Low-velocity impact damage response of fiberglass/magnesium fiber-metal laminates under different size and shape impactors

Low-velocity impact tests are performed on fiberglass/AZ31B-H24 magnesium fiber-metal laminates (FMLs) with various configurations in order to gain a better understanding of the effect of an impactor's features on the response of this type of FML. For that, impactors with two different shapes (hemispherical and sharp-edged) and sizes are used to impact the specimens. The impact response data, such as the deformation of the contact location and energy absorption, is obtained directly during the impact tests through the impact equipment, while mechanical sectioning was carried out to establish the extent of delaminated area and post-impact residual deformation. While the sharp-edged impactor caused the development of cracks on the metal constituent, and delamination within the specimens, the hemispherical ones imposed more influence over the residual deformation. Noticeable differences are observed in response of FML specimens made with two and three layers of magnesium, especially with respect to the energy absorption capacity. Moreover, finite-element analysis, as a major part of this study, has been employed to simulate the low-velocity impact response of FML specimens. The behavior of specimens has been simulated using the commercial finite-element code ABAQUS. The results imply that there is a good agreement between the experimental and numerical results.     

Memristor-based synaptic plasticity and unsupervised learning of spiking neural networks

Journal of Computational Electronics - Synaptic plasticity is studied herein using a voltage-driven memristor model. The bidirectional weight update technique is demonstrated, and significant...     

Enhanced water splitting through different substituted cobalt-salophen electrocatalysts

Synthesis of stable catalysts for water splitting is important for the renewable and clean energy production. Here, water oxidation activities of cobalt (II) complexes CoL¹-CoL³ (1–3) with salophen type ligands (N,N′-bis(salicylidene)-4-chloro-1,2-phenylendiamine (H₂L¹), N,N′-bis(salicylidene)-4-bromo-1,2-phenylendiamine (H₂L²) and N,N′-bis(salicylidene)-4-nitro-1,2-phenylendiamine (H₂L³)) are studied by electrochemical techniques, FE-SEM images and XRD patterns. Linear sweep voltammetry studies indicate that 2 and 3 have superior activities and only require the overpotential of 316 and 247 mV vs. RHE at current density of 10 mA/cm² with Tafel slopes of 75 and 50 mVdec^?1 at pH = 11. Experiments show relationships between the stability of the complexes and their catalytic activity. It is revealed that substituents on ligands affect the catalytic behaviors. Experiments show that in the presence of 2 and 3, the complexed cobalt ions are likely candidates as molecular catalysts for water oxidation. It is speculated that the O–O bond formation occurs by oxidizing the active center of cobalt complexes.     

Electrochemical performance of La0.8Sr0.2MnO3 oxygen electrode promoted by Ruddlesden-Popper structured La2NiO4

The effects of introducing La₂NiO₄ nanocatalyst on the electrochemical performance of La_0.8Sr_0.2MnO₃ are investigated under solid oxide electrolysis cell and fuel cell modes, as well as open circuit voltage. Extracted data from impedance spectroscopy are interpreted with the analysis of distribution of relaxation times. La₂NiO₄ infiltration effectively reduces the activation energy of the oxygen reactions from 1.35 to 0.99 eV. It also changes the rate controlling process of the overall reaction. Polarization behavior of La₂NiO₄-infiltrated La_0.8Sr_0.2MnO₃ electrode shows superior performance under electrolysis mode compared to the fuel cell mode. Drastic increase in the size of low frequency arc during anodic current passage in the non-infiltrated La_0.8Sr_0.2MnO₃ electrode is hampered by infiltration of La₂NiO₄ nanocatalyst. By applying anodic current on infiltrated La_0.8Sr_0.2MnO₃, no displacement is observed in the position of high frequency peaks in the distribution of relaxation time graphs and only a small increase in height occurs for the low frequency arc. Additionally, La₂NiO₄-infiltrated electrode impressively decreases overpotential by 74% compared to the non-infiltrated one under electrolysis mode at 800°C.     

