Nonnegative matrix factorization and metamorphic malware detection

Metamorphic malware change their internal code structure by adopting code obfuscation technique while maintaining their malicious functionality during each infection. This causes change of their signature pattern across each infection and makes signature based detection particularly difficult. In this paper, through static analysis, we use similarity score from matrix factorization technique called Nonnegative Matrix Factorization for detecting challenging metamorphic malware. We apply this technique using structural compression ratio and entropy features and compare our results with previous eigenvector-based techniques. Experimental results from three malware datasets show this is a promising technique as the accuracy detection is more than 95%.

     

Optimal Spectrum Allocation Based on Primary User Activity Model in Cognitive Radio Wireless Sensor Networks

Wireless Personal Communications - In Cognitive Radio Wireless Sensor Networks, the licensed spectrum bands are highly dynamic, and their status varies overtime. With the expansion of these...     

Asymmetric circularly polarized open‐slot antenna

A circularly polarized printed antenna using an asymmetric open‐slot is designed in this paper. The presented antenna consists of conducting ground plane with open wide‐slot, fed electromagnetically by a microstrip feedline. The slot and feedline are positioned at the edge of the ground plane and substrate, hence making the antenna asymmetric. The measured results show that the |S₁₁| < ?10 dB impedance bandwidth is 125% (3.2‐14 GHz) and the broadband axial ratio bandwidth is 61% (3.2‐6 GHz). The antenna is very simple and has a small size of 25 mm × 25 mm, making it attractive for compact wireless WLAN, ISM, WiMAX, and C‐band applications.     

Analysis and improvement of PSRR in an envelope‐tracking power amplifier using a common‐drain amplifier topology

A common‐drain power amplifier (PA) for envelope tracking systems is presented. In envelope tracking, the main PA operates mostly in compression and the power supply rejection ratio (PSRR) is not high. Furthermore, the output noise of the supply modulator can be mixed with the RF signal and generates out‐of‐band emissions. In this article, instead of using a common‐source topology, the PSRR of the envelope tracking PA is inherently improved by utilizing a common‐drain topology. A comprehensive analysis shows that the common‐drain topology is less sensitive to the supply noise, as compared to the conventional common‐source topology. The proposed common‐drain PA is implemented using a discrete LDMOS PD20010‐E RF transistor. Measurement results show that the PSRR of the proposed common‐drain PA is improved by up to 7 dB as compared to that of the common‐source PA. For a two‐tone input with 10 MHz bandwidth at the center frequency of 700 MHz, the power added efficiency (PAE) and IM3 of the envelope tracking common‐drain PA are 20% and ? 28 dBc, respectively, at an average output power of 33.4 dBm. The amplifier also shows a 12.4 dB power gain. Moreover, by utilizing the envelope tracking, the PAE is improved by more than 5%.     

Mangrove tannins and their flavanoid monomers as alternative steel corrosion inhibitors in acidic medium

The inhibitive behaviour on steel of flavanoid monomers that constitute mangrove tannins namely catechin, epicatechin, epigallocatechin and epicatechingallate was investigated in an aerated HCl solution via electrochemical methods. The monomers were found to be mainly cathodic inhibitors and the inhibition efficiency was dependent on concentration. To explain the adsorptive behaviour of the molecules on the steel surface, a semiempirical approach involving quantum chemical calculations using HyperChem 6.0 was undertaken. The HOMO electronic density of the molecule was used to explain the inhibiting mechanism. The most probable adsorption centers were found in the vicinity of the phenolic groups. In a second part, the use of mangrove tannin, extracted from the mangrove barks as steel corrosion inhibitors in acidic media was investigated and its inhibitive efficiency was compared with that of commercial mimosa, quebracho and chestnut tannins. The inhibitive performance of mangrove tannins was comparable to the other tannins investigated, indicating their potential in corrosion protection.     

Design and implementation of a new high step-up DC-DC converter for renewable applications

In this paper, a new structure for a DC-DC boost converter is proposed. The presented converter provides a high voltage transfer gain with lower duty cycle. Low current and low voltage stress on the switch, enlarged area of operating in continuous conduction mode (CCM), reduced size of the inductors, and the input filter are the main advantages of the proposed converter. The high voltage transfer gain with low number of elements has made it suitable to implement. Hence, using only one switch has made the control of the proposed converter easy. Besides, decreased switching losses and higher efficiency are obtained. The proposed structure is a combination of the Luo converter and a booster unit, which its analysis is studied in three modes, CCM, boundary conduction mode (BCM), and discontinuous conduction mode (DCM). Furthermore, in order to validate the analysis and feasibility of the proposed converter, the experimental results are developed on a low power prototype.     

