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Thermal Energy (thermal + energy)
Terms modified by Thermal Energy Selected AbstractsThe OH, + CH3SH reaction: Support for an addition-elimination mechanism from ab initio calculationsJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 6 2005Pedro L. Muiño Abstract Several intermediates for the CH3SH + OH, , CH3S, + H2O reaction were identified using MP2(full) 6-311+g(2df,p) ab initio calculations. An adduct, CH3S(H)OH,, I, with electronic energy 13.63 kJ mol,1 lower than the reactants, and a transition state, II,, located 5.14 kJ mol,1 above I, are identified as the entrance channel for an addition-elimination reaction mechanism. After adding zero-point and thermal energies, ,H(reactants , I) = ,4.85 kJ mol,1 and ,H(I , II,) = +0.10 kJ mol,1, which indicates that the potential energy surface is broad and flat near the transition state. The calculated imaginary vibrational frequency of the transition state, 62i cm,1, is also consistent with an addition,elimination mechanism. These calculations are consistent with experimental observations of the OH, + CH3SH reaction that favored an addition,elimination mechanism rather than direct hydrogen atom abstraction. An alternative reaction, CH3SH + OH, , CH3SOH + H,, with ,H = +56.94 kJ mol,1 was also studied, leading to a determination of ,H(CH3SOH) = ,149.8 kJ mol,1. © 2005 Wiley Periodicals, Inc. J Comput Chem 26: 612,618, 2005 [source] Optimization of a single-effect evaporation system to effectively utilize thermal energyENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 2 2009Raafat Alnaizy Abstract Wastewater treatment facilities at Emirates Gold in Dubai seek to improve the steam economy of the existing single-effect with recirculation and vapor-compression evaporation process. Maximizing steam economy is important as it impacts treatment costs. There are two main approaches for improving steam economy in evaporators. One is to use a multiple-effect evaporator; the other is to use a mechanical vapor recompression. Multiple-effect evaporators were rejected because of higher capital and power cost. One of the suggestions that were made towards improving the steam economy was to recover heat from the steam condensate. A modified process flow diagram was proposed and investigated. The modified process was simulated using SuperPro Designer and Hysys with complete material and energy balance computation. The modified process increased the total water evaporation capacity and gained 40% better steam economy of the process. Another advantage was an increase in the amount of water reused, which is both economical and environmentally friendly. © 2008 American Institute of Chemical Engineers Environ Prog, 2009 [source] Effect of the plate thermal resistance on the heat transfer performance of a corrugated thin plate heat exchangerHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 3 2006Hiroshi Iwai Abstract Two-dimensional conjugate conduction/convection numerical simulations were carried out for flow and thermal fields in a unit model of a counter-flow-type corrugated thin plate heat exchanger core. The effects of the thermal resistance of the solid plate, namely the variation of the plate thickness and the difference of the plate material, on the heat exchanger performance were examined in the Reynolds number range of 100 Merging formation and current amplification of field-reversed configurationIEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING, Issue 4 2007Michiaki Inomoto Member Abstract The merging formation of the field-reversed configuration (FRC) has been developed in the TS-3 merging experiment, leading us to a new scenario of FRC slow formation, heating and current amplification. Two force-free spheromaks with opposing toroidal fields were merged together in the axial direction to form a high-, FRC with higher efficiency than the conventional field-reversed theta-pinch method. This unique relaxation from the force-free (, , 0.05 , 0.1) spheromaks to the high-, (, , 0.7 , 1) FRC is attributed to the conversion of toroidal magnetic energy into ion thermal energy through the reconnection outflow. A central ohmic heating (OH) coil worked successfully to amplify the FRC plasma current by a factor of 2. Toroidal mode analysis of magnetic structure indicated that the tilting stability of the oblate FRC was provided by an ion kinetic effect. This oblate FRC is also useful as an initial equilibrium to produce a high-,p spherical tokamak (ST) with diamagnetic toroidal magnetic field, suggesting the close relationship between FRCs and high-,p STs in the second stable region of the ballooning mode. © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [source] Reversible Infrared Actuation of Carbon Nanotube,Liquid Crystalline Elastomer Nanocomposites,ADVANCED MATERIALS, Issue 12 2008Liqiang Yang Nanocomposite films comprising polymer-functionalized single-walled carbon-nanotubes (SWNTs) and liquid crystal elastomers (LCEs) show a reversible IR-induced strain (,,30%) at very low SWNT loading levels (,0.2 wt%). SWNTs can efficiently transform absorbed IR light into thermal energy, thereby serving as a nanoscale heat-source and thermal- conduction pathway. The absorbed thermal-energy induced a nematic, isotropic phase-transition, generating a shape change in the nanocomposite film. [source] Intermediate Temperature Reversible Fuel CellsINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 2 2007Singaravelu Elangovan Electrolysis of water produces high-purity hydrogen directly, with no need for additional clean-up process. Efficiency and cost of electrolysis are favorable with high-temperature steam electrolyzers where a portion of the required energy can be supplied as thermal energy. With the similarity in requirements, much of the materials and designs aspects for the high-temperature electrolyzers have been derived from solid oxide fuel cell development. Lanthanum gallate electrolyte-based cells were evaluated in fuel cell and electrolysis modes of operation. A modified nickel anode is shown to lower the reactivity with the gallate. [source] Feasibility of long-distance transport of thermal energy using solid sorption processesINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 8 2010Nathalie Mazet Abstract This paper deals with the challenging transportation of thermal energy over long distances (over 10,km). The innovative concept presented in this paper is based on the transportation of a reactive fluid coupled with two sorption systems involving this fluid in two endothermal and exothermal processes respectively on source site and user site. The transport of this fluid at ambient temperature minimizes the thermal losses and it is therefore relevant for long distances. Moreover, an original concept involving a cascade of two sorption cycles can allow a heat upgrading on the user site using a distant source. This paper focuses on the feasibility of such systems. The potentialities have been detailed according to the reactive pairs, such as the well-known hydrates and ammonia solid/gas reactants, and taking into account thermodynamic and technological constraints. The cold production and transport can be carried out by numerous ammonia-based pairs. Nevertheless, such reactive pairs can perform a heat upgrading, but only if an additional heat source is available on the user site. The transportation of the reactive fluid between source and user sites has been investigated and it is not a limiting point. As it is transported at ambient temperature, the thermal losses are very weak. On the other hand, the pressure losses can be overcome with either an acceptable energetic cost or by slightly changing the operating conditions. Compared to current district heating networks based on sensible heat transportation, such thermochemical systems involving the transportation of a reactive fluid seem more efficient when the user is located more than 10,km away from the source site. Copyright © 2009 John Wiley & Sons, Ltd. [source] A review on advances in alkali metal thermal to electric converters (AMTECs)INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 10 2009Shuang-Ying Wu Abstract The alkali metal thermal to electric converter (AMTEC) is one of the most promising technologies for direct conversion of thermal energy to electricity and has been receiving attention in the field of energy conversion and utilization in the past several decades. This paper aims to present a comprehensive review of the state of the art in the research and development of the AMTEC, including its working principles and types, historical development and applications, analytical models, working fluids, electrode materials, as well as the performance and efficiency improvement. The current two major problems encountered by the AMTEC, the time-dependent power degradation and relatively low efficiency compared to its theoretical value, are discussed in depth. In addition, a brief comparison of the AMTEC with other direct thermal to electric converters (DTECs), such as the thermoelectrics converter (TEC), thermionics converter, and thermophotovoltaics converter, is given, and combinations of different DTECs to further improve DTECs' power generation and overall conversion efficiency are demonstrated. Future research and development directions and the issues that need to be further investigated are also suggested. It is believed that this comprehensive review will be beneficial to the design, simulation, analysis, performance assessment, and applications of various types of AMTECs. Copyright © 2009 John Wiley & Sons, Ltd. [source] The effects of momentum diffusers and flow guides on the efficiency of stratified hot water seasonal heat storesINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 10 2008V. Panthalookaran Abstract Hot water seasonal heat stores (HWSHS) carry the solar thermal energy from energy-rich seasons of the year over to energy-poor seasons so as to ensure the availability of solar energy throughout the year. Momentum diffusers and flow guides are designed to charge and discharge the harvested solar thermal energy within HWSHS in a stratified manner to enhance the efficiency of the solar systems. To evaluate the efficiency of an HWSHS, a characterization scheme developed for general stratified thermal energy stores (TES) (Sol Energy 2007; 81:1043,1054) is used. It addresses the First Law and Second Law concerns over a TES simultaneously. This study is confined to systems that use the same nozzles at fixed positions in both charging and discharging cycles. Different parameters related to axial, conical and radial diffusers as well as a variety of flow-guide designs are studied. The results suggest that a nozzle that brings about better diffuser action by minimizing entropy generation may not necessarily improve the energy response and guarantee better overall efficiency of the HWSHS. Of all, the different nozzle designs experimented with the conical diffusers with smaller angles of diffusion produced the best overall efficiency. Copyright © 2008 John Wiley & Sons, Ltd. [source] System study on natural gas-based polygeneration system of DME and electricityINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 8 2008Chen Bin Abstract An innovative system for the polygeneration of dimethyl ether (DME) and electricity was proposed in this paper. The system uses natural gas as the raw material. Polygeneration is sequential, with one-step and once-through DME synthesis. Syngas is made to react to synthesize DME first, and then the residual syngas is sent to the power generation unit as fuel. The exergy analysis from the view of cascade utilization was executed for individual generation and for polygeneration. The analysis results showed that both chemical energy and thermal energy in polygeneration were effectively utilized, and both chemical exergy destruction and thermal exergy destruction in polygeneration were decreased. The cause of the decrease in exergy destruction was revealed. The analysis showed that hydrogen-rich (natural gas-based) polygeneration was as desirable as carbon-rich (coal-based) polygeneration. The energy saving ratio of polygeneration was about 10.2%, which demonstrated that high efficiency natural gas-based polygeneration is attainable, and the cascade utilizations of both chemical energy and thermal energy are key contributors to the improvement of performance. Copyright © 2007 John Wiley & Sons, Ltd. [source] Parametric studies for heating performance of an earth to air heat exchanger coupled with a greenhouseINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 11 2005M. K. Ghosal Abstract A thermal model has been developed to investigate the potential of using the stored thermal energy of the ground for greenhouse heating with the help of an earth to air heat exchanger (EAHE) system integrated with the greenhouse located in the premises of IIT, Delhi, India. Experiments were conducted extensively during the winter period from November 2002 to March 2003, but the model developed was validated against the clear and sunny days. Parametric studies performed for EAHE coupled with the greenhouse illustrate the effects of buried pipe length, pipe diameter, mass flow rate of air, depth of ground and soil types on greenhouse air temperatures. Temperatures of greenhouse air with the experimental parameters of EAHE were found to be on an average 7,8°C more in the winter than the same greenhouse without EAHE. Greenhouse air temperatures increase in the winter with increasing pipe length, decreasing pipe diameter, decreasing mass flow rate of flowing air inside buried pipe and increasing depth of ground up to 4 m. Predicted and measured values of greenhouse air temperature, which were verified in terms of root mean square of percent deviation and correlation coefficient, exhibited fair agreement. Copyright © 2005 John Wiley & Sons, Ltd. [source] Comparison of energy and exergy efficiencies of an underground solar thermal storage systemINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 4 2004H. Hüseyin Öztürk Abstract In this experimental study, solar energy was stored daily using the volcanic material with the sensible heat technique. The external heat collection unit consisted of 27 m2 of south-facing solar air collectors mounted at a 55° tilt angle. The dimensions of the packed-bed heat storage unit were 6 × 2 × 0.6 m deep. The packed-bed heat storage unit was built under the soil. The heat storage unit was filled with 6480 kg of volcanic material. Energy and exergy analyses were applied in order to evaluate the system efficiency. During the charging periods, the average daily rates of thermal energy and exergy stored in the heat storage unit were 1242 and 36.33 W, respectively. Since the rate of exergy depends on the temperature of the heat transfer fluid and surrounding, the rate of exergy increased as the difference between the inlet and outlet temperatures of the heat transfer fluid increased during the charging periods. It was found that the average daily net energy and exergy efficiencies in the charging periods were 39.7 and 2.03%, respectively. The average daily net energy efficiency of the heat storage system remained nearly constant during the charging periods. The maximum energy and exergy efficiencies of the heat storage system were 52.9 and 4.9%, respectively. Copyright © 2004 John Wiley & Sons, Ltd. [source] Electrostatic analysis of charge interactions in proteinsINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 1 2010G. P. Tsironis Abstract We model proteins as continuous electrostatic media immersed in water to investigate charge mediated processes in their interior. We use a Green's function formalism and find analytical expressions for the electrostatic energy in the vicinity of the protein surfaces. We find that due to image charges generated by the protein dielectric medium embedded in water, the effective electrostatic interaction between the two charges in the interior of the protein has an energy larger than the thermal energy. We focus specifically on kinesin to asses the strength of the electrostatic interaction between ATP and ADP molecules. It is known experimentally that ADP expulsion is correlated to ATP kinesin binding while both processes are essential for the kinesin walk. We estimate that the Bjerrum length in the interior of the kinesin dimer protein is of the order of 4 nm and that the pure electrostatic ATP,ADP interaction is of the order of 3,5 kBT. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010 [source] JOURNAL of FOOD PROCESSING and PRESERVATION SEP 2000 Vol-24.4. DEVELOPMENT of A PROCESS FOR DETECTING NONTHERMAL EFFECTS of MICROWAVE ENERGY ON MICROORGANISMS AT LOW TEMPERATURE,JOURNAL OF FOOD PROCESSING AND PRESERVATION, Issue 4 2000MICHAEL KOZEMPEL We developed an experimental process capable of isolating thermal and nonthermal effects of microwave energy relative to the destruction of microorganisms at low temperature. the concept combines instantaneous energy input to the food system by microwaves with rapid removal of thermal energy. the process used a double tube heat exchanger inside a continuous microwave dryer. the outer tube was transparent to microwaves, whereas the inner tube was stainless steel and was used for cooling the system. the microwave energy, 5,6 kW power, was absorbed by the process fluid in the annulus. the cooling water flowing in the inner tube removed the thermal energy from the process fluid to control temperature at or below 45C. the process was at turbulent flow to assure a uniform temperature and dwell time. There were no detected nonthermal effects from microwave energy for yeast, Pediococcus sp., Escherichia coli, Listeria innocua, or Enterobacter aerogenes in various test fluids, such as water, liquid egg, beer, apple juice, apple cider, and tomato juice. [source] CFD modeling of the Wurster bed coaterAICHE JOURNAL, Issue 10 2009Stina Karlsson Abstract In the Wurster bed coater, the wetting, drying, and circulation of particles are combined to produce a high quality coating. The drying and wetting conditions in a laboratory scale Wurster bed coater are modeled and compared with experimental data. A model combining multiphase fluid dynamics with heat and mass transfer is developed to model the particle and gas motion and the transport of thermal energy and moisture. A wetting region is defined, where a specified moisture content is set in the particle phase, above the jet inlet, to describe the injection of coating liquid. The simulation shows the characteristic circulation of particles in the equipment, as well as the behavior of the moisture in the system and agrees well with measurements. The simulation indicates how different process conditions influence the drying regions. The results show that most of the drying, under typical operating conditions, takes place in the Wurster tube. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] The role of viscous heating in Barrovian metamorphism of collisional orogens: thermomechanical models and application to the Lepontine Dome in the Central AlpsJOURNAL OF METAMORPHIC GEOLOGY, Issue 2 2005J.-P. BURG Abstract Thermal models for Barrovian metamorphism driven by doubling the thickness of the radiogenic crust typically meet difficulty in accounting for the observed peak metamorphic temperature conditions. This difficulty suggests that there is an additional component in the thermal budget of many collisional orogens. Theoretical and geological considerations suggest that viscous heating is a cumulative process that may explain the heat deficit in collision orogens. The results of 2D numerical modelling of continental collision involving subduction of the lithospheric mantle demonstrate that geologically plausible stresses and strain rates may result in orogen-scale viscous heat production of 0.1 to >1 ,W m,3, which is comparable to or even exceeds bulk radiogenic heat production within the crust. Thermally induced buoyancy is responsible for crustal upwelling in large domes with metamorphic temperatures up to 200 °C higher than regional background temperatures. Heat is mostly generated within the uppermost mantle, because of large stresses in the highly viscous rocks deforming there. This thermal energy may be transferred to the overlying crust either in the form of enhanced heat flow, or through magmatism that brings heat into the crust advectively. The amplitude of orogenic heating varies with time, with both the amplitude and time-span depending strongly on the coupling between heat production, viscosity and collision strain rate. It is argued that geologically relevant figures are applicable to metamorphic domes such as the Lepontine Dome in the Central Alps. We conclude that deformation-generated viscous dissipation is an important heat source during collisional orogeny and that high metamorphic temperatures as in Barrovian type metamorphism are inherent to deforming crustal regions. [source] Selective transcutaneous delivery of energy to porcine soft tissues using intense ultrasound (IUS),,LASERS IN SURGERY AND MEDICINE, Issue 2 2008W. Matthew White MD Abstract Objective Various energy delivery systems have been utilized to treat superficial rhytids in the aging face. The Intense Ultrasound System (IUS) is a novel modality capable of transcutaneously delivering controlled thermal energy at various depths while sparing the overlying tissues. The purpose of this feasibility study was to evaluate the response of porcine tissues to various IUS energy source conditions. Further evaluation was performed of the built-in imaging capabilities of the device. Materials and Methods Simulations were performed on ex vivo porcine tissues to estimate the thermal dose distribution in tissues after IUS exposures to determine the unique source settings that would produce thermal injury zones (TIZs) at given depths. Exposures were performed at escalating power settings and different exposure times (in the range of 1,7.6 J) using three IUS handpieces with unique frequencies and focal depths. Ultrasound imaging was performed before and after IUS exposures to detect changes in tissue consistency. Porcine tissues were examined using nitro-blue tetrazolium chloride (NBTC) staining sensitive for thermal lesions, both grossly and histologically. The dimensions and depth of the TIZs were measured from digital photographs and compared. Results IUS can reliably achieve discrete, TIZ at various depths within tissue without surface disruption. Changes in the TIZ dimensions and shape were observed as source settings were varied. As the source energy was increased, the thermal lesions became larger by growing proximally towards the tissue surface. Maximum lesion depth closely approximated the pre-set focal depth of a given handpiece. Ultrasound imaging detected well-demarcated TIZ at depths within the porcine muscle tissue. Conclusion This study demonstrates the response of porcine tissue to various energy dose levels of Intense Ultrasound. Further study, especially on human facial tissue, is necessary in order to understand the utility of this modality in treating the aging face and potentially, other cosmetic applications. Lesers Surg. Med. 40:67,75, 2008. © 2008 Wiley-Liss, Inc. [source] Thermal effects of circumplanetary disc formation around proto-gas giant planetsMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2009M. N. Machida ABSTRACT The formation of a circumplanetary disc and accretion of angular momentum on to a protoplanetary system are investigated using three-dimensional hydrodynamical simulations. The local region around a protoplanet in a protoplanetary disc is considered with sufficient spatial resolution: the region from outside the Hill sphere to the Jovian radius is covered by the nested-grid method. To investigate the thermal effects of the circumplanetary disc, various equations of state are adopted. Large thermal energy around the protoplanet slightly changes the structure of the circumplanetary disc. Compared with a model adopting an isothermal equation of state, in a model with an adiabatic equation of state, the protoplanet's gas envelope extends farther, and a slightly thick disc appears near the protoplanet. However, different equations of state do not affect the acquisition process of angular momentum for the protoplanetary system. Thus, the specific angular momentum acquired by the system is fitted as a function only of the protoplanet's mass. A large fraction of the total angular momentum contributes to the formation of the circumplanetary disc. The disc forms only in a compact region in very close proximity to the protoplanet. Adapting the results to the Solar system, the proto-Jupiter and Saturn have compact discs in the region of r < 21rJup(r < 0.028 rH,Jup) and r < 66rSat(r < 0.061rH,Sat), respectively, where