Point Temperature Research Articles

Temperature Prediction of Friction Stir Welding Based on Bayesian Neural Network

This paper established a neural network based on Bayesian regularization, which was used for temperature prediction of feature points in friction stir welding metal. Sample data included rotation speed, welding speed, distance, depth, time and temperature of feature points. The representative sample data was obtained through the orthogonal experiments. Neural network was improved by Bayesian algorithm, and the constraint term representing complexity of network was introduced into the objective function. Then generalization ability of neural networks has been enhanced. Prediction accuracy, training time and stability of network are better than in the traditional neural network. Test proved that this smaller network model operates faster, and it can accurately predict the temperature of feature points of friction stir welding.

Effects of Arc Discharge on Wear Properties of Carbon-Carbon Composites Sliding against Cu Trolley under Electric Current

Influence of arc discharge to the contact strip of carbon-carbon composites was orthogonally studied on the HST-100 tribo-tester under electric current, which simulated working conditions of the pantograph-wire system used in electric railway. The regression equation between specific wear rate and arc discharge were obtained and analyzed through the non-linear regression and orthogonal design. The results of the experiments show that a power function between specific wear rate and arc discharge was obtained. Microstructure and phase composition were observed and analyzed by scanning electron microscope(SEM), energy dispersive X-ray spectrum(EDS) and temperature sensor. The results revealed that the arc discharge dissipation seriously affects tribological characteristics of the carboncarbon composites. The temperature of some local contact points beyond their melting point with the electric arc heat effect, and give rise to the desposite carbon and friber carbon were vaporazated, which form the lubrication film on the wear surface, and with the augmant of the arc discharge, the area of lubrication film of carbon was decrease. Therefore, the main wear form of the arc erosion of the carbon-carbon composites is evaporate erosion and material transfer.

Thermoplastic polyolefin nanocomposites: effect of mechanical, thermal, and morphological properties

The polymer nanocomposites were prepared by melt compounding from polypropylene/thermoplastic elastomer (PP-TPE) with sodium montmorillonite (Na-MMT) and cloisite 20A using maleic anhydride modified PP-grafted maleic anhydride (PP-g-MA) as a compatibilizer. Three different weight percentages (3, 5, and 7 wt%) of nanoclay (Na-MMT or C20A) were used to study the effect on the properties of nanocomposites. The optimized clay composition of 5% was tested by varying the wt% of compatibilizer (5, 10, 15, and 20) to obtain better performance properties of nanocomposites. The excellent improvements in mechanical properties were observed by the incorporation 5 wt% cloisite20A with 5% compatibilizer. TPO nanocomposites show higher melting point and thermal degradation temperature on heat loading. The good thermal stability was confirmed from DSC and TGA. The intercalated/exfoliated phenomenon was indicated by the increase in Tg and storage modulus using DMA. Wide angle X-ray scattering (XRD) was employed to study the size and changes in the morphology; it is also provided conclusive evidence for the formation of exfoliated structures.

Thermal Annealing Effects on the Absorption and Structural Properties of Regioregular Poly(3-Hexylthiophene) Films

Regioregular poly(3-hexylthiophene) (P3HT) was synthesized by a Grignard metathesis method. The annealed and fast cooled P3HT films were studied by UV-vis absorption spectroscopy, atomic force microscopy, and grazing incidence X-ray diffraction (GIXRD) measurements. It is demonstrated that thermal annealing at around the onset temperature of the melting point of the polymer results in the annealed film having the highest interchain and intrachain orders while preserving the original morphological features. However, the film that has the highest or lowest crystallinity does not have the strongest or weakest absorption. The lack of clear correlation between the absorption spectra and GIXRD data is explained by a quasi-ordered phase model, in which crystalline, amorphous, and quasi-ordered chains interconvert into each other depending on annealing temperature.

Numerical Analysis on Propagation Characteristics and Safety Distance of Gas Explosiona

Through a roadway model with cross-section area of 80×80 mm2 and length of 100 m, the changing laws of overpressure, temperature, density, combustion rate and gas velocity after the explosion of methane-air mixtures with concentration of 9.5% and filling lengths of 2 m, 6 m, 10 m and 14 m were simulated by using AutoReaGas software. The results show that in the explosion propagation process, the peak overpressure firstly decreases, then increases, and then attenuates until to zero. However, flame propagation speed firstly increases, then begins to reduce and decreases until to zero. With the increase of methane filling length, the safety distance firstly increases and then decreases slightly, and the maximum distance of flame propagation increases linearly. With the increase of methane filling length, the initial peak overpressure and the maximum peak overpressure obviously increase, the peak overpressure and the maximum temperature in other points almost continually increase, and the distance where peak overpressure begins to rise and obtains its maximum value also increases. The time of flame arrival in the same point at various filling lengths is almost the same before flame speed begins to decrease, indicating that flame speed is almost the same before it decreases. Research results can be used to provide guidance for the safety of underground persons, the disaster relief and treatment of gas explosion in underground coal mines.

