1,102,045 research outputs found

    Radiative heat transfer during turbulent combustion

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    We investigate the radiative heat transfer in a co-flowing turbulent nonpremixed propane-air flame inside a three-dimensional cylindrical combustion chamber. The radiation from the luminous flame, which is due to the appearance of soot particles in the flame, is studied here, through the balance equation of radiative transfer which is solved by the Discrete Ordinates Method (DOM) coupling with a Large Eddy Simulation (LES) of the flow, temperature, combustion species and soot formation. The effect of scattering is ignored as it is found that the absorption dominates the radiating medium. Assessments of the various orders of DOM are also made and we find that the results of the incident radiation predicted by the higher order approximations of the DOM are in good agreement

    From Server to PDA: An HCI Perspective on Porting Wireless Roaming Business Applications

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    Advances in processor design, display technology, and lithium polymer batteries have led to a new generation of powerful, compact, and highly mobile devices. There is a range of different physical interfaces available, from the original Palm Pilots and Psion Organisers to the new generation of pocket PCs and personal digital assistants (PDA's). We focus on the stylus/touch-screen-based Compaq iPaq PDA. Combining a PDA with wireless communication technology has the potential for extending the application of computing in business. Many businesses already use handheld data recording devices. A drawback is the need to return the device to a computer to upload the information into the system, where it can be processed and made available to other applications. Using wireless devices this delay can be removed, providing a more accurate and up-to-date data repository. In order to see how a desktop to PDA migration might be carried out, a prototype interface to a mainstream accounting and stock control system was built to run on a Compaq iPaq 3850. Some of the problem areas of migrating server/desktop functionality to handheld devices, including wireless communication, device limitations, and security were demonstrated and explored with this interface. The informal feedback from the users will be fed into a redeveloped version of the system which will then be evaluated using a formal experiment The main lesson learnt was that providing desktop/server functionality on a mobile device requires more than copying a system's existing functionality and shrinking the interface to fit on a smaller screen. User feedback from a prototype system supported the idea that applications benefit from a redesign process when being ported to a mobile environment

    Inferential stability in systems biology

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    The modern biological sciences are fraught with statistical difficulties. Biomolecular stochasticity, experimental noise, and the “large p, small n” problem all contribute to the challenge of data analysis. Nevertheless, we routinely seek to draw robust, meaningful conclusions from observations. In this thesis, we explore methods for assessing the effects of data variability upon downstream inference, in an attempt to quantify and promote the stability of the inferences we make. We start with a review of existing methods for addressing this problem, focusing upon the bootstrap and similar methods. The key requirement for all such approaches is a statistical model that approximates the data generating process. We move on to consider biomarker discovery problems. We present a novel algorithm for proposing putative biomarkers on the strength of both their predictive ability and the stability with which they are selected. In a simulation study, we find our approach to perform favourably in comparison to strategies that select on the basis of predictive performance alone. We then consider the real problem of identifying protein peak biomarkers for HAM/TSP, an inflammatory condition of the central nervous system caused by HTLV-1 infection. We apply our algorithm to a set of SELDI mass spectral data, and identify a number of putative biomarkers. Additional experimental work, together with known results from the literature, provides corroborating evidence for the validity of these putative biomarkers. Having focused on static observations, we then make the natural progression to time course data sets. We propose a (Bayesian) bootstrap approach for such data, and then apply our method in the context of gene network inference and the estimation of parameters in ordinary differential equation models. We find that the inferred gene networks are relatively unstable, and demonstrate the importance of finding distributions of ODE parameter estimates, rather than single point estimates

    Knowledge, Justification, and Reason-Based Belief

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    Is knowledge definable as justified true belief ("JTB")? We argue that one can legitimately answer positively or negatively, depending on how the notion of justification is understood. To facilitate our argument, we introduce a simple propositional logic of reason-based belief. We show that this logic is sufficiently flexible to accommodate various useful features, including quantification over reasons. We use our framework to contrast two notions of JTB: one internalist, the other externalist. We argue that Gettier cases essentially challenge the internalist notion but not the externalist one. In particular, we may equate knowledge and JTB if the latter is grounded in what we call "adequate" reasons.Comment: v3 edits acknowledgment

    Reynolds number dependence of scalar fluctuations in a high Schmidt number turbulent jet

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    The scalar rms fluctuations in a turbulent jet were investigated experimentally, using high-resolution, laser-induced fluorescence techniques. The experiments were conducted in a high Schmidt number fluid (water), on the jet centerline, over a jet Reynolds number range of 30003000 or 6500