Constant Thermal Conditions Research Articles

Analytical solution to the two-dimensional inverse heat conduction problem in an axisymmetric cylindrical coordinate system

The inverse heat conduction problem involves estimating an unknown cooling or heating action based on internal temperature histories in a body. Such a problem is ill-posed because the estimated results are highly sensitive to input data noise. An analytical solution is developed for the two-dimensional inverse heat conduction problem in an axisymmetric cylindrical coordinate system using the Laplace transform technique. On the basis of the known temperatures at multiple measuring points distributed on two cylindrical measuring surfaces along the axial direction inside the solid, the expressions for the surface temperature and heat flux are explicitly obtained in the form of a power series of time and eigenfunctions of the space variable. A comprehensive estimation error assessment is conducted using the internal temperature distribution that is obtained using a direct heat conduction analysis under the prescribed stationary and moving boundary conditions. The constant thermal condition is well reproduced using the present inverse solution, except in the vicinity of the discontinuity point. In addition, the effective heat flux and effective heat transfer coefficient are introduced to obtain the best estimation of the transient heat transfer in the major cooling area of the rotating cylinder.

Experimental re-melting of a continental crust: probing the deep storage zone of Campi Flegrei and Vesuvius magmas

Mantle magmas interact with surrounding rocks during their ascent and storage in the continental crust, leading to open system processes as wall rock partial melting. In this study, we have experimentally investigated the reactions between a leucosome depleted migmatite and a primitive K-basaltic of Campi Flegrei (Italy). Experiments were carried out at pressure of 0.8 GPa temperatures from 1250 °C to 1050 °C and constant temperature and thermal gradient conditions. The experimental products consist of biotite-free migmatite, glass and crystals of clinopyroxene, olivine, plagioclase and Cr-spinel with proportions that vary as a function of temperature. Open system isothermal experiments indicate that the chemistry of melts and phase relationships are controlled by the high Al2O3 content of leucosome depleted migmatite with the glass composition shifting from K-trachybasalt towards shoshonite as the temperature decreases from 1200 °C to 1125 °C. At temperatures \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\le$$\\end{document}1150°C, migmatite assimilation is not exclusively due to the assimilation fractional crystallization process because evidence of mingling and mixing is observed. T-gradient experiment shows melt composition ranging from shoshonite to phono-tephrite moving from the slightly crystalline zone (T = 1250 –1210 °C) at the bottom of the capsule towards the highly crystalline zone (T = 1160 –1140 °C). This SiO2-constant trend indicates that at temperature below the basalt solidus, the assimilation of leucosome depleted crust is represented almost exclusively by the biotite breakdown, leading to the increase in Al, Mg, Fe, Ti, and K activities in the system. The shoshonitic composition obtained in our experiments could represent the parental magma for both Campi Flegrei volcanic district and Vesuvius magmatic systems, indicating modification in a deep storage zone through mixing with the partial melts derived from restitic continental crust.

A novel optimizing Pulsed Plasma Gas Variable Polarity Plasma Arc Welding (PPG-VPPAW) method for improving weld quality

To enhance the reliability of aluminum alloy welding quality, a novel Pulsed Plasma Gas Variable Polarity Plasma Arc Welding (PPG-VPPAW) system is proposed. This system enables independent control and rapid adjustment of the plasma gas, allowing for flexible modulation of arc pressure output under constant thermal conditions, thereby reducing porosity and refining grain structure. The research analyzed the impact of parameters of different plasma gas on arc characteristics, welding porosity, and welding microstructure. The results reveal that the periodic changes in pulsed plasma gas induce corresponding variations in arc temperature, arc shape, arc pressure, arc voltage, and the morphology of the weld pool keyhole. The magnitude of the difference between the base value and peak value of pulsed plasma gas determines the extent of arc pressure fluctuations and the behavior of the backside keyhole. The maximum oscillation amplitude of the backside keyhole can reach up to 4.5 mm². Additionally, the oscillation of pulsed plasma gas within the molten pool has been demonstrated to effectively reduce weld porosity and refine grain size. Under this process, the grain size of the weld metal can be reduced by up to approximately 25%. Current work provides an important direction for fabricating highly reliable aluminum alloy weldments.

