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In 1971, memristor is claimed as a missing circuit element and almost 40 years later than its prediction a memristive system behaving as a memristor has been found in 2008. Memristor is accepted by many as the new and the fourth fundamental circuit element. Analog applications of memristor have emerged as a new research area in recent years. An analog filter with memristor can have automatically adjustable gain, quality factor and bandwidth characteristics etc. thanks to its variable memristance. In this paper, two different types of secondorder Sallen-Key filters, which are the low-pass and the high-pass Sallen Key filters, are analyzed using simulations. The linear drift model of TiO2 memristor is used in all analysis and simulations. It has been found that the memristor in the filters can go into saturation at very low frequencies and both of the filters operate well at higher frequencies. A criterion is suggested to prevent memristor from going into saturation and to prevent distortion at low frequencies. Using the criteria and choosing a memristor with more appropriate parameters, the simulations are repeated for the low-pass filter and it is shown that the low-pass filter operates better with the new parameters chosen. The analysis and the criteria given in this paper can be used to design memristor-based Sallen-Key filters and adaptable to other memristor-based filters as well. [ABSTRACT FROM AUTHOR]

Voltage sags are one of the most important power quality problems in electrical systems. Dynamic voltage restorer (DVR) is known as the most common custom power device to compensate these power quality problems. DVR is an electronic based device in series to system, and the detection of voltage sags plays an important role for these devices. In electrical grids, different methods are used to detect voltage sags for DVR structures. These problems must be compensated fast and accurately. In this study, second order generalized integrator phase locked loop (SOGI-PLL) is improved to obtain voltage magnitude in addition to phase information in conventional SOGI-PLL. In this paper, the design of a novel controller design is proposed by using voltage magnitude and phase information through improved SOGI-PLL. Balanced/unbalanced voltage sags are compensated by using phase and voltage magnitude information obtained with improved SOGI-PLL in DVR. The simulation results of improved SOGI-PLL based controller are presented through PSCAD/EMDTC program. Proposed detection method shows fast and effective results for compensation of voltage disturbances. [ABSTRACT FROM AUTHOR]

Metamaterials are artificial structures which exhibit different electromagnetic properties contrary to the known materials. One of the features discovered in recent years is performing perfect absorption against the incident electromagnetic wave. Metamaterial absorbers with this property can be used in stealth technology against remote sensing applications over a significant range of electromagnetic spectrum from microwave to optics. According to this, radar cross section of relevant targets representing the visibility in radar can be reduced by coating target with metamaterial absorber. In this paper; design, simulation and measurements of a novel X band metamaterial broadband absorber are investigated. Primarily, a dual band metamaterial absorber is obtained and then, depending on superposition of the different neighboring resonant frequencies of the differently sized unit cells, a super cell of metamaterial absorber has been demonstrated at X band. Due to the optimization of size and location of unit cell, a broadband metamaterial absorber is designed in the frequency range of 8.7 to 11.4 GHz. It is observed that the simulation results are in good agreement with the measurements. At least a 10 dB radar cross section reduction of the metamaterial absorber compared with a fully metallic plate with comparable dimensions is demonstrated both numerically and experimentally in the frequency range of fire control and surveillance radars. [ABSTRACT FROM AUTHOR]

In this paper, a novel control technique which is a particular implementation of the quasi square wave method has been proposed for a single-phase inverter drive. With the proposed control technique, 3rd and 3rd order harmonics together with even harmonics of the inverter output voltage waveform are eliminated as in a six-step inverter. An output voltage waveform with less harmonic content for one output period of the inverter operation is produced using the same switching rate as that of quasi square wave method. Output voltage control is performed by using a variable DC link inverter. Matlab/Simulink models of the proposed system, and the inverter system with quasi square wave modulation technique have been obtained. The comparative simulation results for both techniques are given at various output frequencies. Open-loop V/f control has been applied to both inverters feeding an R-L load, V/f controlled inductive and single-phase induction motor loads. Superiority of the proposed technique to the conventional quasi square wave modulation technique has been shown with the output waveforms and their spectra. [ABSTRACT FROM AUTHOR]

