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Temperature Distribution (temperature + distribution)
Selected AbstractsEffect of Injection Parameters on Velocity and Temperature Distributions of Alumina-Titania In-Flight Particles in Atmospheric Plasma SprayingADVANCED ENGINEERING MATERIALS, Issue 8 2004S. Guessasma Three injection parameters (carrier gas flow rate, injector diameter and injection distance) were correlated to the characteristic distributions in the case of alumina titania in-flight particles. A high speed two color pyrometer was implemented to measure, at the centre of the particle flow, individual in-flight particle characteristics, which were used to build velocity and temperature distributions. Results showed that mean characteristic variations were explained by distribution width flattening and centre shift. These were not significant compared to energetic parameter effects. [source] Heat capacity measurement by flow calorimetry: An exact analysisAICHE JOURNAL, Issue 1 2009T. K. Hei Abstract The principal unsolved problem in flow calorimetry for liquid heat capacity measurement accurate accounting for heat loss from the heater lead-in wires as a function of system properties is analyzed by exact procedures for a five-zone calorimeter model. Temperature distributions in the fluid, and bi-metal wire are obtained from solutions of the governing third-order ODE in the fluid temperature for realistic boundary conditions. Conductive heat losses at the fluid exit qHL/q, are large (up to 20% of energy input), and physical property and flow rate dependent. A new correlating equation for (qHL/q,) gives separately and explicitly, for the first time, its dependence on calorimeter characteristics, flow rates and fluid properties. Experiments on five pure liquids confirmed the predictions of the theoretical model and produced Cp values in close agreement with literature data. Fluid friction and small convection heat losses (UiAi (,T)lm) were accounted for experimentally. © 2008 American Institute of Chemical Engineers AIChE J, 2009 [source] Temperature field design, process analysis and control of SAPMAC method for the growth of large size sapphire crystalsCRYSTAL RESEARCH AND TECHNOLOGY, Issue 8 2007C. H. Xu Abstract In this paper, the relationship between quality of sapphire crystal and growing parameters of SAPMAC (Sapphire growth technique with micro-pulling and shoulder-expanding at cooled center) method was discussed. Optimized temperature distribution and technique control were proposed by theoretical analysis, numerical simulation computation and experimental validation to obtain large size sapphire crystals. For a-axis crystallized direction, with 1.0-5.0mm/h growth velocity and 10-30K/h temperature decreasing speed, large sapphire single crystal (,240mm×210mm, 27.5kg) having high optical quality was successfully grown. The absorption spectrum of standard samples was measured as well. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Study of Joule heating effects on temperature gradient in diverging microchannels for isoelectric focusing applicationsELECTROPHORESIS, Issue 10 2006Brian Kates Abstract IEF is a high-resolution separation method taking place in a medium with continuous pH gradients, which can be set up by applying electrical field to the liquid in a diverging microchannel. The axial variation of the channel cross-sectional area will induce nonuniform Joule heating and set up temperature gradient, which will generate pH gradient when proper medium is used. In order to operationally control the thermally generated pH gradients, fundamental understanding of heat transfer phenomena in microfluidic chips with diverging microchannels must be improved. In this paper, two 3-D numerical models are presented to study heat transfer in diverging microchannels, with static and moving liquid, respectively. Through simulation, the temperature distribution for the entire chip has been revealed, including both liquid and solid regions. The model for the static liquid scenario has been compared with published results for validation. Parametric studies have showed that the channel geometry has significant effects on the peak temperature location, and the electrical conductivity of the medium and the wall boundary convection have effects on the generated temperature gradients and thus the generated pH gradients. The solution to the continuous flow model, where the medium convection is considered, shows that liquid convection has significant effects on temperature distribution and the peak temperature location. [source] Modeling of Hot Ductility During Solidification of Steel Grades in Continuous Casting , Part I,ADVANCED ENGINEERING MATERIALS, Issue 3 2010Dieter Senk The present paper gives an overview of the simultaneous research work carried out by RWTH Aachen University and ThyssenKrupp Steel Europe AG. With a combination of sophisticated simulation tools and experimental techniques it is possible to predict the relations between temperature distribution in the mould, solidification velocity, chemical steel composition