NASA Astrophysics Data System (ADS)
Gan, K. F.; Ahn, J.-W.; Park, J.-W.; Maingi, R.; McLean, A. G.; Gray, T. K.; Gong, X.; Zhang, X. D.
2013-02-01
The divertor heat flux footprint in tokamaks is often observed to be non-axisymmetric due to intrinsic error fields, applied 3D magnetic fields or during transients such as edge localized modes. Typically, only 1D radial heat flux profiles are analyzed; however, analysis of the full 2D divertor measurements provides opportunities to study the asymmetric nature of the deposited heat flux. To accomplish this an improved 3D Fourier analysis method has been successfully applied in a heat conduction solver (TACO) to determine the 2D heat flux distribution at the lower divertor surface in the National Spherical Torus Experiment (NSTX) tokamak. This advance enables study of helical heat deposition onto the divertor. In order to account for heat transmission through poorly adhered surface layers on the divertor plate, a heat transmission coefficient, defined as the surface layer thermal conductivity divided by the thickness of the layer, was introduced to the solution of heat conduction equation. This coefficient is denoted as ? and a range of values were tested in the model to ensure a reliable heat flux calculation until a specific value of ? led to the constant total deposited energy in the numerical solution after the end of discharge. A comparison between 1D heat flux profiles from TACO and from a 2D heat flux calculation code, THEODOR, shows good agreement. Advantages of 2D heat flux distribution over the conventional 1D heat flux profile are also discussed, and examples of 2D data analysis in the study of striated heat deposition pattern as well as the toroidal degree of asymmetry of peak heat flux and heat flux width are demonstrated.
Gan, K F; Ahn, J-W; Park, J-W; Maingi, R; McLean, A G; Gray, T K; Gong, X; Zhang, X D
2013-02-01
The divertor heat flux footprint in tokamaks is often observed to be non-axisymmetric due to intrinsic error fields, applied 3D magnetic fields or during transients such as edge localized modes. Typically, only 1D radial heat flux profiles are analyzed; however, analysis of the full 2D divertor measurements provides opportunities to study the asymmetric nature of the deposited heat flux. To accomplish this an improved 3D Fourier analysis method has been successfully applied in a heat conduction solver (TACO) to determine the 2D heat flux distribution at the lower divertor surface in the National Spherical Torus Experiment (NSTX) tokamak. This advance enables study of helical heat deposition onto the divertor. In order to account for heat transmission through poorly adhered surface layers on the divertor plate, a heat transmission coefficient, defined as the surface layer thermal conductivity divided by the thickness of the layer, was introduced to the solution of heat conduction equation. This coefficient is denoted as ? and a range of values were tested in the model to ensure a reliable heat flux calculation until a specific value of ? led to the constant total deposited energy in the numerical solution after the end of discharge. A comparison between 1D heat flux profiles from TACO and from a 2D heat flux calculation code, THEODOR, shows good agreement. Advantages of 2D heat flux distribution over the conventional 1D heat flux profile are also discussed, and examples of 2D data analysis in the study of striated heat deposition pattern as well as the toroidal degree of asymmetry of peak heat flux and heat flux width are demonstrated. PMID:23464209
Dennis, Brian
difficult or even impossible to place temperature probes, heat flux probes, or strain gauges on certain conditions on parts of a three-dimensional solid body surface by using FEM. It should be pointed out of inverse determination of unknown boundary conditions in two-dimensional steady heat conduction has been
NASA Astrophysics Data System (ADS)
Ahn, J.-W.; Gan, K. F.; Scotti, F.; Lore, J. D.; Maingi, R.; Canik, J. M.; Gray, T. K.; McLean, A. G.; Roquemore, A. L.; Soukhanovskii, V. A.
2013-07-01
Toroidally non-axisymmetric divertor profiles during the 3-D field application and for ELMs are studied with simultaneous observation by a new wide angle visible camera and a high speed IR camera. A newly implemented 3-D heat conduction code, TACO, is used to obtain divertor heat flux. The wide angle camera data confirmed the previously reported result on the validity of vacuum field line tracing on the prediction of split strike point pattern by 3-D fields as well as the phase locking of ELM heat flux to the 3-D fields. TACO calculates the 2-D heat flux distribution allowing assessment of toroidal asymmetry of peak heat flux and heat flux width. The degree of asymmetry (?DA) is defined to quantify the asymmetric heat deposition on the divertor surface and is found to have a strong positive dependence on peak heat flux.
1D-to-3D transition of phonon heat conduction in polyethylene using molecular dynamics simulations
Henry, Asegun
The thermal conductivity of nanostructures generally decreases with decreasing size because of classical size effects. The axial thermal conductivity of polymer chain lattices, however, can exhibit the opposite trend, ...
TACO3D. 3-D Finite Element Heat Transfer Code
Mason, W.E. [Sandia National Labs., Albuquerque, NM (United States)
1992-03-04
TACO3D is a three-dimensional, finite-element program for heat transfer analysis. An extension of the two-dimensional TACO program, it can perform linear and nonlinear analyses and can be used to solve either transient or steady-state problems. The program accepts time-dependent or temperature-dependent material properties, and materials may be isotropic or orthotropic. A variety of time-dependent and temperature-dependent boundary conditions and loadings are available including temperature, flux, convection, and radiation boundary conditions and internal heat generation. Additional specialized features treat enclosure radiation, bulk nodes, and master/slave internal surface conditions (e.g., contact resistance). Data input via a free-field format is provided. A user subprogram feature allows for any type of functional representation of any independent variable. A profile (bandwidth) minimization option is available. The code is limited to implicit time integration for transient solutions. TACO3D has no general mesh generation capability. Rows of evenly-spaced nodes and rows of sequential elements may be generated, but the program relies on separate mesh generators for complex zoning. TACO3D does not have the ability to calculate view factors internally. Graphical representation of data in the form of time history and spatial plots is provided through links to the POSTACO and GRAPE postprocessor codes.
Conduction heat transfer solutions
VanSant, J.H.
1983-08-01
This text is a collection of solutions to a variety of heat conduction problems found in numerous publications, such as textbooks, handbooks, journals, reports, etc. Its purpose is to assemble these solutions into one source that can facilitate the search for a particular problem solution. Generally, it is intended to be a handbook on the subject of heat conduction. There are twelve sections of solutions which correspond with the class of problems found in each. Geometry, state, boundary conditions, and other categories are used to classify the problems. Each problem is concisely described by geometry and condition statements, and many times a descriptive sketch is also included. The introduction presents a synopsis on the theory, differential equations, and boundary conditions for conduction heat transfer. Some discussion is given on the use and interpretation of solutions. Supplementary data such as mathematical functions, convection correlations, and thermal properties are included for aiding the user in computing numerical values from the solutions. 155 figs., 92 refs., 9 tabs.
Heat Transfer Boundary Conditions in the RELAP5-3D Code
Richard A. Riemke; Cliff B. Davis; Richard R. Schultz
2008-05-01
The heat transfer boundary conditions used in the RELAP5-3D computer program have evolved over the years. Currently, RELAP5-3D has the following options for the heat transfer boundary conditions: (a) heat transfer correlation package option, (b) non-convective option (from radiation/conduction enclosure model or symmetry/insulated conditions), and (c) other options (setting the surface temperature to a volume fraction averaged fluid temperature of the boundary volume, obtaining the surface temperature from a control variable, obtaining the surface temperature from a time-dependent general table, obtaining the heat flux from a time-dependent general table, or obtaining heat transfer coefficients from either a time- or temperature-dependent general table). These options will be discussed, including the more recent ones.
Barrash, Warren
Hydraulic conductivity imaging from 3-D transient hydraulic tomography at several pumping August 2013; accepted 7 September 2013; published 13 November 2013. [1] 3-D Hydraulic tomography (3-D HT (primarily hydraulic conductivity, K) is estimated by joint inversion of head change data from multiple
Coolant side heat transfer with rotation: User manual for 3D-TEACH with rotation
NASA Technical Reports Server (NTRS)
Syed, S. A.; James, R. H.
1989-01-01
This program solves the governing transport equations in Reynolds average form for the flow of a 3-D, steady state, viscous, heat conducting, multiple species, single phase, Newtonian fluid with combustion. The governing partial differential equations are solved in physical variables in either a Cartesian or cylindrical coordinate system. The effects of rotation on the momentum and enthalpy calculations modeled in Cartesian coordinates are examined. The flow of the fluid should be confined and subsonic with a maximum Mach number no larger than 0.5. This manual describes the operating procedures and input details for executing a 3D-TEACH computation.
Temperature distributions in the laser-heated diamond anvil cell from 3-D numerical modeling
Rainey, E. S. G.; Kavner, A. [Department of Earth and Space Sciences, University of California, Los Angeles, California 90095 (United States); Hernlund, J. W. [Department of Earth and Planetary Science, University of California, Berkeley, California 94720 (United States); Earth-Life Science Institute, Megoro, Tokyo 152-8551 (Japan)
2013-11-28
We present TempDAC, a 3-D numerical model for calculating the steady-state temperature distribution for continuous wave laser-heated experiments in the diamond anvil cell. TempDAC solves the steady heat conduction equation in three dimensions over the sample chamber, gasket, and diamond anvils and includes material-, temperature-, and direction-dependent thermal conductivity, while allowing for flexible sample geometries, laser beam intensity profile, and laser absorption properties. The model has been validated against an axisymmetric analytic solution for the temperature distribution within a laser-heated sample. Example calculations illustrate the importance of considering heat flow in three dimensions for the laser-heated diamond anvil cell. In particular, we show that a “flat top” input laser beam profile does not lead to a more uniform temperature distribution or flatter temperature gradients than a wide Gaussian laser beam.
Revised Heat Flow Analysis from 3D Coupled Modeling Considerations
NASA Astrophysics Data System (ADS)
Kohl, T.
2003-04-01
Due to the increased exploration of deeper subsurface structures, thermal analyses are becoming more and more important to predict subsurface conditions. Our data interpretation is directed towards resource evaluation to design possible geothermal utilization concepts and towards temperature prediction in deep tunnel constructions. Both aspects require a proper treatment of the impact of heterogeneous distribution of geological units in subsurface and of topography. Under the geological / topographical setting of Switzerland these tasks represent a special challenge for the evaluation of subsurface temperatures and involve, in particular, thermally relevant mechanisms. In the present analysis, temperature data from selected sites in Switzerland of depths down to 2 km are investigated. The numerous data originate from vertical and inclined boreholes, shafts and tunnel profiles. Additional thermal information is provided from laboratory measurements on various samples. Complex 3D models had to be constructed that are based on compilations of geological structures. These comprehensive 3D geological and thermal regional models of 20-40 km extent should identify zones of significant convective flow which are of major importance for geothermal utilization. In contrast to findings obtained from earlier geothermal resource assessments, now, existing geological, hydrogeological information and petrophysical data are comprised by a full 3D numerical evaluation. Results will be illustrated and compared to data from Northern Switzerland. Especially, the role of a hidden permocarbonifereous trough will be discussed that runs in E-W direction along the Swiss border. A further example is taken from an area of severe topography from Central Switzerland which highlights the importance of the interplay of various thermal transport mechanisms such as fluid and mass advection (uplift) as well as for climatic changes. The 3D numerical model extending over an area of ~35 x 40 km and includes Alpine high topographic relief with altitudes between 300 and 3500 m a.s.l.. Without modifying the petrophysical parameters determined from laboratory measurements, all reliable temperature data could be nearly perfectly fitted by adjusting the thermal boundary conditions at the surface and at the bottom. This study reveals that even under Alpine conditions hydraulic influence is generally negligible at depths below ~500 m which is in contrast to results from lower dimensional methods such as 1D Péclet analyses. Vertical heat flow variations are due rather to topographic than to hydraulic impact.
Thermal Conduction Path Analysis in 3-D ICs Boris Vaisband1
Friedman, Eby G.
Thermal Conduction Path Analysis in 3-D ICs Boris Vaisband1 , Ioannis Savidis2 , and Eby G the horizontal and vertical dimensions. The dependence of the thermal conductivity on temperature is integrated, since the thermal conductivity of silicon dioxide is 200 times smaller than the thermal conductivity
3D and NDT using scanning from heating
NASA Astrophysics Data System (ADS)
Belkacemi, M.; Stolz, C.; Aubreton, O.
2015-04-01
A nondestructive inspection method using an infrared detection system is presented in this paper; the system uses a YAG laser as excitation point. The material thermal response to this excitation is processed for the detection of volume defects, this technique integrated into a 3D scanning system allows us to get a 3D scan of the object as well as defects detection.
Manipulating thermal conductance across 3D/1D interface by impedance matching
NASA Astrophysics Data System (ADS)
Zhang, Jingjie; Polanco, Carlos; Ghosh, Avik
2014-03-01
Self-assembled monolayers (SAMs) are of special interest to nano-electronic and thermal devices, because we can tune their properties by changing the bonding strength that links the SAMs to a thin film layer. We explain how this bonding strength influence heat across this 3D-1D interfaces based on a frequency dependent broadening matrix that acts as a generalization of acoustic impedance. We demonstrate both how to build an equivalent ``impedance'' broadening matrix that captures the dimensionality mismatch at the 3D-1D transition and the ``matching'' effect of the end group on an equivalent 1D-1D interface. We calculate thermal boundary conductance (TBC) at metal/polymer interfaces with different terminal groups and polymers. The calculations are done with non-equilibrium Green's function formalism coupled with ab-initio parameters for the chemical group functionalized systems. Our results confirm that in the low frequency spectrum, the stronger the bonding the larger the TBC. Nevertheless, when we consider the whole phonon spectrum, there is a sweet spot in the bonding strength that maximizes TBC. NSF-CAREER (QMHP 1028883), NSF-IDR (CBET 1134311), XSEDE.
Variable conductance heat pipe technology
NASA Technical Reports Server (NTRS)
Marcus, B. D.; Edwards, D. K.; Anderson, W. T.
1973-01-01
Research and development programs in variable conductance heat pipe technology were conducted. The treatment has been comprehensive, involving theoretical and/or experimental studies in hydrostatics, hydrodynamics, heat transfer into and out of the pipe, fluid selection, and materials compatibility, in addition to the principal subject of variable conductance control techniques. Efforts were not limited to analytical work and laboratory experimentation, but extended to the development, fabrication and test of spacecraft hardware, culminating in the successful flight of the Ames Heat Pipe Experiment on the OAO-C spacecraft.
Effects of Heat Loss on the Performance of Micro-Scale 3-D Supersonic Nozzles
NASA Astrophysics Data System (ADS)
Kujawa, Jeffrey; Hitt, Darren
2003-11-01
The performance optimization of supersonic micro-nozzles is a key element in the design of MEMS-based microthrusters for the next generation of miniaturized satellites ("nanosats"). Owing to the large surface area-to-volume ratio on the microscale and the high conductivity of typical substrate materials, heat transfer effects are expected to be significant. This has been corroborated by thermal measurements performed on microthruster prototypes at NASA/Goddard Space Flight Center. To detail the heat transfer and quantify its impact on thruster performance, 2-D and 3-D numerical simulations of the supersonic micro-nozzle flow with insulated and conductive wall boundaries are performed. Geometry and flow parameters are based on the NASA/Goddard H2O2 monopropellant prototype microthruster. Both steady-state and transient thruster operations are considered. The 3-D steady flow results indicate that heat losses approaching 20enthalpy are possible in comparison to an adiabatic wall assumption, resulting in a 10generation.
Residual resistance of 2D and 3D structures and Joule heat release.
Gurevich, V L; Kozub, V I
2011-06-22
We consider a residual resistance and Joule heat release in 2D nanostructures as well as in ordinary 3D conductors. We assume that elastic scattering of conduction electrons by lattice defects is predominant. Within a rather intricate situation in such systems we discuss in detail two cases. (1) The elastic scattering alone (i.e. without regard of inelastic mechanisms of scattering) leads to a transition of the mechanical energy (stored by the electrons under the action of an electric field) into heat in a traditional way. This process can be described by the Boltzmann equation where it is possible to do the configuration averaging over defect positions in the electron-impurity collision term. The corresponding conditions are usually met in metals. (2) The elastic scattering can be considered with the help of the standard electron-impurity collision integral only in combination with some additional averaging procedure (possibly including inelastic scattering or some mechanisms of electron wavefunction phase destruction). This situation is typical for degenerate semiconductors with a high concentration of dopants and conduction electrons. Quite often, heat release can be observed via transfer of heat to the lattice, i.e. via inelastic processes of electron-phonon collisions and can take place at distances much larger than the size of the device. However, a direct heating of the electron system can be registered too by, for instance, local measurements of the current noise or direct measurement of an electron distribution function. PMID:21628783
Zhang, Jun
Iterative Solution and Finite Difference Approximations to 3D Microscale Heat Transport Equation a three dimensional time dependent microscale heat transport equation. A second order finite difference and the efficiency of the proposed computational procedure. Key words: Heat transport equation, finite difference
A Simple, Low-Cost Conductive Composite Material for 3D Printing of Electronic Sensors
Leigh, Simon J.; Bradley, Robert J.; Purssell, Christopher P.; Billson, Duncan R.; Hutchins, David A.
2012-01-01
3D printing technology can produce complex objects directly from computer aided digital designs. The technology has traditionally been used by large companies to produce fit and form concept prototypes (‘rapid prototyping’) before production. In recent years however there has been a move to adopt the technology as full-scale manufacturing solution. The advent of low-cost, desktop 3D printers such as the RepRap and Fab@Home has meant a wider user base are now able to have access to desktop manufacturing platforms enabling them to produce highly customised products for personal use and sale. This uptake in usage has been coupled with a demand for printing technology and materials able to print functional elements such as electronic sensors. Here we present formulation of a simple conductive thermoplastic composite we term ‘carbomorph’ and demonstrate how it can be used in an unmodified low-cost 3D printer to print electronic sensors able to sense mechanical flexing and capacitance changes. We show how this capability can be used to produce custom sensing devices and user interface devices along with printed objects with embedded sensing capability. This advance in low-cost 3D printing with offer a new paradigm in the 3D printing field with printed sensors and electronics embedded inside 3D printed objects in a single build process without requiring complex or expensive materials incorporating additives such as carbon nanotubes. PMID:23185319
Heat Flow Partitioning Between Continents and Oceans - from 2D to 3D
NASA Astrophysics Data System (ADS)
Moresi, L. N.; Cooper, C. M.; Lenardic, A.
2010-12-01
Scalings derived from thermal network theory explain how the presence of continents can influence the Earth’s overall heat loss. Intuitively, it may seem that increasing the proportion of a planet’s surface area covered by continents would decrease the efficiency of heat transfer given that continents do not participate in convective overturn. However, this ignores the potential feedback between the insulating effect of continents and the temperature-dependent viscosity of the mantle (Lenardic et al, 2005, Cooper et al, 2007). When this feedback is considered, a clear regime exists in which the partial stagnation and insulation of the surface by buoyant continental crust can lead to an increase in heat flow compared to the uninsulated case. The numerical results used to verify the scalings have mostly been conducted in two dimensions in order to cover a very wide range of Rayleigh number, fraction of continental coverage, and continental thickness. However as more recent results show that the configuration of the crust also plays a role in determining the heat flow partitioning and global heat flow (See Lenardic et al, “Continents, Super-Continents, Mantle Thermal Mixing, and Mantle Thermal Isolation” in this session), we have begun to repeat this exhaustive and exhausting 2D study in 3D. Cooper, C.M., A. Lenardic, and L.-N. Moresi "Effects of continental insulation and the partioning of heat producing elements on the Earth's heat loss." Geophys. Res. Lett., 33 ,10.1029, 2006. Lenardic, A., L.-N. Moresi, A.M. Jellinek, and M. Manga "Continental insulation, mantle cooling, and the surface area of oceans and continents." Earth Planet. Sci. Lett., 234 ,317-333, 2005.
Heat source parameter estimation from scanned 3D thermal models
Ivan Sovic; Lomislav Lipic; Luko Gjenero; Ivan Grubisic; Karolj Skala
2011-01-01
Thermal imaging is a non-invasive, non-contact functional imaging method used in temperature measurements. It provides an insight to metabolic and other processes within human body. In this paper a general simulation model that can be used to estimate the depth and size of the heat source embedded underneath the surface of an object is presented. Simulations are performed on two
3D fabrication of all-polymer conductive microstructures by two photon polymerization.
Kurselis, Kestutis; Kiyan, Roman; Bagratashvili, Victor N; Popov, Vladimir K; Chichkov, Boris N
2013-12-16
A technique to fabricate electrically conductive all-polymer 3D microstructures is reported. Superior conductivity, high spatial resolution and three-dimensionality are achieved by successive application of two-photon polymerization and in situ oxidative polymerization to a bi-component formulation, containing a photosensitive host matrix and an intrinsically conductive polymer precursor. By using polyethylene glycol diacrylate (PEG-DA) and 3,4-ethylenedioxythiophene (EDOT), the conductivity of 0.04 S/cm is reached, which is the highest value for the two-photon polymerized all-polymer microstructures to date. The measured electrical conductivity dependency on the EDOT concentration indicates percolation phenomenon and a three-dimensional nature of the conductive pathways. Tunable conductivity, biocompatibility, and environmental stability are the characteristics offered by PEG-DA/EDOT blends which can be employed in biomedicine, MEMS, microfluidics, and sensorics. PMID:24514677
Rapid prototyping of electrically conductive components using 3D printing technology
J. Czy?ewski; P. Burzy?ski; K. Gawe?; J. Meisner
2009-01-01
A method of rapid prototyping of electrically conductive components is described. The method is based on 3D printing technology. The prototyped model is made of plaster-based powder bound layer-by-layer by an inkjet printing of a liquid binder. The resulting model is highly porous and can be impregnated by various liquids. In a standard prototyping process, the model is impregnated by
Highly Conductive 3D Nano-Carbon: Stacked Multilayer Graphene System with Interlayer Decoupling
Tianhua Yu; Changdong Kim; Bin Yu
2011-01-01
We investigate electrical conduction and breakdown behavior of 3D nano-carbon-stacked multilayer graphene (s-MLG) system with complete interlayer decoupling. The s-MLG is prepared by transferring and stacking large-area CVD-grown graphene monolayers, followed by wire patterning and plasma etching. Raman spectroscopy was used to confirm the layer number. The D-band peak indicates low defect level in the samples. Electrical current stressing induced
A Numerical Study on the Thermal Conductivity of 3D Woven C/C Composites at High Temperature
NASA Astrophysics Data System (ADS)
Shigang, Ai; Rujie, He; Yongmao, Pei
2015-03-01
Experimental data for Carbon/Carbon (C/C) constituent materials are combined with a three dimensional steady state heat transfer finite element analysis to demonstrate the average in-plane and out-of-plane thermal conductivities (TCs) of C/C composites. The finite element analysis is carried out at two distinct length scales: (a) a micro scale comparable with the diameter of carbon fibres and (b) a meso scale comparable with the carbon fibre yarns. Micro-scale model calculate the TCs at the fibre yarn scale in the three orthogonal directions (x, y and z). The output results from the micro-scale model are then incorporated in the meso-scale model to obtain the global TCs of the 3D C/C composite. The simulation results are quite consistent with the theoretical and experimental counterparts reported in references. Based on the numerical approach, TCs of the 3D C/C composite are calculated from 300 to 2500 K. Particular attention is given in elucidating the variations of the TCs with temperature. The multi-scale models provide an efficient approach to predict the TCs of 3D textile materials, which is helpful for the thermodynamic property analysis and structure design of the C/C composites.
NASA Astrophysics Data System (ADS)
Xu, Hongmei; Wang, Huachun; Wu, Chenping; Lin, Na; Soomro, Abdul Majid; Guo, Huizhang; Liu, Chuan; Yang, Xiaodong; Wu, Yaping; Cai, Duanjun; Kang, Junyong
2015-06-01
Transparent conducting film occupies an important position in various optoelectronic devices. To replace the costly tin-doped indium oxide (ITO), promising materials, such as metal nanowires and graphene, have been widely studied. Moreover, a long-pursued goal is to consolidate these two materials together and express their outstanding properties simultaneously. We successfully achieved a direct 3D coating of a graphene layer on an interlacing Cu nanosilks network by the low pressure chemical vapor deposition method. High aspect ratio Cu nanosilks (13 nm diameter with 40 ?m length) were synthesized through the nickel ion catalytic process. Large-size, transparent conducting film was successfully fabricated with Cu nanosilks ink by the imprint method. A magnetic manipulator equipped with a copper capsule was used to produce high Cu vapor pressure on Cu nanosilks and realize the graphene 3D-coating. The coated Cu@graphene nanosilks network achieved high transparency, low sheet resistance (41 Ohm sq-1 at 95% transmittance) and robust antioxidant ability. With this technique, the transfer process of graphene is no longer needed, and a flexible, uniform and high-performance transparent conducting film could be fabricated in unlimited size.Transparent conducting film occupies an important position in various optoelectronic devices. To replace the costly tin-doped indium oxide (ITO), promising materials, such as metal nanowires and graphene, have been widely studied. Moreover, a long-pursued goal is to consolidate these two materials together and express their outstanding properties simultaneously. We successfully achieved a direct 3D coating of a graphene layer on an interlacing Cu nanosilks network by the low pressure chemical vapor deposition method. High aspect ratio Cu nanosilks (13 nm diameter with 40 ?m length) were synthesized through the nickel ion catalytic process. Large-size, transparent conducting film was successfully fabricated with Cu nanosilks ink by the imprint method. A magnetic manipulator equipped with a copper capsule was used to produce high Cu vapor pressure on Cu nanosilks and realize the graphene 3D-coating. The coated Cu@graphene nanosilks network achieved high transparency, low sheet resistance (41 Ohm sq-1 at 95% transmittance) and robust antioxidant ability. With this technique, the transfer process of graphene is no longer needed, and a flexible, uniform and high-performance transparent conducting film could be fabricated in unlimited size. Electronic supplementary information (ESI) available: Photographs, transmission spectra, Auger electron spectroscopy (AES) and transmission electron microscopy (TEM) images. See DOI: 10.1039/c5nr01711d
NASA Astrophysics Data System (ADS)
Castro, M. C.; Patriarche, D.; Goblet, P.
2004-12-01
The conceptual and practical gains achieved by expanding a 2-D finite element model [Castro and Goblet, 2003] to a true 3-D one through an application in the Carrizo aquifer and surrounding formations in southwestern Texas are investigated through a series of groundwater flow and 4He transport simulations. Such a 3-D model represents 4 formations, covers a surface area of ˜7000 km2, and comprises more than 5 million elements. 3-D simulations allow for a more detailed and accurate definition of the heterogeneities of the system, by specifically identifying and differentiating processes that directly impact the three-dimensional hydraulic conductivity field. It is shown that while hydraulic conductivity decreases exponentially along the regional groundwater flow direction, such decrease is better described as a function of depth rather than recharge distance. This relationship reflects the combined influences of differential compaction of the media as well as down-dip lithological change. The intrinsic permeability derived from this relationship agrees with field information. In addition, our relationship intrinsic permeability-depth derived from the obtained hydraulic conductivity field in the 3-D model domain for depths < 2 km is in agreement with that one proposed by Saar and Manga [2004] for the Oregon Cascades volcanic setting, as well as that proposed by Manning and Ingebritsen [1999]. These findings suggest that large-scale permeability evolution with depth is, to a large extent, independent of the type of medium. The 4He external flux value for which calibration of the 3-D transport model was achieved is 1.5×10-15 mol m-2rock s-1. Calculated hydraulic conductivities vary from 5×10-4 to 3.1×10-8 m s-1 in the Carrizo aquifer from the outcrop to the discharge area. Results also suggest that the solution for groundwater flow simulations based on calibration of hydraulic heads depends on the ratio between hydraulic conductivities of different formations, showing that an infinite number of solutions are available for calibration of 3-D groundwater flow models. Understanding how geological processes directly affect the 3-D hydraulic conductivity field at the regional scale is essential not only to hydrogeological applications, but also at improving our understanding of the Earth\\'{ }s crust and mantle dynamics by allowing for a more accurate quantification of helium and heat fluxes. Castro M. C., and Goblet P. (2003). Calibration of regional groundwater flow models - working toward a better understanding of site-specific systems. Water Resour. Res., 39(6), 1172, doi:10.1029/2002WR001653. Manning C. E., and Ingebritsen S. E. (1999). Permeability of the continental crust; implications of geothermal data and metamorphic systems. Rev. Geophys., 37(1), p. 127-150. Saar M. O., and Manga M. (2004). Depth dependence of permeability in the Oregon Cascades inferred from hydrogeologic, thermal, seismic, and magmatic modeling constraints. J. Geophys. Res., 109(B4), B04204, doi:10.1029/2003JB002855.
Harris, William M; Brinkman, Kyle S; Lin, Ye; Su, Dong; Cocco, Alex P; Nakajo, Arata; DeGostin, Matthew B; Chen-Wiegart, Yu-chen Karen; Wang, Jun; Chen, Fanglin; Chu, Yong S; Chiu, Wilson K S
2014-05-01
The microstructure and connectivity of the ionic and electronic conductive phases in composite ceramic membranes are directly related to device performance. Transmission electron microscopy (TEM) including chemical mapping combined with X-ray nanotomography (XNT) have been used to characterize the composition and 3-D microstructure of a MIEC composite model system consisting of a Ce0.8Gd0.2O2 (GDC) oxygen ion conductive phase and a CoFe2O4 (CFO) electronic conductive phase. The microstructural data is discussed, including the composition and distribution of an emergent phase which takes the form of isolated and distinct regions. Performance implications are considered with regards to the design of new material systems which evolve under non-equilibrium operating conditions. PMID:24615571
Jia, Jingjing; Sun, Xinying; Lin, Xiuyi; Shen, Xi; Mai, Yiu-Wing; Kim, Jang-Kyo
2014-06-24
Cellular-structured graphene foam (GF)/epoxy composites are prepared based on a three-step fabrication process involving infiltration of epoxy into the porous GF. The three-dimensional (3D) GF is grown on a Ni foam template via chemical vapor deposition. The 3D interconnected graphene network serves as fast channels for charge carriers, giving rise to a remarkable electrical conductivity of the composite, 3 S/cm, with only 0.2 wt % GF. The corresponding flexural modulus and strength increase by 53 and 38%, respectively, whereas the glass transition temperature increases by a notable 31 °C, compared to the solid neat epoxy. The GF/epoxy composites with 0.1 wt % GF also deliver an excellent fracture toughness of 1.78 MPa·m(1/2), 34 and 70% enhancements against their "porous" epoxy and solid epoxy counterparts, respectively. These observations signify the unrivalled effectiveness of 3D GF relative to 1D carbon nanotubes or 2D functionalized graphene sheets as reinforcement for polymer composites without issues of nanofiller dispersion and functionalization prior to incorporation into the polymer. PMID:24848106
NASA Astrophysics Data System (ADS)
Harris, William M.; Brinkman, Kyle S.; Lin, Ye; Su, Dong; Cocco, Alex P.; Nakajo, Arata; Degostin, Matthew B.; Chen-Wiegart, Yu-Chen Karen; Wang, Jun; Chen, Fanglin; Chu, Yong S.; Chiu, Wilson K. S.
2014-04-01
The microstructure and connectivity of the ionic and electronic conductive phases in composite ceramic membranes are directly related to device performance. Transmission electron microscopy (TEM) including chemical mapping combined with X-ray nanotomography (XNT) have been used to characterize the composition and 3-D microstructure of a MIEC composite model system consisting of a Ce0.8Gd0.2O2 (GDC) oxygen ion conductive phase and a CoFe2O4 (CFO) electronic conductive phase. The microstructural data is discussed, including the composition and distribution of an emergent phase which takes the form of isolated and distinct regions. Performance implications are considered with regards to the design of new material systems which evolve under non-equilibrium operating conditions.The microstructure and connectivity of the ionic and electronic conductive phases in composite ceramic membranes are directly related to device performance. Transmission electron microscopy (TEM) including chemical mapping combined with X-ray nanotomography (XNT) have been used to characterize the composition and 3-D microstructure of a MIEC composite model system consisting of a Ce0.8Gd0.2O2 (GDC) oxygen ion conductive phase and a CoFe2O4 (CFO) electronic conductive phase. The microstructural data is discussed, including the composition and distribution of an emergent phase which takes the form of isolated and distinct regions. Performance implications are considered with regards to the design of new material systems which evolve under non-equilibrium operating conditions. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr06684c
Xu, Hongmei; Wang, Huachun; Wu, Chenping; Lin, Na; Soomro, Abdul Majid; Guo, Huizhang; Liu, Chuan; Yang, Xiaodong; Wu, Yaping; Cai, Duanjun; Kang, JunYong
2015-06-28
Transparent conducting film occupies an important position in various optoelectronic devices. To replace the costly tin-doped indium oxide (ITO), promising materials, such as metal nanowires and graphene, have been widely studied. Moreover, a long-pursued goal is to consolidate these two materials together and express their outstanding properties simultaneously. We successfully achieved a direct 3D coating of a graphene layer on an interlacing Cu nanosilks network by the low pressure chemical vapor deposition method. High aspect ratio Cu nanosilks (13 nm diameter with 40 ?m length) were synthesized through the nickel ion catalytic process. Large-size, transparent conducting film was successfully fabricated with Cu nanosilks ink by the imprint method. A magnetic manipulator equipped with a copper capsule was used to produce high Cu vapor pressure on Cu nanosilks and realize the graphene 3D-coating. The coated Cu@graphene nanosilks network achieved high transparency, low sheet resistance (41 Ohm sq(-1) at 95% transmittance) and robust antioxidant ability. With this technique, the transfer process of graphene is no longer needed, and a flexible, uniform and high-performance transparent conducting film could be fabricated in unlimited size. PMID:26018299
3D City modeling for urban scale heating energy demand forecasting
Aneta Strzalka; Jürgen Bogdahn; Volker Coors; Ursula Eicker
2011-01-01
An urban energy management tool was developed, which is able to predict the heating energy demand of urban districts and analyze strategies for improving building standards. Building models of different Levels of Detail are investigated and analyzed according to their suitability for forecasting energy demand. Based on the specific 3D city model, an input file is generated, which can be
Pattern Transformation of Heat-Shrinkable Polymer by Three-Dimensional (3D) Printing Technique
NASA Astrophysics Data System (ADS)
Zhang, Quan; Yan, Dong; Zhang, Kai; Hu, Gengkai
2015-03-01
A significant challenge in conventional heat-shrinkable polymers is to produce controllable microstructures. Here we report that the polymer material fabricated by three-dimensional (3D) printing technique has a heat-shrinkable property, whose initial microstructure can undergo a spontaneous pattern transformation under heating. The underlying mechanism is revealed by evaluating internal strain of the printed polymer from its fabricating process. It is shown that a uniform internal strain is stored in the polymer during the printing process and can be released when heated above its glass transition temperature. Furthermore, the internal strain can be used to trigger the pattern transformation of the heat-shrinkable polymer in a controllable way. Our work provides insightful ideas to understand a novel mechanism on the heat-shrinkable effect of printed material, but also to present a simple approach to fabricate heat-shrinkable polymer with a controllable thermo-structural response.
Pattern transformation of heat-shrinkable polymer by three-dimensional (3D) printing technique.
Zhang, Quan; Yan, Dong; Zhang, Kai; Hu, Gengkai
2015-01-01
A significant challenge in conventional heat-shrinkable polymers is to produce controllable microstructures. Here we report that the polymer material fabricated by three-dimensional (3D) printing technique has a heat-shrinkable property, whose initial microstructure can undergo a spontaneous pattern transformation under heating. The underlying mechanism is revealed by evaluating internal strain of the printed polymer from its fabricating process. It is shown that a uniform internal strain is stored in the polymer during the printing process and can be released when heated above its glass transition temperature. Furthermore, the internal strain can be used to trigger the pattern transformation of the heat-shrinkable polymer in a controllable way. Our work provides insightful ideas to understand a novel mechanism on the heat-shrinkable effect of printed material, but also to present a simple approach to fabricate heat-shrinkable polymer with a controllable thermo-structural response. PMID:25757881
3-D thermal modelling applied to stress-induced anisotropy of thermal conductivity
H. Pron; C. Bissieux
2004-01-01
The present work consists in the development of a three-dimensional model of heat diffusion in orthotropic media, based on numerical Fourier transforms, and taking into account the extent of the source. This model has been applied, together with a Gauss–Newton parameter estimation procedure, to identify the components of the conductivity tensor of a steel bar under uniaxial loading. Few percent
An End-to-End Approach to Making Self-Folded 3D Surface Shapes by Uniform Heating
Wood, Robert
a 3D geometric specification using print-and-fold processes. We have pre- viously demonstratedAn End-to-End Approach to Making Self-Folded 3D Surface Shapes by Uniform Heating Byoungkwon An, Robert J. Wood and Daniela Rus Abstract-- This paper presents an end-to-end approach for creating 3D
Microwave heating of conductive powder materials
K. I. Rybakov; V. E. Semenov; S. V. Egorov; A. G. Eremeev; I. V. Plotnikov; Yu. V. Bykov
2006-01-01
In recent years, a considerable interest has been drawn to microwave heating of powder metals and other electrically conductive materials. In this paper a consistent formulation describing the absorption of microwaves in electrically conductive materials under different microwave heating conditions is developed. A special case when conductive powder particles are surrounded by insulating oxide layers is investigated in detail using
Microwave heating of electrically conductive materials
NASA Astrophysics Data System (ADS)
Rybakov, K. I.; Semenov, V. E.
2005-10-01
In recent years, considerable interest has been drawn to microwave heating of powder metals and other electrically conductive materials. In this paper, we consider absorption of electromagnetic waves in materials with different effective conductivities for different microwave heating conditions. Specific features of microwave heating at the maxima of electric and magnetic fields in a standing-wave applicator are discussed. Absorption in materials containing conductive particles with dielectric shells are studied in detail using the effective-medium approximation.
Variable boundary II heat conduction
NASA Technical Reports Server (NTRS)
Gramer, J.; Oneill, R. F.
1972-01-01
Computer program for solving both transient and steady-state heat transfer problems is presented. Specific applications of computer program are described. Formulation for individual nodes of solid medium for heat balance is presented. Diffusion equation is solved for all nodes simultaneously at finite increments of time.
Heat Transfer Derivation of differential equations for heat transfer conduction
Veress, Alexander
Heat Transfer Derivation of differential equations for heat transfer conduction without convection/(hftF). T is the temperature, in C or F. dT=dx is the temperature gradient, in C/m or F/ft. This equation states that the heat sign in the above equation states heat flow is positive in the direction opposite the direction
Microwave heating of conductive powder materials
NASA Astrophysics Data System (ADS)
Rybakov, K. I.; Semenov, V. E.; Egorov, S. V.; Eremeev, A. G.; Plotnikov, I. V.; Bykov, Yu. V.
2006-01-01
In recent years, a considerable interest has been drawn to microwave heating of powder metals and other electrically conductive materials. In this paper a consistent formulation describing the absorption of microwaves in electrically conductive materials under different microwave heating conditions is developed. A special case when conductive powder particles are surrounded by insulating oxide layers is investigated in detail using the effective-medium approximation. The conditions giving rise to skin effect governed, volumetric, and localized microwave heating are analyzed. Experimental observations of different microwave heating regimes in silicon, iron, and copper powder compacts are in general agreement with the theoretical model.
Ballistic-Diffusive Heat-Conduction Equations
Gang Chen; Gang
2001-01-01
We present new heat-conduction equations, named ballistic-diffusive equations, which are derived from the Boltzmann equation. We show that the new equations are a better approximation than the Fourier law and the Cattaneo equation for heat conduction at the scales when the device characteristic length, such as film thickness, is comparable to the heat-carrier mean free path and\\/or the characteristic time,
Heat conduction in heterogeneous materials
J. Baker-Jarvis; R. Inguva
1985-01-01
A new solution to the heat equation in composite media is derived using a variational principle developed by Ben-Amoz. The model microstructure is fed into the equations via a term for the polar moment of the inclusions in a representative volume. The general solution is presented as an integral in terms of sources and a Green function. The problem of
3D modelling of coupled mass and heat transfer of a convection-oven roasting process.
Feyissa, Aberham Hailu; Gernaey, Krist V; Adler-Nissen, Jens
2013-04-01
A 3D mathematical model of coupled heat and mass transfer describing oven roasting of meat has been developed from first principles. The proposed mechanism for the mass transfer of water is modified and based on a critical literature review of the effect of heat on meat. The model equations are based on a conservation of mass and energy, coupled through Darcy's equations of porous media - the water flow is mainly pressure-driven. The developed model together with theoretical and experimental assessments were used to explain the heat and water transport and the effect of the change in microstructure (permeability, water binding capacity and elastic modulus) that occur during the meat roasting process. The developed coupled partial differential equations were solved by using COMSOL Multiphysics®3.5 and state variables are predicted as functions of both position and time. The proposed mechanism was partially validated by experiments in a convection oven where temperatures were measured online. PMID:23305831
Raj, Kovummal Govind; Joy, Pattayil Alias
2015-06-28
The changes in the electrical transport properties and mechanism of conduction in disordered carbon, with the extent of graphitization, are studied and discussed. With heat treatment induced graphitic ordering, the electrical properties are considerably modified, inducing a crossover from strong localization to weak localization behavior. Accordingly, the conduction mechanism is modified from the 3-dimensional variable range hopping (3D VRH) model to the 2-dimensional weak localization (2D WL) model. Results show that carrier-carrier and carrier-phonon interactions play major roles in developing the weak localization behavior with the extent of graphitization. PMID:26035227
NASA Astrophysics Data System (ADS)
Courbet, C.; DICK, P.; Lefevre, M.; Wittebroodt, C.; Matray, J.; Barnichon, J.
2013-12-01
In the framework of its research on the deep disposal of radioactive waste in shale formations, the French Institute for Radiological Protection and Nuclear Safety (IRSN) has developed a large array of in situ programs concerning the confining properties of shales in their underground research laboratory at Tournemire (SW France). One of its aims is to evaluate the occurrence and processes controlling radionuclide migration through the host rock, from the disposal system to the biosphere. Past research programs carried out at Tournemire covered mechanical, hydro-mechanical and physico-chemical properties of the Tournemire shale as well as water chemistry and long-term behaviour of the host rock. Studies show that fluid circulations in the undisturbed matrix are very slow (hydraulic conductivity of 10-14 to 10-15 m.s-1). However, recent work related to the occurrence of small scale fractures and clay-rich fault gouges indicate that fluid circulations may have been significantly modified in the vicinity of such features. To assess the transport properties associated with such faults, IRSN designed a series of in situ and laboratory experiments to evaluate the contribution of both diffusive and advective process on water and solute flux through a clay-rich fault zone (fault core and damaged zone) and in an undisturbed shale formation. As part of these studies, Modular Mini-Packer System (MMPS) hydraulic testing was conducted in multiple boreholes to characterize hydraulic conductivities within the formation. Pressure data collected during the hydraulic tests were analyzed using the nSIGHTS (n-dimensional Statistical Inverse Graphical Hydraulic Test Simulator) code to estimate hydraulic conductivity and formation pressures of the tested intervals. Preliminary results indicate hydraulic conductivities of 5.10-12 m.s-1 in the fault core and damaged zone and 10-14 m.s-1 in the adjacent undisturbed shale. Furthermore, when compared with neutron porosity data from borehole logging, porosity varies by a factor of 2.5 whilst hydraulic conductivity varies by 2 to 3 orders of magnitude. In addition, a 3D numerical reconstruction of the internal structure of the fault zone inferred from borehole imagery has been built to estimate the permeability tensor variations. First results indicate that hydraulic conductivity values calculated for this structure are 2 to 3 orders of magnitude above those measured in situ. Such high values are due to the imaging method that only takes in to account open fractures of simple geometry (sine waves). Even though improvements are needed to handle more complex geometry, outcomes are promising as the fault damaged zone clearly appears as the highest permeability zone, where stress analysis show that the actual stress state may favor tensile reopening of fractures. Using shale samples cored from the different internal structures of the fault zone, we aim now to characterize the advection and diffusion using laboratory petrophysical tests combined with radial and through-diffusion experiments.
Information filtering via biased heat conduction.
Liu, Jian-Guo; Zhou, Tao; Guo, Qiang
2011-09-01
The process of heat conduction has recently found application in personalized recommendation [Zhou et al., Proc. Natl. Acad. Sci. USA 107, 4511 (2010)], which is of high diversity but low accuracy. By decreasing the temperatures of small-degree objects, we present an improved algorithm, called biased heat conduction, which could simultaneously enhance the accuracy and diversity. Extensive experimental analyses demonstrate that the accuracy on MovieLens, Netflix, and Delicious datasets could be improved by 43.5%, 55.4% and 19.2%, respectively, compared with the standard heat conduction algorithm and also the diversity is increased or approximately unchanged. Further statistical analyses suggest that the present algorithm could simultaneously identify users' mainstream and special tastes, resulting in better performance than the standard heat conduction algorithm. This work provides a creditable way for highly efficient information filtering. PMID:22060533
Information filtering via biased heat conduction
NASA Astrophysics Data System (ADS)
Liu, Jian-Guo; Zhou, Tao; Guo, Qiang
2011-09-01
The process of heat conduction has recently found application in personalized recommendation [Zhou , Proc. Natl. Acad. Sci. USA PNASA60027-842410.1073/pnas.1000488107107, 4511 (2010)], which is of high diversity but low accuracy. By decreasing the temperatures of small-degree objects, we present an improved algorithm, called biased heat conduction, which could simultaneously enhance the accuracy and diversity. Extensive experimental analyses demonstrate that the accuracy on MovieLens, Netflix, and Delicious datasets could be improved by 43.5%, 55.4% and 19.2%, respectively, compared with the standard heat conduction algorithm and also the diversity is increased or approximately unchanged. Further statistical analyses suggest that the present algorithm could simultaneously identify users' mainstream and special tastes, resulting in better performance than the standard heat conduction algorithm. This work provides a creditable way for highly efficient information filtering.
A phase-field method for 3D simulation of two-phase heat transfer , H. Babaee a
Dong, Suchuan "Steven"
A phase-field method for 3D simulation of two-phase heat transfer X. Zheng a , H. Babaee a , S s t r a c t We formulate new multi-phase convective heat transfer equations by combining the three for convergence in time/space including a conjugate heat transfer problem and also for a realistic tran- sient
Conductive-bridging random access memory: challenges and opportunity for 3D architecture
NASA Astrophysics Data System (ADS)
Jana, Debanjan; Roy, Sourav; Panja, Rajeswar; Dutta, Mrinmoy; Rahaman, Sheikh Ziaur; Mahapatra, Rajat; Maikap, Siddheswar
2015-04-01
The performances of conductive-bridging random access memory (CBRAM) have been reviewed for different switching materials such as chalcogenides, oxides, and bilayers in different structures. The structure consists of an inert electrode and one oxidized electrode of copper (Cu) or silver (Ag). The switching mechanism is the formation/dissolution of a metallic filament in the switching materials under external bias. However, the growth dynamics of the metallic filament in different switching materials are still debated. All CBRAM devices are switching under an operation current of 0.1 ?A to 1 mA, and an operation voltage of ±2 V is also needed. The device can reach a low current of 5 pA; however, current compliance-dependent reliability is a challenging issue. Although a chalcogenide-based material has opportunity to have better endurance as compared to an oxide-based material, data retention and integration with the complementary metal-oxide-semiconductor (CMOS) process are also issues. Devices with bilayer switching materials show better resistive switching characteristics as compared to those with a single switching layer, especially a program/erase endurance of >105 cycles with a high speed of few nanoseconds. Multi-level cell operation is possible, but the stability of the high resistance state is also an important reliability concern. These devices show a good data retention of >105 s at >85°C. However, more study is needed to achieve a 10-year guarantee of data retention for non-volatile memory application. The crossbar memory is benefited for high density with low power operation. Some CBRAM devices as a chip have been reported for proto-typical production. This review shows that operation current should be optimized for few microamperes with a maintaining speed of few nanoseconds, which will have challenges and also opportunities for three-dimensional (3D) architecture.
Conductive-bridging random access memory: challenges and opportunity for 3D architecture.
Jana, Debanjan; Roy, Sourav; Panja, Rajeswar; Dutta, Mrinmoy; Rahaman, Sheikh Ziaur; Mahapatra, Rajat; Maikap, Siddheswar
2015-01-01
The performances of conductive-bridging random access memory (CBRAM) have been reviewed for different switching materials such as chalcogenides, oxides, and bilayers in different structures. The structure consists of an inert electrode and one oxidized electrode of copper (Cu) or silver (Ag). The switching mechanism is the formation/dissolution of a metallic filament in the switching materials under external bias. However, the growth dynamics of the metallic filament in different switching materials are still debated. All CBRAM devices are switching under an operation current of 0.1 ?A to 1 mA, and an operation voltage of ±2 V is also needed. The device can reach a low current of 5 pA; however, current compliance-dependent reliability is a challenging issue. Although a chalcogenide-based material has opportunity to have better endurance as compared to an oxide-based material, data retention and integration with the complementary metal-oxide-semiconductor (CMOS) process are also issues. Devices with bilayer switching materials show better resistive switching characteristics as compared to those with a single switching layer, especially a program/erase endurance of >10(5) cycles with a high speed of few nanoseconds. Multi-level cell operation is possible, but the stability of the high resistance state is also an important reliability concern. These devices show a good data retention of >10(5) s at >85°C. However, more study is needed to achieve a 10-year guarantee of data retention for non-volatile memory application. The crossbar memory is benefited for high density with low power operation. Some CBRAM devices as a chip have been reported for proto-typical production. This review shows that operation current should be optimized for few microamperes with a maintaining speed of few nanoseconds, which will have challenges and also opportunities for three-dimensional (3D) architecture. PMID:25977660
NASA Astrophysics Data System (ADS)
Püthe, Christoph; Kuvshinov, Alexey
2014-05-01
We present a novel 3-D frequency-domain inversion scheme to recover 3-D mantle conductivity from satellite magnetic data, for example, provided by the Swarm mission. The scheme is based on the inversion of a new set of electromagnetic transfer functions, which form an array that we denote as matrix Q-response and which relate external (inducing) and internal (induced) coefficients of the spherical harmonic expansion of the time-varying magnetic field of magnetospheric origin. This concept overcomes the problems associated with source determination inherent to recent schemes based on direct inversion of internal coefficients. Matrix Q-responses are estimated from time-series of external and internal coefficients with a newly elaborated multivariate analysis scheme. An inversion algorithm that deals with matrix Q-responses has been developed. In order to make the inversion tractable, we elaborated an adjoint approach to compute the data misfit gradient and parallelized the numerical code with respect to frequencies and elementary sources, which describe the external part of the magnetic field of magnetospheric origin. Both parts of the scheme have been verified with realistic test data. Special attention is given to the issue of correlated noise due to undescribed sources.
Lee, Sang-Heon; Jung, Jung-Hwan; Oh, Il-Kwon
2014-10-15
A novel 3D networked graphene-ferromagnetic hybrid can be easily fabricated using one-step microwave irradiation. By incorporating this hybrid material into shape memory polymers, the synergistic effects of fast speed and the enhancement of thermal conductivity and mechanical stiffness can be achieved. This can be broadly applicable to designing magneto-responsive shape memory polymers for multifunction applications. PMID:24912455
3D multifields FEM computation of transverse flux induction heating for moving-strips
Z. Wang; W. Huang; W. Jia; Q. Zhao; Y. Wang; W. Yan; D. Schulze; G. Martin; U. Luedtke
1999-01-01
The numerical and experimental studies on induction heating of continuously moving strips in a transverse field are presented in this paper. The induced eddy current and its coupled thermal field in moving media is computed with FEM. The adopted mathematical model consists of a Fourier thermal conduction equation and a set of differential equations, which describes the steady-state eddy current
The effect of anisotropic heat transport on magnetic islands in 3-D configurations
Schlutt, M. G.; Hegna, C. C. [University of Wisconsin-Madison, 1500 Engineering Drive, 510 ERB, Madison, Wisconsin 53706 (United States)
2012-08-15
An analytic theory of nonlinear pressure-induced magnetic island formation using a boundary layer analysis is presented. This theory extends previous work by including the effects of finite parallel heat transport and is applicable to general three dimensional magnetic configurations. In this work, particular attention is paid to the role of finite parallel heat conduction in the context of pressure-induced island physics. It is found that localized currents that require self-consistent deformation of the pressure profile, such as resistive interchange and bootstrap currents, are attenuated by finite parallel heat conduction when the magnetic islands are sufficiently small. However, these anisotropic effects do not change saturated island widths caused by Pfirsch-Schlueter current effects. Implications for finite pressure-induced island healing are discussed.
Determination of the heat transfer coefficients in transient heat conduction
NASA Astrophysics Data System (ADS)
Nho Hào, Dinh; Thanh, Phan Xuan; Lesnic, D.
