Time in physics

In physics, time is defined by its measurement: time is what a clock reads. In classical, non-relativistic physics, it is a scalar quantity (often denoted by the symbol t) and, like length, mass, and charge, is usually described as a fundamental quantity. Time can be combined mathematically with other physical quantities to derive other concepts such as motion, kinetic energy and time-dependent fields. is a complex of technological and scientific issues, and part of the foundation of recordkeeping. Markers of time History of timekeeping devices Before there were clocks, time was measured by those physical processes which were understandable to each epoch of civilization: *the first appearance (see: heliacal rising) of Sirius to mark the flooding of the Nile each year *the periodic succession of night and day, seemingly eternally *the position on the horizon of the first appearance of the sun at dawn *the position of the sun in the sky *the

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Least-restrictive robust MPC of periodic affine systems with application to building climate control

Colin Neil Jones

Robust state-feedback model predictive control (MPC) of discrete-time periodic affine systems is considered. States and inputs are subject to periodically time-dependent, hard, convex, polyhedral constraints. Disturbances are additive, bounded and subject to periodically time-dependent bounds. The control objective is given in terms of periodically time-dependent costs. First, maximum robust periodic controlled invariant sets are formally characterized and subsequently employed in the design of least-restrictive robustly strongly feasible periodic MPC problems. Finally, the proposed methods are applied to controlling room temperatures in buildings.

IEEE2010

Least-restrictive robust periodic model predictive control applied to room temperature regulation

Colin Neil Jones

State-feedback model predictive control (MPC) of constrained discrete-time periodic affine systems is considered. The periodic systems’ states and inputs are subject to periodically time-dependent, hard, polyhedral constraints. Disturbances are additive, bounded and subject to periodically time-dependent bounds. The objective is to design MPC laws that robustly enforce constraint satisfaction in a manner that is least-restrictive, i.e., have the largest possible domain. The proposed design method is demonstrated on a building climate control example. The proposed method is directly applicable to time-invariant MPC.

Elsevier2013

Advanced visualization of large datasets for Discrete Element Method simulations

Mark Sawley

State-of-the-art Discrete Element Method (DEM) simulations of granular flows produce large datasets that contain a wealth of information describing the time-dependent physical state of the particulate medium. To extract this information, both comprehensive and efficient post-processing methods are essential. Special attention must be paid to the interactive visualization of these large hybrid datasets containing both particle-based and surface-based data. In this paper, we report the use of the open-source visualization package ParaView, which we have customized specifically to perform advanced techniques for the post-treatment of large DEM datasets. Particular attention is given to the method used to render the individual particles, based either on triangulation of glyphs or using GPU-accelerated primitives. A demonstration of these techniques, and their relative merits when applied to the visualization of DEM datasets, is presented via their application to real industrial examples.

2007

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