Landing Speed Research Articles

Bioinspired Tilted Magnetized Flakes as a Self-Powered and Antislip Smart Outsole for Healthcare Monitoring and Human-Machine Interaction.

Footwear smart devices capable of reliably capturing body actions and conveniently transmitting human-made information are of great interest to advance healthcare monitoring, human-machine interactions (HMIs), etc. while remaining challenging. Herein, we present a self-powered, antislip, and multifunctional smart outsole based on the gecko toe-inspired tilted magnetized flakes (TMFs) and underlying flexible coils. With the pressure-induced flake deflection and the built-in magnetic moment alignment, the TMF can produce a variable magnetic field to induce the voltage signals in coils for precise pressure perception and linear velocity sensing. The TMF-based smart outsole can thus serve as a real-time footwear recorder to monitor various body actions for exercise analysis and to track the abnormal landing speed for alerting potential injuries. The gecko toe-like flakes also enable the excellent antislip capability of the outsole with a much higher friction coefficient than the standard one of the low slip risk. By programming the magnetic moment alignments of the TMFs, a single-circuit outsole can further output multiple signals as encoded instructions for controlling the racing game. Along with excellent abrasion resistance and environmental immunity, the proposed outsole exhibits great potential as a convenient platform for reliable healthcare monitoring and efficient HMI.

Rotation of the hammer and performance in hammer throwing.

The purpose of this study was to determine the effects of hammer rotation on performance in hammer throwing. The hammer's velocity increment at different stages, the duration of rotations at different phases, and the horizontal azimuth angle and rotation radius at critical instants were calculated and compared between the long and short trials for 26 female athletes in actual competitions. Compared to short trials, female throwers' long trials exhibited significantly larger release velocity (p < 0.001, ES = 1.42), greater velocity increment during the double support phase (p = 0.006, ES = 0.59), shorter duration during the single support phase (p ≤ 0.043, ES = 0.42-0.83), lower horizontal azimuth angle (p ≤ 0.027, ES = 0.46-0.57), and longer rotational radius at critical instants (p ≤ 0.021, ES = 0.48-0.73). During the process from the hammer head's low point to high point, athletes should focus on increasing the rotation radius of the hammer head and accelerating the right foot's landing speed during the single support phase. This approach aims to reduce the hammer's horizontal azimuth angle at the right foot touchdown, enhance the acceleration performance during the double support phase, and increase the release speed.

Design and test of a novel converging groove-guided seed tube for precision seeding of maize

In precision seeding operations, the irregular shapes of maize seed particles and the suboptimal geometric structure of the seed tube contribute to the rolling and bouncing of seeds upon falling into the furrow, ultimately compromising seeding uniformity. To address this issue, a convergent groove-guided (CGG) seed tube was proposed based on the principle of brachistochrone curve considering friction (BCCF). The discrete element method (DEM) was employed to conduct a comprehensive phenomenological analysis and numerical investigation of particle guide characteristics. Bench tests and field experiments were designed to verify the simulation results. Through response surface analysis, the optimal seeding performance was achieved at a groove angle of 111.34°, tube incline angle of 1.56°, and ground speed of 7.2 km h−1, resulting in a lateral dispersion landing range of 11.10 mm, angular velocity of 17.38 rad s−1, seed landing speed variation coefficient of 2.29%, and plant spacing variation coefficient of 6.04%. Bench test results unveiled that, under a ground speed of 7.2 km h−1, the variation coefficient of plant spacing for CGG seed tubes was measured at 7.63%, with a deviation of 1.59% from the simulation results. At high ground speeds of 9.0–14.4 km h−1, the seed guiding performance was also better than traditional seed tubes. Consistent results were also verified through field experiments. Therefore, the CGG seed tube manifested superior seed guidance efficacy when juxtaposed with its conventional counterpart, and this design can provide technical support for the realization of seed-to-ground positioning technology.

