1,627 research outputs found

    Improving the performance of cascade correlation neural networks on multimodal functions

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    Intrinsic qualities of the cascade correlation algorithm make it a popular choice for many researchers wishing to utilize neural networks. Problems arise when the outputs required are highly multimodal over the input domain. The mean squared error of the approximation increases significantly as the number of modes increases. By applying ensembling and early stopping, we show that this error can be reduced by a factor of three. We also present a new technique based on subdivision that we call patchworking. When used in combination with early stopping and ensembling the mean improvement in error is over 10 in some cases

    A study of early stopping, ensembling, and patchworking for cascade correlation neural networks

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    The constructive topology of the cascade correlation algorithm makes it a popular choice for many researchers wishing to utilize neural networks. However, for multimodal problems, the mean squared error of the approximation increases significantly as the number of modes increases. The components of this error will comprise both bias and variance and we provide formulae for estimating these values from mean squared errors alone. We achieve a near threefold reduction in the overall error by using early stopping and ensembling. Also described is a new subdivision technique that we call patchworking. Patchworking, when used in combination with early stopping and ensembling, can achieve an order of magnitude improvement in the error. Also presented is an approach for validating the quality of a neural network’s training, without the explicit use of a testing dataset

    TIPO, BRAZIL'S 'LIKE': SYNCHRONIC FUNCTIONAL AND PHONETIC ANALYSES OF NOMINAL, GRAMMATICAL, AND DISCOURSE FUNCTIONS

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    Previous research in Brazilian Portuguese has indicated that the noun tipo 'type,' 'kind' is undergoing grammaticalization (Bittencourt, 1999; Lima-Hernandes, 2005). Review of the literature, however, reveals a limited number of studies that provide an account of its current state in conversational speech. Moreover, research on the grammaticalization of tipo has been mostly limited to the examination of its multifunctionality (Bittencourt, 1999; Laurentino,2016; Lima-Hernandes, 2005), resulting in a gap as to how the processes of grammaticalization may be reflected on its use and production. Using data from the Projeto Sociolingüístico Contemporâneo Brasileiro corpus (Thompson & Onosson, 2016), comprised of sociolinguistic interviews conducted with teenage public-school students in Rio de Janeiro, this dissertation presents the findings of a study that examined the current state of tipo in conversational discourse. An innovative multimethodological approach was employed aiming to address tipo's functional diversity. Distributional, functional, acoustic, and perceptual investigations were conducted with the goal to gain insight into some of the processes tipo is undergoing as it sheds its nominal properties and acquires new grammatical, discourse, and pragmatic functions. Results reveal a functional expansion of tipo, which was found to be performing roles such as a preposition, a conjunction, and a discourse marker among others. More notably, results from a subsequent acoustic analysis reveal consistent differences in pronunciation between nominal and non-nominal forms, suggesting that as tipo expands to perform new functions, speakers are encoding such changes at the segment level. A discrimination task conducted with 98 teenage students also confirmed that speakers are able to discriminate nominal from non-nominal forms, suggesting that other processes beyond durational differences may be playing a role in the grammaticalization of that noun

    Intelligent imaging systems for automotive applications

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    In common with many other application areas, visual signals are becoming an increasingly important information source for many automotive applications. For several years CCD cameras have been used as research tools for a range of automotive applications. Infrared cameras, RADAR and LIDAR are other types of imaging sensors that have also been widely investigated for use in cars. This paper will describe work in this field performed in C2VIP over the last decade - starting with Night Vision Systems and looking at various other Advanced Driver Assistance Systems. Emerging from this experience, we make the following observations which are crucial for "intelligent" imaging systems: 1. Careful arrangement of sensor array. 2. Dynamic-Self-Calibration. 3. Networking and processing. 4. Fusion with other imaging sensors, both at the image level and the feature level, provides much more flexibility and reliability in complex situations. We will discuss how these problems can be addressed and what are the outstanding issue

