Search Results (864)

This paper presents a simulation-based 16-quadrature amplitude modulation (16-QAM) direct current-biased optical orthogonal frequency-division multiplexing (DCO-OFDM) visible-light optical wireless system using a 520 nm InGaN directly modulated laser (DML) and direct detection over 500 m. A 1024-point transform with 511 data subcarriers provides approximately 15 Gb/s gross and 14.82 Gb/s payload rates without external optical modulators or amplifiers. Under the adopted static line-of-sight model, the simulated bit-error rate (BER) falls below ${10}^{-3}$ at a receiver-side equivalent optical signal-to-noise ratio (OSNR) of about 17 dB and remains below this threshold for beam divergence up to 9 mrad. Gamma–Gamma simulations show that a 5 cm aperture maintains $\mathrm{BER}<{10}^{-3}$ at 20 dB OSNR up to $C_n^2\approx 5\times {10}^{-14}{\mathrm{m}}^{-2/3}$. Pointing-error analysis gives per-axis angular-jitter standard deviations of 0.425, 0.515, and 0.564 mrad at 1% outage for 5, 10, and 15 cm apertures. The clear-air margin is exhausted at $V_{2\%}\approx 0.66\mathrm{km}$, corresponding to $V_{5\%}\approx 0.50\mathrm{km}$, or near 107 mm/h rain. For a 1.5 GHz bandwidth-limited DML, adaptive bit loading reaches 16.5 Gb/s at 28 dB OSNR. The results support a low-complexity medium-range architecture but remain numerical estimates requiring experimental validation under practical device, alignment, and weather conditions. Full article

Introduction: Pedestrians lying on the road—collapsed through medical emergency, intoxication, or displacement following a prior collision—represent a disproportionately lethal and underaddressed category in road traffic safety. Forensic database analyses derived from Japan’s national police records document a fatality rate of 33.0% for collisions involving pedestrians lying on the road, more than double the rate for upright pedestrian collisions. Standard Advanced Driver-Assistance Systems (ADAS) yield a True Positive Rate (TPR) of only 21.4% for detecting pedestrians lying on the road under night conditions—a classification gap of 73.3 percentage points. Methods: In simulation trials, we evaluated the Advanced Falling Object Detection System (AFODS—where “falling object” denotes the low-profile human form at road level, distinguishing the prone pedestrian from the upright postures addressed by conventional ADAS) on a composite dataset of 3200 annotated fall events and 12,000 negative samples (training/validation), with 320 independent controlled simulation trials used for performance evaluation, spanning real-world, forensic-reconstruction, and Total Human Body Model for Safety (THUMS)-validated synthetic scenarios. No physical prototype has been evaluated; all performance data are derived from simulation, and 37.5% of positive samples are synthetically generated. These simulation conditions represent a first feasibility demonstration pending real-world hardware validation. This paper introduces three original contributions absent from prior work: a three-stage quantitative injury-risk model, a formal ISO 26262 Hazard Analysis and Risk Assessment (HARA), and a medicolegal SHAP interpretability framework. The injury-risk model translated detection latency via impact velocity to Head Injury Criterion (HIC) and estimated fatal injury probability (AIS ≥ 5); these model outputs should be interpreted as exploratory estimates pending ATD validation. Reporting follows principles consistent with the TRIPOD statement. Results: Under clear daytime conditions, AFODS demonstrated a TPR of 98.2% (95% CI: 97.4–98.8%) in simulation, decreasing to 95.6% under night dry-road conditions and 89.4% under night rain. The system achieved an AUC of 0.981 and a mean end-to-end latency of 46.5 ms, representing a 76.8 percentage-point improvement in simulation over the monocular RGB baseline (p < 0.001). The injury-risk model projects a reduction in estimated fatal head injury probability from 66.2% (Monte Carlo mean) (no detection, 50 km/h full-speed impact) to 0.7% under AFODS worst-case night/rain conditions, and to ≈0% under clear daytime simulation conditions. Conclusions: A 73.3 percentage-point classification gap places pedestrians lying on the road outside the effective detection envelope of current ADAS, compounded by the systematic exclusion of non-upright postures from regulatory test protocols and benchmark datasets. AFODS supports proof-of-concept feasibility under simulation conditions. Three translational steps are required: prototype validation on real-world hardware using instrumented Anthropomorphic Test Devices (ATDs); prone-posture biomechanical injury modelling using HIC and BrIC criteria; and regulatory extension of pedestrian AEB test standards to non-upright scenarios. Full article

