Results Of Thermal Measurements Research Articles

Robustness of the pyrochlore structure in rare-earth A2Ir2O7 iridates and pressure-induced structural transformation in IrO2

A comprehensive study of the structural properties of the heavily investigated rare-earth A2Ir2O7 iridate series under extreme conditions is presented. From Pr2Ir2O7 to Lu2Ir2O7, the series is sufficiently covered by iridates with A = Pr, Sm, Dy, Ho, Er, Tm, Yb, and Lu; general trends and systematics within the series, including the understudied heavy-rare-earth members, are dependably followed. Temperature- and pressure-dependent synchrotron X-ray powder diffraction experiments reveal robustness of the pyrochlore structure throughout the series, down to 4 K and up to 20 GPa. The thermal expansivity of the pyrochlore lattice is determined, all falling in the Debye temperature range of θD = 360–420 K. The pressure compressibility shows a systematic increase of the bulk modulus with the rare-earth atomic number from K = 180–210 GPa. Combining the results of thermal measurements (Debye temperature) and pressure measurements (bulk modulus) enables us to determine the Grüneisen parameter of selected members and compare it to previous studies. Temperature and pressure evolution of the fractional coordinate of oxygen at 48f Wyckoff position, the sole free fractional coordinate in the crystal structure, is investigated and discussed regarding the antiferromagnetic ordering of the Ir magnetic moments. In addition to results on A2Ir2O7 iridates, the temperature and pressure evolution of the crystal structure of an IrO2 minority phase is followed. The tetragonal rutile-type structure is stable down to the lowest temperature. However, an application of pressure of approximately 15 GPa induces a structural transition: The tetragonal structure is orthorhombically distorted. The orthorhombic structure is still not fully stabilised at 20 GPa, and further distortion of the lattice (or subsequent structural transformations) is expected with increasing external pressure.

Pengaruh Bukaan Pada Ruangan Rumah Type 36 Terhadap Kenyamanan Termal Menurut Persepsi Pengguna

Abstract. A house as a shelter for the occupants requires ventilation, both natural and artificial, to achieve thermal comfort. Openings allow air to circulate in and out of the building, thus affecting the humidity and temperature of the building. The research was located in the Type 36 Mutiara Baet Residence housing complex, in Baet Village, Baitussalam District, Aceh Besar Regency. The case study is a house facing west, east, north, and south which has openings without direct sunlight. Using a mixed method research method, which combines qualitative and quantitative models. Qualitative methods are carried out using documentation, interviews, and observation. while the quantitative method is carried out through measurements of humidity, wind speed, and temperature. Interview results showed that 70% of building occupants said that the residence they lived in felt hot so it was uncomfortable to be indoors without mechanical cooling, while the existing openings could not be maximized for natural ventilation as intended. The remaining 30% of respondents thought that openings could help reduce heat. The results of thermal measurements, the average temperature in the living room was 30.93°C, while the average temperature in the kitchen room was 30.99°C. The results of measuring the average humidity (RH%) in the living room was 46.40% and the average humidity (RH%) in the kitchen room was 46.18%. Only 20% of residential living rooms and kitchens in Mutiara Baet Residence have wind circulation, while in the other 80% of residences, the detected wind speed is 0.0 m/s, which means there is no wind movement/circulation

Design and Fabrication of a Novel Poly-Si Microhotplate with Heat Compensation Structure.

I Microhotplates are critical devices in various MEMS sensors that could provide appropriate operating temperatures. In this paper, a novel design of poly-Si membrane microhotplates with a heat compensation structure was reported. The main objective of this work was to design and fabricate the poly-Si microhotplate, and the thermal and electrical performance of the microhotplates were also investigated. The poly-Si resistive heater was deposited by LPCVD, and phosphorous doping was applied by in situ doping process to reduce the resistance of poly-Si. In order to obtain a uniform temperature distribution, a series of S-shaped compensation structures were fabricated at the edge of the resistive heater. LPCVD SiNx layers deposited on both sides of poly-Si were used as both the mechanical supporting layer and the electrical isolation layer. The Pt electrode was fabricated on the top of the microhotplate for temperature detection. The area of the heating membrane was 1 mm × 1 mm. Various parameters of the different size devices were simulated and measured, including temperature distribution, power consumption, thermal expansion and response time. The simulation and electrical-thermal measurement results were reported. For microhotplates with a heat compensation structure, the membrane temperature reached 811.7 °C when the applied voltage was 5.5 V at a heating power of 148.3 mW. A 3.8 V DC voltage was applied to measure the temperature distribution; the maximum temperature was 397.6 °C, and the area where the temperature reached 90% covered about 73.8% when the applied voltage was 3.8 V at a heating power of 70.8 mW. The heating response time was 17 ms while the microhotplate was heated to 400 °C from room temperature, and the cooling response time was 32 ms while the device was recovered to room temperature. This microhotplate has many advantages, such as uniform temperature distribution, low power consumption and fast response, which are suitable for MEMS gas sensors, humidity sensors, gas flow sensors, etc.

