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1
DAVID, SINNOU, e AMÍLCAR PACHECO. "LE PROBLÈME DE LEHMER ABÉLIEN POUR UN MODULE DE DRINFEL'D". International Journal of Number Theory 04, n. 06 (dicembre 2008): 1043–67. http://dx.doi.org/10.1142/s1793042108001870.
Abstract (sommario):
Let ϕ be a Drinfel'd module defined over a finite extension K of 𝔽q(T); we establish a uniform lower bound for the canonical height of a point of ϕ, rational over the maximal abelian extension of K, and thus solve the so-called abelian version of the Lehmer problem in this situation. The classical original problem (a non torsion point in 𝔾m(ℚab)) was solved by Amoroso and Dvornicich [1].Soit ϕ un module de Drinfel'd défini sur une extension finie K de 𝔽q(T); nous démontrons une minoration uniforme pour la hauteur canonique d'un point de ϕ, rationnel sur l'extension abélienne maximale de K, et résolvons ainsi la version dite abélienne du problème de Lehmer dans cette situation. Dans le cadre classique (un point d'ordre infini de 𝔾m(ℚab)), cette question a été résolue par Amoroso et Dvornicich dans [1].
2
Boun-jad, Mohamed, e Toufik Zebbiche. "Solution de l’équation de Poisson dans un domaine bidimensionnel par la méthode des éléments finis". Journal of Renewable Energies 16, n. 3 (22 ottobre 2023): 441–84. http://dx.doi.org/10.54966/jreen.v16i3.392.
Abstract (sommario):
Ce travail présente une modeste contribution sur le domaine des éléments finis. On a essayé de résoudre l’équation de Poisson avec les conditions aux limites de type Dirichlet dans un domaine quelconque bidimensionnel simplement connexe. Après une brève théorie sur la résolution de cette équation, on a trouvé les solutions analytiques exactes que pour les sections circulaires, rectangulaires et elliptiques. D’où notre intérêt est orienté vers la recherche des solutions numériques approchées. La méthode utilisée est celle des éléments finis. Deux programmes de calcul numérique ont été réalisés dans ce contexte. Le premier est consacré pour la génération du maillage triangulaire dans les domaines concernés. On a développé ici une technique permettant de générer un maillage de type ‘H’ dans n’importe quel domaine simplement connexe. Le deuxième programme réalisé est celui pour la résolution numérique de l’équation de Poisson dans un domaine simplement connexe avec les conditions aux limites de Dirichlet. Le programme utilise un seul type d’élément fini est le triangle à trois noeuds. Le problème résolu a un grand intérêt physique et pratique dans pas mal de disciplines, telles que, le transfert de chaleur dans des ailettes de moteur, l’écoulement à travers les conduites quelconques et d’autres problèmes tels que, l’étude de la torsion des poutres de sections non circulaires arbitraires comme la torsion des pales d’hélicoptères et les ailettes dans les refroidisseurs ainsi que les aubes dans les compresseurs. Les résultats présentés sont choisis pour des sections simples pour but de comparaison et pour d’autres formes complexes.
3
Lau, Ming G. "Torsional axisymmetric finite element model for problems in elasticity". Canadian Journal of Civil Engineering 13, n. 5 (1 ottobre 1986): 583–87. http://dx.doi.org/10.1139/l86-085.
Abstract (sommario):
This note describes how the displacements and shear stresses of an axisymmetric elastic component, when loaded in torsion, can be computed by modelling the component with torsional axisymmetric finite elements. The model developed represents only minor modifications of the well-known plane stress or plane strain finite element technique.In the analysis, the model is split into a mesh of triangular annuli. Each node of each element has only one degree of freedom, the tangential displacement. The state of strain in each element is represented by a three-term displacement function, one representing a rigid body rotation, the second representing the state of torsion, and the third representing the state of strain in a hollow thin disc.The model has been applied satisfactorily to three torsional problems with known theoretical solutions. The first problem involves the computation of torsional shear stresses of a uniform shaft subjected to pure torsion. In the second problem, the solution is obtained for a conical shaft. In the third problem, known as the Reissner–Sagoci problem, an elastic semi-infinite medium is subjected to a torsional displacement on a small area of the surface.A typical application of the model to the problem of a shrink-fitted assembly subjected to torsion is discussed. Key words: torsion, finite element, elasticity, axisymmetry.
4
Pan, Wen-Hao, Chuan-Hao Zhao, Yuan Tian e Kai-Qi Lin. "Exact Solutions for Torsion and Warping of Axial-Loaded Beam-Columns Based on Matrix Stiffness Method". Nanomaterials 12, n. 3 (4 febbraio 2022): 538. http://dx.doi.org/10.3390/nano12030538.
Abstract (sommario):
The typically-used element torsional stiffness GJ/L (where G is the shear modulus, J the St. Venant torsion constant, and L the element length) may severely underestimate the torsional stiffness of thin-walled nanostructural members, due to neglecting element warping deformations. In order to investigate the exact element torsional stiffness considering warping deformations, this paper presents a matrix stiffness method for the torsion and warping analysis of beam-columns. The equilibrium analysis of an axial-loaded torsion member is conducted, and the torsion-warping problem is solved based on a general solution of the established governing differential equation for the angle of twist. A dimensionless factor is defined to consider the effect of axial force and St. Venant torsion. The exact element stiffness matrix governing the relationship between the element-end torsion/warping deformations (angle and rate of twist) and the corresponding stress resultants (torque and bimoment) is derived based on a matrix formulation. Based on the matrix stiffness method, the exact element torsional stiffness considering the interaction of torsion and warping is derived for three typical element-end warping conditions. Then, the exact element second-order stiffness matrix of three-dimensional beam-columns is further assembled. Some classical torsion-warping problems are analyzed to demonstrate the established matrix stiffness method.
5
ZEMYAN, STEPHEN M. "ON THE EXTREMAL CURVATURE AND TORSION OF STEREOGRAPHICALLY PROJECTED ANALYTIC CURVES". Tamkang Journal of Mathematics 28, n. 2 (1 giugno 1997): 101–17. http://dx.doi.org/10.5556/j.tkjm.28.1997.4324.
Abstract (sommario):
In this paper, we first derive formulas for the curvature and torsion of curves on $S^2$ produced by stereographically projecting the image curves of analytic, univalent functions belonging to the class $\mathcal S$. We are concerned here with the problems of determining the extreme values of the curvatures and torsions, as well as the functions belonging to $\mathcal S$ which attain these extreme values. An analysis of the asymptotic behavior of these curvature and torsion formulas will allow for the formulation of plausible conjectures.
6
Valmassy, R., e B. Stanton. "Tibial torsion. Normal values in children". Journal of the American Podiatric Medical Association 79, n. 9 (1 settembre 1989): 432–35. http://dx.doi.org/10.7547/87507315-79-9-432.
