Copper-Tungsten Composites Sprayed by HVOF

Copper and copper-tungsten composite coatings were produced by high-velocity oxy-fuel spraying (HVOF). After initial optimization of the spraying parameters, coatings of various compositions were made and their structure, composition, mechanical, thermal, and electrical properties were characterized. The HVOF technique was able to produce rather dense coatings with minimal oxide content and relatively good mechanical and thermal properties compared to, for example, plasma-sprayed coatings; however, the achieved tungsten content was quite low.     

Consistency of discrete Bayesian learning

Bayes’ rule specifies how to obtain a posterior from a class of hypotheses endowed with a prior and the observed data. There are three fundamental ways to use this posterior for predicting the future: marginalization (integration over the hypotheses w.r.t. the posterior), MAP (taking the a posteriori most probable hypothesis), and stochastic model selection (selecting a hypothesis at random according to the posterior distribution). If the hypothesis class is countable, and contains the data generating distribution (this is termed the “realizable case”), strong consistency theorems are known for the former two methods in a sequential prediction framework, asserting almost sure convergence of the predictions to the truth as well as loss bounds. We prove corresponding results for stochastic model selection, for both discrete and continuous observation spaces. As a main technical tool, we will use the concept of a potential: this quantity, which is always positive, measures the total possible amount of future prediction errors. Precisely, in each time step, the expected potential decrease upper bounds the expected error. We introduce the entropy potential of a hypothesis class as its worst-case entropy, with regard to the true distribution. Our results are proven within a general stochastic online prediction framework, that comprises both online classification and prediction of non-i.i.d. sequences.     

Interactions between simultaneously activated behavioral systems in the rat.

Interactions between electrically induced attack and teeth-chattering from 1 electrode and grooming from another were examined in male albino rats. The interaction between electrically induced attacks and deprivation-induced feeding, as well as the effect of food deprivation on attack, was also studied. Results indicate that attack appears to be a dominant response, for it suppressed grooming and feeding at a low level of activation. On the other hand, it was not affected by simultaneously induced grooming or feeding. However, food deprivation decreased the threshold for attack, leaving attack latency, attack form, or bite targets unaffected. Teeth-chattering, suggested to be related to attack and flight, was also a dominant response. Results suggest that interactions between behavioral systems are in favor of the systems that must act acutely on activation in order to survive. Apparently, the regulations governing these interactions are represented in the functional organization of the brain. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

InP based semiconductor structures for radiation detection

We report the preparation of semi-insulating InP single crystals of p-type conductivity and intentionally undoped p-type epitaxial layers for radiation detection. We focus on (i) the growth of InP single crystals doped with copper by the Czochralski technique and their subsequent temperature annealing to convert them to a semi-insulating (SI) state of p-type conductivity, and (ii) the growth of thick (>10 μm) p-type InP layers by liquid phase epitaxy with an admixture of Pr and Dy. Grown layers and single crystals were examined by low-temperature photoluminescence spectroscopy, capacitance-voltage and temperature dependent Hall measurements. An efficient purification due to rare earth (RE) admixture has been observed and layers grown with the addition of Pr and Dy exhibit the change of electrical conductivity from n to p at certain RE concentration in the melt. Dominant acceptors responsible for conductivity conversion have been identified. Three types of detection structures exploiting the Schottky or Schottky like contacts on pure and SI p-type InP or exploiting the p–n junction were designed.     

Influence of variable permeability on the dispersion of a chemically reacting solute in porous media

In this paper in the first part, the influence of variable permeability on the two MHD basic flows in porous media is studied numerically. It is seen that the variable permeability due to random packing causes the hydromagnetic channelling in both the flows. Further, it is also observed that the flow in both the cases is retarded for any increase in the magnetic parameter.

In the second part, the influence of variable permeability and the effects of homogeneous and heterogeneous reactions on the dispersion of a solute in the above two basic flows are investigated. In the case of diffusion with a first order homogeneous reaction, in both the flows, the variation of permeability increases the effective dispersion coefficient while it decreases with increase in the magnetic parameter. In the case of diffusion combined with homogeneous and heterogeneous chemical reactions, the variation in permeability again increases the effective dispersion coefficient while with increase in magnetic parameter causes a decrease in the effective dispersion coefficient. Several earlier results follow as particular cases of the present study.     

