A Novel Stealthy Target Detection Based on Stratospheric Balloon-borne Positional Instability due to Random Wind

A novel detection for stealthy target model F-117A with a higher aspect vision is introduced by using Stratospheric Balloon-borne Bistatic system. The potential problem of proposed scheme is platform instability impacted on the balloon by external wind force. The flight control system is studied in detail under typical random process, which is defined by Dryden turbulence spectrum. To accurately detect the stealthy target model, a real Radar Cross Section (RCS) based on physical optics (PO) formulation is applied. The sensitivity of the proposed scheme has been improved due to increasing PO – scattering field of stealthy model with higher aspect angle comparing to the conventional ground -based system. Simulations demonstrate that the proposed scheme gives much higher location accuracy and reduces location errors

Low Complexity V-BLAST MIMO-OFDM Detector by Successive Iterations Reduction

V-BLAST detection method suffers large computational complexity due to its successive detection of symbols. In this paper, we propose a modified V-BLAST algorithm to decrease the computational complexity by reducing the number of detection iterations required in MIMO communication systems. We begin by showing the existence of a maximum number of iterations, beyond which, no significant improvement is obtained. We establish a criterion for the number of maximum effective iterations. We propose a modified algorithm that uses the measured SNR to dynamically set the number of iterations to achieve an acceptable bit-error rate. Then, we replace the feedback algorithm with an approximate linear function to reduce the complexity. Simulations show that significant reduction in computational complexity is achieved compared to the ordinary V-BLAST, while maintaining a good BER performance.Comment: 6 pages, 7 figures, 2 tables. The final publication is available at www.aece.r

Populations indigènes et inégalités sociales : une approche plurielle à partir du recensement mexicain de 2000

Au Mexique, où l'identification censitaire des populations indigènes sur une base linguistique existe sans interruption depuis le début du vingtième siècle, le recensement de 2000 marque un tournant en introduisant comme second critère l'auto déclaration d'appartenance ethnique qui permet l'expression de leur appartenance communautaire aux indigènes non locuteurs. Cet article étend les catégories d'identification de la population indigène mexicaine à ces nouvelles variables. Ce mode d'identification pluriel nous permet ensuite, à partir de l'ensemble de l'information censitaire, une analyse fouillée des caractéristiques démographiques et socioéconomiques des ménages mexicains, indigènes et non indigènes. A la suite d'une ligne de recherche déjà classique dans le pays, nos résultats conduisent à préciser et enrichir le diagnostic sur l'inégalité sociale et les processus de ségrégation ethnique. L'intérêt est aussi, en multipliant les critères d'identification des populations indigènes et les variables d'analyse, de faire apparaître l'hétérogénéité sociale et économique qui existe dans le monde indigène contemporain ; un aspect beaucoup moins documentée au sein des sciences sociales mexicaines, du moins par des approches quantitatives

First Principles Simulations of Boron Diffusion in Graphite

Boron strongly modifies electronic and diffusion properties of graphite. We report the first ab initio study of boron interaction with the point defects in graphite, which includes structures, thermodynamics, and diffusion. A number of possible diffusion mechanisms of boron in graphite are suggested. We conclude that boron diffuses in graphite by a kick-out mechanism. This mechanism explains the common activation energy, but large magnitude difference, for the rate of boron diffusion parallel and perpendicular to the basal plane. © 2007 The American Physical Society

Reaction of 2,5-Disubstituted-1,3,4-oxadiazoles

Some 5-aryl-2-mercapto-1,3,4-oxadiazole (I) reacted with maleic anhydride, maleic acid and p-benzoquinone affording 2-(5-aryl- -1,3,4-oxadiazol-2-ylthio)succinic anhydrides (II), 2-(5-aryl-1,3,4- -oxadiazol-2-ylthio)succinic acids (III) and 2-(2,5 dihydroxyphenylthio)- 5-aryl-l,3,4-oxadiazoles (IV), respectively. Treatment of 2- methylthio-5-phenyl-l,3-oxadiazole (V) with amines gives 2-[(alkyl or aryl)-amino]-5-phenyl-l,3,4-oxadiazoles (VI). Compound VIe condensed with aromatic aldehydes to give 2-(4-cinnamoylanilino)- 5-phenyl-l,3,4-oxadiazoles (VII) which on bromination afforded the dibromo derivative VIlI and on treatment with hydroxylamine afforded 2-[4-(5-aryl-2-isoxazolin-3-yl)anilino]-5-phenyl-1,3,4-oxadiazoles (IX). Reacting VII with hydrazine hydrate gave 2-[4-(5-aryl-2-pyrazolin-3-yl)anilino]-5-phenyl-l,3,4-oxadiazoles (X), while on treatement VII with acetylacetone and ethylacetoacetate afforded 2- [4-(4-acetyl or carbethoxy-5-phenyl-l-cyclohexen -3-one- -1-yl)anilino]-5-phenyl-l,3,4-oxadiazoles (XIIa, b), respectively