On finite dimensional realization theory of discrete time nonlinear systems

We characterize finite dimensional realizability of discrete time nonlinear systems which have a Volterra series development with separable structure of the Volterra kernels.     

Application Level Fault Tolerance in Heterogeneous Networks of Workstations

We have explored methods for checkpointing and restarting processes within the distributed object migration environment (Dome), a C++ library of data parallel objects that are automatically distributed over heterogeneous networks of workstations (NOWs). System level checkpointing methods, although transparent to the user, were rejected because they lack support for heterogeneity. We have implemented application level checkpointing which places the checkpoint and restart mechanisms within Dome's C++ objects. Application level checkpointing has been implemented with a library-based technique for the programmer and a more transparent preprocessor-based technique. Dome's implementation of checkpointing successfully checkpoints and restarts processes on different numbers of machines and different architectures. Results from executing Dome programs across a NOW with realistic failure rates have been experimentally determined and are compared with theoretical results. The overhead of checkpointing is found to be low, while providing substantial decreases in expected runtime on realistic systems.     

Probabilistic analysis of the application of the cross ratio to model based vision

The probability density function for the cross ratio is obtained under the hypothesis that the four image points have independent, identical, Gaussian distributions. The density function has six symmetries which are closely linked to the six different values of the cross ratio obtained by permuting the quadruple of points from which the cross ratio is calculated. The density function has logarithmic singularities corresponding to values of the cross ratio for which two of the four points are coincident. The cross ratio forms the basis of a simple system for recognising or classifying quadruples of collinear image points. The performance of the system depends on the choice of rule for deciding whether four image points have a given cross ratio . A rule is stated which is computationally straightforward and which takes into account the effects on the cross ratio of small errors in locating the image points. Two key properties of the rule are the probabilityR of rejection, and the probabilityF of a false alarm. The probabilitiesR andF depend on a thresholdt in the decision rule. There is a trade off betweenR andF obtained by varyingt. It is shown that the trade off is insensitive to the given cross ratio . LetF _w =max _o {F}. ThenR, F _w are related approximately by , provided ^–1 F _w 4. In the equation, is the accuracy with which image points can be located relative to the width of the image, andr _F is a constant known as the normalised false alarm rate. In the range ^–1 F _w 4 the probabilitiesR andF _w are related approximately by . The value ofr _F is 14.37. The consequences of these relations between R and F_w are discussed. It is conjectured that the above general form of the trade off betweenR andF _w holds for a wide class of scalar invariants that could be used for model based object recognition. Invariants with the same type of trade off between the probability of rejection and the probability of false alarm are said to be nondegenerate for model based vision.     

Breaking the spores of the fungus Ganoderma lucidum by supercritical CO2

The hard sporoderm of Ganoderma lucidum spores prevents the release of bioactive components such as polysaccharides which have significant anti-tumour activity. In the present study, supercritical carbon dioxide (SC–CO₂) was used for the sporoderm breaking of G. lucidum spores, and polysaccharides were subsequently extracted and determined for evaluating the performances of SC–CO₂. The operating parameters were optimized by orthogonal array design (OAD), and the morphological status of sporoderm was observed by scanning electron microscope (SEM). The optimum operating conditions for SC–CO₂ breaking of sporoderm were as follows: pressure 35 MPa, temperature 25 °C, time 4 h, and CO₂ flow rate 10 kg/h. After SC–CO₂ processing, the extraction yield of polysaccharides reached 2.98%, which was 3-fold to that of the intact ones (0.94%). This method is fast, efficient and advanced enough to break the hard sporoderm of G. lucidum, which may provide a scientific reference for the large-scale processing of spores in the pharmaceutical and food industries.     

Relevant aspects of Arcobacter spp. as potential foodborne pathogen

Arcobacter species are Gram-negative spiral-shaped organisms belonging to the family Campylobacteraceae that can grow microaerobically or aerobically. The Arcobacter organisms also have the ability to grow at 15 degrees C, which is a distinctive feature that differentiates Arcobacter species from Campylobacter species. Cultural detection of Arcobacter is generally performed by an enrichment step and takes 4 to 5 days. In the last few years, several studies comparing different culture-based protocols have been published. Furthermore, DNA-based assays have also been established for rapid and specific identification of Arcobacter spp. Recent evidence suggests that Arcobacter, especially A. Butzleri, may be involved in human enteric diseases. Moreover, A. butzleri has also occasionally been found in cases of human extraintestinal diseases. However, up to now, little is known about the mechanisms of pathogenicity or potential virulence factors of Arcobacter spp. There is evidence that livestock animals may be a significant reservoir of Arcobacter spp. and over the last few years, the presence of these organisms in raw meat products as well as in surface and ground water has received increasing attention. In view of control measures to be used to prevent or to eliminate the hazard of Arcobacter spp. in food, several treatments have been evaluated for their effectiveness. While the role of Arcobacter spp. in human disease awaits further evaluation, a precautionary approach is advisable. Measures aimed at reduction or eradication of Arcobacter from the human food chain should be encouraged. With this article, we review the recent literature on this organism with a special emphasis on the information relevant to food safety.     

Assessment of noise attenuating powertrain components

Forschung im Ingenieurwesen - Wind turbine noise used to be dominated by aerodynamic blade noise, effectively masking mechanical noise, originating from the drivetrain. Successful blade noise...     

Revealing the relationships between alloy structure,composition and plastic deformation in a ternary alloy system by a combinatorial approach

A high-throughput approach based on magnetron co-sputtering of alloy libraries is employed to inves-tigate mechanical properties of crystalline and amorphous alloys in a ternary palladium(Pd)-tungsten(W)-silicon(Si)system with the aim to reveal the difference in plastic deformation response and extract the relevant structure-property relationships of the alloys in the system.It was found that in contrast to crystalline alloys,the amorphous ones,i.e.,metallic glasses,exhibited a much smaller fluctuation range in the plasticity parameters(Er2/H and Wp/Wt),indicating a significant difference in the plastic deformation mechanism controlling the mechanical properties for the respective alloys.We propose that the inho-mogeneous deformation of amorphous alloys localized in thin shear bands is responsible for the weaker compositional dependence of both plasticity parameters,while dislocation gliding in crystalline materials is significantly more dependent on the exact structure,thus resulting in a larger scattering range.Based on the representative efficient cluster packing model,a set of composition-dependent atomic structural models is proposed to figure out the structure-property relationships of amorphous alloys in Pd-W-Si alloy system.     

Elastic instabilities,microstructure transformations,and pattern formations in soft materials

Large deformations of soft materials can give rise to the development of various elastic instabilities. The phenomenon is associated with a sudden and dramatic change in structure morphologies. The underlying mechanism is crucial for the formation of complex morphologies in biology. Moreover, the concept of instability-induced pattern transformations is promising for designing novel materials with switchable functions and properties. In this paper, we review the state of the art in elastic instability phenomena in soft materials. We start by considering the classical buckling in beam-based structure lattice designs. Then, we discuss the instability-induced microstructure transformations in soft porous materials, and heterogeneous multiphase and fiber composites. Next, the mechanisms – often involving the post-buckling consideration – leading to the wrinkling and folding, creasing, fringe, and fingering are discussed.     

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