109 results on '"Deformations"'
Search Results
2. Stability of the scattering transform for deformations with minimal regularity.
- Author
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Nicola, Fabio and Trapasso, S. Ivan
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LIPSCHITZ continuity , *DEFORMATIONS (Mechanics) , *WAVELET transforms , *DIFFEOMORPHISMS - Abstract
The wavelet scattering transform introduced by Stéphane Mallat is a unique example of how the ideas of harmonic and multiscale analysis can be ingeniously exploited to build a signal representation with provable geometric stability properties, such as the Lipschitz continuity to the action of small C 2 diffeomorphisms – a remarkable result for both theoretical and practical purposes, inherently depending on the choice of the filters and their arrangement into a hierarchical architecture. In this note, we further investigate the intimate relationship between the scattering structure and the regularity of the deformation in the Hölder regularity scale C α , α > 0. We are able to precisely identify the stability threshold, proving that stability is still achievable for deformations of class C α , α > 1 , whereas instability phenomena can occur at lower regularity levels modeled by C α , 0 ≤ α < 1. While the analysis at the threshold given by Lipschitz (or even C 1) regularity remains beyond reach, we are able to prove a stability bound in that case, up to ε losses. [ABSTRACT FROM AUTHOR]
- Published
- 2023
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3. Integrable deformations of Rikitake systems, Lie bialgebras and bi-Hamiltonian structures.
- Author
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Ballesteros, Angel, Blasco, Alfonso, and Gutierrez-Sagredo, Ivan
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HAMILTONIAN systems , *LIE groups , *DEFORMATIONS (Mechanics) , *DYNAMICAL systems - Abstract
Integrable deformations of a class of Rikitake dynamical systems are constructed by deforming their underlying Lie–Poisson Hamiltonian structures, which are considered linearizations of Poisson–Lie structures on certain (dual) Lie groups. By taking into account that there exists a one-to one correspondence between Poisson–Lie groups and Lie bialgebra structures, a number of deformed Poisson coalgebras can be obtained, which allow the construction of integrable deformations of coupled Rikitake systems. Moreover, the integrals of the motion for these coupled systems can be explicitly obtained by means of the deformed coproduct map. The same procedure can be also applied when the initial system is bi-Hamiltonian with respect to two different Lie–Poisson algebras. In this case, to preserve a bi-Hamiltonian structure under deformation, a common Lie bialgebra structure for the two Lie–Poisson structures has to be found. Coupled dynamical systems arising from this bi-Hamiltonian deformation scheme are also presented, and the use of collective 'cluster variables', turns out to be enlightening in order to analyse their dynamical behaviour. As a general feature, the approach here presented provides a novel connection between Lie bialgebras and integrable dynamical systems. • Integrable deformations of dynamical systems are constructed through Lie bialgebras. • Deformed integrals of the motion can be directly obtained. • Integrable deformations of Rikitake dynamical systems are presented. • Bi-Hamiltonian systems can be also deformed under certain compatibility constraints. • Coupled systems are constructed by making use of Poisson–Lie group structures. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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4. Deformation cohomology for cyclic groups acting on polynomial rings.
- Author
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Lawson, Colin M. and Shepler, Anne V.
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POLYNOMIAL rings , *GROUP algebras , *FINITE groups , *CYCLIC groups - Abstract
We examine the Hochschild cohomology governing graded deformations for finite cyclic groups acting on polynomial rings. We classify the infinitesimal graded deformations of the skew group algebra S ⋊ G for a cyclic group G acting on a polynomial ring S. This gives all graded deformations of the first order. We are particularly interested in the case when the characteristic of the underlying field divides the order of the acting group, which complicates the determination of cohomology. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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5. Structural styles and chronological sequence of the Mianyuzui ductile strike-slip fault along the Shangdan suture Zone: Implications for the Paleozoic tectonic evolution of the Qinling Orogenic Belt, China.
- Author
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Sheir, Falak, Li, Wei, Zhang, Le, Baz, Shair, Jiang, Liuqing, Liang, Li, Wang, Chao, Feng, Zhanwei, and Rehman, Adnanul
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OROGENIC belts , *SUTURE zones (Structural geology) , *PALEOZOIC Era , *LITHOSPHERE , *URANIUM-lead dating , *SHEAR (Mechanics) - Abstract
• Two phases of deformation occured in the south of the Shangdan suture zone across the Mianyuzui ductile strike-slip fault. • The metamorphic temperature of the early stage of shearing deformation is ∼ 600-700℃ and ∼ 300-500℃ for the late stage. • The subduction of the Shangdan Oceanic lithosphere was active till the Early Silurian, and subsequent collisions occurred during the Late Silurian. The Shangdan suture zone (SDSZ) subdivides the Qinling Orogenic Belt into North Qinling and South Qinling belts, marking the main tectonic boundary between the North China and South China Blocks. The Mianyuzi ductile strike-slip fault (MYZF) within the SDSZ separates the North China Block from the South China Block and contains valuable collisional information. This paper integrates the structural and geochronological data of the MYZF to investigate the Paleozoic tectonic evolution of the Qinling Orogenic Belt and the collision between the North China and South China Blocks. Two phases of deformation (D 1 -D 2a-b) are identified along the southern boundary of the SDSZ. The metamorphic temperature of mylonites is ∼ 600–700 ℃ for the early stage and ∼ 300–500 ℃ for the late stage of shearing deformation. U-Pb zircon analysis of the mylonites and diabase dike in the ductile shear reveals that zircons have major younger protolith populations at 480–460 Ma, 450–430 Ma, and 405–425 Ma, which suggests that rocks were probably derived from the North Qinling belt. The metamorphism and deformation cooling age from the MYZF have been constrained to be 339–328 Ma and 259 ± 1.6 Ma using U-Pb and 40Ar/39Ar dating. Combined with previously published data, we concluded that the subduction of the Shangdan Ocean was active until the Early Silurian and subsequent collisions occurred during the Late Silurian. Meanwhile, the shearing might have been related to the intraplate extension-exhumation during the Carboniferous-Late Permian in the Qinling Orogenic Belt. [ABSTRACT FROM AUTHOR]
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- 2024
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6. Numerical investigation and modeling of residual stress field variability impacting the machining deformations of forged part.
- Author
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Chabeauti, Hugo, Ritou, Mathieu, Lavisse, Bruno, Germain, Guenael, and Charbonnier, Virginie
- Abstract
Aluminum alloys are widely used for structural parts in the aerospace industry. Those parts are usually machined from rolled plates or forged blanks, and heat treatments are carried out to reach the necessary mechanical properties. Forming and heat treatments induce residual stresses that generate deformations during and after machining because material removal modifies their balance. One major issue in industry is the important variability of the residual stress field in forged blanks. A better knowledge of the residual stress field will enable the definition of better machining strategy to minimize the deformations. In order to understand and manage this variability, a sensibility analysis was performed to investigate the impact of their different potential sources. It relies on a coupling of 2D-FEM and beam model simulations. Then, this work introduces a model reduction technique (by POD and SVD) to build a model of the variability of a stress field and shows how it could be used on the production line. [ABSTRACT FROM AUTHOR]
- Published
- 2022
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7. The role of the substrate on the mechanical and thermal stability of Pd thin films during hydrogen (de)sorption.
- Author
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Verma, Neha, Delhez, Rob, van der Pers, Niek M., Tichelaar, Frans D., and Böttger, Amarante J.
