A detailed analysis of ambipolar diffusion in nanostructured metal oxide films

In this paper a transport equation is derived which describes the behaviour of the nanostructured metal oxide films in a photoelectrochemical cell. It is shown that a detailed analysis of the charge compensation mechanism necessarily leads to a transport equation with characteristics similar to but logically distinct from the pure diffusion equation. The studied phenomenon was named ambipolar diffusion in the early 1950s. It takes into account the fact that the diffusion processes of ions and electrons occur at different speeds. A weak electric field therefore couples the processes together to preserve charge neutrality. The electric field in turn affects the transport resulting in a deviation from purely diffusive behaviour. However, this has not been widely recognised in the literature for nanostructured semiconductor films until very recently. In this paper a detailed analysis is presented. It is based on the assumption that the current density is solenoidal. It is shown that application of the ambipolar diffusion model to a photoelectrochemical cell based on a nanostructured metal oxide film leads to an additional term in the transport equation, rather than only a new diffusion coefficient as in earlier work. It is also shown that the boundary conditions interact closely with the equation to form a transport model.     

"Temporal encoding in fear conditioning revealed through associative reflex facilitation": Correction to Lindquist and Brown (2004).

Reports an error in "Temporal Encoding in Fear Conditioning Revealed Through Associative Reflex Facilitation" by Derick H. Lindquist and Thomas H. Brown (Behavioral Neuroscience, 2004[Apr], Vol 118[2], 395-402). The article contained several errors. On page 396, second paragraph, the sentence beginning on line 6 should read as follows: "Having a stable baseline is critical for studies of reflex facilitation because the experimental designs invariably entail repetitive CR testing, if only to achieve reasonable statistical power (see Choi et al., 2001b; Lindquist & Brown, 2004)." On page 400, the first heading should read as follows: "Comparison of New and Old Reflex Facilitation Procedures." On page 400, the first sentence under the abovementioned heading should read as follows: "We decided not to use the original measure of reflex facilitation, developed by J. S. Brown et al. (1951), because it suffers from severe interpretational limitations, elaborated in detail elsewhere (Choi et al., 2001b; Leaton & Cranney, 1990; Lindquist & Brown, 2004)." (The following abstract of the original article appeared in record 2004-12681-016.) Temporal encoding in Pavlovian fear conditioning was examined through conditional facilitation of the short-latency (Rl) component of the rat eyeblink reflex. Rats were fear-conditioned to a tone conditional stimulus (CS) with either a 3- or 9-s interstimulus interval (ISI) between CS onset and the onset of the grid-shock unconditional stimulus (US). Rl facilitation was tested over 2 days, in counterbalanced order, at a latency of 3 s and 9 s from CS onset. CS-produced Rl facilitation, the conditional response (CR), was 3-4 times larger when the test latency equaled the conditioning ISI. These results, coupled with the known neurophysiology of Rl facilitation, suggest that this CR could disclose differences in the time course of CS-generated output from the amygdala when driven by cortical versus subcortical CS-CR pathways. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Design of simulator training: a comparative study of Swedish dynamic decision-making training facilities

Cognition, Technology & Work - Simulator training is becoming increasingly important for training of time-critical and dynamic situations. Hence, how simulator training in such domains is...     

Liquid crystal-on-silicon implementation of the partial pixel three-dimensional display architecture

We report the implementation of a liquid crystal-on-silicon, three-dimensional (3-D) diffractive display based on the partial pixel architecture. The display generates multiple stereoscopic images that are perceived as a static 3-D scene with one-dimensional motion parallax in a manner that is functionally equivalent to a holographic stereogram. The images are created with diffraction gratings formed in a thin liquid crystal layer by fringing electric fields from transparent indium tin oxide interdigitated electrodes. The electrodes are controlled by an external drive signal that permits the 3-D scene to be turned on and off. The display has a contrast ratio of 5.8, which is limited principally by optical scatter caused by extraneous fringing fields. These scatter sources can be readily eliminated. The display reported herein is the first step toward a real-time partial pixel architecture display in which large numbers of dynamic gratings are independently controlled by underlying silicon drive circuitry.     

