fluctuations at pressure levels between 166 and 290 hPa on the grid scale of general circulation models for a region covered by the routes of airliners, mainly over the Atlantic, have been determined by evaluation of the data obtained with almost 2000 flights within the MOZAIC programme. It is found that the distributions of the fluctuations cannot be modelled by Gaussian distributions, because large fluctuations appear with a relatively high frequency. Lorentz distributions were used for the analytical representation of the fluctuation distributions. From these a joint probability distribution has been derived for simultaneous temperature and humidity fluctuations. This function together with the criteria for the formation and persistence of contrails are used to derive the maximum possible fractional coverage of persistent contrails in a grid cell of a GCM. This can be employed in a statistical formulation of contrail appearance in a climate model.

  15. On temperature control of buildings by adobe wall design: Duffin ...

    African Journals Online (AJOL)

    Duffin and Knowles (Solar Energy, Vol. 27(3), 1981) developed ... The modelled electrical system and the derived formula for the real attenuation factor of the wall have been critically examined and then modified by taking into cognisance the true conceptualisation of a physical filter network as analogue of the thermal wall.

  16. Temperature fluctuation and heat capacity in relativistic heavy-ion collisions

    CERN Document Server

    Ma, Guo Liang; Chen Jin Gen; He Ze-Jun; Long Jia-Li; Lu Zhao-Hui; Ma Yu-Gang; Sá Ben-Hao; Shen Wen-Qing; Wang Kun; Wei Yi-Bin; Zhang Hu-Yong; Zhong Chen


    We used LUCIAE3.0 model to simulate the Pb+Pb and C+C in SPS energy. The heat capacity was then extracted from event-by-event temperature fluctuation. It is found that the heat capacity per hadron multiplicity decreases with the increasing of beam energy and impact parameter for a given reaction system. While the hadron mass increases, the heat capacity per hadron multiplicity rises. In addition, we found that, for a given hadron, the heat capacity per hadron multiplicity is almost the same regardless of the reaction system. Some discussions were also given.

  17. Mathematical model of the growth of a mollusk affected by a toxicant and by temperature fluctuations

    Energy Technology Data Exchange (ETDEWEB)

    Kurchenko, T.S.; Burtnaya, I.L.


    An attempt is made to model the effect of a gamma isomer of hexachloran (lindane) and of temperature fluctuations on the growth of bivalves. The model is based on an experimental study of the effect of the toxicant on Radix ovata and Viviparus viviparus, and also on the Putter-Bertalanffy-Vinberg models and the model of Zotin. Quite good agreements has been obtained between calculated and experimental data, and growth curves have been constructed for the weight increase of the animals when exposed to lindane concentrations not tested in the experiment.

  18. Toxin production and growth of pathogens subjected to temperature fluctuations simulating consumer handling of cold cuts. (United States)

    Røssvoll, Elin; Rønning, Helene Thorsen; Granum, Per Einar; Møretrø, Trond; Hjerpekjøn, Marianne Røine; Langsrud, Solveig


    It is crucial for the quality and safety of ready-to-eat (RTE) foods to maintain the cold chain from production to consumption. The effect of temperature abuse related to daily meals and elevated refrigerator temperatures on the growth and toxin production of Bacillus cereus, Bacillus weihenstephanensis and Staphylococcus aureus and the growth of Listeria monocytogenes and Yersinia enterocolitica was studied. A case study with temperature loggings in the domestic environment during Easter and Christmas holidays was performed to select relevant time and temperature courses. A model for bacterial surface growth on food using nutrient agar plates exposed to variations in temperatures was used to simulate food stored at different temperatures and exposed to room temperature for short periods of time. The results were compared with predicted growth using the modeling tool ComBase Predictor. The consumers exposed their cold cuts to room temperatures as high as 26.5°C with an average duration of meals was 47 min daily for breakfast/brunch during the vacations. Short (≤ 2 h) daily intervals at 25°C nearly halved the time the different pathogens needed to reach levels corresponding to the levels associated with human infection or intoxication, compared with the controls continuously stored at refrigerator temperature. Although the temperature fluctuations affected growth of both B. weihenstephanensis and S. aureus, toxin production was only detected at much higher cell concentrations than what has been associated with human intoxications. Therefore, growth of L. monocytogenes and Y. enterocolitica was found to be the limiting factor for safety. In combination with data on temperature abuse in the domestic environment, modeling programs such as ComBase Predictor can be efficient tools to predict growth of some pathogens but will not predict toxin production. Copyright © 2014 Elsevier B.V. All rights reserved.

  19. Current-driven and field-driven domain walls at nonzero temperature

    NARCIS (Netherlands)

    Lucassen, M.E.|info:eu-repo/dai/nl/314406913; van Driel, H.J.|info:eu-repo/dai/nl/315885114; de Morais Smith, C.|info:eu-repo/dai/nl/304836346; Duine, R.A.|info:eu-repo/dai/nl/304830127


    We present a model for the dynamics of current-driven and field-driven domain-wall lines at nonzero temperature. We compute thermally averaged drift velocities from the Fokker-Planck equation that describes the nonzero-temperature dynamics of the domain wall. As special limits of this general

  20. Impact of constant versus fluctuating temperatures on the development and life history parameters of Tetranychus urticae (Acari: Tetranychidae). (United States)

    Bayu, M S Y I; Ullah, M S; Takano, Y; Gotoh, T


    The impact of daily temperature fluctuations on arthropod life history parameters is inadequately studied compared with the ample amount of research that has been conducted on the effects of constant temperatures. Fluctuating temperatures are likely to be more realistic, as they are ecologically more similar to what these arthropods experience in nature. Here, we compared the impact of 11 constant temperatures that ranged from 10 to 35 °C with fluctuating temperatures with the same corresponding mean temperature and an amplitude of 10 °C between high (12 h) and low (12 h) temperatures on the development and life history parameters of Tetranychus urticae under continuous light conditions. No eggs hatched at constant 10 °C, whereas 81.5% of eggs successfully completed development at fluctuating 10 °C (15/5 °C). Egg-to-female adult development was faster under fluctuating temperatures from 12.5 to 27.5 °C than under constant temperatures, whereas the opposite trend was observed at >30 °C. The lower thermal thresholds (T) were 11.63 and 8.63 °C, and thermal constants (K) were 127.81 and 150.69 degree-days for egg-to-female adults at constant and fluctuating temperatures, respectively. The numbers of oviposition days were significantly higher at fluctuating 15 °C than at the corresponding constant temperature, whereas the opposite trend was observed from 20 to 30 °C. The intrinsic rate of increase (r) was higher at fluctuating than at constant 15 °C. The net reproductive rate (R 0) was also higher at fluctuating than at constant 15 and 35 °C, but showed an opposite trend at 20 and 25 °C. We conclude that fluctuating temperatures should be considered to accurately predict spider mite population dynamics in nature.

  1. Temperature compensation of [u-C]glucose incorporation by microbial communities in a river with a fluctuating thermal regime. (United States)

    Witzel, K P


    In summer, the river Saar in the southwest of Germany exhibits distinct temperature fluctuations from 8 degrees C at the source to nearly 30 degrees C in the middle region. Temperature optima for bacterial plate counts and the uptake velocity of [U-C]glucose by the natural microbial communities of different regions ranged from 20 to 30 degrees C, which is significantly above the mean annual water temperature. A correlation between temperature optima and different seasons or habitats was not observed. Despite the relatively high temperature optima, the turnover time for glucose was shortest at temperatures around the mean annual water temperature, due to changes in the substrate affinity. At limiting substrate concentrations, the higher substrate affinity at lower temperatures may lead to a higher real activity at in situ temperatures, and a compensatory stabilization of uptake rates at fluctuating temperatures is possible.

  2. Statistics of velocity and temperature fluctuations in two-dimensional Rayleigh-Bénard convection (United States)

    Zhang, Yang; Huang, Yong-Xiang; Jiang, Nan; Liu, Yu-Lu; Lu, Zhi-Ming; Qiu, Xiang; Zhou, Quan


    We investigate fluctuations of the velocity and temperature fields in two-dimensional (2D) Rayleigh-Bénard (RB) convection by means of direct numerical simulations (DNS) over the Rayleigh number range 106≤Ra≤1010 and for a fixed Prandtl number Pr=5.3 and aspect ratio Γ =1 . Our results show that there exists a counter-gradient turbulent transport of energy from fluctuations to the mean flow both locally and globally, implying that the Reynolds stress is one of the driving mechanisms of the large-scale circulation in 2D turbulent RB convection besides the buoyancy of thermal plumes. We also find that the viscous boundary layer (BL) thicknesses near the horizontal conducting plates and near the vertical sidewalls, δu and δv, are almost the same for a given Ra, and they scale with the Rayleigh and Reynolds numbers as ˜Ra-0.26±0.03 and ˜Re-0.43±0.04 . Furthermore, the thermal BL thickness δθ defined based on the root-mean-square (rms) temperature profiles is found to agree with Prandtl-Blasius predictions from the scaling point of view. In addition, the probability density functions of turbulent energy ɛu' and thermal ɛθ' dissipation rates, calculated, respectively, within the viscous and thermal BLs, are found to be always non-log-normal and obey approximately a Bramwell-Holdsworth-Pinton distribution first introduced to characterize rare fluctuations in a confined turbulent flow and critical phenomena.

  3. Thermodynamic Critical Field and Superconducting Fluctuation of Vortices for High Temperature Cuprate Superconductor: La-214

    Energy Technology Data Exchange (ETDEWEB)

    Finnemore, Douglas K. [Iowa State Univ., Ames, IA (United States)


    Thermodynamics has been studied systematically for the high temperature cuprate superconductor La2-xSrxCuO4-δ, La-214, in the entire superconductive region from strongly underdoped to strongly overdoped regimes. Magnetization studies with H $\\parallel$ c have been made in order to investigate the changes in free energy of the system as the number of carriers is reduced. Above the superconducting transition temperature, the normal-state magnetization exhibits a two-dimensional Heisenberg antiferromagnetic behavior. Below Tc, magnetization data are thermodynamically reversible over large portions of the H-T plane, so the free energy is well defined in these regions. As the Sr concentration is varied over the wide range from 0.060 (strongly underdoped) to 0.234 (strongly overdoped), the free energy change goes through a maximum at the optimum doped in a manner similar to the Tc0 vs. x curve. The density of states, N(0), remains nearly constant in the overdoped and optimum doped regimes, taking a broad maximum around x = 0.188, and then drops abruptly towards zero in the underdoped regime. The La2-xSrxCuO4 (La-214) system displays the fluctuating vortex behavior with the characteristic of either 2D or 3D fluctuations as indicated by clearly identifiable crossing points T* close to Tc. The dimensional character of the fluctuations depends on both applied magnetic fields and the density of charge carriers. The dimensional crossover from 2D to 3D occurs in the strongly underdoped regime when the c-axis coherence distance ξc becomes comparable to the spacing between adjacent CuO2 layers s at sufficiently high magnetic field near Hc2.

  4. Wall sticking of high water-cut crude oil transported at temperatures below the gel point (United States)

    Zheng, Haimin; Huang, Qiyu; Wang, Changhui


    Some high water-cut crude oils can flow in the temperature below the oil gel point, while oil particles may adhere to the pipe wall as paste; this process is known as ‘wall sticking’. This can cause partial or even total blocking of the transportation pipe. Several experiments using a laboratory flow loop were conducted to study the wall sticking characteristics of high water-cut crude oils. The experimental results indicated that the predominant influencing factors of wall sticking included shear stress, water-cut and differences between gel point and wall temperature. The wall sticking rate and occurrence temperature decrease with the increase of water-cut and shear stress. The criterion for the wall sticking occurrence temperature (WSOT), and the regression formula of the wall sticking thickness for high water-cut crude oil were then established. Typical case studies indicated that the prediction results obtained from the WSOT criterion and the wall sticking thickness regression formula were in accordance with the measured values. The wall sticking rate and WSOT vary widely under different conditions and it is necessary to consider its non-uniformity in production.

  5. Temperature fluctuation caused by coaxial-jet flow: Experiments on the effect of the velocity ratio R ⩾ 1

    Energy Technology Data Exchange (ETDEWEB)

    Cao, Qiong, E-mail: [Beijing Key Laboratory of Passive Safety Technology for Nuclear Energy, North China Electric Power University, Beijing 102206 (China); Li, Hongyuan, E-mail: [School of Control and Computer Engineering, North China Electric Power University, Beijing 102206 (China); Lu, Daogang, E-mail: [Beijing Key Laboratory of Passive Safety Technology for Nuclear Energy, North China Electric Power University, Beijing 102206 (China); Chang, Mu, E-mail: [Beijing Key Laboratory of Passive Safety Technology for Nuclear Energy, North China Electric Power University, Beijing 102206 (China)


    Highlights: • The effect on temperature fluctuation from velocity ratio was studied by experiment. • The distribution of time-averaged temperatures is the axial-symmetry in R ⩾ 1. • The region of intense temperature fluctuation in R = 1 is different from that of R > 1. • The intensity of temperature fluctuation under R > 1 is weaker than that of R = 1. - Abstract: The temperature fluctuation appears in the core outlet region due to the different of the temperature and velocity of the coolant, which can cause thermal stresses and the high-cycle thermal fatigue on solid boundaries. So, it is necessary to analyze the characteristics of the temperature fluctuation. In the present study, a comparative experiment was performed to analyze the effect on the temperature fluctuation caused by the coaxial-jet flow from the inlet cold and hot fluid velocity ratios (R ⩾ 1). In the condition of R ⩾ 1, the distribution of the time-averaged temperature is the axial-symmetry. In the cold fluid field, the temperature field is divided into four parts, including the first steady region, linear region, nonlinear region and the second steady region along the axial direction, while that is lack of the first steady state region in the hot fluid field. In the condition of R = 1, due to the velocity of the cold fluid is equivalent to that of the hot fluid, the cold fluid flow can be severely disturbed by the hot flow. The intense temperature fluctuation mainly distributed in the annular region at bottom region and the circular region in the upper region. While, in the condition of R > 1, the inertia of the cold fluid is larger than that of the hot fluid. The hot fluid will attach itself to the periphery of the cold fluid. The intense temperature fluctuation distributed in the annular region between the cold and hot fluid and the periphery of the hot fluid. However, the intensity of temperature fluctuation under R > 1 is weaker than that of R = 1.

  6. wall

    Directory of Open Access Journals (Sweden)

    Irshad Kashif


    Full Text Available Maintaining indoor climatic conditions of buildings compatible with the occupant comfort by consuming minimum energy, especially in a tropical climate becomes a challenging problem for researchers. This paper aims to investigate this problem by evaluating the effect of different kind of Photovoltaic Trombe wall system (PV-TW on thermal comfort, energy consumption and CO2 emission. A detailed simulation model of a single room building integrated with PV-TW was modelled using TRNSYS software. Results show that 14-35% PMV index and 26-38% PPD index reduces as system shifted from SPV-TW to DGPV-TW as compared to normal buildings. Thermal comfort indexes (PMV and PPD lie in the recommended range of ASHARE for both DPV-TW and DGPV-TW except for the few months when RH%, solar radiation intensity and ambient temperature were high. Moreover PVTW system significantly reduces energy consumption and CO2 emission of the building and also 2-4.8 °C of temperature differences between indoor and outdoor climate of building was examined.

  7. Note: Demonstration of an external-cavity diode laser system immune to current and temperature fluctuations. (United States)

    Miao, Xinyu; Yin, Longfei; Zhuang, Wei; Luo, Bin; Dang, Anhong; Chen, Jingbiao; Guo, Hong


    We demonstrate an external-cavity laser system using an anti-reflection coated laser diode as gain medium with about 60 nm fluorescence spectrum, and a Rb Faraday anomalous dispersion optical filter (FADOF) as frequency-selecting element with a transmission bandwidth of 1.3 GHz. With 6.4% optical feedback, a single stable longitudinal mode is obtained with a linewidth of 69 kHz. The wavelength of this laser is operating within the center of the highest transmission peak of FADOF over a diode current range from 55 mA to 142 mA and a diode temperature range from 15 °C to 35 °C, thus it is immune to the fluctuations of current and temperature.

  8. Investigation of solidification of thin walled ductile cast iron using temperature measurement

    DEFF Research Database (Denmark)

    Pedersen, Karl Martin; Tiedje, Niels


    Investigation of solidification of thin walled ductile cast iron can be improved using temperature measurement. This article includes some background of the precautions that have to be taken when measuring temperatures in thin walled castings. The aim is to minimize influence of temperature...... measurement on castings and to get sufficient response time of thermocouples. Investigation of thin wall ductile iron has been performed with temperature measurement in plates with thickness between 2,8 and 8mm. The cooling curves achieved are combined with examination of the microstructure in order to reveal...

  9. On the effect of electron temperature fluctuations on turbulent heat transport in the edge plasma of tokamaks

    Energy Technology Data Exchange (ETDEWEB)

    Baudoin, C.; Tamain, P.; Ciraolo, G.; Futtersack, R.; Gallo, A.; Ghendrih, P.; Nace, N.; Norscini, C. [CEA, IRFM, Saint-Paul-lez-Durance (France); Marandet, Y. [Aix-Marseille Universite, CNRS, PIIM, UMR 7345, Marseille (France)


    In this paper we study the impact of electron temperature fluctuations in a two-dimensional turbulent model. This modification adds a second linear instability, known as sheath-driven conducting-wall instability, with respect to the previous isothermal model only driven by the interchange instability. Non-linear simulations, backed up by the linear analysis, show that the additional mechanism can change drastically the dynamics of turbulence (scales, density-potential correlation, and statistical momentum). Moreover, its importance relatively to the interchange instability should be more significant in the private flux region than in the main scrape of layer. Its effect on heat transport is also investigated for different regimes of parameters, results show that both instabilities are at play in the heat transport. Finally, the sheath negative resistance instability could be responsible for the existence of corrugated heat flux profiles in the scrape-off layer leading to a multiple decay length. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  10. Temperature fluctuations in a changing climate: an ensemble-based experimental approach. (United States)

    Vincze, Miklós; Borcia, Ion Dan; Harlander, Uwe


    There is an ongoing debate in the literature about whether the present global warming is increasing local and global temperature variability. The central methodological issues of this debate relate to the proper treatment of normalised temperature anomalies and trends in the studied time series which may be difficult to separate from time-evolving fluctuations. Some argue that temperature variability is indeed increasing globally, whereas others conclude it is decreasing or remains practically unchanged. Meanwhile, a consensus appears to emerge that local variability in certain regions (e.g. Western Europe and North America) has indeed been increasing in the past 40 years. Here we investigate the nature of connections between external forcing and climate variability conceptually by using a laboratory-scale minimal model of mid-latitude atmospheric thermal convection subject to continuously decreasing 'equator-to-pole' temperature contrast ΔT, mimicking climate change. The analysis of temperature records from an ensemble of experimental runs ('realisations') all driven by identical time-dependent external forcing reveals that the collective variability of the ensemble and that of individual realisations may be markedly different - a property to be considered when interpreting climate records.

  11. Growth and lipid accumulation in three Chlorella strains from different regions in response to diurnal temperature fluctuations. (United States)

    Yang, Weinan; Zou, Shanmei; He, Meilin; Fei, Cong; Luo, Wei; Zheng, Shiyan; Chen, Bo; Wang, Changhai


    It was economically feasible to screen strains adaptive to wide temperature fluctuation for outdoor cultivation without temperature control. In this research, three Chlorella strains from arctic glacier, desert soil and temperate native lake were isolated and identified. The growth, biochemical composition, lipid content and fatty acid composition of each strain cultured under the mode of diurnal temperature fluctuations were compared. All the three Chlorella strains showed desirable abilities of accumulating lipid under diurnal temperature fluctuations and their fatty acid profiles were suitable for biodiesel production, although the growth and biochemical composition were seemed to be region-specific. The highest lipid content was at 51.83±2.49% DW, 42.80±2.97% DW and 36.13±2.27% DW under different temperature fluctuation of 11 °C, 25 °C, 7 °C, respectively. The results indicated that the three Chlorella strains could be promising biodiesel feedstock for outdoor cultivation by the cultural mode of diurnal temperature fluctuations. Copyright © 2015 Elsevier Ltd. All rights reserved.

  12. Electron Temperature Fluctuation Measurements and Transport Model Validation at Alcator C-Mod

    Energy Technology Data Exchange (ETDEWEB)

    White, Anne [Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)


    for studying core turbulence are needed in order to assess the accuracy of gyrokinetic models for turbulent-driven particle, heat and momentum transport. New core turbulence diagnostics at the world-class tokamaks Alcator C-Mod at MIT and ASDEX Upgrade at the Max Planck Institute for Plasma Physics have been designed, developed, and operated over the course of this project. These new instruments are capable of measuring electron temperature fluctuations and the phase angle between density and temperature fluctuations locally and quantitatively. These new data sets from Alcator C-Mod and ASDEX Upgrade are being used to fill key gaps in our understanding of turbulent transport in tokamaks. In particular, this project has results in new results on the topics of the Transport Shortfall, the role of ETG turbulence in tokamak plasmas, profile stiffness, the LOC/SOC transition, and intrinsic rotation reversals. These data are used in a rigorous process of “Transport model validation”, and this group is a world-leader on using turbulence models to design new hardware and new experiments at tokamaks. A correlation electron cyclotron emission (CECE) diagnostic is an instrument used to measure micro-scale fluctuations (mm-scale, compared to the machine size of meters) of electron temperature in magnetically confined fusion plasmas, such as those in tokamaks and stellarators. These micro-scale fluctuations are associated with drift-wave type turbulence, which leads to enhanced cooling and mixing of particles in fusion plasmas and limits achieving the required temperatures and densities for self-sustained fusion reactions. A CECE system can also be coupled with a reflectometer system that measured micro-scale density fluctuations, and from these simultaneous measurements, one can extract the phase between the density (n) and temperature (T) fluctuations, creating an nT phase diagnostic. Measurements of the fluctuations and the phase angle between them are extremely useful for

  13. Effects of wall shear stress on unsteady MHD conjugate flow in a porous medium with ramped wall temperature. (United States)

    Khan, Arshad; Khan, Ilyas; Ali, Farhad; Ulhaq, Sami; Shafie, Sharidan


    This study investigates the effects of an arbitrary wall shear stress on unsteady magnetohydrodynamic (MHD) flow of a Newtonian fluid with conjugate effects of heat and mass transfer. The fluid is considered in a porous medium over a vertical plate with ramped temperature. The influence of thermal radiation in the energy equations is also considered. The coupled partial differential equations governing the flow are solved by using the Laplace transform technique. Exact solutions for velocity and temperature in case of both ramped and constant wall temperature as well as for concentration are obtained. It is found that velocity solutions are more general and can produce a huge number of exact solutions correlative to various fluid motions. Graphical results are provided for various embedded flow parameters and discussed in details.

  14. Optical measurements of fluctuating temperatures in a supersonic turbulent flow using one- and two-photon, laser-induced fluorescence (United States)

    Gross, K. P.; Mckenzie, R. L.


    A laser-induced fluorescence technique has been developed that provides a practical means of nonintrusively measuring the instantaneous temperatures in low-temperature turbulent flows. The capabilities of the method are reviewed, and its application to a simple, two-dimensional, turbulent boundary-layer flow at Mach 2 is reported. Measurements of the average temperature distribution through the boundary layer and the magnitudes of temperature fluctuations about their average values are presented.

  15. [Study on Hollow Brick Wall's Surface Temperature with Infrared Thermal Imaging Method]. (United States)

    Tang, Ming-fang; Yin, Yi-hua


    To address the characteristic of uneven surface temperature of hollow brick wall, the present research adopts soft wares of both ThermaCAM P20 and ThermaCAM Reporter to test the application of infrared thermal image technique in measuring surface temperature of hollow brick wall, and further analyzes the thermal characteristics of hollow brick wall, and building material's impact on surface temperature distribution including hollow brick, masonry mortar, and so on. The research selects the construction site of a three-story-high residential, carries out the heat transfer experiment, and further examines the exterior wall constructed by 3 different hollow bricks including sintering shale hollow brick, masonry mortar and brick masonry. Infrared thermal image maps are collected, including 3 kinds of sintering shale hollow brick walls under indoor heating in winter; and temperature data of wall surface, and uniformity and frequency distribution are also collected for comparative analysis between 2 hollow bricks and 2 kinds of mortar masonry. The results show that improving heat preservation of hollow brick aid masonry mortar can effectively improve inner wall surface temperature and indoor thermal environment; non-uniformity of surface temperature decreases from 0. 6 to 0. 4 °C , and surface temperature frequency distribution changes from the asymmetric distribution into a normal distribution under the condition that energy-saving sintering shale hollow brick wall is constructed by thermal mortar replacing cement mortar masonry; frequency of average temperature increases as uniformity of surface temperature increases. This research provides a certain basis for promotion and optimization of hollow brick wall's thermal function.

  16. Andreas Acrivos Dissertation Award Talk: Modeling drag forces and velocity fluctuations in wall-bounded flows at high Reynolds numbers (United States)

    Yang, Xiang


    The sizes of fluid motions in wall-bounded flows scale approximately as their distances from the wall. At high Reynolds numbers, resolving near-wall, small-scale, yet momentum-transferring eddies are computationally intensive, and to alleviate the strict near-wall grid resolution requirement, a wall model is usually used. The wall model of interest here is the integral wall model. This model parameterizes the near-wall sub-grid velocity profile as being comprised of a linear inner-layer and a logarithmic meso-layer with one additional term that accounts for the effects of flow acceleration, pressure gradients etc. We use the integral wall model for wall-modeled large-eddy simulations (WMLES) of turbulent boundary layers over rough walls. The effects of rough-wall topology on drag forces are investigated. A rough-wall model is then developed based on considerations of such effects, which are now known as mutual sheltering among roughness elements. Last, we discuss briefly a new interpretation of the Townsend attached eddy hypothesis-the hierarchical random additive process model (HRAP). The analogy between the energy cascade and the momentum cascade is mathematically formal as HRAP follows the multi-fractal formulism, which was extensively used for the energy cascade.

  17. Thermal fluctuations in Y-Ba-Cu-O thin films near the transition temperature

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, S.; Hallemeier, P.; Surya, C. (Northeastern Univ., Boston, MA (United States). Dept. of Electrical and Computer Engineering); Phillips, J.M. (AT and T Bell Labs., Murray Hill, NJ (United States))


    Detailed studies on the properties of low frequency noise in Y-Ba-Cu-O thin films in the transition region were conducted. The experimental results showed that the low frequency excess noise exhibited a lower cutoff frequency of about 5 Hz, below which the noise power spectra were independent of frequency. At T close to [Tc] and at small current biases the voltage noise power spectra were proportional to I[sup 2], ([partial derivative]R/[partial derivative]T)[sup 2] and inversely proportional to the volume of the device, [Omega]. In addition, low frequency noise measured from two segments separated by a distance of 300 [mu]m was found to be correlated. The lower cutoff frequencies computed for both the noise power spectra and the frequency dependent correlation function, according to the thermal fluctuation model, were found to be in good agreement with the experimental values. The experimental results provide strong evidence that the low frequency excess noise in the device originates from equilibrium temperature fluctuations for small I and T [approx equal] [Tc].

  18. The effect of boundary layer and surface characteristics on non-Gaussian turbulent fluctuations of temperature (United States)

    Graf, A.; Schüttemeyer, D.; Geiß, H.; Knaps, A.; Möllmann-Coers, M.; Schween, J. H.; Kollet, S.; Neininger, B.; Herbst, M.; Vereecken, H.


    We use simultaneously measured near-ground micrometeorological and boundary layer data to examine the relation between the probability density function (PDF) of a turbulent scalar such as temperature and its vertical profile. Turbulent temperature time series of 10 to 20 s-1 resolution are taken from eddy covariance stations measuring at 1.45 to 120 m above ground level, and vertical profiles of potential temperature were composed of tower and aircraft measurements. The relation between skewness and kurtosis of the turbulent near-ground data was evaluated using the Pearson system of distributions, and indicates that a part of their non-Gaussianity is due to the existence of a well-defined lower limit to fluctuations. To a lesser extend, an upper limit is also indicated. During unstable situations, the lower limit could be related to the minimum of potential temperature available in the boundary layer. During stable situations, it was related to the effective surface temperature at the measurement site estimated from outgoing longwave radiation. The upper limit could be related with considerably less rigidity and a systematic underestimation, which we attribute to well mixing by small-scale turbulence, to the surface temperature during unstable situations. Two types of theoretical PDFs are compared to the turbulent histograms. The first type, the beta distribution was empirically chosen from classical statistics based on matching the first four sample moments and has already been used to empirically model scalar concentrations in plumes. The second type was theoretically derived from simplified assumptions on atmospheric dispersion. Both support the assumption that turbulent scalar PDFs in horizontally homogeneous conditions have finite tails.

  19. Influence of temperature fluctuations during cryopreservation on vital parameters, differentiation potential, and transgene expression of placental multipotent stromal cells. (United States)

    Pogozhykh, Denys; Pogozhykh, Olena; Prokopyuk, Volodymyr; Kuleshova, Larisa; Goltsev, Anatoliy; Blasczyk, Rainer; Mueller, Thomas


    Successful implementation of rapidly advancing regenerative medicine approaches has led to high demand for readily available cellular suspensions. In particular, multipotent stromal cells (MSCs) of placental origin have shown therapeutic efficiency in the treatment of numerous pathologies of varied etiology. Up to now, cryopreservation is the only effective way to preserve the viability and unique properties of such cells in the long term. However, practical biobanking is often associated with repeated temperature fluctuations or interruption of a cold chain due to various technical, transportation, and stocking events. While biochemical processes are expected to be suspended during cryopreservation, such temperature fluctuations may lead to accumulation of stress as well as to periodic release of water fractions in the samples, possibly leading to damage during long-term storage. In this study, we performed a comprehensive analysis of changes in cell survival, vital parameters, and differentiation potential, as well as transgene expression of placental MSCs after temperature fluctuations within the liquid nitrogen steam storage, mimicking long-term preservation in practical biobanking, transportation, and temporal storage. It was shown that viability and metabolic parameters of placental MSCs did not significantly differ after temperature fluctuations in the range from -196 °C to -100 °C in less than 20 cycles in comparison to constant temperature storage. However, increasing the temperature range to -80 °C as well as increasing the number of cycles leads to significant lowering of these parameters after thawing. The number of apoptotic changes increases depending on the number of cycles of temperature fluctuations. Besides, adhesive properties of the cells after thawing are significantly compromised in the samples subjected to temperature fluctuations during storage. Differentiation potential of placental MSCs was not compromised after cryopreservation

  20. A Regime Diagram for Autoignition of Homogeneous Reactant Mixtures with Turbulent Velocity and Temperature Fluctuations

    KAUST Repository

    Im, Hong G.


    A theoretical scaling analysis is conducted to propose a diagram to predict weak and strong ignition regimes for a compositionally homogeneous reactant mixture with turbulent velocity and temperature fluctuations. The diagram provides guidance on expected ignition behavior based on the thermo-chemical properties of the mixture and the flow/scalar field conditions. The analysis is an extension of the original Zeldovich’s analysis by combining the turbulent flow and scalar characteristics in terms of the characteristic Damköhler and Reynolds numbers of the system, thereby providing unified and comprehensive understanding of the physical and chemical mechanisms controlling ignition characteristics. Estimated parameters for existing experimental measurements in a rapid compression facility show that the regime diagram predicts the observed ignition characteristics with good fidelity.

  1. Measurement of Turbulent Pressure and Temperature Fluctuations in a Gas Turbine Combustor (United States)

    Povinelli, Louis (Technical Monitor); LaGraff, John E.; Bramanti, Cristina; Pldfield, Martin; Passaro, Andrea; Biagioni, Leonardo


    The report summarizes the results of the redesign efforts directed towards the gas-turbine combustor rapid-injector flow diagnostic probe developed under sponsorship of NASA-GRC and earlier reported in NASA-CR-2003-212540. Lessons learned during the theoretical development, developmental testing and field-testing in the previous phase of this research were applied to redesign of both the probe sensing elements and of the rapid injection device. This redesigned probe (referred to herein as Turboprobe) has been fabricated and is ready, along with the new rapid injector, for field-testing. The probe is now designed to capture both time-resolved and mean total temperatures, total pressures and, indirectly, one component of turbulent fluctuations.

  2. Information entropy of activation process: Application for low-temperature fluctuations of a myoglobin molecule (United States)

    Stepanov, A. V.


    Activation process for unimolecular reaction has been considered by means of radiation theory. The formulae of information entropy of activation have been derived for the Boltzmann-Arrhenius model and the activation process model (APM). The physical meaning of this entropy has been determined. It is a measure of conversion of thermal radiation energy to mechanical energy that moves atoms in a molecule during elementary activation act. It is also a measure of uncertainty of this energy conversion. The uncertainty is due to unevenness of distribution function representing the activation process. It has been shown that Arrhenius dependence is caused by the entropy change. Efficiency comparison of the two models under consideration for low-temperature fluctuations of a myoglobin molecule structure shows that the APM should be favored over the Boltzmann-Arrhenius one.

  3. Pressure dependence of critical temperature of bulk FeSe from spin fluctuation theory (United States)

    Hirschfeld, Peter; Kreisel, Andreas; Wang, Yan; Tomic, Milan; Jeschke, Harald; Jacko, Anthony; Valenti, Roser; Maier, Thomas; Scalapino, Douglas


    The critical temperature of the 8K superconductor FeSe is extremely sensitive to pressure, rising to a maximum of 40K at about 10GPa. We test the ability of the current generation of fluctuation exchange pairing theories to account for this effect, by downfolding the density functional theory electronic structure for each pressure to a tight binding model. The Fermi surface found in such a procedure is then used with fixed Hubbard parameters to determine the pairing strength using the random phase approximation for the spin singlet pairing vertex. We find that the evolution of the Fermi surface captured by such an approach is alone not sufficient to explain the observed pressure dependence, and discuss alternative approaches. PJH, YW, AK were supported by DOE DE-FG02-05ER46236, the financial support of MT, HJ, and RV from the DFG Schwerpunktprogramm 1458 is kindly acknowledged.

  4. Computational characterization of ignition regimes in a syngas/air mixture with temperature fluctuations

    KAUST Repository

    Pal, Pinaki


    Auto-ignition characteristics of compositionally homogeneous reactant mixtures in the presence of thermal non-uniformities and turbulent velocity fluctuations were computationally investigated. The main objectives were to quantify the observed ignition characteristics and numerically validate the theory of the turbulent ignition regime diagram recently proposed by Im et al. 2015 [29] that provides a framework to predict ignition behavior . a priori based on the thermo-chemical properties of the reactant mixture and initial flow and scalar field conditions. Ignition regimes were classified into three categories: . weak (where deflagration is the dominant mode of fuel consumption), . reaction-dominant strong, and . mixing-dominant strong (where volumetric ignition is the dominant mode of fuel consumption). Two-dimensional (2D) direct numerical simulations (DNS) of auto-ignition in a lean syngas/air mixture with uniform mixture composition at high-pressure, low-temperature conditions were performed in a fixed volume. The initial conditions considered two-dimensional isotropic velocity spectrums, temperature fluctuations and localized thermal hot spots. A number of parametric test cases, by varying the characteristic turbulent Damköhler and Reynolds numbers, were investigated. The evolution of the auto-ignition phenomena, pressure rise, and heat release rate were analyzed. In addition, combustion mode analysis based on front propagation speed and computational singular perturbation (CSP) was applied to characterize the auto-ignition phenomena. All results supported that the observed ignition behaviors were consistent with the expected ignition regimes predicted by the theory of the regime diagram. This work provides new high-fidelity data on syngas ignition characteristics over a broad range of conditions and demonstrates that the regime diagram serves as a predictive guidance in the understanding of various physical and chemical mechanisms controlling auto

  5. Temperature measurement during solidification of thin wall ductile cast iron. Part 1: Theory and experiment

    DEFF Research Database (Denmark)

    Pedersen, Karl Martin; Tiedje, Niels Skat


    Temperature measurement using thermocouples (TC’s) influence solidification of the casting, especially in thin wall castings. The problems regarding acquisition of detailed cooling curves from thin walled castings is discussed. Experiments were conducted where custom made TC’s were used to acquir...... of castings with different plate thicknesses....

  6. Assessment of Fluctuation Patterns Similarity in Temperature and Vapor Pressure Using Discrete Wavelet Transform

    Directory of Open Access Journals (Sweden)

    A. Araghi


    Full Text Available Period and trend are two main effective and important factors in hydro-climatological time series and because of this importance, different methods have been introduced and applied to study of them, until now. Most of these methods are statistical basis and they are classified in the non-parametric tests. Wavelet transform is a mathematical based powerful method which has been widely used in signal processing and time series analysis in recent years. In this research, trend and main periodic patterns similarity in temperature and vapor pressure has been studied in Babolsar, Tehran and Shahroud synoptic stations during 55 years period (from 1956 to 2010, using wavelet method and the sequential Mann-Kendall trend test. The results show that long term fluctuation patterns in temperature and vapor pressure have more correlations in the arid and semi-arid climates, as well as short term oscillation patterns in temperature and vapor pressure in the humid climates, and these dominant periods increase with the aridity of region.


    National Research Council Canada - National Science Library

    KRISTANTO Luciana; TANUWIDJAJA Gunawan; ELSIANA Fenny Fenny; WIJAYA Nerissa Arviana Nerissa Arviana; WAHONO Eunice


    .... With concentration we can achieve the maximum and faster result in our work. Some ways to improve concentration that being researched here is by arranging the wall color and the lamp color temperature of the room...

  8. Structural instability and phase co-existence driven non-Gaussian resistance fluctuations in metal nanowires at low temperatures (United States)

    Bid, Aveek; Raychaudhuri, A. K.


    We report a detailed experimental study of the resistance fluctuations measured at low temperatures in high quality metal nanowires ranging in diameter from 15-200 nm. The wires exhibit co-existing face-centered-cubic and 4H hcp phases of varying degrees as determined from the x-ray diffraction data. We observe the appearance of a large non-Gaussian noise for nanowires of diameter smaller than 50 nm over a certain temperature range around ≈30 K. The diameter range ˜30 nm, where the noise has maxima coincides with the maximum volume fraction of the co-existing 4H hcp phase thus establishing a strong link between the fluctuation and the phase co-existence. The resistance fluctuation in the same temperature range also shows a deviation of 1/f behavior at low frequency with appearance of single frequency Lorentzian type contribution in the spectral power density. The fluctuations are thermally activated with an activation energy {E}{{a}}˜ 35 meV, which is of same order as the activation energy of creation of stacking fault in FCC metals that leads to the co-existing crystallographic phases. Combining the results of crystallographic studies of the nanowires and analysis of the resistance fluctuations we could establish the correlation between the appearance of the large resistance noise and the onset of phase co-existence in these nanowires.

  9. Simulated Seasonal Photoperiods and Fluctuating Temperatures Have Limited Effects on Blood Feeding and Life History in Aedes triseriatus (Diptera: Culicidae) (United States)

    Westby, K. M.


    Biotic and abiotic factors change seasonally and impact life history in temperate-zone ectotherms. Temperature and photoperiod are factors that change in predictable ways. Most studies testing for effects of temperature on vectors use constant temperatures and ignore potential correlated effects of photoperiod. In two experiments, we tested for effects of larval rearing environments creating ecologically relevant temperatures and photoperiods simulating early and late season conditions (June and August), or constant temperatures (cool and warm) with the June or August photoperiods, respectively. We determined effects on survivorship, development, size, and a composite performance index in a temperate-zone population of Aedes triseriatus (Say). We followed cohorts of resulting females, all held under the same environmental conditions, to assess carry-over effects of rearing conditions for larvae on longevity, blood feeding, and egg production. Larval survivorship was affected by treatment in one experiment. Development time was greater in the June and cool treatments, but the constant and fluctuating temperatures did not differ. Significantly larger mosquitoes were produced in fluctuating versus constant temperature treatments. There were no significant treatment effects on the composite performance index. Adult female longevity was lower after rearing at constant versus fluctuating temperature, but there was no difference between June and August, nor did size affect longevity. There was no effect of treatments on blood feeding and a limited effect on egg production. We conclude that seasonal temperatures and photoperiods during development have limited effects on this population of A. triseriatus and find little evidence of strong effects of fluctuating versus constant temperatures. PMID:26336255

  10. A comprehensive model to determine the effects of temperature and species fluctuations on reaction rates in turbulent reacting flows (United States)

    Foy, E.; Ronan, G.; Chinitz, W.


    A principal element to be derived from modeling turbulent reacting flows is an expression for the reaction rates of the various species involved in any particular combustion process under consideration. A temperature-derived most-likely probability density function (pdf) was used to describe the effects of temperature fluctuations on the Arrhenius reaction rate constant. A most-likely bivariate pdf described the effects of temperature and species concentrations fluctuations on the reaction rate. A criterion is developed for the use of an "appropriate" temperature pdf. The formulation of models to calculate the mean turbulent Arrhenius reaction rate constant and the mean turbulent reaction rate is considered and the results of calculations using these models are presented.

  11. Supersonic helium beam diagnostic for fluctuation measurements of electron temperature and density at the Tokamak TEXTOR

    Energy Technology Data Exchange (ETDEWEB)

    Kruezi, U.; Stoschus, H.; Schweer, B.; Sergienko, G.; Samm, U. [Institute of Energy and Climate Research, Plasma Physics, Forschungszentrum Juelich GmbH, Association EURATOM-FZJ, Partner in the Trilateral Euregio Cluster, Juelich (Germany)


    A supersonic helium beam diagnostic, based on the line-ratio technique for high resolution electron density and temperature measurements in the plasma edge (r/a > 0.9) was designed, built, and optimised at TEXTOR (Torus Experiment for Technology Oriented Research). The supersonic injection system, based on the Campargue skimmer-nozzle concept, was developed and optimised in order to provide both a high neutral helium beam density of n{sub 0}= 1.5 Multiplication-Sign 10{sup 18} m{sup -3} and a low beam divergence of {+-}1 Degree-Sign simultaneously, achieving a poloidal resolution of {Delta}{sub poloidal}= 9 mm. The setup utilises a newly developed dead volume free piezo valve for operation in a high magnetic field environment of up to 2 T with a maximum repetition rate of 80 Hz. Gas injections are realised for a duration of 120 ms at a repetition rate of 2 Hz (duty cycle 1/3). In combination with a high sensitivity detection system, consisting of three 32 multi-channel photomultipliers (PMTs), measurements of edge electron temperature and density with a radial resolution of {Delta}{sub radial}= 2 mm and a maximum temporal resolution of {Delta}t Asymptotically-Equal-To 2 {mu}s (470 kHz) are possible for the first time. The diagnostic setup at TEXTOR is presented. The newly developed injection system and its theoretical bases are discussed. The applicability of the stationary collisional-radiative model as basis of the line-ratio technique is shown. Finally, an example of a fluctuation analysis demonstrating the unique high temporal and spatial resolution capabilities of this new diagnostic is presented.

  12. Temperature Compensation of [U-14C]Glucose Incorporation by Microbial Communities in a River with a Fluctuating Thermal Regime


    Witzel, Karl-Paul


    In summer, the river Saar in the southwest of Germany exhibits distinct temperature fluctuations from 8°C at the source to nearly 30°C in the middle region. Temperature optima for bacterial plate counts and the uptake velocity of [U-14C]glucose by the natural microbial communities of different regions ranged from 20 to 30°C, which is significantly above the mean annual water temperature. A correlation between temperature optima and different seasons or habitats was not observed. Despite the r...

  13. Quark number fluctuations at finite temperature and finite chemical potential via the Dyson-Schwinger equation approach (United States)

    Xin, Xian-yin; Qin, Si-xue; Liu, Yu-xin


    We investigate the quark number fluctuations up to the fourth order in the matter composed of two light flavor quarks with isospin symmetry and at finite temperature and finite chemical potential using the Dyson-Schwinger equation approach of QCD. In order to solve the quark gap equation, we approximate the dressed quark-gluon vertex with the bare one and adopt both the Maris-Tandy model and the infrared constant (Qin-Chang) model for the dressed gluon propagator. Our results indicate that the second, third, and fourth order fluctuations of net quark number all diverge at the critical endpoint (CEP). Around the CEP, the second order fluctuation possesses obvious pump while the third and fourth order ones exhibit distinct wiggles between positive and negative. For the Maris-Tandy model and the Qin-Chang model, we give the pseudocritical temperature at zero quark chemical potential as Tc=146 MeV and 150 MeV, and locate the CEP at (μEq,TE)=(120,124) MeV and (124,129) MeV, respectively. In addition, our results manifest that the fluctuations are insensitive to the details of the model, but the location of the CEP shifts to low chemical potential and high temperature as the confinement length scale increases.

  14. Fundamental study of FC-72 pool boiling surface temperature fluctuations and bubble behavior (United States)

    Griffin, Alison R.

    A heater designed to monitor surface temperature fluctuations during pool boiling experiments while the bubbles were simultaneously being observed has been fabricated and tested. The heat source was a transparent indium tin oxide (ITO) layer commercially deposited on a fused quartz substrate. Four copper-nickel thin film thermocouples (TFTCs) on the heater surface measured the surface temperature, while a thin layer of sapphire or fused silica provided electrical insulation between the TFTCs and the ITO. The TFTCs were micro-fabricated using the liftoff process to deposit the nickel and copper metal films. The TFTC elements were 50 mum wide and overlapped to form a 25 mum by 25 mum junction. TFTC voltages were recorded by a DAQ at a sampling rate of 50 kHz. A high-speed CCD camera recorded bubble images from below the heater at 2000 frames/second. A trigger sent to the camera by the DAQ synchronized the bubble images and the surface temperature data. As the bubbles and their contact rings grew over the TFTC junction, correlations between bubble behavior and surface temperature changes were demonstrated. On the heaters with fused silica insulation layers, 1--2°C temperature drops on the order of 1 ms occurred as the contact ring moved over the TFTC junction during bubble growth and as the contact ring moved back over the TFTC junction during bubble departure. These temperature drops during bubble growth and departure were due to microlayer evaporation and liquid rewetting the heated surface, respectively. Microlayer evaporation was not distinguished as the primary method of heat removal from the surface. Heaters with sapphire insulation layers did not display the measurable temperature drops observed with the fused silica heaters. The large thermal diffusivity of the sapphire compared to the fused silica was determined as the reason for the absence of these temperature drops. These findings were confirmed by a comparison of temperature drops in a 2-D simulation of

  15. A semi-classical approach of the relationship between simple cells' size and their living temperature limits based on number fluctuations of water coherence domains (United States)

    Preoteasa, E. A.; Negoita, C.


    Starting from the concepts of the quantum electrodynamics (QED) theory of coherence domains (CD) in water we propose a model aimed to evaluate the relationship between the size and the living temperature limits for simple, small cells. Cells are described as spherical potential wells with impenetrable walls, with CDs moving inside. The radius of the spherical potential well was estimated for physiological temperatures and the results match to bacteria and yeasts cells' size. As a CD in the spherical cell exerts a force upon the membrane, a 'gas' formed by CDs bears a pressure on the walls. A classical statistical stability condition relates this pressure to cell volume and to the relative fluctuations of the CD number, allowing the evaluation of an upper temperature limit as a function of cellular volume. Assuming further that the CDs in the living cell form together a coherent state, the number-phase incertitude relationship (Heisenberg limit) applies. The maximum coherence between CDs is found in the ground state, a picture consistent also to Fröhlich's postulate. For a given phase dispersion, a lower temperature limit as a function of the cell volume is found. Although we neglected the rod-like shape of certain bacteria and the presence of nucleus in yeasts, the biological data of volume and optimal living temperature intervals fit well to our model's predictions. Moreover the larger the cell volume, the higher are the number of CDs and the coherence of their system. In addition we suggest a new classification criterion for small cells based on model's parameters, which show discontinuities between Gram negative and positive microorganisms as well as between prokaryotes and the smallest eukaryotes.

  16. Resistive wall wakefields of short bunches at cryogenic temperatures

    Directory of Open Access Journals (Sweden)

    G. Stupakov


    Full Text Available We present calculations of the longitudinal wakefields at cryogenic temperatures for extremely short bunches, characteristic for modern x-ray free electron lasers. The calculations are based on the equations for the surface impedance in the regime of the anomalous skin effect in metals. This paper extends and complements an earlier analysis of B. Podobedov, Phys. Rev. ST Accel. Beams 12, 044401 (2009. into the region of very high frequencies associated with bunch lengths in the micron range. We study in detail the case of a rectangular bunch distribution for parameters of interest of LCLS-II with a superconducting undulator.

