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The aim of the present study was to examine the mechanisms of empathy for pain that contribute to consoling touch, a distress-alleviating contact behavior carried out by an observer in response to the suffering of a target. We tested romantic couples in a paradigm that involves consoling touch and examined the attenuation of the mu/alpha rhythm (8-13Hz) in the consoling partner. During the task, the toucher either held the consoled partner's right hand (human touch) or held onto the armrest of the chair (non-human touch), while the consoled partner experienced inflicted pain (pain condition) or did not experience any pain (no-pain condition). In accordance with our hypotheses, the results revealed an interaction between touch and pain at in mu/alpha rhythms in all central sites (C3, C4, Cz). Specifically, we found that the toucher's mu suppression was higher in the consoling touch condition, i.e., while touching the partner who is in pain, compared to the three control conditions. Additionally, we found that in the consoling touch condition, mu suppression at electrode C4 of the toucher correlated with a measure of situational empathy. Our findings suggest that electrophysiological and behavioral measures that have been associated with empathy for pain are modulated during consoling touch.

This study examines the feasibility of the full-field ultrasonic characterization of fractures in rock. To this end, a slab-like specimen of granite is subjected to in-plane, O(10 4 Hz) excitation while monitoring the induced 2D wavefield by a Scanning Laser Doppler Vibrometer (SLDV) with sub-centimeter spatial resolution. Upon suitable filtering and interpolation, the observed wavefield is verified to conform with the plane-stress approximation and used to: (i) compute the maps of elastic modulus in the specimen (before and after fracturing) via a rudimentary application of the principle of elastography; (ii) reconstruct the fracture geometry ; (iii) expose the fracture's primal (traction-displacement jump) contact behavior, and (iv) identify its profiles of shear and normal specific stiffness. Through the use of full-field ultrasonic data, the approach provides an unobscured, high-resolution insight into the fracture's contact behavior, foreshadowing in-depth laboratory exploration of interdependencies between the fracture geometry, aperture, interphase properties, and its seismic characteristics.

Short-time withstanding current is a key parameter of air circuit breakers. Due to the structure of multiple parallel contacts, the outer movable conductors tilt and slide seriously when withstanding the large short-circuit current. This paper is aimed to investigate the contact behavior of the tilted contact. A new designed experimental setup to measure the minimum repulsion current and the contact resistance of the tilted contact is developed. Contact force and tilt angle can also be measured and adjusted. Based on the measured results and the impression marks of the tilted contact, it is concluded that the repulsion force and the contact resistance are increased seriously when the contact is tilted. During the contact tilting process, the contact type is changed from the line contact to the point contact and the contact center is offset to the edge of the movable contact. In addition, with the help of contact bridge model, it is also found that the contact type transition plays a dominant role on the increase of the repulsion force and contact resistance.

S-lay is a widely used method for offshore pipe installation. In recent years, S-lay has gradually applied to the deepwater condition. Because of the increasing pipe weight in deep S-lay, there exist severe and complex contact problems between the overbend pipe and roller supports of the stinger. In deep S-lay design, it is difficult to solve this nonlinear mechanics problem, and there remain confusion and difficulties to predict the roller contact forces and the pipe strain level in S-lay design. The present paper develops a refined finite element model with the framework of ABAQUS, which considers the complex surface contact behaviors in the overbend section. The features of the contact state of different rollers within one roller box are discussed, and the resultant support forces from each roller box are calculated and compared with the commercial design code. The overbend strain level of five S-lay cases is investigated and the pipelaying safety is checked by DNV rules. The simulation results show that the proposed model can provide more accurate and reasonable predictions on roller forces and pipe strain distribution for deepwater S-lay design.

Human skin possesses complex deformation behaviour in multi-asperity contact. The deformation interaction under multi-asperity contact is prodigious in the skin contact model, must not be neglected. The phenomenon of non-uniform deformation has to be taken into account in order to properly and accurately develop a contact behaviour model of human skin. In this paper, one tribological model of contact behavior of human skin is developed with the concern of non-uniformation deformation behaviour under multi-asperity contact. Hertz, and DMT based theories were optimized for expatiating upon the tribological interaction between the human skin and the product surface. The model has been utilized to analyze the skin in multi-asperity contact. Results from FEM deformation simulation validated that deformation interaction between asperities is one of the important controlling factors which influences the deformation behaviour of skin in multi-asperity contact. Whilst asperities spacing was decreased, deformation interference was strongly noticed, and multi-asperity contact points were interfering adjacent deformation regime in irregular manner causing non-uniform deformation of skin. Furthermore, the total contact area tended to decrease when lambda spacing decreased.

