Journal Articles
Permanent URI for this collectionhttps://mro.massey.ac.nz/handle/10179/7915
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Item Modular neural network modelling for long-range prediction of an evaporator(2000) Russell NT; Bakker HH; Chaplin RIThis paper presents the development of a modular neural network model of a three-effect, falling-film evaporator. The model comprises a number of sub-networks each modelling a specific element of the overall system. The modular structure was employed in order to provide benefits in terms of improved model training and performance. The performance of the modular neural model is demonstrated for long-range prediction by comparing it with process data, an analytical simulation and a linear ARX model. The results show that the modular neural model can satisfactorily predict over a horizon of arbitrary length and is suited for implementation within a predictive control scheme. Benefits in terms of model flexibility and interpretability are also discussed. (C) 2000 Elsevier Science Ltd. All rights reserved.Item An Integrated Wind and Hydro Power System Using Switched Reluctance Generators(Scientific Research Publishing Inc, 9/02/2018) Al-Bahadly IThis research work seeks to make renewable energy more reliable, cost effective, and accessible by exploring a different energy combination system to that currently applied to wind and hydro power. Instead of the usual electrical combination of wind and hydro generators, this work involved combining a water and wind turbine mechanically, before driving an electrical generator. This new combination system was modeled and optimized in MATLAB, using a direct combination system commonly found in multi-engine helicopters. The system was found to operate satisfactorily, however it is mechanically more complex than current electrical combining systems. Research was undertaken regarding wind and water resource availability, and the turbines were chosen with these taken into consideration. Various combination systems were explored, including torque and speed split mechanical combinations, conventional electrical combination, and using a modified switched reluctance generator as a method of electro-mechanical combination. The generator selected for this work is a three phase 12/8 Switched Reluctance (SR) machine. A detailed winding polarity having four poles per phase and their effect on the performance of the machine is observed.Item Portable Multi-Inputs Renewable Energy System for Small Scale Remote Application(Scientific Research Publishing Inc, 14/02/2018) Al-Bahadly IThis paper presents a potable renewable energy system. The portable renewable energy power unit is designed from a need. The need is for first response teams in remote natural disaster situations to have a reliable source of energy to power a small vaccine refrigerator or water purification system and a basic satellite communication system. It is important that such a need is explored as a practical solution has the potential to save the lives of people in remote areas, who would otherwise suffer from a lack of humanitarian aid. Currently diesel generators are the primary source of electricity generation for disaster responders and in most situations work very well and provide a sufficient amount of electricity to meet the power needs. However, in remote areas road infrastructure is often damaged. In this type of situation getting a constant supply of diesel to the area is an expensive or impractical operation. This is where the portable renewable energy power unit bridges the gap and allows a more practical solution to be implemented. The specific aim of the work is to design a compact, stand-alone, product that can be easily transported by people across uneven terrain. It can generate power from wind, solar and hydro energy sources. In this work a new non-isolated multiport DC-DC converter topology for a hybrid energy system in low power applications is proposed. The new topology assimilates multiple renewable energy sources and power up multiple loads with different output levels. A complete Solid works model and FEA analysis, on required components, is completed. The scope of the work encompasses both the electrical and mechanical design of the system.Item How to use programme theory to evaluate the effectiveness of schemes designed to improve the work environment in small businesses(IOS Press, 30/10/2012) Olsen K; Legg S; Hasle PDue to the many constraints that small businesses (SBs) face in meeting legislative requirements, occupational health and safety (OHS) regulatory authorities and other OSH actors have developed programmes which can reach out to SBs and motivate and assist them in improving the work environment. A number of conceptual models help to enhance our understanding of OHS interventions in SBs and their effectiveness. However, they have mainly been evaluated on output rather than the process relating to the change theory underlying the intervention, and hence have seldom been rigorously evaluated. Thus little is known about how particular features of SBs can be taken into account when designing and implementing national programmes. This paper shows how realist analysis and programme theory may be used as a framework for evaluating, developing and improving national intervention programmes for the improvement of the work environment and reducing injuries in SBs. It illustrates this for a specific New Zealand intervention: the Workplace Safety Discount scheme and its implementation in the agriculture sector. In practice, realist analysis should be performed during the planning, implementation and management stages so that ongoing findings can be fed back to the participant social actors to help them make appropriate changes to enhance the likelihood of success.Item Could mild hypoxia impair pilot decision making in emergencies?