Thermal Character Research Articles

Transient Joule- and (ac) Josephson-like photon emission in one- and two- nucleon tunneling processes between superfluid nuclei: Blackbody and coherent spectral functions

Effective charged neutrons involved in one- and two- nucleon tunneling processes in heavy ion collisions between superfluid nuclei are expected to emit photons. Although the centroid, width and integrated energy area characterizing the associated gamma-strength functions are rather similar, the corresponding line shapes reflect the thermal equilibrated-like character of the quasiparticle transfer (1n-channel, blackbody spectral functional dependence), and the quantal coherent character of the Cooper pair transfer (2n-channel, Gaussian functional dependence) respectively. The predicted angular distributions, polarizations and analyzing power provide further insight into the profoundly different physics to be found at the basis of what can be considered a transient Joule-like and a (ac) Josephson-like nuclear processes

Ecofriendly Bio-packing Based on Sugarcane Bagasse Fiber for Potential Application in Agroindustry

The concern about waste in the world is growing because of the significant environmental impact. Therefore, new alternatives are used, such as recycling, biodegradable polymer, agroindustry waste reuse, and many others. In this sense, this paper proposes a production of new bio-packing based on the waste production from agriculture (sugarcane bagasse) and the drinking industry (plastic bottles from Polyethylene Terephthalate (PET)) for agriculture products transportation. Then, this new material was characterized by thermal, chemical, morphological, mechanical, antifungal activity, and hydrophobic character to evaluate its characteristics to use as bio-packing. Following this purpose, all samples are characterized in nature and after production by scanning electron microscopy analysis (SEM), thermogravimetric analysis (TG), infrared spectroscopy analysis (FTIR), surface angle contact, mechanical properties, and antifungal activity. The results indicated that the sample with 15% of bagasse presents the best mechanical properties. In addition, the presence of porosity can provide the material with low thermal conductivity. Moreover, the antifungal activity indicates that inhibition of fungus micellar growth was proportional to the decrease of bagasse in bio-packing. Then, which offers an innovative strategy for the use of waste in the production of environmentally friendly packing.

Quantitative assessment of the relationship between land use/land cover (LULC), topographic elevation and land surface temperature (LST) in Ilorin, Nigeria

The urbanization of landscapes and the increase in impervious land cover materials is known to cause significant changes in the landscape's thermal properties, typically leading to urban heat island (UHI). Although previous studies have investigated the impacts of land cover land use (LULC) and other factors on the urban land surface temperature (LST), the results of such studies are mixed. For instance, it is not yet clear what factors affect the spatial and temporal variation of the relationship between LULC and the LST, as well as the exact trajectory through which identified factors affect the thermal character of the urban landscape. In the current study, we examined the relationship between LULC, elevation and LST in Ilorin from the period of 2002–2020. The overriding aim was to understand the degree of association between LULC, elevation and LST, and the drivers of the spatial and temporal variation in the observed relationship. LST and NDVI were derived from Landsat data products. LST was derived using a mono-window algorithm and NDVI was used as proxy for LULC. The spatial pattern of LULC was analyzed using Moran's I spatial autocorrelation statistics. To investigate the relationship between LULC, elevation and LST, we adopted both ordinary least square (OLS) regression models and the geographically weighted regression (GWR) method to reveal both the linear and the geographically varying relationship between the LULC, elevation and LST. The results of the study show that the LULC pattern of Ilorin has been significantly altered during the 2000 to 2020 period. The urban proportion of the landscape has shown a significant increase, rising by more than 11% relative to 2002 figures, and the vegetation proportion, especially the forest component, has diminished within same temporal extent. LST values varied in both space and time, with high temperature clusters noticeable in the built-up areas and decreasing towards the urban periphery. The result of the autocorrelation analysis using Moran's I index reveals a significant clustering of LST in all the epochs investigated. Across the study area, minimum and maximum LST values of 0 °C and 41 °C were recorded in 2002 and 2020 respectively. Statistically significant relationships were observed between LULC, elevation and LST. However, the relationship between elevation and LST was very weak. Temporally, the strength of the relationship between the variables (as indicated in the variables' coefficient) as well as the overall model predictive performance (indicated by in the R2) fluctuated over the years. Spatially, the strength of relationship between LST and LULC and elevation varied significantly. LULC explained approximately between 26% and 64% of total LST variation in the city between 2002 and 2020. The study findings are relevant for efforts geared towards alleviating the degree of UHI or its impacts, generally, and in the city of Ilorin, in particular. An understanding of the spatial distribution of LULC and their impacts on the LST can be helpful in identifying areas needing attention. The observed relationship between relevant LULC classes can be incorporated into urban planning strategies to ensure a sustainable city development.

