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Evaluating the spatial distribution and the Intensity of urban heat island using remote sensing, Case study of Isfahan city in Iran
摘要： In recent years, urbanization has widely been developed and resulted in great loss of natural resources on earth and many other consequences such as temperature rise which exposes the cities to a phenomenon called heat island. Urban Heat Island (UHI) can be identified and analyzed by thermal remote sensing. In the present study, satellite images of Landsat 7 ETM+ (1999 and 2006) and Landsat 8 (2013 and 2016) were used to retrieve the earth surface temperature of Isfahan, Iran by means of the mono-window algorithm. Analysis of thermal levels showed an increase in the minimum temperature of 2016 compared to 1999. Furthermore, the results revealed that the heat island ratio (URI) in Isfahan in four different years followed a rising trend, moving from 0.16 in 1999 to 0.3 in 2016. The findings of this study indicated that the areas influenced by UHI are often in northern and southern parts of the city where vegetation cover is very sparse, the land is arid, and industrialization and regional settlements are booming.
关键词： Mono-window algorithm,Isfahan,Land surface temperature,Urban heat island,Remote sensing
更新于2025-09-10 09:29:36
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[IEEE 2017 International Renewable and Sustainable Energy Conference (IRSEC) - Tangier (2017.12.4-2017.12.7)] 2017 International Renewable and Sustainable Energy Conference (IRSEC) - Modeling the Solar Station with the Parabolic Trough Collector Receiver
摘要： In this paper, we present a detailed mathematic model of the Parabolic Trough Collector (PTC) receiver, which has been theoretically studied. The PTC receiver contains a circular tube absorber with a suitable selective layer, surrounded by a glass cover locate along the focal line of PTC receiver. We have established a mathematical model to control the fluid temperature as well as the absorber and the glass cover temperatures.
关键词： heat transfer fluid,solar energy,solar flux,outlet temperatures,Parabolic Trough Collector Receiver
更新于2025-09-10 09:29:36
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Heat-Treatment Induced Magnetic Anisotropy of GaMnSb Films
摘要： Conditions and mechanisms of controlled variation of the magnetic anisotropy of GaMnSb films containing magnetic MnSb nanoinclusions by means of heat treatment have been determined. For this purpose, the temperature and magnetic-field dependences of the magnetic moments of samples before and after thermal annealing were measured using a SQUID magnetometer. It is established that the heat treatment of GaMnSb films leads to a significant increase in the values of characteristics determined by the magnetic anisotropy, including the growth of blocking temperature (from 95 to 390 K) and the magnetic anisotropy field (from 330 to 630 Oe). Results of transmission electron microscopy investigation indicate that a change in the magnetic anisotropy of GaMnSb films as a result of their thermal annealing can be related to a transition of the crystalline structure of magnetic MnSb nanoinclusions from hexagonal (space group P62/mmc) to cubic (space group F-43m).
关键词： magnetic anisotropy,GaMnSb films,SQUID magnetometer,transmission electron microscopy,MnSb nanoinclusions,heat treatment
更新于2025-09-10 09:29:36
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Anharmonic stabilization and lattice heat transport in rocksalt <i>β</i> -GeTe
摘要： Peierls-Boltzmann transport equation, coupled with third-order anharmonic lattice dynamics calculations, has been widely used to model lattice thermal conductivity (jl) in bulk crystals. However, its application to materials with structural phase transition at relatively high temperature is fundamentally challenged by the presence of lattice instabilities (imaginary phonon modes). Additionally, its accuracy suffers from the absence of higher-than-third-order phonon scattering processes, which are important near/above the Debye temperature. In this letter, we present an effective scheme that combines temperature-induced anharmonic phonon renormalization and four-phonon scattering to resolve these two theoretical challenges. We apply this scheme to investigate the lattice dynamics and thermal transport properties of GeTe, which undergoes a second-order ferroelectric phase transition from rhombohedral a-GeTe to rocksalt b-GeTe at about 700 K. Our results on the high-temperature phase b-GeTe at 800 K con?rm the stabilization of b-GeTe by temperature effects. We ?nd that considering only three-phonon scattering leads to signi?cantly overestimated jl of 3.8 W/mK at 800 K, whereas including four-phonon scattering reduces jl to 1.7 W/mK, a value comparable with experiments. To explore the possibility to further suppress jl, we show that alloying b-GeTe with heavy cations such as Pb and Bi can effectively reduce jl to about 1.0 W/mK, whereas particle size needs to be around 10 nm through nanostructuring to achieve a comparable reduction in jl.
