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Sawn-timber drying is the wood industry's most time- and energy-consuming process. This process can be more efficient than the conventional method by elevating the dry-bulb temperature to above 100 °C in a high-temperature drying (HTD) process, which for some species shortens the drying process by up to 50% without deteriorating the quality. Comprehending the complex correlation between the wood drying physics at high temperatures and the anatomical features of the specific species, along with its mechanical and physical properties, is crucial, as it limited its application from being broadly implemented in industry and the necessity of generalizing this method for wood species. The present study has been conducted to comprehensively review and tackle the challenges of applying this method on various species and the consequences, such as high moisture content gradients resulting in stress residual, unevenness, and color changes. Energy, environment, and economic (3E) assessments of HTD were evaluated. The accelerated drying process in HTD reduces heat losses and air leaks, resulting in higher energy efficiency than the conventional methods. Furthermore, it was proved to be 20% economically in the long term. Confliction in reported studies, such as HTD's effect on permeability and volatile organic compound (VOC) emissions, was raised, highlighting the importance of further studies for generalizing this method to adapt appropriate drying schedules, focusing on Scandinavian species by referring to previous industrial trials. [ABSTRACT FROM AUTHOR]

Polymer electrolyte membrane water electrolyzers (PEMWE) are currently restricted to an operating temperature range between 50 to 80 °C. This review shows that elevated temperature (ET) above 90 °C can be advantageous with respect to i) reduced cell voltages, ii) a reduction of catalyst loading or possibly the employment of less noble electrocatalysts, and iii) a greater potential for waste heat utilization when the electrolyzer is operated in exothermal mode (when the cell voltage is higher than the thermoneutral voltage). Together with presenting an overview of the materials and components utilized in elevated temperature PEMWE under liquid and steam operation, this article summarizes the experimental and modeling performances reported to date, highlights the challenges ahead, and suggests aspects, which will need to be considered to improve the performance at elevated temperature. Key points, which arise from this work are the extensive need of re‐assessing the material selection both for the cell components and also at a system level, the effects and optimization of working with steam operation, and in the long run, the need for techno‐economic analyses to ultimately assess whether efficiency gains will truly translate to a cost‐effective technology alternative. [ABSTRACT FROM AUTHOR]

In this paper, we investigated the thermoformability of Epoxidized Natural Rubber (ENR)-filled Poly(Lactic Acid) (PLA) films using elevated temperature tensile and ball burst tests. Three different d-Lactide contents of PLA were used to be able to analyze the effect of crystallization and crystallinity. We observed that the ENR acted as a nucleating agent in PLA when the blend was cooled from melt or cold crystallized, but it retarded the drawing-induced crystallization of PLA at elevated temperature tensile testing since ENR droplets acted as obstacles. The effect of NR on PLA crystallization was also found to be dependent on d-Lactide content. In the ball burst test, different behaviors were observed for PLA with the lowest d-Lactide content, which was caused by the complex stress state that even more induced crystallization of PLA and then a single-axis tensile test. [ABSTRACT FROM AUTHOR]

Doped Mott insulators are the starting point for interesting physics such as high temperature superconductivity and quantum spin liquids. For multi-band Mott insulators, orbital selective ground states have been envisioned. However, orbital selective metals and Mott insulators have been difficult to realize experimentally. Here we demonstrate by photoemission spectroscopy how Ca2RuO4, upon alkali-metal surface doping, develops a single-band metal skin. Our dynamical mean field theory calculations reveal that homogeneous electron doping of Ca2RuO4 results in a multi-band metal. All together, our results provide evidence for an orbital-selective Mott insulator breakdown, which is unachievable via simple electron doping. Supported by a cluster model and cluster perturbation theory calculations, we demonstrate a type of skin metal-insulator transition induced by surface dopants that orbital-selectively hybridize with the bulk Mott state and in turn produce coherent in-gap states. Doping is a tried and tested method to tune the properties of a range of quantum materials either by introducing defects into the system or engineering the charge carrier concentration. Here, the authors use photoemission spectroscopy to investigate the effects of surface doping of alkali metals on the Mott insulator Ca2RuO4, revealing an orbital-selective surface metal-insulator transition induced by the surface-dopant interaction. [ABSTRACT FROM AUTHOR]

Doped Mott insulators are the starting point for interesting physics such as high temperature superconductivity and quantum spin liquids. For multi-band Mott insulators, orbital selective ground states have been envisioned. However, orbital selective metals and Mott insulators have been difficult to realize experimentally. Here we demonstrate by photoemission spectroscopy how Ca2RuO4, upon alkali-metal surface doping, develops a single-band metal skin. Our dynamical mean field theory calculations reveal that homogeneous electron doping of Ca2RuO4 results in a multi-band metal. All together, our results provide evidence for an orbital-selective Mott insulator breakdown, which is unachievable via simple electron doping. Supported by a cluster model and cluster perturbation theory calculations, we demonstrate a type of skin metal-insulator transition induced by surface dopants that orbital-selectively hybridize with the bulk Mott state and in turn produce coherent in-gap states. Doping is a tried and tested method to tune the properties of a range of quantum materials either by introducing defects into the system or engineering the charge carrier concentration. Here, the authors use photoemission spectroscopy to investigate the effects of surface doping of alkali metals on the Mott insulator Ca2RuO4, revealing an orbital-selective surface metal-insulator transition induced by the surface-dopant interaction. [ABSTRACT FROM AUTHOR]

