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Context: Horizontal hops can provide insight into how athletes can tolerate high-intensity single-leg stretch loads and are commonly used in athlete monitoring and injury management. Variables like flight, contact, and total time provide valuable diagnostic information to sports science professionals. However, gold-standard assessment tools (eg, 3-dimensional motion capture, force plates) require monetary and technological resources. Therefore, we used a tablet and free software to determine the between-rater, within-rater, and test–retest variability of the temporal events of multiple horizontal hop tests. Design: Reliability study. Methods: Nine healthy males (20.8 [1.3] y, 71.4 [9.8] kg, 171.7 [4.5] cm) across various university sports teams and clubs volunteered and performed several triple (3-Hop) and quintuple (5-Hop) horizontal hops over 3 testing sessions. Six raters detected temporal events from video to determine between-rater variability, while a single rater quantified within-session and test–retest variability. The temporal variables of flight time, ground contact time for each individual hop, and the total time of each hoping series were determined. The consistency of measures was interpreted using the coefficient of variation and interclass correlation coefficients (ICC). Results: Good to excellent between-rater consistency was observed for all hops (ICC =.85–1.00). Absolute (coefficient of variation ≤ 2.0%) and relative consistency (ICC =.98–1.00) was excellent. Test–retest variability showed acceptable levels of absolute consistency (coefficient of variation ≤ 8.7%) and good to excellent consistency in 10/16 variables (ICC =.81–.93), especially those later in the hopping cycle. Conclusions: A tablet and free digitizing software are reliable in detecting temporal events during multiple horizontal hops, which could have exciting implications for power diagnostics and return-to-play decisions. Therefore, rehabilitation and performance professionals can confidently utilize the highly accessible equipment from this study to track multiple hop performances. [ABSTRACT FROM AUTHOR]

Background and Study Aim. Sprinting performance is crucial in many sports, and even marginal improvements in sprint mechanics can provide significant competitive advantages. The aim of this study is to examine the influence of step distance, contact time, and flight time on sprint speed. Material and Methods. The study was conducted on 26 athletes (20 males and 6 females). Body composition was measured using a bioimpedance analysis device. Sprint kinematics (step distance, contact time, and flight time) and sprint speed parameters were assessed using an optical measurement system during a 30-meter sprint test. Multiple linear regression analysis was employed to determine the effects of sprint kinematic parameters on sprint speed, as well as the effects of body composition parameters on sprint kinematics and speed. The linear regression models included one dependent variable and three independent variables. Results. Linear regression analysis revealed that step distance, contact time, and flight time were significant predictors of sprint speed, with the exception of the first step of sprint running (p < 0.05). Furthermore, the effects of body composition parameters (age, body weight, and height) on sprint kinematics and speed were found to be significant (p < 0.05). The proportions of variance explained by body composition parameters were highest for step distance and sprint speed, with R2 values of 0.719 and 0.686, respectively. Conclusions. This study confirms that step distance, contact time, and flight time are significant predictors of sprint speed. Additionally, the results underscore the substantial influence of body composition parameters such as age, body weight, and height on sprint kinematics and speed. These findings highlight the importance of considering both kinematic and physiological factors in the training and development of athletes for optimized sprint performance.

Background and Study Aim Sprinting performance is crucial in many sports, and even marginal improvements in sprint mechanics can provide significant competitive advantages. The aim of this study is to examine the influence of step distance, contact time, and flight time on sprint speed. Material and Methods The study was conducted on 26 athletes (20 males and 6 females). Body composition was measured using a bioimpedance analysis device. Sprint kinematics (step distance, contact time, and flight time) and sprint speed parameters were assessed using an optical measurement system during a 30-meter sprint test. Multiple linear regression analysis was employed to determine the effects of sprint kinematic parameters on sprint speed, as well as the effects of body composition parameters on sprint kinematics and speed. The linear regression models included one dependent variable and three independent variables. Results Linear regression analysis revealed that step distance, contact time, and flight time were significant predictors of sprint speed, with the exception of the first step of sprint running (p < 0.05). Furthermore, the effects of body composition parameters (age, body weight, and height) on sprint kinematics and speed were found to be significant (p < 0.05). The proportions of variance explained by body composition parameters were highest for step distance and sprint speed, with R2 values of 0.719 and 0.686, respectively. Conclusions This study confirms that step distance, contact time, and flight time are significant predictors of sprint speed. Additionally, the results underscore the substantial influence of body composition parameters such as age, body weight, and height on sprint kinematics and speed. These findings highlight the importance of considering both kinematic and physiological factors in the training and development of athletes for optimized sprint performance. [ABSTRACT FROM AUTHOR]

Copyright of Revija Šport is the property of Sport: Revija Za Teoreticna in Praticna Vprasanja Sporta 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.)

