13,040 research outputs found
Orthogonal least squares algorithm for training multi-output radial basis function networks
No full textA constructive learning algorithm for multioutput radial basis function networks is presented. Unlike most network learning algorithms, which require a fixed network structure, this algorithm automatically determines an adequate radial basis function network structure during learning. By formulating the learning problem as a subset model selection, an orthogonal least-squares procedure is used to identify appropriate radial basis function centres from the network training data, and to estimate the network weights simultaneously in a very efficient manner. This algorithm has a desired property, that the selection of radial basis function centres or network hidden nodes is directly linked to the reduction in the trace of the error covariance matrix. Nonlinear system modelling and the reconstruction of pulse amplitude modulation signals are used as two examples to demonstrate the effectiveness of this learning algorithm
Attention to attributes and objects in working memory
No full textIt has been debated on the basis of change-detection procedures whether visual working memory is limited by the number of objects, task-relevant attributes within those objects, or bindings between attributes. This debate, however, has been hampered by several limitations, including the use of conditions that vary between studies and the absence of appropriate mathematical models to estimate the number of items in working memory in different stimulus conditions. We reexamined working memory limits in 2 experiments with a wide array of conditions involving color and shape attributes, relying on a set of new models to fit various stimulus situations. In Experiment 2, a new procedure allowed identical retrieval conditions across different conditions of attention at encoding. The results show that multiple attributes compete for attention, but that retaining the binding between attributes is accomplished only by retaining the attributes themselves. We propose a theoretical account in which a fixed object capacity limit contains within it the possibility of the incomplete retention of object attributes, depending on the direction of attention.</p
Regularity of extremal solutions in fourth order nonlinear eigenvalue problems on general domains
No full textWe examine the regularity of the extremal solution of the nonlinear eigenvalue problem on a general bounded domain in ,
with the Navier boundary condition on .
We establish energy estimates which show that for any non-decreasing convex and superlinear nonlinearity with , the extremal solution is smooth provided .
If in addition , then is regular for , while if , then the same holds for .
It follows that is smooth if and , or if and
.
We also show that if , and , then is smooth for . While these results are major improvements on what is known for general domains, they still fall short of the expected optimal results as recently established on radial domains, e.g., is smooth for when [J. Davila, L. Dupaigne, I. Guerra and M. Montenegro, Stable solutions for the bilaplacian with
exponential nonlinearity, SIAM J. Math. Anal., 39 (2007), 565–592], and for when [C. Cowan, P. Esposito, N. Ghoussoub and A. Moradifam, The critical dimension for a fourth
order elliptic problem with singular nonlinearity, Arch. Ration. Mech. Anal., 198 (2010), 763–787] (see also [A. Moradifam, On the critical dimension of a fourth order elliptic problem with negative exponent, J. Differential Equations, 248 (2010), 594–616]
Sammy Cowan
No full textThis 1961 photograph, taken by Asheville Citizen-Times photographer Ewart McKinley Ball, Jr. (1918-1966), shows Sammy Cowan singing. Founder and director of the Mountain Youth Jamboree, Hubert H. Hayes (1901-1964) auditioned and directed youth to perform in folk dance, music, and folk and ballad singing. The jamboree was held in the Asheville City Auditorium (now known as Thomas Wolfe Auditorium) from 1948 to 1973, and Hayes’ wife, Leona Trantham Hayes (1913-1989) continued to direct the program after his death in 1964. Hubert Hayes was an author, playwright, and alumni of Duke University
An evaluation of near patient tests for detecting herpes simplex virus type-2 antibody
No full textObjectives: To examine the 'in use' test characteristics of the POCkit 'near patient' HSV-2 rapid test for the detection of HSV-2 IgG antibodies for use in the clinic. This test relies on a visual interpretation of the result. Methods: 2093 serum samples, 229 from UK and 919 from Italian genitourinary medicine clinic patients and 945 from obstetric and gynaecology clinic patients in Italy were tested. Tests were carried out according to manufacturers' protocol in the United Kingdom and Italy. Three readers independently recorded a score for each test carried out and the results were compared. Results: In the UK study, the three readers disagreed on the result on 5.2% of tests. In the Italian study, there was disagreement in 10.2% of tests. Conclusions: This study has demonstrated a problem in the subjective nature of the interpretation of the POCkit HSV-2 test. It highlights the need for adequate training of clinic staff and the need for clinics to adopt policies of quality assurance a..
Practical identification of NARMAX models using radial basis functions
No full textA wide class of discrete time non-linear systems can be represented by the non-linear autoregressive moving average model with exogenous inputs or NARMAX model. This paper develops a practical algorithm for identifying NARMAX models based on radial basis functions from noise corrupted data. The algorithm consists of an iterative orthogonal-forward-regression routine coupled with model validity tests. The orthogonal-forward-regression routine selects parsimonious radial-basis-function models while the model validity tests measure the quality of fit. The modelling of a liquid level system and an automotive diesel engine are included to demonstrate the effectiveness of the identification procedure
Models of verbal working memory capacity: What does it take to make them work?