Artificial neural network model and multi-objective optimization of microchannel heat sinks with diamond-shaped pin fins

In this study, laminar, steady-state, incompressible flow with conjugate heat transfer was investigated for one flow passage of a microchannel with staggered diamond-shaped pin fin array. CFD analyzes were performed with OpenFOAM for various configurations and in all cases, the rhomboidal area of each pin fin was kept constant at 0.16 mm2, and the bottom surface of the substrate was subjected to a uniform heat flux of 69.3 kW/m2. Water with temperature-sensitive viscosity was taken as the cooling fluid, and copper with constant thermophysical properties was used for the solid domain. Parametric analyzes have been conducted for various combinations of geometric design variables such as pin fin angle (α), longitudinal pitch-to-diameter ratio (SL/D) and transverse pitch-to-diameter ratio (ST/D) with the flow attribute represented by pin fin Reynolds number (ReD). In the parametric investigations, α ranged from 30∘ to 90∘; ReD ranged from 20 to 100, and SL/D and ST/D were between 2.5 and 4.5. A multi-layer artificial neural network model (ANN), which was coded in Python and trained with parametric CFD results, was utilized to estimate off-design pin fin Nusselt numbers (NuD) and pin fin Poiseuille numbers (PoD), two objective functions representing thermal and hydrodynamic character, respectively. Non-dominated Sorting Genetic Algorithm (NSGA-II) was used to optimize the microchannel configuration, in which the individuals have been evaluated based on the multi-layer neural network prediction model. The constructed multi-layer neural network model predicted NuD and PoD with average errors of 1.39% and 1.02%, respectively. Among all design variables considered, α was found to be the most dominant one on NuD and PoD. Following the genetic algorithm, the majority of the optimal solutions appeared at ST/D around 2.5 and at ReD equal to 20 or 100. Over the entire range of ReD, NSGA-II suggested combinations of optimal α and SL/D yielding 4<NuD<11 and 6<PoD<32 appropriate for thermal or hydrodynamic demands.

EXPERIMENTAL STUDY OF CLINICAL INDICATORS OF INTRATISSUE PRESSURE IN DEEP CIRCULAR BURNS AND ITS DYNAMICS DEPENDING ON THE NATURE AND VOLUME OF SURGERY

The purpose of research. To improve in the experiment the optimal variants of surgical tactics to eliminate the phenomena of compartment syndrome in circular deep burns on the basis of studying the dynamics of intratissue pressure.&#x0D; Materials and methods. An experiment to study the effectiveness of treatment of deep circular burns of III degree, accompanied by compartment-syndrome with objectification of intra-tissue pressure was performed on 18 male WAG rats weighing 190.0-200.0 g, which were divided into three groups depending from the nature and scope of surgery.&#x0D; Research results and their discussion. Based on the assessment of the dependence of the level of intratissue pressure in the tissues on the timing of modeling of deep circular burns in the experiment and tactics and volume of surgical treatment, a clear dependence of indicators in all groups of experimental animals. The primary necrectomy performed in the III main group due to the radical surgical intervention allowed to completely normalize the intratissue pressure within 24 hours.&#x0D; Conclusions. 1. Clinical indicators of intratissue pressure at deep circular burns depending on time of modeling of a thermal trauma and character and volume of surgical intervention are defined in experiment. 2. It is established that primary necrectomy due to radical excision of necrotized tissues and rapid decompression contributes to the nor malization of intratissue pressure.

