Multi-objective optimisation of batch separation processes

This paper considers for the first time the simultaneous multi-objective optimisation of design and operation of batch distillation as well as of batch hybrid distillation/pervaporation processes. The overall problem is formulated as a multi-objective mixed integer dynamic optimisation (MO-MIDO) problem. The optimisation strategy comprises of different ranking procedures that allow the determination of the Pareto optimal set. A case study for the separation of a homogeneous tangent-pinch (acetone–water) mixture is presented for a dual-criteria optimisation case of minimising capital investment while at the same time minimising the energy consumption rate during the batch. It is found that the proposed distance ranking procedure yields the best Pareto optimal set when compared to other non-dominated sorting procedures. Furthermore, the distance ranking procedure was found to be further improved when used with an elitism operator.     

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.     

Skateboarders exploring urban public space: Ollies, obstacles and conflicts

This paper reports on an explorative study about skateboarding practices in Amsterdam. One indoor spot and nine street locations for skateboarding were observed and over thirty skaters were interviewed. The research questions concern the identity of the people involved, the group interactions, and the use of urban space and routes. The majority of the observed skateboarders are male middle-class youngsters. In this respect, the skateboarding scene is not very different from other forms of urban public play where men predominate. At the same time, however, skateboarding can be seen as a way of experimenting with new forms of masculinity. Since hanging about by adolescents is mainly a lower-class phenomenon, the middle-class status of the skateboarding youth is surprising. Notwithstanding their individual skateboarding acts, youngsters involved in skateboarding negotiate their claim on specific spaces in groups. The colonizing of public spaces for skateboarding does not remain free of conflict. Groups of skaters are continuously putting public spaces into and out of use. In a sense, skateboarders can be considered the nomads of the city. Their `traveling in packs' results in a map of skate locations which is constantly changing. To understand the phenomenon of skateboarding, further research is needed, not only in Amsterdam but also in other cities and the suburbs.     

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)     

Functional Networks: A New Network-Based Methodology

In this article we give a general methodology to build and work with functional networks, a network-based alternative to the neural networks paradigm. In functional networks, neural functions are allowed to be not only multivariate but also truly multiargument and different for all neurons. Thus neural functions instead of weights are learned. In addition, outputs coming from different neurons can be connected, that is, forced to output the same values. The topology and neuron functions of functional networks can be selected based on data, domain knowledge, or a combination of the two. Functional equations play an important role in functional networks, since the preceding types of connections lead to functional equations that impose a substantial reduction in the degrees of freedom of the initial neural functions. Some methods are given to obtain equivalent functional and differential equations, and they are applied to approximating the solutions of differential equations problems. The examples of an associative operator, a cantilever beam, and a mass supported by two springs and a viscous damper are given to illustrate the methods and show their power.     

Catalytic combustion of hexane over transition metal modified zeolites NaX and CaA

Hexane deep oxidation was studied over NaX and CaA zeolites modified by ion exchange with transition metals (Mn²⁺, Co²⁺, Fe³⁺), the percentage of ion exchanged, determined by ICP-MS, varying between 39 and 98%. Parent and exchanged zeolites were characterized by X-ray diffraction (XRD), N₂ physisorption, temperature-programmed reduction (TPR), oxygen and ammonia temperature-programmed desorption (TPD) and inverse gas chromatography (IGC). Catalytic activities were evaluated through the recording of light-off curves in a pulsed microreactor, catalytic activity being correlated with physicochemical properties of the solids (crystallinity, surface acidity, adsorption properties and morphological parameters). As general trend, CaA zeolites are more active than NaX zeolites. Mn-exchanged CaA zeolite was the most active catalyst for hexane oxidation, whereas the addition of Fe to the zeolites leads to strong chemical and morphological changes in the parent zeolite.     

Free amino acids and volatile compounds in vinegars obtained from different types of substrate

The present work reports on the free amino acids and volatile compounds in vinegars obtained from different types of raw materials (cider, white wine and red wine). Based on the amino acid contents of three types of vinegar and of the substrates from which they were obtained, the profile of the nitrogen‐supplying compounds and their uptake for the acetic acid bacteria were very similar. The most important amino acid in terms of supply and uptake was found to be L ‐leucine. L ‐Proline proved also important in the wine vinegars, however it was not depleted as L ‐leucine. The different acetification reactions involved were found to yield acetoin, and plus 1,1‐diethoxyethane in the wine vinegars. Copyright © 2004 Society of Chemical Industry     

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.