Non-coherent UWB Radio for Low-rate WPAN Applications: A Chaotic Approach

The requirements of low cost, low power and longer operation range for low-rate wireless personal area network (LR-WPAN) applications has driven the utilization of non linear communication approach. In this paper, a combined ultra-wideband (UWB) and chaotic communication technologies is proposed to meet these challenging demands. Among the candidates, the differential chaos shift keying (DCSK) modulation appears to be a very promising solution. The DCSK is a family of transmit reference (TR) system where a correlator based receiver is used to demodulate the received signal. However, this is not very well understood in the literature and therefore we will exemplify this issue in terms of noise performance. Furthermore, the feasibility study of the proposed DCSK is presented through the scalability and link budget analysis in two different operation modes. The system performance in both additive white Gaussian noise (AWGN) channel and standardized IEEE 802.15.4a UWB multipath channels are provided in order to further demonstrate the capability of the proposed system.     

A Passive Shunt Device to Suppress Torsional Interactions in Synchronous Generators

Torsional interactions encountered with series compensated transmission lines are due to the negative damping effect of subsynchronous frequency currents induced by rotor oscillations. Methods of controlling these currents have appeared in the literature, however, this paper offers an alternative scheme based on enhancing the supersynchronous currents associated with positive damping. This results in cancellation of the negative electrical damping at the mechanical resonant frequency. The countermeasure consists of a passive shunt device connected at the generator terminals and tuned to the proper resonant frequency. The operating principle and design considerations are discussed and the effectiveness of the scheme is demonstrated.     

Inulin mixed esters crosslinked with 2-ethyl-hexyl-acrylate and their promotion as bio-based materials

New inulin-based materials were obtained by graft-copolymerization of inulin (poly-β(1 → 2)-fructoside) with 2-ethyl-hexyl acrylate. Inulin mixed esters were first synthesized by acylation using methacryloyl and palmitoyl chlorides. Further, these esters were copolymerized with 2-ethyl-hexyl acrylate in order to obtain bio-based crosslinked materials that could be used as commodity plastics and that would have biodegradable properties. The obtained products were characterized using FT-IR and ¹H NMR spectroscopies, thermogravimetry; differential scanning calorimetry, and activation energy for the degradation processes (using Kissinger method) was calculated. These biomaterials were also subjected to density measurement, tensile and torsion tests to evaluate their mechanical properties.     

Performance Limit of Chaotic Digital Waveform Communication Systems: Approach of Maximizing a Posteriori Probability

In this paper, we investigate a bandpass chaotic waveform communication system in an additive white Gaussian noise channel environment. By making use of the signalspace diagram and maximizing the a posteriori probability, we derive the conditions under which the optimum bit error performance can be achieved. In particular, we make use of a binary communication system to illustrate how the modulator and demodulator should be constructed in order to achieve the best error performance. Finally, the noise performance bound is determined for chaotic digital waveform communications.     

Synthesis and photocatalytic performance of titanium dioxide nanofibers and the fabrication of flexible composite films from nanofibers

Titanium dioxide nanofibers were synthesized and applied in flexible composite films that are easy to handle and recycle after use. The nanofibers were obtained in a multi-step procedure. First, sodium titanate nanofibers were prepared from TiO2 nanoparticles through the alkali hydrothermal method. In the next step, sodium hydrogen titanate nanofibers were made by washing the sodium titanate nanofibers in HCl solution. Finally, the sodium hydrogen titanate nanofibers were transformed to TiO2 anatase nanofibers by calcination in air. The photocatalytic activity of TiO2 anatase nanofibers were evaluated and compared to a TiO2 nanoparticle catalyst by decomposing methyl orange dye in aqueous solutions. The achieved reaction rate constant of TiO2 anatase nanofibers was comparable to that of Degussa P25. Paper-like flexible composite films were prepared by co-filtrating aqueous dispersions of TiO2 catalyst materials and cellulose. The composite films made from the nanofibers exhibit better mechanical integrity than those of the nanoparticle-cellulose composites.     

Avalanche photodiodes on silicon photonics

Silicon photonics technology has drawn significant interest due to its potential for compact and high-performance photonic integrated circuits.The Ge-or Ⅲ-Ⅴ material-based avalanche photodiodes integrated on silicon photonics provide ideal high sensitivity optical receivers for telecommunication wavelengths.Herein,the last advances of monolithic and hetero-geneous avalanche photodiodes on silicon are reviewed,including different device structures and semiconductor systems.     

Chemical reduction of sulphur dioxide to free sulphur with lignite and coal. 2. Kinetics and proposed mechanism

The reactivity of lignite and different ranks of coal with sulphur dioxide has been investigated in a corrosive-gas, thermogravimetric reactor system. With all coals, the reaction occurred in two distinct stages. A rapid initial stage was controlled primarily by the devolatilization rate of the coal. The second stage limited the overall rate and was controlled by surface properties of the coal char. The portion of lignite associated with the second stage of reaction exhibited a much higher rate of SO₂ reduction than the corresponding material from all other coals. Correlation of the data showed an inverse relation between the reactivity of coal chars and the relative rank of the parent coal. Activation energies associated with the reduction of SO₂ by the coal chars increased slightly from 134 kJ mol^?1 for lignite char to 150 kJ mol^?1 for HVB bituminous coal char. The higher reactivity of lignite or lower-rank coals was due in part to entropy factors or available catalytic sites on the surface of coal. Formation of a thermally stable CS complex on the surface of coal appeared to poison the surface and thus limit further reaction. Alkali and alkaline earth metals in lignite served as active sites for catalysing the reaction of SO₂ with the CS complex and thus enhanced the rate of SO₂ reduction with lignite.