2013-09-01
The determination of the space- or time-dependent heat transfer coefficient which links the boundary temperature to the heat flux through a third-kind Robin boundary condition in transient heat conduction is investigated. The reconstruction uses average surface temperature measurements. In both cases of the space- or time-dependent unknown heat transfer coefficient the inverse problems are nonlinear and ill posed. Least-squares penalized variational formulations are proposed and new formulae for the gradients are derived. Numerical results obtained using the nonlinear conjugate gradient method combined with a boundary element direct solver are presented and discussed.
Ph. Testé; T. Leblanc; F. Uhlig; J.-P. Chabrerie
2000-01-01
Within the framework of the study of the aircraft structural material lightning, we present a work concerning the heating of metal sheets under the action of a moving electric arc. A 2D and 3D modeling of thermal phenomena occurring in the heated electrodes are used in order to study the influence of the arc root velocity and of the power
NASA Astrophysics Data System (ADS)
Mather, B.; Moresi, L. N.; Cruden, A. R.
2014-12-01
Uncertainty of the lithospheric thermal regime greatly increases with depth. Measurements of temperature gradient and crustal rheology are concentrated in the upper crust, whereas the majority of the lithospheric measurements are approximated using empirical depth-dependent functions. We have applied a Monte Carlo approach to test the variation of crustal heat flow with temperature-dependent conductivity and the redistribution of heat-producing elements. The dense population of precision heat flow data in Victoria, Southeast Australia offers the ideal environment to test the variation of heat flow. A stochastically consistent anomalous zone of impossibly high Moho temperatures in the 3D model (> 900°C) correlates well with a zone of low teleseismic velocity and high electrical conductivity. This indicates that transient heat transfer has perturbed the thermal gradient and therefore a steady-state approach to 3D modelling is inappropriate in this zone. A spatial correlation between recent intraplate volcanic eruption points (< 5 Ma) and elevated Moho temperatures is a potential origin for additional latent heat in the crust.
Large variable conductance heat pipe. Transverse header
NASA Technical Reports Server (NTRS)
Edelstein, F.
1975-01-01
The characteristics of gas-loaded, variable conductance heat pipes (VCHP) are discussed. The difficulties involved in developing a large VCHP header are analyzed. The construction of the large capacity VCHP is described. A research project to eliminate some of the problems involved in large capacity VCHP operation is explained.
Heat-Conducting Anchors for Thermocouples
NASA Technical Reports Server (NTRS)
Macdavid, Kenton S.
1987-01-01
Metal particles in adhesive aid heat transfer. Aluminum caps containing silver-filled epoxy used as high-thermal-conductance anchors for thermocouples, epoxy providing thermal path between mounting surfaces and thermocouple measuring junctions. Normally, epoxy-filled aluminum caps used when measuring steady-state temperatures. Silver-filled epoxy used when thermocouple not isolated electrically from surface measured.
High conductive heat-resistant aluminium alloy
Sato, K.; Hanaki, Y.; Kondo, T.; Yamauchi, K.; Yokota, M.
1983-09-06
A heat-resistant aluminum alloy is disclosed for electrical use, having high heat resistance and conductivity, obtained by subjecting an Al-Zr alloy comprising 0.23-0.35% Zr, the balance consisting of ordinary impurities and aluminum, to melting, casting, hot rolling in the state of high temperature or continuous heating, cold working to a predetermined size, ageing at a temperature within the range of 310/sup 0/ C.-390/sup 0/ C. for 50-400 hours so that Al/sub 3/Zr is dispersed uniformly and in fine particles, and, optionally, further cold working to a degree not exceeding 30% of reduction of area. The resultant aluminum alloy has conductivity in excess of 58% IACS, same strength as 1350 aluminum wire, and 10% softening temperature higher than 400/sup 0/ C. at one hour annealing.
3D Digitization of Metallic Specular Surfaces using Scanning from Heating Approach
Paris-Sud XI, Université de
by a camera. Due to specularity of the surface, the classical 3D scanning approach, using laser triangulation sensor embedded in the scanner. Figure 1: (a) Specular object, (b) 3D Reconstruction by Minolta VI-910. As classical laser triangulation based method are not able to measure 3D points on specular surfaces
Heat Rejection from a Variable Conductance Heat Pipe Radiator Panel
NASA Technical Reports Server (NTRS)
Jaworske, D. A.; Gibson, M. A.; Hervol, D. S.
2012-01-01
A titanium-water heat pipe radiator having an innovative proprietary evaporator configuration was evaluated in a large vacuum chamber equipped with liquid nitrogen cooled cold walls. The radiator was manufactured by Advanced Cooling Technologies, Inc. (ACT), Lancaster, PA, and delivered as part of a Small Business Innovative Research effort. The radiator panel consisted of five titanium-water heat pipes operating as thermosyphons, sandwiched between two polymer matrix composite face sheets. The five variable conductance heat pipes were purposely charged with a small amount of non-condensable gas to control heat flow through the condenser. Heat rejection was evaluated over a wide range of inlet water temperature and flow conditions, and heat rejection was calculated in real-time utilizing a data acquisition system programmed with the Stefan-Boltzmann equation. Thermography through an infra-red transparent window identified heat flow across the panel. Under nominal operation, a maximum heat rejection value of over 2200 Watts was identified. The thermal vacuum evaluation of heat rejection provided critical information on understanding the radiator s performance, and in steady state and transient scenarios provided useful information for validating current thermal models in support of the Fission Power Systems Project.
Hydrogels of a conducting conjugated polymer as 3-D enzyme electrode
Peter Åsberg; Olle Inganäs
2003-01-01
We have utilized the highly conducting poly(3,4-ethylenedioxythiophene)\\/poly(styrenesulfonate) aqueous dispersion (PEDOT\\/PSS) to build a conducting hydrogel matrix. Together with appropriate biomolecules this constitutes a hydrogel bio-electrode. The open hydrogel structure makes diffusion of analytes surrounding the cells into the matrix electrode easier. If enzymes are utilized, osmium is used as mediator between the prosthetic group of the enzyme and the conducting
Measurement of 3-D hydraulic conductivity in aquifer cores at in situ effective stresses.
Wright, Martin; Dillon, Peter; Pavelic, Paul; Peter, Paul; Nefiodovas, Andrew
2002-01-01
An innovative and nondestructive method to measure the hydraulic conductivity of drill core samples in horizontal and vertical directions within a triaxial cell has been developed. This has been applied to characterizing anisotropy and heterogeneity of a confined consolidated limestone aquifer. Most of the cores tested were isotropic, but hydraulic conductivity varied considerably and the core samples with lowest values were also the most anisotropic. Hydraulic conductivity decreased with increasing effective stress due to closure of microfractures caused by sampling for all core samples. This demonstrates the importance of replicating in situ effective stresses when measuring hydraulic conductivity of cores of deep aquifers in the laboratory. PMID:12236264
3-D FEM magneto-thermal analysis in microwave ovens
A. Sekkak; L. Pichon; A. Razek
1994-01-01
A 3-D coupled electromagnetic and thermal model has been developed for analysis of microwave heating process. The electromagnetic computation is performed with 3-D edge elements. This technique leads to an accurate deterministic study of the electromagnetic field distribution in excited junctions containing lossy dielectrics. The heat conduction equation is solved with 3-D nodal elements. The temperature dependance of the electromagnetic
Comparison of Conductances derived from IDA3D and TIMEGCM with GUVI
A. S. Reynolds; G. W. Crowley; G. S. Bust; L. Paxton; A. Christensen; J. Secan; R. Smith
2006-01-01
The Global Ultraviolet Imager (GUVI) instrument on the TIMED satellite measures various auroral parameters including the energy and flux distributions, which can then be used to estimate auroral conductances. In this paper, we compare GUVI conductances with those obtained from an ionospheric data assimilation imaging algorithm. The comparison is focused on the Alaska region, where five tomographic receivers collected data
NASA Astrophysics Data System (ADS)
Gasch, Caley K.; Hengl, Tomislav; Gräler, Benedikt; Meyer, Hanna; Magney, Troy; Brown, David J.
2015-04-01
Dynamic soil data collected using automated sensor networks can facilitate our understanding of soil processes, but highly dimensional data may be difficult to analyze in a manner that incorporates correlation in properties through 3-dimensions and time (3D+T). We demonstrate two approaches to making continuous predictions of dynamic soil properties from fixed point observations. For this analysis, we used the Cook Farm data set, which includes hourly measurements of soil volumetric water content, temperature, and electrical conductivity at 42 points and five depths, collected over five years. We compare performance of two modeling frameworks. In the first framework we used random forest algorithms to fit a 3D+T regression model to make predictions of all three soil variables from 2- and 3-dimensional, temporal, and spatio-temporal covariates. In the second framework we developed a 3D+T kriging model after detrending the observations for depth-dependent seasonal effects. The results show that both models accurately predicted soil temperature, but the kriging model outperformed the regression model according to cross-validation; it explained 37%, 96%, and 16% of the variability in water content, temperature, and electrical conductivity respectively versus 34%, 93%, and 4% explained by the random forest model. The full random forest regression model had high goodness-of-fit for all variables, which was reduced in cross-validation. Temporal model components (i.e. day of the year) explained most of the variability in observations. The seamless predictions of 3D+T data produced from this analysis can assist in understanding soil processes and how they change through a season, under different land management scenarios, and how they relate to other environmental processes.
Heat conduction of laser vanadate crystals
Zagumennyi, A I; Zavartsev, Yu D; Kutovoi, S A; Shcherbakov, I A [A.M. Prokhorov General Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation); Popov, P A [Acad. I. G. Petrovskii Bryansk State University, Bryansk (Russian Federation); Zerouk, F [Zecotek Medical Systems Ltd (Singapore)
2008-03-31
The heat conduction of laser vanadate crystals GdVO{sub 4} and YVO{sub 4} and their solid solutions is measured in the temperature interval from 50 to 350 K. Mixed rare-earth vanadates have the common chemical formula Re'{sub 1-x}Re''{sub x}VO{sub 4}, where Re' and Re'' are two or more types of ions from a series La{sup 3+}, Pr{sup 3+}, Nd{sup 3+}, Sm{sup 3+}, Eu{sup 3+}, Gd{sup 3+}, Tb{sup 3+}, Dy{sup 3+}, Ho{sup 3+}, Er{sup 3+}, Tm{sup 3+}, Yb{sup 3+}, Lu{sup 3+}, Sc{sup 3+}, Y{sup 3+}. The heat conduction of Nd:YVO{sub 4} measured at room temperature proved to be more than twice higher than that reported in the literature and in certificate characteristics of laser Nd:YVO{sub 4} elements manufactured by numerous commercial companies. The empirical dependences of the heat conduction along the crystallographic axes <100> and <001> on the composition of rare-earth vanadates Re'{sub 1-x}Re''{sub x}VO{sub 4}, are obtained in the temperature interval from 200 to 350 K. (active media)
NASA Astrophysics Data System (ADS)
Semenov, Alexey; Kuvshinov, Alexey
2012-12-01
The global 3-D electrical conductivity distribution in the mantle (in the depth range between 400 and 1600 km) is imaged by inverting C-responses estimated on a global net of geomagnetic observatories. Very long time-series (up to 51 years; 1957-2007) of hourly means of three components of the geomagnetic field from 281 geomagnetic observatories are collected and analysed. Special attention is given to data processing in order to obtain unbiased C-responses with trustworthy estimates of experimental errors in the period range from 2.9 to 104.2 d. After careful inspection of the obtained C-responses the data from 119 observatories are chosen for the further analysis. Squared coherency is used as a main quality indicator to detect (and then to exclude from consideration) observatories with a large noise-to-signal ratio. During this analysis we found that—along with the C-responses from high-latitude observatories (geomagnetic latitudes higher than 58°)—the C-responses from all low-latitude observatories (geomagnetic latitudes below 11°) also have very low squared coherencies, and thus cannot be used for global induction studies. We found that the C-responses from the selected 119 mid-latitude observatories show a huge variability both in real and imaginary parts, and we investigated to what extent the ocean effect can explain such a scatter. By performing the systematic model calculations we conclude that: (1) the variability due to the ocean effect is substantial, especially at shorter periods, and it is seen for periods up to 40 d or so; (2) the imaginary part of the C-responses is to a larger extent influenced by the oceans; (3) two types of anomalous C-response behaviour associated with the ocean effect can be distinguished; (4) to accurately reproduce the ocean effect a lateral resolution of 1°× 1° of the conductance distribution is needed, and (5) the ocean effect alone does not explain the whole variability of the observed C-responses. We also detected that part of the variability in the real part of the C-responses is due to the auroral effect. In addition we discovered that the auroral effect in the C-responses reveals strong longitudinal variability, at least in the Northern Hemisphere. Europe appears to be the region with smallest degree of distortion compared with North America and northern Asia. We found that the imaginary part of the C-responses is weakly affected by the auroral source, thus confirming the fact that in the considered period range the electromagnetic (EM) induction from the auroral electrojet is small. Assuming weak dependence of the auroral signals on the Earth's conductivity at considered periods, and longitudinal variability of the auroral effect, we developed a scheme to correct the experimental C-responses for this effect. With these developments and findings in mind we performed a number of regularized 3-D inversions of our experimental data in order to detect robust features in the recovered 3-D conductivity images. Although differing in details, all our 3-D inversions reveal a substantial level of lateral heterogeneity in the mantle at the depths between 410 and 1600 km. Conductivity values vary laterally by more than one order of magnitude between resistive and conductive regions. The maximum lateral variations of the conductivity have been detected in the layer at depths between 670 and 900 km. By comparing our global 3-D results with the results of independent global and semi-global 3-D conductivity studies, we conclude that 3-D conductivity mantle models produced so far are preliminary as different groups obtain disparate results, thus complicating quantitative comparison with seismic tomography or/and geodynamic models. In spite of this, our 3-D EM study and most other 3-D EM studies reveal at least two robust features: reduced conductivity beneath southern Europe and northern Africa, and enhanced conductivity in northeastern China.
Remote Sensing of 3-D Conducting Objects in a Layered Medium Using Electromagnetic Surface Waves
Marius Birsan
2007-01-01
Antennas that are located on or near the boundary between two electrically different media, such as air and earth, or seawater and rock, are used as prospective tools for remote sensing and geophysical exploration. As an example, this letter examines the electromagnetic (EM) response of a metallic object that is submerged in a conducting layer of seawater that is situated
Electrical Conductivity Study of Carbon Nanotube Yarns, 3-D Hybrid Braids and their Composites
Philip D. Bradford; Alexander E. Bogdanovich
2008-01-01
Long continuous yarns consisting solely of carbon nanotubes may be the future of specialty composites requiring unique multi-functional properties. Many of such yarns were incorporated in a hybrid composite here, to demonstrate for the first time, their effect on increasing the electrical conductivity of an otherwise insulating composite. Six-ply nanotube yarns produced by University of Texas at Dallas were used
Conductance Fluctuations of the Chiral Surface Sheath in the 3D Quantum Hall Effect
NASA Astrophysics Data System (ADS)
Druist, David P.; Schmidt, D. R.; Walling, H. W.; Gwinn, E. G.; Maranowski, K. D.; Gossard, A. C.
2000-03-01
In quantum Hall(QH) states of semiconductor multilayers, vertical transport at low temperature is along a 2D chiral sheath of edge states that forms at the surface of the multilayer. Sweeping the magnetic field across these QH states produces small, reproducible fluctuations in the vertical conductance about a slowly varying background, similar to the universal conductance fluctuations observed in metallic samples. In inversion layers and heterojunctions, the magnetoconductance pattern is dependent only on the magnetic field perpendicular to the 2DEG, and the fluctuations are interpreted as changes in quantum interference patterns of the electronic wavefunctions produced by magnetic flux through electron trajectories. In order to see if this type of picture holds for the edge state sheath, we measure the vertical conductance of GaAs/AlGaAs modulation doped superlattices at low temperatures as the sample is tilted with respect to the magnetic field. We will discuss the angular dependence of the amplitude and correlation field of the fluctuations, and the role of the method used to prepare the surface of the samples.
Shape factors in conductive heat transfer
Faulkner, Richard Campbell
1954-01-01
Vs L 2/9, ; Ll/9, O. 166V. . . . . 54 XL Vs L 2/Do, L /D 0. 250Q. L Vs L. /9; L /9 0. 5555. . . . . 56 LX Vs L /9 ; Ll/9 0. 3. 667. . . . . 5V LXI Vs L 2/9, ; Ll/9 O. 25OO. . . . . 52 XXII Pactox 1-2 Vs L 2/9 ; L /9 0, 5555, LXV abactor 1-2 Vs Ll/9...: q e -k(~)ZT hT q = Heat flow, Btu/Hr k = Thexmal conductivity, -Btu Jk ~ Lrea, ZtB I ~ length of. heat flow path& Jt 6 T = Temperatux e di f f er ence, dp. R Resistance, (op Zt)pt. ln othex simple cases, such as the cylinder and, the sphex...
Information filtering via weighted heat conduction algorithm
NASA Astrophysics Data System (ADS)
Liu, Jian-Guo; Guo, Qiang; Zhang, Yi-Cheng
2011-06-01
In this paper, by taking into account effects of the user and object correlations on a heat conduction (HC) algorithm, a weighted heat conduction (WHC) algorithm is presented. We argue that the edge weight of the user-object bipartite network should be embedded into the HC algorithm to measure the object similarity. The numerical results indicate that both the accuracy and diversity could be improved greatly compared with the standard HC algorithm and the optimal values reached simultaneously. On the Movielens and Netflix datasets, the algorithmic accuracy, measured by the average ranking score, can be improved by 39.7% and 56.1% in the optimal case, respectively, and the diversity could reach 0.9587 and 0.9317 when the recommendation list equals to 5. Further statistical analysis indicates that, in the optimal case, the distributions of the edge weight are changed to the Poisson form, which may be the reason why HC algorithm performance could be improved. This work highlights the effect of edge weight on a personalized recommendation study, which maybe an important factor affecting personalized recommendation performance.
CONDUCTION HEAT TRANSFER Dr. Ruhul Amin Fall 2011
Dyer, Bill
ME 525 CONDUCTION HEAT TRANSFER Dr. Ruhul Amin Fall 2011 Office: 201C Roberts Hall Lecture Room of conduction heat transfer. Important results which are useful for engineering application will also: 121 Roberts Hall Phone: 994-6295 Lecture Periods: 12:45- 2:00, TR TEXT: Heat Conduction, M. N. Ozisik
Nonintegrability and the Fourier heat conduction law
NASA Astrophysics Data System (ADS)
Chen, Shunda; Wang, Jiao; Casati, Giulio; Benenti, Giuliano
2014-09-01
We study in momentum-conserving systems, how nonintegrable dynamics may affect thermal transport properties. As illustrating examples, two one-dimensional (1D) diatomic chains, representing 1D fluids and lattices, respectively, are numerically investigated. In both models, the two species of atoms are assigned two different masses and are arranged alternatively. The systems are nonintegrable unless the mass ratio is one. We find that when the mass ratio is slightly different from one, the heat conductivity may keep significantly unchanged over a certain range of the system size and as the mass ratio tends to one, this range may expand rapidly. These results establish a new connection between the macroscopic thermal transport properties and the underlying dynamics.
A. Peratta
2008-01-01
Conductive keratoplasty (CK) is a non-ablative surgical technique for the treatment of mild to moderate hyperopia (far-sightedness). In a CK session a thin electrode penetrates the cornea and delivers pulsed radio-frequency energy at 350kHz to the surrounding tissue. The electromagnetic (EM) energy is dissipated into heat in the tissue surrounding the tip yielding thermally localised shrinkage and tightening of the
NASA Astrophysics Data System (ADS)
Cherubini, Y.; Cacace, M.; Scheck-Wenderoth, M.
2011-12-01
Studies that quantify the influence of faults on the fluid and heat transfer in 3D are still sparse. Faults have a significant impact on physical processes controlling heat transfer and fluid motion in the subsurface as they disturb the conformal succession of geological layers. Depending on their hydraulic properties, faults can act either as preferential pathways or as barriers to fluid flow (Barton et al. 1995). It is important to understand the role of faults and their impact on the thermal field for exploitation of geothermal energy. We improved an existing 3D structural model of the geothermal site "Gross Schönebeck" (Moeck et al. 2005) to carry out coupled fluid and heat transfer simulations. The coupled non-linear partial differential equations describing fluid flow and heat transport in a saturated porous medium are numerically solved by the finite element software FEFLOW° (Diersch, 2002). Simulation results are validated with borehole data. The geological model covers an area of 55 x 50 km. It integrates 18 sedimentary layers of Carboniferous to Quaternary age and reaches down to 5 km depth. An up to 1200 m thick Upper Permian (Zechstein) salt layer decouples two fault systems. We focus on the subsalt fault system which comprises the reservoir target zone and which includes major NW-SE and minor NE-SW trending faults cutting the lower part of the model. The major intersecting faults of the subsalt system are integrated as vertical discrete elements within the numerical model. By discrimination of critically stressed and extensional faults within the current stress field, the hydraulic conductivity of the faults is assessed (Moeck et al. 2009). The impact of the main fault characterising parameters, - the permeability and effective width of the fault-, are investigated by sensitivity analyses. We present outcomes from these simulations by comparing them with results from conductive and coupled fluid and heat transfer simulations obtained from models that do not integrate faults. The results pioneer in that they treat the fault-induced transport of fluid and heat in 3D. We find that faults can strongly alter the fluid regime as well as the temperature evolution in response to their contrasting hydraulic properties with respect to the surrounding matrix.
N. A. Anderson; P. Sabharwall
2014-01-01
The Next Generation Nuclear Plant project is aimed at the research and development of a helium-cooled high-temperature gas reactor that could generate both electricity and process heat for the production of hydrogen. The heat from the high-temperature primary loop must be transferred via an intermediate heat exchanger to a secondary loop. Using RELAP5-3D, a model was developed for two of the heat exchanger options a printed-circuit heat exchanger and a helical-coil steam generator. The RELAP5-3D models were used to simulate an exponential decrease in pressure over a 20 second period. The results of this loss of coolant analysis indicate that heat is initially transferred from the primary loop to the secondary loop, but after the decrease in pressure in the primary loop the heat is transferred from the secondary loop to the primary loop. A high-temperature gas reactor model should be developed and connected to the heat transfer component to simulate other transients.
Gustavsen, Arild; Arasteh, Dariush; Jelle, Bjorn Petter; Curcija, Charlie; Kohler, Christian
2008-09-11
While window frames typically represent 20-30% of the overall window area, their impact on the total window heat transfer rates may be much larger. This effect is even greater in low-conductance (highly insulating) windows that incorporate very low-conductance glazing. Developing low-conductance window frames requires accurate simulation tools for product research and development. Based on a literature review and an evaluation of current methods of modeling heat transfer through window frames, we conclude that current procedures specified in ISO standards are not sufficiently adequate for accurately evaluating heat transfer through the low-conductance frames. We conclude that the near-term priorities for improving the modeling of heat transfer through low-conductance frames are: (1) Add 2D view-factor radiation to standard modeling and examine the current practice of averaging surface emissivity based on area weighting and the process of making an equivalent rectangular frame cavity. (2) Asses 3D radiation effects in frame cavities and develop recommendation for inclusion into the design fenestration tools. (3) Assess existing correlations for convection in vertical cavities using CFD. (4) Study 2D and 3D natural convection heat transfer in frame cavities for cavities that are proven to be deficient from item 3 above. Recommend improved correlations or full CFD modeling into ISO standards and design fenestration tools, if appropriate. (5) Study 3D hardware short-circuits and propose methods to ensure that these effects are incorporated into ratings. (6) Study the heat transfer effects of ventilated frame cavities and propose updated correlations.
Modeling a Printed Circuit Heat Exchanger with RELAP5-3D for the Next Generation Nuclear Plant
Not Available
2010-12-01
The main purpose of this report is to design a printed circuit heat exchanger (PCHE) for the Next Generation Nuclear Plant and carry out Loss of Coolant Accident (LOCA) simulation using RELAP5-3D. Helium was chosen as the coolant in the primary and secondary sides of the heat exchanger. The design of PCHE is critical for the LOCA simulations. For purposes of simplicity, a straight channel configuration was assumed. A parallel intermediate heat exchanger configuration was assumed for the RELAP5 model design. The RELAP5 modeling also required the semicircular channels in the heat exchanger to be mapped to rectangular channels. The initial RELAP5 run outputs steady state conditions which were then compared to the heat exchanger performance theory to ensure accurate design is being simulated. An exponential loss of pressure transient was simulated. This LOCA describes a loss of coolant pressure in the primary side over a 20 second time period. The results for the simulation indicate that heat is initially transferred from the primary loop to the secondary loop, but after the loss of pressure occurs, heat transfers from the secondary loop to the primary loop.
Variable-Conductance Heat-Transfer Module
NASA Technical Reports Server (NTRS)
Hewitt, D. R.
1984-01-01
Working lengths of heat pipes electronically controlled. Rate of heat transfer controlled by electrical heaters shorten effective working lengths of heat pipes. Concept not limited to right circular cylindrical shape. Concept adaptable to terrestrial instruments or processes in which atmospheres or fluids must be cooled and returned to instruments or processes at fixed lower temperatures.
Phonon wave heat conduction in thin films and superlattices
G. Chen
1999-01-01
Heat conduction in thin films and superlattices is important for many engineering applications such as thin-film based microelectronic, photonic, thermoelectric, and thermionic divides. Past modeling efforts on the thermal conductivity of thin films were based on solving the Boltzmann transport equation that treats phonons as particles. The effects of phonon interference and tunneling on the heat conduction and the thermal
A numerical investigation of the 3-D flow in shell and tube heat exchangers
Prithiviraj, M.; Andrews, M.J. [Texas A and M Univ., College Station, TX (United States). Dept. of Mechanical Engineering
1996-12-31
A three-dimensional computer program for simulation of the flow and heat transfer inside Shell and Tube Heat Exchangers has been developed. The simulation of shell and tube heat exchangers is based on a distributed resistance method that uses a modified two equation {kappa}-{epsilon} turbulence model along with non-equilibrium wall functions. Volume porosities and non-homogeneous surface permeabilities account for the obstructions due to the tubes and arbitrary arrangement of baffles. Sub-models are described for baffle-shell and baffle-tube leakage, shellside and tubeside heat transfer, with geometry generators for tubes, baffles, and nozzle inlets and outlets. The sub-models in HEATX use parameters that have not been altered from their published values. Computed heat transfer and pressure drop are compared with experimental data from the Delaware project (Bell, 1963). Numerically computed pressure drops are also compared for different baffle cuts, and different number of baffles with the experiments of Halle et al. (1984) which were performed in an industrial sized heat exchanger at Argonne National Labs. Discussion of the results is given with particular reference to global and local properties such as pressure drop, temperature variation, and heat transfer coefficients. Good agreement is obtained between the experiments and HEATX computations for the shellside pressure drop and outlet temperatures for the shellside and tubeside streams.
NASA Astrophysics Data System (ADS)
Brykina, Irina G.
2014-12-01
The three-dimensional hypersonic rarefied gas flow over blunt bodies in the transitional flow regime is studied. The 3D thin viscous shock layer equations are solved by the asymptotic method developed for low Re numbers. The simple analytical solution is obtained for heat transfer and skin friction coefficients as functions of flow parameters and body geometry parameters. The values of these coefficients approach their values in the free molecular flow at unit accommodation coefficient as Reynolds number tends to zero. Comparison with DSMC solutions is carried out.
NASA Astrophysics Data System (ADS)
Vinsard, G.; Dufour, S.; Saatdjian, E.; Mota, J. P. B.
2015-04-01
Chaotic advection can effectively enhance the heat transfer rate between a boundary and fluids with high Prandtl number. These fluids are usually highly viscous and thus turbulent agitation is not a viable solution since the energy required to mix the fluid would be prohibitive. Here, we analyze previously obtained results on chaotic advection and heat transfer in two similar 2-D periodic flows and on their corresponding 3-D periodic flows when an axial velocity component is superposed. The two flows studied are the flow between eccentric rotating cylinders and the flow between confocal ellipses. For both of these flows the analysis is simplified because the Stokes equations can be solved analytically to obtain a closed form solution. For both 2-D periodic flows, we show that chaotic heat transfer is enhanced by the displacement of the saddle point location during one period. Furthermore, the enhancement by chaotic advection in the elliptical geometry is approximately double that obtained in the cylindrical geometry because there are two saddle points instead of one. We also explain why, for high eccentricity ratios, there is no heat transfer enhancement in the cylindrical geometry. When an axial velocity component is added to both of these flows so that they become 3-D, previous work has shown that there is an optimum modulation frequency for which chaotic advection and heat transfer enhancement is a maximum. Here we show that the optimum modulation frequency can be derived from results without an axial flow. We also explain by physical arguments other previously unanswered questions in the published data.
Aerodynamic heating on 3-D bodies including the effects of entropy-layer swallowing
NASA Technical Reports Server (NTRS)
Dejarnette, F. R.; Hamilton, H. H.
1974-01-01
A relatively simple method was developed previously (authors, 1973) for calculating laminar, transitional, and turbulent heating rates on three-dimensional bodies in hypersonic flows. This method was shown to yield reasonably accurate results for laminar heating on blunted circular and elliptical cones and an earlier version of the space shuttle vehicle. As the boundary layer along the surface grows, more and more of the inviscid-flow mass is entrained into the boundary layer, and the streamlines which passed through the nearly normal portion of the bow shock wave are 'swallowed' by the boundary layer. This phenomenon is often referred to as entropy-layer or streamline swallowing, and it can have a significant effect on the calculated heating rates. An approximate, yet simple, method for including the effects of entropy-layer swallowing in the heating-rate calculations is given.
Thermal conductivity and specific heat of sorghum grain
Miller, Clinton Frank
1963-01-01
of Melting Equations and the Quantity of Heat Contained in Grain Sample. . . 78 LIST OF FIGURES Figures Page 1. Thermal Conductivity Apparatus. 2. Cylinder in Test Position and Voltmeter Used to Determine Thermal Conductivity of Sorghum Grain. . . 12 3.... 20 8. Relationship of Moisture Content to the Thermal Conductivity of Sorghum Grain Hybrid RS 610 . 9. Apparatus Used for the Determination of Specific 31 Heat 37 10. Apparatus Used for Specific Heat Tests. . . . . . 11. Test Canister Used...
Extended Development of Variable Conductance Heat Pipes
NASA Technical Reports Server (NTRS)
Antoniuk, D.; Edwards, D. K.; Luedke, E. E.
1978-01-01
A high-capacity vapor-modulated heat pipe was designed and tested. In 1977, a program was undertaken to use the aforementioned heat pipe to study protection from freezing-point failure, increase control sensitivity, and transient behavior under a wide range of operating conditions in order to determine the full performance potential of the heat pipe. A new concept, based on the vapor-induced-dry-out principle, was developed for passive feedback temperature control as a heat pipe diode. This report documents this work and describes: (1) the experimental and theoretical investigation of the performance of the vapor-modulated heat pipe; and (2) the design, fabrication and test of the heat pipe diode.
Superfluid Heat Conduction and the Cooling of Magnetized Neutron Stars
Deborah N. Aguilera; Vincenzo Cirigliano; José A. Pons; Sanjay Reddy; Rishi Sharma
2008-07-29
We report on a new mechanism for heat conduction in the neutron star crust. We find that collective modes of superfluid neutron matter, called superfluid phonons (sPhs), can influence heat conduction in magnetized neutron stars. They can dominate the heat conduction transverse to magnetic field when the magnetic field $B \\gsim 10^{13}$ G. At density $\\rho \\simeq 10^{12}-10^{14} $ g/cm$^3$ the conductivity due to sPhs is significantly larger than that due to lattice phonons and is comparable to electron conductivity when temperature $\\simeq 10^8$ K. This new mode of heat conduction can limit the surface anisotropy in highly magnetized neutron stars. Cooling curves of magnetized neutron stars with and without superfluid heat conduction could show observationally discernible differences.
Superfluid heat conduction and the cooling of magnetized neutron stars
Cirigliano, Vincenzo [Los Alamos National Laboratory; Reddy, Sanjay [Los Alamos National Laboratory; Sharma, Rishi [Los Alamos National Laboratory; Aguilera, Deborah N [BUENOS AIRES
2008-01-01
We report on a new mechanism for heat conduction in the neutron star crust. We find that collective modes of superftuid neutron matter, called superfiuid phonons (sPhs), can influence heat conduction in magnetized neutron stars. They can dominate the heat conduction transverse to magnetic field when the magnetic field B {approx}> 10{sup 13} C. At density p {approx_equal} 10{sup 12}--10{sup 14} g/cm{sup 3} the conductivity due to sPhs is significantly larger than that due to lattice phonons and is comparable to electron conductivity at when temperature {approx_equal} 10{sup 8} K. This new mode of heat conduction can limit the surface anisotropy in highly magnetized neutron stars. Cooling curves of magnetized neutron stars with and without superfluid heat conduction show observationally discernible differences.
Theory and design of variable conductance heat pipes
NASA Technical Reports Server (NTRS)
Marcus, B. D.
1972-01-01
A comprehensive review and analysis of all aspects of heat pipe technology pertinent to the design of self-controlled, variable conductance devices for spacecraft thermal control is presented. Subjects considered include hydrostatics, hydrodynamics, heat transfer into and out of the pipe, fluid selection, materials compatibility and variable conductance control techniques. The report includes a selected bibliography of pertinent literature, analytical formulations of various models and theories describing variable conductance heat pipe behavior, and the results of numerous experiments on the steady state and transient performance of gas controlled variable conductance heat pipes. Also included is a discussion of VCHP design techniques.
Control of heat source in a heat conduction problem
NASA Astrophysics Data System (ADS)
Lyashenko, V.; Kobilskaya, E.
2014-11-01
The mathematical model of thermal processes during the heat treatment of a moving axisymmetric environment, for example wire. is considered. The wire is heated by internal constantly or periodically operating heat source. It is presented in the form of initial-boundary value problem for the unsteady heat equation with internal constantly or periodically operating heat source. The purpose of the work is the definition of control parameter of temperature field of a moving area, which is heated by internal heat source. The control parameters are determined by solving a nonlocal problem for the heat equation. The problem of getting an adequate temperature distribution throughout the heating area is considered. Therefore, a problem of heat source control is solved, in particular, control by electric current. Control of the heat source allows to maintain the necessary, from a technological point of view, temperature in the heating area. In this paper, to find additional information about the source of heat. The integral condition is used in the control problem. Integral condition, which is considered in the work, determines the energy balance of the heating zone and connects the desired temperature distribution in the internal points of area with temperatures at the boundaries. Control quality in an extremum formulation of the problem is assessed using the quadratic functional. In function space, from a physical point of view, proposed functional is the absolute difference between the actual emission of energy and absorbed energy in the heating zone. The absorbed energy is calculated by solving of the boundary value problem. Methods of determining the control parameters of temperature field are proposed. The resulting problem is solved by iterative methods. At different physical conditions, numerical calculations are carried out, control parameters of the heat treatment process are obtained.
3D Numerical Simulation of Turbulent Buoyant Flow and Heat Transport in a Curved Open Channel
Technology Transfer Automated Retrieval System (TEKTRAN)
A three-dimensional buoyancy-extended version of kappa-epsilon turbulence model was developed for simulating the turbulent flow and heat transport in a curved open channel. The density- induced buoyant force was included in the model, and the influence of temperature stratification on flow field was...
Grant L. Hawkes; James E. OBrien; Greg Tao
2011-01-01
A three-dimensional computational fluid dynamics (CFD) electrochemical model has been created to model high-temperature electrolysis cell performance and steam electrolysis in an internally manifolded planar solid oxide electrolysis cell (SOEC) stack. This design is being evaluated at the Idaho National Laboratory for hydrogen production from nuclear power and process heat. Mass, momentum, energy, and species conservation and transport are provided
3D crustal-scale heat-flow regimes at a developing active margin (Taranaki Basin, New Zealand)
NASA Astrophysics Data System (ADS)
Kroeger, K. F.; Funnell, R. H.; Nicol, A.; Fohrmann, M.; Bland, K. J.; King, P. R.
2013-04-01
The Taranaki Basin in the west of New Zealand's North Island has evolved from a rifted Mesozoic Gondwana margin to a basin straddling the Neogene convergent Australian-Pacific plate margin. However, given its proximity to the modern subduction front, Taranaki Basin is surprisingly cold when compared to other convergent margins. To investigate the effects of active margin evolution on the thermal regime of the Taranaki Basin we developed a 3D crustal-scale forward model using the petroleum industry-standard basin-modelling software Petromod™. The crustal structure inherited from Mesozoic Gondwana margin breakup and processes related to modern Hikurangi convergent margin initiation are identified to be the main controls on the thermal regime of the Taranaki Basin. Present-day surface heat flow across Taranaki on average is 59 mW/m2, but varies by as much as 30 mW/m2 due to the difference in crustal heat generation between mafic and felsic basement terranes alone. In addition, changes in mantle heat advection, tectonic subsidence, crustal thickening and basin inversion, together with related sedimentary processes result in variability of up to 10 mW/m2. Modelling suggests that increased heating of the upper crust due to additional mantle heat advection following the onset of subduction is an ongoing process and heating has only recently begun to reach the surface, explaining the relatively low surface heat flow. We propose that the depth of the subducted slab and related mantle convection processes control the thermal and structural regimes in the Taranaki Basin. The thermal effects of the subduction initiation process are modified and overprinted by the thickness, structure and composition of the lithosphere.
Thermal conductivity of iron\\/potassium perchlorate heat powder
C. M. Love; D. E. Etter; J. E. Glaub
1984-01-01
The thermal conductivity of unburned and burned Fe\\/KC10â heat powder pellets, of two different weight ratios, was determined as a function of pellet density and temperature. Thermal diffusivities as a function of temperature were measured by a laser flash diffusivity method and these data were combined with density and specific heat data to obtain the thermal conductivity results. The thermal
Compressible Navier–Stokes Equations with Zero Heat Conductivity
Tai-Ping Liu; Yanni Zeng
1999-01-01
We study the large-time behavior of solutions of the compressible Navier–Stokes equations without heat conductivity. Acoustic waves are dissipative due to the viscosity. Entropy waves are nondissipative due to lack of heat conductivity. Thus the system is of composite type, the simplest prototype of this class of nonlinear partial differential equations. We study the nonlinear interactions of waves using a
Entropy and temperature gradients thermomechanics: dissipation, heat conduction
Boyer, Edmond
, assuming that the heat flux, the specific internal energy and entropy are functions of the temperatureEntropy and temperature gradients thermomechanics: dissipation, heat conduction inequality and heat or entropy gradients, in thermomechanics of materials. Using the balance of energy, an analysis
Efficient numerical solution of the nonlinear inverse heat conduction problem
J. V. Beck; B. Litkouhi; C. R. Saint Clair Jr.
1980-01-01
The nonlinear inverse heat conduction problem is the calculation of surface heat fluxes and temperatures utilizing measured interior temperatures in opaque solids possessing temperature-variable thermal properties. The most widely used numerical method for this problem was developed by Beck. The new procedure presented herein reduces the number of computer calculations by a factor of three or four. The general heat
High Conductance Loop Heat Pipes for Space Application
Sergey Y. Semenov; Wei-Lin Cho; Scott M. Jensen
2006-01-01
Three high conductance Loop Heat Pipes (LHPs) for the Geostationary Imaging Fourier Transform Spectrometer (GIFTS) were designed, fabricated and thermal vacuum tested. One LHP with ammonia working fluid was designed for heat removal from a cryocooler cold head. Two ethane LHPs were designed to reject heat from the aft and fore optics to space. Thermal performance tests were performed in
Grant L. Hawkes; James E. O'Brien; Greg Tao
2011-11-01
A three-dimensional computational fluid dynamics (CFD) electrochemical model has been created to model high-temperature electrolysis cell performance and steam electrolysis in an internally manifolded planar solid oxide electrolysis cell (SOEC) stack. This design is being evaluated at the Idaho National Laboratory for hydrogen production from nuclear power and process heat. Mass, momentum, energy, and species conservation and transport are provided via the core features of the commercial CFD code FLUENT. A solid-oxide fuel cell (SOFC) model adds the electrochemical reactions and loss mechanisms and computation of the electric field throughout the cell. The FLUENT SOFC user-defined subroutine was modified for this work to allow for operation in the SOEC mode. Model results provide detailed profiles of temperature, operating potential, steam-electrode gas composition, oxygen-electrode gas composition, current density and hydrogen production over a range of stack operating conditions. Single-cell and five-cell results will be presented. Flow distribution through both models is discussed. Flow enters from the bottom, distributes through the inlet plenum, flows across the cells, gathers in the outlet plenum and flows downward making an upside-down ''U'' shaped flow pattern. Flow and concentration variations exist downstream of the inlet holes. Predicted mean outlet hydrogen and steam concentrations vary linearly with current density, as expected. Effects of variations in operating temperature, gas flow rate, oxygen-electrode and steam-electrode current density, and contact resistance from the base case are presented. Contour plots of local electrolyte temperature, current density, and Nernst potential indicate the effects of heat transfer, reaction cooling/heating, and change in local gas composition. Results are discussed for using this design in the electrolysis mode. Discussion of thermal neutral voltage, enthalpy of reaction, hydrogen production, cell thermal efficiency, cell electrical efficiency, and Gibbs free energy are discussed and reported herein.
Efficient Reformulation of HOTFGM: Heat Conduction with Variable Thermal Conductivity
NASA Technical Reports Server (NTRS)
Zhong, Yi; Pindera, Marek-Jerzy; Arnold, Steven M. (Technical Monitor)
2002-01-01
Functionally graded materials (FGMs) have become one of the major research topics in the mechanics of materials community during the past fifteen years. FGMs are heterogeneous materials, characterized by spatially variable microstructure, and thus spatially variable macroscopic properties, introduced to enhance material or structural performance. The spatially variable material properties make FGMs challenging to analyze. The review of the various techniques employed to analyze the thermodynamical response of FGMs reveals two distinct and fundamentally different computational strategies, called uncoupled macromechanical and coupled micromechanical approaches by some investigators. The uncoupled macromechanical approaches ignore the effect of microstructural gradation by employing specific spatial variations of material properties, which are either assumed or obtained by local homogenization, thereby resulting in erroneous results under certain circumstances. In contrast, the coupled approaches explicitly account for the micro-macrostructural interaction, albeit at a significantly higher computational cost. The higher-order theory for functionally graded materials (HOTFGM) developed by Aboudi et al. is representative of the coupled approach. However, despite its demonstrated utility in applications where micro-macrostructural coupling effects are important, the theory's full potential is yet to be realized because the original formulation of HOTFGM is computationally intensive. This, in turn, limits the size of problems that can be solved due to the large number of equations required to mimic realistic material microstructures. Therefore, a basis for an efficient reformulation of HOTFGM, referred to as user-friendly formulation, is developed herein, and subsequently employed in the construction of the efficient reformulation using the local/global conductivity matrix approach. In order to extend HOTFGM's range of applicability, spatially variable thermal conductivity capability at the local level is incorporated into the efficient reformulation. Analytical solutions to validate both the user-friendly and efficient reformulations am also developed. Volume discretization sensitivity and validation studies, as well as a practical application of the developed efficient reformulation are subsequently carried out. The presented results illustrate the accuracy and implementability of both the user-friendly formulation and the efficient reformulation of HOTFGM.
Analysis and application of variable conductance heat pipe air preheater
Chengming Shi; Yang Wang; Quan Liao; Ying Yang
2011-01-01
The heat transfer analysis of variable conductance heat pipe air preheater was carried out. The temperature transfer matrix\\u000a was obtained for the air preheater that comprises several discrete heat transfer units with same or different heat transfer\\u000a surface area in a parallel or counter flow mode. By using the temperature transfer matrix, the outlet fluid temperatures could\\u000a be easily calculated
Wang, G.L.; Chew, W.C.; Cui, T.J.; Aydiner, A.A.; Wright, D.L.; Smith, D.V.
2004-01-01
Three-dimensional (3D) subsurface imaging by using inversion of data obtained from the very early time electromagnetic system (VETEM) was discussed. The study was carried out by using the distorted Born iterative method to match the internal nonlinear property of the 3D inversion problem. The forward solver was based on the total-current formulation bi-conjugate gradient-fast Fourier transform (BCCG-FFT). It was found that the selection of regularization parameter follow a heuristic rule as used in the Levenberg-Marquardt algorithm so that the iteration is stable.
NASA Astrophysics Data System (ADS)
Walton, E.; Shaw, C.
2009-12-01
Shergottites are crystalline igneous rocks that record conditions of strong shock >22-55 GPa manifest as mechanical deformation of minerals, complete or partial transformation of plagioclase to maskelynite or vesiculated glass, and local mineral-scale melting (veins and pockets). This study is motivated by two observations: (1) recent experimental data and physical models provide different estimates for shock melt cooling times, and (2) a growing group of shergottites shocked to >45 GPa exhibit recrystallization textures that suggest post-shock cooling was relatively slow. To address these issues the system was modeled within a 3-dimensional mesh using the Heat program developed by K. Wohletz, which allows design and computation of the transient thermal regimes in and around a magmatic intrusion (in this case, a shock melt). The results constrain the heating profiles developed within the meteoroid by considering the post-shock temperature of the bulk rock, the size and distribution of melts, and cooling of the meteoroid in space. We consider the well-documented shock veins and pockets in shergottites Los Angeles, Dar al Gani 476 and Sayh al Uhaymir 150. Three types of model were run: (1) cooling of a homogeneous melt-free meteoroid in space. (2) Single melt pocket models. (3) Multiple melt pocket models. The first model was used to test the effects of conductive heat loss to space, by cooling a homogeneous 50 cm diameter meteoroid heated to 500 oC. For shock melt-bearing models a 10 x 10 cm block of the meteorite was examined. To avoid edge effects, the pockets were placed in the middle of the block. The single melt models examine the effect of melt size on cooling rate, calculated for thicknesses of 1, 0.5, 0.2 and 0.1 cm, and also the effect of temperature gradient between the host rock. Cooling times have been calculated for a melt (2000 oC) in a rock heated to 100, 500, 600 and 1000 oC. Cooling rates are controlled by the size of the largest pocket; the rates increase as the square of the pocket length. When pockets are close together there are interferences such that the local temperature gradient decreases, increasing the cooling time. For example, a single 4 mm x 2 mm pocket cools to the solidus in 7.8 seconds, whereas the same pocket, when adjacent to an additional temperature excursion, takes about 10% longer to cool. These cooling results are between the high values from Beck et al. (2007; ~7 x 106 oC/s) and the longer rates estimated by our earlier dynamic cooling experiments (~0.3 oC/s). For the latter, faster cooling rates are attributed to the nature of the starting material. Synthetic glasses were fused twice at superliquidus temperatures (1700 oC); the use of such homogeneous starting material extends cooling times because of the necessity of developing nuclei in the melt. Following this line of reasoning, we predict that experiments including nuclei in the starting material should require less undercooling for crystallization and develop the same textures at faster cooling rates.
Molecular dynamics study of heat conduction in silicon nanowires
NASA Astrophysics Data System (ADS)
Volz, Sebastian; Chen, Gang
1998-03-01
With the advancement of nanofabrication technologies, nanowires may be produced for both fundamental studies and practical applications. While many former works have been carried out to characterize the electronic and optical properties of nanowires, little attention has been paid to the heat conduction mechanisms occurring in these structures. However, a fundamental understanding of heat conduction in these nanodevices is important for a number of technological areas such as electronics and thermoelectrics. In this works, we performed numerical studies based on molecular dynamics technique to simulate heat conduction in silicon nanowires lying in the vacuum. The device cells are arranged according to a diamond single crystal structure and interatomic forces are derived from the Stillinger-Weber potential currently assumed in solid silicon. By computing the time dependent heat flux and temperature field, the effective thermal conductivity of the wire was derived. The dependence of thermal conductivity on transverse dimensions and temperature is also probed.
Making Conductive, Compliant Heat-Transfer Pads
NASA Technical Reports Server (NTRS)
Douglas, Lawrence E.
1992-01-01
Composite copper/tungsten pads developed for use in thermoelectric generators. Pads thermally and electrically conductive and compliant enough to accommodate large mismatches in thermal expansion between different parts. Each pad consists of tungsten fibers in copper matrix interconnecting pair of tungsten face sheets.
Electrical conductivity of rocks in the heating and cooling cycle
Marcela Lastovicková; F. Janák
1978-01-01
Summary The values of the electrical conductivity, recorded during the heating and cooling cycle, of eclogites and basalts are compared. The observed difference in the values is explained by reversible and irreversible changes which take place in the samples.
Zhigilei, Leonid V.
Heat conduction in carbon nanotube materials: Strong effect of intrinsic thermal conductivity conductivity of interconnected networks of bundles in carbon nanotube (CNT) films reveals a strong effect to the thermal resistance of a CNT segment with Leq ¼ 59 lm. At first sight, this estimation appears to support
Efficient Sequential Solution of the Nonlinear Inverse Heat Conduction Problem
J. V. Beck; B. Litkouhi; C. R. St. Clair Jr.
1982-01-01
The nonlinear inverse heat conduction problem is the calculation of surface heat fluxes and temperatures by utilizing measured interior temperatures in opaque solids possessing temperature-variable thermal properties. The most widely used numerical method for this problem was developed by Beck. The new sequential procedure presented here reduces the number of computer calculations by a factor of 3 or 4.The general
Efficient sequential solution of the nonlinear inverse heat conduction problem
J. V. Beck; B. Litkouhi; C. R. Saint Clair Jr.
1982-01-01
A solution to the nonlinear inverse heat conduction problem is offered which employs a sequential procedure for the calculation of surface heat fluxes and temperatures from measured interior temperatures in opaque solids having temperature-variable thermal properties. The nonlinear problem is linearized, and through the elimination of iteration, computation time can be reduced by a factor of 3 or 4. The
TRANSIENT HEAT CONDUCTION ANALYSIS OF LAMINATED COMPOSITE NOSE CONE
J. M. Mahishi; Ramesh Chandra; M. V. V. Murthy
This paper presents transient heat conduction analysis of composite nose cone subjected to aerodynamic heating by finite element technique in space domain and finite difference technique in time domain. An anisotropic rectangular ring element with four nodal circles, each having tempera- ture as degree of freedom is developed. Application of finite element technique is space domain results in a set
Kipp, K.L.
1987-01-01
The Heat- and Soil-Transport Program (HST3D) simulates groundwater flow and associated heat and solute transport in three dimensions. The three governing equations are coupled through the interstitial pore velocity, the dependence of the fluid density on pressure, temperature, the solute-mass fraction , and the dependence of the fluid viscosity on temperature and solute-mass fraction. The solute transport equation is for only a single, solute species with possible linear equilibrium sorption and linear decay. Finite difference techniques are used to discretize the governing equations using a point-distributed grid. The flow-, heat- and solute-transport equations are solved , in turn, after a particle Gauss-reduction scheme is used to modify them. The modified equations are more tightly coupled and have better stability for the numerical solutions. The basic source-sink term represents wells. A complex well flow model may be used to simulate specified flow rate and pressure conditions at the land surface or within the aquifer, with or without pressure and flow rate constraints. Boundary condition types offered include specified value, specified flux, leakage, heat conduction, and approximate free surface, and two types of aquifer influence functions. All boundary conditions can be functions of time. Two techniques are available for solution of the finite difference matrix equations. One technique is a direct-elimination solver, using equations reordered by alternating diagonal planes. The other technique is an iterative solver, using two-line successive over-relaxation. A restart option is available for storing intermediate results and restarting the simulation at an intermediate time with modified boundary conditions. This feature also can be used as protection against computer system failure. Data input and output may be in metric (SI) units or inch-pound units. Output may include tables of dependent variables and parameters, zoned-contour maps, and plots of the dependent variables versus time. (Lantz-PTT)
NASA Astrophysics Data System (ADS)
Dorfman, S. M.; Nabiei, F.; Cantoni, M.; Badro, J.; Gaal, R.; Gillet, P.
2014-12-01
The laser-heated diamond anvil cell is a unique tool for subjecting materials to pressures over few hundreds of GPa and temperatures of thousands of Kelvins which enables us to experimentally simulate the inaccessible interiors of planets. However, small sample size, laser profile and thermally conductive diamonds cause temperature gradients of 1000s K over a few microns which also affects chemical and structural distribution of phases in the sample. We have examined samples of San Carlos olivine (Mg,Fe)2SiO3 powder melted in the diamond anvil cell by double-sided and single-sided laser heating for 3-6 minutes to ~3000 K at 35-37 GPa. Moreover, MgO is used as an insulating media in one of the sample. Recovered samples were analyzed by a combination of focused ion beam (FIB) and scanning electron microscope (SEM) equipped with energy dispersive x-ray (EDX) detector. Images and chemical maps were acquired for ~300 slices with ~70 nm depth from each sample, comprising about half of the heated zone. Detailed chemical and structural analysis by transmission electron microscopy (TEM) of lamellas prepared from the remaining section of the samples will also be presented. In all samples the heated zone included (Mg,Fe)SiO3 perovskite-structured bridgmanite (PV) phase and two (Mg, Fe)O phases, one of which, magnesiowüstite (MW), is richer in iron than the other one, ferropericlase (FP). In double-side heated samples we observe a Fe-rich quenched melt core surrounded by MW phase. Our results show that with increasing heating time, Fe migrates to the molten center of the sample. In the single-side heated sample, the Fe-rich MW phase is concentrated in the center of heated zone. In all samples a FP crust was observed around the heated zone. This crust, however, is broken in the upper part (colder part) of the single-side heated sample due the high asymmetrical temperature gradient within the sample. The results confirm the importance of double-side heating and insulating media for generating homogenous central temperature and chemical distribution.
