Gravitational Search Based Algorithm for Optimal Coordination of Directional Overcurrent Relays Using User Defined Characteristic

Due to dependency on Plug Setting (PS), Time Dial Setting (TDS), size of the network, more than one back-up relays for one primary relay and other technical constraints, coordination of Directional Overcurrent Relays (DOCRs) is an extremely constrained and nonlinear optimization problem. In this paper, a new Gravitational Search (GS) based algorithm is presented for achieving optimal coordination of directional overcurrent relays. The proposed algorithm utilizes user defined characteristic for inverse time overcurrent relays than the predefined standard curves. The user defined relay characteristic deals with constants that control the shape of the characteristics as variable adjustable values which are optimally chosen along with TDS and Plug Setting Multiplier (PSM). The performance of the proposed algorithm has been evaluated on 8-bus, 15-bus and IEEE 30-bus distribution network at different fault locations (near-end, far-end and middle point). In addition, the time of operation of some of the primary relays at different fault locations on IEEE 30-bus distribution network is also presented. At the end, comparative evaluation of the proposed algorithm with other optimization algorithms having different relay characteristics presented in the literature clearly indicates its effectiveness and superiority in terms of the sum of total primary relays operating time.     

Design of 0.5 V voltage-combiner based OTA with 60 dB gain 250 kHz UGB in CMOS

A gain enhancement technique for a pseudo differential OTA based on voltage combiner, suitable for sub-1 V supply is presented in this letter. The proposed technique uses a G _m boosted voltage combiner. Unlike the typical voltage combiner which has an approximated gain of \(2\,\frac{{\text{V}}}{{\text{V}}}\), this voltage combiner can produce gain more than \(5\,\frac{{\text{V}}}{{\text{V}}}\). So it help us achieve nearly 60 dB DC gain with 250 kHz UGB for the pseudo differential OTA at a capacitive load of 10 pF. Power dissipation is very low i.e. 716 nW at supply of 0.5 V. So as to facilitate maximum swing at 0.5 V supply and lower the power consumption, MOS transistors are biased in weak/moderate inversion. The OTA is designed in standard 45 nm CMOS process. Phase margin of is more than \(55^{\circ }\) for a typical load of 10 pF. The input referred noise is \(150\,\upmu {\text{V}}{/}\sqrt{{\text{Hz}}}\) at 10 Hz and slew rate \(0.02\,{\text{V}}{/}\upmu{\text{s}}\) for 10 pF load.     

Anthropogenic contamination and risk assessment of heavy metals in stream sediments influenced by acid mine drainage from a northeast coalfield,India

The total concentrations and chemical partitioning of heavy metals in streambed sediments, collected around the Jaintia Hills coal deposit of northeast India, were studied using pollution indices and multivariate techniques to evaluate the risk and contamination levels from heavy metals and their possible origins. Results show that sediments close to mining sites have low pH (<4), high organic carbon, and contain significant amounts of Fe-oxyhydroxide phases (mainly, goethite and schwertmannite), which implies direct impact of coal mine drainage. The average concentrations of Fe, Cu, Co, Cd, Cr, and Zn exceeded the World average, and in some cases, Cd, Cu, Ni, and Cr concentrations exceeded the threshold effects level, which suggests they will be toxic to aquatic biota. Contamination factors (CF) show that the sediments are low to highly contaminated with Cd, Cu, Mn, Pb, Fe, and Zn and low to moderately contaminated with Co, Cr and Ni. The pollution load index (PLI), degree of contamination index (C _deg) and Nemerow integrated pollution index (NIPI) show that the sediments are moderately to highly contaminated, with the extent of pollution greatest nearest to the collieries. The potential ecological risk index (RI) shows low to considerable ecological risk from heavy metals in the sediments, with Cd having the high potential of risk, which also agrees with the risk assessment code (RAC). Multivariate statistical analysis suggests that the concentrations of the heavy metals in stream sediments are strongly influenced by Fe-oxyhydroxide phases and organic carbon derived from anthropogenic sources, mainly coal mining activities. Although a significant proportion of the Cd, Mn, and Ni in the sediments are partitioned into exchangeable and organic fractions, a sizable amount of metals are also found in the Fe–Mn fraction, suggesting that Fe-oxyhydroxides play a dominant role in controlling metal mobility in these stream sediments.     

Development and evaluation of ZnO-Fe2O3 based nanocomposite sensors for butanol detection

Olfactory sensing of specific volatile organic compounds released by bacterial pathogens is one of the unique ways for determining microbial contamination in packaged food products. This study reports the development and evaluation of zinc oxide-iron oxide (ZnO-Fe2O3) nanocomposite sensors to detect low concentrations of butanol, one of the VOCs specific to Salmonella contamination in packaged beef, at low operating temperature (100 degrees C). The ZnO-Fe2O3 sensor was developed using modified Sol-gel method on an interdigitated alumina substrate. The sensor thin film characterization confirmed a uniform layer of ZnO-Fe2O3 thin film formation with ZnO nanorods of 100 nm height. Also, ZnO-Fe2O3 nanocomposite sensor demonstrated repeatable responses and good sensitivity to butanol with an estimated lower detection limit of about 26 ppm at 100 degrees C.     

