Search

In this paper, the qualitative behavior of a discrete-time prey-predator model with Allee effect in prey population is discussed. Firstly, the existence of the fixed points and their topological classification are analyzed algebraically. Then, the conditions of existence for both period-doubling and Neimark-Sacker bifurcations arising from coexistence fixed point with the help of the center manifold theorem and bifurcation theory are investigated. OGY feedback control method is implemented to control chaos in the proposed model due to the emergence of bifurcations. Finally, numerical simulations are performed to support the theoretical findings. [ABSTRACT FROM AUTHOR]

The aim of this paper is to establish conditions for the existence and uniqueness of the solution of a nonlinear integro-differential equation. Moreover, it is to propose a quadrature method in order to find an approximate solution and establish the convergence of the method. We conclude by providing the algorithm and some numerical simulation to confirm our theoretical results. [ABSTRACT FROM AUTHOR]

Z-source inverter has recently been introduced to overcome the limitations of conventional voltage source inverter. This paper deals with a novel topology of single-phase Z-source inverter (ZSI). This topology reduced the number of passive elements and active switches in order to make the inverter cheaper and smaller in size compared to traditional ZSI. Detailed analysis of the proposed topology is presented in this paper which includes calculations of boost factor, total harmonic disorder, magnitude of output voltage etc. Modulation technique used to control the switching of the proposed inverter is explained in detail. This paper also compares the proposed topology with conventional topologies of Z-source inverter. Simulation results of MATLAB and real-time simulators are shown to explain the working of the proposed topology. [ABSTRACT FROM AUTHOR]

Flywheel energy storage can store large amounts of kinetic energy in its rotating parts, but its inertia restricts the rate of power exchange. On the other hand, there is supercapacitor with the ability of exchanging large amounts of instantaneous power. Therefore, the combination of these two systems can significantly improve the dynamic response of conventional flywheel energy storage. This paper proposes a novel design for this combined system in which supercapacitors are located inside the rotating disk. Therefore, supercapacitors can significantly improve the dynamic performance of the flywheel energy storage with trivial effects on its size and weight. Moreover, the ability of rotating supercapacitors to store electrical as well as kinetic energy increases the energy storage capacity of the proposed flywheel energy storage. This developed system with its improved performance can be widely employed instead of the conventional flywheel energy storage in various applications. In this paper, the proposed structures with built-in rotating supercapacitors are mechanically analyzed by CATIA and ABAQUS. In addition, the developed flywheel energy storage, which is equipped with a permanent magnet synchronous machine and its modified indirect vector controller, is simulated in MATLAB/Simulink under various conditions. [ABSTRACT FROM AUTHOR]

In this paper, a nonorthogonal multiple access based cooperative relaying system (NOMA-CRS) is considered to increase spectral efficiency. Besides, the simultaneous wireless information and power transfer (SWIPT) is proposed for the relay in NOMA-CRS. In SWIPT-NOMA-CRS, three different energy harvesting (EH) protocols, power sharing (PS), time sharing (TS) and ideal protocols are implemented. The outage performances of the SWIPT-NOMA-CRS are studied for all three EH protocols. In the analysis, to represent practical/reasonable scenarios, imperfect successive interference canceler (SIC) and imperfect channel state information (CSI) are taken into consideration. The derived outage probability (OP) expressions are validated via computer simulations. Besides, the OP for the benchmark scheme, NOMA-CRS without EH, is also derived under imperfect SIC and CSI. Based on extensive simulations, it is revealed that the SWIPT-NOMA-CRS outperforms NOMA-CRS without EH. Finally, the effects of all parameters on the outage performance of the SWIPT-NOMA-CRS are discussed and for the given scenarios, the optimum PS factor, TS factor and power allocation coefficients are demonstrated. [ABSTRACT FROM AUTHOR]

In this paper, we consider the Burgers equation B(2, 2) . Exact and nonstandard finite difference schemes (NSFD) for the Burgers equation B(2, 2) are designed. First, two exact finite difference schemes for the Burgers equation B(2, 2) are proposed using traveling wave solution. Then, two NSFD schemes are represented for this equation. These two NSFD schemes are compared with a standard finite difference (SFD) scheme. Numerical results show that the NSFD schemes are accurate and efficient in the numerical simulation of the kink-wave solution of the B(2, 2) equation. We see that although the SFD scheme yields numerical instability for large step sizes, NSFD schemes provide reliable results for long time integration. Local truncation errors show that the NSFD schemes are consistent with the B(2, 2) equation. [ABSTRACT FROM AUTHOR]