Effects of Dry Land Speed Training on 100-Meter Freestyle Swimming in Adolescent Swimming

Background and Aim: The specific strength development in swimming tends to start at a younger age, so it becomes particularly important to conduct effective Specific strength training during adolescence. It is essential to utilize training methods and means that align with the developmental characteristics of Specific strengths in young swimmers. Thus, this study has developed a specific dry-land training program to enhance the 100-meter freestyle swimming speed of adolescent swimmers. Methods: This study selected 30 male adolescent swimmers from the Shaanxi Provincial Swimming Team and divided them into an experimental group and a control group (15 individuals in each group) based on their 100-meter freestyle speed. Both groups underwent a 12-week training intervention, with 12 training sessions per week, each lasting 2 hours. The total training time and water-based training content were the same for both groups, but the content of dry-land training differed. The experimental group followed a specific dry-land training program, while the control group followed a traditional training program. Comprehensive tests were conducted before and after the 12-week training intervention for both groups, using the physical fitness and test scores of swimmers in the experimental and control groups as research indicators. Experimental and analytical methods, including experimental and statistical methods, were employed to conduct a targeted study on the changes in physical fitness and test scores before and after the training. Results: show that after 12 weeks of training, the scores for both groups are as follows: Pull-ups (Experimental group: P=0.000&lt;0.01, Control group: P=0.777&gt;0.05), Vertical jump (Experimental group: P=0.032&lt;0.05, Control group: P=0.848&gt;0.05), Abdominal muscle endurance (Experimental group: P=0.000&lt;0.01, Control group: P=0.396&gt;0.05), and Back muscle endurance (Experimental group: P=0.004&lt;0.01, Control group: P=0.583&gt;0.05). The post-test results reveal that swimmers in the experimental group performed significantly better in pull-ups, vertical jumps, abdominal muscle endurance, and back muscle endurance compared to the control group. Conclusion: The specialized training program effectively increased the upper limb strength of the participants, with no significant advantage over the traditional training program.

Vibration analysis and control of aircraft landing systems using proposed neural controllers

Nowadays, landing gears used in aircraft are the basic systems that carry the weight of aircraft systems and provide them to move on the ground. During the landing of aircraft, big and sudden vibrations occur as soon as the wheels come into contact with the runway. This situation negatively affects human safety, comfort and also the life of the landing gear system. Therefore, it is important to keep this vibration at permissible levels. This paper presents an improved vibration control method that controls the amplitudes of vibrations of landing systems. This paper presents proposed vibration control method that controls the angular position variables of the landing gear mechanism to control the vibrations occurring during landing. For different runway conditions and 200 km/h landing speed, the angular joint variables of the landing gear mechanism links are controlled using standard controller and a proposed neural controller structure. The simulation results are shown that the proposed neural controllers have better performance at vibration control of landing systems during landing.

Study on the soft-landing of large inertia valve based on multi-objective optimization of annular gap

Variable valve mechanism and its technology are widely used in vehicle diesel engines. As a critical component, the performance of reciprocating actuator is the guarantee for the realization of electro-hydraulic variable valve. In order to solve the problem of high setting speed in electro-hydraulic camless variable valve system, a variable valve actuator based on annular gap buffer is proposed and optimized to realize quick closing and soft landing. The experimental results show that the actuator can achieve the purpose of setting buffer, and the setting speed is 0.5 m/s with 15 ms of closing time. AMESim is used to build the system simulation model and calibrated by experiments. The simulated lift curve is close to the experimental curve, and its Pearson coefficient is 0.9995. The influence of structural parameters on the system driving ability and buffering effect is studied through the model. According to the simulation results, the annular gap eccentricity will affect the buffering effect. When the eccentricity increases from 0.005 to 0.035 mm, the landing velocity increases by 0.1 m/s and the valve closing time decreases by 0.9 ms. NSGA-II method is used to optimize the structural parameters of the annular gap, and an obvious Pareto front is obtained and the optimal solution is applied in next experiments. The landing speed is reduced from 0.5 to 0.25 m/s, and the landing time is still less than 15 ms. This paper provides a simple cushioning scheme for electro-hydraulic camless variable valve soft landing which is independent of proportional valve.

