Discontinuous Galerkin error estimation for hyperbolic problems on unstructured triangular meshes

We extend the error analysis of Adjerid and Baccouch [1], [2] for the discontinuous Galerkin discretization error to variable-coefficient linear hyperbolic problems as well as nonlinear hyperbolic problems on unstructured meshes. We further extend this analysis to transient hyperbolic problems and prove that the local superconvergence results presented in [1] still hold for both steady and transient variable-coefficient linear and nonlinear problems. This local error analysis allows us to construct asymptotically correct a posteriori error estimates by solving local hyperbolic problems with no boundary conditions on each element of general unstructured meshes. We illustrate the superconvergence and the efficiency of our a posteriori error estimates by showing computational results for several linear and nonlinear numerical examples.     

Combining formant frequency based on variable order LPC coding with acoustic features for TIMIT phone recognition

Combination of multiple acoustic features has great potential to improve Automatic Speech Recognition (ASR) accuracy. Our contribution in this research was to investigate one novel method when using voiced formants’ features in combination with standard MFCC features in order to enhance TIMIT phone recognition. These voiced features provide accurate formants frequencies using a Variable Order LPC Coding (VO-LPC) algorithm that was combined with continuity constraints. The overall estimating formants were concatenated with MFCC features when a voiced frame could be detected. For feature-level combination, Heteroscedastic Linear Discriminant Analysis (HLDA) based approach had been used successfully to find an optimal linear combination of successive vectors of a single feature stream.     

The Discontinuous Galerkin Method for Two-Dimensional Hyperbolic Problems. Part I: Superconvergence Error Analysis

In this paper we investigate the superconvergence properties of the discontinuous Galerkin method applied to scalar first-order hyperbolic partial differential equations on triangular meshes. We show that the discontinuous finite element solution is O(h ^p+2) superconvergent at the Legendre points on the outflow edge for triangles having one outflow edge. For triangles having two outflow edges the finite element error is O(h ^p+2) superconvergent at the end points of the inflow edge. Several numerical simulations are performed to validate the theory. In Part II of this work we explicitly write down a basis for the leading term of the error and construct asymptotically correct a posteriori error estimates by solving local hyperbolic problems with no boundary conditions on more general meshes.     

Investigations of High Temperature Wear Mechanisms for Tool Steel Under Open-Sliding Contact

During hot working processes, working tools are subjected to severe conditions. Wear is one of the major life limiting factors of the hot working tools. The identification and understanding of the wear mechanism are extremely important for solving problems related to the hot working process. The ultimate aim of this paper is to assess some wear mechanisms of the tool steel used in hot drawing. The tribological tests were performed on high temperature pin-on-disc tribometer with an open-sliding contact for a simulation of hot-drawing process with a refreshed contact surface. The pin material was X40 CrMoV5 steel and the disc material was Fe 360B steel. Experiments were carried out for different disc temperatures ranging from room temperature to 800°C, a constant sliding speed of 50 rev/min and a constant normal load of 70 N. The evolution surface damage and oxides tribolayers have been investigated by SEM and EDS. The results have shown that an increase in test temperature facilitates the generation of oxide and assists in the compaction of the debris, thus producing a wear protective layer, and therefore, a reduction in friction coefficient.     

An improved extreme learning machine model for the prediction of human scenarios in smart homes

One of the main objectives of smart homes is healthcare monitoring and assistance, especially for elderly and disabled people. Therefore, an accurate prediction of the inhabitant behavior is very helpful to provide the required assistance. This work aims to propose a prediction model that satisfies the accuracy as well as the rapidity of the learning phase. To do so, we propose to improve the existing extreme learning machine (ELM) model by defining a recurrent form. This form ensures a temporal relationship of inputs between observations at different time steps. The new model uses feedback connections to the input layer from the output layer which allows the output to be included in the long-term prediction. A recurrent dynamic network, with feedback connections of the output of the network, is proposed to predict the future series representing future activities of the inhabitant. The resulting model, called Recurrent Extreme Learning Machine (RELM), provides the ability to learn the human behavior and ensures a good balance between the learning time and the prediction accuracy. The input data is based on the real data representing the activities of persons belonging to the profile of first level (i.e. P ₁) as measured by the dependency model called Functional Autonomy Measurement System (SMAF) used in the geriatric domain. The experimental results reveal that the proposed RELM model requires a minimum time during the learning phase with a better performance compared to existing models.     

