3,100 research outputs found
Optimisation of performance in the triple jump using computer simulation
While experimental studies can provide information on what athletes are doing, they are not suited to determining what they should be doing in order to improve their performance. The aim of this study was to develop a realistic computer simulation model of triple jumping in order to investigate optimum technique. A 13-segment subject-specific torque-driven computer simulation model of triple jumping was developed, with wobbling masses within the shank, thigh, and torso. Torque generators were situated at each hip, shoulder, knee, ankle, and ball joint. Kinetic and kinematic data were collected from a triple jump using a force plate and a Vicon motion analysis system. Strength characteristics were measured using an isovelocity dynamometer from which torque-angle and torque-angular velocity relationships were calculated. Segmental inertia parameters were calculated from anthropometric measurements. Viscoelastic parameters were obtained by matching an angle-driven model to performance data for each phase, and a common set for the three contact phases was determined. The torque-driven model was matched to performance data for each phase individually by varying torque generator activation timings using a genetic algorithm. The matching produced a close agreement between simulation and performance, with differences of 3.8%, 2.7%, and 3.1% for the hop, step, and jump phases respectively. The model showed good correspondence with performance data, demonstrating sufficient complexity for subsequent optimisation of performance. Each phase was optimised for jump distance with penalties for excessive angular momentum at take-off. Optimisation of each phase produced an increase in jump distance from the matched simulations of 3.3%, 11.1%, and 8.2% for the hop, step, and jump respectively. The optimised technique showed a symmetrical shoulder flexion consistent with that employed by elite performers. The effects of increasing strength and neglecting angular momentum constraints were then investigated. Increasing strength was shown to improve performance, and angular momentum constraints were proven to be necessary in order to reproduce realistic performances
Optimisation of performance in the triple jump using computer simulation
While experimental studies can provide information on what athletes are doing, they are not suited to determining what they should be doing in order to improve their performance. The aim of this study was to develop a realistic computer simulation model of triple jumping in order to investigate optimum technique. A 13-segment subject-specific torque-driven computer simulation model of triple jumping was developed, with wobbling masses within the shank, thigh, and torso. Torque generators were situated at each hip, shoulder, knee, ankle, and ball joint. Kinetic and kinematic data were collected from a triple jump using a force plate and a Vicon motion analysis system. Strength characteristics were measured using an isovelocity dynamometer from which torque-angle and torque-angular velocity relationships were calculated. Segmental inertia parameters were calculated from anthropometric measurements. Viscoelastic parameters were obtained by matching an angle-driven model to performance data for each phase, and a common set for the three contact phases was determined. The torque-driven model was matched to performance data for each phase individually by varying torque generator activation timings using a genetic algorithm. The matching produced a close agreement between simulation and performance, with differences of 3.8%, 2.7%, and 3.1% for the hop, step, and jump phases respectively. The model showed good correspondence with performance data, demonstrating sufficient complexity for subsequent optimisation of performance. Each phase was optimised for jump distance with penalties for excessive angular momentum at take-off. Optimisation of each phase produced an increase in jump distance from the matched simulations of 3.3%, 11.1%, and 8.2% for the hop, step, and jump respectively. The optimised technique showed a symmetrical shoulder flexion consistent with that employed by elite performers. The effects of increasing strength and neglecting angular momentum constraints were then investigated. Increasing strength was shown to improve performance, and angular momentum constraints were proven to be necessary in order to reproduce realistic performances.EThOS - Electronic Theses Online ServiceGBUnited Kingdo
Impact of future climate change on water temperature and thermal habitat for keystone fishes in the Lower Saint John River, Canada
Water temperature is a key determinant of biological processes in rivers. Temperature in northern latitude rivers is expected to increase under climate change, with potentially adverse consequences for cold water-adapted species. In Canada, little is currently known about the timescales or magnitude of river temperature change, particularly in large (≥104 km2) watersheds. However, because Canadian watersheds are home to a large number of temperature-sensitive organisms, there is a pressing need to understand the potential impacts of climate change on thermal habitats. This paper presents the results of a study to simulate the effects of climate change on the thermal regime of the lower Saint John River (SJR), a large, heavily impounded, socio-economically important watershed in eastern Canada. The CEQUEAU hydrological-water temperature model was calibrated against river temperature observations and driven using meteorological projections from a series of regional climate models. Changes in water temperature were assessed for three future periods (2030–2034, 2070–2074 and 2095–2099). Results show that mean water temperature in the SJR will increase by approximately ~1 °C by 2070–2074 and a further ~1 °C by 2095–2099, with similar findings for the maximum, minimum and standard deviation. We calculated a range of temperature metrics pertaining to the Atlantic Salmon and Striped Bass, key species within the SJR. Results show that while the SJR will become increasingly thermally-limiting for Atlantic Salmon, the Striped Bass growth season may actually lengthen under climate change. These results provide an insight into how climate change may affect thermal habitats for fish in eastern Canadian rivers
Book Reviews
Book Reviews
The Oppenheimer Case: The Trial of a Security System
By Charles P. Curtis
New York: Simon and Schuster, 1955. Pp. xi, 281. 6.65
reviewer: J. Raymond Denney
=============================
Military Law under the Uniform Code of Military Justice
By William B. Aycock and Seymour W. Wurfel
Chapel Hill: University of North Carolina Press, 1955. Pp. xviii, 430.
reviewer: James B. Earle
=================================
Why Johnny Can\u27t Read
By Rudolf Flesch
New York: Harper & Brothers, 1955. Pp. ix, 222.
