After offering an overview of some of the main themes of Popper’s political thought, the paper argues that his account faces two Problems relating to institutions. The first is that while Popper stresses the ‘rational unity of mankind’, and the potential for any of us to furnish criticisms of public policy, it is not clear what institutional means currently exist for this to enable this to take place. Second, Popper has stressed the conjectural character of even our best theories. However, at any point, some theories will have fared better in the face of criticism than others, and they may give us important information about constraints on our actions. At the same time, as ordinary citizens we may not be in a good position to understand the theories in question, let alone appraise the state of the specialised discussion of them. There is, it is suggested, a case for thinking of ways to institutionally entrench such fallible theories, especially in the current setting in which social media play an important role

In this paper, the behavior of a stationary Crack in a generalized diffusion-thermoelasticity medium under temperature and concentration shock has been investigated. Cracks have been modeled using the extended finite element method and stress intensity factors have been obtained using the interaction integral method. To study the phenomenon of heat dissipation and concentration, generalized Green-Naghdi and non-Fickian theories have been used. The extended finite element method has been developed to discrete equations in space and the Newmark implicit method has been used to calculate time integrals. For different loads (heat shock and concentration), stress intensity factors and temperature and concentration distribution at the Crack tip have been studied. The effect of stress wave velocity, concentration wave and temperature wave on stress intensity factors for straight and oblique Cracks has also been investigated. It is observed that for the case where the speed of the stress wave, and the temperature wave are the same and greater than the speed of the concentration wave, the increase of the stress intensity factors is faster and higher in other states.

Challenging and complex nature of the numerical analysis of Crack Problems have attracted the interest of many researchers in past decades and several techniques have been proposed for these Problems. One of these techniques is the extended finite element method in which the Crack tip field modeling is improved by enrichment of shape functions and the Crack can intersect the elements. On the other hand, we have adaptive finite element method which aims to improve the accuracy of displacement and stress fields near the Crack tip by remeshing process. Researchers have reported the drawbacks of each of these two techniques. In this paper the drawbacks of the previous techniques are covered with proper combination of these two techniques. By this combination the Crack can pass through the elements and there is no need for Crack tracking by mesh. In addition the estimated error is limited to desirable bands and stress intensity factor can be computed numerically with acceptable accuracy.

To ensure the rail transportations safety, evaluation of fatigue behavior of the rail steel is necessary. High cycle fatigue behavior of a rail steel was the subject of investigation in this research using fracture mechanics. Finite element method (FEM) was used for analyzing the distribution of the stresses on the rail, exerted by the external load. FEM analysis showed that the maximum longitudinal stresses occurred on the railhead. To find out about the relation of Crack growth with its critical size, and to estimate its lifetime, the behavior of transverse Cracks to rail direction was studied using damage tolerance concept. It revealed that transverse Crack growth initially occurred slowly, but it accelerated once the Crack size became larger. Residual service life was calculated for defective segments of the rails. In addition, allowable Crack size for different non-destructive testing intervals was determined; the allowable Crack size decreased as the NDT intervals increased.

Modeling of Crack propagation by finite element method under mixed mode conditions is of prime importance in fracture mechanics. This paper describes an application of finite element method to the analysis of mixed mode Crack growth in linear elastic fracture mechanics. Crack growth process is simulated by an incremental Crack-extension analysis based on the maximum principal stress criterion, which is expressed in terms of the stress intensity factor.In this paper, a procedure to correct the direction of Crack propagation in the analysis of finite element is presented to ensure that a unique final Crack path is achieved for different analysis of a problem by using different increments of Crack. For each increment of Crack extension, finite element method is applied to perform a single region stress analysis of the Cracked structure. Results of this incremental Crack extension analysis are presented for several geometries.

Modeling of Crack propagation by a finite element method under mixed mode conditions is of prime importance in the fracture mechanics. This article describes an application of finite element method to the analysis of mixed mode Crack growth in linear elastic fracture mechanics. Crack - growth process is simulated by an incremental Crack-extension analysis based on the maximum principal stress criterion which is expressed in terms of the stress intensity factor. In this paper a procedure is employed to correct direction of Crack propagation to ensure that a unique final Crack path is achieved for different analysis of a problem by using different increments of Crack. For each increment of Crack extension, finite element method is applied to perform a single - region stress analysis of the Cracked structure. Results of this incremental Crack – extension analysis are presented for several geometries.