Abstract (sommario):
In-toeing and out-toeing are common foot problems, and frequently are caused by torsional abnormalities of the tibia. Malleolar position, and thus tibial torsion, was measured in 281 children, 1 1/2 to 6 years of age, with a Tractograph, and normal values for the different age groups were determined. The authors discuss the clinical significance of torsional abnormalities of the tibia regarding gait.
7
Trunin, Konstantin. "Mathematical Model of Flexible Link Dynamics in Marine Tethered Systems Considering Torsion and its Influence on Tension Force". Polish Maritime Research 30, n. 2 (1 giugno 2023): 188–96. http://dx.doi.org/10.2478/pomr-2023-0032.
Abstract (sommario):
Abstract The rigidity in bending of a flexible link (is an important characteristic that should be considered during regular service conditions. The tension and bending with torsion of wire ropes are also significant factors. This study proposed a method to calculate the vectors of the generalised forces of bending of flexible links. One of the causes of torsional stresses in the power plant of underwater tethered systems is the interaction with ship equipment, such as spiral winding on the winch drum, friction on the flanges of the pulleys or winch drums, and bends on various blocks and rolls that cause torsion. The source of torsional stresses in the FL may also be related to manufacturing, storage, transportation, and its placement on the ship’s winch drums. Torsion can lead to a decrease in the tensile strength due to load redistribution between power elements, or even a violation of their structure. In some cases, torsion significantly affects the movement of the underwater tethered system as a whole. The development of a mathematical model to describe the marine tethered systems dynamics, taking into account the effect of torsion, is important and relevant. The mathematical model of the marine tethered systems dynamics was improved and solved by accounting for the generalised forces of the torsion rigidity of the flexible link, using an algorithm and computer program. The influence of the bending and torsional rigidity of the FL on its deflection and tensile strength were considered based on the example of two problems. The developed program’s working window image shows the simulated parameters and the initial position of the flexible link. The results show that torsion has almost no effect on the shape of the a flexible link’s deflection in the X0Z plane, but leads to a deviation from the X0Z plane when calculating the static deflection of the flexible link. When the carrier vessel is stationary and the submersible vehicle has no restrictions on movement and has positive buoyancy, torsion leads to a three-dimensional change in the shape of the flexible link both in the X0Z plane and in the X0Y plane. The tension force of the flexible link along its length is distributed unevenly, and the torsion of the flexible link can lead to significant changes in its shape, the trajectory of towed objects, and the forces acting on the elements of the marine tethered systems
8
Lee, Jin Woo. "Optimal Cantilever Design by Topology and Shape Optimization Methods". Applied Mechanics and Materials 789-790 (settembre 2015): 306–10. http://dx.doi.org/10.4028/www.scientific.net/amm.789-790.306.
Abstract (sommario):
This work presents the framework to optimally design a cantilever for torsion mode frequency maximization. A cantilever design problem is formulated by topology and shape optimization methods. The torsion mode frequency is selected as an objective function, and the volume of the cantilever and the first bending mode frequency are constrained. Two optimization problems are defined and sequentially solved for the specific values. A new idea in this work is using a final topology obtained in the topology optimization problem as an initial shape in the shape optimization problem. The torsional mode frequency of the optimized cantilever is well improved in comparison with a nominal cantilever.
9
Sapountzakis, Evangelos J. "Bars under Torsional Loading: A Generalized Beam Theory Approach". ISRN Civil Engineering 2013 (21 marzo 2013): 1–39. http://dx.doi.org/10.1155/2013/916581.
Abstract (sommario):
In this paper both the static and dynamic analyses of the geometrically linear or nonlinear, elastic or elastoplastic nonuniform torsion problems of bars of constant or variable arbitrary cross section are presented together with the corresponding research efforts and the conclusions drawn from examined cases with great practical interest. In the presented analyses, the bar is subjected to arbitrarily distributed or concentrated twisting and warping moments along its length, while its edges are supported by the most general torsional boundary conditions. For the dynamic problems, a distributed mass model system is employed taking into account the warping inertia. The analysis of the aforementioned problems is complete by presenting the evaluation of the torsion and warping constants of the bar, its displacement field, its stress resultants together with the torsional shear stresses and the warping normal and shear stresses at any internal point of the bar. Moreover, the construction of the stiffness matrix and the corresponding nodal load vector of a bar of arbitrary cross section taking into account warping effects are presented for the development of a beam element for static and dynamic analyses. Having in mind the disadvantages of the 3D FEM solutions, the importance of the presented beamlike analyses becomes more evident.
10
Elsayed, M. A., D. W. Dareing e M. A. Vonderheide. "Effect of Torsion on Stability, Dynamic Forces, and Vibration Characteristics in Drillstrings". Journal of Energy Resources Technology 119, n. 1 (1 marzo 1997): 11–19. http://dx.doi.org/10.1115/1.2794215.
Abstract (sommario):
Traditionally, the analysis of stability in drillstrings is based on longitudinal vibrations only. However, field experience indicates the presence of torsional effects in the form of modulations in longitudinal vibrations. Moreover, torsional dynamic forces are significant and lead to joint problems during drilling. In this paper, we discuss the effect of torsional vibrations on the stability and both longitudinal and torsional forces in drillstrings. Using a model of a typical drillstring that incorporates both longitudinal and torsional multi-degree of freedom, we develop the equations governing displacements and forces at any joint. Using time simulation techniques, we obtain the stability diagram and calculate the dynamic forces at any joint as a function of time. We finally show the effect of torsion on the nature of vibrations through frequency analysis, a technique that is useful in the interpretation of field measurements under various drilling conditions.
11
Yin, Changcheng, Zhangbin Lv, Yangting Wang e Guosheng Yue. "Mathematical Problems in Engineering Joint Structure Stiffness Analysis of an Automotive Body in White with the Finite Element Method". Mathematical Problems in Engineering 2022 (27 settembre 2022): 1–11. http://dx.doi.org/10.1155/2022/5059747.
Abstract (sommario):
The finite element model of the seven connection heads of an automotive body in white is established, and the stiffness calculation is carried out by taking the lower joint of the B pillar as an example. Nine stiffness values were obtained for each branch, which can be written as a 3 × 3 symmetric matrix. The front and back bending stiffness, torsional stiffness, and internal and external bending stiffness are obtained with the decoupling method. Based on this, the finite element model for unrigid and rigid joints is established, and the three stiffness ratio coefficients of each branch of the joint are calculated and evaluated. Finally, the effects of the thickness and stiffness of the sheet metal parts on the bending condition, torsion condition, first-order bending, and torsion frequency of the body in white are discussed using the regional sensitivity analysis and strain energy calculation.
12
Homik, Wojciech. "The effect of liquid temperature and viscosity on the amplitude-frequency characteristics of a viscotic torsion damper". Polish Maritime Research 19, n. 4 (1 dicembre 2012): 71–77. http://dx.doi.org/10.2478/v10012-012-0042-2.
