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Статті в журналах з теми "Torsion pairs"
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Bravo, Daniel, and Carlos E. Parra. "tCG torsion pairs." Journal of Algebra and Its Applications 18, no. 07 (July 2019): 1950127. http://dx.doi.org/10.1142/s0219498819501275.
Повний текст джерелаАнотація:
We investigate conditions when the [Formula: see text]-structure of Happel–Reiten–Smalø associated to a torsion pair is a compactly generated [Formula: see text]-structure. The concept of a [Formula: see text]CG torsion pair is introduced and for any ring [Formula: see text], we prove that [Formula: see text] is a [Formula: see text]CG torsion pair in [Formula: see text] if, and only if, there exists, [Formula: see text] a set of finitely presented [Formula: see text]-modules in [Formula: see text], such that [Formula: see text]. We also show that every [Formula: see text]CG torsion pair is of finite type, and show that the reciprocal is not true. Finally, we give a precise description of the [Formula: see text]CG torsion pairs over Noetherian rings and von Neumman regular rings.
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Kerner, Otto. "Reduced torsion pairs." Journal of Pure and Applied Algebra 220, no. 2 (February 2016): 802–9. http://dx.doi.org/10.1016/j.jpaa.2015.07.017.
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Assem, Ibrahim, and Otto Kerner. "Constructing Torsion Pairs." Journal of Algebra 185, no. 1 (October 1996): 19–41. http://dx.doi.org/10.1006/jabr.1996.0310.
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Fan, Chunyan, and Hailou Yao. "Torsion Pairs in Triangulated Categories." Advances in Pure Mathematics 03, no. 03 (2013): 374–79. http://dx.doi.org/10.4236/apm.2013.33054.
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Zhou, Panyue, Jinde Xu, and Baiyu Ouyang. "Torsion Pairs in Stable Categories." Communications in Algebra 43, no. 8 (June 4, 2015): 3498–514. http://dx.doi.org/10.1080/00927872.2014.927686.
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Angeleri Hügel, Lidia, Frederik Marks, and Jorge Vitória. "Torsion pairs in silting theory." Pacific Journal of Mathematics 291, no. 2 (September 14, 2017): 257–78. http://dx.doi.org/10.2140/pjm.2017.291.257.
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Holm, Thorsten, Peter Jørgensen, and Martin Rubey. "Torsion pairs in cluster tubes." Journal of Algebraic Combinatorics 39, no. 3 (June 14, 2013): 587–605. http://dx.doi.org/10.1007/s10801-013-0457-6.
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Banerjee, Abhishek. "On Auslander’s formula and cohereditary torsion pairs." Communications in Contemporary Mathematics 20, no. 06 (August 27, 2018): 1750071. http://dx.doi.org/10.1142/s0219199717500717.
Повний текст джерелаАнотація:
For a small abelian category [Formula: see text], Auslander’s formula allows us to express [Formula: see text] as a quotient of the category [Formula: see text] of coherent functors on [Formula: see text]. We consider an abelian category with the added structure of a cohereditary torsion pair [Formula: see text]. We prove versions of Auslander’s formula for the torsion-free class [Formula: see text] of [Formula: see text], for the derived torsion-free class [Formula: see text] of the triangulated category [Formula: see text] as well as the induced torsion-free class in the ind-category [Formula: see text] of [Formula: see text]. Further, for a given regular cardinal [Formula: see text], we also consider the category [Formula: see text] of [Formula: see text]-presentable objects in the functor category [Formula: see text]. Then, under certain conditions, we show that the torsion-free class [Formula: see text] can be recovered as a subquotient of [Formula: see text].
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Angeleri Hügel, Lidia, and Michal Hrbek. "Parametrizing torsion pairs in derived categories." Representation Theory of the American Mathematical Society 25, no. 23 (July 30, 2021): 679–731. http://dx.doi.org/10.1090/ert/579.
Повний текст джерелаАнотація:
We investigate parametrizations of compactly generated t-structures, or more generally, t-structures with a definable coaisle, in the unbounded derived category D ( M o d - A ) \mathrm {D}({\mathrm {Mod}}\text {-}A) of a ring A A . To this end, we provide a construction of t-structures from chains in the lattice of ring epimorphisms starting in A A , which is a natural extension of the construction of compactly generated t-structures from chains of subsets of the Zariski spectrum known for the commutative noetherian case. We also provide constructions of silting and cosilting objects in D ( M o d - A ) \mathrm {D}({\mathrm {Mod}}\text {-}A) . This leads us to classification results over some classes of commutative rings and over finite dimensional hereditary algebras.
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Bravo, Daniel, and Carlos E. Parra. "Torsion pairs over n-hereditary rings." Communications in Algebra 47, no. 5 (February 22, 2019): 1892–907. http://dx.doi.org/10.1080/00927872.2018.1524005.
Повний текст джерелаДисертації з теми "Torsion pairs"
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Sentieri, Francesco. "On large and small torsion pairs." Doctoral thesis, Università degli studi di Trento, 2022. http://hdl.handle.net/11572/348239.
