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The thermal properties of NERICA (New Rice for Africa) were investigated on differing moisture content levels and temperatures. The NERICA varieties studied includes FARO 44, FARO 52, FARO 57, FARO 60 and FARO 61. The variety samples were later categorized into two; NERICA Raw-Paddy (FAROs 44, 52, 57, 60 and 61) and NERICA Parboiled-Milled (FAROs 44, 52, 57, 60 and 61) samples. The thermal properties studied were thermal conductivity, specific heat, and thermal diffusivity. The thermal conductivity and the specific heat were determined using the thermal conductivity probe method and a digital scanning calorimeter, respectively. The thermal diffusivity was determined from the obtained results of the specific heat and the thermal conductivity. Results indicated that, increase in moisture content and temperature results to increase in the specific heat, thermal conductivity, and thermal diffusivity of NERICA varieties and these ranged from 4.245 to 39.976 kJ kg--1 oC-1; 0.042 to 1.403 W m-1 oC-1; and 1.236 × 10-5 to 5.933 × 10-5 m² s-1 respectively for NERICA Raw-Paddy and 7.033 to 81.657 kJ kg-1 oC-1; 0.067 to 1.876 W m-1 oC-1; and 1.413 × 10-5 to 5.219 × 10-5 m² s-1 respectively for NERICA Parboiled-Milled. Bulk density decreased with an increase in moisture contents and temperature and the obtained results ranged from 760.3 to 698.7 kg m-3 for NERICA Raw-Paddy and 720.4 to 652.4 kg m-3 for NERICA Parboiled. Regression analyses were carried out on the thermal properties of NERICA varieties and moisture content, and there was positive correlation between the parameters. There were significant effects of moisture content (p<0.05) on all the parameters studied. [ABSTRACT FROM AUTHOR]

The fused filament fabrication (FFF) process of polymer‐based composites has been developed due to its capability to make complex geometries and shapes with reasonable mechanical properties. However, the improvement of mechanical properties of the obtained parts and products are still under study and are interesting for designers. There are several strategies to enhance these desired properties of produced pieces, for example optimizing the process parameters and/or using different architecting designs. This paper presents the effect of some overriding process parameters (liquefier temperature, print speed, layer height, and platform temperature) on the temperature evolution and mechanical behavior of PA6 reinforced with chopped carbon fibers produced by FFF. Due to deposition of multilayers, there is a cyclic profile of temperature in the FFF process, which is a considerable note related to fabrication and consequently the strength of the manufactured parts. In parallel with the study of process parameters effect, this cyclic temperature profile has been measured. The preliminary results related to physicochemical and mechanical properties revealed that differences in crystallinity percentage exist and failure stress/strain can be considered as an indicator to evaluate the mechanical properties of FFF manufactured products. Moreover, measuring the temperature profile of the deposited filaments revealed that process parameters have a considerable influence on the cooling process of deposited filaments which itself affects the bonding of adjacent filaments. The higher temperatures led to slower cooling rate. Finally, the results confirm the impact of mentioned parameters roles on the bonding formation in the FFF process and also the subsequent obtained mechanical properties of the printed parts. Therefore, selection of the optimized and suitable process parameters is an important design consideration. [ABSTRACT FROM AUTHOR]

Of late, atomically thin two-dimensional zinc-sulfide (2D-ZnS) shows great potential for advanced nanodevices and as a substitute to graphene and transition metal di-chalcogenides owing to its exceptional optical and electronic properties. However, the functional performance of nanodevices significantly depends on the effective heat management of the system. In this paper, we explored the thermal transport properties of 2D-ZnS through molecular dynamics simulations. The impact of length, temperature, and vacancy defects on the thermal properties of 2D-ZnS are systematically investigated. We found that the thermal conductivity (TC) rises monotonically with increasing sheet length, and the bulk TC of ∼30.67 W mK−1 is explored for an infinite length ZnS. Beyond room temperature (300 K), the TC differs from the usual 1/T rule and displays an abnormal, slowly declining behavior. The point vacancy (PV) shows the largest decrease in TC compared to the bi vacancy (BV) defects. We calculated phonon modes for various lengths, temperatures, and vacancies to elucidate the TC variation. Conversely, quantum corrections are used to avoid phonon modes' icing effects on the TC at low temperatures. The obtained phonon density of states (PDOS) shows a softening and shrinking nature with increasing temperature, which is responsible for the anomaly in the TC at high temperatures. Owing to the increase of vacancy concentration, the PDOS peaks exhibit a decrease for both types of defects. Moreover, the variation of the specific heat capacity and entropy with BV and PV signify our findings of 2D-ZnS TC at diverse concentrations along with the different forms of vacancies. The results elucidated in this study will be a guide for efficient heat management of ZnS-based optoelectronic and nano-electronic devices. [ABSTRACT FROM AUTHOR]

Epoxy resin (EP) insulations are widely considered as potential candidates for various applications. However, it is not suitable for high frequency (HF) and high temperature (HT) applications due to its low thermal conductivity. This research presents the tuning of thermal and electrical properties of EP via resin stoichiometry and incorporation of surface-modified hexagonal boron nitride (h-BN) nanofillers. In this research, the curing agent concentration for pure EP is optimized first based on high thermal stability and sufficiently reliable electrical properties. Second, the optimized pure EP is used as a base material to prepare epoxy/h-BN nanocomposites. Various physicochemical, thermal, and electrical characterizations are performed to analyze the properties of prepared materials. Results show that the higher curing agent concentrations offer a good balance between the thermal and electrical performance of the EP. However, the HF and HT stress exhibits detrimental effects on the breakdown strength and dielectric properties of the materials. Also, the addition of nanofillers further enhances the thermal properties while exhibiting sufficient electrical properties. By the control of resin stoichiometry and nanofiller addition, suitable composites for the HF and HT environment can be realized. [ABSTRACT FROM AUTHOR]

In this paper, a modification method of polypropylene (PP) films is proposed for capacitors by micro doping of carboxylated cellulose nanocrystals (C-CNCs). Results prove that crystallization process of films is promoted, due to the entanglement effect of acicular ultra-structures of C-CNCs on PP molecular chains. With a proper doping content (0.01 wt%), the thermal properties are elevated, and the DC conductivity decreases by raising crystallinity and limiting carrier movement. Modified films possess a restricted dielectric loss at low frequencies because of regular microstructures and decreased conduction loss. Based on DC experiments at different temperatures, the breakdown strength of C-CNC/PP films shows an increase by approximately 51% at 85 °C, basically equaled to the level of pure PP at 25 °C. The mechanism is attributed to deep trap sites, which are introduced by the large crystal region and result in short free path in carrier transport. This novel PP film shows a great potential for application under thermal-electrical compound field in power systems. [ABSTRACT FROM AUTHOR]