Background: General expectations speculated that there are differences between drop jump (DJ) and horizontal drop jump (HDJ) exercises. While these criteria may be valid, we have yet to find a report that explores these differences in competitive level athletes. Objective: The study aimed to compare spatiotemporal variables in the drop jump (DJ) vs. the horizontal drop jump (HDJ) in elite jumpers and sprinters. Methods: Sixteen international-level male athletes performed two DJ attempts at different fall heights 0.3, 0.4, and 0.5 m (DJ30, DJ40, and DJ50), and after 2 h, they performed two HDJ attempts (HDJ30, HDJ40, HDJ50). All jumps were performed on a Kistler force plate. The variables analyzed were ground contact time (GCT), flight time (FT), eccentric phase time, concentric phase time, and time to peak concentric force. Results: The GCT was found to be significantly shorter in DJ vs. HDJ (Z = 4.980; p = 0.0001; ES = 3.11). FT was significantly lower in DJ30 versus HDJ30 (Z = 4.845; p = 0.0001, d = 3.79), but significantly higher in DJ40 vs. HDJ40 (Z = 4.437; p = 0.0001, d = 3.70) and in DJ50 vs. HDJ50 (Z = 4.549; p = 0.0001, d = 4.72). Conclusions: It is concluded that the HDJ requires more time for force production, that the eccentric component requires more time than the concentric and that it is not recommended to use the HDJ over the DJ for reactive purposes. This is the first study that comprehensively compare the differences between DJ and HDJ, which will assist coaches and researchers in the design of future training strategies. [ABSTRACT FROM AUTHOR]

As social media platforms continue to grow in popularity, ensuring the security and privacy of users' accounts has become a critical concern. Traditional authentication methods, such as passwords and PINs, are vulnerable to various attacks, including password guessing, phishing, and brute force attacks. To address these challenges, researchers have turned to keystroke dynamics as a promising solution. Keystroke dynamics, also known as keystroke biometrics, leverages the unique typing patterns and behavioral characteristics of individuals to authenticate their identities. This approach analyzes various keystroke attributes, such as key press duration, flight time, and typing rhythm, to create a user's unique typing profile. By continuously monitoring and comparing these patterns, social media platforms can verify the authenticity of users in real-time. This paper explores the potential of keystroke dynamics in enhancing security for social media users. It discusses the advantages of this approach, including its non-intrusive nature, continuous authentication capabilities, and resistance to common attacks. Additionally, the paper examines the challenges associated with implementing keystroke dynamics, such as user acceptance, system performance, and potential privacy concerns. [ABSTRACT FROM AUTHOR]

Background General expectations speculated that there are differences between drop jump (DJ) and horizontal drop jump (HDJ) exercises. While these criteria may be valid, we have yet to find a report that explores these differences in competitive level athletes. Objective The study aimed to compare spatiotemporal variables in the drop jump (DJ) vs. the horizontal drop jump (HDJ) in elite jumpers and sprinters. Methods Sixteen international-level male athletes performed two DJ attempts at different fall heights 0.3, 0.4, and 0.5 m (DJ30, DJ40, and DJ50), and after 2 h, they performed two HDJ attempts (HDJ30, HDJ40, HDJ50). All jumps were performed on a Kistler force plate. The variables analyzed were ground contact time (GCT), flight time (FT), eccentric phase time, concentric phase time, and time to peak concentric force. Results The GCT was found to be significantly shorter in DJ vs. HDJ (Z = 4.980; p = 0.0001; ES = 3.11). FT was significantly lower in DJ30 versus HDJ30 (Z = 4.845; p = 0.0001, d = 3.79), but significantly higher in DJ40 vs. HDJ40 (Z = 4.437; p ≤ 0.0001, d = 3.70) and in DJ50 vs. HDJ50 (Z = 4.549; p ≤ 0.0001, d = 4.72). Conclusions It is concluded that the HDJ requires more time for force production, that the eccentric component requires more time than the concentric and that it is not recommended to use the HDJ over the DJ for reactive purposes. This is the first study that comprehensively compare the differences between DJ and HDJ, which will assist coaches and researchers in the design of future training strategies.

