A novel weight function for RMS stress intensity factor determination in surface cracks

This paper discusses the problem of stress intensity factor determination in surface cracks. In particular, the concept of root mean square stress intensity factors (RMS SIF) is discussed for the general class of semi-elliptical surface cracks. The weight function SIF derivation method is considered problems with the existing techniques are highlighted, and a novel technique for the derivation of the RMS SIF weight functions for surface cracks is presented and results are compared with numerical solutions for a variety of loadings and geometries

Unified approach to transformations of Painleve equations

Ankara : Department of Mathematics and Institute of Engineering and Sciences, Bilkent Univ., 1993.Thesis (Master's) -- Bilkent University, 1993.Includes bibliographical references leaves 36-37In this thesis, we iind the explicit form of some transformations associated with the second, third, fourth and fifth Painleve equations. These transformations are obtained by using the Schlesinger transformations associated with the linear system of equations of Painleve eciuations.The application of such transformations enables us to generate the new solutions of the given Painleve equation with different values of parameters, from the known solutions.Chahardehi, Ali Reza ModaressiM.S

Antioxidant, Antimicrobial Activity and Toxicity Test of Pilea microphylla

A total of 9 plant extracts were tested, using two different kinds of extracting methods to evaluate the antioxidant and antimicrobial activities from Pilea microphylla (Urticaceae family) and including toxicity test. Antioxidant activity were tested by using DPPH free radical scavenging, also total phenolic contents and total flavonoid contents were determined. Toxicity assay carried out by using brine shrimps. Methanol extract of method I (ME I) showed the highest antioxidant activity at 69.51 ± 1.03. Chloroform extract of method I (CE I) showed the highest total phenolic contents at 72.10 ± 0.71 and chloroform extract of method II (CE II) showed the highest total flavonoid contents at 60.14 ± 0.33. The antimicrobial activity of Pilea microphylla extract was tested in vitro by using disc diffusion method and minimum inhibitory concentration (MIC). The Pilea microphylla extract showed antibacterial activity against some Gram negative and positive bacteria. The extracts did not exhibit antifungal and antiyeast activity. The hexane extract of method I (HE I) was not toxic against brine shrimp (LC50 value was 3880 μg/ml). Therefore, the extracts could be suitable as antimicrobial and antioxidative agents in food industry

Experimental determination of the overturning moment and net lateral force generated by a novel vertical axis wind turbine: experiment design under load uncertainty

Recent developments in harnessing wind energy propose new, radically different designs to alleviate some of the difficulties associated with conventional wind turbines. New designs however require testing for a variety of reasons ranging from gaining confidence in the analytical models used in the design and development through to satisfaction of certification requirements. Medium-scale prototype testing of large-scale concepts, where parameters such as the response of the structure and the loading conditions are often highly uncertain demand special consideration. This article presents the design of a special test rig and calculation methodology for the experimental determination of the overturning moment and net force generated by the NOVA Vertical Axis Wind Turbine using a field experimental setup. The design of the experimental model involves dealing with modelling uncertainties as loads in operation and therefore the response of the structure are largely unknown before testing has been carried out. The variability in the wind speed and direction also need to be accommodated for

Alkaloids: The Potential of Their Antimicrobial Activities of Medicinal Plants

Given the potential adverse effects of chemical drugs, utilizing natural products with diverse therapeutic and antimicrobial compounds is advisable. Countries can use indigenous flora from their regions in vegetation for medicinal purposes. Several nations exhibit distinctive indigenous flora owing to their geographic positioning and climatic conditions. These plants have been the subject of our research, which has explored their antimicrobial properties against fungi, parasites, bacteria, and viruses. Studies have investigated the therapeutic and antimicrobial effects of plants and their bioactive compounds, such as alkaloids, flavonoids, and terpenoids. Among them are alkaloids, a diverse class of naturally occurring chemicals, such as tropanes, terpenoids, and steroids. Some of these medicinal plants have been found to possess antioxidant and anti-inflammatory properties in addition to their antimicrobial effects. This chapter explores the antimicrobial potential of alkaloids found in medicinal plants

