Co-doped ZnO–PVA Nanocomposite for EMI Shielding

The article describes the mechanical properties and electromagnetic shielding of Co-doped ZnO–poly(vinyl alcohol) nanocomposite. Significant improvements in mechanical properties can be obtained by incorporating inorganic nano fillers. The E-modulus and tensile strength were found to be enhanced with the increase in the doping concentration of Co_.05Zn_.95O incorporated in PVA matrix. Further, we have observed that electromagnetic shielding of the composite filled with 2 wt% concentration of Co_.05Zn_.95O in the PVA matrix exhibited utmost reflection loss of ? 47.31 dB in the bandwidth 8–12 GHz which may be attributed to good compatibility of dielectric and magnetic properties of materials.     

Regulated and non-regulated emissions from in-use diesel-electric switching locomotives

Diesel-electric locomotives are vital to the operation of freight railroads in the United States, and emissions from this source category have generated interest in recent years. They are also gaining attention as an important emission source under the larger set of nonroad sources, both from a regulated emissions and health effects standpoint. The present work analyzes regulated (NOx, PM, THC, CO) and non-regulated emissions from three in-use diesel-electric switching locomotives using standardized sampling and analytical techniques. The engines tested in this work were from 1950, 1960, and 1970 and showed a range of NOx and PM emissions. In general, non-regulated gaseous emissions showed a sharp increase as engines shifted from non-idle to idle operating modes. This is interesting from an emissions perspective since activity data shows that these locomotives spend around 60% of their time idling. In terms of polycyclicaromatic hydrocarbon (PAH) contributions, the dominance of naphthalene and its derivatives over the total PAH emissions was apparent, similar to observations for on-road diesel tractors. Among nonnaphthalenic species, itwas observed that lower molecular weight PAHs and n-alkanes dominated their respective compound classes. Regulated emissions from a newer technology engine used in a back-up generator (BUG) application were also compared againstthe present engines; it was determined that use of the newer engine may lower NOx and PM emissions by up to 30%. Another area of interest to regulators is better estimation of the marine engine inventory for port operations. Toward that end, a comparison of emissions from these engines with engine manufacturer data and the newer technology BUG engine was also performed for a marine duty cycle, another application where these engines are used typically with little modifications.     

Microstructure studies on Ti4+- and Zr4+-substituted Li-Zn ferrites

XRD and microstructure studies were carried out on Ti⁴⁺ and Zr⁴⁺-substituted Li-Zn ferrites prepared by standard ceramic technique. All the ferrite compositions exhibit single phase formation. The lattice parametera increases linearly with the content of Zn²⁺Zr⁴⁺ and Zn²⁺Ti⁴⁺, which is attributed to the ionic volumes of the cations involved. With substitution by Zr⁴⁺ the average size decreases, while with substitution by Ti⁴⁺ the grain size increases. In both the series grain size varies with the composition. Excess substitution of Zr⁴⁺ (x>0·4) leads to the formation of secondary images and discontinuous grain growth. Both Zr⁴⁺ and Ti⁴⁺ compositions obey Kurtz theory.     

Novel stereo controlled glycosylation of 1,2,3,4,6-penta-o-acetyl-β-d-glucopyranoside using MgO–ZrO2 as an environmentally benign catalyst

Glycosylation reactions are most commonly encountered in nature. Synthetically, glycosylations are carried out with Lewis acid catalysts or mineral acids. However an environmental threat associated with catalysts has encouraged process modification by alternative development of solid catalysts based glycosylation reactions, which are commercially viable as well. In this contribution comparative study of glycosidic bond formation of 1,2,3,4,6-penta-o-acetyl-β-d-glucopyranoside with various alcohols over variety of reaction promoters/catalyst like p-toluene sulphonic acid, HCl, H₂SO₄ and MgO–ZrO₂ were taken up to evaluate the performance of this potential promoter/catalysts systems. The best catalyst for the selective synthesis of alkyl-β-d-glucopyranosides was MgO–ZrO₂ which remains active upto three runs. This replacement of homogeneous acid catalysts by heterogeneous base catalyst shows alkyl-β-d-glucopyranoside as major product at comparatively low temperature range. The effects of variety of parameters were studied in a batch reactor. The mechanism of the reaction over basic mixed metal oxide at 363 K is put forth.     

Heterogeneous photocatalytic degradation of p-toluenesulfonic acid using concentrated solar radiation in slurry photoreactor

In this work, the photocatalytic degradation (PCD) of p-toluenesulfonic acid (p-TSA) in batch reactor using concentrated solar radiation was investigated. The effect of the various operating parameters such as initial concentration of substrate, catalyst loading, solution pH and types of ions on photocatalytic degradation has been studied in a batch reactor to derive the optimum conditions. The rate of photocatalytic degradation was found to be maximum at the self pH (pH 3.34) of p-TSA. It was also observed that in the presence of anions and cations, the rate of PCD decreases drastically. The kinetics of photocatalytic degradation of p-TSA was studied. The PCD of p-TSA was also carried at these optimized conditions in a bench scale slurry bubble column reactor using concentrated solar radiation.     

