The surface and atmospheric heating fields over the Qinghai-Xizang Plateau are computed by using the observational data of solar radiation during 1982—1983.The mian results are as follows:The central and northern par...The surface and atmospheric heating fields over the Qinghai-Xizang Plateau are computed by using the observational data of solar radiation during 1982—1983.The mian results are as follows:The central and northern parts of the Plateau act as heat sinks in winter from November to January.Both eastern and south- ern parts of the Plateau are of heat sources.In summer,the main part of the Plateau acts as a strong heat source,and the center of the heating field is in the southeastern Plateau.However the main part of the Plateau acts as a heat sink for the atmospheric heating fields from October to March.The maximum intensity of the atmospheric heat sink over the central Plateau appears in December and January.From April to September,the main part of the Plateau acts as a heat source for the atmospheric heating fields.展开更多
The structure and seasonal variation of the East Asian Subtropical Westerly Jet （EAWJ） and associations with heating fields over East Asia are examined by using NCEP/NCAR reanalysis data. Obvious differences exist i...The structure and seasonal variation of the East Asian Subtropical Westerly Jet （EAWJ） and associations with heating fields over East Asia are examined by using NCEP/NCAR reanalysis data. Obvious differences exist in the westerly jet intensity and location in different regions and seasons due to the ocean-land distribution and seasonal thermal contrast, as well as the dynamic and thermodynamic impacts of the Tibetan Plateau. In winter, the EAWJ center is situated over the western Pacific Ocean and the intensity is reduced gradually from east to west over the East Asian region. In summer, the EAWJ center is located over the north of the Tibetan Plateau and the jet intensity is reduced evidently compared with that in winter. The EAWJ seasonal evolution is characterized by the obvious longitudinal inconsistency of the northward migration and in-phase southward retreat of the EAWJ axis. A good correspondence between the seasonal variations of EAWJ and the meridional differences of air temperature （MDT） in the mid-upper troposphere demonstrates that the MDT is the basic reason for the seasonal variation of EAWJ. Correlation analyses indicate that the Kuroshio Current region to the south of Japan and the Tibetan Plateau are the key areas for the variations of the EAWJ intensities in winter and in summer, respectively. The strong sensible and latent heating in the Kuroshio Current region is closely related to the intensification of EAWJ in winter. In summer, strong sensible heating in the Tibetan Plateau corresponds to the EAWJ strengthening and southward shift, while the weak sensible heating in the Tibetan Plateau is consistent with the EAWJ weakening and northward migration.展开更多
In this study, a parameterization scheme based on Moderate Resolution Imaging Spectroradiometer （MODIS） data and in-situ data was tested for deriving the regional surface heating field over a heterogeneous landscape...In this study, a parameterization scheme based on Moderate Resolution Imaging Spectroradiometer （MODIS） data and in-situ data was tested for deriving the regional surface heating field over a heterogeneous landscape. As a case study, the methodology was applied to the whole Tibetan Plateau （TP） area. Four images of MODIS data （i.e., 30 January 2007, 15 April 2007, 1 August 2007, and 25 October 2007） were used in this study for comparison among winter, spring, summer, and autumn. The results were validated using the observations measured at the stations of the Tibetan Observation and Research Platform （TORP）. The results show the following： （1） The derived surface heating field for the TP area was in good accord with the land-surface status, showing a wide range of values due to the strong contrast of surface features in the area. （2） The derived surface heating field for the TP was very close to the field measurements （observations）. The APD （absolute percent difference） between the derived results and the field observations was 〈10%. （3） The mean surface heating field over the TP increased from January to April to August, and decreased in October. Therefore, the reasonable regional distribution of the surface heating field over a heterogeneous landscape can be obtained using this methodology. The limitations and further improvement of this method are also discussed.展开更多
Microwave-induced substitutional combustion reaction was utilized to fabricate porous ceramic composite from Fe_3O_4/Al powder mixtures.The porous composite body was obtained by controlling the combustion reaction pro...Microwave-induced substitutional combustion reaction was utilized to fabricate porous ceramic composite from Fe_3O_4/Al powder mixtures.The porous composite body was obtained by controlling the combustion reaction progress in a 2.45 GHz single mode applicator.Prior to the fabrication of the porous body,heating behavior of the powder mixtures were studied in the separated electric(E)and magnetic(H)fields.In addition,heating ability of the microwave fabricated porous product was also investigated.Fe_3O_4 powder can be heated up easily in both maximum H and E field, but a better heating was observed in the maximum H field.Regardless of the mixtures ratio(mixing compositions), maximum H field shows better heating characteristics.In E-field heating,temperature of the Fe_3O_4 samples decreased sharply when Al powder was added.However,the same phenomenon was not observed in the maximum H field heating. Thus,fabrication of the porous composite body was carrying out in maximum H field.Through an adequate control of the reaction progress,products with a porous structure consisting of well-distributed metal particles in the alumina and/or hercynite matrix were obtained.Consequently,heating of the fabricated porous composite body was also been successfully carried out in the maximum H field.Product phases and microstructure were the main factors influencing the heating ability of the porous composite body.展开更多
