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Real Cases (real + case)
Selected AbstractsSuperalgebras of Dirac operators on manifolds with special Killing-Yano tensorsFORTSCHRITTE DER PHYSIK/PROGRESS OF PHYSICS, Issue 12 2006I.I. Cot Abstract We present the properties of new Dirac-type operators generated by real or complex-valued special Killing-Yano tensors that are covariantly constant and represent roots of the metric tensor. In the real case these are just the so called complex or hyper-complex structures of the Kählerian manifolds. Such a Killing-Yano tensor produces simultaneously a Dirac-type operator and the generator of a one-parameter Lie group connecting this operator with the standard Dirac one. In this way the Dirac operators are related among themselves through continuous transformations associated with specific discrete ones. We show that the group of these continuous transformations can be only U(1) or SU(2). It is pointed out that the Dirac and Dirac-type operators can form ,, = 4 superalgebras whose automorphisms combine isometries with the SU(2) transformation generated by the Killing-Yano tensors. As an example we study the automorphisms of the superalgebras of Dirac operators on Minkowski spacetime. [source] Gravity-enhanced representation of measured geoid undulations using equivalent sourcesGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 1 2004Fernando Guspí SUMMARY Direct Global Positioning System measurement of geoid undulations on accurately levelled stations, usually tens of kilometres apart, can be interpolated by taking advantage of denser surveys of free-air gravity anomalies covering the same area. Using either a spherical or a planar earth model, a two-layer equivalent source is constructed, with the deepest masses located under the geoid stations and the shallower ones under the gravity stations, in such a way that the effect of the masses fits simultaneously, with different precisions, the anomalous potential related to the geoid and its vertical gradient or gravity anomaly. This poses a linear Bayesian problem, whose associated system of equations can be solved directly or by iterative procedures. The ability of the described method to predict the geoid elevation over the gravity stations is assessed in a synthetic example; and in the application to a real case, a gravity-enhanced geoid is mapped for an area of Buenos Aires province, Argentina, where local features are put in evidence. [source] On Clarkson's inequality in the real caseMATHEMATISCHE NACHRICHTEN, Issue 12 2007Lech Maligranda Abstract The best constant in a generalized complex Clarkson inequality is Cp,q(,) = max {21,1/p, 21/q, 21/q ,1/p +1/2} which differs moderately from the best constant in the real case Cp,q(,) = max {21,1/p, 21/q,Bp,q}, where . For 1 < q < 2 < p < , the constant Cp,q(,) is equal to Bp,q and these numbers are difficult to calculate in general. As applications of the generalized Clarkson inequalities the (p, q)-Clarkson inequalities in Lebesgue spaces, in mixed norm spaces and in normed spaces are presented. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] On a third-order Newton-type method free of bilinear operatorsNUMERICAL LINEAR ALGEBRA WITH APPLICATIONS, Issue 4 2010S. Amat Abstract This paper is devoted to the study of a third-order Newton-type method. The method is free of bilinear operators, which constitutes the main limitation of the classical third-order iterative schemes. First, a global convergence theorem in the real case is presented. Second, a semilocal convergence theorem and some examples are analyzed, including quadratic equations and integral equations. Finally, an approximation using divided differences is proposed and used for the approximation of boundary-value problems. Copyright © 2009 John Wiley & Sons, Ltd. [source] Some remarks on the perturbation of polar decompositions for rectangular matricesNUMERICAL LINEAR ALGEBRA WITH APPLICATIONS, Issue 4 2006Wen Li Abstract In this article we focus on perturbation bounds of unitary polar factors in polar decompositions for rectangular matrices. First we present two absolute perturbation bounds in unitarily invariant norms and in spectral norm, respectively, for any rectangular complex matrices, which improve recent results of Li and Sun (SIAM J. Matrix Anal. Appl. 2003; 25:362,372). Secondly, a new absolute bound for complex matrices of full rank is given. When ,A , Ã,2 , ,A , Ã,F, our bound for complex matrices is the same as in real case. Finally, some asymptotic bounds given by Mathias (SIAM J. Matrix Anal. Appl. 1993; 14:588,593) for both real and complex square matrices are generalized. Copyright © 2005 John Wiley & Sons, Ltd. [source] Risk Management with Duration: Potential and LimitationsCANADIAN JOURNAL OF ADMINISTRATIVE SCIENCES, Issue 2 2000Gerald O. Bierwag This paper demonstrates the applicability of duration as a risk