Results 401  450 of 1825  
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Xiong Hui   2009
Kmeans is a wellknown and widely used partitional clustering method. While there are considerable research efforts to characterize the key features of the Kmeans clustering algorithm, further investigation is needed to understand how data distributions can have impact on the performance of Kmeans clustering. To that end, in this paper, ...


Andreopoulos Bill   2009
A challenge involved in applying densitybased clustering to categorical biomedical data is that the "cube" of attribute values has no ordering defined, making the search for dense subspaces slow. We propose the HIERDENC algorithm for hierarchical densitybased clustering of categorical data, and a complementary index for searching for dense subspaces ...


Lakoumentas John   2009
In the rapidly advancing field of flow cytometry, methodologies facilitating automated clinical decision support are increasingly needed. In the case of Bchronic lymphocytic leukemia (BCLL), discrimination of the various subpopulations of blood cells is an important task. In this work, our objective is to provide a useful paradigm of computerbased ...


Jacquez Geoff M   2008
This paper develops and applies new techniques for the simultaneous detection of boundaries and clusters within a probabilistic framework. The new statistic "little b" (written b(ij)) evaluates boundaries between adjacent areas with different values, as well as links between adjacent areas with similar values. Clusters of high values (hotspots) and ...


Cakmakci Mehmet   2008
Breakthrough and terminal head loss are the main parameters that determine the performance of rapid sand filters. CarmanKozeny and Ergun equations can be applied to estimate head loss, but can only be applied to clean filter beds. Elaborated models are needed to predict head loss in dirty filters. In this ...


Lijoi Antonio   2008
Inference for Expressed Sequence Tags (ESTs) data is considered. We focus on evaluating the redundancy of a cDNA library and, more importantly, on comparing different libraries on the basis of their clustering structure. The numerical results we achieve allow us to assess the effect of an error correction procedure for ...


Chandrasekhar B   2008
In this work, a new numerical procedure is developed to generate an almostdiagonal matrix for the solution of boundary integral equation formulation dealing with acoustic scattering problems. The major drawback of the traditional boundary integral equation procedure resulting in a dense system matrix is eliminated in this new procedure by ...


Jo Booil B Department of Psychiatry & Behavioral Sciences, Stanford University, Stanford, CA 943055795, U.S.A.   2008
In cluster randomized trials (CRTs), individuals belonging to the same cluster are very likely to resemble one another, not only in terms of outcomes but also in terms of treatment compliance behavior. Although the impact of resemblance in outcomes is well acknowledged, little attention has been given to the possible ...


Huang Lan   2008
There have been articles on comparing methods for global clustering evaluation and cluster detection in disease surveillance, but power and sample size (SS) requirements have not been explored for spatially correlated data in this area. We are developing such requirements for tests of spatial clustering and cluster detection for regional ...


Ukoumunne Obioha C   2008
This paper evaluates methods for unadjusted analyses of binary outcomes in cluster randomized trials (CRTs). Under the generalized estimating equations (GEE) method the identity, log and logit link functions may be specified to make inferences on the risk difference, risk ratio and odds ratio scales, respectively. An alternative, 'clusterlevel', method ...


Roy Dibyendu   2008
The role of quadratic onsite pinning potentials on determining the size (N) dependence of the disorder averaged steady state heat current J in an isotopically disordered harmonic chain connected to stochastic heat baths is investigated. For two models of heat baths, namely white noise baths and Rubin's model of baths, ...


Sharko John   2008
Radviz is a radial visualization with dimensions assigned to points called dimensional anchors (DAs) placed on the circumference of a circle. Records are assigned locations within the circle as a function of its relative attraction to each of the DAs. The DAs can be moved either interactively or algorithmically to ...


Prossinger Hermann   2008
Of all the paranasal sinuses, frontal sinus (FS) morphology, volumes, outlines, and crosssectional areas vary most and so their statistical noise presents particular challenges. To assess and control this statistical noise requires a suite of mathematical techniques that: model their volume and crosssectional area ontogeny, determine the uniqueness and fractal ...


