3,794 research outputs found

    Complexity and maintenance : a comparative study of object-oriented and structured methodologies : a thesis presented in partial fulfilment of the requirements for the degree of Master of Business Studies in Information Systems at Massey University

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    Maintenance has been found to be one of the most expensive phases in the life of an information system. It has been suggested that the use of object-oriented methods instead of traditional structured methods may be one way of reducing the cost of maintenance required for an information system. This thesis is an attempt to determine whether the object-oriented approach does in fact undergo a relatively smaller increase in complexity when subjected to a change in specifications than a similar system that is developed using a "structured methodology", and is therefore easier to maintain. The methodologies used in this study were Yourdon's (1989) Modern Structured Methodology and Booch's (1994) Object-Oriented methodology. The analysis phase of both methodologies were applied to the same case study twice in order to evaluate the effects of a change in the system's specifications. Once the two models for each methodology were complete, various metrics were applied to the structured system and a separate set of metrics were applied to the object-oriented system. The results of the models and the metrics were then analysed and validated in order to determine which system suffered a smaller proportional increase in complexity as a result of the changes to the system. It was found that overall, the object-oriented system proved to undergo a smaller increase in complexity, and it was therefore easier to maintain as a result of the changes than the structured system

    Boundedness of Maximal Operators of Schr\"odinger Type with Complex Time

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    Results of P. Sj\"olin and F. Soria on the Schr\"odinger maximal operator with complex-valued time are improved by determining up to the endpoint the sharp s0s \geq 0 for which boundedness from the Sobolev space Hs(R)H^s(\mathbb{R}) into L2(R)L^2(\mathbb{R}) occurs. Bounds are established for not only the Schr\"odinger maximal operator, but further for a general class of maximal operators corresponding to solution operators for certain dispersive PDEs. As a consequence of additional bounds on these maximal operators from Hs(R)H^s(\mathbb{R}) into L2([1,1])L^2([-1, 1]), sharp results on the pointwise almost everywhere convergence of the solutions of these PDEs to their initial data are determined.Comment: 12 pages. One further minor correction. To appear in the Revista Matem\'atica Iberoamerican

    Themes of drawing and digital context: student engagement with theory and practice using the tool of the integrated learning portfolio

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    This article presents a reflective visual narrative documenting the learning encounters of BA (Hons) Surface Design undergraduates using the Integrated Learning Portfolio (ILP) tool in Year one. Theoretical themes of drawing, digital drawing design practice, and visual design research experientially blended the physical and the virtual learning tools, environments and collaborative culture through this integrated first year route. Parallel theory and practice on specific themes such as ‘drawing lines within the urban landscape’, ‘creating shadow silhouettes’, ‘using the body as a tool for drawing’, and ‘cultivating fortuitous accidents in drawing practice’, created a conceptual space for students to evaluate the future relevance of these drawing experiences within the context of their design programme

    Innovation in professional services in a context of disruption

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    This research is focussed on how large professional services firms in New Zealand innovate in the context of and as a response to potential disruption. The theory of disruptive innovation describes how incumbents can be overwhelmed by innovative new entrants. Typically these new entrants begin in markets which are unattractive to incumbents because they can’t make money there with their existing business models. Therefore, some have claimed that new businesses must be set up, or various dual approaches adopted, to survive against disruptive new entrants. Semi-structured interviews were held with senior members of large professional services firms to understand their perspective on how innovation is managed in their organisation in the context of potential disruption and the capabilities which support them in doing this. From these interviews, a number of themes emerged which were compared with some of the approaches advocated by the literature in terms of responding to potential disruption. The research found that large professional services firms in New Zealand are focussed on how they can enable innovation from within the firm – typically built off the back of client demand and concentrating on how they work differently with clients, using new methodologies and resourcing models – particularly partnering with third parties to play a service aggregator role – to deliver better outcomes for clients and maintain the professional services firms’ incumbency. At the same time, there are some tentative steps to think about how incubation and/or ‘dual organisations’ might be able to test more disruptive, alternative business models

    Commentary on Guarini

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    Behavioural simulation of biological neuron systems using VHDL and VHDL-AMS

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    The investigation of neuron structures is an incredibly difficult and complex task that yields relatively low rewards in terms of information from biological forms (either animals or tissue). The structures and connectivity of even the simplest invertebrates are almost impossible to establish with standard laboratory techniques, and even when this is possible it is generally time consuming, complex and expensive. Recent work has shown how a simplified behavioural approach to modelling neurons can allow “virtual” experiments to be carried out that map the behaviour of a simulated structure onto a hypothetical biological one, with correlation of behaviour rather than underlying connectivity. The problems with such approaches are numerous. The first is the difficulty of simulating realistic aggregates efficiently, the second is making sense of the results and finally, it would be helpful to have an implementation that could be synthesised to hardware for acceleration. In this paper we present a VHDL implementation of Neuron models that allow large aggregates to be simulated. The models are demonstrated using a system level VHDL and VHDL-AMS model of the C. Elegans locomotory system

    An assessment of oxygen availability, iron build-up and the relative significance of free and attached bacteria, as factors affecting bio-oxidation of refractory gold-bearing sulphides at high solids concentrations