关键词： rocksalt β-GeTe,lattice heat transport,thermal conductivity,phonon scattering,anharmonic stabilization
更新于2025-09-10 09:29:36
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Charge and thermal modeling of a semiconductor-based optical refrigerator
摘要： Despite multiple attempts to achieve optical refrigeration in very high (99.5%) external quantum efficiency (EQE) GaAs, no cooling has been observed to date. In this study, we investigate optical refrigeration in GaAs by numerically solving the transient drift-diffusion equation coupled to Poisson’s equation. The charge carrier distributions we obtain, together with the heat diffusion equation, allow us to observe the spatial and temporal evolution of cooling/heating within GaAs. Our results indicate that maximum cooling occurs at a laser intensity different from that which maximizes EQE. An 11-fold difference in intensity exists with a corresponding 6-fold difference in cooling power. We ultimately find that samples suspended in vacuum using a 250 lm SiO2 fiber cool to 88 K, starting from room temperature. These results emphasize the critical importance of choosing an appropriate laser excitation intensity to achieve optical refrigeration along with minimizing the conductive heat load on the refrigerator. Furthermore, results of this study are applicable towards analyzing the optical response of other optoelectronic systems where accurate charge and/or heat diffusion modeling is critical.
关键词： drift-diffusion equation,external quantum efficiency,Poisson’s equation,cooling power,optical refrigeration,heat diffusion equation,GaAs
更新于2025-09-10 09:29:36
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[ASME ASME 2018 International Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Microsystems - San Francisco, California, USA (Monday 27 August 2018)] ASME 2018 International Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Microsystems - Heat Transfer Characteristics and Flow Pattern Visualization for Flow Boiling in a Vertical Narrow Microchannel
摘要： For improving the functionality and signal speed of electronic devices, components have been miniaturized and an increasing number of elements have been packaged in the device. As a result there has been a steady rise in the amount of heat necessitated to be dissipated from the electronic device. Recently microchannel heat sinks have been emerged as a kind of high performance cooling scheme to meet the heat dissipation requirement of electronics packaging, In the present study an experimental study of subcooled flow boiling in a high-aspect-ratio, one-sided heating rectangular microchannel with gap depth of 0.52 mm and width of 5 mm was conducted with deionized water as the working fluid. In the experimental operations, the mass flux was varied from 200 to 400 kg/m2s and imposed heat flux from 3 to 20 W/cm2 while the fluid inlet temperature was regulated constantly at 90 ℃. The boiling curves, flow pattern and onset of nucleate boiling of subcooled flow boiling were investigated through instrumental measurements and a high speed camera. It was found that the slope of the boiling curves increased sharply once the superheat needed to initiate the onset of nucleate boiling was attained, and the slope was greater for lower mass fluxes, with lower superheat required for boiling incipience. As for the visualization images, for relatively lower mass fluxes the bubbles generated were larger and not easy to depart from the vertical upward placed narrow microchannel wall, giving elongated bubbly flow and reverse backflow. The thin film evaporation mechanism dominated the entire test section due to the elongated bubbles and transient local dryout as well as rewetting occurred. Meanwhile the initiative superheat and heat flux of onset of nucleate boiling were compared with existing correlations in the literature with good agreement.
关键词： microchannel heat sinks,heat transfer,subcooled flow boiling,electronic cooling,flow pattern visualization
更新于2025-09-09 09:28:46
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Numerical investigation and experimental validation of an infrared measurement approach for surface heat flux distribution using a multi-color-reference
摘要： Accurate measurement of heat flux (HF) is significant in both industrial engineering and scientific research. It is acknowledged that the radiative HF can be easily determined by radiometers. In order to measure the conductive or convective HF distribution flowing across a surface, this paper presents a novel non-contact measuring method based on the infrared (IR) technique and inverse heat transfer method (IHTM). In addition, a specially designed multi-color-reference (MCR) which is composed of four sectors with four different known emissivity will be attached to the focused surface in the practical measurement. Therefore, different radiation signals among the four different sectors of MCR as well as the focused surface will be detected by an IR camera, through which a whole radiation temperature map can be obtained. Based on the differences in the radiation temperatures of the surface and MCR, the IHTM can be adopted to yield useful boundary conditions such as emissivity of the surface, convective heat transfer coefficient, and the critical HF distribution. The measuring method presented in this study combines the advantages of contact and non-contact measurement, which can accurately obtain the HF distribution under the difficult-contacted conditions such as the HF monitoring of a boiling furnace, HF estimating of the aerodynamic heating surface, etc. Numerical simulation and experimental verification were organized to justify the newly-developed measuring method. Relative error in the simulation is estimated to be less than 2%, and that in the experiment is calculated to be around 4.23%. The result displays a relatively high precision of the measuring method, demonstrating that such a method can be applied in practical application.
