Search Results (669)

Introduction: Otoliths have been widely used in recent years as tracers of fish life history, ranging from visual aging to chemical analyses that reconstruct environmental conditions, migration patterns, and metabolic changes. Yet, Iberian endemic or endangered species are understudied. This study focuses on Andalusian barbel (Luciobarbus sclateri), endemic to the southern half of the Iberian Peninsula. Objective: The aim was to evaluate whether otolith chemical profiles can simultaneously support age estimation and reveal the impact of environmental variations, particularly hypoxia. Methodology: Fish were caught in two sites with different environmental properties, including strong hypoxia: the Guadalquivir estuary and the dock of Seville (which is isolated from the main river channel by a ship lock and could, therefore, be used as a control). Otolith chemical composition was analyzed from core-to-edge transects with a laser-inductively coupled plasma mass spectrometer (LA ICP-MS). Results: Patterns of variation in Mg and Mn in relation to hypoxia and environmental conditions are discussed. We visually counted growth rings in the sections, and we found a strong correlation (R² = 0.904) in Mg:Ca peaks with growth rings. Body condition, assessed using Fulton’s condition factor (K), differed between sites, with fish from the estuary exhibiting a lower condition than those from the dock. Conclusions: The strong correlation between counter growth rings and Mg:Ca peaks suggests that chemical analysis could be used as a valid method for supporting aging. The pattern of lower condition in fish from the estuary is consistent with persistent hypoxic events documented in the estuary but not within the dock environment. This whole approach provides a powerful framework to assess habitat quality and support conservation of L. sclateri in the Guadalquivir estuary. Full article

Recirculating organic byproducts like food waste, wastewater and manure efficiently and at scale in a circular bioeconomy will be critical to ensuring future food security, energy security, climate resilience, water security and environmental health. Ultimately, we will not be able to live within the safe operating space of our planetary boundaries if we do not stop our wasteful and inefficient habits. Our food, waste, energy and water sectors are starting to transform towards circularity, driven by a diverse range of drivers, from net zero emissions targets, to food waste policies, and to rising fertiliser prices and geopolitical risks. However, these sectors are often not transforming in a coordinated manner, risking unintended consequences like competition between end-uses, technology lock-in, the prevention of scalability, or failure to achieve key sustainability targets, causing rebound effects. For example, society’s organic waste is being earmarked for the production of bioenergy, sustainable aviation fuels, biomaterials, and biofertilisers; however, it is not clear if there will be a sufficient supply of organic waste to meet these diverse demands. Phosphorus flow analyses indicate that we will need to secure almost all of the nutrients in organic waste as fertiliser raw material to produce food. There are some existing pockets of innovation within sectors related to food waste, water and wastewater, fertilisers and agriculture, and bioenergy. However, many initiatives are being driven by short-term challenges, are not operating at scale, or are not sufficiently integrated across sectors. In this paper, we provide examples of innovations and challenges from around the world, including Italy, Australia, Sri Lanka, the UK, Japan, and Malawi. This paper identifies a pathway to navigate tensions to achieve co-existing sustainability goals, including key enablers and barriers, ranging from overcoming regulatory fragmentation to a lack of capital investments. Creating a truly viable circular economy for organic byproducts requires the integration of policies, markets, technologies and people. This means engaging diverse stakeholders, from local councils and private waste contractors, farmers, and fertiliser companies to energy retailers and wastewater utilities, NGOs, informal collectors, and environmental regulators and policy-makers. Full article

To address safety hazards such as line damage and operational instability caused by icing on high-voltage overhead transmission lines, this study conducts numerical simulation research on wire vibration de-icing based on the ANSYS finite element platform. Using a 100 m span transmission line as the research model, 49.8 m ice-covered sections are set on both sides of the line, and the 0.4 m range in the middle is designated as the concentrated excitation force area of the vibration motor. By applying intermittent harmonic loads in the excitation stage, the process of mechanical vibration de-icing is accurately reproduced. At the same time, life and death element technology is introduced to remove ice-covered units with stress exceeding the critical failure threshold, accurately realizing the dynamic simulation of the entire process of ice-covering cracking and detachment. This study selects resonance frequency bands that are suitable for the structural characteristics of the transmission line through static analysis, modal analysis, and harmonic response analysis, and preliminarily locks in candidate excitation frequencies. Combined with transient dynamics simulation, the optimal excitation frequency for vibration de-icing of transmission lines is determined by comprehensively considering the efficiency of de-icing and the safety constraints of conductor dancing. A method for determining the optimal de-icing frequency based on multi-step finite element analysis has been developed, which can provide theoretical support and simulation reference for the structural design, frequency matching, and operational parameter optimization of mechanical vibration de-icing devices for high-voltage transmission lines and overhead cables. Full article