NASA Astrophysics Data System (ADS)
Xin, Shihe; Le Quéré, Patrick
2012-06-01
Following our previous two-dimensional (2D) studies of flows in differentially heated cavities filled with air, we studied the stability of 2D natural convection flows in these cavities with respect to 3D periodic perturbations. The basis of the numerical methods is a time-stepping code using the Chebyshev spectral collocation method and the direct Uzawa method for velocity-pressure coupling. Newton's iteration, Arnoldi's method and the continuation method have been used in order to, respectively, compute the 2D steady-state base solution, estimate the leading eigenmodes of the Jacobian and perform linear stability analysis. Differentially heated air-filled cavities of aspect ratios from 1 to 7 were investigated. Neutral curves (Rayleigh number versus wave number) have been obtained. It turned out that only for aspect ratio 7, 3D stationary instability occurs at slightly higher Rayleigh numbers than the onset of 2D time-dependent flow and that for other aspect ratios 3D instability always takes place before 2D time-dependent flows. 3D unstable modes are stationary and anti-centro-symmetric. 3D nonlinear simulations revealed that the corresponding pitchfork bifurcations are supercritical and that 3D instability leads only to weak flow in the third direction. Further 3D computations are also performed at higher Rayleigh number in order to understand the effects of the weak 3D fluid motion on the onset of time-dependent flow. 3D flow structures are responsible for the onset of time-dependent flow for aspect ratios 1, 2 and 3, while for larger aspect ratios they do not alter the transition scenario, which was observed in the 2D cases and that vertical boundary layers become unstable to traveling waves.
Single-photon heat conduction in electrical circuits
P. J. Jones; J. A. M. Huhtamäki; K. Y. Tan; M. Möttönen
2011-07-14
We study photonic heat conduction between two resistors coupled weakly to a single superconducting microwave cavity. At low enough temperature, the dominating part of the heat exchanged between the resistors is transmitted by single-photon excitations of the fundamental mode of the cavity. This manifestation of single-photon heat conduction should be experimentally observable with the current state of the art. Our scheme can possibly be utilized in remote interference-free temperature control of electric components and environment engineering for superconducting qubits coupled to cavities.
Low-temperature specific heat and thermal conductivity of glasses
L. Gil; M. A. Ramos; A. Bringer; U. Buchenau
1993-01-01
The soft potential model (an extension of the tunneling model to include soft localized vibrations) is shown to describe the anomalous features of the specific heat CP and the thermal conductivity of glasses over the entire low-temperature range, up to an including the peak in CP\\/T3 and the second rise of the thermal conductivity above the plateau.
An Experiment in Heat Conduction Using Hollow Cylinders
ERIC Educational Resources Information Center
Ortuno, M.; Marquez, A.; Gallego, S.; Neipp, C.; Belendez, A.
2011-01-01
An experimental apparatus was designed and built to allow students to carry out heat conduction experiments in hollow cylinders made of different materials, as well as to determine the thermal conductivity of these materials. The evolution of the temperature difference between the inner and outer walls of the cylinder as a function of time is…
Fourier analysis of conductive heat transfer for glazed roofing materials
NASA Astrophysics Data System (ADS)
Roslan, Nurhana Lyana; Bahaman, Nurfaradila; Almanan, Raja Noorliyana Raja; Ismail, Razidah; Zakaria, Nor Zaini
2014-07-01
For low-rise buildings, roof is the most exposed surface to solar radiation. The main mode of heat transfer from outdoor via the roof is conduction. The rate of heat transfer and the thermal impact is dependent on the thermophysical properties of roofing materials. Thus, it is important to analyze the heat distribution for the various types of roofing materials. The objectives of this paper are to obtain the Fourier series for the conductive heat transfer for two types of glazed roofing materials, namely polycarbonate and polyfilled, and also to determine the relationship between the ambient temperature and the conductive heat transfer for these materials. Ambient and surface temperature data were collected from an empirical field investigation in the campus of Universiti Teknologi MARA Shah Alam. The roofing materials were installed on free-standing structures in natural ventilation. Since the temperature data are generally periodic, Fourier series and numerical harmonic analysis are applied. Based on the 24-point harmonic analysis, the eleventh order harmonics is found to generate an adequate Fourier series expansion for both glazed roofing materials. In addition, there exists a linear relationship between the ambient temperature and the conductive heat transfer for both glazed roofing materials. Based on the gradient of the graphs, lower heat transfer is indicated through polyfilled. Thus polyfilled would have a lower thermal impact compared to polycarbonate.
Heat Pipe Embedded AlSiC Plates for High Conductivity - Low CTE Heat Spreaders
Johnson, Matthew (DOE/NNSA Kansas City Plant (United States)); Weyant, J.; Garner, S. (Advanced Cooling Technologies, Inc. (Lancaster, PA (United States)); Occhionero, M. (CPS Technologies Corporation, Norton, MA (United States))
2010-01-07
Heat pipe embedded aluminum silicon carbide (AlSiC) plates are innovative heat spreaders that provide high thermal conductivity and low coefficient of thermal expansion (CTE). Since heat pipes are two phase devices, they demonstrate effective thermal conductivities ranging between 50,000 and 200,000 W/m-K, depending on the heat pipe length. Installing heat pipes into an AlSiC plate dramatically increases the plate’s effective thermal conductivity. AlSiC plates alone have a thermal conductivity of roughly 200 W/m-K and a CTE ranging from 7-12 ppm/ deg C, similar to that of silicon. An equivalent sized heat pipe embedded AlSiC plate has effective thermal conductivity ranging from 400 to 500 W/m-K and retains the CTE of AlSiC.
Junfeng Mei; Michael R. Lovell; Marlin H. Mickle
2005-01-01
One of the greatest challenges for the inkjet printing electrical circuits is formulation and processing of conductive inks. In the present investigation, two different formulations of particle-free conductive solutions are introduced that are low in cost, easy to deposit, and possess good electrical properties. A novel aqueous solution consisting of silver nitrate and additives is initially described. This solution demonstrates
Federal Register 2010, 2011, 2012, 2013, 2014
2012-07-05
...Circuit Packages Provided With Multiple Heat- Conducting Paths and Products Containing...circuit packages provided with multiple heat-conducting paths and products containing...circuit packages provided with multiple heat-conducting paths and products...
Federal Register 2010, 2011, 2012, 2013, 2014
2012-06-06
...Circuit Packages Provided With Multiple Heat- Conducting Paths and Products Containing...Circuit Packages Provided With Multiple Heat-Conducting Paths and Products Containing...circuit packages provided with multiple heat-conducting paths and products...
Induction heating of mastic containing conductive fibers and fillers
Á. García; E. Schlangen; M. Van de Ven; D. Van Vliet
1995-01-01
The objective of this research is to examine the induction heating of mastic through the addition of electrically conductive fillers and fibers (graphite and steel wool), and to prove that this material can be healed with induction energy. The effect of fibers content, sand–bitumen ratio and the\\u000acombination of fillers and fibers on the induction heating of mastic was investigated.
Induction heating of mastic containing conductive fibers and fillers
Álvaro García; Erik Schlangen; Martin van de Ven; Dave van Vliet
2011-01-01
The objective of this research is to examine the induction heating of mastic through the addition of electrically conductive\\u000a fillers and fibers (graphite and steel wool), and to prove that this material can be healed with induction energy. The effect\\u000a of fibers content, sand–bitumen ratio and the combination of fillers and fibers on the induction heating of mastic was investigated.
Mechanical control of heat conductivity in molecular chains.
Savin, A V; Gendelman, O V
2014-01-01
We discuss a possibility to control heat conductivity in molecular chains by means of external mechanical loads. To illustrate such possibilities we consider first well-studied one-dimensional chain with degenerate double-well potential of the nearest-neighbor interaction. We consider varying lengths of the chain with fixed number of particles. Number of possible energetically degenerate ground states strongly depends on the overall length of the chain, or, in other terms, on average length of the link between neighboring particles. These degenerate states correspond to mechanical equilibria; therefore, one can say that formation of such structures mimics a process of plastic deformation. We demonstrate that such modification of the chain length can lead to quite profound (almost fivefold) reduction of the heat conduction coefficient. Even more profound effect is revealed for a model with a single-well nonconvex potential. It is demonstrated that in a certain range of constant external forcing, this model becomes effectively double-well and has a multitude of possible states of equilibrium for fixed value of the external load. Due to this degeneracy, the heat-conduction coefficient can be reduced by two orders of magnitude. We suggest a mechanical model of a chain with periodic double-well potential, which allows control of the heat transport. The models considered may be useful for description of heat transfer in biological macromolecules and for control of the heat transport in microsystems. The possibility of the heat transport control in more realistic three-dimensional systems is illustrated by simulation of a three-dimensional model of polymer ?-helix. In this model, the mechanical stretching also brings about the structural inhomogeneity and, in turn, to essential reduction of the heat conductivity. PMID:24580199
Chen-Wiegart, Yu-chen Karen; Figueroa-Santos, Miriam Aileen; Petrash, Stanislas; Garcia-Miralles, Jose; Wang, Jun
2015-01-21
Conductive adhesives are found favorable in a wide range of applications including a lead-free solder in micro-chips, flexible and printable electronics and enhancing the performance of energy storage devices. Composite materials comprised of metallic fillers and a polymer matrix are of great interest to be implemented as hybrid conductive adhesives. Here we investigated a cost-effective conductive adhesive material consisting of silver-coated copper as micro-fillers using synchrotron-based three-dimensional (3D) X-ray nano-tomography. The key factors affecting the quality and performance of the material were quantitatively studied in 3D on the nanometer scale for the first time. A critical characteristic parameter, defined as a shape-factor, was determined to yield a high-quality silver coating, leading to satisfactory performance. A 'stack-and-screen' mechanism was proposed to elaborate such a phenomenon. The findings and the technique developed in this work will facilitate the future advancement of conductive adhesives to have a great impact in micro-electronics and other applications. PMID:25474162
Heat conduction in one-dimensional aperiodic quantum Ising chains
NASA Astrophysics Data System (ADS)
Li, Wenjuan; Tong, Peiqing
2011-03-01
The heat conductivity of nonperiodic quantum Ising chains whose ends are connected with heat baths at different temperatures are studied numerically by solving the Lindblad master equation. The chains are subjected to a uniform transverse field h, while the exchange coupling Jm between the nearest-neighbor spins takes the two values JA and JB arranged in Fibonacci, generalized Fibonacci, Thue-Morse, and period-doubling sequences. We calculate the energy-density profile and energy current of the resulting nonequilibrium steady states to study the heat-conducting behavior of finite but large systems. Although these nonperiodic quantum Ising chains are integrable, it is clearly found that energy gradients exist in all chains and the energy currents appear to scale as the system size ~N?. By increasing the ratio of couplings, the exponent ? can be modulated from ?>-1 to ?<-1 corresponding to the nontrivial transition from the abnormal heat transport to the heat insulator. The influences of the temperature gradient and the magnetic field to heat conduction have also been discussed.
Heat conduction in one-dimensional aperiodic quantum Ising chains.
Li, Wenjuan; Tong, Peiqing
2011-03-01
The heat conductivity of nonperiodic quantum Ising chains whose ends are connected with heat baths at different temperatures are studied numerically by solving the Lindblad master equation. The chains are subjected to a uniform transverse field h, while the exchange coupling J{m} between the nearest-neighbor spins takes the two values J{A} and J{B} arranged in Fibonacci, generalized Fibonacci, Thue-Morse, and period-doubling sequences. We calculate the energy-density profile and energy current of the resulting nonequilibrium steady states to study the heat-conducting behavior of finite but large systems. Although these nonperiodic quantum Ising chains are integrable, it is clearly found that energy gradients exist in all chains and the energy currents appear to scale as the system size ~N{?}. By increasing the ratio of couplings, the exponent ? can be modulated from ? > -1 to ? < -1 corresponding to the nontrivial transition from the abnormal heat transport to the heat insulator. The influences of the temperature gradient and the magnetic field to heat conduction have also been discussed. PMID:21517475
Explosive crystallization in thin amorphous layers on heat conducting substratesa)
NASA Astrophysics Data System (ADS)
Buchner, Christoph; Schneider, Wilhelm
2015-06-01
A model for explosive crystallization in a thin amorphous layer on a heat conducting substrate is presented. For the thin layer, the energy equation is used in a one-dimensional approximation. Heat conduction into the substrate and thermal contact resistance at the interface between layer and substrate are taken into account. Four rate equations are used to describe the kinetics of the homogeneous amorphous-crystalline transition. The whole process is examined as a plane wave of invariant shape in a moving frame of reference. Heat conduction in the substrate is described by introducing a continuous distribution of moving heat sources at the interface. This gives an integral representation for the temperature in the substrate in terms of the unknown source distribution. The integral term implies that there is a non-local influence of the temperature distribution in the layer on the heat loss. A coupled system of an integro-differential equation and four ordinary differential equations is obtained and solved numerically. The propagation velocity of the wave is obtained as an eigenvalue of the system of equations. Varying a non-dimensional heat loss parameter, a critical value is found beyond which no crystallization wave of invariant shape is possible. This can also be interpreted as a certain minimum layer thickness. Temperature and crystallinity distributions are shown for some interesting configurations. Predictions of crystallization-wave velocities and minimum layer thicknesses are compared with experimental values for explosive crystallization in germanium.
Application of Genetic Algorithms in Nonlinear Heat Conduction Problems
Khan, Waqar A.
2014-01-01
Genetic algorithms are employed to optimize dimensionless temperature in nonlinear heat conduction problems. Three common geometries are selected for the analysis and the concept of minimum entropy generation is used to determine the optimum temperatures under the same constraints. The thermal conductivity is assumed to vary linearly with temperature while internal heat generation is assumed to be uniform. The dimensionless governing equations are obtained for each selected geometry and the dimensionless temperature distributions are obtained using MATLAB. It is observed that GA gives the minimum dimensionless temperature in each selected geometry. PMID:24695517
Application of genetic algorithms in nonlinear heat conduction problems.
Kadri, Muhammad Bilal; Khan, Waqar A
2014-01-01
Genetic algorithms are employed to optimize dimensionless temperature in nonlinear heat conduction problems. Three common geometries are selected for the analysis and the concept of minimum entropy generation is used to determine the optimum temperatures under the same constraints. The thermal conductivity is assumed to vary linearly with temperature while internal heat generation is assumed to be uniform. The dimensionless governing equations are obtained for each selected geometry and the dimensionless temperature distributions are obtained using MATLAB. It is observed that GA gives the minimum dimensionless temperature in each selected geometry. PMID:24695517
Neutrino Heat Conduction and Inhomogeneities in the Early Universe
NASA Technical Reports Server (NTRS)
Heckler, A.; Hogan, C. J.
1993-01-01
Constraints on parameters of inhomogeneous nucteosynthesis, namely, the overdensity and size of baryon lumps, are found by calculatig the blackbody neutrino heat conduction into the lumps, which tends to inflate them away. The scale size for efficient heat conduction is determined by the mean free path lambda of the neutrino, and so we compute lambda in our case of a high-temperature plasma with low chemical potential, and find a general result that many-body effects are unimportant, simplifying the calculation. We find that in the region of interest for nucleosynthesis, neutrino inflation is important for overdensities greater than 10(exp 4).
Tunable heat conduction through coupled Fermi-Pasta-Ulam chains.
Su, Ruixia; Yuan, Zongqiang; Wang, Jun; Zheng, Zhigang
2015-01-01
We conduct a study on heat conduction through coupled Fermi-Pasta-Ulam (FPU) chains by using classical molecular dynamics simulations. Our attention is dedicated to showing how the phonon transport is affected by the interchain coupling. It has been well accepted that the heat conduction could be impeded by the interchain interaction due to the interface phonon scattering. However, recent theoretical and experimental studies suggest that the thermal conductivity of nanoscale materials can be counterintuitively enhanced by the interaction with the substrate. In the present paper, by consecutively varying the interchain coupling intensity, we observed both enhancement and suppression of thermal transport through the coupled FPU chains. For weak interchain couplings, it is found that the heat flux increases with the coupling intensity, whereas in the case of strong interchain couplings, the energy transport is found to be suppressed by the interchain interaction. Based on the phonon spectral energy density method, we attribute the enhancement of the energy transport to the excited phonon modes (in addition to the intrinsic phonon modes), while the upward shift of the high-frequency phonon branch and the interface phonon-phonon scattering account for the suppressed heat conduction. PMID:25679599
Abdul Shakoor; Zhou Zhenggan
2011-01-01
Electrical conductivity undergoes changes in the weld zones of the material. In this study, its anisotropic components along longitudinal, transverse and through-thickness directions have been investigated nondestructively using circular eddy current probe with Hall Effect sensor. The electromagnetic forward model has been solved with material resistivity input profiles corresponding to tensile and compressive residual stresses in a typical welded joint.
Genetic Algorithm in Solution of Inverse Heat Conduction Problems
Miroslav Raudenský; Keith A. Woodbury; J. Kral; T. Brezina
1995-01-01
This report demonstrates the use of a genetic algorithm search in the solution of an inverse problem. The genetic algorithm is used to solve the one-dimensional inverse heat conduction problem using numerical data generated by solution of the corresponding direct problem. Both “pure” and noisy data are considered. If used with regularization, the method is shown to yield reasonable results
Group classification of heat conductivity equations with a nonlinear source
R. Z. Zhdanov; V. I. Lahno
1999-01-01
We suggest a systematic procedure for classifying partial differential equations (PDEs) invariant with respect to low-dimensional Lie algebras. This procedure is a proper synthesis of the infinitesimal Lie method, the technique of equivalence transformations and the theory of classification of abstract low-dimensional Lie algebras. As an application, we consider the problem of classifying heat conductivity equations in one variable with
Disparate quasiballistic heat conduction regimes from periodic heat sources on a substrate
Zeng, Lingping
We report disparate quasiballistic heat conduction trends for periodic nanoscale line heaters deposited on a substrate, depending upon whether measurements are based on the peak temperature of the heaters or the temperature ...
Heat capacity, magnetic susceptibility, EPR, and dc conductivity of some conducting polymers
Pawan Kahol; James Ho; Stefania Deterich; Y. Y. Chen; C. R. Wang; S. Neeleshwar; C. B. Tsai; B. Wessling
2004-01-01
Polyaniline doped with polystyrene-sulfonic-acid (PAN-PSSA), such that y =[sulfonate]\\/[aniline] = 1, exhibits a dc conductivity of 0.1 S\\/cm. On increasing the dopant concentration to y = 6, the conductivity drops by four orders of magnitude. Poly(3,4-ethylenedioxythiophene) doped with polystyrene-sulfonic-acid (PEDOT-PSSA) also exhibits a similar behavior on doping. The results of a study involving heat capacity, magnetic susceptibility, EPR, and dc
Heat, Light, and Videotapes: Experiments in Heat Conduction Using Liquid Crystal Film.
ERIC Educational Resources Information Center
Bacon, Michael E.; And Others
1995-01-01
Presents a range of experiments in heat conduction suitable for upper-level undergraduate laboratories that make use of heat sensitive liquid crystal film to measure temperature contours. Includes experiments mathematically described by Laplace's equation, experiments theoretically described by Poisson's equation, and experiments that involve…
Mechanical behavior of bolted joints under steady heat conduction
Kumano, H. (Tokyo Metropolitan Inst. of Tech., Hino (Japan). Dept. of Mechanical Engineering); Sawa, T.; Hirose, T. (Yamanashi Univ., Kofu (Japan). Dept. of Mechanical Engineering)
1994-02-01
Bolted joints in heat exchangers, cylinder heads in combustion engines, and so on are subjected in heat fluxes. It is necessary to examine the mechanical behavior of such bolted joints under thermal changes in order to establish an optimal design. This paper deals with mechanical behavior of bolted joints, in which two hollow cylinders and two rectangular thick plates made of aluminum are fastened at room temperature by a bolt and nut made of steel, and are subjected to thermal changes or steady heat conduction. Temperature distributions of the joints are analyzed using the finite difference method. Then, methods of estimating an increment in axial bolt force and a maximum stress produced in the bolts are proposed. In the experiments, the aforementioned bolted joints are put in a furnace. Furthermore, the rectangular thick plates fastened by a bolt and nut are heated by an electric heater. Then, the temperature on the surfaces of the clamped parts and the bolts are measured with thermocouples. The increase in axial bolt force and the maximum stress produced in the bolts under steady heat conduction for thermal changes are measured. The analytical results are in fairly good agreement with the experimental ones.
Estimating interfacial thermal conductivity in metamaterials through heat flux mapping
NASA Astrophysics Data System (ADS)
Canbazoglu, Fatih M.; Vemuri, Krishna P.; Bandaru, Prabhakar R.
2015-04-01
The variability of the thickness as well as the thermal conductivity of interfaces in composites may significantly influence thermal transport characteristics and the notion of a metamaterial as an effective medium. The consequent modulations of the heat flux passage are analytically and experimentally examined through a non-contact methodology using radiative imaging, on a model anisotropic thermal metamaterial. It was indicated that a lower Al layer/silver interfacial epoxy ratio of ˜25 compared to that of a Al layer/alumina interfacial epoxy (of ˜39) contributes to a smaller deviation of the heat flux bending angle.
Correlations and scaling in one-dimensional heat conduction.
Deutsch, J M; Narayan, Onuttom
2003-10-01
We examine numerically the full spatiotemporal correlation functions for all hydrodynamic quantities for the random collision model introduced recently. The autocorrelation function of the heat current, through the Kubo formula, gives a thermal conductivity exponent of 1/3 in agreement with the analytical prediction and previous numerical work. Remarkably, this result depends crucially on the choice of boundary conditions: for periodic boundary conditions (as opposed to open boundary conditions with heat baths) the exponent is approximately 1/2. All primitive hydrodynamic quantities scale with the dynamic critical exponent predicted analytically. PMID:14682932
NASA Astrophysics Data System (ADS)
Runov, A. M.; Reiter, D.; Kasilov, S. V.; Heyn, M. F.; Kernbichler, W.
2001-03-01
The heat balance equation is derived and solved for fusion edge plasma conditions with (partially developed) ergodic magnetic-field structures. For this purpose, a three-dimensional (3D) Monte Carlo code, "E3D," based upon the "multiple local magnetic coordinate system approach" has been developed. Parameters typical for the Dynamic Ergodic Divertor (DED) of TEXTOR-94 (Torus Experiment for the Technology Oriented Research) [K. H. Finken et al., Fusion Eng. Des. 37, 1 (1997)] are chosen in the applications. The plasma temperature fields and the profiles of the radial component of heat flux due to the classical parallel and anomalous perpendicular diffusion are calculated. Because of magnetic-field ergodization and diversion of field lines, parallel conduction also can contribute to this radial flux. The results are compared with theoretical predictions for two limiting cases: With the Rechester-Rosenbluth model of ergodization-induced transport and with a "laminar flow model" proposed in the present paper. This latter model describes the effects of field line diversion. The diversion effect is shown to be dominant for TEXTOR-DED conditions.
Revealing the complex conduction heat transfer mechanism of nanofluids
NASA Astrophysics Data System (ADS)
Sergis, A.; Hardalupas, Y.
2015-06-01
Nanofluids are two-phase mixtures consisting of small percentages of nanoparticles (sub 1-10 %vol) inside a carrier fluid. The typical size of nanoparticles is less than 100 nm. These fluids have been exhibiting experimentally a significant increase of thermal performance compared to the corresponding carrier fluids, which cannot be explained using the classical thermodynamic theory. This study deciphers the thermal heat transfer mechanism for the conductive heat transfer mode via a molecular dynamics simulation code. The current findings are the first of their kind and conflict with the proposed theories for heat transfer propagation through micron-sized slurries and pure matter. The authors provide evidence of a complex new type of heat transfer mechanism, which explains the observed abnormal heat transfer augmentation. The new mechanism appears to unite a number of popular speculations for the thermal heat transfer mechanism employed by nanofluids as predicted by the majority of the researchers of the field into a single one. The constituents of the increased diffusivity of the nanoparticle can be attributed to mismatching of the local temperature profiles between parts of the surface of the solid and the fluid resulting in increased local thermophoretic effects. These effects affect the region surrounding the solid manifesting interfacial layer phenomena (Kapitza resistance). In this region, the activity of the fluid and the interactions between the fluid and the nanoparticle are elevated. Isotropic increased nanoparticle mobility is manifested as enhanced Brownian motion and diffusion effects
Revealing the complex conduction heat transfer mechanism of nanofluids.
Sergis, A; Hardalupas, Y
2015-12-01
Nanofluids are two-phase mixtures consisting of small percentages of nanoparticles (sub 1-10 %vol) inside a carrier fluid. The typical size of nanoparticles is less than 100 nm. These fluids have been exhibiting experimentally a significant increase of thermal performance compared to the corresponding carrier fluids, which cannot be explained using the classical thermodynamic theory. This study deciphers the thermal heat transfer mechanism for the conductive heat transfer mode via a molecular dynamics simulation code. The current findings are the first of their kind and conflict with the proposed theories for heat transfer propagation through micron-sized slurries and pure matter. The authors provide evidence of a complex new type of heat transfer mechanism, which explains the observed abnormal heat transfer augmentation. The new mechanism appears to unite a number of popular speculations for the thermal heat transfer mechanism employed by nanofluids as predicted by the majority of the researchers of the field into a single one. The constituents of the increased diffusivity of the nanoparticle can be attributed to mismatching of the local temperature profiles between parts of the surface of the solid and the fluid resulting in increased local thermophoretic effects. These effects affect the region surrounding the solid manifesting interfacial layer phenomena (Kapitza resistance). In this region, the activity of the fluid and the interactions between the fluid and the nanoparticle are elevated. Isotropic increased nanoparticle mobility is manifested as enhanced Brownian motion and diffusion effects. PMID:26058515
Collins, Kimberlee C. (Kimberlee Chiyoko)
2015-01-01
Studies of non-diffusive heat conduction provide insight into the fundamentals of heat transport in condensed matter. The mean free paths (MFPs) of phonons that are most important for conducting heat are well represented ...
ProSEC: Modelling and Simulation in 3D of Brazed Aluminium Core-in-Drum Plate-Fin Heat Exchangers
Florian Picard; David Averous; Xavier Joulia; Denis Barreteau
2009-01-01
A model for steady-state simulation in 3D of a Core-in-Drum plate-fin heat exchanger is presented in this paper. The model takes into account both the geometrical description of the PFHE, layer by layer, and the description of the external piping layout of each stream outside the core. Several steps that allow to define the entire Core-in-Drum model are presented in
Niu, Xufeng; Rouabhia, Mahmoud; Chiffot, Nicolas; King, Martin W; Zhang, Ze
2015-08-01
This study was to demonstrate that an extremely thin coating of poly(3,4-ethylenedioxythiophene) (PEDOT) on nonwoven microfibrous poly(l-lactic acid) (PLLA) web is of sufficient electrical conductivity and stability in aqueous environment to sustain electrical stimulation (ES) to cultured human skin fibroblasts. The PEDOT imparted the web a surface resistivity of approximately 0.1 K?/square without altering the web morphology. X-ray photoelectron spectroscopy demonstrated that the surface chemistry of the PLLA/PEDOT is characteristic of both PLLA and PEDOT. The PEDOT-coated web also showed higher hydrophilicity, lower glass transition temperature and unchanged fiber crystallinity and thermal stability compared with the PLLA web. The addition of PEDOT to the web marginally increased the web's tensile strength and lowered the elongation. An electrical stability test showed that the PLLA/PEDOT structure was more stable than a polypyrrole treated PLLA fabric, showing only a slow deterioration in conductivity when exposed to culture medium. The cytotoxicity test showed that the PLLA/PEDOT scaffold was not cytotoxic and supported human dermal fibroblast adhesion, migration, and proliferation. Preliminary ES experiments have demonstrated that this conductive web mediated effective ES to fibroblasts. Therefore, this new conductive biodegradable scaffold may be used to electrically modulate cellular activity and tissue regeneration. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 103A: 2635-2644, 2015. PMID:25630631
Douglas W. Marshall; Changhu Xing; Charles Folsom; Colby Jensen; Heng Ban
2014-05-01
As an important factor affecting the accuracy of the thermal conductivity measurement, systematic (bias) error in the guarded comparative axial heat flow (cut-bar) method was mostly neglected by previous researches. This bias is due primarily to the thermal conductivity mismatch between sample and meter bars (reference), which is common for a sample of unknown thermal conductivity. A correction scheme, based on a finite element simulation of the measurement system, was proposed to reduce the magnitude of the overall measurement uncertainty. This scheme was experimentally validated by applying corrections on four types of sample measurements in which the specimen thermal conductivity is much smaller, slightly smaller, equal and much larger than that of the meter bar. As an alternative to the optimum guarding technique proposed before, the correction scheme can be used to minimize uncertainty contribution from the measurement system with non-optimal guarding conditions. It is especially necessary for large thermal conductivity mismatches between sample and meter bars.
Superdiffusive heat conduction in semiconductor alloys. I. Theoretical foundations
NASA Astrophysics Data System (ADS)
Vermeersch, Bjorn; Carrete, Jesús; Mingo, Natalio; Shakouri, Ali
2015-02-01
Semiconductor alloys exhibit a strong dependence of effective thermal conductivity on measurement frequency. So far this quasiballistic behavior has only been interpreted phenomenologically, providing limited insight into the underlying thermal transport dynamics. Here, we show that quasiballistic heat conduction in semiconductor alloys is governed by Lévy superdiffusion. By solving the Boltzmann transport equation (BTE) with ab initio phonon dispersions and scattering rates, we reveal a transport regime with fractal space dimension 1 3 ) and cumulative conductivity spectra ??(? ;? ) ˜(?;? ) ? resolved for relaxation times or mean free paths through the simple relations ? =3 -? =1 +3 /n =2 -? . The quasiballistic transport inside alloys is no longer governed by Brownian motion, but instead is dominated by Lévy dynamics. This has important implications for the interpretation of thermoreflectance (TR) measurements with modified Fourier theory. Experimental ? values for InGaAs and SiGe, determined through TR analysis with a novel Lévy heat formalism, match ab initio BTE predictions within a few percent. Our findings lead to a deeper and more accurate quantitative understanding of the physics of nanoscale heat-flow experiments.
Coupled heat conduction and deformation in a viscoelastic composite cylinder
NASA Astrophysics Data System (ADS)
Shah, Sneha; Muliana, Anastasia; Rajagopal, K. R.
2009-05-01
We study the coupled problem of deformation due to mechanical and thermal loading of a composite cylinder made up of two layers of linear isotropic viscoelastic materials. The effect of a time-varying temperature field due to unsteady heat conduction on the short term and long term material response is examined in terms of the stress, displacement, and strain fields. The material properties of the two layers of the composite cylinder at any given location and time are assumed to depend on the temperature at that location at that given instant of time. Sequentially coupled analyses of heat conduction and deformation of the viscoelastic composite cylinder are carried out. Analytical solutions for the stress, strain and displacement fields of the viscoelastic composite cylinder are obtained from the corresponding solution of the linear elasticity problem by applying the Correspondence Principle. We examine the discontinuity in the hoop stress and the radial strain at the interface of the two layers caused by mismatches in material properties, during transient heat conduction. We find that the discontinuities change over time as the mismatch in the moduli of the two layers changes due to the material properties which are time-dependent. We also investigate the effect of the thermal field on the time-dependent field variables in the composite body.
Santhosh Onkaraiah; Chuan Seng Tan
2010-01-01
Thermal modeling of a 3-D IC stack consists of three IC layers bonded back-to-face (or face up) is performed. Significant temperature rise in the top layers is projected with the presence of dielectric isolation films between the IC layers. It is found that by inserting electrically isolated thermal through silicon via (TTSV) having Cu core and oxide liner that extends
Fourier's heat conduction equation: History, influence, and connections
NASA Astrophysics Data System (ADS)
Narasimhan, T. N.
1999-02-01
The equation describing the conduction of heat in solids has, over the past two centuries, proved to be a powerful tool for analyzing the dynamic motion of heat as well as for solving an enormous array of diffusion-type problems in physical sciences, biological sciences, earth sciences, and social sciences. This equation was formulated at the beginning of the nineteenth century by one of the most gifted scholars of modern science, Joseph Fourier of France. A study of the historical context in which Fourier made his remarkable contribution and the subsequent impact his work has had on the development of modern science is as fascinating as it is educational. This paper is an attempt to present a picture of how certain ideas initially led to Fourier's development of the heat equation and how, subsequently, Fourier's work directly influenced and inspired others to use the heat diffusion model to describe other dynamic physical systems. Conversely, others concerned with the study of random processes found that the equations governing such random processes reduced, in the limit, to Fourier's equation of heat diffusion. In the process of developing the flow of ideas, the paper also presents, to the extent possible, an account of the history and personalities involved.
NASA Technical Reports Server (NTRS)
Kachanov, Mark
1998-01-01
Analysis of the effective thermal conductivity of ceramic coatings and its relation to the microstructure continued. Results (obtained in Task 1) for the three-dimensional problem of heat conduction in a solid containing an inclusion (or, in particular, cavity - thermal insulator) of the ellipsoidal shape, were further advanced in the following two directions: (1) closed form expressions of H tensor have been derived for special cases of ellipsoidal cavity geometry: spheroid, crack-like spheroidal cavity and needle shaped spheroidal cavity; (2) these results for one cavity have been incorporated to construct heat energy potential for a solid with many spheroidal cavities (in the approximation of non-interacting defects). This problem constitutes a basic building block for further analyses.
NASA Astrophysics Data System (ADS)
Wei, Meilin; Wang, Xiaoxiang; Sun, Jingjing; Duan, Xianying
2013-06-01
We have succeeded in constructing a 3D POM-MOF, {H[Ni(Hbpdc)(H2O)2]2[PW12O40]·8H2O}n (H2bpdc=2,2'-bipyridyl-3,3'-dicarboxylic acid), by the controllable self-assembly of H2bpdc, Keggin-anions and Ni2+ ions based on the electrostatic and coordination interactions. Interestingly, Hbpdc- as polydentate organic ligands and Keggin-anion as polydentate inorganic ligands are covalently linked transition-metal nickel at the same time. The title complex represents a new example of introducing the metal N-heterocyclic multi-carboxylic acid frameworks into POMs chemistry. Based on Keggin-anions being immobilized as part of the metal N-heterocyclic multi-carboxylic acid framework, the title complex realizes four approaches in the 1D hydrophilic channel used to engender proton conductivity in MOFs. Its water adsorption isotherm at room temperature and pressure shows that the water content in it was 31 cm3 g-1 at the maximum allowable humidity, corresponding to 3.7 water molecules per unit formula. It exhibits good proton conductivities (10-4-10-3 S cm-1) at 100 °C in the relative humidity range 35-98%. The corresponding activation energy (Ea) of conductivity was estimated to be 1.01 eV.
R. Nandan; G. G. Roy; T. J. Lienert; T. DebRoy
2006-01-01
Three-dimensional (3D) viscoplastic flow and temperature field during friction stir welding (FSW) of 304 austenitic stainless steel were mathematically modelled. The equations of conservation of mass, momentum and energy were solved in three dimensions using spatially variable thermophysical properties using a methodology adapted from well established previous work in fusion welding. Non-Newtonian viscosity for the metal flow was calculated considering
M. Slodi?ka; D. Lesnic; T. T. M. Onyango
2010-01-01
In this article, the determination of the time-dependent heat transfer coefficient, involving nonlinear boundary conditions of the third kind in the one-dimensional transient heat conduction from a non-standard boundary measurement is investigated. For this inverse, nonlinear, ill-posed problem, the existence and uniqueness of the solution are proved. Numerical results are obtained, using the boundary element method, and discussed.
Sodium Variable Conductance Heat Pipe for Radioisotope Stirling Systems
NASA Technical Reports Server (NTRS)
Tarau, Calin; Anderson, William G.; Walker, Kara
2009-01-01
In a Stirling radioisotope system, heat must continually be removed from the General Purpose Heat Source (GPHS) modules to maintain the modules and surrounding insulation at acceptable temperatures. Normally, the Stirling convertor provides this cooling. If the converter stops in the current system, the insulation is designed to spoil, preventing damage to the GPHS, and also ending the mission. An alkali-metal Variable Conductance Heat Pipe (VCHP) has been designed to allow multiple stops and restarts of the Stirling convertor in an Advanced Stirling Radioisotope Generator (ASRG). When the Stirling convertor is turned off, the VCHP will activate when the temperatures rises 30 C above the setpoint temperature. A prototype VCHP with sodium as the working fluid was fabricated and tested in both gravity aided and against gravity conditions for a nominal heater head temperature of 790 C. The results show very good agreement with the predictions and validate the model. The gas front was located at the exit of the reservoir when heater head temperature was 790 C while cooling was ON, simulating an operating Advanced Stirling Converter (ASC). When cooling stopped, the temperature increased by 30 C, allowing the gas front to move past the radiator, which transferred the heat to the case. After resuming the cooling flow, the front returned at the initial location turning OFF the VCHP. The against gravity working conditions showed a colder reservoir and faster transients.
Numerical Model for Conduction-Cooled Current Lead Heat Loads
White, M.J.; Wang, X.L.; /Fermilab; Brueck, H.D.; /DESY
2011-06-10
Current leads are utilized to deliver electrical power from a room temperature junction mounted on the vacuum vessel to a superconducting magnet located within the vacuum space of a cryostat. There are many types of current leads used at laboratories throughout the world; however, conduction-cooled current leads are often chosen for their simplicity and reliability. Conduction-cooled leads have the advantage of using common materials, have no superconducting/normal state transition, and have no boil-off vapor to collect. This paper presents a numerical model for conduction-cooled current lead heat loads. This model takes into account varying material and fluid thermal properties, varying thicknesses along the length of the lead, heat transfer in the circumferential and longitudinal directions, electrical power dissipation, and the effect of thermal intercepts. The model is validated by comparing the numerical model results to ideal cases where analytical equations are valid. In addition, the XFEL (X-Ray Free Electron Laser) prototype current leads are modeled and compared to the experimental results from testing at DESY's XFEL Magnet Test Stand (XMTS) and Cryomodule Test Bench (CMTB).
Tunable single-photon heat conduction in electrical circuits
P. J. Jones; J. A. M. Huhtamäki; M. Partanen; K. Y. Tan; M. Möttönen
2012-05-21
We build on the study of single-photon heat conduction in electronic circuits taking into account the back-action of the superconductor--insulator--normal-metal thermometers. In addition, we show that placing capacitors, resistors, and superconducting quantum interference devices (SQUIDs) into a microwave cavity can severely distort the spatial current profile which, in general, should be accounted for in circuit design. The introduction of SQUIDs also allows for in situ tuning of the photonic power transfer which could be utilized in experiments on superconducting quantum bits.
Pseudo-updated constrained solution algorithm for nonlinear heat conduction
NASA Technical Reports Server (NTRS)
Tovichakchaikul, S.; Padovan, J.
1983-01-01
This paper develops efficiency and stability improvements in the incremental successive substitution (ISS) procedure commonly used to generate the solution to nonlinear heat conduction problems. This is achieved by employing the pseudo-update scheme of Broyden, Fletcher, Goldfarb and Shanno in conjunction with the constrained version of the ISS. The resulting algorithm retains the formulational simplicity associated with ISS schemes while incorporating the enhanced convergence properties of slope driven procedures as well as the stability of constrained approaches. To illustrate the enhanced operating characteristics of the new scheme, the results of several benchmark comparisons are presented.
Cristina Radulescu
2012-01-01
It has been established that for certain conditions, such as microgravity boiling, thermocapillary Marangoni flow has associated with it a significant enhancement of heat transfer. Typically, this phenomenon was investigated for the idealized case of an isolated and stationary bubble resting atop a heated solid which is immersed in a semi-infinite quiescent fluid or within a two-dimensional cavity. This paper
Homogeneous Thermal Cloak with Constant Conductivity and Tunable Heat Localization
Han, Tiancheng; Yuan, Tao; Li, Baowen; Qiu, Cheng-Wei
2013-01-01
Invisible cloak has long captivated the popular conjecture and attracted intensive research in various communities of wave dynamics, e.g., optics, electromagnetics, acoustics, etc. However, their inhomogeneous and extreme parameters imposed by transformation-optic method will usually require challenging realization with metamaterials, resulting in narrow bandwidth, loss, polarization-dependence, etc. In this paper, we demonstrate that thermodynamic cloak can be achieved with homogeneous and finite conductivity only employing naturally available materials. It is demonstrated that the thermal localization inside the coating layer can be tuned and controlled robustly by anisotropy, which enables an incomplete cloak to function perfectly. Practical realization of such homogeneous thermal cloak has been suggested by using two naturally occurring conductive materials, which provides an unprecedentedly plausible way to flexibly realize thermal cloak and manipulate heat flow with phonons. PMID:23549139
Time fractional dual-phase-lag heat conduction equation
NASA Astrophysics Data System (ADS)
Xu, Huan-Ying; Jiang, Xiao-Yun
2015-03-01
We build a fractional dual-phase-lag model and the corresponding bioheat transfer equation, which we use to interpret the experiment results for processed meat that have been explained by applying the hyperbolic conduction. Analytical solutions expressed by H-functions are obtained by using the Laplace and Fourier transforms method. The inverse fractional dual-phase-lag heat conduction problem for the simultaneous estimation of two relaxation times and orders of fractionality is solved by applying the nonlinear least-square method. The estimated model parameters are given. Finally, the measured and the calculated temperatures versus time are compared and discussed. Some numerical examples are also given and discussed. Project supported by the National Natural Science Foundation of China (Grant Nos. 11102102, 11472161, and 91130017), the Natural Science Foundation of Shandong Province, China (Grant No. ZR2014AQ015), and the Independent Innovation Foundation of Shandong University, China (Grant No. 2013ZRYQ002).
Zhang, Xian; Wang, Qiuran; Ma, Zhimin; He, Jianqiao; Wang, Zhe; Zheng, Chong; Lin, Jianhua; Huang, Fuqiang
2015-06-01
Two compounds with the formulas of Na4Cu32Sn12S48·4H2O and K11Cu32Sn12S48·4H2O were synthesized via flux (with thiourea as reactive flux) and hydrothermal method, respectively. The black crystals of Na4Cu32Sn12S48·4H2O and K11Cu32Sn12S48·4H2O both crystallize in the cubic space group of Fm3?c with the cell constants a = 17.921(2) Å and a = 18.0559(6) Å, respectively. The crystal structures feature a 3D open-framework with the unique [Cu8Sn6S24](z-) (z = 13 for Na4Cu32Sn12S48·4H2O; z = 14.75 for K11Cu32Sn12S48·4H2O) clusters acting as building blocks. The [Cu8Sn6S24](z-) cluster of the Th symmetry is built up by eight [CuS3] triangles and six [SnS4] tetrahedra. The powder samples were investigated by X-ray diffraction and optical absorption measurements. Both phase-pure compounds show multiabsorption character with a main absorption edge (2.0 eV for Na4Cu32Sn12S48·4H2O and 1.9 eV for K11Cu32Sn12S48·4H2O) and an additional absorption peak (1.61 eV for Na4Cu32Sn12S48·4H2O and 1.52 eV for K11Cu32Sn12S48·4H2O), which are perfectly consistent with the first-principle calculation results. The analyses of the density of states further reveal that the two optical absorption bands in each compound are attributed to the two transitions of Cu-3d-S-3p ? Sn-5s. The multiband nature of two compounds also enhances photocatalytic activity under visible light irradiation, with which the degradation of methyl blue over Na4Cu32Sn12S48·4H2O reached 100% in 3 h. The 3D open-framework features also facilitate the ionic conductivity nature of the Na4Cu32Sn12S48·4H2O compound, which achieved ?10(-5) S/cm at room temperature. PMID:25955506
Zhou, Huan-Ping; Zhang, Ya-Wen; Mai, Hao-Xin; Sun, Xiao; Liu, Qiang; Song, Wei-Guo; Yan, Chun-Hua
2008-01-01
Uniform CeO(2) nanoflowers were synthesized by rapid thermolysis of (NH(4))(2)Ce(NO(3))(6) in oleic acid (OA)/oleylamine (OM), by a unique 3D oriented-attachment mechanism. CeO(2) nanoflowers with controlled shape (cubic, four-petaled, and starlike) and tunable size (10-40 nm) were obtained by adjusting the reaction conditions including solvent composition, precursor concentration, reaction temperature, and reaction time. The nanoflower growth mechanism was investigated by in situ electrical conductance measurements, transmission electron microscopy, and UV/Vis spectroscopy. The CeO(2) nanoflowers are likely formed in two major steps, that is, initial formation of ceria cluster particles capped with various ligands (e.g., OA, OM, and NO(3) (-)) via hydrolysis of (NH(4))(2)Ce(NO(3))(6) at temperatures in the range 140-220 degrees C, and subsequent spontaneous organization of the primary particles into nanoflowers by 3D oriented attachment, due to a rapid decrease in surface ligand coverage caused by sudden decomposition of the precursor at temperatures above 220 degrees C in a strong redox reaction. After calcination at 400 degrees C for 4 h the 33.8 nm CeO(2) nanoflowers have a specific surface area as large as 156 m(2) g(-1) with high porosity, and they are highly active for conversion of CO to CO(2) in the low temperature range of 200-400 degrees C. The present approach has also been extended to the preparation of other transition metal oxide (CoO, NiO, and CuO(x)) nanoflowers. PMID:18260069
Application of inverse heat conduction problem on temperature measurement
NASA Astrophysics Data System (ADS)
Zhang, X.; Zhou, G.; Dong, B.; Li, Q.; Liu, L. Q.
2013-09-01
For regenerative cooling devices, such as G-M refrigerator, pulse tube cooler or thermoacoustic cooler, the gas oscillating bring about temperature fluctuations inevitably, which is harmful in many applications requiring high stable temperatures. To find out the oscillating mechanism of the cooling temperature and improve the temperature stability of cooler, the inner temperature of the cold head has to be measured. However, it is difficult to measure the inner oscillating temperature of the cold head directly because the invasive temperature detectors may disturb the oscillating flow. Fortunately, the outer surface temperature of the cold head can be measured accurately by invasive temperature measurement techniques. In this paper, a mathematical model of inverse heat conduction problem is presented to identify the inner surface oscillating temperature of cold head according to the measured temperature of the outer surface in a GM cryocooler. Inverse heat conduction problem will be solved using control volume approach. Outer surface oscillating temperature could be used as input conditions of inverse problem and the inner surface oscillating temperature of cold head can be inversely obtained. A simple uncertainty analysis of the oscillating temperature measurement also will be provided.
Underground heat conduction near a spherical inhomogeneity: theory and applications
NASA Astrophysics Data System (ADS)
Rabinovich, A.; Dagan, G.; Miloh, T.
2012-04-01
A large underground inhomogeneity, such as a salt dome or cavity, is known to disturb the subsurface temperature field. Such anomalies appear in many geophysical surveys. Detection and knowledge of the magnitude of these disturbances is the objective of both near surface and deep borehole temperature surveys aimed at delineating the inhomogeneities. It also impacts surface temperature history analysis which reconstructs past climate change in an effort to study the recent global warming. This work is aimed at quantifying these effects by solving, for the first time, a problem of heat conduction in Earth's subsurface in the presence of a spherical inhomogeneity. Both the steady state temperature field pertaining to the constant geothermal gradient and the time dependent field caused by a surface jump in temperature are solved. A solution is derived for both cases as an infinite series of spherical harmonics and Bessel functions (in the Laplace domain) for the steady and unsteady problems, respectively. It is found that an accurate solution can be achieved by a small number of terms. The results are illustrated and analyzed for a given accuracy and for a few values of the governing parameters. The general solution can be simplified considerably for asymptotic values of the parameters. Comparison with the exact solution shows that these approximations are accurate for a wide range of parameter values. Some examples of applying the solution to the geophysical methods stated above are discussed. In the case of ground surface temperature history reconstruction from borehole temperature profiles, all current methods assume one-dimensional heat conduction. We present calculations of the anomalies generated near inhomogeneities in the presence of a sudden change in surface temperature used to model climate change. Though the sphere is an idealized shape, the simplicity of the solution makes possible a general analysis toward gaining a better understanding of the process. Furthermore, it can be employed for preliminary assessment of the impact of a body and may serve as a benchmark for numerical solutions. Reference: A. Rabinovich, G. Dagan and T. Miloh, "Heat conduction in a semi-infinite medium with a spherical inhomogeneity and time-periodic boundary temperature", International Journal of Heat and Mass Transfer, 55 (2012) 618-628.
High Temperature Variable Conductance Heat Pipes for Radioisotope Stirling Systems
NASA Technical Reports Server (NTRS)
Tarau, Calin; Walker, Kara L.; Anderson, William G.
2009-01-01
In a Stirling radioisotope system, heat must continually be removed from the GPHS modules, to maintain the GPHS modules and surrounding insulation at acceptable temperatures. Normally, the Stirling convertor provides this cooling. If the Stirling convertor stops in the current system, the insulation is designed to spoil, preventing damage to the GPHS, but also ending the mission. An alkali-metal Variable Conductance Heat Pipe (VCHP) is under development to allow multiple stops and restarts of the Stirling convertor. The status of the ongoing effort in developing this technology is presented in this paper. An earlier, preliminary design had a radiator outside the Advanced Stirling Radioisotope Generator (ASRG) casing, used NaK as the working fluid, and had the reservoir located on the cold side adapter flange. The revised design has an internal radiator inside the casing, with the reservoir embedded inside the insulation. A large set of advantages are offered by this new design. In addition to reducing the overall size and mass of the VCHP, simplicity, compactness and easiness in assembling the VCHP with the ASRG are significantly enhanced. Also, the permanently elevated temperatures of the entire VCHP allows the change of the working fluid from a binary compound (NaK) to single compound (Na). The latter, by its properties, allows higher performance and further mass reduction of the system. Preliminary design and analysis shows an acceptable peak temperature of the ASRG case of 140 C while the heat losses caused by the addition of the VCHP are 1.8 W.
Yifat, Jonathan; Gannot, Israel
2015-03-01
Early detection of malignant tumors plays a crucial role in the survivability chances of the patient. Therefore, new and innovative tumor detection methods are constantly searched for. Tumor-specific magnetic-core nano-particles can be used with an alternating magnetic field to detect and treat tumors by hyperthermia. For the analysis of the method effectiveness, the bio-heat transfer between the nanoparticles and the tissue must be carefully studied. Heat diffusion in biological tissue is usually analyzed using the Pennes Bio-Heat Equation, where blood perfusion plays an important role. Malignant tumors are known to initiate an angiogenesis process, where endothelial cell migration from neighboring vasculature eventually leads to the formation of a thick blood capillary network around them. This process allows the tumor to receive its extensive nutrition demands and evolve into a more progressive and potentially fatal tumor. In order to assess the effect of angiogenesis on the bio-heat transfer problem, we have developed a discrete stochastic 3D model & simulation of tumor-induced angiogenesis. The model elaborates other angiogenesis models by providing high resolution 3D stochastic simulation, capturing of fine angiogenesis morphological features, effects of dynamic sprout thickness functions, and stochastic parent vessel generator. We show that the angiogenesis realizations produced are well suited for numerical bio-heat transfer analysis. Statistical study on the angiogenesis characteristics was derived using Monte Carlo simulations. According to the statistical analysis, we provide analytical expression for the blood perfusion coefficient in the Pennes equation, as a function of several parameters. This updated form of the Pennes equation could be used for numerical and analytical analyses of the proposed detection and treatment method. PMID:24462603
J. Dib; F. Bilteryst; J. L. Batoz; I. Lewon
The present study results from a research collaboration between Laboratory ERMeP (GIP-InSIC) and the company Nordon-Cryogenie\\u000a (Vosges, France), one of the major world manufacturers of heat exchangers for cryogenic processes. A general description of\\u000a a multi-stream brazed aluminium plate-fin heat exchanger is presented in Fig 1. The problem for Nordon Cryogénie is to guarantee\\u000a a thermal performance as well as
Federal Register 2010, 2011, 2012, 2013, 2014
2012-12-12
...Certain Integrated Circuit Packages Provided with Multiple Heat- Conducting Paths and Products Containing Same; Commission...of certain integrated circuit packages provided with multiple heat-conducting paths and products containing same by reason...
