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This paper is devoted to a new gauge of small dynamic bending deformations of structures. Unlike previously existing strain gauges that measure elongation or compression at a certain point on the surface of a deformable body, the proposed gauge measures the change in curvature at a point on the surface of a deformable body and does not respond to elongation–compression strains. The gauge is a layered bar made of piezoelectric and elastic materials. It functions using the direct piezoelectric effect. In order to competently study the deformed state of a structure at points on a surface, it is necessary to determine all components of the strain tensor. The gauges currently used measure only elongational or compressive strains, which does not provide a complete picture of the strain state. It is very important to complement these deformations with bending strains measured by the new gauge.

Several studies have suggested the existence of a positive relationship between the Normalized Difference Vegetation Index (NDVI) derived from AVHRR/NOAA satellite data and either biomass or annual aboveground net primary production (ANPP) for different geographic areas and ecosystems. We calibrated a 4-yr average of the ingegral of the NDVI (NDVI-I) using spatially aggregated values of ANPP. We also provided an estimate of the energy conversion efficiency coefficient (ε) of Monteith's equation. This is the first attempt to calibrate a standard NDVI product for temperate perennial grasslands. We found a positive and statistically significant relationship between NDVI-I and ANPP for grassland areas with mean annual precipitation between 280 and 1150 mm, and mean annual temperature between 4⚬ and 20⚬ C. Depending on the method used to estimate the fraction of photosynthetic active radiation, the energy conversion officency coefficient was constant (0.24 g C/MJ), or varied across the precipitation gradient, from 0.10 g C/MJ for the least productive to 0.20 g C/MJ for the most productive sites.

Solar energy has become an important renewable energy source for reducing the use of fossil fuels and to mitigate global warming, for which solar collectors constitute a technology that is to be promoted. The use of nanofluids can increase the efficiency of solar into thermal energy conversion in solar collectors. Experimental values for the specific heat, thermal conductivity and viscosity of alumina/water nanofluids are needed to evaluate the influence of the solid content (from 0.25 to 5 v%) and the flow rate on the Reynolds, Nusselt and the heat transfer coefficient. In the laminar flow regime, thermal conductivity enhancement over specific heat decrement is key parameter, and a 2.34% increase in the heat transfer coefficient is theoretically obtained for 1 v% alumina nanofluid. To corroborate the results, experimental tests were run in a flat plate solar collector. A reduction in efficiency from 47% to 41.5% and a decrease in the heat removal factor were obtained using the nanofluid due to the formation of a nanoparticle deposition layer adding an addition thermal resistance to heat transfer. Nanofluids are recommended only if the nanoparticle concentration is high enough to enhance thermal conductivity, but no so high so as to avoid wall deposition.

Developing novel low-reflection structures, such as Oscillating Water Column (OWC) wave absorbers, provides a promising solution for enhancing harbor berthing safety. OWCs present the dual advantage of reducing wave reflections while simultaneously capturing wave energy. This study experimentally investigates the reflection characteristics, efficiency of wave energy extraction, and power dissipation behavior of OWC absorbers with different rear wall configurations. Furthermore, it investigates variations in rear wall geometry, incident wave height, and the well turbine located inside the air chamber, which converts wave power into pneumatic power. Controlled wave flume experiments at the University of Port Said were conducted on four models. Key performance parameters analyzed include the dissipation coefficient (C d ), energy coefficient (C e ), transmission coefficient (C t ), reflection coefficient (C r ), and pressure coefficient (C p ). The effects of different draughts, water depths, and air pressure fluctuations inside the pneumatic chambers were also examined. Results indicate that rear wall geometry significantly affects reflection and dissipation rates. Model-D achieved optimal performance at a water depth of 0.30 m with a front wall draught (d 1 ) of 0.10 m, exhibiting low reflection (C r  = 0.139), high energy dissipation (C d  = 0.9), and a high wave energy conversion (C e  = 0.75; C p  = 0.85), making Model-D suitable for floating barriers in deep-water environments. Its superior wave energy dissipation enables effective operation under larger drafts and higher sea states.