  17. Chromatin integrity of ram spermatozoa. Relationships to annual fluctuations of scrotal surface temperature and temperature-humidity index. (United States)

    Malama, E; Bollwein, H; Taitzoglou, I A; Theodosiou, T; Boscos, C M; Kiossis, E


    The objective of the present study was to explore the potential relationships of ovine sperm chromatin integrity, quantified using the sperm chromatin structure assay (SCSA), to the heat load of the scrotum and the discomfort felt by the animals because of fluctuations of microclimatic factors at different time periods before ejaculation. Ejaculates were collected once per week from five Chios rams and four East Friesian rams for 12 months and stored in liquid nitrogen. Frozen-thawed semen samples were analyzed using the SCSA, to determine the DNA fragmentation index (DFI) and the percentage of cells outside the main sperm population (%DFI) in each one of the samples. Scrotal surface temperature (SST) of each ram was measured using an infrared thermometer on a daily basis. Ambient air temperature and relative humidity were recorded at hourly intervals throughout the experimental period and temperature-humidity index (THI) was used to assess the discomfort felt by the rams. Mean values of SST (SST mean) and THI (THI mean) were computed for eight different time periods (up to 61 days) preceding each ejaculation day (Day 0). A linear mixed-effect model analysis was performed to describe the relation of SCSA parameters to collection month, SST mean, and THI mean of different time periods before ejaculation. The results of the statistical analysis revealed a relation of %DFI to the SST mean of the last 12 days preceding ejaculation, namely the period that resembled the phase of epididymal maturation. On the contrary, the variation of DFI was most adequately described by the linear mixed-effect model applied for Days 54 to 48 before ejaculation, which resembled the phase of spermatogonial mitoses. The effect of collection month was significant for DFI and %DFI, with semen samples collected in September and February exhibiting the lowest DFI values; a less profound seasonal pattern was detected for %DFI. The effect of THI mean on DFI and %DFI was proven nonsignificant in

  18. Probing environment fluctuations by two-dimensional electronic spectroscopy of molecular systems at temperatures below 5 K

    Energy Technology Data Exchange (ETDEWEB)

    Rancova, Olga; Abramavicius, Darius [Department of Theoretical Physics, Vilnius University, Sauletekio al 9-III, 10222 Vilnius (Lithuania); Jankowiak, Ryszard [Department of Chemistry and Department of Physics, Kansas State University, 213 CBC Building Manhattan, Kansas 66506-0401 (United States)


    Two-dimensional (2D) electronic spectroscopy at cryogenic and room temperatures reveals excitation energy relaxation and transport, as well as vibrational dynamics, in molecular systems. These phenomena are related to the spectral densities of nuclear degrees of freedom, which are directly accessible by means of hole burning and fluorescence line narrowing approaches at low temperatures (few K). The 2D spectroscopy, in principle, should reveal more details about the fluctuating environment than the 1D approaches due to peak extension into extra dimension. By studying the spectral line shapes of a dimeric aggregate at low temperature, we demonstrate that 2D spectra have the potential to reveal the fluctuation spectral densities for different electronic states, the interstate correlation of static disorder and, finally, the time scales of spectral diffusion with high resolution.

  19. Clarifying the role of fire heat and daily temperature fluctuations as germination cues for Mediterranean Basin obligate seeders (United States)

    Santana, Victor M.; Baeza, M. Jaime; Blanes, M. Carmen


    Background and Aims This study aims to determine the role that both direct effects of fire and subsequent daily temperature fluctuations play in the seed bank dynamics of obligate seeders from the Mediterranean Basin. The short yet high soil temperatures experienced due to passage of fire are conflated with the lower, but longer, temperatures experienced by daily fluctuations which occur after removing vegetation. These germination cues are able to break seed dormancy, but it is difficult to assess their specific level of influence because they occur consecutively after summer fires, just before the flush of germination in the wet season (autumn). Methods By applying experimental fires, seed treatments were imposed that combined fire exposure/non-fire exposure with exposure to microhabitats under a gradient of disturbance (i.e. gaps opened by fire, mechanical brushing and intact vegetation). The seeds used were representative of the main families of obligate seeders (Ulex parviflorus, Cistus albidus and Rosmarinus officinalis). Specifically, an assessment was made of (1) the proportion of seeds killed by fire, (2) seedling emergence under field conditions and (3) seeds which remained ungerminated in soil. Key Results For the three species studied, the factors that most influenced seedling emergence and seeds remaining ungerminated were microhabitats with higher temperature fluctuations after fire (gaps opened by fire and brushing treatments). The direct effect of fire decreased the seedling emergence of U. parviflorus and reduced the proportion of seeds of R. officinalis remaining ungerminated. Conclusions The relevance of depleting vegetation (and subsequent daily temperature fluctuation in summer) suggests that studies focusing on lower temperature thresholds for breaking seed dormancy are required. This fact also supports the hypothesis that the seeding capacity in Mediterranean Basin obligate seeders may have evolved as a response to a wide range of

  20. Finite-temperature magnetism of Ni monolayers: Interplay between flips and amplitude fluctuations of the local moments (United States)

    Garibay-Alonso, R.; Dorantes-Dávila, J.; Pastor, G. M.


    The temperature dependence of the magnetization and spin fluctuation energies in Ni bulk and monolayers are determined in the framework of a functional-integral itinerant-electron theory. The electronic structure is obtained in the static approximation from a realistic spd-band model by using a real-space recursive expansion of the local Green's functions. The statistical averages of the spin fluctuations are performed by treating disorder within the coherent potential approximation. Results for the magnetization M(T) and spin fluctuation energies of (001) fcc monolayers are presented for several values of the nearest-neighbor distance. Local environmental effects are discussed by comparison with bulk results. An interesting transition from simple spin flips to amplitude fluctuations of the local exchange fields is revealed as a function of dimensionality and bond length. Important qualitative differences in the spin fluctuation energies of Ni are observed as compared to Fe, which reflect different mechanisms of the dominant spin excitations in these itinerant-electron ferromagnets. The effects of sp electrons and sp-d hybridizations are discussed.

  1. A Model for Analyzing Temperature Profiles in Pipe Walls and Fluids Using Mathematical Experimentation

    Directory of Open Access Journals (Sweden)

    Moses E. Emetere


    Full Text Available Temperature profiling in both fluid and pipe walls had not been explained theoretically. The equations of energy balance and heat conductivity were queried by introducing known parameters to solveheat transfer using virtual mathematical experimentation. This was achieved by remodelingPoiseuille's equation. Distribution of temperature profiles between pipe wall, fluid flow, and surrounding air was investigated and validated upon comparison with experimental results. A new dimensionless parameter (unified number (U was introduced with the aim of solving known errors of the Reynolds and Nusselts number.

  2. Temperature measurement during solidification of thin wall ductile cast iron. Part 2: Numerical simulations

    DEFF Research Database (Denmark)

    Pedersen, Karl Martin; Tiedje, Niels Skat


    Temperature measurements in castings are carried out with thermocouples (TC’s), which are inserted in the melt. The TC influence solidification of the casting, especially in thin wall castings where the heat content of the melt is small compared to the cooling power of the TC. A numerical analysis...... of factors influencing temperature measurement in thin walled castings was carried out. The calculations are based on and compared with experiments presented in part 1 of this paper. The analysis shows that the presence of the TC has only a minor influence on the microstructure of the casting. The influence...

  3. The effects of the metal temperature and wall thickness on flake graphite layer in ductile iron

    Directory of Open Access Journals (Sweden)

    M. Górny


    Full Text Available This article addresses the effect of mold filling and wall thickness on the flake graphite layer in ductile iron. The research was conducted for castings with different wall thickness (3-8 mm and using molding sand with furan resin. A thermal analysis has been performed along the length of the castings to determine the initial temperature of the metal in the mold cavity and the contact time of the liquid metal with the mold. Results demonstrated the strong influence of the temperature decrease of the metal in the mold cavity on the occurrence and the thickness of the flake graphite in the surface layer in ductile iron.

  4. Changes in core electron temperature fluctuations across the ohmic energy confinement transition in Alcator C-Mod plasmas (United States)

    Sung, C.; White, A. E.; Howard, N. T.; Oi, C. Y.; Rice, J. E.; Gao, C.; Ennever, P.; Porkolab, M.; Parra, F.; Mikkelsen, D.; Ernst, D.; Walk, J.; Hughes, J. W.; Irby, J.; Kasten, C.; Hubbard, A. E.; Greenwald, M. J.; the Alcator C-Mod Team


    The first measurements of long wavelength (kyρs < 0.3) electron temperature fluctuations in Alcator C-Mod made with a new correlation electron cyclotron emission diagnostic support a long-standing hypothesis regarding the confinement transition from linear ohmic confinement (LOC) to saturated ohmic confinement (SOC). Electron temperature fluctuations decrease significantly (∼40%) crossing from LOC to SOC, consistent with a change from trapped electron mode (TEM) turbulence domination to ion temperature gradient (ITG) turbulence as the density is increased. Linear stability analysis performed with the GYRO code (Candy and Waltz 2003 J. Comput. Phys. 186 545) shows that TEMs are dominant for long wavelength turbulence in the LOC regime and ITG modes are dominant in the SOC regime at the radial location (ρ ∼ 0.8) where the changes in electron temperature fluctuations are measured. In contrast, deeper in the core (ρ < 0.8), linear stability analysis indicates that ITG modes remain dominant across the LOC/SOC transition. This radial variation suggests that the robust global changes in confinement of energy and momentum occurring across the LOC/SOC transition are correlated to local changes in the dominant turbulent mode near the edge.

  5. Effect of ripples on the finite temperature elastic properties of hexagonal boron nitride using strain-fluctuation method (United States)

    Thomas, Siby; Ajith, K. M.; Valsakumar, M. C.


    This work intents to put forth the results of a classical molecular dynamics study to investigate the temperature dependent elastic constants of monolayer hexagonal boron nitride (h-BN) between 100 and 1000 K for the first time using strain fluctuation method. The temperature dependence of out-of-plane fluctuations (ripples) is quantified and is explained using continuum theory of membranes. At low temperatures, negative in-plane thermal expansion is observed and at high temperatures, a transition to positive thermal expansion has been observed due to the presence of thermally excited ripples. The decrease of Young's modulus, bulk modulus, shear modulus and Poisson's ratio with increase in temperature has been analyzed. The thermal rippling in h-BN leads to strong anharmonic behaviour that causes large deviation from the isotropic elasticity. A detailed study shows that the strong thermal rippling in large systems is also responsible for the softening of elastic constants in h-BN. From the determined values of elastic constants and elastic moduli, it has been elucidated that 2D h-BN sheets meet the Born's mechanical stability criterion in the investigated temperature range. The variation of longitudinal and shear velocities with temperature is also calculated from the computed values of elastic constants and elastic moduli.

  6. Study on critical places for maximum temperature rise on unexposed surface of curtain wall test specimens

    Directory of Open Access Journals (Sweden)

    Sulik Paweł


    Full Text Available The paper discusses the main issues related to the fire resistance of glazed curtain walls including the tests methodology and way of classification of this type of building elements. Moreover, the paper presents an attempt to determine the weak points of aluminium glazed curtain wall test specimens regarding to the maximum temperature rise measurements, based on the fire resistance tests performed in recent years by Fire Research Department of Building Research Institute. The paper analyse the results of temperature rise on unexposed surface of 17 aluminium glazed curtain wall specimens tested for internal fire exposure in accordance with EN 1364-3:2006 [3] and EN 1364-3:2014 [4], which achieved the fire resistance class of min. EI 15.

  7. Quantitative comparison of electron temperature fluctuations to nonlinear gyrokinetic simulations in C-Mod Ohmic L-mode discharges

    Energy Technology Data Exchange (ETDEWEB)

    Sung, C., E-mail: [University of California, Los Angeles, Los Angeles, California 90095 (United States); White, A. E.; Greenwald, M.; Howard, N. T. [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Mikkelsen, D. R.; Churchill, R. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States); Holland, C. [University of California, San Diego, La Jolla, California 92093 (United States); Theiler, C. [Ecole Polytechnique Fédérale de Lausanne, SPC, Lausanne 1015 (Switzerland)


    Long wavelength turbulent electron temperature fluctuations (k{sub y}ρ{sub s} < 0.3) are measured in the outer core region (r/a > 0.8) of Ohmic L-mode plasmas at Alcator C-Mod [E. S. Marmar et al., Nucl. Fusion 49, 104014 (2009)] with a correlation electron cyclotron emission diagnostic. The relative amplitude and frequency spectrum of the fluctuations are compared quantitatively with nonlinear gyrokinetic simulations using the GYRO code [J. Candy and R. E. Waltz, J. Comput. Phys. 186, 545 (2003)] in two different confinement regimes: linear Ohmic confinement (LOC) regime and saturated Ohmic confinement (SOC) regime. When comparing experiment with nonlinear simulations, it is found that local, electrostatic ion-scale simulations (k{sub y}ρ{sub s} ≲ 1.7) performed at r/a ∼ 0.85 reproduce the experimental ion heat flux levels, electron temperature fluctuation levels, and frequency spectra within experimental error bars. In contrast, the electron heat flux is robustly under-predicted and cannot be recovered by using scans of the simulation inputs within error bars or by using global simulations. If both the ion heat flux and the measured temperature fluctuations are attributed predominantly to long-wavelength turbulence, then under-prediction of electron heat flux strongly suggests that electron scale turbulence is important for transport in C-Mod Ohmic L-mode discharges. In addition, no evidence is found from linear or nonlinear simulations for a clear transition from trapped electron mode to ion temperature gradient turbulence across the LOC/SOC transition, and also there is no evidence in these Ohmic L-mode plasmas of the “Transport Shortfall” [C. Holland et al., Phys. Plasmas 16, 052301 (2009)].

  8. [Periodic fluctuation features of air temperature, precipitation, and aboveground net primary production of alpine meadow ecosystem on Qinghai-Tibetan Plateau]. (United States)

    Zhang, Fa-wei; Li, Hong-qin; Li, Ying-nian; Li, Yi-kang; Lin, Li


    With Mexican Hat function as mother function, a wavelet analysis was conducted on the periodic fluctuation features of air temperature, precipitation, and aboveground net primary production (ANPP) in the Alpine Meadow Ecosystem Research Station, Chinese Academy of Sciences from 1980 to 2007. The results showed that there was a main period of 13 years for the annual fluctuations of air temperature, precipitation, and ANPP. A secondary period of 2 years for the annual fluctuations of air temperature and ANPP had lesser influence, whereas that of 4 years for the annual fluctuation of precipitation had greater effect. Lagged correlation analysis indicated that the annual fluctuation of ANNP was mainly controlled by the air temperature in a 20 years scale and had a weak 5-9 years lag effect, but there was a less correlation between ANPP and precipitation.

  9. Similarity between turbulent kinetic energy and temperature spectra in the near-wall region (United States)

    Antonia, R. A.; Kim, J.


    The similarity between turbulent kinetic energy and temperature spectra, previously confirmed using experimental data in various turbulent shear flows, is validated in the near-wall region using direct numerical simulation data in a fully developed turbulent channel flow. The dependence of this similarity on the molecular Prandtl number is also examined.

  10. Development of a generally valid model for calculating combustion chamber wall temperatures in internal combustion engines. Wall temperature model - final report; Entwicklung eines allgemeingueltigen Modells zur Berechnung der Brennraumwandtemperaturen bei Verbrennungsmotoren. Wandtemperaturmodell - Abschlussbericht

    Energy Technology Data Exchange (ETDEWEB)

    Manz, P. [Volkswagen AG, Wolfsburg (Germany); Bargende, M.; Sargenti, R. [Stuttgart Univ. (DE). Inst. fuer Verbrennungsmotoren und Kraftfahrwesen (IVK)


    Starting from the literature research in the FVV-Project 722, the objective of this project was set on the development of a universally valid model for the calculation of wall temperatures in combustion engines. To reach this target, intensive research work was necessary to improve the simple zero-dimensional modeling of the in-cylinder processes. For this reason, a 2.3 l Otto-engine was fitted with thermocouples in a manner to permit accurate measurements of wall temperatures of both cylinder liner wall and cylinder head. To allow for the calculation of the thermodynamic boundary conditions of the gas phase using a pressure history analysis, the engine was indicated in all four cylinders. The parameters cooling liquid temperature and oil temperature were highly varied to examine their influence on the wall temperature. Simultaneous to the test bench measurements, the components for the numerical calculation of the wall temperature were programmed and analyzed. The modular description of the combustion chamber enables modelling of an arbitrary combustion engine. For the calculation of the influence of the gas phase heat, the working process analyses was performed by an external simulation program. The wall temperature model can be used as an independent tool as well as an integrated part of a coupled simulation. In a pressure history analysis the wall temperatures needed for the calculation of the wall heat can be determined precisely. In case of a coupling with a one-dimensional simulation tool, the wall temperature model is used for an iterative calculation of the wall temperatures and the wall heat fluxes. Due to the possibility of an arbitrary discretisation of the cylinder liner, this model can also be applied to a three-dimensional simulation for the initial calculation of the boundary conditions. (orig.)

  11. Comparison analysis of wooden house thermal comfort in tropical coast and mountainous by using wall surface temperature difference (United States)

    Hendriani, Adinda Septi; Hermawan, Retyanto, Banar


    Passive thermal comfort can be analyzed through several ways including through analyzing thermal of building envelope. The wall is one of building envelope that affect the performance of the thermal buildings. Quantitative research aims to analyze the thermal comfort of the wooden house in the tropical coastal and mountains by using the surface temperature of the walls of the building. Data retrieval was done by measurement of the surface temperature of the outer and inner side of the wall using infrared thermometers at 5 am, 12 pm, 5 pm and 8 pm. The wall is measured the wall which bordering the spaces outside and exposed to the sun light. The measurement was done at 10 wooden house in a tropical coastal and 10 wooden house in tropical mountains. The surface temperature average of the outside wall of a tropical coastal house by 27.1°C, while the inner side wall has a surface temperature by 26.2°C. The difference between the average temperature of the outer surface and its inner surface by 0.9°C (lowering temperature). Tropical mountain residences have an average temperature of the outer side wall by 18.0°C and the average temperature inner side wall by 18.8°C. The difference between the average temperature of the outer surface and inner surface by 0.8 °C (raise the temperature). The nature of the wood is a storage temperature of the radiation so adjusting the temperature of the radiation that exist on a specific area. It can be concluded that the timber wall is more suitable for residential houses in the tropical coast than tropical mountains based on the difference in surface temperature.

  12. Ultrasonic thermometry simulation in a random fluctuating medium: Evidence of the acoustic signature of a one-percent temperature difference. (United States)

    Nagaso, M; Moysan, J; Benjeddou, S; Massacret, N; Ploix, M A; Komatitsch, D; Lhuillier, C


    We study the development potential of ultrasonic thermometry in a liquid fluctuating sodium environment similar to that present in a Sodium-cooled Fast Reactor, and thus investigate if and how ultrasonic thermometry could be used to monitor the sodium flow at the outlet of the reactor core. In particular we study if small temperature variations in the sodium flow of e.g. about 1% of the sodium temperature, i.e., about 5°C, can have a reliably-measurable acoustic signature. Since to our knowledge no experimental setups are available for such a study, and considering the practical difficulties of experimentation in sodium, we resort to a numerical technique for full wave propagation called the spectral-element method, which is a highly accurate finite-element method owing to the high-degree basis functions it uses. We obtain clear time-of-flight variations in the case of a small temperature difference of one percent in the case of a static temperature gradient as well as in the presence of a random fluctuation of the temperature field in the turbulent flow. The numerical simulations underline the potential of ultrasonic thermometry in such a context. Copyright © 2016 Elsevier B.V. All rights reserved.

  13. Wall temperature measurements at elevated pressures and high temperatures in sooting flames in a gas turbine model combustor (United States)

    Nau, Patrick; Yin, Zhiyao; Geigle, Klaus Peter; Meier, Wolfgang


    Wall temperatures were measured with thermographic phosphors on the quartz walls of a model combustor in ethylene/air swirl flames at 3 bar. Three operating conditions were investigated with different stoichiometries and with or without additional injection of oxidation air downstream of the primary combustion zone. YAG:Eu and YAG:Dy were used to cover a total temperature range of 1000-1800 K. Measurements were challenging due to the high thermal background from soot and window degradation at high temperatures. The heat flux through the windows was estimated from the temperature gradient between the in- and outside of the windows. Differences in temperature and heat flux density profiles for the investigated cases can be explained very well with the previously measured differences in flame temperatures and flame shapes. The heat loss relative to thermal load is quite similar for all investigated flames (15-16%). The results complement previous measurements in these flames to investigate soot formation and oxidation. It is expected, that the data set is a valuable input for numerical simulations of these flames.

  14. On the Use of GOES Thermal Data to Study Effects of Land Use on Diurnal Temperature Fluctuation. (United States)

    Shih, S. F.; Chen, E.


    Geostationary Operational Environmental Satellite (GOES) infrared data were used to study the effect of land use on the diurnal surface temperature fluctuation. Five major land use types in southern Florida: the sandy soil agricultural area; the Everglades Agricultural Area (EAA); the conservation areas; the Natural Everglades Area (NEA); and Lake Okeechobee; were observed. The average daytime and nocturnal surface temperatures of sandy soil in agricultural areas was lower than that of organic soil in agricultural areas. The average temperature of organic soil in agricultural areas was lower than that of organic soil in conservation areas. The surface temperature in the wet marsh area was much lower than that in a large water-storage lake. A land use change in the EAA, and an increase in the water storage in Lake Okeechobee and the conservation areas could influence the microclimate.

  15. Interannual variability in temperature and precipitation alone cannot explain Holocene glacier fluctuations in the Southern Alps of New Zealand (United States)

    Doughty, Alice; Mackintosh, Andrew; Anderson, Brian; Putnam, Aaron; Dadic, Ruzica; Barrell, David; Denton, George; Chinn, Trevor; Schaefer, Joerg


    Several glacial modeling studies suggest that interannual climate variability within an unchanged mean climate state can cause large fluctuations in glacier length (~1 km), which would complicate interpretations of moraine records as proxy evidence of past climatic change. We modeled glacier fluctuations forced by stochastic variability in mean annual temperature and total annual precipitation and compared them to the mapped and dated Holocene moraine sequence in the Cameron valley, New Zealand. Using a 2D coupled mass balance - ice flow model, we simulated interannual mass balance, ice volume, and glacier length changes and show that stochastic variability does not cause large advances (>300 m) of the Cameron Glacier. We suggest that the glacier has been responding to shifts in the mean climate, and thus its moraine record is a valuable indicator of past climate.

  16. Effects of solid inertial particles on the velocity and temperature statistics of wall bounded turbulent flow

    DEFF Research Database (Denmark)

    Nakhaei, Mohammadhadi; Lessani, B.


    The effect of solid inertial particles on the velocity and temperature statistics of a non-isothermal turbulentchannel flow is studied using direct numerical simulation. The particles inertia is varied by changingthe particles diameter. The density of particles is kept constant. A two-way coupled...... Eulerian–Lagrangianapproach is adopted to solve the carrier flow field and the motion of dispersed particles. Three differentparticle Stokes numbers of St = 24, 60, 192, at a constant particle mass loading of φm = 0:54, are considered.The mean and rms profiles of velocity and temperature for fluid...... and particles, and the scatter plotsof fluid-particle temperature differences are presented. In addition, the variations of different budgetterms for the turbulent kinetic energy equation and fluctuating temperature variance equation in thepresence of particles are reported. The fluid turbulent heat flux...

  17. Simple theory of low-temperature thermal conductivity in single- and double-walled carbon nanotubes (United States)

    Chalin, D. V.; Avramenko, M. V.; Rochal, S. B.


    Low-temperature phonon thermal conductance (PTC) of any 1D system increases proportionally to the temperature. However, here we show that in single- and double-walled carbon nanotubes (CNTs), starting from 3-6 K, the PTC increases faster than the linear function, since the low-frequency modes of dispersion curves, which do not tend to zero together with the wave vector, are excited. To develop the PTC theory, we combine the Landauer's ballistic approach with the simple continuous model proposed for the calculation of the low-frequency phonon spectra of both free nanotubes and those interacting with an environment. The approach obtained is valid not only for commensurate double-walled CNTs, but also for incommensurate ones. The temperature-dependent relation between the PTC of double-walled CNT and those of its constituent SWNTs is obtained and discussed. The low-temperature heat transfer in bulk materials originated from CNTs is also considered and the upper limit of thermal conductivity of such materials is determined. We argue that the ideal material consisting of CNTs can challenge diamond only when the mean length of its defect-free nanotubes reaches at least one hundred of micrometers.

  18. Bayesian inferences of the thermal properties of a wall using temperature and heat flux measurements

    KAUST Repository

    Iglesias, Marco


    The assessment of the thermal properties of walls is essential for accurate building energy simulations that are needed to make effective energy-saving policies. These properties are usually investigated through in situ measurements of temperature and heat flux over extended time periods. The one-dimensional heat equation with unknown Dirichlet boundary conditions is used to model the heat transfer process through the wall. In Ruggeri et al. (2017), it was assessed the uncertainty about the thermal diffusivity parameter using different synthetic data sets. In this work, we adapt this methodology to an experimental study conducted in an environmental chamber, with measurements recorded every minute from temperature probes and heat flux sensors placed on both sides of a solid brick wall over a five-day period. The observed time series are locally averaged, according to a smoothing procedure determined by the solution of a criterion function optimization problem, to fit the required set of noise model assumptions. Therefore, after preprocessing, we can reasonably assume that the temperature and the heat flux measurements have stationary Gaussian noise and we can avoid working with full covariance matrices. The results show that our technique reduces the bias error of the estimated parameters when compared to other approaches. Finally, we compute the information gain under two experimental setups to recommend how the user can efficiently determine the duration of the measurement campaign and the range of the external temperature oscillation.

  19. Monitoring of Refractory Wall recession using high temperature impact echo instrumentation

    Energy Technology Data Exchange (ETDEWEB)

    University of Dayton


    Regression of refractory linings of furnaces occurs due to a variety of mechanisms. The specific mechanism selected for investigation during this program is the regression of refractories which are in direct contact with a liquid corrodant. Examples include the melting of glass, the production of pig iron and steel, and the melting of aluminum. The rates of regression to a wall thickness which requires reline or extensive reconstruction vary widely, from less than a year to over ten years depending on the specific service environment. This program investigated the feasibility of measuring refractory wall thickness with an impact-echo method while at operating temperature (wall temperatures exceeding 500 C). The impact-echo method uses the impact of a small sphere with the surface of the test object to send a stress wave into the object. In a plate-like structure, the stress wave reflects back to the front surface, reverberating in the structure and causing a periodic surface displacement whose frequency is inversely proportional to the thickness of the test object. Impact-echo testing was chosen because it requires access to only one side of the test object and could be performed during the operation of a refractory structure. Commercially-available impact-echo instrumentation is available for room temperature use for a variety of tests on concrete. The enabling technology for this work was to use a high-temperature piezoelectric material, aluminum nitride, as the receiving sensor for the stress waves, allowing its use on refractories during furnace operation.

  20. The effect of developmental temperature fluctuation on wing traits and stressed locomotor performance in Drosophila melanogaster, and its dependence on heterozygosity

    DEFF Research Database (Denmark)

    Kjaersgaard, Anders; Le, Nguyet; Demontis, Ditte


    Background: Natural environments fluctuate and all organisms experience some degree of environmental variance. Global climate models predict increasing environmental variance in the future. Yet we do not fully understand how environmental variation affects performance traits. Questions: Does...... temperature fluctuation during development affect adult size and wing shape in Drosophila melanogaster? If so, are the effects predictable? Do they depend on heterozygosity? Do fluctuations in developmental temperature affect adult physiological performance at high temperature? Methods: We tested the effect...... of one fluctuating (21 degrees C/29 degrees C) and several constant (21 degrees C, 23 degrees C, 25 degrees C, 27 degrees C, 29 degrees C) developmental temperature regimes on three wing morphometric traits (wing length, wing width, and wing shape) in an experiment using three inbred lines of D...

  1. Identification of microscopic domain wall motion from temperature dependence of nonlinear dielectric response.

    Czech Academy of Sciences Publication Activity Database

    Mokrý, Pavel; Sluka, T.


    Roč. 110, č. 16 (2017), č. článku 162906. ISSN 0003-6951 R&D Projects: GA ČR(CZ) GA14-32228S Institutional support: RVO:61389021 Keywords : microscopic domain wall * electric fields * temperature dependence Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 3.411, year: 2016

  2. Development and Operation of the AEDC High Temperature Wall Laboratory (HTWL) (United States)


    AEDC-TMR-95-P1 III it" DEVELOPMENT AND OPERATION OF THE AEDC HIGH TEMPERATURE WALL LABORATORY (HTWL) G. R. Beitel Micro Craft Technology/AEDC...PROJECT NUMBER 5e. TASK NUMBER 5f. WORK UNIT NUMBER 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) Micro Craft Technology/AEDC Operations...29 5. HTWL Equipment Layout 32 6. Ballast Resistor Bank and Water Flow System Details 33 7. HTL High Pressure Demineralized Water Pump 34 8. Blowdown

  3. Influence of Brick Walls on the Temperature Distribution in Steel Columns in Fire

    Directory of Open Access Journals (Sweden)

    António J. P. Moura Correia


    Full Text Available This paper reports on a study of steel columns embedded in walls in fire. Several fire resistance tests were carried out at the Laboratory of Testing Materials and Structures of the University of Coimbra, in Portugal. The temperatures registered in several points of the experimental models are compared with those obtained in numerical simulations carried out with the SUPERTEMPCALC finite element program. 

  4. Experimental validation of error in temperature measurements in thin walled ductile iron castings

    DEFF Research Database (Denmark)

    Pedersen, Karl Martin; Tiedje, Niels Skat


    An experimental analysis has been performed to validate the measurement error of cooling curves measured in thin walled ductile cast iron. Specially designed thermocouples with Ø0.2 mm thermocouple wire in Ø1.6 mm ceramic tube was used for the experiments. Temperatures were measured in plates...... to a level about 20C lower than the actual temperature in the casting. Factors affecting the measurement error (oxide layer on the thermocouple wire, penetration into the ceramic tube and variation in placement of thermocouple) are discussed. Finally, it is shown how useful cooling curve may be obtained...

  5. The effect of developmental temperature fluctuation on wing traits and stressed locomotor performance in Drosophila melanogaster, and its dependence on heterozygosity

    DEFF Research Database (Denmark)

    Kjaersgaard, Anders; Le, Nguyet; Demontis, Ditte


    temperature fluctuation during development affect adult size and wing shape in Drosophila melanogaster? If so, are the effects predictable? Do they depend on heterozygosity? Do fluctuations in developmental temperature affect adult physiological performance at high temperature? Methods: We tested the effect...... of one fluctuating (21 degrees C/29 degrees C) and several constant (21 degrees C, 23 degrees C, 25 degrees C, 27 degrees C, 29 degrees C) developmental temperature regimes on three wing morphometric traits (wing length, wing width, and wing shape) in an experiment using three inbred lines of D...... temperatures also showed greater plasticity in wing aspect. Conclusion: The widespread use of constant developmental temperatures in laboratory experiments may lead to overestimation of performance....

  6. Temperature-dependent optical resonance in a thin-walled tubular oxide microcavity

    Directory of Open Access Journals (Sweden)

    Yangfu Fang


    Full Text Available This work proposes a temperature-response capability of optical resonance in tubular optical oxide microcavities. The thin wall thickness with a subwavelength scale enables these microcavities to interact with the environment effectively. By optimization of the geometries and materials, the tubular microcavities can be tuned into temperature-inert in vacuum, and the experiments support this design. The experiments prove the idea of utilizing them as temperature-inert microcavities. Contrary wavelength shifts from previous studies were observed, which can be explained with the theoretical model. Furthermore, the theoretical results of the present work suggest that novel rolled-up microtubes could act as an exceptional optical microcavity for the application in temperature response.

  7. The Importance of Water Temperature Fluctuations in Relation to the Hydrological Factor. Case Study – Bistrita River Basin (Romania

    Directory of Open Access Journals (Sweden)

    Cojoc Gianina Maria


    Full Text Available The increase in most components of the climate over the past 50 years, including air and water temperature, is a real phenomenon, as attested by the numerous specialized researches according to IPCC (2013. The water temperature is one of the most important climatic components in analyzing the hydrological regime of the Bistrita River (Romania. The thermal regime of the Bistrita River basin and the frost phenomena associated with the risk factor are particularly important and frequently appear in this area. In recent years, under the Siret Water Basin Administration, this parameter was permanently monitored, so we could do an analysis, which shows that the water temperature fluctuations, influenced by air temperature, lead to the emergence of the ice jam phenomenon. The present study aims to analyze the water temperature, as compared to the air temperature, and the effect of these components on the liquid flow regime (the values were recorded at the hydrological stations on the main course of the Bistrita River. The negative effects resulted from the ice jam phenomenon require developing methods of damage prevention and defense. The frost phenomena recorded after the construction of the Bicaz dam are analyzed in this article

  8. Comparison of electron temperature fluctuations with gyrokinetic sumulations across the ohmic energy confinement transition in Alcator C-Mod (United States)

    Sung, C.; White, A.; Howard, N.; Mikkelsen, D.; Rice, J.; Reinke, M.; Gao, C.; Ennever, P.; Porkolab, M.; Churchill, R.; Theiler, C.; Hubbard, A.; Greenwald, M.


    Long wavelength electron temperature fluctuations (kyρs < 0 . 3) near the edge (r / a ~ 0 . 85) are reduced across the ohmic confinement transition from Linear Ohmic Confinement(LOC) regime to Saturated Ohmic Confinement(SOC) regime in Alcator C-Mod. Linear stability analysis shows that the dominant mode of long wavelength turbulence near the edge is changed from Trapped Electron Mode(TEM) to Ion Temperature Gradient(ITG) mode while the dominant mode is not changed deeper in the core (r / a ~ 0 . 5). This indicates that local turbulence changes near the edge might be responsible for the change of global energy confinement in ohmic plasmas. Further study using nonlinear gyrokinetic simulations is being performed to clarify the relation between the change of local turbulence and global ohmic energy confinement. Through nonlinear gyrokinetic simulation (GYRO), we will investigate the change of fluctuating quantities (T~ , ñ , ϕ~) and their phase relations across ohmic confinement transitions, and relate them to the change of energy transport. A synthetic CECE diagnostic for C-Mod has been developed, and it will be used to validate the gyrokinetic simulations. Research supported by USDoE awards DE-SC0006419, DE-FC02-99ER54512.

  9. The physics of nanoelectronics transport and fluctuation phenomena at low temperatures

    CERN Document Server

    Heikkila, Tero T


    Advances in nanotechnology have allowed physicists and engineers to miniaturize electronic structures to the limit where finite-size related phenomena start to impact their properties. This book discusses such phenomena and models made for their description. The book starts from the semiclassical description of nonequilibrium effects, details the scattering theory used for quantum transport calculations, and explains the main interference effects. It also describes how to treat fluctuations and correlations, how interactions affect transport through small islands, and how superconductivity modifies these effects. The last two chapters describe new emerging fields related with graphene and nanoelectromechanics. The focus of the book is on the phenomena rather than formalism, but the book still explains in detail the main models constructed for these phenomena. It also introduces a number of electronic devices, including the single-electron transistor, the superconducting tunnel junction refrigerator, and the s...

  10. Daily thermal fluctuations to a range of subzero temperatures enhance cold hardiness of winter-acclimated turtles. (United States)

    Wiebler, James M; Kumar, Manisha; Muir, Timothy J


    Although seasonal increases in cold hardiness are well documented for temperate and polar ectotherms, relatively little is known about supplemental increases in cold hardiness during winter. Because many animals are exposed to considerable thermal variation in winter, they may benefit from a quick enhancement of cold tolerance prior to extreme low temperature. Hatchling painted turtles (Chrysemys picta) overwintering in their natal nests experience substantial thermal variation in winter, and recently, it was found that brief subzero chilling of winter-acclimated hatchlings decreases subsequent chilling-induced mortality, increases blood concentrations of glucose and lactate, and protects the brain from cryoinjury. Here, we further characterize that phenomenon, termed 'cold conditioning', by exposing winter-acclimated hatchling turtles to -3.5, -7.0, or -10.5 °C gradually or repeatedly via daily thermal fluctuations over the course of 5 days and assessing their survival of a subsequent cold shock to a discriminating temperature of -12.7 °C. To better understand the physiological response to cold conditioning, we measured changes in glucose and lactate concentrations in the liver, blood, and brain. Cold conditioning significantly increased cold-shock survival, from 9% in reference turtles up to 74% in cold-conditioned turtles, and ecologically relevant daily thermal fluctuations were at least as effective at conferring cryoprotection as was gradual cold conditioning. Cold conditioning increased glucose concentrations, up to 25 μmol g -1 , and lactate concentrations, up to 30 μmol g -1 , in the liver, blood, and brain. Turtles that were cold conditioned with daily thermal fluctuations accumulated more glucose in the liver, blood, and brain, and had lower brain lactate, than those gradually cold conditioned. Given the thermal variation to which hatchling painted turtles are exposed in winter, we suggest that the supplemental protection conferred by cold

  11. Additional double-wall roof in single-wall, closed, convective incubators: Impact on body heat loss from premature infants and optimal adjustment of the incubator air temperature. (United States)

    Delanaud, Stéphane; Decima, Pauline; Pelletier, Amandine; Libert, Jean-Pierre; Stephan-Blanchard, Erwan; Bach, Véronique; Tourneux, Pierre


    Radiant heat loss is high in low-birth-weight (LBW) neonates. Double-wall or single-wall incubators with an additional double-wall roof panel that can be removed during phototherapy are used to reduce Radiant heat loss. There are no data on how the incubators should be used when this second roof panel is removed. The aim of the study was to assess the heat exchanges in LBW neonates in a single-wall incubator with and without an additional roof panel. To determine the optimal thermoneutral incubator air temperature. Influence of the additional double-wall roof was assessed by using a thermal mannequin simulating a LBW neonate. Then, we calculated the optimal incubator air temperature from a cohort of human LBW neonate in the absence of the additional roof panel. Twenty-three LBW neonates (birth weight: 750-1800g; gestational age: 28-32 weeks) were included. With the additional roof panel, R was lower but convective and evaporative skin heat losses were greater. This difference can be overcome by increasing the incubator air temperature by 0.15-0.20°C. The benefit of an additional roof panel was cancelled out by greater body heat losses through other routes. Understanding the heat transfers between the neonate and the environment is essential for optimizing incubators. Copyright © 2016 IPEM. Published by Elsevier Ltd. All rights reserved.

  12. The effect of temperature on photosynthetic induction under fluctuating light in Chrysanthemum morifolium

    DEFF Research Database (Denmark)

    Öztürk, Isik; Ottosen, Carl-Otto; Ritz, Christian


    The temporal course of photosynthetic induction was investigated on Chrysanthemum morifolium under dynamic light and temperature conditions to evaluate the effect of climatic variables on photosynthetic induction. The Plant material was grown under uniform, controlled conditions and analyzed...

  13. Wall Cladding Effects and Occupants' Perception of Indoor Temperature of Typical Student Apartments in Surabaya, Indonesia (United States)

    Mediastika, Christina E.; Hariyono, Johan


    Three types of apartment claddings in Surabaya, Indonesia were studied to analyze their effect into bedroom temperature. They were glass windows in a niche, glass door in a balcony, and glass windows on a plain wall with glass door in a balcony. On-site temperature measurement was recorded and complemented with questionnaire surveys of occupants' perception regarding room temperature. The study showed that an apartment cladding with the largest proportion of opaque material combined with a balcony offered an indoor temperature of up to 9 °C lower than the outdoor compared to the other cladding types. Nevertheless, 72 % of occupants participated in this study, who use air conditioners during night time, including one with the cladding with the largest temperature difference claimed that the indoor temperature before air-conditioners was still too warm, which triggered air-conditioners initial time more than 10 minutes to achieve the desired indoor temperature. It indicated that the opaque material time lag played a significant role in heating the room during night time when the air-conditioner is about to be operated.

  14. Temperature-dependent optical properties of individual vascular wall components measured by optical coherence tomography. (United States)

    van der Meer, Freek J; Faber, Dirk J; Cilesiz, Inci; van Gemert, Martin J C; van Leeuwen, Ton G


    Optical properties of tissues and tissue components are important parameters in biomedical optics. We report measurements of tissue refractive index n and the attenuation coefficient mu(t) using optical coherence tomography (OCT) of individual vascular wall layers and plaque components. Moreover, since the temperature dependence of optical properties is widely known, we compare measurements at room and body temperatures. A decrease of n and mu(t) is observed in all samples, with the most profound effect on samples with high lipid content. The sample temperature is of influence on the quantitative measurements within OCT images. For extrapolation of ex-vivo experimental results, especially for structures with high lipid content, this effect should be taken into account.

  15. Experimental investigations of turbulent temperature fluctuations and phase angles in ASDEX Upgrade (United States)

    Freethy, Simon


    A complete experimental understanding of the turbulent fluctuations in tokamak plasmas is essential for providing confidence in the extrapolation of heat transport models to future experimental devices and reactors. Guided by ``predict first'' nonlinear gyrokinetic simulations with the GENE code, two new turbulence diagnostics were designed and have been installed on ASDEX Upgrade (AUG) to probe the fundamentals of ion-scale turbulent electron heat transport. The first, a 30-channel correlation ECE (CECE) radiometer, measures radial profiles (0.5 opens questions about the role of multi-scale turbulence physics, but also indicates the need for the comparison of more experimental turbulence properties to have a more complete validation hierarchy. In an effort to understand the discrepancy, predictions of the nT-phase and the radial correlation length have been made along with an assessment of their sensitivity to experimental errors. Comparison to experimental measurements will be discussed. This work is supported in part by the US DOE under Grants DE-SC0006419 and DE-SC0017381. This work has also received funding from the European Union's Horizon 2020 research and innovation programme under Grant agreement number 633053.

  16. Measurement of the fluctuating temperature field in a heated swirling jet with BOS tomography (United States)

    Lang, Henning M.; Oberleithner, Kilian; Paschereit, C. Oliver; Sieber, Moritz


    This work investigates the potential of background-oriented schlieren tomography (3D-BOS) for the temperature field reconstruction in a non-isothermal swirling jet undergoing vortex breakdown. The evaluation includes a quantitative comparison of the mean and phase-averaged temperature field with thermocouple and fast-response resistance thermometer as well as a qualitative comparison between the temperature field and the flow field obtained from particle image velocimetry (PIV). Compared to other temperature-measuring techniques, 3D-BOS enables non-invasive capturing of the entire three-dimensional temperature field. In contrast to previous 3D-BOS applications, the present investigation makes use of the special character of the flow, which provides a global instability that leads to a rotational symmetry of the jet. Additionally, the rotational motion of the jet is used to obtain a tomographic reconstruction from a single camera. The quality of 3D-BOS results with respect to the physical setup as well as the numerical procedure is analyzed and discussed. Furthermore, a new approach for the treatment of thin occluding objects in the field of view is presented.

  17. The deal with diel: Temperature fluctuations, asymmetrical warming, and ubiquitous metals contaminants. (United States)

    Hallman, Tyler A; Brooks, Marjorie L


    Climate projections over the next century include disproportionately warmer nighttime temperatures ("asymmetrical warming"). Cool nighttime temperatures lower metabolic rates of aquatic ectotherms. In contaminated waters, areas with cool nights may provide thermal refugia from high rates of daytime contaminant uptake. We exposed Cope's gray tree frogs (Hyla chrysoscelis), southern leopard frogs (Lithobates sphenocephalus), and spotted salamanders (Ambystoma maculatum) to five concentrations of a mixture of cadmium, copper, and lead under three to four temperature regimes, representing asymmetrical warming. At concentrations with intermediate toxicosis at test termination (96 h), temperature effects on acute toxicity or escape distance were evident in all study species. Asymmetrical warming (day:night, 22:20 °C; 22:22 °C) doubled or tripled mortality relative to overall cooler temperatures (20:20 °C) or cool nights (22:18 °C). Escape distances were 40-70% shorter under asymmetrical warming. Results suggest potentially grave ecological impacts from unexpected toxicosis under climate change. Copyright © 2015 Elsevier Ltd. All rights reserved.

  18. Heat Flux and Wall Temperature Estimates for the NASA Langley HIFiRE Direct Connect Rig (United States)

    Cuda, Vincent, Jr.; Hass, Neal E.


    An objective of the Hypersonic International Flight Research Experimentation (HIFiRE) Program Flight 2 is to provide validation data for high enthalpy scramjet prediction tools through a single flight test and accompanying ground tests of the HIFiRE Direct Connect Rig (HDCR) tested in the NASA LaRC Arc Heated Scramjet Test Facility (AHSTF). The HDCR is a full-scale, copper heat sink structure designed to simulate the isolator entrance conditions and isolator, pilot, and combustor section of the HIFiRE flight test experiment flowpath and is fully instrumented to assess combustion performance over a range of operating conditions simulating flight from Mach 5.5 to 8.5 and for various fueling schemes. As part of the instrumentation package, temperature and heat flux sensors were provided along the flowpath surface and also imbedded in the structure. The purpose of this paper is to demonstrate that the surface heat flux and wall temperature of the Zirconia coated copper wall can be obtained with a water-cooled heat flux gage and a sub-surface temperature measurement. An algorithm was developed which used these two measurements to reconstruct the surface conditions along the flowpath. Determinations of the surface conditions of the Zirconia coating were conducted for a variety of conditions.

  19. Oxidative stress and antioxidant defense responses of Etroplus suratensis to acute temperature fluctuations. (United States)

    Joy, Susan; Alikunju, Aneesa Painadath; Jose, Jisha; Sudha, Hari Sankar Haridasanpillai; Parambath, Prabhakaran Meethal; Puthiyedathu, Sajeevan Thavarool; Philip, Babu


    Fishes are always exposed to various environmental stresses and the chances of succumbing to such stresses are of great physiological concern. Any change in temperature from the ambient condition can induce various metabolic and physiological changes in the body. The present study evaluates the effects of temperature induced stress on the antioxidant profile of Etroplus suratensis such as superoxide dismutase, catalase, glutathione peroxidase and lipid peroxidation. Fishes of same size were kept in a thermostatized bath at three different temperature regimes viz 16°C, 27°C (ambient temperature) and 38°C for 72h. These temperatures were selected based on the CT Max (Critical Thermal Maximum) and CT Min (Critical Thermal Minimum) exhibited by E. suratensis. Superoxide dismutase and catalase activity was found maximum in brain and muscle respectively during the 48th hour of exposure in fishes kept at 38°C. At 16°C the antioxidant response of glutathione peroxidase was maximum in muscles, whereas the lipid peroxidation rate was found to be high in gills compared to other tissues. The profound increase in the levels of oxidative stress related biomarkers indicate that the thermal stressors severely affected oxidative state of E. suratensis by the second day of experiment. Such down-regulation of redox state accompanied with the induction of oxidative stress cascade may lead to physiological damage in various tissues in fishes, in vivo. However current data indicate that a transition to low and high temperature environment from ambient condition severely affected the levels and profile of the antioxidant markers overtime in E. suratensis. Copyright © 2017 Elsevier Ltd. All rights reserved.

  20. Temperature-Compensated Force/Pressure Sensor Based on Multi-Walled Carbon Nanotube Epoxy Composites

    Directory of Open Access Journals (Sweden)

    Nghia Trong Dinh


    Full Text Available In this study, we propose a multi-walled carbon nanotube epoxy composite sensor for force and pressure sensing in the range of 50 N–2 kN. A manufacturing procedure, including material preparation and deposition techniques, is proposed. The electrode dimensions and the layer thickness were optimized by the finite element method. Temperature compensation is realized by four nanocomposites elements, where only two elements are exposed to the measurand. In order to investigate the influence of the filler contents, samples with different compositions were prepared and investigated. Additionally, the specimens are characterized by cyclical and stepped force/pressure loads or at defined temperatures. The results show that the choice of the filler content should meet a compromise between sensitivity, temperature influence and noise behavior. At constant temperature, a force of at least 50N can be resolved. The measurement error due to the temperature influence is 150N in a temperature range of –20°C–50°C.

  1. Investigation of mass transfer between two parallel walls at different temperatures by a moment method (United States)

    Sloat, T. N.; Edwards, R. H.; Collins, R. L.


    One-dimensional flow between two fixed parallel walls composed of the same substance but at different temperatures and spaced a distance 1 apart is considered. The hot plate is the evaporating surface (source) and the cold plate is the condensing surface (sink). The vapor between the two plates is assumed to be a monatomic gas consisting of Maxwell molecules. Lee's moment method is used to obtain a set of six nonlinear equations. Both the nonlinear equations and a linearized approximation to them are solved.

  2. Adiabatic wall temperature and heat transfer coefficient influenced by separated supersonic flow

    Directory of Open Access Journals (Sweden)

    Leontiev Alexander


    Full Text Available Investigations of supersonic air flow around plane surface behind a rib perpendicular to the flow direction are performed. Research was carried out for free stream Mach number 2.25 and turbulent flow regime - Rex>2·107. Rib height was varied in range from 2 to 8 mm while boundary layer thickness at the nozzle exit section was about 6 mm. As a result adiabatic wall temperature and heat transfer coefficient are obtained for flow around plane surface behind a rib incontrast with the flow around plane surface without any disturbances.

  3. Heat transfer in MHD unsteady stagnation point flow with variable wall temperature

    Digital Repository Service at National Institute of Oceanography (India)

    Soundalgekar, V.M.; Murty, T.V.R.; Takhar, H.S.

    ) (J~+ P, [ wall temperature varies as Ax N is presented. Temparature profiles arc shown graphicaIIy for different values of N and the numerical values of the rate of heat transfer (- 0' (0», IJ...

  4. Effects of solar wind ultralow-frequency fluctuations on plasma sheet electron temperature: Regression analysis with support vector machine (United States)

    Wang, Chih-Ping; Kim, Hee-Jeong; Yue, Chao; Weygand, James M.; Hsu, Tung-Shin; Chu, Xiangning


    To investigate whether ultralow-frequency (ULF) fluctuations from 0.5 to 8.3 mHz in the solar wind and interplanetary magnetic field (IMF) can affect the plasma sheet electron temperature (Te) near geosynchronous distances, we use a support vector regression machine technique to decouple the effects from different solar wind parameters and their ULF fluctuation power. Te in this region varies from 0.1 to 10 keV with a median of 1.3 keV. We find that when the solar wind ULF power is weak, Te increases with increasing southward IMF Bz and solar wind speed, while it varies weakly with solar wind density. As the ULF power becomes stronger during weak IMF Bz ( 0) or northward IMF, Te becomes significantly enhanced, by a factor of up to 10. We also find that mesoscale disturbances in a time scale of a few to tens of minutes as indicated by AE during substorm expansion and recovery phases are more enhanced when the ULF power is stronger. The effect of ULF powers may be explained by stronger inward radial diffusion resulting from stronger mesoscale disturbances under higher ULF powers, which can bring high-energy plasma sheet electrons further toward geosynchronous distance. This effect of ULF powers is particularly important during weak southward IMF or northward IMF when convection electric drift is weak.

  5. Dominant bryophyte control over high-latitude soil temperature fluctuations predicted by heat transfer traits, field moisture regime and laws of thermal insulation.

    NARCIS (Netherlands)

    Soudzilovskaia, N.A.; Cornelissen, J.H.C.; van Bodegom, P.M.


