Using M-integral for multi-cracked problems subjected to nonconservative and nonuniform crack surface tractions

AbstractIn this paper, an energy parameter based on the concept of the M-integral is proposed for describing the fracture behavior of a multi-cracked solid subjected to nonconservative and nonuniform crack surface tractions. By using the M-integral with a suitably chosen closed contour, one can evaluate the ‘surface creation energy’ (SCE) required for creation of the stressed cracks. Also, it is demonstrated that the property of path-independence holds even under the action of crack surface tractions. Therefore, the singular stress field in the near-tip areas is not directly involved in the calculation so that a complicated finite element model around the crack tips is not required in evaluation of the M-integral

Calculation of near-tip non-singular stresses for pressurized cracks

AbstractWhen the crack surfaces are traction-free, there is only one constant term T in the near-tip stress field, which contributes uniformly to the stress component acting in the direction parallel to the crack flank. As to pressurized cracks, the non-singular part of the asymptotic stresses appears to be more complicated and is no longer characterized only by the constant T. In this work, an effective numerical approach is developed for calculation of the non-singular parts of the asymptotic near-tip stresses under the action of nonuniform crack surface pressures. With this approach, the near-tip non-singular stress field can be accurately evaluated by direct use of regular numerical methods such as finite elements

An immunohistochemical study of the pancreatic endocrine cells of the Korean golden frog, Rana plancyi chosenica

The regional distribution and quantitative frequency of pancreatic endocrine cells were demonstrated in the Korean golden frog (Rana plancyi chosenica Okada), which is known as a Korean endemic species, for the first time by immunohistochemical methods using specific mammalian antisera to insulin, glucagon, somatostatin and human pancreatic polypeptide (PP). In the pancreas of the Korean golden frog, all four endocrine cell types were demonstrated. Insulin- and glucagon-positive cells were located in the pancreas as single cells or islet-like clusters, respectively. Somatostatin-containing cells were also dispersed in the pancreas as single cells or clusters but in the case of clusters, they are exclusively situated in the marginal regions of insulin- or glucagon-positive cell clusters. PP-containing cells were also distributed as single cells or clusters. Clusters consisted of PP-positive cells are distributed as a core type and a marginally distributed type. Overall, there were 40.84±3.81% insulin-, 26.02±1.71% glucagon-, 7.63±2.09% somatostatin- and 25.51±3.26% PP-IR cells

The Effect of ePortfolio Satisfaction on Students’ Learning Motivation and Internet Self-efficacy

This study aims to investigate the effect of e-Portfolio satisfaction on students’ learn­ing motivation and Internet self-efficacy toward the use of e-Portfolio. The data collected for this study occurred over 3 months. Participants were 450 students taking the course of common at an university. The counting of 443 questionnaires was received. The findings revealed that there were positive correlations between learning motivation, Internet self-efficacy, and e-Portfolio satisfac­tion. For gender, the result showed that there were no significant Internet self-efficacy differences between gender. Besides, there were the significant differences in learning motivations and in Internet self-efficacy between the two groups. Furthermore, the multistep regression analysis in­dicated that the learning motivation was the significant predictor of Internet self-efficacy, and In­ternet self-efficacy was the significant predictor of e-Portfolio satisfaction. Based on the findings, educators and researchers needed to pay attention to these influences and take these factors into consideration in e-Portfolio. The study concludes by assessing the overall gains and shortcomings of the reform effort toward using the e-Portfolio to help student self-learning

Evolving temporal association rules with genetic algorithms

A novel framework for mining temporal association rules by discovering itemsets with a genetic algorithm is introduced. Metaheuristics have been applied to association rule mining, we show the efficacy of extending this to another variant - temporal association rule mining. Our framework is an enhancement to existing temporal association rule mining methods as it employs a genetic algorithm to simultaneously search the rule space and temporal space. A methodology for validating the ability of the proposed framework isolates target temporal itemsets in synthetic datasets. The Iterative Rule Learning method successfully discovers these targets in datasets with varying levels of difficulty

Stepwise addition of chemical reagents for enhancing electrokinetic removal of cu from real site contaminated soils

In this study, a circulation-enhanced electrokinetics (CEEK) system integrated with the stepwise addition of chemical reagents was used to remediate copper-contaminated soils collected from a real site. At first, an optimal extraction process of different chemical reagents was found to obtain the highest copper removal efficiency by conducting batch extraction experiments. The chemical reagents served as extracts including EDTA, NaOH, and sodium dithionite + sodium citrate. Then, CEEK integrated this optimal extraction, that is, the treatment of 6-day EDTA, NaOH, EDTA, sodium dithionite + sodium citrate, and EDTA in a series. According to experimental results, the NaOH and sodium dithionite + sodium citrate could effectively facilitate the copper removal during the extraction and electrokinetics (EK) processes. The optimal extraction process for this real contaminated soil (94% copper removal efficiency) was the alternative extraction of EDTA, NaOH, and sodium dithionite + sodium citrate. The copper removal efficiency of the real contaminated soil could reach around 55% after 30-day CEEK treatment. The continuous decline of soil copper concentration of this integrated EK technique could be achieved as the remediation time was extended sufficiently

Dynamics of the Compact, Ferromagnetic \nu=1 Edge

We consider the edge dynamics of a compact, fully spin polarized state at filling factor $\nu=1$. We show that there are two sets of collective excitations localized near the edge: the much studied, gapless, edge magnetoplasmon but also an additional edge spin wave that splits off below the bulk spin wave continuum. We show that both of these excitations can soften at finite wave-vectors as the potential confining the system is softened, thereby leading to edge reconstruction by spin texture or charge density wave formation. We note that a commonly employed model of the edge confining potential is non-generic in that it systematically underestimates the texturing instability.Comment: 13 pages, 7 figures, Revte

Orbit spaces of free involutions on the product of two projective spaces

Let $X$ be a finitistic space having the mod 2 cohomology algebra of the product of two projective spaces. We study free involutions on $X$ and determine the possible mod 2 cohomology algebra of orbit space of any free involution, using the Leray spectral sequence associated to the Borel fibration $X \hookrightarrow X_{\mathbb{Z}_2} \longrightarrow B_{\mathbb{Z}_2}$. We also give an application of our result to show that if $X$ has the mod 2 cohomology algebra of the product of two real projective spaces (respectively complex projective spaces), then there does not exist any $\mathbb{Z}_2$-equivariant map from $\mathbb{S}^k \to X$ for $k \geq 2$ (respectively $k \geq 3$), where $\mathbb{S}^k$ is equipped with the antipodal involution.Comment: 14 pages, to appear in Results in Mathematic