Ahmed M. Assaf

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Let V be a finite set of order u. A (v, ~c, Z) covering design of index ;~ and block size tc is a collection of ~c-element subsets, called blocks, such that every 2-subset of V occurs in at least L blocks. The covering problem is to determine the minimum number of blocks, c~(u, x, ~.), in a covering design. It is well known that c~(u, x, )~) > r v r v-t ~]l(More)
Let v ~ 5 and A be positive integers and let DD(v,k,A) denote the packing number of a directed packing with block size 5 and index A. The values of DD(v, 5, A) have been determined for A = 1,2 with the possible exceptions of (v, A) = (15,1) (19,1) (27,1), [7,8, 19]. In this paper we determine the values of DD(v, 5, A) for all v ~ 5 and A ~ 3 except possibly(More)
To assess the efficacy and stability of simultaneous topography-guided photorefractive keratectomy (PRK) and crosslinking (Athens protocol) followed by phakic intraocular lens (IOL) implantation for managing keratoconus. Ain-Shams University, Cairo, Egypt. Prospective non-randomized study. All patients underwent topography-guided PRK followed immediately by(More)
PURPOSE To study spherical aberration, coma, and trefoil after implantation of a single-piece aspheric Tecnis intraocular lens (IOL) in cataract patients and the influence on photopic and mesopic contrast sensitivity. SETTING Ophthalmology Department, Ain-Shams University Hospitals, Cairo, Egypt. METHODS In this randomized prospective contralateral(More)