温度对菱形花纹的影响

研究了温度对蜂蜡和樟脑制成的尖锥模型上的菱形花纹的影响。烧蚀实验在超音速风洞中进行,得到了温度与花纹波长、压力与花纹波长的关系,并分析了温度和压力对出现花纹的起始位置、出现花纹和形成稳定花纹所需要的时间的影响。     

The coupling influence of airflow and temperature on the wall-wetted fuel film distribution

The coupling influence of airflow and temperature on the two-dimensional distribution of the film resulted from fuel spray impinging on a horizontal flat wall was studied with experiments. The horizontal airflow direction was perpendicular to the vertical axis of the injection spray. The results show that, as air velocity increases, the film shape turns from a circle to an oblong. As wall temperature increases, the film area shrinks. Film thickness decreases as wall temperature or air velocity increases. The boiling point of the fuel is an important temperature to affect the film area and the film thickness. Film center moves more far away in the downstream direction as air velocity increases. For a certain air velocity, film center moves less far away as wall temperature increases.     

The influence of natural convection on the temperature decay of a porous thermal layer

Temperature decay in sealed rockbeds has been recorded. The rockbeds lost energy through the top surface and the results indicated that different natural convective flows occurred in beds of fixed depth and rock size but different lateral dimensions. However, the different flows had no effect on the mean power density dissipated through the top of the beds. A simple numerical conduction model based on the power integral method was used to calculate the temperature decay. The experimental results suggested that an insulated porous lower boundary was appropriate for the model and this gave the best agreement with the experiments.     

The influence of temperature on limestone sulfation and attrition under fluidized bed combustion conditions

The influence of temperature on attrition of two limestones during desulfurization in a fluidized bed reactor was investigated. Differences in the microstructure of the two limestones were reflected by a different thickness of the sulfate shell formed upon sulfation and by a different value of the ultimate calcium conversion degree. Particle attrition and fragmentation were fairly small under moderately bubbling fluidization conditions for both limestones. An increase of temperature from 850 °C to 900 °C led to an increase of the attrition rate, most likely because of a particle weakening effect caused by a faster CO₂ evolution during calcination. This weakening effect, however, was not sufficiently strong to enhance particle fragmentation in the bed. The progress of sulfation, associated to the build-up of a hard sulfate shell around the particles, led in any case to a decrease of the extent of attrition. Sulfation at 900 °C was less effective than at 850 °C, and this was shown to be related to the porosimetric features of the different samples.     

The influence of the brakes friction elements thickness on the contact temperature and wear

This paper is the continuation of the author's investigations [11] where the mathematical model for determination of the contact temperature, sliding speed and wear during braking was proposed. On contrary to the previous investigation, where the working elements were considered as the half-spaces, at the present paper their thickness is taken into account. For three different dependences of the friction coefficient upon the temperature the influence of thickness on the contact temperature and wear is studied. Received on 26 April 1999     

The influence of finite rates of temperature change in the creepT-jump experiment

Summary General equations for nonisothermal creep of a linear viscoelastic solid are presented. Both the time dependent strain and strain rate are predicted for an arbitrary temperature history. The creepT-jump experiment (imposition of a sudden temperature change on a creeping specimen) is analyzed using these equations in order to understand the influence of non-instantaneous temperature changes on the experimental observations. It is shown that an increase in the time required to impose the temperature change causes an increase in the activation energy,H _exp, determined via creepT-jump. This effect is most pronounced for materials with large activation energies. Appropriate extrapolation techniques can be used to obtain the result expected for an instantaneous temperature change. Verification of the theoretical prediction was obtained from isothermal and nonisothermal creep experiments on polymethylmethacrylate in the linear viscoelastic region. The activation energy for a nearly instantaneous temperature change was 43 ± 2 kcal/mol. As the rise time of the temperature change was increased to 600 seconds,H _exp increased to 70 ± 2 kcal/mol. The effects of the rate of temperature change on other aspects of the creepT-jump experiment were also found to be in keeping with the predictions of the nonisothermal linear theory.

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Zusammenfassung Es werden allgemeine Gleichungen für das nichtisotherme Kriechen eines linear-viskoelastischen Festkörpers abgeleitet. Sowohl die zeitabhängige Dehnung als auch die Dehngeschwindigkeit werden für eine beliebige Temperaturvorgeschichte vorausgesagt. Das Kriech-T-Sprung-Experiment, d.h. die Aufbringung einer plötzlichen Temperaturänderung bei einer Kriechprobe, wird mit diesen Gleichungen analysiert, um den Einfluß von kontinuierlichen Temperaturänderungen bei experimentellen Beobachtungen verständlich zu machen. Es wird gezeigt, daß eine Verlängerung der Zeitdauer zur Erzeugung der Temperaturänderung ein Anwachsen der AktivierungsenergieH _exp, verglichen mit derjenigen beim Kriech-T-Sprung, zur Folge hat. Dieser Effekt tritt am ausgeprägtesten bei Stoffen mit großen Aktivierungsenergien auf. Angepaßte Extrapolationsmethoden lassen sich anwenden, um das für eine plötzliche Temperaturänderung erwartete Ergebnis zu erhalten. Die theoretischen Voraussagen wurden mit Hilfe isothermer und nicht-isothermer Kriechexperimente an Polymethylmethacrylat im linearviskoelastischen Bereich verifiziert. Die Aktivierungsenergie für eine nahezu plötzliche Temperaturänderung ergab sich zu 43 ± 2 kcal/mol. Wenn das Zeitintervall für die Temperaturänderung auf 600 Sekunden erhöht wurde, stiegH _exp auf 70 ± 2 kcal/mol. Die Auswirkungen der Temperaturänderungsgeschwindigkeit bezüglich anderer Gesichtspunkte beim Kriech-T-Sprung-Experiment ergeben sich ebenso in Übereinstimmung mit den Voraussagen der nicht-isothermen linearen Theorie.

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With 15 figures     

The influence of side group structure on the glass transition temperature of isomeric vinyl ester polymers

Summary The development of vinyl esters of C₉–C₁₁ carboxylic acids for internal flexibilization of paint latex polymers has led us to study the effect of structural variations. Flexibility being closely connected with the glass-transition temperature,T _g , we have investigated the transition behaviour of a large number of homopolymers and copolymers by dynamic-mechanical methods.The polymers studied were model compounds of uniform structure and a wide variety of copolymers. Of the latter, some were polymers of distillation fractions of the technical vinyl ester mixture, others copolymers of this mixture with a well-defined monomer, e.g. vinyl acetate.As we found a linear dependence ofT _g on composition, we have, in the calculations, treated the technical vinyl ester mixture as a single monomer. Inspection of polymerized fractions clearly revealed the effect of the structure of isomeric side groups, the higherT _g values being found for the more compact structures. The fact that the differences inT _g between polymers made from the various fractions are fairly small implies that their type of branching has led to moderately compact side groups. This has been derived fromT _g determinations on model polymers of highly branched vinyl esters of C₉ carboxylic acids of known structure.

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Zusammenfassung Die Entwicklung von Vinylestern auf der Grundlage von C₉–C₁₁ Carboxylsäuren für die innere Flexibilisierung von Farblatexpolymeren hat uns veranlaßt, den Effekt struktureller Unterschiede zu studieren. Da die Flexibilität eng mit der GlastemperaturT _g zusammenhängt, haben wir das Übergangsverhalten einer großen Zahl Homopolymere und Copolymere mit Hilfe von dynamisch-mechanischen Verfahren untersucht.Die verwendeten Polymere umfaßten sowohl Modellverbindungen einheitlicher Struktur als auch verschiedenartige Copolymeren. Einige der letzteren bestanden aus Polymeren von Destillationsfraktionen des handelsüblichen Vinylestergemisches, andere aus Copolymeren dieses Gemisches mit einem gutdefinierten Monomer, z. B. Vinylacetat.Da wir eine lineare Abhängigkeit der Glastemperatur von der Zusammensetzung feststellten, wurde das handelsübliche Vinylestergemisch bei unseren Berechnungen als ein einfaches Monomer betrachtet. Prüfung der polymerisierten Fraktionen erwies deutlich den Einfluß der Struktur isomerer Seitengruppen, wobei sich die höherenT _g -Werte bei den kompakteren Strukturen ergaben. Aus der Tatsache, daß die auf den verschiedenen Fraktionen basierenden Polymeren einen ziemlich kleinen Unterschied inT _g aufweisen, läßt sich schließen, daß die Verzweigung bei ihnen zu mäßig kompakten Seitengruppen geführt hat. Dieser Befund beruht auf Messungen der Glastemperatur an Modellpolymeren stark verzweigter Vinylester aus C₉ Carboxylsäuren bekannter Struktur.

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Paper presented at the Symposium at Leende of De Nederlandse Rheologische Vereniging on 21st and 22nd May 1970.     

Laser repetitive pulse heating influence of pulse duty on temperature rise

Laser repetitive pulse heating of the solid surface is considered and influence of duty cycle in the repetitive pulses on the temperature rise and temperature difference at the surface is examined. Laser power distribution with Gaussian profile is assumed and 3D heating model is accommodated in the heating analysis. A numerical method is employed to solve governing equations of heat transfer. It is found that the rate of surface temperature rise is high and temperature difference is large for high duty cycle during the consecutive pulse irradiation. This in turn enhances the thermal cyclic loading of the heated surface.     

The influence of temperature on the measurements of Reynolds stresses in shear free turbulence near a wall

 Temperature changes have a significant influence on the measurements of Reynolds stresses in turbulent boundary layers. As compared to the spanwise velocity fluctuations the streamwise turbulence intensity is especially sensitive to temperature deviations. Although this is a general statement its importance is clearly elucidated in a shear-free turbulence near a solid wall, since the mixing due to turbulence production is minimized in this flow. A consequence of temperature influence on hot-wire measurements is that frictional heating from the wall has produced contradictory results in different experiments on shear-free turbulence. In the current paper, measurements of streamwise and spanwise turbulence intensities have been conducted at different wall temperatures, thereby simulating the contradictory results mentioned above. A simple model has been developed showing that the turbulence intensities are affected by both the rms. value of the temperature fluctuations and the correlation between fluctuating temperature and velocity. These correlations are measured and the developed model is used to explain deviations in earlier measurements on shear-free turbulence. Moreover, the individual magnitudes of the two correlations in the temperature correction are estimated and their individual importance is discussed. Received: 17 February 1997 / Accepted: 18 January 1998     

The influence of radiation on the temperature profile of an induced discharge in argon at atmospheric pressure

This study presents a quantitative evaluation of the influence of radiation upon the parameters of a long induced discharge in argon at atmospheric pressure. Radiation heat transfer in the optically transparent tin plasma layers with thickness of the order of several centimeters) and reabsorption spectral intervals is examined. Experimental error produced by inaccurate knowledge of the transfer and optical characteristics of the plasma is evaluated. The effect of convection on radial temperature profile is evaluated.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiztki, No. 6, pp. 35–43, November–December, 1971.     

An influence of temperature on reconstructed middle ear with shape memory prosthesis

In the paper idea of reconstructed middle ear with a prosthesis made of shape memory alloy is proposed. The new design of shape memory prosthesis is used to enable adjusting its length to individual patient’s needs which is a novel contribution of the paper. In order to make a proper fit of prosthesis, a surgeon has to adjust its size and position by cutting step by step classical prosthesis. It takes time of a operation and enlarges a period of patient’s esthesia. Therefore, a shape memory prosthesis (SMP) is proposed to shorten operation time and improve fitting through precisely selected length. A reconstructed middle ear is modelled as a two degree of freedom system with nonlinear shape memory element. Finding advisable periodic and undesirable a periodic and irregular behaviour in various temperature is the main aim of the paper. Results of the study should give an answer whether SMP can be useful in medical practice and should also explain dynamics of the middle ear with SMP. The properties of the shape memory prosthesis, in the form of helical spring, are described here by a polynomial dependence. Firstly, free vibrations are investigated and equilibrium points, next forced vibrations are studied under different parameters of external excitations and temperature range. Bifurcation analysis and stability of periodic solutions are performed in order to reveal the system behaviour. Finally, interesting dynamical findings of chaotic vibrations pure regular and regular oscillations with fluctuation are presented. However, from practical point of view only harmonic response of the stapes is advisable. That can be achieved at the normal temperature of a human body only for small excitation amplitude.     

