Corrosion inhibition using superhydrophobic films

Neutron reflectivity (NR) was used to study the effectiveness of superhydrophobic (SH) films as corrosion inhibitors. A low-temperature, low-pressure technique was used to prepare a rough, highly porous organosilica aerogel-like film. UV/ozone treatments were used to control the surface coverage of hydrophobic organic ligands on the silica framework, allowing the contact angle with water to be continuously varied over the range of 160° (SH) to <10° (hydrophilic). Thin (∼5000 Å) nano-porous films were layered onto aluminium surfaces and submerged in 5 wt% NaCl in D₂O. NR measurements were taken over time to observe interfacial changes in thickness, density, and roughness, and therefore monitor the corrosion of the metal. NR shows that the SH nature of the surface prevents infiltration of water into the porous SH film and thus limits the exposure of corrosive elements to the metal surface.     

Design and Growth of Visible-Blind and Solar-Blind III-N APDs on Sapphire Substrates

GaN-based visible-blind and AlGaN-based solar-blind avalanche photodiodes (APDs) have been grown and fabricated on sapphire substrates. The GaN p-i-n APDs show low dark current with high gain. The AlGaN layers for the Al_0.55Ga_0.45N-based APDs are grown using a newly developed pulsed metalorganic chemical vapor deposition (MOCVD) process, and the material characterization results show excellent material quality. The spectral responsivity of the devices show a bandpass characteristic with cutoffs in the ultraviolet (UV) visible-blind and solar-blind spectrum for GaN- and Al_0.55Ga_0.45N-based APDs, respectively.     

Prediction of carbonisation time in byproduct recovery coke ovens through gooseneck temperature measurement

Precise prediction of the end of carbonisation possesses intangible benefits in the coke making process. The coke ovens in Tata Steel measure the raw gas temperature (at the gooseneck arrangement in the oven top) to identify the end of coking. Based on the gooseneck temperature profile, the carbonisation time is divided into active carbonisation time (ACT) and soaking time. As the soaking time is varied between 45?min and 1.5?h as per the need, the current study focusses on developing a mathematical model to predict the ACT given the coal blend properties and the operating conditions of the oven. Different statistical methods ranging from linear regression to artificial neural network (ANN) have been used to arrive at a robust model. Piece-wise linear regression and ANN have been found to out-perform the other statistical techniques. However, the ANN model is preferred in terms of the predictability of unseen data.     

Preparation of highly substituted carboxymethyl starch using a twin‐screw extruder

Carboxymethyl starch was prepared by reacting corn starch with sodium mono chloro acetate (SMCA) in a Brabender TSE‐20 co‐rotating twin screw extruder. The effects of the SMCA/starch ratio (theoretical degrees of substitutions 2.73, 3.62, and 4.53), aqueous ethanol/(starch + SMCA) ratio (0.13 and 0.25) and the screw configuration (0, 1, and 2 kneading blocks) on the degree of substitution (DS) and reaction efficiency were studied. A 3 × 2 factorial design with 3 levels of the starch/SMCA ratio and 2 levels of the aqueous ethanol/(starch + SMCA) ratio were used. This 3 × 2 factorial design was blocked, with the screw configuration as the blocking variable. The effects of the SMCA/starch ratio and the screw configuration were found to be significant. The carboxymethylated starches were characterized using FTIR, SEM, and XRD. The microstructure of the carboxymethylated starches, studied using SEM, revealed that the integrity of the starch granules was partially preserved at low aqueous ethanol levels when no kneading block was used. However, for all other reaction conditions either granule agglomeration or fusion was observed. XRD analysis indicated substantial loss of crystallinity in the carboxymethylated starches, irrespective of the damage to the granule structure. The highest DS and the highest reaction efficiency obtained were 1.54 and 0.42, respectively.     