Повний текст джерелаАнотація:
Torsion pairs were introduced by Dickson in 1966 as a generalization of the concept of torsion
abelian group to arbitrary abelian categories. Using torsion pairs, we can divide complex abelian
categories in smaller parts which are easier to understand.
In this thesis we discuss torsion pairs in the category of modules over a finite-dimensional algebra, in
particular we explore the relation between torsion pairs in the category of all modules and torsion
pairs in the category of finite-dimensional modules.
In the second chapter of the thesis, we present the analogue of a classical theorem of Auslander in the
context of τ-tilting theory: for a finite-dimensional algebra the number of torsion pairs in the
category of finite-dimensional modules is finite if and only if every brick over such algebra is finite-
dimensional.
In the third chapter, we revisit the Ingalls-Thomas correspondences between torsion pairs and wide
subcategories in the context of large torsion pairs. We provide a nice description of the resulting
wide subcategories and show that all such subcategories are coreflective.
In the final chapter, we describe mutation of cosilting modules in terms of an operation on the Ziegler
spectrum of the algebra.
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Carlton, David 1971. "Moduli for pairs of elliptic curves with isomorphic N-torsion." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/47474.
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Gratz, Sira Helena [Verfasser]. "From finite to infinite : cluster algebras as colimits, and mutating torsion pairs in discrete cluster categrories / Sira Helena Gratz." Hannover : Technische Informationsbibliothek und Universitätsbibliothek Hannover (TIB), 2015. http://d-nb.info/1075261287/34.
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Finski, Siarhei. "On some problems of holomorphic analytic torsion." Thesis, Sorbonne Paris Cité, 2019. https://theses.md.univ-paris-diderot.fr/FINSKI_Siarhei_va.pdf.
Повний текст джерелаАнотація:
Le but de cette thèse est d'étudier la torsion analytique dans deux contextes différents. Dans le premier contexte, on étudie l'asymptotique de la torsion analytique, quand un fibré vectoriel holomorphe hermitien est tordué par une puissance croissant du fibré en droites positif. Dans le deuxième contexte, on généralise la théorie de la torsion analytique pour des surfaces de Riemann avec des pointes hyperboliques. Motivé par des singularités de la métrique complète de courbure scalaire constante -1 sur des surfaces de Riemann stables épointées, on demande que la métrique sur la surface de Riemann soit lisse seulement en dehors d'un nombre fini des points au voisinage auxquelles elle peut avoir des singularités comme la métrique de Poincaré sur un disque épointé. On fixe un fibré vectoriel holomorphe hermitien qui peut avoir au pire des singularités logarithmiques au voisinage des points marqués. Pour ces données, en renormalisant la trace de l'opérateur de la chaleur, on construit la torsion analytique et on étudie ces propriétésIn the first context, we study the asymptotics of the analytic torsion, when a Hermitian holomorphic vector bundle is twisted by an increasing power of a positive line bundle. In the second context, we generalize the theory of analytic torsion for surfaces with hyperbolic cusps. Motivated by singularities appearing in complete metrics of constant scalar curvature -1 on stable Riemann surfaces, we suppose that the metric on the surface is smooth outside a finite number points in the neighborhood of which it can to have singularities like Poincaré metric has on a punctured disc. We fix a Hermitian holomorphic vector bundle which has at worst logarithmic singularities in the neighborhood of the marked points. For these data, by renormalizing the trace of the heat operator, we construct the analytic torsion and study its properties. Then we study the properties of the analytic torsion in family setting: we prove the curvature theorem, we study the behavior of the analytic torsion when the cusps are created by degeneration and we give some applications to the moduli spaces of pointed curves
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Ghazizadeh, Parisa. "On the torsion part in the cohomology of Deligne-Lusztig varieties." Thesis, Université de Paris (2019-....), 2019. https://theses.md.univ-paris-diderot.fr/GHAZIZADEH_Parisa_va2.pdf.
Повний текст джерелаАнотація:
Dans cette thèse, nous étudions quelques méthodes géométriques dues à Deligne et Lusztig pour construire la théorie des représentations des groupes réductifs finis. Nous nous limitons au groupe algébrique linéaire général et étudions les représentations unipotentes via la cohomologie des variétés de Deligne-Lusztig associées à des blocs unipotents du groupe. Les variétés de Deligne-Lusztig sont celles impliquées dans la version géométrique de la conjecture du défaut abélien. Nous trouvons un analogue modulaire pour comprendre la théorie de représentation en caractéristique positive. Pour transférer l’information de la caractéristique zéro à la caractéristique positive, nous devons étudier la cohomologie des variétés de Deligne-Lusztig sur Zι. Notre principal résultat est de montrer une propriété d’absence de torsion pour les groupes de cohomologie. La première application de cette propriété est le calcul des groupes de cohomologie des variétés de Deligne-Lusztig en caractéristique positif. La deuxième est de trouver un représentant pour leur complexe de cohomologie. Comme deuxième résultat, nous prouvons que, sous des hypothèses spécifiques le complexe de cohomologie des variétés de Deligne-Lusztig est un complexe basculement partielIn this thesis, we study some geometric methods due to Deligne and Lusztig to construct the representation theory of finite reductive groups. We restrict ourselves to the general linear algebraic group and study the unipotent representations via the cohomology of Deligne-Lusztig varieties associated to unipotent blocks of the group. The Deligne-Lusztig varieties are those involved in the geometric version of the abelian defect group conjecture. We find a modular analogue for understanding the representation theory in positive characteristic. For transferring the information from characteristic zero to positive characteristic, we need to study the cohomology of Deligne-Lusztig varieties over Zι. Our main result is to show torsion-free property for their cohomology groups. The first usage of this property is to compute the cohomology groups of Deligne-Lusztig varieties in positive characteristic. The second usage is to find a representative for the cohomology complex. As the second result, we prove that, under specific assumptions cohomology complex of Deligne-Lusztig varieties is partial-tilting complex
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Bieniecka, Ewa. "Commutativity and free products in Thompson's Group V." Thesis, University of St Andrews, 2018. http://hdl.handle.net/10023/14652.
