505 research outputs found
Improving Malware Detection Accuracy by Extracting Icon Information
Detecting PE malware files is now commonly approached using statistical and
machine learning models. While these models commonly use features extracted
from the structure of PE files, we propose that icons from these files can also
help better predict malware. We propose an innovative machine learning approach
to extract information from icons. Our proposed approach consists of two steps:
1) extracting icon features using summary statics, histogram of gradients
(HOG), and a convolutional autoencoder, 2) clustering icons based on the
extracted icon features. Using publicly available data and by using machine
learning experiments, we show our proposed icon clusters significantly boost
the efficacy of malware prediction models. In particular, our experiments show
an average accuracy increase of 10% when icon clusters are used in the
prediction model.Comment: Full version. IEEE MIPR 201
A Partitioned FSI Approach to Study the Interaction between Flexible Membranes and Fluids
The interaction between fluids and structures, which is an interdisciplinary problem, has gained importance in a wide range of scientific and engineering applications. Thanks to new advances in computer technology, the numerical analysis of multiphysics phenomena has aroused growing interest.
Fluid-structure interactions have been numerically and experimentally studied by many researchers and published by several books, papers, and review papers. Hou et al. (2012) [3] have also published a review paper entitled âNumerical methods for fluid-structure interactionâ, which provides useful knowledge about different approaches for FSI analysis.
The key challenge encountered in any numerical FSI analysis is the coupling between the two independent domains with clear distinctions. For example, a structure domain requires discretizing by a Lagrangian mesh where the mesh is fixed to the mass and follows the mass motion. In fact, the Lagrangian mesh is able to deform and follows an individual structural mass as it moves through space and time. Nonetheless, the fluid mesh remains intact within the space, where the fluid flows as time passes.
The numerical approaches with regard to FSI phenomena can be divided into two main categories, namely the monolithic approach and the partitioned approach. In the former, a single system equation for the whole problem is solved simultaneously by a unified algorithm; however, in the latter, the fluid and the structure are discretized with their proper mesh and solved separately by different numerical algorithms.
When a fluid flow interacts with a structure, the pressure load arising from the fluid flow is exerted on the structure, followed by deformations, stresses, and strains of the structure. Depending on the resulting deformation and the rate of the variations, a one-way or two-way coupling analysis can be conducted. Fluid-structure interaction (FSI) is characterized by the interaction of some movable or deformable structure with an internal or surrounding fluid flow.
In a fluid-structure interaction (FSI), the laws that describe fluid dynamics and structural mechanics are coupled. There is also another classification for FSI problems on the basis of mesh methods: conforming methods and non-conforming methods. In the first method, the interface condition is regarded as a physical boundary (interface boundary) moving during the solution time, which imposes the mesh for the fluid domain to be updated in conformity with the new position for the interface.
In contrast, the implementation of the second method eliminates a need for the fluid mesh update on the account of the fact that the interface requirement is enforced by constraints on the system equations instead of the physical boundary motion.
In this work, we study numerically and experimentally the fluid-structure interaction comprising a flexible slender shaped structure, free surface flow and potentially interacting rigid structures, categorized in flood protection applications, whereas more emphasis is given to numerical analysis. Objectives of this study are defined in detail as follows:
The initial aim is the numerical analysis of the behavior of a down-scale membrane loaded by hydrostatic pressures, where the numerical results have to be validated against available experimental data.
A further case which has to be investigated is how the full scale flexible flood barrier behaves when approached and impacted by an accelerated massive flotsam. The numerical model has to be built so as to replicate the same physical phenomenon investigated experimentally. It enables a comparison between the numerical and experimental analyses to be drawn.
A more complicated case where the flexible down-scale membrane interacts with a propagated water wave is a further target area to study. Moreover, an experimental investigation is required to validate the numerical results by way of comparison.
The ultimate goal is to perform a similitude analysis upon which a correlation between the full-scale prototype and the down-scale model can be formed. The implementation of the similarity laws enables the behavior of the full scale prototype to be quantitatively assessed on the basis of the available data for the down-scale model. In addition, in order to validate the accuracy of the similitude analysis, numerical analyses have to be carried out.:Contents
Zusammenfassung I
ABSTRACT IV
Nomenclature X
1 Introduction 1
1.1 Work overview 2
1.2 Literature review 3
1.2.1 The non-conforming methods 6
1.2.2 The conforming (partitioned) approaches 11
1.2.2.1 Interface data transfer 16
1.2.2.2 Accuracy, stability and efficiency 16
1.2.2.3 Modification of interface conditions: Robin transmission conditions 18
1.3 Concluding remarks 19
2 Methodology-numerical methods for fluid-structure interaction analysis (FSI) 20
2.1 Single FV framework 21
2.1.1 The prism layer mesher 24
2.1.2 Turbulence modeling 24
2.2 Preparation of the standalone Abaqus model 27
2.2.1 Damping by bulk viscosity 28
2.2.2 Coulomb friction damping 29
2.2.3 Rayleigh damping 29
2.2.4 Determination of the Rayleigh damping parameters based on the Chowdhury procedure 29
2.2.5 The frequency response function (FRF) measurement 30
2.2.6 The half-power bandwidth method 31
2.3 Explicit partitioned coupling 33
2.4 Implicit partitioned coupling 39
2.5 Overset mesh 40
2.6 Concluding remarks 42
3 Verification and validation of the structural model 44
3.1 Numerical model setup of the down-scale membrane 44
3.2 Comparing similarity between numerical and experimental results 46