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THIN films , *THERMAL stability , *SORPTION , *MAGNETRON sputtering , *STRAINS & stresses (Mechanics) , *PHASE transitions , *DELAMINATION of composite materials , *EMBRITTLEMENT - Abstract
In this work, we studied the mechanical and thermal stability of ~100 nm Pd thin films magnetron sputter deposited on a bare oxidized Si(100) wafer, a sputtered Titanium (Ti) intermediate layer, and a spin-coated Polyimide (PI) intermediate layer. The dependence of the film stability on the film morphology and the film-substrate interaction was investigated. It was shown that a columnar morphology with elongated voids at part of the grain boundaries is resistant to embrittlement induced by the hydride formation (α↔β phase transitions). For compact film morphology, depending on the rigidity of the intermediate layer and the adherence to the substrate, complete transformation (Pd-PI-SiO 2 /Si) or partly suppression (Pd-Ti-SiO 2 /Si) of the α to β-phase was observed. In the case of Pd without intermediate layer (Pd-SiO 2 /Si), buckling delamination occurred. The damage and deformation mechanisms could be understood by the analysis of the stresses and dislocation (defects) behavior near grain boundaries and the film-substrate interface. From diffraction line-broadening combined with microscopy analysis, we showed that in Pd thin films, stresses relax at critical stress values via different relaxation pathways depending on film-microstructure and film-substrate interaction. On the basis of the in-situ hydriding experiments, it was concluded that a Pd film on a flexible PI intermediate layer exhibits free-standing film-like behavior besides being strongly clamped on a stiff SiO 2 /Si substrate. • Pd thin film–morphology and substrate interaction studied. • Open columnar morphology inhibits H-induced buckling delamination. • Pd film on a flexible PI interlayer exhibits free-standing film-like behavior. • All Pd films contain similar kinds of defects but differ by defect density. • The softer interface corresponds to the stronger thin film system. [ABSTRACT FROM AUTHOR]
- Published
- 2021
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8. Deformations of modules through butterflies and gerbes.
- Author
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Herr, Leo
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BUTTERFLIES , *TOPOLOGY , *FOOTSTEPS , *CONSTRUCTION - Abstract
Classifying obstructions to the problem of finding extensions between two fixed modules goes back at least to L. Illusie's thesis. Our approach, following in the footsteps of J. Wise, is to introduce an analogous Grothendieck Topology on the category A -mod of modules over a fixed ring A in a topos E. The problem of finding extensions becomes a banded gerbe and furnishes a cohomology class on the site A -mod. We compare our obstruction and that coming from Illusie's work, giving another construction of the exact sequence Illusie used to obtain his obstruction. Our work circumvents the cotangent complex entirely and answers a question posed by Illusie. [ABSTRACT FROM AUTHOR]
- Published
- 2020
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9. Plasticity and phase transition of crystals under continuous deformations by phase field crystal approach.
- Author
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Wang, Kun, Zhang, Fengguo, He, Anmin, and Wang, Pei
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PHASE transitions , *CRYSTALS , *MATERIAL plasticity , *PHASE diagrams , *SIMULATION methods & models - Abstract
Despites of some efforts in deformation simulations by the Phase field crystal (PFC) method, simulations of phase transitions and plasticity of crystals under continuous deformations are still lack and some related fundamental issues remain open as well, for example the definition of stresses and the non-zero stresses of unstrained system. In the present work, we propose a deformation simulation method which conforms to the well-established framework of the PFC model. In contrast to traditional deformation simulation methods, our method could naturally mimic melting/freezing, solid-solid phase transition and plasticity of materials under continuous deformations without any additional parameters. Within the frameworks of our method, the stress is well-defined and isothermal-isobaric simulation method is developed. The isothermal-isobaric simulation method enables us to overcome the drawback of previous PFC simulations, for example the nonzero stress of unstrained system. Numerical examples given in present work confirm our conclusions. Particularly, the physical natures of the plasticity are uncovered at the temporal and spatial scale accessible to the PFC method. • Deformation simulations are performed by PFC method without additional parameters. • Multiple phase transitions and plasticity under deformations are naturally simulated. • Stress defined well conforms to present PFC formalisms. • Isochoric and isobaric simulation techniques are delicately developed. • Equilibrium conditions and instabilities are discussed within the established framework. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
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10. Construction of master yield stress curves for polycarbonate: A coarse-grained molecular dynamics study.
- Author
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Kubo, Atsushi, Albina, Jan-Michael, and Umeno, Yoshitaka
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YIELD stress , *MOLECULAR dynamics , *POLYCARBONATES , *STRAIN rate , *CURVES , *CONSTRUCTION - Abstract
A coarse-grained particle model was developed for the simulation of deformations in polycarbonate. Coarse-grained molecular dynamics simulations of uniaxial and multiaxial deformations are carried out to determine the critical yield stress for various strain rates. From the calculated values, a master curve of the yield stress as a function of the strain rate is built at 300 K. It is found that the predicted results and experimental values are aligned on the same curve and can be described by a simple Cowper-Symonds relation. Furthermore, using the Williams, Landel and Ferry equation, a master curve is built to predict the yield stress at finite temperatures. By investigating additional deformation modes, two supplementary master curves are built at 300 K: one for the void nucleation and one for the shear yielding. Image 1 • A coarse-grained model is developed to study deformations in polycarbonate. • Various deformation modes are investigated. • The critical yield stress is evaluated at different strain rates and temperatures. • Multi-temperature and multi-loading master yield stress curves are built. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
11. On finite-dimensional copointed Hopf algebras over dihedral groups.
- Author
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Fantino, Fernando, García, Gastón Andrés, and Mastnak, Mitja
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HOPF algebras , *DIHEDRAL angles , *DIMENSIONAL analysis , *COHOMOLOGY theory , *ISOMORPHISM (Mathematics) - Abstract
Abstract We classify all finite-dimensional Hopf algebras over an algebraically closed field of characteristic zero such that its coradical is isomorphic to the algebra of functions k D m over a dihedral group D m , with m = 4 a ≥ 12. We obtain this classification by means of the lifting method, where we use cohomology theory to determine all possible deformations. Our result provides an infinite family of new examples of finite-dimensional copointed Hopf algebras over dihedral groups. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
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12. Cohomologies, deformations and extensions of [formula omitted]-Hom-Lie algebras.
- Author
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Song, Lina and Tang, Rong
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ALGEBRA , *LIE algebras - Abstract
In this paper, first we give the cohomologies of an n -Hom-Lie algebra and introduce the notion of a derivation of an n -Hom-Lie algebra. We show that a derivation of an n -Hom-Lie algebra is a 1-cocycle with the coefficient in the adjoint representation. We also give the formula of the dual representation of a representation of an n -Hom-Lie algebra. Then, we study (n − 1) -order deformation of an n -Hom-Lie algebra. We introduce the notion of a Hom-Nijenhuis operator, which could generate a trivial (n − 1) -order deformation of an n -Hom-Lie algebra. Finally, we introduce the notion of a generalized derivation of an n -Hom-Lie algebra, by which we can construct a new n -Hom-Lie algebra, which is called the generalized derivation extension of an n -Hom-Lie algebra. [ABSTRACT FROM AUTHOR]
- Published
- 2019
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13. Embryonic exposure to produced water can cause cardiac toxicity and deformations in Atlantic cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) larvae.
- Author
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Hansen, Bjørn Henrik, Sørensen, Lisbet, Størseth, Trond R., Nepstad, Raymond, Altin, Dag, Krause, Daniel, Meier, Sonnich, and Nordtug, Trond
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OIL field brines , *ATLANTIC cod , *POLYCYCLIC aromatic hydrocarbons , *LARVAE , *ALKANES , *ANTHRACYCLINES - Abstract
Regular discharges of produced water from the oil and gas industry represents the largest direct discharge of effluent into the marine environment worldwide. Organic compound classes typically reported in produced water include saturated hydrocarbons, monoaromatic and polyaromatic hydrocarbons (MAHs, PAHs) as well as oxygenated compounds, such as phenols, acids and ketones. This forms a cocktail of known and suspect toxicants, but limited knowledge is yet available on the sub-lethal toxicity of produced water to cold-water marine fish species. In the present work, we conducted a 4-day exposure of embryos of Atlantic cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) to produced water extracts equivalent to 1:50, 1:500 and 1:5000 times dilutions of raw effluent. No significant reduction in survival or hatching success was observed, however, for cod, hatching was initiated earlier for exposed embryos in a concentration-dependent manner. During recovery, significantly reduced embryonic heart rate was observed for both species. After hatch, larvae subjected to embryonic exposure to produced water extracts were smaller, and displayed signs of cardiotoxicity, jaw and craniofacial deformations. In order to improve risk assessment and regulation of produced water discharges, it is important to identify which produced water components contribute to these effects. • Atlantic cod and haddock embryos were exposed to produced water extracts mimicking 50–5000 times dilution of produced water. • Exposure to produced water caused no significant effects on acute mortality and hatching success. • Delayed effects were observed in larvae displaying symptoms of cardiotoxicity and developmental deformations. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
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14. Main aspects of deformation and rock support in Norwegian road tunnels.