Modular-structured resonant converter for multilevel converters in micro grids

In this work, an isolated modular resonant circuit with effective voltage regulation is presented as front-end for multilevel inverter system to interface renewable sources of energy with micro grid. Inputs of each module of the converter are connected to low-voltage DC sources. Modular-structured module outputs may be linked in sequence or parallel to attain the desired DC link capacitor voltage for multilevel inverter. The proposed converter overcomes imbalance in the capacitor voltage of diode-clamped inverter structure. Interleaved phase shift of 90° is supplied among the gate pulses of all four modules that minimizes the input-side current ripples. An effective zero voltage switching (ZVS) is achieved over wide load range using duty cycle and frequency-duty cycle double control method to improve system performance at light load condition. Adopting powder core magnetics and low forward voltage insulated-gate bipolar transistors (IGBTs) reduces magnetic and conduction loss. A 12-kW prototype of the designed modular resonant converter was verified by experimentation with a different-level diode-clamped inverter structures.     

The release into the atmosphere of hazardous volatiles Part I. Release from porous solids imbued with a liquid mixture in which the volatiles are dissolved

An experimental and theoretical study to investigate the release of toxic volatiles from porous media is presented. Three porous media, one synthetic and the other two natural, have been selected. They were imbued in a solution containing toxic volatiles in dilute concentrations. The heavy oily medium used to hold the volatiles in the liquid phase is tetradecane. The toxic volatiles whose diffusion is studied include benzene, chlorobenzene and 1,3-dichlorobenzene. These chemicals were chosen so that a wide range of volatilities could be studied.

Two different desorbers have been used. The first is a desorption chamber containing a single sphere of the porous medium. The second, more suitable for studying the diffusion of the less volatile components, has a cylindrical fixed bed geometry in which smaller porous spheres are arranged.

The theoretical tools used to model the diffusion process show good accuracy in describing the experimental data.     

Electromagnetic micro energy harvester for human locomotion

This paper reports the design and characterization of a proposed electromagnetic harvester. The harvester is made of permanent magnets and the overall size is of AA battery. Using Faraday’s law of induction, the harvester is capable of producing vibrational energy into electrical energy at low frequencies. The proposed harvester is to be used for bio-medical devices such as pacemakers and hearing aids. Human locomotion is the main source of vibrational energy that will be harnessed. Magnetic harvester can be attached anywhere on the human body in presence of motion such as mounting on the boot when walking. For low frequencies of 0–35 Hz and displacement of 0–7.2 mm, the micro harvester is capable of producing power anywhere from 0 to 38 mW at 0–35 Hz with power density of $4.44 \times 10^{ - 4} {\text{W}}/{\text{cm}}^{3}$ 4.44 × 10 ? 4 W / cm 3 .     

Long-term time-series pollution forecast using statistical and deep learning methods

Neural Computing and Applications - Tackling air pollution has become of utmost importance since the last few decades. Different statistical as well as deep learning methods have been proposed till...     

A linear time deterministic algorithm to find a small subset that approximates the centroid

Given a set of points S in any dimension, we describe a deterministic algorithm for finding a such that the centroid of T approximates the centroid of S within a factor 1+ε for any fixed ε>0. We achieve this in linear time by an efficient derandomization of the algorithm in [M. Inaba, N. Katoh, H. Imai, Applications of weighted Voronoi diagrams and randomization to variance-based k-clustering (extended abstract), in: Proceedings of the Tenth Annual Symposium on Computational Geometry, 1994, pp. 332-339].     

Temperature and precipitation changes in the Midwestern United States: implications for water management

The Midwestern United States is the heartland of agriculture production, and changes in the hydro-climatology may affect both the quantity and the quality of production. Seasonal temperature and precipitation were analyzed for trends and shifts. The results indicate an increasing trend in spring temperature (6.4 °F) and summer precipitation (1.2 inches). Shifts in the variables were dominant during two periods: 1920–1930 and 1970–1990. The observed changes not only provide scientific reference for assessing the impact on water resources as a result of climate change, but also help water managers and planners in taking proactive decisions to mitigate the water stress in the region.