Search Results (42)

Driven by 5G/6G and the Internet of Things (IoT), wireless sensor networks (WSNs) are confronted with core challenges such as limited energy constraints, unbalanced resource allocation, and security vulnerabilities. To address these, WSNs are integrated with cognitive radio networks (CRNs) to alleviate spectrum scarcity, and reconfigurable intelligent surfaces (RIS) are adopted to enhance performance, but traditional passive RIS suffers from “double fading” (signal path loss from transmitter to RIS and RIS to receiver), which undermines WSNs’ energy efficiency and the physical layer security (PLS) (e.g., secrecy rate, SR) of primary users (PUs) in CRNs. This study leverages symmetry to develop an active RIS framework for WSN-integrated CRNs, constructing a tripartite collaborative model where symmetric beamforming and resource allocation improve WSN connectivity, reduce energy consumption, and strengthen PLS. Specifically, three symmetry types—resource allocation symmetry, beamforming structure symmetry, and RIS reflection matrix symmetry—are formalized mathematically. These symmetries reduce the degrees of freedom in optimization (e.g., cutting precoding complexity by ~50%) and enhance the directionality of green interference, while ensuring balanced resource use for WSN nodes. The core objective is to minimize total transmit power while satisfying constraints of PU SR, secondary user (SU) quality-of-service (QoS), and PU interference temperature, achieved by converting non-convex SR constraints into solvable second-order cone (SOC) forms and using an alternating optimization algorithm to iteratively refine CBS/PBS precoding matrices and active RIS reflection matrices, with active RIS generating directional “green interference” to suppress eavesdroppers without artificial noise, avoiding redundant energy use. Simulations validate its adaptability to WSN scenarios: 50% lower transmit power than RIS-free schemes (with four CBS antennas), 37.5–40% power savings as active RIS elements increase to 60, and a 40% lower power growth slope in multi-user WSN scenarios, providing a symmetry-aided, low-power solution for secure and efficient WSN-integrated CRNs to advance intelligent WSNs. Full article

Heat-treated wood is widely used for its eco-friendliness and aesthetic appeal. However, it is prone to fading under ultraviolet (UV) radiation, which diminishes its decorative effect and shortens its service life. To clarify the performance evolution and degradation mechanisms of heat-treated wood, Chinese fir, treated at 190 °C under vacuum, was subjected to artificial weathering, and the dynamic changes in surface appearance, chemical composition, and microstructure were monitored. The results show that after artificial weathering, both heat-treated and untreated wood exhibited similar surface color change trends, characterized by darkening, yellowing, and reddening, but heat treatment significantly inhibited surface color changes. After 372 h of weathering, the total color change of heat-treated wood (ΔE = 24.05) was smaller than that of the untreated wood (ΔE = 37.78), and its yellowness index (b* = 58.93%) was also far lower than the untreated group (b* = 119.85%). Additionally, the gloss of heat-treated Chinese fir increased by 17% during weathering. However, as weathering progressed, the protective effect of heat treatment on the appearance gradually weakened, and it could not prevent long-term structural breakdown. The improved color stability is closely linked to condensed lignin and unsaturated phenolic chromophores, while the preferential thermal decomposition of hemicelluloses creates “weathering-vulnerable zones”. This study provides both a theoretical basis for understanding the weathering behavior of heat-treated wood and practical guidance for optimizing wood protection technologies. Full article