This paper proposes improving the directivity of microstrip patch antennas (MPAs) by using metamaterials. Four different metamaterial types are used as a at lens in front of the MPA, respectively, which are tuned to 12 GHz (Ku-band) resonance frequency. Thus, it can be decided which metamaterial is more proper for antenna directivity enhancement at this band. One additional new metamaterial structure is proposed in this paper, which is called a Euro-shaped resonator, and other metamaterials used are the triangular split ring resonator, symmetrical ring structure, and split ring resonator. The permeability and permittivity of metamaterials are extracted from the S parameters by using a robust method. Microwave Studio by Computer Simulation Technology is used for modeling and simulation. The MPA and metamaterials are fabricated, and measurements are performed in the Yíldíz Technical University RF and Microwave Laboratory. It is observed that measured results are in close agreement with the computer simulations. [ABSTRACT FROM AUTHOR]

Template matching is the process of accurately extracting the interesting regions in a source image according to reference templates. In this paper, the gravitational search algorithm (GSA) is employed as a novel search strategy for template matching. However, the basic GSA is easily trapped in a local optimum and has a poor exploitation ability. In this paper, to enhance the optimization performance of GSA, a novel cross-search strategy based on chaotic global search (CGS) and cloud local search (CLS) is incorporated into GSA. The new variant is named chaotic cloud GSA (CCGSA). CGS makes full use of the ergodicity of chaos theory to improve global search ability and to avoid premature convergence. Inspired by the randomness and stable tendency of the normal cloud model, CLS was formed to realize a refined exploitation in the neighborhood of the current best solution; therefore, it can enhance optimization efficiency. Comparative experiments on six composite benchmark functions indicate that CCGSA convergence performance is superior to that of two advanced variants of GSA. Moreover, when applied to template matching, CCGSA performs better than the other selected intelligent optimization algorithms. [ABSTRACT FROM AUTHOR]

The mathematical model of robot that is used to design control algorithms is mostly reused in numerical simulations as a virtual plant. The use of same model for both control design and simulation tasks makes the outcome idealized. Consequently, the effectiveness and feasibility of designed control methodologies when applied in practice seem to be questionable. The paper presents the quasi-physical modeling of a 6-DOF robot using MATLAB/Simscape Multibody for dynamic and control simulation. The bodies of the robot are assembled into a physical network with connections that represent physical domains. The dynamical manners of the quasi-physical model are close to that of real robot manipulators. This model can be exploited to verify the accuracy of mathematical models. After designing process, the control laws are validated with this model instead of an ideal mathematical model or an actual expensive prototype. The efficiency of the proposed modeling approach is demonstrated through the dynamic and control simulation of robot IRB 120. [ABSTRACT FROM AUTHOR]

This paper focuses on the stabilization problem of a class of fractional-order bidirectional associative memory neural networks with time delays. Based on feedback control, a sufficient condition is derived to achieve the global stabilization of systems by using the fractional inequality, the Lyapunov stability theory, and the comparison principle. In particular, this kind of control scheme is proved to be robust in the presence of external disturbances when the feedback gains are sufficiently large. In addition, a condition is obtained to achieve the global quasi-stabilization of systems with some external disturbances, and the corresponding error bound is estimated. Finally, some numerical simulations are presented to verify the effectiveness of theoretical results. [ABSTRACT FROM AUTHOR]

Owing to current transformer (CT) saturation caused by a decaying direct current component in the magnetizing inrush current, the restricted earth fault (REF) protection of a power transformer could maloperate during magnetizing inrush. This paper presents a new transformer restricted earth fault relay algorithm that can prevent false relay tripping and provide proper action during the energization of a faulty transformer. The integral of the product of the signals that are compared is calculated over 1 half-period of the signals. The performance of the proposed algorithm is tested and verified using a large number of transformer energization trials and fault cases. The signals required for testing of the algorithm were obtained by laboratory measurements, and then the algorithm was tested off-line. The inuence of different levels of CT saturation due to different remanent uxes in CT cores during power transformer energization was investigated. By applying computer simulations, the signals required for algorithm testing were generated. The investigation results presented in this paper show that the new algorithm provided sensitive protection for the power transformer for phase to ground faults and high security and stability during magnetizing inrush conditions in conjunction with CT saturation. [ABSTRACT FROM AUTHOR]

The principal function of circuit breakers (CBs) is to isolate a portion of the power network from the rest of it in a timely manner following an opening command. Any failure in the opening operation of CBs, especially following a fault condition, will almost certainly result in a catastrophic event. Therefore, the issue of failure detection of CBs is essential and has a vital role in power system protection. This paper presents a novel power-based algorithm for failure detection of CBs. The power loss of CBs due to an arcing event increases as the arcing time gets longer. The arcing time of CBs increases with defective operations originating from any failure or malfunction for different reasons. The proposed method uses the power difference between the input and output terminals of CBs to calculate the power loss due to an arcing event, which can then be used to estimate the arcing energy. A trip signal is initiated whenever the estimated arcing energy for a single opening operation reaches a predefined trip level, which shows a failure in CB operation. This predefined trip value is related to the integration of the maximum power capacity of the CB during an opening operation time. Computer simulation studies conducted to analyze the performance of the proposed technique demonstrate that the algorithm is capable of discriminating between normal and abnormal arcing energies and thus identifying malfunctions or failures in the opening operations of CBs. [ABSTRACT FROM AUTHOR]