Rubber is a waste product produced by the industrial sector in large quantities. Due to its non-degradable nature, it has been a serious threat to the environment. Thus, it is recommended to develop concrete or mortar containing rubber, so that it can save our environment, and it is economical too. Crumb rubber, when incorporated in mortar, reduces its strength, so it can be used along with some fibers to enhance its strength. This study examined the effect of elevated temperatures, i.e., 150, 300, 450, 600, and 750 °C, on mortar samples containing 5% crumb rubber replacement of fine aggregate by volume, and with the incorporation of 1% PPF. The findings indicated a rise in compressive strength up to 300 °C, followed by a subsequent decline. It was also observed that the weight loss of the samples increased with an increase in temperature. [ABSTRACT FROM AUTHOR]

Robust retention of ferroelectric polarization in harsh environments is a requirement for the application of ferroelectric materials in space, liquids, and various chemical conditions. Surface screening of the polarization can significantly alter domain states and usually has a strong influence on domain stability in ferroelectrics, hindering applications that require defined and non-volatile polarization states. Here, we show that designer defects in BiFeO3 can be engineered to strongly pin domain walls, which even in harsh environments such as 100% humidity and elevated temperatures of 175 °C leads to a superior polarization retention of several years for domain sizes well below 100 nm. [ABSTRACT FROM AUTHOR]

The stability of strained-layer heterostructure lasers can be assessed by their response to stimuli for the introduction of dislocations. Three-point bending at elevated temperatures has been applied to GaAs/InxGa1−xAs/GaAs heterostructures to apply such a thermomechanical stimulus. In each case, the middle-layer thickness was below the critical thickness predicted by the Matthews–Blakeslee model, so that the pre-test structures were fully strained with no observed misfit dislocations. The tensile stress of 46.4 MPa produced during the tests resulted in the formation of 60° misfit dislocations whose configurations changed according to the alignment of the bending axis. For bending in the [110] orientation, the misfit dislocations formed parallel to each other and to the bending axis. For [100] bending, they formed an orthogonal pattern with each dislocation at 45° to the bending axis. In each case, these misfit dislocations caused relaxation of the strained-layer structures, even though the unloaded structures had been considered thermodynamically stable and the test temperatures were lower than those used during the original fabrication of the structures. These findings challenge existing assumptions of strained-layer stability and have implications for the design of lasers intended to be "buried and forgotten" in optical telecommunications. [ABSTRACT FROM AUTHOR]

The mechanism of vibrational relaxation and dissociation in the O2–O system at elevated temperatures is investigated by means of molecular dynamics. The most recent O3 potential energy surfaces (PESs), obtained from the first principles quantum mechanical calculations [Varga et al., J. Chem. Phys. 147, 154312 (2017)], are used to derive a complete set of state-specific rate coefficients of vibrational energy transfer and dissociation. Unlike most of the previous efforts that utilize only the lowest and supposedly most reactive 11A′ O3 PES [A. Varandas and A. Pais, Mol. Phys. 65, 843 (1988)], this paper demonstrates the necessity to account for a complete ensemble of all excited O3 PESs that correlate with O2(X) and O(3P) when high-temperature kinetics is of interest. At the same time, it is found that the Varandas 11A′ O3 PES adequately describes vibrational energy transfer and dissociating dynamics when compared to the most recent 11A′ O3 PES by Varga et al. [J. Chem Phys. 147, 154312 (2017)]. The differences between this new dataset and previous rate coefficients are quantified by the master equation model. [ABSTRACT FROM AUTHOR]

To investigate the shock response of cyclotetramethylene tetranitramine (HMX) single crystals at elevated temperatures (below the phase transition point), plate impact experiments at elevated temperatures were designed and conducted. The HMX/window interface particle velocities at temperatures of 300 K, 373 K, and 423 K were measured by the velocity interferometry system for any reflector (VISAR) technique. To further analyze the related mesoscale deformation mechanisms, a nonlinear thermoelastic-viscoplastic model was developed, which considers thermal activation and phonon drag dislocation slip mechanisms. The proposed model could well reproduce the measured thermal hardening behavior of Hugoniot elastic limit (HEL) of HMX single crystals. At elevated temperatures, the reduced dislocation mobility was observed, which stems from both phonon scattering and radiative damping effects. Comparatively speaking, radiative damping contributes less than phonon scattering to thermal hardening behavior. The calibrated model was further used to predict shock response of HMX single crystals with different thicknesses at different initial temperatures. Both the stress relaxation and elastic precursor decrease with thickness are mainly due to the rapid dislocation generation. These insights shed light on the interplay between dislocation motion and dislocation generation in thermal hardening behavior, stress relaxation, and elastic precursor decay, which serves to reveal the mesoscale deformation mechanisms at elevated temperatures. [ABSTRACT FROM AUTHOR]

Geopolymer is a new alternative cement binder to produce concrete. In the present study, a novel geopolymer composites containing bamboo shaving (0-2 wt.%) were fabricated and exposed to the temperatures of 200°C, 400°C, 600°C and 800°C. Physical properties, micro-structure, and mechanical strengths of the geopolymer composites were evaluated before and after heating in order to understand their thermal properties, which are essential for the use as building materials. As the temperature rises, the drying shrinkage and apparent porosity of the composites increase, while the compressive and bending strengths decrease. At the temperature range of 200°C-800°C, the residual compressive strength rates of the geopolymer composite containning 2 wt.% bamboo shaving were respective 73.8%, 61.47%, 56.16%, and 29.56%, meanwhile, the residual flexural strength rates were respective 46.69%, 8.68%, 2.52%, and 2.33%. Correspondingly, the residual compressive strength rates of pure geopolymer were respective 72.81%, 61.99%, 54.55%, and 14.64%; the residual flexural strength rates were 48.87%, 5.69%, 3.22%, and 2.47%, respectively. Scanning electron microscope (SEM), optical microscope, and X-ray diffractometry (XRD) were applied to find the microscopic changes. The strength loss in the geopolymer composites was mainly because of the thermal degradation of bamboo shaving and shrinkage of geopolymer matrix. Bamboo shaving has great potential as reinforcer in developing low-cost geopolymer composites and may be used for applications up to 400°C. [ABSTRACT FROM AUTHOR]