Abstract (sommario):
ABSTRACT The article discusses causes of the appearance of transverse, longitudinal and torsional crankshaft vibrations in multi-cylinder internal combustion engines. Particular attention is paid to the torsional vibration which is the most severe threat to engine crankshafts. Damping methods making use of torsion dampers are presented. With the reference to viscotic dampers, problems with their damping efficiency are discussed in the context of viscosity changes of the damping liquid. The article also presents the amplitude-frequency characteristics of a series of viscotic dampers, which were recorded experimentally on the research rig and on a real object. An idea of vibration damper metric is given.
13
Teply, Mark L., e Blas Torrecillas. "A weaker form of Baer’s splitting problem for torsion theories". Czechoslovak Mathematical Journal 43, n. 4 (1993): 663–74. http://dx.doi.org/10.21136/cmj.1993.128426.
14
Klier, Eliana M., Hongying Wang e J. Douglas Crawford. "Three-Dimensional Eye-Head Coordination Is Implemented Downstream From the Superior Colliculus". Journal of Neurophysiology 89, n. 5 (1 maggio 2003): 2839–53. http://dx.doi.org/10.1152/jn.00763.2002.
Abstract (sommario):
How the brain transforms two-dimensional visual signals into multi-dimensional motor commands, and subsequently how it constrains the redundant degrees of freedom, are fundamental problems in sensorimotor control. During fixations between gaze shifts, the redundant torsional degree of freedom is determined by various neural constraints. For example, the eye- and head-in-space are constrained by Donders' law, whereas the eye-in-head obeys Listing's law. However, where and how the brain implements these laws is not yet known. In this study, we show that eye and head movements, elicited by unilateral microstimulations of the superior colliculus (SC) in head-free monkeys, obey the same Donders' strategies observed in normal behavior (i.e., Listing's law for final eye positions and the Fick strategy for the head). Moreover, these evoked movements showed a pattern of three-dimensional eye-head coordination, consistent with normal behavior, where the eye is driven purposely out of Listing's plane during the saccade portion of the gaze shift in opposition to a subsequent torsional vestibuloocular reflex slow phase, such that the final net torsion at the end of each head-free gaze shift is zero. The required amount of saccade-related torsion was highly variable, depending on the initial position of the eye and head prior to a gaze shift and the size of the gaze shift, pointing to a neural basis of torsional control. Because these variable, context-appropriate torsional saccades were correctly elicited by fixed SC commands during head-free stimulations, this shows that the SC only encodes the horizontal and vertical components of gaze, leaving the complexity of torsional organization to downstream control systems. Thus we conclude that Listing's and Donders' laws of the eyes and head, and their three-dimensional coordination mechanisms, must be implemented after the SC.
15
Lee, Jia-Wei, Hong-Ki Hong e Jeng-Tzong Chen. "Generalized complex variable boundary integral equation for stress fields and torsional rigidity in torsion problems". Engineering Analysis with Boundary Elements 54 (maggio 2015): 86–96. http://dx.doi.org/10.1016/j.enganabound.2015.01.003.
16
Losa Iglesias, Marta Elena, Ricardo Becerro de Bengoa Vallejo e Paloma Salvadores Fuentes. "In-toeing in Children with Type I Osteogenesis Imperfecta". Journal of the American Podiatric Medical Association 99, n. 4 (1 luglio 2009): 326–29. http://dx.doi.org/10.7547/0980326.
Abstract (sommario):
Background: Osteogenesis imperfecta is an autosomal-dominant disorder of the connective tissue. Also known as brittle bone disease, it renders those affected susceptible to fractures after minimal trauma. Therefore, it is important to minimize the risk of falls and subsequent fractures in patients with this disease. In-toeing is a common condition in children that can result from various pathologic entities, including anteversion, internal tibial torsion, and metatarsus adductus. These conditions can result in frequent tripping and other functional problems. Methods: A descriptive study was undertaken to determine the prevalence of in-toeing gait attributable to tibial or femoral torsion or metatarsus adductus in children with type I osteogenesis imperfecta. The study involved orthopedic and biomechanical examination of 15 children (9 girls and 6 boys) aged 4 to 9 years with confirmed type I osteogenesis imperfecta. Patients who used assistive ambulatory devices, such as canes, crutches, and wheelchairs, were excluded from the study. Results: Of the 15 children studied, 12 (80%) demonstrated previously undiagnosed in-toeing gait attributable to torsional deformity or metatarsus adductus in all but one child. Conclusions: Many children with confirmed type I osteogenesis imperfecta have in-toeing gait caused by torsional deformity or metatarsus adductus. Detection and control of in-toeing gait in children with osteogenesis imperfecta is important to prevent fractures resulting from trauma directly related to these conditions. (J Am Podiatr Med Assoc 99(4): 326–329, 2009)
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Mishchenko, A. V. "Stress-strain state of rod with heterogeneous structure (Novosibirsk)". Vestnik Tomskogo gosudarstvennogo arkhitekturno-stroitel'nogo universiteta. JOURNAL of Construction and Architecture 25, n. 6 (26 dicembre 2023): 113–24. http://dx.doi.org/10.31675/1607-1859-2023-25-6-113-124.
Abstract (sommario):
Heterogeneous structures have a number of significant advantages over classical homogeneous. Their stress-strain state control allows to more effectively adapt the system to given thermal conditions and, as a result, additionally save weight and cost of the structure. The practical use of elements with heterogeneous structure, requires the creation of engineering calculation approaches with acceptable labor intensity, accuracy and versatility.Purpose: The improvement of design methods implying physical relations in problems of thermal power deformation of rods with heterogeneous structure.Design/methodology: The Timoshenko rod model design involves the approximation of transverse shear functions and membrane analogy of shear deformation in torsion. A threedimensional prismatic rod having a rectangular cross-section, is obtained from quasi-homogeneous parts (phases) made of various structural materials.Research findings: Theoretical calculations are obtained for thermal power spatial bending with tension, transverse shear and torsion. These equations contain stiffness characteristics of zero, first- and second-order tensile bending, shear and torsional stiffnesses of the section.Practical implication: These equations can be used to compactly formulate physical relations and the boundary value problem of spatial deformation of rods with heterogeneous structure.
18
Ahmad, Majd, e Richard Ray. "The Dynamic Properties of Sand under Torsion: A Literature Review". Geotechnics 3, n. 2 (11 giugno 2023): 480–514. http://dx.doi.org/10.3390/geotechnics3020027.
Abstract (sommario):
Resonant column (RC) and the torsional simple shear (TOSS) tests have shown proven competency in acquiring precise and repeatable measurements regarding the shear modulus and damping ratio of soil. For most dynamic geotechnical problems, the shear modulus represents the stiffness of the soil, while the damping ratio describes energy dissipation. Many studies in the last few decades focused on developing the relevant equipment and investigating the effect of different soil properties on the dynamic behavior of soil. Researchers have introduced correlations to approximate this behavior without conducting dynamic torsional testing. Soil models (e.g., Ramberg-Osgood and Hardin-Drnevich) can simulate shear stress-strain curves after finding the curve-fitting parameters. Due to the complexity of dynamic behavior and its dependency on various factors in soils, the RO and HD equations help model the behavior more simply. This paper presents a literature review and evaluation of the studies, correlations, soil models, and parameters affecting the dynamic behavior of dry sand under torsion.