The discrete element method (DEM) has been extensively used to study the micro-mechanical behavior of sand subjected to quasi-static strain rates. In most of these studies, the sand specimens were prepared with an upscaled particle size distribution (PSD) to reduce the computational cost. However, the effectiveness of this upscaling approach in replicating the dynamic sand response is not well understood, especially at high stresses where significant particle breakage occurs. In this paper, several split Hopkinson pressure bar (SHPB) tests reported in literature are modeled in DEM using two methodologies: 1) applying the reported strain rates directly to the DEM specimen without accounting for wave propagation in the incident and transmission bars; and 2) modeling the complete SHPB test setup including the incident and transmission bars. The results show that with well-calibrated parameters for contact behavior and particle crushing, specimens with upscaled PSD provide similar dynamic stress-strain response and PSD evolution as those reported in literature. This study shows the importance of particle breakage in the stress-strain response under high stresses as the specimens without particle breakage provide a much stiffer response compared to the specimens with particle breakage. The developed DEM model may be a useful tool to model the complete SHPB test setup as the incident, reflected and transmitted stress waves can be accurately replicated.

Morphogen gradients are crucial for the development of organisms. The biochemical properties of many morphogens prevent their extracellular free diffusion, indicating the need of an active mechanism for transport. The involvement of filopodial structures (cytonemes) has been proposed for morphogen signaling. Here, we describe an in silico model based on the main general features of cytoneme-meditated gradient formation and its implementation into Cytomorph, an open software tool. We have tested the spatial and temporal adaptability of our model quantifying Hedgehog (Hh) gradient formation in two Drosophila tissues. Cytomorph is able to reproduce the gradient and explain the different scaling between the two epithelia. After experimental validation, we studied the predicted impact of a range of features such as length, size, density, dynamics and contact behavior of cytonemes on Hh morphogen distribution. Our results illustrate Cytomorph as an adaptive tool to test different morphogens gradients and to generate hypotheses that are difficult to study experimentally., Ministerio de Economıía, Industria y Competitividad, Gobierno de España (MINECO) to I.G, BFU2014-59438-P, by the Ministerio de Economía, Industria y Competitividad, Gobierno de España (MINECO) to A.A-T, (FPI) BFU2014-59438-P, the Ministerio de Ciencia, Innovación y Universidades to I.G, BFU2017-83789-P, and the Ministerio de Ciencia, Innovación y Universidades to I.G, RED2018-102411-T

This paper develops a new test method to investigate the factors that influence contact behavior between fully cracked concrete surfaces. This test considers 36 specimens of recycled aggregate concrete (RAC) and conventional concrete. The material variables were the aggregate type (natural coarse aggregate (NCA) and recycled coarse aggregate (RCA)), surface roughness, and curing time before splitting (7 d and 28 d). Experimental results indicated that by increasing the gap between cracked surfaces from 0 mm to 4 mm, the maximum shear load was reduced, by 16.9–79% for different cases. Curing time and aggregate type were strong factors that affected the crack propagation and the contact behavior. Furthermore, for conventional concrete, increasing the curing time of concrete increased the maximum shear load by 0.47 times to 2.86 times; for RAC with higher quality RCA in this test, the shear load decreased by 21.8–65% with the increasing of curing time. The surface roughness has a positive effect on shear load, especially when the surface roughness increases greatly in this study. Walraven’s model predicted stronger effect of interface roughness than shown by the results of these experiments, suggesting that these specimens had limited aggregate interlock. The results suggest that the Walraven model might be modified by an appropriate factor to better account for aggregate properties.