and, furthermore, the mechanical properties of the steel shell. Simulation results as well as experimentally observed microstructure parameters are used as input data for hot tearing criteria. A critical choice of existing hot tearing criteria based on different approaches, like critical strain and critical strain rate, are applied and developed. The new "damage model" is going to replace a basic approach to determine hot cracking susceptibility in a mechanical FEM strand model for continuous slab casting of ThyssenKrupp Steel Europe AG. Critical strains for hot cracking in continuous casting were investigated by in situ tensile tests for four steel grades with carbon contents in the range of 0.036 and 0.76,wt%. Additionally to modeling, fractography of laboratory and industrial samples was carried out by SEM and EPMA and the results are discussed. [source] Microstructure Evolution and Mechanical Properties of Linear Friction Welded Ti-5Al-2Sn-2Zr-4Mo-4Cr (Ti17) Titanium Alloy Joints,ADVANCED ENGINEERING MATERIALS, Issue 1-2 2010Wen-Ya Li The microstructural evolution, microhardness, tensile properties and impact toughness of Ti-5Al-2Sn-2Zr-4Mo-4Cr (Ti17) alloy joints welded by linear friction welding (LFW) are investigated. A narrow, sound weld is formed, consisting of a superfine ,,+,, structure in the weld center. The structure gradually changes from the weld center to the parent Ti17 in the TMAZ, with the highly deformed , and , phases oriented along the deformation direction, owing to the uneven deformation and temperature distribution. The microhardness of the TMAZ is the lowest of the distinct zones and presents a valley-like shape. The tensile strengths of the joints are comparable to that of the parent Ti17 but with a much lower plasticity and impact toughness. The microstructure variation contributes to the resultant properties. [source] Analysis of temperature distribution near the crack tip under constant amplitude loadingFATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 5 2008K. N. PANDEY ABSTRACT An analytical/numerical method has been developed to find the temperature rise near the crack tip under fatigue loading. The cyclic plastic zone ahead of the crack tip is assumed to be the shape of the source of heat generation and some fraction of plastic work done in cyclic plastic zone as heat generation. Plastic work during fatigue load was found by obtaining stress and strain distribution within the plastic zone by Hutchinson, Rice and Rosengren (HRR) crack tip singularity fields applied to small scale yielding on the cyclic stress strain curve. A two-dimensional conduction heat transfer equation, in moving co-ordinates, was used to obtain temperature distribution around the crack tip. Temperature rise was found to be a function of frequency of loading, applied stress intensity factor and thermal properties of the material. A power,law relation was found between the rise in temperature at a fixed point near the crack tip and range of stress intensity factor. [source] Determination of activation temperature of glass bulb sprinklers using a thermal liquid bathFIRE AND MATERIALS, Issue 4 2006Mohammed M. Khan Abstract A thermal liquid bath was used to determine the activation temperature of a wide range of temperature rated (57,182°C) glass bulb (3 and 5 mm diameters) sprinklers using water and glycerine. An optical switch and a thermocouple were installed adjacent to each sprinkler (within 10 mm) to record the activation of each glass bulb in the liquid bath having a uniform temperature distribution (±0.5°C). All the tests for determining the activation temperatures of glass bulb sprinklers were conducted in the liquid bath using a 0.277°C/min rate of temperature rise. Based on a heat transfer analysis, this rate is within the maximum allowable rate of rise of water and glycerine temperatures, which allows the glass bulb temperature to closely follow the liquid temperature. The sprinkler activation temperature was evaluated in terms of percentage rating, which is expressed as the percent variation of the average activation temperature, as measured in the liquid bath, from the nominal rated temperature. Sprinklers (93°C rated or lower) activation temperatures in water were consistently within ±3.5% of rating. In glycerine, the activation temperatures of sprinklers rated between 93 and 182°C performed within 3.5% of their rating. Copyright © 2005 John Wiley & Sons, Ltd. [source] Movement and behaviour of large southern bluefin tuna (Thunnus maccoyii) in the Australian region determined using pop-up satellite archival tagsFISHERIES OCEANOGRAPHY, Issue 5 2008TOBY A. PATTERSON Abstract Pop-up satellite archival tags (PSATs) were deployed on 52 large (156,200 cm length to caudal fork) southern bluefin tuna (Thunnus maccoyii) in the western Tasman Sea during the austral winters of 2001,2005. Southern bluefin tuna (SBT) were resident in the Tasman Sea for up to 6 months with movements away from the tagging area occurring at highly variable rates. The data indicated a general tendency for SBT to move south from the tagging area in the Western