Characterization of Anisotropic Properties of Hot Compacted Self-Reinforced Composites (SRCs) via Thermal Diffusivity Measurement

AbstractThe mechanical properties of self-reinforced composites (SRCs) produced in a hot compaction process significantly depend on the process parameters. Only a little deviation of the process temperature or pressure causes the component to act differently under mechanical load. This is a chance and a challenge at the same time, since this process is difficult to handle but by properly controlling the process parameters, the mechanical properties can be adjusted, even locally for one component. In this research SRC are manufactured in a hot compaction process. A correlation between process parameters and density is found. Density increased from 0,8 to 0,91 g/cm³ by increasing temperature and pressure in the hot compaction process. The different thermal properties in the direction of orientation (IP) and transverse to orientation (TP) are measured with a laser flash device. It was found that, due to a change in density and molecular orientation, diffusivity and conductivity are influenced in different degrees in IP and TP directions. For interpretation of thermal measurement results, microstructures are analysed with a confocal laser scanning microscope after preparing the specimen with a permanganate etching. A schematic model of conductive path is worked out and discussed. With measurement data the anisotropy of IP and TP diffusivity is calculated, and a model is built to describe relative density related to anisotropy. The highest anisotropy between IP and TP diffusivity was calculated with a ratio of 6 at a relative density of approximately 0,82 g/cm³. Since mechanical properties in correlation to process parameters have already been investigated, results of this investigation, in combination with previous research on mechanical properties, will enable the development of a non-destructive testing method for SRCs by measuring the thermal diffusivity.

Based on SWA Sensor Energy Consumption Under the Sports Fitness and Strength of the Correlation Research

SWA sensor is used to measure the treadmill walking running and cycling on the spot when the energy consumption, and compared with the indirect method of measuring thermal measurement results, the SWA to measure the effectiveness of the energy consumption for fitness, provide a reference for accurate application of the sensor. In 15 adult male in tablet exercise treadmill to complete the 4.8 km/h, 6.4 km/h, 8.0 km/h speed of three movement walk, run, and complete 10 km/h in indoor, 13 km/L, 15 km/h cycling sport, using SWA (two software version V6.1, V7.0) and indirect method of measuring thermal forecast movement of energy consumption, to predict data matching test, regression analysis, correlation analysis, Ie coefficient and consistency check. Results: (1) gWA6.1 overestimated the treadmill run go (1% overvalued) and field cycling of energy consumption (9% overvalued), but has good correlation and consistency (r = 0.91, the ICC = 0.91). Gara sensor (2) prediction of energy consumption for fitness value is far greater than the indirect method of measuring thermal prediction of energy consumption, and to predict the energy consumption difference increased with the increase of speed increasing, and the sensor old version overestimate low intensity exercise energy consumption and high intensity of energy consumption is different, but the estimate of the energy consumption and had a

Thermal analysis, design, and characterization of a reconfigurable switch matrix based on LTCC technology for satellite communications

