Search results for "C14"
showing 10 items of 30 documents
Validation procedures in radiological diagnostic models. Neural network and logistic regression
1999
The objective of this paper is to compare the performance of two predictive radiological models, logistic regression (LR) and neural network (NN), with five different resampling methods. One hundred and sixty-seven patients with proven calvarial lesions as the only known disease were enrolled. Clinical and CT data were used for LR and NN models. Both models were developed with cross validation, leave-one-out and three different bootstrap algorithms. The final results of each model were compared with error rate and the area under receiver operating characteristic curves (Az). The neural network obtained statistically higher Az than LR with cross validation. The remaining resampling validatio…
Surfaces of minimal degree of tame representation type and mutations of Cohen–Macaulay modules
2017
We provide two examples of smooth projective surfaces of tame CM type, by showing that any parameter space of isomorphism classes of indecomposable ACM bundles with fixed rank and determinant on a rational quartic scroll in projective 5-space is either a single point or a projective line. For surfaces of minimal degree and wild CM type, we classify rigid Ulrich bundles as Fibonacci extensions. For the rational normal scrolls S(2,3) and S(3,3), a complete classification of rigid ACM bundles is given in terms of the action of the braid group in three strands.
Hundreds of Pits, a New Vision of the Mesolithic in Champagne: Analysis and Mapping of an Unexpected Phenomenon
2017
Actes de la séance de la Société préhistorique française de Châlons-en-Champagne (29-30 mars 2016); International audience; Située en périphérie orientale de l’Île-de-France et de la Picardie, la Champagne crayeuse a longtemps fait figure de véritable« désert mésolithique », contrastant notamment avec les occupations récurrentes du plateau tertiaire situé à l’ouest. Si le développementde l’archéologie préventive a depuis fait progresser les connaissances, il n’a pas fondamentalement remis en cause cette répartition.Dans le même temps, les découvertes de séries de fosses profondes datées de manière récurrente du Mésolithique par le 14C se sontmultipliées dans la région. Elles mettent en évid…
OCCUPATIONS DOMESTIQUE ET FUNÉRAIRE DE L'ÂGE DU FER À LAVAU (AUBE)
2007
Dieser Artikel stellt die Ergebnisse einer Rettungsgrabung (Inrap) vor, die in der Gemeinde Lavau im Departement Aube durchgeführt wurde. Zwei unterschiedliche Besiedlungen konnten klar identifi ziert werden : ein Teil eines Bauernhofs aus der späten Bronze-/ frühen Hallstattzeit sowie eine kleine Nekropole aus der Mittellatènezeit. Während der Bauernhof typisch für einen ländlichen Betrieb dieser Zeit ist, unterscheidet sich die Nekropole von dem, was man erwarten würde. Ihre Lage, ihre Organisation, sowie manche Bestattungsbräuche sind aussergewöhnlich.
Estimating regional differences in returns to education when schooling and location are determined endogenously
2010
While the growing supply of university skills is known to have agglomerated towards the large centers in Finland, there is no research knowledge available on the development of regional demands. This paper attempts to fill this gap by analyzing regional variation in the private-sector return to university education in Finland for the period 1970 - 2004. In the analysis, we focus on studying 1) whether there are differences in the return to university between different region types, and 2) to what extent can these differences - if they exist - be explained by differences in regional skill supply and unemployment. For the econometric analysis, we use a large register-based dataset constructed…
Models Used for Measuring Customer Engagement
2013
The purpose of the paper is to define and measure the customer engagement as a forming element of the relationship marketing theory. In the first part of the paper, the authors review the marketing literature regarding the concept of customer engagement and summarize the main models for measuring it. One probability model (Pareto/NBD model) and one parametric model (RFM model) specific for the customer acquisition phase are theoretically detailed. The second part of the paper is an application of the RFM model; the authors demonstrate that there is no statistical significant variation within the clusters formed on two different data sets (training and test set) if the cluster centroids of t…
Radiocarbono y neolitización en la Península Ibérica
2016
En este trabajo hemos llevado a cabo una recopilación de las dataciones radiocarbónicas disponibles para el conjunto de la Península Ibérica con el objetivo de construir mapas temporales del desarrollo del proceso de neolitización. Hemos representado de este modo la densidad de las dataciones radiocarbónicas calibradas espacialmente, lo cual permite realizar una lectura diacrónica sobre las dinámicas poblacionales de los últimos caza-recolectores y los primeros agricultores y ganaderos. La asunción de partida consiste en considerar el conjunto de las dataciones como una muestra casi aleatoria para indagar sobre la evolución del poblamiento peninsular. En la bibliografía reciente se han seña…
Multinationals, R&D and productivity: Evidence for UK Manufacturing firms
2010
In this study, we analyze multinationality (domestic-based firms versus multinationals) and foreignness (foreign versus domestic firms) effects in the returns of R&D to productivity. We follow a two-step strategy. In the first step, we consistently estimate firm's productivity by GMM and numerically compute the sample distribution of the R&D returns. In the second step, we use stochastic dominance techniques to make inferences on the multinationality and foreignness effects. Results for a panel of UK manufacturing firms suggest that multinationality and foreignness effects operate in an opposite way: whilst the multinationality effect enhances R&D returns, the foreignness diminishes them. C…
An Examination of Tourist Arrivals Dynamics Using Short-Term Time Series Data: A Space—Time Cluster Approach
2013
The purpose of this study is to examine the development of Italian tourist areas ( circoscrizioni turistiche) through a cluster analysis of short time series. The technique is an adaptation of the functional data analysis approach developed by Abraham et al (2003), which combines spline interpolation with k-means clustering. The findings indicate the presence of two patterns (increasing and stable) averagely characterizing groups of territories. Moreover, tests of spatial contiguity suggest the presence of ‘space–time clusters’; that is, areas in the same ‘time cluster’ are also spatially contiguous. These findings appear to be more robust in particular for those series characterized by an…
Fonds structurels, effets de débordement géographique et croissance régionale en Europe.
2008
Les fonds structurels constituent l’un des instruments financiers de la politique regionale europeenne les plus intensement utilises afin de promouvoir la convergence entre les regions des pays membres de l’Union europeenne. Cependant, de nombreuses divergences theoriques et empiriques existent dans la litterature quant a leur capacite a encourager la croissance economique des regions les plus defavorisees. Par consequent, cet article se propose de proceder a des estimations complementaires en integrant des elements nouveaux : tout d’abord, nous adoptons une approche par l’econometrie spatiale afin de prendre en compte de possibles effets de debordement geographique entre regions ; ensuite,…