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In the areas of South China, the asphalt pavement will appear various forms of water damages under the condition of vehicle loads and humid rainy environment. The interface of between aggregate and asphalt is the weaknesses position of the mixture internal structure, which will impose a significant influence on the service life of asphalt mixtures. However, the existing mesomechanics models of asphalt mixtures are almost based on the three-phase composite materials (asphalt mortar, aggregate, void) and have no enough consideration for the actual mechanics characteristics of the weak interface. It is no doubt that the effectiveness of the numerical simulation results will face a great challenge. The main purposes of this paper is to analyze and summary the relative basic characteristics of asphalt-aggregate interface including interface contact behavior, microstructure characterization methods, interface damage features and the macro-micro quantitative evaluation method of the interface damage The results show that the existing mechanical model ignores the asphalt-aggregate interface imperfect bonding, which make the asphalt-aggregate interface mechanical properties difficult to be perceived. Therefore, establishing a more rational micromechanical analysis model to predict asphalt macroscopic mechanical properties of asphalt mixtures will certainly be an urgent task and will provide a theoretical and scientific support for the optimization of asphalt mixture design.

The solid materials׳ surfaces will be found to be rough if magnified sufficiently, no matter how flat they may superficially appear to be. This article establishes a model to examine the effect of rough surface on the contact behavior of magneto-electro-elastic materials with partial or full contact with an orthotropic solid pressed by external loading. The lack between the two surfaces is featured by the gap at the peaks of the rough surfaces. It is found that when the external loading is far less than the critical loading, which is the minimum loading to approach the full contact, the relationship between the contact width and external loading, and the surface contact distribution have the same form as between two purely elastic cylinders in the theory of Hertzian contact. Numerical experiments are done to demonstrate how the component volume fraction of magneto-electro-elastic materials affects the contact behavior. Numerical results show that the contact region between magneto-electro-elastic materials and orthotropic solid is dominated by the external loading other than the component volume fraction of magneto-electro-elastic materials.

Many different types of elastomeric rings have been developed to suit various needs in industry. The X-ring was introduced as a result of the limitations of O-rings that twist, especially during dynamic application. A better understanding of the behavior and the stress distribution of the X-ring under a uniform squeeze rate and internal pressure is needed. We analyzed the contact stresses and internal stresses developed in an X-ring before and after forcing-out by using the photoelastic experimental hybrid method, ascertained the packing ability of an X-ring, and studied the failure criterion of an X-ring under uniform squeeze rate and internal pressure. Forcing-out in the X-ring occurred when the internal pressure was 3.92 MPa. After forcing-out, at an internal pressure of 5.88 MPa, the two lobes on the upper contact surface merged one contact side of the upper side immensely. Even after extrusion of the X-ring, the X-ring can be used to effectively contain the fluid. This is because the effects of extrusion on the X-ring affected the stress distribution of only two lobes close to the assembly gap and the two lobes are merge into one lobe. In addition, our experimental results show that the maximum shear failure criterion is suitable for the prediction of failure in X-ring seals.

With the rapid adoption of mobile computing devices, it is important to analyze and predict the anti-shock performance of hard disk drive (HDD) systems accurately. This paper proposes an advanced air-bearing surface (ABS) model for analyzing the operational shock performance of a 2.5-inch HDD system, including the ramp---disk contact behavior. First, we developed a decoupled simulation method using four linear air-bearing springs using the finite element method and the Lagrange multiplier algorithm for modeling contact between the disk and ramp. With the finite element model, the effect of the linear air-bearing stiffness was investigated. We found that the air-bearing spring model affects the behavior of the slider in the HDD system with ramp---disk contact during the operational shock. Based on the numerical results, an advanced ABS model that reflects air-bearing characteristics and considers the natural frequencies and nodal lines of the ABS pitch and roll modes was proposed and evaluated.

