Academic literature on the topic 'Compact extensions'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the lists of relevant articles, books, theses, conference reports, and other scholarly sources on the topic 'Compact extensions.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Journal articles on the topic "Compact extensions"
1
Gutik, Oleg, and Kateryna Pavlyk. "On pseudocompact topological Brandt λ0-extensions of semitopological monoids." Topological Algebra and its Applications 1 (December 31, 2013): 60–79. http://dx.doi.org/10.2478/taa-2013-0007.
Full textAbstract:
AbstractIn the paper we investigate topological properties of a topological Brandt λ0-extension B0λ(S) of a semitopological monoid S with zero. In particular we prove that for every Tychonoff pseudocompact (resp., Hausdorff countably compact, Hausdorff compact) semitopological monoid S with zero there exists a unique semiregular pseudocompact (resp., Hausdorff countably compact, Hausdorff compact) extension B0λ(S) of S and establish their Stone-Cˇ ech and Bohr compactifications. We also describe a category whose objects are ingredients in the constructions of pseudocompact (resp., countably compact, sequentially compact, compact) topological Brandt λ0- extensions of pseudocompact (resp., countably compact, sequentially compact, compact) semitopological monoids with zeros.
2
Perán, Juan. "Locally compact multivector extensions." Journal of Mathematical Analysis and Applications 287, no. 2 (November 2003): 455–72. http://dx.doi.org/10.1016/s0022-247x(03)00542-0.
Full text
3
KOUSHESH, M. R. "Topological extensions with compact remainder." Journal of the Mathematical Society of Japan 67, no. 1 (January 2015): 1–42. http://dx.doi.org/10.2969/jmsj/06710001.
Full text
4
KOUSHESH, M. R. "ONE-POINT CONNECTIFICATIONS." Journal of the Australian Mathematical Society 99, no. 1 (January 9, 2015): 76–84. http://dx.doi.org/10.1017/s1446788714000676.
Full textAbstract:
A space $Y$ is called an extension of a space $X$ if $Y$ contains $X$ as a dense subspace. An extension $Y$ of $X$ is called a one-point extension if $Y\setminus X$ is a singleton. Compact extensions are called compactifications and connected extensions are called connectifications. It is well known that every locally compact noncompact space has a one-point compactification (known as the Alexandroff compactification) obtained by adding a point at infinity. A locally connected disconnected space, however, may fail to have a one-point connectification. It is indeed a long-standing question of Alexandroff to characterize spaces which have a one-point connectification. Here we prove that in the class of completely regular spaces, a locally connected space has a one-point connectification if and only if it contains no compact component.
5
Berezovski, Tetyana, Oleg Gutik, and Kateryna Pavlyk. "Brandt Extensions and Primitive Topological Inverse Semigroups." International Journal of Mathematics and Mathematical Sciences 2010 (2010): 1–13. http://dx.doi.org/10.1155/2010/671401.
Full textAbstract:
We study (countably) compact and (absolutely) -closed primitive topological inverse semigroups. We describe the structure of compact and countably compact primitive topological inverse semigroups and show that any countably compact primitive topological inverse semigroup embeds into a compact primitive topological inverse semigroup.
6
Székelyhidi, László. "Harmonic Synthesis on Group Extensions." Mathematics 12, no. 19 (September 27, 2024): 3013. http://dx.doi.org/10.3390/math12193013.
Full textAbstract:
Harmonic synthesis describes translation invariant linear spaces of continuous complex valued functions on locally compact abelian groups. The basic result due to L. Schwartz states that such spaces on the reals are topologically generated by the exponential monomials in the space; in other words, the locally compact abelian group of the reals is synthesizable. This result does not hold for continuous functions in several real variables, as was shown by D.I. Gurevich’s counterexamples. On the other hand, if two discrete abelian groups have this synthesizability property, then so does their direct sum, as well. In this paper, we show that if two locally compact abelian groups have this synthesizability property and at least one of them is discrete, then their direct sum is synthesizable. In fact, more generally, we show that any extension of a synthesizable locally compact abelian group by a synthesizable discrete abelian group is synthesizable. This is an important step toward the complete characterization of synthesizable locally compact abelian groups.
7
Sund, Terje. "Remarks on locally compact group extensions." MATHEMATICA SCANDINAVICA 69 (December 1, 1991): 199. http://dx.doi.org/10.7146/math.scand.a-12378.
Full text
8
Kunen, Kenneth. "Compact scattered spaces in forcing extensions." Fundamenta Mathematicae 185, no. 3 (2005): 261–66. http://dx.doi.org/10.4064/fm185-3-4.
Full text
9
Nogura, Tsugunori. "Countably compact extensions of topological spaces." Topology and its Applications 23, no. 3 (August 1986): 313–14. http://dx.doi.org/10.1016/0166-8641(85)90049-5.
Full text
10
Botelho, Geraldo, and Kuo Po Ling. "On compact extensions of multilinear operators." Bulletin of the Brazilian Mathematical Society, New Series 45, no. 2 (June 2014): 343–53. http://dx.doi.org/10.1007/s00574-014-0052-z.
Full textDissertations / Theses on the topic "Compact extensions"
1
Scott, Andrew D. "Livšic theorems and the stable ergodicity of compact group extensions for systems with some hyperbolicity." Thesis, University of Surrey, 2003. http://epubs.surrey.ac.uk/844054/.
Full textAbstract:
We consider Livsic regularity for Lie group valued cocycles over: a class of piecewise expanding maps of the interval, namely Lasota-Yorke maps; uniformly hyperbolic toral maps with singularities and a class of nonuniformly expanding interval maps. As applications of the results we prove stable ergodicity theorems for compact Lie group extension of Lasota-Yorke maps and uniformly hyperbolic toral maps with singularities. Additionally we consider conditions for the ergodicity and weak-mixing of finite group extensions of hyperbolic basic sets given in terms of periodic data and cohomological equations. We also consider stable ergodicity results for a class of nonconnected compact Lie group extensions of hyperbolic basic sets.
2
Benzoni, Séverin. "Classification des filtrations dynamiques et étude des systèmes d'entropie positive." Electronic Thesis or Diss., Normandie, 2024. https://theses.hal.science/tel-04835404.
Full textAbstract:
Dans cette thèse, nous explorons les structures possibles des systèmes dynamiques de la forme $\bfX :=(X, \A, \mu, T)$ et leurs tribus facteur $\B \subset \A$. Les deux premiers chapitres étudient les différentes façons dont une tribu facteur $\B$ peut s'inclure dans un système dynamique $\bfX :=(X, \A, \mu, T)$, c'est-à-dire que nous étudions certaines structures possibles de l'\emph{extension} $\A \arr \B$. Dans le premier chapitre, nous considérons les concepts de \emph{super-innovations} et de \emph{standardité} des extensions, inspirés de la théorie des filtrations. Un point important est l'introduction de la notion d'\emph{extensions confinées}, qui nous intéressent parce qu'elles n'ont pas de super-innovation. Nous donnons plusieurs exemples et étudions des propriétés supplémentaires de ces extensions, y compris des résultats de relèvement. Ensuite, nous montrons notre résultat principal : l'existence d'extensions non-standard. Enfin, ce résultat trouve une application dans l'étude des filtrations dynamiques, qui sont les filtrations de la forme $(\F_n)_{n \leq 0}$ telles que chaque $\F_n$ est une tribu facteur. Nous montrons qu'il existe des \emph{filtrations dynamiques I-confortables non standard}.Le deuxième chapitre approfondit l'étude des extensions confinées en trouvant un nouveau type de telles extensions, dans le cadre des suspensions de Poisson : nous prenons un système dynamique $(X, \mu, T)$ en mesure $\s$-finie infinie et une extension compacte $(X \times G, \mu \otimes m_G, T_\phi)$, puis nous considérons l'extension de Poisson correspondante $((X \times G)^*, (\mu \otimes m_G)^*, (T_\phi)_*) \to (X^*, \mu^*, T_*)$. Nous donnons des conditions sous lesquelles cette extension est confinée et construisons un exemple qui correspond à ces conditions.Enfin, le troisième chapitre se concentre sur une famille de filtrations dynamiques : les \emph{filtrations de Pinsker faible}. L'existence de ces filtrations sur tout système ergodique provient d'un résultat récent d'Austin \cite{austin}, et elles se présentent comme un outil potentiel pour décrire les systèmes à entropie positive. Nous explorons les liens entre la structure asymptotique des filtrations de Pinsker faible et les propriétés du système dynamique sous-jacent. Naturellement, nous demandons aussi si, sur un système donné, la structure des filtrations de Pinsker faible est unique à isomorphisme près. Nous donnons une réponse partielle, dans le cas où le système sous-jacent est un schéma de Bernoulli. Nous concluons notre travail en donnant deux exemples explicites de filtrations de Pinsker faibleIn this thesis, we explore the possible structures of measure preserving dynamical systems of the form $\bfX :=(X, \A, \mu, T)$ and their factor $\s$-algebras $\B \subset \A$. The first two chapters investigate various ways in which a factor $\s$-algebra $\B$ can sit in a dynamical system $\bfX :=(X, \A, \mu, T)$, i.e. we study some possible structures of the \emph{extension} $\A \arr \B$. In the first chapter, we consider the concepts of \emph{super-innovations} and \emph{standardness} of extensions, which are inspired from the theory of filtrations. An important focus of our work is the introduction of the notion of \emph{confined extensions}, which first interested us because they have no super-innovation. We give several examples and study additional properties of confined extensions, including several lifting results. Then, we show our main result: the existence of non-standard extensions. Finally, this result finds an application to the study of dynamical filtrations, i.e. filtrations of the form $(\F_n)_{n \leq 0}$ such that each $\F_n$ is a factor $\s$-algebra. We show that there exist \emph{non-standard I-cosy dynamical filtrations}.The second chapter furthers the study of confined extensions by finding a new kind of such extensions, in the setup of Poisson suspensions: we take an infinite $\s$-finite measure-preserving dynamical system $(X, \mu, T)$ and a compact extension $(X \times G, \mu \otimes m_G, T_\phi)$, then we consider the corresponding Poisson extension $((X \times G)^*, (\mu \otimes m_G)^*, (T_\phi)_*) \to (X^*, \mu^*, T_*)$. We give conditions under which that extension is confined and build an example which fits those conditions.Lastly, the third chapter focuses on a family of dynamical filtrations: \emph{weak Pinsker filtrations}. The existence of those filtrations on any ergodic system comes from a recent result by Austin \cite{austin}, and they present themselves as a potential tool to describe positive entropy systems. We explore the links between the asymptotic structure of weak Pinsker filtrations and the properties of the underlying dynamical system. Naturally, we also ask whether, on a given system, the structure of weak Pinsker filtrations is unique up to isomorphism. We give a partial answer, in the case where the underlying system is Bernoulli. We conclude our work by giving two explicit examples of weak Pinsker filtrations
3
Vaes, Stefaan. "Groupes quantiques localement compacts, actions et extensions." Habilitation à diriger des recherches, Université Paris-Diderot - Paris VII, 2004. http://tel.archives-ouvertes.fr/tel-00007694.
Full textAbstract:
Nous étudions les groupes quantiques dans un cadre d'algèbres d'opérateurs : les espaces quantiques sous-jacents sont des C*-algèbres ou des algèbres de von Neumann. Nous donnons des exemples comme extensions de groupes par des duaux de groupes. Ceci fournit les premiers exemples de groupes quantiques non-semi-réguliers. Nous étudions les coactions extérieures sur des facteurs et plus particulièrement sur les facteurs d'Araki-Woods libres. Nous introduisons un invariant T pour les groupes quantiques et l'utilisons pour démontrer que certains groupes quantiques ne peuvent que coagir extérieurement sur des facteurs de type III.
4
Shapiro, Yakov (Yakov Mikhaylovich). "Extension of the Hodge theorem to certain non-compact manifolds." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/41724.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mathematics, 2007.Includes bibliographical references (p. 92).
We prove an analogue of the Hodge cohomology theorem for a certain class of non-compact manifolds. Specifically, let M be a compact manifold with boundary OM, and let g be a metric on Int(M). Assume that there exists a collar neighborhood of the boundary ... We then describe doubly weighted Sobolev spaces on M. For elements of these spaces the harmonic parts of w1 and w2 lie in one Sobolev space, while the non-harmonic parts of w1 and w2 lie in a differently defined Sobolev space. We prove that ... is Fredholm on almost all of these doubly weighted spaces, except for a finite number of values of w. This gives us an analogue of the Hodge decomposition theorem and leads to the result. This work generalizes earlier theorems of Atiyah, Patodi and Singer for b-metrics (case a = b = 0) and of Melrose for scattering metrics (case a = b = 1).
by Yakov Shapiro.
Ph.D.
5
Bhattacharjee, Papiya. "Minimal Prime Element Space of an Algebraic Frame." Bowling Green State University / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1243364652.
Full text
6
Della, Sala Giuseppe. "Geometric properties of non-compact CR manifolds." Doctoral thesis, Scuola Normale Superiore, 2007. http://hdl.handle.net/11384/85684.
Full text
7
Monteblanco, Vinces Alejandro. "The Extension of Collective Agreements Within Collective Bargaining at Company Level." Derecho & Sociedad, 2017. http://repositorio.pucp.edu.pe/index/handle/123456789/118932.
Full textAbstract:
In this article, a review is conducted to the implementation of Peruvian law of collective agreements and their impact at company level. To achieve this purpose, in principle we mentioned what the Peruvian labor laws and their current application, and then compared with other Latin American visions, and finally outline a more peaceful solution considering the guidelines of the International Labour Organization labor standards and our constitutional current.En el presente artículo, se realizará una crítica a la aplicación de la legislación peruana de los convenios colectivos y sus efectos a nivel de empresa. Para alcanzar tal finalidad, en principio analizaremos lo que menciona la normativa laboral peruano y su aplicación actual, para luego compararla con otras visiones latinoamericanas, y finalmente, esbozar una solución más pacifica considerando los lineamientos de la Organización Internacional de Trabajo y nuestra normativa constitucional laboral vigente.
8
Mey, Jan. "Law and the extension of the human presence with Moon 2.0 - update to Global Compact 2.0?" Thesis, McGill University, 2008. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=21973.
Full textAbstract:
In 1969, humans set foot on the lunar surface for the first time. The space race of the cold war era was at its peak with Moon 1.0. Almost four decades later, there is renewed interest in returning to the Moon and going beyond. This time, the extension of the human presence into outer space is meant to be permanent and sustainable. Space exploration is to be brought into the economic sphere with Moon 2.0. The activities of the public sector mainly represented in the Global Exploration Strategy and those of the private sector, which have been highlighted by the Google Lunar X PRIZE are surveyed and contrasted against the core international legal framework. Arguing that the private sector can play a unique role in reconciling inclusive social interests for the benefit of mankind with their current exclusive economic priorities, the United Nations Global Compact is offered as a suitable gateway.C'est en 1969 que l'homme a mis pieds sur la lune pour la première fois. La course vers l'espace à l'époque de la guerre froide était a son apogée avec Lune 1.0. Près de quatre décades plus tard, l'intérêt de retourner vers la lune et d'aller même encore plus loin est de nouveau réveillé. Cette fois-ci, on a l'intention d'assurer l'extension de la présence humaine dans l'espace de façon permanente et durable. L'exploration spatiale doit gagner une dimension économique avec Lune 2.0. Les activités du secteur public représentées surtout par la Stratégie mondiale d'exploration et celles secteur privé qui ont été mises en évidence par le concours Google Lunar X PRIZE, sont examinées et comparées au principes fondamentales du droit international. Invoquant l'argument que le secteur privé peut jouer un rôle unique en conciliant les intérêts sociaux pour le bienfait de l'humanité et les priorités économiques actuelles excluantes, le Pacte Mondial des Nations Unies est proposé comme moyen d'accès approprié.
9
Sarkis, Frédéric. "Extension des fonctions cr-meromorphes et probleme du bord dans les varietes kahleriennes compactes." Paris 6, 1999. http://www.theses.fr/1999PA066457.
