Controlling the accuracy of unconditionally stable algorithms in Cahn-Hilliard Equation

Given an unconditionally stable algorithm for solving the Cahn-Hilliard equation, we present a general calculation for an analytic time step \d \tau in terms of an algorithmic time step \dt. By studying the accumulative multi-step error in Fourier space and controlling the error with arbitrary accuracy, we determine an improved driving scheme \dt=At^{2/3} and confirm the numerical results observed in a previous study \cite{Cheng1}.Comment: 4 pages, late

Decentralized formation control with connectivity maintenance and collision avoidance under limited and intermittent sensing

A decentralized switched controller is developed for dynamic agents to perform global formation configuration convergence while maintaining network connectivity and avoiding collision within agents and between stationary obstacles, using only local feedback under limited and intermittent sensing. Due to the intermittent sensing, constant position feedback may not be available for agents all the time. Intermittent sensing can also lead to a disconnected network or collisions between agents. Using a navigation function framework, a decentralized switched controller is developed to navigate the agents to the desired positions while ensuring network maintenance and collision avoidance.Comment: 8 pages, 2 figures, submitted to ACC 201

Making a difference : using peers to assess individual students' contributions to a group project.

Accepted ManuscriptPublishe

Having second thoughts : student perceptions before and after a peer assessment exercise

Accepted ManuscriptPublishe

//↗You need to be RUTHless // : entertaining cross-cultural differences

2005-2006 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Peer assessment of language proficiency

2004-2005 > Academic research: refereed > Publication in refereed journalAccepted ManuscriptPublishe

The functions of actually in a corpus of intercultural conversations

2001-2002 > Academic research: refereed > Publication in refereed journalAccepted ManuscriptPublishe

//↗CAN i help you // : the use of rise and rise-fall tones in the Hong Kong Corpus of Spoken English

2005-2006 > Academic research: refereed > Publication in refereed journalAccepted ManuscriptPublishe

Checking understandings : comparing textbooks and a corpus of spoken English in Hong Kong

2007-2008 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Stationary Cycling Induced by Switched Functional Electrical Stimulation Control

Functional electrical stimulation (FES) is used to activate the dysfunctional lower limb muscles of individuals with neuromuscular disorders to produce cycling as a means of exercise and rehabilitation. However, FES-cycling is still metabolically inefficient and yields low power output at the cycle crank compared to able-bodied cycling. Previous literature suggests that these problems are symptomatic of poor muscle control and non-physiological muscle fiber recruitment. The latter is a known problem with FES in general, and the former motivates investigation of better control methods for FES-cycling.In this paper, a stimulation pattern for quadriceps femoris-only FES-cycling is derived based on the effectiveness of knee joint torque in producing forward pedaling. In addition, a switched sliding-mode controller is designed for the uncertain, nonlinear cycle-rider system with autonomous state-dependent switching. The switched controller yields ultimately bounded tracking of a desired trajectory in the presence of an unknown, time-varying, bounded disturbance, provided a reverse dwell-time condition is satisfied by appropriate choice of the control gains and a sufficient desired cadence. Stability is derived through Lyapunov methods for switched systems, and experimental results demonstrate the performance of the switched control system under typical cycling conditions.Comment: 8 pages, 3 figures, submitted to ACC 201