The effect of temperature gradient on the correlation of temperature fluctuations

In this paper we present the experiment results of the space correlations of temperature fluctuations when there is and is not temperature gradient. From those results we can see clearly that the temperature fluctuation field is isotropic without temperature gradient, and it is obviously anisotropic with temperature gradient. The temperature correlation along gradient direction is obviously larger than the vertical to direction. Our experiment results agree with the theory results of D.W. Dunn and W.H. Rend^[1].     

The race to the nociceptor: mechanical versus temperature effects in thermal pain of dental neurons

The sensing of hot and cold stimuli by dental neurons differs in several fundamental ways. These sensations have been characterized quantitatively through the measured time course of neural discharge signals that result from hot or cold stimuli applied to the teeth of animal models. Although various hypotheses have been proposed to explain the underlying mechanism, the ability to test competing hypotheses against experimental recorded data using biophysical models has been hindered by limitations in our understanding of the specific ion channels involved in nociception of dental neurons. Here we apply recent advances in established biophysical models to test the competing hypotheses. We show that a sharp shooting pain sensa-tion experienced shortly following cold stimulation cannot be attributed to the activation of thermosensitive ion channels, thereby falsifying the so-called neuronal hypothesis,which states that rapidly transduced sensations of coldness are related to thermosensitive ion channels. Our results support a central role of mechanosensitive ion channels and the associated hydrodynamic hypothesis. In addition to the hydrodynamic hypothesis, we also demonstrate that the long time delay of dental neuron responses after hot stimulation could be attributed to the neuronal hypothesis—that a relatively long time is required for the temperature around nociceptors to reach some threshold. The results are useful as a model of how multiphysical phenomena can be combined to provide mechanistic insight into different mechanisms underlying pain sensations.     

壁面温度在多参数下对平板边界层的影响研究

为了得到壁面温度在不同来流速度、不同湍流强度条件下对边界层转捩与减阻的影响规律,本文采用Transitionk-kl-ω模型对低来流速度下无压力梯度的光滑平板进行了数值模拟。结果表明,随着来流速度的升高,壁温升高所起到的减阻效果更好,即高来流速度对壁面温度更为敏感。当来流处于中高湍流强度下时,壁温升高能起到推迟转捩的作用,且随着湍流强度的升高,转捩推迟的效果越好,但减阻效果正好相反;当来流处于低湍流强度下时,壁温升高会使得转捩提前发生。壁温升高抑制了边界层内流体的脉动程度,使得层流的稳态不易被破坏,流动更加稳定;同时,壁温升高使得边界层内流体的速度梯度减小,从而降低了壁面摩擦系数,故壁温升高能起到推迟边界层转捩与减阻的作用。     

The influence of distribution intensity form of heat flux on the temperature by the local quasi-stationary heating on external surface of the ring

The solution of the mixed quasi-stationary heat conduction problem for the ring has been obtained by using a finite Fourier transformation. The heating on the external side surface of the ring due to any locally distributed heat flux, as well as the convective cooling from internal side surface and from the end faces are considered. It has been proved that for some special geometrical and thermo-physical parameters of problem the received solution agrees with well known studies. The influence of some distribution intensity form of heat flux on the maximum temperature was studied.     