    Corticosteroids for the common cold

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    BACKGROUND: The common cold is a frequent illness, which, although benign and self limiting, results in many consultations to primary care and considerable loss of school or work days. Current symptomatic treatments have limited benefit. Corticosteroids are an effective treatment in other upper respiratory tract infections and their anti‐inflammatory effects may also be beneficial in the common cold. This updated review has included one additional study. OBJECTIVES: To compare corticosteroids versus usual care for the common cold on measures of symptom resolution and improvement in children and adults. SEARCH METHODS: We searched Cochrane Central Register of Controlled Trials (CENTRAL 2015, Issue 4), which includes the Acute Respiratory Infections (ARI) Group's Specialised Register, the Database of Reviews of Effects (DARE) (2015, Issue 2), NHS Health Economics Database (2015, Issue 2), MEDLINE (1948 to May week 3, 2015) and EMBASE (January 2010 to May 2015). SELECTION CRITERIA: Randomised, double‐blind, controlled trials comparing corticosteroids to placebo or to standard clinical management. DATA COLLECTION AND ANALYSIS: Two review authors independently extracted data and assessed trial quality. We were unable to perform meta‐analysis and instead present a narrative description of the available evidence. MAIN RESULTS: We included three trials (353 participants). Two trials compared intranasal corticosteroids to placebo and one trial compared intranasal corticosteroids to usual care; no trials studied oral corticosteroids. In the two placebo‐controlled trials, no benefit of intranasal corticosteroids was demonstrated for duration or severity of symptoms. The risk of bias overall was low or unclear in these two trials. In a trial of 54 participants, the mean number of symptomatic days was 10.3 in the placebo group, compared to 10.7 in those using intranasal corticosteroids (P value = 0.72). A second trial of 199 participants reported no significant differences in the duration of symptoms. The single‐blind trial in children aged two to 14 years, who were also receiving oral antibiotics, had inadequate reporting of outcome measures regarding symptom resolution. The overall risk of bias was high for this trial. Mean symptom severity scores were significantly lower in the group receiving intranasal steroids in addition to oral amoxicillin. One placebo‐controlled trial reported the presence of rhinovirus in nasal aspirates and found no differences. Only one of the three trials reported on adverse events; no differences were found. Two trials reported secondary bacterial infections (one case of sinusitis, one case of acute otitis media; both in the corticosteroid groups). A lack of comparable outcome measures meant that we were unable to combine the data. AUTHORS' CONCLUSIONS: Current evidence does not support the use of intranasal corticosteroids for symptomatic relief from the common cold. However, there were only three trials, one of which was very poor quality, and there was limited statistical power overall. Further large, randomised, double‐blind, placebo‐controlled trials in adults and children are required to answer this question

    Numerical simulation of two-phase gas-liquid flows in inclined and vertical pipelines

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    The present thesis describes the advances made in modelling two-phase flows in inclined pipes using a transient one-dimensional approach. The research is a developement of an existing numerical methodology, capable of simulating stratified and slugging two-phase flows in horizontal or inclined single pipes. The aim of the present work is to extend the capabilities of the approach in order (i) to account for the effect of the pipe topography in the numerical solution of the two-fluid model, and (ii) to simulate vertical bubbly twophase flows at various pressures in large diameter pipes, and (iii) to model stratified and terrain-induced slugging in two-phase flow pipelines made of several uphill, downhill and level sections. A transient compressible two-fluid model based on the one-dimensional form of the mass and momentum conservation equations for the gas and liquid phases, is developed to predict those flow configurations. The wall to fluid and the interphase interactions are accounted for by constitutive relations which are flow regime dependent. The conservation equations are discretized using a finite volume method. An algorithm is created to enable simulations on pipelines made of several sections, and account for the effect of the topography in the simulations. The methodology is applied to the compressible model in order to evaluate the robustness and accuracy of the numerical schemes, especially for the high-resolution Advection Upwinding Splitting Method (AUSM) associated to the compressible model. It also assesses the ability of the method to predict three physical flow regimes, namely stratified, bubbly and terrain-induced slug flows. The terrain-induced slugging study is performed on a slightly inclined (±1.5°) V-section system. The use of hydrodynamic slug correlations for hilly-terrain slugging is discussed. It shows to be conclusive with a good agreement with experimental measurements obtained for slug frequency and slug length predictions. Mechanisms such as the wave formation at the interface, the slug growth and propagation as well as merging slugs, can also be observed by the model. The bubbly model is extensively tested against available data collected by Nottingham University from experimental systems of 70mm and 189mm vertical pipes. In some cases, void fraction predictions are within 10% with experimental data, and pressure predictions within 4%. The simulation results compare well in overall with the measurements. In large diameter pipes, some variations are observed between the numerical and the measured results: especially the model underpredicts the flow at the bottom of the pipe. Limitations of the model for this particular case are highlighted. It is also observed that, in fully-developed flows, the model does give satisfactory predictions.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

