Showing papers on "Thermal published in 1996"
TL;DR: In this paper, the authors used a three-dimensional spherical convection model to show that a modest increase in mantle viscosity with depth has a marked effect on the planform of convection, resulting in long, linear downwellings from the upper surface boundary layer and a surprisingly'red' thermal heterogeneity spectrum, as observed for the Earth's mantle.
Abstract: LITHOSPHERIC plate motions at the Earth's surface result from thermal convection in the mantle1. Understanding mantle convection is made difficult by variations in the material properties of rocks as pressure and temperature increase from the surface to the core. The plates themselves result from high rock strength and brittle failure at low temperature near the surface. In the deeper mantle, elevated pressure may increase the effective viscosity by orders of magnitude2–5. The influence of depth-dependent viscosity on convection has been explored in two-dimensional numerical experiments6–8, but planforms must be studied in three dimensions. Although three-dimensional plan-forms can be elucidated by laboratory fluid dynamic experiments9,10, such experiments cannot simulate depth-dependent rheology. Here we use a three-dimensional spherical convection model11,12 to show that a modest increase in mantle viscosity with depth has a marked effect on the planform of convection, resulting in long, linear downwellings from the upper surface boundary layer and a surprisingly 'red' thermal heterogeneity spectrum, as observed for the Earth's mantle13. These effects of depth-dependent viscosity may be comparable to the effects of the plates themselves.
303 citations
TL;DR: In this article, a comprehensive general circulation model of the Martian atmosphere is used to simulate the thermotidal oscillations in simulations performed with a newly developed comprehensive GCS model, which produces both realistic zonal-mean temperature distributions and a diurnal surface pressure oscillation of at least roughly realistic amplitude.
Abstract: This paper discusses the thermotidal oscillations in simulations performed with a newly developed comprehensive general circulation model of the Martian atmosphere. With reasonable assumptions about the effective thermal inertia of the planetary surface and about the distribution of radiatively active atmospheric aerosol, the model produces both realistic zonal-mean temperature distributions and a diurnal surface pressure oscillation of at least roughly realistic amplitude. With any reasonable aerosol distribution, the simulated diurnal pressure oscillation has a very strong zonal variation, in particular a very pronounced zonal wavenumber-2 modulation. This results from a combination of the prominent wave-2 component in the important boundary forcings (topography and surface thermal inertia) and from the fact that the eastward-propagating zonal wave-1 Kelvin normal mode has a period near 1 sol (a Martian mean solar day of 88 775 s). The importance of global resonance is explicitly demonstrated w...
303 citations
TL;DR: In this article, a simple one-dimensional model for a three-way catalytic converter is briefly described and solved, and the discrepancies are essentially attributed to the accuracy limit of the time-resolved input data, to the extreme sensitivity of the reactions about light-off temperature, to a possible internal diffusion limitation at high temperature, and to some transient state catalytic process which was neglected in the model.
119 citations
TL;DR: The experiment reveals that the main effect of the surface roughness is to increase the emission of large thermal plumes, which travel vertically through the central region, which enhance the heat transport and also responsible for the anisotropic behavior of velocity fluctuations at the cell center.
Abstract: A light scattering experiment of turbulent convection in water is carried out in a convection cell with rough upper and lower surfaces. The vertical heat flux is found to be increased by $\ensuremath{\sim}20%$ when the Rayleigh number becomes larger than a transition value. The experiment reveals that the main effect of the surface roughness is to increase the emission of large thermal plumes, which travel vertically through the central region. These extra thermal plumes enhance the heat transport, and they are also responsible for the anisotropic behavior of velocity fluctuations at the cell center.
110 citations
TL;DR: In this article, the critical factors for the control of thermal damage in grinding at conventional workspeeds have been established with reference to experimental and previously published work, and a simplified approach has been developed for controlling thermal damage.
97 citations
TL;DR: In this paper, a Coulomb liquid-like structure was found in a bulk of a thermal plasma under atmospheric pressure and a temperature of 1700 K. The particles are charged positively and have about 10 3 electron charges.
88 citations
TL;DR: In this article, a novel storage unit of multiple phase change materials (PCMs) is developed, which consists of a tube which is surrounded by an external coaxial cylinder made up of several segments of different PCMs with different melting points.
79 citations
TL;DR: In this paper, a theoretical comparison between the thermal behavior of a basin type solar still and that from a solar evaporator is presented, and it is shown that the evaporation in solar stills is much less than that in open evapolation despite the higher water temperatures in the former system.
65 citations
TL;DR: In this paper, the authors analyzed the high-speed switching behavior of a wide range of commercial and experimental magnetic tapes and concluded that the results are in reasonable agreement with the Landau-Lifshitz damping-limited switching model but only if values of the damping constant α ≈ 1 are assumed, in conflict with the experimentally reported values in some samples.
64 citations
TL;DR: In this article, a triple dilatometer was developed to measure the thermal expansion of two kinds of marble that are typically used in stonemasonry, namely white crystalline marble from Carrara and Laas (both Italy).
