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The article presents an analysis of electromagnetic transient processes in long ultra-high voltage transmission lines, taking into account shield wires. It was shown that EMTP and Matlab/Simulink software are currently widely used in the study of transient processes in power lines. The EMTP software package uses the finite element method when integrating the equation that mathematically models the distributed parameter transmission line. The Matlab/Simulink software uses the d'Alembert method. In both cases, it is not known how the boundary conditions for the partial differential equation that mathematically models the transmission line are determined. The power line is analyzed as a distributed parameter system, described by a second-order partial differential equation. The advantage of the proposed method of calculating the boundary conditions for the abovementioned equation is the use of boundary conditions of the second and third types of Neumann and Poincaré, which allowed us to take into account the mutual influence of shield wires and phase conductors of the line in one power system. On this basis, the methodology for obtaining time domain graphs, spatial distributions, and traveling wave distributions of voltages and currents for phase conductors and line shielding wires is presented. The results of a computer simulation of transient processes when switching on the power line, taking into account controlled phase commutation and under single-phase earth fault conditions, are presented. All calculation results of transient processes presented in the article were obtained exclusively using numerical methods. [ABSTRACT FROM AUTHOR]

The overhead electrical power lines, which are part of the electricity distribution network, could be considerable threat to different bird species. The main incidents are related to electrocution and bird`s collision with power lines. The biggest danger comes from electrocution – in these cases birds die as a result of contact with the power line. The electrical current generates electric arc through the bird and the power line and leading to the birds’ instant death. The Green Balkans, as а breeder in SPA Sakar BG 002021 Bulgaria, and under the projects “Lesser Kestrel Recovery” LIFE11 NAT/BG/360 and “LIFE for Lesser Kestrel” LIFE19 NAT/BG/001017 succeeded to recover Lesser Kestrel (Falco naumanni, Fleischer 1818) and among the aims of the project was to take measures to mitigate the threat of electrocution. Among the operational over ground power grid lines in Bulgaria, according to the electrical voltage, the most dangerous and life threatening to birds is the mid voltage power supply grid (20 kV) that is also the main cause for death from electrocution. The Green Balkans` team conducted field research of the dangerous types of pylons, on-site isolation of electricity pylons has been identified within a range of 4.5 km of the Lesser Kestrel colony. According to the way of safeguarding the elements of the electrical grid several different devices were used: “Rigid bird protective cover”, perch guards and bird discouragers. Safeguarding by installation of perches has also been done. The isolation of dangerous pylons in the electrical network ensured safe conditions not only for the Lesser Kestrels, but also for other birds that use the power line elements as landing sites, rest spots, or even for nesting. [ABSTRACT FROM AUTHOR]

This paper deals with the reduction in electrical losses and the minimization of voltage deviation in electrical power grids. To this end, a novel heuristic-based approach is proposed for controlling reactive power injections along an electrical grid with distributed generation using distributed photovoltaic (PV) generation. The proposed approach consists of applying a heuristic, namely a genetic or firefly algorithm, to solve the loss and voltage deviation optimization problem by controlling PV reactive power injections. The proposed method was tested on a radial 100-bus network with an intense penetration of PV generation. The obtained results indicate that the proposed method consistently yields superior grid performance when compared to algorithms previously proposed in the literature. In fact, it led to a reduction in the active power supplied by the reference bus to the grid, thereby alleviating the burden imposed on the most upstream parts of the distribution network. As a consequence, the proposed method contributes to a power-efficient network, enhancing its loss performance and voltage stability. [ABSTRACT FROM AUTHOR]

The paper considers the task of creating an instrumental system for optimizing the exchange of active power of the trunk and distribution networks, taking into account the price indicators of electricity in a joint and separate mode of operation. As part of the development of a simulation model of the automated control system of the local intelligent power system MicroGrid, the results of modeling the exchange of active power of the power connection from the main network of the main South of Russia main electrical networks and the distribution network of the university campus (in which classical sources of generation are combined with solar, wind and hydrogen energy) are presented. In a single model, the electrical mode of operation of networks is simulated in the voltage range of 0.4–500 kV. Simulation is carried out in steady state and transient mode. Slow, real and fast time modes are available. Simulation of emergency control systems has been implemented. The modes of synchronization of the main and distribution networks in normal and emergency circuits are considered. Reliability control and monitoring of the main operating parameters are carried out. The active power exchange module created on the basis of the results of the simulation as part of the software package « RETREN » will make it possible to use this complex to automate the management of local power system. The energy system, in addition to power from the grid, includes gas generation, solar panels installed on the roofs of campus buildings, wind turbines and stationary hydrogen power plants operating on hydrogen fuel cells. The complex of designers allows organizing human-machine interfaces of any complexity on completely domestic software products. [ABSTRACT FROM AUTHOR]

One possible device authentication method is based on device fingerprints, such as software- or hardware-based unique characteristics. In this paper, we propose a fingerprinting technique based on passive externally measured information, i.e., current consumption from the electrical network. The key insight is that small hardware discrepancies naturally exist even between same-electrical-circuit devices, making it feasible to identify slight variations in the consumed current under steady-state conditions. An experimental database of current consumption signals of two similar groups containing 20 same-model computer displays was collected. The resulting signals were classified using various state-of-the-art time-series classification (TSC) methods. We successfully identified 40 similar (same-model) electrical devices with about 94% precision, while most errors were concentrated in confusion between a small number of devices. A simplified empirical wavelet transform (EWT) paired with a linear discriminant analysis (LDA) classifier was shown to be the recommended classification method. [ABSTRACT FROM AUTHOR]

