Crystallization behavior of polymer/montmorillonite nanocomposites. Part II. Intercalated poly(ε-caprolactone)/montmorillonite nanocomposites

The combination of surfactant modified montmorillonite (MMT) silicate layers, poly(ε-caprolactone) (PCL) and the adopted melt processing procedure results in intercalated nanocomposites in which the silicate layers act as nucleating agents for the crystallization of the PCL matrix and by which in turn the overall crystallization rate increases. At a sufficiently high MMT concentration and degree of supercooling the polymer-swollen silicate layer stacks disturb crystal growth, resulting in a decrease in the overall crystallization rate. Simultaneous, time resolved, synchrotron small and wide angle X-ray scattering experiments reveal that—when the retarding effect is absent at a sufficiently high temperature—the final semicrystalline structures of pure PCL and its nanocomposites are identical. The poorer nucleation in the case of pure PCL, however, results in a time wise smearing of primary and secondary crystallization whereas in the nanocomposites these events are well separated due to a nucleation induced, efficient and rapid primary crystallization. Secondary crystallization involves the insertion of new lamellar crystals in between the already existing ones.     

Verification of randomized consensus algorithms under round-rigid adversaries

International Journal on Software Tools for Technology Transfer - Randomized fault-tolerant distributed algorithms pose a number of challenges for automated verification: (i) parameterization in...     

Effects of Al:Si and (Al + Na):Si ratios on the properties of the international simple glass,part II: Structure

High-alumina containing high-level waste (HLW) will be vitrified at the Waste Treatment Plant at the Hanford Site. The resulting glasses, high in alumina, will have distinct composition-structure-property (C-S-P) relationships compared to previously studied HLW glasses. These C-S-P relationships determine the processability and product durability of glasses and therefore must be understood. The main purpose of this study is to understand the detailed structural changes caused by Al:Si and (Al + Na):Si substitutions in a simplified nuclear waste model glass (ISG, international simple glass) by combining experimental structural characterizations and molecular dynamics (MD) simulations. The structures of these two series of glasses were characterized by neutron total scattering and ²⁷Al, ²³Na, ²⁹Si, and ¹¹B solid-state nuclear magnetic resonance (NMR) spectroscopy. Additionally, MD simulations were used to generate atomistic structural models of the borosilicate glasses and simulation results were validated by the experimental structural data. Short-range (eg, bond distance, coordination number, etc) and medium-range (eg, oxygen speciation, network connectivity, polyhedral linkages) structural features of the borosilicate glasses were systematically investigated as a function of the degree of substitution. The results show that bond distance and coordination number of the cation-oxygen pairs are relatively insensitive to Al:Si and (Al + Na):Si substitutions with the exception of the B-O pair. Additionally, the Al:Si substitution results in an increase in tri-bridging oxygen species, whereas (Al + Na):Si substitution creates nonbridging oxygen species. Charge compensator preferences were found for Si-[NBO] (Na⁺), ^[3]B-[NBO] (Na⁺), ^[4]B (mostly Ca²⁺), ^[4]Al (nearly equally split Na⁺ and Ca²⁺), and ^[6]Zr (mostly Ca²⁺). The network former-BO-network former linkages preferences were also tabulated; Si-O-Al and Al-O-Al were preferred at the expense of lower Si-O-^[3]B and ^[3]B-O-^[3]B linkages. These results provide insights on the structural origins of property changes such as glass-transition temperature caused by the substitutions, providing a basis for future improvements of theoretical and computer simulation models.     

INSIGMA: an intelligent transportation system for urban mobility enhancement

Intelligent Transportation Systems (ITS) aim to improve safety, mobility and environmental performance of road transport. The INSIGMA project provides a fresh look at the possible innovations in this field, by enhancing the functionality and accuracy of ITS in urban environments. This paper describes the architecture, sensors, processing algorithms, output modules and advantages of the developed system. A comparison of existing ITS systems has been provided as background. Special attention has been given to performance and privacy issues, as the system includes social aspects such as location monitoring.     