The primary objective of the paper is to observe and characterize the flow attributes of gravity-driven dry granular media in vertical cylindrical tubes. Particle packing fractions of ∼60% were the prime focus in the current study as the targeted application is the use of dense particulate media as heat transfer fluids (HTF). Experimental and computational studies were previously conducted to understand the influence of different geometrical parameters on the flow physics [1], [2]. Flowrate, particulate velocity, and packing fraction profiles were studied for different inertial numbers and preliminary observations were made about the corresponding regimes. However, flow characteristics that could have a direct implication on the heat transfer behavior remained unexplored. Hence, the current effort serves as an extension of our previous studies. The three-dimensional computer simulations were conducted by implementing the Discrete Element Method (DEM) for the Lagrangian modelling of particles. Hertz-Mindilin models were used for the soft-particle formulations of inter-particulate contacts. Since the particle contact behavior plays an important role in the conduction heat transfer of these regimes [3], the particle-wall residence times and near-wall packing fractions are studied in the current work. Particle fluctuations, which lead to flow agitation that effect heat transfer [4] are also studied. It was observed that the intermittent nature of the flow resulted in the propagation of wave-like structures in the upstream direction. The characteristics of this phenomenon and its possible influence on the heat transfer physics is also discussed.

For soft materials with Young's moduli below 100 kPa, quantifying mechanical and interfacial properties by small scale indentation is challenging because in addition to adhesion and elasticity, surface tension plays a critical role. Until now, microscale contact of very soft materials has only been studied by static experiments under zero external loading. Here we introduce a combination of the colloidal probe technique and confocal microscopy to characterize the force-indentation and force-contact radius relationships during microindentation of soft silicones. We confirm that the widespread Johnson-Kendall-Roberts theory must be extended to predict the mechanical contact for soft materials. Typically a liquid component is found within very soft materials. With a simple analytical model, we illustrate that accounting for this liquid surface tension can capture the contact behavior. Our results highlight the importance of considering liquid that is often associated with soft materials during small scale contact.

Continuously Variable Crown (CVC) shifting mechanisms represent a control technology with wide range of capability to influence the thickness profile and flatness (shape) of metal strip and sheet in rolling-type manufacturing processes. Further, because of the efficiency and extensive control capability to operate on thin-gauge, high-strength ferrous alloys, the 6-high mill with CVC profiles machined onto the intermediate rolls (IR) represents a popular mill configuration. This is because of the large control range for the strip thickness profile and flatness, which results from lateral shifting of the CVC intermediate rolls. However, together with this efficiency and capability comes very complex contact behaviors between the rolls and strip, including highly non-linear contact force distribution, loss of contact, asymmetric roll wear, unwanted strip wedge profiles, and the need to apply corrective roll tilting. Therefore, for most effective industry use of 6-high mills with intermediate roll CVC shifting, a rapid and accurate mathematical rolling model is needed to predict and account for these complex contact behaviors. This paper introduces an efficient roll-stack computational model capable of simulating such rolling mills under steady-state conditions. The model formulation applies the simplified mixed finite element method (SM-FEM), which is adapted to simulate asymmetric 6-high CVC mill contact behaviors. Results for a specific case study compare favorably to those obtained from a large-scale commercial finite element simulation, yet require a small fraction of the associated computational time and effort.Copyright © 2017 by ASME

Oscillating microprobes avoid high stress and the sticking effect during contact between microprobe and measured surface. The full performance and application scope of oscillating microprobes can be explored and utilized once the reliable prediction of the microprobe contact behavior is understood. Here, an improved contact model considering adhesion forces, surface roughness, and viscoelastic damping for oscillating microprobes is presented and it is validated by exemplary measurements utilizing a uniaxially oscillating electrostatic microprobe. These results show that the nondestructive identification of material classes seems to be feasible by evaluating the phase shift between the sinusoidal signals of sensor and actuator, respectively.

As for the interesting new building blocks, the Ag nanowires (AgNWs) and single-walled carbon nanotubes (SWNTs) as the interesting new building blocks are viewed as the promising candidates for the next-generation interconnects due to their most remarkable electrical, thermal, optical, mechanical, and other properties. The axial nanowelding of head-to-head style and side-to-side style is relatively simulated with the molecular dynamics method. As for the head-to-head structural style, SWNTs will move toward the AgNWs and contact with the head of AgNWs. And, the part of the Ag nanowire may be subsequently encapsulated in SWNT with the core-filling Ag atom chain as the final atomic contact configuration during nanowelding, which is related to the nanowelding temperature. When the SWNTs and AgNWs are arranged by the side-to-side contact style, the SWNTs will move along the SWNT surface and may eventually catch up with the AgNW being neck and neck. Aiming at the final axial atomic configurations and the contact behavior during nanowelding process, the related dominant mechanism is revealed in this paper.

