david wilson

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Papers by david wilson

Respiration, peroxidase, and diphenol oxidase isozymes in reproductive and nonreproductive growth of Glomerella magna

by david wilson and Donald ( N M I ) Huisingh

Canadian Journal of Microbiology, 1972

Respiration rates were measured and respiratory quotients (RQ) were calculated for sexually repro... more Respiration rates were measured and respiratory quotients (RQ) were calculated for sexually reproducing and nonreproducing cultures of Glomerella magna. Oxygen uptake per unit of extractable protein by reproducing cultures was fairly constant until day 7 when it increased markedly as the sexual structures were being differentiated. Oxygen uptake by nonreproducing cultures was highest on days 2, 3, and 4 while initiation of sexual reproduction by exposure to light was still possible. RQ values of reproducing cultures were constant at about 0.85, while the nonreproductive cultures reached a maximum of 1 by day 4 and then declined with culture age to 0.47. The isozymes of peroxidase and o-diphenol oxidase were similar in reproducing and nonreproducing cultures. One "tyrosinase" band and one "laccase" (p-diphenol oxidase) band were observed with tyrosine and p-phenylenediamine as the substrates. Isozymes of peroxidase or diphenol oxidase exhibited different substrate...

Bounds on the GL2 Norm for Siso Systems and Their Implications for Robust Performance Analysis

IFAC Proceedings Volumes, 2002

This paper derives upper and lower bounds on the generalized L 2 (GL 2) norm for SISO systems and... more

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Contemporary Financial Reporting: A Casebook

Active suspensions: a reduced-order H<inf>∞</inf> control design study

This paper studies order reduction issues for a vehicle active suspension system throughout its m... more This paper studies order reduction issues for a vehicle active suspension system throughout its modelling, H-infinity controller design and controller refinement. Computer simulations demonstrate that an H-infinity controller for a full active suspension can be significantly reduced to nearly one third of its full order, while the active suspension performance is only slightly degraded. As a by-product, this paper also provides an explicit algorithm for reduced Hinfinity control for singular and non-singular continuoustime systems.

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Hearing-aid Use and Available Aid Ranges

British Journal of Audiology, 1982

The assertion that a wide range of hearing aids is necessary in auditory rehabilitation has frequ... more The assertion that a wide range of hearing aids is necessary in auditory rehabilitation has frequently been made, but little evidence has been offered as support. Further, little explanation has been offered as to the constitution of an adequate range of aids, nor what determines the adequacy. Comparisons of use rates of two large populations of people, one fitted from a wide range of aids and the other from a narrow range, provides some information on the relationship between extent of the aid range available and the results of fitting. The conclusion is reached that fitting methods and procedures appear to be more significant than aid range in ensuring that hearing aids are used consistently.

Active Suspension Control to Improve Vehicl0e Ride and Steady-State Handling

In this paper, a full-vehicle active suspension system is designed to simultaneously improve vehi... more In this paper, a full-vehicle active suspension system is designed to simultaneously improve vehicle ride comfort and steady-state handling performance. First, a linear suspension model of a vehicle and a nonlinear handling model are described. Next, the link between the suspension model and vehicle steady-state handling characteristics is analysed. Then, an H-infinity controller for the suspension is designed to achieve integrated ride-comfort and handling control. Finally, the controller is verified by computer simulations. I. INTRODUCTION Although active suspension control has been widely studied for decades, most of the research focussed on vehicle ride comfort, with only a few papers [1-3] and some references cited therein studying how an active suspension can improve vehicle handling. Ride comfort of a vehicle, also known as vibration isolation ability, is judged by the level of acceleration, which vehicle passengers are exposed to. Since the manner in which vibration affects comfort is dependent on the vibration frequency, frequency weighting functions are used for a fair judgement. Although vehicle ride comfort is somehow a subjective issue, it is quantified by the energy of the weighted vehicle body acceleration [4]. The most common measure of vehicle steady-state handling performance is the understeer gradient [5], by which vehicles are categorised into three types: neutral steer, understeer and oversteer. In the neutral steer case, the lateral acceleration at the gravity centre of the vehicle will yield an identical increase in slip angle at both front and rear wheels. In the understeer case, the lateral acceleration will cause more front-wheel slip. Oversteer is the opposite of understeer. An oversteer vehicle could lose its directional stability at the critical speed. Neutral steer is an ideal steering condition. However, vehicles are generally designed to be understeered for safety since vehicle understeer gradient varies due to transient manoeuvres. This paper studied the influence of roll moment on vehicle steady-state handling. The roll moment caused by vehicle cornering will transfer vehicle weight from its inside to its

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LQR Weight Selection in Generalised H 2 Control for Continuous and Discrete Systems Using Convex Programming

IFAC Proceedings Volumes, Jun 1, 1996

In a generalised H z optimal control problem, the conventional H] norm is replaced by an operator... more In a generalised H z optimal control problem, the conventional H] norm is replaced by an operator norm, A stabilising controller is sought such that the closed loop gain from time domain input disturbances in L2 to time domain regulated outputs in L_ is minimised. A solution to this problem can be obtained by using a finite dimensional convex programme for weight selection in an LQR problem. Both continuous• and discrete-time versions of problem are considered, and, following the technique of Rotea (1993) the problem is reduced to one of finding a state feedback controller for an auxiliary system, In general. the weight selection method offers a potentially reduced computational burden compared with that in Rotea (1993).

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Mixed GL2/H2/GH2control with pole placement and its application to vehicle suspension systems

International Journal of Control, 2001

Setting Confidence Limits for Multivariate Statistical Quality Control; a new approach

Irish Signals and Systems Conference, 2003

Application of generalized L/sub 2/ synthesis to decoupled active suspension systems

ABSTRACT In this paper, generalized L2 synthesis for the continuous-time case is presented and th... more ABSTRACT In this paper, generalized L2 synthesis for the continuous-time case is presented and this theory is applied to decoupled active suspension systems. The performance of the active suspension systems with H∞, μ, and generalized L2 synthesis is compared, which demonstrates that generalized L2 synthesis can achieve global optimization and is computationally tractable

Continuous-time H<inf>2</inf>/H<inf>∞</inf> control with non-common Lyapunov variables via convergent iterations

This paper presents a multi-objective output-feedback H 2 /H ∞ synthesis framework with non-commo... more This paper presents a multi-objective output-feedback H 2 /H ∞ synthesis framework with non-common Lyapunov variables (NCLV's) for continuous-time systems, and clearly summarized the numerical algorithms for controller design. This H 2 /H ∞ synthesis framework is less conservative than the traditional one with common Lyapunov variables (CLV's). Although the computation of this new method is more timeconsuming, the controller obtained remains the same order as the one designed by the traditional method. Furthermore, this framework is ready to be extended to a more general multiobjective framework with slight changes. The advantage of this framework is illustrated by a numerical example.

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Continuous-time H2/H∞ control with non-common Lyapunov variables via convergent iterations

2003 European Control Conference (ECC), 2003

This paper presents a multi-objective output-feedback H2/H∞ synthesis framework with non-common L... more This paper presents a multi-objective output-feedback H2/H∞ synthesis framework with non-common Lyapunov variables (NCLV's) for continuous-time systems, and clearly summarized the numerical algorithms for controller design. This H2/H∞ synthesis framework is less conservative than the traditional one with common Lyapunov variables (CLV's). Although the computation of this new method is more time-consuming, the controller obtained remains the same order as the one designed by the traditional method. Furthermore, this framework is ready to be extended to a more general multi-objective framework with slight changes. The advantage of this framework is illustrated by a numerical example.

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Hm Robust-Performance Control of Decou led Active Suspension Systems Based on LMI gethod

This paper is concerned with model decoupling and H, robust-performance control of a vehicle acti... more This paper is concerned with model decoupling and H, robust-performance control of a vehicle active suspension system. Firstly, the full-vehicle suspension system with 7 degrees-of-freedom is decoupled into heave-pitch and roll-warp subsystems using linear transformations. Secondly, the uncontrollable mode in the roll-warp subsystem is removed using the derived geometrical constraint equation; Thirdly, based on the LMI method, robust H, output-feedback controllers are designed for the decoupled suspension system. Finally, the system’s performance is evaluated by computer simulations, which demonstrate that the active suspension system has better ride and handling performance than the passive system, and the performance can be maintained despite significant levels of uncertainty in the actuator dynamics.

Expression of an Aspergillus niger Phytase Gene ( phyA ) in Saccharomyces cerevisiae

Applied and Environmental Microbiology, 1999

Phytase improves the bioavailability of phytate phosphorus in plant foods to humans and animals a... more Phytase improves the bioavailability of phytate phosphorus in plant foods to humans and animals and reduces phosphorus pollution of animal waste. Our objectives were to express an Aspergillus niger phytase gene ( phyA ) in Saccharomyces cerevisiae and to determine the effects of glycosylation on the phytase’s activity and thermostability. A 1.4-kb DNA fragment containing the coding region of the phyA gene was inserted into the expression vector pYES2 and was expressed in S. cerevisiae as an active, extracellular phytase. The yield of total extracellular phytase activity was affected by the signal peptide and the medium composition. The expressed phytase had two pH optima (2 to 2.5 and 5 to 5.5) and a temperature optimum between 55 and 60°C, and it cross-reacted with a rabbit polyclonal antibody against the wild-type enzyme. Due to the heavy glycosylation, the expressed phytase had a molecular size of approximately 120 kDa and appeared to be more thermostable than the commercial enzy...

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A Randomized Noninferiority Trial of Wearing Adjustable Glasses versus Standard and Ready-made Spectacles among Chinese Schoolchildren

Ophthalmology, 2019

Purpose: To compare wear of standard, adjustable, and ready-made glasses among children. Design: ... more Purpose: To compare wear of standard, adjustable, and ready-made glasses among children. Design: Randomized, controlled, open-label, noninferiority trial. Participants: Students aged 11 to 16 years with presenting visual acuity (VA) 6/12 in both eyes, correctable to 6/7.5, subjective spherical equivalent refractive error (SER) e1.0 diopters (D), astigmatism and anisometropia both <2.00 D, and no other ocular abnormalities. Methods: Participants were randomly allocated (1:1:1) to standard glasses, ready-made glasses, or adjustable glasses based on self-refraction. We recorded glasses wear on twice-weekly covert evaluation by head teachers (primary outcome), self-reported and investigator-observed wear, best-corrected visual acuity (BCVA) (not prespecified), children's satisfaction, and value attributed to glasses. Main Outcome Measure: Proportion of glasses wear on twice-weekly covert evaluation by head teachers over 2 months. Results: Among 379 eligible participants, 127 were allocated to standard glasses (mean age, 13.7 years; standard deviation [SD], 1.0 years; 54.3% were male), 125 to ready-made (mean age, 13.6; SD, 0.83; 45.6%), and 127 to adjustable (mean age, 13.4 years; SD, 0.85; 54.3%). Mean wear proportion of adjustable glasses was significantly lower than for standard glasses (45% vs. 58%; P ¼ 0.01), although the adjusted difference (90% confidence interval [CI], e19.0% to e3.0%) did not meet the prespecified inferiority threshold of 20%. Selfreported (90.2% vs. 84.8%, P ¼ 0.64) and investigator-observed (44.1% vs. 33.9%, P ¼ 0.89) wear did not differ between standard and adjustable glasses, nor did satisfaction with (P ¼ 0.97) or value attributed to study glasses (P ¼ 0.55) or increase in quality of life (5.53 [SD, 4.47] vs. 5.68 [SD, 4.34] on a 100-point scale, P > 0.30). Best-corrected visual acuity with adjustable glasses was better (P < 0.001) than with standard glasses. Change in power of study lenses at the end of the study (adjustable: 0.65 D, 95% CI, 0.52e0.79; standard, 0.01 D; 95% CI, e0.006 to 0.03, P < 0.001) was greater for adjustable glasses, although interobserver variation in power measurements may explain this. Lens scratches and frame damage were more common with adjustable glasses, whereas lens breakage was less common than for standard glasses. Conclusions: Proportion of wear was lower with adjustable glasses, although VA was better and measures of satisfaction and quality of life were not inferior to standard glasses. Ophthalmology 2020;127:27-37 ª 2019 by the American Academy of Ophthalmology The implementation of the Millennium Developmental Goals in 2000 led to notable improvements in global eye health. 1 However, between 1990 and 2010, uncorrected refractive error remained the most common cause of visual impairment, contributing to more than 50% of all moderate and severe vision impairment. 2 Subsequently, the adoption of the Sustainable Development Goals (SDGs) by United Nations member states in 2015 3 represented a renewed commitment to a just and healthy world for all. Reducing the burden of uncorrected