Synergistic effect on thermal behavior and product characteristics during co-pyrolysis of biomass and waste tire: Influence of biomass species and waste blending ratios

The work aims to get a full understanding of the co-pyrolysis synergy between different biomass and waste tire for high value utilization of both biomass and waste tire. Rice husk (RH), wheat straw (WS) and moso bamboo (MB) were chosen to co-pyrolyze with waste tire (WT). Influence of biomass species and blending ratios on co-pyrolysis synergistic effect was studied by analyzing thermal behavior, product yields and character. Thermogravimetry analysis proved the existence of synergistic effect and measured positive decomposition synergy for MB/WT. Char production showed little synergy for all biomass during co-pyrolysis while positive synergistic effect in liquid production was weakened with WT blending. Co-pyrolysis char integrated both biomass char and WT char characteristic. The pore structure was corresponding to that of biomass char and improved by synergy for all biomass, especially WS and MB. Co-pyrolysis oil mainly consisted of the typical components of bio-oil and WT oil, showing lower oxygenated compounds percentage than bio-oil. Aromatic hydrocarbons formation was inhibited while alicyclic hydrocarbons formation was intensified by co-pyrolysis interaction and MB/WT co-pyrolysis showed significant synergy in ethers and furans production. Co-pyrolysis showed positive synergistic effect on CO and CO2 generation and negative synergistic effect on H2 and CH4 content.

Characterizing soil’s thermal property for earth air heat exchanger through experiment

The energy holding or dissipating capacity of soil is an important parameter for an earth air heat exchanger (EAHE). The present work deals with the experimental investigation of the thermal character of four distinct soil samples to assess the EAHE performance. The EAHE has been modelled as a heat source and the responses of soil samples as a function of time were recorded through a data logger. Results reveal that a soil sample has more effective thermal character compared to other samples for better performance of EAHE. For 6 h of continuous operation, the soil temperature was found to rise by 8 °C, which is the least among all the remaining samples. It is concluded that for longer continuous operation of EAHE, the soil with less thermal storage capacity, which has the potential to dissipate heat quickly, is better. The present study would be useful for EAHE designers to select an appropriate site.

Elastic anisotropies, thermal conductivities and tensile properties of MAX phases Zr2AlC and Zr2AlN: A first-principles calculation

In this study, the mechanical stability, elastic properties, including single-crystal elastic constants, polycrystalline elastic modulus and elastic anisotropy, Debye temperatures, electronic properties, minimum thermal conductivities and tensile character of Zr2AlC and Zr2AlN were calculated by first-principles calculations based on density functional theory. The results showed that Zr2AlX (X = C, N) are mechanically stable and anisotropic in elastic properties, and the degree of elastic anisotropy of Zr2AlN is slightly greater than Zr2AlC, and the sound velocities and minimum thermal conductivities of Zr2AlC and Zr2AlN along the [001] and [100] directions are also anisotropic. Moreover, the density of states (DOS) and charge density difference distributions showed that these Zr2AlX have metallic-covalent-ionic mixed bonds. Finally, the calculated tensile properties along the [001] and [110] directions of these MAX phases showed that the tensile strength along the [110] direction is greater than that along the [001] direction.

Dicke Transition in Open Many-Body Systems Determined by Fluctuation Effects.

We develop an approach to describe the Dicke transition of interacting many-particle systems strongly coupled to the light of a lossy cavity. A mean-field approach is combined with a perturbative treatment of fluctuations beyond mean field, which becomes exact in the thermodynamic limit. These fluctuations completely change the nature of the steady state, determine the thermal character of the transition, and lead to universal properties of the emerging self-organized states. We validate our results by comparing them with time-dependent matrix-product-state calculations.

Synthesis and characterization of tetraethylene pentamine functionalized MIL-101(Cr) for removal of metals from water.