The mathematic model of heating chamber for implementing the prediction of the annealing craft and improving the self adapting with the expansion of the new annealing furnace form, new annealing crafts and new kinds o...The mathematic model of heating chamber for implementing the prediction of the annealing craft and improving the self adapting with the expansion of the new annealing furnace form, new annealing crafts and new kinds of steel coil has been established. The model developed which including the temperature for gas in heating chamber and the heating cover is based on the characteristics of anneal craft and the situations of locale production run. Firstly, the characteristic of the heating cover which limits the temperature was considered. Secondly, the locale production run condition and dispatching condition were considered. Finally, combining with the models and the simulation system, the numerical simulation research of the anneal process for the high performance hydrogen bell-type annealer as well as the spot experiment test were carried out. The results obtained from the developed models, usually finished less than thirty seconds, are in fair agreement with the test values, such as the relative errors of annealing times were within ±5%, and the quality＇ of the annealed steels were guaranteed.展开更多
By use of the NCEP/ NCAR reanalysis data, the seasonal variation of the South Asia high (SAH) is analyzed. The influences of temporal and spatial variations of the middle and upper level atmospheric temperatures, the ...By use of the NCEP/ NCAR reanalysis data, the seasonal variation of the South Asia high (SAH) is analyzed. The influences of temporal and spatial variations of the middle and upper level atmospheric temperatures, the visible heat sources, and the diabatic heating rates in the whole atmospheric column on the seasonal variation of the SAH are discussed. Results show that the SAH has two seasonal balancing modes, one of which is the land high in summer and the other the ocean high in winter. The land high itself can be divided into two patterns as well, that is the Tibetan high and the Iranian high. Heating fields have important impacts on the seasonal variation of the SAH. The SAH is a warm high and its center has the property of heat preference, usually locating over or moving to an area with relatively larger heating rates. The annual cycle of the SAH is mainly controlled by the seasonal process of the latent and sensible heating in South Asia. Strong shortwave radiative heating in the north at high latitudes and over the Tibetan Plateau also has an effects on the northward movement and maintenance of the SAH. The cooling effect of infrared radiation is an important cause in weakening the SAH.展开更多
In this paper, variations of surface water flow and its climatic causes in China are analyzed using hydrological and meteorological observational data, as well as the impact data set （version 2.0） published by the N...In this paper, variations of surface water flow and its climatic causes in China are analyzed using hydrological and meteorological observational data, as well as the impact data set （version 2.0） published by the National Climate Center in November 2009. The results indicate that surface water resources showed an increasing trend in the source region of the Yangtze River over the past 51 years, especially after 2004. The trend was very clearly shown, and there were quasi-periods of 9 years and 22 years, where the Tibetan Plateau heating field enhanced the effect, and the plateau monsoon entered a strong period. Precipitation notably increased, and glacier melt water increased due to climate change, all of which are the main climatic causes for increases in water resources in the source region. Based on global climate model prediction, in the SRESA1B climate change scenarios, water resources are likely to increase in this region for the next 20 years.展开更多
A new numerical technique named interval finite difference method is proposed for the steady-state temperature field prediction with uncertainties in both physical parameters and boundary conditions. Interval variable...A new numerical technique named interval finite difference method is proposed for the steady-state temperature field prediction with uncertainties in both physical parameters and boundary conditions. Interval variables are used to quantitatively describe the uncertain parameters with limited information. Based on different Taylor and Neumann series, two kinds of parameter perturbation methods are presented to approximately yield the ranges of the uncertain temperature field. By comparing the results with traditional Monte Carlo simulation, a numerical example is given to demonstrate the feasibility and effectiveness of the proposed method for solving steady-state heat conduction problem with uncertain-but-bounded parameters.展开更多
The flow field and heat transfer of the strip surface due to the twin slot vertical jet impingement were investigated using the ANSYS FLUENT.The RNG k-ε model was carried out in the turbulent calculation.Systematic p...The flow field and heat transfer of the strip surface due to the twin slot vertical jet impingement were investigated using the ANSYS FLUENT.The RNG k-ε model was carried out in the turbulent calculation.Systematic parametric research was conducted by varying the jet velocity of nozzle exit(V=5 m/s,7.5 m/s,10 m/s),the temperature of cooling water(T_w=280 K,300 K),the normalized spacing from the nozzle to the strip surface(H=10,15,20,33),and the normalized spacing from the nozzle to nozzle centerline(W=0,15,30).The velocity streamline of the flow domain and the general trend of the distribution of the local Nusselt number on the impingement surface of strip were obtained.The result indicate that,the average Nusselt number increases by about70%(90%) as the jet velocity is increased from 5 m/s to 7.5 m/s(from 7.5 m/s to 10 m/s),and T_w,Hand//have minimal effect on it.While the valley Nusselt number decreases by about 10%-43%with the increase of H and W.The functional relationship between the average Nusselt number and the systematic parameters is derived by the least square regression method.展开更多
Through the experiments and the numerical simulation of temperature field in multi-heatsource synthesis Si C furnace, in order to research the feature point in multi-heat-source synthesis furnace, the variation law of...Through the experiments and the numerical simulation of temperature field in multi-heatsource synthesis Si C furnace, in order to research the feature point in multi-heat-source synthesis furnace, the variation law of heat fl ux was studied and the multi-directional energy fl ow diffusion mechanism was revealed. The results show that, due to the shielding action between the heat-source and the superposition effect of thermal fields, the insulating effect is best in multi-heat-source synthesis furnace. The heat emission effect is good outside the common area between heat-sources, but the heat storage is poor. Compared with the synthesis furnace that heat source is parallelly arranged, the furnace of stereoscopic arrangement has a more obvious heat stacking effect and better heat preservation effect, but the air permeability of heat source connecting regions is worse. In the case with the same ingredients, the resistance to thermal diffusion and mass diffusion is higher in heat source connecting regions.展开更多
