1,559 research outputs found

    Sea Level Variation Along the Western Coast of the Arabian Gulf

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    Observed hourly tidal heights from six stations during the period 1980-1987 were used in the analyses. Daily readings of the pressure at mean sea level from three meteorological stations were also used. The variations of the observed daily mean sea level were studied at the six stations, giving low values in the winter season, and high ones in summer and spring seasons. The monthly mean sea level showed higher values during July and August and lower ones in the winter season. As the Arabian Gulf is generally considered a shallow sea, the meteorological conditions are the main cause of the sea level variation. This was shown by the variation of the daily mean sea level residual at the six stations. From the analyses of the coherence of several parameters, the pressure difference over the Gulf area did not give a noticeable effect with either the daily observed sea level or the daily sea level residual. Generally speaking, the important factor affecting the sea level variation in the Arabian Gulf is the pressure system covering the area either during the summer or the winter seasons

    Experimental and analytical investigation of the fracture processes of boron/aluminum laminates containing notches

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    Experimental results for five laminate orientations of boron/aluminum composites containing either circular holes or crack-like slits are presented. Specimen stress-strain behavior, stress at first fiber failure, and ultimate strength were determined. Radiographs were used to monitor the fracture process. The specimens were analyzed with a three-dimensional elastic-elastic finite-element model. The first fiber failures in notched specimens with laminate orientation occurred at or very near the specimen ultimate strength. For notched unidirectional specimens, the first fiber failure occurred at approximately one-half of the specimen ultimate strength. Acoustic emission events correlated with fiber breaks in unidirectional composites, but did not for other laminates. Circular holes and crack-like slits of the same characteristic length were found to produce approximately the same strength reduction. The predicted stress-strain responses and stress at first fiber failure compared very well with test data for laminates containing 0 deg fibers

    Computing the Real Isolated Points of an Algebraic Hypersurface

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    Let R\mathbb{R} be the field of real numbers. We consider the problem of computing the real isolated points of a real algebraic set in Rn\mathbb{R}^n given as the vanishing set of a polynomial system. This problem plays an important role for studying rigidity properties of mechanism in material designs. In this paper, we design an algorithm which solves this problem. It is based on the computations of critical points as well as roadmaps for answering connectivity queries in real algebraic sets. This leads to a probabilistic algorithm of complexity (nd)O(nlog(n))(nd)^{O(n\log(n))} for computing the real isolated points of real algebraic hypersurfaces of degree dd. It allows us to solve in practice instances which are out of reach of the state-of-the-art.Comment: Conference paper ISSAC 202

    Analysis of thermomechanical fatigue of unidirectional titanium metal matrix composites

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    Thermomechanical fatigue (TMF) data was generated for a Ti-15V-3Cr-3Al-3Sn (Ti-15-3) material reinforced with SCS-6 silicon carbide fibers for both in-phase and out-of-phase thermomechanical cycling. Significant differences in failure mechanisms and fatigue life were noted for in-phase and out-of-phase testing. The purpose of the research is to apply a micromechanical model to the analysis of the data. The analysis predicts the stresses in the fiber and the matrix during the thermal and mechanical cycling by calculating both the thermal and mechanical stresses and their rate-dependent behavior. The rate-dependent behavior of the matrix was characterized and was used to calculate the constituent stresses in the composite. The predicted 0 degree fiber stress range was used to explain the composite failure. It was found that for a given condition, temperature, loading frequency, and time at temperature, the 0 degree fiber stress range may control the fatigue life of the unidirectional composite

    Influence of Cultivar Type of Strawberry Fruits on Its Volatile Constituents

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    Five strawberry (Fragaria x ananassa. Duch.) cultivars (Festival, Red Merlin, Suzana, Tamar and Winter Dawn) were analysed using solvent-solvent extraction method and GC/MS system to compare between the volatile constituents responsible for the aroma in different fresh and frozen cultivars. The main identified compounds were Tetradecene (15.41%), 2E-dodecene-1-ol (13.78%), Nerolidol (11.37%), E-14-hexadecenal (17.27%) and Octadecanol (17.65%). The present study explains the effect of freezing on aroma content for different strawberry cultivars. Nutritional value contents of the fruits were also estimated which illustrate the importance of fruits as a main source of vitamin C and potassium. The antimicrobial activity of the volatile constituents were estimated and were exhibited a significant results (20-32mm zone of inhibition) against number of human pathogenic microorganisms, compared with the standard antibiotic (20-22 mm zone of inhibition) using the agar well diffusion method. Keywords:Fragaria x ananassa, antimicrobial, cultivars, volatile constituents

    COMPARISON OF MPPT ALGORITHMS FOR PHOTOVOLTAIC SYSTEMS UNDER UNIFORM IRRIADIANCE BETWEEN PSO AND P&O

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    This paper shows a Comparison between Conventional Method [P&O] and particle swarm optimization [PSO] Based on MPPT Algorithms for Photovoltaic Systems under uniform irradiance and temperature. The main idea is to show that PSO method has a very high tracking speed and has the ability to track MPP under different environmental conditions in addition to an easy hardware implementation using a low-cost microcontroller. MATLAB simulations are carried out under very challenging conditions, namely irradiance and temperature, which reflect a change in the load [KW]. The proposed PSO tracking method Results will be compared with conventional method called [P&O] through MATLAB/SIMULINK

    Quality of Life and obesity among Female Employee at Assiut University

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    Egypt is one of the countries where the problem of obesity has been nearing an epidemic level. Currently, nearly 70% of adult women and 48% of men in Egypt are overweight or obese. This matter should be taken seriously because it can burden the health care system and lower the quality of life. Aim of the study: To identify the relationship between quality of Life and obesity among female employee at Assiut University. Subject and Method: descriptive correlation design was utilized to carry out this study. Sample: The studied sample was consisted of 1000 female. Data were collected by using three tools; the first tool is self administered questionnaire includes socio-demographic characteristics of the studied sample. The second tool was an Anthropometric Measurements (weight, height and BMI) and the third tool was the World Health Organization Quality of life (WHOQOL-BREF). Results: the mean age was 36.97 ± 10.80. There was statistical significant difference between Socio-demographic characteristic such as age, marital status, educational level and obesity, also BMI effect on the three QOL domains (physical, psychological and social) while there was no significance differences with environmental aspects of QOL. Conclusion: Obesity has a negative effect on QOL among obese female employees. Recommendation: Awareness about nutritional needs and balanced diet should be increased for every age group through mass media. As well as developing a health education programs about balanced diet and prevention of obesity. Also regular exercise should be included within the daily routine activities of the female employees. Keywords: Quality Of Life (QOL), Obesity, Body Mass Index and Nursing Intervention

    Experimental assessment of different strengthening techniques for opening in reinforced concrete beams

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    The present experimental study includes testing thirteen reinforced concrete beams with openings at different locations to investigate the efficiency of strengthening such openings. Different strengthening techniques around the opening after and before casting include diagonal bars, upper and lower steel, and carbon fiber reinforced polymers (CFRP), were examined. All beams were made from 30 MPa compressive strength and tested under four-point loading.  The cross section of the beams is 400 mm depth x 160 mm width and beam length 2400 mm. The dimensions of the opening are 200 mm x 200 mm. The stiffness, deflection, failure load, and failure mode of the strengthened beams were discussed. Experimental results showed that the beams strengthened with upper and lower steel around opening at mid-span increase the load-carrying capacity by 16.59%. However, beams strengthened by CFRP sheets around the opening in the shear zone increase the load carrying capacity by 47.7% compared to opened beam
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