Fracture Mechanics Analyses for Interface Crack Problems - A Review

Recent developments in fracture mechanics analyses of the interfacial crack problem are reviewed. The intent of the review is to renew the awareness of the oscillatory singularity at the crack tip of a bimaterial interface and the problems that occur when calculating mode mixity using numerical methods such as the finite element method in conjunction with the virtual crack closure technique. Established approaches to overcome the nonconvergence issue of the individual mode strain energy release rates are reviewed. In the recent literature many attempts to overcome the nonconvergence issue have been developed. Among the many approaches found only a few methods hold the promise of providing practical solutions. These are the resin interlayer method, the method that chooses the crack tip element size greater than the oscillation zone, the crack tip element method that is based on plate theory and the crack surface displacement extrapolation method. Each of the methods is validated on a very limited set of simple interface crack problems. However, their utility for a wide range of interfacial crack problems is yet to be established

Three-Dimensional Geometric Nonlinear Contact Stress Analysis of Riveted Joints

The problems associated with fatigue were brought into the forefront of research by the explosive decompression and structural failure of the Aloha Airlines Flight 243 in 1988. The structural failure of this airplane has been attributed to debonding and multiple cracking along the longitudinal lap splice riveted joint in the fuselage. This crash created what may be termed as a minor "Structural Integrity Revolution" in the commercial transport industry. Major steps have been taken by the manufacturers, operators and authorities to improve the structural airworthiness of the aging fleet of airplanes. Notwithstanding, this considerable effort there are still outstanding issues and concerns related to the formulation of Widespread Fatigue Damage which is believed to have been a contributing factor in the probable cause of the Aloha accident. The lesson from this accident was that Multiple-Site Damage (MSD) in "aging" aircraft can lead to extensive aircraft damage. A strong candidate in which MSD is highly probable to occur is the riveted lap joint

Urokinase-activated Stat1 mediates antiproliferative effect in vascular smooth muscle cells cocultered with monocytes

[no abstract

Studies on nutritional and anti-​nutritional composition of Bambusa multiplex (lour.) raeusch. Ex schult

Bambusa multiplex, a multipurpose ornamental and com. bamboo species used for hedges, construction, basketing and as handicraft material. The shoots are edible and consumed in Southeast Asia and in North eastern regions of India. As earlier investigations does not emphasize on finding out the harvesting time, an attempt has been made to find out the harvesting time to obtain quality shoots. The bamboo shoots were harvested on different days (7-​30 days after emergence from ground) and analyzed for chem., nutritional and anti-​nutritional components. The shoots harvested at various time intervals showed variation in nutritional compn. with an overall decrease in protein and increase in dietary fiber and carbohydrate content. All the nutritional elements except calcium showed decreased content with shoot maturity. The optimum harvesting age for B. multiplex shoots were found to be 7- 10 days with high nutritional content and antinutritional component, cyanide was found to be completely absent

Three-dimensional elastic-plastic analysis of shallow cracks in single-edge-crack-tension specimens

Three dimensional, elastic-plastic, finite element results are presented for single-edge crack-tension specimens with several shallow crack-length-to-width ratios (0.05 less than or equal to a/W less than or equal to 0.5). Results showed the need to model the initial yield plateau in the stress-strain behavior to accurately model deformation of the A36 steel specimens. The crack-tip-opening-displacement was found to be linearly proportional to the crack-mouth-opening displacement. A new deformation dependent plastic-eta factor equation is presented for calculating the J-integral from test load-displacement records. This equation was shown to be accurate for all crack lengths considered

MODIFIED BIPHASIC MEDIA FOR BLOOD CULTURE

ABSTRACTObjective: To evaluate the performance characteristics of Nutrient agar and MacConkey's agar biphasic medium (BPM) with conventional bloodculture.Methods: We prepared two modified biphasic blood culture medium with Nutrient agar (with 1% lactose and 0.004% neutral red) and MacConkey'sagar. A total of 20 standard clinical strains of bacterial pathogens and Candida albicans were inoculated in duplicate in Nutrient agar BPM, MacConkey'sagar, and brain heart infusion broth to evaluate the turn-around time and performance characteristics.Results: All isolates except Streptococcus pyogenes and Streptococcus pneumoniae showed characteristic lactose fermenter and non-lactose fermentercolonies on Nutrient agar and MacConkey's agar BPM within 24 hrs with sufficient growth to carry out biochemical identification and antibioticsusceptibility testing. This resulted in a shorter turn-around time (48 hrs) when compared to that of conventional blood culture (72 hrs).Conclusion: Nutrient agar and MacConkey's agar based modified BPM could be beneficial in reducing the turn-around time of blood culture.Keywords: Biphasic media, Bloodstream infection, Conventional blood culture