Diurnal variation in genetic parameters for locomotor activity in Drosophila melanogaster assessed under natural thermal conditions.

In nature, organisms are exposed to variable and occasionally stressful environmental conditions. Responses to diurnal and seasonal fluctuations, such as temperature and food accessibility, involve adaptive behavioural and physiological changes. While much work has been done on understanding the genetic architecture and evolutionary potential of stress tolerance traits under constant thermal conditions, there has been less focus on the quantitative genetic background in variable environments. In this study, we use the Drosophila Genetic Reference Panel (DGRP) to investigate the locomotor activity, a key behavioural trait, under variable natural thermal conditions during the summer in a temperate environment. Male flies from 100 DGRP lines were exposed to natural thermal and light conditions in Drosophila activity monitors across three experimental days. We found that activity was highly temperature and time dependent and varied between lines both within and between days. Furthermore, we observed variation in genetic and environmental variance components, with low to moderate estimates of the heritability for locomotor activity, consistently peaking in the afternoons. Moreover, we showed that the estimated genetic correlations of locomotor activity between two time points decreased, as the absolute differences in ambient temperature increased. In conclusion, we find that the genetic background for locomotor activity is environment specific, and we conclude that more variable and unpredictable future temperatures will likely have a strong impact on the evolutionary trajectories of behavioural traits in ectotherms.

The Validity of Cross Priming Amplification to Detect SARS-CoV-2 Virus

The standard molecular technique to detect the SARS-CoV-2 virus is The Real-Time Reverse-Transcription Polymerase Chain Reaction (rRT-PCR). It requires sophisticated equipment and a time-consuming sample process. The Cross Priming Amplification (CPA) is a nucleic acid amplification technique that amplifies DNA with high specificity and efficiency under constant thermal conditions. This technique is faster than rRT-PCR and doesn't require a biosafety level-2 (BSL-2) facility. The study aimed to determine the validity of CPA with rRT-PCR as a gold standard and to evaluate its performance as molecular rapid tests for detecting SARS-CoV-2 RNA from nasopharyngeal swab specimens. This study was a descriptive diagnostic test by using data retrospectively from swab nasopharyngeal patient samples who were treated at Palabuhan Ratu Hospital with COVID-19 from 01 January to 31 December 2021. The CPA was performed on a total of 52 nasopharyngeal samples at Pelabuhan Ratu Laboratory and rRT-PCR at Provincial Health Laboratory. The validity and correlation tests were performed. The majority of subjects were female between the ages of 34-50 years. The cut-off Tt-value is 3.25, 0.84 Area Under Curve (AUC), with a p-value <0.001. The CPA has good validity for COVID-19 diagnosis with 77% sensitivity, 94% specificity, 96% PPV, and 71% NPV. The sensitivity was increasing with Ct-value <30 (82%) and Ct-value <25 (87%). The CPA had a good validity for the COVID-19 diagnostic test. The CPA could be used as a rapid molecular test for detecting SARS-CoV-2 viral RNA from nasopharyngeal swab specimens.

Frequency of Temperature Fluctuations Subtly Impacts the Life Histories of a Tropical Snail.

AbstractMost organisms are faced with daily cyclic changes in a suite of environmental conditions, including temperature. In shallow marine waters, populations of the same species may experience either intertidal or subtidal conditions, such that some individuals experience extreme daily fluctuations as the tide ebbs and flows, while others only a few meters away experience less pronounced or less frequent fluctuations or almost constant thermal conditions. This study used a fully factorial combination of three thermal treatments and two diet treatments to test the hypotheses that (1) individuals experiencing fluctuating temperatures perform more poorly than those experiencing the same mean temperature under constant conditions and that (2) the negative impact of fluctuating temperatures is greater under food-limiting conditions. Five life-history components of the slipper snail Crepidula cf. marginalis were used as response variables. We found that temperature fluctuations impacted size at hatching and time to hatching, as well as growth rate, to some extent. Diet treatments impacted growth rates, clutch sizes, time to first brood, and time to hatching. There were no statistically significant interactions between the two factors. These results show that fluctuations between two temperatures that are typically experienced by these animals in the field can significantly affect fitness-related characters and, therefore, suggest the tidal height at which larvae settle can significantly impact individual fitness. This is one of the first studies to demonstrate that differences in the frequency of fluctuations, in the absence of differences in the magnitude or the mean, can have significant impacts on invertebrate life histories.

