Temperature Characteristics of Bilayer Thin-Film Devices Under Organic Interface Limited Current Conduction

Temperature characteristics are important for the performance of organic thin film devices. On the basis of the hopping theory of Miller-Abrahams,an analytical model of charge transport for bilayer organic devices under the organicorganic interface limited current conduction is developed. The dependence of current, field,and carrier distribution in bilayer organic devices with the structure of ＂injection electrode/Layer Ⅰ/Layer Ⅱ/collection electrode＂ on temperature are numerically analyzed. We conclude that, for a given applied voltage, when temperature is raised, the voltage of LayerⅠ will increase,and the field will be higher. Meanwhile, the voltage of Layer Ⅲ will decrease, the field will become weaker accordingly,and the current of the device will increase.

High Temperature Characteristics of 3C-SiC/SiHeterojunctionDiodes Grown by LPCVD

The high temperature (300 ～480K) characteristics of the n-3C-SiC/p-Si heterojunction diodes (HJD) fabr icated by low-pressure chemical vapor deposition on Si (100) substrates are inv estigated.The obtained diode with best rectifying properties has 1.8×104 of ratio at room temperature,and slightly rectifying characteristics with 3.1 of rectification ratio is measured at 480K of an ambient temperature .220V of reverse breakdown voltage is acquired at 300K.Capacitance-voltage char acteristics show that the abrupt junction model is applicable to the SiC/Si HJD structure and the built-in voltage is 0.75V.An ingenious equation is employed to perfectly simulate and explain the forward current density-voltage data meas ured at various temperatures.The 3C-SiC/Si HJD represents a promising approach for the fabrication of high quality heterojunction devices such as SiC-emitter heterojunction bipolar transistors.

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.

Temperature Characteristics of Surface Acoustic Waves Propagating on La_3Ga_5SiO_4 Substrates

Langasite (LGS) is a novel piezoelectric crystal. The authors numerically analyses the temperature stability of surface acoustic waves (SAW) and the relation of SAW propagation with temperature on certain optimal cuts on LGS in this paper. The results show that LGS has better temperature stability than traditional piezo crystals. The results also demonstrate that the velocity of SAW decrease with temperature, the electro-mechanical coupling constant (k2) and temperature coefficient of frequency increases parabolically and the power flow angle increases linearly on certain optimal cuts of LGS. The calculation result compared with the experimental and show good agreement.

High temperature characteristics of AlGaN/GaN high electron mobility transistors

Direct current （DC） and pulsed measurements are performed to determine the degradation mechanisms of A1GaN/GaN high electron mobility transistors （HEMTs） under high temperature. The degradation of the DC characteristics is mainly attributed to the reduction in the density and the mobility of the two-dimensional electron gas （2DEG）. The pulsed measurements indicate that the trap assisted tunneling is the dominant gate leakage mechanism in the temperature range of interest. The traps in the barrier layer become active as the temperature increases, which is conducive to the electron tunneling between the gate and the channel. The enhancement of the tunneling results in the weakening of the current collapse effects, as the electrons trapped by the barrier traps can escape more easily at the higher temperature.

Temperature characteristics of wood during microwave treatments

In order to investigate the temperature characteristics of wood during microwave(MW) treatments,optical fiber sensors were used to measure wood(Pinus sylvestris L. var. mongolica Litv.) temperatures. The results show that the development of internal temperatures in wood basically includes two patterns during the process of MW treatment. The first may be divided into three phases: warming, constant temperature, and a sharply rising phase. The second pattern may be divided into two phases: warming, and constant temperature. The maximum temperature(MT) and rate of temperature increase(RTI)rose as the microwave power increased. The initial wood moisture content decreased while the period of constant temperature fell. Temperatures varied in different positions in the wood. The order of MT and RTI levels were the upper surface, center, bottom surface and the end point.Along the direction of wood thickness, the closer the monitoring point was to the generator, the faster the temperature increased. The MT and RTI of the end point was a minimum value because of the rapid removal of steam.

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.

