Flight Duration Research Articles

Weightlessness leads to an increase granulosa cells in the growing follicle

The participation of women in space programs of increasing flight duration requires research of their reproductive system from the perspective of subsequent childbearing and healthy aging. For the first time, we present hormonal and structural data on the dynamics of recovery after a 157-day space flight in a woman of reproductive age. There were no clinically significant changes in the reproductive system, but detailed analysis shows that weightlessness leads to an increase in the proportion of early antral follicles and granulosa cells in large antral follicles. Returning to Earth’s gravity reduces the number and diameter of early antral follicles.

Development of a Cost-Effective UAV for Extended Duration Disaster Management Operations using Expanded Polystyrene

Commercial UAVs specifically developed for disaster management purposes are frequently priced at an exorbitant level. Usually, unmanned aerial vehicles (UAVs) have a flight length of 15-30 minutes. However, crisis management operations often demand longer mission durations, occasionally in difficult weather circumstances. In order to tackle this problem, Expanded Polystyrene (EPS) was selected as the material for the body and wings of the UAV due to its cost-effectiveness in comparison to materials such as fiberglass, carbon fibre, epoxy, Kevlar, and wooden balsa. The EPS material utilized exhibits a tensile strength of 88 pounds per square inch (psi). For flight testing, a LiPo 3S battery with a voltage of 11.1 volts was used in the UAV. The virtual wind tunnel test was carried out with precise parameters, including an air density of 1.225 kg/m³ and a wind speed of 50 m/s. In order to improve the wing's structural integrity, a lightweight aluminium bar was incorporated. The initial design of the UAV wing showcased an elongated glider-like structure, enabling prolonged flight durations using a solitary propeller. The simulation findings showed that the UAV successfully controlled the drag coefficient with time, maintaining a traction force of 200N during testing. The UAV's capacity to endure gusts of up to 70 knots, achieve elevations of 5000 feet, and travel lengths of up to 90 km was demonstrated in practical trials, contingent upon the control systems employed. Ultimately, the newly designed UAV has the capability to sustain flight for a duration of 8 hours, thereby overcoming the constraints typically encountered with commercial UAVs employed in disaster management.

Adaptive Scheduling of High-Availability Drone Swarms for Congestion Alleviation in Connected Automated Vehicles

The Intelligent Transportation System (ITS) serves as a pivotal element within urban networks, offering decision support to users and connected automated vehicles (CAVs) through comprehensive information gathering, sensing, device control, and data processing. Presently, ITS predominantly relies on sensors embedded in fixed infrastructure, notably Roadside Units (RSUs). However, RSUs are confined by coverage limitations and may encounter challenges in prompt emergency responses. On-demand resources, such as drones, present a viable option to supplement these deficiencies effectively. This paper introduces an approach where Software-Defined Networking (SDN) and Mobile Edge Computing (MEC) technologies are integrated to formulate a high-availability drone swarm control and communication infrastructure framework, comprising the cloud layer, edge layer, and device layer. Drones confront limitations in flight duration attributed to battery limitations, posing a challenge in sustaining continuous monitoring of road conditions over extended periods. Effective drone scheduling stands as a promising solution to overcome these constraints. To tackle this issue, we initially utilized Graph WaveNet, a specialized graph neural network structure tailored for spatial-temporal graph modeling, for training a congestion prediction model using real-world dataset inputs. Building upon this, we further propose an algorithm for drone scheduling based on congestion prediction. Our simulation experiments using real-world data demonstrate that, compared to the baseline method, the proposed scheduling algorithm not only yielded superior scheduling gains but also mitigated drone idle rates.