    Variational based analysis and modelling using B-splines

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    The use of energy methods and variational principles is widespread in many fields of engineering of which structural mechanics and curve and surface design are two prominent examples. In principle many different types of function can be used as possible trial solutions to a given variational problem but where piecewise polynomial behaviour and user controlled cross segment continuity is either required or desirable, B-splines serve as a natural choice. Although there are many examples of the use of B-splines in such situations there is no common thread running through existing formulations that generalises from the one dimensional case through to two and three dimensions. We develop a unified approach to the representation of the minimisation equations for B-spline based functionals in tensor product form and apply these results to solving specific problems in geometric smoothing and finite element analysis using the Rayleigh-Ritz method. We focus on the development of algorithms for the exact computation of the minimisation matrices generated by finding stationary values of functionals involving integrals of squares and products of derivatives, and then use these to seek new variational based solutions to problems in the above fields. By using tensor notation we are able to generalise the methods and the algorithms from curves through to surfaces and volumes. The algorithms developed can be applied to other fields where a variational form of the problem exists and where such tensor product B-spline functions can be specified as potential solutions.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

    On-Farm Participatory Research is an Essential Step Towards Achieving Successful Adoption of Innovation: ‘Lifetime Wool’ a Case Study

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    \u27Lifetime Wool\u27 project (LTW) is a national project that is developing new nutritional guidelines for the management of ewe flocks across Australia funded by farmers through Australian Wool Innovation (AWI EC298; 2001-2008). A large replicated plot-scale experiment was used to define the dose-response of current production (wool and reproduction from the ewe) and future production (survival, growth and wool from progeny over their lifetime) to a range of levels of ewe nutrition (Thompson & Oldham, 2004). However, farmers and research workers have long realised that the difference between the results obtained on experimental plots and those obtained by farmers is of crucial importance if farmers are to be convinced to adopt new technology (Davidson & Martin, 1968). Hence, the LTW was designed from the start to include four distinct phases: (i) plot-scale research (2001 2003; see Oldham et al. 2006); (ii) on-farm paddock-scale research (2003 - 2005); (iii) whole-farm systems modelling (see Young et al. 2004); and (iv) on-farm demonstration or \u27road-testing\u27 of the draft guidelines (2005-2007)

    The evolutionary genetics of highly divergent alleles of the mimicry locus in Papilio dardanus

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    Background: The phylogenetic history of genes underlying phenotypic diversity can offer insight into the evolutionary origin of adaptive traits. This is especially true where single genes have large phenotypic effects, for example in determining polymorphic mimicry in butterflies. Here, we characterise the evolutionary history of two candidate genes for the mimicry switch in the polymorphic Batesian mimic Papilio dardanus coding for the transcription factors engrailed and invected. Results: We show that phased haplotypes associated with the dominant morphs f. poultoni and f. planemoides are phylogenetically highly divergent, in particular at non-synonymous sites. Some non-synonymous changes are shared between the divergent alleles suggesting either convergence or a shared ancestry. Gene trees for invected do not show this pattern. Despite their great divergence, all engrailed alleles of P. dardanus were monophyletic with respect to alleles of closely related species. Phylogenetic analyses therefore reveal no evidence for introgression from other species. A McDonald-Kreitman test conducted on a population sample from South Africa confirms a significant excess of intraspecific non-synonymous diversity in P. dardanus engrailed, suggesting long-term balanced polymorphism at this locus. Conclusions: The divergence between engrailed haplotypes suggests an evolutionary history distorted by selection with multiple changes reflecting recurrent selective sweeps. The high level of intraspecific polymorphism observed is characteristic of balancing selection on this locus, as expected if the gene engrailed is under phenotypic selection for the maintenance of multiple mimetic morphs. Non-synonymous changes in key functional portions of a major transcription factor are likely to be deleterious but if maintained in a dominant allele at low frequency, heterozygosity would reduce the associated genetic load
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