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The effects of the sequence of technology steps of electrical contact formation between carbyne layers and metal electrodes (gold, platinum) on contact parameters were explored. Enhancements in contact parameters were achieved through thermal annealing of the samples. Contact parameters were measured by transmission line method (TLM) and impedance spectroscopy after annealing at atmospheric conditions. Lowering of contact resistivity and sheet resistance of the carbyne layer after annealing was observed for temperatures up to 150${}^{\circ }$C for palladium contacts and up to 100${}^{\circ }$C for gold contacts. It was found that exceeding these temperatures is not recommended, as higher annealing temperatures led to a reduction in the sheet resistance of the carbyne layer. Based on these findings, it can be concluded that the electrical losses at metal contacts of carbyne-based devices, with Au or Pd metallization, can be reduced through annealing. This is particularly critical in carbyne-based gas sensors, where decreasing contact resistance enhances sensitivity.

In this paper, we investigate a novel model problem involving a viscoelastic, frictionless contact model characterized by history-dependent operators. The constitutive relation is formulated based on a time-fractional Kelvin–Voigt model. We represent the contact by incorporating normal compliance within the framework of a time-fractional derivative. In addressing the contact problem, we begin by formulating its weakness and subsequently verify the existence of a solution within this framework. Finally, we study the solution’s behavior concerning the integral term and its relation to the solution, while also presenting convergence results.

We prove that the group of contact diffeomorphisms is closed in the group of all diffeomorphisms with respect to the C⁰-topology. By Gromov's alternative, it suffices to exhibit a diffeomorphism that cannot be approximated uniformly by contact diffeomorphisms. Our construction uses Eliashberg's shape invariant.

We present a novel $C^0$-characterization of symplectic embeddings and diffeomorphisms in terms of Lagrangian embeddings. Our approach is based on the shape invariant, which was discovered by Sikorav and Eliashberg, intersection theory and the displacement energy of Lagrangian submanifolds, and the fact that non-Lagrangian submanifolds can be displaced immediately. This characterization gives rise to a new proof of $C^0$-rigidity of symplectic embeddings and diffeomorphisms. The various manifestations of Lagrangian rigidity that are used in our arguments come from $J$-holomorphic curve methods. An advantage of our techniques is that they can be adapted to a $C^0$-characterization of contact embeddings and diffeomorphisms in terms of coisotropic (or pre-Lagrangian) embeddings, which in turn leads to a proof of $C^0$-rigidity of contact embeddings and diffeomorphisms. We give a detailed treatment of the shape invariants of symplectic and contact manifolds, and demonstrate that shape is often a natural language in symplectic and contact topology. We consider homeomorphisms that preserve shape, and propose a hierarchy of notions of Lagrangian topological submanifold. Moreover, we discuss shape-related necessary and sufficient conditions for symplectic and contact embeddings, and define a symplectic capacity from the shape.

In this paper, as applications of singularity theory, we study the singularities of several worldsheets generated by null Cartan curves in Lorentz–Minkowski space–time. Using the approach of the unfolding theory in singularity theory, we establish the relationships between these worldsheets and invariants such that the cuspidal edge type of singularity and the swallowtail type of singularity can be characterized by these invariants, respectively. Meanwhile, the contact of the tangent curve of a null Cartan curve with some model surfaces are discussed in detail. In addition, we also describe the dual relationships between the tangent curve of a null Cartan curve and these worldsheets. Finally, some concrete examples are provided to explain our theoretical results.

In this paper, we investigate the special properties of geometrical particles with null paths in de Sitter 3-space–time, new Frenet equations and an important invariant associated with null paths are presented. By means of unfolding theory, the local topological structure of the lightlike dual surfaces is revealed. It is found that the lightlike dual surface has some singularities whose types can be determined by the invariant. Based on the theory of Legendrian dualities on pseudospheres and the theory of contact manifolds, it is shown that there exists the ${\mathrm{\Delta }}_4$-dual relationship between the lightlike transversal trajectory of the particle and the lightlike dual surface. In addition, an interesting and important fact mentioned is that the contact of lightlike transversal trajectory with lightcone quadric and the contact of lightlike transversal trajectory with null hyperplane have the same order when they are related to the same type of singularities of the lightlike dual surface.