Node deployment is one of the important issues to be addressed in Wireless Sensor Networks (WSNs). A proper node deployment scheme can reduce the complexity of problems in WSNs such as routing, data fusion, communication, etc. Sensors in Mobile WSNs (MWSNs) have ability to travel in the network with motion capability. This ability can extend the lifetime of WSNs by minimizing energy consumption due to travelling with optimization of deployment. This paper employs two recently proposed multi-objective optimization algorithms, namely multi-objective evolutionary algorithm based on decomposition (MOEA/D) and fast and elitist genetic algorithm (NSGA-II) to find proper deployment scenarios. These multi-objective evolutionary algorithms aim at relocating mobile nodes to provide maximum sensing coverage area while minimizing the energy required for the relocation. The relocation is defined as the total travel distance of the sensors from their initial locations to their final locations. Simulation results clearly show that the non-dominated solutions have tradeoff between the travelled distance and coverage area. [ABSTRACT FROM AUTHOR]

This paper introduces wideband dual polarized stacked suspended plate antenna operating in 1710-2170 Mhz. Antenna consists of two pairs of stacked suspended plate antennas, which have novel capacitively coupled feeding probes different than excitation of classical patch antennas. Antenna is designed to provide independent ±45° linearly polarized dual channels for polarization diversity. Antenna elements of these ±45° channels are separated by a distance in azimuth and interleaved by a distance in elevation to have a good isolation between ports. Starting from single element, antenna is designed, simulated, manufactured and measured. Simulations are in good agreement with the measurement in terms of antenna performance parameters; return losses, channel isolation, radiation patterns and gain. [ABSTRACT FROM AUTHOR]

In this study, to find solutions to problems related to delays in train suggestions were made. In this paper, first of all Yeniçubuk-Çetinkaya railway which have 16 stations and 6 trains worked on, was handled and 0-1 integer programming was proposed to reduce the delays. Train time schedules were regulated with data obtained from solution of this model and delays have been improved by 81.59 %. Also, it was shown, that the delays can be improved 96.52 % by simulating the case of changing 31 km railway line out of totally 240 km with double railway line. [ABSTRACT FROM AUTHOR]

In this paper, the different working structure and unique design of the E-Core Transverse Flux Machine that is combined of transverse flux and reluctance principle is investigated for training bike application. Also, static magnetic characteristics of the machine are obtained with finite element analysis and experimental measurements. The modeling of the E-Core Transverse Flux Machine and its driver system are given. The whole system with all control algorithms for a training bike application is simulated and the performance curves are presented. Finally, the experimental tests done at the laboratory for the indoor training bike application are compared and verified with the results of the simulation. [ABSTRACT FROM AUTHOR]

This paper proposes the design and implementation of high gain array antenna suitable for GSM1800 and UMTS base stations. For this purpose, previously developed wideband, dual polarised antenna module has been used as the basic element of array antenna. The array antenna structure is designed, simulated, manufactured and measured. Network parameters (S-parameters) and radiation characteristics (pattern, gain) of the array antenna have been investigated. The operation bandwidth spans GSM1800 (1710-1880 Mhz) and UMTS (1910-2170 Mhz) bands. The simulations show good agreement with the measurement results that the array antenna has return losses of less than -15 dB and the channel isolation between ± 45° linearly polarised channels is below -25 dB within the operation band. Azimuth and elevation half power beamwidths (HPBW) are 63° and 7° respectively. Gain is around 18 dBi. [ABSTRACT FROM AUTHOR]

In real-time crowd simulations, the complexity of indexing the virtual entities should be kept low at all times in order to maximize the simulation performance. In this paper, a novel indexing technique is proposed. The proposed system is based on the navigation graph that is already commonly used for path finding in the current virtual crowd simulations. By this way, the simulation does not need a separate data structure for indexing the virtual entities, and at the same time it performs faster than the traditional grid based simulations that have narrow and long corridors (such as urban environments). In addition, while indexing static obstacles, the proposed system compresses and embeds the static obstacle information into the graph structure thus requires less memory than the traditional systems. The performance is evaluated for both the proposed and the traditional grid based systems on a virtual city environment. As a result, it has been shown that the proposed system on average works 8% faster than the traditional grid based system and requires significantly less memory while indexing static obstacles. [ABSTRACT FROM AUTHOR]