Search Results (5,949)

This article reviews the reactive magnetron sputtering of piezoelectric Aluminium Nitride (AlN) thin films, with a focus on process parameter optimisation and system-level deposition challenges. AlN is a leading material for MEMS and RF applications owing to its c-axis (002) orientation, high acoustic velocity, wide bandgap (∼6.2 eV), and CMOS compatibility. We review the influence of sputtering power, nitrogen flow ratio, substrate temperature, and target-to-substrate distance on crystallographic quality and document practical hardware challenges, including vacuum leakage, grounding faults, target erosion, and mass flow controller drift, that critically affect reproducibility but are systematically underreported in the literature. A perspective is provided on emerging application domains where optimised AlN films address current performance gaps, including next-generation RF/telecom systems towards 6G and Future Networks, harsh environment sensing and actuation, biomedical ultrasound, and IoT energy harvesting. The complementarity between AlN and Silicon Carbide (SiC) is discussed for high-temperature, high-power, and radiation-hard MEMS, where AlN/SiC heterostructures combine the piezoelectric activity of AlN with the mechanical and chemical robustness of SiC. It also incorporates a discussion of dopant- and heteroepitaxy-based AlN engineering, AlN deposition on a wider range of substrates, the role of seed and electrode underlayers, and pulsed-DC sputtering as a third power supply mode alongside RF and conventional DC. Full article

In high-density cities, limited roof and ground areas constrain conventional photovoltaic (PV) deployment. Vertical bifacial photovoltaic (bPV) modules offer an alternative by making good use of building and infrastructure surfaces while harvesting irradiance on both sides. This study develops an integrated module-level framework for evaluating tilted and vertical bPV modules. It couples two-sided anisotropic irradiance calculations with five-parameter electrical and steady-state thermal models. Unlike irradiance-only or configuration-specific assessments, the framework consistently compares bPV and monofacial PV (mPV) modules across tilt and azimuth configurations while jointly quantifying power output, module temperature, bifacial gain, and angular losses. Predicted power output agreed well with outdoor measurements across four representative mounting configurations, and annual predictions were comparable to PVsyst and SAM results. Applied to Hong Kong, the framework identified optimum tilt angles of approximately 20° for bPV and 18° for mPV modules. A vertical west-facing bPV module achieved 96.3% of the annual energy yield of optimally tilted mPV, with a bifacial gain of 67.2% and an angular-loss-related power loss of 4.8%. These results show that vertical bPV can approach optimally tilted mPV performance while utilizing otherwise unused building surfaces, supporting preliminary design decisions in land-constrained cities. Full article

Pyropiezoelectric energy harvesting has the potential to utilize both environmental vibrations and time-dependent temperature changes to increase the amount of energy harvested compared to harvesting from only one of the two sources. So far, the investigation of such hybrid energy harvesting approaches has mainly been experimental. This makes it difficult to distinguish between their individual physical effects and complicates the optimization of such harvesters. This work presents a numerical framework for solving transient coupled pyropiezoelectric equations using the finite element method. The numerical method can be applied to simulate hybrid energy harvesters by taking into account external electrical circuits. The numerical simulations enable a targeted analysis of the contributions of mechanical, electrical and thermal effects to the harvested energy. This is illustrated by various numerical examples, such as a simple piezoelectric cuboid, a unimorph, a bimorph and a bimetallic beam with a piezoelectric patch. These are subjected to oscillating deformations and/or temperature changes. The simulations calculate the harvested energy resulting from the individual physical effects, depending on the excitation frequency, the external resistance, and the geometric configuration of the harvester. For a bimetallic beam with a piezoelectric patch, which is used as a low frequency hybrid energy harvester, a geometric optimization based on the simulation results showed a possible increase in the harvested energy of up to 386% under idealized circuit conditions compared to the initial design from the literature. Full article

