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Purpose: This study examined whether physical demands during soccer matches differ between sea level and altitude, considering variations by playing position. Methods: Thirty-seven professional players were monitored during 22 matches (11 at sea level and 11 at altitudes of 2200–4090 m) with global navigation satellite systems. Independent mean differences were used to compare in-match physical demands (ie, total distance, distance covered at specific speed intervals, accelerations [ACCs] and decelerations [DECs], and maximal speed) between locations for 5 playing positions (central defenders, fullbacks, central midfielders, wide midfielders, and forwards). Results: At altitude, players covered shorter total distances (P <.001) and less distance in the 14.4- to 19.8-km/h (P <.001), 19.8- to 25.2-km/h (P <.001), and >25.2-km/h (P <.001) speed ranges. They also performed fewer ACCs (2.0–3.5 m/s2, P <.001; 3.5–6.0 m/s2, P <.001) and DECs (−3.5 to −2 m/s2, P <.001; −6.0 to −3.5 m/s2, P <.001) and achieved lower maximal speeds (P <.001). The impact of altitude varied by position: Central midfielders showed reduced performance in all variables, while central defenders (distance > 25.2 km/h, ACCs [2.0 and 3.5 m/s2], DECs [−3.5 and −2.0 m/s2], and maximal speed), fullbacks (distance > 25.2 km/h, ACCs, and DECs [−3.5 and −2.0 m/s2]), and forwards (distances [total, 19.8–25.2 km/h, and >25.2 km/h] and ACCs [−3.5 and −6.0 m/s2]) presented unclear differences (P >.05) between locations. Conclusion: Our study highlights the importance of considering playing positions when assessing the in-match activity profiles of sea-level resident soccer players competing at moderate to high altitudes. [ABSTRACT FROM AUTHOR]

Experimental rate coefficients for the quenching of vibrational levels 0 and 1 of the N 2 + A 2 Π u state by N2 are presented. The experiments were performed using near-infrared observations of the N 2 + Meinel bands excited by electron impact at several pressures of the N2 target/quenching gas. The total removal rate coefficients were derived from a Stern–Volmer analysis of the Meinel band intensities as a function of N2 density and yielded rate coefficients of (2.5 ± 0.5 × 10−10) and (5.6 ± 0.6 × 10−10) cm3⋅molecule−1⋅s−1 for vibrational levels 0 and 1, respectively. It is shown that rate coefficients increase with increasing vibrational level and decreasing energy gap. Our results impact modeling studies of the disturbed atmosphere and ionosphere as the reduced quenching rate coefficients for the preferentially excited A-state vibrational levels <2 lower the quenching altitude in the atmosphere by one scale height, or about 6 km. [ABSTRACT FROM AUTHOR]

Purpose: We examined changes in stride temporal parameters and spring-mass model characteristics during repeated sprints following a 3-week period of "live high–train low and high" (LHTLH) altitude training in team-sport players. Methods: While residing under normobaric hypoxia (≥14 h/d; inspired oxygen fraction [FiO2] 14.5%–14.2%) for 14 days, elite field hockey players performed, in addition to their regular field hockey practice in normoxia, 6 sessions (4 × 5 × 5-s maximal sprints; 25-s passive recovery; 5-min rest) under either normobaric hypoxia (LHTLH; FiO2 ∼14.5%, n = 11) or normoxia (live high–train low; FiO2 20.9%, n = 12). A control group (live low–train low; FiO2 ∼20.9%, n = 9) residing in normoxia without additional repeated-sprint training was included. Before (Pre) and a few days (Post-1) and 3 weeks (Post-2) after the intervention, stride mechanics were assessed during an overground repeated-sprint test (8 × 20 m, 20-s recovery). Two-way repeated-measures analysis of variance (time [Pre, Post-1, and Post-2] × condition [LHTLH, live high–train low, and live low–train low]) were conducted. Results: Peak sprinting speed increased in LHTLH from Pre to Post-1 (+2.2% [2.0%]; P =.002) and Post-2 (+2.0% [2.4%]; P =.025), with no significant changes in live high–train low and live low–train low. There was no main effect of time (all P ≥.062), condition (all P ≥.771), or a significant time × condition interaction (all P ≥.230) for any stride temporal variable (contact time, flight time, stride frequency, and stride length) or spring-mass model characteristics (vertical and leg stiffness). Conclusions: Peak sprinting speed improved in elite field hockey players following LHTLH altitude training, while stride mechanical adjustments to repeated overground sprints remained unchanged for at least 3 weeks postintervention. [ABSTRACT FROM AUTHOR]

Background: Repeated exposure to heat (ie, plasma volume expansion) or altitude (ie, increase in total hemoglobin mass), in conjunction with exercise, induces hematological adaptations that enhance endurance performance in each respective environment. Recently, combining heat and altitude training has become increasingly common for athletes preparing to compete in temperate, sea-level conditions. Purpose: To review the physiological adaptations to training interventions combining thermal and hypoxic stimuli and summarize the implications for temperate, sea-level performance. Current Evidence: To date, research on combining heat and hypoxia has employed 2 main approaches: simultaneously combining the stressors during training or concurrently training in the heat and sleeping at altitude, sometimes with additional training in hypoxia. When environmental stimuli are combined in a training session, improvements in aerobic fitness and time-trial performance in temperate, sea-level conditions are generally similar in magnitude to those observed with heat, or altitude, training alone. Similarly, training in the heat and sleeping at altitude does not appear to provide any additional hematological or nonhematological benefits for temperate; sea-level performance relative to training in hot, hypoxic, or control conditions. Conclusions: Current research regarding combined heat and altitude interventions does not seem to indicate that it enhances temperate, sea-level performance to a greater extent than "traditional" (heat or hypoxia alone) training approaches. A major challenge in implementing combined-stressor approaches lies in the uncertainty surrounding the prescription of dosing regimens (ie, exercise and environmental stress). The potential benefits of conducting heat and altitude exposure sequentially (ie, one after the other) warrants further investigation. [ABSTRACT FROM AUTHOR]

Purpose: Total hemoglobin mass (tHbmass) and blood volume (BV) are important determinants of maximal oxygen uptake and endurance capacity. Higher-caliber endurance athletes usually possess higher tHbmass and BV values. This study aimed to compare tHbmass and BV among swimmers of diverse competitive calibers and distances. Methods: Thirty swimmers (16 female and 14 male) participated in the study: 3 were tier 5, world class (869 [59] FINA points); 15 were tier 4, elite/international (853 [38] points); and 12 were tier 3, highly trained/national (808 [35] points). They specialized in competition distances ranging from 200 m to open-water 10 km. Between February 2019 and February 2020, all swimmers had their tHbmass and BV measured by carbon monoxide rebreathing 1 to 6 times and participated in multiple competitions and race events. Results: Relative tHbmass and BV were not different (P >.05) between tiers among women or among men (pooled tHbmass values 14.5 [0.5], 12.5 [1.5], 12.6 [2.3] g/kg for tier 5, tier 4, and tier 3, respectively). No differences were observed in relative tHbmass (P =.215) and BV (P =.458) between pool and open-water swimmers or between 200-, 400-, and 1500-m specialists (P >.05). No significant correlations were found between the highest measured absolute or relative tHbmass and BV and the highest FINA points scored over the follow-up period (R = −.42–.17, P =.256–.833), irrespective of competition distance. Conclusion: tHbmass and BV values did not differ between swimmers of different calibers or among competition distances. Furthermore, these values did not correlate with FINA points, either in males or in females. The present results indicate that hematological characteristics may have a lesser impact on swimming performance than on land-based endurance sports. [ABSTRACT FROM AUTHOR]

