Temperature-dependent Variation Research Articles

Impedance characterization of hydrothermally synthesized nickel zinc ferrite nanoparticles for electronic application

This study comprehensively investigates the structural, morphological, dielectric, and conductivity properties of Ni0.5Zn0.5Fe2O4 nanoparticles synthesized through a hydrothermal method, focusing on their suitability for technological applications. The nanoparticles exhibited a cubic structure with an average grain size of approximately 19 nm. The dielectric properties were analyzed with respect to frequency and temperature, showcasing behaviors consistent with Maxwell-Wagner and Koop's theories. The dielectric plane plots, corresponding to the impedance circuit in the Smith Chart, were found to align with the Davidson-Cole relaxation model. Moreover, the conductivity properties adhered to the Jonscher Power law, resembling conductive properties akin to semiconductors in accordance with the band theory. Notably, the s parameter, indicative of the DC conduction mechanism, displayed temperature-dependent variations, suggesting compatibility with the small polar and correlated hopping barrier conduction models. The thermal activation energies of the Ni0.5Zn0.5Fe2O4 nanoparticles at 102, 103, 104, 105, and 106 rad/s frequencies have been recorded at 0.115, 0.141, 0.157, 0.133 and 0.121 eV, respectively. The experimental results strongly suggest that Ni0.5Zn0.5Fe2O4 nanoparticles hold promise as an inspiring material for electronic circuit applications.

Temperature Dependent Photoluminescence Spectra of Nanocrystalline Zinc Oxide: Effect of processing condition on the excitonic and defect mediated emissions

Nanocrystalline zinc oxide (ZnO) with crystallite size in the range 85 -89 nm are prepared by the thermal decomposition of carbonate precursor under three different atmospheres, viz., in air ambiance, under nitrogen flow, and in vacuum. O 1s X-ray photoelectron spectra indicate that the atomic percentage of oxygen vacancies is more in the sample prepared under vacuum while adsorbed oxygen is more in the sample prepared in air ambience. Optical band gaps for the samples are in the range 3.17–3.20 eV. Room temperature photoluminescence spectra of the samples reveal band edge emission in the UV range (⁓3.18 eV) and broad defect mediated visible emission (⁓1.60–2.70 eV). Emission profile of excitonic emission at 80 K can be resolved into two free excitonic peaks at 3.42 eV (FX-A) and 3.46 eV (FX-B), donor bound excitonic peaks (D0X), peak due to transition of free electrons to acceptor levels (FA) donor-acceptor pair (DAP) emission and phonon replicas. D0X peak at ⁓3.35 eV has contribution from oxygen vacancies (Vo) and Zn interstitials (Zni). The most intense peak in the case of all the three samples is the FA peak at ⁓ 3.31 eV which has contribution from zinc vacancies (VZn). Temperature dependent variation of the dominant D0X and FA peaks in the range 80–400 K are analyzed using modified Varshni model which considers contributions from electron-phonon scattering and lattice thermal expansion. Defect dependent emission intensity is maximum at 80 K due to freeze-out of phonons and decreases with increase in temperature. The evolution of the colour of luminescence with temperature is studied using CIE plot method.

Temperature Dependent Variations of Low-Frequency Noise Sources in Cryogenic Short-Channel Bulk MOSFETs

Temperature Dependent Variations of Low-Frequency Noise Sources in Cryogenic Short-Channel Bulk MOSFETs

Influence of potassium doping on the structural, conduction mechanism, and dielectric properties of CaFe2O4.