The mathematical model of a fragment of a high-voltage electric network is developed in this paper. The network consists of a long power line with distributed parameters and an equivalent three-phase active-inductive load. Neumann and Robin—Poincare boundary conditions were used to identify the boundary conditions for the long line equation. The parameter output voltage (voltage at the end of the line) is introduced into the paper for further universal use of the developed line model. On the basis of the developed mathematical model, the program code is written in the algorithmic language Visual Fortran. By means of it, oscillograms of transient electromagnetic processes of voltages and currents in the form of spatial, temporal and temporal-spatial distributions during remote two-phase short circuits in the transmission line of high voltage are obtained. Two transient electromagnetic processes are analyzed in the present work. The first one was analyzed during the switching on of the line to the normal mode of operation with the subsequent transition to the emergency mode. The second one was analyzed during the switching on the line in the mode of a remote two-phase short circuit to the ground. The results of transient electromagnetic process simulation in the form of analyzed figures are shown. All the results presented in this paper were obtained exclusively using numerical methods. [ABSTRACT FROM AUTHOR]

Electrically interconnected suspension (EIS) has recently emerged for vehicle vibration control. It utilises direct current (DC) motors and electrical networks (EN) to achieve the interconnection of multiple independent suspensions. This innovative EIS system can decouple heave and roll motions, enabling independent vibration control with corresponding EN resistance adjustments. The continuity and accuracy of the resistance adjustments directly influence the vibration control performance of EIS. In this paper, a novel closed-loop current control unit (CCU) is introduced and designed specifically for the EIS system to adjust the EN resistance continuously and accurately, corresponding to the damping variation method in the previous EIS system, thereby achieving high-performance semi-active vibration control. The CCU employs a pair of high-frequency Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFETs) to create a bidirectional switch in parallel with a resistor. By turning the MOSFET switches on and off with a high-frequency Pulse Width Modulation (PWM) signal with an appropriate duty cycle, the resistance of the EN can be dynamically adjusted, consequently altering the damping characteristics of the EIS. The non-linearities from electrical components like inductors and MOSFET switches are inevitable, potentially causing deviations between the actual EN and its theoretical model. Such deviations might compromise the decoupling characteristics of the EIS. Therefore, a robust sliding mode control (RSMC) strategy is implemented for the resistance control, forming a closed-loop CCU. In addition, two H ∞ controllers are designed to obtain the desired vertical force and rotational torque for EIS, which are feedbacked to the CCU, enhancing the control performance. To validate the effectiveness of the EIS with the proposed closed-loop CCU, a series of experiments is conducted on a half-car test rig. The results show significant improvements in vibration control compared to a traditional passive suspension system, demonstrating the potential of this innovative EIS technology to enhance ride comfort. [ABSTRACT FROM AUTHOR]

We calculate effective impedances of infinite LC- and CL-ladder networks as limits of effective impedances of finite network approximations, using a new method, which involves precise mathematical concepts. These concepts are related to the classical differential operators on weighted graphs. As an auxiliary result, we solve a discrete boundary value Dirichlet problem on a finite ladder network. [ABSTRACT FROM AUTHOR]

In 2019, Ye and Yan computed the effective resistances in the nearly balanced complete bipartite graph K n , n − p K 2 (p ≤ n). Then the result was extended to K m , n − p K 2 (p ≤ min { m , n }) very recently. In this paper, we obtain the effective resistances and the number of spanning trees in any complete bipartite graph plus a matching. [ABSTRACT FROM AUTHOR]

Using the theory of electrical network, we first obtain simple formulas for the number of spanning trees of a complete bipartite graph containing a certain matching or a certain tree. Then we compute the effective resistances (i.e., resistance distance in graphs) in the nearly complete bipartite graph G (m , n , p) = K m , n − p K 2 (p ≤ min { m , n }) , which extends a recent result (Ye and Yan, 2019) on the effective resistances in G (n , n , p). As a corollary, we obtain the Kirchhoff index of G (m , n , p) which extends a previous result by Shi and Chen. Using the effective resistances in G (m , n , p) , we find a formula for the number of spanning trees of G (m , n , p). In the end, we prove a general result for the number of spanning trees of a complete bipartite graph containing several edges in a certain matching and avoiding others. [ABSTRACT FROM AUTHOR]

The electrical network optimization is an important aspect of reducing the development cost of offshore wind farm because it accounts for nearly 25% of total investment. This paper presents an integration of the random fork tree coding scheme, a union-finding algorithm and electrical parameter calculating models for electrical network optimization. The coding scheme is developed for the first time for integrated optimization of the tree connection topology, substation positions, and cable cross sections to solve the defects of conventional step-by-step approaches such as minimum spanning tree, to achieve the most economical solution. The case studies clearly show that the proposed method, when coupled with the Omni-optimizer, achieves optimal economical matching solutions and can be applied for optimization of the tree-structure electrical network with any number of wind turbines and substations. However, the proposed method is not applicable for other topological structures, where the coding schemes need to be re-modelled. Also, gradient algorithms may be used in the optimization for convergence enhancement for hundreds of decision variables of the large-scale offshore wind farm. • A novel method proposed for optimization of wind farm electrical network. • The random fork tree coding proposed for connection topology for the first time. • A union-finding algorithm for loop identifications integrated into optimization. • Electrical network optimization of a discrete wind farm successfully achieved. • Optimal economical topology solutions obtained through the proposed method. [ABSTRACT FROM AUTHOR]