The unremitting development of portable vertical jump equipment emphasizes the need for continual examination of its validity and reliability. Equal representation between sexes should be endorsed in this process to improve precision and application. This study aimed to examine the concurrent validity and reliability of the Exsurgo g-Flight™ photoelectric boxes and the Output Sports V2™ accelerometer for calculating vertical jump height when compared to a dual force plate system (Hawkin Dynamics Force Plate, ME, USA). Twenty (n = 20) female soccer players performed three counter movement jumps on two different sessions for a total of 120 jumps. Comparisons between the criterion method and secondary measures were performed using Bland–Altman plots and were independently examined using a paired samples t-test. Reliability in instrument error was determined by comparing the residuals of each secondary measure over two assessments. Bland–Altman plots revealed ≤ 5.0% of residuals for the accelerometer and photoelectric devices fell outside the limits of agreement. The accelerometer revealed a mean bias (95% CI) of 0.30 ± 0.33 cm, while the photoelectric device demonstrated a negative bias of −1.64 ± 0.45 cm. Mean (± SD) comparisons revealed an overestimation in jump height with the photoelectric device (1.6 ± 4.0 cm, p < 0.0001) and insignificant differences with the accelerometer (0.30 ± 3.7 cm, p > 0.05). Mean differences in residuals between testing dates for secondary measures were insignificant (p ≥ 0.23). Both the photoelectric and accelerometer instruments displayed high reliability, but differences in the accuracy between devices were observed. [ABSTRACT FROM AUTHOR]

The paper shows the possibility of using unmanned aerial vehicles with additional outboard equipment for aerial photography. It is noted that some parameters of the drone and additional suspension equipment are not taken into account by the software when calculating the drone flight time for one battery charge. (Research purpose) To develop an algorithm for calculating the flight time of an unmanned aerial vehicle with installed outboard equipment. (Materials and methods) The technical characteristics of DJI Phantom 4 pro and DJI Matrice 200v2 were studied, as well as the specifications of Parrot Sequoia, MicaSense Altum multispectral cameras mounted on the drone. The existing research results are used to calculate the flight mission time depending on the route length and the battery capacity. (Results and discussion) It is found that the maximum flight time of a drone with additional outboard equipment is reduced due to the additional equipment mass, increased power consumption, the preflight preparation time, the need to return to the take-off point and the necessity to preserve the battery life and save the flight load. The maximum flight time calculated for DJI Phantom 4 pro and DJI Matrice 200v2 with multispectral cameras Parrot Sequoia, MicaSense Altum is 8 minutes and 18 minutes, respectively, with a minimum flight load. A method for calculating the number of batteries for aerial photography with additional outboard equipment is determined. (Conclusions) An algorithm for calculating the flight time of an unmanned aerial vehicle with additional outboard equipment is developed, the parameters ignored by the standard software in the flight time calculation are taken into account.

Aiming at the problem of target allocation in operations of special-shaped anti-ship missile swarms, a target allocation model based on time coordination is established. Firstly, according to the anti-ship combat situation information, the influence of missile flight time, missile-to-target distance and flight velocity on the target allocation of cluster coordination operations is analyzed, and a time coordination advantage function based on the standard deviation of missile flight time is established, and the comprehensive advantage function is formed integrated the distance advantage function with velocity advantage function. Finally, the optimal solution of model is deduced by genetic algorithm, and the allocation results are gotten by simulation. The results of comparative analysis show that the standard deviation of average time of operation scheme with time coordination is lower than that without time coordination. The standard deviation of average time for two cases descends about 49.18% and 63.49%. The simulation results verify the validity of the model.

The rapid growth of electronic assessment in various fields has led to the emergence of issues such as user identity fraud and cheating. One potential solution to these problems is to use a complementary authentication method, such as a behavioral biometric characteristic that is unique to each individual. One promising approach is keystroke dynamics, which involves analyzing the typing patterns of users. In this research, the Deep Belief Networks (DBNs) model is used to implement a dynamic keystroke technique for secure e-assessment. The proposed system extracts various features from the pressure-time measurements, digraphs (dwell time and flight time), trigraphs, and n-graphs, and uses these features to classify the user's identity by applying the DBN algorithm to a dataset collected from participants who typed free text using a standard QWERTY keyboard in a neutral state without inducing specific emotions. The DBN model is designed to detect cheating attempts and is tested on a dataset collected from the proposed e-assessment system using free text. The implementation of the DBN results in an error rate of 5% and an accuracy of 95%, indicating that the system is effective in identifying users' identity and cheating, providing a secure eassessment approach. [ABSTRACT FROM AUTHOR]

Copyright of Aero Weaponry is the property of Aero Weaponry Editorial Office 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.)

Under the looming climate crisis, public concerns have been raised regarding the environmental impacts of private jet flights. Electric aircraft are currently considered one of the most encouraging technological keys to significantly reducing the environmental impacts of aviation. This research aims to study the replacement of currently used business jets with fully electric aircraft. This study is based on actual flight data of a European business carrier. The carbon dioxide emissions reduction potential for different aircraft ranges was estimated. Obtained results showed that with fully electric aircraft the studied business carrier could significantly reduce its annual emissions by up to 93%. On a per-passenger basis, the emissions could decrease from 6,787 g of carbon dioxide equivalent per passenger kilometre to 449 g. However, as electric aircraft will operate at a slower speed than business jets, flight times would increase by 10–41 min, depending on the distance. [ABSTRACT FROM AUTHOR]