Tasman Sea. Four individuals migrated west along the southern continental margin of Australia and into the Indian Ocean. Three individuals moved east into the central Tasman Sea, with one individual reaching New Zealand. We also describe the first observed migration of an SBT from the Tasman Sea to the Indian Ocean spawning grounds south of Indonesia. Individuals spent most of their time relatively close to the Australian coast, with an estimated 84% of time spent in the Australian Fishing Zone. SBT favored temperatures between 19 and 21°C, adjusting their depth to the vertical temperature distribution. Distinct diurnal diving patterns were observed and adjustment of depth to maintain constant ambient light levels over a 24-h period. The findings of this study are a significant advance toward greater understanding of the spatial dynamics of large SBT and understanding the connectivity between distant regions of their distribution. [source] He's homotopy perturbation method for two-dimensional heat conduction equation: Comparison with finite element methodHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 4 2010M. Jalaal Abstract Heat conduction appears in almost all natural and industrial processes. In the current study, a two-dimensional heat conduction equation with different complex Dirichlet boundary conditions has been studied. An analytical solution for the temperature distribution and gradient is derived using the homotopy perturbation method (HPM). Unlike most of previous studies in the field of analytical solution with homotopy-based methods which investigate the ODEs, we focus on the partial differential equation (PDE). Employing the Taylor series, the gained series has been converted to an exact expression describing the temperature distribution in the computational domain. Problems were also solved numerically employing the finite element method (FEM). Analytical and numerical results were compared with each other and excellent agreement was obtained. The present investigation shows the effectiveness of the HPM for the solution of PDEs and represents an exact solution for a practical problem. The mathematical procedure proves that the present mathematical method is much simpler than other analytical techniques due to using a combination of homotopy analysis and classic perturbation method. The current mathematical solution can be used in further analytical and numerical surveys as well as related natural and industrial applications even with complex boundary conditions as a simple accurate technique. © 2010 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20292 [source] A spatially advancing turbulent flow and heat transfer in a curved channelHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 1 2010Koji Matsubara Abstract Direct numerical simulation was performed for a spatially advancing turbulent flow and heat transfer in a two-dimensional curved channel, where one wall was heated to a constant temperature and the other wall was cooled to a different constant temperature. In the simulation, fully developed flow and temperature from the straight-channel driver was passed through the inlet of the curved-channel domain. The frictional Reynolds number was assigned 150, and the Prandtl number was given 0.71. Since the flow field was examined in the previous paper, the thermal features are mainly targeted in this paper. The turbulent heat flux showed trends consistent with a growing process of large-scale vortices. In the curved part, the wall-normal component of the turbulent heat flux was twice as large as the counterpart in the straight part, suggesting active heat transport of large-scale vortices. In the inner side of the same section, temperature fluctuation was abnormally large compared with the modest fluctuation of the wall-normal velocity. This was caused by the combined effect of the large-scale motion of the vortices and the wide variation of the mean temperature; in such a temperature distribution, large-scale ejection of the hot fluid near the outer wall, which is transported into the near inner-wall region, should have a large impact on the thermal boundary layer near the inner wall. Wave number decomposition was conducted for various statistics, which showed that the contribution of the large-scale vortex to the total turbulent heat flux normal to the wall reached roughly 80% inside the channel 135° downstream from the curved-channel inlet. © 2009 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20275 [source] The heat transfer heterogeneities of bends in flow boiling of hairpin tubesHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 8 2009Meng Meng Abstract A series of visual experiments were conducted for liquid, vapor two-phase flow in hairpin tubes, and it was observed that most of the nucleation sites were located at the outer tube wall of the bend. From the simulation, it was concluded that the uneven velocity distribution in the bend induced the heat transfer heterogeneity. Furthermore, the nucleation of both the inner and outer tube wall of the bend and the wall temperature distribution were