Matrix-valued Nevanlinna-Pick interpolation with complexity constraint: an optimization approach

Over the last several years, a new theory of Nevanlinna-Pick interpolation with complexity constraint has been developed for scalar interpolants. In this paper we generalize this theory to the matrix-valued case, also allowing for multiple interpolation points. We parameterize a class of interpolants consisting of "most interpolants" of no higher degree than the central solution in terms of spectral zeros. This is a complete parameterization, and for each choice of interpolant we provide a convex optimization problem for determining it. This is derived in the context of duality theory of mathematical programming. To solve the convex optimization problem, we employ a homotopy continuation technique previously developed for the scalar case. These results can be applied to many classes of engineering problems, and, to illustrate this, we provide some examples. In particular, we apply our method to a benchmark problem in multivariate robust control. By constructing a controller satisfying all design specifications but having only half the McMillan degree of conventional H/sup /spl infin// controllers, we demonstrate the advantage of the proposed method.     

Tribofilm formation from TiC and nanocomposite TiAlC coatings,studied with focused ion beam and transmission electron microscopy

This work demonstrate how two different carbide coatings respond very differently to tribological stress and their very different ability to provide low friction tribofilms in dry sliding against steel. Both coatings, TiC and TiAlC, were deposited by DC-magnetron sputtering, but while the TiC is a thermodynamically stable coating, the TiAlC is made metastable with the addition of Al, and therefore releases carbon upon tribological testing. Thus, the TiAlC coating is shown to be self-lubricating on the atomic scale which makes very low friction achievable. The primary interest in this study is the differences in the tribofilms formed on the steel balls that have been sliding against the two coatings. Cross-section samples for transmission electron microscopy were extracted from the ball tribofilms using a focused ion beam instrument. X-ray photoelectron spectroscopy and Raman analysis were employed to provide information on the chemical and structural characteristics of the tribofilms. It was shown that tribofilms on steel balls largely inherit the structure and composition that evolve in the coating wear tracks, that the tribofilm microstructure greatly affects the friction level. It was also shown that tribofilm delamination, occurring with tribofilm growth, was initiated in weak ribbon like regions inside the tribofilm.     

Polarized Emissivity and Kirchhoff's law

An expression for the polarized emissivity of a material is obtained with the Stokes vector-Mueller matrix polarization formalism. The result obtained is that thermally emitted radiance might have a circular polarization component. In addition, the emissivity depends only on the reflectance matrix.     

A new method for manufacturing nanostructured electrodes on glass substrates

The present paper describes a new method for manufacturing a nanostructured porous layer of TiO₂ on a conducting glass substrate for use in a dye-sensitized photoelectrochemical cell. The method involves deposition of a layer of semiconductor particles onto a conducting substrate and compression of the particle layer to form a mechanically stable, electrically conducting, and porous nanostructured film at room temperature. Photoelectrochemical characteristics and morphology of the resulting nanostructured films are presented. The potential use of the new manufacturing method in the future applications of nanostructured systems is discussed.     

Kullback-Leibler approximation of spectral density functions

We introduce a Kullback-Leibler (1968) -type distance between spectral density functions of stationary stochastic processes and solve the problem of optimal approximation of a given spectral density /spl Psi/ by one that is consistent with prescribed second-order statistics. In general, such statistics are expressed as the state covariance of a linear filter driven by a stochastic process whose spectral density is sought. In this context, we show (i) that there is a unique spectral density /spl Phi/ which minimizes this Kullback-Leibler distance, (ii) that this optimal approximate is of the form /spl Psi//Q where the "correction term" Q is a rational spectral density function, and (iii) that the coefficients of Q can be obtained numerically by solving a suitable convex optimization problem. In the special case where /spl Psi/ = 1, the convex functional becomes quadratic and the solution is then specified by linear equations.