Quasi-static contact behavior of an inflated MAXXIS VICTRA MA-Z1 (235/45/R17) radial tire is reported in this work. Compressional response of the inflated tire with a prescribed weight loaded quasi-statically was examined. Both experimental and numerical results were obtained and compared. In addition, dynamic contact simulation of the tire rolling on a dry-flat roadway was also studied. A commercial finite element commercial Code (LS-DYNA) was used to construct the complex tire model and to perform both quasi-static contact and dynamic rolling simulations. The Mooney-Rivlin constitutive relationship was adopted to describe the non-linear elastic behavior of rubber material, and the classical laminated theory was used to model the stress-strain behavior of the fiber reinforced composite layers of tire. Quasi-static contact force and compression displacement of tire were measured and numerically simulated. Contact pressure distribution of the tire tread in touch with simulated rigid dry-flat road surface was also numerically and experimentally obtained. Good relationship between the test findings and simulated results were reported. In addition, the dynamic contact simulations of the inflated tire rolling on a dry-flat rigid roadway with a prescribed weight loaded are presented, and the deformation pattern and local contact stress distribution are also reported.

Strength degradations in silicon nitride ceramics subject to damage from contact with hard spheres are investigated. Strengths against indentation load, number of cycles in contact, or stress-rate parameter are reported and compared with theoretical models. Silicon nitride ceramics are prepared by nitride pressureless sintering (NPS) process, which process is the continuous process of nitridation reaction of Si metal combined with subsequent pressureless sintering. Microstructure characterizations reveal silicon nitride fabricated by NPS process exhibits a quasi-plastic mode, with continuous strength loss beyond a load above the onset of yield, and falloff at high number of cycles, > 10⁵ at contact load, P = 950 N, using WC sphere r = 1.98mm. The strength degradation is substantially faster by dynamic fatigue. Failures originated from contact damages, quasi-plastic microcrack zones, with developing radial cracks during strength test. The implication is that quasi-plastic damage of NPS silicon nitride itself can preserve benefits from the inherent higher damage tolerance at lower number of cycles of contacts, but fatigue susceptibility at multicycle contacts and lower stressing rate.

We compute the momentum distribution of a homogeneous Fermi gas at unitarity in the normal phase within the framework of the non-self-consistent T-matrix approximation with particle-hole fluctuation. From the large-momentum behavior of momentum distribution, we obtain the contact for the unitary Fermi gas. We also compare our results with experimental data and other theoretical predictions.

Robotic manipulators have very strong nonlinearities. Analytical modeling of the robotic gripper is very challenging task. Therefore in this paper soft computing methods is applied in order to estimate contact forces of the robotic finger. Support vector regression (SVR) with radial and polynomial basis functions and the soft computing methods were used. The primary purpose of this study are in clarification of kinetostatic examining of a new finger mechanism utilizing pseudo-unbending body model. The results show the better prediction accuracy with SVR methodology with radial basis function (RBF).

This study investigates the effects of sliding ratio on the tribological response of the contact between the teeth of a metal/polymer gear in the regions close to the pitch point. For this purpose, a new twin-disc test rig was developed on the basis of two discs of different diameters rotating one above the other at the same angular speed. Two different materials were used: non-alloyed structural steel (C45) and polyamide (PA66). The effect of the slip ratio (4%, 12%, 20% and 28%) was studied at a constant pressure of 34 MPa and a constant angular speed of 300 rpm. In addition, the contact conditions were controlled with measurements of the two discs surface temperatures. The results indicate that the wear and the friction are closely related to the contact temperature generated by the sliding phenomenon. At low slip ratio (4% and 12%), the coefficient of friction and the temperature are characterized by a quasi-linear increase with time, and the wear increases slowly. At higher slip ratio (20% and 28%), the coefficient of friction and the temperature presents a steady state, and the wear increases dramatically. During the test, a film of transferred PA66 is formed on the steel surface causing the development of adhesive interactions between the contacting discs which increase the friction coefficient and the contact temperature. The high thermal conductivity of steel as compared to that of the polymer can reduce enormously the contact temperature generated by the sliding process.

This paper analyzes the dynamic response of space and plane trusses with geometrical and material nonlinear behaviors using different time integration algorithms, considering an alternative Finite Element Method (FEM) formulation called positional FEM. Each algorithm is distinguished from each other by its specific form of position, velocity, acceleration and equilibrium equation concerning the stability, consistency, accuracy and efficiency of solution. Particularly, the impact problems against rigid walls are analyzed considering Null-Penetration Condition. This formulation is based on the minimum potential energy theorem written according to the nodal positions, instead of the structural displacements. It has the advantage of simplicity when compared with the classical counterparts, since it does not necessarily reply on the corotational axes. Moreover, the performance of each temporal integration algorithm is evaluated by numerical simulations.

Buckling may cause drill string damage or even drilling failure. For the 3000-m-long horizontal section drill string, a simplified analysis model of drill string in horizontal well is established, and the dynamic response results of axial displacement, angular displacement and contact force are obtained. When buckling, the closer the position of drill string is to the bottom, the later the buckling time, the smaller the buckling deformation degree, the slower the growth rate of axial displacement, and the smaller the attenuation degree of angular displacement and contact force amplitude. After buckling, drill string undergoes tensile deformation and eventually remains stable in the tensile state. After stabilization, from the top of drill string to the bottom of drill string, axial displacement increment increases first, then remains unchanged and then decreases, and the relative torsion angle between different positions gradually decreases. The drill string is always in horizontal contact with the wellbore, resulting in the same contact force values at different locations. The change of well inclination angle does not affect the change law of displacement and contact force. The absolute value of angular displacement is negatively correlated with the change of well inclination angle, and the value of axial displacement increment and contact force is positively correlated with the change of well deviation angle, but the value of contact force is quite close. The research results can provide reference for alleviating the buckling of drill string in horizontal wells.

In this paper, a simple formula is derived for the modal damping ratio of the bridge using the correlation between the instantaneous amplitudes of the related front and rear contact responses of a two-axle test vehicle by the Hilbert transform (HT). To start, closed-form solutions were derived for the dynamic response of the damped bridge and vehicle-bridge contact responses. Next, the HT was employed to generate the instantaneous amplitudes of the two contact points. Based on their correlation, a simple formula is derived for the bridge damping ratio. Finally, the reliability of the derived formula was verified in the numerical study. It was demonstrated that the proposed formula can be successfully used to determine the first bridge damping ratio, even in the presence of rough pavement, but with the aid of random traffic.

The tibiofemoral joint is known to bear compressive loads of several body-weights during daily activities. These forces are known to be transferred through the joint via compression of the tibial and femoral surfaces against one another. The menisci are also known to enhance this process by increasing the contact area and decreasing contact stress. However, calculations presented in this paper suggest that the load-bearing capacity of contact mechanisms is seemingly several times smaller than tibiofemoral joint loads. This suggests that probably one or more non-contact load-bearing mechanism(s) exist, and share the load with the already known contact mechanisms.