management tool for government organizations. Drawing on a real case, we present methodologies for quantifying (a) the durations of real assets on a government's balance sheet, and (b) the durations of the financial assets represented by shares in state-owned enterprises (SOEs). In the area of real physical assets on the balance sheet we focus on the highway system and on real estate owned by the government. The methodology for measuring durations of SOEs focuses primarily on an electrical utility. Our main conclusion is that it is feasible to derive excellent practical measures of the real durations of physical assets on a government's balance sheet. Far from being academic curiosities,such durations can be estimated with a fair degree of accuracy in practice. The paper also indicates some of the potential limitations of duration analysis as a risk management tool for such organizations. Résumé En tant que grand succès de la finance académique, l'analyse de durée profite d'une application étendue de la part des praticiens de différents millieux du secteur privé. Cet article démontre la possibilité d'utiliser les durées comme outil de gestion du risque dans les organisations gouvernementales. En se basant sur un cas réel, nous présentons les méthodes pour quantifier (1) les durées des valeurs réelles d'un bilan gouvernemental et (2) les durées des valeurs financières représentées par des parts dans des sociétés d'état. Pour ce qui est des valeurs physiques réelles du bilan, nous nous arr,tons sur le système autoroutier et sur les biens immobiliers possédés par le gouvernement. La méthode de mesure des durées des sociétés d'état focalise sur une compagnie de service électrique. Notre conclusion principale est qu'il est possible de tirer d'excellentes mesures pratiques des durées réelles des valeurs physiques du bilan financier d'un gouvernement. Loin d',tre de pures curiosités académiques, de telles durées peuvent ,tre, en pratique, estimées avec un degré raisonnable de précision. L'article mentionne de plus certaines limites potentielles de l'analyse de durée comme outil de gestion de risque pour de telles organisations. [source] Simple method for determination of cocaine and main metabolites in urine by CE coupled to MSELECTROPHORESIS, Issue 12 2009José Luiz da Costa Abstract In this work, a simple method for the simultaneous determination of cocaine (COC) and five COC metabolites (benzoylecgonine, cocaethylene (CET), anhydroecgonine, anhydroecgonine methyl ester and ecgonine methyl ester) in human urine using CE coupled to MS via electrospray ionization (CE-ESI-MS) was developed and validated. Formic acid at 1,mol/L concentration was used as electrolyte whereas formic acid at 0.05,mol/L concentration in 1:1 methanol:water composed the coaxial sheath liquid at the ESI nozzle. The developed method presented good linearity in the dynamic range from 250,ng/mL to 5000,ng/mL (coefficient of determination greater than 0.98 for all compounds). LODs (signal-to-noise ratio of 3) were 100,ng/mL for COC and CET and 250,ng/mL for the other studied metabolites whereas LOQ's (signal-to-noise ratio of 10) were 250,ng/mL for COC and CET and 500,ng/mL for all other compounds. Intra-day precision and recovery tests estimated at three different concentration levels (500, 1500 and 5000,ng/mL) provided RSD lower than 10% (except anhydroecgonine, 18% RSD) and recoveries from 83,109% for all analytes. The method was successfully applied to real cases. For the positive urine samples, the presence of COC and its metabolites was further confirmed by MS/MS experiments. [source] Effect of microcracking on the micromechanics of fatigue crack growth in austempered ductile ironFATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 9 2001J. Ortiz The effect of microcracking on the mechanics of fatigue crack growth in austempered ductile iron is studied in this paper. The mechanism of fatigue crack growth is modelled using the boundary element method, customized for the accurate evaluation of the interaction effects between cracks and microcracks emanating from graphite nodules. The effects of nodule size and distribution and crack closure are considered, with deviation bounds of computed results estimated through weight-function analyses. A continuum approach is employed as a means of quantifying the shielding effect of microcracking on the dominant propagating crack, due to the reduction of stiffness of the material in the neighbourhood of the crack tip. Although the results obtained may not yield actual numbers for real cases, they are in accordance with experimental observations and demonstrate how the main factors affect the crack growth of the macrocrack. [source] The Contested Nature of Empirical Educational Research (and Why Philosophy of Education Offers Little Help)JOURNAL OF PHILOSOPHY OF EDUCATION, Issue 4 2005D. C. PHILLIPS This paper suggests that