Background: Imidacloprid, a widely used neonicotinoid insecticide, is routinely applied to control pests in Astragalus membranaceus var. mongholicus, a crucial medicinal herb producing Astragali Radix. However, the early short-term transcriptional and metabolic responses of its seedlings under imidacloprid gradient stress remain poorly characterized. Methods: In this study, 80-day seedlings were subjected to three foliar spray treatments: blank control (CK), the recommended imidacloprid concentration (2000-fold dilution, 475 mg·L⁻¹), and an excessively high concentration (500-fold dilution, 1900 mg·L⁻¹). Leaf samples were harvested 24 h post-treatment for untargeted ultra-high-performance liquid chromatography-tandem mass spectrometry (UPLC–MS/MS) metabolomics (6 biological replicates) and RNA-seq transcriptome sequencing (3 biological replicates). Results: The low- and high-dose treatments induced 1076 and 860 differential metabolites and 6818 and 7283 differentially expressed genes, respectively. Flavonoids, saponins, terpenoids, amino acid metabolites, and energy-related pathways were prominently affected. KEGG enrichment indicated activation of flavone/flavonol biosynthesis, phenylpropanoid metabolism, amino acid metabolism, MAPK signaling, cutin/suberin/wax biosynthesis, and ABC transporter pathways, whereas high-dose exposure was associated with stronger changes in genes related to DNA replication and cell wall remodeling. Integrated network analysis highlighted CHS, PAL, MYC2, KCS, and ABCG40 as candidate regulators linking stress signaling, secondary metabolism, and metabolite transport. Conclusions: Seedlings of A. membranaceus var. mongholicus exhibit dose-dependent acute responses to imidacloprid. Moderate pesticide exposure primarily activates defensive secondary metabolism, whereas excessive dosage triggers genome-wide transcriptional reprogramming. This work identifies key metabolic pathways and hub genes, offering candidate molecular markers for investigating pesticide stress adaptation in medicinal Astragalus and guiding standardized pesticide application in cultivation. Full article

This study summarizes the design, development, and experimental validation of a new self-powered, multiparametric sensor and valve. The device integrates a miniaturized Cross-Flow-type turbine with a built-in electrical generator, enabling energy harvesting directly from the pressurized water flow. The prototype of the new device was tested under controlled hydraulic conditions, with flow rates ranging from 0 to 3.1 L/s. Results demonstrated a production capability of up to 100 W of electrical power, with a nominal output of approximately 50 W at 2 L/s. Volume measurement error, assessed according to the MID European Directive, confirmed accuracy within acceptable thresholds. Full article

Multistable energy harvesters have attracted considerable attention due to their shallow potential wells, which facilitate low-energy inter-well oscillations. Although bistable or tristable configurations can be realized using combined magnets or springs, two critical challenges remain: (i) the difficulty in obtaining a higher number of stable equilibrium points and (ii) the inability to arbitrarily prescribe the coordinates of these equilibrium points. To address these issues, this paper proposes a piezoelectric cantilever beam-based multistable energy harvester that allows programmable specification of both the number and the positions of equilibrium points. As demonstrations, a tristable and a pentastable energy harvester with user-defined equilibrium coordinates are designed, and their energy harvesting performances are systematically investigated. Simulation and experimental results show that under an excitation acceleration of 0.1 g, both harvesters can only perform intra-well motion, exhibiting softening nonlinearity. When the excitation acceleration increases to 0.2 g, the pentastable harvester successfully overcomes the maximum potential barrier to achieve inter-well oscillation, displaying hardening nonlinearity and significantly broadening the operational bandwidth, while the tristable harvester remains confined to intra-well motion. At an excitation acceleration of 0.4 g, both harvesters can achieve inter-well oscillation, but the pentastable harvester possesses a wider operational bandwidth and a lower starting frequency for energy harvesting. The proposed method enables the design of multistable vibration energy harvesters without increasing structural complexity with the number of equilibrium points, which is of great significance for optimizing multistable vibration energy harvesters. Full article

Cabbage is a major leafy vegetable in China, but its post-harvest stubble—characterized by high lignification, a thick primary taproot, well-developed lateral roots, and strong root–soil anchorage—poses significant challenges for mechanical incorporation. To address this, a discrete element method (DEM) model of ‘Zhonggan 21’ cabbage stubble was developed. A geometric model was established using root depth as the primary characteristic dimension. Intrinsic physical properties and contact mechanical parameters were systematically measured. DEM parameters were calibrated against shear test results, yielding the following optimal parameter set: tangential stiffness per unit area of 5.54 × 10⁹ N·m⁻³, a tangential bond strength of 1.06 × 10⁶ Pa, and a bonding radius coefficient of 1.07. Under this configuration, the simulated peak shear force deviated from the experimental measurement by merely 1.77%. This work delivers a full-scale property profile of cabbage stubble and constructs a validated DEM model, providing a robust foundation for designing stubble incorporation machinery and advancing low-draft, energy-saving tillage equipment to support sustainable vegetable cropping systems. Full article

