Thermodynamic conditions for stability in materials with rate-independent dissipation

A distinctive feature of the examined class of solids is that a part of the entropy production is due to rate-independent dissipation, as in models of plasticity, damage or martensitic transformations. The standard condition for thermodynamic stability is shown to be too restrictive for such solids and, therefore, an extended condition for stability of equilibrium is developed. The classical thermodynamic theory of irreversible processes is used along with the internal variable approach, with the emphasis on the macroscopic effects of micro-scale instabilities in the presence of two different scales of time. Specific conditions for material stability against internal structural rearrangements under deformation-sensitive loading are derived within the incremental constitutive framework of multi-mode inelasticity. Application to spontaneous formation of deformation bands in a continuum is presented. Conditions for stability or instability of a quasi-static process induced by varying loading are given under additional constitutive postulates of normality and symmetry. As illustration of the theory, the stability of equilibrium or a deformation path under uniaxial tension is analysed for a class of inelastic constitutive laws for a metal crystal deformed plastically by multi-slip or undergoing stress-induced martensitic transformation.     

Producing High‐Strength Metals by I‐ECAP

Incremental equal channel angular pressing (I‐ECAP) is used in this work to produce ultrafine‐grained (UFG) pure iron, aluminum alloy 5083, commercial purity titanium (grade 4), and magnesium alloy AZ31B. Pure iron is processed at room temperature, aluminum alloy at 200 °C, titanium at 320 °C, and magnesium alloy at 150 °C. Strength improvement, attributed to the grain refinement below 1 μm, is reported for all processed materials. The yield strength increase is the most apparent in pure iron, reaching almost 500 MPa after one pass of I‐ECAP, comparing to 180 MPa in the as‐forged conditions. UFG titanium, aluminum, and magnesium alloys obtained in this study reached yield stress of 800, 350, and 300 MPa, respectively, in each case exhibiting the yield strength increase by at least 30%, comparing to the alloys processed by conventional metal forming operations such as forging and rolling.     

Intelligent information processing for building university knowledge base

There are many ready-to-use software solutions for building institutional scientific information platforms, most of which have functionality well suited to repository needs. However, there have already been discussions about various problems with institutional digital libraries. As a remedy, an approach that is researcher-centric (rather than document-centric) has been proposed recently in some systems. This paper is devoted to research aimed at tools for building knowledge bases for university research. We focus on the AI methods that have been elaborated and applied practically within our platform for building such knowledge bases. In particular we present a novel approach to data acquisition and the semantic enrichment of the acquired data. In addition, we present the algorithms applied in the real life system for experts profiling and retrieval.     

FARICS: a method of mining spatial association rules and collocations using clustering and Delaunay diagrams

The paper presents problems pertaining to spatial data mining. Based on the existing solutions a new method of knowledge extraction in the form of spatial association rules and collocations has been worked out and is proposed herein. Delaunay diagram is used for determining neighborhoods. Based on the neighborhood notion, spatial association rules and collocations are defined. A novel algorithm for finding spatial rules and collocations has been presented. The approach allows eliminating the parameters defining neighborhood of objects, thus avoiding multiple “test and trial” repetitions of the process of mining for various parameter values. The presented method has been implemented and tested. The results of the experiments have been discussed.     

Features of network formation in the chain crosslinking (co)polymerization

Summary Analysis of experimental results on the chain (co) polymerization of bisunsaturated monomers suggests that cyclization plays a decisive role already at the onset of the reaction. At medium and elevated concentrations of the bisunsaturated compound, compact microgel-like particles are formed, which give rise to a gel mainly by participating in the polymerization reaction only with pendant double bonds in their surface layer, and not with double bonds in the interior. This mechanism is reflected in an apparent decrease in reactivity of the pendant double bonds.     

Modeling the Multi-Stage Classification in a Fluidized Bed Jet Mill

The research and modeling the classification effects in a fluidized bed opposed jet mill are presented. Particle distribution is the result of the interaction between two stages of classification in this mill: gravity classification above the bed, and centrifugal classification in a mill classifier. The objective of the study is to develop a model of multi-stage classification and apply in to the process in question. The universal algorithm of constructing the matrix model of arbitrary complex classification circuit is proposed and the example of its application to modeling the classification in the mill is presented. The experimental identification of the model parameters was carried out.     