Long Range Wide Area Network (LoRaWAN) has become an attractive option for maritime communication because it is low-cost, long-range, and energy-efficient. Yet its performance at sea is often limited by fading, interference, and the strict energy budgets of maritime Internet of Things (IoT) devices. This review, prepared in line with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020 guidelines, examines 23 peer-reviewed studies published between 2019 and 2025 that explore adaptive antenna solutions for LoRaWAN in marine environments. The work covered four main categories: switched-beam, phased array, reconfigurable, and Artificial Intelligence or Machine Learning (AI/ML)-enabled antennas. Results across studies show that adaptive approaches improve gain, beam agility, and signal reliability even under unstable conditions. Switched-beam antennas dominate the literature (45%), followed by phased arrays (30%), reconfigurable designs (20%), and AI/ML-enabled systems (5%). Unlike previous reviews, this study emphasizes maritime propagation, environmental resilience, and energy use. Despite encouraging results in signal-to-noise ratio (SNR), packet delivery, and coverage range, clear gaps remain in protocol-level integration, lightweight AI for constrained nodes, and large-scale trials at sea. Research on reconfigurable intelligent surfaces (RIS) in maritime environments remains limited. However, these technologies could play an important role in enhancing spectral efficiency, coverage, and the scalability of maritime IoT networks. Full article

As an emerging technology, Reconfigurable Intelligent Surfaces (RIS) offers an efficient communication performance optimization solution for the complex and spatially constrained environment of coal mines by effectively controlling signal-propagation paths. This study investigates the channel attenuation characteristics of a semi-circular arch coal-mine tunnel with a dual RIS reflection link. By jointly optimizing the base-station beamforming matrix and the RIS phase-shift matrix, an improved Twin Delayed Deep Deterministic Policy Gradient (TD3)-based algorithm with a Noise Fading (TD3-NF) propagation optimization scheme is proposed, effectively improving the sum rate of the coal-mine wireless communication system. Simulation results show that when the transmit power is 38 dBm, the average link rate of the system reaches 11.1 bps/Hz, representing a 29.07% improvement compared to Deep Deterministic Policy Gradient (DDPG). The average sum rate of the 8 × 8 structure RIS is 3.3 bps/Hz higher than that of the 4 × 4 structure. The research findings provide new solutions for optimizing mine communication quality and applying artificial intelligence technology in complex environments. Full article

Contemporary murals are highly susceptible to rapid color fading due to outdoor urban exposure. This study investigates the photodegradation mechanisms affecting synthetic organic pigments (SOPs) and commercial acrylic–vinyl paints under simulated visible light exposure. Artificial aging experiments were conducted on two types of systems: (a) pigment pellets, composed of pre-fixed pigments on mineral bases, as supplied by the manufacturer, and (b) commercial paints applied on glass substrates. Both systems were aged under controlled and uncontrolled relative humidity (RH) conditions. Colorimetric analyses revealed significant color fading, particularly in pigments PR112, PO5, and PV23. Vibrational spectroscopies highlighted the reduction in pigment-related bands after aging, indicating SOPs’ vulnerability to photodegradation. In paint mock-ups, FTIR-ATR measurements indicated binder degradation and an increase in signals from inorganic fillers. A superficial layer enriched in inorganic components was investigated non-invasively by Micro Spatially Offset Raman spectroscopy (Micro-SORS) in the beamsteer modality. It highlighted a gradient of calcite to pigment with depth. These findings indicate that color fading in mural paints results from the combined degradation of both pigments and binders. Full article

The evolution of sixth-generation (6G) networks enables transformative edge Artificial Intelligence of Things (AIoT) applications but introduces critical security vulnerabilities during model transmission between the central server and edge devices (e.g., unmanned aerial vehicles). Traditional approaches fail to jointly optimize model accuracy and physical layer security against eavesdropping. To address this gap, we propose a novel dynamic user selection framework that integrates three key innovations: (1) closed-form secrecy outage probability derivation for Rayleigh fading channels, (2) a Secure Model Accuracy (SMA) metric unifying recognition accuracy and secrecy outage probability, and (3) an alternating optimization algorithm for joint model–bandwidth selection under secrecy constraints. Comprehensive simulations demonstrate 22% SMA gains over baselines across diverse channel conditions and eavesdropper capabilities, resolving the fundamental accuracy–security tradeoff for trustworthy edge intelligence. Full article