High temperature characteristics of bilayer epitaxial graphene field-effect transistors on SiC Substrate

In this paper,high temperature direct current（DC） performance of bilayer epitaxial graphene device on SiC substrate is studied in a temperature range from 25℃ to 200℃.At a gate voltage of-8 V（far from Dirac point）,the drainsource current decreases obviously with increasing temperature,but it has little change at a gate bias of ＋8 V（near Dirac point）.The competing interactions between scattering and thermal activation are responsible for the different reduction tendencies.Four different kinds of scatterings are taken into account to qualitatively analyze the carrier mobility under different temperatures.The devices exhibit almost unchanged DC performances after high temperature measurements at 200℃ for 5 hours in air ambience,demonstrating the high thermal stabilities of the bilayer epitaxial graphene devices.

850 nm Implant-confined VCSEL Temperature Characteristics

The temperature characteristics of VCSEL using proton implantation are described,compared with its edge-emitting counterpart.Implant-confined VCSEL operation has been realized up to 120 ℃.These records of high operating temperature are caused by high characteristic temperature. The relevant physical mechanisms including their dependence on temperature and carrier density are considered. The temperature sensitivity of the threshold current is not strongly increasing with higher temperature.

Temperature Characteristics of BJMOSFET

The resolution expression for the temperature dependence of the current and threshold voltage is deduced as well as the analysis of temperature characteristics of BJMOSFET. Equivalent circuit of analysis and simulation has been established for the BJMOSFET temperature characteristics. By using the general circuit simulation software of PSpice9 and computer simulation, characteristic graphs of the BJMOSFET output characteristic, transient characteristic and amplitude-frequency characteristic with temperature variation are obtained. The results accorded very good with theoretical analysis and proved that BJMOSFET has better temperature characteristics than traditional MOSFET.

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.

Dielectric properties and temperature increase characteristics of zinc oxide dust from fuming furnace

Cavity perturbation method was used to determine the dielectric properties （ε′,ε″, and tanδ） of zinc oxide dust in different apparent densities. The process was conducted to study the microwave-absorption properties of zinc oxide dust and the feasibility of microwave roasting zinc oxide dust to remove fluorine and chlorine. The dielectric constant, dielectric loss, and loss tangent were proportional to the apparent density of zinc oxide dust. The effects of sample mass and microwave power on the temperature increase characteristics under the microwave field were also studied. The results show that the apparent heating rate of the zinc oxide dust increases with the increase in microwave roasting power and decreases with the increase in the sample mass. The temperature of the samples reaches approximately 800 ＆#176;C after microwave treatment for 8 min, which indicates that the zinc oxide dust has strong microwave-absorption ability.

1.3μm AlInGaAs Strained Single Quantum Well Laser Diodes with High Characteristic Temperature of 200K

A high characteristic temperature （T0） of 200K from a 1.3μm AlInGaAs/AlInAs single-quantum-well laser diode with the asymmetric waveguide layer structure under CW operation at 20 to 80℃ was obtained,which is the best result reported in the laser diodes （LDs） of the same active materials structure and emitting wave- length. AllnGaAs as an active layer,therefore,is very promising for the fabrication of long-wavelength LDs with excellent high-temperature performance. It is found that the asymmetric waveguide layer structure can decrease optical absorption and improve the high-temperature performance and catastrophic optical damage threshold of LDs.

The Evolutionary Characteristics of the Temperature in Typical Counties in Southwest China——Taking Meitan County in Guizhou Province as an Example

Based on the method of linear trending,analysis was made upon the daily temperature statistics of Meitan County from 1951 to 2009,and the results showed that the temperature in general was on the rise.With 1980 as the turning point,it was on the decline before while later the temperature increased quickly.Among these figures,the variation rates of annual average temperature,annual maximum temperature,and annual minimum temperature are 0.11 ℃/10 a,0.08 ℃/10 a,and 0.36 ℃/10 a.The variation rates of average temperature in spring,summer,fall and winter are respectively 0.12 ℃/10 a,0.07 ℃/10 a,0.12 ℃/10 a,and 0.13 ℃/10 a.Morlet wavelet was adopted to analyze the periodicity of temperature change which has periods of different scales.But since 2000,during different time scales most of the areas have been in the period of temperature rises.Besides,certain rule exists in the periodicity of maximum temperature and minimum temperature.Before 1970s,they had opposite changing rules,and the alteration of the peak value occurred.However,in the late 1980s,they had similar changing rules,and their peak values appeared at the same time.It means that against the background of global warming,the reaction of temperature evolution in Meitan County is quite remarkable.

