Dynamics of multichannel feedforward adaptive systems

The role played by reference-signal compensation in the convergence of multichannel feedforward adaptive systems is addressed. Convergence conditions are established, and effects of compensation errors are analyzed. We also explore, by means of altering the reference-signal compensation filtering from the conventional choice, ways to force systems to converge to arbitrary solutions of possible interest other than the standard Wiener solution. This could be useful, for example, if one wished to cancel noise at a very large number of measurement points, which, conventionally, would require a correspondingly complex, possibly prohibitively large, controller. The scheme developed enables very efficient usage of error signals, such that systems with large numbers of disturbance-cancellation points need employ only a relatively small number of error signals in the actual control-system implementation     

Lossy power distribution networks with thin dielectric layersand/or thin conductive layers

Through their inherent skin losses, conductive planes around sufficiently thin dielectric layers may provide good suppression of plane resonances in printed-circuit-board power distribution networks. When combined with thin conductive layers, a resistor-like flat self-impedance and low-pass transfer-impedance profiles can be created. A lossy transmission-line grid model is used to simulate power-ground plane pairs with thin dielectric and thin conductive layers. Some of the modeling errors of the analytical plane-impedance expressions and lossy transmission-line grid plane models are compared. Simulated and measured impedances are compared on test structures with plane separation of 40 and 8 μm (1.6 and 0.3 mils)     

Effects of protein-surface interactions on protein ion signals in MALDI mass spectrometry

The influence of polymer surface-protein binding affinity on protein ion signals in matrix-assisted laser desorption/ionization (MALDI) mass spectrometry is examined. The surfaces of poly(vinylidene fluoride) and poly(ethylene terephthalate) polymer substrates are modified by pulsed rf plasma deposition of allylamine. By varying the on/off duty cycle of the pulsed rf plasma, the polymer substrate surfaces are coated with thin films having varying densities of surface amine groups. The varying surface amine density is shown to lead to systematic changes in the surface binding affinity for the 125I-radiolabeled peptides angiotensin I and porcine insulin. Unlabeled angiotensin I and porcine insulin are then deposited on the pulsed rf plasma-modified substrates and analyzed by MALDI mass spectrometry. The experimental approach involves applying the peptide to the modified polymer surface in an aqueous phosphate-buffered saline solution and allowing the peptide solution to dry completely under ambient conditions. Subsequently, the MALDI matrix alpha-cyano-4-hydroxycinnamic acid in methanol and 10% trifluoroacetic acid in water are added to the peptide-coated modified polymer surfaces. The results of these studies demonstrate that, for the sample preparation method employed, increases in the surface peptide binding affinity lead to decreases in the peptide MALDI ion signal.     

The effect of the particle size and the morphology of alumina powders on the processing of green bodies by electrophoretic deposition

The electrophoretic deposition (EPD) method was investigated for the preparation of compacts from nanosized alumina powders. Ethanol suspensions of commercially available nanosized transition alumina and α-alumina powders were used. In addition, submicron powders were also considered for comparison. Besides the influence of operational pH change, the influence of the addition of three different surfactants – two branched polyethylene imines with molecular masses 1800 and 10,000, and citric acid—on the zeta-potential of the particles in ethanol and afterwards on the EPD was investigated.The packing density of the green parts prepared by the EPD of nanosized α-alumina powders at 30 V/cm was low (the green density was 27 vol. % of the theoretical density—TD), and a bimodal pore size distribution was observed. In contrast, the packing density in deposits made with the transition alumina nanopowder was much higher (the green density was 42 vol. % of the TD) and a monomodal distribution of pores was observed. In general, for all the deposits made from nanosized alumina powders, the particle-packing density was found to be lower than for those made from the submicron alumina powders (a green density equal to 59 vol. % of the TD).     

Can memory requirements account for species' differences in invisible displacement tasks?

We tested the hypothesis that poor performance on the Piagetian invisible displacement task is related to increased memory requirements. Rhesus monkeys and orangutans received 3 types of problems (invisible, visible, and no transfer problems) each containing a number of steps equivalent to that of standard invisible displacements. If failure to solve invisible displacements was due to increased memory requirements, then the primates should perform at chance level on all 3 problems. However, rhesus monkeys solved visible and no transfer problems, but not invisible transfer problems. Half of the orangutans solved all 3 transfer problems, although their performance on invisible transfer problems was lower than that on the other problems. A subsequent cuing phase led to improved performance, and a few monkeys solved invisible transfer problems. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Improvement of the technology and methods of assessing the degree of compaction in fills and soil beds

An improved technology for the vibratory compaction of soils, and also methods of assessing the degree of compaction on the basis of resonance effects are proposed. Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 2, pp. 19–21, March–April, 1997.