The mechanical performance of rock mass subjected to the coupled influences of the elevated temperature and in situ stresses has always been a hot topic in underground rock engineering projects. In this study, a thermal-stress-aperture coupled model was first developed and then incorporated into the particle flow code for the coupled thermomechanical analyses in the fractured rock mass. With thorough considerations of the aperture-dependent thermal and mesomechanical parameters for the fractured rock, the model performed more realistic thermoelastic responses of the fractured rock to the temperatures and confining pressures. Comparative studies between the numerical simulations and previous experimental results indicated that the proposed model was suitable for modeling the thermomechanical behaviors of the fractured rock. Then, a series of numerical compression simulations with heating temperatures of 20°C–600°C and confining pressures of 0–20 MPa were conducted to comprehensively explore the interplay of the temperature and confining pressure on mechanical properties of fractured rock specimens. Finally, the mechanisms that affect the rock thermomechanical properties were further revealed. The results indicated that the compressive strength and elastic modulus increase with an increase in confining pressure for each temperature scenario. The thermal strengthening behavior of rock extrapolated to about 400°C takes place in confined compression tests and is more pronounced at higher confining pressures. The evolutions of thermal properties, microcracks, and mesostructures are the most decisive factors that could induce the variations of rock properties under the coupled temperature and confining pressure treatment. For analyzing the mechanisms behind strengthening and weakening contribution to rock properties, the positive effect of the decrease in average fracture aperture, the dual effects of increased porosity and thermal-induced microcracks, and the negative effect of stress-induced microcracks should be comprehensively considered. [ABSTRACT FROM AUTHOR]

A database of the thermal conductivity of fused quartz was developed using the KD2 Pro thermal properties analyzer. The database contains the thermal conductivity data of fused quartz with changes in soil porosity and temperatures ranging from 5 ℃ to 45 ℃. The measured data show that the thermal conductivity increases with increasing temperature under dry conditions. Five empirical models and three theoretical models are used to calculate the thermal conductivity of fused quartz and natural sands. The experimental thermal conductivity data of dry fused quartz were exceptionally well predicted by models from the literature if the effects of temperature change were not considered. An empirical model was modified considering temperature and porosity. The empirical model successfully captures the variations in the thermal conductivity of the fused quartz and natural sands. [ABSTRACT FROM AUTHOR]

The thermal properties (specific heat capacity, thermal conductivity, and thermal diffusivity) of Jack bean seed (Canavalia ensiformis) were determined for designing the equipment necessary for thermal processes. These thermal properties were determined at 5, 10, 15, 20, and 25 % moisture contents and temperatures at 30, 40, and 50 ° C using the KD2 Pro thermal analyzer. Results showed that the specific heat capacity ranged from 1.55 to 2.47 kJ/kgK, 1.26 to 1.84 kJ/kgK and 1.32 to 1.99 kJ/kgK; thermal conductivity 0.21 to 0.47 W/mK, 0.34 to 0.52 W/mK, and 0.26 to 0.60 W/mK and thermal diffusivity 0.25 to 0.41 x 10-7 m²/s, 0.32 to 0.57 x 10-7 m²/s, and 0.32 to 0.60 x 10-7 m²/s at 30, 40, and 50 °C respectively for the moisture ranges studied. The temperature and moisture content effects were not significant (p>0.05) with specific heat and thermal diffusivity but were significant (p<0.05) with thermal conductivity in third-order polynomial. A non-linear relationship was established between the three thermal properties and moisture content within the studied temperature range. The resulting regression models for the thermal properties gave a high coefficient of determination (R2=0.7995) which implies that the parameters can be used to describe the relationships between temperature, moisture, and thermal properties of Jack bean seeds. [ABSTRACT FROM AUTHOR]

The transverse thermoelectric effect is generally found in a material system with anisotropic electrical/ thermal properties. Herein, we reported a simple way of forming thermoelectric anisotropy in a single piece of Bi-Sb-Te compound by partial doping of Ag elements. A transverse Seebeck effect is experimentally observed on an asymmetrically doped Bi-Sb-Te pellet with an effective Seebeck coefficient of 216 ± 4 μV/K. A two-dimensional distribution of electrical potential and temperatures in the pellet is modeled numerically. The size dependence of thermoelectric power and electrical resistance for asymmetrically doped Bi-Sb-Te compounds is also investigated. [ABSTRACT FROM AUTHOR]

This article proposes an analytic coupled magneto-thermal analysis of an axial-flux (AF) permanent-magnet-assisted (PMA) eddy-current brake (ECB) at high-temperature working conditions. In the topology investigated, permanent magnets (PMs) are placed into stator slot openings to increase the braking torque production capability. This modification enables to control the magnet flux by altering the dc excitation current. However, the utilization of PMs will make the construction vulnerable at high operating temperatures simply because the magnet properties and the brake capability are strongly dependent on temperature. Such problems require complex coupled multiphysics finite-element analyses to obtain the actual brake performance. The proposed approach offers a simple and effective solution that consists of magnetic and thermal models, which are coupled to each other in the time domain. The nonlinear electrical, magnetic, and thermal properties are influenced by the temperature variation in time. An AF-PMA-ECB prototype is manufactured to validate the proposed coupled models and the experimental studies confirm that the proposed approach provides very practical results to determine the working conditions of the AF-PMA-ECB at high-temperature operations. [ABSTRACT FROM AUTHOR]

We focused on the inverse thermal sensation caused by the presence of both hot and cold stimuli, which we named hot–cold confusion. Some researchers have shown that when participants touch a thermal stimulus simultaneously with two opposite thermal stimuli on both sides, the outer temperatures dominate the center temperature; for example, a hot stimulus between two cold stimuli is perceived as cold. However, there has not been sufficient research on the effect of the center stimulus on the outer stimuli. In the current study, we placed a participant's forearm on an alignment where hot and cold stimuli were alternately placed in three locations and found that the participants sometimes selected the inverse thermal sensation of the presented surface not only at the center but also at the outer locations. Namely, opposite thermal stimuli applied at multiple locations affected each other, and the participants sometimes perceived the hot stimulus at the outer location as cold even when the two of three stimuli were hot, and vice versa. In addition, using various alignments of thermal stimuli, we revealed a directional bias of the effect from the cold stimulus and a difference in strength according to its location on the forearm. [ABSTRACT FROM AUTHOR]

The terrestrial subsurface acts as a buffer in regulating land-surface water and energy processes. In integrated modeling with land-surface models, the regulating capacity of the subsurface is largely determined by the bottom boundary condition placement (BBCP). However, the sensitivity of land-surface processes to BBCP in Earth system modeling and integrated hydrologic modeling under conditions of human disturbance has not been investigated. In the research reported here, numerical experiments by integrated hydrologic modeling in the Little Washita Basin (Oklahoma, USA) were conducted to study the behavior of the subsurface buffer in regulating ground-surface temperature (GST) under long-term groundwater pumping and the role of BBCP in modeling such processes. Results reveal that long-term groundwater pumping weakens the subsurface buffer and leads to a warming trend. Under either sustainable or unsustainable pumping scenarios, the increase in GST exhibits temporal nonlinearity by rapidly increasing in the beginning and gradually achieving a dynamic equilibrium. It is also found that the subsurface buffer with deeper BBCP is more effective on damping the nonlinearity and the amplitude of the increase in GST. In addition, variations in GST are more sensitive to BBCP under pumping than in the natural state due to decreased thermal properties. In summary, this study diagnoses the subsurface buffer on variations of GST with the role of BBCP in integrated modeling under long-term groundwater pumping. These results are expected to have important implications on integrated modeling with land-surface models in areas of groundwater depletion worldwide. [ABSTRACT FROM AUTHOR]

The size of graphene nanofillers and the ambient temperature are two important factors for the effective thermal conductivity of graphene nanocomposites. However, these two issues together are seldom considered in theoretical evaluation of the overall thermal property. By introducing the size-dependent thermal transport mechanisms (quasi-ballistic heat flow and diffusive heat transport) to the Landauer-like theory, we established a new method to calculate the in-plane size and temperature dependence of the thermal conductivity of graphene nanofillers from the nanoscale perspective, which is crucial for the overall thermal conductivity of the nanocomposites. The validity of this approach was confirmed by nonequilibrium molecular dynamics simulation. Then the filler-size- and temperature-dependent thermal conductivity of graphene nanocomposites was calculated via an effective-medium approximation based on Maxwell's far-field matching at a microscopic level. We highlight this multiscale approach with its implementation in the estimation of the overall thermal conductivity of graphene-polymer nanocomposites. The results are shown to be in close agreement with the experimental observations over the average filler size from 200 to 1000 nm and over the temperature from 300 to 360 K, respectively. This study revealed the significant effects of the graphene-filler size and the ambient temperature on the thermal conductivity of the nanocomposites. Image 1 [ABSTRACT FROM AUTHOR]

The diameter of the cylindrical waste form must be optimized through the estimated centerline temperature for thermally stable disposal. Salt wastes generated from pyrochemical processes were dechlorinated and vitrified using a universal silica alumina phosphate (U-SAP) glass system. The thermal properties of the waste form were analyzed, and centerline temperatures were calculated based on the analyzed thermal properties to optimize the diameter. Calculation of the centerline temperature was carried out using a steady-state conduction equation in an infinitely long cylindrical waste form. In all cases, the centerline temperatures of the U-SAP below a diameter of 0.4 m were estimated to be below 480 °C. [ABSTRACT FROM AUTHOR]

Considering that SF6 is a potent greenhouse gas, SF6/N2 gas mixtures are preferred to serve as the insulating gas for its environmental friendliness and good insulation. Since heat transfer analysis is very useful for ascertaining the appropriate temperature rise range, which can ensure the safe operation and extension of remaining useful life of GIL, it is essential to study the thermal properties of SF6/N2 gas mixtures. Nevertheless, very few studies investigate on the temperature field of SF6/N2 gas mixtures under ideal conditions. To reflect the heat transfer characteristics accurately, in this paper, by using the finite-element method and multi-physics coupling, the heat transfer properties in the GIL is analyzed by using a three-dimensional (3-D) axisymmetric GIL model. By varying the SF6/N2 mixing ratio and observing the corresponding heat transfer characteristics, the mapping between SF6/N2 mixing ratio and the temperature rise is obtained by using the model. Furthermore, the mappings are studied under different gas pressures, line currents and ambient temperatures, which correspond to different real-life operating conditions. The proposed strategies can effectively give guidance of choosing proper SF6/N2 mixing ratio for desired temperature rise, and thus having great values of practical applications. [ABSTRACT FROM AUTHOR]

The traditional cup-shaped LED packaged with epoxy molding compound materials (EMC-LED) and chip-scale packaged LED (CSP-LED) were prepared and analyzed in this article. It is found that high temperature can result in the spectrum red shift and the photoelectric performance degradation for these LEDs due to the degradation of chip and packaging materials. Compared with EMC-LED, the CSP-LED device has a lower thermal resistance of 3.31 °C/W due to the shorter thermal dissipation path and has better stability under the different temperature and drive current conditions. All the simulation results agree well with experimental and theoretical results, indicating that the photoelectric and thermal properties of the CSP-LED can be improved by introducing ceramic substrate and optimizing the material of the interconnected surface and the size of the conduction area. These results have guiding significance for the future CSP-LED design and application. [ABSTRACT FROM AUTHOR]

The temperature dependence of carrier dynamics in GaNxPyAs1-y-x alloys has been investigated by time resolved photoluminescence. This investigation has shown that the decay time constant does not change significantly up to 100 K, and then starts to decrease rapidly above this temperature. Additionally, the decay times at the high-energy side of the spectrum decrease faster than those at the low-energy side. The effects have been explained by the interplay between carrier capture by radiative and nonradiative recombination centers. Detailed simulations show that the effect of carrier localization in the investigated materials is better described by double-scale potential fluctuations that are related to (i) distribution of localized states energy and (ii) bandgap fluctuations. In addition, it was observed that the increase in nitrogen concentration leads to a shorter decay time at room temperature, which is attributed to a larger concentration of non-radiative recombination centers. Furthermore, a post-growth annealing step leads to a longer decay time at room temperature, which is attributed to a reduction in non-radiative recombination centers. At low temperatures, the role of non-radiative centers is suppressed, and therefore the decay time does not differ significantly for samples with either different nitrogen concentrations or in both the as-grown and annealed samples. [ABSTRACT FROM AUTHOR]

The effect of doping on InSb/Al0.1In0.9Sb quantum wells (QWs) was investigated, and it was found that doping improves the electron mobility at low temperatures and leads to a weaker dependence of the resistivity with temperature. The dependence of the carrier density on the well width revealed trap states at the interfaces of the QW whose sheet density per interface was estimated to be about 4×1010cm-2. The low mobility of undoped InSb QWs, in particular, at low temperature seems to have been caused by positively ionized impurity scattering at the interfacial trap states. Doping compensates for the trap states and enhances mobility by suppressing ionized impurity scattering. Thus, intentional doping is necessary for developing high-mobility InSb QW devices. The origin of the trap states is qualitatively discussed. [ABSTRACT FROM AUTHOR]