Full textAbstract:
Nous donnons une caractis'erisation du probliseme du bord dans les variis'etis'es de la forme $$x = u istimes isomega$$ oisu $$u$$ est une variis'etis'e complexe connexe et $$isomega$$ est une variis'etis'e kis"ahlis'erienne disque convexe. Comme consis'equence, nous obtenons de nouvelles dis'emonstrations de ris'esultats de harvey-lawson, dolbeault-henkin et dinh. Nous obtenons aussi une gis'enis'eralisation des this'eorisemes de hartogs-levi et hartogs-bochner. Enfin, nous montrons qu'une structure cr strictement pseudo-convexe plongeable dans une variis'etis'e kis"ahlis'erienne disque-convexe est plongeable dans $$isccn$$ si et seulement si elle admet une fonction cr non constante. En ris'eponse isa une question de harvey et lawson, on montre le ris'esultat suivant : soient $$y issubset isccn$$ un compacte polynomialement convexe et $$isomega$$ un domaine de $$isccn$$. Alors tout application cr-mis'eromorphe dis'efinie sur $$ispartial isomega$$ et isa valeurs dans une variis'etis'e projective $$v$$ admet une extension mis'eromorphe $$f : isomega isrightarrow v$$. La notion de fonction cr-mis'eromorphe est is'etendue au cas des variis'etis'es cr. Nous donnons alors une autre dis'emonstration du this'eoriseme d'extension cr-mis'eromorphe pouvant se gis'enis'eraliser au cas de la codimension supis'erieure. Comme application de ce ris'esultat, nous montrons que la structure cr d'andreotti-rossi n'est pas plongeable dans l'espace projectif. Nous montrons aussi que les fonctions holomorphes (resp. Meromorphes) au voisinage d'une hypersurface ris'eelle $$m$$ de $$pn (iscc)$$ ($$n isgeq 2$$) admettent une extension holomorphe (resp. Mis'eromorphe) isa l'un des deux cotis'es de $$m$$. En collaboration avec t. C dinh, nous obtenons un this'eoriseme de wedge removability pour les ensemble de mesure de hausdorff de codimension deux nulle. Ce dernier this'eoriseme associis'e a un ris'esultat de marker-porten permet de montrer l'extension des fonctions cr-mis'eromorphes en codimension supis'erieure.
10
Karlubíková, Michaela. "Podnikatelský záměr." Master's thesis, Vysoké učení technické v Brně. Fakulta podnikatelská, 2012. http://www.nusl.cz/ntk/nusl-223736.
Full textAbstract:
Topic of this thesis is to create a practicable business plan for foundation e-shop with hair. Specifically, the hair used for extensions. Company will be founded as limited liability company. The theoretical part deals with setting up company and creating business plan.
Books on the topic "Compact extensions"
1
United States. Congress. House. Committee on Energy and Commerce. Subcommittee on Health and the Environment. Granting additional market exclusivity to the drug Ansaid: Hearing before the Subcommittee on Health and the Environment of the Committee on Energy and Commerce, House of Representatives, One Hundred Second Congress, second session, February 20, 1992. Washington: U.S. G.P.O., 1992.
Find full text
2
Company, Western Union Telegraph. Statement of the origin, organization and progress of the Russian-American Telegraph, Western extension, Collins' overland line via Behring Strait and Asiatic Russia to Europe. [Rochester, N.Y.?: s.n., 1987.
Find full text
3
), San Francisco (Calif. Extension agreement between the City and County of San Francisco and the Turlock Irrigation District for the extension of the short term contract for the sale and purchase of electric power. [San Francisco, CA?]: San Francisco Public Utilities Commission?, 1987.
Find full text
4
), San Francisco (Calif. Extension agreement between the City and County of San Francisco and the Modesto Irrigation District for the extension of the short term contract for the sale and purchase of electric power. [San Francisco, CA?]: San Francisco Public Utilities Commission?, 1987.
Find full text
5
Company, Western Union Telegraph. Statement of the origin, organization and progress of the Russian-American Telegraph, Western Union extension, Collins' overland line via Behring Strait and Asiatic Russia to Europe. [Rochester, N.Y.?: s.n., 1987.
Find full text
6
Assembly, Canada Legislature Legislative. Bill: An act to grant additional aid to the Canadian Line of Steamers, and for the extension of the line of telegraph to Belle-Isle. Quebec: Thompson, 2002.
Find full text
7
Jorgensen, Palle, Feng Tian, and Steen Pedersen. Extensions of Positive Definite Functions: Applications and Their Harmonic Analysis. Springer International Publishing AG, 2016.
Find full text
8
Jorgensen, Palle, Feng Tian, and Steen Pedersen. Extensions of Positive Definite Functions: Applications and Their Harmonic Analysis. Springer London, Limited, 2016.
Find full text
9
Senate, United States, United States Congress, and Committee on Energy and Natural Resources. Extension of funding and program assistance under the Compact of Free Association. CreateSpace Independent Publishing Platform, 2018.
Find full text
10
Notebooks, Creacom. I'm Not Crazy Because I'm an Extension Ranger I'm Crazy Because I Like It: Personal Extension Ranger Notebook, Journal Gift, Diary, Doodle Gift or Notebook 6 X 9 Compact Size- 109 Blank Lined Pages. Independently Published, 2020.
Find full textBook chapters on the topic "Compact extensions"
1
Arhangel’skii, A. V. "Compact Extensions." In Encyclopaedia of Mathematical Sciences, 59–76. Berlin, Heidelberg: Springer Berlin Heidelberg, 1996. http://dx.doi.org/10.1007/978-3-642-77030-2_7.
Full text
2
Møller, Jesper Michael. "Extensions of p-compact Groups." In Algebraic Topology: New Trends in Localization and Periodicity, 307–27. Basel: Birkhäuser Basel, 1996. http://dx.doi.org/10.1007/978-3-0348-9018-2_23.
Full text
3
Sołtan, Piotr. "Self-Adjoint Extensions of Symmetric Operators." In Compact Textbooks in Mathematics, 145–63. Cham: Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-92061-0_11.
Full text
4
Roof, Larry, and Dan Fergus. "Smart Device Extensions." In The Definitive Guide to the .NET Compact Framework, 33–74. Berkeley, CA: Apress, 2003. http://dx.doi.org/10.1007/978-1-4302-0789-4_2.
Full text
5
Cuccuru, Arnaud, Jean-Luc Dekeyser, Philippe Marquet, and Pierre Boulet. "Towards UML 2 Extensions for Compact Modeling of Regular Complex Topologies." In Model Driven Engineering Languages and Systems, 445–59. Berlin, Heidelberg: Springer Berlin Heidelberg, 2005. http://dx.doi.org/10.1007/11557432_34.
Full text
6
Hazod, W. "Semistability and Domains of Attraction on Compact Extensions of Nilpotent Groups." In Probability Measures on Groups X, 189–204. Boston, MA: Springer US, 1991. http://dx.doi.org/10.1007/978-1-4899-2364-6_15.
Full text
7
Jia, Zhenguo. "Design Design of Compact PLC PLC Analog Input Extension Extension." In 2011 International Conference in Electrics, Communication and Automatic Control Proceedings, 69–73. New York, NY: Springer New York, 2011. http://dx.doi.org/10.1007/978-1-4419-8849-2_10.
Full text
8
Mortini, Raymond, and Rudolf Rupp. "The algebras Cb(X, $$ \mathbb{K} $$ ) and C(X, $$ \mathbb{K} $$ ) on non-compact spaces." In Extension Problems and Stable Ranks, 1116–52. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-73872-3_21.
Full text
9
Okada, Susumu. "Does a compact operator admit a maximal domain for its compact linear extension?" In Vector Measures, Integration and Related Topics, 313–22. Basel: Birkhäuser Basel, 2009. http://dx.doi.org/10.1007/978-3-0346-0211-2_28.
Full text
10
Hines, Peter. "On Strictifying Extensional Reflexivity in Compact Closed Categories." In Samson Abramsky on Logic and Structure in Computer Science and Beyond, 917–71. Cham: Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-24117-8_25.
Full textConference papers on the topic "Compact extensions"
1
Jeong, Taemin, Yoonpyo Hong, and Kwanjung Yee. "Extension of the Analytic Vortex Ring State Model for eVTOL Application." In Vertical Flight Society 80th Annual Forum & Technology Display, 1–12. The Vertical Flight Society, 2024. http://dx.doi.org/10.4050/f-0080-2024-1083.
Full textAbstract:
The engineering model determining the onset of Vortex Ring State (VRS) was applied to eVTOL aircraft, and the effect of different landing trajectories and aircraft drag was investigated. Next, the new model to compare the VRS susceptibility according to the different blade geometries and trajectories is proposed by extending Ahlin & Brown's model to incorporate the two-dimensional thrust and inflow distribution on the rotor disc. For validation, two different trajectories crossing the boundary of the onset of the VRS were simulated, and the results were compared with the Vorticity Transport Method (VTM). Furthermore, the disturbance distribution of moderately and highly twisted blades are compared. The extended model can capture the physical phenomena by the distribution of the disturbances and reflect the effect of blade geometries and trajectories. It is essential to investigate the model further through a correlation analysis using experiments or numerical analysis.
