B-GWO based multi-UAV deployment and power allocation in NOMA assisted wireless networks

Wireless Networks - Unmanned Aerial Vehicles (UAVs) deployed as flying base stations is a promising technology for enhancing the quality of service (QoS) and quick recovery from unexpected damages...     

Triple Band Annular Ring Loaded Stacked Circular Patch Microstrip Antenna

In this paper a novel structure of annular ring loaded stacked circular patch microstrip antenna is theoretically analysed to observe various parameters such as return loss, input impedance, gain, directivity and radiation pattern. It is found that antenna possess three band of operation which signify the compactness and multiband operation of antenna. The antenna is resonating at three operating frequencies 1.720, 2.950, 3.060 GHz. The proposed theory is verified by simulation using Ansoft’s HFSS and theoretical results are in good agreement with simulated results. The antenna is useful for multi-services operations such as WLAN, GSM, UMTS, and WiMAX services.     

Tuning and Assessment of Proportional–Integral–Derivative Controller for an Automatic Voltage Regulator System Employing Local Unimodal Sampling Algorithm

Abstract—This article presents an approach for obtaining proportional–integral–derivative controller parameters for an automatic voltage regulator system based on a local unimodal sampling optimization algorithm. A conventional integral time of squared error objective function and modified objective functions in terms of integral time of absolute error, integral of absolute error, integral of squared error, peak overshoot, and settling time with appropriate weighting factors are employed to tune the controller parameters. Different objective functions are employed to obtain optimized proportional–integral–derivative controller gains. Superiority of proposed technique over some recently published modern heuristic optimization techniques, such as artificial bee colony algorithm, particle swarm optimization algorithm, and differential evolution algorithm, for the same automatic voltage regulator system is demonstrated. Simulation results reveal that the proposed proportional–integral–derivative controlled automatic voltage regulator system tuned by the local unimodal sampling algorithm with modified objective function exhibits better performance in terms of settling time, peak overshoot, and stability. The robustness of the system tuned by the proposed algorithm is also studied satisfactorily by varying the time constants of the automatic voltage regulator system in the range of –50% to +50% in steps of 25%.     

Estimation of the daily global solar radiation; Nepal experience

This work focuses on estimation of global solar radiation and, in particular, it explores the effect of precipitation and temperature on solar radiation profile of Kathmandu (Nepal). An accurate knowledge of solar radiation distribution in each particular geographical location is crucial for the promotion of solar energy technology. The best way of knowing the amount of global solar radiation is to install quality instruments at many locations in the given region. This requires their day to day maintenance, recording and calibration, which is very costly in developing countries like Nepal. Thus, the alternative approach is to correlate meteorological measurements with appropriate models and investigate the key parameters. For the research activities the RadEst program has been used. It includes, for evaluating the daily global solar radiation values at a given latitudes, four models which estimate the atmospheric transmissivity by measurements of daily temperature range and precipitations. The model parameters are fitted in 2 years data by iterative procedures. The values obtained by these models are, then, compared with measured radiation data. The paper reports graphical and statistical evaluations suggesting that among the four models, the Modular DCBB is the best model for Kathmandu area. This result is useful for designing solar panels able to maximize the harvesting of solar energy and to reduce the chronic shortage of hydrocarbon fuel that Nepal imports in a significant amount each year.     

Superconductivity in the (Yba2Cu3)1−xNaxO7−δ System

The (YBa₂Cu₃)_1−xNa_xO_7–δ system in the range of x = 0–0.8 was investigated. Experimental data suggest that the sodium doping with x 0.26 does not affect the critical transition temperature T_c, and the crystal structure maintains the orthorhombic lattice with a slightly smaller unit cell. However, sodium doping increases the sintering and grain growth kinetics, resulting in a higher superconducting phase volume and an enhanced Meissner effect. It also lowers the processing temperaturel. The experimental data also suggest that the sodium atoms diffuse into the superconducting YBa₂Cu₃O_7−δ crystallites, which stabilizes the orthorhombic phase. The transition temperature (ortho-rhombic to tetragonal) in sodium-doped materials increases with the increasing concentration of sodium.     

Redox State of Iron and Its Related Effects in the CaO–P2O5–Fe2O3 Glasses

Iron exists in Fe²⁺ and Fe³⁺ states in CaO–P₂O₅–Fe₂O₃ glasses and they impart characteristic optical absorption bands that allow analysis of relative proportion of the two species. This communication reports the redox states of glasses melted under air, argon, and oxygen atmospheres and relates them to the dissolution rates. The dissolution rate was found to be related to the redox state and it is lowered if the glass is melted under oxidizing atmospheres.     

Reaction and Coloration of Glasses with Hydrogen

The reaction of NBS 710 glass with hydrogen at 500°C and the resulting coloration of the glass have been studied using optical spectroscopy. Initially the reaction leads to the reduction of iron from ferrous to ferric state which subsequently combines with sulfur resulting in the formation of FeS. The origin of the color centers is proposed to be related to the formation of FeS.     

Sol-gel processing of SiO2-B2O3 glasses

Glasses from the SiO₂-B₂O₃ binary system containing up to 25 mole percent B₂O₃ have been synthesized. These glasses have been characterized by x-ray diffraction, optical transmission measurement, and I.R. absorption spectroscopy. In order to obtain a homogeneous glass, it was determined that a certain degree of hydrolysis of Si(OC₂H₅)₄ was essential before B(OC₂H₅)₃ could be incorporated. Optical transmission data exhibit characteristic absorption bonds related to Si, B, and OH fundamental and combination frequencies. I.R. absorption spectra in the 620 – 1700 cm^?1 range revealed presence of absorption bands related to vibrations of O-Si-O, Si-O-Si, B-O, and Si-O-B bonds.     

Objective Oriented Multistage Ring Shear Test for Shear Strength of Landslide Soil

Ring shear tests were conducted on five samples of different nature with a modified Imperial College type ring shear machine. The three different testing methods used, (1) individual sample testing for each normal stress, (2) increasing load multistage ring shear test, and (3) reducing load multistage ring shear test, all showed similar effective residual internal friction angle for the samples, irrespective of testing method. However, effective residual shear intercept was different according to the testing methodology. The internal friction angle did not vary, particularly after the first minimum point in the stress displacement curve, although the residual shear intercept decreased with increase in the displacement. The thickness of the shearing zone increased along with the displacement. The remolded peak shear strength for saturated conditions at field dry density varied with the consolidation history. Measurement of remolded peak shear strength was possible in a single sample using the increasing load multistage ring shear test at normal consolidation. The equilibrium water content of the sample after the ring shear test was nearly equal to the plastic limit.