Aluminium nitride (AlN) is a promising material for challenging sensor applications such as process monitoring in harsh environments (e.g., turbine exhaust), due to its piezoelectric properties, its high temperature stability and good thermal match to silicon. Basically, the operational temperature of piezoelectric materials is limited by the increase of the leakage current as well as by enhanced diffusion effects in the material at elevated temperatures. This work focuses on the characterization of aluminum nitride thin films after post deposition annealings up to temperatures of 1000 °C in harsh environments. For this purpose, thin film samples were temperature loaded for 2 h in pure nitrogen and oxygen gas atmospheres and characterized with respect to the film stress and the leakage current behaviour. The X-ray diffraction results show that AlN thin films are chemically stable in oxygen atmospheres for 2 h at annealing temperatures of up to 900 °C. At 1000 °C, a 100 nm thick AlN layer oxidizes completely. For nitrogen, the layer is stable up to 1000 °C. The activation energy of the samples was determined from leakage current measurements at different sample temperatures, in the range between 25 and 300 °C. Up to an annealing temperature of 700 °C, the leakage current in the thin film is dominated by Poole-Frenkel behavior, while at higher annealing temperatures, a mixture of different leakage current mechanisms is observed. [ABSTRACT FROM AUTHOR]

In this study, a RANS model of turbulent conjugate heat transfer has been developed, which is applicable across a range of different combination of fluid and solid thermal properties. This is achieved by focusing on the transport equations for the temperature variance and its dissipation rate across the solid walls which bound the flow region. In this investigation we make use of a wider range of DNS data reported by other researchers, to advance our understanding of the processes involved and to revise and extend the capabilities of the model of Craft et al [12] including a more physical fluid-solid interface condition on the dissipation of thermal fluctuations and a dependence of model coefficients on Prandtl number. The resulting model is shown to successfully reproduce the penetration of thermal fluctuations into solid regions, and their subsequent decay across the solid, for a wide range of fluid to solid thermal property ratios, and Prandtl numbers, thereby bringing a step change to RANS capabilities in turbulent conjugate heat transfer analysis. [ABSTRACT FROM AUTHOR]

Currently, it is still unclear how and to what extent a change in temperature impacts the relative contributions of coherent and incoherent phonons to thermal transport in superlattices. Some seemingly conflicting computational and experimental observations of the temperature dependence of lattice thermal conductivity make the coherent–incoherent thermal transport behaviors in superlattices even more elusive. In this work, we demonstrate that incoherent phonon contribution to thermal transport in superlattices increases as the temperature increases due to elevated inelastic interfacial transmission. On the other hand, the coherent phonon contribution decreases at higher temperatures due to elevated anharmonic scattering. The competition between these two conflicting mechanisms can lead to different trends of lattice thermal conductivity as temperature increases, i.e. increasing, decreasing, or non-monotonic. Finally, we demonstrate that the neural network-based machine learning model can well capture the coherent–incoherent transition of lattice thermal transport in the superlattice, which can greatly aid the understanding and optimization of thermal transport properties of superlattices. [ABSTRACT FROM AUTHOR]

We experimentally analyze the heat capacity and thermal expansion of reference solids in a wide temperature range from several Kelvin to melting temperature, and establish a universal double-linear relation between the experimental heat capacity Cp and thermal expansion β, which is different from the previous models. The universal behavior between heat capacity and thermal expansion is important to predict the thermodynamic parameters at constant pressure, and is helpful for understanding the nature of thermal properties in solids. [ABSTRACT FROM AUTHOR]

Rock debris covers ~30% of glacier ablation areas in the Central Himalaya and modifies the impact of atmospheric conditions on mass balance. The thermal properties of supraglacial debris are diurnally variable but remain poorly constrained for monsoon-influenced glaciers over the timescale of the ablation season. We measured vertical debris profile temperatures at 12 sites on four glaciers in the Everest region with debris thickness ranging from 0.08 to 2.8 m. Typically, the length of the ice ablation season beneath supraglacial debris was 160 days (15 May to 22 October)—a month longer than the monsoon season. Debris temperature gradients were approximately linear (r2 > 0.83), measured as −40°C m–1 where debris was up to 0.1 m thick, −20°C m–1 for debris 0.1–0.5 m thick, and −4°C m–1 for debris greater than 0.5 m thick. Our results demonstrate that the influence of supraglacial debris on the temperature of the underlying ice surface, and therefore melt, is stable at a seasonal timescale and can be estimated from near-surface temperature. These results have the potential to greatly improve the representation of ablation in calculations of debris-covered glacier mass balance and projections of their response to climate change. [ABSTRACT FROM AUTHOR]

This paper experiments the trio influence of nanoparticles size (NS), per cent mass ratio (PWR), and temperature (T) on the thermal properties of MgO–ZnO/deionised water (DIW) nanofluids. MgO nanoparticles (20 nm and 100 nm) were hybridised with ZnO nanoparticles (20 nm) and suspended in DIW to formulate 0.1 vol% hybrid nanofluids at PWRs of 20:80, 40:60, 60:40, and 80:20 (MgO/ZnO). The pH, electrical conductivity (σ), viscosity (μ), and thermal conductivity (κ) of the hybrid nanofluids were experimentally determined at temperatures of 20–50 °C. The stability was monitored, while the morphology was examined using standard instruments. Findings showed that the suspension of the hybrid nanoparticles enhanced the pH and thermal properties of DIW. The hybrid nanofluids with 100 nm-MgO nanoparticles were observed to possess slightly higher values of pH, σ, and μ than those with 20 nm-MgO nanoparticles except for κ. An increase in temperature augmented κ and σ of MgO–ZnO/DIW nanofluids, while it detracted pH and μ. Maximum enhancements of 453.70–550.62% (40:60), 14.95–22.33% (40:60), and 8.29–17.46% (60:40) were evaluated for σ, κ, and μ, respectively. The influence of PWR, NS, and temperature on the σ, κ, μ, and pH of the hybrid nanofluids was in the order of PWR > NS > T, NS > PWR > T, T > NS > PWR, and T > NS > PWR, respectively. Subject to the experimental data obtained, correlations were developed for each hybrid nanofluid and thermal property as a function of temperature. The MgO–ZnO/DIW nanofluids with a 40:60 PWR appeared to be the best in terms of heat transfer capability. [ABSTRACT FROM AUTHOR]

The output characteristics of vertical cavity surface emitting lasers (VCSELs) arrays are largely influenced by temperature. We systematically studied thermal properties in 20-element oxide-confined VCSEL arrays via both theory and experiment. The output power, conversion efficiency, and threshold current dependent on ambient temperatures were measured. According to the relationship of wavelength shift and dissipated power, the device thermal resistance dependent on ambient temperature was obtained. The actual temperature in active region was successfully extracted. A 3-D heat diffusion model was established to simulate temperature distribution accurately. [ABSTRACT FROM AUTHOR]