Investigation on the influence of nonuniform initial temperature on the transient heat transfer measurement of film cooling

Numerical and experimental investigations on the influence of nonuniform initial temperature on the transient heat transfer measurements are presented in this paper. The case of film cooling is investigated. When the initial wall temperature is nonuniform, the results of heat transfer coefficient and film cooling effectiveness, which are calculated by the equations derived with constant initial temperature, could deviate from the true values badly, especially in the condition of short test duration. Using initial wall temperature which is higher than the real values causes the results of heat transfer coefficient and film cooling effectiveness lower than the true values. And lower initial wall temperature produces higher results of heat transfer coefficient and film cooling effectiveness. However, when the initial temperature distribution in the region where conduction plays more influence on the wall surface temperature than the convection is well fitted by the cubic polynomial, accurate results can be obtained by the new equation which is derived from 1-D unsteady conduction model with nonuniform initial wall temperature. Some suggestions are also introduced to reduce the influence of nonuniform initial temperature when the initial temperature distribution is difficult to obtain and the equation derived from constant initial temperature has to be employed.     

固化温度对碳纤维/环氧基体界面行为影响的分析

对界面粘结性能及热残余应力影响下的单纤维复合材料的界面行为进行了分析。采用界面的弹性-软化内聚力模型,用解析法对单纤维复合材料由固化引起的热残余应力、以及单纤维碎断过程纤维的轴向应力分布进行了模拟,得到了碳纤维/环氧树脂在常温和高温固化两种情况的界面粘结性能。结果表明：与常温固化相比,高温固化后,界面的剪切强度增幅不大,界面的断裂韧性显著增加;高温固化后形成的界面,使界面的软化提前、界面的脱粘延迟;高温固化产生的纤维轴向和界面径向热残余应力对界面的软化均有延迟作用;界面径向热残余应力还对界面的脱粘有延迟作用。     

The influence of temperature on flow-induced forces on quartz-crystal-microbalance sensors in a Chinese liquor identification electronic-nose: three-dimensional computational fluid dynamics simulation and analysis

An electronic-nose is developed based on eight quartz-crystal-microbalance(QCM) gas sensors in a sensor box, and is used to detect Chinese liquors at room temperature. Each sensor is a highly-accurate and highly-sensitive oscillator that has experienced airflow disturbances under the condition of varying room temperatures due to unstable flow-induced forces on the sensors surfaces. The three-dimensional(3D) nature of the airflow inside the sensor box and the interactions of the airflow on the sensors surfaces at different temperatures are studied by computational fluid dynamics(CFD) tools. Higher simulation accuracy is achieved by optimizing meshes, meshing the computational domain using a fine unstructural tetrahedron mesh. An optimum temperature, 30°C, is obtained by analyzing the distributions of velocity streamlines and the static pressure, as well as the flow-induced forces over time, all of which may be used to improve the identification accuracy of the electronic-nose for achieving stable and repeatable signals by removing the influence of temperature.     

The influence of body speed on cavitation noise

The present paper analyzes the relationship between the body speed and thecavitation noise.The results indicate that there is the limiting value of cavitation noise.     

The influence of cellular structure on detonation transmission

We present two-dimensional numerical simulations of the transmission of detonation from a rectangular channel into a larger volume. The simulations solve the Euler equations on a Cartesian grid using the method of Flux-Corrected Transport for the fluid equations and a two-step induction parameter model for the chemistry. We simulate detonation in a H₂/O₂/Ar mixture and use sufficient grid resolution to resolve the cellular structure of the detonation. When a planar detonation front without a resolved cellular structure expands into the larger volume, the reaction front separates from the shock front and the detonation fails. When the planar front is perturbed to induce a quasi-regular cellular structure in the detonation, it again initially begins to fail, but now the presence of the transverse waves leads to reignition of the detonation in the larger volume. The form of this reignition shows striking similarities to the reignition of detonation which has been seen experimentally in H₂/O₂ mixtures. We describe this reignition mechanism in detail, and also investigate the dependence of the reignition on the number of cells in the detonation front. An abridged version of this paper was presented at the 15th Int. Colloquium on the Dynamics of Explosions and Reactive Systems at Boulder, Colorado, from July 30 to August 4, 1995