A new methodology for designing PID controllers

It is known that it is impossible to select fixed gains for a PD controller that will critically damp the response to disturbances for all configurations of a given robot system. Because of this the potential for overshoot is always present and cannot be avoided unless the system is severely overdamped. This is not necessarily a practical solution and can be an economically unacceptable approach. On the other hand, however, if overshoot is permissible to some degree for some systems in the case of conventional Serial robots it is still prohibited in the case of Parallel robots as it may easily bring the robot to one of its possible singular configurations, causing damage to the system. This paper introduces a new algorithm for the design of PD controllers that ensures uniform and fast dynamic responses, which are free from overshoots for all robot configurations. The technique also satisfies general stability requirements for the system

Dynamical modelling of the motorised momentum exchange tether incorporating axial elastic effects

A discretised planar tether model is proposed for the Motorised Momentum Exchange Tether (MMET) in which axial elasticity is accommodated. The model uses a generalised co-ordinate defining angular motion of the tether about its centre of mass, as it travels at constant velocity on a circular orbit in the Earth’s equatorial plane and a generalised coordinate depicting the elastic part of the tether length. The system comprises a symmetrical double payload configuration, with outrigger counter inertia, and it is shown that including axial elasticity permits an enhanced level of modelling accuracy for the tether both in librating and spinning modes. A simulation has been devised in MATLAB and SIMULINK for different data cases. This work will be used later within a spin-up control system and will act as a precursor for an in-depth study into the multi-scale dynamics of MMET tethers and space webs, on more complicated orbits. This, in turn, will be assimilated within new mission architectures

Hybrid fuzzy sliding mode control for motorised space tether spin-up when coupled with axial and torsional oscillation

A specialised hybrid controller is applied to the control of a motorised space tether spin-up space coupled with an axial and a torsional oscillation phenomenon. A seven-degree-of-freedom (7-DOF) dynamic model of a motorised momentum exchange tether is used as the basis for interplanetary payload exchange in the context of control. The tether comprises a symmetrical double payload configuration, with an outrigger counter inertia and massive central facility. It is shown that including axial and torsional elasticity permits an enhanced level of performance prediction accuracy and a useful departure from the usual rigid body representations, particularly for accurate payload positioning at strategic points. A simulation with given initial condition data has been devised in a connecting programme between control code written in MATLAB and dynamics simulation code constructed within MATHEMATICA. It is shown that there is an enhanced level of spin-up control for the 7-DOF motorised momentum exchange tether system using the specialised hybrid controller. hybrid controller

Hybrid fuzzy and sliding-mode control for motorised tether spin-up when coupled with axial vibration

A hybrid fuzzy sliding mode controller is applied to the control of motorised tether spin-up coupled with an axial oscillation phenomenon. A six degree of freedom dynamic model of a motorised momentum exchange tether is used as a basis for interplanetary payload exchange. The tether comprises a symmetrical double payload configuration, with an outrigger counter inertia and massive central facility. It is shown that including axial elasticity permits an enhanced level of performance prediction accuracy and a useful departure from the usual rigid body representations, particularly for accurate payload positioning at strategic points. A special simulation program has been devised in MATLAB and MATHEMATICA for a given initial condition data case

Personality and Employees’ Information Security Behavior Among Generational Cohorts

The Big Five Factors Model (FFM) of personality traits theory was tested for its ability to explain employee information security behavior (EISB), when age, measured by generational cohort (GCOHORT), moderated the relationship between the independent variables (IVs) extraversion, agreeableness, conscientiousness, emotional stability, intellect (EACESI) and the dependent variable (DV), employees’ information security behavior (EISB) which is measured by file protection behavior (FPB). Three age groups defined GCOHORT: 52–70 years old (1946–1964, Baby Boomers), 36–51 yrs. old (1965–1980, Generation X), and 18– 35 yrs. Old (1981–1998, Millennial). Results of hierarchical multiple regressions analyses revealed statistically significant relationships between overall personality traits, four individual factors of personality traits, and the DV (p < .05). However, contrary to expectations, GCOHORT did not moderate the relationship between any of the main IVs and the DV (p > .05). Recommendations for future research are offered

Newspaper Coverage of the Bovine Spongiform Encephalopathy Outbreak in the United States: A Content Analysis

Objectivity is a hallmark of good journalism. Objective news writing is particularly important when covering agricultural issues. In this study, researchers used the Hayakawa-Lowry news bias categories to examine the objectivity of news coverage of the bovine spongiform encephalopathy (BSE) outbreak that occurred December 23, 2003, in the United States. The study looked at 149 articles published in USA Today, The Washington Post, and The Seattle Times, dating from the day of the outbreak to February 10, 2004, when the USDA concluded its investigation of the outbreak. Based on the findings, the three newspapers studied were more objective than judgmental in their coverage of the outbreak. Although judgment statements were relatively uncommon, the majority of the judgment statements found were negative toward agriculture. Analysis of the level of objectivity for each newspaper revealed that USA Today was the least objective in its coverage; The Seattle Times was the most objective. This study recommends that reporters be encouraged to include more objective sentences in their writing, that journalism and agricultural communications students be educated about the Hayakawa-Lowry news bias categories, that additional research be conducted on media coverage of other agricultural issues, and that the agricultural literacy level of journalists be examined

