An inductive characterization of matching in binding bigraphs

We analyze the matching problem for bigraphs. In particular, we present a sound and complete inductive characterization of matching in bigraphs with binding. Our results yield a specification for a provably correct matching algorithm, as needed by our prototype tool implementing bigraphical reactive systems.     

A combined analysis of plant connectivity and alarm logs to reduce the number of alerts in an automation system

A process alarm arises when normal operation limits are exceeded and an alarm management system alerts the operator of a process plant. Due to the material, energy and information flow in a plant, single disturbances can cause multiple consequent alarm messages, and the alarm messages may overload the operator by presenting many redundant alarms. This undesired situation is called an ‘alarm flood’. In such situations, the operator might not be able to fulfil his required tasks to keep the plant within safe operation limits and to find the root cause of the disturbance. The aim of the work presented in this paper is to reduce the number of alerts presented to the operator. If alarms are related to one another, those alarms should be grouped and presented as one alarm problem. For the implementation of the concept, a software prototype has been developed to perform this reduction automatically. The analysis process starts with the alarm history which is a log containing all past alarm messages. This is combined with the plant topology of the controlled system and a set of rules. The rules describe typical interrelations between alarm messages which have a common cause. The combination of these three elements yields an effective alarm management strategy that can help plant owners and operators to comply with standards for alarm management such as ANSI/ISA 18.2 (2009) and EEMUA 191 (2007) which set limits on the number of alarms per unit time for an operator. The effectiveness of the approach is illustrated by two industrial examples where a significant reduction of alarms has been achieved.     

Determination of the antioxidant capacity: influence of the sample concentration on the measured values

The aim of the present analysis was to study the influence of the sample concentration on the measured antioxidant capacity, since such investigations are scarce but necessary to ensure the reproducibility of the results. Pure substances (ascorbic acid, gallic acid, Trolox^®, uric acid) and food extracts (strawberry nectar, tomato extract, white tea) were analysed using seven common antioxidant capacity assays (three versions of Trolox equivalent antioxidant capacity, TEAC; ferric reducing antioxidant power, FRAP; photochemiluminescence, PCL; oxygen radical absorbance capacity, ORAC and total phenolics assay). For all applied pure substances and in most of the assays effects of the sample concentration on the measured antioxidant capacity were observed. Since it remains speculative how sample concentration does affect the measured antioxidant capacity exactly, it is strongly recommended to use at least three sample concentrations for analysis to detect and to discuss concentration-dependent effects.     

Critical aspects of sinter-hardening of prealloyed Cr–Mo steel

In recent years, growing demand for greater mechanical properties of PM steel components with competitive fabrication cost has led to significant innovations in different fields of powder metallurgy. Recent research has been focused on reaching higher performance with lower cost. To this end, the possibility of combining the conventional sintering and post-sintering processes for a particular powder composition has been introduced. Sinter-hardening is a result of the research conducted along this line. Elimination of any secondary operation such as quench-hardening by incorporating it in the sintering process (i.e. sinter-hardening) is of great interest, as it will lead to lower processing costs and equal, if not higher mechanical performance. However, to ensure the desired mechanical properties of the final component and robustness of the performance, critical aspects of the sinter-hardening process should be rigorously studied.Hence with specific attention to a Cr–Mo steel powder (FL-5305), this study deals with the influence of density on cooling rate, the effect of different sintering temperatures (e.g. 1120 °C and 1250 °C) on austenite grain size and consequently, hardenability. The microstructure development in sinter-hardened FL-5305 material has been analyzed and predicted by means of the available literature for solid steel and also using the commercial software (JMatPro 5.0) for materials assessment based on thermodynamic and kinetics modeling. Finally, inaccurate carbon control and its adverse impact on excessive formation of cementite have been addressed.     

Upgrading of Raw Gas from Biomass and Waste Gasification: Challenges and Opportunities

The depletion of fossil fuel-based resources and concerns for increasing emissions of CO₂ call for new ways of producing environmentally-friendly substitutes for motor fuels and chemicals. Thermo-chemical conversion of biomass and waste using gasification is a strong candidate to meet these challenges. For efficient and cost-effective application of this technique, novel solutions for hot gas cleaning are needed. This review highlights some important areas for improvement of upgrading technologies for pressurised fluidised bed gasification systems using biomass as a fuel.     

Combined TPS, XPS, EXAFS, and NO-TPD study of the sulfiding of Mo/Al2O3

The sulfiding of Mo/Al₂O₃ in H₂S/Ar versus in H₂S/H₂ has been studied by temperature-programmed sulfiding (TPS), X-ray photon electron spectroscopy (XPS), extended X-ray absorption fine structure (EXAFS), and temperature-programmed desorption of NO (NO-TPD). All the applied techniques agree on the sulfur content in the sulfided catalysts and the findings are in accord with a model for the H₂S production reaction. The nucleation and growth of well-ordered MoS₂ clusters are probed by XPS during sulfiding with and without the presence of hydrogen. The resulting dispersion of the MoS₂ phase is evaluated on the basis of XPS, EXAFS, and NO-TPD, and is found to be highest when the sulfiding occurs in the presence of hydrogen.     

RNA amplification chip with parallel microchannels and droplet positioning using capillary valves

We present results from the MicroActive project which develops an instrument for molecular diagnostics. The instrument is first tested for patient screening for a group of viruses causing cervical cancer. Two disposable polymer chips with reagents stored on-chip are developed and will be inserted into the instrument for each patient sample analysis. The first chip will perform nucleic acid extraction from patient epithelial cervical cells, while mRNA amplification and fluorescent detection takes place in the second chip. This paper reports results on the amplification chip. Purified sample is inserted into the chip and split into ten smaller droplets for simultaneous amplification and detection of ten viruses. The droplets move in parallel channels, each with two chamber extensions containing dried reagents. Experimental results on parallel droplet movement using one external pump combined with hydrophobic restrictions show that the parallel droplet positions can be controlled. There are four valves with increasing burst pressures between 800 and 4,500 Pa in each parallel channel, positioning the droplets in metering zones and reaction chambers. The re-hydration times for the dried reagents in micro chambers have been monitored. After sample insertion, uniform concentration of the reagents in the droplet was reached after respectively 60 s and 10 min. These times are acceptable for successful amplification. Finally we show positive amplification of HPV type 16 viruses in a micro chamber.     

Kinetics of tyre char oxidation under combustion conditions

Combustion of tyre char particles with diameters between 102 and 212 μm was performed in an experimental laboratory reactor, at temperatures between 750 and 850 °C, in an oxidative atmosphere with up to 10 vol.% O₂ at 1 bar. The observed char combustion time varied from about 9 s at 750 °C to about 4 s at 850 °C. Under these conditions the experimental data indicated increasing mass transfer resistance with temperature. A diffusion reaction model was employed to study the effects of simultaneous mass transfer and kinetics in the experiments. An intrinsic reaction rate for tyre char combustion was estimated and comparison with literature data revealed good agreement.     

Multimedia Education in Computer Science: A Little Bit of Everything Is Not Enough

Media Impact usually focuses on the practical impact of multimedia research on IT business. Yet given the pervasiveness of multimedia technology in our everyday life, a thorough reflection on the impact of multimedia progress on education and, in particular, multimedia education is overdue. Multimedia teachers at the 2007 ACM Multimedia conference engaged in a panel discussion on the current state and future of multimedia education. In this issue's,Wolfgang Hürst of Utrecht University and his colleagues Gerald Friedland of the International Computer Science Institute, Berkeley, and Lars Knipping of Berlin University of Technology use this panel as an opportunity to argue the need for a dedicated multimedia curriculum in computer science education.