The maximum drop height of high-altitude parachuting based on dynamic and thermodynamic analysis

This paper explores the maximum possible initial height for skydiving, taking into account the physical and biological constraints of the sport. It develops the dynamic and thermodynamic models of the skydiver before and after deploying the parachute, and uses numerical methods to obtain the optimal parameters for safe landing. It also examines the thermal properties of the protective suit and the maximum heat it can endure. The paper demonstrates that the initial height does not affect the landing speed, and that the heat generated by the fall is within the tolerable range of the skydiver. The paper shows that the key factor for determining the maximum skydiving height is the thermal resistance of the protective material, rather than the conventional dynamic considerations. The paper concludes that the highest height that can be skydived is 45400 meters, the opening height is 3000 meters, and the landing speed is 6.32 m/s. This paper provides a novel perspective on the physics and engineering of skydiving.

An investigation on the application of exercise biomechanics in competitive wushu routine training

Abstract Combining the athletes’ wushu jumping action data from the perspective of sports biomechanics, forming a finite element model based on finite element analysis of the landing speed of wushu jumping action on the landing stability correction finite element model, solving the different heights, can not be difficult to land the PvGRF of the wushu action, the use of kinematics sensitive indexes to diagnose the difficulty of competitive wushu sets of action. Measure the movement data of wushu athletes’ spinning foot 720° catching horse stance movement, and analyze the swing changes and rotational angular velocities of various body segments in the assisted jumping phase and the aerial movement phase. A core stability training method was proposed and tested during a 12-week training period, and an index test of balance was conducted. The results of the balance index test of the wushu athletes showed that after the core stability training, the static right foot standing index was 179.55±196.35, which formed a significant difference with the pre-training period, P&lt;0.05. The combination of core stability and sports biomechanics can improve the completion of difficult movements in the movement training of competitive wushu athletes.

Advanced Hypersonic Transportation Perspectives

High-speed transportation design concepts are examined for advanced civil aviation and space transportation applications. The design concept of transatmospheric vehicles, flying directly from earth to orbit, will enable launching and recovery of small telecommunication and remote sensing satellites, harvesting solar energy from space, and space tourism.Commonality of flight regimes in atmospheric flight, the similarity of fuels, propulsion technology, aerodynamic configuration design, and airframe structure materials used in these high-speed flight regimes for air and space transportation are discussed in detail.A single, Integrated Hypersonic Transport Programme, is recommended, based on small size, low risk, and low cost vehicles. A dual fuel, kerosene-hydrogen system meets the needs of such an Integrated Hypersonic Transportation Programme, with kerosene for take-off, powered landing and low speed ascent/descent flight. Hydrogen is used for high-speed cruise flight. India would greatly benefit by an Integrated Hypersonics Transportation Programme, with leading institutions like ISRO, NAL and ADA working together to jointly study, design and build a strong technology base for small, unmanned hypersonic flight demonstrators. This project could then lead on, safely and economically, to hypersonic Executive Jet aircraft, and small fully Reusable Trans-Atmospheric Vehicles for direct ascent of the hypersonic aerospacecraft to earth orbit.

Characteristics and Driving Mechanism of Urban Construction Land Expansion along with Rapid Urbanization and Carbon Neutrality in Beijing, China

Escalating urban issues in Beijing call for comprehensive exploration of urban construction land expansion towards the goal of carbon neutrality. Firstly, urban construction land in Beijing during the period 2005–2020 was accurately detected using Landsat images and impervious surface data, and then its expansion characteristics were revealed. Finally, the driving mechanism of urban construction land expansion was explored using geographically and temporally weighted regression from the input–output perspective. The results showed that the expansion speed and intensity of urban construction land in Beijing showed an overall tendency to slow down, and the center of urban expansion shifted to the new urban development zone and ecological function conservation zone. Urban construction land expansion in the central urban area was first scattered and then compact, while that in the new urban development zone and ecological function conservation zone primarily followed an outward pattern. The permanent population, per capita GDP, and per capita retail sales of social consumer goods were the primary driving factors of urban construction land expansion in Beijing, the impacts of which varied significantly among different districts of Beijing. All these results can provide a solid foundation for improving land use policies towards the goal of carbon neutrality in highly urbanized areas.

