Conduction Model of Metal Oxide Gas Sensors

Tin dioxide is a widely used sensitive material for gas sensors. Many research and development groups in academia and industry are contributing to the increase of (basic) knowledge/(applied) know-how. However, from a systematic point of view the knowledge gaining process seems not to be coherent. One reason is the lack of a general applicable model which combines the basic principles with measurable sensor parameters.The approach in the presented work is to provide a frame model that deals with all contributions involved in conduction within a real world sensor. For doing so, one starts with identifying the different building blocks of a sensor. Afterwards their main inputs are analyzed in combination with the gas reaction involved in sensing. At the end, the contributions are summarized together with their interactions.The work presented here is one step towards a general applicable model for real world gas sensors.     

Renewable electricity in Europe

Renewable energy use is growing at a much faster pace than the rest of the economy in Europe and world-wide. This and the dramatic oil price increases in 2005 have lead to a remarkable re-evaluation of the renewable energy sector by politics and financing institutions. Despite the fact that there are still discrepancies between the European Union and the USA how to deal with climate change, renewable energies will play an important role for the implementation of the Kyoto Protocol and the world wide introduction of tradable green certificates. Apart from the electricity sector, renewable energy sources for the generation of heat and the use of environmental friendly bio-fuels for the transport sector will become more and more important in the future.     

Kinetics and mechanism of isocyanate reactions. I. Reactions of Aryl Isocyanates with Alcohols

The reaction of aryl isocyanates with alcohols has been kinetically studied as a model reaction for polyurethane formation under conditions similar to those of industrial scale production. Considering the isocyanate and alcohol structure, kinetic isotopic effect, activation enthalpy and entropy and solvent effects it has been found that the most probable mechanism is the alcohol addition through a four-membered cyclic transition state.     

Effects of the Lipid Profile,Type 2 Diabetes and Medication on the Metabolic Syndrome—Associated Gut Microbiome

Metabolic syndrome (MetSyn) is a major health problem affecting approximately 25% of the worldwide population. Since the gut microbiota is highly connected to the host metabolism, several recent studies have emerged to characterize the role of the microbiome in MetSyn development and progression. To this end, our study aimed to identify the microbiome patterns which distinguish MetSyn from type 2 diabetes mellitus (T2DM). We performed 16S rRNA amplicon sequencing on a cohort of 70 individuals among which 40 were MetSyn patients. The microbiome of MetSyn patients was characterised by reduced diversity, loss of butyrate producers (Subdoligranulum, Butyricicoccus, Faecalibacterium prausnitzii) and enrichment in the relative abundance of fungal populations. We also show a link between the gut microbiome and lipid metabolism in MetSyn. Specifically, low-density lipoproteins (LDL) and high-density lipoproteins (HDL) display a positive effect on gut microbial diversity. When interrogating the signature of gut microbiota in a subgroup of patients harbouring both MetSyn and T2DM conditions, we observed a significant increase in taxa such as Bacteroides, Clostridiales, and Erysipelotrichaceae. This preliminary study shows for the first time that T2DM brings unique signatures of gut microbiota in MetSyn patients. We also highlight the impact of metformin treatment on the gut microbiota. Metformin administration was linked to changes in Prevotellaceae, Rickenellaceae, and Clostridiales. Further research focusing on the microbiome-metabolome patterns is needed to clarify the exact association of various gut microbial communities with the progression of T2DM and the occurrence of various complications in MetSyn patients.     

Structural design and kinematics of a new parallel reconfigurable robot

Reconfigurable robots can be defined as a group of robots that can have different geometries, thus obtaining different structures derived from the basic one, having different degrees of freedom and workspaces. Thanks to the optimum dexterity they offer, the user can accomplish a large variety of industrial tasks, using a structurally optimized robot leading towards better energy control and efficiency especially in case of batch size production lines where the task (for the robot) may vary periodically. Reconfigurable systems are a challenge for numerous scientists, due to the advantage of dealing with changes and uncertainties on the ever-changing manufacturing market. One of the main problems of reconfigurable robots is the proper structural geometry determination, so that the resulting structure is able to perform a variety of tasks. This paper presents the structural design of an innovative parallel robot with six degrees of freedom and its proposed configurations with five, four, three and two degrees of freedom. The kinematic analysis and the workspace representations of all the presented configurations of the parallel robot, called Recrob, are also presented.     