The frequency and temperature-related dielectric relaxation and electrical conduction mechanisms in potassium-doped CaFe2O4 oxide ceramic were investigated in this study throughout a temperature range of 313-673 K. The synthesis of the KCaFe2O4 compound was accomplished through a solid-state reaction route. The X-ray diffraction pattern at room temperature confirmed that the ceramic KCaFe2O4 crystallizes in the orthorhombic system with the Pbnm space group. The EDX analysis proved the absence of external elements. The surface morphology of the samples was examined using scanning electron microscopy. The conduction mechanism, validated as CBH conduction, was examined using the temperature-dependent variation of Jonscher's power law exponent. Using Nyquist plots, we have effectively constructed a relevant equivalent circuit that encompasses the influences originating from both the grains and the grain boundaries. Furthermore, in KCaFe2O4, the induced dielectric relaxation from the non-Debye to Debye type model is demonstrated by the thermal analysis of M'' (ω) and -Z'' (ω) as a function of frequency.

Signature of Topological semimetal in harmonic-honeycomb ReO3

Transition-metal honeycomb compounds are capturing scientific attention due to their distinctive electronic configurations, underscored by the triangular-lattice spin-orbit coupling and competition between multiple interactions, paving the way for potential manifestations of phenomena such as Dirac semimetal, superconductivity, and quantum spin liquid states. These compounds can undergo discernible pressure-induced alterations in their crystallographic and electronic paradigms, as exemplified by our high-pressure (HP) synthesis and exploration of the honeycomb polymorph of ReO3 (P6322). This HP-P6322 polymorph bears a phase transition from P6322 to P63/mmc upon cooling around Tp = 250 K, as evidenced by the evolution of temperature-dependent magnetization (M-T curves), cell dimension and conductivity initiated by an inherent bifurcation of the oxygen position in the ab plane. Insightful analysis of its band structure positions suggests this HP-P6322 polymorph being a plausible candidate for Dirac semimetal properties. This phase transition evokes anomalies in the temperature-dependent variation of paramagnetism (non-linearity) and a crossover from semiconductor to temperature-independent metal, showing a temperature independent conductivity behavior below ∼200 K. Under increasing external pressure, both the Tp and resistance of this HP-polymorph are slightly magnetic-field dependent and undergo a “V”-style evolution (decreasing and then increasing) before becoming pressure independent up to 20.2 GPa. Theoretical calculations pinpoint this anionic disorder as a probable catalyst for the decrement in the conductive efficiency and muted temperature-dependent conductivity response.

Temperature dependent color variations and photophysical properties of UV/IR shielding lanthanum titanate perovskite and its binary composite colorants

A2B2O7 type perovskite systems have found widespread use in various applications, owing to their exceptional thermal stabilities and adaptable lattice structure. La2Ti2O7 is one of the most studied system for optoelectronic and energy storage applications. The current work focuses on exploring the potential of La2Ti2O7 for developing ceramic colorants with near-infrared (NIR) reflective properties, ideal for energy-saving applications. Initially, co-precipitated La2Ti2O7 was calcined at different temperatures (600, 800 and 1000 °C) to realize the formation of phase pure perovskite structure. Further the composite ceramic colorants of La2Ti2O7 and Fe3O4 were developed via solid-state route at 600, 800 and 1000 °C. The phase purity and crystallinity of La2Ti2O7 and composite colorants were ascertained by the XRD analysis. The particle and chemical nature of the colorants were further characterized by SEM, TEM and XPS analysis. To comprehend the potential uses of these materials in different optoelectronic sectors, their tuneable optical band gap characteristics were determined. The NIR reflectance range of the synthesised La2Ti2O7 was found to be between 92 and 96 %, whilst the composite colorants showed values between 85 and 93 %. The influence of iron oxide doping and calcination temperature on the colour variations and photophysical characteristics of ceramic composite colorants have received special focus in this study.