As first-hand testimonies and accounts of the Holocaust fade, scholars and artists alike have struggled to depict and contextualize the genocide’s monumental violence. But depicting violence and its aftermath poses several problems, including the question of how to recall loss without artificially filling in or effacing the absence so central to its understanding. In essence, remembering the Holocaust is a paradox: the preservation of an absence. Marianne Hirsch’s influential concept of postmemory addresses this paradox and asks questions about memorial capacity in the twenty-first century. This essay considers Hirsch’s postmemory in the context of W.G. Sebald’s 2001 novel Austerlitz, which uses a combination of prose and photography to engage the difficulties inherent in memory work without access to eyewitnesses. Through the interaction of printed text and images, Austerlitz subtly references Lurianic mysticism’s concept of tikkun and Tree of Life (ilanot) diagrams. The result is a depiction of memory that is both process-based and embodies absence. My reading of Austerlitz traces a Jewish heritage within the work of a non-Jewish German author by attending to a tradition of mystical thought embedded in the novel. This situates Sebald’s fiction in a much longer Jewish history that stretches out on either end of the event of the Holocaust. Structurally, Sebald develops a tikkun-like process of (re)creation which relies on gathering material scraps of the past and imaginatively engaging with their absences in the present. Images, just as much as text, are central to this process. Reading Austerlitz in the context of Kabbalah reveals an intellectual and artistic link to a Jewish history that, while predating the Holocaust, nonetheless sheds light on post-Holocaust memories of loss. Full article

The advancement of intelligent road transport represents a promising direction in the evolution of transportation systems, aimed at improving road safety and reducing traffic accidents. The integration of artificial intelligence, sensors, and machine vision systems enables autonomous vehicles (AVs) to rapidly adapt to changes in the road environment, minimizing human error and significantly reducing collision risks. These technologies provide continuous and highly precise control, including adaptive acceleration, braking, and maneuvering, thereby enhancing overall road safety. Connected vehicles utilizing C-V2X (Cellular Vehicle-to-Everything) communication primarily feature real-time operation, safety, and stability. However, communication flaws, such as signal fading, time delays, packet loss, and malicious network attacks, can affect vehicle-to-vehicle interactions in cooperative intelligent transport systems (C-ITSs). This study explores how C-V2X technology, compared to traditional DSRC, improves communication latency and enhances vehicle communication efficiency. Using SUMO simulations, various traffic scenarios were modeled with different autonomous vehicle penetration rates and communication technologies, focusing on traffic conflict rates, travel time, and communication performance. The results demonstrated that C-V2X reduced latency by over 99% compared to DSRC, facilitating faster communication between vehicles and contributing to a 38% reduction in traffic conflicts at 60% AV penetration. Traffic flow and safety improved with increased AV penetration, particularly in congested conditions. While C-V2X offers substantial benefits, challenges such as data packet loss, communication delays, and security vulnerabilities must be addressed to fully realize its potential. Future advancements in 5G and subsequent wireless communication technologies are expected to further reduce latency and enhance the effectiveness of C-ITSs. This study underscores the potential of C-V2X to enhance collision avoidance, alleviate congestion, and improve traffic management, while also contributing to the development of more reliable and efficient transportation systems. The continued refinement of simulation models and collaboration among stakeholders will be crucial to addressing the challenges in CAV integration and realizing the full benefits of connected transportation systems in smart cities. Full article

This paper presents research on the security performance of a multi-user interference-based mixed RF/FSO system based on SWIPT untrusted relay. In this work, the RF and FSO channels experience Nakagami-m fading distribution and Málaga (M) turbulence, respectively. Multiple users transmit messages to the destination with the help of multiple cooperating relays, one of which may become an untrusted relay as an insider attacker. In a multi-user network, SWIPT acts as a charging device for each user node. In order to prevent the untrusted relays from eavesdropping on the information, some users are randomly assigned to transmit artificial noise in order to interfere with untrusted relays, and the remaining users send information to relay nodes. Based on the above system model, the closed-form expressions of secrecy outage probability (SOP) and average secrecy capacity (ASC) for the mixed RF/FSO system are derived. The correctness of these expressions is verified by the Monte Carlo method. The influences of various key factors on the safety performance of the system are analyzed by simulations. The results show that the security performance of the system is considerably improved by increasing the signal–interference noise ratio, the number of interfering users, the time distribution factor and the energy conversion efficiency when the instantaneous signal-to-noise ratio (SNR) of the RF link instantaneous SNR is low. Full article

