Approaching the Outage Probability of the Amplify-and-Forward Relay Fading Channel

We study coding techniques for the single-relay non-orthogonal amplify-and-forward half-duplex relay fading channel. Unlike the multiple-antenna case, we show that 2times2 rotations induce large gains in outage probability with no increase in decoding complexity under iterative probabilistic decoding. We compare rotated and unrotated turbo-coded schemes and show that they both perform close to their corresponding outage limits.     

Contribution to controlling non-redundant manipulatorsContribution au controle des manipulateurs non surabondants

The paper considers the possibilities of synthesizing the manipulator whose tip moves along the predetermined path and in optimal way, from the standpoint of energy dissipated by an actuator. The analysis has been carried out on the complete dynamic model of an anthoromorphic manipulator with three degrees of freedom and the third order model of actuators. Digital simulation has been performed for two types of control, optimal control for the subsystem of each actuator (suboptimal from the overall system standpoint) and the motion with predetermined change of angular velocities of internal coordinates. Both types of control have been also applied to the manipulator whose gripper (tip) had to be moved with required velocity.     

Large-scale parallel arrays of silicon nanowires via block copolymer directed self-assembly

Extending the resolution and spatial proximity of lithographic patterning below critical dimensions of 20 nm remains a key challenge with very-large-scale integration, especially if the persistent scaling of silicon electronic devices is sustained. One approach, which relies upon the directed self-assembly of block copolymers by chemical-epitaxy, is capable of achieving high density 1?:?1 patterning with critical dimensions approaching 5 nm. Herein, we outline an integration-favourable strategy for fabricating high areal density arrays of aligned silicon nanowires by directed self-assembly of a PS-b-PMMA block copolymer nanopatterns with a L(0) (pitch) of 42 nm, on chemically pre-patterned surfaces. Parallel arrays (5 × 10(6) wires per cm) of uni-directional and isolated silicon nanowires on insulator substrates with critical dimension ranging from 15 to 19 nm were fabricated by using precision plasma etch processes; with each stage monitored by electron microscopy. This step-by-step approach provides detailed information on interfacial oxide formation at the device silicon layer, the polystyrene profile during plasma etching, final critical dimension uniformity and line edge roughness variation nanowire during processing. The resulting silicon-nanowire array devices exhibit Schottky-type behaviour and a clear field-effect. The measured values for resistivity and specific contact resistance were ((2.6 ± 1.2) × 10(5)Ωcm) and ((240 ± 80) Ωcm(2)) respectively. These values are typical for intrinsic (un-doped) silicon when contacted by high work function metal albeit counterintuitive as the resistivity of the starting wafer (～10 Ωcm) is 4 orders of magnitude lower. In essence, the nanowires are so small and consist of so few atoms, that statistically, at the original doping level each nanowire contains less than a single dopant atom and consequently exhibits the electrical behaviour of the un-doped host material. Moreover this indicates that the processing successfully avoided unintentional doping. Therefore our approach permits tuning of the device steps to contact the nanowires functionality through careful selection of the initial bulk starting material and/or by means of post processing steps e.g. thermal annealing of metal contacts to produce high performance devices. We envision that such a controllable process, combined with the precision patterning of the aligned block copolymer nanopatterns, could prolong the scaling of nanoelectronics and potentially enable the fabrication of dense, parallel arrays of multi-gate field effect transistors.     

Influence of filler size and concentration on the low and high temperature dielectric response of poly(vinylidene fluoride) /Pb(Zr0.53Ti0.47)O3 composites