Temperature dependence of acoustic parameters in pure and blended edible oils: Implications for characterization and authentication

This research investigates the temperature-dependent variation of diverse acoustic parameters in samples of edible oils. It further supplements previous studies on the effectiveness of non-destructive ultrasonic inspection in the authentication of edible oils. The oils under examination consist of pure samples of olive, sunflower, and corn oils, as well as variable mixtures ranging from 20 % to 80 % of the more expensive one (olive oil) with the other two, simulating a hypothetical adulteration scenario. The studied acoustic parameters are related to the velocity, attenuation, and frequency components present in 2.25 MHz ultrasonic waves propagating through the oil samples within a temperature range of 24 °C to 34 °C. The results confirm the suitability of non-destructive ultrasonic inspection in evaluating and detecting the adulteration of olive oil with economically inferior oils such as sunflower and corn. Additionally, this study provides added value by laying the groundwork for a non-destructive and innovative determination of the fatty acid profile of an edible oil based on the evolution of the aforementioned ultrasonic parameters with temperature. The findings hold potential for enhancing the authenticity assessment and quality control of edible oils in the food industry.

Impact of temperature on the binding interaction between dsDNA and curcumin: An electrochemical study

In this study, we investigated the binding mode between double-stranded deoxyribonucleic acid (dsDNA) and curcumin (CU) using differential pulse voltammetry (DPV), UV–Vis spectroscopy, and molecular docking. By employing these techniques, we predicted the binding within the minor groove region of dsDNA and CU. Significantly, we employed electrochemistry, specifically cyclic voltammetry (CV), to explore the temperature effect on the dsDNA and CU binding. To the best of our knowledge, this is the first study to utilize electrochemical methods for investigating the temperature-dependent behavior of this binding interaction. Our findings revealed temperature-dependent variations in the binding constants: 2.42 × 103 M−1 at 25 °C, 4.26 × 103 M−1 at 30 °C, 5.44 × 103 M−1 at 35 °C, 6.29 × 103 M−1 at 40 °C, and 7.52 × 103 M−1 at 45 °C. Notably, the binding constant exhibited an increasing trend with elevated temperatures, indicating a temperature-dependent enhancement of the binding interaction.

Experimental measurement and modeling of lattice thermal expansion and specific heat capacity of C15-Cr2Nb Laves phase intermetallic compound

In order to determine the lattice thermal expansion and specific heat capacity (Cp) of the C15-Cr2Nb Laves phase, an experimental investigation and modeling were carried out in the present paper by employing high-temperature X-ray diffraction (HTXRD) and differential scanning calorimetry (DSC). A thorough analytical model was utilized to predict the temperature-dependent variations of enthalpy and specific heat, and the predicted findings were compared to the experimentally measured data. Arc melting was employed to synthesize Cr2Nb samples with distinct hexagonal (C14/C36) and cubic (C15) Laves phase structures, which were then subjected to the appropriate heat treatment. Room temperature XRD patterns, SEM, and EDAX experiments on homogenized samples at 1273 K for 72 h validated the homogeneity and C15 (Fd-3 m) crystal structure of Cr2Nb. Rietveld refinement was used to determine the lattice parameters and relative phase fractions of the constituent phases. The average thermal expansion coefficient was determined to be αai = 0.659 × 10−5 and αVi = 1.977 × 10−5 K−1 respectively. The Cp of the C15-Cr2Nb Laves phase intermetallic compound was measured employing heat flux DSC, utilizing conventional “three-step” procedures, and being reported for the first time. The measured Cp and enthalpy increment data (HT – H298.15) with varying temperatures reported in the present investigation are being correlated utilizing the theoretical model applying the quasi-harmonic Debye Grüneisen model in the temperature range 0–860 K and illustrated different contributions to the total heat capacity i.e., vibrational, anharmonic, and electronic.