19
Cirilo-Lombardo, D. J., e V. D. Gershun. "Integrable hydrodynamic equations for initial chiral currents and infinite hydrodynamic chains from WZNW model and string model of WZNW type with SU(2), SO(3), SP(2), SU(∞), SO(∞), SP(∞) constant torsions". International Journal of Modern Physics A 29, n. 24 (29 settembre 2014): 1450134. http://dx.doi.org/10.1142/s0217751x14501346.
Abstract (sommario):
The WZNW and string models are considered in terms of the initial and invariant chiral currents assuming that the internal and external torsions coincide (anticoincide) and they are the structure constants of the SU(n), SO(n), SP(n) Lie algebras. These models are the auxiliary problems in order to construct integrable equations of hydrodynamic type. It was shown that the WZNW and string models in terms of invariant chiral currents are integrable for the constant torsion associated with the structure constants of the SU(2), SO(3), SP(2) and SU(3) algebras only. The equation of motion for the density of the first Casimir operator was obtained in the form of the inviscid Burgers equation. The solution of this equation is presented through the Lambert function. Also, a new equation of motion for the initial chiral current was found. The integrable infinite hydrodynamic chains obtained from the WZNW and string models are given in terms of invariant chiral currents with the SU(2), SO(3), SP(2) and with SU(∞), SO(∞), SP(∞) constant torsions. Also, the equations of motion for the density of any Casimir operator and new infinite-dimensional equations of hydrodynamic type for the initial chiral currents through the symmetric structure constant of SU(∞), SO(∞), SP(∞) algebras are obtained.
20
Sımsık, Sedat, Bülent Hayri Özokutan, Haluk Ceylan, Abdullah Aydın e Elif Güler. "Ovarian Pathologies in Childhood". European Journal of Therapeutics 16, n. 2 (1 maggio 2010): 1–4. http://dx.doi.org/10.58600/eurjther.2010-16-2-1239-arch.
Abstract (sommario):
Ovarian diseases are not rare in childhood and some problems are encountered with in evaluation of ovarian pathologies such as existance of different terminologies, lack of pathological criteria and different types of tumor classiffications. 55 patients younger than 16 years who had ovarian disease were treated and followed up and then the results were evaluated retrospectively. Patients were seperated in 3 groups as ovarian torsions (n:21), neoplastic ovarian pathologies (n:19) and non-neoplastic ovarian pathologies (n:28). Most frequent clinical symptom was abdominal pain and most frequent clinical finding was abdominal sensitivity in all groups. 1n non-neoplastic ovarian pathology group, 21 patients were treated surgically whereas seven were treated conservatively. As the result of histopathological examinations follicular cysts (n:11), simple cysts (n:8), corpus luteum cysts (n:7), paraovarian cyst (n:1) and massive ovarian edema (n:1) were observed. 1n the neoplastic ovarian pathology group, all patients were treated surgically and 8 serous cystadenoma, 7 mature cystic teratoma, 2 dysgerminoma, 1 juvenile granulosa cell tumor, and 1 seromucinous borderline tumor were observed after histopathological examinations. 1n the ovarian torsion group, torsions were due to non- neoplastic pathology in 7 and neoplastic pathology in 6 patients. Torsions were developed without any cysts or tumor in 8 patients. Oopherectomy or salphingoopherctomy was performed in twenty patients. 1n one patient ovary was preserved as circulation turned normal after detorsion. Ovarian pathologies are not rare in childhood and should be included in the differential diagnosis of abdominal pain in girls. Extensive use of radiological studies have facilitated the diagnosis of these lesions.
21
Futa, Yuichi, Hiroyuki Okazaki, Kazuhisa Nakasho e Yasunari Shidama. "Torsion Z-module and Torsion-free Z-module". Formalized Mathematics 22, n. 4 (1 dicembre 2014): 277–89. http://dx.doi.org/10.2478/forma-2014-0028.
Abstract (sommario):
Summary In this article, we formalize a torsion Z-module and a torsionfree Z-module. Especially, we prove formally that finitely generated torsion-free Z-modules are finite rank free. We also formalize properties related to rank of finite rank free Z-modules. The notion of Z-module is necessary for solving lattice problems, LLL (Lenstra, Lenstra, and Lov´asz) base reduction algorithm [20], cryptographic systems with lattice [21], and coding theory [11].
22
Xu, Zhengyun, Haiqiang Liu, Weihua Feng, Huaming Yang, Xin Nie e Rougang Zhou. "Design and Performance Analysis of a Torsional Soft Actuator Based on Hyperelastic Materials". Robotics 12, n. 4 (28 giugno 2023): 94. http://dx.doi.org/10.3390/robotics12040094.
Abstract (sommario):
Conducting research on soft robots is crucial as there are still many problems that need to be resolved in the areas of material selection, structure design and manufacture, and drive control. Soft manipulators, a subset of soft robots, are now a popular area of study for many researchers. In comparison to typical manipulators, soft manipulators feature a high degree of gripping flexibility and a basic morphological structure. They are composed of flexible materials. They have a wide range of potential applications in healthcare, rehabilitation, bionics, and detection, and they can compensate for the drawbacks of rigid manipulators in some use scenarios. A modular soft-body torsional gripping system is developed after a torsional and gripping actuator is conceived and constructed, and its performance examined. The torsion actuator and the grasping actuator can be combined in the system in a modular fashion. With the help of RGB-D vision algorithms, this multi-modular setup makes it possible to combine soft actuators with various twisting degrees and achieve exact gripping. Through pneumatic control, the target object is precisely grasped and rotated at various angles, enabling the rotation of the target object in three dimensions.
23
Bellieud, Michel. "Problèmes capacitaires en viscoplasticité avec effets de torsion". Comptes Rendus Mathematique 351, n. 5-6 (marzo 2013): 241–45. http://dx.doi.org/10.1016/j.crma.2013.03.005.
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Zinchenko, Olena. "JUSTIFICATION OF THE PROBLEMS OF RESEARCH OF TORSION SHAFTS OF SUSPENSION SYSTEMS OF LIGHT ARMORED VEHICLES ACCORDING TO STRENGTH AND DURABILITY CRITERIA". Bulletin of the National Technical University «KhPI». Series: Automobile and Tractor Construction, n. 1 (19 giugno 2024): 49–56. http://dx.doi.org/10.20998/2078-6840.2024.1.06.