Research on Monte Carlo simulation of CAT III auto-landing system

Approach/Landing is the phase of most accidents occur to endanger civil aircraft safety. CAT III autoland operation can improve the safety and reliability of aircraft when approach and landing in bad weather conditions, and reduce pilot’s working loads, so CAT III autoland control law design is an important task in advanced flight control system research. However, the most of the related researches are requirement based rather and scenario based. Firstly, the article analyzes the Monte Carlo simulation requirements based on airworthiness requirements of auto-landing system and proposes a Monte Carlo simulation model scheme considering the uncertainty of aircraft dynamic model and the actuator model, the error of sensors and the disturbance of wind, then implements the simulation based on a desktop simulation platform. The simulation result shows that the designed auto-landing system can assure the safe and stable landing of the aircraft on the condition of all kinds of uncertainty, the touchdown point, the vertical landing speed and the attitude are all compliance with the expectation criteria, satisfying the requirement of airworthiness items.

Terminal Explosion Power Test Flight Platform of Warhead

Aiming at the shortcomings of high risk, high cost, low landing speed and low attitude accuracy of warhead terminal dynamic performance test, a low cost, recyclable and modular warhead terminal explosion power test flight platform is proposed. The overall scheme of two-stage flight is constructed, and the aerodynamic load of the flight process is analysed. In addition, the flight trajectory is designed. The numerical simulation results show that the flight platform can send the warhead to the specified test window, accurately control the drop velocity and attitude of the warhead in the test window, simulate the real flight environment of the warhead and the motion law of the terminal point. Therefore, the flight platform can realize the terminal explosion power test and test of the subsonic and supersonic warheads, providing technical support for the development of the warhead.

Automatic Retracting and Paying-off System of Tethered Unmanned Aerial Vehicle

With the progress of unmanned aerial vehicle (UAV) technology, people have higher and higher requirements for the working endurance of rotary-wing UAVs. The tethered UAV can be wired to power through the tethered cable, which solves the problem of UAV endurance. During the descent of the UAV, the operator needs to manually rotate the take-up device for take-up manually. When the operator fails to put the redundant tied cables into the retracting and paying-off device timely, the redundant tied cables are prone to be entangled and knotted, causing potential safety hazards. To overcome the shortcomings of the above existing technologies, this project develops an automatic retracting and paying-off device based on the tethered UAV. The tension of the tethered cable is measured in real time by adding a tension monitoring unit to the traditional take-up device. According to the tension of the tethered cable and the takeoff and landing speed of the tethered UAV, the real-time automatic take-up of the tethered cable is realized.

Passive Control of Boundary Layer on Wing: Numerical and Experimental Study of Two Configurations of Wing Surface Modification in Cruise and Landing Speed

Minimizing the carbon footprint of the aviation industry is of critical importance for the forthcoming years, allowing the mitigation of climate change through fossil fuel economy. Significant progress toward this goal can be achieved through the aerodynamic optimization of wing surfaces. In a previous study, a custom-designed wing equipped with an Eppler 420 airfoil, including an appendant custom-designed blended winglet, was developed and studied in flight conditions. The present paper researches potential improvements to the aerodynamic behavior of this wing by attempting to regenerate the boundary layer. The main goal was to achieve passive control of the boundary layer, which would be approached by means of two different configurations. In the first case, dimples were added at the points where the separation of the boundary layer was expected, for the majority of the wing surface; in the second case, bumps of the same diameter were added at the same points. Both wings were studied in two different Reynolds (Re) numbers and five angles of attack (AoA). The computational fluid dynamics (CFD) simulations were implemented using a pressure-based solver, the spatial discretization was conducted with a second-order upwind scheme, and the k-omega SST (k-ω SST) turbulence model was applied by utilizing the pseudo-transient method. The experimental procedure was conducted in an open-type subsonic flow wind tunnel, for Reynolds 86,000, with 3D-printed models of the wings having undergone suitable surface treatment. The numerical and experimental results converged, showing a degradation in the wing’s aerodynamic performance when bumps were implemented, as well as a slight improvement for the configuration with dimples.