Early paternal behavior plays a critical role in behavioral development in monogamous species. The vast majority of laboratory studies investigating the influence of parental behavior on cocaine vulnerability focus on the effects of early maternal separation. However, comparable studies on whether early paternal deprivation influences cocaine-induced behavioral response are substantially lacking. Mandarin vole (Microtus mandarinus) is a monogamous rodent with high levels of paternal care. After mandarin vole pups were subjected to early paternal deprivation, acute cocaine- induced locomotion, anxiety- like behavior and social behavior were examined in 45day old female pups, while hypothalamic oxytocin immunoreactivity and serum oxytocin level were also assessed. We found that cocaine increased locomotion and decreased social investigation, contact behavior and serum oxytocin level regardless of paternal care. Cocaine increased anxiety levels and decreased oxytocin immunoreactive neurons of the paraventricular nuclei and supraoptic nuclei in the bi-parental care group, whilst there were no specific effects in the paternal deprivation group. These results indicate that paternal deprivation results in different behavioral response to acute cocaine exposure in adolescents, which may be in part associated with the alterations in oxytocin immunoreactivity and peripheral OT level.

The fields of nanotechnology and nanoscience are full of opportunities and challenges. The needed modification of classical continuum mechanics to account for the dramatically novel characteristics and phenomena determining the mechanical response of nanomaterials/structures remains an ambitious goal pursued by mechanics researchers. The theory of surface elasticity proposed by Gurtin and Murdoch has been shown to be an important tool in theoretical nanomechanics. In this paper, we present an overview of recent advances in application of surface elasticity theory at the nanoscale. In particular, we focus on the elastic and plastic deformation, vibration and buckling, fracture and contact behavior of nanoscale solids from one dimension to three dimensions. We hope that this contribution can provide a valuable insight into nanomechanics analysis methods by taking surface effects into account. The results may help to bridge the gap between conventional mechanics and findings from simulation and experiment, in such areas as multifunctional material and micro-electro-mechanical systems.

The contact and friction behavior of a medical compression stocking (MCS) under different strains was investigated in friction and compression experiments against a mechanical skin model. In addition, the 3D topography of the MCS surfaces was analyzed in order to study the relationship between macroscopic friction and microscopic surface properties. The load dependence of friction coefficients was found to be in accordance with the adhesion friction model. The surface structure of MCS samples was considerably changed when varying the strain state, while friction coefficients remained comparable, indicating real contact areas independent of strain on the microscopic level. The experimental findings could be confirmed and explained on the basis of the microscopic surface analyses, when interpreting the fabric surfaces to be composed of numerous individual round asperities obeying the Hertz contact model.

X-rings were introduced as a result of the limitations of O-rings that twist, especially during dynamic applications. The X-ring design avoids twisting, and the presence of a groove between the lobes acts as a lubricant reservoir that improves the packing life of these seals. Because of the multiple seal points, less squeeze rate is required to provide an effective seal. In addition, friction and wear is decreased, which increases seal life and decreases maintenance costs. Therefore, a better understanding of the behavior and stress distribution of X-rings under a loading condition of uniform squeeze rate and internal pressure is necessary. However, most research to date has been done on the O-ring. We focused on analysis of contact length and contact stresses developed in X-rings under a uniform squeeze rate of 20% (which is suitable for static applications) using a photoelastic experimental hybrid method, and ascertained the packing ability of the X-ring. We show that sealing rings with the X geometry have considerably higher contact stresses than O-ring seals. Also, the contact stresses were higher than the internal stresses of the X-ring. Therefore, our analysis of the contact stresses is adequate in establishing the behavior of the X-ring.

