Analysis of the Temperature Characteristics of High-speed Train Bearings Based on a Dynamics Model and Thermal Network Method

High-speed trains often use temperature sensors to monitor the motion state of bearings.However,the temperature of bearings can be affected by factors such as weather and faults.Therefore,it is necessary to analyze in detail the relationship between the bearing temperature and influencing factors.In this study,a dynamics model of the axle box bearing of high-speed trains is established.The model can obtain the contact force between the rollers and raceway and its change law when the bearing contains outer-ring,inner-ring,and rolling-element faults.Based on the model,a thermal network method is introduced to study the temperature field distribution of the axle box bearings of high-speed trains.In this model,the heat generation,conduction,and dispersion of the isothermal nodes can be solved.The results show that the temperature of the contact point between the outer-ring raceway and rolling-elements is the highest.The relationships between the node temperature and the speed,fault type,and fault size are analyzed,finding that the higher the speed,the higher the node temperature.Under different fault types,the node temperature first increases and then decreases as the fault size increases.The effectiveness of the model is demonstrated using the actual temperature data of a high-speed train.This study proposes a thermal network model that can predict the temperature of each component of the bearings on a high-speed train under various speed and fault conditions.

CFD-Based Evaluation of Flowand Temperature Characteristics of Airflow in an Aircraft Cockpit

The rational design of airflow distribution is of great importance for comfort and energy conservation.Several numerical investigations of flow and temperature characteristics in cockpits have been performed to study the distinct airflow distribution.This study developed the coupled heat transfer model of radiation,convection,and heat conduction for the cockpit flight environment.A three-dimensional physical model was created and a shear stress transfer(SST)k-w turbulence model was well verified with a high prediction accuracy of 91%for the experimental data.The strong inhomogeneous flow and temperature distribution were captured for various initial operating conditions(inlet temperature,inlet pressure,and gravitational acceleration).The results indicated that the common feature of the flow field was stable in the middle part of the cockpit,while the temperature field showed a large temperature gradient near the cockpit’s top region.It was also found that there was remarkable consistency in the distributed features,regardless of the applied initial operating conditions.Additionally,the mass flux and the top heat source greatly affected the flow and temperature characteristics.This study suggests that an optimized operating condition does exist and that this condition makes the flow and temperature field more stable in the cockpit.The corresponding results can provide necessary theoretical guidance for the further design of the cockpit structure.

Study on the temperature characteristic and high temperature risk of asphalt layer of Beijing-Xinjiang ExpresswayWutong Daquan to Yiwu Section

High temperature rutting is a typical highway damage in Xinjiang, China, and its trigger process usually has a close relationship with characteristics of road temperature distribution. A numerical model of earth-atmosphere coupling heat transfer on a typical section of the Beijing-Xinjiang Expressway(G7) from Wutong Daquan to Yiwu was established in this work. Spatiotemporal characteristics of pavement structure layer temperature distribution, frequency and duration times of road surface high temperature from May 1 to September 30 are statistically studied. The effects of wind speed, weather and air temperature on asphalt layer and pavement temperature are analyzed. The results show that:(1) Spatial and temporal temperature distribution characteristics of pavement structural layers are greatly affected by the coupled earth-atmosphere heat transfer process. Surface temperature increases along the airflow direction and daily temperature variation of the pavement structure layer decreases with an increase of depth.(2) G7 expressway will face the challenge of high rutting damage. The proportion of temperature higher than 50 ℃ for pavement surface and asphalt upper layer both exceeds 50%and high temperature of road lasts for more than six hours in numerous days.(3) High temperatures of asphalt pavement are usually associated with low ambient wind speeds, while the wind flow has little cooling effect when the road surface temperature is relative high. Weather conditions have a significant impact on temperature of the road surface. The probability of high temperature in sunny days is obviously higher than other weather conditions.(4) Pavement temperature rises as air temperature rises. When air temperature is higher than 30 °C, the proportion of pavement daily maximum temperature over softening point reaches up to 78%.