2
Wu, Shengjia, Shin-Jang Sung, Jwo Pan, Poh-Sang Lam, and Douglas A. Scarth. "Crack Extensions in Compact Tension Specimens of Hydrided Irradiated Zr-2.5Nb Materials Using Cohesive Zone Model." In ASME 2017 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/pvp2017-65022.
Full textAbstract:
The crack extension in a compact tension specimen of hydrided irradiated Zr-2.5Nb material is investigated by a two-dimensional plane stress finite element analysis. The stress-strain relation of the Zr-2.5Nb material for the finite element analysis is obtained from fitting the experimental tensile stress-strain curve of the irradiated Zr-2.5Nb material without hydrides by a three-dimensional finite element analysis. The calibration of the cohesive zone model with a trapezoidal traction-separation law is based on fitting the load-displacement-crack extension experimental data of a compact tension specimen of hydrided irradiated Zr-2.5Nb material. The general trends of the load-displacement, crack extension-displacement, and load-crack extension curves obtained from the finite element analysis based on the calibrated cohesive zone model are in agreement with the experimental data.
3
Tsakiridis, Nikolaos L., John B. Theocharis, Raul Perez, Antonio Gonzalez, and George C. Zalidis. "Extensions of the DECO3R algorithm for generating compact and cooperating Fuzzy Rule-based Classification Systems." In 2016 IEEE International Conference on Fuzzy Systems (FUZZ-IEEE). IEEE, 2016. http://dx.doi.org/10.1109/fuzz-ieee.2016.7737857.
Full text
4
Banitalebi-Dehkordi, Amin. "Knowledge Distillation for Low-Power Object Detection: A Simple Technique and Its Extensions for Training Compact Models Using Unlabeled Data." In 2021 IEEE/CVF International Conference on Computer Vision Workshops (ICCVW). IEEE, 2021. http://dx.doi.org/10.1109/iccvw54120.2021.00091.
Full text
5
Williams, Bruce W., William R. Tyson, C. Hari M. Simha, and Bogdan Wasiluk. "Specimen Curvature and Size Effects on Crack Growth Resistance From Compact Tension Specimens of CANDU Pressure Tubes." In ASME 2019 Pressure Vessels & Piping Conference. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/pvp2019-93318.
Full textAbstract:
Abstract CSA Standard N285.8 requires leak-before-break and fracture protection for Zr-2.5Nb pressure tubes in operating CANDU reactors. In-service deuterium uptake causes the formation of hydrides, which can result in additional variability and reduction of fracture toughness. Pressure tube fracture toughness is assessed mainly through rising pressure tube section burst tests. Given the length of the ex-service pressure tubes required for burst testing and the requirement to increase the hydrogen content of irradiated ex-service pressure tubes, only a limited number of burst tests can be performed. Using small-scale compact tension, C(T), specimens are advantageous for obtaining a statistically significant number of fracture toughness measurements while using less ex-service pressure tube material. This work focuses on the study of C(T) geometry designs in order to obtain crack growth resistance and fracture toughness closer to those deduced from burst tests. Because C(T) specimens must be machined from pressure tubes of about 100 mm in diameter and 4 mm in wall thickness, they are out-of-plane curved. As well, they undergo significant tunnelling during crack extension. These two factors can result in a violation of the ASTM standard for fracture toughness testing. The current work examined the influence of specimen curvature and tunnelled crack front on the crack growth resistance curve, or J-R curve. Finite element (FE) models using stationary and growing cracks were used in a detailed numerical investigation. To capture crack tunnelling in the FE models, a damage mechanics approach was adopted, with the critical strain to accumulate damage being a function of crack front stress triaxiality. The J-integral numerically estimated from the domain integral approach was compared to the J-integral calculated from the analytical equations in the ASTM E-1820 standard. In most cases, the difference between the numerical and the standard estimations was less than 10%, which was considered acceptable. It was found that at higher load levels of load-line-displacement, specimen curvature influenced the J-integral results. Crack tunnelling was shown to have a small influence on the estimated J-integrals, in comparison with the straight crack fronts. A modest number of experiments were carried out on unirradiated Zr-2.5Nb pressure tube material using three designs of curved C(T) specimens. It was found that the specimens of both designs that featured a width of 34 mm had more than twice the crack extension of the specimens of the 17-mm width design. The 17-mm width specimens are used mainly to assess the small-scale fracture toughness of pressure tube material. Additionally, the applied J-integral at the maximum load was about 1.4 times higher for the larger-width C(T) specimens. These C(T) specimens also produced J-R curves with greater crack extensions, which were closer to those obtained from the pressure tube section burst tests. Artificially hydrided pressure tube material was not considered in the current work, to avoid any potential source of experimental variability; however, it should be considered in future work.
6
Opalski, Anthony B., and Mark P. Wernet. "Development of Optical Diagnostics for Multiphase Flow Velocity Measurements." In ASME 2005 International Mechanical Engineering Congress and Exposition. ASMEDC, 2005. http://dx.doi.org/10.1115/imece2005-80822.
Full textAbstract:
The NASA Glenn Research Center Two-Phase Flow Facility (TΦFFy) project is conducting a robust technology program to develop enabling products for advanced life support and power conversion systems. Future system safety and reliability will be enhanced by addressing focused microgravity fluid physics issues associated with flow boiling and multi-phase system stability. The project includes both normal gravity testing and reduced gravity aircraft flight campaigns. The development of novel compact heat exchanger designs for use in reduced gravity operations requires advanced quantitative planar velocimetry diagnostics in order to verify system performance. The development of a comprehensive package of non-intrusive and non-invasive optical diagnostics to provide phasic velocity information throughout the range of flow boiling regimes in both gravity and microgravity-based test rigs is discussed. The application of both point-based probe techniques and planar-based imaging techniques to obtain phasic velocity information is analyzed. The application of planar and stereo imaging techniques to multiple flow regimes is presented. Extensions of liquid film thickness and local void fraction measurement techniques are examined to evaluate their potential to provide velocity information for interfacial waves and global void interface tracking. The extension of development efforts applied to ground-based test rigs into aircraft-based microgravity rigs is also presented.
7
De Groot, P. J., Gregg M. Gallatin, and S. H. Macomber. "Ranging and velocimetry signal generation in a backscatter-modulated laser diode." In OSA Annual Meeting. Washington, D.C.: Optica Publishing Group, 1988. http://dx.doi.org/10.1364/oam.1988.mo3.
Full textAbstract:
A compact self-aligning laser radar has been constructed for coherent ranging and velocimetry using a laser diode modulated by feedback from light scattered from a diffusing target. The phenomenology of beat-signal generation in the device is discussed from both experimental and theoretical points of view. The ac-coupled modulation waveform is asymmetric (similar to a sawtooth) and different for the two propagation directions of the light leaving the diode. A theoretical model, based on the mode structure of a three-mirror Fabry-Perot cavity, is shown to describe the signal generation in these experiments, to account for the sawtooth waveform, and to predict the modulation depth of the waveform. Possible applications and extensions of this technology are briefly discussed.
8
Khodzhimuratova, Assem, Daulet Muratkhanov, Raushan Temirkhanova, Yerlan Aksholakov, and Yerbol Uralbayev. "THE STRUCTURAL AND TECTONIC POSITION OF KARST DEPOSITS OF LEAD AND ZINC IN THE GREATER KARATAU RIDGE (SOUTHERN KAZAKHSTAN)." In 22nd SGEM International Multidisciplinary Scientific GeoConference 2022. STEF92 Technology, 2022. http://dx.doi.org/10.5593/sgem2022/1.1/s01.006.
Full textAbstract:
In recent years, the geological service of Kazakhstan has been assigned the task of searching for sites where ores would meet modern industrial requirements. It has become a matter of re-evaluation of lead-zinc deposits and of identification among them of promising non-traditional commercially genetic types. One of these is the karst type, which has the following features: high lead and zinc content, compact ore deposits, effective ore enrichment, wide development in Kazakhstan of carbonate rocks with lead-zinc mineralisation, potentially promising rich karst ores. One of the regions in Kazakhstan with widespread development of the most favourable karst-forming carbonate rocks with numerous occurrences of stratified lead-zinc mineralisation and extensive development of both palaeokarst and modern karst is the Big Karatau. Lead-zinc deposits and ore occurrences represent the main group of ore formations for Karatau, which determine the metallogenic profile of the region. A simpler approach to the identification of transverse zones was proposed using the lead geochemical field. The map of the lead geochemical field (figure) clearly shows that the individual anomalies are combined into zones with northwest and northeast extensions. We interpret the latter as stretching zones developing across the compression zones of the northwestern (Karatau) strike of the structures. Geochemical halos are formed by ore matter "flowing" from the compression zones into the extension zones.