Poly(vinylidene fluoride)/Pb(Zr0.53Ti0.47)O3([PVDF]1 ? x/[PZT]x ) composites of volume fractions x and (0?C3) type connectivity were prepared in the form of thin films. The films were prepared by solvent casting with PZT powder of 0.84, 1.86, and 2.35???m average size with filler contents up to 40?% volume. The crystalline phase of the polymer matrix was the nonpolar ??-phase and the polar ??-phase. Dielectric measurements were performed in order to evaluate the influence of the filler size and content as well as the effect of the polymer matrix in the overall response of the material. No nucleation effect of any of the phases was observed for the used fillers. The spherulitic structure of the pure ??-PVDF and the characteristic porosity of the ??-phase material are destroyed for high PZT volume fractions. The inclusion of ceramic particles in the PVDF polymer matrix increases the complex dielectric constant of the composites independently of the PVDF polymer matrix. The dielectric properties of the composites are mainly affected by the amount of the ceramic particles. With respect to the relaxation processes of the polymer, the activation energy of the ??_a-relaxation increases and the glass transition temperature decreases with increasing particle size and content. The high-temperature conductivity decreases with increasing filler content and there is an important contribution of the Maxwell-Wagner-Sillars effect to the overall dielectric response.     

Effect of gamma radiation on the chlorine overvoltage at a titanium anode provided with an active film of RuO2 and TiO2

High-dose gamma irradiation of electrodes provided with an active film consisting of 5 mol. % RuO₂ and 95 mol. % TiO₂ may produce electrodes whose chlorine overvoltage at 60°C in a solution containing 300 g NaCl per dm³ conforms to the relation

for

A ⁶⁰Co source and doses about 4.9.10⁵ C kg^?1 (1.9 GR) were used. The gamma radiation has a positive effect of short duration in that it decreases the chlorine overvoltage, especially at higher cds. In the course of time the chlorine overvoltage of irradiated electrodes will increase beyond the values obtained with untreated electrodes.     

Potential of proton-enhanced 13C n.m.r. for the classification of kerogens

High resolution n.m.r. spectroscopy, involving the technique of cross-polarization, along with magicangle spinning, was used in the structural characterization of eight kerogens of different origins, selected to represent the three types of kerogens (types I–III evolution paths). The influence of cross-polarization dynamics on the sensitivity of the method and the ratio of individual fractions in the spectrum was studied in more detail. It is suggested that an analysis of the influence of the mixing time is necessary prior to definitive characterization of any sample. Good separation of signals in aliphatic, aromatic, and carboxylic regions was achieved. The general correlation between the ¹³C n.m.r. structural characteristics and the classification based on ultimate analysis of the kerogens (types I–III, van Krevelen atomic H/C vs. O/C diagrams) was found to be satisfactory. The structural features of kerogens derived from ¹³C n.m.r. analysis agreed quite well with characteristics constituting the above mentioned classification. The ¹³C n.m.r. method used in this paper may be considered promising in the classification of kerogens.     

On the role of 2,3-dihydro-3,5-dihydroxy-6-methyl-(4<Emphasis Type="Italic">H</Emphasis>)-pyran-4-one in antioxidant capacity of prunes

Despite available reports on phenolic composition and antioxidant capacity (AOC) of fresh plums and prunes, there is a scarcity of published knowledge on the antioxidants formed and/or released during the drying process in the literature. To evaluate the compounds participating in reducing capacity of prunes, we compared aqueous and methanol extracts of fresh plums, commercial prunes and home-made prunes prepared at different drying temperatures using an HPLC method with amperometric detection (HPLC-ECD). The prunes dried at high temperature (90 °C, 18 h) in kitchen or laboratory oven with restricted ventilation gave up to 3.3 times higher electrochemical capacity (EC) than fresh plums (dry matter; P. domestica cv. Domestica) in dependence on production protocol. Drying at 60 °C (low-temperature drying) for 18 h did not change the EC significantly. Yet, lower EC was found in commercial tenderized prunes with sorbate; they were by a factor of 1.1–8.2 lower in EC than the prepared low-temperature prunes. The principle responsible for the increase in EC in the prunes prepared at high temperatures is 2,3-dihydro-3,5-dihydroxy-6-methyl-(4H)-pyran-4-one (DDMP). It was not detected until 74 °C was set during isothermal 18 h drying or until 6 h of drying passed at 90oC drying. The ultimate acceptable dwell-time for the preparation of conveniently eatable prunes dried at 90oC under the conditions used was assessed to 12 h. The EC of plums and prunes as well as the role of DDMP was confirmed by the use of several methods for the assessment of AOC-DPPH^• assay, β-carotene bleaching method, Oxipres test and Schaal oven test.