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Selected AbstractsThorough analysis of the Oseen system in 2D exterior domainsMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 15 2009Konieczny Abstract We construct Lp -estimates for the inhomogeneous Oseen system studied in a two-dimensional exterior domain , with inhomogeneous slip boundary conditions. The kernel of the paper is a result for the half space ,. Analysis of this model system shows us a parabolic character of the studied problem, resulting as an appearance of the wake region behind the obstacle. Main tools are given by the Fourier analysis to obtain the maximal regularity estimates. The results imply the solvability for the Navier,Stokes system for small velocity at infinity. Copyright © 2009 John Wiley & Sons, Ltd. [source] What Do Data Say About Monetary Policy, Bank Liquidity and Bank Risk Taking?ECONOMIC NOTES, Issue 2 2007Marcella Lucchetta This paper tests empirically the linkage between banks' investment and interbank lending decisions in response to interest rate changes. We draw conclusions for the monetary policy, which uses the interest rate as its main tool. Across European countries we find that the risk-free (i.e. monetary policy) interest rate negatively affects the liquidity retained by banks and the decision of a bank to be a lender in the interbank market. Instead, the interbank interest rate has a positive impact on these decisions. We also find that banks who lend show less risk-taking behaviour and tend to be smaller than those who are borrowers. Most importantly, the risk-free interest rate is positively correlated with loans investment and bank risk-taking behaviour. [source] Retracted: The manufacturing enterprise diagnostic instrument: A tool for assessment of enterprise system manufacturers,HUMAN FACTORS AND ERGONOMICS IN MANUFACTURING & SERVICE INDUSTRIES, Issue 6 2007Ash Genaidy Small- to medium-size manufacturers constitute the bulk of the U.S. manufacturing sector and are in a dire need of a tool that will help them face the challenges of globalization and increasing costs of manufacturing in the United States. The objectives were to develop and validate a diagnostic tool for manufacturing firms to evaluate their enterprise system performance to eliminate trial-and-error decisions and allow quick and informed actions. A pilot version was developed and tested in a small manufacturer. A revised version was then developed and further tested in another firm. Testing of the tool's pilot version provided invaluable feedback for developing the main tool. When tested in a small manufacturing firm, the results demonstrated management's misalignment and identified the root causes hindering performance. The tool demonstrated a quick and effective way to evaluate the manufacturing system's performance and to develop an aligned improvement action plan to guide the managerial team in devising a winning business strategy. © 2007 Wiley Periodicals, Inc. Hum Factors Man 17: 521,574, 2007. [source] Performance comparison of some dynamical and empirical downscaling methods for South Africa from a seasonal climate modelling perspectiveINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 11 2009Willem A. Landman Abstract The ability of advanced state-of-the-art methods of downscaling large-scale climate predictions to regional and local scale as seasonal rainfall forecasting tools for South Africa is assessed. Various downscaling techniques and raw general circulation model (GCM) output are compared to one another over 10 December-January-February (DJF) seasons from 1991/1992 to 2000/2001 and also to a baseline prediction technique that uses only global sea-surface temperature (SST) anomalies as predictors. The various downscaling techniques described in this study include both an empirical technique called model output statistics (MOS) and a dynamical technique where a finer resolution regional climate model (RCM) is nested into the large-scale fields of a coarser GCM. The study addresses the performance of a number of simulation systems (no forecast lead-time) of varying complexity. These systems' performance is tested for both homogeneous regions and for 963 stations over South Africa, and compared with each other over the 10-year test period. For the most part, the simulations method outscores the baseline method that uses SST anomalies to simulate rainfall, therefore providing evidence that current approaches in seasonal forecasting are outscoring earlier ones. Current operational forecasting approaches involve the use of GCMs, which are considered to be the main tool whereby seasonal forecasting efforts will improve in the future. Advantages in statistically post-processing output from GCMs as well as output from RCMs are demonstrated. Evidence is provided that skill should further improve with an increased number of ensemble members. The demonstrated importance of statistical models in operation capacities is a major contribution to the science of seasonal forecasting. Although RCMs are preferable due to physical consistency, statistical models are still providing similar or even better skill and should still be applied. Copyright © 2008 Royal Meteorological Society [source] Toward a general theory of conditional beliefsINTERNATIONAL JOURNAL OF INTELLIGENT SYSTEMS, Issue 3 2006Giulianella Coletti We consider a class of general decomposable measures of uncertainty, which encompasses (as its most specific elements, with respect to the properties of the rules of composition) probabilities, and (as its most general elements) belief functions. The aim, using this general context, is to introduce (in a direct way) the concept of conditional belief function as a conditional generalized decomposable measure ,(·|·), defined on a set of conditional events. Our main tool will be the following result, that we prove in the first part of the article and which is a sort of converse of a well-known result (i.e., a belief function is a lower