As one type of rock slope failures, topping failure can be accurately simulated only when several aspects are correctly calculated such as deformation and stress, contacts between blocks, contact stress, movement of blocks, open/close of contacts between blocks, development of failure plane, and crack generation and propagation. Current numerical methods encounter many difficulties in simulating toppling failure, especially for rock slope with lots of rock-bridges. Numerical manifold method (NMM) can deal with these highly discontinuous problems and be used to model the toppling failure of rock slopes. This paper first introduces the fundamental principles, modeling of contacts, calculation of contact force and stress, and modeling of failure in NMM. Then, several case studies are conducted to testify the accuracy and convergence of method; comparisons with method, based on limit equilibrium principle, which was proposed by Goodman and Bray (G–B method) and centrifuge test are conducted. Finally, the topping failure of left bank of one high dam is simulated. Results show that the NMM can be used to correctly calculate the toppling safety factor, simulate the failure process of slope toppling, and accurately model the whole failure process of rock slopes with many rock-bridges.

The competition between entropy and energy that usually occurs in thermodynamics — an increase in one usually leads to a decrease in the other — was also shown to hold in static–elastic contact mechanics in our previous work on solving contact problems with an iterative algorithm. In this paper, we first present a theoretical analysis of the surrogate duality of the optimization model of contact problems, propose several propositions characterizing the surrogate duality, and identify the condition under which the fractional objective function of the surrogate dual problem is quasi concave. Second, we further clarify the correspondence between the concepts of statistical physics and the finite element model of contact problems so that the concepts of statistical physics can be more cleanly used to solve contact problems. Third, we provide examples to calculate the contact force with an improved iterative algorithm based on the quasi concavity that more clearly verifies the competition between entropy and potential energy, and the competition shows strong negentropy behavior: potential energy increases while entropy decreases throughout the iterative process.

Comprehensive quasistatic, small deformation finite element analysis and photoelastic studies were made of multiple contact between discs. Two aspects of the work were examined. The first was concerned with the finite element implementation of the variational inequalities approach to treat the general contact problem. Quadratic programming and Lagrange multipliers were used to identify the candidate contact surface and to solve the resulting nonlinear equations. The solution strategy was based upon the use of a two-step algorithm, which guaranteed the accurate imposition of the active kinematic contact constraints and evaluated the contact forces without the use of special contact elements. The second aspect of work was concerned with the application of an enhanced image-processing technique to obtain the stress field resulting from an automated photoelastic rig. A hybrid method was also employed to determine the contact forces between the multiple discs. The results revealed close agreement between experimentally determined contact values and finite element predictions. Furthermore, they indicated load redistribution and load sharing as well as the influence of interfacial friction.

In this paper, we use a deterministic multi-asperity model to investigate the elastic contact of rough spheres. Synthetic rough surfaces with controllable spectra were used to identify individual asperities, their locations and curvatures. The deterministic analysis enables to capture both particular deformation modes of individual rough surfaces and also statistical deformation regimes, which involve averaging over a big number of roughness realizations. Two regimes of contact area growth were identified: the Hertzian regime at light loads at the scale of a single asperity, and the linear regime at higher loads involving multiple contacting asperities. The transition between the regimes occurs at the load which depends on the second and the fourth spectral moments. It is shown that at light indentation the radius of circumference delimiting the contact area is always considerably larger than Hertzian contact radius. Therefore, it suggests that there is no scale separation in contact problems at light loads. In particular, the geometrical shape cannot be considered separately from the surface roughness at least for approaching greater than one standard roughness deviation.

The friction between interfaces at bolted joints plays a major role in the damping of structures. This paper deals with the energy losses caused by micro-slips in the joints. The aim of this study is to define in an analytical way these energy dissipation mechanisms which we examine through the analysis of a new benchmark: the flexural vibration of a clamped-clamped beam with original positioning of the interfaces. The joints exhibit the behavior of an interface under constant and uniform normal stress. The stress and strain values are computed at the joints under the assumption of quasi-static motion. This model allows us to understand the evolution of the slip and stick regions along the joint interfaces during the loading process. The expressions of the strain and stress fields during each phase of the loading process are derived. These lead to the quantification of the dissipated energy within the interface. Using this formula, a nonlinear loss factor can then be computed. In the final part of the paper, the dynamic response of the beam is calculated using this nonlinear loss factor.