Search Results (1,223)

Time-varying or temporal metamaterials and metasurfaces, in which electromagnetic parameters are deliberately modulated in time, have emerged as a powerful route to engineer wave–matter interaction beyond what is possible in static media. By enabling the controlled exchange of energy and momentum with the fields, they underpin magnet-free nonreciprocity, low-loss frequency conversion, temporal impedance matching beyond Bode-Fano limit, and unconventional parametric gain and noise control. This survey provides a coherent framework that unifies the main theoretical and experimental developments in the area, from early analyses of velocity-modulated dielectrics to recent demonstrations of temporal photonic crystals, non-Foster temporal boundaries, and spatiotemporally driven metasurfaces relevant to nanophotonic platforms. We systematically compare time-varying permittivity, joint $\epsilon$-$\mu$ modulation, time-varying conductivity, plasmas, and circuit-equivalent implementations, including stochastic and rapidly sign-switching regimes, and relate them to acoustic and quantum analogs using common figures of merit, such as conversion efficiency, isolation versus insertion loss, modulation depth and speed, dynamic range, and stability. Our work concludes by outlining key challenges, loss and pump efficiency, high-speed modulation at the nanoscale, dispersion engineering for broadband operation, and fair benchmarking, which must be addressed for robust, integrable temporal metasurfaces. Full article

Although the combination of solar power and electric vehicles is widely considered beneficial, practical applications reveal substantial variance. To determine the proportion of solar energy used for charging and to identify the main drivers of a high solar share, a dataset containing measured 5 min energy time series of 725 households with PV and EVs was analyzed. In the existing literature, this represents a novelty, as most studies in this field are simulation-based, rely on synthetic profiles, use lower time resolutions, or are based on questionnaires. The share of solar energy used for EV charging is highly dispersed and varies by about ±40% around a median of 60%. The analysis shows that clustering by preferred charging times has strong explanatory potential: at the median, EVs charged predominantly during the daytime achieve a solar share that is more than 40% higher than those charged in the evening. In the latter case, home battery storage increases the solar share by an average of 20 percentage points. A similar magnitude of a 25-percentage-point increase could be reached with solar surplus charging compared to uncontrolled charging. On average, households with PV, battery, and EVs cover more than 56% of their total demand with self-generated solar energy; with solar-adapted charging, median values exceed 77%. If a heat pump is used on site, the self-sufficiency decreases but can still reach median values above 45% and up to 61% for optimized households. Full article

Background: Ageing profoundly alters endocrine regulation and nutrient metabolism, predisposing older adults to thyroid dysfunction. Iodine, an essential micronutrient, lies at the center of this vulnerability due to its narrow physiological range and multiple interactions with nutrition, medications, renal function, and, presumably, gut microbiota. Objective: This narrative review integrates evidence on how ageing modifies iodine–thyroid homeostasis, emphasizing the roles of dietary intake, pharmacologic exposures, microbiota composition, and age-related metabolic alterations that influence iodine handling and thyroid hormone economy. Main Findings: Physiological ageing reduces renal iodine clearance, thyroidal reserve, and peripheral hormone conversion, while chronic inflammation and multimorbidity increase susceptibility to both iodine deficiency and excess. Polypharmacy, including amiodarone, lithium, and proton pump inhibitors, further destabilizes thyroid function. Age-related dysbiosis may impair micronutrient absorption and immune tolerance, linking gut ecology to thyroid autoimmunity. The gut microbiota may influence thyroid function through immune and metabolic pathways, although current evidence in older adults remains limited. Together, these factors shift the balance between iodine intake and utilization, heightening the risk of subclinical or overt hypothyroidism in older adults. Conclusions: Overall, variations in iodine intake emerge as one of the main determinants of thyroid dysfunction in ageing with nutritional, pharmacologic, and other modifiers primarily influencing iodine-related thyroid vulnerability. The adoption of age-adjusted thyroid reference ranges and preventive monitoring can reduce overtreatment and improve metabolic resilience in later life. Full article

To achieve energy savings, reduce consumption, and support the “dual-carbon” strategy in China, this study applies digital twin technology to investigate the centralized air-conditioning water system of a metro-station HVAC installation and develops a high-fidelity digital twin model to reveal the thermal delay and thermal attenuation characteristics of the pipeline network. Using the noncausal modeling approach of the Modelica language, a full digital twin representation of the centralized air-conditioning water network is constructed by covering chillers, cooling towers, pumps, terminal units, the pipeline network, etc. The model is validated against real operation data to ensure high fidelity. Validation shows the predicted chilled water flow rate of the digital twin model agrees well with the measured chilled water flow rate with an RMSE of 0.27 kg/s. Validation also shows the difference is about 0.3 °C between the digital twin prediction and the measurement in the main pipe. Based on the validation digital twin model, the thermal delay and thermal attenuation characteristics of the centralized air-conditioning water system are seriously evaluated. The results indicate that branch K3, due to its longest transport distance, exhibits a delay of 227 s. The overall thermal delay of the system reaches 7.5 min. The temperature attenuation of this water system is about 0.2 °C due to heat loss through pipe walls. The findings may offer theoretical support for the optimal regulation and control, fault detection, and anomaly identification of this centralized air-conditioning water system. Full article