关键词： Infrared technique,Heat flux measurement,Emissivity,Heat transfer,IHTM
更新于2025-09-09 09:28:46
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Thermal performance of vortex-based solar particle receivers for sensible heating
摘要： We report a first-order assessment of a novel vortex-based solar particle receiver and the sensitivity of its thermal performance to a number of key operational parameters. This assessment is made with a one-dimensional numerical model developed here to adapt the zonal method to calculate heat and mass transport within the enclosure of the solar vortex receiver (SVR) and to incorporate radiative and convective heat transfer between the particle phase, the air phase and the receiver wall together with re-radiative and conductive loss from the receiver. This simplified one-dimensional model allows for the systematic assessment of first order trends of mass and energy balance within the SVR and is used here to advance understanding of the dominant mechanisms controlling its thermal performance. Sensitivity studies of the thermal performance of the SVR reveal that the receiver can be configured to operate as either an air-heater or a particle-heater, depending primarily on the particle mass loading. For the present SVR configuration, the critical value of mass loading, / ≈ 1 was found to define the boundary, above which the device acts as a particle heater, and below which it acts as an air heater. Furthermore, an assessment of the two-phase flow direction found that a counter-flow (relative to the incident concentrated solar radiation) tends to result in a higher efficiency than a co-flow direction. The first order trends of the sensitivity of thermal performance of the SVR to the particle and air mass flow rates, particle size and receiver length were also assessed, finding that the ratio of receiver thermal input to heat capacity of the two-phase flow has a controlling influence on the thermal efficiency of the SVR, particularly with the front entry configuration. Overall receiver thermal efficiencies of up to 88% were predicted for the SVR operating with high mass flow rates of both particles and air, but it is expected that the thermal efficiency of the device for all operating conditions assessed here would increase with an increase in receiver scale from the laboratory-scale device considered here.
关键词： Solar particle receiver,Heat transfer,CST,Solar vortex receiver,Concentrated solar thermal
更新于2025-09-09 09:28:46
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Identification of Heat-Induced Proteomes in Tomato Microspores Using LCM- Proteomics Analysis
摘要： Pollen development is highly susceptible to heat stress (HS) and the production of inviable pollen causes reduction in seed- and fruit-set in plants. This study was carried out to identify HS-induced pollen proteins and the associated biological processes in tomato (Solanum lycopersicum). Tomato ‘Micro-Tom’ plants were incubated under 32°C//22°C (day/night, 12/12 h) for two weeks for heat treatment, and the non-treated control plants were incubated for the same time period at 25°C /22°C. Flower buds of 5 mm in length were confirmed to contain the heat sensitive uninucleate microspores. Pollen cells were harvested using laser capture microdissection (LCM) and protein was extracted using a one-step method under high pressure and vacuum. Approximately 60,000 LCM-harvested microspore cells yielded about 18-20 μg proteins. The tandem mass tags (TMT) proteomics analysis identified a total of 6018 proteins, 4784 proteins were quantified, 37 proteins were identified as HS up-regulated significantly changed proteins (SCPs), and 83 proteins as HS down (dn)-regulated SCPs. Further analysis using the plant MetGenMap system showed that the HS up-regulated SCPs were enriched in the heat acclimation, pollen wall formation, protein folding/refolding gene ontology (GO) biological processes, and the HS dn-regulated SCPs were placed in the carbohydrate catabolism and de-novo protein biosynthesis GO terms. Biological processes such as mitosis, resistance to oxidative stresses, and carbohydrate and lipid metabolic processes contain both the HS up-, and dn-regulated SCPs. These results indicate that the LCM-TMT proteomics workflow is highly efficient in the identification of HS-induced pollen proteomes. These HS induced SCPs will be used for exploring heat tolerance of tomato pollens. The proteomics data are available via ProteomeXchange with identifier PXD010218.
关键词： Tomato,Protein functional classification,Heat stress,LCM-TMT-proteomics,Pollen,Viability,Microspores
更新于2025-09-09 09:28:46
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Transparent AgNW-CoNPs conducting film for heat sensor
摘要： We have fabricated transparent conducting film (TCF) from silver nanowires (AgNWs) decorated with cobalt nanoparticles (CoNPs) on a thermoplastic polyimide (PI) substrate by solution processed spin-coating approach. AgNWs and CoNPs were produced by modified polyol methods using poly(N-vinylpyrrolidone) PVP (Mw ≈ 1,300,000). The concentration ratio of AgNWs to CoNPs was varied as 1:0, 0.7:0.3, 0.5:0.5, and 0.3:0.7 (in wt%). The results show that increasing the AgNWs/CoNPs concentration up to 0.5: 0.5 raises the TCF temperature interestingly to 350oC before the Joule heating breakdown occurs at 20 V. However, at a higher content of CoNPs (AgNWs: CoNPs = 0.3:0.7), due to the excessive entanglement of CoNPs in the AgNW network, the temperature further drops down to 65oC. The optimum transmittance (94%), sheet resistance (52 Ω/□), and thermal stability were obtained at a concentration ratio of AgNWs: CoNPs = 0.5:0.3. The stabilization mechanism is also suggested for the extremely high temperature obtained in this work.
关键词： hybrid nanowires,optical transmittance,heat sensing devices,transparent film conductor,cobalt nanoparticles
更新于2025-09-09 09:28:46