discussed to understand the physical phenomena. © 2009 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20269 [source] The influences of thermophysical properties of porous media on superadiabatic combustion with reciprocating flowHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 5 2006Liming Du Abstract The influences of thermophysical properties of porous media on superadiabatic combustion with reciprocating flow is numerically studied in order to improve the understanding of the complex heat transfer and optimum design of the combustor. The heat transfer performance of a porous media combustor strongly depends on the thermophysical properties of the porous material. In order to explore how the material properties influence reciprocating superadiabatic combustion of premixed gases in porous media (short for RSCP), a two-dimensional mathematical model of a simplified RSCP combustor is developed based on the hypothesis of local thermal non-equilibrium between the solid and the gas phases by solving separate energy equations for these two phases. The porous media is assumed to emit, absorb, and isotropically scatter radiation. The finite-volume method is used for computing radiation heat transfer processes. The flow and temperature fields are calculated by solving the mass, moment, gas and solid energy, and species conservation equations with a finite difference/control volume approach. Since the mass fraction conservation equations are stiff, an operator splitting method is used to solve them. The results show that the volumetric convective heat transfer coefficient and extinction coefficient of the porous media obviously affect the temperature distributions of the combustion chamber and burning speed of the gases, but thermal conductivity does not have an obvious effect. It indicates that convective heat transfer and heat radiation are the dominating ways of heat transfer, while heat conduction is a little less important. The specific heat of the porous media also has a remarkable impact on temperature distribution of gases and heat release rate. © 2006 Wiley Periodicals, Inc. Heat Trans Asian Res, 35(5): 336,350, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20120 [source] Development of a finite element radiation model applied to two-dimensional participating mediaHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 6 2005Hong Qi Abstract A finite element method (FEM) for radiative heat transfer has been developed and it is applied to 2D problems with unstructured meshes. The present work provides a solution for temperature distribution in a rectangular enclosure with black or gray walls containing an absorbing, emitting, isotropically scattering medium. Compared with the results available from Monte Carlo simulation and finite volume method (FVM), the present FEM can predict the radiative heat transfer accurately. © 2005 Wiley Periodicals, Inc. Heat Trans Asian Res, 34(6): 386,395, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20076 [source] Thermal radiation effects of a high-temperature developing laminar flow in a tubeHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 5 2004Xin-Lin Xia Abstract The thermal radiation effects of a high-temperature developing laminar flow in a tube are investigated numerically. The two-dimensional steady flow and heat transfer are considered for an absorbing-emitting gray medium, whose density is dependent on the temperature. The governing equations of the coupled process are simultaneously solved by the discrete ordinate method combined with the control volume method. For a moderate optical thickness, the velocity distribution, the temperature distribution, and the radial heat flux distribution in the medium as well as the heat flux distribution on the tube wall are presented and discussed. The results show that the thermal radiation effects of a high-temperature medium are significant under a moderate optical thickness. The flow and convective heat transfer are weakened, and the development of temperature distribution is accelerated noticeably. © 2004 Wiley Periodicals, Inc. Heat Trans Asian Res, 33(5): 299,306, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20018 [source] Estimation of orthotropic thermal conductivity of honeycomb materialHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 8 2002Nagahisa Ogasawara Abstract An experimental,computational hybrid system for measurement of thermal conductivity of orthotropic materials is developed. The system consists of two experimental parts and a finite element analysis part. First, the temperature distribution generated by uniform heating is measured with a thermal video system, and the thermal conductivity of Z direction is calculated. Second, the temperature distribution generated by small area heating is measured with the system. In the final step, thermal transfer analyses simulating the experiment support efficient data, and thermal conductivity of in-plane directions is estimated by comparison between experimental and analytical temperature distributions. The orthotropic equivalent thermal conductivity of honeycomb