The Jinsha River Basin constitutes the largest hydropower base in China. However, its complex terrain results in insufficient accurate data support for numerical forecasts, leading to low accuracy in precipitation predictions. To investigate the spatiotemporal distribution characteristics of precipitation in this basin with high precision, we evaluated the applicability of several mainstream precipitation products—GSMAP (Global Satellite Mapping of Precipitation), GPM-IMERG (Integrated Multi-satellite Retrievals for Global Precipitation Measurement), CMORPH (Climate Prediction Center Morphing technique), and ERA5 (European Center for Medium-Range Weather Forecasts Reanalysis 5)—in the Jinsha River Basin. Based on the XGBoost algorithm, we developed a merging model that integrates satellite and reanalysis data with station observations for daily-scale applications. The results indicate that the GSMAP-Gauge precipitation product exhibits strong performance in both quantitative accuracy and precipitation event detection, with a better correlation coefficient (CC = 0.66), the lowest root mean square error (RMSE = 4.45), and higher probability of detection (POD = 0.88) and critical success index (CSI = 0.59). The ERA5 and GSMAP-Gauge products performed well in detecting light rain events (daily precipitation < 10 mm), with hit rates of 0.92 and 0.90, respectively. Meanwhile, the GPM-IMERG and CMORPH-BLD products showed higher hit rates for heavy rain events (daily precipitation > 25 mm) compared to the other two products. Specifically, the POD indices for GPM-IMERG and CMORPH-BLD were 0.45 and 0.60, respectively, while those for ERA5 and GSMAP-Gauge were below 0.4. Following the precipitation merging experiment, the multi-source precipitation merged product (MSP) substantially enhanced the accuracy of precipitation estimates, and the spatiotemporal distribution characteristics of the merged data aligned more closely with the station observations. This study analyzes the strengths and limitations of various precipitation products in the Jinsha River Basin and provides a feasible multi-source precipitation data merging scheme, offering a novel approach to constructing high-precision daily precipitation datasets in complex terrain regions. Full article

Rainfall-induced landslides are destructive natural hazards that require timely detection and early warning to protect lives and infrastructure. This study presents the development and deployment of an IoT-based, cost-effective, real-time monitoring and early warning system that integrates surface and subsurface sensors to detect slope instability and issue timely warnings for disaster prevention. The monitoring system integrates tilt sensors, volumetric water content sensors, a MEMS-based inclinometer, a rain gauge, and a video camera, all linked to a web-based platform. Field results demonstrated that the tilt sensors effectively detected surface displacement, the volumetric water content sensors responded rapidly to rainfall infiltration, and the MEMS-based inclinometer captured subsurface displacement during rainfall events. Detailed analysis was conducted using multisource monitoring datasets collected during three specific rainfall events. An early warning method for landslides was proposed by combining the tilt rate, horizontal displacement rate derived from the MEMS-based inclinometer, and saturation index. Accordingly, critical threshold values for different warning levels were established based on tilt rate (T_r), displacement rate (D_r), and saturation index (S_i). This study provides a robust strategy and guidelines for early warning systems, enabling generation of warning alarms and demonstrating immense potential to reduce the impacts of rainfall-induced shallow landslides and enhance risk management. Full article

Fall armyworm, Spodoptera frugiperda (J.E. Smith), has emerged as one of the most damaging invasive pests affecting maize production and household food security across sub-Saharan Africa since its first detection in 2016. This systematic review synthesizes empirical evidence published between 2016 and 2025 to assess the agronomic, livelihood, and food security impacts of FAW on smallholder farming systems across Eastern, Southern, Western, and Central Africa. Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and the Population, Intervention, Comparison, Outcome, Time, and Setting (PICOTS) framework, 20 studies (17 empirical and 3 contextual) were identified through comprehensive searches of academic databases and institutional repositories and were included in the final synthesis after methodological screening. The evidence indicates that FAW invasion causes substantial maize yield losses ranging from approximately 20% to 50%, with the greatest reductions reported in rain-fed systems with limited access to pest management technologies. Infestation rates frequently exceeded 50%, particularly during early invasion phases. Beyond agronomic losses, several studies reported reduced household income, constrained food availability, and livelihood disruptions, including increased labor requirements, higher production costs, and reliance on short-term coping strategies. Only a small proportion of studies (n = 4) directly assessed nutrition-related indicators, but the available evidence indicates declines in dietary diversity in severely affected communities. Overall, the agronomic impacts of FAW are consistently documented across regions, whereas the socioeconomic and nutrition outcomes remain comparatively underreported, indicating a significant evidence gap. These findings highlight FAW as both an agronomic and livelihood challenge, underscoring the need for integrated pest management strategies, strengthened extension services, and coordinated policy responses to safeguard food and income security among smallholder farmers in Africa. Full article

