•The aim was to find the limits of twisting techniques in reverse 1½ somersault dives.•The maximum twist possible in a reverse 1½ somersault dive is 5½ twists.•Maximum twist is produced by ...asymmetrical arm and hip movements during flight.•Coordination of the timing of configurational changes with the twist angle is crucial.•For such elite performance divers must be able to time their actions to within 10 ms.
An angle-driven computer simulation model of aerial movement was used to determine the maximum amount of twist that can be produced in a reverse 1½ somersault dive from a three-metre springboard using various aerial and contact twisting techniques. The segmental inertia parameters of an elite springboard diver were used in the simulations and lower bounds were placed on the durations of arm and hip angle changes based on recorded performances of twisting somersaults. A limiting dive was identified as that producing the largest possible odd number of half twists. Simulations of the limiting dives were found using simulated annealing optimisation to produce the required amounts of somersault, tilt and twist after a flight time of 1.5 s. Additional optimisations were then run to seek solutions with the arms less adducted during the twisting phase. It was found that the upper limits ranged from 3½ to 5½ twists with arm abduction ranges lying between 8° and 23°. Similar results were obtained when the inertia parameters of two other springboard divers were used. It may be concluded that a reverse 1½ somersault dive using aerial asymmetrical arm and hip movements to produce 5½ twists is a realistic possibility. To accomplish this limiting dive the diver needs to be able to coordinate the timing of configurational changes with the progress of the twist with a precision of 10 ms or better.
•The limits of aerial techniques for producing forward 1½ somersault twisting dives.•Forward 1½ somersault dive with five twists using asymmetrical arm technique.•Forward 1½ somersault dive with five ...twists using asymmetrical chest technique.
An angle-driven computer simulation model of aerial movement was used to determine the maximum amount of twist that can be produced in a forward 1½ somersault dive from a three-metre springboard using various aerial twisting techniques. The segmental inertia parameters of an elite springboard diver were used in the simulations and lower bounds were placed on the durations of arm and hip angle changes based on recorded performances of twisting somersaults. A limiting dive was identified as that producing the largest possible whole number of twists. Simulations of the limiting dives were found using simulated annealing optimisation to produce the required amounts of somersault, tilt and twist after a flight time of 1.5 s. Additional optimisations were then run to seek solutions with the arms less adducted during the twisting phase. It was found that the upper limits ranged from two to five twists with arm abduction ranges lying between 6° and 17°. Similar results were obtained when the inertia parameters of two other springboard divers were used.
The control of twisting somersaults Yeadon, Maurice R; Hiley, Michael J
Journal of biomechanics,
04/2014, Letnik:
47, Številka:
6
Journal Article
Recenzirano
Odprti dostop
Abstract In the takeoff and early flight phase of a twisting somersault, joint coordination is based on feed-forward control whereas in the late stages of the flight phase configuration adjustments ...are made using feedback control to ensure accurate completion of the movement and appropriate landing orientation. The aim of this study was to use a computer simulation model of aerial movement to investigate the extent to which arm and hip movements can control twist and somersault rotation in the flight phase of a twisting somersault. Two mechanisms were considered for the control of twist in simulated target trampoline movements with flight times of 1.4 s. In the first case a single symmetrical arm adduction correction was made using delayed feedback control based on the difference between the twist rate in a perturbed simulation and the twist rate in a target movement comprising a forward somersault with 1½ twists. Final corrections were made using symmetrical arm abduction and hip flexion to adjust the twist and somersault angles. In the second case continual asymmetrical arm adduction/abduction adjustments were used to remove the tilt from a perturbed full twisting backward somersault using delayed feedback control based on twist angle and angular velocity. The first method was able to cope with perturbations to a forward somersault with 1½ twists providing the feedback time delay was less than 200 ms. The second method was able to correct a perturbed full twisting backward somersault providing the feedback time delay was less than 125 ms.
Fighting crickets, one species of flightless insects optimally chosen by nature for millions of years, have evolved to fairly smooth and streamlined body surfaces. This article tries to answer the ...question how the insects manipulate air resistance when travelling through air after take-off without using their wings and meanwhile keep a high efficiency. We found that fighting crickets,
Velarifictorus micado
, performed two types of movements through air: stable and unstable. The two types both have a high moving efficiency. For the stable type, the moving efficiency is larger than 95%. As a typical example, focusing on the stable type, we firstly predicted each component of aerodynamic drag applied on the crickets and analysed the drag contributions to the initial kinetic energy dissipation. Further investigation revealed the mechanisms of the efficiently moving strategy against air resistance for the insects. The results show that the crickets can spin their hind legs to adjust body posture, thereby changing (increasing or decreasing) the air drag acting on the body to raise the efficiency during aerial movements. This work may advance the understanding of the significance of hind legs to insects’ evolution and provide inspiration for future robot or micro aerial vehicle designs.
