Subsurface Microstructural Evolution during Scratch Testing on Bcc Iron

Subsurface microstructures influence the friction and wear behavior of metallic tribological systems, among other factors. To gain a basic understanding of the microstructural changes occurring during sliding processes, face-centered cubic model systems, for example a copper system with a sapphire sphere sliding against it, were previously characterized. Such systems showed the evolution of the dislocation self-organization phenomenon called the dislocation trace line. To test the occurrence of this dislocation arrangement in bcc metals, in this study a ruby ball was slid against electropolished bcc iron under an increasing normal load. The wear track topography and subsurface microstructure were characterized using white light interferometry and scanning transmission electron microscopy. The analysis suggested that at least for bcc iron, the evolution of a dislocation trace line is connected with the onset of pronounced plastic deformation.

A Novel Noninvasive Method for Quantitative Detection of Colonic Dysmotility Using Real-Time Ultrasonography

<b><i>Introduction:</i></b> Colonic motility disorders are a frequent clinical problem caused by various drugs and diseases. However, the etiology of colonic dysmotility is often unclear due to the lack of in vivo methods, including rapid dynamic assessment. <b><i>Objectives:</i></b> The aim of this study was to establish a novel quantitative method to objectively assess colonic motility using ultrasonography. <b><i>Methods:</i></b> We applied echocardiographic speckle tracking-based strain imaging to analyze murine colonic motility. A trace line was placed on the boundary between the proximal wall of the colon and the inner cavity to analyze colonic wall displacement and strain rate. Locomotion activities of the colonic wall were used to quantify colonic motility via ultrasonography. <b><i>Results:</i></b> We found that ultrasonography can quantitatively detect a decrease in colonic motility induced by loperamide, an antidiarrheal drug. These quantitative data were consistent with the imaging findings of colonic peristalsis and colon transit time. Additionally, ultrasonography also revealed changes in colonic motility over short intervals. Furthermore, we have shown that ultrasonography can quantitatively and noninvasively detect colonic dysmotility and hypervascularity of the colonic wall in colitis mice. <b><i>Conclusions:</i></b> These findings suggest that ultrasonography is a useful in vivo method for objectively monitoring changes in colonic motility caused by drugs and diseases.

A Graphical Method for Displaying the Model Fit of Item Response Theory Trace Lines

Item response theory (IRT) is a statistical paradigm for developing educational tests and assessing students. IRT, however, currently lacks an established graphical method for examining model fit for the three-parameter logistic model, the most flexible and popular IRT model in educational testing. A method is presented here to do this. The graph, which is referred to herein as a “bin plot,” is the IRT equivalent of a scatterplot for linear regression. Bin plots display a conventional IRT trace line (with ability on the horizontal axis and probability correct on the vertical axis). Students are binned according to how well they performed on the entire test, and the proportion of students in each bin who answered the focal question correctly is displayed on the graph as points above or below the trace line. With this arrangement, the difference between each point and the trace line is the residual for the bin. Confidence intervals can be added to the observed proportions in order to display uncertainty. Computer simulations were used to test four alternative ways for binning students. These simulations showed that binning students according to number of questions they answered correctly on the entire test works best. Simulations also showed confidence intervals for bin plots had coverage probabilities close to nominal values for common testing scenarios, but that there are scenarios in which confidence intervals had inflated error rates.

Effect of the vertical relative motion of stock/switch rails on wheel–rail contact mechanics in switch panel of railway turnout

In order to enable the vehicle to change among the tracks, the stock and switch rails are separated and provided with different rail resilience levels on the baseplate in the railway turnout switch panel. Therefore, there will be vertical relative motion between stock/switch rails under wheel loads, and the relative motion will change the combined profile of stock/switch rails and consequently affect the wheel–rail contact mechanics. A method is developed in this article to investigate the effect of the relative motion of stock/switch rails on the wheel–rail contact mechanics along the railway turnout switch panel. First, the possible rigid wheel–rail contact points, called primary and secondary stock/switch rail contact points, are calculated based on the trace line method; second, the actual contact points are determined by the presented equations; finally, the distribution of wheel–rail contact forces on the stock/switch rails is obtained based on the continuity of interface displacements and forces. A numerical example is presented in order to investigate the effect of the relative motion of stock/switch rails on the wheel–rail contact points, stresses, and forces, and the results are presented and discussed.

The New Method of Connecting Projection of Structural Planes Exposed Points into a Line

Structural planes in rock mass play a regulatory role in strength, deformation and fracture. It is the primary task to find out spatial distribution of controlling structural planes. The new method of connecting projection of structural planes exposed points into a line is realized by the certain distance from exposed points to the plane. And the plane is determined by its occurrence. Then select the suitable data and project to the ground surface using trigonometric function conversion. Finally connect these projection points into a line. Computation process can be simplified through MATLAB. This new method is applied to draw the exposed trace line of III-class structure in the left dam abutment adits of Yebatan hydroelectric power station in Jinsha river. The results are accurate, which means this method is feasible.

The Derivation and Simulation of Curved Tooth Face Gear Tooth Theoretical Contract-Point Trace Line Equations

The face gear tooth surface theoretical equation, based on the mesh of curved tooth face gear and involute worm, was deduced by means of differential geometry, meshing theory and so on. According to the conditions of the gear meshing, studying the ideal contract-point trace line theoretical equation under the conditions of no machining errors, installation errors and so on. By solving the equations and simulating in SOLIDWORKS, finally the tooth contact situation of face gear and cylindrical worm in the meshing process was got.

Study on the Effect of Dynamic Wheel-Rail Contact Geometry Relationship in Turnout Region by the Track-Distance Roughness

Because of the complexity of turnout, the wheel-rail contact of turnout region is more complex than that of railway line. In order to study the wheel-rail contact Geometry relationship of turnout region, using cubic spline interpolation method to get the outline of control sections, the ideal wheel-rail contact relationship in turnout region was obtained by the means of trace line, and then analyze the effect of track-distance roughness on the dynamic wheel-rail Geometry contact, the result shows that appropriate gauge widening can improve the structure irregularity.