Reinforcement learning based autonomous multi-rotor landing on moving platforms

Multi-rotor UAVs suffer from a restricted range and flight duration due to limited battery capacity. Autonomous landing on a 2D moving platform offers the possibility to replenish batteries and offload data, thus increasing the utility of the vehicle. Classical approaches rely on accurate, complex and difficult-to-derive models of the vehicle and the environment. Reinforcement learning (RL) provides an attractive alternative due to its ability to learn a suitable control policy exclusively from data during a training procedure. However, current methods require several hours to train, have limited success rates and depend on hyperparameters that need to be tuned by trial-and-error. We address all these issues in this work. First, we decompose the landing procedure into a sequence of simpler, but similar learning tasks. This is enabled by applying two instances of the same RL based controller trained for 1D motion for controlling the multi-rotor’s movement in both the longitudinal and the lateral directions. Second, we introduce a powerful state space discretization technique that is based on i) kinematic modeling of the moving platform to derive information about the state space topology and ii) structuring the training as a sequential curriculum using transfer learning. Third, we leverage the kinematics model of the moving platform to also derive interpretable hyperparameters for the training process that ensure sufficient maneuverability of the multi-rotor vehicle. The training is performed using the tabular RL method Double Q-Learning. Through extensive simulations we show that the presented method significantly increases the rate of successful landings, while requiring less training time compared to other deep RL approaches. Furthermore, for two comparison scenarios it achieves comparable performance than a cascaded PI controller. Finally, we deploy and demonstrate our algorithm on real hardware. For all evaluation scenarios we provide statistics on the agent’s performance. Source code is openly available at https://github.com/robot-perception-group/rl_multi_rotor_landing.

Seasonal patterns and processes of migration in a long-distance migratory bird: energy or time minimization?

Optimal migration theory prescribes adaptive strategies of energy, time or mortality minimization. To test alternative hypotheses of energy- and time-minimization migration we used multisensory data loggers that record time-resolved flight activity and light for positioning by geolocation in a long-distance migratory shorebird, the little ringed plover, Charadrius dubius. We could reject the hypothesis of energy minimization based on a relationship between stopover duration and subsequent flight time as predicted for a time minimizer. We found seasonally diverging slopes between stopover and flight durations in relation to the progress (time) of migration, which follows a time-minimizing policy if resource gradients along the migration route increase in autumn and decrease in spring. Total flight duration did not differ significantly between autumn and spring migration, although spring migration was 6% shorter. Overall duration of autumn migration was longer than that in spring, mainly owing to a mid-migration stop in most birds, when they likely initiated moult. Overall migration speed was significantly different between autumn and spring. Migratory flights often occurred as runs of two to seven nocturnal flights on adjacent days, which may be countering a time-minimization strategy. Other factors may influence a preference for nocturnal migration, such as avoiding flight in turbulent conditions, heat stress and diurnal predators.

Screening, characterization and optimization of potential dichlorodiphenyl trichloroethane (DDT) degrading fungi

Dichlorodiphenyltrichloroethane is an organo-chlorine insecticide used for malaria and agricultural pest control, but it is the most persistent pollutant, endangering both human and environmental health. The primary aim of the research is to screen, characterize, and assess putative fungi that degrade DDT for mycoremediation. Samples of soil and wastewater were gathered from Addis Ababa, Koka, and Ziway. Fungi were isolated and purified using potato dextrose media. Matrix-Assisted Laser Desorption, Ionization, and Flight Duration The technique of mass spectrometry was employed to identify fungi. It was found that the finally selected isolate, AS1, was Aspergillus niger. Based on growth factor optimization at DDT concentrations (0, 3500, and 7000 ppm), temperatures (25, 30, and 35 °C), and pH levels (4, 7, and 10), the potential DDT-tolerant fungal isolates were investigated. A Box-Behnken experimental design was used to analyze and optimize fungal biomass and sporulation. The highest biomass (0.981 ± 0.22 g) and spore count (5.60 ± 0.32 log/mL) of A. niger were found through optimization assessment, and this fungus was chosen as a potential DDT-degrader. For DDT degradation investigations by A. niger in DDT-amended liquid media, gas chromatograph-electron capture detector technology was employed. DDT and its main metabolites, DDE and DDD, were eliminated from both media to the tune of 96–99 % at initial DDT concentrations of 1750, 3500, 5250, and 7000 ppm. In conclusion, it is a promising candidate for detoxifying and/or removing DDT and its breakdown products from contaminated environments.