Wood, a natural and renewable material, is extensively utilized in furniture, construction, and outdoor landscapes due to its sustainability and esthetic appeal. However, exposure to environmental elements, particularly sunlight, leads to photodegradation, affecting wood’s chemical and physical structure. This degradation results in color fading, increased surface roughness, and reduced mechanical properties, shortening the lifespan of wooden products. Artificial accelerated photodegradation tests have become a crucial method for studying wood’s aging process under controlled laboratory conditions, mimicking prolonged exposure to sunlight. This review explores the mechanisms behind wood photodegradation, focusing on the effects of UV radiation on wood’s major components—cellulose, hemicellulose, lignin, and extractives. Additionally, it summarizes the latest advancements in experimental design for artificial aging tests, including factors like radiation source selection, temperature, and humidity control. The paper also highlights performance characterization methods for evaluating the impact of photodegradation on wood’s physical, chemical, and mechanical properties. Understanding these processes is essential for enhancing the durability of wood products and developing effective treatments for wood preservation in outdoor environments. Full article

With the rapid development of wireless communications, the occupation of time and frequency resources becomes more crowded. The exploitation of space resources is necessary and the diversity combining techniques have substantial applications. Diversity combining achieves great diversity gains and improves the ability to combat multipath fading, among which the maximum ratio combining (MRC) performs as the optimal linear combining approach. However, MRC suffers from detrimental factors such as channel fading and no Gaussian noise in practical scenarios. In this paper, we focus on a comprehensive investigation of MRC. Starting from the MRC principle and system model, we summarize typical scenarios and analyze the channel fading statistics. For the influential factors, we further review related literature on channel correlation, cochannel interference (CCI) and impulsive noise. Major performance criteria and performance bounds are derived and compared. MRC confronts new developing challenges and the major development directions are reviewed. The paper finally discusses recent works and open problems for MRC applications and development. Emerging techniques such as artificial intelligence provide novel solutions for MRC performance improvements. The paper aims to present a summarized insight to assist readers in clarifying the analyzed methodology of MRC, so as to motivate new technology integration and extensive applications of advanced communication systems. Full article

The degradation of cadmium yellow in paintings is influenced by various factors, primarily environmental conditions and light exposure. Applying a thin protective layer of linseed oil on the surface could help mitigate these processes. Linseed oil, being a natural material, acts as a barrier against harmful atmospheric agents like moisture and oxygen, which contribute to the degradation of pigments including cadmium yellow. Additionally, linseed oil reduces direct light exposure, thereby lowering the risk of fading and color alteration. In this study, we explored the degradation of cadmium pigments mixed with oil and applied on canvas. We elucidated how the use of a binder prevents the direct oxidation of the pigment, inducing artificial degradation by irradiating samples with UVA (365 nm) and UVC (250 nm) sources. By employing various spectroscopic techniques such as three-dimensional fluorescence mapping (PLE) and Raman, along with colorimetric analysis, we gained a comprehensive understanding of the degradation process, particularly when linseed oil serves as a protective layer. Full article

