1,472 research outputs found

    DYNAMICS OF SELECTED TOWER DIVE TAKE-OFFS

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    The mechanics of platform diving, unlike those of springboard diving. have not been investigated to any great degree. Unlike the springboard, the platform provides no elastic energy to enhance the diver's momentum. At take-off the diver must achieve sufficient linear momentum to ensure the necessary height and distance to travel safely away from the platform and sufficient angular momentum to complete the required number of rotations about the transverse axis. Ground reaction forces (GRF) developed during contact with the diving platform and the body position of the diver at take-off define the magnitude and direction of the diver's momentum. The nature of rotations in springboard diving has been reported by many researchers and coaches (Fairbanks, 1963; Batterman, 1968; Stroup and Bushnell, 1969)...-tn most cases, it was felt that body Jean at take-off determined the number of rotations in the dive. Golden (1984) found that body lean at take-off increases according to the number of rotations being performed. Miller (1984) found that the height obtained in springboard diving was predominantly due to the action of the lower extremities as they accelera ted the trunk upwards. Although a number of investigators have studied springboard diving, there is an apparent Jack of information pertaining to platform diving. Furthermore, it seemes necessary to study the nature of increased rotations in platform diving. The purpose of this study was, therefore, to investigate the kinetics and kinematics of platform dive take-offs in which a rotation or multiple rotations occurred

    Exactness of the Fock space representation of the q-commutation relations

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    We show that for all q in the interval (-1,1), the Fock representation of the q-commutation relations can be unitarily embedded into the Fock representation of the extended Cuntz algebra. In particular, this implies that the C*-algebra generated by the Fock representation of the q-commutation relations is exact. An immediate consequence is that the q-Gaussian von Neumann algebra is weakly exact for all q in the interval (-1,1).Comment: 20 page

    An ensemble approach to assess hydrological models’ contribution to uncertainties in the analysis of climate change impact on water resources

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    Over the recent years, several research efforts investigated the impact of climate change on water resources for different regions of the world. The projection of future river flows is affected by different sources of uncertainty in the hydro-climatic modelling chain. One of the aims of the QBic3 5 project (Que´bec-Bavarian International Collaboration on Climate Change) is to assess the contribution to uncertainty of hydrological models by using an ensemble of hydrological models presenting a diversity of structural complexity (i.e. lumped, semi distributed and distributed models). The study investigates two humid, mid-latitude catchments with natural flow conditions; one located in 10 Southern Que´bec (Canada) and one in Southern Bavaria (Germany). Daily flow is simulated with four different hydrological models, forced by outputs from regional climate models driven by a given number of GCMs’ members over a reference (1971–2000) and a future (2041–2070) periods. The results show that the choice of the hydrological model does strongly affect the climate change response of selected hydrological indicators, especially those related to low flows. Indicators related to high flows seem less sensitive on the choice of the hydrological model. Therefore, the computationally less demanding models (usually simple, lumped and conceptual) give a significant level of trust for high and overall mean flows

    On the need for bias correction in regional climate scenarios to assess climate change impacts on river runoff