materials obtained by this system agreed with the theoretical values. © 2002 Wiley Periodicals, Inc. Heat Trans Asian Res, 31(8): 617,625, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.10063 [source] Prediction of thermal sensation based on simulation of temperature distribution in a vehicle cabinHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 3 2001Takuya Kataoka Abstract Thermal comfort in an automobile is predicted with numerical simulation. The flow field and temperature distribution are solved with a grid system based on many small cubic elements which are generated automatically with cabin and passenger configuration. Simulation of temperature is combined with simulation of cooling cycle and calculation of heat transfer at the wall including solar radiation to treat transient and actual driving conditions of the vehicle. In order to evaluate thermal comfort, transitional effective temperature is calculated from simulated thermal conditions and physiologic values which are calculated by a simple model of a human thermal system. This system can well predict thermal sensation of passengers in a short period of time. © 2001 Scripta Technica, Heat Trans Asian Res, 30(3): 195,212, 2001 [source] Modeling and simulation of bioheat transfer in the human eye using the 3D alpha finite element method (,FEM)INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 8 2010Eric Li Abstract Computational modeling is an effective tool for the detection of eye abnormalities and a valuable assistant to hyperthermia treatments. In all these diagnoses and treatments, predicting the temperature distribution accurately is very important. However, the standard finite element method (FEM) currently used for such purposes has strong reliance on element meshes and the discretized system exhibits the so-called ,overly stiff' behavior. To overcome this shortcoming, this paper formulates an alpha finite element method (,FEM) to compute two-dimensional (2D) and three-dimensional (3D) bioheat transfer in the human eyes. The ,FEM can produce much more accurate results using triangular (2D) and tetrahedron (3D) elements that can be generated automatically for complicated domains and hence is particularly suited for modeling human eyes. In the ,FEM, a scaling factor ,,[0, 1] is introduced to combine the ,overly stiff' FEM model and ,overly soft' node-based finite element method (NS-FEM) model. With a properly chosen ,, the ,FEM can produce models with very ,close-to-exact' stiffness of the continuous system. Numerical results have shown that the present method gives much more accurate results compared with the standard FEM and the NS-FEM. Copyright © 2010 John Wiley & Sons, Ltd. [source] Thermal and mechanical numerical modelling of electric discharge machining processINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 12 2008Nizar Ben Salah Abstract In electric discharge machining (EDM), the heat gradients caused by the electric discharge create a non-uniform local thermal expansion on the level of the surface layers of machined materials from where genesis of thermal stresses takes place. These thermal stresses, if exceeding yield stress, can remain and become residual after the cooling of the part. The modelling of these phenomena, during the heating by the electric discharge and the cooling by the dielectric liquid, requires a heat transfer model, the material behaviour identification, a thermo-mechanical model for the thermal and the residual stress models. This paper presents numerical results concerning the temperature distribution, the thermal and residual stresses of a stable steel material (AISI316L) machined by EDM. Comparison of numerical results with experimental data and numerical results from the literature shows good agreement and is hence quite satisfactory. Copyright © 2008 John Wiley & Sons, Ltd. [source] Starting solutions for the boundary immobilization methodINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 6 2005J. Caldwell Abstract The boundary immobilization method (BIM) is extended to the cases of outward spherical and cylindrical solidifications, which involves the development of starting solutions. When applying the method to time-dependent problems, good agreement is achieved when comparing the positions of the moving boundary and the temperature distribution with those obtained by the perturbation method. Copyright © 2004 John Wiley & Sons, Ltd. [source] Effects of chemical reaction, heat and mass transfer on non-linear MHD flow over an accelerating surface with heat source and thermal stratification in the presence of suction or injectionINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 7 2003S. P. Anjali Devi Abstract An approximate numerical solution for the steady MHD laminar boundary-layer flow over an accelerating vertical surface with suction or injection in the presence of species concentration and mass diffusion has been obtained by solving the governing equations using R.K. Gill method. The fluid is assumed to be viscous, incompressible and electrically conducting with a magnetic field applied transversely to the direction of the flow. It has been observed that in the presence of mass diffusion: (i) in the case of suction, the velocity decreases and the temperature distribution and concentration of the fluid increase and for injection, the velocity increases and the temperature distribution and concentration of the fluid decrease with increase of thermal stratification parameter, (ii) in the presence of thermal stratification parameter in both the cases of suction and injection, the skin friction and rate of mass transfer decrease and the rate of heat transfer of the fluid increases with increase of chemical reaction effects, (iii) in the cases of suction and injection, an increase in the strength of magnetic field leads to fall in the velocity and rise in the temperature and concentration of the fluid along the surface. Copyright © 2003 John Wiley & Sons, Ltd. [source] Modelling and process optimization for functionally graded materialsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 2 2005Ravi S. Bellur-Ramaswamy Abstract We optimize continuous quench process parameters to produce functionally graded aluminium alloy extrudates. To perform this task, an optimization problem is defined and solved using a standard non-linear programming algorithm. Ingredients of this algorithm include (1) the process parameters to be optimized, (2) a cost function: the weighted average of the precipitate number density distribution, (3) constraint functions to limit the temperature gradient (and hence distortion and residual stress) and exit temperature, and (4) their sensitivities with respect to the process parameters. The cost and constraint functions are dependent on the temperature and precipitate size which are obtained by balancing energy to determine the temperature distribution and by using a reaction-rate theory to determine the precipitate particle sizes and their distributions. Both the temperature and the precipitate models are solved via the discontinuous Galerkin finite element method. The energy balance incorporates non-linear boundary conditions and material properties. The temperature field is then used in the reaction rate model which has as many as 105 degrees-of-freedom per finite element node. After computing the temperature and precipitate size distributions we must compute their sensitivities. This seemingly intractable computational task is resolved thanks to the discontinuous Galerkin finite element formulation and the direct differentiation sensitivity method. A three-dimension example is provided to demonstrate the algorithm. Copyright © 2004 John Wiley & Sons, Ltd. [source] Finite element modelling of fibre reinforced polymer sandwich panels exposed to heatINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 1 2004P. Krysl Abstract A finite element model that predicts temperature distribution in a composite panel exposed to a heat source, such as fire, is described. The panel is assumed to be composed of skins consisting of polymer matrix reinforced with fibres and a lightweight core (the paper concentrates on the crucial aspect of the problem, i.e. the behaviour of the ,hot' skin of the panel. The core is assumed not to decompose, and the ,cold' skin is treated exactly as the ,hot' skin.) It is assumed that the polymer matrix undergoes chemical decomposition. Such a model results in a set of coupled non-linear transient partial differential equations. A Galerkin finite element framework is formulated to yield a fully implicit time stepping scheme. The crucial input parameters for the model are carefully identified for subsequent experimental determination. Copyright © 2004 John Wiley & Sons, Ltd. [source] A conservative integral for bimaterial notches subjected to thermal stressesINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 6 2004Leslie Banks-Sills Abstract In this investigation, a conservative integral based on the Betti reciprocal principle is developed to obtain stress intensity factors for a bimaterial notch in which the body is subjected to a thermal load. The bonded materials are linear elastic, isotropic and homogeneous. According to the linear theory of elasticity, stresses in the neighbourhood of the notch tip are generally singular as a result of the mismatch of the elastic constants. Eigenvalues and eigenfunctions depend upon the mechanical properties and wedge angles. They may be real, complex or power-logarithmic. Real and complex eigenvalues are considered in this study. The stress intensity factor represents the amplitude of the stress singularity and depends upon material properties, geometry and load or temperature. Because of the highly singular behaviour of one of the integrals that is part of the conservative integral, the former is carried out by a hybrid analytical/numerical scheme. The finite element method is employed to obtain displacements caused by the temperature distribution in the body. The conservative integral is applied to several problems appearing in the literature. Both good agreement between those results and the ones obtained here, as well as path stability for all problems