An method was proposed to derive the formula of the overlap coefficient and the influence of main parameters on overlap coefficient were also discussed; The load distribution is deduced and the rule of contact load varying with overlap coefficient was revealed; The results indicate that the increasing overlap coefficient can extend the time of rollers engaging, reducing the contact load of globoidal indexing cam mechanism and altering the load distribution.

The dynamic tangential contact of rough surfaces of frictional elements of a stick-slip microdrive is theoretically investigated. By applying the method of dimensionality reduction, the contact areas of the frictional partners are modeled such that the physical properties of the contact can be fully considered and the influence of the roughness is taken into account. The dynamics of the microscopic rough contact is combined with a macroscopic movement of the drive’s runner in a hybrid dynamic simulation. The numerical results show a good agreement with experimental data. Furthermore, an analytical relation between maximal tangential contact displacement and normal force applied to the contact is analyzed, allowing the contact behavior to be theoretically predicted.

A major concern affecting the efficient use of carbon fibre reinforced composite laminates in the aerospace industry is the low velocity impact damage which may be introduced accidentally during manufacture, operation or maintenance of the composite structures. It is widely reported that the contact behavior of composite laminates under low-velocity impact can be obtained under quasi-static loading conditions. This paper focuses on the study of the correlation of the dent depth to the maximum contact force and damage of composite laminates under quasi-static loading. Analytical and finite element simulation approaches were employed to investigate relations between the contact force and the dent depth. Experimental investigations on the correlation between dent depth, maximum contact force and damage include quasi-static indentation testing, optical and scanning electron microscopic examination of the damage under different loading levels. The effect of damage initiation and growth on the contact behaviour has been discussed. Results show that consistent correlations between the dent depth, maximum contact force and damage exist and can be predicted with the analytical and numerical approaches. Dent depth can be used as an engineering parameter in assessing the severity of damage for composite structures that are subjected to low-velocity impact. This may lead to the development of a cost-effective technique for the inspection and maintenance of composite structures in aerospace applications.

The deformation and contact behavior between concrete face and rockfill are important to the safety of concrete face rockfill dams. Based on the monitoring data of Shanxi concrete face rockfill dam, the stress of concrete face, deformation of rockfill and facing joints were studied. It is shown that the rockfill deforms under the water pressure and weight, and the concrete face is compressed in central and otherwise around abutment during the reservoir filling. As the upstream concrete face deforms as the result of the rockfill deformation, the peripheral joints appear tensile, shear and settlement deformation. In addition, the main deformation of peripheral joints is settlement, which has a significant relationship with water level, especially for the upper ones.

Carbon nanotubes (CNTs) are expected to be a substitutional wiring material instead of copper, because of the properties of high maximum allowable current density, and the low resistivity. Especially, bundled vertically aligned CNTs (VA-CNTs) have the flexible structure and it is considered that VA-CNTs are suitable for vertical interconnect among flexible substrates.In this research, we fabricated VA-CNTs as bump shaped structures and located on flexible substrates for flexible multilayer substrates and their electrical property was investigated.At first, VA-CNT bumps were synthesized on SOI substrate by the thermal chemical vapor deposition method using Fe as catalyst and acetylene gas as source gas. Secondly, Au was sputtered on the substrate of VA-CNT bumps by magnetron sputter. In this process, surface shells of top of VA-CNT were torn by plasma energy and sputtered Au particle was directly contacted to the edges of torn layer of VA-CNTs and inner layers of CNTs for low contact resistance. Subsequently, the substrate of VA-CNT bumps was bonded to Au electrodes on polyimide substrate by surface activated bonding method, that surfaces of specimens were cleaned and activated by Ar ion beam or Ar plasma in vacuum, then they were bonded each other.After bonding, the SOI substrate was removed from VA-CNTs and polyimide substrate, then sputtering process and surface activated bonding to polyimide substrate process were performed again to opposite side. The bonded substrates have a flexible structure and its flexibility against the electrical property was evaluated.As a result, the bonded structure was confirmed to be tolerant of bending 2 to 3 mm curvature. Furthermore, the resistivity of VA-CNT bumps was decreased from 106 to 7.8 Ω under more than 0.75 MPa compression.Thereafter, the VA-CNT bump were required to be bonded more than 0.75 MPa for good conductivity, and the conductivity was stable under the compression more than 0.75 MPa.It indicates that the flexibility of VA-CNT/polyimide substrates were effective on condition of preload to VA-CNT bumps.