A. M. Runov; D. Reiter; S. V. Kasilov; M. F. Heyn; W. Kernbichler
2001-01-01
The heat balance equation is derived and solved for fusion edge plasma conditions with (partially developed) ergodic magnetic-field structures. For this purpose, a three-dimensional (3D) Monte Carlo code, ``E3D,'' based upon the ``multiple local magnetic coordinate system approach'' has been developed. Parameters typical for the Dynamic Ergodic Divertor (DED) of TEXTOR-94 (Torus Experiment for the Technology Oriented Research) [K. H.
Molecular Dynamics of Diffusive-Ballistic Heat Conduction in Single-Walled Carbon Nanotubes
Maruyama, Shigeo
Molecular Dynamics of Diffusive-Ballistic Heat Conduction in Single-Walled Carbon Nanotubes-3-1 Hongo, Bunkyo-ku Tokyo 113-8656, Japan Diffusive-ballistic heat conduction of finite-length single. A gradual transition from nearly pure ballistic to diffusive-ballistic heat conduction was identified from
Maruyama, Shigeo
Diffusive-Ballistic Heat Conduction of Carbon Nanotubes and Nanographene Ribbons Junichiro Shiomi-3-5800-6983 Abstract Investigations of diffusive-ballistic heat conduction of finite-length single-walled carbon of the balance between ballistic and diffusive heat conduction. For both systems, the profile indicates
NASA Astrophysics Data System (ADS)
Doi, D.; Shirai, Y.; Shiotsu, M.
2008-03-01
A computer code of three-dimensional heat transfer in superfluid helium named SUPER-3D was developed based on the two-fluid model. Critical heat fluxes (CHFs) on a flat plate located at one end of rectangular ducts having contractions with different rectangular open area were calculated by using the SUPER-3D for the liquid temperatures from 1.8 K to 2.1 K in pressurized He II. The analyses were made for the ducts with one contraction (Case A) and with two contractions (Case B). In case A, effects of the open mouth area and distance of the contraction from the flat plate were clarified. The solutions of CHF for the various open mouth areas agreed well with the experimental data. In Case B, the solutions of CHF for the two contractions with the same open areas were affected by the combination of open mouth figures. It was found from the analysis that several vortices are generated around the contractions and play an important role in determining the CHF. Three dimensional analyses are necessary to evaluate the CHF accurately.
J. Sarkar; Souvik Bhattacharyya; M. Ram Gopal
2007-01-01
Minimization of heat exchanger area for a specified capacity is very important in the design of refrigeration and heat pump systems, yielding space, weight and cost benefits. In this study, minimization of overall conductance and total area per unit capacity of refrigeration and heat pump systems has been performed analytically. The analysis is performed for constant temperature heat sources and
Radiation and gas conduction heat transport across a helium dewar multilayer insulation system
Green, M.A.
1994-10-10
This report describes a method for calculating mixed heat transfer through the multilayer insulation used to insulate a 4 K liquid helium cryostat. The method described here permits one to estimate the insulation potential for a multilayer insulation system from first principles. The heat transfer regimes included are: radiation, conduction by free molecule gas conduction, and conduction through continuum gas conduction. Heat transfer in the transition region between the two gas conduction regimes is also included.
Application of the boundary element method to transient heat conduction
NASA Technical Reports Server (NTRS)
Dargush, G. F.; Banerjee, P. K.
1991-01-01
An advanced boundary element method (BEM) is presented for the transient heat conduction analysis of engineering components. The numerical implementation necessarily includes higher-order conforming elements, self-adaptive integration and a multiregion capability. Planar, three-dimensional and axisymmetric analyses are all addressed with a consistent time-domain convolution approach, which completely eliminates the need for volume discretization for most practical analyses. The resulting general purpose algorithm establishes BEM as an attractive alternative to the more familiar finite difference and finite element methods for this class of problems. Several detailed numerical examples are included to emphasize the accuracy, stability and generality of the present BEM. Furthermore, a new efficient treatment is introduced for bodies with embedded holes. This development provides a powerful analytical tool for transient solutions of components, such as casting moulds and turbine blades, which are cumbersome to model when employing the conventional domain-based methods.
Manipulating Steady Heat Conduction by Sensu-shaped Thermal Metamaterials.
Han, Tiancheng; Bai, Xue; Liu, Dan; Gao, Dongliang; Li, Baowen; Thong, John T L; Qiu, Cheng-Wei
2015-01-01
The ability to design the control of heat flow has innumerable benefits in the design of electronic systems such as thermoelectric energy harvesters, solid-state lighting, and thermal imagers, where the thermal design plays a key role in performance and device reliability. In this work, we employ one identical sensu-unit with facile natural composition to experimentally realize a new class of thermal metamaterials for controlling thermal conduction (e.g., thermal concentrator, focusing/resolving, uniform heating), only resorting to positioning and locating the same unit element of sensu-shape structure. The thermal metamaterial unit and the proper arrangement of multiple identical units are capable of transferring, redistributing and managing thermal energy in a versatile fashion. It is also shown that our sensu-shape unit elements can be used in manipulating dc currents without any change in the layout for the thermal counterpart. These could markedly enhance the capabilities in thermal sensing, thermal imaging, thermal-energy storage, thermal packaging, thermal therapy, and more domains beyond. PMID:25974383
NASA Technical Reports Server (NTRS)
Anderson, O. L.
1985-01-01
An assessment was made of the applicability of a three dimensional boundary layer analysis of heat transfer, total pressure losses, and streamline flow patterns on the surfaces of both stationary and rotating turbine passages. In support of this effort, an analysis was developed to calculate a general nonorthogonal surface coordinate system for arbitrary three dimensional surfaces and also to calculate the boundary layer edge conditions for compressible flow using the surface Euler equations and experimental pressure distributions. Calculations are presented for the pressure, endwall, and suction surfaces of a stationary cascade and for the pressure surface of a rotating turbine blade. The results strongly indicate that the three dimensional boundary layer analysis can give good predictions of the flow field, loss, and heat transfer on the pressure, suction, and endwall surface of a gas turbine passage.
Field-dependent specific heat in Fe2VAl and the question of possible 3d heavy fermion behavior
NASA Astrophysics Data System (ADS)
Lue, C. S.; Ross, Joseph H., Jr.; Chang, C. F.; Yang, H. D.
1999-11-01
Specific heat measurements on Fe2VAl show the previously reported upturn in electronic specific heat coefficient (?) to be sample dependent, and related to magnetic defects. These measurements, in temperatures as low as 0.6 K and magnetic fields up to 8 T, indicate the presence of Schottky anomalies arising from magnetic clusters having a moment 3.7?B. This result is in good agreement with theoretical estimates for Fe antisite defects in the material. The inherent ?=1.5+/-0.3 mJ/mol K2 deduced from this work is considerably less than previously reported, and the behavior does not appear consistent with heavy fermion behavior. However, the mass enhancement is significant when compared to nuclear magnetic resonance and band calculations, and we propose a spin-fluctuation mechanism.
Jolanta Socala; Wojciech M. Zajaczkowski
2011-03-21
We prove long time existence of regular solutions to the Navier-Stokes equations coupled with the heat equation. We consider the system in non-axially symmetric cylinder with the slip boundary conditions for the Navier-Stokes equations and the Neumann condition for the heat equation. The long time existence is possible because we assumed that derivatives with respect to the variable along the axis of the cylinder of the initial velocity, initial temperature and the external force in $L_2$ norms are sufficiently small. We proved the existence of such solutions that velocity and temperature belong to $W_\\sigma^{2,1}(\\Omega\\times(0,T))$, where $\\sigma>{5\\over3}$. The existence is proved by the Leray-Schauder fixed point theorem.
Numerical heat conduction in hydrodynamical models of colliding hypersonic flows
Parkin, E R
2010-01-01
Hydrodynamical models of colliding hypersonic flows are presented which explore the dependence of the resulting dynamics and the characteristics of the derived X-ray emission on numerical conduction and viscosity. For the purpose of our investigation we present models of colliding flow with plane-parallel and cylindrical divergence. Numerical conduction causes erroneous heating of gas across the contact discontinuity which has implications for the rate at which the gas cools. We find that the dynamics of the shocked gas and the resulting X-ray emission are strongly dependent on the contrast in the density and temperature either side of the contact discontinuity, these effects being strongest where the postshock gas of one flow behaves quasi-adiabatically while the postshock gas of the other flow is strongly radiative. Introducing additional numerical viscosity into the simulations has the effect of damping the growth of instabilities, which in some cases act to increase the volume of shocked gas and can re-he...
Demko, Jonathan Alexander
1980-01-01
EFFECTS OF AXIAL PLATE HEAT CONDUCTION ON THE THERMAL PERFORMANCE QF A LAMINAR COUNTERFLON FLAT PLATE HEAT EXCHANGER A Thesis by JONATHAN ALZKVRER DEMKO Submitted to the Graduate College of Texas A&M University in partial fulfillment... of the requirement for the degree of MASTER OF SCIENCE December 1980 Major Subject: Mechanical Engineering EFFECTS OF AXIAL PLATE HEAT CONDUCTION ON THE THERMAL PERFORMANCE OF A SHINAR COUNTERFLOW FLAT PLATE HEAT EXCHANGER A Thesis by JONATHAN ALEXANDER DEMKO...
Scrape-off layer modeling of radiative divertor and high heat flux experiments on D3-D
NASA Astrophysics Data System (ADS)
Campbell, R. B.; Petrie, T. W.; Hill, D. N.
1992-03-01
We use a new multispecies 1-D fluid code, NEWT-1D, to model DIII-D scrape-off layer (SOL) behavior during radiative divertor and high heat flux experiments. The separatrix location and the width of the SOL are uncertain, and affect the comparison of the data in important ways. The model agrees with many of the experimental measurements for a particular prescription for the separatrix location. The model cannot explain the recent data on the separatrix T(sub i) with a conventional picture of ion and electron power flows across the separatrix. Radial transport of particles and heat in some form is required to explain the peak heat flux data before and after gas puffing. For argon puffing in the private flux region, entrainment is poor in the steady state. The calculations suggest that strike point argon puffing in a slot divertor geometry results in substantially better entrainment. Self-consistent, steady-state solutions with radiated powers up to 80 percent of the SOL power input are obtained in 1-D. We discuss significant radial effects which warrant the development of a code which can treat strongly radiating impurities in 2-D geometries.
NASA Astrophysics Data System (ADS)
Enssle, Carl Philipp; Croisé, Jean; Poller, Andreas; Mayer, Gerhard; Wendling, Jacques
An important question related to the long-term safety performance of a repository for long-lived medium and high-level radioactive waste in the Callovo-Oxfordian clay unit is the impact of heat and gas generated in the waste emplacement areas on the gas and water pressure and on the water saturation in the backfilled repository and in the host rock. The current design of such a repository consists of a multitude of different underground structures, such as emplacement drifts for waste canisters and other types of waste packages, access and ventilation drifts, and access shafts in the central part of the repository. The individual underground structures exhibit different thermo-hydraulic and geometrical properties yielding a large and complex system for the flow and transport of gas, water and heat. A detailed 3D modelling of the entire repository would require a tremendous computational effort, even when using high performance simulator codes. A newly developed method ( Poller et al., 2011) allows for the 3D modelling of the two-phase gas-water flow and thermal evolution in the entire repository/host-rock system in a simplified manner. Besides accounting for both the detailed structures at local scale and the global geometry of the drift network, it also allows for an assessment of the gas phase pressure as well as the hydrogen and heat fluxes developing over the complete lifetime of the repository system. In this paper, the results of a reference scenario are presented. The assessment focuses on the two dominant processes, i.e. the dissolution and diffusion of the generated hydrogen, and the advective migration of the forming hydrogen gas phase in space and time (up to 1 million years). Further, the main findings of a sensitivity analysis on different features, physical processes and parameter uncertainty are presented.
NASA Astrophysics Data System (ADS)
Rodrigues, Dario B.; Maccarini, Paolo F.; Salahi, Sara; Colebeck, Erin; Topsakal, Erdem; Pereira, Pedro J. S.; Limão-Vieira, Paulo; Stauffer, Paul R.
2013-02-01
Background: Brown adipose tissue (BAT) plays an important role in whole body metabolism and could potentially mediate weight gain and insulin sensitivity. Although some imaging techniques allow BAT detection, there are currently no viable methods for continuous acquisition of BAT energy expenditure. We present a non-invasive technique for long term monitoring of BAT metabolism using microwave radiometry. Methods: A multilayer 3D computational model was created in HFSSTM with 1.5 mm skin, 3-10 mm subcutaneous fat, 200 mm muscle and a BAT region (2-6 cm3) located between fat and muscle. Based on this model, a log-spiral antenna was designed and optimized to maximize reception of thermal emissions from the target (BAT). The power absorption patterns calculated in HFSSTM were combined with simulated thermal distributions computed in COMSOL® to predict radiometric signal measured from an ultra-low-noise microwave radiometer. The power received by the antenna was characterized as a function of different levels of BAT metabolism under cold and noradrenergic stimulation. Results: The optimized frequency band was 1.5-2.2 GHz, with averaged antenna efficiency of 19%. The simulated power received by the radiometric antenna increased 2-9 mdBm (noradrenergic stimulus) and 4-15 mdBm (cold stimulus) corresponding to increased 15-fold BAT metabolism. Conclusions: Results demonstrated the ability to detect thermal radiation from small volumes (2-6 cm3) of BAT located up to 12 mm deep and to monitor small changes (0.5 °C) in BAT metabolism. As such, the developed miniature radiometric antenna sensor appears suitable for non-invasive long term monitoring of BAT metabolism.
Theory and design of variable conductance heat pipes: Steady state and transient performance
NASA Technical Reports Server (NTRS)
Edwards, D. K.; Fleischman, G. L.; Marcus, B. D.
1972-01-01
Heat pipe technology pertinent to the design and application of self-controlled, variable conductance heat pipes for spacecraft thermal control is discussed. Investigations were conducted to: (1) provide additional confidence in existing design tools, (2) to generate new design tools, and (3) to develop superior variable conductance heat pipe designs. A computer program for designing and predicting the performance of the heat pipe systems was developed.
Long time estimate of solutions to 3d Navier-Stokes equations coupled with the heat convection
Jolanta Socala; Wojciech M. Zajaczkowski
2011-03-21
We examine the Navier-Stokes equations with homogeneous slip boundary conditions coupled with the heat equation with homogeneous Neumann conditions in a bounded domain in $R^3$. The considered domain is a cylinder with $x_3$-axis. The aim of this paper is to show long time estimates without smallness of the initial velocity, the initial temperature and the external force. To prove the estimate we need however smallness of $L_2$ norms of derivatives with respect to $x_3$ of the initial velocity, the initial temperature and the external force.
Ipsita Devi; B. S. D Kumar; Pulak J Bhuyan
2003-01-01
Microwave-assisted three-component cyclocondensation of barbituric acids 1, benzaldehyde 2 and alkyl nitriles 3 proceeds in the absence or presence of triethylamine to afford pyrano[2,3-d]pyrimidines 4 and 6-aminouracils 5 or 6-hydroxyaminouracils 6 react with 2 and 3 under identical conditions to yield pyrido[2,3-d]pyrimidines 7, all in high yields.
Aerodynamic and heat transfer analysis of the low aspect ratio turbine using a 3D Navier-Stokes code
NASA Astrophysics Data System (ADS)
Choi, D.; Knight, C. J.
1991-06-01
The single-stage, high-pressure ratio Garrett Low Aspect Ratio Turbine (LART) test data obtained in a shock tunnel are employed as a basis for evaluating a new three-dimensional Navier Stokes code based on the O-H grid system. It uses Coakley's two-equation turbulence modeling with viscous sublayer resolution. For the nozzle guide vanes, calculations were made based on two grid zones: an O-grid zone wrapping around airfoil and an H-grid zone outside of the O-grid zone, including the regions upstream of the leadig edge and downstream of the trailing edge. For the rotor blade row, a third O-grid zone was added for the tip-gap region leakage flow. The computational results compare well with experiment. These comparisons include heat transfer distributions on the airfoils and end-walls. The leakage flow through the tip-gap clearance is well resolved.
Waluyo, I.; Nordlund, D.; Naslund, L.-A.; Ogasawara, H.; Pettersson, L.G.M.; Nilsson, A.
2009-05-26
The formation of crystalline ice through isothermal heating of 80 layers amorphous ice on Pt(111) at 150 K is studied using X-ray photoelectron spectroscopy and infrared reflection absorption spectroscopy. An early indicator for inhomogeneous crystallization is provided by the uncharacteristically high Pt 4f photoelectron peak for crystalline ice compared with the corresponding uniformly thick amorphous case. O 1s photoelectron spectra unambiguously show that the first monolayer is exposed after crystallization at multilayer total coverage. Using the relative intensities between the first monolayer and multilayer contributions to the O 1s photoelectron spectra, we estimated that -46% and -80% of the first monolayer is exposed to vacuum with an average crystallite height of -41 and -31 layers for an equivalent total coverage of -23 and -7 layers, respectively.
Self assembled structures for 3D integration
NASA Astrophysics Data System (ADS)
Rao, Madhav
Three dimensional (3D) micro-scale structures attached to a silicon substrate have various applications in microelectronics. However, formation of 3D structures using conventional micro-fabrication techniques are not efficient and require precise control of processing parameters. Self assembly is a method for creating 3D structures that takes advantage of surface area minimization phenomena. Solder based self assembly (SBSA), the subject of this dissertation, uses solder as a facilitator in the formation of 3D structures from 2D patterns. Etching a sacrificial layer underneath a portion of the 2D pattern allows the solder reflow step to pull those areas out of the substrate plane resulting in a folded 3D structure. Initial studies using the SBSA method demonstrated low yields in the formation of five different polyhedra. The failures in folding were primarily attributed to nonuniform solder deposition on the underlying metal pads. The dip soldering method was analyzed and subsequently refined. A modified dip soldering process provided improved yield among the polyhedra. Solder bridging referred as joining of solder deposited on different metal patterns in an entity influenced the folding mechanism. In general, design parameters such as small gap-spacings and thick metal pads were found to favor solder bridging for all patterns studied. Two types of soldering: face and edge soldering were analyzed. Face soldering refers to the application of solder on the entire metal face. Edge soldering indicates application of solder only on the edges of the metal face. Mechanical grinding showed that face soldered SBSA structures were void free and robust in nature. In addition, the face soldered 3D structures provide a consistent heat resistant solder standoff height that serve as attachments in the integration of dissimilar electronic technologies. Face soldered 3D structures were developed on the underlying conducting channel to determine the thermo-electric reliability of face soldered structures.
T. P. Fredman
2004-01-01
A boundary identification problem in inverse heat conduction is studied, based on data from internal measurement of temperature and heat flux. Formulated as a sideways heat conduction equation, a spatial continuation technique is applied to extend the solution to a known boundary condition at the desired boundary position. Recording the positions traversed in the continuation for each time instant yields
B. R. Bass; L. J. Ott
1980-01-01
The calculation of the surface temperature and surface heat flux from measured temperature transients at one or more interior points of a body is identified as the inverse heat conduction problem. An inverse solution technique applicable to the two dimensional nonlinear model with temperature dependent thermophysical properties is presented. The technique utilizes a finite element heat conduction model and a
Diffusive-Ballistic Heat Conduction along a Single-Walled Carbon Nanotube Shigeo Maruyama
Maruyama, Shigeo
Diffusive-Ballistic Heat Conduction along a Single-Walled Carbon Nanotube Shigeo Maruyama *E-mail address: maruyama@photon.t.u-tokyo.ac.jp The diffusive-ballistic heat conduction of finite at room temperature. A gradual transition from nearly pure ballistic to diffusive-ballistic heat
NASA Astrophysics Data System (ADS)
Barkett, Laura Ashley
In the past, fuel elements with multiple axial coolant channels have been used in nuclear propulsion applications. A novel fuel element concept that reduces weight and increases efficiency uses a stack of grooved rings. Each fuel ring consists of a hole on the interior and grooves across the top face. Many grooved ring configurations have been modeled, and a single flow channel for each design has been analyzed. For increased efficiency, a fuel ring with a higher surface-area-to-volume ratio is ideal. When grooves are shallower and they have a lower surface area, the results show that the exit temperature is higher. By coupling the physics of fluid flow with those of heat transfer, the effects on the cooler gas flowing through the grooves of the hot, fissioning ring can be predicted. Models also show differences in velocities and temperatures after dense boundary nodes are applied. Parametric studies were done to show how a pressure drop across the length of the channels will affect the exit temperatures of the gas. Geometric optimization was done to show the temperature distributions and pressure drops that result from the manipulation of various parameters, and the effects of model scaling was also investigated. The inverse Graetz numbers are plotted against Nusselt numbers, and the results of these values suggest that the gas quickly becomes fully developed, laminar flow, rather than constant turbulent conditions.
Thermal flywheel effects on the time varying conduction heat transfer through structural walls
P. T Tsilingiris
2003-01-01
Wall time varying conduction heat transfer investigations are very important for the prediction of heating and cooling loads in air conditioning practice and absolutely essential to the passive solar heating design. The walls store heat, absorb and dissipate a fraction of it and transmit the rest into the conditioned space at a later time, which depends on the wall thermal
Maruyama, Shigeo
Isotope Effects on Heat Conduction of Carbon Nanotubes Shigeo Maruyama, Yuki Taniguchi and Yasushi that the inclusion of only 1 % of 13 C natural isotope dramatically reduces the thermal conductivity of diamond. However, isotope effects on heat conduction of SWNTs have not been elucidated. We estimated isotope
In vitro burn model illustrating heat conduction patterns using compressed thermal papers.
Lee, Jun Yong; Jung, Sung-No; Kwon, Ho
2015-01-01
To date, heat conduction from heat sources to tissue has been estimated by complex mathematical modeling. In the present study, we developed an intuitive in vitro skin burn model that illustrates heat conduction patterns inside the skin. This was composed of tightly compressed thermal papers with compression frames. Heat flow through the model left a trace by changing the color of thermal papers. These were digitized and three-dimensionally reconstituted to reproduce the heat conduction patterns in the skin. For standardization, we validated K91HG-CE thermal paper using a printout test and bivariate correlation analysis. We measured the papers' physical properties and calculated the estimated depth of heat conduction using Fourier's equation. Through contact burns of 5, 10, 15, 20, and 30 seconds on porcine skin and our burn model using a heated brass comb, and comparing the burn wound and heat conduction trace, we validated our model. The heat conduction pattern correlation analysis (intraclass correlation coefficient: 0.846, p?heat conduction depth correlation analysis (intraclass correlation coefficient: 0.93, p?heat conduction patterns. PMID:25421614
Multiscale 3D feature extraction and matching with an application to 3D face recognition q
Wolberg, George
representation is obtained by evolving the surface curvatures according to the heat equation. This evolution February 2013 Keywords: 3D feature extraction 3D shape matching 3D face recognition Heat equation Mesh-suited for measuring dissimilarity between (partial) surfaces having unknown position, orientation, and scale. The CS3
NASA Astrophysics Data System (ADS)
Belyaev, Alexander K.
1999-06-01
The heat conduction equation and the dynamic boundary value problem for simple piezothermoelastic materials with time- dependent properties are derived directly from the first and second laws of thermodynamics. It is also shown that the conventional form of the heat conduction equation for geometrically nonlinear anisotropic thermoelastic media does not satisfy the principle of material frame indifference. A consistent form of the heat conduction equation is suggested.
Analysis of heat conduction in a disk brake system
NASA Astrophysics Data System (ADS)
Talati, Faramarz; Jalalifar, Salman
2009-06-01
In this paper, the governing heat equations for the disk and the pad are extracted in the form of transient heat equations with heat generation that is dependant to time and space. In the derivation of the heat equations, parameters such as the duration of braking, vehicle velocity, geometries and the dimensions of the brake components, materials of the disk brake rotor and the pad and contact pressure distribution have been taken into account. The problem is solved analytically using Green’s function approach. It is concluded that the heat generated due to friction between the disk and the pad should be ideally dissipated to the environment to avoid decreasing the friction coefficient between the disk and the pad and to avoid the temperature rise of various brake components and brake fluid vaporization due to excessive heating.
Effective heat conductivity of fuel element bundles and steam generator tube bundles
NASA Astrophysics Data System (ADS)
Fedotovsky, V.; Orlov, A.
2008-06-01
Effective heat conductivity of rod and tube bundles is one of thermophysical properties necessary for calculation of thermo hydraulic characteristics of heat producing devices, heat exchange devices and steam generators. This report introduces results of mathematical modeling of effective heat conductivity of transversally anisotropic rod bundles in solid conductive medium. The considered bundles represented cylindrical rods fitted in corners of stretched and compressed in direction of heat transfer rectangular and triangular grids. The calculated results were compared to analytical solutions and previous numerical results.
High temperature electrically conducting ceramic heating element and control system
C. R. Halbach; R. J. Page
1975-01-01
Improvements were made in both electrode technology and ceramic conductor quality to increase significantly the lifetime and thermal cycling capability of electrically conducting ceramic heater elements. These elements were operated in vacuum, inert and reducing environments as well as oxidizing atmospheres adding to the versatility of the conducting ceramic as an ohmic heater. Using stabilized zirconia conducting ceramic heater elements,
Shrestha, R.; Lee, K. M.; Chang, W. S.; Kim, D. S.; Rhee, G. H.; Choi, T. Y.
2013-01-01
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 ?m to 5 ?m 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. PMID:23556837
NASA Astrophysics Data System (ADS)
Zou, Ling
Subcooled flow boiling is generally characterized by high heat transfer capacity and low wall superheat, which is essential for cooling applications requiring high heat transfer rate, such as nuclear reactors and fossil boilers. In this study, subcooled flow boiling on copper and stainless steel heating surfaces was experimentally investigated from both macroscopic and microscopic points of view. Flow boiling heat flux and heat transfer coefficient were experimentally measured on both surfaces under different conditions, such as pressure, flow rate and inlet subcooling. Significant boiling heat transfer coefficient differences were found between the copper and the stainless steel heating surfaces. To explain the different flow boiling behaviors on these two heating surfaces, nucleation site density and bubble dynamics were visually observed and measured at different experimental conditions utilizing a high-speed digital video camera. These two parameters are believed to be keys in determining flow boiling heat flux. Wall superheat, critical cavity size and wall heat flux were used to correlate with nucleation site density data. Among them, wall heat flux shows the best correlation for eliminating both pressure and surface property effects. The observed nucleation site distribution shows a random distribution. When compared to the spatial Poisson distribution, similarity between them was found, while the measured nucleation site distribution is more uniform. From experimental observations, for the two surface materials investigated, which have similar surface wettability but sharply different thermal properties, bubble dynamics displayed fairly similar behavior. The obtained experimental results indicate that thermal conductivity of heating surface material plays an important role in boiling heat transfer. This is due to thermal conductivity having a significant impact on the lateral heat conduction at the heating surface and consequently temperature uniformity of the heating surface. A model was then developed and solved numerically for heat conduction at the heating surface when bubbles are present. Several key parameters which impact lateral heat conduction and surface temperature profile were studied. These parameters include material thermal conductivity, bubble size, heating surface thickness, etc. Numerical results show that, temperature profile on the heating surface tends to be more uniform and have a lower average value on a heating surface with higher thermal conductivity, which agrees well with the experimental observation.
Maruyama, Shigeo
a significant contribution of the optical phonon modes to the observed wavelike heat conduction. The result suggests that, in carbon nanotubes with finite length where the long wavelength acoustic phonons behave ballistic, even optical phonons can play a major role in the non-Fourier heat conduction. PACS numbers: 61
Thermal conductance of pneumatic conveying preheater for air–gypsum and air–sand heat transfer
K. S. Rajan; S. N. Srivastava; B. Pitchumani; V. Surendiran
2010-01-01
The use of pneumatic conveying duct as gas–solid heat exchanger is in vogue in the form of preheater and dryer in cement and pharmaceutical industries, among several other industries. Experiments were conducted to study the effect of solids feed rate, particle size and air velocity on thermal conductance of a vertical pneumatic conveying heat exchanger for preheating of dry solids.
Cheng-Hung Huang; Yan Jan-Yuan
1995-01-01
An inverse analysis utilizing the conjugate gradient method of minimization and the adjoint equation is used for simultaneously estimating the temperature-dependent thermal conductivity and heat capacity per unit volume of a material. No prior information is used for the functional forms of the unknown thermal conductivity and heat capacity in the present study, thus, it is classified as the function
Alexander K. Belyaev
1999-01-01
The heat conduction equation and the dynamic boundary value problem for simple piezothermoelastic materials with time- dependent properties are derived directly from the first and second laws of thermodynamics. It is also shown that the conventional form of the heat conduction equation for geometrically nonlinear anisotropic thermoelastic media does not satisfy the principle of material frame indifference. A consistent form
A. K. Belyaev
2000-01-01
Summary It is shown that the dynamic boundary value problem and the heat conduction equation for simple piezoelectric materials with time-dependent properties result from the first and second law of thermodynamics. It is also shown that the conventional form of the heat conduction equation for geometrically nonlinear anisotropic thermoelastic media does not satisfy the principle of material frame indifference. A
An Input Estimation Approach to On-Line Two-Dimensional Inverse Heat Conduction Problems
Pan-Chio Tuan; Ching-China Ji; Li-Wei Fong; Wen-Tang Huang
1996-01-01
An on-line methodology to solve two-dimensional inverse heat conduction problems (IHCP) is presented. A new input estimation approach based on the Kalman filtering technique is developed to estimate the two separate unknown heat flux inputs on the two boundaries in real time. A recursive relation between the observed value of the residual sequence with unknown heat flux and the theoretical
Thermal conductivity and diffusivity of biomaterials measured with self-heated thermistors
J. W. Valvano; J. R. Cochran; K. R. Diller
1985-01-01
This paper presents an experimental method to measure the thermal conductivity and thermal diffusivity of biomaterials. Self-heated thermistor probes, inserted into the tissue of interest, are used to deliver heat as well as to monitor the rate of heat removal. An empirical calibration procedure allows accurate thermal-property measurements over a wide range of tissue temperatures. Operation of the instrument in
A Simple Rate Law Experiment Using a Custom-Built Isothermal Heat Conduction Calorimeter
ERIC Educational Resources Information Center
Wadso, Lars; Li, Xi.
2008-01-01
Most processes (whether physical, chemical, or biological) produce or consume heat: measuring thermal power (the heat production rate) is therefore a typical method of studying processes. Here we describe the design of a simple isothermal heat conduction calorimeter built for use in teaching; we also provide an example of its use in simultaneously…
B. F. Blackwell; R. E. Hogan
1991-01-01
A finite control volume technique is developed to solve two-dimensional axisymmetric heat conduction problems using an arbitrary quadrilateral mesh. In this technique, the integral form of the conservation of energy equation is applied to control volumes of finite size. The boundary conditions considered include specified flux, aerodynamic heating, convection, and radiation. Two example problems involving a specified heat flux boundary
Some essential problems with ablation and heat-conduction in solid rocket nozzle
NASA Astrophysics Data System (ADS)
He, Hongqing
1993-06-01
The main problems connected with calculation of ablation and heat conductance in an integral solid-rocket nozzle are discussed. These include: (1) calculations of two-phase viscous transonic flow and heat-transfer between gas and wall in the nozzle, which are the foundation of the ablation and heat-conductance computations, (2) the need for aerodynamic thermochemical ablative models for various compounds used, (3) the need to account for particles' erosion, (4) the need to study the ablative control mechanism, (5) the need for treating moving multiboundaries in transient heat conductance, (6) the need to account for coupling between ablation and heat conductance, (7) the need for precise measurements, and (8) the need of programming ablation and heat transfer in CAD software. Taking into account the above considerations, the ablative rate and temperature distributions for an integral complexly structured solid-rocket nozzle are obtained.
Nonstationary heat conduction in one-dimensional chains with conserved momentum
NASA Astrophysics Data System (ADS)
Gendelman, Oleg V.; Savin, Alexander V.
2010-02-01
This Rapid Communication addresses the relationship between hyperbolic equations of heat conduction and microscopic models of dielectrics. Effects of the nonstationary heat conduction are investigated in two one-dimensional models with conserved momentum: Fermi-Pasta-Ulam (FPU) chain and chain of rotators (CR). These models belong to different universality classes with respect to stationary heat conduction. Direct numeric simulations reveal in both models a crossover from oscillatory decay of short-wave perturbations of the temperature field to smooth diffusive decay of the long-wave perturbations. Such behavior is inconsistent with parabolic Fourier equation of the heat conduction. The crossover wavelength decreases with increase in average temperature in both models. For the FPU model the lowest-order hyperbolic Cattaneo-Vernotte equation for the nonstationary heat conduction is not applicable, since no unique relaxation time can be determined.
B. A. Strukov; S. T. Davitadze; S. N. Kravchun; S. A. Taraskin; M. Goltzman; V. V. Lemanov; S. G. Shulman
2003-01-01
Thermal properties - specific heat and heat conductivity coefficient---of polycrystalline BaTiO3 films on massive substrates were studied as a function of the temperature and the film thickness by the ac-hot probe method. The anomalies of specific heat with the film thickness decreasing from 1100 to 20 nm revealed the reduction of Tc and excess entropy of the ferroelectric phase transition
J. E. Eninger; G. L. Fleischman; E. E. Luedke
1975-01-01
The design and testing of a heat pipe for spacecraft application is presented. The application in mind calls for heat loads up to 20 watts, a set-point temperature of 294K, and a sink that varies from -220K to nearly as high as the set-point. The overall heat pipe length is 137 cm. Two basically different mechanisms of achieving variable conductance
Variable Conductance Heat Pipe Cooling of Stirling Convertor and General Purpose Heat Source
NASA Technical Reports Server (NTRS)
Tarau, Calin; Schwendeman, Carl; Anderson William G.; Cornell, Peggy A.; Schifer, Nicholas A.
2013-01-01
In a Stirling Radioisotope Power System (RPS), heat must be continuously removed from the General Purpose Heat Source (GPHS) modules to maintain the modules and surrounding insulation at acceptable temperatures. The Stirling convertor normally provides this cooling. If the Stirling convertor stops in the current system, the insulation is designed to spoil, preventing damage to the GPHS at the cost of an early termination of the mission. An alkali-metal Variable Conductance Heat Pipe (VCHP) can be used to passively allow multiple stops and restarts of the Stirling convertor. In a previous NASA SBIR Program, Advanced Cooling Technologies, Inc. (ACT) developed a series of sodium VCHPs as backup cooling systems for Stirling RPS. The operation of these VCHPs was demonstrated using Stirling heater head simulators and GPHS simulators. In the most recent effort, a sodium VCHP with a stainless steel envelope was designed, fabricated and tested at NASA Glenn Research Center (GRC) with a Stirling convertor for two concepts; one for the Advanced Stirling Radioisotope Generator (ASRG) back up cooling system and one for the Long-lived Venus Lander thermal management system. The VCHP is designed to activate and remove heat from the stopped convertor at a 19 degC temperature increase from the nominal vapor temperature. The 19 degC temperature increase from nominal is low enough to avoid risking standard ASRG operation and spoiling of the Multi-Layer Insulation (MLI). In addition, the same backup cooling system can be applied to the Stirling convertor used for the refrigeration system of the Long-lived Venus Lander. The VCHP will allow the refrigeration system to: 1) rest during transit at a lower temperature than nominal; 2) pre-cool the modules to an even lower temperature before the entry in Venus atmosphere; 3) work at nominal temperature on Venus surface; 4) briefly stop multiple times on the Venus surface to allow scientific measurements. This paper presents the experimental results from integrating the VCHP with an operating Stirling convertor and describes the methodology used to achieve their successful combined operation.
Glass-Like Heat Conduction in Crystalline Semiconductors
Nolas, G.S.; Cohn, J.L.; Chakoumakos, B.C.; Slack, G.A.
1999-06-13
The thermal conductivity and structural properties of polycrystalline and single crystal semiconductor type-1 germanium clathrates are reported. Germanium clathrates exhibit thermal conductivities that are typical of amorphous materials. This behavior occurs in spite of their well-defined crystalline structure. The authors employ temperature dependent neutron diffraction data in investigating the displacements of the caged strontium atoms in Sr{sub 8}Ga{sub 16}Ge{sub 30} and their interaction with the polyhedral cages that entrap them. Their aim is to investigate the correlation between the structural properties and the low, glass-like thermal conductivity observed in this compound.
Variable Conductance Heat Pipes for Radioisotope Stirling Systems
William G. Anderson; Calin Tarau
2008-01-01
In a Stirling radioisotope system, heat must continually be removed from the GPHS modules, to maintain the GPHS modules and surrounding insulation at acceptable temperatures. Normally, the Stirling convertor provides this cooling. If the Stirling engine stops in the current system, the insulation is designed to spoil, preventing damage to the GPHS, but also ending the mission. An alkali-metal Variable
A high reliability variable conductance heat pipe space radiator
G. L. Fleischman; G. F. Pasley; R. J. McGrath; L. D. Loudenback
1978-01-01
The heat pipes in this radiator for space applications incorporate a central-core wrapped screen wick, which primes and reprimes under adverse conditions in the presence of noncondensable gas. A step change in mesh size provides low resistance to liquid flow in the condenser while at the same time retaining high pumping capability in the evaporator region. The envelope and wick
Paradoxical heat sensation in healthy subjects: peripherally conducted by A delta or C fibres?
Susser, E; Sprecher, E; Yarnitsky, D
1999-02-01
Paradoxical heat sensation upon cooling of the skin has been reported in central as well as in peripheral neurological conditions. In our study, we examined this phenomenon in 35 naive healthy test subjects, of whom 23 experienced paradoxical heat sensation under test conditions. We measured the peripheral conduction velocities of cold sensation, warm sensation and of paradoxical heat sensation by using a quantitative sensory testing model of indirect peripheral conduction velocity measurement. This was based on comparison of measurements at a proximal and a distal site using two measurement methods, one inclusive and the other exclusive of reaction time. We found that the conduction velocity of paradoxical heat sensation (0.70 m/s) was similar to that of warm sensation (0.68 m/s), and that the conduction velocity of cold sensation (7.74-8.01 m/s) was considerably faster. Thus, we conclude that paradoxical heat sensation in healthy subjects is conducted peripherally via slow unmyelinated C fibres and not via the faster A delta fibres. Consequently, we propose that paradoxical heat sensation is encoded via the heat sensing pathway, in accordance with the labelled-line code theory. The mechanisms proposed suggest a malfunctioning cold-sensing pathway disinhibiting the heat-sensing pathway, at peripheral, central or both levels, thus facilitating a paradoxical heat sensation. PMID:10071052
Nanoflare statistics in an active region 3D MHD coronal model
Bingert, Sven
2012-01-01
Context. We investigate the statistics of the spatial and temporal distribution of the coronal heating in a three-dimensional magneto- hydrodynamical (3D MHD) model. The model describes the temporal evolution of the corona above an observed active region. The model is driven by photospheric granular motions which braid the magnetic field lines. This induces currents and their dissipation heats the plasma. We evaluate the transient heating as subsequent heating events and analyze their statistics. The results are then interpreted in the context of observed flare statistics and coronal heating mechanisms. Methods. To conduct the numerical experiment we use a high order finite difference code which solves the partial differential equations for the conservation of mass, the momentum and energy balance, and the induction equation. The energy balance includes the Spitzer heat conduction and the optical thin radiative loss in the corona. Results. The temporal and spatial distribution of the Ohmic heating in the 3D M...
A MOLECULAR DYNAMICS SIMULATION OF HEAT CONDUCTION IN A CARBON NANOTUBE
Maruyama, Shigeo
A MOLECULAR DYNAMICS SIMULATION OF HEAT CONDUCTION IN A CARBON NANOTUBE Shigeo Maruyama conduction of finite length single walled carbon nanotubes (SWNTs) was simulated by the molecular dynamics experiments, several preliminary molecular dynamics simulations4-6 showed very high thermal conductivity
Plate Fin Heat Exchanger Model with Axial Conduction and Variable Properties
Hansen, B J; Klebaner, A; 10.1063/1.4706971
2012-01-01
Future superconducting radio frequency (SRF) cavities, as part of Project X at Fermilab, will be cooled to superfluid helium temperatures by a cryogenic distribution system supplying cold supercritical helium. To reduce vapor fraction during the final Joule-Thomson (J-T) expansion into the superfluid helium cooling bath, counter-flow, plate-fin heat exchangers will be utilized. Due to their compact size and ease of fabrication, plate-fin heat exchangers are an effective option. However, the design of compact and high-effectiveness cryogenic heat exchangers operating at liquid helium temperatures requires consideration of axial heat conduction along the direction of flow, in addition to variable fluid properties. Here we present a numerical model that includes the effects of axial conduction and variable properties for a plate fin heat exchanger. The model is used to guide design decisions on heat exchanger material choice and geometry. In addition, the J-T expansion process is modeled with the heat exchanger ...
NASA Astrophysics Data System (ADS)
Dede, Ercan M.; Nomura, Tsuyoshi; Schmalenberg, Paul; Seung Lee, Jae
2013-08-01
Experimental results are presented for heat flux cloaking, focusing, and reversal in ultra-thin anisotropic composites. A two-material system is utilized in the device design, which features an annular region for heat flow control. The effective thermal conductivity layout of the composite is specified through logical combination of the base material constituents. Heat transfer considering conduction-convection is numerically predicted and experimentally verified via infrared thermography. A Biot number analysis reveals the significance of high rates of convection for large-area planar devices, while the experimental results indicate the feasibility of such heat flow control techniques for advanced electronics applications involving natural convection.
NASA Astrophysics Data System (ADS)
Pletinckx, D.
2011-09-01
The current 3D hype creates a lot of interest in 3D. People go to 3D movies, but are we ready to use 3D in our homes, in our offices, in our communication? Are we ready to deliver real 3D to a general public and use interactive 3D in a meaningful way to enjoy, learn, communicate? The CARARE project is realising this for the moment in the domain of monuments and archaeology, so that real 3D of archaeological sites and European monuments will be available to the general public by 2012. There are several aspects to this endeavour. First of all is the technical aspect of flawlessly delivering 3D content over all platforms and operating systems, without installing software. We have currently a working solution in PDF, but HTML5 will probably be the future. Secondly, there is still little knowledge on how to create 3D learning objects, 3D tourist information or 3D scholarly communication. We are still in a prototype phase when it comes to integrate 3D objects in physical or virtual museums. Nevertheless, Europeana has a tremendous potential as a multi-facetted virtual museum. Finally, 3D has a large potential to act as a hub of information, linking to related 2D imagery, texts, video, sound. We describe how to create such rich, explorable 3D objects that can be used intuitively by the generic Europeana user and what metadata is needed to support the semantic linking.
Simulating coronal condensation dynamics in 3D
Moschou, S P; Xia, C; Fang, X
2015-01-01
We present numerical simulations in 3D settings where coronal rain phenomena take place in a magnetic configuration of a quadrupolar arcade system. Our simulation is a magnetohydrodynamic simulation including anisotropic thermal conduction, optically thin radiative losses, and parametrised heating as main thermodynamical features to construct a realistic arcade configuration from chromospheric to coronal heights. The plasma evaporation from chromospheric and transition region heights eventually causes localised runaway condensation events and we witness the formation of plasma blobs due to thermal instability, that evolve dynamically in the heated arcade part and move gradually downwards due to interchange type dynamics. Unlike earlier 2.5D simulations, in this case there is no large scale prominence formation observed, but a continuous coronal rain develops which shows clear indications of Rayleigh-Taylor or interchange instability, that causes the denser plasma located above the transition region to fall do...
T. V. Noon; E. Marx
1981-01-01
A computer model (CONDUCT) has been developed that simulates corps and subordinate command, control, communications, and intelligence C3I functions with particular emphasis on the integration of the new generation of intelligence, surveillance, and target-acquisition systems within the developing 1982 and 1986 force structure. CONDUCT is an event-by-event simulation model written in GPSS-V (General Purpose Simulation System), representing the combat and
An approximate substitution principle for viscous heat conducting flows
NASA Astrophysics Data System (ADS)
Greitzer, E. M.; Paterson, R. W.; Tan, C. S.
1985-09-01
A new, approximate substitution principle is presented for a class of steady flows in which both heat transfer and momentum interchange by viscous stresses are significant. The principle, which has important implications for the design and scaling of mixing experiments, can be regarded as an extension of the Munk and Prim substitution principle (for steady isentropic flows) to nonisentropic flows (Munk and Prim, 1947). The concepts that are developed explain the scaling and distribution of various fluid dynamic properties observed in several different types of flow mixing experiments. Calculations are done to indicate the expected regimes of applicability of the approximate principle and comparison with experiment is made to show its utility in practical situations.
Sandeep Singh
\\u000a It’s time to bring the ideas you’ve learned in the first couple of chapters and develop a model in SketchUp for 3D printing\\u000a in Shapeways. The goal of this chapter is to get you acquainted with all the basic steps of developing a model for 3D printing.\\u000a You’ll start this chapter off with a brainstorming session where you develop sketches
MOLECULAR DYNAMICS SIMULATION OF QUASI-BALLISTIC HEAT CONDUCTION IN CARBON NANOTUBES
Maruyama, Shigeo
characteristics of short wavelength phonons are strongly influence by the anharmonic effects. This aspect-tube interaction on the heat conduction is of an interest. In addition, we consider an SWNT confining an ice
Molecular dynamics analysis of spectral characteristics of phonon heat conduction in silicon
Henry, Asegun Sekou Famake
2006-01-01
Due to the technological significance of silicon, its heat conduction mechanisms have been studied extensively. However, there have been some lingering questions surrounding the phonon mean free path and importance of ...
NASA Astrophysics Data System (ADS)
Kök, M.; Aydo?du, Y.
2007-04-01
The thermal conductivity of polyvinylchloride (PVC), polysytrene (PS) and polypropylene (PP) were measured by heat flux DSC. Our results are in good agreement with the results observed by different methods.
The importance of electron heat conduction in the energy balance of the F-region
NASA Technical Reports Server (NTRS)
Hoegy, W. R.; Brace, L. H.
1978-01-01
Taking into account heat conduction in the analysis of electron temperature data acquired by the AE-C satellite during the daytime at middle latitudes is shown to bring theoretical electron temperature profiles in good agreement with experimental ones. Middle latitude passes were chosen because in this region the horizontal electron temperature gradient is negligible and the height variation can be approximated by the satellite data. Inclusion of heat conduction is shown to have little effect on low-latitude data.
Pulsed RF heating simulations in normal-conducting L-band cavities.
Pulsed RF heating simulations in normal-conducting L-band cavities. V.V. Paramonov, A and results of pulsed heating effect simulations in L-band cavities, operating with high pulsed RF loss references. At L-band frequency the maximal electric and related magnetic fields are lower. Together
Measurement of the electronic thermal conductance channels and heat capacity of graphene at low opto-electronics, plasmonics, and ultra-sensitive bolometry. Here we present measurements of bipolar relation, Wiedemann- Franz ratio[3, 4], and electronic specific heat[5] . Thermal transport measurements
A Conduction Calorimeter for Measuring the Heat of Cement Hydration in the Initial Hydration Period
W. Zielenkiewicz; M. Kami?ski
2001-01-01
A new-design conduction microcalorimeter is described, which has been used to measure the heat of cement hydration evolved\\u000a in the initial period of hydration. The calorimeter is 30 cm3 in volume; the heat loss coefficient is 27.2700.015 W V–1, the time constant is 300 s.
Hyperbolic heat conduction equation for materials with a nonhomogeneous inner structure
W. Kaminski
1990-01-01
The physical meaning of the constant Ï in Cattaneo and Vernotte's equation for materials with a nonhomogeneous inner structure has been considered. An experimental determination of the constant Ï has been proposed and some values for selected products have been given. The range of differences in the description of heat transfer by parabolic and hyperbolic heat conduction equations has been
J. M. Zhao; L. H. Liu
2007-01-01
A spectral element method is presented to solve coupled radiative and conductive heat transfer problems in multidimensional semitransparent medium. The solution of radiative energy source is based on a second order radiative transfer equation. Both the second order radiative transfer equation and the heat diffusion equation are discretized by spec- tral element approach. Four various test problems are taken as
Fygenson, Deborah Kuchnir
-Be´nard convection Guenter Ahlers Department of Physics and iQUEST, University of California, Santa Barbara transport in Rayleigh-Be´nard convection the correction for the sidewall conductance is usually neglected convection of a fluid heated from below is the global heat transport of the system 1 , as expressed
Finite element formulation of the two-dimensional nonlinear inverse heat conduction problem
B. R. Bass; L. J. Ott
1980-01-01
The calculation of the surface temperature and surface heat flux from measured temperature transients at one or more interior points of a body is identified in the literature as the inverse heat conduction problem. Heretofore, analytical and computational methods of treating this problem have been limited to one-dimensional nonlinear or two-dimensional linear material models. An inverse solution technique applicable to
Heat conduction in anisotropic media: Nonlinear self-adjointness and conservation laws
Nail H. Ibragimov; Elena D. Avdonina
2012-02-27
Nonlinear self-adjointness of the anisotropic nonlinear heat equation is investigated. Mathematical models of heat conduction in anisotropic media with a source are considered and a class of self-adjoint models is identified. Conservation laws corresponding to the symmetries of the equations in question are computed.
Makarenko, A.S. [Kiev State Univ. (Russian Federation)
1994-06-01
Problems in the mathematical modeling of heat-distribution processes on the basis of more general equations than parabolic equations are considered. We study the general structure of the relations between solutions of various approximations to the generalized heat-conductivity equations. We introduce a notion of singularly perturbed dissipative structures and analyze singularly, perturbed blow-up regimes.
Communication Cement of high specific heat and high thermal conductivity, obtained by
Chung, Deborah D.L.
Received 21 December 1999; accepted 19 April 2000 Abstract Cement paste of high specific heat and high; Silica fume; Cement paste; Compressive strength; Silane 1. Introduction Concrete of low thermal of a structure. Cement paste exhibiting high specific heat and low thermal conductivity can be obtained by using
Y. Okamoto; R. Himeno; K. Ushida; A. Ahagon
2006-01-01
In order to reuse all waste plastics containing polyvinyl chloride (PVC) effectively, the removal of chlorine from PVC is required during the preprocess of feedback recycling. In this paper, we explain the detail of heated process in PVC, and a coupled analysis method was developed to investigate the correlation of high frequency electromagnetic wave propagation and heat conduction
Maruyama, Shigeo
Influence of interfaces on diffusive-ballistic heat conduction of carbon nanotubes Shiomi to significant ballistic phonon transport for realistic nanotube length in many applications even at room. In a system with significant ballistic heat transport, the intrinsic phonon distribution function and thus
NASA Astrophysics Data System (ADS)
Piqué, C.; Blanco, J. A.; Burriel, R.; Abad, E.; Fernández-Rodríguez, J.; Artigas, M.
2008-08-01
Using adiabatic calorimetry the heat capacity of a series of RFexMn12-x (R = Gd, Tb and Dy) compounds has been measured from 3 to 350 K. The substitution of Fe for Mn in RFexMn12-x influences both the magnetic interactions on the 3d sublattice and the magnetism of R (the Néel temperature doubles on going from x = 0 to 6 and the compounds become ferromagnetic for x = 8 with Curie temperatures of around 300 K). In pure TbMn12 the heat-capacity data shows a ?-type anomaly associated with the independent cooperative magnetic ordering of the R sublattice (~5 K), while the anomaly related to the Mn magnetic ordering (~100 K) is rather smooth, as observed in other itinerant magnetic systems such as YMn12. In contrast, the substitution of Fe for Mn leads, on the one hand, to a more localized magnetic behaviour of the 3d sublattice, and, on the other, to magnetic polarization effects between the 3d and 4f sublattices, together with the disappearance of the cooperative magnetic ordering of the R sublattice due to the breaking of the antiferromagnetic symmetry in the 3d sublattice. This is reflected in the heat-capacity curve through a smooth Schottky-like anomaly. In the case of Gd compounds the magnitude of the exchange molecular-field parameter has been deduced by fitting the magnetic contribution to the heat capacity within a simple mean-field model. From this analysis we found that this molecular field acting on the rare-earth site increases with the iron concentration, reaching values as large as 48 T for the concentration x = 6. A similar analysis of the heat capacity in the ordered phase on the Tb compounds also leads to an enhancement of the molecular field with increasing Fe content. These results allow checking the possible crystal-field parameters for these RFexMn12-x compounds.