Context This research paper investigates the properties and potential applications of antiperovskite materials. Antiperovskites are a class of materials with a unique crystal structure, where the central atom is surrounded by a cage of anions. We review recent research on antiperovskite-based materials for energy storage, photovoltaics, catalysis, and sensors. We discovered that these materials display direct band gap semiconductors, strong absorption in the visible (VIS), ultra-violet (UV), and near infrared regions (NIR) based on their fundamental features, which is the most admirable quality that may be found in many optoelectronic devices. Both mechanical and thermodynamic stability have been confirmed for these materials. We discovered that these materials exhibit high figures of merit through the calculation of transport properties, which makes them a promising candidate for thermoelectric devices. It is anticipated that the proposed material BiPMg 3 , which has a theoretical efficiency of 11.5%, will make a suitable photovoltaic absorber. This paper highlights the potential of these materials for future technological advancements. Methods Herein, we have used most authentic techniques to compute fundamental physical properties of these antiperovskites. Full-potential linear augmented plane wave (FP-LAPW) method has been used to investigate electronic, magnetic, optical properties, and make antiperovskites attractive for a variety of applications. In light of its implementation, we have checked the theoretical power conversion efficiency by first principles spectroscopic screening methodology, and inspect the fundamental physical parameters of antiperovskites, focusing on their potential as functional materials for energy and information technologies.

Cu 3 SbSe 4 -based materials are ternary chalcogenides thermoelectric compounds with unique sphalerite super-lattice structures and adjustable characteristics which stand them out as promising material for attaining efficient thermal and electrical energy conversion. The crystal structure of Cu 3 SbSe 4 -based materials consists of Cu-Se three dimensional frameworks with inserted CuSe 4 tetrahedra layer. This energy band structure and crystal arrangement in Cu 3 SbSe 4 -based materials lead to large seebeck coefficient, low thermal conductivity and large carrier mobility with restricted number of available carriers which hinders the potential of these materials as thermoelectric compound due to low value of thermoelectric performance. Experimental methods of thermoelectric performance (using figure of merit as a measure of energy conversion efficiency) enhancement are laborious, costly and consume appreciable resources which necessitate the need of computational methods for figure of merit prediction. In this contribution, figure of merit of Cu 3 SbSe 4 -based materials has been modeled through random forest regression (decision trees) and genetic algorithm incorporated support vector regression (structural risk error minimization-based) model using temperature, dopants ionic radii and their respective concentrations as predictors. Genetically optimized support vector regression (GESVR) model outperforms random forest regression (RFR)-based model with improvement of 188.04%, 30.18% and 42.36% using correlation coefficient, mean absolute error and root mean square error, respectively for testing samples of Cu 3 SbSe 4 -based compounds. Influence of inclusions on energy conversion efficiency of Cu 3 Sb 1-x Sn x Se 4 and Cu 3 Sb 1-x Fe x Se 2.8 S 1.2 compounds was investigated using GESVR- based model. The simplicity of descriptors coupled with the demonstrated precision would facilitate the exploration of Cu 3 SbSe 4 -based materials for green applications and ultimately address the current global energy crisis.

The thermoelectric performance of Mg 3 Sb 2 was systematically enhanced through doping with chromium (Cr) and iron (Fe), offering new insights into advanced materials for energy conversion applications. Using first-principles calculations within the CASTEP framework and Boltzmann transport theory in BoltzTraP, the study evaluated the electronic structure and thermoelectric properties of doped Mg 3 Sb 2 . Cr doping led to a significant increase in the Seebeck coefficient, reaching 739 µV/K, and an electronic ZT (eZT) value of 0.82—demonstrating a 40% improvement in thermoelectric efficiency compared to undoped Mg 3 Sb 2 . Fe doping further reduced the bandgap to 0.086 eV, optimizing carrier transport and achieving a Seebeck coefficient of 730 µV/K and a maximum electronic ZT (eZT) of 0.966—a 55% enhancement over the pristine material and 18% higher than Cr-doped variants. These findings represent a significant advancement over previously reported thermoelectric materials, showcasing the potential of Cr and Fe doping to strategically tailor electronic structures and minimize electronic thermal conductivity. With superior eZT values, Fe-doped Mg 3 Sb 2 emerges as a promising candidate for next-generation thermoelectric applications, including waste heat recovery, renewable energy systems, and sustainable power generation technologies. This study underscores the critical role of transition metal doping in driving the design of high-performance thermoelectric materials, offering transformative prospects for energy efficiency and sustainability.