Passively mode-locked lasers, as essential tools for generating ultrashort pulses, have found widespread applications in industrial manufacturing, optical communications, biomedical imaging, and fundamental scientific research. Saturable absorbers serve as the key components governing the performance of such laser systems. Conventional saturable absorber materials, including semiconductor saturable absorber mirrors, carbon nanotubes, and graphene, however, suffer from inherent limitations in operational wavelength range, damage threshold, and environmental stability. In recent years, two-dimensional transition metal carbides and nitrides, known as MXenes, have emerged as a promising class of materials to address these challenges. Their unique metallic conductivity, broadband saturable absorption, ultrafast carrier dynamics, excellent thermal management capability, and versatile chemical tunability offer unprecedented opportunities for advanced saturable absorber applications. This review systematically summarizes the recent progress of MXene-based saturable absorbers, with an emphasis on their distinctive advantages in extending the mode-locked wavelength range, enhancing output pulse stability, and increasing the optical damage threshold. Furthermore, strategies for performance optimization through surface terminal group engineering, defect modulation, and heterostructure design are discussed in depth. Finally, the future prospects and key challenges toward industrial implementation of MXenes in ultrafast photonics are outlined, aiming to stimulate further advancements in high-performance ultrafast laser technology. Full article

Achieving precise docking, reliable locking and damage-free emergency unlocking under complex ocean current conditions remains a key challenge for deep-water multi-way quick connectors (MQCs). This study proposes a novel MQC prototype characterised by a tiered tolerance guidance mechanism, an innovative L-shaped spatial helical cam locking system, and a real-time visual attitude indicator. Using Ansys 2023 R2 and its tools, the safe operating limits were determined through explicit non-linear finite element collision analysis. The results demonstrate that, under a controlled docking speed of 10 mm/s, the hierarchical guidance mechanism successfully accommodated extreme initial misalignments (25 mm lateral offset, 5° horizontal rotation and 15° axial rotation), whilst keeping the peak collision stress within the elastic limit. Furthermore, the L-shaped locking guide was analysed using a fifth-order polynomial motion law and a macro-micro elastoplastic Hertzian contact mechanics model, effectively eliminating rigid-flexible impact forces. Under extreme separation loads of 10,000 psi, the maximum equivalent plastic strain at the base of the locking shaft was strictly controlled at 0.00926. This is well below the failure threshold of 0.0865 specified by ASME, providing a substantial safety margin and completely preventing local yielding. Crucially, the emergency release strategy based on precision locating pins was validated through full-scale prototype testing. Destructive tests conducted under simulated severe jamming conditions demonstrated clean, damage-free disengagement under shear torques ranging from 2100 Nm to 2200 Nm. This threshold ensures that accidental triggering will absolutely not occur during routine operations (1400 Nm) and establishes a safe underwater robotic (ROV) operating speed of ≤4 r/min. This study provides a robust theoretical framework and empirical data for the future design of yield-resistant subsea connectors and safe emergency recovery. Full article

This work investigates Ferro-Rock concrete as a carbon-negative alternative to ordinary Portland cement (OPC), which accounts for 5–9% of global CO₂ emissions, and evaluates its viability as a sustainable construction material. Ferro-Rock is an iron-based binder comprising recycled iron powder, fly ash, metakaolin, limestone powder, and oxalic acid. This is enhanced by a carbonation reaction in which iron particles react with CO₂ and water to form iron (II) carbonate (FeCO₃), the main binding phase, thereby locking in atmospheric CO₂. The experimental program was divided into two groups. Group 1 studied 100% Ferro-Rock binders with different types of aggregate, specimen sizes, and CO₂ curing periods (0–6 days) with a new locally manufactured stainless steel curing chamber that provided a controlled CO₂ environment of 99.9% and 1.2–1.5 bar gauge pressure. Group 2 investigated Ferro-Rock as a partial cement replacement at 0%, 5%, 10%, 15% and 20% levels of substitution with 5% increments. The 7 and 28 days of compressive, flexural and indirect tensile strengths were determined. The results showed the Ferro-Rock with 100% iron ductile waste aggregates (Mix F4) achieved a 28-day compressive strength of 5.5 MPa, 37.5% higher than the standard Ferro-Rock reference mix. The optimum replacement range of Group 2 was 5–10% with an increase in compressive strength by 5–10%, flexural strength by 11%, and indirect tensile strength by 16% over the OPC control. When replacement exceeded 25%, the bonding was weakened, and all strength measures decreased significantly, reaching a 46% reduction in compressive strength at 50% substitution. Scanning electron microscopy–energy-dispersive X-ray spectroscopy (SEM–EDS) microstructural analysis verified the gradual formation of the iron carbonate crystalline phase and provided mechanistic insights into the observed strength trends. Fully cured Ferro-Rock specimens sequestered as much as 11% CO₂ by weight, with a verifiably carbon-negative profile that no OPC-based system can match. Full article