• Novel Closed-Form Expression: Introduced for precise channel temperature estimation in AlGaN/GaN HEMTs. • Comprehensive Validation: Model's credibility established through rigorous comparisons with DC measurements and TCAD simulations. • Enhanced Accuracy: Outperforms assumptions based on constant thermal conductivity, especially crucial for GaN/Sapphire HEMTs. • Concurrent Optimization: Enables simultaneous enhancement of electrical and thermal properties using standard CAD tools. In this study, we introduced a closed-form empirical expression for estimating the channel temperature in AlGaN/GaN HEMTs. This model incorporates parameters such as substrate thickness, gate length, gate width, and temperature-dependent thermal conductivity. The model's validity was rigorously established through comprehensive comparisons involving the channel temperature measurement procedure (DC) and TCAD device simulations. The outcomes exhibited a noteworthy alignment with the observed model data, reinforcing its credibility. The model yields a notably improved accuracy in channel temperature estimation compared to assumptions based on constant thermal conductivity. This observation holds particular significance for GaN/Sapphire HEMTs. The utilization of the closed-form expression enables the simultaneous optimization of both electrical and thermal properties, utilizing conventional computer-aided design tools. [ABSTRACT FROM AUTHOR]

We investigated the thermal transport properties of Cu 1- x Ag x Ir 2 S 4 (0 ≤ x ≤ 0.05). The thermal conductivity of CuIr 2 S 4 exhibits a sudden change at the metal-insulator transition (MIT) temperature, where the phonon thermal conductivity κ ph decreases sharply from the insulating phase (IP) to the metallic phase (MP). The decrease in κ ph is attributed to a decrease in the phonon mean free path l from the IP to the MP, which is caused by anomalous phonon scattering in the MP. The decrease in l at the MIT temperature becomes less pronounced with increasing x, and the absolute values of l in the MP for x = 0.025 and 0.05 are higher than that for x = 0. This behavior suggests that the anomalous phonon scattering is suppressed by Ag substitution. Compared with previously reported results for the effect of Zn substitutions at Cu sites, the phonon relaxation time exhibits a distinct behavior for Ag and Zn substitution. [ABSTRACT FROM AUTHOR]

In this work, we propose an experimental setup to measure the thermal conductivity and specific heat of a single suspended glass fiber, as well as the thermal contact resistance between two glass fibers. By using optical lithography, wet and dry etching and thin film deposition, we prepared suspended glass fibers that are coated by niobium nitride (NbN) thin film used as room temperature thermal transducer. By using the 3ω technique, the thermal conductivity of glass fiber was measured to be 1.1 W m-1 K-1 and specific heat 0.79 J g-1 K-1 around 300 K under vacuum conditions. By introducing exchange gas into the measurement chamber, influence of the gas on the heat transfer was studied, and the convection coefficient h for all the measurement ranges from a pressure of 0.01 hPa to 1000 hPa, over more than five orders of magnitude, has been obtained. By adding a bridging glass fiber on top of two other suspended glass fibers, it was possible to estimate the thermal contact resistance between two glass fibers Rc in the range of 107-108 K W-1. [ABSTRACT FROM AUTHOR]

This study considers solid planets at about 300 K and an inert atmosphere having no interaction with associated radiation. Processes considered include transfer of energy from the surface skin to underlying layers depending on thermal properties. Temperatures of the surface depend on the rates of transfer of energy between soil layers. The atmosphere is warmed at base by contact with the surface, convection and turbulence distributing higher temperatures through the air. Comparisons between theoretical and measured temperatures show a close similarity. Mean planetary temperatures are calculated, depending on thermal parameters and the intensity of light/radiation from the particular solar system. [ABSTRACT FROM AUTHOR]

Photosensitive polymers or dielectric materials such as polyimides (PIs) have been used in fan-out wafer-level packaging process (FOWLP) as a redistribution layer for quite some time. In the condensed 2-D and 3-D packaging processes, the dielectric materials are applied multiple times to create as many as four or five redistribution layers. At the end of the process, the first layer may experience up to four times of heat cycles in which the polymer properties may change. However, the effect of heat cycles on properties of dielectric film as well as their contributions to the wafer-level warpage is still unclear. To understand the changes of materials’ properties after several heat cycles, the thermal and thermo-mechanical properties of negative-tone and positive-tone types of dielectric films are characterized by using the thermomechanical analysis (TMA), dynamic mechanical analysis (DMA), and thermogravimetric analysis (TGA). The glass transition temperature (${T}_{g}$), coefficient of linear thermal expansion (CTE), and modulus (storage, ${E}'$ , and loss, ${E}''$) are analyzed and compared. In addition, the morphology of the films before and after heat cycles is also analyzed. [ABSTRACT FROM AUTHOR]

Better mechanical, thermal properties and longer lifetimes are needed for the die attach layer in high-power electronic packaging. As traditional Sn–Ag–Cu (SAC) solders have many limitations, the sintered nanosilver materials are becoming one of the substitutes for high-power electronic packaging. However, the high performance of sintered nanosilver materials is only achieved when its fine sintering densification is formed. This article investigates the sintering densification process of nanosilver particles based on the design of orthogonal experiments and sintering kinetics modeling in which both the macroproperties and micromorphology are linked and analyzed. The results lead to several conclusions, such as: 1) the orthogonal experiments consider the effects of sintering temperature, dwell time, and sample preparation pressure on the sintering relative shrinkage and relative density—the results show that the most critical impact factor on sintering densification is the sintering temperature. (2) In the sintering kinetic experiments, the sintering densification rates obtained by fitting the relative density versus dwell time curves during 175 °C–250 °C follow the Arrhenius model, and the apparent activation energy of sintering kinetics is calculated to be 36 kJ/mol, while it is calculated from the particle size is 38.1 kJ/mol. 3) Through modeling the relationship between particle size, line shrinkage, and porosity, the line shrinkage and porosity first increase at the initial stage, while the particle size increases, and the macroscopic volume decreases at the end of sintering, the porosity decreases. [ABSTRACT FROM AUTHOR]

The thermophysical properties of carbon fiber‐based ultra‐high temperature ceramic matrix composites have been determined to aid designers who need these properties when considering using the composites in ultra‐high temperature aerospace applications. The coefficient of thermal expansion (CTE) and thermal diffusivity of the composites were measured parallel and perpendicular to the ply direction; the thermal conductivity was measured using the laser‐flash method and the heat capacity calculated from the relationship between the thermal diffusivity, density, and thermal conductivity. Both the CTE and thermal conductivity showed higher values across the ply and increased with increasing temperature as expected, whilst the thermal diffusivity showed higher values parallel to the ply and increased smoothly with temperature. In addition, two different but related oxyfuel torch tests, based on oxyacetylene and oxypropane, were used to evaluate the thermo‐ablation behavior of the composites. The tests showed how good the composites were at withstanding the ultra‐high temperatures, high heat fluxes, and gas velocities involved. [ABSTRACT FROM AUTHOR]

