This paper investigate a sensorless speed control of a separately excited dc motor fed from a buck type dc-dc converter. The control system is designed in digital technique by using a two dimension look-up table. The performance of the drive system was evaluated by digital simulation using Simulink toolbox of Matlab.
This study is concerned with the derivation of differential equation of motion for the free coupled vertical – torsional and lateral vibration of opened thin-walled curved beams. The curved beam to be considered in this study is of isotropic opened thin – walled (I) section with equal top and bottom flanges. The derivation depends on Hamilton's principle which required finding the potential and kinetic energy of the curved beam section due to internal stresses and all types of movements (Vertical,Torsional and Lateral) .The effect of restrained warping displacement is also considered in this study. Three differential equations are derived for vertical, torsional and lateral movement .and approximate solutions are developed by using the
... Show MoreIn the present study benzofuran based chalcones 1 (a, b) are synthesized by condensing aromatic aldehydes with 2-acetylbenzofuran in the presence suitable base. These chalcones are very useful precursors for the synthesis of pyrazoline, isoxazoline, pyrmidine, cyclohexenone and indazole derivatives. All these compounds are characterized by their melting points, FTIR and 1 HMNR (for some of them) spectral dat
The anatomical features of Agave americana L. leaf have been described, transverse sections of the leaf have been examined, the epidermis is single-layered on both surfaces, the stomata are sunken and mesophyll is (2-3) layers of parenchyma cells, vascular bundles are collateral type. The pollen of A. americana was studied. The observation was made with L.M. (Light microscope) and S.E.M. (Scanning electron microscope) to determine the significance of pollen features as taxonomic characters. The pollen was monades, homopolar, monosulcate, and with large size, subprolate in shape from P/E ratio (Polar axis/ Equatorial diameter) and furrow length and width, exine thickness and ornamentation.
It is not long time since globalization has started along with knowledge economy and, communication media and technical information control on the world. As a result serious events appeared like failure in businesses, financial corruption and shortage of administration and control.
In spite of the great efforts held by international organizations and foundations to find organizational frames that adopt independence, que
... Show MoreThis work involves synthesis of novel Schiff bases derivatives contining isoxazoline or pyrazoline units starting with chalcons . 4-Aminoacetophenone was react with pnitrobenzaldehyde or p-chlorobenzaldehyde in basic medium giving chalcones [I]a,b by claisenschemidt reactions. The chalcones [I]a,b were reacted with hydroxylamine hydrochloride giving isoxazolines [II]a,b in basic medium. The chalcone [I]a could also reacted with hydrazine hydrate to give pyrazolines [III]a . The novel Schiff bases with structural formula [VIII]n , [IX]n , [X]m and [XI]m were prepared by the reaction of amino compounds ; isoxazoline [II]a,b and pyrazolines [III]a with monoaldehydes [VI]n and dialdehydes [VII]m , respectively in dry benze
... Show MoreDirect contact membrane distillation is an effective method for production of fresh water from saline water. In this study two samples were used as feed solutions; the first one was RO waste from Al-Hilla Coca-Cola Factory (TDS= 2382 mg/l) and the other was Haji Ali drainage water (TDS= 4127 mg/l). Polytetrafluoroethylene (PTFE) hydrophobic membrane supported with polypropylene (PP) was used as flat sheet form with plate and frame cell. Results proved that membrane distillation is an effective technique to produce fresh water with high quality from brine with low salinity content. With membrane area of 8x8 cm2, the volume of treated water decreased from 34.97 ml at first half hour to 33.02 ml after 180 min of
... Show MoreThat the child in the early years of his life learns a lot of experiences that help him
grow properly, and if the availability of the child family atmosphere full of love and affection
and trust he was able to grow healthy growth and is in accordance with itself and with the
community in which they live, and stop method of the child in the expression of fear on the
nature of situation and on the theme of fear and the reaction of those around the child as well
as the vague positions that can not a child from its interpretation raises his fear, and its lead in
life are the kindergarten of the growing concerns him, causing his social concern, therefore,
targeted current research to identify patterns of parental care(mot
In the present work, steady two – dimensional laminar natural convection heat transfer of Newtonian and non-Newtonian fluids inside isosceles triangular enclosure has been analyzed numerically for a wide range of the modified Rayleigh numbers of (103 ≤ Ra ≤ 105), with non-dimensional parameter (NE) of Prandtl – Eyring model ranging from (0 to 10), and modified Prandtl number take in the range (Pr* =1,10, and 100). Two types of boundary conditions have been considered. The first, when the inclined walls are heated with different uniform temperatures and the lower wall is insulated. The second, when the bottom wall is heated by applying a uniform heat flux while the inclined walls at
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