rJup(rH,Jup) and rSat(rH,Sat) are the Jovian and Saturnian (Hill) radius, respectively. The surface density has a peak in these regions due to the balance between centrifugal force and gravity of the protoplanet. The size of these discs corresponds well to the outermost orbit of regular satellites around Jupiter and Saturn. Regular satellites may form in such compact discs around proto-gas giant planets. [source] The impact of radio feedback from active galactic nuclei in cosmological simulations: formation of disc galaxiesMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2008Takashi Okamoto ABSTRACT In this paper, we present a new implementation of feedback due to active galactic nuclei (AGN) in cosmological simulations of galaxy formation. We assume that a fraction of jet energy, which is generated by an AGN, is transferred to the surrounding gas as thermal energy. Combining a theoretical model of mass accretion on to black holes with a multiphase description of star-forming gas, we self-consistently follow evolution of both galaxies and their central black holes. The novelty in our model is that we consider two distinct accretion modes: standard radiatively efficient thin accretion discs and radiatively inefficient accretion flows which we will generically refer to as RIAFs; motivated by theoretical models for jet production in accretion discs, we assume that only the RIAF is responsible for the AGN feedback. The focus of this paper is to investigate the interplay between galaxies and their central black holes during the formation of a disc galaxy. We find that, after an initial episode of bursting star formation, the accretion rate on to the central black hole drops so that the accretion disc switches to a RIAF structure. At this point, the feedback from the AGN becomes efficient and slightly suppresses star formation in the galactic disc and almost completely halts star formation in the bulge. This suppression of the star formation regulates mass accretion on to the black hole and associated AGN feedback. As a result, the nucleus becomes a stochastically fuelled low-luminosity AGN (Seyfert galaxy) with recurrent short-lived episodes of activity after the star bursts. During the ,on' events, the AGN produces reasonably powerful jets (radio-loud state) and is less luminous than the host galaxy, while in the ,off' phase, the nucleus is inactive and ,radio quiet'. Our model predicts several properties of the low-luminosity AGN including the bolometric luminosity, jet powers, the effect on kpc scale of the radio jet and the AGN lifetime, which are in broad agreement with observations of Seyfert galaxies and their radio activity. We also find that the ratios between the central black hole mass and the mass of the host spheroid at z= 0 are ,10,3 regardless of the strength of either supernova feedback or AGN feedback because the radiation drag model directly relates the star formation activity in the Galactic Centre and the mass accretion rate on to the central black hole. [source] Quenching cluster cooling flows with recurrent hot plasma bubblesMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 3 2004Claudio Dalla Vecchia ABSTRACT The observed cooling rate of hot gas in clusters is much lower than that inferred from the gas density profiles. This suggests that the gas is being heated by some source. We use an adaptive-mesh refinement code (flash) to simulate the effect of multiple, randomly positioned, injections of thermal energy within 50 kpc of the centre of an initially isothermal cluster with mass M200= 3 × 1014 M, and kT= 3.1 keV. We have performed eight simulations with spherical bubbles of energy generated every 108 yr, over a total of 1.5 Gyr. Each bubble is created by injecting thermal energy steadily for 107 yr; the total energy of each bubble lies in the range (0.1,3) ×1060 erg, depending on the simulation. We find that 2 × 1060 erg per bubble (corresponding to an average power of 6.3 × 1044 erg s,1) effectively balances energy loss in the cluster and prevents the accumulation of gas below kT= 1 keV from exceeding the observational limits. This injection rate is comparable to the radiated luminosity of the cluster, and the required energy and periodic time-scale of events are consistent with observations of bubbles produced by central active galactic nuclei in clusters. The effectiveness of this process depends primarily on the total amount of injected energy and the initial location of the bubbles, but is relatively insensitive to the exact duty cycle of events. [source] The temperature of the intergalactic medium and the Compton y parameterMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2004Pengjie Zhang ABSTRACT The thermal Sunyaev,Zeldovich (SZ) effect directly probes the thermal energy of the Universe. Its precision modelling and future high-accuracy measurements will provide a powerful way to constrain the thermal history of the Universe. In this paper, we focus on the precision modelling of the gas density weighted temperature and the mean SZ Compton y parameter. We run high-resolution adiabatic hydrodynamic simulations adopting the WMAP cosmology to study the temperature and density distribution of the intergalactic medium (IGM). To quantify possible simulation limitations, we run n=,1, , 2 self-similar simulations. Our analytical model on is based on energy conservation and matter clustering and has no free parameter. Combining both simulations and analytical models thus provides the precision modelling of and . We find that the simulated temperature probability distribution function and shows good convergence. For the WMAP cosmology, our highest-resolution simulation (10243 cells, 100 Mpc h,1 box size) reliably simulates with better than 10 per cent accuracy for z, 0.5. Toward z= 0, the simulation mass-resolution effect becomes stronger and causes the simulated to be slightly underestimated (at z= 0, ,20 per cent underestimated). Since is mainly contributed by the IGM at z, 0.5, this simulation effect on is no larger than ,10 per cent. Furthermore, our analytical model is capable of correcting this artefact. It passes all tests of self-similar simulations and WMAP simulations and is able to predict and to several per cent