1,142 research outputs found
Periodically driven circulation near the shore of a lake
No full textSolutions are found for a linear model of the circulation near the shore of a lake that is subject to two diurnal forcing mechanisms. The first is the day/night heating/cooling induced horizontal pressure gradient. The second is an unsteady surface stress modelling a sea breeze/gully wind pattern. The two forcing mechanisms can oppose or reinforce each other depending on their relative phase. The interplay of different dynamic balances at different times and locations in the domain lead to complex circulation patterns especially during the period of flow reversal
Coriolis effects and the thermal bar
No full textA model for the thermal bar system in the rotating frame that includes unsteady inertia is formulated. Asymptotic solutions are found to the initial value problem in the frictionless, small bottom slope limit. These solutions include inertial oscillations that are significant enough to reverse the circulation ahead of the thermal bar. These asymptotic solutions are compared with numerical solutions of the full model that includes friction. The consequences of both sets of results on the thermal bar in lakes is discussed
An asymptotic model for the hydrodynamics of the thermal bar
No full textAn asymptotic solution is found for the temperature and circulation structure for an unsteady two-dimensional model of the thermal bar phenomenon. The non-rotating case considered here is relevant to laboratory models of the thermal bar. The main implication of the asymptotic results is that the thermal bar might propagate out from the shore more slowly than predicted by a purely heat-balance-based estimate. The solution is discussed in the context of available experimental results
A numerical model of the hydrodynamics of the thermal bar
No full textThe thermal bar phenomenon is modelled numerically by the natural convection of a fluid contained in a two-dimensional triangular domain. The non-rotating case considered here is appropriate to laboratory models of the thermal bar. Three sets of results are presented reflecting varying degrees of nonlinearity. The results are discussed in relation to available theoretical and experimental results
Review of the thesis: “The activities of the Soviet police to combat crime and public protection in Western Siberia in 1925-1937” by D.E. Kuznetsov
No full textThe article analyses the thesis “The activities of the Soviet police to combat crime and protect public order in Western Siberia in 1925-1937” by D.E. Kuznetsov. The structure and logic of the construction of the work, the validity of the conclusions, the merits of the dissertation research and its controversial points are considered. Special attention is paid to the source of the dissertation. In conclusion, the author of the article summaries that the contents of D.E. Kuznetsov's facts, assessments and conclusions can be used to develop textbooks on the history of crime, the history of law enforcement bodies, the history of Russia
Periodically forced natural convection over slowly varying topography
No full textAsymptotic and numerical methods are used to analyse periodically forced natural convection over slowly varying topography. This models the diurnal heating/cooling cycle in lakes and reservoirs. The asymptotic solution includes the effects of advection on the temperature. The asymptotic results are confirmed by the numerical results. The numerical results are also used to examine flow regimes where the asymptotic results break down. In particular, the presence of a vertical boundary leads to a permanent stratification in the deeper regions due to a nonlinear pumping process in the shallows. Heat transfer calculations and two limiting cases are also presented
A numerical model of periodically forced circulation near the shore of a lake
No full textNumerical calculations for a model of the near-shore circulation in a lake subject to two diurnal forcing mechanisms are presented. The first mechanism is a heating/cooling term in the heat equation representing the daytime heating and nighttime cooling of the diurnal cycle. The second is a periodic surface stress modelling a sea-breeze/gully wind system typical of some coastal regions. The two forcing mechanisms can either act together or against each other depending on their relative phase. The numerical solutions are compared with previously published analytical solutions and used to explore the extra dynamics associated with non-linear effects (specifically advection). The latter dynamics include the formation of gravity currents and unstable density profiles leading to secondary circulation
A model of the thermal bar in the rotating frame including vertically non-uniform heating
No full textSmall bottom slope, inviscid solutions are found for a model of the temperature and circulation structure of the thermal bar system. This model includes Coriolis effects, a vertically non-uniform heat input and is axisymmetric. The model also includes general topography and time dependent heating. These solutions include inertial oscillations that have a significant effect on the circulation, especially for the case when the heating is instantaneously applied
A model for the evolution of the thermal bar system
No full textA new framework for modelling the evolution of the thermal bar system in a lake is presented. The model assumes that the thermal bar is located between two regions: the deeper region, where spring warming leads to overturning of the entire water column, and the near shore shallower region, where a stable surface layer is established. In this model the thermal bar moves out slightly more quickly than predicted by a simple thermal balance. Also, the horizontal extent of the thermal bar region increases as it moves out from the shore
Brain regions concerned with perceptual skills in tennis: An fMRI study
No full textSporting performance makes special demands on perceptual skills, but the neural mechanisms underlying such performance are little understood. We address this issue, making use of fMRI to identify the brain areas activated in viewing and responding to video sequences of tennis players, filmed from the opponent’s perspective. In a block-design, fMRI study, 9 novice tennis players watched video clips of tennis play. The main stimulus conditions were (1) serve sequences, (2) non-serve behaviour (ball bouncing) and (3) static control sequences. A button response was required indicating the direction of serve (left or right for serve sequences, middle button for non-serve and static sequences). By comparing responses to the three stimulus conditions, it was possible to identify two groups of brain regions responsive to different components of the task. Areas MT/MST and STS in the posterior part of the temporal lobe responded either to serve and to non-serve stimuli, relative to static controls. Serve sequences produced additional regions of activation in parietal lobe (bilateral IPL, right SPL) and in right frontal cortex (IFGd, IFGv), and these areas were not activated by non-serve sequences. These regions of parietal and frontal cortex have been implicated in a “mirror neuron” network in the human brain. It is concluded that the task of judgement of serve direction produces two different patterns of response: activations in MT/MST and STS concerned with primarily with the analysis of motion and body actions, and activations in parietal and frontal cortex associated specifically with the task of identification of direction of serve
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