Grid connection is an important consideration when it comes to integrating an energy source. A common problem with the existing wind energy conversion systems is that they are often located far from energy consumption centres. Owing to their remote location these systems are sometimes forced to connect with weak distribution networks which are usually designed for small linear loads. When the nature of these loads is changed, the voltage level at the point of common coupling may go above or below the nominal value which may result in power system instability. To improve the voltage variation, this study discusses an optimal current calculation technique based on Thevenin equivalent parameters of an electrical network. The functional capability of the technique is demonstrated with the help of a traditional converter topology utilised as a power conditioning system for a permanent magnet synchronous generator connected to a weak grid. The system in particular monitors a medium voltage distribution line, measures line load impedance and redistributes the currents in a way that provides maximised power transfer into a network with least incurred losses. A real‐time controller with built‐in data acquisition/field‐programmable gate array modules is used for the execution of experimental investigations. [ABSTRACT FROM AUTHOR]

This study proposes a two-stage game–data envelopment analysis (DEA) approach for cost-efficiency (CE) measurement using centralized and Stackelberg game models. Each decision-making unit (DMU) is proposed to make up two-stage network structures (or processes), where all the first-stage outputs are the only second-stage inputs. The main contribution of this study is the development of cooperative and non-cooperative models for CE measurement and implies a unique CE decomposition. We apply centralized and Stackelberg approaches for cooperative and non-cooperative assumption between two stages. We proposed a simplified version of the two-stage DEA network CE model. Applying the proposed model for CE calculation reduces both the number of constraints and variables, resulting in a sharp reduction in computational requirements. The applicability of the presented model is demonstrated in the context of studying the output of the electrical network in Iran. The results of the case study show that in a two-stage network, the proposed DEA model can provide accurate estimates of CE. This paper aids the two-stage network structures to control the costs by weak DMUs management. To the authors’ knowledge, this paper is the first research on the CE in a network by the DEA approach so that the relationships between the internal stages of the network are considered. [ABSTRACT FROM AUTHOR]

In our study of electrical networks we develop two themes: finding explicit formulas for special classes of functions defined on the vertices of a transient network, namely monopoles, dipoles, and harmonic functions. Secondly, our interest is focused on the properties of electrical networks supported on Bratteli diagrams. We show that the structure of Bratteli diagrams allows one to describe algorithmically harmonic functions as well as monopoles and dipoles. We also discuss some special classes of Bratteli diagrams (stationary, Pascal, trees), and we give conditions under which the harmonic functions defined on these diagrams have finite energy. [ABSTRACT FROM AUTHOR]

Electrical transmission systems consist of a huge number of locations (nodes) with different types of measurements available. Our aim is to derive a subset of nodes which contains almost sufficient information to describe the whole energy network. We derive a parameter set which characterises every single measuring location or node, respectively. Via analysing the behaviour of each node with respect to its neighbours, we construct a feasible random field metamodel over the whole transmission system. The metamodel is used to smooth the measurements across the network. In the next step we work with a subset of locations to predict the unobserved ones. We derive different graph kernels to define the missing covariance matrix from the neighbourhood structures of the network. This results in a metamodel that is able to smooth observed and predict unobserved locations in a spatial domain with non-isotropic distance functions. [ABSTRACT FROM AUTHOR]

A novel finite element (FE) formulation involving external electrical degrees of freedom is proposed for cases dealing with the coupling of mechanical and electrical waveguides through an array of piezoelectric patches. Interconnections between successive periodic unit cells enable the use of the transfer matrix (TM) formalism. It is thus shown that the wave finite element (WFE) method can be applied to electromechanical waveguides. As both mechanical and electrical variables are enclosed in the state vectors, the resulting attenuation and phase constants define waves that propagate in the two domains. For the computation of frequency response functions, it is proposed to employ the Riccati transfer matrix (RTM) method in order to avoid numerical instability. The whole computational method is validated through two examples involving a rod and a beam coupled to passive electrical transmission lines interconnecting a piezoelectric array. [ABSTRACT FROM AUTHOR]

Betweenness centrality measures how a node lies on the paths between other nodes. We propose the so-called resistance-distance betweenness (RDB) which takes a new viewpoint on scoring paths and contribution of each node in the paths. This new betweenness is developed based on the two facts: (1) the resistance distance characterizes the aggregate distance between two nodes in the context of electrical networks; (2) the resistance distance has an edge-wise decomposition form. Thus, the RDB of a node is defined as the sum of resistance distance components associated with the node's incident edges, which measures how a node lies on the "aggregated path" between other nodes. The basic properties of RDB and its relation and difference from current-flow betweenness (CFB) are investigated. Then, we apply the RDB to the study of an open question in linguistic networks, i.e., to check whether the Yuan poems written by Han and non-Han poets are similar. We also compare the performance of RDB with CFB. The betweenness analysis of the character co-occurrence networks of Han's and non-Han's poems provides a fresh and quantitative perspective to support that Han's and non-Han's poems are similar in general. • A novel betweenness centrality called the resistance-distance betweenness (RDB) is proposed. • RDB measures how a node lies on the "aggregated path" between other nodes. • The basic properties of RDB are theoretically studied. • RDB is applied to an open problem in complex linguistic networks to provide new insights. [ABSTRACT FROM AUTHOR]

