Microstructure Evolution as an Effect of Strain Reversal During the Hot Deformation of Microalloyed Steels

Susceptibility of the steel for further cold processing strongly depends on the whole prior history of deformation in the hot working regime.In the industrial hot working processes,e.g.at the roughing stage of hot rolling,or forging,material undergoes complex deformation modes that leads to gradients of both microstructure and properties across the deformed cross-section.Torsion and multiaxial compression tests with different amounts of strain reversals were conducted at elevated temperatures to study the effect of applied strain path on the phenomena occurring during microstructure evolution of Nb-microalloyed steels.Gathered results will provide data for the modification of existing constitutive equations that mostly do not account for the strain path changes.Better through-process modelling will then enable to achieve better properties and quality of the products for further cold processing.     

Epileptic seizure detection.

In this study, radial basis function (RBF) neural networks are used to identify seizure or preseizure states. As input to the RBF networks the study used raw EEG data, coefficients from a Fourier transform, and wavelet decomposition of the raw data. An RBF network consists of an input layer, a single hidden layer, and an output node. The use of half-second windows of raw data as input demonstrates the ability of the RBF network to learn differences in the patterns of ictal and interictal EEG data without feature extraction. Wavelet decomposition of the narrow window of raw data improves performance while transformation of a wider window, up to about five seconds, improves it even further. The ability of wavelet decomposition to transform five seconds of raw data into a vector of manageable length without substantial loss of relevant information makes it an effective tool for preprocessing EEG data     

Microstructure-Sensitive Computational Estimates of Driving Forces for Surface Versus Subsurface Fatigue Crack Formation in Duplex Ti-6Al-4V and Al 7075-T6

Statistical realizations of three-dimensional digital microstructures with different crystallographic orientation distributions, grain shapes, and grain size distributions are subjected to uniaxial cyclic straining to compare the cases of bulk and free surface on driving forces for fatigue crack formation. Crystal plasticity finite element simulations are conducted using both fully periodic (more representative of the bulk) and traction-free (i.e., free surface) boundary conditions for duplex Ti-6Al-4V and rolled Al 7075-T6. Following elastic–plastic shakedown, mesoscale volume-averaged fatigue indicator parameters (FIPs) are computed within fatigue damage process zones of grains and are fit to known extreme value distributions (EVDs). Owing to differences in crystallographic slip symmetry, FIPs for fcc Al 7075-T6 statistically occur much closer to the traction-free surface than for hcp Ti-6Al-4V. Additionally, surface versus bulk EVDs of FIPs vary differently for the two material systems, indicating a coupled role of microstructure and surface proximity that had not been previously elucidated.

     

X-ray Microtomography Analysis of the Aluminum Alloy Composite Reinforced by SiC After Friction Stir Processing

Despite many years of using friction stir processing (FSP), there are many unexplained aspects concerning the processes which appear during FSP: determining the direction of flow and mixing of the materials and the degree of mixing and microstructure fragmentation in specific areas. This paper presents the impact of FSP on the micro- and macrostructure of the composite with hypo-eutectic Si matrix reinforced by SiC particles. The analysis of the structure of the processed area in FSP in the relation to the microstructure of the base material has been made using x-ray microtomography. The results of these studies have been juxtaposed with studies using microscopic methods (light microscopy and SEM). The microtomography images revealed an additional separation on the advancing side and the weld nugget, where on the basis of a 3D reconstruction a layer microstructure on the direction of linear movement of the tool has been demonstrated. The analyses have revealed a limited flow of the material above the weld nugget. The main advantages of the research method applied were the possibility to show the invisible or barely visible elements of the microstructure using standard test methods and the ability to analyze the microstructure changes uninterruptedly in different directions in the volume of the material.     

Framework for application management with dynamic aspects J-EARS case study

The cost of computer system maintenance rises together with the increasing complexity of such systems. The use of an autonomic system architecture saves money by delegating some forms of maintenance to the systems themselves. The aim of this paper is to describe the results of creating a tool which introduces elements of adaptivity to Java applications using dynamic aspects. The impact of introducing aspects on the performance of various Application Servers is also discussed. Finally, benefits and problems arising from the use of the tool are presented, basing on sample use cases.     

Calcium Ions Regulate K+ Uptake into Brain Mitochondria: The Evidence for a Novel Potassium Channel

The mitochondrial response to changes of cytosolic calcium concentration has a strong impact on neuronal cell metabolism and viability. We observed that Ca²⁺ additions to isolated rat brain mitochondria induced in potassium ion containing media a mitochondrial membrane potential depolarization and an accompanying increase of mitochondrial respiration. These Ca²⁺ effects can be blocked by iberiotoxin and charybdotoxin, well known inhibitors of large conductance potassium channel (BK_Ca channel). Furthermore, NS1619 – a BK_Ca channel opener – induced potassium ion–specific effects on brain mitochondria similar to those induced by Ca²⁺. These findings suggest the presence of a calcium-activated, large conductance potassium channel (sensitive to charybdotoxin and NS1619), which was confirmed by reconstitution of the mitochondrial inner membrane into planar lipid bilayers. The conductance of the reconstituted channel was 265 pS under gradient (50/450 mM KCl) conditions. Its reversal potential was equal to 50 mV, which proved that the examined channel was cation-selective. We also observed immunoreactivity of anti-β₄ subunit (of the BK_Ca channel) antibodies with ~26 kDa proteins of rat brain mitochondria. Immunohistochemical analysis confirmed the predominant occurrence of β₄ subunit in neuronal mitochondria. We hypothesize that the mitochondrial BK_Ca channel represents a calcium sensor, which can contribute to neuronal signal transduction and survival.     

Use of the finite elements method for modelling the dynamic load impact on hydraulic leg equipped with gas accumulator

Procedures of preparation of numerical analysis, consisting in a simulation of cooperation of three different media: steel, liquid and gas undergoes dynamic load were discussed. Modelling of the initial static load of the mechanical system was presented. By using the MSC. Software products the following exemplary computer simulations were made: dynamic load impact on the hydraulic leg as well as effectiveness of the hydraulic leg protection against overload with help of gas accumulator.     

Tribological Properties of the Oxide Coatings Produced onto 6061-T6 Aluminum Alloy in the Hard Anodizing Process

The aim of this work was to establish the influence of the thickness of the anodic coatings on their mechanical properties and to understand the relation between their hardness and the abrasion resistance. The coatings were produced in the hard anodizing process onto the 6061-T6 aluminum alloy. Their thickness was in the range between 19 and 43 µm. The abrasion resistance was determined by using Taber abrasion test. The weight losses of the coatings obtained were in the range between 15 and 11 mg and decreased with their increasing thickness. It has been shown that the hardness measured on the cross sections of the coatings did not correspond to their abrasion resistance. Thus, the new approach has been proposed. The hardness of the coatings was estimated on the basis of the results of the scratch test performed at the constant load. The results obtained correspond to the abrasion resistance of the coatings.     

Drying of Herbal Product in Closed System

A new product from a low temperature drying method that reduces the loss of highly volatile essential oils is presented. The proposed drying method consists of evaporation/sublimation of water and aromatic substances in a dryer with a closed drying agent cycle. In parallel, the evaporated compounds are continuously condensed in a heat exchanger. As a result of the drying process, high-quality dried plants and Fluidolat as liquid phase containing water and volatile organic compounds are obtained. The aim of presented investigations was to optimize the developed technology for the herb lavender.