Influence of radial fuel staging on combustion instabilities and exhaust emissions from lean-premixed multi-element hydrogen/methane/air flames

The utilization of hydrogen-blended hydrocarbon fuels, or even completely carbon-free fuels like pure hydrogen and ammonia, will be indispensable in the effort to reduce anthropogenic carbon dioxide emissions from heavy-duty land-based gas turbines. In order to make this energy transition, however, low emissions, low dynamics fuel-flexible gas turbine combustion systems will be required. To address some of the key technological obstacles in the development of such systems, we explore a prototype multi-element injector assembly devised to prevent flashback in extremely fast premixed hydrogen flames, paying particular attention to the impact of radial dual-fuel staging on the generation of self-induced instabilities and the formation of nitrogen oxides and carbon monoxide. In conjunction with phase-averaged OH*/CH* chemiluminescence and OH PLIF flame imaging, we carry out extensive measurements over the full range of 0 to 100% H2/CH4 fuel staging conditions, including even/uneven blends of H2/CH4 fuels between inner and outer nozzle groups, partial/complete fuel split cases, and pure H2 or CH4 fuel for all constituent flames, under a constant thermal power condition of 78 kW. Our measurements demonstrate that whereas carbon monoxide concentrations are largely unaffected by the radial fuel staging conditions except under high and pure hydrogen percentage conditions, there exists a strong correlation between total nitrogen oxides emissions and overall adiabatic flame temperature. Integrated analyses of isocontour instability maps reveal that near XH2,g = 0.50 a discontinuous mode transition takes place, where the intermediate-amplitude lower frequency oscillations associated with relatively low hydrogen concentration conditions give way to stronger, higher frequency instabilities under high hydrogen content conditions. While even-blend (non-staging) conditions are characterized by coherent oscillations of the constituent flames, the responses of clustered flames to radial fuel staging conditions are eccentric and complex, manifested as large-scale asynchronous modulations between inner- and outer-stage heterogeneous reaction zones. This observation suggests that in a multi-element injector environment spatiotemporal incoherence driven by inhomogeneous heat release can be used to neutralize self-excited pressure oscillations, by disrupting pressure-heat release coupling processes.

Improving Thermal and Photostability of Polymer Solar Cells by Robust Interface Engineering.

As the power conversion efficiency (PCE) of organic photovoltaics (OPVs) approaches 19%, increasing research attention is being paid to enhancing the device's long-term stability. In this study, a robust interface engineering of graphene oxide nanosheets (GNS) is expounded on improving the thermal and photostability of non-fullerene bulk-heterojunction (NFA BHJ) OPVs to a practical level. Three distinct GNSs (GNS, N-doped GNS (N-GNS), and N,S-doped GNS (NS-GNS)) synthesized through a pyrolysis method are applied as the ZnO modifier in inverted OPVs. The results reveal that the GNS modification introduces passivation and dipole effects to enable better energy-level alignment and to facilitate charge transfer across the ZnO/BHJ interface. Besides, it optimizes the BHJ morphology of the photoactive layer, and the N,S doping of GNS further enhances the interaction with the photoactive components to enable a more idea BHJ morphology. Consequently, the NS-GNS device delivers enhanced performance from 14.5% (control device) to 16.5%. Moreover, the thermally/chemically stable GNS is shown to stabilize the morphology of the ZnO electron transport layer (ETL) and to endow the BHJ morphology of the photoactive layer grown atop with a more stable thermodynamic property. This largely reduces the microstructure changes and the associated charge recombination in the BHJ layer under constant thermal/light stresses. Finally, the NS-GNS device is demonstrated to exhibit an impressive T80 lifetime (time at which PCE of the device decays to 80% of the initial PCE) of 2712 h under a constant thermal condition at 65°Cin a glovebox and an outstanding photostability with a T80 lifetime of 2000 h under constant AM1.5G 1-sun illumination in an N2 -controlled environment.