Ferroresonance is phenomena, which emerged in case of different circumstances such as short circuit and breaker phase failure. In addition, plant outage is another cause of ferroresonance. Ferroresonance may cause maloperation of some protective devices such as differential protection. In this study, Manitoba hydro network is analysed in power systems computer‐aided design/electro‐magnetic transient design and control to recognise ferroresonant configurations in case of plant outage. Impact of ferroresonance on maloperation of differential protection is analysed. A static var compensator (SVC) is installed at the mid‐point of the network to mitigate ferroresonance. Operation of relay is assessed in the presence of SVC; furthermore, effect of parameters and components of SVC on operation of differential protection is investigated. Then, an adaptive algorithm is designed in differential relay to recognise ferroresonance and prevent maloperation of the relay. [ABSTRACT FROM AUTHOR]

This paper investigates a class of linear multi-agent network systems, in which nodes are coupled by dynamic edges in the sense that each edge has a dynamic system attached as well. The outputs of the edge dynamic systems form the external inputs of the node dynamic systems, which are termed neighboring inputs representing the coupling actions between nodes. The outputs of the node dynamic systems are the inputs of the edge dynamic systems. Several cooperative output regulation problems are posed, including output synchronization, output cooperation and master–slave output cooperation. Output cooperation is specified as making the neighboring input, a weighted sum of edge outputs, track a predefined trajectory by cooperation of node outputs. Distributed cooperative output regulation controllers depending on local states and neighboring inputs are presented, which are designed by combining feedback passivity theories and the internal model principle. A simulation example on the cooperative current control of an electrical network illustrates the potential applications of the analytical results. [ABSTRACT FROM AUTHOR]

Optimal microgrid design is a challenging problem, especially for multi-energy microgrids with electricity, heating, and cooling loads as well as sources, and multiple energy carriers. To address this problem, this paper presents an optimization model formulated as a mixed-integer linear program, which determines the optimal technology portfolio, the optimal technology placement, and the associated optimal dispatch, in a microgrid with multiple energy types. The developed model uses a multi-node modeling approach (as opposed to an aggregate single-node approach) that includes electrical power flow and heat flow equations, and hence, offers the ability to perform optimal siting considering physical and operational constraints of electrical and heating/cooling networks. The new model is founded on the existing optimization model DER-CAM, a state-of-the-art decision support tool for microgrid planning and design. The results of a case study that compares single-node vs. multi-node optimal design for an example microgrid show the importance of multi-node modeling. It has been shown that single-node approaches are not only incapable of optimal DER placement, but may also result in sub-optimal DER portfolio, as well as underestimation of investment costs. [ABSTRACT FROM AUTHOR]

Inverse problem of identifying the unknown spacewise dependent source F ( x ) in 1 D wave equation u t t = c 2 u x x + F ( x ) G ( t ) + h ( x , t ) , ( x , t ) ∈ ( 0 , 1 ) × ( 0 , T ) , from the Neumann-type measured output g ( t ) : = u x ( 0 , t ) is investigated. Most studies have attempted to reconstruct an unknown spacewise dependent source F ( x ) from the final observation u T ( x ) : = u ( x , T ) . Since a boundary measured data is most feasible from an engineering viewpoint, the identification problem has wide applications, in particular, in electrical networks governed by harmonically varying source for the linear wave equation u t t − u x x = F ( x ) c o s ( ω t ) , where ω > 0 is the frequency and F ( x ) is an unknown source term. In this paper Fourier Collocation Algorithm for reconstructing the spacewise dependent source F ( x ) is developed. This algorithm is based on Fourier expansion of the direct problem solution applied to the minimization problem for Tikhonov functional, by taking then a partial N -sum of the Fourier expansion. Tikhonov regularization is then applied to the obtained discrete ill-posed problem. To obtain high quality reconstruction in large values of the noise level, a numerical filtering algorithm is used for smoothing the noisy data. As an application, we demonstrate the ability of the algorithm on benchmark problems, in particular, on source identification problem in electrical networks governed by mono-frequency source. Numerical results show that the proposed algorithm allows to reconstruct the spacewise dependent source F ( x ) with enough high accuracy, in the presence of high noise levels. [ABSTRACT FROM AUTHOR]

This work presents a new approach to design an electrical network which, when coupled to a structure through an array of piezoelectric transducers, provides multimodal vibration mitigation. The characteristics of the network are specified in terms of modal properties. On the one hand, the electrical resonance frequencies are chosen to be close to those of the targeted set of structural modes. On the other hand, the electrical mode shapes are selected to maximize the electromechanical coupling between the mechanical and electrical modes while guaranteeing the passivity of the network. The effectiveness of this modal-based synthesis is demonstrated using a free–free beam and a fully clamped plate. • Passive electrical networks are synthesized based on their modal properties. • The electrical resonance frequencies are close to the mechanical ones. • The electrical mode shapes are optimized for maximum coupling. • Passivity constrains the maximum electrical mode shape amplitudes. • The approach is illustrated on a free–free beam and a fully clamped plate. [ABSTRACT FROM AUTHOR]