    Bryophytes cover large territories in cold biomes, where they control soil temperature regime, and therefore permafrost, carbon and nutrient dynamics. The mechanisms of this control remain unclear. We quantified the dependence of soil temperature fluctuations under bryophyte mats on the interplay of

  6. Growth rate and trapping efficacy of nematode-trapping fungi under constant and fluctuating temperatures

    DEFF Research Database (Denmark)

    Fernandez, A.S.; Larsen, M.; Wolstrup, J.


    degrees C. Spores of each fungal isolate were added to faecal cultures containing eggs of Cooperia oncophora at a concentration of 6250 spores/g faeces. The cultures were incubated for 14 days at the same temperature regimes described above. Control faeces (without fungal material) were also cultured...

  7. Adaptation to fluctuating temperatures in an RNA virus is driven by the most stringent selective pressure.

    Directory of Open Access Journals (Sweden)

    María Arribas

    Full Text Available The frequency of change in the selective pressures is one of the main factors driving evolution. It is generally accepted that constant environments select specialist organisms whereas changing environments favour generalists. The particular outcome achieved in either case also depends on the relative strength of the selective pressures and on the fitness costs of mutations across environments. RNA viruses are characterized by their high genetic diversity, which provides fast adaptation to environmental changes and helps them evade most antiviral treatments. Therefore, the study of the adaptive possibilities of RNA viruses is highly relevant for both basic and applied research. In this study we have evolved an RNA virus, the bacteriophage Qβ, under three different temperatures that either were kept constant or alternated periodically. The populations obtained were analyzed at the phenotypic and the genotypic level to characterize the evolutionary process followed by the virus in each case and the amount of convergent genetic changes attained. Finally, we also investigated the influence of the pre-existent genetic diversity on adaptation to high temperature. The main conclusions that arise from our results are: i under periodically changing temperature conditions, evolution of bacteriophage Qβ is driven by the most stringent selective pressure, ii there is a high degree of evolutionary convergence between replicated populations and also among populations evolved at different temperatures, iii there are mutations specific of a particular condition, and iv adaptation to high temperatures in populations differing in their pre-existent genetic diversity takes place through the selection of a common set of mutations.

  8. Conjugated Conduction-Free Convection Heat Transfer in an Annulus Heated at Either Constant Wall Temperature or Constant Heat Flux

    Directory of Open Access Journals (Sweden)



    Full Text Available In this paper, we investigate numerically the effect of thermal boundary conditions on conjugated conduction-free convection heat transfer in an annulus between two concentric cylinders using Fourier Spectral method. The inner wall of the annulus is heated and maintained at either CWT (Constant Wall Temperature or CHF (Constant Heat Flux, while the outer wall is maintained at constant temperature. CHF case is relatively more significant for high pressure industrial applications, but it has not received much attention. This study particularly focuses the latter case (CHF. The main influencing parameters on flow and thermal fields within the annulus are: Rayleigh number Ra; thickness of inner wall Rs; radius ratio Rr and inner wall-fluid thermal conductivity ratio Kr. The study has shown that the increase in Kr increases the heat transfer rate through the annulus for heating at CWT and decreases the inner wall dimensionless temperature for heating at CHF and vice versa. It has also been proved that as the Rs increases at fixed Ra and Rr, the heat transfer rate decreases for heating at CWT and the inner wall dimensionless temperature increases for heating at CHF at Kr 1 depends on Rr. It has been shown that for certain combinations of controlling parameters there will be a value of Rr at which heat transfer rate will be minimum in the annulus in case of heating at CWT, while

  9. Consistent temperature coupling with thermal fluctuations of smooth particle hydrodynamics and molecular dynamics.

    Directory of Open Access Journals (Sweden)

    Georg C Ganzenmüller

    Full Text Available We propose a thermodynamically consistent and energy-conserving temperature coupling scheme between the atomistic and the continuum domain. The coupling scheme links the two domains using the DPDE (Dissipative Particle Dynamics at constant Energy thermostat and is designed to handle strong temperature gradients across the atomistic/continuum domain interface. The fundamentally different definitions of temperature in the continuum and atomistic domain - internal energy and heat capacity versus particle velocity - are accounted for in a straightforward and conceptually intuitive way by the DPDE thermostat. We verify the here-proposed scheme using a fluid, which is simultaneously represented as a continuum using Smooth Particle Hydrodynamics, and as an atomistically resolved liquid using Molecular Dynamics. In the case of equilibrium contact between both domains, we show that the correct microscopic equilibrium properties of the atomistic fluid are obtained. As an example of a strong non-equilibrium situation, we consider the propagation of a steady shock-wave from the continuum domain into the atomistic domain, and show that the coupling scheme conserves both energy and shock-wave dynamics. To demonstrate the applicability of our scheme to real systems, we consider shock loading of a phospholipid bilayer immersed in water in a multi-scale simulation, an interesting topic of biological relevance.


    Directory of Open Access Journals (Sweden)

    KRISTANTO Luciana


    Full Text Available Concentration has an important role in our life, especially in order to get a quality and productivity in working. With concentration we can achieve the maximum and faster result in our work. Some ways to improve concentration that being researched here is by arranging the wall color and the lamp color temperature of the room. The color used as wall color in this research was the blue 9.8B, 7.4/5.6; and the orange 8.1YR, 8.7/3.7 of the Munsell color palette. Whereas the room lighting was the fluorescent lamp in 6500K (cool daylight and 2700K (warm white color temperature. Respondents of this research were 117 undergraduate students, the average GPA was 3.28; and 20,26 years as the mean age. The concentration and cognition tests are the Army Alfa test and IST subtest 9 that conducted in the room with different condition. Found in this research that the blue with cool daylight lamp has significant impact to concentration in 2,526 Lickert scale; and that orange with cool daylight lamp has correlation 0.781 to cognition result; but the other conditions have no significancy toward concentration and cognition

  11. Zero field splitting fluctuations induced phase relaxation of Gd3+ in frozen solutions at cryogenic temperatures. (United States)

    Raitsimring, A; Dalaloyan, A; Collauto, A; Feintuch, A; Meade, T; Goldfarb, D


    Distance measurements using double electron-electron resonance (DEER) and Gd(3+) chelates for spin labels (GdSL) have been shown to be an attractive alternative to nitroxide spin labels at W-band (95GHz). The maximal distance that can be accessed by DEER measurements and the sensitivity of such measurements strongly depends on the phase relaxation of Gd(3+) chelates in frozen, glassy solutions. In this work, we explore the phase relaxation of Gd(3+)-DOTA as a representative of GdSL in temperature and concentration ranges typically used for W-band DEER measurements. We observed that in addition to the usual mechanisms of phase relaxation known for nitroxide based spin labels, GdSL are subjected to an additional phase relaxation mechanism that features an increase in the relaxation rate from the center to the periphery of the EPR spectrum. Since the EPR spectrum of GdSL is the sum of subspectra of the individual EPR transitions, we attribute this field dependence to transition dependent phase relaxation. Using simulations of the EPR spectra and its decomposition into the individual transition subspectra, we isolated the phase relaxation of each transition and found that its rate increases with |ms|. We suggest that this mechanism is due to transient zero field splitting (tZFS), where its magnitude and correlation time are scaled down and distributed as compared with similar situations in liquids. This tZFS induced phase relaxation mechanism becomes dominant (or at least significant) when all other well-known phase relaxation mechanisms, such as spectral diffusion caused by nuclear spin diffusion, instantaneous and electron spin spectral diffusion, are significantly suppressed by matrix deuteration and low concentration, and when the temperature is sufficiently low to disable spin lattice interaction as a source of phase relaxation. Copyright © 2014 Elsevier Inc. All rights reserved.

  12. Joining and fabrication techniques for high temperature structures including the first wall in fusion reactor

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Ho Jin; Lee, B. S.; Kim, K. B


    The materials for PFC's (Plasma Facing Components) in a fusion reactor are severely irradiated with fusion products in facing the high temperature plasma during the operation. The refractory materials can be maintained their excellent properties in severe operating condition by lowering surface temperature by bonding them to the high thermal conducting materials of heat sink. Hence, the joining and bonding techniques between dissimilar materials is considered to be important in case of the fusion reactor or nuclear reactor which is operated at high temperature. The first wall in the fusion reactor is heated to approximately 1000 .deg. C and irradiated severely by the plasma. In ITER, beryllium is expected as the primary armour candidate for the PFC's; other candidates including W, Mo, SiC, B4C, C/C and Si{sub 3}N{sub 4}. Since the heat affected zones in the PFC's processed by conventional welding are reported to have embrittlement and degradation in the sever operation condition, both brazing and diffusion bonding are being considered as prime candidates for the joining technique. In this report, both the materials including ceramics and the fabrication techniques including joining technique between dissimilar materials for PFC's are described. The described joining technique between the refractory materials and the dissimilar materials may be applicable for the fusion reactor and Generation-4 future nuclear reactor which are operated at high temperature and high irradiation.

  13. Evaluation of acoustic emission signals during monitoring of thick-wall vessels operating at elevated temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Anastasopoulos, A.; Tsimogiannis, A. [Envirocoustics S.A., El. Venizelou 7 and Delfon, Athens (Greece)


    Acoustic Emission testing of thick wall vessels, operating at elevated temperatures is discussed and pattern recognition methodologies for AE data evaluation are presented. Two different types of testing procedures are addressed: Cool Down monitoring and semi-continuous periodic monitoring. In both types of tests, temperature variation is the driving force of AE as opposed to traditional AE testing where controlled pressure variation is used as AE stimulus. Representative examples of reactors cool down testing as well as in-process vessel monitoring are given. AE activity as a function of temperature and pressure variation is discussed. In addition to the real-time limited criteria application, unsupervised pattern recognition is applied as a post-processing tool for multidimensional sorting, noise discrimination, characterizing defects and/or damage. On the other hand, Supervised Pattern Recognition is used for data classification in repetitive critical tests, leading to an objective quantitative comparison between repeated tests. Results show that damage sustained by the equipment can be described by the plotting the cumulative energy of AE, from critical signal classes, versus temperature. Overall, the proposed methodology can reduce the complexity of AE tests in many cases leading to higher efficiency. The possibility for real time signals classification, during permanent AE installations and continuous monitoring is discussed. (orig.)

  14. Temperature evolution of spin dynamics in two- and three-dimensional Kitaev models: Influence of fluctuating Z2 flux (United States)

    Yoshitake, Junki; Nasu, Joji; Motome, Yukitoshi


    The long-sought quantum spin liquid is a quantum-entangled magnetic state leading to the fractionalization of spin degrees of freedom. Quasiparticles emergent from the fractionalization affect not only the ground-state properties but also thermodynamic behavior in a peculiar manner. Here we investigate how the spin dynamics evolves from the high-temperature paramagnet to the quantum spin-liquid ground state, for the Kitaev spin model describing the fractionalization into itinerant matter fermions and localized Z2 fluxes. Beyond the previous studies [J. Yoshitake, J. Nasu, and Y. Motome, Phys. Rev. Lett. 117, 157203 (2016), 10.1103/PhysRevLett.117.157203; J. Yoshitake, J. Nasu, Y. Kato, and Y. Motome, Phys. Rev. B 96, 024438 (2017), 10.1103/PhysRevB.96.024438], in which the mean-field nature of the cluster dynamical mean-field theory prevented us from studying low-temperature properties, we develop a numerical technique by applying the continuous-time quantum Monte Carlo (CTQMC) method to statistical samples generated by the quantum Monte Carlo (QMC) method in a Majorana fermion representation. This QMC+CTQMC method is fully unbiased and enables us to investigate the low-temperature spin dynamics dominated by thermally excited Z2 fluxes, including the unconventional phase transition caused by Z2 flux loops in three dimensions, which was unreachable by the previous methods. We apply this technique to the Kitaev model in both two and three dimensions. Our results clearly distinguish two cases: while the dynamics changes smoothly through the crossover in the two-dimensional honeycomb case, it exhibits singular behaviors at the phase transition in the three-dimensional hyperhoneycomb case. We show that the low-temperature spin dynamics is a sensitive probe for thermally fluctuating Z2 fluxes that behave very differently between two and three dimensions.

  15. Integrity of Ceramic Parts Predicted When Loads and Temperatures Fluctuate Over Time (United States)

    Nemeth, Noel N.


    Brittle materials are being used, and being considered for use, for a wide variety of high performance applications that operate in harsh environments, including static and rotating turbine parts for unmanned aerial vehicles, auxiliary power units, and distributed power generation. Other applications include thermal protection systems, dental prosthetics, fuel cells, oxygen transport membranes, radomes, and microelectromechanical systems (MEMS). In order for these high-technology ceramics to be used successfully for structural applications that push the envelope of materials capabilities, design engineers must consider that brittle materials are designed and analyzed differently than metallic materials. Unlike ductile metals, brittle materials display a stochastic strength response because of the combination of low fracture toughness and the random nature of the size, orientation, and distribution of inherent microscopic flaws. This plus the fact that the strength of a component under load may degrade over time because of slow crack growth means that a probabilistic-based life-prediction methodology must be used when the tradeoffs of failure probability, performance, and useful life are being optimized. The CARES/Life code (which was developed at the NASA Glenn Research Center) predicts the probability of ceramic components failing from spontaneous catastrophic rupture when these components are subjected to multiaxial loading and slow crack growth conditions. Enhancements to CARES/Life now allow for the component survival probability to be calculated when loading and temperature vary over time.

  16. Average Air Temperature Inside a Room With a Semitransparent Wall With a Solar Control Film: Effect of The Emissivity

    Directory of Open Access Journals (Sweden)

    J. Xamán


    Full Text Available In this paper a theoretical study on conjugated heat transfer (natural convection, radiation and conduction in a squareroom (cavity with turbulent flow is presented, taking into account variation on the opaque wall emissivity. The room isformed by an isothermal vertical wall, two adiabatic horizontal walls and a semitransparent wall with and without acontrol solar radiation film. The governing equations for turbulent flow in 2D were solved using a finite volumeformulation and k- turbulent model. Results for an isothermal wall at 21°C and an external temperature of 35°C arepresented. The size of the room is 4.0 m length and height and the solar radiation falling directly on thesemitransparent wall was 750 W/m2 (AM2. The emissivity of the opaque walls was varied between 0.1 ≤ * ≤ 1.0.Results show that, based on the air average temperature and the effective heat flux inside the room, the solar controlfilm under study was advantageous for energy saving purposes, for emissivity values of * ≤ 0.46. A correlation onthis system for the heat transfer as a function of the emissivities was determined.

  17. Numerical simulation of wall temperature on gas pipeline due to radiation of natural gas during combustion

    Directory of Open Access Journals (Sweden)

    Ilić Marko N.


    Full Text Available This paper presents one of the possible hazardous situations during transportation of gas through the international pipeline. It describes the case when at high-pressure gas pipeline, due to mechanical or chemical effect, cracks and a gas leakage appears and the gas is somehow triggered to burn. As a consequence of heat impingement on the pipe surface, change of material properties (decreasing of strength at high temperatures will occur. In order to avoid greater rapture a reasonable pressure relief rate needs to be applied. Standards in this particular domain of depressurizing procedure are not so exact (DIN EN ISO 23251; API 521. This paper was a part of the project to make initial contribution in defining the appropriate procedure of gas operator behaving during the rare gas leakage and burning situations on pipeline network. The main part of the work consists of two calculations. The first is the numerical simulation of heat radiation of combustible gas, which affects the pipeline, done in the FLUENT software. The second is the implementation of obtained results as a boundary condition in an additional calculation of time resolved wall temperature of the pipe under consideration this temperature depending on the incident flux as well as a number of other heat flow rates, using the Matlab. Simulations were done with the help of the “E.ON Ruhrgas AG” in Essen.

  18. The use of fluctuating asymmetry and phenotypic variability as indicators of developmental instability: a test of a new method employing clonal organisms and high temperature stress

    DEFF Research Database (Denmark)

    Kristensen, TN; Pertoldi, C; Andersen, DH


    Developmental instability, as estimated by two measures - fluctuating asymmetry and phenotypic variability - was examined using sternopleural bristle number and two wing traits in a clonal strain of Drosophila mercatorum. Eggs were exposed to short-term (30 min) heat stress in water baths...... variability of both wing measures were significantly higher in adults developed from heat-stressed eggs than in adults developed from eggs kept at 25degreesC. For both wing measures, there was a tendency for the highest fluctuating asymmetry and phenotypic variability to be observed at temperatures of 37......-39degreesC, suggesting that individuals who experienced the greatest developmental instability at very high temperatures (39.5-40degreesC) did not survive the heat stress. For the two wing measures, the fluctuating asymmetry and phenotypic variability were significantly correlated, but this was not the case...

  19. APPLICATIONS OF LASERS AND OTHER TOPICS IN LASER PHYSICS AND TECHNOLOGY: Influence of atmospheric fluctuations of the induced temperature on the characteristics of laser radiation (United States)

    Banakh, Viktor A.; Smalikho, I. N.


    The expression for the function representing the second-order mutual coherence of a laser beam propagating in a turbulent atmosphere under thermal self-interaction conditions is derived in the aberration-free approximation. An analysis is made of the width of a beam, its wind refraction, and the radius of coherence as a function of the initial coherence of the radiation, of conditions of diffraction on the transmitting aperture, and of fluctuations of the wind velocity. It is shown that on increase in the power the coherence radius of cw laser radiation first increases because of thermal defocusing and then decreases due to the appearance (because of fluctuations of the wind velocity) of induced temperature inhomogeneities in air in the beam localization region. The conditions under which fluctuations of the induced temperature have a significant influence on the coherence of the radiation are determined.

  20. Laminar convective heat transfer of non-Newtonian nanofluids with constant wall temperature (United States)

    Hojjat, M.; Etemad, S. Gh.; Bagheri, R.; Thibault, J.


    Nanofluids are obtained by dispersing homogeneously nanoparticles into a base fluid. Nanofluids often exhibit higher heat transfer rate in comparison with the base fluid. In the present study, forced convection heat transfer under laminar flow conditions was investigated experimentally for three types of non-Newtonian nanofluids in a circular tube with constant wall temperature. CMC solution was used as the base fluid and γ-Al2O3, TiO2 and CuO nanoparticles were homogeneously dispersed to create nanodispersions of different concentrations. Nanofluids as well as the base fluid show shear thinning (pseudoplastic) rheological behavior. Results show that the presence of nanoparticles increases the convective heat transfer of the nanodispersions in comparison with the base fluid. The convective heat transfer enhancement is more significant when both the Peclet number and the nanoparticle concentration are increased. The increase in convective heat transfer is higher than the increase caused by the augmentation of the effective thermal conductivity.

  1. Analysis of condensation on a horizontal cylinder with unknown wall temperature and comparison with the Nusselt model of film condensation (United States)

    Bahrami, Parviz A.


    Theoretical analysis and numerical computations are performed to set forth a new model of film condensation on a horizontal cylinder. The model is more general than the well-known Nusselt model of film condensation and is designed to encompass all essential features of the Nusselt model. It is shown that a single parameter, constructed explicitly and without specification of the cylinder wall temperature, determines the degree of departure from the Nusselt model, which assumes a known and uniform wall temperature. It is also known that the Nusselt model is reached for very small, as well as very large, values of this parameter. In both limiting cases the cylinder wall temperature assumes a uniform distribution and the Nusselt model is approached. The maximum deviations between the two models is rather small for cases which are representative of cylinder dimensions, materials and conditions encountered in practice.

  2. The effect of simulated heat-shock and daily temperature fluctuations on seed germination of four species from fire-prone ecosystems

    Directory of Open Access Journals (Sweden)

    Talita Zupo


    Full Text Available ABSTRACT Seed germination in many species from fire-prone ecosystems may be triggered by heat shock and/or temperature fluctuation, and how species respond to such fire-related cues is important to understand post-fire regeneration strategies. Thus, we tested how heat shock and daily temperature fluctuations affect the germination of four species from fire-prone ecosystems; two from the Cerrado and two from the Mediterranean Basin. Seeds of all four species were subjected to four treatments: Fire (F, temperature fluctuations (TF, fire+temperature fluctuations (F+TF and control (C. After treatments, seeds were put to germinate for 60 days at 25ºC (dark. Responses differed according to species and native ecosystem. Germination percentage for the Cerrado species did not increase with any of the treatments, while germination of one Mediterranean species increased with all treatments and the other only with treatments that included fire. Although the Cerrado species did not respond to the treatments used in this study, their seeds survived the exposure to heat shock, which suggests they possess tolerance to fire. Fire frequency in the Cerrado is higher than that in Mediterranean ecosystems, thus traits related to fire-resistance would be more advantageous than traits related to post-fire recruitment, which are widespread among Mediterranean species.

  3. Glass-Transition Temperature Profile Measured in a Wood Cell Wall Using Scanning Thermal Expansion Microscope (SThEM) (United States)

    Antoniow, J. S.; Maigret, J.-E.; Jensen, C.; Trannoy, N.; Chirtoc, M.; Beaugrand, J.


    This study aims to assess the in situ spatial distribution of glass-transition temperatures ( T g) of the main lignocellulosic biopolymers of plant cell walls. Studies are conducted using scanning thermal expansion microscopy to analyze the cross-section of the cell wall of poplar. The surface topography is mapped over a range of probe-tip temperatures to capture the change of thermal expansion on the sample surface versus temperature. For different temperature values chosen between 20 °C and 250 °C, several quantitative mappings were made to show the spatial variation of the thermal expansion. As the glass transition affects the thermal expansion coefficient and elastic modulus considerably, the same data line of each topography image was extracted to identify specific thermal events in their topographic evolution as a function of temperature. In particular, it is shown that the thermal expansion of the contact surface is not uniform across the cell wall and a profile of the glass-transition temperature could thus be evidenced and quantified corresponding to the mobility of lignocellulosic polymers having a role in the organization of the cell wall structures.

  4. A New Prediction Model for Transformer Winding Hotspot Temperature Fluctuation Based on Fuzzy Information Granulation and an Optimized Wavelet Neural Network

    Directory of Open Access Journals (Sweden)

    Li Zhang


    Full Text Available Winding hotspot temperature is the key factor affecting the load capacity and service life of transformers. For the early detection of transformer winding hotspot temperature anomalies, a new prediction model for the hotspot temperature fluctuation range based on fuzzy information granulation (FIG and the chaotic particle swarm optimized wavelet neural network (CPSO-WNN is proposed in this paper. The raw data are firstly processed by FIG to extract useful information from each time window. The extracted information is then used to construct a wavelet neural network (WNN prediction model. Furthermore, the structural parameters of WNN are optimized by chaotic particle swarm optimization (CPSO before it is used to predict the fluctuation range of the hotspot temperature. By analyzing the experimental data with four different prediction models, we find that the proposed method is more effective and is of guiding significance for the operation and maintenance of transformers.

  5. Prediction of strong and weak ignition regimes in turbulent reacting flows with temperature fluctuations: A direct numerical simulation study (United States)

    Pal, Pinaki; Valorani, Mauro; Im, Hong; Wooldridge, Margaret


    The present work investigates the auto-ignition characteristics of compositionally homogeneous reactant mixtures in the presence of thermal non-uniformities and turbulent velocity fluctuations. An auto-ignition regime diagram is briefly discussed, that provides the framework for predicting the expected ignition behavior based on the thermo-chemical properties of the reactant mixture and flow/scalar field conditions. The regime diagram classifies the ignition regimes mainly into three categories: weak (deflagration dominant), reaction-controlled strong and mixing-controlled strong (volumetric ignition/spontaneous propagation dominant) regimes. Two-dimensional direct numerical simulations (DNS) of auto-ignition in a lean thermally-stratified syngas/air turbulent mixture at high-pressure, low-temperature conditions are performed to assess the validity of the regime diagram. Various parametric cases are considered corresponding to different locations on the regime diagram, by varying the characteristic turbulent Damköhler and Reynolds numbers. Detailed analysis of the reaction front propagation and heat release indicates that the observed ignition behaviors agree very well with the corresponding predictions by the regime diagram. U.S. DOE NETL award number DE-FE0007465; King Abdullah University of Science and Technology (KAUST).

  6. Coexistence of magnetic fluctuations and superconductivity in the pnictide high temperature superconductor SmFeAsO1-xFx measured by muon spin rotation. (United States)

    Drew, A J; Pratt, F L; Lancaster, T; Blundell, S J; Baker, P J; Liu, R H; Wu, G; Chen, X H; Watanabe, I; Malik, V K; Dubroka, A; Kim, K W; Rössle, M; Bernhard, C


    Muon spin rotation experiments were performed on the pnictide high temperature superconductor SmFeAsO1-xFx with x=0.18 and 0.3. We observed an unusual enhancement of slow spin fluctuations in the vicinity of the superconducting transition which suggests that the spin fluctuations contribute to the formation of an unconventional superconducting state. An estimate of the in-plane penetration depth lambda ab(0)=190(5) nm was obtained, which confirms that the pnictide superconductors obey an Uemura-style relationship between Tc and lambda ab(0);(-2).

  7. Effect of fluctuations of the linear feedback coefficient on the frequency spectrum of averaged temperature in a simple energy balance climate model (United States)

    Petrov, D. A.


    Using the stochastic approach, we analyze the effect of fluctuations of the linear feedback coefficient in a simple zero-dimensional energy balance climate model on the frequency spectrum of averaged temperature. An expression is obtained for the model spectrum in the weak noise approximation. Its features are investigated in two cases: when the frequency spectrum of the feedback coefficient is a constant (white noise) and when the spectrum contains one resonant frequency and has a Lorentz form. We consider the issue whether the feedback coefficient fluctuations can be an independent mechanism for a qualitative change in the spectrum of the climate system.

  8. UF-CHERS Measurements of Ion Temperature and Toroidal Rotation Fluctuations Associated with the Edge Harmonic Oscillation in Quiescent H-mode Plasmas (United States)

    Truong, D. D.; Fonck, R. J.; McKee, G. R.; Yan, Z.; Grierson, B. A.


    The UF-CHERS (Ultra Fast CHarge Exchange Recombination Spectroscopy) diagnostic at DIII-D measures local, long-wavelength ion temperature and toroidal velocity fluctuations at turbulence-relevant spatiotemporal scales from emission of the CVI n=8 ->7 transition. During Quiescent H-mode (QH-mode) plasmas, which offer ELM-free improved confinement, UF-CHERS measurements observed coherent, low frequency (fo 10kHz) pedestal oscillations in Ti and vtor at the Edge Harmonic Oscillation (EHO) frequency while several modes between 35-75 kHz are suppressed when the EHO appears. Although broadband ion temperature and density fluctuations were reduced by the EHO, the toroidal rotation showed increased fluctuation amplitude. Investigating ion temperature and toroidal fluctuations associated with the EHO may provide insights into the saturated instability driving the EHO. Supported by DOE Grants DE-FG02-08ER54999, DE-FC02-04ER54698, and NSF GRFP Grant DGE-1256259.

  9. Domain walls and perturbation theory in high temperature gauge theory SU(2) in 2+1 dimensions

    CERN Document Server

    Korthals-Altes, C P; Stephanov, M A; Teper, M; Altes, C Korthals


    We study the detailed properties of Z_2 domain walls in the deconfined high temperature phase of the d=2+1 SU(2) gauge theory. These walls are studied both by computer simulations of the lattice theory and by one-loop perturbative calculations. The latter are carried out both in the continuum and on the lattice. We find that leading order perturbation theory reproduces the detailed properties of these domain walls remarkably accurately even at temperatures where the effective dimensionless expansion parameter, g^2/T, is close to unity. The quantities studied include the surface tension, the action density profiles, roughening and the electric screening mass. It is only for the last quantity that we find an exception to the precocious success of perturbation theory. All this shows that, despite the presence of infrared divergences at higher orders, high-T perturbation theory can be an accurate calculational tool.

  10. Fluctuation-dissipation relation on a Melde string in a turbulent flow, considerations on a "dynamical temperature"


    Grenard, Vincent; Garnier, Nicolas; Naert, Antoine


    3,5 new printed pages; We report on measurements of the transverse fluctuations of a string in a turbulent air jet flow. Harmonic modes are excited by the fluctuating drag force, at different wave-numbers. This simple mechanical probe makes it possible to measure excitations of the flow at specific scales, averaged over space and time: it is a scale-resolved, global measurement. We also measure the dissipation associated to the string motion, and we consider the ratio of the fluctuations over...

  11. Temperature dependence of photoconductivity at 0.7 eV in single-wall carbon nanotube films

    Directory of Open Access Journals (Sweden)

    Yukitaka Matsuoka, Akihiko Fujiwara, Naoki Ogawa, Kenjiro Miyano, Hiromichi Kataura, Yutaka Maniwa, Shinzo Suzuki and Yohji Achiba


    Full Text Available Temperature dependence of photoconductivity has been investigated for single-wall carbon nanotube films at 0.7 eV. In order to clarify the effect of atmosphere on photoconductivity, measurements have been performed under helium and nitrogen gas flow in the temperature range from 10 K to room temperature (RT and from 100 K to RT, respectively. Photoconductive response monotonously increases with a decrease in temperature and tends to saturate around 10 K. No clear difference in photoconductive response under different atmosphere was observed. We discuss the mechanism of photoconductivity at 0.7 eV.

  12. Effect of temperature on the selection of semiconducting single walled carbon nanotubes using Poly(3-dodecylthiophene-2,5-diyl)

    NARCIS (Netherlands)

    Gomulya, Widianta; Salazar Rios, Jorge; Derenskyi, Vladimir; Bisri, Satria Zulkarnaen; Jung, Stefan; Fritsch, Martin; Allard, Sybille; Scherf, Ullrich; dos Santos, Maria Cristina; Loi, Maria Antonietta

    We report on the investigation of the temperature effect on the selective dispersion of single-walled carbon nanotubes (SWNTs) by Poly(3-dodecylthiophene-2,5-diy1) wrapping. The interaction mechanism between polymer chains and SWNTs is studied by controlling the polymer aggregation via variation of

  13. CAREER: Hydrothermal vent flow and temperature fluctuations: exploring long-term variability through an integrated research and education program (United States)

    Di Iorio, D.


    An acoustic scintillation system was built in partnership with ASL Environmental Sciences (Sidney BC Canada), which provided a unique opportunity for two engineering undergraduate students to live and work abroad. The acoustic instrumentation was tested in coastal waters and then deployed to study deep-sea hydrothermal plume dynamics. Undergraduate students were involved in the deployment of instrumentation and the development of processing software to give vertical velocities and temperature fluctuations from a vigorous hydrothermal vent. A graduate student thesis has yielded insights into the vertical and azimuthal dependence of entrainment and into plume bending and rise height. Teachers and Ocean Science Bowl students also participated in research cruises describing physical oceanography of estuaries, coastal waters, and deep-sea hydrothermal vents and participated in data collection, processing and analysis. Teachers used the knowledge they gained to develop creative educational curricula at their schools, to present their experiences at national conferences and to publish an article in the National Science Teachers Association - The Science Journal. One of the teachers was recently recognized with the Presidential Award for Excellence in Mathematics and Science Teaching. Working with the ocean bowl team at Oconee County High School has led to top ten placements in the national championships in 2005 (fourth place) and 2006 (sixth place). In order to increase quantitative methods in an undergraduate class, students acquire data from an ocean observatory and analyze the data for specific quantities of interest. One such project led to the calculation of the upper ocean heat content for the Greenland Sea using 7 years of Argo profiles, which showed a 0.04oC/year trend. These results were then published in JGR.

  14. C. albicans increases cell wall mannoprotein, but not mannan, in response to blood, serum and cultivation at physiological temperature. (United States)

    Kruppa, Michael; Greene, Rachel R; Noss, Ilka; Lowman, Douglas W; Williams, David L


    The cell wall of Candida albicans is central to the yeasts ability to withstand osmotic challenge, to adhere to host cells, to interact with the innate immune system and ultimately to the virulence of the organism. Little is known about the effect of culture conditions on the cell wall structure and composition of C. albicans. We examined the effect of different media and culture temperatures on the molecular weight (Mw), polymer distribution and composition of cell wall mannan and mannoprotein complex. Strain SC5314 was inoculated from frozen stock onto yeast peptone dextrose (YPD), blood or 5% serum agar media at 30 or 37°C prior to mannan/mannoprotein extraction. Cultivation of the yeast in blood or serum at physiologic temperature resulted in an additive effect on Mw, however, cultivation media had the greatest impact on Mw. Mannan from a yeast grown on blood or serum at 30°C showed a 38.9 and 28.6% increase in Mw, when compared with mannan from YPD-grown yeast at 30°C. Mannan from the yeast pregrown on blood or serum at 37°C showed increased Mw (8.8 and 26.3%) when compared with YPD mannan at 37°C. The changes in Mw over the entire polymer distribution were due to an increase in the amount of mannoprotein (23.8-100%) and a decrease in cell wall mannan (5.7-17.3%). We conclude that C. albicans alters the composition of its cell wall, and thus its phenotype, in response to cultivation in blood, serum and/or physiologic temperature by increasing the amount of the mannoprotein and decreasing the amount of the mannan in the cell wall.

  15. Fuel property and fuel temperature effects on internal nozzle flow, atomization and cyclic spray fluctuations of a direct injection spark ignition–injector


    Zigan, Lars; Shi, Jun-Mei; Krotow, Ivan; Schmitz, Ingo; Wensing, Michael; Leipertz, Alfred


    The effect of fuel properties and fuel temperature on the behaviour of the internal nozzle flow, atomization and cyclic spray fluctuations is examined for a three-hole direct injection spark ignition injector by combining numerical simulation of the nozzle flow with macroscopic and microscopic spray visualization techniques. A dominant influence of the liquid fuel viscosity on the highly unsteady, cavitating nozzle flow and spray formation was observed. A reduced viscosity (or larger Reynolds...

  16. Unsteady magnetohydrodynamic free convection flow of a second grade fluid in a porous medium with ramped wall temperature. (United States)

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


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

  17. Room temperature ammonia vapor sensing properties of transparent single walled carbon nanotube thin film (United States)

    Shobin, L. R.; Manivannan, S.


    Carbon nanotube (CNT) networks are identified as potential substitute and surpass the conventional indium doped tin oxide (ITO) in transparent conducting electrodes, thin-film transistors, solar cells, and chemical sensors. Among them, CNT based gas sensors gained more interest because of its need in environmental monitoring, industrial control, and detection of gases in warfare or for averting security threats. The unique properties of CNT networks such as high surface area, low density, high thermal conductivity and chemical sensitivity making them as a potential candidate for gas sensing applications. Commercial unsorted single walled carbon nanotubes (SWCNT) were purified by thermal oxidation and acid treatment processes and dispersed in organic solvent N-methyl pyrolidone using sonication process in the absence of polymer or surfactant. Optically transparent SWCNT networks are realized on glass substrate by coating the dispersed SWCNT with the help of dynamic spray coating process at 200ºC. The SWCNT random network was characterized by scanning electron microscopy and UV-vis-NIR spectroscopy. Gas sensing property of transparent film towards ammonia vapor is studied at room temperature by measuring the resistance change with respect to the concentration in the range 0-1000 ppm. The sensor response is increased logarithmically in the concentration range 0 to 1000 ppm with the detection limit 0.007 ppm. The random networks are able to detect ammonia vapor selectively because of the high electron donating nature of ammonia molecule to the SWCNT. The sensor is reversible and selective to ammonia vapor with response time 70 seconds and recovery time 423 seconds for 62.5 ppm with 90% optical transparency at 550 nm.

  18. Effect of dust charge fluctuations on dust acoustic structures in magnetized dusty plasma containing nonextensive electrons and two-temperature isothermal ions

    Energy Technology Data Exchange (ETDEWEB)

    Araghi, F. [Islamic Azad University, North Tehran Branch, Physics Department, Science Faculty (Iran, Islamic Republic of); Dorranian, D., E-mail: [Islamic Azad University, Laser Laboratory, Plasma Physics Research Center, Science and Research Branch (Iran, Islamic Republic of)


    Effect of dust electrical charge fluctuations on the nature of dust acoustic solitary waves (DASWs) in a four-species magnetized dusty plasma containing nonextensive electrons and two-temperature isothermal ions has been investigated. In this model, the negative dust electric charge is considered to be proportional to the plasma space potential. The nonlinear Zakharov–Kuznetsov (ZK) and modified Zakharov–Kuznetsov (mZK) equations are derived for DASWs by using the standard reductive perturbation method. The combined effects of electron nonextensivity and dust charge fluctuations on the DASW profile are analyzed. The different ranges of the nonextensive q-parameter are considered. The results show that solitary waves the amplitude and width of which depend sensitively on the nonextensive q-parameter can exist. Due to the electron nonextensivity and dust charge fluctuation rate, our dusty plasma model can admit both positive and negative potential solitons. The results show that the amplitude of the soliton increases with increasing electron nonextensivity, but its width decreases. Increasing the electrical charge fluctuations leads to a decrease in both the amplitude and width of DASWs.

  19. The decay of radar echoes from meteors with particular reference to their use in the determination of temperature fluctuations near the mesopause

    Directory of Open Access Journals (Sweden)

    W. Jones

    Full Text Available The rate of decay of a radar echo from an ionised meteor train will be governed by the diffusion coefficient of the plasma and this in turn will depend on the temperature. Very recently the temperature fluctuations near the mesopause have been monitored by this means, by the recording of the decay times of underdense trains. The usual derivation of the precise expression relating the underdense echo decay time to the temperature contains two important assumptions, (i that the train is created with a Gaussian ionisation profile, and (ii that kinetic theory may be applied to calculate the diffusion coefficient. We investigate the effect of these assumptions, showing that the first assumption is unnecessary, an underdense backscatter echo decaying exponentially with a decay time equal to λ2/(32π2D, where λ is the wavelength and D the diffusion coefficient, independently of the initial distribution. However, the second assumption is shown to be incorrect, and whereas according to kinetic theory DT1/2/ρ, where T and ρ are the atmospheric temperature and density, the correct result is DTρ. This leads to an appreciable correction to the results for the temperature fluctuations.

  20. Freezing Temperatures, Ice Nanotubes Structures, and Proton Ordering of TIP4P/ICE Water inside Single Wall Carbon Nanotubes. (United States)

    Pugliese, P; Conde, M M; Rovere, M; Gallo, P


    A very recent experimental paper importantly and unexpectedly showed that water in carbon nanotubes is already in the solid ordered phase at the temperature where bulk water boils. The water models used so far in literature for molecular dynamics simulations in carbon nanotubes show freezing temperatures lower than the experiments. We present here results from molecular dynamics simulations of water inside single walled carbon nanotubes using an extremely realistic model for both liquid and icy water, the TIP4P/ICE. The water behavior inside nanotubes of different diameters has been studied upon cooling along the isobars at ambient pressure starting from temperatures where water is in a liquid state. We studied the liquid/solid transition, and we observed freezing temperatures higher than in bulk water and that depend on the diameter of the nanotube. The maximum freezing temperature found is 390 K, which is in remarkable agreement with the recent experimental measurements. We have also analyzed the ice structure called "ice nanotube" that water forms inside the single walled carbon nanotubes when it freezes. The ice forms observed are in agreement with previous results obtained with different water models. A novel finding, a partial proton ordering, is evidenced in our ice nanotubes at finite temperature.

  1. Determining the Temperature Variation of the on the Wall of the Casting Mould during the casting of the Hadfield Steel

    Directory of Open Access Journals (Sweden)

    Constantin Marta


    Full Text Available The present paper approaches the analysis of the metal temperature variation during the filling and solidification of steel in the casting mould. Furthermore we made determinations upon the heat transfer through the wall of the casting mould. The casting temperature, the casting speed and the heat transfer through the walls of the mould have a remarkable impact upon the shrinkage process for the prevention of casting defects (heat cavities and cracks. These cavities are also development cores for the heat cracks and the concentration of strains, which reduce the chemical, physical and mechanical properties of the cast parts. The shrinkage cavities represent one of the main defects of the cast product, and their reduction should be made up to the limits of technical possibilities.

  2. Unsteady MHD free convection flow of rotating Jeffrey fluid embedded in a porous medium with ramped wall temperature (United States)

    Zin, N. A. Mohd; Khan, I.; Shafie, S.


    The effect of radiative heat transfer on unsteady magnetohydrodynamic (MHD) free convection flow of rotating Jeffrey fluid past an infinite vertical plate saturated in a porous medium with ramped wall temperature is investigated. The incompressible fluid is taken electrically conducting under influence of transverse magnetic field which perpendicular to the flow. An appropriate dimensionless variables are employed to the governing equations and solved analytically by Laplace transform technique. The results of several controlling parameters for both ramped wall temperature and an isothermal plate are presented graphically with comprehensive discussions. It has been observed that, an increase in rotation parameter, reduced the primary velocity, but an opposite behaviour is noticed for the secondary velocity. Moreover, large values of Hartmann number tends to retard the fluid flow due to the Lorentz force.

  3. Investigation of the effects of pressure gradient, temperature and wall temperature ratio on the stagnation point heat transfer for circular cylinders and gas turbine vanes (United States)

    Nagamatsu, H. T.; Duffy, R. E.


    Low and high pressure shock tubes were designed and constructed for the purpose of obtaining heat transfer data over a temperature range of 390 to 2500 K, pressures of 0.3 to 42 atm, and Mach numbers of 0.15 to 1.5 with and without pressure gradient. A square test section with adjustable top and bottom walls was constructed to produce the favorable and adverse pressure gradient over the flat plate with heat gages. A water cooled gas turbine nozzle cascade which is attached to the high pressure shock tube was obtained to measuse the heat flux over pressure and suction surfaces. Thin-film platinum heat gages with a response time of a few microseconds were developed and used to measure the heat flux for laminar, transition, and turbulent boundary layers. The laminar boundary heat flux on the shock tube wall agreed with Mirel's flat plate theory. Stagnation point heat transfer for circular cylinders at low temperature compared with the theoretical prediction, but for a gas temperature of 922 K the heat fluxes were higher than the predicted values. Preliminary flat plate heat transfer data were measured for laminar, transition, and turbulent boundary layers with and without pressure gradients for free-stream temperatures of 350 to 2575 K and flow Mach numbers of 0.11 to 1.9. The experimental heat flux data were correlated with the laminar and turbulent theories and the agreement was good at low temperatures which was not the case for higher temperatures.

  4. Shear localization and effective wall friction in a wall bounded granular flow

    Directory of Open Access Journals (Sweden)

    Artoni Riccardo


    Full Text Available In this work, granular flow rheology is investigated by means of discrete numerical simulations of a torsional, cylindrical shear cell. Firstly, we focus on azimuthal velocity profiles and study the effect of (i the confining pressure, (ii the particle-wall friction coefficient, (iii the rotating velocity of the bottom wall and (iv the cell diameter. For small cell diameters, azimuthal velocity profiles are nearly auto-similar, i.e. they are almost linear with the radial coordinate. Different strain localization regimes are observed : shear can be localized at the bottom, at the top of the shear cell, or it can be even quite distributed. This behavior originates from the competition between dissipation at the sidewalls and dissipation in the bulk of the system. Then we study the effective friction at the cylindrical wall, and point out the strong link between wall friction, slip and fluctuations of forces and velocities. Even if the system is globally below the sliding threshold, force fluctuations trigger slip events, leading to a nonzero wall slip velocity and an effective wall friction coefficient different from the particle-wall one. A scaling law was found linking slip velocity, granular temperature in the main flow direction and effective friction. Our results suggest that fluctuations are an important ingredient for theories aiming to capture the interface rheology of granular materials.

  5. Room temperature synthesis of indium tin oxide nanotubes with high precision wall thickness by electroless deposition. (United States)

    Boehme, Mario; Ionescu, Emanuel; Fu, Ganhua; Ensinger, Wolfgang


    Conductive nanotubes consisting of indium tin oxide (ITO) were fabricated by electroless deposition using ion track etched polycarbonate templates. To produce nanotubes (NTs) with thin walls and small surface roughness, the tubes were generated by a multi-step procedure under aqueous conditions. The approach reported below yields open end nanotubes with well defined outer diameter and wall thickness. In the past, zinc oxide films were mostly preferred and were synthesized using electroless deposition based on aqueous solutions. All these methods previously developed, are not adaptable in the case of ITO nanotubes, even with modifications. In the present work, therefore, we investigated the necessary conditions for the growth of ITO-NTs to achieve a wall thickness of around 10 nm. In addition, the effects of pH and reductive concentrations for the formation of ITO-NTs are also discussed.

  6. Room temperature synthesis of indium tin oxide nanotubes with high precision wall thickness by electroless deposition

    Directory of Open Access Journals (Sweden)

    Mario Boehme


    Full Text Available Conductive nanotubes consisting of indium tin oxide (ITO were fabricated by electroless deposition using ion track etched polycarbonate templates. To produce nanotubes (NTs with thin walls and small surface roughness, the tubes were generated by a multi-step procedure under aqueous conditions. The approach reported below yields open end nanotubes with well defined outer diameter and wall thickness. In the past, zinc oxide films were mostly preferred and were synthesized using electroless deposition based on aqueous solutions. All these methods previously developed, are not adaptable in the case of ITO nanotubes, even with modifications. In the present work, therefore, we investigated the necessary conditions for the growth of ITO-NTs to achieve a wall thickness of around 10 nm. In addition, the effects of pH and reductive concentrations for the formation of ITO-NTs are also discussed.

  7. Temperature-dependent optical properties of individual vascular wall components measured by optical coherence tomography

    NARCIS (Netherlands)

    van der Meer, Freek J.; Faber, Dirk J.; Cilesiz, Inci; van Gemert, Martin J. C.; van Leeuwen, Ton G.


    Optical properties of tissues and tissue components are important parameters in biomedical optics. We report measurements of tissue refractive index n and the attenuation coefficient mu(t) using optical coherence tomography (OCT) of individual vascular wall layers and plaque components. Moreover,

  8. Examination of mains water temperatures in a multi-supply wall penetration unit; Untersuchungen zur Trinkwassertemperatur bei der Mehrspartenhauseinfuehrung

    Energy Technology Data Exchange (ETDEWEB)

    Kurz, R.; Scheuring, H. [Hauff-Technik GmbH und Co. KG, Herbrechtingen (Germany)


    The test structure described below is only relevant to the immediate vicinity of the wall gland and was applied to an MSH 3000 multisupply wall penetration unit from Hauff-Technik GmbH and Co. KG, Herbrechtingen. It was installed by SWU Energie GmbH, Ulm, to supply a house in Ulm/Jungingen. The temperature measurements were recorded over a four-week period (from the end of November to the end of December 2002). The building was not occupied during the first seven days, so that water was used only irregularly (extended periods of stagnation). A four-channel meter was used to measure the respective temperatures every hour and store them with an appropriate program. Analysis was by means of an Excel chart. The temperature measurements from the MSH 3000 are summarised and the measurement results are shown. (orig.) [German] Wird die Trinkwassertemperatur durch den Einsatz der Mehrspartenhauseinfuehrung mit Fernwaerme wesentlich beeinflusst? Zur Beantwortung dieser Frage fuehrte die Hauff-Technik GmbH and Co. KG Temperaturmessungen durch. Diese zeigen, dass die Temperatur des Trinkwassers in der MSH wesentlich durch die Einspeisetemperatur aus dem Versorgungsnetz und der Raumtemperatur im Gebaeude bestimmt wird. Der Einfluss der Fernwaermeleitungen innerhalb der MSH ist dagegen gering. (orig.)

  9. Surface Air Temperature Fluctuations and Lapse Rates on Olivares Gamma Glacier, Rio Olivares Basin, Central Chile, from a Novel Meteorological Sensor Network

    Directory of Open Access Journals (Sweden)

    Edward Hanna


    Full Text Available Empirically based studies of glacier meteorology, especially for the Southern Hemisphere, are relatively sparse in the literature. Here, we use an innovative network of highly portable, low-cost thermometers to report on high-frequency (1-min time resolution surface air temperature fluctuations and lapse rates (LR in a ~800-m elevational range (from 3,675 to 4,492 m a.s.l. across the glacier Olivares Gamma in the central Andes, Chile. Temperatures were measured during an intense field campaign in late Southern summer, 19–27 March 2015, under varying weather conditions. We found a complex dependence of high-frequency LR on time of day, topography, and wider meteorological conditions, with hourly temperature variations during this week that were probably mainly associated with short- and long-wave radiation changes and not with wind speed/direction changes. Using various pairs of sites within our station network, we also analyze spatial variations in LR. Uniquely in this study, we compare temperatures measured at heights of 1-m and 2-m above the glacier surface for the network of five sites and found that temperatures at these two heights occasionally differed by more than ±4°C during the early afternoons, although the mean temperature difference is much smaller (~0.3°C. An implication of our results is that daily, hourly, or even monthly averaged LR may be insufficient for feeding into accurate melt models of glacier change, with the adoption of subhourly (ideally 1–10-min resolution LR likely to prove fruitful in developing new innovative high-time-resolution melt modelling. Our results are potentially useful as input LR for local glacier melt models and for improving the understanding of lapse rate fluctuations and glacier response to climate change.

  10. Decadal fluctuations in North Atlantic water inflow in the North Sea between 1958-2003: impacts on temperature and phytoplankton populations

    Directory of Open Access Journals (Sweden)

    Martin J. Attrill


    Full Text Available The circulation of Atlantic water along the European continental slope, in particular the inflow into the North Sea, influences North Sea water characteristics with consequent changes in the environment affecting plankton community dynamics. The long-term effect of fluctuating oceanographic conditions on the North Sea pelagic ecosystem is assessed. It is shown that (i there are similar regime shifts in the inflow through the northern North Sea and in Sea Surface Temperature, (ii long-term phytoplankton trends are influenced by the inflow only in some North Sea regions, and (iii the spatial variability in chemicophysical and biological parameters highlight the influence of smaller scale processes.