Energy supply during nocturnal endurance flight of migrant birds: effect of energy stores and flight behaviour

BackgroundMigrating birds fly non-stop for hours or even for days. They rely mainly on fat as fuel complemented by a certain amount of protein. Studies on homing pigeons and birds flying in a wind-tunnel suggest that the shares of fat and protein on total energy expenditure vary with flight duration and body fat stores. Also, flight behaviour, such as descending flight, is expected to affect metabolism. However, studies on free flying migrant birds under natural conditions are lacking.MethodsOn a Swiss Alpine pass, we caught three species of nocturnal migrant passerines out of their natural migratory flight. Since most night migrants start soon after dusk, we used time since dusk as a measure of flight duration. We used plasma concentrations of metabolites of the fat, protein, and carbohydrate metabolism as indicators of relative fuel use. We used flight altitudes of birds tracked with radar and with atmospheric pressure loggers to characterize flight behaviour.ResultsThe indicators of fat catabolism (triglycerides, very low-density lipoproteins, glycerol) were positively correlated with body energy stores, supporting earlier findings that birds with high fat stores have a higher fat catabolism. As expected, plasma levels of triglycerides, very low-density lipoproteins, glycerol and ß-hydroxy-butyrate increased at the beginning of the night, indicating that nocturnal migrants increased their fat metabolism directly after take-off. Surprisingly, fat catabolism as well as glucose levels decreased in the second half of the night. Data from radar observations showed that the number of birds aloft, their mean height above ground and vertical flight speed decreased after midnight. Together with the findings from atmospheric pressure-loggers put on three species, this shows that nocturnal migrants migrating over continental Europe descend slowly during about 1.5 h before final landfall at night, which results in 11–30% energy savings according to current flight models.ConclusionsWe suggest that this slow descent reduces energy demands to an extent which is noticeable in the plasma concentration of lipid, protein, and carbohydrate metabolites. The slow descent may facilitate the search for a suitable resting habitat and serve to refill glycogen stores needed for foraging and predator escape when landed.

The Risk of Aircraft-Acquired SARS-CoV-2 Transmission during Commercial Flights: A Systematic Review.

The aircraft-acquired transmission of SARS-CoV-2 poses a public health risk. Following PRISMA guidelines, we conducted a systematic review and analysis of articles, published prior to vaccines being available, from 24 January 2020 to 20 April 2021 to identify factors important for transmission. Articles were included if they mentioned index cases and identifiable flight duration, and excluded if they discussed non-commercial aircraft, airflow or transmission models, cases without flight data, or that were unable to determine in-flight transmission. From the 15 articles selected for in-depth review, 50 total flights were analyzed by flight duration both as a categorical variable-short (<3 h), medium (3-6 h), or long flights (>6 h)-and as a continuous variable with case counts modeled by negative binomial regression. Compared to short flights without masking, medium and long flights without masking were associated with 4.66-fold increase (95% CI: [1.01, 21.52]; p < 0.0001) and 25.93-fold increase in incidence rates (95% CI: [4.1, 164]; p < 0.0001), respectively; long flights with enforced masking had no transmission reported. A 1 h increase in flight duration was associated with 1.53-fold (95% CI: [1.19, 1.66]; p < 0.001) increase in the incidence rate ratio (IRR) of cases. Masking should be considered for long flights.

Effects of tag mass on the physiology and behaviour of common noctule bats

BackgroundExternal tags, such as transmitters and loggers, are often used to study bat movements. However, physiological and behavioural effects on bats carrying tags have rarely been investigated, and recommendations on the maximum acceptable tag mass are rather based on rules of thumb than on rigorous scientific assessment.MethodsWe conducted a comprehensive three-step assessment of the potential physiological and behavioural effects of tagging bats, using common noctules Nyctalus noctula as a model. First, we examined seasonal changes in body mass. Second, we predicted and then measured potential changes in flight metabolic rate in a wind tunnel. Third, we conducted a meta-analysis of published data to assess effects of different tag masses on the weight and behaviour of bats.ResultsIndividual body mass of common noctules varied seasonally by 7.0 ± 2.6 g (range: 0.5–11.5 g). Aerodynamic theory predicted a 26% increase in flight metabolic rate for a common noctule equipped with a 3.8 g tag, equating to 14% of body mass. In a wind tunnel experiment, we could not confirm the predicted increase for tagged bats. Our meta-analysis revealed a weak correlation between tag mass and emergence time and flight duration in wild bats. Interestingly, relative tag mass (3–19% of bat body mass) was not related to body mass loss, but bats lost more body mass the longer tags were attached. Notably, relatively heavy bats lost more mass than conspecifics with a more average body mass index.ConclusionBecause heavy tags (> 3 g) were generally used for shorter periods of time than lighter tags (~ 1 g), the long-term effects of heavy tags on bats cannot be assessed at this time. Furthermore, the effects of disturbance and resource distribution in the landscape cannot be separated from those of tagging. We recommend that tags weighing 5–10% of a bat’s mass should only be applied for a few days. For longer studies, tags weighing less than 5% of a bat's body mass should be used. To avoid adverse effects on bats, researchers should target individuals with average, rather than peak, body mass indices.