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Høien, A.H., Nilsen, B., and Olsson, R.
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ROCK deformation , *TUNNELS - Abstract
Highlights • Evaluation of rock support in hard rock tunnelling using Norwegian data. • Review of literature regarding rock support and deformations. • Parameter study using numerical modelling to explore deformations with different rock mass qualities and stresses. Abstract The general geology of Norway makes most of its tunnels to be constructed mainly in strong rock intersected by weakness zones of different sizes and characteristics. The Norwegian support tradition is, to the largest degree as possible, to reinforce the rock to make it self-bearing. In weak rock, this reinforcement has been accomplished by using bolts, sprayed concrete and ribs of reinforced concrete (RRS). RRS are normally designed with 6 rebars mounted on brackets that are attached to rock bolts with a center to center distance of 1.5 m covered in sprayed concrete. The spacing between the RRS in the tunnel direction is usually 1–3 m. In recent years, the application of RRS has gradually changed from following the blasted tunnel profile that formed unarched RRS that reinforced the rock to using RRS with an arched design that supports the rock. Following this development was an increase in the use of materials, as the amount of sprayed concrete used is now considerably larger and the rebar diameter changed from 16 to 20 mm. This change has also caused an abrupt increase in the support measures used for decreasing rock quality, from simple reinforcement by bolts and sprayed concrete to load-bearing arches. The authors believe that a more gradual transition is logical and this article will discuss and evaluate the current Norwegian support strategy by reviewing international theory, performing parameter analysis and presenting data from current and previous Norwegian road tunnels, with a focus on rock mass quality and deformations. It is concluded that arched RRS is not necessary for all cases where it is used today, and that evaluation of the need for load bearing arched RRS should be based on deformation considerations. Norwegian conditions comprise the basis for the discussion, but the problem at hand is also of general interest for hard rock tunnelling conditions. [ABSTRACT FROM AUTHOR]
- Published
- 2019
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15. Local irreversible magnetization rotation of Permalloy thin films on binding papers.
- Author
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Li, Ying and Wang, Hai
- Subjects
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MAGNETIC anisotropy , *DEMAGNETIZATION , *MAGNETIC properties of condensed matter , *CURIE temperature , *MAGNETOSTRICTION - Abstract
Abstract In narrow senses, flexible devices consist of soft upholders and functional materials/devices. Such hybrid devices with elastic deformations are promising for broad applications ranging from displays to sensors/detectors and micro/nano mechanical systems (MEMS). In contrast, plastic deformations are typically avoided, because of the common belief that the functionalities of the flexible devices degrade due to irreversible deformations. In this letter, we show that, for exploiting the competition between macro-elastic and local-plastic deformations, on common binding papers, the direction of magnetization in Permalloy thin films realizes a 90 ∘ rotation. A positive magnetic anisotropic constant starts at the center of sample, approaches zero after leaving from the center, and then increases its strength gradually with a negative sign until the sample edge, following an approximately linear relationship. In addition, the magnetic stability of the samples improved owing to the residual stress of the local-plastic deformations, as well as diversification of functionality and transfer are easy to be implemented by the composite substrate. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
16. Relevance of different Skyrme forces in the dynamics of [formula omitted] reactions.
- Author
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Sharma, Ishita, Kumar, Raj, and Sharma, Manoj K.
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SKYRME model , *COMPOUND nucleus , *HEAVY ions , *NUCLEAR deformation , *NUCLEAR fusion - Abstract
Abstract The role of different Skyrme forces and associated neutron transfer effect is investigated in the view of Ca 40 , 48 + 96 Zr reactions. The fusion cross section has been calculated using Wong formula and extended Wong model, wherein neutron transfer effect is studied by scaling the transmission probability of contributing channel(s). The decay analysis is carried out in the framework of dynamical cluster decay model, where the neck length Δ R and corresponding barrier modification Δ V B are used to explore the neutron transfer effect in the decaying fragments. For fusion and subsequent decay, the nuclear proximity potential is calculated using Skyrme interactions such as SIII, GSkI, SkT1, SkT2, and SkT3. In Ca 40 + 96 Zr case, the fusion hindrance is observed at sub barrier energies for the use of SIII, SkT1, SkT2 Skyrme forces. The cross sections are improved to some extent for GSkI force. Further, the inclusion of 1n-transfer channel in the calculations shows that the experimental data is adequately addressed for GSkI force, however, the correction of 1n-transfer channel for SkT1 (or SIII, SkT2 forces), persists with the poor fit to experimental data. In the decay analysis, the interaction potentials significantly affect the structural properties of decaying fragments as is clear from the fragmentation potential and preformation probability. Both, the fusion and decay analysis consistently advocate that GSkI force comprising of extended density-dependent term is able to address the sub barrier anomalies. The neutron transfer effect is explored in view of different choices of the Skyrme forces, which shows that the forces with higher barrier lead to more neutron transfer channel effect and vice versa. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
17. Monitoring wastewater discharge from the oil and gas industry using passive sampling and Danio rerio bioassay as complimentary tools.
- Author
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Hale, Sarah E., Škulcová, Lucia, Pípal, Marek, Cornelissen, Gerard, Oen, Amy M.P., Eek, Espen, and Bielská, Lucie
- Subjects
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SEWAGE purification , *OIL field brines , *PASSIVE sampling devices (Environmental sampling) , *POLYETHYLENE , *ZEBRA danio - Abstract
Abstract Produced water (PW) represents the largest volume waste stream in oil and gas production operations from most offshore platforms. PW is difficult to monitor as releases are rapidly diluted and concentrations can reach trace levels. The use of passive samplers can over come this. Here polyethylene (PE) was calibrated for a diverse range of PW pollutants. Zebrafish were exposed to dilutions of PW and passive sampler extracts in order to investigate the relationship between freely dissolved chemical concentrations and acute toxic effects. The raw PW had an LC50 of 13% (percentage of PW in the standardized zebrafish medium). Observed non-viable deformations to embryos (at 5 hpf) included heart and yolk edema, head, spine and tail deformations. The dose-response relationship of lethal effects showed that if 0.0041 g of PE is exposed to this PW, then extracted, 50% of exposed D. rerio will suffer lethal effects. The sum of tested freely dissolved concentrations that led to 50% lethal effects (mortality and non-viable deformations) was 2.32 × 10−4 mg/L for PW and 7.92 × 10−2 mg/L for PE. This implies that exposure to raw PW was more toxic than exposure to PE extracts. This toxicity was attributed both to the presence of contaminants as well as PW salinity. Passive samplers are able to detect very low freely dissolved pollutant concentrations which is important for assessing the spatial dilution of PW releases. Bioassays provide complimentary information as they account for all toxic compounds including those that are not taken up by passive samplers. Graphical abstract Image 1 Highlights • Passive sampling and bioassays could both be used in water column monitoring. • Polyethylene was exposed to produced water. • Zebrafish were exposed to produced water and polyethylene extracts. • Exposure to produced water was more toxic than to polyethylene extracts. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
18. Cohomology and deformations of compatible Hom-Lie algebras.
- Author
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Das, Apurba
- Subjects
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ALGEBRA , *LIE algebras , *COHOMOLOGY theory , *DIFFERENTIAL algebra - Abstract
In this paper, we consider compatible Hom-Lie algebras as a twisted version of compatible Lie algebras. Compatible Hom-Lie algebras are characterized as Maurer-Cartan elements in a suitable bidifferential graded Lie algebra. We also define a cohomology theory for compatible Hom-Lie algebras generalizing the recent work of Liu, Sheng and Bai. As applications of cohomology, we study abelian extensions and deformations of compatible Hom-Lie algebras. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
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19. Experimental and numerical analysis of strain gradient in tensile concrete prisms reinforced with multiple bars.