Investigation of the temperature characteristic in SrB4O7：Sm2＋ phosphor-in-glass by analyzing the lifetime of 684 nm

The SrB4O7：Sm2＋ phosphor was synthesized by high temperature solid state reaction method. The phosphor-in-glass was prepared by mixing and firing the phosphor and TeO2-ZnO glass precursor. The XRD results showed that the phosphor-in-glass was in amorphous phase because of the tiny mass fraction of phosphor in glass. The emission spectrum under the 355 nm excitation was measured, and it exhibited the same characteristic emission peaks as the phosphor sample. The temperature characteristic of the SrB4O7：Sm2＋ phosphor-in-glass was discussed by analyzing the lifetime of 684 nm emission at various temperatures. The relative temperature sensitivity of 5%/K around 573 K was obtained for the temperature dependent lifetime, suggesting that the material in this study is a promising candidate for temperature sensor application.

On the temperature characteristics of phase measurement in homodyne fiber interferometer

Different from the traditional way of using piezoelectric （PZT）phase shifter to measure phase difference, a new method is designed to calculate it between signals in the two arms of a homodyne fiber interferometer. A simple homodyne fiber interferometer system is then established to measure the interference photoeurrent and the photocurrents from the two fiber arms generated by the signal power on a temperature control plat. The homodyne fiber interferometer system is composed of fiber and sensitive to the variation of temperature. Thus, is necessary to study the temperature characteristics in the phase measurement of homodyne fiber interferometer. The experimental results show that the variation of the phase difference of signals in the two fiber arms is proportional to the variation of temperature.

Research on the temperature characteristic of Love wave device with structure of multi-waveguides used for gas sensor

This paper aimed at extracting optimal structural parameters for Love wave device with structure of multi-waveguides to improve its temperature stability. The theoretical model dealing with the Love wave propagation in multi-waveguides was established first, the dispersion characteristic is depicted by the acoustic propagation theory of stratified media and boundary conditions. Combing with the dispersion characteristics and Tomar＇s method, the optimal structural parameters for the Love wave device with zero temperature coefficient were extracted, and confirmed by the following experimental results. Excellent temperature coefficient of the Love wave device with SU-8/SiO2 on ST-90°X quartz substrate was evaluated experimentally as only 2.16 ppm/℃, which agrees well with the calculated results. The optimized Love wave device is very promising in gas sensing application.

Characteristic Temperatures of Waxy Crude Oils

Gel point or pour point is widely used to evaluate the low temperature flowability of crude oil. However, it is not adequate to describe the gelling properties of waxy crude oils under flow conditions with gel point or pour point, since the theological behavior of crude oils is dependent on shear history. Waxy crude oils tend to gel at a low temperature. Based on gelation theory, the characteristic temperature of waxy crude oil was determined by analyzing viscosity-temperature data. Two mathematical models were developed for calculating characteristic temperatures of virgin crude oils and pour point depressants （PPD） beneficiated crude oils, respectively. By using these two models, the characteristic temperatures of crude oils that have experienced shearing and thermal histories can be predicted. The model for predicting the characteristic temperature of virgin crude oils has an average relative deviation of 4.5%, and all predicted values have a deviation within 2 ℃. Tested by 42 sets of data, the prediction model for crude oil treated with PPD has a high accuracy, with an average relative deviation of 4.2%, and 95.2 percent of predicted values have a deviation within 2 ℃. These two models provide useful ways for predicting the flowability of crude oils in pipelines when only wax content, wax appearance point and gel point are available.

Characteristics of High Temperature Rupture of a Cast Ni-Based Superalloy M963

The rupture behavior of a cast Ni-base superalloy M963 at high temperature has been investi- gated. The microstructure examination shows that there exists a large amount of the carbide and γ-γ' eutectic, which is very harmful to the mechanical properties of M963 superalloy. The tensile strength of M963 superalloy both at room temperature and at high temperatures is higher than that of K17G alloy, but the tensile ductility of the former is much lower than that of the latter. In tensile fracture process with the high strain rate, the open carbides are the initiation site and the carbide/matrix interface is the propagation path of cracks. But in fracture process with the low strain rate, the carbide/matrix interface and cast microvoids are the initiation sites, and the carbide/matrix interface is the propagation path of cracks. The effective ways to improve ductility of M963 superalloy are also suggested.