Distributed faulty node detection and recovery scheme for wireless sensor networks using cellular learning automata

Wireless Networks - In a wireless sensor network (WSN), there is always the possibility of failure in sensor nodes. Quality of Service (QoS) of WSNs is highly degraded due to the faulty sensor...     

A self‐learning stream classifier for flow‐based botnet detection

Botnets have been recently recognized as one of the most formidable threats on the Internet. Different approaches have been designed to detect these types of attacks. However, as botnets evolve their behavior to mislead the signature‐based detection systems, learning‐based methods may be deployed to provide a generalization capacity in identifying unknown botnets. Developing an adaptable botnet detection system, which incrementally evolves with the incoming flow stream, remains as a challenge. In this paper, a self‐learning botnet detection system is proposed, which uses an adaptable classification model. The system uses an ensemble classifier and, in order to enhance its generalization capacity, updates its model continuously on receiving new unlabeled traffic flows. The system is evaluated with a comprehensive data set, which contains a wide variety of botnets. The experiments demonstrate that the proposed system can successfully adapt in a dynamic environment where new botnet types are observed during the system operation. We also compare the system performance with other methods.     

A novel micromechanical model of nonlinear compression hysteresis in compliant interfaces of multibody systems

A micromechanical model of nonlinear hysteretic compression between interacting bodies of multibody systems, covered with fibrous structures, has been created and validated experimentally in this work. As an application, a multibody dynamic model of an upright piano action mechanism with felt-covered contacting bodies is considered, and the obtained results were verified using experiments. Felt, as a typical nonwoven fiber assembly, has been used in various contact surfaces of piano action mechanisms to transfer the force applied on the key to other components, smoothly and continuously. To keep the simulation time tractable in the mechanistic multibody dynamic model, interaction between felt-lined interfaces has to be simplified enough so that in each step of simulation time, contact forces can be calculated as a function of penetration depth between colliding objects. The developed micromechanical approach is capable of estimating nonlinear bulk response of felt in terms of microstructural parameters of the network, assuming a binomial distribution of the number of fiber contacts and bending of constituent fibers. Hysteresis is included based on a fiber-to-fiber friction approach, which generates a speed-independent response to compressive loading schemes, as has been observed in experiments. A computational algorithm is introduced to apply the sophisticated hysteretic micromechanical model to the multibody systems simulation, including transitions between loading–unloading stages.     

NON‐PDC Observer‐Based T‐S Fuzzy Tracking Controller Design and its Application in CHAOS Control

In many mechanical devices with chaotic behavior, stabilizing unstable periodic orbits (UPOs) of the system has positive effects in the lifetime and effectiveness of these devices. In this study, a new non‐parallel distributed compensation (non‐PDC) observer‐based tracking controller is presented for Takagi–Sugeno fuzzy systems to control the chaotic behavior of such systems. Asymptotic stability synthesis of the closed‐loop system is investigated using a fuzzy Lyapunov function to derive less conservative conditions than common quadratic Lyapunov function‐based approaches. To tackle the main drawback of the fuzzy Lyapunov‐based approaches, which assume some upper bounds on the derivatives of the fuzzy grade functions, we propose a new procedure by considering a constraint on the control signal. The new design conditions are given in the form of linear matrix inequalities (LMIs). The proposed control structure is applied to spinning disks in which chaos phenomena appear in lateral vibration. Simulation results are given to show the applicability of the proposed tracker to the UPO problem.     

Optimization of an Aqueous Extraction Process for Pomegranate Seed Oil

Response surface methodology employing a five-level, four-variable central composite rotatable design was applied to study the effects of extraction time, extraction temperature, pH and water/solid ratio on the extraction yield of pomegranate seed oil using an aqueous extraction approach. In addition, quality indices, fatty acid composition and antioxidant activity of the obtained oil were studied and compared with those of typical hexane-, cold press- and hot press-extracted oil. Aqueous extraction resulted in the maximum oil recovery of 19.3% (w/w), obtained under the following critical values: water/solid ratio (2.2:1.0, mL/g), pH 5.0, extraction temperature = 63 °C and extraction time = 375 min. This yield is lower than that obtained via hexane extraction (26.8%, w/w) and higher than the yields from cold press (7.0%, w/w) and hot press (8.6%, w/w) extraction. A comparison of the characteristics of the oils based on extraction method revealed that the unsaturated fatty acid content was highest for the oil obtained by aqueous extraction. In addition, higher levels of iodine and peroxide and lower levels of acid, p-anisidine and unsaponifiable matter were observed. The oil obtained with aqueous extraction also exhibited higher antioxidant activity than oils obtained by hexane or hot press extraction.     

