Failure mechanisms in granular media: a discrete element analysis

This paper attempts to numerically validate the concept of diffuse failure using a discrete element method. First, the theoretical background is reviewed, and it is shown how the kinetic energy of a system, initially at rest after a loading history, is likely to abruptly increase under the effect of disturbances. The vanishing of the second-order work thus constitutes a basic ingredient, related to both the pioneering work of Hill (J Mech Phys Solids (6):236–249, 1958) and the notion of bifurcation applied to geomechanics (Vardoulakis and Sulem in Bifurcation analysis in geomechanics, Chapman & Hall Publisher, London, 1995). Discrete numerical simulations were performed on homogeneous three-dimensional specimens, and the three basic conditions that must be satisfied in order to observe a failure mechanism are numerically checked. Finally, this work illustrates the phenomena that are likely to affect in situ slopes, for instance, when the loading (due to weather conditions or human activities) meets the three basic conditions for a failure mechanism to develop.     

Failure Analysis of a Cylindrical Roller Bearing from a Rolling Mill

Premature failure of a cylindrical roller bearing of a gear box input shaft from a hot strip mill has been investigated. The pins of the cylindrical rollers of the bearing broke from the welded joints at their ends on the cage ring. Investigations were carried out on the failed roller pin and the welded joint. The investigation consists of visual observation, chemical analysis, characterization of macro- and microstructures, measurement of hardness profile, fractography, and energy dispersive spectroscopy (EDS). The fracture surface of the roller pins exhibits beach marks. Scanning electron microscopy (SEM) of the fracture surfaces reveals striations suggesting fatigue failure. The measured hardness profile along the welded joint shows very high hardness due to the presence of untempered martensite at the fusion boundary as revealed by the microstructural examination. Analyses of the results infer that the roller pins failed by the initiation of fatigue cracks from the welded joint because of the presence of untempered martensite originated due to improper welding process.     

Analysis on the Latest Assessment Criteria of ASME B31G-2009 for the Remaining Strength of Corroded Pipelines

ASME B31G provides the most basic and widespread method in assessing the remaining strength of corroded pipelines. The third edition B31G (ASME B31G-2009) is the latest revision issued by the American National Standards Institute (ANSI) and is used as the basis for this study. This article discusses the development process of ASME B31G, and presents the comparative analysis of ASME B31G, RSTRENG, and DNV RP-F101. The predicted failure pressures are calculated by each standard mentioned above, based on 35 groups of data for full-size pipe tests collected from the literature. The deviations between the predicted values and the actual experiment results are discussed. Finally, practical applications are compared among the assessment methods. The investigation showed that predictions based on ASME B31G-2009 are much more accurate than predictions based on the previous editions of B31G. The applications of ASME B31G-2009 and RSTRENG 0.85 dL effectively improve the pipe’s conveying efficiency and optimize the cost of managing the piping system. However, they both are applicable only for evaluating the medium- and low-strength pipe steels. In contrast, DNV RP-F101 is applicable to the medium- and high-strength pipe steels, but its results are often not safe for application to the lower-strength pipe steels.     

Multilayer Transitions in Spin-3/2 Blume–Capel Model with RKKY Interaction in a Transverse Field

Using mean-field theory, we have studied the effect of quantum transverse field on the magnetic properties and multilayer transitions in the spin-3/2 Blume–Capel model with RKKY interaction. The system is formed by two magnetic multilayer materials, of different thicknesses, separated by a non magnetic spacer of thickness M. It is found that there exist critical transverse fields above which the multilayer transitions occur. This critical value decreases when increasing the thickness of the nonmagnetic spacer M. Phase diagram is established in different plane of space parameter.     

Microstructure and Transport Properties in Tin Boned La<Subscript>0.7</Subscript>Sr<Subscript>0.3</Subscript>MnO<Subscript>3</Subscript> Composites

A novel boned perovskite manganese oxide magnetoresistant material was prepared using La_0.7Sr_0.3MnO₃ (LSMO) as the precursor powders and metal tin (Sn) as the binder. The microstructure and phase characteristics, low-field transport properties were studied. Sn segregated at the grain boundaries of LSMO grains. The insulator–metal (I–M) transition and enhanced LFMR are only observed with a low content of Sn, due to grain boundary disorder and spin polarized tunneling between grain boundaries. The Sn addition induced resistivity decreasing dramatically. In the high temperature PM region, the resistivities for samples with low Sn content follow the adiabatic small-polaron-hopping model.     

Resonances and Complexity: From Stripes to Superstripes

The present issue of Journal of Superconductivity and Novel Magnetism collects the papers presented at the International Conference on “Quantum Phenomena in Complex Matter.” Superstripes 2010 held in Erice, Italy, from July 19 to 25, 2010, at the Ettore Majorana Foundation and Centre for Scientific Culture. In this preface, I discuss the scientific scenario of the search for the mechanism of the macroscopic quantum coherent phase at high temperature “superconductivity in complexity.”     

Effects of phospholipid hydroperoxide glutathione peroxidase mRNA expression on meat quality of <Emphasis Type=Italic>M. longissimus dorsi</Emphasis> in pigs

Antioxidant enzymes protect muscle tissues against oxidation from reactive oxygen species and increase the stability of the muscle. Phospholipid hydroperoxide glutathione peroxidase (GPx4) is an important antioxidant enzyme in muscle tissue. So the aim of this study was to identify the effects of mRNA expression level of GPx4 gene on meat quality properties in Longissimus dorsi of three pig breeds. Total 36 pigs (12 pigs for each breed) were used to measure the meat quality properties and to analyze the expression levels of GPx4 gene by quantitative real-time PCR. The results showed that meat quality, GPx4 activity, and GPx4 mRNA levels were affected by pig breeds. There were the lowest expressible moisture, drip loss, and cooking loss in Laiwu Pig among the three breeds, and also there were the highest GPx4 activity and the expression levels of GPx4 gene in Laiwu Pig compared with the other two pig breeds. Analysis of meat samples divergent for water-holding capacity identified highly negative associations between expressions levels of GPx4 gene and expressible moisture, drip loss and cooking loss. These results suggest that the higher mRNA expression level of GPx4 gene up-regulate the water-holding capacity and the activity of GPx4, and the expression of GPx4 gene plays an important role in physiological changes related to the meat quality properties and the mechanisms of the antioxidant ion of meat.     

Red bean extract reduces inflammation and increases survival in a murine sepsis model

This study used in vitro and in vivo experimental models to investigate the anti-inflammatory potential of the butanol fraction of red bean ethanol extract (BF-RBEE), which contains the biologically active molecule catechin-7-β-d-glucopyranoside. Treatment with BF-RBEE inhibited nitric oxide production in lipopolysaccharide (LPS)-stimulated macrophages through suppression of extracellular signalregulated kinase and IκBα activation. In an in vivo murine sepsis model, oral administration of BF-RBEE improved mouse survival. Specifically, the survival rate of mice injected with LPS was 0 and 40% in ICR and BALB/c mice, respectively, whereas the survival of mice co-treated with BF-RBEE was 100% in both mouse types. This increase in survival with the BF-RBEE administration was correlated with decreased tumor-necrosis factor-α and interferon-γ and increased interleukin-10. Oral administration of BF-RBEE also inhibited total and ovalbumin-specific IgE production in experimental mice. These results suggest the possible usefulness of red beans in the treatment of inflammatory diseases.