3.2.1 Hypothesis test terminology 46
3.2.2 Curve fitting 47
3.2.3 Similarity measures between two curves 48
3.3 Results (down-scale membrane) 52
3.3.1 Similarity tests for the contact length 54
3.3.2 Similarity tests for the slope 58
3.3.3 Similarity tests for the displacement in Y direction 60
3.4 Concluding remarks 63
4 Numerical model setup of the original membrane for impact analysis 66
4.1 Structure domain 67
4.2 Fluid domain 72
4.2.1 Standard mesh and results 74
4.2.2 Overset mesh 80
4.3 Co-simulation model setup and results 88
4.4 Concluding remarks 96
5 Numerical wave generation 100
5.1 Theoretical estimation of the waves 107
5.2 Numerical wave tank setup 110
5.3 Results 114
5.4 Concluding remarks 119
6 Validity of the model with dynamic pressure 121
6.1 Wave tank 123
6.2 Structure domain 127
6.3 Fluid domain 130
6.4 Co-simulation model setup 136
6.5 Experimental approach 137
6.6 Results 141
6.6.1 Similarity tests for the displacement of the membrane in X direction 156
6.6.2 Similarity tests for the displacement of the membrane in Y direction 160
6.6.3 Similarity tests for the displacement of the membrane in Z direction 164
6.7 Concluding remarks 168
7 Similarity 171
7.1 Motivation 171
7.2 Governing equations 174
7.3 Buckingham Pi theorem 175
7.4 Dimensionless numbers 175
Similitude requirement 177
7.5 Simulation setup 178
7.6 Results 179
7.7 Concluding remarks 191
8 Summary, conclusions and outlook 192
List of figures 199
List of tables 209
References 21
A Flexible Joint Longitudinal-Survival Model for Analysis of End-Stage Renal Disease Data
We propose a flexible joint longitudinal-survival framework to examine the
association between longitudinally collected biomarkers and a time-to-event
endpoint. More specifically, we use our method for analyzing the survival
outcome of end-stage renal disease patients with time-varying serum albumin
measurements. Our proposed method is robust to common parametric assumptions in
that it avoids explicit distributional assumptions on longitudinal measures and
allows for subject-specific baseline hazard in the survival component. Fully
joint estimation is performed to account for the uncertainty in the estimated
longitudinal biomarkers included in the survival model
Application of Metal-Semiconductor-Metal Photodetector in High-Speed Optical Communication Systems
Needs Analysis: ESP Perspective on Genre
A great deal about the origin of ESP could be written. Notably, there are three reasons common to the emergence of all ESP: the demands of a Brave New World, a revolution in linguistics, and focus on the learner (Hutchinson & Waters, 1987). The author started this paper with the short review of needs analysis, giving a brief explanation about the approaches to needs analysis, with a particular attention to genre analysis. Bhatia (2004) maintains, âLanguage is power, and the power of language is the âpower of genreâ (p. 189). Accordingly, power of genre is not only to construct, use, interpret and exploit genres, but also to innovate novel generic forms (Bhatia, 2004). The writer argued genre analysis gives teachers a more central role in preparing the learners to learn. The blame, in the writerâs opinion, does not rest with the learners but with the teachers and genre analysts who treat genre analysis as simply textual artifacts. As Bakhtin (1986) points out genre must be fully mastered to be used creatively (cited in Bhatia, 2004). This paper has established that ESP students need to be scaffolded by teachers in order to understand the construct of any professional genre to enable them to produce these genres effectively. Also, this approach is recommended not only as a basis for teaching ESP but also for the teachersâ professional development. In the same line, genre analysis can enable instructors to become aware of the hidden assumptions and gain insight into pedagogical implications. The main purpose of this article is to elucidate the power of genre in the analysis of studentsâ needs. Index items: needs analysis, ESP, genr
Forecasting Stock Exchange Data using Group Method of Data Handling Neural Network Approach
The increasing uncertainty of the natural world has motivated computer scientists to seek out the best approach to technological problems. Nature-inspired problem-solving approaches include meta-heuristic methods that are focused on evolutionary computation and swarm intelligence. One of these problems significantly impacting information is forecasting exchange index, which is a serious concern with the growth and decline of stock as there are many reports on loss of financial resources or profitability. When the exchange includes an extensive set of diverse stock, particular concepts and mechanisms for physical security, network security, encryption, and permissions should guarantee and predict its future needs. This study aimed to show it is efficient to use the group method of data handling (GMDH)-type neural networks and their application for the classification of numerical results. Such modeling serves to display the precision of GMDH-type neural networks. Following the US withdrawal from the Joint Comprehensive Plan of Action in April 2018, the behavior of the stock exchange data stream and commend algorithms has not been able to predict correctly and fit in the network satisfactorily. This paper demonstrated that Group Method Data Handling is most likely to improve inductive self-organizing approaches for addressing realistic severe problems such as the Iranian financial market crisis. A new trajectory would be used to verify the consistency of the obtained equations hence the models' validity
A Comprehensive Analysis of Plasmonics-Based GaAs MSM-Photodetector for High Bandwidth-Product Responsivity
A detailed numerical study of subwavelength nanogratings behavior to enhance the light absorption characteristics in plasmonic-based metal-semiconductor-metal photodetectors (MSM-PDs) is performed by implementation of 2D finite-difference time-domain (FDTD) algorithm. Due to the structure design and changes in the device physical parameters, various devices with different geometries are simulated and compared. Parameters like nano-grating height and duty cycle (DC) are optimized for rectangular and taper subwavelength metal nanogratings on GaAs substrate and their impact on light absorption below the diffraction limits are confirmed. The calculated light enhancement is ~32.7-times for an optimized device in comparison with a conventional MSM-PD. This enhancement is attributed to the plasmonic effects in the near-field region
- âŠ