An Experimental Study on the Temperature Characteristic of a 940 nm Semiconductor Laser Diode

This paper is focused on a 940 nm edge type of semiconductor laser, which is made from 940 nm InGaAs double-quantum-well epitaxial wafer, produced by Metal Organic Chemical Vapor Deposition (MOCVD). In the absence of coating, the efficiency at the room temperature is 0.89 W/A, and the averaged threshold current is 0.307 A. The present study investigates the impact of temperature on the P-I curve, V-I curve and the centre wavelength, the temperature ranging from 286.15 - 333.15 K. It shows that the threshold current increases from 0.28 A to 0.41 A with the increasing temperature. The increase rate is 0.0027 A/K. With the temperature ranging from 286.15 - 333.15 K, the characteristic temperature is calculated to be 120 K. At driven current of 2 A, the output power decreases from 1.47 W to 1.27 W at a rate of 0.00425 W/K. At a constant voltage, the output current initially increases with the temperature within a certain range, beyond which the impact of the temperature is minimum. The ideal factor obtained from V-I curve by curve fitting is 1.076. The series resistance is 0.609 Ω. The centre wavelength shifts to a longer wavelength with the increasing temperature at a rate of 0.275288 nm/K.

Martensite Aging Effect and Thermal Cyclic Characteristics in Ti-Pd and Ti-Pd-Ni High Temperature Shape Memory Alloys

The effect of thermal cycling and aging in martensitic state in Ti-Pd-Ni alloys were investigated by DSC and TEM observations. It is shown that the thermal cycling causes the decreases in M8 and Af temperatures in Ti50Pd50-xNix, (x=10, 20, 30) alloys, but no obvious thermal cycling effect was observed in Ti50Pd50Pd40Ni10 alloys and the aging effect shows a curious feature, i.e., the Af temperature does not saturate even after relatively long time aging, which is considered to be due to the occurrence of recovery recrystallization during aging.

Thermal Analysis by Means of Differential Scanning Calorimetry of the Characteristic Thermodynamic Temperatures of a Cu-Zr-Al Bulk Metallic Glass

In this study a Cu_(43)Zr_(48)Al_(9)bulk metallic glass prepared by the copper mold casting method is considered.In recent years,Cu-Zr-Al systems like this have enjoyed widespread attention due to their high strength,high hardness,high corrosion resistance and low cost.Here samples of this substance are studied using DSC(Differential scanning calorimetry)to determine the effect of different test conditions(heating rate,sample mass,sample specific surface area and sample crystal phase)on the characteristic thermodynamic temperature of the bulk metallic glass.Experimental results show that almost all of the five characteristic thermodynamic temperatures(T_(g),T_(x),T_(p),T_(m),T_(l))of this substance have higher values when the heating rate is increased.The influence of the variation of sample mass,sample specific surface area and sample crystal phase on the amorphous alloy characteristic temperature is very weak.lower the heating rate,the more developed the crystalline phase in the amorphous alloy will be.

Design of Uncooled Thermal Imaging Systems Operating at Multiple Temperatures

The reasons why thermal imaging systems consume power are analyzed,and a low power consumption design scheme is presented for the thermal imaging systems operating at multiple temperatures. The relation between the response performance of α-Si microbolometer detector and its operating temperature is studied by means of formulas of microbolometer detector's noise equivalent temperature difference(NETD) and detectivity. Numerical analysis based on true parameters demonstrates that the detectivity decreases slightly and NETD increases slightly when operating temperature rises,which indicates that α-Si microbolometer detector has approximately uniform response in a wide operating temperature range. According to these analyses,a thermal imaging system operating at multiple temperatures is designed. The power of thermoelectric stabilizer(TEC) is less than 350 mW and NETD is less than 120 mK in the ambient temperature range of-40 ℃-60 ℃,which shows that this system not only outputs high-quality images but consumes low power.

Phase Transformation Strengthening of Hot Extruded Inconel 625 under High-temperature Load Environment

Microstructure evolution and properties of hot-extruded Inconel 625 alloy were investigated at different creep temperatures, aging time and strain rates. The experimental results indicate that the Inconel 625 alloy exhibits an excellent creep resistance at 700 ℃ and below. When the creep temperature rises to 750 ℃, the creep resistance falls drastically due to the failure of phase transformation strengthening and the precipitation of a large amount of δ phase and σ phase at the grain boundary. The special temperature-sensitive characteristics of Inconel 625 alloy play a very important role in its fracture. When the strain rate is 8.33×10^-3s^-1, the strength of the specimen is higher than that of other parameters attributed to the effect of phase transformation strengthening. With the increase of Ni3(Al, Ti), the phase transformation strengthening inhibits thickening of the stacking faults into twins and improves the overall mechanical properties of the alloy. With the increase of the aging time, the granular Cr-rich M23C6 carbides continue to precipitate at the grain boundary, which hinders the movement of the dislocations and obviously increases the strength of the samples. Especially, the yield strength increases several times.