The purpose of the present study was to assess the validity and reliability of the jump height measured by the Polar Vantage V2 sports watch in comparison to a gold-standard force plate measurement. Fifteen healthy adults, seven female, age 20–42 years participated in the study and performed six sets of three CMJs, on two consecutive days. The participants wore the Polar Vantage V2 sports watch (Polar Electro Oy, Kempele, Finland) whilst performing the jumps on two force plates (AMTI, Watertown, Massachusetts, United States). Jump height was on the one hand extracted directly from the watch (“leg recovery test”) and on the other hand calculated by the flight time method with the force plate data. To assess validity, we calculated the mean absolute error, constructed Bland-Altman plots and applied an ordinary least squares regression analysis. To test for left-to-right and day-to-day reliability, we calculated Pearson and intraclass correlations. We found a mean error of ≈5% and a high correlation (r = 0.96; p < 0.001) for the jump height measured by the Polar Vantage V2 sports watch compared to the force plate measurement. The Bland-Altmann plot together with the ordinary least squares regression analysis showed no systematic bias between the methods with a minimal difference at a jump height of 30 cm. For reliability of left-to-right and day-to-day measurements, we found high Pearson and ICC correlations and no indications for systematic bias by Bland-Altmann analysis. The present study has demonstrated that the “leg recovery test” of the Polar Vantage V2 sports watch provide a valid and reliable measurement of the mean vertical jump height of three consecutive CMJs. For the first time the jump height of a CMJ can be measured solely by a sports watch without the need to attach additional sensors or measurement devices. Thus, the “leg recovery test” is an easy to administer, valid and reliable test, that can be used in future studies to measure CMJ-height in the field when lab-based assessments are unavailable or inconvenient. This opens new avenues for cross-sectional and longitudinal assessments of neuromuscular power of the lower extremities in a large number of participants.

High temporal and spatial resolution is required to meet the challenges of changing plant characteristics over time. Solar radiation and reflectance of vegetation canopies vary with the time of day and growing season. Little is known regarding the interactions between daily and seasonally varying irradiation and reflectance of row-planted crops that can be grown in any compass direction. The spectral reflectance of maize grown in four compass directions was recorded across the entire life cycle through highly frequent drone-based multispectral sensing to determine biomass changes over time and make early yield predictions. Comparison of information from spectral bands and indices indicated no differences among the four compass directions at the reproductive stage and only a few differences at the earlier vegetative growth stages. There was no systematic influence of row orientation on the relationships between spectral data, biomass, and grain yield, except at the early growth stages. Spectral relationships to biomass at the reproductive stage varied in row directions with R²-values close to 0.9, already observed at early growth stages for the indices NDVI, SR, GCI, and GNDVI. The spectral relationships to yield were closer in individual compass directions, with R²-values varying between 0.8--0.9 for the best indices GCI and GNDV after BBCH 61. A closer inspection of daytime changes indicated a diurnal trend with 15 and 20% decreased spectral values observed after midday at the growth stages BBCH 81 and 61, respectively, thus requiring standardization of flight timing during the day. Drone-assisted nadir-oriented spectral sensing could be a reference for terrestrial and satellite-based reflectance sensing to relate canopy reflectance to crop characteristics quantitatively. [ABSTRACT FROM AUTHOR]

Quadcopter drones are among the most common and widely used drones due to their ability to hover, which is essential in some applications, in addition to their easy control and their high stability to perform mechanical tasks in areas that can only be reached from the air. This work aims to provide a solution to the problem of the flight time of a quadcopter by proposing a model of an alternative energy system composed of a photovoltaic solar panel, which constitutes hybridization energy besides the Lithium-Ion battery. A fuel cell power generation system can be integrated into the proposed source to give additional flight time. Furthermore, each component of the quadcopter has been carefully selected, by taking into account the weight factor, propulsion efficiency, and energy density. [ABSTRACT FROM AUTHOR]

High temporal and spatial resolution is required to meet the challenges of changing plant characteristics over time. Solar radiation and reflectance of vegetation canopies vary with the time of day and growing season. Little is known regarding the interactions between daily and seasonally varying irradiation and reflectance of row-planted crops that can be grown in any compass direction. The spectral reflectance of maize grown in four compass directions was recorded across the entire life cycle through highly frequent drone-based multispectral sensing to determine biomass changes over time and make early yield predictions. Comparison of information from spectral bands and indices indicated no differences among the four compass directions at the reproductive stage and only a few differences at the earlier vegetative growth stages. There was no systematic influence of row orientation on the relationships between spectral data, biomass, and grain yield, except at the early growth stages. Spectral relationships to biomass at the reproductive stage varied in row directions with R2-values close to 0.9, already observed at early growth stages for the indices NDVI, SR, GCI, and GNDVI. The spectral relationships to yield were closer in individual compass directions, with R2-values varying between 0.8–0.9 for the best indices GCI and GNDV after BBCH 61. A closer inspection of daytime changes indicated a diurnal trend with 15 and 20% decreased spectral values observed after midday at the growth stages BBCH 81 and 61, respectively, thus requiring standardization of flight timing during the day. Drone-assisted nadir-oriented spectral sensing could be a reference for terrestrial and satellite-based reflectance sensing to relate canopy reflectance to crop characteristics quantitatively.