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Bounds on the GL2 norm for SISO systems and their implications for robust performance analysis

Proceedings of the 15th IFAC World Congress, 2002, 2002

This paper derives upper and lower bounds on the generalized L 2 (GL 2) norm for SISO systems and... more

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Comparison of extracellular Escherichia coli AppA phytase expressed in Streptomyces lividans and Pichia pastoris. Biotech Lett

Biotechnology Letters

A phytase gene (appA) from Escherichia coli was cloned into Streptomyces lividans and expressed a... more A phytase gene (appA) from Escherichia coli was cloned into Streptomyces lividans and expressed as an extracellular protein which was then compared with the same enzyme expressed in Pichia pastoris. The phytase expressed in S. lividans was not glycosylated and had a molecular mass of 45 kDa. Compared with the glycosylated phytase expressed in P. pastoris, this non-glycosylated phytase was 25-50% less active (p < 0.05) at pH 2 to 3.5 or at 45 and 55 • C, but 50% more active (p < 0.05) at 75 • C. The thermo-tolerance of the non-glycosylated phytase was 26 and 48% higher (p < 0.05) than that of the glycosylated phytase at 45 and 55 • C, but was 80 and 94% lower (p < 0.05) at 65 • and 75 • C, respectively.

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H/sub /spl infin// robust-performance control of decoupled active suspension systems based on LMI method

Proceedings of the 2001 American Control Conference. (Cat. No.01CH37148), 2001

This paper is concerned with model decoupling and H∞ robust-performance control of a vehicle acti... more This paper is concerned with model decoupling and H∞ robust-performance control of a vehicle active suspension system. Firstly, the full-vehicle suspension system with 7 degrees-of-freedom is decoupled into heave-pitch and roll-warp subsystems using linear transformations. Secondly, the uncontrollable mode in the roll-warp subsystem is removed using the derived geometrical constraint equation; Thirdly, based on the LMI method, robust H∞ output-feedback

Robust control of a lightweight flexible manipulator under the influence of gravity

Proceedings of the 1997 IEEE International Conference on Control Applications, 1997

... and fully expanded, this gives the state space realisation for the augmented plant as. ... 7.... more

Multi-objective control of decoupled vehicle suspension systems

Proceedings of the 40th IEEE Conference on Decision and Control (Cat. No.01CH37228)

A multi-channel multi-objective synthesis framework, involving generalized LZ (GLz), H2, and gene... more A multi-channel multi-objective synthesis framework, involving generalized LZ (GLz), H2, and generalized H2 (GH2) control with minimum damping-factor pole placement, is formulated and applied to a decoupled vehicle suspension system. It is demonstrated that improved vehicle ride comfort and decreased suspension travel are achieved while guaranteeing robust stability.

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