Applications of control theory

Applications of control theory are considered in the areas of decoupling and wake steering control of submersibles, a method of electrohydraulic conversion with no moving parts, and socio-economic system modelling

Emerging infectious diseases in an island ecosystem: the New Zealand perspective.

Several unique features characterize infectious disease epidemiology in New Zealand. Historically, well-organized, government-run control programs have eliminated several zoonoses. More recently, however, communicable disease control has been mixed. Rates of rheumatic fever, tuberculosis, and enteric infectious are high, and rates of meningococcal disease are increasing. These diseases are over-represented in New Zealanders of Polynesian descent, who generally live in more deprived and overcrowded conditions than do those of European descent. Measles and pertussis epidemics are recurring because of inadequate vaccine coverage, despite a well-developed childhood immunization program. A progressive response to the HIV epidemic has resulted in relatively low rates of infection, particularly among injecting drug users; however, the response to other sexually transmitted infections has been poor. A key challenge for the future is to build on successful strategies and apply them to persisting and emerging infectious disease threats in a small, geographically isolated country with limited economic resources

Experimental Predictions of The Functional Response of A Freshwater Fish

The functional response is the relationship between the feeding rate of an animal and its food density. It is reliant on two basic parameters; the volume searched for prey per unit time (searching rate) and the time taken to consume each prey item (handling time). As fish functional responses can be difficult to determine directly, it may be more feasible to measure their underlying behavioural parameters in controlled conditions and use these to predict the functional response. Here, we tested how accurately a Type II functional response model predicted the observed functional response of roach Rutilus rutilus, a visually foraging fish, and compared it with Type I functional response. Foraging experiments were performed by exposing fish in tank aquaria to a range of food densities, with their response captured using a two-camera videography system. This system was validated and was able to accurately measure fish behaviour in the aquaria, and enabled estimates of fish reaction distance, swimming speed (from which searching rate was calculated) and handling time to be measured. The parameterised Type II functional response model accurately predicted the observed functional response and was superior to the Type I model. These outputs suggest it will be possible to accurately measure behavioural parameters in other animal species and use these to predict the functional response in situations where it cannot be observed directly

Rotary drum separator system

A rotary phase separator system generally includes a step-shaped rotary drum separator (RDS) and a motor assembly. The aspect ratio of the stepped drum minimizes power for both the accumulating and pumping functions. The accumulator section of the RDS has a relatively small diameter to minimize power losses within an axial length to define significant volume for accumulation. The pumping section of the RDS has a larger diameter to increase pumping head but has a shorter axial length to minimize power losses. The motor assembly drives the RDS at a low speed for separating and accumulating and a higher speed for pumping

The prevalence of smoking and the knowledge of smoking hazards and smoking cessation strategies among hiv positive patients in johannesburg, south africa

Background: While the detrimental effects of smoking among HIV positive patients have been well documented, there is a paucity of data regarding cigarette smoking prevalence among these patients in South Africa. Objectives: To establish the frequency, demographics, and knowledge of harmful effects and of smoking cessation strategies among HIV-positive patients in Johannesburg, South Africa. Methods: A prospective cross-sectional survey, using a structured questionnaire interview, of HIV-positive patients attending the HIV Clinic at the Charlotte Maxeke Johannesburg Academic Hospital between 1 July 2011 and 31 October 2011. Results: Of 207 HIV positive patients attending an ARV roll-out clinic, 31 (15%) were current smokers (23% of the males and 7.5% of the females) and a further 45 (21.7%) were ex-smokers. Most of the current smokers (30/31 patients) indicated their wish to quit smoking, and among the group as a whole most patients were aware of the general (82.5%) and HIV-related (77.8%) risks of smoking and of methods of quitting smoking. Despite this, however, most (61.8%) were not aware of whom they could approach for assistance and advice. Conclusions: Given the relatively high prevalence of current and ex-smokers amongst HIV positive patients there is a need for the introduction of smoking cessation strategies and assistance at HIV-rollout clinics in South Africa

Resonant forcing of select degrees of freedom of multidimensional chaotic map dynamics

We study resonances of multidimensional chaotic map dynamics. We use the calculus of variations to determine the additive forcing function that induces the largest response, that is, the greatest deviation from the unperturbed dynamics. We include the additional constraint that only select degrees of freedom be forced, corresponding to a very general class of problems in which not all of the degrees of freedom in an experimental system are accessible to forcing. We find that certain Lagrange multipliers take on a fundamental physical role as the efficiency of the forcing function and the effective forcing experienced by the degrees of freedom which are not forced directly. Furthermore, we find that the product of the displacement of nearby trajectories and the effective total forcing function is a conserved quantity. We demonstrate the efficacy of this methodology with several examples.Comment: 11 pages, 3 figure

Are Eye Clinics Safe For The Road? An Observational Report

We report an observational study, based on the examination of 319 medical records, identifying the proportion of patients whose driving status was documented on the first and subsequent glaucoma clinic visits. We also established the proportion of patients with documented Driving and Vehicle Licencing Agency (DVLA)-related advice when they did not meet driving standards based on their visual acuity and/or visual fields (VF). On presentation, driving status was assessed in 61% (n=195) patients. Of the remaining 124, 44% (n=55) had their driving status documented at a subsequent visit, on an average 8 years later. Of all patients (78%, n=250) whose driving status was assessed at some stage, 42% (n=134) were drivers. Of the 203 patients who were either drivers or whose driving status was unknown, 37% (n=75) were assessed as having a visual acuity or bilateral VF defect that was below the legal limit for driving, 39 of whom were known drivers. Only 13 were advised to inform the DVLA, and only 5 patients were advised to update their spectacles or listed for surgery to improve their vision. We therefore potentially failed to perform our DVLA duty in 76% (n=57) of patients. We have made suggestions for improving the current performance in this respect based on the findings of this study