Hawking radiation of dynamical Kinnersley black hole under the new tortoise coordinate transformation

With two new tortoise coordinate transformations, Hawking effect from a dynamical Kinnersley black hole is investigated by using the improved Damour-Ruffini method. After the tortoise coordinate transformation, the Klein-Gordon equation can be written in the standard form at the event horizon. Then extending the outgoing wave from outside to inside of the horizon analytically, the surface gravity and the Hawking temperature can be obtained automatically. It is found that Hawking temperature of different points on the surface are different. There is a problem of dimension in the usual tortoise coordinate and the results are different from those of the same black hole by using two different tortoise coordinate transformations. The results obtained by using two new tortoise coordinate transformations are still different.

Explosive Consolidation and its Application on Preparing of Ultra-Fine Grained Tungsten Plasma Facing Material

Nuclear fusion is a promising source of environmental friendly energy for the future, and the ultra-fine grained Tungsten (W) is a hopeful candidate material to be used as plasma-facing materials (PFMs), which are the key materials in the International Thermonuclear Experimental Reactor (ITER), for its many useful advantages. While, due to its high melting point and high sintering temperature needed, the ultra-fine grain sized tungsten is not easy to be fabricated. In this paper, the method of explosive consolidation of powders as well as its mechanism and improvements are discussed, and finally the possibility of using this method to preparing of ultra-fine grained W plasma facing material are also introduced.

Bilateral Comparison Between CEM and LACOMET in the Range from 83.8058 K to 933.473 K, Linking to CCT Comparisons

A bilateral comparison between Centro Espanol de Metrologia (CEM) and Laboratorio Costarricense de Metrologia (LACOMET) in the range from 83.8058 K to 933.473 K was carried out during 2009, and it is aimed to provide linkage of the CCT key comparisons K3 and K4 to LACOMET. This comparison gives support to the calibration measurement capabilities requested by LACOMET. The participation of CEM in the EURAMET regional comparisons EUROMET-T.K3 and EUROMET-T.K4 is the basis of the link. Two 25 Ω standard platinum resistance thermometers (SPRTs) were used as travelling standards and were hand carried. One of them was used only in the aluminum freezing point while the other one covered the remaining fixed points. At the temperature of the argon triple point (83.8058 K), CEM performed the measurements in an argon triple-point apparatus, but LACOMET calibrated the SPRT at a temperature close to the argon point using a liquid-nitrogen boiling-point apparatus. Both SPRTs were provided by LACOMET, and LACOMET measured them before and after CEM. The SPRTs showed no significant drifts during the comparison. The results for both laboratories agreed within their expanded uncertainties and are summarized. A proposal for the linkage to the results of CCT-K3 and CCT-K4 is presented.

Evaluation of temperature inside contact system of vacuum chambers

A method has been presented for assessing the wear of a contact system of arc-interruption chambers without degrading the operating capacity of the switching module. In order to confirm the suggested method, life tests of vacuum contactor LSM/TEL have been carried out. The rated current was continually conducted and the temperature of the control points and contact resistance have been measured according to the testing procedure. A thermal model of conducting parts has been designed. The results of the actual test have been used to assess the mathematical model.

SANS study of tuning of clouding in charged micellar system

We report the phenomenon of clouding in charged micellar solution of sodium dodecyl sulfate (SDS) surfactant with varying concentration of tetrabutylammonium bromide (TBAB) salt. The cloud point (CP) temperature is found to decrease significantly with TBAB concentration. Small-angle neutron scattering (SANS) studies have been performed on these systems to understand the evolution of structure and interaction of micelles prior and after the CP. Data are analyzed using Baxter’s sticky hard-sphere potential between the micelles as approaching the CP. It is found that the attractive potential amongst micelles increases with temperature leading to clustering at CP. Both the micelles and clusters coexist at CP and even at temperatures much higher than CP. The propensity of cluster formation strongly depends on the TBAB concentration where higher TBAB concentration provides smaller temperature range over which the clusters are formed. SANS data from clusters show a Porod scattering in the low-Q region, suggesting a very large size of the clusters. The stability of these clusters against phase separation is examined by the time-dependent SANS and compared for different TBAB concentrations.

