Superfluid vs Ferromagnetic Behaviour in a Bose Gas of Spin-1/2 Atoms

We study the thermodynamic phases of a gas of spin-1/2 atoms in the Hartree-Fock approximation. Our main result is that, for repulsive or weakly-attractive inter-component interaction strength, the superfluid and ferromagnetic phase transitions occur at the same temperature. For strongly-attractive inter-component interaction strength, however, the ferromagnetic phase transition occurs at a higher temperature than the superfluid phase transition. We also find that the presence of a condensate acts as an effective magnetic field that polarizes the normal cloud. We finally comment on the validity of the Hartree-Fock approximation in describing different phenomena in this system.Comment: 10 pages, 2 figure

Application of a meshless method in electromagnetics

Author name used in this publication: S. L. HoAuthor name used in this publication: J. M. MachadoAuthor name used in this publication: H. C. Wong2001-2002 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

A modified ant colony optimization algorithm modeled on tabu-search methods

Author name used in this publication: S. L. Ho2005-2006 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

A self-learning simulated annealing algorithm for global optimizations of electromagnetic devices

Author name used in this publication: S. L. Ho2000-2001 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

A combined wavelet-element free Galerkin method for numerical calculations of electromagnetic fields

Author name used in this publication: S. L. HoAuthor name used in this publication: J. M. Machado2002-2003 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

A new implementation of population based incremental learning method for optimizations in electromagnetics

Author name used in this publication: S. L. Ho2006-2007 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Covariance Analysis of LAV Robust Dynamic State Estimation in Power Systems

In power system state estimation, the robust Least Absolute Value robust dynamic estimator is well-known. However, the covariance of the state estimation error cannot be obtained easily. In this paper, an analytical equation is derived using Influence Function approximation to analyze the covariance of the robust Least Absolute Value dynamic state estimator. The equation gives insights into the precision of the estimation and can be used to express the variances of the state estimates as functions of measurement noise variances, enabling the selection of sensors for specified estimator precision. Simulations on the IEEE 14-bus, 30-bus and 118-bus systems are given to illustrate the usefulness of the equation. Monte-Carlo experiments can also be used to determine the covariance, but many data points are needed and hence many runs are required to achieve convergence. Our result shows that to obtain the covariance of the state estimation error, the analytical equation proposed in this paper is four orders of magnitude faster than a 10,000-run Monte-Carlo experiment on both the IEEE 14-bus and 30-bus systems.National Research Foundation Singapor

Effects of built environment on walking among Hong Kong older adults

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Wavelet-Galerkin method for computations of electromagnetic fields-computation of connection coefficients

Author name used in this publication: S. L. HoAuthor name used in this publication: H. C. Wong2000-2001 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

An improved tabu-based vector optimal algorithm for design optimizations of electromagnetic devices

Author name used in this publication: S. Y. YangAuthor name used in this publication: S. L. HoAuthor name used in this publication: J. M. MachadoAuthor name used in this publication: Edward W. C. Lo2003-2004 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe