Both researchers and malware authors have demonstrated that malware scanners are unfortunately limited and are easily evaded by simple obfuscation techniques. This paper proposes a novel ensemble ...convolutional neural networks (CNNs) based architecture for effective detection of both packed and unpacked malware. We have named this method Image-based Malware Classification using Ensemble of CNNs (IMCEC). Our main assumption is that based on their deeper architectures different CNNs provide different semantic representations of the image; therefore, a set of CNN architectures makes it possible to extract features with higher qualities than traditional methods. Experimental results show that IMCEC is particularly suitable for malware detection. It can achieve a high detection accuracy with low false alarm rates using malware raw-input. Result demonstrates more than 99% accuracy for unpacked malware and over 98% accuracy for packed malware. IMCEC is flexible, practical and efficient as it takes only 1.18 s on average to identify a new malware sample.
Herein, with the aid of the newly proposed theory of nonlocal strain gradient elasticity, the size-dependent nonlinear buckling and postbuckling behavior of microsized shells made of functionally ...graded material (FGM) and subjected to hydrostatic pressure is examined. As a consequence, the both nonlocality and strain gradient micro-size dependency are incorporated to an exponential shear deformation shell theory to construct a more comprehensive size-dependent shell model with a refined distribution of shear deformation. The Mori–Tanaka homogenization scheme is utilized to estimate the effective material properties of FGM nanoshells. After deduction of the non-classical governing differential equations via boundary layer theory of shell buckling, a perturbation-based solving process is employed to extract explicit expressions for nonlocal strain gradient stability paths of hydrostatic pressurized FGM microsized shells. It is observed that the nonlocality size effect causes to decrease the critical hydrostatic pressure and associated end-shortening of microsized shells, while the strain gradient size dependency leads to increase them. In addition, it is found that the influence of the internal strain gradient length scale parameter on the nonlinear instability characteristics of hydrostatic pressurized FGM microsized shells is a bit more than that of the nonlocal one.
To impart desirable material properties, functionally graded (FG) porous silicon has been produced in which the porosity changes gradually across the material volume. The prime objective of this work ...is to predict the influence of the surface free energy on the nonlinear secondary resonance of FG porous silicon nanobeams under external hard excitations. On the basis of the closed-cell Gaussian-random field scheme, the mechanical properties of the FG porous material are achieved corresponding to the uniform and three different FG patterns of porosity dispersion. The Gurtin–Murdoch theory of elasticity is implemented into the classical beam theory to construct a surface elastic beam model. Thereafter, with the aid of the method of multiple time-scales together with the Galerkin technique, the size-dependent nonlinear differential equations of motion are solved corresponding to various immovable boundary conditions and porosity dispersion patterns. The frequency response and amplitude response associated with the both subharmonic and superharmonic hard excitations are obtained including multiple vibration modes and interactions between them. It is found that for the subharmonic excitation, the nanobeam is excited within a specific range of the excitation amplitude, and this range shifts to higher excitation amplitude by incorporating the surface free energy effects. For the superharmonic excitation, by taking surface stress effect into account, the excitation amplitude associated with the peak of the vibration amplitude enhances. Moreover, in the subharmonic case, it is demonstrated that by increasing the porosity coefficient, the value of the excitation frequency at the joint point of the two branches of the frequency-response curve reduces. In the superharmonic case, it is revealed that an increment in the value of porosity coefficient leads to decrease the peak of the oscillation amplitude and the associated excitation frequency.
Recently, small-sized structures including micro/nanobeams, micro/nanoplates, micro/nanotubes, micro/nanowires, etc. have received great attention among researchers in the fields of nanotechnology ...and nanodevice because of their tremendous applications. These nanostructures are extensively applied in areas involving nano and micro scaled devices and systems including nano electromechanical systems, biosensors, nano actuators, nano probes, etc. Consequently, the stability, vibration, buckling and postbuckling behaviors of these small-sized structures have been studied extensively. Also, understanding the mechanical characteristics of these nanostructures is of a critical significance. In this work, we have reviewed the literature and hereby present a comprehensive state-of-the-art review study on the advances of vibrational analyses of small-sized structures (primarily with a special focus on small-sized beam-like structures) using nonlocal/nonclassical continuum theories. For this purpose, Scopus database is used as the scholarly database in acquiring the reviewed articles. The acquired and reviewed documents are grouped taking several perspectives into account. Summary-based approaches and a detailed-based approach were considered while classifying these documents. In the detailed-based approach, we categorized the studies based on; nonclassical continuum theories and theories applied; small-sized-structure/model investigated; static and dynamic mechanical analyses; issues/challenges addressed or investigated; methodologies and assumptions considered; governing equations of motion formulation methods; governing equations of motion solution techniques; and the parameters investigated. The objective was to present the current research trends in vibration analysis of these small-sized structures, and to deliver some guidance and foundation for future research directions.