Metal contamination in water is a worldwide persistent problem. We developed a nano-adsorbent, TEPA-MIL-101(Cr) that exhibits effective removal of heavy metals from real water samples. MIL-101(Cr) was synthesized under solvo-thermal condition. Then MIL-101(Cr) was dehydrated and degassed at high temperature under vacuum to generate the coordinately unsaturated sites which are used for tetraethylene pentamine (TEPA) grafting. The structures, morphologies, and compositions of the sorbents have been characterized. Langmuir and Freundlich isotherm models were applied for describing the adsorption process onto TEPA-MIL-101(Cr). The successful grafting of TEPA on MIL-101(Cr) was verified by Fourier transform infrared. The results of X-ray diffraction, scanning electron microscopy, and CHN analysis show that the structure of TEPA-MIL-101(Cr) retains the original structure of MIL-101(Cr). Thermogravimetric analysis indicates thermo-stability of the adsorbent up to 300 °C. Optimal conditions for adsorption were determined as pH = 6.5 and contact time = 1h. The adsorption capacities of TEPA-MIL-101(Cr) for Pb(II), Cu(II), Cd(II), and Co(II) from aqueous samples were 227.5, 217.7, 221.4, and 215.6mg/g respectively, which is on average more than 8 times that of MIL-101(Cr). Analysis of Langmuir and Freundlich models for describing the adsorption isotherms of TEPA-MIL-101(Cr) reveals that the metal ions were absorbed onto TEPA-MIL-101(Cr) by a favorable physical absorption process. TEPA-MIL-101(Cr) was synthesized successfully by a simple, and cost-effective method. The removal efficiency of TEPA-MIL-101(Cr) for the metal ions achieved more than 95 % in real water samples, which in addition to its thermal stability character make it a promising candidate for water treatment purposes.

Inverse Modeling of Thermal Decomposition of Flame-Retardant PET Fiber with Model-Free Coupled with Particle Swarm Optimization Algorithm.

The thermal decomposition model of flame-retardant polyethylene terephthalate (FRPET) fiber is essential for predicting its fire behavior and do relevant fire simulation. In this work, the thermal decomposition character of FRPET is investigated via thermogravimetric analysis at four heating rates. Two kinetic schemes are proposed based on the analysis of experimental data and model-free methods. The model-free methods (Friedman and advanced Vyazovkin methods) are employed to determine possible search range for particle swarm optimization algorithm with constriction factor (CFPSO). Thus, this coupled method could evaluate the kinetic parameters for two proposed schemes without initial guess. Both models could reasonably predict the experimental data with obtained parameters, and the second two-step consecutive model shows better performance. The performance of CFPSO on the second model is further compared with improved generalized simulated annealing algorithm, and CFPSO was found to be more effective. Furthermore, global sensitivity analysis was conducted via the Sobol method to investigate the influence of kinetic parameters for the second model on predicted results. The most influential parameters are ln A and Eα of the second reaction and reaction order n of the third reaction.

SN-CUO-ARABIC GUM COMPOSITION FOR RED TRACER PROJECTILE AMMUNITION POTENTIAL

&lt;div&gt;&lt;p class="Els-history-head"&gt;Fundamentally, tracer projectile material based on pyrotechnic composition, and where the pyrotechnic was generally composed of fuel, oxidizer, and binder. The tin (Sn) material is one of the candidates for fuel material because tin has a low melting point, so this composition can ignite at low temperature, while the copper oxide (CuO) can emit the orange-red spectrum. This study aims to evaluate the thermal and spectrum character of Sn-CuO-AG-based composition. The characterization data of these samples was evaluated by tests of morphology and phase, enthalpy change, calorie energy, and spectrum emission. Based on this data, the 17Sn-68CuO-15AG sample was emitted a strong red color too, but this sample has a high or the longest exothermic process. Furthermore, the 27Sn-58CuO-15AG sample has emitted a weak red color with medium exothermic energy. Generally, the 22Sn-63CuO-15AG is more suitable than the two other compositions for the tracer projectile composition of ammunition, this material emits a strong red spectrum and low-calorie energy.&lt;/p&gt;&lt;/div&gt;

Evidence for a thermally driven charge-density-wave transition in 1T-TaS2 thin-film devices: Prospects for GHz switching speed