Purpose: To compare the effects of graded hypoxia during exhaustive intermittent cycling on subsequent rapid and maximal torque-production capacity. Methods: Fifteen well-trained cyclists repeated intermittent cycling bouts (15 s at 30% of anaerobic power reserve; rest = 45 s) until exhaustion at sea level (FiO2 ∼0.21/end-exercise arterial oxygen saturation ∼96%), moderate hypoxia (FiO2 ∼0.16/∼90%), and severe hypoxia (FiO2 ∼0.12/∼79%). Rapid (rate of torque development [RTD]) and maximal isometric torque-production capacities of the knee extensors were assessed at baseline (visit 1) and exhaustion (visits 2–4). Results: Exercise capacity decreased with hypoxia severity (39 [30], 22 [13], and 13 [6] cycle efforts in sea level, moderate hypoxia, and severe hypoxia, respectively; P =.002). Changes in maximal-voluntary-contraction torque between baseline and postexercise in all conditions were not statistically significant (pooled values: −2.6% [5.7%]; P =.162). Peak RTD measured postexercise was reduced below baseline in all conditions (–21.5% [5.1%]; P ≤.015). Compared with baseline, absolute RTD values were lower at 0- to 30-millisecond (–35.1% [5.3%], P ≤.020), 0- to 50-millisecond (–40.0% [3.9%], P ≤.002), 0- to 100-millisecond (–30.7% [3.7%], P ≤.001), and 0- to 200-millisecond (–18.1% [2.4%], P ≤.004) time intervals in all conditions. Conclusions: Exhaustive intermittent cycling induces substantial yet comparable impairments in RTD of knee extensors between normoxia and moderate to severe hypoxia. [ABSTRACT FROM AUTHOR]

Clouds constitute a large portion of uncertainty in predictions of equilibrium climate sensitivity (ECS). While low cloud feedbacks have been the focus of intermodel studies due to their high variability among global climate models, tropical high cloud feedbacks also exhibit considerable uncertainty. Here, we apply the cloud radiative kernel technique of Zelinka et al. to 22 models across the CMIP5 and CMIP6 ensembles to survey tropical high cloud feedbacks and analyze their relationship to ECS. We find that the net high cloud feedback and its altitude and optical depth feedback components are significantly positively correlated with ECS in the tropical mean. On the other hand, the tropical mean high cloud amount feedback is not correlated with ECS. These relationships are most pronounced outside of areas of strong climatological ascent, suggesting the importance of thin cirrus feedbacks. Finally, we explore connections between high cloud feedbacks, climate sensitivity, and mean state high cloud properties. In general, high ECS models are cloudier in the upper troposphere but have a thinner high cloud population. Moreover, we find that having more thin cirrus in the mean state relates to more positive high cloud altitude and optical depth feedbacks, and it either amplifies or dampens the high cloud amount feedback depending on the large-scale dynamical regime (amplifying in descent and dampening in ascent). In summary, our analysis highlights the importance of tropical high cloud feedbacks for driving intermodel spread in ECS and suggests that mean state high cloud characteristics might provide a unique opportunity for observationally constraining high cloud feedbacks. Significance Statement: Clouds play an important role in modulating the effects of climate change through feedback processes involving changes to their amount, altitude, and opacity. In this study, we seek to understand how changes to tropical high clouds under warming are related to the magnitude of warming that global climate models simulate. We find that tropical high cloud feedbacks robustly relate to the amount of warming a model predicts and that warmer models tend to have a thinner tropical high cloud climatology. Our results highlight a potential opportunity to form a new constraint using these relationships in order to narrow the spread of warming estimates among global climate models. [ABSTRACT FROM AUTHOR]

Aerial images can cover a wide area and capture rich scene information. These images are often taken from a high altitude and contain many small objects. It is difficult to detect small objects accurately because their features are not obvious and are susceptible to background interference. The CPDD-YOLOv8 is proposed to improve the performance of small object detection. Firstly, we propose the C2fGAM structure, which integrates the Global Attention Mechanism (GAM) into the C2f structure of the backbone so that the model can better understand the overall semantics of the images. Secondly, a detection layer named P2 is added to extract the shallow features. Thirdly, a new DSC2f structure is proposed, which uses Dynamic Snake Convolution (DSConv) to take the place of the first standard Conv of Bottleneck in the C2f structure, so that the model can adapt to different inputs more effectively. Finally, the Dynamic Head (DyHead), which integrates multiple attention mechanisms, is used in the head to assign different weights to different feature layers. To prove the effectiveness of the CPDD-YOLOv8, we carry out ablation and comparison experiments on the VisDrone2019 dataset. Ablation experiments show that all the improved and added modules in CPDD-YOLOv8 are effective. Comparative experiments suggest that the mAP of CPDD-YOLOv8 is higher than the other seven comparison models. The mAP@0.5 of this model reaches 41%, which is 6.9% higher than that of YOLOv8. The CPDD-YOLOv8's small object detection rate is improved by 13.1%. The generalizability of the CPDD-YOLOv8 model is verified on the WiderPerson, VOC_MASK and SHWD datasets. [ABSTRACT FROM AUTHOR]

Sky View Factor (SVF) is commonly used to describe the impact of urban geometry on the urban thermal environment. Shading effects from plants and buildings also exert a considerable influence. To investigate the influence of view factors on outdoor thermal comfort in residential areas, we employed the Physiological Equivalent Temperature (PET) and view factors (SVF, TVF, BVF) as indicators to determine outdoor thermal comfort and the quantity of shaded spaces. Thermal measurements collected from 13 points in Guangzhou, China, Our findings revealed that high TVF points exhibited more stable air temperature throughout the daytime, with average temperature differentials ranging 0.4–1.9 °C lower than other points. Air temperature demonstrated a positive correlation with SVF (R2 = 0.53), while exhibiting a negative correlation with TVF (R2 = 0.45). Additionally, shading provided by plants and buildings manifests heterogeneity. At similar SVF levels, points predominantly shaded by plants (TVF > BVF) showcased lower Mean Radiant Temperature (MRT) and PET compared to points shaded mainly by buildings (BVF > TVF). The maximum reduction in air temperature and PET reached 1.1 °C and 1.2 °C, respectively. BVF exerted greater influence earlier in the morning, as solar altitude angle rises, the average thermal parameters of sites with BVF > TVF escalated rapidly until eventually surpassing sites with TVF > BVF. Last, superior thermal conditions were only ensured under high shading conditions. When the effective shading ratio of plants and buildings diminished (SVF > 0.3), the microclimate of measurement points might be impacted by the long-wave radiation from the underlying surface. [ABSTRACT FROM AUTHOR]

• This paper focuses on the latest blocks of GNSS satellites and their yaw models. • The distribution of eclipse satellite counts was statistically analyzed. • The current satellite yaw characteristics during the eclipse are analyzed thoroughly. • The influence of yaw correction on the orbital accuracy is discussed. • The accuracy of most satellites are improved by 35.0 % to 50.0 % after yaw correction. The GNSS satellites do not maintain nominal attitude when the solar elevation angle falls into a predetermined threshold, resulting in a period of abnormal yaw attitude which will degrade the accuracies of the orbit and clock products. This paper investigates in depth the distribution rules of GPS/GLONASS/Galileo/BDS satellites' eclipse periods and analyses in detail the correction characteristics of each model in eclipse periods. The models used are GPS IIF and GLONASS-M for GPS IIIA and GLONASS-K modernized satellites, respectively, and the continuous yaw models for BDS-3 and Galileo satellites. Finally, an experimental analysis of the improvement of each block of satellite eclipse periods' orbital accuracy is conducted. The results indicate that most satellites' orbital accuracy is improved by 35.0 % to 50.0 % following yaw correction, but only by 29.0 % and 18.0–35.2 % for GPS IIIA satellites and BDS-3 satellites. [ABSTRACT FROM AUTHOR]

