Mixed-Cation Oxide Powders via Resin Intermediates Derived from a Water-Soluble Polymer

Submicrometer powders of complex oxides were prepared via resin intermediates based on a starch type of organic precursor. A commercially available water-soluble starch derivative was (for the first time) used as the organic base for solution synthesis of ceramic powders. Calcination of the charred, fluffy, amorphous resins at a temperature below 600°C for 4 h yielded perovskite powders of Sr-doped LaMnO₃ and Sr-doped La(Fe,Co)O₃. Sr-doped LaCrO₃ needed to be calcined above 750°C to ensure phase purity and to remove organic residue. Due to the low cost of starch derivatives, the process has the potential of being more economical than the commonly used Pechini's type process, which utilizes citric acid and ethylene glycol.     

Array pattern synthesis in the complex plane optimised by a geneticalgorithm

Array pattern nulling by operating on the roots of the array polynomial in the complex plane using a genetic algorithm (GA) is demonstrated. A pattern envelope constraint and an array efficiency criterion are applied. The algorithm is much faster than a similar GA operating on the complex weights of the array factor     

Solid-state NMR as a probe of porous catalysts and catalytic processes

The power of solid-state NMR for the interrogation of porous catalytic materials is illustrated using three examples. First, for the investigation of catalytic processes occurring within the confines of a microporous catalyst NMR is shown to reveal both the details of shape-selectivity and the nature of internal surface species. Second, NMR is shown to be a powerful short-range tool to reveal precise structural information on highly disordered microporous titanosilicates. Despite long-range disorder the short-range order is maintained and can be easily studied. Finally, the same utility of probing short-range chemical phenomena is shown to be crucial for the investigation of novel-ordered-amorphous-mesoporous materials known generically as M41S. This class of material is currently one of the most important with potential catalytic application.     

Operations standards for global ATM networks: network element view

The International Telecommunication Union (ITU) has completed work on a series of standards on asynchronous transfer mode (ATM) equipment functional operations and network element management. The objective of these standards is to enable flexible design and interoperability of network elements for use in a global ATM network, independent of any specific implementation. This article discusses these standards with respect to their development and application in planning ATM networks. Specifically, it addresses the following: the modeling approach taken in the development of the ITU standards, key operational features specified in the ATM network element functional model, and the capabilities of the ATM network element management interface. Examples of ATM equipment are provided to illustrate how the functional models specified in the ITU standards may be used by network planners and equipment manufacturers to specify and develop ATM equipment tailored to specific needs, while ensuring network interoperability. The article concludes with some points on the future enhancement of these and related ATM equipment operations standards     

Comparison of calcium phosphate cement mixture and pure calcium hydroxide as direct pulp-capping agents

This review reports the different genetic factors that have been identified either as risk factor for Alzheimer's disease (AD) or directly causing the disease. First are reviewed epidemiological data and biological mechanisms about the apoplipoprotein E gene allele epsilon 4 that is a major risk factor for Alzheimer's disease. The second part describes the mutations responsible for early-onset autosomal dominant AD found in three different genes. The gene located on chromosome 21 encodes the amyloid precusor protein (APP). The presenilin 1 and presenilin 2 genes, located on chromosome 14 and 1 respectively, encode not yet known membrane proteins.     

Classroom Presenter: Enhancing Interactive Education with Digital Ink

Classroom Presenter is a Tablet PC-based interaction system that supports the sharing of digital ink on slides between instructors and students. Initial deployments show that using the technology can achieve a wide range of educational goals and foster a more participatory classroom environment.     

The dynamic effects and compensation of load transitions in robotic systems

The problem of a robot handling a payload typically involves pre-load, load, and post-load stages, and payload transitions between these stages. Although considerable work has focused on the control of robots carrying payloads, few consider the problem of load transitions—one of the most important effects on system performance. This article studies these transitions and presents a compensation method. It is shown that load transitions lead to abrupt (jump) parameters and uncertain transition times in the robot/payload model. A control strategy is proposed that takes the load transitions into account and guarantees the stable path tracking of robots in the face of these transitions. The effectiveness of the proposed control strategy is verified via simulation. © 1994 John Wiley & Sons, Inc.