AC transport through a resonant level between ferromagnetic electrodes

We report the investigation of the spin-valve effect through a resonant level between a ferromagnetic electrode in the presence of an external ac bias. We use the current conserving and gauge invariant theory developed by Büttiker to calculate the dynamic conductance. Specifically, we have calculated the tunneling magnetoresistance (TMR) ratio as a function of various system parameters such as the angle between magnetization of the left and right leads, ac frequency, and the Fermi energy. We found that the TMR ratio can be modulated by ac frequency. At large frequency, the TMR ratio can be negative.published_or_final_versio

Study of thermal bubble motion in microchannel

This paper was presented at the 2nd Micro and Nano Flows Conference (MNF2009), which was held at Brunel University, West London, UK. The conference was organised by Brunel University and supported by the Institution of Mechanical Engineers, IPEM, the Italian Union of Thermofluid dynamics, the Process Intensification Network, HEXAG - the Heat Exchange Action Group and the Institute of Mathematics and its Applications.The micro capillary pumped loop system (MCPL) is a highly efficient device for heat transfer because the main driving force is a result of thermo-bubbles in micro-channel. In this study, the scaling effect with respect to the dimensional geometry of MCPL was studied for improving the heat transfer performance. The results showed that when a larger heating power was provided by microheater, the growing rate of thermal bubble was faster. Generally speaking, injecting a larger amount of working fluids resulted in faster thermo bubble motion. When the size of channel was scaled down, the nucleation of thermal bubble occurred easily and a positive performance of heat transfer was expected. These findings will be useful to the further optimal design of MCPL.This study is funded by the National Science Council of the Republic of China, Taiwan, under Contract No. NSC- 98-2221-E-197 –018

Effects of correlation-based VM allocation criteria to cloud data centers

2016-2017 > Academic research: refereed > Refereed conference paper201804_a bcmapreprint_postprin

Crystallization and preliminary crystallographic data for the augmenter of liver regeneration

A new cellular growth factor termed augmenter of liver regeneration (ALR) has been crystallized. ALR has been shown to have a proliferative effect on liver cells while at the same time producing an immunosuppressive effect on liver-resident natural killer cells and liver-resident mononuclear leukocytes. In addition, ALR appears to play an important role in the synthesis and stabilization of mitochondrial gene transcripts inactively regenerating cells. ALR crystals diffract to beyond 2 Å resolution and belong to space group P21212, with a = 125.1, b = 108.1 and c = 38.5 Å. Based on four molecules per asymmetric unit, the Matthews coefficient is calculated to be 2.16 Å3 Da-1 which corresponds to a solvent content of 43%

Cluster-based informed agents selection for flocking with a virtual leader

2014-2015 > Academic research: refereed > Refereed conference paperAccepted ManuscriptPublishe

A stable matching-based virtual machine allocation mechanism for cloud data centers

2016-2017 > Academic research: refereed > Refereed conference paper201803_a bcwhpreprint_postprin

Effect of initial conditions on interaction between a boundary layer and a wall-mounted finite-length-cylinder wake

Author name used in this publication: Y. ZhouAuthor name used in this publication: C. K. ChanAuthor name used in this publication: K. S. Lam2006-2007 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Investigations on dirty paper trellis codes for watermarking

Recently, watermarking has been modelled as communications with side information at the transmitter. The advantage of this is that in theory the interference due to the cover Work or host signal can be eliminated, thereby improving the capacity of the watermarking system. Hence a number of different practical methods have been proposed, one of which is based on dirty paper trellis coding. These codes are a form of spherical code, and as such, have the advantage of being robust to amplitude scaling. Dirty paper trellises have a number of design parameters. There is a lack of understanding on the influence of these parameters on performance, and this thesis attempts to address this. In particular, the thesis examines the following parameters: (i) the number of states and the number of arcs per state in the trellis, (ii) the distribution of the codewords generated by the trellis, and (iii) the cost function associated with each arc. Experimental results are provided on both synthetic signals and real images that demonstrate how performance is affected and a number of suggestions and improved designs are discussed. In particular, a deeper understanding of trellis configurations is provided that serves as a foundation on which to choose the best trellis structure based on bit error rate performance and computational cost. Secondly, trellis coded modulation (TCM) is adapted for use in a dirty paper trellis. This results in an improved distribution of the codewords on the sphere which leads to improved performance. Lastly, during embedding, the embedder usually searches for the codeword that has the highest linear correlation with the cover Work. However, this codeword may be difficult to embed due to perceptual constraints. We show that searching for a codeword that maximises a cost function based on linear correlation and perceptual distance can significantly improve performance

PEDS: Passivity enforcement for descriptor systems via Hamiltonian- symplectic matrix pencil perturbation

Passivity is a crucial property of macromodels to guarantee stable global (interconnected) simulation. However, weakly nonpassive models may be generated for passive circuits and systems in various contexts, such as data fitting, model order reduction (MOR) and electromagnetic (EM) macromodeling. Therefore, a post-processing passivity enforcement algorithm is desired. Most existing algorithms are designed to handle poleresidue models. The few algorithms for state space models only handle regular systems (RSs) with a nonsingular D+D T term. To the authors' best knowledge, no algorithm has been proposed to enforce passivity for more general descriptor systems (DSs) and state space models with singular D + D T terms. In this paper, a new post-processing passivity enforcement algorithm based on perturbation of Hamiltonian-symplectic matrix pencil, PEDS, is proposed. PEDS, for the first time, can enforce passivity for DSs. It can also handle all kinds of state space models (both RSs and DSs) with singular D + D T terms. Moreover, a criterion to control the error of perturbation is devised, with which the optimal passive models with the best accuracy can be obtained. Numerical examples then verify that PEDS is efficient, robust and relatively cheap for passivity enforcement of DSs with mild passivity violations. ©2010 IEEE.published_or_final_versionThe IEEE/ACM International Conference on Computer-Aided Design (ICCAD 2010), San Jose, CA., 7-11 November 2010. In Proceedings of ICCAD, 2010, p. 800-80

Emission mechanism of GeV-quiet soft gamma-ray pulsars: a case for peculiar geometry?

postprin