is attained. A wide range of material parameters is also studied. Copyright © 2004 John Wiley & Sons, Ltd. [source] Two-dimensional unsteady heat conduction analysis with heat generation by triple-reciprocity BEMINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 2 2001Yoshihiro Ochiai Abstract If the initial temperature is assumed to be constant, a domain integral is not needed to solve unsteady heat conduction problems without heat generation using the boundary element method (BEM).However, with heat generation or a non-uniform initial temperature distribution, the domain integral is necessary. This paper demonstrates that two-dimensional problems of unsteady heat conduction with heat generation and a non-uniform initial temperature distribution can be solved approximately without the domain integral by the triple-reciprocity boundary element method. In this method, heat generation and the initial temperature distribution are interpolated using the boundary integral equation. Copyright © 2001 John Wiley & Sons, Ltd. [source] Changes in hot days and heat waves in China during 1961,2007INTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 10 2010Ting Ding Abstract Based on the daily maximum temperature (DMT) records at 512 stations during 1961,2007, the geographical patterns and temporal variations of hot days (HDs) and heat waves (HWs, including those persisting for 3,5 days and longer) over mainland China were studied. The HD (and hence HW) was defined in two ways, one by an absolute criterion, DMT > 35 °C, as applied in the nationwide meteorological agencies and another in a relative sense, DMT > the 90th percentile threshold of a local daily temperature distribution around the day. Two centers of high frequencies (over 5 days per year) of the absolute HDs during June,September were found in the regions of Xinjiang and the mid-lower reaches of the Yangtze River. The highest frequencies of the absolute HWs were about 1.5 times per year in the Xinjiang region and to the south of the mid-lower reaches of the Yangtze River. The frequencies of the relative HWs were about 1,1.5 times per year in most of China. The HDs and HWs increased significantly during the studied period in most of China, especially over the southeastern coast and northern China (by over 4 days per decade for relative HDs and 0.4 times per decade for relative HWs), but decreased significantly at some stations in the lower reaches of the Yellow River. Over most of China except northwestern China, the frequency of HDs was high during the 1960s,1970s, low in the 1980s, and high afterwards, with strong interannual variations. A remarkable increasing trend of HDs occurred after the 1990s in all regions. The changes in HDs and HWs were closely related to those in rain days and atmospheric circulation patterns at the interannual and interdecadal scales. Copyright © 2009 Royal Meteorological Society [source] Changes in temperature extremes over Italy in the last 44 yearsINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 6 2008Andrea Toreti Abstract Changes in temperature extremes over Italy from 1961 to 2004 were evaluated on the basis of minimum and maximum temperatures measured by 49 synoptic stations uniformly distributed over the country. A set of extreme temperature indices of the Commission for Climatology/Climate Variability and Predictability (CCl/CLIVAR) Working Group on Climate Change Detection was calculated and statistically analysed in order to detect the presence of trends and quantify the variations of the indices for different time periods. Most of the indices, averaged over all stations, show a cooling trend until the end of the 1970s followed by a more pronounced warming trend in the last 25 years. The net variation of the indices reflects an increase in the extremes of the temperature distribution. Among the most significant results, an average increase of 12.3 summer days and 12.4 tropical nights in the overall 44 years are estimated. No significant differences between northern, central and southern Italy are found for most indices, indicating that the trends originate from large-scale climate features; however, the largest increase of tropical nights is observed at coastal stations. Copyright © 2007 Royal Meteorological Society [source] Temperature trends in Switzerland and Europe: implications for climate normalsINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 5 2006Simon C. Scherrer Abstract This study discusses problems of the concept of normal period,based anomalies arising from climate variability and ongoing climate change. The widely used WMO 1961,1990 (61,90) standard normal period is compared to other consecutive 30-year normal periods in detail. Focus is given to the temperature distribution in Switzerland and on the European continent. In these regions, the temperature trend of the last decades led to an unusually high number of months with positive temperature anomalies relative to the WMO 61,90 standard normal period. Swiss anomalies based on the 61,90 normal are up to 1.25 K higher than those based on the Latest 30-years Running