A high-density multi-point LAPS set-up using a VCSEL array and FPGA control

A new LAPS (light-addressable potentiometric sensor) set-up will be introduced, in which the light sources are miniaturised by the utilisation of a VCSEL (vertical-cavity surface-emitting laser) array to increase the measurement spot density. An FPGA (field-programmable gate array) is used to generate modulation signals for individual illumination of each measurement spot of the LAPS. The new set-up can operate a large number of measurement spots simultaneously by reading out the sum photocurrent and separate the signals of the individual measurement spots by an FFT analysis. The frequency, amplitude and offset of the modulation signal can be configured for each measurement spot by software. The new system can be combined with a positioning stage allowing the parallel read out of a single line of measurement spots and a scan perpendicular to that line in a similar manner, like for an optical scanner set-up. First measurements demonstrate the functionality of the new LAPS set-up as a chemical imaging system.     

A General Framework for Expressing Preferences in Causal Reasoning and Planning

We consider the problem of representing arbitrary preferencesin causal reasoning and planning systems. In planning, a preferencemay be seen as a goal or constraint that is desirable, but notnecessary, to satisfy. To begin, we define a very general querylanguage for histories, or interleaved sequences of world statesand actions. Based on this, we specify a second language inwhich preferences are defined. A single preference defines abinary relation on histories, indicating that one history ispreferred to the other. From this, one can define global preferenceorderings on the set of histories, the maximal elements of whichare the preferred histories. The approach is very general andflexible; thus it constitutes a ‘base’ languagein terms of which higher-level preferences may be defined. Tothis end, we investigate two fundamental types of preferencesthat we call choice and temporal preferences. We consider concretestrategies for these types of preferences and encode them interms of our framework. We suggest how to express aggregatesin the approach, allowing, e.g. the expression of a preferencefor histories with lowest total action costs. Last, our approachcan be used to express other approaches and so serves as a commonframework in which such approaches can be expressed and compared.We illustrate this by indicating how an approach due to Sonand Pontelli can be encoded in our approach, as well as thelanguage PDDL3.     

Service level management with agent technology

This paper outlines a generic evaluation methodology for multimedia and real time applications. It concentrates on the application layer and the service aspect. Principles of software evaluation for quality assessment and measurement for networked services and distributed applications are used to present a specific method for measuring important characteristics. The method and the measurement procedure allow comparison of the actual characteristics of service quality with the required characteristics and thresholds. The proof of concepts will be made by the implementation of quality measurement agents following the approach outlined in this paper. Our approach of performing service level management (SLM) with agent technology is distributed, slim, minimizable to the maximum, independent in its methodology and offers comparable, objective results.     

Reactor Concept for Contactless Kinetic Measurement in Oscillating Droplets via Raman Spectroscopy

A millistructured reactor and spectroscopic setup for contactless kinetic measurements in oscillating droplets is presented in this work. The polymerization of acrylic acid serves as a model reaction. Design and construction of the reactor focus on the optical access for Raman measurement, the nearly isothermal behavior, and the preservation of droplets during long‐term reactions with a high increase of viscosity. Another key aspect is the possibility of full automation at a later stage.     

Estimation of material functions using system identification techniques

Material properties of an elastic material are characterized by the elastic modulus, which is real-valued and constant. For viscoelastic materials, such as plastics and polymers, the relationship between stress and strain is instead dynamic, and characterized by the complex-valued and frequency-dependent complex modulus. It is in this paper described how system identification techniques can be used to determine the complex modulus using strain data from wave propagation experiments on a test specimen. Modeling, derivation of estimators, and analysis of their numerical and statistical properties are included. Identifiability and experimental design are examined in some detail. Several practical examples are presented using real-world data, and a number of extensions are outlined.