We report on the room-temperature switching of 1T-TaS2 thin-film charge-density-wave devices, using nanosecond-duration electrical pulsing to construct their time-resolved current–voltage characteristics. The switching action is based upon the nearly commensurate to incommensurate charge-density-wave phase transition in this material, which has a characteristic temperature of 350 K at thermal equilibrium. For sufficiently short pulses, with rise times in the nanosecond range, self-heating of the devices is suppressed, and their current–voltage characteristics are weakly nonlinear and free of hysteresis. This changes as the pulse duration is increased to ∼200 ns, where the current develops pronounced hysteresis that evolves nonmonotonically with the pulse duration. By combining the results of our experiments with a numerical analysis of transient heat diffusion in these devices, we clearly reveal the thermal origins of their switching. In spite of this thermal character, our modeling suggests that suitable reduction of the size of these devices should allow their operation at GHz frequencies.

Formation of mullite and mullite-corundum composites from kaolin using spark plasma sintering

Mullite, an excellent and versatile material, was synthesized, alone and in a composite with alumina, from natural kaolin—a primary product of a kaolin clay quarry. Kaolin powder for the mullitization process was inserted into a spark plasma sintering (SPS) apparatus in the form of raw kaolin, and in another experiment in the form of calcinated kaolin freed from bound water. Thermal properties, microstructure and phase composition were studied on the obtained samples. It was found out that the effect of calcination was in dehydration of kaolinite and amorphization of its phase composition. Thermal properties of the dehydrated and as-received kaolinite-based material were very similar. Materials with a perfect thermal insulation character were received. Dehydrated and as-received powders were mixed with alumina powder (corrundum phase) and fired by SPS. Mechanical properties–Vickers microhardness as well as parameters based on instrumented indentation were enhanced in the composite because of alumina content.

How to adjust bubble’s adhesion on solid in aqueous media: Femtosecond laser-ablated patterned shape-memory polymer surfaces to achieve bubble multi-manipulation

Manipulation of the behaviour of gas bubbles in aqueous environment is of vital significance in medical and microfluidic fields, and has attracted much research attention in the past few years. Making clear the interrelation between underwater bubbles’ wettability and the solid surfaces topography to achieve the bubble adhesion regulation is a crucial factor of realizing the precise bubble manipulation without external stimulation, and a great challenge. Here, by combining the fish-scale-like morphology and rose-petal-like morphology into one sample and changing the proportion of each part, the underwater bubble adhesion could be adjusted from ultralow to low, high, and ultrahigh. The square-patterned array shape-memory polymer (SMP) surfaces with various adhesion forces were fabricated by femtosecond laser ablation and used to realize lossless transportation of a bubble in both horizontal and vertical direction. The high adhesion surface could be used to form programmable microbubble patterns. By taking advantage of the excellent thermal shape-memory character of SMP film, we realized the bubble in-situ release and reversely switch of the bubble adhesion based on the macroscopic and microscopic deforming-recovering of as-prepared SMP sample. The present study will inspire people to develop novel strategies to achieve multi-manipulation of bubbles in practical applications.

THE STUDY OF AIR TEMPERATURE IN THE LAST DECADE IN THE BUCHAREST METROPOLITAN AREA

Multiple paleoclimatic studies indicate that the Earth has warmed significantly since the end of the 19th century. The mean temperature of the Earth's surface is rising unnaturally and frighteningly fast, having a large impact and threatening the very near future of human civilization. This paper presents an analysis of the variability of air temperature in the Bucharest metropolitan area in the decade 2011-2020, related to the 1901-2000 period in the context of the global warming. The research includes the study of the mean annual and monthly temperature, the absolute maximum and minimum temperature, the frequency of the thermal character in the cold season and in the hot season and the frequency of days with characteristic temperatures. The 2011-2020 decade was the hottest one since the beginning of meteorological measurements. Related to the 1901-2000- reference period, the air temperature increased by 1.6°C, from 11.1°C to 12.7°C, the mean of the 10 years. The year 2020 was the hottest year, marking the end of the hottest decade since the meteorological measurements were made, the mean annual temperature being 13.5°C, by 2.4°C higher than the mean of the 1901-2010 reference period.