Temperature-time curves were measured for the air cooling and laminar cooling of a steel plate.Convective heat transfer coefficients of steel plate and air as well as steel plate and laminar cooling water were compute...Temperature-time curves were measured for the air cooling and laminar cooling of a steel plate.Convective heat transfer coefficients of steel plate and air as well as steel plate and laminar cooling water were computed inversely. Therefore,the temperature field in the single-face quenching process of a steel pipe was simulated using ABAQUS finite element softw are,and the relationships betw een the temperatures and quenching time at different positions of the steel pipe were obtained. In addition,the relationships betw een the cooling rates and quenching time,as w ell as betw een cooling rates and temperatures,were obtained. The simulation quickly produced accurate results,and it can be used to optimize the quenching process. In addition,the results provide a basis for rationally designing the composition of a single-face quenching steel pipe.展开更多
The effects of ozone on the summer atmospheric general circulation are simulated by use of a zonal model with the pesigma coordinate system. Results show that the simulated properties at the upper levels are remarkabl...The effects of ozone on the summer atmospheric general circulation are simulated by use of a zonal model with the pesigma coordinate system. Results show that the simulated properties at the upper levels are remarkably improved after the ozone effects are introduced to the model. The direct effect of ozone is to enhance the heating rates at the upper levels. In the lower atmosphere. this effect is very little. Furthermore, the ozone can change the distributions and values of other components of heating fields, resulting in the change of the total heating rates, and meanwhile induce evident variation of atmospheric circulation at the lower levels.展开更多
In the present work,Ce_(17)Fe_(76.5)Co_1Zr_(0.5)B_6 ribbons were prepared by a direct melt spinning method.The effects of chamber pressure and magnetic field annealing temperature on the magnetic properties and micros...In the present work,Ce_(17)Fe_(76.5)Co_1Zr_(0.5)B_6 ribbons were prepared by a direct melt spinning method.The effects of chamber pressure and magnetic field annealing temperature on the magnetic properties and microstructures of the alloys were investigated.The grain size and content of Ce_(2)Fe_(14)B phase can be changed by adjusting the chamber pressure,and the optimal magnetic performance is obtained at0.04 MPa.The magnetic properties can be influenced under magnetic field heat treatment.When the annealing temperature is lower than the Curie temperature,the refinement and a uniform distribution of the grains is obtained.The irreversible magnetic susceptibility curve reveals that magnetic field heat treatment enhances the exchange coupling interaction between grains of the Ce_(2)Fe_(14)B phase.When the magnetic field annealing temperature is 438 K,the alloy displays the optimal magnetic properties.Compared with the as-spun sample,the values of intrinsic coercivity(H_(ci)),remanence(B_r) and maximum energy product((BH)max) increase by 3.4%,9.8% and 18.7%,respectively.This work provides an effective approach by which to enhance the magnetic properties of Ce-Fe-B alloys.展开更多
The thermal treatment process of cold-rolled Cu-Al composite strip under magnetic field conditions is systematically investigated by means of metallographic microscope and universal testing machine to observe the inte...The thermal treatment process of cold-rolled Cu-Al composite strip under magnetic field conditions is systematically investigated by means of metallographic microscope and universal testing machine to observe the interface microstructure and test the mechanical properties.The heat treatment parameters' effects to the interface structure and mechanical properties of Al-Cu cold-rolled strip are discussed.The conclusions is showed as follows:(1)when the magnetic field intensity is greater than 0.1 T,the interface layer grow widely and stimulate the interfacial compounds' generation,the shear strength is reduced.(2)When the Cu-Al specimen's annealing temperature is at the condition of 300℃,the interfacial layer narrows when the magnetic field strength stay 0.1T than that without magnetic field,the magnetic filed restrains the interfacial compounds' generation,the shear strength reaches as high as 124Mpa;(3)The interfacial compounds are meanly brittleness intermetallic compounds such as CuAl,CuAl_2,Cu_9Al.展开更多
The study of heat transfer is of significant importance in many biological and biomedical industry problems.This investigation comprises of the study of entropy generation analysis of the blood flow in the arteries wi...The study of heat transfer is of significant importance in many biological and biomedical industry problems.This investigation comprises of the study of entropy generation analysis of the blood flow in the arteries with permeable walls. The convection through the flow is studied with compliments to the entropy generation. Governing problem is formulized and solved for low Reynold's number and long wavelength approximations. Exact analytical solutions have been obtained and are analyzed graphically. It is seen that temperature for pure water is lower as compared to the copper water. It gains magnitude with an increase in the slip parameter.展开更多