The backward double integration method uses one force plate and could calculate jump height for countermovement jumping, squat jumping and drop jumping by analysing the landing phase instead of the push-off phase. This study compared the accuracy and variability of the forward double integration (FDI), backwards double integration (BDI) and Flight Time + Constant (FT+C) methods, against the marker-based rigid-body modelling method. It was hypothesised that the jump height calculated using the BDI method would be equivalent to the FDI method, while the FT+C method would have reduced accuracy and increased variability during sub-maximal jumping compared to maximal jumping. Twenty-four volunteers performed five maximal and five sub-maximal countermovement jumps, while force plate and motion capture data were collected. The BDI method calculated equivalent mean jump heights compared to the FDI method, with only slightly higher variability (2–3 mm), and therefore can be used in situations where FDI cannot be employed. The FT+C method was able to account for reduced heel-lift distance, despite employing an anthropometrically scaled heel-lift constant. However, across both sub-maximal and maximal jumping, it had increased variability (1.1 cm) compared to FDI and BDI and should not be used when alternate methods are available. [ABSTRACT FROM AUTHOR]

Currently Smartphone has become primary necessity for populace. Everyone managetheir personal and confidential data on mobiles. However it is essential to increase the security of the smartphone. Authentication is a process or action to verify the identity of a user or process and it prohibitsthe unauthorised access from intruders. Password is the universal key component of authentication that is easy to crack as everyone can remember the password. Therefore it is required to use advance mechanism to enhance the security. Keystroke dynamics is a secure and authenticbehavioural biometricbased technique based on typing behaviour of any individual. This technique identifies the identity of the userthroughtheir typing behaviour on keyboard. In this paper author comparing the features and methods of keystroke dynamics to find the best accuracy result mention in Table 2 of section 2 and comparing the different positions of using smartphone to get the best EER as well in Table 3of section 5. [ABSTRACT FROM AUTHOR]

• Pix4d Mapper miscalculated the geometric angles of the irradiance sensor. • The irradiance-sensor-based method was effective under cloudy sky with unobstructed direct sunlight. • Changes in reflectance and vegetation indexes with flight altitude were irregular. • Variations in solar radiation during UAV flight affected the estimation of reflectance. 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). [ABSTRACT FROM AUTHOR]

In view of problems that symmetric-double-sided two-way ranging (SDS-TWR) method had low ranging efficiency and poor expansibility and there was still room for improvement in the ranging efficiency and positioning system capacity of asymmetric-double-sided two-way ranging multi-ack(ADS-TWR-MA)method in current ultra-wideband TOF underground accurate positioning technology, a method of asymmetric-double-sided two-way ranging multi-tag multi-anchor (ADS-TWR-MTMA) was proposed. On the basis of ADS-TWR-MA method, the method further multiplexes ranging message in asymmetric-double-sided two-way ranging process, so that multiple tags and multiple anchor nodes can be used for TOF ranging simultaneously. The method greatly improves ranging efficiency and capacity of positioning system under premise of ensuring ranging accuracy. The application in locomotive proximity detection system and accurate positioning system verifies that the ADS-TWR-MTMA method is superior to SDS-TWR method and ADS-TWR-MA method in number of ranging messages, ranging time and system capacity.

Drones can be used in agriculture applications to monitor crop yield and climate conditions and to extend the communication range of wireless sensor networks in monitoring areas. However, monitoring the climate conditions in agriculture applications faces challenges and limitations, such as drone flight time, power consumption, and communication distance, which are addressed in this study. Wireless power transfer (WPT) can be used to charge drone batteries. WPT using a magnetic resonant coupling (MRC) technique was considered in this study because it allows high transfer power and efficiency with tens of centimeters, power transfers can be achieved in misalignment situations, charging several devices simultaneously, and unaffected by weather conditions. WPT was practically implemented based on a solar cell using a proposed flat spiral coil (FSC) in the transmitter circuit and multiturn coil (MTC) in a receiver circuit (drone) for the alignment and misalignment of two coils at different distances. FSC and MTC improved power transfer and efficiency to 20.46 W and 85.25%, respectively, at 0 cm with the loaded system under alignment condition. In addition, the two coils achieved appropriate transfer efficiencies and power for charging the drone battery under misaligned conditions. The maximum power transfer and efficiency were 17.1 W and 71% for the misalignment condition, at an air gap of 1 cm between two coils when the system was loaded with the drone battery. Moreover, the battery life of the drone was extended to 851 minutes based on the proposed sleep/active strategy relative to the traditional operation (i.e., 25.84 minutes). Consequently, a 96.9% battery power saving was achieved based on this strategy. Comparison results showed that the proposed system outperformed some present techniques in terms of the transfer power, transfer efficiency, and drone battery life. The proposed WPT technique developed in this study has been proven to solve the misalignment issue. Thus it offers a great opportunity as a key deployment component for the automation of farming practices toward the Internet of Farming applications.