Abstract: The investigations on hand were performed due to the increasing number of deformations on marble cladding panels on building facades caused by atmospheric influences. A special triple dilatometer was developed to measure the thermal expansion of two kinds of marble that are typically used in stonemasonry, namely white crystalline marble from Carrara and Laas (both Italy). The strong anisotropy of their thermal expansion was investigated systematically, with special consideration of residual dilatations (thermal hysteresis). In analyzing the results, it becomes evident that there is a causal relation between this anisotropy and the observed permanent deformations of marble cladding panels. Measurements of the water absorption capacity of marble after different thermal pretreatments indicate a loosening of the grain boundaries in marble caused by temperature changes. The paper concludes that the strong thermal anisotropy of marble is an important factor for the lack of durability of this building material and therefore should no longer be neglected when producing marble panels.
64 citations
TL;DR: In this paper, the authors investigated the impact of different ground surface boundary conditions on the efficiency of a single and a multiple parallel earth-to-air heat exchanger system, and concluded that soil surface cover might be a significant controllable factor for the improvement of the performance of earth-To-Air heat exchangers.
TL;DR: In this article, an artificial perturbation is applied to the system to determine the stability character of the boundary layers in fully developed flow, and it is shown that the thermal boundary layers have approximately the same stability character as the start-up flow.
TL;DR: In this article, the authors employed computational fluid dynamics (CFD) in the design and optimization of a novel high-temperature solar chemical reactor, where the reaction considered is the thermal reduction of metal oxides, as part of a two-step water splitting cycle for hydrogen production.
TL;DR: The precipitation and dissolution of zirconium hydrides in Zr-25Nb pressure tube material have been tracked directly by neutron diffraction as a function of temperature as discussed by the authors.
TL;DR: In this article, the authors investigated the heating potential of a single earth-to-air heat exchanger as well as of a multiple parallel earth tubes system using real climatic data.
TL;DR: In this paper, a three dimensional numerical model for land-based ice sheets in the shallow ice approximation simulations is performed to determine the velocity and temperature distributions within the Greenland Ice Sheet through time for various climate scenarios.
Abstract: Using a three dimensional numerical model for land based ice sheets in the shallow ice approximation simulations are performed to determine the velocity and temperature distributions within the Greenland Ice Sheet through time for various climate scenarios. The ice is treated as a rheologically nonlinear heat conducting viscous fluid and the substrate is a heat conducting rigid solid. This system is fed from above by prescribing as the climatic inputs the atmospheric temperature and the accumulation-ablation-rate functions at the free surface and from below by the geothermal heat. We present the governing equations in the shallow-ice approximation, discuss the parameterizations used in the descriptions of the ice-surface temperature and accumulation-ablation functions, briefly state how the complicated initial boundary value problem is numerically solved, and how the input data that are available from measurements are implemented. Results of preliminary calculations disclose how the model performs and delimit its validity. We study the role played by basal sliding and make clear that sliding should be accounted for where ever the basal ice is temperate and that the frictional heat generated in this sliding is thermomechanically significant. We also study the reaction of the Greenland Ice Sheet to various climate scenarios and make clear that today's thermal regime depends significantly upon the prior climate history. Moreover, the thermomechanical properties of the ice are equally significant as is the thermal interaction of the Ice Sheet with the rockbed beneath.
TL;DR: In this paper, the secondary phases are selenium and copper selenide compounds which have been determined by composition measurements, and thermal and chemical treatments have been performed to eliminate the semimetallic phases and to improve the semiconductor behavior of the electrodeposited material.
TL;DR: In this paper, an analysis of mixed convective flow through a fluid-saturated porous medium adjacent to a vertical surface with the heating condition of power-law variation in the wall temperature is performed.
TL;DR: In this article, it was shown that the solar radiation with wavelengths 177-220 nm plays the decisive role in deterioration of polytetrafluoroethylene (PFL) films, and the main destructive factor is the fast atomic oxygen (5 eV) which is responsible for erosion of this polymer.
TL;DR: In this article, direct electron spin resonance evidence of profound intrinsic point defect generation in standard thermal SiO2 during postoxidation (PO) vacuum annealing is presented, and the detected isotropic signal (peak-to-peak width 4.5-5.8 G; g=2.0028 at 4.3 K) is assigned to S centers, tentatively ascribed previously to E′−like defects (O3≡Si⋅ with one or two O replaced by Si).
Abstract: Direct electron spin resonance evidence of profound intrinsic point defect generation in standard thermal SiO2 during postoxidation (PO) vacuum annealing is presented. The detected isotropic signal (peak‐to‐peak width 4.5–5.8 G; g=2.0028 at 4.3 K) is assigned to S centers, tentatively ascribed previously to E′‐like defects (O3≡Si⋅ with one or two O replaced by Si). This process is advanced as atomic essence of the electrically well‐known oxide degradation during PO annealing in inert ambient, likely effectuated by interface‐initiated (volatile) SiO interaction. Coproduction of EX and Eδ′ defects is newly reported for thermal SiO2 as well.
TL;DR: In this article, the authors used finite element codes to solve the coupled time-dependent heat transport and fluid flow differential equations, and showed that the inclusion of fractures in layers 2A and 2B promotes convection and causes horizontal thermal gradients.