Modifying hydrogels with catechol functionality is a promising approach for improving their mechanical and interfacial properties in water, particularly in biological environments. However, the effects of this modification on hydrogels' contact behavior with soft tissues are not well-studied due to the complexity of hydrogels and lack of suitable techniques to probe this behavior. In addition, modification can alter the mechanical properties of hydrogels, resulting in consequences for adhesive strength as well. In this work, we report an investigation of the contact behavior of alginate hydrogels with and without conjugation of catechol functionality, aiming to elucidate the role of catechol modification on wet adhesion of alginates to a model tissue-like material, gelatin. To directly characterize this soft-on-soft contact, which has commonly been a challenge, we developed an indentation-based contact adhesion measurement using alginate hydrogel beads as the testing probe. We found that3% conjugation of catechol can significantly improve the adhesion of alginate to gelatin by half an order of magnitude, with this adhesion depending heavily on contact time and pH. In contrast, the reduced elastic modulus from modification resulted in lower adhesive strength on rigid substrates. These findings provide valuable insight into the effects of catechol modification of hydrogels, especially in their interaction with tissue-like soft substrates, as well as a simple method for the direct measurement of time- and pH-dependent hydrogel adhesion behavior underwater.

Concrete-filled steel tubular (CFT) columns and high-strength steel have been increasingly used in construction. However, the application of high-strength steel in CFT columns has not been permitted in many design codes. This paper reports an experimental investigation on the behavior of rectangular CFT beam-columns using high-strength steel. The influences of the in-fill concrete, eccentricity ratio and the width-to-thickness ratio on the resistance of the test columns are discussed. The contact behavior is studied using the finite element analysis. Chinese code DB 29-57 adopts the assumption that the concrete bears the axial load only, and the steel tube withstands the bending moment and part of the axial load. A new N-M interaction approach is developed based on the foresaid assumption to account for the plastic behavior of high-strength steel. The approach is verified by the experimental results and the available current design codes to be reasonably conservative, and it can be employed to design rectangular CFT beam-columns using high-strength steel.

In order to calculate analytically the contact status for rail grinding by abrasive belt with an axis deflection, as well as considering limitations of using Hertz contact theory for that, a numerical contact model (NCM) based on the local geometrical relationship between contact wheel and rail surface was developed. The effectiveness and accuracy of the proposed model have been validated by the corresponding finite element model (FEM) by comparing the contact boundary and contact stress distribution. Comparative cases at two typical grinding positions with different attitudes were involved, and the effects of applying axis deflection on contact behavior were investigated in detail. The results from NCM and FEM both agreed belt grinding with an axis deflection was able to enlarge the contact width of the belt and the total grinding force under the premise of ensuring required width of grinding trace on the rail. The model provides insights into understanding contact behavior under actual working conditions and gives a theoretical basis for future researches based on contact analysis.

Nanoscale silica-silica contacts were recently found to exhibit logarithmic aging for times ranging from 0.1 to 100 s, consistent with the macroscopic rate and state friction laws and several other aging processes. Nanoscale aging in this system is attributed to progressive formation of interfacial siloxane bonds between surface silanol groups. However, understanding or even data for contact behavior for aging times

Background:Some studies have suggested that altered tibiofemoral cartilage contact behavior (arthrokinematics) may contribute to long-term cartilage degeneration, potentially leading to tibiofemoral osteoarthritis. However, few studies have assessed normal tibiofemoral arthrokinematics during dynamic activities.Purpose:To characterize tibiofemoral arthrokinematics during the impact phase of level walking and downhill running.Study Design:Descriptive laboratory study.Methods:Arthrokinematic data were collected on uninjured knees of 44 participants (mean age, 20.7 ± 6.6 years). Using a dynamic stereoradiographic imaging system with superimposed 3-dimensional bone models from computed tomography and magnetic resonance imaging of participant-specific tibiofemoral joints, arthrokinematics were assessed during the first 15% of the gait cycle during level walking and the first 10% of the gait cycle during downhill running.Results:During level walking and downhill running, the medial compartment had a greater cartilage contact area versus the lateral compartment. Both compartments had a significantly less cartilage contact area during running versus walking (medial compartment gait cycle affected: 8%-10%; lateral compartment gait cycle affected: 5%-10%). Further, medial and lateral compartment tibiofemoral contact paths were significantly more posterior and longer during downhill running.Conclusion:There was a decreased tibiofemoral cartilage contact area during downhill running compared with level walking, suggesting that underlying bone morphology may play a key role in determining the size of cartilage contact regions.Clinical Relevance:This study provides the first data characterizing tibiofemoral cartilage contact patterns during level walking and downhill running. These results provide evidence in support of performing biomechanical assessments during both level walking and downhill running to obtain a comprehensive picture of tibiofemoral cartilage behavior after clinical interventions.