In a delay tolerant network (DTN), nodes are connected intermittently and the future node connections are mostly not known. Therefore, effective forwarding based on limited knowledge of contact behavior of nodes is challenging. Most of the previous studies assumed that mobility of a node is independent from mobility of other nodes and looked at only the pairwise node relations to decide routing. In contrast, in this paper, we analyze the temporal correlation between the meetings of each node with other nodes and utilize this correlation for efficient routing. We introduce a new metric called conditional intermeeting time (CIT), which computes the average intermeeting time between two nodes relative to a meeting with a third node. Then, we modify existing DTN routing protocols using the proposed metric to improve their performance. Extensive simulations based on real and synthetic DTN traces show that the modified algorithms perform better than the original ones.

To attain the data of effective dynamic deflection basin utilized to implement modulus backcalculation of asphalt pavement, by dynamic finite element method, the solution method of damping coefficients of pavement structural layers is discussed, the estimation model of subgrade damping coefficients is established, and the influence of testing loading’s dynamic effect and discontinuous contact behavior between structural layers on distribution features of surface dynamic deflection basin is investigated. The results demonstrate that (1) subgrade damping coefficient is a main factor affecting surface dynamic deflection distribution, which is mainly controlled by subgrade modulus, while influence of other structural parameters on subgrade damping coefficients is negligible; (2) when the asphalt pavement is imposed by static and dynamic loadings, the distribution features of dynamic defection basin has a dynamic defection basin for the same asphalt pavement; (3) performing back calculation of modulus ...

In this paper, we studied a compliant tactile sensor with a spherical shell geometry. This bioinspired sensor has been successfully tested in actual robots whose behaviors are guided by tactile feedback. A model of the sensor was developed to study the contact response of the sensor to objects with different geometries. The sensor response is the estimation of both, normal and shear forces (3-D vector). The model was validated using experimental data and used to predict the behavior of sensors with different radii. This information allows us to design sensors with different sizes according to the requirements of a given robotic application.

Dynamic analysis of finger seal can be performed by finite element method or equivalent model based on lumped mass method now available, which is difficult in meeting both the acceptable calculation time and accuracy simultaneously. For this reason, interactions between finger elements are considered and the equivalent dynamic model based on distributed mass method is proposed in this article. Seal dynamic performances are obtained by using this model to calculate the equivalent parameters, air leakage flow, and the contact behavior between finger seal and the rotor. The work to be presented here concerns the mapping of dynamic behavior of the finger seal with a stack of three finger elements, including the dynamic displacement responses of finger elements, the leakage clearances, and the contact pressures between the finger elements and the rotor, as well as the leakage flow rate and the wear rate. The results calculated by the equivalent model presented in this study are evaluated by comparison with the published experimental data and results from the model based on lumped mass method, which shows that the equivalent model based on distributed mass method is far superior to that based on lumped mass method because the calculations are in good agreement with the experimental results.

The corrugated waist rail has been successfully rolled in the Mill Research Institute of Yanshan University. It is necessary to conduct a comparative study on the mechanical properties of this special kind of rail with that of the ordinary rail. ANSYS/LS-DYNA, the finite element code, is used to simulate the contact behavior of wheel and rail. The study aims to investigate the influences of axle and lateral load on the stresses and displacement of the rail. It draws a conclusion that the mechanical properties of the corrugated waist rail is superior to that of the ordinary rail. It also provides a method and useful data for the further research on fatigue and wear of corrugated waist rail.

This paper attempts to analyze dynamic wheel/rail rolling contact through application of a three-dimensional finite element method with large-scale parallel computing. This analysis clarifies the dynamic behavior of the contact patch, when a wheel rolls on a rail at a high speed with loading torque. A rail model which allows efficient calculation was developed to accelerate a wheel on a small size rail model. In addition, this method employs dynamic mesh partitioning to maintain meshes in the contact patch in one partition region during the wheel rolling for efficient parallel calculation. Using this method has made it possible to evaluate the dynamic wheel/rail rolling contact behavior.