accuracy. For a low matter density ,CDM cosmology, the present is 0.32 (,8/0.84)(,m/0.268) keV, which accounts for 10,8 of the critical cosmological density and 0.024 per cent of the cosmic microwave background (CMB) energy. The mean y parameter is 2.6 × 10,6 (,8/0.84)(,m/0.268). The current upper limit of y < 1.5 × 10,5 measured by FIRAS has already ruled out combinations of high ,8, 1.1 and high ,m, 0.5. [source] Protein Matrix Elasticity Determined by Fluorescence Anisotropy of Its Tryptophan Residues,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 1 2003Christian Zentz ABSTRACT Rotational motions of Trp residues embedded within human hemoglobin matrix have been measured by using their steady-state fluorescence anisotropy. The mean square angular displacement ,2 of Trp residues, depending on the temperature, can be expressed by where W is the thermal energy acting on the Trp residues and C the resilient torque constant of the protein matrix. To study the external medium influencing the protein dynamics, comparative experiments were made with protein in aqueous buffer and in the presence of 32% glycerol. The data show that between 5°C and 25°C, external medium acts on the protein matrix elasticity. [source] Spin-filtering effect in a two-dimensional electron gas under a local fringe fieldPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 12 2007Seon-Gu Huh Abstract We fabricated a spin-filtering device which consists of InAs based two-dimensional electron gas and two ferromagnetic pads. A fringe field at the edge of a ferromagnetic pad was used to induce spin polarization of the moving electrons in a two-dimensional electron gas. The direction of the fringe field was determined by the magnetization of the ferromagnetic pad, which was switched by using the external magnetic field. A current of which spins were aligned by one fringe field (polarizer) was filtered by the other fringe field (analyzer). The resistance of the device was in either a high state or a low state depending on the alignment of the fringe fields. The spin-filtering effect diminishes rapidly as the thermal energy exceeds the Zeeman splitting. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Temperature dependence of carrier traps in high sensitivity HARP photoconductive filmPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue S1 2009Yuji Ohkawa Abstract Amorphous selenium (a-Se) avalanche multiplication photoconductive film, what we call HARP (high-gain avalanche rushing amorphous photoconductor) photoconductive film, has been investigated for the purpose of reporting breaking news at night and producing nature and science programs. The purpose of our work is to develop more sensitive HARP films with high reliability. 15-,m-thick HARP film with an avalanche multiplication factor of about 200 that is thicker and more sensitive than the previous 8-,m-thick one has been studied. However, the thick film has a problem that defects easily occurred during shooting of intense spot lights. The defects are caused by trapped electrons which makes an enhanced internal electric field around the incident light side interface of the film. Defects are suppressed by operating the film at high temperatures, because the thermal energy releases the trapped electrons. This paper describes the relationship between the defect occurrence and the temperature dependence of carries trap in the film. To investigate it, the defect occurrence and dark current characteristics were measured. As a result, it was found that the number of released electrons exceeds that of trapped ones at temperatures over 28.5 °C and that defect occurrence is suppressed by operating the film at over 27.5 °C. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Time-resolved photoluminescence and steady-state optical studies of GaInNAs and GaInAs single quantum wellsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 2 2007Y. Sun Abstract Time-resolved photoluminescence spectroscopy is used to investigate carrier dynamics of Ga1,xInxNyAs1,y (x , 0.33, y , 0.01) single quantum well (QW) structures. PL spectra measured as a function of temperature together with the PL decay times at wavelengths around and below the PL peak energy are used to determine de-trapping activation energies and time constants. The results are interpreted in terms of simultaneous thermal excitation of deep localized excitons to shallow localized states. According to the model, with increasing temperatures, localized excitons gain enough thermal energy to populate the free exciton states in quantum well with shorter lifetimes due to coherent nature of free excitons. In addition, at temperatures around and above 80 K, more non-radiative channels become available to compete with the radiative processes leading to shorter time constants. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Structure of reactively extruded rigid PVC/PMMA blendsPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 6 2005Y. Haba Abstract A novel route for producing polymer blends by reactive extrusion is described, starting from poly (vinyl chloride)/methyl methacrylate (PVC/MMA) dry blend and successive polymerization of MMA in an extruder. Small angle X-ray scattering (SAXS) measurements were applied to study the monomer's mode of penetration into the PVC particles and to characterize the supermolecular structure of the reactive poly(vinyl chloride)/poly(methyl methacrylate) (PVC/PMMA) blends obtained, as compared to the corresponding physical blends of similar composition. These measurements indicate that the monomer molecules can easily penetrate into the PVC sub-primary particles, separating the PVC chains. Moreover, the increased mobility of the PVC chains enables formation of an ordered lamellar structure, with an average d -spacing of 4.1,nm. The same characteristic lamellar structure is further detected upon compression molding or extrusion of PVC and PVC/PMMA blends. In this case the mobility of the PVC chains is enabled through thermal energy. Dynamic mechanical thermal analysis (DMTA) and SAXS measurements of reactive and physical PVC/PMMA blends indicate that miscibility occurs between the PVC and PMMA chains. The studied reactive PVC/PMMA blends are