Search Results (439)

The rapid proliferation of connected vehicles equipped with both Vehicle-to-Vehicle (V2V) sidelink and cellular interfaces creates new opportunities for real-time vehicular applications, yet achieving ultra-reliable communication without prohibitive cellular costs remains challenging. This paper addresses reliable inter-vehicle video streaming for safety-critical applications such as See-Through for Passing and Obstructed View Assist, which require stringent Service Level Objectives (SLOs) of 50 ms latency with 99% reliability. Through measurements in Seoul urban environments, we characterize the complementary nature of V2V and Vehicle-to-Network-to-Vehicle (V2N2V) paths: V2V provides ultra-low latency (mean 2.99 ms) but imperfect reliability (95.77%), while V2N2V achieves perfect reliability but exhibits high latency variability ($P_{99}$: 120.33 ms in centralized routing) that violates target SLOs. We propose a hybrid framework that exploits V2V as the primary path while selectively retransmitting only lost packets via V2N2V. The key innovation is a dual loss detection mechanism combining gap-based and timeout-based triggers leveraging Real-Time Protocol (RTP) headers for both immediate response and comprehensive coverage. Trace-driven simulation demonstrates that the proposed framework achieves a 99.96% packet reception rate and 99.71% frame playback ratio, approaching lossless transmission while maintaining cellular utilization at only 5.54%, which is merely 0.84 percentage points above the V2V loss rate. This represents a $7\times$ cost reduction versus PLR Switching (4.2 GB vs. 28 GB monthly) while reducing video stalls by $10\times$. These results demonstrate that packet-level selective redundancy enables cost-effective ultra-reliable V2X communication at scale. Full article

Driven by the global energy transition, the rapid expansion of photovoltaic (PV) capacity—particularly in China’s “sand-Gobi-desert” mega-bases—demands highly efficient collection technologies. DC collection, offering low losses, compactness, and high reliability, is emerging as a critical solution for large-scale integration. This paper provides a comprehensive review of PV DC step-up collection systems. First, it analyzes typical network architectures, compares AC versus DC schemes, and examines design constraints imposed by DC bus voltage levels. Second, control strategies are summarized across device, equipment, and system levels. Third, based on engineering practices in ultra-large-scale bases, key challenges regarding fault detection, efficiency optimization, economic viability, and grid code compatibility are identified alongside representative solutions. Finally, future trends in high-voltage hardware maturation, protection bottlenecks, real-time artificial intelligence, and specialized standardization are proposed. This study serves as a vital reference for the topology design and engineering standardization of PV DC collection systems. Full article

Slickwater fracturing has become an adopted technology for enhancing hydrocarbon recovery from unconventional, low-permeability reservoirs such as shale and tight formations, owing to its ability to generate complex fracture networks at a low cost. Polyacrylamide and polyacrylamide-based gels serve as key additives in these fluids, primarily functioning as drag reducers and thickeners. However, downhole environments of high-temperature (>120 °C) and high-salinity (>1 × 10⁴ mg/L) reservoirs pose challenges, leading to thermal degradation and chain collapse of conventional polyacrylamide, which results in performance loss. To address these limitations, synthesis methods including aqueous solution polymerization, inverse emulsion polymerization, and aqueous dispersion polymerization have been developed. This review provides an overview of molecular design methods aimed at enhancing performance stability of polyacrylamide-based polymers under extreme conditions. Approaches for improving thermal stability involve synthesis of ultra-high-molecular-weight polyacrylamide, copolymerization with resistant monomers, and incorporation of nanoparticles. Methods for enhancing salt tolerance focus on grafting anionic, cationic, or zwitterionic side chains onto the polymer backbone. The drag reduction mechanisms and gelation methods of these polymers in slickwater fracturing fluids are discussed. Finally, this review outlines research directions for developing next-generation polyacrylamide polymers tailored for extreme reservoir conditions, offering insights for academic research and field applications. Full article

