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Photocatalysis utilizes light as the initial driving force for chemical reactions, enabling reactions with high energy barriers in traditionally thermal chemistry to proceed under mild conditions. 1,3‐Dicarbonyl compounds occur as important active molecules in nature and are intermediates in pharmaceutical syntheses. In recent years, there have been numerous studies of these compounds, and it is common practice to pre‐modify them before the reaction, which is, however, unfavorable for the atom economy of the process. This paper provides a comprehensive review of the latest advancements in the site‐specific activation of unmodified 1,3‐dicarbonyl compounds by photoinduction. The focus is on elucidating the mechanisms of these reactions to provide insights and directions for future research in designing novel reactions. [ABSTRACT FROM AUTHOR]

Aquatic systems are warming and exceeding upper thermal limits (UTLs) for many fish species, yet understanding how they inform resilience to climate change is challenging. Using Pacific salmon (Oncorhynchus spp.) as a model, we conducted a systematic review involving 168 papers investigating UTL in five species. We found considerable variation in UTL among species, within species and across life stages; largely attributed to methodological approaches (e.g. CTmax/UILT, Aerobic/Cardiac Scope, Thermal Migration Barriers, Rearing Mortality, Thermal Preference/Avoidance). Given that each method has strengths and weaknesses owing to logistics, time scale and ecological realism, we offer a new framework for assessing vulnerability to warming that stresses the importance of considering UTL metrics in the context of intended use (i.e. the development of management guidelines, projections of future persistence and survival) and what aspect (physiological or behavioural) of thermal response a metric investigates. Comparing studies with identical UTL approaches revealed that within species, UTL was higher for populations historically encountering higher temperatures—suggesting local thermal adaptation. Within populations, UTL differed across the lifecycle, being highest in fry and lowest in embryo and migrating adults, but this was not universal. For spawning Pacific salmon, UTL has not been assessed and few studies have examined estuarine and marine stages. Ultimately, this data gap limits the life‐history thermal perspectives that can be drawn and may indicate a broader gap for all fishes, given that Pacific salmon are among the most well‐studied species. Our framework illustrates the inherent and methodological inconsistencies in UTL and offers a guide for how thermal limits can best be used to assess the warming tolerance and vulnerability of fishes. [ABSTRACT FROM AUTHOR]

As a typical organic phase change material, paraffin occupies the large phase‐transition latent heat, promising electronic insulation, excellent cycling and chemical stability as well as the low corrosivity, which is attractive in the thermal management. In the practical applications, the surface of paraffin should be protected by organic or inorganic layers to inhibit the leakage above the melting point. However, in the reported paraffin composites, the weak cycling stability and the low thermal conductivity restricts their applications. In this paper, the highly thermal conductive hexagonal boron nitride nanosheets (hBNNS) are used as the protective layer for wrapping the paraffin in a microemulsion method to form the hBN‐paraffin thermal management composite, which exhibits the large phase‐transition latent heat ~189 J g−1, the excellent cycling stability over 20 cycles and the high thermal conductivity ~1.2 W m−1 K−1. The developed paraffin@ hBN composite should be promising for the thermal management in electronic packing, and can be used to improve the reliability of electric devices. [ABSTRACT FROM AUTHOR]

India has abundant solar power assets. Many districts get better than expected insulation compared with different parts of the world. The essential innovation for incorporating and changing sun‐based energy into electrical energy in India depends on photovoltaic (PV) cells. Concentrated solar power (CSP) plants have barely added to the nation's general introduced solar‐based force limit. The difficulties that have restrained the development of CSP and CST are part of the discussion and potential arrangements recommended. The primary difficulties for CSP and CST are identified as the absence of a dependable direct normal irradiance database, indigenous assembling, and rivalry from PV. The after‐effects of a contextual analysis evaluated the effect of indigenous assembling and economies of scale on capital expenses and levelized cost of power. We will evaluate the current status of CSP plants in this paper. The paper shows different incorporated technologies in solar thermal application in India with indigenous manufacturing and the energy policy supporting the solar thermal analyzing the barriers to implementation of Jawaharlal Nehru National Solar Mission. Also, the techno‐economic evaluation of the CSP and CST is covered. This paper provides a framework of CSP and CST technology in India's industrial sector with their impact on goods and services provided by the sector and the cost‐effectiveness of the product and technology. Furthermore, the environmental aspects and base electrical load accumulating are researched, and various policy measures and amendments are suggested to the government from this study‐based study. [ABSTRACT FROM AUTHOR]

The residual stress introduced inside a thermal barrier coating (TBC) during manufacturing and service processes is one of the main causes of thermal barrier failure. The formation and evolution of internal stress in the TBC begin at the early stage of service, but studies on the mechanism of the distribution and evolution of the stress in the TBC during the initial thermal cycle are still lacking. To explore the evolution mechanism of the stress in the TBC interior, an experimental study on the regulation mechanism of the initial thermal cycle on the TBC internal stress was carried out in this paper. First, the internal stress of TBC specimens after thermal cycles was characterized based on photoluminescence spectroscopy (PL) and terahertz time‐domain spectroscopy (THz‐TDS) technologies, in which the homogenization of the near‐interface stress field was observed during the initial thermal cycle. Then, the evolution of the microstructure and phase structure of the TBC specimens was characterized. Finally, the phenomenological model of the evolution of the TBC internal structure was established, revealing that the initial thermal cycle regulated the microstructure of the top coating (TC) through phase transformation to realize the homogenization of the near‐interface stress field. [ABSTRACT FROM AUTHOR]

