A comparative analysis of contact algorithms in contact shape optimization problems

This paper presents a comparative analysis of contact algorithms used for solving contact shape optimization problems. Specifically, a nonlinear, feasible direction interior point method (FDIPM) for the frictional contact analysis of hyperelastic materials has been implemented in which the friction is introduced using the return mapping approach. This comparative investigation aims to find the cause of instability in sensitivity of the contact pressure nonuniformity (CPN). The results obtained by the FDIPM are found to be comparable with those by the penalty methods (PM) and the augmented Lagrange multiplier methods (ALMM); however, the FDIPM possesses advantages, including good convergence and convenience in modeling. Furthermore, the basic cause of the unstable sensitivity is revealed to be the discretization of the finite element method, which causes the discontinuous increase of contact area with respect to the continuous increase of contact load. To improve the stability of the CPN, an adaptive post-processing technique is proposed.     

Biosorption potential of the mediterranean plant (Posidonia oceanica) for the removal of Cu2+ ions from aqueous media : Equilibrium,kinetic, thermodynamic and mechanism analysis

The biosorption characteristics of copper(II) ions using Posidonia oceanica biomass were investigated. Experimental parameters affecting the biosorption process such as pH level, contact time, biosorbent dosage and temperature were studied. The equilibrium data were applied to the Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherm models. The Langmuir model fitted very well the equilibrium data, and the maximum uptake of Cu(II) by Posidonia oceanica was found to be 76.92 mg/g. The mean free energy E (10.78 kJ/mol) from the D-R isotherm indicated a chemical ion-exchange mechanism. Kinetic results showed that the pseudo-second-order kinetic model was well fitted to the experimental data. Thermodynamic parameters depicted the exothermic nature of biosorption and the process was feasible and spontaneous. The results of FTIR (Fourier-transform infrared spectroscopy) revealed that carboxyl, amine, and hydroxyl groups on the biomass surface were involved in the biosorption of Cu(II) ions.     

Ontology-Centered Knowledge Management Using Information Retrieval Techniques

The paper argues that an effective solution to information and knowledge management (KM) needs of practitioners in the construction industry can be found in the provision of an adapted knowledge environment that makes use of user profiling and document summarization techniques based on information retrieval sciences. The conceptualization of the domain through ontology takes a pivotal role in the proposed knowledge environment and provides a semantic referential to ensure relevance, accuracy, and completeness of information. A set of KM services articulated around the selected ontology have been developed, using the Web services model, tested, and validated in real organizational settings. This provided the basis for formulating recommendations and key success factors for any KM project development.     

Activity Awareness as an Enabler for Communication and Network Building in Construction Design Teams

The paper reports on ongoing research into the facilitation of communication in distributed design teams of the type typically encountered in the construction sector. Ideas around social aspects in such design teams are discussed followed by our previous research efforts as an evolutionary process that has led us to develop in this direction. It is argued that facilitating timely and contextually grounded communication in a distributed environment can help to build the social networks and associated social capital common in collocated design teams but often absent in distributed ones. We describe our framework for providing such facilitation through monitoring and awareness of the information “space” of a construction project. We believe that by leveraging the relationships in the information space, we can go some way to identifying those individuals who would benefit from developing interpersonal relations in their work and further by exploiting those relationships in real time we can accelerate the formation of personal social networks and social capital between those individuals.     

Ethylene‐methyl acrylate‐glycidyl methacrylate toughened poly(lactic acid) nanocomposites

Poly (lactic acid) (PLA) was melt blended in a twin screw extruder using an ethylene‐methyl acrylate‐glycidyl methacrylate rubber as a toughener. PLA/rubber blends were immiscible as observed by scanning electron microscopy. Impact strength and ductility of PLA were improved by the addition of the rubber at the expense of strength and stiffness. An organo‐montmorillonite (OMMT) was used at 2 wt % to counteract the negative effect of the rubber on modulus, and balanced properties were observed at 10 wt % rubber content. X‐ray diffraction and transmission electron microscopy revealed the formation of intercalated/exfoliated structure in the ternary nanocomposites. Thermal behavior analysis indicated that the degree of crystallinity is slightly affected by the clay and the rubber. Both the clay and the rubber decreased the crystallization temperature of PLA and acted as nucleating agents for PLA. The viscosity of the mixtures as measured by melt flow index was highly influenced by the rubber and the OMMT. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Intra- and Interorganizational Knowledge Services to Promote Informed Sustainability Practices