Aiming at the obvious trend of the contours on the high-altitude geomagnetic map, this paper presents a method of high-altitude geomagnetic matching area selection combining geomagnetic information entropy and geomagnetic direction entropy based on the study of geomagnetic information entropy and geomagnetic direction entropy. The method first uses geomagnetic information entropy to select the region with rich geomagnetic information, and then determines the direction of the flight trajectory according to geomagnetic direction entropy to obtain the optimal matching trajectory. Finally, the method compares and analyzes the matching localization results of three flight trajectories in different directions on the geomagnetic map at an altitude of 30,000 m by using semi-physical simulation. The experimental results show that the flight navigation error along the trajectory with small information entropy is small, and its positioning error is 12.7% of the trajectory positioning error along the maximum information entropy direction. Selecting the flight trajectory according to the value of the geomagnetic direction entropy can greatly improve the precision and reliability of the geomagnetic matching localization. The method in this paper can provide a basis for path planning of the geomagnetic matching navigation. [ABSTRACT FROM AUTHOR]

Purpose: This study aimed to investigate the temporal effects of ~1800 m altitude exposure and energy availability (EA) manipulation on resting metabolic rate (RMR). Methods: Twenty elite female race walkers underwent a 3-wk training camp at an altitude of ~1800 m. During the first 2 wk, athletes consumed a high EA (HEA) diet of 45 kcal·kg fat-free mass (FFM)−1·d−1. During the final week, half the athletes consumed a low EA (LEA) diet of 15 kcal·kg FFM−1·d−1, whereas the others continued on an HEA diet. Athletes followed individualized training plans throughout the study. To assess the effect of altitude on RMR, athletes in the HEA group had RMR measured at baseline (~580 m) before altitude exposure (Pre-alt), at 36 h (36h-alt), 2 wk (Wk2-alt), and 3 wk into altitude exposure (Wk3-alt), and at 36 h post-altitude exposure at ~580 m (36h-post). To assess the effect of LEA exposure on RMR while at altitude, athletes in the LEA group underwent RMR measurements at Pre-alt and before (Wk2-alt) and after the 7 d of LEA (Wk3-alt). Results: Compared with Pre-alt, the RMR of HEA athletes was increased at 36h-alt (+5.3% ± 3.1%; P = 0.026) and Wk2-alt (+4.9% ± 4.9%; P = 0.049), but was no longer elevated at Wk3-alt (+1.7% ± 4.2%; P = 0.850). The RMR of HEA athletes at 36h-post was lower than all timepoints at altitude (P < 0.05) but was not different from Pre-alt (−3.9% ± 7.2%; P = 0.124). The 7-d period of LEA exposure at altitude did not affect RMR (P = 0.347). Conclusions: RMR was transiently increased with ~1800-m altitude exposure in female athletes and was unaffected by short-term LEA. However, the altitude-induced increase was small (~25–75 kcal·d−1) and was unlikely to have clinically significant implications for daily energy requirements. [ABSTRACT FROM AUTHOR]

Purpose: Altitude training is a common strategy used with the intent to increase hemoglobin mass (Hbmass) in athletes. However, if the Hbmass is increased during altitude camps, it seems to decline rapidly upon returning to sea level. This study aimed to examine the efficacy of three weekly heat training sessions over a 3.5-wk period after a 3-wk altitude camp on the maintenance of Hbmass in elite cyclists. Methods: Eighteen male cyclists (maximal oxygen consumption: 76 ± 5 mL·min−1·kg−1) underwent a 3-wk altitude training camp at ~2100 m above sea level. After the camp, participants were divided into one group performing three weekly heat sessions that were subtracted from their usual training (HEAT) while the other continuing usual training (CON). Training characteristics were recorded during the intervention, whereas hematological measurements were recorded before the camp as well as 2 d and 3.5 wk after the altitude camp. Results: The 3-wk altitude camp led to an overall increase in total Hbmass of 4.1%. Afterward, HEAT maintained Hbmass (0.2%, P = 0.738), whereas CON group experienced a significant reduction (−3.3%, P < 0.001) (ΔHEAT vs ΔCON, P < 0.001). Moreover, HEAT increased plasma volume (PV) by 11.6% (P = 0.007) and blood volume (BV) by 5.8% (P = 0.007), whereas CON only showed an increase in PV (5.5%, P = 0.041). Exercise intensity and training load were not different between groups during the maintenance period. Conclusions: This study suggests that incorporating three weekly heat training sessions into the usual training routine preserves a moderately increased Hbmass in elite cyclists after an altitude camp. [ABSTRACT FROM AUTHOR]

In order to improve and optimize the advance classification and prediction method of tunnel surrounding rock, a prediction method based on Tunnel Seismic Prediction (TSP) and Probabilistic Neural Network (PNN) is proposed. Based on the characteristics of science, maneuverability and representativeness, several factors that greatly affect rock mass classification are selected as evaluation indices based on analysis of numerous TSP data, establishing an advance classification index system for surrounding rock, and designing the "Advance classification and prediction system for surrounding rock" to predict the classification. Engineering application of Jinpingyan Tunnel of Chenglan Railway in high altitude and high intensity area of China is taken as a case study, and proved that the evaluation indices are easy to obtain and the evaluation results are accurate and reliable, and compared with Back Propagation (BP) neural network prediction results, the results show that PNN has some advantages in predicting the calculation speed of surrounding rock classification, the ability to add samples and the classification accuracy in practical engineering applications. The PNN-TSP method can be further used for other tunnel engineering. [ABSTRACT FROM AUTHOR]

A learning-based guidance method is proposed to address the problem of continuously avoiding multiple online-detected no-fly zones for hypersonic cruise vehicles. Compared with previous research on the no-fly zone avoidance problem, this paper further considers the challenges posed by non-global information and the variation in the number of no-fly zones. The method comprises two components: the approach for the design and offline training of a reinforcement learning agent with heading decision-making capabilities, and the cruise guidance framework based on a multiagent coordination strategy. Firstly, considering the adaptability to a variety of tasks and training efficiency, the Markov decision process for solving the no-fly zone avoidance problem is designed. On this basis, by setting up training environments with progressive difficulty, the agent interacts with environments to complete multistage training and gradually improves the heading decision-making ability for the no-fly zone. During the guidance process, each detected no-fly zone is assigned to a trained agent to make independent heading decisions, and these agents form a coordination committee to determine the final heading command through the coordination strategy. Then the cruise guidance framework implements the commands of heading, altitude, and velocity. A series of training and testing experiments are conducted. The theoretical analysis and simulation results demonstrate the proposed method's efficacy, robustness, and adaptability. [ABSTRACT FROM AUTHOR]

The clogging of the gravel surface layer in gravel-bedded channels with finer sediment (<2 mm) is a common problem that negatively impacts streambed habitat quality. Most existing measurements of surface-layer sediment clean-out depth are from experiments with narrow gravel size distributions; therefore, a new set of experiments was conducted to explore the effect of widely distributed bimodal gravel fractions on the clean-out depth of interstitial sand. Experiments were used to measure the terminal clean-out depth of 0.115-mm sand from bed material substrates composed of unimodal median diameter gravel of 7.16 mm and bimodal bed material with modes of 7.31 and 34.66 mm and a median diameter of 33.46 mm. It was found that the clean-out depth of sand from immobile gravel beds could be predicted by scaling the bed shear stress using the cumulative probability distribution of the elevations of the surface of the gravel bed. [ABSTRACT FROM AUTHOR]