Normal (LRN). The probability to observe a positive temperature anomaly with respect to the 61,90 normal increased from 50% to near 80% for certain months of the year. Compared to the LRN, this change is statistically significant for 7 out of the 12 months on the 95% level. The strongest signal can be found for the summer months, whereas temperatures in fall do not show any trends. Similar results are found for more than 90% of the European continental area. For most regions, 2,5 are statistically inconsistent with the 61,90 distribution. For southern France, parts of Spain and southern Scandinavia even 7,9 months are inconsistent. Copyright © 2005 Royal Meteorological Society. [source] Trends in indices for extremes in daily temperature and precipitation in central and western Europe, 1901,99INTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 9 2005Anders Moberg Abstract We analyse 20th century trends in six indices for precipitation extremes and four indices for temperature extremes, calculated from daily observational data for European stations. The indices chosen reflect rather moderate extremes. Most of the ,80 stations used are situated in central and western Europe; therefore, results mainly refer to this region. Trends are calculated over 1901,99, 1921,99, 1901,50 and 1946,99. Two different trend estimators are used, and significance is assessed with a bootstrap technique. We find that: Significant increasing precipitation trends over the 20th century dominate in winter for both average precipitation intensity and moderately strong events. Simultaneously, the length of dry spells generally increased insignificantly. There are few significant trends of any sign for precipitation indices in summer, but there are insignificant drying trends over Scandinavia and wetting trends over central and western Europe for 1921,99. The length of dry spells in summer generally increased insignificantly. Both the warm and cold tails of the temperature distribution in winter warmed over the entire 20th century. Notably low values in the cold tail for daily Tmax and Tmin occurred in the early 1940s, leading to strong but insignificant negative trends for 1901,50, whereas little change occurred before 1940. Warming of winters during 1946,99 occurred in both the warm and cold tails for both Tmax and Tmin, with the largest warming in the cold tail for Tmin. The warm tail of daily Tmin (and to a smaller extent Tmax) in summer warmed significantly during the past century. There is more evidence for summer warming in the first half of the century compared with the second half. During 1946,99, the warm tail of daily Tmax in summer was generally warming while the cold tail was cooling (both insignificantly). More digitized daily observational data from various European sub-regions are needed to permit a spatially more extensive analysis of changes in climate extremes over the last century. Copyright © 2005 Royal Meteorological Society [source] Estimating missing daily temperature extremes using an optimized regression approachINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 11 2001Robert J. Allen Abstract A variation of a least squares regression approach to estimate missing daily maximum and minimum temperatures is developed and evaluated, specifically for temperature extremes. The method focuses on obtaining accurate estimates of annual exceedence counts (e.g. the number of days greater than or equal to the 90th percentile of daily maximum temperatures), as well as counts of consecutive exceedences, while limiting the estimation error associated with each individual value. The performance of this method is compared with that of two existing methods developed for the entire temperature distribution. In these existing methods, temperature estimates are based on data from neighbouring stations using either regression or temperature departure-based approaches. Evaluation of our approach using cold minimum and warm maximum temperatures shows that the median percentage of correctly identified exceedence counts is 97% and the median percentage of correctly identified consecutive exceedence counts is 98%. The other existing methods tend to underestimate both single and consecutive exceedence counts. Using these procedures, the estimated exceedence counts are generally less than 80% of those that actually occurred. Despite the fact that our method is tuned to estimate exceedence counts, the estimation accuracy of individual daily maximum or minimum temperatures is similar to that of the other estimation procedures. The median absolute error (MAE) using all temperatures greater than or equal to the 90th percentile (T90),1.1°C for ten climatically diverse stations is 1.28°C for our method, while the other methods give MAEs of 1.27 and 1.17°C. In terms of median error, however, the tendency for underprediction by the existing methods is pronounced with ,0.77 and ,0.61°C biases. Our optimized method is relatively unbiased as the resulting mean error is ,0.12°C. Copyright © 2001 Royal Meteorological Society [source] | ||||||||||||||||||||||||||||||||||||||||||||||