In this paper, a fast form of nonsingular, terminal, decoupled, sliding-mode control, which utilizes timevarying sliding surfaces, is proposed for a class of fourth-order, single-input, multioutput, nonlinear systems. The novel control law features a fast term, in the manner of fast terminal sliding-mode control, which markedly improves the finite-time sliding-mode convergence speed near zero. Numerical simulation results, which are illustrated with a cartpole inverted pendulum system and a ball-beam system, demonstrate that the proposed control law achieves, in general, favorable transient response and lower steady-state errors compared to state-of-the-art decoupled terminal sliding-mode control methods. [ABSTRACT FROM AUTHOR]

In this paper, neural network theory is used to improve the positioning accuracy of smooth impact drive mechanisms (SIDMs), by designing a displacement controller that consists of a neural network identification (NNI) and a neural network controller (NNC). The dynamics of the SIDM are described by the NNI, which consists of an input layer, hidden layer, and output layer. The parameters of the NNI are adjusted using back propagation. The NNC is designed as a proportional-derivative (PD) controller, which is used to accurately control the displacement of the SIDM. The PD parameters are adjusted with an adaptive adjustment algorithm. A prototype of the SIDM was fabricated and an experimental control system was built that consists of a laser displacement sensor, power amplifier, data acquisition board, and SIDM prototype. The experimental results show that nanoscale positioning accuracy can be obtained. The control system can maintain steady operation, even if the output load mass is changed. [ABSTRACT FROM AUTHOR]

Inverse dynamics control is considered for flexible-joint parallel manipulators in order to obtain a good trajectory tracking performance in the case of modeling error and disturbances. It is known that, in the absence of modeling error and disturbance, inverse dynamics control leads to linear fourth-order error dynamics, which is asymptotically stable if the feedback gains are chosen to make the real part of the eigenvalues of the system negative. However, when there are modeling errors and disturbances, a linear time-varying error dynamics is obtained whose stability is not assured only by keeping the real parts of the frozen-time eigenvalues of the system negative. In this paper, the stability of such systems is investigated and it is proved that the linear time-varying system can be rendered stable by selecting the feedback gains such that the variation of the system becomes sufficiently slow. To illustrate the performance of the control method, deployment motion of a 3-RPR planar parallel manipulator subject to impact is simulated. For the impact model, the impulse-momentum and the coefficient of restitution equations for the system are derived. [ABSTRACT FROM AUTHOR]

Power system robustness against overload condition is a challenging issue in the fields of power system planning and operation. In this paper, two indices are proposed to evaluate power system robustness. The proposed indices are used to identify critical lines whose failure is due to overload, leading the power system to cascading outages and blackout. The first proposed index is a linear index. The second index is based on graph theory metrics. To prevent cascading outages, system robustness is calculated for all N - 1 and N - 2 contingencies. The lines whose outages lead to the smallest robustness values are considered as critical lines. The proposed indices are validated by applying to the IEEE 118-bus test system. Simulation results demonstrate the capability of both indices in identifying critical lines. Therefore, the purposed indices could be used as a reliable metric to apply preventive actions against possible cascading outages and blackouts. [ABSTRACT FROM AUTHOR]

In this paper, we introduce an Lp-norm aggregation to present a signal-to-noise ratio expression unified not only for such diversity combining schemes as equal-gain combining, maximal-ratio combining, and selection combining, but also for such transmission techniques as multihop transmission. Accordingly, we propose two moment-generating function-based approaches that both respectively unify the exact analyses of the averaged channel capacity and averaged effective capacity over generalized fading channels with respect to the diversity combining and multihop transmission schemes. Finally, the mathematical formalism is illustrated by numerical special cases and verified by simulations. [ABSTRACT FROM AUTHOR]

Plasmonic nanoparticles have been mostly studied using conventional light sources. Recently, electron energy loss spectroscopy (EELS) has started to be used to analyze plasmonic nanoparticles where incident electromagnetic fields are created by swift electrons. To accurately simulate EELS experiments, several numerical methods have been adapted. In this paper, a frequency domain surface integral equation (FDSIE) solver is modified to simulate EELS for plasmonic nanoparticles of gold and silver. Accuracy and versatility of the proposed FDSIE solver are shown by several numerical examples and compared to existing numerical, analytical, and experimental results. [ABSTRACT FROM AUTHOR]

This paper proposes a sensorless second-order switching surface to control a three-level boost converter (TLBC). A predictive current method is proposed to reduce the number of sensors in the normal second-order switching surface method. Based on a developed model of the TLBC, the current is estimated and a switching surface is formulated in the state-energy plane. Simulation and hardware tests are carried out to verify the viability and the effectiveness of the proposed control technique. Results obtained show a good performance of the converter in term of DC-bus balancing and fast dynamic response under sudden load change. [ABSTRACT FROM AUTHOR]