- Author
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Gribniak, Viktor, Jakubovskis, Ronaldas, Rimkus, Arvydas, Ng, Pui-Lam, and Hui, David
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CONCRETE , *STRAINS & stresses (Mechanics) , *TENSILE tests , *BARS (Engineering) , *DEFORMATIONS (Mechanics) , *FINITE element method - Abstract
Graphical abstract Highlights • Deformation behavior of concrete is dependent on arrangement of the reinforcement. • A new test methodology of concrete prisms with multiple bars is presented. • The design concept and the components of the test setup are explained. • Average deformations of concrete and reinforcement are different. • Finite element technique as a versatile tool for analysis of the strain gradient. Abstract This work is a continuation of the ongoing research on deformation behavior of reinforced concrete elements under tension. The previous studies have revealed that deformation behaviors of elements reinforced with multiple bars and the traditional prismatic members reinforced with a center bar are essentially different. The latter layout, though typical of laboratory specimens, could not represent the norm of structures in real-life. Thus, a new test methodology to investigate the strain distribution in concrete prismatic members reinforced with multiple bars subjected to axial tension is devised. Prismatic concrete specimens with different reinforcement configurations were fabricated and tested using the proposed setup. Deformation behavior of the specimens is modeled with a tailor-designed bond modeling approach for rigorous finite element analysis. It is revealed that the average deformations of the concrete could be different from the prevailing approach of average deformations of the steel, and are dependent on the reinforcement configurations. Therefore, the efficiency of concrete in tension should be carefully taken into account for rational design of structural elements. The study endorses promising abilities of finite element technique as a versatile analysis tool whose full potential is to be revealed with the advent of computer hardware. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
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20. An experimental study on cracking and deformations of tensile concrete elements reinforced with multiple GFRP bars.
- Author
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Gribniak, Viktor, Rimkus, Arvydas, Torres, Lluis, and Hui, David
- Subjects
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CARBON fiber-reinforced plastics , *CRACKING of concrete , *TENSILE strength , *STIFFNESS (Engineering) , *DEFORMATIONS (Mechanics) - Abstract
Although different setups have been developed for analysis of the serviceability properties (cracking and deformations) of reinforced concrete elements, tensile tests are remaining the most often used testing layouts. Recent studies, however, have revealed noticeable limitations of the traditional tests of concrete prisms reinforced with a centre bar. The essential aspect responsible for adequate interpretation of the test outcomes could be addressed to inter-correlation of the basic cross-section parameters, i.e. bar diameter, reinforcement ratio, and cover depth. Furthermore, the test equipment has a limited possibility comparing outcomes of the tensile prisms reinforced with bars made of steel and fibre reinforced polymer materials. To solve these problems, a special equipment for the anchorage of multiple bars has been developed. This manuscript presents and discusses the tests results of 16 prismatic specimens reinforced with steel and glass fibre reinforced polymer (GFRP) bars provided by different producers. At the same deformation range of reinforcement, almost identical crack distances are characteristic of the prisms reinforced with steel and GFRP bars with similar axial stiffness. This result enables formulating a hypothesis that crack spacing in tensile elements of equivalent axial stiffness is predominantly dependent on geometry of the concrete and, particularly, on the cover depth. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
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21. Simulation of A Hot-rolled H-section Steel Beam Subject to Static Loading Based on Discrete Element Method.
- Author
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Zhou, Li-Qiang and Yang, Bo
- Subjects
DISCRETE element method ,GRANULAR flow ,FINITE element method ,DEFORMATIONS (Mechanics) ,STEEL buildings - Abstract
In this paper, a new discrete element method (DEM) containing particle flow code (PFC) is presented as an efficient-to-implement alternative to the existing finite element method (FEM) for simulating internal forces and deformations of a hot-rolled H-section steel beam subject to static loading. Unlike FEM, which is efficient to solve continuous problems, the PFC method can solve discontinuous problems, such as collapse procedure of structures, and the collapse procedure of the structure can be monitored at different times in a more time-saving way. First of all, a linear constitutive model in FEM was built to compare with the linear parallel bond model built in PFC, a hot-rolled H-section steel beam considering geometrically non-linearity subject to static loading was simulated and the simulation results were compared with theoretical solution and FEM results. Both internal forces and deformations before yielding were compared and good agreements were achieved. Secondly, with the object-oriented programming technique and the redeveloped interface of PFC, a user-defined parallel bond model was developed to consider material nonlinearity and compared with the bilinear constitutive model built in FEM. Both internal forces and deformations before and after yielding were compared and good agreements were observed. Thus, the DEM model adopted in this paper can be efficiently used to simulate the behavior of the H-section steel beam. In the future, the developed parallel bond model can be used to simulate the performance of H-section steel beam subject to vertical impact loading and three-dimensional steel framed structure subject to horizontal collision. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
22. Effects on Chilean Vertical Reference Frame due to the Maule Earthquake co-seismic and post-seismic effects.
- Author
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Montecino, Henry D., de Freitas, Silvio R.C., Báez, Juan C., and Ferreira, Vagner G.
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- *
CHILE Earthquake, Chile, 2010 (February 27) , *DEFORMATIONS (Mechanics) , *CRUST of the earth , *GLOBAL Positioning System , *TIME series analysis - Abstract
The Maule Earthquake (M w = 8.8) of February 27, 2010 is among the strongest earthquakes that occurred in recent years throughout the world. The crustal deformation caused by this earthquake has been widely studied using GNSS, InSAR and gravity observations. However, there is currently no estimation of the possible vertical deformations produced by co-seismic and post-seismic effects in segments of the Chilean Vertical Reference Frame (CHVRF). In this paper, we present an estimation of co-seismic and post-seismic deformations on the CHVRF using an indirect approach based on GNSS and Gravity Recovery and Climate Experiment (GRACE) data as well as by applying a trajectory model. GNSS time series were used from 10 continuous GNSS stations in the period from 2007 to 2015, as well as 28 GNSS temporary stations realized before and after the earthquake, and 34 vertical deformation vectors in the region most affected by the earthquake. We considered a set of 147 monthly solutions of spherical harmonic gravity field that were expanded up to degree, as well as order 96 of the GRACE mission provided by Center for Space Research, University of Texas at Austin (UT-CSR) process center. The magnitude of vertical deformation was estimated in part of the Chilean vertical network due to the co-seismic and post-seismic effects. Once we evaluated the hydrological effect, natural and artificial jumps, and the effect of glacial isostatic adjustment in GNSS and GRACE time series, the maximum values associated to co- and post-seismic deformations on orthometric height were found to be ∼−34 cm and 5 cm, respectively. Overall, the deformation caused by the Maule earthquake in orthometric heights is almost entirely explained by the variation in the ellipsoidal heights (over 85% in co-seismic jump); however, coseismic jump in the geoid reached −3.3 mm, and could influence the maintenance of a modern vertical reference network in a medium to long term. We evaluated the consistency for a segment of the CHVRF after the earthquake and recommended precautions for using the CHVRF in the region. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
