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The flooding behaviour of two- and three-phase operating stirred reactors . The present state of research concerning the flooding behaviour of aerated fluids and suspensions is presented. The author's own investigations, undertaken partly on a semi-technical scale (tank diameter D = 1.5 m) show the most important parameters of this undesirable aerated state during the operation of stirred reactors. For a given stirrer speed the superficial gas velocity, the tank size, and the fluid viscosity are important. Solid particles sediment out when flooding is reached. An objective measuring method for determining the occurrence of flooding was adopted.     

Towards an optimised lab procedure for long-term oxidative ageing of asphalt mix specimen

Ageing of bitumen leads to increased stiffness and brittleness. Thus, bituminous bound pavements become more prone to failure by low-temperature and fatigue cracking. Therefore, the ageing behaviour of bitumen has a crucial impact on durability, as well as recyclability of pavements. To assess ageing of bitumen, the rolling thin film oven test and pressure ageing vessel are standardised methods for short-term and long-term ageing in the lab. For lab-ageing of hot mix asphalt (HMA), various methods have been developed in the last decades. This paper presents a study on the potential of employing a highly oxidant gas for simulating the long-term oxidative ageing of asphalt mix specimens in the lab. Based on the results, an optimised lab-ageing procedure (Viennese Ageing Procedure – VAPro) for compacted HMA specimens to assess mix performance of long-term lab-aged specimens is developed. Thus, it is possible to optimise mix design not only for short-term performance but to take into account effects of oxidative ageing during its in-service life. VAPro is based on a triaxial cell with forced flow of a gaseous oxidant agent through the specimen. The oxidant agent is enriched in ozone and nitric oxides to increase the rate of oxidation. It is shown by stiffness tests of unaged and lab-aged specimens, as well as by Dynamic Shear Rheometer tests of recovered binder from aged specimens that asphalt mixes can be long-term aged at moderate temperatures (+60°C) and within 4 days and a flow rate of 1 l/min by applying VAPro. Thus, an ageing procedure is at hand that can simulate long-term ageing at conditions that are representative of conditions that occur in the field within an efficient amount of time.     

A single crystal of YALO3: Ce3+ as a fast scintillator in SEM

A new single-crystal scintillator intended for applications in a scanning electron microscope (SEM) is presented. It is a single-crystal disc of yttrium aluminium perovskite activated by trivalent cerium free of traces of Fe ions. The single crystals of YAlO₃: Ce³⁺ (YAP: Ce³⁺) were prepared by the Czochralski method in a reducing atmosphere of Ar and H₂ with an excess amount of Y³⁺ ions. Effective methods of purification and purity control of the raw material are described. The highest achievable concentration of Ce³⁺ ions in as grown crystals amounted to 0.3 wt%, concentration in the melt was 8–9 times higher. The best properties were found with samples of the maximum possible concentration of Ce³⁺. Compared with the previous aluminate Y₃ Al₅ O₁₂: Ce³⁺ (YAG: Ce³⁺) these samples showed higher efficiency, a shorter decay time of luminescence (40 ns) and an emission band in a more advantageous spectral region (378 nm). Because of high resistance to radiation damage, high chemical resistance and applicability to ultra-high vacuum it is also suitable for detection of other kinds of ionizing radiation.     

Subtle but distinct impairments of rats with chemical lesions in the thalamic mediodorsal nucleus, tested in a radial arm maze.

Tested the performance of 18 hybrid BD9?×?BD10 rats trained in a radial arm maze before and after chemical lesions of the thalamic mediodorsal nucleus or the ventral tegmental area. Their behavior was compared with that of 18 sham-operated controls. Lesions were produced with ibotenic acid, a compound that selectively destroys neurons while apparently leaving fibers of passage intact. Results revealed no intergroup differences in the number of errors performed when all 6 trials were given in 1 session without interruption. The group with mediodorsal lesions, however, made significantly more errors than either of the other 2 groups when a delay of 1 hr was interposed between the 1st 4 and the last 2 trials. Furthermore, these Ss differed from Ss of the other groups in the number of sessions necessary to reach criterion, in the time needed to finish a session, and in the directness with which a goal was approached. Ss with lesions of the ventral tegmental area did not differ from Ss of the sham-operated control group in any of the measures taken. It is suggested that the deficits of rats with mediodorsal lesions resemble qualitatively those found in human patients with lesions of the mediodorsal nucleus. (63 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Rückgewinnung von Metallen aus niedrigkonzentrierten Lösungen