Повний текст джерелаАнотація:
We broaden the theory of dynamical interpretation, investigate the property of commutativity and explore the subject of subgroups forming free products in Thompson's group V. We expand Brin's terminology for a revealing pair to an any tree pair. We use it to analyse the dynamical behaviour of an arbitrary tree pair which cannot occur in a revealing pair. Hence, we design a series of algorithms generating Brin's revealing pair from any tree pair, by successively eliminating the undesirable structures. To detect patterns and transitioning between tree pairs, we introduce a new combinatorial object called the chains graph. A newly defined, unique and symmetrical type of a tree pair, called a balanced tree pair, stems from the use of the chains graphs. The main theorem of Bleak et al. in "Centralizers in the R. Thompson's Group V_n" states the necessary structure of the centraliser of an element of V. We provide a converse to this theorem, by proving that each of the predicted structures is realisable. Hence we obtain a complete classification of centralisers in V. We give an explicit construction of an element of V with prescribed centraliser. The underlying concept is to embed a Cayley graph of a finite group into the flow graph (introduced in Bleak et al.) of the desired element. To reflect the symmetry, we present the resulting element in terms of a balanced tree pair. The group V is conjectured to be a universal coCF group, which generates interest in studying its subgroups. We develop a better understanding of embeddings into V by providing a necessary and sufficient dynamical condition for two subgroups (not both torsion) to form a free product in V. For this, we use the properties, explored in Bleak and Salazar-Díaz "Free Products in Thompson's Group V", of sets of so--called important points, and the Ping-Pong action induced on them.
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Pospíšil, David. "Moduly nad Gorensteinovými okruhy." Doctoral thesis, 2011. http://www.nusl.cz/ntk/nusl-311380.
Повний текст джерелаАнотація:
Title: Modules over Gorenstein rings Author: David Pospíšil Department: Department of Algebra Supervisor: Prof. RNDr. Jan Trlifaj, DSc. Supervisor's e-mail address: trlifaj@karlin.mff.cuni.cz Abstract: The dissertation collects my actual contributions to the clas- sification of (co)tilting modules and classes over Gorenstein rings. Com- pared with the original intent we get a more general result in classification of (co)tilting classes namely for general commutative noetherian rings (see the third paper in this dissertation). The dissertation consists of an introduction and three papers with coauthors. The first paper (published in Contemp. Math.) contains a classification of all (co)tilting modules and classes over 1- Gorenstein commutative rings. The second paper (published in J. Algebra) contains a classification of all tilting classes over regular rings of Krull dimen- sion 2 and also a classification of all tilting modules in the local case. Finally the third paper (preprint) contains a classification of all (co)tilting classes and also torsion pairs over general commutative noetherian rings. All these classi- fications are in terms of subsets of the spectrum of the ring and by associated prime ideals of modules. Keywords: (co)tilting module, (co)tilting class, torsion pair, Gorenstein ring, regular ring,...
Книги з теми "Torsion pairs"
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Baloh, Robert W. Semont and Epley Maneuvers. Oxford University Press, 2016. http://dx.doi.org/10.1093/med/9780190600129.003.0020.
Повний текст джерелаАнотація:
Until 1980, treatment of benign paroxysmal positional vertigo (BPPV) mainly consisted of reassuring patients of the benign nature of the condition and a recommendation that they avoid the critical position changes that induced the vertigo. Most patients had a spontaneous remission, although not infrequently the condition recurred. The same benign course was seen whether BPPV occurred after head trauma or an ear infection or if it occurred spontaneously. Although brain lesions could produce positional vertigo and nystagmus, the stereotyped torsional vertical nystagmus of BPPV was a reliable signature of a benign inner ear disorder. In the 1980s, Alan Semont, a physical therapist in Paris, and John Epley, an otolaryngologist in Oregon, proposed the first treatment maneuvers specifically designed to remove otoconial debris from the posterior semicircular canal and cupula. Although initially there was skepticism regarding the efficacy of these maneuvers, they have been proven effective in multiple controlled treatment trials.
Частини книг з теми "Torsion pairs"
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Mattiello, Francesco, Sergio Pavon, and Alberto Tonolo. "Tilting Modules and Tilting Torsion Pairs." In Springer Proceedings in Mathematics & Statistics, 317–39. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-43416-8_18.