Through the comparison of calcination conditions between cement preclinkering technology and cement precalcining technology,we studied the characteristics of temperature field distribution of cement preclinkering tech...Through the comparison of calcination conditions between cement preclinkering technology and cement precalcining technology,we studied the characteristics of temperature field distribution of cement preclinkering technology systems including cyclone preheater,preclinkering furnace,and rotary kiln.We used numericalsimulation method to obtain data of temperature field distribution.Some results are found by system study.The ratio of tailcoalof cement preclinkering technology is about 70%,and raw mealtemperature can reach 1070 ℃.Shorter L/D kiln type of preclinkering technology can obtain more stable calcining zone temperature.The highest solid temperature of cement preclinkering technology is higher than 80 ℃,and high temperature region（〉1450 ℃）length is 2 times,which is beneficialfor calcining clinker and higher clinker quality.So cement preclinkering technology can obtain more performance temperature filed,which improves both the solid-phase reaction and liquid-phase reaction.展开更多
Miniaturization of electronic package leads to high heat density and heat accumulation in electronics device, resulting in short life time and premature failure of the device. Junction temperature and thermal resistan...Miniaturization of electronic package leads to high heat density and heat accumulation in electronics device, resulting in short life time and premature failure of the device. Junction temperature and thermal resistance are the critical parameters that determine the thermal management and reliability in electronics cooling. Metal oxide field effect transistor（MOSFET）is an important semiconductor device for light emitting diode-integrated circuit（LED IC） driver application, and thermal management in MOSFET is a major challenge. In this study, investigations on thermal performance of MOSFET are performed for evaluating the junction temperature and thermal resistance. Suitable modifications in FR4 substrates are proposed by introducing thermal vias and copper layer coating to improve the thermal performance of MOSFET. Experiments are conducted using thermal transient tester（T3ster） at 2.0 A input current and ambient temperature varying from25℃ to 75℃. The thermal parameters are measured for three proposed designs： FR4 with circular thermal vias, FR4 with single strip of copper layer and embedded vias, and FR4 with I-shaped copper layer, and compared with that of plain FR4 substrate. From the experimental results, FR4I-shaped shows promising results by 33.71% reduction in junction temperature and 54.19% reduction in thermal resistance. For elevated temperature, the relative increases in junction temperature and thermal resistance are lower for FR4I-shaped than those for other substrates considered. The introduction of thermal vias and copper layer plays a significant role in thermal performance.展开更多
In this paper,a primitive equation linear wave model is used to examine the effects of three-dimen- sional structure of heating field on the behavior of stationary planetary waves in summer and to compare the roles of...In this paper,a primitive equation linear wave model is used to examine the effects of three-dimen- sional structure of heating field on the behavior of stationary planetary waves in summer and to compare the roles of different heating functions for the formation and maintenance of summer monsoon circulation in Asia.It is shown that the aloft heating connected with the latent heating,especially the deep condensation heating associated with the cumulus convection in low latitudes,plays a crucial part in the Asian summer mon- soon and the structures of planetary wave responses are quite sensitive to the vertical distribution of heating.展开更多
To reach the target of smaller pressure drop and better heat transfer performance, packed beds with small tube-to-particle diameter ratio(D/dp<10) have now been considered in many areas. Fluid-to-wall heat transfer...To reach the target of smaller pressure drop and better heat transfer performance, packed beds with small tube-to-particle diameter ratio(D/dp<10) have now been considered in many areas. Fluid-to-wall heat transfer coefficient is an important factor determining the performance of this type of beds. In this work, local fluid-to-wall heat transfer characteristic in packed beds was studied by Computational Fluid Dynamics(CFD) at different Reynolds number for D/dp=1.5, 3.0 and 5.6. The results show that the fluid-to-wall heat transfer coefficient is oscillating along the bed with small tube-to-particle diameter ratio. Moreover, this phenomenon was explained by field synergy principle in detail. Two arrangement structures of particles in packed beds were recommended based on the synergy characteristic between flow and temperature fields. This study provides a new local understanding of fluid-to-wall heat transfer in packed beds with small tube-to-particle diameter ratio.展开更多
This paper deals with the study of experimental current intensity/voltage characteristicsof a free burning arc that appears to be singular:At low intensity current,the arc voltagedecreases until a minimum value,corres...This paper deals with the study of experimental current intensity/voltage characteristicsof a free burning arc that appears to be singular:At low intensity current,the arc voltagedecreases until a minimum value,corresponding to a critical current intensity Ic.Forcurrent intensities higher than Ic,there is an increase of the arc voltage with the currentintensity.Dimensional analysis and Pi theorem coupled with a large set of experimentaldata allow us to evaluate the main physical processes responsible for the characteristicsshape.At low current intensity,the plasma is mostly driven by thermal conduction effectswhile at high current intensity,it is principally governed by radiation losses.Finally,theresults obtained from dimensional analysis allow to propose a 1D numerical simulationof the plasma column that gives rather good qualitative results.展开更多
文摘The surface and atmospheric heating fields over the Qinghai-Xizang Plateau are computed by using the observational data of solar radiation during 1982—1983.The mian results are as follows:The central and northern parts of the Plateau act as heat sinks in winter from November to January.Both eastern and south- ern parts of the Plateau are of heat sources.In summer,the main part of the Plateau acts as a strong heat source,and the center of the heating field is in the southeastern Plateau.However the main part of the Plateau acts as a heat sink for the atmospheric heating fields from October to March.The maximum intensity of the atmospheric heat sink over the central Plateau appears in December and January.From April to September,the main part of the Plateau acts as a heat source for the atmospheric heating fields.
