In term of material used in redox flow batteries, electrodes nano-material carbon-based composites are the most common (including carbon nano-tubes and graphene). Such materials have high porosity, enlarging the active surface area of the electrode. In these Nano- porous materials the electrolyte flow through a 3D electrode. Unlike in planar materials the electrolyte flow past 2D electrode. To study the effect of porosity on electrical properties and electrochemical response of the electrode; porosity and morphology of the sample were varied in a systematic approach. Then the effect on electrochemical response and kinetics were captured by cyclic voltammetry. This allows correlating pore structure variation to electrochemical properties. This have shown that the increase in porosity results in an enhancement in the diffusivity and kinetics.
Development of optical epoxy coating with self-healing abilities to withstand the harsh desert environment. Two self-healing approaches, intrinsic and capsule based, are incorporated into the epoxy using Cellulose Acetate Butyrate as the self-healing agent. Fabrication methods of the mixture preparation and coating technique are briefly discussed along with the outdoor testing of samples and the results obtained.
The ability of hygroscopic materials to adsorb moisture (H2O) from the humid air has been extensively studied and their applications are countless. Hygroscopic materials used as cloud seeding are capable to modify weather conditions and augment precipitations. Conventional cloud seeding such as NaCl has a limited water uptake performance. This study demonstrates that novel hygroscopic materials of NaCl coated with thin layer of either TiO2 or SiO2 show better hygroscopic properties and water uptake capacity.
In order to partially or totally replace defective hard tissues, biomaterial scientists have been looking for synthetic ceramic-polymer composites to match the composition, microstructure and properties of natural hard tissues.This work aims at the study of using alumina (Al2O3) nanoparticles as a reinforcing agent for a polymeric matrix based on ultrahigh molecular weight polyethylene (UHMWPE). Groups of alumina nanoparticles (Al2O3) dispersed UHMWPE samples were prepared using injection molding technique at different nanofiller concentrations. The mechanical and thermal properties of the injection molded samples were measured to investigate the impact of alumina nanoparticles concentration on the characteristics of the produced composites. Different characterization techniques have been used. Among these tensile testing, thermo-gravermetric analysis (TGA), differential scanning calorimetry (DSC), and scanning electron microscope (SEM).
Light weight cores are widely used in composite sandwich structures due to their unique ability to provide low weight and high stiffness to weight ratios. These unique properties stem from cores' highly porous structure, which also renders them inherently weak. Accordingly, cores used in sandwich structures are susceptible to sustain damage due to inadvertent loading. Since the honeycomb is sandwiched between two sheets, nondestructive methods are much more appealing. However, common nondestructive techniques have limited effectiveness in inspecting light weight cores as their porous structure renders them dispersive to ultrasound waves, while inspecting them using sub-ultrasound frequencies has been introduced lately as a promising alternative to ultrasound inspection. However, this approach requires a priori knowledge of the wave propagation characteristics in the inspected material. Accordingly, this work relies on finite element computations to quantify the phase velocities and dispersive properties of low frequency elastic wave propagating in aluminum honeycombs.
Pollution is one of the main problems that today's world is facing. It can be of different types such as air and soil pollution. This research aims to reduce these kinds of pollution by reducing the space cooling, energy consumption and recycling tire rubber waste. While polystyrene (PS) was used as a matrix in this research, Devulcanized rubber (DVR) was used as a filler in the matrix. The measured thermal conductivity of 30 % DVR composite is lower than that of scrape rubber-polyester composite, crumb rubber-concrete panel and plaster-rubber board, by 46.5 %, 73.34 % and 54.11%, respectively. This makes DVR-PS developed composites good alternatives to be used in building insulation industries. In addition the developed DVR-PS has good thermal properties, if they were compared with the available commercial thermal insulators.
The dynamical relationship between prey and predator has long been and will continue to be one of the effective themes in ecology because of its universal existence and importance. In this paper, we propose a delay differential model for predator-prey system with hunting cooperation on predator (cooperative hunting increases as predator density increases). We consider that the rate of change of density of population depends on growth, death and intra-specific competition for the predators, with logistic growth rate for preys. We incorporate time-delay in the growth component for prey and predator to represent the gestation period for preys. We study the existence of positive equilibrium points and their asymptotic stabilities. Hopf bifurcation is obtained in terms of critical values of time-delays. The system may have a stable periodic orbit, depending on parameter values. The presence of time-delays in the model improves the stability of the solutions and enriches the dynamics of the model. Numerical simulations are provided to validate the derived theoretical results.
Due to the huge number of mobile devices expected to be connected to 5G wireless networks and their expected demand in high data-rate, the core network and the backhaul links are expected to be congested with the large amount of data traffic. Caching the most popular files at the network edge and in user?s devices will provide a close proximity to the end user which will help to offload traffic in the core network, minimize the overall system latency, and to increase the cache hit probability. Device to Device (D2D) communication can be utilized to exchange the cached files between any pair of devices upon request. However, there are many challenges that are needed to be addressed including popularity index, interference management, mode selection, device discovery, and content placement. This work attempts to solve most of the abovementioned problems via collaborative content caching and sharing using D2D communication in 5G networks. The proposed system model will exploit the social-networking concept, assuming the cell structure in a condensed populated area. It will be validated and simulated, and the results will be compared to the base-line system performance reported in literature.
Bullying and stalking through cyberspace have become serious phenomena in the Internet era, impacting mainly young users and teenagers. Many tragic incidents have occurred, especially in the West, including self-harm and suicide due to these problems. To protect the victims, many countries such as the United Arab Emirates (UAE), the United States (US), England and Canada have codified laws dealing with cyber-crimes, including cyber-harassment. To determine the adequacy of the laws in addressing these issues, we present in this paper a legal analysis of the existing anti-bullying and stalking laws in the UAE, the US, England, and Canada. The purpose is to gain perspective on the characteristics of the laws and their ability to protect the society from various forms of crimes associated with cyberbullying and stalking. The paper also presents recommendations and steps to help combat cyberbullying and cyberstalking and protect our youth from these issues.
Databases are very crucial for the implementation of any kind of system, and integrity and confidentiality of stored data is what makes it valuable. Attacks on databases may differ in nature from those on normal operating systems, nonetheless it requires a forensic approach that might be specific for databases. In this paper, we discuss SQL injection for malicious SQL statements execution from an insider and how digital forensics might help in discovering it. We also discuss how the concept of rootkit can be planted by an insider into a relational database system to conceal a user account from the view of a database administrator and thus can use this account as a backdoor to access the database for malicious purposes.