Realistic modelling of textiles using interacting particle systems

This article describes a new technique for modelling the dynamic behaviour of elastic textiles. The technique is derived from cellular automata theory and describes the folds and wrinkles that can be seen on garments draped over one or more obstacles, the human body being one example. Integrating immovable objects into the model requires some form of collision and self-collision detection. Computing a final state on a normal PC is done in real time. Compared to other published methods, this new approach enables fast and flexible modelling that provides a realistic impression of elastic textile behaviour.     

Size and boundary effects on desiccation cracking in hardened cement paste

The density of cracks or size of fragments formed in hardened cement paste upon first drying is affected by specimen size as measured with a crack-impregnation technique in free shrinking specimens with a thickness of 4 cm. Fragment size on the drying surface increased with distance away from the specimen corner, resulting in smaller average surface crack densities in larger specimens. Size effect on three- dimensional crack density, that was measured from sections through the impregnated specimens, was weaker. The size effect is explained by higher residual thermal stresses in larger specimens due to the cement hydration process. For comparison a desiccation crack pattern in a 5-mm-thick cement paste layer on a marble substrate was studied. Residual thermal stresses in this specimen were probably low and a uniform crack-pattern with a Gaussian-like fragment size distribution formed.     

Positioning of goods in a cross-docking environment

Cross docking is one of the options to reduce lead times and inventories and to improve customer response time in supply chains. Cross-docking centres are dynamic environments where products arrive, are regrouped, and leave the same day. In this paper we focus on the process of short-term storage of unit-loads in a cross-docking environment. The goal is to determine temporary storage locations for incoming unit loads such that the travel distances of the forklift trucks with these unit loads are minimised. We model this problem as a novel application of the minimum cost flow problem and show the applicability of the model for different types of layouts and priorities. We demonstrate both the efficiency and effectiveness of the method in the operational and design phase at cross-docking environments by applying it to practice-oriented examples. Furthermore, we show that the approach is superior to a commonly used heuristic method.     

Hierarchical image segmentation based on similarity of NDVI time series

Although a variety of hierarchical image segmentation procedures for remote sensing imagery have been published, none of them specifically integrates remote sensing time series in spatial or hierarchical segmentation concepts. However, this integration is important for the analysis of ecosystems which are hierarchical in nature, with different ecological processes occurring at different spatial and temporal scales. Therefore, the objective of this paper is to introduce a multi-temporal hierarchical image segmentation (MTHIS) methodology to generate a hierarchical set of segments based on spatial similarity of remote sensing time series. MTHIS employs the similarity of the fast Fourier transform (FFT) components of multi-seasonal time series to group pixels with similar temporal behavior into hierarchical segments at different scales. Use of the FFT allows the distinction between noise and vegetation related signals and increases the computational efficiency. The MTHIS methodology is demonstrated on the area of South Africa in an MTHIS protocol for Normalized Difference Vegetation Index (NDVI) time series. Firstly, the FFT components that express the major spatio-temporal variation in the NDVI time series, the average and annual term, are selected and the segmentation is performed based on these components. Secondly, the results are visualized by means of a boundary stability image that confirms the accuracy of the algorithm to spatially group pixels at different scale levels. Finally, the segmentation optimum is determined based on discrepancy measures which illustrate the correspondence of the applied MTHIS output with landcover-landuse maps describing the actual vegetation. In future research, MTHIS can be used to analyze the spatial and hierarchical structure of any type of remote sensing time series and their relation to ecosystem processes.     

Fault-tolerance in balanced sorting networks

Much research has been done on sorting networks but there are very few results concerning their robustness. Our starting point is the balanced sorting network introduced by Dowd et al. and its single-block robust design of Rudolph obtained at the cost of some redundancy and two permuters external to the network. In this article we introduce a new implementation which is more robust than Rudolph's network and needs no redundancy or external permuters. We also consider a class of single-stage designs with redundancy and compare the characteristics of networks discussed.