Повний текст джерела
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Husak, Ermin, and Erzad Haskić. "Torsional Vibration of Shafts Connected Through Pair of Gears." In Advanced Technologies, Systems, and Applications III, 303–8. Cham: Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-030-02577-9_29.
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Husak, Ermin, and Erzad Haskić. "Analysis of Torsional Vibration of the Engine Connected with Propeller Through Pair of Gears." In Lecture Notes in Networks and Systems, 128–34. Cham: Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-90893-9_15.
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Evans, Dorinda. "5. A Challenge to International Neoclassicism." In William Rimmer, 117–64. Cambridge, UK: Open Book Publishers, 2022. http://dx.doi.org/10.11647/obp.0304.05.
Повний текст джерелаАнотація:
Rimmer's major sculptural works, such as St. Stephen, Falling Gladiator, Dying Centaur, and Osirus (destroyed), were created for exhibition and in response to the international neoclassical movement. In different ways, they are actually critiques of the rage for neoclassicism. Much of what Rimmer was trying to do is conveyed in his teaching, and he used his exhibited art as an extension of this. He wanted an art based not on copying from antique casts or from life but, rather, on the artist's own imagination so that the work is self-expressive. The fact that the man in Falling Gladiator assumes an impossible position is an instance of his insistence on the imaginative. The St. Stephen and a cast of the Falling Gladiator were exhibited in Paris at the Salon des Refusés, where the Gladiator created a stir as it seemed, wrongly, to be a cast of a live person. Rimmer broke new ground in producing fragmented human figures with an antique reference, such as his Osiris, a classical-Greek-looking nude male without parts of his arms. They resembled the broken ancient sculpture of the present rather than of the revered past. Originally Osiris had the head of a hawk. As with his pictures, Rimmer also was unusual in frankly accepting and portraying abnormalities as in his Seated Man (Despair). The late Fighting Lions, showing a male and female in vicious combat is arguably an allegory of male dominance. As an original thinker, Rimmer, more than once, explored the problem of expressing the spiritual in the material, most effectively in his relatively abstract Torso, which is an attempt to show the divine awakening or creation of a human soul. Following the Bible, the plaster cast retains the effect of a man’s torso having been crudely fashioned from clay. Perhaps just as unexpected was his plan for a colossal sculpture, Tri Mountain (never executed), which amalgamated the effect of three men and three hills as a symbol of the city of Boston. His one major public statue is the over-life-size Alexander Hamilton on Commonwealth Mall in Boston.
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Sokolov, Elisaveta, Vinod K. Metta, and K. Ray Chaudhuri. "Parkinsonism and other extrapyramidal diseases." In Oxford Textbook of Medicine, edited by Christopher Kennard, 5946–56. Oxford University Press, 2020. http://dx.doi.org/10.1093/med/9780198746690.003.0585.
Повний текст джерелаАнотація:
The human basal ganglia is a complex functional organization, with important interconnections with the nigrostriatal pathway, which dominates the dopaminergic innervation of the striatum (caudate nucleus and the putamen). The principal clinical syndromes affecting it are Parkinson’s disease; other syndromes with parkinsonian features (including drug-induced parkinsonism); progressive supranuclear palsy; multisystem atrophy; dementia with Lewy bodies; neuroacanthosis; torsion dystonia; and chorea. Apart from the use of dopaminergic agents, several drugs have beneficial effects in the management of parkinsonism and other extrapyramidal diseases. Parkinson’s disease affects about 0.2% of the population, including 2% of those over 80 years of age. The main pathological feature is degeneration of neuromelanin-containing neurons and Lewy body inclusions in the pars compacta of the substantia nigra, which leads directly and indirectly to excessive inhibition of the thalamus and consequent bradykinesia.
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Goldman, Jane. "Cross-Channel Modernisms and the Vicissitudes of a Laughing Torso: Nina Hamnett, Artist, Bohemian and Writer in London and Paris." In Cross-Channel Modernisms, edited by Claire Davison, Derek Ryan, and Jane Goldman, 96–119. Edinburgh University Press, 2020. http://dx.doi.org/10.3366/edinburgh/9781474441872.003.0007.
Повний текст джерелаАнотація:
Laughing Torso (1932), the memoir of Nina Hamnett (1890-1956), recounts her notorious cross-channel vicissitudes as a struggling artist in the 1910s and 1920s in bohemian London and Paris. This chapter will explore Hamnett’s astonishing career not only as a visual artist (whose reputation has only recently been recovered from undeserved obscurity), and as a muse, model, and a self-fashioning bohemian (whose excesses in the bars of Fitzrovia, Soho and Montparnasse, for many of her critics, eclipsed her other talents), but also as a writer. Reappraisal of Hamnett, and in particular her neglected and misunderstood Laughing Torso, opens fascinating cross-channel conduits to numerous modernist circles and to many pressing as well as entrenched critical and theoretical questions on modernism, including its transnational and geopolitical, trans-temporal and interdisciplinary, (trans-)performative and cross-gender framings.
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Bechhoefer, Eric. "Automated Condition Monitoring of a Cycloid Gearbox." In Maintenance Management - Current Challenges, New Developments, and Future Directions [Working Title]. IntechOpen, 2022. http://dx.doi.org/10.5772/intechopen.105724.
Повний текст джерелаАнотація:
While condition monitoring techniques have been developed for many gearbox types, there has been almost no research on condition monitoring of cycloid driver gearboxes. Cycloid gearboxes are used where high reduction ratios are needed in a single stage. While most gear designs are based on an involute subject to a sliding force, cycloid gear designs are subject to compression. As a result, cycloid gearboxes are quiet, have low backlash, and have large torsional stiffness. Because there is no typical pinion-gear pair in this gearbox, the calculation of the reduction ratio is non-standard. Further, as the eccentric bearing which drives the cycloid gears is in the rotating frame, the calculated fault frequency rates are not as expected. This paper describes the dynamics needed to identify cycloid gearbox fault features to achieve automated fault detection and alerting.
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Farne, Hugo, Edward Norris-Cervetto, and James Warbrick-Smith. "Flank pain." In Oxford Cases in Medicine and Surgery. Oxford University Press, 2015. http://dx.doi.org/10.1093/oso/9780198716228.003.0024.
Повний текст джерелаАнотація:
The diagnoses shown in bold in Figure 18.1 are all surgical emergencies that you must exclude as you clerk the patient. In women, you should consider gynaecological causes, e.g. ectopic pregnancy, ovarian torsion (you can of course narrow these down depending on whether the woman is of childbearing age or not). Also, bear in mind that other abdominal pathology can occasionally present as flank pain (e.g. pancreatitis, diverticulitis, appendicitis). You should ask the standard array of questions about the pain—remember the mnemonic SOCRATES: Site: Where is the pain, and has it always been there? Is it unilateral or bilateral? Kidney stones are almost always unilateral, but the location of the pain may radiate from loin to groin. Often they start with a vague discomfort that is ignored until it becomes a severe pain. Onset: Any trauma or other trigger, or spontaneous? Gradual or sudden? Trauma may lead to musculoskeletal pain or internal bleeding. Character: Is the pain colicky or constant? Is it sharp or dull? Ureteric stones give a colicky (waxing and waning) pain because of periodic spasms of the ureteric smooth muscle walls trying to dislodge the blockage. A constant pain is more consistent with a stone lodged in the kidney, which does not periodically contract (‘vermiculate’) like the ureters, or an inflammatory cause. Musculoskeletal pain is more typically an ache, while nerve impingement causes shooting pains. Radiation: Does the pain radiate to the groin (typical of ureteric pain)? Does it radiate down the leg (typical of lumbar nerve root pain)? Alleviating factors: Does anything make the pain better, e.g. a given posture, eating/drinking, any medications, etc.? Timing: How long has the pain been present? Musculoskeletal back pain can last many weeks, whereas a leaking abdominal aortic aneurysm (AAA) is unlikely to persist for more than a day without resolution, one way or another. Exacerbating factors: Does anything make the pain worse? Patients with peritonitis (e.g. due to a perforated peptic ulcer) are very sensitive to movement. Severity: How severe is the pain (e.g. on a scale of 1–10)? Kidney stones are said to be excruciatingly painful, comparable to childbirth.
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Mark, James E., Dale W. Schaefer, and Gui Lin. "General Properties." In The Polysiloxanes. Oxford University Press, 2015. http://dx.doi.org/10.1093/oso/9780195181739.003.0007.
Повний текст джерелаАнотація:
Many of the properties of the polysiloxanes have been tabulated in handbooks of polymer science and engineering. Recent work has included the stretching of polydimethylsiloxane (PDMS) chains, in some cases to their rupture points. The nature of the bonding in siloxane molecules has been of long-standing interest. Force fields for calculations of PDMS properties have been revised over the years and are now at an advanced state of development. Some of the simplest approaches employ the methods of molecular mechanics. Most of the experimental results have been obtained on solutions of polysiloxanes in thermodynamically good solvents. The first member of this series, poly(dimethylsiloxane) (PDMS), [–Si(CH3)2O–]x, has been studied extensively with regard to its configuration-dependent properties. PDMS (figure 2.1) is very similar in structure to the polyphosphate chain in that the successive bond angles are not equal. The Si–O bond length in polysiloxanes is 1.64 Å, and bond angles at the Si and O atoms are 110 and 143°, respectively. This inequality of bond angles causes the all-trans form of the molecule (with rotational angles ϕ = 0°) to form a closed structure after approximately eleven repeat units. The torsional barrier for rotations about the skeletal bonds is very low, which accounts for the high dynamic flexibility and low glasstransition temperature of the PDMS chain. Not surprisingly, low temperature properties are superb. Trans states are of lower energy than gauche states (ϕ = ±120°) in the PDMS chain. This conformational preference may arise from favorable van der Waals interactions between pairs of CH3 groups separated by four bonds in trans states. This factor is apparently more important than favorable coulombic interactions between oppositely charged Si and O atoms separated by three bonds, which are larger in gauche states because of the reduced distance. Comparisons between experimental and theoretical values of various configuration-dependent properties, however, yield a value for this energy difference that is significantly larger than that obtained from the semi-empirical calculations of interactions between nonbonded atoms.
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Goldman, Jane. "Chapter 4 Cross-Channel Modernisms and the Vicissitudes of a Laughing Torso: Nina Hamnett, Artist, Bohemian and Writer in London and Paris." In Cross-Channel Modernisms, 96–119. Edinburgh University Press, 2020. http://dx.doi.org/10.1515/9781474441896-009.
Повний текст джерелаТези доповідей конференцій з теми "Torsion pairs"
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Koh, Je-sung, Sa-reum Kim, and Kyu-jin Cho. "Self-Folding Origami Using Torsion Shape Memory Alloy Wire Actuators." In ASME 2014 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/detc2014-34822.
Повний текст джерелаАнотація:
Self-folding origami requires a low-profile actuator to be embedded in a sheet of paper-like planar material. Various actuation methods have been employed to actively fold such sheets. This paper presents a torsion shape-memory alloy (SMA) wire actuator embedded in patterned origami structures that actively folds the origami by twisting the SMA wire. A simple wire is aligned with the fold line, and each end is fixed to a facet. The twisting of the wire directly rotates the facets. This method has the advantage of using an easily available wire SMA and the advantage of a flat form factor similar to that of sheet SMA. Generally, SMA wire is used in a linear manner or as a spring. The torsion SMA wire presented in this paper is trained to generate torsional force when heated. The amount of rotation depends on the length of the wire; a 200-μm-diameter SMA wire 12 mm in length can induce 540° rotation. SMA wires are arranged in pairs side by side to rotate the facets in both directions. Maximum torque of 70 mNcm is generated in this antagonistic arrangement. The torsion SMA wire actuators enable a novel design for a programmable folding sheet that is easily manufactured and exhibits fast folding and unfolding.
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Vega, Almudena, Roque Corral, Achim Zanker, and Peter Ott. "Experimental and Numerical Assessment of the Aeroelastic Stability of Blade Pair Packages." In ASME Turbo Expo 2014: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/gt2014-25607.
Повний текст джерелаАнотація:
The stabilizing effect of grouping rotor blades in pairs has been assessed both, numerically and experimentally. The bending and torsion modes of a low aspect ratio high speed turbine cascade tested in the non-rotating test facility at EPFL (Ecole Polytechnique Fédérale de Lausanne) have been chosen as the case study. The controlled vibration of 20 blades in travelling wave form was performed by means of an electromagnetic excitation system, enabling the adjustement of the vibration amplitude and inter blade phase at a given frequency. Unsteady pressure transducers located along the blade mid-section were used to obtain the modulus and phase of the unsteady pressure caused by the airfoil motion. The stabilizing effect of the torsion mode was clearly observed both in the experiments and the simulations, however the effect of grouping the blades in pairs in the minimum damping at the tested frequency was marginal in the bending mode. A numerical tool was validated using the available experimental data and then used to extend the results at lower and more relevant reduced frequencies. It is shown that the stabilizing effect exists for the bending and torsion modes in the frequency range typical of low-pressure turbines. It is concluded that the stabilizing effect of this configuration is due to the shielding effect of the pressure side of the airfoil that defines the passage of the pair on the suction side of the same passage, since the relative motion between both is null. This effect is observed both in the experiments and simulations.
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Tuantranont, Adisorn, Tanom Lomas, and V. M. Bright. "MEMS Mirror Switch for Multi-Channel Spectrophotometer." In ASME 2003 International Electronic Packaging Technical Conference and Exhibition. ASMEDC, 2003. http://dx.doi.org/10.1115/ipack2003-35329.
Повний текст джерелаАнотація:
In this paper, the design, fabrication and performance of a MEMS-based micromirror switch used for routing a probing light signal in a multi-channel fiber optics spectrophotometer are presented. Our MEMS-based micromirror switch is a surface micromachined mirror fabricated through commercial available Multi-User MEMS Process (MUMPs) foundry service. The mirror is suspended by the double-gimbal structure, which consists of two pairs of torsion bars for X and Y axis scanning. Self-assembly by solders is used to elevate the torsion mirror 30 micron over the substrate to achieve large scan angle. The operating scan angle is in the range of 3.5 degrees with driving voltage of 0–100 V. The fastest switching time of 4 millisecond (1 ms rise time and 3 ms fall time) is measured corresponding to the maximum speed of the mirror of 0.25 kHz when the mirror is scanning at +/− 1.5 degree. The micromirror switch is packaged with a multi-mode fiber bundle using active alignment technique. Maximum insertion loss of 5 dB has been obtained.
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Vogt, Damian M., and Torsten H. Fransson. "Experimental Investigation of Mode Shape Sensitivity of an Oscillating LPT Cascade at Design and Off-Design Conditions." In ASME Turbo Expo 2006: Power for Land, Sea, and Air. ASMEDC, 2006. http://dx.doi.org/10.1115/gt2006-91196.