Simulation of future land use/cover change (LUCC) in typical watersheds of arid regions under multiple scenarios

The rapid development of the social economy has promoted a continuous increase in the intensity and scale of land use by humans, which has seriously affected the sustainable development of the region. It is important to understand the land use/cover change (LUCC) in the arid region and its future development trends and to make reasonable planning recommendations for the sustainable development of the ecological environment. This study validates the patch-generating land use simulation (PLUS) model in a typical arid region, the Shiyang River Basin (SRB), and analyzes the applicability of the model in arid regions. On this basis, the PLUS model is combined with the scenario analysis method to design four scenarios including no policy intervention, farmland protection, ecological protection and sustainable development to analyze the dynamic changes in past and future land use in the SRB and to make corresponding planning recommendations for the development of each type of land use in the arid region. The results showed that the PLUS model had a better simulation effect in the SRB (its overall accuracy reached 0.97). Coupled models obtain better simulation results than quantitative and spatial models by comparing the mainstream models, with PLUS model that combines CA model and patch generation strategy showing better simulation results in the same category. From 1987 to 2017, the spatial centroid of each LUCC in the SRB moved to varying degrees due to a continuous increase in human activities. The spatial centroid of water bodies had the most obvious change, with a moving speed of 1.49 km/a, while the moving speed of built-up land increased year by year. The spatial centroid of farmland, built-up land and unused land all shifted toward the middle and lower plains, which is a further indication of increased human activity. Due to different government policies, the development trend of land use was also different under different scenarios. However, the four scenarios all showed that the area of built-up land will be increasing exponentially from 2017 to 2037, which would seriously affect the surrounding ecological land and have a negative impact on the local agro-ecological environment. Therefore, we proposed the following planning recommendations: (1) Land leveling work should be carried out on scattered farmland located at high altitudes and with slopes over 25°. Additionally, the land use of low-altitude areas should strictly adhere to basic farmland, increase the diversification of cropping patterns and improve the efficiency of agricultural water. (2) The relationship between ecology, farmland and cities should be reasonably coordinated and the existing idle built-up land should be efficiently used. (3) Forestland and grassland resources should be strictly protected and the ecological redline should be strictly observed. This study can provide new ideas for LUCC modeling and prediction in other parts of the world and provide a strong basis for ecological management and sustainable development in arid areas.

Thrust Vectoring Control of a Novel Tilt-Rotor UAV Based on Backstepping Sliding Model Method.

In this paper, a control method of a novel tilt-rotor UAV with a blended wing body layout is studied. The novel UAV is capable of vertical take-off and landing and has strong stealth capabilities that can be applied to carrier-borne reconnaissance aircraft. However, the high aspect ratio of blended wing body UAVs leads to a wingtip or oar-tip touchdown problem when adopting the conventional position-attitude control (CPAC) scheme with a large crosswind disturbance. Moreover, when the UAV is subject to interference during reconnaissance, aerial photography, and landing missions, the conventional scheme cannot provide both attitude stability and track accuracy. First, a direct thrust vectoring control (DTVC) scheme is proposed. The control authority of the rotor tilt mechanism was added to enable the decoupling of the attitude and trajectory and to improve the response rate and response bandwidth of the flight trajectory. Second, considering the problems of strong couplings and parameter uncertainties and the nonlinear features and mismatched perturbations that are inevitable in the tilt-rotor, we designed a robust UAV controller based on the backstepping sliding mode control method and determined the stability of the control system through the Lyapunov function. Finally, in the case of crosswire interference during vertical takeoff and landing and the aerial photography missions of the UAV, the numerical simulation of the CPAC scheme and the DTVC scheme was carried out, respectively, and the Monte Carlo random test method was introduced to conduct the statistical test of the landing accuracy. The simulation results show that the DTVC scheme improves the landing accuracy and speed compared to the CAPC scheme and decouples the position control loop from the attitude control loop, finally enabling the UAV to complete the flight control in the VTOL phase.