This paper presents the design, fabrication, and experimental validation of a 3.45 GHz RF-to-DC voltage-doubler rectifier intended for sub-6 GHz wireless power transfer and RF energy harvesting applications. The proposed rectifier uses low-barrier SMS7630 Schottky diodes, a distributed microstrip impedance-matching network, and an FR4 substrate optimized for low RF input power operation. The design was developed using nonlinear Harmonic Balance simulations in Advanced Design System (ADS) and experimentally characterized through reflection-coefficient measurements, output DC voltage measurements, and RF input power sweeps. A quantitative comparison between simulated and measured results demonstrates good agreement in the impedance-matching characteristics, with a measured resonance frequency of 3.438 GHz and a minimum reflection coefficient of −25.22 dB. The fabricated prototype achieved a maximum measured output DC voltage of 1.58 V and a peak RF-to-DC conversion efficiency of 25.9% at an RF input power of +2.9 dBm. The experimental results validate the practical implementation of the proposed rectifier topology and demonstrate its feasibility as a proof-of-concept RF energy harvesting building block for ultra-low-power IoT and wireless sensing applications. The presented implementation also provides a solid foundation for future optimization using low-loss microwave substrates, improved matching networks, and complete rectenna integration. Full article

The building envelope is a key lever for reducing energy demand and carbon emissions in the built environment. However, conventional envelope systems remain largely static and are unable to respond effectively to changing climatic conditions. Biomimetics has emerged as a promising approach for the development of climate-adaptive envelope solutions. Nevertheless, research in this field remains fragmented across disciplines, and its evolution and technological maturity have not yet been systematically assessed. This study proposes an integrated analytical framework combining a bibliometric analysis of 2.007 Scopus-indexed documents, based on a VOSviewer keyword co-occurrence network, with a cluster-guided state of the art review, and a Technology Readiness Level (TRL) assessment of selected biomimetic envelope solutions. The TRL assessment is conducted using explicit operational criteria. The analysis identifies three main research clusters: (C1) environmental-performative, focusing on energy efficiency and envelope optimisation; (C2) material-experimental, addressing biomimetic composites and innovative materials; and (C3) technological fabrication, centred on digital fabrication, smart materials, and 4D printing. Temporal trends reveal a shift after 2018 from materials science-oriented studies towards computational design and adaptive manufacturing, providing quantitative evidence of a transition previously described mainly in qualitative terms. The review highlights a strong focus on solar-shading applications, while energy harvesting and passive thermoregulation remain comparatively underexplored. The TRL assessment shows that more than 80% of the analysed solutions are concentrated at TRL 3, indicating an early stage of technological development. The main barriers include limited material durability, non-standardised production costs, and regulatory constraints. The findings suggest that future progress will depend less on the identification of new biological inspirations and more on advancing the technological maturity and industrial scalability of existing concepts. This will require integrated developments in materials, parametric design, life-cycle assessment, and regulatory frameworks. Full article

