On the application of higher‐order elements in the hierarchical interface‐enriched finite element method

This article introduces a new algorithm for evaluating enrichment functions in the higher‐order hierarchical interface‐enriched finite element method (HIFEM), which enables the fully mesh‐independent simulation of multiphase problems with intricate morphologies. The proposed hierarchical enrichment technique can accurately capture gradient discontinuities along materials interfaces that are in close proximity, in contact, and even intersecting with one another using nonconforming finite element meshes for discretizing the problem. We study different approaches for creating higher‐order HIFEM enrichments corresponding to six‐node triangular elements and analyze the advantages and shortcomings of each approach. The preferred method, which yields the lowest computational cost and highest accuracy, relies on a special mapping between the local and global coordinate systems for evaluating enrichment functions. A comprehensive convergence study is presented to show that this method yields similar convergence rate and precision as those of the standard FEM with conforming meshes. Finally, we demonstrate the application of the higher‐order HIFEM for simulating the thermal and deformation responses of several materials systems and engineering problems with complex geometries. Copyright © 2015 John Wiley & Sons, Ltd.     

Three‐dimensional FDTD modeling of neurons to solve EEG and MEG forward problem

Neuronal activities including calcium sodium current, ligands current, and synaptic transmembrane current create electromagnetic fields. Here, an analytic method is suggested to obtain the electromagnetic fields and potential signals resulting from the function of nerve cells inside the brain. Modeling simulates the behavior of cells three‐dimensionally. The proposed method employs the electric scalar potential and magnetic vector potential to solve the time‐domain three‐dimensional equations using the partial differential method. All ion flows are considered as electrical current densities. In this method, the brain and desired cells are meshed to solve the problem using the numerical method. As an example, the electric fields, magnetic fields, and signals generated by cingulum nerve fibers are illustrated and compared in C_z, F_z, and T3 electrode positions. A direct analysis method based on the same mechanism and biophysics of the nervous system is proposed. Employing this direct method leads not only to a better understanding of neuronal activity but also to a more accurate vision regarding the accuracy/inaccuracy of experimental and inverse methods. The analysis of these data provides insights into the brain function processes.     

Novel mesoporous Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>/SiO<Subscript>2</Subscript>/CTAB–SiO<Subscript>2</Subscript> as an effective adsorbent for the removal of amoxicillin and tetracycline from water

The current study was carried out to investigate the efficiency of using magnetic mesoporous of cetyltrimethylammonium bromide-functionalized silica-coated magnetite for removing amoxicillin (AMX) and tetracycline (TC) from tap water, river water, and medical wastewater as real samples. The properties of the synthesized adsorbent were characterized through transmission electron microscopy (TEM), scanning electron microscopy, X-ray diffraction spectrometry, Fourier transform infrared spectroscopy, vibrating sample magnetometry, pH_pzc, and also Brunauer, Emmett, and Teller (BET) methods. The BET surface area and the average diameter of mesoporous Fe₃O₄/SiO₂/CTAB–SiO₂ in accordance with TEM were 157.8 m² g^?1 and around 55 nm, respectively. In batch tests, the adsorption parameters, including the initial concentration, contact time, pH of solution, ionic strength, and adsorbent dose, were analysed. The experimental adsorption data were modelled using different classical and recently developed models. According to the results, the maximum adsorption capacities of AMX and TC on mesoporous Fe₃O₄/SiO₂/CTAB–SiO₂ were found to be 362.66 and 220.70 mg g^?1, respectively. Also, the results indicated that AMX and TC loaded on the adsorbent could be easily desorbed with 0.1 mol L^?1 HNO₃⁺ acetonitrile (1:1, v/v) and the adsorbent showed good reusability for the adsorption of the drugs studied.     

An overview of dynamic anomaly detection in social networks via control charts

Detection of anomalies in social networks has always been a topic of interest in the realm of social network analysis. However, in recent years, researchers from industrial process monitoring area have applied their methods for monitoring social networks. In this review paper, we discuss social network monitoring approaches that apply control charts to detect anomalies in social networks. We mention the characteristics of the approaches and will shed some light on different topics that can be considered for further investigation by interested researchers.     

Quarter car active suspension system: Minimum time controller design using singular perturbation method

Suspension systems have been widely applied to vehicles. Every vehicle moving on the randomly profiled road is exposed to vibration and shocks which is harmful both for the passengers in terms of comfort and for the durability of the vehicle itself. From this point of view, it is important to reset to zero displacement, velocity and acceleration of car in minimum time. So, this paper proposes a new minimum time controller based on bang-bang control for the quarter car active suspension systems. First by using singular perturbation method the original suspension system is decomposed into two fast and slow singular subsystems in theory, and then by Pontryagain’s Minimum Principle (PMP) and switching functions, the controller is designed for each subsystem and finally the optimal final time is obtained as maximum optimal time concluded of two subsystems. By using a degree of stability technique with two parameters (instead of four parameters), the optimal time is more reduced and leads to great simplifications in practical implementation. The performance of the controller is compared with the Sub optimal Linear Quadratic Regulator (SLQR) controller using two types of road profiles (step and bump) implemented in MATLAB/Simulink. Test results demonstrate the proposed controller is very more effective and simpler in eliminating fluctuations in suspension systems that finally provide the passengers comfort.     

Multi-robot, dynamic task allocation: a case study

This article presents a subgrouping approach to the multi-robot, dynamic multi-task allocation problem. It utilizes the percentile values of the distributional information of the tasks to reduce the task space into a number of subgroups that are equal to the number of robotic agents. The subgrouping procedure takes place at run-time and at every designated decision-cycle to update the elements of these subgroups using the relocation information of the elements of the task space. Furthermore, it reduces the complexity of the decision-making process proportional to the number of agents via introduction of the virtual representatives for these subgroups. The coordination strategy then uses the votes of the robotic agents for these virtual representatives to allocate the available subgroups. We use the elapsed time, the distance traveled, and the frequency of the decision-cycle as metrics to analyze the performance of this strategy in contrast to the prioritization, the instantaneous, and the time-extended coordination strategies.     

MHD natural convection in a nanofluid filled inclined enclosure with sinusoidal wall using CVFEM

Magnetohydrodynamic flow in a nanofluid filled inclined enclosure is investigated numerically using the Control Volume based Finite Element Method. The cold wall of cavity is assumed to mimic a sinusoidal profile with different dimensionless amplitude, and the fluid in the enclosure is a water-based nanofluid containing Cu nanoparticles. The effective thermal conductivity and viscosity of nanofluid are calculated using the Maxwell–Garnetts and Brinkman models, respectively. Numerical simulations were performed for different governing parameters namely the Hartmann number, Rayleigh number, nanoparticle volume fraction and inclination angle of enclosure. The results show that in presence of magnetic field, velocity field retarded, and hence, convection and Nusselt number decreases. At Ra = 10³, maximum value of enhancement for low Hartmann number is obtained at γ = 0°, but for higher values of Hartmann number, maximum values of E occurs at γ = 90°. Also, it can be found that for all values of Hartmann number, at Ra = 10⁴ and 10⁵, maximum value of E is obtained at γ = 60° and γ = 0°, respectively.     

Systematic integrated process design and control of binary element reactive distillation processes

Integrated process design and control of reactive distillation processes is considered through a computer‐aided framework. First, a set of simple design methods for reactive distillation column (RDC) that are similar in concept to nonreactive distillation design methods are extended to design‐control of RDCs. These methods are based on the element concept where the reacting system of compounds is represented as elements. When only two elements are needed to represent the reacting system of more than two compounds, a binary element system is identified. It is shown that the same design‐control principles that apply to a nonreacting binary system of compounds are also valid for a reactive binary system of elements for distillation columns. Application of this framework shows that designing the reactive distillation process at the maximum driving force results in a feasible and reliable design of the process as well as the controller structure. © 2016 American Institute of Chemical Engineers AIChE J, 62: 3137–3154, 2016     

Novel CuO/polymethylenedisulfide nanocomposite for high performance electrocatalytic determination of hydrochlorothiazide in real samples

Journal of Porous Materials - Surface of a carbon paste electrode was modified by using copper oxide nanoparticles/polymethylenedisulfide (CuO NPs/PMDS) nanocomposite. X-ray diffraction...     

Unrestricted deep metric learning using neural networks interaction

Pattern Analysis and Applications - In many machine learning applications and algorithms, the algorithm performance and accuracy are highly dependent on the metric used to measure the distance...