No full textTheories of working memory (WM) capacity limits will be more useful when we know what aspects of performance are governed by the limits and what aspects are governed by other memory mechanisms. Whereas considerable progress has been made on models of WM capacity limits for visual arrays of separate objects, less progress has been made in understanding verbal materials, especially when words are mentally combined to form multiword units or chunks. Toward a more comprehensive theory of capacity limits, we examined models of forced-choice recognition of words within printed lists, using materials designed to produce multiword chunks in memory (e.g., leather brief case). Several simple models were tested against data from a variety of list lengths and potential chunk sizes, with test conditions that only imperfectly elicited the interword associations. According to the most successful model, participants retained about 3 chunks on average in a capacity-limited region of WM, with some chunks being only subsets of the presented associative information (e.g., leather brief case retained with leather as one chunk and brief case as another). The addition to the model of an activated long-term memory component unlimited in capacity was needed. A fixed-capacity limit appears critical to account for immediate verbal recognition and other forms of WM. We advance a model-based approach that allows capacity to be assessed despite other important processing contributions. Starting with a psychological-process model of WM capacity developed to understand visual arrays, we arrive at a more unified and complete model.</p
The Social Tenant, the Law and the UK's Politics of Austerity
No full textThis paper considers current cuts to social housing provision in the UK made in the name of austerity. It focuses particularly on the ‘bedroom tax’ —the cut to housing benefit for working-age social housing tenants whose property is deemed to provide more bedrooms than they need. It begins by explaining the long-standing political project of social housing in the UK. This background is important to explain the emergence of a discursively ghettoized population within social housing. We then turn to the ‘bedroom tax’ itself. We consider the two quite separate rationales underpinning its introduction. One rationale —fairness— is the focus of the politicians; the other —under-occupation— provides the focus for policy analysts. Both offer different versions of truth about the social in social housing and both are unconvincing. For us, this is significant because the politics of austerity require the support of public opinion. We then consider some strategies of resistance to the ‘bedroom tax’ which harness the disruptive potential of fairness before concluding that the bedroom tax requires relatively little unpacking to reveal it as an ideological device which operates to increase inequality whilst deploying a rhetoric of fairness. Este artículo analiza los recortes en las prestaciones de viviendas sociales que se realizan actualmente en el Reino Unido en nombre de la austeridad. Se centra particularmente en el 'impuesto dormitorio' -el recorte en el subsidio de vivienda para inquilinos en edad de trabajar, cuya vivienda se considera que tiene más dormitorios de los que necesitan. Comienza explicando el proyecto político de viviendas sociales, de larga tradición en el Reino Unido. Estos antecedentes son importantes para explicar el surgimiento de guetos en las viviendas sociales. A continuación se centra en el "impuesto dormitorio” en sí mismo. Se analizan los dos diferentes motivos que sustentan su promulgación. Una es la razón esgrimida por los políticos -legitimidad-, la otra –baja ocupación-, la esgrimen los analistas políticos. Ambos ofrecen diferentes versiones de la verdad acerca de lo social en materia de vivienda social y ambos son poco convincentes. En nuestra opinión, esto es relevante porque las políticas de austeridad requieren del apoyo de la opinión pública. Después consideramos algunas estrategias de resistencia al "impuesto dormitorio" que aprovechan el potencial disruptivo de equidad, antes de concluir que es relativamente sencillo revelarlo como un instrumento ideológico que opera para aumentar la desigualdad, a la vez que utiliza una retórica de equidad. DOWNLOAD THIS PAPER FROM SSRN: http://ssrn.com/abstract=2565733 </p
Orthogonal least squares learning algorithm for radial basis function networks
No full textThe radial basis function network offers a viable alternative to the two-layer neural network in many applications of signal processing. A common learning algorithm for radial basis function networks is based on first choosing randomly some data points as radial basis function centers and then using singular-value decomposition to solve for the weights of the network. Such a procedure has several drawbacks, and, in particular, an arbitrary selection of centers is clearly unsatisfactory. The authors propose an alternative learning procedure based on the orthogonal least-squares method. The procedure chooses radial basis function centers one by one in a rational way until an adequate network has been constructed. In the algorithm, each selected center maximizes the increment to the explained variance or energy of the desired output and does not suffer numerical ill-conditioning problems. The orthogonal least-squares learning strategy provides a simple and efficient means for fitting radial basis function networks. This is illustrated using examples taken from two different signal processing applications
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