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    In climate change impact research, the assessment of future river runoff as well as the catchment scale water balance is impeded by different sources of modeling uncertainty. Some research has already been done in order to quantify the uncertainty of climate 5 projections originating from the climate models and the downscaling techniques as well as from the internal variability evaluated from climate model member ensembles. Yet, the use of hydrological models adds another layer of incertitude. Within the QBic3 project (Qu´ebec-Bavaria International Collaboration on Climate Change) the relative contributions to the overall uncertainty from the whole model chain (from global climate 10 models to water management models) are investigated using an ensemble of multiple climate and hydrological models. Although there are many options to downscale global climate projections to the regional scale, recent impact studies tend to use Regional Climate Models (RCMs). One reason for that is that the physical coherence between atmospheric and land-surface 15 variables is preserved. The coherence between temperature and precipitation is of particular interest in hydrology. However, the regional climate model outputs often are biased compared to the observed climatology of a given region. Therefore, biases in those outputs are often corrected to reproduce historic runoff conditions from hydrological models using them, even if those corrections alter the relationship between temperature and precipitation. So, as bias correction may affect the consistency between RCM output variables, the use of correction techniques and even the use of (biased) climate model data itself is sometimes disputed among scientists. For those reasons, the effect of bias correction on simulated runoff regimes and the relative change in selected runoff indicators is explored. If it affects the conclusion of climate change analysis in 25 hydrology, we should consider it as a source of uncertainty. If not, the application of bias correction methods is either unnecessary in hydro-climatic projections, or safe to use as it does not alter the change signal of river runoff. The results of the present paper highlight the analysis of daily runoff simulated with four different hydrological models in two natural-flow catchments, driven by different regional climate models for a reference and a future period. As expected, bias correction of climate model outputs is important for the reproduction of the runoff regime of the 5 past regardless of the hydrological model used. Then again, its impact on the relative change of flow indicators between reference and future period is weak for most indicators with the exception of the timing of the spring flood peak. Still, our results indicate that the impact of bias correction on runoff indicators increases with bias in the climate simulations

    Hypercontractivity on the qq-Araki-Woods algebras

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    Extending a work of Carlen and Lieb, Biane has obtained the optimal hypercontractivity of the qq-Ornstein-Uhlenbeck semigroup on the qq-deformation of the free group algebra. In this note, we look for an extension of this result to the type III situation, that is for the qq-Araki-Woods algebras. We show that hypercontractivity from LpL^p to L2L^2 can occur if and only if the generator of the deformation is bounded.Comment: 17 page

    Free Meixner states

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    Free Meixner states are a class of functionals on non-commutative polynomials introduced in math.CO/0410482. They are characterized by a resolvent-type form for the generating function of their orthogonal polynomials, by a recursion relation for those polynomials, or by a second-order non-commutative differential equation satisfied by their free cumulant functional. In this paper, we construct an operator model for free Meixner states. By combinatorial methods, we also derive an operator model for their free cumulant functionals. This, in turn, allows us to construct a number of examples. Many of these examples are shown to be trivial, in the sense of being free products of functionals which depend on only a single variable, or rotations of such free products. On the other hand, the multinomial distribution is a free Meixner state and is not a product. Neither is a large class of tracial free Meixner states which are analogous to the simple quadratic exponential families in statistics.Comment: 30 page

    Non equilibrium inertial dynamics of colloidal systems

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    We consider the properties of a one dimensional fluid of brownian inertial hard-core particles, whose microscopic dynamics is partially damped by a heat-bath. Direct interactions among the particles are represented as binary, instantaneous elastic collisions. Collisions with the heath bath are accounted for by a Fokker-Planck collision operator, whereas direct collisions among the particles are treated by a well known method of kinetic theory, the Revised Enskog Theory. By means of a time multiple time-scale method we derive the evolution equation for the average density. Remarkably, for large values of the friction parameter and/or of the mass of the particles we obtain the same equation as the one derived within the dynamic density functional theory (DDF). In addition, at moderate values of the friction constant, the present method allows to study the inertial effects not accounted for by DDF method. Finally, a numerical test of these corrections is provided.Comment: 13 pages+ 3 Postscript figure

    Factors Influencing the Filing of Complaints, Their Investigation, and Subsequent Legal Judgment in Cases of Sexual Assault.

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    In Geneva, examination of victims of sexual assault is performed by a gynecologist and a medical examiner. 48% of the victims file a complaint and we wanted to investigate the factors leading to file a complaint, those leading the Prosecutor to go to trial, and those influencing a conviction. Between 2006 and 2012, 676 victims of sexual assault were investigated (averaged age 26 year, mean 22). Information on injuries, perpetrators, and circumstances of the assault was collected and analyzed. The attacker being the ex-spouse or a friend and the presence of semen were factors leading to file a complaint. The assailant being a family member or ex-spouse and the presence of genital/anal lesions were factors influencing the Prosecutor. The presence of nongenital lesions, the assailant being known by the victim, influenced conviction. This study shows that the medical examiner plays a vital role in the investigation of cases of sexual assault
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