937 research outputs found
Air Pollution and Mortality for 60 US Cities in 1960
No full textData includes measurements on mortality rate and explanatory variables(air-pollution, socio-economic and meteorological) for 60 US cities in 1960. This data was originally published in McDonald, G.C. and Schwing,R.C. (1973) 'Instabilities of regression estimates relating air pollution to mortality', Technometrics, vol.15, 463-482. It was redistributed through Carnegie Mellon University's StatLib (lib.stat.cmu.edu
Wake Vortex Scenarios Simulation Package for Take-Off and Departure
No full textThe WakeScene-D software package (Wake Vortex Scenarios Simulation Package for Departure) has been developed for comprehensive airspace simulations of take-off and departure. WakeScene-D consists of modules that model traffic mix, aircraft trajectories, meteorological conditions, wake vortex evolution, and potential hazard area. The software package estimates the probability to encounter wake vortices in different traffic and crosswind scenarios using Monte Carlo simulation in a domain ranging from the runway to an altitude of 3000 ft above ground. A comparison to measured vortex tracks of about 10,000 departures from runway 25R of Frankfurt airport indicates good agreement of global wake vortex transport characteristics in ground proximity. The standard departure situation employing a two-minute aircraft separation is compared to scenarios with reduced departure separations and various crosswind conditions. Comprehensive sensitivity analyses have been conducted which are briefly recapitulated. Effects related to departure route combinations and wind direction sectors are reported in more detail. Finally, an advanced scenario with an asymmetric crosswind criterion is introduced
Simulation of wake vortex effects for UAVs in close formation flight
No full textThis paper addresses the development of multiple UAV deployment simulation
models that include representative aerodynamic cross-coupling effects.
Applications may include simulations of autonomous aerial refuelling and
formation flying scenarios. A novel wake vortex model was developed and
successfully integrated within a Matlab/Simulink simulation environment. The
wake vortex model is both sufficiently representative to support studies of
aerodynamic interaction between multiple air vehicles, and straightforward
enough to be used within real time or near real time air-to-air simulations. The
integration process is described, and simulation results of a two vehicles
formation flight are presented
High-resolution CFD modelling of Lillgrund Wind farm
No full textWe report on a fully dynamic simulation of Vattenfall’s Lillgrund offshore Wind Farm, with a focus on the wake effects of turbines on the performance of individual turbines, and of the farm as a whole.The model uses a dynamic representation of a wind turbine to simulate interaction between the wind and the turbine rotors, calculating the instantaneous power output and forces on the air; this was embedded in a finite element, large eddy simulation (LES) computational fluid dynamics code. This model was applied to the wind farm for a selection of key wind speeds and directions, to investigate cases where a row of turbines would be fully aligned with the wind or at specific angles to the wind. The simulation results were then compared to actual performance measurements from the wind farm spanning several years’ of operation.<br/>These results demonstrate that time-resolving LES simulations are able to reproduce realistic wake structures, including wake meandering and wake recovery, as well as the effect of wakes on turbine performance
Circumveiloped by Obscuritads. The nature of interpretation in quantum mechanics, hermeneutic circles and physical reality, with cameos of James Joyce and Jacques Derrida
No full textThe quest for finding the right interpretation of Quantum Mechanics (QM) is as old as QM and still has not ended, and may never end. The question what an interpretation of QM is has hardly ever been raised explicitly, let alone answered. We raise it and answer it. Then the quest for the right interpretation can continue self-consciously, for we then know exactly what we are after. We present a list of minimal requirements that something has to meet in order to qualify as an interpretation of QM. We also raise, as a side issue, the question how the discourse on the interpretation of QM relates to hermeneutics in Continental Philosophy
Modelling tidal current turbine wakes using a coupled RANS-BEMT approach as a tool for analysing power capture of arrays of turbines
No full textThe downstream evolution of the wake generated by a rotating tidal energy conversion device influences the performance of the device itself as well as the performance of any downstream device. An improved method is proposed for coupling a blade element momentum theory inner solution for a horizontal axis tidal turbine with an outer domain flow solved using a commercial finite volume computational Fluid Dynamics solver. A mesh sensitivity study is carried out and shows that for wake evolution of distance 10 diameters a high resolution mesh (>10M cells) is required. The importance of swirl is shown in retarding the wake spreading and that the inclusion of a suitableturbulence intensity term is also required to capture the spread of the near wake. A final section demonstrates the use of such a technique for analysing the energy capture of an array of multiple turbines distributed over 1km2 of seabed. The use of staggered lateral position between longitudinal arrays demonstrates a potential for more effective power capture
Lyapunov functions and global stability for SIR, SIRS, and SIS epidemiological models
No full textLyapunov functions for classical SIR, SIRS, and SIS epidemiological models are introduced. Global stability of the endemic equilibrium states of the models is thereby established
Stability of flow in a model of a hydrothermal system
No full textA model of a geothermal system is described. The critical Rayleigh number for convective flow in this model is found for two cases: first when the system is closed, and secondly when there is a small net upward through flow. The equations for the isotherms and streamlines at marginal stability are found for the first case
Riccati matrix differential equations and oscillation theory
No full textChapter 1. A Survey of Classical Oscillation Theory.
Starting with the work of Sturm [39], some of the developments in this area are treated. One section deals with the most modern work on the second order equation, and some time is devoted to equations of higher order. It is also shown that all of this theory is a special case of first order matrix oscillation theory. Another section is given over to a discussion of the role of self-adjointness, including a physical interpretation in terms of conservation laws.
Chapter 2. Matrix Boundary Value Problems of the First Order, and the Riccati Matrix Differential Equation.
We begin our study of the first order boundary value problem: y'=A(x)y My(a)+Ny(b)=0, where M and N are matrices, A is a matrix function and y a vector function. Some standard properties of this system are derived for future use. It is also shown that this problem can be studied with the aid of a Riccati matrix initial value problem (equation (2.20)). In the case where y is two dimensional the Riccati equation has a simple geometrical interpretation.
Chapter 3. Properties of a Riccati Matrix Differential Equation.
Some properties, most of which are standard, of the matrix Riccati equation are discussed. These include the derivation of the general solution, and the effect on the solution when a parameter, upon which the coefficients depend, is varied. It is also shown that an important class of self-adjoint problems can be made to give rise to Riccati equations whose solutions are hermitean. Finally the effect on the Riccati equation of various transformations is discussed.
Chapter 4. Comparison Theorems for Hermitean Riccati Equations.
Various monotoneity properties of the Riccati equation's solutions are derived. Theorems 4-4 and 4-7, two comparison theorems for the hermitean Riccati equation, are proved. They are then used to establish comparison theorems for the associated self-adjoint linear problems. Two alternative approaches are used to derived theorems 4-4 and 4-7.
Chapter 5. The Unit Circle Theory of Atkinson.
Wherein an ingenious transformation developed by Atkinson [1] is used to reduce the self-adjoint matrix boundary value problem to a linear initial value problem, whose solution is a unitary matrix function. The resulting comparison theorems are compared with those of chapter 4.
Chapter 6. Linear Equations of the Third Order.
In the case of a scalar linear equation of the third order it is shown that, for certain boundary conditions, the Riccati equation degenerates to two coupled scalar equations of the first order. These are used to derive a disconjugacy criterion for the equation. This is the only non- self-adjoint problem considered. During the proof of the disconjugacy criterion a transformation is used which is capable of a geometric interpretation
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