Fatigue crack growth under remote and local compression – a state-of-the-art review

There is an ever increasing need for accurate understanding of the fatigue crack growth behaviour in major engineering materials and components. With the move towards more complex, probabilistic assessments, the traditional ‘safe’ or conservative approach for prediction of fatigue crack growth rate may no longer be attractive. Current codes and standards tend to be ambiguous about the treatment of compressive stress cycles: on the one hand code guidance on fatigue crack initiation may be non-conservative, while assessment of crack propagation may be inconsistently conservative. Where codes are non-conservative they could lead to dangerous assessments. The current paper provides a critical review of state-of-the-art in literature and a study of current code implications

Distribution and Prevalence Potato virus Y Isolates Obtained from Potatoes Grown in the Iran by RT-PCR

To survey the distribution and prevalence of potato virus Y (PVY) strains in north western Iran, 381 symptomatic infected samples of the main potatoes grown in the said region were collected from the fields between (Hall et al., 1998) 2007 and 2008. The collected samples were first tested for PVY infection via a double antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) technique. Of the total number of collected samples, 79 (20.73%) tested positive for PVY infection. The highest level of PVY infection was observed in the district of Gilak-Abad in Sarab County, whereas the lowest infection was observed in the district of Oughan in the suburbs of Sarab city. The RT-PCR detection of PVY strains by using specific primers resulted in the amplification of DNA fragments specific to the PVY strains NTN, C, O, and N at 725, 1553, 352, and 616 bp, respectively. The highest strain diversity of PVY was detected in the district of Shirehjin in Sarab city and the lowest in the district of Ghaleh Jugh in Bostan-Abad city. Both single and multiple infection types of the PVY stains were observed in the region. Of the 79 PVY-infected samples, 77.21% were infected with strain O, 62.02% with strain C, 39.24% with strain N, and 8.86% with strain NTN. The highest level of multiple infections was observed in the combinations of the strains C+O (27.84%) and the triple strains O+N+C (15.18%). This paper is the first to report the detection of the PVY strain NTN in Iran. Keywords: RT-PCR, Molecular diagnosis, Potato, ELISA, Potato Virus Y (PVY

Re-evaluation of fatigue design curves for offshore wind monopile foundations using thick as-welded test specimens

The dominant majority of existing offshore wind turbines are supported using monopile foundations which are fabricated by welding thick steel plates. In the current fatigue design recommendations for welded steel structures, which are commonly used in the design of monopile structures, the initial inverse slope of the S-N curve is fixed to −3. The historic rationales for this assumption are the ease of fatigue life calculations, the effect of long-range residual stresses that were not originally captured in the test data on thin welded specimens, and analogy with fatigue crack growth. While this introduces an unquantified level of conservatism to deterministic fatigue calculations, it was an acceptable (and wise) assumption when the S-N design curves were generated a few decades ago; however, current designs and assessments require more accurate calculations and the need to more confidently quantify the likelihoods attached to these evaluations. In the present study, it is argued that unlike large braced structures (e.g. jackets) in which long-range residual stresses may remain in place as fatigue cracks propagate, in circumferential welds of monopile structures the natural relaxation of residual stresses, in the absence of long-range residual stresses, must be accounted for by performing fatigue tests on thick welded samples. This paper presents a thorough analysis of the fatigue test results obtained from 50 mm thick as-welded samples with representative profiles of residual stresses that exist in monopiles. Basic and advanced statistical approaches were employed in the analysis and higher values of inverse slope were found using the large thickness test data. The results from this study are compared with the recommended fatigue design curves available in international standards. The outcomes from this research draw important observations concerning the need to employ an appropriate value of inverse slope in the design of monopile structures by excluding the conservative approach imposed by a fixed value of −3 which was originally implemented for braced structures with the assumption of large and long-range residual stresses