First–Order Representations of Discrete Linear Multidimensional Systems

The classical localstate–space models for discrete multidimensional linearsystems, as proposed by Roesser or Fornasini and Marchesini,require causality of the resulting transfer matrices. We considera generalization comprising non-causal systems, based on Willems'state-space behaviors. A vector of manifest and a vector of latentvariables are supposed to be linked via a first–order dynamicequation and a static equation. Any system of linear constant–coefficientpartial difference equations gives rise to such an ``output–nulling'(ON) representation. Controllable systems possess driving–variablerepresentations, which are the dual counterpart of ON repsin many aspects. We study these representations with respectto their minimality, observability and controllability, and wederive conditions for their reducibility to the standard input–state–outputsetting.     

Integrating explicit path planning with reactive control of mobile robots using Trulla

This article describes and investigates a method of interleaving explicit path planning with reactive control. The Trulla all-paths planner computes an a priori set of optimal paths. Minor reactions to obstacles and terrain changes serve to switch the robot from the precomputed path to a new precomputed path, eliminating subgoal obsession. Major deviations suggest that the a priori map is significantly wrong; explicit replanning should be triggered to ensure continued progress of the robot. The dot product is used as the intrinsic measure of a major deviation. This methodology is particularly well-suited for computationally bound robots such as planetary rovers and robots operating in indoor environments with a large number of minor unmodeled obstacles.

The article describes the Trulla and dot product algorithms, and reports on experimental data collected from a mobile robot under representative scenarios. The method is compared to continuous and fixed frequency replanning under differing environments and robot velocities. The results show that the deferred replanning with the Trulla/dot product methodology produced actual paths similar to more frequent replanning in distance and time but with up to 100 times less computation. The reduced computation led to a 8.75% increase in distance traveled and 24% increase in travel time. In the presence of faulty sensor data, Trulla outperformed the other methods which radically changed the path back and forth due to spurious sensor readings.     

Maternal intrusive support in the academic context: Transactional socialization processes.

Although transactional models of socialization have received support, there has been little investigation of the processes involved. The goal of this research was to move in this direction in the context of the socialization of achievement. Mothers and their elementary school children (N?=?166) took part in an 18-month longitudinal study including a 2-week daily checklist. The results suggested that children's low achievement elicits intrusive support from mothers through 2 mechanisms. Mothers worried over their children's performance, and this was associated with heightened intrusive support. Children's low achievement manifested itself in uncertainty, which was linked to heightened intrusive support. The achievement of children whose mothers frequently used intrusive support improved over time but did not exceed that of children whose mothers infrequently used intrusive support. Day-to-day analyses suggested that although intrusive support promotes success, it also fosters failure for low-achieving children. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A survey on participating media rendering techniques

Rendering participating media is important for a number of domains, ranging from commercial applications (entertainment, virtual reality) to simulation systems (driving, flying, and space simulators) and safety analyses (driving conditions, sign visibility). This article surveys global illumination algorithms for environments including participating media. It reviews both appearance-based and physically-based media methods, including the single-scattering and the more general multiple-scattering techniques. The objective of the survey is the characterization of all these methods: identification of their base techniques, assumptions, limitations, and range of utilization. It concludes with some reflections about the suitability of the methods depending on the specific application involved, and possible future research lines.     

Changes in contrast thresholds with mean luminance for chromatic and luminance gratings: A reexamination of the transition from the DeVries–Rose to Weber regions

We have examined the influence of the mean luminance level on the detection thresholds for luminance and red–green chromatic gratings for three different spatial frequencies. The changes in detection thresholds according to the mean luminance level reflect the two different regions, the DeVries–Rose and Weber ranges, found in previous studies. The results for luminance gratings suggest that the transition luminance is proportional to the spatial frequency of the grating. Predictions based on the constant‐flux hypothesis indicate, however, that the transition luminance is proportional to the square of the spatial frequency of the grating and so do not describe the distributions of luminance contrast thresholds adequately. For chromatic gratings, we obtained the same transition luminance for the two lowest spatial frequencies, showing that luminance and chromatic mechanisms behave differently as far as the dependence of the transition luminance on spatial frequency is concerned. Our results suggest that the transition luminance is related to the peak spatial frequency of visual mechanisms that respond to luminance and chromatic gratings. © 2004 Wiley Periodicals, Inc. Col Res Appl, 29, 177–182, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20003     

Organspende unter Lebenden: Über den Vorrang der Mißbrauchsverhütung

Ohne Zusammenfassung     

Macroscopic-scale carbon nanotube alignment via self-assembly in lyotropic liquid crystals

By dispersing carbon nanotubes (CNTs) in a lyotropic liquid crystalline matrix, uniaxial alignment of the nanotubes can easily be achieved over macroscopic areas. We briefly describe the principles behind the technique and then show that it can be applied to multiwall as well as single-wall nanotubes and that a variety of different dispersing materials can be used, from industrial surfactants to DNA. We also present a new microfluidics-based method for transferring the liquid crystal-dispersed CNTs to a substrate, maintaining a fair control of tube direction.     

Microstructure of cobalt oxide doped sintered ceria solid solutions

The sintering of ceria solid solutions, such as Ce_0.9Gd_0.1O_1.95 (CGO10), is strongly promoted by the addition of 1 cat% of cobalt oxide, lowering the maximum sintering temperature by 200^∘C and triplicating the maximum densification rate. This change in sintering behavior results from cobalt ion segregated at the grain boundaries. An average cobalt ion boundary coverage is at maximum 3.0 ± 1.9 at/nm² and is shown to depend on the cooling rate. Coverage by segregated gadolinium is also found and amounts to 13.2 ± 11.4 at/nm² for a slowly cooled sample. From cobalt excess measured at the boundary, an estimated concentration of only 0.06 cat% of cobalt oxide is necessary to promote the sintering effect. The remaining amount of cobalt oxide is found in triple points and as particles in clusters. It is expected that the amount of cobalt oxide necessary for fast densification can be reduced with a doping process that distributes the additives more homogeneously.     

Parent?×?child socialization: Implications for the development of depressive symptoms.

A Parent?×?Child model of socialization was applied to the development of depressive symptoms. It was expected that when parents used intrusive support frequently, children engaging in negative self-evaluative processes would be more vulnerable to depressive symptoms than children engaging in positive self-evaluative processes. Children in the 5th through 7th grades took part in a 2-wave longitudinal study over 6 months. Parents' use of intrusive support was assessed using reports from children (N?=?806) and mothers (N?=?74). Children's self-evaluative processes and depressive symptoms were assessed using reports from children. The results suggest that both parents and children contribute to the development of depressive symptoms. When parental intrusive support was high, children engaging in negative self-evaluative processes experienced more depressive symptoms over time than did children engaging in positive self-evaluative processes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)