On the steady-state motion in the vertical plane of an airship of the classical scheme

We consider the construction of the mathematical model of motion in the vertical plane of an airship of the classical scheme and algorithms for calculating the parameters of its steady-state motion in various cases. The motion of an airship of rather small volume, for example, a remotely piloted airship, is investigated. Some types of possible motions in the vertical plane satisfying the proposed system of equations of steady-state motions are described. Such motions include horizontal flight with constant velocity, rectilinear flight in climbing mode, and descent at a constant trajectory slope angle. The cases of rectilinear flight of an airship along inclined trajectories, the inclination angle of which is not small, taking into account the nonlinear components of the aerodynamic characteristics, are also considered. We have developed algorithms for calculating the steady-state motions of an airship for various cases of flight along inclined trajectories corresponding to various methods of takeoff and landing of an airship without a special cable landing system. This allows us to construct trajectories that provide short takeoff distances and low landing speeds of the airship, which corresponds to the solution of the problem of safe operation of the airship as a technical system. The results of numerical calculations of steady-state motion parameters obtained in accordance with the constructed algorithms are presented. The calculation results are presented graphically.

Efficiency and Fatigue/Endurance Laboratory Tests of Aviation Friction Brakes

Abstract Brakes are one of the most important safety systems in moving vehicles and machines. In vehicles such as cars or motorcycles brakes are used for stopping, controlling speed, and sometimes changing direction of travel. In aircraft, the main function of brakes is to reduce landing speed. As landing is one of the most dangerous maneuvers in aircraft operation, brakes must be efficient and reliable in order to ensure safety of the crew, passengers, and cargo. The most efficient brakes nowadays are friction brakes where velocity is controlled by friction of a pair of specially designed materials, which ensure stable and high friction coefficient over the course of the required braking process. The process itself is the dissipation of energy during aircraft movement which generates very high temperatures in friction materials during the time of the braking process. The materials and the whole brakes have to be temperature resistant, and we must ensure braking parameters are stable during the whole process. The same principle relates to the endurance/fatigue of the brake assemblies which must be durable enough to survive as high number of braking cycles as possible without any failure, which can result in fatal consequences. Every friction pair and every newly designed brake assembly must be laboratory tested for efficiency and endurance/fatigue in order to be used in an aircraft or vehicle. In this paper, we present the basic set of laboratory tests in the scope of friction materials and brake assemblies. Results of the tests are used as confirmations/proofs of proper and safe operation of the brakes for use in vehicles, especially in aircraft but also in land-based vehicles.

Use of the vibroacoustic system for determining the range of a ski jump for training athletes

The principle of vibroacoustic systems operation for determining the distance of a ski jump from a springboard, the possible location of sensors on the springboard and sensor signals that occur when athlete lands are considered. The problems of calculating the jump distance and methods for solving these problems are described. The interrelation of the technique of performing a jump (the spatial position of the skis at the time of landing and the normal component of the landing speed relative to the surface of the springboard) with the form of sensor signals is considered. Real waveforms of signals obtained both during the summer artificial covering of the springboard and in winter, as well as generalized results of experimental operation of the system on springboards with different heights of the acceleration mountain are presented. It is shown that the use of vibroacoustic systems allows achieving the required accuracy of determining the ski jump distance – 0.5 m, and the integration of the system with the general jump monitoring system opens up new opportunities for independent training of athletes and training of a group of athletes under the guidance of a coach.

25 Year Ago October 1997

New land speed record some feat; Sandvik Coromant and Kennametal reach agreement; Trump hits the web; EMO Hanover attracts 180,000 visitors; and Bowers makes name changes as business booms