Investigation of a new solar greenhouse drying system for peppers

Solar drying is the oldest preservation technique of agricultural products using several types of solar crop dryers based mostly on solar energy, which is abundant, renewable and sustainable. This study aimed to modeling a new solar greenhouse drying system (SGDS) for the drying of red peppers. The proposed mixed-mode (SGDS) consists of two main parts, namely a flat plate solar air collector and an experimental greenhouse. A mathematical model is developed using the TRNSYS simulation program to predict the change in the drying kinetics during the drying process under our proposed (SGDS). The experimental part consisted in testing the solar air collector to investigate its performance. The test showed that this solar air collector has a good performance; its efficiency varies between 0, 5 and 0, 65. The model was validated with the observed data and showed good agreement with experimental values. The influence of the area of the product to be dried, airflow rate and collector area, on moisture content changes, air temperature and humidity inside the greenhouse was studied. For the case study of this SGDS, the results obtained from simulation showed that the optimum values of area of the product to be dried, the exhaust airflow rate and the collector area were found to be 40 m², 250 kg/h and 2 m², respectively.     

Preparation,characterization and evaluation of the catalytic power of an hybrid compound [H3PMo12O40-chitosan] for the azoic-colored solutions

Inorganic–organic hybrid structures have become novel alternatives for many applications as they combine the advantages of both systems. In this current study, a hybrid compound [H₃PMo₁₂O₄₀-chitosan] was prepared using a wet impregnation method with different proportions (0-100 wt. %, considering the polymer as the main component). The chemical structure and the morphology of the synthesized compounds were studied using FT-IR and SEM. Their catalytic powers were evaluated for Naphtol Blue Black and Eriochrome Blue Black B. Experimental data revealed that the decolorization phenomenon depends on the structure of the dye it-self, the pH value, the initial dye concentration, the time contact, the oxidant dose and the temperature. Kinetic data, well described using the first order model, allowed us to establish the thermodynamic parameters. The calculated low values of Ea (7.48 and 8.14 KJ. mol-1) proved the efficiency of the prepared catalyst. Eriochrome Blue Black B could be decomposed more rapidly than Naphtol Blue Black. As example, after a period of 30 min of reaction, the target removals were, respectively, 70% and 15% for mono and bi-azoic dyes. The reuse of the catalyst is carried out and it was found to be recyclable more than three consecutives cycles.     

Removal of a wide range of dyes using 4-methyl-2-(naphthalen-2-yl)-N-propylpentanamide-functionalized ethoxy-silica and raw silica

The present research offers a comparative study on the character of the performance of dye removal using either functionalized silica or raw silica gel as adsorbents. First, these supports were characterized in terms of FT-IR and SEM analyses. Then, four different dye solutions were checked for the adsorption phenomenon: Eriochrome Black B (an acid dye), Methylene Blue (a basic dye), Direct Yellow 50 (a direct dye), and Reactive Blue 49 (a reactive dye). Experimental data revealed a dependence on the experimental conditions. Functionalized silica presented a higher removal of dyes than the raw silica. Among the four studied dyes, the highest capacity removal was achieved with Eriochrome Blue Black B (140 mg g^?1) using functionalized silica as adsorbent. This value was reduced to 55 mg g^?1 for raw silica. Further, kinetic and thermodynamic investigations of Eriochrome were discussed. Results gleaned from this study suggest that the functionalized silica could be considered as an efficient candidate to treat colored waters.     

Effect of recycling and injection parameters on gloss properties of smooth colored polypropylene parts: Contribution of surface and skin layer

The aim of this article is to investigate the optical properties of a recycled polymer during numerous processes. The effects of different process parameters (number of grinding‐injection cycles, material temperature, mold temperature, and injection rate) on gloss and color properties of a buff‐colored polypropylene containing 2wt%/wt of pigment was considered. The variations of properties are in the same range that is observed by changing processing parameters. It is found that the roughness is not able to explicate the variation of the optical properties for these variations of conditions. In addition, the optical properties of the skin layer of the injected parts are associated with the observed gloss and color variations. Moreover, the change of spherulite dimensions is related with optical changes. POLYM. ENG. SCI., 59:1288–1299 2019. © 2019 Society of Plastics Engineers