An important part of UAV technological development consists of improvements in the scope of path planning. Different choices can be made in path planning according to operational priorities, it may be preferred to reach the destination as fast as possible or to increase the airtime by compromising speed. For every speed and altitude that the UAV can fly; fuel data of cruise, climb and descent phases are used in the path planning algorithm. Thus, economical and airtime-maximizing paths could be produced on the basis of performance characteristics compatible with the kinematic constraints customized for the UAV. In this study, Cellular (cGA) and Segmented Cellular Genetic Algorithm (scGA) are proposed. The novel overprotective algorithm which has a fixed initial population and segmented chromosome structure achieves a high convergence speed to optimal solution and can generate paths which have 5.2 times higher fitness value on average compared with a conventional Genetic Algorithm (GA). It has been seen that scGA improves the initial population in terms of the best solutions 1.9 times and the general population 5.8 times better compared with GA. [ABSTRACT FROM AUTHOR]

This study investigates the characteristics of wind speed in two synoptic weather stations in Niger. Hence, three hourly wind data including wind speed and direction from 2009 to 2019 were used. Prior to the analysis, the dataset was pre‐processed to remove corrupted and irrelevant data. Statistical analysis was conducted on the dataset to understand the variability of the wind speed and wind direction at the two synoptic stations. The results showed that the highest prevailing wind is recorded in the Agadez region with average wind speeds ranging from [3; 6] m/s and [6; 10] m/s at 10 m altitude. The dominant directions are the East from September to May, then the West from June to August. At the Tahoua station, the prevailing winds have average speeds also belonging to [3; 6] m/s and [6; 10] m/s at 10 m altitude, but the dominant directions are East and East‐North‐East from October to April, then West and South‐West from May to September. These findings are useful for the effective planning of a wind energy project in Niger as they provide useful insight regarding the wind characteristics in two windy regions in Niger. [ABSTRACT FROM AUTHOR]

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On January 1, 2024, a moment magnitude (Mw) 7.5 earthquake struck the Noto Peninsula area in Japan, triggering a tsunami and causing significant casualties and massive economic and property damage. Many wave gauges around the Sea of Japan recorded the tsunami. In this study we inverted the observed tsunami waveforms for the distributed slip on the JSPJ (Japan Sea Earthquake and Tsunami Research Project) fault model, and the initial water elevation, respectively. The results show that the earthquake’s slip distribution concentrates mainly on the NT4 subfault located to the northeast of the peninsula, with the maximum slip reaching about 5m. This slip model results in a maximum initial tsunami wave height that reaches ∼3m. The inversion of initial water elevation indicates a main tsunami source roughly located in 137.3∘E−137.6∘E and 37.5∘N−37.8∘N, with the maximum initial elevation of 2.7m, which is consistent with the finite-fault inversion. We also simulated the tsunami waveforms at observation stations using the inverted JSPJ fault model and the initial water elevation to evaluate the effects of wave dispersion. The results indicate that the effects of dispersion were minor at most stations, and only observable at far-field stations along the eastern Russian coast and the western coast of Hokkaido. [ABSTRACT FROM AUTHOR]

Background: Posttraumatic osteoarthritis (PTOA) is directly associated with early acute articular cartilage injury. Inhibition of cartilage destruction immediately following joint damage can effectively slow or prevent PTOA progression. Therefore, we sought to determine intervention targets and therapeutic strategies in the acute stage of cartilage injury. The benefits of chronic intermittent hypobaric hypoxia (CIHH) extend to various body tissues, but its impact on acute cartilage injury remains unclear. We selected PTOA initiation as the therapeutic window and administered CIHH treatment immediately following cartilage injury initiation to investigate its protective effect on cartilage and molecular mechanism changing with time-varying. Methods: The non-invasive PTOA mouse model was established by applying a single rapid specific impact force to the right knee's tibial plateau, initiating load-induced PTOA development, closely resembling the pathological changes in human diseases. Following loading, we inhibited cartilage destruction by treating mice immediately in a hypobaric chamber with a hypobaric hypoxia mimic at 5000 m altitude. Cohorts of mice subjected to distinct experimental conditions were monitored for 3, 7, 14 or 28 days. Safranin O-Fast Green staining, Immunohistochemistry, immunofluorescence, ELISA, and western blotting were performed to evaluate the therapeutic effects of CIHH on cartilage in vivo. The nuclear translocation of NF-κB p65 and Nrf2 were detected by immunofluorescence. Results: The results showed that inhibiting cartilage destruction using CIHH immediately following acute articular cartilage injury initiation delayed the progression of PTOA, decreased the Mankin score and suppressed the expression of proinflammatory factors, including iNOS, NO, TNF-α, and IL-1β. Meanwhile, immediate CIHH treatment reduced levels of the catabolic enzymes ADAMTS5 and MMP13 in the cartilage matrix, reversed degradation of Collagen II and COMP, and inhibited oxidative stress by decreasing ROS levels. Moreover, CIHH suppressed NF-κB signaling by activating the Nrf2 in vivo studies. Conclusion: Our study demonstrated that immediate CIHH treatment following cartilage injury initiation can attenuate load-induced cartilage damage by activating Nrf2/HO-1 and inhibiting the NF-κB p65 signalling pathways to counteract oxidative stress and inflammatory reactions, enhance the metabolic balance of the cartilage matrix and delay cartilage degeneration. This treatment may represent a potential therapeutic strategy for limiting PTOA progression. [ABSTRACT FROM AUTHOR]

Mosaicking of Unmanned Aerial Vehicles (UAV) imagery over featureless water bodies has been known to be challenging, and poses a significant impediment to water monitoring applications. Techniques such as Structure-from-motion typically fail under such conditions due to the lack of distinctive features in the scene, and direct georeferencing is currently the only practical solution, albeit lower georeferencing accuracy is expected. However, hardware issues, particularly the typical time delay between the GPS unit and the image capture, can lead to systematic image misalignment and further reducing the accuracy. The systematic image misalignment arises as the recording of the geographical coordinates by the GPS unit may not precisely correspond to the exact moment of image exposure, and the image exposure may not always occur at the mid-exposure time. Hardware solutions can mitigate this issue but require technical expertise and resources. Alternatively, software solutions can address the problem without necessitating any hardware modifications. This study introduces an open-source solution for the correction of the systematic image alignment by accounting for the time delay and distance discrepancy between the measurements of the GPS coordinates and the image capture. The method was validated with field UAV surveys conducted in this study under various flight configurations (different flight altitudes and overlap ratios), and effective image alignment was obtained using the proposed open-source solution which reduced the georeferencing error by around 67.7%. Specifically, a georeferencing error of RMSE = 1.409 m and $\sigma $σ = 0.6356 m was achieved without the use of any ground control points (GCPs). Finally, as demonstrated in this study, low flight altitudes (e.g. 15 m) should be discouraged for such conditions as georeferencing errors could amplify due to the limited accuracy of the GPS, resulting in visual artefacts. [ABSTRACT FROM AUTHOR]

We propose a lightweight method for constructing a global digital elevation and terrain database in consideration of the satellite flight path. First, a global maximum/minimum elevation database with a grid size of 0.05° × 0.05° was generated using Shuttle Radar Topography Mission data and the Global Multi-resolution Terrain Elevation Data along with other multi-source digital elevation model (DEM) data. A global database of maximum terrain fluctuation with a grid size of 0.05°× 0.05° and distances of 140 and 700 m was then constructed on the basis of the ICESat-2 satellite flight path and the main frame/super frame distance criterion. The databases, which achieve global coverage while occupying a small storage space, can be used to assist in the in-orbit preprocessing of onboard data. The database accuracy was evaluated using ICESat-2 data. In the 10 validation areas, the global DEM database had an error of only 3 m in two validation areas, and the error was less than the accuracy range of each DEM data source. The global terrain database can characterize the degree of surface relief in each verification area, confirming the effectiveness of the method used in this study. [ABSTRACT FROM AUTHOR]

