Poly(3-octylthiophene) as semiconductor for schottky barrier: Effects of doping and storage time

Schottky diodes of aluminium/poly(3-octylthiophene)(P30T)/indium-tin oxide with large active area are prepared by using the proposed new casting technique. Their rectifying behavior and junction characteristics are dependent on whether the P30T is doped and on the storage time, but independent of the thickness of the P30T layer. The present technique can also be applied in a fabrication of electronic devices with other soluble conjugated polymers.     

Corrosion protection of iron by polypyrrole coatings electrosynthesised from a surfactant solution

This work is a study of the electropolymerisation of pyrrole onto iron electrodes in the presence of sodium bis(2-ethylhexyl) sulfosuccinate in a wide pH interval. The characterisation of the films was done using electrochemical techniques, SEM/EDX and IR spectroscopy. We show that it is possible to synthesise homogeneous, adherent and very compact films in the pH range between 7 and 12 under potentiodynamic, galvanostatic and potentiostatic conditions without substrate dissolution. The effects of various parameters on electrodeposition were investigated. The new procedure for the electrochemical synthesis of polypyrrole results in improved anticorrosion properties. The inhibition is proposed to be due to the sum of a repulsion of chloride ions because AOT remains entrapped in the polymer matrix and the presence of the iron oxide. Advantages of the use of surfactants in the electropolymerisation solution are discussed.     

Multilevel barrel shifter for CORDIC design

The coordinate rotation digital computer (CORDIC) algorithm is used in numerous special purpose systems for real-time signal processing applications. It uses barrel shifters to complete shift operations. However, the barrel shifter occupies most of the area of the CORDIC chip. A new structure of multilevel barrel shifters is presented. With this structure the shifter size is reduced by 68%. The novel structure can also slightly reduce the latency time of shift operations     

Time-limited leases in radio systems [Topics in Radio Communications]

A time-limited lease is a set of rights that expires after a specified duration. We analyze ways to use leases to facilitate innovation in radio devices and wireless communication. In our vision, manufacturers include in their devices a simple, secure subsystem that contains a clock and disables specific transmit capabilities if no extension message is received by the end of the lease period. When devices provide this support, regulators may use certification leases rather than permanent grants to accelerate deployment of innovative radios. Spectrum rights holders may use leases to reduce risk in secondary spectrum market transactions. Firms collaborating in innovative wireless service business models can better retain control of their respective rights. We examine both the technical and policy issues associated with leases.     

COGNITIVE RADIOS FOR DYNAMIC SPECTRUM ACCESS - The Path to Market Success for Dynamic Spectrum Access Technology

Rapid progress is being made in the technology for dynamic spectrum access (DSA) radio systems. However, the structure and dynamics of the wireless services market must also evolve for DSA to succeed. This article examines the interlinked technical and economic issues associated with markets for DSA-based wireless services. We use this analysis to make technical and policy recommendations supporting the commercial success of DSA technology     

Physical properties of transition to chaos in RF-driven Josephson junction analog

An analog circuit is used to investigate the behavior of the transition to chaos in the rf-driven Josephson junction under the variation of excitation amplitude and frequency with McCumber parameter >1. A series of transitions is observed, including a hysteretic jump, symmetry breaking, period doubling, and intermittency prior to chaos, and the transition boundaries are given in a state diagram in the vs. parameter space. Thus, the sequence of transitions to chaos can be inferred from this diagram. Based on these results, the harmonic balance method and Floquet theory are applied to study the instability of the transition series. It is suggested that all these transitions to chaos can be explained as parametric excitations. In addition, the transition boundaries in the state diagram can be satisfactorily computed from the conditions with a Floquet multiplier =±1.     

Preparation of fluoroacrylate nanocopolymer by miniemulsion polymerization used in textile finishing

Latex based on fluoroacrylate (TAN) and other comonomers was prepared via miniemulsion polymerization in the presence of stearyl trimethyl ammonium chloride (STAC) and 2, 2′‐azobis (2‐amidinopropane) dihydrochloride (ABAP) as a water soluble initiator. Light transmittance studies demonstrated that the light transmittance of prepared emulsions increases with the amount of TAN, STAC, cosolvent DPM, and hydrophobe DM. Given suitable reaction temperature and quantities of TAN, STAC, DPM, and DM, a copolymer emulsion of fluoroacylate with a particle size of 50 nm was produced. The water repellency tested on polyester fabrics displayed greater effectiveness than that of commercial products with higher fluorine content. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1466–1472, 2004     

Novel method of preparing Ag–Hg alloy on polyacrylamide films and their structure

A novel method is proposed of preparing thin Ag–Hg alloy on PAAm film surface at room temperature: The film of interest is formed by holding PAAm aqueous solution with AgNO₃ in Hg-saturated atmosphere. Two kinds of films, one of which is a conductor and the other an insulator, can be selectively formed with pH-controlled PAAm solution by ammonia. The conducting surface is assigned to the α phase of Ag–Hg alloy by means of X-ray analysis. Potentiometric titration and IR spectral studies suggest the existence of PAAm–Ag⁺ complexes. On the basis of their structure and the oxidation and reduction potential of Ag⁺ and Hg²⁺, the mechanism of film formation is also discussed.     

Sliding‐Mode Velocity Control of a Two‐Wheeled Self‐Balancing Vehicle

Underactuated vehicles are those in which the number of control inputs is less than the degrees of freedom to be controlled. Using actuated wheels, velocity control of the two‐wheeled self‐balancing vehicle drives the vehicle at a desired speed and balances the body of the vehicle. First, we investigate the effects of friction on the wheel and derive the hybrid model of rolling and slipping. Second, we propose a nonlinear sliding mode velocity control scheme for the pure rolling model of the two‐wheeled vehicle. We present the design of the corresponding sliding surfaces and internal dynamics of the two‐wheeled vehicle. Our stability analysis reveals that the proposed sliding mode method can guarantee the asymptotic stability of the error dynamics for velocity control of the underactuated vehicle. Compared to linear optimal control, our numerical simulations demonstrate that the proposed sliding mode schemes can effectively control the velocity under the circumstances of parametric variations, emergency braking, and rapid acceleration in slippery road conditions. The proposed velocity control and the simulation improve our understanding on designing velocity control of the two‐wheeled self‐balancing vehicle.     

Morphology and characterization of conductive films based on polyaniline‐coated polystyrene latexes

The polyaniline (PANI)‐coated polystyrene (PS) latexes were synthesized, and the electrically conductive films were prepared thereafter. The weight ratio of PANI was 5%. Thermal analysis of the latices was performed using DSC and TGA. In this study, the electrically conductive films were prepared above the PS glass transition temperature (T_g). During the film formation, the effects of the annealing temperature and atmosphere (air or N₂) on the film resistance were investigated. In addition, the film morphology was observed utilizing scanning electron microscopy. The film resistance decreased in the initial heating stage due to the increasing temperature and the compaction of film. Then the film resistance increased with further annealing due to the aging of PANI. Typically, the film resistance was about 6000 Ω/sq, and the conductivity was 0.3 S/cm. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5406–5413, 2006