The influence of temperature on fluorescence spectra used for pressure calibration in a diamond anvil cell (i.e., that of ruby) was always considered as an undesirable phenomenon decreasing the accuracy of pressure measurement in high-temperature experiments. Consequently, nearly temperature-independent fluorescence lines of such pressure calibrants as Sm2+:SrB4O7 and Sm3+:YAG were proposed as the best suited for pressure measurement. We analyzed pressure- and temperature-induced shifts of eight fluorescence lines in Sm2+:SrB4O7 spectrum, extending previous calibrations to 60 GPa and 580 °C, and demonstrated that both pressure and temperature in a "high-pressure + high-temperature" experiment can be reliably estimated by analysis of shifts of two fluorescence lines with different sensitivity to pressure and temperature. We tested the proposed method in an experiment with simultaneous pressure and temperature (up to 7 GPa and 400 °C) and proved that the temperature may be successfully estimated together with pressure from a single Sm2+:SrB4O7 spectrum with an e.s.d. of 8 °C. [ABSTRACT FROM AUTHOR]

A thermionic energy converter (TIC) functioning in collisionless regime at high emitter temperatures demonstrates very high output performance. In practice, such a regime has been realized at moderate temperatures (up to 2300 K) when its inter-electrode gap is filled with Cs and Ba vapors. Changing the Ba vapor pressure, one can vary the emitter work function and obtain optimum output performances, moreover maximum output power being available with any emitter material. The higher the emitter temperature, the more pronounced a shift of this maximum is toward higher Ba pressure, and at high temperature a TIC happens to be working in the collision regime before the maximum power point. We have analysed some experimental data in the literature when studying the emission parameters of refractory metals in the presence of the Ba vapor as well as in the Cs-Ba TIC experiments. Through our analysis, as well as results on the TIC optimization, the Ba optimum pressure is evaluated to obtain maximum power at the high emitter temperature for a set of refractory metals. We conclude that the maximum output performance of the Knudsen TIC with W and Re emitters can be reached up to the emitter temperature as high as 2600 K. [ABSTRACT FROM AUTHOR]

In-situ time-of-flight neutron diffraction experiments were conducted on the uranium-niobium alloy with 6 wt. % Nb (U–6Nb) at pressures up to 4.7 GPa and temperatures up to 1073 K. Upon static compression at room temperature, the monoclinic structure of U–6Nb (α″ U–6Nb) remains stable up to the highest experimental pressure. Based on the pressure-volume measurements at room temperature, the least-squares fit using the finite-strain equation of state (EOS) yields an isothermal bulk modulus of B0 = 127 ± 2 GPa for the α″-phase of U–6Nb. The calculated zero-pressure bulk sound speed from this EOS is 2.706 ± 0.022 km/s, which is in good agreement with the linear extrapolation of the previous Hugoniot data above 12 GPa for α″ U–6Nb, indicating that the dynamic response under those shock-loading conditions is consistent with the stabilization of the initial monoclinic phase of U-6Nb. Upon heating at ambient and high pressures, the metastable α″ U–6Nb exhibits complex transformation paths leading to the diffusional phase decomposition, which are sensitive to applied pressure, stress state, and temperature-time path. These findings provide new insight into the behavior of atypical systems such as U-Nb and suggest that the different U-Nb phases are separated by rather small energies and hence highly sensitive to compositional, thermal, and mechanical perturbations. [ABSTRACT FROM AUTHOR]

In the present work, finite element analysis is carried out for the minimization of springback in the V-bending process for high-strength brass sheet metal. Firstly, the uniaxial tensile test is conducted to determine the various material properties required for finite element analysis. The various test parameters considered in the V-Bending process are temperature (573 K, 673 K and 773K), punch speeds (1 mm/min, 5 mm/min and 10 mm/min), holding time (30 s, 60 s and 90 s) and sheet orientation concerning rolling direction RD (0°), ND (45°) and TD (90°) for finite element analysis. The bending under tension test is used to determine the coefficient of friction at different temperatures and lubrication conditions, and these values are implemented in finite element simulations of the V-bending process. Taguchi analysis is carried out to determine springback of high-strength brass alloy by selecting four control factors (temperature, punch speed, holding time, and orientation). From the analysis of the signal-to-noise (S/N) ratio, it is reported that the temperature (46.93%) is the most significant parameter which influences the springback followed by holding time (26.29%), sheet orientation (24.07%) and punch speed (2.69%). The optimal set obtained for the minimum springback of brass alloy and the conformation test is performed at the optimum set conditions (773 K temperature, 1 mm/min punch speed, 90 s holding time, and 90° to the rolling direction of a sheet). With the optimal set of process parameters, Springback decreased significantly to around 68.68%. Through the investigation of springback analysis, it is directly proportional to the temperature and holding time and inversely proportional to the punch speed, but sheet orientation doesn't follow any trends. [ABSTRACT FROM AUTHOR]

The thermal degradation of flame-resistant fabrics reduces the protective ability of clothing and affects firefighters' safety. Making clear the influence factors of fabric thermal degradation is important for predicting and prolonging the service life of fire-protection clothing. Experiments were conducted for open and sealed air gaps with different thicknesses under flame exposure. The degradation the of outer shell fabric was evaluated by observing the variation in fabric morphology, mass loss and tensile strength of specimens after heat exposure. The influence mechanism of the type and thickness of the air gap on thermal degradation was analyzed by the surface temperature curve and thermal stability of the fabric, as well as the microstructure of the fiber. The results indicated that the type and thickness of the air gap have a significant effect on thermal degradation, and a more serious negative effect was observed under the condition of an open air gap. After being exposed to heat fluxes of 30 and 50 kW/m2 for 40 s, the mass loss rates were 1.8% and 3.3% higher than those of the sealed air gap, and the tensile strength retention rates were 9.1% and 10.1% lower on average, respectively. Air gap type and thickness affected the heat storage and heat transfer efficiency in the fabric system by changing the heat transfer mode. The decomposition and fracture of the fabric were affected, which made the flame-resistant fabrics show different degrees of thermal degradation. [ABSTRACT FROM AUTHOR]

For creating complex geometric shapes in the cast part, salt was used to produce core instead of sand which is thermo-chemical or chemical process using resin as a binder. In salt core casting, the efficiency will be increased by reducing the core gas-induced errors in the part. The harmful effect on the environment will be reduced with the absence of odor and smoke from the core gas. Using water in salt core breaking instead of mechanical impact and vibration during sand core breaking will bring benefits such as eliminating the noise source and using less energy. By eliminating the dust generated during sand core breaking, its harmful effects on the environment will be reduced. Since the salt core can be dissolved in water and removed from the piece without any residue, there will be no problem of sand remaining in the sand core from time to time. [ABSTRACT FROM AUTHOR]

Metal matrix composites are mainly used as a cutting tool insert material. These types of materials are essential to maintain desired mechanical and microstructure properties at elevated temperatures due to friction and wear. Nano sized Tungsten Carbide reinforced composites are mostly used for these conditions. The production of sintered nano sized Tungsten Carbide reinforced composites are done by using powder metallurgy. The different mass ratios of elements including mostly Cobalt and the others could be added as binder phase. The binder phase provides to metal matrix composite superior features including high elasticity, good solubility, similar thermal conduction coefficient and, effective liquid phase sintering mechanism. Cobalt is one of the base elements of high-performance superalloys and rechargeable battery technology. Also, 40% of global need supplied by a single country makes itself higher-priced. It is also known that Cobalt is a high skin allergen and carcinogenic. Together with these obstacles, the investigations of low-cost, nontoxic, or reduced-toxicity materials are always needed. In this study, the related current literature has been investigated in detail. The studies focus on an alternative matrix that providing mentioned conditions explained with pros and cons. [ABSTRACT FROM AUTHOR]

Understanding of plastic deformation mechanisms and/or microstructural changes of metals and alloys at elevated temperatures makes possible to control their hot working behavior and final mechanical properties. The aim of the present work is to optimize the conditions to achieve maximum ductility in terms of initial grain size, process temperature and deformation rate. In this study, the OFHC (oxygen-free high conductivity) copper samples of different initial grain sizes (25, 50, 100 and 150 µm) were subjected to tensile tests at temperatures 300, 405, 500 and 700 °C (0.42 - 0.75 Tm) and cross-head speeds of 1, 2, 5, 10, 20 and 50 mm/min (strain rates of 5.6x10-4 - 2.8x10-2 s-1). Experimental results indicated that particular conditions (initial grain size of 50 µm; 700 °C of working temperature and 5.6x10-3 s-1 of strain rate) should be provided in terms of process temperature and deformation rate depending upon initial grain size for dynamic recrystallization and also maximum ductility. [ABSTRACT FROM AUTHOR]

The paper assessed the impact of the heat treatment of spruce wood, the (radial and tangential) side of the specimens exposed to fire, and the type of material (prism—higher density, floor—lower density) on the combustion process and the rate of fire spread. Five groups of specimens were used—untreated spruce wood specimens, two groups of heat-treated spruce wood specimens from the prism (higher density specimens), and two groups of heat-treated spruce wood specimens from the floor (lower density specimens). In one group, the flame was applied to the radial side, and in the other group to the tangential side of the specimens. The effect on the combustion process was assessed based on the parameters of mass loss and mass loss rate over time. The effect on the rate of fire spread across the specimens was assessed by the parameter fire spread rate. These parameters were determined using a simple test method where the specimens were exposed to a direct flame at an angle of 45°. To complement the results and to assess the processes involved, the temperatures at the specimen surfaces were also measured during the experiment. The main achieved results of the study are the findings on how the heat treatment, the density, and the side of the wood along which the fire spreads affect the burning process of the wood. The results indicated a significant effect of the density of the spruce thermowood on its combustion process. The higher density radial specimens exhibited a higher mass loss rate, and the overall average mass loss of the higher density samples was 27% of the original mass higher than that of the lower density samples. Additionally, the results suggested that the heat treatment of lower-density spruce wood (floor) does not significantly affect the mass loss and the mass loss rate. The difference in the overall average mass loss of the thermowood of floor and untreated wood samples was less than 2%, which is statistically insignificant. It was also found that for thermowood, fire will spread faster on the tangential side, where the fire spread rate is 29% higher compared with the radial side (for the floor samples). Based on the findings of other authors in a similar field, the results confirm that heat-treated spruce wood is more easily ignitable than untreated wood, which was proven by the spontaneous combustion of most of the thermowood samples during the experiment compared with the untreated wood samples. [ABSTRACT FROM AUTHOR]

Polyimide (PI) films with extremely high breakdown strength (451 kV/mm), energy density (5.2 J/cm³), and discharge efficiency (86.7%) at the room temperature are fabricated by simple solution casting method. Barium titanate (BaTiO3) nanoparticles are introduced into PI matrix, giving rise to enhanced dielectric permittivity (6.8) and low dielectric loss (0.012). Dielectric and energy storage performances of the BTO/PI nanocomposites are thoroughly investigated up to 200 °C. The breakdown strengths of both pure PI and BTO/PI nanocomposites decrease dramatically with the increase in the temperature, owing to the low thermal conductivity of PI and the consequent thermal runaway caused by the accumulation of Joule heat under high electric field. Despite of the enhanced electric displacement, BTO/PI nanocomposites exhibit low discharge energy density due to the substantially compromised breakdown strength induced by the BTO nanoparticles. [ABSTRACT FROM AUTHOR]