To promote sustainable construction, the construction industry needs to intensify its efforts to move to a knowledge intensive mode. Sustainability goals can only be achieved if new resources of knowledge and expertise inform construction activities. Some of this comes in the form of good practice and standards, but much will have to come from situated and contextual appreciations of sustainability goals and local practices developed across organizational, professional, and multicultural boundaries. The paper describes a knowledge management environment based on the web-services model aimed at promoting informed sustainability practices. This validation of the knowledge environment provided the basis for formulating recommendations for promoting knowledge-based sustainable construction.     

Microarchitected Stretching‐Dominated Mechanical Metamaterials with Minimal Surface Topologies

Historically, the creation of lightweight, yet mechanically robust, materials have been the most sought‐after engineering pursuit. For that purpose, research efforts are dedicated to finding pathways to emulate and mimic the resilience offered by natural biological systems (i.e., bone and wood). These natural systems evolved over time to provide the most attainable structural efficiency through their architectural characteristics that can span over multiple length scales. Nature‐inspired man‐made cellular metamaterials have effective properties that depend largely on their topology rather than composition and are hence remarkable candidates for a wide range of application. Despite their geometrical complexity, the fabrication of such metamaterials is made possible by the emergence of advanced fabrication techniques that permit the fabrication of complex architectures down to the nanometer scale. In this work, we report the fabrication and mechanical testing of nature‐inspired, mathematically created, micro‐architected, cellular metamaterials with topologies based on triply periodic minimal surfaces (TPMS) with cubic symmetries fabricated through direct laser writing two‐photon lithography. These TPMS‐based microlattices are sheet/shell‐ and strut‐based metamaterials with high geometrical complexity. Interestingly, results show that TPMS sheet‐based microlattices follow a stretching‐dominated mode of deformation, and further illustrate their mechanical superiority over the traditional and well‐known strut‐based microlattices and microlattice composites. The TPMS sheet‐based polymeric microlattices exhibited mechanical properties superior to other micrloattices comprising metal‐ and ceramic‐coated polymeric substrates and, interestingly, are less affected by the change in density, which opens the door for fabricating ultralightweight materials without much sacrificing mechanical properties.

     

Mixing Static and Dynamic Partitioning to Parallelize a Constraint Programming Solver

This paper presents an external parallelization of Constraint Programming (CP) search tree mixing both static and dynamic partitioning. The principle of the parallelization is to partition the CP search tree into a set of sub-trees, then assign each sub-tree to one computing core in order to perform a local search using a sequential CP solver. In this context, static partitioning consists of decomposing the CP variables domains in order to split the CP search tree into a set of disjoint sub-trees to assign them to the cores. This strategy performs well without adding an extra cost to the parallel search, but the problem is the load imbalance between computing cores. On the other hand, dynamic partitioning is based on preservation of the search state to generate, dynamically or on demand, the sub-trees that are assigned to the cores. This strategy offers good load balancing between the different computing cores, but computing overcosts appear due to the initialisation of the search when a sub-tree is migrated from one core to another. In this paper, we propose a new partitioning strategy that mixes the static and dynamic partitioning and enjoys the benefits of each strategy. This mixed partitioning is designed to run on shared and distributed memory architectures. The performances obtained are illustrated by solving the CP problems modelled using the FlatZinc format and solved using the Google OR-Tools solver on top of the parallel Bobpp framework.     

Change detection in urban areas from remote sensing data: a multidimensional classification scheme

Change detection (CD) from remote sensing data is a very challenging research problem, especially when we analyse an urban scene. Urban scenes are composed of many different types of objects, both natural and man-made. The building class is one of the important and most complex classes to analyse, important because it is useful for so many applications and complex because it exhibits many changes due to human activity and natural catastrophes. For these reasons, we focus our study on building change detection (BCD). In this paper we propose a classification scheme for BCD research according to several important dimensions including objective, input data, temporal resolution, analysis unit, target output unit, building features, processing technique, change categories, and assessment of results. This classification scheme can guide practitioners in choosing appropriate change detection methods to achieve their goals as well as informing new research efforts. Based on this multidimensional characterisation of BCD, we offer a number of suggestions for further work to be done in this field.