9
Smith, J. Cole, Alfonso Ortega, Colleen M. Gabel, and Dale Henderson. "Parameter Optimization for a Temperature Estimation Model." In ASME 2003 International Electronic Packaging Technical Conference and Exhibition. ASMEDC, 2003. http://dx.doi.org/10.1115/ipack2003-35254.
Full textAbstract:
We consider a problem arising in designing Compact Thermal Models (CTMs) for the purpose of simulating the thermal response of a package. CTMs are often preferred over more detailed models due to their minimal representation and the reduced computations required to obtain accurate nodal temperature predictions under hypothetical scenarios. The quality of CTM performance depends on the determination of an appropriate set of parameters that drive the model. The subject of this paper is a heuristic nonlinear optimization approach to computing the set of CTM parameters that best predicts the thermal response of a package. Our algorithm solves a series of one-dimensional nonconvex optimization problems to obtain these parameters, exploiting the special structure of the CTM in order to improve both the execution time of the algorithm and the quality of the CTM performance. We conclude the paper by providing a brief array of computational results as a proof of concept, along with several possible future research extensions.
10
Hayes, Layton, Prashant Doshi, Swaraj Pawar, and Hari Teja Tatavarti. "State-Based Recurrent SPMNs for Decision-Theoretic Planning under Partial Observability." In Thirtieth International Joint Conference on Artificial Intelligence {IJCAI-21}. California: International Joint Conferences on Artificial Intelligence Organization, 2021. http://dx.doi.org/10.24963/ijcai.2021/348.
Full textAbstract:
The sum-product network (SPN) has been extended to model sequence data with the recurrent SPN (RSPN), and to decision-making problems with sum-product-max networks (SPMN). In this paper, we build on the concepts introduced by these extensions and present state-based recurrent SPMNs (S-RSPMNs) as a generalization of SPMNs to sequential decision-making problems where the state may not be perfectly observed. As with recurrent SPNs, S-RSPMNs utilize a repeatable template network to model sequences of arbitrary lengths. We present an algorithm for learning compact template structures by identifying unique belief states and the transitions between them through a state matching process that utilizes augmented data. In our knowledge, this is the first data-driven approach that learns graphical models for planning under partial observability, which can be solved efficiently. S-RSPMNs retain the linear solution complexity of SPMNs, and we demonstrate significant improvements in compactness of representation and the run time of structure learning and inference in sequential domains.
Reports on the topic "Compact extensions"
1
Baader, Franz, Gerhard Brewka, and Oliver Fernández Gil. Adding Threshold Concepts to the Description Logic EL. Technische Universität Dresden, 2015. http://dx.doi.org/10.25368/2022.215.
Full textAbstract:
We introduce an extension of the lightweight Description Logic EL that allows us to de_ne concepts in an approximate way. For this purpose, we use a graded membership function, which for each individual and concept yields a number in the interval [0, 1] expressing the degree to which the individual belongs to the concept. Threshold concepts C~t for ~ then collect all the individuals that belong to C with degree ~ t. We generalize a well-known characterization of membership in EL concepts to construct a specific graded membership function deg, and investigate the complexity of reasoning in the Description Logic τEL(deg), which extends EL by threshold concepts defined using deg. We also compare the instance problem for threshold concepts of the form C>t in τEL(deg) with the relaxed instance queries of Ecke et al.
2
Kodupuganti, Swapneel R., Sonu Mathew, and Srinivas S. Pulugurtha. Modeling Operational Performance of Urban Roads with Heterogeneous Traffic Conditions. Mineta Transportation Institute, January 2021. http://dx.doi.org/10.31979/mti.2021.1802.
Full textAbstract:
The rapid growth in population and related demand for travel during the past few decades has had a catalytic effect on traffic congestion, air quality, and safety in many urban areas. Transportation managers and planners have planned for new facilities to cater to the needs of users of alternative modes of transportation (e.g., public transportation, walking, and bicycling) over the next decade. However, there are no widely accepted methods, nor there is enough evidence to justify whether such plans are instrumental in improving mobility of the transportation system. Therefore, this project researches the operational performance of urban roads with heterogeneous traffic conditions to improve the mobility and reliability of people and goods. A 4-mile stretch of the Blue Line light rail transit (LRT) extension, which connects Old Concord Rd and the University of North Carolina at Charlotte’s main campus on N Tryon St in Charlotte, North Carolina, was considered for travel time reliability analysis. The influence of crosswalks, sidewalks, trails, greenways, on-street bicycle lanes, bus/LRT routes and stops/stations, and street network characteristics on travel time reliability were comprehensively considered from a multimodal perspective. Likewise, a 2.5-mile-long section of the Blue Line LRT extension, which connects University City Blvd and Mallard Creek Church Rd on N Tryon St in Charlotte, North Carolina, was considered for simulation-based operational analysis. Vissim traffic simulation software was used to compute and compare delay, queue length, and maximum queue length at nine intersections to evaluate the influence of vehicles, LRT, pedestrians, and bicyclists, individually and/or combined. The statistical significance of variations in travel time reliability were particularly less in the case of links on N Tryon St with the Blue Line LRT extension. However, a decrease in travel time reliability on some links was observed on the parallel route (I-85) and cross-streets. While a decrease in vehicle delay on northbound and southbound approaches of N Tryon St was observed in most cases after the LRT is in operation, the cross-streets of N Tryon St incurred a relatively higher increase in delay after the LRT is in operation. The current pedestrian and bicycling activity levels seemed insignificant to have an influence on vehicle delay at intersections. The methodological approaches from this research can be used to assess the performance of a transportation facility and identify remedial solutions from a multimodal perspective.
3
Alwan, Iktimal, Dennis D. Spencer, and Rafeed Alkawadri. Comparison of Machine Learning Algorithms in Sensorimotor Functional Mapping. Progress in Neurobiology, December 2023. http://dx.doi.org/10.60124/j.pneuro.2023.30.03.
Full textAbstract:
Objective: To compare the performance of popular machine learning algorithms (ML) in mapping the sensorimotor cortex (SM) and identifying the anterior lip of the central sulcus (CS). Methods: We evaluated support vector machines (SVMs), random forest (RF), decision trees (DT), single layer perceptron (SLP), and multilayer perceptron (MLP) against standard logistic regression (LR) to identify the SM cortex employing validated features from six-minute of NREM sleep icEEG data and applying standard common hyperparameters and 10-fold cross-validation. Each algorithm was tested using vetted features based on the statistical significance of classical univariate analysis (p<0.05) and extended () 17 features representing power/coherence of different frequency bands, entropy, and interelectrode-based distance. The analysis was performed before and after weight adjustment for imbalanced data (w). Results: 7 subjects and 376 contacts were included. Before optimization, ML algorithms performed comparably employing conventional features (median CS accuracy: 0.89, IQR [0.88-0.9]). After optimization, neural networks outperformed others in means of accuracy (MLP: 0.86), the area under the curve (AUC) (SLPw, MLPw, MLP: 0.91), recall (SLPw: 0.82, MLPw: 0.81), precision (SLPw: 0.84), and F1-scores (SLPw: 0.82). SVM achieved the best specificity performance. Extending the number of features and adjusting the weights improved recall, precision, and F1-scores by 48.27%, 27.15%, and 39.15%, respectively, with gains or no significant losses in specificity and AUC across CS and Function (correlation r=0.71 between the two clinical scenarios in all performance metrics, p<0.001). Interpretation: Computational passive sensorimotor mapping is feasible and reliable. Feature extension and weight adjustments improve the performance and counterbalance the accuracy paradox. Optimized neural networks outperform other ML algorithms even in binary classification tasks. The best-performing models and the MATLAB® routine employed in signal processing are available to the public at (Link 1).
4
Yoel, David, Tina Sicilia, Matthew Bogaart, and Jeremy Fernandes. PR-417-203902-R01 Remote Sensing and Leak Detection Platform That Can Deploy Multiple Sensor Types. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), January 2024. http://dx.doi.org/10.55274/r0000052.