Vapor cells with antirelaxation coating are widely used in modern atomic physics experiments due to the coating's ability to maintain the atoms' spin polarization during wall collisions. We characterize the performance of vapor cells with different coating materials by measuring longitudinal spin relaxation and vapor density at temperatures up to 95 °C. We infer that the spin-projection-noise-limited sensitivity for atomic magnetometers with such cells improves with temperature, which demonstrates the potential of antirelaxation coated cells in applications of future high-sensitivity magnetometers. [ABSTRACT FROM AUTHOR]

The high entropy alloys (HEA) are made up of at least five metallic chemical elements, which participate in equiatomic proportions, sometimes other chemical elements (metallic or non-metallic) in low quantity being added. Due to its unique chemical composition, HEA can have special properties, such as: high strength and hardness, outstanding wear resistance, exceptional high temperature resistance, stable structure, good resistance to corrosion and oxidation. The paper shows the results obtained by using a high entropy alloy as filler metal to clad a Mn-base steel surface. To characterize and test the layers cladded using high entropy alloy, microstructural analyses, hardness, wear and corrosion resistance tests were performed. The microstructural analysis highlighted a good adhesion and uniformity of the deposition (Fig. 1), and the alloying elements diffused to a depth of only 20 microns in the steel substrate (Fig. 2). The tests carried out showed double values of wear and corrosion resistance of the cladded layer compared to the Mn-steel substrate. [ABSTRACT FROM AUTHOR]

An improved numerical model is developed for coupled heat and moisture transport in fire protective suits exposed to flash fire. This model is combined with Pennes' bioheat transfer model and subsequently, second-degree burn time is estimated using Henriques' burn integral. Natural convection is considered inside the airgap present between the multilayer clothing ensemble and the skin. Comparisons of temperature and moisture distribution within the multilayer clothing, airgap, and the skin during the exposure are presented considering combined heat and moisture transport and only heat transport. The effect of moisture transport on the protective performance of the fire protective suits is shown. The impact of both horizontal and vertical airgap orientations on second-degree burn time is studied. The effect of temperature-dependent thermophysical properties, relative humidity, fiber regain, different exposure conditions, and fabric combinations for the fire protective suits on burn time is analyzed. [ABSTRACT FROM AUTHOR]

Alkali metal dispensers have become an indispensable tool in the production of atomic vapors for magnetometry, alkali vapor cell clocks, and laser cooling experiments. A primary advantage of these dispensers is that they contain alkali metal in an inert form that can be exposed to air without hazard. However, their high temperature of operation (>600 °C) is undesirable for many applications, as it shifts the atomic speed distribution to higher values and presents a radiative heat source that can raise the temperature of its surroundings. For this reason, dispensers are typically not used in line-of-sight applications, such as atomic beam generation. In this work, we present an integrated rubidium dispenser collimating device with a thickness of only 2 mm that produces a beam of atoms traveling primarily in the forward direction. We find that the collimator plate serves to both shield the dispenser's radiation and moderate the velocity of the atomic beam so that the measured longitudinal speed distribution is comparable to that of an ordinary alkali oven at only a slightly elevated temperature of 200 °C. To confirm our theory, we also constructed another compact apparatus consisting of a dispenser and a silicon collimator and the measurements support our conclusion. Our integrated dispenser collimator will particularly be useful in integrated photonics and cavity QED on-chip, where a localized, directed source of Rb vapor in small quantities is needed. [ABSTRACT FROM AUTHOR]

The main characteristic of clothing for protection against heat and flame is the protection of users from external influences and danger in the conditions of elevated temperatures and exposure to flame, fire, smoke, and water. The paper presents research on the clothing system for protection against heat and flame using a fire manikin and systematically analyses the damage caused after testing. As part of the damage analysis, the existence of microdamage and impurities on the clothing system was determined using a USB Dino-Lite microscope. In addition, the intensities and composition of gaseous decomposition products during the thermogravimetric analysis of samples were investigated. The results of the research using a fire manikin showed that the user of the examined clothing system would not have sustained injuries dangerous to health and life, which confirmed the protective properties. The results of the TG-FTIR indicate that the decomposition of the fabric sample of the modacrylic–cotton fiber mixture takes place in three stages, and the identified gaseous degradation products were H2O, CO2, and CO. [ABSTRACT FROM AUTHOR]

In the millisecond time domain, deflagration curves of the methane, CH4, have been observed at low and elevated initial temperatures. 20-L closed spherical chamber have been adopted for low and high initial temperatures measurements. Methane air mixtures were studied experimentally and numerically for different equivalence ratios between 0.2 and 2.5 and initial temperatures of -20, -10, 0, 10, 20, 30, 40, 50 °C. More than three hundred pressure-time curves were recorded. Twenty-five deflagration curves of the CH4 have been observed in the below-zero temperature region in 20-L volume for the first time, including two pressure-time curves in -20 °C. The effects of temperature on the maximum explosion pressure, maximum rate of pressure rise, and deflagration index were investigated. The evaluated experiments' actual results are the maximum pressure rise rate for -20 °C. Our results should also provide critical information applicable to thermodynamic and kinetic modeling of methane explosion and flame low-temperature chemistry. This work allowed a systematic comparison of the structural and bonding properties among the CnH2n analogs in the physics and chemistry of low temperatures explosions. [ABSTRACT FROM AUTHOR]