Grassland highways present a distinctive application context for human–machine co-driving (HMCODR), yet the evidence on takeover behavior in such environments remains limited. This study employed a driving simulator experiment to investigate how takeover scenarios, weather conditions, and driver gender influence eye-movement behavior during automated-driving takeovers on a representative Inner Mongolia grassland highway. 36 student participants completed a 2 (gender) × 3 (scenario: stationary vehicle ahead, ramp vehicle merging, and livestock intruding into lane) × 3 (weather: clear, rain–snow, and sandstorm) mixed experimental design. The mean fixation duration (MFD), fixation rate (FR), mean saccade duration (MSD), saccade amplitude (SA), and relative change in pupil area (RCPA) were recorded using a wearable eye tracker, and a mixed-design ANOVA was conducted based on these five metrics. The scenario and weather had significant effects on all eye-movement measurements (p < 0.05), with interactions observed for some indices. The ramp vehicle merging scenario elicited denser visual scanning, as reflected by a shorter MFD and a higher FR. In the livestock intruding into lane scenario, drivers exhibited a broader visual search, characterized by a longer MSD and a larger SA, along with greater pupil-area fluctuations (a higher RCPA); these effects tended to be more pronounced under rain–snow and sandstorm conditions. Across most of the condition combinations, the female drivers tended to show a higher FR, a shorter MFD, and a higher RCPA, whereas male drivers tended to show a slightly larger MSD and SA. Among all the eye-movement indices, RCPA showed a relatively more pronounced gender difference, with female drivers exhibiting values approximately 16–32% higher than male drivers. These findings extend the takeover research to grassland highway contexts and suggest that takeover assistance should place greater emphasis on hazard-relevant cues and timely gaze guidance under complex scenarios and adverse weather conditions, while the observed differences in the visual-response patterns may also inform more personalized prompting strategies to better support safety in high-risk takeover situations. Full article

A study of agricultural yield sensitivity in Peru to climate variations is conducted from 1961 to 2024 to identify climate drivers and statistical tools for early warning and risk management. The statistical basis is year-on-year change in standardized crop yield rate (CYR) across the southeastern highlands of Peru 7–15° S, 70–77° W. Crops favoring La Nina include citrus, cotton, fruit, and sugar-cane. Based on temporal and spatial correlation and composite analysis, our findings indicate that (i) east Pacific and Caribbean sea temperatures and Atlantic upper winds provide advance warning signals of CYR fluctuations; (ii) during El Niño, the subtropical jet subsides over the Peruvian highlands, raising temperatures and lowering humidity; (iii) during La Niña, cooler temperatures conspire with rising motion and beneficial rains; and (iv) CYR fluctuations account for 26% of macro-economic variance, ~$66 B at the current value. Bringing technological information to agricultural decision making will improve resilience and help meet the twin challenges of a growing population and changeable climate. Adaptive measures are suggested to take advantage of Southern Oscillation’s influence on austral summer weather and subsequent annual crop yield. Full article