V. A. Karkhin; A. Pittner; C. Schwenk; M. Rethmeier
2011-01-01
The paper presents bounded volume heat sources and the corresponding functional-analytical expressions for the temperature\\u000a field. The power density distributions considered here are normal, exponential and parabolic. The sources model real heat\\u000a sources like the welding arc, laser beam, electron beam, etc., the convection in the weld pool as well as the latent heat\\u000a due to fusion and solidification. The
NASA Astrophysics Data System (ADS)
Rushmer, T.; Beier, C.; Turner, S.
2007-12-01
Melting anomalies in the Earth's upper mantle have often been attributed to the presence of mantle plumes that may originate in the lower mantle, possibly from the core-mantle boundary. Globally, mantle plumes exhibit a large range in buoyancy flux that which is proportional to their temperature and volume. Plumes with higher buoyancy fluxes should have higher temperatures and experience higher degrees of partial melting. Excess heat in mantle plumes could reflect either a) an enrichment of the heat producing elements (HPE: U, Th, K) in their mantle source leading to an increase of heat production by radioactive decay or b) advective or conductive heat transport across the core-mantle boundary. The advective transport of heat may result in a physical contribution of material from the core to the lower mantle. If core material is incorporated into the lower mantle, mantle plumes with a higher buoyancy flux should have higher core tracers, e.g. increased 186Os and Fe concentrations. Geophysical and dynamic modelling indicate that at least Afar, Easter, Hawaii, Louisville and Samoa may all originate at the core-mantle boundary. These plumes encompass the whole range of known buoyancy fluxes from 1.2 Mgs -1(Afar) to 6.5 Mgs -1 (Hawaii) providing evidence that the buoyancy flux is largely independent of other geophysical parameters. In an effort to explore whether the heat producing elements are the cause of excess heat we looked for correlations between fractionation corrected concentrations of the HPE and buoyancy flux. Our results suggest that there is no correlation between HPE concentrations and buoyancy flux (with and without an additional correction for variable degrees of partial melting). As anticipated, K, Th and U are positively correlated with each other (e.g. Hawaii, Iceland and Galapagos have significantly lower concentrations than e.g. Tristan da Cunha, the Canary Islands and the Azores). We also find no correlation between currently available Fe concentration data and buoyancy flux. The apparent lack of correlation suggests that excess heat may be a result of conductive heat contribution from the core. Additional precise 186Os and Fe data are needed to further assess these conclusions.
NASA Astrophysics Data System (ADS)
Dimopoulos, Dimitrios; Pelekasis, Nikos A.
2014-10-01
Rayleigh-Bénard stability of a liquid metal layer of rectangular cross section is examined in the presence of a strong magnetic field that is aligned with the horizontal direction of the cross section. The latter is much longer than the vertical direction and the cross section assumes a large aspect ratio. The side walls are treated as highly conducting. Linear stability analysis is performed allowing for three-dimensional instabilities that develop along the longitudinal direction. The finite element methodology is employed for the discretization of the stability analysis formulation while accounting for the electrical conductivity of the cavity walls. The Arnoldi method provides the dominant eigenvalues and eigenvectors of the problem. In order to facilitate parallel implementation of the numerical solution at large Hartmann numbers, Ha, domain decomposition is employed along the horizontal direction of the cross section. As the Hartmann number increases a real eigenvalue emerges as the dominant unstable eigenmode, signifying the onset of thermal convection, whose major vorticity component in the core of the layer is aligned with the direction of the magnetic field. Its wavelength along the longitudinal direction of the layer is on the order of twice its height and increases as Ha increases. The critical Grashof was obtained for large Ha and it was seen to scale like Ha 2 signifying the balance between buoyancy and Lorentz forces. For well conducting side walls, the nature of the emerging flow pattern is determined by the combined conductivity of Hartmann walls and Hartmann layers, cH + Ha -1. When poor conducting Hartmann walls are considered, cH ? 1, the critical eigensolution is characterized by well defined Hartmann and side layers. The side layers are characterized by fast fluid motion in the magnetic field direction as a result of the electromagnetic pumping in the vicinity of the Hartmann walls. Increasing the electrical conductivity of the Hartmann walls was seen to delay the onset of thermal convection, while retaining the above scaling at criticality. Furthermore, for both conducting and insulating Hartmann walls and the entire range of Ha numbers that was examined, there was no tendency for a well defined quasi two-dimensional structure to develop owing to the convective motion in the core. A connection is made between the above findings and previous experimental investigations indicating the onset of standing waves followed by travelling waves as Gr is further increased beyond its critical value.
On Thermo-viscoelasticity with Variable Thermal Conductivity and Fractional-Order Heat Transfer
NASA Astrophysics Data System (ADS)
Ezzat, M. A.; El-Karamany, A. S.; El-Bary, A. A.
2015-04-01
The equations of generalized thermo-viscoelasticity for an isotropic medium with variable thermal conductivity and fractional-order heat transfer are given. The resulting formulation is applied to a half-space subjected to arbitrary heating which is taken as a function of time and is traction free. The Laplace transform technique is used. A numerical method is employed for the inversion of the Laplace transforms. Numerical results for temperature, displacement, and stress distributions are given and illustrated graphically for the problem. The effects of the fractional order and the variable thermal conductivity for heat transfer on a viscoelastic material such as poly(methyl methacrylate) (Perspex) are discussed.
Phonon Heat Conduction in Corrugated Silicon Nanowires Below the Casimir Limit Christophe Blanc,1
, 2013) The thermal conductance of straight and corrugated monocrystalline silicon nanowires has beenPhonon Heat Conduction in Corrugated Silicon Nanowires Below the Casimir Limit Christophe Blanc,1. This result suggests an original approach to transforming a monocrystalline material into a phonon glass. PACS
Phonon Heat Conduction in Corrugated Silicon Nanowires Below the Casimir Limit Christophe Blanc,1
Paris-Sud XI, UniversitÃ© de
, 2013) The thermal conductance of straight and corrugated monocrystalline silicon nanowires has beenPhonon Heat Conduction in Corrugated Silicon Nanowires Below the Casimir Limit Christophe Blanc,1 an original approach to transforming a monocrystalline material into a phonon glass. PACS numbers: 63.22.-m
H. Q. Yang
1990-01-01
For extremely short durations oral very low temperatures (near absolute zero), the classical Fourier heat conduction equation fails and has to be replaced by a hyperbolic equation to account for finite thermal wave propagation. During the last few years, there has been a growing interest in numerical simulation of the hyperbolic heal conduction problem. The schemes used in previous studies
Thermal conductivity of cementitious grouts for geothermal heat pumps. Progress report FY 1997
Allan, M.L.
1997-11-01
Grout is used to seal the annulus between the borehole and heat exchanger loops in vertical geothermal (ground coupled, ground source, GeoExchange) heat pump systems. The grout provides a heat transfer medium between the heat exchanger and surrounding formation, controls groundwater movement and prevents contamination of water supply. Enhanced heat pump coefficient of performance (COP) and reduced up-front loop installation costs can be achieved through optimization of the grout thermal conductivity. The objective of the work reported was to characterize thermal conductivity and other pertinent properties of conventional and filled cementitious grouts. Cost analysis and calculations of the reduction in heat exchanger length that could be achieved with such grouts were performed by the University of Alabama. Two strategies to enhance the thermal conductivity of cementitious grouts were used simultaneously. The first of these was to incorporate high thermal conductivity filler in the grout formulations. Based on previous tests (Allan and Kavanaugh, in preparation), silica sand was selected as a suitable filler. The second strategy was to reduce the water content of the grout mix. By lowering the water/cement ratio, the porosity of the hardened grout is decreased. This results in higher thermal conductivity. Lowering the water/cement ratio also improves such properties as permeability, strength, and durability. The addition of a liquid superplasticizer (high range water reducer) to the grout mixes enabled reduction of water/cement ratio while retaining pumpability. Superplasticizers are commonly used in the concrete and grouting industry to improve rheological properties.
Two-phase numerical model for thermal conductivity and convective heat transfer in nanofluids
2011-01-01
Due to the numerous applications of nanofluids, investigating and understanding of thermophysical properties of nanofluids has currently become one of the core issues. Although numerous theoretical and numerical models have been developed by previous researchers to understand the mechanism of enhanced heat transfer in nanofluids; to the best of our knowledge these models were limited to the study of either thermal conductivity or convective heat transfer of nanofluids. We have developed a numerical model which can estimate the enhancement in both the thermal conductivity and convective heat transfer in nanofluids. It also aids in understanding the mechanism of heat transfer enhancement. The study reveals that the nanoparticle dispersion in fluid medium and nanoparticle heat transport phenomenon are equally important in enhancement of thermal conductivity. However, the enhancement in convective heat transfer was caused mainly due to the nanoparticle heat transport mechanism. Ability of this model to be able to understand the mechanism of convective heat transfer enhancement distinguishes the model from rest of the available numerical models. PMID:21711746
Heat conduction: hyperbolic self-similar shock-waves in solids
Imre Ferenc Barna; Robert Kersner
2012-04-19
Analytic solutions for cylindrical thermal waves in solid medium is given based on the nonlinear hyperbolic system of heat flux relaxation and energy conservation equations. The Fourier-Cattaneo phenomenological law is generalized where the relaxation time and heat propagation coefficient have a general power law temperature dependence. From such laws one cannot form a second order parabolic or telegraph-type equation. We consider the original non-linear hyperbolic system itself with the self-similar Ansatz for the temperature distribution and for the heat flux. As results continuous and shock-wave solutions are presented. For physical establishment numerous materials with various temperature dependent heat conduction coefficients are mentioned.
NASA Astrophysics Data System (ADS)
Dhar, Purbarun; Sen Gupta, Soujit; Chakraborty, Saikat; Pattamatta, Arvind; Das, Sarit K.
2013-04-01
A thermal transport mechanism leading to the enhanced thermal conductivity of graphene nanofluids has been proposed. The graphene sheet size is postulated to be the key to the underlying mechanism. Based on a critical sheet size derived from Stokes-Einstein equation for the poly-dispersed nanofluid, sheet percolation and Brownian motion assisted sheet collisions are used to explain the heat conduction. A collision dependant dynamic conductivity considering Debye approximated volumetric specific heat due to phonon transport in graphene has been incorporated. The model has been found to be in good agreement with experimental data.
Allan, M.L.
1996-06-01
Preliminary studies were preformed to determine whether thermal conductivity of cementitious grouts used to backfill heat exchanger loops for geothermal heat pumps could be improved, thus improving efficiency. Grouts containing selected additives were compares with conventional bentonite and cement grouts. Significant enhancement of grout alumina grit, steel fibers, and silicon carbide increased the thermal conductivity when compared to unfilled, high solids bentonite grouts and conventional cement grouts. Furthermore, the developed grouts retained high thermal conductivity in the dry state, where as conventional bentonite and cement grouts tend to act as insulators if moisture is lost. The cementitious grouts studied can be mixed and placed using conventional grouting equipment.
S. Martens; M. Fink; W. Mack; F. Voelklein; J. Wilde
2010-01-01
The trends of 3D integration and System-in-Package (SiP) require the adaptation of target preparation methods for failure analysis of these complex integrated devices. Recent improvements in laser-based target preparation make laser cross-sections through several stacked silicon dies possible with remarkably small visible Heat-Affected Zones (HAZs). The distinct removal of Molding Compound (MC), silicon dies, and metal interconnects with a single
C. Piqué; J. A. Blanco; R. Burriel; E. Abad; J. Fernández-Rodríguez; M. Artigas
2008-01-01
Using adiabatic calorimetry the heat capacity of a series of RFexMn12-x (R = Gd, Tb and Dy) compounds has been measured from 3 to 350 K. The substitution of Fe for Mn in RFexMn12-x influences both the magnetic interactions on the 3d sublattice and the magnetism of R (the Néel temperature doubles on going from x = 0 to 6
Lijuan He; Shengbiao Hu; Shaopeng Huang; Wencai Yang; Jiyang Wang; Yusong Yuan; Shuchun Yang
2008-01-01
The Chinese Continental Scientific Drilling (CCSD) Project offers a unique opportunity for studying the thermal regime of the Dabie-Sulu ultrahigh-pressure metamorphic belt. In this paper, we report measurements of borehole temperature, thermal conductivity, and radiogenic heat production from the 5158 m deep main hole (CCSD MH). We have obtained six continuous temperature profiles from this borehole so far. The temperature
Dimakogianni, M; Triberis, G P
2010-09-01
According to percolation theory the investigation of charge transport in disordered systems is equivalent to the study of the possibility of the passage of the carriers through a random network of impedances which interconnect the different lattice sites. When the site energies are not the same, the energy of a site affects the incoming as well as the outgoing impedances connected to the given site and this gives rise to correlations between neighboring impedances. This new condition characterizes the transport process and imposes the evaluation of the average number of sites accessible by a bond from a given site for all possible configurations of sites that satisfy the percolation condition. The generalized molecular crystal model, appropriate for the study of small-polaron hopping transport in disordered systems, and the Kubo formula permit the evaluation of these impedances. Taking correlations into account, theoretical percolation considerations applicable to one-dimensional and three-dimensional disordered systems, lead to analytical expressions for the temperature and electric field dependence of the DC conductivity at high (multi-phonon-assisted hopping) and low (few-phonon-assisted hopping) temperatures. The theoretical analysis reveals the effect of correlations on the non-ohmic behavior of the small-polaron hopping conductivity and permits the evaluation of the maximum hopping distance. Quantitative estimates of this effect are presented comparing the theoretical results, including correlations with those ignoring them, previously reported, applying them to recent experimental data for a wide temperature range and from low up to moderate electric fields. PMID:21403284
V. Vashook; R. Müller; J. Zosel; K. Ahlborn; F. Gerlach; P. Tietz; G. Stöver; U. Guth
2007-01-01
Six $$ {\\\\text{La}}_{{0.4}} {\\\\text{Ca}}_{{0.5}} {\\\\text{Ti}}_{{0.5}} {\\\\text{Cr}}_{{0.4}} {\\\\text{M}}_{{0.1}} {\\\\text{O}}_{{3 - \\\\delta }} $$ (M?=?Cr, Mn, Fe, Co, Ni, Cu) and two $$ {\\\\text{La}}_{{0.4}} {\\\\text{Ca}}_{{0.4}} {\\\\text{Ti}}_{{0.4}} {\\\\text{Cr}}_{{0.4}} {\\\\text{M}}_{{0.2}} {\\\\text{O}}_{{3 - \\\\delta }} $$ (M?=?Ni, Cu) single-phase compositions were prepared by conventional solid-state reactions. Oxygen nonstoichiometry, electrical\\u000a conductivity, phase transformations under reduction-reoxidation at high temperatures and catalytic activity for hydrocarbons\\u000a oxidation of these
The program FANS-3D (finite analytic numerical simulation 3-dimensional) and its applications
NASA Technical Reports Server (NTRS)
Bravo, Ramiro H.; Chen, Ching-Jen
1992-01-01
In this study, the program named FANS-3D (Finite Analytic Numerical Simulation-3 Dimensional) is presented. FANS-3D was designed to solve problems of incompressible fluid flow and combined modes of heat transfer. It solves problems with conduction and convection modes of heat transfer in laminar flow, with provisions for radiation and turbulent flows. It can solve singular or conjugate modes of heat transfer. It also solves problems in natural convection, using the Boussinesq approximation. FANS-3D was designed to solve heat transfer problems inside one, two and three dimensional geometries that can be represented by orthogonal planes in a Cartesian coordinate system. It can solve internal and external flows using appropriate boundary conditions such as symmetric, periodic and user specified.
NASA Astrophysics Data System (ADS)
Fushimi, K.; Ono, A.; Matsushita, K.; Kumagai, H.; Konno, H.
2011-07-01
A simple heat treatment was used to fabricate carbonaceous layer-coated electrodes: micro-ring electrodes and conductive stainless steel. Substrates of sharpened quartz capillaries or type-316 stainless steel plates were put in an alumina boat with powder of petroleum pitch A240F separately and heated at 1073-1273 K in a flow of nitrogen or argon. By this treatment, both of the substrates were coated with a uniform carbonaceous layer of several hundred nano-meters in thickness. The electric conductivity of the layer was improved by increases in temperature and period of the heating. The quartz glass-capillary covered with the conductive layer was modified to a needle-type microelectrode by coating with an insulating polymer and baring the tip. At least a dozen carbon micro-ring electrodes with an outer radius of about 1 ?m were successfully prepared by the simple heat treatment. On the other hand, the carbonaceous layer formed on type-316 stainless steel showed relatively poor conductivity due to the formation of oxides in the layer. However, the conductivity was improved by electroplating of nickel on the substrate before the heating. The carbonaceous layer-coated stainless steel showed good corrosion resistance in sulphuric acid.
The radiant component of steam heat conductivity at high pressures and temperatures
NASA Astrophysics Data System (ADS)
Panchenko, S. V.; Dli, M. I.; Borisov, V. V.
2015-07-01
The problem of energy transfer by heat conduction and radiation is brought to a differential equation containing temperature derivatives at the boundaries and based on the selectively gray approximation of absorbing medium. A method for analytically solving the linearized problem radiant-conductive heat transfer in a flat layer of selectively absorbing medium is proposed, using which an unsymmetrical temperature profile more accurately approximating the experimental results can be obtained. The adequacy of the solution method is demonstrated by comparing the calculation results with the experimental and the results obtained using numerical methods. The effect the intermolecular interactions have on the optical properties of highly compressed media is analyzed. A dependence for determining the integral intensity of steam bands at pressures of up to 100 MPa is obtained. Quite satisfactory agreement is obtained between the calculated values of absorption intensities at increased pressures, including those for steam. The radiant component values obtained from steam heat conductivity measurements carried out in a wide range of temperatures taking into account the absorption selectivity and deviation of heat conductivity coefficients with absorption and for a transparent gas model are presented. The study results can be used for estimating the radiant component in heat conductivity measurements of absorbing fluids.
NASA Astrophysics Data System (ADS)
Liu, D.; Medley, S. S.; Gorelenkova, M. V.; Heidbrink, W. W.; Stagner, L.
2014-10-01
A cloud of halo neutrals is created in the vicinity of beam footprint during the neutral beam injection and the halo neutral density can be comparable with beam neutral density. Proper modeling of halo neutrals is critical to correctly interpret neutral particle analyzers (NPA) and fast ion D-alpha (FIDA) signals since these signals strongly depend on local beam and halo neutral density. A 3D halo neutral model has been recently developed and implemented inside TRANSP code. The 3D halo neutral code uses a ``beam-in-a-box'' model that encompasses both injected beam neutrals and resulting halo neutrals. Upon deposition by charge exchange, a subset of the full, one-half and one-third beam energy components produce thermal halo neutrals that are tracked through successive halo neutral generations until an ionization event occurs or a descendant halo exits the box. A benchmark between 3D halo neural model in TRANSP and in FIDA/NPA synthetic diagnostic code FIDASIM is carried out. Detailed comparison of halo neutral density profiles from two codes will be shown. The NPA and FIDA simulations with and without 3D halos are applied to projections of plasma performance for the National Spherical Tours eXperiment-Upgrade (NSTX-U) and the effects of halo neutral density on NPA and FIDA signal amplitude and profile will be presented. Work supported by US DOE.
Elaine C. Meng; Benjamin J. Polacco; Patricia C. Babbitt
Three-dimensional (3D) motifs are patterns of local structure associated with function, typically based on residues in binding\\u000a or catalytic sites. Protein structures of unknown function can be annotated by comparing them to known 3D motifs. Many methods\\u000a have been developed for identifying 3D motifs and for searching structures for their occurrence. Approaches vary in the type\\u000a and amount of input
3d And 2d Automatic Inverse Modelling Of Sedimentary Basin Formation
NASA Astrophysics Data System (ADS)
Schmalholz, S. M.; Podladchikov, Yu. Yu.; Schmid, D.; Kaus, B. J. P.
We present 3D and 2D forward models (TECMOD2D and 3D), which numerically simulate sedimentary basin formation and are coupled with automatic inversion algo- rithms. The forward models are based on depth-dependent kinematic stretching and/or asymmetric extension along faults. The inversion algorithm iteratively finds the opti- mal set of thinning factors or fault offsets (which fit any observed basin stratigraphy best) in such a way that symmetric versus asymmetric mode of extension is not as- sumed a priori. The inversion algorithms are able to fit thinning factors that corre- spond to multiple, finite rifting events. The 2D inversion algorithms generally find the optimal set of thinning factors within 10 to 20 iterations for given initial condi- tions. For 3D applications, the inversion algorithm has to fit the horizontal stretching direction in addition to the thinning factors. Necessary modifications of the 2D inver- sion algorithms for 3D applications are discussed. The 3D forward model includes the effects of finite rift duration, thermal sediment blanketing, sediment compaction, radiogenic heat production, lateral heat conduction and advection, flexural isostasy and depth of necking. The 2D model additionally includes faulting and new oceanic crust formation. A 3D forward run with a numerical resolution of 41x41x51 nodes and 28 time steps takes around 15 minutes on a standard PC (1.3 GHz). The influ- ence of finite rift duration, thermal sediment blanketing and lateral heat conduction on the basin subsidence is evaluated. The coupled forward/inverse models are applied to restore the palaeo heat flow at the basement-sediment contact using observed basin stratigraphies. The effects of thermal sediment blanketing and lateral heat conduction in combination with radiogenic heat production are shown to strongly influence the palaeo heat flow reconstructions.
Wang, Hsin [ORNL; Porter, Wallace D [ORNL; Bottner, Harold [Fraunhofer-Institute, Freiburg, Germany; Konig, Jan [Fraunhofer-Institute, Freiburg, Germany; Chen, Lidong [Chinese Academy of Sciences; Bai, Shengqiang [Chinese Academy of Sciences; Tritt, Terry M. [Clemson University; Mayolett, Alex [Corning, Inc; Senawiratne, Jayantha [Corning, Inc; Smith, Charlene [Corning, Inc; Harris, Fred [ZT-Plus; Gilbert, Partricia [Marlow Industries, Inc; Sharp, J [Marlow Industries, Inc; Lo, Jason [CANMET - Materials Technology Laboratory, Natural Resources of Canada; Keinke, Holger [University of Waterloo, Canada; Kiss, Laszlo I. [University of Quebec at Chicoutimi
2013-01-01
For bulk thermoelectrics, figure-of-merit, ZT, still needs to improve from the current value of 1.0 - 1.5 to above 2 to be competitive to other alternative technologies. In recent years, the most significant improvements in ZT were mainly due to successful reduction of thermal conductivity. However, thermal conductivity cannot be measured directly at high temperatures. The combined measurements of thermal diffusivity and specific heat and density are required. It has been shown that thermal conductivity is the property with the greatest uncertainty and has a direct influence on the accuracy of the figure of merit. The International Energy Agency (IEA) group under the implementing agreement for Advanced Materials for Transportation (AMT) has conducted two international round-robins since 2009. This paper is Part II of the international round-robin testing of transport properties of bulk bismuth telluride. The main focuses in Part II are on thermal diffusivity, specific heat and thermal conductivity.
NASA Astrophysics Data System (ADS)
Vasyliunas, Vytenis M.
1987-12-01
Heat produced at the surface of Mercury by the highly time-variable precipitation of charged particles need not be radiated away immediately but can also be conducted into the interior of the planet. For a given precipitated energy flux density, the rise of surface temperature can be computed taking both heat conduction and radiation into account. When the energy input varies on time scales shorter than a characteristic period, estimated to be one (terrestrial) day for conditions typical of Mercury's dark side, heat conduction dominates over radiation and the predicted surface temperature rise becomes negligibly small. Possible observable calorimetric effects are therefore confined to long time scales, and their magnitude is constrained by the average rate of energy input from the solar wind together with limits on the observable area of precipitation.
NASA Technical Reports Server (NTRS)
Tamma, Kumar K.; D'Costa, Joseph F.
1991-01-01
This paper describes the evaluation of mixed implicit-explicit finite element formulations for hyperbolic heat conduction problems involving non-Fourier effects. In particular, mixed implicit-explicit formulations employing the alpha method proposed by Hughes et al. (1987, 1990) are described for the numerical simulation of hyperbolic heat conduction models, which involves time-dependent relaxation effects. Existing analytical approaches for modeling/analysis of such models involve complex mathematical formulations for obtaining closed-form solutions, while in certain numerical formulations the difficulties include severe oscillatory solution behavior (which often disguises the true response) in the vicinity of the thermal disturbances, which propagate with finite velocities. In view of these factors, the alpha method is evaluated to assess the control of the amount of numerical dissipation for predicting the transient propagating thermal disturbances. Numerical test models are presented, and pertinent conclusions are drawn for the mixed-time integration simulation of hyperbolic heat conduction models involving non-Fourier effects.
R. G. Keanini; Xianwu Ling; H. P. Cherukuri
2005-01-01
A method for enhancing the stability of parabolic inverse heat conduction problems (IHCP) is presented. The investigation extends recent work on non-iterative finite element-based IHCP algorithms which, following Beck’s two-step approach, first derives a discretized standard form equation relating the instantaneous global temperature and surface heat flux vectors, and then formulates a least squares-based linear matrix normal equation in the
Author's personal copy Pyroelectric waste heat energy harvesting using heat conduction
Pilon, Laurent
-product of power, refrigeration, or heat pump cycles according to the second law of thermodynamics [1]. In 2009 pump, cryogenic refrigeration, and air liquefaction applications [3]. Organic Rankine cycles use thermoelectric devices have been studied inten- sively. They make use of the Seebeck effect to convert a steady
Radiative heat exchange of a meteor body in the approximation of radiant heat conduction
N. N. Pilyugin; T. A. Chernova
1986-01-01
The problem of the thermal and dynamic destruction of large meteor bodies moving in planetary atmospheres is fundamental for the clarification of optical observations and anomalous phenomena in the atmosphere, the determination of the physicochemical properties of meteoroids, and the explanation of the fall of remnants of large meteorites. Therefore, it is important to calculate the coefficient of radiant heat
Naoki Asai; Naoya Fukuda; Ryoji Matsumoto
2004-04-07
Recent Chandra observations of clusters of galaxies revealed the existence of a sharp ridge in the X-ray surface brightness where the temperature drops across the front. This front is called the cold front. We present the results of two-dimensional magnetohydrodynamic simulations of the time evolution of a dense subcluster plasma moving in a cluster of galaxies. Anisotropic heat conduction along the magnetic field lines is included. In the models without magnetic fields, the numerical results indicate that the heat conduction from the hot ambient plasma heats the cold dense plasma of the subcluster and diffuses out the cold front. When magnetic fields exist in a cluster of galaxies, however, cold fronts can be maintained because the heat conduction across the magnetic field lines is suppressed. We found that, even when the magnetic fields in a cluster of galaxies are disordered, heat conduction across the front is restricted because the magnetic field lines are stretched along the front. Numerical results reproduced the X-ray intensity distribution observed in the A3667 cluster of galaxies.
ERIC Educational Resources Information Center
Hastings, S. K.
2002-01-01
Discusses 3 D imaging as it relates to digital representations in virtual library collections. Highlights include X-ray computed tomography (X-ray CT); the National Science Foundation (NSF) Digital Library Initiatives; output peripherals; image retrieval systems, including metadata; and applications of 3 D imaging for libraries and museums. (LRW)
Masahiro Yamaguchi; Nagaaki Ohyama; Toshio Honda
1990-01-01
This paper proposes a holographic printer, which produces 3-D hard copies of computer processed objects. For the purpose of automatic making of 3-D hard copies of distortion free, a new method to synthesize holographic stereogram is proposed. It is is flat format and lippmann type holographic stereogram which can be printed by one optical step. The proposed hologram has not
Are X-ray Clusters Cooled by Heat Conduction to the Surrounding Intergalactic Medium?
Abraham Loeb
2002-04-29
We show that X-ray clusters would have cooled substantially over a Hubble time by transport of heat from their hot interior to the their envelope, if the heat conductivity had not been heavily suppressed relative to the Spitzer value due to magnetic fields. The suppression is required in order for the observed abundance of hot X-ray clusters to be consistent with predictions from popular cosmological models. If a similar or stronger suppression factor applies to cluster cores, then thermal conduction can not be the mechanism that prevents cooling flows there.
Heat capacities and electrical conductivities of 1-ethyl-3-methylimidazolium-based ionic liquids
Ya-Hung Yu; Allan N. Soriano; Meng-Hui Li
2009-01-01
We present the heat capacities and electrical conductivities of five [Emim] 1-ethyl-3-methylimidazolium-based ionic liquids: [Emim][BF4] (tetrafluoroborate), [Emim][CF3SO3] (trifluoromethanesulfonate), [Emim][C2N3] (dicyanamide), [Emim][C2H5SO4] (ethylsulfate), and [Emim][MDEGSO4] (2-(2-methoxyethoxy) ethylsulfate). The heat capacities were measured using a differential scanning calorimeter (DSC) over the temperature ranging from (303.2 to 358.2)K. The electrical conductivities were measured over the temperature ranging from (293.2 to 353.2)K using a
Basic Inquiry: Radiation and Heat Transfer by Conduction (title provided or enhanced by cataloger)
NSDL National Science Digital Library
David Robison
This activity consists of two parts in which students investigate heat transfer by radiation and by conduction. In the first part, students design and conduct an experiment to test the effect of color on an object's ability to radiate energy (heat). In the second part, they investigate the transfer of energy from a hotter object to a cooler one, in this case, containers of hot and cold water. In both experiments, they are required to state a hypothesis, make a list of materials and procedures needed for the experiment, collect and graph data, and state a conclusion. Each experiment is accompanied by a set of analysis and conclusion questions.
NASA Technical Reports Server (NTRS)
Enginer, J. E.; Luedke, E. E.; Wanous, D. J.
1976-01-01
Continuing efforts in large gains in heat-pipe performance are reported. It was found that gas-controlled variable-conductance heat pipes can perform reliably for long periods in space and effectively provide temperature stabilization for spacecraft electronics. A solution was formulated that allows the control gas to vent through arterial heat-pipe walls, thus eliminating the problem of arterial failure under load, due to trace impurities of noncondensable gas trapped in an arterial bubble during priming. This solution functions well in zero gravity. Another solution was found that allows priming at a much lower fluid charge. A heat pipe with high capacity, with close temperature control of the heat source and independent of large variations in sink temperature was fabricated.
Electrical conductivity of carbonaceous chondrites and electric heating of meteorite parent bodies
NASA Technical Reports Server (NTRS)
Duba, AL
1987-01-01
Electromagnetic heating of rock-forming materials most probably was an important process in the early history of the solar system. Electrical conductivity experiments of representative materials such as carbonaceous chondrites are necessary to obtain data for use in electromagnetic heating models. With the assumption that carbon was present at grain boundaries in the material that comprised the meteorite parent bodies, the electrical heating of such bodies was calculated as a function of body size and solar distance using the T-Tauri model of Sonett and Herbert (1977). The results are discussed.
LDEF (Prelaunch), AO076 : Cascade Variable-Conductance Heat Pipe, Tray F09
NASA Technical Reports Server (NTRS)
1983-01-01
LDEF (Prelaunch), AO076 : Cascade Variable-Conductance Heat Pipe, Tray F09 EL-1994-00302 LDEF (Prelaunch), AO076 : Cascade Variable-Conductance Heat Pipe, Tray F09 The prelaunch photograph was taken in SAEF II at KSC prior to installation of the Cascade Variable Conductance Heat Pipe Experiment (CVCHPE) on the LDEF. The Cascade Variable Conductance Heat Pipe Experiment (CVCHPE) occupies a 6 inch deep LDEF peripheral experiment tray and consist of two series connected variable conductance heatpipes, a black chrome solar collector panel and a silvered TEFLON® radiator panel, a power source to support six thermistor-type temperature monitoring sensors and actuations of two valves. Fiberglass standoffs and internal insulation blankets thermally isolated the experiment from the experiment tray and the LDEF interior. The outside of the CVCHPE, except the collector and radiator panels, was covered with an aluminumized Kapton multilayer insulation (MLI) blanket with an outer layer of 0.076 mm thick Kapton. The two patches of thin film materials, part of Experiment S1001 by NASA GSFC, were attached to the cover of the external thermal blanket with Kapton tape. The experiment was assembled and mounted in the experiment tray with non-magnetic stainless steel fasteners.
B. R. Bass; L. J. Ott
1980-01-01
The calculation of the surface temperature and surface heat flux from measured temperature transients at one or more interior points of a body is identified in the literature as the inverse heat conduction problem. An inverse solution technique applicable to the two-dimensional nonlinear model with temperature dependent thermophysical properties is presented. The technique utilizes a finite element heat conduction model
August 2003 3D Watermarking 3D WATERMARKING
Alatan, Aydin
August 2003 3D Watermarking 3D WATERMARKING: Data Hiding on 3-D Triangle Meshes Mustafa Teke 2003 3D Watermarking Problem Definition Hiding information into 3D Objects with minimum distrotion rate, And make the watermark robust against attacks. #12;August 2003 3D Watermarking Intro The Method is Robust
Dongming Zhu; Robert A. Miller
2000-01-01
Laser high heat flux test approaches have been established to obtain critical properties of ceramic thermal barrier coatings\\u000a (TBCs) under near-realistic temperature and thermal gradients that may be encountered in advanced engine systems. Thermal\\u000a conductivity change kinetics of a thin ceramic coating were continuously monitored in real time at various test temperatures.\\u000a A significant thermal conductivity increase was observed during
Sumin Kim; Lawrence T. Drzal
2009-01-01
Using exfoliated graphite nanoplatelets (xGnP), paraffin\\/xGnP composite phase change materials (PCMs) were prepared by the stirring of xGnP in liquid paraffin for high electric conductivity, thermal conductivity and latent heat storage. xGnP of 1, 2, 3, 5 and 7wt% was added to pure paraffin at 75°C. Scanning electron microscopy (SEM) morphology showed uniform dispersion of xGnP in the paraffin wax.
NASA Astrophysics Data System (ADS)
Zhang, Liqiang; Reilly, Carl; Li, Luoxing; Cockcroft, Steve; Yao, Lu
2014-07-01
The interfacial heat transfer coefficient (IHTC) is required for the accurate simulation of heat transfer in castings especially for near net-shape processes. The large number of factors influencing heat transfer renders quantification by theoretical means a challenge. Likewise experimental methods applied directly to temperature data collected from castings are also a challenge to interpret because of the transient nature of many casting processes. Inverse methods offer a solution and have been applied successfully to predict the IHTC in many cases. However, most inverse approaches thus far focus on use of in-mold temperature data, which may be a challenge to obtain in cases where the molds are water-cooled. Methods based on temperature data from the casting have the potential to be used however; the latent heat released during the solidification of the molten metal complicates the associated IHTC calculations. Furthermore, there are limits on the maximum distance the thermocouples can be placed from the interface under analysis. An inverse conduction based method have been developed, verified and applied successfully to temperature data collected from within an aluminum casting in proximity to the mold. A modified specific heat method was used to account for latent heat evolution in which the rate of change of fraction solid with temperature was held constant. An analysis conducted with the inverse model suggests that the thermocouples must be placed no more than 2 mm from the interface. The IHTC values calculated for an aluminum alloy casting were shown to vary from 1,200 to 6,200 Wm-2 K-1. Additionally, the characteristics of the time-varying IHTC have also been discussed.
Ultrafine particle emissions from desktop 3D printers
NASA Astrophysics Data System (ADS)
Stephens, Brent; Azimi, Parham; El Orch, Zeineb; Ramos, Tiffanie
2013-11-01
The development of low-cost desktop versions of three-dimensional (3D) printers has made these devices widely accessible for rapid prototyping and small-scale manufacturing in home and office settings. Many desktop 3D printers rely on heated thermoplastic extrusion and deposition, which is a process that has been shown to have significant aerosol emissions in industrial environments. However, we are not aware of any data on particle emissions from commercially available desktop 3D printers. Therefore, we report on measurements of size-resolved and total ultrafine particle (UFP) concentrations resulting from the operation of two types of commercially available desktop 3D printers inside a commercial office space. We also estimate size-resolved (11.5 nm-116 nm) and total UFP (<100 nm) emission rates and compare them to emission rates from other desktop devices and indoor activities known to emit fine and ultrafine particles. Estimates of emission rates of total UFPs were large, ranging from ˜2.0 × 1010 # min-1 for a 3D printer utilizing a polylactic acid (PLA) feedstock to ˜1.9 × 1011 # min-1 for the same type of 3D printer utilizing a higher temperature acrylonitrile butadiene styrene (ABS) thermoplastic feedstock. Because most of these devices are currently sold as standalone devices without any exhaust ventilation or filtration accessories, results herein suggest caution should be used when operating in inadequately ventilated or unfiltered indoor environments. Additionally, these results suggest that more controlled experiments should be conducted to more fundamentally evaluate particle emissions from a wider arrange of desktop 3D printers.
Cristina Radulescu
2012-01-01
It has been established that for certain conditions, such as microgravity boiling, thermocapillary Marangoni flow has associated with it a significant enhancement of heat transfer. Typically, this phenomenon was investigated for the idealized case of an isolated and stationary bubble resting atop a heated solid that is immersed in a semi-infinite quiescent fluid or within a two-dimensional cavity. This article
Heat Flow, Thermal Conductivity, and the Plausibility of the White Mars Hypothesis
NASA Technical Reports Server (NTRS)
Urquhart, M. L.; Gulick, V. C.
2002-01-01
Due to the low thermal conductivity of CO2 ice and clathrate vs. water ice, we find that liquid water reservoirs would not be confined to the deep subsurface as predicted by the controversial White Mars model, even assuming low global heat flow. Additional information is contained in the original extended abstract.
Lattice thermal conductivity of lower mantle minerals and heat flux from Earth’s core
Manthilake, Geeth M.; de Koker, Nico; Frost, Dan J.; McCammon, Catherine A.
2011-01-01
The amount of heat flowing from Earth’s core critically determines the thermo-chemical evolution of both the core and the lower mantle. Consisting primarily of a polycrystalline aggregate of silicate perovskite and ferropericlase, the thermal boundary layer at the very base of Earth’s lower mantle regulates the heat flow from the core, so that the thermal conductivity (k) of these mineral phases controls the amount of heat entering the lowermost mantle. Here we report measurements of the lattice thermal conductivity of pure, Al-, and Fe-bearing MgSiO3 perovskite at 26 GPa up to 1,073 K, and of ferropericlase containing 0, 5, and 20% Fe, at 8 and 14 GPa up to 1,273 K. We find the incorporation of these elements in silicate perovskite and ferropericlase to result in a ?50% decrease of lattice thermal conductivity relative to the end member compositions. A model of thermal conductivity constrained from our results indicates that a peridotitic mantle would have k = 9.1 ± 1.2 W/m K at the top of the thermal boundary layer and k = 8.4 ± 1.2 W/m K at its base. These values translate into a heat flux of 11.0 ± 1.4 terawatts (TW) from Earth’s core, a range of values consistent with a variety of geophysical estimates. PMID:22021444
INSTABILITIES ASSOCIATED WITH HEAT CONDUCTION IN THE SOLAR WIND AND THEIR CONSEQUENCES
D. W. Forslund
1970-01-01
Associated with the large heat conduction in the solar wind is a skewing of the ion and electron distribution functions. It is shown that this collisional skewing of the electron distribution function can linearly excite collisionless ion-acoustic, electrostatic ion cyclotron, magnetoacoustic, and ion cyclotron waves in the steady-state solar wind even though the net equilibrium current parallel to B is
Tien-Chang Lee; A. D. Duchkov; S. G. Morozov
2003-01-01
The formation temperature below the sea or lake floor is frequently measured with a sensor probe that is inserted into the unconsolidated sediment, and the thermal conductivity of sediment is measured in situ with an independent heating experiment. Friction during the insertion raises the temperature of a probe. This paper presents the method and the test results of using the
Numerical study of conductive heat losses from a magmatic source at Phlegraean Fields
NASA Astrophysics Data System (ADS)
Di Maio, Rosa; Piegari, Ester; Mancini, Cecilia; Scandone, R.
2015-01-01
The thermal evolution of the Phlegraean magmatic system (southern Italy) is studied by analyzing the influence of the thermal property variations on the solution of the heat conduction equation. The aim of this paper is to verify if appropriate choices of thermal parameters can reproduce, at least to greater depths, the high temperatures measured in the geothermal wells, drilled inside the caldera, under the assumption of heat loss from a magma chamber by conduction. Since the main purpose is to verify the plausibility of such an assumption, rather simple models of the magmatic system are adopted and only major volcanic events (i.e., the Campanian Ignimbrite and the Neapolitan Yellow Tuff eruptions) are considered. The results of the simulated two-dimensional model scenarios show that by assuming an extended source region, whose emplacement time is longer than 40 ka, heat conduction mechanisms can provide temperatures as high as those measured at depths deeper than about 2000 m. On the other hand, the 1D simulations show that appropriate choices for the thermal conductivity depth profiles can reproduce the observed temperatures at depths deeper than about 1000 m. These findings question the apparent consensus that convection is the only dominant form of heat transfer at Phlegraean Fields and might motivate new research for reconstructing the thermal evolution of the Phlegraean magmatic system.
Global large solutions of magnetohydrodynamics with temperature-dependent heat conductivity
NASA Astrophysics Data System (ADS)
Hu, Yuxi; Ju, Qiangchang
2015-06-01
In this paper, we consider an initial boundary value problem for the magnetohydrodynamic compressible flows. By assuming that the heat conductivity depends on temperature with ? (?) = ? q , q > 0, we prove the existence and uniqueness of global strong solutions with large initial data and show that neither shock waves nor vacuum and concentration of mass in the solutions are developed in a finite time.
COYOTE: a finite-element computer program for nonlinear heat-conduction problems
Gartling, D.K.
1982-10-01
COYOTE is a finite element computer program designed for the solution of two-dimensional, nonlinear heat conduction problems. The theoretical and mathematical basis used to develop the code is described. Program capabilities and complete user instructions are presented. Several example problems are described in detail to demonstrate the use of the program.
Effect of Heat Treatment on Thermal Conductivity of U-Mo\\/Al Alloy Dispersion Fuel
S. H. Lee; J. C. Kim; J. M. Park; C. K. Kim; S. W. Kim
2003-01-01
The molybdenum content of fuel core whose matrix is aluminium 1060, was varied to be 7, 8, and 10 wt% and the volume fraction of U-Mo fuel powders was varied to be 10, 30, and 40 vol%. In this work, thermal conductivities were calculated from measured thermal diffusivities, specific heat capacities, and densities, which were determined using the laser flash,
Review and Comparison of Nanofluid Thermal Conductivity and Heat Transfer Enhancements
Wenhua Yu; David M. France; Jules L. Routbort
2008-01-01
This study provides a detailed literature review and an assessment of results of the research and development work forming the current status of nanofluid technology for heat transfer applications. Nanofluid technology is a relatively new field, and as such, the supporting studies are not extensive. Specifically, experimental results were reviewed in this study regarding the enhancement of the thermal conductivity
C. H. Huang; M. N. Özi?ik
1991-01-01
One of the difficulties in the solution of inverse heat conduction problems is that of making sufficiently accurate initial guesses for the unknowns in order to start the iterations. In this work a direct integration method is developed for determining good initial guesses for the unknown property coefficients within about 10% error. The Levenberg-Marquardt method is then applied to refine
Martin, Timothy
Summary Weusedthreemethodstomeasureboundarylayer conductance to heat transfer (gbH) and water vapor (rsV) measured with a porometer from the total branch vapor phase resistance were unusually small, water vapor transfer. Introduction Water loss from plant leaves is controlled by boundary layer
A chemical heat pump using carbon fibers as additive. Part I: enhancement of thermal conduction
T Dellero; D Sarmeo; Ph Touzain
1999-01-01
To use carbon fibers as additive in a chemical heat pump, based on a solid–gas reaction, three mixtures of carbon fibers with the reagent compounds are proposed: simple mixture, impregnation of the carbon fibers with reagent compounds and intercalation of the reagent compounds into graphite fibers. By adding carbon fibers, the thermal conductivity of the reagent bed is enhanced. While
ERIC Educational Resources Information Center
Mendez, Sergio; AungYong, Lisa
2014-01-01
To help students make the connection between the concepts of heat conduction and convection to real-world phenomenon, we developed a combined experimental and computational module that can be incorporated into lecture or lab courses. The experimental system we present requires materials and apparatus that are readily accessible, and the procedure…
N. Daouas; M.-S. Radhouani
2007-01-01
A new approach combining the use of the Kalman filter with an extended version of a smoothing technique and introducing the use of future time measurements is developed in order to improve the solution of a nonlinear Inverse Heat Conduction Problem (IHCP). The behaviour of the proposed algorithm is analysed in presence of a real set of experimental noisy temperature
Identification methods in nonlinear heat conduction. Part II: inverse problem using a reduced model
Manuel Girault; Daniel Petit
2005-01-01
A method for solving nonlinear Inverse Heat Conduction Problems (IHCPs) using a Reduced Model (RM) is proposed in this numerical study. In a first step, RM is identified through a specific procedure using optimization techniques and a Detailed Model (DM). Compared to DM, RM allows drastic reduction of computing time without significant loss of accuracy. The second step is the
A simplified approach for heat conduction analysis of CNT-based nano-composites
Jianming Zhang; Masataka Tanaka; Toshiro Matsumoto
2004-01-01
The unique thermal properties of carbon nanotubes (CNT) may offer possibilities for the development of fundamentally new composite materials. Numerical simulation for such CNT-based composites usually demands extremely large and expensive computer resources. In preliminary computations, temperature distribution in the CNT has been turned out to be almost uniform, due to its exceptionally high heat conductivity in comparison with the
The form of Abstract Molecular dynamics simulations of diffusive-ballistic heat conduction
Maruyama, Shigeo
The form of Abstract Molecular dynamics simulations of diffusive-ballistic heat conduction carbon bonds and quasi-one-dimensional confinement of phonons. As a consequence, the ballistic phonon, phonon transport exhibits complex diffusive-ballistic feature, which gives rise to unique steady
Conductive heat loss in recent eruptions at mid-ocean ridges
NASA Astrophysics Data System (ADS)
Johnson, Paul; Hutnak, Michael
A new technique for measuring conductive heat flow from unsedimented volcanic rocks on the sea floor has been tested on two new eruption sites in the NE Pacific. This technique consists of isolating the surficial rocks from sea water using water-saturated urethane foam as an insulating thermal blanket. The thermal gradient transferred from the outcrop to the thermal blanket is a quantitative measurement of the conductive heat flow that takes place in unsedimented volcanic areas. We deployed two thermal blankets at 13 sites on the 1993 and 1996 Juan de Fuca/Gorda Ridge flows and found (1) a factor of 10 decrease in heat flow over a period of 12 months on the 1993 CoAxial flow, (2) a value of 6950 mW/m² on the 8 month old Gorda flow, and (3) measurements of heat flow versus age-since-eruption indicate that newly extruded volcanic units are quite permeable to fluid circulation and cool rapidly by convection in only a few years. These new heat flux data confirm that the extrusive volcanic layer is not the primary heat source for long-lived, high temperature hydrothermal systems, which must instead rely on a more isolated thermal reservoir within the lower crustal rocks.
Guajardo-Cuéllar, Alejandro; Go, David B; Sen, Mihir
2010-03-14
Equilibrium molecular dynamics combined with the Green-Kubo formula can be used to calculate the thermal conductivity of materials such as germanium and carbon. The foundation of this calculation is extracting the heat current from the results and implementing it into the Green-Kubo formula. This work considers all formulations from the literature that calculate the heat current for the Tersoff potential, the interatomic potential most applicable to semiconductor materials. The formulations for the heat current are described, and results for germanium and carbon are presented. The formulations are compared with respect to how well they capture the physics of the Tersoff potential and how well the calculated value of the thermal conductivity reflects the experimentally measured value. PMID:20232951
Finite element formulation of the two-dimensional nonlinear inverse heat conduction problem
Bass, B.R.; Ott, L.J.
1980-01-01
The calculation of the surface temperature and surface heat flux from measured temperature transients at one or more interior points of a body is identified in the literature as the inverse heat conduction problem. Heretofore, analytical and computational methods of treating this problem have been limited to one-dimensional nonlinear or two-dimensional linear material models. An inverse solution technique applicable to the two-dimensional nonlinear model with temperature-dependent thermophysical properties is presented. This utilizes a finite element heat conduction model and a generalization of Beck's one-dimensional nonlinear estimation procedure. The formulation is applied to the cross section of a composite cylinder with temperature-dependent material properties. Results are presented to demonstrate that the inverse formulation is capable of successfully treating experimental data. An important feature of the method is that small time steps are permitted while avoiding severe oscillations or numerical instabilities due to experimental errors in measured data.
NASA Astrophysics Data System (ADS)
Gong, Feng; Tam, Yong Siang; Nguyen, Son T.; Duong, Hai M.
2015-05-01
Heat conduction in single-walled carbon nanotube (SWNT) aerogels is investigated by an off-lattice Monte Carlo method. Thermal boundary resistances (TBRs) between the SWNT and four permeated gases of argon, nitrogen, neon and hydrogen are reported from fitting simulation results with experimental data. It is found that the TBRs between the SWNT and the permeated gases decrease with larger gas molecular masses. Effects of volume fractions and complex morphologies of SWNTs on thermal conductivities of SWNT aerogels are also quantified. The effective thermal conductivities of SWNT aerogels increase with the larger volume fraction, the greater length and the smaller diameter of the SWNTs.
NASA Astrophysics Data System (ADS)
Jiang, Xiaoyun; Xu, Mingyu
2010-09-01
In this paper a time fractional Fourier law is obtained from fractional calculus. According to the fractional Fourier law, a fractional heat conduction equation with a time fractional derivative in the general orthogonal curvilinear coordinate system is built. The fractional heat conduction equations in other orthogonal coordinate systems are readily obtainable as special cases. In addition, we obtain the solution of the fractional heat conduction equation in the cylindrical coordinate system in terms of the generalized H-function using integral transformation methods. The fractional heat conduction equation in the case 0heat conduction equation (?=1) and the Localized heat conduction equation (??0). Finally, numerical results are presented graphically for various values of order of fractional derivative.
NSDL National Science Digital Library
This Moveable Museum article, available as a printable PDF file, looks at how astronomers use data to create 3-D models of the universe. Explore these concepts further using the recommended resources mentioned in this reading selection.
None
2011-01-01
In this animation of a 3D plasmon ruler, the plasmonic assembly acts as a transducer to deliver optical information about the structural dynamics of an attached protein. (courtesy of Paul Alivisatos group)
Naya, Daniel E.; Spangenberg, Lucía; Naya, Hugo; Bozinovic, Francisco
2013-01-01
Thermal conductance measures the ease with which heat leaves or enters an organism's body. Although the analysis of this physiological variable in relation to climatic and ecological factors can be traced to studies by Scholander and colleagues, only small advances have occurred ever since. Here, we analyse the relationship between minimal thermal conductance estimated during summer (Cmin) and several ecological, climatic and geographical factors for 127 rodent species, in order to identify the exogenous factors that have potentially affected the evolution of thermal conductance. In addition, we evaluate whether there is compensation between Cmin and basal metabolic rate (BMR)—in such a way that a scale-invariant ratio between both variables is equal to one—as could be expected from the Scholander–Irving model of heat transfer. Our major findings are (i) annual mean temperature is the best single predictor of mass-independent Cmin. (ii) After controlling for the effect of body mass, there is a strong positive correlation between log10 (Cmin) and log10 (BMR). Further, the slope of this correlation is close to one, indicating an almost perfect compensation between both physiological variables. (iii) Structural equation modelling indicated that Cmin values are adjusted to BMR values and not the other way around. Thus, our results strongly suggest that BMR and thermal conductance integrate a coordinated system for heat regulation in endothermic animals and that summer conductance values are adjusted (in an evolutionary sense) to track changes in BMRs. PMID:23902915
Armstrong, Jeff; Bresme, Fernando
2014-06-28
The coupling of mass and heat fluxes is responsible for the Soret effect in fluid mixtures containing particles of dissimilar mass and/or size. We investigate using equilibrium and non-equilibrium molecular dynamics simulations the relevance of these coupling effects in determining the thermal transport in fluids consisting of binary mixtures where the individual components feature significant mass, 1?:?8, or size, 1?:?3, asymmetries. We quantify the thermal transport by using both boundary driven molecular dynamics simulations (NEMD) and the equilibrium Green-Kubo (GK) approach and investigate the impact of different heat flux definitions, relevant in kinetic theory and experiments, in the quantification of the thermal conductivity. We find that the thermal conductivities obtained from the different definitions agree within numerical accuracy, suggesting that the Soret coefficient does not lead to significant changes in the thermal conduction, even for the large asymmetries considered here, which lead to significant Soret coefficients (?10(-2) K(-1)). The asymmetry in size and mass introduces large differences in the specific enthalpy of the individual components that must be carefully considered to compute accurate thermal conductivities using the GK approach. Neglecting the enthalpic contributions, results in large overestimations of the thermal conductivity, typically between 20% and 50%. Further, we quantify the time dependent behavior of the internal energy and mass flux correlation functions and propose a microscopic mechanism for the heat transport in these asymmetric mixtures. PMID:24818599
Heat conduction in double-walled carbon nanotubes with intertube additional carbon atoms.