The evolution of double warm‐cores (DWC) during the secondary eyewall formation (SEF) and the subsequent eyewall replacement cycle (ERC) in Typhoon Trami (2018) was investigated in this study. Using a coupled atmosphere‐ocean model, the impacts of the typhoon‐induced sea surface cooling (SSC) on the DWC structure were also examined. In both the coupled and uncoupled simulations, the middle‐level warm‐core (MWC) decayed as the tangential wind expanded outward during the SEF, even in the absence of SSC. Under the thermal wind balance, the cooling of the MWC was an inherent result to ensure the dynamic consistency during the SEF. In contrast to the uncoupled simulation, the upper‐level warm‐core (UWC) decayed under the influence of SSC, significantly contributing to the rapid weakening of Trami. The negative effects of the SSC on the UWC were more detrimental to the intensity of Trami. Results from the potential temperature (PT) budget of improved accuracy indicated that the decrease in the warming due to the radial eddy advection was mainly responsible for the decay of the MWC. The flattened radial gradient of PT during the SEF accounted for the reduction in the dynamical eye warming associated with the asymmetric mixing. In addition to the convectively induced subsidence, the upper‐level asymmetric structures could also be affected by the SSC. Consequently, the increase in the cooling due to the enhanced asymmetry collaborated with the decrease in the adiabatic warming, leading to the decay of the UWC in the coupled simulation. Plain Language Summary: A warm‐core, characterized by higher temperature than the environment, is a typical feature at the center of typhoons. It is encircled by an eyewall where strong winds and heavy rain prevail that constitutes the most destructive region of typhoons. In intense typhoons, an outer eyewall may develop and gradually replace the original eyewall, a phenomenon commonly called the eyewall replacement cycle (ERC). In addition, a second warm‐core can also frequently form at a different altitude in intense typhoons, generally known as the double warm‐core (DWC) structure. When a double‐eyewall typhoon possesses the DWC structure, the relationship between these two unique structures still remains unknown. Using an atmosphere‐ocean coupled simulation, this study examines how the two warm‐cores evolve during the ERC of Typhoon Trami. The results show that the midlevel warm‐core naturally cools as the wind field expanded outward during the ERC. Additionally, the typhoon‐induced sea surface cooling (SSC) can weaken the upper‐level warm core, corresponding to the rapid weakening of Trami. Understanding these internal changes is crucial for better predicting typhoon's intensity and its hazards. Key Points: The decrease in the dynamic eye warming dominates the decay of the midlevel warm‐core during the eyewall replacement cycleThe typhoon‐induced sea surface cooling results in the decay of the upper‐level warm‐core, contributing to the rapid weakeningThe asymmetry within the eye region is modulated by the eyewall replacement cycle and air‐sea interaction, affecting how the warm cores evolve [ABSTRACT FROM AUTHOR]

The West African Sahel, situated as a semiarid transition area between the Sahara Desert and the savannah subregion, has garnered considerable research interest in recent years due to its distinctive climate characteristics. Of particular focus in this study are the patterns of moisture flux convergence and summer monsoon rainfall in the Sahel, and their interconnected variability. This study aims to enhance our comprehension of the dynamics governing the variation of the West African Monsoon (WAM) through the Vertical Integrated Moisture Flux Convergence. (VIMFC). This study findings reveal a notable upward trend in rainfall within the Sahel region over the past thirty years, primarily attributed to the climate's response to atmospheric warming. Projections indicate that, with future warming, the frequency of rainy days and the occurrence of rainfall are expected to increase in the Sahel. While the dominant circulation systems exhibit no significant deviations, the lower-level wind patterns play a crucial role in transporting moisture from the Atlantic Ocean to the Sahel. Moreover, strengthening of wind patterns at higher altitudes correlates with wetter conditions in the Sahel in the latter decades. [ABSTRACT FROM AUTHOR]

This paper considers the problem of flying a UAV along a given trajectory at speeds close to the speed of sound and above. A novel pitch channel control system is presented using the example of a trajectory with rapid and large changes in flight height. The control system uses a proportional–integral–differential (PID) controller, whose gains were first determined using the Ziegler-Nichols II method. The determined gains were then optimised to minimise height error using a recurrent back-propagation neural network (PIDNN), with which new controller gains were determined, which is also a novelty of this study. Simulations were carried out for flights at subsonic speeds close to the speed of sound and supersonic speeds, at low and high altitudes. The simulations showed that determining controller gains using a recurrent neural network significantly minimises height errors and increases the flexibility of the PID controller. [ABSTRACT FROM AUTHOR]

A commercially available 100 kW PEM fuel cell system designed for efficient operation on ground-level was tested at low ambient pressures between 750 mbar and 940 mbar in a low-pressure chamber. The current–voltage characteristics at 940 mbar and 900 mbar showed only small differences, while the system performed worse at lower ambient pressures. To enable operation at these low pressures, an additional current-limiting strategy had to be implemented, as it was found that the compressor could not deliver sufficient mass flow at ambient pressures below 867 mbar to reach the maximum current allowed by the system (420 A). The results show that the fuel cell system, which was designed for ground-level applications, can be operated at lower pressures if the proposed current-limiting strategy is implemented, although at the cost of a lower maximum current output at low ambient pressures. Based on the results, suggestions for further hardware measures to optimise the system for flight conditions are made. [ABSTRACT FROM AUTHOR]

Temperature and precipitation are important abiotic factors affecting net primary productivity (NPP) in grassland ecosystems. However, findings on how elevation influences the effects of these factors on NPP in alpine grasslands are not yet consistent. In addition, the impact of varied patterns of climate change on NPP sensitivity with elevation remain unclear. Therefore, alpine grassland on the Tibetan Plateau (TP) was selected to profile the spatial and temporal patterns of NPP from 2001 to 2022, and subsequently to reveal the effects of temperature and precipitation on the sensitivity of NPP with altitudinal gradient. The results showed that (1) 91% of the TP grassland experienced positive NPP trends, and the NPP trends followed a unimodal curve with elevation, with the largest mean value at 2500 m; (2) a positive correlation between precipitation and NPP dominated the grassland NPP up to an elevation of 3400 m, and a positive correlation between temperature and NPP dominated the grassland NPP above an elevation of 3400 m; (3) temperature, precipitation, and their interaction explained, on average, 21% of the temporal variation in the NPP of TP grassland, and the explanatory capacity decreased significantly with elevation; and (4) elevation, temperature, and precipitation variations together explained 35% of the NPP sensitivity of the TP grasslands. This study reveals the altitudinal characteristics of NPP in grasslands affected by climate, and reminds us to take elevation into account when carrying out grassland management. [ABSTRACT FROM AUTHOR]

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Copyright of Baghdad Science Journal is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In the valve hall of the converter station of a UHV transmission project at high altitudes, the shielding sphere and the wall/floor form a large-size sphere–plane long air gap. Burr defects on the surface of the shielding sphere can affect its discharge characteristics. The streamer-to-leader transition is a key process in the discharge of the long air gap. The existing research is limited to the discharge characteristics of small-size electrodes at low altitudes and cannot be directly extended to those of large-size electrodes at high altitudes. Therefore, this paper constructs a discharge test platform with optical–electrical synchronous detection at an altitude of 2200 m. The instantaneous optical power, electric field intensity, high potential current, and other physical parameters during the discharge in the long air gap of a 1.3 m diameter sphere–plane system were collected for both a sphere electrode with burrs and one without burrs. The injection current of the initial streamer was used as the input variable and substituted into Gallimberti's model to analyse the transformation process of the streamer stem's vibrational energy into translational energy. A modified model that is more suitable for high altitudes was developed by taking into account convective diffusion and the thermal expansion of the streamer, and the influence of burr defects on the characteristics of the transition from streamer to leader was analysed and compared with the experimental results. Overall, burr defects reduced the duration of the streamer-to-leader transition and facilitated discharge. The analysis results generally agree with the experimental results. The research results are of great significance for the design of the valve hall insulation in converter stations at high altitudes. [ABSTRACT FROM AUTHOR]