Circulation is one of the most prevalent and severe complications during the drilling and completion of deep and ultra-deep wells, especially in fractured and karstic formations. In regions such as the Sichuan Basin, bottom-hole temperatures exceeding 200 °C, limited formation strength, and frequent lithological alternations significantly reduce the effectiveness of conventional granular materials under high-temperature and long open-hole conditions. Bridging-type plugging systems based on particle gradation or principles often exhibit low success rates due to fiber softening, rubber aging, and erosion-induced deterioration of the sealing structure. In this study, a high-temperature-resistant bridging composite system was developed to meet the extreme conditions in deep and ultra-deep wells. By incorporating temperature-resistant bridging particles and flexible reinforcing components, the slurry establishes a synergistic “bridging–filling–densification” sealing mechanism. Meanwhile, the combined use of retarders, fluid-loss reducers, and rheology modifiers ensures stable pumpability and adequate curing densification at 200 °C. Overall, the results provide new insights and experimental evidence for the design of high-temperature cement-based plugging materials, offering a promising approach for improving loss-control effectiveness and wellbore strengthening in complex intervals. Full article

The entire system collapses due to the issues of inadequate centralized storage capacity, poor scalability, low storage efficiency, and susceptibility to single point of failure brought on by huge power consumption data in the smart grid; thus, an alliance chain-driven multi-cloud storage and verifiable deletion method for smart grid data is proposed. By leveraging the synergy between alliance blockchain and multi-cloud architecture, the encrypted power data originating from edge nodes is dispersed across a decentralized multi-cloud infrastructure, which effectively mitigates the danger of data loss resulting from single-point failures or malicious intrusions. The removal of expired and user-defined data is guaranteed through a transaction deletion algorithm integrated into the indexed storage deletion chain and strengthens the flexibility and security of the storage architecture. Based on the Practical Byzantine Fault-Tolerant Consensus Protocol with Ultra-Low Storage Overhead (ULS-PBFT), by the hierarchical grouping of nodes, the system communication overhead and storage overhead are reduced. Security analysis proves that the scheme can resist tampering attacks, impersonation attacks, collusion attacks, double spend attacks, and replay attacks. Performance evaluation shows that the scheme improves compared to similar methods. Full article

To clarify how flow-channel configuration and wall spacing govern the hydrodynamic performance of an oscillating-hydrofoil biomimetic pumping device, this study conducted a systematic numerical investigation under confined-flow conditions. Using a finite-volume solver with an overset-grid technique, we compared pumping performance across three channel configurations and a range of channel–wall distances. The results showed that bidirectional-channel confinement suppresses wake deflection and irregular vorticity evolution, enabling symmetric and periodic vortex organization and thereby improving pumping efficiency by approximately 33.6% relative to the single-channel case and by 62.7% relative to the no-channel condition. Wall spacing exhibited a distinctly non-monotonic influence on performance, revealing two high-performance regimes: under extreme confinement (gap ratio $h/c=$ 1.4), the device attains peak pumping and thrust efficiencies of 19.9% and 30.7%, respectively, associated with a strongly guided jet-like transport mode; and under moderate spacing ($h/c=$ 2.2–2.6), both efficiencies remain high due to an improved balance between directional momentum transport and reduced vortex-evolution losses. These findings identify key confinement-driven mechanisms and provide practical guidance for optimizing flow-channel design in ultralow-head oscillating-hydrofoil pumping applications. Full article

High electrostrain, excellent thermal stability, and low hysteresis are critical requirements for advanced high-precision actuators. However, simultaneously achieving these synergistic properties in lead-free ferroelectric ceramics remains a significant challenge. In this work, a targeted B-site doping strategy was employed to develop novel lead-free (0.99-x)BaTiO₃-xBaZrO₃-0.01Bi(Zn_2/3Nb_1/3)O₃ (BT-xBZ-BZN, x = 0–0.2) ceramics. Systematic investigation identified optimal Zr⁴⁺ substitution at x = 0.1, which yielded an outstanding combination of electromechanical properties. For this optimal composition, a high unipolar electrostrain (S_max = 0.11%) was achieved at 50 kV/cm, accompanied by an ultra-low hysteresis (H_S = 1.9%). Concurrently, a large electrostrictive coefficient (Q₃₃ = 0.0405 m⁴/C²) was determined, demonstrating excellent thermal robustness with less than 10% variation across a broad temperature range of 30–120 °C. This superior comprehensive performance is attributed to a composition-driven evolution from a long-range ferroelectric to a pseudocubic relaxor state. In this state, the dominant electrostrictive effect, propelled by reversible dynamics of polar nanoregions (PNRs), minimizes irreversible domain switching. These findings not only present BT-xBZ-BZN (x = 0.1) as a highly promising lead-free candidate for high-precision, low-loss actuator devices, but also provide a viable design strategy for developing high-performance electrostrictive materials with synergistic large strain and superior thermal stability. Full article