The radial structure and azimuthal asymmetry of tropical cyclone (TC) eyewall winds are critical for intensity change and wind-related hazards, yet they remain difficult to characterize using conventional observations. Using multi-platform C-band synthetic aperture radar (SAR) wind fields and collocated Stepped Frequency Microwave Radiometer (SFMR) wind speed and rain-rate observations, this study examined TC inner-core structure, eyewall asymmetry, and rainfall-dependent wind retrieval uncertainty for 51 TCs and 130 SAR scenes. The TC inner-core structure was characterized using a best-track-constrained center refinement and quality control procedure, in which the storm center was refined from the minimum of a Gaussian-smoothed SAR wind field and scenes were screened by eye/annulus sampling, eye–eyewall contrast, and annular wind organization. Of the 130 SAR scenes, 53 were retained for refined-center evaluation, and the 32 QC-passed scenes were used for the primary storm-centered structural analysis. The RMW showed a weak tendency to decrease with an increasing SAR-derived maximum azimuthal-mean wind speed, and the normalized wavenumber-1 asymmetry at the RMW decreased in stronger storms. Under strict temporal collocation ($\left|\Delta t\right|\le 30$ min), the SAR–SFMR comparison achieved an RMSE of 4.22 m s⁻¹, a bias of −1.61 m s⁻¹, $R^2$ = 0.82, and a regression slope of 0.90. Rainfall-related SAR–SFMR mismatch was most evident around the eyewall and adjacent outer-eyewall region, indicating the need to consider center uncertainty, scene suitability, temporal collocation, and rain-sensitive retrieval effects when interpreting SAR-derived TC inner-core structure. Full article

Maize production in the black soil region of Northeast China is highly vulnerable to drought and flood stress, yet stage-specific mechanisms under rain-fed conditions remain unclear. Daily meteorological records from 1951 to 2024 were used to calculate the Crop Water Surplus Deficit Index (CWSDI) for four maize phenological stages, and 2025 in situ soil moisture and temperature observations were used to derive root-zone soil water storage (SWS), soil water depletion rate (SWDR), and the soil temperature–moisture coupling index (STMI). The growing season showed a persistent water deficit (mean CWSDI = −39.19%). Drought risk was greatest during sowing–jointing (S1; CWSDI = −64.73%; drought frequency = 73.0%) and milk–maturity (S4; CWSDI = −49.84%; drought frequency = 58.1%), whereas jointing–tasseling (S2) had the highest flood frequency (13.5%). Soil hydrothermal indicators showed that S1 drought was evaporation-driven, S2 involved potential hot-wet compound stress, tasseling–milk (S3) had rapid root-zone water depletion, and S4 drought was driven by insufficient late-season precipitation. These findings show that maize water stress is a sequence of stage-specific mechanisms rather than a uniform seasonal phenomenon. We therefore propose a regulation strategy combining soil moisture conservation, rainwater harvesting, precision supplemental irrigation, and field drainage to improve maize resilience. Full article

Photoperiod-sensitive sweet sorghum (Sorghum bicolor L. Moench) accumulates biomass and sugars during vegetative growth, making it a silage candidate where water limits maize production. This study examined how harvest date and nitrogen (N) rate affect its forage quality and in vitro rumen gas production under rain-fed conditions. In a randomized complete block design with three replications, we evaluated dry matter (DM) yield, morphology, and chemical composition of sweet sorghum harvested at 80 and 110 days after planting (DAP) under five N rates (0, 75, 150, 225, and 300 kg N/ha). Each treatment was ensiled in laboratory-scale bag silos for 90 days. Silage was analyzed for silage quality and 48-h in vitro rumen gas production and fermentation parameters. Delaying harvest from 80 to 110 DAP increased DM yield and fiber fractions (NDF, ADF, lignin), but reduced crude protein (CP), water-soluble carbohydrates (WSC), and in vitro dry matter digestibility (IVDMD) in fresh forage (p < 0.001). Increasing the N rate up to 225 kg N/ha enhanced DM yield, CP, and WSC at both harvest dates. A harvest date × N rate interaction occurred for WSC (p < 0.05). After ensiling, CP and IVDMD were higher in 80-DAP silage. Butyric acid (BA) and ammonia-N (NH₃-N) increased with N rate, but at ≥225 kg N/ha both were lower in 80 DAP silage. The highest 48-h gas production (71.2 and 61.0 mL/200 mg DM) occurred in forage and silage from 110 DAP with 150 kg N/ha. Ruminal pH remained optimal range (6.2–6.8) across treatments. Harvest date and N rate interactively influence sweet sorghum silage quality and rumen fermentability. Under rain-fed conditions, 80 DAP with 225 kg N/ha optimizes silage quality, while 110 DAP with 150 kg N/ha maximizes rumen fermentation potential. These findings support sweet sorghum as a viable silage option where maize production is constrained by water availability. Full article