Full textAbstract:
The PRCI Project #417-203902 - ROW 3-1-A Final Report is attached for Member review and comment. The report includes a summary of all work completed in all Tasks which include: - Catalog, taxonomy, and sample data set for the threats detected. - Benchmarks of the sensitivity, accuracy, reliability, and robustness of an automated multi sensor, multi-threat detection and near real-time reporting comparing performance on conventional aircraft and UAS. - Technical synopsis for operators on integrating automated near real-time aerial threat reports into pipeline performance and safety improvement programs. - Report on status of integrating UAS into the National Airspace System in an application that contributes to improving the safety and integrity of the Nation's critical pipeline infrastructure. The project is complete. Full testing on the multi-spectral sensor is complete and Flight 4 of Phase 1 Flight Tests, scheduled for Oct/Nov 2021 was completed with approval of a no-cost extension in 2022. These delayed tasks are excusable due to delays caused in 2020 and 2021 by Novel Coronavirus (2019-nCoV), inclement weather and wildfires impacting several western states, and aviation delays (i.e., licenses from government authorities, misrepresentation of the specification and performance of the Sentera camera), which caused impacts to the contractor's capability to maintain a schedule under ROW 3-1-A and were completed under extension under ROW-3-1. The scope for this research project is to integrate PRCI Project ROW-3-1 multi-threat sensors, algorithms and communications systems onto the unmanned aircraft system (UAS); select Test Range(s) and complete Threat Staging Planning, while developing an Aviation Safety Case to the FAA for use of long endurance UAS on pipeline patrol. In addition, the project includes conducting UAS Test Program flights with automated multi-threat detection system on long endurance UAS flying hundreds of miles of pipeline corridor and perform analysis of data, benchmark automated threat detection system and UAS performance, report on advances in the integration of the remote sensing platform outputs with existing pipeline operator performance and safety programs. Lastly, it provided data of value to the FAA with respect to the integration of long-range Unmanned Aircraft Systems (UASs) into the National Airspace System. The program objectives stated in the contract include: - Produce a data set that enables benchmarking the sensitivity, accuracy, reliability and robustness of an automated multi-sensor, multi-threat detection and near real-time reporting system operating on a long-range Unmanned Aircraft System (UAS) for damage prevention and other pipeline integrity applications. - Generate data to compare and benchmark the detection and reporting system operating on conventional aircraft and UAS and with standard patrol methods for evaluating the value of integrating generated threat reports into performance and safety improvement programs. - Provide data to the United States Department of Transportation (US DOT) Federal Aviation Administration (FAA), PHMSA, and the PRCI research team to assist with information for safe integration of UAS into the National Airspace System for pipeline infrastructure.
5
Kohon, Jorge. Ferrocarriles suburbanos de pasajeros en América Latina: banco de datos, caracterización, indicadores y benchmarks. Edited by Julieta Abad, Cristian Moleres, and Lorena Peinado. Banco Interamericano de Desarrollo, August 2022. http://dx.doi.org/10.18235/0004410.
Full textAbstract:
Se denominan servicios ferroviarios de pasajeros suburbanos a los que se prestan entre el centro de una ciudad cabecera mediana a grande y sus suburbios y otras ciudades cercanas, movilizando volúmenes muy importantes de pasajeros que en general viajan diariamente en servicios que tienen menos de 100 km entre estaciones extremas. Son siete los países de la región que cuentan con servicios ferroviarios de pasajeros suburbanos: Argentina, Brasil, Chile, Costa Rica, México, Uruguay y Venezuela. De ellos, resultan relevantes en el desempeño de cinco de las grandes áreas metropolitanas de América Latina: San Pablo, Río de Janeiro y Belo Horizonte en Brasil; Buenos Aires en Argentina; y Ciudad de México (CDMX) en ese país. En otras 14 ciudades de la región (de Argentina, Brasil, Chile, Costa Rica y Venezuela) poseen un rol menor pero también realizan aportes a la calidad de vida y la reducción de la congestión. Por sus efectos positivos en cuanto a la reducción de emisiones de gases de efecto invernadero, el transporte ferroviario de pasajeros es fundamental para apoyar la descarbonización del sector, contribuyendo así a la mitigación del Cambio Climático, uno de los pilares fundamentales de la Visión 2025 del BID: Reinvertir en las Américas. En sólo tres ciudades de la región los servicios se prestan mediante verdaderas redes ferroviarias, con múltiples líneas accediendo a diversas zonas de sus respectivas áreas metropolitanas: en San Pablo y Río de Janeiro en Brasil, y en Buenos Aires en Argentina. En las restantes, se trata de sistemas que tienen hasta dos líneas con menos de 100 kilómetros de extensión total. Aun así, en alguno de estos casos poseen relevancia en el movimiento de los pasajeros de sus respetivas áreas de influencia directa: son los casos de Belo Horizonte en Brasil y CDMX; en un nivel menor, los de Santiago y Valparaíso, ambos en Chile. Todos los datos acerca de los indicadores y benchmarks que se presentan en este documento se encuentran contenidos en la “Base de datos de ferrocarriles suburbanos en América Latina”. Se obtuvieron 56 indicadores y benchmarks para cada servicio, agrupados en 11 grandes temáticas. De estos, en este documento se revisa y compara los 14 índices más relevantes y que aportan información estratégica sobre los servicios y las empresas. Esa información permite, por un lado, entender la dimensión y características del nivel de actividad de cada uno de ellos, y por otro, mediante los benchmarks conocer la eficiencia operativa-financiera de su desempeño al compararlos con sus ferrocarriles pares (“peers”). Cabe mencionar que el documento no busca calificar ni valorizar ni juzgar mejores o peores desempeños empresariales, sino explicitarlos. Con el objetivo de hacer más comparables y graficables los indicadores y benchmarks, los distintos operadores fueron agrupados en función de la demanda anual que trasladaron en 2018.
6
McCarthy, Noel, Eileen Taylor, Martin Maiden, Alison Cody, Melissa Jansen van Rensburg, Margaret Varga, Sophie Hedges, et al. Enhanced molecular-based (MLST/whole genome) surveillance and source attribution of Campylobacter infections in the UK. Food Standards Agency, July 2021. http://dx.doi.org/10.46756/sci.fsa.ksj135.
Full textAbstract:
This human campylobacteriosis sentinel surveillance project was based at two sites in Oxfordshire and North East England chosen (i) to be representative of the English population on the Office for National Statistics urban-rural classification and (ii) to provide continuity with genetic surveillance started in Oxfordshire in October 2003. Between October 2015 and September 2018 epidemiological questionnaires and genome sequencing of isolates from human cases was accompanied by sampling and genome sequencing of isolates from possible food animal sources. The principal aim was to estimate the contributions of the main sources of human infection and to identify any changes over time. An extension to the project focussed on antimicrobial resistance in study isolates and older archived isolates. These older isolates were from earlier years at the Oxfordshire site and the earliest available coherent set of isolates from the national archive at Public Health England (1997/8). The aim of this additional work was to analyse the emergence of the antimicrobial resistance that is now present among human isolates and to describe and compare antimicrobial resistance in recent food animal isolates. Having identified the presence of bias in population genetic attribution, and that this was not addressed in the published literature, this study developed an approach to adjust for bias in population genetic attribution, and an alternative approach to attribution using sentinel types. Using these approaches the study estimated that approximately 70% of Campylobacter jejuni and just under 50% of C. coli infection in our sample was linked to the chicken source and that this was relatively stable over time. Ruminants were identified as the second most common source for C. jejuni and the most common for C. coli where there was also some evidence for pig as a source although less common than ruminant or chicken. These genomic attributions of themselves make no inference on routes of transmission. However, those infected with isolates genetically typical of chicken origin were substantially more likely to have eaten chicken than those infected with ruminant types. Consumption of lamb’s liver was very strongly associated with infection by a strain genetically typical of a ruminant source. These findings support consumption of these foods as being important in the transmission of these infections and highlight a potentially important role for lamb’s liver consumption as a source of Campylobacter infection. Antimicrobial resistance was predicted from genomic data using a pipeline validated by Public Health England and using BIGSdb software. In C. jejuni this showed a nine-fold increase in resistance to fluoroquinolones from 1997 to 2018. Tetracycline resistance was also common, with higher initial resistance (1997) and less substantial change over time. Resistance to aminoglycosides or macrolides remained low in human cases across all time periods. Among C. jejuni food animal isolates, fluoroquinolone resistance was common among isolates from chicken and substantially less common among ruminants, ducks or pigs. Tetracycline resistance was common across chicken, duck and pig but lower among ruminant origin isolates. In C. coli resistance to all four antimicrobial classes rose from low levels in 1997. The fluoroquinolone rise appears to have levelled off earlier and among animals, levels are high in duck as well as chicken isolates, although based on small sample sizes, macrolide and aminoglycoside resistance, was substantially higher than for C. jejuni among humans and highest among pig origin isolates. Tetracycline resistance is high in isolates from pigs and the very small sample from ducks. Antibiotic use following diagnosis was relatively high (43.4%) among respondents in the human surveillance study. Moreover, it varied substantially across sites and was highest among non-elderly adults compared to older adults or children suggesting opportunities for improved antimicrobial stewardship. The study also found evidence for stable lineages over time across human and source animal species as well as some tighter genomic clusters that may represent outbreaks. The genomic dataset will allow extensive further work beyond the specific goals of the study. This has been made accessible on the web, with access supported by data visualisation tools.