In this paper we define two feature representations for grasping. These representations capture hand-object geometric relationships at the near-contact stage — before the fingers close around the object. Their benefits are: 1) They are stable under noise in both joint and pose variation. 2) They are largely hand and object agnostic, enabling direct comparison across different hand morphologies. 3) Their format makes them suitable for direct application of machine learning techniques developed for images.We validate the representations by: 1) Demonstrating that they can accurately predict the distribution of $\epsilon$-metric values generated by kinematic noise. I.e., they capture much of the information inherent in contact points and force vectors without the corresponding instabilities. 2) Training a binary grasp success classifier on a real-world data set consisting of 588 grasps.

A deterministic adhesive model for the contact between an elastic layered medium with surface roughness and a smooth elastic microsphere was developed on the basis of the Lennard–Jones surface force law. Through numerical simulations, the adhesive contact behavior of the layered medium with the measured three-dimensional (3D) surface topography was comparatively analyzed with that of the homogeneous medium. Furthermore, the contact characteristics of the layered medium with pre-assigned roughness parameters were investigated with the aid of a computer-generated technique for simulating surface roughness. Results showed that the pull-off force for the contact problem involving rough surfaces was influenced by the contact location, and the average value for the contact between an alumina (SiO2) microsphere and a diamond-like carbon/silicon (DLC/Si)-layered medium was smaller than that for the contact between a SiO2 microsphere and a Si homogeneous half-space. In addition, the effect of the diamond-like carbon (DLC) layer on reducing adhesion was smaller than that of the surface roughness. Finally, the average pull-off force for a DLC/Si-layered medium with computer-generated surface roughness rapidly decreased; however, it eventually became almost unchangeable with the increase in the root-mean-square (RMS) deviation.

Contact behavior in a public space influences the risk of contact infection because public spaces have many environmental surfaces contaminated with pathogens. It is useful for risk reduction to examine the factor of infection risk among behaviors. In the present study, a video monitoring survey was conducted in a simulated cabin of a commuter train, we had built, to investigate the relationship between face-touching frequencies and individual attributes. As a result, the average face-touching frequency was 17.8 times per hour. Of all face touches, mucosal contact was 42.2%. Focusing on the sex, the face-touching frequency was significantly higher for the males than for the females. Focusing on the skin condition, the face-touching frequency of those who did not wear makeup was significantly higher than that of those who did. The significant sex differences may depend on the makeup. Focusing on pollution awareness, higher pollution awareness related to lower frequency. Thus, by improving pollution awareness of the environmental surfaces in public spaces, it is possible to reduce effectively face-touching frequency and, hence, infection risk.

The rough contact behavior of thin layers in the presence of interfacial friction is investigated by means of an innovative fundamental elastic solution. A certain degree of geometrical coupling between normal and tangential elastic field is found which, depending on the layer thickness, may lead to larger contact areas compared to the frictionless case. A specific focus has been devoted to investigate the behavior of the local quantities at the interface, in terms of both the displacement field and the gap distribution. We found that significant thinner gaps are predicted due to elastic coupling and frictional interactions, which may lead to larger hydraulic impedance of the contact interface. The latter result is specifically interesting for applications such as seals, where lubrication and leakage are the governing phenomena.

Both the pancake coiling and conductor on round core (CORC) cabling processes consist of winding second-generation high-temperature superconducting tape (REBCO) in a core. The contact behavior between the tape and the core during the winding process directly affects the critical current, cable flexibility, mechanical support and electrical contact resistance. Therefore, the winding process needs to be optimized to produce pancake coils and CORC cables with the desired electrical and mechanical properties. This paper comprehensively considers the role of the relaxation and Poisson effects. The theoretical model and the finite element model (FEM) for calculating the contact stress during the winding process are established, and a formula for the estimation of the contact force is proposed. The suitable winding pre-tension force, winding curvature radius of SCS2030 (2 mm width and 30 μ m substrate thickness) and SCS4050 (4 mm width and 50 μ m substrate thickness) of REBCO tapes are obtained and discussed by accounting for the relaxation effect and the critical current degradation limit. With consideration of the Poisson effect, the nonlinear contact behavior is investigated. In addition, the relaxation effect, Poisson effect and plasticity of the REBCO tape are taken into account in the FEM model. The results show that the axial strain in the REBCO layer during the winding process is related to the contact behavior. The greater the winding pre-tension force, the smaller the helical curvature radius, and the greater the contact force. The distribution of contact stress for several winding factors (winding pre-tension force, winding angle and the core radius) is divided into three contact types: the single-line contact, the double-line contact and the surface contact. The FEM model results are consistent with the theoretical evaluation and are more suitable for practical winding cases. This research is the basis for designing and optimizing pancake coils and CORC cables.