probability): a coherent conditional lower probability P(·|K) extending a coherent probability P(Hi),where the events His are a partition of the certain event , and K is the union of some (possibly all) of them,is a belief function. © 2006 Wiley Periodicals, Inc. Int J Int Syst 21: 229,259, 2006. [source] Determinants of inselberg floras in arid Nama Karoo landscapesJOURNAL OF BIOGEOGRAPHY, Issue 10 2001Antje Burke Aim This study investigated the relationship between inselberg floras in floristic and functional terms and their correlation with environmental variables at macro-scale and landscape level. Location Four inselberg landscapes in Namibia's arid Nama Karoo in southern Africa were selected. Methods Plant surveys were undertaken over a 3-year period and species composition, growth form and dispersal spectra were used as measures for floristic and functional composition. Canonical correspondence analysis (CCA) was employed as the main tool to explain the perceived patterns. Results Regarding floristic affinities, inselberg floras formed distinct groups per study area and thus geographical position, with strong correlations between inselbergs within a particular study area. Neither growth form nor dispersal spectra closely resembled the pattern that emerged in the ordination of floristic composition. The influence of geographical position lessened when functional rather than floristic measures were introduced in the analysis. Main conclusions (1) On landscape and macro-scale, floristic composition of inselberg floras was largely determined by geographical position, geology, elevation, habitat diversity, rock outcrop in the surrounding and surface area of inselbergs. (2) Environmental variables operating at landscape level had greater influence on functional composition than on floristic composition. (3) Stochastic variables were more important in shaping the flora of these arid Nama Karoo inselbergs than deterministic processes such as niche relations and competition. [source] Strong stabilization of a structural acoustic model, which incorporates shear and thermal effects in the structural componentMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 12 2010Marié Grobbelaar-Van Dalsen Abstract In this paper we consider the question of stabilization of a linear three-dimensional structural acoustic model, which incorporates displacement, rotational inertia, shear and thermal effects in the flat flexible structural component of the model. We show strong stabilization of the coupled model without incorporating viscous or boundary damping in the equations for the gas dynamics and without imposing geometric conditions. It turns out that damping is needed in the interior of the plate. Our main tool is an abstract resolvent criterion due to Y. Tomilov. Copyright © 2009 John Wiley & Sons, Ltd. [source] Mod p classification of Shimura F -crystalsMATHEMATISCHE NACHRICHTEN, Issue 8 2010A. Vasiu Abstract Let k be an algebraically closed field of positive characteristic p. We first classify the D -truncations mod p of Shimura F -crystals over k and then we study stratifications defined by inner isomorphism classes of these D -truncations. This generalizes previous works of Kraft, Ekedahl, Oort, Moonen, and Wedhorn. As a main tool we introduce and study Bruhat F -decompositions; they generalize the combined form of Steinberg theorem and of classical Bruhat decompositions for reductive groups over k (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] DNA reassociation kinetics and diversity indices: richness is not rich enoughOIKOS, Issue 2 2008Bart Haegeman DNA reassociation kinetics, also known as Cot curves, were recently used by Gans and co-workers to estimate the number of bacterial species present in soil samples. By reanalysing the mathematical model we show that rather than the number of species, Simpson and Shannon diversity indices are encoded in the experimental data. Our main tool to establish this result are the so-called Rényi diversities, closely related to Hill numbers, illustrating the power of these concepts in interpreting ecological data. We argue that the huge diversity encountered in microbial ecology can be quantified more informatively by diversity indices than by number of species. [source] Electrocardiographic Body Surface Mapping: Potential Tool for the Detection of Transient Myocardial Ischemia in the 21st Century?ANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 2 2009Monique R. Robinson D.Phil Coronary artery disease (CAD) is one of the leading causes of cardiovascular mortality and morbidity worldwide. CAD presents as a wide spectrum of clinical disease from stable angina to ST segment elevation myocardial infarction. The 12-lead electrocardiogram (ECG) has been the main tool for the diagnosis of these events for almost a century but is limited in its diagnostic ability. For patients with suspected angina, the exercise tolerance test is often used to provoke and detect stress-induced ischemia but does not provide a definitive answer in a substantial proportion of patients. Body surface mapping (BSM) is a technique that samples multiple points around the thorax to provide a more comprehensive electrocardiographic data set than the conventional 12-lead ECG. Moreover, recent preliminary data demonstrate that BSM can detect and display transient regional myocardial ischemia in an intuitive fashion, employing subtraction color mapping, making it potentially valuable for diagnosing CAD causing transient regional ischemia. Research is ongoing to determine the full extent of its utility. [source] On the evolution of sharp fronts for the quasi-geostrophic equationCOMMUNICATIONS ON PURE & APPLIED MATHEMATICS, Issue 6 2005José Luis Rodrigo We consider the problem of the evolution of sharp fronts for the surface quasi-geostrophic (QG) equation. This problem is the analogue to the vortex patch problem for the two-dimensional Euler equation. The special interest of the quasi-geostrophic equation