Tortoise coordinate and Hawking effect in a dynamical Kerr black hole

Hawking effect from a dynamical Kerr black hole is investigated using the improved Damour-Ruffini method with a new tortoise coordinate transformation. Hawking temperature of the black hole can be obtained point by point at the event horizon. It is found that Hawking temperatures of different points on the surface are different. Moreover, the temperature does not turn to zero while the dynamical black hole turns to an extreme one.

Equation of state of the transitive layer in a one-component system and some of its applications

We obtain the equation of state relating the interphase tension at the planar interface of a crystal—the melt proper with the surface tension of free surfaces in one-component system. Numerical calculations for metals are performed at the temperature of the triple point. Using the obtained equation, we solve a number of problems, including determination of the work of adhesion, the limiting wetting angle of a crystal by the melt proper, the diffluence coefficient due to Harkins, and construction of a Neumann triangle.

Indirect Determination of the Thermodynamic Temperature of a Gold Fixed-Point Cell

Since the value T90(Au) was fixed on the ITS-90, some determinations of the thermodynamic temperature of the gold point have been performed which form, with other renormalized results of previous measurements by radiation thermometry, the basis for the current best estimates of (T − T90)Au = 39.9 mK as elaborated by the CCT-WG4. Such a value, even if consistent with the behavior of T − T90 differences at lower temperatures, is quite influenced by the low values of TAu as determined with few radiometric measurements. At INRIM, an independent indirect determination of the thermodynamic temperature of gold was performed by means of a radiation thermometry approach. A fixed-point technique was used to realize approximated thermodynamic scales from the Zn point up to the Cu point. A Si-based standard radiation thermometer working at 900 nm and 950 nm was used. The low uncertainty presently associated to the thermodynamic temperature of fixed points and the accuracy of INRIM realizations, allowed scales with an uncertainty lower than 0.03 K in terms of the thermodynamic temperature to be realized. A fixed-point cell filled with gold, 99.999 % in purity, was measured, and its freezing temperature was determined by both interpolation and extrapolation. An average TAu = 1337.395 K was found with a combined standard uncertainty of 23 mK. Such a value is 25 mK higher than the presently available value as derived by the CCT-WG4 value of (T − T90)Au = 39.9 mK.

An empirical theoretical investigation into phase and structural behaviour in Ti–Al alloys

According to the average lattice and atom models of the empirical electron theory of solids and molecules (EET), effects of interstitial impurities on valence electron structures and phase transformation of Ti–Al alloys are analysed. Furthermore, the descendant degree of bond energy, melting point, and liquidus temperatures affected by interstitial impurities are calculated based on the bond energy formula of the EET. Moreover, the main controversial experimental results on the phase transformation in Ti–Al alloys are explained well. It is demonstrated that because of the effects of interstitial impurities, atom states increase, bond structures are seriously anisotropic, which results in very complex phase transformations in intermediate Al content. It is also shown that the melting point and liquidus temperatures decrease due to interstitial impurities, and the average decreased degree can be estimated very well using the EET.

Filter materials for bag filters with pulsed regeneration

The effect of dust properties, parameters and composition of gases for cleaning on the choice of synthetic filter materials for bag filters with pulsed regeneration is considered. Particular attention is devoted to cleaning high-temperature moist gases containing corrosive components. Recommendations are proposed for calculating the temperature of the acid dew point of gases being cleaned. Comparative characteristics are provided for synthetic materials produced overseas and used in gas filtration.

Application of Transfer Functions to Canned Tuna Fish Thermal Processing

Design and optimization of thermal processing of foods need accurate dynamic models to ensure safe and high quality food products. Transfer functions had been demonstrated to be a useful tool to predict thermal histories, especially under variable operating conditions. This work presents the development and experimental validation of a dynamic model (discrete transfer function) for the thermal processing of tuna fish in steam retorts. Transfer function coefficients were obtained numerically, using commercial software of finite elements (COMSOL Multiphysics) to solve the heat transfer balance. Dependence of transfer function coefficients on the characteristic dimensions of cylindrical containers (diameter and height) and on the sampling interval is reported. A simple equation, with two empirical parameters that depends on the container dimensions, represented the behavior of transfer function coefficients with very high accuracy. Experimental runs with different size containers and different external conditions (constant and variable retort temperature) were carried out to validate the developed methodology. Performance of the thermal process simulation was tested for predicting internal product temperature of the cold point and lethality and very satisfactory results were found. The developed methodology can play an important role in reducing the computational effort while guaranteeing accuracy by simplifying the calculus involved in the solution of heat balances with variable external conditions and emerges as a potential approach to the implementation of new food control strategies leading not only to more efficient processes but also to product quality and safety.

