Implementation of RNS-Based Distributed Arithmetic Discrete Wavelet Transform Architectures Using Field-Programmable Logic

Currently there are design barriers inhibiting the implementation of high-precision digital signal processing (DSP) objects with field programmable logic (FPL) devices. This paper explores overcoming these barriers by fusing together the popular distributed arithmetic (DA) method with the residue number system (RNS) for use in FPL-centric designs. The new design paradigm is studied in the context of a high-performance filter bank and a discrete wavelet transform (DWT). The proposed design paradigm is facilitated by a new RNS accumulator structure based on a carry save adder (CSA). The reported methodology also introduces a polyphase filter structure that results in a reduced look-up table (LUT) budget. The 2C-DA and RNS-DA are compared, in the context of a FPL implementation strategy, using a discrete wavelet transform (DWT) filter bank as a common design theme. The results show that the RNS-DA, compared to a traditional 2C-DA design, enjoys a performance advantage that increases with precision (wordlength).     

A new look at rotational and vibrational excitation in the scattering of Li+ from N2 and CO at energies between 4 and 17 eV

New experimental time-of-flight distributions are reported for Li⁺-N₂ and Li²-CO at two center-of-mass energies of about 8 and 16 eV and large scattering angles θ_lab ? 120°. The Li⁺-N₂ spectra show two widely spaced maxima, whereas the Li⁺-CO spectra show two and sometimes three maxima. The results are consistent with the model of rotational rainbows, and have also been analyzed in terms of an impulsive model involving collisions with the individual atoms of the molecules with energy-dependent masses. Classical trajectories for a simple model potential reveal only small contributions from vibrational excitation.     

Intramolekulare Cyclisierung von Aminofluorsilanen

Aminofluorosilanes react with lithiated amines undergoing LiF-elimination and substitution (1). The acyclic silicon-nitrogen-compound2 is isolated in the reaction with a difluorosilane after renewed lithiation.2 is cyclisated in the reaction with butyllithium by butane- and LiF-elimination (3). Aminofluorosilanes with bulky (4) or mesomeric stabilized (5) ligands form stable lithioaminofluorosilanes, which react with fluorosilanes giving substitution products (6, 7).6 and7 react with the lithium salt oftert-butylamin in a molar ratio of 12 to give8 and9 by intramolecular cyclisation.—The mass,¹H and¹⁹F nmr spectra of the compounds are reported.     

Reaktion von Alkyl- und Arylchlorsilanen mit Phosph(III) en-imidamiden

The reaction of RSiCl₃ (R=CH₃, C₂H₅, C₆H₅) and R₂SiCl₂ (R=CH₃) with one mole of the phosphenimidous amides R₂N–P=NR [R=R=Si(CH₃)₃; R=Si(CH₃)₃, R=C(CH₃)₃] yieds a four membered PN₂Si-ring system under elimination of (CH₃)₃SiCl.     

Cycloadditionsreaktionen der aminofluorsilane

Aminofluorsilanes are obtained by the reaction of fluorosilanes with the lithium salts of the corresponding amines. The reaction of aminofluorosilanes with butyllithium in a (2 + 2)cyclo addition reaction leads to the formation of fourmembered silicon-nitrogen ring compounds. The mechanism of the reaction is discussed, the mass, ¹H and ¹⁹F NMR spectra of the compounds are reported.     

RS-485网络设计降低功耗问题

本文主要讨论在ＲＳ－４８５网络设计中,如何在保持良好的传输特性的同时降低率损耗。     

Hydrogen-bonded diketopyrrolopyrrole (DPP) pigments as organic semiconductors

Diketopyrrolopyrroles (DPPs) have recently gained attention as building-blocks for organic semiconducting polymers and small molecules, however the semiconducting properties of their hydrogen-bonded (H-bonded) pigment forms have not been explored. Herein we report on the performance of three archetypical H-bonded DPP pigments, which show ambipolar carrier mobilities in the range 0.01–0.06 cm²/V s in organic field-effect transistors. Their semiconducting properties are correlated with crystal structure, where an H-bonded crystal lattice supports close and relatively cofacial π–π stacking. To better understand transport in these systems, density functional theory calculations were carried out, indicating theoretical maximum ambipolar mobility values of ∼0.3 cm²/V s. Based on these experimental and theoretical results, H-bonded DPPs represent a viable alternative to more established DPP-containing polymers and small molecules where H-bonding is blocked by N-alkylation.     

Analytical derivation of a formula for the reduction of computation time by the voxel crossing technique used in room acoustical simulation

Computation times of room acoustical simulation algorithms still suffer from the time consuming search for ray-wall-intersections. Spatial subdivision may speed up ray tracing considerably. For room acoustics, where the number of surface polygons (walls) is not so high, the voxel technique appears suitable. The voxel crossing algorithm is very fast. However, its performance was not yet investigated up to now. Voxels are small cubes by which the space is subdivided periodically. The advantage: Only in the rare case a voxel intersects a wall the intersection point needs to be computed. In this paper, by estimating the probabilities of such intersections, an analytical formula is derived, by which the optimum degree of spatial subdivision and the factor of acceleration of the algorithm can be forecasted. It turns out that the computation time increases only with instead of with K₀ (the number of polygons of the room). Thus, on a modern PC, computation time for a full room acoustical simulation even for highly complicated rooms may be reduced by a factor in the order of 100, i.e. to a few seconds.