Soybean rust (Phakopsora pachyrhizi) has recently invaded North America and has the potential to be the most destructive foliar disease of soybean. As part of the response to this threat, the ...Integrated Aerobiology Modeling System (IAMS) was constructed to forecast the aerial movement of this pathogen from subtropical to middle latitude portions of the continent. IAMS simulations have been conducted daily for the past two growing seasons and integrated with information from a nationwide observation network into a decision support system for soybean farmers. After the 2005 season, the United States Department of Agriculture reported that many millions of United States (U.S.) soybean hectares that would have been treated for soybean rust in 2005 were not due to this decision support system. In 2006, soybean rust appeared for the first time in the major U.S. soybean production region over 1000 km from known areas of inoculum production. IAMS predictions of the geographical extent and timing of disease symptom expression were well matched with subsequent observations of the disease in the field.
We present an open source software implementation of a popular mathematical method developed by M.R. Yeadon for calculating the body and segment inertia parameters of a human body. The software is ...written in a high level open source language and provides three interfaces for manipulating the data and the model: a Python API, a command-line user interface, and a graphical user interface. Thus the software can fit into various data processing pipelines and requires only simple geometrical measures as input.
To develop an integrated pest management (IPM) program, one must rely on detailed knowledge of pest movement at several levels. The tenets of IPM and the three tiers of information (fundamental, ...tactical, and operational) needed to deploy an IPM program are considered. I highlight the soybean mosaic potyvirus pathosystem, a pest system that is nearly impossible to control once the pathogen enters a field, to illustrate how the pathogen can be contained through IPM practices, but only with a reasonable understanding of pathogen transport by insect vectors. The virus is transmitted by a suite of aphids with different flight activity modes. Disease spread is rapid and irreversible if initial inoculum is high and vector flight activity is great. For that reason, the management mode must be preventive, not remedial. The complex epidemiology involves vector movement over both landscape and ecoregional scales, and movement, especially as it is influenced by atmospheric motion systems over both scales, should be understood to effectively manage soybean mosaic virus epidemics. The importance of conceptual, simulation, and predictive models that take into consideration vector movement cannot be overstated when dealing with a pest complex of this nature.
A variety of organisms change their geographic locations during their life history, and many use the atmosphere to accomplish this shift. Biota that flow in the atmosphere range from very small ...(viruses, bacteria, pollen, and spores) to quite large (weed seeds, aphids, butterflies and moths, songbirds, and waterfowl). As these organisms move, they experience meteorological and ecological conditions that occur at a wide range of spatial and temporal scales. We present an ecological scaling approach that integrates concepts and elements of spatial and temporal scaling to understanding aerobiology and provide examples of the ecological scales important to the long-distance aerial movement of organisms and associated biological events and processes.
An operational framework for ecological scaling of long distance biota movement is achieved by linking spatially-static ecoregion classification systems with temporally-dynamic measures of vegetation phenology. The ecoregions provide ecological boundaries for the phenological dynamics of plants. Operationally, this approach integrates the bi-weekly vegetation greening indices (NDVI) derived from AVHRR or TM satellite data (representing temporal scaling) with the less dynamic land cover–land use classification (IGBP) and the relatively static ecoregion boundaries (representing the spatial scaling). We argue that the correlation of the life histories of species, especially the timing of take-off, to ecosystem phenology through meteorological-based variables and indices (e.g., degree days and moisture indices), allows for dynamic characterization of source ecosystems and can be used to parameterize atmospheric models to forecast the flow of biota in the air.
The scale of these processes, the diversity of the types of biota involved in long-distance movement, and the complexity of the processes require systems thinking. We anticipate that this paper will stimulate studies to enhance our understanding of the flow of organisms in the biosphere.
A technique is presented for determining the angular momentum of the human body about its mass centre for general three-dimensional movements. The three orthogonal components of the angular momentum ...X, Y, and Z of 15 body segments composed of a transfer term and a local term were computed. The total angular momentum of the whole body was considered to be composed of the sum of the angular momentum of each body segment. The three-dimensional coordinates for determining the angular momentum were computed by a Direct Linear Transformation Method from film data. For calculated individual angular momentum the relative error is estimated to be within 7.2%. The application of the principle of conservation of angular momentum was discussed for the jumping smash of badminton. A large angular momentum was generated by rotation of the smash arm during the airborne phases. The lower limbs react upon the arm with an equal and opposite angular momentum to keep the angular momentum constant. This kind of counter rotation to the smash arm was useful to keep the body balance and reinforce the hitting arm.
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