Distributed energy resources play a substantial role in today's electrical distribution networks. Combined heat and power (CHP) is a great example of the technologies with potential of combining different energy infrastructures such as gas and electricity. In this study, optimal planning (placing and sizing) of CHPs at arbitrary nodes within a system containing an electrical and natural gas network is considered. Energy hub (EH) approach is employed in order to calculate the energy consumption (operation) of each bus along with its relevant costs. CHP is optimally planned (placed and sized) at the network by considering the operation costs, power loss, network reliability, and voltage penalty. Simulation is carried out on a 33 bus radial distribution system containing electrical and gas networks. The network is integrated by wind and energy storage in some electrical buses. Genetic algorithm of Matlab and Cplex solver of GAMS are used to solve the optimisation problem. The results show that optimal planning of the CHPs reduces total costs, operation costs, network reliability, power loss, and voltage penalty by 9.4, 10.8, 15.4, 16.8, and 10.1%, respectively. The results also show operation of the formed EHs at the arbitrary nodes with optimal planning of the CHPs. [ABSTRACT FROM AUTHOR]

Urgent problems of the power industry in the 21st century require the creation of smart energy systems, providing a high effectiveness of generation, transmission, and consumption of electric power. Simultaneously, the requirements for controllability of power systems and ecological and resource-saving characteristics at all stages of production and distribution of electric power are increased. One of the decision methods of many problems of the power industry is the development of new high-efficiency electrical equipment for smart power systems based on superconducting technologies to ensure a qualitatively new level of functioning of the electric power industry. The intensive research and development of new types of electrical devices based on superconductors are being carried out in many industrialized advanced countries. Interest in such developments has especially increased in recent years owing to the discovery of so-called high-temperature superconductors (HTS) that do not require complicated and expensive cooling devices. Such devices can operate at cooling by inexpensive and easily accessible liquid nitrogen. Taking into account the obvious advantages of superconducting cable lines for the transmission of large power flows through an electrical network, as compared with conventional cables, the Federal Grid Company of Unified Energy System (JSC FGC UES) initiated a research and development program including the creation of superconducting HTS AC and DC cable lines. Two cable lines for the transmitted power of 50 MVA/MW at 20 kV were manufactured and tested within the framework of the program. [ABSTRACT FROM AUTHOR]

We consider random walks associated with conductances on Delaunay triangulations, Gabriel graphs and skeletons of Voronoi tilings generated by point processes in R d . Under suitable assumptions on point processes and conductances, we show that, for almost any realization of the point process, these random walks are recurrent if d = 2 and transient if d ≥ 3 . These results hold for a large variety of point processes including Poisson point processes, Matérn cluster and Matérn hardcore processes which have clustering or repulsive properties. In order to prove them, we state general criteria for recurrence or transience which apply to random graphs embedded in R d . [ABSTRACT FROM AUTHOR]

This paper present solution of optimal power flow problem using a firefly algorithm (FA) with consideration of FACTS devices "UPFC". The objective is to minimize the total fuel cost of generation and also maintain an acceptable system performance in terms of limits on generator real power and reactive power outputs, bus voltages and power flow of transmission lines. In order to maximize the relief of congestion in power system, to reduce the total system real power loss and improves the loadability of the system we propose also the optimization of the placement of FACTS devices in the power system (UPFC). The proposed method is tested on IEEE 30-bus system and the Algerian electrical network. The result of this method is compared with those obtained by biogeography based optimization (BBO), genetic algorithm (GA), and artificial bee colony (ABC) algorithm. [ABSTRACT FROM AUTHOR]

Owing to the random nature of the lightning phenomenon, the statistical based methods such as Monte Carlo simulation are the best tool to perform the lightning‐related studies. However, Monte Carlo simulation is complex and time consuming, especially, for larger networks where a lot of regions must be investigated, separately. Although some researches have been carried out to evaluate the lightning flashover outage rates based on artificial intelligence (AI) techniques, but, so far, any work has not been reported to perform a risk assessment of lightning surges by means of AI. This study presents a meta‐model based on adaptive neural‐fuzzy inference system (ANFIS) that can be utilised to perform the lightning‐related risk analysis with a good accuracy. The inputs of ANFIS are tower footing resistance, critical flashover voltage and the rate of lightning occurrence; and its outputs include the failure risk of both the insulation and arrester. The trained ANFIS can be very efficient in terms of time and computational resources for the further analysis, like placement of arresters or insulation coordination studies, on the electrical network on which the training is performed. To demonstrate the effectiveness of the ANFIS meta‐model, an optimisation method, based on genetic algorithm, has been implemented in order to find the optimum location of a specified set of line arresters on power network. Also, in order to consider the environmental condition, that is, pollution and altitude, a new method to determine the importance of each node of interest in protection is introduced. [ABSTRACT FROM AUTHOR]

• The equivalent circuit is proposed to study the decoupling characteristics of EIS. • The vertical and roll decoupling control method for EIS are designed. • The mHIL test platform is designed to verify the vibration control effect of EIS. This paper proposes a novel decoupling vibration control method for the semi-active electrically interconnected suspension (EIS) and develops a mechanical hardware-in-the-loop (mHIL) test platform to verify the effectiveness of the method. Firstly, according to the decoupling characteristic of the interconnected electrical network, the half-car model is divided into vertical and roll ones, and their frequency response could show the capability of EIS on vibration control. Then, two H ∞ state feedback controllers are designed based on the decoupled model to acquire the ideal force and torque for vertical and roll vibration control; the adjustment logics of the resistance control unit are proposed to track the ideal force and torque. Finally, the mHIL experiment platform is designed to validate the decoupling vibration control performance of the EIS system. In the experiment, the EIS can significantly improve the vehicle suspension's overall performance under sinusoidal and bump road excitations compared with that of the passive suspension. On the C-level random road, the test results show that the EIS can reduce the root-mean-square vertical and roll angular accelerations of the sprung mass by 22.90% and 21.75%, respectively, which significant improvement the ride comfort of the vehicle. [ABSTRACT FROM AUTHOR]