Abstract: Small-scale seafloor heat-flow variations with a characteristic wavelength of about 1200 m have been observed on a profile over a sediment-sealed ridge flank Two theories have been advanced to explain them-low aspect ratio hydrothermal convection in a highly permeable basement layer 600 m thick or high aspect ratio convection in an anisotropic permeable layer 200 m thick, induced by 20 m topographic variations with a 1000 m half wavelength Neither theory is totally satisfactory The first requires a very thick highly permeable zone while the absence of any resolvable basement relief on a complementary seismic survey limits the credibility of the second
We hypothesize that sub-critical hydrothermal convection in normal upper oceanic crust, driven by discrete fractures, can cause the observed heat flow anomalies We test the hypothesis by using a finite-element code to solve the coupled time-dependent heat transport and fluid flow differential equations Discrete fractures are incorporated explicitly We show that the inclusion of fractures in layers 2A and 2B promotes convection Fluid flow through fractures causes horizontal thermal gradients, and initiates and maintains sub-critical convection within the upper basalts The predicted heat flow variations are comparable with the observed data
TL;DR: In this paper, the relationship between the entropies of the atmosphere and the radiation field was discussed, and it was shown that for clear skies in the thermal region of the spectrum, the two are directly proportional, and that the atmospheric term can be inferred with useful accuracy from an empirical relation.
Abstract: We discuss two practical issues concerning the relationship between the entropies of the atmosphere and of the radiation field. The first is whether the radiative flux of entropy can be determined from a satellite with sufficient accuracy for climate studies. We conclude that an accuracy much better than 1% is required, but that this can be achieved in the thermal spectrum with spectrometers having spectral resolutions ∼ 1 cm−1; it is also possible that the required accuracy can be achieved with a non-spectral approach. The second is whether the rate of change of the atmospheric entropy inventory can be inferred from the outgoing radiative-entropy flux. We conclude that, for clear skies in the thermal region of the spectrum, the two are directly proportional, and that the atmospheric term can be inferred with useful accuracy from an empirical relation.
TL;DR: In this article, a finite-element model describing the melt-growth of cylindrical sapphire single crystals via the gradient solidification method is presented, which can accurately capture complex physical phenomena associated with heat transfer through the system, while remaining modest in its computational requirements.
TL;DR: In this paper, a quantitative theory of thermal forces on spherically symmetric LAGEOS-like satellites is developed, based on more general assumptions than used so far, to model such radiation forces.
TL;DR: In this paper, the effects of thermal dispersion and thermal stratification on mixed convection about a vertical surface in a porous medium are studied and the conservation equations that govern the problem are reduced to a system of nonlinear ordinary differential equations.
Abstract: The effects of thermal dispersion and thermal stratification on mixed convection about a vertical surface in a porous medium are studied. The conservation equations that govern the problem are reduced to a system of nonlinear ordinary differential equations. The resulting equations are solved on the basis of the local similarity approximation. The results indicate that both dispersion and stratification effects have considerable influence on the heat transfer rate.
TL;DR: In this article, the effects of natural convection on temperature and solute distributions, growth rate and growth uniformity along the interface are studied for CdTe single crystal growth by the traveling heater method (THM).
Patent•
08 Feb 1996TL;DR: In this article, the thermal characteristics of a system having at least two electronic devices (100, 102, 300, 302, 304) connected to a common substrate were improved by forming an opening (200, 306) through the substrate between the two devices.
Abstract: A system and method of improving the thermal characteristics of a system having at least two electronic devices (100, 102; 300, 302) connected to a common substrate (104; 304). Thermal characteristics include the amount of heat transferred from one device to another and spatial uniformity of heat transferred from one device to another. Thermal conductive paths between two electronic devices are lengthened by forming an opening (200; 306) through the substrate between the two devices. Heat conduction between the devices is reduced due to increased radiation and convection in the longer thermal conductive paths. The uniformity of heat distribution between the devices is improved due to a narrower range of conducting path lengths. In a specific embodiment, heat conduction is reduced between amplifiers and photosensors used in spectrometers. In the specific embodiment, a temperature sensor (308) is used to further reduce thermal effects.
Patent•
IBM1
TL;DR: In this article, a lifting ring of bimetallic structure or memory metal is matched to a solder softening or melting temperature to apply forces to lift a chip from a supporting structure, such as a substrate or multi-chip module, only when the solder connections between the chip and the supporting structure are softened or melted.
Abstract: Deformation of a lifting ring of bimetallic structure or memory metal is matched to a solder softening or melting temperature to apply forces to lift a chip from a supporting structure, such as a substrate or multi-chip module, only when the solder connections between the chip and the supporting structure are softened or melted. The temperature of the chip, module and solder connections there between is achieved in a commercially available box oven or belt furnace or the like and results in much reduced internal chip temperatures and thermal gradients within the chip as compared to known hot chip removal processes. Tensile and/or shear forces at solder connections and chip and substrate contacts are much reduced in comparison with known cold chip removal processes. Accordingly, the process is repeatable at will without significant damage to or alteration of electrical characteristics of the chip or substrate.