Efficient photocatalysts by hydrothermal treatment of TiO2

The aim of this work was to identify the optimum synthesis conditions and the most effective technique for noble metal deposition in a perovskite/palladium-based catalyst for natural gas combustion. The solution combustion synthesis (SCS) of perovskite/zirconia-based materials was investigated, by starting from metal nitrates/glycine mixtures. Characterization and catalytic activity tests were performed on as-prepared powders and then repeated after calcination for 2 h at 900 °C in calm air. Calcination appeared to be beneficial in that, despite lowering the specific surface area, it promoted the simultaneous crystallization of both LaMnO₃ and ZrO₂ and the half-conversion temperature (T₅₀), regarded as an index of catalytic activity, was lowered. Two phases, both active towards methane oxidation – lanthanum manganate and palladium oxide – were combined so as to evaluate their synergism in terms of catalytic activity. Pd was therefore added either via incipient wetness impregnation on LaMnO₃·2ZrO₂ or through a one-step SCS-based route. Characterization and catalytic activity tests followed suit. Optimal composition and preparation routes were found: T₅₀ was lowered from 507 °C – pure LaMnO₃ prepared via SCS – to 432 °C attained with a 2% (w/w) Pd load on pre-calcined LaMnO₃·2ZrO₂.     

Asymptotic performance analysis of arbitrary rectangular QAM over fading channels

In this paper, the asymptotic performance of arbitrary rectangular Quadrature Amplitude Modulation (QAM) signals over fading channels is investigated. A novel unified asymptotic average Symbol Error Probability (SEP) expression is derived in terms of diversity and coding gain. The validity and accu-racy of the analytical result are verified by means of computer simulations. Furthermore, the results pre-sented are very easy to be extended to the systems with multi-channel diversity receivers.     

Functional Supramolecular Ruthenium Cyclodextrin Dyes for Nanocrystalline Solar Cells

A supramolecular complex [Ru(dcb)₂(α‐CD‐5‐bpy)]Cl₂ ( 1‐α‐CD ) (dcb = 4,4′‐dicarboxyl‐2,2′‐bipyridine, α‐CD‐5‐bpy = 6‐mono[5‐methyl(5′‐methyl‐2,2′‐bipyridyl)]‐permethylated α‐CD) (CD: cyclodextrin) based on a ruthenium tris‐bipyridyl core with an appended α‐CD cavity is designed and synthesised, in order to facilitate dye/redox couple interaction and dye regeneration in nanocrystalline TiO₂ solar cells. The luminescent complex is fully characterized and anchored on mesoporous titania electrodes showing increased power‐conversion efficiency in solid‐state dye‐sensitized solar cells using a composite polymer electrolyte. Direct comparison of the properties of the CD complex with an analogous ruthenium complex [Ru(dcb)₂(5,5′‐dmbpy)]Cl₂ ( 2 ) (5,5′‐dmbpy = 5,5′‐dimethylbipyridine) without the CD cavity reveals that the photovoltaic performance of 1‐α‐CD is enhanced by about 40 % compared to 2 . Independent studies have shown complexation of the iodide redox couple to the CD in 1‐α‐CD . These results indicate that the CD moiety is able to act as a mediator and fine tune the photoelectrode/electrolyte interface.     

Anomalous activation of shallow B+ implants in Ge

The electrical activation of B⁺ implantation at 2 keV to doses of 5.0 × 10¹³–5.0 × 10¹⁵ cm^?2 in crystalline and pre-amorphized Ge following annealing at 400 °C for 1.0 h was studied using micro Hall effect measurements. Preamorphization improved activation for all samples with the samples implanted to a dose of 5.0 × 10¹⁵ cm^?2 displaying an estimated maximum active B concentration of 4.0 × 10²⁰ cm^?3 as compared to 2.0 × 10²⁰ cm^?3 for the crystalline sample. However, incomplete activation was observed for all samples across the investigated dose range. For the sample implanted to a dose of 5.0 × 10¹³ cm^?2, activation values were 7% and 30%, for c-Ge and PA-Ge, respectively. The results suggest the presence of an anomalous clustering phenomenon of shallow B⁺ implants in Ge.     

Design of Efficiently Encodable Rate-Compatible LDPC Codes Using Vandermonde Extension Matrices

A low-complexity algorithm for the design of efficiently-encodable rate-compatible (RC) low-density parity-check (LDPC) codes by deterministically extending an irregular repeat-accumulate (IRA) is introduced. The extending structure is based on circulants shifted according a truncated Vandermonde matrix (VM) and therefore termed as “extended VM” (eVM). The novel extending algorithm is significantly less computationally complex than other known similar methods since it does not require any optimization of the extending profile or any post-construction girth conditioning. To improve the codes’ properties and correcting capabilities in low code rate applications, the optimal proportions of degree-1 and degree-2 parity bits for the extended nodes are investigated and, in contrast to existing deterministic extending approaches for RC-IRA codes, an extending increment step equal to half the information block length is chosen. Various bit error rate (BER) and frame error rate (FER) have been obtained for different code rates, R, and information block length k ₀ = 512 and 1024 bits considering an additive white Gaussian noise (AWGN) channel. The results have demonstrated that the proposed eVM RC-LDPC codes, despite their very simple structure and very low computational complexity, exhibit excellent performance only slightly inferior to both dedicated IRA and previously known RC-IRA codes for different data block sizes.