This study represents experimental techniques for testing the high‐voltage polluted insulators under conditions simulating the natural environment. International Electrotechnical Commission (IEC) fog method is used for testing the insulators of type π‐ϕ‐E4.5, but it does not simulate the desert pollution environments. For that reason, other two suggested techniques are added to explain the performance of the polluted insulators under dew and under simultaneous fog and dew, respectively. The leakage current bursts are recorded in each test type. Also the effect of the wetting method of the insulators under testing on the flashover voltage is investigated. The results of the three types of tests are compared with each other, under different surface layer conductivities. It is concluded that the analysis of leakage current bursts can be used to monitor the severity of pollution on the electrical network. [ABSTRACT FROM AUTHOR]

A spiral mandrel die fed by coat-hanger type distributors was designed systematically in the present study. At the first stage, the preliminary design of the distributor was completed by use of analytical approach. At the second stage, the performance of the preliminary distributor design was evaluated based on the analogy between fluid flow systems and electrical network systems. Computational Fluid Dynamics (CFD) Simulations were performed for the preliminary distributor design. With respect to the pressure drop and velocity distribution at the die exit, it is confirmed that there is a good agreement between the results of electrical network analogy and CFD analysis. At the third stage, the geometric parameters of the coat-hanger die were optimized with the aid of reverse engineering approach in electrical network analogy in order to obtain uniform velocity distribution at the distributor exit. A CFD analysis was carried out for the designed distributor. The geometric parameters of the spiral mandrel die were optimized using an analytical approach from literature [13]. A CFD simulation was performed for the designed spiral mandrel die and it is shown that a quitely uniform velocity distribution is obtained at the die exit. Aforementioned analytical approach showed a satisfying performance in terms of estimating pressure drop and obtaining balanced flow at the die exit. [ABSTRACT FROM AUTHOR]

Abstract: This paper performs analyzes using mathematical model of Fractional Brownian Distribution, M/G/∞ Model Described by Pareto Distribution, ‘Heavy Tail’ Distribution, and Gamma Distribution with Intergroup Characteristic. For performed analyses into this research are used measurements for power consumption into overall electrical network in Macedonia in time period of 16years. The results enclosed with mathematical analytical model are compared with results from real measurements. The calculated discrepancies confirms that enclosed analytical model with Intergroup Characteristic is optimal estimation model for modeling of the power consumption of electrical network. The real-time analyses for consumption of electrical energy into the overall network or for the part of electrical network are very important for everyday real operations into the electrical networks in order to achieve the services into the electrical network with best performance and the smaller cost as it is possible. In this research are prepared and predictions for power consumption quantities into the network, so the evaluated model is used as the best practice model for direct planning of the power consumption values into the electrical network (indirectly can be planned costs and operations into the electrical network related with the values of power consumption). [Copyright &y& Elsevier]

Network meta-analysis is an active field of research in clinical biostatistics. It aims to combine information from all randomized comparisons among a set of treatments for a given medical condition. We show how graph-theoretical methods can be applied to network meta-analysis. A meta-analytic graph consists of vertices (treatments) and edges (randomized comparisons). We illustrate the correspondence between meta-analytic networks and electrical networks, where variance corresponds to resistance, treatment effects to voltage, and weighted treatment effects to current flows. Based thereon, we then show that graph-theoretical methods that have been routinely applied to electrical networks also work well in network meta-analysis. In more detail, the resulting consistent treatment effects induced in the edges can be estimated via the Moore-Penrose pseudoinverse of the Laplacian matrix. Moreover, the variances of the treatment effects are estimated in analogy to electrical effective resistances. It is shown that this method, being computationally simple, leads to the usual fixed effect model estimate when applied to pairwise meta-analysis and is consistent with published results when applied to network meta-analysis examples from the literature. Moreover, problems of heterogeneity and inconsistency, random effects modeling and including multi-armed trials are addressed. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

We consider periodic square tilings of the plane. By extending a formalism introduced in 1940 for tiling of rectangles by squares we build a correspondence between periodic plane maps endowed with a periodic harmonic vector and periodic square tilings satisfying a regularity condition. The space of harmonic vectors is isomorphic to the first homology group of a torus. So, periodic plane square tilings are described by two parameters and the set of parameters is split into angular sectors. The correspondence between symmetry of the square tiling and symmetry of the corresponding plane map and harmonic vector is discussed and a method for enumerating the regular periodic plane square tilings having $$r$$ orbits of squares is outlined. [ABSTRACT FROM AUTHOR]

Abstract: A simulation and optimization process based on the electrical network model is presented to recover selenium from solutions using S 108 resins in a continuous counter-current decantation ion exchange system (CCDS). The system''s performance is affected by multiple parameters, including the selenium concentration, inlet flow rate, cycle operating time, desorption solution flow rate, resin mass transferred per cycle, diffluent ratio, and so forth. In a simulation process, normally, 20 to 25 cycles are required for the electrical analogue model to reach the cyclic steady state. The average error between the experimental and modeled outlet selenium concentrations was 1.89%. After optimization, the S 108 resin initially adsorbed 856.19mg/L Se(VI) and 855.33mg/L Se(IV), which resulted in selenium concentrations of 27.4 and 21.6g/L. In addition, recovery rates were 91.45 and 88.06% following the 164mL/min Se(VI) and 128mL/min Se(IV) solution treatments, respectively. [Copyright &y& Elsevier]