基金the National Natural Science Foundation of China(Grant No.40333026)
文摘The structure and seasonal variation of the East Asian Subtropical Westerly Jet （EAWJ） and associations with heating fields over East Asia are examined by using NCEP/NCAR reanalysis data. Obvious differences exist in the westerly jet intensity and location in different regions and seasons due to the ocean-land distribution and seasonal thermal contrast, as well as the dynamic and thermodynamic impacts of the Tibetan Plateau. In winter, the EAWJ center is situated over the western Pacific Ocean and the intensity is reduced gradually from east to west over the East Asian region. In summer, the EAWJ center is located over the north of the Tibetan Plateau and the jet intensity is reduced evidently compared with that in winter. The EAWJ seasonal evolution is characterized by the obvious longitudinal inconsistency of the northward migration and in-phase southward retreat of the EAWJ axis. A good correspondence between the seasonal variations of EAWJ and the meridional differences of air temperature （MDT） in the mid-upper troposphere demonstrates that the MDT is the basic reason for the seasonal variation of EAWJ. Correlation analyses indicate that the Kuroshio Current region to the south of Japan and the Tibetan Plateau are the key areas for the variations of the EAWJ intensities in winter and in summer, respectively. The strong sensible and latent heating in the Kuroshio Current region is closely related to the intensification of EAWJ in winter. In summer, strong sensible heating in the Tibetan Plateau corresponds to the EAWJ strengthening and southward shift, while the weak sensible heating in the Tibetan Plateau is consistent with the EAWJ weakening and northward migration.
基金performed under the auspices of the Chinese National Key Programme for Developing Basic Sciences (Grant No. 2010CB951701)the Innovation Projects of the Chinese Academy of Sciences (Grant No. KZCX2-YW-Q11-01)+1 种基金the National Natural Science Foundation of China (Grant Nos. 40825015and 40810059006)EU-FP7 project "CEOP-AEGIS"(Grant No. 212921)
文摘In this study, a parameterization scheme based on Moderate Resolution Imaging Spectroradiometer （MODIS） data and in-situ data was tested for deriving the regional surface heating field over a heterogeneous landscape. As a case study, the methodology was applied to the whole Tibetan Plateau （TP） area. Four images of MODIS data （i.e., 30 January 2007, 15 April 2007, 1 August 2007, and 25 October 2007） were used in this study for comparison among winter, spring, summer, and autumn. The results were validated using the observations measured at the stations of the Tibetan Observation and Research Platform （TORP）. The results show the following： （1） The derived surface heating field for the TP area was in good accord with the land-surface status, showing a wide range of values due to the strong contrast of surface features in the area. （2） The derived surface heating field for the TP was very close to the field measurements （observations）. The APD （absolute percent difference） between the derived results and the field observations was 〈10%. （3） The mean surface heating field over the TP increased from January to April to August, and decreased in October. Therefore, the reasonable regional distribution of the surface heating field over a heterogeneous landscape can be obtained using this methodology. The limitations and further improvement of this method are also discussed.
文摘Microwave-induced substitutional combustion reaction was utilized to fabricate porous ceramic composite from Fe_3O_4/Al powder mixtures.The porous composite body was obtained by controlling the combustion reaction progress in a 2.45 GHz single mode applicator.Prior to the fabrication of the porous body,heating behavior of the powder mixtures were studied in the separated electric(E)and magnetic(H)fields.In addition,heating ability of the microwave fabricated porous product was also investigated.Fe_3O_4 powder can be heated up easily in both maximum H and E field, but a better heating was observed in the maximum H field.Regardless of the mixtures ratio(mixing compositions), maximum H field shows better heating characteristics.In E-field heating,temperature of the Fe_3O_4 samples decreased sharply when Al powder was added.However,the same phenomenon was not observed in the maximum H field heating. Thus,fabrication of the porous composite body was carrying out in maximum H field.Through an adequate control of the reaction progress,products with a porous structure consisting of well-distributed metal particles in the alumina and/or hercynite matrix were obtained.Consequently,heating of the fabricated porous composite body was also been successfully carried out in the maximum H field.Product phases and microstructure were the main factors influencing the heating ability of the porous composite body.