This paper introduces a new method to track the saliency of a permanent magnet synchronous motor (PMSM) motor fed by a 4-leg inverter in the case of a single-phase open circuit fault through measuring the dynamic current response of the motor line currents due to the insulated-gate bipolar transistor (IGBT) switching actions. In the case of a single-phase open circuit fault, a fault-tolerant control strategy that includes taking appropriate actions to control the 2 remaining healthy currents results in minor system performance degradation. The new strategy introduced in this paper includes software modifications only to the saliency tracking algorithm used in healthy mode in order to make it applicable to the reconfigured converter in the presence of a fault. The new method uses only the fundamental pulse width modulation (PWM) waveform (i.e. there is no modification to the operation of the 4-leg inverter), similar to the fundamental PWM method proposed for a 3-leg inverter. Simulation results are provided to verify the effectiveness of the proposed strategy of saliency tracking of a PMSM motor driven by fault-tolerant 4-phase inverter over a wide range of speeds under the case of a single-phase open circuit fault. [ABSTRACT FROM AUTHOR]

Grid-connected inverters are now increasingly used in distributed microgrid and smart-grid applications. The advantages of a quasi-Z-source inverter (QZSI), like single-stage operation, lower component rating, continuous input current, and common DC rail, led to an investigation of this converter for grid-connected applications. This paper presents a grid-connected QZSI with both AC and DC side controls. A new battery-charging configuration is also suggested across the capacitor through which the DC side control loop is regulated. Fast dynamic response and reduced harmonics are demonstrated through simulation and experimental results. [ABSTRACT FROM AUTHOR]

In this paper, we study the location optimization problem of remote antenna units (RAUs) in generalized distributed antenna systems (GDASs). We propose a composite vector quantization (CVQ) algorithm that consists of unsupervised and supervised terms for RAU location optimization. We show that the CVQ can be used i) to minimize an upper bound to the cell-averaged SNR error for a desired/demanded location-specific SNR function, and ii) to maximize the cell-averaged effective SNR. The CVQ-DAS includes the standard VQ, and thus the well-known squared distance criterion (SDC) as a special case. Computer simulations confirm the findings and suggest that the proposed CVQ-DAS outperforms the SDC in terms of cell-averaged "effective SNR". [ABSTRACT FROM AUTHOR]

In this paper, an adaptive tracking controller based on a three-layer neural network (NN) with an online weight tuning algorithm is proposed for a nonholonomic wheeled mobile robot in the presence of unknown wheel slips, model uncertainties, and unknown bounded disturbances. The online weight tuning algorithm is modified from the backpropagation with an e-modification term required to assure that the NN weights are bounded. Preliminary neural network offline training is not essential for the weights. Thanks to this proposed controller, the desired tracking performance is achieved where position tracking errors converge to an arbitrarily small neighborhood of the origin regardless of their initial values. According to Lyapunov theory and LaSalle extension, the stability of the whole closed- loop system is ensured to obtain the desired tracking performance. Computer simulations are implemented to certify the validity of the proposed controller. [ABSTRACT FROM AUTHOR]

This article presents the application of the harmony search (HS) optimization algorithm for selective harmonic elimination PWM (SHEPWM) in a new topology of multilevel inverters with reduced number of electronic switching elements. The main objective of the harmonic elimination strategy is eliminating undesired low-rank harmonics in order to improve the quality of the output waveform. The harmonic elimination strategy is achieved by solving a system of nonlinear equations. In this paper harmony search optimization is applied using artificial neural networks (ANNs) on a new 21-level inverter topology. The algorithm is based on a music improvisation process. MATLAB programming software is used to develop a harmony search optimization program for harmonic elimination. A small-scale laboratory of the proposed 21-level inverter is built to validate the simulation results and to prove the efficiency of the proposed control scheme. [ABSTRACT FROM AUTHOR]

In order to achieve better control performance within the facility environment, this paper proposes a distributed model predictive control method, aiming at increasing the control precision of actuators, reducing energy consumption and equipment loss at the same time. Regarding optimizing this facility environment model, it could be treated as a multiobjective optimization problem. Referring to the cooperative game theory, each objective is regarded as a gamer. Each gamer considers both its own interests and other gamers' interests to achieve a balanced result when cooperation is achieved. The simulation experiments illustrate that the proposed control method is able to adjust the parameters of the facility environment to a preset interval properly. Moreover, in this specific simulation environment, the proposed method achieves better performances than the single objective control method and traditional linear weighted multiobjective control method in most of the evaluation criteria. [ABSTRACT FROM AUTHOR]