WSSL: Weighted Self-supervised Learning Framework For Image-inpainting

Image inpainting is the process of regenerating lost parts of the image. Supervised algorithm-based methods have shown excellent results but have two significant drawbacks. They do not perform well when tested with unseen data. They fail to capture the global context of the image, resulting in a visually unappealing result. We propose a novel self-supervised learning framework for image-inpainting: Weighted Self-Supervised Learning (WSSL) to tackle these problems. We designed WSSL to learn features from multiple weighted pretext tasks. These features are then utilized for the downstream task, image-inpainting. To improve the performance of our framework and produce more visually appealing images, we also present a novel loss function for image inpainting. The loss function takes advantage of both reconstruction loss and perceptual loss functions to regenerate the image. Our experimentation shows WSSL outperforms previous methods, and our loss function helps produce better results.Comment: 9 Pages, document submitted for publication at CGVCVIP 202

Some Observations on the Current Status of Performing Finite Element Analyses

Aerospace structures are complex high-performance structures. Advances in reliable and efficient computing and modeling tools are enabling analysts to consider complex configurations, build complex finite element models, and perform analysis rapidly. Many of the early career engineers of today are very proficient in the usage of modern computers, computing engines, complex software systems, and visualization tools. These young engineers are becoming increasingly efficient in building complex 3D models of complicated aerospace components. However, the current trends demonstrate blind acceptance of the results of the finite element analysis results. This paper is aimed at raising an awareness of this situation. Examples of the common encounters are presented. To overcome the current trends, some guidelines and suggestions for analysts, senior engineers, and educators are offered

A COMPARISON OF MECHANICAL AND FIRE PROPERTIES OF ECO-CORE WITH A COMPATITIVE COMMERCIAL MATERIAL

ABSTRACT A fire resistant insulation panel material called Eco-Core has been developed at North Carolina A&T State University. Eco-Core is composed of about 83% fly ash, a waste material from coalfired power plants. The remainder is a fire resistant organic binder. It is visualized that one application of this new material would be in the construction industry where fire resistance is of primary concern. The mechanical and fire resistant properties of a commercial material, U.S. Gypsum's Type X SHEETROCK, commonly used for these type applications was compared with those of Eco-Core. The results of this study have indicated that the mechanical properties of the Eco-Core are superior in virtually all respects, for example the compression strength was about 4x greater, the tension strength 3x greater, and the flexural strength was 8x greater. In addition, the fire resistance is comparable and the density is about 40% less. The details of this research are provided in the paper

Nicotine, IFN-γ and retinoic acid mediated induction of MUC4 in pancreatic cancer requires E2F1 and STAT-1 transcription factors and utilize different signaling cascades

BACKGROUND: The membrane-bound mucins are thought to play an important biological role in cell–cell and cell–matrix interactions, in cell signaling and in modulating biological properties of cancer cell. MUC4, a transmembrane mucin is overexpressed in pancreatic tumors, while remaining undetectable in the normal pancreas, thus indicating a potential role in pancreatic cancer pathogenesis. The molecular mechanisms involved in the regulation of MUC4 gene are not yet fully understood. Smoking is strongly correlated with pancreatic cancer and in the present study; we elucidate the molecular mechanisms by which nicotine as well as agents like retinoic acid (RA) and interferon-γ (IFN-γ) induce the expression of MUC4 in pancreatic cancer cell lines CD18, CAPAN2, AsPC1 and BxPC3. RESULTS: Chromatin immunoprecipitation assays and real-time PCR showed that transcription factors E2F1 and STAT1 can positively regulate MUC4 expression at the transcriptional level. IFN-γ and RA could collaborate with nicotine in elevating the expression of MUC4, utilizing E2F1 and STAT1 transcription factors. Depletion of STAT1 or E2F1 abrogated the induction of MUC4; nicotine-mediated induction of MUC4 appeared to require α7-nicotinic acetylcholine receptor subunit. Further, Src and ERK family kinases also mediated the induction of MUC4, since inhibiting these signaling molecules prevented the induction of MUC4. MUC4 was also found to be necessary for the nicotine-mediated invasion of pancreatic cancer cells, suggesting that induction of MUC4 by nicotine and other agents might contribute to the genesis and progression of pancreatic cancer. CONCLUSIONS: Our studies show that agents that can promote the growth and invasion of pancreatic cancer cells induce the MUC4 gene through multiple pathways and this induction requires the transcriptional activity of E2F1 and STAT1. Further, the Src as well as ERK signaling pathways appear to be involved in the induction of this gene. It appears that targeting these signaling pathways might inhibit the expression of MUC4 and prevent the proliferation and invasion of pancreatic cancer cells