Abstract (sommario):
The paper shows the necessity of improving the torsion shafts of the suspension systems of light armored vehicles in order to improve their main characteristics. As a result of the analysis of the existing methods and methodologies of torsion shafts calculation, we came to the conclusion about the need to create an adequate model, which would include an assessment of the stress-strain state of the torsion shaft in different zones, taking into account many factors. Known simplified methods for calculating the stress-strain state of torsion shafts are not suitable for the complex non-homogeneous components distribution of the stress-strain state and are a source of potential errors. Therefore, there is a need to apply the incremental flow theory, taking into account the load history of the torsion shaft material. In the work, it is proposed to reduce the problem to a sequence of problems with the breakdown of the load history into separate steps and within each step to simultaneously take into account the elastic-plastic deformation and contact interaction and their relationship and mutual influence. The necessity of generalized parametric modeling of the torsion shaft is shown, according to which the generalized parameters represent a set of distributions, functions, dependencies, structures, forms, properties, etc., which uniquely identify the torsion shaft. At the same time, this method makes it possible to purposefully change the current technical solution. All these studies will provide an opportunity to substantiate the parameters of torsion shafts in the context of improving their strength and durability.
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Lal, Radha Krishna, Vikas Kumar Choubey, J. P. Dwivedi e V. P. Singh. "Springback analysis of channel cross-sectioned bar of work-hardening materials under torsional loading". Engineering Computations 33, n. 7 (3 ottobre 2016): 1899–928. http://dx.doi.org/10.1108/ec-05-2015-0142.
Abstract (sommario):
Purpose The purpose of this paper is to deal with the springback problems of channel cross-section bars of linear and non-linear work-hardening materials under torsional loading. Using the deformation theory of plasticity, a numerical scheme based on the finite difference approximation has been proposed. The growth of the elastic-plastic boundary and the resulting stresses while loading, and the springback and the residual stresses after unloading are calculated. Design/methodology/approach The numerical method which has been described in this paper for obtaining the solution of elasto-plastic solution can also be used for other sections. The only care that needs to be taken is to decrease the mesh size near points of stress concentration. The advantage of this technique is that it automatically takes care of all plastic zones developing over the section at different loads and gives a solution satisfying the elastic and plastic torsion equations in their respective regions. Findings As expected, elastic recovery is found to be more with decreasing values of n and λ. The difference in springback becomes more and more with increasing values of angle of twist. The material will approach an elastic ideally plastic behavior with increasing values of λ and n. Originality/value It seems that no attempt has been made to study residual stresses in elasto-plastic torsion of a work-hardening material for a channel cross-section.
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Staricky, Annie. "La topologie du désir". Revue des Collèges de Clinique psychanalytique du Champ Lacanien N° 23, n. 1 (27 marzo 2024): 77–83. http://dx.doi.org/10.3917/rccpcl.023.0077.
Abstract (sommario):
Le désir est d’abord le désir de l’Autre, à partir duquel le sujet constitue son propre désir par une torsion. En 1964, dans Les quatre concepts fondamentaux de la psychanalyse , Lacan identifie cette torsion au recouvrement de deux manques : c’est avec son manque-à-être (aliénation) que le sujet se fait disparaître au lieu de l’Autre (séparation) pour poser la question de son désir, Che Vuoi ? Dans la cure, cette torsion se produit de la chute du sujet supposé savoir, où le sujet se destitue et rencontre l’objet a , cause du désir. En 1965, dans Les problèmes cruciaux , Lacan fait de cette torsion « une clé pour la topologie du désir. »
27
Vaskovskyi, M. I., A. B. Struk, M. V. Makoviichuk e I. P. Shatskyi. "Abnormal stresses in underground pipeline due to static and dynamic reversal of several foundation blocks". Prospecting and Development of Oil and Gas Fields, n. 3(76) (27 settembre 2020): 53–60. http://dx.doi.org/10.31471/1993-9973-2020-3(76)-53-60.
Abstract (sommario):
The article discusses the issues of forecasting the strength of underground pipelines laid in seismically active areas through sections composed of relatively rigid moving blocks. In such dangerous areas, in addition to the normal pressure load of the transported product, the pipe is subjected to additional effects from the movements of the fragments of the block foundation. As the literature data show, the problems of the influence of the interaction of faults on the stress state of the pipeline have not yet been studied. The aim of the study is to develop a model for the analysis of abnormal stresses in the underground pipeline on a damaged foundation caused by static or time-harmonic reciprocal turns of the blocks around the axis of the pipe on both sides of several faults. Static equilibrium and harmonic oscillations of the pipeline are investigated in a linear setting, modelling it with a rod with an annular cross section. The inertia of the transported product is not taken into account. To consider the issues of the ultimate equilibrium of the pipe, the momentless theory of shells and the energy theory of strength are used. The soil backfill is considered as Winkler’s elastic layer. Multiple damages to the solid foundation are presented in the form of several faults on which there is a rupture of the angle of rotation around the axis of the pipe. We formulated boundary value problems for differential equations of static torsion and torsional harmonic oscillations with discontinuous right-hand sides. Based on the analytical solutions of these problems for the cases of antisymmetric and symmetrical reversal of the foundation blocks, the distributions of the torsion angle and equivalent stress in the pipe, depending on the distance between faults and the frequency of forced oscillations of the system, are investigated.
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Asok, Aravind. "Rationality problems and conjectures of Milnor and Bloch–Kato". Compositio Mathematica 149, n. 8 (3 giugno 2013): 1312–26. http://dx.doi.org/10.1112/s0010437x13007021.
Abstract (sommario):
AbstractWe show how the techniques of Voevodsky’s proof of the Milnor conjecture and the Voevodsky–Rost proof of its generalization the Bloch–Kato conjecture can be used to study counterexamples to the classical Lüroth problem. By generalizing a method due to Peyre, we produce for any prime number $\ell $ and any integer $n\geq 2$, a rationally connected, non-rational variety for which non-rationality is detected by a non-trivial degree $n$ unramified étale cohomology class with $\ell $-torsion coefficients. When $\ell = 2$, the varieties that are constructed are furthermore unirational and non-rationality cannot be detected by a torsion unramified étale cohomology class of lower degree.
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Cui, Tingqiong, Yinong Li, Chenglin Zan e Yuanchang Chen. "Dynamic Modeling and Analysis of Nonlinear Compound Planetary System". Machines 10, n. 1 (1 gennaio 2022): 31. http://dx.doi.org/10.3390/machines10010031.