Investigating the causes and consequences of controlled rest on the flight deck

IntroductionFatigue is a known issue in aviation due to long and irregular working hours. In some regions, pilots are permitted to sleep during a controlled rest period on the flight deck to manage unexpected sleepiness. We aimed to determine: (1) the relative influence of pre-flight sleep-wake history and time of day on the likelihood to take controlled rest; (2) whether neurobehavioral measures taken pre-flight are predictive of controlled rest use in-flight; and (3) the impact of controlled rest on neurobehavioral measures at top-of-descent.MethodsData from 120 long (&amp;gt;6 h flight duration), unaugmented (two-pilot) flights were analyzed (n = 31 pilots). Pilots wore actiwatches and completed sleep logs before and during trips. At pre-flight and top-of-descent, pilots completed a 5-min psychomotor vigilance task (PVT) and Karolinska Sleepiness Scale (KSS). A series of mixed-effects models with relevant covariates were conducted to assess the likelihood of controlled rest based on several predictors and the impact of controlled rest on outcome measures at top-of-descent.ResultsPilots were more likely to take controlled rest on night flights [p = .01, η2p = .13, OR = 13.81, 95% CI: (1.99, 95.80)] and when pre-flight sleepiness ratings were higher [p = .01, η2p = .14, OR = 4.14, 95% CI: (1.48, 11.57)]. Pilots who took controlled rest had faster response speeds [1000/reaction time (ms)] [p = .03, η2p = 0.07; estimated marginal mean (EMM) = 4.19, standard error (SE) = 0.07, 95% CI: (4.08, 4.29)] than those who did not [EMM = 4.00, SE = 0.05, 95% CI: (3.86, 4.14)].DiscussionOur results suggest that taking controlled rest may improve vigilant attention at critical phases of flight and may be a useful fatigue management tool, particularly during unaugmented night flights. Further research is needed to determine the impact of psychological and cultural influences on controlled rest and to understand how the policy is applied in practice.

Modern approaches to compression and noise resistant encoding of photo and video information in radio channels of complexes with unmanned aerial vehicle

Modern complexes with unmanned aerial vehicles (UAVs) of long flight duration (heavy class) are in practice equipped with a wide range of target loads, which leads to the need to transmit a large amount of useful information in real time with the required quality to a remote ground control station (GCS). The large volume of transmitted information imposes serious technical requirements on the capacity of communication channels, which, on the one hand, when designing communication systems within UAVs, is ensured by the use of directional antenna systems, multi-position signal-code structures, noise-resistant coding, high energy in the communication channel, etc. On the other hand, developers simultaneously solve the problem of minimizing the amount of information from target loads supplied to the input of the communication system while maintaining the required quality after compression. This article discusses the main information compression standards used by CUAVs developers, their advantages and disadvantages, as well as video codecs based on three-dimensional orthogonal transformations.

