963 research outputs found
Portrait of E.H. Sedgwick, May 1949 [picture].
No full textInscription: "E.H. Sedgwick, May 1949"--On reverse.; Part of G.M. Mathews collection of portraits of ornithologists.; Title devised by cataloguer from inscription.; Also available in an electronic version via the Internet at: http://nla.gov.au/nla.pic-vn3798161; Papers of Gregory M. Mathews, 1900-1949; located at; National Library of Australia Manuscript collection MS 1465
Portrait of E.H. Sedgwick in Royal Australian Air Force uniform [picture].
No full textInscription: "E.H. Sedgwick, during the war of 1939-15"--On reverse.; Part of G.M. Mathews collection of portraits of ornithologists.; Title devised by cataloguer from inscription.; Also available in an electronic version via the Internet at: http://nla.gov.au/nla.pic-vn3798166; Papers of Gregory M. Mathews, 1900-1949; located at; National Library of Australia Manuscript collection MS 1465
Optimising of a domestic paraffin geyser for rural application
No full textA water heating system based on paraffin was investigated. Such a system fulfils a need in rural areas where electrify is not available and solar geysers are not practical. The solution is particularly apt due to the abundant use of paraffin in rural communities. The system was modelled for the previous conference and it was apparent that the product required some optimisation in order to be practical. The product was then optimised in terms of increasing the heat transfer area available and an improvement of 87% in terms of performance was achieved with an 8% reduction in cost to manufacture. This provided a solution that proved more practical when heating water to a suitable showering temperature of 38°C. A flow rate of 4.71/min with warmer summer water inlet conditions was achieved and 3.21/min with colder winter water inlet conditions. The product offers a great deal of versatility due to the nature of inline heat exchangers. It is possible to adjust the outlet water temperature by adjusting only the water flow rate. Thus the product can provide water at any range of temperature from a warm temperature for showering to boiling waterhttp://140.98.202.196/xpl/mostRecentIssue.jsp?punumber=682008
Further refinements and a new efficient solution of a novel model for predicting indoor climate
No full textDissertation (MEng)--University of Pretoria, 1990.In the first two chapters of this thesis, the novel method, developed by Mathews and Richards1, for predicting the thermal performance of buildings is introduced. The further enhancement and theoretical clarification of this method is the objective of this thesis. The method is based on a very simple thermo-flow network which models only the most important aspects of heat-flow in buildings. While Mathews and Richards based their network on analysis of the primary aspects of heat-flow in buildings, this thesis derives the simplified model by reduction from a comprehensive model. In this way, the assumptions and limitations is illuminated and the theoretical foundation of the method can be established. As a result of the investigation, a new simplified model with certain theoretical benefits is suggested. In later chapters, the method is extended and refined. Also, a new calculation procedure for finding solutions of the model is presented. In particular the method is extended to include multi-zone heat-flow, structural storage- and variable thermal systems. The new solution method is powerful, simple and efficient. This thesis contributes to the establishment of a viable tool for thermal analysis of buildings.Mechanical and Aeronautical Engineeringunrestricte
The integrated effect of moderate exercise on coronary heart disease
No full textBackground: Moderate exercise is associated with a lower risk for coronary heart disease (CHD). A suitable integrated model of the CHD pathogenetic pathways relevant to moderate exercise may help to elucidate this association. Such a model is currently not available in the literature.
Methods: An integrated model of CHD was developed and used to investigate pathogenetic pathways of importance between exercise and CHD. Using biomarker relative-risk data, the pathogenetic effects are representable as measurable effects based on changes in biomarkers.
Results: The integrated model provides insight into higherorder interactions underlying the associations between CHD and moderate exercise. A novel ‘connection graph’ was developed, which simplifies these interactions. It quantitatively illustrates the relationship between moderate exercise and various serological biomarkers of CHD. The connection graph of moderate exercise elucidates all the possible integrated actions through which risk reduction may occur.