South China is characterized by abundant and complex precipitation, with frequent typhoons, heavy rainfall, and pronounced extreme events, making it an ideal region for precipitation microphysics research. This study uses rainfall observations from an OTT Parsivel² (Parsivel) laser disdrometer and a Micro Rain Radar–2 (MRR–2) collected in Zhuhai during 2022–2023 to analyze the characteristics of stratiform rainfall (SR) and convective rainfall (CR). The results show that, although SR lasts longer, CR contributes much more to the total accumulated rainfall. In SR, samples with rain rate (RR) < 5 mm h⁻¹ account for about 27% of occurrences and contribute less than 10% of total rainfall, whereas in CR, samples with RR > 8 mm h⁻¹ represent only 7% of occurrences but contribute more than 45% of the accumulated rainfall. CR is characterized by a larger mass-weighted mean diameter (Dm), while SR shows a higher normalized intercept parameter (Nw). In SR, Dm increases with RR, whereas Nw changes little; in CR, both Dm and Nw increase with RR. Finally, by analyzing temporal/spatial collocated vertical rain profiles from MRR and Global Precipitation Measurement Dual-frequency Precipitation Radar (GPM DPR), the results show that CR exhibits larger RR, radar reflectivity and stronger vertical variability than SR, along with greater variations in Dm and log₁₀(Nw). Ground-based MRR also provides an independent vertical reference for evaluating DPR-derived precipitation structure and interpreting the consistency and discrepancies between satellite and ground-based observations. Although the results are not conclusive due to a limited number of events, both instruments capture distinct microphysical characteristics in the analyzed SR and CR cases, despite differences in their retrieved vertical DSD structures. Full article

Various global precipitation datasets have been used in precipitation-related fields such as hydrology, meteorology, climatology, and ecology to achieve different research objectives. Error analysis is an integral part before applying them to operational fields. However, the growing number of precipitation products and the absence of comprehensive error comparison research jointly impede users in distinguishing product-specific error patterns and constrain developers from enhancing precipitation estimation accuracy. To address this issue, we performed error analysis and comparison of thirteen global precipitation products—categorized as delayed time (DT), near real-time (NRT), and real-time (RT) types—across mainland China. Results revealed that GSMaP-Gauge (Gauge-adjusted Global Satellite Mapping of Precipitation) performed best in terms of detection indicators, while MGP (Multi-source merged global precipitation product) performed best in estimating precipitation accuracy. However, IMERG-Final (Integrated Multisatellite Retrievals for Global Precipitation Measurement Final Run) proved ineffective in reducing the overestimations of both storm and light precipitation events in regions of complex topography. Furthermore, two DT products (i.e., ERA5 (Fifth generation of ECMWF atmospheric reanalyses of the global climate) and MGP) overestimated the frequency of light precipitation events, with relative rainfall occurrence biases exceeding 80%. This bias is attributable to both false detections and the misclassification of high intensity rainfall as light precipitation. Although GSMaP-NOW (based exclusively on passive microwave data) detected precipitation more effectively than the infrared-only PDIRNow (Precipitation Estimation from Remotely Sensed Information Using Artificial Neural Networks (PERSIANN)—Dynamic Infrared Rain Rate (Now)), it achieved lower accuracy. This discrepancy reflects the tradeoff between the higher precipitation sensitivity of passive microwave observations and their sparse temporal sampling, compared with the continuous coverage provided by infrared data. Finally, our findings indicated that current evaluation approaches do not reliably determine the optimal precipitation product, since product superiority is contingent upon the selected error metric. This underscores the urgent need to develop theoretically grounded and operationally reliable methods for selecting optimal precipitation products to support data users in deriving robust and reliable conclusions in hydrology, meteorology, and ecology. Full article