  11. Effects of reducing temperatures on the hydrogen storage capacity of double-walled carbon nanotubes with Pd loading. (United States)

    Sheng, Qu; Wu, Huimin; Wexler, David; Liu, Huakun


    The effects of different temperatures on the hydrogen sorption characteristics of double-walled carbon nanotubes (DWCNTs) with palladium loading have been investigated. When we use different temperatures, the particle sizes and specific surface areas of the samples are different, which affects the hydrogen storage capacity of the DWCNTs. In this work, the amount of hydrogen storage capacity was determined (by AMC Gas Reactor Controller) to be 1.70, 1.85, 2.00, and 1.93 wt% for pristine DWCNTS and for 2%Pd/DWCNTs-300 degrees C, 2%Pd/DWCNTs-400 degrees C, and 2%Pd/DWCNTs-500 degrees C, respectively. We found that the hydrogen storage capacity can be enhanced by loading with 2% Pd nanoparticles and selecting a suitable temperature. Furthermore, the sorption can be attributed to the chemical reaction between atomic hydrogen and the dangling bonds of the DWCNTs.

  12. Sub-250nm room temperature optical gain from AlGaN materials with strong compositional fluctuations (United States)

    Pecora, Emanuele; Zhang, Wei; Sun, Haiding; Nikiforov, A.; Yin, Jian; Paiella, Roberto; Moustakas, Theodore; Dal Negro, Luca


    Compact and portable deep-UV LEDs and laser sources are needed for a number of engineering applications including optical communications, gas sensing, biochemical agent detection, disinfection, biotechnology and medical diagnostics. We investigate the deep-UV optical emission and gain properties of AlxGa1-xN/AlyGa1-yN multiple quantum wells structure. These structures were grown by molecular-beam epitaxy on 6H-SiC substrates resulting in either homogeneous wells or various degrees of band-structure compositional fluctuations in the form of cluster-like features within the wells. We measured the TE-polarized amplified spontaneous emission in the sample with cluster-like features and quantified the optical absorption/gain coefficients and gain spectra by the Variable Stripe Length (VSL) technique under ultrafast optical pumping. We report blue-shift and narrowing of the emission, VSL traces, gain spectra, polarization studies, and the validity of the Schalow-Townes relation to demonstrate a maximum net modal gain of 120 cm-1 at 250 nm in the sample with strong compositional fluctuations. Moreover, we measure a very low gain threshold (15 μJ/cm2) . On the other hand, we found that samples with homogeneous quantum wells lead to absorption only. In addition, we report gain measurements in graded-index-separate-confined heterostructure (GRINSCH) designed to increase the device optical confinement factor.

  13. Seasonal variation in parasite infection patterns of marine fish species from the Northern Wadden Sea in relation to interannual temperature fluctuations (United States)

    Schade, Franziska M.; Raupach, Michael J.; Mathias Wegner, K.


    Marine environmental conditions are naturally changing throughout the year, affecting life cycles of hosts as well as parasites. In particular, water temperature is positively correlated with the development of many parasites and pathogenic bacteria, increasing the risk of infection and diseases during summer. Interannual temperature fluctuations are likely to alter host-parasite interactions, which may result in profound impacts on sensitive ecosystems. In this context we investigated the parasite and bacterial Vibrionaceae communities of four common small fish species (three-spined stickleback Gasterosteus aculeatus, Atlantic herring Clupea harengus, European sprat Sprattus sprattus and lesser sand eel Ammodytes tobianus) in the Northern Wadden Sea over a period of two years. Overall, we found significantly increased relative diversities of infectious species at higher temperature differentials. On the taxon-specific level some macroparasite species (trematodes, nematodes) showed a shift in infection peaks that followed the water temperatures of preceding months, whereas other parasite groups showed no effects of temperature differentials on infection parameters. Our results show that even subtle changes in seasonal temperatures may shift and modify the phenology of parasites as well as opportunistic pathogens that can have far reaching consequences for sensitive ecosystems.

  14. Assessing the relationship between global warming and mortality: Lag effects of temperature fluctuations by age and mortality categories

    Energy Technology Data Exchange (ETDEWEB)

    Yu Weiwei, E-mail: [School of Public Health and Institute of Health and Biomedical Innovation, Queensland University of Technology, Kelvin Grove, QLD 4050, Brisbane (Australia); Mengersen, Kerrie [Discipline of Mathematical Sciences, Faculty of Science and Technology, Queensland University of Technology, Brisbane (Australia); Hu Wenbiao [School of Population Health and Institute of Health and Biomedical Innovation, University of Queensland, Brisbane (Australia); Guo Yuming [School of Public Health and Institute of Health and Biomedical Innovation, Queensland University of Technology, Kelvin Grove, QLD 4050, Brisbane (Australia); Pan Xiaochuan [School of Public Health, Peking University, Beijing 100191 (China); Tong Shilu, E-mail: [School of Public Health and Institute of Health and Biomedical Innovation, Queensland University of Technology, Kelvin Grove, QLD 4050, Brisbane (Australia)


    Although interests in assessing the relationship between temperature and mortality have arisen due to climate change, relatively few data are available on lag structure of temperature-mortality relationship, particularly in the Southern Hemisphere. This study identified the lag effects of mean temperature on mortality among age groups and death categories using polynomial distributed lag models in Brisbane, Australia, a subtropical city, 1996-2004. For a 1 deg. C increase above the threshold, the highest percent increase in mortality on the current day occurred among people over 85 years (7.2% (95% CI: 4.3%, 10.2%)). The effect estimates among cardiovascular deaths were higher than those among all-cause mortality. For a 1 deg. C decrease below the threshold, the percent increases in mortality at 21 lag days were 3.9% (95% CI: 1.9%, 6.0%) and 3.4% (95% CI: 0.9%, 6.0%) for people aged over 85 years and with cardiovascular diseases, respectively. These findings may have implications for developing intervention strategies to reduce and prevent temperature-related mortality. - Highlights: > A longer lag effects in cold days and shorter lag effects in hot days. > The very old people were most vulnerable to temperature stress. > The cardiovascular mortality was also sensitive to the temperature variation. - In Brisbane, the lag effects lasted longer for cold temperatures, and shorter for hot temperatures. Elderly people and cardiovascular mortality were vulnerable to temperature stress.

  15. Effects of Operating Temperature on Droplet Casting of Flexible Polymer/Multi-Walled Carbon Nanotube Composite Gas Sensors. (United States)

    Chiou, Jin-Chern; Wu, Chin-Cheng; Huang, Yu-Chieh; Chang, Shih-Cheng; Lin, Tse-Mei


    This study examined the performance of a flexible polymer/multi-walled carbon nanotube (MWCNT) composite sensor array as a function of operating temperature. The response magnitudes of a cost-effective flexible gas sensor array equipped with a heater were measured with respect to five different operating temperatures (room temperature, 40 °C, 50 °C, 60 °C, and 70 °C) via impedance spectrum measurement and sensing response experiments. The selected polymers that were droplet cast to coat a MWCNT conductive layer to form two-layer polymer/MWCNT composite sensing films included ethyl cellulose (EC), polyethylene oxide (PEO), and polyvinylpyrrolidone (PVP). Electrical characterization of impedance, sensing response magnitude, and scanning electron microscope (SEM) morphology of each type of polymer/MWCNT composite film was performed at different operating temperatures. With respect to ethanol, the response magnitude of the sensor decreased with increasing operating temperatures. The results indicated that the higher operating temperature could reduce the response and influence the sensitivity of the polymer/MWCNT gas sensor array. The morphology of polymer/MWCNT composite films revealed that there were changes in the porous film after volatile organic compound (VOC) testing.

  16. Effects of Operating Temperature on Droplet Casting of Flexible Polymer/Multi-Walled Carbon Nanotube Composite Gas Sensors

    Directory of Open Access Journals (Sweden)

    Jin-Chern Chiou


    Full Text Available This study examined the performance of a flexible polymer/multi-walled carbon nanotube (MWCNT composite sensor array as a function of operating temperature. The response magnitudes of a cost-effective flexible gas sensor array equipped with a heater were measured with respect to five different operating temperatures (room temperature, 40 °C, 50 °C, 60 °C, and 70 °C via impedance spectrum measurement and sensing response experiments. The selected polymers that were droplet cast to coat a MWCNT conductive layer to form two-layer polymer/MWCNT composite sensing films included ethyl cellulose (EC, polyethylene oxide (PEO, and polyvinylpyrrolidone (PVP. Electrical characterization of impedance, sensing response magnitude, and scanning electron microscope (SEM morphology of each type of polymer/MWCNT composite film was performed at different operating temperatures. With respect to ethanol, the response magnitude of the sensor decreased with increasing operating temperatures. The results indicated that the higher operating temperature could reduce the response and influence the sensitivity of the polymer/MWCNT gas sensor array. The morphology of polymer/MWCNT composite films revealed that there were changes in the porous film after volatile organic compound (VOC testing.

  17. Effects of subchronic exposures to concentrated ambient particles (CAPs) in mice. III. Acute and chronic effects of CAPs on heart rate, heart-rate fluctuation, and body temperature. (United States)

    Hwang, Jing-Shiang; Nadziejko, Christine; Chen, Lung Chi


    Normal mice (C57) and mice prone to develop atherosclerosis (ApoE-/-) were implanted with electrocardiograph (EKG), core body temperature, and motion transmitters were exposed daily for 6 h to Tuxedo, NY, concentrated ambient particles (CAPs) for 5 day/wk during the spring and summer of 2003. The series of 5-min EKG monitoring and body-temperature measurements were obtained for each animal in the CAPs and filtered air sham exposure groups. Our hypothesis was that chronic exposure could cause cumulative health effects. We used our recently developed nonparametric method to estimate the daily time periods that mean heart rates (HR), body temperature, and physical activity differed significantly between the CAPs and sham exposed group. CAPs exposure most affected heart rate between 1:30 a.m. and 4:30 a.m. With the response variables being the average heart rate, body temperature, and physical activity, we adopted a two-stage modeling approach to obtain the estimates of chronic and acute effects on the changes of these three response variables. In the first stage, a time-varying model estimated daily crude effects. In the second stage, the true means of the estimated crude effects were modeled with a polynominal function of time for chronic effects, a linear term of daily CAPs exposure concentrations for acute effects, and a random component for unknown noise. A Bayesian framework combined these two stages. There were significant decreasing patterns of HR, body temperature, and physical activity for the ApoE-/- mice over the 5 mo of CAPs exposure, with smaller and nonsignificant changes for the C57 mice. The chronic effect changes of the three response variables for ApoE-/- mice were maximal in the last few weeks. There was also a significant relationship between CAPs exposure concentration and short-term changes of heart rate in ApoE-/- mice during exposure. Response variables were also defined for examining fluctuations of 5-min heart rates within long (i.e., 3-6 h

  18. Fluctuating pressures measured beneath a high-temperature, turbulent boundary layer on a flat plate at Mach number of 5 (United States)

    Parrott, Tony L.; Jones, Michael G.; Albertson, Cindy W.


    Fluctuating pressures were measured beneath a Mach 5, turbulent boundary layer on a flat plate with an array of piezoresistive sensors. The data were obtained with a digital signal acquisition system during a test run of 4 seconds. Data sampling rate was such that frequency analysis up to 62.5 kHz could be performed. To assess in situ frequency response of the sensors, a specially designed waveguide calibration system was employed to measure transfer functions of all sensors and related instrumentation. Pressure time histories were approximated well by a Gaussian prohibiting distribution. Pressure spectra were very repeatable over the array span of 76 mm. Total rms pressures ranged from 0.0017 to 0.0046 of the freestream dynamic pressure. Streamwise, space-time correlations exhibited expected decaying behavior of a turbulence generated pressure field. Average convection speed was 0.87 of freestream velocity. The trendless behavior with sensor separation indicated possible systematic errors.

  19. Rayleigh-Bénard convection instability in the presence of temperature variation at the lower wall

    Directory of Open Access Journals (Sweden)

    Jovanović Miloš M.


    Full Text Available This paper analyzes the two-dimensional viscous fluid flow between two parallel plates, where the lower plate is heated and the upper one is cooled. The temperature difference between the plates is gradually increased during a certain time period, and afterwards it is temporarily constant. The temperature distribution on the lower plate is not constant in x-direction, and there is longitudinal sinusoidal temperature variation imposed on the mean temperature. We investigate the wave number and amplitude influence of this variation on the stability of Rayleigh-Benard convective cells, by direct numerical simulation of 2-D Navier-Stokes and energy equation.

  20. Material and structural mechanical modelling and reliability of thin-walled bellows at cryogenic temperatures. Application to LHC compensation system

    CERN Document Server

    Garion, Cédric; Skoczen, Blazej

    The present thesis is dedicated to the behaviour of austenitic stainless steels at cryogenic temperatures. The plastic strain induced martensitic transformation and ductile damage are taken into account in an elastic-plastic material modelling. The kinetic law of →’ transformation and the evolution laws of kinematic/isotropic mixed hardening are established. Damage issue is analysed by different ways: mesoscopic isotropic or orthotropic model and a microscopic approach. The material parameters are measured from 316L fine gauge sheet at three levels of temperature: 293 K, 77 K and 4.2 K. The model is applied to thin-walled corrugated shell, used in the LHC interconnections. The influence of the material properties on the stability is studied by a modal analysis. The reliability of the components, defined by the Weibull distribution law, is analysed from fatigue tests. The impact on reliability of geometrical imperfections and thermo-mechanical loads is also analysed.

  1. Exact Solutions for Unsteady Free Convection Flow of Casson Fluid over an Oscillating Vertical Plate with Constant Wall Temperature

    Directory of Open Access Journals (Sweden)

    Asma Khalid


    Full Text Available The unsteady free flow of a Casson fluid past an oscillating vertical plate with constant wall temperature has been studied. The Casson fluid model is used to distinguish the non-Newtonian fluid behaviour. The governing partial differential equations corresponding to the momentum and energy equations are transformed into linear ordinary differential equations by using nondimensional variables. Laplace transform method is used to find the exact solutions of these equations. Expressions for shear stress in terms of skin friction and the rate of heat transfer in terms of Nusselt number are also obtained. Numerical results of velocity and temperature profiles with various values of embedded flow parameters are shown graphically and their effects are discussed in detail.

  2. Low temperature highlights the functional role of the cell wall integrity pathway in the regulation of growth in Saccharomyces cerevisiae. (United States)

    Córcoles-Sáez, Isaac; Ballester-Tomas, Lídia; de la Torre-Ruiz, Maria A; Prieto, Jose A; Randez-Gil, Francisca


    Unlike other stresses, the physiological significance and molecular mechanisms involved in the yeast cold response are largely unknown. In the present study, we show that the CWI (cell wall integrity) pathway plays an important role in the growth of Saccharomyces cerevisiae at low temperatures. Cells lacking the Wsc1p (wall integrity and stress response component 1) membrane sensor or the MAPKs (mitogen-activated protein kinases) Bck1p (bypass of C kinase 1), Mkk (Mapk kinase) 1p/Mkk2p or Slt2p (suppressor of lyt2) exhibited cold sensitivity. However, there was no evidence of either a cold-provoked perturbation of the cell wall or a differential cold expression program mediated by Slt2p. The results of the present study suggest that Slt2p is activated by different inputs in response to nutrient signals and mediates growth control through TORC1 (target of rapamycin 1 complex)-Sch9p (suppressor of cdc25) and PKA (protein kinase A) at low temperatures. We found that absence of TOR1 (target of rapamycin 1) causes cold sensitivity, whereas a ras2Δ mutant shows increased cold growth. Lack of Sch9p alleviates the phenotype of slt2Δ and bck1Δ mutant cells, as well as attenuation of PKA activity by overexpression of BCY1 (bypass of cyclase mutations 1). Interestingly, swi4Δ mutant cells display cold sensitivity, but the phenotype is neither mediated by the Slt2p-regulated induction of Swi4p (switching deficient 4)-responsive promoters nor influenced by osmotic stabilization. Hence, cold signalling through the CWI pathway has distinct features and might mediate still unknown effectors and targets.

  3. Temperature considerations in non-spherical bubble collapse near a rigid wall (United States)

    Alahyari Beig, Shahaboddin; Johnsen, Eric


    The inertial collapse of cavitation bubbles is known to be capable of damaging its surroundings. While significant attention has been dedicated to investigating the pressures produced by this process, less is known about heating of the surrounding medium, which may be important when collapse occurs near objects whose mechanical properties strongly depend on temperature (e.g., polymers). Using a newly developed computational approach that prevents pressure and temperature errors generated by naively implemented shock- and interface-capturing schemes, we investigate the dynamics of shock-induced collapse of gas bubbles near rigid surfaces. We characterize the temperature fields based on the relevant nondimensional parameters entering the problem. In particular, we show that bubble collapse causes temperature rises in neighboring solid objects via two mechanisms: the shock produced at collapse and heat diffusion from the hot bubble close to the object.

  4. Hydrogen Storage in Single-Walled Carbon Nanotubes at Room Temperature

    National Research Council Canada - National Science Library

    C. Liu; Y. Y. Fan; M. Liu; H. T. Cong; H. M. Cheng; M. S. Dresselhaus


    .... A hydrogen storage capacity of 4.2 weight percent, or a hydrogen to carbon atom ratio of 0.52, was achieved reproducibly at room temperature under a modestly high pressure (about 10 megapascal...

  5. Ameliorative effects of melatonin administration and photoperiods on diurnal fluctuations in cloacal temperature of Marshall broiler chickens during the hot dry season (United States)

    Sinkalu, Victor O.; Ayo, Joseph O.; Adelaiye, Alexander B.; Hambolu, Joseph O.


    Experiments were performed with the aim of determining the effect of melatonin administration on diurnal fluctuations in cloacal temperature (CT) of Marshall broiler chickens during the hot dry season. Birds in group I (12L:12D cycle) were raised under natural photoperiod of 12-h light and 12-h darkness, without melatonin supplementation, while those in group II (LL) were kept under 24-h continuous lighting, without melatonin administration. Broiler chickens in group III (LL + melatonin) were raised under 24-h continuous lighting, with melatonin supplementation at 0.5 mg/kg per os. The cloacal temperatures of 15 labeled broiler chickens from each group were measured at 6:00, 13:00, and 19:00 h, 7 days apart, from days 14-42. Temperature-humidity index was highest at day 14 of the study, with the value of 36.72 ± 0.82 °C but lowest at day 28 with the value of 30.91 ± 0.80 °C ( P broiler chickens but was delayed till day 42 in LL + MEL broiler chickens. In conclusion, melatonin administration alleviated the deleterious effects of heat stress on broiler chickens by maintaining their cloacal temperature at relatively low values.

  6. Towards the unified non-classical physics: account for quantum fluctuations in equilibrium thermodynamics via the effective temperature

    Directory of Open Access Journals (Sweden)



    Full Text Available The concept of effective temperature (ET T*(T0, T is used in order to approximately "quantize" the thermodynamic functions of the dynamical object which is in the thermal equilibrium with thermal bath being at constant temperature T (T0=E0/kB, where E0 is the ground-state energy, kB - Boltzmann constant, is the characteristic ``quantum'' temperature of the system itself. On these grounds the extensive comparative investigation is carried out for the ``standard model'' of statistical mechanics - the one-dimensional harmonic oscillator (HO. Three well-known approaches are considered and their thermodynamic consequences thoroughly studied. These are: the exact quantum, or non-classical Planck-Einstein approach, intermediate, or semiclassical Bloch-Wigner approach and, finally, the pure classical, or Maxwell-Boltzmann approach.

  7. Influence of temperature fluctuations on Escherichia coli O157:H7 and Salmonella enterica serovar Typhimurium in manure.

    NARCIS (Netherlands)

    Semenov, A.V.; Bruggen, van A.H.C.; Overbeek, van L.S.; Termorshuizen, A.J.; Semenov, A.M.


    The effects of four average temperatures (7, 16, 23 and 33°C) and daily oscillations with three amplitudes (0, ±4, ±7°C) on the survival of the enteropathogens Escherichia coli O157:H7 and Salmonella serovar Typhimurium were investigated in small microcosms. Manure was inoculated with a green

  8. Possibility for low temperature fluid-wall neutron bottle with very low neutron upscattering losses

    CERN Document Server

    Pokotilovski, Yu N


    The new recently synthesized polymers - perfluorinated polyformaldehydes have long liquid range and low melting point. Due to the expected low upscattering losses of ultracold neutrons, at low temperatures, these fluids may be good candidates for precision measurement of neutron lifetime by the method of storage of ultracold neutrons in traps.

  9. Possibility for low temperature fluid-wall neutron bottle with very low neutron upscattering losses

    Energy Technology Data Exchange (ETDEWEB)

    Pokotilovski, Yu.N


    The new recently synthesized polymers - perfluorinated polyformaldehydes have long liquid range and low melting point. Due to the expected low upscattering losses of ultracold neutrons, at low temperatures, these fluids may be good candidates for precision measurement of neutron lifetime by the method of storage of ultracold neutrons in traps.

  10. Thermal element for maintaining minimum lamp wall temperature in fluorescent fixtures (United States)

    Siminovitch, Michael J.


    In a lighting fixture including a lamp and a housing, an improvement is disclosed for maintaining a lamp envelope area at a cooler, reduced temperature relative to the enclosed housing ambient. The improvement comprises a thermal element in thermal communication with the housing extending to and springably urging thermal communication with a predetermined area of the lamp envelope surface.

  11. Temperature drives abundance fluctuations, but spatial dynamics is constrained by landscape configuration: Implications for climate-driven range shift in a butterfly. (United States)

    Fourcade, Yoan; Ranius, Thomas; Öckinger, Erik


    Prediction of species distributions in an altered climate requires knowledge on how global- and local-scale factors interact to limit their current distributions. Such knowledge can be gained through studies of spatial population dynamics at climatic range margins. Here, using a butterfly (Pyrgus armoricanus) as model species, we first predicted based on species distribution modelling that its climatically suitable habitats currently extend north of its realized range. Projecting the model into scenarios of future climate, we showed that the distribution of climatically suitable habitats may shift northward by an additional 400 km in the future. Second, we used a 13-year monitoring dataset including the majority of all habitat patches at the species northern range margin to assess the synergetic impact of temperature fluctuations and spatial distribution of habitat, microclimatic conditions and habitat quality, on abundance and colonization-extinction dynamics. The fluctuation in abundance between years was almost entirely determined by the variation in temperature during the species larval development. In contrast, colonization and extinction dynamics were better explained by patch area, between-patch connectivity and host plant density. This suggests that the response of the species to future climate change may be limited by future land use and how its host plants respond to climate change. It is, thus, probable that dispersal limitation will prevent P. armoricanus from reaching its potential future distribution. We argue that models of range dynamics should consider the factors influencing metapopulation dynamics, especially at the range edges, and not only broad-scale climate. It includes factors acting at the scale of habitat patches such as habitat quality and microclimate and landscape-scale factors such as the spatial configuration of potentially suitable patches. Knowledge of population dynamics under various environmental conditions, and the

  12. Fast domain wall motion in the vicinity of the angular momentum compensation temperature of ferrimagnets (United States)

    Kim, Kab-Jin; Kim, Se Kwon; Hirata, Yuushou; Oh, Se-Hyeok; Tono, Takayuki; Kim, Duck-Ho; Okuno, Takaya; Ham, Woo Seung; Kim, Sanghoon; Go, Gyoungchoon; Tserkovnyak, Yaroslav; Tsukamoto, Arata; Moriyama, Takahiro; Lee, Kyung-Jin; Ono, Teruo


    Antiferromagnetic spintronics is an emerging research field which aims to utilize antiferromagnets as core elements in spintronic devices. A central motivation towards this direction is that antiferromagnetic spin dynamics is expected to be much faster than its ferromagnetic counterpart. Recent theories indeed predicted faster dynamics of antiferromagnetic domain walls (DWs) than ferromagnetic DWs. However, experimental investigations of antiferromagnetic spin dynamics have remained unexplored, mainly because of the magnetic field immunity of antiferromagnets. Here we show that fast field-driven antiferromagnetic spin dynamics is realized in ferrimagnets at the angular momentum compensation point TA. Using rare earth-3d-transition metal ferrimagnetic compounds where net magnetic moment is nonzero at TA, the field-driven DW mobility is remarkably enhanced up to 20 km s-1 T-1. The collective coordinate approach generalized for ferrimagnets and atomistic spin model simulations show that this remarkable enhancement is a consequence of antiferromagnetic spin dynamics at TA. Our finding allows us to investigate the physics of antiferromagnetic spin dynamics and highlights the importance of tuning of the angular momentum compensation point of ferrimagnets, which could be a key towards ferrimagnetic spintronics.

  13. Influence of wall thickness and properties of structural materials on the discharge temperature and strength characteristics of slow-speed long-stroke stages (United States)

    Yusha, V. L.; Busarov, S. S.; Aistov, I. P.; Titov, D. S.; Vansovich, K. A.


    The article analyzes the influence of the wall thickness of the working chamber cylinder on the cooling efficiency of the compressed gas with the required strength. The obtained results indicate an ambiguous decision regarding the choice of the wall thickness. The performed calculations make it possible to develop the design of the stage, using, depending on the situation, one or another priority criterion (the minimum temperature of the compressed gas, the cost, or the mass of the stage).

  14. Electromechanical properties of multi-walled carbon nanotube/gelatin hydrogel composites: effects of aspect ratios, electric field, and temperature. (United States)

    Tungkavet, Thawatchai; Seetapan, Nispa; Pattavarakorn, Datchanee; Sirivat, Anuvat


    The effects of multi-walled carbon nanotube (MWNT) aspect ratio, electric field strength and temperature on the electromechanical properties of MWNT/gelatin hydrogel composites were investigated. The highest aspect ratio of MWNT provides the composites with the highest dynamic moduli under electric field. The MWNT/gelatin hydrogel composites of 0.01, 0.1, 0.5, and 1 vol.% and the pure gelatin hydrogel possess the storage modulus sensitivity values of 0.69, 1.23, 0.94, 0.81 and 0.47, respectively, at 800 V/mm. The results can be interpreted in terms of the enhanced polarizability between the carboxyl groups of gelatin under the presence of MWNT. The effect of temperature on the electromechanical properties of MWNT/gelatin hydrogel composites investigated between 30 °C and 90 °C shows three distinct regimes of temperature-dependent storage modulus behavior. In the deflection testing, the effects of electric field on the deflection distance and the dielectrophoresis force of the MWNT/gelatin hydrogel composites were also investigated. MWNT/gelatin hydrogel composites suspended in the silicone oil between electrodes, respond rapidly with a deflection toward the anode site, indicating the attractive force between anode and the polarized carboxyl group as the gelatin structure possesses negative charges. Copyright © 2014 Elsevier B.V. All rights reserved.

  15. Optimization of growth temperature of multi-walled carbon nanotubes synthesized by spray pyrolysis method and application for arsenic removal

    Directory of Open Access Journals (Sweden)

    S. Mageswari


    Full Text Available Multi-walled carbon nanotubes have been synthesized at different temperatures ranging from 550 °C to 750 °C on silica supported Fe-Co catalyst by spray pyrolysis method using Citrus limonum oil under nitrogen atmosphere. The as-grown MWNTs were characterized by scanning electron microscope (SEM, high resolution transmission electron microscope (HRTEM, X-ray diffraction analysis (XRD and Raman spectral studies. The HRTEM and Raman spectroscopic studies confirmed the evolution of MWNTs with the outer diameter between 25 and 38 nm. The possibility of use of as-grown MWNTs as an adsorbent for removal of As (V ions from drinking water was studied. Adsorption isotherm data were interpreted by the Langmuir and Freundlich equations. Kinetic data were studied using Elovich, pseudo-first order and pseudo-second order equations in order to elucidate the reaction mechanism.

  16. Silver nanocrystal-decorated polyoxometalate single-walled nanotubes as nanoreactors for desulfurization catalysis at room temperature. (United States)

    Zhang, Hao; Xu, Xiaobin; Lin, Haifeng; Ud Din, Muhammad Aizaz; Wang, Haiqing; Wang, Xun


    Ultrathin nanocrystals generally provide a remarkable catalytic performance due to their high specific surface area and exposure of certain active sites. However, deactivation caused by growth and gathering limits the catalytic application of ultrathin nanocrystals. Here we report Ag nanocrystal-decorated polyoxometalate (Ag-POM) single-walled nanotubes assembled via a concise, surfactant-free soaking method as a new kind of well-defined core-sheath nanoreactor. The diameter of Ag nanocrystals inside polyoxometalate nanotubes can be controlled via simply adjusting the reactant concentration. Ag-POM provided outstanding oxidative desulfurization (ODS) catalytic performance for aromatic sulfocompounds at room temperature. It was suggested that Ag nanocrystals decorated on the inner surface played a key role in adjusting the electronic distribution and enhancing the catalytic activity. The as-prepared Ag-POM nanotubes are promising candidate catalysts with enhanced performance for practical catalytic applications in the gasoline desulfurization industry.

  17. A Room-temperature Hydrogen Gas Sensor Using Palladium-decorated Single-Walled Carbon Nanotube/Si Heterojunction

    Directory of Open Access Journals (Sweden)

    Yong Gang DU


    Full Text Available We report a room-temperature (RT hydrogen gas (H2 sensor based on palladium-decorated single-walled carbon nanotube/Si (Pd-SWNTs/Si heterojunction. The current-voltage (I-V curves of the Pd-SWNTs/Si heterojunction in different concentrations of H2 were measured. The experimental results reveal that the Pd-SWNTs/Si heterojunction exhibits high H2 response. After exposure to 0.02 %, 0.05 %, and 0.1 % H2 for 10 min, the resistance of the heterojunction increases dramatically. The response is 122 %, 269 % and 457 %, respectively. A simple interfacial theory is used to understand the gas sensitivity results. This approach is a step toward future CNTs-based gas sensors for practical application.DOI:

  18. Calculation of arterial wall temperature in atherosclerotic arteries: effect of pulsatile flow, arterial geometry, and plaque structure

    Directory of Open Access Journals (Sweden)

    Kim Taehong


    Full Text Available Abstract Background This paper presents calculations of the temperature distribution in an atherosclerotic plaque experiencing an inflammatory process; it analyzes the presence of hot spots in the plaque region and their relationship to blood flow, arterial geometry, and inflammatory cell distribution. Determination of the plaque temperature has become an important topic because plaques showing a temperature inhomogeneity have a higher likelihood of rupture. As a result, monitoring plaque temperature and knowing the factors affecting it can help in the prevention of sudden rupture. Methods The transient temperature profile in inflamed atherosclerotic plaques is calculated by solving an energy equation and the Navier-Stokes equations in 2D idealized arterial models of a bending artery and an arterial bifurcation. For obtaining the numerical solution, the commercial package COMSOL 3.2 was used. The calculations correspond to a parametric study where arterial type and size, as well as plaque geometry and composition, are varied. These calculations are used to analyze the contribution of different factors affecting arterial wall temperature measurements. The main factors considered are the metabolic heat production of inflammatory cells, atherosclerotic plaque length lp, inflammatory cell layer length lmp, and inflammatory cell layer thickness dmp. Results The calculations indicate that the best location to perform the temperature measurement is at the back region of the plaque (0.5 ≤ l/lp ≤ 0.7. The location of the maximum temperature, or hot spot, at the plaque surface can move during the cardiac cycle depending on the arterial geometry and is a direct result of the blood flow pattern. For the bending artery, the hot spot moves 0.6 millimeters along the longitudinal direction; for the arterial bifurcation, the hot spot is concentrated at a single location due to the flow recirculation observed at both ends of the plaque. Focusing on the

  19. A remark on the vertical transport of large-scale temperature fluctuations by smaller-scale convection (United States)

    Gough, D. O.


    A simple mixing-length discussion of vertical diffusive transport of a scalar by small-scale turbulent convection is presented, likening it to the microscopic transport in a classical gas. If the scalar is passive, the transport is governed by the well known telegraph equation. Temperature, on the other hand, influences the dynamics of the small-scale motion by modifying the buoyancy that drives the turbulent eddies; it leads to a rather more complicated equation, which, for relatively rapid variation reduces to the same wave equation as for a passive scalar, with maximal propagation speed comparable with the rms vertical eddy velocity; but in the slow diffusive limit it reduces, for good reason, to the classical diffusion equation with a diffusivity enhanced by a factor 3/2 over that pertaining to a passive scalar.

  20. Steady flows of a highly rarefied gas induced by nonuniform wall temperature (United States)

    Kosuge, Shingo; Aoki, Kazuo; Takata, Shigeru; Hattori, Ryosuke; Sakai, Daisuke


    Steady behavior of a rarefied gas between parallel plates with sinusoidal temperature distribution is investigated on the basis of the Boltzmann equation. The Cercignani-Lampis (CL) model or the Lord model for diffuse scattering with incomplete energy accommodation is adopted as the boundary condition on the plates. Most of the analysis is carried out numerically with special interest in the free-molecular limit. In the case of the CL model, the nonuniform temperature distribution of the plates may induce a steady free-molecular flow, which is in contrast with the earlier results for the Maxwell-type model [Y. Sone, J. Méc. Théor. Appl. 3, 315 (1984); J. Méc. Théor. Appl. 4, 1 (1985)]. This fact is confirmed through an accurate deterministic computation based on an integral equation. In addition, computations for a wide range of parameters by means of the direct simulation Monte Carlo method reveal that the flow field changes according to the accommodation coefficients and is classified into four types. The effect of intermolecular collisions on the flow is also examined. In the case of the Lord model, no steady flow of the free-molecular gas is induced as in the case of the Maxwell-type model. This result is extended to the case of a more general boundary condition that gives the cosine law (Lambert's law) for the reflected molecular flux.

  1. Fluctuations in solidification

    Energy Technology Data Exchange (ETDEWEB)

    Karma, A. (Physics Department, Northeastern University, Boston, Massachusetts 02115 (United States))


    We present an analytical treatment of (i) the incorporation of thermal noise in the basic continuum models of solidification, (ii) fluctuations about nonequilibrium steady states, and (iii) the amplification of noise near the onset of morphological instability. In (i), we find that the proper Langevin formalism, consistent with both bulk and interfacial equilibrium fluctuations, consists of the usual bulk forces and an extra stochastic force on the interface associated with its local kinetics. At sufficiently large solidification rate, this force affects interfacial fluctuations on scales where they are macroscopically amplified and, thus, becomes relevant. An estimate of this rate is given. In (ii), we extend the Langevin formalism outside of equilibrium to characterize the fluctuations of a stationary and a directionally solidified planar interface in a temperature gradient. Finally, in (iii), we derive an analytic expression for the linear growth of the mean-square amplitude of fluctuations slightly above the onset of morphological instability. The amplitude of the noise is found to be determined by the small parameter [ital k][sub [ital B]T[ital E]d0][sup [ital c]l][sub [ital T

  2. On the recovery of ISW fluctuations using large-scale structure tracers and CMB temperature and polarization anisotropies (United States)

    Bonavera, L.; Barreiro, R. B.; Marcos-Caballero, A.; Vielva, P.


    In this work we present a method to extract the signal induced by the integrated Sachs-Wolfe (ISW) effect in the cosmic microwave background (CMB). It makes use of the Linear Covariance-Based filter introduced by Barreiro et al., and combines CMB data with any number of large-scale structure (LSS) surveys and lensing information. It also exploits CMB polarization to reduce cosmic variance. The performance of the method has been thoroughly tested with simulations taking into account the impact of non-ideal conditions such as incomplete sky coverage or the presence of noise. In particular, three galaxy surveys are simulated, whose redshift distributions peak at low (z ≃ 0.3), intermediate (z ≃ 0.6) and high redshift (z ≃ 0.9). The contribution of each of the considered data sets as well as the effect of a mask and noise in the reconstructed ISW map is studied in detail. When combining all the considered data sets (CMB temperature and polarization, the three galaxy surveys and the lensing map), the proposed filter successfully reconstructs a map of the weak ISW signal, finding a perfect correlation with the input signal for the ideal case and around 80 per cent, on average, in the presence of noise and incomplete sky coverage. We find that including CMB polarization improves the correlation between input and reconstruction although only at a small level. Nonetheless, given the weakness of the ISW signal, even modest improvements can be of importance. In particular, in realistic situations, in which less information is available from the LSS tracers, the effect of including polarization is larger. For instance, for the case in which the ISW signal is recovered from CMB plus only one survey, and taking into account the presence of noise and incomplete sky coverage, the improvement in the correlation coefficient can be as large as 10 per cent.

  3. Real gas effects on receptivity to kinetic fluctuations (United States)

    Tumin, Anatoli; Edwards, Luke


    Receptivity of high-speed boundary layers is considered within the framework of fluctuating hydrodynamics where stochastic forcing is introduced through fluctuating shear stress and heat flux stemming from kinetic fluctuations (thermal noise). The forcing generates unstable modes whose amplification downstream and may lead to transition. An example of high-enthalpy (16 . 53 MJ / kg) boundary layer at relatively low wall temperatures (Tw = 1000 K - 3000 K), free stream temperature (Te = 834 K), and low pressure (0 . 0433 atm) is considered. Dissociation at the chosen flow parameters is still insignificant. The stability and receptivity analyses are carried out using a solver for calorically perfect gas with effective Prandtl number and specific heats ratio. The receptivity phenomenon is unchanged by the inclusion of real gas effects in the mean flow profiles. This is attributed to the fact that the mechanism for receptivity to kinetic fluctuations is localized near the upper edge of the boundary layer. Amplitudes of the generated wave packets are larger downstream in the case including real gas effects. It was found that spectra in both cases include supersonic second Mack unstable modes despite the temperature ratio Tw /Te > 1 . Supported by AFOSR.

  4. Effects of ionic strength and temperature on the aggregation and deposition of multi-walled carbon nanotubes. (United States)

    Wang, Lixin; Yang, Xuezhi; Wang, Qi; Zeng, Yuxuan; Ding, Lei; Jiang, Wei


    The aggregation and deposition of carbon nanotubes (CNTs) determines their transport and fate in natural waters. Therefore, the aggregation kinetics of humic-acid treated multi-walled carbon nanotubes (HA-MWCNTs) was investigated by time-resolved dynamic light scattering in NaCl and CaCl2 electrolyte solutions. Increased ionic strength induced HA-MWCNT aggregation due to the less negative zeta potential and the reduced electrostatic repulsion. The critical coagulation concentration (CCC) values of HA-MWCNTs were 80mmol/L in NaCl and 1.3mmol/L in CaCl2 electrolyte, showing that Ca(2+) causes more serious aggregation than Na(+). The aggregation behavior of HA-MWCNTs was consistent with Derjaguin-Landau-Verwey-Overbeek theory. The deposition kinetics of HA-MWCNTs was measured by the optical absorbance at 800nm. The critical deposition concentrations for HA-MWCNT in NaCl and CaCl2 solutions were close to the CCC values, therefore the rate of deposition cannot be increased by changing the ionic strength in the diffusion-limited aggregation regime. The deposition process was correlated to the aggregation since larger aggregates increased gravitational deposition and decreased random Brownian diffusion. HA-MWCNTs hydrodynamic diameters were evaluated at 5, 15 and 25°C. Higher temperature caused faster aggregation due to the reduced electrostatic repulsion and increased random Brownian motion and collision frequency. HA-MWCNTs aggregate faster at higher temperature in either NaCl or CaCl2 electrolyte due to the decreased electrostatic repulsion and increased random Brownian motion. Our results suggest that CNT aggregation and deposition are two correlated processes governed by the electrolyte, and CNT transport is favored at low ionic strength and low temperature. Copyright © 2016. Published by Elsevier B.V.

  5. Shallow subsurface temperature and moisture monitoring at rock walls during freeze thaw cycles in the Northern Calcareous Alps, Austria (United States)

    Rode, Matthias; Sass, Oliver


    The process of frost weathering as well as the contribution of further weathering processes (e.g. hydration, thermal fatigue) is poorly understood. For this purpose, different measuring systems were set up in two study areas (Dachstein massif - permafrost area (2700m asl, 47° 28' 32″ N, 13° 36' 23″ E) and Gesäuse mountains - non permafrost area (900m asl, 47° 35' 19″ N, 14° 39' 32″ E) located in Styria, Austria within the framework of the research project ROCKING ALPS (FWF-P2444). A key to understand frost weathering is to observe the rock temperature with several high resolution temperature sensors from the rock surface down to -20cm depth. The temperatures are measured hourly at north and south exposed rock walls since 2012 in the headwalls of the Dachstein glacier at the Koppenkarstein (built up of limestone) in about 2600m asl. Since 2013 the same measurement setup is installed in the lower Johnsbachtal (Gesäuse mountains, prevailing rock type is dolomite) in about 800m asl. To know the temperature is crucial to understand internal heat flow and transport and latent heat effects during freezing and thawing caused by night frost (lasting some hours), cold fronts (lasting some days) or winter frost of several weeks or months. At these study points we also have installed small-scale 2D-geoelectric survey lines, supplemented by moisture sensors. Moisture is determined by means of resistivity measurements which are difficult to calibrate, but provide good time series. Additional novel moisture sensors were developed which use the heat capacity of the surrounding rock as a proxy of water content. These sensors give point readings from a defined depth and are independent from soluble salt contents. First results from the Dachstein show that short term latent heat effects during the phase change have crucial influence on the moisture content. The moisture distribution and movements during temperature changes inside the rock are discussed upon the two main

  6. Rotation-excited perfect oscillation of a tri-walled nanotube-based oscillator at ultralow temperature (United States)

    Cai, Kun; Zhang, Xiaoni; Shi, Jiao; Qin, Qing H.


    In recent years, carbon-nanotube (CNT)-based gigahertz oscillators have been widely used in numerous areas of practical engineering such as high-speed digital, analog circuits, and memory cells. One of the major challenges to practical applications of the gigahertz oscillator is generating a stable oscillation process from the gigahertz oscillators and then maintaining the stable process for a specified period of time. To address this challenge, an oscillator from a triple-walled CNT-based rotary system is proposed and analyzed numerically in this paper, using a molecular dynamics approach. In this system, the outer tube is fixed partly as a stator. The middle tube, with a constant rotation, is named Rotor 2 and runs in the stator. The inner tube acts as Rotor 1, which can rotate freely in Rotor 2. Due to the friction between the two rotors when they have relative motion, the rotational frequency of Rotor 1 increases continuously and tends to converge with that of Rotor 2. During rotation, the oscillation of Rotor 1 may be excited owing to both a strong end barrier at Rotor 2 and thermal vibration of atoms in the tubes. From the discussion on the effects of length of Rotor 1, temperature, and input rotational frequency of Rotor 2 on the dynamic response of Rotor 1, an effective way to control the oscillation of Rotor 1 is found. Being much longer than Rotor 2, Rotor 1 will have perfect oscillation, i.e., with both stable (or nearly constant) period and amplitude—especially at relatively low temperature. This discovery can be taken as a useful guidance for the design of an oscillator from CNTs.

  7. An Innovative Application of a Solar Storage Wall Combined with the Low-Temperature Organic Rankine Cycle

    Directory of Open Access Journals (Sweden)

    Tzu-Chen Hung


    Full Text Available The objective of this study is to collect energy on the waste heat from air produced by solar ventilation systems. This heat used for electricity generation by an organic Rankine cycle (ORC system was implemented. The advantages of this method include the use of existing building’s wall, and it also provides the region of energy scarcity for reference. This is also an innovative method, and the results will contribute to the efforts made toward improving the design of solar ventilation in the field of solar thermal engineering. In addition, ORC system would help generate electricity and build a low-carbon building. This study considered several critical parameters such as length of the airflow channel, intensity of solar radiation, pattern of the absorber plate, stagnant air layer, and operating conditions. The simulation results show that the highest outlet temperature and heat collecting efficiency of solar ventilation system are about 120°C and 60%, respectively. The measured ORC efficiency of the system was 6.2%. The proposed method is feasible for the waste heat from air produced by ventilation systems.

  8. Improving Station Performance by Building Isolation Walls in the Tunnel (United States)

    Jia, Yan; Horn, Nikolaus; Leohardt, Roman


    Conrad Observatory is situated far away from roads and industrial areas on the Trafelberg in Lower Austria. At the end of the seismic tunnel, the main seismic instrument of the Observatory with a station code CONA is located. This station is one of the most important seismic stations in the Austrian Seismic Network (network code OE). The seismic observatory consists of a 145m long gallery and an underground laboratory building with several working areas. About 25 meters away from the station CONA, six temporary seismic stations were implemented for research purposes. Two of them were installed with the same equipment as CONA, while the remaining four stations were set up with digitizers having lower noise and higher resolution (Q330HR) and sensors with the same type (STS-2). In order to prevent possible disturbances by air pressure and temperature fluctuation, three walls were built inside of the tunnel. The first wall is located ca 63 meters from the tunnel entrance, while a set of double walls with a distance of 1.5 meters is placed about 53 meters from the first isolation wall but between the station CONA and the six temporary stations. To assess impact of the isolation walls on noise reduction and detection performance, investigations are conducted in two steps. The first study is carried out by comparing the noise level and detection performance between the station CONA behind the double walls and the stations in front of the double walls for verifying the noise isolation by the double walls. To evaluate the effect of the single wall, station noise level and detection performance were studied by comparing the results before and after the installation of the wall. Results and discussions will be presented. Additional experiment is conducted by filling insulation material inside of the aluminium boxes of the sensors (above and around the sensors). This should help us to determine an optimal insulation of the sensors with respect to pressure and temperature

  9. Plio-Pleistocene sea level and temperature fluctuations in the northwestern Pacific promoted speciation in the globally-distributed flathead mullet Mugil cephalus

    Directory of Open Access Journals (Sweden)

    Durand Jean-Dominique


    among these three lineages, indicating that speciation has been achieved. Conclusions This study successfully identified three cryptic species in M. cephalus inhabiting the NW Pacific, using a combination of microsatellites and mitochondrial genetic markers. The current genetic architecture of the M. cephalus species complex in the NW Pacific is the result of a complex interaction of contemporary processes and historical events. Sea level and temperature fluctuations during Plio-Pleistocene epochs probably played a major role in creating the marine species diversity of the NW Pacific that is found today.

  10. Quantum fluctuations from thermal fluctuations in Jacobson formalism

    Energy Technology Data Exchange (ETDEWEB)

    Faizal, Mir [University of British Columbia-Okanagan, Irving K. Barber School of Arts and Sciences, Kelowna, BC (Canada); University of Lethbridge, Department of Physics and Astronomy, Lethbridge, AB (Canada); Ashour, Amani; Alcheikh, Mohammad [Damascus University, Mathematics Department, Faculty of Science, Damascus (Syrian Arab Republic); Alasfar, Lina [Universite Clermont Auvergne, Laboratoire de Physique Corpusculaire de Clermont-Ferrand, Aubiere (France); Alsaleh, Salwa; Mahroussah, Ahmed [King Saud University, Department of Physics and Astronomy, Riyadh (Saudi Arabia)


    In the Jacobson formalism general relativity is obtained from thermodynamics. This is done by using the Bekenstein-Hawking entropy-area relation. However, as a black hole gets smaller, its temperature will increase. This will cause the thermal fluctuations to also increase, and these will in turn correct the Bekenstein-Hawking entropy-area relation. Furthermore, with the reduction in the size of the black hole, quantum effects will also start to dominate. Just as the general relativity can be obtained from thermodynamics in the Jacobson formalism, we propose that the quantum fluctuations to the geometry can be obtained from thermal fluctuations. (orig.)

  11. Experimental determination of temperatures of the inner wall of a boiler combustion chamber for the purpose of verification of a CFD model

    Directory of Open Access Journals (Sweden)

    Petr Trávníček


    Full Text Available The paper focuses on the non-destructive method of determination of temperatures in the boiler combustion chamber. This method proves to be significant mainly as regards CFD (Computational Fluid Dynamics simulations of combustion processes, in case of which it is subsequently advisable to verify the data calculated using CFD software application with the actually measured data. Verification of the method was based on usage of reference combustion equipment (130 kW which performs combustion of a mixture of waste sawdust and shavings originating in the course of production of wooden furniture. Measuring of temperatures inside the combustion chamber is – considering mainly the high temperature values – highly demanding and requires a special type of temperature sensors. Furthermore, as regards standard operation, it is not possible to install such sensors without performing structural alterations of the boiler. Therefore, for the purpose of determination of these temperatures a special experimental device was constructed while exploiting a thermal imaging system used for monitoring of the surface temperature of outer wall of the reference boiler. Temperatures on the wall of the boiler combustion chamber were determined on the basis of data measured using the experimental device as well as data from the thermal imaging system. These values might serve for verification of the respective CFD model of combustion equipment.

  12. Molecular Dynamics Study on the Effect of Temperature on the Tensile Properties of Single-Walled Carbon Nanotubes with a Ni-Coating

    Directory of Open Access Journals (Sweden)

    Fulong Zhu


    Full Text Available The effect of temperature on the tensile behavior of the armchair (6, 6 single-walled carbon nanotubes with a Ni-coating (SWCNT-Ni was investigated using molecular dynamics (MD methods. The mechanical properties of SWCNT-Ni and SWCNT were calculated and analyzed at different temperatures in the range from 220 K to 1200 K. From the MD results, temperature was determined to be the crucial factor affecting the mechanical properties of SWCNT-Ni and SWCNT. After coating nickel atoms onto the surface of a SWCNT, the Young’s modulus, tensile strength, and tensile failure strain of SWCNT were greatly reduced with temperature rising, indicating that the nickel atoms on the surface of SWCNT degrade its mechanical properties. However, at high temperature, the Young’s modulus of both the SWCNT and the SWCNT-Ni exhibited significantly greater temperature sensitivity than at low temperatures, as the mechanical properties of SWCNT-Ni were primarily dominated by temperature and C-Ni interactions. During these stretching processes at different temperatures, the nickel atoms on the surface of SWCNT-Ni could obtain the amount of energy sufficient to break the C-C bonds as the temperature increases.

  13. Gambling with Superconducting Fluctuations (United States)

    Foltyn, Marek; Zgirski, Maciej


    Josephson junctions and superconducting nanowires, when biased close to superconducting critical current, can switch to a nonzero voltage state by thermal or quantum fluctuations. The process is understood as an escape of a Brownian particle from a metastable state. Since this effect is fully stochastic, we propose to use it for generating random numbers. We present protocol for obtaining random numbers and test the experimentally harvested data for their fidelity. Our work is prerequisite for using the Josephson junction as a tool for stochastic (probabilistic) determination of physical parameters such as magnetic flux, temperature, and current.