Abstract: This paper is on tilings of polygons by rectangles. A celebrated physical interpretation of such tilings by R.L. Brooks, C.A.B. Smith, A.H. Stone and W.T. Tutte uses direct-current circuits. The new approach of this paper is an application of alternating-current circuits. The following results are obtained: [•] a necessary condition for a rectangle to be tilable by rectangles of given shapes; [•] a criterion for a rectangle to be tilable by rectangles similar to it but not all homothetic to it; [•] a criterion for a “generic” polygon to be tilable by squares. These results generalize those of C. Freiling, R. Kenyon, M. Laczkovich, D. Rinne, and G. Szekeres. [ABSTRACT FROM AUTHOR]

Abstract: A rapid method for sizing and placing of distributed electricity generation (DES) systems in an electric transmission network in respect to voltage has been developed and successfully validated. The new tool presented is in particularly useful for avoiding overvoltage situations, which are critical for the whole electricity system. The results show that DES placement closer to the transformer side is always more beneficial in terms of voltage than at the end of the line. Depending on the size of the DES unit, both up and downstream flow of power may occur. The method can be used for investigating a range of different placement and sizing configurations. [Copyright &y& Elsevier]

The effective resistance between two nodes of a weighted graph is the electrical resistance seen between the nodes of a resistor network with branch conductances given by the edge weights. The effective resistance comes up in many applications and fields in addition to electrical network analysis, including, for example, Markov chains and continuous-time averaging networks. In this paper we study the problem of allocating edge weights on a given graph in order to minimize the total effective resistance, i.e., the sum of the resistances between all pairs of nodes. We show that this is a convex optimization problem and can be solved efficiently either numerically or, in some cases, analytically. We show that optimal allocation of the edge weights can reduce the total effective resistance of the graph (compared to uniform weights) by a factor that grows unboundedly with the size of the graph. We show that among all graphs with n nodes, the path has the largest value of optimal total effective resistance and the complete graph has the least. [ABSTRACT FROM AUTHOR]

The effective resistance between two nodes of a weighted graph is the electrical resistance seen between the nodes of a resistor network with branch conductances given by the edge weights. The effective resistance comes up in many applications and fields in addition to electrical network analysis, including, for example, Markov chains and continuous-time averaging networks. In this paper we study the problem of allocating edge weights on a given graph in order to minimize the total effective resistance, i.e., the sum of the resistances between all pairs of nodes. We show that this is a convex optimization problem and can be solved efficiently either numerically or, in some cases, analytically. We show that optimal allocation of the edge weights can reduce the total effective resistance of the graph (compared to uniform weights) by a factor that grows unboundedly with the size of the graph. We show that among all graphs with n nodes, the path has the largest value of optimal total effective resistance and the complete graph has the least. [ABSTRACT FROM AUTHOR]

We have modeled the effect of passive copper shielding applied to the outside of an actively shielded, axisymmetric z-gradient coil assembly, with the aim of substantially reducing induced eddy currents in the cryostat inner bore that create acoustic noise. For the purpose of calculation, the cylindrical cryostat inner bore and the passive copper shielding are coaxial and are imagined to be sliced into thin ring sections. Each ring section has a finite thickness and is further divided into several concentric layers. The thin cylindrical sections become elements in an electrical network that includes the actively shielded gradient coil. We calculate eddy currents both for single frequency excitations and for time-dependent excitations by modeling a series of trapezoidal pulses. Our results take into account time dependence, diffusion of eddy currents among cylindrical sections and skin depth effects. Two configurations are analyzed. The first is a thin copper layer wrapped around the outer diameter of the gradient assembly, and the second extends the copper over the ends of the gradient assembly. A 2-mm-thick copper layer around the gradient assembly reduces power deposited in the cryostat inner bore by 13.5 dB for a 1 kHz gradient excitation. Extending the passive shield, for the same 2 mm thickness, to cover the ends of the gradient reduces cryostat inner bore power deposition, by 26.7 dB for the same frequency. [ABSTRACT FROM AUTHOR]

Abstract: The implantation of a nuclear facility, such as ITER (about 20 buildings on 40ha) requires many preparatory studies, particularly with respect to underground characteristics, topography, layout, deforestation, excavations, networks, fences and roads and impact of seismic hazard on design. This paper presents the main results of these studies, carried out within the European ITER Site Studies Framework. A dedicated paper in the conference deals with the transport studies. To choose the site for ITER implantation, detailed geological, hydrogeological and geophysical investigations have been carried out. Taking into account the meteorological data (particularly the main wind direction), topography, access, electrical supply, fluid needs and constraints (gravity systems), buildings and roads have been implemented. [Copyright &y& Elsevier]