Dynamic effects of frequent step changes in outdoor microclimate environments on thermal sensation and dissatisfaction of pedestrian during summer

• Subjects’ dynamic thermal responses to frequent microclimatic step changes are investigated. • Comparison between surveyed dynamic thermal sensation and predicted sensation is made. • Equivalent UTCI* based on SWI and frequent step change effectiveness is proposed. • Applicability of UTCI* in evaluating thermal sensations under frequent step changes is evaluated. • Impacts of frequent microclimatic step changes on thermal dissatisfaction in summer are revealed. Humans engaging in outside activities are more likely to be exposed to frequent spatiotemporal step changes in outdoor thermal conditions, as opposed to constant thermal conditions staying indoors. Understanding pedestrians’ thermal reactions to such dynamic thermal settings is helpful for enhancing outdoor thermal comfort by providing spatiotemporal variations in thermal conditions. In this study, 48 subjects were tested about their thermal perceptions while being exposed alternately to direct sunlight and shade at different defined frequencies, in a series of 45 min experiment period. The experiments were designed to create step changes in microclimate environments. The study was carried out from May to July in a university campus in Hong Kong with subtropical weather conditions. Results show that subjective thermal perceptions varied with alternating exposure to sunlight and shade at different frequencies. UTCI was modified to an equivalent UTCI* for evaluating thermal environments with frequent step changes by taking into account impacts of mixed changes in sun and wind conditions, alternating frequency and expectation on thermal perceptions. With a higher alternating frequency, there was reduced thermal dissatisfaction with hot summer days and a lower comfort requirement for shade, as well as the upper limit of acceptable UTCI* approaching 43.7 °C.

Effects of heat exchange fluid characteristics and pipe configuration on the ultimate bearing capacity of energy piles

This paper examines the ultimate bearing capacity of energy piles in sandy and clayey soils by conducting numerical modeling under different thermal loads, fluid-pipe configurations and fluid characteristics. Accordingly, U and W-shaped fluid-pipes with different diameters were simulated using ANSYS-FLUENT software, under different inlet flow rates, fluid temperatures and ground temperatures. Moreover, a semi-empirical analytical solution is proposed for predicting the outlet temperature for different pipe configurations. Then, the energy piles were modeled using ABAQUS FE-software, and the effect of temperature distribution in U, double-U and W-shaped pipes on the ultimate bearing capacity was studied, in heating/cooling conditions. Both numerical simulations and the analytical solution were validated against experimental data. Results showed that under constant flow rate, initial inlet temperature and pipe diameter, the differences between the inlet and outlet temperature of the heat exchange fluid in the U-shaped pipes was less than that obtained for the W-shaped pipes. Also, for constant inlet temperature and pipe diameter, the temperature difference decreased when the inlet flow rate increased. It was found that under constant thermal loading conditions, the changes in the ultimate bearing capacity were higher in piles with double U-shaped pipes, followed by U-shaped pipes, and lowest for W-shaped pipes.