Ultrasonic guided wave has received significant attention in the field of nondestructive testing because of their advantages in detecting the entire wall thickness. Since pipe elbows are an important component of the piping system, it is desirable to study the propagation behavior of the guided wave in the elbows. In this paper, instead of using the traditional method of a ring of transducers to generate guided wave at the same time, the propagation behavior of the guided wave in the elbows under the action of a single excitation source is simulated. Using the chirp excitation signal, the transmission signals of the guided wave at different excitation central frequencies are extracted with high efficiency, and the behavior of the guided wave in the elbow under different excitation frequencies is studied. In addition, it is proposed to use the flight time quantity to characterize the complete information of the structure, and the influence of the defects on the flight time is also studied. The results prove that the flight time feature has good detection sensitivity to the defects with varying depth in different locations of the elbow.

The purpose of this study was to compare step-by-step kinematics of unresisted and resisted 10-m sprints measured with the Optojump or Musclelab on elite sprinters. Six subjects (age 30.0 ± 5.1 years, body mass 76.3 ± 5.3 kg, body height 1.79 ± 0.09 m, and 100-m personal best 10.51 ± 0.3 s) performed 2 unresisted and 2 sets of 2 resisted (10 and 20% of body mass) 30-m sprints in random order (6 sprints in total) in 1 session in which kinematics of the first 10 m were measured with the Optojump and Musclelab. The main finding was that there were no significant differences between the measurements made with the Optojump and Musclelab systems. In addition, it was possible to discriminate most kinematic variables per step of the first 10 m when different loads (10 and 20% of body mass) had to be pulled during the 30-m sprints. The variations in sprint times associated with changes in the resistance provided by the dynaSpeed were mainly caused by a decrease in step length as the resistance increased. It was concluded that the 2 systems are valid and could help coaches, researchers, and athletes by providing more detailed information about possible changes to kinematics during training and sprinting with different resistances. [ABSTRACT FROM AUTHOR]

This study compared the kinematics (step and joint) and muscle activity of unresisted and active resisted 30 m sprints with different loads (10–40% body mass) in experienced male and female sprinters. Step kinematics were measured using a laser gun and contact mat in 28 male and female participants during unresisted 30 m sprint, and sprints with 10–40% of body mass (BM) active resistance, while peak angular velocities of lower limb was measured, together with muscle activation of nine muscles. Increased resisted loads resulted in slower 30 m times, as a result of lower step velocity mainly caused by shorter step lengths and frequencies, flight times and longer contact times, with a greater effect on women than on men. These step kinematic differences, due to increasing load were accompanied with lower peak joint movements. However, gender differences were only found for peak plantar flexion with unresisted and 10% BM resisted sprints. Furthermore, increasing load decreased calf and hamstring muscles activity, while medial vastus activity increased. Based upon these findings, it was concluded that when introducing active resisted sprints, women should sprint with approximately 10% less active loads than men to have equal step and joint kinematics development over the sprint distance. [ABSTRACT FROM AUTHOR]

Copyright of Journal of China University of Petroleum is the property of China University of Petroleum 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.)

Remote sensing can provide useful imagery data to monitor sugarcane in the field, whether for precision management or high-throughput phenotyping (HTP). However, research and technological development into aerial remote sensing for distinguishing cultivars is still at an early stage of development, driving the need for further in-depth investigation. The primary objective of this study was therefore to analyze whether it could be possible to discriminate market-grade cultivars of sugarcane upon imagery data from an unmanned aerial vehicle (UAV). A secondary objective was to analyze whether the time of day could impact the expressiveness of spectral bands and vegetation indices (VIs) in the biophysical modeling. The remote sensing platform acquired high-resolution imagery data, making it possible for discriminating cultivars upon spectral bands and VIs without computational unfeasibility. 12:00 PM especially proved to be the most reliable time of day to perform the flight on the field and model the cultivars upon spectral bands. In contrast, the discrimination upon VIs was not specific to the time of flight. Therefore, this study can provide further information about the division of cultivars of sugarcane merely as a result of processing UAV imagery data. Insights will drive the knowledge necessary to effectively advance the field’s prominence in developing low-altitude, remotely sensing sugarcane.

