Stress intensity factors for fatigue cracking of round bars

The stress intensity factor for a single edge crack of either straight or circular front in a round bar has been determined using both the degenerated quarter-point isoparametric finite element and experimental fatigue crack growth data, and compared with values found by earlier investigators.The results of this study confirm that the stress intensity factors for straight edged surface cracks are lower in round bars than in square bars and a comparison of finite element and experimental results indicates that the effective stress intensity factor at the centre of the fatigue crack front in a round bar is 17% greater than its theoretical value.A correction function is proposed to account for the effect on the stress intensity factor of the circular boundary of a round bar.     

THE MIOCENE KAREEM FORMATION IN THE SOUTHERN GULF OF SUEZ, EGYPT: A REVIEW OF STRATIGRAPHY AND PETROLEUM GEOLOGY

The middle Miocene Kareem Formation in the Gulf of Suez is up to 500-m thick, and is composed of interbedded sandstones, shales and carbonates; minor anhydrites are present in the lower part of the formation. The siliciclastics were deposited in alluvial and submarine fans building out from the rift shoulders, while the carbonates and anhydrites were precipitated in local lagoons as a result of sea-level fluctuations. The formation is divided into the Rahmi and overlying Shagar Members, and is Langhian to Serravallian in age.
Three main sandstone lithologies have been identified (quartz arenites, arkoses and quartz wackes) each of which differ in their content of secondary minerals, cements and matrix types, reflecting their differing depositional settings and diagenetic histories.
The sandstones of the Kareem Formation form one of the most prolific reservoir lithologies in the Gulf of Suez oil province, and produce oil and/or gas in almost 30 fields. These sandstones have a good reservoir quality throughout the basin, with gross- and net-pay thicknesses of up to 235 m and 195 m, respectively. The sandstones' porosity varies from 9% to 33%, and permeabilities range from 20 md to 730 md. Reservoir quality depends on the sandstones' shaliness, diagenetic history and degree of compaction.
The sandstones still have high exploration potential particularly in the southernmost portion of the Gulf of Suez where they are extensive and thick but where there has been little drilling. Organic-rich shales within the Kareem Formation constitute potential source rocks for oil and gas, especially in the southernmost part of the Gulf of Suez where the geothermal gradient is high and where, according to previous studies, these sediments are located within the oil-generation "window ".     

Semi-automatic system for defining free-form curves and surfaces

Among curves and surfaces defined by parametric polynomials, the cases dealt with here are those which only have to comply with the requirement to run through a certain number of points previously located in space. The process can be totally automatic, but the results are liable to be altered by arbitrary decisions.     

Studies on cyanine dyes. IV. Synthesis of new styryl oxa-cyanine dyes

The condensation reaction of benzoxazole-2-carboxaldehyde (I) with quaternary salts of heterocyclic compounds, in the presence of piperidine as a catalyst, afforded styryl cyanines (II). Interaction of (I) with the non-quaternised heterocyclic compounds at a longer time gave the corresponding dimethine bases (III). On the other hand, benzoxazole-2-carboxaldehyde-3-ethiodide (IV) interacted with quaternised and non-quaternised heterocyclic compounds achieved styryl cyanines of the type (V) and (VI), respectively. Absorption spectra for these compounds in EtOH are discussed.     

Optical Absorption and Oxidation States of Uranium in Alkali Aluminoborate Glasses

The optical absorption spectra of 22R₂O.13Al₂O₃.65B₂O₃ (mol%) glasses contain ing uranium indicate the presence of U⁶⁺, U⁵⁺, and U⁴⁺. The presence of U⁶⁺ in the uranyl group is favored as alkali ion (R) is replaced in the direction Li6+ coordinated diflerently from that in uranyl groups (possibly 4-coordinated). A suggestion for making use of such findings in estimating the uranium content of a sample is given.     

Asphaltene aggregation onset during high-salinity waterflooding of reservoirs (a molecular dynamic study)

Abstract

The primary objective of this study is to establish an understanding of the role of high-salinity brine on the intensity of asphaltene aggregation onset during waterflooding of petroleum reservoirs. We already have shown that asphaltenes have a high tendency to form aggregates during waterflooding process when pure- and low salinity-water are injected into reservoirs. To fulfill the present objective, molecular dynamic simulations are performed on asphaltenic-oil/aqueous systems at 550 K-200?bar. The oil phase consists of asphaltenes (10?wt.%) and ortho-xylene, in which asphaltene molecules are completely soluble. Our simulations results reveal that the “salt-in effect” of high-salinity brine (25 wt.% NaCl) on seven different model asphaltenic oils causes a significant reduction of the onset of asphaltene aggregation as compared with pure-water. Such “salt-in effect” is primarily due to a considerable reduction of water miscibility in the oil phase at high pressure and temperature.     

Reducing the mean squared error of quantile-based estimators by smoothing

Many univariate robust estimators are based on quantiles. As already theoretically pointed out by Fernholz (in J. Stat. Plan. Inference 57(1), 29–38, 1997), smoothing the empirical distribution function with an appropriate kernel and bandwidth can reduce the variance and mean squared error (MSE) of some quantile-based estimators in small data sets. In this paper we apply this idea on several robust estimators of location, scale and skewness. We propose a robust bandwidth selection and bias reduction procedure. We show that the use of this smoothing method indeed leads to smaller MSEs, also at contaminated data sets. In particular, we obtain better performances for the medcouple which is a robust measure of skewness that can be used for outlier detection in skewed distributions.