Solid state hydrogen storage: Decoding the path through machine learning

We present a machine learning (ML) framework HEART (HydrogEn storAge propeRty predicTor) for identifying suitable families of metal alloys for hydrogen storage under ambient conditions. Our framework includes two ML models that predict the hydrogen storage capacity (HYST) and the enthalpy of hydride formation (THOR) of multi-component metal alloys. We demonstrate that a chemically diverse set of features effectively describes the hydrogen storage properties of the alloys. In HYST, we use absorption temperature as a feature which improved H2wt% prediction significantly. For out-of-the-bag samples, HYST predicted H2wt% with R2 score of 0.81 and mean absolute error (MAE) of 0.45 wt% whereas R2 score is 0.89 and MAE is 4.53 kJ/molH2 for THOR. These models are further employed to predict H2wt% and ΔH for ∼ 6.4 million multi-component metal alloys. We have identified 6480 compositions with superior storage properties (H2wt% > 2.5 at room temperature and ΔH < 60 kJ/molH2). We have also discussed in detail the interesting trends picked up by these models like temperature dependent variation in the rate of hydrogenation and alloying effect on H2wt% and ΔH in different families of alloys. Importantly certain elements like Al, Si, Sc, Cr, and Mn when mixed in small fractions with hydriding elements like Mg, Ti, V etc. systematically reduce ΔH without significantly compromising the storage capacity. Further upon increasing the number of elements in the alloy i.e from binary to ternary to quaternary, the number of compositions with lower enthalpies also increases. From the 6.4 million compositions, we have reported new alloy families having potential for hydrogen storage at room temperature. Finally, we demonstrate that HEART has the potential to scan vast chemical spaces by narrowing down potential materials for hydrogen storage.

Characterizing the line emission from molecular clouds

Aims. We aim to characterize and compare the molecular-line emission of three clouds whose star-formation rates span one order of magnitude: California, Perseus, and Orion A. Methods. We used stratified random sampling to select positions representing the different column density regimes of each cloud and observed them with the IRAM 30 m telescope. We covered the 3 mm wavelength band and focused our analysis on CO, HCN, CS, HCO+, HNC, and N2H+. Results. We find that the line intensities depend most strongly on the H2 column density, with which they are tightly correlated. A secondary effect, especially visible in Orion A, is a dependence of the line intensities on the gas temperature. We explored a method that corrects for temperature variations and show that, when it is applied, the emission from the three clouds behaves very similarly. CO intensities vary weakly with column density, while the intensity of traditional dense-gas tracers such as HCN, CS, and HCO+ varies almost linearly with column density. N2H+ differs from all other species in that it traces only cold dense gas. The intensity of the rare HCN and CS isotopologs reveals additional temperature-dependent abundance variations. Overall, the clouds have similar chemical compositions that, as the depth increases, are sequentially dominated by photodissociation, gas-phase reactions, molecular freeze-out, and stellar feedback in the densest parts of Orion A. Our observations also allowed us to calculate line luminosities for each cloud, and a comparison with literature values shows good agreement. We used our HCN(1–0) data to explore the behavior of the HCN conversion factor, finding that it is dominated by the emission from the outermost cloud layers. It also depends strongly on the gas kinetic temperature. Finally, we show that the HCN/CO ratio provides a gas volume density estimate, and that its correlation with the column density resembles that found in extragalactic observations.

Understanding Antiferromagnetic and Ligand Field Effects on Spin Crossover in a Triple-Decker Dimeric Cr(II) Complex.

Two possible explanations for the temperature dependence of spin-crossover (SCO) behavior in the dimeric triple-decker Cr(II) complex ([(η5-C5Me5)Cr(μ2:η5-P5)Cr(η5-C5Me5)]+) have been offered. One invokes variations in antiferromagnetic interactions between the two Cr(II) ions, whereas the other posits the development of a strong ligand-field effect favoring the low-spin ground state. We perform multireference electronic structure calculations based on the multiconfiguration pair-density functional theory to resolve these effects. We find quintet, triplet, and singlet electronic ground states, respectively, for the experimental geometries at high, intermediate, and low temperatures. The ground-state transition from quintet to triplet at an intermediate temperature derives from increased antiferromagnetic interactions between the two Cr(II) ions. By contrast, the ground-state transition from triplet to singlet at low temperature can be attributed to increased ligand-field effects, which dominate with continued variations in antiferromagnetic coupling. This study provides quantitative detail for the degree to which these two effects can act in concert for the observed SCO behavior in this complex and others subject to temperature-dependent variations in geometry.

