Md. Shamim Anower

Fuzzy-Proportional Integral Controller for an AGC in a Single Area Power System

In the present work, the intelligent load frequency controllers have been developed to regulate the power output and system frequency by controlling the speed of the generator with the help of fuel rack position control. This paper presents the implementation of fuzzy-proportional integral controller (FPIC) for controlling AGC in a single area power system. The aim of the proposed controller is to restore the frequency in a very smooth way to its nominal value in the shortest possible time whenever there is any change in the load demand etc. The action of this controller provides a satisfactory balance between frequency overshoot and transient oscillations with zero steady-state error. It is found that the proposed controller exhibits satisfactorily well dynamic performance and overcome all possible drawbacks associated with conventional PI controller.

A node estimation technique in underwater wireless sensor network

The number of nodes in a deployed wireless sensor network might vary due to ad hoc nature, natural disaster. Counting the number is very important in useful data collection, network maintenance, node localisation. Although protocols are being used to count the number in terrestrial networks, harsh environment limits their use in underwater networks. A statistical signal processing approach of node estimation is proposed in this paper. The nodes are considered as acoustic signal sources and their number is obtained through the cross-correlation of the acoustic signals received at two sensors in the network. The ratio of mean and standard deviation of the cross-correlation function is related with the number of nodes and used as the estimation parameter in the process. Theoretical and simulation results are provided which shows effectiveness of the signal processing approach instead of protocols in node estimation process.

Tellurite glass defect-core spiral photonic crystal fiber with low loss and large negative flattened dispersion over S + C + L + U wavelength bands

A defected-core spiral photonic crystal fiber is proposed to achieve very large negative flattened dispersion and small confinement loss. Simulation results reveal that the designed structure exhibits very large flattened dispersion over S+C+L+U wavelength bands and an average dispersion of about -720.7  ps nm(-1) km(-1) with an absolute dispersion variation of 12.7  ps nm(-1)  km(-1) over the wavelength ranging from 1.45 to 1.65 μm. The proposed fiber has five air-hole rings in the cladding leading to very small confinement loss of 0.00111  dB/km at the excitation wavelength of 1.55 μm. The tolerance of the fiber dispersion of ±2% changing in the structural parameters is investigated for practical conditions.

Effect of sensor number and location in cross-correlation based node estimation technique for underwater communications network

In underwater wireless sensor network (UWSN), node estimation poses a great challenge using conventional protocol techniques due to underwater propagation characteristics. For this reason, a cross-correlation based technique is applied to estimate the number of nodes, which is equally suitable for any environment networks. The nodes are considered as acoustic signal sources in an underwater network and sensors are considered as receiving nodes. In this paper, the estimation of the number of nodes (N) in a spherical region of an underwater acoustic sensor network (UASN) has been investigated by cross-correlating the acoustic signals received at three sensors to analyze the effect of sensor number and location.

Polarization Maintaining Low-Loss Slotted Core Kagome Lattice THz Fiber

A polarization maintaining ultra-low effective material loss based on slotted core kagome lattice fiber is proposed for terahertz (THz) wave propagation. Numerical study demonstrates that by using rectangular slotted air holes in the core of the kagome lattice exhibits simultaneously an ultra-high birefringence of 8.22 × 10-2, an ultra-low effective material loss of 0.05 cm-1, and a very low confinement loss of 4.13×10-5 cm-1 at the frequency of 1 THz. Further investigation shows that about half of the total mode power confines into the air slots at 50% core porosity. The proposed fiber can be used for polarization maintaining applications in THz regime.

A signal processing approach of underwater network node estimation with three sensors

Estimation of the number of nodes in a communication network is very important, particularly in ad hoc networks. But it is difficult to estimate in underwater wireless sensor networks due to long propagation delay, high absorption, and dispersion. Cross-correlation, a statistical signal processing approach is applied for this purpose, which is suitable for any environment networks. Nodes are considered as transmitters and sensors are considered as receivers. In this work, a node estimation technique for underwater networks is proposed by cross-correlating the signals received at three sensors.

Fuzzy Frequency Controller for an AGC for the Improvement of Power System Dynamics

A very important matter of discussion in power system operation is the oscillations damping problem. In this paper the authors propose a fuzzy frequency controller (FFC) to improve the dynamic performance of a single-area power system. This paper represents the implementation of fuzzy frequency controller for an AGC in single-area power system. The aim of the proposed controller is to restore the frequency to its nominal value in the smallest possible time whenever there is any change in the load demand etc. The controller provides a satisfactory balance between frequency overshoot and transient oscillations with zero steady-state error. It is found that the proposed controller exhibits satisfactorily well dynamic performance and overcome all possible drawbacks associated with conventional PI controller

A Polarization Maintaining Single-Mode Photonic Crystal Fiber for Residual Dispersion Compensation

A single-mode octagonal photonic crystal fiber (OPCF) is proposed to simultaneously achieve high birefringence and ultra-flattened ultra-high negative dispersion. Simulation results demonstrate that by introducing an elliptical air hole in the center of the core, it is possible to obtain a large average dispersion of -608.93 ps/nm/km with an absolute dispersion variation of -12.7 ps/nm/km over 1.46-1.625 μm wavelength bands for fundamental slow-axis mode. Besides, with optimal design parameters, a high birefringence of 1.81×10-2 and a very low confinement loss of 0.04 dB/km are achieved at 1.55 μm. The proposed OPCF can be used in cost-effective residual dispersion compensation and optical sensors.

Polarization maintaining highly nonlinear photonic crystal fiber with closely lying two zero dispersion wavelengths

Abstract. A simple hexagonal photonic crystal fiber is proposed to simultaneously achieve ultrahigh birefringence, large nonlinear coefficient, and two zero dispersion wavelengths (ZDWs). The finite element method with circular perfectly matched layer boundary condition is used to simulate the designed structure. Simulation results show that it is possible to achieve two closely lying ZDWs of 1.08 and 1.29  μm for x-polarization with 0.88 and 1.20  μm for y-polarization modes, respectively. In addition, an ultrahigh birefringence of 3.15×10−2 and a high nonlinear coefficient of 58  W−1 km−1 are also obtained at the excitation wavelength of 1.55  μm. The proposed fiber can have important applications in supercontinuum generation, parametric amplification, four-wave mixing, and optical sensors design.

Low-loss and bend-insensitive terahertz fiber using a rhombic-shaped core

A novel porous-core photonic crystal fiber is presented, and its guiding properties are numerically investigated by using the finite element method. It is demonstrated that by introducing a rhombic-shaped core made of circular air holes inside the conventional hexagonal cladding, it is possible to obtain very low bending loss of 3.04×10-11  cm-1 at the operating frequency of 1.0 THz. In addition to this, low effective material loss of 0.089  cm-1 and very small confinement loss of 1.17×10-3  dB/cm are achieved for optimal design parameters. Other guiding properties, including effective area, dispersion, and higher order mode characteristics are also discussed thoroughly. The design of this porous fiber is relatively simple, since it contains fewer air holes and consists of circular air holes only. Due to promising wave-guiding properties, the proposed fiber would have a great potential for terahertz imaging and flexible communication applications.