  14. Electronic setup for fluorescence emission measurements and long-time constant-temperature maintenance of Single-Walled Carbon Nano-Tubes in water solutions

    Directory of Open Access Journals (Sweden)

    De Rosa Matteo


    Full Text Available In our previous research we have observed that the fluorescence emission from water solutions of Single-Walled Carbon Nano-Tubes (SWCNT, excited by a laser with a wavelength of 830nm, diminishes with the time. We have already proved that such a fading is a function of the storage time and the storage temperature. In order to study the emission of the SWCNT as a function of these two parameters we have designed and realized a special measurement compartment with a cuvette holder where the SWCNT solutions can be measured and stored at a fixed constant temperature for periods of time as long as several weeks. To maintain the measurement setup under a constant temperature we have designed special experimental setup based on two Peltier cells with electronic temperature control.

  15. Numerical analysis of ion temperature effects to the plasma wall transition using a one-dimensional two-fluid model. I. Finite Debye to ionization length ratio. (United States)

    Gyergyek, T; Kovačič, J


    A one-dimensional, two-fluid, steady state model is used for the analysis of ion temperature effects to the plasma-wall transition. In this paper, the model is solved for a finite ratio ε between the Debye and the ionization length, while in Part II [T. Gyergyek and J. Kovačič, Phys Plasmas 24, 063506 (2017)], the solutions for [Formula: see text] are presented. Ion temperature is treated as a given, independent parameter and it is included in the model as a boundary condition. It is shown that when the ion temperature larger than zero is selected, the ion flow velocity and the electric field at the boundary must be consistent with the selected ion temperature. A numerical procedure, how to determine such "consistent boundary conditions," is proposed, and a simple relation between the ion temperature and ion velocity at the boundary of the system is found. The effects of the ion temperature to the pre-sheath length, potential, ion temperature, and ion density drops in the pre-sheath and in the sheath are investigated. It is concluded that larger ion temperature results in a better shielding of the plasma from the wall. An attempt is made to include the ion heat flux q i into the model in its simplest form [Formula: see text], where [Formula: see text] is a constant heat conduction coefficient. It is shown that inclusion of such a term into the energy transfer equation introduces an additional ion heating mechanism into the system and the ion flow then becomes isothermal instead of adiabatic even in the sheath.

  16. Selective detection of SO2 at room temperature based on organoplatinum functionalized single-walled carbon nanotube field effect transistors

    NARCIS (Netherlands)

    Cid, C.C.; Jimenez-Cadena, G.; Riu, J.; Maroto, A.; Rius, F.X.; Batema, G.D.; van Koten, G.


    We report a field effect transistor (FET) based on a network of single-walled carbon nanotubes (SWCNTs) that for the first time can selectively detect a single gaseous molecule in air by chemically functionalizing the SWCNTs with a selective molecular receptor. As a target model we used SO2. The


    Uma, B; Ayyaswamy, P S; Radhakrishnan, R; Eckmann, D M


    A direct numerical simulation adopting an arbitrary Lagrangian-Eulerian based finite element method is employed to simulate the motion of a nanocarrier in a quiescent fluid contained in a cylindrical tube. The nanocarrier is treated as a solid sphere. Thermal fluctuations are implemented using two different approaches: (1) fluctuating hydrodynamics; (2) generalized Langevin dynamics (Mittag-Leffler noise). At thermal equilibrium, the numerical predictions for temperature of the nanoparticle, velocity distribution of the particle, decay of the velocity autocorrelation function, diffusivity of the particle and particle-wall interactions are evaluated and compared with analytical results, where available. For a neutrally buoyant nanoparticle of 200 nm radius, the comparisons between the results obtained from the fluctuating hydrodynamics and the generalized Langevin dynamics approaches are provided. Results for particle diffusivity predicted by the fluctuating hydrodynamics approach compare very well with analytical predictions. Ease of computation of the thermostat is obtained with the Langevin approach although the dynamics gets altered.

  18. Gas temperature measurements in a microwave plasma by optical emission spectroscopy under single-wall carbon nanotube growth conditions

    Energy Technology Data Exchange (ETDEWEB)

    Garg, R K [Cummins Inc, 1900 McKinley Ave, MC 50180, Columbus, IN 47201 (United States); Anderson, T N; Lucht, R P; Fisher, T S; Gore, J P [School of Mechanical Engineering, Purdue University, West Lafayette, IN 47907 (United States)], E-mail:


    Plasma gas temperatures were measured via in situ optical emission spectroscopy in a microwave CH{sub 4}-H{sub 2} plasma under carbon nanotube (CNT) growth conditions. Gas temperature is an important parameter in controlling and optimizing CNT growth. The temperature has a significant impact on chemical kinetic rates, species concentrations and CNT growth rates on the substrate. H{sub 2} rotational temperatures were determined from the Q-branch spectrum of the d{sup 3}{pi}{sub u}(0){yields}a{sup 3}{sigma}{sub g}{sup +}(0) transition. N{sub 2} rotational and vibrational temperatures were measured by fitting rovibrational bands from the N{sub 2} emission spectrum of the C {sup 3}{pi}{sub u} {yields} B {sup 3}{pi}{sub g} transition. The N{sub 2} rotational temperature, which is assumed to be approximately equal to the translational gas temperature, increases with an increase in input microwave plasma power and substrate temperature. The measured H{sub 2} rotational temperatures were not in agreement with the measured N{sub 2} rotational temperatures under the CNT growth conditions in this study. The measured N{sub 2} rotational temperatures compared with the H{sub 2} rotational temperatures suggest the partial equilibration of upper excited state due to higher, 10 Torr, operating pressure. Methane addition in the hydrogen plasma increases the gas temperature slightly for methane concentrations higher than 10% in the feed gas.

  19. Geometric fluctuation theorem for a spin-boson system. (United States)

    Watanabe, Kota L; Hayakawa, Hisao


    We derive an extended fluctuation theorem for geometric pumping of a spin-boson system under periodic control of environmental temperatures by using a Markovian quantum master equation. We obtain the current distribution, the average current, and the fluctuation in terms of the Monte Carlo simulation. To explain the results of our simulation we derive an extended fluctuation theorem. This fluctuation theorem leads to the fluctuation dissipation relations but the absence of the conventional reciprocal relation.

  20. Adsorption in single-walled carbon nanotubes by experiments and molecular simulation II: Effect of morphology and temperature on organic adsorption (United States)

    Agnihotri, S.; Rostam-Abadi, M.; Mota, J.P.B.; Rood, M.J.


    Hexane adsorption on single-walled carbon nanotube (SWNT) bundles was studied. Hexane adsorption capacities of two purified SWNT samples was gravimetrically determined at isothermal conditions of 25??, 37??, and 50??C for 10-4 Simulation of hexane adsorption under similar temperature and pressure conditions were performed on the external and internal sites of nanotube bundles of diameters same as those in experimental samples. The simulations could predict isotherms for a hypothetical scenario where all nanotubes in a sample would be open. This is an abstract of a paper presented at the AIChE Annual Meeting and Fall Showcase (Cincinnati, OH 10/30/2005-11/4/2005).

  1. Computer simulations of phospholipid - membrane thermodynamic fluctuations

    DEFF Research Database (Denmark)

    Pedersen, U.R.; Peters, Günther H.j.; Schröder, T.B.


    This paper reports all-atom computer simulations of five phospholipid membranes, DMPC, DPPC, DMPG, DMPS, and DMPSH, with a focus on the thermal equilibrium fluctuations of volume, energy, area, thickness, and order parameter. For the slow fluctuations at constant temperature and pressure (defined...

  2. Seasonal fluctuations in photochemical efficiency of Symbiodinium ...

    African Journals Online (AJOL)

    A. formosa and P. verucosa responded significantly to seasonal fluctuation in both solar radiation and sea surface temperature by regulating their Symbiodinium cells densities and photochemical efficiencies except P. cylindrica. However, such seasonal fluctuations in these environmental parameters are not accompanied ...

  3. Low temperature caused modifications in the arrangement of cell wall pectins due to changes of osmotic potential of cells of maize leaves (Zea mays L.). (United States)

    Bilska-Kos, Anna; Solecka, Danuta; Dziewulska, Aleksandra; Ochodzki, Piotr; Jończyk, Maciej; Bilski, Henryk; Sowiński, Paweł


    The cell wall emerged as one of the important structures in plant stress responses. To investigate the effect of cold on the cell wall properties, the content and localization of pectins and pectin methylesterase (PME) activity, were studied in two maize inbred lines characterized by different sensitivity to cold. Low temperature (14/12 °C) caused a reduction of pectin content and PME activity in leaves of chilling-sensitive maize line, especially after prolonged treatment (28 h and 7 days). Furthermore, immunocytohistological studies, using JIM5 and JIM7 antibodies, revealed a decrease of labeling of both low- and high-methylesterified pectins in this maize line. The osmotic potential, quantified by means of incipient plasmolysis was lower in several types of cells of chilling-sensitive maize line which was correlated with the accumulation of sucrose. These studies present new finding on the effect of cold stress on the cell wall properties in conjunction with changes in the osmotic potential of maize leaf cells.

  4. Superradiance from Two Dimensional Brick-Wall Aggregates of Dye Molecules: The Role of Size and Shape for the Temperature Dependence (United States)

    Eisfeld, Alexander; Marquardt, Christian; Paulheim, Alexander; Sokolowski, Moritz


    Aggregates of interacting molecules can exhibit electronically excited states that are coherently delocalized over many molecules. This can lead to a strong enhancement of the fluorescence decay rate which is referred to as superradiance (SR). To date, the temperature dependence of SR is described by a 1 /T law. Using an epitaxial dye layer and a Frenkel-exciton based model we provide both experimental and theoretical evidence that significant deviations from the 1 /T behavior can occur for brick-wall-type aggregates of finite size leading even to a maximum of the SR at finite temperature. This is due to the presence of low energy excitations of weak or zero transition strength. These findings are relevant for designing light-emitting molecular materials.

  5. Analytical solutions for the temperature field in a 2D incompressible inviscid flow through a channel with walls of solid fuel

    Directory of Open Access Journals (Sweden)

    Sorin BERBENTE


    Full Text Available A gas (oxidizer flows between two parallel walls of solid fuel. A combustion is initiated: the solid fuel is vaporized and a diffusive flame occurs. The hot combustion products are submitted both to thermal diffusion and convection. Analytical solutions can be obtained both for the velocity and temperature distributions by considering an equivalent mean temperature where the density and the thermal conductivity are evaluated. The main effects of heat transfer are due to heat convection at the flame. Because the detailed mechanism of the diffusion flame is not introduced the reference chemical reaction is the combustion of premixed fuel with oxidizer in excess. In exchange the analytical solution is used to define an ideal quasi-uniform combustion that could be realized by an n adequate control. The given analytical closed solutions prove themselves flexible enough to adjust the main data of some existing experiments and to suggest new approaches to the problem.

  6. Temperature-calibrated imaging of seasonal changes in permafrost rock walls by quantitative electrical resistivity tomography (Zugspitze, German/Austrian Alps) (United States)

    Krautblatter, Michael; Verleysdonk, Sarah; Flores-Orozco, AdriáN.; Kemna, Andreas


    Changes of rock and ice temperature inside permafrost rock walls crucially affect their stability. Permafrost rocks at the Zugspitze were involved in a 0.3-0.4 km3 rockfall at 3.7 ka B.P. whose deposits are now inhabited by several thousands of people. A 107 year climate record at the summit (2962 m asl) shows a sharp temperature increase in 1991-2007. This article applies electrical resistivity tomography (ERT) to gain insight into spatial thaw and refreezing behavior of permafrost rocks and presents the first approach to calibrating ERT with frozen rock temperature. High-resolution ERT was conducted in the north face adjacent to the Zugspitze rockfall scarp in February and monthly from May to October 2007. A smoothness-constrained inversion is employed with an incorporated data error model, calibrated on the basis of normal reciprocal measurement discrepancy. Laboratory analysis of Zugspitze limestone indicates a bilinear temperature-resistivity relationship divided by a 0.5 ± 0.1°C and 30 ± 3 kΩm equilibrium freezing point and a twentyfold increase of the frozen temperature-resistivity gradient (19.3 ± 2.1 kΩm/°C). Temperature dominates resistivity changes in rock below -0.5°C, while in this case geological parameters are less important. ERT shows recession and readvance of frozen conditions in rock correspondingly to temperature data. Maximum resistivity changes in depths up to 27 m coincide with maximum measured water flow in fractures in May. Here we show that laboratory-calibrated ERT does not only identify frozen and unfrozen rock but provides quantitative information on frozen rock temperature relevant for stability considerations.

  7. Data indicating temperature response of Ti–6Al–4V thin-walled structure during its additive manufacture via Laser Engineered Net Shaping

    Directory of Open Access Journals (Sweden)

    Garrett J. Marshall


    Full Text Available An OPTOMEC Laser Engineered Net Shaping (LENS™ 750 system was retrofitted with a melt pool pyrometer and in-chamber infrared (IR camera for nondestructive thermal inspection of the blown-powder, direct laser deposition (DLD process. Data indicative of temperature and heat transfer within the melt pool and heat affected zone atop a thin-walled structure of Ti–6Al–4V during its additive manufacture are provided. Melt pool temperature data were collected via the dual-wavelength pyrometer while the dynamic, bulk part temperature distribution was collected using the IR camera. Such data are provided in Comma Separated Values (CSV file format, containing a 752×480 matrix and a 320×240 matrix of temperatures corresponding to individual pixels of the pyrometer and IR camera, respectively. The IR camera and pyrometer temperature data are provided in blackbody-calibrated, raw forms. Provided thermal data can aid in generating and refining process-property-performance relationships between laser manufacturing and its fabricated materials.

  8. Data indicating temperature response of Ti-6Al-4V thin-walled structure during its additive manufacture via Laser Engineered Net Shaping. (United States)

    Marshall, Garrett J; Thompson, Scott M; Shamsaei, Nima


    An OPTOMEC Laser Engineered Net Shaping (LENS(™)) 750 system was retrofitted with a melt pool pyrometer and in-chamber infrared (IR) camera for nondestructive thermal inspection of the blown-powder, direct laser deposition (DLD) process. Data indicative of temperature and heat transfer within the melt pool and heat affected zone atop a thin-walled structure of Ti-6Al-4V during its additive manufacture are provided. Melt pool temperature data were collected via the dual-wavelength pyrometer while the dynamic, bulk part temperature distribution was collected using the IR camera. Such data are provided in Comma Separated Values (CSV) file format, containing a 752×480 matrix and a 320×240 matrix of temperatures corresponding to individual pixels of the pyrometer and IR camera, respectively. The IR camera and pyrometer temperature data are provided in blackbody-calibrated, raw forms. Provided thermal data can aid in generating and refining process-property-performance relationships between laser manufacturing and its fabricated materials.

  9. Athermal domain-wall creep near a ferroelectric quantum critical point. (United States)

    Kagawa, Fumitaka; Minami, Nao; Horiuchi, Sachio; Tokura, Yoshinori


    Ferroelectric domain walls are typically stationary because of the presence of a pinning potential. Nevertheless, thermally activated, irreversible creep motion can occur under a moderate electric field, thereby underlying rewritable and non-volatile memory applications. Conversely, as the temperature decreases, the occurrence of creep motion becomes less likely and eventually impossible under realistic electric-field magnitudes. Here we show that such frozen ferroelectric domain walls recover their mobility under the influence of quantum fluctuations. Nonlinear permittivity and polarization-retention measurements of an organic charge-transfer complex reveal that ferroelectric domain-wall creep occurs via an athermal process when the system is tuned close to a pressure-driven ferroelectric quantum critical point. Despite the heavy masses of material building blocks such as molecules, the estimated effective mass of the domain wall is comparable to the proton mass, indicating the realization of a ferroelectric domain wall with a quantum-particle nature near the quantum critical point.

  10. Biomolecules: Fluctuations and relaxations (United States)

    Parak, F.; Ostermann, A.; Gassmann, A.; Scherk, C.; Chong, S.-H.; Kidera, A.; Go, N.


    The normal-mode refinement of X-ray crystallographic data opened a new possibility to analyze the mean-square displacements in a protein molecule. A comparison of the X-ray structure of myoglobin at several temperatures with Mössbauer data is performed. In the low-temperature regime below 180 K the iron mean-square displacements obtained by Mössbauer spectroscopy are in good agreement with a normal-mode analysis. The X-ray mean-square displacements at the position of the iron, after the motion originated from the external degrees of freedom are subtracted, have practically the same temperature dependence as those from Mössbauer spectroscopy. The difference between the X-ray mean-square displacements and those predicted by normal-mode analysis measures the distribution of molecules into conformational substates. Above 180 K the Mössbauer effect indicates fluctuations between conformational substates. The relaxation from a Fe(III) conformation to a Fe(II) conformation is shown for superoxide dismutase of Propionibacterium shermanii.

  11. Quantum Fluctuation Relations


    Facchi, Paolo; Garnero, Giancarlo; Ligabò, Marilena


    We present here a set of lecture notes on exact fluctuation relations. We prove the Jarzynski equality and the Crooks fluctuation theorem, two paradigmatic examples of classical fluctuation relations. Finally we consider their quantum versions, and analyze analogies and differences with the classical case.

  12. Hydraulic and heat transfer study of SiO{sub 2}/water nanofluids in horizontal tubes with imposed wall temperature boundary conditions

    Energy Technology Data Exchange (ETDEWEB)

    Ferrouillat, Sebastien, E-mail: sebastien.ferrouillat@ujf-grenoble.f [Universite Joseph Fourier, LEGI, BP 53X, 38041 Grenoble cedex (France); Bontemps, Andre [Universite Joseph Fourier, LEGI, BP 53X, 38041 Grenoble cedex (France); Ribeiro, Joao-Paulo; Gruss, Jean-Antoine; Soriano, Olivier [CEA/LITEN/DTS/LETH, 17, Avenue des martyrs, 38052 Grenoble cedex (France)


    The convective heat transfer of SiO{sub 2}/water colloidal suspensions (5-34 wt.%) is investigated experimentally in a flow loop with a horizontal tube test section whose wall temperature is imposed. Experiments were performed at different inlet temperatures (20, 50, 70 {sup o}C) in cooling and/or heating conditions at various flow rates (200 < Re < 10,000). The Reynolds and Nusselt numbers were deduced by using thermal conductivity and viscosity values measured with the same temperature conditions as those in the tests. Results indicate that the heat transfer coefficient values are increased from 10% to 60% compared to those of pure water. They also show that the general trend of standard correlations is respected. The problem of suspension stability at the highest temperatures is discussed. In order to evaluate the benefits provided by the enhanced properties of the nanofluids studied, an energetic performance evaluation criterion (PEC) is defined. This PEC decreases as the nanoparticle concentration is increased. This process is also discussed in this paper.

  13. Research and Analyses on Unsteady Heat Transfer of Inner Thermal Insulation Wall during Multi-temperature Refrigerated Transportation (United States)

    Liu, Guanghai; Xie, Ruhe; Sun, Yongcai

    There are lots of differences between multi-temperature refrigerated vehicles and ordinary ones in many aspects such as structure and running circumstances, hence the hugely different heat-transfer characters and response coefficients. This paper researched the unsteady heat transfer process of the multi-temperature refrigerated vehicle by response coefficients method, numerically calculated the unsteady heat transfer of inner thermal insulation materials in the multi-temperature refrigerated vehicle by computers, and studied the influences of different term numbers of equation root, term numbers of response coefficients on load calculation accuracy. It showed that the accuracy requirement could be met when the root of equation was -25 and the term number of response coefficient was 30.

  14. Analysis of soft wall AdS/QCD potentials to obtain the melting temperature of scalar hadrons (United States)

    Vega, Alfredo; Ibañez, Adolfo


    We consider an analysis of potentials related to Schrödinger-type equations for scalar fields in a 5D AdS black hole background with dilaton in order to obtain melting temperatures for different hadrons in a thermal bath. The approach does not consider calculations of spectral functions, and it is easy to yield results for hadrons with an arbitrary number of constituents. We present results for scalar mesons, glueballs, hybrid mesons and tetraquarks, and we show that mesons are more resistant to being melted in a thermal bath than other scalar hadrons, and in general the melting temperature increases when hadrons contain heavy quarks.

  15. Green walls in Vancouver

    Energy Technology Data Exchange (ETDEWEB)

    Sharp, R. [Sharp and Diamond Landscape Architecture Inc., Vancouver, BC (Canada)


    With the renewed interest in design for microclimate control and energy conservation, many cities are implementing clean air initiatives and sustainable planning policies to mitigate the effects of urban climate and the urban heat island effect. Green roofs, sky courts and green walls must be thoughtfully designed to withstand severe conditions such as moisture stress, extremes in temperature, tropical storms and strong desiccating winds. This paper focused on the installation of green wall systems. There are 2 general types of green walls systems, namely facade greening and living walls. Green facades are trellis systems where climbing plants can grow vertically without attaching to the surface of the building. Living walls are part of a building envelope system where plants are actually planted and grown in a wall system. A modular G-SKY Green Wall Panel was installed at the Aquaquest Learning Centre at the Vancouver Aquarium in Stanley Park in September 2006. This green wall panel, which was originally developed in Japan, incorporates many innovative features in the building envelope. It provides an exterior wall covered with 8 species of plants native to the Coastal Temperate Rain Forest. The living wall is irrigated by rainwater collected from the roof, stored in an underground cistern and fed through a drip irrigation system. From a habitat perspective, the building imitates an escarpment. Installation, support systems, irrigation, replacement of modules and maintenance are included in the complete wall system. Living walls reduce the surface temperature of buildings by as much as 10 degrees C when covered with vegetation and a growing medium. The project team is anticipating LEED gold certification under the United States-Canada Green Building Council. It was concluded that this technology of vegetated building envelopes is applicable for acoustical control at airports, biofiltration of indoor air, greywater treatment, and urban agriculture and vertical

  16. Continuous high and low temperature induced a decrease of photosynthetic activity and changes in the diurnal fluctuations of organic acids in Opuntia streptacantha.

    Directory of Open Access Journals (Sweden)

    Zaida Zarely Ojeda-Pérez

    Full Text Available Opuntia plants grow naturally in areas where temperatures are extreme and highly variable in the day during the entire year. These plants survive through different adaptations to respond to adverse environmental conditions. Despite this capability, it is unknown how CAM photosynthetic activity and growth in Opuntia plantlets is affected by constant heat or cold. Therefore, the main objective of this research was to evaluate the short-term effect of high (40°C and low (4°C continuous temperatures on the photosynthetic efficiency, the organic acid content (malic acid and the relative growth rate (RGR in seven-month-old Opuntia streptacantha plantlets during 5, 10, and 15 days. Chlorophyll fluorescence analysis allowed us to determine that high temperatures negatively impact the photosynthetic efficiency of O. streptacantha plantlets, which exhibited the lowest values of maximum quantum efficiency of the photosystem II (Fv/Fm = 52%, Fv/F0 = 85%, operational quantum yield of PS (ΦPSII = 65% and relative electron transport rate (rETR = 65%, as well as highest values of basal fluorescence (F0 = 226% during 15 days of treatment. Similarly, low temperatures decreased Fv/Fm (16%, Fv/F0 (50%, ΦPSII and rETR (16%. High temperatures also decreased nocturnal acidification in approximately 34-50%, whereas low temperatures increased it by 30-36%. Additionally, both continuous temperatures affected drastically diurnal consumption of malic acid, which was related to a significant RGR inhibition, where the specific photosynthetic structure area component was the most affected. Our results allowed determining that, despite the high tolerance to extreme temperatures described for Opuntia plants, young individuals of O. streptacantha suffered photosynthetic impairment that led to the inhibition of their growth. Thus, the main findings reported in this study can help to predict the potential impact of climatic change on the establishment and survival of succulent

  17. Effects of Ambient Air and Temperature on Ionic Gel Gated Single-Walled Carbon Nanotube Thin-Film Transistor and Circuits. (United States)

    Li, Huaping; Zhou, Lili


    Single-walled carbon nanotube thin-film transistor (SWCNT TFT) and circuits were fabricated by fully inkjet printing gold nanoparticles as source/drain electrodes, semiconducting SWCNT thin films as channel materials, PS-PMMA-PS/EMIM TFSI composite gel as gate dielectrics, and PEDOT/PSS as gate electrodes. The ionic gel gated SWCNT TFT shows reversible conversion from p-type transistor behavior in air to ambipolar features under vacuum due to reversible oxygen doping in semiconducting SWCNT thin films. The threshold voltages of ionic gel gated SWCNT TFT and inverters are largely shifted to the low value (0.5 V for p-region and 1.0 V for n-region) by vacuum annealing at 140 °C to exhausively remove water that is incorporated in the ionic gel as floating gates. The vacuum annealed ionic gel gated SWCNT TFT shows linear temperature dependent transconductances and threshold voltages for both p- and n-regions. The strong temperature dependent transconductances (0.08 μS/K for p-region, 0.4 μS/K for n-region) indicate their potential application in thermal sensors. In the other hand, the weak temperature dependent threshold voltages (-1.5 mV/K for p-region, -1.1 mV/K for n-region) reflect their excellent thermal stability.

  18. A comparative study of 1/f noise and temperature coefficient of resistance in multiwall and single-wall carbon nanotube bolometers. (United States)

    Lu, Rongtao; Kamal, Rayyan; Wu, Judy Z


    The 1/f noise and temperature coefficient of resistance (TCR) are investigated in multiwall carbon nanotube (MWCNT) film bolometers since both affect the bolometer detectivity directly. A comparison is made between the MWCNT film bolometers and their single-wall carbon nanotube (SWCNT) counterparts. The intrinsic noise level in the former has been found at least two orders of magnitude lower than that in the latter, which outweighs the moderately lower TCR absolute values in the former and results in higher bolometer detectivity in MWCNT bolometers. Interestingly, reduced noise and enhanced TCR can be obtained by improving the inter-tube coupling using thermal annealing in both SWCNT and MWCNT films, suggesting much higher detectivity may be achieved via engineering the inter-tube coupling.

  19. Chemical reaction and radiation effects on the transient MHD free convection flow of dissipative fluid past an infinite vertical porous plate with ramped wall temperature

    Directory of Open Access Journals (Sweden)



    Full Text Available A finite-difference analysis is performed to study the effects of thermal radiation and chemical reaction on the transient MHD free convection and mass transform flow of a dissipative fluid past an infinite vertical porous plate subject to ramped wall temperature. The fluid considered here is a gray, absorbing/ /emitting radiation but a non-scattering medium. The dimensionless governing equations are unsteady, coupled and non-linear partial differential equations. An analytical method fails to give a solution. Hence an implicit finite difference scheme of Crank-Nicolson method is employed. The effect of the magnetic parameter (M, chemical reaction parameter (K, radiation parameter (F, buoyancy ratio parameter (N, Schmidt number (Sc on the velocity field and skin friction for both air (Pr = 0.71 and water (Pr = 7 in the presence of both aiding (N>0 and opposing (N<0 flows are extensively discussed with the help of graphs.

  20. Highly sensitive room temperature carbon monoxide detection using SnO2 nanoparticle-decorated semiconducting single-walled carbon nanotubes (United States)

    Zhang, Yang; Cui, Shumao; Chang, Jingbo; Ocola, Leonidas E.; Chen, Junhong


    We demonstrate a practical sensing platform, consisting of SnO2 nanoparticle-decorated semiconducting single-walled carbon nanotubes assembled on gold electrodes via a dielectrophoretic process, for highly sensitive CO detection with fast response at room temperature. The highest sensitivity obtained was 0.27 and the response time was ˜2 s for 100 ppm CO detection. The lower detection limit was ˜1 ppm. These results indicate that the sensing performance of our device is among the best of CO sensors implemented with SWNTs. Further, we observed a significant increase in sensitivity to 0.67 after subjecting the device to an electrical breakdown at 8 V. We also proposed a theoretical model to reveal the relationship between the sensitivity and the gas concentration. The new model not only resulted in a nice fit to our data, but also allowed us to estimate the contact resistance between an individual SWNT and the gold electrodes.

  1. Magnetically insulated baffled probe for real-time monitoring of equilibrium and fluctuating values of space potentials, electron and ion temperatures, and densities. (United States)

    Demidov, V I; Koepke, M E; Raitses, Y


    By restricting the electron-collection area of a cold Langmuir probe compared to the ion-collection area, the probe floating potential can become equal to the space potential, and thus conveniently monitored, rather than to a value shifted from the space potential by an electron-temperature-dependent offset, i.e., the case with an equal-collection-area probe. This design goal is achieved by combining an ambient magnetic field in the plasma with baffles, or shields, on the probe, resulting in species-selective magnetic insulation of the probe collection area. This permits the elimination of electron current to the probe by further adjustment of magnetic insulation which results in an ion-temperature-dependent offset when the probe is electrically floating. Subtracting the floating potential of two magnetically insulated baffled probes, each with a different degree of magnetic insulation, enables the electron or ion temperature to be measured in real time.

  2. The response of a simple Antarctic ice-flow model to temperature and sea-level fluctuations over the Cenozoic era

    NARCIS (Netherlands)

    van Tuyll, C.I.|info:eu-repo/dai/nl/304831875; van de Wal, R.S.W.|info:eu-repo/dai/nl/101899556; Oerlemans, J.|info:eu-repo/dai/nl/06833656X


    An ice-flow model is used to simulate the Antarctic ice-sheet volume and deep-sea temperature record during Cenozoic times. We used a vertically integrated axisymmetric ice-sheet model, including bedrock adjustment. In order to overcome strong numerical hysteresis effects during climate change, the

  3. Turbulent Kinetic Energy and Temperature Variance Dissipation in Laboratory Generated Rayleigh-Benard Turbulence Designed to Study the Distortion of Light by Underwater Microstructure Fluctuations (United States)


    vertical velocity ( Uz ) (middle) and the Index of Refraction (IOR) calculated from the temperature field (bottom). The data is shown on the center...plane of the tank. Fig. 4. Model results at time t = 1050s, showing streamlines in the domain colored by vertical velocity Uz

  4. Temperature and pressure dependence of the order parameter fluctuations, conformational compressibility, and the phase diagram of the PEP-PDMS diblock copolymer

    DEFF Research Database (Denmark)

    Schwahn, D.; Frielinghaus, H.; Mortensen, K.


    The structure factor of a poly(ethylene-propylene)-poly(dimethylsiloxane) diblock copolymer has been measured by small-angle neutron scattering as a function of temperature and pressure. The conformational compressibility exhibits a pronounced maximum at the order-disorder phase transition...

  5. MHD Effect on Unsteady Mixed Convection Boundary Layer Flow past a Circular Cylinder with Constant Wall Temperature (United States)

    Ismail, M. A.; Mohamad, N. F.; Ilias, M. R.; Shafie, S.


    Magnetohydrodynamic (MHD) effect is a study on motion of electrical-conducting fluid under magnetic fields. This effect has great intention due to its applications such as design of heat exchanger and nuclear reactor. In the problem in fluid motion, flow of separation can reduced the effectiveness of the system as well as can increased the energy lost. This study will present the results on reducing the flow separation by considering magnetic effect. In this study, unsteady mixed convection boundary layer flow past a circular cylinder is given attention. Focus of study is on the separation times that affected by the magnetic fields. The mathematical models in the form of partial differential equations are transformed into nonlinear coupled ordinary differential equations and solved numerically using an implicit finite-difference scheme known as Keller-box method. The effect of magnetic parameter on velocity and temperature profiles as well as skin friction and Nusselt number are studied.

  6. Modeling multiphase flow using fluctuating hydrodynamics. (United States)

    Chaudhri, Anuj; Bell, John B; Garcia, Alejandro L; Donev, Aleksandar


    Fluctuating hydrodynamics provides a model for fluids at mesoscopic scales where thermal fluctuations can have a significant impact on the behavior of the system. Here we investigate a model for fluctuating hydrodynamics of a single-component, multiphase flow in the neighborhood of the critical point. The system is modeled using a compressible flow formulation with a van der Waals equation of state, incorporating a Korteweg stress term to treat interfacial tension. We present a numerical algorithm for modeling this system based on an extension of algorithms developed for fluctuating hydrodynamics for ideal fluids. The scheme is validated by comparison of measured structure factors and capillary wave spectra with equilibrium theory. We also present several nonequilibrium examples to illustrate the capability of the algorithm to model multiphase fluid phenomena in a neighborhood of the critical point. These examples include a study of the impact of fluctuations on the spinodal decomposition following a rapid quench, as well as the piston effect in a cavity with supercooled walls. The conclusion in both cases is that thermal fluctuations affect the size and growth of the domains in off-critical quenches.

  7. Effects of Ramped Wall Temperature on Unsteady Two-Dimensional Flow Past a Vertical Plate with Thermal Radiation and Chemical Reaction

    Directory of Open Access Journals (Sweden)

    V. Rajesh


    Full Text Available The interaction of free convection with thermal radiation of a viscous incompressible unsteady flow past a vertical plate with ramped wall temperature and mass diffusion is presented here, taking into account the homogeneous chemical reaction of first order. The fluid is gray, absorbing-emitting but non-scattering medium and the Rosseland approximation is used to describe the radiative flux in the energy equation. The dimensionless governing equations are solved using an implicit finite-difference method of the Crank-Nicolson type, which is stable and convergent. The velocity profiles are compared with the available theoretical solution and are found to be in good agreement. Numerical results for the velocity, the temperature, the concentration, the local and average skin friction, the Nusselt number and Sherwood number are shown graphically. This work has wide application in chemical and power engineering and also in the study of vertical air flow into the atmosphere. The present results can be applied to an important class of flows in which the driving force for the flow is provided by combination of the thermal and chemical species diffusion effects.

  8. Thickness fluctuations in turbulent soap films. (United States)

    Greffier, O; Amarouchene, Y; Kellay, H


    Rapidly flowing soap films provide a simple and attractive system to study two-dimensional hydrodynamics and turbulence. By measuring the rapid fluctuations of the thickness of the film in the turbulent regime, we find that the statistics of these fluctuations closely resemble those of a passive scalar field in a turbulent flow. The scalar spectra are well described by Kolmogorov-like scaling while the high-order moments show clear deviations from regular scaling just like dye or temperature fluctuations in 3D turbulent flows.

  9. Negative correlation between enhanced crossover temperature and fluctuation-free critical current of the second switch in Bi2Sr2CaCu2O{}_{8+\\delta } intrinsic Josephson junction (United States)

    Nomura, Y.; Okamoto, R.; Kakeya, I.


    We have investigated the switching dynamics of the first and second switches in intrinsic Josephson junctions (IJJs) of Bi2Sr2CaCu2O{}8+δ with different maximum Josephson current density J c to reveal the doping evolution of interaction between IJJs. For the second switch, the crossover temperature between temperature-independent switching similar to quantum tunneling and thermally activated switching {T}2{nd}* is remarkably higher than that for the first switch. Moreover, {T}2{nd}* slightly decreases with increasing J c, which violates the conventional relation between the crossover temperature and the critical current density. These features can be explained not by a change in the Josephson coupling energy but by a change in the charging energy of the Josephson junction. We argue that the capacitive coupling model explains the increase in the fluctuation in the quantum regime of the second switch and the anti-correlation between {T}2{nd}* and J c. Furthermore, inductive coupling does not contribute to these peculiar phenomena in the switching dynamics of stacked IJJs.

  10. Particle density fluctuations

    Energy Technology Data Exchange (ETDEWEB)

    Aggarwal, M.M.; Ahammed, Z.; Angelis, A.L.S.; Antonenko, V.; Arefiev, V.; Astakhov, V.; Avdeitchikov, V.; Awes, T.C.; Baba, P.V.K.S.; Badyal, S.K.; Bathe, S.; Batiounia, B.; Bernier, T.; Bhalla, K.B.; Bhatia, V.S.; Blume, C.; Bucher, D.; Buesching, H.; Carlen, L.; Chattopadhyay, S.; Das, A.C.; Decowski, M.P.; Donni, P.; Dubey, A.K.; Dutta Majumdar, M.R.; Enosawa, K.; Fokin, S.; Frolov, V.; Ganti, M.S.; Garpman, S.; Gavrishcuk, O.; Geurts, F.J.M.; Glasow, R.; Guskov, B.; Gustafsson, H.A.; Gutbrod, H.H.; Hrivnacova, I.; Ippolitov, M.; Kalechofsky, H.; Kamermans, R.; Karadjev, K.; Karpio, K.; Kolb, B.W.; Kosarev, I.; Koutcheryaev, I.; Kugler, A.; Kulinich, P.; Kurata, M.; Lebedev, A.; Loehner, H.; Mahapatra, D.P.; Manko, V.; Martin, M.; Miake, Y.; Mishra, G.C.; Mohanty, B.; Morrison, D.; Mukhopadhayay, D.S.; Naef, H.; Nandi, B.K.; Nayak, S.K.; Nayak, T.K.; Nianine, A.; Nikitine, V.; Nikolaev, S.; Nishimura, S.; Nomokov, P.; Petracek, V.; Plasil, F.; Purschke, M.L.; Rak, J.; Raniwala, R.; Raniwala, S.; Rao, N.K.; Retiere, F.; Reygers, K.; Roland, G.; Rosselet, L.; Roufanov, I.; Rubio, J.M.; Sambyal, S.S.; Santo, R.; Sato, S.; Schlagheck, H.; Schmidt, H.-R.; Schutz, Y.; Shabratova, G.; Sibiriak, I.; Siemiarczuk, T.; Sinha, B.C.; Slavine, N.; Soederstroem, K.; Sood, G.; Soerensen, S.P.; Stankus, P.; Steinberg, P.; Stenlund, E.; Sumbera, M.; Svensson, T.; Trivedi, M.D.; Tsvetkov, A.; Tykarski, L.; Urbahn, J.; Eijinhoven, N. van; Niewenhuizen, G.J. van; Vinogradov, A.; Viyogi, Y.P.; Vodopianov, A.; Voeroes, S.; Wyslouch, B.; Young, G.R


    Event-by-event fluctuations in the multiplicities of charged particles and photons at SPS energies are discussed. Fluctuations are studied by controlling the centrality of the reaction and rapidity acceptance of the detectors. Results are also presented on the event-by-event study of correlations between the multiplicity of charged particles and photons to search for DCC-like signals.

  11. Particle density fluctuations

    CERN Document Server

    Mohanty, Bedangadas; Ahammed, Z.; Angelis, A.L.S.; Antonenko, V.; Arefev, V.; Astakhov, V.; Avdeitchikov, V.; Awes, T.C.; Baba, P.V.K.S.; Badyal, S.K.; Bathe, S.; Batiounia, B.; Bernier, T.; Bhalla, K.B.; Bhatia, V.S.; Blume, C.; Bucher, D.; Busching, H.; Carlen, L.; Chattopadhyay, S.; Das, A.C.; Decowski, M.P.; Donni, P.; Dubey, A.K.; Dutta Majumdar, M.R.; Enosawa, K.; Fokin, S.; Frolov, V.; Ganti, M.S.; Garpman, S.; Gavrishchuk, O.; Geurts, F.J.M.; Glasow, R.; Guskov, B.; Gustafsson, H.A.; Gutbrod, H.H.; Hrivnacova, I.; Ippolitov, M.; Kalechofsky, H.; Kamermans, R.; Karadjev, K.; Karpio, K.; Kolb, B.W.; Kosarev, I.; Koutcheryaev, I.; Kugler, A.; Kulinich, P.; Kurata, M.; Lebedev, A.; Lohne, H.; Mahapatra, D.P.; Manko, V.; Martin, M.; Miake, Y.; Mishra, G.C.; Morrison, D.; Mukhopadhyay, D.S.; Naef, H.; Nandi, B.K.; Nayak, S.K.; Nayak, T.K.; Nianine, A.; Nikitine, V.; Nikolaev, S.; Nishimura, S.; Nomokov, P.; Nystrand, J.; Oskarsson, A.; Otterlund, I.; Phatak, S.C.; Pavliouk, S.; Peitzmann, T.; Petracek, V.; Plasil, F.; Purschke, M.L.; Rak, J.; Raniwala, R.; Raniwala, S.; Rao, N.K.; Retiere, F.; Reygers, K.; Roland, G.; Rosselet, L.; Roufanov, I.; Rubio, J.M.; Sambyal, S.S.; Santo, R.; Sato, S.; Schlagheck, H.; Schmidt, H.R.; Schutz, Y.; Shabratova, G.; Sibiriak, I.; Siemiarczuk, T.; Sinha, B.C.; Slavine, N.; Soderstrom, K.; Sood, G.; Sorensen, S.P.; Stankus, P.; Stefanek, G.; Steinberg, P.; Stenlund, E.; Sumbera, M.; Svensson, T.; Trivedi, M.D.; Tsvetkov, A.; Tykarski, L.; Urbahn, J.; van Eijndhoven, N.; van Nieuwenhuizen, G.J.; Vinogradov, A.; Viyogi, Y.P.; Vodopianov, A.S.; Voros, S.; Wyslouch, B.; Young, G.R.; Mohanty, Bedangadas


    Event-by-event fluctuations in the multiplicities of charged particles and photons at SPS energies are discussed. Fluctuations are studied by controlling the centrality of the reaction and rapidity acceptance of the detectors. Results are also presented on the event-by-event study of correlations between the multiplicity of charged particles and photons to search for DCC-like signals.

  12. Fluctuation Diamagnetism in Two-Band Superconductors


    Adachi, Kyosuke; Ikeda, Ryusuke


    Anomalously large fluctuation diamagnetism around the superconducting critical temperature has been recently observed on iron selenide (FeSe) [S. Kasahara et al., unpublished]. This indicates that superconducting fluctuations (SCFs) play a more significant role in FeSe, which supposedly has two-band structure, than in the familiar single-band superconductors. Motivated by the data in FeSe, SCF-induced diamagnetism is examined in a two-band system, on the basis of a phenomenological approach w...

  13. Quantum and Thermal Fluctuations in Field Theory


    Liao, Sen-Ben; Polonyi, Janos; Xu, Dapeng


    Blocking transformation is performed in quantum field theory at finite temperature. It is found that the manner temperature deforms the renormalized trajectories can be used to understand better the role played by the quantum fluctuations. In particular, it is conjectured that domain formation and mass parameter generation can be observed in theories without spontaneous symmetry breaking.

  14. Chest wall ectopic synovial bursa cyst. (United States)

    Michail, P; Filis, C; Pikoulis, E; Varelas, P; Kyrochristos, D; Mihail, S; Bastounis, E


    We report an unusual case of chest wall tumor in a 27-year-old patient. A complete resection was accomplished, and the patient had an excellent postoperative course. Histologically, the mass was confirmed to be an ectopic synovial bursa cyst. Although rare, synovial cysts should be considered in any case of a fluctuating chest wall mass. We also discuss the etiology and diagnostic approach of cystic masses of the chest wall.

  15. Continuous information flow fluctuations (United States)

    Rosinberg, Martin Luc; Horowitz, Jordan M.


    Information plays a pivotal role in the thermodynamics of nonequilibrium processes with feedback. However, much remains to be learned about the nature of information fluctuations in small-scale devices and their relation with fluctuations in other thermodynamics quantities, like heat and work. Here we derive a series of fluctuation theorems for information flow and partial entropy production in a Brownian particle model of feedback cooling and extend them to arbitrary driven diffusion processes. We then analyze the long-time behavior of the feedback-cooling model in detail. Our results provide insights into the structure and origin of large deviations of information and thermodynamic quantities in autonomous Maxwell's demons.

  16. Short-term high temperature growth conditions during vegetative-to-reproductive phase transition irreversibly compromise cell wall invertase-mediated sucrose catalysis and microspore meiosis in grain sorghum (United States)

    Grain sorghum (Sorghum bicolor L. Moench) crop yield is significantly compromised by high temperature stress-induced male sterility, and is attributed to reduced cell wall invertase (CWI)-mediated sucrose hydrolysis in microspores and anthers leading to altered carbohydrate metabolism and starch def...

  17. Multifractal conductance fluctuations in graphene (United States)

    Bid, Aveek; Rafsanjani Amin, Kazi; Pal, Nairita; Sankar Ray, Samriddhi; Pandit, Rahul

    A multifractal (MF) system is characterized by scaling laws involving an infinite number of exponents. In condensed-matter systems, signatures of multifractality have typically been found in the structure of the critical wave functions at localization delocalization (LD) transitions. We report here the first experimental observation of MF statistics in the transport coefficients of a quantum-condensed matter system. We unearth this through a careful investigation of the magneto-conductance fluctuations in ultra-high mobility single layer graphene at ultra-low temperatures. We obtain the MF spectra over a wide range of temperature and doping levels and show that the multifractality decreases as the temperature increases or as the doping moves the system away from the Dirac point. We show that the fractal exponents are a universal function of the phase coherence length of the carriers. We propose that a probable origin of the MF magneto-conductance fluctuations observed by us is an incipient Anderson LD transition in graphene near the charge neutrality point - a phenomenon predicted but never observed in single layer graphene. We also explore alternate possibilities of the origin of the multifractality namely relativistic quantum scars. AB acknowledges funding from Nanomission, DST, Govt. of India and SERB, DST, Govt. of India.

  18. Highly sensitive room temperature carbon monoxide detection using SnO2 nanoparticle-decorated semiconducting single-walled carbon nanotubes. (United States)

    Zhang, Yang; Cui, Shumao; Chang, Jingbo; Ocola, Leonidas E; Chen, Junhong


    We demonstrate a practical sensing platform, consisting of SnO(2) nanoparticle-decorated semiconducting single-walled carbon nanotubes assembled on gold electrodes via a dielectrophoretic process, for highly sensitive CO detection with fast response at room temperature. The highest sensitivity obtained was 0.27 and the response time was ∼2 s for 100 ppm CO detection. The lower detection limit was ∼1 ppm. These results indicate that the sensing performance of our device is among the best of CO sensors implemented with SWNTs. Further, we observed a significant increase in sensitivity to 0.67 after subjecting the device to an electrical breakdown at 8 V. We also proposed a theoretical model to reveal the relationship between the sensitivity and the gas concentration. The new model not only resulted in a nice fit to our data, but also allowed us to estimate the contact resistance between an individual SWNT and the gold electrodes.

  19. A Temperature Window for the Synthesis of Single-Walled Carbon Nanotubes by Catalytic Chemical Vapor Deposition of CH4over Mo2-Fe10/MgO Catalyst

    Directory of Open Access Journals (Sweden)

    Yu Ouyang


    Full Text Available Abstract A temperature window for the synthesis of single-walled carbon nanotubes by catalytic chemical vapor deposition of CH4over Mo2-Fe10/MgO catalyst has been studied by Raman spectroscopy. The results showed that when the temperature is lower than 750 °C, there were few SWCNTs formed, and when the temperature is higher than 950 °C, mass amorphous carbons were formed in the SWCNTs bundles due to the self-decomposition of CH4. The temperature window of SWCNTs efficient growth is between 800 and 950 °C, and the optimum growth temperature is about 900 °C. These results were supported by transmission electron microscope images of samples formed under different temperatures. The temperature window is important for large-scale production of SWCNTs by catalytic chemical vapor deposition method.

  20. Scaling metabolic rate fluctuations


    Labra, Fabio A.; Marquet, Pablo A.; Bozinovic, Francisco


    Complex ecological and economic systems show fluctuations in macroscopic quantities such as exchange rates, size of companies or populations that follow non-Gaussian tent-shaped probability distributions of growth rates with power-law decay, which suggests that fluctuations in complex systems may be governed by universal mechanisms, independent of particular details and idiosyncrasies. We propose here that metabolic rate within individual organisms may be considered as an example of an emerge...

  1. Hydrodynamic fluctuations in thermostatted multiparticle collision dynamics. (United States)

    Híjar, Humberto; Sutmann, Godehard


    In this work we study the behavior of mesoscopic fluctuations of a fluid simulated by Multiparticle Collision Dynamics when this is applied together with a local thermostatting procedure that constrains the strength of temperature fluctuations. We consider procedures in which the thermostat interacts with the fluid at every simulation step as well as cases in which the thermostat is applied only at regular time intervals. Due to the application of the thermostat temperature fluctuations are forced to relax to equilibrium faster than they do in the nonthermostatted, constant-energy case. Depending on the interval of application of the thermostat, it is demonstrated that the thermodynamic state changes gradually from isothermal to adiabatic conditions. In order to exhibit this effect we compute from simulations diverse correlation functions of the hydrodynamic fluctuating fields. These correlation functions are compared with those predicted by a linearized hydrodynamic theory of a simple fluid in which a thermostat is applied locally. We find a good agreement between the model and the numerical results, which confirms that hydrodynamic fluctuations in Multiparticle Collision Dynamics in the presence of the thermostat have the properties expected for spontaneous fluctuations in fluids in contact with a heat reservoir.

  2. Pressure Fluctuations Induced by a Hypersonic Turbulent Boundary Layer (United States)

    Duan, Lian; Choudhari, Meelan M.; Zhang, Chao


    Direct numerical simulations (DNS) are used to examine the pressure fluctuations generated by a spatially-developed Mach 5.86 turbulent boundary layer. The unsteady pressure field is analyzed at multiple wall-normal locations, including those at the wall, within the boundary layer (including inner layer, the log layer, and the outer layer), and in the free stream. The statistical and structural variations of pressure fluctuations as a function of wall-normal distance are highlighted. Computational predictions for mean velocity pro les and surface pressure spectrum are in good agreement with experimental measurements, providing a first ever comparison of this type at hypersonic Mach numbers. The simulation shows that the dominant frequency of boundary-layer-induced pressure fluctuations shifts to lower frequencies as the location of interest moves away from the wall. The pressure wave propagates with a speed nearly equal to the local mean velocity within the boundary layer (except in the immediate vicinity of the wall) while the propagation speed deviates from the Taylor's hypothesis in the free stream. Compared with the surface pressure fluctuations, which are primarily vortical, the acoustic pressure fluctuations in the free stream exhibit a significantly lower dominant frequency, a greater spatial extent, and a smaller bulk propagation speed. The freestream pressure structures are found to have similar Lagrangian time and spatial scales as the acoustic sources near the wall. As the Mach number increases, the freestream acoustic fluctuations exhibit increased radiation intensity, enhanced energy content at high frequencies, shallower orientation of wave fronts with respect to the flow direction, and larger propagation velocity.

