Liquid-phase hydrogenation of bio-refined succinic acid to 1,4-butanediol using bimetallic catalysts

open access articleDevelopment of a Crotalaria juncea based biorefinery produce large quantity of waste glycerol after trans-esterification of the juncea seeds. This glycerol, after purification, is used as a substrate for producing succinic acid on a microbial route. Hydrogenation of this bio-refined succinic acid is carried out under high pressure in order to produce 1,4- butanediol (BDO) using a batch slurry reactor with cobalt supported ruthenium bimetallic catalysts, synthesized inhouse. It is demonstrated that, using small amounts of ruthenium to cobalt increases the overall hydrogenation activity for the production of 1,4-butanediol. Hydrogenation reactions are carried out at various operating temperatures and pressures along with changes in the mixing ratios of ruthenium chloride and cobalt chloride hexahydrate, which are used to synthesize the catalyst. The Ru-Co bimetallic catalysts are characterized by XRD, FE-SEM and TGA. Concentrations of the hydrogenation product are analyzed using Gas chromatography-Mass spectrometry (GC-MS). Statistical analysis of the overall hydrogenation process is performed using a Box-Behnken Design (BBD)

EXPERIMENTAL STUDY ON SELFCOMPACTING CONCRETE CONTAINING INDUSTRIAL BY-PRODUCTS

Self-Compacting Concrete (SCC) is a type of concrete that has thecapacity to consolidate under its own weight. The current trend all over theworld is to utilize the treated and untreated industrial by-products, domesticwaste etc. as a raw material in concrete, which gives an eco-friendly edge tothe concrete preparation process. This practice not only helps in reuse of thewaste material but also creates a cleaner and greener environment. This studyaims to focus on the possibility of using industrial by-products like GroundGranulated Blast furnace Slag (GGBS) and Silica fumes (SF) in preparationof SCC. The usage of these powders is proposed as a replacement for cementin the production of SCC by adopting the much popular Nan Su et al. methodof mix design. The paper deals with comparison of performances of GGBSand SF based SCC mixes

Scattering of positronium by H, He, Ne, and Ar

The low-energy scattering of ortho positronium (Ps) by H, He, Ne, and Ar atoms has been investigated in the coupled-channel framework by using a recently proposed time-reversal-symmetric nonlocal electron-exchange model potential with a single parameter $C$. For H and He we use a three-Ps-state coupled-channel model and for Ar and Ne we use a static-exchange model. The sensitivity of the results is studied with respect to the parameter $C$. Present low-energy cross sections for He, Ne and Ar are in good agreement with experiment.Comment: 8 pages Latex with 4 postscript figure

To study the effects of degradation of phonon distribution on the high frequency response in nano structures

low dimensional semiconductor nano structures, Frolich coupling, LO phonons , phonon lifetimeThere has been an intense interest in low dimensional semiconductor nano structures, because of subtle and profound changes that occurs, as length scale becomes comparable to the exciton Bohr radii and the dimensionality is reduced significantly.[1] In nano structures, hot electron conditions are developed if the applied electric field is sufficiently high so as to cause a pronounced deviation from Ohm’s law. At these fields, drift energy of electrons may be compared with the thermal energy at the lattice temperature. The average electron energy is also much higher than that in the thermal equilibrium with the lattice. Under such high electric fields, the carrier mobility exhibits a complicated dependence on the applied electric field. Under hot electron condition, the hot carriers, photon excited by ultra short pulses in polar semiconductors, initially loose energy rapidly by emitting longitudinal optic phonons via dominant Frolich coupling. Thus, the energy supplied to the carriers by the high electric field goes into phonon generation. As the phonon lifetime is long enough, phonon distribution is disturbed and a nonequilibrium population of LO phonons or hot phonons are produced, leading to their reabsorption by the carriers. The measurement of energy loss rate in low dimensional nano structures and other analysis show that the nonequilibrium LO phonons play an important role in slowing down the carrier cooling rate[2]. In the present work the high frequency performance of GaN nano structures is studied in the framework of heated, drifted, Fermi-Dirac distribution function incorporating the relevant scattering mechanisms and the influence of nonequilibrim LO phonons. The effects of large q-LO phonons and electron-LO phonon interaction at low qLZ (Lz is channel length ) are also studied. The ac mobility normalized by dc value is found to decrease with increasing frequency of the applied field beyond about 80GHz while the drift velocity lags behind the applied field above around about 20GHz. The f3dB cutoff frequency at which the ac mobility drops to 0.707 of its low frequency value is found to decrease with increasing LZ and carrier concentration. The weakening of scattering for a wider channel width, combined scattering mechanisms and the increasing degeneracy of the carriers at higher concentration account for such behaviour. However, it is always higher when degradation of phonon distribution is incorporated. This behaviour is attributed to the slowing down of the carrier energy and momentum loss rates in the presence of non equilibrium phonons[2]. Thus, we find that the degradation of phonon distribution enhances significantly the 3-dB cut-off frequency thereby makes the high frequency response flatter reflecting that high frequency response is better if effects of nonequilibrium phonon distribution are included in the calculations. References : 1. A. Majumdar, L. P. Rokhinson and D. C. Tsui : - Appl. Phys. Lett - 76, 3600 (2000) 2. A. S. Vengurlkar, S. S. Prabhu, S. K. Roy and J. Shah : Phy. Rev .B-50,461(1994