Повний текст джерелаАнотація:
The effect of negative incidence operation on mode shape sensitivity of an oscillating low pressure (LP) turbine rotor blade row has been studied experimentally. An annular sector cascade has been employed in which the middle blade has been made oscillating in controlled three-dimensional rigid-body modes. Unsteady blade surface pressure data were acquired at midspan on the oscillating blade and two pairs of non-oscillating neighbor blades and reduced to aeroelastic stability data. The test program covered variations in reduced frequency, flow velocity and inflow incidence; at each operating point a set of three orthogonal modes was tested such as to allow for generation of stability plots by mode recombination. At nominal incidence it has been found that increasing reduced frequency has a stabilizing effect on all modes. The analysis of mode shape sensitivity yielded that the most stable modes are of bending type with axial to chordwise character whereas high sensitivity has been found for torsion-dominated modes. Negative incidence operation caused the flow to separate on the fore pressure side. This separation was found to have a destabilizing effect on bending modes of chordwise character whereas an increase in stability could be noticed for bending modes of edgewise character. Variations of stability parameter with inflow incidence have hereby found being largely linear within the range of conditions tested. For torsion-dominated modes the influence on aeroelastic stability was close to neutral.
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Han, Yong, Dan Mateescu, and Arun K. Misra. "Study of Aerospace Structures With Bonded Piezoelectric Strips Subjected to Unsteady Aerodynamic Loads for Structural Health Monitoring." In ASME 2012 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/smasis2012-8005.
Повний текст джерелаАнотація:
This paper studies the aeroelastic oscillations of wing-like structures with the aim to detect at an incipient stage the presence of structural cracks. Such oscillations occur normally in certain flight evolutions of aircraft or can be excited by piezoelectric actuators bonded on the wing structure. These oscillations can be used to detect at an early stage the presence of cracks by monitoring the response of several piezoelectric sensors bonded on both sides of the structure during the aeroelastic oscillations. The proposed method of crack detection uses pairs of piezoelectric strip sensors bonded on the opposite sides of the structure and is based on the fact that the presence of a crack causes a difference between the strains measured by the two sensors of a pair. The structural analysis presented in this paper uses a nonlinear model for the cracks and a finite element formulation for the piezoelectric strips coupled with the structure. A 3D panel method developed by the authors is used to determine the unsteady aerodynamic loads acting on the oscillating wing structure. The dynamic analysis in the time domain is performed for the oscillating structures with piezoelectric strips subjected to unsteady aerodynamic loads. In the present work, the efficiency of this crack detection method is studied in realistic situations, by considering the aeroelastic oscillations in flexion and torsion of a wing-like structure which are excited in one of the following modes: (i) the aeroelastic oscillations excited by a pair of piezoelectric actuators bonded on the opposite sides of the structure; (ii) the aeroelastic oscillations excited by the harmonic oscillation of the angle of attack corresponding to the flight in atmospheric turbulence (harmonic gust); (iii) the aeroelastic oscillations generated by a sudden change in the angle of attack or in the airplane velocity due to a pilot control input. The numerical simulations for these cases have been performed by the simultaneous solution of the coupled equations of unsteady fluid flow and of the structure deformation motion, by using a finite element method for the dynamic of the structures with cracks and bonded piezoelectric strips, and a 3D panel method developed by the authors for the calculation of the unsteady aerodynamic loads. These numerical simulations have shown that the presence of a crack in the structure can be efficiently detected at an early stage by monitoring the response of the pairs of piezoelectric sensors.
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Paouris, Leonidas I., Stephanos Theodossiades, Homer Rahnejat, Adam Kidson, Gregory Hunt, and William Barton. "Nonlinear Dynamics of an Automotive Differential Hypoid Gear Pair." In ASME 2015 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/detc2015-47324.
Повний текст джерелаАнотація:
The dynamics of an automotive differential hypoid gear pair is investigated. The gear pair model is a 4 degree-of-freedom torsional model, including the torsional deflections of the supporting shafts of the pinion and the gear. It also includes the dynamic transmission error of the mating teeth pairs. The variations in teeth contact stiffness/contact, principal radii of contact and static transmission error are determined during the meshing cycle, using the CALYX software. The equations of motion are solved using a numerical integration scheme. A preliminary parametric study is presented, enabling identification of different periodic responses as the vehicle cruising speed alters.
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Chao, Chang-Po, and Steven W. Shaw. "Dynamically Stable Non-Linear Modes of Multiple Subharmonic Torsional Vibration Absorbers." In ASME 1999 Design Engineering Technical Conferences. American Society of Mechanical Engineers, 1999. http://dx.doi.org/10.1115/detc99/vib-8073.
Повний текст джерелаАнотація:
Abstract Recent studies have demonstrated an arrangement of centrifugal pendulum vibration absorbers that is very effective at reducing torsional vibrations in rotating machinery. The basic system is composed of a pair of identical absorbers that are tuned to a one-half subharmonic order relative to the applied fluctuating torque. These absorbers, when moving in an out of phase manner along a particular path relative to the rotor, are capable of significantly reducing torsional vibrations of a desired order. In this paper we consider the response of systems composed of multiple pairs of these absorbers, with the goal of determining the dynamic stability of the desired response and the effects of small imperfections in the absorbers’ paths. The desired response of this system is one in which the N absorbers act as a single pair, with two groups of N/2 each moving with equal amplitude but exactly out of phase with respect to one another. It is shown that this response can be made to be dynamically stable and robust to certain model uncertainties by a slight, identical overtuning of each absorber. The analytical results, obtained by the method of averaging and symmetric bifurcation theory, are confirmed by simulations for the cases with two and three pairs of absorbers.
