An Evaluation of Phosphates as Dispersing Agents in the Deinking of Catalogue Wastepaper by Flotation

Employing a Wemco three liter laboratory flotation cell and using the dispersing agent as the independent variable erratic trends suggested that trisodium phosphate and tetrasodium pyrophosphate increase the brightness gain in froth flotation deinking and that trisodium phosphate promotes higher brightness gains than tetrasodium pyrophosphate in concentrations ranging from 0.02 to 0.2 percent, (based on oven dry wastepaper). Conclusions could not be drawn for other salts evaluated and also are definitely not decisive for the two salts described. With a material like wastepaper it is difficult, even with the best endeavor to composit the sample, to obtain a large number of specimens, each of which is truly representative of the composite. It would have been desirable if time had been available, to have worked with a much more extensive experimental procedure

Modelling and Simulation of a Network Management System using Hierarchical Coloured Petri Nets: Extended version

Development of distributed software systems is a complex task. This paper argues that design and specification can be supported by modelling and simulation using Hierarchical Coloured Petri Nets (CP-nets). This conclusion is based on a case study of a project in which CP-nets were used in the detailed design of a software module. The software module is part of the Network Management System of the RcPAX X.25 wide area network. The module was designed using the Design/CPN tool which allows editing and simulation of CP-nets. Furthermore invariant techniques were used to prove properties of the module.Genoptrykt i Oktober 1994 i 100 eksemplarer

Computer-Mediated Communication and Innovation: Do Communication Media Properties Influence Innovative Thinking Processes?

This paper concerns potential impacts that characteristics of communication media in computer-mediated problem solving in groups have on group-members’ innovative thinking. Different processes involved in effective idea generation and problem solving are presented, and we discuss how three characteristics of communication media relevant for group collaboration aiming at producing innovative ideas might influence the group process. A research model is presented, and hypotheses regarding the effects of affordances on innovative thinking are put forth. We finally describe a possible methodological approach that might be applied in order to test the proposed hypotheses

Robot Navigation in Distorted Magnetic Fields

This thesis investigates the utilization of magnetic field distortions for the localization and navigation of robotic systems. The work comprehensively illuminates the various aspects that are relevant in this context. Among other things, the characteristics of magnetic field environments are assessed and examined for their usability for robot navigation in various typical mobile robot deployment scenarios. A strong focus of this work lies in the self-induced static and dynamic magnetic field distortions of complex kinematic robots, which could hinder the use of magnetic fields because of their interference with the ambient magnetic field. In addition to the examination of typical distortions in robots of different classes, solutions for compensation and concrete tools are developed both in hardware (distributed magnetometer sensor systems) and in software. In this context, machine learning approaches for learning static and dynamic system distortions are explored and contrasted with classical methods for calibrating magnetic field sensors. In order to extend probabilistic state estimation methods towards the localization in magnetic fields, a measurement model based on Mises-Fisher distributions is developed in this thesis. Finally, the approaches of this work are evaluated in practice inside and outside the laboratory in different environments and domains (e.g. office, subsea, desert, etc.) with different types of robot systems

Immunological analysis of pesticides: a new tool in groundwater testing

Groundwater is the major source of drinking water in many European countries, and in Denmark alone it accounts for more than 99% of the drinking water supply. Within the past decade pesticide residues have frequently been detected in groundwater, in many cases at levels exceeding the 0.1 µg/l limit set by the European Community. As a consequence, drinking water abstraction wells have had to be closed in many places in Denmark and other European countries, and a vast amount of money is expended to monitor groundwater pesticide levels. A degradation product of the herbicide dichlobenil, 2,6-dichlorobenzamide (BAM), is the most common cause of drinking water well closure in Denmark. Triazines and their metabolites also contaminate groundwater in many countries, and pose a similar risk to the drinking water supply. Analysis of most pesticides and their degradation products is usually carried out by concentrating the samples by solvent extraction, and identifying the contaminants using gas chromatography (GC) or high-pressure liquid chromatography (HPLC) combined with mass spectrometry (MS). These methods, although robust and well established, are very time-consuming and require specialised instrumentation. The large quantity of solvents used is another draw back to these methods, as the solvents themselves may be carcinogenic and are also well known contaminants of groundwater. The development of cheap, more sensitive and more rapid pesticide assays is therefore urgent. Due to their very high sensitivity, immunological methods have long been used in biological science for analysing a large variety of organic structures, but have only recently been introduced to environmental analysis. The benefit of such assays is primarily their high sensitivity, which allows the analysis to be undertaken without the need to concentrate the samples, but also the facility of dealing with large numbers of samples. Compared to conventional analyses, immunological methods face two major drawbacks – one related to specificity and the other to the fact that only very few chemicals can currently be analysed simultaneously. The crux of the specificity problem is that although antibodies react very specifically with particular chemical structures, these same structures may be present in analogous compounds. Thus antibodies developed to recognise, for example the herbicide atrazine might also recognise other triazines (Bruun et al. 2001). An important scientific challenge is therefore the development of highly specific assays recognising each individual compound, as well as assays recognising groups of related chemicals. With respect to the simultaneous analysis of numerous chemicals, this can be resolved by implementing the new biochip technology, which incorporates the parallellity of sample screening. On a pesticide biochip many specific immunological assays are carried out in isolated small spots on a glass or polymer surface. Each spot has a size of approximately 150 micrometers and forms a specific analysis. Such a miniaturised platform will be usable for monitoring programmes where water samples have to be screened for a range of chemical contaminants. The overall objectives of this study have been (1) to develop immunoassays for high-sensitivity analysis of specific pesticides and chemically related groups of pesticides, and (2) to transfer the developed assays to a miniaturised biochip platform in a manner allowing analysis of several pesticides simultaneously

Unidirectional frequency conversion in microring resonators for on-chip frequency-multiplexed single-photon sources

Microring resonators are attractive for low-power frequency conversion via Bragg-scattering four-wave-mixing due to their comb-like resonance spectrum. However, conversion efficiency is limited to 50% due to the equal probability of up- and down-conversion. Here, we demonstrate how two coupled microrings enable highly directional conversion between the spectral modes of one of the rings. An extinction between up- and down-conversion of more than 40 dB is experimentally observed. Based on this method, we propose a design for on-chip multiplexed single-photon sources that allow localized frequency modes to be converted into propagating continuous-mode photon wave packets using a single operation. The key is that frequency conversion works as a switch on both spatial and spectral degrees of freedom of photons if the microring is interferometrically coupled to a bus waveguide. Our numerical results show 99% conversion efficiency into a propagating mode with a wave packet having a 90% overlap with a Gaussian for a ratio between intrinsic and coupling quality factors of 400