Design of Heating Cycle in Hydrogen Annealing Furnaces

Cold-rolled steel strips are annealed in batch annealing furnaces after coiling to release rolling residual stresses and to obtain desirable physical properties upon reaching recrystallization temperature. Simulation of coil behavior during heating cycle can be used to predict the temperature of coil middle points that cannot be measured directly so that furnace turn-off is properly scheduled. Using heat transfer equations and experimental data, a mathematical model of coil heating in hydrogen annealing furnaces was developed. This model is not only capable of predicting temperature distribution of all coil under various annealing conditions, but can also be used to design the heating cycles in a manner that all the constraints on temperature differences within coils are satisfied. Experiments confirmed the accuracy of the model in terms of its temperature predictive power and heating cycle scheduling capability.

Experimental observations of flow modifications in nanofluid boiling utilizing particle image velocimetry

In order to understand the effects of nanofluids upon boiling, pool boiling experiments involving both pure water and water based nanofluids were investigated. Point temperature and full velocity field measurements were obtained during pool boiling conditions using state-of-the-art dynamic particle image velocimetry (DPIV). Specifically, results of nanofluid's effect upon nucleate boiling heat transfer are investigated, in an effort to find engineering solutions in critical applications such as nuclear energy. A change in the hydrodynamic behavior of bubbles was observed with the introduction of nanoparticles. The measured velocity fields exhibited different fluid behavior for the various cases investigated which in turn highlights the complexity of the fluid flow in the pool boiling experiment. The results show a relation between wall temperature and nanofluid concentration.

The development of rubber-thermoplastic blends from ground tyre rubber and waste polypropylene

Ground Tyre Rubber (GTR) from scrap automotive and truck tyres was blended with Waste Polypropylene (WPP) from injection moulded products to prepare GTR/WPP blends . The blends were prepared in a Haake Rheocord PolyLab System, operating at 180 0 C and 30 rpm for 8 minutes. The degree of crystallinity of the WPP in the GTR/WPP blend was found to be unchanged up to a GTR level of 60 % by weight. Crystalline melting point and re-crystallization temperature showed a significant decrease with GTR content. Optical micrograph of the blends containing up to 60 wt% GTR showed a similar morphology, in which the GTR was dispersed in a continuous WPP phase. The GTR dispersed phase grew in size with GTR content until at 70 wt%, it changed to a continuous phase. However, all blends showed a mixture of cohesive, adhesive and ductile failures. The response to tensile loading ranged from a ductile plastic response with WPP-rich blends to a high extension-rubbery response with GTR-rich blends. Under impact loads, brittle fracture occurred in blends containing up to 40 wt% GTR, with ductile fracture thereafter. Hardness, tensile strength, secant modulus at 7% strain and tear resistance decreased with increase in GTR content, while % elongation at break and impact failure energy increased.

Temperature-Sensitive Association Properties of End-Functionalized Poly(N-isopropylacrylamide) in Dilute Aqueous Solutions

It is well known that a thermo-responsive poly(N-isopropylacrylamide) (PNIPAM) becomes turbid above a cloud point (CP) temperature. In this study, the phase transition changes of PNIPAM end-functionalized with pyrenyl group (Py-PNIPAM) were investigated in dilute aqueous solutions. Two types of Py-PNIPAMs were prepared; one is an ester-linkage type (Py-OCO-PNIPAM), and the other an amide-linkage type (Py-NHCO-PNIPAM). From temperature dependence of fluorescence and fluorescence-excitation spectra for these polymer solutions, the micelle-like aggregates formation was found to be more favorable in Py-OCO-PNIPAM. To elucidate the cause of the difference, the partial dipole moments (PDM) of end-pyrenyl groups was obtained by molecular orbital calculations. The PDM value of the ester linkage type was smaller than that of the amide linkage type. The smaller value of PDM in the ester linkage type may explain the reason for the higher ability to form a micelle of Py-OCO-PNIPAM if the pyrenyl groups are assumed to be the core in the micelle.