Carbon nanotube/polymer nanocomposites: A study on mechanical integrity through nanoindentation

Carbon nanotubes (CNTs) are under intense investigation in materials science owing to their potential for modifying the mechanical proprieties of their composites. In this work, nanomechanical and nanotribological properties of polymer composites, reinforced with multiwall carbon nanotubes (MWCNTs) and single wall carbon nanotubes (SWCNTs), have been studied using the nanoindentation and nanoscratch technique. In particular, three different epoxy resins reinforced using several percentage of two different types of MWCNTs have been studied (range 0–7 wt%). Another resin was reinforced using MWCNTs (range 0–2.5 wt%) and SWCNTs (range 0–5 wt%) as fillers. Hardness and elastic modulus using nanoindenter instrument have been evaluated, while the coefficient of friction of the nanocomposites is obtained using nanoscratch. The results show an evident dependence with the percentage of CNTs. For all types of resins, an optimum in nanomechanical properties is found at intermediate levels of CNTs filling. POLYM. COMPOS., 36:1432–1446, 2015. © 2014 Society of Plastics Engineers     

HTTPScout: A Machine Learning based Countermeasure for HTTP Flood Attacks in SDN

International Journal of Information Security - Nowadays, the number of Distributed Denial of Service (DDoS) attacks is growing rapidly. The aim of these type of attacks is to make the prominent...     

Mechanism of glucose electrochemical oxidation on gold surface

The complex oxidation of glucose at the surface of gold electrodes was studied in detail in different conditions of pH, buffer and halide concentration. As observed in previous studies, an oxidative current peak occurs during the cathodic sweep showing a highly linear dependence on glucose concentration, when other electrolyte conditions are unchanged. The effect of the different conditions on the intensity of this peak has stressed the limitations of the previously proposed mechanisms. A mechanism able to explain the presence of this oxidative peak was proposed. The mechanism takes into account ion-sorption and electrochemical adsorption of OH⁻, buffer species (K₂HPO₄/KH₂PO₄) and halides.     

Mechanical behavior of masonry materials at high temperatures

An experimental campaign is presented to determine the effects of high temperatures on the mechanical properties of several materials for masonry walls (blocks and mortars), testing a series of cylindrical specimens (diameter of 100 mm and height of 200 mm). After compression tests at 20 °C, an experimental procedure was designed for high‐temperature testing. The cylindrical samples were heated in a muffle furnace, then were inserted into a specific apparatus (called ‘thermos’) for maintaining the prescribed temperature, and finally were subjected to a mechanical compression test. The results obtained by applying this procedure show a common variation of the strength, reduction of modulus of elasticity, and corresponding increments of the ultimate strain with temperature enhancement. Specific diagrams and discussion on the results are performed for each material. Copyright © 2014 John Wiley & Sons, Ltd.     

Improving the security of image manipulation detection through one-and-a-half-class multiple classification

Multimedia Tools and Applications - Protecting image manipulation detectors against perfect knowledge attacks requires the adoption of detector architectures which are intrinsically difficult to...     

Determining the liquidus viscosity of glass-forming liquids through differential scanning calorimetry

Viscosity at the liquidus temperature (T_L), η_L, is a critical parameter for the design of new glasses, particularly for industrial glass production where crystallization must be suppressed. However, a direct viscometric determination of η_L for a glass-forming system is difficult due to crystallization. Here we propose an alternative approach for determining η_L through differential scanning calorimetry (DSC). Specifically, DSC is used to measure both the viscosity curve and liquidus temperature of a glass-forming system and then derive its η_L value. The η_L values determined using DSC are found to be in excellent agreement with those measured through viscometry. The DSC approach is applicable to various glass-forming systems covering a wide range of fragilities and η_L values spanning over five orders of magnitude. Other advantages of this approach are its accuracy and small sample requirements.     

Maxwell relaxation time for nonexponential α-relaxation phenomena in glassy systems

We examine the mean relaxation time predicted by the Maxwell relation for stress and structural α-relaxation phenomena. We express this relation using the Markov network framework and present an expression for the average relaxation time under equilibrium and nonequilibrium conditions that is rooted in the energy landscape of a material. We show that structural relaxation times calculated using the Maxwell relation must systematically underpredict the relaxation time. Finally, we report experimental evidence suggesting that the relaxation time obtained from shear viscosity measurements must correspond to a stress relaxation time.