We Need to Talk

Americans today are affectively polarized: they dislike and distrust those from the opposing political party more than they did in the past, with damaging consequences for their democracy. This Element tests one strategy for ameliorating such animus: having ordinary Democrats and Republicans come together for cross-party political discussions. Building on intergroup contact theory, the authors argue that such discussions will mitigate partisan animosity. Using an original experiment, they find strong support for this hypothesis – affective polarization falls substantially among subjects who participate in heterogeneous discussion (relative to those who participate in either homogeneous political discussion or an apolitical control). This Element also provides evidence for several of the mechanisms underlying these effects, and shows that they persist for at least one week after the initial experiment. These findings have considerable importance for efforts to ameliorate animus in the mass public, and for understanding American politics more broadly.

The Research and Experiments on Contact Sealing Theory of the Underwater Clamp Connector

With regard to the sealing structure characteristics of the underwater clamp connector, based on the Hertz contact theory, this article studies the method of solving the extreme value of the radius of curvature on the two curved surfaces at the sealing contact point; first, the method of calculating the extreme value of the radius of curvature at any surface point of the rotary part is obtained, and then the equivalent radius of curvature is solved. Using finite element simulation to study the contact sealing characteristics without considering the edge thickness and width of the sealing gasket, it is verified that the Hertz contact theory is applicable to the metal contact theory of underwater clamp connectors. Then, the sealing simulation with the influence of the detailed dimensions of the sealing gasket is compared with the theoretical result of the direct application of the Hertz contact theory in the underwater clamp connector contact, and the theoretical correction coefficient of metal contact seal for underwater clamp connectors is introduced to solve the errors. The pressure sealing experiment is carried out on six-inch flange and metal sealing gasket, which proves that the coefficient can greatly enhance the theoretical calculation accuracy of the contact sealing of the underwater clamp connector.

A Theoretical Model For Predicting The Surface Topography of Inhomogeneous Materials After Shot Peening

Shot peening is widely used in engineering as a classical strengthening process. Although many studies on shot peening have been done, most have focused on homogeneous target materials. In this paper, a theoretical model is proposed for predicting the surface morphology of inhomogeneous target materials. The topography of target materials after single-shot impact is calculated on the basis of energy conservation and Hertz contact theory, and the final three-dimensional surface topography after multiple-shot impact is obtained through superposition. Single-shot and random multiple-shot finite element models are used to show the advantages of the proposed model over the existing theoretical model for homogeneous target materials. The roughness is found to increase with the shot velocity and shot radius.

Nonlinear behavior of disk spring with complex contact state

Disk springs are widely used as preload and isolation due to their unique mechanical properties. In the prior research, the effect of linear friction on the disk spring was considered, but contact stiffness, another nonlinear contact factor, is ignored. Accordingly, in this paper, the asymmetric displacements of the contact edges are first derived, and the accurate friction dissipations are obtained, as a way to evaluate the effect of friction on the system. Then the velocity of the edges was obtained to establish a dynamic friction model. Meanwhile, the contact displacement and contact stiffness of the edge are obtained by fractal contact theory. Then the nonlinear static and dynamic models of disk spring with friction and contact stiffness are established by the energy method. The load–deflection relationship, stiffness, and hysteresis of disk spring are studied with different contact states. The results show that the model considering contact stiffness and asymmetric friction dissipation can effectively evaluate the static properties of the disk spring. Friction reinforces the nonlinear behavior of the system, while contact stiffness weakens the nonlinearity of the system. And due to the influence of nonlinear contact factors, the transmissibility curves produce multiple resonance peaks.

Contact characteristics of steel-rubber rollers based on modified contact theory considering viscoelasticity

This paper mainly studied the contact characteristics of steel-rubber rollers. First, according to the dynamic mechanical experimental data of rubber, the hyperelastic-viscoelastic composite constitutive model was constructed to accurately describe the properties of rubber. Then, for the contact problem of steel-rubber rollers, the elastic modulus of rubber presents an instantaneous change due to the influence of rubber's viscoelasticity, so the Hertz contact theory was modified through the instantaneous elastic modulus. Next, a dimensionless parameter [Formula: see text] was constructed to judge the viscoelastic influence degree of rubber. Finally, based on modified contact theory and the dimensionless parameter [Formula: see text], the influence of compressive force and rolling speed on the contact characteristics of steel-rubber rollers was analyzed. The research in this paper is helpful to the analysis of dynamic contact problem of rollers structure and the development of contact theory.

Investigation of Fracture Width Change under Closure Pressure in Unconventional Reservoir Based on the Hertz Contact Theory

To describe the fracture width is crucial for the flow conductivity evaluation, which influences the exploitation efficiency of unconventional oil and gas resources. Commonly, as the proppants fill in the fracture, the deformation will happen under the closure pressure to resist the fracture width change. Therefore, it is significant to develop the theoretical model to predict the variation. In this work, the mathematical model for the propping behavior of proppants in the fracture under closure pressure is established based on the Hertz contact theory. Compared with the existing models, the developed model considers both the proppant insertion and the elastic compression among the proppants, which is closer to the actual physical process. Furthermore, the experimental cases with different proppant sizes are taken to verify the model, and the good conformity presents its rationality. The parameter sensitivity analysis of this model shows that the fracture width change increases with the increase of the average diameters of proppants ( D ) and it declines with the improving of proppant elasticity modulus ( E 1 ) and Poisson’s ratio ( v 1 ).