Chitosan Microparticles as Oral Delivery System for Tetanus Toxoid

Systemic and local immune response against Chitosan encapsulated tetanus toxoid (CS-TT) microparticles is studied, prepared by ionic cross-linking using Sodium Tripolyphosphate (STPP). Final formulation was evaluated in terms of release of TT in 0.1 N HCl and PBS (pH 7.4), sedimentation profile and stability. CS-TT microparticles, TT in PBS and plain CS microparticles were orally administered to mice and TT (adsorbed) was administered through intramuscular route. Sera were analyzed for anti-TT IgG and intestinal lavage, faeces, intestinal washings for anti-TT IgA levels using an ELISA. Entrapment efficiency of about 100% was obtained. A dose dependent immune response was observed in mice vaccinated with Chitosan-TT microparticles. A strong enhancement of the systemic and local immune response against TT were found when compared with oral feeding of TT in PBS. The study shows the efficacy of chitosan microparticle suspension system, containing a high molecular protein (TT), in inducing the IgA in intestine and IgG in systemic circulation. This demonstrates that chitosan microparticles can prove to be a promising oral vaccine delivery system for mucosal and systemic immunity.     

Silt erosion study on the performance of an impulse turbine in small hydropower

Silt particle laden flow through hydro turbine components causes erosion to the surface which comes in contact with it. Silt size, silt concentration, velocity of flow, properties of silt materials and operating hours of turbine play a vital role in damaging the turbine components. Efficiency of the turbine decreases with increase in erosive wear. The present study has been carried out to experimentally investigate the effect of silt size, silt concentration, jet velocity and operating time on performance of Turgo impulse turbine under actual flow conditions. It has been found that turbine efficiency loss strongly depends upon silt parameters. Existing test bed has shown erosion wear up to 1.8%, therefore resulting in the loss of power generation. Based on experimental data obtained for different parameters, correlations have been developed for the prediction of percentage efficiency loss of Turgo impulse turbine.     

CRYSTAL SIZE GROWTH IN THE LIQUID PHASE METHANOL SYNTHESIS CATALYST

ABSTRACT

The phenomenon of crystal growth in the methanol synthesis catalyst has been studied. Crystallite size distributions in the cuo/ZnO/Al₂O₃ methanol synthesis catalyst have been determined. The effects of temperature, reaction environment and time under reaction conditions have been studied. It is observed that water in the reaction mixture promotes crystal growth.     

Evaluation of Solid-Solution Hardening in Several Binary Alloy Systems Using Diffusion Couples Combined with Nanoindentation

Analysis of solid-solution hardening (SSH) in alloys requires the synthesis of large composition libraries and the measurement of strength or hardness from these compositions. Conventional methods of synthesis and testing, however, are not efficient and high-throughput approaches have been developed in the past. In the present study, we use a high-throughput combinatorial approach to examine SSH at large concentrations in binary alloys of Fe-Ni, Fe-Co, Pt-Ni, Pt-Co, Ni-Co, Ni-Mo, and Co-Mo. The diffusion couple (DC) method is used to generate concentration (c) gradients and the nanoindentation (NI) technique to measure the hardness (H) along these gradients. The obtained H –c profiles are analyzed within the framework of the Labusch model of SSH, and the \( c^{2/3} \) dependence of H predicted by the model is found to be generally applicable. The SSH behavior obtained using the combinatorial method is found to be largely consistent with that observed in the literature using conventional and DC-NI methods. This study evaluates SSH in Fe-, Ni-, Co-, and Pt-based binary alloys and confirms the applicability of the DC-NI approach for rapidly screening various solute elements for their SSH ability.     

Modeling the [dV/dt] of the IGBT during inductive turn off

Insulated gate bipolar transistor (IGBT)-based pulsewidth modulation (PWM) inverters are commonly used in inductive load circuits such as motor control. During clamped inductive load turn off of the IGBT, high-power losses occur during two phases. Due to the large inductive motor load, the voltage across the IGBT rises to the bus voltage while carrying the full-rated current. In the second phase, the current decreases as the IGBT goes into its forward blocking mode. In this paper, the turn-off process during the first phase is analyzed in detail for the first time. A simple analytical model has been derived, based upon the initial steady-state minority carrier distribution, which allows predicting the rate of rise of the voltage during this time period where the collector current remains constant. The predictions of the analytical model are in excellent agreement with results obtained from two-dimensional (2-D) numerical simulations over a broad range of minority carrier lifetime values. This analytical model provides a good estimate (within 10%) of the power losses incurred during the first phase of turn off