Detecting communities of triangles in complex networks using spectral optimization

The study of the sub-structure of complex networks is of major importance to relate topology and functionality. Many efforts have been devoted to the analysis of the modular structure of networks using the quality function known as modularity. However, generally speaking, the relation between topological modules and functional groups is still unknown, and depends on the semantic of the links. Sometimes, we know in advance that many connections are transitive, and as a consequence, triangles have a specific meaning. Here we propose the study of the modular structure of networks considering triangles as the building blocks of modules. The method generalizes the standard modularity and uses spectral optimization to find its maximum. We compare the partitions obtained with those resulting from the optimization of the standard modularity in several real networks. The results show that the information reported by the analysis of modules of triangles complements the information of the classical modularity analysis.     

Fire retardancy effect of phosphorus‐modified halloysite on polyamide‐11 nanocomposites

Halloysite nanotubes (HNTs) were successfully incorporated as flame retardants in polyamide‐11 (PA11) after their modification with methyl phosphonic acid. Fourier transform infrared spectroscopy, thermal gravimetric analysis (TGA) and pyrolysis–gas chromatography–mass spectrometry were used to evidence the functionalization of the clay. Raw and modified HNTs were then incorporated by melt mixing in PA11 at 20 wt%. Compositions containing both ammonium polyphosphate (APP) and HNTs were also prepared. TGA and pyrolysis combustion flow calorimeter exhibited enhancement in thermal stability upon incorporation of both raw and modified halloysite nanotubes while APP causes degradation at lower temperature. Cone calorimeter data showed that modified halloysite acts by forming an insulating barrier during the combustion, which limits heat and mass transfers. Moreover, elemental analysis of sample residues after cone test evidenced that a part of the phosphorus of the modified halloysite was transferred to the gaseous phase. These results suggest the full potential of halloysite as fire retardant agent for polyamides. POLYM. ENG. SCI., 59:526–534, 2019. © 2018 Society of Plastics Engineers     

Synthesis of isosorbide based polyurethanes: An isocyanate free method

The synthesis of isocyanate free polyurethanes is a major concern. This paper first reports the synthesis of new biobased isosorbide dicyclocarbonates from isosorbide. Then polyhydroxyurethanes (PHUs) were synthesized by a cyclocarbonate–amine step growth polyaddition with four commercial diamines (e.g. jeffamine D-400, 1,10 diaminodecane, diethylenetriamine and isophoronediamine). These unprecedented products, obtained with high yield, were characterized by ¹H NMR, FTIR, DSC, SEC and TGA analyses. PHUs exhibited glass transition temperatures from ?8 °C to 59 °C, and degradation temperatures (Td 5%) between 234 °C and 255 °C. Last but not least, the compounds produced during the degradation of these PHUs were analyzed by ATG-IR technique and showed that carbon dioxide and secondary amines are released.     

Fully automatic multisegmentation approach for magnetic resonance imaging brain tumor detection using improved region-growing and quasi-Monte Carlo-expectation maximization algorithm

Magnetic resonance imaging (MRI) is widely used in the medical field, especially for detecting serious abnormalities affecting the organs of the human body, such as tumors. Automatic detection of tumors needs high-performance recognition techniques. In this paper, we have developed a new automatic method based on the multisegmentation of brain tumor region. We used an improved region-growing algorithm, which is based on quasi-Monte Carlo and expectation maximization methods to define the desired classes. Several metrics were calculated to evaluate the performance of our technique. The fully automatic multisegmentation approach, developed in this study, showed good performance, and it can offer a new option to replace conventional techniques used for tumor detection in MRI images.     

Event driven Hybrid Bond Graph for Hybrid Renewable Energy Systems part I: Modelling and operating mode management

This paper proposes a generic tool named Event-Driven Hybrid Bond Graph (EDHBG). The main objective of the proposed approach is the use only one global model to represent all the distinct dynamics resulting from the switching behaviour of the system. Compared with classical approaches such as the hybrid automata, the Operating Mode Management (OMM) is more effective due to the separation between the continuous dynamics, represented by the BG continuous state, and the discrete state governed by a classical automaton. The innovative interest in this work is that it allows for a non-expert user to perform modelling without expressing the algebraic equations of the system and regardless of its hybrid aspect. The modelling approach is applied to Hybrid Renewable Energy Systems (HRES) represented by a multi-sources system which composed of Solar Photovoltaic Panels (PV) and Wind Turbine (WT) coupled with an EL to produce green hydrogen stored and when needed feeding a Fuel Cell (FC). A reduced size experimental HRES is presented to demonstrate the effectiveness of the proposed technique.     

Effects of partial shear connection on the behavior of semi-continuous composite beams

In this paper, the effects of partial shear connection on the behavior of semi-continuous composite beams were studied numerically using two-dimensional finite element model with plane stress elements. The finite element model takes into account the nonlinearity of the different materials involved. For the shear connectors, a non-linear (shear-slip) relation, drawn from the push-out tests, was used. The accuracy of the proposed finite element model was verified against test results available in the literature. A simplified method to predict load capacity and deflection of the semi-continuous composite beams was also proposed. Based on the results obtained from the finite element analysis, the concept of partial shear connection in the hogging moment regions can be accepted provided that the shear connectors are sufficiently ductile.     

Optimized Station to Estimate Atmospheric Integrated Water Vapor Levels Using GNSS Signals and Meteorology Parameters

The atmospheric meteorology parameters of the earth, such as temperature, pressure, and humidity, strongly influence the propagation of signals in Global Navigation Satellite Systems (GNSSs). The propagation delays associated with GNSS signals can be modeled and explained based on the atmospheric temperature, pressure, and humidity, as well as the locations of the satellites and receivers. In this paper, we propose an optimized and simplified low cost GNSS base weather station that can be used to provide a global estimate of the integrated water vapor value. Our algorithm can be used to measure the zenith tropospheric delay based on the measured propagation delays in the received signals. We also present the results of the data measurements performed at our station located in the Tlemcen region of Algeria.