The thermal characteristics of a reconfigurable switch matrix (RSM) module based on low temperature co-fired ceramic (LTCC) technology are presented. Owing to the PIN-diodes based design, a static power of 1.6 W is dissipated on the ceramic package; the double-sided mounting and integrated bias circuitry demands determination of the temperature distribution within the module. A finite-element thermal simulation model was validated by an infrared (IR) thermograph; the steady-state temperature distribution on the surface of the package estimated by the simulation model differs to the IR measurements by < 1%. This temperature distribution is the result of the thermal interaction among components on the multi-die package with different electrical power dissipation. The temperature on the multi-throw switch monolithic microwave integrated circuit (MMIC) is elevated by ~36.7 K relative to the ambient temperature. The peak temperature occurs on the current-limiting resistors in the bias circuitry; the peak temperature is estimated to be ~45 K above the ambient. In a later version of the RSM, the bias current was reduced by 50%, current-limiting resistor was replaced by two parallel resistors, and additional thermal vias and conductive pads were introduced on the ceramic package. The cumulative effect is a temperature distribution on the package with lowered values. Compared to its predecessor, the temperatures at the current-limiting resistor and the MMIC are reduced by ~20 K and ~14 K, respectively. With one heat source active on the ceramic package at a time, the resulting steady-state temperatures on this source and the remaining heat sources provided an estimate of the self- and transfer-thermal resistances, respectively. The reciprocity of the heat flow on the package and the three-dimensional symmetric layout required only ‘4’ thermal simulations to determine the symmetric thermal resistance matrix. The significantly reduced values of the computed matrix for the later version of the RSM module demonstrated lower thermal resistance to the ambient, compared to its predecessor. Lastly, the results of thermal measurements conducted with a vacuum wafer prober are presented, in order to validate RSM functionality for vacuum pressures (≤ 1 mPa) and temperatures between 248 K and 338 K; the control current and the transmission coefficient demonstrated variations of ≤ 0.5% and −0.015 dB/K, respectively.

Synthesis and thermal properties of poly(ethylene 2,6-naphthalate) copolyesters containing modified diacid monomer

A series of poly(ethylene 2,6-naphthalate) (PEN) copolyesters was synthesized using three monomers (newly prepared 1,4-bis[(methoxycarbonylethoxy)methyl]benzene, dimethyl 2,6-naphthalenedicarboxylate, and ethylene glycol) with various molar ratios to investigate the effects of these compositions on thermal properties of the copolyesters. Copolyesters having weight average molecular weights of 11,000–22,000 were obtained by melt polycondensation in the presence of metallic catalysts. The structures and thermal properties of the resulting random PEN copolyesters were characterized by nuclear magnetic resonance, differential scanning calorimetry, thermal-mechanical analyzer, and X-ray diffraction analysis. The results of thermal measurements revealed that thermal properties depended on the corresponding new diacid comonomer content of the PEN copolyesters. Nonetheless, the crystal structures of PEN copolyesters and PEN homopolymer are identical. POLYM. ENG. SCI., 54:2641–2644, 2014. © 2013 Society of Plastics Engineers

Synthesis, structural and catalytic activity of binaphthyl macrocyclic complexes

The binaphthyl macrocyclic ligand, N,N′-diethyl-[3,3′-(2,2′-dihydroxy-1,1′-binaphthyl)carboxamide]-2,2′-dihydroxy-1,1′-binaphthyl-3,3′-dicarboxylic acid (DDCDB), has been synthesized and investigated. The ligand (DDCDB) and its metal complexes involving CuII, ZnII, UO2II, ThIV, CeIII, MoVI and WVI ions have been prepared and characterized by spectral (i.r., u.v.–vis.), elemental analyses, magnetic moments and thermal analyses measurements. DDCDB behaves as a tridentate ligand towards CuII, ZnII and UO2II ions coordinating via CO, NH and the deprotonated naphthyl OH groups in a ratio of 2:1 (M:L). On the other hand, DDCDB behaves in a bidentate manner coordinatingvia the NH and the deprotonated naphthyl OH groups only in case of the ThIV, CeIII, MoVI, and WIV ions and in ratio 1:1 (M:L). Results of thermal measurements confirm the existence of solvent molecules inside and outside the coordination sphere. ThVI complex has been applied for the hydrolysis of phosphodiester and the results show a significant rate enhancement of ~5.8 million fold with respect to the auto-hydrolysis of bis-(p-nitrophenyl) phosphate (BNPP) under the same conditions Also, CuII complex accelerates the photodegradation of the hazardous pollutant (acid green dye) in the presence of hydrogen peroxide by degrading 90% of the dye within 23 min.

Quasi-reversible solid-phase reaction in the superprotonic conductor Cs5H3(SO4)4·xH2O

The thermal effect and heat capacity in a single crystal of nonstoichiometric cesium sulfate hydrate were measured. It was established that superprotonic conduction in this material is caused by an isothermal solid-phase transformation in the bulk of the single crystal. The results of thermal measurements were compared with experimental data on the electrical conductivity.