Hydraulic thrust cylinders in hard-rock tunnel boring machines (TBMs) often exhibit slow response and sluggish acceleration during start-up, which degrades early-stage tracking performance and limits overall operational accuracy. Most existing studies primarily enhance start-up behavior through advanced control algorithms, yet the achievable improvement is ultimately constrained by the system’s flow–pressure capacity. Meanwhile, reported system-level optimization approaches are either difficult to implement under practical TBM operating conditions or fail to consistently deliver high-accuracy tracking. To address these limitations, this paper proposes a “dual-pump–single-cylinder” control framework for the TBM thrust system, where a large-displacement pump serves as the main supply and a parallel small-displacement pump provides auxiliary flow compensation to mitigate the start-up flow deficit. Building on this architecture, an adaptive compensation algorithm is developed for the auxiliary pump, with its output updated online according to the system’s dynamic states, including displacement error and velocity-related error components. Comparative simulations and test-bench experiments show that, compared with a single-pump scheme, the proposed method notably accelerates cylinder start-up while effectively suppressing overshoot and oscillations, thereby improving both transient smoothness and tracking accuracy. This study provides a feasible and engineering-oriented solution for achieving “rapid and smooth start-up” of TBM hydraulic cylinders. Full article

Despite the growing adoption of hybrid energy systems integrating solar photovoltaic (PV), pumped storage hydropower (PSH), and battery energy storage (BES), comprehensive studies on their dynamic stability and interaction mechanisms remain limited, particularly under weak grid conditions. Due to the high impedance of weak grids, ensuring stability across varied operating scenarios is crucial for advancing grid resilience and energy reliability. This paper addresses these research gaps by examining the interaction dynamics between PV, PSH, and BES on the DC side and the utility grid on the AC side. The study identifies operating-region-dependent instability mechanisms arising from negative incremental resistance behavior and weak grid interactions and proposes a virtual-impedance-based active damping control strategy to suppress poorly damped oscillatory modes. The proposed controller effectively reshapes the converter output impedance, shifts unstable eigenmodes into the left-half plane, and improves phase margins without requiring additional hardware components or introducing steady-state power losses. System stability is analytically assessed using root-locus, Bode, and Nyquist criteria within a developed small-signal state-space model, and further validated through large-signal real-time simulations on an OPAL-RT platform. The main contributions of this study are threefold: (i) a comprehensive stability analysis of a utility-scale grid-connected hybrid PV–PSH–BES system under weak grid conditions, (ii) identification of operating-region-dependent instability mechanisms associated with DC–link interactions, and (iii) development and real-time validation of a practical virtual-impedance-based active damping strategy for enhancing system stability and grid integration reliability. Full article

A one-dimensional analytical model for a proton exchange membrane fuel cell (PEMFC) engine is presented. The model is structured into three main subsystems: the fuel cell stack, the intake and exhaust system, and the thermal management system. The modeling of the thermal management system specifically encompasses key components such as the expansion tank, thermostat, pump, fan, and radiator. The heat transfer and fluid flow within key thermal management components—primarily fans and radiators—are analyzed via three-dimensional modeling. A porous media model represents the unit parallel-flow radiator, where the complex fin structures are replaced by a homogenized medium. This allows for the efficient calculation of 3D thermal and flow fields once the necessary constitutive parameters are identified. Ultimately, the one-dimensional (1D) thermal management system is coupled with the three-dimensional (3D) flow field analysis. This integrated 1D-3D co-simulation framework is implemented to enhance the computational fidelity of the PEMFC engine’s thermal management model. Full article

The overprescription of gastroprotectants, in particular acid suppressants in dogs, is of increasing concern in veterinary medicine. There have been specific guidelines published to document the appropriate use of this class of drugs; however, the injudicious use of gastroprotectants continues to be a concern and is often not evidence-based. The primary objective of the present study was to evaluate the veterinary prescription of gastroprotectants for dogs in Spain. A survey employing a snowball recruitment effect was distributed among small animal medicine veterinarians practicing in Spain. A total of 265 veterinarians participated in the survey. Proton pump inhibitors (PPIs) were found to be the most commonly prescribed gastroprotectant utilised by 50.6% of the participants. Veterinarians with fewer years of clinical experience and those focusing on the fields of internal medicine, emergency, and anaesthesia were more likely to adhere to evidence-based guidelines in their prescribing practices. Those who prescribed gastroprotectants less frequently tended to rely on PPIs and on international consensus guidelines. Although the main indications in which Spanish veterinarians used gastroprotectants was supported by scientific evidence, the injudicious administration of this class of drugs for disorders lacking robust scientific evidence or recommendations was well documented. Full article

This study investigates the role of biogas and biomethane in accelerating the decarbonization of district heating systems in Europe. A structured literature review combined with two representative case studies evaluate technological, economic, and environmental performance across different system scales. The Meppel optimization model developed for the Netherlands and the large-scale Backbone energy system modelling framework for Finland are compared to identify methodological synergies and operational insights for integrating bioenergy into heating networks. The results show that biogas-based combined heat and power systems can reduce carbon dioxide emissions by more than 70 percent compared with fossil-based alternatives and significantly improve local energy security, especially when coupled with heat pumps and thermal storage. Large-scale modelling further demonstrates that biomethane and bioenergy resources provide valuable system flexibility, facilitating sector coupling and supporting the balancing of variable renewable electricity production. This study’s main contribution is an integrated comparative assessment at two different scales (local and regional), linking operational data, modelling, and performance results to determine how biogas and biomethane can optimize the energy system in the short and long term for centralized heat supply. The findings confirm that biogas and biomethane are essential, dispatchable renewable resources capable of supporting scalable, low-carbon, and resilient district heating systems across Europe. Full article

Semi-open impeller sewage pumps are widely used in fields such as municipal wastewater treatment. However, they often face performance degradation and operational instability when conveying solid–liquid two-phase flows containing solid particles. This study aims to systematically elucidate the influence mechanisms of particle diameter (0.5–3.0 mm) and volume fraction (1–20%) on the external characteristics and internal flow field of semi-open impeller sewage pumps, providing a theoretical basis for optimizing their design and operational stability. Using an 80WQ4QG-type sewage pump as the research subject, this study employed a combination of numerical simulation and experimental research. The standard k-ε turbulence model coupled with the Discrete Phase (Particle) approach was adopted for multi-condition solid–liquid two-phase flow simulations. Furthermore, two-way analysis of variance (two-way ANOVA) was utilized to quantify the main effects and interaction effects of the parameters. The results indicate that the pump head and efficiency generally exhibit a decreasing trend with increasing particle diameter or volume fraction, with particle diameter exerting a more pronounced effect (p < 0.01). When the particle diameter increased to 3.0 mm, the head decreased by 5.66%; when the volume fraction rose to 20%, the head decreased by 4.17%. It is noteworthy that the combination of a 0.5 mm particle diameter and a 20% volume fraction resulted in an abnormal increase in head, suggesting a possible flow pattern optimization under specific conditions. Analysis of the internal flow field reveals that coarse particles (≥1.5 mm) intensify the pressure gradient disparity between the front and rear shroud cavities of the impeller, thereby increasing the axial thrust. A high volume fraction (≥10%) promotes pronounced flow separation in the volute tongue region and exacerbates the risk of localized erosion at the outlet. Full article

Eosinophilic esophagitis (EoE) is a chronic, allergic, immune-mediated inflammation of the esophagus caused by food antigens. The prevalence in pediatric population is approximately 34 to 57 cases per 100,000 children, with a male to female ration 3:1. This number may be underestimated due to diagnostic challenges and variety of clinical presentations in different age groups. Diagnosis of EoE requires histopathological assessment of esophageal biopsies retrieved during gastroscopy, with at least 15 eosinophils per high-power field (HPF) in the esophageal tissue being the cut off value. According to recommendations, treatment options of EoE include dietary interventions (elimination diets), medical treatment (inhibitors of proton pump, steroids, biologics), and in some cases surgical intervention (dilation). Dietary intervention, such as elimination diets, target the triggering factors of the disease and, if supervised by professional nutritionist, have the least systemic side effects. On the other hand, depending on the number of allergens eliminated from the pediatric patients’ diet, the quality of life both of the child and their caretakers may be compromised. Additional challenges such as nutritional risks, feeding disorders, financial burden, and social life impairment also have to be taken into consideration. On top of this, an effectiveness assessment of chosen therapy requires repeated endoscopic examination with several biopsies of the esophagus, further increasing diseases burden in EoE patients. Taking all of this factors into consideration, the main objective of this narrative review was to address challenges that pediatric patients with EoE on dietary treatment face with reference to current research and daily practice. Full article