Kucik James E   2008
BACKGROUND: Investigations of clusters of birth defects have been challenging endeavors that have had only modest success identifying causes or risk factors. Some of the challenges to individual cluster investigations have been small sample size and limited data collection. We describe a novel approach for investigating and analyzing pooled information ...


Xu Dong   2008
In this work, we systematically study the problem of event recognition in unconstrained news video sequences. We adopt the discriminative kernelbased method for which video clip similarity plays an important role. First, we represent a video clip as a bag of orderless descriptors extracted from all of the constituent frames ...


Mihalache Dumitru   2008
We analyze spatiotemporal dissipative solitons in twodimensional photonic lattices in the presence of gain and loss. In the framework of the continuousdiscrete cubicquintic GinzburgLandau model, we demonstrate the existence of novel classes of twodimensional spatiotemporal dissipative lattice solitons, which also include surface solitons located in the corners or at the ...


Navarro Daniel J   2008
One of the central problems in cognitive science is determining the mental representations that underlie human inferences. Solutions to this problem often rely on the analysis of subjective similarity judgments, on the assumption that recognizing likenesses between people, objects, and events is crucial to everyday inference. One such solution is ...


Glänzel Wolfgang   2008
A common problem in comparative bibliometric studies at the meso and micro level is the differentiation and specialization of research profiles of the objects of analysis at lower levels of aggregation. In this study, institutional profile clusters are used to examine which level of the hierarchical subject classification should preferably ...


Weber Thomas C   2008
It has recently been shown [Weber, T. C. et al. (2007). "Acoustic propagation through clustered bubble clouds," IEEE J. Ocean. Eng. 32, 513523] that gas bubble clustering plays a role in determining the acoustic field characteristics of bubbly fluids. In particular, it has been shown that clustering changes the bubbleinduced ...


Cui Weiwei   2008
Graphs have been widely used to model relationships among data. For large graphs, excessive edge crossings make the display visually cluttered and thus difficult to explore. In this paper, we propose a novel geometrybased edgeclustering framework that can group edges into bundles to reduce the overall edge crossings. Our method ...


Linsen Lars   2008
Data sets resulting from physical simulations typically contain a multitude of physical variables. It is, therefore, desirable that visualization methods take into account the entire multifield volume data rather than concentrating on one variable. We present a visualization approach based on surface extraction from multifield particle volume data. The surfaces ...


Hyde J M   2009
Statistical analysis of atom probe data has improved dramatically in the last decade and it is now possible to determine the size, the number density and the composition of individual clusters or precipitates such as those formed in reactor pressure vessel (RPV) steels during irradiation. However, the characterisation of the ...


Chirot Fabien   2008
A novel experimental scheme has been developed in order to measure the heat capacity of mass selected clusters. It is based on controlled sticking of atoms on clusters. This allows one to construct the caloric curve, thus determining the melting temperature and the latent heat of fusion in the case ...


Jose Jovan   2008
A molecular electrostatic potential (MESP)guided method for building metal aggregates is proposed and tested on prototype lithium (Li)(n) clusters from n=4 to 58. The smaller clusters are subsequently subjected to direct density functional theory based geometry optimization, while the larger ones are optimized via molecular tailoring approach (MTA). The calculations ...


Xu Hua   2009
To develop methods for building corpusspecific sense inventories of abbreviations occurring in clinical documents. A corpus of internal medicine admission notes was collected and instances of each clinical abbreviation in the corpus were clustered to different sense clusters. One instance from each cluster was manually annotated to generate a final ...


Napari Ismo   2008
Density functional theory is applied to investigate the possibility of using the data from atomic and molecular clusters for the prediction of equilibrium vapor pressure and surface tension. For this purpose free energies of center of mass clusters constrained to a spherical volume are calculated at various temperatures. Clusters composed ...