Improvement of railway performance: a study of Swedish railway infrastructure

The volume of rail traffic was increased by 5 % from 2006 to 2010, in Sweden, due to increased goods and passenger traffic. This increased traffic, in turn, has led to a more rapid degradation of the railway track, which has resulted in higher maintenance costs. In general, degradation affects comfort, safety, and track quality, as well as, reliability, availability, speed, and overall railway performance. This case study investigated the needs of railway stakeholders responsible for analysing the track state and what information is necessary to make good maintenance decisions. The goal is to improve the railway track performance by ensuring increased availability, reliability, and safety, along with a decreased maintenance cost. Interviews of eight experts were undertaken to learn of general areas in need of improvement, and a quantitative analysis of condition monitoring data was conducted to find more specific information. The results show that by implementing a long-term maintenance strategy and by conducting preventive maintenance actions maintenance costs would be reduced. In addition to that, problems with measured data, missing data, and incorrect location data resulted in increased and unnecessary maintenance tasks. The conclusions show that proactive solutions are needed to reach the desired goals of improved safety, improved availability, and improved reliability. This also includes the development of a visualisation tool and a life cycle cost model for maintenance strategies.

     

Visible-light-active silver- , vanadium-codoped TiO<Subscript>2</Subscript> with improved photocatalytic activity

Optimized doped TiO₂ is necessary for efficient visible light harvesting and widening the applications spectrum of TiO₂-based materials. Titanium dioxide doped with silver and/or vanadium has been synthesized by one-pot hydrothermal method without post-calcination. Codoping induced visible light absorption while maintaining the photoactive anatase phase along with good crystallinity. Synthesized products are in nanometer range and possess high specific surface area. Having nearly spherical morphology, the particles are distributed and the particle size estimated from TEM observation is in accordance with the XRD results. Spectroscopic investigations reveal that the doped atoms successfully entered the TiO₂ lattice modifying the band structure. The narrowed band gap allows visible light photons for absorption, and the codoped samples displayed enhanced visible light absorption among the synthesized samples. Photodegradation performance evaluated under visible light irradiations showed that silver- , vanadium-codoped TiO₂ have the best visible light photocatalytic activity attributed to stable configuration, high visible light absorption, coupling between silver and vanadium and their optimal doping concentration.     

A critical review on asphaltenes scaling equations

Asphaltenes precipitation and deposition are complex phenomena. The latter can mainly be investigated experimentally under certain conditions. Due to convenient experimental time and cost, several thermodynamic approaches/models have been developed. Albeit these models include a variety of complex parameters, they could not be applied effectively. Scaling equations are simply formulated to predict precipitation under different conditions. The present study was intended to make a critical review on developed asphaltene equations. It was concluded that current scaling equations need to be further developed for wider applications.     

Predicting the response of Hamilton Harbour to the nutrient loading reductions: A modeling analysis of the “ecological unknowns”

We examine the likelihood of delisting the Hamilton Harbour as an Area of Concern, if the nutrient loading reductions proposed by the Remedial Action Plan are actually implemented. Our analysis suggests that the chl a criterion of 10 μg L^{− 1} is achievable, but the water quality setting process should explicitly accommodate the natural variability by allowing for a realistic percentage of violations, e.g., exceedences of less than 10–15% of the weekly samples during the stratified period should still be considered as compliance of the system. The current epilimnetic total phosphorus criterion of 17 μg L^{− 1} is probably stringent and therefore a somewhat higher value (e.g., 20 μg L^{− 1}) may provide a more realistic goal. Phosphorus dynamics in the sediment–water column interface need to be revisited, as the internal nutrient loading can conceivably be a regulatory factor of the duration of the transient phase and the recovery resilience of the Harbour. We also pinpoint two critical aspects of the system dynamics that invite further investigation and will likely determine our predictive capacity to assess compliance with the chlorophyll a criterion of 10 μg L^{− 1}, i.e., the nutrient recycling mediated by the microbial food web and the structural shifts towards a zooplankton community dominated by large-sized and fast-growing herbivores. The latter prospect highlights the notion that the bottom-up (i.e., nutrient loading reduction) approach historically followed in the Harbour was sufficient to bring the system in its present state, but any further improvements should be viewed in the context of a combined bottom-up and top-down (i.e., alleviation of the zooplanktivorous pressure) control.     

Photocatalytic decomposition of methyl tert-butyl ether in aqueous slurry of titanium dioxide

The photocatalytic degradation of methyl tert-butyl ether (MTBE) was investigated in the aqueous slurry of titanium dioxide (TiO₂) particles irradiated with xenon lamp in a batch reactor. The reaction was found to follow a pseudo-first-order kinetics and the reaction rate increased by raising the TiO₂ loading and the UV light intensity. The reaction rate constant was proportional to the square root of the UV intensity. An upper plateau level was observed for the reaction rate constant, corresponding to a steady photoproduction of hydroxyl radicals at high catalyst concentrations. The experimental data was analyzed using a modified Turchi–Ollis model to account for changes in the catalyst loading. It was found that this model predicted the observed trend in the pseudo-first-order rate constant if the reaction pathway involves the interaction between adsorbed hydroxyl radicals and solvated molecules.