Abstract: With the electrical network model and object-oriented programming technique, a pressure swing adsorption (PSA) system may be decomposed to four objects: adsorbent column, tank, pressure source, and pipeline. Various flowsheets and operating patterns of PSA may be constructed with different combinations of objects and their topology. The objects are represented by class inheritance and encapsulation. The classes encapsulate the methods of setting up and solving the state equations according to the topological constraints and elemental constraints of resistor, capacitor, inductor and voltage and current sources. A PSA flowsheet may be represented with a heterogeneous list that creates the instances of the classes. The state equations are solved numerically on the basis of the polymorphic mechanism via virtual member functions in . A four-bed PSA process, consisting of four adsorbent columns, eight tanks, two constant pressure sources, four variable pressure sources and 30 pipelines, are simulated with the electrical network model. The simulated results agree well with the experimental data, and only 7–20 outer cyclic iterations are required to reach the cyclic steady state. The effect of the dead volume and fluid resistances in pipelines on operating results is examined. Optimal searching for the valve coefficients and operating time can suggest the corresponding suitable values to increase the experimental recovery. [Copyright &y& Elsevier]

A polynomial P in n complex variables is said to have the “half-plane property” (or Hurwitz property) if it is nonvanishing whenever all the variables lie in the open right half-plane. Such polynomials arise in combinatorics, reliability theory, electrical circuit theory and statistical mechanics. A particularly important case is when the polynomial is homogeneous and multiaffine: then it is the (weighted) generating polynomial of an r-uniform set system. We prove that the support (set of nonzero coefficients) of a homogeneous multiaffine polynomial with the half-plane property is necessarily the set of bases of a matroid. Conversely, we ask: For which matroids M does the basis generating polynomial PB(M) have the half-plane property? Not all matroids have the half-plane property, but we find large classes that do: all sixth-root-of-unity matroids, and a subclass of transversal (or cotransversal) matroids that we call “nice.” Furthermore, the class of matroids with the half-plane property is closed under minors, duality, direct sums, 2-sums, series and parallel connection, full-rank matroid union, and some special cases of principal truncation, principal extension, principal cotruncation and principal coextension. Our positive results depend on two distinct (and apparently unrelated) methods for constructing polynomials with the half-plane property: a determinant construction (exploiting “energy” arguments), and a permanent construction (exploiting the Heilmann–Lieb theorem on matching polynomials). We conclude with a list of open questions. [Copyright &y& Elsevier]

In 1986, Janson showed that the number of edges in the union of k random spanning trees in the complete graph K n is a shifted Poisson distribution. Using results from the theory of electrical networks, we provide a new proof of this result, and we obtain an explicit rate of convergence. This rate of convergence allows us to show a new upper tail bound on the number of trees in G (n , p) , for p a constant not depending on n. The number of edges in the union of k random trees is related to moments of the number of spanning trees in G (n , p). As an application, we prove the law of the iterated logarithm for the number of spanning trees in G (n , p). More precisely, consider the infinite random graph G (N , p) , with vertex set N and where each edge appears independently with constant probability p. By restricting to { 1 , 2 , ... , n } , we obtain a series of nested Erdős–Réyni random graphs G (n , p). We show that a scaled version of the number of spanning trees satisfies the law of the iterated logarithm. [ABSTRACT FROM AUTHOR]

Muscle functional MRI (mfMRI) is an imaging technique that assess muscles' activity, exploiting a shift in the T2-relaxation time between resting and active state on muscles. It is accompanied by the use of electromyography (EMG) to have a better understanding of the muscle electrophysiology; however, a technique merging MRI and EMG information has not been defined yet. In this paper, we present an anatomical and quantitative evaluation of a method our group recently introduced to quantify its validity in terms of muscle pattern estimation for four subjects during four isometric tasks. Muscle activation pattern are estimated using a resistive network to model the morphology in the MRI. An inverse problem is solved from sEMG data to assess muscle activation. The results have been validated with a comparison with physiological information and with the fitting on the electrodes space. On average, over 90% of the input sEMG information was able to be explained with the estimated muscle patterns. There is a match with anatomical information, even if a strong subjectivity is observed among subjects. With this paper we want to proof the method's validity showing its potential in diagnostic and rehabilitation fields. [ABSTRACT FROM AUTHOR]

• High concentrated graphene nanosheets dispersion (20 mg/ml) in water was synthesized. • Electrical conductivity as high as 0.5 S/m at graphene loading level of 1.5 wt% was obtained. • A Facile processing method was used to fabricate conductive coatings. • High electrical permittivity values were achieved at graphene loading level of 1.5 wt%. In this work, we present a novel method to exfoliate graphite to graphene oxide nanosheets with single to 3 layers at concentration as high as 15 mg/ml. In the first step, graphite intercalated compound (GIC) was obtained through a chemical intercalation process. In the next step, GIC was expanded and used as the precursor to obtain oxidized graphite. Oxidized graphite was introduced into a high alkaline medium and a high-speed homogenizer was used to complete the exfoliation process. Raman spectroscopy, XPS, XRD, TGA, SEM and TEM were used to characterize the synthesized graphene oxide nanosheets. Electrically conductive coatings were prepared by adding and stirring graphene oxide dispersion into an epoxy-hardener pre-mixture. The prepared coatings were post cured at 100 °C followed by annealing at 225 °C to in situ reduce the incorporated graphene oxide to graphene nanosheets. High electrical conductivity values as 0.5 S/m was obtained for the epoxy-graphene nanocomposite at graphene loading level of 1.5 wt%, which is comparable to previously reported data using more complex and laborious fabrication methods. Cryo-SEM images were captured in the liquid phase to investigate electrical network formation in the polymeric matrix. [ABSTRACT FROM AUTHOR]