Osmanthus fragrans, belonging to the family Oleaceae, is listed as one of the most important traditional ornamental plant species in China. A new cultivar O. fragrans ‘Wucaigui’ has a very diversified form in terms of leaf colors, in which the leaf color changes from red to yellow-green and finally to dark green. To understand the mechanisms involved in leaf color changes, metabolome and transcriptome studies were performed on leaves at different developmental stages. A total of 79 metabolites, two chlorophyll, 26 carotenoids, and 51 anthocyanins, were detected in the 6 different developmental stages. An orthogonal partial least squares discriminant analysis identified key metabolites at different developmental stages, including lutein, pelargonidin-3-O-(6-O-p-coumaroyl)-glucoside, neoxanthin, and α-carotene. A total of 48,837 genes were obtained by transcriptome sequencing, including 3295 novel genes. Using a weighted gene co-expression network analysis to study the correlations between key metabolites and differentially expressed genes, we determined the characteristic modules having the highest correlations with key metabolites and selected associated candidate genes. Five genes (OfSHOU4L, OfATL1B, OfUGE5 OfEIF1AX, and OfUGE3) were finally identified as hub genes using real-time fluorescence quantitative PCR. In addition, we proposed a model based on the changes in key metabolite contents and the network regulatory map during the changes in O. fragrans ‘Wucaigui’ leaf color. The positive regulation of OfUGE3 led to an increase in the lutein content, which resulted in the leaves changing from grayish brown to moderate brown; during the change from moderate brown to dark greenish-yellow, the positive regulation of three genes (OfHOU4L, OfATL1B, and OfUGE5) increased the content of pelargonidin-3-O-(6-O-p-coumaroyl)-glucoside and the red color of the leaves gradually faded to dark greenish-yellow and then to strong yellow-green; the positive regulation of OfEIF1AX increased the content of neoxanthin; the stages in which the color changed from strong yellow-green to yellow-green and then to moderate olive-green were positively regulated by OfUGE3, which resulted in higher α-carotene content. These findings provided new insights into the mechanisms underlying the processes involved in O. fragrans ‘Wucaigui’ leaf color changes at the metabolic and transcriptional levels. This work seeks to contribute to the development of artificial regulate and control technology in the breeding and production of O. fragrans and other ornamental plants. Full article

The exponential growth of electric and hybrid vehicles, now numbering close to 6 million on the roads, has highlighted the urgent need to address the environmental impact of their lithium-ion batteries as they approach their end-of-life stages. Repurposing these batteries as second-life batteries (SLBs) for less demanding non-automotive applications is a promising avenue for extending their usefulness and reducing environmental harm. However, the shorter lifespan of SLBs brings them perilously close to their ageing knee, a critical point where further use risks thermal runaway and safety hazards. To mitigate these risks, effective battery management systems must accurately predict the state of health of these batteries. In response to this challenge, this study employs time-series artificial intelligence (AI) models to forecast battery degradation parameters using historical data from their first life cycle. Through rigorous analysis of a lithium-ion NMC cylindrical cell, the study tracks the trends in capacity and internal resistance fade across both the initial and second life stages. Leveraging the insights gained from first-life data, predictive models such as the Holt–Winters method and the nonlinear autoregressive (NAR) neural network are trained to anticipate capacity and internal resistance values during the second life period. These models demonstrate high levels of accuracy, with a maximum error rate of only 2%. Notably, the NAR neural network-based algorithm stands out for its exceptional ability to predict local noise within internal resistance values. These findings hold significant implications for the development of specifically designed battery management systems tailored for second-life batteries. Full article

Corrosion is one of the critical factors leading to the failure of steel structures. Ultrasonic C-scans are widely used to identify corrosion damage. Limited by the range of C-scans, multiple C-scans are usually required to cover the whole component. Thus, stitching multiple C-scans into a panoramic image of the area under detection is necessary for interpreting non-destructive testing (NDT) data. In this paper, an image mosaic method for ultrasonic C-scan based on scale invariant feature transform (SIFT) is proposed. Firstly, to improve the success rate of registration, the difference in the probe starting position in two scans is used to filter the matching pairs of feature points obtained by SIFT. Secondly, dynamic programming methods are used to search for the optimal seam path. Finally, the pixels in the overlapping area are fused by fade-in and fade-out fusion along the seam line. The improved method has a higher success rate of registration and lower image distortion than the conventional method in the mosaic of ultrasonic C-scan images. Experimental results show that the proposed method can stitch multiple C-scan images of a testing block containing artificial defects into a panorama image effectively. Full article