  3. Doping dependence of fluctuation diamagnetism in high Tc superconductors (United States)

    Sarkar, Kingshuk; Banerjee, Sumilan; Mukerjee, Subroto; Ramakrishnan, T. V.


    Using a recently proposed Ginzburg-Landau-like lattice free energy functional due to Banerjee et al. (2011) we calculate the fluctuation diamagnetism of high-Tc superconductors as a function of doping, magnetic field and temperature. We analyse the pairing fluctuations above the superconducting transition temperature in the cuprates, ranging from the strong phase fluctuation dominated underdoped limit to the more conventional amplitude fluctuation dominated overdoped regime. We show that a model where the pairing scale increases and the superfluid density decreases with underdoping produces features of the observed magnetization in the pseudogap region, in good qualitative and reasonable quantitative agreement with the experimental data. In particular, we explicitly show that even when the pseudogap has a pairing origin the magnetization actually tracks the superconducting dome instead of the pseudogap temperature, as seen in experiment. We discuss the doping dependence of the 'onset' temperature for fluctuation diamagnetism and comment on the role of vortex core-energy in our model.

  4. Fluctuating shells under pressure (United States)

    Paulose, Jayson; Vliegenthart, Gerard A.; Gompper, Gerhard; Nelson, David R.


    Thermal fluctuations strongly modify the large length-scale elastic behavior of cross-linked membranes, giving rise to scale-dependent elastic moduli. Whereas thermal effects in flat membranes are well understood, many natural and artificial microstructures are modeled as thin elastic shells. Shells are distinguished from flat membranes by their nonzero curvature, which provides a size-dependent coupling between the in-plane stretching modes and the out-of-plane undulations. In addition, a shell can support a pressure difference between its interior and its exterior. Little is known about the effect of thermal fluctuations on the elastic properties of shells. Here, we study the statistical mechanics of shape fluctuations in a pressurized spherical shell, using perturbation theory and Monte Carlo computer simulations, explicitly including the effects of curvature and an inward pressure. We predict novel properties of fluctuating thin shells under point indentations and pressure-induced deformations. The contribution due to thermal fluctuations increases with increasing ratio of shell radius to thickness and dominates the response when the product of this ratio and the thermal energy becomes large compared with the bending rigidity of the shell. Thermal effects are enhanced when a large uniform inward pressure acts on the shell and diverge as this pressure approaches the classical buckling transition of the shell. Our results are relevant for the elasticity and osmotic collapse of microcapsules. PMID:23150558

  5. Ambiguous walls

    DEFF Research Database (Denmark)

    Mody, Astrid


    of “ambiguous walls” as a more “critical” approach to design [1]. The concept of ambiguous walls refers to the diffuse status a lumious and possibly responsive wall will have. Instead of confining it can open up. Instead of having a static appearance, it becomes a context over time. Instead of being hard...... and flat, “ambiguous walls” combine softness, tectonics and three-dimensionality. The paper considers a selection of luminious surfaces and reflects on the extent of their ambiguous qualities. Initial ideas for new directions for the wall will be essayed through the discussion....

  6. Dependence of intermittent density fluctuations on collisionality in TJ-K

    Energy Technology Data Exchange (ETDEWEB)

    Reuther, Kyle; Garland, Stephen; Ramisch, Mirko [Institut fuer Grenzflaechenverfahrenstechnikund Plasmatechnologie, Universitaet Stuttgart (Germany); Manz, Peter [Physik-Department E28, Technische Universitaet Muenchen, Garching (Germany)


    Particle and heat transport losses due to edge turbulence are well known phenomena commonly seen in toroidal magnetic confinement devices. Furthermore in the scrape-off layer (SOL), turbulent density fluctuations are often observed to be intermittent and dominate particle transport to the vessel walls. In the adiabatic limit (small collisionality), of the two-field Hasegawa-Wakatani model, simulated turbulent density fluctuations are observed to couple to potential fluctuations and exhibit Gaussian behavior. However, in the hydrodynamic limit (large collisionality) the density and potential decouple. As a result, the density becomes passively advected, evolves towards the vorticity, and exhibits intermittent behavior. The relationship between collisionality and intermittency is investigated experimentally at the stellarator TJ-K. To vary the plasma collisionality, which is related to electron density and temperature, parameters such as gas type, neutral gas pressure, magnetic field, and heating power are varied. Radial profiles of plasma density, temperature, floating potential, and vorticity are recorded via a scanning 7-tip Langmuir probe array. First results are presented.

  7. Spin fluctuations and the

    Directory of Open Access Journals (Sweden)

    V.M. Loktev


    Full Text Available We analyze the spectral properties of a phenomenological model for a weakly doped two-dimensional antiferromagnet, in which the carriers move within one of the two sublattices where they were introduced. Such a constraint results in the free carrier spectra with the maxima at k=(± π/2 , ± π/2 observed in some cuprates. We consider the spectral properties of the model by taking into account fluctuations of the spins in the antiferromagnetic background. We show that such fluctuations lead to a non-pole-like structure of the single-hole Green's function and these fluctuations can be responsible for some anomalous "strange metal" properties of underdoped cuprates in the nonsuperconducting regime.

  8. Measurement of temperature fluctuations and anomalous transport ...

    Indian Academy of Sciences (India)

    Coulomb collisions in a magnetised plasma give rise to electrical resistivity and particle diffusion across the magnetic field. This diffusion process is known as classical trans- port and can be calculated exactly. For the curved magnetic geometry of a tokamak, the collisional transport is termed as neoclassical transport.

  9. Critical point fluctuations in supported lipid membranes. (United States)

    Connell, Simon D; Heath, George; Olmsted, Peter D; Kisil, Anastasia


    In this paper, we demonstrate that it is possible to observe many aspects of critical phenomena in supported lipid bilayers using atomic force microscopy (AFM) with the aid of stable and precise temperature control. The regions of criticality were determined by accurately measuring and calculating phase diagrams for the 2 phase L(d)-L(o) region, and tracking how it moves with temperature, then increasing the sampling density around the estimated critical regions. Compositional fluctuations were observed above the critical temperature (T(c)) and characterised using a spatial correlation function. From this analysis, the phase transition was found to be most closely described by the 2D Ising model, showing it is a critical transition. Below T(c) roughening of the domain boundaries occurred due to the reduction in line tension close to the critical point. Smaller scale density fluctuations were also detected just below T(c). At T(c), we believe we have observed fluctuations on length scales greater than 10 microm. The region of critically fluctuating 10-100 nm nanodomains has been found to extend a considerable distance above T(c) to temperatures within the biological range, and seem to be an ideal candidate for the actual structure of lipid rafts in cell membranes. Although evidence for this idea has recently emerged, this is the first direct evidence for nanoscale domains in the critical region.

  10. Quantum fluctuations in FRLW space-time


    Rabochaya, Y.


    In this paper we study a quantum field theoretical approach, where a quantum probe is used to investigate the properties of generic non-flat FRLW space time. The fluctuations related to a massless conformal coupled scalar field defined on a space-time with horizon is identified with a probe and the procedure to measure the local temperature is presented.

  11. Depolarization of D-T plasmas by recycling in material walls

    Energy Technology Data Exchange (ETDEWEB)

    Greenside, H.S.; Budny, R.V.; Post, D.E.


    The feasibility of using polarized deuterium (D) and tritium (T) plasmas in fusion reactors may be seriously affected by recycling in material walls. Theoretical and experimental results are reviewed which show how the depolarization rates of absorbed D and T depend on first wall parameters such as the temperature, the bulk and surface diffusivities, the density of electronic states at the Fermi surface, the spectral density of microscopic fluctuating electric field gradients, and the concentration of paramagnetic impurities. Nuclear magnetic resonance (NMR) spectroscopy of hydrogenated and deuterated amorphous semiconductors suggests that low-Z nonmetallic materials may provide a satisfactory first wall or limiter coating under reactor conditions with characteristic depolarization times of several seconds. Experiments are proposed to test the consequences of our analysis.

  12. Wall Pressure Fluctuations and Acoustics in Turbulent Pipe Flow (United States)


    finite-sized %’*’• pressure sensors--which average over space --need to be at least as small as the smallest eddies; otherwise, an attenuation of the...high-frequency (small wavelength) spectral contributions (particularly those in this convective ridge) will occur. Kolmogoroff (see Hinze, 1959. for

  13. Heat fluctuations of Brownian oscillators in nonstationary processes: Fluctuation theorem and condensation transition. (United States)

    Crisanti, A; Sarracino, A; Zannetti, M


    We study analytically the probability distribution of the heat released by an ensemble of harmonic oscillators to the thermal bath, in the nonequilibrium relaxation process following a temperature quench. We focus on the asymmetry properties of the heat distribution in the nonstationary dynamics, in order to study the forms taken by the fluctuation theorem as the number of degrees of freedom is varied. After analyzing in great detail the cases of one and two oscillators, we consider the limit of a large number of oscillators, where the behavior of fluctuations is enriched by a condensation transition with a nontrivial phase diagram, characterized by reentrant behavior. Numerical simulations confirm our analytical findings. We also discuss and highlight how concepts borrowed from the study of fluctuations in equilibrium under symmetry-breaking conditions [Gaspard, J. Stat. Mech. (2012) P0802110.1088/1742-5468/2012/08/P08021] turn out to be quite useful in understanding the deviations from the standard fluctuation theorem.

  14. Microcanonical quantum fluctuation theorems. (United States)

    Talkner, Peter; Hänggi, Peter; Morillo, Manuel


    Previously derived expressions for the characteristic function of work performed on a quantum system by a classical external force are generalized to arbitrary initial states of the considered system and to Hamiltonians with degenerate spectra. In the particular case of microcanonical initial states, explicit expressions for the characteristic function and the corresponding probability density of work are formulated. Their classical limit as well as their relations to the corresponding canonical expressions are discussed. A fluctuation theorem is derived that expresses the ratio of probabilities of work for a process and its time reversal to the ratio of densities of states of the microcanonical equilibrium systems with corresponding initial and final Hamiltonians. From this Crooks-type fluctuation theorem a relation between entropies of different systems can be derived which does not involve the time-reversed process. This entropy-from-work theorem provides an experimentally accessible way to measure entropies.

  15. Fluctuation diamagnetism in two-band superconductors (United States)

    Adachi, Kyosuke; Ikeda, Ryusuke


    Anomalously large fluctuation diamagnetism around the superconducting critical temperature has been recently observed in iron selenide (FeSe) [Kasahara et al. (unpublished)]. This indicates that superconducting fluctuations (SCFs) play a more significant role in FeSe, which supposedly has a two-band structure, than in the familiar single-band superconductors. Motivated by the data on FeSe, SCF-induced diamagnetism is examined in a two-band system, on the basis of a phenomenological approach with a Ginzburg-Landau functional. The obtained results indicate that the SCF-induced diamagnetism may be more enhanced than that in a single-band system due to the existence of two distinct fluctuation modes. Such enhancement of diamagnetism unique to a two-band system seems consistent with the large diamagnetism observed in FeSe, though still far from a quantitative agreement.

  16. Wall Art (United States)

    McGinley, Connie Q.


    The author of this article, an art teacher at Monarch High School in Louisville, Colorado, describes how her experience teaching in a new school presented an exciting visual challenge for an art teacher--monotonous brick walls just waiting for decoration. This school experienced only minimal instances of graffiti, but as an art teacher, she did…

  17. Forced convection of ammonia. 2. part.: gaseous ammonia - very high wall temperatures (1000 to 3000 K); Convection forcee de l'ammoniac. 2. partie: ammoniac gazeux - cas de tres hautes temperatures de paroi (1000 a 3000{sup 0} K)

    Energy Technology Data Exchange (ETDEWEB)

    Perroud, P.; Rebiere, J.; Strittmatter, R. [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires


    Heat transfer coefficients and pressure drop of gaseous ammonia in forced convection are experimentally determined. The fluid flows (mass flow rate 0.6 to 2.4 g/s) in a long tungsten tube (d{sub i} = 2.8 mm, d{sub e} = 5.1 mm, L = 700 mm) electrically heated. The temperature of the wall reaches 3000 deg. K and the fluid 2500 deg. K; maximum heat flux 530 w/cm{sup 2}. Ammonia is completely dissociated and the power necessary for dissociation reaches 30 per cent of the total power exchanged. Inlet pressure varies between 6 and 16 bars and the maximum pressure drop in the tube reaches 15 bars. Two regimes of dissociation have been shown: catalytic and homogeneous and the variation of dissociation along the length of the tube is studied. The measured heat transfer coefficients may be about 10 times these calculated by the means of classical formulae. A correlation of experimental results using enthalpy as a driving force for heat transmission is presented. Pressure drops may be calculated by the means of a classical friction factor. (authors) [French] On determine experimentalement les coefficients d'echange thermique et les pertes de charge de l'ammoniac gazeux en convection forcee. Le fluide circule avec un debit en masse compris entre 0.6 et 2.4 g/s (G = 10 a 40 g/cm{sup 2}.s) dans un tube long en tungstene (d{sub i} = 2.8 mm, d{sub e} = 5.1 mm, L = 700 mm), chauffe electriquement. La temperature de paroi atteint 3000 deg. K, celle du fluide 2500 deg. K et le flux de chaleur maximal est de 530 W/cm{sup 2}. L'ammoniac se dissocie completement, la puissance correspondant a la dissociation atteint 30 pour cent de la puissance totale echangee. La pression d'entree varie entre 6 et 16 bars et la chute de pression maximale dans le canal est de 15 bars. On distingue deux regimes de dissociation, catalytique et homogene, et on etudie la variation du taux de dissociation en fonction de la longueur du tube. Les coefficients d'echange thermique mesures

  18. Nernst effect and diamagnetism in phase fluctuating superconductors. (United States)

    Podolsky, Daniel; Raghu, Srinivas; Vishwanath, Ashvin


    We study superconducting systems in the regime where superconductivity is destroyed by phase fluctuations. We find that the Nernst effect has a much sharper temperature decay than predicted by Gaussian fluctuations, with an onset temperature that tracks Tc rather than the pairing temperature. We find a close quantitative connection with diamagnetism--the ratio of magnetization to transverse thermoelectric conductivity reaches a fixed value at high temperatures. We interpret measurements on underdoped cuprates in terms of a dilute vortex liquid over a wide temperature range above Tc.

  19. Local thermal behaviour of a massive scalar field near a reflecting wall

    Energy Technology Data Exchange (ETDEWEB)

    Lorenci, V.A. De [Instituto de Física e Química, Universidade Federal de Itajubá,Itajubá, MG 37500-903 (Brazil); Gomes, L.G.; Moreira, E.S. Jr. [Instituto de Matemática e Computação, Universidade Federal de Itajubá,Itajubá, MG 37500-903 (Brazil)


    The mean square fluctuation and the expectation value of the stress-energy-momentum tensor of a neutral massive scalar field at finite temperature are determined near an infinite plane Dirichlet wall, and also near an infinite plane Neumann wall. The flat background has an arbitrary number of dimensions and the field is arbitrarily coupled to the vanishing curvature. It is shown that, unlike vacuum contributions, thermal contributions are free from boundary divergences, and that the thermal behaviour of the scalar field near a Dirichlet wall differs considerably from that near a Neumann wall. Far from the wall the study reveals a local version of dimensional reduction, namely, corrections to familiar blackbody expressions are linear in the temperature, with the corresponding coefficients given only in terms of vacuum expectation values in a background with one less dimension. It is shown that such corrections are “classical” (i.e., not dependent on Planck’s constant) only if the scalar field is massless. A natural conjecture that arises is that the “local dimensional reduction” is universal since it operates for massless and massive fields alike and regardless of the boundary conditions.

  20. Studies on the thermodynamics and solute–solvent interaction of Polyvinyl pyrrolidone wrapped single walled carbon nanotubes (PVP-SWNTs in water over temperature range 298.15–313.15 K

    Directory of Open Access Journals (Sweden)

    Malahah Mohamed


    Full Text Available The water solubilisation of single walled carbon nanotubes (SWNTs has been achieved by polymer wrapping. The present study aims at highlighting the solute–solvent interaction and thermodynamic parameters in the solubilisation of polyvinyl pyrrolidone wrapped single walled carbon nanotubes (PVP-SWNTs in water. Conductivity and density values of both PVP and PVP-SWNTs have been determined in water maintaining different concentrations (0.005–0.1 g/L at temperatures 298.15, 303.15, 308.15 and 313.15 K. The conductance values have been used to evaluate the limiting molar conductance (∧om and the activation energy (Es. From the density values, the limiting partial molar volumes and expansibilities have been calculated. The estimated parameters were discussed in terms of solute–solvent interactions.

  1. SOL width and intermittent fluctuations in KSTAR

    Directory of Open Access Journals (Sweden)

    O.E. Garcia


    Full Text Available Radial profiles of the ion saturation current and its fluctuation statistics are presented from probe measurements in L-mode, neutral beam heated plasmas at the outboard mid-plane region of KSTAR. The results are consistent with the familiar two-layer structure, seen elsewhere in tokamak L-mode discharges, with a steep near-SOL profile and a broad far-SOL profile. The profile scale length in the far-SOL increases drastically with line-averaged density, thereby enhancing plasma interactions with the main chamber walls. Time series from the far-SOL region are characterised by large-amplitude bursts attributed to the radial motion of blob-like plasma filaments. Analysis of a data time series of several seconds duration under stationary plasma conditions reveals the statistical properties of these fluctuations, including the rate of level crossings and the average duration of periods spent above a given threshold level. This is shown to be in excellent agreement with predictions of a stochastic model, giving novel predictions of plasma–wall interactions due to transient transport events.

  2. Wall Layers (United States)


    Sydney, Australia. December 6, 1990. Lumley, J. L. A dynamical-systems-theory approach to the wall region. Environmental Engineering Laboratory, CSIRO...Nonlinear Science. Holmes, P. Editor in Chief, Nonlinear Scinece Today. Holmes, P. Reviewer for Physica D, J. Sound Vib., J. Phys., Q. Appl. Math, Phys...Spring, 1994; Organizing committee member. Holmes, P. Editorial Board Member: Archive for Rational Mechanics and Analysis; Journal of Nonlinear Scinece


    CERN Multimedia


    The FIRE AND RESCUE Group of TIS Commission informs that the climbing wall in the yard of the Fire-fighters Station, is intended for the sole use of the members of that service, and recalls that access to this installation is forbidden for safety reasons to all persons not belonging to the Service.CERN accepts no liability for damage or injury suffered as a result of failure to comply with this interdiction.TIS/DI

  4. Thermal control wall prototype and test results

    Energy Technology Data Exchange (ETDEWEB)

    Nakao, M.; Ohshima, K.; Jitsukawa, H.


    This paper describes a heat exchanger prototype and test results. The heat exchanger, called a thermal control wall, functions as a skin wall and as a means to vary the exterior wall thermal resistance of a building. Test results confirm that the capacity of the TCW is influenced by solar radiation. Furthermore, this TCW capacity can be evaluated by an overall heat transmission coefficient defined using the same sol air temperature difference as for a conventional wall.

  5. The correlation between the Nernst effect and fluctuation diamagnetism in strongly fluctuating superconductors (United States)

    Sarkar, Kingshuk; Banerjee, Sumilan; Mukerjee, Subroto; Ramakrishnan, T. V.


    We study the Nernst effect in fluctuating superconductors by calculating the transport coefficient {α }{xy} in a phenomenological model where the relative importance of phase and amplitude fluctuations of the order parameter is tuned continuously to smoothly evolve from an effective XY model to the more conventional Ginzburg-Landau description. To connect with a concrete experimental realization we choose the model parameters appropriate for cuprate superconductors and calculate {α }{xy} and the magnetization {M} over the entire range of experimentally accessible values of field, temperature and doping. We argue that {α }{xy} and {M} are both determined by the equilibrium properties of the superconducting fluctuations (and not their dynamics) despite the former being a transport quantity. Thus, the experimentally observed correlation between the Nernst signal and the magnetization arises primarily from the correlation between {α }{xy} and {M}. Further, there exists a dimensionless ratio {M}/(T{α }{xy}) that quantifies this correlation. We calculate, for the first time, this ratio over the entire phase diagram of the cuprates and find it agrees with previous results obtained in specific parts of the phase diagram. We conclude that there appears to be no sharp distinction between the regimes dominated by phase fluctuations and Gaussian fluctuations for this ratio in contrast to {α }{xy} and {M} individually. The utility of this ratio is that it can be used to determine the extent to which superconducting fluctuations contribute to the Nernst effect in different parts of the phase diagram given the measured values of magnetization.

  6. Fluctuation relations for anisotropic systems (United States)

    Villavicencio-Sanchez, R.; Harris, R. J.; Touchette, H.


    Currents of particles or energy in driven non-equilibrium steady states are known to satisfy certain symmetries, referred to as fluctuation relations, determining the ratio of the probabilities of positive fluctuations to negative ones. A generalization of these fluctuation relations has been proposed recently for extended non-equilibrium systems of dimension greater than one, assuming, crucially, that they are isotropic (Hurtado P. I., Pérez-Espigares C., del Pozo J. J. and Garrido P. L., Proc. Natl. Acad. Sci. U.S.A., 108 (2011) 7704). Here we relax this assumption and derive a fluctuation relation for d-dimensional systems having anisotropic bulk driving rates. We test the validity of this anisotropic fluctuation relation by calculating the particle current fluctuations in the 2d anisotropic zero-range process, using both exact and fluctuating hydrodynamic approaches.

  7. Stress fluctuations in sheared Stokesian suspensions. (United States)

    Dasan, J; Ramamohan, T R; Singh, Anugrah; Nott, Prabhu R


    We report an analysis, using the tools of nonlinear dynamics and chaos theory, of the fluctuations in the stress determined from simulations of shear flow of Stokesian suspensions. The simulations are for shear between plane parallel walls of a suspension of rigid identical spheres in a Newtonian fluid, over a range of particle concentration. By analyzing the time series of the stress, we find that the dynamics underlying these fluctuations is deterministic, low-dimensional, and chaotic. We use the dynamic and metric invariants of the underlying dynamics as a means of characterizing suspension behavior. The dimension of the chaotic attractor increases with particle concentration, indicating the increasing influence of multiple-body interactions on the rheology of the suspension with rise in particle concentration. We use our analysis to make accurate predictions of the short-term evolution of a stress component from its preceding time series, and predict the evolution of one component of the stress using the time series of another. We comment on the physical origin of the chaotic stress fluctuations, and on the implications of our results on the relation between the microstructure and the stress.


    Energy Technology Data Exchange (ETDEWEB)

    Yang, Shuhong; Zhang, Jun [Key Laboratory of Solar Activity, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China); Erdélyi, Robert, E-mail: [Solar Physics and Space Plasma Research Centre, School of Mathematics and Statistics, University of Sheffield, Hicks Building, Hounsfield Road, Sheffield S3 7RH (United Kingdom)


    Based on the Interface Region Imaging Spectrograph observations, we study the response of a solar sunspot light wall to external disturbances. A flare occurrence near the light wall caused material to erupt from the lower solar atmosphere into the corona. Some material falls back to the solar surface and hits the light bridge (i.e., the base of the light wall), then sudden brightenings appear at the wall base followed by the rise of wall top, leading to an increase of the wall height. Once the brightness of the wall base fades, the height of the light wall begins to decrease. Five hours later, another nearby flare takes place, and a bright channel is formed that extends from the flare toward the light bridge. Although no obvious material flow along the bright channel is found, some ejected material is conjectured to reach the light bridge. Subsequently, the wall base brightens and the wall height begins to increase again. Once more, when the brightness of the wall base decays, the wall top fluctuates to lower heights. We suggest, based on the observed cases, that the interaction of falling material and ejected flare material with the light wall results in the brightenings of wall base and causes the height of the light wall to increase. Our results reveal that the light wall can be not only powered by the linkage of p -mode from below the photosphere, but may also be enhanced by external disturbances, such as falling material.

  9. Evaluating the role of ivy (Hedera helix) in moderating wall surface microclimates and contributing to the bioprotection of historic buildings

    Energy Technology Data Exchange (ETDEWEB)

    Sternberg, Troy; Viles, Heather [Oxford University, School of Geography, South Parks Road, Oxford OX1 3QY (United Kingdom); Cathersides, Alan [English Heritage, Conservation Department, Kemble Drive, Swindon SN2 2GZ (United Kingdom)


    The role of ivy (Hedera helix L.) on building walls is much debated, with arguments being put forward for it playing a biodeteriorative role (for example through ivy rootlets exploiting cracks and holes) as well as suggestions that it might provide some bioprotection (for example by the ivy canopy protecting the walls from other agents of deterioration such as frost). We have carried out a year-long study of the influence that ivy canopies play on wall surface microclimates at five sites across a range of climatic settings within England, using iButtons to monitor temperature and relative humidity fluctuations at the wall surface on ivy-covered and exposed walls. Hourly data illustrates a general mediating effect of ivy canopies on both temperature and relative humidity regimes. The ivy reduces extremes of temperature and relative humidity, with the most clearcut differences for temperature. Across all five sites the average daily maximum temperature was 36% higher and the average daily minimum temperature 15% lower on exposed vs ivy-covered surfaces. Differences in the exposure level of studied walls (i.e. whether they are shaded or not by trees or other walls) influenced the degree of microclimatic alteration provided by the ivy canopy. Other important factors influencing the strength of the ivy impact on microclimate were found to be thickness of the canopy and aspect of the wall. A detailed analysis of one site, Byland in North Yorkshire, illustrates the seasonal differences in impact of ivy on microclimates, with insulation against freezing being the dominant effect in January, and the removal of high temperature 'spikes' the dominant effect in July. The observed moderating role of ivy canopies on wall surface microclimates will reduce the likelihood of frost and salt deterioration to the building materials, thus contributing to their conservation. Further research needs to be done on other potentially deteriorative roles of ivy before an overall

  10. Quantum work-fluctuation theorem: exact case study for a perturbed oscillator. (United States)

    Monnai, Takaaki


    We analytically explore the fluctuation of the work-induced entropy production of an externally perturbed quantum harmonic oscillator interacting with several reservoirs. The quantum fluctuation of the work amounts to a non-Gaussian fluctuation of the entropy production, which interpolates the Gaussian and the Poissonian distributions at high- and low-temperature regimes. Also, it is shown that the corresponding fluctuation theorem symmetry is rigorously satisfied.

  11. Fluctuations in a Spin Chain and the Entanglement Hamiltonian (United States)

    Turner, Ari; Demler, Eugene


    How are quantum fluctuations and thermal fluctuations different in many-body systems? I will compare the variance of the fluctuations of spin in a segment of a spin chain in the ground state and at a finite temperature, showing that fluctuations in the ground state are much more correlated than in the thermal state. The full distribution function of spin can also be determined, and is non-Gaussian. These effects could possibly be measured in a chain of sodium atoms in an optical lattice. The method involves mapping the system to an imaginary thermal system called the ``entanglement Hamiltonian.'' Measuring the ground state fluctuations of the spin chain gives an indirect way of measuring the entanglement Hamiltonian.

  12. Conduction and convection heat transfer characteristics of water-based au nanofluids in a square cavity with differentially heated side walls subjected to constant temperatures

    Directory of Open Access Journals (Sweden)

    Ternik Primož


    Full Text Available The present work deals with the natural convection in a square cavity filled with the water-based Au nanofluid. The cavity is heated on the vertical and cooled from the adjacent wall, while the other two horizontal walls are adiabatic. The governing differential equations have been solved by the standard finite volume method and the hydrodynamic and thermal fields were coupled together using the Boussinesq approximation. The main objective of this study is to investigate the influence of the nanoparticles’ volume fraction on the heat transfer characteristics of Au nanofluids at the given base fluid’s (i.e. water Rayleigh number. Accurate results are presented over a wide range of the base fluid Rayleigh number and the volume fraction of Au nanoparticles. It is shown that adding nanoparticles in a base fluid delays the onset of convection. Contrary to what is argued by many authors, we show by numerical simulations that the use of nanofluids can reduce the heat transfer rate instead of increasing it.

  13. Control of Microstructures and the Practical Properties of API X80 Grade Heavy-Wall High-Frequency Electric Resistance-Welded Pipe with Excellent Low-Temperature Toughness (United States)

    Goto, Sota; Nakata, Hiroshi; Toyoda, Shunsuke; Okabe, Takatoshi; Inoue, Tomohiro


    This paper describes development of heavy-walled API X80 grade high-frequency electric resistance-welded (HFW) line pipes and conductor-casing pipes with wall thicknesses up to 20.6 mm. A fine bainitic-ferrite microstructure, which is preferable for low-temperature toughness, was obtained by optimizing the carbon content and applying the thermomechanical controlled hot-rolling process. As a result, the Charpy ductile-brittle transition temperature (DBTT) was well below 227 K (-46 °C) in the base metal of the HFW line pipe. When the controlled hot-rolling ratio (CR) was increased from 23 to 48 pct, the area average grain size decreased from 15 to 8 μm. The dependence of CTOD properties on CR was caused by the largest grain which is represented by the area average grain size. No texture development due to the increase of CR from 23 to 48 pct was observed. In addition, because controlled in-line heat treatment of the longitudinal weld seam also produced the fine bainitic-ferrite microstructure at the weld seam, DBTT was lower than 227 K (-46 °C) at the weld portion. The developed pipes showed good girth weldability without preheat treatment, and fracture in the tensile test initiated from the base metal in all cases.

  14. Simulation of fluctuations of temperature and flow at the entrance of the nucleus of Trillo NPP; Simulacion de fluctuaciones de temperatura y caudal a la entrada del nucleo de C.N. Trillo

    Energy Technology Data Exchange (ETDEWEB)

    Bermejo, J. A.; Pelaez, S. B.; Lopez, A.; Ortego, A.


    One of the lines of work of the r and d program initiated in CNAT, to investigate the causes increasing the level of neutronic noise in C.N. Trillo, is the simulation of fluctuations thermohydraulics at the entrance of the neutron kernel with capability of simulation transient. The paper summarizes the status of this line of work and are presented some of the main results obtained so far.

  15. Temperature-calibrated imaging of seasonal changes in permafrost rock walls by quantitative electrical resistivity tomography (Zugspitze, German/Austrian Alps)

    National Research Council Canada - National Science Library

    Michael Krautblatter; Sarah Verleysdonk; Adrián Flores-Orozco; Andreas Kemna


    .... This article applies electrical resistivity tomography (ERT) to gain insight into spatial thaw and refreezing behavior of permafrost rocks and presents the first approach to calibrating ERT with frozen rock temperature...

  16. Cell wall, cell membrane, and volatile metabolism are altered by antioxidant treatment, temperature shifts, and peel necrosis during apple fruit storage (United States)

    The transition from cold storage to ambient temperature alters apple quality through accelerated softening, flavor and color changes, and symptom development of physiological peel disorders, such as superficial scald, in susceptible cultivars. To reveal global metabolism associated with the transit...

  17. Quantum critical scaling and fluctuations in Kondo lattice materials. (United States)

    Yang, Yi-Feng; Pines, David; Lonzarich, Gilbert


    We propose a phenomenological framework for three classes of Kondo lattice materials that incorporates the interplay between the fluctuations associated with the antiferromagnetic quantum critical point and those produced by the hybridization quantum critical point that marks the end of local moment behavior. We show that these fluctuations give rise to two distinct regions of quantum critical scaling: Hybridization fluctuations are responsible for the logarithmic scaling in the density of states of the heavy electron Kondo liquid that emerges below the coherence temperature [Formula: see text], whereas the unconventional power law scaling in the resistivity that emerges at lower temperatures below [Formula: see text] may reflect the combined effects of hybridization and antiferromagnetic quantum critical fluctuations. Our framework is supported by experimental measurements on CeCoIn5, CeRhIn5, and other heavy electron materials.

  18. Quantum critical scaling and fluctuations in Kondo lattice materials (United States)

    Yang, Yi-feng; Pines, David; Lonzarich, Gilbert


    We propose a phenomenological framework for three classes of Kondo lattice materials that incorporates the interplay between the fluctuations associated with the antiferromagnetic quantum critical point and those produced by the hybridization quantum critical point that marks the end of local moment behavior. We show that these fluctuations give rise to two distinct regions of quantum critical scaling: Hybridization fluctuations are responsible for the logarithmic scaling in the density of states of the heavy electron Kondo liquid that emerges below the coherence temperature T∗, whereas the unconventional power law scaling in the resistivity that emerges at lower temperatures below TQC may reflect the combined effects of hybridization and antiferromagnetic quantum critical fluctuations. Our framework is supported by experimental measurements on CeCoIn5, CeRhIn5, and other heavy electron materials. PMID:28559308

  19. Effect of quantum fluctuation in error-correcting codes. (United States)

    Otsubo, Yosuke; Inoue, Jun-ichi; Nagata, Kenji; Okada, Masato


    We discuss the decoding performance of error-correcting codes based on a model in which quantum fluctuations are introduced by means of a transverse field. The essential issue in this paper is whether quantum fluctuations improve the decoding quality compared with the conventional estimation based on thermal fluctuations, which is called finite-temperature decoding. We found that an estimation incorporating quantum fluctuations approaches the optimal performance of finite-temperature decoding. The results are illustrated by numerically solving saddle-point equations and performing a Monte Carlo simulation. We also evaluated the upper bound of the overlap between the original sequence and the decoded sequence derived from the equations of state for the order parameters, which is a measure of the decoding performance.

  20. Application of infrared thermography for online monitoring of wall temperatures in inductively coupled plasma torches with conventional and low-flow gas consumption (United States)

    Engelhard, Carsten; Scheffer, Andy; Maue, Thomas; Hieftje, Gary M.; Buscher, Wolfgang


    Inductively coupled plasma (ICP) sources typically used for trace elemental determination and speciation were investigated with infrared (IR) thermography to obtain spatially resolved torch temperature distributions. Infrared thermographic imaging is an excellent tool for the monitoring of temperatures in a fast and non-destructive way. This paper presents the first application of IR thermography to inductively coupled plasma torches and the possibility to investigate temperatures and thermal patterns while the ICP is operating and despite background emission from the plasma itself. A fast and easy method is presented for the determination of temperature distributions and stress features within ICP torches. Two different ICP operating torches were studied: a commercially available Fassel-type ICP unit with 14 L min - 1 total Ar consumption and a SHIP torch with the unusually low Ar flow of 0.6 L min - 1 . Spatially resolved infrared images of both torches were obtained and laterally resolved temperature profiles were extracted. After temperature-resolved calibration of the emissivity (between 0.5 and 0.35 at 873-1323 K) and transmission (20% between 3.75 and 4.02 μm) of the fused quartz used in the torch construction, an image correction was applied. Inhomogeneous temperature distributions with locally defined stress areas in the conventional Fassel-type torch were revealed. As a general trend, it was found that the SHIP torch exhibited higher temperatures ( Tmax = 1580 K) than the conventional torch ( Tmax = 730 K). In the former case, torch sites with efficient and inefficient cooling were discovered and the external flow of cooling air (24-48 m s - 1 ) was identified as the limiting factor.

  1. Lake level fluctuations boost toxic cyanobacterial "oligotrophic blooms". (United States)

    Callieri, Cristiana; Bertoni, Roberto; Contesini, Mario; Bertoni, Filippo


    Global warming has been shown to strongly influence inland water systems, producing noticeable increases in water temperatures. Rising temperatures, especially when combined with widespread nutrient pollution, directly favour the growth of toxic cyanobacteria. Climate changes have also altered natural water level fluctuations increasing the probability of extreme events as dry periods followed by heavy rains. The massive appearance of Dolichospermum lemmermannii ( = planktonic Anabaena), a toxic species absent from the pelagic zone of the subalpine oligotrophic Lake Maggiore before 2005, could be a consequence of the unusual fluctuations of lake level in recent years. We hypothesized that these fluctuations may favour the cyanobacterium as result of nutrient pulses from the biofilms formed in the littoral zone when the lake level is high. To help verify this, we exposed artificial substrates in the lake, and evaluated their nutrient enrichment and release after desiccation, together with measurements of fluctuations in lake level, precipitation and D. lemmermannii population. The highest percentage of P release and the lowest C:P molar ratio of released nutrients coincided with the summer appearance of the D. lemmermannii bloom. The P pulse indicates that fluctuations in level counteract nutrient limitation in this lake and it is suggested that this may apply more widely to other oligotrophic lakes. In view of the predicted increase in water level fluctuations due to climate change, it is important to try to minimize such fluctuations in order to mitigate the occurrence of cyanobacterial blooms.

  2. Lake level fluctuations boost toxic cyanobacterial "oligotrophic blooms".

    Directory of Open Access Journals (Sweden)

    Cristiana Callieri

    Full Text Available Global warming has been shown to strongly influence inland water systems, producing noticeable increases in water temperatures. Rising temperatures, especially when combined with widespread nutrient pollution, directly favour the growth of toxic cyanobacteria. Climate changes have also altered natural water level fluctuations increasing the probability of extreme events as dry periods followed by heavy rains. The massive appearance of Dolichospermum lemmermannii ( = planktonic Anabaena, a toxic species absent from the pelagic zone of the subalpine oligotrophic Lake Maggiore before 2005, could be a consequence of the unusual fluctuations of lake level in recent years. We hypothesized that these fluctuations may favour the cyanobacterium as result of nutrient pulses from the biofilms formed in the littoral zone when the lake level is high. To help verify this, we exposed artificial substrates in the lake, and evaluated their nutrient enrichment and release after desiccation, together with measurements of fluctuations in lake level, precipitation and D. lemmermannii population. The highest percentage of P release and the lowest C:P molar ratio of released nutrients coincided with the summer appearance of the D. lemmermannii bloom. The P pulse indicates that fluctuations in level counteract nutrient limitation in this lake and it is suggested that this may apply more widely to other oligotrophic lakes. In view of the predicted increase in water level fluctuations due to climate change, it is important to try to minimize such fluctuations in order to mitigate the occurrence of cyanobacterial blooms.

  3. A Comparison of Simple Methods to Incorporate Material Temperature Dependency in the Green's Function Method for Estimating Transient Thermal Stresses in Thick-Walled Power Plant Components. (United States)

    Rouse, James; Hyde, Christopher


    The threat of thermal fatigue is an increasing concern for thermal power plant operators due to the increasing tendency to adopt "two-shifting" operating procedures. Thermal plants are likely to remain part of the energy portfolio for the foreseeable future and are under societal pressures to generate in a highly flexible and efficient manner. The Green's function method offers a flexible approach to determine reference elastic solutions for transient thermal stress problems. In order to simplify integration, it is often assumed that Green's functions (derived from finite element unit temperature step solutions) are temperature independent (this is not the case due to the temperature dependency of material parameters). The present work offers a simple method to approximate a material's temperature dependency using multiple reference unit solutions and an interpolation procedure. Thermal stress histories are predicted and compared for realistic temperature cycles using distinct techniques. The proposed interpolation method generally performs as well as (if not better) than the optimum single Green's function or the previously-suggested weighting function technique (particularly for large temperature increments). Coefficients of determination are typically above 0 . 96 , and peak stress differences between true and predicted datasets are always less than 10 MPa.

  4. The Role of Plant Cell Wall Proteins in Response to Salt Stress

    Directory of Open Access Journals (Sweden)

    Lyuben Zagorchev


    Full Text Available Contemporary agriculture is facing new challenges with the increasing population and demand for food on Earth and the decrease in crop productivity due to abiotic stresses such as water deficit, high salinity, and extreme fluctuations of temperatures. The knowledge of plant stress responses, though widely extended in recent years, is still unable to provide efficient strategies for improvement of agriculture. The focus of study has been shifted to the plant cell wall as a dynamic and crucial component of the plant cell that could immediately respond to changes in the environment. The investigation of plant cell wall proteins, especially in commercially important monocot crops revealed the high involvement of this compartment in plants stress responses, but there is still much more to be comprehended. The aim of this review is to summarize the available data on this issue and to point out the future areas of interest that should be studied in detail.

  5. Fluctuating attention in Parkinson's disease

    DEFF Research Database (Denmark)

    Starrfelt, Randi; Aarsland, Dag; Janvin, Carmen


    Lewy body dementia (DLB), which share many clinical and pathological features with Parkinson’s disease (PD), is charac- terised by marked fluctuations in cognition and consciousness. Fluctuating cognition has not been formally studied in PD, although some studies indicate that PD patients show...

  6. Fluctuating Selection in the Moran. (United States)

    Dean, Antony M; Lehman, Clarence; Yi, Xiao


    Contrary to classical population genetics theory, experiments demonstrate that fluctuating selection can protect a haploid polymorphism in the absence of frequency dependent effects on fitness. Using forward simulations with the Moran model, we confirm our analytical results showing that a fluctuating selection regime, with a mean selection coefficient of zero, promotes polymorphism. We find that increases in heterozygosity over neutral expectations are especially pronounced when fluctuations are rapid, mutation is weak, the population size is large, and the variance in selection is big. Lowering the frequency of fluctuations makes selection more directional, and so heterozygosity declines. We also show that fluctuating selection raises dn /ds ratios for polymorphism, not only by sweeping selected alleles into the population, but also by purging the neutral variants of selected alleles as they undergo repeated bottlenecks. Our analysis shows that randomly fluctuating selection increases the rate of evolution by increasing the probability of fixation. The impact is especially noticeable when the selection is strong and mutation is weak. Simulations show the increase in the rate of evolution declines as the rate of new mutations entering the population increases, an effect attributable to clonal interference. Intriguingly, fluctuating selection increases the dn /ds ratios for divergence more than for polymorphism, a pattern commonly seen in comparative genomics. Our model, which extends the classical neutral model of molecular evolution by incorporating random fluctuations in selection, accommodates a wide variety of observations, both neutral and selected, with economy. Copyright © 2017 by the Genetics Society of America.

  7. Quantum Correction of Fluctuation Theorem


    Monnai, T.; Tasaki, S.


    Quantum analogues of the transient fluctuation theorem(TFT) and steady-state fluctuation theorem(SSFT) are investigated for a harmonic oscillator linearly coupled with a harmonic reservoir. The probability distribution for the work done externally is derived and quantum correction for TFT and SSFT are calculated.

  8. Fluctuation conductivity in cuprate superconductors

    Indian Academy of Sciences (India)

    superconducting layers in each unit cell is also not adequate. We suggest the fluctuation conductivity to be reduced due to the reduction in the density of states (DOS) of the quasiparticles which results due to the formation of Cooper pairs at the onset of the fluctuations. The data agrees with the theory proposed by Dorin et al ...

  9. Pressure Fluctuations in Nonideal Plasma

    NARCIS (Netherlands)

    Lankin, A.; Norman, G.; Saitov, I.

    Fluctuations of pressure of singly ionized nonideal plasma are studied using the fluctuation approach which provides the self-consistent joint description of free and weakly bound electron states. The classical molecular dynamics method is used. The electron-ion interaction is described by the

  10. Current regulation of universal conductance fluctuations in bilayer graphene

    Energy Technology Data Exchange (ETDEWEB)

    Liao Zhimin; Han Binghong; Zhou Yangbo; Zhao Qing; Yu Dapeng [State Key Laboratory for Mesoscopic Physics, Department of Physics, Peking University, Beijing 100871 (China); Zhang Hongzhou, E-mail:, E-mail: [School of Physics and Centre for Research on Adaptive Nanostructures and Nanodevices (CRANN), Trinity College, Dublin 2 (Ireland)


    We report experimental results on the universal conductance fluctuations (UCFs) in the bilayer graphene system. The UCF properties under different temperatures, magnetic fields and current bias were investigated. An anomalous current-dependent UCF was observed: the rms amplitude of the conductance fluctuations is inversely proportional to the current bias. The detailed physical mechanisms were discussed by involving the confined scattering of chiral fermions in graphene.

  11. Fluctuation theorem in quantum heat conduction. (United States)

    Saito, Keiji; Dhar, Abhishek


    We consider steady-state heat conduction across a quantum harmonic chain connected to reservoirs modeled by infinite collection of oscillators. The heat, Q, flowing across the oscillator in a time interval tau is a stochastic variable and we study the probability distribution function P(Q). We compute the exact generating function of Q at large tau and the large deviation function. The generating function has a symmetry satisfying the steady-state fluctuation theorem without any quantum corrections. The distribution P(Q) is non-Gaussian with clear exponential tails. The effect of finite tau and nonlinearity is considered in the classical limit through Langevin simulations. We also obtain the prediction of quantum heat current fluctuations at low temperatures in clean wires.

  12. Nonmotor Fluctuations in Parkinson's Disease. (United States)

    Franke, Christiana; Storch, Alexander


    The advanced stage of Parkinson's disease (PD) is characterized by motor complications such as motor fluctuations and dyskinesias induced by long-term levodopa treatment. Recent clinical research provides growing evidence that various nonmotor symptoms such as neuropsychiatric, autonomic, and sensory symptoms (particularly pain) also show fluctuations in patients with motor fluctuations (called nonmotor fluctuations or NMF). However, NMF have not yet been adequately considered in routine care of advanced PD patients and only few therapeutic studies are available. Since the pathophysiology of NMF remains largely unknown, innovative therapeutic concepts are largely missing. The close connection of NMF and motor fluctuations, however, strongly suggests that the strategies used to treat motor complications-namely continuous dopaminergic stimulation-also apply for the therapy of NMF. Future controlled clinical trials specifically addressing NMF are urgently warranted. © 2017 Elsevier Inc. All rights reserved.

  13. Staggered Schemes for Fluctuating Hydrodynamics

    CERN Document Server

    Balboa, F; Delgado-Buscalioni, R; Donev, A; Fai, T; Griffith, B; Peskin, C S


    We develop numerical schemes for solving the isothermal compressible and incompressible equations of fluctuating hydrodynamics on a grid with staggered momenta. We develop a second-order accurate spatial discretization of the diffusive, advective and stochastic fluxes that satisfies a discrete fluctuation-dissipation balance, and construct temporal discretizations that are at least second-order accurate in time deterministically and in a weak sense. Specifically, the methods reproduce the correct equilibrium covariances of the fluctuating fields to third (compressible) and second (incompressible) order in the time step, as we verify numerically. We apply our techniques to model recent experimental measurements of giant fluctuations in diffusively mixing fluids in a micro-gravity environment [A. Vailati et. al., Nature Communications 2:290, 2011]. Numerical results for the static spectrum of non-equilibrium concentration fluctuations are in excellent agreement between the compressible and incompressible simula...

  14. Fluctuations in catalytic surface reactions

    CERN Document Server

    Imbihl, R


    The internal reaction-induced fluctuations which occur in catalytic CO oxidation on a Pt field emitter tip have been studied using field electron microscopy (FEM) as a spatially resolving method. The structurally heterogeneous Pt tip consists of facets of different orientations with nanoscale dimensions. The FEM resolution of roughly 2 nm corresponds to a few hundred reacting adsorbed particles whose variations in the density are imaged as brightness fluctuations. In the bistable range of the reaction one finds fluctuation-induced transitions between the two stable branches of the reaction kinetics. The fluctuations exhibit a behaviour similar to that of an equilibrium phase transition, i.e. the amplitude diverges upon approaching the bifurcation point terminating the bistable range of the reaction. Simulations with a hybrid Monte Carlo/mean-field model reproduce the experimental observations. Fluctuations on different facets are typically uncorrelated but within a single facet a high degree of spatial cohere...

  15. Critical thermal limits affected differently by developmental and adult thermal fluctuations

    DEFF Research Database (Denmark)

    Salachan, Paul Vinu; Sørensen, Jesper Givskov


    Means and variances of the environmental thermal regime play an important role in determining the fitness of terrestrial ectotherms. Adaptive phenotypic responses induced by heterogeneous temperatures have been shown to be mediated by molecular pathways independent of the classic heat shock...... responses, however, an in-depth understanding of plasticity induced by fluctuating temperatures is still lacking. We investigated high and low temperature acclimation induced by fluctuating thermal regimes at two different mean temperatures, at two different amplitudes of fluctuation and across...... fluctuating and constant regimes, cold tolerance was shown to be dictated by developmental temperature conditions irrespective of the adult treatments, while the acquired heat tolerance was readily lost when flies developed at fluctuating temperature were shifted to a constant regime as adults. Interestingly...

  16. Characteristics of Humidity-Temperature Changing in the Below-Grade Concrete Structure by Applying Waterproofing Materials on the Exterior Wall

    Directory of Open Access Journals (Sweden)

    Sang-Mook Chang


    Full Text Available The water leakage in an underground space cannot easily be repaired owing to the characteristics of the underground space, which not only causes continuous inconvenience to the apartment residents but also facilitates condensation. Thus, the effects of different waterproofing methods in underground spaces on changes in temperature and humidity should be quantitatively studied to establish strong measures for the condensation issue. In this study, two types of specimens were produced separately by dividing the waterproofing materials applied to underground structures into exterior and interior waterproofing construction methods; thereafter, changes in the temperature and humidity inside the specimens were observed. The test results of the evaluation regarding condensation in underground structures indicated that when exterior waterproofing materials are applied, thermal insulation maintains a steady interior temperature and keeps the humidity at an appropriate level, thereby preventing the creation of an environment conducive to the occurrence of condensation.

  17. Fluctuations in Hertz chains at equilibrium. (United States)

    Przedborski, Michelle; Sen, Surajit; Harroun, Thad A


    We examine the long-term behavior of nonintegrable, energy-conserved, one-dimensional systems of macroscopic grains interacting via a contact-only generalized Hertz potential and held between stationary walls. Such systems can be set up to have no phononic background excitation and represent examples of a sonic vacuum. Existing dynamical studies showed the absence of energy equipartitioning in such systems, hence their long-term dynamics was described as quasiequilibrium. Here we show that these systems do in fact reach thermal equilibrium at sufficiently long times, as indicated by the calculated heat capacity. As a by-product, we show how fluctuations of system quantities, and thus the distribution functions, are influenced by the Hertz potential. In particular, the variance of the system's kinetic energy probability density function is reduced by a factor related to the contact potential.