Chen YouHua   2009
Identification of priority areas is a fundamental goal in conservation biology. Because of a lack of detailed information about species distributions, conservation targets in the Zhoushan Archipelago (China) were established on the basis of a speciesareahabitat relationship (choros model) combined with an environmental cluster analysis (ECA). An environmentaldistinctness index was ...


Olson Matthew T MT Section on Metabolism and Mass Spectrometry, National Institutes of Child Health and Human Development, National Institutes of Health, Baltimore, Maryland 21287, USA.   2009
This paper presents a novel theoretical basis for accurately calculating the isotope cluster of polypeptides. In contrast to previous approaches to this problem, which consider exhaustive or near exhaustive combinations of isotopic species, the program, Neutron Cluster, groups probabilities to yield highly accurate information without elucidating any fine structure within ...


GómezLaberge Camille   2008
Functional MRI (fMRI) may be possible without a priori models of the cerebral hemodynamic response. First, such datadriven fMRI requires that all cerebral territories with distinct patterns be identified. Second, a systematic selection method is necessary to prevent the subjective interpretation of the identified territories. This paper addresses the second ...


Lähivaara Timo   2008
The modeling of acoustic waves in the timedomain poses a significant challenge in scientific computing. A promising candidate for solving the three dimensional wave equation is the discontinuous Galerkin (DG) method. Advantages of the DG method are the easy parallelization and a special matrix structure which can reduce the overall ...


Abete T   2008
We present a systematic study of dynamical heterogeneity in a model for permanent gels upon approaching the gelation threshold. We find that the fluctuations of the selfintermediate scattering function are increasing functions of time, reaching a plateau whose value, at large length scales, coincides with the mean cluster size and ...


Williams B   2008
Crosssectional surveys of disease prevalence, including for tuberculosis (TB), often use a two (or more) stage sampling procedure. By choosing clusters of people randomly from all possible clusters, the logistic costs of doing the survey can be reduced. However, this increases the statistical uncertainty in the estimate of prevalence, and ...


Bullock John D   2008
PURPOSE: The Poisson distribution can be used to model discrete events that occur infrequently in time, and it was applied, retrospectively, to recently reported clusters of Fusarium keratitis. METHODS: This distribution was utilized with data reported from 6 geographically diverse ophthalmic centers during the worldwide Fusarium keratitis epidemic of 20042006. ...


Stanek Edward J   2008
Prediction of random effects is an important problem with expanding applications. In the simplest context, the problem corresponds to prediction of the latent value (the mean) of a realized cluster selected via twostage sampling. Recently, Stanek and Singer (JASA, 2004) developed best linear unbiased predictors (BLUP) under a finite population ...


Tashmukhambetov Arslan M   2008
The full threedimensional field of a seismic airgun array is modeled using an enhanced parabolic equation run on a parallel cluster computer system, which is part of the Louisiana Optical Network Initiative network cluster. Source signatures are calculated using GUNDALF and NUCLEUS softwares. The calculated results are compared to available ...


Shaffer Juliet Popper   2008
Multiple test procedures are usually compared on various aspects of error control and power. Power is measured as some function of the number of false hypotheses correctly identified as false. However, given equal numbers of rejected false hypotheses, the pattern of rejections, i.e. the particular set of false hypotheses identified, ...


Kiss Istvan Z   2008
We consider a procedure for generating clustered networks previously reported by Newman [Phys. Rev. E 68, 026121 (2003)]. In the same study, clustered networks generated according to the proposed model have been reported to have a lower epidemic threshold under susceptibleinfectiverecoveredtype network epidemic dynamics. By rewiring networks generated by this ...


Tzanetakis George   2008
Learning happens at the boundary interactions beween prior knowledge and incoming data. The same interplay takes place when trying to analyze and separate complex mixtures of sound sources such as music. Many approaches to this problem can be broadly categorized as either model based or grouping based. Although it is ...


