Interpenetrating polymer networks of photocrosslinkable cellulose derivatives

A series of interpenetrating polymer networks has been prepared from two cellulose derivatives, one of which contains cinnamate groups and the other containing randomly substituted cinnamate and allyl groups. The latter derivative forms a crosslinked network in less than 5 min on exposure to ultraviolet radiation and can be used to make amorphous interpenetrating polymer networks containing 50% by weight loading level of crosslinked vinyl polymers. The syntheses of both derivatives and the thermal properties and film morphologies of their interpenetrating polymer networks are discussed. © 1996 John Wiley & Sons, Inc.     

Quantitative measurement of voids formed during liquid impregnation of nonwoven multifilament glass networks using an optical visualization technique

A technique based on matching the refractive index of an invading liquid to that of a fiber mat has been used to study entrapment of air (“voids”) that occurs during forced in-plane radial flow into nonwoven multifilament glass networks. The usefulness of this technique is demonstrated in quantifying and mapping the air pockets. Experiments with a series of fluids, with surface tensions varying from 28 × 10^?3 to 36 × 10^?3 N/m, viscosities from 45 × 10^?3 to 80 × 10^?3 Pa · s, and inlet flow rates from 0.15 × 10^?6 to 0.75 × 10^?6 m³/s, have shown that void content is a function of the capillary number characterizing the flow process. A critical value of capillary number Ca = 2.5 × 10^?3 identifies a zone below which void content increases exponentially with decreasing capillary number. Above this critical value, negligible entrapment of voids is observed.     

Atomistic insights into solvation dynamics and conformational transformation in thermo-sensitive and non-thermo-sensitive oligomers

Solvation dynamics and conformational transformation in oligomers with varying degree of temperature sensitivity is studied using molecular dynamics (MD) simulations. Conformational transformation in three model systems namely poly(N-isopropylacrylamide) (PNIPAM), poly(acrylamide) (PAA), and poly(ethylene glycol) (PEG) are compared and contrasted to understand the origin of a coil-to-globule transformations across the lower critical solution temperature (LCST) in thermo-sensitive oligomers. PNIPAM, PAA, and PEG are water-soluble oligomers. However, for the temperature range used in these simulations, PNIPAM shows an LCST whereas PAA and PEG are non-thermo-sensitive. Oligomers of PNIPAM, PAA, and PEG consisting of 30 monomer units (30-mer) each were simulated at 5 °C (278 K) and 37 °C (310 K). Conformational transformations in the oligomers are evaluated using structural and dynamical correlation functions such as radius of gyration, radial distribution function, residence time probabilities and hydrogen-bonding life-times. Our simulations suggest that the solubility, solvation dynamics, and conformation of the oligomers are dictated by two factors: (a) the local structure of proximal water and (b) the diffusion and exchange kinetics of proximal water with bulk water. In thermo-sensitive oligomer such as PNIPAM, we find that the coil-to-globule transition is closely related to the local ordering and solvation dynamics of PNIPAM. We have identified stable configurations of proximal water molecules for an oligomer undergoing conformational transition. The slow diffusional properties of proximal water molecules near PNIPAM oligomers suggests that water forms a stable network near hydrophilic groups of PNIPAM as compared to the hydrophilic groups of PAA and PEG. Thermal perturbation of this solvated structure results in significant reduction in local ordering of water, which contributes to the globular collapse and the reduced solubility of PNIPAM above its LCST. On the other hand, non-thermo-sensitive oligomers such as PAA and PEG are characterized by much faster diffusion and exchange kinetics of proximal water at the two simulated temperatures compared to PNIPAM. This faster exchange kinetics helps in maintaining higher hydration level of the oligomers and is responsible for the apparent hydrophilic character and thereby the observed solubility at the two simulated temperatures.     

Bi2O3 modified cobalt hydroxide as an electrode for alkaline batteries

Manganese dioxide electrode shows reversible charge storage capacity, if the charge-discharge process is limited to 0.3e⁻ exchange. Addition of small amount of Bi₂O₃ to manganese dioxide induces reversibility with an exchange of 2e⁻/Mn. Nickel hydroxide is known to reversibly exchange 1e⁻. In spite of isostructural relationship between the cobalt hydroxide, nickel hydroxide and manganese dioxide, cobalt hydroxide does not show any electrochemical activity. Bi₂O₃ modified cobalt hydroxide electrodes exchanges 0.3-0.5e⁻/Co during the charge discharge process. The oxidation-reduction process in cobalt hydroxide and Bi₂O₃ modified cobalt hydroxide electrodes were monitored using the PXRD patterns.     

Photoelectrochemical water splitting using CuIn1−xGaxS2/CdS thin-film solar cells for hydrogen generation

Photoelectrochemical (PEC) efficiency of a PEC cell constructed by series connecting two 0.43 cm² size, 5.95% (AM1.5) efficient CuIn_1−xGa_xS₂ (CIGS2) thin-film photovoltaic (PV) cells having transparent and conducting back contacts, outside the electrolyte, to RuS₂ photoanode and platinum cathode, in the electrolyte, for oxygen and hydrogen generation by water splitting was 2.99%. PV electrolysis efficiency of a similar setup prepared using two CIGS2 PV cells having opaque Mo back contacts and highest achieved efficiency of 11.99% (AM1.5) connected to RuS₂ and Pt electrodes was 8.78%. This significant result points a way toward attaining higher PEC efficiencies.     

Inducing oblique decision trees with evolutionary algorithms

This paper illustrates the application of evolutionary algorithms (EAs) to the problem of oblique decision-tree (DT) induction. The objectives are to demonstrate that EAs can find classifiers whose accuracy is competitive with other oblique tree construction methods, and that, at least in some cases, this can be accomplished in a shorter time. We performed experiments with a (1+1) evolution strategy and a simple genetic algorithm on public domain and artificial data sets, and compared the results with three other oblique and one axis-parallel DT algorithms. The empirical results suggest that the EAs quickly find competitive classifiers, and that EAs scale up better than traditional methods to the dimensionality of the domain and the number of instances used in training. In addition, we show that the classification accuracy improves when the trees obtained with the EAs are combined in ensembles, and that sometimes it is possible to build the ensemble of evolutionary trees in less time than a single traditional oblique tree.