Thermal and rheological characterization of cellulose spinning dopes modified with nanosilica and antibacterial agents

AbstractThe present study concerns cellulose spinning solutions prepared with the use of the organic solvent N‐methylmorpholine‐N‐oxide (NMMO). These solutions were modified with two types of antibacterial agents: an inorganic agent zirconium‐silver phosphate (Alphasan®) and an organic one Triclosan (Irgasan® DP300). Such spinning solutions allow to obtain antibacterial fibers of the Lyocell type. A nanomodifier, colloidal silica (Ludox SM 30®), was also incorporated into the spinning solutions as an additional component to increase the antibacterial activity of fibers. The effect of the compounds incorporated into the spinning solutions on their rheological and thermal properties was assessed by means of the oscillatory method and differential scanning calorimetry (DSC), respectively. The incorporation of nanosilica exerts a clear influence on the rheological properties of spinning solutions, whereas this effect is negligible in the simultaneous presence of nanosilica and antibacterial agents. The results of thermal measurements show that nanosilica affects the crystallization of the solutions examined. Depending on the type of antibacterial agent, nanosilica brings about either a delay or acceleration of the crystallization of the modified solutions. The effect of nanosilica can be explained in terms of interactions between hydroxyl groups occurring on the surface of silica nanoparticles and NMMO molecules. Copyright © 2007 John Wiley & Sons, Ltd.

Properties of 19P/Borrelly

Properties as temperatures, sublimation, and outgassing rates, are determined for different surface parameters to model the surface of the nucleus of comet 19P/Borrelly. The derived outgassing properties indicate that only about 6% of the day-side surface of this cometary nucleus can be expected to contribute to the astronomically observed gas production rate. This is in agreement with DS-1 imaging and thermal measurement results. The small value of the day-side active areas indicates a Halley-type surface of only locally restricted active areas or zones, while most of the surface is passive but hot with maximum temperatures above 300 K. Thus, it is expected that the comet surface is mainly covered by a hot upper surface layer of refractory materials. The temperature of the local active areas with free sublimation is expected in the range of about 200 K.

Characterizations of a branched ester-type lithium imide in methoxy ether-substituted poly(organophosphazenes)-based solid polymer electrolytes

A branched ester-type lithium imide—lithium bis[(1,1,1,3,3,3-hexafluoro-2-propoxy) sulfonyl] imide (LiN[SO 2OCH(CF 3) 2] 2, LiHFPSI) was used as the salt for methoxy ether-substituted poly(organophosphazenes) {NP[(OCH 2CH 2) x OCH 3] 2} n (where x = 2–4, ME x P) based polymer electrolytes. Their ionic conductivity, electrochemical stability and thermal stability have been characterized. The highest conductivity at 25 °C for ME x P–LiHFPSI complexes (4.48 × 10 −4 S/cm) was obtained when x = 4 and the molar ratio of Li + to repeat unit was 3:8. The results of the FT-IR spectroscopy were examined to gain further insight into the structure of the electrolytes. The results of thermal measurements showed that these electrolytes were fully amorphous materials and were stable up to 200 °C. The electrochemical experiments showed the electrochemical stability window of these electrolytes were in excess of 6.0 V (versus Li +/Li).

A ventilated courtyard as a passive cooling strategy in the warm humid tropics

The paper investigates the potential of a courtyard for passive cooling in a single storey high mass building in a warm humid climate. The inclusion of an internal courtyard in building design is attributed to the optimization of natural ventilation in order to minimize indoor overheating conditions. However, the efficiency of this strategy greatly depends on the design details of the building composition in providing appropriate airflow pattern to the courtyard. From the results of thermal measurements, a significant correlation between wall surface temperatures and indoor air temperatures is evident. A reduction of indoor air temperature below the levels of ambient is seen as a function of heat exchange between the indoor air and high thermal mass of the building fabric. However, this behavior is affected by indoor airflow patterns, which are controlled through the composition between envelope openings and the courtyard of the building. From a computational analysis, several airflow patterns are identified. A relatively better indoor thermal modification is seen when the courtyard acts as an air funnel discharging indoor air into the sky, than the courtyard acts as a suction zone inducing air from its sky opening. The earlier pattern is promoted when the courtyard is ventilated through openings found in the building envelope. The computational simulation utilizing the standard k- ϵ turbulent model with isothermal condition agrees closely with the measurements taken from the field investigation.