The spatial and temporal evolution of real contact area of contact interface with loads is a challenge. It is generally believed that there is a positive linear correlation between real contact area and normal load. However, with the development of measuring instruments and methods, some scholars have found that the growth rate of real contact area will slow down with the increase of normal load under certain conditions, such as large-scale interface contact with small roughness surface, which is called the nonlinear phenomenon of real contact area. At present, there is no unified conclusion on the explanation of this phenomenon. We set up an experimental apparatus based on the total reflection principle to verify this phenomenon and analyze its mechanism. An image processing method is proposed, which can be used to quantitative analysis micro contact behaviors on macro contact phenomenon. The weighted superposition method is used to identify micro contact spots, to calculate the real contact area, and the color superimposed image is used to identify micro contact behaviors. Based on this method, the spatiotemporal evolution mechanism of real contact area nonlinear phenomena is quantitatively analyzed. Furthermore, the influence of nonlinear phenomenon of real contact area on the whole loading and unloading process is analyzed experimentally. It is found that the effects of fluid between contact interface, normal load amplitude and initial contact state on contact behavior cannot be ignored in large-scale interface contact with small roughness surface.

In this study, we established a performance analysis model of two types of ball continuously variable transmissions (CVT), conformal type and non-conformal type, by modifying the rheological model based on the elastohydrodynamic contact behavior for the existing toroidal traction drive to suit the working mechanism of ball CVTs. The main purpose of this study is, based on our analysis model, to identify the tendency of performance change according to design factors of ball CVTs and to compare the performance between two ball CVTs. Performance was analyzed in terms of torque capability, torque density and efficiency; factors affecting performance were selected through analysis of individual shapes and operating conditions. In this process, all design and performance factors were expressed as dimensionless quantities. It was confirmed that the conformal ball CVT has superior traction capability compared to the non-conformal ball CVT. In addition, by solving an example problem for ball CVT design and describing the process of designing optimal ball CVTs, it was proved that this study is applicable to real on-site problems.

Focusing on the oblique frictional contact problem of hydrogel for soft robot, a numerical contact model is developed to analyze the nonlinear behaviors including local contact large deformation and friction effect of hydrogel soft material during oblique contact. Based on the constitutive relation of hyperelastic material, the updated free energy function of hydrogel is derived. The contact algorithm is given to compute the contact responses of both collinear contact example and oblique contact example. The applicability of classical Hertz contact theory is discussed. The influence of coefficient of friction on the stress distribution of contact zone and the contact states of contact surface are also investigated. The numerical results show that the material nonlinearity and the geometric nonlinearity (i.e. large deformation) of hydrogel lead to the invalidation of classical Hertz contact theory. For the oblique contact, the internal stress grads of hydrogel will be redistributed as the coefficient of friction increases. Meanwhile, the maximum stress position moves from underside to the contact surface. Two high stress zones occur inside and on the contact surface at the same time, respectively. Besides, when the coefficient of friction is smaller (i.e. μ < 0.05), for the collinear contact all contact points on the contact surface are in critical state from static friction to dynamic friction. But for the oblique contact, some contact points are always in stable static friction state.

