Automatic seizure detection using a highly adaptive directional time–frequency distribution

Multidimensional Systems and Signal Processing - Electroencephalogram (EEG) signals can be used by a proficient neurologist to detect the presence of seizure activity inside the brain. Automated...     

New radial basis function network method based on decision trees to predict flow variables in a curved channel

Neural Computing and Applications - Open channel bends have fascinated engineers and scientists for decades while providing water for domestic, irrigation and industrial consumption. The presence...     

Assessment of offshore platforms under extreme waves by probabilistic incremental wave analysis

In this study, a novel probabilistic framework named Probabilistic Incremental Wave Analysis (PIWA) is established in order to assess the performance of jacket offshore platforms under extreme waves. The PIWA can take into account the uncertainties in three main elements consisting of sea state parameters, structural response and collapse capacity. The main advantage of the PIWA approach is reflected in decoupling of the wave hazard and structural analyses via an intermediate variable known as the wave height intensity measure. Despite the fact that most of the uncertainties associated with structural response are concentrated in wave hazard, this will enable the PIWA to estimate the probability of failure accurately. Moreover, both static and dynamic wave analyses can be utilized in the PIWA procedure. In this approach, multiple incremental wave analyses are employed to estimate the distribution of structural demand for a wide range of wave height intensities. Subsequently, the mean annual frequency of exceeding a structural limit state is calculated for which this research addresses two different methodologies including demand-based and wave height-based approaches. Furthermore, a new probabilistic-based Reserve Strength Ratio (RSR) is proposed and the probability of exceeding various levels of RSR is provided. To reduce the large number of simulations and hence improving the computational effort in the PIWA procedure, a combination of Latin Hypercube Sampling and Simulated Annealing optimization technique is utilized as an efficient sampling scheme. The PIWA procedure is employed in probabilistic assessment of an existing jacket offshore platform located in the Persian Gulf as well.     

Utilization of Rice Husk Ash as viscosity modifying agent in Self Compacting Concrete

Self Compacting Concrete (SCC) is defined by two primary properties: Deformability and Segregation resistance. Deformability or flowability is the ability of SCC to flow or deform under its own weight (with or without obstructions). Segregation resistance or stability is the ability to remain homogeneous while doing so. High range water reducing admixtures are utilized to develop sufficient deformability. At the same time, segregation resistance is ensured, which is accomplished either by introducing a chemical viscosity modifying admixture (VMA) or by increasing the amount of fines in the concrete. These viscosity modifying admixtures are very expensive and the main cause of increase in the cost of SCC. Therefore, for producing low cost SCC, it is prudent to look at the alternates to help reducing the SSC cost. This research is aimed at evaluating the usage of Rice Husk Ash (RHA) as viscosity modifying agent in SCC, and to study the relative costs of the materials used in SCC.In this research, the main variables are the proportion of RHA, dosage of superplasticizer for flowability and water/binder ratio. The parameters kept constant are the amount of cement, water, fine and coarse aggregate contents.Test results substantiate the feasibility to develop low cost SCC using RHA. In the fresh state of concrete, the different mixes of concrete have slump flow in the range of 595–795 mm, L-box ratio ranging from 0 (stucked) to 1 and flow time ranging from 2.2 to 29.3 s. Out of nine mixes, four mixes were found to satisfy the requirements suggested by European federation of national trade associations representing producers and applicators of specialist building products (EFNARC) guide for making SCC. The compressive strengths developed by the SCC mixes with RHA were comparable to the control concrete. Cost analysis showed that the cost of ingredients of specific SCC mix is 42.47% less than that of control concrete.     

A Cost-Effective Method to Control Seawater Intrusion in Coastal Aquifers

Intrusion of seawater into coastal aquifers is considered one of the most important processes that degrade water-quality by raising the salinity to levels exceeding acceptable drinking standards. Therefore saltwater intrusion should be prevented or at least controlled to protect groundwater resources. This paper presents a cost-effective method to control seawater intrusion in coastal aquifers. This methodology ADR (Abstraction, Desalination and Recharge) includes; abstraction of saline water and recharge to the aquifer after desalination. A coupled transient density-dependent finite element model is developed for simulation of fluid flow and solute transport and used to simulate seawater intrusion. The simulation model has been integrated with an optimization model to examine three scenarios to control seawater intrusion including; abstraction, recharge and a combination system, ADR. The main objectives of the models are to determine the optimal depths, locations and abstraction/recharge rates for the wells to minimize the total costs for construction and operation as well as salt concentrations in the aquifer. A comparison between the combined system (ADR) and the individual abstraction or recharge system is made in terms of total cost and total salt concentration in the aquifer and the amount of repulsion of seawater achieved. The results show that the proposed ADR system performs significantly better than using abstraction or recharge wells alone as it gives the least cost and least salt concentration in the aquifer. ADR is considered an effective tool to control seawater intrusion and can be applied in areas where there is a risk of seawater intrusion.     