文摘The mathematic model of heating chamber for implementing the prediction of the annealing craft and improving the self adapting with the expansion of the new annealing furnace form, new annealing crafts and new kinds of steel coil has been established. The model developed which including the temperature for gas in heating chamber and the heating cover is based on the characteristics of anneal craft and the situations of locale production run. Firstly, the characteristic of the heating cover which limits the temperature was considered. Secondly, the locale production run condition and dispatching condition were considered. Finally, combining with the models and the simulation system, the numerical simulation research of the anneal process for the high performance hydrogen bell-type annealer as well as the spot experiment test were carried out. The results obtained from the developed models, usually finished less than thirty seconds, are in fair agreement with the test values, such as the relative errors of annealing times were within ±5%, and the quality＇ of the annealed steels were guaranteed.
基金This research was jointly sponsored by "The National Key Programme for Developing Basic Sciences"project (1998040900)Part Ⅰ, and the National Natural Science Foundation of China Project:"Studies on Interaction between the South Asia High and the Asian Monsoon and lts Mechanisms"under Grant No.40175021.
文摘By use of the NCEP/ NCAR reanalysis data, the seasonal variation of the South Asia high (SAH) is analyzed. The influences of temporal and spatial variations of the middle and upper level atmospheric temperatures, the visible heat sources, and the diabatic heating rates in the whole atmospheric column on the seasonal variation of the SAH are discussed. Results show that the SAH has two seasonal balancing modes, one of which is the land high in summer and the other the ocean high in winter. The land high itself can be divided into two patterns as well, that is the Tibetan high and the Iranian high. Heating fields have important impacts on the seasonal variation of the SAH. The SAH is a warm high and its center has the property of heat preference, usually locating over or moving to an area with relatively larger heating rates. The annual cycle of the SAH is mainly controlled by the seasonal process of the latent and sensible heating in South Asia. Strong shortwave radiative heating in the north at high latitudes and over the Tibetan Plateau also has an effects on the northward movement and maintenance of the SAH. The cooling effect of infrared radiation is an important cause in weakening the SAH.
文摘In this paper, variations of surface water flow and its climatic causes in China are analyzed using hydrological and meteorological observational data, as well as the impact data set （version 2.0） published by the National Climate Center in November 2009. The results indicate that surface water resources showed an increasing trend in the source region of the Yangtze River over the past 51 years, especially after 2004. The trend was very clearly shown, and there were quasi-periods of 9 years and 22 years, where the Tibetan Plateau heating field enhanced the effect, and the plateau monsoon entered a strong period. Precipitation notably increased, and glacier melt water increased due to climate change, all of which are the main climatic causes for increases in water resources in the source region. Based on global climate model prediction, in the SRESA1B climate change scenarios, water resources are likely to increase in this region for the next 20 years.
基金supported by the National Special Fund for Major Research Instrument Development(2011YQ140145)111 Project (B07009)+1 种基金the National Natural Science Foundation of China(11002013)Defense Industrial Technology Development Program(A2120110001 and B2120110011)
文摘A new numerical technique named interval finite difference method is proposed for the steady-state temperature field prediction with uncertainties in both physical parameters and boundary conditions. Interval variables are used to quantitatively describe the uncertain parameters with limited information. Based on different Taylor and Neumann series, two kinds of parameter perturbation methods are presented to approximately yield the ranges of the uncertain temperature field. By comparing the results with traditional Monte Carlo simulation, a numerical example is given to demonstrate the feasibility and effectiveness of the proposed method for solving steady-state heat conduction problem with uncertain-but-bounded parameters.
基金Project(2012 BAF04B01)Supported by the National Science and Technology Pillar Program during the Twelfth Five-year Plan of China
文摘The flow field and heat transfer of the strip surface due to the twin slot vertical jet impingement were investigated using the ANSYS FLUENT.The RNG k-ε model was carried out in the turbulent calculation.Systematic parametric research was conducted by varying the jet velocity of nozzle exit(V=5 m/s,7.5 m/s,10 m/s),the temperature of cooling water(T_w=280 K,300 K),the normalized spacing from the nozzle to the strip surface(H=10,15,20,33),and the normalized spacing from the nozzle to nozzle centerline(W=0,15,30).The velocity streamline of the flow domain and the general trend of the distribution of the local Nusselt number on the impingement surface of strip were obtained.The result indicate that,the average Nusselt number increases by about70%(90%) as the jet velocity is increased from 5 m/s to 7.5 m/s(from 7.5 m/s to 10 m/s),and T_w,Hand//have minimal effect on it.While the valley Nusselt number decreases by about 10%-43%with the increase of H and W.The functional relationship between the average Nusselt number and the systematic parameters is derived by the least square regression method.
