The Microstructure,Texture and Mechanical Properties of Friction Stir Welded Aluminum Alloy

Russian Journal of Non-Ferrous Metals - The microstructure and texture of 7075-T6 FSW weld with optimal parameters are investigated using optical microscopy, electron back scatter diffraction and...     

Comparison of uncertainty quantification process using statistical and data mining algorithms

Uncertainty quantification has always been an important topic in model reduction and simulation of complex systems. In this aspect, global sensitivity anal     

Self‐Limiting Galvanic Growth of MnO2 Monolayers on a Liquid Metal—Applied to Photocatalysis

Liquid metals offer unprecedented chemistry. Here it is shown that they can facilitate self‐limiting oxidation processes on their surfaces, which enables the growth of metal oxides that are atomically thin. This claim is exemplified by creating atomically thin hydrated MnO₂ using a Galvanic replacement reaction between permanganate ions and a liquid gallium–indium alloy (EGaIn). The “liquid solution”–“liquid metal” process leads to the reduction of the permanganate ions, resulting in the formation of the oxide monolayer at the interface. It is presented that under mechanical agitation liquid metal droplets are established, and simultaneously, hydrated gallium oxides and manganese oxide sheets delaminate themselves from the interfacial boundaries. The produced nanosheets encapsulate a metallic core, which is found to consist of solid indium only, with the full migration of gallium out of the droplets. This process produces core/shell structures, where the shells are made of stacked atomically thin nanosheets. The obtained core/shell structures are found to be an efficient photocatalyst for the degradation of an organic dye under simulated solar irradiation. This study presents a new research direction toward the modification and functionalization of liquid metals through spontaneous interfacial redox reactions, which has implications for many applications beyond photocatalysis.     

Unprecedented Selective Oxidation of Styrene Derivatives using a Supported Iron Oxide Nanocatalyst in Aqueous Medium

Iron oxide nanoparticles supported on mesoporous silica‐type materials have been successfully utilized in the aqueous selective oxidation of alkenes under mild conditions using hydrogen peroxide as green oxidant. The supported catalyst could be easily recovered after completion of the reaction and reused several times without any loss in activity (no metal leaching observed during the reaction), constituting a facile and straightforward example of aqueous oxidation chemistry promoted by iron‐based heterogeneous systems.     

Adsorption of Cr(VI) on Stipa tenacissima L (Alfa): Characteristics,kinetics and thermodynamic studies

This study aims to remove ionic Cr(IV) from aqueous solution using Stipa tenacissima L as a biomass source. The Arabic name for the plant Stipa tenacissima L is HALFA (ALFA) ; it belongs to the category of biosorbents agro-industrial origin. Stipa tenacissima L is from the center of the province of Djelfa Algeria. This biomass was characterized by various analytical techniques such as scanning electron microscopy, energy dispersive spectroscopy and Fourier-transform infrared spectroscopy. In order to optimize the operating conditions for the determination of ions of Cr(VI), the initial concentration of Cr(VI) ions, temperature, pH of the solution and the solid/liquid ratio were individually studied. According to the results, a fix rate of about 90% was recorded. Optimum biosorption conditions were found to be pH ~1, C_o = 50 mg/L, R = 5 g/L and T = 296 K. It was found that biosorption of Cr(VI) ions onto biomass of Stipa tenacissima L was better suitable to Langmuir model. The correlation coefficients for the second-order kinetic model obtained were found to be 0.996 for all concentrations. These indicate that the biosorption system studied belongs to the second-order kinetic model. Thermodynamics parameters as enthalpy, entropy of system and free energy were evaluated, which confirms the feasibility of the process. An empirical modeling was performed by using a 2⁴ full factorial design, and the regression equation for adsorption chromium (VI) was determined from the data. The initial metal ion concentration has the most positive pronounced effect in increasing the chromium (VI) adsorption, whereas the pH and adsorbent dosage have the most negative effect on the process.     

Fitting Spheres to Range Data From 3-D Imaging Systems

Two error functions used for nonlinear least squares (LS) fitting of spheres to range data from 3-D imaging systems are discussed: the orthogonal error function and the directional error function. Both functions allow unrestricted gradient-based minimization and were tested on more than 40 data sets collected under different experimental conditions (e.g., different sphere diameters, instruments, data density, and data noise). It was found that the orthogonal error function results in two local minima and that the outcome of the optimization depends on the choice of starting point. The centroid of the data points is commonly used as the starting point for the nonlinear LS solution, but the choice of starting point is sensitive to data segmentation and, for some sparse and noisy data sets, can lead to a spurious minimum that does not correspond to the center of a real sphere. The directional error function has only one minimum; therefore, it is not sensitive to the starting point and is more suitable for applications that require fully automated sphere fitting.     

Refractive index changes in AlGaN/GaN heterostructure field-effect transistors

Using the envelope wavefunction approximation and the compact density matrix formalism, we have investigated theoretically the linear and nonlinear refractive index changes in AlGaN/GaN quantum well heterostructures aimed for designing electro-optical modulators. The confining potential in the heterostructures is assumed to be semiparabolic. Simulated results reveal that the refractive index changes strongly depend on both the Al composition and the delta-doping concentration. On the other hand an applied electric field further enhances the refractive index changes. Compared with AlGaAs/GaAs heterostructures and quantum dots, the amount of the refractive index is larger in the AlGaN/GaN quantum well heterostructures studied. The fact to have a large refractive index change leads to the use of relatively weaker incident beam intensities.     

Preparation and properties of electroless Ni–Zn–P alloy films

Electroless deposition of Ni–Zn–P layers was studied on steel electrodes by varying the bath temperature (40–90°C), pH and chemical composition. The deposition parameters were optimized. Alloys containing 70–86 wt % Ni, 6–20 wt % Zn and 6–10 wt % P are obtained at 20 m h^–1 and 85°C. Corrosion measurements were performed in aerated 5% sodium chloride solution, the corrosion potential and current density are, respectively, –0.49 V/SCE and 2.6 A cm^–2.     

RIP – A robust IP access architecture

This research is of the view that only tightly coordinated work among security components as we know them today including firewalls, traffic analysis modules, intrusion detection systems, antivirus remediation systems, etc., is likely to take us closer to a more effective solution against some security threats. A structured Robust IP (RIP) access architecture is described and its components are analyzed through the use of a proof of concept testbed. Examples of the use of RIP and the heuristics it implements are evaluated. We also compare RIP performance to existing work. We show that there are currently some tradeoffs that need to be made between accuracy and responsiveness. We believe that this collaborative communication style between the components represents a significant step in the direction of self-defending networks and innovation in the area.     

Appraisal and reporting of security assurance at operational systems level

In this paper we discuss the issues relating the evaluation and reporting of security assurance of runtime systems. We first highlight the shortcomings of current initiatives in analyzing, evaluating and reporting security assurance information. Then, the paper proposes a set of metrics to help capture and foster a better understanding of the security posture of a system. Our security assurance metric and its reporting depend on whether or not the user of the system has a security background. The evaluation of such metrics is described through the use of theoretical criteria, a tool implementation and an application to a case study based on an insurance company network.