Influence of thermal disturbances on profilometric measurements of surface asperities

During the surface topography measurements, changes in the ambient temperature affect the elongation of both the tested object and the measuring device. This influence is insignificant and often negligible, when measuring a single two-dimensional profile, which lasts from a few to several minutes. However, during spatial measurements lasting over several hours, changes in the ambient temperature cause texture mapping errors. The research included assessment of impact of changes in the ambient temperature of a tactile profilometer on the results of surface topography measurements.In the paper methodology of surface topography measurements under controlled temperature conditions is described. Thermal influence of the environment on the errors in mapping of surface topography were also determined. Measurements were carried out in a specially designed climatic chamber. Results of multiple measurements of the same reference surface profile in constant and variable thermal conditions of the environment were presented. Such procedure allowed for the presentation of a two-dimensional transverse profile of a generated surface, varying as a function of temperature. Generated surfaces were parameterized and compared with each other. The results of the research allowed us to state that changes in the ambient temperature during the measurements of the surface topography affect the mapping errors of the measured structure. Temperature changes and measurement results are strongly linearly correlated with each other.

Application of differential transformation method for an annular fin with variable thermal conductivity

The thermal analysis of the annular fin is performed by applying the differential transformation method. The thermal conductivity of the annular fin has been considered as a function of temperature. The effects of non-dimensional parameters, namely thermal conductivity and thermo-geometric fin parameters on the fin efficiency and temperature distribution are determined. Obtained results from the differential transformation method are also compared with the exact analytical results and the results of the finite difference method in the constant thermal conductivity condition. It has been concluded that the differential transformation method provides accurate results in the solution of non-linear problems.

INFLUENCE OF CONTOUR RADIUS AND FIBER ORIENTATION ON HEAT ACCUMULATION DURING MACHINING OF UNIDIRECTIONAL CFRP

The production of carbon fiber reinforced plastic (CFRP) parts requires edge trimming after primary shaping. Heat accumulates in convex workpiece sections, leading to increased temperatures compared to straight edges, possibly compromising the material. Existing analytical models assume constant thermal conditions and are therefore unable to calculate temperature fields of curved workpiece contours. Accordingly, a numerical simulation for straight contours was extended to convex geometry sections with different radii. The paper outlines this temperature simulation and presents results for various radii and fiber orientations when machining unidirectional CFRP. Temperature measurements during milling of unidirectional CFRP are used to calibrate the simulation.

Effect of thermal treatment on fracture behavior of solder joints at various strain rates: Comparison of cyclic and constant temperature

Fracture tests on Sn93Pb37 solder joints in a double cantilever beam (DCB) configuration were performed at two different strain rates of 10−5 and 0.03 s−1 under mode I loading conditions. In each case, the critical strain energy release rate for crack initiation, Jci, was obtained. Effects of storing specimens at a constant temperature of 75 °C and cyclic temperature varying between 32 and 75 °C were examined at these strain rates. In the strain rate of 0.03 s−1, storing samples in a constant or cyclic temperature caused the fracture energy to decrease significantly with respect to the specimens maintained in ambient temperature. The significant reduction in fracture energy by placing the samples at high temperatures in the intermediate strain rate was due to the considerable rise in IMC layer thickness. Also, in this strain rate, the decrease in fracture energy under the constant thermal condition was greater in comparison to the thermal cycling case. This behavior was attributed to microstructural differences in the solder layer of samples; in the specimens aged at a constant temperature of 75 °C, Cu6Sn5 and Cu3Sn phases were observed in the solder joint microstructure. No such phases formed in the samples experienced the thermal cyclic profile. In quasi-static loading conditions, however, the fracture energy in cyclic and constant thermal conditions was approximately equal with the fracture energy of the sample stored in ambient temperature. In both thermal conditions, fracture energy increased significantly by rising the strain rate from quasi-static (i.e. 10−5 s−1) to 0.03 s−1. Moreover, the influence of strain rate was greater in cyclic thermal condition compared to constant thermal condition.

Thermal tolerance and routine oxygen consumption of convict cichlid, Archocentrus nigrofasciatus, acclimated to constant temperatures (20°C and 30°C) and a daily temperature cycle (20°C → 30°C).