Taking the over-track development project of a metro depot in Chongqing as the engineering background, this study investigates the socket-type disc-lock full-hall scaffold system beneath the long-span transfer beam of Tower 9. A finite element model was established using MIDAS Civil to analyze the stress distribution and deformation characteristics of the scaffold system under construction loads, and the model was validated through field monitoring. On this basis, a parametric analysis was conducted to investigate the effects of erection height, step spacing of vertical standards, spacing between vertical standards, sweeping rod height, and joint stiffness on the overall stability of the scaffold system. A fitted analytical model for the buckling eigenvalue was further established. The results show that the scaffold system was mainly subjected to compression during construction. The measured maximum compressive stress of the vertical standards was 90.92 MPa, with an error of 12.50% compared with the finite element result of 80.82 MPa. The measured maximum tensile stress was 22.37 MPa, which was close to the calculated value of 21.96 MPa. The measured maximum average cumulative vertical displacement of the scaffold was 1.69 mm, which did not exceed the allowable deformation range during construction. The parametric analysis indicates that increases in erection height, step spacing of vertical standards, spacing between vertical standards, and sweeping rod height reduce the overall stability of the scaffold system, among which the step spacing of vertical standards has the most significant influence. In contrast, increasing joint stiffness is beneficial for enhancing the stability reserve. In this study, the overall stability of the scaffold system is characterized by the buckling eigenvalue obtained from linear eigenvalue buckling analysis. These findings can provide a reference for parameter selection, scheme comparison, and construction control of similar disc-lock high-formwork support systems for heavily loaded transfer beams. However, the conclusions of this study are mainly based on linear eigenvalue buckling analysis and single-factor parametric investigation, without further consideration of material nonlinearity and multi-parameter interaction effects. Full article

Spoof surface plasmon polaritons (SSPPs) offer a powerful way to confine and guide light at terahertz and gigahertz frequencies, but their functionality is typically locked by their static geometries. This study demonstrates the active tuning of SSPP resonances using nematic liquid crystals (LCs) integrated into metallic grating structures. Through full-wave numerical simulations, we show that both reorienting the LC director and inducing the nematic–isotropic phase transition enable the efficient modulation of the SSPP resonance frequency. In the terahertz regime, tuning ranges exceeding 150 GHz are achieved while preserving strong resonant absorption. For GHz-scale structures, we identify optimal configurations—such as partially dielectric-filled grooves topped with an LC layer—that overcome field confinement challenges and provide practical frequency shifts of several gigahertz. These results establish LCs as an effective tuning medium for reconfigurable SSPP devices for future applications in emerging THz and GHz photonics. Full article

Mechanical locks have not been fully replaced by electrical locks and are still being researched and improved, along with advanced electronic methods of attack. Moreover, reading pin lengths by detecting their natural frequencies (lock decoding) to forge copies of a legitimate key can be done quickly using active or passive ultrasonic detectors. One possible method of defence against them is manufacturing lock pins using functionally graded materials (FGMs). A pin’s natural frequency (in the range 100 kHz–1 MHz) and hence its ultrasonic pulse transit/reflection time can be correlated to its length if it is made of a homogeneous material. The idea is to design pins made of functionally graded alloys to achieve equal natural frequencies, but also desired positions of standing wave nodes regardless of pin length. To calculate the composition of the FGM alloy, we must first develop mathematical models of a pin’s vibrations. Two simple and fast mathematical models are first derived from the finite-element model (FEM) of a pin. These models are used in an optimization procedure based on the Nelder–Mead simplex method to calculate optimal profiles of Young’s modulus and density along a pin’s longitudinal axis. A successful optimization procedure for 10 key pin lengths is performed to make a pin-tumbler lock resistant to ultrasonic attacks. Full article