Abstract (sommario):
In the vehicle composite planetary gear transmission system, nonlinear excitations such as time-varying meshing stiffness, backlash and comprehensive error would lead to large vibration and noise, uneven load distribution, unstable operation and other problems. To address these issues, this work focuses on compound planetary gears and develops the bending-torsion coupling nonlinear dynamic model of the system based on the Lagrange equation. There are internal and external multi-source excitations applied to the system. This model is used to study the bending-torsion coupling meshing deformation relationship of each meshing pair along with the translational and torsional directions. The natural frequencies and vibration modal characteristics of the system are extracted from the model, and the influence of rotational inertia and meshing stiffness on the inherent characteristics of the system are studied. The coupling vibration characteristics of the system under operating condition are analyzed in terms of the inherent characteristics and time–frequency characteristics of the system. The simulation results exhibit that the planetary gear system has three modes. The change in natural frequency trajectory has two phenomena: modal transition and trajectory intersection. The main frequencies include engine rotating frequency, meshing frequency and its double frequency, and the rotation frequency and harmonic frequency of the engine have a great influence on the vibration response of the system. Finally, the virtual prototype of the composite planetary system is used to verify the accuracy of the established model from speed, inherent characteristics, meshing force and frequency composition.
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Fabbri, Luca. "Fundamental Theory of Torsion Gravity". Universe 7, n. 8 (18 agosto 2021): 305. http://dx.doi.org/10.3390/universe7080305.
Abstract (sommario):
In this work, we present the general differential geometry of a background in which the space–time has both torsion and curvature with internal symmetries being described by gauge fields, and that is equipped to couple spinorial matter fields having spin and energy as well as gauge currents: torsion will turn out to be equivalent to an axial-vector massive Proca field and, because the spinor can be decomposed in its two chiral projections, torsion can be thought as the mediator that keeps spinors in stable configurations; we will justify this claim by studying some limiting situations. We will then proceed with a second chapter, where the material presented in the first chapter will be applied to specific systems in order to solve problems that seems to affect theories without torsion: hence the problem of gravitational singularity formation and positivity of the energy are the most important, and they will also lead the way for a discussion about the Pauli exclusion principle and the concept of macroscopic approximation. In a third and final chapter, we are going to investigate, in the light of torsion dynamics, some of the open problems in the standard models of particles and cosmology which would not be easily solvable otherwise.
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Chen, Y. Z. "Multiple crack problems for torsion thin-walled cylinder". International Journal of Pressure Vessels and Piping 76, n. 1 (gennaio 1999): 49–53. http://dx.doi.org/10.1016/s0308-0161(98)00107-0.
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Popławski, Nikodem. "The simplest origin of the big bounce and inflation". International Journal of Modern Physics D 27, n. 14 (ottobre 2018): 1847020. http://dx.doi.org/10.1142/s021827181847020x.
Abstract (sommario):
Torsion is a geometrical object, required by quantum mechanics in curved spacetime, which may naturally solve fundamental problems of general theory of relativity and cosmology. The black-hole cosmology, resulting from torsion, could be a scenario uniting the ideas of the big bounce and inflation, which were the subject of a recent debate of renowned cosmologists.
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ARCOS, H. I., e J. G. PEREIRA. "TORSION GRAVITY: A REAPPRAISAL". International Journal of Modern Physics D 13, n. 10 (dicembre 2004): 2193–240. http://dx.doi.org/10.1142/s0218271804006462.
Abstract (sommario):
The role played by torsion in gravitation is critically reviewed. After a description of the problems and controversies involving the physics of torsion, a comprehensive presentation of the teleparallel equivalent of general relativity is made. According to this theory, curvature and torsion are alternative ways of describing the gravitational field, and consequently related to the same degrees of freedom of gravity. However, more general gravity theories, like for example Einstein–Cartan and gauge theories for the Poincaré and the affine groups, consider curvature and torsion as representing independent degrees of freedom. By using an active version of the strong equivalence principle, a possible solution to this conceptual question is reviewed. This solution ultimately favors the teleparallel point of view, and consequently the completeness of general relativity. A discussion of the consequences for gravitation is presented.
34
Chen, Wen-Hwa, e Ray Jan. "The Torsion Effect on Fully Developed Laminar Flow in Helical Square Ducts". Journal of Fluids Engineering 115, n. 2 (1 giugno 1993): 292–301. http://dx.doi.org/10.1115/1.2910138.
Abstract (sommario):
The continuity equation and Navier-Stokes equations derived from a non-orthogonal helical coordinate system are solved by the Galerkin finite-element method in an attempt to study the torsion effect on the fully developed laminar flow in the helical square duct. Since high-order terms of curvature and torsion are considered, the approach is also applicable to the problems with finite curvature and torsion. The interaction effects of curvature, torsion, and the inclined angle of the cross section on the secondary flow, axial velocity, and friction factor in the helical square duct are presented. The results show that the torsion has more pronounced effect on the secondary flow rather than the axial flow. In addition, unlike the flow in the toroidal square duct, Dean’s instability of the secondary flow, which occurs near the outer wall in the helical square duct, can be avoided due to the effects of torsion and/or inclined angle. In such cases, a decrease of the friction factor is observed. However, as the pressure gradient decreases to a small value, the friction factor for the toroidal square duct is also applicable to the helical square duct.
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Wardhana, I. Gede Adhitya Wisnu. "The Decomposition of a Finitely Generated Module over Some Special Ring". JTAM (Jurnal Teori dan Aplikasi Matematika) 6, n. 2 (12 aprile 2022): 261. http://dx.doi.org/10.31764/jtam.v6i2.6769.
Abstract (sommario):
This research aims to give the decompositions of a finitely generated module over some special ring, such as the principal ideal domain and Dedekind domain. One of the main problems with module theory is to analyze the objects of the module. This research was using a literature study on finitely generated modules topics from scientific journals, especially those related to the module theory. And by selective cases we find a pattern to build a conjecture or a hypothesis, by deductive proof, we prove the conjecture and state it as a theorem. The main result in this study is the decomposition of the finitely generated module is a direct sum of the torsion submodule and torsion-free submodule. Since the torsion-free module is always a free module over a principal ideal domain, then the torsion-free submodule is a free module. Last, we generalize the ring, from a principal ideal domain, to a Dedekind domain. We found then the torsion-free submodule became a projective module. Then the decomposition of the finitely generated module is a direct sum of the torsion submodule and the projective submodule. These results should help the researchers to analyze the objects on module theory.
36
Chen, Xin, Jun Ping Wang e Xin Yan. "Simplified Calculation of Internal Force of Steel Structure in Torsion". Applied Mechanics and Materials 444-445 (ottobre 2013): 12–17. http://dx.doi.org/10.4028/www.scientific.net/amm.444-445.12.
Abstract (sommario):
It cant be ignored when steel members generating forces and stresses in torsion. To get the exact results, you need to solve several higher order differential equations, and it is much difficult for actual engineering designs. Based on Elastic theory of thin-walled structures, this thesis tries to introduce an approximate, convenient and high-precision way to solve problems about torsion.
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Heitzmann, Daniel WW, Kai Pieschel, Merkur Alimusaj, Julia Block, Cornelia Putz e Sebastian I. Wolf. "Functional effects of a prosthetic torsion adapter in trans-tibial amputees during unplanned spin and step turns". Prosthetics and Orthotics International 40, n. 5 (10 luglio 2016): 558–65. http://dx.doi.org/10.1177/0309364615592698.