Study on the structural and photophysical properties of N-acyl amino acid europium complexes

In this paper, a series of acyl amino acid europium complexes (Eu[CH3(CH2CH2)nCONHCH(CH3)COO]3, n = 0 ∼ 5) were synthesized using N-acyl amido alanine as ligands, and their structures and photophysical properties were studied.The structural and functional group information of europium complexes was obtained by elemental analysis, as well as infrared and hydrogen nuclear magnetic spectral analysis (1H NMR). The theoretical structure of the complexes was obtained by density functional theory (DFT) calculations; the theoretical structure of the complex was shown to be reliable by the comparison of theoretical and experimental vibrational and 1H NMR spectra. Additionally, the photophysical properties of the solid complexes at room temperature were determined by analysis of Ultraviolet–visible spectroscopy(UV–vis) and luminescence spectra. From the test results, it can be seen that the complex had good light absorption capacity in the range of 200–––300 nm; By comparison of the luminescence intensities of the complexes and EuCl3 proved that acyl amino acid ligands played a role in sensitizing Eu3+ characteristic luminescence. In addition, the effect of solution concentration on fluorescence performance has been studied. It can be inferred that complexes with longer carbon chains are less prone to aggregation in solution (increasing repulsive forces with increasing hydrophobicity), and the concentration, where fluorescence quenching occurs, is higher. Moreover, the solvent effect on the luminescence performance of the complexes was investigated by testing the luminescence spectrum of the complexes with different carbon chain lengths in a methanol solution(0.01 mol/L). Finally, the variable temperature spectral analysis provided information on the temperature-dependent variation of the luminescence properties of the complexes. The fluorescence performance of complexes with different carbon chain lengths that having different changing trends with temperature, with long carbon chain complexes exhibiting better high-temperature fluorescence stability.

Synthesis and Characterization of Dibenzothieno[a,f]pentalenes Enabling Large Antiaromaticity and Moderate Open-Shell Character through a Small Energy Barrier for Bond-Shift Valence Tautomerization.

Experimental and theoretical rationalization of bond-shift valence tautomerization, characterized by double-well potential surfaces, is one of the most challenging topics of study among the rich electronic properties of antiaromatic molecules. Although the pseudo-Jahn-Teller effect (PJTE) is an essential effect to provide attractive characteristics of 4nπ systems, an understanding of the structure-property relationship derived from the PJTE for planar 4nπ electron systems is still in its infancy. Herein, we describe the synthesis and characterization of two regioisomers of the thiophene-fused diareno[a,f]pentalenes 6 and 7. The magnetic and optoelectronic properties characterize these sulfur-doped diareno[a,f]pentalenes as open-shell antiaromatic molecules, in sharp contrast to the closed-shell antiaromatic systems of 3 and 5, in which these main cores consist of the same number of π electrons as 6 and 7. Notably, thiophene-fused 6b and 7b showed pronounced antiaromaticity, the strongest among the previous systems, as well as moderate open-shell characteristics. Our experimental and theoretical investigations concluded that these properties of 6b and 7b are derived from the small energy barrier Ea‡ for the bond-shift valence tautomerization. The energy profile of the single crystal of 6b showed the temperature-dependent structural variations assigned to the dynamic mutual exchange between the two Cs-symmetric structures, which was also supported by changes in the chemical shifts of variable-temperature 1H NMR spectra in the solution phase. Both experimental and computational results revealed the importance of introducing heteroaromatic rings into 4nπ systems for controlling the PJTE and manifesting the antiaromatic and open-shell natures originating from the high-symmetric structure. The findings of this study advance the understanding of antiaromaticity characterized by the PJTE by controlling the energy barrier for bond-shift valence tautomerizations, potentially leading to the rational design of optoelectronic devices based on novel antiaromatic molecules possessing the strong contributions of their high-symmetric geometries.