Analysis of the essential factors for the adoption of mobile learning in higher education: A case study of students of the University of Technology

This paper analyzed the adoption of using mobile learning (m-learning) in higher education. Mobile Learning as a model of e-learning refers to the acquisition of knowledge, skills and attitudes by utilizing mobile technologies. With the increasing coverage of mobile networks, learning services can play the increasing and effective role in education at any time and place. Continuous access via mobile devices creates special facilities like sending and saving the learning content to learners etc, it is accompanied with continuous education. This paper, with a study of “what is the impact of the mobile phone usage in education?” provides approaches and theories of mobile learning in training. The paper aimed to evaluate the essential factors for the adoption and application of education information system that has been created by students. The survey was based on the history of technology adoption and covered students. Furthermore, a case study from students of K. N. Toosi University in Iran was presented to indicate the performance of this method in practice. The statistical society included 300 members from Information Technology students of Iran's K. N. Toosi University of Technology. The factors related to adoption of mobile learning in higher education was classified into seven main categories as: ease of use, trust, characters and personal qualities, context, perceived usefulness of using, behavioral intention, and culture of using a research model. From the results, mobile learning could be one of the promising educational technologies for development in educational environments and culture of using. The context of applications has a significant positive effect on the ease of use factor and usefulness and the ease of use has a positive effect on the usefulness factor. The trust factor has a positive and significant effect on the behavioral intention. The personal features and characters factor have a significant positive effect on the culture of using and the culture of using the application has a significant positive effect on the behavioral intention.     

Covert timing channels: analyzing WEB traffic

In case there is a communication contrary to the system security policies, a covert channel has been created. The attacker can easily disclosure information from the victim’s system with just one public access permission. Covert timing channels, unlike covert storage channels, do not have memory storage and they draw less attention. Different methods have been proposed for their identification, which generally benefit from the shape of traffic and the channel’s regularity. The application nature of HTTP protocol allows the creation of a covert timing channel based on different features of this protocol (or different levels) that has not been addressed in previous researches. This research tries to study the effect of using different features (or levels) of HTTP protocol on identifying the covert channel. The amount of channel’s entropy could be manipulated by changing the channel’s level or adding intentional noise on the channel to protect from the analyzer’s detection. The difference in the placement of the covert channel and the detector causes the amount of channel entropy to be far from the detection threshold. Therefore, we concluded that the analyzer must investigate traffic at all possible levels. Adding noise on the covert channel decrease its capacity, but as entropy increases, it would be harder to detect it.

     

Partial stabilisation of non-homogeneous bilinear systems

In this work, we study in a Hilbert state space, the partial stabilisation of non-homogeneous bilinear systems using a bounded control. Necessary and sufficient conditions for weak and strong stabilisation are formulated in term of approximate observability like assumptions. Applications to parabolic and hyperbolic equations are presented.     

Hybrid particle swarm optimization for rule discovery in the diagnosis of coronary artery disease

Coronary artery disease (CAD) is one of the major causes of mortality worldwide. Knowledge about risk factors that increase the probability of developing CAD can help to understand the disease better and assist in its treatment. Recently, modern computer‐aided approaches have been used for the prediction and diagnosis of diseases. Swarm intelligence algorithms like particle swarm optimization (PSO) have demonstrated great performance in solving different optimization problems. As rule discovery can be modelled as an optimization problem, it can be mapped to an optimization problem and solved by means of an evolutionary algorithm like PSO. An approach for discovering classification rules of CAD is proposed. The work is based on the real‐world CAD data set and aims at the detection of this disease by producing the accurate and effective rules. The proposed algorithm is a hybrid binary‐real PSO, which includes the combination of categorical and numerical encoding of a particle and a different approach for calculating the velocity of particles. The rules were developed from randomly generated particles, which take random values in the range of each attribute in the rule. Two different feature selection methods based on multi‐objective evolutionary search and PSO were applied on the data set, and the most relevant features were selected by the algorithms. The accuracy of two different rule sets were evaluated. The rule set with 11 features obtained more accurate results than the rule set with 13 features. Our results show that the proposed approach has the ability to produce effective rules with highest accuracy for the detection of CAD.