Showing papers by "Cairo University published in 1983"

Investigation of Two Plane Parallel Jets

Abstract: Results of an experimental study on the interaction of two two-dimensional turbulent parallel jets are reported. The investigation includes measurements of mean velocity, turbulence intensities, and Reynolds shear stress. The structure of the combined flow is compared with that of a single jet. The results show that the velocity profiles of the combined flow are similar and agree well with that of the single jet. Up to 120 slot widths downstream from the nozzles, true similarity is not found. For a spacing of 12.5 slot widths between the axes of the two nozzles, the half-width of the combined flow grows linearly with downstream distance, but its spread angle is slightly lower than that of a single jet. The centerline velocity decays with the same rate as the single jet, but with a higher value of UM/ U0. Nomenclature 5 = spacing between the two nozzles tp =

A New Planning Model for Distribution Systems

Abstract: This work presents an efficient algorithm for the static investment planning of large radial distribution systems. It takes into account the fixed costs, concave nonlinearities in the cost functions of all elements and the operational constraints. A concave fixed cost model is used to represent elements with large fixed costs (substations and possibly some feeders) and linear cost functions are assumed for the remaining elements. A branch and bound algorithm is used with bounding criteria dependent on the cost and operational constraints. The fixed costs of the remaining elements is then accounted for through an iterative procedure which modifies the solution of the first step. The validity and efficiency of the model have been tested against published results. Results for a large rural radial system are presented.

New Approach for the Application of Shunt Capacitors to the Primary Distribution Feeders

Abstract: This paper deals with the application of permanent shunt capacitors to primary distribution feeders. Two distinct optimization techniques have been developed for selection of capacitor size and location depending on the location of the additional loads that can be served with the capacitors present. The objective cost function minimized includes revenues due to energy loss reduction in the feeder and released kVA at the substation. The minimization is subject to voltage drop constraints. These techniques have been applied to a typical rural distribution zone in Egypt and the results are briefly summarized.

Buoyancy Effects in the Entrance Region of Horizontal Rectangular Channels

Abstract: Analyse numerique de l'influence de la convection naturelle sur le transfert de chaleur par convection forcee laminaire dans la zone entree de conduites rectangulaires ayant des rapports largeur/hauteur de 1 et 4 pour differentes valeurs du nombre de Prandtl

Influence of Atomizer Design Features on Mean Drop Size

Abstract: Measurements of mean drop size, using the light-scattering technique, were carried out on eight different airblast atomizers. The liquids employed were water and kerosine. The test range included wide variations in atomizing air velocity, air pressure, and liquid and air flow rates, but the main objective was to examine the influence of scale and various design features on atomization performance. The results obtained show, for all types of airblast atomizer, that atomization quality is improved by increase in ambient air pressure, decrease in atomizer size, and by minimizing the angle of impact between the fuel jet and the high-Velocity air stream.

Thermodynamics of the system iron-aluminum-oxygen between 1073 K and 1573 K

Abstract: Equilibrium oxygen pressures of the univariant ternary coexistences hematite + spinel + alumina, alloy + wustite + spinel, and alloy + spinel + alumina were determined at temperatures in the range 1123 to 1423 K using solid state electrochemical cells. The compositions of alloys and oxide phases of this Fe-Al-0 system that equilibrated with one another at 1273, 1423, and 1573 K were determined. These results and those from the literature are used to determine stabilities of the ternary oxide phases as a function of oxygen pressure and composition by constructing equilibrium oxygen pressure diagrams at 1073, 1173, and 1273 K.