7
E, Flemyng, and Mitchell D. Increased versus stable doses of inhaled steroids for exacerbations of chronic asthma in adults and children: Protocol. Epistemonikos Interactive Evidence Synthesis, January 2022. http://dx.doi.org/10.30846/ies.b984bf9656.v3.
Full textAbstract:
Abstract Rationale Early treatment of asthma exacerbations with inhaled corticosteroids is the best strategy for management, although use of an increased or stable dose is questioned. Objectives To compare the clinical effectiveness and safety of increased versus stable doses of inhaled corticosteroids as part of a patient-initiated action plan for the home management of exacerbations in children and adults with persistent asthma. Search methods We searched the Cochrane Airways Group Specialised Register (part of CENTRAL), MEDLINE, Embase, CINAHL, major trials registries and handsearched abstracts up to 20 December 2021. Eligibility criteria Parallel and cross-over blinded randomised controlled trials (RCTs) Outcomes Treatment failure (the need for rescue oral steroids) in the randomised population and in the subset who initiated the study inhaler, unscheduled physician visits, unscheduled acute care, emergency department or hospital visits, serious and non-serious adverse events, and duration of exacerbation. Risk of bias We used Risk of Bias 2 (RoB 2)and the tool's extension for cross-over trials. Synthesis methods We conducted meta-analyses using fixed-effect models to calculate odds ratios (OR) and 95% confidence intervals (CI) for all but one outcome, which used random-effects models due to heterogeneity (treatment failure in the subset who initiated the study inhaler). We summarised certainty of evidence according to GRADE methods. Included studies We included nine RCTs (seven parallel and two cross‐over) with a total of 1923 participants. The studies were conducted in Europe, North America, and Australasia and were published between 1998 and 2018. Five studies evaluated adult populations (1247 participants; ≥ 15 years), and four studies evaluated child or adolescent populations (676 participants; < 15 years). Approximately 50% of randomised participants initiated the study inhaler (range 23% to 100%). The studies reported treatment failure in various ways, so we made assumptions to allow us to combine data. Synthesis of results People randomised to increase their inhaled corticosteroids dose at the first signs of an exacerbation probably had similar odds of needing rescue oral corticosteroids to those randomised to a placebo inhaler (OR 0.97, 95% CI 0.76 to 1.25; 8 studies, 1774 participants; moderate-certainty evidence). Results for the same outcome in the subset of participants who initiated the study inhaler (approximately 50%) gives a different point estimate with very low certainty due to heterogeneity, imprecision and risk of bias (OR 0.84, 95% CI 0.54 to 1.30; 7 studies, 766 participants; random-effects model used). For adverse effects, imprecision and risk of bias from missing data, outcome measurement and reporting meant we were very uncertain about the effect estimate (serious adverse events OR 1.69, 95% CI 0.77 to 3.71; 2 studies, 394 participants; non-serious adverse events OR 2.15, 95% CI 0.68 to 6.73; 2 studies, 142 participants). We had very low confidence in the effect estimates for unscheduled physician visits, unscheduled acute care, emergency department or hospital visits and duration of exacerbation due to risk of bias. Authors' conclusions Evidence suggests that adults and children with mild to moderate asthma are unlikely to have an important reduction in the need for oral steroids from increasing a patient's inhaled corticosteroid dose at the first sign of an exacerbation. Other clinically important benefits and potential harms cannot be ruled out due to wide confidence intervals, risk of bias in the studies, and assumptions made for synthesis when combining data. Included studies reflect evolving clinical practice and study methods, and the data do not support thorough investigation of effect modifiers such as baseline dose, fold increase, asthma severity and timing. The review does not include recent evidence from pragmatic, unblinded studies showing benefits of larger dose increases in those with poorly controlled asthma. Differences between the blinded and unblinded studies should be investigated. Funding This Cochrane Review had no dedicated funding. Registration Protocol (2009): doi.org/10.1002/14651858.CD007524 Original review (2010): doi.org/10.1002/14651858.CD007524.pub3 Review update (2014): doi.org/10.1002/14651858.CD007524.pub4
8
E, Flemyng, and Mitchell D. Increased versus stable doses of inhaled steroids for exacerbations of chronic asthma in adults and children: Protocol. Epistemonikos Interactive Evidence Synthesis, January 2022. http://dx.doi.org/10.30846/ies.b984bf9699.v2.
Full textAbstract:
Abstract Rationale Early treatment of asthma exacerbations with inhaled corticosteroids is the best strategy for management, although use of an increased or stable dose is questioned. Objectives To compare the clinical effectiveness and safety of increased versus stable doses of inhaled corticosteroids as part of a patient-initiated action plan for the home management of exacerbations in children and adults with persistent asthma. Search methods We searched the Cochrane Airways Group Specialised Register (part of CENTRAL), MEDLINE, Embase, CINAHL, major trials registries and handsearched abstracts up to 20 December 2021. Eligibility criteria Parallel and cross-over blinded randomised controlled trials (RCTs) Outcomes Treatment failure (the need for rescue oral steroids) in the randomised population and in the subset who initiated the study inhaler, unscheduled physician visits, unscheduled acute care, emergency department or hospital visits, serious and non-serious adverse events, and duration of exacerbation. Risk of bias We used Risk of Bias 2 (RoB 2)and the tool's extension for cross-over trials. Synthesis methods We conducted meta-analyses using fixed-effect models to calculate odds ratios (OR) and 95% confidence intervals (CI) for all but one outcome, which used random-effects models due to heterogeneity (treatment failure in the subset who initiated the study inhaler). We summarised certainty of evidence according to GRADE methods. Included studies We included nine RCTs (seven parallel and two cross‐over) with a total of 1923 participants. The studies were conducted in Europe, North America, and Australasia and were published between 1998 and 2018. Five studies evaluated adult populations (1247 participants; ≥ 15 years), and four studies evaluated child or adolescent populations (676 participants; < 15 years). Approximately 50% of randomised participants initiated the study inhaler (range 23% to 100%). The studies reported treatment failure in various ways, so we made assumptions to allow us to combine data. Synthesis of results People randomised to increase their inhaled corticosteroids dose at the first signs of an exacerbation probably had similar odds of needing rescue oral corticosteroids to those randomised to a placebo inhaler (OR 0.97, 95% CI 0.76 to 1.25; 8 studies, 1774 participants; moderate-certainty evidence). Results for the same outcome in the subset of participants who initiated the study inhaler (approximately 50%) gives a different point estimate with very low certainty due to heterogeneity, imprecision and risk of bias (OR 0.84, 95% CI 0.54 to 1.30; 7 studies, 766 participants; random-effects model used). For adverse effects, imprecision and risk of bias from missing data, outcome measurement and reporting meant we were very uncertain about the effect estimate (serious adverse events OR 1.69, 95% CI 0.77 to 3.71; 2 studies, 394 participants; non-serious adverse events OR 2.15, 95% CI 0.68 to 6.73; 2 studies, 142 participants). We had very low confidence in the effect estimates for unscheduled physician visits, unscheduled acute care, emergency department or hospital visits and duration of exacerbation due to risk of bias. Authors' conclusions Evidence suggests that adults and children with mild to moderate asthma are unlikely to have an important reduction in the need for oral steroids from increasing a patient's inhaled corticosteroid dose at the first sign of an exacerbation. Other clinically important benefits and potential harms cannot be ruled out due to wide confidence intervals, risk of bias in the studies, and assumptions made for synthesis when combining data. Included studies reflect evolving clinical practice and study methods, and the data do not support thorough investigation of effect modifiers such as baseline dose, fold increase, asthma severity and timing. The review does not include recent evidence from pragmatic, unblinded studies showing benefits of larger dose increases in those with poorly controlled asthma. Differences between the blinded and unblinded studies should be investigated. Funding This Cochrane Review had no dedicated funding. Registration Protocol (2009): doi.org/10.1002/14651858.CD007524 Original review (2010): doi.org/10.1002/14651858.CD007524.pub3 Review update (2014): doi.org/10.1002/14651858.CD007524.pub4
9
E, Flemyng, and Mitchell D. Increased versus stable doses of inhaled steroids for exacerbations of chronic asthma in adults and children: Update. Epistemonikos Interactive Evidence Synthesis, January 2022. http://dx.doi.org/10.30846/ies.b984bf9639.v2.