Introduction: Altitudinal changes in soil bacterial diversity, composition, biotic interactions, and function are prevalent. However, the overall patterns and associations among these dimensions remain unclear, particularly in vulnerable alpine mountain ecosystems. Methods: Here, we investigated soil bacterial communities along a high-altitude gradient to elucidate patterns and associations in taxonomic and phylogenetic diversity, co-occurrence networks, and functional potentials. Results: We observed increasing altitudinal trends in bacterial richness and phylogenetic diversity, along with significant differences in taxonomic and phylogenetic composition across altitudes. The connectivity component of the co-occurrence network properties showed a negative association with altitude. We also observed high redundancy in functional potentials, resulting in insignificant variation in functional diversity along the altitudinal gradient. However, the strength of functional diversity varied based on the interaction between network connectivity and phylogenetic diversity. Additionally, functional dissimilarity was more closely associated with phylogenetic rather than taxonomic dissimilarity or differences in network properties, highlighting the role of phylogenetic lineages in functional redundancy. Discussion: This study characterizes the altitudinal distribution of soil bacteria and explores their covariations, enhancing our understanding of soil bacterial diversity and functional potentials along altitudinal gradients and providing valuable insights for predicting community changes and improving alpine ecosystem conservation. [ABSTRACT FROM AUTHOR]

Exploring the elevation distribution characteristics, biomass allocation strategies, and the effects of elevation, soil factors, and functional traits on the biomass of Gentianella turkestanorum (Gand.) Holub is of great significance for the production, development, utilization, and protection of the medicinal material resources. In this study, we investigated the biomass and functional traits of the root, stem, leaf, and flower of G. turkestanorum, analyzing their elevation distribution patterns, allometric growth trajectories, and their correlations. The results showed that the biomass of different organs of G. turkestanorum decreases with increasing elevation, and the belowground biomass/aboveground biomass increases with elevation. The flower biomass accounts for 59.24% of the total biomass, which was significantly higher than that of other organs. G. turkestanorum biomass follows the optimal allocation theory, adopting a 'pioneering' growth strategy at low elevations and a 'conservative' strategy at high elevations. Chlorophyll content and leaf thickness of G. turkestanorum were positively correlated with elevation, but leaf dry matter content and the number of flowers were negatively correlated with elevation. Compared to functional traits, elevation and soil factors have a stronger explanatory power regarding the biomass of G. turkestanorum. Elevation, soil moisture content, pH, available phosphorus, total nitrogen, and ammonium nitrogen significantly affect the biomass of G. turkestanorum, with only pH showing a positive correlation with biomass. Among these factors, elevation, soil moisture content, and pH significantly impact the accurate prediction of G. turkestanorum biomass. The number of flowers, crown width, root length, root diameter, and leaf dry matter content all have a significantly positive correlation with the biomass of G. turkestanorum, with the number of flowers and root diameter making significant contributions to the accurate prediction of biomass. Elevation can directly affect the biomass of G. turkestanorum and can also indirectly affect it through other pathways, with the direct effect being greater than the indirect effect. [ABSTRACT FROM AUTHOR]

Due to factors that include systematic sensor delay, it is difficult for synthetic aperture radar (SAR) satellite stereo positioning to meet the requirements of large-scale mapping. In traditional stereo positioning methods, ground control points (GCP) are required to eliminate errors. In this study, a method is proposed to improve the stereo positioning accuracy without GCP. First, the factors influencing the Gaofen-3 (GF-3) satellite stereo positioning accuracy were analysed. The errors were divided into systematic fixed errors, spatial and temporal variation errors, and random errors. Subsequently, a systematic geometric error compensation model and a stereo adjustment model were constructed, and a method to improve the multiscene and multimode stereo positioning accuracy without GCP was proposed. Finally, the effects of different intersection angles on the accuracy of stereo positioning were compared and analysed, and the optimal intersection angle of the SAR satellite was quantitatively analysed. The effectiveness and accuracy of this method were verified using GF-3 high-resolution image data. The experimental results indicate that the proposed method can improve the SAR satellite stereo positioning accuracy. The plane positioning accuracy improved by 95.1%, and the elevation positioning accuracy improved by 97.9%. In general, the plane and elevation positioning accuracies of the GF-3 satellite were better than 3 m and 2 m, respectively. The stereo-positioning accuracy of the SAR satellite was the best and most stable when the intersection angle was between 40° and 50°. [ABSTRACT FROM AUTHOR]

Purpose Methods Results Conclusion To compare the parameters and indices of a novel swept‐source optical coherence tomography device (SS‐OCT, ANTERION) with those of a rotating Scheimpflug camera (RSC)‐based tomograph (Pentacam) in normal and keratoconic (KC) eyes.This prospective, monocentric, cross‐sectional study included individuals with unoperated normal and KC eyes, selecting one eye per subject. Ectasia‐specific parameters analysed with the SS‐OCT were difference in mean keratometry (Kmean) in the inferior and superior meridians, maximum keratometry value (Kmax), elevation of the posterior surface at the thinnest point, screening corneal objective risk of ectasia (SCORE) and thinnest point thickness. With the RSC, parameters determined were Belin/Ambrosio total deviation value (BAD‐D), index of height decentration and index of vertical asymmetry. KC classification with the SS‐OCT was based on the anterior and posterior radii of curvature and thinnest point thickness according to the ABCD classification of the RSC system.This study included 117 individuals with healthy eyes and 335 eyes with KC. The indices with the highest diagnostic discriminatory ability between the two cohorts were SCORE, difference of Kmean in the inferior and superior meridians and posterior elevation of the thinnest point (SS‐OCT), as well as the index of height decentration, index of vertical asymmetry and BAD‐D (RSC). The classifications using SS‐OCT defined mild‐stage KC as Kmax, posterior elevation of the thinnest point and thinnest point thickness as ≤50.9 D, ≤30 and ≥472 μm, respectively. Moderate stage values were 51–55.9 D, 31–69 and 471–438 μm, respectively, while respective advanced stage were ≥56 D, ≥70 and ≤437 μm.The diagnostic capabilities for both devices were found to be comparable. KC classification using SS‐OCT can be independently based on the anterior surface, posterior surface and corneal thickness. [ABSTRACT FROM AUTHOR]

This study examines biases in scientific research on bird biodiversity in the provinces of San Juan and Mendoza located in drylands of central-western Argentina. We analyzed the amount, nature, and spatial distribution of research, identifying under- or over-represented topics and trends in sampling design. We found differences in research trends between San Juan and Mendoza, with studies clustered around a limited number of taxa, protected areas, and lower altitudes, highlighting important knowledge gaps. The accessibility and availability of publications, as well as their indexing in national and international databases, were also assessed. The findings reveal a limited and skewed database of temporally and spatially biased data. Furthermore, our results indicate that certain species, taxonomic groups, and IUCN conservation categories are over-represented in the literature. We underline the urgency of promoting primary data generation and focusing on less explored topics and regions. These findings provide valuable insights into research trends and priorities, suggesting the need for more balanced and comprehensive studies to inform conservation strategies in these arid regions. This review emphasizes the need to address these biases to improve understanding and conservation of biodiversity in central-western Argentina, with implications for arid regions globally. [ABSTRACT FROM AUTHOR]