found to be miscible, while the physical PVC/PMMA blends are only partially miscible. It can be suggested that the miscible PMMA chains weaken dipole,dipole interactions between the PVC chains, leading to high mobility and resulting in an increased PVC crystallinity degree and decreased PVC glass transition temperature (Tg). These phenomena are shown in the physical PVC/PMMA blends and further emphasized in the reactive PVC/PMMA blends. Copyright © 2005 John Wiley & Sons, Ltd. [source] Effects of Viscous Dissipation on Heat Transfer between an Array of Long Circular Cylinders and Power Law FluidsTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 6 2007R. P. Chhabra Abstract The free surface model has been combined with the equations of motion and of thermal energy to investigate the role of viscous dissipation on heat transfer between banks of long cylinders and power law (shear-thinning and shear-thickening) fluids. The equations of motion cast in the stream function/vorticity formulation have been solved numerically using a second-order accurate finite difference method to obtain extensive information on the behaviour of local and surface-averaged Nusselt numbers over a range of Reynolds numbers 1 , 500, for a wide range of power law indices (0.4 , n , 2.0), Brinkman numbers (0 , Br , 5) and Prandtl numbers (Pr = 1, 1000) at two representative solid volume fractions corresponding to the porosities of e = 0.4 and 0.9. Two different thermal boundary conditions are considered at the cylinder surface: constant temperature (CT) and constant heat flux (CHF). The results presented herein provide a fundamental knowledge about the influence of viscous dissipation on the heat transfer characteristics. The results reported herein further show that the effect of Brinkman number on heat transfer is strongly conditioned by the thermal boundary condition, Prandtl number and the power law index. On a combiné le modèle de surface libre aux équations de mouvement et de transfert de chaleur afin d'étudier le rôle de la dissipation visqueuse sur le transfert de chaleur entre des rangées de cylindres longs pour des fluides de loi de puissance (rhéofluidifiants et rhéoépaississants). Les équations de mouvement formulées en fonction de courant/vorticité ont été résolues numériquement à l'aide d'une méthode de différences finies du second ordre, afin d'obtenir des informations détaillées sur le comportement des nombres de Nusselt locaux et moyennés en surface pour une gamme de nombres de Reynolds compris entre 1 et 500, une large gamme d'indices de loi de puissance (0,4 , n , 2,0), de nombres de Brinkman (0 , Br , 5) et de nombres de Prandtl (Pr = 1,1000) à deux fractions de volume de solides correspondant à une porosité de e = 0,4 et 0,9. Deux conditions aux limites thermiques ont été considérées à la surface du cylindre: la température constante (CT) et le flux de chaleur constant (CHF). Les résultats présentés permettent de rendre compte de l'influence de la dissipation visqueuse sur les caractéristiques du transfert de chaleur et l'effet du nombre de Brinkman sur le transfert de chaleur qui est fortement influencé par la condition aux limites thermique, le nombre de Prandtl et l'indice de loi de puissance. [source] Soret Diffusion and Non-Ideal Dufour Conduction in Macroporous Catalysts with Exothermic Chemical Reaction at Large Intrapellet Damköhler NumbersTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 3 2007Laurence A. Belfiore Abstract The adiabatic temperature rise in catalytic pellets is predicted from a modified version of the Prater equation. Onsager reciprocal relations for coupled heat and mass transfer are violated in an analysis of thermal diffusion in macroporous catalysts with exothermic chemical reaction when Dufour conduction (i.e., the diffusion-thermo effect) is neglected. In this contribution, Dufour conduction is analyzed for both ideal and non-ideal pseudo-binary gas mixtures that simulate the production of methanol from carbon monoxide and hydrogen. In the diffusion-controlled regime at large intrapellet Damköhler numbers where intermolecular collisions provide the dominant resistance to mass transfer within the catalytic pores, temperatures in the catalytic core could be much greater than predictions based on the original Prater equation when the Prater number exceeds 0.30. The molecular flux of thermal energy includes Fourier's law, the interdiffusional flux, and Dufour conduction. Diffusional mass flux includes Fick's law and the Soret effect. All physicochemical properties of the reactive gas mixture exhibit temperature dependence. There is essentially no difference between maximum intrapellet temperature predictions that include or neglect ideal Dufour conduction when external catalytic surface temperatures range from 300-400 K and thermal diffusion enhances the flux of "smaller" reactants toward the centre of the catalyst. For "large-molecule reactants" that participate in exothermic reactions, thermal diffusion opposes Fick's law and Dufour conduction opposes Fourier's law. Under these conditions, it is demonstrated that core temperatures are overestimated by neglecting both off-diagonal coupling mechanisms (i.e., Soret diffusion and Dufour conduction). Prater numbers greater than unity and unrealistically high gas pressures are required to distinguish between maximum intrapellet temperatures for ideal and real gas simulations, where the latter consider two-body interactions for Lennard-Jones molecules in the virial equation of state. On prédit l'augmentation de la température adiabatique dans les pastilles catalytiques à partir d'une version modifiée de l'équation de Prater. Les relations réciproques d'Onsager pour le transfert de chaleur et de matière couplé sont violées dans une analyse de la diffusion thermique dans les catalyseurs macroporeux avec réaction chimique exothermique lorsque la conduction de Dufour (p.ex., l'effet de thermo-diffusion) est négligée. Dans cet article, on analyse la conduction de Dufour pour des mélanges de gaz pseudo-binaires idéaux et non idéaux qui simulent la production de méthanol à partir d'oxyde de carbone et d'hydrogène. Dans le régime à diffusion contrôlée à grand nombre de Damköhler entre