lies in its strong similarities with the three-dimensional Euler equation, while being a two-dimen-sional model. In particular, an analogue of the problem considered here, the evolution of sharp fronts for QG, is the evolution of a vortex line for the three-dimensional Euler equation. The rigorous derivation of an equation for the evolution of a vortex line is still an open problem. The influence of the singularity appearing in the velocity when using the Biot-Savart law still needs to be understood. We present two derivations for the evolution of a periodic sharp front. The first one, heuristic, shows the presence of a logarithmic singularity in the velocity, while the second, making use of weak solutions, obtains a rigorous equation for the evolution explaining the influence of that term in the evolution of the curve. Finally, using a Nash-Moser argument as the main tool, we obtain local existence and uniqueness of a solution for the derived equation in the C, case. © 2004 Wiley Periodicals, Inc. [source] Quantifying curvelike structures of measures by using L2 Jones quantitiesCOMMUNICATIONS ON PURE & APPLIED MATHEMATICS, Issue 9 2003Gilad Lerman We study the curvelike structure of special measures on ,n in a multiscale fashion. More precisely, we consider the existence and construction of a sufficiently short curve with a sufficiently large measure. Our main tool is an L2 variant of Jones' , numbers, which measure the scaled deviations of the given measure from a best approximating line at different scales and locations. The Jones function is formed by adding the squares of the L2 Jones numbers at different scales and the same location. Using a special L2 Jones function, we construct a sufficiently short curve with a sufficiently large measure. The length and measure estimates of the underlying curve are expressed in terms of the size of this Jones function. © 2003 Wiley Periodicals, Inc. [source] Elastic properties of dry clay mineral aggregates, suspensions and sandstonesGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 1 2003Tiziana Vanorio SUMMARY The presence of clay minerals can alter the elastic behaviour of rocks significantly. Although clay minerals are common in sedimentary formations and seismic measurements are our main tools for studying subsurface lithologies, measurements of elastic properties of clay minerals have proven difficult. Theoretical values for the bulk modulus of clay are reported between 20 and 50 GPa. The only published experimental measurement of Young's modulus in a clay mineral using atomic force acoustic microscopy (AFAM) gave a much lower value of 6.2 GPa. This study has concentrated on using independent experimental methods to measure the elastic moduli of clay minerals as functions of pressure and saturation. First, ultrasonic P - and S -wave velocities were measured as functions of hydrostatic pressure in cold-pressed clay aggregates with porosity and grain density ranging from 4 to 43 per cent and 2.13 to 2.83 g cm,3, respectively. In the second experiment, P - and S -wave velocities in clay powders were measured under uniaxial stresses compaction. In the third experiment, P -wave velocity and attenuation in a kaolinite,water suspension with clay concentrations between 0 and 60 per cent were measured at ambient conditions. Our elastic moduli measurements of kaolinite, montmorillonite and smectite are consistent for all experiments and with reported AFAM measurements on a nanometre scale. The bulk modulus values of the solid clay phase (Ks) lie between 6 and 12 GPa and shear (,s) modulus values vary between 4 and 6 GPa. A comparison is made between the accuracy of velocity prediction in shaley sandstones and clay,water and clay,sand mixtures using the values measured in this study and those from theoretical models. Using Ks= 12 GPa and ,s= 6 GPa from this study, the models give a much better prediction both of experimental velocity reduction due to increase in clay content in sandstones and velocity measurements in a kaolinite,water suspension. [source] Particle Markov chain Monte Carlo methodsJOURNAL OF THE ROYAL STATISTICAL SOCIETY: SERIES B (STATISTICAL METHODOLOGY), Issue 3 2010Christophe Andrieu Summary., Markov chain Monte Carlo and sequential Monte Carlo methods have emerged as the two main tools to sample from high dimensional probability distributions. Although asymptotic convergence of Markov chain Monte Carlo algorithms is ensured under weak assumptions, the performance of these algorithms is unreliable when the proposal distributions that are used to explore the space are poorly chosen and/or if highly correlated variables are updated independently. We show here how it is possible to build efficient high dimensional proposal distributions by using sequential Monte Carlo methods. This allows us not only to improve over standard Markov chain Monte Carlo schemes but also to make Bayesian inference feasible for a large class of statistical models where this was not previously so. We demonstrate these algorithms on a non-linear state space model and a Lévy-driven stochastic volatility model. [source] Dealing with Diversity in the Construction of Indigenous Autonomy in the Sierra Norte of OaxacaBULLETIN OF LATIN AMERICAN RESEARCH, Issue 3 2008ROSA GUADALUPE MENDOZA ZUANY Building autonomy in the Sierra Norte of Oaxaca has not depended on the development of Zapotec ethnic identities, isolation or rejection of the integration of outsiders into the communities. The communities of Ixtlán and Guelatao have developed strong local identities and strategies related to the appropriation of external legal categories, and the combination of these with their own customary practices to integrate newcomers into their social, political and economic organisation. Dialogue has been one of the main tools for building autonomy and achieve the integration of outsiders, while continuing the dynamic reproduction of their internal organisation and way of life. [source] | ||||||||||||||||