Jbabdi S S Oxford Centre for Functional Magnetic Resonance Imaging of the Brain (FMRIB), University of Oxford, John Radcliffe Hospital, Oxford, Oxford, UK.   2009
We propose a hierarchical infinite mixture model approach to address two issues in connectivitybased parcellations: (i) choosing the number of clusters, and (ii) combining data from different subjects. In a Bayesian setting, we model voxelwise anatomical connectivity profiles as an infinite mixture of multivariate Gaussian distributions, with a Dirichlet process ...


Blavatska Viktoria   2008
We consider selfavoiding walks on the backbone of percolation clusters in space dimensions d=2,3,4. Applying numerical simulations, we show that the whole multifractal spectrum of singularities emerges in exploring the peculiarities of the model. We obtain estimates for the set of critical exponents that govern scaling laws of higher moments ...


Lee Michael J   2008
Selected pseudorandomnumber generators are applied to a Monte Carlo study of the twodimensional squarelattice site percolation model. A generator suitable for high precision calculations is identified from an application specific test of randomness. After extended computation and analysis, an ostensibly reliable value of p_{c}=0.59274598(4) is obtained for the percolation threshold.


EstradaPeña A   2008
A comparison of the performance of five modelling methods using presence/absence (generalized additive models, discriminant analysis) or presenceonly (genetic algorithm for ruleset prediction, ecological niche factor analysis, Gower distance) data for modelling the distribution of the tick species Boophilus decoloratus (Koch, 1844) (Acarina: Ixodidae) at a continental scale (Africa) using ...


Carroll Melissa K   2009
We explore to what extent the combination of predictive and interpretable modeling can provide new insights for functional brain imaging. For this, we apply a recently introduced regularized regression technique, the Elastic Net, to the analysis of the PBAIC 2007 competition data. Elastic Net regression controls via one parameter the ...


Zhang Hui   2009
Cluster extent and voxel intensity are two widely used statistics in neuroimaging inference. Cluster extent is sensitive to spatially extended signals while voxel intensity is better for intense but focal signals. In order to leverage strength from both statistics, several nonparametric permutation methods have been proposed to combine the two ...


Sugár István P   2008
It has been shown on model and biological systems that membrane clusters can affect inplane membrane reactions and can control biochemical reaction cascades. Clusters of twocomponent phospholipid bilayers have been simulated by two Isingtype lattice models: the monomer and the dimer model. In each model the plane of one layer ...


Li ChangTsun   2008
There is a growing interest in extracting statistical patterns from gene expression timeseries data, in which a key challenge is the development of stable and accurate probabilistic models. Currently popular models, however, would be computationally prohibitive unless some independence assumptions are made to describe largescale data. We propose an unsupervised ...


Chen Y   2008
A new analytical approach is proposed to model aggregation of molecules with isotropic, nearestneighbor, attractive interactions. By treating the clustering process as a chain reaction, equations with the exact high temperature limit are derived by evaluating the occupation probabilities of nearest neighbors based on the OnoKondo approach for a hexagonal ...


Chakraborty Hrishikesh   2009
Cluster randomized trials have become the design of choice for evaluating the effect of selected interventions on wellknown health indicators such as neonatal mortality rate, episiotomy rate, and postpartum hemorrhage rate in a community setting. Determining the sample size of a cluster randomized trial requires a reliable estimate of cluster ...


Wang Yin   2008
A timegoingbackward quasidynamics method is developed for global optimization of cluster structures, and its merits are examined by a simple classical mechanics model, indicating that the probability for the system to jump over high potential barriers by this method is much higher than that by common annealing methods. The method ...


Meng Deyu   2008
A new method, which is called decompositioncomposition (DC) method, is proposed for the nonlinear dimensionality reduction (NLDR) of data lying on the multicluster manifold. The main idea is first to decompose a given data set into clusters and independently calculate the lowdimensional embeddings of each cluster by the decomposition procedure. ...


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