Insider threats remain a serious concern for organisations in both public and private sectors. Detecting anomalous behaviour in enterprise environments is critical for preventing insider incidents. While many prior studies demonstrate promising results using deep learning on offline datasets, few address real-time operationalisation or calibrated alert control within a Security Information and Event Management (SIEM) workflow. This paper presents a SIEM-integrated prototype that fuses the Computer Emergency Response Team Insider Threat Test Dataset (CERT) enterprise logs (Logon, Device, HTTP, and Email) with behavioural biometrics from the Balabit mouse dynamics dataset. Per-modality one-dimensional convolutional neural network (1D CNN) branches are trained independently using imbalance-aware strategies, including downsampling, class weighting, and focal loss. A unified 20 × N feature schema ensures train–serve parity and consistent feature validation during live inference. Post-training calibration using Platt and isotonic regression enables analyst-controlled threshold tuning and stable alert budgeting inside the SIEM. The models are deployed in Splunk’s Machine Learning Toolkit (MLTK), where dashboards visualise anomaly timelines, risky users or hosts, and cross-stream overlaps. Evaluation emphasises operational performance, precision–recall balance, calibration stability, and throughput rather than headline accuracy. Results show calibrated, controllable alert volumes: for Device, precision ≈0.70 at recall ≈0.30 (PR-AUC = 0.468, ROC-AUC = 0.949); for Logon, ROC-AUC = 0.936 with an ultra-low false-positive rate at a conservative threshold. Batch CPU inference sustains ≈70.5 k windows/s, confirming real-time feasibility. This study’s main contribution is to demonstrate a calibrated, multi-modal CNN framework that integrates directly within a live SIEM pipeline. It provides a reproducible path from offline anomaly detection research to Security Operations Centre (SOC)-ready deployment, bridging the gap between academic models and operational Cybersecurity practice. Full article

To address the energy and environmental challenges, this study targets the need for ultra-low energy buildings in China’s hot summer-cold winter region (HSCW) by developing high-performance alkali-activated foam concrete (AAFC) insulation material. Initially, a target performance indicator system was established. Subsequently, a mix proportion design method based on the volume method was proposed, and preliminary mix proportions were designed and tested to achieve the target performance. Accordingly, eight factors, including alkali equivalent and SiO₂ aerogel content, were selected for further optimization. A systematic optimization of performance was then conducted using an L₃₂(4⁸) orthogonal experimental design. Range analysis and analysis of variance indicated that foam content significantly affected all target properties. The water-to-binder ratio notably influenced mechanical performance and dry density. Alkali equivalent and activator modulus directly regulated the reaction process. Notably, the incorporation of 2.5 wt% SiO₂ aerogel reduced the thermal conductivity to 0.1107 W/(m·K), highlighting its significant role in improving thermal insulation and effectively resolving the common trade-off between insulation and mechanical properties in FC. Furthermore, the waterproofing agent played a critical role in reducing water absorption and enhancing frost resistance. Finally, the optimal mix proportion was determined through matrix analysis, with all material properties meeting the expected targets. Test results confirmed that the optimized FC achieved a dry density of 576.34 kg/m³, compressive and flexural strengths of 5.83 MPa and 1.41 MPa, respectively, a drying shrinkage rate of only 0.614 mm/m, a mass water absorption of 3.87%, and strength and mass loss rates below 10.5% and 1.8% after freeze–thaw cycles. Therefore, this material presents a novel solution for the envelope structures of low-energy buildings. Full article