23. Stable reflexive sheaves of degree zero on Calabi–Yau manifolds.
- Author
-
Nakashima, Tohru
- Subjects
- *
CALABI-Yau manifolds , *ARBITRARY constants , *SHEAF theory , *MATHEMATICAL equivalence , *HYPERSURFACES - Abstract
We give sufficient conditions for the existence of μ -stable reflexive sheaves E on a Calabi–Yau threefold such that the first Chern classes c 1 ( E ) satisfy c 1 ( E ) ⋅ H 2 = 0 for some ample line bundle H . We also prove a result concerning deformations to construct rank two μ -stable sheaves on arbitrary smooth projective varieties. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
24. Experimental investigation of cracking and deformations of concrete ties reinforced with multiple bars.
- Author
-
Rimkus, Arvydas and Gribniak, Viktor
- Subjects
- *
REINFORCED concrete , *REINFORCING bars , *TENSILE tests , *DEFORMATIONS (Mechanics) , *CRACKS in reinforced concrete , *DIGITAL image correlation - Abstract
Interpretation of test results may be inadequate even for simple test layouts. On the one hand, conventional tests, that investigate a concrete prism reinforced with a single bar in the centre, do not allow to account for the effect of variation of the diameter-to-reinforcement ratio (∅/ p ). This important limitation should be related to the use of simple specimens in constitutive modelling. On the other hand, a tie-test typically provides measurements of average deformations of the internal reinforcing bar and the concrete surface. The experimental evidence, however, often contradicts the general assumption of the equivalence of the mean strains of reinforcement and concrete. The strain difference is closely related to the width of the concrete cover. This paper investigates the effect of distribution of bar reinforcement on deformation and cracking behaviour of tensile elements. Special testing equipment has been developed to investigate ties reinforced with multiple bars. The test program consists of 23 ties. The number and diameter of the bars vary from 4 to 16 and from 5 mm to 14 mm, respectively. Two different covers (30 mm and 50 mm) are considered as well. The deformation analysis is based on measurements of the average reinforcement and concrete surface strains. The development of cracks was investigated using digital image correlation (DIC). The Model Code 2010 and Eurocode 2 predictions are compared with the experimental data. While the Design Codes predict that the maximum crack spacing is dependent on the ∅/ p ratio, the test results indicate that the crack distances are actually much less dependent on the reinforcement characteristics. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
25. Prediction of Natural and Technogenic Negative Processes Based on the Analysis of Relief and Geological Structure.
- Author
-
Kuzin, A.A., Grishchenkova, E.N., and Mustafin, M.G.
- Subjects
LANDSLIDE prediction ,SURFACE of the earth ,AIRBORNE laser altimeter ,DIGITAL elevation models ,ARTIFICIAL neural networks - Abstract
The article presents research on predicting landslides of different origin; also addressed an important question of spatial specification of earth surface displacement in undermining areas. Normative and methodological sources have no concrete solutions to these issues for a variety of territory conditions. For prediction of natural landslides used digital elevation models built on the basis of the airborne laser scanning data. Dangerous areas are modeled on the landslide potential and with neural network analysis. Suggested the technique of technogenic landslide prediction. Determined the influence of landslide curvature parameter (in horizontal plane) on the basis of numerical 3D simulations. Showed technological schemes of pit edge deformation observations. Described the technique of instrumental observations on the spatial determination of earth surface subsidence zone in undermining. Used laser scanning system. Dynamic visualization of the earth surface is implemented in 3ds Max. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
26. Curvature-Based Feature Detection for Head Modeling.
- Author
-
Prantl, Martin, Skorkovská, Věra, Martínek, Petr, and Kolingerová, Ivana
- Subjects
FEATURE selection ,HEAD models ,3-D animation ,INFORMATION & communication technologies ,COMPUTER science - Abstract
In the field of 3D head modeling and animation, feature points are often needed to mark important regions of the face and can be used to animate or deform the input model. However, an automatic detection of features remains a challenging task. This paper presents a novel approach to feature detection based on curvature and its derived descriptors, such as shape index, curvedness and Willmore energy. Four important feature regions are detected using the proposed approach - eyes, nose, mouth, ears. For each region, feature points are detected. Results show that the feature points are detected with sufficient accuracy for further use. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
27. Erosion-Inspired Simulation of Aging for Deformation-Based Head Modeling.
- Author
-
Skorkovská, Vĕra, Prantl, Martin, Martínek, Petr, and Kolingerová, Ivana
- Subjects
COMPUTER graphics ,COMPUTER simulation ,HEAD models ,EROSION ,DEFORMATIONS (Mechanics) ,SERVICE life - Abstract
Simulation of age progression of 3D head models is an open problem in the field of computer graphics. Existing methods usually require a large set of training data, which may not be available. In this paper, a method for aging simulation of models created by deformation-based modeling is proposed that requires no training data. A user defines the position of wrinkles by selecting the position of endpoints of the desired wrinkles and the wrinkles are then generated using an erosion-inspired approach. The method can be used to simulate aging of any head model, however, if used for models created by deformations of a base model, the erosion factors can be calculated only for the base model and applied to the derived models. The results show that the approach is capable of creating visually plausible aged models. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
28. Experimental Identification of Cracking Parameters of Concrete Ties with Different Reinforcement and Testing Layouts.
- Author
-
Rimkus, Arvydas, Jakstaite, Ruta, Kupliauskas, Rimantas, Torres, Lluis, and Gribniak, Viktor
- Subjects
CRACKING of concrete ,TENSILE tests ,DEFORMATIONS (Mechanics) ,REINFORCED concrete ,DIGITAL image correlation - Abstract
Despite a seeming simplicity of the direct tensile test layout, analysis of sources of scatter of the experimental results on cracking and deformations of reinforced concrete ties inspired the authors to investigate representativeness of the specimens. In the current context, the representativeness is understood as a property of the tie to isolate the investigated parameter (e.g., cracking deformations) from others uncontrolled effects characteristic for the samples of limited size. The present experimental study aims at determination of representative length of the samples that allows reduce the end effect. A consistent procedure is proposed for identification of the cracking parameters in the cases of limited capability of monitoring deformations of internal reinforcement. The proposed procedure was applied for the cracking analysis of concrete prisms with different reinforcement and testing layouts. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
29. Deformations and rigidity in varieties of Lie algebras.
- Author
-
Barrionuevo, Josefina, Tirao, Paulo, and Sulca, Diego
- Subjects
- *
LIE algebras , *ALGEBRAIC varieties , *FACTORS (Algebra) , *GEOMETRIC rigidity - Abstract
We present a novel construction of linear deformations for Lie algebras and use it to prove the non-rigidity of several classes of Lie algebras in different varieties. In particular, we address the problem of k -rigidity for k -step nilpotent Lie algebras and k -solvable Lie algebras. We show that Lie algebras with an abelian factor are not rigid, even for the case of a 1-dimensional abelian factor. This holds in the more restricted case of k -rigidity. We also prove that the k -step free nilpotent Lie algebras are not (k + 1) -rigid, but however they are k -rigid. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