The present study establishes a solving model for analyzing the interwire wear evolution of a wire rope strand subjected to cyclic bending load, in which the frictional contact and sliding between the wires are considered simultaneously. A wear experiment between the wires is conducted to study the wear behavior of the wires. Meanwhile, the proposed model is verified experimentally. Then the interwire wear and its effect on the contact behavior of the strand are analyzed. The results show that the interwire wear only happens on the side further from the curvature center of the bended strand than its neutral layer, and no wear happens when the wires are apart from each other or the interwire slippage is zero. As the wear process goes on, the wear region extends only along the normal direction of the core-wire contact line, and the maximum wear depth occurs at the middle position between the neutral layer and the furthest location from the curvature center. The contact pressure is distributed uniformly along the normal direction of contact line, but a significant stress concentration and local deformation happen at the position furthest from the curvature center of the bended strand.

The inter-wire contact effect on mechanical performances of a wire rope strand is studied with a new semi-analytical method. The mathematical model of the wire rope strand subjected to axial tension and torsion loads is established first, into which the wire deformation parameters considering the combining effects of Poisson's ratio and inter-wire contact are incorporated. Then this model is solved to achieve the mechanical performances for the wire rope with the semi-analytical method, in which the conjugate gradient method and fast Fourier transform are simultaneously used for calculating the contact deformation, contact pressure and inside stress of the wires caused by the inter-wire contact. The numerical results show that the proposed method is accurate and efficient in evaluating the inter-wire contact behavior. And the large axial load results in the large contact pressure and deformation. The contact deformation results in a reduction in the stiffness of the strand with a lay angle larger than 20°.

The behavior of an elastic layer in contact with a wavy rigid substrate is analyzed depending on layer thickness, substrate geometry, energy of adhesion, for given value of remote applied load or penetration. Two different slab configurations are considered: (i) a free layer with uniform pressure acting on the upper boundary, and (ii) a confined layer with uniform displacement assigned to the upper boundary. These two different geometries have been considered as exemplar cases which are of great relevance in a large number of applications of crucial importance as structural adhesives, pressure sensitive adhesives, coatings and protective adhesives. Our study shows that the layer thickness affects the contact behavior differently depending on the constraints configuration. In particular, reducing the thickness of the layer makes the latter more or less compliant depending on the considered configuration. Thus, the free layer becomes more sticky and, as the layer thickness is reduced, an increasingly large amount of external work needs to be provided to detach the layer from the substrate. On the contrary, the confined layer significantly stiffens by decreasing the layer thickness. This leads to an increase of the pull-off force for detachment accompanied by a decrease of the energy needed to bring the layer and substrate apart.

The contact resistance between Au/Mo and HgCdTe was investigated. The influence of thermal annealing on metal–semiconductor contact on short and middle-wavelength HgCdTe is also discussed in this paper. The specific contact resistance ρc (300 K, 80 K) of Au/Mo/HgCdTe was measured by the transmission line method. Good ohmic contacts can be formed with Au/Mo on long-wavelength infrared p-HgCdTe (x = 0.23) with a low specific contact resistivity of 3.78E−04 Ωcm2 measured at 80 K. For the mid-wavelength infrared p-HgCdTe (x = 0.30), the metal–semiconductor contact is ohmic, and the minimum specific contact resistivity of 7.40E−04 Ωcm2 is obtained after annealing at 120°C/10 min. The as-deposited contact between Au/Mo and the short-wavelength infrared HgCdTe (x = 0.47) shows non-ohmic behavior. After annealing at 120°C/5 min, although the contact behavior is still a Schottky contact, the contact resistance decreases. For the n-HgCdTe (x = 0.27), the metal–semiconductor contact is ohmic with a specific contact resistivity of 5.70E−04 Ωcm2 at 80 K.

Superconducting cable-in-conduct-conductors (CICC) are multi-stage structures with complex geometries. We study the contact behavior and tensile stiffness for a new design of CICC. The geometrical configurations of the new design of CICC is first formulated. Based on the superposition principle, a simple theoretical model is proposed to study the contact behavior of the new design of CICC. A wide range of numerical simulations have been performed by using finite element method. The contact force and tensile stiffness are analyzed by changing the winding laps of C u strand. Further, an extensive parametric study is conducted in which the effect of tensile stiffness on the contact properties are also considered. The results show the trend of the contact properties and tensile stiffnesses in the new design of CICC which can be used to optimize the superconducting CICC. This analytical and computational studies provide a guide for new design of CICC to improve the mechanical properties of CICC by controlling the winding patterns of each strand.