This paper presents a deadbeat-based proportional-integral (PI) controller for a stand-alone single-phase voltage source inverter using a battery cell as the primary energy source. The inverter system is simulated in MATLAB/ Simulink. It consists of a lead acid battery, third-order Butterworth low-pass DC filter and AC filter, H-bridge inverter, step-up transformer, and a variety of loads, as well as its sinusoidal pulse-width modulation (SPWM) deadbeat-based PI controller. In this paper, 2 simulation case studies are carried out, which are the abrupt load changes from a 400 W resistive load to a 500 W resistive load, and from a 400 W resistive load to an inductive load of 500 W 0.85 power factor lagging. From the simulation results for both cases, the state-of-charge of the battery decreases due to supplying power to the loads, yet the battery voltage remains constant at about 36 V and the battery current exhibits a smooth ripple despite the current spikes produced by the H-bridge inverter, which will prolong the lifespan of the battery. This shows that the DC filter performs satisfactorily to isolate the current spikes generated by the SPWM controller and H-bridge inverter. Moreover, even though the load varies for both cases, the sinusoidal inverter output voltage can be tracked and maintained at 230 Vrms with a 50 Hz frequency within a few cycles from the instant that the load is changed, as well as a low total harmonic distortion voltage (THDv) content of 1.53% and 2.78%, respectively. This indicates that the controller proves its robustness and stiffness characteristics in maintaining the output load voltage at the desired value to supply the power for a variety of loads with a minimum THDv. [ABSTRACT FROM AUTHOR]

Air combat simulation systems (ACSSs) are developed to train fighter pilots (trainees) in a virtual combat environment. In general, an ACSS consists of the following stages: planning the scenario, training, flight analysis, and performance evaluation. In this paper, the details of the framework, which is developed to analyze and evaluate the performance of the trainees, is introduced. First, the evaluation criteria for the pilot performance are defined. Next, a dynamic pilot performance evaluation system is developed that can be controlled and modified by experienced instructor pilots (instructors/trainers) to define the performance criteria details using predefined evaluation parameters. The evaluation of the trainees is conducted at the end of the flight and then a report related to the trainees' performance is generated. Eleven of the performance criteria are within the scope of this paper; however, the proposed system provides an extensible infrastructure to define new criteria and parameters. [ABSTRACT FROM AUTHOR]

In blind source separation problems that are implemented based on the independent component analysis (ICA) algorithm, the separation speed and quality are related inversely. In this paper, the proposed algorithms eliminate this tradeoff by generating a faster separation while maintaining the quality. In the proposed algorithms, in each frequency bin and in all of the learning steps, the separation quality of the separating matrix is compared with another one that we define as a situated matrix, and the best matrix is considered as an initial separating matrix in the next learning step. In this paper, we propose 2 algorithms based on the constant situated matrix (CSM) and the variable situated matrix (VSM). Using the simulation results, on average, the proposed CSM and VSM algorithms are about 3 and 6 times faster than the ICA algorithm, respectively, while the quality of the separated signals remains almost unchanged or becomes slightly better. [ABSTRACT FROM AUTHOR]

The restructuring of the electrical market, improvement in the technologies of energy production, and energy crisis have paved the way for increasing applications of distributed generation (DG) resources in recent years. Installing DG units in a distribution network may result in positive impacts, such as voltage profile improvement and loss reduction, and negative impacts, such as an increase in the short-circuit level. These impacts depend on the type, capacity, and place of these resources. Therefore, finding the optimal place and capacity of DG resources is of crucial importance. Accordingly, this paper is aimed at finding the optimal place and capacity of DG resources, in order to improve the technical parameters of the network, including the power losses, voltage profile, and short-circuit level. The proposed formulation of this paper significantly increases the convergence and the speed of the finding the answers. Furthermore, to select the optimal weighting coefficients, an algorithm is proposed. The weighting coefficients are decided on according to the requirements of each network and deciding on them optimally prevents the arbitrarily selection of these resources. The genetic algorithm is used to minimize the objective function and to find the best answers during the investigation. Finally, the proposed algorithm is tested on the Zanjan Province distribution network in Iran and the simulation results are presented and discussed. [ABSTRACT FROM AUTHOR]

Active noise control (ANC) systems are used to reduce the sound noise level by generating antinoise signals. M-Estimators are widely employed in ANC systems for updating the adaptive FIR filter taps used as the system controller. Observing the state-of-the-art M-estimators design shows that there is a need for further improvements. In this paper, a feedback ANC based on the reinforcement learning (RL) method is proposed. The sensitivity of the constant parameter in the RL method is checked. The effectiveness of the proposed method is proven by comparing the results with previous feedforward studies through computer simulations. [ABSTRACT FROM AUTHOR]

Onshore applications of direct current resistivity (DCR) along shorelines suffer a short-circuit-like phenomenon due to electrical current flowing through a more conductive body of water rather than ground. Our study of the numerical simulation of DCR data with a three-dimensional forward model demonstrated that the apparent resistivity was reduced as a function of the sea depth and the distance of measurement site to the shoreline. Furthermore, it was concluded that the "marine effects" on DCR data (i.e. reduction in apparent resistivity) become nonnegligible as the ratio of half-electrode expansion (AB/2) to the distance to the shoreline is larger than one. The reduction in apparent resistivity reaches its highest levels as the ratio approaches ten. Our survey conducted along the coastal line of Northwest Turkey clearly showed that if the "marine effects" are left untreated, one- or two-dimensional inversion yields incorrect resistivities for underlying units and therefore undermines the credibility of survey results. In the paper suggestions are made to handle such situations. [ABSTRACT FROM AUTHOR]