Streamflow Modeling in a Highly Managed Mountainous Glacier Watershed Using SWAT: The Upper Rhone River Watershed Case in Switzerland

Streamflow simulation is often challenging in mountainous watersheds because of irregular topography and complex hydrological processes. Rates of change in precipitation and temperature with respect to elevation often limit the ability to reproduce stream runoff by hydrological models. Anthropogenic influence, such as water transfers in high altitude hydropower reservoirs increases the difficulty in modeling since the natural flow regime is altered by long term storage of water in the reservoirs. The Soil and Water Assessment Tool (SWAT) was used for simulating streamflow in the upper Rhone watershed located in the south western part of Switzerland. The catchment area covers 5220 km², where most of the land cover is dominated by forest and 14 % is glacier. Streamflow calibration was done at daily time steps for the period of 2001–2005, and validated for 2006–2010. Two different approaches were used for simulating snow and glacier melt process, namely the temperature index approach with and without elevation bands. The hydropower network was implemented based on the intake points that form part of the inter-reservoir network. Subbasins were grouped into two major categories with glaciers and without glaciers for simulating snow and glacier melt processes. Model performance was evaluated both visually and statistically where a good relation between observed and simulated discharge was found. Our study suggests that a proper configuration of the network leads to better model performance despite the complexity that arises for water transaction. Implementing elevation bands generates better results than without elevation bands. Results show that considering all the complexity arising from natural variability and anthropogenic influences, SWAT performs well in simulating runoff in the upper Rhone watershed. Findings from this study can be applicable for high elevation snow and glacier dominated catchments with similar hydro-physiographic constraints.     

High electrocatalytic effect of Au–Pd alloy nanoparticles electrodeposited on microwave assisted sol–gel-derived carbon ceramic electrode for hydrogen evolution reaction

Various Au–Pd bimetallic nanoparticles were electrodeposited on microwave irradiated carbon ceramic electrodes (MWCCE). Au:Pd molar ratios of 75:25, 50:50 and 25:75 were electrodeposited on MWCCE and their electrocatalytic activities for hydrogen evolution reaction (HER) were evaluated. Among them, the alloy with Au:Pd molar ratio of 25:75 showed highest electrocatalytic activity for HER. The structure and nature of these alloys were characterized by scanning electron microscopy, X-ray diffraction, energy dispersive X-ray spectroscopy, inductively coupled plasma, and cyclic voltammetry. Alloying degree of bimetallic nanoparticles and electrodeposition time were optimized. The electrocatalytic activity of bimetallic nanoparticles was also compared with individual non-alloyed Au and Pd catalysts and the results showed that alloy nanoparticles have higher electrocatalytic activity for hydrogen evolution. The Tafel slopes ranges are obtained from 136 mV dec⁻¹ to 165 mV dec⁻¹ for HER on bare and modified MWCCE and kinetic parameters show that the Volmer step must control the HER. The stability of the best electrode is determined by chronopotentiometric and it showed a good stability.     

Photocathodic protection of 316L stainless steel by coating of anatase nanoparticles

Uniform nanostructure anatase films were coated on 316L stainless steel by the sol-gel dip coating method. Sols with different values of pH were applied. The corrosion protective behavior of coated samples was investigated by electrochemical measurements in 0.5 molar NaCl solutions on samples placed under UV illumination and dark condition using Tafel curves. It was found that in addition to acting as a physical barrier, anatase thin films are more protective under UV illumination due to photocathodic protection. Neutral sols give better protection due to formation of more uniform and less defective coatings.     

In situ growth of carbon nanotubes in alumina–zirconia nanocomposite matrix prepared by solution combustion method

In this work successful synthesis of multiwall carbon nanotube (CNT) using solution combustion and chemical vapor deposition (CVD) methods are reported. Ceramic nanocomposite samples of (Al_2?xFe_xO₃)–(y)ZrO₂ formula with x = 0.017, 0.034 and 0.17 and y = 0.15 were initially prepared. These were then subjected to CVD process during which the in situ reduction of iron oxide to metallic iron (Fe/Fe₃C) phase/s provided the necessary catalyst for the CNT formation. The formation of long flexible filaments with a smooth and regular surface bridging between alumina–zirconia (AZ) grains could be detected. The diameters of the formed filaments were in the range of ～70 to ～320 nm and length of the order of some tens of micrometers. However, transmission electron microscope (TEM) examinations also revealed the existence of small amounts of Bamboo-like carbon along with more or less straight CNTs. This could be related to the lack of strong interactions between the metallic iron phase/s and the nanocomposite support.