The effect of chronic leg press exercises on hamstring muscle length and different vertical jump performance

Background and Study Aim. As it is known, chronic resistance exercises cause limitations in some joints and this negatively affects the normal range of motion. In the present study, it was aimed to analyse the quadriceps-hamstring balance by analysing different vertical jump performances after six weeks of leg press exercise. Material and Methods. Eleven university students aged between 18-30 years were included in this study. The hamstring muscle length, 1 repetition maximum (1-RM) leg press performance were analysed before and after six weeks of leg press exercise. In addition, the vertical jump performances of the participants were analysed with My Jump 2 software programme. In this study, counter movement jumps (CMJ) and squat jump (SJ) performances of the participants were determined. Results. According to the findings, 1 repetition maximum (1-RM) leg press performance and hamstring length of the participants improved significantly (t=-7.609, ES: -2.29, p&lt;.001; t=-2.540, -0.76, p=.029, respectively). CMJ and SJ parameters of the participants did not change (p&lt;0.05). It was concluded that the lengthened hamstring length after the leg press exercise programme had a positive relationship with vertical jump height (r=0.656, p=0.028), flight duration (r=0.663, p=0.026), speed (r=0.657, p=0.028), and average speed (r=0.669, p=0.024). These relationships were observed among CMJ parameters following the exercise programme. Likewise, a positive correlation was found between hamstring length, which lengthened after the leg press exercise programme, and vertical jump height (r=0.625, p=0.040), flight duration (r=0.646, p=0.032), speed (r=0.646, p=0.032), and average speed (r=0.637, p=0.035). These correlations were identified among the SJ parameters after the exercise. Conclusions. As a result, it was determined that chronic leg press exercises positively affected hamstring muscle length and muscle strength. Different vertical jump performances such as CMJ and SJ did not change. However, the relationship between hamstring length and vertical jump parameters is interesting.

Modeling the Propagation of Infectious Diseases across the Air Transport Network: A Bayesian Approach

The COVID-19 pandemic, caused by the SARS-CoV-2 virus, continues to impact the world even three years after its outbreak. International border closures and health alerts severely affected the air transport industry, resulting in substantial financial losses. This study analyzes the global data on infected individuals alongside aircraft types, flight durations, and passenger flows. Using a Bayesian framework, we forecast the risk of infection during commercial flights and its potential spread across an air transport network. Our model allows us to explore the effect of mitigation measures, such as closing individual routes or airports, reducing aircraft occupancy, or restricting access for infected passengers, on disease propagation, while allowing the air industry to operate at near-normal levels. Our novel approach combines dynamic network modeling with discrete event simulation. A real-case study at major European hubs illustrates our methodology.

Effect of Spaceflight and Microgravity on the Musculoskeletal System: A Review.

With National Aeronautics and Space Administration's plans for longer distance, longer duration spaceflights such as missions to Mars and the surge in popularity of space tourism, the need to better understand the effects of spaceflight on the musculoskeletal system has never been more present. However, there is a paucity of information on how spaceflight affects orthopaedic health. This review surveys existing literature and discusses the effect of spaceflight on each aspect of the musculoskeletal system. Spaceflight reduces bone mineral density at rapid rates because of multiple mechanisms. While this seems to be recoverable upon re-exposure to gravity, concern for fracture in spaceflight remains as microgravity impairs bone strength and fracture healing. Muscles, tendons, and entheses similarly undergo microgravity adaptation. These changes result in decreased muscle mass, increased tendon laxity, and decreased enthesis stiffness, thus decreasing the strength of the muscle-tendon-enthesis unit with variable recovery upon gravity re-exposure. Spaceflight also affects joint health; unloading of the joints facilitates changes that thin and atrophy cartilage similar to arthritic phenotypes. These changes are likely recoverable upon return to gravity with exercise. Multiple questions remain regarding effects of longer duration flights on health and implications of these findings on terrestrial medicine, which should be the target of future research.

Frequent flight responses, but low escape distance of wild boar to nonlethal human disturbance

Abstract Human activities can affect the behaviour and fitness of wildlife. However, the response of animals to nonlethal human activities has not been well‐studied in wild boar, Sus scrofa, even though it is a widespread species in Europe and has become of increasing concern because of crop damages and its vector capacity for diseases. We study the behavioural responses of GPS‐collared wild boar to nonlethal experimental human approaches in the Bohemian Forest Ecosystem along the border between Germany and the Czech Republic. We describe and quantify the flight responses of the animals and assess whether they vary with the distance to recreational paths and the occurrence of hunting in the area. We show that wild boar were disturbed and displaced by human approaches on foot in 69% of the trials, but the average flight initiation and escape distances were relatively small (93 and 256 m, respectively). The probability of a flight response decreased with distance from the paths and increased with the ruggedness of the terrain. In the non‐hunting zone, the flight initiation distances and flight durations were shorter than in the hunting zone. Our results suggest a weak effect of nonlethal human disturbances on the movement of wild boar, although the animals were sensitive to the perceived risk in relation to recreation infrastructure and hunting. For the management of diseases such as African swine fever, it can be concluded that nonlethal disturbances are unlikely to accelerate the spread of the disease due to far‐distance movements. Guidelines for restrictions in case of an outbreak might be adjusted accordingly.