Disordered Type-II Superconductors: A Universal Phase Diagram for Low-Tc_c Systems

A universal phase diagram for weakly pinned low-T$_c$ type-II superconductors is revisited and extended with new proposals. The low-temperature ``Bragg glass'' phase is argued to transform first into a disordered, glassy phase upon heating. This glassy phase, a continuation of the high-field equilibrium vortex glass phase, then melts at higher temperatures into a liquid. This proposal provides an explanation for the anomalies observed in the peak effect regime of 2H-NbSe$_2$ and several other low-T$_c$ materials which is independent of the microscopic mechanisms of superconductivity in these systems.Comment: 23 pages, 9 figure

Glassy Phase Transition and Stability in Black Holes

Black hole thermodynamics, confined to the semi-classical regime, cannot address the thermodynamic stability of a black hole in flat space. Here we show that inclusion of correction beyond the semi-classical approximation makes a black hole thermodynamically stable. This stability is reached through a phase transition. By using Ehrenfest's scheme we further prove that this is a glassy phase transition with a Prigogine-Defay ratio close to 3. This value is well placed within the desired bound (2 to 5) for a glassy phase transition. Thus our analysis indicates a very close connection between the phase transition phenomena of a black hole and glass forming systems. Finally, we discuss the robustness of our results by considering different normalisations for the correction term.Comment: v3, minor changes over v2, references added, LaTeX-2e, 18 pages, 3 ps figures, to appear in Eour. Phys. Jour.

On two-dimensionalization of three-dimensional turbulence in shell models

Applying a modified version of the Gledzer-Ohkitani-Yamada (GOY) shell model, the signatures of so-called two-dimensionalization effect of three-dimensional incompressible, homogeneous, isotropic fully developed unforced turbulence have been studied and reproduced. Within the framework of shell models we have obtained the following results: (i) progressive steepening of the energy spectrum with increased strength of the rotation, and, (ii) depletion in the energy flux of the forward forward cascade, sometimes leading to an inverse cascade. The presence of extended self-similarity and self-similar PDFs for longitudinal velocity differences are also presented for the rotating 3D turbulence case

Mechanical performance and capillary water absorption of sewage sludge ash concrete (SSAC)

Disposal of sewage sludge from waste water treatment plants is a serious environmental problem of increasing magnitude. Waste water treatment generates as much as 70 g of dry solids per capita per day. Although one of the disposal solutions for this waste is through incineration, still almost 30% of sludge solids remain as ash. This paper presents results related to reuse of sewage sludge ash in concrete. The sludge was characterised for chemical composition (X-ray flourescence analysis), crystalline phases (X-ray diffraction analysis) and pozzolanic activity. The effects of incineration on crystal phases of the dry sludge were investigated. Two water/cement (W/C) ratios (0.55 and 0.45) and three sludge ash percentages (5%,10% and 20%) per cement mass were used as filler. The mechanical performance of sewage sludge ash concrete (SSAC) at different curing ages (3, 7, 28 and 90 days) was assessed by means of mechanical tests and capillary water absorption. Results show that sewage sludge ash leads to a reduction in density and mechanical strength and to an increase in capillary water absorption. Results also show that SSAC with 20% of sewage sludge ash and W/C=0.45 has a 28 day compressive strength of almost 30 MPa. SSAC with a sludge ash contents of 5% and 10% has the same capillary water absorption coefficient as the control concrete; as for the concrete mixtures with 20% sludge ash content, the capillary water absorption is higher but in line with C20/25 strength class concretes performance

Modeling the role of constant and time varying recycling delay on an ecological food chain

summary:We consider a mathematical model of nutrient-autotroph-herbivore interaction with nutrient recycling from both autotroph and herbivore. Local and global stability criteria of the model are studied in terms of system parameters. Next we incorporate the time required for recycling of nutrient from herbivore as a constant discrete time delay. The resulting DDE model is analyzed regarding stability and bifurcation aspects. Finally, we assume the recycling delay in the oscillatory form to model the daily variation in nutrient recycling and deduce the stability criteria of the variable delay model. A comparison of the variable delay model with the constant delay one is performed to unearth the biological relevance of oscillating delay in some real world ecological situations. Numerical simulations are done in support of analytical results