基金Funded by the National Natural Science Foundation of China(No.51074123)the Scientif ic Research Program Funded by Shaanxi Provincial Education Department(No.12JK0785)+1 种基金the Cooperation Project of Industry,Academe and Research of Yulin City(2011)the Ph D Foundation of Xi’an University of Science and Technology(No.2011QDJ022)
文摘Through the experiments and the numerical simulation of temperature field in multi-heatsource synthesis Si C furnace, in order to research the feature point in multi-heat-source synthesis furnace, the variation law of heat fl ux was studied and the multi-directional energy fl ow diffusion mechanism was revealed. The results show that, due to the shielding action between the heat-source and the superposition effect of thermal fields, the insulating effect is best in multi-heat-source synthesis furnace. The heat emission effect is good outside the common area between heat-sources, but the heat storage is poor. Compared with the synthesis furnace that heat source is parallelly arranged, the furnace of stereoscopic arrangement has a more obvious heat stacking effect and better heat preservation effect, but the air permeability of heat source connecting regions is worse. In the case with the same ingredients, the resistance to thermal diffusion and mass diffusion is higher in heat source connecting regions.
文摘Temperature-time curves were measured for the air cooling and laminar cooling of a steel plate.Convective heat transfer coefficients of steel plate and air as well as steel plate and laminar cooling water were computed inversely. Therefore,the temperature field in the single-face quenching process of a steel pipe was simulated using ABAQUS finite element softw are,and the relationships betw een the temperatures and quenching time at different positions of the steel pipe were obtained. In addition,the relationships betw een the cooling rates and quenching time,as w ell as betw een cooling rates and temperatures,were obtained. The simulation quickly produced accurate results,and it can be used to optimize the quenching process. In addition,the results provide a basis for rationally designing the composition of a single-face quenching steel pipe.
文摘The effects of ozone on the summer atmospheric general circulation are simulated by use of a zonal model with the pesigma coordinate system. Results show that the simulated properties at the upper levels are remarkably improved after the ozone effects are introduced to the model. The direct effect of ozone is to enhance the heating rates at the upper levels. In the lower atmosphere. this effect is very little. Furthermore, the ozone can change the distributions and values of other components of heating fields, resulting in the change of the total heating rates, and meanwhile induce evident variation of atmospheric circulation at the lower levels.
基金supported by the National Natural Science Foundation of China (51971125)。
文摘In the present work,Ce_(17)Fe_(76.5)Co_1Zr_(0.5)B_6 ribbons were prepared by a direct melt spinning method.The effects of chamber pressure and magnetic field annealing temperature on the magnetic properties and microstructures of the alloys were investigated.The grain size and content of Ce_(2)Fe_(14)B phase can be changed by adjusting the chamber pressure,and the optimal magnetic performance is obtained at0.04 MPa.The magnetic properties can be influenced under magnetic field heat treatment.When the annealing temperature is lower than the Curie temperature,the refinement and a uniform distribution of the grains is obtained.The irreversible magnetic susceptibility curve reveals that magnetic field heat treatment enhances the exchange coupling interaction between grains of the Ce_(2)Fe_(14)B phase.When the magnetic field annealing temperature is 438 K,the alloy displays the optimal magnetic properties.Compared with the as-spun sample,the values of intrinsic coercivity(H_(ci)),remanence(B_r) and maximum energy product((BH)max) increase by 3.4%,9.8% and 18.7%,respectively.This work provides an effective approach by which to enhance the magnetic properties of Ce-Fe-B alloys.
基金Item Sponsored by National Natural Science Foundation of China(No.51174058)
文摘The thermal treatment process of cold-rolled Cu-Al composite strip under magnetic field conditions is systematically investigated by means of metallographic microscope and universal testing machine to observe the interface microstructure and test the mechanical properties.The heat treatment parameters' effects to the interface structure and mechanical properties of Al-Cu cold-rolled strip are discussed.The conclusions is showed as follows:(1)when the magnetic field intensity is greater than 0.1 T,the interface layer grow widely and stimulate the interfacial compounds' generation,the shear strength is reduced.(2)When the Cu-Al specimen's annealing temperature is at the condition of 300℃,the interfacial layer narrows when the magnetic field strength stay 0.1T than that without magnetic field,the magnetic filed restrains the interfacial compounds' generation,the shear strength reaches as high as 124Mpa;(3)The interfacial compounds are meanly brittleness intermetallic compounds such as CuAl,CuAl_2,Cu_9Al.