Printed electronics has emerged as a versatile eco-friendly fabrication technique to create sintered nanoparticle (NP) films on arbitrary surfaces with an excellent control over the film microstructure. While applicability of such films for high-temperature applications is not explored previously, herein we report the high-temperature electrical stability of silver (Ag) metal NP films fabricated using an Aerosol Jet based printing technique and demonstrate that this behavior is dictated by changes in the film microstructure. In-situ high temperature (24-500 °C) impedance spectroscopy measurements show that the real part of the impedance increases with increasing temperature up to 150 ° C, at which point a decreasing trend prevails until 300 ° C, followed again by an increase in impedance. The electrical behavior is correlated with the in-situ grain growth of the Ag NP films, as observed afterwards by scanning electron microscopy and X-ray diffraction (XRD), and could be tailored by controlling the initial microstructure through sintering conditions. Using combined diffraction and spectroscopic analytical methods, it is demonstrated the Aerosol Jet printed Ag NP films exhibit enhanced thermal stability and oxidation resistance. In addition to establishing the conditions for stability of Ag NP films, the results provide a fundamental understanding of the effect of grain growth and reduction in grain boundary area on the electrical stability of sintered NP films. [ABSTRACT FROM AUTHOR]

The high-temperature gas-cooled reactor (HTGR) has long been considered a promising nuclear technology, and several countries are either considering the construction of new HTGRs or pursuing research into the field. In the past, both Germany and the United States spent large amounts of money to design and construct HTGRs, four of which fed electricity into the grid. Examining the performances of these HTGRs offers a useful guide to what one can expect from future HTGRs, if and when more are constructed, and reasons to reject that option altogether. [ABSTRACT FROM AUTHOR]

We report new assignments of vibration-rotation line positions of methane (12CH4) in the so-called dyad (ν2/ν4) region (1100-1500 cm−1), and the resulting update of the vibration-rotation effective model of methane, previously reported by Nikitin et al. [Phys. Chem. Chem. Phys. 15, 10071 (2013)], up to and including the tetradecad. High resolution (0.01 cm−1) emission spectra of methane have been recorded up to about 1400 K using the high-enthalpy source developed at Institut de Physique de Rennes associated with the Fourier transform spectrometer of the SOLEIL synchrotron facility (AILES beamline). Analysis of these spectra allowed extending rotational assignments in the well-known cold band (dyad-ground state (GS)) and related hot bands in the pentad-dyad system (3000 cm−1) up to Jmax = 30 and 29, respectively. In addition, 8512 new transitions belonging to the octad-pentad (up to J = 28) and tetradecad-octad (up to J = 21) hot band systems were successfully identified. As a result, the MeCaSDa database of methane was significantly improved. The line positions assigned in this work, together with the information available in the literature, were fitted using 1096 effective parameters with a dimensionless standard deviation σ = 2.09. The root mean square deviations dRMS are 3.60 × 10−3 cm−1 for dyad-GS cold band, 4.47 ×10−3 cm−1 for the pentad-dyad, 5.43 × 10−3 cm−1 for the octad-pentad, and 4.70 × 10−3 cm−1 for the tetradecad-octad hot bands. The resulting new line list will contribute to improve opacity and radiative transfer models for hot atmospheres, such as those of hot-Jupiter type exoplanets. [ABSTRACT FROM AUTHOR]

Above room temperature, the accumulation of radiation damage in 3C-SiC is strongly influenced by dynamic defect interaction processes and remains poorly understood. Here, we use a combination of ion channeling and transmission electron microscopy to study lattice disorder in 3C-SiC irradiated with 500?keV Ar ions in the temperature range of 25-250?°C. Results reveal sigmoidal damage buildup for all the temperatures studied. For 150?°C and below, the damage level monotonically increases with ion dose up to amorphization. Starting at 200?°C, the shape of damage–depth profiles becomes anomalous, with the damage peak narrowing and moving to larger depths and an additional shoulder forming close to the ion end of range. As a result, damage buildup curves for 200 and 250?°C exhibit an anomalous two-step shape, with a damage saturation stage followed by rapid amorphization above a critical ion dose, suggesting a nucleation-limited amorphization behavior. Despite their complexity, all damage buildup curves are well described by a phenomenological model based on an assumption of a linear dependence of the effective amorphization cross section on ion dose. In contrast to the results of previous studies, 3C-SiC can be amorphized by bombardment with 500?keV Ar ions even at 250?°C with a relatively large dose rate of ~2 × 1013 cm-2 s-1, revealing a dominant role of defect interaction dynamics at elevated temperatures. [ABSTRACT FROM AUTHOR]

Effects of high-temperature annealing on deep-level defects in a high-purity semi-insulating 4H silicon carbide substrate have been studied by employing current-voltage, capacitance-voltage, junction spectroscopy, and chemical impurity analysis measurements. Secondary ion mass spectrometry data reveal that the substrate contains boron with concentration in the mid 1015cm-3 range, while other impurities including nitrogen, aluminum, titanium, vanadium and chromium are below their detection limits (typically ~1014cm-3). Schottky barrier diodes fabricated on substrates annealed at 1400-1700 °C exhibit metal/p-type semiconductor behavior with a current rectification of up to 8 orders of magnitude at bias voltages of ±3V. With increasing annealing temperature, the series resistance of the Schottky barrier diodes decreases, and the net acceptor concentration in the substrates increases approaching the chemical boron content. Admittance spectroscopy results unveil the presence of shallow boron acceptors and deep-level defects with levels in lower half of the bandgap. After the 1400 °C annealing, the boron acceptor still remains strongly compensated at room temperature by deep donor-like levels located close to mid-gap. However, the latter decrease in concentration with increasing annealing temperature and after 1700 °C, the boron acceptor is essentially uncompensated. Hence, the deep donors are decisive for the semi-insulating properties of the substrates, and their thermal evolution limits the thermal budget for device processing. The origin of the deep donors is not well-established, but substantial evidence supporting an assignment to carbon vacancies is presented. [ABSTRACT FROM AUTHOR]