==================================
Plain Words: Their ABC
By Sir Ernest Gowers
New York: Alfred A. Knopf, 1955. Pp. viii, 298.
===================================
Effective Legal Writing
By Frank E. Cooper
Indianapolis, The Bobbs-Merrill Company, Inc., 1953. Pp. x, 313.
reviewer: J. Allen Smith
==================================
The Moral Decision: Right and Wrong in the Light of American law
By Edmond Cahn
Bloomington, Ind.: Indiana University Press, Pp. ix, 315. $5.00
reviewer: Samuel Enoch Stump
A Quantitative Test of the Predicted Relationship between Countershading and Lighting Environment
Countershading, a vertical luminance gradient from a dark back to a light belly, is perhaps the most common coloration phenotype in the animal kingdom. Why? We investigated whether countershading functions as self-shadow concealment (SSC) in ruminants. We calculated “optimal” countershading for SSC by measuring illumination falling onto a model ruminant as a function of time of day and lighting environment. Calibrated images of 114 species of ruminant were compared to the countershading model, and phylogenetic analyses were used to find the best predictors of coats’ countershading characteristics. In many species, countershading was close to the model’s prediction of “optimal” countershading for SSC. Stronger countershading was associated with increased use of open lighting environments, living closer to the equator, and small body size. Abrupt transitions from dark to light tones were more common in open lighting environments but unassociated with group size or antipredator behavior. Though the SSC hypothesis prediction for stronger countershading in diurnal species was not supported and noncountershaded or reverse-countershaded species were unexpectedly common, this basic pattern of associations is explained only by the SSC hypothesis. Despite extreme variation in lighting conditions, many terrestrial animals still find protection from predation by compensating for their own shadows
Reconstructing the colonization history of Indo-Pacific bottlenose dolphins (Tursiops aduncus) in Northwestern Australia
Bottlenose dolphins (Tursiops spp.) are found in waters around Australia, with T. truncatus typically occupying deeper, more oceanic habitat, while T. aduncus occur in shallower, coastal waters. Little is known about the colonization history of T. aduncus along the Western Australian coastline; however, it has been hypothesized that extant populations are the result of an expansion along the coastline originating from a source in the north of Australia. To investigate the history of coastal T. aduncus populations in the area, we generated a genomic SNP dataset using a double-digest restriction-site-associated DNA (ddRAD) sequencing approach. The resulting dataset consisted of 103,201 biallelic SNPs for 112 individuals which were sampled from eleven coastal and two offshore sites between Shark Bay and Cygnet Bay, Western Australia. Our population genomic analyses showed a pattern consistent with the proposed source in the north with significant isolation by distance along the coastline, as well as a reduction in genomic diversity measures along the coastline with Shark Bay showing the most pronounced reduction. Our demographic analysis indicated that the expansion of T. aduncus along the coastline began around the last glacial maximum and progressed southwards with the Shark Bay population being founded only 13 kya. Our results are in line with coastal colonization histories inferred for Tursiops globally, highlighting the ability of delphinids to rapidly colonize novel coastal niches as habitat is released during glacial cycle-related global sea level and temperature changes
Automated Absorber Attachment for X-ray Microcalorimeter Arrays
Our goal is to develop a method for the automated attachment of large numbers of absorber tiles to large format detector arrays. This development includes the fabrication of high quality, closely spaced HgTe absorber tiles that are properly positioned for pick-and-place by our FC150 flip chip bonder. The FC150 also transfers the appropriate minute amount of epoxy to the detectors for permanent attachment of the absorbers. The success of this development will replace an arduous, risky and highly manual task with a reliable, high-precision automated process
Determination of the Cosmic Distance Scale from Sunyaev-Zel'dovich Effect and Chandra X-ray Measurements of High Redshift Galaxy Clusters
We determine the distance to 38 clusters of galaxies in the redshift range
0.14 < z < 0.89 using X-ray data from Chandra and Sunyaev-Zeldovich Effect data
from the Owens Valley Radio Observatory and the Berkeley-Illinois-Maryland
Association interferometric arrays. The cluster plasma and dark matter
distributions are analyzed using a hydrostatic equilibrium model that accounts
for radial variations in density, temperature and abundance, and the
statistical and systematic errors of this method are quantified. The analysis
is performed via a Markov chain Monte Carlo technique that provides
simultaneous estimation of all model parameters. We measure a Hubble constant
of 76.9 +3.9-3.4 +10.0-8.0 km/s/Mpc (statistical followed by systematic
uncertainty at 68% confidence) for an Omega_M=0.3, Omega_Lambda=0.7 cosmology.
We also analyze the data using an isothermal beta model that does not invoke
the hydrostatic equilibrium assumption, and find H_0=73.7 +4.6-3.8 +9.5-7.6
km/s/Mpc; to avoid effects from cool cores in clusters, we repeated this
analysis excluding the central 100 kpc from the X-ray data, and find H_0=77.6
+4.8-4.3 +10.1-8.2 km/s/Mpc. The consistency between the models illustrates the
relative insensitivity of SZE/X-ray determinations of H_0 to the details of the
cluster model. Our determination of the Hubble parameter in the distant
universe agrees with the recent measurement from the Hubble Space Telescope key
project that probes the nearby universe.Comment: ApJ submitted (revised version
- …