Topology optimization and 3D printing of a unibody quadcopter airframe

The performance of any unmanned aerial vehicle largely depends upon its weight as this characteristic dictates its payload capacity and flight duration. This paper presents a multiphysics simulation method for designing a unibody quadcopter airframe with optimum weight in SolidWorks. By adopting the computer-aided topology optimization concept, the mass of the frame is decreased by 91% (from 1558.44 to 134.738 grams) after getting rid of the unwanted elements, while not compromising its structural rigidity. The efficacy of the model is assessed by finite element analysis and it is found that the stress would remain within the acceptable limit. The optimized structure shows an operating life of 1.6×105 cycles in the fatigue analysis and experiences significantly less drag force in the computational fluid dynamics test than the original airframe for several angles of attack, thus proving the superiority of the optimized frame over the initial model. Finally, additive manufacturing is performed to fabricate the optimized structure using PLA material. 3D printing through the fused deposition modeling technique is chosen since it is ideal for fabricating intricate engineering prototypes compared to orthodox manufacturing processes. While creating the frame, a 45° overhang angle is maintained to ensure the usage of less support material.

Research on Improvement Methods for Driven System of Bio-Inspired Aircraft to Increase Flight Speed

The flapping-wing ornithopter is an aircraft that imitates the flight of birds in nature. It has significant potential and value in various fields such as surveying, search and rescue, military reconnaissance, and unmanned warfare, due to its biomimetic stealth and high efficiency in low Reynolds number flight. However, the cruising speed of current flapping-wing ornithopters is generally lower than that of birds of the same size, which seriously affects biomimicry, mission capability, and wind resistance. Increasing the cruising speed can make the aircraft fly more like a bird, improve the efficiency of reconnaissance missions and wind resistance per unit time, and has important research significance. However, the methods to increase the cruising speed of flapping-wing ornithopters are currently lacking. Firstly, this paper presents improvements to the propulsion system based on the team’s “Dove” aircraft to meet the speed requirements. The actual flapping frequency and rocking arm end torque of the “Dove” aircraft under different voltages are tested. To select and match the motor and gearbox in the propulsion system, a method for matching and selection among the motor, gearbox, and load is proposed. Finally, wind tunnel experiments and flight validations are conducted on the improved flight prototype. The wind tunnel experiments show that the increase in flapping frequency has a significant impact on thrust. The trimmed states at different speeds are obtained. The flight validation demonstrates the sustained high-speed flight capability of the aircraft. At a flapping frequency of approximately 15 Hz, the average flight speed of the aircraft is 13.3 m/s within a 15 min duration, which is close to the actual flight speed of pigeons. The duration of high-speed flight is tripled compared to the initial duration. The speed improvement successfully enhances the biomimicry and efficiency of reconnaissance missions per unit time for the aircraft.

A Survey on Methods to Optimize Power Harvesting in Drones

This paper explores the challenges associated with limited battery capacity in drones and presents a comprehensive analysis of strategies to optimize energy harvesting and extend flight durations. Various energy generation methods, including piezoelectric and solar harvesting, are discussed, along with electrical circuit generation for wireless charging and communication-enabled energy delivery. The interdisciplinary nature of drone technology is highlighted, emphasizing the need for ongoing research in renewable energy models and innovative solutions like laser charging. The paper concludes with recommendations for further exploration and refinement of these strategies to enhance the future of UAVs.

