Pure perceptual-based sequence learning.

Learning a sequence of target locations when the sequence is uncorrelated with a sequence of responses and target location is not the response dimension (pure perceptual-based sequence learning) was examined. Using probabilistic sequences of target locations, the author shows that such learning can be implicit, is unaffected by distance between target locations, and is mostly limited to first-order transition probabilities. Moreover, the mechanism underlying learning affords processing of information at anticipated target locations and appears to be attention based. Implications for hypotheses of implicit sequence learning are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Response Surface Optimization in the Presence of Internal Noise With Application to Optimal Alignment of Carbon Nanotubes

Internal noise, which means fluctuation of input factors around their set values, is common in many experiments in the physical and engineering sciences. Existing methods for response surface optimization in the presence of internal noise typically adopt a two-step approach: (a) fitting a response model as a function of the set value and (b) using Monte Carlo methods to account for internal noise while optimizing the response. In this article, motivated by a problem in optimizing alignment of carbon nanotubes (CNT), we propose a Bayesian approach for response surface optimization in the presence of internal noise. A unit-free and interpretable measure to quantify the strength of internal noise is proposed. Suitable objective functions or performance measures consistent with the overall goal of optimizing the response function are identified, methods for estimating them from available experimental data are suggested, and simulations are conducted to compare them with respect to their ability to account for internal noise in the optimization problem. The loss accrued by ignoring the internal noise in the optimization problem is quantified and studied via simulation. The proposed method is demonstrated through its application in the CNT alignment problem.     

A closed slot-line resonator filter

A microwave bandpass filter made from three-dimensional (3-D) slot-line resonators is described. This structure readily lent itself to the design and realization of a 16-pole filter. By concentrating the losses on the resonant element, very high Q can be achieved by using low surface resistance material, such as high temperature superconductor, for the slot-line resonator. The filter is five to ten times smaller than previous generation 3-D filters made using high temperature superconductors.     

Fluorescence characteristics of Cu-ZSM-5 zeolites in reactive gas mixtures: mechanisms for a fiber-optic-based gas sensor

In situ measurements of the fluorescence spectra, intensity, and response time were made at elevated temperatures (~500 degrees C) for samples of Cu-ZSM-5 exposed to dilute mixtures of O(2) in N(2) and to various O(2)-reductant combinations in N(2). The results of these experiments are interpreted with a physical model of the oxidation/reduction kinetics of the copper ions. The fluorescence signal depends strongly on the gas composition, providing a mechanism for a gas composition sensor. A prototype sensor configuration is described that uses a visible (488-nm) excitation source and a fiber-optic geometry to generate and detect the fluorescence. The results indicate that for a weakly reducing gas the fluorescence signal correlates well with the oxygen concentration, whereas for strongly reducing gases the signal correlates more closely with the reductant-to-oxidant ratio.     

Implicit learning of first-, second-, and third-order transition probabilities.

Most sequence-learning studies have confounded different types of information, making it difficult to know precisely what is learned. Addressing many of the confounds, the current study shows that people can learn 1st-, 2nd-, and 3rd-order transition probabilities. Measures directly assessing awareness of the probabilities show that the knowledge is implicit early in training and becomes explicit with extended training. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Pure perceptual-based sequence learning: A role for visuospatial attention.

Learning the structure of a sequence of target locations when target location is not the response dimension and the sequence of target locations is uncorrelated with the sequence of responses is called pure perceptual-based sequence learning. The paradigm introduced by G. Remillard (2003) was used to determine whether orienting of visuospatial attention is an important component of the learning process. Three experiments revealed that the presence of an attention-capturing distractor impaired learning, whereas the presence of a distractor that was expected not to capture attention did not impair learning. These results suggest that the learning mechanism associates only those locations receiving visuospatial attention. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Three-tone intermodulation distortion generated by superconducting bandpass filters

Microwave bandpass filters constructed from materials exhibiting some nonlinearity, such as superconductors, will generate intermodulation distortion (IMD) when subjected to signals at more than one frequency. In commercial applications of superconductive receive filters, it is possible for IMD to be generated when a weak receive signal mixes with very strong out-of-band signals, such as those coming from the transmitter. A measurement procedure was developed and data were taken on several different types of superconducting bandpass filters, all developed for commercial application. It was found that in certain interference situations, the three-tone mixing can produce a spur that is noticeable by the receiver, but that there are simple preventative design solutions.     

Local State‐of‐Charge Mapping of Lithium‐Ion Battery Electrodes

Current lithium‐ion battery technology is gearing towards meeting the robust demand of power and energy requirements for all‐electric transportation without compromising on the safety, performance, and cycle life. The state‐of‐charge (SOC) of a Li‐ion cell can be a macroscopic indicator of the state‐of‐health of the battery. The microscopic origin of the SOC relates to the local lithium content in individual electrode particles and the effective ability of Li‐ions to transport or shuttle between the redox couples through the cell geometric boundaries. Herein, micrometer‐resolved Raman mapping of a transition‐metal‐based oxide positive electrode, Li_1‐x(Ni_yCo_zAl_1‐y‐z)O₂, maintained at different SOCs, is shown. An attempt has been made to link the underlying changes to the composition and structural integrity at the individual particle level. Furthermore, an SOC distribution at macroscopic length scale of the electrodes is presented.     

Synthesis,structure, and optical properties of Au–TiO2 composite thin films

Titanium dioxide (TiO₂) films with varying concentrations of gold particles were synthesized using pulsed DC magnetron sputtering, with the intent to develop infrared reflecting films for use on cars and planes to reduce solar heat load. Under our deposition conditions, the films are smooth (RMS roughness on the order of 1.0–2.0 nm) and consist of rutile TiO₂ with embedded gold. The average gold particle diameter on the sample surface was found to change from 60 to 200 nm as the volume fraction of gold in the films increased from 1.9 to 4.3% (3.5 to 7.9 mol% Au). The maximum reflectance of these films in the infrared region (800–2500 nm) is > 50%, compared with 30% for pure TiO₂. The Maxwell–Garnett equation does not model the reflectance data very well, due to the relatively large gold particle size. Instead, by assuming that the contribution of gold particles to the reflectance response is proportional to their projected areal fraction in an effective medium approximation, we were able to fit the observed reflectance data quite well.