Foot-worn electromagnetic harvesters are driven by irregular rigid-body motion, while their response is limited by mechanical stroke, coil geometry, mounting direction, and the electrical interface. This paper presents a reproducible numerical design study of a finite-stroke magnetic quasi-zero-stiffness (QZS) moving-magnet harvester. Two public three-axis foot-IMU records are processed with stated gyroscope-bias estimation, six-axis attitude estimation, gravity removal, residual-offset correction, filtering, and angular-acceleration calculation. Three explicit axes are used in the design screen, and the selected candidate is then evaluated over a 62-direction spherical grid. Rigid-body angular-acceleration and centripetal terms are included for specified sensor-to-harvester offsets. Two normalized magnetic force laws are compared. The electrical model uses position-dependent flux linkage, explicit series connection and polarity of coil sections, winding-derived resistance, and a position-dependent electromagnetic reaction force. A fixed-seed random screen evaluates 720 geometry-constrained candidates. The highest-ranked nominal candidate is a 150 mm external foot-worn module with a 40.6 g moving mass, a 30 mm hard half-stroke, 1649 turns in two series sections, and a 25.27 mm coil outer diameter. Across 72 design-screen cases formed from 12 five-second windows, three mounting axes, and two magnetic laws, this candidate remained hard-stroke- and design-stroke-safe. Its conditional ideal load-side power had a 10th percentile of 1.38 mW and a median of 2.03 mW. In the 62-direction check, all 1488 cases remained hard-stroke-safe; two opposite directions each produced one design-stroke exceedance, with a maximum displacement of 24.15 mm. Re-ranking all 30 Stage-2 candidates under coupling and magnetic-stiffness changes retained the long geometry family, although a 30% coupling reduction changed the highest-ranked candidate from 600 to 632. Soft-stop sensitivity, equation-level consistency, and multi-case Runge–Kutta convergence are also reported. The results support finite-stroke design screening, but they do not constitute prototype, finite-element, or delivered-power validation. Full article

Industrial chili peppers are specialized varieties primarily used for the extraction of capsaicinoids and paprika red. Their post-harvest processing level directly affects product quality and industrial economic benefits. Most existing studies have focused on a single unit operation or on edible chili peppers, and a systematic review of the entire post-harvest processing chain for industrial chili peppers is still lacking. Taking the standardized post-harvest processing workflow of industrial chili peppers as its core theme, this paper systematically reviews the current research approaches and application status of industrial chili pepper post-harvest processing technologies across six core unit operations, namely cleaning and impurity removal, grading and sorting, drying, stem and seed removal, crushing and grinding, and extraction of bioactive compounds. The analysis indicates that the field currently faces four common challenges: the lack of standardized processing parameters for classified processing, relatively low drying energy efficiency, insufficient online sensing and intelligent collaborative control, and a scarcity of industrial-scale validation for emerging technologies. This paper further constructs a technical route and technology evaluation framework for the entire post-harvest processing chain of industrial chili peppers, clarifies the applicable boundaries and scale suitability of different processing technologies, and provides a theoretical basis for industrial technological upgrading and process selection. Full article

This paper studies a cooperative wireless system in which a single-antenna base station (BS) communicates with a destination user (U) via a half-duplex energy-harvesting amplify-and-forward relay, while the direct BS–U link is unavailable. The destination (U) is equipped with a fluid antenna system (FAS) comprising multiple closely spaced receive ports, enabling spatial reconfigurability through instantaneous port selection. A power-splitting architecture is adopted at the relay to support simultaneous energy harvesting and information forwarding. All wireless links are modeled as flat Rayleigh fading, and the spatial correlation among the FAS ports is explicitly incorporated. To analytically characterize the impact of correlated port selection, a Gaussian copula framework is employed to model the joint distribution of the FAS-channel power gains. Exact integral expressions for the cumulative distribution function of the end-to-end signal-to-noise ratio are derived, from which the outage probability is obtained. For the special case of uncorrelated FAS ports, closed-form expressions are further developed using order statistics and special functions. In addition, asymptotic analysis is carried out to provide further insight into system performance in the high-signal-to-noise-ratio region. Numerical and Monte Carlo simulation results validate the analytical derivations and demonstrate that FAS-based receiver selection yields significant gains in outage performance, even in the presence of strong spatial correlation and energy-harvesting constraints. Full article