30. Preservation of Urban Historic Centers.
- Author
-
Bezrodny, Konstantin, Lebedev, Mikhail, and Larionov, Roman
- Subjects
SUBWAY design & construction ,URBANIZATION ,SANDSTONE ,THICKNESS measurement ,HISTORIC buildings - Abstract
The subway construction in St. Petersburg is a very important challenge for the development of the city. The existing stations are dramatically deficient, especially in the city's bedroom suburbs. The end stations are overloaded, and parallel subway lines have to be built to relieve the available ones. The subway in St. Petersburg is mainly a deep-level one, as stable water-free rocks (Proterozoic clays) are at depths of over 40 m. Located higher are unstable aqueous sand-clay Quaternary varieties prone to frost heave, and parent Upper Vendian clays, characterized by fissures and sandstone interbeds of varying thickness. But even at significant bore depths, ground surface movements occur on large areas covering several hectares of the city's territory. The current technology of construction of subway station hubs and inclined escalator tunnels lead to significant deformations of the overlying rock and of buildings and structures erected on it, sometimes resulting in loss of structural strength and full decommissioning of buildings. The rehousing of dangerous buildings and their repair require sizeable funds and time for reconditioning of the buildings. This is especially intolerable for subway construction in the historic center of the city when memorial buildings and samples of architecture are subjected to total destruction. For instance, during the construction of the exit to the Griboyedov Canal from Nevsky Prospekt Station, one half of a historic building was dismantled, and for the construction of the surface concourse of Admiralteiskaya Station, an available house had to be totally pulled down, with a new one having similar facades erected in its place later. Therefore, extremely important is development and implementation of proposals to prevent intolerable deformations of existing buildings and structures in the construction of the subway and other underground facilities in the central districts of St. Petersburg. To solve the problem of ground surface deformation, an integrated approach is needed, comprising low-subsidence sinking techniques with parallel geotechnical monitoring including monitoring of low-depth displacements of the surrounding rocks, both in the vertical and horizontal plane. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
31. Classification of filiform Lie algebras of order 3.
- Author
-
Navarro, Rosa María
- Subjects
- *
LIE algebras , *ISOMORPHISM (Mathematics) , *GENERALIZATION , *SUPERALGEBRAS , *CONTINUATION methods - Abstract
Lie algebras of order 3 constitute a generalization of Lie algebras and superalgebras. Throughout this paper the classification problem of filiform Lie algebras of order 3 is considered and therefore this work is a continuation papers seen in the literature. We approach this classification by extending Vergne’s result for filiform Lie algebras and by considering algebras of order 3 of high nilindex. We find the expression of the law to which any elementary filiform Lie algebra of order 3 is isomorphic. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
32. In-situ polymerization of PANI on hydrogel electrolyte enabling all-in-one supercapacitors mechanically stable at low temperatures.
- Author
-
Wang, Dingkun, Yang, Fusheng, Wang, Chunpeng, Chu, Fuxiang, Nan, Jingya, and Chen, Riqing
- Subjects
- *
SUPERCAPACITOR electrodes , *LOW temperatures , *SUPERCAPACITORS , *ELECTROLYTES , *HYDROGELS , *ENERGY storage , *ETHYLENE glycol - Abstract
• A mechanically stable and anti-freezing hydrogel electrolyte is obtained. • The hydrogel electrolyte has extensive intermolecular interactions. • The electrolyte has a higher binding energy between ethylene glycol and water. • An all-in-one supercapacitor with highly integrated structure is fabricated. • The supercapacitor shows good electrochemical performance and mechanical stability. Flexible supercapacitors are becoming increasingly popular in portable and wearable electronics. However, conventional flexible supercapacitors typically exhibit laminated multilayer configurations, inevitably causing the irreversibly interfacial slippage or even delamination under deformations. In this study, an all-in-one supercapacitor with highly integrated structure is constructed through in-situ polymerization of conducting polyaniline on a hydrogel electrolyte. Because the extensive intermolecular interactions between polymer chains and nanoparticles can dissipate energy, the prepared hydrogel electrolyte shows outstanding mechanical properties. At the same time, the introduction of ethylene glycol endows hydrogel electrolyte with a higher binding energy between ethylene glycol and water molecule to break hydrogen bonds between water molecules, thus enabling the hydrogel electrolyte to be anti-freezing. Benefiting from the novel all-in-one structure, the device maintains 100% and 97.5% of its initial capacitance after 6000 charging/discharging cycles at room temperature and −20 ℃ respectively. Besides, the highly integrated structure endows the device with excellent capacitance retentions of 99.2% and 97.5% after 5000 bending and stretching cycles respectively. More importantly, the device still works well under bending, twisting, and stretching states at −20 ℃. This work provides an inspiring pathway to develop flexible all-in-one supercapacitors and broadens the practical application range of energy storage devices in various fields. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
33. Yang-Baxter deformations of the flat space string.
- Author
-
Idiab, Khalil and van Tongeren, Stijn J.
- Subjects
- *
SYMMETRIC spaces , *OPERATOR equations , *MINKOWSKI space , *SYMMETRY groups , *APARTMENTS , *STRING theory - Abstract
We define integrability preserving Yang-Baxter deformations of symmetric space sigma models with non-semi-simple symmetry group, in particular the flat space string, using only the essential structures of a symmetric space sigma model. For homogeneous deformations, the Lax connection is of the same form as the semi-simple case, although the R operator no longer satisfies a freestanding operator equation. For inhomogeneous deformations, the form of the Lax connection needs to be relaxed, by modifying the underlying algebra. We illustrate the construction by discussing nonabelian deformations of three dimensional Minkowski space. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
34. Effect of arrangement of tensile reinforcement on flexural stiffness and cracking.
- Author
-
Gribniak, Viktor, Pérez Caldentey, Alejandro, Kaklauskas, Gintaris, Rimkus, Arvydas, and Sokolov, Aleksandr
- Subjects
- *
TENSILE strength , *FLEXURAL strength , *STIFFNESS (Engineering) , *CRACKING of concrete , *REINFORCED concrete , *DEFORMATIONS (Mechanics) - Abstract
Due to the highly complex cracking behaviour of reinforced concrete structures, their design for serviceability is one of the most challenging tasks of engineering practice. Existing test data support a general inference that the deformation behaviour of concrete elements is affected by the arrangement of reinforcement in the tensile zone. Most of the current design approaches are based on the experimental data of laboratory specimens with simplified arrangement of the reinforcement. Consequently, the corresponding models are often inadequate to predict deformations and cracking of elements with non-conventional distribution of the bars. In the current study, the number of the reinforcement layers is found to correlate with the flexural stiffness. The paper also compares the crack width and crack spacing experimentally determined in the beams with different numbers of reinforcement layers. The results to some extent seem to be in conflict with the generally accepted concept relating crack widths to the cracking distances. Although the observed crack distances of the beams with three layers of bars were larger, their maximum crack openings were smaller than in the conventionally reinforced specimens with the same reinforcement ratio. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
35. Symmetrical and non-symmetrical 3D wing deformation of flapping micro aerial vehicles.
- Author
-
Tay, W.B.
- Subjects
- *
DEFORMATIONS (Mechanics) , *FLAPS (Airplanes) , *SMART materials , *THREE-dimensional modeling , *AEROSPACE engineering - Abstract
Wing deformation can improve the performance of flapping wing MAV. Although this can be achieved through passive wing deformation, it is not possible to tune the deformation easily to obtain maximum performance. With the advancement in smart materials, prescribed deformation to improve maximum performance is becoming more practical. In this study, we study different forms of deformation, including a unique single-sided deformation to improve the wing's performance. This study extends the previous 2D study to 3D, and investigates if the favorable results in the earlier study are also applicable in 3D. Results show that we can obtain improvements as much as 111% for thrust and 125% for efficiency through careful selection of parameters. Positive lift coefficient of up to 1.45 is also observed when non-symmetrical single sided flexing is used. This study will be helpful in the design of future flapping wing MAV. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
36. Depth Study of Compressible Thickness of the Base in Full-scale Experiment.
- Author
-
Osipova, O.N., Dyba, V.P., and Galashev, Yu.V.
- Subjects
COMPRESSIBLE flow ,SEDIMENTS ,DEFORMATIONS (Mechanics) ,LOESS ,DISPLACEMENT (Mechanics) - Abstract
The article presents the results of the depth study of compressible thickness of the base in a full-scale experiment where a hard round stamp with a diameter of 800 mm served as a foundation model. Loading was made by steps of 0.05 MPa, the load is maintained until stabilization of the sediments. We studied the development of deformities and change of the lower limit of the compressible strata of a silty loess foundation folded in slightly wet macroporous loams with increasing load, we fixed displacements of deep marks in the process of loading, a deformation of the base was analyzed. Also, the fields of soil density were built before deformation and the deformed base. During the study of bundle movement in the array loess grounds, we made conclusions about changes in precipitation, the lower boundary of a compressible base thickness and about changing of soil density. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
37. 3D Model deformations with arbitrary control points.