The total partition functions Q(T) and their first two moments QQ(T) and Q"(T), together with the isobaric heat capacities Cp(T), are computed a priori for three major MgH isotopologues on the temperature range of T = 100-3000 K using the recent highly accurate potential energy curve, spin-rotation, and non-adiabatic correction functions of Henderson et al. [J. Phys. Chem. A 117, 13373 (2013)]. Nuclear motion computations are carried out on the ground electronic state to determine the (ro)vibrational energy levels and the scattering phase shifts. The effect of resonance states is found to be significant above about 1000 K and it increases with temperature. Even very short-lived states, due to their relatively large number, have significant contributions to Q (T) at elevated temperatures. The contribution of scattering states is around one fourth of that of resonance states but opposite in sign. Uncertainty estimates are given for the possible error sources, suggesting that all computed thermochemical properties have an accuracy better than 0.005% up to 1200 K. Between 1200 and 2500 K, the uncertainties can rise to around 0.1%, while between 2500 K and 3000 K, a further increase to 0.5% might be observed for Q"(T) and Cp(T), principally due to the neglect of excited electronic states. The accurate thermochemical data determined are presented in the supplementary material for the three isotopologues of 24MgH, 25MgH, and 26MgH at 1 K increments. These data, which differ significantly from older standard data, should prove useful for astronomical models incorporating thermodynamic properties of these species. [ABSTRACT FROM AUTHOR]

A thorough control of the machining operations is essential to ensure the successful postprocessing of additively manufactured components, which can be assessed through machinability tests endowed with numerical simulation of the metal cutting process. However, to accurately depict the complex metal cutting mechanism, it is not only necessary to develop robust numerical models but also to properly characterize the material behavior, which can be a long-winded process, especially for state-of-stress sensitive materials. In this paper, an efficient mechanical characterization methodology has been developed through the usage of both direct and inverse calibration procedures. Apart from the typical axisymmetric specimens (such as those used in compression and tensile tests), plane strain specimens have been applied in the constitutive law calibration accounting for plastic and damage behaviors. Orthogonal cutting experiments allowed the validation of the implemented numerical model for simulation of the metal cutting processes. Moreover, the numerical simulation of an industrial machining operation (longitudinal cylindrical turning) revealed a very reasonably prediction of cutting forces and chip morphology, which is crucial for the identification of favorable cutting scenarios for difficult-to-cut materials. [ABSTRACT FROM AUTHOR]

Based on the concept of Process Signatures, the deep rolling process is analyzed, aiming at functional relationships between material modifications and internal material loads during the process. The focus of this work is to investigate the influence of the workpiece temperature on the generated residual stress components. For this purpose, extensive finite element simulations of deep rolling were conducted, taking into account the effect of neighboring tool paths on the internal material loads and residual stress. A kinematic strain hardening model was parameterized and utilized and the simulations were validated experimentally. Simulated residual stresses agree qualitatively well with measurements and show a strong influence of the workpiece temperature as expected. Process Signature Components were generated, taking into account the maximal and minimal residual stress as well as their respective positions beneath the workpiece surface. [ABSTRACT FROM AUTHOR]

Parabolic rate constants, kp, were collected from published reports and calculated from corrosion product data (sample mass gain or corrosion product thickness) and tabulated for 75 alloys exposed to temperatures between ~800 and 2000 K (~500–1700 oC; 900–3000 oF). Data were collected for environments including lab air, ambient and supercritical carbon dioxide, supercritical water, and steam. Materials studied include low- and high-Cr ferritic and austenitic steels, nickel superalloys, and aluminide materials. A combination of Arrhenius analysis, simple linear regression, supervised and unsupervised machine learning methods were used to investigate the relations between composition and oxidation kinetics. The supervised machine learning techniques produced the lowest mean standard errors. The most significant elements controlling oxidation kinetics were Ni, Cr, Al, and Fe, with Mo and Co composition also found to be significant features. The activation energies produced from the machine learning analysis were in the correct distributions for the diffusion constants for the oxide scales expected to dominate in each class. [ABSTRACT FROM AUTHOR]

To address the challenges posed by large propagation loss and severe multipath delay spread, while aiming to improve communication rates in long-range underwater acoustic (UWA) communication, this paper introduces a novel approach: multi-beam (MB) Orthogonal Frequency Division Multiplexing (OFDM) based on deconvolved conventional beamforming (dCv). The proposed method establishes a signal processing framework for UWA channel receivers, wherein received signals corresponding to each angle beam are isolated and concentrated using the dCv technique. Subsequently, the separated signals from each angle undergo maximal-ratio combining (MRC) channel equalization followed by demodulation. Compared to conventional single-beam (SB) processing methods, the proposed approach capitalizes on multipath diversity gain achieved by combining MB outputs originating from various arrival angles. Moreover, employing dCv processing demonstrates superior performance compared to popularly employed beamforming techniques, especially when dealing with paths arriving from closely aligned angles. Additionally, the array beamforming utilized significantly enhances the signal-to-noise ratio (SNR) of each beam output, mitigating the elevated error rates in channel estimation associated with combining low SNR signals received from individual elements. Simulation results utilizing BELLHOP and experimental data from the South China Sea showcase notably improved bit error rate (BER) performance for the proposed method compared to SB equalization, MB-MRC equalization based on conventional beamforming (CBF), minimum variance distortionless response (MVDR), and worst-case performance optimization (WCPO), as well as standard MRC equalization techniques. The proposed receiver achieves error-free decoding results at a communication distance of 80 km with a data rate of 247 bps. [ABSTRACT FROM AUTHOR]

