Hydric,morphological and thermo-physical characterization of glass wools: From macroscopic to microscopic approach

In this paper, experiments to investigate fibrous insulating materials used in buildings have been performed. Two kinds of glass fibers based products were studied. Scanning electron microscopy (SEM) coupled with an EDX detector, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and X-ray diffraction diagnostic method were used to assess materials properties. Through the coupling of thermal analyses with morphological and structural characterization techniques, a fast and safer comparison between the insulators becomes possible. So, after being tested at various rates of humidities, it is shown that the aim cause of ageing in the glass wools studied is mainly due to their binders. In fact, the alteration of glass constituting fibers comes much later. Besides, there is no preferential orientation for the vapor transfer inside glass wools.     

New Boolean Equation for Orthogonalizing of Disjunctive Normal Form based on the Method of Orthogonalizing Difference-Building

In this paper a new Boolean equation for the orthogonalization of Boolean functions respectively of Ternary-Vector-Lists of disjunctive normal form is presented. It provides the mathematical solution of orthogonalization for the first time. The new equation is based on the new method of orthogonalizing difference-building ?. In contrast to other methods the new method has a faster computation time. Another advantage is the smaller number of product terms respectively of Ternary-Vectors in the orthogonalized result in contrast to other methods. Furthermore, the new equation can be used as a part in the calculation procedure of getting suitable test patterns for combinatorial circuits for verifying feasible logical faults.     

An Adaptive PRB,Power and MCS Allocation Using AMC for MIMO-OFDMA Systems

Long Term Evolution (LTE) is a promising technology for a high communication quality thanks to its radio link flexibility using Adaptive Modulation and Coding (AMC), Multiple Input Multiple Output (MIMO) and Orthogonal Frequency Division Multiple Access (OFDMA) technologies. In this paper, we address the adaptive resource allocation problem in down-link transmission of MIMO-OFDMA systems. We aim at maximizing the total system capacity to meet the 4G-technologies promises. In order to reduce the computational complexity, the original optimization problem is divided into sub-optimal ones. Firstly, a recursive Physical Resource Block (PRB) allocation algorithm is developed where the Effective Signal-to-Interference-plus-Noise Ratio (ESINR) metric is investigated to properly characterize the channel condition. Secondly, a power allocation procedure is performed. As all resource blocks allocated to the same user must use the same Modulation and Coding Scheme (MCS) according to the LTE standard requirements, power optimization sub-problem is divided into three steps: power allocation among PRBs, power allocation among antennas and power allocation among users. Finally, a more effective MCS is obtained, which ensures a better system capacity. Simulation results prove the efficiency of the proposed method to maximize the total system capacity with a low complexity even in the case of loaded systems compared to Minimum-MCS (Min-MCS) and Maximum-SINR (Max-SINR) algorithms.     

Oscillatory natural convection of water-glycerin mixture in a tall rectangular cavity: Transition to the chaos

This paper presents results of a numerical investigation involving bifurcation sequence leading to chaos in natural convection inside a vertically tall rectangular cavity having an aspect ratio equal to 15 and a Prandtl number equal to 125, corresponding to water-glycerin mixture. The flow is characterized by a vertical stratification of the temperature field for Grashof numbers greater than or equal to 200 that is outside the conduction regime and it is stationary monocellular up to a critical value Gr_c = 2800 where a periodic oscillatory regime appears. As Grashof number is increased, a transition from a steady periodic bicellular flow to an oscillatory multicellular flow, with 2 main central cells and 2 secondary cells, occurs. The regime remains periodic until Gr = 3100 where there is a first appearance of the chaotic regime which extends over a narrow interval of the Grashof number delimited by Gr = 3200.     

Velocity gradient elasticity for nonlinear vibration of carbon nanotube resonators

In this study, for the first time, we investigate the nonlocality superimposed to the size effects on the nonlinear dynamics of an electrically actuated single-walled carbon-nanotube-based resonator. We undertake two models to capture the nanostructure nonlocal size effects: the strain and the velocity gradient theories. We use a reduced-order model based on the differential quadrature method (DQM) to discretize the governing nonlinear equation of motion and acquire a discretized-parameter nonlinear model of the system. The structural nonlinear behavior of the system assuming both strain and velocity gradient theories is investigated using the discretized model. The results suggest that nonlocal and size effects should not be neglected because they improve the prediction of corresponding dynamic amplitudes and, most importantly, the critical resonant frequencies of such nanoresonators. Neglecting these effects may impose a considerable source of error, which can be amended using more accurate modeling techniques.     

Estimation of Coalescence Parameters in an Agitated Extraction Column Using a Hybrid Algorithm

A method based on a genetic algorithm (GA) combined with Levenberg‐Marquardt (LM) method applicable to the population balance model for coalescence parameter estimation in a liquid‐liquid biphasic system is presented. The toluene/water system in a rotating disk contactor was taken as an example. Estimation methods for such a problem are often based on deterministic optimization models that are rather instable and divergent around a local minimum. To overcome these limitations, the present study involves the introduction of a semi‐stochastic method that is able to provide at first the estimation of coalescence parameters from the GA based on an inverse approach, exploiting the principle of GA. The LM algorithm was applied to ensure that the results are not restricted to a local minimum.     

Bioactive composites of hydroxyapatite/polyvinylpyrrolidone for bone regeneration applications

The implantation of bioactive composites for bone repair applications has recently gained the attention of many research groups. The present paper introduces a method for grafting of polyvinylpyrrolidone on the surface of hydroxyapatite (CaHAp) microcrystals by wet precipitation method to manufacture new composite scaffolds with suitability for bone tissue engineering. After grafting with the polymer, the degree of CaHAp crystallinity decreased, and its thermal behavior changed indicating a strong interaction between them. Homogenous clusters of CaHAp particles within the polymeric matrix were observed in combination with an increase in the roughness of the resulting structures. Bioactivity of the composites was tested using MTT assay; a higher viability of the seeded cells was observed relative to those cultured with CaHAp powder.