Dasypus novemcinctus (Nine-banded Armadillo) is the only species of armadillo in the US and is notable because it alters ecosystems by excavating extensive burrows used by many other wildlife species. Relatively little is known about its habitat use or population densities, particularly in developed areas, which may be important to facilitating its range expansion. We used camera traps to explore patterns in armadillo detection and occupancy and applied the random-encounter model to calculate population densities at 12 study sites in the Ozark Mountains of Arkansas along an urban-to-rural gradient. Armadillo detection probability was best predicted by temperature (positively) and precipitation (negatively). We found that armadillo occupancy probability decreased on steep slopes and increased at higher elevations. Contrary to our predictions, we found no evidence that other landcover or anthropogenic variables influenced probability of armadillo occupancy. Armadillo density varied considerably between sites (mean = 4.88-46.20 armadillos per km²) but was not correlated with any environmental or anthropogenic variables that we measured. Nine-banded Armadillos occurred at all of our study sites demonstrating that the species is a habitat generalist which likely contributes to its remarkable range expansion across most of the southeastern and midwestern US. [ABSTRACT FROM AUTHOR]

The availability of an adequate network of services of general interest (SGI) is a major issue for the vitality of rural areas, which is very much on the political agendas of different governmental levels. This is also true for the narrow field of food retailing, which is the subject of this paper. Here we focus on the provision of commercial services in the province of Sondrio, a small stretch of land in the Alps on the border between Italy and Switzerland. This paper investigates the rearrangement of the provincial distribution system between 2010 and 2022, focusing on the dynamics of food retail density in terms of shops and available floor area with respect to the resident population. What emerges is a progressive commercial rarefaction that plays a role in reshaping the relationship between the populations of builtup areas at different altitudes and leads to a sharp increase in instances of under-provision and commercial desertification in the strict sense. The way these critical situations affect the different municipalities depends on their individual position within their settlement networks, with residential municipalities being the most affected, even though they are not necessarily isolated or in remote locations. Retail dynamics in disadvantaged rural mountain areas must not be underestimated, as it also contributes to territorial cohesion. [ABSTRACT FROM AUTHOR]

Many bird species fly at high altitudes for short periods and/or shift seasonally in altitude during migration, but little is known about the physiology of these behaviors. Transient high-altitude flight, or short-term flight at extreme altitudes, is a strategy used by lowland-native birds, often in the absence of topographic barriers. Altitudinal migration, or seasonal roundtrip movement in altitude between the breeding and non-breeding seasons, is a form of migration that occurs as a regular part of the annual cycle and results in periods of seasonal residency at high altitudes. Despite their nuanced differences, these two behaviors share a common challenge: exposure to reduced oxygen environments during at least part of the migratory journey. In this perspective piece, we compare what is known about the physiology of oxygen transport during transient high-altitude flight and altitudinal migration by highlighting case studies and recent conceptual advances from work on captive and wild birds. We aim to open avenues for integrative research on the ecology, evolution, and physiology of high-flying and mountain-climbing birds. [ABSTRACT FROM AUTHOR]

We present improvements to the physical optics method for high-frequency computations. This involves refining the calculation model such that the number of triangular facets is adequate to accurately represent the target structure. An illumination assessment is performed using the mesh model, and this is followed by a predetermined subdivision of the illuminated facets to achieve the required computational resolution. Subsequently, using a group of high-speed vehicle RAM C-II models with surfaces of different roughness, we calculate their one-dimensional high-resolution range profile and two-dimensional inverse synthetic aperture radar images at different reentry heights. The results demonstrate that the smooth-surfaced RAM C-II exhibits imaging limited to its head and tail, whereas the rough-surfaced RAM C-II reveals its entire contour. Furthermore, the presence of plasma diminishes the imaging efficacy of rough-surfaced targets, with the effect becoming more pronounced at lower altitudes. This study provides valuable insights for the identification of high-speed vehicles. [ABSTRACT FROM AUTHOR]

This study examines the impact of a bottom explosion on wave generation in an inertial surface, considering the roles of fluid viscosity, wave current, and the nature of a slippery porous sea bottom. The Fourier and Laplace transform techniques are employed to calculate the surface elevation in terms of an infinite integral. Further, the infinite integral is evaluated asymptotically using the stationary-phase approach for larger time and distance values. The influence of viscosity, inertial surface, current, and slip parameters on wave generation is analyzed for different times and distances. The study reveals that the presence of an inertial surface lessens the amplitude of free surface elevation. Further, the free surface elevation's amplitude reduces as the current speed and liquid viscosity approach closer to a small value. In the case of a slippery porous bottom, as the slip parameter increases, the free surface elevation's amplitude decreases. [ABSTRACT FROM AUTHOR]

Motivated by the need for improving the lift of unmanned aerial vehicle and replacing the trailing-edge flap under high-altitude environment, the electrical and the flow characteristics of an asymmetrical plasma actuator for a range of elevations [0.2 km ≤ E (elevations) ≤ 4 km] in quiescent air were studied in the present work. In general, compared with the plasma actuator under normal environment, the disturbance capability of the plasma actuator can be enhanced in high-elevation environments and more beneficial to flow control. Initially, the average total power consumption and the maximum amplitude of the induced current increase monotonously with the elevation. Meanwhile, the maximum velocity, Vmax, of the wall jet created by the plasma actuator increases with increasing the elevation and Vmax (velocity) ∼ E0.36. The velocity profile becomes irregular at E ≥ 2 km. Moreover, the relationship between the electrical and the flow characteristics of the plasma actuator is revealed based on the body force and the power consumption. In addition, compared with the case of normal condition, the starting vortex travels further from the upper electrode and the traveling angle is lower at higher elevation, which is benefit for momentum transfer and mixing. It is of great importance that a series of coherent structures in the vicinity of the wall surface were first observed at higher elevation, which is quite different from the case with normal condition. [ABSTRACT FROM AUTHOR]

Microdroplet impact icing is a common occurrence in high altitudes or cloud environments. There is a lack of in-depth understanding regarding the icing behaviors of microdroplets interacting with anti-icing microstructures. While the impact of microstructure pitch on delaying icing is extensively studied, the microstructure height, as a similarly technology-controllable structural parameter, has received comparatively little attention in research. This study investigates the impact dynamics of microdroplets on supercooled superhydrophobic microgrooves, utilizing the coupled level-set and volume of fluid and enthalpy-porosity technologies for precise simulation. The behaviors of microdroplets impact on supercooled surface manifest distinctive characteristics compared with ambient surface, particularly evident when We < 170 (βmax (maximum spreading diameter)/βMod (predicted spreading diameter) ∼ 0.8). Unlike flat surfaces, microgrooves have been shown to reduce βmax by 52%. Additionally, an increase in H/Do (ratio of microgroove height H and droplet diameter Do) leads to a diminishing trend in βmax, showing a reduction of 13%. The outcomes of microdroplet impact progress from complete bouncing, partial bouncing, bouncing with satellite droplet breakup, to deposition, sequentially as the We and surface supercooling degree escalate. Heightening the microstructure alters the transition point between partial bouncing and bouncing with breakup, thereby expanding the range of droplet bouncing (with thresholds being doubled). This effect is attributed to satellite droplet breakup, supported by simulation results suggesting that droplet breakup reduces interface curvature, thus facilitating bouncing. Moreover, microgroove structures have the potential to decrease the dimensionless contact time of droplets by 33% when comparing H/Do = 0.4 with H/Do = 0.1. [ABSTRACT FROM AUTHOR]