Cui, Liu; Feng, Yanhui; Tan, Peng; Zhang, Xinxin
2015-07-01
Heat conduction of double-walled carbon nanotubes (DWCNTs) with intertube additional carbon atoms was investigated for the first time using a molecular dynamics method. By analyzing the phonon vibrational density of states (VDOS), we revealed that the intertube additional atoms weak the heat conduction along the tube axis. Moreover, the phonon participation ratio (PR) demonstrates that the heat transfer in DWCNTs is dominated by low frequency modes. The added atoms cause the mode weight factor (MWF) of the outer tube to decrease and that of the inner tube to increase, which implies a lower thermal conductivity. The effects of temperature, tube length, and the number and distribution of added atoms were studied. Furthermore, an orthogonal array testing strategy was designed to identify the most important structural factor. It is indicated that the tendencies of thermal conductivity of DWCNTs with added atoms change with temperature and length are similar to bare ones. In addition, thermal conductivity decreases with the increasing number of added atoms, more evidently for atom addition concentrated at some cross-sections rather than uniform addition along the tube length. Simultaneously, the number of added atoms at each cross-section has a considerably more remarkable impact, compared to the tube length and the density of chosen cross-sections to add atoms. PMID:26051798
NASA Astrophysics Data System (ADS)
Kshirsagar, Jagdeep M.; Shrivastava, Ramakant
2015-03-01
Nanofluids, the fluid suspensions of nonmaterials, have shown many interesting properties and the unique features offer unprecedented potential for many applications. Research on nanofluids has progressed rapidly since its enhanced thermal conductivity was first noted, about a decade ago, though much debate and inconsistency have been reported. Insufficient understanding of the formulation, mechanism of nanofluids further limits their applications [1-34]. Inconsistent data have been presented in the literature on the effect that nanofluids have on the boiling heat-transfer coefficient; however, almost all researchers [35-43] have noted an enhancement in the critical heat flux during nanofluid boiling. Some researchers have observed nanoparticle deposition at the heater surface, which they have related back to the critical heat flux augmentation. In the review, the future developments of these technologies are discussed. In order to be able to put the nanofluid heat transfer technologies into practice, fundamental of these studies are greatly needed to comprehend the physical mechanisms.
Mehdizadeh, Seyedeh Neda; Eskicioglu, Cigdem; Bobowski, Jake; Johnson, Thomas
2013-09-15
Microwave (2.45 GHz, 1200 W) and conventional heating (custom pressure vessel) pretreatments were applied to dewatered municipal waste sludge (18% total solids) using identical heating profiles that span a wide range of temperatures (80-160 °C). Fourteen lab-scale semi-continuous digesters were set up to optimize the energy (methane) output and sludge retention time (SRT) requirements of untreated (control) and thermally pretreated anaerobic digesters operated under mesophilic and thermophilic temperatures. Both pretreatment methods indicated that in the pretreatment range of 80-160 °C, temperature was a statistically significant factor (p-value < 0.05) for increasing solubilization of chemical oxygen demand and biopolymers (proteins, sugars, humic acids) of the waste sludge. However, the type of pretreatment method, i.e. microwave versus conventional heating, had no statistically significant effect (p-value >0.05) on sludge solubilization. With the exception of the control digesters at a 5-d SRT, all control and pretreated digesters achieved steady state at all three SRTs, corresponding to volumetric organic loading rates of 1.74-6.96 g chemical oxygen demand/L/d. At an SRT of 5 d, both mesophilic and thermophilic controls stopped producing biogas after 20 d of operation with total volatile fatty acids concentrations exceeding 1818 mg/L at pH <5.64 for mesophilic and 2853 mg/L at pH <7.02 for thermophilic controls, while the pretreated digesters continued producing biogas. Furthermore, relative (to control) organic removal efficiencies dramatically increased as SRT was shortened from 20 to 10 and then 5 d, indicating that the control digesters were challenged as the organic loading rate was increased. Energy analysis showed that, at an elevated temperature of 160 °C, the amount of methane recovered was not enough to compensate for the energy input. Among the digesters with positive net energy productions, control and pretreated digesters at 80 °C were more favorable at an SRT of 10 d. PMID:23866153
Spitzen, Jeroen; Spoor, Cornelis W; Grieco, Fabrizio; ter Braak, Cajo; Beeuwkes, Jacob; van Brugge, Sjaak P; Kranenbarg, Sander; Noldus, Lucas P J J; van Leeuwen, Johan L; Takken, Willem
2013-01-01
Female mosquitoes use odor and heat as cues to navigate to a suitable landing site on their blood host. The way these cues affect flight behavior and modulate anemotactic responses, however, is poorly understood. We studied in-flight behavioral responses of females of the nocturnal malaria mosquito Anopheles gambiae sensu stricto to human odor and heat. Flight-path characteristics in a wind tunnel (flow 20 cm/s) were quantified in three dimensions. With wind as the only stimulus (control), short and close to straight upwind flights were recorded. With heat alone, flights were similarly short and direct. The presence of human odor, in contrast, caused prolonged and highly convoluted flight patterns. The combination of odor+heat resulted in longer flights with more landings on the source than to either cue alone. Flight speed was greatest (mean groundspeed 27.2 cm/s) for odor+heat. Odor alone resulted in decreased flight speed when mosquitoes arrived within 30 cm of the source whereas mosquitoes exposed to odor+heat maintained a high flight speed while flying in the odor plume, until they arrived within 15 cm of the source. Human odor evoked an increase in crosswind flights with an additive effect of heat at close range (<15 cm) to the source. This was found for both horizontal and vertical flight components. However, mosquitoes nevertheless made upwind progress when flying in the odor+heat generated plume, suggesting that mosquitoes scan their environment intensively while they progress upwind towards their host. These observations may help to improve the efficacy of trapping systems for malaria mosquitoes by (1) optimizing the site of odor release relative to trap entry and (2) adding a heat source which enhances a landing response. PMID:23658792
Spitzen, Jeroen; Spoor, Cornelis W.; Grieco, Fabrizio; ter Braak, Cajo; Beeuwkes, Jacob; van Brugge, Sjaak P.; Kranenbarg, Sander; Noldus, Lucas P. J. J.; van Leeuwen, Johan L.; Takken, Willem
2013-01-01
Female mosquitoes use odor and heat as cues to navigate to a suitable landing site on their blood host. The way these cues affect flight behavior and modulate anemotactic responses, however, is poorly understood. We studied in-flight behavioral responses of females of the nocturnal malaria mosquito Anopheles gambiae sensu stricto to human odor and heat. Flight-path characteristics in a wind tunnel (flow 20 cm/s) were quantified in three dimensions. With wind as the only stimulus (control), short and close to straight upwind flights were recorded. With heat alone, flights were similarly short and direct. The presence of human odor, in contrast, caused prolonged and highly convoluted flight patterns. The combination of odor+heat resulted in longer flights with more landings on the source than to either cue alone. Flight speed was greatest (mean groundspeed 27.2 cm/s) for odor+heat. Odor alone resulted in decreased flight speed when mosquitoes arrived within 30 cm of the source whereas mosquitoes exposed to odor+heat maintained a high flight speed while flying in the odor plume, until they arrived within 15 cm of the source. Human odor evoked an increase in crosswind flights with an additive effect of heat at close range (<15 cm) to the source. This was found for both horizontal and vertical flight components. However, mosquitoes nevertheless made upwind progress when flying in the odor+heat generated plume, suggesting that mosquitoes scan their environment intensively while they progress upwind towards their host. These observations may help to improve the efficacy of trapping systems for malaria mosquitoes by (1) optimizing the site of odor release relative to trap entry and (2) adding a heat source which enhances a landing response. PMID:23658792
Crandall, K.R.
1987-08-01
TRACE 3-D is an interactive beam-dynamics program that calculates the envelopes of a bunched beam, including linear space-charge forces, through a user-defined transport system. TRACE 3-D provides an immediate graphics display of the envelopes and the phase-space ellipses and allows nine types of beam-matching options. This report describes the beam-dynamics calculations and gives detailed instruction for using the code. Several examples are described in detail.
Fourier heat conduction as a phenomenon described within the scope of the second law
NASA Astrophysics Data System (ADS)
Jesudason, Christopher G.
2014-12-01
The historical development of the Carnot cycle necessitated the construction of isothermal and adiabatic pathways within the cycle that were also mechanically "reversible" which lead eventually to the Kelvin-Clausius development of the entropy function S where for any reversible closed path C, ?C dS = 0 based on an infinite number of concatenated Carnot engines that approximated the said path and where for each engine ?Q1/T1+?Q2/T2 = 0 where the Q's and T's are the heat absorption increments and temperature respectively with the subscripts indicating the isothermal paths (1;2) where for the Carnot engine, the heat absorption is for the diathermal (isothermal) paths of the cycle only. Since 'heat' has been defined as that form of energy that is transferred as a result of a temperature difference and a corollary of the Clausius statement of the Second law is that it is impossible for heat to be transferred from a cold to a hot reservoir with no other effect on the environment, these statements suggested that the local mode of transfer of 'heat' in the isothermal segments of the pathway does imply a Fourier heat conduction mechanism (to conform to the definition of 'heat') albeit of a "reversible" kind, but on the other hand, the Fourier mechanism is apparently irreversible, leading to an increase in entropy of the combined reservoirs at either end of the material involved in the conveyance of the heat energy. These and several other considerations lead Benofy and Quay (BQ) to postulate the Fourier heat conduction phenomenon to be an ancillary principle in thermodynamics, with this principle being strictly local in nature, where the global Second law statements could not be applied to this local process. Here we present equations that model heat conduction as a thermodynamically reversible but mechanically irreversible process where due to the belief in mechanical time reversible symmetry, thermodynamical reversibility has been unfortunately linked to mechanical reversibility, that has discouraged such an association. The modeling is based on an application of a "recoverable transition", defined and developed earlier on ideas derived from thermal desorption of particles from a surface where the Fourier heat conduction process is approximated as a series of such desorption processes. We recall that the original Carnot engine required both adiabatic and isothermal steps to complete the zero entropy cycle, and this construct lead to the consequent deduction that any Second law statement that refers to heat-work conversion processes are only globally relevant. Here, on the other hand, we examine Fourier heat conduction from MD simulation and model this process as a zero-entropy forward scattering process relative to each of the atoms in the lattice chain being treated as a system where the Carnot cycle can be applied individually. The equations developed predicts the "work" done to be equal to the energy transfer rate. The MD simulations conducted shows excellent agreement with the theory. Such views and results as these, if developed to a successful conclusion could imply that the Carnot cycle be viewed as describing a local process of energy-work conversion and that irreversible local processes might be brought within the scope of this cycle, implying a unified treatment of thermodynamically (i) irreversible, (ii) reversible, (iii) isothermal and (iv) adiabatic processes.
NASA Astrophysics Data System (ADS)
Imamura, K.; Tanaka, Y.; Nishiguchi, N.; Tamura, S.; Maris, H. J.
2003-12-01
We report on a molecular dynamics study of the cross-plane lattice thermal conductivity in GaAs/AlAs superlattices. The layers of the superlattice are modelled by a three-dimensional face centred cubic lattice with cubic anharmonicity, and with atomic scale roughness at the interfaces. We perform the simulation of heat flow for a section of a superlattice with high- and low-temperature thermal reservoirs attached to opposite ends. The calculation reproduces qualitatively the features observed experimentally, i.e., the dramatic reduction of the conductivity relative to the conductivity of the bulk constituent materials, and the variation of the thermal conductivity with the superlattice repeat distance. The results are also in agreement with those obtained previously by Daly et al (2002 Phys. Rev. B 66 024301) who determined the thermal conductivity from the time taken for an initially inhomogeneous temperature distribution to relax.
Thermal Characterization for a Modular 3-D Multichip Module
NASA Technical Reports Server (NTRS)
Fan, Mark S.; Plante, Jeannette; Shaw, Harry
2000-01-01
NASA Goddard Space Flight Center has designed a high-density modular 3-D multichip module (MCM) for future spaceflight use. This MCM features a complete modular structure, i.e., each stack can be removed from the package without damaging the structure. The interconnection to the PCB is through the Column Grid Array (CGA) technology. Because of its high-density nature, large power dissipation from multiple layers of circuitry is anticipated and CVD diamond films are used in the assembly for heat conduction enhancement. Since each stacked layer dissipates certain amount of heat, designing effective heat conduction paths through each stack and balancing the heat dissipation within each stack for optimal thermal performance become a challenging task. To effectively remove the dissipated heat from the package, extensive thermal analysis has been performed with finite element methods. Through these analyses, we are able to improve the thermal design and increase the total wattage of the package for maximum electrical performance. This paper provides details on the design-oriented thermal analysis and performance enhancement. It also addresses issues relating to contact thermal resistance between the diamond film and the metallic heat conduction paths.
NASA Technical Reports Server (NTRS)
Parker, Hermon M
1953-01-01
An analysis is made of the transient heat-conduction effects in three simple semi-infinite bodies: the flat insulated plate, the conical shell, and the slender solid cone. The bodies are assumed to have constant initial temperatures and, at zero time, to begin to move at a constant speed and zero angle of attack through a homogeneous atmosphere. The heat input is taken as that through a laminar boundary layer. Radiation heat transfer and transverse temperature gradients are assumed to be zero. The appropriate heat-conduction equations are solved by an iteration method, the zeroeth-order terms describing the situation in the limit of small time. The method is presented and the solutions are calculated to three orders which are sufficient to give reasonably accurate results when the forward edge has attained one-half the total temperature rise (nose half-rise time). Flight Mach number and air properties occur as parameters in the result. Approximate expressions for the extent of the conduction region and nose half-rise times as functions of the parameters of the problem are presented. (author)
Wang, Wen-Jie; Cui, Song; Liu, Wei; Zu, Yuan-Gang; Sun, Wei; Wang, Hui-Min
2008-10-01
Based on a 3-year (2003-2005) observation of soil heat flux (SHF) in a larch (Larix gmelinii) plantation, the characteristics of soil heat conduction in the plantation and their relationships with environment factors were analyzed. The results showed that there was an obvious seasonal variation of SHF in different years and sampling sites. The SHF was positive from April to August and mostly negative from September to next March, with an almost balance between heat income and outcome at annual scale. Solar net radiation had significant effects on the SHF and soil heat conductance (k), and an obvious time-lag effect was found, with 4-5 hours' time-lag in winter and 2-3 hours' time-lag in summer. Based on the real-time measurement of SHF and soil temperature difference at the study sites, the k value was significantly higher in early spring (P < 0.05), but no significant difference was observed in other seasons (P > 0.05). Therefore, when we use the observation data of soil temperature from weather stations to estimate soil heat flux, the k value in spring (from March to May) could induce a bias estimation. PMID:19123344
Low conductivity water loop heat pump study at Lawrence Livermore National Laboratory
Chen, C.C.; Onu, C. [Southern Univ., Baton Rouge, LA (United States). College of Engineering; Smith, T.; Holda, M. [Lawrence Livermore National Lab., CA (United States)
1995-12-31
Based on results of the new Water Source Heat Pump (WSHP) systems operating in the US, these highly efficient heat pumps provide energy saving that will make them economically feasible to replace the inefficient, conventional HVAC systems. Additionally, an option to replace a centrifugal-compressor CFC chiller with a non-CFC chiller can be to replace the system with a highly efficient Water-Loop Heat Pump (WSHP) system. This replacement can result in a reduction of 20 to 30% in heating and air-conditioning energy costs. Low Conductivity Water (LCW) is purified water used for cooling in experimental laboratory, process, and air-conditioning equipment. It is one of several lab-wide mechanical utilities systems provided at Lawrence Livermore National Laboratory (LNL). The system is designed to maintain a supply temperature between 65 F and 85 F, with 100 psi at the inlet of the user building, 50--55 psi minimum differential pressures in the building, 35 psi maximum return pressure, and 0.4 umho/cm conductivity. However, this study is to utilize the existing LCW water loop to achieve the energy-efficiency improvement in a water resource heat pump (WRHP) system. The study will also utilize the life cycle costs as a tool to as the general selected criteria.
Statistical properties of Joule heating rate, electric field and conductances at high latitudes
NASA Astrophysics Data System (ADS)
Aikio, A. T.; Selkälä, A.
2009-07-01
Statistical properties of Joule heating rate, electric field and conductances in the high latitude ionosphere are studied by a unique one-month measurement made by the EISCAT incoherent scatter radar in Tromsø (66.6 cgmlat) from 6 March to 6 April 2006. The data are from the same season (close to vernal equinox) and from similar sunspot conditions (about 1.5 years before the sunspot minimum) providing an excellent set of data to study the MLT and Kp dependence of parameters with high temporal and spatial resolution. All the parameters show a clear MLT variation, which is different for low and high Kp conditions. Our results indicate that the response of morning sector conductances and conductance ratios to increased magnetic activity is stronger than that of the evening sector. The co-location of Pedersen conductance maximum and electric field maximum in the morning sector produces the largest Joule heating rates 03-05 MLT for Kp?3. In the evening sector, a smaller maximum occurs at 18 MLT. Minimum Joule heating rates in the nightside are statistically observed at 23 MLT, which is the location of the electric Harang discontinuity. An important outcome of the paper are the fitted functions for the Joule heating rate as a function of electric field magnitude, separately for four MLT sectors and two activity levels (Kp<3 and Kp?3). In addition to the squared electric field, the fit includes a linear term to study the possible anticorrelation or correlation between electric field and conductance. In the midday sector, positive correlation is found as well as in the morning sector for the high activity case. In the midnight and evening sectors, anticorrelation between electric field and conductance is obtained, i.e. high electric fields are associated with low conductances. This is expected to occur in the return current regions adjacent to auroral arcs as a result of ionosphere-magnetosphere coupling, as discussed by Aikio et al. (2004) In addition, a part of the anticorrelation may come from polarization effects inside high-conductance regions, e.g. auroral arcs. These observations confirm the speculated effect of small scale electrodynamics, which is not included in most of the global modeling efforts of Joule heating rate.
Variation of thermal conductivity and heat flux at the Earth's core mantle boundary
NASA Astrophysics Data System (ADS)
Ammann, Michael W.; Walker, Andrew M.; Stackhouse, Stephen; Wookey, James; Forte, Alessandro M.; Brodholt, John P.; Dobson, David P.
2014-03-01
The two convective systems that dominate Earth's internal dynamics meet at the boundary between the rocky mantle and metallic liquid core. Energy transfer between processes driving plate tectonics and the geodynamo is controlled by thermal conduction in the lowermost mantle (D?). We use atomic scale simulations to determine the thermal conductivity of MgSiO3 perovskite and post-perovskite under D? conditions and probe how these two convective systems interact. We show that the thermal conductivity of post-perovskite (?12 W/mK) is 50% larger than that of perovskite under the same conditions (?8.5 W/mK) and is anisotropic, with conductivity along the a-axis being 40% higher than conductivity along the c-axis. This enhances the high heat flux into cold regions of D? where post-perovskite is stable, strengthening the feedback between convection in the core and mantle. Reminiscent of the situation in the lithosphere, there is potential for deformation induced texturing associated with mantle convection to modify how the mantle is heated from below. We test this by coupling our atomic scale results to models of texture in D? and suggest that anisotropic thermal conductivity may help to stabilise the roots of mantle plumes over their protracted lifetime.
Hartenstine, J.R.
1991-08-01
Sodium-sulfur batteries can provide electrical power to satellite instrumentation operating in geosynchronous-earth-orbit (GEO) and low-earth-orbit (LEO) conditions. While on orbit, the sodium-sulfur battery requires thermal management as the battery is cycled between discharge in solar eclipse and recharge in sunlight. As the battery discharges in solar eclipses, waste heat is generated and the battery requires cooling. During recharge in sunlight, the battery temperature needs to be maintained above 320 C. In this Phase I program, Thermacore developed and demonstrated a dual titanium/cesium heat pipe to provide passive, lightweight management of the battery during orbital cycling. The dual heat pipe concept uses both constant and variable conductance heat pipes. Constant conductance heat pipes are inserted between sodium-sulfur cells. The cells radiate to the constant conductance heat pipes and this energy is transferred to a variable conductance heat pipe and radiated to deep space.
Thermal conductance of and heat generation in tire-pavement interface and effect on aircraft braking
NASA Technical Reports Server (NTRS)
Miller, C. D.
1976-01-01
A finite-difference analysis was performed on temperature records obtained from a free rolling automotive tire and from pavement surface. A high thermal contact conductance between tire and asphalt was found on a statistical basis. Average slip due to squirming between tire and asphalt was about 1.5 mm. Consequent friction heat was estimated as 64 percent of total power absorbed by bias-ply, belted tire. Extrapolation of results to aircraft tire indicates potential braking improvement by even moderate increase of heat absorbing capacity of runway surface.
Self-gravitational instability of rotating anisotropic heat-conducting plasma
Prajapati, R. P.; Parihar, A. K.; Chhajlani, R. K. [School of Studies in Physics, Vikram University, Ujjain-456010 (India)
2008-01-15
The self-gravitational instability of rotating anisotropic heat-conducting plasma with modified Chew-Goldberger-Low equations is investigated. The general dispersion relation is obtained using normal mode analysis by constructing the linearized set of equations. This dispersion relation is further reduced for propagation parallel and perpendicular to the direction of magnetic field. These conditions are discussed for axis of rotation along and perpendicular to the magnetic field. It is found that the heat flux vector does not influence the transverse mode of propagation for both cases of rotation and Jeans condition remains unchanged. In case of propagation parallel to the magnetic field with axis of rotation perpendicular to the magnetic field, we get the dispersion relation, which shows the joint effect of rotation and heat flux vector. The two separate modes of propagation are obtained in terms of rotation and heat flux vector for rotation parallel to the magnetic field. It is demonstrated that the Alfven wave and the associated firehose instability are not affected by the presence of heat flux corrections and rotation also. The numerical analysis is performed to show the effect of rotation, pressure anisotropy, and heat flux parameter on the condition of instability in the spiral arms of galaxy. The Jeans condition of gravitational instability is obtained for both the cases of propagation.
Lateral conduction effects on heat-transfer data obtained with the phase-change paint technique
NASA Technical Reports Server (NTRS)
Maise, G.; Rossi, M. J.
1974-01-01
A computerized tool, CAPE, (Conduction Analysis Program using Eigenvalues) has been developed to account for lateral heat conduction in wind tunnel models in the data reduction of the phase-change paint technique. The tool also accounts for the effects of finite thickness (thin wings) and surface curvature. A special reduction procedure using just one time of melt is also possible on leading edges. A novel iterative numerical scheme was used, with discretized spatial coordinates but analytic integration in time, to solve the inverse conduction problem involved in the data reduction. A yes-no chart is provided which tells the test engineer when various corrections are large enough so that CAPE should be used. The accuracy of the phase-change paint technique in the presence of finite thickness and lateral conduction is also investigated.
NASA Astrophysics Data System (ADS)
Oldham, Mark
2015-01-01
Radiochromic materials exhibit a colour change when exposed to ionising radiation. Radiochromic film has been used for clinical dosimetry for many years and increasingly so recently, as films of higher sensitivities have become available. The two principle advantages of radiochromic dosimetry include greater tissue equivalence (radiologically) and the lack of requirement for development of the colour change. In a radiochromic material, the colour change arises direct from ionising interactions affecting dye molecules, without requiring any latent chemical, optical or thermal development, with important implications for increased accuracy and convenience. It is only relatively recently however, that 3D radiochromic dosimetry has become possible. In this article we review recent developments and the current state-of-the-art of 3D radiochromic dosimetry, and the potential for a more comprehensive solution for the verification of complex radiation therapy treatments, and 3D dose measurement in general.
Lenticular Sheet 3-D Pictures And 3-D Projections
NASA Astrophysics Data System (ADS)
Marraud, A.; Bonnet, M.; Rambourg, A.
1980-06-01
The concept of lenticular sheet 3-D pictures dates from the beginning of this century. This method is responsible of commercial 3-D post-cards and 3-D photographic portraits. New applications are presented in this paper. They concern two domains where direct holographic 3-D reconstructions are impossible. These applications are the 3-D reconstruction of electron microscope pictures and the 3-D projection on a lenticular screen.
Jianhua Zhou; Jing Liu
2004-01-01
Tissue vasculature plays an important role in the temperature responses of biological bodies subject to laser heating. For example, interfaces between blood vessel and its surrounding tissues may lead to reflection or absorption of the coming laser light. However, most of the previous efforts just treat this by considering a collective model. To date, little attention has been paid to
Ram Kumar-Krishnasamy; Dieter Siegele
2010-01-01
A dissimilar tube welding is performed between the nickel based Alloy617 and creep resistant steel VM12 using the former as the weld material. SYSWELD welding software is used to model the thermal and mechanical analysis. A readily available thermal history is used to calibrate the heat source input for the thermal analysis to generate the adequate thermal cycle by fitting
Self-similar ablative flow of nonstationary accelerating foil due to nonlinear heat conduction
Murakami, M.; Sakaiya, T.; Sanz, J. [Institute of Laser Engineering, Osaka University, Osaka (Japan)
2007-02-15
Ablating plasma flow of an accelerating foil driven by nonlinear heat conduction is investigated theoretically. It is shown that the hydrodynamic system admits a new self-similar solution describing the nonstationary ablation process, through which the payload mass decreases to burn out at the end. In contrast to previous analyses based on stationary flow, the present solution provides a practical physical picture with a finite peak density and a distinct vacuum boundary at the front. The system is solved as a novel eigenvalue problem such that the acceleration and the heat conductivity are restrictive with each other under the self-similar evolution. Scaling laws are obtained to describe the temporal evolution for the shell acceleration and such ablation performances as the mass ablation rate and the ablation pressure.
Two-Gradient Convection in a Vertical Slot with Maxwell-Cattaneo Heat Conduction
Papanicolaou, N. C. [Department of Computer Science, University of Nicosia, P.O. Box 24005, 1700 Nicosia (Cyprus); Christov, C. I. [Department of Mathematics, University of Louisiana at Lafayette, LA 70504-1010 (United States); Jordan, P. M. [Entropy Reversal Consultants (L.L.C), P. O. Box 691, Abita Springs, LA 70420 (United States); Code 7181, Naval Research Lab., Stennis Space Ctr., MS 39529 (United States)
2009-10-29
We study the effect of the Maxwell-Cattaneo law of heat conduction (MCHC) on the 1D flow in a vertical slot subject to both vertical and horizontal temperature gradients. The gravitational acceleration is allowed to oscillate, which provides an opportunity to investigate the quantitative contribution of thermal inertia as epitomized by MCHC. The addition of the time derivative in MCHC increases the order of the system. We use a spectral expansion with Rayleigh's beam functions as the basis set, which is especially suited to fourth order boundary value problems (BVP). We show that the time derivative (relaxation of the thermal flux) has a dissipative nature and leads to the appearance of purely real negative eigenvalues. Yet it also increases the absolute value of the imaginary part and decreases the absolute value of the real part of the complex eigenvalues. Thus, the system has a somewhat more oscillatory behavior than the one based on Fourier's heat conduction law (FHC)
Sandeep Singh
\\u000a I didn’t want to keep you waiting for too long, so in this chapter you’ll print your first 3D model using the Shapeways Creator\\u000a and Co-Creator. “What? I thought this book was about using SketchUp to develop models for 3D printing!” Well, you aren’t done\\u000a with SketchUp yet. You’ll be learning how to develop custom models using SketchUp starting in
Luca Mezincescu; Paul K. Townsend
2011-10-21
The classical Green-Schwarz superstring action, with N=1 or N=2 spacetime supersymmetry, exists for spacetime dimensions D=3,4,6,10, but quantization in the light-cone gauge breaks Lorentz invariance unless either D=10, which leads to critical superstring theory, or D=3. We give details of results presented previously for the bosonic and N=1 closed 3D (super)strings and extend them to the N=2 3D superstring. In all cases, the spectrum is parity-invariant and contains anyons of irrational spin.
A blow-up criterion for compressible viscous heat-conductive flows
Song Jiang; Yaobin Ou
2010-06-12
We study an initial boundary value problem for the Navier-Stokes equations of compressible viscous heat-conductive fluids in a 2-D periodic domain or the unit square domain. We establish a blow-up criterion for the local strong solutions in terms of the gradient of the velocity only, which coincides with the famous Beale-Kato-Majda criterion for ideal incompressible flows.
Cheng-Ying Lo; Bo-Yo Chen
2009-01-01
This article presents a hybrid differential transform\\/control-volume method to solve hyperbolic heat conduction problems. First, the governing equations are transformed using the differential transform technique. Second, the temperature spectra, given by predefined shape functions are calculated through a recursive formula after applying the control-volume method to each individual subinterval. Finally, the inverse differential transform technique is adopted to determine the
Specific heat and thermal conductivity of thin film amorphous magnetic semiconductors
Barry Lee Zink
2002-01-01
Amorphous Gd-Si is a spin glass which has many characteristics of classic spin glasses but displays as yet unexplained phenomena, including large magnetic entropy and enhanced effective magnetic moment near the metal-insulator transition. Specific heat and thermal conductivity measurements are important contributions to the understanding of amorphous solids, spin-glasses and the physics of the metal-insulator transition. This thesis presents specific
William J. Fisk; Woody Delp; Rick Diamond; Darryl Dickerhoff; Ronnen Levinson; Mark Modera; Matty Nematollahi; Duo Wang
2000-01-01
Through field studies in large commercial buildings and reviews of building plans, we investigated the effective leakage areas (ELAs), air-leakage rates, and conduction heat gains of duct systems. Different methods for measuring air-leakage rates were also compared. ELAs of supply ducts ranged from 0.4 to 2.0 cm2 per square meter of floor area served, and from 1.0 to 4.8 cm2
Second law analysis of coupled conduction–radiation heat transfer with phase change
D. Makhanlall; L. H. Liu
2010-01-01
This work considers an exergy-based analysis of two-dimensional solid-liquid phase change processes in a square cavity enclosure. The phase change material (PCM) concerns a semi-transparent absorbing, emitting and anisotropically scattering medium with constant thermodynamic properties. The enthalpy-based energy equation is solved numerically using computational fluid dynamics. Once the energy equation is solved, local exergy loss due to heat conduction and
Yong Liu; R. D. Reitz
1998-01-01
A two-dimensional (axisymmetric) transient heat conduction in components computer program (HCC) was successfully developed for predicting engine combustion chamber wall temperatures. The alternating direction explicit (ADE) Saul'yev method, an explicit, unconditionally stable finite difference method, was used in the code. Special treatments for the head gasket and the piston-liner air gap, the piston movement, and a grid transformation for describing
Meng-Bi Cheng; Verica Radisavljevic; Chung-Cheng Chang; Chia-Fu Lin; Wu-Chung Su
2009-01-01
This note presents a sampled-data strategy for a boundary control problem of a heat conduction system modeled by a parabolic partial differential equation (PDE). Using the zero-order-hold, the control law becomes a piecewise constant signal, in which a step change of value occurs at each sampling instant. Through the dasialiftingpsila technique, the PDE is converted into a sequence of constant
Siu N. Leung; Omer M. Khan; Ellen Chan; Hani E. Naguib; Francis Dawson; Vincent Adinkrah; Laszlo Lakatos-Hayward
2011-01-01
Today's smaller, more powerful electronic devices, communications equipment, and lighting apparatus required optimum heat dissipation solutions. Traditionally, metals are widely known for their superior thermal conductivity; however, their good electrical conductivity has limited their applications in heat management components for microelectronic applications. This prompts the requirement to develop novel plastic composites that satisfy multifunctional requirements thermally, electrically, and mechanically. Furthermore,
A. R. Zokayi; M. Hadizadeh; P. Darania; A. Rajabi
2006-01-01
The main objective of this article is to analyze the RF-pair approach for the relation between the Emden–Fowler equation and the nonlinear heat conduction problem with variable transfer coefficient. The nonlinear heat conduction equation, by means of appropriate series of operators and transformations is transformed into the classical Emden–Fowler equation.
A. K. Belyaev; V. A. Palmov
1996-01-01
Summary It is shown that the dynamic boundary value problem and the heat conduction equation for some simple materials are derivable from the first and second laws of thermodynamics. The dynamic boundary value problem, the heat conduction equation and two variational principles are derived for thermoelastic materials with time-dependent properties, for the case when the volume and surface forces are
Tree-Shaped Fluid Flow and Heat Storage in a Conducting Solid
Combelles, L.; Lorente, S.; Anderson, R.; Bejan, A.
2012-01-01
This paper documents the time-dependent thermal interaction between a fluid stream configured as a plane tree of varying complexity embedded in a conducting solid with finite volume and insulated boundaries. The time scales of the convection-conduction phenomenon are identified. Two-dimensional and three-dimensional configurations are simulated numerically. The number of length scales of the tree architecture varies from one to four. The results show that the heat transfer density increases, and the time of approach to equilibrium decreases as the complexity of the tree designs increases. These results are then formulated in the classical notation of energy storage by sensible heating, which shows that the effective number of heat transfer units increases as the complexity of the tree design increases. The complexity of heat transfer designs in many applications is constrained by first cost and operating cost considerations. This work provides a fundamental basis for objective evaluation of cost and performance tradeoffs in thermal design of energy systems with complexity as an unconstrained parameter that can be actively varied over a broad range to determine the optimum system design.
A direct approach to finding unknown boundary conditions in steady heat conduction
NASA Technical Reports Server (NTRS)
Martin, Thomas J.; Dulikravich, George S.
1993-01-01
The capability of the boundary element method (BEM) in determining thermal boundary conditions on surfaces of a conducting solid where such quantities are unknown was demonstrated. The method uses a non-iterative direct approach in solving what is usually called the inverse heat conduction problem (IHCP). Given any over-specified thermal boundary conditions such as a combination of temperature and heat flux on a surface where such data is readily available, the algorithm computes the temperature field within the object and any unknown thermal boundary conditions on surfaces where thermal boundary values are unavailable. A two-dimensional, steady-state BEM program was developed and was tested on several simple geometries where the analytic solution was known. Results obtained with the BEM were in excellent agreement with the analytic values. The algorithm is highly flexible in treating complex geometries, mixed thermal boundary conditions, and temperature-dependent material properties and is presently being extended to three-dimensional and unsteady heat conduction problems. The accuracy and reliability of this technique was very good but tended to deteriorate when the known surface conditions were only slightly over-specified and far from the inaccessible surface.
Pradhan, N R; Duan, H; Liang, J; Iannacchione, G S
2008-12-01
We report simultaneous specific heat (c(p)) and thermal conductivity (?) measurements for anisotropic and random macroscopic composites of cobalt nanowires (Co NWs), from 300 to 400 K. Anisotropic composites of Co NW consist of nanowires grown within the highly ordered, densely packed array of parallel nanochannels in anodized aluminum oxide. Random composites are formed by drop-casting a thin film of randomly oriented Co NWs, removed from the anodized aluminum oxide host, within a calorimetric cell. The specific heat measured with the heat flow parallel to the Co NW alignment ([Formula: see text]) and that for the random sample (c(p)(R)) deviate strongly in temperature dependence from that measured for bulk, amorphous, powder cobalt under identical experimental conditions. The thermal conductivity for random composites (?(R)) follows a bulk-like behavior though it is greatly reduced in magnitude, exhibiting a broad maximum near 365 K indicating the onset of boundary-phonon scattering. The thermal conductivity in the anisotropic sample ([Formula: see text]) is equally reduced in magnitude but increases smoothly with increasing temperature and appears to be dominated by phonon-phonon scattering. PMID:21836319
Xu, Zhijie
2012-07-01
We introduce a method of solution for the convective heat transfer under forced laminar flow that is confined by two parallel plates with a distance of 2a or by a circular tube with a radius of a. The advection-conduction equation is first mapped onto the boundary. The original problem of solving the unknown field is reduced to seek the solutions of T at the boundary (r=a or r=0, r is the distance from the centerline shown in Fig. 1), i.e. the boundary functions and/or . In this manner, the original problem is significantly simplified by reducing the problem dimensionality from 3 to 2. The unknown field can be eventually solved in terms of these boundary functions. The method is applied to the convective heat transfer with uniform wall temperature boundary condition and with heat exchange between flowing fluids and its surroundings that is relevant to the geothermal applications. Analytical solutions are presented and validated for the steady state problem using the proposed method.
3D Computer Vision and Video Computing 3D Vision3D Vision
Zhu, Zhigang
;3 3D Computer Vision and Video Computing Problem StatementProblem Statement Two Subproblems1 3D Computer Vision and Video Computing 3D Vision3D Vision CSc I6716 Fall 2011 Topic 4 of Part II@cs.ccny.cuny.edu 3D Computer Vision and Video Computing Outline of MotionOutline of Motion Problems and Applications
NSDL National Science Digital Library
Dan Bunker
2011-01-01
This interactive Flash applet provides a Concentration-type game (called pelmanism in the UK) in which students must discern the properties of three-dimensional solids and their colors in order to match them in pairs. Spheres, cones, prisms and other standard 3-D shapes are hidden face down on cards. Time and number of trials needed to solve are recorded.
Van, B.T.; Pajon, J.L.; Joseph, P. (Inst. Francais du Petrole (FR))
1991-11-01
This paper shows how some simple 3D computer graphics tools can be combined to provide efficient software for visualizing and analyzing data obtained from reservoir simulators and geological simulations. The animation and interactive capabilities of the software quickly provide a deep understanding of the fluid-flow behavior and an accurate idea of the internal architecture of a reservoir.
L. I. Tuchinskii; E. M. Veksler; V. G. Zatovskii
1992-01-01
The most important characteristic of materials used for development of heat exchangers is their thermal conductivity. Knowledge of it is necessary for making calculations andfor selection of the optimum design of equipment. In connection with this it is of interest to analyze the thermal conductivity of polycapillary composite materials (PCM) developed in the Institute of Materials Science of the Academy
Review and comparison of nanofluid thermal conductivity and heat transfer enhancements.
Yu, W.; France, D. M.; Routbort, J. L.; Choi, S. U.S.; Energy Systems; Univ. of Illinois at Chicago; Korea Inst. of Energy Research
2008-05-01
This study provides a detailed literature review and an assessment of results of the research and development work forming the current status of nanofluid technology for heat transfer applications. Nanofluid technology is a relatively new field, and as such, the supporting studies are not extensive. Specifically, experimental results were reviewed in this study regarding the enhancement of the thermal conductivity and convective heat transfer of nanofluids relative to conventional heat transfer fluids, and assessments were made as to the state-of-the-art of verified parametric trends and magnitudes. Pertinent parameters of particle volume concentration, particle material, particle size, particle shape, base fluid material, temperature, additive, and acidity were considered individually, and experimental results from multiple research groups were used together when assessing results. To this end, published research results from many studies were recast using a common parameter to facilitate comparisons of data among research groups and to identify thermal property and heat transfer trends. The current state of knowledge is presented as well as areas where the data are presently inconclusive or conflicting. Heat transfer enhancement for available nanofluids is shown to be in the 15-40% range, with a few situations resulting in orders of magnitude enhancement.
A. Mohammadian Pourtalari; M. A. Jafarizadeh; M. Ghoranneviss
2011-11-23
Electron heat conduction is one of the ways that energy transports in laser heating of fusible target material. The aim of Inertial Confinement Fusion (ICF) is to show that the thermal conductivity is strongly dependent on temperature and the equation of electron heat conduction is a nonlinear equation. In this article, we solve the one-dimensional (1-D) nonlinear electron heat conduction equation with a self-similar method (SSM). This solution has been used to investigate the propagation of 1-D thermal wave from a deuterium-tritium (DT) plane source which occurs when a giant laser pulse impinges onto a DT solid target. It corresponds to the physical problem of rapid heating of a boundary layer of material in which the energy of laser pulse is released in a finite initial thickness.
On the equilibrium of heated self-gravitating masses - Cooling by conduction
NASA Technical Reports Server (NTRS)
Lerche, I.; Low, B. C.
1980-01-01
An investigation is given of the equilibrium states available to a self-gravitating mass of gas, cooling by conduction, and being heated at a rate proportional to the local gas density. The plane geometry situation is shown to be reducible to quadratures for the pressure, density, temperature, and gravitational potential. For a constant thermal conductivity it is shown that the gas density has either a central maximum or a central minimum, depending on the ratio of the thermal conductivity to a parameter taken to be a measure of the rate of heating. For a thermal conductivity which is a positive power of the temperature, it is shown that the gas density always has a central minimum and a maximum at the outer boundary of the configuration. For cylindrical and spherical geometrical configurations the same general properties are obtained. The physical origin of this behavior is discussed, and it is suggested that these exploratory calculations provide an effect which may not only aid in understanding thin filamentary structure observed in supernova remnants, but also help to assuage the difficulties of producing maser activity in the interior regions of 'cocoon' protostars.
NaK Variable Conductance Heat Pipe for Radioisotope Stirling Systems
NASA Technical Reports Server (NTRS)
Tarau, Calin; Anderson, William G.; Walker, Kara
2008-01-01
In a Stirling radioisotope power system, heat must continually be removed from the General Purpose Heat Source (GPHS) modules to maintain the modules and surrounding insulation at acceptable temperatures. The Stirling convertor normally provides most of this cooling. If the Stirling convertor stops in the current system, the insulation is designed to spoil, preventing damage to the GPHS, but also ending use of that convertor for the mission. An alkali-metal Variable Conductance Heat Pipe (VCHP) was designed to allow multiple stops and restarts of the Stirling convertor. In the design of the VCHP for the Advanced Stirling Radioisotope Generator, the VCHP reservoir temperature can vary between 40 and 120 C. While sodium, potassium, or cesium could be used as the working fluid, their melting temperatures are above the minimum reservoir temperature, allowing working fluid to freeze in the reservoir. In contrast, the melting point of NaK is -12 C, so NaK can't freeze in the reservoir. One potential problem with NaK as a working fluid is that previous tests with NaK heat pipes have shown that NaK heat pipes can develop temperature non-uniformities in the evaporator due to NaK's binary composition. A NaK heat pipe was fabricated to measure the temperature non-uniformities in a scale model of the VCHP for the Stirling Radioisotope system. The temperature profiles in the evaporator and condenser were measured as a function of operating temperature and power. The largest delta T across the condenser was 2S C. However, the condenser delta T decreased to 16 C for the 775 C vapor temperature at the highest heat flux applied, 7.21 W/ square cm. This decrease with increasing heat flux was caused by the increased mixing of the sodium and potassium in the vapor. This temperature differential is similar to the temperature variation in this ASRG heat transfer interface without a heat pipe, so NaK can be used as the VCHP working fluid.
First Principles Modeling of Phonon Heat Conduction in Nanoscale Crystalline Structures
Sandip Mazumder; Ju Li
2010-06-30
The inability to remove heat efficiently is currently one of the stumbling blocks toward further miniaturization and advancement of electronic, optoelectronic, and micro-electro-mechanical devices. In order to formulate better heat removal strategies and designs, it is first necessary to understand the fundamental mechanisms of heat transport in semiconductor thin films. Modeling techniques, based on first principles, can play the crucial role of filling gaps in our understanding by revealing information that experiments are incapable of. Heat conduction in crystalline semiconductor films occurs by lattice vibrations that result in the propagation of quanta of energy called phonons. If the mean free path of the traveling phonons is larger than the film thickness, thermodynamic equilibrium ceases to exist, and thus, the Fourier law of heat conduction is invalid. In this scenario, bulk thermal conductivity values, which are experimentally determined by inversion of the Fourier law itself, cannot be used for analysis. The Boltzmann Transport Equation (BTE) is a powerful tool to treat non-equilibrium heat transport in thin films. The BTE describes the evolution of the number density (or energy) distribution for phonons as a result of transport (or drift) and inter-phonon collisions. Drift causes the phonon energy distribution to deviate from equilibrium, while collisions tend to restore equilibrium. Prior to solution of the BTE, it is necessary to compute the lifetimes (or scattering rates) for phonons of all wave-vector and polarization. The lifetime of a phonon is the net result of its collisions with other phonons, which in turn is governed by the conservation of energy and momentum during the underlying collision processes. This research project contributed to the state-of-the-art in two ways: (1) by developing and demonstrating a calibration-free simple methodology to compute intrinsic phonon scattering (Normal and Umklapp processes) time scales with the inclusion of optical phonons, and (2) by developing a suite of numerical algorithms for solution of the BTE for phonons. The suite of numerical algorithms includes Monte Carlo techniques and deterministic techniques based on the Discrete Ordinates Method and the Ballistic-Diffusive approximation of the BTE. These methods were applied to calculation of thermal conductivity of silicon thin films, and to simulate heat conduction in multi-dimensional structures. In addition, thermal transport in silicon nanowires was investigated using two different first principles methods. One was to apply the Green-Kubo formulation to an equilibrium system. The other was to use Non-Equilibrium Molecular Dynamics (NEMD). Results of MD simulations showed that the nanowire cross-sectional shape and size significantly affects the thermal conductivity, as has been found experimentally. In summary, the project clarified the role of various phonon modes - in particular, optical phonon - in non-equilibrium transport in silicon. It laid the foundation for the solution of the BTE in complex three-dimensional structures using deterministic techniques, paving the way for the development of robust numerical tools that could be coupled to existing device simulation tools to enable coupled electro-thermal modeling of practical electronic/optoelectronic devices. Finally, it shed light on why the thermal conductivity of silicon nanowires is so sensitive to its cross-sectional shape.
Acousto-thermometric recovery of the deep temperature profile using heat conduction equations
NASA Astrophysics Data System (ADS)
Anosov, A. A.; Belyaev, R. V.; Vilkov, V. A.; Dvornikova, M. V.; Dvornikova, V. V.; Kazanskii, A. S.; Kuryatnikova, N. A.; Mansfel'd, A. D.
2012-09-01
In a model experiment using the acousto-thermographic method, deep temperature profiles varying in time are recovered. In the recovery algorithm, we used a priori information in the form of a requirement that the calculated temperature must satisfy the heat conduction equation. The problem is reduced to determining two parameters: the initial temperature and the temperature conductivity coefficient of the object under consideration (the plasticine band). During the experiment, there was independent inspection using electronic thermometers mounted inside the plasticine. The error in the temperature conductivity coefficient was about 17% and the error in initial temperature determination was less than one degree. Such recovery results allow application of this approach to solving a number of medical problems. It is experimentally proved that acoustic irregularities influence the acousto-thermometric results as well. It is shown that in the chosen scheme of experiment (which corresponds to measurements of human muscle tissue), this influence can be neglected.
Perano, Kristen M; Usack, Joseph G; Angenent, Largus T; Gebremedhin, Kifle G
2015-08-01
The objective of this research was to test the effectiveness of conductive cooling in alleviating heat stress of lactating dairy cows. A conductive cooling system was built with waterbeds (Dual Chamber Cow Waterbeds, Advanced Comfort Technology Inc., Reedsburg, WI) modified to circulate chilled water. The experiment lasted 7 wk. Eight first-lactation Holstein cows producing 34.4±3.7kg/d of milk at 166±28 d in milk were used in the study. Milk yield, dry matter intake (DMI), and rectal temperature were recorded twice daily, and respiration rate was recorded 5 times per day. During wk 1, the cows were not exposed to experimental heat stress or conductive cooling. For the remaining 6 wk, the cows were exposed to heat stress from 0900 to 1700h each day. During these 6 wk, 4 of the 8 cows were cooled with conductive cooling (experimental cows), and the other 4 were not cooled (control cows). The study consisted of 2 thermal environment exposures (temperature-humidity index mean ± standard deviation of 80.7±0.9 and 79.0±1.0) and 2 cooling water temperatures (circulating water through the water mattresses at temperatures of 4.5°C and 10°C). Thus, a total of 4 conductive cooling treatments were tested, with each treatment lasting 1 wk. During wk 6, the experimental and control cows were switched and the temperature-humidity index of 79.0±1.0 with 4.5°C cooling water treatment was repeated. During wk 7, waterbeds were placed directly on concrete stalls without actively cooling the water. Least squares means and P-values for the different treatments were calculated with multivariate mixed models. Conductively cooling the cows with 4.5°C water decreased rectal temperature by 1.0°C, decreased respiration rate by 18 breaths/min, increased milk yield by 5%, and increased DMI by 14% compared with the controls. When the results from the 2 cooling water temperatures (4.5°C and 10°C circulating water) were compared, we found that the rectal temperature from 4.5°C cooling water was 0.3°C lower than the rectal temperature with 10°C cooling water, but the other measurements (respiration rate, milk production, and DMI) did not show a statistically significant difference between the cooling water temperatures. Placing waterbeds on concrete stalls without additional cooling did not have a measurable effect in alleviating the heat stress of the cows. PMID:26074243
Dongming Zhu; Robert A. Miller; Ben A. Nagaraj; Robert W. Bruce
2001-01-01
The thermal conductivity of electron beam-physical vapor deposited (EB-PVD) ZrO2–8 wt.%Y2O3 thermal barrier coatings was determined by a steady-state laser heat flux technique. Thermal conductivity change kinetics of the EB-PVD ceramic coatings were also obtained in real time, at high temperatures, under the laser high heat flux, long-term test conditions. The thermal conductivity increase due to micro-pore sintering and the
X. Fu; D. D. L. Chung
1997-01-01
Due to their poor conductivity, latex (20–30% by weight of cement), methylcellulose (0.4–0.8% by weight of cement), and silica fume (15% by weight of cement) decreased the thermal conductivity of cement paste by up to 46%. In addition, these admixtures increased the specific heat of cement paste by up to 10%. The thermal conductivity decreased and the specific heat increased
Waite, W.F.; Stern, L.A.; Kirby, S.H.; Winters, W.J.; Mason, D.H.
2007-01-01
Thermal conductivity, thermal diffusivity and specific heat of sI methane hydrate were measured as functions of temperature and pressure using a needle probe technique. The temperature dependence was measured between ?20°C and 17°C at 31.5 MPa. The pressure dependence was measured between 31.5 and 102 MPa at 14.4°C. Only weak temperature and pressure dependencies were observed. Methane hydrate thermal conductivity differs from that of water by less than 10 per cent, too little to provide a sensitive measure of hydrate content in water-saturated systems. Thermal diffusivity of methane hydrate is more than twice that of water, however, and its specific heat is about half that of water. Thus, when drilling into or through hydrate-rich sediment, heat from the borehole can raise the formation temperature more than 20 per cent faster than if the formation's pore space contains only water. Thermal properties of methane hydrate should be considered in safety and economic assessments of hydrate-bearing sediment.
Volman, Vladimir; Zhu, Yu; Raji, Abdul-Rahman O; Genorio, Bostjan; Lu, Wei; Xiang, Changsheng; Kittrell, Carter; Tour, James M
2014-01-01
Deicing heating layers are frequently used in covers of large radio-frequency (RF) equipment, such as radar, to remove ice that could damage the structures or make them unstable. Typically, the deicers are made using a metal framework and inorganic insulator; commercial resistive heating materials are often nontransparent to RF waves. The preparation of a sub-skin-depth thin film, whose thickness is very small relative to the RF skin (or penetration) depth, is the key to minimizing the RF absorption. The skin depth of typical metals is on the order of a micrometer at the gigahertz frequency range. As a result, it is very difficult for conventional conductive materials (such as metals) to form large-area sub-skin-depth films. In this report, we disclose a new deicing heating layer composite made using graphene nanoribbons (GNRs). We demonstrate that the GNR film is thin enough to permit RF transmission. This metal-free, ultralight, robust, and scalable graphene-based RF-transparent conductive coating could significantly reduce the size and cost of deicing coatings for RF equipment covers. This is important in many aviation and marine applications. This is a demonstration of the efficacy and applicability of GNRs to afford performances unattainable by conventional materials. PMID:24328320
Surface roughness and three-dimensional heat conduction in thermophysical models
NASA Astrophysics Data System (ADS)
Davidsson, Björn J. R.; Rickman, Hans
2014-11-01
A thermophysical model is presented that considers surface roughness, cast shadows, multiple or single scattering of radiation, visual and thermal infrared self heating, as well as heat conduction in one or three dimensions. The code is suitable for calculating infrared spectral energy distributions for spatially resolved or unresolved minor Solar System bodies without significant atmospheres or sublimation, such as the Moon, Mercury, asteroids, irregular satellites or inactive regions on comet nuclei. It is here used to explore the effects of surface roughness on spatial scales small enough for heat conduction to erase lateral temperature gradients. Analytically derived corrections to one-dimensional models that reproduce the results of three-dimensional modeling are presented. We find that the temperature of terrains with such small-scale roughness is identical to that of smooth surfaces for certain types of topographies and non-scattering material. However, systematic differences between smooth and rough terrains are found for scattering materials, or topographies with prominent positive relief. Contrary to common beliefs, the roughness on small spatial scales may therefore affect the thermal emission of Solar System bodies.