Following the Fukushima Daiichi accident, significant efforts from industry and the scientific community have been directed towards the development of alternative nuclear reactor fuels with enhanced accident tolerance. Among the proposed materials for such fuels is a uranium silicide compound (U3Si2), which has been selected for its enhanced thermal conductivity and high density of uranium compared to the reference commercial light water reactor (LWR) nuclear fuel, uranium oxide (UO2). To be a viable candidate LWR fuel, however, U3Si2 must also demonstrate that, in the event of this fuel coming in contact with aqueous media, it will not degrade rapidly. In this contribution, we report the results of experiments investigating the stability of U3Si2 in pressurized water at elevated temperatures and identify the mechanisms that control the interaction of U3Si2 under these conditions. Our data indicate that the stability of this material is primarily controlled by the formation of a layer of USiO4 (the mineral, coffinite) at the surface of U3Si2. The results also show that these layers are destabilized at T > 300 °C, leading to the complete decomposition of U3Si2 and its pulverization due to its full oxidation to UO2. Uranium silicide is proposed as a highly accident tolerant light water reactor nuclear fuel, but its behavior under high-temperature, aqueous conditions is poorly studied. Here, uranium silicide is shown to decompose and fully oxidize when the passive uranium silicate layer is destabilized under hydrothermal conditions over 300 °C. [ABSTRACT FROM AUTHOR]

SiC/SiC ceramic matrix composites (CMCs) are being developed for use in aero-engines to replace nickel superalloy components. Sub-element testing acts as the key stepping stone in bridging understanding derived from basic coupon testing and more complex component testing. This study presents the development of high temperature C-shape sub-element testing with the use of digital image correlation to study damage progression. The specimen is designed with a bias towards a mixed mode-stress state more similar to what a CMC component may see in service. Both monotonic and fatigue tests were completed on C specimens and compared with predicted behaviour from modelling. Test data from both test types suggested that specimens were failing once they reached a critical radial stress level. However evidence from fractography of specimens showed that in both monotonic and fatigue tests radial cracks (driven by hoop stresses) are initiating prior to circumferential cracks. [ABSTRACT FROM AUTHOR]

The influence of elevated temperatures on mechanical behavior of glued laminated timber beams is examined on the basis of tensile tests. Dog bone samples prepared from beams exposed to fire of variable duration were categorized with respect to the type and position of the failure crack, type and number of discontinuities such as knots, and the level of browning. The acquired experimental results suggest that the wood variability and the effect of growth discontinuities are probably more significant than the effect of elevated temperatures. To support this conclusion, further study is currently under way, exploring samples from the second series of the fire tests. [ABSTRACT FROM AUTHOR]

The kinetic Monte-Carlo algorithm as well as standard micromagnetics are used to simulate MH loops of high anisotropy magnetic recording media at both short and long time scales over a wide range of temperatures relevant to heat-assisted magnetic recording. Microscopic parameters, common to both methods, were determined by fitting to experimental data on single-layer FePt-based media that uses the Magneto-Optic Kerr effect with a slow sweep rate of 700 Oe/s. Saturation moment, uniaxial anisotropy, and exchange constants are given an intrinsic temperature dependence based on published atomistic simulations of FePt grains with an effective Curie temperature of 680 K. Our results show good agreement between micromagnetics and kinetic Monte Carlo results over a wide range of sweep rates. Loops at the slow experimental sweep rates are found to become more square-shaped, with an increasing slope, as temperature increases from 300 K. These effects also occur at higher sweep rates, typical of recording speeds, but are much less pronounced. These results demonstrate the need for accurate determination of intrinsic thermal properties of future recording media as input to micromagnetic models as well as the sensitivity of the switching behavior of thin magnetic films to applied field sweep rates at higher temperatures. [ABSTRACT FROM AUTHOR]

Temperature dependent photoluminescence (PL) of MgZnO epitaxial layers with high Mg content were studied to understand the effect of carrier localization on the PL dynamics, including the PL dependence on excitation power density and temperature. A double blueshift of the PL peak position with increase of measurement temperature was discovered. The blueshift took place at low as well as high temperature and could be attributed to the effect of carrier localization. It has been deduced that the randomly distributed carrier localization centers in the MgZnO films create two energy separated Gaussian-shape density-of-states tails in the vicinity of the fundamental band gap edge. Filling of these tail states by the thermally activated carriers with increase of temperature causes the temperature-induced double blueshift of the PL peak position. By analyzing the temperature dependent PL spectra, two parameters, σ and γ were extracted, which characterize the average energy depth distribution of the localizing potential field fluctuations. The value of these parameters were found to depend on the Mg content and crystalline structure of the MgZnO epitaxial layers. [ABSTRACT FROM AUTHOR]

In this study, in-situ X-ray diffraction has been carried out to investigate the effect of temperature and pressure on hydrogen induced lattice parameter variation in size selected Pd-Ag and Pd-Cu alloy nanoparticles. The nanoparticles of three different mobility equivalent diameters (20, 40, and 60 nm) having a narrow size distribution were prepared by gas phase synthesis method. In the present range of temperature (350K to 250 K) and pressure (10-4 to 100 millibars), no α (H/Pd≤0.03) ↔ β (H/Pd≥0.54) phase transition is observed. At temperature higher than 300 °C or pressure lower than 25 millibars, there is a large difference in the rate at which lattice constant varies as a function of pressure and temperature. Further, the lattice variation with temperature and pressure is also observed to depend upon the nanoparticle size. At lower temperature or higher pressure, size of the nanoparticle seems to be relatively less important. These results are explained on the basis of the relative dominance of physical absorption and diffusion of H in Pd alloy nanoparticles at different temperature and pressure. In the present study, absence of a α ↔ β phase transition points towards the advantage of using Pd-alloy nanoparticles in applications requiring long term and repeated hydrogen cycling. [ABSTRACT FROM AUTHOR]