Constitutive modeling of the mechanical behavior of high strength ferritic steels for static and dynamic applications

A constitutive relation is presented in this paper to describe the plastic behavior of ferritic steel over a broad range of temperatures and strain rates. The thermo-mechanical behavior of high strength low alloy (HSLA-65) and DH-63 naval structural steels is considered in this study at strains over 40%. The temperatures and strain rates are considered in the range where dynamic strain aging is not effective. The concept of thermal activation analysis as well as the dislocation interaction mechanism is used in developing the flow model for both the isothermal and adiabatic viscoplastic deformation. The flow stresses of the two steels are very sensitive to temperature and strain rate, the yield stresses increase with decreasing temperatures and increasing strain rates. That is, the thermal flow stress is mainly captured by the yield stresses while the hardening stresses are totally pertained to the athermal component of the flow stress. The proposed constitutive model predicts results that compare very well with the measured ones at initial temperature range of 77 K to 1000 K and strain rates between 0.001 s⁻¹ and 8500 s⁻¹ for both steels.     

Objective evaluation of multidirectional fabric wrinkling using image analysis

In the textile industry, the wrinkled fabrics are regularly evaluated subjectively in reference to a set of visual standards. However, due to the disadvantages of visual evaluation, which are unreliable and time-inefficient, several objective methods were recently developed. In this paper, a new objective evaluation of multidirectional realistic fabric's wrinkling generated by the French method of “cylindre creux” was proposed using the image processing. Four characteristics of wrinkled fabrics were evaluated to estimate wrinkle grade with a statistical model. The study reveals a good correlation between the objective wrinkling evaluation (using image analysis) and the subjective evaluation (using the visual standards).     

Fluorescent dye labeled bacteriophages--a new tracer for the investigation of viral transport in porous media: 1. Introduction and characterization

A new method for the study of pathogen transport in porous media is presented. The method is based on conjugation of fluorescent dyes to target bacteriophages and application of the modified bacteriophages for tracer studies. We demonstrate that the relevant transport determining properties of Rhodamine and several fluorescein-labeled phages are practically identical to those of the native bacteriophages. The advantages of the proposed method relative to direct enumeration of bacteriophages by plaque forming unit method, turbidity, fluorescent microspheres, and other alternative tracers are discussed. Notable advantages include simple quantitation by optical methods, unbiased signals even when virus aggregates are formed, and the ability to decouple inactivation kinetics from transport phenomena. Additionally, the signal reflects the removal and transport of the studied microorganism and not a surrogate.     

Rheology and thermal conductivity of calcium grease containing multi-walled carbon nanotube

Recently, nanofluids attract considerable interest for enhanced rheological behavior and thermal performance. The aim of this research is to study the influence of additives Multi-Walled Carbon Nanotubes (MWCNTs) on the rheological behavior and its structure, thermal conductivity, and the influence of shear thinning rate on oil separation at different temperatures for calcium grease. Various concentrations of MWCNTs (0.5, 1, 2, 3, and 4%) have been added to the grease to obtain the best percentages that improve the properties of nanofluid. The microstructure of MWCNTs and nanofluid were examined by X-ray diffraction (XRD), Transmission Electron Microscope (TEM), and Scanning Electron Microscope (SEM). These experimental investigations were evaluated with a Brookfield programmable Rheometer DV-III ULTRA. The results indicated that the optimum concentration of MWCNTs was 3%, and the dropping point increasing about 11%. The rheological behaviors of the nanofluids show that the grease with various concentrations of MWCNTs demonstrates non Newtonian behaviors and the results indicated that the shear stress, apparent viscosity and thermal conductivity increase with the increase of volume concentration of MWCNTs to 65%, 52%, and% 56, respectively.     

Plasticized poly(vinyl chloride) composites: Influence of different nanofillers as antimigration agents