Synthesis, crystal structure, 19F, 1H NMR, thermogravimetry, and DSC investigation of indium(III) fluoride complexes with β-alanine amino acid

Indium(III) fluoride complexes with β-alanine amino acid (β-AlaH)[InF4(H2O)2]·0.5H2O and (β-AlaH)2[InF5(H2O)]·2H2O have been synthesized for the first time and investigated by the methods of single crystal X-ray diffraction, 19F, 1H NMR spectroscopy, thermogravimetry (TG, DTG, DTA), and DSC. The crystal structure of (β-AlaH)[InF4(H2O)2]·0.5H2O has been investigated at 296 K, whereas that of (β-AlaH)2[InF5(H2O)]·2H2O – at 173 K. The structure of (β-AlaH)2[InF5(H2O)]·2H2O was found to be disordered. Two disordered "resonance" structures of the β-alaninium cation with different arrangement of the proton in the carboxylic groups were obtained. The thermal behavior and character of ionic motions in the investigated compounds have been studied.

Performance and emission characteristics of a diesel engine operated on diverse modes using renewable and sustainable fuels derived from dairy scum and municipal solid waste

Abstract Continuous utilization of crude oil in a diesel engine produces detrimental environmental effects. Therefore use of renewable fuels can at least lower the emission levels because such fuels are recyclable, provide energy safety and significantly deal with social, economic and environment. It is well known that diesel engine have several benefits compared to counterpart petrol engine and produce greater smoke and nitric oxide (NOx) levels. As a result, in this current work an effort has been carried out lower both smoke and NOx emission levels. To achieve this, homogeneous charge compression ignition engine (HCCI) is a better option. The influence of producer gas and dairy scum oil methyl ester (DiSOME) on the thermal efficiency and emission character of a compression ignition engine under dual and HCCI mode has been investigated. The HCCI engine was operated at constant air temperature (80 °C) because DiSOME cannot be vaporized at atmospheric temperature. The obtained with DiSOME-producer gas operated dual fuel mode provided amplified thermal efficiency (BTE) and declined hydrocarbon (HC), carbon monoxide (CO) and marginally augmented smoke and NOx levels compared to HCCI operation.

Исследование диэлектрического отклика, проводимости и тока термостимулированной деполяризации в релаксорном сегнетоэлектрике PbNi-=SUB=-1/3-=/SUB=-Nb-=SUB=-2/3-=/SUB=-O-=SUB=-3-=/SUB=-

This paper presents results of a study of temperature dependences of dielectric response and DC and AC - conductivity in single crystals of the relaxor ferroelectric PbNi1/3Nb2/3O3 (PNN) in a wide range of frequencies (10 Hz - 100 kHz) and temperatures (80 - 750 K). Anomalies in the dielectric response in the form of broad frequency-dependent maxima in the vicinity of 153 and 730 K are observed. The thermal activation character of DC conductivity has been obtained, and activation energies determined as Ea = 770 meV (T &gt; 310 K) and Ea = 23 meV (T &lt;310 K). The analysis of conductivity gives reason to assume the existence of local conductivity in the low-temperature region. It is shown that the conductivity character changes above 350 K from the local to the bulk one. Measurement by thermally stimulated depolarization has shown the presence of a residual polarization below 130 K.

Analog Hawking effect: BEC and surface waves

We take into account two further physical models which play an utmost importance in the framework of Analogue Gravity. We first consider Bose--Einstein condensates (BEC) and then surface gravity waves in water. Our approach is based on the use of the master equation we introduced in a previous work. A more complete analysis of the singular perturbation problem involved, with particular reference to the behavior in the neighbourhood of the (real) turning point and its connection with the WKB approximation, allows us to verify the thermal character of the particle production process. Furthermore, we can provide a simple scheme apt to calculate explicitly the greybody factors in the case of BEC and surface waves. This corroborates the improved approach we proposed for studying the analogue Hawking effect in the usual limit of small dispersive effects.