Architectural Decomposition of Video Decoders by Meansof an Intermediate Data Stream Format

The microprocessor industry trend towards many-core architectures introduced the necessity of devising appropriately scalable applications. While implementing software based video decoding, the main challenges are the optimized partitioning of decoder operations, efficient tracking of dependencies and resource synchronization for multiple parallel units. The same applies for hardware implementations of video decoders where monolithic approaches anticipate scalability of the design and reusability of already implemented core components.In this paper, we propose an intermediate data stream format (Meta Format Stream) which is suited for architectural decomposition of video decoding by replacing the conventional monolithic decoder architecture design with a pipelined structure. The Meta Format is forward-oriented and self contained and multistandard capable, so that processing of Meta Streams is independent of the originating bit stream. Our approach does not require special coding settings and is applicable to accelerated decoding of any standards-compliant bit stream. A H.264/AVC multiprocessing proposal is presented as a case study for the potential our our concept. The case study combines coarse grained frame-level parallel decoding of the bit stream with fine-grained macroblock level parallelism in the image processing stage.The proposed H.264 decoder achieved speedup factors of up to 7.6 on an 8 core machine with 2-way SMT. We are reporting actual decoding speeds of up to 150 frames per second in 2160p-resolution.     

Crystallization of different polypropylene matrices in the presence of wood fillers

The increasing global energy crisis and ecological risks in recent years have led to the interest in lignocellulosic fillers reinforced polymer composites. In this study, the nucleation ability of pine wood in polypropylene (PP) matrices was studied by differential scanning calorimetry. PPs with different melt flow index values (in range 3.2–25 g/10 min.) were used as the polymer matrix. Moreover, a new technique of wood treatment using γ‐irradiation was used. The experimental results clearly show that the nucleation activity of the wood particles is strongly dependent on the rheological parameter (e.g., MFI) of PP matrix. The composites containing PP matrix with lower MFI exhibited higher degree of crystal conversion, lower half‐times of crystallization, and higher crystallization temperatures. Moreover, the applied γ‐irradiation of wood resulted in a negative effect on the crystallization rate of PP matrix and a distinct deterioration of the nucleation ability of wood surface. The interesting differences in nucleation activity of wood have been interpreted in the context of polymer chains length and relaxation times during crystallization. This article will spotlight the nucleating efficiency of filler, which is critical in polymer processing e.g., optimization of injection molding cycle time of composite materials. POLYM. COMPOS., 36:1813–1818, 2015. © 2014 Society of Plastics Engineers     

Melnikov Functions in Quadratic Perturbations of Generalized Lotka–Volterra Systems

Journal of Dynamical and Control Systems - We present a detailed analysis of Melnikov functions which arise in quadratic perturbations of generalized Lotka–Volterra vector fields with the...     

Structural Characterization of EnpA D,L-Endopeptidase from Enterococcus faecalis Prophage Provides Insights into Substrate Specificity of M23 Peptidases

The best-characterized members of the M23 family are glycyl-glycine hydrolases, such as lysostaphin (Lss) from Staphylococcus simulans or LytM from Staphylococcus aureus. Recently, enzymes with broad specificities were reported, such as EnpA_CD from Enterococcus faecalis, that cleaves D,L peptide bond between the stem peptide and a cross-bridge. Previously, the activity of EnpA_CD was demonstrated only on isolated peptidoglycan fragments. Herein we report conditions in which EnpA_CD lyses bacterial cells live with very high efficiency demonstrating great bacteriolytic potential, though limited to a low ionic strength environment. We have solved the structure of the EnpA_CD H109A inactive variant and analyzed it in the context of related peptidoglycan hydrolases structures to reveal the bases for the specificity determination. All M23 structures share a very conserved β-sheet core which constitutes the rigid bottom of the substrate-binding groove and active site, while variable loops create the walls of the deep and narrow binding cleft. A detailed analysis of the binding groove architecture, specificity of M23 enzymes and D,L peptidases demonstrates that the substrate groove, which is particularly deep and narrow, is accessible preferably for peptides composed of amino acids with short side chains or subsequent L and D-isomers. As a result, the bottom of the groove is involved in interactions with the main chain of the substrate while the side chains are protruding in one plane towards the groove opening. We concluded that the selectivity of the substrates is based on their conformations allowed only for polyglycine chains and alternating chirality of the amino acids.