This article presents a fast-locking phase-locked loop (PLL) that incorporates a low-power extended phase frequency detector (LPEPFD) and a discriminator-aided phase detector (DAPD) to simultaneously address cycle slippage and frequency overshoot issues during frequency and phase acquisition, respectively. Specifically, the proposed LPEPFD introduces a novel finite state machine architecture that extends the linear range of a conventional PFD without requiring a power-hungry counter, thereby eliminating cycle slippage and reducing the time required for frequency acquisition while maintaining switching activity and power consumption comparable to those of the conventional design. Moreover, after frequency convergence, the DAPD quantizes the accumulated phase error, which is corrected by adaptively tuning the programmable delay lines without causing significant frequency overshoot seen in conventional PLLs, resulting in improved settling time. Fabricated using a 28 nm complementary metal oxide semiconductor (CMOS) process, the proposed fast-locking PLL occupies an area of 0.36 mm² and operates over a frequency range of 2.6 to 3.2 GHz. Experimental results demonstrate a 0.84-μs settling time for a frequency hop from 2.6 to 3.1 GHz. The designed PLL consumes 5.6 mW of power from a supply of 1 V with an integral root-mean-square jitter of 1.27 ps from 1 kHz to 100 MHz. Full article

This paper proposes the Branch-Priority Exploration (BPE) framework for autonomous coverage in confined industrial corridor environments. BPE integrates three components: (1) a symmetry-aware LiDAR branch detector; (2) a hierarchical BFS/DFS mode-switching policy; and (3) a barrier-based branch memory. Frontier-based methods often struggle in industrial corridors where branches split off from the main corridor. The symmetric layout of such environments, featuring T-shaped junctions and L-shaped turns, creates recurring geometric patterns that conventional frontier scoring fails to exploit. When the robot reaches a junction, nearby frontier candidates often receive similar scores, causing repeated target switching as the local map changes. Meanwhile, frontier cells inside a branch tend to score lower than those along the main corridor; so, the robot often bypasses the branch and continues forward, which leads to additional backtracking later. Even when the robot eventually returns, residual frontier cells near the entrance may attract the planner repeatedly, causing redundant re-entry into already-covered branches. To address these issues, a branch-priority exploration framework is developed. A symmetry-aware branch detection module uses LiDAR range measurements from multiple directions to identify T-shaped junctions and lateral openings, applying identical geometric criteria to lateral openings on either side of the robot. This allows branch entry to be triggered by explicit geometric evidence, rather than frontier score comparisons that tend to be unreliable near intersections. When a branch is detected, the robot transitions from BFS mode to DFS mode for systematic branch coverage. Entry and post-return locks prevent mode reversal before the robot commits to the new heading. Once a branch is completed, a permanent virtual barrier is placed at its entrance; so, the planner no longer routes the robot back into that branch. The framework is formalized as a constrained coverage problem on occupancy grids, and monotonic coverage progress and finite branch completion under barrier memory are established theoretically. A fully reproducible ROS implementation on a wheeled platform with differential drive is validated. Experiments span several corridor environments of increasing topological complexity. Compared to a nearest-frontier baseline, the proposed method substantially reduces both exploration time and goal cancellations while achieving complete coverage across all trials. The cancellation count matches the number of T-branches per environment, with near-zero variance across repeated runs. Full article

Ground-based scatterometers are widely used for quantitative microwave backscattering measurements in soil moisture retrieval, vegetation monitoring, and satellite scatterometer validation. However, low-cost software-defined radio (SDR) transceivers provide limited instantaneous bandwidth, making it difficult to transmit and process signals with bandwidths on the order of hundreds of MHz for fine range resolution, especially for systems requiring real-time onboard processing. To address this problem, this paper presents a vehicular, fully polarimetric, SDR-based scatterometer that achieves an equivalent wideband response by sequentially transmitting adjacent narrow subbands and coherently synthesizing them onboard. To enable real-time operation on a resource-limited field-programmable gate array/system-on-chip (FPGA/SoC) platform, we adopt a frequency-domain synthesis-pulse-compression pipeline that avoids interpolation and eliminates repeated matched filtering across subbands. A slot-based online phase calibration is performed within the settling window after each fast lock to estimate and compensate random local oscillator (LO) phase offsets, preserving coherent stitching. In addition, pulse repetition within each subband and coherent accumulation are integrated to improve the signal-to-noise ratio (SNR) under real-time throughput constraints. A Zynq-based implementation demonstrates deterministic onboard range-profile output, with a minimum processing latency of about 1.57 ms per frame. Loopback and outdoor experiments validate the equivalent 200 MHz bandwidth (five 40 MHz subbands), achieving approximately 0.75 m resolution and yielding sidelobe metrics consistent with the designed windowing, including a peak sidelobe ratio (PSLR) of −27.43 dB and an integrated sidelobe ratio (ISLR) of −12.38 dB. Field scans over farmland further show consistent ${\mathsf{\sigma }}_0$ trends across incidence angle and azimuth, indicating reliable onboard quantitative backscattering measurement. These results demonstrate that the proposed method provides a feasible solution for deterministic real-time equivalent wideband scatterometry on a low-cost SDR platform. Full article