文摘The study of heat transfer is of significant importance in many biological and biomedical industry problems.This investigation comprises of the study of entropy generation analysis of the blood flow in the arteries with permeable walls. The convection through the flow is studied with compliments to the entropy generation. Governing problem is formulized and solved for low Reynold's number and long wavelength approximations. Exact analytical solutions have been obtained and are analyzed graphically. It is seen that temperature for pure water is lower as compared to the copper water. It gains magnitude with an increase in the slip parameter.
基金Funded by the Major State Basic Research Perelopment Program of China(973 Program)(No.2009CB623102)the Key Fund Project of Sichuan Provincial Department of Education(No.14ZA0086)the Key Fund Project of Professional Scientific Research Innovation Team of Southwest University of Science and Technology(No.14tdfk01)
文摘Through the comparison of calcination conditions between cement preclinkering technology and cement precalcining technology,we studied the characteristics of temperature field distribution of cement preclinkering technology systems including cyclone preheater,preclinkering furnace,and rotary kiln.We used numericalsimulation method to obtain data of temperature field distribution.Some results are found by system study.The ratio of tailcoalof cement preclinkering technology is about 70%,and raw mealtemperature can reach 1070 ℃.Shorter L/D kiln type of preclinkering technology can obtain more stable calcining zone temperature.The highest solid temperature of cement preclinkering technology is higher than 80 ℃,and high temperature region（〉1450 ℃）length is 2 times,which is beneficialfor calcining clinker and higher clinker quality.So cement preclinkering technology can obtain more performance temperature filed,which improves both the solid-phase reaction and liquid-phase reaction.
基金Project supported by the Collaborative Research in Engineering,Science&Technology(Grant No.P28C2-13)
文摘Miniaturization of electronic package leads to high heat density and heat accumulation in electronics device, resulting in short life time and premature failure of the device. Junction temperature and thermal resistance are the critical parameters that determine the thermal management and reliability in electronics cooling. Metal oxide field effect transistor（MOSFET）is an important semiconductor device for light emitting diode-integrated circuit（LED IC） driver application, and thermal management in MOSFET is a major challenge. In this study, investigations on thermal performance of MOSFET are performed for evaluating the junction temperature and thermal resistance. Suitable modifications in FR4 substrates are proposed by introducing thermal vias and copper layer coating to improve the thermal performance of MOSFET. Experiments are conducted using thermal transient tester（T3ster） at 2.0 A input current and ambient temperature varying from25℃ to 75℃. The thermal parameters are measured for three proposed designs： FR4 with circular thermal vias, FR4 with single strip of copper layer and embedded vias, and FR4 with I-shaped copper layer, and compared with that of plain FR4 substrate. From the experimental results, FR4I-shaped shows promising results by 33.71% reduction in junction temperature and 54.19% reduction in thermal resistance. For elevated temperature, the relative increases in junction temperature and thermal resistance are lower for FR4I-shaped than those for other substrates considered. The introduction of thermal vias and copper layer plays a significant role in thermal performance.
文摘In this paper,a primitive equation linear wave model is used to examine the effects of three-dimen- sional structure of heating field on the behavior of stationary planetary waves in summer and to compare the roles of different heating functions for the formation and maintenance of summer monsoon circulation in Asia.It is shown that the aloft heating connected with the latent heating,especially the deep condensation heating associated with the cumulus convection in low latitudes,plays a crucial part in the Asian summer mon- soon and the structures of planetary wave responses are quite sensitive to the vertical distribution of heating.
基金supported by the National Natural Science Foundation of China(5127618151476173)the National Basic Research Program of China(2011CB 710705)
文摘To reach the target of smaller pressure drop and better heat transfer performance, packed beds with small tube-to-particle diameter ratio(D/dp<10) have now been considered in many areas. Fluid-to-wall heat transfer coefficient is an important factor determining the performance of this type of beds. In this work, local fluid-to-wall heat transfer characteristic in packed beds was studied by Computational Fluid Dynamics(CFD) at different Reynolds number for D/dp=1.5, 3.0 and 5.6. The results show that the fluid-to-wall heat transfer coefficient is oscillating along the bed with small tube-to-particle diameter ratio. Moreover, this phenomenon was explained by field synergy principle in detail. Two arrangement structures of particles in packed beds were recommended based on the synergy characteristic between flow and temperature fields. This study provides a new local understanding of fluid-to-wall heat transfer in packed beds with small tube-to-particle diameter ratio.
文摘This paper deals with the study of experimental current intensity/voltage characteristicsof a free burning arc that appears to be singular:At low intensity current,the arc voltagedecreases until a minimum value,corresponding to a critical current intensity Ic.Forcurrent intensities higher than Ic,there is an increase of the arc voltage with the currentintensity.Dimensional analysis and Pi theorem coupled with a large set of experimentaldata allow us to evaluate the main physical processes responsible for the characteristicsshape.At low current intensity,the plasma is mostly driven by thermal conduction effectswhile at high current intensity,it is principally governed by radiation losses.Finally,theresults obtained from dimensional analysis allow to propose a 1D numerical simulationof the plasma column that gives rather good qualitative results.