We introduce a general framework for analyzing the thermodynamics of small systems that are driven by both a periodic temperature variation and some external parameter modulating their energy. This setup covers, in particular, periodic micro- and nano-heat engines. In a first step, we show how to express total entropy production by properly identified time-independent affinities and currents without making a linear response assumption. In linear response, kinetic coefficients akin to Onsager coefficients can be identified. Specializing to a Fokker-Planck-type dynamics, we show that these coefficients can be expressed as a sum of an adiabatic contribution and one reminiscent of a Green-Kubo expression that contains deviations from adiabaticity. Furthermore, we show that the generalized kinetic coefficients fulfill an Onsager-Casimir-type symmetry tracing back to microscopic reversibility. This symmetry allows for nonidentical off-diagonal coefficients if the driving protocols are not symmetric under time reversal. We then derive a novel constraint on the kinetic coefficients that is sharper than the second law and provides an efficiency-dependent bound on power. As one consequence, we can prove that the power vanishes at least linearly when approaching Carnot efficiency. We illustrate our general framework by explicitly working out the paradigmatic case of a Brownian heat engine realized by a colloidal particle in a time-dependent harmonic trap subject to a periodic temperature profile. This case study reveals inter alia that our new general bound on power is asymptotically tight.

For the process of photovoltaic conversion in organic solar cells (OSCs) and quantum‐dot solar cells (QDSCs), three of four steps are determined by exciton behavior, namely, exciton generation, exciton diffusion, and exciton dissociation. Therefore, it is of great importance to regulate exciton behavior in OSCs and QDSCs for achieving high power conversion efficiency. Due to the rapid development in materials and device fabrication, great progress has been made to manage the exciton behavior to achieve prolonged exciton diffusion length and improved exciton dissociation in recent years. In this review, we first introduce the parameters that affect exciton behavior, followed by the methods to measure exciton diffusion length. Then, we provide an overview of the recent advances with regard to exciton behavior investigation in OSCs and QDSCs, including exciton lifetime, exciton diffusion coefficient, and exciton dissociation. Finally, we propose future directions in deepening the understanding of exciton behavior and boosting the performance of OSCs and QDSCs. Exciton behavior plays a crucial role in the photovoltaic conversion process of organic solar cells (OSCs) and quantum‐dot solar cells (QDSCs). Great progress has been made to regulate the exciton behavior in recent years. Herein, we summarize the advancement in exciton behavior studies of OSCs and QDSCs from the exciton diffusion coefficient, exciton lifetime, and exciton dissociation.

At present, the advancement of thermoelectric technology remains largely focused on developing high-performance thermoelectric materials, while comparatively little attention is directed towards its fundamental principles. To address this gap, this study introduces a new physical quantity, the “thermoelectric diffusion potential”, which clarifies the physical interpretations of various thermoelectric coefficients. Analyses reveal that, within a thermoelectric element, the Seebeck coefficient represents a balance between the thermoelectric diffusion field and electrostatic field, rather than between temperature and voltage differences. Using the thermoelectric diffusion potential, the relationship between the Seebeck and Peltier coefficients can be derived directly. Building on this framework, two additional physical quantities, namely the “thermoelectric energy” and “thermoelectric energy flow”, associated with the thermoelectric diffusion potential, are introduced. The formulation of thermoelectric energy flow helps derive the energy conversion relationship at the interface on a macroscopic level. Specifically, energy conversion at the interface occurs between thermoelectric and thermal energy flows, while within the element, it takes place between thermoelectric and electrical energy flows. Owing to the dual nature of internal energy in thermoelectric materials, manifesting as both thermal and electrical energy, the conversion within the element can also be regarded as one between thermal and electrical energy flows. The proposed quantities constitute an important complementary interpretation for the existing thermoelectric framework.