Mathematical and computational models for bone tissue engineering in bioreactor systems

Research into cellular engineered bone grafts offers a promising solution to problems associated with the currently used auto- and allografts. Bioreactor systems can facilitate the development of functional cellular bone grafts by augmenting mass transport through media convection and shear flow-induced mechanical stimulation. Developing successful and reproducible protocols for growing bone tissue in vitro is dependent on tuning the bioreactor operating conditions to the specific cell type and graft design. This process, largely reliant on a trial-and-error approach, is challenging, time-consuming and expensive. Modelling can streamline the process by providing further insight into the effect of the bioreactor environment on the cell culture, and by identifying a beneficial range of operational settings to stimulate tissue production. Models can explore the impact of changing flow speeds, scaffold properties, and nutrient and growth factor concentrations. Aiming to act as an introductory reference for bone tissue engineers looking to direct their experimental work, this article presents a comprehensive framework of mathematical models on various aspects of bioreactor bone cultures and overviews modelling case studies from literature

Dynamical modelling of the motorised momentum exchange tether incorporating axial elastic effects

Abstract A discretised planar tether model is proposed for the Motorised Momentum Exchange Tether (MMET) in which axial elasticity is accommodated. The model uses a generalised co-ordinate defining angular motion of the tether about its centre of mass, as it travels at constant velocity on a circular orbit in the Earth's equatorial plane and a generalised coordinate depicting the elastic part of the tether length. The system comprises a symmetrical double payload configuration, with outrigger counter inertia, and it is shown that including axial elasticity permits an enhanced level of modelling accuracy for the tether both in librating and spinning modes. A simulation has been devised in MATLAB and SIMULINK for different data cases. This work will be used later within a spin-up control system and will act as a precursor for an in-depth study into the multi-scale dynamics of MMET tethers and space webs, on more complicated orbits. This, in turn, will be assimilated within new mission architectures

Remediation of bromate contaminated groundwater

Bromate (BrO3") is a by-product formed at concentrations of 0.4 - 60 µg L'' during potable water ozonation. Following World Health Organisation designation as a 'possible human' carcinogen, a 10 pg L" drinking water limit was introduced in England and Wales. Discovery of bromate contamination within a UK aquifer highlighted a knowledge gap, addressed by this project, relating to environmental behaviour and groundwater remediation. Following selection of an anion analysis strategy utilising Ion Chromatography (IC), bromate behaviour in wastewater was investigated as contaminated groundwater ingress to treatment processes was deemed possible. Respiration of wastewater biomass was unaffected by spiking of 1000 pg L" hr t. An alteration in microbial composition was noted over this period, from a denitrifying 'co-metabolic' culture to predomination of 'high-rate' specific bromate degraders. Operational parameters including pH, temperature, carbon source, influent bromate and glucose, and retention times were investigated, with all parameters apart from pH shown to affect bromate reduction rates. For example increased bromate influent enhanced reduction rate, although potentially toxic effects were noted with an influent > 75 - 80 mg L"'. Batch studies suggested glucose was rapidly fermented ( 90% of a 1.1 mg L"1 bromate influent within unspiked contaminated groundwater. Plating studies were successful in producing a range of isolates from the mixed chemostat culture. Overall the project demonstrated, for the first time, continuous remediation of bromate groundwater contamination within a bioreactor system.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Children's chatter: Daily reflections of young children during Covid-19 lockdown

Adults perceive the world using existing knowledge and experience (Gregory, 1970). However, adults may then impose their perspectives onto their children, whilst failing to understand the world through their child’s eyes (Christakis, 2017). This qualitative study provides an exploratory insight into the perspectives of nineteen children, aged 7-11 years, during the coronavirus (Covid-19) pandemic lockdown in the UK, when national restrictions on movement and online learning for all children were mandatory. Over a 10-day period, parents asked their children four short open questions at the end of each day: 1) ‘What was the best thing that happened today?’, 2) ‘What was your least favourite part of today?’, 3) ‘What did you learn today that you didn’t know yesterday?’, and 4) ‘What made you smile or laugh today?’ Parents were specifically asked to make no mention of lockdown or school or virus (Covid-19). Thematic analysis revealed the importance of technology (both for online lessons, social communication, and recreation), proximity to family (parents and siblings), time with pets, and joint pastimes (walking, cooking, creative arts). This study provides insight into the world in which children were living and coping with the challenges of a lockdown during a national crisis and provides alternative methods for obtaining and evaluating qualitative data within a population of young children