- Author
-
Cerveró, M. Àngels, Vinacua, Àlvar, and Brunet, Pere
- Subjects
- *
THREE-dimensional modeling , *DEFORMATIONS (Mechanics) , *DIGITAL image editing , *MATHEMATICAL combinations , *MATHEMATICAL models , *GEOMETRIC vertices - Abstract
Cage-based space deformations are often used to edit and animate images and geometric models. The deformations of the cage are easily transferred to the model by recomputing fixed convex combinations of the vertices of the cage, the control points. In current cage-based schemes the configuration of edges and facets between these control points affects the resulting deformations. In this paper we present a family of similar schemes that includes some of the current techniques, but also new schemes that depend only on the positions of the control points. We prove that these methods afford a solution under fairly general conditions and result in an easy and flexible way to deform objects using freely placed control points, with the necessary conditions of positivity and continuity. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
38. Magnetic resonance imaging of mechanical deformations.
- Author
-
Koder, Gregor and Serša, Igor
- Subjects
- *
MAGNETIC resonance imaging , *DIAGNOSTIC imaging , *DEFORMATIONS (Mechanics) , *OSCILLATIONS , *MAGNETIC fields - Abstract
A method for magnetic resonance imaging of mechanical deformations is presented. The method utilizes an MRI compatible device for inducing elastic deformations of a sample and a modified spin-echo imaging sequence with two position-encoding gradients added to the sequence symmetrically to the RF refocusing pulse. At the end of the first position-encoding gradient pulse, a sample deformation was induced by the deformational device, which applied a force to a plastic rod embedded in a gelatin cylindrical sample. The sample had to withstand repeated elastic deformations. Sample displacements up to 400 μm were encoded in the image signal phase by the use of position-encoding gradients. Images of different displacement components were acquired first by the use of position-encoding gradients in different directions and then processed by the 2D phase unwrap algorithm. Finally, images of normal and shear strain distribution were calculated from the displacement images. The obtained displacement and strain images enabled clear visualization of deformations and their extent in the sample with the displacement detection threshold in the range 0.3–0.6 μm, depending on the image echo time. The results of displacements were verified also by a DANTE tagging method and by an optical method. The presented method enables studying of various types of deformations in different soft materials as well as dynamic response of deformations to different stress functions (static, oscillatory, pulsed…). [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
39. Effect of reinforcing steel bond on the cracking behaviour of lightly reinforced concrete members.
- Author
-
Patel, V.J., Van, B.C., Henry, R.S., and Clifton, G.C.
- Subjects
- *
REINFORCED concrete , *BOND strengths , *STRAINS & stresses (Mechanics) , *FRACTURE mechanics , *STEEL , *DUCTILITY - Abstract
The ductility of lightly reinforced concrete (RC) members is dependent on the distribution of cracks, as well as the strain penetration of reinforcement at each crack. A series of experimental tests were conducted to investigate how the bond characteristics of reinforcing steel would influence the strain penetration and crack distribution in lightly reinforced concrete members. To vary the bond characteristics, reinforcement with three different deformation patterns were investigated, including a standard deformation pattern and two modified bars with either half the rib height or double the rib spacing of a standard bar. Pull-out tests were conducted to quantify the bond strength of the reinforcement with different deformations patterns, followed by direct tension prism tests that represented the end region of an RC wall with minimum vertical reinforcement. The pull-out tests indicated that the standard deformation pattern achieved the highest initial bond stiffness, whereas the double rib spaced deformation pattern achieved the highest ultimate bond strength. The direct tension prism tests showed similar crack distributions for the two modified bar types, but increased secondary cracking for the standard bar due to higher initial bond strength. However, only the half rib height bar displayed a higher ductility than the standard bar, with significantly greater yield penetration at each crack causing larger ultimate crack widths prior to bar fracture. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
40. Deformation classification of typical configurations of 7 points in the real projective plane.
- Author
-
Finashin, Sergey and Zabun, Remziye Arzu
- Subjects
- *
PROJECTIVE planes , *CONFIGURATIONS (Geometry) , *MONADS (Mathematics) , *SET theory , *MATHEMATICAL analysis - Abstract
A configuration of 7 points in RP 2 is called typical if it has no collinear triples and no coconic sextuples of points. We show that there exist 14 deformation classes of such configurations. This yields classification of real Aronhold sets. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
41. Experimental Determination of Deformations of the Hard Faced Samples Made of Steel for Operating at Elevated Temperatures.
- Author
-
Lazić, Vukić, Arsić, Dušan, Nikolić, Ružica, Aleksandrović, Srbislav, Djordjević, Milan, Hadzima, Branislav, and Bujnak, Jan
- Subjects
DEFORMATIONS (Mechanics) ,IRON & steel building ,MECHANICAL behavior of materials ,RESIDUAL stresses ,HEAT resistant materials - Abstract
An experimental procedure for determination of the lateral and longitudinal deformations of the multi-layer hard faced samples made of steel for operating at elevated temperatures is presented in this paper. Two plates, which were hard faced in three passes, were used to determine the level of residual stresses. The cored electrodes UTOP 38 and UTOP 55 were used. Deformations were measured in two phases: before and after the hard facing. The objective of deformations measurements was to establish the correlation between deformations, namely the applied technology (the input energy/heat) and the level of residual stresses, for different plate thicknesses. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
42. Tensile and flexural behaviour of LWAC members under short-term service loads.
- Author
-
Carmo, R.N.F. and Dias-da-Costa, D.
- Subjects
- *
FLEXURAL strength , *TENSILE strength , *MECHANICAL loads , *LIGHTWEIGHT concrete , *DEFORMATIONS (Mechanics) - Abstract
This paper presents a detailed study concerning the behaviour of Lightweight Aggregate Concrete (LWAC) members subjected to short-term tensile or flexural loading. For this purpose, a comprehensive experimental programme was carried out covering a wide range of LWAC specimens with different reinforcement ratios and classes of LWAC concrete, with compressive strength ranging from 40 MPa up to 70 MPa. The performance of Eurocode-2 (EC2) and Model Code (MC) guidelines were checked against experimental results, namely in what concerns deformation and cracking prediction for typical service stress levels. In the case of pure tensile loads, it was observed that MC adequately predicts the experimental deformations, whereas EC2 estimates are more adequate for higher reinforcement ratios. In the case of flexural loading, EC2 shows good agreement with experimental results. Furthermore, safe estimates were obtained when using EC2 to predict the crack widths in LWAC members under pure tensile load, whereas MC provided estimates in agreement with the experimental results. Finally, the paper addresses the viability of proposing a new parameter for quantifying deflections and cracking without relying on the tensile strength of concrete, thus avoiding the high variability of this experimental parameter. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
43. Analysis of Dynamic Characteristics for Face Gas Dynamic Seal.
- Author
-
Falaleev, S.V. and Vinogradov, A.S.