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Fernando, Upul S., Michelle Davidson, Kun Yan, Matthew J. Roy, Thilo Pirling, Philip J. Withers, and John A. Francis. "Evolution of Residual Stress in Tensile Armour Wires of Flexible Pipes During Pipe Manufacture." In ASME 2017 36th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/omae2017-61490.
Повний текст джерелаАнотація:
Tensile armour layers in unbonded flexible pipes are constructed by the parallel helical wrapping of several rectangular wires. Pairs of layers, wound in opposite directions and with different helical shapes are used to provide the necessary axial strength, water depth capacity and torsion balance. The forming of armour wires as supplied by the vendor into a helix shape on the pipe involves significant plastic straining; twisting and repeated bending of the wires in different planes. The wires that are wrapped on the pipe are not unloaded. Therefore the armour wires in flexible pipes are considered to contain residual stress (RS). Knowledge of RS in the wires of the manufactured pipe is essential in making appropriate design decisions with high confidence to meet material utilization requirements and subsequently predict the integrity and fatigue durability of the pipe. This paper describes an investigation performed to examine the evolution of RS in the tensile wires during various stages of the pipe manufacturing process. To this end, different methods including a relatively simple and inexpensive stress relaxation method termed the contour method, as well as diffraction methods were used to evaluate RS in the wire. A finite element (FE) model has been developed to simulate the wire deformation involved in the pipe manufacturing process. The procedure was used to predict the evolution of RS in a tensile wire and change in material response during the pipe manufacturing process. A comparison of FE model predictions and measured data is given. The results show that the RS measured by the contour method give comparable values to those obtained from more advanced methods such as high energy synchrotron X-ray and neutron diffraction. The need for using representative material properties and deformation boundary conditions in FE models to predict RS accurately is highlighted.
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Natarajan, R. N., R. B. Garretson, H. An, and G. B. J. Andersson. "Stability of Isthmic Spondylolisthesis: Finite Element Model Study." In ASME 2000 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2000. http://dx.doi.org/10.1115/imece2000-2620.
Повний текст джерелаАнотація:
Abstract Spondylolysis is a developmental condition or a stress fracture phenomenon, in which a defect in the pars interarticularis leads to varying degrees of instability in the lumbar spine. A finite element model was used to study the effect of pars defect as well as pars defect combined with varying slip on the change in flexibility of the lumbar motion segments under mechanical loading. Compared to the intact model, a pars defect at L3–L4 level allowed a small increase in motion at L2 with respect to L5 under all loading modes except torsion. Motion of L2 with respect to L5 was further increased by 3% to 20% with 50% translation prior to loading in all loading modes except torsion. Fifty percent translation increased the torsion motion further by 50%. In every model, the increase in motion was greatest under torsion. This study showed that stability of a motion segment in spondylolysis depends on the amount of spondylolisthesis and the loading condition. There was more motion with increased slip in all-loading modes with largest increase with torsion moment load. The type of loading also affects the degree of motion, with torsion creating significant instability.
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Mgebrishvili, Nikoloz, Marina Tatanashvili, Tengiz Nadiradze, and Ketevan Kekelia. "Increase of Railway Transportation Safety by a New Method of Determination of Wheel Pair and Rail Wear and Damage." In ASME 2007 Rail Transportation Division Fall Technical Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/rtdf2007-46024.
Повний текст джерелаАнотація:
As a result of interaction between the wheel pairs and rails during rolling stock movement, lateral, longitudinal and torsional creep forces are created. Over the long term these forces cause wear and damage of the wheel pairs and rails. Accordingly railway safety decreases and the probability of derailment increases. Development of modern railways largely depends on controlling the proper functionality of wheel pairs and rails. It is impossible to ensure safety and increase the speed of railway traffic without providing such control. Detection of the wheel pair and rail wear damage is one of the key problems of railway science. Many scientific studies have been performed and a number of devices have been developed in this field, but the mentioned problem still remains urgent. In order to increase railway safety, the authors of this paper have proposed a conceptual design of a mobile device for detection of wheel pair and rail wear and damage. Such a device does not currently exist. By installation of the proposed device on each wheel pair of each railcar, the automatic control of wheel pair and rail condition will be achieved. Namely: • Detection of the worn out wheel pair and determination of the degree of wear; • Detection of the damaged wheel pair; • Identification of the worn out or damaged wheel pair. Also possible, on the basis of elaborated mathematical model: • Detection of the worn out rail; • Detection of the damaged rail; • Identification of location of the worn out or damaged rail. Information obtained from the device would be constantly connected to the locomotive computer system. Therefore, for checking rolling stock, there could no longer be a need to build expensive stationary systems or to move trains great distances for their inspection. As a result, the time lost due to equipment stoppage will be saved. Also, with the help of the proposed mobile device, railway safety could improve, while at the same time expenses for detection of wheel pair wear and damage could potentially decrease. This could result in significant economic savings.