In this work, we consider a mathematical foundation for elastic-wave reconstruction of multiply-connected fractures in a finite solid body by way of the Generalized Linear Sampling Method. To allow for the presence of partially-closed fractures as is often the case in non-destructive testing applications, we describe the contact behavior of "hidden" fractures by the Schoenberg's linear slip model. We further assume that the elastic body (probed for fractures) is supported by either by Robin or Dirichlet boundary conditions, while the rest of its boundary is taken to be of Neumann type and used for both fracture illumination and gathering of sensory data. To cater for the application of GLSM to laboratory ultrasonic sensing of fractures in slab-like material specimens, we assume the finite elastic body to be a subset of Ralt;supagt;2alt;/supagt;; however the results of this study are mostly dimenson-generic and allow for a straightforward extension to inverse elastic scattering in finite subsets of Ralt;supagt;3alt;supagt;.

Mobile opportunistic networks (MONs) have been attracting increasing amounts of attention in recent years. Characterizing user contact behavior provides a baseline to evaluate the performance of these networks. However, because the contact distribution of nodes in MONs is conventionally modeled from a large-scale perspective, i.e., by aggregating all node pairs, the contact features of nodes with multiple social relationships are not reflected. Thus, it is not clear whether friends and strangers have similar or different contact behaviors. In this study, we aggregated the contact information of users from the real world, and discovered that two phenomena exist: (1) Most friends or strangers make contact at public hotspots, rather than private hotspots; (2) The distribution of intra-contact time (ICT) exhibits different decay factors---the ICT distribution of strangers is predominantly faster than that of friends.

This paper considers the two-dimensional adhesive contact problem for a rigid insulating cylindrical punch acting on a gradient piezoelectric coating bonded to half-space.It is assumed that the material parameters of functionally gradient piezoelectric materials vary exponentially along the thickness direction.The adhesion between the punch and the contact surface of the coating is described according to the adhesion Model given by Maugis. By using the Fourier integral transform, the adhesive contact problem of gradient piezoelectric coatings is reduced to singular integral equations. the numerical method is applied to solve the singular integral equations with Cauthy kernel.The numerical results show that both non-homogeneous parameters of gradient piezoelectric material and adhesion effect have significiant impact on the adhesive contact behavior of gradient piezoelectric coating.

Vertically aligned carbon nanotubes (VACNT) arrays were designed to mimic natural foot-hairs of geckos in order to elucidate the adhesion mechanism. We fabricated and systematically investigated adhesive properties of the VACNT arrays with different top structures. Balancing the gas ratio and pressure used for low pressure chemical vapor deposition (CVD) processing controls the top structures of VACNT arrays which determine the strength of adhesion. Their contact behaviors were observed using a scanning electron microscope (SEM). The VACNT arrays attached the target surface by different contact behavior based on the different top structures. The different contact behavior varied adhesive properties of VACNT arrays. VACNT arrays with free top structure present higher adhesion strength due to the side contact with target surface, which indicated that the top structure is an important factor enabling generation of a strong adhesion. These results present clear implications for the role of top structures in VACNT arrays based synthetic gecko systems, which is important for fabrication of gecko-inspired dry adhesives.

Mother–calf interactions and the behaviors of mothers during separation from their calves were examined in four Commerson’s dolphin (Cephalorhynchus commersonii) mother–calf pairs. Four infants were observed: 56.8 h over 30 days from birth to 263 days of age, 36.9 h over 20 days from birth to 149 days of age, 10.4 h over 3 days from birth to 2 days of age, and 15.0 h over 3 days from birth to 2 days of age. All four pairs shared common characteristics in the rate and frequencies of mother–calf interactions and the behaviors of mothers during the first week of life. After the first week, individual differences in changes in the frequency of each behavior were observed. The three behaviors considered representative of maternal care (parallel swimming, synchronous breathing, and body-to-body contact) were frequently performed in the first week; thereafter, the frequencies declined. Separate behaviors of mothers were infrequent during the first week and increased with an increase in infants’ age. Bumping by infants increased with time, suggesting an increase in soliciting by calves and conflict between mothers and calves. The frequency of flipper-to-body rubbing also changed but in a complex manner, probably because the calves needed to learn how to perform this behavior from their mothers and because initiator and recipient of this behavior can be changed quickly.