- Subjects
GAS turbines -- Design & construction ,GAS dynamics ,AIRCRAFT engine industry ,SEALING (Technology) ,POWER plants - Abstract
Increasing of aircraft gas turbine engines and power plants efficiency is one of important design problems. One of possible ways of this problem solution is decreasing of leakage through the support seals. Some kinds of seals applied in supports of aircraft engines are known. A face gas dynamic seal is one of the most effective. The considerable part of damages in face gas dynamic seals takes place from dangerous vibration in it. A two-mass dynamic model which is the most applicable in practical cases for face gas dynamical seal is considered in a present paper. The theoretical and experimental analysis of dynamic condition of seal is fulfilled. Range of applicability for face gas dynamical seals on amplitude and frequency is defined. It is possible to use the results of present researches for development of new seal structures, and for application of seals at compressors with magnetic supports. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
44. Numerical analysis of the elastic response of a floating collar in waves.
- Author
-
Zhao, Yun-Peng, Bai, Xiao-Dong, Dong, Guo-Hai, Bi, Chun-Wei, and Gui, Fu-Kun
- Subjects
- *
HIGH density polyethylene , *ELASTIC deformation , *AQUACULTURE , *FISHERY technology , *THEORY of wave motion , *NUMERICAL analysis - Abstract
Gravity-type fish cages are playing an increasingly important role in fishery aquaculture. As the main load-bearing component of gravity-type fish cages, the floating collar supports the whole cage and undergoes large deformations. In this paper, a numerical method is developed to study the motions and elastic deformations of an HDPE floating collar in waves. The governing equations of motions are established by Newton׳s second law, and those governing the deformations are obtained according to the curved beam theory and the modal superposition method. Damping of the elastic deformations is introduced and analysed in detail to improve the numerical model. To validate the numerical model, a series of physical model tests are conducted. Good agreement between the numerical and experimental data is obtained. The numerical results indicate that the in-plane and out-of-plane deformations calculated using the first four modes yield satisfactory precision. The positions of the maximum deformations in different wave propagation directions and the effect of the forms of the mooring line arrangement have also been investigated. The numerical results show that the four-point-mooring cage is more reliable than the single-point-mooring cage. The endpoints of the diameters that are parallel or perpendicular to the wave direction have the largest deformation. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
45. Deformations of Lie 2-algebras.
- Author
-
Liu, Zhangju, Sheng, Yunhe, and Zhang, Tao
- Subjects
- *
LIE algebras , *DEFORMATIONS of singularities , *COHOMOLOGY theory , *MATHEMATICAL proofs , *PARAMETER estimation - Abstract
In this paper, we consider deformations of Lie 2-algebras via the cohomology theory. We prove that a 1-parameter infinitesimal deformation of a Lie 2-algebra g corresponds to a 2-cocycle of g with the coefficients in the adjoint representation. A Nijenhuis operator on a Lie 2-algebra is introduced to describe trivial deformations. We also study abelian extensions of Lie 2-algebras from the viewpoint of deformations of semidirect product Lie 2-algebras. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
46. In-plane and out-of-plane deformations of gilt utero-sacral ligaments.
- Author
-
Donaldson, Kandace, Thomas, Joseph, Zhu, Yizheng, Clark-Deener, Sherrie, Alperin, Marianna, and De Vita, Raffaella
- Subjects
PELVIC floor ,DIGITAL image correlation ,LIGAMENTS ,OPTICAL coherence tomography ,PELVIC organ prolapse ,PLASTIC surgery - Abstract
The uterosacral ligaments (USLs) are supportive structures of the uterus and apical vagina. The mechanical function of these ligaments within the pelvic floor is crucial not only in normal physiological conditions but also in reconstructive surgeries for pelvic organ prolapse. Discrepancies in their anatomical and histological description exist in the literature, but such discrepancies are likely due to large variations of these structures. This makes mechanical testing very challenging, requiring the development of advanced methods for characterizing their mechanical properties. This study proposes the use of planar biaxial testing, digital image correlation (DIC), and optical coherence tomography (OCT) to quantify the deformations of the USLs, both in-plane and out-of-plane. Using the gilts as an animal model, the USLs were found to deform significantly less in their main direction (MD) of in vivo loading than in the direction perpendicular to it (PD) at increasing equibiaxial stresses. Under constant equibiaxial loading, the USLs deform over time equally, at comparable rates in both the MD and PD. The thickness of the USLs decreases as the equibiaxial loading increases but, under constant equibiaxial loading, the thickness increases in some specimens and decreases in others. These findings could contribute to the design of new mesh materials that augment the support function of USLs as well as noninvasive diagnostic tools for evaluating the integrity of the USLs. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
47. First evidence of cell deformation occurrence during a Dinophysis bloom along the shores of the Gulf of Tunis (SW Mediterranean Sea).
- Author
-
Aissaoui, Awatef, Dhib, Amel, Reguera, Beatriz, Ben Hassine, Oum Khaltoum, Turki, Souad, and Aleya, Lotfi
- Subjects
- *
CELL division , *CYTOKINESIS , *DINOFLAGELLATE blooms , *REGENERATION (Biology) , *ALGAE - Abstract
Never before observed or cited in Dinophysis studies, deformations in Dinophysis acuminata and Dinophysis sacculus are reported throughout their cellular division phases (cytokinesis, and sulcal list regeneration) in 5 in situ cell cycle studies in the Punic harbors of Carthage (northern Tunisia). Two types of deformation were observed: invaginations in the ventral and dorsal margin and protuberances at the base of the left sulcal list. No virus or bacteria were detected with Syber green stain. In situ division rates ( μ ) varied among seasons and stations for the same species. D. acuminata exhibited moderate (0.22 day −1 ) to high (0.68 day −1 ) μ rates which were however very low (0.02–0.17 day −1 ) for D. sacculus in autumn and moderate (0.21–0.35 day −1 ) in late spring. In 2009 the seasonal distribution of Dinophysis indicates maximum Dinophysis cf. ovum abundance in March and a high number of D. acuminata in early June, while in 2010 maximum abundance of the same species was found in mid-June. Molecular and genetic studies and staining with specific fluorescent strains should be addressed to hopefully explain these Dinophysis cell deformations during their in situ division. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
48. A survey on stability and rigidity results for Lie algebras.
- Author
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Crainic, Marius, Schätz, Florian, and Struchiner, Ivan
- Abstract
We give simple and unified proofs of the known stability and rigidity results for Lie algebras, Lie subalgebras and Lie algebra homomorphisms. Moreover, we investigate when a Lie algebra homomorphism is stable under all automorphisms of the codomain (including outer automorphisms). [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
49. Role of rotational energy and deformations in the dynamics of reaction.
- Author
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Kaur, Gurvinder, Grover, Neha, Sandhu, Kirandeep, and Sharma, Manoj K.
- Subjects
- *
DEFORMATIONS (Mechanics) , *NEUTRONS , *ROTATIONAL motion , *COMPARATIVE studies , *MATHEMATICAL bounds , *CROSS-sectional method - Abstract
Abstract: In reference to recent experimental data, the dynamical cluster-decay model (DCM) has been applied to study the neutron evaporation residue (ER) cross sections of intermediate mass nucleus 96Tc⁎ spread over a wide range of incident energy across the Coulomb barrier. In order to analyze the effect of rotational energy in the dynamics of reaction, the cross sections have been calculated using the sticking ( ) and the non-sticking ( ) limits of moment of inertia with inclusion of quadrupole ( ) deformation within optimum orientation approach. The effect of either of the two approaches on the angular momentum, and hence the rotational energy associated with it, is assessed through the fragment mass distribution, preformation factor and the barrier penetrability. Also, the role of deformations is studied through a comparative analysis of decay path for spherical and deformed fragmentation. The calculated evaporation residue cross sections show excellent agreement with the reported data at all incident energies for both spherical and -deformed approach. Finally, the incomplete fusion (ICF) process observed due to loosely bound projectile 6Li is addressed within the framework of DCM. [Copyright &y& Elsevier]
- Published
- 2014
- Full Text
- View/download PDF
50. Evaluation of elastic compensation using elastic/plastic rotating circular disk problems.
- Author
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Khalili, A. and Peddieson, J.
- Subjects
- *
ELASTICITY , *STRAINS & stresses (Mechanics) , *PROBLEM solving , *ROTATIONAL motion , *PREDICTION models , *QUANTITATIVE research , *NUMERICAL analysis - Abstract
Highlights: [•] Evaluation of elastic compensation using rotating disk problems is discussed. [•] Quantitative numerical predictions of stresses and deflections are provided. [•] Good to excellent agreement with previously published results is found. [•] Further support for elastic compensation is provided by the reported findings. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
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