Exposed and isolated alpine ecosystems present evolutionary challenges for flying species worldwide. Many insects have undergone dramatic wing reduction in response to these harsh conditions, losing the ability to fly. By contrast, some taxa have countered alpine conditions by evolving larger wings to improve flight ability. In this study, we investigated how two independent clades of Zelandoperla fenestrata stoneflies respond to upland environments. Our results revealed strikingly different adaptations to elevation across the two closely related clades. In Clade 1 (southern South Island), wing length decreases sharply with increasing elevation. In contrast, wing length in the geographically adjacent Clade 2 (northern South Island, and North Island) increases with elevation. These contrasting strategies highlight the diverse adaptive pathways that may exist even for closely related lineages encountering similar environmental challenges. [ABSTRACT FROM AUTHOR]

Clouds and aerosols, as important factors in the Earth's climate system, have significant impacts on the atmospheric environment and global climate. This study investigated the optical and physical properties of clouds and aerosols over South America from 2006 to 2021 using CALIPSO Level 2 products. South America was divided into four regions: A (Western Andean Mountains), B (Northern Orinoco and Amazon plains), C (Southern La Plata Plains), and D (Eastern Brazilian Highlands). Seasonal variations in the optical properties of low clouds and their interactions with the lowest-layer aerosols were analyzed and compared. The results indicate that Region C had the highest OPlc (probability of low clouds) and AODlc (AOD (Aerosol Optical Depth) of low clouds, likely due to its flat terrain and westerly influences. Both AODlc and OPlc were higher in September–November compared to other seasons. DRlc (depolarization ratio of low clouds) values were higher in Regions C and D, particularly in September–February, possibly due to topographic effects and more precipitation and higher humidity during this period. The elevated CRlc (color ratio of low clouds) in Region A may be attributed to the Andes blocking warm, moist air, leading to increased precipitation and cloud particle content. HLlc (top height of low clouds) and BLlc (base altitude of low clouds) were positively correlated with geographic elevation, while Tlc (thickness of low clouds) was greater at night, potentially due to enhanced atmospheric stability. Furthermore, strong correlations among certain parameters suggested significant interactions between aerosols and clouds. [ABSTRACT FROM AUTHOR]

Using the high-resolution version of the QUODDY-4 3D finite-element hydrostatic model, the fields of the dynamic characteristics (amplitudes of tidal elevations and ellipses of the baroclinic tidal velocities) at the pycnocline depth and the average (over a tidal cycle) depth-integrated components of the baroclinic tidal energy budget in the ice-free East Siberian Sea are presented. These include the density, the advective transport and horizontal wave flux of baroclinic tidal energy, the mutual conversion rate of tidal energy, and the dissipation rate of baroclinic tidal energy due to bottom friction. On average (over a tidal cycle and the sea area), their values were equal to J/m2, 11 and 269 W/m, and , W/m2, respectively. These values are in general smaller than their analogs in the Laptev Sea. [ABSTRACT FROM AUTHOR]

Phlomis floccosa D. Don populations are distributed in different microhabitats within Al‐Akhdar mountainous landscape, in Libya. Five populations were selected for the study. Spatial relationships among individuals were investigated using the spatial point pattern analysis. Functional traits were recorded at the vegetative, flowering and fruiting stages. Seeds were collected at the dispersal stage to estimate the regeneration potential. Greater degree of aggregation was found at higher elevations on both northern and southern sides of the mountain but with different demography and traits. On the northern side, greater degree of aggregation was accompanied by absence of large adults and greater percentage of seedlings, and it was positively associated with the reproductive output, while negatively associated with the size and regeneration indices. On the southern side, greater degree of aggregation was accompanied by greater contribution of large adults and greater percentage of seedlings, and it was positively associated with the size and regeneration indices, while negatively associated with the reproductive output. On the other hand, the population in the wadi (valley) microhabitat showed coarse‐scale clumped pattern, higher values for most of the functional traits and higher contribution of seedlings but with lower facilitation offered by adults. The variations in the degree of aggregation and the functional traits trade‐offs in P. floccosa populations ensured successful survival and regeneration in the heterogeneous microhabitats. Meanwhile, stressed conditions greatly affect the survival and regeneration of the species suggesting the need for conservation measures to overcome the adverse effects of climate change. [ABSTRACT FROM AUTHOR]

Aiming at the noise, cost and safety problems of current unmanned aerial vehicle (UAV) operation within cities, this paper divides the airspace into layers by altitudes and proposes an operation cost and crash risk model based on noise protection zones under aerodynamic and other constraints. This model satisfies the standard operation conditions of UAVs, and reduces the noise impact on the environment and the ground population, as well as operation cost and crash risk. Thus, based on the noise protection zone, the improved Dubins path planning method is used. It combines the Dubins path planning idea with the tangent line of the geometric circle, and adds node processing to enrich the optional paths for UAV operation and optimize the paths. As the Dijkstra algorithm is used as the the best path searching algorithm, and the lowest total cost is set as the goal, a UAV optimal operation path is searched and compared with the A* algorithm. Simulation experiments verify the effectiveness of the proposed model and the improved method. They reduce the noise impact of UAV operation and the operation cost, and improve the safety and efficiency of the operation. The results indicate that the optimal operation altitude of the example UAV, a biplane medium-sized UAV with a mass of 15 kg and a paddle disk area of about 1.313 m², is 40 m, and its operation minimum total cost is 5.42; compared with the results in the other altitude layers, the total operation cost is reduced by 37.56% at most and 5.91% at least. [ABSTRACT FROM AUTHOR]

With the continuous reforms of low-altitude economy, the advancement of low-altitude aircraft are presenting a new landscape characterized by high density, heterogeneity, autonomy, and mixed manned/ unmanned operations. Low-altitude surveillance, as an important safeguard for the safety of low-altitude operations, can ensure the safe and efficient operation of aircraft at low altitudes. To address current issues of inadequate low-altitude surveillance means, it is necessary to construct a low-altitude surveillance technology system with no blind spots, covering mixed manned/unmanned operations, based on the characteristics of the complex low-altitude environment. Firstly, current difficulties in low-altitude surveillance are analyzed from the perspectives of the concept of low-altitude surveillance and its development trends, including weight, size and power limitations of airborne equipment, tight channel resources, and significant differences among aircraft. Secondly, from the perspectives of the cooperative surveillance technology and the non-cooperative surveillance technology, the current status of key surveillance technologies worldwide is elaborated, and a systematic comparison and summary of the relevant characteristics of each technology are provided. Finally, facing the development of a new generation of low-altitude surveillance, the development directions of future cooperative surveillance, non-cooperative surveillance, and integrated surveillance technologies are discussed, with the expectation of providing certain guidance for the safe operation of low-altitude aircraft in the future. [ABSTRACT FROM AUTHOR]

It is challenging to estimate the elevation angle of low-altitude targets due to the multipath effect. Various signal processing techniques have been proposed to mitigate these effects, including the use of multi-frequency signals as opposed to single narrowband signals. However, the optimal type of multi-frequency signals and their effective utilization have not been thoroughly explored. Compressive sensing was also proposed as a high-resolution angle estimation method. But, that was conducted with narrowband signals. In this paper, we employ MIMO-OFDM signals along with a block sparse Bayesian learning fast marginalized (BSBL-FM) method. This combination allows for the effective processing of multi-frequency signals and provides high resolution estimates. The MIMO-OFDM approach represents radar signals in a block-sparse matrix form, and the BSBL-FM method leverages this sparsity to achieve high-resolution angle estimates. Simulation results demonstrate that our method can accurately estimate angles at extremely low altitudes where the elevation angle is less than 1 degree. [ABSTRACT FROM AUTHOR]