The vector form intrinsic finite element (V-5) method and the gap element method are combined to solve the static wheel/rail contact in two-dimensions in this paper to obtain the wheel/rail normal contact pressure, which would be compared with the normal contact pressure of ABAQUS and Hertz theory. The results showed that the contact pressure distribution of V-5 was consistent with ABAQUS and Hertzs, and the mechanical behavior of contact area was reasonable under the circumstance of different axle loads. Besides, it also verified the feasibility of adopting gap elements method to solve the static wheel/rail contact on the basis of vector form finite element method, which with the superiority of large rotation and large deformation, and laid the foundation of rolling wheel-rail contact behavior analysis.

Opportunistic networking differs from more conventional architectures by the lack of existing network infrastructure, which can cause intermittent connectivity or increased communication delay between nodes. From a message routing perspective,solving these problems require a different set of techniques thanthose used in more traditional network schemes. Forwarding algorithms in these scenarios aim to improve performance metrics such as message delivery ratio and message delay time, while trying to keep the number of message copies small. A common approach used for testing the performance of opportunistic protocols relies on existing opportunistic contact traces. These datasets are widely available on the Internet, and provide a convenient way of simulating realistic usage scenarios. As such, studying the contact patterns between nodes can lead to useful observations to take into account on future experiments. This paper presents the results of a study on four different datasets. First, we describe the main characteristics of each trace. Then, we propose a graphical representation of the contact behavior for each pair of nodes. The next step was to perform an analysis in terms of the distribution of connectivity among nodes, having found that the contacts follow a roughly lognormal distribution and noting that a small group of nodes is usually much more popular than the rest. We have also made a temporal analysis over the duration of each collection experiment. It was noticeable that individual nodes have very similar contact patterns over time, as well as revealing some cyclic variation over time (namely over weekends). Using dataset derived time-varying graph models, a significant performance decrease was achieved with simple remotion of few critical nodes, FEDER through the Competitiveness Factors Operational Programme - COMPETE FCT - Foundation for Science and Technology under the Project: FCOMP-01-FEDER-0124-022674

We conduct three-dimensional transient finite-element analysis to study the contact behavior during touchdown detection by a thermal flying-height control (TFC) recording head on continuous and patterned elastic-plastic layered media. The heat generated during touchdown and the plastic strain of the media are calculated in the model. We investigated key factors such as the radius of curvature of the TFC protrusion, media compositions, bit-patterned media (BPM), and the effect of planarization. Our analysis shows that when subjected to the same TFC over-push, BPM is much more likely to result in plastic deformation than the continuous media. The temperature distribution of planarized BPM with ${\hbox{SiO}}_{2}$ as filling material exhibits a complex and distinctive pattern different from the one without planarization. More importantly, the maximum plastic strain of the planarized BPM is 50% larger than the one without planarization, which means that filling with ${\hbox{SiO}}_{2}$ deteriorates the media's robustness to the touchdown probably due to the mismatch of thermal properties between ${\hbox{SiO}}_{2}$ and recording material. This suggests the filling material must be carefully chosen to avoid the excessive plastic strain.

This study presents a first attempt to develop a numerical three-dimensional multilayered (more than 2 composite layered coatings) elasticperfectly plastic rough solids model to investigate the contact behavior under combined normal loading and tangential traction. Contact analyses are performed to study the effects composite thin film layers. Local contact pressure profiles, von Mises stresses, and shear stresses as a function of material properties and applied normal and tangential friction loads are calculated.

Understanding the characteristics and mechanics of granular flows along sloping channels is fundamental and vital for the study of different in situ geophysical flows. Using the discrete element method (DEM), three-dimensional (3-D) dry granular flows are numerically modeled to study the contact behavior of solid particles along sloping channels, determine the 3-D velocity profiles along the flow height, and computer the corresponding shear rate. The channel confinement effect on granular flows is also investigated. By capturing the flow height and utilizing the definition of the Savage number, the variation in flow regimes inside a granular body along a sloping channel is researched. Finally, the fluctuation of solid particles in the flow is investigated with the use of granular temperature, and is proven to be influenced by the Savage number. Analysis shows that the combination of granular temperature and the Savage number is a good way to identify the flow regimes of granular flows. Crown Copyright (C) 2013 Published by Elsevier B.V. All rights reserved.