Context-aware handover decision has recently been considered as a candidate for next-generation heterogeneous wireless networks. The context-aware handover methods proposed in the literature differ in some aspects, including the location of the handover decision (distributed or centralized). Depending on the location of the decision point, the appropriate part of the context knowledge should be transferred in those methods. This paper proposes a context gathering mechanism for a policy-based context-aware handover method, which implements mobile-initiated and network-assisted handover. The proposed network context gathering mechanism is based on a media-independent handover (MIH) framework and the paper justifies the usability of the extension using some analysis on signaling overhead and latency. Another part of the context is the preferences of the users, applications, and network operators, where this paper has proposed an automatic policy construction procedure to gather and employ them in generating policies. This procedure eliminates the complexity of making policies in previous policy-based context-aware methods and allows employing up-to-date network context information to dynamically modify the policies. Simulation results show better performance in terms of perceived quality for sensitive traffic. [ABSTRACT FROM AUTHOR]

This paper demonstrates double bow-tie frequency selective surface (FSS) geometry for X-band applications with a bandwidth value of 1.82 GHz and Ku-band applications with a bandwidth value of 3.44 GHz. Throughout this study, parametric analyses of the proposed structure are also performed. Alterations in the reection and transmission characteristics of this specially designed structure by virtue of defined variables are analyzed. Those variables are determined by considering the geometric and material properties of the proposed structure. To analyze the reection and transmission coefficients, two different simulators, namely the High Frequency Structure Simulator (ANSYS HFSS), which is based on the finite element method (FEM), and the Computer Simulation Technology Studio Suite (CST Studio Suite), which is based on the finite integration method (FIM), are used. The structure is validated via those two solvers. Good agreement is obtained by both solvers, and the results are compared in terms of frequency, return loss, insertion loss, and fractional bandwidth. [ABSTRACT FROM AUTHOR]

Independently from artificial intelligence applications, an artificial neural network can be viewed as a powerful tool for function reconstruction. Previous papers used this property to model an implicit surface out of some control points by reconstructing its underlying scalar field. Such an approach requests the neural network to memorize the control points, which has turned problematic for complex surfaces. In our paper, we show that this problem can be efficiently tackled by adapting the architecture of the neural network to the features compounding the surface: by learning first these features independently and then blending them gradually together, our modular architecture readily comprehends the whole surface. As an example, we model the surface of an animated human body. This approach could eventually help model 3-D textures and be used as well for more classic applications of neural networks. [ABSTRACT FROM AUTHOR]

This paper presents a new constant frequency hysteresis current controller for the grid interface of a PVfed three-phase voltage source inverter (VSI) for a dual mode operation, feeding real power during the daytime and reactive power alone during nights, thereby acting as a STATCOM. The constant frequency is inherently achieved by means of digital implementation in a simplified manner without any complex manipulations to choose a variable band width; rather the hysteresis band varies as a natural consequence of selecting appropriate constant sampling frequency. Analytical proof is presented for the switching frequency to remain constant, without compromising on the performance indices. The design of the proposed controller for a grid-connected inverter operating in dual mode is presented, along with simulation results. The proposed controller is successfully implemented using a 1.1 kW PV array-fed inverter. The hardware results presented show the grid current harmonics complies with IEEE 1547 and has been achieved in a simpler means when compared to other existing techniques. The proposed controller is expected to be an attractive solution for grid-connected inverter applications including distributed generation, power quality, and drive applications. [ABSTRACT FROM AUTHOR]

Automatic generation control (AGC) is an important service used for the secure and reliable operation of a power system. In this paper, a suitable AGC scheme for a deregulated environment has been studied for various load perturbation scenarios. A proportional integral derivative (PID) controller has been utilized to control the real power output of the generators. The optimal parameters of the PID controller have been determined using the big bang big crunch (BBBC) algorithm, (BBBC-PID). The performance of the BBBC-PID controller has been checked on three different sized multiarea power systems. The results obtained with the applied algorithm have also been compared with the results of other algorithms, namely imperialistic competition algorithm (ICA) and harmony search (HS). MATLAB/Simulink was used as a simulation tool for this study. The results show the superiority of the BBBC-PID over the others. [ABSTRACT FROM AUTHOR]

This paper presents an improved version of the extended Luenberger observer with joint estimation of rotor speed and disturbance torque. The mechanical model of the induction motor is also utilized for the estimation of disturbance torque to add to the robustness of the observer. The estimated disturbance torque is treated as a model disturbance and physically incorporated into the observer state dynamic equation. The dynamic performance and efficacy of the modified observer is tested for variations in external load and inertia coefficient in the mechanical model. The above observer model is first built offline, using MATLAB/Simulink block sets, and simulated. Further, the offline simulated results are validated in real time by incorporating RT-Lab block sets into the Simulink model and implementing it in the 0P4500 real-time simulator developed by Opal-RT. The implementation of the above concept in a relatively new real-time environment adds more strength to the offline findings and provides an exact replica of how the actual physical system would behave. [ABSTRACT FROM AUTHOR]