ORMDIN: a finite element program for two-dimensional nonlinear inverse heat conduction analysis
Bass, B.R.; Drake, J.B.; Ott, L.J.
1980-12-01
The calculation of the surface temperature and surface heat flux from measured temperature transients at one or more interior points of a body is identified in the literature as the inverse heat conduction problem. Heretofore, analytical and computational methods of treating this problem have been limited to one-dimensional nonlinear or two-dimensional linear material models. This report presents, to the authors' knowledge, the first inverse solution technique applicable to the two-dimensional nonlinear model with temperature-dependent thermophysical properties. This technique, representing an extension of the one-dimensional formulation previously developed by one of the authors, utilizes a finite element heat conduction model and a generalization of Beck's one-dimensional nonlinear estimation procedure. A digital computer program ORMDIN (Oak Ridge Multi-Dimensional INverse) is developed from the formulation and applied to the cross section of a composite cylinder with temperature-dependent material properties. Results are presented to demonstrate that the inverse formulation is capable of successfully treating experimental data. An important feature of the method is that small time steps are permitted while avoiding severe oscillations or numerical instabilities due to experimental errors in measured data.
Katsumoto, Shingo
XX 3d X 3d X X XX X XX SrTiO3Ti 2p 3d SrTiO3Ti 2p 3d 2p 2p SrTiO3 ts) 2p3/2 (t2g) 2p3/2 (e ) 2p1/2 (eg)2p SrTiO3 3d unit (t2g) (eg) (eg)2p1/2 (t2g)3d (Ti Fe Cu) arb. ( 2g) (Ti, Fe, Cu) y(ansitynten 3d In 3d 468464460456 · Photon Energy (e
NASA Astrophysics Data System (ADS)
Connors, M. G.; Schofield, I. S.
2012-12-01
Modern technologies in imaging greatly extend the potential to present visual information. With recently developed software tools, the perception of the third dimension can not only dramatically enhance presentation, but also allow spatial data to be better encoded. 3-D images can be taken for many subjects with only one camera, carefully moved to generate a stereo pair. Color anaglyph viewing now can be very effective using computer screens, and active filter technologies can enhance visual effects with ever-decreasing cost. We will present various novel results of 3-D imaging, including those from the auroral observations of the new twinned Athabasca University Geophysical Observatories.; Single camera stereo image for viewing with red/cyan glasses.
NSDL National Science Digital Library
How much liquid can that glass hold? What are the dimensions of that package that's heading off to a friend overseas? Answers to both of those questions (and many more) can be found in this lovely interactive feature on 3D shapes created by experts at the Annenberg Media group. Visitors to this site will learn about three-dimensional geometric shapes by examining a number of objects through a number of interactive exercises and games. The materials are divided into four sections, which include "3D Shapes", "Surface Area & Volume", and "Platonic Solids". The "Platonic Solids" area is quite a bit of fun, as visitors will get the opportunity to print out foldable shapes such as a tetrahedron. A short fifteen question quiz that tests the materials covered by these various activities rounds out the site.
GRABER: The Duct Tape of Space and JIMO Heat Conducting Foam
NASA Technical Reports Server (NTRS)
Gamble, Eleanor A.
2004-01-01
Crack formation in the space shuttle's heat shield during flight poses a major safety concern to everyone on board. Cracking weakens the structure of the shield and lessens the protection it offers against the high temperatures and forces encountered during re-entry. Astronauts need a way to mend these cracks while in space. This is GRABER s function; it can be spackled into the cracks by an astronaut. The material then hardens, or cures, due to being in a vacuum and the heat encountered when it faces the sun. A great deal of work and testing is necessary to create a material that will be workable in a vacuum over a wide range of temperatures, will cure without cracking, will adhere to the sides of the crack, and that can withstand the extreme temperatures of re-entry. A Brookfield PVS Rheometer is being used to characterize GRABER's viscosity at various temperatures and stirring rates. Various compositions of GRABER are being heat treated in a vacuum to determine probably curing times in space. The microstructures of cured samples of each composition are being examined using both optical and electron microscopy. Jupiter s Icy Moon Orbiter (JIMO) will be lifting off sometime around 2013. JIMO will have more power than its predecessor, Galileo, allowing it to change orbits to circle three of Jupiter s moons. Both of the engine types being considered require large heat dissipation systems. These systems will be comprised of heat conductive tubing and plates with a liquid flowing through them. In order to maximize the speed of heat transfer between the tubes and the panels, the in-between areas will be filled with heat conductive silicon carbide foam. Two different foam systems are being considered for this foam. Currently, experimentation is underway with adding Sic, carbon, and carbon fibers to a two part fuel retardant foam. The foam is them pyrolized and its mass and dimensional changes are measured. The structure of the foam will be examined using optical and electron microscopy as well. Work is also planned with a foam system developed by an Italian team.
Jean-francis Balaguer; Enrico Gobbetti
1995-01-01
We are interested in providing animators with a general-purpose tool allowing them to create animations using straight-ahead actions as well as pose-to-pose techniques. Our approach seeks to bring the expressiveness of real-time motion capture systems into a general-purpose multi-track system running on a graphics workstation. We emphasize the use of high-bandwidth interaction with 3D objects together with specific data reduction
NSDL National Science Digital Library
Marvin Simkin
2005-01-01
This collection of 3D flyover movies depicts geologically interesting localities in the Southwest United States. The selection includes well-known landmarks such as Meteor Crater, Monument Valley, Hopi Buttes, and others. They are available in a number of different formats and file sizes. The movies, the data files used to make them, and the software to view them are all available for free download. There is also a link to a tutorial on how to make Fledermaus scenes and movies.
Thermally conductive cementitious grouts for geothermal heat pumps. Progress report FY 1998
Allan, M.L.; Philippacopoulos, A.J.
1998-11-01
Research commenced in FY 97 to determine the suitability of superplasticized cement-sand grouts for backfilling vertical boreholes used with geothermal heat pump (GHP) systems. The overall objectives were to develop, evaluate and demonstrate cementitious grouts that could reduce the required bore length and improve the performance of GHPs. This report summarizes the accomplishments in FY 98. The developed thermally conductive grout consists of cement, water, a particular grade of silica sand, superplasticizer and a small amount of bentonite. While the primary function of the grout is to facilitate heat transfer between the U-loop and surrounding formation, it is also essential that the grout act as an effective borehole sealant. Two types of permeability (hydraulic conductivity) tests was conducted to evaluate the sealing performance of the cement-sand grout. Additional properties of the proposed grout that were investigated include bleeding, shrinkage, bond strength, freeze-thaw durability, compressive, flexural and tensile strengths, elastic modulus, Poisson`s ratio and ultrasonic pulse velocity.
Deposition of high photo-conductivity a-Si:H film using ICPs without substrate heating
Goto, M.; Toyoda, H.; Sugai, H. [Nagoya Univ. (Japan). Dept. of Electrical Engineering; Kitagawa, M. [Matsushita Electric Industrial Co., Kyoto (Japan). Central Research Lab.; Hirao, T. [Matsushita Technoresearch Inc., Moriguchi, Osaka (Japan)
1996-12-31
Hydrogenated amorphous silicon (a-Si:H) films have been commonly prepared by glow discharge decomposition of silane (SiH{sub 4}) using capacitively coupled plasmas (CCP). In course of the film deposition with CCP, however, substrates must be heated at moderate temperatures around 250 C to obtain high quality films. This fact makes it impossible to deposit films on materials with no heat resistance such as polymer sheets. To break through this problem, a-Si:H deposition by ECR plasmas has been proposed. Inductively coupled plasmas (ICPs) are also very attractive for a-Si:H film deposition because high density plasmas at low pressures can be produced with compact and simple configurations compared with ECR discharges. The authors in this paper, demonstrate deposition of high photo-conductivity a-Si:H films at low substrate temperature, using a SiH{sub 4} ICP. Photo- and dark-conductivities are measured as a function of rf power, SiH{sub 4} pressure and substrate position with respect to the gas feed position. It is found that, at proper discharge conditions, high photo-conductivity films (10{sup {minus}6} {approximately} 10{sup {minus}5} {Omega}{sup {minus}1} cm{sup {minus}1}) can be deposited even at a substrate temperature of 40 C. This result is very promising for the a-Si:H deposition using ICP near room temperatures.
Stamos, Ioannis
Spring 2010 3D Photography -------------------------------------------------------------- Project I a specified viewpoint. This range image is expressed as a two-dimensional array of 3-D points. 3-D points that are neighbors in this array are probably neighbors in the actual 3-D surface, unless the points lie on a shape
NASA Astrophysics Data System (ADS)
Min, Dong; Shen, Jun; Lai, Shiqiang; Chen, Jie; Xu, Nan; Liu, Hui
2011-01-01
The effects of heat input on the low power Nd:YAG pulse laser conduction weldability of magnesium alloy AZ61 plates were investigated. The results show that for a hot-extruded AZ61 magnesium alloy plate laser conduction welding, the penetration depth and area of welds cross-section increased with an increase of the heat input. The microstructure of a band zone, which is located in the fusion zone (FZ) and close to the fusion boundary, evolved with an increase of the heat input. Moreover, an increase of the heat input increased the tendency of the formation of solidification cracking and liquation cracking. The porosities and average diameters of pores increased with an increase of the heat input but reduced sharply when a relatively large heat input was achieved. In addition, the degree of formation of craters increased linearly with an increase of the heat input.
The improved element-free Galerkin method for three-dimensional transient heat conduction problems
NASA Astrophysics Data System (ADS)
Zhang, Zan; Wang, JianFei; Cheng, YuMin; Liew, Kim Meow
2013-08-01
With the improved moving least-squares (IMLS) approximation, an orthogonal function system with a weight function is used as the basis function. The combination of the element-free Galerkin (EFG) method and the IMLS approximation leads to the development of the improved element-free Galerkin (IEFG) method. In this paper, the IEFG method is applied to study the partial differential equations that control the heat flow in three-dimensional space. With the IEFG technique, the Galerkin weak form is employed to develop the discretized system equations, and the penalty method is applied to impose the essential boundary conditions. The traditional difference method for two-point boundary value problems is selected for the time discretization. As the transient heat conduction equations and the boundary and initial conditions are time dependent, the scaling parameter, number of nodes and time step length are considered in a convergence study.
Layered thermal metamaterials for the directing and harvesting of conductive heat
NASA Astrophysics Data System (ADS)
Bandaru, P. R.; Vemuri, K. P.; Canbazoglu, F. M.; Kapadia, R. S.
2015-05-01
The utility of a metamaterial, assembled from two layers of nominally isotropic materials, for thermal energy re-orientation and harvesting is examined. A study of the underlying phenomena related to heat flux manipulation, exploiting the anisotropy of the thermal conductivity tensor, is a focus. The notion of the assembled metamaterial as an effective thermal medium forms the basis for many of these investigations and will be probed. An overarching aim is to implement in such thermal metamaterials, functionalities well known from light optics, such as reflection and refraction, which in turn may yield insights on efficient thermal lensing. Consequently, the harness and dissipation of heat, which are for example, of much importance in energy conservation and improving electrical device performance, may be accomplished. The possibilities of energy harvesting, through exploiting anisotropic thermopower in the metamaterials is also examined. The review concludes with a brief survey of the outstanding issues and insights needed for further progress.
Held, Markus; Steigmeir, Andreas
2015-01-01
We present and discuss three discontinuous Galerkin (dG) discretizations for the anisotropic heat conduction equation on non-aligned cylindrical grids. Our most favourable scheme relies on a self-adjoint local dG (LDG) discretization of the elliptic operator. It conserves the energy exactly and converges with arbitrary order. The pollution by numerical perpendicular heat fluxes degrades with superconvergence rates. We compare this scheme with aligned schemes that are based on the flux-coordinate independent approach for the discretization of parallel derivatives. Here, the dG method provides the necessary interpolation. The first aligned discretization can be used in an explicit time-integrator. However, the scheme violates conservation of energy and shows up stagnating convergence rates for very high resolutions. We overcome this partly by using the adjoint of the parallel derivative operator to construct a second self-adjoint aligned scheme. This scheme preserves energy, but reveals unphysical oscillations ...
An implicit-iterative solution of the heat conduction equation with a radiation boundary condition
NASA Technical Reports Server (NTRS)
Williams, S. D.; Curry, D. M.
1977-01-01
For the problem of predicting one-dimensional heat transfer between conducting and radiating mediums by an implicit finite difference method, four different formulations were used to approximate the surface radiation boundary condition while retaining an implicit formulation for the interior temperature nodes. These formulations are an explicit boundary condition, a linearized boundary condition, an iterative boundary condition, and a semi-iterative boundary method. The results of these methods in predicting surface temperature on the space shuttle orbiter thermal protection system model under a variety of heating rates were compared. The iterative technique caused the surface temperature to be bounded at each step. While the linearized and explicit methods were generally more efficient, the iterative and semi-iterative techniques provided a realistic surface temperature response without requiring step size control techniques.
NASA Technical Reports Server (NTRS)
Ngo, Quoc; Cruden, Brett A.; Cassell, Alan M.; Sims, Gerard; Li, Jun; Meyyappa, M.; Yang, Cary Y.
2005-01-01
Efforts in integrated circuit (IC) packaging technologies have recently been focused on management of increasing heat density associated with high frequency and high density circuit designs. While current flip-chip package designs can accommodate relatively high amounts of heat density, new materials need to be developed to manage thermal effects of next-generation integrated circuits. Multiwall carbon nanotubes (MWNT) have been shown to significantly enhance thermal conduction in the axial direction and thus can be considered to be a candidate for future thermal interface materials by facilitating efficient thermal transport. This work focuses on fabrication and characterization of a robust MWNT-copper composite material as an element in IC package designs. We show that using vertically aligned MWNT arrays reduces interfacial thermal resistance by increasing conduction surface area, and furthermore, the embedded copper acts as a lateral heat spreader to efficiently disperse heat, a necessary function for packaging materials. In addition, we demonstrate reusability of the material, and the absence of residue on the contacting material, both novel features of the MWNT-copper composite that are not found in most state-of-the-art thermal interface materials. Electrochemical methods such as metal deposition and etch are discussed for the creation of the MWNT-Cu composite, detailing issues and observations with using such methods. We show that precise engineering of the composite surface affects the ability of this material to act as an efficient thermal interface material. A thermal contact resistance measurement has been designed to obtain a value of thermal contact resistance for a variety of different thermal contact materials.
2011-01-01
An alternative insight is presented concerning heat propagation velocity scales in predicting the effective thermal conductivities of nanofluids. The widely applied Brownian particle velocities in published literature are often found too slow to describe the relatively higher nanofluid conductivities. In contrast, the present model proposes a faster heat transfer velocity at the same order as the speed of sound, rooted in a modified kinetic principle. In addition, this model accounts for both nanoparticle heat dissipation as well as coagulation effects. This novel model of effective thermal conductivities of nanofluids agrees well with an extended range of experimental data. PMID:21711892
Analytical evaluation of thermal conductance and heat capacities of one-dimensional material systems
Saygi, Salih [Department of Physics, Gaziosmanpasa University, Tokat, 60200 Turkey (Turkey)] [Department of Physics, Gaziosmanpasa University, Tokat, 60200 Turkey (Turkey)
2014-02-15
We theoretically predict some thermal properties versus temperature dependence of one dimensional (1D) material nanowire systems. A known method is used to provide an efficient and reliable analytical procedure for wide temperature range. Predicted formulas are expressed in terms of Bloch-Grüneisen functions and Debye functions. Computing results has proved that the expressions are in excellent agreement with the results reported in the literature even if it is in very low dimension limits of nanowire systems. Therefore the calculation method is a fully predictive approach to calculate thermal conductivity and heat capacities of nanowire material systems.
Subsurface Temperature, Moisture, Thermal Conductivity and Heat Flux, Barrow, Area A, B, C, D
Cable, William; Romanovsky, Vladimir
Subsurface temperature data are being collected along a transect from the center of the polygon through the trough (and to the center of the adjacent polygon for Area D). Each transect has five 1.5m vertical array thermistor probes with 16 thermistors each. This dataset also includes soil pits that have been instrumented for temperature, water content, thermal conductivity, and heat flux at the permafrost table. Area C has a shallow borehole of 2.5 meters depth is instrumented in the center of the polygon.
Multiply scaled constrained nonlinear equation solvers. [for nonlinear heat conduction problems
NASA Technical Reports Server (NTRS)
Padovan, Joe; Krishna, Lala
1986-01-01
To improve the numerical stability of nonlinear equation solvers, a partitioned multiply scaled constraint scheme is developed. This scheme enables hierarchical levels of control for nonlinear equation solvers. To complement the procedure, partitioned convergence checks are established along with self-adaptive partitioning schemes. Overall, such procedures greatly enhance the numerical stability of the original solvers. To demonstrate and motivate the development of the scheme, the problem of nonlinear heat conduction is considered. In this context the main emphasis is given to successive substitution-type schemes. To verify the improved numerical characteristics associated with partitioned multiply scaled solvers, results are presented for several benchmark examples.
Subsurface Temperature, Moisture, Thermal Conductivity and Heat Flux, Barrow, Area A, B, C, D
Cable, William; Romanovsky, Vladimir
2014-03-31
Subsurface temperature data are being collected along a transect from the center of the polygon through the trough (and to the center of the adjacent polygon for Area D). Each transect has five 1.5m vertical array thermistor probes with 16 thermistors each. This dataset also includes soil pits that have been instrumented for temperature, water content, thermal conductivity, and heat flux at the permafrost table. Area C has a shallow borehole of 2.5 meters depth is instrumented in the center of the polygon.
Heat conductivity from molecular chaos hypothesis in locally confined billiard systems.
Gilbert, Thomas; Lefevere, Raphaël
2008-11-14
We study the transport properties of a large class of locally confined Hamiltonian systems, in which neighboring particles interact through hard-core elastic collisions. When these collisions become rare and the systems large, we derive a Boltzmann-like equation for the evolution of the probability densities. We solve this equation in the linear regime and compute the heat conductivity from a Green-Kubo formula. The validity of our approach is demonstrated by comparing our predictions with the results of numerical simulations performed on a new class of high-dimensional defocusing chaotic billiards. PMID:19113325
Mathematical equations for heat conduction in the fins of air-cooled engines
NASA Technical Reports Server (NTRS)
Harper, R R; Brown, W B
1923-01-01
The problem considered in this report is that of reducing actual geometrical area of fin-cooling surface, which is, of course, not uniform in temperature, to equivalent cooling area at one definite temperature, namely, that prevailing on the cylinder wall at the point of attachment of the fin. This makes it possible to treat all the cooling surface as if it were part of the cylinder wall and 100 per cent effective. The quantities involved in the equations are the geometrical dimensions of the fin, thermal conductivity of the material composing it, and the coefficient of surface heat dissipation between the fin and the air streams.
Effects of fiber direction on heat conduction in unidirectionally aligned fiber composites
Havis, Clark Reagan
1987-01-01
distribution and measured temperatures, st = 60 qe = 0. 66 W/cm, kgf f = 0. 498 W/m K 38 sss gas A 341 3 K~ B ~ 388 ' 7 KI C 393 9 K D ~ 401 7 KI E = 412 ' 5 K, B ~ 429 ' 5 K, G = 458. 7 K Fig. 18 Predicted two-dimensional temperature distribution... of MASTER OF SCIENCE December 1987 Major Subject: Mechanical Engineering EFFECTS OF FIBER DIRECTION ON HEAT CONDUCTION IN UNIDIRECTIONALLY ALIGNED FIBER COMPOSITES A Thesis CLARK REAGAN HAVIS Approved as to style and content by: G. P. Peterson...
NASA Astrophysics Data System (ADS)
Nath, G.; Vishwakarma, J. P.
2014-05-01
The propagation of a spherical (or cylindrical) shock wave in a non-ideal gas with heat conduction and radiation heat-flux, in the presence of a spacially decreasing azimuthal magnetic field, driven out by a moving piston is investigated. The heat conduction is expressed in terms of Fourier's law and the radiation is considered to be of the diffusion type for an optically thick grey gas model. The thermal conductivity K and the absorption coefficient ?R are assumed to vary with temperature and density. The gas is assumed to have infinite electrical conductivity and to obey a simplified van der Waals equation of state. The shock wave moves with variable velocity and the total energy of the wave is non-constant. Similarity solutions are obtained for the flow-field behind the shock and the effects of variation of the heat transfer parameters, the parameter of the non-idealness of the gas, both, decreases the compressibility of the gas and hence there is a decrease in the shock strength. Further, it is investigated that with an increase in the parameters of radiative and conductive heat transfer the tendency of formation of maxima in the distributions of heat flux, density and isothermal speed of sound decreases. The pressure and density vanish at the inner surface (piston) and hence a vacuum is form at the center of symmetry. The shock waves in conducting non-ideal gas with conductive and radiative heat fluxes can be important for description of shocks in supernova explosions, in the study of central part of star burst galaxies, nuclear explosion, chemical detonation, rupture of a pressurized vessels, in the analysis of data from exploding wire experiments, and cylindrically symmetric hypersonic flow problems associated with meteors or reentry vehicles, etc. The findings of the present works provided a clear picture of whether and how the non-idealness parameter, conductive and radiative heat transfer parameters and the magnetic field affect the flow behind the shock front.
B. A. Strukov; S. T. Davitadze; S. N. Kravchun; S. A. Taraskin; M Goltzman; V. V. Lemanov; S. G. Shulman
2003-01-01
Thermal properties - specific heat and heat conductivity coefficient—of polycrystalline BaTiO3 films on massive substrates were studied as a function of the temperature and the film thickness by the ac-hot probe method. The anomalies of specific heat with the film thickness decreasing from 1100 to 20 nm revealed the reduction of Tc and excess entropy of the ferroelectric phase transition
NASA Technical Reports Server (NTRS)
Perkins, R. A.; Cieszkiewicz, M. T.
1991-01-01
Experimental measurements of thermal conductivity and thermal diffusivity obtained with a transient hot-wire apparatus are reported for three mixtures of nitrogen, oxygen, and argon. Values of the specific heat, Cp, are calculated from these measured values and the density calculated with an equation of state. The measurements were made at temperatures between 65 and 303 K with pressures between 0.1 and 70 MPa. The data cover the vapor, liquid, and supercritical gas phases for the three mixtures. The total reported points are 1066 for the air mixture (78.11 percent nitrogen, 20.97 percent oxygen, and 0.92 percent argon), 1058 for the 50 percent nitrogen, 50 percent oxygen mixture, and 864 for the 25 percent nitrogen, 75 oxygen mixture. Empirical thermal conductivity correlations are provided for the three mixtures.
NASA Astrophysics Data System (ADS)
Vishwakarma, V.; Jain, A.
2014-12-01
The separator is a critical, multi-functional component of a Li-ion cell that plays a key role in performance and safety during energy conversion and storage processes. Heat flow through the separator is important for minimizing cell temperature and avoiding thermal runaway. Despite the critical nature of thermal conduction through the separator, very little research has been reported on understanding and measuring the thermal conductivity and heat capacity of the separator. This paper presents first-ever measurements of thermal conductivity and heat capacity of the separator material. These measurements are based on thermal response to an imposed DC heating within a time period during which an assumption of a thermally semi-infinite domain is valid. Experimental data are in excellent agreement with the analytical model. Comparison between the two results in measurement of the in-plane thermal conductivity and heat capacity of the separator. Results indicate very low thermal conductivity of the separator. Measurements at an elevated temperature indicate that thermal conductivity and heat capacity do not change much with increasing temperature. Experimental measurements of previously unavailable thermal properties reported here may facilitate a better fundamental understanding of thermal transport in a Li-ion cell, and enhanced safety due to more accurate thermal prediction.
3D Computer Vision and Video Computing 3D Vision3D Vision
Zhu, Zhigang
1 3D Computer Vision and Video Computing 3D Vision3D Vision CSc I6716 Fall 2010 Topic 4 of Part II@cs.ccny.cuny.edu 3D Computer Vision and Video Computing Outline of MotionOutline of Motion Problems and Applications The importance of visual motion Problem Statement The Motion Field of Rigid Motion Basics Â Notations
NSDL National Science Digital Library
Ensley, Doug
Developed by Barbara Kaskosz of the University of Rhode Island and Doug Ensley of Shippensburg University, this resource from The Mathematical Association of America's Digital Classroom Resources collection will prove quite valuable for educators and anyone with an interest in computer graphics or geometry. Through this resource, visitors will learn how to draw and rotate 3D objects via a series of short tutorials. Along the way, users will learn about the mathematics behind manipulating cubes, the geometry involved with the manipulation of cubes, and they will also get a chance to work on their own structures. Overall, it's a fine resource and it offers insights for students in several different disciplines.
NSDL National Science Digital Library
Developed by Barbara Kaskosz of the University of Rhode Island and Doug Ensley of Shippensburg University, this resource from The Mathematical Association of America's Digital Classroom Resources collection will prove quite valuable for educators and anyone with an interest in computer graphics or geometry. Through this resource, visitors will learn how to draw and rotate 3D objects via a series of short tutorials. Along the way, users will learn about the mathematics behind manipulating cubes, the geometry involved with the manipulation of cubes, and they will also get a chance to work on their own structures. Overall, it's a fine resource and it offers insights for students in several different disciplines
NASA Technical Reports Server (NTRS)
1992-01-01
Ames Research Center research into virtual reality led to the development of the Convolvotron, a high speed digital audio processing system that delivers three-dimensional sound over headphones. It consists of a two-card set designed for use with a personal computer. The Convolvotron's primary application is presentation of 3D audio signals over headphones. Four independent sound sources are filtered with large time-varying filters that compensate for motion. The perceived location of the sound remains constant. Possible applications are in air traffic control towers or airplane cockpits, hearing and perception research and virtual reality development.
Song, Y.; Yao, Y.; Na, W.
2006-01-01
In this paper the composition and thermal property of soil are discussed. The main factors that impact the soil thermal conductivity and several commonly-used pipe materials are studied. A model of heat exchanger with horizontal pipes of ground...
Song, Y.; Yao, Y.; Na, W.
2006-01-01
In this paper the composition and thermal property of soil are discussed. The main factors that impact the soil thermal conductivity and several commonly-used pipe materials are studied. A model of heat exchanger with horizontal pipes of ground...
On the dynamical Rayleigh-Taylor instability in compressible viscous flows without heat conductivity
Fei Jiang; Song Jiang
2014-03-20
We investigate the instability of a smooth Rayleigh-Taylor steady-state solution to compressible viscous flows without heat conductivity in the presence of a uniform gravitational field in a bounded domain $\\Omega\\subset{\\mathbb R}^3$ with smooth boundary $\\partial\\Omega$. We show that the steady-state is linearly unstable by constructing a suitable energy functional and exploiting arguments of the modified variational method. Then, based on the constructed linearly unstable solutions and a local well-posedness result of classical solutions to the original nonlinear problem, we further reconstruct the initial data of linearly unstable solutions to be the one of the original nonlinear problem and establish an appropriate energy estimate of Gronwall-type. With the help of the established energy estimate, we show that the steady-state is nonlinearly unstable in the sense of Hadamard by a careful bootstrap argument. As a byproduct of our analysis, we find that the compressibility has no stabilizing effect in the linearized problem for compressible viscous flows without heat conductivity.
NASA Astrophysics Data System (ADS)
Vermeersch, Bjorn; Mohammed, Amr M. S.; Pernot, Gilles; Koh, Yee Rui; Shakouri, Ali
2015-02-01
Nearly all experimental observations of quasiballistic heat flow are interpreted using Fourier theory with modified thermal conductivity. Detailed Boltzmann transport equation (BTE) analysis, however, reveals that the quasi-ballistic motion of thermal energy in semiconductor alloys is no longer Brownian but instead exhibits Lévy dynamics with fractal dimension ? <2 . Here, we present a framework that enables full three-dimensional experimental analysis by retaining all essential physics of the quasiballistic BTE dynamics phenomenologically. A stochastic process with just two fitting parameters describes the transition from pure Lévy superdiffusion as short length and time scales to regular Fourier diffusion. The model provides accurate fits to time domain thermoreflectance raw experimental data over the full modulation frequency range without requiring any "effective" thermal parameters and without any a priori knowledge of microscopic phonon scattering mechanisms. Identified ? values for InGaAs and SiGe match ab initio BTE predictions within a few percent. Our results provide experimental evidence of fractal Lévy heat conduction in semiconductor alloys. The formalism additionally indicates that the transient temperature inside the material differs significantly from Fourier theory and can lead to improved thermal characterization of nanoscale devices and material interfaces.
BEAMS3D Neutral Beam Injection Model
NASA Astrophysics Data System (ADS)
McMillan, Matthew; Lazerson, Samuel A.
2014-09-01
With the advent of applied 3D fields in Tokamaks and modern high performance stellarators, a need has arisen to address non-axisymmetric effects on neutral beam heating and fueling. We report on the development of a fully 3D neutral beam injection (NBI) model, BEAMS3D, which addresses this need by coupling 3D equilibria to a guiding center code capable of modeling neutral and charged particle trajectories across the separatrix and into the plasma core. Ionization, neutralization, charge-exchange, viscous slowing down, and pitch angle scattering are modeled with the ADAS atomic physics database. Elementary benchmark calculations are presented to verify the collisionless particle orbits, NBI model, frictional drag, and pitch angle scattering effects. A calculation of neutral beam heating in the NCSX device is performed, highlighting the capability of the code to handle 3D magnetic fields. Notice: this manuscript has been authored by Princeton University under Contract Number DE-AC02-09CH11466 with the US Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes.
Mannoor, Manu S.; Jiang, Ziwen; James, Teena; Kong, Yong Lin; Malatesta, Karen A.; Soboyejo, Winston O.; Verma, Naveen; Gracias, David H.; McAlpine, Michael C.
2013-01-01
The ability to three-dimensionally interweave biological tissue with functional electronics could enable the creation of bionic organs possessing enhanced functionalities over their human counterparts. Conventional electronic devices are inherently two-dimensional, preventing seamless multidimensional integration with synthetic biology, as the processes and materials are very different. Here, we present a novel strategy for overcoming these difficulties via additive manufacturing of biological cells with structural and nanoparticle derived electronic elements. As a proof of concept, we generated a bionic ear via 3D printing of a cell-seeded hydrogel matrix in the precise anatomic geometry of a human ear, along with an intertwined conducting polymer consisting of infused silver nanoparticles. This allowed for in vitro culturing of cartilage tissue around an inductive coil antenna in the ear, which subsequently enables readout of inductively-coupled signals from cochlea-shaped electrodes. The printed ear exhibits enhanced auditory sensing for radio frequency reception, and complementary left and right ears can listen to stereo audio music. Overall, our approach suggests a means to intricately merge biologic and nanoelectronic functionalities via 3D printing. PMID:23635097
Mannoor, Manu S; Jiang, Ziwen; James, Teena; Kong, Yong Lin; Malatesta, Karen A; Soboyejo, Winston O; Verma, Naveen; Gracias, David H; McAlpine, Michael C
2013-06-12
The ability to three-dimensionally interweave biological tissue with functional electronics could enable the creation of bionic organs possessing enhanced functionalities over their human counterparts. Conventional electronic devices are inherently two-dimensional, preventing seamless multidimensional integration with synthetic biology, as the processes and materials are very different. Here, we present a novel strategy for overcoming these difficulties via additive manufacturing of biological cells with structural and nanoparticle derived electronic elements. As a proof of concept, we generated a bionic ear via 3D printing of a cell-seeded hydrogel matrix in the anatomic geometry of a human ear, along with an intertwined conducting polymer consisting of infused silver nanoparticles. This allowed for in vitro culturing of cartilage tissue around an inductive coil antenna in the ear, which subsequently enables readout of inductively-coupled signals from cochlea-shaped electrodes. The printed ear exhibits enhanced auditory sensing for radio frequency reception, and complementary left and right ears can listen to stereo audio music. Overall, our approach suggests a means to intricately merge biologic and nanoelectronic functionalities via 3D printing. PMID:23635097
Sarman, Sten; Laaksonen, Aatto
2013-03-14
The lack of a centre of inversion in a cholesteric liquid crystal allows linear cross couplings between thermodynamic forces and fluxes that are polar vectors and pseudovectors, respectively. This makes it possible for a temperature gradient parallel to the cholesteric axis to induce a torque that rotates the director, a phenomenon known as the Lehmann effect or thermomechanical coupling. The converse is also possible: a torque applied parallel to the cholesteric axis rotates the director and drives a heat flow. In order to study this phenomenon, nonequilibrium molecular dynamics simulation algorithms and Green-Kubo relations evaluated by equilibrium molecular dynamics simulation have been used to calculate the Leslie coefficient, i.e. the cross coupling coefficient between the temperature gradient and the director angular velocity, for a model system composed of soft prolate ellipsoids of revolution interacting via the Gay-Berne potential augmented by a chiral interaction potential causing the formation of a cholesteric phase. It is found that the Leslie coefficient is two orders of magnitudes smaller than other transport coefficients such as the heat conductivity and the twist viscosity, so that very long simulations are required to evaluate it. The Leslie coefficient decreases with the pitch but it has not been possible to determine the exact functional dependence of this coefficient on the pitch. Since very long simulations have been performed to evaluate the Leslie coefficient, very accurate values have been obtained for the twist viscosity and the heat conductivity as a by-product and it is found that they are very similar to the values of the corresponding quantities in the achiral nematic phase that arises when the pitch goes to infinity. PMID:23223192
Subhash C. Mishra; T. B. Pavan Kumar; Bittagopal Mondal
2008-01-01
This article concerns the application of the lattice Boltzmann method (LBM) to solve the energy equation of a combined radiation and non-Fourier conduction heat transfer problem. The finite propagation speed of the thermal wave front is accounted by non-Fourier heat conduction equation. The governing energy equation is solved using the LBM. The finite-volume method (FVM) is used to compute the
B. R. Bass
1978-01-01
The application is presented of a solution technique for the inverse problem that utilizes a finite element heat conduction model and Beck's nonlinear estimation procedure. The technique is applicable to the one-dimensional nonlinear model with temperature-dependent thermophysical properties. The formulation is applied first to a numerical example with a known solution. The example treated is that of a periodic heat
N. Daouas; M.-S. Radhouani
2004-01-01
An extended version of a smoothing technique applied to the Kalman filter estimates is developed in order to solve a nonlinear one-dimensional inverse heat conduction problem. This new algorithm introduces the use of future time measurements and so provides a best estimation of the surface conditions, involving heat flux density and temperature, in which time lag and sensitivity to measurement
Ibrahim A. Abdallah
In this work the uncopled thermoelastic model based on the Dual Phase Lag (DPL) heat conduction equation is used to investigate the thermoelastic properties of a semi-infinite medium induced by a homogeneously illuminating ultrashort pulsed laser heating. The exact solution for the temperature, the displacement and the stresses distributions ob- tained analytically using the separation of variables method (SVM) hybrid
Schramm, Wolfgang; Yang, Deshan; Wood, Bradford J; Rattay, Frank; Haemmerich, Dieter
2007-01-01
Both radiofrequency (RF) and microwave (MW) ablation devices are clinically used for tumor ablation. Several studies report less dependence on vascular mediated cooling of MW compared to RF ablation. We created computer models of a cooled RF needle electrode, and a dipole MW antenna to determine differences in tissue heat transfer.We created Finite Element computer models of a RF electrode (Cooled needle, 17 gauge), and a MW antenna (Dipole, 13 gauge). We simulated RF ablation for 12 min with power controlled to keep maximum tissue temperature at 100 masculineC, and MW ablation for 6 min with 75 W of power applied. For both models we considered change in electric and thermal tissue properties as well as perfusion depending on tissue temperature. We determined tissue temperature profile at the end of the ablation procedure and calculated effect of perfusion on both RF and MW ablation.Maximum tissue temperature was 100 masculineC for RF ablation, and 177 masculineC for MW ablation. Lesion shape was ellipsoid for RF, and tear-drop shaped for MW ablation. MW ablation is less affected by tissue perfusion mainly due to the shorter ablation time and higher tissue temperature, but not due to MW providing deeper heating than RF. Both MW and RF applicators only produce significant direct heating within mm of the applicator, with most of the ablation zone created by thermal conduction.Both RF and MW applicators only directly heat tissue in close proximity of the applicators. MW ablation allows for higher tissue temperatures than RF since MW propagation is not limited by tissue desiccation and charring. Higher temperatures coupled with lower treatment times result in reduced effects of perfusion on MW ablation. PMID:19662127
E3D. 3D Elastic Seismic Wave Propagation Code
Larsen, S.; Harris, D.; Schultz, C.; Maddix, D.; Bakowsky, T.; Bent, L. [Lawrence Livermore National Lab., CA (United States)
1998-01-01
E3D is capable of simulating seismic wave propagation in a 3D heterogeneous earth. Seismic waves are initiated by earthquake, explosive, and/or other sources. These waves propagate through a 3D geologic model, and are simulated as synthetic seismograms or other graphical output.
E3D. 3D Elastic Seismic Wave Propagation Code
S. Larsen; D. Harris; C. Schultz; D. Maddix; T. Bakowsky; L. Bent
1998-01-01
E3D is capable of simulating seismic wave propagation in a 3D heterogeneous earth. Seismic waves are initiated by earthquake, explosive, and\\/or other sources. These waves propagate through a 3D geologic model, and are simulated as synthetic seismograms or other graphical output.
Nathenson, Menuel; Tilling, Robert I.
1993-01-01
A steady-state solution for heat transfer from an isothermal, spherical magma chamber, with an imposed regional geothermal gradient far from the chamber, is developed. The extensive published heat-flow data set for Mount Hood, Oregon, is dominated by conductive heat transfer in the deeper parts of most drill holes and provides an ideal application of such a model. Magma-chamber volumes or depths needed to match the distribution of heat-flow data are larger or shallower than those inferred from geologic evidence.
Fu, X.; Chung, D.D.L. [State Univ. of New York, Buffalo, NY (United States). Composite Materials Research Lab.] [State Univ. of New York, Buffalo, NY (United States). Composite Materials Research Lab.
1997-12-01
Due to their poor conductivity, latex (20--30% by weight of cement), methylcellulose (0.4--0.8% by weight of cement), and silica fume (15% by weight of cement) decreased the thermal conductivity of cement paste by up to 46%. In addition, these admixtures increased the specific heat of cement paste by up to 10%. The thermal conductivity decreased and the specific heat increased with increasing latex or methylcellulose content. Short carbon fibers (0.5--1.0% by weight of cement) either did not change or decreased the thermal conductivity of cement paste, such that the thermal conductivity decreased with increasing fiber content due to the increase in air void content. The fibers increased the specific heat due to the contribution of the fiber-matrix interface to vibration.
Evaluation of vision training using 3D play game
NASA Astrophysics Data System (ADS)
Kim, Jung-Ho; Kwon, Soon-Chul; Son, Kwang-Chul; Lee, Seung-Hyun
2015-03-01
The present study aimed to examine the effect of the vision training, which is a benefit of watching 3D video images (3D video shooting game in this study), focusing on its accommodative facility and vergence facility. Both facilities, which are the scales used to measure human visual performance, are very important factors for man in leading comfortable and easy life. This study was conducted on 30 participants in their 20s through 30s (19 males and 11 females at 24.53 ± 2.94 years), who can watch 3D video images and play 3D game. Their accommodative and vergence facility were measured before and after they watched 2D and 3D game. It turned out that their accommodative facility improved after they played both 2D and 3D games and more improved right after they played 3D game than 2D game. Likewise, their vergence facility was proved to improve after they played both 2D and 3D games and more improved soon after they played 3D game than 2D game. In addition, it was demonstrated that their accommodative facility improved to greater extent than their vergence facility. While studies have been so far conducted on the adverse effects of 3D contents, from the perspective of human factor, on the imbalance of visual accommodation and convergence, the present study is expected to broaden the applicable scope of 3D contents by utilizing the visual benefit of 3D contents for vision training.
NASA Astrophysics Data System (ADS)
Fong, Kin Chung; Wollman, Emma E.; Ravi, Harish; Chen, Wei; Clerk, Aashish A.; Shaw, M. D.; Leduc, H. G.; Schwab, K. C.
2013-10-01
The ability to transport energy is a fundamental property of the two-dimensional Dirac fermions in graphene. Electronic thermal transport in this system is relatively unexplored and is expected to show unique fundamental properties and to play an important role in future applications of graphene, including optoelectronics, plasmonics, and ultrasensitive bolometry. Here, we present measurements of bipolar thermal conductances due to electron diffusion and electron-phonon coupling and infer the electronic specific heat, with a minimum value of 10kB (10-22J/K) per square micron. We test the validity of the Wiedemann-Franz law and find that the Lorenz number equals 1.32×(?2/3)(kB/e)2. The electron-phonon thermal conductance has a temperature power law T2 at high doping levels, and the coupling parameter is consistent with recent theory, indicating its enhancement by impurity scattering. We demonstrate control of the thermal conductance by electrical gating and by suppressing the diffusion channel using NbTiN superconducting electrodes, which sets the stage for future graphene-based single-microwave photon detection.
A Global Stability Analysis of Clusters of Galaxies with Conduction and AGN Feedback Heating
NASA Astrophysics Data System (ADS)
Guo, Fulai; Oh, S. Peng; Ruszkowski, M.
2008-12-01
We investigate a series of steady state models of galaxy clusters, in which the hot intracluster gas is efficiently heated by active galactic nucleus (AGN) feedback and thermal conduction, and in which the mass accretion rates are highly reduced compared to those predicted by the standard cooling flow models. We perform a global Lagrangian stability analysis. We show for the first time that the global radial instability in cool core clusters can be suppressed by the AGN feedback mechanism, provided that the feedback efficiency exceeds a critical lower limit. Furthermore, our analysis naturally shows that the clusters can exist in two distinct forms. Globally stable clusters are expected to have either (1) cool cores stabilized by both AGN feedback and conduction or (2) noncool cores stabilized primarily by conduction. Intermediate central temperatures typically lead to globally unstable solutions. This bimodality is consistent with the recent observation by Dunn & Fabian of anticorrelation between the flatness of the temperature profiles and the AGN activity and the observation by Rafferty et al. that the shorter central cooling times tend to correspond to significantly younger AGN X-ray cavities.
Caspi, S.; Helm, M.; Laslett, L.J.
1991-03-30
We have developed an harmonic representation for the three dimensional field components within the windings of accelerator magnets. The form by which the field is presented is suitable for interfacing with other codes that make use of the 3D field components (particle tracking and stability). The field components can be calculated with high precision and reduced cup time at any location (r,{theta},z) inside the magnet bore. The same conductor geometry which is used to simulate line currents is also used in CAD with modifications more readily available. It is our hope that the format used here for magnetic fields can be used not only as a means of delivering fields but also as a way by which beam dynamics can suggest correction to the conductor geometry. 5 refs., 70 figs.
LDEF (Flight), AO076 : Cascade Variable-Conductance Heat Pipe, Tray F09
NASA Technical Reports Server (NTRS)
1990-01-01
LDEF (Flight), AO076 : Cascade Variable-Conductance Heat Pipe, Tray F09 EL-1994-00020 LDEF (Flight), AO076 : Cascade Variable-Conductance Heat Pipe, Tray F09 The flight photograph of the Cascade Variable Conductance Heat Pipe Experiment (CVCHPE) was taken while the LDEF was attached to the Orbiter's RMS arm prior to berthing in the Orbiter's cargo bay. The white paint dots on the center clamp blocks of the experiment trays right flange and lower flange appear to be slightly discolored. The LDEF structure, top intercostal, has a dark brown discoloration adjacent to the black thermal panel. Aluminum particles from the degraded CVCHPE thermal blanket are also visible in this area. The Cascade Variable Conductance Heat Pipe Experiment (CVCHPE) occupies a 6 inch deep LDEF peripheral experiment tray and consist of two series connected variable conductance heatpipes, a black chrome solar collector panel and a silvered TEFLON® radiator panel, a power source to support six thermistor-type temperature monitoring sensors and actuations of two valves. Fiberglass standoffs and internal insulation blankets thermally isolated the experiment from the experiment tray and the LDEF interior. The outside of the CVCHPE, except the collector and radiator panels, was covered with an aluminumized Kapton multilayer insulation (MLI) blanket with an outer layer of 0.076 mm thick Kapton. The two patches of thin film materials, part of an atomic oxygen experiment (see S1001) by NASA GSFC, were attached to the cover of the external thermal blanket with Kapton tape. The experiment was assembled and mounted in the experiment tray with non-magnetic stainless steel fasteners. The external CVCHPE materials have changed significantly. The Kapton on the thermal blanket aluminized Kapton cover appears to be completely eroded, except under Kel-F buttons used to secure the blanket, leaving only the very thin vapor deposited aluminum coating as a cover. Parts of the aluminum coating residue has moved to cover a portion of the black solar absorber panel and also areas of the trays upper and lower flanges. The shadow on the tray lower flange would indicate that the aluminum extends several inches out of the tray envelope. One of the two thin film atomic oxygen experiment patches is gone and the other does not appear to be securely attached. The layer of Kapton tape over the thin film strips appears to be eroded with only the adhesive remaining. The remaining atomic oxygen experiment materials have changed colors and most appear to be severely degraded. The silvered TEFLON® coating of the radiator panel appears diffuse with a light brown discoloration over most of the surface. The white, evenly spaced, discolorations along the vertical centerline and across the top of the panel appear to be above counter sunk flat head screws used to assemble the experiment. The black spots on the radiator panel appear to be impact craters where the impact penetrated the TEFLON® material and exposed the silver beneath to the atomic oxygen flux. Particles of the degraded thermal blanket material appear to be adhered to the surface of the radiator panel.
Bass, B.R.; Ott, L.J.
1980-01-01
The calculation of the surface temperature and surface heat flux from measured temperature transients at one or more interior points of a body is identified in the literature as the inverse heat conduction problem. An inverse solution technique applicable to the two-dimensional nonlinear model with temperature dependent thermophysical properties is presented. The technique utilizes a finite element heat conduction model and a generalization of Beck's one-dimensional nonlinear estimation procedure. Results are presented to demonstrate that the inverse formulation is capable of successfully treating experimental data.
Jing-Jing Fang
2003-01-01
This preliminary research revolute the conventional clothing design process by true designs from three-dimensional (3D) rather than two-dimensional. The aim of the research is to develop a handy 3D clothing design software tool for general garment designers. Work carried out in this paper is the preliminary result of the 3D software infrastructure. In addition, 3D collar design based on a
NASA Technical Reports Server (NTRS)
Zhu, Dong-Ming; Miller, Robert A.
2004-01-01
The development of low conductivity and high temperature capable thermal barrier coatings requires advanced testing techniques that can accurately and effectively evaluate coating thermal conductivity under future high-performance and low-emission engine heat-flux conditions. In this paper, a unique steady-state CO2 laser (wavelength 10.6 microns) heat-flux approach is described for determining the thermal conductivity and conductivity deduced cyclic durability of ceramic thermal and environmental barrier coating systems at very high temperatures (up to 1700 C) under large thermal gradients. The thermal conductivity behavior of advanced thermal and environmental barrier coatings for metallic and Si-based ceramic matrix composite (CMC) component applications has also been investigated using the laser conductivity approach. The relationships between the lattice and radiation conductivities as a function of heat flux and thermal gradient at high temperatures have been examined for the ceramic coating systems. The steady-state laser heat-flux conductivity approach has been demonstrated as a viable means for the development and life prediction of advanced thermal barrier coatings for future turbine engine applications.
Nanoparticle synergies in modifying thermal conductivity for heat exchanger in condensing boilers
NASA Astrophysics Data System (ADS)
Yang, Kai; He, Shan; Butcher, Thomas; Trojanowski, Rebecca; Sun, Ning; Gersappe, Dilip; Rafailovich, Miriam
2013-03-01
The heat exchanger we are using for condensing boilers is mainly made from aluminum alloys and stainless steel. However, the metal is relatively expensive and corrosion together with maintenance is also a big problem. Therefore, we have developed a new design and material which contain carbon black, carbon nanotube, aluminum oxide and graphene as additives in polypropylene. When multiple types of particles can be melt blended simultaneously and synergies can be achieved, imparting particles to the nanocomposite, achieved much higher thermal conductivity rather than single additive. Here we show the flame retardant nanocomposite which can pass the UL-94-V0 vertical burning test, perform nice in Cone Calorimetry Test and has relatively good mechanical properties. SEM images of the blend show that the Carbon nanobute and other additives well dispersed within the polymer matrix which match our computational calculation for getting the percolation to achieve thermal conductivity around 1.5W/m .K rather than 0.23W/m .K as pure polypropylene. The heat exchanger we are using for condensing boilers is mainly made from aluminum alloys and stainless steel. However, the metal is relatively expensive and corrosion together with maintenance is also a big problem. Therefore, we have developed a new design and material which contain carbon black, carbon nanotube, aluminum oxide and graphene as additives in polypropylene. When multiple types of particles can be melt blended simultaneously and synergies can be achieved, imparting particles to the nanocomposite, achieved much higher thermal conductivity rather than single additive. Here we show the flame retardant nanocomposite which can pass the UL-94-V0 vertical burning test, perform nice in Cone Calorimetry Test and has relatively good mechanical properties. SEM images of the blend show that the Carbon nanobute and other additives well dispersed within the polymer matrix which match our computational calculation for getting the percolation to achieve thermal conductivity around 1.5W/m .K rather than 0.23W/m .K as pure polypropylene. Haydale/Cheap Tubes
Response-coefficient method for heat-conduction transients with time-dependent inputs
NASA Technical Reports Server (NTRS)
Ceylan, Tamer
1993-01-01
A theoretical overview of the response coefficient method for heat conduction transients with time-dependent input forcing functions is presented with a number of illustrative applications. The method may be the most convenient and economical if the same problem is to be solved many times with different input-time histories or if the solution time is relatively long. The method is applicable to a wide variety of problems, including irregular geometries, position-dependent boundary conditions, position-dependent physical properties, and nonperiodic irregular input histories. Nonuniform internal energy generation rates within the structure can also be handled by the method. The area of interest is long-time solutions, in which initial condition is unimportant, and not the early transient period. The method can be applied to one dimensional problems in cartesian, cylindrical, and spherical coordinates as well as to two dimensional problems in cartesian and cylindrical coordinates.
A search for the dominant heat conducting phonon modes in graphene: An atomistic simulation study
NASA Astrophysics Data System (ADS)
Zhang, Hengji; Cho, Kyeongjae
2011-03-01
We have performed an equilibrium molecular dynamic (MD) simulation study to investigate phonon thermal transport in graphene at 300K with Green-Kubo method. Using a newly optimized reactive empirical bond order carbon potential (Lindsay, et al. Physical Review B 81, 205441, 2010), our calculated thermal conductivity (TC) of defect free graphene is about 3000 W/mK in good agreement with experiments(~ 3000-5000 W/mK). A maximum of ~ 1000 fold reduction in TC is possible to achieve for graphene with defects and surrounding viscous medium. As we decompose the in-plane and out-plane phonon vibration modes of graphene in MD simulations, the out of plane vibration modes (ZA phonon) contribute to about 50% of the overall TC. This large contribution from ZA modes is explained with density of states analysis. We have clarified a recent controversy on which polarization mode in graphene is the main heat carrier.
Effect of the time window on the heat-conduction information filtering model
NASA Astrophysics Data System (ADS)
Guo, Qiang; Song, Wen-Jun; Hou, Lei; Zhang, Yi-Lu; Liu, Jian-Guo
2014-05-01
Recommendation systems have been proposed to filter out the potential tastes and preferences of the normal users online, however, the physics of the time window effect on the performance is missing, which is critical for saving the memory and decreasing the computation complexity. In this paper, by gradually expanding the time window, we investigate the impact of the time window on the heat-conduction information filtering model with ten similarity measures. The experimental results on the benchmark dataset Netflix indicate that by only using approximately 11.11% recent rating records, the accuracy could be improved by an average of 33.16% and the diversity could be improved by 30.62%. In addition, the recommendation performance on the dataset MovieLens could be preserved by only considering approximately 10.91% recent records. Under the circumstance of improving the recommendation performance, our discoveries possess significant practical value by largely reducing the computational time and shortening the data storage space.
NASA Technical Reports Server (NTRS)
Zhu, Dongming; Miller, Robert A.; Nagaraj, Ben A.; Bruce, Robert W.
2000-01-01
The thermal conductivity of electron beam-physical vapor deposited (EB-PVD) Zr02-8wt%Y2O3 thermal barrier coatings was determined by a steady-state heat flux laser technique. Thermal conductivity change kinetics of the EB-PVD ceramic coatings were also obtained in real time, at high temperatures, under the laser high heat flux, long term test conditions. The thermal conductivity increase due to micro-pore sintering and the decrease due to coating micro-delaminations in the EB-PVD coatings were evaluated for grooved and non-grooved EB-PVD coating systems under isothermal and thermal cycling conditions. The coating failure modes under the high heat flux test conditions were also investigated. The test technique provides a viable means for obtaining coating thermal conductivity data for use in design, development, and life prediction for engine applications.