In this study, plasticized poly(vinyl chloride) (PVC) composites with different nanofillers, including single‐walled carbon nanotubes (SWCNTs), organoclay, TiO₂, and ZnO nanoparticles, were prepared, and their effects on plasticizer migration were investigated. Scanning electron micrographs revealed the dispersion quality of the nanofillers in the polymer matrix. It had a significant influence on the performance of the nanofillers in the process of plasticizer migration. Migration and exudation tests showed that the nanofillers could efficiently hinder plasticizer migration. On the basis of these results, we concluded that carbon nanotubes were the best antimigration agent in the plasticized system. This was ascribed to the high aspect ratio of the SWCNTs and the good interactions between them and the plasticizer. Also, TiO₂ nanoparticles showed a better performance compared to the ZnO nanoparticles. This was due to the more homogeneous dispersion of the TiO₂ in the polymer matrix and the higher surface area of the particles. The differential scanning calorimetry thermograms were in good agreement with the migration tests. The lowest change in the glass‐transition temperature was observed for the composite filled with SWCNTs. This indicated that a lower amount of the plasticizer migrated from PVC. The thermogravimetric analysis curves showed that the incorporation of the nanofillers improved the thermal stability of the PVC. The results could be useful for determining the efficiency of plasticized PVC in applications. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42559.     

The other guys: automated analysis of marginalized malware

In order to thwart dynamic analysis and bypass protection mechanisms, malware have been using several file formats and evasive techniques. While publicly available dynamic malware analysis systems are one of the main sources of information for researchers, security analysts and incident response professionals, they are unable to cope with all types of threats. Therefore, it is difficult to gather information from public systems about CPL, .NET/Mono, 64-bits, reboot-dependent, or malware targeting systems newer than Windows XP, which result in a lack of understanding about how current malware behave during infections on modern operating systems. In this paper, we discuss the challenges and issues faced during the development of this type of analysis system, mainly due to security features available in NT 6.x kernel versions of Windows OS. We also introduce a dynamic analysis system that addresses the aforementioned types of malware as well as present results obtained from their analyses.     

Proposed generalized models for estimating the reliability of a stand-alone solar photovoltaic power system

New mathematical models for the reliability of a stand-alone solar photovoltaic power system (SPV) are proposed in this paper. One of the important reliability indices is the loss-of-load probability (LOLP), so its dependence on the design parameters is modelled. The special role that the battery storage can play to fulfil the desired reliability level (RL) is clearly demonstrated. For a given size of solar cells array (SCA), an econometric model of LOLP is developed to yield the incremental change in the system's total lifetime costs on modifying the LOLP level.The effect of the failure rate of each system component on the SPV reliability level has been estimated and is fully discussed. The behaviour of the SPV reliability level with SCA tilt angle and series-parallel configuration is established under the prevailing working conditions. The significance of the relationship between the preventive maintenance schedule for each of the system components and its reliability is analysed, resulting in a new chart that enables schedules which yield the required system reliability to be planned directly.     

Natural ageing of tri-layer polyethylene film: Evolution of properties and lifetime in North Africa region

The effects of natural ageing in the north Algeria of tri-layer films lay down hot greenhouse made of low-density polyethylene are presented in this work. Ageing was monitored by observing the changes of physical, mechanical and structural effects on the various greenhouse faces. It has been shown that the structural change occur on the outside face of the films, while the inside faces are protected by the dye. The study shows that the measured parameters are directly related to the criteria of evaluation of the greenhouse effectiveness. The lifetime of these films under natural conditions in north Algerian was estimated to be 10 months.     

Carbon Nanotube (10, 0) and Silicon Nanotube (7, 0) as a Novel Material for Drug Delivery of Substituted Eugenols as Antioxidant Drugs

Silicon - The potential of CNT(10, 0) and SiNT(7, 0) and their metal doped CNT(10, 0) and SiNT(7, 0) to adsorb the NH2, OH and Ethyl eugenols are examined. The antioxidant potential of NH2-, OH-...     

Analysis of capacity and coverage region for Rayleigh fading MIMO relay channel

In this paper, we consider Rayleigh fading MIMO relay channel with channel state information at the receivers. First, we extend the previously obtained results for the ergodic capacity of uncorrelated and semi‐correlated MIMO channels and derive closed‐form expressions for the capacity bounds of MIMO relay channel. Next, we study this channel from a new point of view, maximizing coverage region for a desired transmission rate, and investigate the optimal relay location in the sense of maximizing coverage region. However, in order to overcome the mathematical complexity in desired transmission rate analysis, because of the randomness of the multiple antenna channel matrices, we evaluate this rate by using an existing exact formula and also by an approximation we find in the high signal‐to‐noise ratio regime. Numerical results show a perfect match between the Monte Carlo simulations and the obtained analytical closed‐form expressions and also confirm the effectiveness of our approach in cooperative vehicular communication for determining optimal relay location at which the coverage region is maximum. Copyright © 2013 John Wiley & Sons, Ltd.