Today, power consumption presents a critical issue when designing embedded systems. It has become a key factor in a product's success when being marketed, especially for mobile systems. In this paper, we have developed a typical design for video zoom-in processing with low power consumption. The proposed design has been implemented on the Xilinx Virtex-5 with the integration of different important resources like embedded processor, embedded memory, MPMC, DDR, and various interfaces. The design results show a significant gain in power at the simulation level as well as the physical one. In addition, the proposed design provides an important gain in power without degrading other parameters such as frequency, area, and others. [ABSTRACT FROM AUTHOR]

Direct instantaneous torque control (DITC) is one way of controlling torque in switched reluctance motors. Despite the presence of DITC control, torque ripple at nominal or higher speeds is considerable due to the back emf increasing. To overcome this drawback, many converters have been proposed. In most convertors proposed for fast excitation in DITC, controlling of boost capacity is an important problem. This paper presents a DITC for a switched reluctance motor using a proposed converter to reduce the torque ripple with controlled boost capacitor automatically. The proposed converter reduces the torque ripple at rated or higher speeds and no controller requires controlling the boost capacitor. The proposed converter is compared with an asymmetric one via simulation results using MATLAB and experimental results. [ABSTRACT FROM AUTHOR]

In this paper, a scheme is presented for properly compensating current power quality problems in a network. In this method, only by measuring grid current and using an adaptive notch filter (ANF), a reference sinusoidal current that is in phase with the grid voltage is created for the control system. Using ANFs guarantees the proper efficiency of the network when its frequency changes. A proportional controller and a resonance bank along with pulse width modulation are used in the shunt active power filter (SAPF) control system. One of the features of the resonant controller is its extremely high open-loop gain at its resonance frequency. This high gain causes the controller to accurately track the harmonic components. Simulations are carried out in MATLAB software under various conditions of load and network voltage, such as unbalanced and distortional voltage and changing load. These simulations verify the capabilities of this scheme. [ABSTRACT FROM AUTHOR]

In this paper, a new two-parameter window obtained by the combination of two windows, known as exponential and Hamming, is proposed and applied for the design of finite impulse response (FIR) digital filters. First of all, the quality of the proposed window is analyzed in terms of window spectral parameters and then compared with other two-parameter windows, namely Kaiser, cosh, and exponential. The window simulation results show that the proposed window can provide better ripple ratio than other windows for fixed window length and mainlobe width. Secondly, the performance of the proposed window is analyzed in digital filter design. The filter numerical comparison with Saramaki, Kaiser, Dolph-Chebyshev, cosh, and exponential windows confirms that the filter designed by the proposed window can exhibit a better filtering performance compared to well-known two-parameter windows in the literature because it can provide better minimum stopband attenuation for fixed filter length and transition width. [ABSTRACT FROM AUTHOR]

This paper presents optimal tuning of the controller parameters of a proportional-integral-derivate (PID) controller for an automatic voltage regulator (AVR) system using a heuristic gravitational search algorithm (GSA) based on mass interactions and Newton's law of gravity. The determination of optimal controller parameters is considered an optimization problem in which different performance indexes and a performance criterion in the time domain have been used as objective functions to test the performance and effectiveness of the GSA. In the determining process of the parameters, the designed PID controller with the proposed approach is simulated under different conditions and the performance of the controller is compared with those reported in the literature. From the numerical simulation results it is clear that the GSA approach is successfully applied to reveal the performance and the feasibility of the proposed controller in the AVR system. [ABSTRACT FROM AUTHOR]

This paper presents a speciation procedure that improves the local search capability of the genetic algorithm in analog circuit design. There is no need for additional circuit simulation in order to apply this procedure. The procedure is tested in Gaussian, sigmoid, cube, and square circuit design problems. Two sets of 125 simulations with the same seed values are performed for each problem using both the proposed procedure and the canonical genetic algorithm. The simulation results show that the method is statistically better than the canonical genetic algorithm, which suffers from bad locality. The effects of the population size and speciation threshold coefficient on the performance of the speciation algorithm are investigated. Confidence intervals of the simulation results are calculated. The results show that the speciation procedure improves the quality of solutions with at least 99% confidence, and the effectiveness of the method, which is statistically determined, increases in small populations. [ABSTRACT FROM AUTHOR]