Rheological properties of hydrophobically modified alkali-swellable acrysol emulsions

The rheological behaviour of aqueous solutions of two commercial anionic hydrophobically modified alkali-swellable emulsions (HASE), Acrysol TT615 and RM5, was studied. These polymeric systems, initially in the form of low-viscosity latices at low pH, tend to swell and increase their viscosity when neutralised with base. The steady-shear and dynamic properties of these polymers were measured over a wide range of concentration, at constant pH=9 and temperature of 20°C. The intrinsic and zero-shear viscosities were used to identify the concentration regimes of the polymer solutions. In the case of Acrysol TT615, the solution exhibited shear-thinning characteristics at a concentration above 500 ppm. The Carreau model described well the viscosity function of the 1000 and 2000 ppm solutions. Considerable viscosity enhancement and a change in the flow curve profile were observed at concentrations above 2000 ppm. At high polymer concentration. the zero-shear viscosity was not detectable, and the power law model was adequate to characterize these solutions. By contrast, the RM5 solutions exhibited nearly Newtonian behaviour over the whole concentration range considered. Elasticity measured from the first normal stress difference indicated that Acrysol TT615 was more elastic than Acrysol RM5. Dynamic measurements revealed that both storage (G′) and loss (G″) moduli increased with polymer concentration. In the higher frequency and concentration regions, G′ > G″ was obseved for TT615, whereas G″ > G′ for RM5.     

Modeling,simulation and manufacturing of drill flutes

The designing of twist drill flutes (as well as that of end mills and of some combined tools) cannot be separated from the way they are manufactured. The aim of this paper is to present an intuitive direct method for modelling, simulation and manufacturing of the drill flutes with different shapes using conical grinding wheels with standardized shapes. The mathematical approach is described, which enables us to determine the flute profile in a section perpendicular to its axis as well as the manufacturing parameters. The grinding wheel has an initial position with respect to the cylindrical work piece, which is described using four parameters (Denavit Hartenberg parameters). We have presented algorithms in pseudocode that produce the flute shape and that compute the optimum parameters of the wheel position in the manufacturing process. Subsequently, a software application based on the aforementioned model is able to create visualizations of the flute shape. The analysis of the flute shape has enabled us to understand the influence of the geometrical parameters and the position of the grinding wheel on the resulting product in the grinding process. The order in which these parameters are to be set is also specified. We have built atlases of maps presenting the influence of the geometrical parameters and the position of the grinding wheel in the grinding process upon the shape of the flute. The validity of the method is proven by the agreement of the computed values with the input and output data produced by experiment. The proposed method allows helical flutes to be generated solely by using cylindrical and conical grinding wheels of standard shapes.     

Heat treatment influence on the structural properties of supported Ni nanoclusters

Ni nanoclusters supported on Al₂O₃ were prepared using a coprecipitation method. A heat treatment at different temperatures was applied. The obtained samples were analyzed by X-ray diffraction (XRD), X-ray absorption spectroscopy and X-ray photoelectron spectroscopy in order to determine their global, local and electronic structures. The average particle size, the mean squares of the microstrain, the particle size and microstrain distribution functions of the supported Ni nanoclusters were determined by the XRD method using a generalized Fermi function for the approximation of the X-ray line. The recrystallization induced during the heat treatment process was analyzed. The present study indicated strong deformation of the local structure of the active metal in all of the samples investigated due to the metal-support interaction and the effects of the small particle size. Electronic structural investigations showed the presence of Ni in a metallic state as well as Ni²⁺ on the cluster surfaces.