The comparison of low‐velocity impact resistance of aluminum/carbon and glass fiber metal laminates

This article presents the low‐velocity impact response of fiber metal laminates, based on aluminum with a polymer composite, reinforced with carbon and glass fibers. The influence of fiber orientations as well as analysis of load‐time history, damage area and damage depth in relation to different energy levels is presented and discussed. The obtained results made it possible to determine characteristic points, which may be responsible for particular stages of the laminate structure degradation process: local microcracks and delaminations, leading to a decrease in the stiffness of the laminate, as well as further damage represented by laminate cracks and its perforation. The damage mechanism of fiber metal laminates is rather complex. In case of carbon fiber laminates, a higher tendency to perforation was observed in comparison to laminates containing glass fibers. Delaminations in composite interlayers and at the metal/composite interface constitute a significant damage form of fiber metal laminates resulting from dynamic loads. Fiber metal laminates with glass fibers absorb energy mainly through plastic deformation as well as through delamination initiation and propagation, whereas laminates containing carbon fibers absorb energy for penetration and perforation of the laminate. POLYM. COMPOS. 37:1056–1063, 2016. © 2014 Society of Plastics Engineers     

Determination of Gel Point of Epoxy Thermosets via Electric Resistance Measurements

A new, nickel‐coated graphite resistance‐change‐based method for gel‐point determination for epoxy‐based thermoset resins is presented and compared with DSC and rheological methods. Gelation times determined by this new method are in very good agreement with conventional techniques; this new method is potentially simpler and less time consuming than existing ones.

     

Benzene-induced hydro(solvo)thermal synthesis of Cu and Zn coordination polymers based on 1,3-benzenedicarboxylate

Hydro(solvo)thermal reactions of Cu(NO₃)₂·2.5H₂O or Zn(NO₃)₂·6H₂O with 1,3-H₂bdc provided two structurally different coordination polymers; a 2D network “metallacalixarene” based on the paddlewheel-type cluster with the formula [Cu(1,3-bdc)·H₂O]·H₂O (1) and a 3D framework [Zn(1,3-bdc)] (2), respectively. The use of a base was unnecessary in this synthesis; however, the presence of benzene played a crucial role in the crystallization of the desired products and could act as a template molecule in the synthesis of polymer (1). The unsaturated apical sites in the Cu₂ cluster of polymer (1) were occupied by water molecules, what consequently led to the structural decomposition of the framework after exposing the sample in air, which was not the case of the Zn-coordination polymer (2).     

A call to arms for task parallelism in multi‐scale materials modeling

Simulations based on multi‐scale material models enabled by adaptive sampling have demonstrated speedup factors exceeding an order of magnitude. The use of these methods in parallel computing is hampered by dynamic load imbalance, with load imbalance measurably reducing the achieved speedup. Here we discuss these issues in the context of task parallelism, showing results achieved to date and discussing possibilities for further improvement. In some cases, the task parallelism methods employed to date are able to restore much of the potential wall‐clock speedup. The specific application highlighted here focuses on the connection between microstructure and material performance using a polycrystal plasticity‐based multi‐scale method. However, the parallel load balancing issues are germane to a broad class of multi‐scale problems. Copyright © 2011 John Wiley & Sons, Ltd.     

Large scale multiple sequence alignment with simultaneous phylogeny inference

Multiple sequence alignment (MSA) and phylogenetic tree reconstruction are one of the most important problems in the computational biology. While both these problems are of great practical significance, in most cases they are very computationally demanding. In this paper we propose a new approach to the MSA problem which simultaneously infers an underlying phylogenetic tree. To process large data sets we provide parallel implementation of our method, which is based on the distributed caching of intermediate results. Finally, we show a parallel server designed for grid environments, and we report results of experiments performed with actual biological data, e.g. 1000 ribosomal RNA sequences.     

Structural aspects of the lindlar catalyst for selective hydrogenation

Unsupported intermetallic phases of palladium and lead, formed by reduction possess attractive catalytic properties for selective hydrogenation. The significance of the ease of reduction of divalent lead in Lindlar (supported) catalysts is also discussed.We thank the Science and Engineering Research Council for supporting this work.     

薄板的高阶振动

对薄板的高阶振动进行了讨论。应用模型基于Kirchhoff平板理论的假定和公差平均值的假定[Wo■ niak Cz,Wierzbicki E.Averaging techniques in thermomechanics of composite solids.Tolerance averaging versus homogenization.Poland,Czestochowa:Czestochowa University of Technology;2000],这使得模型可以考虑到周期单元对于整块板性能的影响。假设对周期单元振动的影响参数过多,可以对模型进行比基本振型更高阶的振动分析。这些函数是通过从边界条件中分离周期单元,对其自振时的特征值方程分析选取的近似值[JedrysiakJ.On vibrations of thin plates with one-dimensional periodic structure.Int J Eng Sci 2000;38:2023-2043]。通过应用平面板模型-正交各向异性模型、有限元模型和离散模型,对提议模型进行了论证。