Thermophysical properties reference data for some key engineering alloys

A summary is given of the results of various NPL measurements carried out over a number of years on specimens of 310 and 430 stainless steel, Inconel 600, and Nimonic 75 alloys. The properties measured were thermal conductivity, λ, thermal diffusivity, a, specific heat capacity, C p , and electric resistivity, p. Linear thermal expansivity values are also included to allow corrections to be made to the results of thermal measurements, including density, due to dimensional changes that occur on heating. Definitive NPL values are presented for selected thermophysical properties for three key engineering alloys, over the temperature ranges from ambient to 750 °C and for one alloy up to 500 °C. In addition comparisons are made between the measured thermal conductivity values and those obtained indirectly from measurements of (i) thermal diffusivity, specific heat capacity, and density; and (ii) electric resistivity via the Wiedemann-Franz relationship. This comparison study is important, as thermal conductivity is often calculated when direct measurements are either not available or not possible. Overall, the average of the measured values of thermal conductivity and those calculated via measurement of electric resistivity agree to within 4%; and those calculated via measurements of thermal diffusivity, specific heat capacity, and density are in good to moderate agreement within 10%. For austenitic and ferrite steels and nickel-chromium alloys, calculation of thermal conductivity via electric resistivity has proved to be reliable and convenient and its use can be recommended. The derivation of thermal conductivity from thermal diffusivity is reliable, except at temperatures where phase changes occur.

Compact Modeling Approach using GA for Accurate Thermal Simulation.

In this paper, we propose a technique that uses thermal measurement results for improved accuracy in thermal simulation of electronic apparatuses. Because the modeling of the electronic components in such apparatuses has hitherto been very poor, the thermal simulation results cannot satisfy the required accuracy. To solve this problem, we first represent a component as a set of cubic blocks with equivalent thermal conductivities and contact thermal resistances, and then identify these by using the thermal measurement results for the component. We regard the identification of parameters as an optimization problem that involves minimizing the difference between the calculated and measured results.n To solve the problem, we combine genetic algorithms and a thermal simulation tool. Our technique was successfully applied to the construction of an accurate thermal model, which we validated by using thermal measurement results.

Comments on the interpretation of temperature dependence of processes in polymers

The interpretation of the results of thermal measurements followed over decades the Arrhenius law. In recent years an apparently different interpretation (Eyring's equation) has been emerging in the literature on polymers. As the main reason for this, a direct connection to material properties has been claimed. The paper shows some weak points in the Eyring theory and in its application as well. Firstly, the parameters of the two equations are mathematically convertible to each other. Thus Eyring's conceptual quantities (entropy and enthalpy of activation) give no new physical information. Secondly, the Eyring theory postulates an equilibrium for the activated state. In the case of processes, however, in which change is an inherent characteristic, this assumption seems to be unjustified.

Interaction of CO2 laser and soft tissue. The basic mechanism of the carbon dioxide laser irradiation of the soft tissue.

The purpose of this paper was to investigate the immediate effects of CO2 laser radiation on soft tissue. The morphological changes were studied with gross observations, light microscopy, scanning electron microscopy and were related to the results of thermal measurements . The events which take place during the irradiation were viewed with ultra high speed photography. Air-borne tisssue particles were investigated with cytosmear test and tissue culture. Based upon the various observations, the following conclusions were drawn. The immediate effects of CO2 laser irradiation consit of two factors : physio-mechanical factor and physio-chemical factor. And the nature of the laser injury, in soft tissue, make laser surgery a practical and satisfactory method of controlled tissue removal.

Thermodynamic properties and phase transitions of solid hydrogen halides and deuterium halides

By analyzing the results of thermal measurements on solid hydrogen halides and deuterium halides described in the preceding papers, the vibrational properties and the mechanism of the phase transitions are discussed. From the low-temperature region, a number of properties have been derived, in particular, the apparent Debye characteristic temperatures at T = 0 and as a function of temperature, the enthalpies of sublimation at T = 0, the static lattice energies, and the energies required to reorient a molecule in the lowest phase III. In the region below the triple point the enthalpies of vacancy formation have been obtained. In the transition region the configurational heat capacities have been separated and the thermodynamic properties of the transitions have been derived. The existence of local order in phase I and the peculiar behavior of the disordering process in the chlorides have been suggested. The mechanisms of phase transitions have been correlated with the molecular interactions.

Solidification in continuous casting of aluminum

During casting of aluminum ingot by a new process utilizing level pouring, variations in cooling rate within the surface band occur as a result of the discontinuous nature of metal flow. Associated segregation contributes to a marked cyclic pattern of the macrostructure in that region. The kinetics of metal flow into the surface zone are explained graphically using a sequence of macrographs. The proposed mechanism is also supported by results of thermal measurements and Electron Microprobe analyses.