The distribution, habitat, behaviour and life history of the graceful sun-moth Synemon gratiosa Westwood, 1877 was studied over a ten-year period between 2009 and 2018. The species is endemic to south-west Western Australia where it occurs in a series of disjunct subpopulations between Binningup and Kalbarri, a range of ~625km. It is mainly restricted to coastal and near-coastal sand dunes, but extends into Banksia L.f. woodlands near Perth. Larvae feed in the leaf bases and rhizomes of two host plants, Lomandra maritima T.S. Choo (on coastal dunes) and L. hermaphrodita (C.R.P. Andrews) C.A. Gardner (in Banksia woodlands). Abundance is typically low, despite the host plant being abundant, and occasionally the dominant species, at some sites. As they reach maturity the larvae damage or kill parts of the host plant, which enables them to be detected fairly readily. Details of the species biology, ecology and life history are recorded. The impact of anthropogenic land clearing and fragmentation on the conservation of S. gratiosa is discussed. [ABSTRACT FROM AUTHOR]

Uncrewed Aerial Vehicles (UAV) constitute a rapidly evolving technology field that is becoming more accessible and capable of supplementing, expanding, and even replacing some traditionally manual bridge inspections. Given the classification of the bridge inspection types as initial, routine, in-depth, damage, special, and fracture critical members, specific UAV mission requirements can be developed, and their suitability for UAV application examined. Results of a review of 23 applications of UAVs in bridge inspections indicate that mission sensor and payload needs dictate the UAV configuration and size, resulting in quadcopter configurations being most suitable for visual camera inspections (43% of visual inspections use quadcopters), and hexa- and octocopter configurations being more suitable for higher payload hyperspectral, multispectral, and Light Detection and Ranging (LiDAR) inspections (13%). In addition, the number of motors and size of the aircraft are the primary drivers in the cost of the vehicle. 75% of vehicles rely on GPS for navigation, and none of them are capable of contact inspections. Factors that limit the use of UAVs in bridge inspections include the UAV endurance, the capability of navigation in GPS deprived environments, the stability in confined spaces in close proximity to structural elements, and the cost. Current research trends in UAV technologies address some of these limitations, such as obstacle detection and avoidance methods, autonomous flight path planning and optimization, and UAV hardware optimization for specific mission requirements.

This paper presents new solutions for twodimensional projectile motion in a free and resistive medium, obtained within the newly established conformable derivative. For free motion, we obtain analytical solutions and show that the trajectory, height, flight time, optimal angle, and maximum range depend on the order of the conformable derivative, 0 < γ ≤ 1. Likewise, we analyse and simulate the projectile motion in a resistive medium by assuming several scenarios. The obtained trajectories never exceed the ordinary ones, given by γ = 1, unlike results reported in other studies.

In this article, the research aimed at determining the impact of the intensification of actions on the pilot's cognitive load in a simulated flight is presented. The tests were divided into two groups: pre-flight verification tests and flight tests of increasing intensity. The work was carried out at flight simulator CKAS MotionSim5. Based on the collected data, it has been proved that along with the intensification of the tasks imposed on the pilot, the level of his cognitive load also increases. Further inference leads to the conclusion that cognitive overload is one of the main reasons for pilots' mistakes. The linear relationship between experience and cognitive load has also been proven in the studied group. [ABSTRACT FROM AUTHOR]

Vertical jump performance is a commonly used test to measure lower-limb muscle power that is carried out with several types of equipment. The aim of this study was to validate an open-source jump mat (Chronojump Boscosystems) against a proprietary jump mat (Globus Ergo Tester). Sixty-three active sportsmen (age 23.3 ± 2.4 years) completed 8 maximal-effort countermovement jumps (CMJ). The heights of the 504 CMJ were measured from the two jump mats simultaneously. Reliability was examined with intra-class correlation coefficients (ICC), paired samples t-tests, coefficient of variation (CV) and Cronbach's α. Bivariate Pearson's correlation coefficient (r) was used to examine validity. Effects were evaluated using non-clinical magnitudebased inference. There was almost perfect agreement between instruments (ICC = 0.999-1.000, most likely positive 100/0/0). Paired t-test showed a mean difference of 0.03 ± 0.21 cm (90% CI -0.04 -- -0.01) between instruments (most likely trivial 0/100/0). Both instruments showed very good stability (α = 1.00, CV = 4.28±1.95%). The smallest worthwhile change and typical error values were 1.3 and 0.29 cm, respectively and therefore, the signal-to-noise ratio of both instruments was large: 4.5. Finally, almost perfect correlation between instruments was observed (r = 0.999, most likely positive 100/0/0). Chronojump can be regarded as a sensitive instrument to detect changes in jump height performance over the possible noise around the measure. The results supported the open-source jump mat to be a useful, valid and reliable, low-cost testing device to monitor variations in vertical jumping performance. [ABSTRACT FROM AUTHOR]

