PN code acquisition using signed-rank-based nonparametric detectorsin DS/SS systems

In this paper, signed-rank based nonparametric detectors are used for pseudonoise (PN) code acquisition in direct-sequence spread-spectrum (DS/SS) systems. We first derive the locally optimum rank (LOR) detector and then propose the locally suboptimum rank (LSR) and modified signed-rank (MSR) detectors using approximate score functions. We compare the single-dwell scheme without the verification mode using the proposed LSR and MSR detectors with that using the conventional squared-sum (SS) and modified sign (MS) detectors. From the simulation results, it is shown that the proposed LSR and MSR detectors perform better than the MS detector by about 2-3 dB and are nearly optimum     

Optimum antireflection coatings for heteroface AlGaAs/GaAs solar cells—Part I: The influence of window layer oxidation

This paper details both the theoretical and experimental results of a modified model for designing MgF₂/ZnS double-layer antireflection coatings for AlGaAs/GaAs heteroface solar cells. The main contribution of the model presented is that it takes into account the possible existence of an oxide layer in the AlGaAs window layer. In a first step the optical behavior of the oxide is modeled and that model is used to recalculate optimal double-layer antireflection coating when a thin AlGaAs oxide layer is present. Significant differences with classical double-layer antireflection coating design are found, such as, the antireflection properties of the oxide layer when formed onto originally thick windows or its equivalent role to that of the ZnS layer (as a high refractive index media) in the coating. Finally, an experimental analysis is carried out to assess empirically the conclusions of the model. These experiments have yielded an excellent agreement with the proposed theory.     

Production and characterization of a new dextrin based hydrogel

Dextrin is a polymer composed of α-(1→4) d-glucose units produced by partial hydrolysis of starch. In this work, the transesterification of the soluble polysaccharide with vinyl acrylate (VA) was carried out in anhydrous dimethylsulfoxide (DMSO). The effect of the water activity and of the enzyme Proleather, on the reaction rates, was analysed. Different degrees of substitution (DS) ranging from ca. 10% to 70% were obtained by controlling the molar ratio of VA to dextrin. Gels were obtained by free radical polymerization of dextrin-VA, with different degrees of substitution and monomer concentration, in water. A comprehensive solid state-NMR analysis of the hydrogels was performed. These hydrogels are being developed as scaffold materials for bioactive molecule and cell delivery, tissue engineering and a variety of other biomedical applications.     

Collision between scalar and vector spatial solitons in Kerr media

Experimental observation and numerical results concerning collisions between scalar and vector spatial solitons in a Kerr planar waveguide are presented. It is shown that this configuration allows for the full control of spatial and polarization dynamics of the interacting vector solitons. On the one hand, the ability to achieve polarization control of a single-hump vector soliton is demonstrated. On the other hand, the effect of collision on the spatial symmetry-breaking dynamics of multimode vector solitons is investigated.     

Enantioselective sensing of dicarboxylates. Influence of the stoichiometry of the complexes on the sensing mechanism

Two new cyclohexane-based thiourea chiral ligands have been synthesized in their enantiomerically pure forms. Both the ability of these ligands in the complexation of chiral dicarboxylates and their sensing properties have been studied. The influence of the stoichiometry of the formed complexes on the fluorescent properties of the systems has been established. The effect of additional substitution in the cyclohexyl moiety was considered by comparing the properties of the newly prepared ligands with those of similar compounds previously described.