empirical educational research has not, on the whole, been treated well by philosophers of education. A variety of criticisms have been offered, ranging from triviality, conceptual confusion and the impossibility of empirically studying normative processes. Furthermore, many of those who criticise, or dismiss, empirical research do so without subjecting any specific examples to careful scholarly scrutiny. It is suggested that both philosophy of education, and the empirical research enterprise, stand to profit if philosophers pay more attention to real cases,and this attention is especially important at present, when research funding is being based on spurious scientistic criteria such as the use of ,gold standard' randomised experimental research designs. [source] Protein probabilities in shotgun proteomics: Evaluating different estimation methods using a semi-random sampling modelPROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 23 2006Xiaofang Xue Abstract The calculation of protein probabilities is one of the most intractable problems in large-scale proteomic research. Current available estimating methods, for example, ProteinProphet, PROT_PROBE, Poisson model and two-peptide hits, employ different models trying to resolve this problem. Until now, no efficient method is used for comparative evaluation of the above methods in large-scale datasets. In order to evaluate these various methods, we developed a semi-random sampling model to simulate large-scale proteomic data. In this model, the identified peptides were sampled from the designed proteins and their cross-correlation scores were simulated according to the results from reverse database searching. The simulated result of 18 control proteins was consistent with the experimental one, demonstrating the efficiency of our model. According to the simulated results of human liver sample, ProteinProphet returned slightly higher probabilities and lower specificity than real cases. PROT_PROBE was a more efficient method with higher specificity. Predicted results from a Poisson model roughly coincide with real datasets, and the method of two-peptide hits seems solid but imprecise. However, the probabilities of identified proteins are strongly correlated with several experimental factors including spectra number, database size and protein abundance distribution. [source] Characterization of the improvised explosive urea nitrate using electrospray ionization and atmospheric pressure chemical ionizationRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 14 2005Tsippy Tamiri Mass spectra of urea nitrate were measured in electrospray ionization and in atmospheric pressure chemical ionization in the negative mode. In both ionization methods two characteristic adduct ions containing the intact molecule [urea nitrate+NO3], and [urea nitrate+HNO3+NO3], are shown. The structure of the two adduct ions was deduced using measurements of isotopically labeled urea nitrate. Collision-induced dissociation measurements of the adduct ions show typical losses enabling the identification of urea nitrate in trace amounts. Using these methods urea nitrate was identified in real cases. Copyright © 2005 John Wiley & Sons, Ltd. [source] An automated velocity dealiasing method based on searching for zero isodopsTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 651 2010Nan Li Abstract A new automated velocity dealiasing method based on zero isodop searching has been developed primarily for linear wind fields. Its essence is to partition the radial velocity field obtained with a Doppler radar into two distinct regions of opposite velocity signs by two zero isodops. Zero isodops are searched point by point from the radar origin to the maximum detection range, and the accepted sign of each region separated by the zero isodops is determined. After that, the velocity sign at each gate is compared with the accepted sign of the region wherein the gate is. If they are consistent, the velocity is true; otherwise it is dealiased. Dealiasing results in real cases indicate that the new algorithm is practicable and effective, especially on aliasing lack of references affected by discontinuous echo or range folding, which is difficult for traditional methods of space continuity checking. Copyright © 2010 Royal Meteorological Society [source] MAD phasing: probabilistic estimate of |Foa|ACTA CRYSTALLOGRAPHICA SECTION D, Issue 6-2 2002Maria Cristina Burla The method of the joint probability distribution function is applied in order to estimate the structure-factor moduli of the anomalous scatterer substructure. The two-wavelength case is examined: the prior knowledge of the moduli is used to predict the value of |Foa| arising from the normal scattering of the anomalous scatterers. The conclusive formula is applied to ideal and to real cases: evidence of the usefulness of the approach is obtained. [source] | ||||||||||||||||