Organismal temperature tolerance and metabolic responses are correlated to recent thermal history, but responses to thermal variability are less frequently assessed. There is great interest in whether organisms that experience greater thermal variability can gain metabolic or tolerance advantages through phenotypic plasticity. We compared thermal tolerance and routine aerobic metabolism of Convict cichlid acclimated for 2weeks to constant 20°C, constant 30°C, or a daily cycle of 20 → 30°C (1.7°C/h). Acute routine mass-specific oxygen consumption ([Formula: see text]O2) and critical thermal maxima/minima (CTMax/CTMin) were compared between groups, with cycle-acclimated fish sampled from the daily minimum (20°C, 0900h) and maximum (30°C, 1600h). Cycle-acclimated fish demonstrated statistically similar CTMax at the daily minimum and maximum (39.0°C, 38.6°C) but distinct CTMin values, with CTMin 2.4°C higher for fish sampled from the daily 30°C maximum (14.8°C) compared to the daily 20°C minimum (12.4°C). Measured acutely at 30°C, [Formula: see text]O2 decreased with increasing acclimation temperature; 20°C acclimated fish had an 85% higher average [Formula: see text]O2 than 30°C acclimated fish. Similarly, acute [Formula: see text]O2 at 20°C was 139% higher in 20°C acclimated fish compared to 30°C acclimated fish. Chronic [Formula: see text]O2 was measured in separate fish continually across the 20 → 30°C daily cycle for all 3 acclimation groups. Chronic [Formula: see text]O2 responses were very similar between groups between average individual hourly values, as temperatures increased or decreased (1.7°C/h). Acute [Formula: see text]O2 and thermal tolerance responses highlight "classic" trends, but dynamic, chronic trials suggest acclimation history has little effect on the relative change in oxygen consumption during a thermal cycle. Our results strongly suggest that the minimum and maximum temperatures experienced more strongly influence fish physiology, rather than the thermal cycle itself. This research highlights the importance of collecting data in both cycling and static (constant) thermal conditions, and further research should seek to understand whether ectotherm metabolism does respond uniquely to fluctuating temperatures.

Enhancing Long‐Term Thermal Stability of Non‐Fullerene Organic Solar Cells Using Self‐Assembly Amphiphilic Dendritic Block Copolymer Interlayers

AbstractHerein, interfacial engineering is demonstrated to improve the thermal stability of non‐fullerene bulk‐heterojunction (BHJ) OPVs to a practical level. An amphiphilic dendritic block copolymer (DBC) is developed through a facile coupling method and employed as the surface modifier of ZnO electron‐transporting layer in inverted OPVs. Besides showing distinct self‐assembly behavior, the synthesized DBC possesses high compatibility with plasmonic gold nanoparticles (NPs) due to the constituent malonamide and ethylene oxide units. The hybrid DBC@AuNPs interlayer is shown to improve device's performance from 14.0% to 15.4% because it enables better energy‐level alignment and improves interfacial compatibility at the ZnO/BHJ interface. Moreover, the DBC@AuNPs interlayer not only improves the interfacial thermal stability at the ZnO/BHJ interface but also endows a more ideal BHJ morphology with an enhanced thermal robustness. The derived device reserves 77% of initial PCE after thermal aging at 65 °C for 3000 h and yields an extended T80 lifetime of >1100 h when stored at a constant thermal condition at 65 °C, outperforming the control device. Finally, the device is evaluated to possess a T80 lifetime of over 1.79 years at room temperature (298 K) when stored in an inert condition, showing great potential for commercialization.

Thermal variability during ectotherm egg incubation: A synthesis and framework.

Natural populations of ectothermic oviparous vertebrates typically experience thermal variability in their incubation environment. Yet an overwhelming number of laboratory studies incubate animals under constant thermal conditions that cannot capture natural thermal variability. Here, we systematically searched for studies that incubated eggs of ectothermic vertebrates, including both fishes and herpetofauna, under thermally variable regimes. We ultimately developed a compendium of 66 studies that used thermally variable conditions for egg incubation. In this review, we qualitatively discuss key findings from literature in the compendium, including the phenotypic effects resulting from different patterns of thermally variable incubation, as well as the ontogenetic persistence of these effects. We also describe a physiological framework for contextualizing some of these effects, based on thermal performance theory. Lastly, we highlight key gaps in our understanding of thermally variable incubation and offer suggestions for future studies.