Featured Application: It is recommended that high-level sportswomen and men should be assessed with the force platform through the take-off velocity method in a vertical jump as gold standard technology to ensure correct performance and/or fatigue-overload control during the sport season. The main purpose of this study was to compare the validity of the take-off velocity method (TOV) measured with a force platform (FP) (gold standard) versus the flight time method (FT) in a vertical jump to measure jumping performance or neuromuscular fatigue-overload in professional female football players. For this purpose, we used a FP and a validated smartphone application (APP). A total of eight healthy professional female football players (aged 27.25 ± 6.48 years) participated in this study. All performed three valid trials of a countermovement jump and squat jump and were measured at the same time with the APP and the FP. The results show that there is a lack of validity and reliability between jump height (JH) calculated through the TOV method with the FP and the FT method with the FP (r = 0.028, p > 0.84, intraclass correlation coefficient (ICC) = −0.026) and between the JH measured with the FP through the TOV method and the APP with the FT method (r = 0.116, p > 0.43, ICC = −0.094 (−0.314–0.157)). A significant difference between the JH measured through the TOV with the FP versus the APP (p < 0.05), and a trend between the JH obtained with the FP through the TOV and the FT (p = 0.052) is also shown. Finally, the JH with the FP through the FT and the APP did not differ (p > 0.05). The eta-squared of the one-way ANOVA was η2 = 0.085. It seems that only the TOV measured with a FP could guarantee the accuracy of the jump test in SJ+CMJ and SJ, so it is recommended that high-level sportswomen and men should be assessed with the FP through TOV as gold standard technology to ensure correct performance and/or fatigue-overload control during the sport season. [ABSTRACT FROM AUTHOR]

Flight time is widely used to calculate jump height because of its simple and inexpensive application. However, this method is known to give different results than the calculation from vertical velocity at takeoff. The purpose of this study is to quantify the effect of postural changes between takeoff and landing on the jump height from flight time. Twenty-seven participants performed three vertical jumps with arm swing. Three-dimensional coordinates of anatomical landmarks and the ground reaction force were analyzed. Two methods of calculating jump height were used: (1) the vertical velocity of the whole-body center of mass (COMwb) at takeoff and (2) flight time. The jump height from flight time was overestimated by 0.025 m compared to the jump height from the takeoff velocity (p < 0.05) due to the lower COMwb height at landing by −0.053 m (p < 0.05). The postural changes in foot, shank, and arm segments mainly contributed to decreasing the COMwb height (−0.025, −0.014, and −0.017 m, respectively). The flight time method is reliable and had low intra-participant variability, but it cannot be recommended for a vertical jump when comparing with others (such as at tryouts) because of the potential "cheating" effect of differences in landing posture. [ABSTRACT FROM AUTHOR]

This research aimed to determine whether: (1) shoe-worn magnetic and inertial sensors can be used to detect hurdle clearance and identify the leading leg in 400-m hurdles, and (2) to provide an analysis of the hurdlers’ spatiotemporal parameters in the intervals defined by the hurdles’ position. The data set is composed of MIMU recordings of 15 athletes in a competitive environment. The results show that the method based on the duration of the flight phase was able to detect hurdle clearance and identify the leading leg with 100% accuracy. Moreover, by combining the swing phase duration with the orientation of the foot, we achieved, in unipedal configuration, 100% accuracy in hurdle clearance detection, and 99.7% accuracy in the identification of the leading leg. Finally, this study provides statistical evidence that contact time significantly increases, while speed and step frequency significantly decrease with time during 400 m hurdle races. [ABSTRACT FROM AUTHOR]

Purpose: This study was intended to explore the continuous changes in the kinematic parameters of hurdlers in a 110 meter (110m) high hurdle race from hurdles 1 through 10. Method: Ten excellent college athletes who specialized in the 110m high hurdle race volunteered for this study. Inertial measurement units (IMUs) strapped to the back of the athlete's feet and 10 high-speed cameras were used to document the movements of the hurdlers as they were hurdling along the entire track. Kwon3D and MATLAB computer programs were employed for the analysis of kinematic parameters (take-off distance, landing distance, take-off distance percentage, landing distance percentage, flight time, time between hurdles, hurdle cycle time, hurdle cycle velocity, height of centre gravity above the hurdle and take-off angles). The trend analysis was introduced to test the changes of the parameters between hurdles. The level of significance was set to α =.05. Results: The results showed that the subjects averaged 14.31±0.29 seconds in their 110m high hurdle tests. Regarding the trend analysis, all kinematic parameters except landing distance displayed quadratic linear patterns along the 110m race. Conclusion: The athletes rapidly gained speed as they sprinted from the starting line and reached their maximum speeds between hurdles 5 and 6, after which their speed declined. In addition, the kinematic parameters changed as the running velocity varied. [ABSTRACT FROM AUTHOR]