Abstract (sommario):
Background:Shear stress at the stump in trans-tibial amputees induced by turning movements may be reduced with the use of torsion adapters in the prosthesis.Objective:Monitoring the motion and kinetic effects of a regular torsion adapter in comparison to a rigid placebo in unplanned spin and step turns.Study design:Single-blinded placebo-controlled cohort study.Methods:In total, 10 trans-tibial amputees underwent three-dimensional gait analysis in level walking and unplanned spin and step turns with a torsion adapter and with a rigid placebo.Results:Kinetic effects varied among participants. No statistically significant reduction of peak internal and peak external transverse plane moments was found for the torsion adapter in any walking condition. However, transverse plane rotation of the adapter was monitored in all participants.Conclusion:Motion between the socket and the residual limb may be reduced during turns due to transverse plane motion of the torsion adapter and shear stress on the residual limb may be reduced. However, there may be good and bad responders to torsion adapters due to differences in coupling between the residual limb and the socket.Clinical relevanceStrong coupling between stump and socket will help the user controlling his prosthesis. Shear stress at the stump may increase in stump–socket interface stiffness and may be the reason for residual limb problems. Torsion adapters therefore may be beneficial for comfort and stump condition in individual cases.
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Han, Yang, Junfeng Duan e Shoumei Wang. "Benchmark Problems of Hyper-Elasticity Analysis in Evaluation of FEM". Materials 13, n. 4 (17 febbraio 2020): 885. http://dx.doi.org/10.3390/ma13040885.
Abstract (sommario):
The paper proposes benchmark problems on exact solutions of hyper-elastic analysis, which can be used to evaluate analysis capabilities of rubber-like materials provided by a finite element program or other approximate solution methods. Special attention was concentrated on analysis and derivation of the exact solutions for the thick-walled rubber cylinders under internal pressure and axial extension, the thick-walled rubber balloons under internal pressure and the rubber cylinders under torsion or tension-torsion. Deformation and stress analysis on the above three cases were conducted to provide equations and methods for data processing. Exact standard solutions of the problems combined with the strain energy function of generalized high-order polynomials are given. Numerical examples and evaluation results of two commercial packages that are in common use (ABAQUS and ANSYS) are presented. Good agreements are found in the comparisons between the present exact standard solutions and the simulation results.
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Pisani, G. "Problèmes de torsion et de rotation intersegmentaires du membre inférieur*". Médecine et Chirurgie du Pied 22, n. 1 (marzo 2006): 24–29. http://dx.doi.org/10.1007/s10243-006-0073-4.
40
Shen, Chuanliang, Jincheng Zhan, Yifei Deng e Yaohui Gao. "Design and Characteristics of Shape Memory Alloy Bidirectional Torsional Actuator". Journal of Physics: Conference Series 2587, n. 1 (1 settembre 2023): 012036. http://dx.doi.org/10.1088/1742-6596/2587/1/012036.
Abstract (sommario):
Abstract To overcome the problems of the low power/weight ratio of traditional servo motors, complex transmission systems, and large space occupied by hydraulic drive systems, this paper designs a bidirectional torsional actuator using the shape memory effect of Ti-Ni shape memory alloy (SMA) wire, which aims to realize the folding and unfolding of the wings of flying cars. The model of the designed actuator was established and the theoretical calculation was analyzed, based on which the experimental verification was carried out. It is found that when the heating current is 1.6 A, the mechanism can take into account the economy under the premise of meeting a certain folding speed. When the pre-stretching amount of SMA wire is 3%, the residual strain corresponding to the wire is small, about 0.577%, and it can provide driving torque and torsion angle to meet the design requirements of the actuator. This verifies the feasibility of the actuator and obtains the driving characteristics of the actuator. Finally, the shortcomings and improvement measures of the actuator are analyzed briefly.
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Bejan, Cornelia-Livia, e Ana Velimirovic. "Linear connections with and without torsion, making parallel an integrable endomorphism on a manifold". Filomat 33, n. 10 (2019): 2943–49. http://dx.doi.org/10.2298/fil1910943b.
Abstract (sommario):
Our study is developed in a general framework, namely a manifold M endowed with a (1,1)- tensor field ?, which is integrable. The present paper solves the following two problems: how many linear connections with torsion and without torsion exist, having the property of being parallel with respect to ?. To count all these connections with the given properties, certain algebraic techniques and results are used throughout the paper.
42
Hernandez, Esmeralda, Ana Silvia Salinas Perez, Alberto León Atilano e Jose M. Montaño Sandoval. "Torsión, esfuerzos y deformaciones". TEPEXI Boletín Científico de la Escuela Superior Tepeji del Río 8, n. 16 (5 luglio 2021): 43–47. http://dx.doi.org/10.29057/estr.v8i16.6727.
Abstract (sommario):
En el trabajo que se muestra a continuación, se analizaron diversas fuentes de investigación con la finalidad de recabar información confiable, para así dar a conocer el tema Torsión “esfuerzos y deformaciones”. La información que se presenta es en su totalidad veraz y concisa por lo que la presente base teórica se encuentra en los resultados de esta investigación presentada. De forma correcta se dan a conocer definiciones, características y aplicaciones en un entorno de ingeniería industrial, tanto a su vez en un enfoque a universitarios ya que los temas mencionados en este trabajo son de importancia y tienden a ser presentes a lo largo del campo laboral industrial, como lo pude ser en un problema de manufactura o bien de calidad, para ello la información aquí presentada demuestra con veracidad de lo que puede ser el momento torsor de una barra cilíndrica, ejemplos de torsión uniforme y no uniforme, ejes independientes al instante de que una fuerza actúa sobre ellos. En esta investigación se proporciona información certera de términos, aplicaciones y ejemplos. Este trabajo fue realizado con el objetivo de así facilitar la información a estudiantes universitarios de ingeniería industrial, deseando que este conocimiento sea de suma importancia en su futura vida profesional laboral.
43
Zheng, S. Y., R. Y. Huang, J. Li e Z. Wang. "Reassembling 3D Thin Fragments of Unknown Geometry in Cultural Heritage". ISPRS Annals of Photogrammetry, Remote Sensing and Spatial Information Sciences II-5 (28 maggio 2014): 393–99. http://dx.doi.org/10.5194/isprsannals-ii-5-393-2014.
Abstract (sommario):
Many fragile antiques had already been broken upon being discovered at archaeology sites. The fragments of these objects cannot be effectively interpreted and studied unless they are successfully reassembled. However, there still exists many problems in the reassembly procedure in existing methods, such as the numerical instabilities of curvature and torsion based methods, the limitation of geometric assumption, and the error accumulation of the pairwise matching approach, etc. Regarding these problems, this paper proposed an approach to match the fragments to each other for their original 3D reconstruction. Instead of the curvatures and torsions, the approach is based on establishing a local Cartesian coordinate at every point of the 3D contour curves. First of all, the 3D meshes of the fragments are acquired by a structure-light based method, with the corresponding 3D contour curves extracted from the outer boundaries. Then, the contour curves are matched and aligned to each other by estimating all the possible 3D rigid transformations of the curve pairs with our defined local Cartesian coordinates, and then the maximum likelihood rigid transformations are selected. Finally, a global refinement is introduced to adjust the alignment errors and improve the final reassembling accuracy. In addition, experiments with two groups of fragments suggest that this approach cannot only match and align fragments effectively, but also improve the accuracy significantly. Comparing with the original 3D model acquired before being broken, the final reassembling accuracy reaches 0.47 mm.