Background: Comprehensive and accurate compound composition characterization in natural sources has high relevance in food and nutrition, health and medicine, environmental and agriculture research areas, though profiling of plant metabolites is a challenging task due to the structural complexity of natural products. This study delves into the identification and characterization of compounds within the Plantago genus, leveraging state-of-the-art analytical techniques. Methods: Utilizing an ultra-high-performance liquid chromatography (UHPLC) system in conjunction with Orbitrap™ IQ-X™ Tribrid™ mass spectrometer (MS), we employed a Phenyl-Hexyl HPLC column alongside optimized extraction protocols to analyze both husk and leaf samples. To maximize compound identification, we implemented data-dependent acquisition (DDA) methods including MS² (ddMS2), MS³ (ddMS3), AcquireX™ deep scan, and real-time library search (RTLS). Results: Our results demonstrate a significant increase in the number of putatively yet confidently assigned compounds, with 472 matches in P. lanceolata leaves and 233 in P. ovata husk identified through combined acquisition methods. The inclusion of an additional fragmentation level (MS³) noticeably enhanced the confidence in compound annotation, facilitating the differentiation of isomeric compounds. Furthermore, the application of low-energy fragmentation (10 normalized collision energy (NCE) for higher-energy collisional dissociation (HCD)) improved the detection and grouping of MS¹ fragments by 55% in positive mode and by 16% in negative mode, contributing to a more comprehensive analysis with minimal loss in compound identification. Conclusions: These advancements underscore the potential of our methodologies in expanding the chemical profile of plant materials, offering valuable insights into natural product analysis and dereplication of untargeted data. Full article

This work presents a compact printed MIMO antenna specifically designed for portable wireless applications, offering strong isolation between its elements. The antenna consists of two ultra-low-profile inverted-F antenna (IFA) elements placed back to back with a close spacing of just 0.05λ at the resonance frequency (2.4 GHz). To improve isolation, a parasitic structure is strategically positioned between the two IFAs. Additionally, a slot is introduced into the ground plane, which excites an extra resonance, effectively broadening the antenna’s operational bandwidth. The proposed design was successfully fabricated and tested, with measurement results closely matching the simulations. The antenna demonstrates a good impedance bandwidth ranging from 2.28 to 2.85 GHz, maintaining a return loss better than 10 dB, and achieving excellent isolation levels exceeding 40 dB. It also delivers a high peak efficiency of 90% and a realized gain pattern of around 2 dBi over the band of interest. In addition, the inclusion of the parasitic element further enhances the antenna’s performance by promoting pattern diversity and reducing the correlation between radiation patterns, ensuring robust MIMO and diversity characteristics. Full article

High-performance dielectric materials that can be processed at ultra-low temperatures are essential for next-generation LTCC technologies and compact RF–microwave components. In this work, a multicomponent Bi–Fe–Nb oxide system was synthesized using a modified citrate sol–gel method and thermally treated at only 400 °C to investigate its structural evolution and dielectric behavior. XRD and Raman analysis revealed the coexistence of a well-crystallized BiOCl phase embedded within a partially amorphous Bi–Fe–Nb–O matrix. SEM and EDS mapping confirmed the presence of two distinct microstructural regions, reflecting differences in local composition and crystallization kinetics. Microwave measurements at 2.7 and 5.0 GHz showed low dielectric losses and a stable dielectric response. Impedance spectroscopy in the RF range revealed strong Maxwell–Wagner polarization at low frequencies and thermally activated relaxation evidenced by the temperature shift in the modulus and impedance peaks. Arrhenius analysis of the relaxation frequencies yielded similar activation energies from both modulus and impedance formalisms, indicating a single underlying relaxation mechanism. Equivalent-circuit fitting confirmed non-Debye behavior, with nearly temperature-independent capacitance and decreasing resistance consistent with thermally activated conduction. These results demonstrate that the Bi–Fe–Nb system exhibits promising dielectric stability and functional behavior even when processed at exceptionally low temperatures. Full article