Mechanical damage to estabragh fibers in the production of thermobonded layers

Estabragh (Asclepias procerais) fibers are natural, hollow fibers, and the mechanical behavior of these fibers plays a major role in mechanical processing. This work explores the mechanical behavior of estabragh fibers in three different areas—tensile failure, carding behavior, and the construction of nonwoven layers—and reports the main barriers in the spinning process of these fibers. In the first step, a typical stress–strain curve of estabragh fibers is plotted. Fractography of the broken ends by scanning electron microscopy shows the granular nature of the fracture. The likely mechanism of tensile failure is discussed and compared with the fracture of cotton fibers under tensile loading. In the second stage, the carding behavior and likely mechanism of fiber damage during the carding process of estabragh fibers are studied. Both qualitative and quantitative studies show that estabragh fibers experience serious damage during the carding process. The effect of the hollowness of the fibers on their mechanical properties is discussed as well. In the final approach, thermobonded layers of two different blends of estabragh fibers and bicomponent poly(ethylene terephthalate) fibers are produced. Some properties of the produced layers, including moisture absorption, ultraviolet absorption, and bending length, are reported. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

An innovative bed temperature-oriented modeling and robust control of a circulating fluidized bed combustor

Circulating fluidized bed (CFB) combustion systems are increasingly used as superior coal burning systems in power generation due to their higher efficiency and lower emissions. However, because of their non-linearity and complex behavior, it is difficult to build a comprehensive model that incorporates all the system dynamics. In this paper, a mathematical model of the circulating fluidized bed combustion system based on mass and energy conservation equations was successfully extracted. Using these correlations, a state space dynamical model oriented to bed temperature has been obtained based on subspace method. Bed temperature, which influences boiler overall efficiency and the rate of pollutants emission, is one of the most significant parameters in the operation of these types of systems. Having dynamic and parametric uncertainties in the model, a robust control algorithm based on linear matrix inequalities (LMI) have been applied to control the bed temperature by input parameters, i.e. coal feed rate and fluidization velocity. The controller proposed properly sets the temperature to our desired range with a minimum tracking error and minimizes the sensitivity of the closed-loop system to disturbances caused by uncertainties such as change in feeding coal, while the settling time of the system is significantly decreased.     

Simulation, construction and testing of a two-cylinder solar Stirling engine powered by a flat-plate solar collector without regenerator

In this research, a gamma-type, low-temperature differential (LTD) solar Stirling engine with two cylinders was modeled, constructed and primarily tested. A flat-plate solar collector was employed as an in-built heat source, thus the system design was based on a temperature difference of 80 °C. The principles of thermodynamics as well as Schmidt theory were adapted to use for modeling the engine. To simulate the system some computer programs were written to analyze the models and the optimized parameters of the engine design were determined. The optimized compression ratio was computed to be 12.5 for solar application according to the mean collector temperature of 100 °C and sink temperature of 20 °C. The corresponding theoretical efficiency of the engine for the mentioned designed parameters was calculated to be 0.012 for zero regenerator efficiency. Proposed engine dimensions are as follows: power piston stroke 0.044 m, power piston diameter 0.13 m, displacer stroke 0.055 m and the displacer diameter 0.41 m. Finally, the engine was tested. The results indicated that at mean collector temperature of 110 °C and sink temperature of 25 °C, the engine produced a maximum brake power of 0.27 W at 14 rpm. The mean engine speed was about 30 rpm at solar radiation intensity of 900 W/m² and without load. The indicated power was computed to be 1.2 W at 30 rpm.     

Optimal Long-term Operation of Reservoir-river Systems under Hydrologic Uncertainties: Application of Interval Programming

Long-term basin-wide reservoir-river operation optimization problems are usually complex and nonlinear especially when the water quality issues and hydrologic uncertainties are incorporated. It is due to non-convex functions in water quality modeling and a large number of computational iterations required by most of stochastic programming methods. The computational burden of uncertainty modeling can be reduced by a special combination of uncertainty modeling and interval programming, though the problem solution is still a challenge due to model nonlinearity. In this paper, an integrated water quantity-quality model is developed for optimal water allocation at river-basin scale. It considers water supply and quality targets as well as hydrologic, water quality and water demand uncertainties within the nonlinear interval programming (NIP) framework to minimize the slacks in water supply and quality targets during a long-term planning horizon. A fast iterative linear programming (ILP) method is developed to convert the NIP into a linear interval programming (LIP). The ILP resolves two challenges in NIP, first converting the large non-linear programming (NLP) into a linear programming (LP) with minimum approximation and second reducing the iterations needed in interval programming for NLP into just two iterations for the upper and lower limits of decision variables. This modeling approach is applied to the Zayandehrood river basin in Iran that has serious water supply and pollution problems. The results show that in this river basin at dry conditions when available surface water resources are below 85 % of normal hydrologic state and water demands are 115 % of current water demands, the total dissolved solids (TDS) concentration can be reduced by 50 % at the inlet of the Gavkhuni wetland located downstream of the river basin.     

Characterization of reinforcing effect of alumina nanoparticles on the novolac phenolic resin

Very fine alumina nanoparticles were loaded in novolac type phenolic resin (PF) using solution mixing method. The concentration of nanoalumina in PF was varied between 2.5 to 20 wt%. All the compounds were compression molded and then subjected to scanning electron microscopy (SEM), tensile, flexural, and dynamic mechanical analysis (DMA) tests. SEM analysis showed that the nanoalumina were dispersed uniformly at low concentrations, however, at high concentrations, dispersion was suppressed leading to agglomerates in the composites. Mechanical testing revealed that the nanoalumina had a great influence on the strength and stiffness of PF resin particularly at concentrations below 5 wt%. However, at concentration above 5 wt%, the stress concentrations were developed because of the formation of big aggregates that results in strength reduction. Theoretical analyses based on Pukanszky and micromechanical models of tensile modulus revealed that strong interfacial interaction and thick interphase region around the alumina nanoparticles is formed. DMA results suggested that the nanoalumina increased the crosslinking density of the PF resin, possibly around the interface region. It was also postulated that an apparent percolation state is established above 5 wt% loading of nanoalumina in which interphase region comes to contact before direct contact of particle leading to continuous interphase region. POLYM. COMPOS., 35:1285–1293, 2014. © 2013 Society of Plastics Engineers