Native sweet potato starch was gelatinized at temperatures between 57 and 69 °C and then spray dried, to verify the changes caused by this process. The spray dried starch granules initially swelled with the increase in preheating temperature, displaying a larger diameter, but shrank upon colling. There was an increase in the gelatinization temperature and a decrease in the enthalpy change of the spray dried starches relative to those of native starch. Spray dried starch preheating at 69 °C showed highly reduced enthalpy change (80%) and relative crystallinity. Based on the parameters studied, the best preheating temperature was 67 °C. Under this condition, the starch can be applied in more viscous products that require a greater thickness, and with great process yield (65%). This study showed the feasibility of the application of this process to produce sweet potato starches with specific properties for different purposes in the food and non-food industries. • Spray-drying improve use of sweet potato starch as partial and fully gelatinized. • Pretreatment temperature influenced intensively the gelatinization properties. • Swelling power and solubility increased with increase in pretreatment temperature. [ABSTRACT FROM AUTHOR]

The study examines problems of heat conduction in a half-space with a thermal conductivity coefficient that is dependent on temperature. A boundary plane is heated locally in a circle zone at a given temperature as a function of radius. A solution is obtained for any function that describes temperature in the heating zone. Two special cases are investigated in detail, namely Case 1 with given constant temperature in the circle zone and Case 2 with temperature given as a function of radius, r. The temperature of the boundary on the exterior of the heating zone is assumed as zero. The Hankel transform method is applied to obtain a solution for the formulated problem. The effect of thermal properties on temperature distributions in the considered body is investigated. The obtained results were compared with finite element method model. [ABSTRACT FROM AUTHOR]

The room temperature reaction of Na4Sn2S6·5H2O with CoCl2·6H2O and 2‐(aminomethyl)pyridine (2‐AMP) or trans‐1,2‐diamino‐cyclohexane (DACH) leads to crystallization of two compounds with the compositions [Co(2‐(aminomethyl)pyridine)3]2 Sn2S6·10H2O (1) and [Co(trans‐1,2‐diaminocyclohexane)3]2Sn2S6·8H2O (2). In both compounds [Sn2S6]4– anions are present that are charge balanced each by two Co2+ centered complexes. Each of the two CoII cations are sixfold coordinated by six N atoms of three 2‐AMP or DACH ligands within slightly distorted octahedra. In compound 1, the two complexes are linked by one [Sn2S6]4– anion via strong N–H···S hydrogen bonds into centrosymmetric charge neutral trimeric units, that are further linked by weak C–H···S and N–H···S hydrogen bonds into chains that are directed along the a axis. These chains are further joined by N–H···O and O–H···O hydrogen bonds into a 3D network, with the H2O molecules forming chains along the b axis. The crystal structure of 2 is similar to that of 1 featuring trimeric units which are also linked into chains. Between the chains water molecules are embedded that link the chains into a 3D network. Upon heating 2 in a thermobalance the water and ligand molecules are removed in discrete steps, indicating that compounds with more condensed thiostannate networks will form. [ABSTRACT FROM AUTHOR]

The effect of thermal nonlinearity (TN) owing to the temperature dependence of the thermal parameters of the substrate, gas layer, and an opaque sample, as well as its black-body coefficient, on the characteristics of the nonlinear photoacoustic (PA) signal at the fundamental (FH) and second (SH) harmonics during gas-microphone reception is studied theoretically. It is shown that the frequency dependence of the FH is ~ω–1/2 and of the SH, ~ω–3/2. The dependence of the amplitude of the FH on the incident beam intensity is nontrivial and is expressed in terms of the dependence of the temperature increments of the irradiated Θ0 and back W0 sides of the sample surface on I0, while this dependence for the SH is ∼ l 0 2 . [ABSTRACT FROM AUTHOR]

Polyamide 1010 (PA1010) is a representative of long-chain polyamides, used in applications requiring good mechanical, thermal and chemical properties. It has a lower melting point and slightly higher flexible properties compared to nylon 66. Very few reports have been focused on the structures and properties of long-chain polyamides, which brings some troubles on their processing and applications. For the purpose of understanding mechanical changes within different temperature interval, dynamic structure transition of PA1010 was investigated by wide-angle X-ray diffractometer (WAXD) equipped with a hot stretching stage. During the process of the simultaneous thermal stretched, in addition to the Brill transition phenomenon, it was also accompanied by changes in crystallinity, orientation and tensile force. Both annealing and stretching can promote crystallization, in addition, stretching can also induce and destroy crystallization. With stretch ratios increasing, the crystallinity increases firstly, reaches the maximum when stretch ratio is 2.25 times and then decreases. The degree of orientation increase firstly but increase poorly after 2.50 times. The stretch force increase gradually too. The stretch force has a stronger ability than temperature to induce the PA1010 undergo the Brill transition. The presented results show that Brill transition is completed and the α-crystal structure completely transformed into γ-crystal structure when the stretch ratio is 2.50 times. [ABSTRACT FROM AUTHOR]

This paper introduces a new nonlinear multidisciplinary design approach (NMDA) for axial-flux (AF) eddy current brakes (ECBs). The proposed NMDA is developed by nonlinear magnetic–thermal–structural coupled modeling. The nonlinear behaviors of the AF-ECB covering the BH curve, resistivity, heat capacity, thermal conductivity, and the temperature are jointly analyzed in time domain to investigate the actual brake properties and to determine brake operating range. In this paper, the nonlinear magnetic modeling based on two-dimensional (2-D) reluctance network is studied by a modified Newton–Raphson method. Furthermore, the nonlinear thermal modeling is carried out by lumped-parameters considering the change of heat capacity, thermal conductivity, and the temperature and updating the data in the evaluation process. Finally, the nonlinear structural modeling is performed to obtain the deflection and the mechanical safety factor of the brake. The nonlinear modeling methods in the proposed NMDA are validated by independent 3-D electromagnetic, thermal, and structural finite element analyses (FEAs), and the proposed NMDA is tested with two different AF-ECB prototypes. The experimental results confirm that the proposed NMDA has high accuracy, and compared to 3-D-FEA approaches, it provides a fast solution to predict the AF-ECB performance. [ABSTRACT FROM AUTHOR]

The thermal conductivity of lateritic ores was determined by using the transitory commonly known Hot- Ball method. An experimental facility was built and an experimental design was used for analyzing the property performance for three temperature values. It was obtained the thermal conductivity of lateritic reaches values from 1.5 to 3.5 W/(m.k). An adjusted model of 0.98 correlations that estimates the thermal conductivity for the lateritic ores with temperature ranges of 40 °C to 70 °C was established. [ABSTRACT FROM AUTHOR]

Thermal buckling behavior of a functionally graded material (FGM) Timoshenko beam is studied based on the transformed-section method. The material and thermal properties of the FGM beam are assumed to vary across the beam thickness according to a power-law function, a sigmoid function and an exponential function. The results of buckling temperature for the FGM beams with respective temperature-dependent and temperature-independent properties under uniform and non-linear temperature rises are presented. Some results are compared with those in the published literature to verify the accuracy of the present work. The effects of the material distributions, temperature fields, temperature-dependent properties and slenderness ratios on the thermal buckling behaviors of FGM beams are discussed. It is believed that the present model provides engineers with a simple and effective method to study the effects of various parameters of the FGM beam on its thermal buckling behavior. [ABSTRACT FROM AUTHOR]