Plant communities along the Medina-Badr road across the Hejaz mountains, Saudi Arabia

Abstract: The present study gives an assessment of the environmental factors and their effect on the pattern and distribution of the plant communities in the area along the road from Medina to Badr, Saudi Arabia The road crosses the Hejaz mountains and the study area presents three main ecogeomorphological systems which are differentiated into various habitats Rainfall and plant cover show wide variation, both in quantity and distribution in the different sectors of the study area Also, the wide variations in topography, rock types and soil characteristics, have a marked influence on the water resources and consequently on the vegetation Twenty-three communities, recognized by species dominance and habitat features, have been distinguished These include ten communities dominated by trees and shrubs; five of them are dominated by one of the Acacia spp growing in the area Seven communities are dominated by suffrutescent species and six are dominated by ephemeral species The latter communities appear only during the wet season and disappear at the beginning of summer The floristic conoposition and the habitat features are described and the ecological relationships between the communities are briefly discussed

Effects of some biocides on Fusarium oxysporum formae speciales causing cotton and tomato wilts in Egypt

Abstract: The comparative effects of four herbicides and a fungicide, representing various groups of compounds, on macroconidial germination, germ-tube lengths, growth and sporulation of two formae speciales of Fusarium oxysporum that cause cotton and tomato wilts in Egypt, were studied. All five biocides inhibited germination, germ-tube elongation, growth and sporulation of the two fungi. The degree of inhibition depended on the biocide used, its concentration and the phase of development of the fungus.

Fractional crystallization and gas chromatographie analysis of fatty acids as a means of detecting butterfat adulteration

Abstract: A method has been devised which gives the distribution of saturated and unsaturated fatty acids of pure and adulterated cow and buffalo ghee with lard or margarine. It involves fractionation of pure and adulterated butterfat into fractions by fractional crystallization. The composition of the fatty acids liberated by the hydrolysis of each of the fractions was determined by gas chromatography. Adulteration of cow and buffalo ghee with various levels of lard or margarine caused significant changes in certain fatty acids, i.e., 22:0, 18:1, 18:0 and 16:0. It is possible to determine the extent of admixture of lard or margarine to either cow or buffalo ghee by applying a simple regression equation for certain fatty acids. This technique provides a basis for the detection of lipid adulteration.

New approach to failure detection in large-scale systems

Abstract: In this paper, a new approach is developed for the detection of malfunctioning sensors for large-scale linear interconnected dynamical systems. The main idea used is to do an overlapping decomposition in order to design multiple decentralised observers. Differences between the same state as estimated by the different observers can be used to isolate the malfunctioning sensors. A sixth-order ladder network example is used to illustrate the approach.

Interaction of the dissociable glycerol-3-phosphate dehydrogenase and fructose-1,6-bisphosphate aldolase. Quantitative analysis by an extrinsic fluorescence probe.

Abstract: Cytoplasmic sn-glycerol-3-phosphate dehydrogenase, labelled covalently with fluorescein isothiocyanate, shows an enzyme-concentration-dependent fluorescence anisotropy. The anisotropy versus enzyme concentration curves is shifted towards higher concentrations when substrates are present. The comparison of the dissociation constants estimated from anisotropy measurements and derived from kinetic experiments suggests that the substrate-induced dissociation of the dimeric dehydrogenase is slow with respect to the enzymatic reaction catalyzed by either its monomeric or dimeric form. The fluorescence anisotropy of the fluorescent dye-labelled dehydrogenase increases with time upon addition of unlabelled fructose-1,6-bisphosphate aldolase approaching a limiting value. This fact indicates the binding of fructose-1,6-bisphosphate aldolase to glycerolphosphate dehydrogenase. A model is proposed assuming simuitaneous binding of tetrameric fructose-1,6-bisphosphate aldolase to monomeric and dimeric glycerolphosphate dehydrogenase with 1:1 stoichiometry. The dissociation constants, as parameters fitted to the experimental curves, were estimated as 0.2 μM and 1 μM for aldolase–dimeric-glycerolphosphate-dehydrogenase and aldolase–monomeric-glycerolphosphate-dehydrogenase complexes respectively.