  18. Fluctuation theorem in driven nonthermal systems with quenched disorder

    Energy Technology Data Exchange (ETDEWEB)

    Reichhardt, Charles [Los Alamos National Laboratory; Reichhardt, C J [Los Alamos National Laboratory; Drocco, J A [PRINCETON UNIV.


    We demonstrate that the fluctuation theorem of Evans and Searles can be used to characterize the class of dynamics that arises in nonthermal systems of collectively interacting particles driven over random quenched disorder. By observing the frequency of entropy-destroying trajectories, we show that there are specific dynamical regimes near depinning in which this theorem holds. Hence the fluctuation theorem can be used to characterize a significantly wider class of non-equilibrium systems than previously considered. We discuss how the fluctuation theorem could be tested in specific systems where noisy dynamics appear at the transition from a pinned to a moving phase such as in vortices in type-II superconductors, magnetic domain walls, and dislocation dynamics.


    Directory of Open Access Journals (Sweden)

    Jan Fořt


    Full Text Available The current outdated state of many institutional and administrative buildings in the EU region poses a significant burden from the energy sustainability point of view. According to the contemporary EU requirements on the energy efficiency of buildings maintenance, an evaluation of performed improvements is essential for the assessment of expended investments. This paper describes the effect of building envelope reconstruction works consisting in the installation of a thermal insulation system. Here, a long-term continuous monitoring is used for the extensive assessment of the seasonal and daily temperature and relative humidity fluctuations. The obtained results include temperature and relative humidity profiles in the wall cross-section as a response to the changing exterior climatic conditions. The analysis of measured data reveals substantial improvements in thermal stability of the analyzed wall during temperature peaks. While the indoor temperatures exceeding 28 °C are recorded during summer before application of the thermal insulation layer, the thermal stability of the indoor environment is distinctly upgraded after performed improvements. Based on the complex long-term monitoring, a relevant experience is gained for the future work on energy sustainability and fulfilment of the EU directives.

  20. Falling walls

    CERN Multimedia

    It was 20 years ago this week that the Berlin wall was opened for the first time since its construction began in 1961. Although the signs of a thaw had been in the air for some time, few predicted the speed of the change that would ensue. As members of the scientific community, we can take a moment to reflect on the role our field played in bringing East and West together. CERN’s collaboration with the East, primarily through links with the Joint Institute for Nuclear Research, JINR, in Dubna, Russia, is well documented. Less well known, however, is the role CERN played in bringing the scientists of East and West Germany together. As the Iron curtain was going up, particle physicists on both sides were already creating the conditions that would allow it to be torn down. Cold war historian Thomas Stange tells the story in his 2002 CERN Courier article. It was my privilege to be in Berlin on Monday, the anniversary of the wall’s opening, to take part in a conference entitled &lsquo...

  1. Estimation of Several Turbulent Fluctuation Quantities Using an Approximate Pulsatile Flow Model

    Energy Technology Data Exchange (ETDEWEB)

    Dechant, Lawrence J. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)


    Turbulent fluctuation behavior is approximately modeled using a pulsatile flow model analogy.. This model follows as an extension to the turbulent laminar sublayer model developed by Sternberg (1962) to be valid for a fully turbulent flow domain. Here unsteady turbulent behavior is modeled via a sinusoidal pulsatile approach. While the individual modes of the turbulent flow fluctuation behavior are rather crudely modeled, approximate temporal integration yields plausible estimates for Root Mean Square (RMS) velocity fluctuations. RMS pressure fluctuations and spectra are of particular interest and are estimated via the pressure Poisson expression. Both RMS and Power Spectral Density (PSD), i.e. spectra are developed. Comparison with available measurements suggests reasonable agreement. An additional fluctuating quantity, i.e. RMS wall shear fluctuation is also estimated, yielding reasonable agreement with measurement.

  2. Turbulent channel flows over complex walls (United States)

    Rosti, Marco Edoardo; Brandt, Luca


    We perform numerical simulations of turbulent channel flows over porous walls and deformable hyper-elastic walls. The flow over porous walls is simulated using volume-averaged Navier ``Stokes equations within the porous layers, while the multiphase flow over deformable walls is solved with a one-continuum formulation which allows the use of a fully Eulerian formulation. New insights on the effect of these complex walls on the turbulent flows in terms of friction, statistics and flow structures are discussed using a number of post-processing techniques. The turbulent flow in the channel is affected by the porous and moving walls in a similar manner even at low values of porosity and elasticity due to the non-zero fluctuations of vertical velocity at the interface that influence the flow dynamics. The near-wall streaks and the associated quasi-streamwise vortices are strongly reduced near porous and deformable isotropic wall while the flow becomes more correlated in the spanwise direction. On the contrary, an opposite behavior is noticed in the case of anisotropic porous layers, with an increase of streamwise correlation due to a strengthening of the low- and high-speed streaks.

  3. SOL width and intermittent fluctuations in KSTAR

    CERN Document Server

    Garcia, O E; Theodorsen, A; Bak, J -G; Hong, S -H; Kim, H -S; Pitts, R A


    Radial profiles of the ion saturation current and its fluctuation statistics are presented from probe measurements in L-mode, neutral beam heated plasmas at the outboard mid-plane region of KSTAR. The familiar two-layer structure, seen elsewhere in tokamak L-mode discharges, with a steep near-SOL profile and a broad far-SOL profile, is observed. The profile scale length in the far-SOL increases drastically with line-averaged density, thereby enhancing plasma interactions with the main chamber walls. Time series from the far-SOL region are characterised by large-amplitude bursts attributed to the radial motion of blob-like plasma filaments. Analysis of a data time series of several seconds duration under stationary plasma conditions reveals the statistical properties of these fluctuations, including the rate of level crossings and the average duration of periods spent above a given threshold level. This is shown to be in excellent agreement with predictions of a stochastic model, giving novel predictions of pl...

  4. Numerical analysis of ion temperature effects to the plasma wall transition using a one-dimensional two-fluid model. II. Asymptotic two-scale limit (United States)

    Gyergyek, T.; Kovačič, J.


    A one-dimensional, steady state, two fluid model, presented in Part I [T. Gyergyek and J. Kovačič, Phys. Plasmas 24, 063505 (2017)] is extended to the asymptotic two-scale limit. Separate solutions in the pre-sheath and in the sheath region are presented. Ion temperature is treated as an independent parameter, which is included in the model as a boundary condition. For the pre-sheath solutions, it is shown that when the ion temperature is increased, the ion flow velocity at the boundary of the system must also be increased. A simple relationship between ion temperature and ion flow velocity at the boundary is found. This relationship is the same as the corresponding relationship found in Part I. If ion temperature is increased, both the potential drop and the density drop in the pre-sheath decrease. The same is true for the pre-sheath length. As for the solutions in the sheath scale, it is shown that the ion velocity, electron velocity, and electric field at the sheath edge must all be above a certain minimum value in order to obtain physically acceptable monotonic solutions. It is proposed to select the ion velocity at the sheath edge equal to the ion sound velocity. If, at the same time, the zero electron flow velocity at the sheath edge is selected, the electric field at the sheath edge must be larger than roughly 3 × 10-6, in order to obtain monotonic solutions of the model. The selection of the electron velocity at the sheath edge is elaborated extensively. It is concluded that increased ion temperature improves the shielding of the plasma from the electrode.

  5. Critical thermal limits affected differently by developmental and adult thermal fluctuations. (United States)

    Salachan, Paul Vinu; Sørensen, Jesper Givskov


    Means and variances of the environmental thermal regime play an important role in determining the fitness of terrestrial ectotherms. Adaptive phenotypic responses induced by heterogeneous temperatures have been shown to be mediated by molecular pathways independent of the classic heat shock responses; however, an in-depth understanding of plasticity induced by fluctuating temperatures is still lacking. We investigated high and low temperature acclimation induced by fluctuating thermal regimes at two different mean temperatures, at two different amplitudes of fluctuation and across the developmental and adult life stages of Drosophila melanogaster For developmental acclimation, we found mildly detrimental effects of high-amplitude fluctuations for critical thermal minima, while the critical thermal maxima showed a beneficial response to higher amplitude fluctuations. For adult acclimation involving shifts between fluctuating and constant regimes, cold tolerance was shown to be dictated by developmental temperature conditions irrespective of the adult treatments, while the acquired heat tolerance was readily lost when flies developed at fluctuating temperature were shifted to a constant regime as adults. Interestingly, we also found that the effect of fluctuations at any life stage was gradually lost with prolonged adult maintenance, suggesting a more prominent effect of fluctuations during developmental compared with adult acclimation in D.melanogaster. © 2017. Published by The Company of Biologists Ltd.

  6. Low-frequency fluctuations in plasma magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Cable, S.; Tajima, T.


    It is shown that even a non-magnetized plasma with temperature T sustains zero-frequency magnetic fluctuations in thermal equilibrium. Fluctuations in electric and magnetic fields, as well as in densities, are computed. Four cases are studied: a cold, gaseous, isotropic, non-magnetized plasma; a cold, gaseous plasma in a uniform magnetic field; a warm, gaseous plasma described by kinetic theory; and a degenerate electron plasma. For the simple gaseous plasma, the fluctuation strength of the magnetic field as a function of frequency and wavenumber is calculated with the aid of the fluctuation-dissipation theorem. This calculation is done for both collisional and collisionless plasmas. The magnetic field fluctuation spectrum of each plasma has a large zero-frequency peak. The peak is a Dirac {delta}-function in the collisionless plasma; it is broadened into a Lorentzian curve in the collisional plasma. The plasma causes a low frequency cutoff in the typical black-body radiation spectrum, and the energy under the discovered peak approximates the energy lost in this cutoff. When the imposed magnetic field is weak, the magnetic field were vector fluctuation spectra of the two lowest modes are independent of the strength of the imposed field. Further, these modes contain finite energy even when the imposed field is zero. It is the energy of these modes which forms the non-magnetized zero-frequency peak of the isotropic plasma. In deriving these results, a simple relationship between the dispersion relation and the fluctuation power spectrum of electromagnetic waves if found. The warm plasma is shown, by kinetic theory, to exhibit a zero-frequency peak in its magnetic field fluctuation spectrum as well. For the degenerate plasma, we find that electric field fluctuations and number density fluctuations vanish at zero frequency; however, the magnetic field power spectrum diverges at zero frequency.

  7. Skewness of elliptic flow fluctuations (United States)

    Giacalone, Giuliano; Yan, Li; Noronha-Hostler, Jacquelyn; Ollitrault, Jean-Yves


    Using event-by-event hydrodynamic calculations, we find that the fluctuations of the elliptic flow (v2) in the reaction plane have a negative skew. We compare the skewness of v2 fluctuations to that of initial eccentricity fluctuations. We show that skewness is the main effect lifting the degeneracy between higher-order cumulants, with negative skew corresponding to the hierarchy v2{4 } >v2{6 } observed in Pb+Pb collisions at the CERN Large Hadron Collider. We describe how the skewness can be measured experimentally and show that hydrodynamics naturally reproduces its magnitude and centrality dependence.

  8. Fluctuation theorem: A critical review (United States)

    Malek Mansour, M.; Baras, F.


    Fluctuation theorem for entropy production is revisited in the framework of stochastic processes. The applicability of the fluctuation theorem to physico-chemical systems and the resulting stochastic thermodynamics were analyzed. Some unexpected limitations are highlighted in the context of jump Markov processes. We have shown that these limitations handicap the ability of the resulting stochastic thermodynamics to correctly describe the state of non-equilibrium systems in terms of the thermodynamic properties of individual processes therein. Finally, we considered the case of diffusion processes and proved that the fluctuation theorem for entropy production becomes irrelevant at the stationary state in the case of one variable systems.

  9. Density fluctuations in traffic flow

    CERN Document Server

    Yukawa, S


    Density fluctuations in traffic current are studied by computer simulations using the deterministic coupled map lattice model on a closed single-lane circuit. By calculating a power spectral density of temporal density fluctuations at a local section, we find a power-law behavior, \\sim 1/f^{1.8}, on the frequency f, in non-congested flow phase. The distribution of the headway distance h also shows the power law like \\sim 1/h^{3.0} at the same time. The power law fluctuations are destroyed by the occurence of the traffic jam.

  10. Optical and Structural Properties of Multi-wall-carbon-nanotube-modified ZnO Synthesized at Varying Substrate Temperatures for Highly Efficient Light Sensing Devices

    Directory of Open Access Journals (Sweden)

    Valentine Saasa


    Full Text Available Structural, optical and light detection properties on carbon-nanotube-modified ZnO thin films grown at various temperatures from room to 1173 K are investigated. The optical band gap values calculated from reflectivity data show a hump at a critical temperature range of 873-1073 K. Similar trends in surface roughness as well as crystallite size of the films are observed. These changes have been attributed to structural change from wurzite hexagonal to cubic carbon modified ZnO as also validated by x-ray diffraction, RBS and PIXE of these layers. UV and visible light detection properties show similar trends. It is demonstrated that the present films can sense both UV and visible light to a maximum response efficiency of 66 % which is much higher than the last reported efficiency 10 %. This high response is given predominantly by cubic crystallite rather than the wurzite hexagonal composites.

  11. Characteristics of Humidity-Temperature Changing in the Below-Grade Concrete Structure by Applying Waterproofing Materials on the Exterior Wall


    Sang-Mook Chang; Sang-Keun Oh; Deok-Suk Seo; Sung-Min Choi


    The water leakage in an underground space cannot easily be repaired owing to the characteristics of the underground space, which not only causes continuous inconvenience to the apartment residents but also facilitates condensation. Thus, the effects of different waterproofing methods in underground spaces on changes in temperature and humidity should be quantitatively studied to establish strong measures for the condensation issue. In this study, two types of specimens were produced separatel...

  12. Development of a multi-point two-color pyrometer for tube and wall temperature and emissivity measurement at the CFFF (United States)

    Benton, R. D.; Jang, P. R.

    The Diagnostic Instrumentation and Analysis Laboratory (DIAL) has been actively engaged in developing and applying advanced optical diagnostic techniques and instrumentation systems to high temperature coal-fired gas streams for over a decade. DIAL's systems have been used primarily in support of the US Department of Energy's (DOE) magnetohydrodynamic (MHD) research program. One of the earliest diagnostic systems developed by DIAL was a two color pyrometer (TCP). The TCP is used to measure surface temperature and emissivity. This system has been used extensively to make measurements in support of the national MHD program. In this system, two commercial single-color pyrometers and a microprocessor system were used to form a TCP to make accurate measurements of surfaces of unknown emissivity and temperature. This paper describes an improvement in the DIAL TCP which provides for near simultaneous multipoint measurements, reduced dependence on electronic circuits, and a greatly improved data display system. Commercial two-color pyrometer systems are not suitable for our work because they do not provide for emissivity measurement. The emissivity measurement provides insight into changes in surface characteristics and is an important consideration in our work. A second and important reason for our development of this system is the need to make simultaneous measurements at widely separated points. Finally, the data measured by this system is stored on magnetic media and can be correlated with other measurements on the system, e.g. furnace, under study.

  13. Limited Quantum Helium Transportation through Nano-channels by Quantum Fluctuation. (United States)

    Ohba, Tomonori


    Helium at low temperatures has unique quantum properties such as superfluidity, which causes it to behave differently from a classical fluid. Despite our deep understanding of quantum mechanics, there are many open questions concerning the properties of quantum fluids in nanoscale systems. Herein, the quantum behavior of helium transportation through one-dimensional nanopores was evaluated by measuring the adsorption of quantum helium in the nanopores of single-walled carbon nanohorns and AlPO4-5 at 2-5 K. Quantum helium was transported unimpeded through nanopores larger than 0.7 nm in diameter, whereas quantum helium transportation was significantly restricted through 0.4-nm and 0.6-nm nanopores. Conversely, nitrogen molecules diffused through the 0.4-nm nanopores at 77 K. Therefore, quantum helium behaved as a fluid comprising atoms larger than 0.4-0.6 nm. This phenomenon was remarkable, considering that helium is the smallest existing element with a (classical) size of approximately 0.27 nm. This finding revealed the presence of significant quantum fluctuations. Quantum fluctuation determined the behaviors of quantum flux and is essential to understanding unique quantum behaviors in nanoscale systems.

  14. Temperature effects on the electrical properties of multiphase polymer composites (United States)

    De Vivo, Biagio; Guadagno, Liberata; Lamberti, Patrizia; Raimondo, Marialuigia; Spinelli, Giovanni; Tucci, Vincenzo; Vertuccio, Luigi; Vittoria, Vittoria


    A study concerning the temperature dependence of some electrical properties of multiphase nanocomposite systems based on epoxy matrix, loaded with a 1% of multi-walled carbon nanotube (MWCNT) and different amounts of Hydrotalcite clay (HT), is presented. An extensive electrical characterization in DC was carried out highlighting that, consistently with the fluctuation-induced tunneling model, the electrical resistivity of the composites are characterized by a negative temperature coefficient (NTC) since it decreases monotonically with increasing temperature in the range 30-110°C. Furthermore, current-voltage (I-V) and temperature-voltage (T-V) characteristics with a perfect linear behavior are detected. The influence of different clay content on the electrical performance of the composites is also investigated. The interesting results open a new routes for such composites due their possible applications in the field of temperature sensor.

  15. Purification of 1.9-nm-diameter semiconducting single-wall carbon nanotubes by temperature-controlled gel-column chromatography and its application to thin-film transistor devices (United States)

    Thendie, Boanerges; Omachi, Haruka; Hirotani, Jun; Ohno, Yutaka; Miyata, Yasumitsu; Shinohara, Hisanori


    Large-diameter semiconductor single-wall carbon nanotubes (s-SWCNTs) have superior mobility and conductivity to small-diameter s-SWCNTs. However, the purification of s-SWCNTs with diameters larger than 1.6 nm by gel filtration has been difficult owing to the low selectivity of the conventional purification method in these large-diameter regions. We report a combination of temperature-controlled gel filtration and the gradient elution technique that we developed to enrich a high-purity s-SWCNT with a diameter as large as 1.9 nm. The thin-film transistor (TFT) device using the 1.9-nm-diameter SWCNT shows an average channel mobility of 23.7 cm2 V-1 s-1, which is much higher than those of conventional SWCNT-TFTs with smaller-diameters of 1.5 and 1.4 nm.

  16. Fluctuations and Instability in Sedimentation

    KAUST Repository

    Guazzelli, Élisabeth


    This review concentrates on the fluctuations of the velocities of sedimenting spheres, and on the structural instability of a suspension of settling fibers. For many years, theoretical estimates and numerical simulations predicted the fluctuations of the velocities of spheres to increase with the size of the container, whereas experiments found no such variation. Two ideas have increased our understanding. First, the correlation length of the velocity fluctuations was found experimentally to be 20 interparticle separations. Second, in dilute suspensions, a vertical variation in the concentration due to the spreading of the front with the clear fluid can inhibit the velocity fluctuations. In a very dilute regime, a homogeneous suspension of fibers suffers a spontaneous instability in which fast descending fiber-rich columns are separated by rising fiber-sparse columns. In a semidilute regime, the settling is hindered, more so than for spheres. © 2011 by Annual Reviews. All rights reserved.

  17. Molecular evolution under fitness fluctuations. (United States)

    Mustonen, Ville; Lässig, Michael


    Molecular evolution is a stochastic process governed by fitness, mutations, and reproductive fluctuations in a population. Here, we study evolution where fitness itself is stochastic, with random switches in the direction of selection at individual genomic loci. As the correlation time of these fluctuations becomes larger than the diffusion time of mutations within the population, fitness changes from an annealed to a quenched random variable. We show that the rate of evolution has its maximum in the crossover regime, where both time scales are comparable. Adaptive evolution emerges in the quenched fitness regime (evidence for such fitness fluctuations has recently been found in genomic data). The joint statistical theory of reproductive and fitness fluctuations establishes a conceptual connection between evolutionary genetics and statistical physics of disordered systems.

  18. Gaussian fluctuations in chaotic eigenstates

    CERN Document Server

    Srednicki, M A; Srednicki, Mark; Stiernelof, Frank


    We study the fluctuations that are predicted in the autocorrelation function of an energy eigenstate of a chaotic, two-dimensional billiard by the conjecture (due to Berry) that the eigenfunction is a gaussian random variable. We find an explicit formula for the root-mean-square amplitude of the expected fluctuations in the autocorrelation function. These fluctuations turn out to be O(\\hbar^{1/2}) in the small \\hbar (high energy) limit. For comparison, any corrections due to scars from isolated periodic orbits would also be O(\\hbar^{1/2}). The fluctuations take on a particularly simple form if the autocorrelation function is averaged over the direction of the separation vector. We compare our various predictions with recent numerical computations of Li and Robnik for the Robnik billiard, and find good agreement. We indicate how our results generalize to higher dimensions.

  19. Thermodynamic magnon recoil for domain wall motion

    NARCIS (Netherlands)

    Yan, P.; Cao, Y.; Sinova, J.


    We predict a thermodynamic magnon recoil effect for domain wall motions in the presence of temperature gradients. All current thermodynamic theories assert that a magnetic domain wall must move toward the hotter side, based on equilibrium thermodynamic arguments. Microscopic calculations, on the

  20. Phase transitions in polypeptides: analysis of energy fluctuations

    DEFF Research Database (Denmark)

    Yakubovich, Alexander V.; Solov'yov, Ilia; Solov'yov, Andrey V.


    The helix random coil transition in alanine, valine, and leucine polypeptides consisting of 30 amino acids is studied in vacuo using the Langevin molecular dynamics approach. The influence of side chain radicals on internal energy and heat capacity of the polypeptides is discussed. The heat...... capacity of these polypeptides is calculated as a function of temperature using two different methods, namely, as the derivative of the energy with respect to temperature, and on the basis of energy fluctuations in the system. The convergence of the fluctuations based approach is analyzed as a function...... of simulation time. This study provides a comparison of methods for the description of structural transitions in polypeptides....

  1. Climatically driven fluctuations in Southern Ocean ecosystems. (United States)

    Murphy, Eugene J; Trathan, Philip N; Watkins, Jon L; Reid, Keith; Meredith, Michael P; Forcada, Jaume; Thorpe, Sally E; Johnston, Nadine M; Rothery, Peter


    Determining how climate fluctuations affect ocean ecosystems requires an understanding of how biological and physical processes interact across a wide range of scales. Here we examine the role of physical and biological processes in generating fluctuations in the ecosystem around South Georgia in the South Atlantic sector of the Southern Ocean. Anomalies in sea surface temperature (SST) in the South Pacific sector of the Southern Ocean have previously been shown to be generated through atmospheric teleconnections with El Niño Southern Oscillation (ENSO)-related processes. These SST anomalies are propagated via the Antarctic Circumpolar Current into the South Atlantic (on time scales of more than 1 year), where ENSO and Southern Annular Mode-related atmospheric processes have a direct influence on short (less than six months) time scales. We find that across the South Atlantic sector, these changes in SST, and related fluctuations in winter sea ice extent, affect the recruitment and dispersal of Antarctic krill. This oceanographically driven variation in krill population dynamics and abundance in turn affects the breeding success of seabird and marine mammal predators that depend on krill as food. Such propagating anomalies, mediated through physical and trophic interactions, are likely to be an important component of variation in ocean ecosystems and affect responses to longer term change. Population models derived on the basis of these oceanic fluctuations indicate that plausible rates of regional warming of 1oC over the next 100 years could lead to more than a 95% reduction in the biomass and abundance of krill across the Scotia Sea by the end of the century.

  2. Communication: Nanoscale ion fluctuations in Nafion polymer electrolyte

    Energy Technology Data Exchange (ETDEWEB)

    Rumberger, Brant; Bennett, Mackenzie; Zhang, Jingyun; Israeloff, N. E. [Department of Physics, Northeastern University, Boston, Massachusetts 02115 (United States); Dura, J. A. [National Institute of Standards and Technology, Center for Neutron Research, Gaithersburg, Maryland 20899 (United States)


    Ion conduction mechanisms and the nanostructure of ion conduction networks remain poorly understood in polymer electrolytes which are used as proton-exchange-membranes (PEM) in fuel cell applications. Here we study nanoscale surface-potential fluctuations produced by Brownian ion dynamics in thin films of low-hydration Nafion™, the prototype PEM. Images and power spectra of the fluctuations are used to derive the local conductivity-relaxation spectrum, in order to compare with bulk behavior and hopping-conductivity models. Conductivity relaxation-times ranged from hours to milliseconds, depending on hydration and temperature, demonstrating that the observed fluctuations are produced by water-facilitated hydrogen-ion hopping within the ion-channel network. Due to the small number of ions probed, non-Gaussian statistics of the fluctuations can be used to constrain ion conduction parameters and mechanisms.

  3. Communication: nanoscale ion fluctuations in Nafion polymer electrolyte. (United States)

    Rumberger, Brant; Bennett, Mackenzie; Zhang, Jingyun; Dura, J A; Israeloff, N E


    Ion conduction mechanisms and the nanostructure of ion conduction networks remain poorly understood in polymer electrolytes which are used as proton-exchange-membranes (PEM) in fuel cell applications. Here we study nanoscale surface-potential fluctuations produced by Brownian ion dynamics in thin films of low-hydration Nafion™, the prototype PEM. Images and power spectra of the fluctuations are used to derive the local conductivity-relaxation spectrum, in order to compare with bulk behavior and hopping-conductivity models. Conductivity relaxation-times ranged from hours to milliseconds, depending on hydration and temperature, demonstrating that the observed fluctuations are produced by water-facilitated hydrogen-ion hopping within the ion-channel network. Due to the small number of ions probed, non-Gaussian statistics of the fluctuations can be used to constrain ion conduction parameters and mechanisms.

  4. Quantum phase fluctuations and density of states in superconducting nanowires (United States)

    Radkevich, Alexey; Semenov, Andrew G.; Zaikin, Andrei D.


    We argue that quantum fluctuations of the phase of the order parameter may strongly affect the electron density of states (DOS) in ultrathin superconducting wires. We demonstrate that the effect of such fluctuations is equivalent to that of a quantum dissipative environment formed by soundlike plasma modes propagating along the wire. We derive a nonperturbative expression for the local electron DOS in superconducting nanowires which fully accounts for quantum phase fluctuations. At any nonzero temperature these fluctuations smear out the square-root singularity in DOS near the superconducting gap and generate quasiparticle states at subgap energies. Furthermore, at sufficiently large values of the wire impedance this singularity is suppressed down to T =0 in which case DOS tends to zero at subgap energies and exhibits the power-law behavior above the gap. Our predictions can be directly tested in tunneling experiments with superconducting nanowires.

  5. The influence of near-wall density and viscosity gradients on turbulence in channel flows

    CERN Document Server

    Patel, Ashish; Pecnik, Rene


    The influence of near-wall density and viscosity gradients on near-wall turbulence in a channel are studied by means of Direct Numerical Simulation (DNS) of the low-Mach number approximation of the Navier--Stokes equations. Different constitutive relations for density and viscosity as a function of temperature are used in order to mimic a wide range of fluid behaviours and to develop a generalised framework for studying turbulence modulations in variable property flows. Instead of scaling the velocity solely based on local density, as done for the van Driest transformation, we derive an extension of the scaling that is based on gradients of the semi-local Reynolds number $Re_\\tau^*$. This extension of the van Driest transformation is able to collapse velocity profiles for flows with near-wall property gradients as a function of the semi-local wall coordinate. However, flow quantities like mixing length, turbulence anisotropy and turbulent vorticity fluctuations do not show a universal scaling very close to th...

  6. Temperature dependence of strain energy and thermodynamic properties of V2 O5 -based single-walled nanotubes: Zone-folding approach. (United States)

    Porsev, Vitaly V; Bandura, Andrei V; Evarestov, Robert A


    A zone-folding approach is applied to estimate the thermodynamic properties of V2 O5 -based nanotubes. The results obtained are compared with those from the direct calculations. It is shown that the zone-folding approximation allows an accurate estimation of nanotube thermodynamic properties and gives a gain in computation time compared to their direct calculations. Both approaches show that temperature effects do not change the relative stability of V2 O5 free layers and nanotubes derived from the α- and γ-phase. The internal energy thermal contributions into the strain energy of nanotubes are small and can be ignored. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

  7. Hydrodynamic fluctuations, long-time tails, and supersymmetry (United States)

    Kovtun, Pavel; Yaffe, Laurence G.


    Hydrodynamic fluctuations at a nonzero temperature can cause slow relaxation toward equilibrium even in observables which are not locally conserved. A classic example is the stress-stress correlator in a normal fluid, which, at zero wave number, behaves at large times as t-3/2. A novel feature of the effective theory of hydrodynamic fluctuations in supersymmetric theories is the presence of Grassmann-valued classical fields describing macroscopic supercharge density fluctuations. We show that hydrodynamic fluctuations in supersymmetric theories generate essentially the same long-time power-law tails in real-time correlation functions that are known in simple fluids. In particular, a t-3/2 long-time tail must exist in the stress-stress correlator of N=4 supersymmetric Yang-Mills theory at non-zero temperature, regardless of the value of the coupling. Consequently, this feature of finite-temperature dynamics can provide an interesting test of the AdS/CFT correspondence. However, the coefficient of this long-time tail is suppressed by a factor of 1/N2c. On the gravitational side, this implies that these long-time tails are not present in the classical supergravity limit; they must instead be produced by one-loop gravitational fluctuations.

  8. Direct numerical simulation of expiratory crackles: Relationship between airway closure dynamics and acoustic fluctuations. (United States)

    Ii, Satoshi; Wada, Shigeo


    This paper investigates the relationship between airway closure dynamics and acoustic fluctuations in expiratory crackles using direct numerical simulation. A unified mathematical model is proposed to deal with flow in an airway, elastic deformation of the airway wall, surface tension driven motion of the liquid film that lines the airway, and their acoustic fluctuations because of material compressibility. Airway closure is induced by increasing the surrounding pressure, then the source of the pressure fluctuations is measured over time. Our results show that the airway closure occurs suddenly because of a bridge formation of the liquid film, and high energy transfer occurs between the kinetic energy, the surface energy of the liquid interface, and the elastic energy of the airway wall, invoking a large acoustic fluctuation that causes the expiratory crackles. Nonlinear behavior is observed in terms of the airway wall stiffness; the dynamic motion of the airway closure becomes moderate and both the energy transfer and acoustic fluctuations are dramatically reduced with an increase in airway wall stiffness. Copyright © 2016 Elsevier Ltd. All rights reserved.

  9. Thermal Bridge Effects in Walls Separating Rowhouses

    DEFF Research Database (Denmark)

    Rose, Jørgen


    In this report the thermal bridge effects at internal wall/roof junctions in rowhouses are evaluated. The analysis is performed using a numerical calculation programme, and different solutions are evaluated with respect to extra heat loss and internal surface temperatures.......In this report the thermal bridge effects at internal wall/roof junctions in rowhouses are evaluated. The analysis is performed using a numerical calculation programme, and different solutions are evaluated with respect to extra heat loss and internal surface temperatures....

  10. Quantum fluctuations of voltage in superconducting nanowires (United States)

    Semenov, Andrew G.; Zaikin, Andrei D.


    At low temperatures non-equilibrium voltage fluctuations can be generated in current-biased superconducting nanowires due to proliferation of quantum phase slips (QPS) or, equivalently, due to quantum tunneling of magnetic flux quanta across the wire. In this paper we review and further extend recent theoretical results related to this phenomenon. Employing the phase-charge duality arguments combined with Keldysh path integral technique we analyze such fluctuations within the two-point and four-point measurement schemes demonstrating that voltage noise detected in such nanowires in general depends on the particular measurement setup. In the low frequency limit we evaluate all cumulants of the voltage operator which turn out to obey Poisson statistics and exhibit a power law dependence on the external bias. We also specifically address a non-trivial frequency dependence of quantum shot noise power spectrum SΩ for both longer and shorter superconducting nanowires. In particular, we demonstrate that SΩ decreases with increasing frequency Ω and vanishes beyond a threshold value of Ω at T → 0. Furthermore, we predict that SΩ may depend non-monotonously on temperature due to quantum coherent nature of QPS noise. The results of our theoretical analysis can be directly tested in future experiments with superconducting nanowires.

  11. Numerical Study of Laminar Forced Convection of Water/Al2o3 Nanofluid in an Annulus with Constant Wall Temperature

    Directory of Open Access Journals (Sweden)

    Amin Kashani


    Full Text Available Laminar forced convection of a nanofluid consisting of water and Al2O3 in a horizontal annulus has been studied numerically. Two-phase mixture model has been used to investigate thermal behaviors of the nanofluid over constant temperature thermal boundary condition and with different volume concentration of nanoparticles. Comparisons with previously published experimental and analytical works on flow behavior in horizontal annulus show good agreements between the results as volume fraction is zero. In general convective heat transfer coefficient increases with nanoparticle concentration. ABSTRAK: Kertaskerja ini mengkaji secara numerik olakan paksa bendalir lamina yang menganduangi air dan Al2O3 didalam anulus mendatar. Model campuran dua fasa digunakan bagi mengkaji tingkah laku haba bendalir nano pada keadaan suhu malar dengan kepekatan nanopartikel berbeza. Perbandingan dengan karya eksperimen dan analitikal yang telah diterbitkan menunjukkan bahawa kelakuan aliran didalm anulus mendatar adalah baik apabila pecahan isipadu adalah sifar. Pada amnya, pekali pemindahan haba olakan meningkat dengan kepekatan nanopartikel. KEYWORDS: nanofluid; volume concentration; heat transfer enhancement; laminar flow convection; annulus

  12. Noisy zigzag transition, fluctuations, and thermal bifurcation threshold (United States)

    Delfau, Jean-Baptiste; Coste, Christophe; Saint Jean, Michel


    We study the zigzag transition in a system of particles with screened electrostatic interaction, submitted to a thermal noise. At finite temperature, this configurational phase transition is an example of noisy supercritical pitchfork bifurcation. The measurements of transverse fluctuations allow a complete description of the bifurcation region, which takes place between the deterministic threshold and a thermal threshold beyond which thermal fluctuations do not allow the system to flip between the symmetric zigzag configurations. We show that a divergence of the saturation time for the transverse fluctuations allows a precise and unambiguous definition of this thermal threshold. Its evolution with the temperature is shown to be in good agreement with theoretical predictions from noisy bifurcation theory.

  13. Hygrothermal behavior for a clay brick wall (United States)

    Allam, R.; Issaadi, N.; Belarbi, R.; El-Meligy, M.; Altahrany, A.


    In Egypt, the clay brick is the common building materials which are used. By studying clay brick walls behavior for the heat and moisture transfer, the efficient use of the clay brick can be reached. So, this research studies the hygrothermal transfer in this material by measuring the hygrothermal properties and performing experimental tests for a constructed clay brick wall. We present the model for the hygrothermal transfer in the clay brick which takes the temperature and the vapor pressure as driving potentials. In addition, this research compares the presented model with previous models. By constructing the clay brick wall between two climates chambers with different boundary conditions, we can validate the numerical model and analyze the hygrothermal transfer in the wall. The temperature and relative humidity profiles within the material are measured experimentally and determined numerically. The numerical and experimental results have a good convergence with 3.5% difference. The surface boundary conditions, the ground effect, the infiltration from the closed chambers and the material heterogeneity affects the results. Thermal transfer of the clay brick walls reaches the steady state very rapidly than the moisture transfer. That means the effect of using only the external brick wall in the building in hot climate without increase the thermal resistance for the wall, will add more energy losses in the clay brick walls buildings. Also, the behavior of the wall at the heat and mass transfer calls the three-dimensional analysis for the whole building to reach the real behavior.

  14. Thermodynamic constraints on fluctuation phenomena (United States)

    Maroney, O. J. E.


    The relationships among reversible Carnot cycles, the absence of perpetual motion machines, and the existence of a nondecreasing globally unique entropy function form the starting point of many textbook presentations of the foundations of thermodynamics. However, the thermal fluctuation phenomena associated with statistical mechanics has been argued to restrict the domain of validity of this basis of the second law of thermodynamics. Here we demonstrate that fluctuation phenomena can be incorporated into the traditional presentation, extending rather than restricting the domain of validity of the phenomenologically motivated second law. Consistency conditions lead to constraints upon the possible spectrum of thermal fluctuations. In a special case this uniquely selects the Gibbs canonical distribution and more generally incorporates the Tsallis distributions. No particular model of microscopic dynamics need be assumed.

  15. Fluctuation theorems for quantum processes. (United States)

    Albash, Tameem; Lidar, Daniel A; Marvian, Milad; Zanardi, Paolo


    We present fluctuation theorems and moment generating function equalities for generalized thermodynamic observables and quantum dynamics described by completely positive trace preserving maps, with and without feedback control. Our results include the quantum Jarzynski equality and Crooks fluctuation theorem, and clarify the special role played by the thermodynamic work and thermal equilibrium states in previous studies. We show that for a specific class of generalized measurements, which include projective measurements, unitality replaces microreversibility as the condition for the physicality of the reverse process in our fluctuation theorems. We present an experimental application of our theory to the problem of extracting the system-bath coupling magnitude, which we do for a system of pairs of coupled superconducting flux qubits undergoing quantum annealing.

  16. Fluctuation theorems for stochastic dynamics (United States)

    Harris, R. J.; Schütz, G. M.


    Fluctuation theorems make use of time reversal to make predictions about entropy production in many-body systems far from thermal equilibrium. Here we review the wide variety of distinct, but interconnected, relations that have been derived and investigated theoretically and experimentally. Significantly, we demonstrate, in the context of Markovian stochastic dynamics, how these different fluctuation theorems arise from a simple fundamental time-reversal symmetry of a certain class of observables. Appealing to the notion of Gibbs entropy allows for a microscopic definition of entropy production in terms of these observables. We work with the master equation approach, which leads to a mathematically straightforward proof and provides direct insight into the probabilistic meaning of the quantities involved. Finally, we point to some experiments that elucidate the practical significance of fluctuation relations.

  17. Fluctuation theorems for quantum processes (United States)

    Albash, Tameem; Lidar, Daniel A.; Marvian, Milad; Zanardi, Paolo


    We present fluctuation theorems and moment generating function equalities for generalized thermodynamic observables and quantum dynamics described by completely positive trace preserving maps, with and without feedback control. Our results include the quantum Jarzynski equality and Crooks fluctuation theorem, and clarify the special role played by the thermodynamic work and thermal equilibrium states in previous studies. We show that for a specific class of generalized measurements, which include projective measurements, unitality replaces microreversibility as the condition for the physicality of the reverse process in our fluctuation theorems. We present an experimental application of our theory to the problem of extracting the system-bath coupling magnitude, which we do for a system of pairs of coupled superconducting flux qubits undergoing quantum annealing.

  18. Modeling fluctuations in scattered waves

    CERN Document Server

    Jakeman, E


    Fluctuations in scattered waves limit the performance of imaging and remote sensing systems that operate on all wavelengths of the electromagnetic spectrum. To better understand these fluctuations, Modeling Fluctuations in Scattered Waves provides a practical guide to the phenomenology, mathematics, and simulation of non-Gaussian noise models and discusses how they can be used to characterize the statistics of scattered waves.Through their discussion of mathematical models, the authors demonstrate the development of new sensing techniques as well as offer intelligent choices that can be made for system analysis. Using experimental results and numerical simulation, the book illustrates the properties and applications of these models. The first two chapters introduce statistical tools and the properties of Gaussian noise, including results on phase statistics. The following chapters describe Gaussian processes and the random walk model, address multiple scattering effects and propagation through an extended med...

  19. Fluctuations in the site-disordered traveling salesman problem

    Energy Technology Data Exchange (ETDEWEB)

    Dean, David S [Laboratoire de Physique Theorique, UMR CNRS 5152, IRSAMC, Universite Paul Sabatier, 118 route de Narbonne, 31062 Toulouse Cedex 04 (France); Lancaster, David [Harrow School of Computer Science, University of Westminster, Harrow HA1 3TP (United Kingdom)


    We extend a previous statistical mechanical treatment of the traveling salesman problem by defining a discrete 'site-disordered' problem in which fluctuations about saddle points can be computed. The results clarify the basis of our original treatment, and illuminate but do not resolve the difficulties of taking the zero-temperature limit to obtain minimal path lengths.

  20. ECE imaging of plasma T-e profiles and fluctuations

    NARCIS (Netherlands)

    Deng, B.H.; Burns, S. R.; Domier, C.W.; Hillyer, T. R.; Hsia, R. P.; N C Luhmann Jr.,; Brower, D.L.; Cima, G.; Donne, A. J. H.; Oyevaar, T.; R. T. P. Team,


    A novel electron cyclotron emission (ECE) radiometry technique, Electron Cyclotron Emission Imaging (ECEI), has been developed and applied to the TEXT-U and RTP tokamaks for the study of electron temperature profiles and fluctuations. Instead of a single receiver located in the tokamak midplane as

  1. Mean square number fluctuation for a fermion source and its ...

    Indian Academy of Sciences (India)

    Mean square number fluctuation for a fermion source and its dependence on neutrino mass for the universal cosmic neutrino background ... Using the general formulation for obtaining chemical potential of an ideal Fermi gas of particles at temperature , with particle rest mass m 0 and average density ⟨ N ⟩ / V , the ...

  2. Quantum fluctuation effects on nuclear fragment and atomic cluster formation

    Energy Technology Data Exchange (ETDEWEB)

    Ohnishi, Akira [Hokkaido Univ., Sapporo (Japan). Dept. of Physics; Randrup, J.


    We investigate the nuclear fragmentation and atomic cluster formation by means of the recently proposed quantal Langevin treatment. It is shown that the effect of the quantal fluctuation is in the opposite direction in nuclear fragment and atomic cluster size distribution. This tendency is understood through the effective classical temperature for the observables. (author)

  3. Chromodynamic Fluctuations in Quark-Gluon Plasma


    Mrowczynski, Stanislaw


    Fluctuations of chromodynamic fields in the collisionless quark-gluon plasma are found as a solution of the initial value linearized problem. The plasma initial state is on average colorless, stationary and homogeneous. When the state is stable, the initial fluctuations decay exponentially and in the long-time limit a stationary spectrum of fluctuations is established. For the equilibrium plasma it reproduces the spectrum which is provided by the fluctuation-dissipation relation. Fluctuations...

  4. Glacier fluctuations during the past 2000 years (United States)

    Solomina, Olga N.; Bradley, Raymond S.; Jomelli, Vincent; Geirsdottir, Aslaug; Kaufman, Darrell S.; Koch, Johannes; McKay, Nicholas P.; Masiokas, Mariano; Miller, Gifford; Nesje, Atle; Nicolussi, Kurt; Owen, Lewis A.; Putnam, Aaron E.; Wanner, Heinz; Wiles, Gregory; Yang, Bao


    A global compilation of glacier advances and retreats for the past two millennia grouped by 17 regions (excluding Antarctica) highlights the nature of glacier fluctuations during the late Holocene. The dataset includes 275 time series of glacier fluctuations based on historical, tree ring, lake sediment, radiocarbon and terrestrial cosmogenic nuclide data. The most detailed and reliable series for individual glaciers and regional compilations are compared with summer temperature and, when available, winter precipitation reconstructions, the most important parameters for glacier mass balance. In many cases major glacier advances correlate with multi-decadal periods of decreased summer temperature. In a few cases, such as in Arctic Alaska and western Canada, some glacier advances occurred during relatively warm wet times. The timing and scale of glacier fluctuations over the past two millennia varies greatly from region to region. However, the number of glacier advances shows a clear pattern for the high, mid and low latitudes and, hence, points to common forcing factors acting at the global scale. Globally, during the first millennium CE glaciers were smaller than between the advances in 13th to early 20th centuries CE. The precise extent of glacier retreat in the first millennium is not well defined; however, the most conservative estimates indicate that during the 1st and 2nd centuries in some regions glaciers were smaller than at the end of 20th/early 21st centuries. Other periods of glacier retreat are identified regionally during the 5th and 8th centuries in the European Alps, in the 3rd-6th and 9th centuries in Norway, during the 10th-13th centuries in southern Alaska, and in the 18th century in Spitsbergen. However, no single period of common global glacier retreat of centennial duration, except for the past century, has yet been identified. In contrast, the view that the Little Ice Age was a period of global glacier expansion beginning in the 13th century

  5. Fluctuations and associated transport in L mode in tore supra

    Energy Technology Data Exchange (ETDEWEB)

    Devynck, P.; Clairet, F.; Zou, X.L.; Garbet, X.; Colas, L.; Moreau, P.; Laviron, C.; Hoang, G.T. [Association Euratom-CEA, Centre d`Etudes de Cadarache, 13 - Saint-Paul-lez-Durance (France). Dept. de Recherches sur la Fusion Controlee]|[Ecole Polytechnique, 91 - Palaiseau (France). Lab. de Physique des Milieux Ionises


    A parametric experimental study of fluctuations has been performed in L mode plasmas during steady-state phases in Tore Supra. Simultaneous measurements of density and magnetic fluctuations in the gradient region of the discharge show that both components are strong functions of the local electron temperature decreasing lengths. The wave number spectrum of density fluctuations is obtained with the CO2 scattering diagnostic both in the bulk and at the edge of the discharge. In the bulk, in L mode compared to ohmic plasmas, the k spectrum increases below k = 7 cm{sup -1} and is globally shifted towards low k values. At the edge (r/a>0.9) an increase on all k values is observed. At r/a=0.5, the level of both types of fluctuations is found to be linearly correlated with the local heat diffusivity {chi}{sub e}. The heat flux ratio advected by electrostatic eddies in the bulk of the discharge, is estimated by using fluctuation measurements and generic predictions for the parametric dependency of the thermal flux. The calculated level of density fluctuation necessary to account for the heat transport at mid radius is found to be compatible with values measured in other tokamaks. It is also found that the heat flux ratio behaviour conducted by electrostatic fluctuations is compatible with most of the experimental heat flux ratio behaviour in the plasma core (0.4fluctuation level does not allow to state clearly about their relative importance in the transport process and suggests that they could be coupled. (author) 25 refs.

  6. Generalized fluctuation relation for power-law distributions (United States)

    Budini, Adrián A.


    Strong violations of existing fluctuation theorems may arise in nonequilibrium steady states characterized by distributions with power-law tails. The ratio of the probabilities of positive and negative fluctuations of equal magnitude behaves in an anomalous nonmonotonic way [H. Touchette and E. G. D. Cohen, Phys. Rev. EPLEEE81539-375510.1103/PhysRevE.76.020101 76, 020101(R) (2007)]. Here, we propose an alternative definition of fluctuation relation (FR) symmetry that, in the power-law regime, is characterized by a monotonic linear behavior. The proposal is consistent with a large deviationlike principle. As an example, we study the fluctuations of the work done on a dragged particle immersed in a complex environment able to induce power-law tails. When the environment is characterized by spatiotemporal temperature fluctuations, distributions arising in nonextensive statistical mechanics define the work statistics. In that situation, we find that the FR symmetry is solely defined by the average bath temperature. The case of a dragged particle subjected to a Lévy noise is also analyzed in detail.

  7. Steady heat conduction-based thermal conductivity measurement of single walled carbon nanotubes thin film using a micropipette thermal sensor. (United States)

    Shrestha, R; Lee, K M; Chang, W S; Kim, D S; Rhee, G H; Choi, T Y


    In this paper, we describe the thermal conductivity measurement of single-walled carbon nanotubes thin film using a laser point source-based steady state heat conduction method. A high precision micropipette thermal sensor fabricated with a sensing tip size varying from 2 μm to 5 μm and capable of measuring thermal fluctuation with resolution of ±0.01 K was used to measure the temperature gradient across the suspended carbon nanotubes (CNT) film with a thickness of 100 nm. We used a steady heat conduction model to correlate the temperature gradient to the thermal conductivity of the film. We measured the average thermal conductivity of CNT film as 74.3 ± 7.9 W m(-1) K(-1) at room temperature.

  8. Linear modeling of glacier fluctuations

    NARCIS (Netherlands)

    Oerlemans, J.|info:eu-repo/dai/nl/06833656X


    In this contribution a linear first-order differential equation is used to model glacier length fluctuations. This equation has two parameters describing the physical characteristics of a glacier: the climate sensitivity, expressing how the equilibrium glacier length depends on the climatic state,

  9. Fluctuating hydrodynamics for ionic liquids

    Energy Technology Data Exchange (ETDEWEB)

    Lazaridis, Konstantinos [Department of Mathematics and Statistics, Washington State University, Pullman, 99163 (United States); Wickham, Logan [Department of Computer Science, Washington State University, Richland, 99354 (United States); Voulgarakis, Nikolaos, E-mail: [Department of Mathematics and Statistics, Washington State University, Pullman, 99163 (United States)


    We present a mean-field fluctuating hydrodynamics (FHD) method for studying the structural and transport properties of ionic liquids in bulk and near electrified surfaces. The free energy of the system consists of two competing terms: (1) a Landau–Lifshitz functional that models the spontaneous separation of the ionic groups, and (2) the standard mean-field electrostatic interaction between the ions in the liquid. The numerical approach used to solve the resulting FHD-Poisson equations is very efficient and models thermal fluctuations with remarkable accuracy. Such density fluctuations are sufficiently strong to excite the experimentally observed spontaneous formation of liquid nano-domains. Statistical analysis of our simulations provides quantitative information about the properties of ionic liquids, such as the mixing quality, stability, and the size of the nano-domains. Our model, thus, can be adequately parameterized by directly comparing our prediction with experimental measurements and all-atom simulations. Conclusively, this work can serve as a practical mathematical tool for testing various theories and designing more efficient mixtures of ionic liquids. - Highlights: • A new fluctuating hydrodynamics method for ionic liquids. • Description of ionic liquid morphology in bulk and near electrified surfaces. • Direct comparison with experimental measurements.

