3,306 research outputs found
On the Convergence of Ritz Values, Ritz Vectors, and Refined Ritz Vectors
No full textThis paper concerns the Rayleigh--Ritz method for computing an approximation to an eigenpair (; x) of a non-Hermitian matrix A. Given a subspace W that contains an approximation to x, this method returns an approximation (; ~ x) to (; x). We establish four convergence results that hold as the deviation ffl of x from W approaches zero. First, the Ritz value converges to . Second, if the residual A~x \Gamma ~x approaches zero, then the Ritz vector ~ x converges to x. Third, we give a condition on the eigenvalues of the Rayleigh quotient from which the Ritz pair is computed that insures convergence of the Ritz vector. Finally, we show that certain refined Ritz vectors, introduced by the first author, converge unconditionally. This report is available by anonymous ftp from thales.cs.umd.edu in the directory pub/reports or on the web at http://www.cs.umd.edu/ stewart/. y Department of Applied Mathematics, Dalian University of Technology, Dalian 116024, P.R. China, ([email protected]..
Suncoast Ritz Building, B
No full textThe Suncoast Ritz building exterior.https://digitalcommons.usf.edu/gandy_street/5291/thumbnail.jp
The use of positive and negative penalty functions in solving constrained optimization problems and partial differential equations
No full textThe Rayleigh-Ritz Method together with the Penalty Function Method is used to investigate the use of different types of penalty parameters. The use of artificial springs as penalty parameters is a very well established procedure to model constraints in the Rayleigh-Ritz Method, the Finite Element Method and other numerical methods. Historically, large positive values were used to define the stiffness coefficient of artificial springs, until recent publications demonstrated that it is possible to use negative values to define the stiffness coefficients of the springs. Furthermore, recent publications show that constraints can be enforced using positive and negative mass or inertia in vibration problems and in a more generic sense using eigenpenalty parameters which are penalty parameters in the matrix associated with the eigenvalue. Before the commencement of this thesis, solutions using artificial inertia were published only for beams and simple spring-mass systems.
In this thesis the use of all possible types of penalty parameters are investigated in vibration problems of Euler-Bernoulli beams, thin plates and shallow shells and in elastic stability analysis of Euler-Bernoulli beams, including penalty parameters associated with the geometrical stiffness matrix. The study includes the use of penalty parameters for both enforcing support boundary conditions and continuity conditions along structural joints.
This investigation started with the selection of the set of admissible functions that would: (a) allow modelling of beams, plates and shells in completely free boundary conditions; (b) not present any limitation in the number of functions that can be used in the solution. This gives the possibility to converge to the constraint solution and to model any type of boundary conditions.
The procedure proposed in this work combines several advantages: accuracy of the results, relative fast convergence, simplicity of the set of admissible functions and flexibility to define boundary conditions. While there are other procedures that may give better accuracy for specific cases, the proposed method is more widely applicable.
The procedure used in this work also includes a way to check for round-off errors and ill-conditioning in the results; as well as a way to bracket the exact solution with upper and lower-bound results
Availability and use of molecular microbiological and immunological tests for the diagnosis of tuberculosis in Europe - public dataset
No full textThe original data are accessible as .csv file. This dataset supports the publication Tebruegge M, Ritz N, Koetz K, Noguera-Julian A, Seddon JA, et al. (2014) Availability and Use of Molecular Microbiological and Immunological Tests for the Diagnosis of Tuberculosis in Europe. PLOS ONE 9(6): e99129. https://doi.org/10.1371/journal.pone.0099129</span
A Unified Framework for the Analysis of Germination, Emergence, and other Time-to-Event Data in Weed Science
No full textGermination and emergence assays represent the most notable examples of time-to-event data in agriculture and related disciplines. In spite of the peculiar characteristics of this type of data, there has been little effort to establish a specific and comprehensive framework for their analyses. Indeed, a brief survey of the literature shows that germination and emergence data, along with other phenological measurements such as flowering time, have been analyzed through myriad approaches, giving rise to confusion and uncertainty among scientists and practitioners as to what may represent the best statistical practice. This lack of coherence in statistical approach may reduce the efficiency of research, while making the communication of results and the cross-study comparisons extremely challenging. Here, we attempt to provide a coherent framework and protocol for the analyses of germination/emergence and other time-to-event data in weed science and related disciplines, together with a software implementation in the form of a new R package. We propose a similar approach to biological assays in ecotoxicology, based on: (1) fitting a time-to-event model to describe the whole time course of events; (2) comparing time-to-event curves across experimental treatments, and (3) deriving further information from the fitted model to better focus on some traits of interest. The most appropriate methods to accomplish this procedure were carefully selected from the framework of survival analysis and related sources and were modified to comply with the specific needs of weed, seed, and plant sciences. Finally, they were implemented in the new R package drcte. In this article, we describe the procedure and its limitations by way of providing examples of several types of germination/emergence assays. We highlight that our proposed procedure can also serve as the first step of data analyses, with its output subsequently submitted to traditional or meta-analytic approaches.</p