Theory of triangular-barrier bulk unipolar diodes including minority-carrier effects

Abstract: The effect of the minority-carrier charge on the barrier height of the triangular-barrier (TB) majority-carrier diode is considered. The consequences of this effect on the device performance as a diode, transistor, photodetector, and a thyristor is briefly delineated. A two-carrier model of the TB diode is developed to account for this effect. Four other approximate models of the TB diode are compared with the two-carrier model, and the range of their validity established. A high-gain TB "transistor" is proposed based on the mechanism of barrier-height modulation via minority-carrier injection in the TB diode.

The effect of hydrogen ion on the steady-state multiplicity of substrate-inhibited enzymatic reactions. II. Transient behavior.

Abstract: In this paper we concentrate our attention on the stability and transient behavior of the isothermal system (CSTR) with a substrate-inhibited enzyme reaction producing hydrogen ions. Our investigation covers the region of multiple steady states uncovered previously (1) (ordinary hysteresis and isola). We investigate the local stability characteristics of the different steady states, the effect of the initial condition on the transient behavior and the response of the system to feed disturbances of various magnitudes and durations.

A generalized bubble rise velocity correlation

Abstract: A generalized bubble rise velocity correlation is developed to cover the range of conditions: liquid-phase density = 45.1 to 74.7 lb/ft3, liquid-phase viscosity = 0.233 to 59 cP., and interfacial tension = 15 to 72 dynes/cm The gas-phase is air and the bubble size ranged from 1.2 to 15 mm. The developed correlation is based upon new dimensionless groups which contain the parameters affecting bubble rise velocity as well as their interaction, The correlation is independent of flow regimes and applicable for Reynolds numbers from 0.1 to 104. It is in good agreement with work appearing in the literature.

Inelastic interactions of 340-GeV/c π - with emulsion nuclei

Abstract: Pion-nucleus interactions in nuclear emulsions from 340-GeV/, gray , black , and heavily ionizing particles are measured. Linear correlations between these numbers were obtained. The Koba-Nielsen-Olesen--type scaling behavior of the shower particles is investigated. A test of the collective tube model is carried out. The gray particles are studied in the framework of the Pomeron interaction with nuclei applying the tree approximation.

Life Events and Depression in Transit Populations

Abstract: Undesirable recent life events in the period of three months preceding primary depressive illness were studied in two Arabian Gulf countries: Qatar (235 patients) and Kuwait (164 patients). Transit population patients, who come to these countries from employment, differ from native patients in the significant predominance of work as a source of recent life events. The difference is discussed in relation to the existential committments and attitudes to work among native and transient populations. Intergenerational conflict as an undesirable recent life event is prevalent among family recent life events in native patients where rapid sociocultural changes are associated with conflict of traditional and modern value systems.

Studies on spironolactone polymorphic forms

Abstract: The phenomenon of polymorphism of spironolactone was studied using melting point and aqueous solubility determinations, infrared spectroscopy, differential thermal analysis, X-ray powder diffraction and powder dissolution. The results showed that spironolactone crystals obtained from ethyl acetate had the lowest melting range, while those obtained from acetonitrile had the highest range. The aqueous solubility data indicated the presence of different forms of spironolactone, each with a specific solubility, although practically all of these forms could be considered to be water-insoluble. The infrared spectra were not useful in clearly distinguishing between the different forms. Differential thermal analysis curves indicated that some of the forms obtained by treating spironolactone with different solvents were somewhat similar, others were variable, but all of them were different from the original form of the drug. Moreover, the thermal study proved the absence of any solvates. X-ray patterns wer...

Copolymerization of N -Arylmaleimides with Vinyl Acetate

Abstract: Copolymerization of N-α-naphthylmaleimide with vinylacetate was investigated in different solvents. The solvent was found to play an important role in the reactivity of the maleimide due to molecular association of solvent/monomer molecules. The overall rate of copolymerization was found to increase as the ability of the solvent to associate with the maleimide increased. ZnCl2 enhanced the reactivity of the maleimide due to a complex formation with growing radicals. The effect of substitution with a phenyl group on the reactivity of the double bond was also investigated.