HFPaC: GPU friendly height field parallel compression

In this paper, we present a novel method for fast lossy or lossless compression and decompression of regular height fields. The method is suitable for SIMD parallel implementation and thus inherently suitable for modern GPU architectures. Lossy compression is achieved by approximating the height field with a set of quadratic Bezier surfaces. In addition, lossless compression is achieved by superimposing the residuals over the lossy approximation. We validated the method’s efficiency through a CUDA implementation of compression and decompression algorithms. The method allows independent decompression of individual data points, as well as progressive decompression. Even in the case of lossy decompression, the decompressed surface is inherently seamless. In comparison with the GPU-oriented state-of-the-art method, the proposed method, combined with a widely available lossless compression method (such as DEFLATE), achieves comparable compression ratios. The method’s efficiency slightly outperforms the state-of-the-art method for very high workloads and considerably for lower workloads.     

The making of the Xian terra‐cotta soldiers

Abstract

This paper describes the making of a short film on the Xian terra‐cotta soldiers using our integrated HU‐MANOID software. The method of creating and animating the soldiers’ faces is first presented. Then, we show how our approach, based on metaballs and spline surfaces, was used for designing and deforming soldiers’ bodies. For the animation of the bodies, we describe the motion control methods. Clothes for the soldiers are then described as well as horses and decor design. For the rendering, we explained our strategy using parallel machines. Finally, problems of integration are addressed.     

A novel electromyographic signal simulator for muscle contraction studies

Mathematical simulation has been widely used in biomedical and biological sciences. In the case of the surface electromyographic (SEMG) activity, some models have been proposed aiming to study muscle contraction strategies that are used during different tasks and conditions. Most of SEMG simulators are based on energy modulation of a Gaussian noise. This work proposes a novel simulator in which the user-defined parameters are associated with the motor units (MUs) recruitment and their firing rate. Comparison between the mean spectrum of real SEMG signals collected in isometric contraction of the muscle biceps brachii and the mean spectrum obtained from simulated SEMG signals showed a good agreement, pointing the proposed simulator seems to be capable to generate consistent electromyographic signals in time and frequency domains and that can be used in many studies, in particular in the evaluation of automatic methods aimed to detect muscular contraction.     

Towards interactive simulation in automotive design

One of the important tasks in Mechanical Engineering is to increase the safety of the vehicle and decrease its production costs. This task is typically solved by means of Multiobjective Optimization, which formulates the problem as a mapping from the space of design variables to the space of target criteria and tries to find an optimal region in these multidimensional spaces. Due to high computational costs of numerical simulations, the sampling of this mapping is usually very sparse and scattered. Combining design of experiments methods, metamodeling, new interpolation schemes and innovative graphics methods, we enable the user to interact with simulation parameters, optimization criteria, and come to a new interpolated crash result within seconds. We denote this approach as Simulated Reality, a new concept for the interplay between simulation, optimization and interactive visualization. In this paper we show the application of Simulated Reality for solution of real life car design optimization problems.

Decomposition Approaches for Constrained Spatial Auction Market Problems

We consider several equilibrium formulations for the problem of managing spatially distributed auction markets of a homogeneous commodity, which are joined by transmission lines in a network. At each market, traders and buyers are determined by their price functions and choose their offer/bid values. We present equivalent variational inequality, optimization, and saddle point formulations of this problem. The corresponding models possess a special structure of constraint and cost functions and lead to different decomposition schemes. We propose proximal and splitting type methods and discuss their properties and preliminary computational results.     

The ortho-to-para conversion in solid hydrogen,catalyzed by hydrogen atoms

The combined techniques of ESR and NMR were used to investigate the process of ortho-para conversion in solid molecular hydrogen, containing small amounts ( 500 ppm) of hydrogen atoms as impurity. Although the impurity atoms catalyze the effective conversion of the neighboring ortho-H₂, the total catalyzed conversion rate at temperatures from 2.2 K to 4.4 K is much less than expected from the rate of the H atoms recombination. A possible explanation is given in terms of the diffusion of H atoms, which is confined to some defects in the crystal.