Quantized resistance revealed at the criticality of the quantum anomalous Hall phase transitions

In multilayered magnetic topological insulator structures, magnetization reversal processes can drive topological phase transitions between quantum anomalous Hall, axion insulator, and normal insulator states. Here we report an examination of the critical behavior of two such transitions: the quantum anomalous Hall to normal insulator (QAH-NI), and quantum anomalous Hall to axion insulator (QAH-AXI) transitions. By introducing a new analysis protocol wherein temperature dependent variations in the magnetic coercivity are accounted for, the critical behavior of the QAH-NI and QAH-AXI transitions are evaluated over a wide range of temperature and magnetic field. Despite the uniqueness of these different transitions, quantized longitudinal resistance and Hall conductance are observed at criticality in both cases. Furthermore, critical exponents were extracted for QAH-AXI transitions occurring at magnetization reversals of two different magnetic layers. The observation of consistent critical exponents and resistances in each case, independent of the magnetic layer details, demonstrates critical behaviors in quantum anomalous Hall transitions to be of electronic rather than magnetic origin. Our finding offers a new avenue for studies of phase transition and criticality in QAH insulators.

Variable fluid properties and concentration species analysis of a chemically reactive flow of micropolar fluid between two plates in a rotating frame with cross diffusion theory

The importance of this study is that the physical properties no longer to be consider as a constant, therefore dynamics of the mechanism of temperature dependent fluid properties and species concentration variation on the magnetized flow of a micropolar fluid in a rotating frame is studied in this article. The flow is considered between two porous plates with slip boundary conditions on the lower plate. The cross-diffusion theory on the thermal and solutal transportation investigation is presented by the help of non-uniflorm source / sink and nonlinear chemical reaction. The equations of motion and energy are reduced into the set of couple nonlinear ordinary differential equations by the usage of appropriative transformation. These couple nonlinear equations are tackled numerically with the utilization of BVP4C function on MATLAB. The graphical and numerical outcomes are obtained with physical discussion for various parameter. The study concludes that as the material parameter approaches to zero, the flow of micropolar fluids approaches to the Newtonian fluids. It is worth mentioning that the variable viscosity reduces the fluid velocity near the lower plate due to domination of viscous forces, while fluid temperature shows rising trend by the improvement of variable thermal conductivity because of the more heat production. Further, it is noticed that the Soret and Dufour impacts precludes the solutal deposition and coolant the bounding at surface, as a result fluid temperature and concentration enhances.

Analysis of the Responses to Pasteurization Temperatures of Methicillin Resistant Staphylococcus aureus Derived from Milk Items

Background and Aim: One of the leading causes of both community- and hospital-acquired infections is the superbug," multidrug-resistant Staphylococcus aureus (MRSA). Milk and dairy products seem to be highly vulnerable to a wide range of diseases. Therefore, we require processing procedures that both eliminate pathogens and lengthen the useful life of these products. The purpose of this study was to determine how susceptible MRSA isolates were to pasteurization temperatures after being recovered from dairy products.&#x0D; Materials and Methods: For the purpose of pasteurization, ten MRSA isolates were exposed to both a 63°C LTLT (low temperature, long time) therapy for 30 minutes and a 72°C HTST (high temperature, short time) treatment for 16 seconds.&#x0D; Results: The findings indicated that all isolates were killed by a pasteurization-like treatment at low temperature for a long time (63°C for 30 minutes), but that particular adaptable isolates could survive a pasteurization-like treatment at high temperature for a short time (72°C for 16 seconds), which may point to a time- and temperature-dependent variation in the thermal tolerance mechanism.&#x0D; Conclusion: The results showed that all isolates seemed extremely susceptible to damage from heat using LTLT pasteurization-like treatment (63°C for 30 minutes). Nevertheless, a particular number of these isolates succeeded in establishing colonies because they have quorum sensing structures that survive being handled by using heat damage at 72°C for 16 seconds. Pasteurized milk producers should be alerted to the fact that this microorganism has been found in contaminated milk since it compromises the product's safety and diminishes its value to consumers. As a result, it is strongly advised that manufacturers utilize varied temperatures for milk processing in order to remove the contaminating methicillin- and heat-resistant S. aureus (MHRSA).