NASA Technical Reports Server (NTRS)
2004-01-01
This 3-D, microscopic imager mosaic of a target area on a rock called 'Diamond Jenness' was taken after NASA's Mars Exploration Rover Opportunity ground into the surface with its rock abrasion tool for a second time.
Opportunity has bored nearly a dozen holes into the inner walls of 'Endurance Crater.' On sols 177 and 178 (July 23 and July 24, 2004), the rover worked double-duty on Diamond Jenness. Surface debris and the bumpy shape of the rock resulted in a shallow and irregular hole, only about 2 millimeters (0.08 inch) deep. The final depth was not enough to remove all the bumps and leave a neat hole with a smooth floor. This extremely shallow depression was then examined by the rover's alpha particle X-ray spectrometer.
On Sol 178, Opportunity's 'robotic rodent' dined on Diamond Jenness once again, grinding almost an additional 5 millimeters (about 0.2 inch). The rover then applied its Moessbauer spectrometer to the deepened hole. This double dose of Diamond Jenness enabled the science team to examine the rock at varying layers. Results from those grindings are currently being analyzed.
The image mosaic is about 6 centimeters (2.4 inches) across.
NASA Technical Reports Server (NTRS)
1997-01-01
Many prominent rocks near the Sagan Memorial Station are featured in this image, taken in stereo by the Imager for Mars Pathfinder (IMP) on Sol 3. 3D glasses are necessary to identify surface detail. Wedge is at lower left; Shark, Half-Dome, and Pumpkin are at center. Flat Top, about four inches high, is at lower right. The horizon in the distance is one to two kilometers away.
Mars Pathfinder is the second in NASA's Discovery program of low-cost spacecraft with highly focused science goals. The Jet Propulsion Laboratory, Pasadena, CA, developed and manages the Mars Pathfinder mission for NASA's Office of Space Science, Washington, D.C. JPL is an operating division of the California Institute of Technology (Caltech). The Imager for Mars Pathfinder (IMP) was developed by the University of Arizona Lunar and Planetary Laboratory under contract to JPL. Peter Smith is the Principal Investigator.
Click below to see the left and right views individually. [figure removed for brevity, see original site] Left [figure removed for brevity, see original site] Right
NSDL National Science Digital Library
When one thinks of the vast number of influential architects the world has seen during the past centuries, one is reminded of Dies van der Rohe, Walter Gropius, Le Corbusier, and of course, that Master from the Midwest, Frank Lloyd Wright. It's hard to imagine that a website would be able to conjure up the spirit of this famous and controversial architect, but it does just that. With the assistance of a user-friendly interface, the Architect Studio 3D site allows users to build a model home for a number of clients and their very specific needs. With a small icon of the master residing in the bottom of the left-hand corner of the screen, visitors will get the chance to create their own building for one of these clients, and then submit it to a design gallery for consideration by others. For those visitors who may be less familiar with the world of architecture, there is a handy section titled "About Architecture". Here they will find a glossary of terms that provide brief descriptions of such important concepts and design elements as site, wall, client, roof, and exterior material. Of course, no such site would be complete without a brief biography of the man himself, and as such, a nice overview of his work and life is provided here as well.
NASA Astrophysics Data System (ADS)
Kühmstedt, Peter; Bräuer-Burchardt, Christian; Munkelt, Christoph; Heinze, Matthias; Palme, Martin; Schmidt, Ingo; Hintersehr, Josef; Notni, Gunther
2007-09-01
Here a new set-up of a 3D-scanning system for CAD/CAM in dental industry is proposed. The system is designed for direct scanning of the dental preparations within the mouth. The measuring process is based on phase correlation technique in combination with fast fringe projection in a stereo arrangement. The novelty in the approach is characterized by the following features: A phase correlation between the phase values of the images of two cameras is used for the co-ordinate calculation. This works contrary to the usage of only phase values (phasogrammetry) or classical triangulation (phase values and camera image co-ordinate values) for the determination of the co-ordinates. The main advantage of the method is that the absolute value of the phase at each point does not directly determine the coordinate. Thus errors in the determination of the co-ordinates are prevented. Furthermore, using the epipolar geometry of the stereo-like arrangement the phase unwrapping problem of fringe analysis can be solved. The endoscope like measurement system contains one projection and two camera channels for illumination and observation of the object, respectively. The new system has a measurement field of nearly 25mm × 15mm. The user can measure two or three teeth at one time. So the system can by used for scanning of single tooth up to bridges preparations. In the paper the first realization of the intraoral scanner is described.
NSDL National Science Digital Library
Terese Herrera
This resource guide from the Middle School Portal 2 project, written specifically for teachers, provides links to exemplary resources including background information, lessons, career information, and related national science education standards. The online resources featured in Geometry in 3-D actively engage students in exploring a variety of geometric shapes, at times through lessons that involve building models or creating paper nets that fold into three-dimensional shapes; at other times, through technology that allows students to rotate and zoom in on figures, noting their attributes and complexity. Other lessons offer problems on surface area and volume, a part of every middle school curriculum. The problems, each with a different twist on the subject, challenge students to reconsider their understanding of how to measure solids. Activities for developing spatial sense, another primary objective in teaching geometry, are also featured. Finally, there are online galleries of geometric solids, included for the rare opportunity they offer to show your students the beauty in mathematics. In Background Information, you will find workshop sessions developed for teachers and other materials that may interest you as a professional. Each resource deals specifically with three-dimensional geometry topics that align with the geometry and measurement standards recommended by NCTM.
Influence of heat conductivity on the performance of RTV SIR coatings with different fillers
NASA Astrophysics Data System (ADS)
Siderakis, K.; Agoris, D.; Gubanski, S.
2005-10-01
Room temperature vulcanized silicone rubber (RTV SIR) coatings are employed in order to improve the pollution performance of high voltage ceramic insulators by imparting surface hydrophobicity. In this paper, the performance of three RTV SIR coatings containing different fillers is investigated in a salt-fog test. Alumina trihydrate (ATH) and silica are the fillers included in the formulation, aiming to increase the material endurance to the energy supplied by the surface electrical activity during periods of hydrophobicity loss. The primary action of these fillers is to increase the material heat conductivity, i.e. the amount of energy conducted to the substrate. In addition, in the case of ATH relief is also achieved due to particle decomposition. The results indicate that for the compositions commercially available, where low amounts of fillers are used, and under the conditions of the test, ATH filled coatings performed better than the silica filled ones. This is attributed to ATH decomposition which further relieves the material structure and therefore decelerates material aging.
Ján Benacka
2008-01-01
The paper gives the analytical solution to the one dimensional hyperbolic heat conduction equation in an insulated slab-shaped\\u000a sample that is heated uniformly on the front face with ? or laser impulse. The solution results in a formula that enables\\u000a to estimate the minimum mean free path of energy carriers in the sample to detect the second sound (i.e. the
Characterization and Modeling of TSV Based 3-D Integrated Circuits
community are discussed, and guidelines are provided for designing these evolving through silicon via (TSV. Finally, generation and spreading of heat in 3-D integrated circuits are discussed as part design, and DC and high frequency electrical measurements for TSV based 3-D integrated circuits. Ioannis
Radiative thermal conductivity in obsidian and estimates of heat transfer in magma bodies
Stein, J.; Shankland, T.J.; Nitsan, U.
1981-05-10
The optical transmission spectra of four ryholitic obsidian samples were measured in order to determine the importance of radiative heat transfer in granite magmas. The spectra, obtained in the temperature range 20-800/sup 0/C, show that the radiative spectral window in these samples is limited by a charge transfer band in the UV (400 nm) and Si-O stretching overtone in the IR (4500 nm). Within this window the main obstacles to radiative transfer, in order of decreasing importance, are background scattering, a water band centered at 2800 nm, and an Fe/sup 2 +/ crystal field band at 1100 nm. Unlike crystalline silicates the absorption bands in obsidian do not broaden significantly as temperature increases. As a result, the temperature dependence of the calculated radiative thermal conductivity K/sub R/ is dominated by the T/sup ..beta../ term. Actual values of K/sub R/ increase from 9 x 10/sup -5/ to 1 x 1/sup -3/ cal cm/sup -1/ s/sup -1/ deg/sup -1/ between 300/sup 0/ and 800/sup 0/C, the high-temperature value being comparable to the lattice thermal conductivity in obsidian and a lower limit for K/sub R/ in granitic melts. As the scattering coefficient in melts is probably significantly lower than in obsidian, the radiative conductivity in active plutons is likely to be much higher. As an example, if scattering and the water band are removed from the observed spectra of the obsidian samples, calculated values of K/sub R/ could increase by a factor of 5, to about 5 x 10/sup -3/ cal cm/sup -1/ s/sup -1/ deg/sup -1/ at 1000/sup 0/C.
LDEF (Postflight), AO076 : Cascade Variable-Conductance Heat Pipe, Tray F09
NASA Technical Reports Server (NTRS)
1990-01-01
LDEF (Postflight), AO076 : Cascade Variable-Conductance Heat Pipe, Tray F09 EL-1994-00354 LDEF (Postflight), AO076 : Cascade Variable-Conductance Heat Pipe, Tray F09 The postflight photograph was taken in the SAEF II at KSC prior to removal of the experiment from the LDEF. The color of the white paint dots on the exper- iment tray clamp blocks appear to be unchanged. The LDEF structure, the intercostal on the right, has a dark brown discoloration adjacent to the black Earth end thermal panel. Aluminum pieces of the degraded CVCHPE thermal cover that were shown lodged in the vent area between the intercostal and the black thermal panel in the flight photograph are gone. The Cascade Variable Conductance Heat Pipe Experiment (CVCHPE) occupies a 6 inch deep LDEF peripheral experiment tray and consist of two series connected variable conductance heatpipes, a black chrome solar collector panel and a silvered TEFLON® radiator panel, a power source to support six thermistor-type temperature monitoring sensors and actuations of two valves. Fiberglass standoffs and internal insulation blankets thermally isolated the experiment from the experiment tray and the LDEF interior. The outside of the CVCHPE, except the collector and radiator panels, was covered with an aluminized Kapton multilayer insulation (MLI) blanket with an outer layer of 0.076 mm thick Kapton. The two patches of thin film materials, part of Experiment S1001 by NASA GSFC, were attached to the cover of the external thermal blanket with Kapton tape. The experiment was assembled and mounted in the experiment tray with non-magnetic stainless steel fasteners. The external surface of the CVCHPE has changed from that observed in the flight photograph. The thin vapor deposited aluminum coating, left after the Kapton eroded, is essentially gone with only fragments left near the edges of the thermal blanket. Pieces of a layer of Dacron mesh (bridle vail) material, used to separate the thermal cover from the thermal blanket and between thermal blanket sheets of aluminized Kapton, are visible along the edges of the blanket and near Kel-F buttons used to secure the blanket. A large fragment of the material is folded over the left side of the radiator panel. The large area of discoloration on the right side of the black solar absorber panel appears to be approximately the same shape as the aluminum coating that covered the area in the flight photograph. The orientation of the remaining thin film atomic oxygen experiment patch would indicate that the patch is attached to the Dacron mesh and that the attachment is very fragile. The layer of Kapton tape that covered the ends of the thin film strips appears to be eroded with only the adhesive remaining. The remaining strips of the atomic oxygen experiment materials have changed colors and most appear to be severely degraded. The silvered TEFLON® coating of the radiator panel appears diffuse with a light brown discoloration over most of the surface. The white, evenly spaced, discolorations along the horizontal centerline and along the edges of the panel appear to be above counter sunk flat head screws used to assemble the experiment. The black spots on the radiator panel appear to be impact craters that penetrated the TEFLON® material and exposed the silver beneath to the atomic oxygen flux. Particles of the degraded thermal blanket material that appeared to adhere to the surface of the radiator panel in the flight photograph are gone.
NASA Astrophysics Data System (ADS)
Su Na, Young; David Kihm, Kenneth; Sik Lee, Joon
2012-08-01
The dynamic thermal conductivities of nanofluids (Al2O3) in heating or cooling under fully developed laminar flow conditions show opposite dependence on Reynolds numbers, i.e., the dynamic conductivities under the heating conditions increase with increasing ReD but under the cooling conditions, the dynamic conductivities decrease with increasing ReD. Furthermore, the dynamic conductivities for cooling are higher than those for heating, and the thermal conductivities of stationary nanofluids with uniform distributions fall between these two values, for the entire tested ReD range from 300 to 800. We believe that the main reason for this distinction is because of the drastically different cross-sectional nanoparticle concentration distributions that are in turn attributed to the opposite thermophoretic behavior near the tube wall between heating and cooling. The near-wall nanoparticle concentrations for cooling are substantially higher than those for heating; however, the stationary nanofluid with no thermophoresis maintains its uniform concentration in the middle between the two concentrations.
Reza, Ahmed Wasif
2014-01-01
Non-Fourier heat conduction model with dual phase lag wave-diffusion model was analyzed by using well-conditioned asymptotic wave evaluation (WCAWE) and finite element method (FEM). The non-Fourier heat conduction has been investigated where the maximum likelihood (ML) and Tikhonov regularization technique were used successfully to predict the accurate and stable temperature responses without the loss of initial nonlinear/high frequency response. To reduce the increased computational time by Tikhonov WCAWE using ML (TWCAWE-ML), another well-conditioned scheme, called mass effect (ME) T-WCAWE, is introduced. TWCAWE with ME (TWCAWE-ME) showed more stable and accurate temperature spectrum in comparison to asymptotic wave evaluation (AWE) and also partial Pade AWE without sacrificing the computational time. However, the TWCAWE-ML remains as the most stable and hence accurate model to analyze the fast transient thermal analysis of non-Fourier heat conduction model. PMID:25019096
3D printing of a multifunctional nanocomposite helical liquid sensor
NASA Astrophysics Data System (ADS)
Guo, Shuang-Zhuang; Yang, Xuelu; Heuzey, Marie-Claude; Therriault, Daniel
2015-04-01
A multifunctional 3D liquid sensor made of a PLA/MWCNT nanocomposite and shaped as a freeform helical structure was fabricated by solvent-cast 3D printing. The 3D liquid sensor featured a relatively high electrical conductivity, the functionality of liquid trapping due to its helical configuration, and an excellent sensitivity and selectivity even for a short immersion into solvents.A multifunctional 3D liquid sensor made of a PLA/MWCNT nanocomposite and shaped as a freeform helical structure was fabricated by solvent-cast 3D printing. The 3D liquid sensor featured a relatively high electrical conductivity, the functionality of liquid trapping due to its helical configuration, and an excellent sensitivity and selectivity even for a short immersion into solvents. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr00278h
Conductive heat flux in VC-1 and the thermal regime of Valles caldera, Jemez Mountains, New Mexico
Sass, J.H.; Morgan, P.
1988-06-10
Over 5% of heat in the western United States is lost through Quaternary silicic volcanic centers, including the Valles caldera in north central New Mexico. These centers are the sites of major hydrothermal activity and upper crystal metamorphism, metasomatism, and mineralization, producing associated geothermal resources. We present new heat flow data from Valles caldera core hole 1 (VC-1), drilled in the southwestern margin of the Valles caldera. Thermal conductivities were measured on 55 segments of core from VC-1, waxed and wrapped to preserve fluids. These values were combined with temperature gradient data to calculate heat flow. Above 335 m, which is probably unsaturated, heat flow is 247 +- 16 mW m/sup -2/. The only deep temperature information available is from an uncalibrated commercial log made 19 months after drilling. Gradients, derived from uncalibrated temperature logs, and conductivities are inversely correlated between 335 and 737 m, indicating a conductive thermal regime, and component heat fluxes over three depth intervals (335--539 m, 549--628 m, and 628--737 m) are in excellent agreement with each other with an average of 504 +- 15 mW m/sup -2/. Temperature logs to 518 m depth with well-calibrated temperature sensors result in a revised heat flow of 463 +- 15 mW m. We use shallow thermal gradient data from 75 other sites in and around the caldera to interpret the thermal regime at the VC-1 site. A critical review of published thermal conductivity data from the Valles caldera yields an average thermal conductivity of greater than or equal to1 W m/sup -1/ K/sup -1/ for the near-surface tuffaceous material, and we assume that shallow gradient values (/sup 0/C km/sup -1/) are approximately numerically equal to heat flow (mW m/sup -2/).
Ahmet Sar?; Ali Karaipekli
2007-01-01
This study aimed determination of proper amount of paraffin (n-docosane) absorbed into expanded graphite (EG) to obtain form-stable composite as phase change material (PCM), examination of the influence of EG addition on the thermal conductivity using transient hot-wire method and investigation of latent heat thermal energy storage (LHTES) characteristics of paraffin such as melting time, melting temperature and latent heat
Spherical 3D isotropic wavelets
NASA Astrophysics Data System (ADS)
Lanusse, F.; Rassat, A.; Starck, J.-L.
2012-04-01
Context. Future cosmological surveys will provide 3D large scale structure maps with large sky coverage, for which a 3D spherical Fourier-Bessel (SFB) analysis in spherical coordinates is natural. Wavelets are particularly well-suited to the analysis and denoising of cosmological data, but a spherical 3D isotropic wavelet transform does not currently exist to analyse spherical 3D data. Aims: The aim of this paper is to present a new formalism for a spherical 3D isotropic wavelet, i.e. one based on the SFB decomposition of a 3D field and accompany the formalism with a public code to perform wavelet transforms. Methods: We describe a new 3D isotropic spherical wavelet decomposition based on the undecimated wavelet transform (UWT) described in Starck et al. (2006). We also present a new fast discrete spherical Fourier-Bessel transform (DSFBT) based on both a discrete Bessel transform and the HEALPIX angular pixelisation scheme. We test the 3D wavelet transform and as a toy-application, apply a denoising algorithm in wavelet space to the Virgo large box cosmological simulations and find we can successfully remove noise without much loss to the large scale structure. Results: We have described a new spherical 3D isotropic wavelet transform, ideally suited to analyse and denoise future 3D spherical cosmological surveys, which uses a novel DSFBT. We illustrate its potential use for denoising using a toy model. All the algorithms presented in this paper are available for download as a public code called MRS3D at http://jstarck.free.fr/mrs3d.html
Luca Chittaro; Roberto Ranon
2007-01-01
In recent years, technological developments have made it possible to build interactive 3D models of objects and 3D Virtual Environments that can be experienced through the Web, using common, low-cost personal computers. As in the case of Web-based hypermedia, adaptivity can play an important role in increasing the usefulness, effectiveness and usability of 3D Web sites, i.e., Web sites distributing
E3D, The Euro3D Visualization Tool
NASA Astrophysics Data System (ADS)
Sánchez, S. F.
2004-07-01
We present the first version of E3D, the Euro3D visualization tool for data from integral field spectroscopy. We describe its major characteristics, based on the proposed requirements, the current state of the project, and some planned future upgrades. We show examples of its use and capabilities.
E3D, The Euro3D Visualization Tool
S. F. Sánchez
2004-01-01
We present the first version of E3D, the Euro3D visualization tool for data from integral field spectroscopy. We describe its major characteristics, based on the proposed requirements, the current state of the project, and some planned future upgrades. We show examples of its use and capabilities.
3D Ear Print Authentication using 3D Radon Transform
W. A. Mahmoud; M. R. Shaker
2006-01-01
This paper introduces a proposed method authentication based upon 3D Radon transform. It considers the three dimensional ear of human as a personal identification number. Next, it produces the required features using the 3D Radon transform. This transform is adapted from its 2D form to adequate this application. The neural network was used in the identification phase, the evaluation test
3D printing of a multifunctional nanocomposite helical liquid sensor.
Guo, Shuang-zhuang; Yang, Xuelu; Heuzey, Marie-Claude; Therriault, Daniel
2015-04-21
A multifunctional 3D liquid sensor made of a PLA/MWCNT nanocomposite and shaped as a freeform helical structure was fabricated by solvent-cast 3D printing. The 3D liquid sensor featured a relatively high electrical conductivity, the functionality of liquid trapping due to its helical configuration, and an excellent sensitivity and selectivity even for a short immersion into solvents. PMID:25793923
T. Hadgu; S. Webb; M. Itamura
2004-02-12
Yucca Mountain, Nevada has been designated as the nation's high-level radioactive waste repository and the U.S. Department of Energy has been approved to apply to the U.S. Nuclear Regulatory Commission for a license to construct a repository. Heat transfer in the Yucca Mountain Project (YMP) drift enclosures is an important aspect of repository waste emplacement. Canisters containing radioactive waste are to be emplaced in tunnels drilled 500 m below the ground surface. After repository closure, decaying heat is transferred from waste packages to the host rock by a combination of thermal radiation, natural convection and conduction heat transfer mechanism?. Current YMP mountain-scale and drift-scale numerical models often use a simplified porous medium code to model fluid and heat flow in the drift openings. To account for natural convection heat transfer, the thermal conductivity of the air was increased in the porous medium model. The equivalent thermal conductivity, defined as the ratio of total heat flow to conductive heat flow, used in the porous media models was based on horizontal concentric cylinders. Such modeling does not effectively capture turbulent natural convection in the open spaces as discussed by Webb et al. (2003) yet the approach is still widely used on the YMP project. In order to mechanistically model natural convection conditions in YMP drifts, the computational fluid dynamics (CFD) code FLUENT (Fluent, Incorporated, 2001) has been used to model natural convection heat transfer in the YMP emplacement drifts. A two-dimensional (2D) model representative of YMP geometry (e.g., includes waste package, drip shield, invert and drift wall) has been developed and numerical simulations made (Francis et al., 2003). Using CFD simulation results for both natural convection and conduction-only heat transfer in a single phase, single component fluid, equivalent thermal conductivities have been calculated for different Rayleigh numbers. Correlation equations for equivalent thermal conductivity as a function of Rayleigh number were developed for the Yucca Mountain geometry and comparisons were made to experimental data and correlations found in the literature on natural convection in horizontal concentric cylinders, a geometry similar to YMP. The objective of this work is to compare the results of CFD natural convection simulations and conduction-only calculations that used the equivalent thermal conductivity to represent heat transfer by turbulent natural convection. The FLUENT code was used for both simulations with heat generation boundary condition at the waste package and constant temperature boundary condition 5 meters into the host rock formation. Comparisons are made of temperature contours in the drift air and temperature profiles at surfaces of the different engineered components using the two approaches. The results show that for the two-dimensional YMP geometry considered, the average surface temperatures of the CFD natural convection and conduction-only using the equivalent thermal conductivity are similar and the maximum local temperature differences for the different surfaces were within two 2 C. The differences in temperature profiles reflect the use of a constant equivalent thermal conductivity. The effect of the differences is discussed.
Second Order Corrector in the Homogenization of a Conductive-Radiative Heat Transfer Problem
Paris-Sud XI, UniversitÃ© de
. For simplicity, we consider a cross section (orthogonal to the cylindrical channels) of such a periodic domain (we refer to our other paper [4] for a discussion of the fully 3D case). In a cross section the gas is the case in our application to nuclear reactor physics), a strong gradient of the temperature takes place
Self-heating of metallic carbon nanotube bundles in the regime of the Luttinger-liquid conductivity
NASA Astrophysics Data System (ADS)
Danilchenko, B. A.; Tripachko, N. A.; Voytsihovska, E. A.; Obukhov, I. A.; Yaskovets, I. I.; Sundqvist, B.
2011-08-01
The conductivity of bundles of carbon single-walled nanotubes with metallic conductivity (metallic nanotubes) is investigated over the wide temperature range 4.2-330 K and electrical fields up to 50 V. The usage of short electrical pulses of the duration of 10 ns allowed to avoid an influence of a self-heating of the investigated structures on current-voltage characteristics. It is shown that the temperature dependence of conductivity is described by the power function G?T?. At helium temperatures the asymptotic dependence of current on applied voltage is close to J?V1+? with ? = 0.45. From comparison of the obtained results of measurements with calculations, it is shown that the conductivity of nanotube bundles is well described within the theory of the Luttinger-liquid conductivity for one-dimensional conductors. The self-heating of the carbon nanotube bundles was observed in the case of measurements in the regime of dc current. A method for determination of the self-heating temperature of nanotube bundles as a function of an applied electrical field is proposed. The power dependence of the self-heating temperature on voltage T?Vp with the exponent p = 2.1 was observed above some threshold voltage in the temperature range 4.2-200 K. Above 200 K the exponent decreased down to p = 1.35.
A boundary-dispatch Monte Carlo (Exodus) method for analysis of conductive heat transfer problems
Naraghi, M.H.N. [Manhattan Coll., Riverdale, NY (United States); Shunchang Tsai [Harvard Univ., Cambridge, MA (United States)
1993-12-01
A boundary-dispatch Monte Carlo (Exodus) method, in which the particles are dispatched from the boundaries of a conductive medium or source of heat, is developed. A fixed number of particles are dispatched from a boundary node to the nearest internal node. These particles make random walks within the medium similar to that of the conventional Monte Carlo method. Once a particle visits an internal node, a number equal to the temperature of the boundary node from which particles are dispatched is added to a counter. Performing this procedure for all boundary nodes, the temperature of a node can be determined by dividing the flag, or the counter of this node by the total number of particle visits to this node. Two versions of the boundary-dispatch method (BDM) are presented, multispecies and bispecies BDM. The results of bispecies BDM based on the Exodus dispatching method compare well with the Gauss-Seidel method in both accuracy and computational time. Its computational time is much less than the shrinking-boundary Exodus method.
Steady-State and Transient Boundary Element Methods for Coupled Heat Conduction
NASA Technical Reports Server (NTRS)
Kontinos, Dean A.
1997-01-01
Boundary element algorithms for the solution of steady-state and transient heat conduction are presented. The algorithms are designed for efficient coupling with computational fluid dynamic discretizations and feature piecewise linear elements with offset nodal points. The steady-state algorithm employs the fundamental solution approach; the integration kernels are computed analytically based on linear shape functions, linear elements, and variably offset nodal points. The analytic expressions for both singular and nonsingular integrands are presented. The transient algorithm employs the transient fundamental solution; the temporal integration is performed analytically and the nonsingular spatial integration is performed numerically using Gaussian quadrature. A series solution to the integration is derived for the instance of a singular integrand. The boundary-only character of the algorithm is maintained by integrating the influence coefficients from initial time. Numerical results are compared to analytical solutions to verify the current boundary element algorithms. The steady-state and transient algorithms are numerically shown to be second-order accurate in space and time, respectively.
Aamir, Muhammad; Liao, Qiang; Zhu, Xun; Aqeel-ur-Rehman; Wang, Hong
2014-01-01
An experimental study was carried out to investigate the effects of inlet pressure, sample thickness, initial sample temperature, and temperature sensor location on the surface heat flux, surface temperature, and surface ultrafast cooling rate using stainless steel samples of diameter 27?mm and thickness (mm) 8.5, 13, 17.5, and 22, respectively. Inlet pressure was varied from 0.2?MPa to 1.8?MPa, while sample initial temperature varied from 600°C to 900°C. Beck's sequential function specification method was utilized to estimate surface heat flux and surface temperature. Inlet pressure has a positive effect on surface heat flux (SHF) within a critical value of pressure. Thickness of the sample affects the maximum achieved SHF negatively. Surface heat flux as high as 0.4024?MW/m2 was estimated for a thickness of 8.5?mm. Insulation effects of vapor film become apparent in the sample initial temperature range of 900°C causing reduction in surface heat flux and cooling rate of the sample. A sensor location near to quenched surface is found to be a better choice to visualize the effects of spray parameters on surface heat flux and surface temperature. Cooling rate showed a profound increase for an inlet pressure of 0.8?MPa. PMID:24977219
MT3D was first developed by Chunmiao Zheng in 1990 at S.S. Papadopulos & Associates, Inc. with partial support from the U.S. Environmental Protection Agency (USEPA). Starting in 1990, MT3D was released as a pubic domain code from the USEPA. Commercial versions with enhanced capab...
NASA Technical Reports Server (NTRS)
1977-01-01
A market study of a proposed version of a 3-D eyetracker for initial use at NASA's Ames Research Center was made. The commercialization potential of a simplified, less expensive 3-D eyetracker was ascertained. Primary focus on present and potential users of eyetrackers, as well as present and potential manufacturers has provided an effective means of analyzing the prospects for commercialization.
Spherical 3D Isotropic Wavelets
Lanusse, F; Starck, J -L
2011-01-01
Future cosmological surveys will provide 3D large scale structure maps with large sky coverage, for which a 3D Spherical Fourier-Bessel (SFB) analysis in is natural. Wavelets are particularly well-suited to the analysis and denoising of cosmological data, but a spherical 3D isotropic wavelet transform does not currently exist to analyse spherical 3D data. The aim of this paper is to present a new formalism for a spherical 3D isotropic wavelet, i.e. one based on the Fourier-Bessel decomposition of a 3D field and accompany the formalism with a public code to perform wavelet transforms. We describe a new 3D isotropic spherical wavelet decomposition based on the undecimated wavelet transform (UWT) described in Starck et al. 2006. We also present a new fast Discrete Spherical Fourier-Bessel Transform (DSFBT) based on both a discrete Bessel Transform and the HEALPIX angular pixelisation scheme. We test the 3D wavelet transform and as a toy-application, apply a denoising algorithm in wavelet space to the Virgo large...
Virginia Tech
Heat Transfer - 1 You are given the following information for a fluid with thermal conductivity the flow is laminar near the wall. a) (30 points) Determine the corresponding heat transfer coefficient the heat transfer coefficient as a function of x. c) (25 points) Determine the average heat transfer
Improving 3D resist profile compact modeling by exploiting 3D resist physical mechanisms
NASA Astrophysics Data System (ADS)
Fan, Yongfa; Wu, Cheng-En R.; Ren, Qian; Song, Hua; Schmoeller, Thomas
2014-03-01
3D Resist profile aware OPC has becoming increasingly important to address hot spots generated at etch processes due to the mass occurrence of non-ideal resist profile in 28nm technology node and beyond. It is therefore critical to build compact models capable of 3D simulation for OPC applications. A straightforward and simple approach is to build individual 2D models at different image depths either based on actual wafer measurement data or virtual simulation data from rigorous lithography simulators. Individual models at interested heights can be used by downstream OPC/LRC tools to account for 3D resist profile effects. However, the relevant image depths need be predetermined due to the discontinuous nature of the methodology itself. Furthermore, the physical commonality among the individual 2D models may deviate from each other as well during the separate calibration processes. To overcome the drawbacks, efforts are made in this paper to compute the whole bulk image using Hopkins equation in one shot. The bulk image is then used to build 3D resist models. This approach also opens the feasibility of including resist interface effects (for example, top or bottom out-diffusion), which are important to resist profile formation, into a compact 3D resist model. The interface effects calculations are merged into the bulk image Hopkins equation. Simulation experiments are conducted to demonstrate that resist profile heavily rely on interface conditions. Our experimental results show that those interface effects can be accurately simulated with reference to rigorous simulation results. In modeling reality, such a 3D resist model can be calibrated with data from discrete image planes but can be used at arbitrary interpolated planes. One obvious advantage of this 3D resist model approach is that the 3D model is more physically represented by a common set of resist parameters (in contrast to the individual model approach) for 3D resist profile simulation. A full model calibration test is conducted on a virtual lithography process. It is demonstrated that 3D resist profile of the process can be precisely captured by this method. It is shown that the resist model can be carried to a different lithography process with same resist setup but a different illumination source without model any accuracy degradation. In an additional test, the model is used to demonstrate the capability of resist 3D profile correction by ILT.
NASA Astrophysics Data System (ADS)
Walsh, J. R.
2004-02-01
The Euro3D RTN is an EU funded Research Training Network to foster the exploitation of 3D spectroscopy in Europe. 3D spectroscopy is a general term for spectroscopy of an area of the sky and derives its name from its two spatial + one spectral dimensions. There are an increasing number of instruments which use integral field devices to achieve spectroscopy of an area of the sky, either using lens arrays, optical fibres or image slicers, to pack spectra of multiple pixels on the sky (``spaxels'') onto a 2D detector. On account of the large volume of data and the special methods required to reduce and analyse 3D data, there are only a few centres of expertise and these are mostly involved with instrument developments. There is a perceived lack of expertise in 3D spectroscopy spread though the astronomical community and its use in the armoury of the observational astronomer is viewed as being highly specialised. For precisely this reason the Euro3D RTN was proposed to train young researchers in this area and develop user tools to widen the experience with this particular type of data in Europe. The Euro3D RTN is coordinated by Martin M. Roth (Astrophysikalisches Institut Potsdam) and has been running since July 2002. The first Euro3D science conference was held in Cambridge, UK from 22 to 23 May 2003. The main emphasis of the conference was, in keeping with the RTN, to expose the work of the young post-docs who are funded by the RTN. In addition the team members from the eleven European institutes involved in Euro3D also presented instrumental and observational developments. The conference was organized by Andy Bunker and held at the Institute of Astronomy. There were over thirty participants and 26 talks covered the whole range of application of 3D techniques. The science ranged from Galactic planetary nebulae and globular clusters to kinematics of nearby galaxies out to objects at high redshift. Several talks were devoted to reporting recent observations with newly completed 3D instruments - CIRPASS, GMOS, PMAS and SPIFFI. Work on 3D software, being developed as part of the Euro3D RTN, was also described and demonstrated. This proceedings volume, consisting of carefully refereed and edited manuscripts, represents the bulk of the talks at the conference and amply demonstrates that 3D spectroscopy is a lively and burgeoning field of optical observation.
Temperature distribution in powder beds during 3D printing
M. Dressler; M. Röllig; M. Schmidt; A. Maturilli; J. Helbert
2010-01-01
Purpose – This purpose of this paper is to report about the temperature distribution in metal and ceramic powder beds during 3D printing. The differing powders are thoroughly characterized in terms of thermal conductivity, thermal diffusivity, emissivity spectra and density. Design\\/methodology\\/approach – The temperature distribution was measured in a 3D printing appliance (Prometal R1) with the help of thin thermocouples
Array servo scanning micro EDM of 3D micro cavities
NASA Astrophysics Data System (ADS)
Tong, Hao; Li, Yong; Yi, Futing
2011-05-01
Micro electro discharge machining (Micro EDM) is a non-traditional processing technology with the special advantages of low set-up cost and few cutting force in machining any conductive materials regardless of their hardness. As well known, die-sinking EDM is unsuitable for machining the complex 3D micro cavity less than 1mm due to the high-priced fabrication of 3D microelectrode itself and its serous wear during EDM process. In our former study, a servo scanning 3D micro-EDM (3D SSMEDM) method was put forward, and our experiments showed it was available to fabricate complex 3D micro-cavities. In this study, in order to improve machining efficiency and consistency accuracy for array 3D micro-cavities, an array-servo-scanning 3D micro EDM (3D ASSMEDM) method is presented considering the complementary advantages of the 3D SSMEDM and the array micro electrodes with simple cross-section. During 3D ASSMEDM process, the array cavities designed by CAD / CAM system can be batch-manufactured by servo scanning layer by layer using array-rod-like micro tool electrodes, and the axial wear of the array electrodes is compensated in real time by keeping discharge gap. To verify the effectiveness of the 3D ASSMEDM, the array-triangle-micro cavities (side length 630 ?m) are batch-manufactured on P-doped silicon by applying the array-micro-electrodes with square-cross-section fabricated by LIGA process. Our exploratory experiment shows that the 3D ASSMEDM provides a feasible approach for the batch-manufacture of 3D array-micro-cavities of conductive materials.
Array servo scanning micro EDM of 3D micro cavities
NASA Astrophysics Data System (ADS)
Tong, Hao; Li, Yong; Yi, Futing
2010-12-01
Micro electro discharge machining (Micro EDM) is a non-traditional processing technology with the special advantages of low set-up cost and few cutting force in machining any conductive materials regardless of their hardness. As well known, die-sinking EDM is unsuitable for machining the complex 3D micro cavity less than 1mm due to the high-priced fabrication of 3D microelectrode itself and its serous wear during EDM process. In our former study, a servo scanning 3D micro-EDM (3D SSMEDM) method was put forward, and our experiments showed it was available to fabricate complex 3D micro-cavities. In this study, in order to improve machining efficiency and consistency accuracy for array 3D micro-cavities, an array-servo-scanning 3D micro EDM (3D ASSMEDM) method is presented considering the complementary advantages of the 3D SSMEDM and the array micro electrodes with simple cross-section. During 3D ASSMEDM process, the array cavities designed by CAD / CAM system can be batch-manufactured by servo scanning layer by layer using array-rod-like micro tool electrodes, and the axial wear of the array electrodes is compensated in real time by keeping discharge gap. To verify the effectiveness of the 3D ASSMEDM, the array-triangle-micro cavities (side length 630 ?m) are batch-manufactured on P-doped silicon by applying the array-micro-electrodes with square-cross-section fabricated by LIGA process. Our exploratory experiment shows that the 3D ASSMEDM provides a feasible approach for the batch-manufacture of 3D array-micro-cavities of conductive materials.
Pradhan, N R; Duan, H; Liang, J; Iannacchione, G S
2009-06-17
We present a study of the specific heat and effective thermal conductivity in anisotropic and randomly oriented multi-wall carbon nanotube (MWCNT) and randomly oriented single-wall carbon nanotube (SWCNT) composites from 300 to 400 K. Measurements on randomly oriented MWCNTs and SWCNTs were made by depositing a thin film of CNTs within a calorimetric cell. Anisotropic measurements were made on MWCNTs grown inside the highly ordered, densely packed nanochannels of anodic aluminum oxide. The specific heat of randomly oriented MWCNTs and SWCNTs showed similar behavior to the specific heat of bulk graphite powder. However, the specific heat of aligned MWCNTs is smaller and has weaker temperature dependence than that of the bulk above room temperature. The effective thermal conductivity of randomly oriented MWCNTs and SWCNTs is similar to that of powder graphite, exhibiting a maximum value near 364 K indicating the onset of phonon-phonon scattering. The effective thermal conductivity of the anisotropic MWCNTs increased smoothly with increasing temperature and is indicative of the one-dimensional nature of the heat flow. PMID:19471077
Boyer, Edmond
Eurotherm Seminar N°81 Reactive Heat Transfer in Porous Media, Ecole des Mines d'Albi, France June 4-6, 2007 ET81- 1 HEAT TRANSFER BY SIMULTANEOUS RADIATION-CONDUCTION AND CONVECTION IN A HIGH for the packed bed. The comparison between the radiative heat transfer and the exchanges by conduction and forced
M. A. Alim
2008-01-01
In this paper, the effect of viscous dissipation and pressure stress work on free convection flow along a vertical flat plate has been investigated. Heat conduction due to wall thickness b is considered in this investigation. With a goal to attain similarity solutions of the problem posed, the developed equations are made dimensionless by using suitable transformations. The non-dimensional equations
NASA Technical Reports Server (NTRS)
Conel, J. E.
1975-01-01
A computer program (Program SPHERE) solving the inhomogeneous equation of heat conduction with radiation boundary condition on a thermally homogeneous sphere is described. The source terms are taken to be exponential functions of the time. Thermal properties are independent of temperature. The solutions are appropriate to studying certain classes of planetary thermal history. Special application to the moon is discussed.
S. Rainieri; F. Bozzoli; G. Pagliarini
2008-01-01
An experimental analysis and a data processing procedure, aimed to the characterization of an uncooled microbolometric infrared camera, have been carried out. The instrument performance test is addressed to the application of infrared thermography to the parameter estimation problem based on the solution of the inverse heat conduction problem. With this regard, a new figure of merit, which enables to
AGN heating, thermal conduction and Sunyaev-Zeldovich effect in galaxy groups and clusters
S. Roychowdhury; M. Ruszkowski; B. B. Nath
2005-08-04
(abridged) We investigate in detail the role of active galactic nuclei on the physical state of the gas in galaxy groups and clusters, and the implications for anisotropy in the CMB from Sunyaev-Zeldovich effect. We include the effect of thermal conduction, and find that the resulting profiles of temperature and entropy are consistent with observations. Unlike previously proposed models, our model predicts that isentropic cores are not an inevitable consequence of preheating. The model also reproduces the observational trend for the density profiles to flatten in lower mass systems. We deduce the energy E_agn required to explain the entropy observations as a function of mass of groups and clusters M_cl and show that E_agn is proportional to M_cl^alpha with alpha~1.5. We demonstrate that the entropy measurements, in conjunction with our model, can be translated into constraints on the cluster--black hole mass relation. The inferred relation is nonlinear and has the form M_bh\\propto M_cl^alpha. This scaling is an analog and extension of a similar relation between the black hole mass and the galactic halo mass that holds on smaller scales. We show that the central decrement of the CMB temperature is reduced due to the enhanced entropy of the ICM, and that the decrement predicted from the plausible range of energy input from the AGN is consistent with available data of SZ decrement. We show that AGN heating, combined with the observational constraints on entropy, leads to suppression of higher multipole moments in the angular power spectrum and we find that this effect is stronger than previously thought.
NASA Astrophysics Data System (ADS)
Zheng, D.; Tanaka, S.; Miyazaki, K.; Takashiri, M.
2015-06-01
To investigate the effect of strain on specific heat, sound velocity and lattice thermal conductivity of nanocrystalline bismuth antimony telluride thin films, we performed both experimental study and modeling. The nanocrystalline thin films had mostly preferred crystal orientation along c-axis, and strains in the both directions of c-axis and a- b-axis. It was found that the thermal conductivity of nanocrystalline thin films decreased greatly as compared with that of bulk alloys. To gain insight into the thermal transport in the strained nanocrystalline thin films, we estimated the lattice thermal conductivity based on the phonon transport model of full distribution of mean free paths accounting for the effects of grain size and strain which was influenced to both the sound velocity and the specific heat. As a result, the lattice thermal conductivity was increased when the strain was shifted from compressive to tensile direction. We also confirmed that the strain was influenced by the lattice thermal conductivity but the reduction of the lattice thermal conductivity of thin films can be mainly attributed to the nano-size effect rather than the strain effect. Finally, it was found that the measured lattice thermal conductivities were in good agreement with modeling.
Sayer, Robert A; Piekos, Edward S; Phinney, Leslie M
2012-12-01
Accurate knowledge of thermophysical properties is needed to predict and optimize the thermal performance of microsystems. Thermal conductivity is experimentally determined by measuring quantities such as voltage or temperature and then inferring a thermal conductivity from a thermal model. Thermal models used for data analysis contain inherent assumptions, and the resultant thermal conductivity value is sensitive to how well the actual experimental conditions match the model assumptions. In this paper, a modified data analysis procedure for the steady state Joule heating technique is presented that accounts for bond pad effects including thermal resistance, electrical resistance, and Joule heating. This new data analysis method is used to determine the thermal conductivity of polycrystalline silicon (polysilicon) microbridges fabricated using the Sandia National Laboratories SUMMiT V™ micromachining process over the temperature range of 77-350 K, with the value at 300 K being 71.7 ± 1.5 W/(m K). It is shown that making measurements on beams of multiple lengths is useful, if not essential, for inferring the correct thermal conductivity from steady state Joule heating measurements. PMID:23278015
NASA Technical Reports Server (NTRS)
Gedeon, L.
1979-01-01
A variable-conductance heat-pipe system (VCHPS) with methanol as the working fluid and a nitrogen and helium mixture as the control gas was used for the thermal control of a 200 W RF traveling wave tube of the Communication Technology Satellite. Three stainless steel heat pipes (one redundant) and an aluminum radiator were designed to transfer 196 watts for an evaporator temperature of 50 C. The system has operated for three years with no noticeable change in performance. On four occasions the heat pipes apparently deprimed. A short time after reducing the tube power, the heat pipes reprimed and the system continued to operate normally. The description, qualification testing, and orbit data of the VCHPS are presented.
Carolan, Michael Francis (Allentown, PA); Bernhart, John Charles (Fleetwood, PA)
2012-08-21
Method for processing an article comprising mixed conducting metal oxide material. The method comprises contacting the article with an oxygen-containing gas and either reducing the temperature of the oxygen-containing gas during a cooling period or increasing the temperature of the oxygen-containing gas during a heating period; during the cooling period, reducing the oxygen activity in the oxygen-containing gas during at least a portion of the cooling period and increasing the rate at which the temperature of the oxygen-containing gas is reduced during at least a portion of the cooling period; and during the heating period, increasing the oxygen activity in the oxygen-containing gas during at least a portion of the heating period and decreasing the rate at which the temperature of the oxygen-containing gas is increased during at least a portion of the heating period.
Unassisted 3D camera calibration
NASA Astrophysics Data System (ADS)
Atanassov, Kalin; Ramachandra, Vikas; Nash, James; Goma, Sergio R.
2012-03-01
With the rapid growth of 3D technology, 3D image capture has become a critical part of the 3D feature set on mobile phones. 3D image quality is affected by the scene geometry as well as on-the-device processing. An automatic 3D system usually assumes known camera poses accomplished by factory calibration using a special chart. In real life settings, pose parameters estimated by factory calibration can be negatively impacted by movements of the lens barrel due to shaking, focusing, or camera drop. If any of these factors displaces the optical axes of either or both cameras, vertical disparity might exceed the maximum tolerable margin and the 3D user may experience eye strain or headaches. To make 3D capture more practical, one needs to consider unassisted (on arbitrary scenes) calibration. In this paper, we propose an algorithm that relies on detection and matching of keypoints between left and right images. Frames containing erroneous matches, along with frames with insufficiently rich keypoint constellations, are detected and discarded. Roll, pitch yaw , and scale differences between left and right frames are then estimated. The algorithm performance is evaluated in terms of the remaining vertical disparity as compared to the maximum tolerable vertical disparity.
Stanton, M M; Samitier, J; Sánchez, S
2015-07-14
Three-dimensional (3D) bioprinting has recently emerged as an extension of 3D material printing, by using biocompatible or cellular components to build structures in an additive, layer-by-layer methodology for encapsulation and culture of cells. These 3D systems allow for cell culture in a suspension for formation of highly organized tissue or controlled spatial orientation of cell environments. The in vitro 3D cellular environments simulate the complexity of an in vivo environment and natural extracellular matrices (ECM). This paper will focus on bioprinting utilizing hydrogels as 3D scaffolds. Hydrogels are advantageous for cell culture as they are highly permeable to cell culture media, nutrients, and waste products generated during metabolic cell processes. They have the ability to be fabricated in customized shapes with various material properties with dimensions at the micron scale. 3D hydrogels are a reliable method for biocompatible 3D printing and have applications in tissue engineering, drug screening, and organ on a chip models. PMID:26066320
3D or not 3D - that is the question!
Gregory P. Garvey
2006-01-01
Should an introduction to 3D computer graphics and animation be a part of a general core curriculum requirement for all design majors regardless their concentration, track or degree?At ACM-SIGGRAPH it is taken for granted that a working knowledge of 3D computer graphics is a valuable if not necessary part of a versatile skill set to prepare design graduates for future
MONA 3D -- MOBILE NAVIGATION USING 3D CITY MODELS
Volker Coors; Alexander Zipf
Within this paper we present and discuss the goals and first results of a new collaborative pro- ject on mobile navigation using 3d city models call ed MoNa3D. In addition to the author's institutions (HFT Stuttgart and FH Mainz\\/University of Bonn) project partners include Navigon, Teleatlas, CPA Geoinformatik, Heidelberg Mobil and Bureau of Surveying Stuttgart. Here we investigate two main
3D Multifunctional Ablative Thermal Protection System
NASA Technical Reports Server (NTRS)
Feldman, Jay; Venkatapathy, Ethiraj; Wilkinson, Curt; Mercer, Ken
2015-01-01
NASA is developing the Orion spacecraft to carry astronauts farther into the solar system than ever before, with human exploration of Mars as its ultimate goal. One of the technologies required to enable this advanced, Apollo-shaped capsule is a 3-dimensional quartz fiber composite for the vehicle's compression pad. During its mission, the compression pad serves first as a structural component and later as an ablative heat shield, partially consumed on Earth re-entry. This presentation will summarize the development of a new 3D quartz cyanate ester composite material, 3-Dimensional Multifunctional Ablative Thermal Protection System (3D-MAT), designed to meet the mission requirements for the Orion compression pad. Manufacturing development, aerothermal (arc-jet) testing, structural performance, and the overall status of material development for the 2018 EM-1 flight test will be discussed.
GRAPHICS PROGRAMMING SECTION D -JAVA 3D
Hill, Gary
GRAPHICS PROGRAMMING SECTION D - JAVA 3D 1SECTION D - GRAPHICS 3-D........................................................................................... 2 30 Graphics 3D: Introduction to Java 3D........................................................................................ 78 ©Gary Hill September 2004 Java 3-D 1 of 13 #12;GRAPHICS PROGRAMMING SECTION D - GRAPHICS 3-D 30
Visuohaptic discrimination of 3D gross shape.
Kim, Kwangtaek; Barni, Mauro; Prattichizzo, Domenico; Tan, Hong Z
2012-01-01
Human sensitivity to 3D gross shape changes was measured for the visual and haptic sensory channels. Three volume-invariant affine transformations were defined: compressing, shearing and stretching. Participants discriminated a reference 3D object (cube or sphere) from its deformed shape under three experimental conditions: visual only (on a computer monitor), haptic only (through a point-contact force-feedback device) and visuohaptic simulations. The results indicate that vision is more sensitive to gross shape changes than point-based touch, and that vision dominated in the visuohaptic condition. In the haptic alone condition, thresholds were higher for shearing and stretching than for compressing. Thresholds were otherwise similar for the three transformations in the vision only or visuohaptic conditions. These trends were similar for the two shapes tested. A second experiment, conducted under similar conditions but preventing participants from manipulating object orientations, verified that the main conclusion of our research still holds when visual inspection can rely only on a single perspective view of the object. Our earlier studies on 3D visuohaptic watermarking showed that the haptic channel is more sensitive to surface texture and roughness changes than vision. The thresholds from the present and our earlier studies can potentially be used as the upper limits for selecting watermark strengths in order to ensure watermark imperceptibility in a 3D visuohaptic watermarking system. PMID:22472054
3-D microwave simulation in fusion plasmas
NASA Astrophysics Data System (ADS)
Williams, Thomas; Vann, Roddy; O'Brien, Martin; Koehn, Alf
2013-10-01
The propagation of EM radiation past wavelength-sized 3D inhomogeneities is not well understood, yet is of importance for both microwave heating and diagnostic applications in tokamaks. To improve this understanding, a new cold-plasma code has been written to extend full-wave simulations of propagation and mode conversion in magnetized plasmas to 3D. Studies of propagation past density filaments (``blobs'') are presented and compared with 2D simulations. This work supports MAST experiments using the SAMI diagnostic to image microwave emission from the plasma edge due to mode conversion from electron Bernstein waves. Significant fluctuations in the SAMI data mean that detailed modelling is required to improve its interpretation, since analytic and experimental work suggests that electron density fluctuations and magnetic shear can affect the mode conversion efficiency. The propagation of EM radiation past wavelength-sized 3D inhomogeneities is not well understood, yet is of importance for both microwave heating and diagnostic applications in tokamaks. To improve this understanding, a new cold-plasma code has been written to extend full-wave simulations of propagation and mode conversion in magnetized plasmas to 3D. Studies of propagation past density filaments (``blobs'') are presented and compared with 2D simulations. This work supports MAST experiments using the SAMI diagnostic to image microwave emission from the plasma edge due to mode conversion from electron Bernstein waves. Significant fluctuations in the SAMI data mean that detailed modelling is required to improve its interpretation, since analytic and experimental work suggests that electron density fluctuations and magnetic shear can affect the mode conversion efficiency. This work was funded in part by the University of York, the UK EPSRC under grant EP/G003955, and the European Communities under the contract of Association between EURATOM and CCFE.
Highly compressible 3D periodic graphene aerogel microlattices
NASA Astrophysics Data System (ADS)
Zhu, Cheng; Han, T. Yong-Jin; Duoss, Eric B.; Golobic, Alexandra M.; Kuntz, Joshua D.; Spadaccini, Christopher M.; Worsley, Marcus A.
2015-04-01
Graphene is a two-dimensional material that offers a unique combination of low density, exceptional mechanical properties, large surface area and excellent electrical conductivity. Recent progress has produced bulk 3D assemblies of graphene, such as graphene aerogels, but they possess purely stochastic porous networks, which limit their performance compared with the potential of an engineered architecture. Here we report the fabrication of periodic graphene aerogel microlattices, possessing an engineered architecture via a 3D printing technique known as direct ink writing. The 3D printed graphene aerogels are lightweight, highly conductive and exhibit supercompressibility (up to 90% compressive strain). Moreover, the Young's moduli of the 3D printed graphene aerogels show an order of magnitude improvement over bulk graphene materials with comparable geometric density and possess large surface areas. Adapting the 3D printing technique to graphene aerogels realizes the possibility of fabricating a myriad of complex aerogel architectures for a broad range of applications.