This paper presents a simulation of the automatic steering control system on a vehicle model using particle swarm optimization (PSO) to optimize the parameters of the control system. The control system involves fuzzy logic control (FLC) and proportional-integral-derivative (PID) control working in a cascade; the main control (FLC) is used to control lateral motion, and the secondary control (PID) is an enhancement to control the yaw motion in vehicle models representing 10 degrees of freedom of the vehicle dynamics system. Optimization by PSO is carried out simultaneously on both control systems. On FLC it is done by setting the width and the center point of the membership function (MF) in the input and output FLC so that the optimal composition of the MF parameter is obtained. The optimization process also determines the constants of optimal gain in the PID control. Testing is done through software in the loop simulation. Based on the test results it can be stated that FLC and PID control tuned by PSO can steer the vehicle rate well in accordance with desired trajectory and the vehicle motion can always be maintained at the specified path. [ABSTRACT FROM AUTHOR]

This paper investigates the design and performance of a 150 W single-phase current-source grid-connected inverter topology that is based on a PV array and DC link inductor acting as a constant-current source. The inverter is implemented using a single boost switch, an H-bridge inverter, and a CL output filter. The inverter output current is simply controlled using the boost switch and open-loop or feedforward control. The dark I-V configuration is used to simulate two series PV modules. Comprehensive test results are obtained to validate the computer simulation results. Furthermore, the proposed inverter's ability to deliver a sinusoidal current to the grid while meeting the appropriate standards, i.e. total harmonic distortion and power factor requirements, is also examined for various modulation index values and irradiances. [ABSTRACT FROM AUTHOR]

Incremental encoders have attracted significant attention to measure motor speed worldwide. Due to the advantages of incremental encoders a noticeable percentage of Servo system drives have been built based on these sensors. The nonideality of encoders, especially mechanical misalignments, is one of their most important problems, affecting the precision of calculations. In the current paper we present an analytical formula to model the nonideal incremental encoder and calculate both the frequency and magnitude of vibrations due to this nonideality. Moreover, a nonideality identity parameter of the encoder is defined. This parameter can be used for quality assurance purposes. Moreover, it is possible to design exible filters for measured speed based on this parameter, especially in low resolution encoders. The simulation and experimental results corroborate the precision of the proposed method in a wide range of speeds. [ABSTRACT FROM AUTHOR]

In this paper we propose an improved adaptive media access (MAC) layer routing algorithm for the broadband power line communication (BPLC) access network founded on the fixed basic approach routing algorithm, which is integrated within the IEEE P1901 standard. The proposed adaptive algorithm incorporates a new dynamically scaled threshold for the selection of the next hop station based on the information from the physical layer. Furthermore, the procedures for the route and the time allocation modifications during the connection setup and later adjustments are developed. Simulation of the new adaptive and existing fixed routing algorithm is performed on the model of a realistic BPLC network using the OMNeT++-based BPLC cross-layer simulator BPlcSim. The simulation results showed that the adaptive routing algorithm outperforms the fixed routing in all aspects, since each station can perform routing functions and make the selection of the most reliable next hop station. [ABSTRACT FROM AUTHOR]

In this paper, robust PI controllers are designed to control the speed of induction motors based on a vector control strategy. The design methodology defines the robust stability and robust performance regions in the kp - ki (PI controller coefficients) plane using the Kharitonov theorem. In the control system design procedure, a nonlinear induction motor is modeled as an uncertain linear model. The procedure of modeling the uncertainties is presented. The required scientific foundations for designing a robust PI controller are also introduced in the general case while the necessary equations are derived. In the final step, the design procedure for a special motor is presented thoroughly. The simulation results indicate the efficiency of the method. [ABSTRACT FROM AUTHOR]

In this paper, we introduce an extended Sprott E system by a general quadratic control scheme with 3 arbitrary parameters for the new system. The resulting system can exhibit codimension-one Hopf bifurcations as parameters vary. The control strategy used can be applied to create degenerate Hopf bifurcations at desired locations with preferred stability. A complex chaotic attractor with only one stable equilibrium is derived in the sense of having a positive largest Lyapunov exponent. The chaotic attractor with only one stable equilibrium can be generated via a period-doubling bifurcation. To further suppress chaos in the extended Sprott E system coexisting with only one stable equilibrium, adaptive control laws are designed to stabilize the extended Sprott E system based on adaptive control theory and Lyapunov stability theory. Numerical simulations are shown to validate and demonstrate the effectiveness of the proposed adaptive control. [ABSTRACT FROM AUTHOR]

In this paper, we deal with the improvement of the positioning accuracy of distance vector (DV)-based positioning algorithms, which use angular information DV- angle of arrival (AoA). This algorithm belongs to an ad-hoc positioning system. We focus on the improvement of the algorithm and its enhanced version is presented. The angular information of particular nodes is obtained and processed by the original algorithm; however, the final position estimation is determined by the proposed novel algorithm using only a subset of all intersections. We assign weights to the individual intersections according to their positions and the positions of the RNs. For the final position estimation, only intersections with the highest weights are used. The performance of the proposed enhanced algorithm is verified by simulations and it is compared with the original DV-AoA algorithm. [ABSTRACT FROM AUTHOR]