Validation of critical strain technique for assessing stability of coal mine intersections and its potential for development of roof control plans

Both room-and-pillar and longwall mining systems develop underground excavations whose stability must be ensured over their entire service life. Even though rock bolts have been extensively used as a support element in US coal mines for about 40 years, limited research has been conducted in quantifying its composite reinforcement effects. Recently, the authors suggested an approach to quantify the reinforcement effect of roof supports over a designated area based on critical failure strains in tension, compression and shear. This paper validates the critical strain technique(CST) using a case study and justifies the magnitude of selected critical strain by corroborating with the US roof fall statistics. Intersections are vulnerable to failure due to the larger exposed roof span and associated stress concentrations. Through numerical application of the CST to a case study, it was demonstrated that modifying the opening orientation and installing reinforcement at critical locations can help to improve the overall stability of intersections.

Failure analysis study of railway draw-hook coupler

Failure analysis of railway draw-hook coupler was carried out.The nondestructive testing method was undertaken on some failed couplers in service to designate critical areas of a coupler.Draw-Hook coupler is used to connect with the same hook coupler or automatic coupler.The influence of each connection types on the coupler strength in this study was discussed.A numerical stress analysis using FEM was performed,and many approaches including critical plane approach were carried out on fatigue life prediction of coupler under different conditions.The results of the proposed fatigue criterion and fatigue life predictions,as well as static numerical analysis,are validated with experimental results.

The Effect of Surface Pit Treatment on Fretting Fatigue Crack Initiation

This paper analyses the effect of surface treatment on fretting fatigue specimen by numerical simulations using Finite Element Analysis.The processed specimen refers to artificially adding a cylindrical pit to its contact surface.Then,the contact radius between the pad and the specimen is controlled by adjusting the radius of the pit.The stress distribution and slip amplitude of the contact surface under different contact geometries are compared.The critical plane approach is used to predict the crack initiation life and to evaluate the effect of processed specimen on its fretting fatigue performance.Both crack initiation life and angle can be predicted by the critical plane approach.Ruiz parameter is used to consider the effect of contact slip.It is shown that the crack initial position is dependent on the tensile stress.For same type of model,three kinds of critical plane parameters and Ruiz method provide very similar position of crack initiation.Moreover,the improved sample is much safer than the flat-specimen.

Studies on Interdiscursivity

The present paper defines interdiscursivity as the mixing of diverse genres, discourses, or styles in a single text. It also traces the origin of interdiscursivity and takes it as a special kind of intertextuality. Then the paper gives a review of interdiscursivity studies in literary and non-literary fields. The former is usually conducted from the stylistic approach, while the latter from the CDA （critical discourse analysis） approach. The contributions and limitations of the previous studies are also summarized with the purpose of presenting an objective picture of the research. Based upon the detailed review, the paper offers some perspectives for the future research. It is hoped that this will shed some light on our understanding of interdiscursivity.

A UNIFIED MULTIAXIAL FATIGUE DAMAGE PARAMETER

According to the critical plane principle, a unified multiaxialfatigue damage parameter is presented based on the varying behaviourof the strains on the critical plane. Both the parameters of themaximum shear strain amplitude and normal strain excursion betweenadjacent turning points of the maximum shear strain on the criticalplane are considered in the multiaxial fatigue damage parme- terpresented. An equivalent strain amplitude is made with bothparameters of the maximun shear strain amplitude and normal strainexcursion by means of von Mises criterion. Thus a new multiaxialfatigue damage model is given based on the critical plane approach.

The Literature Criticism Approach Applied in English Teaching

Aimed at the negligence of literature side in foreign language teaching, the reduction of literary texts in foreign language teaching for non-foreign language majors, and the minimized proportion of literary criticism in the related teachers books, this paper stressed the dialectic complementary relationship between foreign language teaching and literature teaching, advances the application of the literature criticism approach with an attached analytic case study and a summary of the advantage of the approach.

Critical flow-storm approach to total maximum daily load (TMDL) development:an analytical conceptual model

One of the key challenges in the total maximum daily load(TMDL)development process is how to define the critical condition for a receiving waterbody.The main concern in using a continuous simulation approach is the absence of any guarantee that the most critical condition will be captured during the selected representative hydrologic period,given the scarcity of long-term continuous data.The objectives of this paper are to clearly address the critical condition in the TMDL development process and to compare continuous and event-based approaches in defining critical condition during TMDL development for a waterbody impacted by both point and nonpoint source pollution.A practical,event-based critical flow-storm(CFS)approach was developed to explicitly addresses the critical condition as a combination of a low stream flow and a storm event of a selected magnitude,both having certain frequencies of occurrence.This paper illustrated the CFS concept and provided its theoretical basis using a derived analytical conceptual model.The CFS approach clearly defined a critical condition,obtained reasonable results and could be considered as an alternative method in TMDL development.