The dynamics of piezoelectric stick–slip actuators is important for structural optimization and positioning control, yet challenging to model because of the potentially inconsistent stepping of these actuators in the forward and backward directions. This step inconsistency is found to be strongly associated with the inconsistent dynamic response of the piezoelectric feeding element arising from the contact behavior between the piezoelectric stack and its flexure-based preload mechanism. With this understanding, an improved dynamical model for the typical stick–slip actuator is established in which a non-smooth contact model is introduced. A prototype was built and tested, and with it the contact behavior was proved to cause the inconsistent responses of the piezoelectric feeding element, which in turn was verified to cause the inconsistent stepping characteristics of the stick–slip actuator. The simulated results obtained using the proposed model were in good agreement with the stepping curves of the slider in bi-directional motion under different working conditions. The proposed model provides a new perspective to explain and model the step inconsistency for stick–slip actuators in bi-directional motion, and has great potential in aiding the design and control of stick–slip actuators for bi-directional driving.

The behavior at an interface between carbon nanotubes (CNTs) and silver nanowire (AgNW) could hardly be observed experimentally on an atomic scale, and the interaction is difficult to accurately calculate due to nanometer size effects. In this work, the contact behavior is studied with the molecular dynamics (MD) simulation, which indicates that the CNTs and AgNW can move towards each other to form aligned structures with their interfaces in full contact. In these different composite systems, nanotubes may either keep their form of an inherent cylindrical structure or completely collapse into the nanoribbons that can tightly scroll on the AgNW periphery while wrapping it in a core-shell structure. Thus, the atomic configuration evolution that is affected by the van der Waals (vdW) interaction is closely analyzed to assist the understanding of interfacial contact behavior.

Tolerance analysis is an important approach for evaluating the accuracy and function of mechanical products. Research on tolerance analysis has mainly focused on the transfer and accumulation of geometric deviations during assembly, while the effects of contact behavior have not been considered in detail. Therefore, this paper presents a tolerance analysis approach to spur gears that takes into account the effects of contact behavior between mating tooth surfaces on transmission performance. Machining and assembly errors are represented based on the concept of skin model shapes. The contact behavior between mating tooth surfaces is calculated using the boundary element method (BEM) to perform tooth contact analysis (TCA). The proposed tolerance analysis approach is applied to a pair of spur gears as an example. The manner in which the transmission error, tooth contact pattern and contact pressure distribution are affected by machining and assembly errors is discussed. This research demonstrates the notable effects of contact behavior between mating tooth surfaces on transmission performance and provides a potential method for the tolerance analysis of other mechanisms.

The surface roughness induced by geometric irregularities (asperities) has substantial influence on the contact stiffness, which further affects the working performance and service life of mechanical equipment. In this study, an elastic–plastic contact law between a sinusoidal asperity and a rigid smooth flat is first studied, which is then applied on a statistical model to simulate the contact behavior of a pair of 18CrMo4 steel surfaces to investigate the influences of morphology parameters on the contact stiffness. The analysis shows that smaller shape ratios [Formula: see text] and larger wavelengths [Formula: see text] induce larger normal contact stiffness [Formula: see text] for surfaces with identical roughness, wherein the roughness is defined by the mean value of asperity heights [Formula: see text] and the standard deviation of asperity heights [Formula: see text]. The normal contact stiffness increases as [Formula: see text] decreases under the same loading conditions, while the normal contact stiffness increases as [Formula: see text] decreases for surfaces with a fixed [Formula: see text]. Besides, the normal pressure and normal contact stiffness derived from the proposed contact model are validated. The results demonstrate the potential of the proposed model in contact design due to its ability of establishing the relations between the normal contact stiffness and surface morphology parameters.

This paper presents an analysis for the PIM behavior on coaxial connector using statistical method. A novel PIM prediction method for coaxial connector considering random contact behavior is proposed and demonstrated. In this work, by using numerical approximation to reconstruct the micro contact force on contact surface based on Monte-Carlo and micro-measurement, the fluctuated PIM level on contact unit can be calculated based on the contact height distribution. In experiment, the tested PIM of coaxial connector was compared with predication. A good agreement between theoretical prediction and test proves the proposed PIM prediction method is efficient. It gives a confidence interval for the potential PIM levels on coaxial connector, which provides a new way to predict the fluctuated PIM behavior.