Comparisons of piecewise Ritz and weighted-residual methods
No full textTo date, finite element techniques using the Ritz Method have found wide use in solving differential equations in the applied sciences, particularly in structural analysis. Finite Element Techniques using weighted-residual methods, however, have not been tried. This thesis develops Finite Element Techniques using the Collocation, Subdomain, Galerkin, and Least-Squares weighted-residual methods, and compares them to the Ritz Method. Numerical results are presented for a one-dimensional problem using all weighted-residual methods and the Ritz Method. From a standpoint of accuracy and ease of formulation and programming, the Subdomain Method compared favorably with the Ritz Method. The solution of a two-dimensional problem was attempted. The weighted-residual techniques led to a singular matrix. This was due, probably, to the poor choice of an approximation family.Mechanical Engineering, Department o
Application of load-dependent Ritz vectors to probabilistic
No full textThis paper demonstrates the possibility of incorporating load-dependent Ritz vectors, as an alternative to modal parameters, into a Bayesian probabilistic framework for detecting damages in a structure. Recent research has shown that it is possible to extract load-dependent Ritz vectors from vibration tests. This paper shows that load-dependent Ritz vectors have the following potential advantages for damage detection over modal vectors: (1) In general, loaddependentRitzvectors are more sensitive to damage than the corresponding modal vectors, and (2) substructures of interest can be made more observable using the load-dependent Ritz vectors generated from particular load patterns. An eight-bay truss structure and a five-story frame example are presented to illustrate the applicability of the proposed approach
Inclusion of latent tuberculosis infection as a separate entity into the international classification of diseases
No full textThe 11th revision of the International Classification of Diseases (ICD-11) proposed by the WHO is currently in the consultation phase. In common with previous versions of the ICD this revised version does not contain a code for latent tuberculosis infection (LTBI), contrasting with the inclusion of a large number of codes for various manifestations of active tuberculosis (TB). Inclusion of a separate code for LTBI into ICD-11 is critically important for epidemiological, clinical and research purposes. On behalf of the Paediatric Tuberculosis Network European Trialsgroup, we encourage colleagues worldwide who are caring for TB patients or are involved in TB research to join us in supporting the case for a long overdue ICD code for LTBI. <br/
Einstein’s Investigations of Galilean Covariant Electrodynamics prior to 1905
No full textEinstein learned from the magnet and conductor thought experiments how to use field transformation laws to extend the covariance to Maxwell’s electrodynamics. If he persisted in his use of this device, he would have found that the theory cleaves into two Galilean covariant parts, each with different field transformation laws. The tension between the two parts reflects a failure not mentioned by Einstein: that the relativity of motion manifested by observables in the magnet and conductor thought experiment does not extend to all observables in electrodynamics. An examination of Ritz’s work shows that Einstein’s early view could not have coincided with Ritz’s on an emission theory of light, but only with that of a conveniently reconstructed Ritz. One Ritz-like emission theory, attributed by Pauli to Ritz, proves to be a natural extension of the Galilean covariant part of Maxwell’s theory that happens also to accommodate the magnet and conductor thought experiment. Einstein's famous chasing a light beam thought experiment fails as an objection to an ether-based, electrodynamical theory of light. However it would allow Einstein to formulate his general objections to all emission theories of light in a very sharp form. Einstein found two well known experimental results of 18th and19th century optics compelling (Fizeau’s experiment, stellar aberration), while the accomplished Michelson-Morley experiment played no memorable role. I suggest they owe their importance to their providing a direct experimental grounding for Lorentz’ local time, the precursor of Einstein’s relativity of simultaneity, and do it essentially independently of electrodynamical theory. I attribute Einstein’s success to his determination to implement a principle of relativity in electrodynamics, but I urge that we not invest this stubbornness with any mystical prescience
Measurement of the electron's electric dipole moment using YbF molecules: methods and data analysis
No full text21.06.13 KB. Ok to add the author accepted version to spiral. IO
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