Room temperature magnetoelectric effect in Sr2FeNbO6 perovskite: A theory supported experimental investigation

Magnetoelectric multiferroic materials are those which can be influenced by both electric and magnetic fields and have wide applications. Single-phase materials that show magnetoelectric effects are very few compared to composites. Recently, several studies have been conducted on magnetic and dielectric properties of single-phase double perovskite Sr2FeNbO6, while magnetoelectric effects have not been reported yet. The present study aims to explore the magnetoelectric effects of Sr2FeNbO6 prepared through solid-state reaction route. Rietveld refinement confirms the orthorhombic symmetry of the material with Pbnm space group. The existence of Fe2+, Fe3+, and Nb5+ ions were investigated by XPS analysis. The room temperature magnetic and electric hysteresis loops display the simultaneous existence of magnetism and ferroelectricity in Sr2FeNbO6. A high Curie temperature of 727 K is obtained from temperature-dependent variation of magnetization, making it suitable for spintronics applications. Further, this room temperature multiferroicity of Sr2FeNbO6 was confirmed using magnetoelectric coupling measurement and obtained a coupling coefficient of 4.4 mV cm−1 Oe−1. The conclusion of Sr2FeNbO6 showing ferrimagnetic nature is obtained through density functional theory (DFT) calculations.

Empirical extinction coefficients for the Swift-UVOT optical-through-ultraviolet passbands

ABSTRACT We calculated empirical reddening and extinction coefficients with respect to the dust reddening map of Schlegel et al. (1998) for the Swift-UVOT passbands, using the ‘star pair’ method and photometric data from the UVOT Serendipitous Source Catalogue and 2MASS as well as spectroscopic data from LAMOST Data Release 7. The reddening coefficients for the UVW2 − UVM2, UVM2 − UVW1, UVW1 − U, U − B, and B − V colours are −1.39, 2.08, 0.78, 0.72, and 0.84, respectively. The extinction coefficients for the UVW2, UVM2, UVW1, U, B, and V bands are 5.60, 6.99, 4.91, 4.13, 3.41, and 2.57, respectively. The numbers are consistent with predictions by the Fitzpatrick’s extinction law of R(V) = 3.0. Temperature-dependent variations of the coefficients are found and discussed, particularly for the ultraviolet passbands. We recommend using the new reddening and extinction coefficients in future when dereddening the Swift-UVOT data.

Entropy generation studies of turbulent fluid flow through novel hybrid corrugated channels with variable thermophysical properties

The investigation of the effects associated with the temperature-dependent property (viscosity, density and thermal conductivity) variations on fluid flow, entropy generation, and heat transfer in the various hybrid corrugated channels is performed numerically. Water enters the flow domain with a constant inlet temperature of 300[Formula: see text]K and constant inlet velocity corresponding to the different Re values. An in-depth numerical investigation is performed for the two cases that have the least entropy generation among all the cases and these cases are inward arc-outward triangular and inward trapezoidal-outward triangular corrugated channels. The use of corrugated channels with variable properties substantially affects the Nu. The effect of temperature-dependent property variation corresponding to the Re on frictional and heat transfer entropy generation is also presented in this work. The rise in the Re and consideration of variable fluid properties resulted in a decrement in the total entropy generation. Under the considered conditions, the frictional entropy generation contribution in the total entropy generation is very small as compared to the heat transfer entropy generation with constant and variable fluid properties. Furthermore, the consideration of temperature-dependent property variation results in a lower augmentation entropy generation number as compared to the constant property cases at higher Re.