  10. Reaction rates when barriers fluctuate


    Reimann, Peter


    Reaction rates when barriers fluctuate : a path integral approach / P. Hänggi and P. Reimann. - In: International Conference on Path Integrals from peV to TeV : Proceedings of the ... / eds.: R. Casalbuoni ... - Singapore u.a. : World Scientific, 1999. - S. 407-409

  11. Duality in spin fluctuation in correlated electron systems

    Energy Technology Data Exchange (ETDEWEB)

    Yanagisawa, Takashi, E-mail:; Hase, Izumi


    Highlights: • We propose improved wave functions, based on the well-known Gutzwiller wave function, for the two-dimensional Hubbard model. • Our wave function gives the best variational energy compared to several wave functions previously proposed for the Hubbard model. It is now a best wave function for the Hubbard model. • We found that the antiferromagnetic state becomes instable due to charge fluctuation of carriers when the on-site repulsive interaction U is greater than the bandwidth. • The superconducting-condensation energy becomes large due to large spin fluctuation indicating a possibility of high-temperature superconductivity. - Abstract: An origin of high-temperature superconductivity for cuprate superconductors is investigated on the basis of the two-dimensional Hubbard model. The Coulomb interaction is a candidate that can bring about high-temperature superconductivity because its characteristic energy is of the order of eV. It is not trivial whether the on-site Coulomb interaction U leads to a pairing interaction between two electrons. We argue that the antiferromagnetic fluctuation and the kinetic charge fluctuation are responsible for high-temperature superconductivity. The kinetic charge fluctuation is induced by large U to get the kinetic energy gain in the strongly correlated region. We consider electron correlation beyond the Gutzwiller ansatz, by taking account of inter-site correlation such as doublon–holon correlation and kinetic correlation. We show that high-temperature superconductivity is possible in the strongly correlated region, where U is greater than the bandwidth, by using the variational Monte Carlo method.

  12. Influence of the wall on the droplet evaporation

    Directory of Open Access Journals (Sweden)

    Misyura S. Y.


    Full Text Available Evaporative influence of the wall material and its thickness has been investigated in the present study. The wall influence for heat exchangers is particularly important in the boiling transition regime and in the event of the Leidenfrost temperature. The experimental points significantly diverge in the transition area of the boiling crisis. This fact can be explained by a different residence time of droplet on the wall surface. The discrepancy between the experimental data also takes place at the Leidenfrost temperature. The lower the thermal diffusivity of the wall material (high thermal inertia, the more the wall is cooled under a droplet.

  13. Solid substrate-room temperature phosphorimetry for the determination of trace lead using p-nitro-phenyl-fluorone-multi-wall carbon nanotubes-Tween-80 micellae compound and diagnosis about human diseases (United States)

    Tianlong, Yang; Zhenbo, Liu; Jiaming, Liu; Haizhu, Liu; Yahong, Huang; Jianqin, Liu; Xuebing, Chen; Yibing, Zhao


    The structures of multi-wall carbon nanotubes (MWNTs) were modified by H 2SO 4-HNO 3 and H 2SO 4-H 2O 2, respectively. The corresponding products were water-soluble MWNTs-A and MWNTs-B. According to the experiment, it was found that MWNTs-B could emit stable solid substrate-room temperature phosphorescence (RTP) on the surface of paper with Ag + as perturber. Under the conditions of 70 °C and 15 min, MWNTs-B can react with Tween-80 and p-nitro-phenyl-fluorone (R) to form R-MWNTs-B-Tween-80 micellae compound, which could emit RTP of R and MWNTs-B on the surface of paper, respectively. Pb 2+ could cause the RTP of R and MWNTs-B enhanced sharply, respectively. Δ Ip is directly proportional to the content of Pb 2+. A new solid substrate-room temperature phosphorimetry (SS-RTP) for the determination of trace Pb 2+ has been established based on R-MWNTs-B-Tween-80 micellae compound containing double luminescent molecule. The detection limit of this method were 0.035 ag Pb 2+ spot -1 (8.8 × 10 -17 g Pb 2+ ml -1, MWNTs-B) and 0.028 ag Pb 2+ spot -1 (7.1 × 10 -17 g Pb 2+ ml -1, R). This method is of high sensitivity, good selectivity, high precision and accuracy. It could be applied to determine trace Pb 2+ in serum samples at wavelength of 453.7/623.0 nm (R) or 475.9/645.0 nm (MWNTs-B) with satisfactory results, showing that SS-RTP has flexibility and utility value. Simultaneously, this method can be used to diagnose human diseases. The reaction mechanism for the determination of trace Pb 2+ by SS-RTP based on R-MWNTs-B-Tween-80 micellae compound containing double luminescent molecule was also discussed.

  14. High-temperature calcined fullerene nanowhiskers as well as long needle-like multi-wall carbon nanotubes have abilities to induce NLRP3-mediated IL-1β secretion. (United States)

    Cui, Hongyan; Wu, Weijia; Okuhira, Keiichiro; Miyazawa, Kun'ichi; Hattori, Takayuki; Sai, Kimie; Naito, Mikihiko; Suzuki, Kazuhiro; Nishimura, Tetsuji; Sakamoto, Yoshimitsu; Ogata, Akio; Maeno, Tomokazu; Inomata, Akiko; Nakae, Dai; Hirose, Akihiko; Nishimaki-Mogami, Tomoko


    Because multi-wall carbon nanotubes (MWCNTs) have asbestos-like shape and size, concerns about their pathogenicity have been raised. Contaminated metals of MWCNTs may also be responsible for their toxicity. In this study, we employed high-temperature calcined fullerene nanowhiskers (HTCFNWs), which are needle-like nanofibers composed of amorphous carbon having similar sizes to MWCNTs but neither metal impurities nor tubular structures, and investigated their ability to induce production a major proinflammatory cytokine IL-1β via the Nod-like receptor pyrin domain containing 3 (NLRP3)-containing flammasome-mediated mechanism. When exposed to THP-1 macrophages, long-HTCFNW exhibited robust IL-1β production as long and needle-like MWCNTs did, but short-HTCFNW caused very small effect. IL-1β release induced by long-HTCFNW as well as by long, needle-like MWCNTs was abolished by a caspase-1 inhibitor or siRNA-knockdown of NLRP3, indicating that NLRP3-inflammasome-mediated IL-1β production by these carbon nanofibers. Our findings indicate that the needle-like shape and length, but neither metal impurities nor tubular structures of MWCNTs were critical to robust NLRP3 activation. Copyright © 2014 Elsevier Inc. All rights reserved.

  15. Forced convection of liquid hydrogen - part 2 - case of large temperature differences between the fluid and the wall - final report (cylindrical channel); Convection forcee de l'hydrogene liquide - 2. partie - cas de grands ecarts de temperatures entre fluide et paroi - rapport final (canal cylindrique)

    Energy Technology Data Exchange (ETDEWEB)

    Perroud, P.; Rebiere, J. [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires


    Measurements have been performed in a smooth Inconel tube of 2 mm ID and 2.5 mm OD, electrically heated on 300 mm by Joule effect (AC) The liquid enters the test section subcooled at the constant temperature of 25 deg. K of average; then it is heated till, most-often, complete vaporization. The conditions are: inlet pressure (subcritical) 8 atm (a number of experiences have been made under supercritical pressure of 16 atm), mass velocity 11 to 115 g/cm{sup 2}.s, heat flux density 9 to 385 W/cm{sup 2}, wall temperature reaching 800 deg. K. The liquid hydrogen used was composed of about 60 per cent of para-hydrogen (the transformation para-ortho does not happen in the process). A flow model, connected with the wall temperatures observed, is established. In the region of two-phase flow, the wall temperature highly decreases and passes through a minimum just when the steam quality reaches unity. A correlation for the heat transfer coefficients is given, in the two-phase flow region (steam quality from 0 to 1) and in the region of homogeneous gaseous phase (Reynolds varying from 15 000 to 420 000). Comparison with former correlations is also given. In the mixed-phase region, head losses due to friction are negligible with the respect to the pressure drop due to the variation of momentum. This latter can be calculated with good approximation using one-dimensional model. The head losses in gaseous phase follows the classical laws. Physical properties of liquid hydrogen extracted from the most recent literature, are given in supplement. (authors) [French] Les mesures ont ete effectuees a l'aide d'un tube cylindrique lisse en inconel de 2 x 2,5 mm de diametre, chauffe electriquement sur une longueur de 300 mm par effet Joule (courant alternatif). Le liquide entre sous-refroidi a la temperature de 25 deg. K en moyenne; il est ensuite chauffe jusqu'a vaporisation complete le plus souvent. Le domaine explore est le suivant: pression d'entree (subcritique) 8

  16. Superconducting fluctuations and pseudogap in high-Tc cuprates

    Directory of Open Access Journals (Sweden)

    Alloul H.


    Full Text Available Large pulsed magnetic fields up to 60 Tesla are used to suppress the contribution of superconducting fluctuations (SCF to the ab-plane conductivity above Tc in a series of YBa2Cu3O6+x. These experiments allow us to determine the field Hc’(T and the temperature Tc’ above which the SCFs are fully suppressed. A careful investigation near optimal doping shows that Tc’ is higher than the pseudogap temperature T*, which is an unambiguous evidence that the pseudogap cannot be assigned to preformed pairs. Accurate determinations of the SCF contribution to the conductivity versus temperature and magnetic field have been achieved. They can be accounted for by thermal fluctuations following the Ginzburg-Landau scheme for nearly optimally doped samples. A phase fluctuation contribution might be invoked for the most underdoped samples in a T range which increases when controlled disorder is introduced by electron irradiation. Quantitative analysis of the fluctuating magnetoconductance allows us to determine the critical field Hc2(0 which is found to be be quite similar to Hc’ (0 and to increase with hole doping. Studies of the incidence of disorder on both Tc’ and T* allow us to to propose a three dimensional phase diagram including a disorder axis, which allows to explain most observations done in other cuprate families.

  17. Charged Domain Walls


    Campanelli, L.; Cea, P.; Fogli, G. L.; Tedesco, L.


    In this paper we investigate Charged Domain Walls (CDW's), topological defects that acquire surface charge density $Q$ induced by fermion states localized on the walls. The presence of an electric and magnetic field on the walls is also discussed. We find a relation in which the value of the surface charge density $Q$ is connected with the existence of such topological defects.

  18. Parity fluctuations in stellar dynamos (United States)

    Moss, D. L.; Sokoloff, D. D.


    Observations of the solar butterfly diagram from sunspot records suggest persistent fluctuations in parity, away from the overall, approximately dipolar pattern. A simple mean-field dynamo model is used with a solar-like rotation law and perturbed α effect. The parity of the magnetic field relative to the rotational equator can demonstrate can be described as resonance behavior, while the magnetic energy behaves in a more or less expected way. Possible applications of this effect are discussed in the context of various deviations of the solar magnetic field from dipolar symmetry, as reported from analyses of archival sunspot data. The model produces fluctuations in field parity, and hence in the butterfly diagram, that are consistent with observed fluctuaions in solar behavior.

  19. Great Wall of China (United States)


    This ASTER sub-image covers a 12 x 12 km area in northern Shanxi Province, China, and was acquired January 9, 2001. The low sun angle, and light snow cover highlight a section of the Great Wall, visible as a black line running diagonally through the image from lower left to upper right. The Great Wall is over 2000 years old and was built over a period of 1000 years. Stretching 4500 miles from Korea to the Gobi Desert it was first built to protect China from marauders from the north.This image is located at 40.2 degrees north latitude and 112.8 degrees east longitude.Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is one of five Earth-observing instruments launched December 18, 1999, on NASA's Terra satellite. The instrument was built by Japan's Ministry of International Trade and Industry. A joint U.S./Japan science team is responsible for validation and calibration of the instrument and the data products. Dr. Anne Kahle at NASA's Jet Propulsion Laboratory, Pasadena, Calif., is the U.S. Science team leader; Moshe Pniel of JPL is the project manager. ASTER is the only high resolution imaging sensor on Terra. The primary goal of the ASTER mission is to obtain high-resolution image data in 14 channels over the entire land surface, as well as black and white stereo images. With revisit time of between 4 and 16 days, ASTER will provide the capability for repeat coverage of changing areas on Earth's surface.The broad spectral coverage and high spectral resolution of ASTER will provide scientists in numerous disciplines with critical information for surface mapping, and monitoring dynamic conditions and temporal change. Example applications are: monitoring glacial advances and retreats, monitoring potentially active volcanoes, identifying crop stress, determining cloud morphology and physical properties, wetlands Evaluation, thermal pollution monitoring, coral reef degradation, surface temperature mapping of soils and geology, and measuring surface

  20. Extended dynamic spin-fluctuation theory of metallic magnetism. (United States)

    Melnikov, N B; Reser, B I; Grebennikov, V I


    A dynamic spin-fluctuation theory that directly takes into account nonlocality of thermal spin fluctuations and their mode-mode interactions is developed. The Gaussian approximation in the theory is improved by a self-consistent renormalization of the mean field and spin susceptibility due to the third-and fourth-order terms of the free energy, respectively. This eliminates the fictitious first-order phase transition, which is typical for the Gaussian approximation, and yields a proper second-order phase transition. The effect of nonlocal spin correlations is enhanced by taking into account uniform fluctuations in the single-site mean Green function. Explicit computational formulae for basic magnetic characteristics are obtained. The extended theory is applied to the calculation of magnetic properties of Fe-Ni Invar. Almost full agreement with experiment is achieved for the magnetization, Curie temperature, and local and effective magnetic moments.

  1. Extended dynamic spin-fluctuation theory of metallic magnetism

    Energy Technology Data Exchange (ETDEWEB)

    Melnikov, N B [Moscow State University, Moscow 119991 (Russian Federation); Reser, B I; Grebennikov, V I, E-mail:, E-mail:, E-mail: [Institute of Metal Physics, Ural Branch of the Russian Academy of Sciences, Ekaterinburg 620990 (Russian Federation)


    A dynamic spin-fluctuation theory that directly takes into account nonlocality of thermal spin fluctuations and their mode-mode interactions is developed. The Gaussian approximation in the theory is improved by a self-consistent renormalization of the mean field and spin susceptibility due to the third- and fourth-order terms of the free energy, respectively. This eliminates the fictitious first-order phase transition, which is typical for the Gaussian approximation, and yields a proper second-order phase transition. The effect of nonlocal spin correlations is enhanced by taking into account uniform fluctuations in the single-site mean Green function. Explicit computational formulae for basic magnetic characteristics are obtained. The extended theory is applied to the calculation of magnetic properties of Fe-Ni Invar. Almost full agreement with experiment is achieved for the magnetization, Curie temperature, and local and effective magnetic moments.

  2. Charge-Induced Fluctuation Forces in Graphitic Nanostructures

    Directory of Open Access Journals (Sweden)

    D. Drosdoff


    Full Text Available Charge fluctuations in nanocircuits with capacitor components are shown to give rise to a novel type of long-ranged interaction, which coexist with the regular Casimir–van der Waals force. The developed theory distinguishes between thermal and quantum mechanical effects, and it is applied to capacitors involving graphene nanostructures. The charge fluctuations mechanism is captured via the capacitance of the system with geometrical and quantum mechanical components. The dependence on the distance separation, temperature, size, and response properties of the system shows that this type of force can have a comparable and even dominant effect to the Casimir interaction. Our results strongly indicate that fluctuation-induced interactions due to various thermodynamic quantities can have important thermal and quantum mechanical contributions at the microscale and the nanoscale.

  3. Net baryon fluctuations from a crossover equation of state

    Energy Technology Data Exchange (ETDEWEB)

    Kapusta, J.; Albright, M. [University of Minnesota, School of Physics and Astronomy, Minneapolis, MN (United States); Young, C. [Michigan State University, National Superconducting Cyclotron Laboratory, East Lansing, MI (United States)


    We have constructed an equation of state which smoothly interpolates between an excluded-volume hadron resonance gas at low energy density to a plasma of quarks and gluons at high energy density. This crossover equation of state agrees very well with lattice calculations at both zero and nonzero baryon chemical potential. We use it to compute the variance, skewness, and kurtosis of fluctuations of baryon number, and compare to measurements of proton number fluctuations in central Au-Au collisions as measured by the STAR Collaboration in a beam energy scan at the Relativistic Heavy-Ion Collider. The crossover equation of state can reproduce the data if the fluctuations are frozen out at temperatures well below than the average chemical freeze-out. (orig.)

  4. Magnetic disorder in superconductors: Enhancement by mesoscopic fluctuations (United States)

    Burmistrov, I. S.; Skvortsov, M. A.


    We study the density of states (DOS) and the transition temperature Tc in a dirty superconducting film with rare classical magnetic impurities of an arbitrary strength described by the Poissonian statistics. We take into account that the potential disorder is a source of mesoscopic fluctuations of the local DOS, and, consequently, of the effective strength of magnetic impurities. We find that these mesoscopic fluctuations result in a nonzero DOS for all energies in the region of the phase diagram where without this effect the DOS is zero within the standard mean-field theory. This mechanism can be more efficient in filling the mean-field superconducting gap than rare fluctuations of the potential disorder (instantons). Depending on the magnetic impurity strength, the suppression of Tc by spin-flip scattering can be faster or slower than in the standard mean-field theory.

  5. Green Walls Utilizing Internet of Things

    Directory of Open Access Journals (Sweden)

    Andrejs BONDAREVS


    Full Text Available A wireless sensor network was used to automatically control the life-support equipment of a green wall and to measure its influence on the air quality. Temperature, relative humidity, particulate matter, volatile organic compound and carbon dioxide were monitored during different tests. Green wall performance on improving the air quality and the influence of the air flow through the green wall on its performance were studied. The experimental results show that the green wall is effective to absorb particulate matter and volatile organic compound. The air flow through the green wall significantly increases the performance. The built-in fan increases the absorption rate of particulate matter by 8 times and that of formaldehyde by 3 times.

  6. Magnetic Alfvén-Cyclotron Fluctuations of Anisotropic Non-Thermal Plasmas (United States)

    Navarro, R.; Munoz, V.; Araneda, J. A.; Vinas, A. F.; Moya, P. S.; Valdivia, J. A.


    Remote and in situ observations in the solar wind show that ion and electron velocity distributions persistently present deviations from thermal equilibrium. Ion anisotropies seem to be constrained by instability thresholds which are in agreement with linear kinetic theory. For plasma states below these instability thresholds, the quasi-stable solar wind plasma sustains a small but detectable level of magnetic fluctuation power. These fluctuations may be related to spontaneous electromagnetic fluctuations arising from the discreteness of charged particles. Here, we study electromagnetic fluctuations propagating along a background magnetic field in a plasma composed of thermal and suprathermal protons and electrons via the fluctuation-dissipation theorem. The total fluctuating magnetic power is estimated in a proton temperature anisotropy-beta diagram for three different families of proton distribution functions, which can be compared to a number of recent measurements in the solar wind.

  7. Transitional Flow in an Arteriovenous Fistula: Effect of Wall Distensibility (United States)

    McGah, Patrick; Leotta, Daniel; Beach, Kirk; Aliseda, Alberto


    Arteriovenous fistulae are created surgically to provide adequate access for dialysis in patients with end-stage renal disease. Transitional flow and the subsequent pressure and shear stress fluctuations are thought to be causative in the fistula failure. Since 50% of fistulae require surgical intervention before year one, understanding the altered hemodynamic stresses is an important step toward improving clinical outcomes. We perform numerical simulations of a patient-specific model of a functioning fistula reconstructed from 3D ultrasound scans. Rigid wall simulations and fluid-structure interaction simulations using an in-house finite element solver for the wall deformations were performed and compared. In both the rigid and distensible wall cases, transitional flow is computed in fistula as evidenced by aperiodic high frequency velocity and pressure fluctuations. The spectrum of the fluctuations is much more narrow-banded in the distensible case, however, suggesting a partial stabilizing effect by the vessel elasticity. As a result, the distensible wall simulations predict shear stresses that are systematically 10-30% lower than the rigid cases. We propose a possible mechanism for stabilization involving the phase lag in the fluid work needed to deform the vessel wall. Support from an NIDDK R21 - DK08-1823.

  8. Relationship among phenotypic plasticity, phenotypic fluctuations ...

    Indian Academy of Sciences (India)


    These results provide quantitative formulation on canalization and genetic assimilation, in terms of fluctuations of gene expression levels. [Kaneko K 2009 Relationship among phenotypic plasticity, phenotypic fluctuations, robustness, and evolvability; Waddington's legacy revisited under the spirit of Einstein; J. Biosci.

  9. Some comments to the quantum fluctuation theorems


    Kuzovlev, Yu. E.


    It is demonstrated that today's quantum fluctuation theorems are component part of old quantum fluctuation-dissipation relations [Sov.Phys.-JETP 45, 125 (1977)], and typical misunderstandings in this area are pointed out.

  10. Correlated interaction fluctuations in photosynthetic complexes

    CERN Document Server

    Vlaming, Sebastiaan M


    The functioning and efficiency of natural photosynthetic complexes is strongly influenced by their embedding in a noisy protein environment, which can even serve to enhance the transport efficiency. Interactions with the environment induce fluctuations of the transition energies of and interactions between the chlorophyll molecules, and due to the fact that different fluctuations will partially be caused by the same environmental factors, correlations between the various fluctuations will occur. We argue that fluctuations of the interactions should in general not be neglected, as these have a considerable impact on population transfer rates, decoherence rates and the efficiency of photosynthetic complexes. Furthermore, while correlations between transition energy fluctuations have been studied, we provide the first quantitative study of the effect of correlations between interaction fluctuations and transition energy fluctuations, and of correlations between the various interaction fluctuations. It is shown t...

  11. Smoothed dissipative particle dynamics model for mesoscopic multiphase flows in the presence of thermal fluctuations

    Energy Technology Data Exchange (ETDEWEB)

    Lei, Huan; Baker, Nathan A.; Wu, Lei; Schenter, Gregory K.; Mundy, Christopher J.; Tartakovsky, Alexandre M.


    Thermal fluctuations cause perturbations of fluid-fluid interfaces and highly nonlinear hydrodynamics in multiphase flows. In this work, we develop a novel multiphase smoothed dissipative particle dynamics model. This model accounts for both bulk hydrodynamics and interfacial fluctuations. Interfacial surface tension is modeled by imposing a pairwise force between SDPD particles. We show that the relationship between the model parameters and surface tension, previously derived under the assumption of zero thermal fluctuation, is accurate for fluid systems at low temperature but overestimates the surface tension for intermediate and large thermal fluctuations. To analyze the effect of thermal fluctuations on surface tension, we construct a coarse-grained Euler lattice model based on the mean field theory and derive a semi-analytical formula to directly relate the surface tension to model parameters for a wide range of temperatures and model resolutions. We demonstrate that the present method correctly models the dynamic processes, such as bubble coalescence and capillary spectra across the interface.

  12. Modeling 100,000-year climate fluctuations in pre-Pleistocene time series (United States)

    Crowley, Thomas J.; Kim, Kwang-Yul; Mengel, John G.; Short, David A.


    A number of pre-Pleistocene climate records exhibit significant fluctuations at the 100,000-year (100-ky) eccentricity period, before the time of such fluctuations in global ice volume. The origin of these fluctuations has been obscure. Results reported here from a modeling study suggest that such a response can occur over low-altitude land areas involved in monsoon fluctuations. The twice yearly passage of the sun across the equator and the seasonal timing of perihelion interact to increase both 100-ky and 400-ky power in the modeled temperature field. The magnitude of the temperature response is sufficiently large to leave an imprint on the geologic record, and simulated fluctuations resemble those found in records of Triassic lake levels.

  13. Fluctuation theory of luminance and chromaticity discrimination

    NARCIS (Netherlands)

    Bouman, M.A.; Vos, J.J.; Walraven, P.L.


    An attempt has been made to describe brightness and color discrimination in the framework of a fluctuation theory. The fluctuation theory states that a difference between two stimuli will be just noticeable if it exceeds, by some factor, the average of the fluctuations in the stimuli. If the

  14. Abdominal wall fat pad biopsy (United States)

    Amyloidosis - abdominal wall fat pad biopsy; Abdominal wall biopsy; Biopsy - abdominal wall fat pad ... method of taking an abdominal wall fat pad biopsy . The health care provider cleans the skin on ...

  15. Heat Flux and Entropy Produced by Thermal Fluctuations

    DEFF Research Database (Denmark)

    Ciliberto, S.; Imparato, Alberto; Naert, A.


    We report an experimental and theoretical analysis of the energy exchanged between two conductors kept at different temperature and coupled by the electric thermal noise. Experimentally we determine, as functions of the temperature difference, the heat flux, the out-of-equilibrium variance......, and a conservation law for the fluctuating entropy, which we justify theoretically. The system is ruled by the same equations as two Brownian particles kept at different temperatures and coupled by an elastic force. Our results set strong constraints on the energy exchanged between coupled nanosystems held...

  16. Transcriptional responses to fluctuating thermal regimes underpinning differences in survival in the solitary bee Megachile rotundata. (United States)

    Torson, Alex S; Yocum, George D; Rinehart, Joseph P; Kemp, William P; Bowsher, Julia H


    The transcriptional responses of insects to long-term, ecologically relevant temperature stress are poorly understood. Long-term exposure to low temperatures, commonly referred to as chilling, can lead to physiological effects collectively known as chill injury. Periodically increasing temperatures during long-term chilling has been shown to increase survival in many insects. However, the transcripts responsible for this increase in survival have never been characterized. Here, we present the first transcriptome-level analysis of increased longevity under fluctuating temperatures during chilling. Overwintering post-diapause quiescent alfalfa leafcutting bees (Megachile rotundata) were exposed to a constant temperature of 6°C, or 6°C with a daily fluctuation to 20°C. RNA was collected at two different time points, before and after mortality rates began to diverge between temperature treatments. Expression analysis identified differentially regulated transcripts between pairwise comparisons of both treatments and time points. Transcripts functioning in ion homeostasis, metabolic pathways and oxidative stress response were up-regulated in individuals exposed to periodic temperature fluctuations during chilling. The differential expression of these transcripts provides support for the hypotheses that fluctuating temperatures protect against chill injury by reducing oxidative stress and returning ion concentrations and metabolic function to more favorable levels. Additionally, exposure to fluctuating temperatures leads to increased expression of transcripts functioning in the immune response and neurogenesis, providing evidence for additional mechanisms associated with increased survival during chilling in M. rotundata. © 2015. Published by The Company of Biologists Ltd.

  17. Wall Clutter Mitigation in Through-the-Wall Imaging Radar with Sparse Array Antenna Based on Independent Component Analysis

    Directory of Open Access Journals (Sweden)

    Zhang Chi


    Full Text Available For Through-the-Wall Imaging Radar (TWIR, wall clutter is critical for detecting target signals behind a wall. For a system with a sparse antenna array, the lack of observation channels makes it more difficult to separate the target signals and wall clutter. On the basis of fluctuation of the range profile in real transmit/receive channels, this paper proposes to use Independent Component Analysis (ICA on multiple down-range observations of each transmit/receive channel to remove the wall clutter. The simulation and experimental results show that the proposed method effectively separate target and clutter components, even though the signal-to-clutter ratio is only -30 dB.

  18. On the phase-correlation and phase-fluctuation dynamics of a strongly excited Bose gas

    Energy Technology Data Exchange (ETDEWEB)

    Sakhel, Roger R., E-mail: [Department of Basic Sciences, Faculty of Information Technology, Isra University, Amman 11622 (Jordan); The Abdus Salam International Center for Theoretical Physics, Strada Costiera 11, Trieste 34151 (Italy); Sakhel, Asaad R. [Department of Applied Sciences, Faculty of Engineering Technology, Balqa Applied University, Amman 11134 (Jordan); The Abdus Salam International Center for Theoretical Physics, Strada Costiera 11, Trieste 34151 (Italy); Ghassib, Humam B. [Department of Physics, The University of Jordan, Amman 11942 (Jordan)


    The dynamics of a Bose–Einstein condensate (BEC) is explored in the wake of a violent excitation caused by a strong time-dependent deformation of a trapping potential under the action of an intense stirring laser. The system is a two-dimensional BEC confined to a power-law trap with hard-wall boundaries. The stirring agent is a moving red-detuned laser potential. The time-dependent Gross–Pitaevskii equation is solved numerically by the split-step Crank–Nicolson method in real time. The phase correlations and phase fluctuations are examined as functions of time to demonstrate the evolving properties of a strongly-excited BEC. Of special significance is the occurrence of spatial fluctuations while the condensate is being excited. These oscillations arise from stirrer-induced density fluctuations. While the stirrer is inside the trap, a reduction in phase coherence occurs, which is attributed to phase fluctuations.

  19. Fluctuation Modes of a Twist-Bend Nematic Liquid Crystal

    Directory of Open Access Journals (Sweden)

    Z. Parsouzi


    Full Text Available We report a dynamic light-scattering study of the fluctuation modes in a thermotropic liquid crystalline mixture of monomer and dimer compounds that exhibits the twist-bend nematic (N_{TB} phase. The results reveal a spectrum of overdamped fluctuations that includes two nonhydrodynamic modes and one hydrodynamic mode in the N_{TB} phase, and a single nonhydrodynamic mode plus two hydrodynamic modes (the usual nematic optic axis or director fluctuations in the higher temperature, uniaxial nematic phase. The properties of these fluctuations and the conditions for their observation are comprehensively explained by a Landau-de Gennes expansion of the free-energy density in terms of heliconical director and helical polarization fields that characterize the N_{TB} structure, with the latter serving as the primary order parameter. A “coarse-graining” approximation simplifies the theoretical analysis and enables us to demonstrate quantitative agreement between the calculated and experimentally determined temperature dependence of the mode relaxation rates.

  20. DNS of turbulent wall bounded flows with a passive scalar (United States)

    Araya, Juan Guillermo

    In this thesis, Direct Numerical Simulations (DNS) of the velocity and temperature fields are performed for incompressible turbulent flows in plane channels and spatially-developing boundary layers. The main goal is to numerically analyze the behavior of the momentum and thermal boundary layers subjected to different external and upstream conditions, the main focus is given to: (i) local flow perturbations, (ii) different Reynolds numbers, and, (iii) external pressure gradient. Two types of turbulent wall-bounded flows are examined in this investigation. One of them consists of the fully developed turbulent channel. Furthermore, after the developing section, the boundary layers generated by the lower and upper walls collapse. From this point to downstream, periodic boundary conditions are applicable due to the existent homogeneity. The second type of wall bounded flow explored possesses no restriction in the upper zone; consequently, the boundary layer may grow infinitely downstream. This streamwise non-homogeneous state does not allow to prescribe periodic boundary conditions along the direction of the flow. Therefore, time-dependent turbulent information must be assigned at the domain inlet, turning the numerical problem into a very challenging one. The spatially-developing turbulent boundary layer in a flat plate is a typical example of non-homogeneous flow. In the first part of this thesis, the influence of local forcing on an incompressible turbulent channel flow is numerically investigated. The extensive information provided by the DNS enable us to have a better understanding of the physical mechanism responsible for local heat transfer enhancement and drag reduction. Time-periodic blowing/suction is applied by means of thin spanwise slots located at the lower and upper walls of the channel at several forcing frequencies. It was found in Araya et al. (2008-a) the existence of a characteristic frequency, i.e. of f = 0.64 or f* = 0.044, at which maximum local

  1. Low Mach number fluctuating hydrodynamics of multispecies liquid mixtures

    Energy Technology Data Exchange (ETDEWEB)

    Donev, Aleksandar, E-mail:; Bhattacharjee, Amit Kumar [Courant Institute of Mathematical Sciences, New York University, New York, New York 10012 (United States); Nonaka, Andy; Bell, John B. [Center for Computational Science and Engineering, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Garcia, Alejandro L. [Department of Physics and Astronomy, San Jose State University, San Jose, California 95192 (United States)


    We develop a low Mach number formulation of the hydrodynamic equations describing transport of mass and momentum in a multispecies mixture of incompressible miscible liquids at specified temperature and pressure, which generalizes our prior work on ideal mixtures of ideal gases [Balakrishnan et al., “Fluctuating hydrodynamics of multispecies nonreactive mixtures,” Phys. Rev. E 89 013017 (2014)] and binary liquid mixtures [Donev et al., “Low mach number fluctuating hydrodynamics of diffusively mixing fluids,” Commun. Appl. Math. Comput. Sci. 9(1), 47-105 (2014)]. In this formulation, we combine and extend a number of existing descriptions of multispecies transport available in the literature. The formulation applies to non-ideal mixtures of arbitrary number of species, without the need to single out a “solvent” species, and includes contributions to the diffusive mass flux due to gradients of composition, temperature, and pressure. Momentum transport and advective mass transport are handled using a low Mach number approach that eliminates fast sound waves (pressure fluctuations) from the full compressible system of equations and leads to a quasi-incompressible formulation. Thermal fluctuations are included in our fluctuating hydrodynamics description following the principles of nonequilibrium thermodynamics. We extend the semi-implicit staggered-grid finite-volume numerical method developed in our prior work on binary liquid mixtures [Nonaka et al., “Low mach number fluctuating hydrodynamics of binary liquid mixtures,” (2015)] and use it to study the development of giant nonequilibrium concentration fluctuations in a ternary mixture subjected to a steady concentration gradient. We also numerically study the development of diffusion-driven gravitational instabilities in a ternary mixture and compare our numerical results to recent experimental measurements [Carballido-Landeira et al., “Mixed-mode instability of a

  2. Chaotic fluctuations in mathematical economics

    Energy Technology Data Exchange (ETDEWEB)

    Yoshida, Hiroyuki, E-mail: [College of Economics, Nihon University, Chiyoda-ku, Tokyo 101-8360 (Japan)


    In this paper we examine a Cournot duopoly model, which expresses the strategic interaction between two firms. We formulate the dynamic adjustment process and investigate the dynamic properties of the stationary point. By introducing a memory mechanism characterized by distributed lag functions, we presuppose that each firm makes production decisions in a cautious manner. This implies that we have to deal with the system of integro-differential equations. By means of numerical simulations we show the occurrence of chaotic fluctuations in the case of fixed delays.

  3. Noise and fluctuations an introduction

    CERN Document Server

    MacDonald, D K C


    An understanding of fluctuations and their role is both useful and fundamental to the study of physics. This concise study of random processes offers graduate students and research physicists a survey that encompasses both the relationship of Brownian Movement with statistical mechanics and the problem of irreversible processes. It outlines the basics of the physics involved, without the strictures of mathematical rigor.The three-part treatment starts with a general survey of Brownian Movement, including electrical Brownian Movement and ""shot-noise,"" Part two explores correlation, frequency

  4. Electrostatic fluctuations in soap films. (United States)

    Dean, D S; Horgan, R R


    A field theory to describe electrostatic interactions in soap films, described by electric multilayers with a generalized thermodynamic surface-charging mechanism, is studied. In the limit where the electrostatic interactions are weak, this theory is exactly soluble. The theory incorporates in a consistent way, the surface-charging mechanism and the fluctuations in the electrostatic field that correspond to the zero-frequency component of the van der Waals force. It is shown that these terms lead to a Casimir-like attraction that can be sufficiently large to explain the transition between the common black film to a Newton black film.

  5. An objective fluctuation score for Parkinson's disease.

    Directory of Open Access Journals (Sweden)

    Malcolm K Horne

    Full Text Available Establishing the presence and severity of fluctuations is important in managing Parkinson's Disease yet there is no reliable, objective means of doing this. In this study we have evaluated a Fluctuation Score derived from variations in dyskinesia and bradykinesia scores produced by an accelerometry based system.The Fluctuation Score was produced by summing the interquartile range of bradykinesia scores and dyskinesia scores produced every 2 minutes between 0900-1800 for at least 6 days by the accelerometry based system and expressing it as an algorithm.This Score could distinguish between fluctuating and non-fluctuating patients with high sensitivity and selectivity and was significant lower following activation of deep brain stimulators. The scores following deep brain stimulation lay in a band just above the score separating fluctuators from non-fluctuators, suggesting a range representing adequate motor control. When compared with control subjects the score of newly diagnosed patients show a loss of fluctuation with onset of PD. The score was calculated in subjects whose duration of disease was known and this showed that newly diagnosed patients soon develop higher scores which either fall under or within the range representing adequate motor control or instead go on to develop more severe fluctuations.The Fluctuation Score described here promises to be a useful tool for identifying patients whose fluctuations are progressing and may require therapeutic changes. It also shows promise as a useful research tool. Further studies are required to more accurately identify therapeutic targets and ranges.

  6. Entropic Fluctuations in Thermally Driven Harmonic Networks (United States)

    Jakšić, V.; Pillet, C.-A.; Shirikyan, A.


    We consider a general network of harmonic oscillators driven out of thermal equilibrium by coupling to several heat reservoirs at different temperatures. The action of the reservoirs is implemented by Langevin forces. Assuming the existence and uniqueness of the steady state of the resulting process, we construct a canonical entropy production functional S^t which satisfies the Gallavotti-Cohen fluctuation theorem. More precisely, we prove that there exists κ _c>1/2 such that the cumulant generating function of S^t has a large-time limit e(α ) which is finite on a closed interval [1/2-κ _c,1/2+κ _c], infinite on its complement and satisfies the Gallavotti-Cohen symmetry e(1-α )=e(α ) for all α in R. Moreover, we show that e(α ) is essentially smooth, i.e., that e'(α )→ ∓ ∞ as α → 1/2 ∓ κ _c. It follows from the Gärtner-Ellis theorem that S^t satisfies a global large deviation principle with a rate function I( s) obeying the Gallavotti-Cohen fluctuation relation I(-s)-I(s)=s for all sin R. We also consider perturbations of S^t by quadratic boundary terms and prove that they satisfy extended fluctuation relations, i.e., a global large deviation principle with a rate function that typically differs from I( s) outside a finite interval. This applies to various physically relevant functionals and, in particular, to the heat dissipation rate of the network. Our approach relies on the properties of the maximal solution of a one-parameter family of algebraic matrix Riccati equations. It turns out that the limiting cumulant generating functions of S^t and its perturbations can be computed in terms of spectral data of a Hamiltonian matrix depending on the harmonic potential of the network and the parameters of the Langevin reservoirs. This approach is well adapted to both analytical and numerical investigations.

  7. Protrusion Fluctuations Direct Cell Motion (United States)

    Caballero, David; Voituriez, Raphaël; Riveline, Daniel


    Many physiological phenomena involve directional cell migration. It is usually attributed to chemical gradients in vivo. Recently, other cues have been shown to guide cells in vitro, including stiffness/adhesion gradients or micropatterned adhesive motifs. However, the cellular mechanism leading to these biased migrations remains unknown, and, often, even the direction of motion is unpredictable. In this study, we show the key role of fluctuating protrusions on ratchet-like structures in driving NIH3T3 cell migration. We identified the concept of efficient protrusion and an associated direction index. Our analysis of the protrusion statistics facilitated the quantitative prediction of cell trajectories in all investigated conditions. We varied the external cues by changing the adhesive patterns. We also modified the internal cues using drug treatments, which modified the protrusion activity. Stochasticity affects the short- and long-term steps. We developed a theoretical model showing that an asymmetry in the protrusion fluctuations is sufficient for predicting all measures associated with the long-term motion, which can be described as a biased persistent random walk. PMID:24988339

  8. Entropic fluctuations in DNA sequences (United States)

    Thanos, Dimitrios; Li, Wentian; Provata, Astero


    The Local Shannon Entropy (LSE) in blocks is used as a complexity measure to study the information fluctuations along DNA sequences. The LSE of a DNA block maps the local base arrangement information to a single numerical value. It is shown that despite this reduction of information, LSE allows to extract meaningful information related to the detection of repetitive sequences in whole chromosomes and is useful in finding evolutionary differences between organisms. More specifically, large regions of tandem repeats, such as centromeres, can be detected based on their low LSE fluctuations along the chromosome. Furthermore, an empirical investigation of the appropriate block sizes is provided and the relationship of LSE properties with the structure of the underlying repetitive units is revealed by using both computational and mathematical methods. Sequence similarity between the genomic DNA of closely related species also leads to similar LSE values at the orthologous regions. As an application, the LSE covariance function is used to measure the evolutionary distance between several primate genomes.

  9. Consistency of detrended fluctuation analysis (United States)

    Løvsletten, O.


    The scaling function F (s ) in detrended fluctuation analysis (DFA) scales as F (s ) ˜sH for stochastic processes with Hurst exponent H . This scaling law is proven for stationary stochastic processes with 0 DFA is equal in expectation to (i) a weighted sum of the ACF and (ii) a weighted sum of the second-order structure function. These results enable us to compute the exact finite-size bias for signals that are scaling and to employ DFA in a meaningful sense for signals that do not exhibit power-law statistics. The usefulness is illustrated by examples where it is demonstrated that a previous suggested modified DFA will increase the bias for signals with Hurst exponents 1 application of these developments, an estimator F ̂(s ) is proposed. This estimator can handle missing data in regularly sampled time series without the need of interpolation schemes. Under mild regularity conditions, F ̂(s ) is equal in expectation to the fluctuation function F (s ) in the gap-free case.

  10. Pulsed Neutron Scattering Studies of Strongly Fluctuating solids, Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Collin Broholm


    The conventional description of a solid is based on a static atomic structure with small amplitude so-called harmonic fluctuations about it. This is a final technical report for a project that has explored materials where fluctuations are sufficiently strong to severely challenge this approach and lead to unexpected and potentially useful materials properties. Fluctuations are enhanced when a large number of configurations share the same energy. We used pulsed spallation source neutron scattering to obtain detailed microscopic information about structure and fluctuations in such materials. The results enhance our understanding of strongly fluctuating solids and their potential for technical applications. Because new materials require new experimental techniques, the project has also developed new techniques for probing strongly fluctuating solids. Examples of material that were studied are ZrW2O8 with large amplitude molecular motion that leads to negative thermal expansion, NiGa2S4 where competing interactions lead to an anomalous short range ordered magnet, Pr1- xBixRu2O7 where a partially filled electron shell (Pr) in a weakly disordered environment produces anomalous metallic properties, and TbMnO3 where competing interactions lead to a magneto-electric phase. The experiments on TbMnO3 exemplify the relationship between research funded by this project and future applications. Magneto-electric materials may produce a magnetic field when an electric field is applied or vise versa. Our experiments have clarified the reason why electric and magnetic polarization is coupled in TbMnO3. While this knowledge does not render TbMnO3 useful for applications it will focus the search for a practical room temperature magneto-electric for applications.

  11. Glacial greenhouse-gas fluctuations controlled by ocean circulation changes. (United States)

    Schmittner, Andreas; Galbraith, Eric D


    Earth's climate and the concentrations of the atmospheric greenhouse gases carbon dioxide (CO(2)) and nitrous oxide (N(2)O) varied strongly on millennial timescales during past glacial periods. Large and rapid warming events in Greenland and the North Atlantic were followed by more gradual cooling, and are highly correlated with fluctuations of N(2)O as recorded in ice cores. Antarctic temperature variations, on the other hand, were smaller and more gradual, showed warming during the Greenland cold phase and cooling while the North Atlantic was warm, and were highly correlated with fluctuations in CO(2). Abrupt changes in the Atlantic meridional overturning circulation (AMOC) have often been invoked to explain the physical characteristics of these Dansgaard-Oeschger climate oscillations, but the mechanisms for the greenhouse-gas variations and their linkage to the AMOC have remained unclear. Here we present simulations with a coupled model of glacial climate and biogeochemical cycles, forced only with changes in the AMOC. The model simultaneously reproduces characteristic features of the Dansgaard-Oeschger temperature, as well as CO(2) and N(2)O fluctuations. Despite significant changes in the land carbon inventory, CO(2) variations on millennial timescales are dominated by slow changes in the deep ocean inventory of biologically sequestered carbon and are correlated with Antarctic temperature and Southern Ocean stratification. In contrast, N(2)O co-varies more rapidly with Greenland temperatures owing to fast adjustments of the thermocline oxygen budget. These results suggest that ocean circulation changes were the primary mechanism that drove glacial CO(2) and N(2)O fluctuations on millennial timescales.

  12. Spin and charge fluctuations in the Hubbard model (United States)

    Sherman, A.


    Using the strong coupling diagram technique for calculating the electron Green's function of the two-dimensional Hubbard model we have summed infinite sequences of ladder diagrams, which describe interactions of electrons with spin and charge fluctuations. For sufficiently low temperatures and doping a pronounced four-band structure is observed in spectral functions. Its appearance is related to the proximity of the transition to the long-range antiferromagnetic order.

  13. Fluctuation and dissipation at a quantum critical point. (United States)

    Tong, David; Wong, Kenny


    In nonrelativistic field theories, quantum fluctuations give rise to dissipative behavior even at zero temperature. Here we use holographic methods to explore the dissipative dynamics of massive particles coupled to quantum critical theories. We present analytic expressions for correlation functions and response functions. The behavior changes qualitatively as the dynamical exponent passes through z=2. In particular, for z>2, the long-time dynamics of the particle is independent of its inertial mass.

  14. Fluctuation-Induced Pattern Formation in a Surface Reaction

    DEFF Research Database (Denmark)

    Starke, Jens; Reichert, Christian; Eiswirth, Markus


    Spontaneous nucleation, pulse formation, and propagation failure have been observed experimentally in CO oxidation on Pt(110) at intermediate pressures ($\\approx 10^{-2}$mbar). This phenomenon can be reproduced with a stochastic model which includes temperature effects. Nucleation occurs randomly...... due to fluctuations in the reaction processes, whereas the subsequent damping out essentially follows the deterministic path. Conditions for the occurence of stochastic effects in the pattern formation during CO oxidation on Pt are discussed....

  15. Compressibilities and Volume Fluctuations of Archaeal Tetraether Liposomes (United States)

    Chong, Parkson Lee-Gau; Sulc, Michael; Winter, Roland


    Bipolar tetraether lipids (BTLs) are abundant in crenarchaeota, which thrive in both thermophilic and nonthermophilic environments, with wide-ranging growth temperatures (4–108°C). BTL liposomes can serve as membrane models to explore the role of BTLs in the thermal stability of the plasma membrane of crenarchaeota. In this study, we focus on the liposomes made of the polar lipid fraction E (PLFE). PLFE is one of the main BTLs isolated from the thermoacidophilic crenarchaeon Sulfolobus acidocaldarius. Using molecular acoustics (ultrasound velocimetry and densimetry), pressure perturbation calorimetry, and differential scanning calorimetry, we have determined partial specific adiabatic and isothermal compressibility, their respective compressibility coefficients, partial specific volume, and relative volume fluctuations of PLFE large unilamellar vesicles (LUVs) over a wide range of temperatures (20–85°C). The results are compared with those obtained from liposomes made of dipalmitoyl-L-α-phosphatidylcholine (DPPC), a conventional monopolar diester lipid. We found that, in the entire temperature range examined, compressibilities of PLFE LUVs are low, comparable to those found in gel state of DPPC. Relative volume fluctuations of PLFE LUVs at any given temperature examined are 1.6–2.2 times more damped than those found in DPPC LUVs. Both compressibilities and relative volume fluctuations in PLFE LUVs are much less temperature-sensitive than those in DPPC liposomes. The isothermal compressibility coefficient (βTlipid) of PLFE LUVs changes from 3.59 × 10−10 Pa−1 at 25°C to 4.08 × 10−10 Pa−1 at 78°C. Volume fluctuations of PLFE LUVs change only 0.25% from 30°C to 80°C. The highly damped volume fluctuations and their low temperature sensitivity, echo that PLFE liposomes are rigid and tightly packed. To our knowledge, the data provide a deeper understanding of lipid packing in PLFE liposomes than has been previously reported, as well as a molecular

  16. Supersymmetric domain walls

    NARCIS (Netherlands)

    Bergshoeff, Eric A.; Kleinschmidt, Axel; Riccioni, Fabio


    We classify the half-supersymmetric "domain walls," i.e., branes of codimension one, in toroidally compactified IIA/IIB string theory and show to which gauged supergravity theory each of these domain walls belong. We use as input the requirement of supersymmetric Wess-Zumino terms, the properties of

  17. Thin Wall Iron Castings

    Energy Technology Data Exchange (ETDEWEB)

    J.F. Cuttino; D.M. Stefanescu; T.S. Piwonka


    Results of an investigation made to develop methods of making iron castings having wall thicknesses as small as 2.5 mm in green sand molds are presented. It was found that thin wall ductile and compacted graphite iron castings can be made and have properties consistent with heavier castings. Green sand molding variables that affect casting dimensions were also identified.

  18. Timber frame walls

    DEFF Research Database (Denmark)

    Hansen, Ernst Jan de Place; Brandt, Erik


    A ventilated cavity is usually considered good practice for removing moisture behind the cladding of timber framed walls. Timber frame walls with no cavity are a logical alternative as they are slimmer and less expensive to produce and besides the risk of a two-sided fire behind the cladding...

  19. International Divider Walls

    NARCIS (Netherlands)

    Kruis, A.; Sneller, A.C.W.(L.)


    The subject of this teaching case is the Enterprise Resource Planning (ERP) system implementation at International Divider Walls, the world market leader in design, production, and sales of divider walls. The implementation in one of the divisions of this multinational company had been successful,

  20. Experiment and Simulation Study on the Amorphous Silicon Photovoltaic Walls

    Directory of Open Access Journals (Sweden)

    Wenjie Zhang


    Full Text Available Based on comparative study on two amorphous silicon photovoltaic walls (a-Si PV walls, the temperature distribution and the instant power were tested; and with EnergyPlus software, similar models of the walls were built to simulate annual power generation and air conditioning load. On typical sunshine day, the corresponding position temperature of nonventilated PV wall was generally 0.5~1.5°C higher than that of ventilated one, while the power generation was 0.2%~0.4% lower, which was consistent with the simulation results with a difference of 0.41% in annual energy output. As simulation results, in summer, comparing the PV walls with normal wall, the heat per unit area of these two photovoltaic walls was 5.25 kWh/m2 (nonventilated and 0.67 kWh/m2 (ventilated higher, respectively. But in winter the heat loss of nonventilated one was smaller, while ventilated PV wall was similar to normal wall. To annual energy consumption of heating and cooling, the building with ventilated PV wall and normal wall was also similar but slightly better than nonventilated one. Therefore, it is inferred that, at low latitudes, such as Zhuhai, China, air gap ventilation is suitable, while the length to thickness ratio of the air gap needs to be taken into account.