Influence of strain and strain rate on microstructural evolution during superplasticity of Mg–Al–Zn sheet

Strain-induced abnormal grain growth was observed along the gage length during high-temperature uniaxial tensile testing of rolled Mg–Al–Zn (AZ31) sheet. Effective strain and strain rates in biaxial forming of AZ31 sheets also affected the nature of grain growth in the formed sheet. For the uniaxial testing done at 400 °C and a strain rate of 10^?1 s^?1, abnormal grain growth was prevalent in the gage sections that experienced true strain values between 0.2 and 1.0. Biaxial forming of AZ31 at 5 × 10^?2 s^?1 and 400 °C also exhibited abnormal grain growth at the cross sections which experienced a true strain of 1.7. Uniaxially tested sample at 400 °C and a strain rate of 10^?3 s^?1, however, showed no abnormal grain growth in the gage sections which experienced true local strain values ranging from 1.0 to 2.3. The normalized flow stress versus temperature and grain size compensated strain rate plot showed that the deformation kinetics of the current AZ31 alloy was similar to that reported in the literature for AZ31 alloys. Orientation image microscopy (OIM) was used to study the texture evolution, grain size, and grain boundary misorientation during uniaxial and biaxial forming. Influence of deformation parameters, namely strain rate, strain, and temperature on grain growth and refinement were discussed with the help of OIM results.     

Achieving High Strength and High Ductility in Friction Stir-Processed Cast Magnesium Alloy

Friction stir processing (FSP) is emerging as an effective tool for microstructural modification and property enhancement. As-cast AZ91 magnesium alloy was friction stir processed with one-pass and two-pass to examine the influence of processing conditions on microstructural evolution and corresponding mechanical properties. Grain refinement accompanied with development of strong basal texture was observed for both processing conditions. Ultrafine-grained (UFG) AZ91 was achieved under two-pass FSP with fine precipitates distributed on the grain boundary. The processed UFG AZ91 exhibited a high tensile strength of ~435 MPa (117 pct improvement) and tensile fracture elongation of ~23 pct. The promising combination of strength and ductility is attributed to the elimination of casting porosity, and high density of fine precipitates in an UFG structure with quite low dislocation density. The effects of grain size, precipitate, and texture on deformation behavior have been discussed.     

The weld pool region of welded cast metal-matrix ceramic-particulate composites

The successful application of ceramic-particulate reinforced metal matrix composites as engineering materials requires that they be amenable to fabrication by joining processes such as welding. In such a case, the weld pool would undergo intense agitation during welding and the ceramic particulates would tend to segregate, causing deterioration in the mechanical and wear properties of the joined portion. In the present work, a thermo-physical model has been used to predict the velocities of fluid movement in the weld pool as a function of heat input. An attempt has been made to combine analytical and numerical methods in order to ensure the accuracy of the model's predictions and at the same time to make the computation faster. Aluminium-alumina and aluminum-silicon carbide composites were prepared by casting and the resultant plates of standard dimensions and thicknesses were welded using the MIG process. The distribution of the ceramic particulates and their reaction with the matrix in the welded zone were determined using metallographic and SEM techniques. The distribution was then simulated from the fluid flow velocities obtained by the model developed by the authors. A good correlation was seen between the intensity of molten metal velocities and the particle distribution. Particle pushing and engulfment by the solidifying melt interface also appeared to be affecting the particle distribution in the weld zone.     

Thin-Layer Drying of Flax Fiber: I. Analysis of Modeling Using Fick's Second Law of Diffusion

Thin-layer drying of moist flax fiber was performed at four temperatures of 30, 50, 70, and 100°C with a constant absolute humidity of 0.0065 kg water per kg dry air. The coefficients of diffusion of the fiber at different drying conditions were estimated by modeling the drying process using the one- to five-term solutions of the second Fick's law of diffusion. The models underestimated the drying process during the initial stages of drying and overestimated this process during the final stages. The estimated coefficient of diffusions ranged from 5.11 × 10^?9 to 1.92 × 10^?8 m²/s and linearly increased with the drying air temperature.     

Thin-Layer Drying of Flax Fiber: III. Influence of Layer Thickness on Drying Parameters

Wet flax fiber was dried after rinsing at four layer thicknesses of 5, 10, 15, and 20 mm using four drying air temperatures of 30, 50, 70, and 100°C. The coefficients of diffusion of flax fiber at different drying conditions were estimated using a three-term series solution of Fick's second law of diffusion. The Page model was used to model the drying characteristic curves. The estimated coefficient of diffusion of the flax fiber and the drying constant of the Page model were both linearly proportional to drying air temperature and increased exponentially with the thickness of the drying layer.