城市热岛效应对宜宾站气温变化的影响(英文)

Based on the observation data of temperature from Yibin station and other five surrounding meteorological stations in 1961-2009,temperature variation in Yibin station affected by urbanization was studied.The results showed that urban heat island effect in Yibin became more and more strong,and it had great influence on minimum temperature and little influence on maximum temperature,with obvious daily variation.In addition,heat island effect was more obvious at night than daytime,while temperature went up most greatly in summer,and next came spring,but it was weakest in winter.Compared with 1960s,the average warming rate of temperature at 02:00,08:00,14:00 and 20:00,daily average temperature,maximum temperature and minimum temperature reached 0.483 2,0.168 0,0.001 4,0.209 8,0.215 4,-0.013 4 and 0.333 2 ℃ in 40 years,respectively.Moreover,regional background had certain effect on urban climate,and the influence of urban heat island effect on various meteorological stations was distinct in different stages of urbanization process.

Temperature and pressure characteristics of ultrasonic transducer and the amplitude spectra correction of echoes

In this paper,the transfer functions of ultrasonic transducers under different temperatures are imitated according to Mason equivalent circuit. The relevant experiments are carried out. The results show that the transfer characteristic of ultrasonic transducer varies with temperature and pressure. Therefore, we present an approach to correct the amplitude spectra of ultrasonic echoes got in different temperature and pressure environmeots. The theoretical simulation and experimental results prove that the approach is simple, effective and practical.

High-temperature energy storage dielectric with inhibition of carrier injection/migration based on band structure regulation

Dielectric capacitors have a high power density,and are widely used in military and civilian life.The main problem lies in the serious deterioration of dielectric insulation performance at high temperatures.In this study,a polycarbonate(PC)-based energy storage dielectric was designed with BN/SiO_(2)heterojunctions on its surface.Based on this structural design,a synergistic suppression of the carrier injection and transport was achieved,significantly improving the insulating properties of the polymer film.In particular,the composite film achieves optimal high-temperature energy-storage properties.The composite film can withstand an electric field intensity of 760 MV m^(-1)at 100℃and obtain an energy storage density of 8.32 J cm^(-3),while achieving a breakthrough energy storage performance even at 150℃(610 MV m^(-1),5.22 J cm^(-3)).Through adjustment of the heterojunction structure,free adjustment of the insulation performance of the material can be realized;this is of great significance for the optimization of the material properties.

Investigation of Carrier Conduction Mechanism over InAs/InP Quantum Dashes and InAs/GaAs Quantum Dots Based p-i-n Laser Heterostructures

Charge transfer characteristics of the long wavelength semiconductor laser structures, containing quantum dot layers (QDs), were investigated by means of temperature dependent current-voltage and electroluminescence measurements over InAs/InP, and InAs/GaAs based p-i-n structures. In InAs/InP elongated QDs (QDashes) structure, injected carriers were tunneled from the quantum well into QDashes through a thin barrier and subsequently recombined within QDashes. Meanwhile, for InAs/GaAs structure, tunneling kind transport was exhibited in both forward and reverse bias voltage directions. The onset of light took place when the forward bias exceeded 1.3 V (3 V) for InAs/InP (InAs/GaAs) p-i-n structure through electroluminescence measurements. The peak value of emitted laser light for InAs/InP QDashes and InAs/GaAs QDs occurred in 1.55 μm and 1.3 μm, respectively.

Flow Properties of Entrained Flow Gasifier Fine Slag and Network Structure of its Molten Slag

The entrained flow gasification has been identified as the most promising gasification technology.Serious environmental pollution and waste of land resources are caused by the increasing amount of storage and production of coal gasification slag.The aim of this work is to explore the feasibility of high-temperature combustion and melting technology for treating coal gasification fine slag and determine the important parameters of system operation.The flow properties and molten slag structure characteristics of three fine slags from different entrained flow gasifiers were studied.Depending on the melting mechanism of melt-dissolution,the melting time of fine slags is short.Three fine slags all produce glassy slags,which is conducive to slag discharge.The degree of polymerization of silicate melt is proportionate to the amount of SiO_(2)in the slag.A part of Al^(3+)exist in the form of[AlO_(4)]^(5-)because of the effect of CaO and Na_(2)O,as the network former.Finally,the degree of polymerization of the three type molten slag was calculated by considering the role of Si and Al in molten slag and the property of each one.