44
Liu, Tonghua, Ziqiang Liu, Jiamin Wang, Shengnan Gong, Man Li e Shuo Cao. "Revisiting Friedmann-like cosmology with torsion: newest constraints from high-redshift observations". Journal of Cosmology and Astroparticle Physics 2023, n. 07 (1 luglio 2023): 059. http://dx.doi.org/10.1088/1475-7516/2023/07/059.
Abstract (sommario):
Abstract As one of the possible extensions of Einstein's General Theory of Relativity, it has been recently suggested that the presence of space-time torsion could solve problems of the very early and the late-time universe undergoing accelerating phases. In this paper, we use the latest observations of high-redshift data, coming from multiple measurements of quasars and baryon acoustic oscillations, to phenomenologically constrain such cosmological model in the framework of Einstein-Cartan (EC) endowed with space-time torsion. Such newly compiled quasar datasets in the cosmological analysis is crucial to this aim, since it will extend the Hubble diagram to high-redshift range in which predictions from different cosmologies can be distinguished. Our results show that out of all the candidate models, the torsion plus cosmological constant model is strongly favoured by the current high-redshift data, where torsion would be expected to yield the late-time cosmic acceleration. Specially, in the framework of Friedmann-like cosmology with torsion, the determined Hubble constant is in very good agreement with that derived from the Planck 2018 CMB results. On the other hand, our results are compatible with zero spatial curvature and there is no significant deviation from flat spatial hypersurfaces. Finally, we check the robustness of high-redshift observations by placing constraints on the torsion parameter α, which is strongly consistent with other recent works focusing on torsion effect on the primordial helium-4 abundance.
45
Sapountzakis, EJ, e IN Tsiptsis. "Generalized vibration analysis of beams including warping effects by isogeometric methods". Journal of Vibration and Control 24, n. 6 (5 gennaio 2017): 1032–50. http://dx.doi.org/10.1177/1077546316685679.
Abstract (sommario):
In this paper, the Isogeometric tools, either integrated in the Finite Element Method (FEM) or in a Boundary Element based Method (BEM) called Analog Equation Method (AEM), are employed for the vibration analysis of homogeneous beams of arbitrary cross section (thin- or thick- walled) taking into account nonuniform warping and shear deformation effects (shear lag due to both flexure and torsion). The beam is subjected to the combined action of arbitrarily distributed or concentrated axial and transverse loading, as well as to bending, twisting and warping moments. Its edges are subjected to the most general boundary conditions. By employing a distributed mass model system accounting for longitudinal, transverse, rotatory, torsional and warping inertia, ten boundary value problems with respect to the variable along the beam time-dependent 1-D kinematical components are formulated. The numerical solution or the spectrum analysis of the aforementioned problems is performed through IGA, FEM and AEM, leading to a system of second-order differential equations, which are quasi-static and solved for the free vibration case, formulating a generalized eigenvalue problem. Special cases of the generalized problem have also been studied in order to demonstrate the efficiency of AEM in reducing computational effort and improving accuracy, especially when combined to Isogeometric tools, such as NURBS and B-splines.
46
Macdonald, Jeremy, Alexei Miasnikov e Denis Ovchinnikov. "Low-complexity computations for nilpotent subgroup problems". International Journal of Algebra and Computation 29, n. 04 (giugno 2019): 639–61. http://dx.doi.org/10.1142/s021819671950019x.
Abstract (sommario):
We solve the following algorithmic problems using [Formula: see text] circuits, or in logspace and quasilinear time, uniformly in the class of nilpotent groups with bounded nilpotency class and rank: subgroup conjugacy, computing the normalizer and isolator of a subgroup, coset intersection, and computing the torsion subgroup. Additionally, if any input words are provided in compressed form as straight-line programs or in Mal’cev coordinates, the algorithms run in quartic time.
47
Sayidmuradov, Mirzokhid, Abdukarim Khudayberdiyev e Nosirjon Abdullajonov. "Study of dynamics of the turning process in pneumechanical spinning in the presence of false torsion". Journal of Physics: Conference Series 2697, n. 1 (1 febbraio 2024): 012022. http://dx.doi.org/10.1088/1742-6596/2697/1/012022.
Abstract (sommario):
Abstract The paper presents the results of a study of the dynamics of the process of torsion of yarn of pneumomechanical spinning in the presence of false torsion. Dynamic mathematical models of the process of torsion of yarn of pneumomechanical spinning in the presence of false torsion in unsteady modes of starting and stopping the forming-twisting device are constructed. By now, the question of yarn twisting in a transient mode of operation in rotor spinning remains unexplored. We have here made an attempt to fill the indicated gap by constructing mathematical models of a forming-twisting device during torsion. In connection with the above-mentioned problem arises to systematize the accumulated information on new methods of forming yarn and constructions of forming and torque devices, to clarify a number of questions of theory and technology, and also to classify methods of forming yarn. The main direction of development of new methods of yarn formation remains the improvement of the high-speed modes of the working organs and, above all, of the forming and turning devices, which raises a number of important problems of both technological and structural nature.
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Panov, A. D., e V. V. Shumaev. "Using the logarithmic strain measure for solving torsion problems". Mechanics of Solids 47, n. 1 (febbraio 2012): 71–78. http://dx.doi.org/10.3103/s0025654412010062.
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Buscaglia, Gustavo C., Rau´l A. Feijo´o e Edgardo Taroco. "Adjoint Shape Sensitivity Analysis for Steady Creep Torsion Problems". Applied Mechanics Reviews 50, n. 11S (1 novembre 1997): S20—S27. http://dx.doi.org/10.1115/1.3101837.
Abstract (sommario):
Taking the total complementary dissipation energy as the cost function and the compatibility as the state equation, the first and second order shape sensitivity analysis for steady-state creep torsion problems are presented in this paper. Using the variational formulation, the fixed domain technique and the adjoint approach, integral expressions over the domain are obtained. Moreover, a particular case with known analytical solution is analyzed in order to show the equivalence between exact differentiation and the shape sensitivity approach. Finally, this example is also used to stress that the extension of the velocity field to the interior of the domain is irrelevant.
50
Chen, Y. Z. "Numerical solution for multiple crack problems of torsion bar". Computer Methods in Applied Mechanics and Engineering 174, n. 1-2 (maggio 1999): 203–9. http://dx.doi.org/10.1016/s0045-7825(98)00314-4.