In this paper, we study the effects of rotational modulation on heat and mass transport due to double‐diffusive magnetoconvection in an electrically conducting fluid. In the study, different modes of rotational modulation are considered. Using a perturbation method, a Ginzburg–Landau equation which is nonautonomous is obtained for the modulation amplitude. The effect of rotational modulation on the heat and mass transfer is studied. For the investigation of the effect of buoyancy ratio on the onset of convection, the system of Lorenz type equations is solved using the recent multistage spectral relaxation method. Furthermore, the influence of other fluid parameters on thermal convection and heat and mass transport is analyzed and presented graphically. We find among other results that the effect of increasing the Taylor number is to reduce the Nusselt and Sherwood numbers. A comparison between the sinusoidal and non‐sinusoidal modes of rotational modulation on their influence on heat and mass transport in a magneto‐diffusive fluid layer is made. We show that the square wave rotational modulation is the most destabilizing type of modulation in the sense that it leads to the early onset of thermal instabilities while the triangular modulation is the most stabilizing type of modulation. The effect of the buoyancy ratio on the nature of the flow pattern has been determined using streamlines, isotherms, and isoconcentrations. [ABSTRACT FROM AUTHOR]

Effective heat capacity is a key index to estimate the performance of the thermal protection system of reentry vehicles subjected to aerodynamic heating. To explore the effect of gradient density on the effective heat capacity in this paper, considering variable density we develop the one-dimensional pyrolysis interface model with surface ablation, and design two kinds of the gradient density of AVCOAT composites. The computer codes are written to simulate the thermal behavior of a homogeneous AVCOAT composites and that of two types of gradient AVCOAT composites under aerodynamic heat flux during Apollo capsule reentry. Numerical results indicate that gradient density can improve the thermal protection performance of homogeneous AVCOAT composites, e.g. the piecewise linear and the parabola designs have larger effective heat capacity than homogeneous AVCOAT composites, which owe to exceptional thermal response of gradient density. This study will be helpful for the design of the thermal protection system in re-entry vehicles. [ABSTRACT FROM AUTHOR]

Search for new thermal barrier materials with high-temperature stability is very difficult because there are intractable choices among thousands of possible candidates. The present paper shows that identifying and developing new low thermal conductivity materials can be accomplished by first-principles calculations of equilibrium crystal structure and elasticity, and thereafter making theoretical prediction of minimum high-temperature lattice thermal conductivity basing on David Clarke's method for insulating materials. We highlight a new oxynitride ceramic, Y4 Si2 O7 N2, with a low theoretical minimum thermal conductivity of 1.12 W·m−1·K−1. The theoretical result is further validated by experimental measurement of thermal conductivity of dense and bulk Y4 Si2 O7 N2. The experimental thermal conductivity is 1.50 W·m−1·K−1 at 1300 K. Furthermore, thermal properties of Y4 Si2 O7 N2 are investigated for evaluating its potential performances. [ABSTRACT FROM AUTHOR]

Thermal barrier coatings (TBCs) are increasingly susceptible to degradation by molten calcium–magnesium alumino silicate (CMAS) deposits in advanced engines that operate at higher temperatures and in environments laden with siliceous debris. This paper investigates the thermochemical aspects of the degradation phenomena using a model CMAS composition and ZrO2–7.6%YO1.5 (7YSZ) grown by vapor deposition on alumina substrates. The changes in microstructure and chemistry are characterized after isothermal treatments of 4 h at 1200°–1400°C. It is found that CMAS rapidly penetrates the open structure of the coating as soon as melting occurs, whereupon the original 7YSZ dissolves in the CMAS and reprecipitates with a different morphology and composition that depends on the local melt chemistry. The attack is minimal in the bulk of the coating but severe near the surface and the interface with the substrate, which is also partially dissolved by the melt. The phase evolution is discussed in terms of available thermodynamic information. [ABSTRACT FROM AUTHOR]

Mechanical behavior of free-standing, plasma-sprayed ZrO2-8wt% Y2O3 thermal barrier coatings, including strength, fracture toughness, fatigue, constitutive relation, elastic modulus, and directionality, have been determined under various loading-specimen configurations. This paper presents and describes a summary of mechanical properties of the plasma-sprayed coating material to provide them as a design database. [ABSTRACT FROM AUTHOR]

The microwave drill is a novel process for creating shaped holes in nonconductive materials. Its inherent material selectivity makes the microwave drill ideally suited for the controllied removal of ceramic coatings from underlying metallic substrates. In this paper, it is shown that the microwave drill process can drill through ceramic thermal barrier coatings (TBCs) to uncover an array of simulated cooling holes. The concept, apparatus, and procedure for successful drilling are described, and the potential for use in the production of advanced gas turbine components is discussed. [ABSTRACT FROM AUTHOR]