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    Bibliography: pages 121-132.Bacterial oxidation is currently finding significant application for the oxidative pretreatment of refractory gold-bearing sulphides. Plants processing sulphide concentrates have commonly been operated at solids concentrations of between 18 and 20 per cent (m/v) (Le 180 and 200 kg.m-3). At higher concentrations, a decline in the bio-oxidation rate has been observed. Other metallurgical processes, such as chemical leaching and cyanidation, are performed at higher solids concentrations of between 40 and 50 per cent (400 and 500 kg.m-3), providing an incentive to increase the solids concentration at which bio-oxidation plants are operated. A review of literature indicated the following factors to be potential causes of reduced bio-oxidation rates at high solids concentrations: oxygen and carbon dioxide mass transfer; a low bacteria-to-solids ratio; mechanical damage of the bacte.ria; and the build-up of inhibitory oxidation products. Interaction of these factors in the completely-mixed reactors that are commonly used for biooxidation, has confounded the interpretation of the effects of individual factors. Analysis of literature data revealed a link between the sulphide grade of a particular material and the highest solids concentration at which the bacterial oxidation rate was maximal. The oxygen demand is directly proportional to the sulphide concentration in the reactor. Correlations were used to predict the oxygen transfer potential in the experimental reactors and it was found that as long as the oxygen transfer potential exceeded the oxygen demand, the biooxidation rate was proportional to the solids concentration for a specific material. Wh~n the oxygen demand equalled or exceeded the oxygen transfer potential, then the bacterial oxidation rate was limited by oxygen availability. The sulphide grade is characteristic of a particular ore or concentrate and from the data analysis oxygen availabiiity appeared to be the underlying reason why low grade materials could be oxidised at the maximum specific bio-oxidation rate at far higher solids concentrations than high-grade f!laterials. Abstract ii The experiments performed in this study were designed to further investigate the apparent relationship, identified by analysis of literature data, between sulphide grade and the solids concentration at which the bacterial oxidation rate was maximal. The effect of both solids concentration and sulphide grade on the biooxidation rate was investigated and related to the oxygen availability in the reactor

    An exploratory investigation of crossflow microfiltration for solid/liquid separation in biological wastewater treatment

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    This thesis contains the results and discussion of an exploratory investigation into the application of Crossflow Microfiltration (CFMF) for solid/liquid separation in biological wastewater treatment systems. The principal objective of the study was to assess the influence of CFMF on the performance of identified biological wastewater treatment systems. It was not the objective to optimise filtration performance. A literature review indicated that the crossflow mode of filtration has been widely accepted as a unit operation in the fermentation industry. The filtration mode is now being applied not only for solid/liquid separation but also for separations on a molecular and ionic level. Very few applications of crossflow filtration in the context of biological wastewater treatment solid/liquid separation are reported in the literature. The reasons for this limited experience would appear to be the scale involved and the perceived high costs; separations in the fermentation industry are usually conducted at relatively small scale (laboratory or pilot-scale) and involve high-value products, justifying high capital and operating costs. Also, the high level of separation performance attained is perhaps not necessary for many wastewater treatment applications. No doubt these reservations are largely valid. However, these arguments cannot be applied equally to all filtration methods and wastewater treatment schemes. For example, the costs of microfiltration are substantially less than ultrafiltration or reverse osmosis, and in certain cases effluents with extremely low suspended solids contents may be required. In the light of these observations an investigation of CFMF for solid/liquid separation in biological wastewater treatment systems appears justified. Two biological treatment systems were selected for study: the Upflow Anaerobic Sludge Bed (UASB) reactor and the Activated Sludge system. The envisaged benefits accruing from the application of CFMF were different in each case


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    Ion channels are the molecular units that underlie electrical signaling in cells. Many physiological processes are dependent upon this signaling mechanism, as dysregulation often leads to severe pathophysiological consequences. The intermediate conductance calcium-activated potassium channel (KCa3.1) functions as heteromeric complexes with calmodulin (CaM), which is constitutively bound to the calmodulin-binding domain (CaMBD) of KCa3.1 located in the C-terminus, just distal to the sixth transmembrane domain (S6). This arrangement enables CaM to function as an intracellular Ca2+-sensor, coupling changes in the intracellular Ca2+ concentration to the regulation of channel activity. Understanding how channels gate or transition from the closed to the open conformation is a fundamental question in the field of ion channel biophysics. A chemomechanical gating model was proposed to explain how Ca2+-binding causes the channel to transition from a non-conducting to a conducting configuration. However, this model lacks a specific mechanism explaining how the conformational change in the CaMBD is coupled to the activation gate. Therefore, the goal of this dissertation was to investigate the role of S6 in the activation mechanism of KCa3.1. Specifically, I tested the hypothesis that the non-luminal residues in the C-terminal portion of S6 function as an interacting surface to couple CaM to the activation gate. Biochemical perturbation and site directed mutagenesis targeting predicted non-luminal residues in S6 act to shift the gatingequilibrium toward the open state by increasing the apparent Ca2+ affinity and dramatically slowing the deactivation process. Kinetic modeling using a 6-state gating scheme showed these perturbations act to slow the transition between the open state back to the closed state. The modification in the steady-state and kinetic behavior of the channel in combination with the kinetic analysis indicate the shift in gating equilibrium is caused by slowing the closing transition, suggesting the non-luminal surface of S6 is allosterically coupled to the activation gate. Therefore, in addition to being a structural component of the pore; S6 is also a dynamic component of the activation mechanism. Continuing to identify regions of the channel participating in the activation mechanism is critical to understand how Ca2+ binding leads to channel opening