les pastilles pour lesquels les collisions entre les molécules fournit la résistance dominante au transfert de matière à l'intérieur des pores catalytiques, les températures dans le noyau catalytique pourraient être bien plus grandes que les prédictions basées sur l'équation de Prater originale lorsque le nombre de Prater excède 0,30. Le flux moléculaire de l'énergie thermique inclut la loi de Fourier, le flux interdiffusionnel, et la conduction de Dufour. Le flux massique diffusionnel inclut la loi de Fick et l'effet Soret. Toutes les propriétés physicochimiques du mélange de gaz réactif montre une dépendance thermique. Il n'y a essentiellement pas de différence entre les prédictions des températures maximales entre les pastilles qui incluent ou négligent la conduction de Dufour idéale quand les températures de surface catalytiques externes sont comprises entre 300 et 400 K; la diffusion thermique améliore le flux des réactifs «plus petits» vers le centre du catalyseur. Pour les «réactifs composés de grandes molécules» qui participent aux réactions exothermiques, la diffusion thermique s'oppose à la loi de Fick et la conduction de Dufour à la loi de Fourier. Dans ces conditions, il est démontré que les températures de noyau sont surestimées en négligeant les deux mécanismes de couplage hors-diagonales (c.à-d. la diffusion de Soret et la conduction de Dufour). Des nombres de Prater plus grands que l'unité et des pressions de gaz élevées peu réalistes sont nécessaires pour distinguer les températures maximales entre les pastilles entre les simulations de gaz idéales et réelles, en considérant pour ces dernières les interactions à deux corps pour les molécules de Lennard-Jones dans l'équation d'état du viriel. [source] Energy scavenging for energy efficiency in networks and applicationsBELL LABS TECHNICAL JOURNAL, Issue 2 2010Kyoung Joon Kim Telecommunication networks will play a huge part in enabling eco-sustainability of human activity; one of the first steps towards this is to dramatically increase network energy efficiency. In this paper we present two novel approaches for energy scavenging in networks. One involves thermal energy scavenging for improving wireless base station energy efficiency, and the other involves mechanical energy scavenging for powering sensors in sensor networks, for machine-to-machine (M2M) communications, and for smart grid applications. Power amplifier (PA) transistors in base stations waste 30 percent of the total energy used in a wireless access network (WAN) as heat to the environment. We propose a thermoelectric energy recovery module (TERM) to recover electricity from the waste heat of PA transistors. A fully coupled thermoelectric (TE) model, combining thermoelectricity and heat transfer physics, is developed to explore the power generation performance and efficiency as well as the thermal performance of the TERM. The TE model is comprehensively used to determine optimized pellet geometries for power generation and efficiency as a function of PA transistor heat dissipation, heat sink performance, and load resistance. Maximum power generation and efficiency for various parametric conditions are also explored. Untapped kinetic energy is almost everywhere in the form of vibrations. This energy can be converted into electrical energy by means of transducers to power wireless sensors and mobile electronics in the range of microwatts to a few milliwatts. However, many problems limit the efficiency of current harvesting generators: narrow bandwidth, low power density, micro-electro-mechanical system (MEMS) scaling, and inconsistency of vibrating sources. We explore energy scavenger designs based on multiple-mass systems to increase harvesting efficiency. A theoretical and experimental study of two degrees-of-freedom (2-DOF) vibration-powered generators is presented. Both electromagnetic and piezoelectric conversion methods are modeled by using a general approach. Experimental results for the multi-resonant system are in agreement with the analytical predictions and demonstrate significantly better performance in terms of maximum power density per total mass and a wider bandwidth compared to single DOF (1-DOF) generators. © 2010 Alcatel-Lucent. [source] Non-thermal cytocidal effect of infrared irradiation on cultured cancer cells using specialized deviceCANCER SCIENCE, Issue 6 2010Yohei Tanaka As infrared penetrates the skin, thermal effects of infrared irradiation on cancer cells have been investigated in the field of hyperthermia. We evaluated non-thermal effects of infrared irradiation using a specialized device (1100,18000 nm with filtering of wavelengths between 1400 and 1500 nm and contact cooling) on cancer cells. In in vitro study, five kinds of cultured cancer cell lines (MCF7 breast cancer, HeLa uterine cervical cancer, NUGC-4 gastric cancer, B16F0 melanoma, and MDA-MB435 melanoma) were irradiated using the infrared device, and then the cell proliferation activity was evaluated by 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) assay. Proliferation of all the cancer cell lines was significantly suppressed by infrared irradiation. Total infrared output appeared to be correlated with cell survival. Increased temperature during infrared irradiation appeared not to play a role in cell survival. The maximum temperature elevation in the wells after each shot in the 20 and 40 J/cm2 culture was 3.8°C and 6.9°C, respectively. In addition, we have shown that infrared irradiation significantly inhibited the tumor growth of MCF7 breast cancer transplanted in severe combined immunodeficiency mice and MDA-MB435 melanoma transplanted in nude mice in vivo. Significant differences between control and irradiated groups were observed in tumor volume and frequencies of TUNEL-positive and Ki-67-positive cells. These results indicate that infrared, independent of thermal energy, can induce cell killing of cancer cells. As this infrared irradiation schedule reduces discomfort and side effects, reaches the deep subcutaneous tissues, and facilitates repeated irradiations, it may have potential as an application for treating various forms of cancer. (Cancer Sci 2010) [source]
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