The transverse elastic properties of chiral honeycombs

This work describes the out-of-plane linear elastic mechanical properties of trichiral, tetrachiral and hexachiral honeycomb configurations. Analytical models are developed to calculate the transverse Young’s modulus and the Voigt and Reuss bounds for the transverse shear stiffness. Finite Element models are developed to validate the analytical results, and to identify the dependence of the transverse shear stiffness vs. the gauge thickness of the honeycombs. The models are then validated with experimental results from flatwise compressive and simple shear tests on samples produced with rapid prototype (RP)-based techniques.     

Numerical and Experimental Study of the Impact of Key Parameters on a PVT Air Collector: Mass Flow Rate and Duct Depth

The PVT-air solar system simultaneously generates electrical and thermal energy. Therefore, increasing the cost-effectiveness of the system requires an appropriate choice of key parameters such as mass flow rate and air channel depth. In this paper, a PVT-air kit of a single module with a 30° slope was used to measure photovoltaic electricity and air heating power in the city of Sfax, Tunisia. Besides, a computer method was implemented using the ANSYS Fluent 17.0 software and the MATLAB program to analyse the properties of the airflow and to characterise PVT-air yields under different mass flow rates and depths. From the comparison of numerical and experimental data, the numerical method was validated with a good agreement. Indeed, we have found that increasing of the airflow rate improves the thermal efficiency with a slight change on electrical output. However, the reduction in depth shows an improvement on thermal efficiency and a negligible effect on electrical efficiency. Also, we have presented the thermal and electrical performance of PVT-air as a function of the key parameters with the Hottel-Whillier-Bliss formulation.     

Towards Securing Machine Learning Models Against Membership Inference Attacks

From fraud detection to speech recognition, including price prediction, Machine Learning (ML) applications are manifold and can significantly improve different areas. Nevertheless, machine learning models are vulnerable and are exposed to different security and privacy attacks. Hence, these issues should be addressed while using ML models to preserve the security and privacy of the data used. There is a need to secure ML models, especially in the training phase to preserve the privacy of the training datasets and to minimise the information leakage. In this paper, we present an overview of ML threats and vulnerabilities, and we highlight current progress in the research works proposing defence techniques against ML security and privacy attacks. The relevant background for the different attacks occurring in both the training and testing/inferring phases is introduced before presenting a detailed overview of Membership Inference Attacks (MIA) and the related countermeasures. In this paper, we introduce a countermeasure against membership inference attacks (MIA) on Conventional Neural Networks (CNN) based on dropout and L2 regularization. Through experimental analysis, we demonstrate that this defence technique can mitigate the risks of MIA attacks while ensuring an acceptable accuracy of the model. Indeed, using CNN model training on two datasets CIFAR-10 and CIFAR-100, we empirically verify the ability of our defence strategy to decrease the impact of MIA on our model and we compare results of five different classifiers. Moreover, we present a solution to achieve a trade-off between the performance of the model and the mitigation of MIA attack.     

Improved preventive maintenance in the framework of forecasting problem under subcontractor constraint

The paper presents a new improved preventive maintenance strategy for a forecasting problem of production and maintenance optimisation under subcontractor constraint. In order to satisfy the customer, the manufacturing system consists of a principal machine M₁ and called upon subcontractor machine M_s. Knowing that both machines are subjected to random failures, failure rate of main machine increases with time and according to production rates. An improved preventive maintenance strategy is used for control of the machine M₁, whereas subcontractor machine M_s is uncontrollable from preventive maintenance point of view. An analytic formulation of problem has been proposed in order to determine the economical production plans for M₁ and M_s. An improved maintenance strategy (IMS) is developed in order to minimise the total production loss, when the subcontractor machine is unavailable. It consists of determining the best time to perform preventive maintenance actions taking into account production rates, history of M₁ and the state of subcontractor machine M_s. Numerical results and sensitivity analysis are presented to highlight the performance measure and the usefulness of the IMS.     

Emotional speaker recognition in real life conditions using multiple descriptors and i-vector speaker modeling technique

Multimedia Tools and Applications - Emotional speaker recognition under real life conditions becomes an urgent need for several applications. This paper proposes a novel approach using multiple...     

Speech enhancement based on perceptual filter bank improvement

In this paper, a new denoising approach is presented based on perceptual analysis. The noisy signal is split by a gammatone filterbank with nonlinear frequency distributions according to ERB scale. The frequency masking threshold is calculated in each sub-band according to the Johnston model in the output of the Wiener filter. This threshold is then used in the gain function given by the perceptual filter. The evaluation tests are performed by using objective criterion including perceptual evaluation of speech quality as well as subjective criterion including mean opinion score. Obtained results show that the proposed method achieves best results in terms of quality and intelligibility of enhanced signal.     

Graphical Programming and the Development of Construction Robots

Abstract: Complexity, multidisciplinarity, and algorithmic inherency are characteristics of construction robotic systems. Controlling the development process of such systems requires the adoption of a development model based on Systems Engineering principles. The software‐development process is an important aspect of the system, which requires a development environment that can cope with this complexity. Using traditional programming languages (textual) requires highly trained programmers for this purpose, which involves high cost and long development time. In the present work Graphical Programming (iconic) is used as the software development environment because it is highly modular and allows concurrent development, both of which save on time and cost. It also enables nonexpert programmers to produce software capable of coping with the system complexity. A detailed case study of the software development process for an existing tool manipulation robot known as Starlifter is presented. Use of the LabVIEW package is demonstrated for both onboard system control and off‐line project management.     

The in-plane linear elastic constants and out-of-plane bending of 3-coordinated ligament and cylinder-ligament honeycombs

Four novel cylinder-ligament honeycombs are described, where each cylinder has 3 tangentially-attached ligaments to form either a hexagonal or re-entrant hexagonal cellular network. The re-entrant cylinder-ligament honeycombs are reported for the first time. The in-plane linear elastic constants and out-of-plane bending response of these honeycombs are predicted using finite element (FE) modelling and comparison made with hexagonal and re-entrant hexagonal honeycombs without cylinders. A laser-crafted re-entrant cylinder-ligament honeycomb is manufactured and characterized to verify the FE model. The re-entrant honeycombs display negative Poisson’s ratios and synclastic curvature upon out-of-plane bending. The hexagonal and ‘trichiral’ honeycombs possess positive Poisson’s ratios and anticlastic curvature. The ‘anti-trichiral’ honeycomb (short ligament limit) displays negative Poisson’s ratios when loaded in the plane of the honeycomb, but positive Poisson’s ratio behaviour (anticlastic curvature) under out-of-plane bending. These responses are understood qualitatively through considering deformation occurs via direct ligament flexure and cylinder rotation-induced ligament flexure.     

Duration modelling and evaluation for Arabic statistical parametric speech synthesis

Multimedia Tools and Applications - Sound duration is responsible for rhythm and speech rate. Furthermore, in some languages phoneme length is an important phonetic and prosodic factor. For...