Dogs' looking times and pupil dilation response reveal expectations about contact causality

Contact causality is one of the fundamental principles allowing us to make sense of our physical environment. From an early age, humans perceive spatio-temporally contiguous launching events as causal. Surprisingly little is known about causal perception in non-human animals, particularly outside the primate order. Violation-of-expectation paradigms in combination with eye-tracking and pupillometry have been used to study physical expectations in human infants. In the current study, we establish this approach for dogs ( Canis familiaris ). We presented dogs with realistic three-dimensional animations of launching events with contact (regular launching event) or without contact between the involved objects. In both conditions, the objects moved with the same timing and kinematic properties. The dogs tracked the object movements closely throughout the study but their pupils were larger in the no-contact condition and they looked longer at the object initiating the launch after the no-contact event compared to the contact event. We conclude that dogs have implicit expectations about contact causality.

Experimental And Numerical Study On Surface Generated Mechanism of Robotic Belt Grinding Process Considering The Dynamic Deformation of Elastic Contact Wheel

In the robotic belt grinding process, the elastic contact condition between the flexible tool and the workpiece is a critical issue which extremely influences the surface quality of the manufactured part. The existing analysis of elastic removal mechanism is based on the statistic contact condition but ignoring the dynamic removal phenomenon. In this paper, we discussed the dynamic contact pressure distribution caused by the non-unique removal depth in the grinding process. Based on the analysis of the equivalent removal depth of a single grit and the trajectories of grits in manufacturing procedure, an elastic grinding surface topography model was established with the consideration of the dynamic contact condition in the removing process. Robotic belt grinding experiments were accomplished to validate the precision of this model, while the result showed that the surface roughness prediction error could be confined to 11.6%, which meant this model provided higher accuracy than the traditional predicting methods.

Visualization of wheel-rail contact area of running vehicle using film sensor

Proper evaluation of the wheel-rail contact is necessary to understand the dynamics of railway vehicles and the causes of wear and damage to components such as wheels and rails. Numerical methods are often used to evaluate the dynamic contact condition between the wheel and rail; however, there are few promising methods for experimental evaluation. It is important to develop a measurement method because the wheel-rail contact is easily changed owing to vehicle-track dynamic interactions. In this study, we used a film-based pressure sensor equipped with force-sensitive resistors to measure the contact area between the wheel and rail during vehicle operation. Using the film-based pressure sensor, we evaluated the geometry of the contact area and position. The validity of the measured contact position is evaluated by comparing it with the contact position based on the cross-sectional profiles of the wheel and rail and the wheelset displacement during a vehicle running.

Effect of Different Road Obstacles on the Structural Behavior of a Honeycomb Nonpneumatic Tire

ABSTRACT The nonpneumatic tire (NPT), as the name suggests, is a type of tire that does not use air to support the load. Because of their outstanding advantages, such as durability and low rolling resistance, these tires have attracted much interest. The study of NPTs has drawn considerable recent attention, and some research was conducted to investigate their mechanical response. However, these studies did not consider an analysis of an NPT against obstacles. Therefore, in this article, the static and dynamic behaviors of an NPT with honeycomb structures rolling over different obstacles are investigated using numerical simulation. The flexible spokes, which are the most important part of NPTs, are assumed to have a honeycomb structure with the same cell wall thickness and angle. Based on the mesostructures hypothesis, these spokes are considered to be made of polyurethane material. To perform a more precise analysis, various parameters such as nonlinear properties of the material and contact condition are taken into account to establish the finite element model. The results, which can be used as a benchmark and are suitable for design purposes, are presented elaborately.

Research on the Influence of Contact Parameters on the Wear Characteristics of Fixture-bar Friction Pair in Low-stress Cropping

New structure of grooved fixture with cambered surface is proposed to reduce wear of bar surface caused by fixture in low-stress cropping. The influence of fixture contact parameters and surface quality on wear characteristics of fixture-bar friction pair is researched by using FEM and orthogonal experiment. The radial wear degree is proposed to evaluate the wear degree of bars under four contact conditions, and the wear mechanism of the friction pair is analyzed by SEM. AE-stress-strain cropping platform is established to research the influence of roughness on the comprehensive wear state of the friction pair. Results indicate that the friction pair under A4B1C2D1E4 combination of contact parameters has the best wear reduction effect and lowest radial wear degree which is 0.0469mm2 and 34.50% lower than one of line contact. AE characteristic parameters curves reflect that under different contact condition, when Ra=0.4μm, the values of AE characteristic parameters are all the minimum and comprehensive wear state of the friction pair is the best.

Fluid Stiction From a Contact Condition

This paper considers modeling of fluid stiction between two separating plates that start from a mechanical contact condition. Published experimental work on initially contacting plates showed significant variations in stiction force peak values. In order to describe the observed strong force variations with mathematical models, the models should be quite sensitive to some of the input parameters of the stiction problem. The model in this paper assumes that small air bubbles are entrapped between the contact areas of the asperity peaks and that the fluid film flow between the cavitation bubbles is guided by Reynolds equation. The proposed model exhibits high sensitivity to initial bubble size and initial contact force compared to state-of-the art models. A delay of about 1 ms in the simulated stiction force evolution and the experiments was found. Potential causes for this discrepancy are discussed at the end of this paper and an outlook to future work, which can reduce the discrepancy between the model and experimental results is given.

A method for three-dimensional modelling of the shear-clinching process

Three-dimensional modelling enables to determine the in-plane material flow in asymmetrical situation. Thus, the distortion of the sheets to be joined can be characterized more exactly. This study shows a method for building up a three-dimensional shear-clinching framework without damage criteria. In fact, the die-sided sheet in shear-clinching was designed as a pre-punched sheet and slugs. The material separation in the die-sided joining partner, which in two-dimensional simulation is often described by macro- and micromechanical fracture criteria, was realised in this study based on a defined contact condition. By means of a shear-cutting simulation, a correlation between the break angle and the separation stress was determined, which was used as a separation criterion in the shear-clinching simulation. The separation line was confirmed using post-particles. To validate this model, the results of the simulation using a quadratic single-point specimen were compared to the experiments with respect to the distortion of the joining partner. In general, the built three-dimensional framework provides for further tool developments with regard to the reduction of distortion in shear-clinching.

Social touch in mother–infant interaction affects infants’ subsequent social engagement and object exploration

Infants’ social touch with caregivers has been considered a means of regulating infant physiological and emotional state. In non-human mammals, such regulatory function also facilitates infant exploration and social behavior. However, the types of social touch in human mother–infant interaction that contribute to specific behavioral responses toward people and objects remain unclear. Using a pre- and post-task design, this study investigated the effects of social touch during mother–infant interactions on infants’ subsequent preferential looking at social stimuli, social engagement with strangers, and object exploration. Between tasks, mothers and infants spent the time playing in one of two conditions, More Physical Contact or Less Physical Contact. We found that infants in the More Physical Contact Condition showed a greater decrease in evasive behavior with the stranger and enhanced object exploration than those in the Less Physical Contact Condition. Conversely, social touch did not affect infants’ preferential looking at static social images. Among the types of social touch, the frequency of affectionate touch reduced evasive behavior to the stranger and facilitated object exploration. These results suggest that social touch, especially affectionate touch, during mother–infant interactions, assist in the modulation of infants’ evasive behaviors toward people and object exploration.