All-medium metamaterial absorbers (MMAs) have attracted considerable attention for ultra-broadband electromagnetic wave (EMW) absorption. Herein, a lightweight graphene aerogel (GA) was synthesized through a low-temperature, atmospheric-pressure reduction route. Benefiting from its 3D porous network, enriched oxygen-containing functional groups, and improved graphitization, the GA offers diverse intrinsic attenuation pathways and a limited effective absorption bandwidth (EAB) of only 6.46 GHz (11.54–18.00 GHz at 1.95 mm). To clarify its attenuation mechanism, nonlinear least-squares fitting was used to quantitatively separate electrical loss contributions. Compared with graphene, the GA shows markedly superior attenuation capability, making it a more suitable medium for MMA design. Guided by equivalent circuit modeling, a stacked frustum-configured GA-based MMA (GA-MMA) was developed, where structure-induced resonances compensate for the intrinsic absence of magnetic components in the GA, thereby substantially broadening its absorption range. The GA-MMA achieves an EAB of 40.7 GHz (9.1–49.8 GHz, reflection loss < −10 dB) and maintains stable absorption under incident angles up to ± 70°. Radar cross-section simulations further indicate its potential in electromagnetic interference mitigation, human health protection, and defense information security. This work provides a feasible route for constructing ultralight and broadband MMAs by coupling electrical loss with structural effects. Full article

Efficient last-mile delivery remains a critical challenge for rural agricultural logistics, globally, particularly in cold-climate regions with dispersed agricultural operations. Truck–drone hybrids can reduce delivery times but face payload limits, cold-weather battery loss, and beyond-visual-line-of-sight regulations. This review evaluates the potential of GIS-enabled truck–drone hybrid systems to overcome infrastructural, environmental, and operational barriers in such settings. This study uses the state of North Dakota (USA) as a representative case because of its cold climate, low density, and weak connectivity. These conditions require different routing and system assumptions than typical regions. The study conducts a systematic review of 81 high-quality publications. It identifies seven interconnected research domains: GIS analytics, truck–drone coordination, smart agriculture integration, rural implementation, sustainability assessment, strategic design, and data security. The findings stipulate that GIS enhances hybrid logistics through route optimization, launch site planning, and real-time monitoring. Additionally, this study emphasizes the rural, low-density context and identifies specific gaps related to cold-weather performance, restrictions to line-of-sight operations, and economic feasibility in ultra-low-density delivery networks. The study concludes with a roadmap for research and policy development to enable practical deployment in cold-climate agricultural regions. Full article

To address the research bottlenecks in the performance mechanism and engineering application of high-content SBS-modified asphalt (SBS content ≥ 6%), this study used 70# and 90# base asphalts as raw materials to prepare modified asphalts with SBS contents of 5%, 8%, 10%, and 12% via a high-speed shearing-stirring process. Combined with conventional performance tests (penetration, ductility, elastic recovery), rheological analysis (dynamic shear rheology (DSR), rotational viscosity), and micro-characterization (Scanning Electron Microscopy (SEM), X-ray photoelectron spectroscopy (XPS)), the regulatory mechanisms of SBS content, base asphalt type, and aging process (RTFOT short-term aging, PAV long-term aging) on asphalt performance were systematically investigated. The results showed that with the increase in SBS content, the asphalt’s increased consistency (as indicated by decreased penetration), low-temperature crack resistance (5 °C ductility increased by more than 5 times), and high-temperature rutting resistance (60 °C complex shear modulus G* increased by 17 times) were significantly enhanced. Due to its higher content of light components, the 90# base asphalt exhibited a better modification effect than the 70# base asphalt. At 12% SBS content, the 5 °C ductility and 60 °C G* of the 90# base asphalt system reached 49.42 cm and 41.62 kPa, respectively. High-content SBS optimized the viscoelastic balance of asphalt: the 70# base asphalt system with 10–12% SBS content showed a phase angle δ < 45° (elasticity-dominated), and the modified asphalt with 12% SBS content exhibited a decrease in fatigue factor (G*sinδ) after PAV aging, indicating excellent fatigue resistance stability. The aging process significantly increased asphalt viscosity (the viscosity of 70# base asphalt with 10% SBS increased by 242% after PAV aging at 135 °C), while high-content SBS inhibited aging deterioration—the penetration ratio of both systems exceeded 96% at 10% SBS content. At the microscale, 10% SBS content enabled the asphalt to form a continuous and dense network structure, reducing carbon loss and slowing oxygen incorporation. Based on PG classification, the modified asphalt with 12% SBS content reached the PG100 grade, which can meet the needs of heavy-load and high-temperature scenarios such as high-toughness ultra-thin asphalt wearing courses. This study provides a key theoretical basis and data support for the content design and engineering promotion of high-content SBS-modified asphalt. Full article