Assessing radiometric calibration methods for multispectral UAV imagery and the influence of illumination, flight altitude and flight time on reflectance, vegetation index and inversion of winter wheat AGB and LAI

Radiometric correction is essential to unmanned aerial vehicle (UAV) precision agriculture applications, especially for crop multi-period analysis and quantitative inversion of phenotypic and physiological parameters. In this study, we investigated the performance of four radiometric correction methods: “Camera only” (A), “Camera and sun irradiance” (B) and “Camera, sun irradiance and sun angle” (C) methods provided by Pix4d Mapper and an irradiance sensor-based method (D) implemented with the R software. UAV campaigns were conducted at flight altitudes of 30 m, 60 m and 90 m under clear and cloudy skies at different times over an experimental field of winter wheat. The influences of illumination, flight altitude and flight time on reflectance and vegetation indexes derived from different radiometric calibration methods were analyzed. Moreover, we further assessed the impact of reflectance and vegetation index variations on the above-ground biomass (AGB) and leaf area index (LAI) estimations of winter wheat. Results showed that method D is a promising approach for radiometric calibration, which produced consistent reflectance with method A at noon (e.g., 10:44:41 AM March 17 and 11:39:37 AM April 7) and mid-afternoon (e.g., 15:30:02 PM May 1) and more reliable reflectance in the morning (e.g., 7:15:44 AM March 17). Methods B and C seriously underestimated the reflectance at 10:44:41 AM March 17 and 11:39:37 AM April 7. This was caused by the incorrect attitude angles of the irradiance sensor and further miscalculation of the solar irradiance by Pix4d Mapper. Interestingly, these errors were eliminated in the calculation of the ratio type of vegetation indexes. Methods B and C yielded vegetation indexes that were almost the same as those of methods A and D. Under cloudy sky, when direct sunlight is not blocked by clouds, method D was effective; with cloud occlusion, results on April 24 indicated that the method failed to estimate the total sunlight and direct sunlight ratio. Reflectance and vegetation indexes obtained from different radiometric correction methods were all obviously affected by flight altitude. Furthermore, the variations of NDVI with flight altitude increasing were different with reflectance. Changes in reflectance and vegetation indexes with flight altitude had little effect on the correlation coefficients yielded with AGB, but showed a significant influence on those of LAI. Through analyzing the variation of observed solar radiation at different time intervals, caution is recommended when using the assumption that solar radiation is stable during the UAV flight. The longer the flight, the greater the variation in solar radiation, especially at sunrise and sunset. Even at noon, when the flight duration is 30 min, the change in solar radiation may exceed 10 % (e.g., 16.5 % on March 20).

COMPOUND TRAINING: A STUDY ON THE INFLUENCE ON THE BOUNCING FORCE OF VOLLEYBALL PLAYERS WHEN THEY JUMP AND SPIKE THE BALL

Objective: This paper aims to investigate the impact of compound training (CT) on the jumping spike performance of volleyball players. Methods: Twenty athletes were randomly assigned to either the CT group or the resistance training (RT) group. After eight weeks of training, the results for in-situ jump and reach, run-up jump and reach, as well as squat jump (SJ), counter-movement jump (CMJ), and run-up jump measured using the Just Jump test system were compared between the two groups. Results: Prior to the experiment, there were no significant differences in any of the test parameters between the two groups ([Formula: see text]). Following the experiment, the one-repetition maximum (1RM) weighted deep squat result for the CT group was [Formula: see text][Formula: see text]kg, the in-situ jump and reach height was [Formula: see text][Formula: see text]m, and the run-up jump and reach height was [Formula: see text][Formula: see text]m, all with [Formula: see text] compared to pre-experiment values and the RT group. Additionally, the duration and height of flight of SJ in the CT group were [Formula: see text][Formula: see text]s and [Formula: see text][Formula: see text]cm, respectively; the duration and height of flight of CMJ were [Formula: see text][Formula: see text]s and [Formula: see text][Formula: see text]cm, respectively; the duration and height of flight of run-up jumps were [Formula: see text][Formula: see text]s and [Formula: see text][Formula: see text]cm, respectively. All of the above results were significantly higher than those before the experiment and those of the RT group ([Formula: see text]). Conclusion: The superior results observed in the CT group’s jumping tests suggest that the effects of CT on bouncing force are more pronounced, making it a viable approach for practical training.