The interaction among multiple microbial strains affects the spread of infectious diseases and the efficacy of interventions. Genomic tools have made it increasingly easy to observe pathogenic strains diversity, but the best interpretation of such diversity has remained difficult because of relationships with host and environmental factors. Here, we focus on host-to-host contact behavior and study how it changes populations of pathogens in a minimal model of multi-strain interaction. We simulated a population of identical strains competing by mutual exclusion and spreading on a dynamical network of hosts according to a stochastic susceptible-infectious-susceptible model. We computed ecological indicators of diversity and dominance in strain populations for a collection of networks illustrating various properties found in real-world examples. Heterogeneities in the number of contacts among hosts were found to reduce diversity and increase dominance by making the repartition of strains among infected hosts more uneven, while strong community structure among hosts increased strain diversity. We found that the introduction of strains associated with hosts entering and leaving the system led to the highest pathogenic richness at intermediate turnover levels. These results were finally illustrated using the spread of Staphylococcus aureus in a long-term health-care facility where close proximity interactions and strain carriage were collected simultaneously. We found that network structural and temporal properties could account for a large part of the variability observed in strain diversity. These results show how stochasticity and network structure affect the population ecology of pathogens and warn against interpreting observations as unambiguous evidence of epidemiological differences between strains., Author summary Pathogens are structured in multiple strains that interact and co-circulate on the same host population. This ecological diversity affects, in many cases, the spread dynamics and the efficacy of vaccination and antibiotic treatment. Thus understanding its biological and host-behavioral drivers is crucial for outbreak assessment and for explaining trends of new-strain emergence. We used stochastic modeling and network theory to quantify the role of host contact behavior on strain richness and dominance. We systematically compared multi-strain spread on different network models displaying properties observed in real-world contact patterns. We then analyzed the real-case example of Staphylococcus aureus spread in a hospital, leveraging on a combined dataset of carriage and close proximity interactions. We found that contact dynamics has a profound impact on a strain population. Contact heterogeneity, for instance, reduces strain diversity by reducing the number of circulating strains and leading few strains to dominate over the others. These results have important implications in disease ecology and in the epidemiological interpretation of biological data.

Extensive investigations have been carried out in the present paper to understand polymer gear performance, i.e., wear and contact behaviors. The experimental results and possible wear mechanisms for polymer gears run against themselves have been presented, especially the wear rate of the polymer gears under different running speeds and loads. The tested samples were made of three different materials (acetal, nylon, and polycarbonate (PC)) and the effects of two different manufacturing techniques were also investigated (i.e., machine-cut and injection-molded polymer gears). The polymer gear performances (wear and life) were recorded using a uniquely designed and built test rig for this purpose. The testing results have been compared with the existing literature for polymer fatigue and wear theory. Further extensive investigations have been carried out to understand the wear phenomena on tooth flank surface profile of these gears and the data obtained have been discussed.

Tethered Space Net (TSN) is one of the most promising solutions for active space debris removal. However, due to the flexibility, its deployment dynamics is complex and not completely understood. Moreover, the purpose of research on deployment dynamics is to draw some conclusions about preferable releasing conditions, which can make the net successfully wrap the target after contacting the target. Therefore, in this paper, a different way, the contact behavior based opinion, is proposed to analyze the deployment dynamics of TSN. Three critical contact parameters are put forward and influence of initial deployment conditions on these three parameters is investigated by simulation results. Finally, some conclusions for preferable releasing condition are given for TSN based on three critical contact parameters.

This chapter provides an account of ultrasonic vocalizations (USVs) in all southern African gerbil species, excluding Gerbilliscus inclusa. Vocalizations can be described as sweeps, clicks, stutters, whistles, peeps, and a postejaculatory series of calls. They occurred more frequently during contact behavior than during solitary activities. Comparisons of characteristics of USVs among species generally agree with phylogenies based on molecular and chromosomal data. Closely related allopatric species have very similar repertoires of USVs. Less closely related sympatric species differed in their USVs. The findings support divergence in USVs in sympatry rather than allopatry. There is a general relationship between body size and frequency of vocalizations, with some exceptions. The frequencies of USVs also accord with habitat and social structure in general. Considering all the evidence, it appears that USVs play an important role in close-contact communication and conspecific recognition in southern African gerbil species.