Thermal analysis of lubricated three-dimensional contact bodies considering interface roughness

Surface roughness and thermal action are of remarkable importance in the lubrication performance of mechanical components,especially in extreme conditions.However,available studies mainly focus on the full-film lubrication conditions without considering temperature rise and real 3D surface roughness due to the complexity of surface topography and temperature characteristics.Moreover,studies on the interfacial thermal behaviors of 3D rough surface lubricated contact in an extended range of working conditions remain limited.In this paper,a deterministic mixed thermal elastohydrodynamic lubrication model considering real 3D surface roughness and thermal effects is proposed.In this model,pressure and temperature are coupled with each other,the computation of elastic deformation is accelerated through the discrete convolution and fast Fourier transform method,the temperature field is calculated with the column sweeping technique,and the semi-system method is introduced to improve convergence and numerical stability under severe conditions.The model is validated by comparing its results with available published numerical and experimental results.The thermal behaviors of the contact interface are studied in a wide range of working conditions.The influences of surface roughness and thermal effect on lubrication performance are revealed.The results show that the proposed model can be used as a powerful analysis tool for lubrication performance and temperature prediction in various heavy-load,high-speed lubricated components over a wide range of lubrication conditions.

Robust frequency-upconversion lasing operated at 400 K from inorganic perovskites microcavity

Multi-photon-pumped lasing based on metal-halide perovskites is promising for nonlinear optics and practical frequency-upconversion devices in integrated photonic systems.However,at present almost all the multi-photon-pumped lasing emissions from perovskite microcavities were limited for two-photon excitation,and also suffered from a compromise in room temperature or low temperature operation conditions.In this study,based on the vapor-phase epitaxial CsPbBr3 microplatelets with high crystallinity,self-formed high-quality microcavities,and great thermal stability,low-threshold and high-quality factor whispering gallery mode lasing was realized under single-,two-,and three-photon excitation,and the lasing action is very stable under continuous pulsed laser irradiation(~3.6×10^(7) laser shots).More importantly,the three-photon-pumped lasing can be efficiently sustained at a high temperature of~400 K,and the characteristic temperature was determined to be as high as~152.6 K,indicating the highly temperature-insensitive gain threshold.Note that this is the first report on high-temperature three-photon-pumped lasing on perovskite microcavities.Moreover,an aggressive thermal cycling test(two cycles,290-400-290 K)was further performed to indicate the stability and repeatability of the multi-photon-pumped lasing characteristics.It can be anticipated that the results obtained represent a significant step toward the temperature-insensitive frequency-upconversion lasing,inspiring the exploitation of advantageous perovskites for novel applications.

春季偏晚终雪记录隐示的南宋杭州1131-1270年气候变化

We collected and verified documentary records of the latest spring snowing dates(LSSD)in Hangzhou during Southern Song Dynasty.Furtherly,the statistical correlation between this proxy and February–April mean temperature in Hangzhou was examined,and samples later than the perennial mean of the LSSD during Southern Song Dynasty were transformed into the decadal mean of LSSD by means of Boltzmann function.General characteristics of this reconstructed LSSD series with a 10-year temporal resolution was analyzed,and it was also compared with other documentary evidences and reconstructed climate series in China for the period 1131–1270.The results and discussion suggested that:(1)Records of the LSSD in Hangzhou during Southern Song Dynasty did not refer to ice pellets and graupels,which had an explicit climate significance(–0.34℃/10 d,R2=0.37,p<0.001).However,when this proxy is used to reconstruct temperature changes,all dates should be converted into proleptic Gregorian style and meet the same criterion of"true Qi"as the Chinese traditional calendar after 1929.(2)The decadal mean of LSSD can be effectively estimated by using the forefront of LSSD in the decade on the basis of Boltzmann function,whose extrapolation has a lesser uncertainty than those on the basis of linear models or polynomial models.(3)The spring climate in Hangzhou during 1131–1270 was almost as warm as the period 1951–1980.At the centennial scale,this period can be divided into two phases:the cold 1131–1170 and the warm 1171–1270.In the latter,1181–1200 and 1221–1240 were two cold intervals at the multi-decadal scale.(4)The reconstructed LSSD series was consistent well with other documentary evidences and reconstructed climate series in China for 1131–1270,which may reflect the influence on the climate over most regions of China imposed by the Pacific Decadal Oscillation(PDO).