This paper introduces a zero-carbon heating solution called High-Performance Heat-Powered Heat Pumps (HP³), which combine the best attributes of hydrogen boilers and electric heat pumps. HP³ systems allow us to continue using the existing gas infrastructure, offer higher efficiencies than hydrogen boilers, and avoid overwhelming the electricity grid. An HP³ blends a heat engine and a heat pump into a single, fully integrated system sharing a common working fluid. This differentiates HP³ systems from gas-engine-driven heat pumps (GEHP), where the integration between subsystems is limited to a mechanical shaft. A parametric analysis of a propane-based system is presented. The heat engine section has two main design variables: the working fluid’s temperature ($T_{max}$) and pressure ($P_{high}$) after collecting high-grade heat from hydrogen combustion. Typical GEHPs achieve CoPs of around 1.8. The HP³ concept achieves a CoP of 2.59 considering a $T_{max}$ of 650 °C, $P_{high}$ of 250 bar, and an ambient temperature of −9 °C. The paper presents a model for the expander’s efficiency, which indicates that increasing the system’s output makes it possible to achieve a higher expansion efficiency with a lower rotational speed. Results show that HP³ is a promising concept for larger applications such as commercial buildings or district heating systems. Full article

Seawater intrusion forms a significant environmental and hydrogeological phenomenon that raises significant risks for the sustainability and quality of coastal aquifer hydrosystems. The present review study critically examines the available methodologies for assessing aquifer susceptibility to seawater intrusion, including the GALDIT and SEAWAT models. The GALDIT model is a parametric model that uses six main hydrogeological parameters for assessing groundwater vulnerability to seawater intrusion. Numerous researchers have proposed improvements to GALDIT either by adding new variables such as well density, well pumping rates, and hydrochemical indicators, or by applying machine learning (ML), fuzzy logic, and optimization algorithms to improve spatial resolution and accuracy. The SEAWAT code can be used for simulating variable-density groundwater flow and solute transport and has been widely used to model the salinization process under different pumping and sea-level rise scenarios. The presented case studies show that the combination of GALDIT and SEAWAT offers a stronger and robust framework for both vulnerability zoning and dynamic flow and transport simulation. Recent SEAWAT studies show that paleo-salinization has a significant influence, highlighting the need to measure both the trapped saline water in confined layers and the lateral intrusion of seawater. The present review concludes that future efforts need to focus on hybrid modeling approaches, integration of hydrochemical and geophysical data, and the inclusion of anthropogenic and climate-associated factors to enhance the accuracy and applicability of seawater intrusion risk assessments in coastal areas. Full article

Compared to conventional solid-fueled reactors, the liquid fuel transport in molten salt reactors (MSRs) leads to a strong coupling between thermal-hydraulics and neutronics. To enable system-level analysis of MSR, this study focuses on the main loop of the Molten Salt Reactor Experiment (MSRE). A system model is developed using the open-source, multiphysics modeling platform Modelica/TRANSFORM. The model is validated against ORNL experimental data under various conditions, including zero-power pump start/stop, natural circulation. In addition, the xenon transport behavior is compared with predictions from a two-region analytical model. Results indicate that the number of discretized core nodes significantly influences the estimation of delayed neutron precursor (DNP) losses due to fuel circulation. The applicability of the ANSI/ANS-5.1 decay heat model, originally developed for light water reactors, is confirmed to be conservative when applied to MSRE conditions. Finally, natural circulation behavior with decay heat transport is further analyzed. Full article

This study presents a comprehensive thermo-economic evaluation of a pumped thermal energy storage (PTES) system based on a supercritical carbon dioxide (s-CO₂) recompression Brayton cycle (RBC). A multiparametric analysis was conducted through systematic parameterization of key design variables, including mass fractions directed to the recompressor during charging and to the high-pressure turbine during discharging, as well as compressor inlet pressure and temperature and turbine inlet temperature. Performance optimization focused on two main indicators: round-trip efficiency (${\eta }_{RT}$) and levelized cost of storage (LCOS), enabling identification of trade-offs between thermodynamic and economic performance. Results show that minimizing LCOS yields 148.72 $/MWh with an ${\eta }_{RT}$ of 57.1%, whereas maximizing efficiency achieves 61.5% at an LCOS of 158.4 $/MWh. Exergy destruction analysis highlights the strategic role of the main compressor and thermal storage tanks in overall irreversibility distribution. These findings confirm the technical feasibility of the s-CO₂ recompression Brayton cycle as a competitive solution for long-duration thermal energy storage. Full article