Underwater acoustic monitoring is a critical technology for marine resource development and modern aquaculture. The performance of acoustic sensors directly determines the effectiveness of biological behavior tracking in complex marine environments. This paper presents the design, fabrication, and characterization of a custom hydrophone utilizing a polyvinylidene fluoride (PVDF) piezoelectric film configured in a biomimetic tympanic cavity structure. Operating on the direct piezoelectric effect, the device employs a pre-tensioned PVDF diaphragm integrated with a dedicated charge amplifier circuit to condition high-impedance signals. Laboratory calibrations demonstrate a stable frequency response (with a sensitivity variation within ±1 dB) in the low-frequency range (1–200 Hz) with an average acoustic pressure sensitivity of approximately −206 dB (re 1 V/μPa), providing a higher relative voltage gain compared to a commercial reference hydrophone with a nominal sensitivity of −210 dB (re 1 V/μPa). Furthermore, extensive field evaluations were conducted in a marine net pen to analyze acoustic data across multiple fish feeding scenarios (baseline, pre-feeding, active feeding, and post-feeding). The proposed custom hydrophone exhibited a superior dynamic range and successfully locked onto a 24.4 Hz Golden Pompano (Trachinotus blochii) bioacoustic signature, maintaining remarkable feature stability even after active feeding ceased. This study validates the efficacy of the biomimetic PVDF hydrophone for low-frequency acoustic detection, providing a robust hardware foundation for automated behavioral recognition systems in aquaculture. Full article

Fully leveraging the four-wheel independent drive characteristics of distributed-drive electric vehicles has become essential for enhancing their driving range. However, conventional regenerative braking strategies applied to such vehicles often fail to consider individual wheel slip ratios, which can easily lead to wheel lock and low energy recovery efficiency. To address these issues, this paper proposes a novel energy management method that integrates hybrid braking control with intelligent connected speed planning. A hierarchical control strategy for the hybrid braking system is first developed, explicitly accounting for the slip ratio of each wheel. The upper-level controller calculates the slip ratio for each wheel based on vehicle speed and wheel speed information and subsequently determines the braking torque distribution between the front and rear axles. The lower-level controller then allocates the motor braking torque and hydraulic braking torque to each wheel, subject to system constraints such as battery status and motor torque limits. Building on this framework, vehicle state and road information are incorporated as inputs to formulate a Markov decision process, which optimizes traffic efficiency, energy economy, and ride comfort as multiple objectives. The deep deterministic policy gradient (DDPG) algorithm is employed to achieve collaborative optimization of speed planning and energy management. Simulation results demonstrate that the proposed DDPG-based control strategy outperforms both rule-based control methods and classical dynamic programming algorithms in terms of comprehensive performance across traffic efficiency, energy consumption, and ride comfort. These findings validate its superiority in complex traffic conditions. Full article

This paper presents a numerical investigation of vortex-induced vibration (VIV) of six elastically mounted circular cylinders in oscillatory flow, three smooth and three biofouled with triangular surface roughness elements. The study aims to characterise the influence of the longitudinal spacing ratio ($L/D=3,4,$ and $5$) on the two-degree-of-freedom (2DOF) vibration response at a constant Keulegan–Carpenter number of $KC=10$. Simulations are performed using the transient RANS equations with the SST $k–\omega$ turbulence model, and structural motion is resolved using a dynamic mesh approach. Lock-in behaviour is observed over the reduced velocity range $5\le U_r\le 10$. Biofouled cylinders generally exhibit higher in-line displacement amplitudes than smooth cylinders in the initial and lower lock-in branches, whereas smooth cylinders tend to attain higher in-line amplitudes in the upper lock-in branch. The spacing ratio $L/D$ is found to significantly influence the response, with peak vibration amplitudes varying non-uniformly across the array and no single spacing configuration being optimal for all cylinders. This behaviour is further supported by analyses of trajectories, frequency content, and vorticity fields. Among the smooth cylinders, the middle cylinder exhibits the largest in-line displacement amplitude of $3.28D$ at $L/D=5$ and the largest cross-flow displacement of $1.34D$ at $L/D=3$. For the biofouled configurations, the middle and upstream cylinders show the highest in-line displacement amplitude of $2.69D$ at $L/D=4$, while the maximum cross-flow displacement of $1.27D$ is observed for the upstream cylinder at $L/D=5$. Full article