THERMAL MONITORING AND CONTROL BY INFRARED CAMERA IN THE MANUFACTURE OF PARTS WITH LASER METAL DEPOSITION

Techniques included in Additive Manufacturing (FA), especially Laser Metal Deposition (LMD), are subject to variable conditions during the manufacturing process. To achieve the required homogeneity in the manufacture of 3D components layer by layer, these instabilities must be compensated by adapting the process parameters. In this work, it is proposed to use an infrared (IR) thermal camera to monitor the evolution and thermal distribution of the surface of the parts produced, throughout the LMD deposition process. On the one hand, the influence of the temperature of the component on the resulting thickness is demonstrated. On the other hand, a control system is developed and implemented based on the adaptation of waiting times in order to maintain constant thermal conditions of the surface at the time prior to the deposition of each bead. The proposed control system is validated through LMD experimentation, demonstrating an increase in geometric homogeneity and the optimization of the time required for manufacture. This study is part of a wider development on LMD monitoring and control systems and its final objective is to increase the production capacities of this technology. Keywords: Additive Manufacturing, Laser Metal Deposition, infrared camera, thermal monitoring, thermal control, interlayer wait time.

Modulation of the optical properties of transition metal doped PbSe quantum dots in silicate glasses

Optical properties of lead chalcogenide quantum dots (QDs) can be controlled by tuning its bandgaps. We prepared silicate glasses using the melt-quenching method and heat-treated 510 °C–540 °C for 10 h to precipitate transition metal ions into PbSe QDs. Transition metals oxide such as TiO, MnO & NiO were used in our experiment due to relative ease of incorporation of Ti2+, Mn2+, or Ni2+ ions in PbSe crystal structure lattice compared to rare-earth ions. Emission spectra of PbSe QDs were tuned in a wide wavelength range through changing concentration of transition metals oxide in glasses. For instance, photoluminescence bands of Pb1−xTixSe QDs QDs moved from 1890 nm to 1625 nm with increasing TiO from 0.0 to 0.5 mol% at heat treatment 530 °C for 10 h. Absorption bands of QDs also shifted to shorter wavelength sides as concentration of TiO or MnO increased under constant thermal treatment conditions mainly due to the change in the bandgap of QDs. However, absorption & PL peaks moved to longer wavelength sides (red-shifted) with increasing the duration of thermal annealing while keeping the amount of transition metal oxides constant mainly due to enlargement of the QDs sizes with thermal treatment. Tunable optical properties of QDs make them a promising candidate for various photoelectric devices, for example, fiber-optics amplifiers in optical communication and fiber lasers.

Development of a Data-Driven Predictive Model of Clothing Thermal Insulation Estimation by Using Advanced Computational Approaches

Clothing condition was selected as a key human-subject-relevant parameter which is dynamically changed depending on the user’s preferences and also on climate conditions. While the environmental components are relatively easier to measure using sensor devices, clothing value (clo) is almost impossible to visually estimate because it varies across building occupants even though they share constant thermal conditions in the same room. Therefore, in this study we developed a data-driven model to estimate the clothing insulation value as a function of skin and clothing surface temperatures. We adopted a series of environmental chamber tests with 20 participants. A portion of the collected data was used as a training dataset to establish a data-driven model based on the use of advanced computational algorithms. To consider a practical application, in this study we minimized the number of sensing points for data collection while adopting a wearable device for the user’s convenience. The study results revealed that the developed predictive model generated an accuracy of 88.04%, and the accuracy became higher in the prediction of a high clo value than in that of a low value. In addition, the accuracy was affected by the user’s body mass index. Therefore, this research confirms that it is possible to develop a data-driven predictive model of a user’s clo value based on the use of his/her physiological and ambient environmental information, and an additional study with a larger dataset via using chamber experiments with additional test participants is required for better performance in terms of prediction accuracy.