Recycling of metals from low concentrated solutions. A review is given of processes used for the separation of metals from aqueous solutions, especially low concentration waste waters. Purification processes for waste water used only to reach values set by law are compared with processes that allow recovery of metals. Precipitation with and without additives, adsorption, processes with ion exchange resins, solvent extraction and membrane processes, especially liquid membrane permeation, are described. As a result of these considerations, a qualitative comparison of all the described processes becomes possible. For the separation of zinc from a waste water stream, a special economic comparison is also shown between precipitation processes and the liquid membrane permeation process. Finally, the latest developments in the fields of solvent extraction and liquid membrane permeation are discussed.     

Texture crack detection

Automatic visual inspection has become one of the active research issues in machine vision technology in the past decades. Most of the methodologies developed address the problems of defect detection on a nontextured or regularly textured surface. However, problems in detecting defects on a randomly textured surface, especially cracks, have not received much attention. In this paper, we present a novel algorithm that uses a Wigner model to identify cracks in complex textural backgrounds, regardless of whether the inspected surface is randomly or regularly textured. We also investigate the windowing characteristics of the Wigner distribution and their impact on crack detection. Some of the Brodatz' natural texture images have been used for evaluating the performance of the algorithm. Promising results are obtained and presented in this paper.     

Smart Antennas with Two-Dimensional Array Configurations for Performance Enhancement of a Joint Detection CDMA Mobile Radio System

Smart antennas for base stations of cellular mobile radio systems offer the potential of system performance enhancement by taking advantage of the directionally inhomogeneous signal reception at the receiver. In this paper, two-dimensional array configurations employed at the uplink receiver of a joint detection CDMA (JD-CDMA) mobile radio system are investigated. This smart antenna concept can be split up into a novel channel estimator and data detector which incorporate explicitely the information of the direction-of-arrival (DOA) of signals emerging from users assigned to the considered base station. Proceeding from channel models that model the directional inhomogeneity of the mobile radio channel with single DOAs, the link level performance of a JD-CDMA mobile radio system using this smart antenna concept is evaluated for the rural propagation environment. The performance evaluation is based on Monte Carlo simulations of data transmission and average bit error rates versus the average signal to noise ratio per net information bit are presented for different array configurations. Although these results should be considered as upper bounds for the link level performance, they reveal the advantages of implementing two-dimensional array configurations at the uplink receiver of a JD-CDMA mobile radio system.     

ATP and Presentation Service for Mizar Formalizations

This paper describes the Automated Reasoning for Mizar ( $\textsf{Miz}\mathbb{AR}$ ) service, which integrates several automated reasoning, artificial intelligence, and presentation tools with Mizar and its authoring environment. The service provides ATP assistance to Mizar authors in finding and explaining proofs, and offers generation of Mizar problems as challenges to ATP systems. The service is based on a sound translation from the Mizar language to that of first-order ATP systems, and relies on the recent progress in application of ATP systems in large theories containing tens of thousands of available facts. We present the main features of $\textsf{Miz}\mathbb{AR}$ services, followed by an account of initial experiments in finding proofs with the ATP assistance. Our initial experience indicates that the tool offers substantial help in exploring the Mizar library and in preparing new Mizar articles.     

Fracture resistance of a doped PZT ceramic for multilayer piezoelectric actuators: Effect of mechanical load and temperature

The fracture resistance behaviour of a doped lead zirconate titanate (PZT) ceramic after combined thermo-mechanical loading is investigated between room temperature (RT) and 400 °C, i.e. above the Curie temperature (T_C). The thermal- and stress-induced depolarisation effects due to domain switching have been assessed by the indentation method on bulk PZTs. This has been extended to multilayered actuators. Experimental findings show a depolarisation effect with the temperature, which is significantly enhanced when combined with mechanical loading. This partial or even full depolarisation of the PZT material below T_C leads to important anisotropy effects in the fracture resistance of the piezo-ceramic, which should be taking into account in the design of multilayer actuators where the direction of crack propagation (i.e. parallel or normal to electrodes) can affect the actuator functionality.