The aim of this study was to evaluate the effect of Sida hermaphrodita harvest timing on biomass composition, properties, and methane fermentation performance. In addition, an energy–economic assessment was performed for biomass obtained at different stages of the growing season. The economic assessment assumed CHP electrical and thermal efficiencies of 38% and 47%, electricity and heat prices of 0.18 and 0.05 EUR/kWh, respectively, month-specific agrotechnical costs, and OPEX equal to 30% of total energy revenue. The biomass exhibited clear seasonal changes, transitioning from a material with high bioavailability during the summer period to a structurally more recalcitrant substrate in the autumn and winter months, as indicated by increasing lignification and fibrous fraction contents. The highest CH₄ production yields, ranging from 300 to 320 mL/g VS, and maximum production rates of up to 33.5 mL/g VS·d were obtained between June and August. In December, the CH₄ yield decreased to 180 ± 9 mL/g VS, accompanied by a substantial deterioration in kinetic performance. Despite the relatively stable theoretical methane potential, which ranged from 405 to 430 mL/g VS, its conversion efficiency declined from 77.1% in the summer period to 41.9% in the winter period. Regression analysis confirmed the key influence of the C/N ratio and total solids content, with model fits reaching R² values of 0.74–0.80, while the structure of lignocellulosic complexes had a less pronounced but still relevant effect. The maximum CH₄ production per unit cultivation area, approaching 3380 m³/ha, was achieved in July–August, reflecting a balance between high specific methane yield and biomass productivity. At the same time, the results demonstrated that the maximum biomass yield did not translate into the highest energy and economic performance. The highest net economic return, 1789 ± 330 EUR/ha, was obtained in July, despite biomass yield being 13.6% higher in September. These findings indicate a seasonal decoupling between biomass yield and energy performance, highlight biomass quality as a critical determinant of anaerobic digestion efficiency, and support harvest-date optimization as a low-cost strategy for the practical use of S. hermaphrodita in agricultural biogas plants. Further long-term continuous and semi-continuous studies are required to validate process stability and performance under industrial operating conditions. Full article

Water-intensive industries in the Mediterranean face supply stress and decarbonisation pressure simultaneously. We develop an operations-research decision-support framework that treats the firm as one node of a small industrial resource cluster and prices the cost and carbon-equivalent emissions of five alternative supply trains—municipal water, river water, groundwater, rainwater harvesting and brewery wastewater reuse—within a multi-objective Linear Program. Each train carries engineering-grounded expenditures, energy intensities and grid emissions, and a weighted-sum scalarisation is solved daily for 365 days under three managerial scenarios. On a Cretan microbrewery whose 2022 demand of 5250 m³ is met from the municipal network, the balanced and cost-focused scenarios coincide on a single optimum that cuts the Levelised Cost of Water by 25.3% and emissions by 40.7%, while the eco-friendly scenario yields a 19.3% cost and 51.7% emissions reduction. LP duality, shadow prices and an extended sensitivity programme (diversification, capacity, grid factor, discount rate, RO recovery and demand profile) turn the optimisation into a decision-support package: optimal daily allocations, shadow-price signals on capacity and demand, and robustness diagnostics for capital planning, dispatch and risk management. Results are site-specific, but the framework and its diagnostics transfer in structure to clusters sharing the same convex-polytope source geometry; transposition to energy cooperatives is future work. Full article

This study explores the energy-harvesting performance of aluminum (Al)- and iron (Fe)-filled styrene–butadiene rubber (SBR) composites, with a focus on their mechanical durability and triboelectric properties. Comprehensive mechanical characterization—including tensile strength, elongation at break, fracture toughness, and elasticity—reveals that Fe-filled composites exhibit significantly enhanced reinforcement compared to Al-filled systems at equivalent filler loadings. Raman spectroscopy indicates that Fe atoms can coordinate with the benzene rings of SBR chains through stronger physicochemical bonding, a feature less present in Al-based composites. In addition to improved mechanical properties, Fe-filled composites demonstrate higher electrical conductivity and superior triboelectric energy-harvesting performance. Notably, the composite containing 15 vol% Fe under 1% cyclic compressive strain achieves a peak current density of 127.05 µA/m², a total generated charge of 5.01 nC, and a peak power density of 48.22 µW/m². These values represent substantial enhancements of 246%, 236%, and 2398%, respectively, compared to Al-filled counterparts. Cyclic energy-harvesting tests confirm stable performance with negligible degradation in output or mechanical integrity over repeated cycles. Rubber composite shows good humidity resistance in current and voltage outputs. Furthermore, a layer-by-layer triboelectric nanogenerator (TENG) based on the Fe-filled composite produces output signals of approximately ±1.0 µA and ±5 V under biomechanical hand patting. The superior performance of Fe-based composites is attributed to stronger filler–rubber interactions, likely facilitated by electrostatic interactions, which enhances interfacial charge transfer during mechanical deformation. Overall, Fe-filled SBR composites demonstrate strong potential for cost-effective, environmentally friendly, and durable self-powered energy-harvesting applications. Full article