Recursive linearization of multibody dynamics equations of motion

The equations of motion of a multibody system are nonlinear in nature, and thus pose a difficult problem in linear control design. One approach is to have a first-order approximation through the numerical perturbations at a given configuration, and to design a control law based on the linearized model. Here, a linearized model is generated analytically by following the footsteps of the recursive derivation of the equations of motion. The equations of motion are first written in a Newton-Euler form, which is systematic and easy to construct; then, they are transformed into a relative coordinate representation, which is more efficient in computation. A new computational method for linearization is obtained by applying a series of first-order analytical approximations to the recursive kinematic relationships. The method has proved to be computationally more efficient because of its recursive nature. It has also turned out to be more accurate because of the fact that analytical perturbation circumvents numerical differentiation and other associated numerical operations that may accumulate computational error, thus requiring only analytical operations of matrices and vectors. The power of the proposed linearization algorithm is demonstrated, in comparison to a numerical perturbation method, with a two-link manipulator and a seven degrees of freedom robotic manipulator. Its application to control design is also demonstrated

Impact of Teat Order on Feed Consumption in Swine from Birth to Nursery

A relationship between teat order and feed consumption has been assumed in pigs, but no study has looked at this exact relationship. Pigs were observed shortly after birth to be in either a cranial, middle, or caudal teat positon. Growth performance data and active and total plasma ghrelin concentrations were analyzed at birth, weaning, and at the end of the nursery stage of production to see if a relationship with teat order was present. Overall, no effect of teat order was found on average daily gain, average daily feed intake, gain-to-feed ratio, or body weight among pigs from each section of the udder. Differences did occur during certain stages of nursery, which can be of economic importance to producers. No difference was seen in active or total ghrelin levels or the active-to-total ghrelin ratio in relation to teat order, although there were differences in active and total ghrelin concentrations among the sampling days. Further research should be carried out to investigate what factors would contribute to this data contradicting previous inferences about the relationship of teat order and feed consumption in pigs

Man-in-the-control-loop simulation of manipulators

A method to achieve man-in-the-control-loop simulation is presented. Emerging real-time dynamics simulation suggests a potential for creating an interactive design workstation with a human operator in the control loop. The recursive formulation for multibody dynamics simulation is studied to determine requirements for man-in-the-control-loop simulation. High speed computer graphics techniques provides realistic visual cues for the simulator. Backhoe and robot arm simulations are implemented to demonstrate the capability of man-in-the-control-loop simulation

Quantum Informational Dark Energy: Dark energy from forgetting

We suggest that dark energy has a quantum informational origin. Landauer's principle associated with the erasure of quantum information at a cosmic horizon implies the non-zero vacuum energy having effective negative pressure. Assuming the holographic principle, the minimum free energy condition, and the Gibbons-Hawking temperature for the cosmic event horizon we obtain the holographic dark energy with the parameter $d\simeq 1$, which is consistent with the current observational data. It is also shown that both the entanglement energy and the horizon energy can be related to Landauer's principle.Comment: revtex,8 pages, 2 figures more detailed arguments adde

Theory of single-photon transport in a single-mode waveguide coupled to a cavity containing a two-level atom

The single-photon transport in a single-mode waveguide, coupled to a cavity embedded with a two-leval atom is analyzed. The single-photon transmission and reflection amplitudes, as well as the cavity and the atom excitation amplitudes, are solved exactly via a real-space approach. It is shown that the dissipation of the cavity and of the atom respectively affects distinctively on the transport properties of the photons, and on the relative phase between the excitation amplitudes of the cavity mode and the atom.Comment: 28 pages, 6 figures. Accepted by Physical Review A (2009

South Asian students' educational experience and attainment: learning Chinese as a second/additional language in Hong Kong

published_or_final_versio