Recently, with the emergence of Industry 4.0 (I4.0), smart systems, machine learning (ML) within artificial intelligence (AI), predictive maintenance (PdM) approaches have been extensively applied in ...industries for handling the health status of industrial equipment. Due to digital transformation towards I4.0, information techniques, computerized control, and communication networks, it is possible to collect massive amounts of operational and processes conditions data generated form several pieces of equipment and harvest data for making an automated fault detection and diagnosis with the aim to minimize downtime and increase utilization rate of the components and increase their remaining useful lives. PdM is inevitable for sustainable smart manufacturing in I4.0. Machine learning (ML) techniques have emerged as a promising tool in PdM applications for smart manufacturing in I4.0, thus it has increased attraction of authors during recent years. This paper aims to provide a comprehensive review of the recent advancements of ML techniques widely applied to PdM for smart manufacturing in I4.0 by classifying the research according to the ML algorithms, ML category, machinery, and equipment used, device used in data acquisition, classification of data, size and type, and highlight the key contributions of the researchers, and thus offers guidelines and foundation for further research.
•A unified solution for free vibration analysis of rotating FG-GPLRC cylindrical shells is proposed.•General boundary conditions are represented by using artificial spring techniques.•Effects of ...boundary spring stiffness, GPL weight fractions, layer number and geometry are evaluated.•Variations of natural frequencies are highly dependent on boundary conditions.
This paper studies traveling wave motions of rotating multi-layered functionally graded graphene platelet reinforced composite (FG-GPLRC) cylindrical shell under general boundary conditions. Theoretical equations are obtained according to Donnell shell theory, and artificial spring technique, where centrifugal and Coriolis effects caused by rotation are considered. By employing general orthogonal polynomials using a Gram-Schmidt process as admissible functions, solutions are achieved via Rayleigh-Ritz approach. Then, the accuracy and convergence of solutions are validated by the comparison of the obtained results with those reported in literature. Finally, free vibrations of FG-GPLRC cylindrical shells in both stationary and rotating states are investigated. The influences of boundary spring stiffness, GPL weigh fraction, total layer number, and geometry parameters on shell vibration characteristics are evaluated. It is revealed that the frequency variation trends along with material and geometric parameters are consistent for different boundary conditions, while variation rates and frequency values are highly dependent on boundary spring stiffness.
In this paper, size-dependent dynamic stability of axially loaded functionally graded (FG) composite truncated conical microshells with magnetostrictive facesheets surrounded by nonlinear ...viscoelastic foundations including a two-parameter Winkler–Pasternak medium augmented via a Kelvin–Voigt viscoelastic approach is analyzed considering nonlinear cubic stiffness. To this purpose, von Karman-type kinematic nonlinearity along with modified couple stress theory of elasticity was applied to third-order shear deformation conical shell theory in the presence of magnetic permeability tensor and magnetic fluxes. The numerical technique of generalized differential quadrature (GDQ) was used for the solution of microstructural-dependent dynamic stability responses of FG composite truncated conical microshells. It was seen that moving from prebuckling to postbuckling domain somehow increased the significance of couple stress type of size dependency on frequency. In addition, within both prebuckling and postbuckling regimes, an increase of material gradient index decreased the importance of couple stress type of size dependency on the frequency of an axially loaded FG composite truncated conical microshell. Furthermore, it was revealed that by applying a positive magnetic field to an axially loaded truncated conical microshell with magnetostrictive facesheets, its frequency at a specific axial load value was increased in prebuckling domain and decreased in postbuckling domain. However, this pattern was reversed by applying a negative magnetic field.
Nonclassical continuum theories of elasticity (NCTE) have been extensively used in the mechanical analyses of small-sized structures due to their effective and tremendous ability of incorporating the ...small size effects into account than the classical continuum theories. The prevalent usage of these theories has to do with the necessity of understanding the mechanics of these small-sized as they are being used in serval areas of applications and today’s nanotechnological applications. Consequently, a glimpse into this extensive open literature of NCTE for static bending characteristics of small-sized structures is paid. Subsequently, in this piece of work, by focusing on plate-based structures, we present an ample and novel review on the advances of NCTE for linear and nonlinear bending characteristics of microplate/nanoplate-based structures. We consider several classifications of documents while presenting these advancements. These categorizations of documents involve those reported on linear and nonlinear bending characteristics of small-scale plates (microplates and nanoplates), with a sub classification of documents within the investigated/reported plate types. Further, at the end, a summary, comparison and discussion of some significant studies are presented. At large, in this piece of work, we intent to deliver the existing research trends and primary gaps in static bending behaviors of microplates and nanoplates.
Nowadays, there is a massive necessity to develop fully automated and efficient distress assessment systems to evaluate pavement conditions with the minimum cost. Due to having complex training ...processes, most of the current supervised learning-based practices in this area are not suitable for smaller, local-level projects with limited resources. This paper aims to develop an automatic crack assessment method to detect and classify cracks from 2-D and 3-D pavement images. A tile-based image processing method was proposed to apply a localized thresholding technique on each tile and detect the cracked ones (tiles containing cracks) based on crack pixels’ spatial distribution. For longitudinal and transverse cracking, a curve is then fitted on the cracked tiles to connect them. Next, cracks are classified, and their lengths are measured based on the orientation axes and length of the crack curves. This method is not limited to the pavement texture type, and it is cost-efficient as it takes less than 20 s per image for a commodity computer to generate results. The method was tested on 130 images of Portland Cement Concrete (PCC) and Asphalt Concrete (AC) surfaces; test results were found to be promising (Precision = 0.89, Recall = 0.83,
F
1
score = 0.86, and Crack length measurement accuracy = 80%).
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