Summary Acute infectious diseases are transmitted over networks of social contacts. Epidemic models are used to predict the spread of emergent pathogens and to compare intervention strategies. Many of these models assume equal probability of contact within mixing groups (homes, schools, etc.), but little work has inferred the actual contact network, which may influence epidemic estimates. We develop a penalized likelihood method to infer contact networks within households, which are a key area for disease transmission. Using egocentric surveys of contact behaviour in Belgium, we estimate within-household contact networks for six different age compositions. Our estimates show dependence in contact behaviour and vary substantively by age composition, with fewer contacts in older households. Our results are relevant for epidemic models that are used to make policy recommendations.

In this paper we consider the effect of friction force on the contact behavior of an elastica inside a circular channel with clearance. The elastica is partially clamped at both the input and output ends of the channel. Coulomb friction is assumed to be present at the output end and on the constraining walls. Focused is placed on the relative motion between the input end and the output end of the elastica. Shooting method is adopted to solve for the quasi-static behavior of the elastica movement. Four types of contact patterns between the elastica and the constraining channel walls may occur when the input end moves in and out of the channel; they are rolling point contact, combined rolling and sliding point contact, rolling line contact, and sliding line contact. When the input end undergoes a sinusoidal motion, the output end either ceases to move at all, or follows exactly the input end motion. These two phases of output end motion occur subsequently, one immediately after the other. In general, the output end lags behind the input end. Experimental observations on the lagging phenomenon at the output end confirm the theoretical prediction.

In the real world application of railguns, the launch efficiency is one of the most important parameters. This efficiency directly relates to the capacity of the electrical energy storage that is needed for the launch. In this study, the rail/armature contact behavior for two different armature technologies was compared. To this end, experiments using aluminum c-shaped armature and copper brush armature type projectiles were performed under same initial conditions. The c-shaped armature type showed a superior behavior with respect to electrical contact to the rails and in acceleration. A 300 g projectile with a c-shaped armature reached a velocity of 3100 m/s and an overall launch efficiency including the power supply of 41%. This is to be compared to 2500 m/s and 23% for the launching of a projectile using a brush armature., Presented at the 18th Electromagnetic Launch Technology Symposium October 24-28, 2016, at Wuhan University, Wuhan, China submitted to the IEEE Transactions on Plasma Physics Special Issue Electromagnetic Launch 2016

The use of bolted sleeve joints has been proposed for assembling pultruded glass fiber-reinforced polymer (GFRP) tubular profiles into space lattice shell structures. Such joint configurations may introduce a semi-rigid end condition and further affect the capacity of the connecting members in compression. Three batches of specimens assembled with pultruded GFRP profiles of different lengths and bolted sleeve joints at both ends were prepared and tested under static axial compression. A detailed three-dimensional finite element model considering bolt geometry, contact behavior, bolt pretension, initial geometric imperfection, and failure criterion for fiber-reinforced polymer (FRP) composites was developed and validated with experimental results showing good comparisons. It was found that the bolted sleeve joints exhibited semi-rigid behavior and that the failure modes and the effective length factor were dependent on member slenderness. The relationship between effective length factor and member ...

A theory of reciprocating contacts for linear viscoelastic materials is presented. Results are discussed for the case of a rigid sphere sinusoidally driven in sliding contact with a viscoelastic half-space. Depending on the size of the contact, the frequency and amplitude of the reciprocating motion, and on the relaxation time of the viscoelastic body, we establish that the contact behavior may range from the steady-state viscoelastic solution, in which traction forces always oppose the direction of the sliding rigid punch, to a more elaborate trend, never observed before, which is due to the strong interaction between different regions of the path covered during the reciprocating motion. Practical implications span a number of applications, ranging from seismic engineering to biotechnology., Comment: 8 pages, 5 figures, accepted for publication on Physical Review E, March 22, 2016