(IOS PRESS, 2012) Legg S; Hill S; Mundel T; Gilbey A; Schlader Z; Raman AThe decreased pressure in the cabin of a pressurised aircraft (typically equivalent to ~8000 ft) reduces the oxygen level so that the blood oxygen saturation of all occupants falls from >97% (normoxia) at sea-level to below 92% (mild hypoxia). Although exposure to mild hypoxia does not affect well-learned cognitive and motor performance of aircrew, it has been proposed that it can affect the performance of some complex cognitive performance tasks involving multiple demands typical of emergency tasks that may have to be performed by pilots. In order to simulate some of these complex cognitive demands, 25 student volunteers participated in an experiment which assessed performance of complex logical reasoning and and multiple memory tasks before and after 2 hours of exposure to normoxia and mild hypoxia. Performance for the more difficult components of the complex reasoning task, especially involving conflict decisions, were marginally significantly degraded by mild hypoxia. Since the effects were only marginally significant future studies should investigate the effects of mild hypoxia on more subtle complex decision-making tasks.Item Enhancement of Wind Energy Conversion Using Axial Flux Generator(Scientific Research Publishing Inc, 25/02/2019) Al-Bahadly I; Neppalli SCThis paper investigates the application of the axial flux machine (AFM) to the wind energy conversion systems (WECS) to obtain high power and torque at reduced cost. By developing mathematical equations using the phase and active transformations, the three-phase model is transformed to two-phase equations by making both the stator and rotor as reference frames, finally converting to arbitrary reference frame, which is useful for the modelling of the axial flux machine. The torque, current, and voltage equations are expressed to improve the simulation reliability. Based on the developed equations, the mathematical model for the axial flux machine is developed using the MATLAB/Simulink. Starting with the axial flux motor model, when the load on the motor increases, how the parameters like torque, current, and speed of the motor vary are explored in this paper. Then for the axial flux generator model, when the wind speed exceeds the rated speed how the torque, line voltages, currents, power and speed of the generator behave are investigated and presented in this paper. The developed model in this paper could be extended to a twin-rotor axial flux synchronous machine, which will lead to the development of more efficient WECS.Item The effects of dispersion on time-of-flight acoustic velocity measurements in a wooden rod(Elsevier BV, 2023-03) Bakar AHA; Legg M; Konings D; Alam FThe stiffness of wood can be estimated from the acoustic velocity in the longitudinal direction. Studies have reported that stiffness measurements obtained using time-of-flight acoustic velocity measurements are overestimated compared to those obtained using the acoustic resonance and bending test methods. More research is needed to understand what is causing this phenomenon. In this work, amplitude threshold time-of-flight, resonance, and guided wave measurements are performed on wooden and aluminium rods. Using guided wave theory, it is shown through simulations and experimental results that dispersion causes an overestimation of time-of-flight measurements. This overestimation was able to be mitigated using dispersion compensation. However, other guided wave techniques could potentially be used to obtain improved measurements.Item Effect on the mechanical properties of type I collagen of intra-molecular lysine-arginine derived advanced glycation end-product cross-linking(Elsevier, 28/11/2017) Collier TA; Nash A; Birch HL; de Leeuw NHNon-enzymatic advanced glycation end product (AGE) cross-linking of collagen molecules has been hypothesised to result in significant changes to the mechanical properties of the connective tissues within the body, potentially resulting in a number of age related diseases. We have investigated the effect of two of these cross-links, glucosepane and DOGDIC, on the tensile and lateral moduli of the collagen molecule through the use of a steered molecular dynamics approach, using previously identified preferential formation sites for intra-molecular cross-links. Our results show that the presence of intra-molecular AGE cross-links increases the tensile and lateral Young’s moduli in the low strain domain by between 3.0 - 8.5 % and 2.9 - 60.3 % respectively, with little effect exhibited at higher strains.Item Estimation of the Rod Velocity in Wood using Multi-frequency Guided Wave Measurements(Elsevier Ltd, 2023-01) Bakar AHA; Legg M; Konings D; Alam FThis study presents a new approach for measuring the acoustic “rod velocity” in wood using guided wave measurements. The approach fits the acoustic guided wave longitudinal L(0,1) wave mode dispersion curve, through experimental guided wave phase velocity measurements taken over a range of frequencies. The rod velocity is obtained by measuring the phase velocity of the fitted L(0,1) wave mode dispersion curve at zero frequency. This technique is used to obtain rod velocity measurements for cylindrical wood and aluminium samples. The same approach was also performed on resonance measurements at a wide range of harmonics. These rod velocities are then compared to acoustic velocities obtained using the traditional time of flight and resonance methods.Item Occupational health and safety professionals strategies to improve working environment and their self-assessed impact(IOS PRESS, 2012) Olsen KResearch suggests that Occupational Health and Safety (OHS) practitioners have difficulty influencing the decision-making process because they are placed on the sidelines in the organisation. This paper analyses the strategies that OHS practitioners use to fulfill their job role and the impact they have on the working environment and OHS management systems. Semi-structured interviews were conducted with ten New Zealand OHS practitioners from mainly large private and public organisations about their job role, OHS tasks, strategies and their impact. The interviews were tape recorded, transcribed, entered into a qualitative data management programme and analysed thematically in relation to their strategies, barriers and their impact on the OHS management system and working environment. The analysis revealed that these OHS practitioners used multiple strategies - chosen in relation to the situation, the stakeholders and their own resources. They saw themselves as change agents or facilitators. They preferred to use a knowledge strategy, supported by an audit strategy. Their last resort was a regulation strategy. All of the practitioners had a positive impact on stakeholders' knowledge, attitude and behavior and on OHS management systems. Some practitioners improved the working environment but few were involved in introduction of new technology.