To solve the problem of low temperature inside the solar greenhouses during the winter nights in Northwest desert area of China, a case study was conducted on the assembled solar greenhouse, which is widely used in Hetian area, Xinjiang Province. Three types of walls with different building materials, i.e., the brick wall, block wall, and the sand-filled block wall, were built in the north sides of the solar greenhouses with the purpose to improve its heat storage properties and consequently to increase the indoor temperatures during the winter nights. Temperatures of the north walls and indoor environments of the solar greenhouses were continuously monitored with the TC100 sensors. The effect of different heat storage walls on strawberry cultivation inside the greenhouses was evaluated. The mass weight and solid soluble content of the strawberry were measured by ACS-30 balance and LH-B55 digital refractometer, respectively. Results showed that the heat storage performances of the three types of north walls with identical volumes and dimensions were as followings: Sand-filled block wall > block wall > brick wall. The internal temperatures of the three heat storage walls were 9.7, 10.4, and 11.3 ℃, respectively. The brick wall, block wall and sand-filled block wall averagely increased the indoor temperatures of the assembled solar greenhouses by 2.2, 2.9, and 3.8 ℃ at 07:00 in the morning, respectively. The indoor temperatures of four greenhouses are 7.4, 9.6, 10.3, and 11.2 ℃ respectively. The same planting management technology was adopted for the three tested solar greenhouses. The flowering dates of the cultivated strawberries using the three heat storage walls were 7 days, 11 days, and 14 days earlier than those of the original solar greenhouses without any modifications, and the maturities of strawberries were 14 days, 17 days, and 20 days earlier, respectively. The strawberry yields were 24.2%, 30.1%, and 33.4% higher, and meanwhile, the soluble solid contents of the strawberry in the treated groups were 1.4 percentage points, 2.1 percentage points, and 2.6 percentage points greater than those in the original fabricated greenhouses. The average soluble solids content of strawberry cultivated in three greenhouses reached 11.5%, 12.2%, and 12.7% respectively. The results again verify the importance of thermal properties of the north wall on the microenvironment of the solar greenhouses. Among the modifications, the mortar block wall is more effective than the brick wall, providing a better environment for strawberry growth in the greenhouse. The heat storage capacity of the new tested walls was consistent with the calculated heat load of the assembled greenhouses, indicating that the newly built walls in the greenhouse without supplemental heating systems were the driven source for the indoor environment improvement during the nighttime. The thermal load of fabricated solar greenhouse envelope was 70.3 MJ/h. The calculated value of heat emitted from the heat storage wall into the greenhouse was 91.1 和 119.3 MJ, respectively. This paper provides a reference for the heat storage material selection and structural design, as well as a basis for the application and research of mortar blocks in assembled solar greenhouses in the desert area of Northwest China. [ABSTRACT FROM AUTHOR]

One of the key challenges in the development of high‐temperature energy harvesting (HTEH) technology is to clarify the relationship between temperature‐dependent material parameters and device power generation capabilities. However, at present, the research on temperature stability of piezoceramics mainly relies on thermal annealing technology, which cannot follow the actual temperature dependence of the piezoelectricity, and it is even more difficult to predict the temperature stability of HTEH. To shed light on this field, here, (1−x)BiScO3–xPbTiO3 system was chosen for building HTEH material, and the temperature‐dependent electrical parameters, such as d33, εr, and g33, have been measured by multiple in situ techniques. It was found that the synergistic effect of d33 and εr with temperature helps to obtain a stable g33 value in a wide temperature range. Moreover, in the mode of the cantilever‐type energy harvester, a stable output voltage was obtained at x = 0.64 harvester with <20% change over a broad temperature range of 100‐250°C, and it was verified that the temperature stability of g33 is crucial to the operation stability of HTEH devices. [ABSTRACT FROM AUTHOR]

While many microwave studies related to tree emission have been undertaken, a few have considered the effect of phenological change on the emission from coniferous trees. The permittivity of vegetation tissue is known to be influenced by water content, while the water content and phase is sensitive to temperature in particular at temperatures below freezing. In addition to temperature, canopy-intercepted snow might also modify the tree emission and transmissivity in the microwave range. In this paper, a season-long experiment was designed to quantify the effect of snow accumulation and temperature on the observed microwave transmissivity from tree. A ground-based, upward-pointing multifrequency radiometer was used to monitor the microwave emissivity of a single coniferous tree at a site in Northern Finland. Radiometer measurements were combined with measurements of the canopy-intercepted snow cover and tree skin temperature. This paper presents two important findings. First, the tree transmissivity was strongly correlated with tree skin temperature under subzero temperature conditions, but uncorrelated with skin temperature changes above freezing. Second, although the tree transmissivity was slightly affected by the snow accumulation on the tree canopy, the overall influence on tree emission was statistically insignificant in this paper. [ABSTRACT FROM AUTHOR]

To solve the problem of low temperature inside the solar greenhouses during the winter nights in Northwest desert area of China, a case study was conducted on the assembled solar greenhouse, which is widely used in Hetian area, Xinjiang Province. Three types of walls with different building materials, i.e., the brick wall, block wall, and the sand-filled block wall, were built in the north sides of the solar greenhouses with the purpose to improve its heat storage properties and consequently to increase the indoor temperatures during the winter nights. Temperatures of the north walls and indoor environments of the solar greenhouses were continuously monitored with the TC100 sensors. The effect of different heat storage walls on strawberry cultivation inside the greenhouses was evaluated. The mass weight and solid soluble content of the strawberry were measured by ACS-30 balance and LH-B55 digital refractometer, respectively. Results showed that the heat storage performances of the three types of north walls with identical volumes and dimensions were as followings: Sand-filled block wall > block wall > brick wall. The internal temperatures of the three heat storage walls were 9.7, 10.4, and 11.3 °C, respectively. The brick wall, block wall and sand-filled block wall averagely increased the indoor temperatures of the assembled solar greenhouses by 2.2, 2.9, and 3.8 °C at 07:00 in the morning, respectively. The indoor temperatures of four greenhouses are 7.4, 9.6, 10.3, and 11.2 °C respectively. The same planting management technology was adopted for the three tested solar greenhouses. The flowering dates of the cultivated strawberries using the three heat storage walls were 7 days, 11 days, and 14 days earlier than those of the original solar greenhouses without any modifications, and the maturities of strawberries were 14 days, 17 days, and 20 days earlier, respectively. The strawberry yields were 24.2%, 30.1%, and 33.4% higher, and meanwhile, the soluble solid contents of the strawberry in the treated groups were 1.4 percentage points, 2.1 percentage points, and 2.6 percentage points greater than those in the original fabricated greenhouses. The average soluble solids content of strawberry cultivated in three greenhouses reached 11.5%, 12.2%, and 12.7% respectively. The results again verify the importance of thermal properties of the north wall on the microenvironment of the solar greenhouses. Among the modifications, the mortar block wall is more effective than the brick wall, providing a better environment for strawberry growth in the greenhouse. The heat storage capacity of the new tested walls was consistent with the calculated heat load of the assembled greenhouses, indicating that the newly built walls in the greenhouse without supplemental heating systems were the driven source for the indoor environment improvement during the nighttime. The thermal load of fabricated solar greenhouse envelope was 70.3 MJ/h. The calculated value of heat emitted from the heat storage wall into the greenhouse was 91.1 和 119.3 MJ, respectively. This paper provides a reference for the heat storage material selection and structural design, as well as a basis for the application and research of mortar blocks in assembled solar greenhouses in the desert area of Northwest China. [ABSTRACT FROM AUTHOR]