Conclusion: An integrated model of CHD provides a summary of the effects of moderate exercise on CHD. It also shows the importance of each CHD pathway that moderate exercise influences. The CHD risk-reducing effects of exercise appear to be primarily driven by decreased inflammation and altered metabolis
The cost effects of DSM interventions on vertical roller mills in the cement industry
No full textLoad management is a successful way to implement evening load reduction and load shift DSM projects on cement plants. However, finishing grinding in the cement production process requires accurate temperature control. To achieve this, Vertical Roller Mills burn fuel to heat the mill interior before grinding initiates. In this paper the fuel cost of reheating a vertical roller mill after an evening load reduction event is compared to the electricity saving gained. Results show that the standard deviation in the paraffin costs experienced in day to day operations is larger than the paraffin costs generated when reheating a Vertical Roller Mill after a load reduction event. It is concluded in this paper that the paraffin costs are relatively small when compared to the electricity saving gained. It is therefore feasible to implement load management projects on vertical roller mills used for cement milling despite the additional fuel costs experiencedhttp://www.ieee.org/conferences_events/conferences/xplore_conference_proceedings.htm
Quadratic mode shape components from linear finite element analysis
No full textPoints on a vibrating structure move along curved paths rather than straight lines; however, this is largely ignored in modal analysis. Applications where the curved path of motion cannot be ignored include beamlike structures in rotating systems, e.g., helicopter rotor blades, compressor and turbine blades, and even robot arms. In most aeroelastic applications the curvature of the motion is of no consequence. The flutter analysis of T-tails is one notable exception due to the steady-state trim load on the horizontal stabilizer. Modal basis buckling analyses can also be performed when taking the curved path of motion into account. The effective application of quadratic mode shape components to capture the essential kinematics has been shown by several researchers. The usual method of computing the quadratic mode shape components for general structures employs multiple nonlinear static analyses for each component. It is shown here how the quadratic mode shape components for general structures can be obtained using linear static analysis. The derivation is based on energy principles. Only one linear static load case is required for each quadratic component. The method is illustrated for truss structures and applied to nonlinear static analyses of a linear and a geometrically nonlinear structure. The modal method results are compared to finite element nonlinear static analysis results. The proposed method for calculating quadratic mode shape components produces credible results and offers several advantages over the earlier method, viz., the use of linear analysis instead of nonlinear analysis, fewer load cases per quadratic mode shape component, and user-independenc
Quadratic mode shape components from ground vibration testing
No full textPoints on a vibrating structure generally move along curved paths rather than straight lines. For example, the tip of a cantilever beam vibrating in a bending mode experiences axial displacement as well as transverse displacement. The axial displacement is governed by the inextensibility of the neutral axis of the beam and is proportional to the square of the transverse displacement; hence the name “quadratic mode shape component.” Quadratic mode shape components are largely ignored in modal analysis, but there are some applications in the field of modal-basis structural analysis where the curved path of motion cannot be ignored. Examples include vibrations of rotating structures and buckling. Methods employing finite element analysis have been developed to calculate quadratic mode shape components. Ground vibration testing typically only yields the linear mode shape components. This paper explores the possibility of measuring the quadratic mode shape components in a sine-dwell ground vibration test. This is purely an additional measurement and does not affect the measured linear mode shape components or the modal parameters, i.e., modal mass, frequency, and damping ratio. The accelerometer output was modeled in detail taking into account its linear acceleration, its rotation, and gravitational acceleration. The response was correlated with the Fourier series representation of the output signal. The result was a simple expression for the quadratic mode shape component. The method was tested on a simple test piece and satisfactory results were obtained. The method requires that the accelerometers measure down to steady state and that up to the second Fourier coefficients of the output signals are calculated. The proposed method for measuring quadratic mode shape components in a sine-dwell ground vibration test seems feasible. One drawback of the method is that it is based on the measurement and processing of second harmonics in the acceleration signals and is therefore sensitive to any form of structural nonlinearity that may also cause higher harmonics in the acceleration signals. Another drawback is that only the quadratic components of individual modes can be measured, whereas coupled quadratic terms are generally also required to fully describe the motion of a point on a vibrating structur
Optimisation of a storage facility used to effect power control in the PBMR power cycle
No full textThis article presents the optimization of a gas storage facility used to effect power control in South Africa's PBMR power cycle. It was shown in the article, a multitank storage facility to affect power control in the PBMR power cyclel, that a multi tank design with heat capacitance improves storage effictiveness, which could make the system cheaper. This storage facility is known as the Inventory Control System (ICS). The focus in this article is to determine an optimum number of tanks and heat capacitance that will achieve a spectfied performance for the lowest possible cost. Please note the values used in this exercise are not the actual valaes used by PBMR. However this article serves to demonstrate an approach to achieving an optimum solution for the ICS
A new telemetry monitoring system to enable Industry 4.0 initiatives in the South African heavy industry sector
No full textPhD (Electronic and Computer Engineering), North-West University, Potchefstroom CampusIndustry 4.0 initiatives aim to increase and maintain the operational efficiency of existing manufacturing methods and processes, as well as to enhance existing automation methods and technologies. Established heavy industries, such as the mining and steelmaking industry, water distribution schemes and power utilities, have been less proactive in adopting Industry 4.0 initiatives and methods. Machine-to-Machine communication and wireless networks form the backbone of the Industry 4.0 network layer. The aim of this thesis is to illustrate the current limitations present in wide-area wireless communications and to present a new telemetry monitoring system to address these limitations in the South African heavy industry sector.
In the first article, listed in Appendix B, a clear architectural description is presented that can be used to guide heavy industry players in the adoption of key Industry 4.0 principles in practice. An input-output methodological approach was followed to deconstruct the Industry 4.0 paradigm into two parts, namely the digital framework and the digital toolbox, with both
terms being coined in this article. Together, these two components form a roadmap that can be utilised to navigate the tides of Industry 4.0 adoption in the heavy industry sector.
In the second article, listed in Appendix C, a new software-based system is developed that actively monitors the network layer vital signs of a wide-area wireless telemetry system. The proposed monitoring system was implemented on a wide-area wireless telemetry network utilised by multiple industrial facilities within South Africa. The system successfully monitored more than 80 remote sites, with communication failures being detected immediately. The average connection uplink time was also increased by more than 25%.
In the third article, listed in Appendix D, the proposed monitoring system is integrated into existing real-time information systems. This integration allowed for the introduction of enhanced troubleshooting and maintenance procedures that can be followed on-site to rectify any network anomalies. Positive impacts were made on condition-based maintenance agreements between an energy services company and a South African gold mining company. The aim of the third article is to emphasise the value of the developed telemetry monitoring system in industry.
In the conference paper, listed in Appendix E, the value of an information and asset management system for the management of subscriber identification module (SIM) cards utilised in heavy industry is emphasised. The paper aims to analyse and present the current architecture of existing industrial information systems and discuss key challenges that contribute to communication disruptions. The paper introduces a new information and asset management system to address the challenges presented. The system is validated, and the results reflect the value of such a system in industry, with a communication cost reduction of 62%.Doctora
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