Topology-preserving simplification of 2D nonmanifold meshes with embedded structures

Mesh simplification has received tremendous attention over the years. Most of the previous work in this area deals with a proper choice of error measures to guide the simplification. Preserving the topological characteristics of the mesh and possibly of data attached to the mesh is a more recent topic and the subject of this paper. We introduce a new topology-preserving simplification algorithm for triangular meshes, possibly nonmanifold, with embedded polylines. In this context, embedded means that the edges of the polylines are also edges of the mesh. The paper introduces a robust test to detect if the collapse of an edge in the mesh modifies either the topology of the mesh or the topology of the embedded polylines. This validity test is derived using combinatorial topology results. More precisely, we define a so-called extended complex from the input mesh and the embedded polylines. We show that if an edge collapse of the mesh preserves the topology of this extended complex, then it also preserves both the topology of the mesh and the embedded polylines. Our validity test can be used for any 2-complex mesh, including nonmanifold triangular meshes, and can be combined with any previously introduced error measure. Implementation of this validity test is described. We demonstrate the power and versatility of our method with scientific data sets from neuroscience, geology, and CAD/CAM models from mechanical engineering.     

Hydrogen production for fuel cells from the catalytic ethanol steam reforming

Alumina-supported rhodium catalysts were shown to be active, selective and stable catalysts in the catalytic ethanol steam reforming when the reaction is carried out under pressure (1.1 MPa). Both the nature of the metal precursor salt, the metal loading and the reaction conditions were shown to influence the activity, the selectivity and the stability of the catalysts. Some trends observed when the reaction is carried out under moderate pressure were shown to be different from the conclusions drawn from earlier results obtained at atmospheric pressure. In fact, rhodium catalysts derived from a chlorinated metal precursor were shown to be the most active, selective and stable.

     

A study of depth/texture bit-rate allocation in multi-view video plus depth compression

Multi-view video plus depth (MVD) data offer a reliable representation of three-dimensional (3D) scenes for 3D video applications. This is a huge amount of data whose compression is an important challenge for researchers at the current time. Consisting of texture and depth video sequences, the question of the relationship between these two types of data regarding bit-rate allocation often raises. This paper questions the required ratio between texture and depth when encoding MVD data. In particular, the paper investigates the elements impacting on the best bit-rate ratio between depth and color: total bit-rate budget, input data features, encoding strategy, and assessed view.     

Optimal configuration of assembly supply chains using analytical target cascading

This paper proposes to apply analytical target cascading (ATC) for configuring assembly supply chains with convergent structures. Individual enterprises in a supply chain are represented as separate elements in an ATC hierarchy. They are able to maintain autonomous and heterogeneous decision systems for optimising their private decision variables and objectives. They collaborate vertically and laterally along the ATC hierarchy through their common decisions to achieve the overall consistency and optimality. ATC offers a competitive balance between computational efficiency and effectiveness while providing an opportunity for parallel computation to further improve the efficiency. This paper also investigates the feasibility for individual enterprises to set local targets while participating in the supply chain configuration (SCC). SCC usually involves discrete decision variables, causing significant difficulties for existing ATC techniques to achieve system consistency. Therefore, a new consistency scheme has to be proposed in this paper, including two techniques: importance weighting factor (IWF) and dynamic constraints (DC). A case study is used to demonstrate the application of the ATC method for solving typical SCC problems. A series of comparative analyses are conducted to identify the strengths of the ATC method and demonstrate the effectiveness of the proposed consistency scheme.     

An Imbricate Finite Element Method (I-FEM) using full, reduced, and smoothed integration

A method to design finite elements that imbricate with each other while being assembled, denoted as imbricate finite element method, is proposed to improve the smoothness and the accuracy of the approximation based upon low order elements. Although these imbricate elements rely on triangular meshes, the approximation stems from the shape functions of bilinear quadrilateral elements. These elements satisfy the standard requirements of the finite element method: continuity, delta function property, and partition of unity. The convergence of the proposed approximation is investigated by means of two numerical benchmark problems comparing three different schemes for the numerical integration including a cell-based smoothed FEM based on a quadratic shape of the elements edges. The method is compared to related existing methods.     

Effects of high temperatures on mortar specimens containing Portland cement and GGBFS

During a fire, concrete is submitted to very high temperatures which can lead to structural collapse. The aim of this research is to study the behaviour of mortar specimens made of Portland cement and ground granulated blast furnace slag (GGBFS) which are heated to 900?°C. The samples are submitted to compressive and flexural strength tests and the microstructure is analysed by thermogravimetric analysis (TG and DTA), analysis and mercury intrusion porosimetry. The results indicate that a substitution rate of Portland cement by GGBFS of over 50?% gives residual compressive strengths that, after heating to 600?°C, are close to initial strengths before heating. The greater quantities of bound water, an acceleration of the hydration process due to heating and a lower porosity for specimens with GGBFS explain this increase. At 900?°C, the strong degradation of the microstructure results in strengths of less than 20?% of the initial strengths for specimens with or without GGBFS. Also, after cooling, the GGBFS reduces lime rehydration because of the decomposition of the portlandite between 450 and 550?°C, thus avoiding the risk of concrete cracking.     

Nt_STM: A step forward in Scanning Tunneling Microscopy (STM) simulations

We present the Nt_STM software suite designed to help analysis and interpretation of Scanning Tunneling Microscope (STM) images, via the simulation of STM data under different tip and bias conditions and facilitating their comparison against the experimental ones. The Nt_STM package includes two components: (i) an intuitive and directive Graphical User Interface (GUI) designed to build a precise model of the STM set-up and analyze the simulation results and, (ii) a powerful simulation engine (GREEN) allowing an efficient, yet accurate, calculation of the tunneling current necessary to generate current or topographic images, I(V) spectra as well as various properties such as band structures, Local Density Of State (LDOS), etc. The Nt_STM package, at its current version 2.0, gives the opportunity to access parallel computation, a new collection of objects and new Extended Hückel parameters.     

Solid-spaced filters: an alternative for narrow-bandpass applications

Solid-spaced filters are composed of one or several thin wafers of excellent optical quality acting as Fabry-Perot spacer layers. We study the different steps of the design and the manufacture of filters following dense-wavelength-division-multiplexing specifications. The design method of such filters requires a tight synergy between numerical simulations and experimental characterizations to correct possible thickness errors. Experimental results of the manufacture and characterization of a three-cavity narrow-bandpass filter and of an interleaver filter are given.     

Large-scale optical-field measurements with geometric fibre constructs

Optical fields are measured using sequential arrangements of optical components such as lenses, filters, and beam splitters in conjunction with planar arrays of point detectors placed on a common axis. All such systems are constrained in terms of size, weight, durability and field of view. Here a new, geometric approach to optical-field measurements is presented that lifts some of the aforementioned limitations and, moreover, enables access to optical information on unprecedented length and volume scales. Tough polymeric photodetecting fibres drawn from a preform are woven into light-weight, low-optical-density, two- and three-dimensional constructs that measure the amplitude and phase of an electromagnetic field on very large areas. First, a three-dimensional spherical construct is used to measure the direction of illumination over 4pi steradians. Second, an intensity distribution is measured by a planar array using a tomographic algorithm. Finally, both the amplitude and phase of an optical wave front are acquired with a dual-plane construct. Hence, the problem of optical-field measurement is transformed from one involving the choice and placement of lenses and detector arrays to that of designing geometrical constructions of polymeric, light-sensitive fibres.