One of the main threats to freshwater turtle populations is habitat destruction, which occurs as a result of human activities such as infrastructure development, forestry, aggregate extraction, and agriculture. However, the impacts of these activities on thermoregulatory opportunities for turtles are not well understood. We examined the impacts of forestry and aggregate extraction on thermal characteristics of wood turtle (Glyptemys insculpta) habitat in the Sudbury District, Ontario, by measuring the differences in absolute temperature, thermal landscape structure, and habitat thermal quality among relatively undisturbed sites (N = 2), harvested forestry sites (N = 2), and aggregate pits (N = 2) in 2015. We also tested the potential use of the thermal landscape concept as a predictor of habitat thermal quality. Undisturbed habitats were of higher thermal quality than impacted sites in terms of temperatures experienced in situ by wild wood turtles in their natural home ranges, and never reached temperatures that would be injurious to turtles (i.e., below CT MIN or above CT MAX). The undisturbed sites were of lower quality in terms of optimal temperatures (i.e., T set), and were generally cooler and their temperatures less variable than those in impacted habitats. The thermal landscape concept provided a useful predictor of habitat thermal quality when the influence of time of day was factored into the predictive model. Our data are important to the conservation and management of wood turtles because they provide a preliminary quantification of the thermal impacts of natural resource extraction on the habitat of an endangered species, and can guide the development of mitigation and rehabilitation plans by providing measures of, and targets for, thermal habitat quality. • We examined impacts of forestry and gravel extraction on thermal properties of wood turtle (Glyptemys insculpta) habitat. • Undisturbed habitats rarely reached injurious temperatures and were less variable than temperatures in impacted habitats. • Our study can guide mitigation and rehabilitation plans by providing measures of, and targets for, thermal habitat quality. [ABSTRACT FROM AUTHOR]

Modulated temperature techniques allow to separate the reversing and non‐reversing contributions of material transitions. To investigate reversible crystallization and melting of isotactic polypropylene (iPP) at microstructural level, in this research, modulated temperature Fourier transform infrared (MTFTIR) and quasi‐isothermal FTIR (QIFTIR) analyses are used. By following the intensity variation of iPP regularity bands, associated with 31 helix structures of different lengths (n repeating units), MTFTIR evidences that, independently from helix length, a reversing coil–helix transition takes place few degrees below the non‐reversing crystallization onset. By comparing spectroscopic and differential scanning calorimetry experiments performed in quasi‐isothermal conditions, the reversing transition was found to be associated with the reversible melting‐crystallization phenomenon. Moreover, QIFTIR evidences that helices of different lengths contribute differently to the reversible transition: the helices composed of n = 10 and n = 12 are active into all the explored temperature range (30–130 °C) whereas the shortest (n = 6) and the longest (n > 15) helices contribute to reversibility at T > 100 °C. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019, 57, 922–931 [ABSTRACT FROM AUTHOR]

Biopolymer composites using poly(3-hydroxybutyrate-co-10 mol % 3-hydroxyhexanoate) (P(3HB-co-10 mol % 3HHx)) and ZnO nanoparticles (NPs) were prepared by solution casting method and the effect of ZnO NPs on thermal properties of the prepared biopolymer composites (P(3HB-co-10 mol % 3HHx)/ZnO NPs) were studied using DSC, TGA, GPC, and thermal conductivity analyzer. DSC analysis revealed the dual melting behavior of both neat P(3HB-co-10 mol % 3HHx) and its composites. It also showed that the incorporation of ZnO NPs into P(3HB-co-10 mol % 3HHx) decreased the melting temperature Tm, but increased the melting enthalpy ΔHm and degree of crystallinity Xc of the composites. Compared to neat P(3HB-co-10 mol % 3HHx), the initial degradation temperature T99 of the prepared composites was decreased and vice versa for final degradation temperature due to the addition of ZnO NPs which was revealed from TGA results. The observed thermal conductivity value of neat P(3HB-co-10 mol % 3HHx) and its composites were in between ~5.6 × 10–2 and ~7.9 × 10–2 W m/K with the very high value noticed for 30% ZnO NPs reinforced P(3HB-co-10 mol % 3HHx) composites. Overall P(3HB-co-10 mol % 3HHx)/ZnO NPs composites exhibited high thermal diffusivity and thermal effusivity compared to neat P(3HB-co-10 mol % 3HHx) with very high value noted for 30% ZnO NPs and 5% ZnO NPs reinforced P(3HB-co-10 mol % 3HHx) composites respectively which is essential for thermal related applications. [ABSTRACT FROM AUTHOR]

We report on a molecular dynamics simulation based study of the thermal and mechanical properties of the elastin mimetic peptide [LGGVG]n (n = 3, 7). Our findings indicate that this peptide undergoes an inverse temperature transition as the temperature is raised from ∼20 °C to 42 °C. The thermal behavior is similar to what has been observed in other well studied short mimetic peptides of elastin. Both [LGGVG]n (n = 3, 7) peptides exhibit an increase in the number of side chain contacts and peptide-peptide hydrogen bonds when the temperature is raised from ∼20 °C to 42 °C. These observations are accompanied by a decrease in the number of proximal water molecules and number of peptide-water hydrogen bonds. This work also reports on a comparison of the thermal and mechanical properties of [LGGVG]3 and [VPGVG]3 and quantifies the interaction with surrounding waters of hydration under mechanically strained conditions. It is demonstrated, via a quasi-harmonic approach, that both model peptides exhibit a reduction in the population of low-frequency modes and an increase in population of high-frequency modes upon elongation. The shift in population of frequency modes causes the peptide entropy to decrease upon elongation and is responsible for the development of an entropic force that gives rise to elasticity. These observations are in disagreement with a previously published notion that model elastin peptides, such as [VPGVG]18, increase in entropy upon elongation. [ABSTRACT FROM AUTHOR]