Acid rain is a severe global environmental issue, and clarifying its impacts on litter decomposition and underlying mechanisms is critical for accurately forecasting future climate change. Litter consists of components (e.g., non-structural carbohydrates, lignin, cellulose, and hemicellulose) with distinct decomposition resistance, but how acid rain affects these components to modulate overall litter decomposition across different decomposition stages remains unclear. Therefore, a microcosm experiment was conducted to determine decomposition rates of Chinese fir (Cunninghamia lanceolata) litter and its components based on litter mass loss under different simulated acid rain intensities (pH 4.5, moderate acid rain, MA; pH 3.0, severe acid rain, SA; and pH ≈ 7.0, tap water, CK) over two decomposition stages (0–5 months: initial decomposition stage; 6–16 months: late decomposition stage). Meanwhile, to analyze the factors influencing the litter decomposition rate, soil samples were collected at 5 and 16 months of decomposition for soil property analysis. Results showed that MA had no significant effect on litter decomposition in either stage. Conversely, SA led to a significant 43.7% increase in the litter decomposition rate in the initial decomposition stage, driven by its acid dissolution effect that accelerated the decomposition of cellulose and hemicellulose. However, SA significantly decreased the decomposition rate by 42.0% in the late decomposition stage by inhibiting the decomposition of lignin, cellulose, and hemicellulose, which was due to the reduced activities of soil peroxidase and xylosidase under soil acidification. Notably, neither MA nor SA significantly affected the litter decomposition rate over the entire decomposition period (0–16 months). This study indicates that acid rain’s effect on litter decomposition depends on its intensity and decomposition stage, emphasizing the necessity of distinguishing litter components and decomposition stages to explore its underlying mechanisms and precisely predict global climate change. Full article

Agricultural nets are increasingly used for crop protection, although their long-term outdoor mechanical durability remains poorly investigated. This study evaluates the tensile behavior of five HDPE nets (anti-rain and anti-insect) subjected to accelerated ageing in an artificial chamber for 2, 4, 8, and 12 weeks (approximately corresponding to 3–18 months of natural exposure). Unidirectional tensile tests were performed in both weft (machine) and warp (transversal) directions to determine Maximum Strength (Fm), Tensile Stress at Maximum Strength (Sm), and Elongation at Maximum Strength (A). The results showed pronounced mechanical anisotropy, with differences in elongation between test directions reaching up to 47%, depending on the net structure and thread arrangement. Accelerated ageing caused a progressive reduction in both tensile strength and ductility, with strength losses in some cases reaching 40–45% after 12 weeks of exposure. Based on the nets analyzed in this study, anti-rain nets tended to exhibit higher initial strength values but faster degradation rates, whereas anti-insect nets showed lower initial strength values (1200–1500 N) and a comparatively more stable response over time. These results suggest that the durability of agricultural nets is strongly influenced by structural configuration and load direction. From an engineering perspective, mechanical durability can be considered a key parameter when selecting crop-protection systems intended for long-term field applications. Full article

Wheat is a globally important food crop, and its yield is crucial for ensuring food security. Lunxuan 13 is an elite wheat variety developed by the Institute of Crop Sciences, Chinese Academy of Agricultural Sciences. It has high yield potential and outstanding agronomic traits, such as excellent seed setting rate, plump kernels, and good lodging resistance. However, this variety is highly susceptible to pre-harvest sprouting (PHS) when exposed to rain during the maturation period, leading to premature grain germination on the spike, which causes yield losses and quality deterioration, severely restricting its popularization. This study focused on addressing the PHS susceptibility of Lunxuan 13 by employing CRISPR/Cas9 technology for the targeted knockout of the three homoeologous copies (A, B, and D subgenomes) of TaQsd1, a key gene regulating seed dormancy. A total of 41 transgenic plants were obtained, achieving a transformation efficiency of 52.6%, among which 27 plants exhibited edits at the target sites, resulting in an editing efficiency of 65.9%. Phenotypic analysis of homozygous T₂ edited lines revealed significant functional redundancy among the three TaQsd1 homoeologs: a significant extension of the seed dormancy period and a substantial increase in PHS resistance were achieved only when all three A, B, and D copies underwent loss-of-function mutation (aabbdd genotype). After-ripened seeds from these mutants showed normal germination ability, indicating enhanced dormancy rather than loss of germination capacity. Importantly, all of the edited lines exhibited no significant differences compared to the wild type in key agronomic traits such as plant height, spike length, and grains per spike, thus retaining the excellent characteristics of Lunxuan 13. This study successfully optimized Lunxuan 13 for significantly enhanced PHS resistance while retaining its superior agronomic traits. This work provides an effective approach for improving PHS resistance in white-grained wheat and removes a key barrier to the potential commercialization of this variety. Full article