Full textAbstract:
Abstract Rationale Early treatment of asthma exacerbations with inhaled corticosteroids is the best strategy for management, although use of an increased or stable dose is questioned. Objectives To compare the clinical effectiveness and safety of increased versus stable doses of inhaled corticosteroids as part of a patient-initiated action plan for the home management of exacerbations in children and adults with persistent asthma. Search methods We searched the Cochrane Airways Group Specialised Register (part of CENTRAL), MEDLINE, Embase, CINAHL, major trials registries and handsearched abstracts up to 20 December 2021. Eligibility criteria Parallel and cross-over blinded randomised controlled trials (RCTs) Outcomes Treatment failure (the need for rescue oral steroids) in the randomised population and in the subset who initiated the study inhaler, unscheduled physician visits, unscheduled acute care, emergency department or hospital visits, serious and non-serious adverse events, and duration of exacerbation. Risk of bias We used Risk of Bias 2 (RoB 2)and the tool's extension for cross-over trials. Synthesis methods We conducted meta-analyses using fixed-effect models to calculate odds ratios (OR) and 95% confidence intervals (CI) for all but one outcome, which used random-effects models due to heterogeneity (treatment failure in the subset who initiated the study inhaler). We summarised certainty of evidence according to GRADE methods. Included studies We included nine RCTs (seven parallel and two cross‐over) with a total of 1923 participants. The studies were conducted in Europe, North America, and Australasia and were published between 1998 and 2018. Five studies evaluated adult populations (1247 participants; ≥ 15 years), and four studies evaluated child or adolescent populations (676 participants; < 15 years). Approximately 50% of randomised participants initiated the study inhaler (range 23% to 100%). The studies reported treatment failure in various ways, so we made assumptions to allow us to combine data. Synthesis of results People randomised to increase their inhaled corticosteroids dose at the first signs of an exacerbation probably had similar odds of needing rescue oral corticosteroids to those randomised to a placebo inhaler (OR 0.97, 95% CI 0.76 to 1.25; 8 studies, 1774 participants; moderate-certainty evidence). Results for the same outcome in the subset of participants who initiated the study inhaler (approximately 50%) gives a different point estimate with very low certainty due to heterogeneity, imprecision and risk of bias (OR 0.84, 95% CI 0.54 to 1.30; 7 studies, 766 participants; random-effects model used). For adverse effects, imprecision and risk of bias from missing data, outcome measurement and reporting meant we were very uncertain about the effect estimate (serious adverse events OR 1.69, 95% CI 0.77 to 3.71; 2 studies, 394 participants; non-serious adverse events OR 2.15, 95% CI 0.68 to 6.73; 2 studies, 142 participants). We had very low confidence in the effect estimates for unscheduled physician visits, unscheduled acute care, emergency department or hospital visits and duration of exacerbation due to risk of bias. Authors' conclusions Evidence suggests that adults and children with mild to moderate asthma are unlikely to have an important reduction in the need for oral steroids from increasing a patient's inhaled corticosteroid dose at the first sign of an exacerbation. Other clinically important benefits and potential harms cannot be ruled out due to wide confidence intervals, risk of bias in the studies, and assumptions made for synthesis when combining data. Included studies reflect evolving clinical practice and study methods, and the data do not support thorough investigation of effect modifiers such as baseline dose, fold increase, asthma severity and timing. The review does not include recent evidence from pragmatic, unblinded studies showing benefits of larger dose increases in those with poorly controlled asthma. Differences between the blinded and unblinded studies should be investigated. Funding This Cochrane Review had no dedicated funding. Registration Protocol (2009): doi.org/10.1002/14651858.CD007524 Original review (2010): doi.org/10.1002/14651858.CD007524.pub3 Review update (2014): doi.org/10.1002/14651858.CD007524.pub4
10
E, Flemyng, and Mitchell D. Increased versus stable doses of inhaled steroids for exacerbations of chronic asthma in adults and children: Protocol. Epistemonikos Interactive Evidence Synthesis, January 2022. http://dx.doi.org/10.30846/ies.b984bf9656.v2.
Full textAbstract:
Abstract Rationale Early treatment of asthma exacerbations with inhaled corticosteroids is the best strategy for management, although use of an increased or stable dose is questioned. Objectives To compare the clinical effectiveness and safety of increased versus stable doses of inhaled corticosteroids as part of a patient-initiated action plan for the home management of exacerbations in children and adults with persistent asthma. Search methods We searched the Cochrane Airways Group Specialised Register (part of CENTRAL), MEDLINE, Embase, CINAHL, major trials registries and handsearched abstracts up to 20 December 2021. Eligibility criteria Parallel and cross-over blinded randomised controlled trials (RCTs) Outcomes Treatment failure (the need for rescue oral steroids) in the randomised population and in the subset who initiated the study inhaler, unscheduled physician visits, unscheduled acute care, emergency department or hospital visits, serious and non-serious adverse events, and duration of exacerbation. Risk of bias We used Risk of Bias 2 (RoB 2)and the tool's extension for cross-over trials. Synthesis methods We conducted meta-analyses using fixed-effect models to calculate odds ratios (OR) and 95% confidence intervals (CI) for all but one outcome, which used random-effects models due to heterogeneity (treatment failure in the subset who initiated the study inhaler). We summarised certainty of evidence according to GRADE methods. Included studies We included nine RCTs (seven parallel and two cross‐over) with a total of 1923 participants. The studies were conducted in Europe, North America, and Australasia and were published between 1998 and 2018. Five studies evaluated adult populations (1247 participants; ≥ 15 years), and four studies evaluated child or adolescent populations (676 participants; < 15 years). Approximately 50% of randomised participants initiated the study inhaler (range 23% to 100%). The studies reported treatment failure in various ways, so we made assumptions to allow us to combine data. Synthesis of results People randomised to increase their inhaled corticosteroids dose at the first signs of an exacerbation probably had similar odds of needing rescue oral corticosteroids to those randomised to a placebo inhaler (OR 0.97, 95% CI 0.76 to 1.25; 8 studies, 1774 participants; moderate-certainty evidence). Results for the same outcome in the subset of participants who initiated the study inhaler (approximately 50%) gives a different point estimate with very low certainty due to heterogeneity, imprecision and risk of bias (OR 0.84, 95% CI 0.54 to 1.30; 7 studies, 766 participants; random-effects model used). For adverse effects, imprecision and risk of bias from missing data, outcome measurement and reporting meant we were very uncertain about the effect estimate (serious adverse events OR 1.69, 95% CI 0.77 to 3.71; 2 studies, 394 participants; non-serious adverse events OR 2.15, 95% CI 0.68 to 6.73; 2 studies, 142 participants). We had very low confidence in the effect estimates for unscheduled physician visits, unscheduled acute care, emergency department or hospital visits and duration of exacerbation due to risk of bias. Authors' conclusions Evidence suggests that adults and children with mild to moderate asthma are unlikely to have an important reduction in the need for oral steroids from increasing a patient's inhaled corticosteroid dose at the first sign of an exacerbation. Other clinically important benefits and potential harms cannot be ruled out due to wide confidence intervals, risk of bias in the studies, and assumptions made for synthesis when combining data. Included studies reflect evolving clinical practice and study methods, and the data do not support thorough investigation of effect modifiers such as baseline dose, fold increase, asthma severity and timing. The review does not include recent evidence from pragmatic, unblinded studies showing benefits of larger dose increases in those with poorly controlled asthma. Differences between the blinded and unblinded studies should be investigated. Funding This Cochrane Review had no dedicated funding. Registration Protocol (2009): doi.org/10.1002/14651858.CD007524 Original review (2010): doi.org/10.1002/14651858.CD007524.pub3 Review update (2014): doi.org/10.1002/14651858.CD007524.pub4